JP2002371161A - Low hardness rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low hardness rubber composition having non-bleeding property, and suitably used as a molding raw material for a sealing material of electric parts such as a secondary battery, fuel cell, condenser. SOLUTION: This peroxide curable low hardness rubber composition consists of 95-30 wt.% EPDM having 10<4> -10<6> order of number-average molecular weight and 5-70 wt.% ethylene/an α-olefin copolymer having 10<3> -10<5> order of number- average molecular weight, and can give a cross-linked molded product having <=50 hardness (Duro A). Since the rubber having a low molecular weight is cured by a peroxide, the rubber composition does not have any bleeding material, and the low hardness rubber having the hardness as low as <=50 Duro A hardness if obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a low-hardness rubber composition. More specifically, the present invention relates to a peroxide-crosslinkable low-hardness rubber composition suitably used as a molding material of a sealing material for electric parts.

[0002]

2. Description of the Related Art Sealing materials used for electric parts such as nickel metal hydride secondary batteries, lithium ion secondary batteries, polymer electrolyte fuel cells, aluminum electrolytic capacitors, electric double layer capacitors, etc. include electrolytes, water vapor and the like. It is necessary to prevent the internal liquid from leaking to the outside and to prevent impurities from the outside from entering the inside.

For this reason, sealing materials such as gaskets, O-rings and packings are used. In such a case, in addition to heat resistance and electric insulation, there is no oozing component from the sealing material, and the durability of the seal is high. It is required that the material has excellent compression set characteristics that affect the performance, and that the material hardness is low in order to reduce the surface pressure when the seal is assembled.

Conventionally, as a gasket for this kind of application,
Polyolefin-based resins such as polyethylene and polypropylene and olefin-based thermoplastic elastomers are used, but they are insufficient from the viewpoint of seal durability.
On the other hand, for the purpose of lowering the surface pressure, a large amount of a plasticizer is compounded in an olefin-based rubber material, and those having a reduced hardness are also known. There was a problem and no real application was seen.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-hardness and non-leaching material which is suitably used as a molding material for a sealing material for electric parts such as secondary batteries, fuel cells and capacitors. It is to provide a rubber composition.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
Approximately 95 to 30 weight of EPDM with number average molecular weight Mn of 10 ⁴ to 10 ⁶ order
% And an ethylene / α-olefin copolymer rubber of about 5 to 70% by weight on the order of 10 ³ to 10 ⁵ and a peroxide crosslinkable low hardness rubber composition which gives a crosslinked molded article having a hardness (Duro A) of 50 or less. Achieved by

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS EPDM (ethylene-propylene-diene terpolymer rubber) has a number average molecular weight Mn of 10 ⁴ or more.
Commercial products on the order of 10 ⁶ can be used as they are.
Ethylene / α-olefin copolymer rubber used by blending with propylene
-1, pentene-1, hexene-1, heptene-1, octene-1
Mn obtained by copolymerizing at least one α-olefin such as
0 ^{3 to 105} a rubbery copolymer of order, preferably ethylene - propylene copolymer rubber (EPR) is used.

[0008] EPDM and ethylene / α-olefin copolymer rubber are used in a proportion of about 95 to 30% by weight, preferably about 90 to 60% by weight, and about 5 to 70% by weight, preferably about 1
It is used by blending at a ratio of 0 to 40% by weight. If the blending ratio of the latter is lower, the hardness is
On the other hand, if the rubber is blended at a higher ratio and used, the rubber becomes strongly adhered at the time of kneading, making it impossible to form a uniform rubber compound. Further, the reason why Mn of each of these blend rubber components is limited to the above range is to obtain a necessary plasticizing effect.

[0009] The blended rubber is used in an amount of about 100 parts by weight thereof.
It is crosslinked by an organic peroxide used in a proportion of 0.2 to 10 parts by weight, preferably about 0.5 to 8 parts by weight. Examples of the organic peroxide include commonly used benzoyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, 1,3-di (
(3-butylperoxy) isopropylbenzene, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, m-Trail peroxide, dipropionyl peroxide and the like are used.

The preparation of a composition containing the above-mentioned components as essential components is generally carried out as a rubber compounding agent within a range that does not prevent the hardness Duro A of the obtained rubber vulcanized molded product from 20 to 50. An acid acceptor comprising a divalent metal oxide or hydroxide used, a lubricant, a multifunctional crosslinking aid, a vulcanization accelerator, etc. are blended as necessary, and a kneader, a Banbury mixer, an intermix, It is performed by kneading using an open roll or the like. However, it induces corrosion of fillers such as carbon black, carbon fiber, and metal particles that impart conductivity, a plasticizer with extractability, an organic aging inhibitor or a sulfur-based vulcanization accelerator, and a chlorine-containing compounding agent. It is desirable not to add a compounding agent or the like, or to keep the compounding amount to a very small amount. Therefore, as a filler,
Silica is preferably used.

The crosslinking of the composition is carried out at a temperature of about 150 to 230 ° C. for about 1 to 10 minutes by using an injection molding machine, a compression molding machine or the like, and if necessary at about 150 to 180 ° C. for about 1 to 10 minutes. Secondary crosslinking is also performed for about 15 hours.

[0012]

According to the rubber composition of the present invention, since rubber having a low molecular weight is peroxide-crosslinked, there is no exudate (extractable component) and Duro A hardness of 50 or less can be reduced. Achieved. The low-hardness rubber composition having such properties is suitably used as a molding material for various sealing materials used for electric components such as secondary batteries, fuel cells, aluminum electrolytic capacitors, and electric double layer capacitors.

[0013]

Next, the present invention will be described with reference to examples.

[0014] Example EPDM (Mitsui Chemicals product EPT4045, Mn: 10 ⁵ order) 65 parts by weight of ethylene · alpha-olefin copolymer rubber 35 〃 (Uniroyal product Torairen 65, Mn: 10 ⁴ order) white carbon (Nippon Silica Product Nip seal LP) 15 ポ リ Polymerized (2,2,4-trimethyl-1,2-dihydroquinoline) 0.2 〃 Dicumyl peroxide 2 〃 Each of the above components is kneaded with an open roll, and the obtained kneaded material is 170 ° C. Perform press crosslinking for 30 minutes, 150x
It was cross-linked into a 150 × 2 mm sheet.

The following items were measured for the sheet-like crosslinked molded product. Hardness (Duro A): JIS K6253 compliant Tensile strength: JIS K6251 compliant Elongation: JIS K6251 compliant Compression set: JIS K6262 compliant (120 ° C, 70 hours) Volume fixed resistance: Yokogawa Hewlett Packard 16008A Res
Measured by istivity Cell Acetone extract: 5 g of crosslinked rubber is subjected to Soxhlet extraction, and the extract after acetone removal is visually observed for viscousness.

[0016] In Comparative Example 1 Example, EPDM instead of EPDM (EPT4045) (Mitsui Chemicals product EPT4010, Mn: 10 ⁵ orders) are used 100 parts by weight,
No ethylene / α-olefin copolymer rubber was used.

Comparative Example 2 In the example, the amount of EPDM was adjusted to 20 parts by weight,
The amount of the α-olefin copolymer rubber was changed to 80 parts by weight. The rubber was strongly adhered during kneading and could not be formed into a uniform rubber compound, and molding was impossible.

Comparative Example 3 In Comparative Example 1, EPDM (EPT4010) was replaced with the same amount of oil-added oil.
EPDM (Mitsui Chemicals EPT3041E) was used.

The results of measurement and evaluation in the above Examples and Comparative Examples are shown in the following table. Table Measurement / Evaluation items Example ratio-1 Comparison-3 Hardness (Duro A) 50 60 45 Tensile strength (MPa) 6.6 8.9 6.7 Elongation (%) 350 260 510 Compression set (%) 11 8 15 Volume resistivity (MΩ ・ m) 2.1 × 10 ¹⁰ 2.2 × 10 ¹⁰ 2.1 × 10 ¹⁰ Viscosity of acetone extract No No Yes

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 2/08 H01M 2/08 X 8/02 8/02 S 8/10 8/10 F term (reference) 4J002 BB05X BB15W BB15X EK036 EK046 EK056 FD146 GJ02 5H011 AA17 FF01 GG02 HH02 JJ02 JJ25 JJ27 KK02 KK04 KK05 KK07 5H026 AA06 CX08 EE18 HH05

Claims (2)

[Claims] An EP having a number average molecular weight Mn of the order of 10 ⁴ to 10 ^6.
About 95 to 30% by weight of DM and about 10 ³ to 10 ⁵
α-Olefin copolymer rubber about 5-70% by weight, hardness
A peroxide-crosslinkable low-hardness rubber composition that gives a crosslinked molded article having a (Duro A) of 50 or less. 2. The low-hardness rubber composition according to claim 1, which is used as a molding material for a sealing material for electric parts.