JPH02289650A - Fluorosilicone rubber composition - Google Patents

Abstract

PURPOSE:To obtain a composition suitable as packings, gaskets, etc., for automobiles, airplanes, etc., having excellent heat resistance, freeze resistance, oil resistance and solvent resistance by blending a specific polyorganosiloxane with specific amounts of silica subjected to specific surface treatment and vulcanizing agent. CONSTITUTION:(A) 100 pts.wt. polyorganosiloxane containing A1: 15-99.95mol% unit shown by formula I (Rf is 3-9C perfluoroalkyl group) and A2: 0.05-10mol% unit shown by formula II (R is alkyl or aryl; R<1> is vinyl or alkenyl) and having >=1X10<6> viscosity is blended with (B) 10-100 pts.wt. silica having >=50m<2>/g, preferably >=100m<2>/g specific surface area subjected to surface treatment with an organosilicon compound containing a fluoroalkyl group and (C) 0.01-5 pts.wt. vulcanizing agent (e.g. di-t-butyl peroxide).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluorosilicone rubber composition. [Prior Art] Fluorosilicone rubber has excellent heat resistance, cold resistance, and oil resistance, and is useful for use under harsh conditions where these properties are required. It is known from Japanese Patent Publication No. 34-2185 that silicone rubber containing a barfluoroalkyl group has low swelling in automobile fuel and lubricating oil. [(CFsCHiCH
*) (CHs) 6.5 to 15 mol% of Sill units and [
Rubbers based on organoborisiloxanes containing 85 to 93.5 mol% of (CHs)isiO] units are known to have excellent resistance to hydrocarbon solvents and low-temperature properties.

It is known from JP-A-60-123533 that a polysiloxane-based rubber having a fluorosilicone content of 45 mol % or more has excellent resistance to fuel oil and heat aging resistance.

It is known from Industrial and Engineering Chemistry Vol. 52, No. 9, p. 783 that the oil resistance of rubber is not affected by the type of perfluoroalkyl group. However, although conventional fluorosilicone rubber has better resistance to liquids such as fuel oil than dimethyl silicone rubber, it swells to a greater extent than dimethyl silicone rubber when exposed to polar solvents such as acetone. Furthermore, the heat resistance was also inferior to that of dimethyl silicone rubber.

On the other hand, according to research conducted by the present inventors, it has been found that as the number of carbon atoms in the perfluoroalkyl group increases, the cold resistance significantly improves, but the vulcanizability of the rubber tends to decrease.

[Problems to be solved by the invention] Although conventional dimethylene silicone rubber has excellent heat resistance, cold resistance, and solvent resistance, it has poor oil resistance and cannot be used in applications where it comes into contact with fuel oil. . On the other hand, conventional fluorosilicone rubber improves the oil resistance of dimethyl silicone rubber by introducing barfluoroalkyl groups, but on the other hand, it has poor solvent resistance. Heat resistance was sacrificed.

The present invention eliminates these drawbacks of conventional dimethyl silicone rubber and fluorosilicone rubber, and has excellent heat resistance, cold resistance,
This product provides rubber with excellent oil resistance and solvent resistance.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems. ) is a perfluoroalkyl group of 15 to 99. 95 mol%, and [
R'SiO] units (wherein R is an alkyl group or an aryl group, and R1 is a vinyl group or an alkenyl group) in a proportion of 0.05 to 10 mol%, and 25
100 parts by weight of polyorganosiloxane having a viscosity of 1 x 106 centipoise or more at °C (B) Silica 10 with a specific surface area of 50 m''/g or more, surface-treated with an organosilicon compound having a fluoroalkyl group.
-100 parts by weight and (C) a vulcanizing agent.

The polyorganosiloxane (A) according to the present invention has at least RfCH. C}I! 1 (Rf has 3 to 9 carbon atoms
Siloxane unit (1) having a fluoroalkyl group represented by [(Rf
CHaCHi)(CHs)SiO] and a siloxane unit with unsaturated groups (2) [R R' Sill is important. Because it contains the fluoroalkyl group-containing siloxane unit (1) containing a barfluoroalkyl group having 3 to 9 carbon atoms, it has excellent heat resistance, oil resistance, and solvent resistance, as well as excellent vulcanizability and vulcanization. It is possible to achieve excellent mechanical properties of rubber. When the number of carbon atoms in the perfluoroalkyl group is less than 3,
It is not possible to obtain a rubber that has a good balance of heat resistance, oil resistance, and solvent resistance. In addition, when the number of carbon atoms in the perfluoroalkyl group is greater than 9, heat resistance. Oil resistance,
Not only is no improvement in effects such as solvent resistance observed, but the vulcanizability and mechanical properties of the vulcanized rubber tend to deteriorate, which is undesirable. Vulcanizability, mechanical properties of vulcanized rubber. In view of the balance of chemical properties, those having a perfluoroalkyl group having 4 to 6 carbon atoms, particularly a perfluoroalkyl group having 4 carbon atoms, are preferred. Further, the siloxane unit (1) having a fluoroalkyl group is contained in a proportion of 15 mol% or more of the total polymerized units. If the proportion of the siloxane unit (1) having a fluoroalkyl group is less than the above-mentioned proportion, good heat resistance, oil resistance, solvent resistance, etc. will not be achieved.

Moreover, the siloxane unit (2) having an unsaturated group [R R
' Sill is important in carrying out vulcanization.

Here, R is an alkyl group or an aryl group, and R
1 is a vinyl group or an alkenyl group. Also, R is
If the number of carbon atoms is too large, it may become difficult to obtain an organoborisiloxane, which is not preferable. Usually, an alkyl group or a phenyl group having about 1 to 6 carbon atoms is preferred, and a methyl group or a phenyl group is particularly preferred. R' is important as a vulcanization site. As R', a vinyl group is most preferable, but in the case of an alkenyl group, a group having an unsaturated group at the end is preferably employed from the viewpoint of vulcanizability. Moreover, the siloxane unit (2) having an unsaturated group is contained in a proportion of 0.05 to 10 mol%. If the proportion of this unit is less than the above-mentioned ratio, the vulcanizability decreases, resulting in a product that cannot be used as a vulcanized rubber, which is not preferable. On the other hand, if the amount is too large, heat resistance may be impaired or unreacted unsaturated groups may remain in the vulcanized rubber, resulting in deterioration of chemical properties, which is not preferable.

Further, the polyorganosiloxane (A) has a viscosity at 25° C. (hereinafter simply referred to as viscosity) of 1×10 6 centipoise (hereinafter abbreviated as cP) or more. If the viscosity is lower than the above value, sufficient mechanical properties cannot be obtained. Preferably, it has a viscosity of I x 10' cP or more. Further, the upper limit of the viscosity is not particularly limited, but is appropriately selected in consideration of processing conditions and the like.

The polyorganosiloxane (A) in the present invention may contain other siloxane units (3) in addition to the above-mentioned siloxane units (1) and siloxane units (2). Even if the siloxane unit (3) is included, the ratio of the siloxane unit (l) and the siloxane unit (2) needs to be within the above range. As a siloxane unit, [(Rf'CHiCHi) (CHs)SIOI,
There is a unit represented by [R” R” Sill, etc. Here, Rf' is a trifluoromethyl group or a pentafluoroethyl group, and R! ．． ip is each a lower alkyl group or a phenyl group. In addition, the siloxane unit (3) may contain a plurality of types, but the total is 84. The proportion is preferably 95 mol% or less. Polyorganosiloxanes containing other siloxane units (3) are preferably employed because they have excellent vulcanizability. Also, [( Rf'CHiCHa)(
Those containing units represented by [R"
Those containing the unit represented by O 2 have thick oil resistance (without deterioration) and improved vulcanizability.

Therefore, depending on the desired physical properties, the siloxane unit (3)
The introduction, type, and ratio can be selected as appropriate. Further, in consideration of the balance of heat resistance, oil resistance, solvent resistance, vulcanizability, etc., the content of the siloxane unit (3) is preferably about 50 mol% or less.

Moreover, the polyorganosiloxane (A) in the present invention is [(Rf C}I-CH-)(CHs) SiO
]-[R R' SiO ], and if necessary, [
(Rf'CHiCHa)(CHa)SiO]-
．． t R” R” SiO ]l, (Rf , Rf'R
, R', R'', R'' are the same as above 1 kll+all
+l'l is an integer of 3 to 5) can be produced by ring-opening polymerization of a cyclic siloxane represented by the following formula (individually, +l'l is an integer of 3 to 5) in the presence of a catalyst such as a basic catalyst. Also,[(
Rf CH. Since polyorganosiloxanes having CH-)(CH-)SiO2 units undergo active depolymerization after ring-opening polymerization, it is preferable to stop the polymerization when a desired degree of polymerization is reached. The composition of the present invention has a specific surface area of 50 m
”/g or more of silica is blended. Because this specific silica is blended, the fluorosilicone rubber composition of the present invention can be re-kneaded after storage,
Vulcanized rubber has the advantage of providing a good balance of tensile strength and elongation.

Such silicas include fumed silica, precipitated silica, etc., which are commonly used as fillers for reinforcing silicone rubber. Silica powder such as quartz powder is surface-treated with an organosilicon compound having a fluoroalkyl group. Here, examples of the organosilicon compound having a fluoroalkyl group include a cyclic siloxane, a linear siloxane, a silane compound, and a silazane. Further, the fluoroalkyl group is a group having a perfluoroalkyl group having 1 or more carbon atoms, for example, R
f''CH*CHi- (Rf'' is a barfluoroalkyl group having 1 or more carbon atoms), and the like.

Here, a perfluoroalkyl group having an excessively large number of carbon atoms is not preferable because surface treatment of the silica becomes difficult. Usually, those having a perfluoroalkyl group having 9 or less carbon atoms are employed.

This surface treatment with an organosilicon compound having a fluoroalkyl group is easily achieved by bringing the silica powder into contact with the organosilicon compound. In addition, this surface treatment is 30 to 60 mol% of the amount of silanol groups on the silica powder surface.
It is preferable to carry out the treatment in such a way that the degree of inactivation is achieved. Also,
The surface treatment of the silicate powder may be performed before the preparation of the composition, or at the same time as the preparation.

Moreover, such surface-treated silica has a specific surface area of 50
m”/g or more.

Silica having a too small specific surface area is not preferred because its reinforcing effect as a filler is insufficient.

Particularly preferred are those having a specific surface area of 100 m''/g or more.

The surface-treated silica (B) is blended in an amount of 10 to 100 parts by weight per 100 parts by weight of the polyorganosilixane (A). If the amount of surface-treated silica (B) is less than 10 parts by weight, no reinforcing effect will be obtained, and if it is too large, the silicone rubber will become too hard and difficult to process.

Further, the vulcanizing agent (C) is necessary to vulcanize the polyorganosiloxane (A).

As such a vulcanizing agent, various vulcanizing agents used in ordinary thermosetting silicone rubber can be employed. For example, hydroperoxide, dialkyl peroxide. These include peroxides such as diasilver oxide, peroxyester, and ketone peroxide.

More specifically, di-t-butyl peroxide, dicumyl peroxide. 2.5-dimethyl-2,5-di(t-butylbaroxy)hexane. Examples include dibenzoyl peroxide and t-butyl peroxybenzoate.

Further, the vulcanizing agent (C) is blended in a catalytic amount. Specifically, it is 0.00 parts per 100 parts by weight of the polyorganosiloxane (A). An amount of about 5 parts by weight is employed.

In addition to the above three components, the composition of the present invention may optionally contain a processing aid, a heat stabilizer. Anti-aging agents, colorants, etc. may be added. Examples of processing aids include methylvinylpolysiloxane, metal soaps, and polytetrafluoroethylene. Further, examples of the heat-resistant stabilizer include iron oxide, titanium oxide, and cerium oxide.

[Action 1 In the present invention, [(RfCH-CHi) in eA)
(CHs)SiO ] unit (in the formula, Rf is a barfluoroalkyl group having 3 to 9 carbon atoms) is thought to impart heat resistance, oil and solvent resistance to silicone rubber due to the protective effect of fluorine.

In addition, the reinforcing silica treated with a fluoroorganosiloxane or a fluoroorganosilicon compound (B) is
It is thought that by forming a homogeneous mixture with the organoborisiloxane (A), it exerts a reinforcing effect and at the same time imparts oil resistance. [Examples] Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. Note that the catalyst solution used in the synthesis example was prepared by the following method. Further, parts used in the following Examples and Comparative Examples are parts by weight unless otherwise specified.

[(C.F.
CHsCH*)(CHi)SiO]s 11.7 g
, KOH 9.0mg+ dicyclohexyl-18
-Crown-6 71.7 mg was charged at room temperature. When stirring was continued at room temperature, the reaction solution became viscous after about 10 minutes, and the viscosity decreased after 1 hour. After stirring for an additional 12 hours, the reaction solution was used as a catalyst. This reaction solution is a mixture of KOH silanolate and cyclic ether [(CJ*Ct{icH*)(CHs) SiO 1
- (- is an integer of 4 or more) It is considered to be a solution dissolved in.

Synthesis example 1 [(C.F@CHIGH!) (CH.)SiO] 1 2
0 g (22 mmol) and [(CHz=CH)(
CHs)SiO]sO. 227 g (0.88
mmol) was placed in a 50 ml flask under an argon atmosphere and maintained at 25°C. Equimolar complex of κOH and dicyclohexyl-18-crown-6 [(C.
F. CHICHi) (CHa) SiO]-(
- is an integer of 4 or more) using a homogeneous solution as a catalyst, KO
H was added in an amount such that Si/K = 34,000 to initiate polymerization. After polymerization was carried out for 2.5 hours, the catalyst was neutralized with an excess amount of dimethylvinylchlorosilane to stop the polymerization. The product was dissolved in trichlorotrifluoroethane, washed with water, reprecipitated from hebutane, and heated at 100°C under reduced pressure.
to obtain 18 g of a polymer having a viscosity of 10 million centivoices at 25°C. Synthesis example 2 [(CHi=CH) (CHm) SiO ] s is 0
．． The same procedure as in Synthesis Example 1 was performed except that 114 g (0.44 mmol) was used, and the viscosity at 25°C was 10.
18 g of a million centivoice polymer was obtained. Synthesis example 3 [(C4F@C}IICH!)(CHI)SiO]1
20 g (22 mmol). [(CHs) gsi
O]m 2.2 g (10 mmol) and ((c
ha=CI)(CHs)SiO1s 0.124 g
(0.48 mmol) in an internal volume of 5 under an argon atmosphere.
It was placed in a 0 ml flask and kept at 75°C. CsOH
0.0048 g (0.032 1ffImol)
was added to start polymerization, and 20 minutes later, the catalyst was neutralized with an excess amount of dimethylvinylchlorosilane to stop polymerization. The product was dissolved in trifluoroethane, washed with water, reprecipitated from hebutane, and dried at 100°C under reduced pressure.
19 g of a polymer having a viscosity of 9 million centipoise at 25°C was obtained.

Synthesis example 4 [(C4FeCHiCH*)(CH-)SiO]sl4
．． 8g (16.1mmol). [(CHs)asio
]s 3.6 g (16.2 mmol) and [(
CH. =CH)(CHs)SiO1s 0.0425
The same operation as in Synthesis Example 3 was carried out except that 15 g of a polymer having a viscosity of 11 million centiboise at 25° C. was used, except that 15 g of the polymer was used.

Synthesis example 5 [(CJsCH*CHi)(CHs)SiO]x 39
．． 5g (43 mmol), [(CFaF-CH*C
H*)(CHs)SiOls 20.5g (44.m
mol), and [(C}Im=CI)(CHs)SiO
]s O. 223 g (0.863 mmol) was charged into a 50 ml flask with a stirrer under an argon atmosphere.
It was kept at 25°C. Add 0.53 of the catalyst solution to this flask.
g (approximately 7 ppm in terms of KOH) and heated at 25°C.
Stirring was performed with After about 1.5 hours, the viscosity of the reaction solution reached almost its maximum, at which point about 10 B of dimethylvinylchlorosilane was added. Then, the reaction product was converted into Freon R-
113 (1,1.2-trichlorofluoroethane), washed with water, reprecipitated with hebutane, and heated at 100°C under reduced pressure.
It was dried. As a result, fluorosilicone copolymer 5
3.5 g was obtained, and its viscosity at 25°C (hereinafter simply referred to as viscosity) was 34 million cP (centiboise, hereinafter the same). When the molar ratio of polymerized units of each monomer of the copolymer was measured by HNMR and FNMR, it was approximately 1:1:0.02 in the above order.
The molar ratio was almost the same as the charged molar ratio.

Synthesis Examples 6-8 [(CJsCHmCHi)(CHs)SiO]s. [
Polymerization was carried out in the same manner as in Synthesis Example 5 except that the composition ratios of (CFaCHzCHz)(CHs)Sin] s and [(CH1CI) (CH-)Sill - were changed, and a copolymer was produced by purification. Table 1 below shows the composition ratio (mole ratio) of the monomers used to produce each copolymer and the viscosity of the obtained copolymer. The composition ratio of monomer units in each copolymer was determined by 'HNMR. "As measured by FNMR, the composition ratio was almost the same as the composition ratio of the charged monomers. Examples 1 to 5 Fumed silica (specific surface area 300 m"/g) was added to the polymers obtained in Synthesis Examples 1 to 5. in advance [(C.F9CH2C
HI) (CHs) Silica 50 treated with Sill s
peroxide (Toray Silicone “RC-450”)
": Product name) 2 parts (Example 1.2) or 1 part (Examples 3, 4.5) were blended, pressure vulcanized at 170°C for XIO minutes, and further oven-cured at 200°C for 4 hours. .Synthesis example 1
Immersion test (JIS
The results of K-6301) are shown in Table 2 together with the results of dimethyl silicone rubber and methyltrifluroprovir silicone rubber.

In addition, the polymers obtained in Synthesis Examples 1 to 5 and vinyl group-free [(C4F-CI-CHa) (CI{i)SiO
] Table 3 shows the change in torque (hereinafter referred to as Δtorque) during vulcanization of the homopolymer blend of s (blended with 2 parts of the above-mentioned peroxide) using a curelast meter.

It is clear from Table 2 that the fluorosilicone rubber of the present invention exhibits greater resistance values in both oil resistance and solvent resistance than dimethyl silicone rubber and methyl trifluorofurobyl silicone rubber. From Table 3, in order to impart vulcanizability to the fluorosilicone rubber of the present invention, [R R' Si
It is clear that the ll unit (R, R' are the same as above) is essential. In addition, in the polyorganosiloxane (A), [(Rf'CH-CHi)(CH3) SiO
] unit (in the formula, Rf' is a perfluoroalkyl group having 1 to 2 carbon atoms) or [R"a SiO ] unit (in the formula, R2 is a lower alkyl group, a phenyl group), the vulcanizability can be further improved. It is clear that the improvement is achieved. Examples 6 to 9 100 parts of the polymer obtained in Synthesis Examples 5.6 and 7.8 and fumed silica (specific surface area 300 m"/g) were mixed in advance [(
CFsCHmCHi) (CHs) 50 parts treated with SiO Is and peroxide (Tore Silicone ■
RC: -450p'') was sufficiently kneaded with two rolls, press vulcanized (170°C x 10 minutes) and then oven vulcanized (200°C x 4 hours) to obtain a vulcanized product. The solvent resistance of the vulcanizate was measured based on JIS K 6301. The volume change rate (%) after 72 hours at 25° C. is shown in Table 4 below.

Example 10 The amount of reinforcing silica in Example 6 was 35 parts,
Example 6 except that 0.5 part of cerium oxide was further added.
A vulcanizate was obtained by the same operation as above. Mechanical properties of the obtained vulcanizate were measured based on JIS K6301, and found to be hardness 50, strength 94 kg/cm'', elongation 350%, and 100% modulus 18 kg/cm''. In addition, this vulcanizate and methyltrifluoropropyl silicone rubber (LS 63 manufactured by Toray Silicone)
u) heat aging test at 200℃ according to JIS K
Table 5 shows the results of the investigation based on 6301.

It is clear from Table 4 that the fluorosilicone rubber of the present invention exhibits greater resistance in both oil resistance and solvent resistance than dimethyl silicone rubber and methyl trifluoropropyl silicone rubber. From Table 5 [(RfCH.CHl){C}i. ) S
It is clear that the fluorosilicone rubber of the present invention having 1 unit of iO (in the formula, Rf is a barfluoroalkyl group having 3 to 9 carbon atoms) has superior heat resistance compared to methyltrifluorobrobyl silicone rubber.

Comparative Example 1 100 parts by weight of the polymer obtained in Synthesis Example 5 was mixed with fumed silica (specific surface area: 300 m"/g) without surface treatment.
) When 35 parts of the mixture was kneaded, the mixture was very hard.
Crosstalk was virtually impossible. Comparative Example 2 100 parts by weight of the polymer obtained in Synthesis Example 5 was mixed with fumed silica (specific surface area 300+g+") without surface treatment.
/g) 30 copies. 3 parts diphenylsilanediol, silanol group-terminated dimethyl silicone oil (viscosity 50
cs) and 1 part of the peroxide of Example 1 were blended, and vulcanization was performed in the same manner as in Example 1. The surface of the vulcanizate was orange skin-like.

In addition, the mechanical properties measured according to JIS K 6301 are hardness 67, strength 53 kg/cm", and elongation 140.
%ioo% modulus was 42 kg/c+n''.

From the results of Example 10 and Comparative Example 1.2, it is clear that the reinforcing silica (B) of the present invention is essential for imparting a sufficient reinforcing effect to rubber.

[Effect of the invention] The fluorosilicone rubber composition of the invention has high vulcanizability.
It has the effect of being able to provide fluorosilicone rubber with excellent heat resistance, cold resistance, oil resistance and solvent resistance. The fluorosilicone rubber obtained by the method of the present invention has excellent corrosion resistance to various solvents, acid and alkali resistance, oxidation resistance, resistance to oxidizing atmosphere, heat resistance, and cold resistance, and is suitable for use as rubber parts used under these conditions. It's useful. For example, fuel oil resistant, lubricating oil resistant packings, gaskets, O-rings, etc. for automobiles, aircraft, vehicles, etc.
Oil seals, shaft seals, valve stem seals,
Sealing materials such as crank oil seals, hoses and tubes such as fuel hoses and vacuum control tubes,
Useful for anti-vibration rubber, diaphragms, etc. for fuel bomb mounts, engine mounts, etc. It is also useful for corrosion-resistant packing for polar and non-polar liquids, gaskets, various sealing materials such as O-rings, hoses and tubes, cable jackets, diaphragms, etc. in various industries including the chemical industry. Furthermore, it is useful as rubber products such as various sealing materials, hoses and tubes, cable jackets, diaphragms, and rolls in the mechanical, electrical, general, and other industrial fields.

Claims (1)

[Claims] 1. (A) [(RfCH_2CH_2)(CH_3)S
iO] unit (however, Rf is a perfluoroalkyl group having 3 to 9 carbon atoms) in an amount of 15 to 99.95 mol%, and [RR^
1SiO] unit (where R is an alkyl group or an aryl group, and R^1 is a vinyl group or an alkenyl group) at a ratio of 0.05 to 10 mol%, and has a viscosity of 1 x 10 at 25°C. 100 parts by weight of polyorganosiloxane having a particle size of ^6 centipoise or more (B) Silica 1 having a specific surface area of 50 m^2/g or more and surface-treated with an organosilicon compound having a fluoroalkyl group
A fluorosilicone rubber composition comprising 0 to 100 parts by weight and (C) a vulcanizing agent.