JPH0784560B2 - Silicone rubber composition - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a silicone rubber composition, more specifically, a condensation reaction type liquid silicone rubber composition which cures rapidly at room temperature to form a rubber having an extremely small compression set. Regarding

[Technical Background of the Invention and Problems Thereof] An alkoxysilane having at least three alkoxy groups in a molecule as a cross-linking agent for a polyorganosiloxane having hydroxyl groups at both ends of a molecular chain and / or a partial hydrolysis / condensation product thereof. A condensation reaction type room temperature curable liquid silicone rubber composition obtained by blending an organotin compound-based catalyst with is known, and is widely used in various fields as a room temperature curable silicone rubber.

Such a silicone rubber has excellent workability and good releasability, but has a property of significantly large compression set, as compared with a so-called heat-vulcanizable silicone rubber which is vulcanized by an organic peroxide. Therefore, in general, when condensation reaction type silicone rubber is used as a rubber material for a conveyance roll such as paper or an image fixing roll, paper wrinkles, abnormal noises, and copying occur due to long-time heating and distortion due to pressure. Problems such as image distortion can often occur. for that reason,
When the condensation reaction type silicone rubber is used for such an application, there is a problem in that the rubber portion constituting this roll needs to be mechanically designed so that pressure is applied only during use.

In order to reduce the compression set of such a condensation reaction type silicone rubber, a method of lowering the compounding amount of the curing catalyst is generally considered. However, this method is not industrially advantageous because the curing speed is significantly slowed. Therefore, in order to solve such a problem, a method of using a tin compound containing a hydrocarbon ester group of a dicarboxylic acid as a catalyst for curing a condensation reaction type silicone rubber has been proposed (JP-A-60-4555). . However, this method cannot be said to be industrially advantageous because the deep hardening rate of the tin compound is slow, and the compression set cannot be said to be sufficiently low.

[Object of the Invention] An object of the present invention is to solve the problems of the prior art and to provide a condensation reaction type silicone rubber composition which exhibits good curability at room temperature and has a very small compression set of the rubber after curing. That is.

[Structure of the Invention] As a result of repeated studies to obtain such a condensation reaction type silicone rubber composition, the present inventors used an organotin compound having a monohydroxy group as a catalyst and a specific alkoxysilane as a crosslinking agent. It was found that a condensation reaction type silicone rubber composition which gives a rubber having good curability and a small compression set can be obtained by using a hydrolysis / condensation product of an alkoxysilane, and the present invention has been completed here. .

The silicone rubber composition of the present invention comprises (A) the following general formula: (In the formula, R is an alkyl group having 1 to 8 carbon atoms and 2 carbon atoms, respectively.
~ 4 alkenyl group, C6-10 aryl group, C7-10 aralkyl group or C1-4 haloalkyl group; n is the viscosity of polydiorganosiloxane at 25 ° C is 500-200,000 cSt. 100 parts by weight of a polydiorganosiloxane in which both ends of the molecular chain are capped with silanol groups represented by the formula: (B) General formula: R ¹ Si (OR ² ) ₃ (wherein R ¹ is Represents a monovalent hydrocarbon group; R ² represents 1 to 1 carbon atoms
4 represents an alkyl group, a phenyl group and a vinyl group and represents a monovalent hydrocarbon group) 0.5 to 100 parts by weight of an alkoxysilane; (C) General formula: R ³ Si (OR ⁴ ) ₃ (formula In the formula, R ³ represents a monovalent hydrocarbon group; R ⁴ has 1 to 1 carbon atoms.
4 represents a monovalent hydrocarbon group selected from an alkyl group, a phenyl group and a vinyl group) or the above alkoxysilane and a general formula; Si (OR ⁴ ) ₄ (in the formula, meaning of R ⁴ ) Is the same as the above) and a partial hydrolysis / condensation product with an alkoxysilane, and a partial hydrolysis / condensation product containing at least one aryl group bonded to a silicon atom in the molecule 0.5 to 10 parts by weight; (D) _{^{formula: (R 5) 2 (OH}} ) Sn-O-Sn (OCOR 6) (R 5)
₂ or the formula: (R ⁵ ) ₂ (OH) SnOCOR ⁶ [wherein, R ⁵ represents the same or different monovalent hydrocarbon groups; R ⁶ represents a monovalent hydrocarbon group or the formula —QOCOR ⁷ ( In the formula,
Q represents a divalent hydrocarbon group; R ⁷ represents a monovalent hydrocarbon group)] and 0.01 to 0.3 part by weight of a compound represented by the formula:

The polydiorganosiloxane which is the component (A) of the composition of the present invention is a chain polymer in which both terminals are capped with silanol groups. The component (A) may contain a branched polymer.

The organic groups bonded to the silicon atom in the diorganosiloxane which is the structural unit of the component (A) may be the same or different, and examples thereof include a methyl group, an ethyl group, a propyl group,
Alkyl groups such as butyl, hexyl and dodecyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl such as benzyl, β-phenylethyl and β-phenylpropyl groups Groups; and
Examples include monovalent substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group and chloromethyl group. Among these, a methyl group, a vinyl group or a phenyl group is preferable from the viewpoint of easiness of synthesis, and moreover, the case where the organic group bonded to the silicon atom is a methyl group, compared to the case of other organic groups, It is most preferable because the intermediate can be easily synthesized, the viscosity of the obtained polymer is the lowest as compared with the degree of polymerization, and the balance of the physical properties of the rubber-like elastic body, which is a cured product, is favorably influenced. Therefore, it is most preferable that substantially all are methyl groups, but when heat resistance is required for the cured product, among the organic groups bonded to the silicon atom,
It is preferable that a part thereof is a phenyl group. Even when the organic group other than the methyl group is contained in this manner, it is preferable that 85% or more of the total number of organic groups in the polymer is a methyl group for the reason described above.

In addition, such a polydiorganosiloxane has 25
Viscosity at 100 ~ 500,000 cSt, preferably 500 ~ 10
It is 0,000 cSt. If the viscosity is less than 100 cSt, it is difficult to impart excellent mechanical properties to the cured product. Again 500,000c
If it exceeds St, it is impossible to impart appropriate fluidity to the composition.

The alkoxysilane, which is the component (B) of the composition of the present invention, is necessary for the composition to cure and form a good elastic body, and the alkoxysilane is represented by the general formula R ¹ Si.
(OR ² ) ₃ (wherein R ¹ and R ² are as described above).

In the general formula, the group R ¹ is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group or a dodecyl group; an alkenyl group such as a vinyl group or an allyl group; an aryl such as a phenyl group or a tolyl group. Examples of the group include an aralkyl group such as a benzyl group, a β-phenylethyl group and a β-phenylpropyl group, but the number of carbon atoms is 1 to 4 from the viewpoint of being able to impart appropriate curability to the composition and easiness of synthesis. It is preferable that it is a group selected from an alkyl group, a phenyl group and a vinyl group. Examples of R ² include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, and a propyl group, a phenyl group, and a vinyl group. Generally, a methyl group or an ethyl group is used because of the hydrolyzability of the group OR ^2. And propyl group are preferred.

The blending amount of the component (B) is 0.5 with respect to 100 parts by weight of the component (A).
~ 10 parts by weight. If the amount of the component (B) is less than 0.5 parts by weight, the rubber after curing of the composition will not have sufficient strength, and if it exceeds 10 parts by weight, the compression set of the rubber will be large and the object of the present invention cannot be achieved.

The partial hydrolysis / condensation product of the alkoxysilane, which is the component (C) of the composition of the present invention, is an essential component for curing the composition together with the component (B) to give a good elastic body. ) And component (D) in combination, the compression set of the rubber elastic body can be reduced, and the curability and the deep part curability at the time of thin film molding can be improved. . This hydrolysis / condensation product is R ³ Si (OR ⁴ ) ₃ or R ³ Si (OR ⁴ ) ₃ and Si (OR ⁴ ) ₄
It is obtained by partial hydrolysis / condensation of.

In the general formula, the groups R ³ are the same or different monovalent hydrocarbon groups, and examples thereof include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group and dodecyl group; vinyl group, allyl group. aryl groups such as phenyl and tolyl; alkenyl group such as a benzyl group, beta-phenylethyl, beta-phenylpropyl may be mentioned an aralkyl group such, at least one of the radicals R ³ in a molecule It is necessary that one is an aryl group, and it is more preferable that all are phenyl groups in order to reduce the compression set of the rubber elastic body. Further, the group R ⁴ may be an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group and a propyl group, a phenyl group and a vinyl group, and in order to achieve the object of the present invention, an alkyl group having 1 to 4 carbon atoms. It is preferably a group.

The blending amount of component (C) is 0.5 with respect to 100 parts by weight of component (A).
~ 10 parts by weight. If the amount of component (C) is less than 0.5 parts by weight, the rubber after curing of the composition will not have sufficient strength, and if it exceeds 10 parts by weight, the compression set of the rubber will be too large to achieve the object of the present invention.

The tin compound which is the component (D) of the composition of the present invention is
It is a characteristic component in the present invention that gives a condensation reaction type silicone rubber having a small compression set when used in combination with the component (B) and the component (C). This ingredient is
_{^{Formula; (R 5) 2 (OH}} ) Sn-O-Sn (OCOR 6) (R 5) 2 or the formula: in _{^{(R 5) 2 Sn (OH}} ) OCOR 6 ( wherein, R ⁵ and R ⁶ are described above As described above).

In the general formula, the groups R ⁵ are the same or different monovalent hydrocarbon groups, for example, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group and dodecyl group; vinyl group , Alkenyl groups such as allyl groups; aryl groups such as phenyl groups and tolyl groups; benzyl groups, β
Examples thereof include aralkyl groups such as -phenylethyl group and β-phenylpropyl group. The group R ⁶ is represented by a monovalent hydrocarbon group or —QOCOR ⁷ , and examples of the monovalent hydrocarbon group of the groups R ⁶ and R ⁷ include a methyl group, an ethyl group, a propyl group,
Alkyl groups such as butyl group, hexyl group and dodecyl group; alkenyl groups such as vinyl group and allyl group; aryl groups such as phenyl group and tolyl group; aralkyl such as benzine group, β-phenylethyl group and β-phenylpropyl group Examples of the divalent hydrocarbon represented by Q in the above formula include alkylene groups such as ethylene group, propylene group and butylene group; alkenylene groups such as vinylene group; arylene groups such as phenylene group; benzylene. Group, and aralkylene groups such as β-phenylethylene group.

Such tin compounds include dibutyltin hydroxyacetate, dioctyltin hydroxyacetate,
Dimethyltin hydroxyoleate, dibutyltin hydroxyoleate, dibutyltin hydroxybenzyl maleate, dibutyltin hydroxyoctyl phthalate, tetrabutyl-1-hydroxy-3-acetosidistanoxane, tetrabutyl-1-hydroxy-3-benzylmaleyloxydistanoxane And so on.

The blending amount of component (D) is 0.01 per 100 parts by weight of component (A).
˜0.5 parts by weight, preferably 0.02 to 0.3 parts by weight. 0.01
If it is less than parts by weight, the curing rate will be too slow to be suitable for practical use, and if it exceeds 0.5 parts by weight, the curing rate will be too fast and will adversely affect the compression set.

The composition of the present invention may optionally contain an inorganic filler for the purpose of improving the strength of rubber and the like. Such fillers may be those used for general liquid silicone rubber, for example, fumed silica,
Powders of wet silica, calcined silica, ground quartz, diatomaceous earth, calcium carbonate, etc., or titanium dioxide, red iron oxide, etc. for the purpose of coloring and improving heat resistance can be mentioned, and the pH thereof is not particularly limited. The blending amount of this inorganic filler can be selected according to the required characteristics, but the component (A)
200 parts by weight or less based on 100 parts by weight.

Further, in the composition of the present invention, a low molecular weight polyorganosiloxane containing silanol groups at both ends of the molecular chain is used for the purpose of extending its pot life, and both ends are treated with tri-functional for the purpose of improving releasability. A so-called silicone oil blocked with an organosilyl group can be appropriately blended according to the purpose.

[Effect of the Invention] As described above, the composition of the present invention has an appropriate curability and at the same time has an excellent deep curability, and the cured product has an extremely low compression set. . Since the composition of the present invention has such excellent properties, it has good workability, and the composition is used especially in a heated state for a long time. It is useful as a constituent material for various industrial rolls.

[Examples of the Invention] The present invention is described below by referring to Examples, but the present invention is not limited thereto. In addition, "part" in the examples represents "part by weight", and the viscosity represents a value at 25 ° C.

Examples 1 to 5 and Comparative Examples 1 to 4 Viscosity 3,000 cP in which both ends of the molecular chain are blocked with dimethylhydroxysilyl groups and the rest are dimethylsiloxane units.
100 parts of polydimethylsiloxane, 10 parts of ground quartz, 3 parts of red iron oxide, 4 parts of phenyltriethoxysilane and 2 parts of partial hydrolysis / condensation product of phenyltrimethoxysilane were mixed in a mixing vessel to obtain a uniform mixture. . Next, 100 parts by weight of the obtained mixture was uniformly mixed with 0.1 part of various organotin compounds shown in Table 1 to obtain a composition of the present invention and a comparative composition. Using each such composition,
The following tests were conducted. The results are shown in Table 1.

Deep-curing: After putting the composition into a test tube with a diameter of 18 mm and a depth of 200 mm, 2
The cured state was observed when kept for 24 hours in an environment of 5 ° C. and 60% RH. The judgment was made according to the following criteria.

Good deep-curing property: The whole was cured to become a rubber elastic body.

Poor deep-curing: The bottom did not become rubber.

Compression set: After pouring the composition into a mold to a thickness of 12 mm,
Using the rubber kept for 72 hours in the environment of 25 ℃, 60% RH,
According to JIS K6301, the compression set after heating at 180 ° C. for 22 hours was measured.

As is clear from Table 1, the compositions of Examples 1 to 5 exhibited excellent deep-part curability, and the cured products had a small compression set. On the other hand, the compositions of Comparative Examples 1 to 4 using a tin compound other than the constituent components of the present invention as a catalyst,
The deep-curing property was also insufficient and the cured product had a large compression set.

Examples 6-9 and Comparative Examples 5-8 Viscosity 5,000 cP in which both ends of the molecular chain are blocked with dimethylhydroxysilyl groups and the rest are dimethylsiloxane units.
100 parts of polydimethylsiloxane, Carplex # 112
0 (wet silica, pH 10.7, Shionogi Seiyaku Co., Ltd., trade name) 40 parts, methyltriethoxysilane 5 parts and phenyltriethoxysilane hydrolysis / condensation product 2 parts were mixed in a mixing container, A homogeneous mixture was obtained. Next, 100 parts of this mixture was uniformly mixed with 0.2 parts of various organotin compounds shown in Table 2 to obtain a composition of the present invention and a comparative composition. For these, the deep-part curability and compression set were measured in the same manner as in Example 1. The result is the second
Shown in the table.

As is clear from Table 2, the compositions of Examples 6 to 9 exhibited excellent deep-part curability, and the cured products had a small compression set. On the other hand, the compositions of Comparative Examples 5 to 8 using the tin compound other than the constituent components of the present invention as the catalyst,
The deep-curing property was also insufficient and the cured product had a large compression set.

Examples 10-14 and Comparative Examples 9-14 Both ends of the molecular chain are blocked with dimethylhydroxysilyl groups, and the balance is composed of dimethylsiloxane units.
cP polydimethylsiloxane 100 parts, diatomaceous earth powder 20
Parts and various crosslinking agents and tin-based catalysts shown in Table 3 were mixed and uniformly mixed to obtain a composition of the present invention and a comparative composition. The pot life and thin film curability of these compositions were measured by the following methods, and the deep curability and compression set were measured by the same methods as in Example 1. The results are shown in Table 3.

Pot life: Put each composition in a polyethylene container, then 25 ℃, 60
Viscosity was measured using a rotational viscometer every 10 minutes in an environment of% RH, and the time when the viscosity reached 100,000 cP or more was defined as the pot life.

Thin film curability: Cast each composition into a flat plate with a thickness of 0.5 mm,
After being left in an environment of ℃ and 60% RH for 24 hours, it was touched with a finger and its cured state was observed. The judgment was made according to the following criteria.

○: Completely cured △: Surface is sticky ×: Uncured material sticks to finger As is apparent from Table 3, the compositions of Examples 10-14 were
Not only does it have excellent deep-curing properties, the compression set of the cured product is small, but it also exhibits a moderate pot life, that is, a moderate curing rate that makes it easy to handle in actual work. It was also excellent in the curability when On the other hand, the comparative compositions using components (B) and (C) other than the constituents of the present invention each have a small compression set of the cured product, and also have a long working life, thin film curability and The balance of deep part curability was not good.

Claims (6)

[Claims] 1. (A) The following general formula; (In the formula, R is an alkyl group having 1 to 12 carbon atoms and 2 carbon atoms, respectively.
~ 4 alkenyl group, C6-10 aryl group, C7-10 aralkyl group or C1-4 haloalkyl group; n is the viscosity of polydiorganosiloxane at 25 ° C is 500-200,000 cSt. 100 parts by weight of a polydiorganosiloxane in which both ends of the molecular chain are capped with silanol groups represented by the formula: (B) General formula: R ¹ Si (OR ² ) ₃ (wherein R ¹ is Represents a monovalent hydrocarbon group; R ² represents 1 to 1 carbon atoms
4 represents an alkyl group, a phenyl group and a vinyl group and represents a monovalent hydrocarbon group) 0.5 to 100 parts by weight of an alkoxysilane; (C) General formula: R ³ Si (OR ⁴ ) ₃ (formula In the formula, R ³ represents a monovalent hydrocarbon group; R ⁴ has 1 to 1 carbon atoms.
4 represents a monovalent hydrocarbon group selected from an alkyl group, a phenyl group and a vinyl group) or the above alkoxysilane and a general formula; Si (OR ⁴ ) ₄ (in the formula, meaning of R ⁴ ) Is the same as the above) and a partial hydrolysis / condensation product with an alkoxysilane, and a partial hydrolysis / condensation product containing at least one aryl group bonded to a silicon atom in the molecule 0.5 to 10 parts by weight; (D) _{^{formula: (R 5) 2 (OH}} ) Sn-O-Sn (OCOR 6) (R 5)
₂ or the formula: (R ⁵ ) ₂ (OH) SnOCOR ⁶ [wherein, R ⁵ represents the same or different monovalent hydrocarbon group; R ⁶ represents the monovalent hydrocarbon group or the formula -QOCOR ⁷ (formula In the formula, Q represents a divalent hydrocarbon group; and R ⁷ represents a monovalent hydrocarbon group). 0.01 to 0.3 part by weight of a compound represented by the formula: 2. The silicone rubber composition according to claim 1, wherein 85% or more of the total number of organic groups bonded to silicon atoms of the polydiorganosiloxane as the component (A) is a methyl group. 3. The silicone rubber composition according to claim ¹ , wherein the group R ^{1 of the} component (B) is a group selected from an alkyl group having 1 to 4 carbon atoms, a phenyl group and a vinyl group. 4. The silicone rubber composition according to claim 1, wherein the group R ^{3 of the} component (C) is a phenyl group. 5. The silicone rubber composition according to claim 1, wherein the compounding amount of the component (D) is 0.02 to 0.3 part by weight with respect to 100 parts by weight of the component (A). 6. The composition according to claim 1, which contains 200 parts by weight or less of an inorganic filler with respect to 100 parts by weight of the component (A).