JP3344241B2 - Method for producing compression-resistant silicone rubber composition, method for producing compression-resistant silicone rubber, and method for improving compression resistance of silicone rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a compression-resistant silicone rubber composition capable of obtaining a silicone rubber having a small compression set, a method for producing such a low compression set silicone rubber, and a method for compressing a silicone rubber. The present invention relates to a method for improving resistance.

[0002]

2. Description of the Related Art A vinyl group-containing organopolysiloxane, a silicon-bonded hydrogen atom-containing organohydrogenpolysiloxane, a platinum-based catalyst, and an inorganic filler are used. Silicone rubber compositions that are cured by the addition reaction with atoms have excellent moldability, and after molding, they become silicone rubber molded products with excellent properties such as heat resistance and electrical insulation. Used in large quantities.

However, this type of silicone rubber molded product has low resistance to compression and is difficult to use as a molded product subjected to compression deformation for a long time, for example, a roll member, a connector material for automobile parts, and the like.

[0004] Therefore, as a method for improving the compression resistance of silicone rubber, conventionally, a molded product obtained by primary curing such as press molding, injection molding, transfer molding or the like is further subjected to high temperature conditions of 150 to 250 ° C. (Secondary heating, secondary curing).

However, this method is based on the idea of reducing the amount of unreacted functional groups remaining in the silicone rubber molded article and improving the compression resistance of the silicone rubber molded article. However, a step of placing the molded silicone rubber article in an oven at a high temperature and heating it for a long time is required, the work efficiency is low, and the final molded article obtained is disadvantageous in cost.

[0006] Therefore, there has been a demand for a compression-resistant silicone rubber composition which does not have such a problem, that is, a compression-resistant silicone rubber composition which does not require secondary vulcanization.

Conventionally, Japanese Patent Application Laid-Open No. Hei 5-9388 (C
Since the A2071787A), NC- (CH ₂₎ but to achieve a low compression set silicone rubbers by addition of the organic compound represented by the _n -CN disclosed, the compound is toxic, it There is a problem that the use of the silicone rubber is limited by the addition. Also,
JP-A-4-139258 (CA2052410)
A, EP 477984 A) describes that low compression set can be achieved by crosslinking with an organopolysiloxane having an alkenyl group in a side chain and an organopolysiloxane having a SiH bond at both ends. In many cases, sufficient curability and physical properties of rubber cannot be obtained.

Accordingly, an object of the present invention is to provide a method for producing a compression-resistant silicone rubber composition which can be formed into a silicone rubber molded article having high compression resistance without secondary vulcanization after curing, and such a compression set. And a method for improving the compression resistance of silicone rubber.

[0009]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies to achieve the above object, and as a result, (A) the following average composition formula (1) R _a SiO _{(4- a) / 2} (1) (wherein, R represents an unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number from 1.95 to 2.05). (B) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to a silicon atom in a molecule, (C) a platinum-based organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to a silicon atom, A catalyst and (D) 2 to 30 parts by weight of a wet silica fine powder having a specific surface area of 30 m ² / g or more based on 100 parts by weight of the total amount of the components (A) to (C) are mixed to prepare a silicone rubber composition. At the time of production, the addition and mixing of the wet silica fine powder at 80 ° C. After performing at a temperature controlled below, the composition is kept at a temperature of 80 ° C. or less until it is cured, so that only the primary curing of the obtained silicone rubber composition is performed, and the cured product (silicone rubber) is obtained. The inventors have found that the compression set can be made sufficiently small, and that the compression resistance can be made high without performing secondary vulcanization after curing, and the present invention has been accomplished.

Accordingly, the present invention provides a method for producing a silicone rubber composition by mixing the above components (A) to (D).
After the addition and mixing of the wet silica fine powder at a temperature controlled to 80 ° C. or less, the composition is kept at 80 ° C. until it is cured.
A method for producing a compression-resistant silicone rubber composition that gives a cured silicone rubber having a compression set of 25% or less after curing, and a silicone rubber composition obtained by the method. A method for producing a compression-resistant silicone rubber, which is cured to obtain a silicone rubber having a compression set of 25% or less, and a silicone rubber composition is produced by mixing the above components (A) to (D). At this time, the addition and mixing of the wet silica fine powder
After performing at a temperature controlled at 0 ° C. or less, the compression-resistant silicone rubber composition obtained by keeping the composition at a temperature of 80 ° C. or less until the composition is cured to have a compression set of 25% or less. The present invention provides a method for improving the compression resistance of a silicone rubber, comprising obtaining the silicone rubber described in (1).

Hereinafter, the present invention will be described in more detail.
Method for producing compression-resistant silicone rubber composition of the present invention
In the above, the component (A) constituting this composition is
Uniform composition formula (1) R _aSiO_{(4-a) / 2} (1) an organopolysiloxane represented by the formula
It is the main component of the corn rubber composition.

Here, R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms, bonded to a silicon atom, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl, neopentyl , Hexyl, heptyl, octyl, nonyl, decyl, alkyl groups such as dodecyl, cyclopentyl, cyclohexyl, cycloalkyl groups such as cycloheptyl, vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexyl, alkenyl groups such as cyclohexyl, Aryl groups such as phenyl, tolyl, xylyl, naphthyl and biphenyl;
Aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl, and chloromethyl groups in which part or all of the hydrogen atoms in these hydrocarbon groups are substituted with halogen atoms such as F, Cl, and Br, and cyano groups; 2-bromoethyl group, 3,3,3-trifluoropropyl group, 3
-Chloropropyl group, cyanoethyl group and the like.

In this case, in the organopolysiloxane, at least two of the organic groups represented by R are aliphatically unsaturated hydrocarbon groups, especially alkenyl groups, and preferably 0.001 to 5 in all R groups. Mole%, more preferably 0.01 to 2 mol% are alkenyl groups. If the proportion of the alkenyl group is too small, the curability of the resulting composition will be reduced, and if it is too large, physical properties such as tensile strength, tear strength and elongation of the cured product will be reduced. The alkenyl group may be bonded to a silicon atom at the terminal of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be present at both.

In the above formula (1), a is from 1.95 to
It is a positive number of 2.05, preferably 1.98 to 2.02. The molecular structure of this organopolysiloxane is preferably basically linear and has an alkenyl group at both ends of the molecular chain. It is preferable that it has a branched structure. The organopolysiloxane is preferably one whose molecular chain end is blocked with a triorganosilyl group such as trivinylsilyl, methyldivinylsilyl, dimethylvinylsilyl or trimethylsilyl.

The molecular weight of the above-mentioned organopolysiloxane is appropriately selected. However, the viscosity at 25 ° C. is 100 to 300,000 centipoise in view of curing into a rubbery elastic material and providing a liquid silicone rubber composition. And particularly preferably 1,000 to 100,000 centipoise.

The component (B) of the compression-resistant silicone rubber composition of the present invention is an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to a silicon atom in the molecule, which acts as a crosslinking agent. I do. That is,
The silicon-bonded hydrogen atom of the component (B) is subjected to an addition reaction to the silicon-bonded aliphatic unsaturated hydrocarbon group of the component (A), particularly an alkenyl group in the presence of the platinum catalyst of the following component (C). By crosslinking, the silicone rubber composition is cured. Therefore, the organohydrogenpolysiloxane of the component (B) of the present invention has at least two, usually 2 to 200, preferably 3 to 50 silicon-bonded hydrogen atoms (i.e.,
(SiH group).

This organohydrogenpolysiloxane is
The following average composition formula (2) ’_bH_cSiO_{(4-bc) / 2} The one represented by (2) is preferably used.

Here, R 'has 1 to 12 carbon atoms, particularly 1 to 12 carbon atoms.
8 unsubstituted or substituted monovalent hydrocarbon groups, and include the same groups as those exemplified above for R, preferably those containing no aliphatic unsaturated bond, and particularly include alkyl groups, aryl groups, and aralkyl groups. And substituted alkyl groups are preferred. b is 0.8 ≦ b ≦ 2.2, more preferably 1.2 ≦ b ≦ 2, c is 0.002 ≦ c ≦ 1.0,
More preferably a positive number of 0.01 ≦ c ≦ 0.8, b
+ C is 0.8 <b + c ≦ 3, more preferably 1.5 ≦ b
+ C ≦ 2.7, and the molecular structure of the component (B) may be any of linear, cyclic, branched, and three-dimensional network. The SiH group exists at the terminal of the molecular chain. Or in the middle of the molecular chain, or in both of them. Further, the molecular weight of the component (B) is not particularly limited, but the viscosity at 25 ° C. is preferably in the range of 1 to 1,000 centipoise, particularly preferably in the range of 3 to 500 centipoise.

The amount of the organohydrogenpolysiloxane of the component (B) is determined by the number of silicon-bonded hydrogen atoms (ie, SiH groups) in the component (B), and the number of the aliphatic hydrogen in the component (A). The ratio with the number of saturated hydrocarbon groups is 0.5:
The amount is preferably 1 to 20: 1, more preferably 1: 1 to 3: 1. If the ratio of silicon-bonded hydrogen atoms to alkenyl groups is too low, the composition may not be sufficiently cured, and if it is too high, foaming may occur.

The platinum catalyst of the component (C) of the present invention is a catalyst for curing the composition of the present invention. Such platinum-based catalysts include, for example, fine powdered metal platinum catalysts (for example, those described in US Pat. No. 2,970,150),
Chloroplatinic acid catalysts (for example, those described in U.S. Pat. No. 2,823,218) and platinum-hydrocarbon complex compounds (for example, U.S. Pat. Nos. 3,159,601 and 3,159,662)
JP-A No. 3516946, chloroplatinic acid-olefin compounds (for example, those described in US Pat. No. 3,516,946), and platinum-vinylsiloxane complexes (for example, those described in US Pat. No. 3,775,452 or 3,814,780). ). The added amount of the component (C) is desirably 0.1 to 1,000 ppm as platinum metal with respect to the total amount of the components (A) and (B), but is more preferably 1 to 1,000 ppm. 100 ppm. If the amount is less than 0.1 ppm, the curing of the composition often does not proceed sufficiently, and if it exceeds 1,000 ppm, the cost increases.

Next, the component (D) of the compression-resistant silicone rubber composition of the present invention has a specific surface area (for example, by a BET method) of 30 m ² / g or more, usually 30 to 800 m ² / g, preferably 50 to 800 m ² / g. 400 m ² / g wet silica fine powder. Such wet silica has an average particle size of 1
It is preferably about 100 μm or less, usually about 0.1 to 100 μm, and preferably about 0.2 to 50 μm. As a commercially available product, Nipsil LP (manufactured by Nippon Silica Co.,
m ² / g, average particle size 9 μm), Toksil USA (manufactured by Tokuyama Soda Co., Ltd., specific surface area 200 m ² / g, average particle size 11 μm)
m) and the like can be used.

[0022] The above-mentioned wet silica fine powder may be any of the above (A) to
It is necessary to add 2 to 30 parts by weight based on 100 parts by weight of the total amount of the component (C). The wet silica fine powder having a specific surface area of at least 30 m ² / g is added in order to reduce the compression set after the primary curing, and if the added amount is less than 2 parts by weight, the compression set is reduced. When the amount exceeds 30 parts by weight, not only is the compounding difficult, but also the viscosity changes over time are large, which is not suitable for practical use.

The silicone rubber composition of the present invention may contain other optional components in addition to the above components. For example, when it is necessary to impart strength to the composition, quartz powder, diatomaceous earth, calcium carbonate, alumina, quasi-reinforcing fillers such as carbon black, dry silica, finely divided silica such as fumed silica, etc. It is effective to add a reinforcing filler. As such a reinforcing filler, specifically, Aerosil as hydrophilic silica is used.
130, 200, 300 (Deg, manufactured by Nippon Aerosil Co., Ltd.)
ussa), Cabosil MS-5, MS-7
(Cabot), Rheosil QS-10
2,103 (manufactured by Tokuyama Soda Co., Ltd.) and Nipsil LP (manufactured by Nippon Silica Co., Ltd.).
rosilR-812, R-812S, R-972, R
-974 (Degussa), Rheosil
MT-10, DM-20 (manufactured by Tokuyama Soda Co., Ltd.), Nips
Il SS series (manufactured by Nippon Silica Co., Ltd.) and the like are exemplified.

Further, in order to put these materials into practical use,
When it is necessary to adjust the curing time, a vinyl group-containing organopolysiloxane such as vinylcyclotetrasiloxane, triallyl isocyanate, alkyl maleate, acetylene alcohols such as ethynylcyclohexanol, and its silane and siloxane are used as control agents. A compound selected from the group consisting of a modified product, hydroperoxide, tetramethylethylenediamine, benzotriazole, and a mixture thereof may be used.

It is also possible to add an inorganic pigment such as cobalt blue, a coloring agent such as an organic dye, and a heat-resistant and flame-retardant improver such as cerium oxide, zinc carbonate, manganese carbonate, red iron oxide, titanium oxide and carbon black. It is.

The compression-resistant silicone rubber composition of the present invention is formed by the above-mentioned components. In the present invention, when producing such a silicone rubber composition,
The addition and mixing of the wet silica fine powder of the component (D) is carried out under a temperature condition controlled to 80 ° C. or lower. That is, conventionally, the wet silica fine powder is mixed in order to impart mechanical strength to the cured silicone rubber. In this case, if the temperature at the time of mixing is low, the composition thickens, and in terms of workability, Since it is disadvantageous or may take a long time to mix uniformly, a temperature exceeding 80 ° C., usually 100 to 250 ° C., from the viewpoint of minimizing the increase in viscosity due to the addition of silica.
However, as shown in a comparative example described later, when a wet silica fine powder is added and mixed at a temperature of each component itself exceeding 80 ° C. at the time of mixing, silicone rubber having a small compression set due to only primary curing is used. Can not get. On the other hand, by adding and mixing wet silica fine powder at a temperature of 80 ° C. or less, a silicone rubber having a small compression set can be produced only by primary curing. The addition and mixing temperature of the wet silica fine powder is 80 ° C. or lower as described above, but is preferably 60 ° C. or lower, more preferably 50 ° C. or lower. The lower limit temperature is not particularly limited, but is 0 ° C.
In particular, the temperature is preferably 5 ° C. or higher.

The order of addition and mixing of the wet silica fine powder is not limited. For example, after mixing the wet silica fine powder with the component (A), the components (B) and (C) and further optional components are added and mixed. Although it does not matter, if the temperature exceeds 80 ° C. during or after the addition of the wet silica fine powder, the effect of reducing the compression set will be impaired. , Preferably 0 to
It must be kept at 60 ° C, more preferably between 5 and 50 ° C. Therefore, it is recommended to add and mix the wet silica fine powder after mixing the components (A) to (C) and optional components from the viewpoint that the wet silica fine powder is added and mixed, and furthermore, the components (A) to (C) and optional components are surely controlled after mixing. Is done.

For mixing the above components, a usual mixing device, for example, a planetary mixer (manufactured by Inoue Seisakusho),
It can be performed using a universal mixing stirrer (Dalton).

The silicone rubber composition thus obtained is generally used at room temperature (for example, 5 to 35 ° C.) to 250 ° C. for 10 seconds to 120 minutes, and more preferably at 85 to 200 ° C.
Although primary curing is performed under the conditions of 120 minutes, the cured product (silicone rubber) obtained here has a small compression set without performing secondary vulcanization. Not required. Therefore, in the present invention, vulcanization can be only primary vulcanization under the above conditions.

Here, the obtained silicone rubber is excellent in general rubber properties such as mechanical strength and elongation, and is usually subjected to a compression set test at 150 ° C. for 22 hours in accordance with JIS K6301. The compression set is 25% or less, particularly 20% or less.

[0031]

According to the present invention, a silicone rubber having a small compression set can be obtained only by primary curing.

[0032]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. In addition, in the following examples, a part shows a weight part.

Example 1 100 parts of dimethylpolysiloxane (I) having both ends of a molecular chain having a viscosity of 1,000 cs and blocked with a dimethylvinylsiloxy group was mixed with 100 parts of dimethylsiloxane represented by the following formula (II) as a crosslinking agent. A silicone rubber was prepared by adding 2.5 parts of a dimethylhydrogensiloxane copolymer, 0.1 part of a 1% isopropyl alcohol solution of chloroplatinic acid, and 0.1 part of ethynylcyclohexanol as a reaction control agent, and uniformly mixing the resultant mixture. Compound (A) was obtained. This silicone rubber compound (A)
To 100 parts, 4 parts of wet silica (Nipsil LP, manufactured by Nippon Silica Co., Ltd.) having a specific surface area of 200 m ² / g was added,
After mixing at room temperature (25 ° C, the same applies hereinafter),
Press molding was performed for 0 minutes to obtain a cured product. In addition, the temperature of each component did not exceed 50 ° C. during the mixing process. This was measured for general rubber properties such as hardness (A type), tensile strength and elongation of the cured silicone rubber according to JIS K6301. A compression set test was performed at 150 ° C. for 22 hours. Table 1 shows the results.

[0034]

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Example 2 100 parts of the silicone rubber compound (A) prepared in the same manner as in Example 1 was added to the wet silica of Example 1 (Nipsil, manufactured by Nippon Silica Industry Co., Ltd.).
LP), and mixed at room temperature.
Press molding for a minute to obtain a cured product. In addition, the temperature of each component did not exceed 50 ° C. during the mixing process.
The general rubber properties of the cured product were measured in the same manner as in Example 1, and the results of a compression set test conducted at 150 ° C. for 22 hours are shown in Table 1.

Example 3 To 100 parts of the silicone rubber compound (A) prepared in the same manner as in Example 1, 8 parts of wet silica having a specific surface area of 200 m ² / g (Tokusil USA, manufactured by Tokuyama Soda Co., Ltd.) was added. After mixing at room temperature, 120
Press molding was performed at 10 ° C. for 10 minutes to obtain a cured product. In addition, the temperature of each component did not exceed 50 ° C. during the mixing process. The general rubber properties of the cured product were measured in the same manner as in Example 1, and the results of a compression set test conducted at 150 ° C. for 22 hours are shown in Table 1.

Comparative Example 1 100 parts of the silicone rubber compound (A) prepared in the same manner as in Example 1 was directly press-molded at 120 ° C. for 10 minutes to obtain a cured product. The general rubber properties of the cured product were measured in the same manner as in Example 1, and the results of a compression set test conducted at 150 ° C. for 22 hours are shown in Table 1.

Comparative Example 2 100 parts of a silicone rubber compound (A) prepared in the same manner as in Example 1 were mixed with 4 parts of dry silica having a specific surface area of 300 m ² / g (fumed silica Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.). Was added at room temperature, followed by press molding at 120 ° C. for 10 minutes to obtain a cured product. In addition, the temperature of each component did not exceed 50 ° C. during the mixing process. The general rubber properties of the cured product were measured in the same manner as in Example 1, and 150
Table 1 shows the results of a compression set test performed at 22 ° C. for 22 hours.

Comparative Example 3 The wet silica of Example 1 (Nipsil LP, manufactured by Nippon Silica Industry Co., Ltd.) was added to 100 parts of dimethylpolysiloxane (I) having both ends of a molecular chain having a viscosity of 1,000 cs and blocked with dimethylvinylsiloxy groups. ) 30 parts were put into a kneader mixer, heated until the internal temperature became 150 ° C, and stirring was continued for 3 hours, and then cooled to obtain a silicone rubber base. 35 parts of this silicone rubber base (8 parts of silica), 73 parts of dimethylpolysiloxane (I) having a viscosity of 1,000 cs and both ends blocked with dimethylvinylsiloxy groups, and dimethylsiloxane / dimethylhydrogen of Example 1. Siloxane copolymer (II)
1.1 parts, 0.1 part of a 1% isopropyl alcohol solution of chloroplatinic acid and 0.1 part of ethynylcyclohexanol as a reaction control agent were added, and the mixture was uniformly mixed at room temperature to obtain a silicone rubber compound (B). And This was press-molded at 120 ° C. for 10 minutes in the same manner as in Example 1 to obtain a cured product.
Table 1 shows the results of a compression set test performed at 22 ° C. for 22 hours.

Example 4 A dimethylsiloxane represented by the following formula (IV) was used as a crosslinking agent in 100 parts of dimethylpolysiloxane (III) in which both ends of a molecular chain having a viscosity of 10,000 cs were blocked with a dimethylvinylsiloxy group. A silicone rubber obtained by adding 1.1 parts of a dimethylhydrogensiloxane copolymer, 0.1 part of a 1% isopropyl alcohol solution of chloroplatinic acid, and 0.1 part of ethynylcyclohexanol as a reaction control agent, and uniformly mixing the resultant mixture. Compound (C) was obtained. To 100 parts of this silicone rubber compound (C), 16 parts of wet silica (Nipsil LP, manufactured by Nippon Silica Kogyo Co., Ltd.) having a specific surface area of 200 m ² / g were added, mixed at room temperature, and press-molded at 120 ° C. for 10 minutes. A cured product was obtained. In addition, the temperature of each component did not exceed 50 ° C. during the mixing process. The general rubber properties of the cured product were measured in the same manner as in Example 1, and 15
Table 1 shows the results of a compression set test performed at 0 ° C. for 22 hours.

[0041]

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[Comparative Example 4] 100 parts of the silicone rubber compound (C) prepared in the same manner as in Example 4 was directly press-molded at 120 ° C for 10 minutes to obtain a cured product. The general rubber properties of the cured product were measured in the same manner as in Example 1, and the results of a compression set test conducted at 150 ° C. for 22 hours are shown in Table 1.

Example 5 40 parts of fumed silica having a specific surface area of 200 m ² / g were added to 100 parts of dimethylpolysiloxane (III) in which both ends of a molecular chain having a viscosity of 10,000 cs were blocked with a dimethylvinylsiloxy group, 6 parts of hexamethyldisilazane and 2 parts of water were added, and after stirring at room temperature for 1 hour, the internal temperature was heated to 150 ° C., and stirring was continued for 3 hours.

The obtained liquid rubber compound base 50
To 50 parts of dimethylpolysiloxane (I) in which both ends of the molecular chain having a viscosity of 1,000 cs were blocked with a dimethylvinylsiloxy group, and dimethylsiloxane / dimethylhydrogensiloxane copolymer (II) of Example 1.
3 parts, 0.1 part of a 1% isopropyl alcohol solution of chloroplatinic acid, and 0.1 part of ethynylcyclohexanol as a reaction control agent were blended to obtain a silicone rubber compound (D). This silicone rubber compound (D)
100 parts of wet silica (Nippon Silica Industry, Nips)
il LP), and mixed at room temperature.
For 10 minutes to obtain a cured product. During the mixing process, the temperature of each component did not exceed 50 ° C. The general rubber properties of the cured product were measured in the same manner as in Example 1, and the results of a compression set test conducted at 150 ° C. for 22 hours are shown in Table 1.

[Comparative Example 5] 100 parts of the silicone rubber compound (D) of Example 5 was directly press-molded at 120 ° C for 10 minutes to obtain a cured product. The general rubber properties of the cured product were measured in the same manner as in Example 1.
Table 1 shows the results of the time compression set test.

[0046]

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A 7-3034 (JP, A) Kunio Ito, "Silicone Handbook", Nikkan Kogyo Shimbun, Japan, August 31, 1990, pp. 287-289. (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 83/05 C08L 83/07 C08K 3/36

Claims (6)

(57) [Claims] (A) The following average composition formula (1): R _a SiO _{(4-a) / 2} (1) (wherein R represents an unsubstituted or substituted monovalent hydrocarbon group, and a is An organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in the molecule, and (B) a silicon atom in the molecule. (C) a platinum-based catalyst, and (D) 2 to 30 parts by weight based on 100 parts by weight of the total amount of the components (A) to (C). In producing a silicone rubber composition by mixing a wet silica fine powder having a specific surface area of 30 m ² / g or more, the above wet silica fine powder is added and mixed at a temperature controlled to 80 ° C. or less, and then cured. Is characterized in that the composition is kept at a temperature of 80 ° C. or less. Method for producing a compression-resistant silicone rubber composition which compression set gives the following silicone rubber cured product 25%. 2. After mixing the components (A) to (C),
2. The production method according to claim 1, wherein the wet silica fine powder of the component (D) is added and mixed at a temperature controlled to 80 ° C. or lower. 3. The silicone rubber composition obtained by the method according to claim 1 is cured to have a compression set of 25%.
A method for producing a compression-resistant silicone rubber, comprising obtaining the following silicone rubber. 4. Curing is performed at room temperature to 250 ° C. for 10 seconds to 120.
4. The method according to claim 3, wherein the primary curing is performed only under the condition of minutes.
The manufacturing method as described. 5. (A) The following average composition formula (1) R _a SiO _{(4-a) / 2} (1) (wherein R represents an unsubstituted or substituted monovalent hydrocarbon group, and a is An organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in the molecule, and (B) a silicon atom in the molecule. (C) a platinum-based catalyst, and (D) 2 to 30 parts by weight based on 100 parts by weight of the total amount of the components (A) to (C). After mixing a wet silica fine powder having a specific surface area of 30 m ² / g or more at a controlled temperature of 80 ° C. or less, the composition is kept at a temperature of 80 ° C. or less until it is cured, and the obtained compression-resistant silicone rubber composition is obtained. The product is cured to obtain a silicone rubber having a compression set of 25% or less. How to improve the compression resistance of the silicone rubber consists. 6. Curing is performed at room temperature to 250 ° C. for 10 seconds to 120.
6. The method according to claim 5, wherein the primary curing is performed only under the condition of minute
A method for improving the compression resistance of the silicone rubber described.