Fluororubber composition

Abstract

A fluororubber composition comprising 10 to 50 parts by weight of wollastonite and 0.5 to 10 parts by weight of organic peroxide based on 100 parts by weight of peroxide-crosslinkable fluororubber, the wollastonite being needle-like or fibrous wollastonite having an average fiber diameter of 5 m or less and an average fiber length of 40 to 80 m, and the wollastonite being surface-treated with an amino silane coupling agent or an epoxy silane coupling agent. The fluororubber composition that can be suitably used as, for example, a molding material for normal/reverse rotation oil seals that allow continuous excellent sealing of fluid in the operation of normal and reverse rotation.

Claims

1. A fluororubber composition comprising 10 to 50 parts by weight of wollastonite and 0.5 to 10 parts by weight of organic peroxide based on 100 parts by weight of peroxide-crosslinkable fluororubber, the wollastonite being needle-like or fibrous wollastonite having an average fiber diameter of 5 m or less and an average fiber length of 40 to 80 m, and the wollastonite being surface-treated with an amino silane coupling agent.

2. The fluororubber composition according to claim 1, wherein the wollastonite is used in an amount of 25 to 50 parts by weight based on 100 parts by weight of fluororubber.

3. A sealing material molded by vulcanizing of the fluororubber composition according to claim 2.

4. The sealing material according to claim 3, which is used as oil seal.

5. The sealing material according to claim 4, which is used as a normal/reverse rotation oil seal.

6. The sealing material according to claim 5, which is used as a normal/reverse rotation oil seal for railway vehicles.

7. A sealing material molded by vulcanizing of the fluororubber composition according to claim 1.

8. The sealing material according to claim 7, which is used as oil seal.

9. The sealing material according to claim 8, which is used as a normal/reverse rotation oil seal.

10. The sealing material according to claim 9, which is used as a normal/reverse rotation oil seal for railway vehicles.

Description

EXAMPLES

(1) The following describes the present invention with reference to Examples.

Example 1

(2) TABLE-US-00001 Fluororubber (Tecnoflon BR9171, produced by 100 parts by weight Solvey; a VdF-HFP-TFE-E-FMVE quinary copolymer) MT carbon black (THERMAX N-990LSR, 2 parts by weight produced by Cancarb Limited) Wollastonite surface-treated with amino silane 25 parts by weight coupling agent (NYGLOS 4W Wollastcoat 10012, produced by NYCO Minerals; average fiber diameter: 4.5 m, average fiber length: 50 m, aspect ratio: 11) Hydrotalcite (DHT-4A, produced by Kyowa 6 parts by weight Chemical Industry Co., Ltd.) Carnauba wax (VPA No. 2, produced by DuPont 2 parts by weight Dow Elastomers) Organic peroxide (Perhexa 25B-40, produced by 2 parts by weight NOF Corporation) Triallyl isocyanurate (TAIC WH-60, produced by 2 parts by weight Nippon Kasei Co., Ltd.)

(3) The above components were kneaded by a kneader and an open roll, and primary vulcanization at 180 C. for 4 minutes and secondary vulcanization at 200 C. for 15 hours were performed. Thus, a rubber sheet (test piece) having a thickness of 2 mm and an oil seal having an inner diameter of 80 mm, an outer diameter of 105 mm, and a width of 11.5 mm were vulcanization-molded.

Example 2

(4) In Example 1, the amount of wollastonite was changed to 35 parts by weight.

Example 3

(5) In Example 1, the amount of wollastonite was changed to 50 parts by weight.

Comparative Example 1

(6) In Example 1, the amount of wollastonite was changed to 60 parts by weight.

Example 4

(7) In Example 1, the amount of wollastonite was changed to 15 parts by weight.

Example 5

(8) In Example 1, the amount of wollastonite was changed to 10 parts by weight.

Comparative Example 2

(9) In Example 1, the amount of wollastonite was changed to 5 parts by weight.

Comparative Example 3

(10) In Example 1, the same amount of a NYGLOS 4W produced by NYCO Minerals that is not surface-treated with a silane coupling agent (average fiber diameter: 4.5 m, average fiber length: 50 m, aspect ratio: 11) was used as the wollastonite.

Comparative Example 4

(11) In Example 1, 35 parts by weight of a NYGLOS 4W produced by NYCO Minerals that is not surface-treated with a silane coupling agent (average fiber diameter: 4.5 m, average fiber length: 50 m, aspect ratio: 11) was used as the wollastonite.

Example 6

(12) In Example 1, the same amount of a NYGLOS 4W Wollastcoat 10222 produced by NYCO Minerals that is surface-treated with an epoxy silane coupling agent (average fiber diameter: 4.5 m, average fiber length: 50 m, aspect ratio: 11) was used as the wollastonite.

Comparative Example 5

(13) In Example 1, the same amount of a NYGLOS 4W Wollastcoat 10412 produced by NYCO Minerals that is surface-treated with a vinyl silane coupling agent (average fiber diameter: 4.5 m, average fiber length: 50 m, aspect ratio: 11) was used as the wollastonite.

Comparative Example 6

(14) In Example 1, the same amount of a NYAD 400 produced by NYCO Minerals that is not surface-treated with a silane coupling agent (average fiber diameter: 7 m, average fiber length: 35 m, aspect ratio: 5) was used as the wollastonite.

Comparative Example 7

(15) In Example 1, the same amount of a NYAD 400 Wollastcoat 10012 produced by NYCO Minerals that is surface-treated with a amino silane coupling agent (average fiber diameter: 7 m, average fiber length: 35 m, aspect ratio: 5) was used as the wollastonite.

Comparative Example 8

(16) In Example 1, the same amount of a NYAD 400 Wollastcoat 10222 produced by NYCO Minerals that is surface-treated with an epoxy silane coupling agent (average fiber diameter: 7 m, average fiber length: 35 m, aspect ratio: 5) was used as the wollastonite.

Example 7

(17) In Example 1, the same amount of a Tecnoflon P757 produced by Solvey (a VdF-HFP-TFE tenary copolymer) was used as the fluororubber.

(18) Using the rubber sheets and oil seals obtained in the above Examples and Comparative Examples, the normal state physical properties and durability were measured. Further, rotation tests of oil seal products were also performed for Examples 1, 4, and 5.

(19) Normal state physical properties (hardness): According to JIS K6253 (1997) corresponding to ISO 7619-1, hardness was measured using a type A durometer

(20) Normal state physical properties (tensile strength, elongation): According to JIS K6251 (2010) corresponding to ISO 37

(21) Moldability: The presence of fracture during molding was visually confirmed

(22) Durability: An oil seal was set in a rotation tester, gear oil (EP3080 alternative oil) was sealed in a state centering on the rotating shaft, and the oil temperature was naturally raised from room temperature. A cycle of normal rotation for 5 hours, pause for 2 minutes, reverse rotation for 5 hours, and pause for 2 minutes was performed for 1000 hours in total at a rotational frequency of 6500 rpm (peripheral speed: 27.2 m/sec). The presence of leakage was confirmed.

(23) Flon foaming test: A test piece having a width of 20 mm and a length of 25 mm was dipped in a refrigerant R134a at room temperature for 24 hours, and then heated at 50 C. or 60 C. for 1 hour. The presence of foaming after completion of heating was visually confirmed.

(24) The test results are shown in the following Tables 1 to 2.

(25) TABLE-US-00002 TABLE 1 Ex. Ex. Ex. Comp. Ex. Ex. Comp. Measurement item 1 2 3 Ex. 1 4 5 Ex. 2 [Normal-state physical properties] Hardness (durometer A) 75 79 83 86 72 68 65 Tensile strength (MPa) 13.9 16.0 16.6 18.6 16.4 12.7 13.2 Elongation at break (%) 380 310 270 190 450 440 480 [Moldability] Fracture none none none yes none none none [Durability] Leakage after a none none none rotation test [Flon foaming test] 50 C. none none none none none none yes 60 C. none none none non yes yes yes

(26) TABLE-US-00003 TABLE 2 Ex. Comp. Comp. Comp. Comp. Comp. Comp. Ex. Measurement item 6 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 7 [Normal-state physical properties] Hardness (durometer A) 76 76 79 76 70 71 72 74 Tensile strength (MPa) 12.0 20.1 15.5 11.8 14.5 11.9 12.4 14.3 Elongation at break (%) 440 520 470 460 540 480 500 400 [Moldability] Fracture none none none none none none none none [Flon foaming test] 50 C. none yes yes yes yes yes yes none 60 C. yes yes yes yes yes yes yes none

(27) The above results demonstrate the following:

(28) (1) In Examples 1 to 3, in which 25 to 50 parts by weight of wollastonite surface-treated with an amino silane coupling agent was used, foaming was not confirmed in the flon foaming test at a temperature of either 50 C. or 60 C.

(29) (2) In Examples 4 and 5, in which 10 to 15 parts by weight of wollastonite surface-treated with an amino silane coupling agent was used, and in Example 6, in which 25 parts by weight of wollastonite surface-treated with an epoxy silane coupling agent was used, foaming was not confirmed in the flon foaming test at a temperature of 50 C.

(30) Foaming was confirmed at 60 C.; thus, when 10 to 15 parts by weight of wollastonite surface-treated with an amino silane coupling agent, or 25 parts by weight of wollastonite surface-treated with an epoxy silane coupling agent was used, a heat resistance-improving effect was recognized, compared with when wollastonite not surface-treated with a silane coupling agent was used. The effect, however, was smaller than that obtained when wollastonite surface-treated with 25 to 50 parts by weight of amino silane coupling agent was used.

(31) This indicates that the heat resistance-improving effect is low, when the compounding ratio of wollastonite surface-treated with an amino silane coupling agent is low (10 to 15 parts by weight), and when wollastonite surface-treated with an epoxy silane coupling agent is used, even though the wollastonite compounding ratio is 25 parts by weight.

(32) (3) In Comparative Example 1, in which 60 parts by weight (equal to or more than the predetermined amount) of wollastonite surface-treated with an amino silane coupling agent was used, foaming was not confirmed in the flon foaming test at a temperature of either 50 C. or 60 C.; however, the occurrence of fracture during molding was confirmed.

(33) (4) In Comparative Example 2, in which 5 parts by weight (equal to or less than the predetermined amount) of wollastonite surface-treated with an amino silane coupling agent was used, foaming was confirmed in the flon foaming test at both temperatures of 50 C. and 60 C. Even in the case where wollastonite surface-treated with an amino silane coupling agent, which has a high foaming-preventing effect, is used, the desired heat resistance-improving effect cannot be obtained when wollastonite is used in an amount equal to or less than the predetermined amount, and the polymer ratio is higher.

(34) (5) In Comparative Examples 3 and 4, in which wollastonite not surface-treated with a silane coupling agent was used, foaming was confirmed in the flon foaming test at both temperatures of 50 C. and 60 C.

(35) (6) In Comparative Example 5, in which wollastonite surface-treated with a vinyl silane coupling agent was used, foaming was confirmed in the flon foaming test at both temperatures of 50 C. and 60 C. Even in the case where wollastonite surface-treated with a silane coupling agent is used, it is difficult to obtain an effect of improving heat resistance when surface treatment is not preformed using an amino silane coupling agent or an epoxy silane coupling agent.

(36) (7) Even when wollastonite surface-treated with an amino silane coupling agent or an epoxy silane coupling agent was used, in Comparative Examples 7 and 8, in which wollastonite whose average fiber diameter and average fiber length were outside of the predetermined ranges was used, foaming was confirmed in the flon foaming test at both temperatures of 50 C. and 60 C. Thus, even in the case where wollastonite surface-treated with a specific silane coupling agent is used, the desired heat resistance-improving effect cannot be obtained when the wollastonite has a small aspect ratio.

INDUSTRIAL APPLICABILITY

(37) Crosslinked products (e.g., sealing materials) of the fluororubber compositions according to the present invention can be effectively used as sliding seals, such as oil seals for railways, automobiles, aircraft, or industrial machines, all of which require normal and reverse rotation.