KR101729990B1 - Curable silicon rubber composition having improved mold release property and high hardness - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a room temperature curable organopolysiloxane composition for forming a high hardness mold having excellent releasability to a modified epoxy resin, and more particularly to a composition for curing an organopolysiloxane, an organohydrogenpolysiloxane, a fumed silica, And which can be used as a material for a reversing mold for molding at the time of curing, which has improved durability and durability.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable silicone rubber composition having excellent releasability,

TECHNICAL FIELD The present invention relates to a room temperature curable organopolysiloxane composition for forming a high hardness mold having excellent releasability to a modified epoxy resin, and more particularly to a composition for curing an organopolysiloxane, an organohydrogenpolysiloxane, a fumed silica, And which can be used as a material for a reversing mold for molding at the time of curing, which has improved durability and durability.

BACKGROUND ART Conventionally, it has been a well-known technology to produce reproduced products such as urethane resin, epoxy resin, dicyclopentadiene resin, and polyester resin with a molding reversal model. In recent years, resin moldings obtained as described above have been widely used for automobile parts, And the like, the characteristics of the resin molded product are increasingly emphasized. For this reason, studies for improving mold resin have actively been made. However, such an improvement leads to a deterioration in the durability of the silicone rubber model, so that the number of replicas that can be manufactured from one mold is reduced. Therefore, it is strongly desired to improve the mold release durability of the silicone mold for such a resin.

Japanese Patent Application Laid-Open No. 9-217009 discloses that steric hindrance phenols, aromatic amines and zinc dithiophosphate are excellent in improvement in mold release durability against modified epoxy resins. Japanese Patent Application Laid-open No. Hei 10-279805 discloses a radical scavenging agent Discloses a technique for improving the durability of modified epoxy molding. However, these techniques have a problem in that a hardening failure of the modified epoxy resin occurs at the contact surface with the silicone rubber.

Japanese Patent Application Laid-Open No. 9-217009 Japanese Patent Laid-Open No. 10-279805

In order to solve the problems of the prior art as described above, the present invention has a high hardness, a rubber elasticity, little surface stickiness, and a hardening defect of the modified epoxy resin on the contact surface with the silicone rubber does not occur It is an object of the present invention to provide a room temperature curing organopolysiloxane composition for molding which is also excellent in releasability and durability against modified epoxy resins and urethane resins.

According to the present invention, there is provided an addition-curable silicone rubber composition comprising the following (A) to (E):

(A) an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms and at least one cyclic reactor bonded to silicon atoms in one molecule and having an average degree of polymerization of 2500 or less and being liquid at room temperature

(B) an organopolysiloxane having an average degree of polymerization of 2000 or more and being a raw monolayer at room temperature

(C) an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule

(D) Fumed silica

(E) an addition reaction catalyst.

Hereinafter, the composition of the present invention will be described in more detail by constituent components.

(A) Liquid phase Organopolysiloxane

The component (A) contained in the silicone rubber composition of the present invention contains at least two alkenyl groups bonded to silicon atoms and at least one cyclic reactor bonded to silicon atoms in one molecule, and has an average degree of polymerization of 2500 or less, Is an organopolysiloxane that is in a liquid phase. Examples of the component (A) include an organopolysiloxane represented by the following average formula (1).

Formula 1

R1 _a SiO _{(4-a) / 2}

In the above formula (1), R 1 is an unsubstituted or substituted monovalent organic group of 1 to 20 carbon atoms, preferably 1 to 15 carbon atoms, and a is a positive number in the range of 1.2 to 3.2, preferably 1.8 to 2.5. to be. If a is less than 1.2, the resin may become too single-molecule and the final molded product may be broken. If it is larger than 3.2, there may be a problem in storage stability.

In the above formula (1), R 1 is an unsubstituted or substituted monovalent hydrocarbon group bonded to a silicon atom, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, An alkyl group such as a neopentyl group, a hexyl group, a cyclohexyl group, an octyl group, a nonyl group and a decyl group; Aryl groups such as phenyl group, tolyl group, xylyl group and naphthyl group; An aralkyl group such as benzyl group, phenylethyl group and phenylpropyl group; Alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl; And cyclic organic groups such as epoxy, cyclopropyl, cyclopentyl, etc., and preferably 80 mol% or more of the entire R1 is a methyl group, but it is not limited thereto.

However, in one molecule of the component (A), at least two of R < 1 > are an alkenyl group, preferably an alkenyl group having 2 to 15 carbon atoms, more preferably an alkenyl group having 2 to 6 carbon atoms. The content of the alkenyl group is preferably 2.0 x ^10-6 mol / g to 8.0 x ^10-4 mol / g, more preferably 3.0 x ^10-5 mol / g to 5.0 g / g, based on 1 g of the organopolysiloxane (A) × 10 ^-4 mol / g. The amount of the alkenyl groups is less than 2.0 × 10 ^-6 mol / g, and the rubber hardness is too low, the gel phase, 8.0 × 10 ^-4 mol / g as the high and more high, the crosslinking density excessively there is a problem in that the hardness is high the plastic . The alkenyl group may be bonded to the silicon atom at the end of the molecular chain, or may be bonded to the silicon atom in the molecular chain, or may be bonded to both sides.

In the molecule of the component (A), at least one of R < 1 > is a cyclic type reactive group bonded to a silicon atom, preferably an epoxy group. When a reactive ring-type substituent such as an epoxy group is present, the cross-linking point is increased during curing, and there is no tackiness of the surface, and the silicon surface is prevented from being damaged when the next mold is opened. The structure of such an organopolysiloxane is basically a straight chain structure in which both ends of the branch chain are blocked with a triorganosiloxy group and the main chain contains repeating units of a diorganosiloxane unit but is partially branched, And so on.

(A) is 2500 or less (e.g., 100 to 2500), preferably 200 to 2000, more preferably 300 to 1000 in terms of the weight average degree of polymerization (hereinafter referred to as average polymerization degree). If the average degree of polymerization is too low, a satisfactory rubber feeling can not be obtained. If the average degree of polymerization is higher than 2500, the viscosity becomes high and molding becomes difficult.

(B) Raw Organopolysiloxane

The component (B) contained in the silicone rubber composition of the present invention is an organopolysiloxane having an average degree of polymerization of not less than 2000 and a raw rubber phase at room temperature. Examples of the component (B) include an organopolysiloxane represented by the following average formula (2).

(2)

R2 _b SiO _{(4-b) / 2}

In the above formula (2), R 2 is an unsubstituted or substituted monovalent hydrocarbon group of 1 to 8 carbon atoms, preferably 2 to 6 carbon atoms, and b is a positive number in the range of 1.4 to 3.0, preferably 1.5 to 2.5. to be. If b is less than 1.4, the final molded product may become too single-molecule, and if it is larger than 3.0, there may be a problem in storage stability.

In the above formula (2), R 2 represents an unsubstituted or substituted monovalent hydrocarbon group bonded to a silicon atom, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, An alkyl group such as a neopentyl group, a hexyl group, a cyclohexyl group, an octyl group, a nonyl group and a decyl group; Aryl groups such as phenyl group, tolyl group, xylyl group and naphthyl group; An aralkyl group such as benzyl group, phenylethyl group and phenylpropyl group; And alkenyl groups such as a vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group and cyclohexenyl group. It does not.

Also, R2 may or may not contain an alkenyl group, and when included, is preferably an alkenyl group having 2 to 15 carbon atoms, more preferably an alkenyl group having 2 to 6 carbon atoms. The content of the alkenyl group is preferably 2.0 × 10 ^-4 mol / g or less, more preferably 8.0 × 10 ^-8 mol / g to 8.0 × 10 ^-4 mol / g or less based on 1 g of the organopolysiloxane (B) 10 < ^-5 > mol / g. If the amount of the alkenyl group is more than 2.0 x 10 < ^-4 > mol / g, the rubber hardness becomes too high and the properties of the plastic may be exhibited. The alkenyl group may be bonded to the silicon atom at the molecular chain terminal, or may be bonded to the silicon atom in the molecular chain, or may be bonded to both. The structure of the organopolysiloxane is basically the same as the component (A), except that both ends of the molecular chain are blocked with a triorganosiloxy group and the main chain has a linear structure including repetition of diorganosiloxane units, May be a branched structure, a cyclic structure, or the like.

The average degree of polymerization of the component (B) is at least 2000 (for example, from 2000 to 80,000), preferably from 2500 to 80,000, and more preferably from 3500 to 50,000. When the average degree of polymerization is less than 2000, not only a satisfactory rubber feeling can not be obtained but also stickiness is caused on the surface. If the average degree of polymerization is too high, the viscosity becomes high and molding may become difficult.

The amount of the component (B) to be used is preferably 8 to 50 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the component (A). If the amount of the component (B) is less than 8 parts by weight based on 100 parts by weight of the component (A), it is difficult to obtain the desired elastic rubber feel. If the amount exceeds 50 parts by weight, the viscosity of the composition may be high.

(C) Organohydrogenpolysiloxane

The component (C) contained in the silicone rubber composition of the present invention is preferably at least two, preferably at least three (for example, from 3 to 250, more preferably from 3 to 20) hydrogen atoms bonded to silicon atoms Is an organohydrogenpolysiloxane containing in a molecule from 5 to 100). Examples of the component (C) include an organohydrogenpolysiloxane represented by the following average formula (3).

(3)

R3 _c H _d SiO _{(4-cd) / 2}

In the above formula (3), R 3 is a substituted or unsubstituted monovalent hydrocarbon group of 1 to 15 carbon atoms which may be the same as the monovalent hydrocarbon group exemplified for R 1, but is preferably not an aliphatic unsaturated group. c is a positive number of 0.7 to 2.7 (preferably 0.9 to 1.5), d is 0.01 to 2.0 (preferably 0.05 to 1.0), and c + d is 0.5 to 3.5 (preferably 0.9 to 2.0). The molecular structure of the organohydrogenpolysiloxane (C) may be a linear, cyclic, branched, or three-dimensional mesh structure, preferably a liquid at room temperature (25 ° C). In this case, the number (or degree of polymerization) of silicon atoms in one molecule of the component (C) is 2 to 500, preferably 5 to 200. The hydrogen atom bonded to the silicon atom may be located at either the molecular chain terminal or the molecular chain, or may be located on both sides.

Examples of the component (C) include a methylhydrogenpolysiloxane having both terminals blocked with a trimethylsiloxy group, a dimethylsiloxane-methylhydrogensiloxane copolymer having both terminals blocked with a trimethylsiloxy group, a dimethylhydrogensiloxy group having both terminals Blocked dimethylsiloxane-methylhydrogensiloxane copolymer with both ends blocked with dimethylhydrogensiloxy groups, methylhydrogensiloxane-diphenylsiloxane copolymer with both terminal ends blocked with trimethylsiloxy groups, trimethylsiloxane-diphenylsiloxane copolymer having both terminals trimethylsiloxane- the methylhydrogen siloxy capped with siloxane and diphenyl siloxane and dimethyl siloxane copolymer, (CH _{3) 2} HSiO copolymer comprising a _1/2 units and SiO _4/2 units, (CH _{3) 2} HSiO _1/2 and the like units and SiO _4/2 units and _{(C 6 H 5) 3 SiO} 1 copolymer containing a _{/ 2} units. The amount of the organohydrogenpolysiloxane (C) to be used is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 10 parts by weight based on 100 parts by weight of the total amount of the components (A) and (B). If the amount of the component (C) is less than 0.1 parts by weight based on 100 parts by weight of the total amount of the components (A) and (B), there is a problem that the curing time is excessively delayed at the time of curing the final molded product, If the amount is more than 15 parts by weight, the resulting molded product may become overcured when the final molded product is cured, resulting in a problem that the molded product becomes hard.

The molar ratio (SiH group / alkenyl group) of the hydrogen atom bonded to the silicon atom in the organohydrogenpolysiloxane (C) to the total amount of the alkenyl group bonded to the silicon atom in the component (A) and the component (B) Preferably 0.5 to 15.0, more preferably 1.0 to 8.0. If the ratio is less than 0.5, the crosslinking becomes insufficient and the rubber becomes sticky. If it is larger than 15.0, foaming may be found in the molded article, or mold release from the mold may become difficult.

(D) Fume  Silica ( fumed silica )

The fumed silica of the component (D) contained in the silicone rubber composition of the present invention is intended to provide sufficient strength to the silicone rubber. The specific surface area of the fumed silica (D) according to the BET method is preferably 100 m ² / g to 250 m ² / g, more preferably 150 to 200 m ² / g. If the specific surface area is less than 100 m ² / g, not only sufficient strength can not be obtained but transparency of the molded article is also deteriorated. If the specific surface area is more than 250 m ² / g, mixing may become difficult or discolored. These fumed silica may be used as it is, but it is preferable that the fumed silica is pre-treated with a surface hydrophobicizing agent or treated with a surface treating agent when kneaded with a silicone oil. As the surface treatment agent, any known one such as an alkylalkoxysilane, an alkylchlorosilane, an alkylsilazane, a silane coupling agent or a titanate-based treatment agent may be used singly or two or more kinds thereof may be used at the same time. The amount of the fumed silica (D) to be used is preferably 5 to 30 parts by weight, more preferably 10 to 25 parts by weight based on 100 parts by weight of the total amount of the components (A) and (B). If the amount of the component (D) is less than 5 parts by weight based on 100 parts by weight of the total amount of the components (A) and (B), sufficient rubber strength can not be obtained. If the amount is more than 30 parts by weight, have.

(E) an addition reaction catalyst

Examples of the addition reaction catalyst of component (E) contained in the silicone rubber composition of the present invention include platinum black, platinum chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, Platinum-based catalysts such as bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts. In the composition of the present invention, the addition reaction catalyst (E) may be contained at a level of the catalytic amount and is usually from 0.1 to 1000 ppm, preferably from 1 to 300 ppm (relative to the total amount of the components (A) Metal basis). If the amount of the catalyst component (E) used is too small, the reaction rate may become slow, and a molded product may not be formed at a desired time. If the amount is too high, Wrinkles and the like may occur.

(F) non-adductivity Organopolysiloxane

The silicone rubber composition of the present invention may further comprise a non-addition reactive organopolysiloxane (F) having an average degree of polymerization of 1000 or less, if necessary, for the purpose of use when improvement of releasability is required. The component (F) does not have an addition reaction functional group (for example, an alkenyl group such as a vinyl group and a functional group capable of participating in a hydrosilylation addition reaction such as a silicon atom-bonded hydrogen atom (SiH group) An organopolysiloxane having a number of 1000 or less (e.g., 10 to 1000), preferably 500 or less (e.g., 20 to 500) is preferred. If the average degree of polymerization is more than 1000, the surface of the silicone rubber cured product tends to become sticky even in a small amount. On the contrary, if the average degree of polymerization is too low, the rubber cured product may become too hard. Examples of the component (F) include linear organopolysiloxanes represented by the following average formula (4).

Formula 4

In the above formula, R ⁴ represents a C 1 to C 15, preferably C 1 to C 6 alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a cyclohexyl group, a 3,3,3- Unsubstituted or halogen-substituted alkyl group; Or an aryl group such as a phenyl group, preferably a methyl group, a phenyl group or a 3,3,3-trifluoropropyl group, more preferably a methyl group. R ⁴ may be the same or different, but preferably 95 mol% or more of the total R ⁴ is a methyl group. n is an integer of 0 to 1000, preferably 0 to 500, more preferably 0 to 250, still more preferably 2 to 100. As the component (F), an organopolysiloxane having a cyclic structure or a branched structure other than the linear organopolysiloxane described above may be contained. When the component (E) is contained in the composition of the present invention, the amount thereof is preferably 1 to 40 parts by weight, more preferably 5 to 30 parts by weight, more preferably 5 to 30 parts by weight, per 100 parts by weight of the total amount of the components (A) Still more preferably 10 to 15 parts by weight. If the amount of the component (F) is less than 1 part by weight based on 100 parts by weight of the total amount of the components (A) and (B), the effect of use may not be exhibited. If the amount is more than 40 parts by weight, There may be a problem.

The silicone rubber composition of the present invention has a viscosity in the liquid phase at room temperature, preferably in the range of 1000 to 100000 Pa.s, and is particularly suitable for mold-forming, and commonly used methods are employed for the production, molding and curing methods thereof . As the molding method, a liquid phase injection molding method can be preferably adopted. As the curing condition, it is preferable to perform heat treatment at 120 to 250 DEG C for 10 seconds to 10 minutes, more preferably at 150 to 200 DEG C for about 15 seconds to 2 minutes Can be adopted. The cured product (silicone rubber) obtained by curing the silicone rubber composition of the present invention has a hardness of 50 to 75, preferably 55 to 70, as measured by a durometer A hardness meter. The rebound resilience of the cured product obtained by curing the silicone rubber composition of the present invention is preferably 30% or more, the tensile strength is 4.50 MPa or more, and the elongation upon cutting is less than 200%.

The silicone rubber composition of the present invention not only has excellent releasability to modified epoxy resin but also improves durability durability which has been pointed out as a problem in existing resins and minimizes hardening failure of epoxy resin on the contact surface with silicone rubber. Further, when it is cured, it is possible to obtain a flexible silicone rubber having no surface stickiness, favorable molding, high tensile strength and high rebound resilience, which is particularly suitable for use as a material for a molding reverse mold.

Hereinafter, the present invention will be described in detail by way of examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, parts indicate parts by weight, the average degree of polymerization represents the weight-average degree of polymerization, and the capital letters in the parentheses indicate that they correspond to the corresponding components described above.

≪ Example 1 >

70 parts of a dimethylpolysiloxane (A) having an average degree of polymerization of 750 and an aqueous phase at room temperature, containing epoxy groups (epoxy group content 0.0025 mol / g) bonded at both ends with dimethylvinylsiloxy groups and bonded to silicon atoms and having a specific surface area of 150 m the fumed silica (D) ² / g (Degussa manufacture, QS-20) 25 parts of a silica surface treated with hexamethyldisilazane, 5 parts for, after mixing for 30 minutes, 1.0 parts of room temperature water, the temperature was raised to 180 ℃ 3 Stirring was continued for a period of time to obtain a silicone rubber base.

After 30 parts of dimethylpolysiloxane (A) were added to 95 parts of the silicone rubber base and stirring was continued for 30 minutes, 20 parts of the dimethylpolysiloxane raw material (B) having an average degree of polymerization of 5,000, both ends of which were blocked with trimethylsiloxy groups, 1.2 parts of methylhydrogenpolysiloxane (C) having a SiH group at both ends and side chains (degree of polymerization 23, amount of SiH groups = 0.0075 mol / g) [SiH group in methylhydrogenpolysiloxane (C) The mixture was stirred for 15 minutes, and a silicone rubber composition (measured at 25 占 폚 in a BS-type viscometer, rotor No. 6, at 10 rpm) was added thereto, The result was 15000 Pa 占 퐏!].

To 100 parts of this silicone rubber composition, 0.1 part of platinum catalyst (E) (Pt concentration 1 wt%) was mixed and press curing at 170 占 폚 for 10 minutes was carried out.

The hardness, tensile strength, tear strength, elongation and specific gravity of the obtained cured product were measured based on JIS-K6249, and the rubber surface was judged by finger touch. The results are shown in Table 1 below.

≪ Example 2 >

Both ends of the dimethyl and vinyl siloxane capped with time and containing the epoxy group (epoxy group content 0.0050 mol / g) combined with a silicon atom, and the average degree of polymerization of 750 and a polydimethylsiloxane (A) 70 parts in a liquid state at room temperature and a specific surface area of 150m ² , 25 parts of fumed silica (D) (manufactured by Degussa, QS-20), 3 parts of hexamethyldisilazane for surface treatment of silica and 1.0 part of water were mixed at room temperature for 30 minutes, Followed by cooling and stirring to obtain a silicone rubber base.

After 30 parts of dimethylpolysiloxane (A) were added to 95 parts of the silicone rubber base and stirring was continued for 30 minutes, 20 parts of the dimethylpolysiloxane raw material (B) having an average degree of polymerization of 5,000, both ends of which were blocked with trimethylsiloxy groups, 0.5 parts of a methylhydrogenpolysiloxane (C) having a SiH group at both ends and side chains (degree of polymerization 23, amount of SiH groups = 0.0075 mol / g) [SiH group in methylhydrogenpolysiloxane (C) And the reaction was continued for 15 minutes to obtain a silicone rubber composition (measured at 25 ° C using a BS-type viscometer, rotor No. 6, 10 rpm) And the result was 35000 Pa 占 퐏].

To 100 parts of this silicone rubber composition, 0.1 part of platinum catalyst (E) (Pt concentration 1 wt%) was mixed and press curing at 170 占 폚 for 10 minutes was carried out.

The hardness, tensile strength, tear strength, elongation and specific gravity of the obtained cured product were measured based on JIS-K6249, and the rubber surface was judged by finger touch. The results are shown in Table 1 below.

≪ Example 3 >

70 parts of a dimethylpolysiloxane (A) having an average degree of polymerization of 500 and a liquid at room temperature and containing epoxy groups (epoxy group content: 0.0075 mol / g) bonded at both ends with dimethylvinylsiloxy groups and bonded with silicon atoms and having a specific surface area of 150 m ² , 10 parts of fumed silica (D) (manufactured by Degussa, QS-20), 3 parts of hexamethyldisilazane for surface treatment of silica and 1.0 part of water were mixed at room temperature for 30 minutes, Followed by cooling and stirring to obtain a silicone rubber base.

After 30 parts of dimethylpolysiloxane (A) were added to 95 parts of the silicone rubber base and stirring was continued for 30 minutes, 20 parts of the dimethylpolysiloxane raw material (B) having an average degree of polymerization of 5,000, both ends of which were blocked with trimethylsiloxy groups, 1.9 parts of a methylhydrogenpolysiloxane (C) having a SiH group at both terminals and a side chain (degree of polymerization 23, amount of SiH groups = 0.0075 mol / g) [SiH group in methylhydrogenpolysiloxane (C) The resultant mixture was stirred for 15 minutes to obtain a silicone rubber composition (measured at 25 ° C using a BS-type viscometer, rotor No. 6, 10 rpm, 23500 Pa 占 퐏].

To 100 parts of this silicone rubber composition, 0.1 part of platinum catalyst (E) (Pt concentration 1 wt%) was mixed and press curing at 170 占 폚 for 10 minutes was carried out.

The hardness, tensile strength, tear strength, elongation and specific gravity of the obtained cured product were measured based on JIS-K6249, and the rubber surface was judged by finger touch. The results are shown in Table 1 below.

≪ Comparative Example 1 &

70 parts of dimethylpolysiloxane having an average degree of polymerization of 750 (both of which are free from a cyclic reactor, liquid at room temperature) with both ends blocked with dimethylvinylsiloxy groups, and fumed silica having a specific surface area of 150 m ² / g (manufactured by Degussa, 20), 2.5 parts of hexamethyldisilazane, and 1.0 part of water were mixed at room temperature for 30 minutes, and then the mixture was heated to 180 DEG C and stirred for 3 hours, followed by cooling to obtain a silicone rubber base.

5 parts of the above dimethylpolysiloxane and 15 parts of dimethylpolysiloxane having an average degree of polymerization of 6000 (vinyl group content: 1.5 x 10 ^-6 mol / g) blocked with dimethylvinylsiloxy groups were put in 90 parts of this silicone rubber base and stirred for 30 minutes , 15 parts of dimethylpolysiloxane having an average degree of polymerization of 50, both ends of which were blocked with trimethylsiloxy groups, methylhydrogenpolysiloxane having H (hereinafter referred to as SiH group) bonded to Si at both terminals and side chains as a crosslinking agent (SiH group in the methylhydrogenpolysiloxane / (alkenyl group in the sum of dimethylpolysiloxane and dimethylpolysiloxane raw material) = 1.6 (mol / mol)) as a reaction control agent, 0.05 part of thionylcyclohexanol was added and stirring was continued for 15 minutes to obtain a silicone rubber composition (measurement result of 2000 Pa 占 퐏 at 25 占 폚, BS type viscometer, rotor No. 6, 10 rpm).

To 100 parts of this silicone rubber composition, 0.1 part of a platinum catalyst (Pt concentration 1 wt%) was mixed, and press curing at 170 DEG C for 10 minutes was carried out.

The hardness, tensile strength, tear strength, elongation and specific gravity of the obtained cured product were measured based on JIS-K6249, and the rubber surface was judged by finger touch. The results are shown in Table 1 below.

≪ Comparative Example 2 &

75 parts of a dimethylpolysiloxane having an average degree of polymerization of 550 (both of which are free from a cyclic reactor, liquid at room temperature) with both ends blocked with dimethylvinylsiloxy groups, and fumed silica having a specific surface area of 100 m ² / g (manufactured by Degussa, 10), 3 parts of hexamethyldisilazane and 1.0 part of water were mixed at room temperature for 30 minutes, then heated to 180 ° C, stirred for 3 hours and then cooled to obtain a silicone rubber base.

8 parts of the above dimethylpolysiloxane and 250 parts of dimethylpolysiloxane having an average degree of polymerization of 5,000 without containing an alkenyl group were added to 90 parts of the silicone rubber base, and stirring was continued for 30 minutes. Then, both ends were blocked with trimethylsiloxy groups 25 parts of dimethylpolysiloxane having an average degree of polymerization of 350 and 1.5 parts of methylhydrogenpolysiloxane (degree of polymerization: 23, amount of SiH groups = 0.0075 mol / g) as a crosslinking agent [SiH group in methylhydrogenpolysiloxane / alkenyl group in dimethylpolysiloxane (Mol / mol)], 0.05 part of ethynylcyclohexanol as a reaction controlling agent was added, and stirring was continued for 15 minutes to obtain a silicone rubber composition [25 deg. C, measured at 25 deg. C in a BS type viscometer, S].

To 100 parts of this silicone rubber composition, 0.1 part of a platinum catalyst (Pt concentration 1 wt%) was mixed, and press curing at 170 DEG C for 10 minutes was carried out.

The hardness, tensile strength, tear strength, elongation and specific gravity of the obtained cured product were measured based on JIS-K6249, and the rubber surface was judged by finger touch. The results are shown in Table 1 below.

≪ Comparative Example 3 &

60 parts of a dimethylpolysiloxane having an average degree of polymerization of 550 (both of which are free from a cyclic reactor, liquid at room temperature) blocked with dimethylvinylsiloxy groups at both terminals and used in Comparative Example 2, 60 parts of fumed silica having a specific surface area of 300 m ² / g (QS-30, manufactured by Degussa Corporation), 2.5 parts of hexamethyldisilazane and 1.0 part of water were mixed at room temperature for 30 minutes, and then the temperature was raised to 180 占 폚, stirring was continued for 3 hours, .

10 parts of the dimethylpolysiloxane used above and 30 parts of dimethylpolysiloxane having an average degree of polymerization of 3,500 [vinyl group content: 2.0 x 10 ^-5 mol / g] were added to 95 parts of the silicone rubber base and stirring was continued for 30 minutes. 2.1 parts of methylhydrogenpolysiloxane having a SiH group at both ends (degree of polymerization: 15, SiH group: 0.0018 mol / g), methylhydrogenpolysiloxane (polymerization degree: 23, amount of SiH groups = 0.0075 mol / g) used in Example 1 (SiH group in the sum of methylhydrogenpolysiloxane and methylhydrogenpolysiloxane) / (alkenyl group in the sum of dimethylpolysiloxane and dimethylpolysiloxane raw material) = 2.0 (mol / mol)), 0.05 part of ethynylcyclohexanol as a reaction controlling agent And the stirring was continued for 15 minutes to obtain a silicone rubber composition (measurement result of 255 占 폚, BS type viscometer, rotor No. 6, 10 rpm, 42500 Pa 占 퐏).

To 100 parts of this silicone rubber composition, 0.1 part of a platinum catalyst (Pt concentration 1 wt%) was mixed, and press curing at 170 DEG C for 10 minutes was carried out.

The hardness, tensile strength, tear strength, elongation and specific gravity of the obtained cured product were measured based on JIS-K6249, and the rubber surface was judged by finger touch. The results are shown in Table 1 below.

[Table 1]

As can be seen from the above table, the tensile strength, tear strength, elongation and hardness of the examples of the present invention were superior to those of the comparative examples, and more excellent physical properties and replica counts were reproduced in the finger touch test and the copy number test .

Claims (13)

An additional curable silicone rubber composition comprising (A) - (E)
(A) an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms and at least one epoxy group bonded to silicon atoms in one molecule and having an average degree of polymerization of 2500 or less and being liquid at room temperature
(B) an organopolysiloxane having an average degree of polymerization of 2000 or more and being a raw monolayer at room temperature
(C) an organohydrogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in one molecule
(D) Fumed silica
(E) an addition reaction catalyst. The silicone rubber composition according to claim 1, wherein the component (A) is an organopolysiloxane represented by the following average formula 1:

Formula 1
R1 _a SiO _{(4-a) / 2}

In Formula 1,
R1 is an identical or different unsubstituted or substituted monovalent organic group having 1 to 20 carbon atoms, at least two of them are alkenyl groups bonded with silicon atoms, at least one is an epoxy group bonded with a silicon atom, It is a positive number in the range of 3.2. The silicone rubber composition according to claim 1, wherein the alkenyl group content in the component (A) is 2.0 × 10 ^-6 mol / g to 8.0 × 10 ^-4 mol / g based on 1 g of the component (A). The silicone rubber composition according to claim 1, wherein the component (B) is an organopolysiloxane represented by the following average formula (2):

(2)
R2 _b SiO _{(4-b) / 2}

In Formula 2,
R 2 is an identical or different unsubstituted or substituted monovalent hydrocarbon group of 1 to 8 carbon atoms, and b is a positive number in the range of 1.4 to 3.0. The silicone rubber composition according to claim 1, wherein the component (B) comprises an alkenyl group and the content thereof is 2.0 × 10 ^-4 mol / g or less based on 1 g of the component (B). The silicone rubber composition according to claim 1, wherein the component (C) is an organohydrogenpolysiloxane represented by the following average formula (3):

(3)
R3 _c H _d SiO _{(4-cd) / 2}

In Formula 3,
R3 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 15 carbon atoms, c is 0.7 to 2.7, d is 0.01 to 2.0, and c + d is 0.5 to 3.5. The silicone rubber composition according to claim 1, wherein the specific surface area of the fumed silica component (D) according to the BET method is from 100 m ² / g to 250 m ² / g. The silicone rubber composition according to claim 1, wherein the component (E) is a platinum catalyst, a palladium catalyst, a rhodium catalyst, or a mixture thereof. The silicone rubber composition according to claim 1, further comprising a non-addition reactive organopolysiloxane (F) having an average degree of polymerization of 1000 or less. The silicone rubber composition according to claim 9, wherein the component (F) is a linear organopolysiloxane represented by the following average formula (4):

Formula 4

In Formula 4,
R ⁴ is an unsubstituted or halogen-substituted alkyl group having 1 to 15 carbon atoms or an aryl group, and n is an integer of 0 to 1000. A silicone rubber obtained by curing the silicone rubber composition according to any one of claims 1 to 10. The silicone rubber according to claim 11, which is used as a material for a molding reverse mold. A reversing mold for molding, which is produced by using the silicone rubber of claim 11.