JPH04224866A - Silicone rubber composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. giving a cured article resistant to repeated deformation such as repeated flexing or repeated elongation. CONSTITUTION:The title compsn. comprises an organopolysiloxane shown by general formula 1 (wherein R<1> is a monovalent hydrocarbon group; and a is 1.90-2.05), a reinforcing filler, a silanolated organosilicon compd. shown by general formula II (wherein R<2> and R<3> are each a monovalent hydrocarbon group contg. no alkenyl group; R<4> is a monovalent hydrocarbon group; A is a divalent hydrocarbon group; b is 0 or 1; and n is 1-30), and a curing catalyst.

Description

Description: [0001] The present invention relates to a silicone rubber composition, and more specifically, a silicone rubber that exhibits excellent durability against repeated deformation such as bending and elongation after curing. Regarding the composition. [0002] Silicone rubber is used for various purposes because it has excellent heat resistance and cold resistance. However, silicone rubber has poor durability against repeated deformation such as bending and stretching, and has not been a material that is fully satisfactory in applications that require durability against repeated deformation, such as keyboards and constant velocity joint boots for automobiles. Conventionally, in order to improve such durability, it was recommended to reduce the amount of filler added to the silicone rubber composition, improve the dispersion of the filler, and strengthen filtration to remove as much foreign matter as possible. However, even by these methods, a silicone rubber composition having sufficiently satisfactory durability has not been obtained. [0003] The present inventors have conducted extensive research to solve the above problems, and have found that if a small amount of a special silicone compound is added to a silicone rubber composition, the resistance to repeated deformation can be improved. The present invention was achieved by discovering that durability can be dramatically improved. That is, an object of the present invention is to provide a silicone rubber composition that can be made into a silicone rubber molded article having excellent durability against repeated deformation such as bending and elongation after curing. [Means for Solving the Problems and Their Effects] The present invention provides (
A) General formula: R1aSiO(4-a)/2 (wherein R1
is a monovalent hydrocarbon group, and a is a number from 1.90 to 2.05. ) Organopolysiloxane 100 represented by
Parts by weight, (B) 5 to 100 parts by weight of reinforcing filler, (C)
General formula: [Chemical formula 1] (wherein, R2 and R3 are monovalent hydrocarbon groups containing no alkenyl group, R4 is a monovalent hydrocarbon group, A is a divalent hydrocarbon group, and b is a divalent hydrocarbon group. 0 or 1, and n is an integer of 1 to 30.) Silanol group-containing organosilicone compound 0.05 to 20
and (D) a curing agent (in an amount sufficient to cure the composition of the present invention). These will be explained in detail below. The organopolysiloxane (A) component is the main component of the composition of the present invention, in the above formula, R1 is a methyl group,
Alkyl groups such as ethyl, propyl and butyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; cycloalkyl groups such as cyclohexyl groups, or hydrogen bonded to the carbon atom of these groups It is an unsubstituted or substituted monovalent hydrocarbon group exemplified by a chloromethyl group, a trifluoropropyl group, a cyanomethyl group, etc. in which some or all of the atoms are substituted with a halogen atom, a cyano group, etc. Further, a is a number from 1.90 to 2.05. Such organopolysiloxanes include methylvinylpolysiloxane with trimethylsiloxy groups blocked at both ends, methylvinylsiloxane/dimethylsiloxane copolymer with both ends blocked with trimethylsiloxy groups, and dimethylsiloxane/methyl with both ends blocked with dimethylvinylsiloxy groups. Phenylsiloxane copolymer, dimethylsiloxane/diphenylsiloxane copolymer with both ends blocked with dimethylvinylsiloxy groups, dimethylsiloxane/methylphenylsiloxane/methylvinylsiloxane copolymer with both ends blocked with trimethylsiloxy groups, both ends with dimethylvinylsiloxy groups Blocked methyl(3,3,3-trifluoropropyl)polysiloxane, dimethylsiloxane/methyl(3,3,3-trifluoropropyl)siloxane copolymer with both terminals blocked by dimethylvinylsiloxy groups, CH2=CH(CH3 )2S
Examples include organopolysiloxanes consisting of iO1/2 units, (CH3)3SiO1/2 units, and SiO4/2 units. The degree of polymerization of component (A) is 100 to 30,000
The range is preferably 1000, more preferably 1000
It is in the range of ~20,000. In the present invention, the various organopolysiloxanes mentioned above may be used in combination. [0007] Component (B), a reinforcing filler, is a component for improving the mechanical strength of a silicone rubber molded product obtained by curing the composition of the present invention. Such reinforcing fillers include precipitated silica, fumed silica, pyrogenic silica, fumed titanium oxide, and surfaces of these fillers with organosilicon compounds such as hexamethyldisilazane, trimethylchlorosilane, and polymethylsiloxane. The processed ones are exemplified. The blending amount of this component is in the range of 5 to 100 parts by weight per 100 parts by weight of component (A). The silanol group-containing organosilicone compound (C) is essential for imparting durability against repeated deformation such as bending and elongation to the silicone rubber molded product obtained by curing the composition of the present invention. It is an ingredient. In the above formula, R2 and R3 are monovalent hydrocarbon groups excluding alkenyl groups from the same monovalent hydrocarbon groups as R1 described in the explanation of component (A) above, and R4 is It is a monovalent hydrocarbon group similar to R1 described in the component explanation,
A is a divalent hydrocarbon group exemplified by alkylene groups such as ethylene group, propylene group, butylene group, and pentylene group. Further, b is 0 or 1, and n is an integer of 1 to 30. Such a silanol group-containing organosilicone compound also acts as a plasticizer to reduce the interaction between the polymer component of the silicone rubber composition and the reinforcing filler before curing, and for this purpose, the higher the silanol group content, the higher the silanol group content. good. In addition, the amount of component (C) added is as follows: (A) component 1
The amount ranges from 0.05 to 20 parts by weight per 00 parts by weight. Such a compound can be synthesized by the following method. i.e., tetrakis(dimethylsiloxy)
By carrying out an addition reaction between silane and dimethylvinylchlorosilane or an organosilicone compound in which one end of the molecular chain is capped with a silicon-bonded vinyl group and the other end is capped with a silicon-bonded chlorine atom in the presence of a platinum-based catalyst.
An adduct having (4-b) silicon-bonded chlorine atoms at the end of the molecular chain is obtained. The silicon-bonded chlorine atoms of this adduct are then carefully hydrolyzed with a dilute basic aqueous solution. Their reaction formulas are shown below. [Formula 1] Component (D) is a curing agent for curing the composition of the present invention. Typical examples of component (D) include organic peroxides, specifically dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2 ,5-di(
t-butylperoxy)hexane, 2,5-dimethyl-
2,5-di(benzoylperoxy)hexane, 2,5
-dimethyl-2,5-di(t-butylperoxy)-3
, 3,5-trimethylcyclohexane, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, parachlorobenzoyl peroxide and the like. The amount of component (D) added is sufficient to cure the composition of the present invention, and is usually preferably in the range of 0.1 to 15 parts by weight per 100 parts by weight of component (A). [0010] Component (D) is a curing agent that uses a combination of an organohydrogenpolysiloxane containing three or more silicon-bonded hydrogen atoms per molecule and a platinum catalyst. Here, an example of the organohydrogenpolysiloxane containing three or more silicon-bonded hydrogen atoms is a dimethylsiloxane/methylhydrogensiloxane copolymer blocked with trimethylsiloxy groups at both ends, and its degree of polymerization is 3 to 700. Preferably within the range. The amount added is such that the ratio of the total number of moles of silicon-bonded hydrogen atoms in component (D) to the total number of moles of alkenyl groups in component (A) is between (0.5:1) and (20:1). 1)
The amount is such that In this case, a platinum-based catalyst is used in combination as an addition reaction promoting catalyst. Platinum-based catalysts include chloroplatinic acid and those dissolved in alcohols, ketones, ethers, etc., complex compounds of chloroplatinic acid and olefins, complex compounds of chloroplatinic acid and alkenylsiloxanes, platinum black, and platinum. Examples include those held on a carrier. The amount of the platinum-based catalyst added is preferably 0.1 to 500 parts by weight based on 1 million parts by weight of the total weight of components (A) and (D). In order to secure working time with such hardening agents, acetylene compounds, hydrazine compounds, triazole compounds, phosphine compounds,
Known curing retarders such as mercaptan compounds may also be used. The composition of the present invention can be easily obtained by uniformly mixing the above components (A) to (D), but if necessary, crushed quartz, diatom, etc., which are known additives for silicone rubber, may be added. Expanding fillers such as earth, asbestos, calcium carbonate, aluminosilicate; iron oxide, cerium oxide,
Heat resistant agents or flame retardants such as aluminum oxide, zinc oxide, manganese carbonate, etc. may be added. [Examples] The present invention will be explained in more detail with reference to Examples below. In the examples, parts refer to parts by weight. Further, in the examples, constant elongation fatigue durability was measured according to the following method. ○Constant Elongation Fatigue Durability Test A 2 mm thick sheet was punched out as a test piece from a silicone rubber sheet as a dumbbell size 3 according to JIS K 6301. This test piece was tested according to JIS K 6301.
, set it in the desmatcher type testing machine shown in Section 15, and make it reciprocate at a speed of 300 ± 10 times/min so that the gauge distance is 40 mm at the maximum and 20 mm at the minimum, until the test piece breaks. The number of reciprocations was quantified as constant elongation fatigue durability. In addition, in this test method, the test piece held between the gripping jigs is repeatedly stretched at an elongation between 0 and 100%. [Reference Example 1] In a four-neck flask equipped with a stirring device, 10.89 parts of tetrakis(dimethylsiloxy)silane, 50 parts of an organosilicone compound represented by the formula: [Chemical formula 2], 100 parts of toluene, and platinum chloride were placed. A complex of acid and tetramethyldivinyldisiloxane was added so that the platinum concentration was 40 ppm based on the total amount of the two types of organosilicone compounds, and the mixture was reacted under heating under reflux for 2 hours. Infrared spectroscopic analysis of the sampled reaction mixture confirmed that the characteristic absorption of silicon-bonded hydrogen atoms had disappeared. Then, excess formula: [Formula 2] and low boiling point substances were distilled off under reduced pressure to obtain an organosilicone compound represented by the formula: [Formula 3]. 250 parts of water, 250 parts of ice, 125 parts of diethyl ether, and 15 parts of sodium bicarbonate were placed in a four-necked flask equipped with a stirrer, and while cooling and stirring, 53.9 parts of the above adduct and 50 parts of diethyl ether were combined. The mixture was added dropwise. After hydrolysis, the ether layer was separated and dried by adding anhydrous sodium sulfate. After drying, the ether was distilled off at room temperature under reduced pressure to obtain a silanol group-containing organosilicone compound (Silicone A) represented by the formula: embedded image. It was confirmed by the following method that Silicone A had the above structure. That is, after silylating the silanol group of silicone A with tetramethyldisilazane, excess tetramethyldisilazane was distilled off under reduced pressure with heating. The silicon-bonded hydrogen atom content of the residue was determined to be 0.214% by weight, with a calculated value of 0.21.
It was in good agreement with 5% by weight. The reaction formula is as follows. [Formula 2] [Reference Example 2] 50.0 parts of tetrakis(dimethylsiloxy)silane, formula: [Chemical 5
] 81 parts of chlorosilane, 100 parts of toluene,
A complex of chloroplatinic acid and tetramethyldivinyldisiloxane was added so that the platinum concentration was 20 ppm based on the total amount of the two types of organosilicone compounds, and the mixture was reacted under heating under reflux for 2 hours. Infrared spectroscopic analysis of the sampled reaction mixture confirmed that the characteristic absorption of silicon-bonded hydrogen atoms had disappeared, and excess dimethylvinylchlorosilane and low-boiling substances were distilled off under reduced pressure.
An organosilicone compound represented by the formula: [Image Omitted] was obtained. 300 parts of water, 300 parts of ice, 300 parts of diethyl ether, and 35 parts of sodium hydrogen carbonate were placed in a four-neck flask equipped with a stirrer, and the mixture of 65 parts of the adduct and 50 parts of diethyl ether was added while cooling and stirring. dripped. After hydrolysis, the layers were separated and anhydrous sodium sulfate was added to the ether layer to dry it. After drying, ether was distilled off at room temperature under reduced pressure,
Organosilicone compound (Silicone B) represented by the formula:
) 55 copies were obtained. It was confirmed in the same manner as in Reference Example 1 that Silicone B had the above structure. That is, after the silanol group of silicone B was silylated with tetramethyldisilazane, excess tetramethyldisilazane was distilled off under reduced pressure with heating. The silicon-bonded hydrogen content of the residue was determined to be 0.40 weight percent, in good agreement with the calculated value of 0.41 weight percent. The reaction formula is as follows. [Formula 3] [Example 1] 100 parts of an organopolysiloxane with an average degree of polymerization of 7000, consisting of 99.92 mol percent of dimethylsiloxy units and 0.18 mol percent of methylvinylsiloxy units, and a specific surface area of 300 square meters/g. 25 parts of dry process silica, silicone A obtained in Reference Example 1
were added as shown in Table 1, kneaded with a kneader mixer, and then heat treated at 170° C. for 1 hour to obtain a silicone rubber base. Add 2.5 parts to 100 parts of this silicone rubber base.
-Dimethyl-2,5-di(t-butylperoxy)hexane (0.7 part) was added and mixed uniformly to obtain a silicone rubber composition. Next, this composition was press-molded under conditions of a temperature of 170° C., a pressure of 20 kg/cm 2 and a heating time of 10 minutes to obtain a silicone rubber molded sheet with a thickness of 2 mm. This sheet was placed in a heat circulation oven set at 200°C and left for 4 hours. Dumbbells for evaluation tests were made from the sheet thus obtained, and 100% constant elongation fatigue properties were measured using a desmatcher fatigue tester, and the results shown in Table 1 were obtained. For comparison, a silicone rubber composition (comparative The composition of Example 1) was obtained. This composition was tested for physical properties and constant elongation fatigue durability of a silicone rubber sheet using the same method as above. These measurement results are also listed in Table 1 as Comparative Example 1. From these results, the composition of the present invention has the following properties:
The cured silicone rubber sheet withstood elongation more than 2 million times and exhibited constant elongation fatigue durability superior to that of the silicone rubber composition of Comparative Example 1. [Table 1] 1) Organopolysiloxane 10 with an average degree of polymerization of 7000
[Example 2] 100 parts of an organopolysiloxane with an average degree of polymerization of 7000, consisting of 99.92 mol% dimethylsiloxy units and 0.18 mol% methylvinylsiloxy units, specific surface area 200 square meters/ 40 parts of wet process silica, silicone B obtained in Reference Example 2
were blended as shown in Table 2, kneaded in a kneader mixer, and heat treated at 170°C for 1.5 hours to obtain a silicone rubber base. To 100 parts of this silicone rubber base, 2
,5-dimethyl-2,5-di(t-butylperoxy)
0.6 part of hexane was added and mixed uniformly to obtain a silicone rubber composition. Next, this composition was heated to a temperature of 170°C.
A silicone rubber molded sheet having a thickness of 2 mm was obtained by press molding under conditions of a pressure of 20 kg/cm 2 and a heating time of 10 minutes. This sheet was placed in a heat circulation oven set at 200°C and left for 4 hours. Dumbbells for evaluation tests were prepared from the silicone rubber sheets thus obtained, and their constant elongation fatigue durability was examined in the same manner as in Example 1, and the results shown in Table 2 were obtained. For comparison, a silicone rubber composition was produced in the same manner as above except that silicone C, which was used in the composition of Comparative Example 1 in Example 1, was added instead of silicone B. A silicone rubber composition was also produced in the same manner as above except that neither silicone B nor silicone C was added. These silicone rubber compositions were evaluated in the same manner as above. These results are also listed in Table 2. From these results, it was found that the cured silicone rubber of the composition of the present invention was 150%
It withstood elongation more than 10,000 times and showed superior constant elongation fatigue durability than the composition of Comparative Example 2. [Table 2] 1) Organopolysiloxane 10 with an average degree of polymerization of 7000
[Example 3] 100 parts of an organopolysiloxane with an average degree of polymerization of 7000, consisting of 99.92 mol% dimethylsiloxy units and 0.18 mol% methylvinylsiloxy units, specific surface area 300 square meters/ 25 parts of dry process silica, silicone A obtained in Reference Example 1
were blended as shown in Table 3, kneaded with a kneader mixer, and then heat treated at 170°C for 1 hour to obtain a silicone rubber base. Add 100 parts of this silicone rubber base at 25°C.
When the viscosity is 5 centistokes, the silicon-bonded hydrogen atom content is 0.8.
Weight percentage of dimethylsiloxane/methylhydrogensiloxane copolymer 0.5 part, monomethyltris(monomethylbutynoxy)silane 0.06 part, complex of chloroplatinic acid and tetramethylvinyldisiloxane as platinum to total weight A silicone rubber composition was obtained by adding an amount of 15 ppm to the mixture and uniformly mixing with two rolls. This composition was mixed at a temperature of 150°C and a pressure of 20k.
A silicone rubber molded sheet having a thickness of 2 mm was obtained by press molding under conditions of g/cm2 and heating time of 5 minutes. Dumbbells for evaluation tests were prepared from the silicone rubber sheet thus obtained, and the physical properties and constant elongation fatigue durability were measured in the same manner as in Example 1. The results of these measurements are shown in Table 3. For comparison, a silicone rubber composition was produced in the same manner as above except that silicone C, which was used in the composition of Comparative Example 1 in Example 1, was added instead of silicone A. Furthermore, a silicone rubber composition was produced in the same manner as above except that silicone A and silicone C were not added. The properties of these silicone rubber compositions were measured in the same manner as above. These results are also listed in Table 3. From these results,
The composition of the present invention has a cured silicone rubber of 2
It withstood elongation of 500,000 times or more and showed superior constant elongation fatigue durability than the silicone rubber composition of Comparative Example 3. [Table 3] 1) Organopolysiloxane 10 with an average degree of polymerization of 7000
[0018] Effects of the Invention The silicone rubber composition of the present invention has (A
) to (D), and especially contains component (C), a special silanol group-containing organosilicone compound, so it has excellent durability against repeated deformation such as bending and elongation after heat curing. It has the characteristic that it can be made into a silicone rubber molded product.

Claims (1)

[Claims] Claim 1 (A) General formula: R1aSiO(4-a
)/2 (wherein R1 is a monovalent hydrocarbon group, and a is 1.
The number is between 90 and 2.05. ) 100 parts by weight of organopolysiloxane represented by (B) reinforcing filler 5 to 1
00 parts by weight, (C) General formula: [Formula 1] (In the formula, R2 and R3 are monovalent hydrocarbon groups containing no alkenyl group, R4 is a monovalent hydrocarbon group, and A is a divalent hydrocarbon group. is a hydrogen group, b is 0 or 1, and n is 1 to 3
It is an integer of 0. ) and 0.05 to 20 parts by weight of a silanol group-containing organosilicone compound represented by (D
) A curing agent (in an amount sufficient to cure the composition of the present invention).