JPS61159448A - Heat-curing silicone rubber composition - Google Patents

Abstract

PURPOSE:To make it possible to retain surface nonstickiness in heat curing, high resiliency and low compression set, by forming a composition comprising a polydiorganosiloxane, specified polymethylsilsesquioxane as a filler and an organic peroxide. CONSTITUTION:A title composition consists essentially of (A) of 100pts.wt. polydiorganosiloxane of an average degree of polymerization >=3,000, (B) 0.5-300pts.wt. polymethylsilsequioxane of an average particle diameter 0.1-100mum and (C) 0.05-15pts.wt. of organic peroxide. As said polymethylsilsesquioxane B, one obtained by the hydrolysis and condensation of a methyltrialkoxysilane or a condensate of its partial hydrolyzate in an aqueous solution of ammonia or amine is desirable. As said component (A), one in which the organic group directly bonded to the silicon is selected from among methyl, vinyl, phenyl and 3,3,3-trifluoropropyl groups, is preferable.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a silicone rubber composition, and more particularly to a silicone rubber composition that is cured by heating and has excellent surface non-stick properties, high rebound elasticity, and low compression set. The present invention relates to a heat-curable silicone rubber composition that provides rubber.

[Technical background of the invention and its problems] Heat-curable silicone rubber is generally produced by blending reinforcing silica as a filler with polyorganosiloxane having an alkenyl group, and heating the composition in which an organic peroxide is added. Because it has excellent heat resistance and electrical insulation properties, it is widely used as a material for automobile parts and electric/electronic parts. Furthermore, the surface tackiness of silicone rubber is generally lower than that of organic rubber, and rubber rollers that take advantage of this excellent property are used in electronic copying machines, industrial laminators, and the like.

However, by increasing the amount of reinforcing silica in these heat-curable silicone rubbers, compression set and sometimes surface non-tackiness tend to be significantly impaired. On the other hand, the actual situation is that unless reinforcing silica is blended, not only will it not be possible to obtain the desired hardness and non-adhesive surface, but the mechanical strength will be extremely low, making it impractical.

Therefore, in order to obtain a silicone rubber with excellent non-adhesiveness and desired hardness, the actual situation is to mix as little reinforcing silica as possible with the desired semi-reinforcing filler such as quartz powder, diatomaceous earth, or calcium carbonate. However, I have not been able to obtain anything satisfactory.

[Objective of the Invention] The present invention provides a novel heat-curable silicone rubber composition that maintains the inherent advantages of conventional heat-curable silicone rubbers and has superior surface non-stick properties, high rebound elasticity, and low compression set. The purpose is to provide something.

[Structure of the Invention] The present inventors have particularly studied fillers in order to improve these properties, and have found that by using polymethylsilsesquioxane as a filler, superior surface non-stick properties and high repulsion properties can be achieved. The present invention was completed based on the discovery that a heat-curable silicone rubber composition having elasticity can be obtained.

That is, the thermosetting silicone rubber of the present invention contains (A) 100 parts by weight of polydiorganosiloxane having an average degree of polymerization of 3,000 or more, and (B) 0.5 parts by weight of polymethylsilsesquioxane having an average particle size of 0.1 to 100 μm. ~300 parts by weight (C) 0.05 to 15 parts by weight of organic peroxide.

The polydiorganosiloxane of component (A) used in the present invention is one used in ordinary silicone rubber, and the repeating units are dimethylsiloxy, phenylmethylsiloxy,
Polymers, copolymers, or mixtures thereof represented by units such as diphenylsiloxy, methylvinylsiloxy, phenylvinylsiloxy, and methyl(3,3,3-trifluoropropyl)siloxy. Further, the terminal unit of this polydiorganosiloxane is a triorganosiloxy unit, which may be a hydroxy group or an alkoxy group. Examples of the above triorganosiloxy units include trimethylsiloxy, dimethylvinylsiloxy, methylphenylvinylsiloxy, methyldiphenylsiloxy, and analogs thereof.

The average degree of polymerization of the polydiorganosiloxane (A) is 3,
000 or more, and if it is less than 3,000, mechanical strength cannot be obtained. Furthermore, it is preferably in the range of 5,000 to io, ooo. This is because if it is less than s, ooo, sufficient mechanical strength cannot be obtained, and if it exceeds io, ooo, it may be difficult to add.

Polymethylsilsesquioxane, component (B), used in the present invention is a reinforcing agent and/or a mold release improving agent for silicone rubber. This filler has a lower specific gravity when compounded than other silica-based fillers with similar average particle sizes, such as crushed quartz and diatomaceous earth, so even when filled in large quantities, the specific gravity of the system is low. It doesn't get too expensive. Polymethylsilsesquioxane is obtained by hydrolyzing and condensing methyltrialkoxysilane or its hydrolyzed/condensed product in an aqueous solution of ammonia or amines, and contains chlorine atoms and alkaline earth metals. It is preferable because it contains almost no impurities such as alkali metals, is spherical, and has excellent free-flowing properties. The average particle size of polymethylsilsesquioxane is 0.1 to 100 μm, preferably 0.1 to 100 μm.
1-20. It is czm. If it is less than 0.1 μm, it is difficult to manufacture and it is difficult to fill it with more than necessary. If it exceeds 100 μm, the necessary reinforcing effect cannot be obtained and the function necessary for the present invention cannot be obtained. In addition, the blending amount is 0.5 to 300 parts by weight, preferably 0.5 to 300 parts by weight, per 100 parts by weight of polydiorganosiloxane as component (A).
It is 200 parts by weight. If it is less than 0.5 parts by weight, no mold release effect will be obtained, and if it exceeds 300 parts by weight, it will be difficult to incorporate into the system, and furthermore, the elasticity of the rubber will be poor until curing, not only will the reinforcing effect be lost, but the mechanical properties will deteriorate. .

The organic peroxide (C) used in the present invention is a vulcanizing agent used to cure the composition consisting of the polyorganosiloxane (A) and the inorganic filler (B), and is It is a known vulcanizing agent for thermosetting silicone rubber.

Examples of this organic peroxide include acyl peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, 0-chlorobenzoyl peroxide, and 2゜4-dichlorobenzoyl peroxide; di-t-butyl peroxide; , 2,5-dimethyl-2,
5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(1-butylperoxy)-3-hexyne, 1,3-bis(t-butylperoxyprobyl)benzene , 1,1-di(t-butylperoxy)-3
, 5,5-trimethylcyclohexane, [-butylperoxybenzoate, [-butylperoxyisopropyl carbonate, dicumyl peroxide and the like]. These organic peroxides can be used alone or as a mixture of two or more.

The blending amount of the organic peroxide (C) is selected from the range of 0.05 to 15 parts by weight based on 100 parts by weight of the polyorganosiloxane (A). If the amount of the organic peroxide (C) is less than 0.05 parts by weight, vulcanization will not be carried out sufficiently;
If the amount exceeds 1 part by weight, not only will there be no particular effect, but it may also have an adverse effect on the physical properties of the resulting silicone rubber molded article, which is not preferable.

In addition to components (A) to (C), the silicone rubber composition of the present invention also contains crushed quartz, diatomaceous earth, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, magnesium carbonate, calcium carbonate, magnesium silicate, and aluminum sulfate. , calcium sulfate, barium sulfate, mica, asbestos, glass powder, etc. Further, known heat resistance improvers, flame retardants, vulcanization aids, processing aids, coloring agents, etc. may be blended.

The silicone rubber composition of the present invention comprises the above-mentioned (A) to (C).
It is obtained by blending the ingredients and various additives as necessary and mixing them uniformly, and becomes a rubber-like elastic body by heating.

[Effects of the Invention] The silicone rubber elastic body obtained by heating and curing the composition of the present invention exhibits excellent surface non-adhesion, has a small compression set, and has excellent anti-resilience properties, making it suitable for use in tableware and industrial applications. Packaging, parts for electronic devices and equipment, packaging for automobiles, RP
Low compression set such as C roll, laminator roll, etc.
Extremely useful for applications requiring plateau elasticity and excellent surface non-stick properties.

[Examples of the Invention] The present invention will be described below with reference to Examples. In the examples, all parts indicate parts by weight. It should be noted that the described examples do not limit the present invention.

Reference Example 1 (Production of polymethylsilsesquioxane) 500 parts of water and 50 parts of an ammonia aqueous solution with a concentration of 28% were charged into a four-bottle flask equipped with a thermometer, a reflux device, and a stirrer. , methyltrimethoxysilane shown in Table 1 was added to 'PI1. 60~ while itching
It was gradually added dropwise over 120 minutes. The reaction temperature started at 10°C and reached 30°C at the end of the dropwise addition. Next, the mixture was heated with a mantle heater to reflux at 84°C, and stirring was continued at this temperature for about 1 hour.

After cooling, the product precipitated in the flask is collected, washed with water, dried, and then subjected to a pulverization process to produce powdered polymethylsilsesquioxane (F-1 to
F-3) was obtained.

(Left below) Table 1 Reference Example 2 (Production of polymethylsilsesquioxane) Methyltriethoxysilane 118 containing 1% by weight of chlorine atoms
9 parts of water were added to the mixture and heated at 80° C. for about 2 hours to obtain a partially hydrolyzed composition. This is ethylenediamine 3
It was dropped into 500 parts of aqueous solution, hydrolyzed and condensed under the same conditions as in Reference Example 1, dried and pulverized to form powdered polymethylsilsesquioxane (F- 4) was obtained.

Example 1 The average degree of polymerization was 5000 and the methylvinylsiloxy unit was 0.
100 parts of polydimethylsiloxane containing 2 mol % and end-capped with hydroxyl groups and 130 parts of P-powder were uniformly blended using two rolls, and coarsely mixed with 2,5-dimethyl-2,5
Composition 11 was prepared by adding and mixing 0.5 part of -di-t-butylperoxyhexane at room temperature.

Example 2 Composition 12 was prepared under the same conditions as in Example 1 except that the amount of powder P-1 was changed to 50 parts.

Example 3 Composition 13 was prepared under the same conditions as in Example 1 except that powder P-2 was used instead of powder P-1 and the blended amount was 100 parts.
was prepared.

Comparative Example 1 In Example 1, instead of powder P-1, specific surface area 230
Comparative composition 21 was subjected to 1 lfJ under the same conditions except that 30 parts of i210 wet silica carplex #80 (manufactured by Geotsugi Pharmaceutical ■) was used.

Comparative Example 2 Crystallite V was used instead of powder P-1 in Example 1.
Comparative composition 22 was obtained in the same manner except that 100 parts of X-3 (trade name, manufactured by Ryumori Co., Ltd.) was used.

Comparative Example 3 Celite Super Cloth (manufactured by John Manville) 4 was used instead of Powder P-1 in Example 1.
Comparative composition 23 was obtained in the same manner except that 0 part was used.

Comparative Example 4 Comparative composition 24 was obtained in which the powder P-1 in Example 1 was not used at all.

The above compositions 11 to 13 and comparative compositions 21 to 23 were placed in a chrome-plated mold, and the mold was heated to 100 kQ/c.
Pressing was performed for 10 minutes at 170° C. to obtain silicone rubber sheets with a thickness of 2 mm and a thickness of 61 mm. Next, this sheet was subjected to atto-vulcanization at 200° C. for 4 hours, and then tested for mechanical properties, compression set, and surface tack according to JISK 6301 at room temperature. The result is the second
Shown in the table. The compression set was measured by heating the plate at 180° C. for 22 hours, and the surface tack test was performed according to the following method.

[Surface adhesion test] Width 2.5c+a, length toc on silicone rubber sheet
+m tape (Sumitomo 3M, Scotch 5490)
180 mm at a peeling speed of 10 mm/n+in using Shun Autograph, which was pressed at room temperature for about 5 hours at a pressure of og/ci.
9 Peeling tests were conducted, and the average load at that time was expressed as peeling force (unit: Q/CI) calculated per tape width icl. The smaller the peeling force, the better the surface non-adhesion.

(Hereinafter in the margin) (Hereinafter in the margin) From Table 2, it can be seen that the composition of the present invention has small flakes, that is, excellent surface non-stick properties, and exhibits low compression set and high rebound resilience.

Example 4 100 parts of polydimethylsiloxane with an average degree of polymerization of 6,000, containing 0.2 mol% of methylsiloxane units, 5 mol% of diphenylsiloxane units, and whose terminals were blocked with dimethylvinylsiloxy groups, powder P -350 parts of wet silica with a specific surface area of 7 g are kneaded in a kneader until uniform, and then 0.6 parts of dicumyl peroxide is uniformly mixed at room temperature using two rolls to form a composition. Item 31 was obtained.

Example 5 Composition 32 was obtained under the same conditions as in Example 4, except that 20 parts of surface-treated fumed silica R-912 (manufactured by Degussa) was used instead of wet silica.

Comparative Example 5 Composition 41 was obtained in the same manner as in Example 4, except that 50 parts of Crystallite VX-8 (manufactured by Ryumori Co., Ltd.) was used instead of powder P-3.

Comparative Example 6 Comparative composition 42 was obtained in the same manner as in Example 5, except that heavy calcium carbonate NS #400 (manufactured by Nitto Funka Kogyo ■) was used instead of powder P-3.

The physical properties and peeling force of the above compositions 31 to 32 and comparative compositions 41 to 42 were measured in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 3.

Example 6 Poly(3,
3,3-trifluoropropylmethyl)siloxane 10
0 parts, 5 parts of polydimethylsiloxane processing aid with an average degree of polymerization of 5 and whose ends are capped with hydroxyl groups, 30 parts of calcined silica carplex FPS-5 (manufactured by Geotsugi Pharmaceutical ■), powder P-
4 to 50 parts were kneaded in a kneader until uniform, and further 1 part of di-t-butyl peroxide was added and blended using a two-roll mill to obtain Composition 51.

Comparative Example 7 Comparative composition 61 was prepared in the same manner as in Example 6 except that 20 parts of Celite Superfloss was used instead of powder P-4.
I got it.

The physical properties and peeling properties of Composition 51 and Comparative Composition 61 were measured in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 4.

Table 4 Representative Patent Attorney Satoshi Suyama - Procedural Amendment January 31, 1985 Commissioner of the Patent Office Michi Tono (1. Indication of Case Patent Application No. 1988-280860 2. Name of Invention Heat Curing Silicone Relationship with the Rubber Composition 3° Amendment Case - Patent Applicant 6-2-31 Roppongi, Minato-ku, Tokyo Representative - Toshio Ki 4, Agent 101 Kanda, Chiyoda-ku, Tokyo Toshiba Silicone Co., Ltd. 1111, 2-1 Tamachi, 7. Details of the amendment as shown in the attached sheet.

Correction details Direction 1, Name of the invention Heat-curable silicone rubber composition 2, Claims (1) (A) 100 parts by weight of polydiorganosiloxane having an average degree of polymerization of 3.000 or more, (B) Average particle size A heat-curable silicone rubber composition basically consisting of 0.5-300 parts by weight of polymethylsilsesquioxane (0.05-15 parts by weight of suspended organic peroxide) of 0.1-100 μm thing.

(2) The organic group directly bonded to the silicon atom of (A>
The composition according to claim 1, which is a polydiorganosiloxane selected from the group consisting of methyl groups, vinyl groups, phenyl groups, and 3,3,3-trifluorobyl groups.

(3) The composition according to claim 1, wherein the average degree of polymerization of the polydiorganosiloxane (A>) is in the range of 5,000 to 10,000.

(4) The polymethylsilsesquioxane of (B) is a polymethylsilsesquioxane obtained by hydrolyzing and condensing methyltrialkoxysilane or its partially hydrolyzed condensate in an aqueous solution of ammonia or amines. A composition according to claim 1.

(5) The average particle diameter of (B) is 0.1 to 20 μll
A composition according to certain claims 1 to 4.

3. Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a silicone rubber composition, and more particularly to a silicone rubber composition that is cured by heating and has excellent surface non-stick properties, high rebound elasticity, and low compression set. The present invention relates to a heat-curable silicone rubber composition that provides rubber.

[Technical background of the invention and its problems] Heat-curable silicone rubber is generally produced by blending reinforcing silica as a filler with polyorganosiloxane having an alkenyl group, and heating the composition in which an organic peroxide is added. Because it has excellent heat resistance and electrical insulation properties, it is widely used as a material for automobile parts and electric/electronic parts. Furthermore, the surface tackiness of silicone rubber is generally lower than that of organic rubber, and rubber rollers that take advantage of this excellent property are used in electronic copying machines, industrial laminators, and the like.

However, by increasing the amount of reinforcing silica in these heat-curable silicone rubbers, compression set and sometimes surface non-tackiness tend to be significantly impaired. On the other hand, the actual situation is that unless reinforcing silica is blended, not only will it not be possible to obtain the desired hardness and non-adhesive surface, but the mechanical strength will be extremely low, making it impractical.

Therefore, in order to obtain a silicone rubber with excellent non-adhesiveness and desired hardness, we blend as little reinforcing silica as possible and the required amount of short-strength fillers such as quartz powder, diatomaceous earth, and calcium carbonate. This is the reality, but we have not been able to achieve anything satisfactory.

[Objective of the Invention] The present invention provides a new heat-curable silicone rubber composition that maintains the advantages of conventional heat-curable silicone rubber, but has superior surface non-stick properties, high rebound elasticity, and low compression set. The purpose is to provide something.

[Structure of the Invention] The present inventors have particularly studied fillers in order to improve these properties, and have found that by using polymethylsilsesquioxane as a filler, superior surface non-stick properties and high repulsion properties can be achieved. The present invention was completed based on the discovery that a heat-curable silicone rubber composition having elasticity can be obtained.

That is, the thermosetting silicone rubber of the present invention comprises (A) a polydiorganosiloxane having an average degree of polymerization of 3,000 or more.
00 parts by weight, (B) 0.5 to 300 parts by weight of polymethylsilsesquioxane with an average particle diameter of 0.1 to 100 μm, and (C) 0.05 to 15 parts by weight of an organic peroxide. .

The polydiorganosiloxane of component (A) used in the present invention is one used in ordinary silicone rubber, and the repeating units are dimethylsiloxy, phenylmethylsiloxy,
Polymers, copolymers, or mixtures thereof represented by units such as diphenylsiloxy, methylvinylsiloxy, phenylvinylsiloxy, and methyl(3,3,3-trifluoropropyl)siloxy. Further, the terminal unit of this polydiorganosiloxane is a triorganosiloxy unit, which may be a hydroxy group or an alkoxy group. Examples of the above triorganosiloxy units include trimedelsiloxy, dimethylvinylsiloxy, methylphenylvinylsiloxy, methyldiphenylsiloxy, and the like.

The average degree of polymerization of the polydiorganosiloxane (A>) is 3,
000 or more, and if it is less than 3,000, mechanical strength cannot be obtained. Furthermore, it is preferably in the range of 5,000 to io, ooo. This is because if it is less than 5,000, sufficient mechanical strength cannot be obtained, and if it exceeds 10,000, it may be difficult to add it.

Polymethylsilsesquioxane, component (B), used in the present invention is a reinforcing agent and/or a mold release improving agent for silicone rubber. This filler has a lower specific gravity when compounded than other silica-based fillers with similar average particle sizes, such as crushed quartz and diatomaceous earth, so even when filled in large quantities, the specific gravity of the system is low. It doesn't get too expensive. Polymethylsilsesquioxane is obtained by hydrolyzing and condensing methyltrialkoxysilane or its hydrolyzed/condensed product in an aqueous solution of ammonia or amines, and is produced by hydrolyzing and condensing methyltrialkoxysilane or its hydrolyzed/condensed product in an aqueous solution of ammonia or amines. It is preferable because it contains almost no impurities such as metals, is spherical, and has excellent free-flowing properties. The average particle size of polymethylsilsesquioxane is 0.1 to 100, czm, preferably o,
i~20 μm. Those smaller than 0.1μ are difficult to manufacture and have the disadvantage of being difficult to fill more than necessary.
If the thickness exceeds 100 μm, the necessary reinforcing effect cannot be obtained and the functions necessary for the present invention cannot be obtained. In addition, this blended amount is
0.5 to 300 parts by weight, preferably 0.5 to 20 parts by weight per 100 parts of polydiorganosiloxane as component (A)
It is 0 parts by weight. If it is less than 0.5 parts by weight, no mold release effect will be obtained, and if it exceeds 300 parts by weight, it will be difficult to incorporate it into the system.
Furthermore, the elasticity of the rubber after curing is poor, and not only does it lose its reinforcing effect, but it also deteriorates its mechanical properties.

The organic peroxide (C) used in the present invention is a vulcanizing agent used to cure the composition consisting of the polyorganosiloxane (A) and the inorganic filler (B), and is It is a known vulcanizing agent for thermosetting silicone rubber.

Examples of this organic peroxide include acyl peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, O-chlorobenzoyl peroxide, and 2゜4-dichlorobenzoyl peroxide; di-t-butyl peroxide; , 2,5-dimethyl-2,
5-di([-butylperoxy)hexane, 2.5-dimethyl=2.5-di(t-butylperoxy)-3-hexyne, 1.3-bis(t-butylperoxyprobyl)benzene , 1,1-di(t-butylperoxy)-3
, 5,5-t-limethylcyclohexane, butylperoxybenzoate, [-butylperoxyisopropyl carbonate, and dicumyl peroxide. These organic peroxides can be used alone or as a mixture of two or more.

The blending amount of the organic peroxide ('C) is selected from the range of 0.05 to 15 parts by weight based on the 100 suspended portion of the polyorganosiloxane (A). If the amount of the organic peroxide (C) is less than 0.05 parts by weight, vulcanization will not be performed sufficiently;
If the amount exceeds 5 parts by weight, not only will there be no particular effect, but it may also have an adverse effect on the physical properties of the silicone rubber molded product, which is not preferred.

In addition to components (A) to (C), the silicone rubber composition of the present invention also contains crushed quartz, diatomaceous earth, titanium oxide, aluminum oxide, zinc oxide, magnesium oxide, magnesium carbonate, calcium carbonate, magnesium silicate, and aluminum sulfate. , calcium sulfate, barium sulfate, mica, asbestos, glass powder, etc. Further, known heat resistance improvers, flame retardants, vulcanization aids, processing aids, coloring agents, etc. may be blended.

The silicone rubber composition of the present invention comprises the above-mentioned (A) to (C).
It is obtained by blending various additives as necessary with the ingredients and grains and kneading them uniformly, and becomes a rubber-like elastic body by heating.

[Effects of the Invention] The silicone rubber elastic body obtained by heating and curing the composition of the present invention exhibits excellent surface non-adhesion, has a small compression set, and has excellent anti-resilience properties, making it suitable for use in tableware and industrial applications. Packaging, parts for electronic devices and equipment, packaging for automobiles, RP
Low compression set such as C roll, laminator roll, etc.
Extremely useful for applications requiring plateau elasticity and excellent surface non-stick properties.

[Examples of the Invention] The present invention will be described below with reference to Examples. In the examples, all parts indicate parts by weight. It should be noted that the described examples do not limit the present invention.

Reference Example 1 (Production of polymethylsilsesquioxane) A four-bottle flask equipped with a thermometer, a reflux device, and a stirrer was charged with water and an aqueous ammonia solution with a concentration of 28% as shown in Table 1. Methyltrimethoxysilane was gradually added dropwise into the aqueous solution over 60 to 120 minutes while stirring. The reaction temperature started at 10°C and reached 30°C at the end of the dropwise addition. Next, the mixture was heated with a mantle heater to reflux at 84°C, and stirring was continued at this temperature for about 1 hour. After cooling, the product precipitated in the flask is collected, washed with water, dried, and then pulverized to produce powdered polymethylsilsesquioxane (F-
1 to F-3) were obtained.

(Left below) Table 1 Reference Example 2 (Production of polymethylsilsesquioxane) Methyltriethoxysilane 118 containing 1% by weight of chlorine atoms
9 parts of water were added to the mixture and heated at 80° C. for about 2 hours to obtain a partially hydrolyzed composition. This is ethylenediamine 3
It was dropped into 500 parts of a wt% aqueous solution, hydrolyzed and condensed under the same conditions as in Reference Example 1, dried and pulverized to form powdered polymethylsilsesquioxane (F-4>) with an average particle size of 8 μm. was gotten.

Example 1 The average degree of polymerization was 5000 and the methylvinylsiloxy unit was 0.
100 parts of polydimethylsiloxane containing 2 mol % and end-capped with hydroxyl groups and 130 parts of Powder F-2 were uniformly blended using two rolls, and further 2,5-dimethyl-2, 2,5-dimethyl-2,
Composition 11 was prepared by adding and mixing 0.5 part of 5-di-butylperoxyhexane at room temperature.

Example 2 Composition 12 was prepared under the same conditions as in Example 1 except that the amount of powder F-1 was changed to 50 parts.

Example 3 Composition 13 was prepared under the same conditions as in Example 1, except that F-2 was used instead of powder F-1 and the blended amount was 100 parts.
was prepared.

Comparative Example 1 In Example 1, instead of powder F-1, specific surface area 230
Comparative composition 21 was prepared under the same conditions except that 30 parts of m'10 wet silica carplex #8° (manufactured by Geotsugi Pharmaceutical RM) was used.

Comparative Example 2 Crystallite V was used instead of powder F-1 in Example 1.
Comparative composition 22 was obtained in the same manner except that 100 parts of X-8 (■Tatsumori Co., Ltd.) was used.

Comparative Example 3 Comparative composition 23 was obtained in the same manner as in Example 1, except that 40 parts of Celite Super 70 (manufactured by John Mannville) was used instead of powder F-1.

Comparative Example 4 Comparative composition 24 was obtained in which the powder F-1 in Example 1 was not used at all.

The above compositions 11 to 13 and comparative compositions 21 to 23 were placed in a chrome-plated mold and heated to 100k (lj'
Pressing was performed at 170° C. for 10 minutes under a pressure of /cd to obtain silicone rubber sheets of 2IRI11 thickness and 6IIIll thickness. Next, this sheet was subjected to atto-vulcanization at 200° C. for 4 hours, and then tested for mechanical properties, compression set, and surface tack according to JISK 6301 at room temperature. The results are shown in Table 2. The compression set was determined by heating at 180° C. for 22 hours, and the surface tack test was conducted according to the following method.

[Surface adhesion test] 2.5 cm wide and 10 cm long on a silicone rubber sheet
10L of tape (Sumitomo 3M, Scotch 5490)
After pressure bonding at room temperature for about 5 hours at a pressure of Jf/at, a 180° peel test was performed using an autograph at a peeling speed of 10 nu++/min, and the average load at that time was calculated as the peeling force ( Unit gf/Cll
1). The smaller the peeling force, the better the surface non-adhesion.

(Hereinafter in the margin) (Hereinafter in the margin) From Table 2, it can be seen that the composition of the present invention has a small peel force, that is, an excellent surface non-stick property, and exhibits a low compression set and a high rebound elasticity.

Note that Comparative Example 24 cannot withstand practical use in terms of strength.

Example 4 0.2 mol% of methylvinylsiloxane units and 5 mol% of diphenylsiloxane units with an average degree of polymerization of 6,000.
100 parts of polydimethylsiloxane whose ends are blocked with dimethylvinylsiloxy groups, 350 parts of powder F-1, and 20 parts of wet silica with a specific surface area of 230TI+2/IJ were kneaded until uniform in a kneader, and further kneaded with two rolls. Composition 31 was obtained by uniformly mixing 0.6 part of dicumyl peroxide at room temperature.

Example 5 Composition 32 was obtained under the same conditions as in Example 4 except that 20 parts of surface-treated Yanga Silica R-972 (manufactured by Degussa) was used instead of the wet silica.

Comparative Example 5 Composition 41 was obtained in the same manner as Example 4, except that 50 parts of Crystallite VX-3 (manufactured by Snashoku Co., Ltd.) was used in place of the odor-C1 powder F-3.

Comparative Example 6 Comparative composition 42 was obtained in the same manner as in Example 5, except that heavy calcium carbonate NS #400 (manufactured by Nitto Funka Kogyo ■) was used instead of powder F-3.

The physical properties and peeling force of the above compositions 31 to 32 and comparative compositions 41 to 42 were measured in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 3.

Example 6 Poly(3,
3,3-trifluoropropylmethyl)siloxane 10
0 parts, 5 parts of polydimethylsiloxane processing aid with an average degree of polymerization of 5 and whose ends are capped with hydroxyl groups, 30 parts of calcined silica carplex FPS-5 (manufactured by Geotsugi Pharmaceutical ■), powder F-
450 parts were kneaded in a kneader until uniform, and 1 part of di-butyl peroxide was added and blended using a two-roll mill to obtain Composition 51.

Comparative Example 7 Comparative composition 61 was prepared in the same manner as in Example 6 except that 20 parts of Celite Superfloss was used instead of powder F-4.
I got it.

The physical properties and peeling force of Composition 51 and Comparative Composition 61 were measured in the same manner as in Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 4.

Table 4

Claims (5)

[Claims] (1) (A) 100 parts by weight of polydiorganosiloxane with an average degree of polymerization of 3,000 or more, (B) 0.5 to 300 parts by weight of polymethylsilsesquioxane with an average particle size of 0.1 to 100 μm (C) Organic A heat-curable silicone rubber composition essentially consisting of 0.05 to 15 parts by weight of peroxide. (2) Claims in which the organic group directly bonded to the silicon atom in (A) is a polydiorganosiloxane selected from the group consisting of a methyl group, a vinyl group, a phenyl group, and a 3,3,3-trifluoropropyl group. The composition according to item 1. (3) The composition according to claim 1, wherein the polydiorganosiloxane (A) has an average degree of polymerization in the range of 5,000 to 10,000. (4) The polymethylsilsesquioxane of (B) is a polymethylsilsesquioxane obtained by hydrolyzing and condensing methyltrialkoxysilane or its partially hydrolyzed condensate in an aqueous solution of ammonia or amines. A composition according to claim 1. (5) The composition according to claims 1 to 4, wherein the average particle diameter of (B) is 0.1 to 20 μm.