JPH0553185B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention provides a fluorosilicone rubber composition, particularly a rubber elastic body having excellent heat resistance, cold resistance, oil resistance, and solvent resistance when cured, as well as excellent compression recovery properties during rolling operation. The present invention relates to a fluorosilicone rubber composition useful as diaphragms, packing, connectors, gaskets, hose materials, etc. for transportation equipment such as automobiles and aircraft. (Prior art) Silicone rubber is usually put into practical use by adding and reinforcing it with an ultrafine silica filler, which helps in its dispersion and prevents creep hardening. Therefore, silanes such as dimethyldimethoxysilane and diphenylsilanediol, and siloxane oligomers such as α,ω-dimethylsiloxanediol and hexamethyldisilazane are added as wetters. Fluorosilicone rubbers in which some of the dimethylsiloxane units have trifluoropropyl groups are also known, and these fluorosilicone rubbers are also used in the wetter when blending ultrafine silica fillers. However, in this case, the addition of fluorosilicone rubber has the disadvantage of reducing the oil resistance and solvent resistance, which are the original properties of fluorosilicone rubber.
It has been proposed to add an alkoxysilane containing a -trifluoropropyl group or a partially hydrolyzed condensate thereof (see Japanese Patent Publication No. 57868/1986). 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, and Creep hardening occurs when the alkoxy group decreases and its wetter effect decreases, and when it is added in excess, the tackiness of the compound increases, resulting in poor rollability. When hydrolysis occurs within the compounding system, the alcohol produced by this hydrolysis acts as a co-catalyst for the polymerization catalyst of the fluorosilicone polymer and promotes cracking of the polymer, resulting in a decrease in roll workability. This also has the disadvantage of reducing the mechanical strength of the rubber elastic body, so countermeasures against this are considered necessary. (Structure of the Invention) The present invention relates to a fluorosilicone rubber composition that solves the above-mentioned disadvantages. and/or [Here, R ¹ , R ² , R ³ , R ⁴ are unsubstituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, R ⁵ is unsubstituted or substituted saturated monovalent hydrocarbon groups having 1 to 8 carbon atoms, X is a hydrogen atom,
The same saturated monovalent hydrocarbon group as R ⁵ or the formula

【formula】

[Formula] An atom or group selected from the silyl group represented by (R ₆ and R ₇ are the same saturated monovalent hydrocarbon groups as R ⁵ ), m
= 1 to 30, n≧500, p = an integer of 2 to 4] and at least one end of the molecular chain is blocked with a vinyldiorganosiloxy group.
100 parts by weight, (b) 10 to 100 parts by weight of reinforcing silica filler with a specific surface area of 50 m ² /g or more, (c) Structural formula

[Formula] (where R ⁸ is the same monovalent hydrocarbon group as R ¹ above, n is 3
The viscosity at 25°C is 15
It is characterized in that it consists of 0.5 to 20 parts by weight of a γ-trifluoropropyl group-containing siloxane oligomer having a molecular weight of ~50 cS, and (d) 0.1 to 10 parts by weight of an organic peroxide. That is, the present inventors have studied various ways to solve the disadvantages caused by the addition of wetters to fluorosilicone rubber, and have found that the above-mentioned fluoropolysiloxane containing a trifluoropropyl group with at least one terminal end capped with a vinyl group. When the 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, heat resistance,
The oil and solvent resistance of fluorosilicone rubber, which has excellent cold resistance, oil resistance, and solvent resistance, has been further improved, and the fluorosilicone rubber obtained by curing this rubber has improved mechanical strength, compression recovery properties, and rollability. After discovering that this would be an improvement on the above, the present invention was completed by conducting research on the types and amounts of each component to be used. The present invention will be explained in detail below. The organopolysiloxane as component (a) constituting the composition of the present invention has the general formula and/or R ¹ , R ² , R ³ , and R ⁴ are alkyl groups such as methyl, ethyl, propyl, and butyl, alkenyl groups such as vinyl and allyl groups, and aryl groups such as phenyl and tolyl groups. 1 carbon number
~8 unsubstituted monovalent hydrocarbon groups, R ⁵ is a methyl group,
Alkyl groups such as ethyl group and propyl group, aryl groups such as phenyl group and tolyl group, or a group with 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 saturated monovalent hydrocarbon group, X is a hydrogen atom,
Saturated monovalent hydrocarbon group same as R ⁵ or formula

【formula】

[Formula] An atom or group selected from the silyl group represented by (R ⁶ and R ⁷ are the same saturated monovalent hydrocarbon groups as R ⁵ ), m
= 1 to 30, n≧500, p = an integer of 2 to 4,
At least one end of the molecular chain is blocked with a vinyldiorganosiloxy group, and it is preferable that the viscosity at 25°C is 10,000 cs or more. Such organopolysiloxanes have the formula The following are examples. Further, the reinforcing silica filler as component (b) constituting the composition of the present invention is finely powdered silica having a specific surface area of 50 m ² /g or more, preferably 100 m ² /g or more, but this is generally Commercially available smoke-based silica, precipitated silica, silica aerogel, and other known materials may be used. The surface of this product may be treated with an organosilicon compound such as dimethyldichlorosilane or hexamethyldisilazane, but from the viewpoint of roll workability, oil resistance, and solvent resistance, it is preferable to leave it untreated. preferable. However, if the amount of reinforcing silica filler added is less than 10 parts by weight based on 100 parts by weight of the above-mentioned organopolysiloxane, the desired mechanical strength will not be obtained for the resulting silicone rubber composition; If it exceeds this, it will be difficult to knead, and the rubber-like elastic body obtained by curing the silicone rubber composition to which it is added will be brittle and have poor mechanical strength.
It is necessary to range from 10 to 100 parts by weight, and the preferred range is from 15 to 70 parts by weight. Next, the γ-trifluoropropyl group-containing siloxane oligomer as component (c) constituting the composition of the present invention is one used as a wetter when kneading the reinforcing silica filler described above into the organopolysiloxane described above. However, this one has the formula R ⁸ is the same unsubstituted or substituted monovalent hydrocarbon group as R ¹ described above, preferably 1 to 6 carbon atoms.
An alkyl group or a phenyl group, more preferably a methyl group from the viewpoint of ease of synthesis and compatibility with the organopolysiloxane of component (a).
Furthermore, if the n value of this product is less than 3, the oligomer will lack stability, and if it exceeds 6, the stickiness of the composition will increase as the amount added increases, resulting in poor roll workability. Since addition of this large amount also increases costs, the number is set to an integer of 3 to 6. If the amount of this substance added is less than 0.5 parts by weight per 100 parts by weight of the organopolysiloxane as component (a), the wetter effect will be poor and creep hardening will not be prevented, and if it exceeds 20 parts by weight, This increases the tackiness of the composition blended with it, impairing roll workability and increasing costs, so it is necessary to use it in a range of 0.5 to 20 parts by weight, but this preferred range is 1 to 10 parts by weight.
Parts by weight. In addition, the organic peroxide as component (2) constituting the composition of the present invention is considered to be a curing agent for this silicone rubber composition, and this is a known curing agent used for the vulcanization of ordinary silicone rubber. Anything is fine. Therefore, this includes benzoyl peroxide,
2,4-dichlorobenzoyl peroxide, p
-chlorobenzoyl peroxide, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5- Examples include di(t-butylperoxy)hexane, and the amount added may be 0.1 to 10 parts by weight per 100 parts by weight of the organopolysiloxane as component (a), and this preferred range is The amount 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 (d) using a kneader 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 desired condition, but in addition to this, known heat resistance improvers and colorants, non-reinforcing fillers such as diatomaceous earth and ground silica, and carbon black and graphite are added. conductivity imparting agents such as, lubricity improvers such as Teflon powder,
Addition of dimethylpolysiloxane or the like is optional to improve roll operation. The fluorosilicone rubber composition of the present invention thus obtained can be used as a wetter with the above-mentioned γ
-Since trifluoropropyl group-containing siloxane oligomer is added, it has excellent heat resistance, cold resistance, oil resistance, and solvent resistance, and the silicone rubber obtained by heating and vulcanizing this is particularly heat resistant. This material has excellent compression and recovery properties, making it suitable for use as diaphragms, packing, connectors, gaskets, hose materials, etc. in transportation equipment such as automobiles and aircraft. is obtained. 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 1-2, Comparative Example 1 Formula 100 parts of organopolysiloxane A with a degree of polymerization of about 4000, which has both ends of the molecular chain blocked with dimethylvinylsilyl groups and has (γ-trifluoropropyl)methylsiloxy groups in the chain, has a specific surface area of
200 m ² /g of 32 parts of smoke-based silica and the following three types of α,ω-dihydroxy (γ) in the amounts shown in Table 1.
-trifluoropropyl) methylsiloxane oligomer (hereinafter abbreviated as TFPM) TFPM-1 polymerization degree (n) = 3, viscosity 24cS, TFPM-2 polymerization degree (n) = 6, viscosity 32cS, TFPM-3 polymerization degree (n) ) = 18, viscosity 120 cS, were added, kneaded in a kneader, and heat treated at 160°C for 2 hours to produce three types of fluorosilicone rubber compounds. Next, to 100 parts of this compound, 0.6 part of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane was added to increase the polymerization degree to improve roll workability.
After adding and kneading 1.0 part of methylvinyl polysiloxane containing 0.5 mol% of 5000 methylvinylsiloxy units, it was divided into 2 mm thick pieces and heated at 165°C for 10 minutes.
A test piece with a thickness of 2 mm was made by vulcanization molding under a pressure of 30 kg/cm ² for minutes, and a sheet separated to a thickness of 13 mm was vulcanized and molded under a pressure of 30 kg/cm ² for 15 minutes at 165°C. A test piece for measuring compression set with a thickness of 12.7 mm and a diameter of 28.70 mm was prepared. Next, after secondary vulcanization of these test pieces at 200℃ for 4 hours, we examined the physical properties of this material.
The results as listed in Table 1 were obtained,
Examples using TFPM-1 and -2 are TFPM
It was confirmed that the material had superior physical properties compared to that of the comparative example using -3.

【table】

【table】

[Table] * Roll processability...◎: Excellent, ○: Good, △: Acceptable Examples 3 to 5, Comparative Example 2 Formula One end of the molecular chain represented by is blocked with a dimethylvinylsilyl group, and (trifluoropropyl)
100 parts of organopolysiloxane B, which has a methylsiloxy group and has a degree of polymerization of about 3500, has a specific surface area of
300 m ² /g of 40 parts of fumed silica, 3 parts of diphenylsilanediol, and the TFPM-1 used in Example 1 and Comparative Example 1 in the amounts shown in Table 2.
A fluorosilicone rubber compound was prepared in the same manner as in Example 1 except that TFPM-3 was added. Next, to 100 parts of this compound, 0.6 part of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane was added to Example 1 to improve roll workability.
After adding 1.5 parts of the methylvinylpolysiloxane used in Example 1 and 3 parts of iron oxide as a heat resistance improver using two rolls and kneading, a sample was prepared in the same manner as in Example 1, and then heated at 200°C for 4 hours. After secondary vulcanization, it was used as a test sample. The results are shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1 (a) General formula and/or [Here, R ¹ , R ² , R ³ , R ⁴ are unsubstituted monovalent hydrocarbon groups having 1 to 8 carbon atoms, R ⁵ is unsubstituted or substituted saturated monovalent hydrocarbon groups having 1 to 8 carbon atoms, X is selected from a hydrogen atom, the same saturated monovalent hydrocarbon group as R ⁵ , or a silyl group represented by the formula [formula] [formula] (R ⁶ and R ⁷ are the same saturated monovalent hydrocarbon groups as R ⁵ ) Atom or group, m=1 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 vinyldiorganosiloxy group; (b) 10 to 100 parts by weight of a reinforcing silica filler having a specific surface area of 50 m ² /g or more; C) Structural formula [Formula] (where R ⁸ is the same monovalent hydrocarbon group as R ¹ above,
γ-trifluoropropyl group-containing siloxane oligomer having a viscosity of 15 to 50 cS at 25°C, where n is an integer of 3 to 6)
0.5 to 20 parts by weight; and (d) 0.1 to 10 parts by weight of an organic peroxide. 2 R ¹ and R ² of organopolysiloxane as component (a)
is a group selected from a methyl group and a vinyl group,
The fluorosilicone rubber composition according to claim 1, wherein R ³ and R ⁴ are methyl groups. 3. The fluorosilicone rubber composition according to claim 1, wherein R ⁸ of 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 of component (c) is a methyl group.