JPH0618935B2 - Rubber composition - Google Patents

Description

The present invention relates to a rubber composition having improved rubber physical properties, and in particular, it has excellent reversion resistance in the vulcanization step, and has a resistance to heat deterioration and flex cracking resistance after vulcanization. The present invention relates to a rubber composition having excellent physical properties.

In recent years, rubber products such as tires and belts are required to have higher mechanical properties and heat resistance than ever before.

As a method of improving mechanical properties, a method of using a large amount of sulfur as a crosslinking agent to improve the crosslinking density has been known for a long time. However, when a large amount of sulfur is used, mechanical properties such as hardness and breaking strength of the vulcanized rubber are improved, but vulcanization reversion in the vulcanization process is remarkable, and the heat resistance and flex cracking resistance of the vulcanized rubber are significant. Has a major drawback that

In order to improve the drawbacks of sulfur crosslinking, a method of adding a bismaleimide compound to a sulfur vulcanization system containing dibenzothiazyl disulfide (DM) or tetramethylthiuram disulfide (TT) has also been proposed. However, even if this method is used, the above-mentioned drawbacks are improved to some extent, but they are not always sufficiently satisfactory, and in addition,
Since a large amount of expensive bismaleimide compound is required, it causes a large increase in the cost of the rubber compound. Furthermore, sulfene is used mainly in tires in the rubber industry instead of DM and TT. When an amide type vulcanization accelerator is used, the addition effect of the bismaleimide compound is hardly recognized, and the vulcanization accelerator combined with the bismaleimide compound is limited to DM, TT, etc., which have fast scorch properties, and its use. Was limited to some areas such as footwear products.

In view of such a situation, the present inventors show excellent vulcanization reversion resistance at the time of vulcanization in all sulfur vulcanization systems including a sulfenamide vulcanization accelerator, and after vulcanization, As a result of extensive studies on a rubber composition exhibiting excellent properties in rubber physical properties such as heat deterioration and flex cracking deterioration, a bismaleimide represented by the general formula (I) and a specific carboxylic acid anhydride were blended. For the first time in the rubber composition, all sulfur vulcanization systems including sulfenamide vulcanization accelerators have mechanical properties that are as good as or better than when a large amount of sulfur is used, and are a drawback of sulfur vulcanization. The present invention has been completed by finding that physical properties such as reversion property, heat resistance and bending resistance are remarkably improved.

That is, the invention has the general formula (I) (In the formula, R is a divalent acyclic aliphatic group, a cycloaliphatic group, an aromatic group, or an alkylaromatic group, and these are in the chain or in the side substituents such as O, N, and S. A rubber composition excellent in reversion resistance to vulcanization, heat aging resistance, and flex cracking resistance, characterized by containing a bismaleimide represented by a hetero atom) and an aromatic carboxylic acid anhydride. It is to provide things.

Examples of the bismaleimides represented by the general formula (I) of the present invention include: N, N'-ethylene bismaleimide N, N'-hexamethylene bismaleimide N, N'-dodecamethylene bismaleimide N, N '-( 2,2,4-Trimethyl-hexamethylene) bismaleimide N, N '-(oxy-dipropylene) bismaleimide N, N'-(amino-dipropylene) bismaleimide N, N '-(ethylene-dioxydiene Propylene) bisimide N, N '-(1,4-cyclohexylene) bismaleimide N, N'-(1,3-cyclohexylene) bismaleimide N, N '-(methylene-1,4-dicyclohexylene)
Bismaleimide N, N '-(isopropylidene-1,4-dicyclohexylene) bismaleimide N, N'-(oxy-1,4-dicyclohexylene) bismaleimide N, N '-(m-phenylene) bis Maleimide N, N '-(p-phenylene) bismaleimide N, N'-(o-phenylene) bismaleimide N, N '-(1,3-naphthylene) bismaleimide N, N'-(1,4-naphthylene) ) Bismaleimide N, N '-(1,5-naphthylene) bismaleimide N, N'-(3,3'-dimethyl-4,4'-biphenylene) bismaleimide N, N '-(3,3'- Dichloro-4,4'-biphenylene) bismaleimide N, N '-(2,4-pyridyl) bismaleimide N, N'-(2,6-pyridyl) bismaleimide N, N '-(4-me Cyl-2,6-pyridyl) bismaleimide N, N ′-(1,4-anthraquinonediyl) bismaleimide N, N ′-(m-tolylene) bismaleimide N, N ′-(p-tolylene) bismaleimide N , N '-(4,6-dimethyl-1,3-phenylene)
Bismaleimide N, N '-(2,3-dimethyl-1,4-phenylene)
Bismaleimide N, N '-(4,6-dichloro-1,3-phenylene)
Bismaleimide N, N '-(5-chloro-1,3-phenylene) bismaleimide N, N'-(5-hydroxy-1,3-phenylene) bismaleimide N, N '-(5-methoxy-1, 3-phenylene) bismaleimide N, N '-(m-xylylene) bismaleimide N, N'-(p-xylylene) bismaleimide N, N '-(methylene-di-p-phenylene) bismaleimide N, N' -(Isopropylidene-di-p-phenylene)
Bismaleimide N, N '-(oxy-di-p-phenylene) bismaleimide N, N'-(thio-di-p-phenylene) bismaleimide N, N '-(dithio-di-p-phenylene) bismaleimide N, N '-(sulfo-di-p-phenylene) bismaleimide N, N'-(carbonyl-di-p-phenylene) bismaleimide and the like can be mentioned.

The aromatic carboxylic acid anhydride, which is another important component in the present invention, is an anhydride of a divalent or higher valent aromatic carboxylic acid, such as phthalic anhydride, 1,2,4,5-
Examples thereof include benzenetetracarboxylic dianhydride, benzenehexacarboxylic dianhydride, 4-methyl-phthalic anhydride, trimellitic anhydride, and 4-chloro-phthalic anhydride.

Here, the phthalic anhydride or the like has been known as a scorch retarder for a long time in the rubber industry, but other than those known as a scorch retarder, that is, an organic acid such as salicylic acid or benzoic acid, Maleic anhydride, N-nitrolidiphenylamine, N-cyclohexylphthalimide and the like do not show the effect of the present invention when combined with the above-mentioned bismaleimides (I), and when combined with the above-mentioned aromatic acid anhydrides. Only specific effects are obtained.

The rubber composition of the present invention is characterized by containing the above-mentioned bismaleimides (I) and an aromatic acid anhydride. As the rubber applied to the present invention, natural rubber (N
R), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (I
R), acrylonitrile-butadiene copolymer rubber (NB
R), polychloroprene rubber (CR), ethylene / propylene / diene terpolymer rubber (EPDM), isoprene / isobutylene copolymer rubber (IIR), etc., or a single rubber or a mixed rubber of two or more thereof. The amount of the bismaleimides (I) added to the rubber is 0.1 to 8 parts by weight, preferably 0.3 to 4 parts by weight, and the aromatic carboxylic acid anhydride is 0.1 to 4 parts by weight, based on 100 parts by weight of the rubber. It is preferably 0.3 to 3 parts by weight.

These may be mixed in advance,
You may add separately with other compounding agents at the time of compounding. In compounding, usually sulfur cross-linking components, ie sulfur and / or sulfur donors, and vulcanization accelerators such as dibenzothiazyl disulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide, pentamethylene thiuram hexasulfide, N -Cyclohexyl-2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, Nt-butyl-2-
Benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide, etc. are added together with other compounding agents such as H, if necessary.
Carbon black such as AF, ISAF and SRF, a reinforcing agent such as silica and calcium carbonate, stearic acid, zinc white, process oil, a tackifier, waxes, an antiaging agent and the like are blended.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

In the examples, “parts” means “parts by weight”.

Example 1 Natural rubber 100 parts, HAF carbon 45 parts, zinc flower 5
Parts, stearic acid 1 part, process oil 1 part, wax 3
Part, N-phenyl-N'-1,3-dimethylbutyl-p
2 parts of phenylenediamine (anti-aging agent) and the sample shown in Appendix 1 were compounded by a conventional method using a 6 ″ φ open roll to prepare various rubber compositions.

The obtained various rubber compositions are 170 ° C. in an oscillating disc rheometer in accordance with ASTM-D-2084.
Under the conditions, the maximum crosslink density ( _MH ) and the reversion property (time until the reduction from the maximum torque value by 1 kg · cm, Rt) were measured.

Further, various rubber compositions were vulcanized under the conditions of 170 ° C. for 20 minutes to prepare predetermined test pieces, and then a heat aging test and a bending crack test were conducted in accordance with JIS-K-6301. In the heat aging test, after heat aging at 100 ° C. for 48 hours using a gear oven, the retention rate (%) of the breaking strength is measured. The length of the scratch after 10,000 times was measured.

The results are shown in Table 1.

Example 2 100 parts of styrene-butadiene rubber, HAF carbon 5
0 parts, process oil 5 parts, zinc white 5 parts, stearic acid 3
Parts, wax 3 parts, 2,2,4-trimethyl-1,2-
A rubber composition was prepared by blending 2 parts of the dihydroquinoline polymer (antiaging agent) and the sample shown in Appendix-2 in the same manner as in Example 1, and measuring the respective performances, the results are shown in Table-2. . The heat aging test is 110 ° C. × 48 hours.

Example 3 Acrylonitrile-butadiene rubber 100 parts, stearic acid 3 parts, zinc white 5 parts, process oil 10 parts, light calcium carbonate 40 parts, titanium oxide 10 parts, hydrous silica 30
Parts, 2,2'-methylenebis (4-methyl-6-t-butylphenol) (antiaging agent) and the sample shown in Appendix-3 were compounded in the same manner as in Example 1 to prepare a rubber composition. , Each performance was measured. The heat aging test is 1
30 ° C. × 48 hours.

Claims (1)

[Claims] 1. A general formula (I) (In the formula, R is a divalent acyclic aliphatic group, a cycloaliphatic group, an aromatic group or an alkylaromatic group, and these are in the chain or in the side substituents such as O, N and S. A rubber composition containing a bismaleimide represented by the formula (4) and an anhydride of a divalent or higher valent aromatic carboxylic acid.