TWI844665B - Silicone rubber composition for molding and silicone rubber mold - Google Patents

Abstract

The present invention provides a composition, which is a molding silicone rubber composition containing the following (A) to (C) for providing a silicone rubber mold having excellent demolding properties for glass masks and being reusable; (A) an organic polysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule; (B) an organic hydropolysiloxane represented by the average formula (1); (C) a silylation reaction catalyst; wherein the amount of (B) is such that the number of hydrogen atoms bonded to silicon atoms in component (B) is 0.5 to 5.0 for each alkenyl group bonded to silicon atoms in component (A); (R ¹ 's each independently represent an unsubstituted or substituted monovalent hydrocarbon group having no addition-reactive carbon-carbon unsaturated bond, s represents 0 or 2, t and u represent 2≦t, 5≦t+u≦800, and satisfy 0.1≦t/(t+u)≦0.4).

Description

Silicone rubber composition for molding and silicone rubber mold

The present invention relates to a silicone rubber composition for molding and a silicone rubber mold, and more specifically to an addition-curing silicone rubber composition for molding, and a mother mold (so-called mother mold) for making a silicone mold obtained by curing the silicone rubber composition.

In the past, silicone rubber has been widely used in various fields due to its excellent heat resistance, cold resistance, electrical properties, etc., and can be used as silicone rubber molds (mother molds) because of its good demolding properties. Especially in the fields of electronic equipment, office machines, home appliances, and automobile parts, for the use of prototype molding in the product development stage or commercial sample production, it has the advantages of being effective in improving costs or required time, or having good workability, and as a molding material using silicone rubber compositions, addition reaction type liquid silicone rubber compositions are often used.

Although addition-reaction silicone rubber compositions have better molding properties as molding materials, more complex shapes or reverse slopes make it difficult to demold the glass mask. To solve this problem, various methods of adding mold release components to silicone rubber compositions to improve demoldability have been reviewed. For example, there are reports of adding non-reactive silicone oil (Patent Document 1), adding dimethyl silicone oil as an oil layer to a water-in-oil emulsion (Patent Document 2), adding a composition containing a dimethyl silicone oil effluent component containing a phenyl group, a higher fatty acid or a higher fatty acid metal salt, and a dimethyl silicone oil having an alkoxysilyl group at the molecular end (Patent Documents 3-5), adding water (Patent Document 6), adding wax (Patent Document 7), etc. However, in these methods, the addition of a release agent that is not related to the cross-linking of silicone rubber will lead to a decrease in the transparency or mechanical strength of the silicone rubber mold. The added release agent will leak out and contaminate the replica, so it is not suitable for use. There is also a problem that the release agent will be exhausted due to repeated use, which will lead to the deterioration of the release property. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 58-225152 [Patent Document 2] Japanese Patent Publication No. 2001-098153 [Patent Document 3] Japanese Patent Publication No. 2002-188008 [Patent Document 4] Japanese Patent Publication No. 2686903 [Patent Document 5] Japanese Patent Publication No. 5319905 [Patent Document 6] Japanese Patent Publication No. 9-143372 [Patent Document 7] Japanese Patent Publication No. 2004-107373

[Problem solved by the invention]

The present invention is made in view of the above matters, and aims to provide a silicone rubber composition for molding, and a method for manufacturing an epoxy resin replica of the silicone rubber mold. The silicone rubber composition for molding is a silicone rubber composition for molding that can provide a silicone rubber mold that has excellent demolding properties for a glass mask and can be reused. [Means for solving the problem]

The inventors of the present invention have conducted detailed studies to solve the above problems and have found that the structure of the organohydropolysiloxane has a great influence on the mold release property from a glass mask in a liquid addition-curing silicone rubber composition. They have also found that by accurately selecting the structure, a silicone rubber molding material having excellent mechanical strength and excellent mold release property from a glass mask or from a molded product such as an epoxy resin can be obtained. The silicone rubber molding material is suitable for molding materials that require high mold release properties such as complex and reverse slope molding materials, and the present invention has been completed.

That is, the present invention provides the following 1. to 5.: 1. A silicone rubber composition for molding containing the following (A) to (C), characterized by: (A) 100 parts by mass of an organic polysiloxane having at least 2 alkenyl groups bonded to silicon atoms in one molecule, (B) a linear or cyclic organic hydropolysiloxane represented by the following average formula (1): for each alkenyl group bonded to a silicon atom in component (A), the number of hydrogen atoms bonded to a silicon atom in component (B) is 0.5 to 5.0; (wherein, ^R1 independently represents a non-substituted or substituted monovalent hydrocarbon group having no addition-reactive carbon-carbon unsaturated bond, s represents 0 or 2, t and u represent numbers satisfying 2≦t, 5≦t+u≦800, and 0.1≦t/(t+u)≦0.4); (C) a siloxane catalyst. 2. a molding polysiloxane rubber composition as described in 1, wherein the amount of (D) silica is 5 to 100 parts by mass per 100 parts by mass of component (A). 3. a glass molding agent formed from the molding polysiloxane rubber composition as described in 1 or 2. 4. a polysiloxane rubber mold formed by hardening the molding polysiloxane rubber composition as described in 1 or 2. 5. A method for manufacturing epoxy resin replicas characterized by using the silicone rubber mold as described in 4. [Effect of the invention]

The silicone rubber mold obtained by curing the silicone rubber composition for molding of the present invention has excellent demolding properties from a glass mask and from a molded product such as epoxy resin, so productivity can be improved.

[Type of implementation of the invention]

The present invention is described in detail below. In the present invention, the so-called silicone rubber composition for molding means a composition that has fluidity in an uncured state, is brought into contact with the entire surface or a part of the surface of a prototype by a method such as injection molding or coating, and is cured in this state to form an uncured (liquid) composition provided to a mold (mother mold for molding) to be replicated by resin or the like. In addition, in the present invention, the so-called demolding property means not only demolding property from the prototype of the hardened mold (mother mold), but also demolding property from the replica of the obtained mold (mother mold).

The silicone rubber composition for molding of the present invention comprises the following components (A) to (C). (A) an organic polysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule; (B) the following average unit formula (1): (wherein, R ¹ independently represents a non-substituted or substituted monovalent hydrocarbon group having no addition-reactive carbon-carbon unsaturated bond, s represents 0 or 2, t and u represent a number satisfying 2≦t, 5≦t+u≦800, and 0.1≦t/(t+u)≦0.4) a linear or cyclic organohydropolysiloxane (C) silylation catalyst

[1] (A) Component Component (A) is an organic polysiloxane having at least 2, preferably 2 to 10, and more preferably 2 to 5 alkenyl groups bonded to silicon atoms in one molecule. If the number is less than 2, the curing of the composition will be insufficient. Although there is no particular upper limit, from the perspective of preventing the cured product from becoming brittle, 10 or less is preferred. The alkenyl group bonded to the silicon atom is not particularly limited and may be any of a linear, branched, or cyclic type, but preferably has 2 to 8 carbon atoms such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, etc., more preferably has 2 to 4 carbon atoms, and more preferably vinyl. The alkenyl group may be present at either or both of the molecular chain terminal and the molecular chain non-terminal (i.e., molecular chain side chain), but preferably exists at least at both molecular chain terminals.

For the organopolysiloxane of component (A), the organic group bonded to the silicon atom other than the alkenyl group is not particularly limited if it is a carbon-carbon unsaturated bond without addition reactivity, and may be any of linear, branched, and cyclic, but preferably a monovalent hydrocarbon group having 1 to 20 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, and even more preferably a monovalent hydrocarbon group having 1 to 5 carbon atoms. As specific examples, there can be cited linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, and n-hexyl; cyclic alkyl groups such as cyclohexyl; aryl groups such as phenyl and tolyl; aralkyl groups such as benzyl and phenylethyl, etc. Furthermore, part or all of the hydrogen atoms of these monovalent alkyl groups may be replaced by halogen atoms such as F, Cl, Br, cyano, etc. Specific examples of such groups include halogen-substituted alkyl groups such as 3,3,3-trifluoropropyl, and cyano-substituted alkyl groups such as 2-cyanoethyl. Among these, methyl is also preferred.

As the component (A), for example, there can be mentioned an organopolysiloxane represented by the following average composition formula (2). (In the formula, ^R2 each independently represents a non-substituted or substituted monovalent hydrocarbon group having no addition-reactive carbon-carbon unsaturated bond, ^R3 each independently represents an alkenyl group, c represents 1.9 to 2.1, d represents 0.005 to 1.0, and c+d represents a number satisfying 1.95 to 3.0)

As the monovalent hydrocarbon group for ^R2 , the same groups as those exemplified above as the organic group bonded to the silicon atom other than the alkenyl group can be mentioned, but a methyl group is preferred. As the alkenyl group for ^R3 , the same groups as those exemplified above as the alkenyl group bonded to the silicon atom can be mentioned, but a vinyl group is preferred. c is preferably a number of 1.95 to 2.0, d is preferably a number of 0.01 to 0.5, and c+d is preferably 1.96 to 2.5.

Examples of the component (A) represented by the average composition formula (2) include, but are not limited to, organopolysiloxanes represented by the following formulae (3) to (9). (In the formula, Vi represents a vinyl group (the same applies hereinafter). R ² represents the same meaning as above)

For each of the above formulas, e, f, and g are integers greater than 0. In particular, e is preferably an integer satisfying 10≦e≦10,000, and more preferably an integer satisfying 50≦e≦2,000. Moreover, f and g are preferably integers satisfying 10≦f+g≦10,000 and 0≦f/(f+g)≦0.2, and more preferably an integer satisfying 50≦f+g≦2,000. Although h is an integer greater than 2, it is preferably an integer satisfying 2≦h, 10≦f+g≦10,000, and 0≦h/(g+h)≦0.2, and more preferably an integer satisfying 50≦g+h≦2,000.

The viscosity of the component (A) at 25°C is preferably 1 to 100,000 mPa·s, more preferably 5 to 10,000 mPa·s. When the viscosity is within this range, the fluidity is high and the workability is excellent. The viscosity in the present invention is a measured value obtained using a rotational viscometer. In addition, the component (A) may be used alone or in combination of two or more.

[2] Component (B) Component (B) is an organohydropolysiloxane represented by the following average formula (1), and acts as a crosslinking agent by undergoing a silylation reaction with the alkenyl groups in component (A). (wherein, ^R1 independently represents a non-substituted or substituted monovalent hydrocarbon group having no addition-reactive carbon-carbon unsaturated bond, s represents 0 or 2, t and u represent 2≦t, 5≦t+u≦800, and satisfy 0.1≦t/(t+u)≦0.4)

The monovalent hydrocarbon group of ^R1 may be the same group as exemplified for ^R2 in component (A), preferably a methyl group. s is 0 or 2, i.e., component (B) is a linear or cyclic organohydropolysiloxane, s is preferably 2, i.e., a linear structure. t and u are 2≦t, 5≦t+u≦800, and satisfy 0.1≦t/(t+u)≦0.4, but t is preferably 2 to 300, more preferably 3 to 200. Moreover, t/(t+u) is preferably in the range of 0.14 to 0.25.

The viscosity of the component (B) at 25°C is not particularly limited, but is preferably 1 to 3,000 mPa·s, more preferably 5 to 200 mPa·s, in order to improve the workability of the composition or the mechanical properties of the cured product.

Examples of the organohydropolysiloxane as the component (B) include a mixture of two or more of these organohydropolysiloxanes, such as methylhydropolysiloxane having trimethylsiloxy groups blocked at both ends, dimethylsiloxane/methylhydropolysiloxane copolymer having trimethylsiloxy groups blocked at both ends, methylhydropolysiloxane/diphenylsiloxane copolymer having trimethylsiloxy groups blocked at both ends, methylhydropolysiloxane/diphenylsiloxane/dimethylsiloxane copolymer having trimethylsiloxy groups blocked at both ends, methylhydropolysiloxane/methylphenylsiloxane/dimethylsiloxane copolymer, and dimethylsiloxane/methylhydropolysiloxane cyclic copolymer. More specifically, organohydropolysiloxanes represented by the following formula can be cited. Wherein Me represents a methyl group (the same applies hereinafter).

(In the formula, the order of arrangement of the siloxane units is arbitrary.)

The amount of component (B) is such that the number of hydrogen atoms bonded to the silicon atom in component (B) is 0.5 to 5.0, preferably 0.7 to 3.0, for each olefin group bonded to the silicon atom in component (A). When the amount is less than 0.5, the silicone rubber mold obtained by curing the composition becomes sticky due to insufficient crosslinking, and the demolding property of the mask and replica is reduced. When the amount exceeds 5.0, foaming is easily caused by the generation of hydrogen during curing, the replication accuracy is reduced due to the unevenness of the surface of the silicone rubber mold, and the rubber strength is reduced due to the generation of voids inside the cured product. In addition, component (B) can be used alone or in combination of two or more.

[3] Component (C) Component (C) is a catalyst for promoting the silylation reaction between the alkenyl group in component (A) and the SiH group in component (B). Specific examples thereof include platinum group metal monomers such as platinum (including platinum black), rhodium, and palladium; H ₂ PtCl ₄ ･nH ₂ O, H ₂ PtCl ₆ ･nH ₂ O, NaHPtCl ₆ ･nH ₂ O, KHPtCl ₆ ･nH ₂ O, Na ₂ PtCl ₆ ･nH ₂ O, K ₂ PtCl ₄ ･nH ₂ O, PtCl ₄ ･nH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ ･nH ₂ O (where n is an integer of 0 to 6, preferably 0 or 6) platinum chloride, platinum chloride acid and platinum chloride salt; alcohol-modified platinum chloride acid (see U.S. Patent No. 3,220,972); complex of platinum chloride acid and olefin (see U.S. Patent No. 3,159,601, No. 3,159,662, and No. 3,775,452); a platinum group metal such as platinum black and palladium supported on a carrier such as alumina, silicon dioxide, carbon, etc.; rhodium-olefin complex; triphenylphosphine (Wilkinson) rhodium chloride catalyst); platinum group metal catalysts such as platinum chloride, platinum chloride acid or platinum chloride salt and vinyl-containing polysiloxane complex. Component (C) may be used alone or in combination of two or more.

The amount of component (C) is not particularly limited as long as it is an amount that can promote the hardening (hydrosilicification reaction) of the composition. For the total mass of the components of the present composition, the metal atoms in the present component are preferably in the range of 0.1 to 1,000 ppm, more preferably in the range of 1 to 500 ppm, and even more preferably in the range of 3 to 100 ppm. Within this range, the reaction rate of the addition reaction becomes appropriate, and a hardened material with high strength can be obtained.

[4] (D) Component In order to improve the physical strength such as hardness and tensile strength of the silicone rubber composition for molding of the present invention, silica as the (D) component may be added. Silica includes, for example, fumed silica, crystalline silica (quartz powder), precipitated silica, silica having the surface of these silicas subjected to hydrophobic treatment, etc. These may be used alone or in combination of two or more.

Examples of such silica include hydrophilic silica such as Aerosil 130, 200, 300 (manufactured by Nippon Aerosil Co., Ltd.), Cabosil MS-5, MS-7 (manufactured by Cabot Corporation), Rheorosil QS-102, 103 (manufactured by Tokuyama Co., Ltd.), and precipitable silica such as TOKUSIL US-F (manufactured by Tokuyama Co., Ltd.), Nipsil LP (manufactured by Nippon Silica Industries Co., Ltd.). Examples of hydrophobic silica include Aerosil R-812, R-812S, R-972, R-974 (manufactured by Nippon Aerosil Co., Ltd.), Rheorosil MT-10 (manufactured by Tokuyama Co., Ltd.), and Nipsil LP (manufactured by Nippon Silica Industries Co., Ltd.). SS series (manufactured by Nippon Silica Industry Co., Ltd.) and other precipitated silica; crystalite (manufactured by Ryumori Co., Ltd.), MIN-U-SIL (manufactured by U.S. Silica Company), Imisil (manufactured by Illinois Mineral Co., Ltd.) and other crystalline silica, etc.

Although these silicas can be used directly, it is preferred to use a surface treatment agent to pre-treat the surface hydrophobicity, or to add a surface treatment agent during the mixing of component (A) to treat the surface hydrophobicity of the silica. Examples of surface treatment agents include alkyl alkoxysilane, alkyl hydroxysilane, alkyl chlorosilane, alkyl silazane, silane coupling agent, low molecular weight polysiloxane, titanium salt treatment agent, fatty acid ester, etc., preferably alkyl disilazane, and more preferably hexamethyldisilazane. These surface treatment agents can be used alone, or two or more can be used simultaneously or at different time points. The amount of the surface treatment agent used is preferably 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 2 to 30 parts by mass per 100 parts by mass of silicon dioxide. If the amount of the surface treatment agent used is within the above range, no surface treatment agent or decomposition products will remain in the composition, fluidity can be obtained, and the viscosity increase can be suppressed over time.

The specific surface area of the component (D) as measured by the BET method is preferably 50 to 400 m ² /g, particularly preferably 100 to 350 m ² /g. Within this range, sufficient rubber strength can be obtained.

When the component (D) is used, the amount thereof added is preferably 5 to 100 parts by mass, more preferably 20 to 50 parts by mass, based on 100 parts by mass of the component (A), from the viewpoint of the handleability of the composition and the mechanical strength of the cured product.

[5] (E) Component In the silicone rubber composition for molding of the present invention, a (E) reaction control agent may be added as necessary for the purpose of controlling the reactivity of the catalyst for the silanization reaction without causing viscosity increase or gelation when preparing the composition or before heat curing during molding. Specific examples of the reaction control agent include 3-methyl-1-butyne-3-ol, 3-methyl-1-pentyne-3-ol, 3,5-dimethyl-1-hexyne-3-ol, 1-ethynylcyclohexanol, ethynylmethyldecylmethanol (Carbinol), 3-methyl-3-trimethylsilyloxy-1-butyne, 3-methyl-3-trimethylsilyloxy-1-pentyne, 3,5-dimethyl- 3-Trimethylsilyloxy-1-hexyne, 1-ethynyl-1-trimethylsilyloxycyclohexane, bis(2,2-dimethyl-3-butynyloxy)dimethylsilane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,1,3,3-tetramethyl-1,3-divinyldisiloxane, etc. These can be used alone or in combination of two or more. Among these, 1-ethynylcyclohexanol, ethynylmethyldecylmethanol (Carbinol), and 3-methyl-1-butyn-3-ol are also preferred.

When the component (E) is used, the added amount is preferably 0.01 to 2.0 parts by weight, more preferably 0.01 to 0.1 parts by weight, based on 100 parts by weight of the total of the components (A) and (B). Within this range, the reaction control effect can be fully exerted.

[6] Other components In addition to the above-mentioned components (A) to (E), other components listed below may be added to the molding silicone rubber composition of the present invention without compromising the purpose of the present invention. As other components, conductive agents such as iron oxide, carbon black, conductive zinc flakes, and metal powder; heat resistant agents such as titanium oxide and calcium oxide; internal mold release agents such as dimethyl polysilicone oil; adhesion imparting agents; thixotropic imparting agents, etc. can be cited.

The silicone rubber composition for molding of the present invention is prepared by mixing the above-mentioned (A) to (C) components, the (D) and (E) components used as necessary, and other components using a kneader, planetary mixer, etc. in a known manner. The silicone rubber composition for molding of the present invention can be prepared as the following composition, and a first agent containing the (A) component, the (C) component, and other necessary components, and a second agent containing the (A) component, the (B) component, and other necessary components are prepared separately, and the first agent and the second agent are mixed before use. In addition, it can also be a component that can be used in common in the first agent and the second agent. By making the composition into such a two-part composition, its storage stability can be further ensured.

In addition, as the curing conditions of the silicone rubber composition for molding of the present invention, curing can be carried out at room temperature (5 to 35°C), but curing can also be accelerated by heating, which is effective when mass production is to be improved. When heat curing is carried out, it is preferably cured at 70 to 200°C for 30 seconds to 60 minutes, especially at 90 to 120°C for 1 minute to 30 minutes. [Example]

The present invention is described below with reference to embodiments and comparative examples, but the present invention is not limited to these embodiments.

[Examples 1 to 4, Comparative Examples 1 to 3] The following ingredients were mixed in the proportions (by mass) shown in Table 1 to prepare a silicone rubber composition. Specifically, 85 parts by mass of component (A), 30 parts by mass of component (D), 5 parts by mass of hexamethyldisilazane and 2 parts by mass of water were mixed at 25°C for 30 minutes using a kneader, and then the mixture was heated to 150°C and stirred for 4 hours. After cooling to 25°C, component (C) was added to the silicone rubber matrix obtained by mixing 15 parts by mass of component (A), and the mixture was stirred and mixed at 25°C for 15 minutes using a planetary mixer. Component (B) was added, and the mixture was stirred and mixed at 25°C for 15 minutes using a planetary mixer. The mixture was further decompressed and defoamed at 25°C for 30 minutes to obtain a silicone rubber composition.

(A) Ingredients: (A-1) Dimethyl polysiloxane with a viscosity of 5,000 mPa･s at 25°C (vinyl content 0.006 mol/100 g) and sealed at both ends with dimethyl vinyl polysiloxy groups

(B) Component: (B-1) an organohydropolysiloxane having the following average structural formula (content of hydrogen atoms bonded to silicon atoms = 0.0018 mol/g) (In the formula, the arrangement of siloxane units is random or block)

(B-2) An organohydropolysiloxane represented by the following average structural formula (the content of hydrogen atoms bonded to silicon atoms = 0.0034 mol/g) (In the formula, the arrangement of siloxane units is random or block)

(B-3) An organohydropolysiloxane represented by the following average structural formula (content of hydrogen atoms bonded to silicon atoms = 0.0021 mol/g) (In the formula, the arrangement of siloxane units is random or block)

(B-4) Organic hydropolysiloxane represented by the following average structural formula (comparative component) (In the formula, the arrangement of siloxane units is random or block)

(B-5) An organohydropolysiloxane represented by the following average structural formula (comparative component: content of hydrogen atoms bonded to silicon atoms = 0.0042 mol/g) (In the formula, the arrangement of siloxane units is random or block)

(B-6) An organohydropolysiloxane represented by the following average structural formula (comparative component: content of hydrogen atoms bonded to silicon atoms = 0.00088 mol/g) (In the formula, the arrangement of siloxane units is random or block)

(C) Components: (C-1) Platinum 1,3-divinyl-1,1,3,3-tetramethyl dipolysiloxane complex dimethyl polysiloxane solution (platinum content 1.0 mass %)

(D) Components: (D-1) Fumed silica (AEROSIL300 manufactured by Nippon Aerosil Co., Ltd., BET specific surface area 300 m ² /g)

(E) Ingredients: (E-1) Ethynyl cyclohexanol

The following properties were evaluated using the obtained composition. The results are shown in Table 2. [Releasability] As shown in Figures 1(A) to (C), the silicone rubber composition 3 for molding prepared by Examples 1 to 3 and Comparative Examples 1 to 3 was poured into the interior of a frame 2 on which a glass mask 1 with an inverse slope was placed, and cured at 100°C and for 50 minutes to produce a silicone rubber mold 4. The releasability of the silicone rubber mold 4 was evaluated by whether the silicone rubber mold 4 could be easily peeled off from the glass mask 1 by hand and by visually observing the surface of the peeled silicone rubber mold 4. The silicone rubber mold 4 can be easily peeled off from the glass mask, and the surface of the silicone rubber mold 4 is smooth and the surface condition is good. The silicone rubber mold 4 is partially broken by coagulation and attached to the glass mask 1. It is represented by ×. [Epoxy Resin Replica Number] As shown in Figures 2(A) to (C), the same procedure as above is used to make the epoxy replica 6 by pouring a thermosetting epoxy resin 5 (trade name: NM102A/B, manufactured by Pelnox) into the gap 4A of the silicone mold 4 peeled off from the glass mask 1, and hardening it at 100°C for 60 minutes. The operation of removing the manufactured epoxy resin replica 6 from the silicone mold 4 was repeated to check the number of times the epoxy resin replica 6 could be easily removed without any resin adhering to the silicone mold 4.

As shown in Table 2, the cured products obtained from the molding silicone composition of the present invention prepared in Examples 1 to 3 have excellent demolding properties for glass masks and epoxy resins, and the number of epoxy resin replications is good. On the other hand, it is known that in Comparative Examples 1 to 3, which do not use the component (B) of the present invention, it is difficult to peel off from glass and epoxy resin, and the number of epoxy resin replications is also small, and they are not suitable for molding.

1: Glass mask 2: Frame 3: Silicone rubber composition for molding 4: Silicone rubber mold 4A: Gap 5: Epoxy resin 6: Epoxy resin replica

[Figure 1] is a schematic cross-sectional view showing a method for evaluating the demolding property of a silicone rubber mold in an embodiment. [Figure 2] is a schematic cross-sectional view showing a method for evaluating the number of epoxy resin replications used in a silicone rubber mold in an embodiment.

Claims (5)

A silicone rubber composition for molding, characterized by comprising the following (A) to (E); (A) 100 parts by weight of an organic polysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule; (B) a linear or cyclic organic hydropolysiloxane represented by the following average formula (1): the number of hydrogen atoms bonded to silicon atoms in component (B) is 0.5 to 5.0 for each alkenyl group bonded to silicon atoms in component (A); (R ¹ ₃ SiO _1/2 ) _s [R ¹ ₁ (H)SiO _2/2 ] _t (R ¹ ₂ SiO _2/2 ) _u (1) (wherein R ¹ each independently represents an unsubstituted or substituted monovalent hydrocarbon group having no addition-reactive carbon-carbon unsaturated bond, s represents 0 or 2, t and u represent numbers satisfying 2≦t, 5≦t+u≦800, and 0.1≦t/(t+u)≦0.4); (C) a silylation catalyst; (D) 5 to 100 parts by weight of silicon dioxide based on 100 parts by weight of component (A); and (E ⁾ a reaction control agent; the component (A) is an _{organopolysiloxane} represented by the following formula ( ₃ ): ^ViR22SiO ( ^R22SiO ) _eSiR22Vi ( ₃ ) (wherein Vi represents a vinyl group: R ² represents a methyl group, and e represents an integer satisfying 50≦e≦2,000); the aforementioned component (E) is one or more selected from 1-ethynylcyclohexanol, ethynylmethyldecylmethanol and 3-methyl-1-butyn-3-ol. For example, in the silicone rubber composition for molding of claim 1, the content of (D) silicon dioxide is 20 to 50 parts by mass based on 100 parts by mass of component (A). A glass molding agent, characterized in that it is composed of a molding polysilicone rubber composition as described in claim 1 or 2. A silicone rubber mold, characterized in that the silicone rubber composition for molding as in claim 1 or 2 is hardened. A method for manufacturing epoxy resin replicas, characterized by using a silicone rubber mold as claimed in claim 4.

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