TWI726025B - Sponge-forming liquid silicone rubber composition and silicone rubber sponge - Google Patents

Abstract

The present invention provides a sponge-forming liquid silicone rubber composition that forms a low-density sponge with a uniform and fine continuous bubble structure.

The sponge-forming liquid silicone rubber composition of the present invention contains at least: (A) an organopolysiloxane having at least two alkenyl groups in one molecule; (B) at least two bonded silicon atoms in one molecule Organopolysiloxane containing hydrogen atoms; (C) a mixture composed of water and an inorganic thickener; (D) a nonionic surfactant with an HLB value of 3 or more and a nonionic surfactant with an HLB value of less than 3. A surfactant composed of an ionic surfactant; (E) a hydrosilation reaction catalyst; and (F) a hardening retarder.

Description

Sponge-forming liquid silicone rubber composition and silicone rubber sponge

The present invention relates to a sponge-forming liquid silicone rubber composition and a silicone rubber sponge obtained by removing water after crosslinking the composition.

Silicone rubber sponge has excellent heat resistance, weather resistance and light weight, so it is used for rollers or conveyor belts of image forming devices such as automobile parts, photocopiers or printers, and various other sealing parts.

As a silicone rubber composition used to form such a silicone rubber sponge, for example, a sponge-forming liquid silicone rubber composition is known, which comprises: a molecule having at least two bonds with silicon atoms Two organopolysiloxanes of bound alkenyl groups, organopolysiloxanes with at least 2 hydrogen atoms bonded to silicon atoms in a molecule, water containing bentonite clay, nonionic surfactants, and hydrosilation reactions Catalyst (refer to Patent Document 1); a sponge-forming liquid silicone rubber composition comprising: a diorganopolysiloxane in which both ends of the molecular chain are terminated with alkenyl groups and the side chains of the molecular chain do not have alkenyl groups Alkanes, two organopolysiloxanes with at least 2 alkenyl groups in the side chain of the molecular chain, organopolysiloxanes with at least 2 hydrogen atoms bonded to silicon atoms in one molecule, a mixture of water and bentonite clay, Nonionic surfactant, catalyst for hydrosilation reaction, and curing retarder (see Patent Document 2).

However, if such a sponge-forming liquid silicone rubber composition is used, in order to form a low density It is difficult to uniformly disperse the silicone rubber composition in the water by increasing the amount of water used to increase the amount of water. Moreover, it is difficult to form a uniform and fine continuous bubble structure in the obtained silicone rubber sponge.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2004-346248

[Patent Document 2] Japanese Patent Laid-Open No. 2008-214625

The object of the present invention is to provide a sponge-forming liquid silicone rubber composition that forms a low-density silicone rubber sponge with a uniform and fine continuous cell structure. In addition, another object of the present invention is to provide a low-density silicone rubber sponge with a uniform and fine continuous cell structure.

The sponge-forming liquid silicone rubber composition of the present invention contains at least: (A) 100 parts by mass of organopolysiloxane having at least two alkenyl groups in one molecule; (B) having at least two bonds in one molecule Organopolysiloxanes of hydrogen atoms bonded to silicon atoms {The hydrogen atoms bonded to silicon atoms in this component are 0.4-20 mol relative to the alkenyl group 1 mol in the above component (A). The amount}; (C) 100~1000 parts by mass of a mixture of water and inorganic thickener; (D) (D-1) a nonionic surfactant with an HLB value of 3 or more and (D- 2) Surfactant composed of nonionic surfactant with HLB value less than 3 {wherein, the mass ratio of (D-1) component to (D-2) component is at least 1} 0.1-15 parts by mass; (E) Catalyst for hydrosilation reaction (amount sufficient to crosslink the composition); and (F) 0.001 to 5 parts by mass of hardening retarder.

The component (A) preferably contains (A-1) 10~90% by mass and (A-2) 10~90% by mass of organopolysiloxane, and (A-1) has an average of 2 at the end of the molecular chain The diorganopolysiloxane having an alkenyl group and no alkenyl group in the side chain of the molecular chain, (A-2) is a diorganopolysiloxane having at least 2 alkenyl groups in the side chain of the molecular chain.

(C) The inorganic tackifier in the component is preferably bentonite clay.

Furthermore, the present composition preferably contains at most 20 parts by mass of (G) silica fine powder with respect to 100 parts by mass of component (A).

In addition, the silicone rubber sponge of the present invention is obtained by crosslinking the sponge-forming liquid silicone rubber composition and removing water from the silicone rubber.

The silicone rubber sponge preferably has an average bubble diameter of 1 μm or more and less than 50 μm, and the continuous bubble rate is 90% or more.

The sponge-forming liquid silicone rubber composition of the present invention can form a low-density sponge with a uniform and fine continuous cell structure with good moldability. In addition, the silicone rubber sponge of the present invention has a uniform and fine continuous bubble structure and low density.

The component (A) is the main agent of the composition, and it is an organopolysiloxane having at least two alkenyl groups in one molecule. As the alkenyl group in the component (A), an alkenyl group having 2 to 12 carbon atoms such as a vinyl group, an allyl group, and a hexenyl group can be exemplified, and a vinyl group is preferred. In addition, examples of organic groups bonded to silicon atoms other than alkenyl groups in component (A) include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, and nonyl groups. , Decyl, undecyl, dodecyl and other C1-C12 alkyl groups; phenyl, tolyl, xylyl, naphthyl and other C6-C12 aryl groups; benzyl, styrene C7~12 aralkyl groups such as bases; The above-mentioned alkyl substituted with halogen such as 3-chloropropyl and 3,3,3-trichloropropyl. Preferably it is methyl.

(A) The molecular structure of component (A) is not limited, and examples can be: linear, partially branched linear, branched, cyclic, dendritic, preferably linear, partially branched Chain-like. (A) The component may also be a mixture of two or more kinds of these molecular structures.

Such (A) component is preferably (A-1) having an average of 2 alkenyl groups at the end of the molecular chain and no alkenyl group in the side chain of the molecular chain and (A-2) in the molecular chain A mixture of two organopolysiloxanes with at least 2 alkenyl groups in the side chain.

(A-1) The component is a diorganopolysiloxane having an average of 2 alkenyl groups at the end of the molecular chain and no alkenyl groups in the side chain of the molecular chain. Specifically, dimethylvinylsilyloxy is exemplified End-capped dimethylpolysiloxane, dimethylvinylsiloxy-terminated dimethylsiloxane-methylphenylsiloxane copolymer, the main chain contains dimethylsiloxane repeating units And the main chain is partially branched, and the molecular chain end is a branched dimethyl polysiloxane terminated by a dimethyl vinyl silanoxy group, preferably a diorganopolysiloxane whose main chain is substantially linear Oxane. The viscosity of this component (A-1) at 25°C is not limited, but it is preferably in the range of 0.05 to 1000 Pa‧s.

(A-2) The component is a diorganopolysiloxane having at least 2 alkenyl groups in the side chain of the molecular chain. Specifically, it can be exemplified: trimethylsiloxy terminated methyl vinyl polysiloxane , Trimethylsilyloxy-terminated dimethylsiloxane-methylvinylsiloxane copolymer, trimethylsilyloxy-terminated dimethylsiloxane-methylvinylsiloxane -Methylphenylsiloxane copolymer, the main chain contains dimethylsiloxane repeating units and methylvinylsiloxane repeating units, and the main chain is partially branched, and the molecular chain ends with trimethylsilyloxy The blocked branched dimethylsiloxane-methylvinylsiloxane copolymer is preferably a diorganopolysiloxane whose main chain is substantially linear. The viscosity of this component (A-2) at 25°C is not limited, but it is preferably in the range of 0.05 to 1000 Pa‧s.

The blending ratio of (A-1) component and (A-2) component is not limited, but the obtained silicone rubber In terms of improving the shrinkage rate of the sponge, the above-mentioned (A) component preferably contains 10 to 90% by mass of (A-1) and 10 to 90% by mass of (A-2).

The component (B) is the crosslinking agent of the composition, which is an organopolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule. (B) The bonding position of the hydrogen atom of the silicon atom in the component (B) is not limited, and the molecular chain end and/or the molecular chain side chain can be exemplified. Examples of the organic group bonded to the silicon atom in the component (B) include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and undecane. Alkyl groups with carbon numbers 1-12 such as phenyl and dodecyl groups; aryl groups with carbon numbers 6-12 such as phenyl, tolyl, xylyl, naphthyl, etc.; benzyl and phenethyl groups with carbon numbers 7-12 The aralkyl group; the above-mentioned alkyl substituted by halogen such as 3-chloropropyl, 3,3,3-trichloropropyl, etc. Preferably it is methyl.

As such (B) component, exemplified are: dimethylpolysiloxane terminated with dimethylhydrosilalkoxy, dimethylsilicone-methylhydrosiloxane terminated with dimethylhydrosiloxane Oxyane copolymer, trimethylsilyloxy-terminated methylhydropolysiloxane, trimethylsiloxyl-terminated dimethylsiloxane-methylhydrosiloxane copolymer, containing (CH ₃ ) _{Organopolysiloxanes of siloxane units represented by 3} SiO _1/2 , siloxane units represented by H(CH ₃ ) ₂ SiO _1/2 , and siloxane units represented by _{SiO 4/2} , Preferably a linear organopolysiloxane.

The content of the component (B) is an amount within the range of 0.4-20 mol, preferably 1.5-20 mol, relative to 1 mol of the alkenyl group in the component (A). The amount within the range of mol may become the amount within the range of 1.5-10 mol. This is because if the molar number of hydrogen bonding silicon atoms in component (B) is within the above range, the compression set of the obtained silicone rubber sponge can be improved.

The component (C) is a mixture composed of water and an inorganic tackifier, which is made by removing the water in the component (C) from the silicone rubber obtained by cross-linking the composition The composition of silicone rubber sponge. As far as (C) component is stably dispersed in (A) component, (C) component The water is preferably ion exchange water.

The purpose of the formulation of the inorganic tackifier in the component (C) is to increase the viscosity of water so that the component (C) is easily dispersed in the component (A), and the dispersion state of the component (C) is kept stable. As the inorganic tackifier, there are natural or synthetic ones, such as bentonite clay, montmorillonite, hectorite, saponite, zinc bentonite, aluminum bentonite and nontronite, and other natural or synthetic bentonite clays; Magnesium aluminum silicate; and these compounds with water-soluble organic polymers such as carboxyvinyl polymers. Preferably, it is bentonite clay such as bentonite or montmorillonite. As such a bentonite clay, for example, Smectone SA (manufactured by KUNIMINE INDUSTRIES Co., Ltd.) which is a hydrothermal composition, and Bengel (manufactured by Ho Jun Co., Ltd.) which is a natural refined product can be obtained. The pH value of the bentonite clay is preferably in the range of pH 5.0 to 9.0 in terms of maintaining the heat resistance of the silicone rubber sponge. In addition, the content of the inorganic thickener in the component (C) is preferably within a range of 0.1 to 10 parts by mass or within a range of 0.5 to 5 parts by mass relative to 100 parts by mass of water.

The content of component (C) is in the range of 100 to 1000 parts by mass relative to 100 parts by mass of the component (A), preferably in the range of 100 to 800 parts by mass, 100 to 500 parts by mass, 200 to 500 parts by mass Within the range, or within the range of 200 to 350 parts by mass. This is because if the content of component (C) is more than the lower limit of the above range, a low-density silicone rubber sponge can be formed. On the other hand, if the content of the component (C) is less than the upper limit of the above range, continuous bubbles with uniform and fine particles can be formed. Structure of the sponge.

The surfactant of component (D) consists of (D-1) a nonionic surfactant with an HLB value of 3 or more and (D-2) a nonionic surfactant with an HLB value of less than 3. As the surfactant of the component (D), exemplified are glycerin fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, sucrose fatty acid esters, polyethylene glycol fatty acid esters, polypropylene glycol fatty acid esters, Polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene-polyoxypropylene block copolymers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters amine.

The component (D) is composed of the component (D-1) and the component (D-2), and the mass ratio of the component (D-1) to the component (D-2) is at least 1, preferably at least 5, and at least 8. At least 10, or at least 15. In addition, the mass ratio of the (D-1) component relative to the (D-2) component is preferably at most 100 or less, more preferably at most 80, at most 70, at most 60, or at most 50. This is because if the mass ratio is more than the above lower limit, a low-density sponge having a uniform and fine continuous cell structure can be formed. On the other hand, if the mass ratio is less than the above upper limit, the component (C) can be dispersed with good stability. In the component (A), a sponge with a uniform and fine continuous bubble structure can be formed as a result.

The content of the component (D) is in the range of 0.1 to 15 parts by mass relative to 100 parts by mass of the component (A), preferably in the range of 0.2 to 3 parts by mass. This is because if the content of component (D) is more than the lower limit of the above range, a sponge having a uniform and fine continuous cell structure can be formed. On the other hand, if the content of the component (D) is less than the upper limit of the above range, a sponge with excellent heat resistance can be formed Silicone rubber sponge.

The component (E) is a catalyst for the hydrosilation reaction for promoting the hydrosilation reaction of the composition, and examples thereof include platinum-based catalysts, palladium-based catalysts, and rhodium-based catalysts, and platinum-based catalysts are preferred. Examples of such (E) component include: chloroplatinic acid; alcohol-modified chloroplatinic acid; coordination compounds of chloroplatinic acid and olefins, vinyl silicone or acetylene compounds; platinum and olefins, vinyl silicon Coordination compounds of oxane or acetylene compounds; other tetrakis (triphenylphosphine) palladium, tris (triphenylphosphine) rhodium chloride.

The content of component (E) is an amount sufficient to cross-link the composition. Specifically, it is preferable that the catalyst metal in component (E) is relative to the total amount of component (A) and component (B), in terms of mass The unit is the amount in the range of 0.01 to 500 ppm or the amount in the range of 0.1 to 100 ppm.

The component (F) is a hardening retarder used to adjust the hardening speed or working life of the composition. Examples of such component (F) include 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, and 3-phenyl-1-butane Alkyn-3-ol, 1-ethynyl-1-cyclohexanol and other alkynols; 3-methyl-3-pentene-1-yne, 3,5-dimethyl-3-hexene-1-yne And other enyne compounds; tetramethyltetravinylcyclotetrasiloxane, Tetramethyltetrahexenylcyclotetrasiloxane and other alkenyl-containing cyclic siloxanes; methyl-tris(3-methyl-1-butyne-3-oxy)silane, vinyl-tris( 3-methyl-1-butyne-3-oxy)silane and the like contain alkyne silane.

The content of the component (F) is appropriately selected according to the usage method or molding method of the composition, but in general, it is in the range of 0.001 to 5 parts by mass relative to 100 parts by mass of the component (A).

In order to improve the strength of the obtained silicone rubber sponge, the composition may further contain (G) silica fine powder. Examples of this (G) component include: smoked silica, precipitated silica; for example, chain organopolysiloxane, cyclic organopolysiloxane, hexamethyldisilazane or various organic Silane, etc. are formed by surface-treating the surface of these fine silica powders. In addition, the BET (Brunauer-Emmett-Teller, Buert) specific surface area of this (G) component is not limited, but it is preferably in ^{the range of 50~350m 2} /g or 80~250m ² /g .

Regarding the content of the (G) component, it is at most 20 parts by mass relative to 100 parts by mass of the (A) component, preferably at most 15 parts by mass or at most 10 parts by mass. In addition, the content of the (G) component is at least 0.1 parts by mass relative to 100 parts by mass of the (A) component.

The composition may also contain reinforcing fillers such as smoked titanium oxide within the scope that does not impair the purpose of the present invention; crushed quartz, crystalline silica, diatomaceous earth, asbestos, aluminosilicic acid, iron oxide, zinc oxide, Non-reinforcing fillers such as calcium carbonate; surface treatment of these fillers with organosilicon compounds such as organosilanes and organopolysiloxanes; pigments such as carbon black and iron oxide; other heat-resistant agents and flame retardants , Internal mold release agent, plasticizer, etc.

This composition can be easily manufactured by uniformly mixing the above-mentioned components or the composition obtained by blending various additives to the above-mentioned components using a well-known kneading method. The mixer used here is not particularly limited as long as it can sufficiently disperse the (C) component and the (D) component in the (A) component, and examples include homomixers, paddle mixers, and homogenizers. Phase dispersing machine, colloid mill, vacuum mixing and stirring mixer, rotation and revolution mixer.

The silicone rubber composition containing these (A) to (F) components or (A) to (G) components can be produced by the following method, for example. Furthermore, in the case of blending the (G) component, it is preferable to prepare a silica masterbatch that blends a part of the (A) component and the (G) component in advance, and then mix the remaining (A) component and other components.

The following method can be exemplified: Put (A) component, (B) component, (C) component, (D) component, (F) component and optionally (G) component into the mixer, stir and mix for a specific time, Immediately prepare (E) component before use; put (A) component, (C) component, (D) component, (E) component and optionally (G) component into the mixer, stir and mix for a specific time, and then Mix (B) component and (F) component before use; put (A) component, (C) component, (D) component and if necessary (G) component into the mixer, stir and mix for a specific time, just before use (B) component, (E) component, and (F) component are pre-mixed.

In terms of storage stability, it is preferable to store in the form of a 3-component sponge-forming liquid silicone rubber composition including the compositions (I) to (III), and to combine them immediately before forming Compounds (I) ~ (III) are mixed, and the composition (I) ~ (III) contains (A) component, (C) component, (D) component, (E) component and optionally (G) respectively Composition (I) containing no ingredients (B) and (F), containing (A), (C), (D), (F) and optionally (G) and not Composition (II) containing (B) component and (E) component, composition (III) containing (B) component and not containing (C) component, (E) component and (F) component; or respectively containing (A) component, (C) component, (D) component, (E) component and optionally (G) component without (B) component and (F) component composition (I); containing (F) Composition (II) without ingredients (B), (C) and (E); compositions containing (B) without (C), (E) and (F) (III). In addition, it is preferable to store in the form of a two-component sponge-forming liquid silicone rubber composition including the compositions (I') and (II"), and to prepare the composition (I') immediately before forming Mix with (II"), the composition (I') and (II") respectively contain (A) component, (C) component, (D) component, (E) component and optionally (G) component And does not contain (B) component and (F) component Composition (I') contains (B) component and (F) component and does not contain (C) component and (E) component (II').

The silicone rubber sponge can be formed from the composition by various methods. Specifically, the composition is injected into the cavity of a molding mold, and kept under pressure at a temperature of less than 100°C, preferably 50 to 90°C, to shape a silicone rubber molded body in a water-containing state, Take it out of the mold and heat it at 120-250°C, and remove water from the silicone rubber molded body in a hydrated state, thereby obtaining a silicone rubber sponge with fine and uniform continuous bubbles. In addition, the composition is sprayed in a rod shape from a nozzle, for example, it is introduced into hot water at 80 to 100°C to harden, and the hardened product is dried with hot air, thereby making a rope-shaped silicone rubber sponge. In addition, apply the composition on a peelable substrate such as a resin film, for example, heat it to 50 to 120°C to harden it and then dry it with hot air to remove water, or heat it to remove the water and harden it, and then remove the peeling. The base material can be formed into a silicone rubber sponge sheet. Or apply this composition on synthetic fiber fabric or glass cloth, for example, heat it to 50~120℃ to harden it and then dry it with hot air to remove water, or heat it to remove water and harden it to form polysilicon Oxygen rubber sponge coated cloth.

Furthermore, the thickness of the silicone rubber layer can be appropriately selected. In terms of effectively utilizing the rubber elasticity of the silicone rubber, it is preferably 0.05 to 80 mm, and particularly preferably 0.1 to 50 mm. In addition, the thickness of the fluororesin or fluororubber layer formed thereon is preferably 5 to 200 μm, and particularly preferably 10 to 100 μm.

In the silicone rubber sponge of the present invention, in terms of small thermal deformation (thermal expansion) caused by heating and excellent deformation recovery, it is preferable that more than 90% of the bubbles are continuous bubbles. Here, whether the bubbles are continuous bubbles can be checked by immersing the sponge in water and performing decompression for a specific time to replace the air in the sponge bubbles with water.

[Example]

The sponge-forming liquid silicone rubber composition and silicone rubber sponge of the present invention will be described in detail with examples. Furthermore, the viscosity in the examples is a value at 25°C.

<density>

Measure the density of silicone rubber sponge according to JIS K 6268.

<Hardness (Asker C)>

The hardness of the silicone rubber sponge is measured according to the test method using the C-type hardness tester specified in JIS K 7312. In addition, during the measurement, two 6mm thick silicone rubber sponge test pieces were used in stacking.

<Tensile strength, elongation>

Measure the tensile strength and elongation of silicone rubber sponge according to JIS K 6251.

<The state of bubbles>

Visually observe the cross section of the silicone rubber sponge test piece, and perform the following evaluations: ‧If the bubble state is uniform throughout the cross section, it is evaluated as uniform; ‧If a part of excessive bubbles is confirmed, it is evaluated as uneven.

<Average bubble diameter>

Use a scanning electron microscope to observe the central part of the silicone rubber sponge test piece cut by a razor blade, measure ^{the diameter of the bubbles per 0.04mm 2} area (the number of bubbles is about 200~300), and average the values Set as the average bubble diameter.

<Shrinkage rate>

Use a mold with a cavity of 70mm in length, 50mm in width, and 6mm in thickness to form a silicone rubber sponge, and measure the length of the long-side direction of the test piece for hardness measurement containing the silicone rubber sponge, and obtain it by the following formula Shrinkage.

[Number 1]

<Continuous bubble rate>

Measure the mass and density of the silicone rubber sponge test piece, and substitute the following formula to obtain the volume of the bubble. Furthermore, the density of the silicone rubber in the formula is a silicone rubber composition made by cross-linking and hardening a silicone rubber composition prepared by the same method except that it does not contain the (C) and (D) components. The density of the rubber test piece.

Furthermore, the silicone rubber sponge test piece was kept in water and placed under a reduced pressure of 760mmHg for 3 minutes to absorb water. The mass of the absorbed water was measured. The density of the water was set to 1.0g/cm ³ and substituted into the following formula Obtain the continuous bubble rate.

[Examples 1, 2, Comparative Examples 1, 2]

Put the following silica masterbatch, component (A), component (C), component (D) and other components into a homomixer (manufactured by Special Machinery Co., Ltd.) at 25°C at the mixing ratio in Table 1. Mix well. A part of the obtained mixture was stored, and the storage stability was checked. Then, the (B) component, (E) component, and (F) component are blended in the obtained mixture, and degassed to prepare a sponge-forming liquid silicone rubber composition. In addition, [SiH/Vi] in Table 1 indicates that the hydrogen atom of the bonded silicon atom in the component corresponding to component (B) in the composition is relative to the component corresponding to component (A) The total molar ratio of the vinyl.

A compression molding machine was used to crosslink and harden the obtained sponge-forming liquid silicone rubber composition under the conditions of 90°C/10 minutes to prepare a water-containing silicone rubber test piece. Then, the test piece was placed in an open system at 200° C. for 4 hours to remove the water in the test piece, and a silicone rubber sponge test piece was obtained. Using this silicone rubber sponge test piece, the density, hardness, tensile strength, elongation, shrinkage, and open cell ratio were measured. The results are shown in Table 1.

Use the following as a silica masterbatch: 100 parts by mass of dimethylpolysiloxane capped at both ends of the molecular chain with a viscosity of 40Pa‧s with a dimethylvinylsiloxy group, and a BET specific surface area of 225m ² /g of 40 parts by mass of smoked silica, 7 parts by mass of hexamethyldisilazane, 2 parts by mass of water, and a viscosity of 20mPa‧s at both ends of the molecular chain terminated by dimethylhydroxysilyloxy 0.2 parts by mass of dimethylsiloxane-methylvinylsiloxane copolymer (vinyl content of about 10.9% by mass) was put into the Ross mixer, mixed uniformly at room temperature, and then heated to 200% under reduced pressure. Heat treatment at ℃ for 2 hours.

As the component (A-1), the following components are used:

(a-1) Ingredients: Dimethylpolysiloxane with a viscosity of 9Pa‧s at both ends of the molecular chain blocked by dimethylvinylsiloxy groups (vinyl content is 0.14% by mass).

(a-2) Ingredients: Dimethylpolysiloxane with a viscosity of 2Pa‧s at both ends of the molecular chain blocked by dimethylvinylsilyloxy groups (vinyl content is 0.23% by mass).

As the (A-2) component, the following components are used:

(a-3) Ingredients: Dimethylvinylpolysiloxane with a viscosity of 7.5Pa‧s at both ends of the molecular chain terminated by trimethylsilyloxy groups (vinyl content is 0.31% by mass).

(a-4) Ingredients: dimethylsiloxane-methylvinylsiloxane copolymer with a viscosity of 350mPa‧s at both ends of the molecular chain blocked by dimethylvinylsiloxane groups (vinyl content is about 1.17 quality the amount%).

(a-5) Ingredients: dimethylsiloxane-methylvinylsiloxane copolymer with a viscosity of 350mPa‧s at both ends of the molecular chain terminated by trimethylsilyloxy groups (vinyl content is about 0.9 quality%).

As component (B), a dimethylsiloxane-methylhydrosiloxane copolymer with a viscosity of 63mPa‧s at both ends of the molecular chain terminated by trimethylsiloxy groups (hydrogen atoms bonded to silicon atoms) The content is about 0.70% by mass).

As the component (C), the following mixture was used: 1 part by mass of bentonite clay (organic polymer composite refined bentonite manufactured by Ho Jun Co., Ltd.; pH 6.5) and 99.0 parts by mass of ion-exchanged water were put into a homomixer, Mix well at room temperature to prepare a mixture of water and bentonite clay.

As the (D) component, the following components are used:

(d-1) Ingredient: HLB4.3 nonionic surfactant (sorbitan fatty acid ester, RHEODOL SP-O10V manufactured by Kao Corporation).

(d-2) Ingredient: HLB1.8 nonionic surfactant (sorbitan fatty acid ester, RHEODOL SP-O30V manufactured by Kao Corporation).

As component (E), 1,3-divinyltetramethyldisiloxane solution of 1,3-divinyltetramethyldisiloxane complex of platinum (platinum metal content is about 4000ppm) .

As component (F), 2 parts by mass of 1-ethynyl-1-cyclohexanol and dimethylpolysiloxane with a viscosity of 10Pa‧s at both ends of the molecular chain blocked by dimethylvinylsiloxy groups are used (The vinyl content is 0.13% by mass) 98 parts by mass of the mixture.

As the pigment masterbatch, 40 parts by mass of iron dan (trade name: Bayferrox, manufactured by Bayer) and a viscosity of 10 Pa‧s of molecular chain end capped with dimethyl vinyl silanoxy groups are used. A mixture of 60 parts by mass of alkanes (vinyl content of 0.13% by mass).

[Industrial availability]

The sponge-forming liquid silicone rubber composition of the present invention can form a low-density sponge with a uniform and fine continuous bubble structure, so it is suitable for use in electrophotographic photocopiers, laser beam printers, and on-demand printing Elastic materials for rollers or conveyor belts used in image forming devices such as printers and fax machines; heat insulation materials, sound-absorbing materials, cushions, gaskets, gaskets, and welding pads are equivalent to the formation of silicone rubber sponges used at high temperatures.

Claims (6)

A sponge-forming liquid silicone rubber composition comprising at least: (A) 100 parts by mass of organopolysiloxane having at least 2 alkenyl groups in one molecule; (B) having at least 2 bonds in one molecule For organopolysiloxanes of hydrogen atoms bonded to silicon atoms, the hydrogen atoms bonded to silicon atoms in this component are 0.4-20 mol relative to 1 mol of the alkenyl group in the above-mentioned component (A); (C) ) 100~1000 parts by mass of a mixture of water and inorganic tackifier; (D) (D-1) non-ionic surfactant with HLB value of 3 or more and (D-2) HLB value less than 3 0.1-15 parts by mass of the nonionic surfactant, wherein the mass ratio of (D-1) component to (D-2) component is at least 8 and at most 100; (E) A catalyst for hydrosilation reaction in an amount sufficient to crosslink the composition; and (F) 0.001 to 5 parts by mass of a hardening retarder. Such as the sponge-forming liquid silicone rubber composition of claim 1, wherein the component (A) is an organic polymer containing 10 to 90% by mass of the component (A-1) and 10 to 90% by mass of the component (A-2) Silicone, the above (A-1) is a diorganopolysiloxane with an average of 2 alkenyl groups at the end of the molecular chain and no alkenyl groups on the side chain of the molecular chain, and the above (A-2) is on the side of the molecular chain Two organopolysiloxanes with at least 2 alkenyl groups in the chain. Such as the sponge-forming liquid silicone rubber composition of claim 1 or 2, wherein the inorganic tackifier in component (C) is bentonite. The sponge-forming liquid silicone rubber composition of claim 1, which further contains at most 20 parts by mass of (G) silica fine powder with respect to 100 parts by mass of (A) component. A silicone rubber sponge obtained by cross-linking the sponge-forming liquid silicone rubber composition according to any one of claims 1 to 4 and removing water from the silicone rubber. For example, the silicone rubber sponge of claim 5 has an average bubble diameter of 1 μm or more and less than 50 μm, and the continuous bubble rate is more than 90%.