JPH0629342B2 - Rubber composition - Google Patents

Description

The present invention relates to a rubber composition having improved rubber physical properties, and in particular, in the processing and vulcanization steps, the scorch property is stable and the reversion resistance is excellent, and the rubber property after vulcanization is excellent. Relates to a rubber composition excellent in heat resistance deterioration and flex crack resistance deterioration.

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 for 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 step is remarkable, and the heat resistance and flex crack resistance of the vulcanized rubber are improved. There was a major drawback that it was significantly reduced.

In order to improve the drawbacks of such sulfur crosslinking, a method of adding a bismaleimide compound to a sulfur vulcanization system containing benzothiazyl disulfide (DM) or tetramethylthiuram disulfide (TT) has also been proposed.

However, even if this method is used, the above-mentioned drawbacks are remedied to some extent, but the degree thereof is not always sufficiently satisfactory. In addition, in this method, the vulcanization accelerator used is D
There is a big problem that the scorch property is fast, probably because it is M or TT, and the field of use thereof is limited to some fields such as footwear.

Further, in the above-mentioned method, when a sulfenamide-based vulcanization accelerator having a slow scorch property, which is used in the largest amount in the rubber industry, is used instead of DM and TT, the addition effect of bismaleimide is hardly recognized. .

As described above, the known rubber composition was not able to satisfy all of the scorch stability, reversion resistance, heat resistance deterioration, and flex crack resistance deterioration at the same time.

In view of such a situation, the present invention is to find a rubber composition which is excellent in scorch stability during processing and vulcanization, excellent in reversion resistance to vulcanization, and in heat resistance deterioration and flex crack deterioration resistance in rubber physical properties after vulcanization. As a result of repeated intensive studies, a rubber compounded with bismaleimides represented by the general formula (I) and sulfenamides represented by the general formula (II), and dithiophosphoric acids represented by the general formula (III) and sulfur. The composition has stable scorch for the first time and shows mechanical properties comparable to those when sulfur is used in a large amount, and physical properties such as revulcanization, heat resistance and flex resistance, which are the drawbacks of sulfur vulcanization. The present invention has been completed by finding out that the above is also significantly improved.

That is, the present invention provides a natural rubber and / or a synthetic rubber (A) with the general formula (I) And bismaleimides represented by (B) general formula (II) And sulfeneamides represented by (C) general formula (III) (Wherein R ₃ and R ₄ represent an aliphatic group) and (D) sulfur are blended, and the scorch resistance is stable and the reversion resistance and heat deterioration are stable. It is intended to provide a rubber composition having excellent flex crack resistance.

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-dioxydipropylene) 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) bismaleimide N, N '-(p-phenylene) bis Maleimide N, N '-(o-phenylene) bismaleimide N, N'-(1,3-naphthylene) bismaleimide N, N '-(1,4-naphthylene) bismaleimide N, N'-(1,5 -Naphthile ) 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 ′-(4-methyl-2,6-pyridyl) bismaleimide N, N ′-(1,4-anthraquinonediyl) bismaleimide N, N ′-( m-tolylene) bismaleimide N, N '-(p-trelin) bismaleimide N, N'-(4,6-dimethyl-1,3-phenylene) bismaleimide N, N '-(2,3-dimethyl- 1,4-phenylene) bismaleimide N, N '-(4,6-cyclolo-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-pphenylene) bismaleimide N, N'-(oxy-di-p-phenylene) bismaleimide N, N '-(thio-di-p- Phenylene) bismaleimide N, N '-(dithio-di-p-phenylene) bismaleimide N, N'-(sulfodi-p-phenylene) bismaleimide N, N '-(carbonyl-di-p-phenylene) Examples of the sulfenamides represented by the general formula (II) of the present invention include bismaleimide and N-cyclohexyl-2-benzothiazylsulfenamide N-oxydiethylene-2-benene. Thiadyl sulfenamide Nt-butyl-2-benzothiazyl sulfenamide N, N-diisopropyl-2-benzothiazyl sulfenamide N, N-dicyclohexyl-2-benzothiazyl sulfenamide To be

Examples of the dithiophosphoric acid represented by the general formula (III) of the present invention include diethyldithiophosphoric acid disulfide di-iso-propyldithiophosphoric acid disulfide di-n-propyldithiophosphoric acid disulfide di-butyldithiophosphoric acid disulfide di-hexyldithiophosphoric acid disulfide disulfide -Cyclohexyldithiophosphoric acid disulfide, di-octyldithiophosphoric acid disulfide, etc. are exemplified, and as the sulfur, various kinds of sulfur such as powdered sulfur, precipitable sulfur and insoluble sulfur are exemplified.

The rubber applicable to the present invention includes natural rubber (NR), styrene / butadiene copolymer rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), acrylonitrile / butadiene copolymer rubber (NBR), polychloroprene. Examples thereof include rubber (CR), ethylene / propylene / diene terpolymer rubber (EPDM), isoprene / isobutylene copolymer rubber (IIR), and other single rubbers, or rubbers obtained by mixing two or more of these.

The rubber composition of the present invention is characterized by blending these rubbers with the above-mentioned bismaleimides (I), sulfenamides (II), dithiophosphoric acids (III) and sulfur. The amount of bismaleimides (I) is usually 0.1 to 8 parts by weight, preferably 0.1 to 100 parts by weight of rubber.
3 to 4 parts by weight, sulfenamides (II) are usually 0.1 to 8 parts by weight, preferably 0.3 to 6 parts by weight, dithiophosphoric acids (III)
Is usually 0.1 to 8 parts by weight, preferably 0.3 to 6 parts by weight, and sulfur is usually 0.1 to 14 parts by weight, preferably 0.5 to 8 parts by weight. These may be used as a premix. You may add and mix separately at the time of mix | blending.

The rubber composition of the present invention also contains other compounding agents such as HAF,
Carbon blacks such as ISAF and SRF, reinforcing agents such as silica and calcium carbonate, stearic acid, zinc white, process oils, tackifiers, waxes, and antiaging agents can be added as required.

The rubber composition of the present invention thus obtained is processed, excellent scorch stability at the time of vulcanization, shows reversion resistance, and is extremely excellent in heat resistance in rubber physical properties after vulcanization,
Shows flex crack resistance.

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 have a scorch property according to JIS-K-6300 and an oscillating disc rheometer at 170 ° C. according to ASTM-D-2084.
The maximum crosslink density (M _H ) and vulcanization reversion property (time from the maximum torque value to decrease 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 performed according to 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 breaking strength was measured. The length of the scratch after turning was measured.

The results are shown in Table 1.

Example 2 100 parts of styrene-butadiene rubber, 50 HAF carbon
Parts, 5 parts of process oil, 5 parts of zinc white, 3 parts of stearic acid,
3 parts of wax, 2 parts of 2,2,4-trimethyl-1,2-dihydroquinoline polymer (antiaging agent) and Appendix-2
The sample shown in Table 1 was prepared in the same manner as in Example 1 and the performance of each sample was measured. The results are shown in Table 2. The heat deterioration test is 110 ° C. × 48 hours.

Claims (1)

[Claims] Claims: 1. Natural rubber and / or synthetic rubber (A) General formula (I) And bismaleimides represented by (B) general formula (II) And sulfeneamides represented by (C) general formula (III) (In the formula, R ₃ and R ₄ represent an aliphatic group.) A rubber composition comprising a dithiophosphoric acid represented by the formula (D) and sulfur (D).