JPH02222453A - Fluorosilicone rubber composition - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in processability. oil resistance, mold nonstainability, etc., thus suitable as a sealing material for rolls, connectors, etc., by incorporating a specific organopolysiloxane with each specified amount of a specific oily organopolysiloxane, reinforcing silica powder, etc. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100 pts.wt. of an organopolysiloxane >=1000cps in viscosity of formula I [R is made up of 25-50mol% of group of formula II (Rf is 1-3C perfluoroalkyl) and 75-50mol% of (saturated)monovalent hydrocarbon; a is 1.98-2.02] with (B) 3-15 pts.wt. of an oily organopolysiloxane 20-10000cps in viscosity of formula III [R' is made up of 5-30mol% of the group of the formula II (the difference from that in the component A being 20-45 mol%) and 95-70mol% of methyl, etc.; b is 1.98-2.02]. (C) 10-100 pts.wt. of reinforcing silica powder >=50m<2>/g in specific surface area, and (D) a curing agent.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Field of Application) The present invention relates to a fluorosilicone rubber composition, and in particular to an oil having excellent processability, oil resistance, mold non-staining property, and mechanical strength. The present invention relates to a bleedable fluorosilicone rubber composition.

(Prior art) Fluorosilicone rubber has excellent oil and solvent resistance as well as heat and cold resistance, so it is suitable for use in harsh conditions where these properties are required, such as in the automobile industry. It is put to practical use as a component material in the aviation industry and the aircraft industry, taking advantage of its gasoline resistance and cold resistance. In addition, when assembling silicone rubber molded products, the silicone rubber composition (Funbound) whose main component is dimethylpolysiloxane is incompatible so that parts can be easily assembled due to the lubrication effect on the surface. oily silicone compound, i.e., containing 5 to 5 phenylsiloxy units.
A technique has already been put into practical use in which a cured product exhibiting oil-bleeding properties on the surface is obtained by containing an appropriate amount of silicone oil containing 30 mol % as a bleed component.

(Problem to be Solved by the Invention) However, when a fluorosilicone rubber composition is prepared by the same method as in the case of a conventional oil-bleed silicone rubber composition containing dimethylpolysiloxane as a main component, the bleed component used is Regardless of whether the oil is dimethyl silicone oil or phenylmethyl silicone oil, if the content is less than 10% by weight, sufficient bleedability cannot be obtained, and if the content is 12 to 15% by weight, bleedability is exhibited, but this product has not yet been developed. Oil bleeds already in the vulcanized rubber compound state, which significantly impairs processability. In addition, oil resistance and solvent resistance are significantly reduced, and mechanical strength is also reduced, making it impractical.

As a means to solve the above problems, it has been proposed to blend phenylmethyl silicone oil with a small degree of polymerization (degree of polymerization 2 to 7) as a bleed component (JP-A-6
2-190254) is the vulcanization condition generally adopted when heating and curing silicone rubber because the degree of polymerization of the bleed component is small. There is a problem in that a part of the liquid evaporates, causing variations in bleedability.

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

Therefore, an object of the present invention is to provide a curable fluorosilicone rubber that maintains the excellent oil resistance and solvent resistance inherent to fluorosilicone rubber, and has even better processability, non-contaminating mold properties, and stable oil bleed properties. An object of the present invention is to provide a composition.

[Structure of the Invention] (Means for Solving the Problems) The fluorosilicone rubber composition of the present invention has (A) an average composition formula % formula % [wherein 25 to 50 mol% of R is of the formula -CH2CH2
A group represented by Rf (here, R represents a perfluoroalkyl group having 1 to 3 carbon atoms), and the remaining 75 to 5
0 mol% represents a saturated or unsaturated monovalent hydrocarbon group, a is a number from 1,98 to 2.02],
100 parts by weight of an organopolysiloxane having a viscosity of 1000 centipoise or more at 25°C, (B) average composition formula % formula % [wherein R/ is less than 5 to 30 mol% of the formula -CH2C
H2R, (here, Rf represents a perfluoroalkyl group having 1 to 3 carbon atoms), and the above (A
) The difference from the average compositional formula -CHCH2R is 20 to 45 mol%, the remaining 95 to 70 mol% is selected from methyl groups and phenyl groups, and b is a number of 1.98 to 2.02] The viscosity at 25°C is 20 to 10.00.
Oil bleed consisting of 3 to 15 parts by weight of an oily organopolysiloxane having a 0 centivoise, (C) 10 to 100 parts by weight of reinforcing silica powder having a specific surface area of 50rd/z or more, and (D) a vulcanizing agent as essential components. fluorosilicone rubber composition.

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

In the organopolysiloxane component (A), -CH
Examples include Rf of 2cH2Rf and Citeha, trifluoromethyl, pentafluoroethyl, and the like.

The proportion of 10H2CH2Rf group in R is 25 to 5
It is 0 mol%. If this proportion is less than 25 mol%,
The oil and solvent resistance of the cured product decreases, and the original characteristics of the fluorosilicone rubber are lost, and it is generally difficult to increase the amount by more than 50 mol% in terms of production.

The remaining 75 to 50 mol% of R is exemplified by a methyl group, an ethyl group, a phenyl group, a vinyl group, etc. The finally prepared silicone rubber composition is heated and cured with a vulcanizing agent to form a good rubber. In order to obtain a shaped elastic body, the vinyl group is added to 0.01
It is preferable to contain about 5 mol%. Furthermore, the viscosity of this component (A) at 25°C is 1000 centivoise or more, preferably 3000 to IO, ooO,
000 centiboise. If the viscosity is less than 0,000 centipoise, the mechanical strength of the resulting cured product will be low. The organopolysiloxane of component (A) can be obtained by adding a terminal capping agent to a cyclic siloxane mixture and carrying out ring-opening copolymerization using a well-known method so as to obtain the desired polymer represented by the above-mentioned average composition formula. It can be easily manufactured.

The oily organopolysiloxane (B) component is (A
) is a component that is moderately incompatible with the organopolysiloxane component and exhibits oil bleed properties after the prepared silicone rubber composition is cured. In this organopolysiloxane, examples of R in -CHCH2R include trifluoromethyl, pentafluoroethyl, etc. The proportion of -CHCH2Rf groups in R is 5 to less than 30 mol%. If this proportion is less than 5 mol%, the processability, oil/solvent resistance, and mechanical strength of the composition obtained by blending it will be poor, and if it exceeds 30 mol% (A
) component has improved compatibility with organopolysiloxane,
Good bleedability is no longer exhibited. But-CHCH
The proportion of 2Rf groups is 1CH2CH2 in component (A)
R.

The difference from the group is selected to be in the range of 20 to 45 mol%.

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, but from the viewpoint of synthesis, preferably the number of phenyl groups is 0 to 7.
It is 5 mol%. 25℃ of this organopolysiloxane
The viscosity is in the range of 20 to 10,000 centivoise; if it is less than 20 centivoise, stable bleed characteristics cannot be obtained, and if it exceeds 10,000 centivoise, the oily organoborisiloxane becomes difficult to bleed. Component (B) needs to be added in an amount of 3 parts by weight or more per 100 parts by weight of component (A) in order to impart good oil bleed properties to the cured product, but if it exceeds 15 parts by weight, the resulting mixture may impair the processability of the product and the mechanical strength and oil/solvent resistance of the cured product. Preferably it is 4 to 10 parts by weight.

The reinforcing silica powder of component (C) is fine powder silica with a specific surface area of 50 d1g or more, which is known as a filler for silicone rubber, and its type is not particularly limited, with examples including fumed silica, precipitated silica, and silica aerogel. . These may have their surfaces treated with various organosilanes, organosiloxanes, organosilazanes, and the like. The blending amount is 10 to 100 parts by weight per 100 parts by weight of component (A) in order to provide preferable mechanical properties to the cured product.
It is preferable to use parts by weight.

The vulcanizing agent (D) is necessary for heat-curing the composition of the present invention, and various known vulcanizing agents used in ordinary heat-curable silicone rubber compositions can be used. be able to. For example, ditert-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-
Examples include organic peroxides such as 2,5-di(tert-butyl)peroxyhexane and dibenzoyl peroxide, and platinum-based catalysts for addition reactions such as chloroplatinic acid, platinum vinyl siloxane, and platinum black. In addition, when using a platinum-based catalyst for addition reaction as a vulcanizing agent, the above (A
) to (D), it is necessary to use an appropriate amount of an organopolysiloxane containing 18i-H groups as a crosslinking agent.

In addition, the fluorosilicone rubber composition of the present invention includes:
If necessary, in addition to the above components (A) to (D), fillers commonly used in ordinary silicone rubber compositions, such as crushed quartz, clay, talc, calcium carbonate, diatomaceous earth, alumina, etc. It can also be blended with surface property modifiers such as tetrafluoroethylene powder, heat resistance improvers such as iron oxide, titanium oxide, cerium oxide, magnesium oxide,
Oil resistance improvers such as magnesium carbonate, processing aids such as metal soaps, and formulation aids such as silane and low molecular weight siloxane can be optionally added.

The fluorosilicone rubber composition of the present invention has the above-mentioned (A)
It is obtained by blending components (D) and various additives as necessary and kneading them uniformly, and becomes a rubber-like elastic body by heating.

(Function) As described above, according to the present invention, in the oil-bleeding silicone rubber composition which is based on an organopolysiloxane containing a predetermined amount of perfluoroalkyl groups, the organopolysiloxane as a bleed component is a perfluoroalkyl group. Organopolysiloxanes with different group contents are added and blended. Therefore, since both the base component and the bleed component have perfluoroalkyl groups, they are relatively easy to mix and prepare, and on the other hand, the bleed component sufficiently exhibits the required oil bleed property in the form of a molded product formed by vulcanization and hardening. In addition, there is no deterioration in processability, mechanical properties, etc.

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

Example 1 99.5 mol% of methyl(3,3,3-)lifluoropropyl)siloxy units, 0 methylvinylsiloxy units
．． 100 parts of organopolysiloxane containing 5 mol% and end-capped with hydroxyl groups (viscosity at 25°C: 8 million centiboise), fumed silica with a specific surface area of 130 rf/g (AERO3IL 130 manufactured by Nippon Aerosil ■)
Base compound A was prepared by uniformly mixing and kneading 25 parts using a Ni-Goo.

Components (B) and (D) were added to the base compound A prepared above in the proportions shown in Table 1 and kneaded uniformly using two rolls to prepare six types of compounds (compositions) including comparative examples. .

The roll processability of each compound (composition) obtained was evaluated using two 4-inch rolls, and those that rolled well were marked with ○, those that were difficult to roll were marked with Δ, and those that did not roll were marked with Δ. It is shown in Table 1 with an X mark.

Next, each of the above compounds (compositions) was vulcanized at 170°C for 10 minutes using a press molding machine, and after removing the vulcanized rubber piece from the mold, the mold was observed for dirt. O
In Table 1, those with slight stains are marked with Δ, and those with severe stains are marked with X. After that, the vulcanized rubber piece was subjected to secondary vulcanization in an oven at 200℃ for 2 hours to a thickness of 2m.
A cured sheet of m and a test piece for compression set test (right cylindrical shape with thickness 12.71111% diameter 29 m and 0 m+*) were obtained. After the secondary vulcanization, leave it at room temperature for 1 hour,
The bleedability of the rubber surface was observed by finger touch, and those with good bleedability were marked with a 0 mark, those with some bleeding were marked with a Δ, and those with no bleeding were marked with an X in Table 1. Further, the physical properties of the rubber were measured and determined in accordance with JIS K8301, and the results are shown in Table 1.

Table 1: *1 used in the preparation of the above compound (
B) Component compounds (I), (n), (III) and (■) are the following oily organopolysiloxanes, respectively.

(1) 10 mol% methyl(3,3,3-)lifluoropropyl)siloxy units, 5 diphenylsiloxy units
An oily organopolysiloxane containing 85 mol% of dimethylsiloxy units, terminally blocked by trimethylsilyl groups, and having a viscosity of 85 centiboise at 25°C.

(If) Methyl (3,3,3-trifluoropropyl)
25 mol% siloxy units, 7 dimethylsiloxy units
An oily organopolysiloxane containing 5 mol%, terminally blocked by trimethylsilyl groups, and having a viscosity of 50 centipoise at 25°C.

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

(IV) An oily organopolysiloxane containing 70 mol% of dimethylsiloxy units and 30 mol% of diphenylsiloxy units, whose terminals are blocked by trimethylsilyl groups, and whose viscosity at 25°C is 70 centiboise.

*2 Conditions: 25% compression, 150°C x 70 hours *3 Test oil Light oil, conditions 25°C 0 methylvinylsiloxy units
．． Organopolysiloxane containing 5 mol% and end-capped with trimethylsilyl groups (viscosity at 25°C is 60°C)
00,000 centiboise) 100 parts and specific surface area 200d7
g fumed silica (AERO8I manufactured by Nippon Aerosil)
25 parts of surface-treated silica obtained by surface-treating L 200) with tri(3,3,3-trifluoropropyl)trimethyltricyclosiloxane were uniformly mixed and kneaded using a kneader, and then kneaded at 150°C for 2 hours in the kneader. Base compound B was prepared by heating and kneading.

Components (B) and (D) were added to the base compound B prepared above in the proportions shown in Table 2 and kneaded uniformly with two rolls to form five types of compounds (including comparative examples).
composition) was prepared.

The roll processability of each compound (composition) prepared above was evaluated under the same conditions as in Example 1, and the results are shown in Table 2.

Next, these compounds (compositions) were press-cured under the same conditions as in Example 1, and then staining of the mold was further observed under the same conditions as in Example 1, and the results are shown in Table 2. Ta.

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

(Margins below) Table 2 Note that *4 (
B) Component compounds (I) and (■) are the same as those in Example 1, and (V), (V[) and (■) are the following oily organopolysiloxanes, respectively.

(V) 30 mol% of methyl(3,3,3-trifluoropropyl)siloxy units, 70 mol% of dimethylsiloxy units
An oily organopolysiloxane having a mol% content of 65 centivoids at 25° C. and whose ends are blocked by trimethylsilyl groups.

(VT) Methyl (3,3,3-trifluoropropyl)
70 mol% siloxy units, 3 dimethylsiloxy units
An oily organopolysiloxane containing 0 mol%, terminally blocked by trimethylsilyl groups, and having a viscosity of 2300 centipoise at 25°C.

(■) An oily organopolysiloxane containing 40 mol% of diphenylsiloxy units and 60 mol% of dimethylsiloxy units, terminally blocked by trimethylsilyl groups, and having a viscosity of 10 centivoices at 25°C.

*5 Conditions: 25% compression, 150°C x 70 hours *6 Test section: Light oil, conditions: 25°C Excellent oil resistance inherent to rubber
In addition to exhibiting solvent resistance, heat resistance, cold resistance, etc., by using a polydiorganosiloxane having a perfluoroalkyl group (Rf) as a bleed component, it has excellent mechanical strength, good processability, and gold resistance. It also brings many advantages in the molding process, such as non-contaminating molds and mold M-shape properties. Furthermore, the silicone rubber elastic body obtained by heat curing exhibits stable and good oil bleed properties.

In other words, by appropriately balancing the compatibility or incompatibility between the base component and the bleed component, both the above-mentioned good mold non-contamination property and oil bleed property are fully satisfied. Thus, the fluorosilicone rubber composition according to the present invention has
Release properties, oil resistance, water resistance, etc. of rolls, connector seal materials, dynamic oil seal materials, packing materials, diaphragm materials, etc.
It is extremely useful in various applications where foreign matter sealing properties and electrical insulation properties are required.

Applicant: Toshiba Silicone Corporation Agent Patent Attorney Su Yamasa - (1 idiot)

Claims (1)

[Scope of Claims] (A) Average compositional formula RaSiO_(_4_-_4_)_/_2 [wherein, 25 to 50 mol% of R is of the formula -CH_2CH_2R_f (here, R_f is a percentage of carbon atoms of 1 to 3 The remaining 75 to 50 mol% represents a saturated or unsaturated monovalent hydrocarbon group, and a is a number from 1.98 to 2.02. 100 parts by weight of an organopolysiloxane having a viscosity of 1000 centipoise or more at 25°C;
' is less than 5 to 30 mol% of the formula -CH_2CH_2R
A group represented by _f (here, R_f represents a perfluoroalkyl group having 1 to 3 carbon atoms), and the above (A)
The difference from the average compositional formula -CH_2CH_2R_f is 20 to 45 mol%, the remaining 95 to 70 mol% is selected from methyl groups and phenyl groups, and b is a number from 1.98 to 2.02]. Oily organopolysiloxanes having a viscosity of 20 to 10,000 centipoise at 25° C.
15 parts by weight, (C) 10 to 100 parts by weight of reinforcing silica powder having a specific surface area of 50 m^2/g or more, and (D) a vulcanizing agent.