Low density cast silicone foam and preparation thereof

Abstract

A curable composition for making a low density cast silicone foam includes a first portion and a second portion. The first part comprises a specific amount of an alkenyl-terminated polyorganosiloxane; an alkenyl substituted copolymerized organosiloxane; an alkenyl substituted MQ polyorganosiloxane; curing the catalyst; an inorganic filler; and a chemical blowing agent. The second portion comprises a hydride substituted polyorganosiloxane. The resulting silicone foam advantageously has a density of less than 240 kg / m3; and a closed cell content of at least 50%. Also described are cured silicone foams and methods of making the same.

Description

[0001] Cross-references to related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 462,607, filed April 28, 2023, and U.S. Provisional Patent Application No. 63 / 455,802, filed March 30, 2023, the contents of which are incorporated herein by reference in their entirety. Background Technology

[0002] Flexible silicone foams are widely used for sealing and vibration damping in various applications such as transportation and electronic equipment. However, while dimensional and weight performance requirements are decreasing, technical performance requirements are increasing. Therefore, there remains a continued need for thin silicone foams with excellent physical properties.

[0003] The development of low-density cast silicone foams has attracted attention due to the anticipated improvement in compression and weight distribution. However, thin cast foams tend to suffer from high density due to the compression of the foam sheet during manufacturing and the rupture of air bubbles within it.

[0004] Therefore, there is a need for compositions and methods to form low-density cast silicone foams that meet the currently desired physical properties. Another advantage is the avoidance of fluorinated surfactants, which can affect the uniformity of the foamed product and provide suboptimal properties. Summary of the Invention

[0005] A curable composition for preparing low-density cast silicone foam comprises: a first portion, based on the total weight of the first portion, comprising 40 to 70 wt% of an alkenyl-terminated polysiloxane; 0.1 to 10 wt% of an alkenyl-substituted copolymeric silicone; 5 to 30 wt% of an alkenyl-substituted MQ polysiloxane; a curing catalyst; an inorganic filler; and 0.1 to 1.5 wt% of a chemical blowing agent comprising water, a silanol-terminated polysiloxane; and optionally an alcohol; and a second portion comprising a hydride-substituted polysiloxane; wherein the density of the low-density cast silicone foam is less than 240 kg / m³. 3 ; and the closed-cell content of the low-density cast silicone foam is at least 50%.

[0006] Cured silicone foam layers containing curable compositions represent another aspect of this disclosure.

[0007] A method for forming a silicone foam sheet includes casting (flowing) a curable composition onto a first release layer; placing a second release layer on a side of the casted curable composition opposite the first release liner to form a multi-layer structure; and passing the casted curable composition on the substrate through a nip of two rotating rollers to regulate the amount of curable composition; and curing the curable composition to form a silicone foam sheet.

[0008] The silicone foam sheet formed according to the method represents another aspect of the present disclosure.

[0009] The above described and other features are exemplified by the following detailed description. DETAILED DESCRIPTION

[0010] The present inventors have unexpectedly discovered a curable composition for producing a low density casted silicone foam having desirable properties, particularly density, compressive force deflection, and cell morphology. In one unexpected and advantageous feature, the curable compositions described herein can be used in a casting process to provide a low density foam that is not subject to the limitations of the above-mentioned techniques. In another advantageous feature, the low density casted silicone foam can be produced without the use of fluorinated surfactants. For many years, the art has relied on fluorinated surfactants and other compounds to stabilize silicone foams during casting and curing. Thus, as used herein, "fluorinated surfactant" includes non-ionic fluorinated polymers known in the art for stabilizing silicone foams, such as fluorinated polyethers and fluorinated polyorganosiloxanes. Special types of fluorinated surfactants have been used, such as the co-foamers described in U.S. Patent No. 4,608,396 to Bauman et al. and references cited therein. However, fluorinated surfactants are under strict scrutiny due to their environmental health and safety properties. Thus, moving away from fluorinated surfactants is desirable, but these surfactants have previously had to be used to obtain desirable cell structure. Thus, it is unexpected that low density casted silicone foams having superior properties can be produced using the curable compositions described herein even in the absence of fluorinated surfactants. Thus, a significant advantage is provided by the present disclosure.

[0011] Accordingly, one aspect of the present disclosure is a curable composition for making a low density casted silicone foam. To obtain the advantageous properties of a low density casted silicone foam, a particular combination of materials for the curable composition is used, as described in greater detail herein. The relative amounts of the components in the curable composition can be adjusted to provide the desired properties in the cured silicone foam.

[0012] The curable composition includes a first part and a second part. The first part and the second part can be mixed to provide the curable composition.

[0013] The first part comprises an alkenyl-terminated polyorganosiloxane. Suitable alkenyl-terminated polyorganosiloxanes are generally represented by the formula: M a D b T c Q d , wherein subscripts a, b, c, and d are zero or positive integers, subject to the following limitations: if both subscripts a and b equal zero, then subscript c is greater than or equal to two; M has the formula R3SiO 1 / 2 ; D has the formula R2SiO 2 / 2 ; T has the formula RSiO 3 / 2 ; and Q has the formula SiO 4 / 2 wherein each R group independently represents hydrogen, a terminally substituted C 1-6 alkenyl group, substituted and unsubstituted monovalent hydrocarbon groups each having from one to forty, or 1 to 6, carbon atoms, subject to the limitation that at least 1, for example at least 2, of the R groups are alkenyl R groups. Suitable alkenyl R groups are exemplified by vinyl, allyl, 1-butenyl, 1-pentenyl, and 1-hexenyl, with vinyl being particularly useful. The alkenyl groups are bonded at the end of the molecular chain, i.e., the alkenyl-terminated polyorganosiloxane. Preferably, the alkenyl-terminated polyorganosiloxane is a vinyl-terminated polyorganosiloxane, wherein both of the chain ends are vinyl. As used herein, vinyl is a group having the formula -CH=CH2, and "substituted vinyl" has the formula -CH=CR2, wherein the R groups can independently be hydrogen or C 1-6 alkyl. The vinyl concentration in the alkenyl-terminated polyorganosiloxane can be, for example, 0.001 to 1 weight percent, or 0.01 to 0.5 weight percent, or 0.01 to 0.15 weight percent, or 0.01 to 0.1 weight percent.

[0014] In one aspect, the alkenyl-terminated polyorganosiloxane can have a viscosity greater than 500 centipoise (cP), for example greater than 1,000 cP, or greater than 5,000 cP, or greater than 10,000 cP. In one particular aspect, the alkenyl-terminated polyorganosiloxane can have a viscosity of 50,000 to 70,000 cP.

[0015] When present, other silicon-bonded organic groups in the alkenyl-terminated polyorganosiloxane are exemplified by substituted and unsubstituted monovalent hydrocarbon groups having from one to forty carbon atoms, for example alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, and hexyl; aryl groups such as phenyl, tolyl, and xylyl; aralkyl groups such as benzyl and phenethyl; and haloalkyl groups such as 3-chloropropyl and 3,3,3-trifluoropropyl. Methyl and phenyl are particularly useful.

[0016] Alkenyl-terminated polyorganosiloxanes can have a linear, partially branched linear, branched, or network molecular structure, or can be a mixture of such structures. Alkenyl-terminated polyorganosiloxanes are exemplified by vinyl-terminated polydimethylsiloxane; vinyl-terminated dimethylsiloxane-diphenylsiloxane copolymer; vinyl-terminated dimethylsiloxane-methylphenylsiloxane copolymer; vinyl-terminated dimethylsiloxane-methylphenylsiloxane-diphenylsiloxane copolymer; vinyl-terminated dimethylsiloxane-methylphenylsiloxane copolymer; vinyl dimethylsiloxane-methylvinylsiloxane copolymer; vinyl-terminated methylvinylsiloxane-methylphenylsiloxane copolymer; vinyl-terminated dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer; dimethylvinylsiloxy-terminated methylvinylpolyorganosiloxane; dimethylvinylsiloxy-terminated methylvinylphenylsiloxane; dimethylvinylsiloxy-terminated dimethylvinylsiloxane-methylvinylsiloxane copolymer; dimethylvinylsiloxy-terminated dimethylsiloxane-methylphenylsiloxane copolymer; dimethylvinylsiloxy-terminated dimethylsiloxane-diphenylsiloxane copolymer; or combinations thereof. In a particular aspect, the alkenyl-substituted polyorganosiloxane comprises a vinyl-terminated polydimethylsiloxane.

[0017] The alkenyl-terminated polyorganosiloxane can be present in the first part of the curable composition in an amount of 40 to 70 weight percent or 50 to 60 weight percent, each based on the total weight of the first part of the curable composition.

[0018] In addition to the alkenyl-terminated polyorganosiloxane, the first part of the curable composition comprises an alkenyl-substituted copolyorganosiloxane. Suitable alkenyl-substituted copolyorganosiloxanes are generally represented by the formula: M a D b T c Q d , wherein subscripts a, b, c, and d are zero or positive integers, subject to the following limitations: if both subscripts a and b equal zero, then subscript c is greater than or equal to two; M has the formula R3SiO 1 / 2 ; D has the formula R2SiO 2 / 2 ; T has the formula RSiO 3 / 2 ; and Q has the formula SiO 4 / 2 wherein each R group independently represents hydrogen, a terminally substituted C 1-6Alkenyl, substituted and unsubstituted monovalent hydrocarbon groups each having from one to forty, or 1 to 6 carbon atoms, subject to the limitation that at least 1, for example at least 2, of the R groups are alkenyl R groups. Suitable alkenyl R-groups are exemplified by vinyl, allyl, 1-butenyl, 1-pentenyl, and 1-hexenyl, with vinyl being particularly useful. The alkenyl groups can be bonded at the end of the molecular chain, at a pendant position on the molecular chain, or both. Preferably, the alkenyl-substituted copolyorganosiloxane is an alkenyl bis-terminated polyorganosiloxane that also contains alkenyl groups at pendant positions on the molecular chain. For example, the alkenyl-substituted copolyorganosiloxane can include a vinyl-terminated polydimethylsiloxane having vinyl pendant groups along the polymer chain.

[0019] In one aspect, the alkenyl content of the alkenyl-substituted copolyorganosiloxane can be higher than the alkenyl content of the vinyl-terminated polyorganosiloxane. For example, the vinyl content of the alkenyl-substituted copolyorganosiloxane can be from 0.001 weight percent to 5 weight percent, or from 0.1 weight percent to 4 weight percent, or from 0.5 weight percent to 4 weight percent, or from 1 weight percent to 4 weight percent, or from 2 weight percent to 3 weight percent.

[0020] In one aspect, the viscosity of the second alkenyl-substituted polyorganosiloxane is less than 1,000 cP, preferably from 100 cP to 500 cP.

[0021] The alkenyl-substituted copolyorganosiloxane can be present in the first part of the curable composition in an amount of from 0.1 weight percent to 10 weight percent, or from 0.5 weight percent to 5 weight percent, based on the total weight of the first part.

[0022] The first part of the curable composition further comprises an alkenyl-substituted MQ polyorganosiloxane. As used herein, “MQ polyorganosiloxane” means a polyorganosiloxane represented by the following formula: M´ a D´ b T´ c Q´ d , wherein subscripts a, b, c, and d are zero or positive integers, subject to the limitation that if both subscripts a and b equal zero, then subscript c is greater than or equal to two; M has the formula R3SiO 1 / 2 ; D has the formula R2SiO 2 / 2 ; T has the formula RSiO 3 / 2 ; and Q has the formula SiO 4 / 2 wherein each R group independently represents hydrogen, a terminally substituted C 1-6Alkenyl, substituted and unsubstituted monovalent hydrocarbon radicals having from one to forty, or 1 to 6 carbon atoms each, subject to the limitation that at least 1, for example at least 2, of the R groups are alkenyl R groups. Preferably, subscripts a and d are not zero. Suitable alkenyl R- groups are exemplified by vinyl, allyl, 1-butenyl, 1-pentenyl, and 1-hexenyl, with vinyl being particularly useful. The alkenyl groups can be bonded at the end of the molecular chain, at a pendant position on the molecular chain, or both. In one particular aspect, the alkenyl-substituted MQ polyorganosiloxane is a vinyl-substituted MQ polyorganosiloxane.

[0023] In one aspect, the viscosity of the alkenyl-substituted MQ polyorganosiloxane can be greater than 500 cP, for example greater than 1,000 cP, or greater than 5,000 cP, or greater than 10,000 cP. In one particular aspect, the viscosity of the alkenyl-terminated polyorganosiloxane can be from 5,000 cP to 20,000 cP, or from 10,000 cP to 20,000 cP.

[0024] The alkenyl-substituted MQ polyorganosiloxane can be present in the first part of the curable composition in an amount of from 5 to 30 weight percent, based on the total weight of the first part of the curable composition. Within this range, the alkenyl-substituted MQ polyorganosiloxane can be present in an amount of from 10 to 25 weight percent, or from 15 to 20 weight percent.

[0025] The first part of the curable composition can generally include a cure catalyst, in particular a hydrosilylation reaction catalyst, as a component of the portion comprising the polyorganosiloxane having at least two alkenyl groups per molecule. An effective catalyst promotes the addition of silicon-bonded hydrogen to the alkenyl multiple bond to accelerate curing. Such a catalyst can include a noble metal, for example platinum, rhodium, palladium, ruthenium, iridium, or combinations thereof. The catalyst can also include a support material, for example activated carbon, alumina, silica, polymeric resin, or combinations thereof.

[0026] In one aspect, the cure catalyst can be present in an amount of up to 1,000 parts per million by weight (ppmw) of metal, for example platinum. In one aspect, the cure catalyst can be present in an amount of from 1 to 500 ppmw, or from 1 to 250 ppmw, or from 1 to 100 ppmw, or from 1 to 50 ppmw, or from 5 to 50 ppmw, or from 10 to 50 ppmw.

[0027] Platinum and platinum-containing compounds are preferred and include, for example, platinum black, platinum on alumina powder, platinum on silica powder, platinum on carbon powder, chloroplatinic acid, alcoholic solutions of platinum-chloroplatinic acid-olefin complexes, platinum-alkenylsiloxane complexes, and catalysts provided by the micronization of dispersions of the catalyst in polymer resins such as methyl methacrylate, polycarbonate, polystyrene, silicone, and the like. Combinations of different catalysts can also be used. When platinum catalytic systems are used, catalyst poisoning can occur, which can result in the formation of silicone compositions that are weakly cured or not cured at all. Additional platinum can be added, but when large amounts of platinum are added to improve curing, the pot life or working time can be adversely affected. Methyl vinyl cyclic compounds can be used as cure retarders, such as 1-2287 Cure Inhibitor from Dow Corning. Such materials bind platinum at room temperature to prevent curing and thus improve working time, but release platinum at higher temperatures to affect curing over the desired time period. The levels of platinum and cure retarder can be adjusted to vary the cure time and working time / pot life. When higher levels of platinum are used, they are typically less than or equal to 100 ppmw, based on the total weight of the curable polyorganosiloxane composition. Within this range, additional platinum concentration (i.e., beyond the amount needed) can be greater than or equal to 50 ppmw, or greater than or equal to 60 ppmw, based on the total weight of the curable polyorganosiloxane composition. Further within this range, the additional platinum concentration can be less than or equal to 90 ppmw, or less than or equal to 80 ppmw, based on the total weight of the curable polyorganosiloxane composition.

[0028] The cure retarder concentration, if a cure retarder is used, is less than or equal to 0.3 weight percent of the total curable polyorganosiloxane composition. Within this range, the cure retarder concentration is greater than or equal to 0.005 weight percent, or greater than or equal to 0.025 weight percent, based on the total weight of the curable polyorganosiloxane composition. Further within this range, the cure retarder concentration is less than or equal to 0.2 weight percent, or less than or equal to 0.1 weight percent, based on the total weight of the curable composition and the desired working time or pot life.

[0029] The first part of the curable composition for making a low density cast silicone foam further includes an inorganic filler to provide desired properties, particularly filling, reinforcement, flame retardation, or combinations thereof. The inorganic filler can be in the form of a particulate material. The particles can be in any regular or irregular shape, such as disc, fibrous, flaky, platy, rod (solid or hollow), spherical (solid or hollow), or whisker. In one aspect, the particles are in the form of irregularly spherical. The median diameter (which can mean the equivalent spherical diameter as defined herein) of each of the particulate fillers can be from 0.1 pm (micrometer) to 1 millimeter (mm), or from 0.5 pm to 500 pm, or from 1 pm to 50 pm. The particulate material can optionally exhibit a multimodal distribution of median particle size. The multimodal distribution can be a result of using two different particulate materials or a single material having two or more size modes.

[0030] Suitable inorganic fillers can include, for example, ceramics, clays, silicates, multiple ceramics, or glass microspheres. Particular particulate materials can include alumina, aluminum trihydrate, aluminum nitride, aluminum silicate, barium titanate, beryllia, boron nitride, borates (e.g., zinc borate, sodium borate, etc., and hydrates thereof), calcium carbonate, clay, kaolin, corundum, magnesium oxide, magnesium hydroxide, glass, mica, nanoclay, quartz, silicon carbide, strontium titanate, talc, titanium dioxide (e.g., rutile and anatase), wollastonite, etc., or combinations thereof. In one aspect, the filler includes a flame retardant, such as aluminum trihydrate. In one particular aspect, the inorganic filler can include aluminum trihydrate and at least one of silica or calcium carbonate.

[0031] The inorganic filler can optionally have an outer surface that is chemically modified by treatment with a coupling agent. The coupling agent can be a silane or an epoxy resin, such as an organosilane having a group at one end that can react with hydroxyl groups present on the outer surface of the particulate filler and an organic group at the other end that will facilitate dispersability of the particulate filler in a polymer matrix, such as a silicone foam. A bifunctional silane coupling can have a combination of groups such as vinyl, hydroxyl, and amino groups, such as 3-amino-propyl triethoxysilane. The silane coating can also minimize water absorption.

[0032] The inorganic filler can be present in the first part of the curable composition in an amount of from 3 weight percent to 35 weight percent, or from 10 weight percent to 30 weight percent, or from 15 weight percent to 28 weight percent, each based on the total weight of the first part of the curable composition.

[0033] The curable composition for making a low density cast silicone foam also includes a chemical blowing agent. In one aspect, a physical blowing agent is excluded from the curable composition. The chemical blowing agent includes water, a silanol-terminated polyorganosiloxane, and optionally an alcohol having 1 to 16 carbon atoms (which includes diols, triols, and the like). The silanol-terminated polyorganosiloxane can have a viscosity of 20 cP to 40,000 cP, or 400 cP to 2,000 cP, or 500 cP to 1,000 cP. In a particular aspect, the silanol-terminated polyorganosiloxane includes a hydroxyl-terminated polydimethylsiloxane. In one aspect, the alcohol preferably includes a C 1-12 alcohol or a C 1-6 alcohol. In a particular aspect, the alcohol includes 1-butanol. In one aspect, the alcohol can consist of a monohydric alcohol. Thus, in some aspects, a polyhydric alcohol (e.g., diols, triols, and the like) can be excluded from the curable composition.

[0034] In one aspect, the chemical blowing agent includes water, a C 1-12 monohydric alcohol, and a silanol-terminated polyorganosiloxane. For example, the chemical blowing agent can include 0.1 weight percent to 0.6 weight percent water, 0.1 weight percent to 0.9 weight percent of the C 1-12 monohydric alcohol; and 0.4 weight percent to less than 1 weight percent of the silanol-terminated polyorganosiloxane; each based on the total weight of the first portion of the curable composition.

[0035] In one aspect, the chemical blowing agent includes water and a silanol-terminated polyorganosiloxane. For example, the chemical blowing agent can include greater than 0.5 weight percent water, and 0.08 weight percent to less than 1 weight percent of the silanol-terminated polyorganosiloxane, each based on the total weight of the first portion of the curable composition.

[0036] In one aspect, the chemical blowing agent can also include a monomethyl alcohol-substituted polyorganosiloxane, a monofunctional silanol, or both. In a particular aspect, the chemical blowing agent includes a silanol-terminated polyorganosiloxane, water, an alcohol (e.g., butanol), and a monomethyl alcohol-substituted polyorganosiloxane.

[0037] The chemical blowing agent can be present in the composition in a total amount of 0.1 weight percent to 2.5 weight percent, based on the total weight of the first portion of the curable composition. The silanol-terminated polyorganosiloxane can be included in the first portion of the composition in an amount of 0.01 weight percent to less than 1 weight percent, or 0.4 weight percent to less than 1 weight percent, based on the total weight of the first portion of the curable composition.

[0038] The curable composition further comprises a second part. The second part comprises a co-curable hydride-substituted polyorganosiloxane. The hydride-substituted polyorganosiloxane can have at least two silicon-bonded hydrogen atoms per molecule and is generally represented by the formula: M´´ a D´´ b T´´ c Q´´ d wherein subscripts a, b, c, and d are zero or positive integers, subject to the following limitations: if both subscripts a and b equal zero, then subscript c is greater than or equal to two; M´´ has the formula R3SiO 1 / 2 ; D´´ has the formula R2SiO 2 / 2 ; T´´ has the formula RSiO 3 / 2 ; and Q´´ has the formula SiO 4 / 2 wherein each R group independently represents hydrogen, substituted and unsubstituted monovalent hydrocarbon groups having from one to forty, or one to six carbon atoms, subject to the limitation that at least two of the R groups are hydrogen. For example, each of the R groups of the polyorganosiloxane having at least two silicon-bonded hydrogen atoms per molecule is independently selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, aryl, phenyl, tolyl, xylyl, aralkyl, benzyl, phenethyl, haloalkyl, 3-chloropropyl, 3,3,3-trifluoropropyl, or combinations thereof. Methyl and phenyl groups can be preferred.

[0039] The hydrogens can be bonded to silicon at the end of the molecular chain, at a pendant position on the molecular chain, or both. In one aspect, the hydrogens are substituted at terminal positions. In one aspect, there are at least 3 to 4 hydrogens per molecule. The hydrogen-containing polyorganosiloxane component can have a linear, partially branched linear, branched, cyclic, or network molecular structure, or can be a mixture of two or more different polyorganosiloxanes having the exemplified molecular structures.

[0040] The hydride-containing polyorganosiloxane can include, for example, trimethylsiloxy-terminated methylhydrogenpolysiloxane; trimethylsiloxy-terminated dimethylsiloxane- methylhydrogensiloxane copolymer; trimethylsiloxy-terminated methylhydrogensiloxane- methylphenylsiloxane copolymer; trimethylsiloxy-terminated dimethylsiloxane- methylhydrogensiloxane-methylphenylsiloxane copolymer; dimethylhydrogensiloxy-terminated dimethylpolysiloxane; dimethylhydrogensiloxy-terminated methylhydrogenpolysiloxane; dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogensiloxane copolymer; dimethylhydrogensiloxy-terminated dimethylsiloxane-methylphenylsiloxane copolymer; and dimethylhydrogensiloxy-terminated methylphenylpolysiloxane. In one particular aspect, the hydride-substituted polyorganosiloxane includes trimethylsiloxy-terminated methylhydrogenpolysiloxane.

[0041] In one aspect, the silane-containing crosslinker can have a hydride content ranging from 0.02 weight percent to 10 weight percent and a viscosity at 25 °C ranging from 10 centipoise to 10,000 centipoise. In a particular aspect, the hydride-substituted polyorganosiloxane includes a trimethylsiloxy-terminated methylhydrogenpolysiloxane having a hydride content of 0.1 weight percent to 5 weight percent, or 0.5 weight percent to 2 weight percent, or 1 weight percent to 2 weight percent. In a particular aspect, the hydride-substituted polyorganosiloxane includes a trimethylsiloxy-terminated methylhydrogenpolysiloxane having a viscosity of 10 cP to 50 cP, or 10 cP to 30 cP, or 15 cP to 30 cP, or 20 cP to 30 cP. In yet another particular aspect, the hydride-substituted polyorganosiloxane includes a trimethylsiloxy-terminated methylhydrogenpolysiloxane having a hydride content of 0.1 weight percent to 5 weight percent, or 0.5 weight percent to 2 weight percent, or 1 weight percent to 2 weight percent, and a viscosity of 10 cP to 50 cP, or 10 cP to 30 cP, or 15 cP to 30 cP, or 20 cP to 30 cP.

[0042] The hydride-substituted polyorganosiloxane component is used in an amount sufficient to cure the composition, for example, in an amount to provide a molar ratio of hydride groups to the sum of vinyl and hydroxyl groups of 1.1 to 2.5.

[0043] In one aspect, the hydride-substituted polyorganosiloxane component can be provided with a carrier fluid. The carrier fluid is preferably a polyorganosiloxane, for example, having the structure M a D b T c Q d , where M, D, T, Q, and subscripts a, b, c, and d are as previously defined. In one aspect, the carrier fluid can include a second alkenyl-terminated polyorganosiloxane, which can be the same as or different from the alkenyl-terminated polyorganosiloxane described previously. For example, the second alkenyl-terminated polyorganosiloxane can differ from the alkenyl-terminated polyorganosiloxane described previously in chemical composition, viscosity, or both. In one aspect, the second alkenyl-terminated polyorganosiloxane can differ from the alkenyl-terminated polyorganosiloxane described previously in viscosity. Preferably, the second alkenyl-terminated polyorganosiloxane is an alkenyl di-terminated polyorganosiloxane, in which both chain ends are alkenyl groups. As used herein, a vinyl group is a group having the formula -CH=CH2, and a “substituted vinyl” group has the formula -CH=CR2, where the R group can independently be hydrogen or a C 1-6alkyl groups. The vinyl concentration in the second alkenyl-terminated polyorganosiloxane can be, for example, 0.001 weight percent to 1 weight percent, or 0.01 weight percent to 0.5 weight percent, or 0.01 weight percent to 0.15 weight percent, or 0.01 weight percent to 0.1 weight percent.

[0044] In one aspect, the carrier fluid can include a second alkenyl-terminated polyorganosiloxane having a viscosity greater than 500 cP, for example, greater than 1,000 cP, or greater than 5,000 cP. In one particular aspect, the second alkenyl-terminated polyorganosiloxane can have a viscosity of 500 cP to 10,000 cP.

[0045] When included in the carrier fluid, the hydride-substituted polyorganosiloxane component can be present in the carrier fluid in a weight ratio of 10:90 to 90:10, or 50:50 to 85:15, or 60:40 to 70:30.

[0046] Other additives can be present in any portion of the curable composition, such as ultraviolet (UV) stabilizers, antistatic agents, dyes, pigments, antimicrobial or antiviral agents, and the like, or combinations thereof. When present, the amount used is selected so that the desired properties of the cured silicone composition are not adversely affected by the presence of the additive.

[0047] The curable silicone composition can be manufactured by combining the various components in any suitable order. In one aspect, the components including the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted copolyorganosiloxane, the alkenyl-substituted MQ polyorganosiloxane, the catalyst, the filler, and the chemical blowing agent are mixed as a first portion (also referred to herein as "Part A") and then combined with the hydride-containing polyorganosiloxane as a second portion (also referred to herein as "Part B"). In one aspect, the weight ratio of Part A to Part B is 6:1 to 25:1, or 9:1 to 20:1, or 9:1 to 15:1, or 9:1 to 12:1.

[0048] The portions can be conditioned, mixed, and cast onto a coating line, such as a continuous coating line. Foaming (blowing) and curing are then performed on the coating line.

[0049] A cured silicone foam layer can be formed by casting the curable composition and then curing the cast composition. The present inventors have unexpectedly discovered that the curable composition can unexpectedly provide a low density in the cast silicone foam. Post-curing can be used to advance the cure to a near complete state, developing the desired physical properties.

[0050] The liquid material of the curable composition can be inputted into Part A and Part B and cast onto a moving release layer. In one aspect, an additional release layer is pulled over the top of the cast mixture, and then the sandwich mixture is passed through the nip of two rotating rollers to regulate the amount of curable composition, which determines the thickness of the partially cured foam, and ultimately the final foam thickness. The gap thickness between the rollers (i.e., the nip gap) can be adjusted to reduce the thickness of the sandwich mixture as it passes between them. In one aspect, the nip gap can be, for example, 0.005 inches to 0.5 inches (0.127 mm to 12.7 mm), or 0.01 inches to 0.1 inches (0.254 mm to 2.54 mm), or 0.01 inches to 0.05 inches (0.254 mm to 1.27 mm), or 0.02 inches to 0.04 inches (0.508 mm to 1.016 mm). During the regulating step, the width of the sandwich mixture can be maintained, but the length of the sandwich mixture can increase as the thickness is reduced. In another aspect, the second release layer on top of the cast mixture and the rollers are not used, and a process such as knife-over-roll can be used to determine the thickness of the partially cured foam, and ultimately the final foam thickness.

[0051] The coated release layer is passed through an oven, which can be heated by at least one platen, by heated air, other means, or a combination thereof to foam and at least partially cure the cast composition. Two or more curing ovens at the same or different temperatures can be used. The temperature in the oven can be 80°F to 200°F (43.3°C to 60°C), and the residence time of the coated carrier in the oven can vary to achieve the desired level of cure. After exiting the oven, when an additional top layer of carrier film is used, this additional top layer can be removed.

[0052] It has been found that only certain carriers provide sufficient adhesion to the release layer. For example, it has been found that under the curing conditions described above, sufficient adhesion to polycarbonate could not be achieved, making further processing infeasible. It has also been found that when the process conditions described above are not used, excessive adhesion to the release layer occurs. Suitable carriers for use with the curing conditions described above are polyesters (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or polybutylene naphthalate). Polyethylene terephthalate is preferred. The processing conditions can be adjusted to achieve effective adhesion with other release layers such as polyolefins (e.g., polyethylene, polypropylene, or ethylene-propylene copolymers), polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyvinyl acetate, polyamides, polyimides, cellulose, fluorinated resins, polyethers, polystyrene resins (e.g., polystyrene), polycarbonates, polyethersulfones, or combinations thereof. In one aspect, the substrate comprises polyethylene terephthalate.

[0053] The foam can be wound on a drum for storage and optional heating / post-curing, for example at a temperature of 100 °F to 300 °F (65.6 °C to 121.1 °C) for 6 hours to 48 hours. Post-curing is particularly useful to reduce compression set, to eliminate volatile compounds, and for full cure if necessary.

[0054] As previously described, an advantage of the present disclosure is that the curable compositions described herein do not rely on the addition of fluorinated surfactants to achieve the desired low density cast silicone foams. The curable compositions (and thus the resulting cured silicone foams) comprise less than 0.1 weight percent, or less than 0.01 weight percent fluorinated surfactant, based on the total weight of the curable composition. In one aspect, fluorinated surfactants are excluded from the curable composition. In one aspect, the cured silicone foams prepared from the curable compositions described herein comprise less than 0.1 weight percent, or less than 0.01 weight percent fluorinated surfactant, based on the total weight of the foamed product. Fluorine concentration can be determined by, for example, energy dispersive x-ray spectroscopy (EDS or EDX). In one aspect, no fluorine is detectable in the foamed product by energy dispersive x-ray spectroscopy.

[0055] In another advantageous feature, no additional solvents (including aqueous buffer solutions) are required for the curable compositions. Thus, additional solvents or aqueous buffer solutions can be present in the curable composition in an amount of less than 0.1 weight percent, or less than 0.01 weight percent, based on the total weight of the curable composition. In one aspect, additional solvents or aqueous buffer solutions are excluded from the curable composition. In one aspect, the pH of the curable composition is no higher than 9, preferably no higher than 8.

[0056] The silicone foams obtained from the curable compositions of the present disclosure are low density cast silicone foams. The low density cast silicone foams according to the present disclosure have a density of less than 240 kilograms per cubic meter (kg / m 3 The term “foam” as used herein refers to a material having a cellular structure (i.e., void content). The foams produced by this method have predominantly closed cells. For example, the low density cast silicone foams can have a closed cell content of at least 50%, or at least 60%. The cell morphology can be characterized, for example, using various microscopy techniques such as optical microscopy or scanning electron microscopy. The low density cast foams are thin foams, for example, having a thickness of less than 1.5 inches (38.1 millimeters), or less than 0.25 inches (6.35 millimeters), or from 0.05 inches to 1.5 inches (1.27 millimeters to 38.1 millimeters), or from 0.05 inches to 1 inch (1.27 millimeters to 25.4 millimeters), or from 0.05 inches to 0.75 inches (1.27 millimeters to 19.05 millimeters), or from 0.05 inches to 0.5 inches (1.27 millimeters to 12.7 millimeters), or from 0.05 inches to 0.25 inches (1.27 millimeters to 6.35 millimeters), or from 0.075 inches to 0.2 inches (1.905 millimeters to 5.08 millimeters), or from 0.08 inches to 0.15 inches (2.032 millimeters to 3.81 millimeters).

[0057] The low density cast silicone foams can advantageously retain their elastic behavior over many compression deformation cycles over the life of the foam, which properties are reflected by the foam’s compression force deflection and compression set. Foams with good resistance to compression set provide cushioning and retain their original shape or thickness under prolonged loads. In one aspect, the silicone foams have a compression force deflection (CFD) of from 0.4 pounds per square inch to 10 pounds per square inch (psi (2.76 kilopascals (kPa) to 68.9 kPa), or from 1 psi to 10 psi (6.9 kPa to 68.9 kPa), or from 1 psi to 5 psi (6.9 kPa to 34.5 kPa), or from 0.4 psi to 5 psi (2.76 kPa to 34.5 kPa) each at 25% deflection and determined according to ASTM D3574-17. The silicone foams can have a compression set of from 0% to 5% determined according to ASTM D1056-20 B2.

[0058] In another advantageous feature, the low density cast silicone foam can have a low water absorption, for example less than 5 wt%, or less than 3 wt%, or less than 2 wt%, as determined by heating a sample at 50 °C for 24 hours, then immersing the sample in water at room temperature for 30 seconds, and determining the weight of water absorbed. In one aspect, the water absorption can be determined by cutting a sample size of 100 mm x 100 mm sample, storing at 50 °C for at least 24 hours, then weighing the sample as W1. Immersing the sample in water at room temperature for 30 seconds, then removing from the water. Removing the water from the surface of the sample, and recording its weight as W2. The percent water absorption is calculated using the formula ((W2-W1) / W1)*100.

[0059] Silicone foams are particularly useful for sealing, vibration management, sound management, pressure management, or a combination thereof in a wide variety of applications including transportation and aerospace.

[0060] Accordingly, one aspect of the present disclosure is a curable composition for making a low density cast silicone foam, comprising: a first part comprising, based on the total weight of the first part, 40 to 70 weight percent of an alkenyl-terminated polyorganosiloxane; 0.1 to 10 weight percent of an alkenyl-substituted co-polyorganosiloxane; 5 to 30 weight percent of an alkenyl-substituted MQ polyorganosiloxane; a cure catalyst; an inorganic filler; and 0.1 to 1.5 weight percent of a chemical blowing agent comprising water, a silanol-terminated polyorganosiloxane; and optionally an alcohol; and a second part comprising a hydride-substituted polyorganosiloxane. The low density cast silicone foam has a density of less than 240 kg / m3 3The low density cast silicone foam has a closed cell content of at least 50%. In one aspect, the first part comprises, based on the total weight of the first part, 50 to 60 weight percent of an alkenyl-terminated polyorganosiloxane; 0.5 to 5 weight percent of an alkenyl-substituted co-polyorganosiloxane; 10 to 25 weight percent, or 15 to 20 weight percent, of an alkenyl-substituted MQ polyorganosiloxane; a cure catalyst; 3 to 35 weight percent, or 10 to 30 weight percent, or 15 to 28 weight percent, of an inorganic filler; and a chemical blowing agent comprising water, an alcohol, and 0.4 to less than 1 weight percent of a silanol-terminated polyorganosiloxane. The first part and the second part can be mixed together to provide a curable composition. The alkenyl-terminated polyorganosiloxane can include a vinyl-terminated polydimethylsiloxane, preferably having a viscosity greater than 10,000 cP, preferably a viscosity of 50,000 to 70,000 cP. The alkenyl-substituted co-polyorganosiloxane can include a vinyl-terminated polydimethylsiloxane containing pendant vinyl groups, preferably having a viscosity less than 1,000 cP, preferably a viscosity of 100 to 500 cP. The cure catalyst can include platinum. The chemical blowing agent can include water, C 1-12 The monohydric alcohol is butanol. The chemical blowing agent can include 0.1 to 0.6 weight percent water, 0.1 to 0.9 weight percent C 1-12 The monohydric alcohol is butanol. The chemical blowing agent can include 0.1 to 0.6 weight percent water, 0.1 to 0.9 weight percent C 1-12a monohydric alcohol; and 0.4 to less than 1 weight percent of a silanol-terminated polyorganosiloxane; each based on the total weight of the first part of the curable composition. The chemical blowing agent can include greater than 0.5 weight percent water and 0.08 to less than 1 weight percent of a silanol-terminated polyorganosiloxane. The curable composition can further include a monomethanol-substituted polyorganosiloxane or a monofunctional silanol. The thickness of the low density cast silicone foam can be less than 1.5 inches (38.1 millimeters), or less than 0.25 inches (6.35 millimeters). The curable composition can include a molar ratio of hydride groups to the sum of vinyl and hydroxyl groups of 1.1 to 2.5. The curable composition can be prepared by a method comprising: combining an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted co-polyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a cure catalyst, an inorganic filler, and a chemical blowing agent to provide a first part; and combining the first part with a second part comprising a hydride-substituted polyorganosiloxane to provide the curable composition. The first part and the second part can be combined in a weight ratio of the first part to the second part of 6: 1 to 25: 1, or 9: 1 to 20: 1, or 9: 1 to 15: 1, or 9: 1 to 12: 1. A fluorinated surfactant can be present in an amount of less than 0.1 weight percent based on the total weight of the curable composition. Preferably, the fluorinated surfactant is excluded from the curable composition. The cured silicone foam layer comprises a cured product of the curable composition.

[0061] In one aspect, a method for forming a silicone foam sheet includes casting a curable composition onto a first release layer; placing a second release layer on a side of the cast curable composition opposite the first release liner to form a multi-layer structure; passing the cast curable composition on the substrate through a nip of two rotating rollers to regulate the amount of curable composition; and curing the curable composition to form a silicone foam sheet. The method can further include combining an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted co-polyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a cure catalyst, an inorganic filler, and a chemical blowing agent to provide a first portion; and combining the first portion with a second portion comprising a hydride-substituted polyorganosiloxane to provide the curable composition. The first portion and the second portion can be combined in a weight ratio of first portion: second portion of 6: 1 to 25: 1, or 9: 1 to 20: 1, or 9: 1 to 15: 1, or 9: 1 to 12: 1. The silicone foam sheet formed according to the methods described herein can have a thickness of 0.05 inches to 1.5 inches (1.27 millimeters to 38.1 millimeters), or 0.05 inches to 1 inch (1.27 millimeters to 25.4 millimeters), or 0.05 inches to 0.75 inches (1.27 millimeters to 19.05 millimeters), or 0.05 inches to 0.5 inches (1.27 millimeters to 12.7 millimeters), or 0.05 inches to 0.25 inches (1.27 millimeters to 6.35 millimeters), or 0.075 inches to 0.2 inches (1.905 millimeters to 5.08 millimeters), or 0.08 inches to 0.15 inches (2.032 millimeters to 3.81 millimeters). The silicone foam sheet can have a closed cell content of at least 50%. The silicone foam sheet can have a density of less than 240 kg / m 3 The silicone foam sheet can have a compressive force deflection at 25% deflection and determined according to ASTM D1056-20 B2 of 1 pound per square inch to 5 pounds per square inch.

[0062] The present disclosure is further illustrated by the following non-limiting examples.

[0063] Example

[0064] The materials used in the following examples are described in Table 1.

[0065] Table 1

[0066] The following general mixing protocol was used to prepare the foams of the present examples.

[0067] A first foam precursor mixture was prepared by adding polyorganosiloxane A, polyorganosiloxane B, polyorganosiloxane C, polyorganosiloxane D, DI water, Pt catalyst, and, when present, BuOH and optional methanol-PDMS to a mixing cup. The mixture was mixed in a FlackTek speedmixer at 2000 revolutions per minute (rpm) for 30 seconds. To this mixture, the fillers (ATH, calcium carbonate, silica) were added sequentially. The mixture was mixed in the speedmixer according to the following protocol: 2100 rpm for 8 seconds, 2300 rpm for 8 seconds, 2500 rpm for 10 seconds, 2650 rpm for 8 seconds, and 2750 rpm for 8 seconds. After mixing, the cup was removed and allowed to cool to 40 °F (4.4 °C).

[0068] A second foam precursor mixture was prepared by mixing a trimethyl terminated MeHSiO siloxane polymer with a vinyl carrier in a 65:35 weight ratio to provide polyorganosiloxane E.

[0069] The first and second foam precursor mixtures were combined in a 10:1 first precursor: second precursor weight ratio. After manually mixing the two components thoroughly for 35 seconds, the mixed composition was dispensed as quickly as possible onto a thin polyethylene terephthalate (PET) sheet (4 mil (0.1016 millimeter (mm)) and drawn between rollers set to a 25 mil (0.025 inch (in); 0.635 mm) nip gap. The resulting foamed material sandwiched between two PET films was placed in a convection oven set to 60 °C for 3 minutes and then placed for an additional 2 minutes for further cure to proceed. After a total of 5 minutes, the cast material was peeled from the backing PET film. The thickness of the foam was then measured and the expansion calculated. After 24 hours (h), the laminated foamed sheet was placed in a convection oven set to 100 °C for 24 hours for post-cure. The post-cured foam was then characterized for density, compression set (25%), and compression permanent set (22 hours, 100 °C) (ASTM D1056-20B2). Pore morphology was characterized using optical microscopy or scanning electron microscopy.

[0070] The amounts of the components used to prepare the foams of the various examples are provided in Table 2, reported as weight fractions based on the total weight of the first foam precursor mixture. Table 2 also shows properties of the various foamed examples.

[0071] Table 2

[0072] The processing conditions for these compositions were as follows: 60 °C for 4 minutes, then 100 °C for 2 minutes as a cure profile. The subsequent post-cure profile at 100 °C for 24 hours was as described for other examples.

[0073] As shown in Table 2, particular combinations of components in particular amounts can provide desirable cast foams having a low density (i.e., less than 15 pcf (240 kg / m3)). Advantageously, Examples 2 and 3 demonstrate that the density can be further reduced (relative to Example 1) by including a combination of DI water, BuOH, and methanol-PDMS. Comparative Example 4 and Example 1 demonstrate that increasing the amount of BuOH can undesirably increase the density of the cast foam. Interestingly, Example 4 demonstrates that DI water can be used as a chemical blowing agent alone (i.e., in the absence of BuOH), provided that the amount of water and hydroxyl-substituted polyorganosiloxane is increased to compensate for the absence of BuOH. Comparative Example 5 demonstrates that even small adjustments to the components of the curable composition can affect the final properties of the cast silicone foam.

[0074] The present disclosure also encompasses the following aspects.

[0075] Aspect 1 : A curable composition for making a low density cast silicone foam, the curable composition comprising: a first portion comprising, based on the total weight of the first portion, 40 to 70 weight percent of an alkenyl-terminated polyorganosiloxane; 0.1 to 10 weight percent of an alkenyl-substituted co-polyorganosiloxane; 5 to 30 weight percent of an alkenyl-substituted MQ polyorganosiloxane; a cure catalyst; an inorganic filler; and 0.1 to 1.5 weight percent of a chemical blowing agent comprising water, a silanol-terminated polyorganosiloxane; and optionally an alcohol; and a second portion comprising a hydride-substituted polyorganosiloxane; wherein the low density cast silicone foam has a density of less than 240 kg / m3. 3 ; and wherein the low density cast silicone foam has a closed cell content of at least 50%.

[0076] Aspect 2: The curable composition of aspect 1, wherein the first part comprises, based on the total weight of the first part: 50 to 60 weight percent of the alkenyl-terminated polyorganosiloxane; 0.5 to 5 weight percent of the alkenyl-substituted co- polyorganosiloxane; 10 to 25 weight percent, or 15 to 20 weight percent of the alkenyl- substituted MQ polyorganosiloxane; the cure catalyst; 3 to 35 weight percent, or 10 to 30 weight percent, or 15 to 28 weight percent of the inorganic filler; and the chemical blowing agent comprising water, an alcohol, and 0.4 to less than 1 weight percent of the silanol-terminated polyorganosiloxane.

[0077] Aspect 3: The curable composition of aspect 1 or 2, wherein the first part and the second part are mixed together to provide the curable composition.

[0078] Aspect 4: The curable composition of any one of aspects 1 to 3, wherein the alkenyl- terminated polyorganosiloxane comprises a vinyl bis-terminated polydimethylsiloxane, preferably having a viscosity greater than 10,000 cP, preferably a viscosity of 50,000 cP to 70,000 cP.

[0079] Aspect 5: The curable composition of any one of aspects 1 to 4, wherein the alkenyl- substituted co-polyorganosiloxane comprises a vinyl bis-terminated polydimethylsiloxane containing pendant vinyl groups, preferably having a viscosity less than 1,000 cP, preferably a viscosity of 100 cP to 500 cP.

[0080] Aspect 6: The curable composition of any one of aspects 1 to 5, wherein the cure catalyst comprises platinum.

[0081] Aspect 7: The curable composition of any one of aspects 1 to 6, wherein the inorganic filler comprises aluminum trihydrate.

[0082] Aspect 8: The curable composition of any one of aspects 1 to 7, wherein the chemical blowing agent comprises water, a C 1-12 monohydric alcohol, and the silanol-terminated polyorganosiloxane, preferably wherein the C 1-12 monohydric alcohol is butanol.

[0083] Aspect 9: The curable composition of aspect 8, wherein the chemical blowing agent comprises: 0.1 to 0.6 weight percent of water, 0.1 to 0.9 weight percent of the C 1-12a monohydric alcohol; and 0.4 to less than 1 weight percent of the silanol-terminated polyorganosiloxane; each based on the total weight of the first portion of the curable composition.

[0084] Aspect 10: The curable composition of any one of aspects 1 to 7, wherein the chemical blowing agent comprises: greater than 0.5 weight percent water and 0.08 to less than 1 weight percent of the silanol-terminated polyorganosiloxane.

[0085] Aspect 11 : The curable composition of any one of aspects 1 to 10, wherein the curable composition further comprises a monomethanol-substituted polyorganosiloxane or a monofunctional silanol.

[0086] Aspect 12: The curable composition of any one of aspects 1 to 11, wherein the low density cast silicone foam has a thickness of less than 1.5 inches (38.1 millimeters), or less than 0.25 inches (6.35 millimeters).

[0087] Aspect 13: The curable composition of any one of aspects 1 to 12, wherein the curable composition comprises a molar ratio of hydride groups to the sum of vinyl and hydroxyl groups of 1.1 to 2.5.

[0088] Aspect 14: The curable composition of any one of aspects 1 to 13, wherein the curable composition is prepared by a process comprising: combining the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted co-polyorganosiloxane, the alkenyl-substituted MQ polyorganosiloxane, the cure catalyst, the inorganic filler, and the chemical blowing agent to provide the first portion; and combining the first portion with the second portion comprising the hydride-substituted polyorganosiloxane to provide the curable composition.

[0089] Aspect 15: The curable composition of aspect 14, wherein the first portion and the second portion are combined in a weight ratio of first portion: second portion of 6: 1 to 25: 1, or 9: 1 to 20: 1, or 9: 1 to 15: 1, or 9: 1 to 12: 1.

[0090] Aspect 16: The curable composition of any one of aspects 1 to 15, wherein a fluorinated surfactant is present in an amount of less than 0.1 weight percent, based on the total weight of the curable composition, preferably wherein fluorinated surfactants are excluded from the curable composition.

[0091] Aspect 17: A cured silicone foam layer comprising a cured product of the curable composition of any one of aspects 1 to 16.

[0092] Aspect 18: A method for forming a silicone foam sheet, the method comprising: casting a curable composition according to any one of aspects 1 to 16 onto a first release layer; placing a second release layer on a side of the casted curable composition opposite the first release liner to form a multi-layer structure; passing the casted curable composition on the substrate through a nip of two rotating rollers to regulate the amount of curable composition that is passed; and curing the curable composition to form the silicone foam sheet.

[0093] Aspect 19: The method of aspect 18, further comprising: combining the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted co-polyorganosiloxane, the alkenyl- substituted MQ polyorganosiloxane, the curing catalyst, the inorganic filler, and the chemical blowing agent to provide a first portion; and combining the first portion with a second portion comprising the hydride-substituted polyorganosiloxane to provide the curable composition.

[0094] Aspect 20: The method of aspect 19, wherein the first portion and the second portion are combined in a first portion:second portion weight ratio of 6: 1 to 25: 1, or 9: 1 to 20: 1, or 9: 1 to 15: 1, or 9: 1 to 12: 1.

[0095] Aspect 21: A silicone foam sheet formed according to the method of any one of aspects 18 to 20.

[0096] Aspect 22: The silicone foam sheet of aspect 21, wherein the silicone foam sheet has a thickness of 0.05 inches to 1.5 inches (1.27 millimeters to 38.1 millimeters), or 0.05 inches to 1 inch (1.27 millimeters to 25.4 millimeters), or 0.05 inches to 0.75 inches (1.27 millimeters to 19.05 millimeters), or 0.05 inches to 0.5 inches (1.27 millimeters to 12.7 millimeters), or 0.05 inches to 0.25 inches (1.27 millimeters to 6.35 millimeters), or 0.075 inches to 0.2 inches (1.905 millimeters to 5.08 millimeters), or 0.08 inches to 0.15 inches (2.032 millimeters to 3.81 millimeters); and the silicone foam sheet has a closed cell content of at least 50%; and a density of less than 240 kg / m 3

[0097] Aspect 23: The silicone foam sheet of aspect 22, wherein the silicone foam sheet has a compression force deflection of 0.4 pounds per square inch to 10 pounds per square inch, or 1 pound per square inch to 5 pounds per square inch at 25% deflection and determined according to ASTM D3574-17.

[0098] ​The compositions, methods, and articles can alternatively be comprised of, consist of, or consist essentially of, any appropriate materials disclosed herein, the

[0099] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other. “Combination” is inclusive of blends, mixtures, alloys, reaction products, or the like. The terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The terms “a” and “an” and “the” do not denote a limitation of quantity and are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. “Or” means “and / or” unless otherwise indicated herein or clearly contradicted by context. Reference throughout this document to “one aspect” means that a particular element described in connection with the aspect is included in at least one aspect described herein, and can or can not be present in other aspects. The term “combination thereof’ as used herein includes one or more of the listed elements, and is open, allowing for the presence of one or more additional unnamed like elements. In addition, it is to be understood that the described elements can be combined in any suitable manner in the various aspects.

[0100] Unless specified to the contrary herein, all test standards are the most recent standard in effect as of the filing date of this application (or, if priority is claimed, the filing date of the earliest priority application in which the test standard is found).

[0101] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The citations of references herein are intended to be, and are, hereby expressly incorporated by reference in their entirety. However, if a term in the present application contradicts or conflicts with a term in the incorporated reference, the term from the present application prevails. The citation of any reference herein is not to be construed as an admission that it is prior art to the present application.

[0102] Compounds are described using standard nomenclature. For example, any position not substituted by any indicated group is understood to have its valency filled by a bond as indicated, or a hydrogen atom. A dash ("-") that is not between two letters or symbols is used to indicate a point of attachment in a substituent. For example, -CHO is attached through carbon of the carbonyl group.

[0103] Exemplary embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments. Variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are expected. Thus, embodiments described herein are not to be construed as being limited to the particular shapes illustrated herein but are to include deviations in shapes that result from, for example, manufacturing. For example, a region illustrated or described as flat can often have rough and / or nonlinear features. Moreover, sharp angles illustrated can be rounded. Thus, the regions illustrated in the figures are schematic and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims.

[0104] While specific embodiments have been described, alternative, modified, changed, and equivalent embodiments, as well as modifications, variations, and equivalents that are apparent to those having ordinary skill in the art may be made without departing from the spirit and scope of the claims. Accordingly, the submitted claims are intended to cover all such alternatives, modifications, changes, equivalents, and variations as falling within the true scope of the claims.

Claims

1. A curable composition for making a low density cast silicone foam, comprising: a first part, the first part comprising, based on the total weight of the first part: 40 to 70 weight percent of an alkenyl-terminated polyorganosiloxane; 0.1 to 10 weight percent of an alkenyl-substituted co-polyorganosiloxane; 5 to 30 weight percent of an alkenyl-substituted MQ polyorganosiloxane; a cure catalyst; an inorganic filler; and 0.1 to 1.5 weight percent of a chemical blowing agent, the chemical blowing agent comprising water, a silanol-terminated polyorganosiloxane; and optionally an alcohol; and a second part, the second part comprising a hydride-substituted polyorganosiloxane; wherein the low density cast silicone foam has a density of less than 240 kg / m 3 ; and wherein the low density cast silicone foam has a closed cell content of at least 50%.

2. The curable composition of claim 1, wherein the first part comprises, based on the total weight of the first part: 50 to 60 weight percent of the alkenyl-terminated polyorganosiloxane; 0.5 to 5 weight percent of the alkenyl-substituted co-polyorganosiloxane; 10 to 25 weight percent, or 15 to 20 weight percent, of the alkenyl-substituted MQ polyorganosiloxane; the cure catalyst; 3 to 35 weight percent, or 10 to 30 weight percent, or 15 to 28 weight percent, of the inorganic filler; and the chemical blowing agent, the chemical blowing agent comprising water, an alcohol, and 0.4 to less than 1 weight percent of the silanol-terminated polyorganosiloxane.

3. The curable composition of claim 1 or 2, wherein the first part and the second part are mixed together to provide the curable composition.

4. The curable composition of any one of claims 1 to 3, wherein the alkenyl-terminated polyorganosiloxane comprises a vinyl bis-terminated polydimethylsiloxane, preferably the alkenyl-terminated polyorganosiloxane has a viscosity greater than 10,000 cP, preferably a viscosity of 50,000 cP to 70,000 cP.

5. The curable composition of any one of claims 1 to 4, wherein the alkenyl-substituted co-polyorganosiloxane comprises a vinyl bis-terminated polydimethylsiloxane containing pendant vinyl groups, preferably the alkenyl-substituted co-polyorganosiloxane has a viscosity less than 1,000 cP, preferably a viscosity of 100 cP to 500 cP.

6. The curable composition of any one of claims 1 to 5, wherein the cure catalyst comprises platinum.

7. The curable composition of any one of claims 1 to 6, wherein the inorganic filler comprises aluminum trihydrate.

8. The curable composition of any one of claims 1 to 7, wherein the chemical blowing agent comprises water, C 1-12 a monohydric alcohol and the silanol-terminated polyorganosiloxane, preferably wherein the C 1-12 The monohydric alcohol is butanol.

9. The curable composition of claim 8, wherein the chemical blowing agent comprises: 0.1 to 0.6 weight percent of water, 0.1 to 0.9 weight percent of the C 1-12 Monohydric alcohol; and 0.4 to less than 1 weight percent of the silanol-terminated polyorganosiloxane; each based on the total weight of the first part of the curable composition.

10. The curable composition of any one of claims 1 to 7, wherein the chemical blowing agent comprises: greater than 0.5 weight percent water, and 0.08 to less than 1 weight percent of the silanol-terminated polyorganosiloxane.

11. The curable composition of any one of claims 1 to 10, wherein the curable composition further comprises a monomethanol-substituted polyorganosiloxane or a monofunctional silanol.

12. The curable composition of any one of claims 1 to 11, wherein the low-density cast silicone foam has a thickness of less than 1.5 inches (38.1 millimeters), or less than 0.25 inches (6.35 millimeters).

13. The curable composition of any one of claims 1 to 12, wherein the curable composition comprises a molar ratio of hydride groups to the sum of vinyl and hydroxyl groups of 1.1 to 2.

5.

14. The curable composition of any one of claims 1 to 13, wherein the curable composition is prepared by a method comprising: combining the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted co- polyorganosiloxane, the alkenyl-substituted MQ polyorganosiloxane, the cure catalyst, the inorganic filler, and the chemical blowing agent to provide the first part; and combining the first part with the second part comprising the hydride-substituted polyorganosiloxane to provide the curable composition.

15. The curable composition of claim 14, wherein the first part and the second part are combined in a first part:second part weight ratio of 6: 1 to 25: 1, or 9: 1 to 20: 1, or 9: 1 to 15: 1, or 9: 1 to 12:

1.

16. The curable composition of any one of claims 1 to 15, wherein a fluorinated surfactant is present in an amount of less than 0.1 weight percent based on the total weight of the curable composition, preferably wherein fluorinated surfactants are excluded from the curable composition.

17. A cured silicone foam layer comprising a cured product of the curable composition of any one of claims 1 to 16.

18. A method for forming a silicone foam sheet, the method comprising: casting the curable composition of any one of claims 1 to 16 onto a first release layer; placing a second release layer on a side of the cast curable composition opposite the first release liner to form a multi-layer structure; passing the cast curable composition on the substrate through a nip of two rotating rollers to regulate the amount of curable composition passed; and curing the curable composition to form the silicone foam sheet.

19. The method of claim 18, further comprising: combining the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted co- polyorganosiloxane, the alkenyl-substituted MQ polyorganosiloxane, the cure catalyst, the inorganic filler, and the chemical blowing agent to provide the first part; and combining the first portion with the second portion comprising the hydride-substituted polyorganosiloxane to provide the curable composition.

20. The method of claim 19, wherein the first portion and the second portion are combined in a first portion:second portion weight ratio of 6: 1 to 25: 1, or 9: 1 to 20: 1, or 9: 1 to 15: 1, or 9: 1 to 12:

1.

21. A silicone foam sheet formed according to the method of any one of claims 18 to 20.

22. The silicone foam sheet of claim 21, wherein the silicone foam sheet has a thickness of 0.05 inches to 1.5 inches (1.27 millimeters to 38.1 millimeters), or 0.05 inches to 1 inch (1.27 millimeters to 25.4 millimeters), or 0.05 inches to 0.75 inches (1.27 millimeters to 19.05 millimeters), or 0.05 inches to 0.5 inches (1.27 millimeters to 12.7 millimeters), or 0.05 inches to 0.25 inches (1.27 millimeters to 6.35 millimeters), or 0.075 inches to 0.2 inches (1.905 millimeters to 5.08 millimeters), or 0.08 inches to 0.15 inches (2.032 millimeters to 3.81 millimeters); and the silicone foam sheet has a closed cell content of at least 50%; and less than 240 kg / m 3 of density.

23. The silicone foam sheet of claim 22, wherein the silicone foam sheet has a compression force deflection of 0.4 pounds per square inch to 10 pounds per square inch, or 1 pound per square inch to 5 pounds per square inch at 25% deflection and determined according to ASTM D1056-20.

Images