RUBBER COMPOSITION AND A SEALING MATERIAL FOR FUEL CELL SEPARATORS

Abstract

A rubber composition comprising a nitroxide compound crosslinking agent containing 2.3 to 5.0 parts by weight of organic peroxide having a one-hour half-life temperature of 110 to 130 C., based on 100 parts by weight of an ethylene-butene-non-conjugated diene copolymer. Then, the ethylene-butene-non-conjugated diene copolymer can be used by being blended with EPDM in an amount of 50 wt % or less in the total amount of the ethylene-butene-non-conjugated diene copolymer and EPDM. A sealing material for fuel cell separators comprising a crosslinked molded article of the rubber composition, having functions required as a sealing material for separators, and having improved low temperature sealing properties and scorch resistance as well as excellent injection molding properties.

Claims

1: A rubber composition comprising a nitroxide compound crosslinking agent containing 2.3 to 5.0 parts by weight of organic peroxide having a one-hour half-life temperature of 110 to 130 C., based on 100 parts by weight of an ethylene-butene-non-conjugated diene copolymer.

2: The rubber composition according to claim 1, wherein the organic peroxide having a one-hour half-life temperature of 110 to 130 C. is a peroxyketal-based or peroxyester-based organic peroxide.

3: The rubber composition according to claim 1, wherein the nitroxide compound crosslinking agent is a nitroxide compound-crosslinking accelerator composition crosslinking agent.

4: The rubber composition according to claim 1, wherein the ethylene-butene-non-conjugated diene copolymer is blended with EPDM in an amount of 50 wt % or less in the total amount of the ethylene-butene-non-conjugated diene copolymer and EPDM.

5: The rubber composition according to claim 1, which does not contain the plasticizers.

6: The rubber composition according to claim 1, which does not contain a resorcinol-based compound-melamine-based compound, an aluminate-based coupling agent, or a silane coupling agent.

7: The rubber composition according to claim 1, which is used for crosslinking molding of a sealing material for fuel cell separators.

8: A sealing material for fuel cell separators comprising a crosslinked molded article of the rubber composition according to claim 7.

9: The rubber composition according to claim 4, which is used for crosslinking molding of a sealing material for fuel cell separators.

10: A sealing material for fuel cell separators comprising a crosslinked molded article of the rubber composition according to claim 9.

Description

EXAMPLES

[0052] The following describes the present invention with reference to Examples.

Comparative Example 1

[0053]

TABLE-US-00001 EBT copolymer (EBT K-9330, produced by 100 parts by weight Mitsui Chemicals, Inc.) Peroxyketal (Perhexa C, produced by 6 parts by weight NOF Corporation; purity: 70%, 1,1-di(tert-butylperoxy)cyclohexane, one-hour half-life temperature: 111 C.) MT carbon black (THERMAX N990, 60 parts by weight produced by Cancarb)
The above components were kneaded using an open roll, a Banbury mixer, a kneader, etc., and the kneaded product was vulcanized at 180 C. for 10 minutes, followed by oven vulcanization (secondary vulcanization) at 150 C. for 24 hours.

[0054] The obtained kneaded products and vulcanizates were evaluated or measured for characteristics described in the following items.

[0055] Vulcanization degree T90: The time (T90) until torque corresponding to 90% of the maximum torque was achieved was revealed from the vulcanization curve of each rubber kneaded product under 180 C. temperature conditions. When T90 was 150 seconds or less, this case was evaluated as , and when T90 was greater than 150 seconds, this case was evaluated as x.

[0056] Scorch T5: The time (T5) required for torque to increase by 5 Mooney units at 125 C. or less was revealed. When T5 was 15 minutes or more, this case was evaluated as , and when T5 was less than 15 minutes, this case was evaluated as x.

[0057] Elongation at break: according to JIS K-6251 (in consideration of pressing crack) [0058] The evaluation was as follows: 300% or more: , and less than 300%: x. Low-temperature elasticity recovery test test: according to JIS K-6261 [0059] (TR10 value) : 55 or less, : 50 or less, x: less than 50 [0060] (TR 70 value) : 40 or less, : 35 or less, x: less than 35

Comparative Example 2

[0061] In Comparative Example 1, 2 parts by weight of dicumyl peroxide (Percumyl D, produced by NOF Corporation; purity: 90% or more, one-hour half-life temperature: 136 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Comparative Example 3

[0062] In Comparative Example 1, 3 parts by weight of n-butyl-4,4-di(t-butylperoxy)valerate (Perhexa V, produced by NOF Corporation; purity: 90% or more, one-hour half-life temperature: 127 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Comparative Example 4

[0063] In Comparative Example 1, 5 parts by weight (2.0 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 331 XL40-SP, produced by Arkema; organic peroxide concentration: 40%, remainder: silica and anti-scorch components) containing 1,1-di(tert-butylperoxy)cyclohexane (one-hour half-life temperature: 110 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Example 1

[0064] In Comparative Example 1, 7 parts by weight (2.8 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 331 XL40-SP) containing 1,1-di(tert-butylperoxy)cyclohexane was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Example 2

[0065] In Comparative Example 1, 10 parts by weight (4.0 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 331 XL40-SP) containing 1,1-di(tert-butylperoxy)cyclohexane was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Example 3

[0066] In Comparative Example 1, 12 parts by weight (4.8 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 331 XL40-SP) containing 1,1-di(tert-butylperoxy)cyclohexane was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Comparative Example 5

[0067] In Comparative Example 1, 14 parts by weight (5.6 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 331 XL40-SP) containing 1,1-di(tert-butylperoxy)cyclohexane was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Comparative Example 6

[0068] In Example 2, the same amount (100 parts by weight) of EPDM (JSR EP27, produced by JSR) was used in place of EBT copolymer.

Comparative Example 7

[0069] In Comparative Example 1, 4 parts by weight (1.6 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 230 XL40-SP, produced by Arkema; organic peroxide concentration: 40%, remainder: silica, calcium carbonate and anti-scorch components) containing n-butyl-4,4-di(t-butylperoxy)valerate (one-hour half-life temperature: 127 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Example 4

[0070] In Comparative Example 1, 6 parts by weight (2.4 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 230 XL40-SP) containing n-butyl-4,4-di(t-butylperoxy)valerate (one-hour half-life temperature: 127 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Example 5

[0071] In Comparative Example 1, 7.5 parts by weight (3.0 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 230 XL40-SP) containing n-butyl-4,4-di(t-butylperoxy)valerate (one-hour half-life temperature: 127 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Example 6

[0072] In Comparative Example 1, 10 parts by weight (4.0 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 230 XL40-SP) containing n-butyl-4,4-di(t-butylperoxy)valerate (one-hour half-life temperature: 127 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

Comparative Example 8

[0073] In Comparative Example 1, 13 parts by weight (5.2 parts by weight as an organic peroxide) of nitroxide compound crosslinking agent (LUPEROX 230 XL40-SP) containing n-butyl-4,4-di(t-butylperoxy)valerate (one-hour half-life temperature: 127 C.) was used in place of 6 parts by weight of 1,1-di(tert-butylperoxy)cyclohexane.

[0074] Table below shows the results obtained in the above Examples and Comparative Examples.

TABLE-US-00002 TABLE Evaluation measurement Comp. Comp. Comp. Comp. Comp. item Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Ex. 5 Vulcanization 50 280 145 44 43 44 42 42 degree T90 (sec) Evaluation X Scorch T5 5.2 24.1 13.7 15.8 15.6 15.3 15.2 15.0 (min) Evaluation X X Elongation 330 320 400 450 400 340 310 290 (%) Evaluation X TR10 value 58 58 58 55 57 58 59 59 ( C.) Evaluation TR70 value 40 43 39 32 36 40 44 45 ( C.) Evaluation X Evaluation measurement Comp. Comp. Comp. item Ex. 6 Ex. 7 Ex. 4 Ex. 5 Ex. 6 Ex. 8 Vulcanization 45 128 126 128 125 110 degree T90 (sec) Evaluation Scorch T5 15.5 31.5 30.5 30.5 28.8 25.6 (min) Evaluation Elongation 310 470 430 390 300 220 (%) Evaluation X TR10 value 48 54 56 58 58 59 ( C.) Evaluation X TR70 value 26 32 36 39 42 44 ( C.) Evaluation X x

[0075] The above results reveal the following:

[0076] (1) The products crosslinked using the nitroxide compound crosslinking agents of the present invention each containing a specific amount of an organic peroxide having a specific one-hour half-life temperature satisfy all of the vulcanization degree T90, scorch T5, elongation at break, and low-temperature elasticity recovery test, all of which are required for sealing materials for fuel cell separators.

[0077] (2) When only an organic peroxide crosslinking agent having a specific one-hour half-life temperature is used, scorch T5 is not satisfied (Comparative Examples 1 and 3).

[0078] (3) When only an organic peroxide crosslinking agent having a one-hour half-life temperature higher than the specified temperature is used, the vulcanization degree T90 is not satisfied (Comparative Example 2).

[0079] (4) When the amount of organic peroxide in the nitroxide compound crosslinking agent containing a specific amount of an organic peroxide having a specific one-hour half-life temperature is less than the predetermined amount, the TR70 value is not satisfied (Comparative Examples 4 and 7).

[0080] (5) When the amount of organic peroxide in the nitroxide compound crosslinking agent containing a specific amount of an organic peroxide having a specific one-hour half-life temperature is greater than the predetermined amount, the elongation at break is not satisfied (Comparative Examples 5 and 8).

[0081] (6) When EPDM is used in place of the EBT copolymer, the low-temperature elasticity recovery test is not satisfied (Comparative Example 6).