JPH01203467A - Fluorosilicone rubber composition - Google Patents

Abstract

PURPOSE:To provide the present composition outstanding in heat, low- temperature and oil resistances, comprising a vinyl group-blocked organopolysiloxane, reinforcing silica filler, gamma-trifluoropropyl group-contg. siloxane oligomer and organic peroxide. CONSTITUTION:The objective composition comprising (A) 100pts.wt. of an organopolysiloxane blocked with vinyl group at one or both the molecular chain ends, of formula I and/or formula II [R<1>-R<4> are each 1-8C (substituted) monovalent hydrocarbon group; R<5> is 1-8C (substituted)saturated monovalent hydrocarbon group; X is H, R<5> etc., m=0-30; n>=500; p=2-4], (B) 10-100pts. wt. of reinforcing silica with a specific surface area of >=50m<2>/g, (C) 0.5-20pts. wt. of a gamma-trifluoropropyl group-contg. siloxane oligomer with a viscosity (at 25 deg.C) of 15-50cS, of formula III (R<8> is the same as R<1>; n is 3-6), and (D) 0.1-10pts.wt. of an organic peroxide.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a fluorosilicone rubber composition, particularly when cured, which exhibits heat resistance, cold resistance, oil resistance, solvent resistance, as well as compression recovery properties during rolling operation. Because it provides excellent rubber elasticity, it is suitable for diaphragms in transportation equipment such as automobiles and aircraft.
The present invention relates to a fluorosilicone rubber composition useful as backings, connectors, gaskets, hose materials, etc.

(Prior art) Silicone rubber is usually put into practical use by adding ultrafine silica filler to it for reinforcement.
In this case, silanes such as dimethyldimethoxysilane and diphenylsilanediol, and siloxane oligomers such as α,ω-dimethylsiloxanediol and hexamethyldisilazane are added as a wetter to aid dispersion and prevent creep hardening. ing.

Regarding this silicone rubber, fluorosilicone rubber in which some of the dimethylsiloxane units have trifluoropropyl groups is also known, and this fluorosilicone rubber is also used in the above-mentioned wetter when blending the ultrafine silica filler. However, in this case, there is a disadvantage that the addition of 3,3,3-trifluoro It has been proposed to add a propyl group-containing alkoxysilane or its partially hydrolyzed wire (see Japanese Patent Publication No. 61-57868).

However, this alkoxysilane or the siloxane obtained by its partial hydrolysis lacks stability because the alkoxysilane is hydrolyzable, and therefore it is difficult to control the amount added. Creep hardening occurs as the group decreases and its wetting effect decreases, and adding too much of it increases the tackiness of the compound, which has the disadvantage of poor rollability. If this occurs in the system, the alcohol produced by this hydrolysis acts as a co-catalyst for the polymerization catalyst of the fluorosilicone polymer and promotes cranking of the polymer, resulting in a decrease in roll workability and the resulting mechanical failure of the rubber elastic body. This measure is considered necessary because it also has the disadvantage of reducing the strength of the target.

(Structure of the Invention) The present invention relates to a fluorosilicone rubber composition that solves the above-mentioned disadvantages. 8 unsubstituted or substituted monovalent hydrocarbon group, R5 is an unsubstituted or substituted saturated monovalent hydrocarbon group having 1 to 8 carbon atoms, X is a hydrogen atom, R
An atom or group selected from the same saturated monovalent hydrocarbon group as in 5 or a silyl group represented by the formula (R', R7 is the same saturated monovalent hydrocarbon group as R5), m = o ~ 3
0. 100 parts by weight of an organopolysiloxane in which at least one end of the molecular chain is capped with a vinyl group, represented by n≧500, p=an integer of 2 to 4), with a specific surface area of 50rrr/
10 to 100 parts by weight of a reinforcing silica filler with a viscosity of 15 to 50 c at 25°C, R8 is the same monovalent hydrocarbon group as R1, and n is an integer of 3 to 6.
0.5 to 20 parts by weight of γ-trifluoropropyl group-containing siloxane oligomer that is S, 2) 0.1 part of organic peroxide
~10 parts by weight.

That is, the present inventors have studied various ways to solve the disadvantages caused by adding a wetter to fluorosilicone rubber. When a γ-trifluoropropyl group-containing siloxane oligomer represented by the above formula is added as a wetter to a fluorosilicone rubber composition consisting of a finely powdered silica filler and an organic peroxide, it improves heat resistance, cold resistance, oil resistance, and solvent resistance. The excellent oil resistance and solvent resistance of fluorosilicone rubber are further improved, and the fluorosilicone rubber obtained by curing this rubber has improved mechanical strength, compression recovery properties, and rollability. The present invention was completed by conducting research on the types and amounts of each component used.

The present invention will be explained in detail below.

The organopolysiloxane as component a) constituting the composition of the present invention is represented by the general formula %, where R1, R2, R3, and R4 are alkyl groups such as methyl, ethyl, propyl, and butyl groups; Alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups and tolyl groups, or alkenyl groups such as phenyl groups and tolyl groups, or alkenyl groups having 1 to 1 carbon atoms in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc. 8, an unsubstituted or substituted monovalent hydrocarbon group, R5 is an alkyl group such as a methyl group, ethyl group, or propyl group, an aryl group such as a phenyl group or tolyl group, or a hydrogen atom bonded to a carbon atom of these groups. A saturated monovalent hydrocarbon group having 1 to 8 carbon atoms partially or entirely substituted with a halogen atom, a cyano group, etc.

X is a hydrogen atom, an atom or group selected from the same saturated monovalent hydrocarbon group as R5, or a silyl group represented by the formula (R″, R7 is the same saturated monovalent hydrocarbon group as R5), m=o ~3
0, n≧500, P=an integer of 2 to 4, and at least one end of the molecular chain is blocked with a vinyl group, and the viscosity at 25°C should be 10 + OOOcs or more. Preferred examples of such organopolysiloxanes include those represented by the formula %.

Further, the reinforcing silica filler as a component constituting the composition of the present invention has a specific surface area of 50rrr/g or more, preferably 100rrr/g or more. It is said that the fine powder siliency is more than /g, but this can be made of publicly known products such as commercially available fumed silica, precipitated silica, and silica airgel. Although it may be treated with an organosilicon compound such as disilazane, it is preferable to use an untreated one in terms of roll workability, oil resistance, and solvent resistance.However, addition of this reinforcing silica filler If the amount is less than 10 parts by weight based on 100 parts by weight of the above-mentioned organopolysiloxane, the resulting silicone rubber composition will not have the desired mechanical strength, and if it exceeds 100 parts by weight, crosstalk will become difficult.
The rubber-like elastic body obtained by curing the silicone rubber composition to which this is added becomes brittle and has poor mechanical strength, so the amount must be in the range of 10 to 100 parts by weight, but this preferred range is The amount is 15 to 70 parts by weight.

Next, c) γ- as the component constituting the composition of the present invention.
The trifluoropropyl group-containing siloxane oligomer is used as a unit when kneading the above-mentioned reinforcing silica filler into the above-mentioned organopolysiloxane, and this product is represented by the formula, where R8 is the same as R1 above. Similar unsubstituted or substituted monovalent hydrocarbon groups, preferably alkyl groups or phenyl groups having 1 to 6 carbon atoms, more preferably ease of synthesis,
A) It is assumed to be a methyl group because of its compatibility with the organopolysiloxane component.

In addition, if the n value of this product is less than 3, this oligomer will lack stability, and if it exceeds 6, the tackiness of the composition will increase due to the increase in the amount added, resulting in poor roll workability. Since addition of a large amount also increases cost, it is set to an integer of 3 to 6. In addition, the amount of this material added is 10% of the organopolysiloxane as the above-mentioned component (a).
If it is less than 0.5 parts by weight, the wetter effect is poor and creep hardening cannot be prevented.
If it exceeds 0.5 to 20 parts by weight, the tackiness of the composition containing it will increase, resulting in poor roll workability and increased costs, so it is necessary to keep it in the range of 0.5 to 20 parts by weight. However, the preferred range is 1 to 10 parts by weight.

Further, the organic peroxide as the second component constituting the composition of the present invention is considered to be a curing agent for this silicone rubber composition, and this is a known organic peroxide used for the vulcanization of ordinary silicone rubber. That's fine.

So benzoyl peroxide for this.

2.4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane,
Examples include dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and the amount added is based on the component (a) above. The amount may be 0.1 to 10 parts by weight per 100 parts by weight of the organopolysiloxane, and the preferred range is 0.2 to 4 parts by weight.

The composition of the invention is prepared by uniformly mixing predetermined amounts of the above-mentioned components (a) to (ii) using a mixer commonly used for compounding silicone rubber, such as a two-roll, kneader, or Banbury mixer. It can be obtained by heat treatment according to the conditions, but in addition to this, known heat resistance improvers and colorants, non-reinforcing fillers such as diatomaceous earth and ground silica, and conductive materials such as carbon black and graphite are added. Lubricity improvers such as lubricity imparting agents and Teflon powder.

Addition of dimethylpolysiloxane or the like is optional to improve roll operation.

The thus obtained fluorosilicone rubber composition of the present invention has excellent heat resistance, cold resistance, oil resistance, and solvent resistance because the above-mentioned γ-trifluoroprobyl group-containing siloxane oligomer is added as a wetter. The silicone rubber obtained by heating and vulcanizing this has particularly excellent heatability and compression recovery properties.
This product has the advantage of being suitable for use as diaphragms, backings, connectors, gaskets, hose materials, etc. in transportation equipment such as automobiles and aircraft.

Next, examples of the present invention will be given, in which parts are parts by weight, and viscosity is a value measured at 25°C.

Examples 1 to 2, Comparative Example 1 Both ends of the molecular chain represented by the formula are blocked with dimethylvinylsilyl groups, and the chain has (γ-trifluoropropyl)methylsiloxy groups, and the degree of polymerization is about 4,000. 100 parts of organopolysiloxane A has a specific surface area of 200rrr/g.
32 parts of fumed silica, and the following three types of α,ω-dihydroxy(γ-trifluoropropyl)methylsiloxane oligomers (hereinafter abbreviated as TFPM) TEPM-1 degree of polymerization (n )=3, viscosity 24cS.

TEPM-2 polymerization degree (n) = 6, viscosity 32 cS.

TEPM-3 polymerization degree (n) = 18, viscosity 120 cS.

was added, kneaded in a kneader, and heat treated at 160°C for 2 hours to produce three types of fluorosilicone rubber compounds.

Next, 2,5 dimethyl-
0.6 parts of 2,5-di(t-butylperoxy)hexane and 1°0 of methylvinylpolysiloxane containing 0.5 mol% of methylvinylsiloxy units with a degree of polymerization of 5,000 to improve roll workability. After adding and kneading, it was dispensed into a 2-inch thick plate and vulcanized and molded at 165°C for 10 minutes under a pressure of 30 kg/aJ to make a 2-inch thick test piece. The separated sheet was vulcanized and molded at 165°C for 15 minutes under a pressure of 30 kg/al to a thickness of 12.7 m.
Test pieces for measuring compression set with a diameter of 28.70 mm were prepared.Next, these test pieces were subjected to secondary vulcanization at 200°C for 4 hours, and the physical properties of this material were investigated and are listed in Table 1. The same results were obtained, and it was confirmed that the examples using TEPM-1 and TEPM-2 had superior physical properties compared to the comparative example using TEPM-3.

Table 1 (Notes) 10-R workability...O: Excellent, 0: Good, Δ: Possible Example 3
~5, Comparative Example 2 Organopolysiloxane B100 with a degree of polymerization of about 3,500, which has a (trifluoropropyl)methylsiloxy group in the chain, with one end of the molecular chain represented by the formula blocked with a dimethylvinylsilyl group, and a (trifluoropropyl)methylsiloxy group in the chain. Part has a specific surface area of 300rrr/g
Example 1 except that 40 parts of fumed silica, 3 parts of diphenylsilanediol, and TFPM-1 and TFPM-3 used in Example 1 and Comparative Example 1 were added in the amounts shown in Table 2. A fluorosilicone rubber compound was prepared in the same manner.

Next, 2,5-dimethyl- was added to 100 parts of this compound.
0.6 parts of 2,5-di(t-butylperoxy)hexane, 1.5 parts of methylvinylpolysiloxane used in Example 1 to improve roll workability, and 2 parts of 3 parts of iron oxide as a heat resistance improver. After adding with the main roll and kneading, Example 1
A sample was prepared in the same manner as above, followed by secondary vulcanization at 200° C. for 4 hours, and then used as a test sample. The results are shown in Table 2.Table 2

Claims (1)

[Claims] 1. A) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ and/or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [Here are R^1, R^2, R^3 , R^4 has 1 or more carbon atoms
8 unsubstituted or substituted monovalent hydrocarbon group, R^5 is an unsubstituted or substituted saturated monovalent hydrocarbon group having 1 to 8 carbon atoms, X is a hydrogen atom, the same saturated monovalent hydrocarbon group as R^5, Or formula ▲ Numerical formula, chemical formula, table, etc. ▼ (R^6, R^7 are saturated monovalent hydrocarbon groups same as R^5)
An atom or group selected from silyl groups represented by m=
0 to 30, n≧500, p=an integer of 2 to 4] 100 parts by weight of an organopolysiloxane in which at least one end of the molecular chain is blocked with a vinyl group, b) a specific surface area of 50 m^2/g or more; 10 to 100 parts by weight of a certain reinforcing silica filler, C) Structural formula ▲ Numerical formula, chemical formula, table, etc. ▼ (Here, R^8 is the same monovalent hydrocarbon group as R^1 above, and n is 3 ~
The viscosity at 25°C is 15 to 5 (an integer of 6).
0.5 to 20 parts by weight of a γ-trifluoropropyl group-containing siloxane oligomer having a 0cS ratio, d) organic peroxide 0
．． 1 to 10 parts by weight of a fluorosilicone rubber composition. 2. A) R^1, R^ of the component organopolysiloxane
2 is a group selected from a methyl group and a vinyl group, and R^
3. The fluorosilicone rubber composition according to claim 1, wherein R^4 is a methyl group. 3. The fluorosilicone rubber composition according to claim 1, wherein R^8 in component (c) is an alkyl group having 1 to 6 carbon atoms or a phenyl group. 4. The fluorosilicone rubber composition according to claim 3, wherein R^8 in component (c) is a methyl group.