WO2000005970A1 - Gel-coated microcapsules - Google Patents

Gel-coated microcapsules Download PDF

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Publication number
WO2000005970A1
WO2000005970A1 PCT/US1999/016159 US9916159W WO0005970A1 WO 2000005970 A1 WO2000005970 A1 WO 2000005970A1 US 9916159 W US9916159 W US 9916159W WO 0005970 A1 WO0005970 A1 WO 0005970A1
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WO
WIPO (PCT)
Prior art keywords
microcapsules
gel
metal
weight percent
catalyst
Prior art date
Application number
PCT/US1999/016159
Other languages
French (fr)
Inventor
Mark E. Holman
Original Assignee
Frisby Technologies, Inc.
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Filing date
Publication date
Application filed by Frisby Technologies, Inc. filed Critical Frisby Technologies, Inc.
Priority to AT99934109T priority Critical patent/ATE288319T1/en
Priority to DE69923566T priority patent/DE69923566T2/en
Priority to EP99934109A priority patent/EP1100342B1/en
Priority to AU50015/99A priority patent/AU5001599A/en
Priority to JP2000561836A priority patent/JP2002521186A/en
Publication of WO2000005970A1 publication Critical patent/WO2000005970A1/en

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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28HEAT EXCHANGE IN GENERAL
    • F28DHEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/02Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat
    • F28D20/023Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat the latent heat storage material being enclosed in granular particles or dispersed in a porous, fibrous or cellular structure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02Making microcapsules or microballoons
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/02Making microcapsules or microballoons
    • B01J13/20After-treatment of capsule walls, e.g. hardening
    • B01J13/22Coating
    • CCHEMISTRY; METALLURGY
    • C09DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09KMATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2323/00Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
    • C09K2323/06Substrate layer characterised by chemical composition
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/14Thermal energy storage
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/29Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2984Microcapsule with fluid core [includes liposome]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/29Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2984Microcapsule with fluid core [includes liposome]
    • Y10T428/2985Solid-walled microcapsule from synthetic polymer
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/29Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2989Microcapsule with solid core [includes liposome]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/29Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2991Coated
    • Y10T428/2993Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/29Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982Particulate matter [e.g., sphere, flake, etc.]
    • Y10T428/2991Coated
    • Y10T428/2993Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
    • Y10T428/2995Silane, siloxane or silicone coating

Definitions

  • the invention relates to microencapsulated phase change materials which are coated with a metal oxide or metalloid oxide gel .
  • PCMs Phase-change materials, or "PCMs" are compositions that absorb and emit large amounts of heat by changing from one physical state to another, most often reversibly. Typical PCMs change from solid to liquid and back. Paraffinic hydrocarbons are commonly used as PCMs that melt at a desired temperature or over a desired temperature range, as disclosed, for example, in U.S. Patent No. 5,637,389.
  • Phase-change materials find use or have been proposed for use in apparel for thermal management, either as discrete layers (see U.S. Patent No. 5,499,460), as foam additives (see U.S. Patent No. 5,637,389), as fabric coatings (see U.S. Patent No.
  • PCMs may be encapsulated to minimize loss of their integrity, dissipation, or evaporation. Encapsulated PCMs are available as microcapsules ("MicroPCMs") having average diameters typically in the range of a few to a few hundred microns. MicroPCMs have been prepared for use as additives to heat exchange fluids, including motor oil (see U.S. Patent No. 5,141,079). PCMs which contain paraffinic hydrocarbons are typically flammable. This flammability is often an unacceptable condition.
  • Sol -gel methods are generally covered in Sol -Gel Science - The Physics and Chemistry of Sol -Gel Processing, C. Jeffrey Brinker & George W. Scherer, 1st o Ed., Academic Press, (1990), which is hereby incorporated by reference in its entirety.
  • the invention provides microencapsulated phase- change materials (“MicroPCMs”) that have improved solvent s resistance, increased hardness and reduced flammability, and methods for making them.
  • the MicroPCMs of this invention are MicroPCMs coated with a glass-like gel material. They can be produced through sol -gel processing of MicroPCMs.
  • the gel coating provides a o degree of physical and flame protection for the microcapsules.
  • the oxidative resistance of such particles is improved significantly, since the coating is believed to minimize oxygen contact with the microcapsules. This can result in reduced incidence of 5 oxidation from atmospheric oxygen for the contents of the microcapsules, e.g., reduced flammability for flammable contents, or reduced chemical oxidation for atmospheric oxidation sensitive contents.
  • the contents contemplated for use in the gel-coated microcapsules include 0 temperature stabilization materials, optical materials or magnetic materials, to name a few examples.
  • the invention further provides a method for providing a gel coating on MicroPCMs by a sol -gel process.
  • This method involves creating a sol, allowing 5 the gel reaction to take place, mixing MicroPCMs into the sol, and spraying the mixture into, or pouring the mixture onto, a collection area. Curing of the gel takes place in the collection area, and the gel-coated MicroPCMs are collected and ready for use.
  • the invention further provides a two-component heat transfer slurry, which can be circulated for heating or cooling purposes in a heat transport loop in which heat is transported from a heat source to a heat sink with the use of a pump.
  • the method of this invention has applicability beyond MicroPCMs. It can be used to coat microcapsules containing optical or magnetic materials, for example.
  • this invention also includes gel -coated microcapsules containing such materials.
  • a "non-released material” is a substance or mixture of substances, which interact with the environment surrounding the microcapsules primarily indirectly. Such materials are not designed to escape the microcapsule under normal operating conditions. Such materials are to be contrasted with others such as flavorings, fragrances, cosmetic products, pharmaceutical or other medical products, which are contained in microcapsules as a means of controlled release of such substances.
  • microcapsule means a unicellular, hollow particle, that is a particle having a peripheral wall or shell enclosing or surrounding a single, hollow cavity, space or void within the interior of the particle which, unless otherwise noted, can be evacuated or filled with a gas, liquid, or solid, such particle being so small as to require means such as an optical microscope for purposes of measuring the dimensions thereof.
  • a microcapsule characterized herein as “spherical” is one which has the shape of a true sphere or spheroid, that is, like a sphere, e.g., oblate or prolate.
  • a microcapsule characterized herein as "porous” is one whose wall has interconnected submicroscopic pores or passages and is permeable to liquid and/or gas
  • an "impermeable” microcapsule is one whose wall is sealed, non-porous or closed or that has submicroscopic pores or passages so small as to minimize transmission of liquid and/or gas and to maintain the contents within the interior void of the microcapsule.
  • metal refers to elements which are the central and ligand-bearing atoms in the gel precursors of the invention. As such, it refers not only to those elements commonly referred to as metals, but also the elements such as boron, silicon and germanium which are not traditionally considered metals.
  • potting compounds refers to semiflexible epoxies with thixotropic and curing agents added, used to affix and cool electronic components.
  • optical material refers to a material that undergoes physical or chemical changes upon the absorption of photons. The physical changes include the emission of light and/or heat and the reflection of light. Metastable excited states can also be formed. The chemical changes include chemical bond formation and breakage, including various rearrangements, isomerizations and the formation of metastable chemical states .
  • the coated microcapsules of the invention feature microcapsules coated with a gel, specifically a gel produced by the sol -gel process.
  • the gel coating provides certain resistances to the microcapsules, resulting in enhanced protection for their contents.
  • Microcapsules containing different types of materials are known, as are microencapsulation techniques to prepare such materials, which are used as starting materials in the process of this invention. Microcapsules can be used in many applications in which materials are to be contained either indefinitely or temporarily. Microcapsules have been designed to allow the slow release of pharmaceutical preparations, cosmetic products and food products such as flavoring agents.
  • the microcapsules used in the present invention on the other hand, are adapted to contain materials that interact indirectly with the environments in which they are used.
  • Microcapsules are prepared according to known procedures.
  • the material which makes up the microcapsule wall can be chosen from a wide variety of materials. The choice of materials depends primarily on the physical and chemical characteristics of the contents, and on the intended use of the microcapsules.
  • the microcapsules should also be readily coatable with the metal oxide gel.
  • Preferred microcapsule wall -forming materials include various thermoplastic materials, such as natural or synthetic fatty alcohols, fatty acids, fatty esters and waxes .
  • Natural waxes include the vegetable waxes such as carnuba, cauassu, candelilla, farria, palm, esparto, sugar cane and cotton waxes; animal waxes such as beeswax, ghedda, Chinese insect, shellac, spermaceti and lanolin waxes; and mineral wax such as paraffin, microcrystalline, ozokerite, montan and syncera waxes.
  • Synthetic and modified waxes useful as microcapsule wall- forming materials include the Carbowaxes, Abril waxes, Armid and Armowaxes (Armour & Co.) and Chlorax chlorinated paraffin wax (Watford Chemical Co.) . It will be appreciated that waxes are a mixture of various components, and that each type of wax is itself available in a number of different grades.
  • thermoplastic materials are useful as microcapsule wall -forming materials, including polyethylenes such as PolywaxTM from Petrolite, Inc., polypropylenes, polyesters, polyvinyl chlorides, tristarch acetates, polyethylene oxides, polypropylene oxides, polyvinylidene chloride or fluoride, polyvinyl alcohols, polyvinyl acetates, polyacrylates, polymethacrylates, vinyl functional polymers, urethanes, polycarbonates, and polylactones . Further details on microencapsulation are found in U.S. Patent Nos. 5,589,194 and 5,433,953.
  • a colloid is a suspension in which the dispersed phase is not affected by gravitational forces, due to the dimensions of the dispersed phase (1-1000 nm) .
  • a sol is a colloidal suspension of solid particles in a liquid.
  • a gel can be considered to be the agglomeration of these particles into a structure of macroscopic dimensions, such that it extends throughout the solution. It is therefore, a substance that contains a continuous solid skeleton enclosing a continuous liquid phase.
  • Sol -gel processing involves chemical processing of gel precursors to prepare a colloid. These precursors consist of metal atoms surrounded by ligands. The metal atoms and the ligands fall into wide classes. Generally, chemical processing of the gel precursors involves hydrolysis and condensation reactions in which the ligands of the precursors are replaced by bonds to the ligands of other metal or metalloid elements. This process results in a growing network of metal or metalloid elements linked together, eventually forming a gel .
  • the gels for use in the invention can be prepared via reactions which use monomeric, metal oxides as gel precursors.
  • Metal oxides for use in such reactions include Ti0 2 , Zr0 2 , Ru0 2 , Ru0 4 , V 2 0 5 , W0 3 , Th0 2 , Fe 2 0 3 , MgO, Y 2 0 3 , Hf0 2 , Nb 2 0 5/ U0 2 , BeO, CoO, NiO, CuO, ZnO, ln 2 0 3 , Sb 2 0 3 , A1 2 0 3 and Sn0 2 .
  • ZeroO-Ti0 2 Ti0 2 -Fe 2 0 3 , Sn0 2 -Ti0 2 , Nd 2 0 3 -Ti0 2 , Al 2 0 3 - Cr 2 0 3 , MgO-Al 2 0 3 , MgO-Ti0 2 , MgO-Zr0 2 , Th0 2 -U0 2 , Th0 2 -Ce0 2 , Bi 2 0 3 -Ti0 2 , BeO-Al 2 0 3 , Ti0 2 -Fe 2 0 3 -Al 2 0 3 , Al 2 0 3 -Cr 2 0 3 -Fe 2 0 3 , PbO- Zr0 2 -Ti0 2 , ZnO-Al 2 0 3 -Cr 2 0 3 , Al 2 0 3 -Cr 2 0 3 -Fe 2 0 3 -
  • dispersions or sols of the ceramic metal oxides in combination or admixture with dispersions or sols of one or more metal oxides which are unstable in normal air environment (such as Li 2 0, Na 2 0, K 2 0, CaO, SrO, and BaO) and/or ceramic oxides having an atomic number of 14 or greater (such as Si0 2 As 2 0 3 , and P 2 0 5 ) , representative combinations including Al 2 0 3 -Li 2 0, Ti0 2 -K 2 0, Zr0 2 -CaO, Zr0 2 -Al 2 0 3 -CaO, Zr0 2 -Sr0, Ti0 2 -BaO, B 2 0 3 -Si0 2 , Ti0 2 -Zr0 2 -BaO, Al 2 0 3 -Na 2 0, Ti0 2 -Si0 2 , MgO-Si0 2 , Fe 2 0 3 -BaO, Zr0
  • the precursor material in the form of dispersions or sols of the oxides
  • the precursor materials in the form of water soluble or dispersible inorganic or organic compounds which are calcinable to the corresponding metal oxide or metalloid oxide.
  • These compounds representatively include many carboxylates and alcoholates, e.g., acetates, formates, oxalates, lactates, propylates, citrates, and acetylacetonates, and salts of mineral acids, e.g., bromides, chlorides, chlorates, nitrates, sulfates, and phosphates, selection of the particular precursor compound being dictated by availability and ease of handling.
  • Representative precursor compounds useful in this invention include ferric chloride or nitrate, chromium chloride, cobalt nitrate, nickel chloride, copper nitrate, zinc chloride or carbonate, lithium propylate, sodium carbonate or oxalate, potassium chloride, beryllium chloride, magnesium acetate, calcium lactate, strontium nitrate, barium acetate, yttrium bromide, zirconium acetate, hafnium oxychloride, vanadium chloride, ammonium tungstate, aluminum chloride, indium iodide, titanium acetylacetonate, stannic sulfate, lead formate, antimony chloride, bismuth nitrate, neodymium chloride, phosphoric acid, cerium nitrate, uranium nitrate, and thorium nitrate .
  • the sol -gels for use in the invention can also be prepared via reactions which use monomeric, metal alkoxide precursors.
  • This class of compounds is represented by M(OR) n , where M is a metal, OR is an alkoxide (an alkoxide with from one to six carbons which may be further substituted), and n is from 2 to 8 , depending on the coordination state of the metal .
  • the metals used in the metal alkoxide precursors are Ti , Cr, W, Th, Fe, Mg, Y, Zr, Hf , V, Nb, U, Be, Co, Ni , Cu, Zn, In, Sb, Al , Sn and Si.
  • the alkoxy ligands are generally alkoxides with from one to six carbons such as methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy ligands, or substituted or unsubstituted aryloxy groups.
  • Oligomeric precursors can be used such as ethoxypolysiloxane (ethyl polysilicate) , hexamethoxydisiloxane (Si 2 (OCH 3 ) 6 ) and octamethoxytrisilioxane (Si 3 (OCH 3 ) 8 ) .
  • the monomeric, tetrafunctional alkoxysilane precursors are represented by the following formula.
  • RO is a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group.
  • Typical examples include methoxy, ethoxy, n-propoxy, n- butoxy, 2 -methoxyethoxy, and phenylphenoxy groups.
  • Ethoxypolysiloxane ethyl polysilicate
  • Si 2 (OCH 3 ) 6 hexamethoxydisiloxane
  • Si 3 (OCH 3 ) 8 octamethoxytrisilioxane
  • Si 3 (OCH 3 ) 8 can also be used, as well as the cubic octamer (Si 8 0 12 ) (OCH 3 ) 8 .
  • Organically modified silicates having various organic ligands can be used, such as those formed by combining tetraalkoxysilanes with alkyl-or aryl -substituted and organofunctional alkoxysilanes .
  • Organic functionality can be introduced to the alkoxy ligands with substituents such as - (CH 2 ) nl NH 2 , - (CH 2 ) nl NHCO-0-NH 2 , - (CH 2 ) nl S (CH 2 ) n2 CHO, and like substituents, where nl and n2 are from 0 to 6.
  • Polymerizible ligands can also be employed, such as epoxides, to form organic networks in addition to an inorganic network. Choice of precursor can be made according to solubility or thermal stability of the ligands .
  • organotrialkoxysilanes (R'Si(OR) 3 ) or diorganodialkoxysilanes (R' 2 Si(OR) 2 ) can be used as gel precursors.
  • the groups R' need not be the same as each other on a given precursor molecule. Examples of such precursors are methyltriethoxysilane, methyltrimethoxysilane, methyltri-n-propoxysilane, phenyltriethoxysilane, and vinyltriethoxysilane .
  • Catalysts are optionally but generally present in 5 sol -gel processing.
  • Acids and bases are suitable catalysts for sol -gel processing as carried out in the invention. Such catalysts facilitate both hydrolysis and condensation reactions, and can play a role in product structures.
  • Preferred catalysts include inorganic acids 0 (e.g., hydrochloric, nitric, sulfuric and hydrofluoric acid) , amines including ammonia and ammonium hydroxide, organic acids (e.g., acetic acid), bases (e.g., potassium hydroxide), potassium fluoride, metal alkoxides (e.g., titanium alkoxide, vanadium alkoxide) .
  • acid catalysis produces gels which are cross-linked to a lesser extent than gels produced by base catalysis.
  • a suitable catalyst for the sol -gel processing reactions of the invention is nitric acid. Sol -gel processing can also take place in the o presence of solvents.
  • Suitable solvents include water, alcohols (e.g., methanol, ethanol) , amides (e.g., formamide, dimethylformamide) , ketones (e.g., acetone), nitriles (e.g., acetonitrile) , and aliphatic or alicyclic ethers (e.g., diethyl ether, tetrahydrofuran, or 5 dioxane) .
  • alcohols e.g., methanol, ethanol
  • amides e.g., formamide, dimethylformamide
  • ketones e.g., acetone
  • nitriles e.g., acetonitrile
  • aliphatic or alicyclic ethers e.g., diethyl ether, tetrahydrofuran, or 5 dioxane
  • the first reaction generally taking place is hydrolysis, in which the alkoxide ligands of the alkoxysilanes are replaced by hydroxide ligands, from water. This reaction is represented here.
  • RO is a substituted or unsubstituted alkoxy group, or substituted or unsubstituted aryloxy group.
  • the product of this reaction is an alcohol, reducing the need for alcohol or other mutual solvents as the reaction proceeds. Since the reaction is reversible, the alcohol can also participate in reverse reactions, reesterification and transesterification. All substituents attached to silicon are labile, and populations of substituents will depend in an equilibrium sense on control exerted over the concentrations of alcohol and water, the type of catalyst used and the extent of reaction. Under acid-catalysed hydrolysis conditions, the alkoxide ligand is likely to be protonated as a first step, making it a better leaving group as water attacks from the backside of the central silicon atom.
  • silicate gel formation is distinct from that of organic polymers, in that the silicic acid (Si(OH) 4 ) polymerizes into discrete particles. These particles then aggregate into chains and networks.
  • the resulting macroscopic structure of the gel can be characterized as either a dense network with well-defined solid-liquid interfaces, a uniformly porous network, or an open network.
  • This gel is then desirably dried to eventually produce a glassy material .
  • Dried gels are referred to as xerogels or aerogels.
  • Xerogels are produced by evaporation of liquid, while aerogels are dried by supercritical extraction of solvent.
  • consolidation of the gel occurs.
  • the gel initially tends to shrink as liquid is removed, through removal of liquid at the surface of the gel.
  • the amount of shrinkage that occurs initially is dependent both on how the gel is produced and how it is dried. Drying by evaporation of solvent produces xerogels which are denser than aerogels produced by supercritical extraction of liquid.
  • gels produced through acid-catalysis are cross-linked to a lesser extent. Such gels shrink more o during initial drying because the structures can interpenetrate each other more. The pores in such a gel are smaller, so that capillary pressure which is exerted during final stages of drying further compacts the structure.
  • the resulting gel is characterized by an s extremely fine texture.
  • the pores in gels produced by acid-catalysis and drying by evaporation range in size from 10 to 50 A.
  • gel coatings of metal oxides or metalloid oxides are produced on the surface of 0 microcapsules.
  • the gel coatings must completely surround the microcapsules, providing isolation from the external environment.
  • the coating must be a continuous coating.
  • the coating should be thick enough on average to significantly inhibit the diffusion of atmospheric oxygen into the interior of the microcapsules, thus preventing combustion.
  • the coating must be thick enough on average to withstand a certain amount of mechanical stress without breaking. The acceptable amount of mechanical stress will vary depending on the 5 application. According to preferred embodiments of the invention, the integrity of the microcapsules is maintained. For applications in which heat must be transferred through the gel coating to the interior, the coating must not be so thick on average so as to inhibit the conduction of heat.
  • the coating For applications in which light must be efficiently transferred to or from the microcapsule interior from or to the outside, the coating must allow sufficiently efficient transmission at the wavelength of light appropriate for such applications. These applications will rely both on the coating thickness and the absorption and reflectivity of light at various wavelengths. For applications in which magnetic fields are to extend through the microcapsules, the coating must allow the passage of such fields without significant losses. These considerations lead to practicable gel coating thicknesses of from 0.5 to 7.0 microns .
  • Microcapsules suitable for the present invention may contain a wide variety of materials. The choice of materials is limited only by the conditions for processing of the gel -coated microcapsules of the invention. Suitable materials include phase change materials, magnetic materials, and optical materials.
  • the microcapsules of the present invention are designed to contain materials that interact with the surrounding environment indirectly, rather than being released from the microcapsule.
  • the microcapsules can comprise MicroPCMs which absorb or emit heat from or to the environment.
  • optical materials contained in the microcapsules of the invention can absorb or emit light from or to the environment.
  • Other materials include magnetic materials which interact with the environment without direct contact with the environment .
  • Phase change materials are well suited for inclusion in microcapsules. These materials will absorb or emit heat at a constant temperature (their phase change temperature) before changing phase. Thus, the material can be used as an absorber of heat to protect an object from additional heat as a quantity of thermal energy will be absorbed by the phase change material before its temperature can rise.
  • the phase change material can also be preheated and used as a barrier to cold, as a larger quantity of heat must be removed from the phase change material before its temperature can begin to drop. Heat transfer across the microcapsule material into its interior can be efficient. Coated microcapsules must retain the ability to transfer significant heat to and from the phase change materials if the microcapsules are to effectively function as temperature stabilizers.
  • Gel -coated microcapsules containing phase change materials are useful for incorporation into foams, fibers, heat transfer slurries, coatings, thermal greases, potting compounds and many other applications. Potting compounds are described in U.S. Patent No. 5,224,356.
  • phase change materials are paraffinic hydrocarbons, namely normal (straight -chain) hydrocarbons represented by the formula C n H 2n+2 , wherein n can range from 10 to 30.
  • Preferred paraffinic hydrocarbons are those in which n ranges from 13 to 28.
  • Other compounds which are suitable for phase change materials are 2,2- dimethyl-1 , 3-propanediol (DMP), 2-hydroxymethyl-2-methyl- 1, 3-propanediol (HMP) and similar compounds.
  • DMP 2,2- dimethyl-1 , 3-propanediol
  • HMP 2-hydroxymethyl-2-methyl- 1, 3-propanediol
  • fatty esters such as methyl palmitate.
  • Preferred phase change materials are paraffinic hydrocarbons.
  • Optical materials include those which can absorb, emit, reflect or refract light.
  • the light can be visible, ultraviolet or infrared light.
  • Light emitting materials include fluorescent or phosphorescent materials.
  • Light absorbing materials include those with electronic absorption bands in the visible, ultraviolet and infrared regions of the spectrum. These materials can be useful for monitoring purposes, and can find applications in harsh chemical environments, since the sol -gel coating provides physical insulation from such environments which would otherwise render the materials inoperable.
  • the sol -gel coated microcapsules are small enough to be used to monitor flow conditions in harsh environments without disrupting flow themselves, for example .
  • Magnetic materials can also be used inside the gel -coated microcapsules of the present invention, and can be used for monitoring of magnetic fields in harsh environments which would otherwise render the materials inoperable .
  • Microcapsules suitable for the present invention have diameters ranging from 1.0 to 2,000 microns. Preferably, the microcapsules have diameters of from 5 to 500 microns. Most preferably, the microcapsules have diameters of from 10 to 200 microns.
  • the invention also provides a method for producing gel -coated microcapsules, by the method of sol -gel processing.
  • microcapsules as described above containing any of the materials mentioned herein are mixed with a sol .
  • Sols are generally prepared by mixing metal - containing gel precursor and solvent together in a precursor/solvent ratio which can vary from about 3:1 to about 5 : 1 by volume.
  • the precursor/solvent ratio varies from about 3.5:1 to about 4.2:1.
  • catalyst and water were mixed in a catalyst/water ratio which can vary from about 1:12 to about 1:22 by volume.
  • the two solutions are mixed together with stirring. As the mixture warms and cools, the onset and completion of reaction is indicated, at which time microcapsules are added to the mixture and mixing continued.
  • the pH of this mixture can range from about 1.0 to about 2.0, preferably the pH of the mixture is from about 1.1 to about 1.4.
  • the mixture is then immediately passed through an aperture (e.g., a spray nozzle) with pressure in order to atomize the mixture.
  • An airless spray system can also be used, in which air is not a propellant, but rather the system pressurizes a container of sol mixture. This requires somewhat smaller batches, and a larger collection chamber to prevent the sprayed gel -coated microcapsules from sheeting out on the chamber walls.
  • An internal mix spray gun can be used, if the concentration of the microcapsules in the sol is increased by approximately 20% or more above that described above. The greater viscosity of the microcapsule sol can also allow the use of a pressure feed gun. Bleed-type guns are not preferred since the air flowing through the gun can cause the sol to cure inside the gun.
  • the atomized mixture may be directed into one of several types of areas.
  • One of these types of areas is a collection and curing chamber.
  • the preferred collection chamber size for a batch process is at least three feet in diameter by 12 feet long. It is possible to use larger collection chambers to allow larger batches to be run and to reduce the chance of product loss through sheeting on the chamber walls. However, product recovery becomes more difficult as the product is dispersed over larger areas. It is recommended that the chamber be cleared of product after each batch is run. This will prevent new microcapsule-containing sol from attaching to product remaining from previous runs, thereby minimizing the amount of unacceptably large particles.
  • the chamber walls can be lined with polypropylene, polymethyl propylene, or Teflon to prevent product from permanently adhering to the walls.
  • the chamber can optionally have a gas passing through it.
  • This passage of a gas through the collection and curing chamber acts to suspend the sol -gel coated microcapsules, permit and maintain separation of microcapsules from one another if this is a desirable result, evaporate residual surface alcohol and/or water, and begin the curing process .
  • Flow rates of the mixture into the chamber and gas through the chamber may be adjusted to allow complete evaporation of residual alcohol and/or water.
  • the gel -coated microcapsules are preferably substantially isolated from each other during gel curing, with little agglomeration of microcapsules.
  • Flow rates of the mixture into the chamber may be adjusted to control the amount of substantially isolated gel-coated microcapsules.
  • Chamber input spray rates and rates of sol -gel curing can be adjusted so that microcapsules can be found in an agglomerated state. Generally, pressures of less than 20 psig will tend to promote agglomeration of particles. Pressures of more than 50 psig will tend to minimize agglomeration. In these cases, the gel-coated microcapsule agglomerates will have greater average coating thicknesses and therefore increase flame resistance. If an airless spray system is employed, the pressures recited above are somewhat less .
  • Curing of the gel coating should be substantially completed before the coated microcapsules settle to the floor of the chamber for collection.
  • the flowing gas may be air, oxygen, nitrogen, argon, or any other gas, although it must be noted that oxygen will often form explosive mixtures with the sol mixtures of the invention, so extreme caution should be used in the case of oxygen.
  • the choice of gas depends on the particular requirements of the sol coating used. In some instances the gas will be chemically inert toward the coated microcapsules. In other cases, . the gas may be used to chemically react with the gel coating.
  • the gas may be 5 warmed in order to facilitate evaporation of alcohol and curing of the coating layer. The gas may also be cooled to slow the solvent evaporation and/or sol -gel curing process .
  • a continuous process collection chamber (e.g., o with a forced air system, vortex design and/or conveyor belt) can be much smaller than that used for batch operations .
  • the sol solution and microcapsules are mixed together as above and poured onto s a surface.
  • the surface can be flat or have any desired texture.
  • the surface can be any suitable non-reactive surface, for example a metallic surface such as stainless steel, a polymeric surface, or a surface coated with Teflon or a like material.
  • the pouring operation results o in a film.
  • the thickness of the film will depend on the viscosity of the sol/microcapsule mixture.
  • the surface can also be heated or cooled depending on the desired curing rate .
  • the poured mixture Upon curing, the poured mixture generally cracks 5 into flakes of varying sizes.
  • the flakes generally contain a plurality of microcapsules. In this way the microcapsules are effectively surrounded by a thicker sol -gel coating. Increased chemical and flame resistance can be achieved for the microcapsules in this way.
  • the 0 cured flakes can be subsequently reduced to smaller crystals by a variety of processes, including pulverization, sonication, and tumbling.
  • the gel-coating process can also be repeated to make a microcapsule with several layers of gel -coating.
  • microcapsules or gel- coated microcapsules can be used as starting 5 material for the coating process. Variations in the sol can thereby result in coatings of different types on the microcapsules .
  • the gel -coated microPCMs of the invention can be used to make flame-resistant, and mechanical stress- resistant thermal control materials.
  • examples of such materials include flame-resistant foams, fibers, slurries, coatings, greases and potting compounds. These materials generally act as a thermal barrier between heat sources and heat sinks.
  • the materials are characterized by the presence of a base material, which encapsulates the gel-coated MicroPCMs of the invention and has embedded within it a plurality of the gel -coated MicroPCMs of the invention.
  • the microcapsules are individually surroundingly encapsulated and embedded within the base material, and substantially all the microcapsules are spaced apart from one another with base material in the space between the neighboring adjacent microcapsules.
  • the gel -coated MicroPCMs of the invention are incorporated into foams which serve as base material .
  • foams can be useful in environments in which flame-resistance coupled with thermal control is desirable. Incorporation of the foams into clothing used by fire fighters is envisioned, for example. These foams can also be useful in environments in which thermal control and mechanical stress-resistance is desirable, such as in foot wear, for example.
  • the base material is a foam, chosen from any class of foam, including open cell and closed cell foams. Of each type, either hydrophilic or hydrophobic foams could be utilized. These foams are made by methods familiar to those skilled in the art.
  • the foams are generally provided with a plurality of gel -coated MicroPCMs.
  • MicroPCMs are added to the foam resin prior to manufacturing the foam. But they may also be added using adhesives, coatings, or by physically pressing them into the foam material .
  • the gel -coated MicroPCMs of the invention are incorporated into fibers. These fibers can be formed into a fabric by conventional weaving, knitting, or non-woven methods.
  • the desired gel-coated MicroPCMs are added to the liquid polymer, polymer solution, or other base material and the fiber is then expanded according to conventional methods such as dry or wet spinning of polymer solutions and extrusion of polymer melts.
  • gel -coated MicroPCMs can be applied to fabrics using adhesives or coatings. Further details on the production and uses of such fibers and fabrics are found in U.S. Patent No. 4,756,958.
  • the gel -coated MicroPCMs of the invention can be used in slurries utilized in heat transfer applications. These applications can make use of the mechanical stress-resistance of the gel-coated MicroPCMs of the invention. These slurries can be used to enhance heat transfer in circulating heat pumps, as described in U.S. Patent No. 4,911,232.
  • the slurry containing gel-coated MicroPCMs is made up of a carrier fluid, and the MicroPCMs as described above.
  • the carrier fluid can be almost any fluid depending on the system requirements under which it must operate. Factors that influence the selection of a particular carrier fluid included temperature, toxicity, viscosity, pressure, etc.
  • Lubricating oils are often used instead of water to prevent corrosion of the workpiece material in most cases.
  • Preferred carrier fluids include water, hydrocarbon oils, and silicone oils.
  • Other preferred fluids include halogenated hydrocarbons, including chlorotrifluoroethylene (CTFE) , also known as 1-chloro-l, 1 , 2-trifluoroethylene , and 5 available as Kel-F (San Diego Plastics, San Diego) . Also useful are poly ⁇ -olefins.
  • Mixtures of these fluids are also useful as carrier fluids, such as a mixture of poly ⁇ -olefin to halogenated hydrocarbon of from about 1:1 to about 10:1 in weight percent.
  • carrier fluids such as a mixture of poly ⁇ -olefin to halogenated hydrocarbon of from about 1:1 to about 10:1 in weight percent.
  • the particular embodiment which makes up a heat transfer slurry is useful for obtaining enhanced thermal energy transfer between a thermal energy source and a thermal energy sink in a closed loop thermodynamic system, for example.
  • a two component heat transfer s slurry as described above comprising a plurality of gel- coated MicroPCMs is circulated in a close proximity to a thermal energy source, so that heat is deposited from the thermal energy source to the heat transfer fluid.
  • the MicroPCMs undergo a reversible latent energy transition o upon transfer of thermal energy to the fluid.
  • the closed loop system allows circulation of the fluid to close proximity to a thermal heat sink, where the heat stored in the MicroPCMs is deposited to the thermal energy sink.
  • the closed loop system is generally tuned to a minimum 5 change in the temperature between the thermal energy source and thermal energy sink in order to maximize the heat transport.
  • the tuning can involve adjusting the thermal energy sink 5 temperature.
  • the tuning can involve adjusting the thermal energy source temperature. This procedure is carried out according to methods known to those skilled in the art, as described in U.S. Patent No. 4,911,232.
  • the gel -coated MicroPCMs of the invention can be used in coatings of all types, including paints, gels, and a variety of other coatings.
  • the gel-coated MicroPCMs of the invention can also be used without being incorporated into a base material . And example of such an application is given in U.S. Patent No. 5,415,222.
  • a particular gel -coated microcapsule one containing phase change material (a MicroPCM) was carried out as follows. These procedures require handling materials that are hazardous to human health. Suitable protective equipment was worn and appropriate precautions were taken to prevent the inhalation of MicroPCM dust, and particular care was taken to avoid the inhalation or skin contact with nitric acid and tetraethyl orthosilicate . No open flames were allowed in the vicinity during the procedure. It should be noted that hazardous volatile compounds can remain in the collection chamber for several hours after a production run.
  • the reactions were carried out in a fume hood with a filter for volatile organic compounds.
  • the operator wore protective clothing, latex gloves, protective goggles and a respirator for dust and volatile organic compounds. All transfers were done by pipette.
  • 16.5 mL of 95% ethanol and 63 mL of 98% tetraethyl orthosilicate (TEOS) were added to a 150 mL polypropylene or polymethyl 5 propylene container, and mixed well.
  • TEOS tetraethyl orthosilicate
  • 20.4 mL of deionized water and 1.62 g of nitric acid were mixed.
  • the acidic solution was added to the TEOS solution and stirred with a Teflon-coated stirring stick for 30 minutes.
  • M-lll MicroPCM powder (docosane-based MicroPCM of 50 ⁇ diameter with I ⁇ shell thickness, phase change temperature of 111°F, Frisby Technologies, Inc.) was added to the fully s reacted sol, and the contents mixed.
  • a double action, siphon fed non-bleeder style spray gun with external mix was adjusted with 30 psig air pressure from a 3 cfm tank style air compressor outfitted o with an air filter and a pressure regulator.
  • the spray was adjusted to produce a fan pattern approximately 1 inch wide by 6 inches high measured one foot from the spray head.
  • a spray collection chamber was set up.
  • the 5 chamber has a minimum diameter of four feet and was vented to an organic filter. Before use, all chamber access holes are sealed, except the spray port.
  • the operator wore protective gloves, goggles, respirator and clothing.
  • the MicroPCM sol was poured 0 into the cup of a spray gun.
  • the spray gun nozzle was inserted in to the collection chamber spray port and spraying was commenced. Care was taken to avoid spraying the walls of the chamber.
  • a stream of air continued to be sprayed through 5 the gun for several minutes to help purge the chamber of volatile compounds.
  • the spray gun was removed and the spray port closed.
  • the gun and its parts were cleaned thoroughly with alcohol to prevent solidification of the sol inside the gun.
  • the coated particles were allowed to 5 settle for 4-5 hours, at which time the chamber was opened and the product collected.

Abstract

The invention relates to gel-coated microcapsules which have improved mechanical stress- and flame-resistance. A method for making the gel coated microcapsules is also provided. Phase change materials can be included in the microcapsules to provide thermal control in a wide variety of environments.

Description

GEL-COATED MICROCAPSULES
Field of the Invention The invention relates to microencapsulated phase change materials which are coated with a metal oxide or metalloid oxide gel .
Background of the Invention Phase-change materials, or "PCMs" are compositions that absorb and emit large amounts of heat by changing from one physical state to another, most often reversibly. Typical PCMs change from solid to liquid and back. Paraffinic hydrocarbons are commonly used as PCMs that melt at a desired temperature or over a desired temperature range, as disclosed, for example, in U.S. Patent No. 5,637,389.
Phase-change materials find use or have been proposed for use in apparel for thermal management, either as discrete layers (see U.S. Patent No. 5,499,460), as foam additives (see U.S. Patent No. 5,637,389), as fabric coatings (see U.S. Patent No.
5,366,801), and as additives to fibers (see U.S. Patent No. 4,756,958) . Where not used as discrete layers, PCMs may be encapsulated to minimize loss of their integrity, dissipation, or evaporation. Encapsulated PCMs are available as microcapsules ("MicroPCMs") having average diameters typically in the range of a few to a few hundred microns. MicroPCMs have been prepared for use as additives to heat exchange fluids, including motor oil (see U.S. Patent No. 5,141,079). PCMs which contain paraffinic hydrocarbons are typically flammable. This flammability is often an unacceptable condition. In the past, these difficulties have been overcome by either avoiding problematic physical environments, or by modification of the environments. This approach severely limits the applicability of MicroPCMs in many desirable applications. One approach to this particular problem is found in U.S. Patent No. 5,435,376, which describes 5 MicroPCMs which include flame resistant halogenated paraffins .
Sol -gel methods are generally covered in Sol -Gel Science - The Physics and Chemistry of Sol -Gel Processing, C. Jeffrey Brinker & George W. Scherer, 1st o Ed., Academic Press, (1990), which is hereby incorporated by reference in its entirety.
Summary of the Invention The invention provides microencapsulated phase- change materials ("MicroPCMs") that have improved solvent s resistance, increased hardness and reduced flammability, and methods for making them. The MicroPCMs of this invention are MicroPCMs coated with a glass-like gel material. They can be produced through sol -gel processing of MicroPCMs. The gel coating provides a o degree of physical and flame protection for the microcapsules. The oxidative resistance of such particles is improved significantly, since the coating is believed to minimize oxygen contact with the microcapsules. This can result in reduced incidence of 5 oxidation from atmospheric oxygen for the contents of the microcapsules, e.g., reduced flammability for flammable contents, or reduced chemical oxidation for atmospheric oxidation sensitive contents. The contents contemplated for use in the gel-coated microcapsules include 0 temperature stabilization materials, optical materials or magnetic materials, to name a few examples.
The invention further provides a method for providing a gel coating on MicroPCMs by a sol -gel process. This method involves creating a sol, allowing 5 the gel reaction to take place, mixing MicroPCMs into the sol, and spraying the mixture into, or pouring the mixture onto, a collection area. Curing of the gel takes place in the collection area, and the gel-coated MicroPCMs are collected and ready for use. The invention further provides a two-component heat transfer slurry, which can be circulated for heating or cooling purposes in a heat transport loop in which heat is transported from a heat source to a heat sink with the use of a pump. The method of this invention has applicability beyond MicroPCMs. It can be used to coat microcapsules containing optical or magnetic materials, for example. Accordingly, this invention also includes gel -coated microcapsules containing such materials. As used herein, a "non-released material" is a substance or mixture of substances, which interact with the environment surrounding the microcapsules primarily indirectly. Such materials are not designed to escape the microcapsule under normal operating conditions. Such materials are to be contrasted with others such as flavorings, fragrances, cosmetic products, pharmaceutical or other medical products, which are contained in microcapsules as a means of controlled release of such substances. As used herein, the term "microcapsule" means a unicellular, hollow particle, that is a particle having a peripheral wall or shell enclosing or surrounding a single, hollow cavity, space or void within the interior of the particle which, unless otherwise noted, can be evacuated or filled with a gas, liquid, or solid, such particle being so small as to require means such as an optical microscope for purposes of measuring the dimensions thereof. A microcapsule characterized herein as "spherical" is one which has the shape of a true sphere or spheroid, that is, like a sphere, e.g., oblate or prolate. A microcapsule characterized herein as "porous" is one whose wall has interconnected submicroscopic pores or passages and is permeable to liquid and/or gas, whereas an "impermeable" microcapsule is one whose wall is sealed, non-porous or closed or that has submicroscopic pores or passages so small as to minimize transmission of liquid and/or gas and to maintain the contents within the interior void of the microcapsule. The term "metal" refers to elements which are the central and ligand-bearing atoms in the gel precursors of the invention. As such, it refers not only to those elements commonly referred to as metals, but also the elements such as boron, silicon and germanium which are not traditionally considered metals. The term "potting compounds" refers to semiflexible epoxies with thixotropic and curing agents added, used to affix and cool electronic components. The term "optical material" refers to a material that undergoes physical or chemical changes upon the absorption of photons. The physical changes include the emission of light and/or heat and the reflection of light. Metastable excited states can also be formed. The chemical changes include chemical bond formation and breakage, including various rearrangements, isomerizations and the formation of metastable chemical states .
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting .
Detailed Description of the Invention The coated microcapsules of the invention feature microcapsules coated with a gel, specifically a gel produced by the sol -gel process. The gel coating provides certain resistances to the microcapsules, resulting in enhanced protection for their contents. Microcapsules containing different types of materials are known, as are microencapsulation techniques to prepare such materials, which are used as starting materials in the process of this invention. Microcapsules can be used in many applications in which materials are to be contained either indefinitely or temporarily. Microcapsules have been designed to allow the slow release of pharmaceutical preparations, cosmetic products and food products such as flavoring agents. The microcapsules used in the present invention on the other hand, are adapted to contain materials that interact indirectly with the environments in which they are used.
Microcapsules are prepared according to known procedures. The material which makes up the microcapsule wall can be chosen from a wide variety of materials. The choice of materials depends primarily on the physical and chemical characteristics of the contents, and on the intended use of the microcapsules. The microcapsules should also be readily coatable with the metal oxide gel.
Preferred microcapsule wall -forming materials include various thermoplastic materials, such as natural or synthetic fatty alcohols, fatty acids, fatty esters and waxes . Natural waxes include the vegetable waxes such as carnuba, cauassu, candelilla, farria, palm, esparto, sugar cane and cotton waxes; animal waxes such as beeswax, ghedda, Chinese insect, shellac, spermaceti and lanolin waxes; and mineral wax such as paraffin, microcrystalline, ozokerite, montan and syncera waxes. Synthetic and modified waxes useful as microcapsule wall- forming materials include the Carbowaxes, Abril waxes, Armid and Armowaxes (Armour & Co.) and Chlorax chlorinated paraffin wax (Watford Chemical Co.) . It will be appreciated that waxes are a mixture of various components, and that each type of wax is itself available in a number of different grades.
Other thermoplastic materials are useful as microcapsule wall -forming materials, including polyethylenes such as Polywax™ from Petrolite, Inc., polypropylenes, polyesters, polyvinyl chlorides, tristarch acetates, polyethylene oxides, polypropylene oxides, polyvinylidene chloride or fluoride, polyvinyl alcohols, polyvinyl acetates, polyacrylates, polymethacrylates, vinyl functional polymers, urethanes, polycarbonates, and polylactones . Further details on microencapsulation are found in U.S. Patent Nos. 5,589,194 and 5,433,953.
A colloid is a suspension in which the dispersed phase is not affected by gravitational forces, due to the dimensions of the dispersed phase (1-1000 nm) . A sol is a colloidal suspension of solid particles in a liquid. A gel can be considered to be the agglomeration of these particles into a structure of macroscopic dimensions, such that it extends throughout the solution. It is therefore, a substance that contains a continuous solid skeleton enclosing a continuous liquid phase.
Sol -gel processing according to this invention involves chemical processing of gel precursors to prepare a colloid. These precursors consist of metal atoms surrounded by ligands. The metal atoms and the ligands fall into wide classes. Generally, chemical processing of the gel precursors involves hydrolysis and condensation reactions in which the ligands of the precursors are replaced by bonds to the ligands of other metal or metalloid elements. This process results in a growing network of metal or metalloid elements linked together, eventually forming a gel .
The gels for use in the invention can be prepared via reactions which use monomeric, metal oxides as gel precursors. Metal oxides for use in sol -gel processing are generally represented by M(-0H2)n (aquo ligand) , M(- 0H)n (hydroxo ligand) , and M(=0)n (oxo ligand) , where M is the metal atom, and n depends on the coordination state of M. Metal oxides for use in such reactions include Ti02, Zr02, Ru02, Ru04, V205, W03, Th02, Fe203, MgO, Y203, Hf02, Nb205/ U02, BeO, CoO, NiO, CuO, ZnO, ln203, Sb203, A1203 and Sn02. Mixtures of such oxides are also useful, such as ZnO-Ti02, Ti02-Fe203, Sn02-Ti02, Nd203-Ti02, Al203- Cr203, MgO-Al203, MgO-Ti02, MgO-Zr02, Th02-U02, Th02-Ce02, Bi203-Ti02, BeO-Al203, Ti02-Fe203-Al203, Al203-Cr203-Fe203, PbO- Zr02-Ti02, ZnO-Al203-Cr203, Al203-Cr203-Fe203-Ti02, and Th02- Al203-Cr203-Fe203-Ti02. It is also within the scope of this invention to use dispersions or sols of the ceramic metal oxides in combination or admixture with dispersions or sols of one or more metal oxides which are unstable in normal air environment (such as Li20, Na20, K20, CaO, SrO, and BaO) and/or ceramic oxides having an atomic number of 14 or greater (such as Si02 As203, and P205) , representative combinations including Al203-Li20, Ti02-K20, Zr02-CaO, Zr02-Al203-CaO, Zr02-Sr0, Ti02-BaO, B203-Si02, Ti02-Zr02-BaO, Al203-Na20, Ti02-Si02, MgO-Si02, Fe203-BaO, Zr02-Si02, Al203-As203, Zr02-P205, Al203-Si02, Al203-B203, and Al203-Cr203-Si02.
Instead of using the precursor material in the form of dispersions or sols of the oxides, it is within the scope of the invention to use the precursor materials in the form of water soluble or dispersible inorganic or organic compounds which are calcinable to the corresponding metal oxide or metalloid oxide. These compounds representatively include many carboxylates and alcoholates, e.g., acetates, formates, oxalates, lactates, propylates, citrates, and acetylacetonates, and salts of mineral acids, e.g., bromides, chlorides, chlorates, nitrates, sulfates, and phosphates, selection of the particular precursor compound being dictated by availability and ease of handling. Representative precursor compounds useful in this invention include ferric chloride or nitrate, chromium chloride, cobalt nitrate, nickel chloride, copper nitrate, zinc chloride or carbonate, lithium propylate, sodium carbonate or oxalate, potassium chloride, beryllium chloride, magnesium acetate, calcium lactate, strontium nitrate, barium acetate, yttrium bromide, zirconium acetate, hafnium oxychloride, vanadium chloride, ammonium tungstate, aluminum chloride, indium iodide, titanium acetylacetonate, stannic sulfate, lead formate, antimony chloride, bismuth nitrate, neodymium chloride, phosphoric acid, cerium nitrate, uranium nitrate, and thorium nitrate .
The sol -gels for use in the invention can also be prepared via reactions which use monomeric, metal alkoxide precursors. This class of compounds is represented by M(OR)n, where M is a metal, OR is an alkoxide (an alkoxide with from one to six carbons which may be further substituted), and n is from 2 to 8 , depending on the coordination state of the metal . The metals used in the metal alkoxide precursors are Ti , Cr, W, Th, Fe, Mg, Y, Zr, Hf , V, Nb, U, Be, Co, Ni , Cu, Zn, In, Sb, Al , Sn and Si. The alkoxy ligands are generally alkoxides with from one to six carbons such as methoxy, ethoxy, propoxy, butoxy, pentoxy, and hexoxy ligands, or substituted or unsubstituted aryloxy groups. Oligomeric precursors can be used such as ethoxypolysiloxane (ethyl polysilicate) , hexamethoxydisiloxane (Si2(OCH3)6) and octamethoxytrisilioxane (Si3(OCH3)8) .
The monomeric, tetrafunctional alkoxysilane precursors are represented by the following formula.
OR
I OR-Si-OR
I OR
where RO is a
Figure imgf000011_0001
substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group. Typical examples include methoxy, ethoxy, n-propoxy, n- butoxy, 2 -methoxyethoxy, and phenylphenoxy groups. Ethoxypolysiloxane (ethyl polysilicate) , hexamethoxydisiloxane (Si2(OCH3)6) and octamethoxytrisilioxane (Si3(OCH3)8) can also be used, as well as the cubic octamer (Si8012) (OCH3) 8. Organically modified silicates having various organic ligands can be used, such as those formed by combining tetraalkoxysilanes with alkyl-or aryl -substituted and organofunctional alkoxysilanes . Organic functionality can be introduced to the alkoxy ligands with substituents such as - (CH2)nlNH2, - (CH2) nlNHCO-0-NH2, - (CH2) nlS (CH2) n2CHO, and like substituents, where nl and n2 are from 0 to 6. Polymerizible ligands can also be employed, such as epoxides, to form organic networks in addition to an inorganic network. Choice of precursor can be made according to solubility or thermal stability of the ligands .
To produce gels with somewhat less dense structure, to impart more organic character to the gel, or to allow for derivitization, organotrialkoxysilanes (R'Si(OR)3) or diorganodialkoxysilanes (R'2Si(OR)2) can be used as gel precursors. The groups R' need not be the same as each other on a given precursor molecule. Examples of such precursors are methyltriethoxysilane, methyltrimethoxysilane, methyltri-n-propoxysilane, phenyltriethoxysilane, and vinyltriethoxysilane .
Catalysts are optionally but generally present in 5 sol -gel processing. Acids and bases are suitable catalysts for sol -gel processing as carried out in the invention. Such catalysts facilitate both hydrolysis and condensation reactions, and can play a role in product structures. Preferred catalysts include inorganic acids 0 (e.g., hydrochloric, nitric, sulfuric and hydrofluoric acid) , amines including ammonia and ammonium hydroxide, organic acids (e.g., acetic acid), bases (e.g., potassium hydroxide), potassium fluoride, metal alkoxides (e.g., titanium alkoxide, vanadium alkoxide) . All other factors s being equal, acid catalysis produces gels which are cross-linked to a lesser extent than gels produced by base catalysis. A suitable catalyst for the sol -gel processing reactions of the invention is nitric acid. Sol -gel processing can also take place in the o presence of solvents. Suitable solvents include water, alcohols (e.g., methanol, ethanol) , amides (e.g., formamide, dimethylformamide) , ketones (e.g., acetone), nitriles (e.g., acetonitrile) , and aliphatic or alicyclic ethers (e.g., diethyl ether, tetrahydrofuran, or 5 dioxane) . These solvents can facilitate hydrolysis reactions as described below, especially if the ligands present on the sol -gel precursor molecules are bulky, such as phenylphenoxy ligands.
Inasmuch as water is often a reactant involved in 0 sol-gel processing reactions, as in the hydrolysis reaction described below, it is included in the list of solvents to the extent that water in excess of a stoichiometric minimum amount is provided. Solvents other than water are generally employed to prevent phase 5 separation in those sol -gel processing reactions which involve water- immiscible components. Control over the concentration of the reactants is also provided through the use of a solvent .
The first reaction generally taking place is hydrolysis, in which the alkoxide ligands of the alkoxysilanes are replaced by hydroxide ligands, from water. This reaction is represented here.
OR OH
I I
OR-Si-OR + 4 H2O ^— - OH-Si-OH + 4 ROH I I
OR OH
where RO is a
Figure imgf000013_0001
substituted or unsubstituted alkoxy group, or substituted or unsubstituted aryloxy group. The product of this reaction is an alcohol, reducing the need for alcohol or other mutual solvents as the reaction proceeds. Since the reaction is reversible, the alcohol can also participate in reverse reactions, reesterification and transesterification. All substituents attached to silicon are labile, and populations of substituents will depend in an equilibrium sense on control exerted over the concentrations of alcohol and water, the type of catalyst used and the extent of reaction. Under acid-catalysed hydrolysis conditions, the alkoxide ligand is likely to be protonated as a first step, making it a better leaving group as water attacks from the backside of the central silicon atom. Seemingly for this reason, steric effects of the ligands play a significant role in determining the rate of this reaction. Under base-catalysed hydrolysis, dissociation of water to produce hydroxide ion likely takes place. The hydroxide attacks the backside of the central silicon atom, displacing the alkoxide ion. Inductive effects of the ligands are likely to be important here since the silicon atom develops charge in the transition state. The subsequent condensation reactions can either be between Si-OR and Si-OH or between two molecules of Si-OH to produce a silicate gel as shown in the following reactions .
OR OH OR OH
I I I I
OR-Si-OR + OH-Si-OH y-- OR-Si-O-Si-OH + ROH I I I I
OR OH OR OH
The mechanism of silicate gel formation is distinct from that of organic polymers, in that the silicic acid (Si(OH)4) polymerizes into discrete particles. These particles then aggregate into chains and networks. The resulting macroscopic structure of the gel can be characterized as either a dense network with well-defined solid-liquid interfaces, a uniformly porous network, or an open network.
This gel is then desirably dried to eventually produce a glassy material . Dried gels are referred to as xerogels or aerogels. Xerogels are produced by evaporation of liquid, while aerogels are dried by supercritical extraction of solvent. During this phase of the process, consolidation of the gel occurs. The gel initially tends to shrink as liquid is removed, through removal of liquid at the surface of the gel. The amount of shrinkage that occurs initially is dependent both on how the gel is produced and how it is dried. Drying by evaporation of solvent produces xerogels which are denser than aerogels produced by supercritical extraction of liquid.
At pH values below about 2, hydrolysis reactions involve protonated alkoxide groups and the rate of hydrolysis is large compared to the rate of condensation. The supply of precursor monomers is essentially depleted at an early point in the condensation reaction. Resulting cluster-cluster aggregation leads to weakly branched structures. Above pH of about 7, hydroxide and SiO" ions are the reactive species in hydrolysis and condensation reactions, respectively. If at least stoichiometric ratios of water to gel precursor are used 5 ( [H20] / [Si] >4), more compact and highly branched structures result as described in Brinker et al . Sol -Gel Science, Chapter 3.
Thus, gels produced through acid-catalysis are cross-linked to a lesser extent. Such gels shrink more o during initial drying because the structures can interpenetrate each other more. The pores in such a gel are smaller, so that capillary pressure which is exerted during final stages of drying further compacts the structure. The resulting gel is characterized by an s extremely fine texture. The pores in gels produced by acid-catalysis and drying by evaporation range in size from 10 to 50 A.
According to the invention, gel coatings of metal oxides or metalloid oxides are produced on the surface of 0 microcapsules. The gel coatings must completely surround the microcapsules, providing isolation from the external environment. Thus, the coating must be a continuous coating.
For applications in which the gel -coated 5 microcapsules are used to encapsulate flammable materials, the coating should be thick enough on average to significantly inhibit the diffusion of atmospheric oxygen into the interior of the microcapsules, thus preventing combustion. For applications in which the o sol -gel coated microcapsules are expected to maintain their integrity under mechanical stress, the coating must be thick enough on average to withstand a certain amount of mechanical stress without breaking. The acceptable amount of mechanical stress will vary depending on the 5 application. According to preferred embodiments of the invention, the integrity of the microcapsules is maintained. For applications in which heat must be transferred through the gel coating to the interior, the coating must not be so thick on average so as to inhibit the conduction of heat. For applications in which light must be efficiently transferred to or from the microcapsule interior from or to the outside, the coating must allow sufficiently efficient transmission at the wavelength of light appropriate for such applications. These applications will rely both on the coating thickness and the absorption and reflectivity of light at various wavelengths. For applications in which magnetic fields are to extend through the microcapsules, the coating must allow the passage of such fields without significant losses. These considerations lead to practicable gel coating thicknesses of from 0.5 to 7.0 microns .
Microcapsules suitable for the present invention may contain a wide variety of materials. The choice of materials is limited only by the conditions for processing of the gel -coated microcapsules of the invention. Suitable materials include phase change materials, magnetic materials, and optical materials. The microcapsules of the present invention are designed to contain materials that interact with the surrounding environment indirectly, rather than being released from the microcapsule. For example, the microcapsules can comprise MicroPCMs which absorb or emit heat from or to the environment. In another embodiment, optical materials contained in the microcapsules of the invention can absorb or emit light from or to the environment. Other materials include magnetic materials which interact with the environment without direct contact with the environment .
Phase change materials are well suited for inclusion in microcapsules. These materials will absorb or emit heat at a constant temperature (their phase change temperature) before changing phase. Thus, the material can be used as an absorber of heat to protect an object from additional heat as a quantity of thermal energy will be absorbed by the phase change material before its temperature can rise. The phase change material can also be preheated and used as a barrier to cold, as a larger quantity of heat must be removed from the phase change material before its temperature can begin to drop. Heat transfer across the microcapsule material into its interior can be efficient. Coated microcapsules must retain the ability to transfer significant heat to and from the phase change materials if the microcapsules are to effectively function as temperature stabilizers. Gel -coated microcapsules containing phase change materials are useful for incorporation into foams, fibers, heat transfer slurries, coatings, thermal greases, potting compounds and many other applications. Potting compounds are described in U.S. Patent No. 5,224,356.
Examples of phase change materials are paraffinic hydrocarbons, namely normal (straight -chain) hydrocarbons represented by the formula CnH2n+2, wherein n can range from 10 to 30. Preferred paraffinic hydrocarbons are those in which n ranges from 13 to 28. Other compounds which are suitable for phase change materials are 2,2- dimethyl-1 , 3-propanediol (DMP), 2-hydroxymethyl-2-methyl- 1, 3-propanediol (HMP) and similar compounds. Also useful are fatty esters such as methyl palmitate. Preferred phase change materials are paraffinic hydrocarbons.
Optical materials include those which can absorb, emit, reflect or refract light. The light can be visible, ultraviolet or infrared light. Light emitting materials include fluorescent or phosphorescent materials. Light absorbing materials include those with electronic absorption bands in the visible, ultraviolet and infrared regions of the spectrum. These materials can be useful for monitoring purposes, and can find applications in harsh chemical environments, since the sol -gel coating provides physical insulation from such environments which would otherwise render the materials inoperable. The sol -gel coated microcapsules are small enough to be used to monitor flow conditions in harsh environments without disrupting flow themselves, for example . Magnetic materials can also be used inside the gel -coated microcapsules of the present invention, and can be used for monitoring of magnetic fields in harsh environments which would otherwise render the materials inoperable . Microcapsules suitable for the present invention have diameters ranging from 1.0 to 2,000 microns. Preferably, the microcapsules have diameters of from 5 to 500 microns. Most preferably, the microcapsules have diameters of from 10 to 200 microns.
Methods of making gel -coated microcapsules
The invention also provides a method for producing gel -coated microcapsules, by the method of sol -gel processing. In general, microcapsules as described above containing any of the materials mentioned herein are mixed with a sol .
Sols are generally prepared by mixing metal - containing gel precursor and solvent together in a precursor/solvent ratio which can vary from about 3:1 to about 5 : 1 by volume. Preferably, the precursor/solvent ratio varies from about 3.5:1 to about 4.2:1. Separately, catalyst and water were mixed in a catalyst/water ratio which can vary from about 1:12 to about 1:22 by volume. The two solutions are mixed together with stirring. As the mixture warms and cools, the onset and completion of reaction is indicated, at which time microcapsules are added to the mixture and mixing continued. The pH of this mixture can range from about 1.0 to about 2.0, preferably the pH of the mixture is from about 1.1 to about 1.4. The mixture is then immediately passed through an aperture (e.g., a spray nozzle) with pressure in order to atomize the mixture. An airless spray system can also be used, in which air is not a propellant, but rather the system pressurizes a container of sol mixture. This requires somewhat smaller batches, and a larger collection chamber to prevent the sprayed gel -coated microcapsules from sheeting out on the chamber walls. An internal mix spray gun can be used, if the concentration of the microcapsules in the sol is increased by approximately 20% or more above that described above. The greater viscosity of the microcapsule sol can also allow the use of a pressure feed gun. Bleed-type guns are not preferred since the air flowing through the gun can cause the sol to cure inside the gun.
The atomized mixture may be directed into one of several types of areas. One of these types of areas is a collection and curing chamber. The preferred collection chamber size for a batch process is at least three feet in diameter by 12 feet long. It is possible to use larger collection chambers to allow larger batches to be run and to reduce the chance of product loss through sheeting on the chamber walls. However, product recovery becomes more difficult as the product is dispersed over larger areas. It is recommended that the chamber be cleared of product after each batch is run. This will prevent new microcapsule-containing sol from attaching to product remaining from previous runs, thereby minimizing the amount of unacceptably large particles. The chamber walls can be lined with polypropylene, polymethyl propylene, or Teflon to prevent product from permanently adhering to the walls.
The chamber can optionally have a gas passing through it. This passage of a gas through the collection and curing chamber acts to suspend the sol -gel coated microcapsules, permit and maintain separation of microcapsules from one another if this is a desirable result, evaporate residual surface alcohol and/or water, and begin the curing process . Flow rates of the mixture into the chamber and gas through the chamber may be adjusted to allow complete evaporation of residual alcohol and/or water.
In many applications, the gel -coated microcapsules are preferably substantially isolated from each other during gel curing, with little agglomeration of microcapsules. Flow rates of the mixture into the chamber may be adjusted to control the amount of substantially isolated gel-coated microcapsules. Chamber input spray rates and rates of sol -gel curing can be adjusted so that microcapsules can be found in an agglomerated state. Generally, pressures of less than 20 psig will tend to promote agglomeration of particles. Pressures of more than 50 psig will tend to minimize agglomeration. In these cases, the gel-coated microcapsule agglomerates will have greater average coating thicknesses and therefore increase flame resistance. If an airless spray system is employed, the pressures recited above are somewhat less .
Curing of the gel coating should be substantially completed before the coated microcapsules settle to the floor of the chamber for collection. The flowing gas may be air, oxygen, nitrogen, argon, or any other gas, although it must be noted that oxygen will often form explosive mixtures with the sol mixtures of the invention, so extreme caution should be used in the case of oxygen. The choice of gas depends on the particular requirements of the sol coating used. In some instances the gas will be chemically inert toward the coated microcapsules. In other cases, .the gas may be used to chemically react with the gel coating. The gas may be 5 warmed in order to facilitate evaporation of alcohol and curing of the coating layer. The gas may also be cooled to slow the solvent evaporation and/or sol -gel curing process .
A continuous process collection chamber (e.g., o with a forced air system, vortex design and/or conveyor belt) can be much smaller than that used for batch operations .
As another variation, the sol solution and microcapsules are mixed together as above and poured onto s a surface. The surface can be flat or have any desired texture. The surface can be any suitable non-reactive surface, for example a metallic surface such as stainless steel, a polymeric surface, or a surface coated with Teflon or a like material. The pouring operation results o in a film. The thickness of the film will depend on the viscosity of the sol/microcapsule mixture. The surface can also be heated or cooled depending on the desired curing rate .
Upon curing, the poured mixture generally cracks 5 into flakes of varying sizes. The flakes generally contain a plurality of microcapsules. In this way the microcapsules are effectively surrounded by a thicker sol -gel coating. Increased chemical and flame resistance can be achieved for the microcapsules in this way. The 0 cured flakes can be subsequently reduced to smaller crystals by a variety of processes, including pulverization, sonication, and tumbling. The gel-coating process can also be repeated to make a microcapsule with several layers of gel -coating. Thus, as starting 5 material for the coating process, microcapsules or gel- coated microcapsules can be used. Variations in the sol can thereby result in coatings of different types on the microcapsules .
Thermal control materials
The gel -coated microPCMs of the invention can be used to make flame-resistant, and mechanical stress- resistant thermal control materials. Examples of such materials include flame-resistant foams, fibers, slurries, coatings, greases and potting compounds. These materials generally act as a thermal barrier between heat sources and heat sinks.
In each case, the materials are characterized by the presence of a base material, which encapsulates the gel-coated MicroPCMs of the invention and has embedded within it a plurality of the gel -coated MicroPCMs of the invention. Preferably, the microcapsules are individually surroundingly encapsulated and embedded within the base material, and substantially all the microcapsules are spaced apart from one another with base material in the space between the neighboring adjacent microcapsules.
In some embodiments, the gel -coated MicroPCMs of the invention are incorporated into foams which serve as base material . These foams can be useful in environments in which flame-resistance coupled with thermal control is desirable. Incorporation of the foams into clothing used by fire fighters is envisioned, for example. These foams can also be useful in environments in which thermal control and mechanical stress-resistance is desirable, such as in foot wear, for example. In these embodiments, the base material is a foam, chosen from any class of foam, including open cell and closed cell foams. Of each type, either hydrophilic or hydrophobic foams could be utilized. These foams are made by methods familiar to those skilled in the art. The foams are generally provided with a plurality of gel -coated MicroPCMs. In general, MicroPCMs are added to the foam resin prior to manufacturing the foam. But they may also be added using adhesives, coatings, or by physically pressing them into the foam material . In other embodiments, the gel -coated MicroPCMs of the invention are incorporated into fibers. These fibers can be formed into a fabric by conventional weaving, knitting, or non-woven methods. In fabricating the fiber, the desired gel-coated MicroPCMs are added to the liquid polymer, polymer solution, or other base material and the fiber is then expanded according to conventional methods such as dry or wet spinning of polymer solutions and extrusion of polymer melts. Again, gel -coated MicroPCMs can be applied to fabrics using adhesives or coatings. Further details on the production and uses of such fibers and fabrics are found in U.S. Patent No. 4,756,958.
In other embodiments, the gel -coated MicroPCMs of the invention can be used in slurries utilized in heat transfer applications. These applications can make use of the mechanical stress-resistance of the gel-coated MicroPCMs of the invention. These slurries can be used to enhance heat transfer in circulating heat pumps, as described in U.S. Patent No. 4,911,232. The slurry containing gel-coated MicroPCMs is made up of a carrier fluid, and the MicroPCMs as described above. The carrier fluid can be almost any fluid depending on the system requirements under which it must operate. Factors that influence the selection of a particular carrier fluid included temperature, toxicity, viscosity, pressure, etc. However, it will be noted that for the majority of applications, water or any one of a variety of lubricating oils well known to those skilled in the art could be employed. Lubricating oils are often used instead of water to prevent corrosion of the workpiece material in most cases. Preferred carrier fluids include water, hydrocarbon oils, and silicone oils. Other preferred fluids include halogenated hydrocarbons, including chlorotrifluoroethylene (CTFE) , also known as 1-chloro-l, 1 , 2-trifluoroethylene , and 5 available as Kel-F (San Diego Plastics, San Diego) . Also useful are poly α-olefins. Mixtures of these fluids are also useful as carrier fluids, such as a mixture of poly α-olefin to halogenated hydrocarbon of from about 1:1 to about 10:1 in weight percent. o The particular embodiment which makes up a heat transfer slurry is useful for obtaining enhanced thermal energy transfer between a thermal energy source and a thermal energy sink in a closed loop thermodynamic system, for example. A two component heat transfer s slurry as described above comprising a plurality of gel- coated MicroPCMs is circulated in a close proximity to a thermal energy source, so that heat is deposited from the thermal energy source to the heat transfer fluid. The MicroPCMs undergo a reversible latent energy transition o upon transfer of thermal energy to the fluid. The closed loop system allows circulation of the fluid to close proximity to a thermal heat sink, where the heat stored in the MicroPCMs is deposited to the thermal energy sink. The closed loop system is generally tuned to a minimum 5 change in the temperature between the thermal energy source and thermal energy sink in order to maximize the heat transport. The flow rate is reduced until the overall heat transfer coefficient Cp is maximized according to the formula Cp = Q/m ΔT, where Q is heat o input, m is the mass flow rate, and ΔT is Tout - Tin. This will maximize the efficiency of heat transfer systems which utilize phase change materials. In cases in which the thermal energy source temperature is fixed, the tuning can involve adjusting the thermal energy sink 5 temperature. Conversely, when the thermal energy sink temperature is fixed, the tuning can involve adjusting the thermal energy source temperature. This procedure is carried out according to methods known to those skilled in the art, as described in U.S. Patent No. 4,911,232.
In another embodiment, the gel -coated MicroPCMs of the invention can be used in coatings of all types, including paints, gels, and a variety of other coatings.
The gel-coated MicroPCMs of the invention can also be used without being incorporated into a base material . And example of such an application is given in U.S. Patent No. 5,415,222.
The invention will be further described in the following examples, which do not limit the scope of the invention described in the claims.
EXAMPLES The following examples illustrate certain embodiments of the gel -coated microcapsules, their properties, and methods of their production.
Example 1: Preparation of MicroPCM Sol
An example preparation of a particular gel -coated microcapsule, one containing phase change material (a MicroPCM) was carried out as follows. These procedures require handling materials that are hazardous to human health. Suitable protective equipment was worn and appropriate precautions were taken to prevent the inhalation of MicroPCM dust, and particular care was taken to avoid the inhalation or skin contact with nitric acid and tetraethyl orthosilicate . No open flames were allowed in the vicinity during the procedure. It should be noted that hazardous volatile compounds can remain in the collection chamber for several hours after a production run.
The reactions were carried out in a fume hood with a filter for volatile organic compounds. The operator wore protective clothing, latex gloves, protective goggles and a respirator for dust and volatile organic compounds. All transfers were done by pipette. 16.5 mL of 95% ethanol and 63 mL of 98% tetraethyl orthosilicate (TEOS) were added to a 150 mL polypropylene or polymethyl 5 propylene container, and mixed well. In a separate container, 20.4 mL of deionized water and 1.62 g of nitric acid were mixed. The acidic solution was added to the TEOS solution and stirred with a Teflon-coated stirring stick for 30 minutes. The mixture was observed o to become warm and then cool as the reaction was completed. Upon completion of reaction, 26.3 g of M-lll MicroPCM powder (docosane-based MicroPCM of 50μ diameter with Iμ shell thickness, phase change temperature of 111°F, Frisby Technologies, Inc.) was added to the fully s reacted sol, and the contents mixed.
Example 2 : Gel Coating Procedure
A double action, siphon fed non-bleeder style spray gun with external mix was adjusted with 30 psig air pressure from a 3 cfm tank style air compressor outfitted o with an air filter and a pressure regulator. The spray was adjusted to produce a fan pattern approximately 1 inch wide by 6 inches high measured one foot from the spray head.
A spray collection chamber was set up. The 5 chamber has a minimum diameter of four feet and was vented to an organic filter. Before use, all chamber access holes are sealed, except the spray port.
The operator wore protective gloves, goggles, respirator and clothing. The MicroPCM sol was poured 0 into the cup of a spray gun. The spray gun nozzle was inserted in to the collection chamber spray port and spraying was commenced. Care was taken to avoid spraying the walls of the chamber. When the spray gun was emptied, a stream of air continued to be sprayed through 5 the gun for several minutes to help purge the chamber of volatile compounds. The spray gun was removed and the spray port closed. The gun and its parts were cleaned thoroughly with alcohol to prevent solidification of the sol inside the gun. The coated particles were allowed to 5 settle for 4-5 hours, at which time the chamber was opened and the product collected. Mechanical removal of the product from the chamber wall was accomplished by brushing with a soft brush, lint-free cloth or a soft plastic or rubber scraper. Alternatively, the product o was removed by washing the chamber with water, and filtering the wash water with a 5μ or smaller filter which removes 90% of the product.
Example 3 : Testing by Flame
Flame testing was performed on foam samples s containing MicroPCMs according to Federal Method 5903 (Vertical Flame Test) in a Govmark VC-2 vertical flame test chamber. The MicroPCM foam to be tested was mounted in the Govmark VC-2 and exposed to an open flame for 12 seconds. After removing the flame, the afterflame (the 0 flame remaining after the initial flame was removed) was timed. Samples which supported an afterflame of more than two seconds failed the flame test . Samples which supported afterflames of two seconds or less passed the flame test . 5 Preliminary testing on open cell silicon foam (Magnafoam Technology, Inc., Ontario Canada) containing gel-coated M-lll MicroPCMs indicated that the gel provides twice the flame resistance of uncoated MicroPCMs (twice the number of samples passed the test) . MicroPCMs o which have been twice-coated provided six times the flame resistance of uncoated MicroPCMs (six times as many samples passed the test) .
It is to be understood that while the invention has been described in conjunction with the detailed 5 description thereof, the foregoing description is intended to illustrate and not limit the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims.

Claims

What is claimed is:
1. Coated microcapsules comprising a non-released material encapsulated in a polymeric shell, including a continuous metal oxide gel coating.
2. The microcapsules of claim 1, wherein the average size of the microcapsules is less than 50 microns.
3. The microcapsules of claim 1, wherein the non- released material is flammable, and the microcapsules are non-flammable .
4. The microcapsules of claim 3, wherein the non- released material is a phase-change material.
5. The microcapsules of claim 4, wherein the phase- change material is at least one paraffinic hydrocarbon.
6. The microcapsules of claim 1, wherein the continuous metal oxide gel coating comprises a silicon oxide gel.
7. The microcapsules of claim 1, wherein the non- released material is an optical material.
8. The microcapsules of claim 1, wherein the non- released material is a magnetic material.
9. A method of producing gel-coated microcapsules, the method comprising:
(a) providing a mixture of microcapsules and an aqueous sol, wherein the aqueous sol comprises a mixture of at least one gel precursor, a catalyst, an alcohol and water;
(b) spray drying the mixture of microcapsules and aqueous sol before the mixture has gelled; and (c) allowing the spray dried mixture to gel.
10. The method of claim 9, wherein the gel precursor is a metal oxide, wherein the metal oxide is selected from the group consisting of the oxides of titanium, 5 zirconium, ruthenium, vanadium, tungsten, thorium, iron, magnesium, yttrium, hafnium, niobium, uranium, beryllium, chromium, cobalt, nickel, copper, zinc, indium, antimony, aluminum, tin, lithium, sodium, potassium, calcium, strontium, barium, silicon, arsenic, and phosphorous.
o 11. The method of claim 9, wherein the gel precursor is a mixed metal oxide, selected from the group consisting of aluminosilicate, borosilcate, and titanosilicate .
12. The method of claim 9, wherein the gel precursor is a material calcinable to form a metal oxide, wherein the s material is chosen from the group consisting of metal acetates, metal formates, metal oxalates, metal lactates, metal propylates, metal citrates, metal acetylacetonates, metal bromides, metal chlorides, metal chlorates, metal nitrates, metal sulfates, and metal phosphates.
o 13. The method of claim 9, wherein the gel precursor is a metal alkoxide.
14. The method of claim 13 , wherein the metal alkoxide is tetraalkoxy silicone.
15. The method of claim 14, wherein the tetraalkoxy 5 silicone is chosen from the group consisting of tetramethoxy silicone, tetraethoxy silicone, and tetrapropoxy silicone.
16. The method of claim 9, wherein the alcohol is ethanol .
17. The method of claim 9, wherein the catalyst is an acidic catalyst .
18. The method of claim 9, wherein the gel precursor, catalyst, and alcohol are present in the aqueous sol in
5 the following weight ratios: a) gel precursor from 50 to 90 weight percent; b) catalyst from 0.05 to 5.0 weight percent; c) alcohol from 5 to 30 weight percent; d) water in an amount sufficient to bring the o total to 100 weight percent.
19. The method of claim 18, wherein the gel precursor, catalyst, and alcohol are present in the aqueous sol in the following weight ratios: a) gel precursor from 60 to 80 weight percent; s b) catalyst from 0.1 to 3.0 weight percent; c) alcohol from 10 to 20 weight percent; d) water in an amount sufficient to bring the total to 100 weight percent.
20. The method of claim 19, wherein the gel precursor, o catalyst, and alcohol are present in the aqueous sol in the following weight ratios: a) gel precursor from 65 to 80 weight percent; b) catalyst from 0.5 to 2.0 weight percent; c) alcohol from 12 to 20 weight percent; 5 d) water in an amount sufficient to bring the total to 100 weight percent.
21. The method of claim 9, wherein the gel precursor is tetraethoxy silicone, the catalyst is nitric acid, and the alcohol is ethanol .
o 22. The method of claim 9, wherein the aqueous sol is produced by preparing a first mixture of the alcohol and gel precursor and a second mixture of the catalyst and water, adding the first and second mixtures together with stirring.
23. The method of claim 9, wherein the microcapsule 5 ranges in diameter from 1.0 micron to 2000 microns.
24. The method of claim 9, wherein the microcapsule contains a phase change material .
25. The method of claim 24, wherein the phase change material is at least one paraffinic hydrocarbon selected ╬╣o from the group consisting of n-hexatriacontane, n- pentatriacontane, n-tetratriacontane, n-tritriacontane, n-dotriacontane, n-nentriacontane, n-triacontane, n- nonacosane, n-octacosane, n-heptacosane, n-hexacosane, n- pentacosane, n-tetracosane, n-tricosane, n-docosane, n- i5 heneicosane, n-eicosane, n-nonadecane, n-octadecane, n- heptadecane, n-hexadecane, n-pentadecane, n-tetradecane, and n-tridecane.
26. The method of claim 9, wherein the microcapsule contains a magnetic material .
20 27. The method of claim 9, wherein the microcapsule contains an optical material.
28. The method of claim 27, wherein the optical material is a selected from a group consisting of a light absorbing material, a light emitting material, and a
25 light reflecting material.
29. A flame-resistant thermal control material having thermal energy storage and insulative properties for use as a thermal barrier when placed between a heat source and a heat sink, the material comprising: a base material ; and a plurality of flame-resistant gel-coated microcapsules integral with and dispersed throughout the base material wherein the microcapsules are encapsulated and embedded within the base material, the microcapsules containing a phase change material .
30. The thermal control material of claim 29, wherein the gel -coated microcapsules are individually surroundingly encapsulated and embedded within the base material .
31. The thermal control material of claim 30, wherein substantially all the microcapsules are spaced apart from each other, the space between neighboring adjacent microcapsules contain base material .
32. The thermal control material of claim 29, wherein the base material is foam.
33. The thermal control material of claim 32, wherein the foam is selected from the group consisting of open cell foams, closed cell foams, hydrophobic and hydrophilic foams.
34. A method of imparting flame-resistant temperature stabilization to microcapsules in a foam, the method comprising : providing a foam of the type having a base material with a plurality of flame-resistant gel-coated microcapsules containing a phase change material in a manner so that the microcapsules are embedded within the base material .
35. A heat transfer fluid comprising: the gel -coated microcapsules of claim 4, and a carrier fluid.
36. A method of obtaining enhanced thermal energy transfer between a thermal energy source and a thermal energy sink in a closed loop thermodynamic system, the method comprising: a) circulating a two component heat transfer fluid in a close proximity to the thermal energy source, the heat transfer fluid of claim 35 that undergo a reversible latent energy transition upon transfer of thermal energy to the fluid so that thermal energy is transferred thereto; b) circulating the heat transfer fluid in proximity to a thermal energy sink so that thermal energy is removed therefrom; c) tuning the closed loop thermodynamic system to maximize the latent heat transport.
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AU50015/99A AU5001599A (en) 1998-07-27 1999-07-16 Gel-coated microcapsules
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6986818B2 (en) * 2000-06-02 2006-01-17 The Regents Of The University Of California Method for producing nanostructured metal-oxides
WO2001094276A2 (en) * 2000-06-02 2001-12-13 The Regents Of The University Of California Metal-oxide-based energetic material synthesis using sol-gel chemistry
US6447692B1 (en) * 2000-08-04 2002-09-10 Hrl Laboratories, Llc Nanometer sized phase change materials for enhanced heat transfer fluid performance
ATE302209T1 (en) * 2000-09-08 2005-09-15 San Ei Gen Ffi Inc TETRAPHENYLBACTERIOCHLORINE DERIVATIVES AND COMPOSITIONS CONTAINING SAME
US7160612B2 (en) * 2000-09-21 2007-01-09 Outlast Technologies, Inc. Multi-component fibers having enhanced reversible thermal properties and methods of manufacturing thereof
US6793856B2 (en) 2000-09-21 2004-09-21 Outlast Technologies, Inc. Melt spinable concentrate pellets having enhanced reversible thermal properties
US6689466B2 (en) 2000-09-21 2004-02-10 Outlast Technologies, Inc. Stable phase change materials for use in temperature regulating synthetic fibers, fabrics and textiles
US6855422B2 (en) * 2000-09-21 2005-02-15 Monte C. Magill Multi-component fibers having enhanced reversible thermal properties and methods of manufacturing thereof
GB0025940D0 (en) * 2000-10-24 2000-12-13 Secr Defence Solvogels & a method of manufacturing the same
TWI261640B (en) * 2001-01-25 2006-09-11 Outlast Technologies Inc Coated articles having enhanced reversible thermal properties and exhibiting improved flexibility, softness, air permeability, or water vapor transport properties
US7320357B2 (en) * 2001-04-17 2008-01-22 Barbara Hildegard Pause Thermal control of automotive interiors with phase change material
DE10134168C2 (en) * 2001-07-13 2003-05-22 Head Sport Ag Bregenz Grip for ball game rackets
US9434869B2 (en) 2001-09-21 2016-09-06 Outlast Technologies, LLC Cellulosic fibers having enhanced reversible thermal properties and methods of forming thereof
US20030082217A1 (en) * 2001-10-25 2003-05-01 Isabelle Afriat Use of heat-stabilizing microcapsules to improve the activity or penetration of cosmetic or pharmaceutical active principles
US6517648B1 (en) * 2001-11-02 2003-02-11 Appleton Papers Inc. Process for preparing a non-woven fibrous web
US6806227B2 (en) * 2001-11-05 2004-10-19 The Regents Of The University Of California Solid materials for removing metals and fabrication method
US6699266B2 (en) * 2001-12-08 2004-03-02 Charles A. Lachenbruch Support surface with phase change material or heat tubes
US6755852B2 (en) 2001-12-08 2004-06-29 Charles A. Lachenbruch Cooling body wrap with phase change material
US6856690B1 (en) * 2002-01-09 2005-02-15 Plantronis, Inc. Comfortable earphone cushions
US6621702B2 (en) 2002-01-25 2003-09-16 Lockheed Martin Corporation Method and apparatus for absorbing thermal energy
US7002800B2 (en) 2002-01-25 2006-02-21 Lockheed Martin Corporation Integrated power and cooling architecture
US6858666B2 (en) 2002-03-04 2005-02-22 Aveka, Inc. Organogel particles
US6737394B2 (en) 2002-03-04 2004-05-18 Unilever Home & Personal Care Usa, Division Of Conopco, Inc. Isotropic cleansing composition with benefit agent particles
US6797683B2 (en) 2002-03-04 2004-09-28 Unilever Home & Personal Care Usa, Division Of Conopco, Inc. Ordered liquid crystalline cleansing composition with benefit agent particles
DE10218977A1 (en) * 2002-04-27 2003-11-06 Merck Patent Gmbh Surface modification of phase change material
DE10221222A1 (en) * 2002-05-13 2003-11-27 Basf Ag Flame retardant finishing of objects containing organic latent heat storage materials
FR2841632B1 (en) * 2002-07-01 2004-09-17 Bouygues Offshore "DEVICE FOR THERMAL INSULATION OF AT LEAST ONE SUBSEA PIPE COMPRISING AN INSULATING MATERIAL WITH CONFINED PHASE CHANGE IN POCKETS"
US20040026659A1 (en) * 2002-07-08 2004-02-12 China Textile Institute Composition for fabricating phase-change-material microcapsules and a method for fabricating the microcapsules
US6814882B2 (en) * 2002-07-08 2004-11-09 China Textile Institute Fabric coating composition with latent heat effect and a method for fabricating the same
US8337893B2 (en) * 2002-07-10 2012-12-25 Florida Research Foundation, Inc, University Of Sol-gel derived bioactive glass polymer composite
US6939610B1 (en) * 2002-07-31 2005-09-06 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Thermal insulating coating for spacecrafts
US6619049B1 (en) * 2002-08-12 2003-09-16 Cheng Loong Corporation Method for manufacturing temperature-maintaining material
JP4211322B2 (en) * 2002-08-26 2009-01-21 日産自動車株式会社 Multilayer battery, battery pack, battery module and electric vehicle
JP2004083765A (en) * 2002-08-27 2004-03-18 China Textile Inst Method for producing microcapsule-combined aqueous polyurethane
US7153754B2 (en) * 2002-08-29 2006-12-26 Micron Technology, Inc. Methods for forming porous insulators from “void” creating materials and structures and semiconductor devices including same
US20050008763A1 (en) * 2002-09-24 2005-01-13 Schachter Steven C. Antimicrobial coatings for medical applications
JP3723554B2 (en) * 2003-03-19 2005-12-07 正隆股▲ふん▼有限公司 Waterproof and moisture-permeable thin film having a heat retaining function and method for manufacturing the same
US7833578B2 (en) * 2003-07-07 2010-11-16 Taiwan Textile Research Institute Composition and method for fabricating microcapsules encapsulating phase-change material
IE20030601A1 (en) * 2003-08-14 2005-02-23 Loctite R & D Ltd Curable compositions having a reduced enthalpy output
DE10356159A1 (en) * 2003-12-02 2005-07-07 Schardey, Arnd, Dr. Process for controlling the temperature of gaseous, liquid or bulk goods
FR2875432A1 (en) * 2004-09-17 2006-03-24 Air Liquide Preparation of composite material, used in structure to carry out thermal exchange between coolant and structure, comprises incorporating microencapsulated phase change material into porous network of continuous matrix
US20060094635A1 (en) * 2004-11-01 2006-05-04 Unilever Home & Personal Care Usa, Division Of Conopco, Inc. Aqueous cleansing composition with gel flakes
US20060111001A1 (en) * 2004-11-23 2006-05-25 Jan Kosny Cellulosic insulation containing a phase change material as an active thermal mass component
WO2006082221A1 (en) * 2005-02-03 2006-08-10 Cinvention Ag Drug delivery materials made by sol/gel technology
US7301465B2 (en) * 2005-03-24 2007-11-27 Tengshe Vishwas V Drowsy driving alarm system
US8109324B2 (en) * 2005-04-14 2012-02-07 Illinois Institute Of Technology Microchannel heat exchanger with micro-encapsulated phase change material for high flux cooling
CN100336834C (en) * 2005-05-11 2007-09-12 浙江大学 Process for preparing micro capsule of imitating active fine emulsion polymerizing by oil-soluble initiating agent
US8814861B2 (en) 2005-05-12 2014-08-26 Innovatech, Llc Electrosurgical electrode and method of manufacturing same
US7147634B2 (en) 2005-05-12 2006-12-12 Orion Industries, Ltd. Electrosurgical electrode and method of manufacturing same
US20070084460A1 (en) * 2005-05-31 2007-04-19 Vaughn Beckman Solar collector
US9476123B2 (en) 2005-05-31 2016-10-25 Aspen Aerogels, Inc. Solvent management methods for gel production
US20060270248A1 (en) * 2005-05-31 2006-11-30 Gould George L Solvent Management Methods for Gel Production
US20060286319A1 (en) * 2005-06-21 2006-12-21 Magill Monte C Beverage bottle labels for reducing heat transfer
US8003028B2 (en) * 2005-07-26 2011-08-23 The Boeing Company Composite of aerogel and phase change material
US8066834B1 (en) 2005-08-04 2011-11-29 University Of Central Florida Research Foundation, Inc. Burn rate sensitization of solid propellants using a nano-titania additive
CN1730128B (en) * 2005-08-05 2011-05-25 泉耀新材料科技(上海)有限公司 Highly effective (hydrated) oxide aqueous sol gel fire-extinguishing agent and application thereof
CN1931396B (en) * 2005-09-15 2011-02-09 泉耀新材料科技(上海)有限公司 High efficiency hydroxide/oxide aerosol gel extinguishant
NL1030122C2 (en) * 2005-10-06 2007-04-10 Kobato Polytechnologie B V Polymer composition containing a heat-accumulating phase transition material, method of preparation thereof, and product in which this polymer composition is used.
US20070148459A1 (en) * 2005-12-28 2007-06-28 Kimberly-Clark Worldwide, Inc. Microencapsulated delivery vehicles
US7442439B2 (en) * 2005-12-28 2008-10-28 Kimberly-Clark Worldwide, Inc. Microencapsulated heat delivery vehicles
US20070148446A1 (en) * 2005-12-28 2007-06-28 Kimberly-Clark Worldwide, Inc. Wipes including microencapsulated delivery vehicles and processes of producing the same
US7914891B2 (en) * 2005-12-28 2011-03-29 Kimberly-Clark Worldwide, Inc. Wipes including microencapsulated delivery vehicles and phase change materials
US20070145618A1 (en) * 2005-12-28 2007-06-28 Kimberly-Clark Worldwide, Inc. Methods of making microencapsulated delivery vehicles
US20070149435A1 (en) * 2005-12-28 2007-06-28 Kimberly-Clark Worldwide, Inc. Cleansing composition including microencapsulated delivery vehicles
US20070148448A1 (en) * 2005-12-28 2007-06-28 Kimberly-Clark Worldwide, Inc. Microencapsulated delivery vehicles including cooling agents
US7648046B2 (en) * 2006-05-30 2010-01-19 Kimberly-Clark Worldwide, Inc. Dispensing system for dispensing warm wet wipes
US7654412B2 (en) * 2006-05-30 2010-02-02 Kimberly-Clark Worldwide, Inc. Wet wipe dispensing system for dispensing warm wet wipes
US7497351B2 (en) * 2006-05-30 2009-03-03 Kimberly-Clark Worldwide, Inc. Wet wipe dispensing system
WO2008045451A1 (en) * 2006-10-10 2008-04-17 Applechem Inc Novel natural oil gels and their applications
US8192841B2 (en) * 2006-12-14 2012-06-05 Kimberly-Clark Worldwide, Inc. Microencapsulated delivery vehicle having an aqueous core
FR2913688A1 (en) * 2007-03-15 2008-09-19 Bluestar Silicones France Soc ARTICLE COMPRISING AN ADDITIVE SILICONE GEL WITH ACTIVE ANTI-ODOR PRINCIPLE
US20080233368A1 (en) * 2007-03-20 2008-09-25 Outlast Technologies, Inc. Articles having enhanced reversible thermal properties and enhanced moisture wicking properties to control hot flashes
US7953247B2 (en) 2007-05-21 2011-05-31 Snap-On Incorporated Method and apparatus for wheel alignment
US8685323B2 (en) * 2007-09-19 2014-04-01 Massachusetts Institute Of Technology Virus/nanowire encapsulation within polymer microgels for 2D and 3D devices for energy and electronics
GB0721847D0 (en) * 2007-11-07 2007-12-19 Ciba Sc Holding Ag Heat storage compositions and their manufacture
DE102008004485A1 (en) 2008-01-14 2009-07-16 Bayerisches Zentrum für Angewandte Energieforschung e.V. Covering of organic and inorganic phase change material, comprises introducing the phase change material into a porous, open-cellular carrier structure and providing the filled porous granulates with water vapor-tight layer
EP2234711B1 (en) * 2008-01-25 2017-11-01 RJ Reynolds Tobacco Company Process for manufacturing breakable capsules useful in tobacco products
EP2087998B1 (en) * 2008-02-07 2013-01-23 OCE-Technologies B.V. A heat regulated printer element, use of a rubber material having a phase change material dispersed therein, a printer and a method of printing
US8377555B2 (en) 2008-02-22 2013-02-19 Toyota Motor Engineering & Manufacturing North America, Inc. Gas storage materials, including hydrogen storage materials
US7924142B2 (en) * 2008-06-30 2011-04-12 Kimberly-Clark Worldwide, Inc. Patterned self-warming wipe substrates
WO2010042566A1 (en) * 2008-10-08 2010-04-15 Microtek Laboratories, Inc. Microencapsulation of a phase change meterial with enhanced flame resistance
US8381399B2 (en) * 2009-01-05 2013-02-26 Gregory B. Mills Adaptive re-use of waste insulated glass window units as thermal solar energy collection panels
WO2011075541A1 (en) 2009-12-15 2011-06-23 Pcm Innovations Llc Phase change material fire resistant blanket and method of making
US20110108758A1 (en) * 2009-01-20 2011-05-12 Driscoll Joseph A Method for Making Phase Change Aggregates From a Microencapsulated Phase Change Material Liquid Emulsion
GB2462740B (en) * 2009-10-15 2010-10-20 Michael Trevor Berry Phase change materials with improved fire-retardant properties
GB2474544A (en) 2009-10-15 2011-04-20 Michael Trevor Berry Latent heat storage panel
US20110117353A1 (en) * 2009-11-17 2011-05-19 Outlast Technologies, Inc. Fibers and articles having combined fire resistance and enhanced reversible thermal properties
BR112012012023A2 (en) 2009-12-31 2016-05-17 Sol Gel Technologies Ltd process for preparing microcapsules, microcapsules, composition, method for treating a superficial condition in an individual, and use of microcapsules
US10653899B2 (en) 2009-12-31 2020-05-19 Sol-Gel Technologies Ltd. Core stabilized microcapsules, method of their preparation and uses thereof
KR101199615B1 (en) * 2010-06-28 2012-11-08 연세대학교 산학협력단 Microcapsules comprising Phase Change Materials and Method for Manufacturing the same
EP2611466B1 (en) 2010-08-30 2019-06-12 President and Fellows of Harvard College Shear controlled release of thrombolytic therapies for stenotic lesions
CN101982231B (en) * 2010-09-13 2012-08-29 大连工业大学 Preparation method of aromatic polyamide core-shell paraffin phase change microcapsule
US20120193572A1 (en) * 2011-02-01 2012-08-02 Sleep Innovations, Inc. Bedding product having phase change material
DE102011001932B3 (en) 2011-04-08 2012-08-02 Heiko Schöning Device for non-invasive cooling
CN103619216A (en) * 2011-04-27 2014-03-05 埃迪佐恩有限责任公司 Cushioning elements comprising elastomeric material and methods of forming same
US20120095605A1 (en) 2011-09-17 2012-04-19 Tran Bao Q Smart building systems and methods
US8359750B2 (en) 2011-12-28 2013-01-29 Tran Bao Q Smart building systems and methods
FR2993890B1 (en) 2012-07-25 2014-08-01 Hutchinson RUBBER COMPOSITION BASED ON AT LEAST ONE EPDM AND A PHASE CHANGE MATERIAL, THE INCORPORATING PIPE AND PROCESS FOR PREPARING THE SAME.
EP2727646A1 (en) * 2012-11-05 2014-05-07 Flamco B.v. Capsule comprising phase change material, assembly, thermal buffer, and method
WO2015025529A1 (en) * 2013-08-23 2015-02-26 国立大学法人神戸大学 Latent heat transfer material micro-encapsulated in hard shell, and production method for same
CN103468218B (en) * 2013-08-30 2015-10-21 贵州中益能低碳节能科技股份有限公司 A kind of Inorganic nano phase change energy storage material and preparation method thereof
CN103484076B (en) * 2013-08-30 2016-06-22 贵州中益能低碳节能科技股份有限公司 A kind of Inorganic nano phase change energy storage material utilizing Gypsum Fibrosum to prepare and preparation method thereof
CN103484077B (en) * 2013-08-30 2016-04-13 贵州华兴伟业科技有限公司 Inorganic nano phase change energy storage material prepared by a kind of replacement(metathesis)reaction and preparation method
CN103468217B (en) * 2013-08-30 2015-10-21 贵州中益能低碳节能科技股份有限公司 A kind of High-temperature inorganic nano phase change energy storage material and preparation method thereof
CN103468216B (en) * 2013-08-30 2016-04-13 贵州中益能低碳节能科技股份有限公司 A kind of Phosphate inorganic nano phase change energy storage material and preparation method thereof
CN103468221B (en) * 2013-08-30 2015-10-21 贵州中益能低碳节能科技股份有限公司 A kind of Composite inorganic nano phase change energy storage material and preparation method thereof
CN103468220B (en) * 2013-08-30 2015-10-21 贵州中益能低碳节能科技股份有限公司 A kind of method reducing Inorganic nano phase change energy storage material fusing point
CN103484075B (en) * 2013-08-30 2016-04-13 贵州华兴伟业科技有限公司 A kind of Room-temperature inorganic nano phase-change energy storage material and preparation method thereof
CN104592946B (en) * 2013-11-04 2017-08-22 中国石油化工股份有限公司 A kind of Nano capsule composite phase-change energy storage material preparation method
CN103933907B (en) * 2014-05-15 2015-11-25 中国工程物理研究院激光聚变研究中心 A kind of preparation method of elasticity phase-change microcapsule
FR3023181B1 (en) * 2014-07-03 2019-07-12 Commissariat A L'energie Atomique Et Aux Energies Alternatives HYBRID ALLOPHANE SYNTHESIS METHOD
MX2017000515A (en) * 2014-07-16 2017-08-18 Owens Corning Intellectual Capital Llc Non-voc processing aids for use in manufacturing foams using low global warming potential blowing agents.
US10569493B2 (en) 2014-11-24 2020-02-25 Sabic Global Technologies B.V. Enclosure with a condensation-resistant interior surface
JP5914622B1 (en) * 2014-11-27 2016-05-11 國家中山科學研究院 Method for producing phase change microcapsules with heat transfer skeleton layer
CN104829856B (en) * 2015-05-14 2018-03-27 贵州省材料产业技术研究院 The method that critical carbon dioxide wraps epoxy resin layer in microsphere surface
CN106521974B (en) * 2016-09-21 2019-01-01 台州市莱恩克智能科技有限公司 A kind of outdoor fabric of temperature control heat insulation and heat control intelligence based on microcapsules and aeroge
US10602250B2 (en) * 2016-10-13 2020-03-24 Bose Corporation Acoustaical devices employing phase change materials
WO2018160527A1 (en) * 2017-02-28 2018-09-07 Microtek Laboratories, Inc. Moisture wicking and cooling capsules having an outer shell comprising a siloxane and methods for making same
DE102017207253B3 (en) 2017-04-28 2018-06-14 Schott Ag filter glass
CN109370023A (en) * 2018-08-29 2019-02-22 浙江工业大学温州科学技术研究院 A kind of foamed plastic filler material and preparation method thereof by silicon rubber cracking slag preparation
CN110157386B (en) * 2019-06-12 2020-07-07 北京科技大学 Preparation method of metal silver shell composite phase change capsule with high thermal conductivity
KR102087322B1 (en) * 2019-10-08 2020-03-11 (주)바이오제닉스 Manufacturing method of core-shell PCM microcapsules with thermostatic function
DE102020100112A1 (en) * 2020-01-06 2021-07-08 Axiotherm GmbH Latent storage material and method for heat storage
CN115044177B (en) * 2022-08-16 2022-11-04 杭州和顺科技股份有限公司 Flame-retardant master batch, polyester composite film and preparation method thereof

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5039559A (en) * 1988-05-24 1991-08-13 Sang Jean V Method of making magnetically attractable particles
US5387622A (en) * 1987-02-26 1995-02-07 Yamamoto; Tohru Perfume compositions produced by sol-gel methods

Family Cites Families (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3933679A (en) * 1972-01-14 1976-01-20 Gulf Oil Corporation Uniform microspheroidal particle generating method
US4349456A (en) * 1976-04-22 1982-09-14 Minnesota Mining And Manufacturing Company Non-vitreous ceramic metal oxide microcapsules and process for making same
US4340642A (en) * 1980-06-20 1982-07-20 Pq Corporation Surface modified hollow microspheres
US4336338A (en) * 1980-08-15 1982-06-22 The United States Of America As Represented By The United States Department Of Energy Hollow microspheres of silica glass and method of manufacture
FR2501062A1 (en) * 1980-12-29 1982-09-10 Ugine Kuhlmann GAS PHASE FLUORURIZATION CATALYSTS OF ALIPHATIC CHLORINE DERIVATIVES, BASED ON CHROMIUM OXIDE MICROBALLS, AND FLUORURIZATION METHODS USING THE SAME CATALYSTS
US4459245A (en) * 1982-01-19 1984-07-10 The United States Of America As Represented By The United States Department Of Energy Method and apparatus for controlled size distribution of gel microspheres formed from aqueous dispersions
JPS59173132A (en) * 1983-03-22 1984-10-01 Matsumoto Yushi Seiyaku Kk Solvent-resistant heat expansive microcapsule
US4618525A (en) * 1985-06-03 1986-10-21 Minnesota Mining And Manufacturing Company Coated glass microbubbles and article incorporating them
US4911232A (en) * 1988-07-21 1990-03-27 Triangle Research And Development Corporation Method of using a PCM slurry to enhance heat transfer in liquids
US4964402A (en) * 1988-08-17 1990-10-23 Royce Medical Company Orthopedic device having gel pad with phase change material
US5077241A (en) * 1988-11-17 1991-12-31 Minnesota Mining And Manufacturing Company Sol gel-derived ceramic bubbles
US5000813A (en) * 1989-06-30 1991-03-19 Sorrento Engineering, Inc. Method of improving foam fire resistance through the introduction of metal oxides thereinto
US5023208A (en) * 1989-12-19 1991-06-11 Orion Laboratories, Inc. Sol-gel process for glass and ceramic articles
US5063179A (en) * 1990-03-02 1991-11-05 Cabot Corporation Process for making non-porous micron-sized high purity silica
DE4201179A1 (en) * 1992-01-17 1993-07-22 Alfatec Pharma Gmbh Granulates or pellets comprising dispersion of active agent in hydrophilic macromolecules - are e.g. for treatment of depression, hypertension, rheumatism, etc.
US5435376A (en) * 1992-08-17 1995-07-25 Microtek Laboratories, Inc. Flame resistant microencapsulated phase change materials
US5476696A (en) * 1993-04-16 1995-12-19 Martin Marietta Corporation White thermal control surfaces containing ZrSiO4
US5589194A (en) * 1993-09-20 1996-12-31 Minnesota Mining And Manufacturing Company Method of encapsulation and microcapsules produced thereby
US5433953A (en) * 1994-01-10 1995-07-18 Minnesota Mining And Manufacturing Microcapsules and methods for making same
US5492870A (en) * 1994-04-13 1996-02-20 The Board Of Trustees Of The University Of Illinois Hollow ceramic microspheres by sol-gel dehydration with improved control over size and morphology
WO1996007538A1 (en) * 1994-09-06 1996-03-14 Thermacell Technologies, Inc. Insulation microspheres and method of manufacture
IT1271312B (en) * 1994-12-21 1997-05-27 Enirisorse Spa SOL-GEL PROCESS FOR OBTAINING SPHERES, MICROSPHERES OR COATINGS OF CELL-SHAPED MONOLITES, CONSTITUTED FROM PURE OR ZIRCONIUM OXIDE WITH OTHER OXIDES, USEFUL AS CATALYSTS OR SUPPORTS FOR CATALYSTS
US5576097A (en) * 1995-04-24 1996-11-19 Brite-Line Industries, Inc. High brightness durable retro-reflecting microspheres and method of making the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5387622A (en) * 1987-02-26 1995-02-07 Yamamoto; Tohru Perfume compositions produced by sol-gel methods
US5039559A (en) * 1988-05-24 1991-08-13 Sang Jean V Method of making magnetically attractable particles

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1152885A1 (en) * 1999-01-22 2001-11-14 Frisby Technologies, Inc. Gel-coated materials with increased flame retardancy
EP1152885A4 (en) * 1999-01-22 2007-03-14 Outlast Holding Ltd Gel-coated materials with increased flame retardancy
US6848500B1 (en) 1999-03-11 2005-02-01 Skyworks Solutions, Inc. Cooling system for pulsed power electronics
WO2000054332A1 (en) * 1999-03-11 2000-09-14 Conexant Systems, Inc Cooling system for pulsed power electronics
EP1886714A3 (en) * 2005-09-16 2008-03-05 Blücher GmbH Textile material, charged with microcapsules containing agents with physiological and/or technical effect and its use
US7670968B2 (en) 2005-09-16 2010-03-02 Blucher Gmbh Functional textile material provided with microcapsules containing an active ingredient and use thereof
EP2058139A1 (en) * 2007-11-09 2009-05-13 Van Wijhe Verf B.V. Latent-energy heat control of paint viscosity
DE102008003392B4 (en) * 2008-01-08 2016-11-17 Airbus Defence and Space GmbH A paint composition, a process for the preparation of a paint composition and a use of the paint composition
DE102008003392A1 (en) * 2008-01-08 2009-07-16 Eads Deutschland Gmbh Active corrosion protection by encapsulated inhibitors
DE102008021005A1 (en) * 2008-04-25 2009-10-29 Byk-Chemie Gmbh Particular wax composites with core / shell structure and process for their preparation and their use
FR2930021A1 (en) * 2008-05-30 2009-10-16 Valeo Systemes Thermiques Heat exchanger i.e. radiator, for heating, ventilation and/or air-conditioning system of motor vehicle, has dissipation unit for dissipating heat produced by metastable solution, where air flow is passed through dissipation unit
WO2011104501A3 (en) * 2010-02-23 2011-10-27 Michael Trevor Berry Acoustic composite panel assembly containing phase change materials
CN101824307A (en) * 2010-04-30 2010-09-08 北京化工大学 Composite phase-change energy storage material for microcapsule and preparation method thereof
CN101824307B (en) * 2010-04-30 2012-07-25 北京化工大学 Composite phase-change energy storage material for microcapsule and preparation method thereof
EP3629843A4 (en) * 2017-05-25 2021-03-03 Sunrise Medical (US) LLC Seating system having pressure compensating fluid with thermal absorption and distribution properties
US11248153B2 (en) 2017-05-25 2022-02-15 Sunrise Medical (Us) Llc Seating system having pressure compensating fluid with thermal absorption and distribution properties
CN107459967A (en) * 2017-09-07 2017-12-12 湘潭大学 A kind of luminous shaping phase-change material and preparation method thereof
CN109486472A (en) * 2017-09-09 2019-03-19 中国石油化工股份有限公司 A kind of capsule-type phase-changing energy storage material and preparation method thereof
CN109486472B (en) * 2017-09-09 2021-08-31 中国石油化工股份有限公司 Capsule type phase change energy storage material and preparation method thereof
WO2024006102A1 (en) * 2022-06-30 2024-01-04 Corning Incorporated Methods for formation of surface features on soft matter materials through supercritical fluid exchange

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