Aging and extracting wet gels in single container

Abstract

A method of aging a wet gel material is described herein. The method includes aging the wet gel material by heating the wet gel material in an aging fluid at an aging temperature above a normal boiling point of the aging fluid. This is achieved by maintaining the pressure of the aging fluid above the vapor pressure of the aging fluid during heating.

Description

Technical Field

[0001] The present invention relates generally to aerogel technology. In various embodiments, the present invention more specifically relates to improved methods of producing aerogels and improved aerogel composites. Background Art

[0002] Low-density aerogel materials are widely considered to be the best solid insulators available. Aerogels function as insulators primarily by minimizing conduction (low structural density results in a tortuous path for energy to transfer through the solid framework), convection (large pore volume and very small pore size result in minimal convection), and radiation (IR absorbing or scattering dopants are easily dispersed throughout the aerogel matrix). Aerogels can be used in a wide range of applications including: heating and cooling insulation, soundproofing, electronic dielectrics, aerospace, energy storage and production, and filtration. In addition, aerogel materials display many other interesting acoustic, optical, mechanical, and chemical properties that make them very useful in a variety of insulating and non-insulating applications.

[0003] Large-scale production of aerogel materials or compositions can be complicated by difficulties associated with continuous formation of large-scale gel materials; and difficulties associated with liquid phase extraction from large quantities of gel materials. There is a need to develop efficient techniques for large-scale production of aerogel materials. Summary of the invention

[0004] It is an object of the present disclosure to obviate or mitigate at least one disadvantage of the above-mentioned previous methods and materials.The methods and systems described herein are designed to improve the process of manufacturing aerogel materials.

[0005] In one aspect of the present disclosure, a method of aging a wet gel material includes: placing the wet gel material in a container; introducing an aging fluid into the container; aging the wet gel material by heating the wet gel material and the aging fluid at an aging temperature and an aging pressure, wherein the aging temperature is above a normal boiling point of the aging fluid, and wherein the pressure of the container is maintained above the vapor pressure of the aging fluid during heating.

[0006] In one aspect of the present disclosure, a wet gel material is obtained by a method comprising the following steps: providing a precursor solution comprising a silica precursor material and a solvent; and allowing the silica precursor material in the precursor solution to transform into a wet gel material, wherein the wet gel material comprises a silica-based framework and a solvent.

[0007] In one aspect of the present disclosure, the aging fluid comprises ethanol. In another aspect of the present disclosure, the aging pressure is a pressure higher than the vapor pressure of the aging fluid at the aging temperature, and the aging temperature is higher than the critical temperature of CO2. In an exemplary aspect, during the aging of the wet gel material, the wet gel material and the aging fluid are heated to an aging temperature between about 80°C (176°F) and about 110°C (230°F) under an aging pressure between about 1000psi and about 2500psi. In another exemplary aspect, during the aging of the wet gel material, the wet gel material and the aging fluid are heated to an aging temperature between about 95°C (203°F) and about 110°C (230°F) under an aging pressure between about 1000psi and about 1500psi. In an exemplary aspect, the wet gel material is aged for a time between about 1 hour and about 24 hours. In another exemplary aspect, the wet gel material is aged for a time between about 40 minutes and about 200 minutes. In one aspect of the present disclosure, the wet gel material is aged for a certain time, which is determined by the aging temperature and the normal severity factor.

[0008] In one aspect of the disclosure, during aging of the wet gel material, an aging fluid is removed and an aging fluid is introduced substantially continuously. In one aspect of the disclosure, the wet gel material is washed with an aging fluid prior to heating the wet gel material. The aging fluid removes and displaces at least a portion of the liquid present in the wet gel material.

[0009] In one aspect of the present disclosure, the wet gel material comprises a reinforcing material. The reinforcing material may be in the form of a continuous sheet.

[0010] In another aspect of the present disclosure, a method of producing an aerogel composition includes: placing a wet gel material in a container; introducing an aging fluid into the container; heating the wet gel material and the aging fluid at an aging temperature and an aging pressure, wherein the aging temperature is above the normal boiling point of the aging fluid, wherein the pressure of the container is maintained above the vapor pressure of the aging fluid during heating; and extracting the aging fluid from the aged gel material with an extraction fluid at an extraction temperature and an extraction pressure, wherein the extraction temperature and the extraction pressure are greater than the critical temperature and critical pressure of the extraction fluid; wherein the heating of the wet gel material and the extraction of the aging fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and the extraction steps, and without reducing the temperature or pressure of the container between the heating and the extraction steps.

[0011] In one aspect of the present disclosure, extracting an aged fluid from an aged gel material comprises: introducing an extraction fluid into a container, wherein the temperature and pressure of the extraction fluid entering the container are substantially the same as the aging temperature and the aging pressure; and adjusting the temperature and pressure within the container to maintain the extraction fluid in a supercritical state. In one aspect of the present disclosure, during the extraction of the aged fluid from the aged gel material, the extraction fluid is removed and the extraction fluid is introduced substantially continuously during the extraction.

[0012] In one aspect of the present disclosure, the extraction process includes monitoring the density of the extraction fluid removed from the container. The extraction of the aged fluid can be continued until the density of the extraction fluid removed from the container is within 10% of the density of the extraction fluid entering the container. When the extraction fluid is supercritical carbon dioxide (CO2), the extraction process includes adjusting the pressure and / or temperature within the container to maintain the density of the supercritical fluid between about 0.30 g / cc and 0.60 g / cc.

[0013] In one aspect of the present disclosure, the extraction process further comprises removing fluid from the container while the extraction fluid is introduced into the container, wherein the removed fluid comprises at least a portion of the aged fluid.

[0014] In one aspect of the disclosure, during the heating of the wet gel material to form the aged gel material, the aging pressure is maintained at or above the critical pressure and above the critical temperature of the extraction fluid. In another aspect of the disclosure, the aging temperature and aging pressure are raised to the extraction temperature and extraction pressure before the extraction fluid is introduced into the container.

[0015] In one aspect of the present disclosure, a method for producing an aerogel composition comprises: placing a wet gel material in a container, the wet gel comprising a silica-based framework; introducing ethanol into the container; aging the wet gel material by heating the wet gel material and the ethanol at an aging temperature and an aging pressure, wherein the aging temperature is greater than 80° C. (186° F.), and wherein the pressure of the container is maintained above 1000 psi during heating; introducing carbon dioxide into the container, wherein the temperature and pressure of the carbon dioxide entering the container are substantially the same as the aging temperature and the aging pressure; extracting an aging fluid from the aged gel material with supercritical carbon dioxide at an extraction temperature and an extraction pressure; and adjusting the extraction temperature and / or the extraction pressure within the container to maintain the carbon dioxide in a supercritical state; wherein heating the wet gel material and extracting the aging fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and extraction steps, and without reducing the temperature or pressure of the container between the heating and extraction steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Advantages of the present invention will become apparent to those skilled in the art upon benefit of the following detailed description of embodiments and with reference to the accompanying drawings, in which:

[0017] Figure 1 Schematic diagram depicting the conventional method of processing continuous rolls of aerogel.

[0018] Figure 2 A schematic diagram of the improved method is depicted, in which aging and extraction of the wet gel material are accomplished in the same vessel.

[0019] Figure 3 A schematic diagram of this process superimposed on the CO2 phase diagram is depicted.

[0020] Figure 4 shows a comparison of the physical properties of the gel material produced using the combined aging / extraction process with the standard process of aging and extraction in separate vessels.

[0021] Although the present invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will be described in detail herein. The drawings may not be drawn to scale. However, it should be understood that the drawings and their detailed description are not intended to limit the invention to the disclosed form, but rather, the invention is intended to cover all modifications, equivalents and substitutes falling within the spirit and scope of the invention as defined by the appended claims. DETAILED DESCRIPTION

[0022] It should be understood that the present invention is not limited to specific devices or methods, which can certainly vary. It will also be understood that the terms used herein are only for the purpose of describing specific embodiments and are not intended to be limiting. Unless the content clearly stipulates otherwise, as used in this specification and the appended claims, the singular forms "one", "a kind of" and "the" include singular and plural indicators. In addition, the word "may" is used in the entire application in a permissive sense (i.e., it is possible, can) rather than a mandatory sense (i.e., must). The term "includes" and its derivatives mean "including but not limited to" and the term "coupled" means directly or indirectly connected.

[0023] Aerogels are a class of porous materials with open pores, including a framework of interconnected structures, a corresponding pore network integrated within the framework, and the interstitial phase within the pore network consisting primarily of a gas (such as air). Aerogels are typically characterized by low density, high porosity, large surface area, and small pore size. Aerogels can be distinguished from other porous materials by their physical and structural properties.

[0024] In the context of the present disclosure, in some instances, the term "framework" or "framework structure" refers to a network of nano- and / or microstructural elements, such as fibrils, struts, and / or colloidal particles that form the solid structure of a gel or aerogel. The structural elements that make up the framework structure have at least one characteristic dimension (e.g., length, width, diameter) of about 100 angstroms or less. In the example of pyrolyzed or carbonized aerogels, the term "framework" or "framework structure" may refer to an interconnected network of linear fibrils, nanoparticles, bicontinuous networks (e.g., networks that transition between fibrils and spherical morphologies, having aspects of both), or a combination thereof. In some instances, linear fibrils, nanoparticles, or other structural elements may be connected together (at nodes in some instances) to form a framework that defines pores.

[0025] As used herein, the terms "aerogel" and "aerogel material" refer to a solid object, regardless of shape or size, comprising a framework of interconnected solid structures, a corresponding network of interconnected pores integrated within the framework, and containing a gas (such as air) as a dispersed interstitial medium. Thus, an aerogel is an open, non-fluid colloid or polymer network that is expanded throughout its volume by a gas and formed by removing all of the swelling agent from the corresponding wet gel without significant volume reduction or network compression. Aerogels are generally characterized by the following physical and structural properties attributed to aerogels (according to nitrogen porosimetry and helium pycnometer determination): (a) an average pore size ranging from about 2 nm to about 100 nm; (b) a porosity of at least 60% or more, and (c) a porosity of about 50 nm or more. 2 / g or more, such as from about 100 to about 1500 m 2 / g. It is understood that the inclusion of additives (such as reinforcing materials) will reduce the porosity and specific surface area of ​​the resulting aerogel composite. Densification can also reduce the porosity of the resulting aerogel composite. The aerogel material of the present disclosure includes any aerogel that meets the definition elements described in the previous paragraph.

[0026] Aerogels disclosed herein have a pore size distribution. As used herein, the term "pore size distribution" refers to the statistical distribution or relative amount of each pore size within the sample volume of a porous material. A narrow pore size distribution refers to a relatively large proportion of pores being in a narrow pore size range. In some embodiments, a narrow pore size distribution may be desirable, for example, to optimize the number of pores that can surround electrochemically active species and maximize the use of available pore volume. In contrast, a wide pore size distribution refers to a relatively small proportion of pores being in a narrow pore size range. Therefore, the pore size distribution is usually measured as a function of pore volume and recorded as the unit size of the half-maximum full width of the main peak in the pore size distribution diagram. The pore size distribution of a porous material can be determined by methods known in the art, such as, but not limited to, surface area, skeletal density, and porosity determination, from which the pore size distribution can be calculated. Suitable methods for determining such features include, but are not limited to, gas adsorption / desorption (e.g., nitrogen) measurements, helium pycnometer determination, mercury porosimetry, etc. Unless otherwise stated, the pore size distribution measurements reported herein are obtained by nitrogen adsorption analysis.

[0027] The aerogel materials or compositions of the present disclosure may have a pore size at the maximum peak in a distribution of about 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 5 nm or less, 2 nm or less, or in a range between any two of these values.

[0028] Aerogel disclosed herein has pore volume. As used herein, the term "pore volume" refers to the total volume of the pores in the sample of porous material. Pore volume is specifically measured as the volume of the void space in the porous material, and is usually recorded as cubic centimeters / grams (cm3 / g or cc / g). The pore volume of porous material can be measured by methods known in the art, such as, but not limited to, surface area and porosity analysis (e.g., nitrogen porosimetry, mercury porosimetry, helium pycnometric method, etc.). In certain embodiments, polyimide or carbon aerogel disclosed herein have about 1cc / g or more, 1.5cc / g or more, 2cc / g or more, 2.5cc / g or more, 3cc / g or more, 3.5cc / g or more, 4cc / g or more, or a relatively large pore volume in the range between any two values ​​in these values. In other embodiments, the polyimide or carbon aerogel and xerogel of the present disclosure has a pore volume of about 0.03cc / g or more, 0.1cc / g or more, 0.3cc / g or more, 0.6cc / g or more, 0.9cc / g or more, 1.2cc / g or more, 1.5cc / g or more, 1.8cc / g or more, 2.1cc / g or more, 2.4cc / g or more, 2.7cc / g or more, 3.0cc / g or more, 3.3cc / g or more, 3.6cc / g or more, or in a range between any two of these values.

[0029] Aerogel frameworks can be made from a range of precursor materials, including: inorganic precursor materials (such as precursors for producing silica-based aerogels); organic precursor materials (such precursors are used to produce carbon-based aerogels); mixed inorganic / organic precursor materials; and combinations thereof. In the context of the present disclosure, the term "amalgam aerogel" refers to an aerogel produced by a combination of two or more different gel precursors. In the context of the present disclosure, the term "framework" or "framework structure" refers to a network of interconnected oligomers, polymers, or colloidal particles that form the solid structure of a gel or aerogel. The polymers or particles that make up the framework structure typically have a diameter of about 100 angstroms. However, the framework structure of the present disclosure may also include a network of interconnected oligomers, polymers, or colloidal particles of all diameter sizes that form a solid structure within a gel or aerogel. Furthermore, the term "silica-based aerogel" or "silica-based framework" refers to an aerogel framework in which silica comprises at least 50% by weight of oligomers, polymers or colloidal particles that form a solid framework structure in the gel or aerogel.

[0030] Inorganic aerogels are usually formed by metal oxides or metal alkoxide materials. Metal oxides or metal alkoxide materials can be based on oxides or alkoxides of any metal capable of forming oxides. Such metals include, but are not limited to, silicon, aluminum, titanium, zirconium, hafnium, yttrium, vanadium, cerium, and the like. Inorganic silica aerogels are traditionally prepared by hydrolysis and condensation of silica-based alkoxides, or by gelation of silicic acid or water glass. Inorganic precursor materials for the synthesis of silica-based aerogels include, but are not limited to, metal silicates, such as sodium silicate or potassium silicate; alkoxysilanes, such as tetraethoxysilane (TEOS), tetramethoxysilane (TMOS), and tetrapropoxysilane; partially hydrolyzed alkoxysilanes, such as partially hydrolyzed TEOS and partially hydrolyzed TMOS; condensation polymers of alkoxysilanes, such as condensation polymers of TEOS and condensation polymers of TMOS; alkylalkoxysilanes, and combinations thereof.

[0031] In certain aspects of the present disclosure, pre-hydrolyzed TEOS, such as Silbond H-5 (SBH5, Silbond Corp) (which is hydrolyzed at a water / silica ratio of about 1.9-2) can be used commercially, or can be further hydrolyzed before incorporation into the gelation process. Partially hydrolyzed TEOS or TMOS (such as polyethyl silicate (Silbond 40) or polymethyl silicate) can also be used commercially, or can be further hydrolyzed before incorporation into the gelation process.

[0032] Inorganic aerogels may also include a gel precursor comprising at least one hydrophobic group, such as an alkyl metal alkoxide, a cycloalkyl metal alkoxide, and an aryl metal alkoxide, which may impart or improve certain properties in the gel, such as stability and hydrophobicity. In the context of the present disclosure, the term "hydrophobicity" refers to a measure of the ability of an aerogel material or composition to repel water. The hydrophobicity of an aerogel material or composition may be represented by measuring the equilibrium contact angle of a water droplet at the interface with the surface of the material. Aerogel materials or compositions of the present disclosure having a water contact angle greater than 90° are considered to be hydrophobic. Aerogel materials or compositions having a water contact angle less than 90° are considered to be hydrophilic.

[0033] Inorganic silica aerogels can specifically include hydrophobic precursors, such as alkylsilanes or arylsilanes. Hydrophobic gel precursors can be used as primary precursor materials to form the framework of gel materials. However, in the formation of amalgam aerogels, hydrophobic gel precursors are more commonly used as co-precursors in combination with metal alkoxides. Hydrophobic inorganic precursor materials for silica-based aerogel synthesis include, but are not limited to, trimethylmethoxysilane [TMS], dimethyldimethoxysilane [DMS], methyltrimethoxysilane [MTMS], trimethylethoxysilane, dimethyldiethoxysilane [DIVIDES], methyltriethoxysilane [MTES], ethyltriethoxysilane [ETES], diethyldiethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane [PhTES], hexamethyldisilazane, and hexaethyldisilazane.

[0034] In exemplary aspects of the present disclosure, the relative amounts of hydrophobic gel precursors or precursors and other inorganic precursor materials are selected to provide aerogel materials or compositions having hydrophobic properties disclosed herein while maintaining other properties, such as thermal conductivity, heat of combustion, thermal decomposition start and / or processability. For example, using a smaller amount of hydrophobic gel precursors can reduce hydrophobic properties, for example, providing a material with higher liquid water absorption or water vapor absorption. Using a higher amount of hydrophobic gel precursors can have a negative impact on thermal conductivity, combustion and / or self-heating properties. In exemplary embodiments, the hydrophobic aerogel materials and compositions of the present disclosure can have a hydrophobic content of about 20% by weight, about 30% by weight, about 40% by weight, about 50% by weight, or within a range between any two of these values. For example, an exemplary aerogel composition has a hydrophobic content of about 36% by weight. Further details on the synthesis and characterization of hydrophobic aerogels are described in U.S. Patent Application Publication No. 2016 / 0096949 to Evans et al., which is incorporated herein by reference.

[0035] The production of aerogels generally includes the following steps: i) forming a sol-gel solution; ii) forming a gel from the sol-gel solution; and iii) extracting the solvent from the gel material to obtain a dry aerogel material. This process will be discussed in more detail below, particularly in the context of forming inorganic aerogels (such as silica aerogels). However, the specific examples and descriptions provided herein are not intended to limit the present disclosure to any specific type of aerogel and / or preparation method. The present disclosure may include any aerogel formed by any relevant preparation method known to those skilled in the art.

[0036] The first step in forming an inorganic aerogel is typically to form a precursor solution by hydrolysis and condensation of a metal alkoxide precursor in an alcohol-based solvent. The main variables in the formation of an inorganic aerogel include the type of alkoxide precursor contained in the precursor solution, the nature of the solvent, the processing temperature and pH of the precursor solution (which can be changed by adding acid or base), and the precursor / solvent / water ratio in the precursor solution. Controlling these variables in forming the precursor solution can allow control of the growth and aggregation of the gel framework during the subsequent transition of the gel material from the "sol" state to the "gel" state. Although the properties of the resulting aerogel are affected by the pH of the precursor solution and the molar ratio of the reactants, any pH and any molar ratio that allows the formation of a gel can be used in the present disclosure.

[0037] The precursor solution is formed by combining at least one gelling precursor with a solvent. Suitable solvents for forming the precursor solution include lower alcohols having 1 to 6 carbon atoms (including any integer therebetween, preferably 2 to 4), although other solvents may be used as known to those skilled in the art. Examples of useful solvents include, but are not limited to, methanol, ethanol, isopropanol, ethyl acetate, ethyl acetoacetate, acetone, dichloromethane, tetrahydrofuran, and the like. Multiple solvents may also be combined to obtain a desired dispersion level or to optimize the properties of the gel material. Therefore, the selection of the best solvent for the sol-gel and gel forming steps depends on the specific precursors, fillers, and additives incorporated into the sol-gel solution; as well as the target processing conditions for gelation and liquid phase extraction and the desired properties of the final aerogel material.

[0038] Water may also be present in the precursor solution. Water serves to hydrolyze the metal alkoxide precursor into a metal hydroxide precursor. The hydrolysis reaction may be (taking TEOS-containing ethanol solvent as an example)

[0039] Si(OC2H5)4+4H2O→Si(OH)4+4(C2H5OH) (1)

[0040] The resulting hydrolyzed metal hydroxide precursor is suspended in the precursor solution in a "sol" state, either as a single molecule or as a small polymeric (or oligomeric) molecular colloidal cluster. For example, the polymerization / condensation of a Si(OH)4 precursor can occur as follows:

[0041] 2 Si(OH)4→(OH)3Si-O-Si(OH)3+H2O (2)

[0042] This polymerization can be continued until colloidal clusters of polymeric (or oligomeric) SiO2 (silicon dioxide) molecules are formed.

[0043] Acids and bases can be added to the precursor solution to control the pH of the precursor solution and catalyze the hydrolysis and condensation reactions of the precursor materials. Although any acid can be used to catalyze the precursor reaction and obtain a lower pH solution, preferred acids include: HCl, H2SO4, H3PO4, oxalic acid and acetic acid.

[0044] Any base can also be used to catalyze the precursor reaction and obtain a higher pH solution. In one aspect of the present disclosure, the base can be used to catalyze the precursor reaction or adjust the pH of the precursor solution. In one aspect of the present disclosure, the metal hydroxide base can be used to catalyze the precursor reaction or adjust the pH of the precursor solution. Exemplary metal hydroxide bases include but are not limited to sodium hydroxide, lithium hydroxide, calcium hydroxide, potassium hydroxide, strontium hydroxide and barium hydroxide. In another aspect of the present disclosure, amine bases can be used to catalyze the precursor reaction and / or adjust the pH of the precursor solution. Exemplary amine bases include but are not limited to tetraalkylammonium hydroxide, choline hydroxide, trialkylamine, amidine, guanidine and imidazole. Specific examples of amine bases include tetramethylammonium hydroxide, tetrabutylammonium hydroxide, guanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,4-diazabicyclo[2.2.2]octane (DABCO), pyridine, imidazole and 4,5-dihydroimidazole.

[0045] The precursor solution may include additional co-gel precursors, as well as fillers and other additives. The fillers and other additives may be dispersed in the precursor solution at any time before or during gel formation. The fillers and other additives may also be incorporated into the gel material after gelation by various techniques known to those skilled in the art. Preferably, the precursor solution comprising the gelation precursor, solvent, catalyst, water, fillers and other additives is a homogeneous solution that can effectively form a gel under suitable conditions.

[0046] Once the precursor solution is formed and optimized, the gel-forming components in the precursor solution can be converted into a gel material. The process of converting the gel-forming components into a gel material includes an initial gel formation step, in which the gel solidifies to the gel point of the gel material. The gel point of the gel material can be regarded as the point at which the gel solution exhibits flow resistance and / or forms a substantially continuous polymer framework throughout its volume. A range of gel formation techniques are known to those skilled in the art. Examples include, but are not limited to: maintaining the mixture in a static state for a sufficient period of time; adjusting the pH of the solution; adjusting the temperature of the solution; directing a form of energy to the mixture (ultraviolet light, visible light, infrared, microwave, ultrasound, particle radiation, electromagnetic); or a combination thereof.

[0047] In certain embodiments, the gel material of the present disclosure can be produced by continuous casting and gelation process. In the continuous casting process, the continuous sheet of fiber material can be used as a support in the continuous casting process. The fiber support can improve the flexibility and / or strength of the aerogel material. In one aspect of the present disclosure, the aerogel composite material is formed by adding a gel precursor composition to a fiber-reinforced material and forming a wet gel from the gel precursor composition. In one aspect of the present disclosure, the precursor solution is incorporated into the fiber-reinforced material, and the resulting composite material is formed into a fiber-supported wet gel material.

[0048] During large-scale production of aerogels, the fiber reinforcement material is in the form of a continuous sheet of interconnected or interwoven fiber reinforcement material. The precursor solution is incorporated into the aerogel composite as a continuous sheet of interconnected or interwoven fiber reinforcement material. The initial wet gel material is made into a continuous sheet of fiber reinforced gel by casting or impregnating the gel precursor solution into the continuous sheet of interconnected or interwoven fiber reinforcement material. As will be described in more detail, the liquid phase can then be at least partially extracted from the fiber reinforced wet gel material to produce a sheet-like fiber reinforced aerogel composite.

[0049] Aerogel composites can be fiber reinforced with various fiber reinforcements to obtain softer, more flexible and comfortable composite products. Fiber reinforcements can be in the form of discrete fibers, woven materials, nonwoven materials, cotton wool, nets, mats and felts. Fiber reinforcements can be made of organic fiber materials, inorganic fiber materials or their combinations. Fiber reinforcements can include a series of materials, including but not limited to: polyester, polyolefin terephthalate, poly (ethylene) naphthalate, polycarbonate (e.g., rayon, nylon), cotton (e.g., lycra manufactured by DuPont), carbon (e.g., graphite), polyacrylonitrile (PAN), oxidized PAN, uncarbonized heat-treated PAN (such as those manufactured by SGL carbon), glass fiber-based materials (such as S-glass, 901 glass, 902 glass, 475 glass, E-glass), silica-based fibers (such as quartz) (e.g., Quartzel manufactured by Saint-Gobain), Q felt (manufactured by Johns Manville), Saffil (manufactured by Saffil), Durablanket (manufactured by Unifrax) and other silica fibers, Duraback (manufactured by Carborundum), polyaramid fibers such as Kevlar, Nomex, Sontera (all manufactured by DuPont), Conex (manufactured by Taijin), polyolefins such as Tyvek (manufactured by DuPont), Dyneema (manufactured by DSM), Spectra (manufactured by Honeywell), other polypropylene fibers such as Typar, Xavan (all manufactured by DuPont), fluoropolymers such as PTFE sold under the trade name Teflon (manufactured by DuPont), Goretex (manufactured by WLGORE), silicon carbide fibers such as Nicalon (manufactured by COI Ceramics), ceramic fibers such as Nextel (manufactured by 3M), acrylic polymers, wool fibers, silk, hemp, leather, suede, PBO-Zylon fibers (manufactured by Tyobo), liquid crystal materials such as Vectan (manufactured by Hoechst), cambrelle fibers (manufactured by DuPont), polyurethanes, polyamides, metal fibers such as boron, aluminum, iron, and stainless steel fibers, and thermoplastics such as PEEK, PES, PEI, PEK, PPS. The aerogel composites of the present disclosure may have a thickness of 15 mm or less, 10 mm or less, 5 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less.

[0050] The aerogel composites of the present disclosure may have a thickness of 15 mm or less, 10 mm or less, 5 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less.

[0051] In one aspect of the present disclosure, the aerogel composite material may include an opaque additive to reduce the radiative component of heat transfer. At any time before the gel is formed, the opaque compound or its precursor may be dispersed into the mixture containing the gel-forming material. Exemplary opaque additives include, but are not limited to, B4C, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, Ag2O, Bi2O3, TiC, WC, carbon black, titanium oxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide, iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, silicon carbide, or mixtures thereof.

[0052] The process of converting the gel-forming components into a gel material may also include an aging step (also known as curing) prior to liquid phase extraction. Aging the gel material after it reaches its gel point can further strengthen the gel framework by increasing the number of crosslinks in the network. The duration of gel aging can be adjusted to control various properties of the resulting aerogel material. This aging process can be used to prevent potential volume loss and shrinkage during liquid phase extraction. Aging can involve: keeping the gel (before extraction) in a static state for a long time; keeping the gel at an elevated temperature; adding a crosslinking promoting compound; or any combination thereof.

[0053] The time period that gel-forming material is transformed into gel material comprises the duration (starting from gelation to gel point) of initial gel formation, and any subsequent solidification and aging duration (starting from gel point to liquid phase extraction) of gel material before liquid phase extraction. The total time period that gel-forming material is transformed into wet gel material is usually between about 1 minute and several days, preferably about 30 hours or less, about 24 hours or less, about 15 hours or less, about 10 hours or less, about 6 hours or less, about 4 hours or less, about 2 hours or less, about 1 hour or less, about 30 minutes or less or about 15 minutes or less.Ideally, the total time period is minimized to allow the effective production of aerogel.Although ethanol is hereinafter described as aged fluid, different process conditions (for example, temperature and pressure) can be adjusted based on the standard temperature and pressure boiling point of the specific aged fluid used.

[0054] The aging of the wet gel material can be completed by heating the wet gel material for a time sufficient to complete the aging process. In a typical aging process, the wet gel material is placed in an aging container. The wet gel material is then heated to the aging temperature and maintained at the aging temperature until the aging process is completed. Optionally, before heating and during heating, the wet gel material can be washed with an aging fluid. The aging fluid can be used to replace the main reaction solvent present in the wet gel. Exemplary aging fluids are C1-C6 alcohols, cyclic alcohols, alicyclic alcohols, aromatic alcohols, polyols, ethers, ketones or cyclic ethers. Preferred aging fluids include methanol and ethanol. During the aging period, the aging fluid can flow through and / or pass through the wet gel material and pass through the aging container substantially continuously. The aging fluid passing through the aging container and the wet gel can be a fresh aging fluid, or a recycled aging fluid.

[0055] The time required to complete the aging process is related to the aging temperature of the wet gel material. Generally, the higher the aging temperature, the faster the aging process is completed. However, the maximum temperature that can be used is limited to the liquid present in the wet gel material. At atmospheric pressure (1atm, 101,325Pa), the aging temperature is limited to the boiling point of the liquid in the wet gel material. In addition, it is not desirable to heat the aging material to or near the boiling point of the liquid. When the aging fluid is heated to or near the boiling point of the aging fluid, the evaporation of the aging fluid will cause damage to the framework structure of the wet gel material. In order to reduce the chance of damaging the wet gel material, the aging process is usually carried out below the boiling point of the aging fluid in the wet gel material. For example, when ethanol is used as the aging fluid, the wet gel material is usually aged at a temperature of 160℉ (71.1℃) for a period of 1 hour to 24 hours, which is lower than the boiling point of ethanol (the boiling point at 1atm (101,325Pa) is 173℉ (78.3℃)).

[0056] In one aspect of the present disclosure, the aging time of the wet gel material can be reduced by increasing the aging temperature of the wet gel material. Although the aging temperature is generally limited to the normal boiling point of the aging fluid, the temperature can be increased to exceed the normal boiling point of the aging fluid by increasing the pressure in the aging container to exceed the equilibrium value (i.e., by applying an externally supplied pressure). In order to inhibit accidental boiling of the aging fluid when the container is heated, the container is pressurized to a vapor pressure higher than the liquid during the entire heating period (i.e., when the temperature of the container is raised to the final aging temperature and during the aging of the wet gel material). When the pressure within the aging container ("aging pressure") remains higher than the vapor pressure of the aging fluid, the temperature of the aging fluid can be raised to exceed the normal boiling point of the aging fluid without boiling the aging fluid. As used herein, the "normal boiling point" of a liquid is the temperature at which the liquid boils at 1 atm (101,325 Pa).

[0057] In one aspect of the present disclosure, the wet gel material is placed in a container that can be pressurized. The container also includes an inlet for an aging fluid and an outlet for the fluid to leave the container. The container is sealed and the aging fluid is introduced into the container. The aging fluid can be a fluid that is the same or different from the fluid used to make the wet gel material. In a preferred aspect of the present disclosure, the aging fluid is an alcohol (e.g., methanol or ethanol). The aging fluid is heated while maintaining the pressure in the container above the vapor pressure of the aging fluid. The aging fluid can be heated by a heating element located in or near the container.

[0058] In one aspect of the present disclosure, during the aging of the wet gel material, the aging fluid can be removed and the aging fluid can be introduced substantially continuously. For example, the aging fluid can be recirculated through the container. The aging fluid can be heated outside the container before being reintroduced into the container. During the aging period, the pressure within the container (the "aging pressure") remains above the vapor pressure of the liquid, particularly the vapor pressure of the liquid at the aging temperature, because the vapor pressure of the aging fluid will increase with increasing temperature.

[0059] The aging time can be shortened by increasing the aging temperature by increasing the pressure. At the increased aging temperature, the aging time can be between 40 minutes and about 200 minutes.

[0060] Table 1 provides a vapor pressure-temperature table for ethanol. Such a table can be used to determine the minimum pressure inside the container that is required to allow the temperature of the aging fluid to increase to the desired aging temperature. For example, if an aging temperature of 230°F (110°C) is desired, the vapor pressure inside the container needs to be at or above 315 kPa to ensure that the liquid does not begin to damage the frame structure due to evaporation or boiling. In practice, the pressure in the container is maintained at a pressure of at least 2 times, at least 3 times, at least 5 times, at least 10 times, or at least 20 times the vapor pressure of the aging liquid. For example, using ethanol as the aging fluid, the pressure inside the container can be maintained at a pressure of at least 630 kPa, at least 945 kPa, at least 1575 kPa, at least 3150 kPa, or at least 6300 kPa.

[0061]

[0062] Table 1

[0063] Assuming that the aging chemical reaction follows first-order kinetics, the aging time will be halved for every 10°C increase in temperature. The relative effectiveness of different aging schemes can be evaluated by comparing the severity factors. The severity factor (R0) is determined using equation (1):

[0064] R0=t*e ((T-T0) / 14.75)) (1)

[0065] Where "t" is the aging time in minutes, "T" is the aging temperature (°C), and T0 is the starting temperature (25°C). "Normal Severity Factor" is defined as the severity factor calculated based on the time required to age the wet gel material when the wet gel material is heated at a temperature above room temperature (e.g., about 25°C) and below the normal boiling point of the aging fluid at a pressure of 1 atm.

[0066] The severity factor for a given system can be used to predict the aging time of a wet gel material at any given aging temperature. For a given aging process, the normal severity factor R0 can be calculated according to equation (1). Using the severity factor, the aging time (t) at any given temperature can then be calculated according to equation (2):

[0067] t=R0 / e ((T-T0) / 14.75)) (2)

[0068] Where T0 is 25℃.

[0069] In an exemplary case, the aging process is conventionally performed using ethanol as the aging fluid at a temperature of 160°F (71.1°C) and a pressure of 1 atm for a period of 840 minutes. The normal severity factor can be calculated according to Equation 1 as follows:

[0070] R0=(840)*e (71.1-25) / 14.75) =19,126

[0071] Based on the normal severity factors calculated above, the aging time of the ethanol aging process at any given temperature can be calculated according to Equation 2. Table 2 lists the predicted aging times calculated based on the normal severity factors (19, 126) for an exemplary ethanol aging process.

[0072]

[0073] Table 2

[0074] The use of severity factors to estimate the aging time of a gel material can allow the aging time to be determined without the need for lengthy trial and error and waste of material. During the formation of an aerogel composition, the gel material is heated in an aging fluid for a time sufficient to complete the chemical reactions that form the gel material framework. Once aging is complete, an aerogel composition is produced by removing liquid from the gel material. After drying, the aerogel composition is tested to ensure that the aerogel framework is intact and that the aerogel composition has the desired properties. Before the aerogel is formed, it is difficult to determine whether the aging time is sufficient to produce an aerogel composition with the desired properties. In order to ensure that the aging process is complete, additional aging times are used to complete the process. Once the aging time of the aging fluid at room temperature is determined, the severity factor can be used to determine a new aging time and be confident that the properties of the resulting aged gel will meet the desired performance.

[0075] As part of the aging process, the resulting wet gel material can be washed in a suitable auxiliary solvent to replace the main reaction solvent present in the wet gel material. Such auxiliary solvents can be linear monohydric alcohols with 1 or more aliphatic carbon atoms, dihydric alcohols with 2 or more carbon atoms, branched alcohols, cyclic alcohols, alicyclic alcohols, aromatic alcohols, polyols, ethers, ketones, cyclic ethers or their derivatives. In a preferred aspect of the present disclosure, the initial wet gel material comprises water or a mixture of ethanol and water. During the aging period, the water in the initial wet gel material is washed away with ethanol.

[0076] Once the gel material has been formed and aged, an extraction method can then be used to at least partially extract the liquid phase of the gel from the wet gel to form an aerogel material. Liquid phase extraction plays an important role in engineering the characteristics of the aerogel, such as porosity and density, and related properties, such as thermal conductivity, among other factors. Typically, an aerogel is obtained when the liquid phase is extracted from the gel in a manner that causes low shrinkage of the porous network and framework of the wet gel.

[0077] Aerogels are typically formed by removing a liquid mobile phase from a gel material at a temperature and pressure close to or above the critical point of the liquid mobile phase. Once the critical point (near critical) or beyond the critical point (supercritical) is reached (i.e., the pressure and temperature of the system are equal to or above the critical pressure and critical temperature, respectively), a new supercritical phase appears in the fluid, which is different from the liquid or vapor phase. The solvent can then be removed without introducing a liquid-vapor interface, capillary pressure, or any mass transfer limitations typically associated with liquid-vapor boundaries. In addition, the supercritical phase is typically more miscible with organic solvents and therefore has better extraction capabilities. Cosolvents and solvent exchange are also commonly used to optimize supercritical fluid drying processes.

[0078] A disclosed method for extracting a liquid phase from a wet gel uses supercritical conditions of carbon dioxide, including, for example: first fully exchanging the primary solvent present in the gel pore network with liquid carbon dioxide; then heating the wet gel (usually in an autoclave) above the critical temperature of carbon dioxide (about 31.06°C), and increasing the pressure of the system to a pressure greater than the critical pressure of carbon dioxide (about 1070 psig). The pressure surrounding the gel material can be slightly fluctuated to facilitate the removal of the supercritical carbon dioxide fluid from the gel. The carbon dioxide can be recycled through the extraction system to facilitate the continuous removal of the primary solvent from the wet gel. Finally, the temperature and pressure are slowly restored to ambient conditions to produce a dry aerogel material. The carbon dioxide can also be pretreated to a supercritical state before being injected into the extraction chamber.

[0079] In one aspect of the present disclosure, the aging process and the extraction of the liquid can be performed in the same container. Using the same container for the aging and extraction processes allows the formation of an aerogel composition without the need to remove the aged gel material from the container between the heating and extraction steps, and without the need to reduce the temperature or pressure of the container between the heating and extraction steps.

[0080] During the combined aging and extraction process, the wet gel material is placed in a container. A container is selected that can be used at the pressure and temperature required to achieve supercritical conditions for the extraction fluid. For example, when carbon dioxide is used as a supercritical fluid, the container is rated for a temperature of at least 35°C and a pressure of at least about 1100 psig. In some aspects, the rated use pressure and temperature of the container are significantly higher than the pressure and temperature required to achieve supercritical conditions for the extraction fluid. For example, the rated temperature of a container for supercritical extraction of carbon dioxide should be greater than 100°C and the pressure should be greater than 2500 psig. In more general aspects, the upper limit of the pressure is defined based on the rated pressure of the container.

[0081] After the wet gel material is placed in the container, an aging fluid is introduced into the container and the aging process begins. As previously described, the aging process is conducted at an aging temperature above the normal boiling point of the aging fluid by maintaining the container pressure above the vapor pressure of the aging fluid during heating. Because the container is selected to be able to handle the high temperature and high pressure conditions of supercritical extraction, the container is also able to handle the high temperature aging conditions (temperature and pressure) used during aging.

[0082] Once the aging process is complete, the extraction process is performed in the container without removing the aged gel material from the container between the aging and extraction steps. After the aging process is complete, the extraction fluid is introduced into the container. In a preferred aspect of the present disclosure, when transitioning from the aging process to the extraction process, the temperature or pressure of the container is not reduced between the heating and extraction steps.

[0083] After the extraction fluid is introduced into the aging vessel, the aged gel material is subjected to an extraction process by passing the supercritical fluid through the vessel. The extraction process is carried out at an extraction temperature and an extraction pressure. The extraction temperature and the extraction pressure are greater than the critical temperature and the critical pressure of the extraction fluid. For example, if carbon dioxide is used as the extraction fluid, the extraction temperature is maintained above the supercritical temperature of carbon dioxide (31° C.), and the extraction pressure is maintained above the supercritical temperature of carbon dioxide (1000 psi).

[0084] As described above, the aging process can be conducted at a temperature and pressure above the normal boiling point and normal vapor pressure of the aging fluid. To minimize stresses that may occur when transitioning from the aging process to the extraction process, the container is maintained at or above the aging temperature and pressure. For example, in one embodiment, at the end of the aging process, the extraction fluid is introduced into the container without reducing the temperature of the container or reducing the pressure inside the container. In another embodiment, at the end of the aging process, the temperature and pressure inside the container are raised to or near the supercritical conditions of the extraction fluid before the extraction fluid is introduced into the container.

[0085] In one aspect of the present disclosure, the aging conditions are performed at or near the supercritical point of the extraction fluid. For example, if the extraction fluid is supercritical carbon dioxide, the aging pressure is a pressure above the critical pressure of CO2, and the aging temperature is above the critical temperature of CO2. For example, when CO2 is used as the extraction fluid, during the aging of the wet gel material, the aging temperature is between about 80°C (186°F) and about 110°C (230°F), and the aging pressure is between about 1000 psi and about 2500 psi. Preferably, when supercritical CO2 is the extraction fluid, during the aging of the wet gel material, the wet gel material and the aging fluid are heated to an aging temperature between about 95°C (203°F) and about 110°C (230°F) at an aging pressure between about 1000 psi and about 1500 psi. By aging the wet gel material at a temperature and pressure at, near, or above the supercritical temperature of the extraction fluid, the stress on the gel material can be minimized during the transition from aging to extraction.

[0086] In one aspect of the present disclosure, after the aging process, an extraction fluid is introduced into the container. The temperature and pressure of the extraction fluid entering the container are substantially the same as the aging temperature and aging pressure. After a sufficient amount of the extraction fluid is introduced into the container, the temperature and pressure within the container are adjusted to maintain the extraction fluid in a supercritical state. In a preferred embodiment, the extraction fluid is carbon dioxide, and the temperature and pressure within the container are maintained at or above the supercritical temperature and pressure of carbon dioxide.

[0087] During extraction of the aged fluid from the aged gel material, the extraction fluid is introduced into the container and removed from the container substantially continuously during the extraction. For example, the extraction fluid may be recirculated through the container. If the extraction fluid is recirculated, the recirculation loop may include a separator that removes at least some of the aged fluid from the extraction fluid before the extraction fluid is reintroduced into the container. The extraction fluid may be heated outside the container before being reintroduced into the container. During the extraction, the extraction pressure is maintained above the supercritical pressure of the extraction fluid. Likewise, the extraction temperature is maintained above the supercritical temperature of the extraction fluid. For the carbon dioxide extraction process, the container is maintained above the supercritical temperature of carbon dioxide (31° C.) and the extraction pressure is maintained above the supercritical temperature of carbon dioxide (1000 psi).

[0088] Additionally, aged fluid that remains in the pores of the aerogel material is also removed. This "pore fluid" is essentially a mixture of aged fluid and unreacted precursors from the sol state. In some aspects, the composition of the pore fluid will have a varying composition and be different from the composition of the bulk aged fluid. This is due to limited diffusion in and out of the pores. Because detectability of pore fluid is challenging in practice, this disclosure generally refers to the fluid that is removed during extraction without specifically indicating the presence of pore fluid.

[0089] Like the aging process, it is difficult to determine when the extraction process is complete while the extraction is ongoing. Since the extraction process is carried out at elevated temperatures and pressures, obtaining samples for testing is difficult and time consuming. Obtaining a sample will require lowering the temperature and pressure so that the sample can be obtained. In addition, if the extraction is incomplete, the aged gel material will need to be returned to the extraction temperature and pressure. The process of increasing the temperature and pressure to supercritical conditions is a time consuming process. Significant changes in pressure and temperature within the container will also impose stress on the forming aerogel, potentially damaging the aerogel's framework.

[0090] It is possible to monitor the progress of the extraction process without having to remove the aerogel composition from the container. The density of the supercritical fluid changes as the amount of aged fluid dissolved in the supercritical extraction fluid changes. In one aspect of the present disclosure, the density of the entering supercritical fluid is compared to the density of the extraction fluid leaving the container. The density of the entering extraction fluid is at or close to the density of the pure extraction fluid. As the extraction fluid passes through the aged gel material, the extraction fluid can mix with the aged fluid to form an extraction / aged fluid mixture. The density of such a mixture is typically significantly different from the density of the pure extraction fluid. Therefore, when there is a large amount of aged fluid in the container / aged gel material, the density of the extraction fluid leaving the container will be significantly different from the density of the fluid entering the container. As the extraction process approaches completion, the amount of aged fluid in the extraction fluid decreases and the density begins to approach the density of the pure supercritical extraction fluid. When this point is reached during the extraction of the aged gel material, the extraction process can be considered complete. In one aspect of the present disclosure, extraction of the aging fluid is continued until the density of the extraction fluid removed from the vessel is within about 10%, within about 8%, within about 5%, within about 3%, within about 2%, or within about 1% of the density of the extraction fluid entering the vessel.

[0091] As described above, the density of the mixture of extraction fluid and aging fluid is typically significantly different from the density of the pure extraction fluid. In one embodiment, the density of the extraction fluid leaving the container is monitored periodically or continuously. The density of the extraction fluid can be used to determine the approximate concentration of the extraction fluid in the container. When the mixture of extraction fluid and aging fluid is formed, the conditions for forming a supercritical fluid will change. In order to keep the fluid in the container at or near the supercritical temperature of the extraction fluid / aging fluid mixture, it may be necessary to change the extraction conditions (extraction temperature and / or extraction pressure). The density of the extraction fluid passing through the container is determined in part by monitoring the density of the outflowing extraction fluid. If the density changes significantly, the temperature and / or pressure of the container can be increased to return the extraction fluid to supercritical conditions. For supercritical carbon dioxide based extraction, the density of the liquid in the container should be maintained at a density of 0.30 g / cc to about 0.60 g / cc by adjusting the temperature and / or pressure of the container.

[0092] Further details describing aerogel synthesis can be found in U.S. Patent Application Publication No. 2016 / 0096949 to Evans et al. and U.S. Patent Application Publication No. 2021 / 03095227 to Evans et al., both of which are incorporated herein by reference.

[0093] The aerogel composites of the present disclosure may have a thickness of 15 mm or less, 10 mm or less, 5 mm or less, 3 mm or less, 2 mm or less, or 1 mm or less.

[0094] In one aspect of the present disclosure, the aerogel composite material may include an opaque additive to reduce the radiative component of heat transfer. At any time before the gel is formed, the opaque compound or its precursor may be dispersed into the mixture containing the gel-forming material. Exemplary opaque additives include, but are not limited to, B4C, diatomaceous earth, manganese ferrite, MnO, NiO, SnO, Ag2O, Bi2O3, TiC, WC, carbon black, titanium oxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron (I) oxide, iron (III) oxide, manganese dioxide, iron titanium oxide (ilmenite), chromium oxide, silicon carbide, or mixtures thereof.

[0095] In some aspects of the present disclosure, the aerogel materials or compositions of the present disclosure are produced on a large scale, which requires the use of a large scale extraction vessel. The large scale extraction vessel of the present disclosure may include a 3 or larger, about 0.25m 3 or larger, about 0.5m 3 or larger or about 0.75m 3 or larger volume extraction vessels.

[0096] Figure 1 A schematic diagram of a conventional method for processing a continuous roll of aerogel is depicted. During the formation of a wet gel material, a continuous roll of fibrous support material is used to supply the fibrous support material through a loading system. The loading system includes a container for storing an aerogel precursor solution. As the fibrous support material is transported through the loading system, the aerogel precursor solution is applied to the fibrous support material. After the aerogel precursor solution has been dispensed onto the material, the fibrous support material is collected in a take-up reel. The supported wet gel material is transported to an aging station where it is placed in an aging container. As described herein, the supported gel material is aged in the container. After the aging process is complete, the supported aged gel material is removed from the aging container and transported to an extraction container. The supported aged gel material is extracted as described herein. After the extraction process is complete, the resulting supported aerogel is removed from the extractor and transported to a separate area for final processing.

[0097] Figure 2A schematic diagram of an improved method is depicted in which aging and extraction of the wet gel material are completed in the same container. The initial steps of forming the supported wet gel material are essentially the same as those used in conventional processes. Once the supported wet gel material is formed, the material is transported to an extraction vessel. Once loaded into the extraction vessel, the supported wet gel material is first aged. Aging can be performed at ambient pressure, or, if the extraction vessel is rated for supercritical extraction conditions, the aging process can be performed at elevated temperatures and pressures. As previously described, aging the wet gel material at elevated temperatures and pressures can significantly reduce the aging time. Once the aging process is completed, there is no need to transfer the wet gel material to a different container. Instead, the extraction process begins by washing the aging fluid out of the container with the extraction fluid. The extraction process is then initiated and completed without removing the initial wet gel material from the container. As with conventional processes, after the extraction process is completed, the resulting supported aerogel is removed from the extractor and transported to a separate area for final processing

[0098] The low thermal conductivity of aerogel materials and aerogel composites makes them ideal materials for insulation applications. In one exemplary use, aerogel composites can be used as a thermal barrier between single or multiple battery cells. Under "abuse conditions", battery cells are prone to catastrophic failure. Abuse conditions include mechanical abuse, electrical abuse, and thermal abuse. One of these abuse conditions may be triggered from the outside or inside. For example, service-induced stress, aging, design errors, for example, configuration parameters such as battery spacing, battery interconnection methods, battery form factors, manufacturing, operation, and maintenance are internal mechanical factors that may lead to various abuses. External mechanical factors include damage or injury to the LIB, such as falling or penetrating the battery. Electrical abuse conditions mainly include internal or external short circuits, overcharging, and overdischarging of battery cells. Thermal abuse is usually triggered by overheating. For example, battery cell overheating may be caused by operating the battery cell at high ambient temperatures. Internally, thermal abuse may be caused by electrical and mechanical defects in the battery cell.

[0099] Battery modules and battery packs can be used to supply electrical energy to devices or vehicles. Devices using battery modules or battery packs include, but are not limited to, laptop computers, PDAs, mobile phones, label scanners, audio devices, video devices, display panels, video cameras, digital cameras, desktop computers, military portable computers, military phones, laser rangefinders, digital communication devices, intelligence collection sensors, electronic integrated clothing, night vision equipment, power tools, calculators, radios, remote control devices, GPS devices, handheld and portable televisions, car starters, flashlights, acoustic devices, portable heating devices, portable vacuum cleaners, or portable medical tools. When used in vehicles, the battery pack can be used in all-electric vehicles or hybrid vehicles.

[0100] Example

[0101] The following examples are included to illustrate various aspects of the present disclosure. It will be appreciated by those skilled in the art that the techniques disclosed in the following examples represent techniques that the inventors have found to work well in the practice of the present invention and therefore can be considered to constitute preferred modes for its practice. However, in light of the present disclosure, it will be appreciated by those skilled in the art that many changes may be made to the specific embodiments disclosed without departing from the spirit and scope of the present invention and still obtaining the same or similar results.

[0102] Method for aging and extraction in a single vessel

[0103] A wet gel composite material based on silica consisting of a wet gel incorporated into a nonwoven fiber reinforcement is obtained as a continuous sheet. The continuous sheet is rolled onto a support and placed in an aging / extraction vessel. Ethanol is added to the vessel as an aging fluid. The temperature of the ethanol added to the vessel is 35°C (95°F). During aging, the heated ethanol is recirculated through the vessel by continuously removing ethanol from the vessel while continuously adding ethanol to the vessel.

[0104] After the heated ethanol is introduced into the container, the extraction pressure in the container is increased to an aging pressure of 1100 psig (7584 kPa), thereby starting the aging process. During the aging process, the temperature of the ethanol in the container is increased to 98.9°C (210°F). In addition, during the aging process, the pressure can be increased to about 1500 psig (Pa). The aging process runs for about 130 minutes.

[0105] When the aging process is complete, the extraction process begins. The pressure in the vessel is raised to an extraction pressure of 2200 psig. The extraction temperature is initially 98.9°C (210°F), which is the final temperature of the vessel at the end of the aging process. Carbon dioxide is introduced into the vessel, and the extraction process is started by continuously removing the carbon dioxide while the carbon dioxide is continuously introduced into the vessel. The carbon dioxide removed from the vessel is depressurized, which separates the carbon dioxide from any ethanol and water carried out of the vessel by the carbon dioxide. After removing ethanol and water from the carbon dioxide collected at the outlet, the carbon dioxide can be recycled into the vessel. The carbon dioxide is introduced into the vessel at or near the extraction temperature.

[0106] The extraction temperature was maintained at the aging temperature to minimize stress on the aerogel and save production time. The extraction pressure was approximately 2,200 psig and was adjusted to maintain the density of the supercritical carbon dioxide in the range of 0.36-0.60 g / cc.

[0107] In one aspect of the present disclosure, the extraction fluid can be used as an aging fluid for subsequent aging of the wet gel material. The extraction fluid removed from the container consists of a mixture of the extraction fluid and the aging fluid. The extraction fluid can be maintained at the extraction temperature and extraction pressure and introduced into another container for aging of the wet gel material. In this regard, the amount of aging fluid required to age multiple batches of wet gel material can be minimized. In addition, the reuse of the extraction fluid as an aging fluid can minimize the processing time of filling (during the aging step) and draining (during the extraction step). In an exemplary process, supercritical carbon dioxide can be used as an extraction fluid to remove ethanol used as an aging fluid. The supercritical carbon dioxide is saturated with ethanol during the extraction process and can be used as an aging fluid in a subsequent aging step.

[0108] Figure 3 A schematic diagram of this process superimposed on the CO2 phase diagram is depicted.

[0109] By monitoring the density of carbon dioxide removed from the container, three discrete extraction transitions were noted: 1) a large amount of aged ethanol was discharged from the container, 2) a mixture of ethanol and carbon dioxide was discharged, and 3) carbon dioxide with less than 10% ethanol / water was discharged. The timing and relative spacing of these transitions depend on the thickness of the aerogel sample. The junctions between the transitions are depicted by characteristic density changes. The extraction endpoint is represented by the convergence of the inlet and outlet densities of the supercritical carbon dioxide. The endpoint can also be predicted based on the container volume and the calculated total amount of ethanol removed. Once the extraction endpoint is reached, plus a certain safety margin, a drainage procedure can be initiated to remove carbon dioxide from the fully extracted aerogel material. As used herein, reference to removing carbon dioxide refers to the process of reducing the pressure to allow the carbon dioxide to return to the gaseous state and diffuse out of the aerogel material (displaced by air).

[0110] Figure 4 shows a comparison of the physical properties of the gel material produced using the combined aging / extraction process with the standard process of aging and extraction in separate vessels.

[0111] In this patent, certain U.S. patents, U.S. patent applications, and other materials (e.g., articles) have been incorporated by reference. However, the text of these U.S. patents, U.S. patent applications, and other materials is incorporated by reference only to the extent that there is no conflict between such text and other statements and drawings set forth herein. In the event of such a conflict, any such conflicting text in such incorporated by reference U.S. patents, U.S. patent applications, and other materials is specifically not incorporated by reference in this patent.

[0112] In view of this description, further modifications and alternative aspects of the present invention will be apparent to those skilled in the art. Therefore, this specification is intended to be interpreted as illustrative only, and its purpose is to teach those skilled in the art to implement the general mode of the present invention. It should be understood that the form of the present invention shown and described herein is an example as an embodiment. The elements and materials shown and described herein can be replaced, parts and processes can be reversed, and certain features of the present invention can be utilized independently, all of which are apparent to those skilled in the art after benefiting from the description of the present invention. Changes can be made to each element described herein without departing from the spirit and scope of the present invention as described in the appended claims.

[0113] When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean including the specified features, steps or integers. These terms should not be interpreted to exclude the presence of other features, steps or components. The present invention comprises, consists of or consists essentially of the disclosed and claimed features.

[0114] The present invention may also be present broadly in the parts, elements, steps, examples and / or features individually mentioned or indicated in the specification, or in any and all combinations of two or more of the parts, elements, steps, examples and / or features. Specifically, one or more features in any embodiment, example and aspect described herein may be combined with one or more features in any other embodiment, example and aspect described herein.

[0115] Protection may be sought in conjunction with the present disclosure for any feature disclosed in any one or more of the publications cited herein.

[0116] Although certain exemplary embodiments of the present invention have been described, the scope of the appended claims is not intended to be limited to only these embodiments. The claims should be interpreted literally, objectively, and / or include equivalents.

Claims

1. A method for aging a wet gel material, comprising: placing the wet gel material in a container; introducing an aging fluid into the container; The wet gel material is aged at an aging temperature and an aging pressure, wherein the aging temperature is above the normal (standard temperature / pressure) boiling point of the aging fluid, and wherein the aging pressure is maintained above the vapor pressure of the aging fluid during aging.

2. The method of claim 1, wherein the wet gel material is obtained by a method comprising the steps of: providing a precursor solution comprising a silica gel precursor material and a solvent; and The silica gel precursor material in the precursor solution is allowed to transform into a wet gel material, wherein the wet gel material comprises a silica-based framework and the solvent.

3. The method of claim 1 or 2, wherein the aged fluid comprises ethanol.

4. The method according to any one of claims 1 to 3, wherein the aging pressure is a pressure higher than the critical pressure of CO2, and the aging temperature is higher than the critical temperature of CO2.

5. The method of any one of claims 1 to 3, wherein during aging of the wet gel material, the wet gel material and an aging fluid are heated to an aging temperature between about 80°C (176°F) and about 110°C (230°F) at an aging pressure between about 1000 psi and about 2500 psi.

6. The method of any one of claims 1 to 3, wherein during aging of the wet gel material, the wet gel material and an aging fluid are heated to an aging temperature between about 95°C (203°F) and about 110°C (230°F) at an aging pressure between about 1100 psi and about 1500 psi.

7. The method of any one of claims 1 to 6, wherein the wet gel material is aged for a time between about 1 hour and about 24 hours.

8. The method of any one of claims 1 to 6, wherein the wet gel material is aged for a time between about 40 minutes and about 200 minutes.

9. The method of any one of claims 1 to 8, wherein the wet gel material is aged for a time determined by the aging temperature and a normal severity factor.

10. The method of any one of claims 1 to 9, wherein during aging of the wet gel material, an aging fluid is removed and an aging fluid is introduced substantially continuously.

11. The method of any one of claims 1 to 10, further comprising washing the wet gel material with the aging fluid prior to heating the wet gel material, wherein the aging fluid removes and displaces at least a portion of liquid present in the wet gel material.

12. The method of any one of claims 1 to 11, wherein the wet gel material comprises a reinforcing material.

13. The method of claim 12, wherein the reinforcement material is in the form of a continuous sheet.

14. A method for producing an aerogel composition, comprising: placing a wet gel material in a container; introducing an aging fluid into the container; heating the wet gel material and the aged fluid at an aging temperature and an aging pressure, wherein the aging temperature is above a normal boiling point of the aged fluid, and wherein the aging pressure is maintained above a vapor pressure of the aged fluid during heating; as well as extracting the aged fluid from the aged gel material with an extraction fluid at an extraction temperature and an extraction pressure, wherein the extraction temperature and the extraction pressure are greater than a critical temperature and a critical pressure of the extraction fluid; wherein heating the wet gel material and extracting the aged fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and the extracting steps, and without reducing the temperature or pressure of the container between the heating and the extracting steps.

15. The method of claim 14, wherein the wet gel material is obtained by a method comprising the steps of: providing a precursor solution comprising a silica gel precursor material and a solvent; and The silica gel precursor material in the precursor solution is allowed to transform into a wet gel material, wherein the wet gel material comprises a silica-based framework and the solvent.

16. The method of claim 14 or 15, wherein the aged fluid comprises ethanol.

17. The method of any one of claims 14 to 16, wherein the aging pressure is a pressure above the critical pressure of CO2, and the aging temperature is above the critical temperature of CO2.

18. The method of any one of claims 14 to 16, wherein during aging of the wet gel material, the aging temperature is between about 80°C (86°F) and about 110°C (230°F), and the aging pressure is between about 1000 psi and about 2500 psi.

19. The method of any one of claims 14 to 17, wherein during aging of the wet gel material, the aging temperature is between about 95°C (203°F) and about 110°C (230°F), and the aging pressure is between about 1000 psi and about 1500 psi.

20. The method of any one of claims 14 to 19, wherein the wet gel material is aged for a time between about 30 minutes and about 24 hours.

21. The method of any one of claims 14 to 19, wherein the wet gel material is aged for a time between about 40 minutes and about 200 minutes.

22. The method of any one of claims 14 to 21, wherein the wet gel material is aged for a time determined by the aging temperature and a normal severity factor.

23. The method of any one of claims 14 to 22, wherein during aging of the wet gel material, aging fluid is removed and aging fluid is introduced substantially continuously.

24. The method of any one of claims 14 to 23, further comprising washing the wet gel material with the aging fluid prior to heating the wet gel material, wherein the aging fluid removes and displaces at least a portion of liquid present in the wet gel material.

25. The method of any one of claims 14 to 24, wherein the wet gel material comprises a reinforcing material.

26. A method as claimed in claim 25, wherein the reinforcing material is in the form of a continuous sheet.

27. The method of any one of claims 14 to 26, wherein extracting the aged fluid from the aged gel material comprises: introducing the extraction fluid into the vessel, wherein the temperature and pressure of the extraction fluid entering the vessel are substantially the same as the aging temperature and the aging pressure; and The temperature and pressure within the vessel are adjusted to maintain the extraction fluid in a supercritical state.

28. The method of claim 27, wherein during extraction of the aged fluid from the aged gel material, extraction fluid is removed and extraction fluid is introduced substantially continuously during the extraction.

29. The method of claim 28, further comprising monitoring the density of the extraction fluid removed from the vessel.

30. The method of claim 29, wherein said extracting of said aged fluid is continued until the density of said extraction fluid removed from said vessel is within 10% of the density of said extraction fluid entering said vessel.

31. The method of any one of claims 14 to 30, wherein the supercritical fluid comprises carbon dioxide.

32. The method of any one of claims 14 to 31, further comprising adjusting the pressure within the container to maintain a density of the supercritical fluid between about 0.30 g / cc and 0.60 g / cc.

33. The method of any one of claims 14 to 32, further comprising removing fluid from the container while the extraction fluid is introduced into the container, wherein the removed fluid comprises at least a portion of the aged fluid.

34. The method of any one of claims 14 to 33, wherein during heating of the wet gel material to form the aged gel material, the aging pressure is maintained at or above the critical pressure and above the critical temperature of the extraction fluid.

35. The method of any one of claims 14 to 34, wherein the aging temperature and the aging pressure are increased to the extraction temperature and the extraction pressure prior to introducing the extraction fluid into the vessel.

36. A method of producing an aerogel composition, comprising: placing a wet gel material in a container, the wet gel comprising a silica-based framework; introducing ethanol into the container; aging the wet gel material by heating the wet gel material and the ethanol at an aging temperature and an aging pressure, wherein the aging temperature is greater than 80° C. (186° F.), and wherein the pressure of the container is maintained greater than 1000 psi during heating; introducing carbon dioxide into the container, wherein the temperature and pressure of the carbon dioxide entering the container are substantially the same as the aging temperature and the aging pressure; extracting the aged fluid from the aged gel material with supercritical carbon dioxide at an extraction temperature and an extraction pressure; as well as adjusting the extraction temperature and / or the extraction pressure in the container to keep the carbon dioxide in a supercritical state; wherein heating the wet gel material and extracting the aged fluid from the aged gel material are performed in the container without removing the aged gel material from the container between the heating and the extracting steps, and without reducing the temperature or pressure of the container between the heating and the extracting steps.

37. The method of claim 36, wherein during aging of the wet gel material, the container is pressurized to a pressure above the critical pressure of CO2 and the internal temperature of the container is above the critical temperature of CO2.

38. The method of claim 36 or 37, wherein during aging of the wet gel material, the wet gel material and aging fluid are heated to an aging temperature between about 95°C (203°F) and about 110°C (230°F) at an aging pressure between about 1000 psi and about 1500 psi.

39. The method of any one of claims 36 to 38, wherein the wet gel material is aged for a time between about 40 minutes and about 200 minutes.

40. The method of any one of claims 36 to 39, wherein during aging of the wet gel material, aging fluid is removed and aging fluid is introduced substantially continuously.

41. The method of any one of claims 36 to 40, wherein during extraction of the aged fluid from the aged gel material, carbon dioxide is removed and extraction fluid is introduced substantially continuously during the extraction.

42. The method of any one of claims 36 to 41 further comprising monitoring the density of carbon dioxide removed from said vessel, wherein said extraction of said aged fluid is continued until the density of said extraction fluid removed from said vessel is within 10% of the density of said extraction fluid entering said vessel.

43. The method of any one of claims 36 to 42, further comprising adjusting the extraction pressure within the vessel to maintain a density of the supercritical fluid between about 0.36 g / cc and 0.60 g / cc.

44. The method of any one of claims 36 to 42, wherein the aging pressure is maintained at or above the critical pressure of carbon dioxide, and wherein during heating of the wet gel material to form an aged gel material, the aging temperature is at or above the critical temperature of carbon dioxide.

45. The method of any one of claims 36 to 44, wherein the aging temperature and the aging pressure are increased to the extraction temperature and the extraction pressure prior to introducing the extraction fluid into the vessel.

46. ​​The method of any one of claims 36 to 45, wherein the wet gel material comprises a reinforcing material.

47. A method as claimed in claim 46, wherein the reinforcing material is in the form of a continuous sheet.

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