Silicone composition, a cured silicone rubber product and a power cable

Abstract

The present invention provides a silicone composition comprising components (A) to (F); (A) 100 parts by mass of a raw rubber-like, at 25 degrees C., organopolysiloxane having at least two alkenyl groups each bonded to a silicon atom; (B) 5 to 100 parts by mass of silica powder having a specific surface area of 50 m.sup.2/g or more; (C) platinum or a platinum compound in an amount of 1 to 1,000 ppm by mass as a platinum atom, relative to the mass of component (A); (D) 0.01 to 5 parts by mass of a compound selected from an organic silicon compound having a nitrogen-containing organic group and an unsaturated hydrocarbon group, and benzotriazole and a derivative thereof; (E) an addition reaction curing agent other than said component (C), or an organic peroxide in an effective amount to cure the composition, and (F) 0.01 to 5 parts by mass of an aromatic hydrocarbon group-containing organopolysiloxane represented by the general formula (1) wherein a proportion of the number of the monovalent aromatic hydrocarbon group to the total number of the substituents R.sup.1, R.sup.2 and R.sup.3 is 41% or more and less than 46%.

Claims

1. A silicone composition comprising components (A) to (F), (A) 100 parts by mass of a raw rubber-like, at 25 degrees C., organopolysiloxane having at least two alkenyl groups each bonded to a silicon atom, (B) 5 to 100 parts by mass of silica powder having a specific surface area of 50 m.sup.2/g or more, (C) platinum or a platinum compound in an amount of 1 to 1,000 ppm by mass as a platinum atom, relative to the mass of component (A), (D) 0.01 to 5 parts by mass of a compound selected from an organic silicon compound having a nitrogen-containing organic group and an unsaturated hydrocarbon group, and benzotriazole and a derivative thereof, (E) an addition reaction curing agent other than said component (C), or an organic peroxide in an effective amount to cure the composition, and (F) 0.01 to 5 parts by mass of an aromatic hydrocarbon group-containing organopolysiloxane represented by the following general formula (1):
(R.sup.1.sub.3SiO.sub.1/2).sub.n1(R.sup.1R.sup.2SiO.sub.2/2).sub.n2(R.sup.3SiO.sub.3/2).sub.n3(SiO.sub.4/2).sub.n4(1) wherein R.sup.1 is, independently of each other, a monovalent saturated aliphatic hydrocarbon group having 1 to 10 carbon atoms, R.sup.2 is, independently of each other, a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, R.sup.3 is, independently of each other, a monovalent saturated aliphatic hydrocarbon group having 1 to 10 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 12 carbon atoms, wherein a proportion of the number of the monovalent aromatic hydrocarbon group to the total number of the substituents R.sup.1, R.sup.2 and R.sup.3 is 41% or more and less than 46%, n1 is an integer of from 2 to 5, n2 is an integer of from 15 to 25, a total of n3 and n4 is an integer of from 0 to 3, 0<={n4/(n3+n4)}100<=5, and a total of n1, n2, n3 and n4 is an integer of from 17 to 30.

2. The silicone composition according to claim 1, wherein component (A) comprises the following components (A-1) and (A-2); (A-1) a raw rubber-like, at 25 degrees C., organopolysiloxane having 0.001 to 2% of the alkenyl group, based on the total number of the substituents bonded to silicon atoms in an amount of 60 to 99 parts by mass, and (A-2) a raw rubber-like, at 25 degrees C., organopolysiloxane having more than 2% and 20% or less of the alkenyl group, based on the total number of substituents bonded to silicon atoms, in an amount such that a total amount of components (A-1) and (A-2) is 100 parts by mass.

3. The silicone composition according to claim 1 or 2, wherein component (F) is represented by the following formula (2), ##STR00020## wherein R.sup.1 and R.sup.2 are as defined above, m is an integer of from 0 to 3, m is an integer of from 0 to 3, n is an integer of from 0 to 3, n is an integer of from 10 to 20, and a total of m, m, n and n is an integer of from 14 to 27.

4. The silicone composition according to claim 1 for a power cable.

5. A cured silicone rubber product obtained by curing the silicone composition according to claim 1.

6. The cured silicone rubber product according to claim 5, having a tensile strength of 8 MPa or more, as determined according to the Japanese Industrial Standards (JIS) K 6249: 2003.

7. The cured silicone rubber product according to claim 5 or 6, having tear strength (crescent) of 25 N/mm or more, as determined according to the Japanese Industrial Standards (JIS) K 6249: 2003.

8. The cured silicone rubber product according to claim 5, having elongation at break of 600% or more, as determined according to the Japanese Industrial Standards (JIS) K 6249: 2003.

9. A power cable provided with the cured silicone rubber product according to claim 5.

Description

EXAMPLES

(1) The present invention will be explained below in further detail with reference to a series of the Examples and the Comparative Examples, though the present invention is in no way limited by these Examples.

(2) [Method for Determination of Properties of Cured Products]

(3) [Mechanical Properties: Hardness, Tensile Strength, Tear Strength (Crescent Shape), Elongation at Break, and Tensile Permanent Strain]

(4) Each silicone composition was compression-molded under heating conditions of 165 degrees C. for 10 minutes into a sheet shape having a thickness of 2 mm. Further, the sheet was subjected to secondary vulcanization at 200 degrees C. for 4 hours to obtain a silicone rubber sheet. Mechanical properties of the sheet were determined according to the Japanese Industrial Standards (JIS) K 6249:2003. The results are as shown in Table 1.

(5) [Tracking Test]

(6) A tracking test was carried out according to the IEC Publ.587 Standards, Method. 1 test, to thereby evaluate a silicone rubber sheet whether pass or fail.

(7) Thus, the silicone rubber sheet having a thickness of 6 mm was prepared similarly as in the preceding paragraph 0061. A contaminated liquid (aqueous solution of 0.1 mass % of NH.sub.4Cl and 0.02 mass % of a nonionic surfactant) was dropped from an upper electrode on the five test sheets at a rate of 0.6 ml/min for 6 hours, at an applied voltage of 3.5 kV or 4.5 kV, a frequency of 50 Hz and an inter-electrode distance of 50 mm. When a track occurred on the test sheet and the sheet was broken by the leakage current, the test sheet was evaluated as fail. When the sheet was not broken, the test sheet was evaluated as pass. The presence or absence of the through holes on the five test sheets was confirmed, and the number of the test sheets having the through hole is shown in Table 1. Further, the minimum destruction time in minute, the maximum erosion depth in mm, and the average weight loss in %, are as shown in Table 1.

Preparation Example 1

(8) 95 parts by mass of (A-1) a raw rubber-like organopolysiloxane comprising 99.975 mol % of dimethylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 5 parts by mass of (A-2) a raw rubber-like organopolysiloxane comprising 89.993 mol % of dimethylsiloxane units and 9.982 mol % of methylvinylsiloxane units and having an average polymerization degree of about 8,000, 35 parts by mass of (B) fumed silica hydrophobilized by dichlorodimethylsilane and having a specific surface area of 300 m.sup.2/g, and 3 parts by mass of dimethylpolysiloxane as a dispersant which had silanol groups at the both terminals, an average polymerization degree of 13, and a viscosity at 25 degrees C. of 15 mm.sup.2/s were kneaded with a kneader. Further, 1.0 part by mass of (D) polymer A represented by the following formula (3) was added to the mixture, kneaded, and heated at 180 degrees C. for 3 hours to obtain mixture A.

(9) ##STR00008##

Preparation Example 2

(10) 99 parts by mass of (A-1) a raw rubber-like organopolysiloxane comprising 99.975 mol % of dimethylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 1 part by mass of (A-2) a raw rubber-like organopolysiloxane comprising 97.000 mol % of dimethylsiloxane units, 2.975 mol % of methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 35 parts by mass of (B) fumed silica hydrophobilized by dichlorodimethylsilane and having a specific surface area of 300 m.sup.2/g, and 3 parts by mass of dimethylpolysiloxane as a dispersant which had silanol groups at the both terminals, an average polymerization degree of 13, and a viscosity at 25 degrees C. of 15 mm.sup.2/s were kneaded with a kneader. Further, 1.0 part by mass of (D) polymer A represented by the aforesaid formula (3) was added to the mixture, kneaded, and heated at 180 degrees C. for 3 hours to obtain mixture B.

Preparation Example 3

(11) 90 parts by mass of (A-1) a raw rubber-like organopolysiloxane comprising 98.500 mol % of dimethylsiloxane units, 1.475 mol % of methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 10 parts by mass of (A-2) a raw rubber-like organopolysiloxane comprising 90.000 mol % of dimethylsiloxane units, 9.975 mol % of methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 35 parts by mass of (B) fumed silica hydrophobilized by dichlorodimethylsilane and having a specific surface area of 300 m.sup.2/g, and 3 parts by mass of dimethylpolysiloxane as a dispersant which had silanol groups at the both terminals, an average polymerization degree of 13, and a viscosity at 25 degrees C. of 15 mm.sup.2/s were kneaded with a kneader. Further, 1.0 part by mass of (D) polymer A represented by the aforesaid formula (3) was added to the mixture, kneaded, and heated at 180 degrees C. for 3 hours to obtain mixture C.

Preparation Example 4

(12) 95 parts by mass of (A-1) a raw rubber-like organopolysiloxane comprising 99.975 mol % of dimethylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 5 parts by mass of (A-2) a raw rubber-like organopolysiloxane having 89.993 mol % of dimethylsiloxane units, 9.982 mol % of methylvinylsiloxane units and 0.025 mol % of dimethylvinylsiloxane units and having an average polymerization degree of about 8,000, 35 parts by mass of (B) fumed silica hydrophobilized by dichlorodimethylsilane and having a specific surface area of 300 m.sup.2/g, and 3 parts by mass of dimethylpolysiloxane as a dispersant which had silanol groups at the both terminals, an average polymerization degree of 13, and a viscosity at 25 degrees C. of 15 mm.sup.2/s were kneaded with a kneader, and heated at 180 degrees C. for 3 hours to obtain mixture D.

Example 1

(13) 100 parts by mass of mixture A obtained in Preparation Example 1, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 parts by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 42% of a phenyl group, based on the total number of the substituents were mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 1. Silicone composition 1 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the products were evaluated. The results are as shown in Table 1.

(14) ##STR00009##
wherein the amount of the phenyl group is 42 mole %.

Example 2

(15) 100 parts by mass of mixture A obtained in Preparation Example 1, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula, comprising T units, and had 41% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 2. Silicone composition 2 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the products were evaluated. The results are as shown in Table 1.

(16) ##STR00010##
wherein the amount of the phenyl group is 41 mole %.

Example 3

(17) 100 parts by mass of mixture A obtained in Preparation Example 1, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 45% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 3. Silicone composition 3 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the products were evaluated. The results are as shown in Table 1.

(18) ##STR00011##
wherein the amount of the phenyl group is 45 mole %.

Example 4

(19) 100 parts by mass of mixture A, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula, comprising T units, and had 41% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.91 part by mass of (E) methylhydrogenpolysiloxane having SiH group at a side chain (a dimethylsiloxane-methylhydrogensiloxane copolymer whose both terminals are capped with a trimethylsiloxy group, having a polymerization degree of 40 and a SiH group of 0.074 mol/g) was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 4. Silicone composition 4 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the products were evaluated. The results are as shown in Table 1.

(20) ##STR00012##
wherein the amount of the phenyl group is 41 mole %.

Example 5

(21) 100 parts by mass of mixture B obtained in Preparation Example 2, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 42% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 5. Silicone composition 5 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

(22) ##STR00013##
wherein the amount of the phenyl group is 42 mole %.

Example 6

(23) 100 parts by mass of mixture C obtained in Preparation Example 3, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 42% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 6. Silicone composition 6 was molded and cured according to the aforesaid method so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

(24) ##STR00014##
wherein the amount of the phenyl group is 42 mole %.

Comparative Example 1

(25) 100 parts by mass of mixture A obtained in Preparation Example 1, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, and 0.15 part by mass of (D) benzotriazole were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 7. Silicone composition 7 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

Comparative Example 2

(26) 100 parts by mass of mixture A obtained in Preparation Example 1, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 27% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 8. Silicone composition 8 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

(27) ##STR00015##
wherein the amount of the phenyl group is 27 mole %.

Comparative Example 3

(28) 100 parts by mass of mixture A, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 39% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 9. Silicone composition 9 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

(29) ##STR00016##
wherein the amount of the phenyl group is 39 mole %.

Comparative Example 4

(30) 100 parts by mass of mixture A, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 47% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 10. The silicone composition was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

(31) ##STR00017##

Comparative Example 5

(32) 100 parts by mass of mixture A, 0.1 parts by mass of carbon black, 5.0 parts by mass of titanium oxide, 0.5 part by mass of cerium oxide, 0.15 part by mass of (D) benzotriazole and 1 part by mass of (F) silicone oil which is represented by the following formula and had 44% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 11. Silicone composition 11 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured products were evaluated. The results are as shown in Table 1.

(33) ##STR00018##
wherein the amount of the phenyl group is 44 mole %.

Comparative Example 6

(34) 100 parts by mass of mixture D obtained in preparation 4, 0.1 part by mass of a solution of chloroplatinic acid hexahydrate in 2-ethylhexanol, containing 2 mass % of platinum, 0.1 part by mass of carbon black, 5.0 parts by mass of titanium oxide, and 0.5 part by mass of cerium oxide, and 1 part by mass of (F) silicone oil which is represented by the following formula and had 44% of a phenyl group, based on the total number of the substituents were added and mixed by a two-roll mill. Further, 0.6 part by mass of (E) dicumyl peroxide was added as a curing agent and mixed by the two-roll mill to prepare silicone composition 12. Silicone composition 12 was molded and cured according to the aforesaid methods so as to prepare cured rubber products. The properties of the cured product were evaluated. The results are as shown in Table 1.

(35) ##STR00019##
wherein the amount of the phenyl group is 44 mole %.

(36) TABLE-US-00001 TABLE 1 Ex. Ex. Ex. Ex. Ex. Ex. Com. Com. Com. Com. Com. Com. 1 2 3 4 5 6 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Composition No. 1 2 3 4 5 6 7 8 9 10 11 12 Hardness 60 59 59 58 56 64 61 60 58 59 60 60 Tensile strength, MPa 9.2 9.1 9.2 9.1 8.1 8.2 9.1 8.9 8.9 8.7 8.9 9.1 Elongation at break, % 700 690 700 650 850 600 680 690 710 720 690 690 Tear strength, kN/m 39 39 38 41 31 30 35 38 34 35 35 36 Tensile permanent strain, % 8.2 7.8 7.9 3.2 10.2 10.5 8.1 7.8 8.3 8.5 8.3 7.9 The minimum destruction time, 360< 360< 360< 360< 360< 360< 48 360< 360< 360< 25 220 min The number of the test sheet 0/5 0/5 0/5 0/5 0/5 0/5 5/5 2/5 4/5 4/5 5/5 5/5 having the through hole/ Total number of the sheets The maximum erosion depth, mm, 4.0 3.9 4.2 4.0 4.6 4.0 5.8 5.8 5.8 5.8 5.8 5.8 Evaluation Good Good Good Good Good Good Bad Bad Bad Bad Bad Bad The average weight loss, % 0.94 0.67 0.99 0.79 1.04 0.80 9.41 1.33 7.20 6.71 15.00 9.20 Evaluation Good Good Good Good Good Good Bad Poor Bad Bad Bad Bad Tracking test Pass Pass Pass Pass Pass Pass Fail Pass Pass Pass Fail Fail

(37) As shown in Table 1 above, the cured products obtained from the compositions which do not contain component (C), (D) or (F) had poor tracking resistance (Comparative Examples 1, 5 and 6).

(38) Further, the compositions of Comparative Examples 2 and 3 which comprised the organopolysiloxane having the smaller amount of the aromatic hydrocarbon groups in place of the present component (F) and the composition of Comparative Example 4 which comprised the organopolysiloxane having the excessive amount of the aromatic hydrocarbon groups in place of the present component (F) provided the cured products having good tracking resistance, but the erosion depth was somewhat large and the progress of the breakdown of the sheet was not prevented.

(39) In contrast, the cured products obtained by curing the present silicone compositions had the small tensile permanent strains and were excellent in the mechanical strength such as tensile strength and tear strength. Furthermore, they were superior in tracking resistance and the progress of erosion was prevented. These results show that the present silicone composition has excellent high-voltage electrical insulation properties.

(40) The cured product obtained by curing the present silicone composition is suitable for use in power cable connection and is useful as a material for connecting a power cable.