JPH08208852A - Production of polyorganosiloxane elastomer - Google Patents

Abstract

PURPOSE: To obtain a polyorganosiloxane elastomer uncured at ordinary temperature, capable of curing in a short time by heating, providing a cured product having excellent adhesiveness and oil resistance and useful for gasket and packing material, etc., by heat-curing a specific curable polyorganosiloxane composition at a specific temperature. CONSTITUTION: A curable polyorganosiloxane composition containing (A) 100 pts.wt. α,ω-dihydroxypolydiorganosiloxane of formula I [R<1> and R<2> are each a (substituted) monovalent hydrocarbon group; (m) is a number capable of providing 100-200000cSt viscosity at 25 deg.C], (B) 0.5-20 pts.wt. compound of the formula R<3> a Si(ON=X)4-a [R<3> is R<1> ; X is a group of CR<4> 2 (R<4> is R<1> ) or a group of formula II (R<5> is a (substituted) divalent hydrocarbon group; (a) is 0 or 1)] or its partial hydrolysis condensation product and (C) 0.1-10 pts.wt. compound of the formula R<6> Si(OR<7> )3 [R<6> is R<1> ; R<7> is a 1-8C (substituted) monovalent hydrocarbon group] or its partial hydrolysis condensation product and not containing a curing catalyst having metal in the molecule is cured by heating at 50-200 deg.C to provide the objective elastomer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyorganosiloxane elastic body, and more specifically, it is cured in a short time to exhibit excellent adhesiveness, has excellent oil resistance, and is useful as a gasket / packing material. To a method for producing a flexible polyorganosiloxane elastic body.

[0002]

2. Description of the Related Art Conventionally, gaskets and packing materials made of various kinds of organic rubber have been used for seals around the engine of automobiles, but they have the drawback of poor oil resistance and rapid deterioration. . In order to avoid the problem of working environment and pollution due to dust, a gasket made by binding aramid fiber with NBR and a gasket such as stainless steel or carbon are used to replace asbestos. However, since the sealing property is poor, a method of covering a part or all of the surface of these gaskets with an elastic body is adopted. Even in such applications, an elastic body having excellent oil resistance is earnestly desired.

Silicone rubbers obtained by curing a flowable polyorganosiloxane as a base polymer by the action of a cross-linking agent and a curing catalyst are generally called liquid silicone rubbers, and are condensed depending on the mechanism of the curing reaction. Reaction-curable silicone rubber (hereinafter simply referred to as condensation-type silicone rubber), addition reaction-curable silicone rubber (hereinafter simply referred to as addition-type silicone rubber)
Since it is easy to handle, you can obtain gaskets and packings of any shape by applying and curing it on the required parts, so there is no need to rationalize the process or store packings of various shapes in advance. It is widely used for rationalization of material management.

Of these, the addition type silicone rubber is
Although it has the process advantage of being cured by heating for a short time, it is cured by a trace amount of platinum-based catalyst, so it does not cure when a trace amount of a catalyst inhibitor is present on the treated surface, especially aramid which is a mainstream asbestos substitute. NB fiber
Since the surface of the gasket bound by R does not cure, there are restrictions on the application.

On the other hand, the condensation type silicone rubber functions as a cross-linking agent in a polyorganosiloxane which is a base polymer, typically with a silanol group or a silicon functional group present at the molecular end of a linear polydiorganosiloxane. The silane or the silicon-functional group present in the low molecular weight siloxane undergoes a condensation reaction mediated by moisture in the air to form a crosslinked structure and cure at room temperature. This product does not require heating for curing and has the advantage of exhibiting excellent adhesiveness, but since the curing reaction proceeds at room temperature, the viscosity of the composition can be reduced in a short time by contact with moisture in the air. As a result, the workability is restricted in the work of coating the surface of the gasket or packing by screen printing, for example. On the other hand, it takes a long time to completely cure, which is an obstacle to the process. In the case of the conventional condensation type silicone rubber, this curing reaction has a smaller effect of shortening the curing speed than the addition type silicone rubber even if the temperature is raised for curing, rather, it is cured in the presence of a curing catalyst. If the temperature is raised significantly, the polysiloxane chain may be cleaved, resulting in deterioration of the physical properties of the rubber.

A deoxime reaction-curable silicone rubber composition (hereinafter simply referred to as an oxime type silicone rubber) using an oxime group-containing silane or a partial hydrolysis-condensation product thereof as a cross-linking agent is a representative of the above condensation type silicone rubbers. One of these is a compound having a metal atom in its molecule, such as an organotin compound, as a curing catalyst.
Those that cure at room temperature are known. Further, in order to improve the adhesiveness of this type of silicone rubber, an amino group-containing alkoxysilane (Japanese Patent Publication No. 46-11272, etc.) or a reaction product of an epoxy group-containing alkoxysilane and an amino compound (Japanese Patent Application Laid-Open No. S60-187242). 54-90348
It is also known to incorporate a carbon-functional silicon compound such as the above-mentioned publication). However, when such an alkoxy group-containing silicon compound is blended to heat-cure an oxime-type silicone rubber, there is a problem that the polysiloxane chain is cleaved due to the presence of the above-mentioned curing catalyst.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above problems and is a condensation type silicone rubber which can be stably stored in an uncured state at room temperature and is cured in a short time by heating. It exhibits excellent adhesiveness, and there is no drawback that the physical properties of rubber are degraded due to the cleavage of polysiloxane chains.
An object of the present invention is to provide a method for producing a polyorganosiloxane elastic body which has excellent oil resistance and is useful as a gasket / packing material and the like.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, have found that an elastic body obtained by heating and curing a polyorganosiloxane composition having the following composition is expected. The present invention has been completed by finding out that it has the performance of.

That is, the present invention provides (A) the general formula:

[0010]

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(Wherein R ¹ and R ² are each independently the same or different substituted or unsubstituted 1
Represents a valent hydrocarbon group; m has a viscosity of 10 at 25 ° C.
Α, ω-dihydroxypolydiorganosiloxane 100 having a number of 0 to 200,000 cSt)
Parts by weight; (B) General formula: R ³ _a Si (ON = X) _4-a (II) (In the formula, R ³ represents a substituted or unsubstituted monovalent hydrocarbon group; X is = CR ⁴ ₂ or

[0012]

[Chemical 4]

[0013] represents a group, R ⁴ represents mutually same or different substituted or unsubstituted monovalent hydrocarbon group, R ⁵
Represents a substituted or unsubstituted divalent hydrocarbon group; a is 0
Or 20) 0.5 to 20 parts by weight of an oxime group-containing silane or a partial hydrolysis-condensation product thereof; and (C) general formula: R ⁶ Si (OR ⁷ ) ₃ (III) (wherein R is ⁶ represents a substituted or unsubstituted monovalent hydrocarbon group; R ⁷ represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms) or an alkoxy group-containing silane represented by A polyorganosiloxane composition containing 0.1 to 10 parts by weight of a decomposition condensate and containing substantially no curing catalyst having a metal atom in the molecule is used in an amount of 50 to 200.
The present invention relates to a method for producing a polyorganosiloxane elastic body which is cured by heating at ° C.

The component (A) used in the present invention, α, ω-
Dihydroxypolydiorganosiloxane has the general formula:

[0015]

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(Wherein R ¹ , R ² and m are as described above) is a substantially linear polysiloxane having both ends blocked with silanol groups. It is a base polymer for forming.

R ¹ and R ² are respectively methyl, ethyl, propyl, butyl, pentyl, hexyl,
Chain or branched alkyl groups such as octyl, decyl, dodecyl; cycloalkyl groups such as cyclohexyl;
Alkenyl groups such as vinyl, allyl and 1-butenyl; aryl groups such as phenyl and tolyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; chloromethyl, 3-chloropropyl, 3,3,3-trifluoro Examples thereof include halogen-substituted hydrocarbon groups such as propyl and p-chlorophenyl; cyano-substituted hydrocarbon groups such as 3-cyanopropyl; and alkoxy-substituted hydrocarbon groups such as 3-methoxypropyl. The same or different May be. The composition before curing has a viscosity range that is easy to handle, the composition after curing has excellent rubber elasticity, and the heat resistance characteristic of polyorganosiloxane,
Since it typically shows various properties such as cold resistance and weather resistance,
It is preferable that 90% or more of R ¹ and R ² be methyl groups, and it is more preferable that substantially all of them be methyl groups. Particularly when heat resistance, cold resistance and / or radiation resistance are required, a phenyl group is used, and particularly when solvent resistance is required, a 3,3,3-trifluoropropyl group is used, R ¹ and / or It can be appropriately introduced as at least a part of R ² .

M is 25 of the polydiorganosiloxane
The viscosity at 100C is 100 to 200,000 cSt, preferably 500 to 100,000 cSt. When (A) is less than 100 cP, the elastic body obtained by curing does not exhibit sufficient physical properties, and the elastic body has a viscosity of 200,000 cP.
If it exceeds, the apparent viscosity in the uncured state of the composition is high, and it is difficult to mix the composition to obtain a uniform composition and to extrude the composition onto the surface of an adherend, and the curability tends to be poor. .

The component (B) used in the present invention functions as a cross-linking agent and an adhesiveness-imparting agent for the component (A) together with the component (C) described below in order to form an elastic body according to the present invention. General formula: An oxime group-containing silane compound represented by R ³ _a Si (ON = X) _4-a (wherein R ³ , X and a are as described above) or a partial hydrolysis-condensation product thereof.

Examples of R ³ include those within the ranges exemplified as R ¹ and R ² described above. Since they are easy to synthesize and show excellent curability, they are lower groups such as methyl, ethyl, propyl and butyl. Alkyl groups and vinyl groups are preferred.

Examples of R ⁴ which constitutes X as ═CR ⁴ ₂ include those within the range exemplified as R ¹ and R ² described above. Since they are easy to synthesize and have appropriate curability, methyl, Ethyl, propyl and the like are preferable, and it is particularly preferable that two R ^{4 s in} X are both methyl, or one is methyl and the other is ethyl. Examples of R ⁵ include divalent hydrocarbon groups such as pentamethylene and hexamethylene; and divalent halogenated hydrocarbon groups such as chloropentamethylene.

Examples of the oxime group-containing silane compound include methyltris (acetoneoxime) silane, methyltris (methylethylketoxime) silane, methyltris (cyclopentanoneoxime) silane, vinyltris (acetoneoxime) silane, vinyltris (methylethylketoxime) silane. , Tetrakis (acetone oxime) silane, tetrakis (methylethylketoxime) silane and the like.

Such oxime group-containing silane compounds may be used alone or in combination of two or more, and a low molecular weight siloxane compound obtained by partial hydrolysis condensation of these is used as a part or the whole. May be.

The amount of component (B) in the curable polyorganosiloxane composition is 0.5 to 20 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of component (A). If the amount is less than 0.5 parts by weight, curing is insufficient,
If it exceeds 20 parts by weight, the resulting elastic body becomes too hard and becomes brittle.

The component (C) used in the present invention functions as a cross-linking agent and an adhesiveness-imparting agent for the component (A) together with the above-mentioned component (B), and has the general formula: R ⁶ Si (OR ⁷ ). A silane represented by ₃ (wherein R ⁶ and R ⁷ are as described above), or a partial hydrolysis-condensation product thereof.

R ⁶ is a lower alkyl group such as methyl, ethyl, propyl or butyl; an alkenyl group such as vinyl or allyl; an aryl group such as phenyl; and 3
-Glycidoxypropyl, 2- (3,4-oxycyclohexyl) ethyl, 3-methacryloxypropyl, 3-
Aminopropyl, N-methyl-3-aminopropyl, N
Substituted hydrocarbon groups such as-(2-aminoethyl) -3-aminopropyl are exemplified, and a vinyl group or a substituted hydrocarbon group is preferable because it gives excellent adhesiveness.

Examples of R ⁷ include a lower alkyl group such as methyl, ethyl, propyl and butyl; and an alkoxy-substituted alkyl group such as 2-methoxyethyl, 2-ethoxyethyl and 2-butoxyethyl. Methyl, ethyl and 2-methoxyethyl are preferred, with methyl being most preferred, as provided.

Examples of the component (C) include methoxysilane such as methyltrimethoxysilane, ethyltrimethoxysilane and phenyltrimethoxysilane; vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- ( 3,4-oxycyclohexyl) ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, N- (2-aminoethyl)- Carbon-functional methoxysilane such as 3-aminopropyltrimethoxysilane; ethoxysilane such as methyltriethoxysilane and phenyltriethoxysilane; vinyl-functional ethoxysilane such as vinyltriethoxysilane and 3-aminopropyltriethoxysilane Isopropoxysilane such as methyltriisopropoxysilane; 2-methoxyethoxysilane such as methyltris (2-methoxyethoxy) silane; carbon-functional 2-methoxyethoxysilane such as vinyltris (2-methoxyethoxy) silane; Partially hydrolyzed condensates are exemplified, and vinyltrimethoxysilane and methyltriethoxysilane are preferable because they give a fast curing rate.

Further, since it exhibits excellent adhesiveness to an adherend upon curing, as the component (C), vinyl bonded to a silicon atom, 3-glycidoxypropyl, 2-
(3,4-oxycyclohexyl) ethyl, 3-methacryloxypropyl, 3-aminopropyl, N-substituted-3
It is preferred to use carbon-functional methoxysilanes or ethoxysilanes having carbon-functional groups such as aminopropyl, or their partial hydrolysis-condensates.

These alkoxy-containing silanes or partial hydrolysates thereof may be used alone or in combination of two or more, but those having an aminoalkyl group as R ⁶ are
^When used in combination with those having an unsubstituted hydrocarbon group as ⁶ ,
Since the curing reaction occurs at room temperature, the characteristic of the present invention, which is excellent in storage stability at room temperature and hardened in a short time by heating to obtain a rubber-like elastic body, cannot be obtained.

As the component (C), Si (OR ⁷ ) ₄
When such a tetrafunctional alkoxysilane or a partial hydrolyzate thereof is used, sufficient adhesion and oil resistance cannot be obtained.

The amount of the component (C) in the curable polyorganosiloxane composition is 0.1% by weight per 100 parts by weight of the component (A).
It is 1 to 10 parts by weight, preferably 0.5 to 8 parts by weight.
If the amount is less than 0.1 parts by weight, the adhesion of the cured product to the substrate is poor,
If it exceeds 10 parts by weight, the cured product becomes brittle.

The curable polyorganosiloxane composition used in the method for producing a polyorganosiloxane elastic body of the present invention contains the above-mentioned components (A), (B) and (C). According to the finding of the present inventor, the curable composition is characterized by the presence of the component (B) and the component (C).
By heating at 50 to 200 ° C., curing is performed while exhibiting excellent adhesiveness, and an elastic body having excellent oil resistance is formed. When such a curable composition contains a curing catalyst having a metal atom in the molecule, the curing proceeds when exposed to air even at room temperature, and the viscosity of the system increases. Therefore, for example, when the coating work is continuously performed by a method such as screen printing, the workability decreases with time. Moreover, the presence of such a curing catalyst affects the heat resistance of the silicone rubber. From these facts, the curable composition of the present invention functions as a curing catalyst that accelerates the curing reaction based on the crosslinking reaction of the silanol group of the component (A),
Substantially no organic compound having a metal atom in the molecule is contained.

In order to impart desired physical properties to the elastic body obtained from the curable polyorganosiloxane composition of the present invention, various fillers may be added in appropriate amounts, if necessary. As the filler used, fine powder silica, silica aerogel, precipitated silica, diatomaceous earth, ground quartz,
Oxides such as fused silica, aluminum oxide, iron oxide, zinc oxide and titanium oxide; or their surfaces treated with hydrophobizing agents such as trimethylchlorosilane, dimethyldichlorosilane, hexamethyldisilazane or octamethylcyclotetrasiloxane Materials; hydroxides such as aluminum hydroxide; carbonates such as calcium carbonate, magnesium carbonate, zinc carbonate; complex oxides such as talc, clay, glass wool, mica fine powder; carbon black, copper powder, nickel powder, etc. Examples of the conductive filler include polymethylsilsesquioxane powder.

Further, the composition of the present invention contains a pigment, a dye,
A flame retardant, a heat resistance improver, a thermal conductivity improver, a thixotropy imparting agent and the like may be added. It may also be diluted with a non-reactive silicone oil, such as polydimethylsiloxane, to control fluidity. Furthermore, dilute with a hydrocarbon solvent such as toluene, xylene, petroleum ether, gasoline, benzine, kerosene; a ketone solvent such as acetone or methyl ethyl ketone; or an organic solvent typified by an ester solvent such as ethyl acetate or butyl acetate. You may use it.

Such a curable composition has (A) to
(C) component and other components to be blended as necessary,
It is prepared by uniformly mixing and defoaming with a mixing means such as a kneader or a stirring mixer. Preparation and storage of such a composition are preferably carried out in a sealed container or in dry nitrogen in order to avoid the influence of moisture in the air, but the curable composition of the present invention is stable at room temperature, It cures only when heated.

A feature of the present invention is to cure such a curable composition by heating to obtain a polyorganosiloxane elastic body. The heating temperature is in the range of 50 to 200 ° C, preferably 70 to 150 ° C. If it is less than 50 ° C, the curable composition does not cure sufficiently. On the other hand, when the temperature exceeds 200 ° C, the obtained polyorganosiloxane elastic body is deteriorated by heat and becomes brittle. The time required for curing varies depending on the curing temperature, but is about 15 minutes to 2 hours.

Such curing can be performed on the surface of the adherend, and upon curing, various kinds of adherends such as iron, stainless steel, aluminum, carbon and NBR
Exhibits excellent adhesiveness.

[0039]

According to the present invention, it is possible to easily obtain a polyorganosiloxane elastic body which is cured by heating for a short time, exhibits excellent adhesiveness at that time, and is excellent in oil resistance. Moreover, the polyorganosiloxane elastic body of the present invention is
It does not cause curing inhibition like addition-type silicone rubber and is easy to handle.

INDUSTRIAL APPLICABILITY The elastic body of the present invention is extremely useful as a gasket / packing material and an industrial adhesive / sealing material, particularly as a gasket / packing material requiring excellent oil resistance and sealing property in the automobile industry and the like.

[0041]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. In these examples, all parts are parts by weight, and physical properties such as viscosity are all 25 parts.
It is a value in ° C. The invention is not limited by these examples.

The oil resistance of the obtained elastic body was evaluated with respect to mechanical properties and shear bond strength.

Regarding the mechanical properties, each of the prepared compositions was heated (in some comparative examples, left at room temperature) to obtain an elastic body. From this elastic body, JIS K 6301
No. 4 dumbbell sample was prepared. Hardness, tensile strength and elongation were measured with one sample to obtain initial values. The other sample was immersed in engine oil SD grade 10W-30 kept at 120 ° C. for 240 hours, and then the same measurement was performed to compare with the initial value to evaluate the oil resistance.

Regarding shear adhesive strength, first, 100 ×
The surface of 25 × 1 mm SUS304 stainless steel plate was cleaned in advance with ethanol, and two of them were lengthwise 10
The test pieces were arranged in parallel at an interval of 1 mm so as to overlap with each other, and the prepared compositions were filled in the gaps and heated (in some comparative examples, allowed to stand at room temperature) to cure the test pieces. Got This test piece was set to 5 by a tensile tester.
The shear bond strength was measured by pulling in the length direction at a speed of 0 mm / min, and set as the initial value. In addition, another test piece manufactured by the same method was used as engine oil SD grade 10W-at 120 ° C.
After soaking in 30 for 240 hours, the shear adhesive strength was measured by the same method and compared with the initial value.

Example 1 Polydimethylsiloxane 1 having both ends of its molecular chain blocked with silanol groups and having a viscosity at 25 ° C. of 10,000 cSt 1
To 00 parts, 50 parts of quartz powder, 5 parts of methyltris (methylethylketoxime) silane and 2 parts of 3-glycidoxypropyltrimethoxysilane were added and mixed by stirring.
A defoaming treatment was performed to prepare a composition.

Using the composition thus obtained,
By the above-mentioned method, the mechanical properties and shear bond strength of the elastic body sample and the adhesive test piece obtained by heating at 150 ° C. for 30 minutes, and the oil resistance thereof were measured. The results are as shown in Table 1.

Comparative Example 1 0.5 part of dibutyltin dilaurate was mixed with the composition prepared in Example 1 and subjected to defoaming treatment to obtain a composition for comparison. This was molded or filled as described above and left standing in an atmosphere of 25 ° C. and 60% RH for 7 days to be cured to obtain an elastic body sample and an adhesive test piece. The same evaluation was performed on these, and the results shown in Table 1 were obtained.

Example 2 Polydimethylsiloxane 10 having both ends of its molecular chain blocked with silanol groups and having a viscosity at 25 ° C. of 5,000 cSt.
To 0 part, 80 parts of calcium carbonate, 10 parts of vinyltris (methylethylketoxime) silane, and 5 parts of 3-aminopropyltrimethoxysilane were added, mixed by stirring, and defoamed to prepare a composition.

From the composition thus obtained, an elastic body sample and an adhesive test piece were prepared by heat curing,
Similar evaluation was performed. However, the heating condition was 80 ° C. for 1 hour. Table 1 shows the results.

Comparative Example 2 A composition for comparison was obtained in the same manner as in Example 2 except that 0.1 part of dibutyltin dilaurate was added instead of 3-aminopropyltrimethoxysilane. Using this composition, an elastic body sample and an adhesive test piece were prepared and evaluated in the same manner as in Comparative Example 1. Table 1 shows the results.

Example 3 Polydimethylsiloxane 1 having both ends of its molecular chain blocked with silanol groups and having a viscosity at 25 ° C. of 20,000 cSt.
To 00 parts, 15 parts of hydrophobic fumed silica whose surface was treated with hexamethyldisilazane, 3 parts of vinyltris (methylethylketoxime) silane, and 1 part of a partially hydrolyzed condensate of methyltriethoxysilane were added and mixed by stirring. Then, defoaming treatment was performed to prepare a composition.

From the composition thus obtained, an elastic body sample and an adhesive test piece were prepared by heat curing,
Similar evaluation was performed. However, the heating conditions are 150 ° C and 3
It was 0 minutes. Table 1 shows the results.

Comparative Example 3 Polydimethylsiloxane 1 having both ends of its molecular chain blocked with silanol groups and having a viscosity at 25 ° C. of 20,000 cSt.
To 00 parts, 15 parts of hydrophobic fumed silica whose surface is treated with hexamethyldisilazane, 3 parts of vinyltris (methylethylketoxime) silane and 1 of tetraethoxysilane
Parts were added, mixed by stirring, and defoamed to prepare a composition.

From the composition thus obtained, an elastic body sample and an adhesive test piece were prepared by heat curing,
Similar evaluation was performed. However, the heating conditions are 120 ° C and 3
It was 0 minutes. Table 1 shows the results.

[0055]

[Table 1]

Claims (1)

[Claims] 1. (A) General formula: (In the formula, R ¹ and R ² each independently represent a same or different substituted or unsubstituted monovalent hydrocarbon group; m has a viscosity at 25 ° C. of 100 to 200,
100 parts by weight of α, ω-dihydroxypolydiorganosiloxane represented by the formula: (B) general formula: R ³ _a Si (ON = X) _4-a (II) (wherein R ³ is Represents a substituted or unsubstituted monovalent hydrocarbon group; X is a = CR ⁴ ₂ group or Represents a group, R ⁴ independently represents a substituted or unsubstituted monovalent hydrocarbon group which is the same or different from each other, R ⁵ represents a substituted or unsubstituted divalent hydrocarbon group; a represents 0 or 1 0.5 to 20 parts by weight of an oxime group-containing silane or a partial hydrolysis-condensation product thereof; and (C) General formula: R ⁶ Si (OR ⁷ ) ₃ (III) (wherein R ⁶ is a substituent) Or an unsubstituted monovalent hydrocarbon group; R ⁷ represents a substituted or unsubstituted monovalent hydrocarbon having 1 to 8 carbon atoms) or an alkoxy group-containing silane or a partial hydrolysis-condensation product thereof 0 1 to 10 parts by weight, and a curable polyorganosiloxane composition containing substantially no curing catalyst having a metal atom in the molecule,
A method for producing a polyorganosiloxane elastic body, which comprises heat-curing at 200 ° C.