JPH0693186A - Oil-bleeding silicone rubber composition and cure product thereof - Google Patents

Abstract

PURPOSE:To provide a silicone rubber compsn. suppressed in decrease of self- adhesion to rolls and improved in oil bleeding properties by using a specific organopolysiloxane, silica in the form of a fine powder, a phenylsilicone oil and a low-mol.-wt. silicone oil. CONSTITUTION:100 pts.wt. organopolysiloxane of formula I [wherein R<1> is a monovalent (un)substd. hydrocarbon group, provided that 0.0001 to 0.5mol.% of R<1> is alkenyl; and a is 1.95 to 2.05] having a degree of polymn. of at least 3,000 is blended with 5-100 pts.wt. silica in the form of a fine powder having a specific surface area of at least 50m<2>/g, 0.5-15 pts.wt. phenylsilicone oil of formula II [wherein R<2> is alkenyl or hydroxyl; R<2> is a monovalent (un)substd. hydrocarbon group, provided that 5 to 50mol.% of R<3> is phenyl; and n is at least 3], and 0.3-10 pts.wt. low-mol.-wt. silicone oil of formula III (wherein Me is methyl ; Ph is phenyl ; and R<4> is methyl, ethyl, or phenyl) to obtain an oil- bleeding silicone rubber compsn. This compsn. is heated at 100 to 400 deg.C for 1 minute to 5 hours to be cured.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of suppressing a decrease in roll adhesiveness, so that workability is improved, and since oil bleeds onto the surface after molding, a cured product particularly suitable for automobile parts is provided. The present invention relates to an oil-bleedable silicone rubber composition.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
Silicone rubber is processed and molded into various shapes, heat resistance,
Due to its excellent weather resistance, durability, releasability, and electrical characteristics, it is used in various fields such as building materials, electric / electronic parts, automobile parts, and OA equipment parts.

Further, in recent years, it has been remarkably popularized as an automobile part and is used for an oil seal, a connector, an O-ring, a diaphragm, a grommet for a distributor, etc., particularly in the field of a connector and a grommet for a distributor. As a result of pursuing workability, sealing property after mounting, insulation property, etc., it was confirmed that the oil bleeding silicone rubber in which oil bleeds on the surface after molding is effective, and such oil bleeding silicone rubber is widely used. It is being appreciated. in this case,
Bleed oil has a phenyl group content of 15-30
Oils with a mol% and a viscosity of 100 to 500 cs are used.

However, when such a bleed oil is added, the surface becomes flaky when the silicone rubber composition is applied to a roll, depending on the type of the base organopolysiloxane (raw rubber), and when the silicone rubber composition is bare, silicone is applied to both sides of the roll. There is a problem in that the rubber compound sticks to the work, which reduces workability.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide an oil bleeding silicone rubber composition that improves roll workability and gives a cured product having excellent physical properties.

[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. When a phenyl silicone oil represented by the following general formula (2) and a low molecular weight silicone oil represented by the following general formula (3) are blended with a fine powder silica having a specific surface area of 50 m ² / g or more, It was found that an extremely small amount of low-molecular-weight silicone oil migrates to the roll surface, resulting in improved roll workability, excellent oil bleeding properties during use, and a cured product with good physical properties, The present invention has been completed.

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 It is an alkenyl group, and a is a positive number of 1.95 to 2.05.)

[0008]

[Chemical 3] (In the formula, R ² represents an alkyl group or a hydroxyl group, R ³ represents an unsubstituted or substituted monovalent hydrocarbon group, 5 to 50 mol% of R ³ is a phenyl group, and n is an integer of 3 or more. .)

[0009]

[Chemical 4] (In the formula, Me represents a methyl group, Ph represents a phenyl group, R ⁴ represents a methyl group, an ethyl group or a phenyl group.)

Therefore, the present invention provides (A) an organopolysiloxane represented by the above general composition formula (1) having a polymerization degree of 3,000 or more, and (B) a fine powder silica having a specific surface area of 50 m ² / g or more. , (C) a phenyl silicone oil represented by the above composition formula (2), (D) a silicone rubber composition containing a low molecular weight silicone oil represented by the above composition formula (3), and the above silicone rubber Provided is a silicone rubber cured product obtained by curing the composition.

The present invention will be described in more detail below. As described above, the silicone rubber composition of the present invention comprises (A)
An organopolysiloxane having a degree of polymerization of 3,000 or more,
(B) Fine powder silica having a specific surface area of 50 m ² / g or more,
(C) Phenyl silicone oil, (D) low molecular weight silicone oil Main components are constituted.

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)

[0013] Here, R ¹ is an unsubstituted or substituted, preferably monovalent hydrocarbon group having 1 to 20 carbon atoms, 0.001 to 5 mol% of R ^1, preferably 0.01 to 0. It is necessary that 3 mol% be an alkenyl group such as a vinyl group or an allyl group. If the content of alkenyl groups is less than 0.001 mol%, the curability of this organopolysiloxane will be insufficient, and if it exceeds 5 mol%, the physical properties of the cured product obtained from the composition will be poor. .

Further, as R ¹ other than the alkenyl group,
For example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group or a dodecyl group, an aryl group such as a phenyl group or a tolyl group, and an aralkyl group such as a β-phenylethyl group. Groups, and some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms such as fluorine, cyano groups, etc.
Examples include 3,3-trifluoropropyl group and cyanoethyl group. Of these, a methyl group is generally used, but in the case where a silicone rubber cured product is required to have cold resistance, radiation resistance and transparency, it is preferable that 3 to 20 mol% of R ¹ is a phenyl group. Used for. Further, when oil resistance and gasoline resistance are required, those having 1 to 70 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.
000 or more, and particularly preferably 4,000 to 10,000.

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

The organopolysiloxane of 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.

The component (A) may be used alone or in combination of two or more.

The finely divided silica as the component (B) 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 compounded is preferably 5 to 100 parts, especially 10 to 50 parts, per 100 parts (parts by weight, the same applies hereinafter) of the component (A) organopolysiloxane. 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.

The composition of the present invention preferably contains a silica dispersant as a wetting component when compounding the organopolysiloxane as the component (A) and the finely powdered silica as the component (B). Specific examples of such a silica dispersant include α, ω-polysiloxane diol, hexamethyldisilazane, methoxysilane, and diphenylsilanediol.

The content of the wetter component is preferably 0.1 to 20 parts, more preferably 1 to 10 parts per 100 parts of the component (A). If the blending amount of the wetter component is less than 0.1 part, the component (B) may not be blended uniformly,
If it exceeds 20 parts, the physical properties of the silicone rubber compound after curing may deteriorate.

The phenyl silicone oil as the component (C) is represented by the following formula (2), is usually added to the oil bleeding silicone rubber, and is essential for the oil bleeding silicone rubber.

[0024]

[Chemical 5]

In the formula (2), R ² is an alkyl group or a hydroxyl group, and the alkyl group preferably has 1 to 3 carbon atoms. R ³ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and 5 to 50 mol% of R ³ is a phenyl group. The same as R other than the phenyl group can be mentioned. n is an integer of 3 or more, but an integer of 5 to 100 is particularly preferable.

Examples of such oils include those represented by the following formula.

[0027]

[Chemical 6]

These phenyl silicone oils may be used simultaneously with compounds having two or more kinds of structures. The compounding amount of this phenyl silicone oil is 0.5 to 15 with respect to 100 parts of the organopolysiloxane (A).
Parts, particularly preferably 3 to 10 parts. If the compounding amount is less than 0.5 part, the effect of bleeding is not sufficiently exhibited,
On the other hand, if it exceeds 15 parts, the physical properties may deteriorate and weld lines may be generated during molding.

When the silicone rubber composition is produced, the oil as the component (C) may be mixed with other components or added later. Further, since the phenyl silicone oil is a liquid, it may be added as it is, but when the addition property is poor, a small amount of a carrier such as crystallite or zeolite may be mixed and added.

The low molecular weight silicone oil as the component (D) is a characteristic component of the present invention and is represented by the following general formula (3).

[0031]

[Chemical 7]

In the formula, Me represents a methyl group, Ph represents a phenyl group, and R ⁴ represents a methyl group, an ethyl group or a phenyl group. Specific examples of such a low molecular weight silicone oil include those represented by the following formula.

[0033]

[Chemical 8]

The amount of the component (D) added is the amount of the component (A) 10
It is preferably 0.3 to 10 parts, especially 1 to 4 parts with respect to 0 parts. If the amount is less than 0.3 part, the effect of roll processability is not sufficiently exhibited, and if it exceeds 10 parts, the physical properties of the cured silicone rubber product may be impaired, which further increases the cost. Further, the mixing ratio of the component (C) with the phenyl silicone oil is a weight ratio of the component (C) :( D).
It is preferable to set component = 1: 0.25 to 2.

When the silicone rubber composition of the present invention is produced, the addition timing of the component (D) is not particularly limited, but it is preferably added after considering the volatility due to the low molecular weight.

The composition of the present invention contains various compounding agents, such as ground silica, diatomaceous earth, iron oxide, and the like, which are appropriately compounded in the silicone rubber composition in an amount that does not impair the object of the present invention.
Zinc oxide, 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. Furthermore, if necessary, pigments, dyes, antioxidants, antioxidants, antistatic agents, flame retardants such as antimony oxide, chlorinated paraffin platinum compounds, etc., heat conduction improvers such as boron nitride and aluminum oxide, azobisisobutylnitrile. , Azodicarbonamide, p-toluenesulfone hydrazide and other foaming agents may be added.

As a method for producing the silicone rubber composition of the present invention, known methods can be adopted.

As the method for curing the silicone rubber composition of the present invention, any one of a method of vulcanizing using an organic peroxide as a catalyst and a method of utilizing a conventionally known hydrosilylation reaction is used. be able to.

When the silicone rubber composition is vulcanized using an organic peroxide as a catalyst, the organic peroxide is not particularly limited as long as it is one usually used for curing a peroxide curable silicone rubber. Can be used.
Specifically, benzoyl peroxide, bis (2,4
-Dichlorobenzoyl) peroxide, di-t-butylperoxide, 2,5-dimethyl-di-t-butylperoxyhexane, t-butylperbenzoate, t
-Butyl peroxyisopropyl carbonate, dicumyl peroxide, etc. may be mentioned. These may be used alone or in combination of two or more. The amount of the organic peroxide to be compounded is usually 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 of the composition using this organic peroxide are not particularly limited, but the composition can be cured by heating at a temperature of 100 to 400 ° C. for about 1 minute to 5 hours.

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 a straight-chain organopolysiloxane having two or more SiH groups in one molecule.
It may be annular or branched. Further, such SiH group may be at the end of the polysiloxane chain or may be in the middle thereof. It is preferable to use such an organohydrogenpolysiloxane in an amount ratio of 0.5 to 3 mol, particularly 1 to 2 mol of SiH group per 1 mol of the alkenyl group of the organopolysiloxane of the component (A).

The platinum group metal catalyst used at the same time is the alkenyl group in the organopolysiloxane (A) and the Si in the organohydrogenpolysiloxane.
It acts as a catalyst for the hydrosilylation reaction with the H group. As such a catalyst, known catalysts can be used. For example, a fine powder metal platinum catalyst described in US Pat. No. 2,970,150 and US Pat.
Chloroplatinic acid catalysts described in U.S. Pat. No. 823,218, U.S. Pat. Nos. 3,159,601 and 3,159,6.
No. 62, a platinum-hydrocarbon complex compound, U.S. Pat. No. 3,516,946, a chloroplatinic acid-olefin complex compound, U.S. Pat. No. 3,775,45.
The platinum-vinyl siloxane complexes described in No. 2 and No. 3,814,780 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.

The silicone rubber cured product thus obtained has excellent oil bleeding properties and is particularly suitable as a material for automobile parts.

[0046]

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.
975 mol%, dimethylvinylsiloxy unit 0.025
An average polymerization consisting of 60 parts of organopolysiloxane having an average degree of polymerization of 8,000 and a dimethylsiloxy unit of 99.5 mol%, methylvinylsiloxy unit of 0.475 mol%, and dimethylvinylsiloxy unit of 0.025 mol%. 40 parts of organopolysiloxane with a degree of 8,000,
Dimethyldimethoxysilane 4.0 parts, specific surface area 190
35 parts of m ² / g wet silica (Nipsi LP, manufactured by Nippon Silica Co., Ltd.) was added and kneaded with a kneader to obtain 17
A base compound I was prepared by heat treatment at 0 ° C. for 2 hours.

In this base compound I, 8 parts of bleed oil I represented by the following structural formula, crystallite VXS
Two parts (manufactured by Tatsumori Co., Ltd.) were mixed in advance, then added by a roll, and sufficiently kneaded until the bleed oil I was uniformly mixed.

[0049]

[Chemical 9]

Then, the oil A represented by the following structural formula was post-added with a roll, and after sufficiently observing the roll processability, 2,5-bis (tertiary butyl peroxy) was added.
Add 1.0 part by weight of 50% hexane paste and add 165
A test piece was prepared by performing press cure at 10 ° C. for 10 minutes and post cure at 200 ° C. for 4 hours.

[0051]

[Chemical 10]

The physical properties of this test piece were measured according to JIS-K6301. The results are shown in Table 1. The roll adhesiveness was evaluated according to the following criteria. ◯: Silicone rubber does not stick to the roll and mastication is easy. Δ: Silicone rubber adheres to the roll to some extent, but mastication is not so difficult. X: Silicone rubber sticks to the roll and mastication is difficult.

Example 2 A test piece was prepared in the same manner as in Example 1 except that oil B having the following structural formula was post-added by a roll instead of oil A post-added in Example 1. The same measurement as in Example 1 was performed. The results are also shown in Table 1.

[0054]

[Chemical 11]

Comparative Example 1 A test piece was prepared in the same manner as in Example 1 except that the oil A was not added later to the silicone rubber compound prepared in Example 1 and the same measurement as in Example 1 was carried out. The results are also shown in Table 1.

[0056]

[Table 1]

From the results shown in Table 1, the silicone rubber compositions of Examples 1 and 2 in which the oils A and B were blended did not impair the physical properties as compared with the composition of Comparative Example 1 and were very good. It can be seen that it exhibits excellent roll processability.

Example 3 Dimethylsiloxy Unit 99.
975 mol%, dimethylvinylsiloxy unit 0.025
15 parts of organopolysiloxane consisting of mol% and having an average degree of polymerization of 4,000, dimethylsiloxy unit 99.975
Mol%, dimethylvinylsiloxy unit 0.025 mol%
Which has an average degree of polymerization of 4,000 and an average degree of polymerization of dimethylsiloxy units of 99.825 mol%, methylvinylsiloxy units of 0.15 mol% and dimethylvinylsiloxy units of 0.025 mol%. 50 parts of 8,000 organopolysiloxane, 23 parts of silica obtained by treating the surface of dry silica (A-300, manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 300 m ² / g with hexamethyldisilazane, and a specific surface area of 190 m ² / g
Wet silica (Nipsil LP, Nippon Silica Co., Ltd.)
1.) 11 parts, 5 parts of dry silica (A-200, manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of 200 m ² / g, α, ω-dimethylpolysiloxane diol having a degree of polymerization of 16.
0 parts, 1.0 part of diphenyldisilanediol, 0.2 parts of vinyltrimethoxysilane, 4 parts of silicone oil having a viscosity of 400 cs and containing 25 mol% of phenyl groups (bleed oil II) were added until uniform. Mix until uniform. After that, knead with a kneader and 170 ° C
Was heat-treated for 2 hours to prepare a base compound II.

This base compound II was kneaded in advance by thoroughly mixing 5.7 parts of bleed oil II and the same oil B as used in Example 2 and 2 parts of diatomaceous earth (celite), and kneading the mixture. The product was evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 4 A kneaded product was produced in the same manner as in Example 3 except that the bleed oil II was changed to 4.3 parts and the oil B was changed to 2.8 parts, and the same measurement was carried out. It was The results are also shown in Table 2.

Example 5 A kneaded product was produced in the same manner as in Example 3 except that bleed oil II was 2.8 parts and oil B was 4.3 parts, and the same measurement was carried out. It was The results are also shown in Table 2.

[Comparative Example 2] Bleed oil II of 7.1
As a part, a kneaded product was produced in the same manner as in Example 3 except that the oil B was not used, and the same measurement was performed. The results are also shown in Table 2.

[0063]

[Table 2]

From the results of Table 2, it is understood that the workability is improved as the amounts of Examples 3, 4, 5 and oil B are increased.

[0065]

According to the present invention, it is possible to obtain an oil bleeding silicone rubber in which physical properties are not impaired while suppressing deterioration in workability due to addition of bleeding oil, particularly reduction in roll adhesiveness, and workability. It can be used in a wide range and easily for applications such as automobile packing, for which improvement is required, and applications such as automobile grommets, for which water resistance and insulation are required.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaharu Takahashi 1 Hitomi, Osamu Matsuida-cho, Usui-gun, Gunma Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research 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 positive number of 1.95 to 2.05.)
(B) Fine powder silica having a specific surface area of 50 m ² / g or more (C) Phenyl silicone oil represented by the following general composition formula (2): (In the formula, R ² represents an alkyl group or a hydroxyl group, R ³ represents an unsubstituted or substituted monovalent hydrocarbon group, 5 to 50 mol% of R ³ is a phenyl group, and n is an integer of 3 or more. .) (D)
Low molecular weight silicone oil represented by the following general formula (3): (In the formula, Me represents a methyl group, Ph represents a phenyl group, and R ⁴ represents a methyl group, an ethyl group or a phenyl group.) An oil bleeding silicone rubber composition. 2. A silicone rubber cured product obtained by curing the composition according to claim 1.