JP2767270B2 - Fluorosilicone rubber composition - Google Patents

Description

The present invention relates to a fluorosilicone rubber composition, and more particularly to an oil excellent in processability, oil resistance, mold non-staining, and mechanical strength. The present invention relates to a bleeding fluorosilicone rubber composition.

(Prior art) Fluorosilicone rubber is excellent in oil resistance and solvent resistance, and also excellent in heat resistance and cold resistance, so that it is used under severe conditions where these characteristics are required. And in the aviation industry as parts materials that make use of gasoline resistance and cold resistance. Also,
When assembling a silicone rubber molded product, a silicone rubber composition (compound) containing dimethylpolysiloxane as a main component should be incompatible with an oil-like silicone compound so that components can be easily incorporated by lubrication of the surface. That is, the phenylsiloxy unit is 5 to
A technique of obtaining a cured product having oil bleeding properties by adding an appropriate amount of silicone oil containing 30 mol% as a bleed component has already been put to practical use.

(Problems to be Solved by the Invention) However, when a fluorosilicone rubber composition is prepared by the same method as the conventional method of mixing an oil-bleed silicone rubber composition containing dimethylpolysiloxane as a main component, the bleed component used If the content of dimethyl silicone oil or phenyl methyl silicone oil is less than 10% by weight, sufficient bleeding property cannot be obtained, and if the content is 12 to 15% by weight, bleeding property is exhibited. Since the oil already bleeds in the state of the vulcanized rubber compound, workability is significantly impaired. In addition, oil resistance and solvent resistance are significantly reduced, and mechanical strength is also reduced.

As a means for solving the above problems, it has been proposed to blend phenylmethyl silicone oil having a low degree of polymerization (degree of polymerization: 2 to 7) as a bleed component (Japanese Patent Application Laid-Open No. 62-190254). In the temperature range of 150 to 200 ° C., which is the vulcanization condition generally used when heating and curing silicone rubber,
There is a problem that a part of the oil of the blended bleed component volatilizes, and the bleeding property varies.

In addition, the processability of the unvulcanized rubber compound is extremely poor,
In addition, there is a problem that the inner surface of the molding die is contaminated and the releasability is reduced, and this is not a sufficient solution.

Accordingly, an object of the present invention is to provide a curable fluorosilicone rubber having better processability, mold non-staining property and stable oil bleed property while maintaining the excellent oil resistance and solvent resistance inherent to the fluorosilicone rubber. It is to provide a composition.

[Constitution of the Invention] (Means for Solving the Problems) The fluorosilicone rubber composition of the present invention comprises (A) an average composition formula Wherein R is a group represented by the formula —CH ₂ CH ₂ R _f (where R _f is a perfluoroalkyl group having 1 to 3 carbon atoms); 5050 mol% represents a saturated or unsaturated monovalent hydrocarbon group, and a is 1.98 to 2.02
And 100 parts by weight of an organopolysiloxane having a viscosity at 25 ° C. of 1000 centipoise or more, and (B) an average compositional formula. [Wherein R 'is less than 5 to 30 mol% of the formula -CH ₂ CH ₂ R _f
(Where R _f represents a perfluoroalkyl group having 1 to 3 carbon atoms) and the difference from -CH ₂ CH ₂ R _{f in} the above average composition formula (A) is 20 to 45 mol. % And the remaining 95
~ 70 mol% is selected from methyl and phenyl groups, and b is
1.98 to 2.02], 3 to 15 parts by weight of an oily organopolysiloxane having a viscosity at 25 ° C. of 20 to 10,000 centipoise, and (C) a reinforcing property having a specific surface area of 50 m ² / g or more. Silica powder 10
An oil-bleed fluorosilicone rubber composition comprising, as essential components, 100 parts by weight and (D) a vulcanizing agent.

 Next, each of these components will be described in detail.

In the organopolysiloxane of the component (A), -CH
As R _f is a ₂ CH ₂ R _f, trifluoromethyl, pentafluoroethyl, and the like. The proportion of —CH ₂ CH ₂ R _f groups in R is from 25 to 50 mol%. If this ratio is less than 25 mol%, the oil resistance and solvent resistance of the cured product will be reduced, and the inherent characteristics of the fluorosilicone rubber will be lost. It is generally difficult to increase the ratio to more than 50 mol% in production. The remaining 75 to 50 mol% of R is exemplified by methyl group, ethyl group, phenyl group, vinyl group, etc., and the silicone rubber composition finally prepared is cured by heating with a vulcanizing agent. It is preferable to contain a vinyl group in an amount of about 0.01 to 5 mol% in order to obtain a rubber elastic body. Further, the viscosity of the component (A) at 25 ° C. is 1000 centipoise or more, and preferably
3000-10,000,000 centipoise. This viscosity is 1000
When it is less than centipoise, the mechanical strength of the obtained cured product is reduced. The organopolysiloxane of the above component (A) is prepared by adding a terminal terminator to a cyclic siloxane mixture and subjecting it to ring-opening copolymerization by a well-known method so as to obtain a desired polymer represented by the above average composition formula. It can be easily manufactured.

The component (B) oily organopolysiloxane is
(A) A component which is moderately incompatible with the organopolysiloxane of the component and exhibits oil bleeding property after curing of the prepared silicone rubber composition. In this organopolysiloxane, as R _f is a -CH ₂ CH ₂ R _f, trifluoromethyl, pentafluoroethyl, and the like, R
Proportion of -CH ₂ CH ₂ R _f groups occupied in is less than 5 to 30 mol%. If the proportion is less than 5 mol%, the processability, oil resistance and solvent resistance and mechanical strength of the composition obtained by blending the composition are inferior, and if it exceeds 30 mol%, the organopolysiloxane of component (A) is used. , And no good bleeding property is exhibited. Thus the ratio of the -CH ₂ CH ₂ R _f groups,
(A) the difference between the -CH ₂ CH ₂ R _f groups in the component 20 to 45 mol%
Is selected in the range. The remaining 95 to 70 mol% of R 'is a methyl group or a phenyl group, and the number of methyl groups and the number of phenyl groups are not particularly limited. However, the number of phenyl groups is preferably 0 to 75 mol% in terms of synthesis. . The viscosity at 25 ° C. of this organopolysiloxane is in the range of 20 to 10,000 centipoise, and if it is less than 20 centipoise, stable bleeding characteristics cannot be obtained. . The component (B) is used in an amount of 3 parts per 100 parts by weight of the component (A) in order to impart good oil bleeding property to the cured product.
It is necessary to add it in an amount of at least 15 parts by weight. Preferably 4
~ 10 parts by weight.

The reinforcing silica powder of the component (C) is finely divided silica having a specific surface area of 50 m ² / g or more, which is known as a filler for silicone rubber, and examples thereof include fumed silica, precipitated silica, and silica aerogel. There is no particular limitation. These may be those whose surfaces have been treated with various organosilanes, organosiloxanes, organosilazanes and the like. The compounding amount is preferably 10 to 100 parts by weight per 100 parts by weight of the component (A) in order to give preferable mechanical properties to the cured product.

The vulcanizing agent of the component (D) is necessary for heat-curing the composition according to the present invention, and various known vulcanizing agents used in ordinary heat-curable silicone rubber compositions are used. be able to. For example, ditertiary butyl peroxide, dicumyl peroxide, 2,5-dimethyl-
2,5-di (tertiary butyl) peroxyhexane,
Platinum-based catalysts for addition reactions such as organic peroxides such as dibenzoyl peroxide, chloroplatinic acid, platinum vinylsiloxane, and platinum black can be mentioned. When a platinum-based catalyst for an addition reaction is used as a vulcanizing agent, the above (A)
It is necessary to use an appropriate amount of a -Si-H group-containing organopolysiloxane as a crosslinking agent in addition to the components (D) to (D).

In addition, the fluorosilicone rubber composition of the present invention may contain, in addition to the components (A) to (D), if necessary, a filler generally used in ordinary silicone rubber compositions, for example, crushed quartz, Clay, talc, calcium carbonate, diatomaceous earth, alumina, etc. can be blended, surface property modifiers such as tetrafluoroethylene powder, heat-resistant improvers such as iron oxide, titanium oxide, cerium oxide, magnesium oxide, magnesium carbonate Such oil resistance improvers, processing aids such as metal soaps, and compounding aids such as silane and low molecular siloxane can be arbitrarily added.

The fluorosilicone rubber composition of the present invention is obtained by blending the above-mentioned components (A) to (D) and, if necessary, various additives, and uniformly kneading the mixture. Becomes

(Function) As described above, according to the present invention, in an oil-bleed silicone rubber composition based on an organopolysiloxane containing a predetermined amount of a perfluoroalkyl group, the organopolysiloxane is used as a bleed component in a perfluoroalkyl group. Are added and blended. Thus, the base component and the bleed component both have a perfluoroalkyl group and thus are relatively easy to knead and adjust, while the bleed component sufficiently exhibits the required oil bleeding property in the state of a molded product obtained by vulcanization and curing. At the same time, there is no reduction in workability and mechanical properties.

(Examples) Hereinafter, the present invention will be described with reference to examples. In the examples, all parts are by weight, and the present invention is not limited to these examples.

Example 1. Organopolysiloxane containing 99.5 mol% of methyl (3,3,3-trifluoropropyl) siloxy unit and 0.5 mol% of methylvinylsiloxy unit and having a hydroxyl group-capped terminal (viscosity at 25 ° C) 8 million centipoise) 100 copies,
25 parts of fumed silica having a specific surface area of 130 m ² / g (AEROSIL 130 manufactured by Nippon Aerosil Co., Ltd.) were uniformly blended and kneaded using a kneader to prepare a base compound A.

To the prepared base compound A, the components (B) and (D) are added at the ratios shown in Table 1 and uniformly kneaded with two rolls to prepare six types of compounds (compositions) including comparative examples. did.

Each of the resulting compounds (compositions) is 4 inches 2
The roll workability was evaluated using the present roll. Table 1 shows that those that could be wound well were marked with a circle, those that were hardly wound with a triangle, and those that were not wound well were marked with a cross in Table 1.

Next, each of the above compounds (compositions) is vulcanized at 170 ° C. for 10 minutes using a press molding machine, and after removing the vulcanized rubber piece from the mold, the stain on the mold is observed. ○
In Table 1, a mark with a slight mark and dirt is indicated by a mark, and a mark with severe stain is indicated by a cross in Table 1. Then, the vulcanized rubber piece is subjected to secondary vulcanization at 200 ° C. for 2 hours in an open state, and a cured sheet having a thickness of 2 mm and a test piece for compression set test (thickness 12.7 m)
m, a right circular cylinder having a diameter of 29.0 mm). After the secondary vulcanization,
Leave at room temperature for 1 hour and observe the bleeding property of the rubber surface by touching with a finger. If the bleeding property is good, mark 、, if slight bleeding is recognized, mark 、, and if no bleeding is recognized, mark ×. Are shown in Table 1. Rubber properties were measured in accordance with JISK6301, and the results are shown in Table 1.

The compounds (I), (II), (III) and (I) of the component (B) * 1 used in the preparation of the above compound were used.
V) are the following oily organopolysiloxanes, respectively.

(I) 10 mol% of methyl (3,3,3-trifluoropropyl) siloxy unit, 5 mol% of diphenylsiloxy unit, 85 mol% of dimethylsiloxy unit, the terminal is blocked by a trimethylsilyl group, and 25 ° C. The viscosity at
Oily organopolysiloxane with 85 sensor poise.

(II) It contains 25 mol% of methyl (3,3,3-trifluoropropyl) siloxy units and 75 mol% of dimethylsiloxy units, and is capped at its end with a trimethylsilyl group,
An oily organopolysiloxane having a viscosity of 50 centipoise.

(III) An oily organopolysiloxane containing 100 mol% of dimethylsiloxy units, having a terminal capped by a trimethylsilyl group, and having a viscosity of 30 centipoise at 25 ° C.

(IV) An oily organopolysiloxysan containing 70 mol% of dimethylsiloxy units and 30 mol% of diphenylsiloxy units, the terminal of which is blocked by a trimethylsilyl group, and having a viscosity of 70 sensor poise at 25 ° C.

* 2 Conditions: 25% compression, 150 ° C x 70 hours * 3 Test oil Light oil, conditions 25 ° C x 10 hours Example 2. Methyl (3,3,3-trifluoropropyl) siloxy unit 99.5 mol%, methyl vinyl 100 parts of organopolysiloxane (viscosity at 25 ° C. is 6 million centipoise) containing 0.5 mol% of siloxy units and capped with trimethylsilyl groups, and fumed silica having a specific surface area of 200 m ² / g (AEROSIL manufactured by Nippon Aerosil Co., Ltd.) 200) was uniformly mixed and kneaded using a kneader with 25 parts of surface-treated silica, which had been surface-treated with tri (3,3,3-trifluoropropyl) trimethyltricyclosiloxane, and then heated and mixed in a kneader at 150 ° C. for 2 hours. The mixture was kneaded to prepare a base compound B.

To the prepared base compound B, the components (B) and (D) were added at the ratios shown in Table 2 and kneaded evenly with two rolls to obtain five types of compounds (compositions) including Comparative Examples. Prepared.

Each of the prepared compounds (compositions) was evaluated for roll workability under the same conditions as in Example 1, and the results are shown in Table 2.

Next, these compounds (compositions) were press-vulcanized under the same conditions as in Example 1, and then stained on the mold under the same conditions as in Example 1, and the results are shown in Table 2. Was.

Further, the vulcanized rubber pieces were subjected to secondary vulcanization in an oven at 200 ° C. for 2 hours to obtain test pieces having the same shape as in Example 1. After the secondary vulcanization, the oil bleeding property and the rubber properties were evaluated and measured under the same conditions as in Example 1, and the results are shown in Table 2.

The (B) component compounds (I) and (II) of * 4 used in the preparation of the compound were the same as those in Example 1, and (V), (VI) and (VII) were respectively The following is an oily organopolysiloxane.

(V) Methyl (3,3,3-trifluoropropyl) siloxy unit contains 30 mol% and dimethylsiloxy unit 70 mol%, the terminal is blocked by a trimethylsilyl group, and 25 ° C.
An oily organopolysiloxane having a viscosity of 65 centipoise in the above.

(VI) 70 mol% of methyl (3,3,3-trifluoropropyl) siloxy unit and 30 mol% of dimethylsiloxy unit, the terminal is blocked by a trimethylsilyl group, and 25 ° C.
An oily organopolysiloxane having a viscosity of 2,300 centipoise in the above.

(VII) An oily organopolysiloxane containing 40 mol% of diphenylsiloxy units and 60 mol% of dimethylsiloxy units, having a terminal capped with a trimethylsilyl group and having a viscosity at 25 ° C of 10 centipoise.

* 5 Conditions: 25% compression, 150 ° C. × 70 hours * 6 Test oil Light oil, conditions 25 ° C. × 10 hours [Effect of the Invention] The silicone rubber elastic body obtained by heat-curing the composition of the present invention is fluoropolymer In addition to exhibiting excellent oil resistance, solvent resistance, heat resistance, cold resistance, etc. inherent in silicone rubber, the use of a polydiorganosiloxane having a perfluoroalkyl group (R _f ) as a bleed component makes it excellent in mechanical strength. In addition to the above, there are many advantages in the molding process such as good workability, non-contamination of the mold and mold releasability. Moreover, the silicone rubber elastic body obtained by heat curing shows stable and good oil bleeding properties. In other words, both the good mold non-staining property and the like and the oil bleed property are sufficiently satisfied by a proper compatibility or incompatibility between the base component and the bleed component. Thus, the fluorosilicone rubber composition according to the present invention comprises a roll, a connector seal material, a dynamic oil seal material, a packing material,
It is extremely useful for various applications such as diaphragm materials that require release properties, oil resistance, water and foreign matter sealing properties, and electrical insulation properties.

Claims (1)

(57) [Claims] (A) Average composition formula [Wherein, R is a group that 25 to 50 mol%, wherein (here R _f shows a perfluoroalkyl group having 1 to 3 carbon atoms) -CH ₂ CH ₂ R _f is represented by the remainder Represents a saturated or unsaturated monovalent hydrocarbon group, a is a number of 1.98 to 2.02], and 100% by weight of an organopolysiloxane having a viscosity at 25 ° C. of 1,000 centipoise or more. Part, (B) average composition formula [Wherein R 'is less than 5 to 30 mol% of the formula, -CH ₂ CH ₂ R _f
(Where R _f represents a perfluoroalkyl group having 1 to 3 carbon atoms), and the difference from —CH ₂ CH ₂ R _{f in the} above average composition formula (A) is 20 to 45. Mol% and the remaining 95 ~
70 mol% is selected from methyl groups and phenyl groups, and b is
1.98 to 2.02], 3 to 15 parts by weight of an oily organopolysiloxane having a viscosity at 25 ° C. of 20 to 10,000 centipoise, and (C) a reinforcing silica having a specific surface area of 50 m ² / g or more. Powder 10 ~
A fluorosilicone rubber composition comprising 100 parts by weight and (D) a vulcanizing agent.