JPH06256658A - Silicone rubber composition and cured product thereof - Google Patents

Abstract

PURPOSE:To obtain a silicone rubber composition which is excellent in workability of extrusion and can give a cured product having excellent physical properties, low hardness and excellent flexibility by mixing a specified organopolysiloxane with a specified organopolysiloxane resin and a specified fine silica powder. CONSTITUTION:This rubber composition is prepared by mixing 100 pts.wt. organopolysiloxane of a degree of polymerization of 3000 or above represented by compositional formula I (wherein R<1> is an (un)substituted monovalent hydrocarbon group; and 0.0001-0.5mol% of R<1> groups are alkenyl groups; and (a) is 1.95-2.05), with 0.5-30 pts.wt. organopolysiloxane resin of a liquefaction temperature of 50-150 deg.C and an average molecular weight of 500-50000 represented by compositional formula II (wherein R<2> is an (un)substituted monovalent hydrocarbon group;(m)is 0.8-1.2; and(n)is 0.12-0.18) and 5-100 pts.wt. fine silica powder (fumed silica) of a specific surface area of 50m<2>/g or above. The obtained mixture is agitated at the liquefaction temperature of the organopolysiloxane resin or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a high plasticity of a base compound and is suitable as an extrusion molding material.
Further, the present invention relates to a silicone rubber composition capable of giving a cured silicone rubber product which can be a molded product having a low hardness.

[0002]

2. Description of the Related Art A cured product of a silicone rubber composition (silicone rubber) is excellent in heat resistance, weather resistance, durability, releasability, electrical characteristics, etc. Materials, electric / electronic parts, automobile supplies, O
It is used after being processed and formed into various shapes in various fields such as A equipment parts. In this case, for cost reduction and unmanned production by mass production, in recent years, a molding process by an extrusion molding method in which a silicone rubber composition extruded from an extruder is sent to a hot-air oven and continuously heat-cured has significantly increased. There is.

Therefore, a large amount of extrusion molding silicone rubber compositions have been used. Recently, as such silicone rubber compositions, a small amount of a filler has been added and excellent flexibility and rubber elasticity have been obtained. Silicone rubber compositions capable of obtaining low-hardness (JIS-A hardness of 40 or less) silicone rubber having characteristics have begun to be used.

However, since this silicone rubber composition has a small amount of filler, the plasticity of the rubber compound when uncured is low, and therefore the workability during extrusion molding is poor and it cannot be manufactured at low cost. There is a problem.

The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a silicone rubber composition which has a high plasticity of an uncured rubber compound, is suitable for extrusion molding, and can give a silicone rubber cured product which can be a molded product of low hardness.

[0006]

MEANS TO SOLVE THE PROBLEMS As a result of intensive studies for achieving the above object, the present inventor has shown that the organopolysiloxane represented by the following general composition formula (1) and having a degree of polymerization of 3,000 or more. (Raw rubber) and specific surface area of 50 m ² / g
With respect to the base compound containing the above fine powder silica, it is represented by the following general composition formula (2) and has an average molecular weight of 50.
Use in combination with an organopolysiloxane resin having a liquefaction temperature of 0 to 50,000 and a liquefaction temperature in the range of 50 to 150 ° C., and heating to a temperature above the liquefaction temperature of the organopolysiloxane resin of formula (2) to mix. When a base compound is obtained by the above method, this base compound has high workability because it has a high degree of plasticity when uncured, so that a silicone rubber composition suitable for extrusion molding can be obtained, and this base compound is vulcanized. It was found that a silicone rubber having good physical properties such as hardness, elongation and tensile strength can be obtained when an agent is added, and the present invention has been accomplished.

R ¹ _a SiO _{(4-a) / 2} (1) (In the formula, R ¹ represents an unsubstituted or substituted monovalent hydrocarbon group, of which 0.0001 to 0.5 mol% is Alkenyl group, a is a number of 1.95 to 2.05.) R ² _m (OH) _n SiO _{(4-mn) / 2} (2) (In the formula, R ² is an unsubstituted or substituted one. It represents a valent hydrocarbon group, m is 0.8 to 1.2, and n is a number of 0.12 to 0.18.)

Therefore, the present invention comprises (A) an organopolysiloxane having a composition of the above general formula (1), a degree of polymerization of 3,000 or more, and (B) an general composition formula (2).
The average molecular weight is 500 to 50,000 and 0.0
Liquefaction temperature including 001 to 0.01 mol of OH groups is 5
An organopolysiloxane resin in the range of 0 to 150 ° C., (C) a fine powder silica having a specific surface area of 50 m ² / g or more as a main component, and mixed at a liquefaction temperature of the organopolysiloxane resin of the formula (2) or more. A silicone rubber composition obtained by the above method, and a silicone rubber cured product obtained by curing the above silicone rubber composition are provided.

The present invention will be described in more detail below. The silicone rubber composition of the present invention is (A) as described above.
An organopolysiloxane having a degree of polymerization of 3,000 or more,
(B) Main component is an organopolysiloxane resin having an average molecular weight of 500 to 50,000 and containing 0.0001 to 0.01 mol of OH groups in 1 g and having a liquefaction temperature of 50 to 150 ° C. It

In this case, the organopolysiloxane as the component (A) is represented by the following general composition formula (1).

R ¹ _a SiO _{(4-a) / 2} (1)

Here, R ¹ is an unsubstituted or substituted monovalent hydrocarbon group, and 0.001 to 5 mol%, preferably 0.
It is necessary that 01 to 0.3 mol% be an alkenyl group such as a vinyl group or an allyl group. When the content of alkenyl groups is less than 0.001 mol%, the curability of this organopolysiloxane becomes insufficient, and when it exceeds 5 mol%, the hardness of the cured product obtained from the composition becomes too high. Properties such as elongation and tensile strength deteriorate. Examples of R ¹ other than alkenyl group include, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group,
Alkyl groups such as octyl group, decyl group and dodecyl group, aryl groups such as phenyl group and tolyl group, aralkyl groups such as β-phenylethyl group, and some or all of hydrogen atoms bonded to carbon atoms of these groups. Examples include a 3,3,3-trifluoropropyl group in which is substituted with a halogen atom such as fluorine, a cyano group, and a cyanoethyl group. Of these, a methyl group is generally used, but if the silicone rubber cured product is required to have cold resistance and transparency, ¹ to 2 of R ¹ is used.
Those in which 0 mol% is a phenyl group are preferably used.
Furthermore, when oil resistance and gasoline resistance are required, 1
Those having 0 to 50 mol% of a cyanoethyl group or a 3,3,3-trifluoropropyl group are preferably used.

This organopolysiloxane has a degree of polymerization of 3, in order to give a silicone rubber of sufficient mechanical strength.
It is preferably 5,000 or more, and particularly preferably 5,000 to 10,000.

In the above formula (1), a is 1.95.
It is a number of ˜2.05, and is usually a number substantially close to 2. When a is less than 1.95, it is not easy to synthesize an organopolysiloxane having a degree of polymerization of 3,000 or more, and when a is more than 2.05, the degree of polymerization is 3,0.
It is not easy to stably synthesize an organopolysiloxane of 00 or more with good reproducibility.

The organopolysiloxane as the component (A) is
Although it is substantially composed of diorganopolysiloxane units, it may contain a small amount of triorganosiloxy units, monoorganosiloxy units, and SiO ₂ units. Further, the molecular chain terminal may be blocked with a hydroxyl group or a triorganosiloxy unit.

As the component (A), one type thereof may be used alone, or two or more types may be used in combination.

The organopolysiloxane resin as the component (B) has an average molecular weight of 500 to 50,000, contains 0.0001 to 0.01 mol of OH groups in 1 g, and has a liquefaction temperature of 50 to 150 ° C. Within the range, when it is not dissolved in a solvent such as toluene or benzene, it is solid at room temperature and is represented by the following general composition formula (2).

R ² _m (OH) _n SiO _{(4-mn) / 2} (2)

Here, R ² is an unsubstituted or substituted monovalent hydrocarbon, and examples thereof include those similar to R ¹ .
In order not to increase the rubber hardness of the processed product obtained by curing the silicone rubber too much, Si—H group, Si—CH =
It is desirable not to include a functional group that participates in crosslinking of silicone rubber such as CH ₂ .

Examples of R ² include a methyl group, an ethyl group, an isopropyl group, a phenyl group and a trifluoropropyl group. In addition, R ² in the formula (2) may be the same or may be a combination of two or more kinds.

The blending amount of this component (B) is 10 parts of the component (A).
It is preferably 0.5 to 30 parts, especially 1 to 20 parts with respect to 0 parts (parts by weight, the same hereinafter). If the amount is less than 0.5 part, the silicone rubber compound cannot be made sufficiently highly plasticized, and if it exceeds 30 parts, the physical properties after curing the silicone rubber compound may be deteriorated.

The finely divided silica as the component (C) is for imparting appropriate hardness and mechanical strength such as tensile strength to the silicone rubber and has a specific surface area of 50 m ² / g or more, particularly 100 to 400 m ^2. / G silica is preferably used.
Specific examples of such fine powder silica include fumed silica, calcined silica, and precipitated silica. These can be used alone or in combination of two or more kinds. Further, these silicas may be surface-treated with a chain organopolysiloxane, a cyclic organopolysiloxane, hexamethyldisilazane, dichlorodimethylsilane or the like.

The amount of such finely divided silica blended is 5 to 10 with respect to 100 parts of the organopolysiloxane of the component (A).
It is preferably 0 part, especially 10 to 50 parts. If the amount is more than 100 parts or less than 5 parts, the processability of the silicone rubber may be deteriorated or sufficient mechanical strength may not be obtained.

In the composition of the present invention, various compounding agents, such as ground silica, diatomaceous earth, iron oxide and zinc oxide, which are appropriately compounded in the silicone rubber composition, are used in amounts that do not impair the object of the present invention. , Titanium oxide, carbon black, barium oxide, magnesium oxide, cerium hydroxide, calcium carbonate, magnesium carbonate, zinc carbonate, asbestos,
Glass wool, finely powdered mica, fused silica powder and the like may be added and blended. Further, if necessary, a pigment, a dye, an antioxidant, an antioxidant, an antistatic agent, a flame retardant such as antimony oxide or chlorinated paraffin, or a heat conduction improver such as boron nitride or aluminum oxide may be added. Absent.

Although the method for producing the silicone rubber composition of the present invention is not particularly limited, the organopolysiloxane as the component (A), the organopolysiloxane resin as the component (B), and the finely powdered silica as the component (C) are kneader. It can be obtained by heating in a kneading machine such as the above, blending at room temperature, and then heat-treating at a temperature not lower than the liquefaction temperature of the component (B), particularly at 120 to 200 ° C. for 1 to 10 hours. Further, at this time, ammonium carbonate, stearic acid, zinc stearate, in order to accelerate the dehydration condensation between the silanol groups of the organopolysiloxane resin as the component (B) and the silanol groups present on the surface of the finely powdered silica as the component (C), It is also possible to add a catalyst such as copper dioctanoate.

As a method for curing the silicone rubber composition of the present invention, a method utilizing a conventionally known hydrosilylation reaction or a method of vulcanizing with an organic peroxide as a catalyst can be used for curing. it can.

When the curing is carried out by utilizing a hydrosilylation reaction, a combination of an organohydrogenpolysiloxane and a platinum group metal-based catalyst is used as a curing agent. The organohydrogenpolysiloxane may be an organopolysiloxane having two or more SiH groups in one molecule, which may be linear, cyclic,
It may be branched. In addition, such Si
The H group may be at the end of the polysiloxane chain or may be in the middle thereof. The organohydrogenpolysiloxane is preferably used in an amount ratio such that the SiH group is 0.5 to 3 mol, and particularly 1 to 2 mol per 1 mol of the alkenyl group of the organopolysiloxane of the component (A).

As the platinum group metal-based catalyst used at the same time, known ones can be used. For example, a fine powder metal platinum catalyst described in US Pat. No. 2,970,150, US Pat. Chloroplatinic acid catalysts described in US Pat. No. 2,823,218, US Pat. No. 3,159,6
01 and U.S. Pat. No. 3,159,662, platinum-hydrocarbon complex compounds, U.S. Pat. No. 3,516,94.
Chloroplatinic acid-olefin complex compounds described in US Pat. Nos. 3,775,452 and 3,81.
The platinum-vinyl siloxane complex described in 4,780 and the like can be used.

The amount of the platinum group metal catalyst blended is 0.1 as platinum metal based on the total amount of the organopolysiloxane (A) and the organohydrogenpolysiloxane.
It is preferably 1 to 1,000 ppm, particularly preferably 1 to 100 ppm. Further, at the time of curing, in order to maintain good storage stability at room temperature and to maintain an appropriate pot life,
It is also possible to add a reaction control agent such as methylvinylcyclotetrasiloxane and acetylene alcohols.

The curing by hydrosilylation reaction is
It can be performed by heating at a temperature of 60 to 400 ° C. for about 1 minute to 5 hours.

When the silicone rubber composition is vulcanized by using an organic peroxide as a catalyst, the organic peroxide is particularly preferably one that is usually used for curing a peroxide-curable silicone rubber. It can be used without limitation. Specifically, benzoyl peroxide, bis (2,4-dichlorobenzoyl) peroxide, di-
t-butyl peroxide, 2,5-dimethyl-di-t
-Butyl peroxyhexane, t-butyl perbenzoate, t-butyl peroxy isopropyl carbonate, dicumyl peroxide, etc. are mentioned. These may be used alone or in combination of two or more.

The blending amount of this organic peroxide is usually
It is preferably 0.01 to 3 parts, and particularly preferably 0.05 to 1 part, relative to 100 parts of the component (A) organopolysiloxane. The curing conditions are not particularly limited, but usually 100 to 4
It can be cured by heating at a temperature of 00 ° C. for about 1 minute to 5 hours.

The silicone rubber cured product thus obtained is suitable as an extrusion molding material for construction gaskets, facsimile rolls, medical tubes, etc. because of its high Williams plasticity in silicone rubber compounds. It is also suitable as a material for contacts, nipples, constant velocity joint boots, plug boots, anode caps, electric wires and the like.

[0034]

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

[Example 1] Dimethylsiloxy unit 99.
100 parts of organopolysiloxane having an average degree of polymerization of 8,000 consisting of 825 mol%, methylvinylsiloxy unit 0.15 mol% and dimethylvinylsiloxy unit 0.025 mol%, CH ₃ SiO _3/2 unit, GPC measurement Styrene conversion average molecular weight was 3,000 and 0.
It contains 0023 mol of silanol groups and has a liquefaction temperature of 8
5 parts of methyl siloxane resin at 1 ℃ and specific surface area of 20
20 parts of 0 m ² / g fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) was added, kneaded with a kneader, and heat-treated at 180 ° C. for 3 hours to prepare a base compound I.

Example 2 Instead of 5 parts of the methylsiloxane resin used in Example 1, a C ₆ H ₅ SiO _3/2 unit was used, and the styrene-converted average molecular weight measured by GPC was 2,50.
A phenylsiloxane resin 5 containing 0,35 mol of silanol groups in 1 g and having a liquefaction temperature of 73 ° C.
A base compound II was produced in the same manner as in Example 1 except that parts were used.

Example 3 Instead of 5 parts of the methylsiloxane resin used in Example 1, CH ₃ (CH ₂ ) ₂ SiO was used.
_3/2 unit consisting of 80 mol% GPC measurement Styrene-equivalent molecular weight 2800, 1 g containing 0.0032 mol of silanol groups, except that 4.5 parts of phenylpropylsiloxane resin having a liquefaction temperature of 78 ° C was used. Is Example 1
A base compound III was prepared in the same manner as in.

Comparative Example A base was prepared in the same manner as in Example 1 except that 4.5 parts of terminal silanol group dimethylpolysiloxane (polymerization degree: 10) was used in place of 5 parts of the methylsiloxane resin used in Example 1. Compound IV was made.

Next, in accordance with JIS-C2137, the above base compounds I to IV were kneaded again, weighted 10 minutes later, and the height after 3 minutes was measured with a dial gauge to obtain Williams of each base compound. The plasticity was measured. The results are shown in Table 1.

Further, 0.6 part of 2,4-chlorobenzoyl peroxide was added to 100 parts of each base compound and uniformly mixed, followed by press vulcanization at 120 ° C. for 10 minutes and then post vulcanization at 200 ° C. for 4 hours. It was vulcanized to obtain a vulcanized rubber sheet. The cured physical properties of these rubber sheets are JIS-
It measured according to K6301. The results are also shown in Table 1.

Further, each base compound containing the above vulcanizing agent was attached to a die having a cylinder diameter of 40 mm / 10 mm, a ratio of cylinder length L to diameter D of L / D = 12, and a diameter of 20 mm / 10 mm. Was supplied to the extruder, and at room temperature (15 to 30 ° C.), a round bar-shaped silicone rubber molding having an outer diameter of 5 mm was continuously extruded from the extruder at a speed of 1 m / min, and hot air of 300 ° C. was circulated. It was molded by passing it through a heating furnace having a total length of 2 m at a conveying speed of 1 m / min. The extrusion moldability in this case was visually determined. The results are also shown in Table 1.

[0042]

[Table 1] ◯: The shape was retained, and a round bar shaped product was obtained. X: The shape could not be maintained and a molded product could not be obtained.

[0043]

EFFECTS OF THE INVENTION The silicone rubber composition of the present invention has excellent workability during extrusion molding due to the high plasticity of the base compound when uncured, and the silicone rubber obtained by curing this composition is It has excellent physical properties, low hardness and excellent flexibility, and is suitable for various applications.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Terukazu Sato 1 Hitomi, Oita, Matsuida-cho, Usui-gun, Gunma Prefecture, Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (72) Masayuki Yoshida Matsui, Usui-gun, Gunma Prefecture Tamachi Daiji Hitomi 1-10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Technology Laboratory

Claims (2)

[Claims] 1. (A) represented by the following general composition formula (1):
Organopolysiloxane having a degree of polymerization of 3,000 or more, R ¹ _a SiO _{(4-a) / 2} (1) (wherein R ¹ represents an unsubstituted or substituted monovalent hydrocarbon group, of which 0 0.0001 to 0.5 mol% is an alkenyl group, and a is a number of 1.95 to 2.05.) (B) It is represented by the following general composition formula (2) and has an average molecular weight of 5:
0.001-50,000 in 1 g
Organopolysiloxane resin containing 1 mol of OH group and having a liquefaction temperature in the range of 50 to 150 ° C., R ² _m (OH) _n SiO _{(4-mn) / 2} (2) (wherein R ² is not It represents a substituted or substituted monovalent hydrocarbon group, m is a number of 0.8 to 1.2, and n is a number of 0.12 to 0.18.) (C) Specific surface area of 50 m ² / g or more A silicone rubber composition obtained by mixing powdery silica as a main component with an organopolysiloxane resin of formula (2) at a liquefaction temperature or higher. 2. A silicone rubber cured product obtained by curing the composition according to claim 1.