JPH1060281A - Addition-curable silicone rubber composition filled with calcium carbonate - Google Patents

Abstract

(57) [Problem] To provide an addition reaction-curable silicone rubber composition filled with calcium carbonate. SOLUTION: (A) A diorganopolysiloxane containing at least two alkenyl groups in one molecule, (B)
An organohydrogenpolysiloxane containing at least two hydrogen atoms in one molecule bonded to a silicon atom,
A calcium carbonate-filled addition reaction-curable silicone rubber composition containing (C) a platinum group metal-based catalyst and (D) calcium carbonate powder surface-treated with a partially hydrolyzed condensate of tetraalkoxysilane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an addition reaction-curable silicone rubber composition filled with calcium carbonate, a method for producing the same, and a cured product obtained by curing the composition.

[0002]

2. Description of the Related Art Conventionally, calcium carbonate has been used for the purpose of improving the properties of silicone rubber, such as heat resistance and electrical insulation, and is mainly used for millable silicone rubber by organic peroxide crosslinking or condensation crosslinking. Used in RTV silicone rubber. However, it is not used for silicone rubber by addition reaction crosslinking. The reason is that calcium carbonate powder usually used as a filler contains an alkali component as an impurity, and the alkali component is contained as a crosslinking agent in an addition reaction-curable silicone rubber composition. This is because hydrogen gas is generated by reacting with genpolysiloxane. The generation of hydrogen gas in this manner may cause foaming of the composition during storage or increase the internal pressure of the container containing the composition, causing the container to burst.

On the other hand, an addition-reaction-curable silicone rubber composition does not require a long curing time unlike a condensation-type RTV silicone rubber composition. In a high-temperature state under sealing like silicone rubber, the polysiloxane of the component is cleaved, which is advantageous in that so-called reversion does not occur, so that an addition reaction-curable silicone rubber composition filled with calcium carbonate is used. Is desired. However, a calcium carbonate-filled addition reaction-curable silicone rubber composition has not yet been provided for the above-mentioned reason.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an addition-curable silicone rubber composition filled with calcium carbonate, a method for producing the same, and a cured product obtained by curing the composition. is there.

[0005]

The present invention provides (A) a diorganopolysiloxane containing at least two alkenyl groups in one molecule, and (B) at least a hydrogen atom bonded to a silicon atom in one molecule. Calcium carbonate-filled addition reaction curable silicone containing calcium carbonate powder surface-treated with two organohydrogenpolysiloxanes, (C) a platinum group metal-based catalyst, and (D) a partially hydrolyzed condensate of tetraalkoxysilane A rubber composition is provided.

The present invention also relates to a method for producing the above composition, comprising mixing calcium carbonate powder and a partially hydrolyzed condensate of tetraalkoxysilane and then subjecting the mixture to heat treatment or the method (A). After mixing a part or all of the component and the calcium carbonate powder and the partially hydrolyzed condensate of tetraalkoxysilane, the mixture is heat-treated, and the mixture is mixed with the components (A), (B) and ( Provided is a process for producing an addition reaction-curable silicone rubber composition filled with calcium carbonate, which comprises mixing the remaining components of the group consisting of component (C).

[0007] The present invention also provides a cured product obtained by curing the above composition.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

(A) Alkenyl group-containing diorganopolicy
Loxane The alkenyl group-containing diorganopolysiloxane used in the composition of the present invention contains at least two alkenyl groups in one molecule, and usually has a main chain portion consisting essentially of repeating diorganosiloxane units. In general, both ends of the molecular chain are straight-chained with triorganosiloxy groups, but even if the molecular structure contains a branched structure as part of the molecular structure. Although it may be a cyclic body, a linear diorganopolysiloxane is preferred from the viewpoint of physical properties such as mechanical strength of the cured product. Even if the alkenyl group is present only at both ends of the molecular chain,
Alternatively, it may be present at both ends of the molecular chain and in the middle of the molecular chain. As a typical example of such an alkenyl group-containing diorganopolysiloxane, for example, the following general formula (1):

[0010]

Embedded image (Wherein, R ¹ is independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond, X is an alkenyl group, n is an integer of 0 or 1 or more, and m is Which is an integer of 0 or 1 or more).

In the formula, the unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond represented by R ¹ includes, for example,
Methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group,
Alkyl groups such as neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl;
Cycloalkyl groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and biphenylyl group;
Benzyl group, phenylethyl group, phenylpropyl group,
An aralkyl group such as a methylbenzyl group; and a group in which part or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with a halogen atom such as fluorine, chlorine, bromine, or a cyano group, for example, chloro Methyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6
6,6-nonafluorohexyl group and the like, a typical one having 1 to 10 carbon atoms, a particularly typical one having 1 to 6 carbon atoms, preferably a methyl group, An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group, a cyanoethyl group, and a phenyl group, a chlorophenyl group, and a fluoro group. It is an unsubstituted or substituted phenyl group such as a phenyl group.

In the formula, the alkenyl group represented by X includes, for example, those having about 2 to 8 carbon atoms, such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl and cyclohexenyl. Among them, lower alkenyl groups such as vinyl group and allyl group are preferable.

In the formula, n is 0 or an integer of 1 or more;
Is 0 or an integer of 1 or more. Also, n and m are 10 ≦
It is preferably an integer satisfying n + m ≦ 10,000, more preferably 50 ≦ n + m ≦ 2,000, and 0 ≦ m /
It is an integer satisfying (n + m) ≦ 0.2.

The alkenyl group-containing diorganopolysiloxane has a viscosity at 25 ° C. of 10 to 1,000.
It is preferable to use those having a cSt of about 000 cSt, especially about 100 to 500,000 cSt.

(B) Organohydrogen polysiloxane
The organohydrogenpolysiloxane used in the composition of the present invention contains at least two, preferably 3 or more per molecule.
Hydrogen atoms bonded to one or more silicon atoms (ie, SiH
And a resin having a linear, branched, cyclic, or three-dimensional network structure. Representative examples of such organohydrogenpolysiloxanes include, for example, the following average composition formula (2): H _a R ² _b SiO _{(4-ab) / 2} (2) (wherein R ² is independently a fat An unsubstituted or substituted monovalent hydrocarbon group containing no group unsaturated bond;
<A <2, 0.8 ≦ b ≦ 2 and 0.8 <a + b ≦ 3, preferably 0.05 ≦ a ≦ 1, 1.5 ≦ b ≦ 2 and 1.
8 ≦ a + b ≦ 2.7).

In the formula, as the unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bond of R ² , the same as those exemplified as R ^{1 in the} general formula (1) can be mentioned. Typical are those having 1 to 10 carbon atoms, particularly 1 to 7 carbon atoms, preferably lower alkyl groups having 1 to 3 carbon atoms such as methyl group, phenyl group, 3, 3
, 3-trifluoropropyl group. Examples of such organohydrogenpolysiloxanes include, for example, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, 1,3,5,7, Siloxane oligomers such as 8-pentamethylpentacyclosiloxane; methylhydrogenpolysiloxane blocked with trimethylsiloxy groups at both ends of molecular chain, dimethylsiloxane / methylhydrogensiloxane copolymer blocked with trimethylsiloxy groups at both ends of molecular chain, silanol at both ends of molecular chain Group-blocked methyl hydrogen polysiloxane, molecular chain terminal silanol group-blocked dimethylsiloxane / methyl hydrogen siloxane copolymer, molecular chain terminal dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, molecular chain terminal dimethylhydrogensiloxy group-blocked Methyl hydrogen Polysiloxane with both molecular chain terminals blocked with dimethylhydrogensiloxy groups dimethylsiloxane-methylhydrogensiloxane copolymers; R ₂ (H)
It consists of SiO _1/2 units and SiO _4/2 units, and optionally R ₃
SiO _1/2 unit, R ₂ SiO _2/2 unit, R (H) SiO
_A silicone resin which may contain _2/2 units, (H) SiO _3/2 units or RSiO _3/2 units, wherein R is an unsubstituted or substituted monovalent hydrocarbon group exemplified as R ¹ above. And the like; and the following formula:

[0017]

Embedded image And the like.

The organohydrogenpolysiloxane used in the composition of the present invention can be obtained by a known method. For example, the following general formulas: R ² SiHCl ₂ and R ² ₂ SiHCl (where R ² is as defined above) cohydrolysis of at least one chlorosilane selected from the same a is), or the chlorosilanes with the following formula: from R ² ₃ SiCl and R ^{₂ 2} SiCl ² (wherein, R ² is as defined above) It can be obtained by co-hydrolyzing a combination of at least one selected chlorosilane. Further, the organohydrogenpolysiloxane may be one obtained by equilibrating the polysiloxane obtained by co-hydrolysis in this manner.

Component (B) is used in an amount of hydrogen bonded to silicon atoms in organohydrogenpolysiloxane of component (B) per mole of alkenyl groups in alkenyl group-containing diorganopolysiloxane of component (A). An amount such that the atoms (i.e., SiH groups) are usually 0.5-4 moles,
Preferably, the amount is from 1 to 2.5 mol.

(C) Platinum Group Metal-Based Catalyst The platinum group metal-based catalyst used in the present invention comprises the above-mentioned component (A)
And a hydrogen atom bonded to a silicon atom of the component (B). The catalyst is a catalyst for promoting an addition reaction, and includes well-known catalysts used for the hydrosilylation reaction. Specific examples thereof include, for example, platinum group metals 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 , N
a ₂ HPtCl ₄ .nH ₂ O (wherein, n is an integer of 0 to 6, preferably 0
Or 6), such as platinum chloride, chloroplatinic acid and chloroplatinate; alcohol-modified chloroplatinic acid (US Pat. No. 3,22)
No. 0,972); complex of chloroplatinic acid and an olefin (US Pat. Nos. 3,159,601, 3,159,662 and 3,773).
No. 5,452); platinum group metals such as platinum black and palladium supported on a carrier such as alumina, silica and carbon; rhodium-olefin complex; chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst) A complex of platinum chloride, chloroplatinic acid or chloroplatinate and a vinyl group-containing siloxane, particularly a vinyl group-containing cyclic siloxane.

The amount of component (C) used may be a so-called catalytic amount, and is usually 0.1 to 500 ppm, especially 0.5 to 500 ppm in terms of platinum group metal weight based on the total amount of component (A) and component (B).
It may be about 200 ppm.

(D) Surface Treated Calcium Carbonate Powder The calcium carbonate powder used in the present invention is a surface treated with a partially hydrolyzed condensate of tetraalkoxysilane. In addition reaction-curable silicone rubber compositions containing calcium carbonate powder subjected to such surface treatment,
The dehydrogenation reaction of the organohydrogenpolysiloxane caused by the elution of the alkali component from the calcium carbonate powder is reduced. Therefore, the component (D) prevents foaming during storage of the composition and prevents the container containing the composition from rupture due to an increase in internal pressure of the container. It imparts properties such as properties and electrical insulation.

The partially hydrolyzed condensate of tetraalkoxysilane The tetraalkoxysilane used in the present invention is represented by the following general formula: Si (OR ³ ) ₄ (wherein R ³ is independently an unsubstituted or lower alkoxy-substituted alkyl group. Is). In the formula, as the unsubstituted or lower alkoxy-substituted alkyl group for R ³ , for example,
Methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group,
Usually 1 to 12 carbon atoms, preferably 1 to 12 carbon atoms, such as neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl and methoxymethyl, methoxyethyl, ethoxymethyl, ethoxyethyl About 1 to 6 are exemplified.

Examples of such a partially hydrolyzed condensate of tetraalkoxysilane include, for example, the following average composition formula: [(OR ³ ) ₃ SiO _1/2 ] _K [(OR ³ ) ₂ SiO _2/2 ] _L [ (OR ³ ) SiO _3/2 ] _M [S
iO _4/2 ] _N (wherein R ³ is the same as above, and K, L, M and N
Are K + L + M + N = 1, 0.002 ≦ K ≦ 1, 0 ≦ L ≦ 0.
998, which satisfies 0 ≦ M ≦ 0.998 and 0 ≦ N ≦ 0.35). Particularly typical ones are represented by the following general formula (3): R ³ O— [Si (OR ³ ) ₂ O] _j -R ³ (3) (wherein R ³ is the same as above, and j is an integer of 1 or more). Such a partially hydrolyzed condensate of tetraalkoxysilane has a weight average molecular weight of
Those having 150 to 100,000 are preferred.

Calcium carbonate powder As the calcium carbonate powder to be subjected to the surface treatment, known ones can be used, but preferably precipitated calcium carbonate produced by a chemical method is preferred because of its high purity. The average particle size of the calcium carbonate powder is usually 0.1
It may be about 30 μm, and can be appropriately selected depending on the application.

Surface treatment As a surface treatment method, a known wet treatment method or dry treatment method can be used. Specific examples of such a surface treatment method include, for example, dissolving the partial hydrolysis condensate of the tetraalkoxysilane in an appropriate solvent, or dispersing it in a dispersion medium, and then adding the carbonic acid to the solution or dispersion. After mixing the calcium powder, a method of heating and drying may be used. Examples of the solvent or dispersion medium include toluene and xylene. The heating and drying conditions may be, for example, about 80 to 200 ° C. for about 0.5 to 10 hours.

As another surface treatment method, for example, a part or all of the component (A) (usually 30% or more,
50% or more), and calcium carbonate powder and a partially hydrolyzed condensate of tetraalkoxysilane.
A method of subjecting the mixture to heat treatment can be used. The conditions of the heat treatment are, for example, 0.5 to 10 at 80 to 200 ° C.
It takes about an hour. As described above, the surface treatment by mixing a part or all of the component (A) with the calcium carbonate powder and the partially hydrolyzed condensate of tetraalkoxysilane is carried out by mixing the components in the production process of the composition of the present invention. In the step or the kneading step, the surface treatment of the calcium carbonate powder can be performed at the same time.

The amount of the partially hydrolyzed condensate of tetraalkoxysilane can be appropriately adjusted according to the specific surface area and other properties of the calcium carbonate powder.
0.1 to 20 per 100 parts by weight of calcium carbonate powder
It may be about parts by weight. By such a surface treatment, a siloxane coating is formed on the surface of the calcium carbonate powder,
Prevents elution of alkaline components from calcium carbonate powder.

The amount of the surface-treated calcium carbonate powder is usually 5 to 200 parts by weight per 100 parts by weight of the alkenyl group-containing diorganopolysiloxane of the component (A).
Preferably it is 10 to 100 parts by weight. If the amount is too small, the heat resistance and electrical insulation of the obtained cured product may be insufficient, and if it is too large, the viscosity of the obtained curable silicone rubber composition increases and the fluidity is poor. May be.

Other Components In addition to the above-mentioned components (A), (B), (C) and (D), the composition of the present invention may further comprise, if necessary, for example, fumed silica or fumed silica. Reinforcing inorganic fillers such as titanium; non-reinforcing inorganic fillers such as calcium silicate, titanium dioxide, ferric oxide and carbon black can be added. The amount of the inorganic filler to be used is usually 0 to 200 parts by weight per 100 parts by weight of the total amount of the components excluding the inorganic filler.

Curable silicone rubber composition and curing thereof
The composition of the present invention may be the same as the ordinary curable silicone rubber composition, for example, the components (A), (C) and (D), and the components (A) and (B). May be divided into two liquids, and the two liquids may be mixed and cured at the time of use to form a so-called two-part composition. Also, (A)
In the case of using a method in which a part or all of the components are mixed with the calcium carbonate powder and the partially hydrolyzed condensate of tetraalkoxysilane and the surface treatment of the calcium carbonate powder is performed at the same time, for example, the component (A) Alternatively, a partially hydrolyzed condensate of all and alkoxysilane and calcium carbonate powder are mixed together, and the mixture is heat-treated to prepare a preliminarily prepared two-pack composition using this as one liquid. . Also, a so-called one-pack type composition in which the components (A) to (D) are mixed and a small amount of a curing inhibitor (for example, acetylene alcohol or the like) is added to the composition may be used. For the purpose of improving the adhesiveness of the composition, an epoxy group-containing polysiloxane compound or an ester siloxane compound may be added, if necessary, in addition to the above components. The composition of the present invention thus obtained has good flowability. The cured product of the present invention is obtained by curing the composition. The curing conditions may be the same as those of a known addition reaction-curable silicone rubber composition. For example, the composition may be sufficiently cured at room temperature, but may be heated if necessary. Such a cured product of the present invention is excellent in heat resistance and electrical insulation.

[0032]

The present invention will be described more specifically below with reference to examples and comparative examples. Example 1 The following formula (4): Vi (Me) ₂ Si- (OSiMe ₂ ) _n -OSi (Me) ₂ Vi (4) (wherein Me is the same as above, Vi is a vinyl group, n is a viscosity of 1000 cS at 25 ° C. of the siloxane.
40 parts by weight of a vinyl group-containing linear organopolysiloxane represented by the following general formula (4): In the general formula (4), n represents a viscosity of 5000 cS at 25 ° C.
t: 60 parts by weight of a linear organopolysiloxane blocked with a vinyl group at both ends of the molecular chain, calcium carbonate [FP manufactured by Nichia Chemical Co., Ltd., average particle size: 1.2 μm, alkali content] : 0.02% by weight (calcium hydroxide equivalent)] 40 parts by weight, partially hydrolyzed condensate of tetraethoxysilane (SiO ₂ content 40% by weight) [manufactured by Colcoat Co., Ltd., (trade name) ethyl polysilicate 40T ] 2
After kneading the parts by weight with three rolls, the kneaded material was kneaded at 160 ° C. for 3 hours using a planetary mixer. Next, methyl kneaded polysiloxane (hydrogen atom (SiH group) bonded to silicon atom) is added to this kneaded material.
Of octyl alcohol modified with chloroplatinic acid (platinum content: 2% by weight) and stirred with stirring to obtain a curable silicone rubber composition. Was. As a result of measuring the viscosity of the composition using a B-type rotational viscometer, it was 36 P (the same applies to poise (25 ° C.) or less). For the obtained composition, the following extracted water conductivity, hydrogen gas generation amount, rubber properties (hardness, tensile strength, elongation) of the cured product, and electrical properties of the cured product (volume resistivity, dielectric breakdown voltage, dielectric Rate, dielectric loss tangent), and heat resistance of the cured product were measured, and the foamed state of the cured product was observed. Table 1 shows the results. 20 parts by weight of the composition obtained by extraction water conductivity , 40 parts by weight of special grade toluene,
100 parts by weight of pure water was poured into a separating funnel, which was shaken for 1 hour and allowed to stand, and the aqueous phase was separated therefrom. And
The conductivity (μS / cm) of the separated water was measured using a conductometer. Amount of hydrogen gas generated 5 g of the obtained composition was sealed in a 500 ml headspace bottle, left at room temperature for 48 hours, and the amount of hydrogen gas generated in the bottle was measured by gas chromatography. Rubber Composition of Cured Product The resulting composition was poured into a 150 mm × 100 mm × 2 mm mold, which was degassed in vacuo and heated at 150 ° C. for 4 hours to obtain a sheet-shaped cured product. The obtained cured product was measured according to JIS K6301. The hardness used was A type spring hardness tester. Electrical Properties of Cured Product The obtained composition was poured into a 150 mm × 100 mm × 1 mm mold, which was degassed under vacuum and heated at 150 ° C. for 4 hours to obtain a sheet-shaped cured product. The obtained cured product was measured according to JIS C 2123. Heat resistance of cured product The hardness of a sheet-like cured product similar to the one used for the measurement of the rubber physical properties after heating at 250 ° C. for 24 hours and the hardness after heating at the same temperature for 48 hours were determined by JISK. 630
The measurement was carried out in accordance with No. 1 (using a spring type hardness tester type A). The foamed state of the cured product The obtained cured product was visually observed to determine the presence or absence of foaming. Example 2 Example 2 was repeated except that 2 parts by weight of a partially hydrolyzed condensate of tetramethoxysilane [weight average molecular weight (Mw): 788] was used instead of the partially hydrolyzed condensate of tetraethoxysilane. In the same manner as in 1, a curable silicone rubber composition was obtained. As a result of measuring the viscosity of the composition using a B-type rotational viscometer, it was 37 P. Then, using the obtained composition, in the same manner as in Example 1, the extraction water conductivity, the amount of generated hydrogen gas, the rubber properties (hardness, tensile strength, elongation) of the cured product, and the electrical properties (volume) of the cured product Resistance, dielectric breakdown voltage, dielectric constant, dielectric loss tangent), and heat resistance of the cured product.
The foamed state of the cured product was observed. Table 1 shows the results. Comparative Example 1 A curable silicone rubber composition was obtained in the same manner as in Example 1, except that 3 parts by weight of hexamethyldisilazane was used instead of the partially hydrolyzed condensate of tetraethoxysilane. . As a result of measuring the viscosity of the composition using a B-type rotational viscometer, it was 41 P. Then, using the obtained composition, in the same manner as in Example 1, the extraction water conductivity, the amount of generated hydrogen gas, the rubber properties (hardness, tensile strength, elongation) of the cured product, and the electrical properties (volume) of the cured product Resistance, dielectric breakdown voltage, dielectric constant, dielectric loss tangent), and heat resistance of the cured product.
The foamed state of the cured product was observed. Table 1 shows the results. Comparative Example 2 A curable silicone rubber composition was obtained in the same manner as in Example 1 except that the partially hydrolyzed condensate of tetraethoxysilane was not used. As a result of measuring the viscosity of the composition using a B-type rotational viscometer, it was 46 P. Then, using the obtained composition, in the same manner as in Example 1, the extraction water conductivity, the amount of generated hydrogen gas, the rubber properties (hardness, tensile strength, elongation) of the cured product, and the electrical properties (volume) of the cured product The resistivity, the dielectric breakdown voltage, the dielectric constant, the dielectric loss tangent) and the heat resistance of the cured product were measured, and the foamed state of the cured product was observed. Table 1 shows the results. Comparative Example 3 A curable silicone rubber composition was obtained in the same manner as in Example 1, except that 3 parts by weight of monomethyltriethoxysilane was used instead of the partially hydrolyzed condensate of tetraethoxysilane. . As a result of measuring the viscosity of the composition using a B-type rotational viscometer, it was 42P. Then, using the obtained composition, in the same manner as in Example 1, the extraction water conductivity, the amount of generated hydrogen gas, the rubber properties (hardness, tensile strength, elongation) of the cured product, and the electrical properties (volume) of the cured product The resistivity, the dielectric breakdown voltage, the dielectric constant, the dielectric loss tangent) and the heat resistance of the cured product were measured, and the foamed state of the cured product was observed. Table 1 shows the results.

[0033]

[Table 1] As shown in Evaluation Table 1, the composition of the present invention (see Examples 1 and 2) uses silazane (see Comparative Example 1) or carbon functional silane (see Comparative Example 3) as a surface treatment agent for calcium carbonate. The amount of hydrogen gas generated is smaller and the physical properties of the cured product are superior to those obtained by heat treatment of calcium carbonate and silicone oil (see Comparative Example 2).

[0034]

According to the present invention, it is possible to provide a calcium carbonate-filled addition reaction-curable silicone rubber composition which generates an extremely small amount of hydrogen gas during storage. The composition is excellent in fluidity, heat resistance after curing, electric properties such as electric insulation, and rubber properties. Further, the manufacturing method of the present invention can achieve rationalization by saving energy and reducing the process time in the manufacturing process.

Claims (3)

[Claims] 1. A diorganopolysiloxane containing at least two alkenyl groups per molecule, (B)
An organohydrogenpolysiloxane containing at least two hydrogen atoms in one molecule bonded to a silicon atom,
A calcium carbonate-filled addition reaction-curable silicone rubber composition containing (C) a platinum group metal-based catalyst and (D) calcium carbonate powder surface-treated with a partially hydrolyzed condensate of tetraalkoxysilane. 2. The method for producing a composition according to claim 1, wherein the calcium carbonate powder and a partially hydrolyzed condensate of tetraalkoxysilane are mixed, and then the mixture is heat-treated, or A) some or all of the components;
After mixing the calcium carbonate powder and the partially hydrolyzed condensate of tetraalkoxysilane, the mixture is heat-treated, and the mixture is mixed with the components (A), (B) and (C).
A process for producing an addition reaction-curable silicone rubber composition filled with calcium carbonate, characterized by mixing the remaining components of the group consisting of the components. 3. A cured product obtained by curing the composition according to claim 1.