WO2006105163A2 - Particules enrobees destinees a l'isolation thermique, composition et procede de production des particules - Google Patents

Particules enrobees destinees a l'isolation thermique, composition et procede de production des particules Download PDF

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Publication number
WO2006105163A2
WO2006105163A2 PCT/US2006/011415 US2006011415W WO2006105163A2 WO 2006105163 A2 WO2006105163 A2 WO 2006105163A2 US 2006011415 W US2006011415 W US 2006011415W WO 2006105163 A2 WO2006105163 A2 WO 2006105163A2
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WO
WIPO (PCT)
Prior art keywords
particles
coating
aerogels
aerogel
coated particles
Prior art date
Application number
PCT/US2006/011415
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English (en)
Other versions
WO2006105163A3 (fr
Inventor
Stuart G. Jr. Burchill
Robert E. Sparks
Original Assignee
Burchill Stuart G Jr
Sparks Robert E
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Burchill Stuart G Jr, Sparks Robert E filed Critical Burchill Stuart G Jr
Publication of WO2006105163A2 publication Critical patent/WO2006105163A2/fr
Publication of WO2006105163A3 publication Critical patent/WO2006105163A3/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
    • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
    • C04B41/4584—Coating or impregnating of particulate or fibrous ceramic material
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/157—After-treatment of gels
    • C01B33/158—Purification; Drying; Dehydrating
    • C01B33/1585—Dehydration into aerogels
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/16—Preparation of silica xerogels

Definitions

  • the present invention relates to thermally insulating material comprised of particles of a highly porous, low density material in which the particles are encapsulated with a protective, durable coating.
  • the invention also relates to compositions and articles comprising such particles, and methods for producing such particles, compositions and articles.
  • Aerogels or "xerogels”, which terms will be used interchangeably in the description of the present invention.
  • the term "aerogel” is used to describe a material obtained by drying a wet sol-gel at temperatures above the critical temperature and at pressures above the critical pressure. Under such conditions, the removal of the gel liquid, for example, water, from the sol-gel results in a porous structure without damaging the structure of the gel, so that a high porosity is obtained.
  • Silica aerogels were the first extensively studied aerogels. However, aerogels and xerogels may be made with a wide range of chemical compositions. In addition to inorganic aerogels other than silica aerogels, there are organic aerogels prepared from organic polymers and sometimes called "carbon aerogels.”
  • Aerogels and xerogels can also be surface treated to alter their properties.
  • silica aerogel can be made less hydrophilic by converting the surface -OH groups into -OR groups (wherein R is an aliphatic group).
  • R is an aliphatic group.
  • Aerogels are known to have excellent thermal insulation properties, and xerogels having a porosity and pore structure approximating those of aerogels are also good insulators. Under laboratory conditions, they have exhibited thermal conductivity at ambient air pressure as low as 0.017w/mk. Aerogels and xerogels have been the subject of scientific and commercial investigation for use as the thermally insulating component of a variety of thermal barriers and in a variety of applications. Examples of current commercially available aerogel forms include fine particles, beads, or slabs.
  • aerogels and xerogels as a general purpose insulation has been limited, in spite of the fact that they are generally recognized to be the best thermally insulating material in existence. While manufacturing processes have made the material more cost effective, to date the extremely fragile nature of the material, its tendency to disintegrate under minor pressure or torque, and the tendency for its pores to absorb impurities from its surroundings, e.g., moisture, oils, have made it a material with limited use in real world applications such as residential or industrial insulation.
  • Aerogels in the form of fine particles, beads, chunks, blocks, or slabs have been vacuum sealed in plastic wrap or containers, for example, as described in U.S. patent No. 6,132,837.
  • These "shrink wrapped" or vacuum-sealed forms of aerogel insulating material are relatively large, as compared to the individual particles. They are not as versatile in that they cannot be incorporated or blended into different medium in the same manner as the particles. These pieces are not readily usable in the construction business, in industrial settings, or for installation by consumers.
  • the unwrapped forms of aerogel insulating material described above suffer from a lack of durability, general functionality, or general usefulness in any but a few applications which accommodate the fragile nature of the material. They cannot be used in harsh environments or in the presence of abrasive materials, which would both destroy them.
  • the present invention overcomes the deficiencies inherent in the use of highly porous material such as aerogels for insulation as known in the prior art.
  • One goal of the present invention is to provide insulation in the form of discrete units, i.e., particles of a highly porous, low density material, which particles are encapsulated in a durable, abrasion resistant, protective coating of a material which has an inherent low thermal conductivity.
  • the coating protects the delicate infrastructure of the particles from destruction by pressure and/or abrasion from the surrounding materials or environment, and imparts to the particles a high resistance to abrasion and shear.
  • the coating also prevents impurities in the surrounding materials or environment from invading the pore structure of the particles and reducing or eliminating the thermal resistance of the particles that is a function of the pore structure.
  • the highly porous, low density material is an aerogel or xerogel
  • the coated particles are characterized by a thermal conductivity approaching that of a pure aerogel or a xerogel material at ambient pressure.
  • Another goal of the present invention is to provide a composition comprising the coated porous particles described above, and methods for preparing such particles and such compositions.
  • Fig. 1 is a schematic diagram depicting a spinning disk coating process for preparing an embodiment of the coated particles according to the invention.
  • the present invention provides insulating material in the form of discrete units or particles of highly porous material in which the particles are encapsulated in a durable, abrasion resistant,' thin coating of material which has an inherent low thermal conductivity.
  • T The particles of highly porous material
  • the highly porous particles used in the invention are made of a material which is obtained by drying a sol-gel, and have a porosity of at least 80% and a particle size in the range from 1 ⁇ m to 5.0 mm.
  • a material which is obtained by drying a sol-gel and have a porosity of at least 80% and a particle size in the range from 1 ⁇ m to 5.0 mm.
  • the chemistry and the production of such materials derived from a sol-gel are well documented in the chemical literature, which discloses various methods for drying the sol-gel and for modifying its surface properties.
  • Such material includes, but is not limited to, aerogels and xerogels.
  • Aerogels, and xerogels which have the required high porosity approximating the porosity of aerogels are suitable for use in the present invention.
  • inorganic aerogels such as silica aerogels, and other inorganic aerogels may be used, as well as aerogels prepared from organic polymers, sometimes called "carbon aerogels.”
  • Inorganic xerogels and organic xerogels are also suitable for use in the present invention, provided that they have properties similar to aerogels.
  • Chemically modified aerogels are also suitable for use in the present invention, as well as chemically modified xerogels that have properties similar to those of aerogels.
  • the highly porous particles suitable for the invention include, but are not limited to, aerogel particles prepared by a process wherein the wet sol-gel is dried under supercritical pressure, and xerogel particles prepared by a process wherein the wet sol-gel is dried at a pressure below the supercritical pressure.
  • Particles of amorphous silica aerogels or xerogels may be used, as well as particles of carbon aerogels or xerogels.
  • the size of the highly porous particles suitable for this invention is in the range of from 1 ⁇ m to about 5.0 mm.
  • ultrafine particle are used which have a particle size in the range from 1 ⁇ m to 1,200 ⁇ m, preferably from 1 ⁇ m to 500 ⁇ m, and more preferably from 1 ⁇ m to 15 ⁇ m.
  • particles having a size in the range from about 1.0 mm to about 5.0 mm are used.
  • the highly porous particles used in the invention have a porosity of at least 80%, and preferably at least 90%, the porosity being a measure of the proportion of the volume of the particles that is taken up by air.
  • the shape of the particles is not particularly limited and includes irregular shapes as well as smooth and symmetrical shapes.
  • the highly porous particles typically have small pores with a pore size not exceeding 50 nm.
  • the particles are characterized by a pore size of about 20 nm.
  • the particles suitable for use in the invention have a high surface area, for example in the range from 600 to 800 m 2 /g.
  • the aerogel or xerogel from which the highly porous particles are made may be hydrophobic or hydrophilic.
  • the aerogel or xerogel is a non-metal oxide aerogel or xerogel in which the hydrogen atom in terminal -OH groups is substituted by a non-polar group which imparts hydrophibicity to the aerogel or xerogel.
  • the aerogel or xerogel is a carbon aerogel or xerogel of an organic compound, in which the hydrogen atom in terminal -CH groups is substituted by a non-polar group which imparts hydrophibicity to the aerogel or xerogel.
  • aerogels and xerogels suitable for use in the invention may be prepared by methods known in the art, and are available from commercial suppliers.
  • the material for the protective coating is characterized by the ability to form a continuous, strong and impermeable protective shell around the highly porous particle, in the desired thickness within the range of 5 nm - 0.5 mm. This material must have a low thermal conductivity.
  • the coating material is selected to have a melting point sufficiently higher than the maximum temperature of the environment and application for which the particles are used.
  • Suitable compounds from which the coating material may be selected include ethyl cellulose, ethylene vinyl acetate, hydroxypropylmethyl cellulose phthalate, waxes, acrylic resins, epoxy resins, the family of polymers described as poly-para-xylylene polymers (known by the generic name parylene) commonly used as conformal coatings, polyvinylidene chloride polymers, other synthetic polymers used for conformal coating, and metal oxides. Parylene is one preferred embodiment of the protective coating. It condenses on the surface of the substrate particle in a polycrystalline fashion to provide a coating that is conformal and pinhole free.
  • Polyvinylidene chloride latexes are another preferred embodiment of the protective coating. They have sufficiently high melting points to meet the requirements of many of the anticipated applications for the coated particles, and are commercially available. These latexes may be applied by processes such as spinning disk coating represented schematically in Fig.1.
  • the material for the protective coating is selected taking into consideration the following factors: the desired level of low thermal conductivity, the abrasion resistance and impact resistance required of the coated particles, and the nature of the product into which the coated particles will be incorporated as the principal constituent material.
  • the thickness of the coating is determined taking into consideration the size of the substrate particle, the thermal conductivity of the coating material, and the desired end use for the particles.
  • the total volume of the coating should be smaller than the volume of the substrate particle, preferably not more than 50% of the volume of the particle, and more preferably not more than 20% of the volume of the particle.
  • the coating materials are distinguished from those used in the pharmaceutical industry in that they are not designed to degrade, but are selected so as to retain their structural integrity over time, and provide a permanent, continuous protective coating around the particles.
  • the specific coating process may be selected taking into consideration the nature of the coating material, which itself is determined by the end use application of the particles and the volume of particulate product required for the application.
  • a metal oxide such titanium oxide may be used in a thickness small enough not to offset the low thermal conductivity of the particle.
  • parylene may be used in applications not requiring a very hard coating. Examples of the coating methods are further described below.
  • a suitable manufacturing method for the coated particles is the pulsed-laser ablation technique described in U.S. Patent No. 6,406,745, the disclosure of which is hereby incorporated in its entirety.
  • parylene process a pyrolytic deposition process known as the "parylene process."
  • a cyclic di-para-xylylene dimer usually in granular form, is first vaporized at a temperature around 150 - 175 0 C to a dimer gas.
  • the dimer gas is pyrolytically cleaved at temperatures of about 400 to 750 0 C. to form a reactive para-xylylene monomer vapor.
  • the reactive monomer vapor is then transferred to a deposition chamber, usually kept at a low pressure, in which the particles are kept in fluid motion.
  • the reactive monomer vapor condenses upon the surfaces of the particles to form a transparent film of para-xylylene polymer. Any monomer vapor which fails to condense within the deposition chamber is subsequently removed, for example by a cold trap maintained at a sufficiently low temperature such as -70 0 C.
  • the entire parylene process is generally carried out in a closed system under constant negative pressure.
  • Such closed system may incorporate separate chambers for the (a) vaporization, (b) pyrolysis, and (c) deposition steps of the process, with such chambers being connected by way of appropriate plumbing or tubular connections.
  • the deposition steps take place at a lower temperature than the two previous steps, and may even be carried out a room temperature.
  • the condensation deposition of parylene coatings is capable of depositing even ultrathin films without running of the coating or without uneven thickness of the coating, provided that the monomer vapor is homogeneously and evenly distributed on the surface of the substrates.
  • the coating forms slowly and uniformly over surfaces with both sharp edges and deep crevices, with no pin holes.
  • the thickness of the coating can be controlled easily in the range from hundreds of angstroms to several mils.
  • spinning disk coating Another suitable coating process for producing the particles of the invention is commonly known as spinning disk coating, for example as described in U.S. Patent No. 4,675,140, the disclosure of which is hereby incorporated in its entirety.
  • spinning disk coating represented schematically in Fig.1
  • the particles are suspended in the coating liquid, and this suspension (2) of particles in a continuous liquid phase is passed over a spinning disk (1) and spreads outward under conditions giving at the outer edge of the disk a thin liquid film between the particles.
  • This liquid film leaves the disk as discrete streams with embedded particles.
  • the streams break into drops of excess coating (3) and discrete coated particles (4) each having a thin coating.
  • the coated particles fall through a flow of air or gas, optionally heated, which dries the coating around the particles.
  • a polyvinylidene latex (DARAN 8730 available from OSI) in the amount of 235 grams was added with stirring to 154 g of water. To this was added a non-ionic wetting agent (polyethylene glycol-co-propylene glycol-co ethylene glycol available as PLURONlC L62 from BASF) in the amount of 2.6 grams. Fine particles of silica aerogel available from Cabot Corporation (NANOGEL Product Number 101), having a particle size in the range of 0.1 to 0.7 mm and a pore diameter of approximately 20nm, in the amount of 50 grams were added to the aqueous latex suspension with stirring.
  • DARAN 8730 available from OSI
  • PLURONlC L62 polyethylene glycol-co-propylene glycol-co ethylene glycol available as PLURONlC L62 from BASF
  • This suspension was then applied to the surface of a spinning disk atomizer rotating at a speed of 8,000 rpm for spinning disk coating of the aerogel particles.
  • the total amount of finished product, consisting of the aerogel particles encapsulated in the poly vinylidene chloride polymer, collected after drying and sieving was 100.6 grams.
  • coated particles according to the invention present many advantages over untreated and uncoated particles. They are not fragile, but are durable and abrasion resistant because of the protective coating which also prevents absorption of liquids, oils or other substance into the pore chambers, thus avoiding the resultant loss of thermal insulating power.
  • coated particles according to the invention Another advantage of the coated particles according to the invention is that their coating can be made very thin, as thin as 20 - 40 nm, therefore adding little to the thermal conductivity of the porous material, especially when the coating material itself has an inherent low thermal conductivity.
  • coated particles according to the invention can be incorporated into insulating compositions and components, or used as stand alone insulation material. These coated particles are particularly useful in severe service environments.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Dispersion Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Structural Engineering (AREA)
  • Materials Engineering (AREA)
  • Manufacturing Of Micro-Capsules (AREA)
  • Glanulating (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)
  • Silicon Compounds (AREA)
  • Compositions Of Macromolecular Compounds (AREA)

Abstract

L'invention concerne des particules d'un matériau présentant une porosité d'au moins 80 %. Les particules sont encapsulées dans un enrobage de protection ayant une épaisseur d'au plus 0,5 mm. Les particules sont particulièrement utiles comme matériau d'isolation thermique durable.
PCT/US2006/011415 2005-03-29 2006-03-29 Particules enrobees destinees a l'isolation thermique, composition et procede de production des particules WO2006105163A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US66593205P 2005-03-29 2005-03-29
US60/665,932 2005-03-29

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WO2006105163A2 true WO2006105163A2 (fr) 2006-10-05
WO2006105163A3 WO2006105163A3 (fr) 2006-11-23

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108884175A (zh) * 2016-01-26 2018-11-23 国立大学法人京都大学 低密度凝胶体及低密度凝胶体的制造方法
CN112999988A (zh) * 2019-12-18 2021-06-22 航天特种材料及工艺技术研究所 一种防掉粉透波气凝胶及其制备方法和应用

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6132837A (en) * 1998-09-30 2000-10-17 Cabot Corporation Vacuum insulation panel and method of preparing the same

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6132837A (en) * 1998-09-30 2000-10-17 Cabot Corporation Vacuum insulation panel and method of preparing the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108884175A (zh) * 2016-01-26 2018-11-23 国立大学法人京都大学 低密度凝胶体及低密度凝胶体的制造方法
EP3409695A4 (fr) * 2016-01-26 2019-10-16 Kyoto University Article en gel à faible densité et procédé de production d'article en gel à faible densité
CN112999988A (zh) * 2019-12-18 2021-06-22 航天特种材料及工艺技术研究所 一种防掉粉透波气凝胶及其制备方法和应用
CN112999988B (zh) * 2019-12-18 2022-09-20 航天特种材料及工艺技术研究所 一种防掉粉透波气凝胶及其制备方法和应用

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