RUBBER COMPOSITION AND A SEALING MATERIAL FOR FUEL CELL SEPARATORS

Abstract

A rubber composition comprising 1 to 10 parts by weight of an organic peroxide crosslinking agent 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. 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 has, in addition to functions required as a sealing material for separators, improved low temperature sealing properties.

Claims

1: A rubber composition comprising 1 to 10 parts by weight of an organic peroxide crosslinking agent 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, and neither a resorcinol-based compound-melamine-based compound, an aluminate-based coupling agent, nor a silane coupling agent.

2: 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.

3: 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.

4: The rubber composition according to claim 1, which contains no plasticizer.

5. (canceled)

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

7: A sealing material for fuel cell separators comprising a crosslinked molded article of the rubber composition according to claim 6.

8: The rubber composition according to claim 2, 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.

9: The rubber composition according to claim 2, which contains no plasticizer.

10: The rubber composition according to claim 2, which is used for crosslinking molding of a sealing material for fuel cell separators.

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

Description

EXAMPLES

[0035] The following describes the present invention with reference to Examples.

Example 1

[0036]

TABLE-US-00001 EBT copolymer (EBT K-9330, produced by 100 parts by weight Mitsui Chemicals, Inc.) Peroxyketal (Perhexa C, produced by 4 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.

[0037] The obtained kneaded products and vulcanizates were evaluated or measured for characteristics described in the following items.

[0038] Kneading properties: When roll winding properties during kneading were good, this case was evaluated as ; and when there was no problem in kneading, although slight sticking was observed, this case was evaluated as .

[0039] 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 60 seconds or less, this case was evaluated as , and when T90 was greater than 60 seconds, this case was evaluated as x.

[0040] Elongation at break: according to JIS K-6251 corresponding to ISO 37 [0041] The evaluation was as follows: 300% or more: , and less than 300%: x.

[0042] Low-temperature elasticity recovery test: according to JIS K-6261 [0043] (TR10 value) : 55 or less, : 50 or less, x: less than 50 [0044] (TR70 value) : 40 or less, : 35 or less, x: less than 35

Example 2

[0045] In Example 1, the same amount (4 parts by weight) of another peroxyketal (Perbutyl 355, produced by NOF Corporation; purity: 97% or more, di(3,5,5-trimethylhexanoyl)peroxide, one-hour half-life temperature: 119 C.) was used in place of the peroxyketal used in Example 1.

Example 3

[0046] In Example 2, the amount of the EBT copolymer was changed to 90 parts by weight, and 10 parts by weight of EPDM (JSR EP27, produced by JSR) was used.

Example 4

[0047] In Example 2, the amount of the EBT copolymer was changed to 70 parts by weight, and 30 parts by weight of EPDM (JSR EP27) was used.

Example 5

[0048] In Example 2, the amount of the EBT copolymer was changed to 50 parts by weight, and 50 parts by weight of EPDM (JSR EP27) was used.

Comparative Example 1

[0049] In Example 2, the amount of the EBT copolymer was changed to 30 parts by weight, and 70 parts by weight of EPDM (JSR EP27) was used.

Comparative Example 2

[0050] In Example 2, the amount of the EBT copolymer was changed to 10 parts by weight, and 90 parts by weight of EPDM (JSR EP27) was used.

Comparative Example 3

[0051] In Example 1, 2 parts by weight of dialkyl peroxide (Percumyl D, produced by NOF Corporation; purity: 98% or more, dicumyl peroxide, one-hour half-life temperature: 136 C.) was used in place of peroxyketal.

[0052] Table 1 below shows the results obtained.

TABLE-US-00002 TABLE 1 Evaluation .Math. measurement Comp. Comp. Comp. item Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 1 Ex. 2 Ex. 3 Kneading properties T90 (sec) 50 50 50 50 50 50 50 280 Evaluation X Elongation 330 310 330 350 310 320 320 320 (%) Evaluation TR10 value 58 58 58 57 56 53 50 58 ( C.) Evaluation TR70 value 40 42 40 39 37 34 30 43 ( C.) Evaluation X X

Comparative Example 4

[0053] 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 5

[0054] In Comparative Example 4, the amount of peroxyketal was changed to 5 parts by weight, and 20 parts by weight of adipic acid ester (DIDA, produced by Showa Kosan Co., Ltd.) was further used.

Comparative Example 6

[0055] In Comparative Example 5, 1 part by weight of maleimide compound crosslinking aid (VULNOC PM, produced by Ouchi Shinko Chemical Industrial Co., Ltd.) was further added.

Comparative Example 7

[0056]

TABLE-US-00003 EPDM (EP27) 100 parts by weight Peroxyketal (Perhexa C) 2 parts by weight Crosslinking aid (VULNOC PM) 1 part by weight MAF carbon black (Shoblack IP200 40 parts by weight produced by Cabot Japan K.K. Process oil (PW-380) 40 parts by weight
Using the above components, kneading, vulcanization, and evaluation or measurement of various properties were performed in the same manner as in Example 1.

Comparative Example 8

[0057]

TABLE-US-00004 EPDM (EP51) 100 parts by weight peroxyester (Perbutyl 355) 2 parts by weight Crosslinking aid (VULNOC PM) 1 part by weight MAF carbon black (Shoblack IP200) 30 parts by weight Process oil (PW-380) 40 parts by weight
Using the above components, kneading, vulcanization, and evaluation or measurement of various properties were performed in the same manner as in Example 1.

[0058] Table 2 below shows the results obtained in Comparative Examples 4 to 8. When a plasticizer with good low temperature characteristics was added to EPDM, a crosslinking aid was added to improve the TR70 value, and crosslinking density was increased, the elongation was not good, as shown in the results of Comparative Example 6.

TABLE-US-00005 TABLE 2 Evaluation Comp. Comp. Comp. Comp. Comp. measurement item Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Kneading properties T90 (sec) 50 50 50 50 48 Evaluation Elongation 330 450 230 410 450 (%) Evaluation X TR10 value 48 55 56 47 28 ( C.) Evaluation X X X TR70 value 26 29 31 30 +5 ( C.) Evaluation X X X X X