JP3341381B2 - Heat-curable silicone rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-curable silicone elastomer composition which cures to give an organopolysiloxane having a low compression set.

[0002]

2. Description of the Related Art
Vinyl group-containing organopolysiloxane, silicon-bonded hydrogen atom-containing organohydrogenpolysiloxane,
A platinum-based catalyst and, if necessary, an inorganic filler,
A silicone rubber composition that is cured by an addition reaction between a vinyl group and a silicon-bonded hydrogen atom has excellent moldability when using any method such as press molding, injection molding, and transfer molding, and has heat resistance after curing. Since it can be a silicone rubber molded product having excellent properties such as electrical insulation properties, it is widely used in fields where these properties are required.

However, this type of silicone rubber molded article has a low resistance to compression, and cannot be used as it is in applications requiring compression resistance. And 15 more
A method of improving the compression resistance by performing heat treatment (secondary vulcanization) at a high temperature of 0 to 250 ° C. has been adopted.

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

For this reason, there is a demand for a silicone rubber composition which does not have such a problem, that is, a silicone rubber composition which can improve the compression resistance of a molded article without performing secondary heating after heat curing. .

The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a silicone rubber composition capable of providing a silicone rubber molded article having high compression resistance without secondary vulcanization after curing.

[0007]

The present inventors have conducted intensive studies in order to achieve the above object. As a result, (A) two aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule were obtained. (B) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule, (C) a silicone rubber composition containing a platinum-based catalyst, A silicone rubber composition that contains a compound that controls or inhibits the hydrosilylation reaction of the present invention, and that does not hinder the hydrosilylation reaction during curing by blending a thermoplastic resin having a melting point or softening point of 40 to 200 ° C. After curing, the hydrosilylation reaction can be prevented from proceeding, so that the compression resistance of the molded article can be improved without performing secondary vulcanization after heat curing. It was found that, the present invention has been accomplished.

Accordingly, the present invention relates to (A) an organopolysiloxane having two or more aliphatically unsaturated hydrocarbon groups bonded to a silicon atom in one molecule, and (B) a hydrogen atom bonded to a silicon atom in one molecule. An organohydrogenpolysiloxane having two or more atoms,
The ratio of the number of moles of hydrogen atoms bonded to silicon atoms in component (B) to the number of moles of aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in component (A) is 0.5: 1 to 20: 1. And (C) a platinum-based catalyst in an amount of 0.1 to 500 as platinum metal with respect to 1,000,000 parts by weight of the total of components (A) and (B).
(D) a thermoplastic resin having a melting point or a softening point of 40 to 200 ° C. containing a compound that controls or inhibits a hydrosilylation reaction by platinum; Provided is a heat-curable silicone rubber composition characterized by being blended in an amount of 100 mol or less per mol.

Hereinafter, the present invention will be described in more detail.
The organopolysiloxane (A) is the main component of the silicone rubber composition of the present invention, and has two or more aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in one molecule.

Here, the aliphatic unsaturated hydrocarbon group typically includes an alkenyl group such as a vinyl group, an allyl group, and a propenyl group. The organic group other than the aliphatic unsaturated hydrocarbon group contained in the component (A) includes an alkyl group such as a methyl group, an ethyl group, and a propyl group;
And aryl groups such as phenyl group and tolyl group, and substituted alkyl groups such as 3,3,3-trifluoropropyl group and 3-chloropropyl group.

The molecular structure of the organopolysiloxane of the component (A) may be linear, cyclic, or network.

The molecular weight of the organopolysiloxane is not particularly limited, and it can be used from a liquid having a low viscosity to a raw rubber having a high viscosity, but when the rubber composition of the present invention is cured. In order to obtain a rubber-like elastic body, the viscosity at 25 ° C. is preferably 100 centistokes (cs) or more, particularly preferably 500 to 500,000 cs.

The organopolysiloxane of the component (B) is
It acts as a crosslinking agent in the rubber composition of the present invention,
In the presence of the platinum catalyst of the component (C), the silicon-bonded hydrogen atom of the component (B) undergoes an addition reaction with the silicon-bonded aliphatic unsaturated hydrocarbon group of the component (A), resulting in crosslinking and curing. Is everything.

It is necessary that the organopolysiloxane of the component (B) has at least two silicon-bonded hydrogen atoms in one molecule.

Examples of the organic group other than the hydrogen atom bonded to the silicon atom include an alkyl group such as a methyl group, an ethyl group, and a propyl group; an aryl group such as a phenyl group and a tolyl group;
And a substituted alkyl group such as a 3,3-trifluoropropyl group and a 3-chloropropyl group.

The molecular structure of the organopolysiloxane of the component (B) may be linear, cyclic, or network.

The molecular weight of the component (B) is not particularly limited.
Preferably, the viscosity at 25 ° C. is in the range of 3 to 10,000 cs.

The amount of the component (B) in the composition is as follows:
The ratio of the number of moles of hydrogen atoms bonded to silicon atoms in component (B) to the number of moles of aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in component (A) is 0.5: 1 to 20: 1. It is preferable to set the amount so as to be 1: 1 to 3: 1. When the number of moles of the hydrogen atom bonded to the silicon atom of the component (B) is less than 0.5 with respect to 1 mole of the silicon atom-bonded aliphatic unsaturated hydrocarbon group of the component (A), the rubber containing the compound is used. The composition cannot be cured sufficiently, and if the molar number is larger than 20, the rubber composition may foam.

The platinum catalyst as the component (C) is a catalyst for curing the silicone rubber composition.
Examples thereof include chloroplatinic acid, an alcohol solution of chloroplatinic acid, a complex compound of chloroplatinic acid and olefins, platinum black, and those carrying platinum.

Component (C) is added in an amount of 0.1 to 500 parts, preferably 1 to 1, as platinum metal, based on a total of 1,000,000 parts (parts by weight, hereinafter the same) of components (A) and (B). 50
It is preferable to use a part. If the amount is less than 0.1 ppm, curing will not proceed sufficiently, and if it exceeds 500 ppm, it is economically disadvantageous.

The thermoplastic resin containing a compound that controls or inhibits the hydrosilylation reaction of component (D) with platinum and having a melting point or softening point of 40 to 200 ° C. is a main component for achieving the object of the present invention. It is. The component (D) can be obtained by dispersing or microencapsulating a compound that controls or inhibits a hydrosilylation reaction in a thermoplastic resin.

Here, as the compound which controls or inhibits the hydrosilylation reaction, conventionally known compounds can be used, and specifically, triphenylphosphine, tributylphosphine, tributoxyphosphine, tributylphosphine, and the like. Phosphorus compounds such as fin oxide, nitrogen compounds such as tetramethylenediamine, benzotriazole, dibutylamine, triphenylamine, N, N-dimethylbenzylamine, morpholine, and sulfur such as thiophenol, dibutylsulfur, diphenylsulfur, and thioacetic acid. Compounds, acetylene compounds such as propargyl alcohol, hydroperoxy compounds such as t-butyl hydroperoxide, diisopropylbenzene and hydroperoxide, dibutyltin dilaurate, dioctyltin malate and the like. Such compounds.

The thermoplastic resin in which the above compound is dispersed is
It has a melting point or softening point of 40 to 200 ° C., and those having a melting point or softening point within a range of ± 50 ° C., particularly ± 20 ° C. of the curing temperature of the silicone rubber composition are particularly preferable.

Examples of the thermoplastic resin include various vinyl copolymers such as polystyrene, polyacrylate, polyacrylonitrile, polymethacrylate, polyacetate or partially hydrolyzed compounds thereof, polyvinyl alcohol or copolymers thereof, and polyesters. , Polyamides, polyurethanes, condensation polymers such as cellulose derivatives and the like, and inorganic polymer compounds such as silicone resins. These thermoplastic resins are inert to other components of the silicone rubber composition. Preferably, there is.

Although the shape of the thermoplastic resin is not particularly limited, it is preferable that the compound contained in the thermoplastic resin is uniformly dispersed in the silicone rubber composition. Powder or particulate form (preferably 500 μm or less in average particle diameter, particularly preferably 50 μm or less).
μm or less). In this case, a known method can be adopted as a method for converting the thermoplastic resin into fine powder or particles.

The amount of the thermoplastic resin is 1 to 1 mol of platinum in terms of the above compound contained in the thermoplastic resin.
It is preferably at most 00 mol, particularly preferably 1 to 50 mol.

The silicone rubber composition of the present invention may contain, in addition to the above-mentioned components, various known additives such as a filler and a reaction control agent which are usually compounded in the silicone rubber composition to such an extent that the object of the present invention is not impaired. May be added to the mixture.

When the silicone rubber composition of the present invention is produced, for example, the components (A), (B) and (C) and, if necessary, the above-mentioned additives are mixed, and a mixture such as a two-roll mixer or a Banbury mixer is used. Using a kneader at room temperature to 25 ° C and 0.1 to
After kneading for 10 hours, a method of adding a fine powder or a particulate component (D) to the mixture and further kneading the mixture can be adopted.

In order to cure the silicone rubber composition obtained as described above, at a temperature of 50-280 ° C.
0.1 to 60 minutes, preferably at a temperature of 80 to 250C.
It can be performed by heating for 1 to 10 minutes.

[0030]

The heat-curable silicone rubber composition of the present invention improves the compression resistance of a molded article without the need for secondary vulcanization, in which a heat-curable silicone rubber composition is placed in a high-temperature oven after heating and heated for a long time. Work efficiency is high,
The cost of the final molded article obtained can be reduced.

[0031]

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. Prior to the description of the examples, a synthesis example of the component (D) of the present invention will be described.

Synthesis Example 1 A mixture of 12 ml of methanol and 80 ml of water was placed in a reaction vessel having a mechanical stirrer and a nitrogen inlet, and partially hydrolyzed polyvinyl alcohol (Shin-Etsu Chemical Co., Ltd.)
Was dissolved, and 1 g of thiophenol was further added and stirred. Next, 600 ml of water was added dropwise while stirring at a stirring speed of 500 rpm, and polyvinyl alcohol was gradually precipitated. The mixture was further stirred at 40 ° C. for 5 hours and left overnight.

Next, the mixture was centrifuged, the resulting microcapsules were concentrated, the microcapsules were isolated by filtration, washed twice with water, and dried for one day. The average particle size of the obtained microcapsules is 10 μm
Met.

[Synthesis Example 2] Phenyltrichlorosilane 7
0 mol%, 25 mol% of methyltrichlorosilane and 5 mol% of diphenyldichlorosilane are hydrolyzed to give a softening point of 1.
A silicone resin at 00 ° C. was obtained, a solution of 20 g of the silicone resin dissolved in 100 g of dichloromethane was placed in the same reaction vessel as in the above Synthesis Example, and 2 g of N, N-dimethylbenzylamine was mixed with the solution and aged overnight. Was.

Next, this solution was made into fine particles by a spray drier. Here, the inlet temperature of the spray dryer was 110 ° C. and the outlet temperature was 50 ° C. The average particle diameter of the obtained fine particles was 5 μm.

[Examples 1 and 2, Comparative Examples 1 to 3] Viscosity 1
To 100 parts of dimethylpolysiloxane having both ends capped with dimethylvinylsiloxy groups at 000 cs, 30 parts of fumed silica whose surface was hydrophobized with trimethylsiloxy group units having a specific surface area of 200 m ² / g was added. 3
The mixture was heated and mixed for a time to obtain a base compound.

To 100 parts of this base compound, 1.0 part of methylhydrogenpolysiloxane represented by the following average composition formula (1), 0.1 part of a 1% isopropyl alcohol solution of chloroplatinic acid, and ethynylcyclohexane as a reaction control agent Hexanol was added in an amount of 0.05 part, and the microcapsules obtained in Synthesis Example 1 were further added in the amounts shown in Table 1 to prepare a silicone rubber composition.

[0038]

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Next, using an oscillating disc rheometer (manufactured by Toyo Seiki Seisaku-sho, Ltd.), the curing characteristics of the silicone rubber composition obtained above at 150 ° C. were measured. Press molding at 120 ° C for 10 minutes
A compression set test was performed at 150 ° C. for 22 hours in accordance with IS-K6301.

For comparison, a similar experiment was conducted in the case where the above microcapsules were not added, and where thiophenol was added instead of the microcapsules. Table 1 shows the results. In Table 1, T10 indicates the time until the torque becomes 10% when the torque after 2 minutes is 100%, and T90 indicates the time until the torque becomes 90% as described above.

[0041]

[Table 1]

Examples 3, 4 and Comparative Examples 4 to 6 100 parts of dimethylpolysiloxane having a viscosity of 10,000 cs and both ends blocked with a dimethylvinylsiloxy group were added to
1.4 parts of methyl hydrogen polysiloxane represented by the following average composition formula (2), 0.1 part of a 1% isopropyl alcohol solution of chloroplatinic acid, and 0.05 part of ethynyl chlorohexanol as a reaction control agent were blended. Furthermore, the silicone rubber composition was prepared by adding the microcapsules obtained in Synthesis Example 2 in the amounts shown in Table 2.

[0043]

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Next, the curability and compression set were measured in the same manner as in Example 1. The results are also shown in Table 2. For comparison, the same experiment was performed for the case where the above microcapsules were not added, and where N, N-dimethylbenzylamine was added instead of the microcapsules.

[0045]

[Table 2]

Continuation of the front page (56) References JP-A-5-5063 (JP, A) JP-A-5-148423 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 83 / 07 C08L 83/05

Claims (3)

(57) [Claims] 1. An organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to a silicon atom in one molecule, and (B) two hydrogen atoms bonded to a silicon atom in one molecule. An organohydrogenpolysiloxane having the above,
The ratio of the number of moles of hydrogen atoms bonded to silicon atoms in component (B) to the number of moles of aliphatic unsaturated hydrocarbon groups bonded to silicon atoms in component (A) is 0.5: 1 to 20: 1. And (C) a platinum-based catalyst in an amount of 0.1 to 500 as platinum metal with respect to 1,000,000 parts by weight of the total of components (A) and (B).
(D) a thermoplastic resin having a melting point or softening point of 40 to 200 ° C. containing a compound that controls or inhibits the hydrosilylation reaction by platinum, and platinum (1) in terms of the compound contained in the thermoplastic resin. A heat-curable silicone rubber composition characterized by being blended in an amount of 100 mol or less with respect to mol. 2. The compound which controls or inhibits the hydrosilylation reaction contained in the component (D) is a compound selected from a phosphorus compound, a nitrogen compound, a sulfur compound, an acetylene compound, a hydroperoxy compound and a tin compound. The heat-curable silicone rubber composition according to claim 1. 3. The thermoplastic resin as the component (D) is polystyrene, polyacrylate, polyacrylonitrile, polymethacrylate, polyacetate and partially hydrolyzed compounds thereof, polyvinyl alcohol and copolymers thereof, polyester, polyamide, and polyurethane. 3. The heat-curable silicone rubber composition according to claim 1, wherein the composition is selected from the group consisting of cellulose derivatives, cellulose derivatives and silicone resins.