JP3121773B2 - Silicone rubber composition for sponge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone rubber composition for a sponge and a silicone rubber sponge using the same.
The present invention relates to a silicone rubber composition for sponge having extremely excellent storage stability capable of maintaining stable foaming characteristics for a long period of time.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS The silicone rubber sponge has heat resistance, weather resistance, cold resistance, electrical properties, flame retardancy,
It has excellent heat insulation properties and is used for many applications by taking advantage of these properties. This silicone rubber sponge is basically obtained by heating a composition obtained by blending a foaming agent and a curing agent with a silicone rubber base polymer at a temperature higher than the decomposition temperature of the foaming agent (generally, 150 to 400 ° C.) and foaming. Can be However, these silicone rubber compositions for sponges have a problem that the foaming characteristics change over time. That is, since the moisture content in the silicone rubber composition for sponge changes due to changes in humidity and temperature, for example,
Despite the same foaming conditions, the moisture content of the silicone rubber composition is high during humid times such as during the rainy season. As the temperature increases, the cells become coarser. Conversely, in the dry season, the foaming ratio decreases due to a decrease in the water content. For this reason, there is a problem that the foaming characteristics change depending on the season, and this improvement has been strongly desired.

[0003]

SUMMARY OF THE INVENTION The present invention has been made to solve such problems. That is, the present invention relates to a silicone rubber composition for a sponge and a silicone rubber sponge using the same, which has excellent workability and moldability, and has excellent storage stability capable of maintaining stable foaming characteristics over a long period of time. It is an object of the present invention to provide a silicone rubber composition for a sponge having a property.

[0004]

The present inventors have conducted intensive studies to achieve the above object. As a result, the polyorganosiloxane containing finely powdered fumed silica was replaced with a polyorganosiloxane having a terminal blocked with a hydroxyl group or an alkoxy group. A specific heat-decomposable catalyst is used in combination, and this is heated to a temperature equal to or higher than the decomposition temperature of the catalyst.
A silicone rubber composition for a sponge obtained by blending a foaming agent and a curing agent at 0 ° C or higher has good workability and moldability,
The present inventors have found that they have extremely excellent storage stability capable of maintaining stable foaming characteristics over a long period of time, and have completed the present invention.

That is, the present invention relates to (A) mixing a silicone rubber composition containing the following (a-1) to (a-4) at a temperature lower than the decomposition temperature of the component (a-4); Four)
100 parts by weight of a silicone rubber composition heat-treated at a temperature not lower than the decomposition temperature of the components (a-1) Average unit formula: R _a SiO _{(4-a) / 2} (where R is a substituted or unsubstituted monovalent compound ₎ A hydrocarbon group of
a represents a number in the range of 1.98 to 2.02) 100 parts by weight of polyorganosiloxane having an average degree of polymerization of 4000 to 20000 (a-2) Average unit formula: R ¹ _b SiO _{(4-b) / 2} (formula Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group,
b represents a number in the range of 1.98 to 2.02), the terminal is blocked with a hydroxyl group or an alkoxy group, and the degree of polymerization is 6 to 70.
0 to 20 parts by weight of polyorganosiloxane (a-3) 5 to 200 parts by weight of finely powdered fumed silica (a-4) Average unit formula: M ¹ O (R ² _c SiO) _z M ² (wherein , M ¹ is a tetraalkylammonium group or tetraalkylphosphonium group, M ² is the same or hydrogen and M ^1, R ² is a hydrocarbon group substituted or unsubstituted monovalent, c is the 1.98 to 2.02 Indicates the number of ranges, where z is 1-1000
(B) 0.1 to 10 parts by weight of an organic foaming agent having a decomposition temperature of 100 ° C. or higher (C) 0.01 to 10 parts by weight of an organic peroxide It is a silicone rubber composition for sponge characterized by the following.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Component (A) used in the present invention is a polyorganosiloxane containing finely powdered fumed silica, and a combination of a polyorganosiloxane having a terminal blocked with a hydroxyl group or an alkoxy group and a specific heat-decomposable catalyst. This is a silicone rubber composition obtained by heating this to a temperature higher than the decomposition temperature of the catalyst.

The average unit formula of the component (a-1): R _a SiO _{(4-a) / 2} (where R is a substituted or unsubstituted monovalent hydrocarbon group,
a represents a number in the range of 1.98 to 2.02), which is a base polymer of the curable silicone composition and is mainly used as a linear polymer. A branched or three-dimensional structure may be formed, and a homopolymer, a copolymer, or a mixture thereof may be used. The substituted or unsubstituted monovalent hydrocarbon group bonded to the silicon atom of the polyorganosiloxane includes, for example, an alkyl group such as a methyl group, an ethyl group and a propyl group; a vinyl group, an allyl group and a butadienyl group. An alkenyl group; an aryl group such as a phenyl group, a xenyl group, and a naphthyl group; a cycloalkyl group such as a cyclohexyl group; a cycloarenyl group such as a cyclohexenyl group; an aralkyl group such as a benzyl group; Alkylaryl group and the like. As the monovalent hydrocarbon group bonded to these silicon atoms, a methyl group is mainly used. For example, in the case of a vinyl group, 0 to 5 relative to the total number of organic groups from the viewpoint of mechanical strength and crosslinkability. %, And particularly preferably in the range of 0.05 to 3%. In addition, as a molecular chain terminal of the polyorganosiloxane, a hydroxyl group, an alkoxy group or a triorganosilyl group is exemplified, and a triorganosilyl group is more preferable. Examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, and a methyldiphenylsilyl group. The average polymerization degree of the component (a-1) is in the range of 4,000 to 20,000, preferably 6,000 to 1,000.
0. If the degree of polymerization is too small, it is difficult to obtain a sufficient mechanical strength, while if it is too large, it is difficult to mix the compound into the system.

The component (a-2) used in the present invention has an average unit formula: R ¹ _b SiO _{(4-b) / 2} (where R ¹ is a substituted or unsubstituted monovalent hydrocarbon group) ,
b represents a number in the range of 1.98 to 2.02), the terminal is blocked with a hydroxyl group or an alkoxy group, and the degree of polymerization is 6 to 70.
0, preferably 10 to 300, more preferably 15 to 200, a polyorganosiloxane which is mainly used in the form of a straight chain, but may have a partially branched or three-dimensional structure. Good. The substituted or unsubstituted monovalent hydrocarbon group used in the polyorganosiloxane includes
For example, alkyl groups such as methyl group, ethyl group and propyl group; alkenyl groups such as vinyl group, allyl group and butadienyl group; aryl groups such as phenyl group, xenyl group and naphthyl group; cycloalkyl groups such as cyclohexyl group A cycloarenyl group such as a cyclohexenyl group; an aralkyl group such as a benzyl group; an alkylaryl group such as a tolyl group or a xylyl group.
In consideration of the compatibility with the polyorganosiloxane of the component (a-1) serving as the base polymer, a group similar to the monovalent hydrocarbon group used in the component (a-1) is preferable. Further, the terminal of the molecular chain of the polyorganosiloxane is either a hydroxyl group or an alkoxy group. When the molecular weight of the component (a-2) is too high, the effect as a treating agent is reduced, and when the molecular weight is too low, the workability of the obtained compound is deteriorated. Ten
To 300, more preferably 15 to 200. (A-2)
If the compounding amount of the component is too large, the obtained compound becomes sticky, and if it is too small, the effect of suppressing the temporal change of the foaming characteristic, which is the original purpose, cannot be obtained, so the component (a-1)
It is used in the range of 0.5 to 20 parts by weight per 100 parts by weight.

The finely powdered fumed silica of the component (a-3)
A known material generally mixed with silicone rubber or the like may be used. The preferred particle size of these fumed silicas is 20
μm or less. These fumed silicas may not be surface-treated, or may be surface-treated with organosilane, organochlorosilane, organosiloxane, organosilazane, or the like. Wet silica is
It is not preferable because the water content is high and the catalytic action of the component (a-4) is reduced. If the compounding amount of the component (a-3) is too large, the mechanical properties of the silicone rubber sponge obtained by foaming decrease, and if too small, the mechanical properties decrease. It is used in the range of 5 to 200 parts by weight based on 100 parts by weight of the component.

The component (a-4) used in the present invention has an average unit formula: M ¹ O (R ² _c SiO) _z M ² (where M ¹ is a tetraalkylammonium group or a tetraalkylphosphonium group) , M ² is the same or hydrogen and M ^1, R ² is a substituted or unsubstituted monovalent hydrocarbon radical, c is the number of range of 1.98 to 2.02, z is 1 to 1000
Is the number of the heat-decomposable catalyst. As the component (a-4), those having a degree of polymerization z in the range of 1 to 1000 are used, and preferably 5 to 100. Polymerization degree z is 1000
If it exceeds, the viscosity becomes high, handling becomes difficult, and workability decreases. The component (a-4) can be obtained by reacting a tetraalkylammonium hydroxide, a tetraalkylphosphonium hydroxide with a polyorganosiloxane by a known method. Here, it is conceivable that these hydroxides are used for the present purpose, but they are usually present as an aqueous solution of 50% by weight or less, so that the dispersibility in the silicone rubber compound becomes very poor, The desired shortening of the kneading time is not achieved, and even if dispersed, the water containing the catalyst which reduces the catalytic action is contained in the composition, so that control of the reaction is difficult, and the cohesion of the silicone rubber compound is lost. In some cases, it is difficult to obtain stable characteristics due to the fact that the device may fall apart and become unmanufacturable. In addition, an aqueous solution exceeding 50% by weight cannot be prepared, and in this case, it becomes solid, and it is very difficult to disperse this too. On the other hand, the component (a-4) of the present invention comprises:
Extremely good dispersibility in silicone rubber compounds,
In addition, the reaction control is easy because it does not contain water,
The desired silicone rubber composition can be easily obtained in a short time. From the viewpoint of catalyst stability, tetraalkylammonium silanolate is more preferable.
This component (a-4) is obtained by polycondensing a hydroxyl group or an alkoxy group of the component (a-2) with a hydroxyl group on the component (a-3), performing a filler treatment, and simultaneously adding the components (a-2) to each other. It is considered that a slight amount of water contained in the component (a-3) also promotes some equilibration of the silicone rubber composition at the same time. Thereby, the residual hydroxyl groups and alkoxy groups in the present silicone rubber composition are extremely small, and (a-1)
The compatibility between the component and the component (a-3) is very good, and a silicone rubber composition having good workability and moldability, and little change in foaming characteristics over time and excellent storage stability can be obtained. The amount of the component (a-4) is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the component (a-1). When the amount is less than 0.01 part by weight, the reaction does not proceed sufficiently, and when the amount is more than 5 parts by weight. The odor of the catalytic decomposition material is a problem. The decomposition temperature of component (a-4) is not particularly limited, but is preferably 70 ° C. or higher from the viewpoint of stability, and is preferably 130 ° C. or lower from the viewpoint of reaction temperature.

The silicone rubber composition of the component (A) comprises (a-
1) A silicone rubber composition comprising (a-3) a fumed silica and (a-2) a low-viscosity polyorganosiloxane in which a terminal is blocked with a hydroxyl group or an alkoxy group, and (a-3) a fumed silica, a-4) It can be obtained simply by adding a pyrolytic catalyst and reacting. In producing the silicone rubber composition of the component (A), the components (a-1) to (a-4) may be mixed together, or the components (a-1) to (a-3) may be mixed. After that, the component (a-4) may be added. However, (a-
4) Components must be added below their decomposition temperature,
After the addition, the temperature must be higher than the decomposition temperature. However, the manufacturing process shown here is only a process for adding a component (a-4) to a normal method for manufacturing a silicone rubber composition, and those skilled in the art may introduce special manufacturing equipment. And can be easily manufactured.

The organic foaming agent of the component (B) is for foaming the silicone rubber composition of the component (A) into a sponge. The organic foaming agent may be any of those conventionally used in the production of silicone rubber sponges, such as azobisisobutyronitrile and 1,1'-azobis-1.
Azo compounds such as -acetoxy-1-phenylethane, azodicarbonamide, diazoaminobenzene, dinitrosopentamethylenetetramine, N, N-dimethyl-N,
Examples include nitroso compounds such as N-dinitrosoterephthalamide. When these compounds are heated to a temperature higher than the decomposition temperature, they decompose to generate N ₂ or CO ₂ gas. The compounding amount of the organic foaming agent of the component (B) is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight based on 100 parts by weight of the component (A). If the amount is less than 0.1 part by weight, a sponge cannot be obtained, and if it exceeds 10 parts by weight, the obtained sponge tends to be easily deformed and the quality of the sponge may be deteriorated.

The peroxide containing component (C) is a vulcanizing agent. The organic peroxide of the component (C) may be any one usually used in this type of silicone rubber composition, and may be benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide. , Dicumyl peroxide, 2,5-bis (t-butylperoxy) -2,5-dimethylhexane, 2,5-bis (t-butylperoxy) -2,5-dimethylhexyne, di-t -Butyl peroxide, t-butyl peroxybenzoate, bis (4-t-butylcyclohexyl) peroxydicarbonate, and the like. These organic peroxides may be used alone or in a combination of two or more. In general, it is well known that a plurality of types of organic peroxides may be used in combination for producing a sponge in consideration of the size of foam, surface condition or expansion ratio of the sponge. The compounding amount of the organic peroxide of the component (C) is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the component (A). The amount is 0.01
If it is less than 10 parts by weight, vulcanization becomes difficult, and if it exceeds 10 parts by weight, properties such as heat resistance deteriorate.

The silicone rubber composition for a sponge used in the present invention may contain a semi-reinforcing or non-reinforcing filler in addition to the above-mentioned components as long as the effect of the present invention is not impaired. Examples of the semi-reinforcing or non-reinforcing filler include crushed silica, diatomaceous earth, metal carbonate, clay, talc, mica, and titanium oxide. Further, a heat-resistant additive, a flame retardant, an antioxidant, a processing aid, and the like, which have been conventionally used, can be added to the silicone rubber composition. Furthermore, it is also possible to mix carbon ferrite powder and the like and to mold by high frequency dielectric heating.

[0015]

The silicone rubber composition for sponge obtained by the present invention has good workability and moldability, good workability and moldability, and can maintain stable foaming properties for a long period of time. It is possible to obtain a silicone rubber sponge having extremely excellent storage stability and always having stable characteristics. And the obtained silicone rubber sponge is very useful as a gasket, a heat insulating material, a cushion material, a sealing material, etc. with a wide use temperature range due to these excellent properties.

[0016]

EXAMPLES Next, examples of the present invention will be described, but the present invention is not limited to the following examples. Also,
Parts in the examples represent parts by weight. Example 1 99.88 mol% of (CH ₃ ) ₂ SiO units, (CH ₃ ) (CH ₂ = CH) SiO units
100 parts of a 12 mol% polyorganosiloxane having a degree of polymerization of 6000, the end of which is blocked by a dimethylvinylsilyl group; 5 parts of a polydiorganosiloxane having a degree of polymerization of 50, the end of which is closed by a silanol group; Silica (AE
ROSIL 130) 45 parts are kneaded with a kneader mixer until uniform, and tetramethylammonium silanolate (z = 2
0) 0.2 part was added and kneaded. The temperature at this time is 60 ° C
Met. Thereafter, heat treatment was performed at 130 ° C. for 30 minutes to obtain a silicone rubber composition. The plasticity of the obtained silicone rubber composition (A-1) was 270, there was no stickiness, and the workability was good. To 100 parts by weight of this (A-1), azobisisobutyronitrile (decomposition temperature: 103
℃) 1.8 parts, 0.5 parts of paramethylbenzoyl peroxide and 0.8 parts of dicumyl peroxide as organic peroxides.
Parts were blended to obtain a silicone rubber compound. The above silicone rubber compound is continuously extruded at a rate of 5 m / min and supplied to an extruder equipped with a die having an outer diameter of 18 mmφ,
A hollow sponge tube with a fine cell having a specific gravity of 0.39 was obtained. When this cross-sectional shape was confirmed, it was almost round, and the shape at the time of extrusion was maintained.

Example 2 99.88 mol% of (CH ₃ ) ₂ SiO units, (CH ₃ ) (CH ₂ CHCH) SiO units
100 parts of a polyorganosiloxane having a polymerization degree of 6000, comprising 12 mol% and capped at the ends with a dimethylvinylsilyl group; 2 parts of a polydiorganosiloxane capped with a silanol group and having a degree of polymerization of 50; 2 parts of polydiorganosiloxane closed with trimethylsilyl group and having a degree of polymerization of 20, surface treated fumed silica (AEROSIL R-97
4) 50 parts were kneaded with a kneader mixer until uniform, 0.3 part of tetramethylammonium silanolate (z = 25) was added and kneaded. The temperature at this time was 70 ° C.
Thereafter, heat treatment was performed at 150 ° C. for 30 minutes to obtain a silicone rubber composition. The plasticity of the obtained silicone rubber composition (A-2) was 310, there was no stickiness, and the workability was good. (A-2) 100 parts by weight of organic blowing agent
3.5 parts of 1,1'-azobis-1-acetoxy-1-phenylethane (decomposition temperature: 106 ° C.), 0.6 parts of paramethylbenzoyl peroxide and 0.8 parts of dicumyl peroxide as organic peroxides were blended, and silicone rubber was added. I got the compound. Next, continuous extrusion was performed in the same manner as in Example 1 to obtain a hollow sponge tube having a fine cell of specific gravity 0.38.
When this cross-sectional shape was confirmed, it was almost round,
The shape at the time of extrusion was maintained.

COMPARATIVE EXAMPLE 1 99.88 mol% of (CH ₃ ) ₂ SiO units, (CH ₃ ) (CH ₂ = CH) SiO units
100 parts of a polyorganosiloxane having a polymerization degree of 6000, which is composed of 12 mol% and capped with a dimethylvinylsilyl group, and whose terminal is capped with a trimethylsilyl group.
5 parts of polydiorganosiloxane and 45 parts of fumed silica (AEROSIL 130) were kneaded with a kneader mixer until uniform, and then heat-treated at 150 ° C. for 30 minutes to obtain a silicone rubber composition. The obtained silicone rubber composition (A'-1) had a plasticity of 260, and some stickiness was felt. Subsequently, an organic foaming agent and an organic peroxide were added to (A'-1) in the same manner as in Example 1 to obtain a silicone rubber compound, which was continuously extruded, and a hollow sponge tube of a fine cell having a specific gravity of 0.40 was obtained. I got When this cross-sectional shape was confirmed, it was almost round, and the shape at the time of extrusion was maintained.

COMPARATIVE EXAMPLE 2 99.88 mol% of (CH ₃ ) ₂ SiO units, (CH ₃ ) (CH ₂ = CH) SiO units
100 parts of a polyorganosiloxane having a polymerization degree of 6000, which is composed of 12 mol% and capped with a dimethylvinylsilyl group, and whose terminal is capped with a trimethylsilyl group.
5 parts of polydiorganosiloxane and 45 parts of fumed silica (AEROSIL 130) were kneaded with a kneader mixer until uniform, and 2 parts of hexamethyldisilazane was added and kneaded. The temperature at this time was 50 ° C. After this, 150 ℃
Heat treatment was performed for 3 hours to obtain a silicone rubber composition. The obtained silicone rubber composition (A'-2) had a plasticity of 210, was very sticky, and had a very poor roll workability. Next, an organic foaming agent and an organic peroxide were added to (A'-2) in the same manner as in Example 1 to obtain a silicone rubber compound, which was subjected to continuous extrusion, and a hollow sponge tube of a fine cell having a specific gravity of 0.38 was obtained. I got When this cross-sectional shape was confirmed, it was elliptical, and the shape at the time of extrusion was not maintained at all.

Next, the silicone rubber compounds of Examples 1 and 2 and Comparative Examples 1 and 2 were cured at 25 ° C. and 90% humidity.
After standing for a week, extrusion was performed in the same manner as in Example 1,
The sponge specific gravity and cell were evaluated. Table 1 shows the results.

[0021]

[Table 1]

As is clear from the results in Table 1, Examples 1 and 2 showed little change in specific gravity, and were in a state very close to those extruded first, while Comparative Examples 1 and 2 showed specific gravity. And the cell was coarse.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI C08L 83/08 C08L 83/08 (58) Investigated field (Int.Cl. ⁷ , DB name) C08L 83/04 C08K 3/36 C08K 5/5415 C08L 83/06 C08L 83/08 C08L 83/07

Claims (1)

(57) [Claims] (A) A silicone rubber composition containing the following components (a-1) to (a-4) is mixed at a temperature lower than the decomposition temperature of the component (a-4), and then the component (a-4) is mixed. 100 parts by weight of a silicone rubber composition heat-treated at or above the decomposition temperature of (a-1) Average unit formula: R _a SiO _{(4-a) / 2} (where R is a substituted or unsubstituted monovalent A hydrocarbon group,
a represents a number in the range of 1.98 to 2.02) 100 parts by weight of polyorganosiloxane having an average degree of polymerization of 4000 to 20000 (a-2) Average unit formula: R ¹ _b SiO _{(4-b) / 2} (formula Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group,
b represents a number in the range of 1.98 to 2.02), the terminal is blocked with a hydroxyl group or an alkoxy group, and the degree of polymerization is 6 to 70.
0 to 20 parts by weight of polyorganosiloxane (a-3) 5 to 200 parts by weight of finely powdered fumed silica (a-4) Average unit formula: M ¹ O (R ² _c SiO) _z M ² (wherein , M ¹ is a tetraalkylammonium group or tetraalkylphosphonium group, M ² is the same or hydrogen and M ^1, R ² is a hydrocarbon group substituted or unsubstituted monovalent, c is the 1.98 to 2.02 Indicates the number of ranges, where z is 1-1000
(B) 0.1 to 10 parts by weight of an organic foaming agent having a decomposition temperature of 100 ° C. or higher (C) 0.01 to 10 parts by weight of an organic peroxide A silicone rubber composition for a sponge, comprising: