Low-density cast silicone foam and its manufacturing

Abstract

A curable composition for producing low-density cast silicone foam comprises a first part and a second part. The first part comprises a specific amount of alkenyl-terminated polyorganosiloxane, alkenyl-substituted copolyorganosiloxane, alkenyl-substituted MQ polyorganosiloxane, curing catalyst, inorganic filler, and chemical blowing agent. The second part comprises a hydride-substituted polyorganosiloxane. The resulting silicone foam has a yield of 240 kg / m³. 3 It is advantageous to have a density of less than 50% and a closed-cell content of at least 50%. Cured silicone foam and methods for producing the same are also described.

Description

[Technical Field]

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

[0002] Flexible silicone foams are widely used for sealing and vibration damping in a wide range of applications, including transportation and electronic equipment. However, while size and mass performance requirements are decreasing, technical performance requirements are increasing. Therefore, there remains a continuing demand for thin silicone foams with superior physical properties.

[0003] The development of low-density cast silicone foams is of great interest due to the expected improvements in compression and mass profile. However, thin cast foams tend to become denser during manufacturing due to compression of the foam sheet and rupture of internal air bubbles. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] U.S. Patent No. 4,608,396 [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, there is a demand for compositions and methods for forming low-density cast silicone foams that meet currently desired physical properties. Furthermore, avoiding the use of fluorinated surfactants, which can affect the uniformity of the foam product and result in suboptimal properties, would be an additional advantage. [Means for solving the problem]

[0006] The curable composition for producing a low-density cast silicone foam comprises a first part and a second part, wherein the first part comprises, based on the total mass of the first part, 40 to 70 mass percent of an alkenyl-terminated polyorganosiloxane; 0.1 to 10 mass percent of an alkenyl-substituted copolyorganosiloxane; 5 to 30 mass percent of an alkenyl-substituted MQ polyorganosiloxane; a curing catalyst; an inorganic filler; and 0.1 to 1.5 mass percent of a chemical blowing agent, the chemical blowing agent comprising water, a silanol-terminated polyorganosiloxane; and optionally, an alcohol, and the second part comprises a hydride-substituted polyorganosiloxane, and the density of the low-density cast silicone foam is less than 240 kg / m , ,

[0011] , and the content of closed cells of the low-density cast silicone foam is at least 50%.

[0007] A cured silicone foam layer comprising a cured product of the curable composition represents another aspect of the present disclosure.

[0008] A method for forming a silicone foam sheet includes the steps of casting a curable composition on a first release layer; disposing a second release layer on a surface of the cast curable composition opposite to the first release liner to form a multilayer structure; passing the cast curable composition on a substrate through a nip of two rotating rollers to meter the amount of the curable composition; and curing the curable composition to form a silicone foam sheet.

[0009] A silicone foam sheet formed by the method represents another aspect of the present disclosure.

[0010] The above and other features are illustrated by the following detailed description.

Embodiments for Carrying Out the Invention

[0011] The inventors have unexpectedly discovered a curable composition for producing low-density cast silicone foams having desired properties, particularly density, compressive deflection, and cellular morphology. An unexpected advantage is that the curable composition described herein can be used in a casting process to provide low-density foams without the aforementioned technical limitations. A further advantage is that low-density cast silicone foams can be produced without the use of fluorinated surfactants. Fluorinated surfactants and other compounds have long been relied upon in the art to stabilize silicone foams during casting and curing. Therefore, as used herein, “fluorinated surfactant” includes nonionic fluorinated polymers known in the art for stabilizing silicone foams, such as fluorinated polyethers and fluorinated polyorganosiloxanes. Special types of fluorinated surfactants, such as the foaming accelerators described in U.S. Patent No. 4,608,396 by Bauman et al. and the references cited in that patent, have been used. However, fluorinated surfactants have come under scrutiny due to their environmental health and safety profile. Therefore, it is desirable to avoid fluorinated surfactants, but conventionally, the use of these surfactants has been necessary to obtain the desired foam structure. Consequently, it was unexpected that low-density cast silicone foams with excellent properties can be produced using the curable compositions described herein, even in the absence of fluorinated surfactants. Thus, this disclosure provides significant advantages.

[0012] Accordingly, one aspect of the present disclosure is a curable composition for producing low-density cast silicone foam. To obtain favorable properties of the low-density cast silicone foam, a specific combination of materials is used for the curable composition, as will be described in more detail herein. The relative amounts of each component in the curable composition can be adjusted to provide desirable properties to the curable silicone foam.

[0013] The curable composition includes a first part and a second part. The curable composition can be produced by mixing the first part and the second part.

[0014] The first part includes an alkenyl-terminated polyorganosiloxane. Suitable polyorganosiloxanes with alkenyl groups at the ends generally have the formula: M a D b T c Q d [where the subscripts a, b, c, and d are zero or positive integers, provided that when both subscripts a and b are equal to zero, there is a restriction that subscript c is 2 or more; M has the formula R3SiO 1 / 2 ; D has the formula R2SiO 2 / 2 ; T has the formula RSiO 3 / 2 ; Q has the formula SiO 4 / 2 ; each R group independently represents hydrogen, a terminally substituted C 1~6 alkenyl group, or a substituted or unsubstituted monovalent hydrocarbon group having 1 to 40 or 1 to 6 carbon atoms each, provided that there is a restriction that at least 1, for example at least 2, of the R groups are alkenyl R groups] represented by. Suitable alkenyl R groups are exemplified by vinyl, allyl, 1-butenyl, 1-pentenyl, and 1-hexenyl, and vinyl is particularly useful. The alkenyl group is bonded to the end of the molecular chain, that is, it is an alkenyl-terminated polyorganosiloxane. Preferably, the alkenyl-terminated polyorganosiloxane is an alkenyl diterminated polyorganosiloxane, and 2 of the 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 groups can independently be hydrogen or a C 1~6 alkyl group]. The vinyl concentration in the alkenyl-terminated polyorganosiloxane can be, for example, 0.001 to 1 mass percent, or 0.01 to 0.5 mass percent, or 0.01 to 0.15 mass percent, or 0.01 to 0.1 mass percent.

[0015] In one embodiment, alkenyl-terminated polyorganosiloxanes may have a viscosity greater than 500 centipoise (cP), for example, greater than 1,000 cP, greater than 5,000 cP, or greater than 10,000 cP. In a particular embodiment, the viscosity of the alkenyl-terminated polyorganosiloxane may be 50,000 to 70,000 cP.

[0016] Other silicon-bonded organic groups in alkenyl-terminated polyorganosiloxanes, if present, are substituted and unsubstituted monovalent hydrocarbon groups having 1 to 40 carbon atoms, e.g., alkyl groups, e.g., methyl, ethyl, propyl, butyl, pentyl, and hexyl; aryl groups, e.g., phenyl, tolyl, and xylyl; aralkyl groups, e.g., benzyl and phenethyl; and halogenated alkyl groups, e.g., 3-chloropropyl and 3,3,3-trifluoropropyl. Methyl and phenyl are particularly useful.

[0017] Alkenyl-terminated polyorganosiloxanes can have linear, partially branched linear, branched, or network molecular structures, or mixtures of such structures. Alkenyl-terminated polyorganosiloxanes include 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-terminated methylvinylsiloxane-methylphenylsiloxane copolymer Examples include vinyl-terminated dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer; dimethylvinylsiloxy-terminated methylvinylpolysiloxane; dimethylvinylsiloxy-terminated methylvinylphenylsiloxane; dimethylvinylsiloxy-terminated dimethylvinylsiloxane-methylvinylsiloxane copolymer; dimethylvinylsiloxy-terminated dimethylsiloxane-methylphenylsiloxane copolymer; dimethylvinylsiloxy-terminated dimethylsiloxane-diphenylsiloxane copolymer; or combinations thereof. In a particular embodiment, alkenyl-substituted polyorganosiloxanes include vinyl-terminated polydimethylsiloxanes.

[0018] Alkenyl-terminated polyorganosiloxanes may be present in the first portion of the curable composition in an amount of 40 to 70 mass percent or 50 to 60 mass percent, respectively, based on the total mass of the first portion of the curable composition.

[0019] In addition to alkenyl-terminated polyorganosiloxanes, the first part of the curable composition comprises an alkenyl-substituted copolyorganosiloxane. Suitable alkenyl-substituted copolyorganosiloxanes generally have the formula: M a D b T c Q d [In the formula, the subscripts a, b, c, and d are zero or positive integers, provided that if both subscripts a and b are equal to zero, then subscript c must be 2 or greater; M is the formula R3SiO] 1 / 2 It has; D is formula R2SiO 2 / 2 It has; T is formula RSiO 3 / 2 It has; Q is formula SiO 4 / 2 It has a hydrogen atom and a terminally substituted carbon atom, and each R group is independently hydrogen. 1~6 The term "alkenyl group" refers to a substituted and unsubstituted monovalent hydrocarbon group having 1 to 40 or 1 to 6 carbon atoms, respectively, provided that at least one of the R groups, for example, at least two, are alkenyl R groups. This is represented as follows. Preferred alkenyl R groups are exemplified by vinyl, allyl, 1-butenyl, 1-pentenyl, and 1-hexenyl, with vinyl being particularly useful. The alkenyl group 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 two-terminated polyorganosiloxane further containing an alkenyl group at a pendant position on the molecular chain. For example, the alkenyl-substituted copolyorganosiloxane may include a vinyl-terminated polydimethylsiloxane having a vinyl pendant group along the polymer chain.

[0020] In one embodiment, an alkenyl-substituted copolyorganosiloxane may have a higher alkenyl content than that of an alkenyl-terminated polyorganosiloxane. For example, the vinyl content of the alkenyl-substituted copolyorganosiloxane can be 0.001 to 5 mass percent, or 0.1 to 4 mass percent, or 0.5 to 4 mass percent, or 1 to 4 mass percent, or 2 to 3 mass percent.

[0021] In one embodiment, the viscosity of the second alkenyl-substituted polyorganosiloxane may be less than 1000 cP, preferably 100 to 500 cP.

[0022] Alkenyl-substituted copolymerosiloxanes may be present in the first portion of the curable composition in an amount of 0.1 to 10 mass percent or 0.5 to 5 mass percent relative to the total mass of the first portion.

[0023] The first part of the curable composition further comprises an alkenyl-substituted MQ polyorganosiloxane. As used herein, "MQ polyorganosiloxane" is defined by the formula: M' a D' b T' c Q' d [In the formula, the subscripts a, b, c, and d are zero or positive integers, provided that if both subscripts a and b are equal to zero, then subscript c must be 2 or greater; M is the formula R3SiO] 1 / 2 It has; D is formula R2SiO 2 / 2 It has; T is formula RSiO 3 / 2 It has; Q is formula SiO 4 / 2 It has a hydrogen atom and a terminally substituted carbon atom, and each R group is independently hydrogen. 1~6 The term "alkenyl group" refers to a substituted and unsubstituted monovalent hydrocarbon group having 1 to 40 or 1 to 6 carbon atoms, respectively, provided that at least one of the R groups, for example, at least two, are alkenyl R groups. This refers to a polyorganosiloxane represented by . Preferably, the 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 group can be bonded at the molecular chain terminus, at a pendant position on the molecular chain, or both. In a particular embodiment, an alkenyl-substituted MQ polyorganosiloxane is a vinyl-substituted MQ polyorganosiloxane.

[0024] In one embodiment, alkenyl-substituted MQ polyorganosiloxanes may have viscosities exceeding 500 cP, for example, exceeding 1,000 cP, or exceeding 5,000 cP, or exceeding 10,000 cP. In a particular embodiment, the viscosity of alkenyl-terminated polyorganosiloxanes may be 5,000 to 20,000 cP, or 10,000 to 20,000 cP.

[0025] Alkenyl-substituted MQ polyorganosiloxanes may be present in the first part of the curable composition in an amount of 5 to 30 mass percent relative to the total mass of the first part of the curable composition. Within this range, alkenyl-substituted MQ polyorganosiloxanes may be present in an amount of 10 to 25 mass percent, or 15 to 20 mass percent.

[0026] The first part of the curable composition may include a curing catalyst, specifically a hydrosilylation reaction catalyst, as a component of a part generally containing a polyorganosiloxane having at least two alkenyl groups per molecule. An effective catalyst accelerates curing by promoting the addition of silicon-bonded hydrogens to the alkenyl multiple bonds. Such catalysts may include noble metals, such as platinum, rhodium, palladium, ruthenium, iridium, or combinations thereof. The catalyst may also include a supporting material, such as activated carbon, aluminum oxide, silicon dioxide, polymer resin, or combinations thereof.

[0027] In one embodiment, the curing catalyst may be present in an amount of up to parts per million by mass (ppmw) of a metal (e.g., platinum). In one embodiment, the curing catalyst may be present in an amount of 1 to 500 ppmw, or 1 to 250 ppmw, or 1 to 100 ppmw, or 1 to 50 ppmw, or 5 to 50 ppmw, or 10 to 50 ppmw.

[0028] Platinum and platinum-containing compounds are preferred, and include, for example, platinum black, alumina-supported platinum powder, silica-supported platinum powder, carbon-supported platinum powder, chloroplatinic acid, alcoholic solutions of chloroplatinic acid, platinum-olefin complexes, platinum-alkenylsiloxane complexes, and catalysts obtained by micronizing dispersions of catalysts in polymer resins such as methyl methacrylate, polycarbonate, polystyrene, and silicone. Combinations of different catalysts can also be used. When using platinum catalyst systems, catalyst poisoning may occur, which can lead to the formation of low-strength uncured or poorly cured silicone compositions. Additional platinum can also be added, but if large amounts of platinum are added to improve curing, the pot life or working time may be adversely affected. Methyl vinyl cyclic compounds can be used as curing retarders, such as Dow Corning's 1-2287 curing inhibitor. Such materials bind to platinum at room temperature to prevent curing, thereby improving working time, but at higher temperatures they release platinum, affecting curing in the required time. The curing time and working time / pot life can be altered by adjusting the levels of platinum and curing retarder. When using higher platinum levels, the typical amount is 100 ppmw or less relative to the total mass of the curable polyorganosiloxane composition. Within this range, the additional platinum concentration (i.e., the amount exceeding the required amount) can be 50 ppmw or more, or 60 ppmw or more, relative to the total mass of the curable polyorganosiloxane composition. Also within this range, the additional platinum concentration can be 90 ppmw or less, or 80 ppmw or less, relative to the total mass of the curable polyorganosiloxane composition.

[0029] The curing retarder concentration (when a curing retarder is used) is 0.3 wt% or less of the total curable polyorganosiloxane composition. Within this range, the curing retarder concentration is 0.005 wt% or more, or 0.025 wt% or more, relative to the total mass of the curable polyorganosiloxane composition. Also within this range, the curing retarder concentration is 0.2 wt% or less, or 0.1 wt% or less, relative to the total mass of the curable composition and the required working time or pot life.

[0030] The first part of a curable composition for the manufacture of low-density cast silicone foam further comprises an inorganic filler for providing desired properties, particularly filling, reinforcing, flame retardancy, or a combination thereof. The inorganic filler may be in the form of a particulate material. The particles may be of any regular or irregular shape, e.g., disc-shaped, fibrous, flake-shaped, plate-shaped, rod-shaped (solid or hollow), spherical (solid or hollow), or whisker-shaped. In one embodiment, the particles are in an irregular spherical shape. The median diameter (which may mean equivalent spherical diameter as defined herein) of each particulate filler may be 0.1 μm (micrometer) to 1 millimeter (mm), or 0.5 to 500 μm, or 1 to 50 μm. The particulate material may optionally exhibit a multimodal distribution of median particle size. The multimodal distribution may result from using two different particulate materials, or a single material having two or more size modes.

[0031] Suitable inorganic fillers may include, for example, ceramics, clays, silicates, and multiple ceramic or glass microspheres. Specific particulate materials may include alumina, aluminum trihydrate, aluminum nitride, aluminum silicate, barium titanate, beryllium, boron nitride, borates (e.g., zinc borate, sodium borate, etc., and their hydrates), calcium carbonate, clay, kaolin, corundum, magnesia, magnesium hydroxide, glass, mica, nanoclay, quartz, silicon carbide, strontium titanate, talc, titanium dioxide (e.g., rutile and anatase, etc.), wollastonite, etc., or combinations thereof. In one embodiment, the filler includes a flame retardant, such as aluminum trihydrate. In a particular embodiment, the inorganic filler may include aluminum trihydrate and at least one of silica or calcium carbonate.

[0032] Inorganic fillers may optionally have an outer surface chemically modified by treatment with a coupling agent. The coupling agent may be a silane or epoxy, for example, 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 helps disperse the particulate filler in a polymer matrix (e.g., silicone foam). Bifunctional silane couplings may have combinations of groups such as vinyl, hydroxyl, and amino groups, for example, 3-aminopropyltriethoxysilane. Silane coatings can also minimize water absorption.

[0033] The inorganic fillers may be present in the first part of the curable composition in amounts of 3 to 35 mass percent, 10 to 30 mass percent, or 15 to 28 mass percent, respectively, based on the total mass of the first part of the curable composition.

[0034] A curable composition for the production of low-density cast silicone foam further comprises a chemical blowing agent. In one embodiment, a physical blowing agent is not included in the curable composition. The chemical blowing agent comprises water, a silanol-terminated polyorganosiloxane, and optionally, an alcohol having 1 to 16 carbon atoms (including diols, triols, etc.). The silanol-terminated polyorganosiloxane may have a viscosity of 20 to 40,000 cP, or 400 to 2,000 cP, or 500 to 1,000 cP. In a particular embodiment, the silanol-terminated polyorganosiloxane comprises a hydroxyl-terminated polydimethylsiloxane. In one embodiment, the alcohol is preferably C 1~12 Alcohol, or C 1~6 It contains an alcohol. In a particular embodiment, the alcohol contains 1-butanol. In a particular embodiment, the alcohol may consist of a monoalcohol. Therefore, in some embodiments, polyols (e.g., diols, triols, etc.) may not be included in the curable composition.

[0035] In one embodiment, the chemical blowing agent is water, C 1~12It contains monoalcohols and silanol-terminated polyorganosiloxanes. For example, the chemical blowing agent is 0.1 to 0.6 mass percent water and 0.1 to 0.9 mass percent C, respectively, based on the total mass of the first part of the curable composition. 1~12 It may contain monoalcohols and silanol-terminated polyorganosiloxanes in a mass percentage of less than 0.4 to 1 percent.

[0036] In one embodiment, the chemical blowing agent comprises water and a silanol-terminated polyorganosiloxane. For example, the chemical blowing agent may contain more than 0.5 mass percent of water and 0.08 to less than 1 mass percent of a silanol-terminated polyorganosiloxane, respectively, based on the total mass of the first part of the curable composition.

[0037] In one embodiment, the chemical blowing agent may further comprise a monocarbinol-substituted polyorganosiloxane, a monofunctional silanol, or both. In a particular embodiment, the chemical blowing agent comprises a silanol-terminated polyorganosiloxane, water, an alcohol (e.g., butanol), and a monocarbinol-substituted polyorganosiloxane.

[0038] Chemical blowing agents may be present in the composition in a total amount of 0.1 to 2.5 mass percent relative to the total mass of the first part of the curable composition. Silanol-terminated polyorganosiloxanes may generally be included in the first part of the composition in an amount of 0.01 to less than 1 mass percent, or 0.4 to less than 1 mass percent, relative to the total mass of the first part of the curable composition.

[0039] The curable composition further comprises a second part. The second part comprises a co-curable hydride-substituted polyorganosiloxane. The hydride-substituted polyorganosiloxane may have at least two silicon-bonded hydrogen atoms per molecule and generally has the formula: M'' a D'' b T'' c Q'' d [In the formula, the subscripts a, b, c, and d are zero or positive integers, provided that if both subscripts a and b are equal to zero, then subscript c is 2 or greater; M'' is the formula R3SiO 1 / 2 It has; D'' is formula R2SiO 2 / 2 It has; T'' is formula RSiO 3 / 2 It has; Q'' is formula SiO 4 / 2 [The R group has the following characteristics, and each R group independently represents a substituted and unsubstituted monovalent hydrocarbon group having hydrogen and 1 to 40 or 1 to 6 carbon atoms, provided that at least two of the R groups are hydrogen.] It is represented as follows: For example, each of the R groups of a polyorganosiloxane having at least two silicon-bonded hydrogen atoms per molecule is independently selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, aryl, phenyl, toluyl, xylyl, aralkyl, benzyl, phenethyl, alkyl halide, 3-chloropropyl, 3,3,3-trifluoropropyl, or a combination thereof. Methyl and phenyl may be preferred.

[0040] Hydrogen can be bonded to silicon at the molecular chain terminus, at a pendant position on the molecular chain, or both. In one embodiment, hydrogen is substituted at the terminus. In one embodiment, at least 3 to 4 hydrogen atoms are present per molecule. The hydrogen-containing polyorganosiloxane component may have a linear, partially branched linear, branched, cyclic, or network molecular structure, or may be a mixture of two or more different polyorganosiloxanes having the exemplified molecular structures.

[0041] Hydride-containing polyorganosiloxanes may include, for example, trimethylsiloxy-terminated methylhydrogen polysiloxane; trimethylsiloxy-terminated dimethylsiloxane-methylhydrogen siloxane copolymer; trimethylsiloxy-terminated methylhydrogen siloxane-methylphenylsiloxane copolymer; trimethylsiloxy-terminated dimethylsiloxane-methylhydrogen siloxane-methylphenylsiloxane copolymer; dimethylhydrogen siloxy-terminated dimethylpolysiloxane; dimethylhydrogen siloxy-terminated methylhydrogen polysiloxane; dimethylhydrogen siloxy-terminated dimethylsiloxane-methylhydrogen siloxane copolymer; dimethylhydrogen siloxy-terminated dimethylsiloxane-methylphenylsiloxane copolymer; and dimethylhydrogen siloxy-terminated methylphenylpolysiloxane. In a particular embodiment, the hydride-substituted polyorganosiloxane includes trimethylsiloxy-terminated methylhydrogen polysiloxane.

[0042] In one embodiment, the silicone hydride-containing crosslinking agent may have a hydride content in the range of 0.02 to 10 mass percent and a viscosity in the range of 10 to 10,000 centipoise at 25°C. In a particular embodiment, the hydride-substituted polyorganosiloxane comprises a trimethylsiloxy-terminated methylhydrogen polysiloxane having a hydride content of 0.1 to 5 mass percent, or 0.5 to 2 mass percent, or 1 to 2 mass percent. In a particular embodiment, the hydride-substituted polyorganosiloxane comprises a trimethylsiloxy-terminated methylhydrogen polysiloxane having a viscosity of 10 to 50 cP, or 10 to 30 cP, or 15 to 30 cP, or 20 to 30 cP. In yet another specific embodiment, the hydride-substituted polyorganosiloxane comprises a trimethylsiloxy-terminated methylhydrogen polysiloxane having a hydride content of 0.1 to 5 mass percent, or 0.5 to 2 mass percent, or 1 to 2 mass percent, and a viscosity of 10 to 50 cP, or 10 to 30 cP, or 15 to 30 cP, or 20 to 30 cP.

[0043] The hydride-substituted polyorganosiloxane component is used in an amount sufficient to cure the composition, for example, in an amount that results in a molar ratio of 1.1 to 2.5 of hydride groups to the total of vinyl and hydroxyl groups.

[0044] In one embodiment, the hydride-substituted polyorganosiloxane component can be supplied together with a carrier fluid. The carrier fluid is preferably, for example, structural M a D b T c Q d [In the formula, M, D, T, Q, and the subscripts a, b, c, and d are as defined above.] This is a polyorganosiloxane having the following characteristics. In one embodiment, the carrier fluid may contain a second alkenyl-terminated polyorganosiloxane, which may be the same as or different from the alkenyl-terminated polyorganosiloxane described above. For example, the second alkenyl-terminated polyorganosiloxane may differ from the alkenyl-terminated polyorganosiloxane described above in terms of chemical composition, viscosity, or both. In one embodiment, the second alkenyl-terminated polyorganosiloxane may differ from the alkenyl-terminated polyorganosiloxane described above in terms of viscosity. Preferably, the second alkenyl-terminated polyorganosiloxane is an alkenyl biterminated polyorganosiloxane, where two of the chain ends are alkenyl groups. As used herein, a vinyl group is a group having the formula -CH=CH2, and a "substituted vinyl group" is a group having the formula -CH=CR2[wherein the formula, the R group is independently hydrogen or C 1~6 It may have an alkyl group. The vinyl concentration in the second alkenyl-terminated polyorganosiloxane can be, for example, 0.001 to 1 mass percent, or 0.01 to 0.5 mass percent, or 0.01 to 0.15 mass percent, or 0.01 to 0.1 mass percent.

[0045] In one embodiment, the carrier fluid may contain 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 a particular embodiment, the viscosity of the second alkenyl-terminated polyorganosiloxane may be between 500 and 10,000 cP.

[0046] When present in the carrier fluid, the hydride-substituted polyorganosiloxane component may be present in the carrier fluid in mass ratios of 10:90 to 90:10, 50:50 to 85:15, or 60:40 to 70:30.

[0047] Other additives, such as ultraviolet (UV) stabilizers, antistatic agents, dyes, pigments, antimicrobial agents, or antiviral agents, or combinations thereof, may be present in any part of the curable composition. If additives are present, the amount used should be selected so as not to adversely affect the desired properties of the curable silicone composition.

[0048] Curable silicone compositions can be produced by combining various components in any preferred order. In one embodiment, a component comprising an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted copolyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a catalyst, a filler, and a chemical blowing agent is mixed as a first part (also referred to herein as "Part A") and then combined with a hydride-containing polyorganosiloxane as a second part (also referred to herein as "Part B"). In one embodiment, the mass 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.

[0049] The mixture is weighed, mixed, and cast onto a coating line, such as a continuous coating line. Then, blowing (foaming) and curing are performed on the coating line.

[0050] A curable silicone foam layer can be formed by casting a curable composition and then curing the cast composition. The inventors unexpectedly discovered that the curable composition can provide an unexpectedly low density in the cast silicone foam. Post-curing treatments can be used to advance the curing to a near-complete state, thereby developing desirable physical properties.

[0051] The liquid material inputs of the curable composition, parts A and B, can be mixed and cast onto a moving release layer. In one embodiment, another release layer is passed over the cast mixture, and the sandwiched mixture is then passed through the nip of two rotating rollers to measure the amount of curable composition, thereby determining the thickness of the partially cured foam and ultimately the thickness of the final foam. The gap thickness between the rollers (i.e., the nip gap) can be adjusted to reduce the thickness of the sandwiched mixture as it passes between them. In one embodiment, the nip gap can be, for example, 0.005 to 0.5 inches (0.127 to 12.7 mm), or 0.01 to 0.1 inches (0.254 to 2.54 mm), or 0.01 to 0.05 inches (0.254 to 1.27 mm), or 0.02 to 0.04 inches (0.508 to 1.016 mm). During the metering process, the width of the sandwiched mixture can be maintained, but the length of the sandwiched mixture may increase as the thickness decreases. In another embodiment, the thickness of the partially cured foam and ultimately the final foam can be determined using a process such as knife-over-rolling, without using a second release layer and rollers on top of the cast mixture.

[0052] The coated release layer is passed through an oven that can be heated by at least one platen, heated air, other means, or a combination thereof, to foam the cast composition and at least partially cure it. Two or more curing ovens of the same or different temperatures can be used. The temperature inside the oven can be 80-200°F (43.3-60°C), and the residence time of the coated carrier in the oven can be varied to achieve the desired curing level. After being removed from the oven, any additional top layers of the carrier film can be removed if used.

[0053] It has been found that only certain carriers exhibit sufficient adhesion to the release layer. For example, it has been found that under the curing conditions described above, sufficient adhesion to polycarbonate is not obtained, making further processing impossible. It has also been found that excessive adhesion to the release layer occurs when the above process conditions are not used. Suitable carriers for use under the above curing conditions are polyesters (e.g., polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, or polybutylene naphthalate). Polyethylene terephthalate is preferred. It may be possible to adjust the processing conditions to achieve effective adhesion with other release layers, such as polyolefins (e.g., polyethylene, polypropylene, or ethylene-propylene copolymer), polyvinyl alcohol, polyvinylidene chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyamide, polyimide, cellulose, fluorinated resin, polyether, polystyrene resin (e.g., polystyrene), polycarbonate, polyethersulfone, or combinations thereof. In one embodiment, the substrate comprises polyethylene terephthalate.

[0054] The foam can be rolled into a drum for storage and optionally subjected to a heat / curing treatment at a temperature of, for example, 100-300°F (65.6-121.1°C) for 6-48 hours. The curing treatment is particularly useful for reducing compression set, removing volatile compounds, and achieving complete curing if necessary.

[0055] As discussed above, the advantage of the present disclosure is that the curable compositions described herein do not rely on the addition of a fluorinated surfactant to achieve the desired low-density cast silicone foam. The curable composition (and thus the resulting cured silicone foam) contains less than 0.1 mass percent or less than 0.01 mass percent of a fluorinated surfactant based on the total mass of the curable composition. In one embodiment, the fluorinated surfactant is not included in the curable composition. In one embodiment, the cured silicone foam produced from the curable composition described herein contains less than 0.1 mass percent or less than 0.01 mass percent of a fluorinated surfactant based on the total mass of the foam product. The fluorine concentration can be determined, for example, by energy-dispersive X-ray spectroscopy (EDS or EDX). In one embodiment, there is no fluorine in the foam product that can be detected by energy-dispersive X-ray spectroscopy.

[0056] In a further advantageous feature, additional solvents, including aqueous buffers, are not required in the curable composition. Therefore, additional solvents or aqueous buffers may be present in the curable composition in an amount of less than 0.1 mass percent or less than 0.01 mass percent relative to the total mass of the curable composition. In one embodiment, the additional solvent or aqueous buffer is not included in the curable composition. In one embodiment, the pH of the curable composition does not exceed 9, preferably not exceeding 8.

[0057] The silicone foam obtained from the curable composition of this disclosure is a low-density cast silicone foam. The density of the low-density cast silicone foam according to this disclosure is 240 kilograms per cubic meter (kg / m³). 3The density is less than 15 pounds per cubic foot. As used herein, the term “foam” refers to a material having a cellular structure, i.e., void content. Foams produced by this method mainly have closed cells. For example, the closed cell content of low-density cast silicone foam may be at least 50%, or at least 60%. The cellular morphology can be characterized, for example, using various microscopy techniques, such as optical microscopy or scanning electron microscopy. Low-density cast foams are thin foams, for example, with thicknesses of less than 1.5 inches (38.1 mm), or less than 0.25 inches (6.35 mm), or 0.05 to 1.5 inches (1.27 to 38.1 mm), or 0.05 to 1 inch (1.27 to 25.4 mm), or 0.05 to 0.75 inches (1.27 to 19.05 mm), or 0.05 to 0.5 inches (1.27 to 12.7 mm), or 0.05 to 0.25 inches (1.27 to 6.35 mm), or 0.075 to 0.2 inches (1.905 to 5.08 mm), or 0.08 to 0.15 inches (2.032 to 3.81 mm).

[0058] Low-density cast silicone foams can favorably maintain their elastic behavior over many compression deflection cycles throughout the foam's lifespan, and their properties are reflected in the foam's compressive deflection and compression set. Foams with good compression set resistance provide cushioning and maintain their original shape or thickness under load over extended periods. In one embodiment, the compressive deflection (CFD) of a silicone foam at 25% deflection, as determined according to ASTM D3574-17, is 0.4–10 pounds per square inch (psi) (2.76–68.9 kilopascals (kPa)), or 1–10 psi (6.9–68.9 kPa), or 1–5 psi (6.9–34.5 kPa), or 0.4–5 psi (2.76–34.5 kPa). The silicone foam may have a compression set of 0–5%, as determined according to ASTM D1056-20 B2.

[0059] In another advantageous feature, low-density cast silicone foam can have low water absorption, for example, less than 5 wt%, less than 3 wt%, or less than 2 wt%, when the water absorption rate is determined by heating the sample at 50°C for 24 hours, then immersing the sample in water at room temperature for 30 seconds, and determining the mass of water absorbed. In one embodiment, the water absorption rate can be determined by cutting out a sample of size 100 mm × 100 mm, storing it at 50°C for at least 24 hours, and then weighing the sample as W1. The sample is immersed in water at room temperature for 30 seconds and removed from the water. The water is removed from the surface of the sample and its mass is recorded as W2. The water absorption percentage is calculated using the formula ((W2-W1) / W1)×100.

[0060] Silicone foams are particularly useful for sealing, vibration control, acoustic control, pressure control, or a combination thereof in a variety of applications, including transportation and aerospace.

[0061] Accordingly, one aspect of the present disclosure is a curable composition for producing a low-density cast silicone foam, comprising a first part and a second part, wherein the first part comprises, based on the total mass of the first part, 40 to 70% by mass of an alkenyl-terminated polyorganosiloxane; 0.1 to 10% by mass of an alkenyl-substituted copolyorganosiloxane; 5 to 30% by mass of an alkenyl-substituted MQ polyorganosiloxane; a curing catalyst; an inorganic filler; and 0.1 to 1.5% by mass of a chemical blowing agent, wherein the chemical blowing agent comprises water, a silanol-terminated polyorganosiloxane, and optionally an alcohol; and the second part comprises a hydride-substituted polyorganosiloxane. The density of the low-density cast silicone foam is 240 kg / m³. 3The closed-cell content of the low-density cast silicone foam is less than 50%. In one embodiment, the first part comprises, with respect to the total mass of the first part, 50 to 60 mass percent of alkenyl-terminated polyorganosiloxane; 0.5 to 5 mass percent of alkenyl-substituted copolyorganosiloxane; 10 to 25 mass percent or 15 to 20 mass percent of alkenyl-substituted MQ polyorganosiloxane; a curing catalyst; 3 to 35 mass percent, or 10 to 30 mass percent, or 15 to 28 mass percent of inorganic filler; and a chemical blowing agent comprising water, alcohol, and less than 0.4 to 1 mass percent of silanol-terminated polyorganosiloxane. The first part and the second part can be mixed together to produce a curable composition. Alkenyl-terminated polyorganosiloxanes may include vinyl-two-terminated polydimethylsiloxanes having a viscosity greater than 10,000 cP, preferably 50,000 to 70,000 cP. Alkenyl-substituted copolyorganosiloxanes may include vinyl-two-terminated polydimethylsiloxanes containing vinyl pendent groups, having a viscosity less than 1,000 cP, preferably 100 to 500 cP. The curing catalyst may include platinum. The chemical blowing agent is water, C 1~12 It may contain monoalcohols and silanol-terminated polyorganosiloxanes, preferably C 1~12 The monoalcohol is butanol. The chemical blowing agent is 0.1 to 0.6 mass percent water and 0.1 to 0.9 mass percent C, respectively, based on the total mass of the first part of the curable composition. 1~12The composition may contain monoalcohols and silanol-terminated polyorganosiloxanes in amounts of less than 0.4 to 1 mass percent. The chemical blowing agent may contain more than 0.5 mass percent of water and silanol-terminated polyorganosiloxanes in amounts of less than 0.08 to 1 mass percent. The curable composition may further contain monocarbinol-substituted polyorganosiloxanes or monofunctional silanols. The thickness of the low-density cast silicone foam may be less than 1.5 inches (38.1 mm) or less than 0.25 inches (6.35 mm). The curable composition may contain a molar ratio of hydride groups to the total of vinyl groups and hydroxyl groups of 1.1 to 2.5. The curable composition can be prepared by a method comprising the steps of: providing a first portion by combining an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted copolyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a curing catalyst, an inorganic filler, and a chemical blowing agent; and providing a curable composition by combining the first portion with a second portion containing a hydride-substituted polyorganosiloxane. The first and second portions can be combined in a mass 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. A fluorinated surfactant may be present in an amount of less than 0.1 mass percent of the total mass of the curable composition. Preferably, the fluorinated surfactant is not included in the curable composition. The cured silicone foam layer contains the curing product of the curable composition.

[0062] In one embodiment, a method for forming a silicone foam sheet includes the steps of: casting a curable composition onto a first release layer; arranging a second release layer on the side of the cast curable composition opposite to the first release liner to form a multilayer structure; measuring the amount of the curable composition by passing the cast curable composition on a substrate through the nibs of two rotating rollers; and curing the curable composition to form a silicone foam sheet. The method may further include the steps of: providing a first portion by combining an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted copolyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a curing catalyst, an inorganic filler, and a chemical blowing agent; and providing a curable composition by combining the first portion with a second portion comprising a hydride-substituted polyorganosiloxane. The first and second parts can be combined in a mass 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. The thickness of the silicone foam sheet formed by the method described herein can be 0.05 to 1.5 inches (1.27 to 38.1 mm), or 0.05 to 1 inch (1.27 to 25.4 mm), or 0.05 to 0.75 inches (1.27 to 19.05 mm), or 0.05 to 0.5 inches (1.27 to 12.7 mm), or 0.05 to 0.25 inches (1.27 to 6.35 mm), or 0.075 to 0.2 inches (1.905 to 5.08 mm), or 0.08 to 0.15 inches (2.032 to 3.81 mm). The closed-cell content of the silicone foam sheet may be at least 50%. The density of the silicone foam sheet is 240 kg / m³. 3 It may be less than 1-5 pounds / square inch. The compressive deflection of the silicone foam sheet at 25% deflection may be 1-5 pounds / square inch, as determined according to ASTM D1056-20 B2.

[0063] The present disclosure will be further illustrated by the following non-limiting embodiments. [Examples]

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

[0065] [Table 1]

[0066] The foam of this example was produced using the following general mixing protocol.

[0067] A first foam precursor mixture was prepared by adding polyorganosiloxane A, polyorganosiloxane B, polyorganosiloxane C, polyorganosiloxane D, DI water, Pt catalyst, and BuOH if present, and optionally carbinol-PDMS, to a mixing cup. The mixture was mixed in a FlackTek speed mixer at 2000 revolutions per minute (rpm) for 30 seconds (s). Fillers (ATH, calcium carbonate, silica) were sequentially added to this mixture. The mixture was mixed in a speed mixer 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 cooled to 40°F (4.4°C).

[0068] A second foam precursor mixture was produced by generating polyorganosiloxane E by mixing a trimethyl-terminated MeHSiO siloxane polymer and a vinyl support in a mass ratio of 65:35.

[0069] The first foam precursor mixture and the second foam precursor mixture were combined in a mass ratio of 10:1. After thoroughly mixing the two components by hand for 35 seconds, the mixed composition was distributed as quickly as possible onto a thin polyethylene terephthalate (PET) sheet (4 mil (0.1016 mm)) and stretched between rollers with a nip gap set to 25 mil (0.025 inch (in); 0.635 mm). The resulting foam material, sandwiched between two PET films, was placed in a convection oven set to 60°C for 3 minutes, followed by an additional 2 minutes to further accelerate curing. After a total of 5 minutes, the cast material was peeled off the backing PET film. The thickness of the foam was then measured and the expansion rate was calculated. After 24 hours (h), for post-curing treatment, the peeled foam sheet was placed in a convection oven set to 100°C for 24 hours. Next, the post-cured foam was characterized for density, compression deflection (25%), and compression set (22 hours, 100°C) (ASTM D1056-20 B2). The cell morphology was characterized using an optical microscope or a scanning electron microscope.

[0070] The amounts of components used in the production of the foam in each example are shown in Table 2, and these are reported as mass fractions relative to the total mass of the first foam precursor mixture. Table 2 also shows the characterization results for each foaming example.

[0071] [Table 2]

[0072] As shown in Table 2, by using specific combinations of components in specific amounts, it is possible to provide a desired cast foam with low density (i.e., less than 15 pcf (240 kg per cubic meter)). Advantageously, Examples 2 and 3 demonstrate that density can be further reduced (compared to Example 1) by including a combination of DI water, BuOH, and carbinol-PDMS. Comparative Examples 4 and 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 alone (i.e., without BuOH) as a chemical blowing agent, however, the amounts of water and hydroxyl-substituted polyorganosiloxane are increased to compensate for the BuOH deficiency. Comparative Example 5 demonstrates that even slight adjustments to the components of the curable composition can affect the final properties of the cast silicone foam.

[0073] This disclosure further encompasses the following aspects:

[0074] Embodiment 1: A curable composition for producing a low-density cast silicone foam, comprising a first part and a second part, wherein the first part comprises, in proportion to the total mass of the first part, 40 to 70 mass percent of alkenyl-terminated polyorganosiloxane; 0.1 to 10 mass percent of alkenyl-substituted copolyorganosiloxane; 5 to 30 mass percent of alkenyl-substituted MQ polyorganosiloxane; a curing catalyst; an inorganic filler; and 0.1 to 1.5 mass percent of a chemical blowing agent, wherein the chemical blowing agent comprises water, silanol-terminated polyorganosiloxane; and optionally, an alcohol, and the second part comprises a hydride-substituted polyorganosiloxane, and the density of the low-density cast silicone foam is 240 kg / m³ 3 A curable composition having a closed-cell content of at least 50% in the low-density cast silicone foam, and less than .

[0075] Embodiment 2: The curable composition according to Embodiment 1, wherein the first part comprises, with respect to the total mass of the first part, 50 to 60 mass percent of an alkenyl-terminated polyorganosiloxane; 0.5 to 5 mass percent of an alkenyl-substituted copolyorganosiloxane; 10 to 25 mass percent or 15 to 20 mass percent of an alkenyl-substituted MQ polyorganosiloxane; a curing catalyst; 3 to 35 mass percent, or 10 to 30 mass percent, or 15 to 28 mass percent of an inorganic filler; and a chemical blowing agent containing water, alcohol, and less than 0.4 to 1 mass percent of a silanol-terminated polyorganosiloxane.

[0076] Embodiment 3: The curable composition according to Embodiment 1 or 2, wherein the first part and the second part are mixed together to produce a curable composition.

[0077] Embodiment 4: The curable composition according to any one of Embodiments 1 to 3, wherein the alkenyl-terminated polyorganosiloxane comprises a vinyl-two-terminated polydimethylsiloxane having a viscosity of more than 10,000 cP, preferably 50,000 to 70,000 cP.

[0078] Embodiment 5: A curable composition according to any one of Embodiments 1 to 4, wherein the alkenyl-substituted copolymerorganosiloxane comprises a vinyl pendent group-containing vinyl two-terminated polydimethylsiloxane having a viscosity of less than 1,000 cP, preferably 100 to 500 cP.

[0079] Embodiment 6: The curable composition according to any one of Embodiments 1 to 5, wherein the curing catalyst contains platinum.

[0080] Embodiment 7: A curable composition according to any one of Embodiments 1 to 6, wherein the inorganic filler comprises aluminum trihydrate.

[0081] Embodiment 8: Chemical blowing agent is water, C 1~12 It comprises a monoalcohol and a silanol-terminated polyorganosiloxane, preferably C 1~12 A curable composition according to any one of embodiments 1 to 7, wherein the monoalcohol is butanol.

[0082] Embodiment 9: The chemical blowing agent is 0.1 to 0.6 mass percent water and 0.1 to 0.9 mass percent C, respectively, relative to the total mass of the first part of the curable composition. 1~12 A curable composition according to embodiment 8, comprising a monoalcohol and a silanol-terminated polyorganosiloxane in a mass of less than 0.4 to 1 percent.

[0083] Embodiment 10: A curable composition according to any one of Embodiments 1 to 7, wherein the chemical blowing agent comprises more than 0.5 mass percent of water and less than 0.08 to 1 mass percent of silanol-terminated polyorganosiloxane.

[0084] Embodiment 11: The curable composition according to any one of Embodiments 1 to 10, further comprising a monocarbinol-substituted polyorganosiloxane or a monofunctional silanol.

[0085] Embodiment 12: The curable composition according to any one of Embodiments 1 to 11, wherein the thickness of the low-density cast silicone foam is less than 1.5 inches (38.1 mm) or less than 0.25 inches (6.35 mm).

[0086] Embodiment 13: A curable composition according to any one of Embodiments 1 to 12, comprising a hydride group with a molar ratio of 1.1 to 2.5 relative to the total of vinyl and hydroxyl groups.

[0087] Aspect 14: A curable composition according to any one of aspects 1 to 13, prepared by a method comprising: providing a first portion by combining an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted copolyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a curing catalyst, an inorganic filler, and a chemical blowing agent; and providing a curable composition by combining the first portion with a second portion comprising a hydride-substituted polyorganosiloxane.

[0088] Embodiment 15: The curable composition according to Embodiment 14, wherein the first part and the second part are combined in a mass 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.

[0089] Embodiment 16: The curable composition according to any one of Embodiments 1 to 15, wherein the fluorinated surfactant is present in an amount of less than 0.1 mass percent of the total mass of the curable composition, and preferably the fluorinated surfactant is not included in the curable composition.

[0090] Embodiment 17: A cured silicone foam layer comprising a cured product of a curable composition according to any one of Embodiments 1 to 16.

[0091] Embodiment 18: A method for forming a silicone foam sheet, comprising the steps of: casting a curable composition according to any one of Embodiments 1 to 16 onto a first release layer; arranging a second release layer on the side of the cast curable composition opposite to the first release liner to form a multilayer structure; measuring the amount of the cast curable composition on a substrate by passing it through the nips of two rotating rollers; and curing the curable composition to form a silicone foam sheet.

[0092] Embodiment 19: The method according to Embodiment 18, further comprising the steps of: providing a first portion by combining an alkenyl-terminated polyorganosiloxane, an alkenyl-substituted copolyorganosiloxane, an alkenyl-substituted MQ polyorganosiloxane, a curing catalyst, an inorganic filler, and a chemical blowing agent; and providing a curable composition by combining the first portion with a second portion comprising a hydride-substituted polyorganosiloxane.

[0093] Embodiment 20: The method according to Embodiment 19, wherein the first part and the second part are joined in a mass 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.

[0094] Embodiment 21: A silicone foam sheet formed by the method described in any one of Embodiments 18 to 20.

[0095] Embodiment 22: The silicone foam sheet has a thickness of 0.05 to 1.5 inches (1.27 to 38.1 mm), or 0.05 to 1 inch (1.27 to 25.4 mm), or 0.05 to 0.75 inches (1.27 to 19.05 mm), or 0.05 to 0.5 inches (1.27 to 12.7 mm), or 0.05 to 0.25 inches (1.27 to 6.35 mm), or 0.075 to 0.2 inches (1.905 to 5.08 mm), or 0.08 to 0.15 inches (2.032 to 3.81 mm); the silicone foam sheet has a closed-cell content of at least 50% and a weight of 240 kg / m². 3 A silicone foam sheet according to embodiment 21, having a density of less than 100%.

[0096] Embodiment 23: The silicone foam sheet according to Embodiment 22, wherein the compressive deflection at 25% deflection, as determined in accordance with ASTM D3574-17, is 0.4 to 10 pounds per square inch, or 1 to 5 pounds per square inch.

[0097] Compositions, methods, and articles may, alternatively, include, consist of, or essentially consist of any suitable materials, processes, or components disclosed herein. Compositions, methods, and articles may, additionally or alternatively, be constructed to exclude, or substantially exclude, any materials (or types), processes, or components that are not otherwise required to achieve the function or purpose of the composition, method, or article.

[0098] All scope disclosed herein includes endpoints, which are independently combinable. “Combination” includes blends, mixtures, alloys, reaction products, etc. Terms such as “first,” “second,” etc., do not indicate any order, quantity, or importance, but are used to distinguish one element from another. The terms “a,” “an,” and “the” do not indicate a limit on quantity, and are construed to encompass both singular and plural forms unless otherwise specified herein or unless clearly contradicted by the context. “Or” means “and / or” unless explicitly stated otherwise. Throughout this specification, any reference to “one aspect” means that a particular element described in relation to an aspect is included in at least one aspect described herein, and may or may not be present in other aspects. As used herein, the term “that combination” includes one or more of the enumerated elements, is open, and allows for the presence of one or more similar elements not described. In addition, the elements described may be combined in any preferred manner in various aspects.

[0099] Unless otherwise specified herein, all test standards are the most current standards in effect on the filing date of this application, or, if priority is claimed, on the filing date of the earliest priority application in which the test standard appears.

[0100] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which this application pertains. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, in the event of any conflict or inconsistency between the terms of this application and the terms of the incorporated references, the terms of this application shall prevail over the conflicting terms of the incorporated references.

[0101] The compounds are described using standard nomenclature. For example, any position not substituted by any group shown is understood to have its valence filled by the indicated bond or hydrogen atom. A dash ("-") without a space between two letters or symbols is used to indicate a substituent bond. For example, -CHO is bonded via the carbonyl group's carbon.

[0102] Exemplary embodiments are described herein with reference to schematic cross-sectional views of idealized embodiments. Therefore, differences in shape from those shown are expected, for example, as a result of manufacturing techniques and / or tolerances. Accordingly, embodiments described herein should be interpreted as not being limited to specific shapes of regions illustrated herein, but including, for example, deviations in shape resulting from manufacturing. For example, a region illustrated or described as flat may typically have rough and / or nonlinear features. Furthermore, an acute angle illustrated may be rounded. Therefore, the regions shown in the figures are essentially schematic, and their shapes are not intended to illustrate the exact shape of the regions, nor are they intended to limit the scope of the claims of the present invention.

[0103] While specific embodiments have been described, alternatives, variations, changes, improvements, and substantially equivalents may arise that are not, or may not, currently foreseeable by the applicant or those skilled in the art. Therefore, the claims filed and potentially amended appendices are intended to encompass all such alternatives, variations, changes, improvements, and substantially equivalents.

Claims

1. A curable composition for producing low-density cast silicone foam, Including the first part and the second part, The first part, with respect to the total mass of the first part, 40–70 mass percent alkenyl-terminated polyorganosiloxanes; 0.1 to 10 mass percent of alkenyl-substituted copoliorganosiloxanes; 5-30 mass percent alkenyl-substituted MQ polyorganosiloxane; Curing catalyst; Inorganic fillers; and Contains 0.1 to 1.5 mass percent of a chemical blowing agent, The aforementioned chemical blowing agent, water, Silanol-terminated polyorganosiloxanes; and Optionally, it includes alcohol. The second portion comprises a hydride-substituted polyorganosiloxane, The density of the low-density cast silicone foam is 240 kg / m³. ３ It is less than, The closed-cell content of the low-density cast silicone foam is at least 50%. Curable composition.

2. The first part, with respect to the total mass of the first part, 50–60 mass percent of alkenyl-terminated polyorganosiloxane; 0.5 to 5 mass percent of alkenyl-substituted copoliorganosiloxanes; 10–25 mass percent or 15–20 mass percent alkenyl-substituted MQ polyorganosiloxane; Curing catalyst; 3 to 35 mass percent, or 10 to 30 mass percent, or 15 to 28 mass percent of inorganic fillers; and A chemical blowing agent containing water, alcohol, and less than 0.4 to 1 mass percent of silanol-terminated polyorganosiloxane. A curable composition according to claim 1, comprising:

3. The curable composition according to claim 1 or 2, wherein the first portion and the second portion are mixed together to produce a curable composition.

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

5. The curable composition according to any one of claims 1 to 4, wherein the alkenyl-substituted copolymerosiloxane comprises a vinyl pendent group-containing vinyl two-terminated polydimethylsiloxane having a viscosity of less than 1,000 cP, preferably 100 to 500 cP.

6. The curable composition according to any one of claims 1 to 5, wherein the curing catalyst contains platinum.

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

8. The aforementioned chemical blowing agent is water, C １～１２ It comprises a monoalcohol and a silanol-terminated polyorganosiloxane, preferably the C １～１２ A curable composition according to any one of claims 1 to 7, wherein the monoalcohol is butanol.

9. Each of the chemical blowing agents is, with respect to the total mass of the first portion of the curable composition, 0.1 to 0.6 mass percent of water, 0.1 to 0.9 mass percent of C １～１２ Monoalcohols; and Silanol-terminated polyorganosiloxanes (0.4 to less than 1 mass percent) The curable composition according to claim 8, comprising:

10. The aforementioned chemical blowing agent, Water exceeding 0.5 mass percent, and Silanol-terminated polyorganosiloxanes (0.08 to less than 1 mass percent) A curable composition according to any one of claims 1 to 7, comprising:

11. A curable composition according to any one of claims 1 to 10, further comprising a monocarbinol-substituted polyorganosiloxane or a monofunctional silanol.

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

13. A curable composition according to any one of claims 1 to 12, comprising a hydride group with a molar ratio of 1.1 to 2.5 relative to the total of vinyl and hydroxyl groups.

14. A step of providing a first portion by combining the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted copolyorganosiloxane, the alkenyl-substituted MQ polyorganosiloxane, the curing catalyst, the inorganic filler, and the chemical blowing agent, A step of providing a curable composition by combining the first portion and the second portion containing the hydride-substituted polyorganosiloxane. A curable composition according to any one of claims 1 to 13, prepared by a method comprising the above.

15. The curable composition according to claim 14, wherein the first part and the second part are combined in a mass 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.

16. The curable composition according to any one of claims 1 to 15, wherein the fluorinated surfactant is present in an amount of less than 0.1 mass percent of the total mass of the curable composition, and preferably the curable composition does not contain the fluorinated surfactant.

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

18. A method for forming a silicone foam sheet, A step of casting a curable composition according to any one of claims 1 to 16 onto a first release layer, A step of forming a multilayer structure by placing a second release layer on the side of the cast curable composition opposite to the first release liner, A step of measuring the amount of curable composition by passing the cast curable composition on the substrate through the nip of two rotating rollers, The process of curing the curable composition to form a silicone foam sheet Methods that include...

19. A step of providing the first portion by combining the alkenyl-terminated polyorganosiloxane, the alkenyl-substituted copolyorganosiloxane, the alkenyl-substituted MQ polyorganosiloxane, the curing catalyst, the inorganic filler, and the chemical blowing agent, A step of providing a curable composition by combining the first portion and the second portion containing the hydride-substituted polyorganosiloxane. The method according to claim 18, further comprising:

20. The method according to claim 19, wherein the first part and the second part are combined in a mass 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.

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

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

23. The silicone foam sheet according to claim 22, wherein the compressive deflection at 25% deflection, as determined in accordance with ASTM D1056-20, is 0.4 to 10 pounds per square inch, or 1 to 5 pounds per square inch.

Images