JPH07118534A - Production of organopolysiloxane composition for matrix for mold making - Google Patents

Abstract

PURPOSE:To obtain the title compsn. which gives a matrix for mold making excellent in releasability and its persistence. CONSTITUTION:The compsn. is prepd. by mixing a mixture comprising a diorganopolysiloxane having at least two alkenyl groups in the molecule and a viscosity at 25 deg.C of 500-30,000cp and a fine silica powder pretreated with a silylating agent and dispersed therein with an organohydrogenpolysiloxane having at least two SiH groups in the molecule, a hydrosilylation catalyst, and a diorganopolysiloxane having a viscosity equal to or higher than that of the alkenylated diorganopolysiloxane and not having a hydrosilylatable group.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an organopolysiloxane composition for a molding master.

[0002]

2. Description of the Related Art Conventionally, a urethane resin having a silicone rubber mold as an inversion mother mold,
It is a known technology to produce a duplicate of epoxy resin, gypsum, etc., but recently, the resin molding obtained in this way has been actually used for automobile parts and household appliances parts. However, the characteristics of resin molded products are becoming more important. For this reason, there are some remarkable improvements in the properties of the casting resin, but this improvement is a factor that reduces the durability of the silicone rubber mold, and the number of duplicates that can be produced from one mold is decreasing. The current situation is. Therefore, there is a strong demand for improvement in the mold release durability of the silicone mother mold against these resins.

Various attempts have heretofore been made to improve the mold release durability of such a silicone matrix. For example, a reinforcing silica filler which is hydrophobized is used, or the reinforcing hydrophilic silica is treated with various silazanes represented by a silazane compound represented by the following formula, and the silazane is represented by the following formula. Reinforcing hydrophilic silica is treated in combination with a compound having such an additional functional group as described above, and hydrophobic silica is also similarly treated again.

[0004]

[Chemical 1]

Although these methods have been confirmed to improve the mold release durability of conventional products, they are superior to epoxy resins and urethane resins having high physical properties, which are the mainstream of the current casting resin materials. However, the durability of the silicone rubber matrix material is still insufficient.

On the other hand, the present inventors have proposed to add an alkali metal compound to the silicone composition in order to improve the durability of the mold. However, although the number of times of duplication is surprisingly increased by such a method, it has been found that when a resin duplicate is extracted from a silicone mother die, it is difficult to take out because of the high degree of adhesion, and there is room for improvement in workability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing an organopolysiloxane composition for a mold making master block which is excellent in mold releasability and mold release durability.

[0008]

Means and Actions for Solving the Problems The present inventors have
As a result of intensive studies to achieve the above purpose, 25 ° C
Having a viscosity of 500 to 30,000 cp and having a finely divided silica treated with a silylating agent dispersed in a diorganopolysiloxane having at least two alkenyl groups in one molecule, at least 2 in one molecule. Pieces of Si
An H-group-containing organohydrogenpolysiloxane, a hydrosilylation reaction catalyst, and a hydrosilylation-reactive functional group-free diorganopolysiloxane having a viscosity equal to or higher than that of the alkenyl group-containing diorganopolysiloxane. The resulting composition is effective as a material for a mold making mold for molding a resin molded product such as an epoxy resin or a urethane resin, and a mold making mold made from such a composition is The inventors have found that the degree of adhesion when a resin replica such as an epoxy resin or a urethane resin is extracted is remarkably reduced, and that the release durability is very good, and the present invention has been completed.

The present invention will be described in more detail below. In the method for producing a releasable organopolysiloxane composition of the present invention, the viscosity at 25 ° C. is 500 to 30,000 cp, and at least two alkenyl groups are contained in one molecule. An organohydrogenpolypolysiloxane having at least two SiH groups in one molecule is added to a mixture of the finely divided silica (B) treated with the silylating agent (C) in the diorganopolysiloxane (A). Siloxane (D), hydrosilylation reaction catalyst (E), and diorganopolysiloxane (F) having the same or higher viscosity as the alkenyl group-containing diorganopolysiloxane and having no hydrosilylation-reactive functional group. Is to mix with.

The alkenyl group-containing diorganopolysiloxane as the component (A) has a viscosity at 25 ° C. of 500 to 30,000 centipoise, preferably 100.
It is necessary to have a viscosity of 0 to 10,000 centipoise and to have at least two alkenyl groups in one molecule.

Specific examples of such a diorganopolysiloxane include the diorganopolysiloxane represented by the following general formula (1).

[0012]

[Chemical 2]

In this formula, R ¹ has 1 to 1 carbon atoms, respectively.
0, preferably 1-8 monovalent hydrocarbon groups such as alkyl groups such as methyl group, ethyl group, propyl group, alkenyl groups such as vinyl group, propenyl group, butenyl group, phenyl group, xylyl group, etc. And the halogen-substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group and the like, and R ^{1 s} may be the same or different. However, it is necessary to contain at least two alkenyl groups in one molecule. a is in the range of 1.9 to 2.4, and even if this diorganopolysiloxane is linear, R
^It may have a branched shape including a unit such as ¹ SiO _3/2 unit or SiO _4/2 unit. Although the substituent of the silicon atom may be any of the above, a vinyl group is preferred as the alkenyl group, a methyl group is preferred as the other substituent, and a trifluoropropyl group is preferred when solvent resistance is required. Such a diorganopolysiloxane can be produced by a known method in which an organocyclopolysiloxane and R ¹ ₃ SiO _1/2 are subjected to an equilibration reaction in the presence of an alkali or acid catalyst. Specific examples of such a diorganopolysiloxane include the following.

[0014]

[Chemical 3] (However, R is a monovalent hydrocarbon group other than an alkenyl group, and n ≧
It is 0, and m is the number of CH = CH ₂ groups in the molecule being 2 or more in total. )

Next, the finely powdered silica as the component (B) is a component which imparts strength when the present composition is cured into an elastomer. Here, when the present composition is used as a material for a molding master, it is required to have strength, particularly tear strength, so that a master including an inverse taper can be replicated. The finely divided silica used as the agent is 50 m ² / g or more, preferably 15
It is recommended to use one with a specific surface area of 0 to 350 m ² / g. Examples of such finely divided silica include Aerosil / 30,200,3 as hydrophilic silica.
00 (Nippon Aerosil Co., Degussa), Ca
bosil MS-5, MS-7 (manufactured by Cabot),
Rheorosil QS-102, 103 (made by Tokuyama Soda Co., Ltd.), Nipsil LP (made by Nippon Silica Co., Ltd.), etc. are mentioned. In addition, as a hydrophobic silica, Aerosi
l R-812, R-812S, R-972, R-97
4 (manufactured by Degussa), Rheorosil MT
-10, MT-30 (manufactured by Tokuyama Soda Co., Ltd.), Nipsil
Examples include SS series (manufactured by Nippon Silica Co., Ltd.).

The blending amount of such finely divided silica is 100 parts by weight of component (A) (parts by weight;
It is desirable that the amount is 5 to 50 parts, preferably 10 to 40 parts.

Further, as the silylating agent as the component (C),
Examples thereof include silazane compounds having no carbon functional group, and when it is necessary to further improve the tear strength, addition of an alkenyl group-containing silazane represented by the following formula is also effective. is there.

[0018]

[Chemical 4]

The amount of the silylating agent used is (B)
It is preferably in the range of 5 to 100% by weight of the finely divided silica of the component, and water is preferably used in the range of 0 to 100% by weight of the component (B) in order to accelerate the silylation treatment.

In the present invention, first, a mixture in which the finely divided silica treated with the silylating agent is dispersed in the diorganopolysiloxane (A) is prepared. As a method of preparing this mixture, a method of mixing finely powdered silica previously treated with a silylating agent with diorganopolysiloxane can be adopted, and particularly, the alkenyl group-containing diorganopolysiloxane of the component (A) and finely powdered silica can be used. 1 silica and silylating agent
A method of mixing at a temperature of less than 00 ° C and then heating and mixing at 100 to 200 ° C is recommended from the viewpoint of improving releasability and fluidity.

To further elaborate on this step, this step first performs the initial mixing at a temperature below 100.degree.
In this case, if mixing is carried out at a temperature of 100 ° C. or higher, silazane or water which is a silylating agent is volatilized and the treatment of finely divided silica cannot be sufficiently carried out. Actually, when the alkenyl group-containing diorganopolysiloxane of the component (A) and the silylating agent of the component (C) are mixed with each other, heat generation is recognized, but this heat generation is suppressed to at least less than 100 ° C. to perform the low temperature mixing operation. There is a need. An ordinary kneader or the like can be used as a mixing device for performing this low temperature mixing operation, and the time is generally in the range of 0.5 to 2 hours.

Next, the mixture after the above low temperature mixing operation is heated to a temperature of 100 to 200 ° C., preferably 120 to 180 ° C., and a heating and mixing operation is performed. If the temperature is lower than 100 ° C, the treatment becomes insufficient. On the other hand, if the temperature is higher than 200 ° C, combustible volatile substances are generated and the risk of explosion increases.
There is a problem in operation.

The heating and mixing operation is preferably performed for at least 1 hour in a batch system production apparatus. During this heating and mixing operation, silazane is decomposed to generate a large amount of ammonia gas. Therefore, in order to avoid the danger of explosion due to this gas, it is preferable to introduce an inert gas such as nitrogen into the reactor, or the pressure can be reduced to accelerate the removal of reaction by-products.

During this heating and mixing operation, R ¹ ₃ SiO _1/2
Alternatively, a resin consisting essentially of SiO ₂ and SiO ₂ may be added to the mixture and heat-treated at the same time. Specific examples of such a resin include (CH ₃ ) ₃ SiO _1/2 , (CH ₂ = CH) (C
H ₃ ) ₂ SiO _1/2 and SiO ₂ , vinyl group equivalent is 0.08 mol / 100 g, and (CH ₃ ) ₃ Si
An example is a toluene-soluble vinyl group-containing silicone resin in which the sum of O _1/2 and (CH ₂ ═CH) (CH ₃ ) ₂ SiO _1/2 is 0.9 with respect to SiO ₂ . This resin-like compound has a silanol group substantially and is effective in reducing the viscosity and imparting physical strength when the composition is cured.

The amount of this resin blended is 5 to 1 with respect to 100 parts of the alkenyl group-containing organopolysiloxane.
It is preferably set to 00 parts.

In the present invention, for the above mixture, an organohydrogenpolysiloxane (D) having at least two SiH groups in one molecule, a hydrosilylation reaction catalyst (E), and the above alkenyl group-containing diamine. The organopolysiloxane is mixed with a diorganopolysiloxane (F) having the same or higher viscosity and having no hydrosilylation-reactive functional group.

The organohydrogenpolysiloxane as the component (D) reacts with the alkenyl group-containing diorganopolysiloxane as the component (A) and acts as a cross-linking agent. At least two organohydrogenpolysiloxanes per molecule. , Preferably 3 or more SiH groups (hydrogen atoms directly bonded to silicon atoms)
Need to have. There is no particular limitation on its molecular structure,
Any of linear, cyclic, and branched organohydrogenpolysiloxanes that have been conventionally used can be used. In addition, as a substituent of a silicon atom other than hydrogen, a saturated hydrocarbon group such as a methyl group, an ethyl group and a propyl group, an aryl group such as a phenyl group and a xylyl group, and a 3,3,3-trifluoropropyl group Examples thereof include a halogen-substituted hydrocarbon group, and among these, a methyl group and a trifluoropropyl group are preferable when solvent resistance is required.

The amount of the organohydrogenpolysiloxane compounded is 0.4 to 4 equivalents of hydrogen atoms directly bonded to silicon atoms per one alkenyl group in the alkenyl group-containing diorganopolysiloxane of component (A). It is desirable to set it in the range of preferably 0.8 to 2 equivalents. If it is less than 0.4 equivalent, the crosslinking density will be too low, which will adversely affect the heat resistance of the cured silicone rubber. On the other hand, if it is more than 4 equivalent, foaming problem due to dehydrogenation reaction will occur or heat resistance will be adversely affected. May be given.

As the catalyst for hydrosilylation of the component (E), known catalysts can be used, but platinum or a platinum compound is particularly preferable, for example, platinum black, chloroplatinic acid,
Examples include alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid with olefins, aldehydes, vinyl siloxanes, acetylene alcohols and the like. The amount of this component added is a catalytic amount and can be appropriately adjusted according to the desired curing rate. Generally, the amount of platinum is 0.1 to 1000 ppm, particularly 1 to 200 ppm based on the component (A). Ranges are preferred.

The component (F), a diorganopolysiloxane, is used as a mold release component, and particularly when a replica mold is prepared from the composition of the present invention as a silicone rubber master mold, it is replicated from the silicone rubber master mold. It is effective for easily peeling the resin and uses a so-called non-functional silicone oil. When this organopolysiloxane has an aliphatic unsaturated group or a hydrosilyl group which is a hydrosilylation functional group, it is fixed in the cured rubber and does not bring about the effect of reducing the peeling force. Therefore, as the substituent bonded to the silicon atom, 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 xylyl group, and a halogen-substituted carbon atom such as a 3,3,3-trifluoropropyl group. Examples include non-functional groups such as hydrogen group and hydroxyl group.

The viscosity of this component (F), the diorganopolysiloxane, is 5,000 to 100,000 cp at 25 ° C.
It is preferable that In this case, it is necessary to use, as the component (F), one whose viscosity is the same as or higher than that of the alkenyl group-containing diorganopolysiloxane of the component (A). When the degree of polymerization is lower than that of the component (A), the diorganopolysiloxane, the effect on the releasability of the copy is reduced.

The blending amount of this component (F) is the same as that of component (A) 1.
It is desirable to set the range of 1 to 50 parts, preferably 5 to 20 parts relative to 00 parts. If the amount is less than 1 part,
The effect of lightening the mold release is small, while when it is more than 50 parts, oil bleeding from the surface of the molded product increases, and the transfer of silicone to the resin replica may increase. In addition,
The effect of the component (F) is exhibited only when it is added to the above-mentioned mixture, and the components (A), (B) and (C) are added together during the heating and mixing treatment. If so, the releasing effect is reduced and the object of the present invention cannot be achieved. However, the temperature at the time of blending may be high or low as long as it is blended in the above mixture.

The composition of the present invention comprises the above mixture (D),
It can be obtained by mixing the components (E) and (F), but in many cases, it is supplied in two packages as the form actually used. In this case, one package is basically composed of a mixture of the components (A), (B), and (C) to which a catalyst of the component (E) is added, and the other package is basically ( It is composed of the component D), and the component (F) may be mixed in any package.

If desired, the composition of the present invention may contain components other than the above-mentioned components within a range not impairing the object of the present invention. For example, when the curing time needs to be adjusted in order to put the alkali metal compounds already proposed by the present inventors and these materials into practical use, a control agent or the like can be added.

When this alkali metal compound is blended with the above-mentioned component (F), the lightness of mold release is further improved.
In this case, as the alkali metal compound, lithium hydroxide, sodium, potassium, cesium and their siliconate compounds (≡SiOM), Li ₂ O, Na ₂ O, K are used.
Oxides such as ₂ O and Cs ₂ O can be used, and the compounding amount thereof is preferably 5 to 10000 ppm as alkali metal atoms with respect to the entire composition.

Examples of the control agent include vinyl group-containing organopolysiloxanes such as vinylcyclotetrasiloxane, triallyl isocyanurate, alkyl maleates, acetylene alcohols and their silanes, siloxane modified products, hydroperoxides, and tetramethylethylenediamine. , Benzotriazole and mixtures thereof.

Further, an inorganic pigment such as cobalt blue, a coloring agent such as an organic dye, a heat resistance and flame retardance improving agent such as cerium oxide, zinc carbonate, manganese carbonate, red iron oxide, titanium oxide and carbon black are blended. Is also good.

The order of blending these components is not particularly limited, but they are usually added and dispersed after mixing the composition of the present invention.

The composition obtained by the present invention is suitable as a material for a reversal type master block such as urethane resin, epoxy resin and gypsum. When such a master block is prepared, it is usually molded into a predetermined shape, A mother mold can be obtained by curing at a temperature of 0 to 100 ° C. for about 10 minutes to 24 hours.

[0040]

According to the present invention, it is possible to obtain an organopolysiloxane composition which gives a mold making mold excellent in releasability and releasability.

[0041]

EXAMPLES Hereinafter, the present invention will be specifically shown by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] Both ends of the molecular chain were blocked with vinyldimethylsilyl groups, and the viscosity at 25 ° C was about 5000 cp.
Dimethylpolysiloxane of 800g and specific surface area BET
About 200 m ² / g by method Aerosil 200
(Nippon Aerosil Co., Ltd.) 200 g was put in a kneader, and 80 g of hexamethylene disilazane was stirred well.
And 10 g of water were added and mixed for 1 hour without heating. After that, the temperature was raised to 150 ° C., mixing was continued for 2 hours, and then the temperature was lowered to room temperature.

To 500 g of the mixture thus obtained, 2 g of dimethylpolysiloxane having a viscosity of 10000 cp at 25 ° C. and a terminal blocked with a trimethylsilyl group, and hydrogenpolysiloxane 25 represented by the following average formula:
g, octyl chloroplatinate octyl alcohol complex as platinum 1
After adding 00 ppm and stirring well, defoaming was performed under vacuum, curing was performed at 60 ° C./2 hours, a sheet was prepared according to JIS K6301, and general physical properties were measured.

[0044]

[Chemical 5]

On the other hand, a concave mother die was formed by the same method as described above, and a urethane resin (30 made by H & K Co.
90) was cast and cured at 60 ° C. for 1 hour, the obtained urethane resin molded product was taken out from the mother mold, and this casting, curing and taking out were repeated, and the surface glossiness of each molded product was measured. . Further, the lightness of peeling when taking out the molded product was evaluated according to the following criteria. ◎: Very light ○: Light △: Heavy ×: Very heavy or bonded

[Examples 2 to 4] Both ends of the molecular chain were blocked with vinyldimethylsilyl groups, and the viscosity at 25 ° C was about 5000.
cp dimethylpolysiloxane 800g and specific surface area B
Hydrophobic fumed silica treated with (CH ₃ ) ₂ SiCl ₂ of about 240 m ² / g by ET method [Aerosil
R-976 (manufactured by Nippon Aerosil Co., Ltd.)] and 200 g were put in a kneader and mixed for 1 hour without heating while well stirring and mixing. After that, the temperature was raised to 150 ° C., mixing was continued for 2 hours, and then the temperature was lowered to room temperature.

500 g of the mixture thus obtained
0.5 g of a compound represented by the following average structural formula at 25 ° C.
Each of which has a viscosity of 10000 cp and is blocked with a trimethylsilyl group at each end.
g, 5 g, 10 g, 25 g of the same organohydrogenpolysiloxane as in Example 1, 100 ppm of chloroplatinic acid octyl alcohol complex was added as platinum, and after thoroughly stirring, defoaming was performed under vacuum, and at 60 ° C./2 hours. After curing, a sheet was prepared according to JIS K6301, and general physical properties were measured.

[0048]

[Chemical 6]

Further, a concave mother die was molded in the same manner as in Example 1, and the urethane resin was cast, cured, and taken out repeatedly in the concave portion, and the surface glossiness of the obtained urethane resin molded product was measured. The lightness of peeling was observed.

[Comparative Example 1] A sheet was prepared in the same manner as in Example 1 except that the dimethylpolysiloxane having a trimethylsilyl group-terminated dimethylpolysiloxane having a viscosity of 10000 cp at 25 ° C used in Example 1 was not added. In addition to measuring general physical characteristics, molding a concave mold in the same manner, repeating casting, curing, and taking out of the urethane resin, measuring the surface gloss of the resulting urethane resin molded product, and reducing peeling. It was observed.

[Comparative Example 2] A non-functional silicone oil was mixed at the time of preparing the mixture as follows to obtain a composition of Comparative Example.

800 g of dimethylpolysiloxane with both ends of the molecular chain blocked with vinyldimethylsilyl groups and a viscosity of about 5000 cp at 25 ° C., dimethylpolysiloxane with both ends of the molecular chain blocked with trimethylsilyl groups and a viscosity of about 100,000 cp at room temperature 3 g, and Aerosil R-812 having a specific surface area of about 200 m ² / g by the BET method.
Hexamethyldisilazane 80 was put into a kneader, and 200 g (manufactured by Degussa of West Germany) was put into a kneader while stirring and mixing well.
g and 10 g of water were added and mixed for 1 hour without heating. After that, the temperature was raised to 150 ° C., mixing was continued for 2 hours, and then the temperature was lowered to room temperature.

To 500 g of the mixture thus obtained, 25 g of the same organohydrogenpolysiloxane as in Example 1 and 100 ppm of octyl alcohol chloroplatinate complex were added as platinum, and after stirring well, defoaming was carried out under vacuum. Was cured at 60 ° C. for 2 hours to prepare a sheet according to JISK6301, and its general physical properties were measured.

In the same manner as in Example 1, a concave mother die was molded, and the urethane resin was cast, cured and taken out repeatedly in the concave portion to measure the surface gloss of the urethane resin molded product obtained. The lightness of peeling was observed.

Comparative Example 3 A composition was prepared as follows, in which a silylating agent was not used during preparation of the mixture, and an alkali metal was used in place of the nonfunctional silicone oil.

200 g of Aerosil R-976 (manufactured by Nippon Aerosil Co., Ltd.), whose both ends of the molecular chain are blocked with vinyldimethylsilyl groups, have a viscosity of about 5000 cp at 25 ° C., and a specific surface area of about 240 m ² / g. Was put into a kneader and mixed for 1 hour without heating while stirring well. After this, increase the temperature to 1
The temperature was raised to 50 ° C., mixing was continued for 2 hours, and then the temperature was lowered to room temperature.

The main component composition 50 thus obtained
In 0 g, 0.5 g of a compound represented by the following average structural formula, the same organohydrogenpolysiloxane 2 as in Example 1
5g, 100ppm of chloroplatinic acid octyl alcohol complex was added as platinum, stirred well, degassed under vacuum, cured at 60 ° C / 2 hours, made into a sheet according to JISK6301, and measured for general physical properties .

[0058]

[Chemical 7]

Further, a concave mother die was molded in the same manner as in Example 1, and the urethane resin was cast, cured and taken out repeatedly in the concave portion to measure the surface gloss of the obtained urethane resin molded article. The lightness of peeling was observed.

Comparative Example 4 A composition was prepared as follows using a non-functional silicone oil having a viscosity lower than that of the alkenyl group-containing diorganopolysiloxane.

Both ends of the molecular chain were blocked with vinyldimethylsilyl groups, 800 g of dimethylpolysiloxane having a viscosity of about 5000 cp at 25 ° C., and a specific surface area of about 240 by the BET method.
200 g of Aerosil R-976 (manufactured by Nippon Aerosil Co., Ltd.), which is m ² / g, was put into a kneader and mixed for 1 hour without heating while stirring well. After this,
The temperature was raised to 150 ° C., and after mixing for 2 hours, the temperature was lowered to room temperature.

500 g of the mixture thus obtained
0.5 g of a compound represented by the following average structural formula at 25 ° C.
10 g of a dimethylpolysiloxane end-capped with a trimethylsilyl group having a viscosity of 100 cp in Example 1, Example 1
25 g of the same organohydrogenpolysiloxane as
100% octyl chloroplatinate octyl alcohol complex as platinum
After adding ppm and stirring well, defoaming under vacuum,
It was cured at 60 ° C./2 hours, a sheet was prepared according to JIS K6301, and general physical properties were measured.

[0063]

[Chemical 8]

Further, a concave mother die was molded in the same manner as in Example 1, and the urethane resin was cast, cured and taken out repeatedly in the concave portion to measure the surface glossiness of the obtained urethane resin molded article. The lightness of peeling was observed.

[0065]

[Table 1] * Viscosity is measured using Brookfield viscometer (BH)
Rotor No. The measurement was performed under the measurement conditions of 6 and 10 revolutions.

From the results shown in Table 1, it can be seen that the cured product obtained from the composition according to the method of the present invention has good general physical properties, good peeling durability, and light peeling.

On the other hand, when the non-functional silicone oil is not blended (Comparative Example 1), the releasability is poor, and when the non-functional silicone oil is added when the mixture is heated and mixed (Comparative Example 2), the releasability is also improved. When the alkali metal was not mixed and the nonfunctional silicone oil was not added (Comparative Example 3), the peeling durability was good, but the peeling was very heavy and the viscosity of the nonfunctional silicone oil contained an alkenyl group. When the one smaller than the diorganopolysiloxane was used (Comparative Example 4), the peeling durability was good because the alkali metal was blended, but the peeling was heavy and the effect of adding the nonfunctional silicone oil was recognized. It was not there.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Morio Ohashi No. 1 Hitomi, Osamu, Matsuida-cho, Usui-gun, Gunma Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (2)

[Claims] 1. A viscosity at 25 ° C. of 500 to 30,000 cp
A mixture of finely divided silica treated with a silylating agent in a diorganopolysiloxane having at least two alkenyl groups in one molecule, and having at least two SiH groups in one molecule An organohydrogenpolysiloxane, a catalyst for hydrosilylation reaction,
An organopolysiloxane composition for a casting mold, which comprises mixing the above-mentioned alkenyl group-containing diorganopolysiloxane with a diorganopolysiloxane having a viscosity equal to or higher than that having no hydrosilylation-reactive functional group. Manufacturing method. 2. The mixture is obtained by mixing the alkenyl group-containing diorganopolysiloxane, finely divided silica and a silylating agent at less than 100 ° C. and then heating and mixing at 100 to 200 ° C. 1. The manufacturing method according to 1.