Silicone foam adhesive composition and use thereof

Abstract

The present disclosure relates to a silicone foam adhesive composition comprising (a) at least one polyorganosiloxane containing at least 2 silicon-bonded alkenyl groups per molecule, (b) at least one polyorganosiloxane containing at least 2 silicon-bonded hydrogen atoms per molecule, (c) a porogen capable of generating hydrogen gas in the presence of (b), comprising (c1) a polyorganosiloxane containing at least 1 silicon-bonded hydroxyl group per molecule, and (c2) water, and (d) a hydrosilylation catalyst; provided that the molar ratio of the hydroxyl groups in component (c2) to the hydroxyl groups in component (c1) is in the range of 1:5 to 20:1. The composition has a lower viscosity, a longer working time, and the cured foam has a lower density, fine and uniform cells.

Description

Technical Field

[0001] This disclosure relates to an organosilicon foam composition and its application. Background Technology

[0002] In accidents involving new energy vehicles, lithium battery fires or explosions are the leading cause. One way to reduce or even eliminate these accidents is to use liquid silicone as a potting material, which serves to conduct heat, dissipate heat, and provide flame retardancy and explosion protection. However, liquid silicone has a relatively high specific gravity, and using it as a battery potting material would increase the weight of the battery pack, reduce the energy density per unit volume, and ultimately affect the energy density.

[0003] Liquid foamed silicone can reduce the weight of battery packs to some extent, but there are few reports on its application in battery potting.

[0004] US4760098B describes a viscous liquid composition comprising a portion A and a portion B, wherein portion A is substantially composed of a vinyl-terminated siloxane, a reactive diluent, a hydroxyl-terminated polysiloxane, water, and a catalyst, and portion B is primarily composed of a hydrosiloxane and a filler. The viscosity of portion A is about 30,000–65,000 cp at 32–34 °C, and the addition of portion B has no significant effect on the viscosity of the foamed mixture. This viscous liquid composition is unsuitable for battery potting.

[0005] CN106589954A discloses a low-viscosity, flame-retardant, room-temperature vulcanizing foamed silicone rubber, comprising α,ω-dihydroxy polydimethylsiloxane with a viscosity of 300–5,000 mPa·s as the main polymer, hydrogen-containing silicone oil, and hydroxyl-terminated silicone oil with a viscosity of 60–150 mPa·s as a pore-forming agent. The density of this foamed silicone rubber is 0.58–0.68 g / cm³. 3 Within this range, it can be used for potting and protection of new energy battery modules. The resulting foam requires a planetary mixer to exhibit the desired properties; however, ensuring uniform foaming remains quite challenging, and the cost of such products is relatively high.

[0006] Example 4 of US4189545A discloses another foamed silicone rubber composition comprising a vinyl polydimethylsiloxane with a viscosity of 380 cps as the host polymer, a hydrogen-containing silicone oil, and water as a pore-forming agent. The pot life of this composition is only 45 s, and the water exhibits poor compatibility with the siloxane.

[0007] Battery potting materials generally have low viscosity due to flowability requirements, and a relatively long workability time is also required for convenient potting operations. However, preparing low-density, uniformly porous silicone foam from foaming compositions with relatively low viscosity and relatively long workability time has always been a challenge in this field. Lower viscosity usually means that bubbles formed by the reaction of silanol groups and hydroxyl groups can easily escape from the composition; a relatively long workability time usually means that the reaction between silanol groups and alkenyl groups starts slowly, making it difficult to quickly solidify and form a network structure to lock in the bubbles generated during foaming. As a result, the density of the resulting foam will be higher. Summary of the Invention

[0008] To address the aforementioned issues, the silicone foam composition provided in this disclosure uses a specific ratio of water and silanol as pore-forming agents, effectively resolving the contradiction between the relatively low viscosity and relatively long workability of the composition and the relatively low density of the foam.

[0009] A first aspect of this disclosure provides an organosilicon foam composition comprising:

[0010] (a) at least one polyorganosiloxane containing at least two alkenyl groups bonded to silicon per molecule.

[0011] (b) at least one polyorganosiloxane containing at least two hydrogen atoms bonded to silicon per molecule.

[0012] (c) A porogen capable of generating hydrogen gas in the presence of (b), comprising

[0013] (c1) Polyorganosiloxanes containing at least one hydroxyl group bonded to silicon per molecule, and

[0014] (c2) Water, and

[0015] (d) Hydrosilylation catalyst;

[0016] The condition is that the molar ratio of the hydroxyl groups in component (c2) to the hydroxyl groups in component (c1) is in the range of 1:5 to 20:1.

[0017] Component (a)

[0018] The polyorganosiloxane (a) is a well-known base polymer in the art. Suitable alkenyl groups contain 2 to 6 carbon atoms, such as vinyl, allyl, propenyl, butenyl, and hexenyl, preferably vinyl, allyl, and propenyl, more preferably vinyl. The organic groups bonded to the remaining silicon atoms on the polyorganosiloxane (a) are each independently selected from monovalent organic groups containing 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, without aliphatic unsaturated groups, such as alkyl groups like methyl, ethyl, propyl, butyl, pentyl, hexyl, and octyl; aryl or alkylaryl groups like phenyl, tolyl, xylyl, mesitylene, ethylphenyl, benzyl, and naphthyl; and halogenated or organofunctionalized derivatives of the above groups such as 3,3,3-trifluoropropyl, o-, p-, and m-chlorophenyl, aminopropyl, propyl 3-isocyanate, and cyanoethyl, preferably methyl and phenyl, more preferably methyl.

[0019] The polyorganosiloxane (a) is typically linear. Some exemplary polyorganosiloxanes (a) can be described by the following formula:

[0020] R 1 R 2 2SiO(R 2 2SiO) m (R 1 R 2 SiO) n SiR 2 2R 1

[0021] In the formula, R 1 Each is an alkenyl group containing 2 to 6 carbon atoms, as shown in the examples above;

[0022] R 2 Each of the above examples refers to a monovalent organic group, particularly a monovalent hydrocarbon group, containing 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and which is either substituted or unsubstituted;

[0023] m is a positive number, and n is 0 or a positive number. Preferably, m+n satisfies that the dynamic viscosity of the polyorganosiloxane (a) at 25°C is in the range of 10 to 5,000 mPa·s, for example, 50 to 2,000 mPa·s.

[0024] The polyorganosiloxane (a) can be a single alkenyl-containing polyorganosiloxane or a mixture of different alkenyl-containing polyorganosiloxanes, differing for example in molecular structure (such as the type and number of substituents) or polysiloxane viscosity. For mixtures of polyorganosiloxanes, m+n represents the average value, and the viscosity range satisfied by m+n is relative to the viscosity of the mixture.

[0025] Generally, silicone foam compositions used as potting materials require low viscosity, and correspondingly, polyorganosiloxanes containing alkenyl groups typically have low viscosity. In one embodiment, component (a) comprises (a1) a first polyorganosiloxane containing at least two silicon-bonded alkenyl groups per molecule and a dynamic viscosity of 10–1,000 mPa·s at 25°C, for example, 100–500 mPa·s, and (a2) a second polyorganosiloxane containing at least two silicon-bonded alkenyl groups per molecule and a dynamic viscosity of 1,000–50,000 mPa·s at 25°C, for example, 5,000–20,000 mPa·s. In this embodiment, the content of component (a1) is preferably greater than or equal to 80 wt%, the percentage being based on the total weight of component (a).

[0026] To improve foam hardness and increase crosslinking sites, component (a) may also contain branched or network-like polyorganosiloxanes, which contain, for example, R 1 SiO 3 / 2 R 2 SiO 3 / 2 The trifunctional unit, and / or SiO 4 / 2 The four functional units, of which R 1 R 2 As previously stated. In one embodiment, component (a) comprises essentially R 1 R 2 2SiO 1 / 2 and SiO 4 / 2 Polyorganosiloxane composed of units, wherein R 1 R 2 As previously stated, “basic” here means that the polyorganosiloxane contains at least 80 mol%, for example at least 90 mol%, or even at least 95 mol% of the aforementioned units.

[0027] In this disclosure, the amount of component (a) is suitably between 20 and 80 wt%, for example, 30 to 70 wt%, the percentage being based on the total weight of the composition.

[0028] Component (b)

[0029] The polyorganosiloxane (b) can be linear, cyclic, branched, or network-like. Linear or cyclic polyorganosiloxanes (b) are typically composed of materials selected from R... 2 3SiO 1 / 2 HR 2 SiO 2 / 2 HR 2 2SiO 1 / 2 and R 2 2SiO 2 / 2 The unit composition, where R 2As mentioned above, branched or network-like polyorganosiloxanes (b) also contain substances such as HSiO 3 / 2 R 2 SiO 3 / 2 The trifunctional unit, and / or SiO 4 / 2 The four functional units, of which R 2 As mentioned above.

[0030] Polyorganosiloxanes (b) used as crosslinking agents are well known in the art and typically contain at least three hydrogen atoms bonded to silicon. To properly balance the two competing reactions of the curing reaction between silanol groups and alkenyl groups and the foaming reaction between silanol groups and hydroxyl groups, the hydrogen content of the polyorganosiloxane used as a crosslinking agent is preferably 1.2 to 1.7 wt%.

[0031] Component (b) of this disclosure also includes polyorganosiloxanes, which, as chain extenders, contain two hydrogen atoms per molecule bonded to the silicon atoms at the ends of the molecular chain, typically expressed by formula HR. 2 2SiO(R 2 2SiO) w SiR 2 Described by 2H, where R 2 As mentioned earlier, w is a positive number. The dynamic viscosity of the polyorganosiloxane as a chain extender at 25°C is suitably between 10 and 2,000 mPa·s, particularly 50 to 2,000 mPa·s. The chain extender can be a single hydrogen-terminated polyorganosiloxane or a mixture of different hydrogen-terminated polyorganosiloxanes. For mixtures, the above viscosity range refers to the overall viscosity of the mixture. It should be understood that the polyorganosiloxane (b) as a crosslinking agent is different from the polyorganosiloxane (b) as a chain extender.

[0032] In one embodiment, component (b) comprises (b1) a polyorganosiloxane containing at least three hydrogen atoms bonded to silicon per molecule as a crosslinking agent and (b2) a polyorganosiloxane containing two hydrogen atoms bonded to the silicon atoms at the end of the molecular chain per molecule as a chain extender. In this embodiment, the hydrogen content of component (b1) is preferably 1.2 to 1.7 wt%, and the content of the polyorganosiloxane containing two hydrogen atoms bonded to the silicon atoms at the end of the molecular chain per molecule and having a dynamic viscosity of 10 to 2,000 mPa·s, for example 50 to 2,000 mPa·s, particularly 500 to 2,000 mPa·s, at 25°C is preferably greater than or equal to 80 wt%, the percentage being based on the total weight of component (b2).

[0033] In this disclosure, the molar ratio of silane groups in component (b) to alkenyl groups in component (a) is preferably in the range of 2:1 to 15:1, for example, 2:1 to 12:1, particularly 2:1 to 8:1.

[0034] In this disclosure, the amount of component (b) is suitably between 20 and 70 wt%, for example, 30 to 60 wt%, the percentage being based on the total weight of the composition.

[0035] Component (c)

[0036] Component (c) acts as a pore-forming agent in the composition, affecting foaming behavior by generating hydrogen gas through reaction with the silanol groups in component (b), but contributing nothing to crosslinking. The molar ratio of the hydroxyl groups in component (c2) to those in component (c1) is preferably in the range of 1:2 to 10:1, for example, 1:1 to 8:1, particularly 2:1 to 6:1.

[0037] Certain exemplary polyorganosiloxanes (c1) can be described by the following formula:

[0038] R 3 R 2 2SiO(R 2 2SiO) p (R 3 R 2 SiO) q SiR 2 2R 3

[0039] Among them, R 2 As mentioned above;

[0040] R 3 Each independently is a hydroxyl group, R 2 As long as at least one R is satisfied 3 The hydroxyl group is acceptable, but R is preferably bonded to the silicon atom at the end of the molecular chain. 3 All are hydroxyl groups;

[0041] p is a positive number, q is 0 or a positive number, preferably p+q satisfies the dynamic viscosity of polyorganosiloxane (C1) at 25°C in the range of 10 to 1,000 mPa·s, for example 50 to 500 mPa·s.

[0042] Polyorganosiloxanes (c1) with the following molecular formula are particularly preferred: HO(Me2SiO) p (HOMeSiO) q OH, where p and q are defined as above.

[0043] The water (c2) is preferably introduced in the form of an aqueous emulsion, such as an oil-in-water silicone emulsion or a water-in-oil silicone reverse emulsion, to promote the dispersion of water in the composition. The aqueous silicone emulsion comprises a polysiloxane oil phase, an aqueous phase, and an emulsifier. The emulsifier may be a nonionic emulsifier, an anionic surfactant, a cationic surfactant, or an amphoteric surfactant, preferably a nonionic surfactant. The aqueous silicone emulsion can be obtained through emulsification processes well known to those skilled in the art. There are no particular limitations on the viscosity of the aqueous silicone emulsion. In a preferred embodiment, component (c2) is an aqueous emulsion of polysiloxane with a dynamic viscosity in the range of 1,000–30,000 mPa·s at 25°C.

[0044] Component (c) may also contain a certain amount of alkanols, which may be organic alcohols containing at least one hydroxyl group, but not alcohols such as alkynols that act as inhibitors of hydrosilylation reactions. These include monohydric alcohols with 1-12 carbon atoms, such as ethanol, n-propanol, isopropanol, n-butanol, n-hexanol, n-octanol, cyclopentanol, cyclohexanol, and cycloheptanol, and polyhydric alcohols with 2-12 carbon atoms, such as ethylene glycol, propylene glycol, glycerol, butanediol, pentanediol, and heptanol. In a preferred embodiment, component (c) does not contain alkanols.

[0045] In this disclosure, the amount of component (c) is suitably less than or equal to 15 wt%, the percentage being based on the total weight of the composition. The amount of component (c1) is preferably 1 to 15 wt%, for example 2 to 10 wt%, and the amount of component (c2) is preferably 0.01 to 1 wt%, for example 0.05 to 0.5 wt%, the percentage being based on the total weight of the composition.

[0046] In this disclosure, the molar ratio of the silane group in component (b) to the hydroxyl group in component (c) is preferably in the range of 1:2 to 15:1, for example 2:1 to 12:1, especially 2:1 to 8:1.

[0047] Component (d)

[0048] Component (d) can be any type of hydrosilylation catalyst used in the prior art for addition curing, preferably a platinum-based catalyst, such as chloroplatinic acid, chloroplatinate, platinum olefin complexes, or platinum alkenylsiloxane complexes. The amount of the platinum-based catalyst is controlled by considerations of the desired curing rate and economy; generally, only an effective amount as a catalyst for the hydrosilylation reaction is required. Typically, the weight of platinum metal in the silicone foam composition is 0.1 to 1,000 ppm, for example, 1-200 ppm.

[0049] Component (e)

[0050] The foam composition may further include an inhibitor (e) to control the workability and curing rate of the composition. The inhibitor may be any type of inhibitor conventionally used in the art, such as alkynyl alcohols like 1-ethynyl-1-cyclohexanol and 2-methyl-3-butyn-2-ol, polyvinylsiloxanes like 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane, and alkyl maleates. The amount of the inhibitor used can be determined based on the chemical structure of the specific inhibitor selected and the desired curing rate. Generally, these inhibitors are added in amounts of 1-50,000 ppm, for example, 10-10,000 ppm, relative to the total weight of the composition.

[0051] Other optional ingredients

[0052] The foaming composition may also contain appropriate amounts of other components, such as fillers (f), diluents (g), color pastes (h), etc., as long as they do not impair the achievement of the purpose of this invention.

[0053] Non-limiting examples of filler (f) include calcium carbonate, silica, silica powder, diatomaceous earth, organomontmorillonite, and titanium dioxide, with silica being particularly preferred. The silica includes fumed silica, precipitated silica, and mixtures thereof. The specific surface area of ​​the silica is determined according to the BET method, suitably within 50 m². 2 / g or more, preferably 100-400m 2 / g, for example, 150-350 mg 2 / g. The silica can be either hydrophilic or hydrophobic.

[0054] Examples of diluents (g) that can be mentioned include dimethyl silicone oil with a dynamic viscosity of 10–5,000 mPa·s at 25°C, MDT-type silicone oil with a dynamic viscosity of 15–300 mPa·s at 25°C, and silicone oil with a kinematic viscosity of 10–100 mm at 25°C. 2 / s mineral oil. While adding diluents typically reduces the viscosity of a composition and alters its rheological properties, the foaming compositions disclosed herein preferably do not contain diluents, considering potential exudation issues.

[0055] In a preferred embodiment of this disclosure, the silicone foam composition comprises:

[0056] (a) 20 to 80 wt% of at least one polyorganosiloxane containing at least two alkenyl groups bonded to silicon per molecule.

[0057] (b1) 1–8 wt% of polyorganosiloxanes containing at least 3 hydrogen atoms bonded to silicon per molecule.

[0058] (b2) 20–70 wt% of polyorganosiloxanes containing two hydrogen atoms bonded to the silicon atoms at the end of the molecular chain per molecule.

[0059] (c1) 1–15 wt% of polyorganosiloxanes containing at least one hydroxyl group bonded to silicon per molecule, and

[0060] (c2) 0.01–1 wt% water, and

[0061] (d) Hydrosilylation catalyst.

[0062] The silicone foam composition disclosed herein is preferably stored in two or more separate packages, wherein the separate packages do not simultaneously contain components (b) and (c), and do not simultaneously contain components (a), (b) and (d).

[0063] The viscosity of the compositions described in this disclosure is suitably between 200 and 10,000 mPa·s at room temperature (23 ± 2) °C, for example, 500 to 5,000 mPa·s, particularly 500 to 2,000 mPa·s. Here, viscosity refers to the mixed viscosity of the composition before curing, and when the composition is stored in two or more separate packages, it also refers to the viscosity of the components in each package. Generally, the higher the viscosity of the composition, the more likely a low-density foam material is to be obtained. This disclosure enables the curing of low-viscosity compositions to obtain low-density foam materials, which is technically challenging.

[0064] The workability time of the compositions described in this disclosure is suitably between 60 s and 5 min, for example, 80 s to 3 min or 100 s to 3 min. Generally, the shorter the workability time of the composition, the faster the reaction between the silanyl and alkenyl groups starts, and the more likely a low-density foam material is obtained. This disclosure enables compositions with relatively long workability times to cure into low-density foam materials, which is technically challenging.

[0065] The second aspect of this disclosure also provides a foam made from the silicone foam composition of the first aspect of this disclosure.

[0066] The composition described in the first aspect of this disclosure is crosslinked or cured, or the components in individually packaged forms as described above are mixed and then crosslinked or cured to obtain the desired product.

[0067] The crosslinking or curing is typically carried out at 15–180°C for 10 min–72 h. Low curing temperature and short curing time are desirable. Considering that the curing and foaming reactions occur simultaneously and are highly sensitive to temperature, to balance these two reactions and obtain a good cell structure, this disclosure preferably involves curing at 20–80°C for 15–60 min, for example, curing at room temperature for 60 min. In this disclosure, room temperature, unless otherwise specified, refers to 23 ± 2°C.

[0068] The density of the foam obtained in this disclosure is between 0.3 and 0.6 g / cm³. 3Within the specified range, the closed-cell ratio is above 90%. Foam density is determined according to standard GB / T 6343-2009, "Determination of Apparent Density of Foamed Plastics and Rubber." Closed-cell ratio is determined according to standard GB / T 10799-2008, "Determination of Open and Closed-Cell Volume Percentage of Rigid Foamed Plastics."

[0069] The third aspect of this disclosure also provides the application of the silicone foam composition of the first aspect of this disclosure as a potting material, particularly a battery potting material.

[0070] The foaming composition disclosed herein exhibits low viscosity, good flowability, and a relatively long workable time, facilitating potting operations. The resulting foam possesses excellent high and low temperature resistance, weather resistance, and electrical insulation properties, effectively protecting the battery during operation, promptly dissipating battery heat, and the presence of cell-like structures further enhances thermal insulation, improving battery safety and lifespan. Furthermore, the relatively low density of the foam disclosed herein effectively mitigates the problem of reduced battery pack energy density caused by the higher specific gravity of traditional liquid potting silicone.

[0071] In this disclosure, "viscosity" is determined according to conventional methods in the art unless otherwise specified. Detailed Implementation

[0072] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0073] Viscosity

[0074] The viscosities of components A and B were measured using a Brookfield viscometer with rotor No. 2 at room temperature (23±2)℃ and a rotation speed of 10 rpm.

[0075] Operable time

[0076] The workable time refers to the time during which components A and B can be used after mixing. "Workable" means that the mixture of components A and B remains a fluid slurry and has not yet begun to solidify. The workable time of this disclosure was measured at room temperature (23±2)℃ and relative humidity 50±10%.

[0077] Foam density

[0078] The test was conducted in accordance with the national standard GB / T 6343-2009.

[0079] Porosity

[0080] Visually observe the uniformity of pores in the cross-sectional area of ​​the foam. When excessively large pores or the absence of pores in certain areas are observed in the cross-section, the uniformity of pores is evaluated as "non-uniform." When no excessively large pores are found in the cross-section and the pores are uniform, the uniformity of pores is evaluated as "uniform."

[0081] Hole size

[0082] The pore size in the central part of the foam cross-section was observed under an electron microscope. When more than 90% of the pores were found to have a maximum diameter of less than or equal to 1 mm, the pore size was evaluated as "fine pores"; otherwise, it was evaluated as "coarse pores".

[0083] The components involved in the following examples and comparative examples

[0084] a1: Dimethylvinylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of approximately 20,000 mPa·s at 25°C and a vinyl content of 0.042 mmol / g, supplied by Wacker Chemie.

[0085] a2: Dimethylvinylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of approximately 500 mPa·s at 25°C and a vinyl content of 0.17 mmol / g, supplied by Wacker Chemie.

[0086] a3: Dimethylvinylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of approximately 200 mPa·s at 25°C and a vinyl content of 0.26 mmol / g, supplied by Wacker Chemie.

[0087] a4: Polyvinyl dimethylsiloxane, dynamic viscosity at 25°C 20,000–23,000 mPa·s, vinyl content 0.24 mmol / g, supplied by Wacker Chemie.

[0088] b1: Hydrogen-containing polydimethylsiloxane, with a dynamic viscosity of approximately 20 mPa·s at 25°C and a hydrogen content of 16.3 mmol / g, provided by Wacker Chemie.

[0089] b2: Dimethylhydrosiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of approximately 1,000 mPa·s at 25°C and a hydrogen content of 0.12 mmol / g, supplied by Wacker Chemie.

[0090] c1: Dimethylhydroxysiloxy-terminated polydimethylsiloxane with a dynamic viscosity of 50–110 mPa·s at 25°C and a hydroxyl content of 1.2 wt%, provided by Wacker Chemie.

[0091] c2: Aqueous emulsion of polydimethylsiloxane with a dynamic viscosity of 5,000–10,000 mPa·s at 25°C and a hydroxyl content of 59.9 wt%, provided by Wacker Chemie.

[0092] d: Platinum-based catalyst, CATALYST EP, supplied by Wacker Chemie.

[0093] e: inhibitor INHIBITOR PT 88, supplied by Wacker Chemie.

[0094] f: Vinyl MQ resin, with a molar ratio of M units to Q units of 0.7:1 and a vinyl content of 0.78 mmol / g, supplied by Wacker Chemie.

[0095] g: Trimethylsiloxy-terminated polydimethylsiloxane, with a dynamic viscosity of approximately 100 mPa·s at 25°C, supplied by Wacker Chemie.

[0096] h: pigment, COLOR PASTE FL BLACK RAL 9005F, supplied by Wacker Chemie.

[0097] Examples 1-3 and Comparative Examples 1-2

[0098] According to the formula in Table 1, mix the components of component A and component B evenly, and then cure the resulting components A and B at room temperature for 60 minutes to obtain silicone foam.

[0099] Table 2 lists the workability, foam density, porosity, and pore size of the foams in each example and comparative example. Examples 1-3 used water and hydroxyl-terminated polydimethylsiloxane as porogens, resulting in foams with low density and fine, uniform pores. Comparative Example 1 used only hydroxyl-terminated polydimethylsiloxane as a porogen, resulting in foams with high density. Comparative Example 2 used only water as a porogen, resulting in foams with coarse pores, non-uniform pores, and high density.

[0100] Table 1

[0101]

[0102]

[0103] *: The molar number of Si-Vi groups is calculated based on components a1-a4 and f.

[0104] Table 2

[0105]

Claims

1. A silicone foam composition comprising: (a) 20-80 wt% of at least one polyorganosiloxane containing at least two alkenyl groups bonded to silicon per molecule, (b) at least one polyorganosiloxane containing at least two hydrogen atoms bonded to silicon per molecule, comprising (b1) 1-8 wt% of a polyorganosiloxane containing at least three hydrogen atoms bonded to silicon per molecule and (b2) 20-70 wt% of a polyorganosiloxane containing two hydrogen atoms bonded to the silicon atoms at the end of the molecular chain per molecule. (c) A porogen capable of generating hydrogen gas in the presence of (b), comprising (c1) 1-15 wt% of polyorganosiloxanes containing at least one hydroxyl group bonded to silicon per molecule, and (c2) 0.01~1 wt% water, and (d) Hydrosilylation catalyst; The conditions are that the molar ratio of hydroxyl groups in component (c2) to hydroxyl groups in component (c1) is in the range of 1:5 to 20:1, and the dynamic viscosity of the composition before curing is 200 to 10,000 mPa·s at (23±2) °C, and the dynamic viscosity is measured by a Brookfield viscometer using rotor No. 2 at a speed of 10 rpm.

2. The composition according to claim 1, characterized in that, The molar ratio of the hydroxyl groups in component (c2) to the hydroxyl groups in component (c1) is in the range of 1:2 to 10:

1.

3. The composition according to claim 1 or 2, characterized in that, The content of component (c) is less than or equal to 15 wt% of the total weight of the composition.

4. The composition according to claim 1 or 2, characterized in that, The molar ratio of silane groups in component (b) to alkenyl groups in component (a) is in the range of 2:1 to 15:

1.

5. The composition according to claim 1 or 2, characterized in that, The molar ratio of silane groups in component (b) to hydroxyl groups in component (c) is in the range of 1:2 to 15:

1.

6. The composition according to claim 1 or 2, characterized in that, The dynamic viscosity of component (c1) at 25°C is 10~1,000 mPa·s.

7. The composition according to claim 1 or 2, characterized in that, The content of polyorganosiloxane in component (a) having at least 2 alkenyl groups bonded to silicon per molecule and a dynamic viscosity of 10~1,000 mPa·s at 25°C is greater than or equal to 80 wt%.

8. The composition according to claim 1, characterized in that, The hydrogen content of component (b1) is 1.2~1.7 wt%.

9. The composition according to claim 1 or 8, characterized in that, The content of polyorganosiloxane in component (b2) containing 2 hydrogen atoms bonded to the silicon atoms at the end of the molecular chain per molecule and having a dynamic viscosity of 10~2,000 mPa·s at 25°C is greater than or equal to 80 wt%.

10. A foam formed after crosslinking the composition according to any one of claims 1 to 9.

11. The use of the composition according to any one of claims 1 to 9 as a potting material.

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