JPH04136049A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition improved in modulus at high temperature, breaking strength and heat resistance by mixing a rubbery polymer with a lactam compound and a bismaleimide compound. CONSTITUTION:A lactam is condensed with S2Cl2 in the presence of sodium formate to obtain a lactam compound of formula I [wherein R is a bivalent group of an (un)substituted aliphatic hydrocarbon]. 100 pts.wt. rubbery polymer comprising a natural rubber and/or a synthetic rubber is mixed with 0.1-10 pts.wt. above lactam compound, 0.1-5 pts.wt. bismaleimide compound of formula II (wherein X is a group of any one of formulas III-VI; R is H, Cl or alkyl; Y is-0-,-CH2-,-S-or-SO2-; and n is 2-12) and optionally a filler, a metal oxide, a softener, a colorant, a sulfur (donor), a vulcanization accelerator, etc., to obtain a rubber composition.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a rubber composition with improved physical properties at high temperatures;
In particular, the present invention relates to a rubber composition that has a high modulus of elasticity at high temperatures while maintaining sufficient fracture strength and heat resistance.

[Conventional technology] In recent years, with the improvement in the performance of automobiles and the development of highway networks, the usage conditions for rubber products such as tires have become increasingly strict depending on the application, and improvements in physical properties have been required accordingly. However, many characteristic factors such as high elastic modulus, excellent fracture strength, and high heat resistance to suppress product deformation are now required at the same time, especially in high-temperature regions. However, the reality is that the ability to simultaneously satisfy these requirements has not yet been resolved, as described below.

Conventionally, as an attempt to solve these demands, there is a rubber composition described in, for example, Japanese Patent Application Laid-open No. 166844/1983. This is an attempt to improve scorch stability, reversion resistance, heat deterioration resistance, and bending resistance by blending bismaleimides, sulfenamides, dithiophosphoric acids, and sulfur with rubber. In addition, in JP-A No. 61-168642, bismaleimides and aromatic carboxylic acid anhydrides are blended to improve reversion resistance and provide excellent heat deterioration resistance and flex crack resistance after vulcanization. A rubber composition is described. Furthermore, an attempt was made to improve scorch stability and heat aging resistance by using 4,4''-dithiodimorpholine in place of some or all of the sulfur in the Journal of the Japan Rubber Association, Vol. 38, p. 549 (1965). However, these techniques do not provide sufficient rubber properties after vulcanization, especially the elastic modulus, strength and resistance, and heat resistance at high temperatures, and in particular, it is difficult to make the product to suppress deformation at high temperatures. There is a problem that if the elastic modulus is set to high, the breaking strength etc. further decreases.For example, when the tire is used under high speed conditions and/or high load conditions, tires to which such a rubber composition is applied There is a problem in that tires are extremely susceptible to deterioration due to the effects of heat and distortion, and problems occur early on.

[Means for solving the problem] As a result of intensive research into rubber compositions that have high elastic modulus and breaking strength at high temperatures and also have excellent heat resistance, the present inventors have discovered a specific solution that can solve the above problems. The present invention was completed by discovering a combination of these compounds.

That is, the present invention provides at least one rubber-like polymer 1 selected from the group consisting of natural rubber and/or synthetic rubber.
(A) represents a divalent group of general formula (1) in 00 parts by weight. ] The lactam compound represented by 0
．． 1 to 10 parts by weight (B) General formula (II) group, Y is O, CHz, S, 50
2-, n represents an integer from 2 to 12. )] The present invention provides a rubber composition containing 0.1 to 5 parts by weight or more of the bismaleimide compounds (A) to (B).

The rubbery polymer targeted by the present invention is selected from the group consisting of natural rubber and/or synthetic rubber, and one or two rubber-like polymers are selected from the group consisting of natural rubber and/or synthetic rubber.
Blends of more than one species are used.

Examples of synthetic rubber include polyisoprene rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber.

Isoprene-isobutylene copolymer rubber and its halides, ethylene-propylene-diene ternary copolymer rubber,
Butadiene-propylene copolymer rubber.

Examples include butadiene-ethylene copolymer rubber, butadiene-isoprene copolymer rubber, polychloroprene rubber, and the like. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiengo copolymer rubber, and blends of two or more thereof are highly versatile and are particularly suitable.

The lactam compound represented by the general formula (1) of the present invention is
Lactams and S2C12 are condensed in the presence of sodium formate according to the methods of U.S. Pat. No. 3,525,737 (1970) and West German Patent No. 3,012,895 (1981). 6 Synthesized lactam compounds represented by formula (I) of the present invention include N,N'-di(5-methyl-γ-butyrolactam) disulfide, N,N'-di(5-ethyl-γ -butyrolagam) disulfide N.

N"-di(5-isopropyl-γ-butyrolactam) disulfide, N,N'-di(5-methoxy-γ-butyrolactam) disulfide, N,N'-di(5-ethoxy-γ-butyrolactam) disulfide, N , N'-di(
5-chloro-γ-butyrolactam) disulfide, N,
N'-di(5-nitro-γ-butyrolactam) disulfide, N,N'-di(5-amino-γ-butyrolactam) disulfide, N,N'-di(δ-valerolactam)
Disulfide, N,N'-di(ε-caprolactam) disulfide, N,N'-di(3-methyl-ε-caprolactam) disulfide, N,N'-di(3-ethyl-ε
-caprolactam) disulfide, N,N'-di(3-
Isopropyl-ε-caprolactam) disulfide, N
, N'-di(3-methoxy-ε-caprolactam) disulfide, N,N'-di(3-1methoxy-ε-caprolactam) disulfide.

N,N'-di(3-ethoxy-e-caprolactam) disulfide, N,N'-di(3-chloro-E-prolactam) disulfide, N,N'-di(3-ditroepsilon)
-caprolactam) disulfide, N.

Examples include No-di(3-amino-E-caprolactam) disulfide, N,N'-di(ω-hebutalactam) disulfide, N,N'-di(ω-octalactam) disulfide, and the like.

Further, as the bismaleimide compound represented by the general formula (n) of the present invention, N,N'-ethylene bismaleimide, N,N'-hexamethylene bismaleimide, N,N'
-α, ω-dodecylene bismaleimide FtN, N'-m or p-phenylene bismaleimide, N, N'-4,4
'-diphenyl ether bismaleimide, N, N'-4
, 4'-diphenylthiobismaleimide, N, N'-4
, 4''-diphenylsulfone bismaleimide and the like.

The rubber composition according to the present invention is characterized by containing the lactam compound and bismaleimide compound described above. The blending amount of these is 100% of the rubbery polymer.
The amount of the lactam compound is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and the amount of the bismaleimide compound is 0.1 to 5 parts by weight, preferably 0.5 parts by weight.
~4 parts by weight.

The present invention also includes fillers or reinforcing agents such as calcium carbonate, silica, and carbon black, and metal oxides such as zinc white as target rubber components.

Softeners such as paraffinic, naphthenic or aromatic processed oils, various higher fatty acids such as stearic acid.

Various additives such as colorants and pigments, vulcanization accelerators, sulfur and sulfur donors, anti-aging agents, and ultraviolet absorbers can be added as necessary. Also, open rolls for kneading rubber, which have traditionally been used.

The mixture can be mixed using a Banbury mixer, a pressure kneader, or the like.

[Examples] Examples of the present invention will be described in detail below, but the present invention is not limited thereto.

The high temperature physical properties (elastic modulus, breaking strength) and heat resistance of the rubber compositions of the following invention examples and comparative examples were measured by the following test method. For the high-temperature physical property test, a rubber composition was obtained by mixing in a conventional manner according to the formulation shown in Table 1. These samples were vulcanized at 160° C. for 20 minutes to prepare rubber composition samples with a thickness of 2 mm. Further, these samples were left in an oven at a temperature of 120°C for 20 minutes, and then immediately taken out, and the stress of the high temperature samples was measured in accordance with JIS K 6301-197°5 (vulcanized rubber physical testing method). In addition, the blowout temperature (heat resistance test) is approximately 25mm x 25mm x 6
．． A 35 mm vulcanized rubber test piece of the test rubber composition is placed in an electric furnace, and the temperature is appropriately increased stepwise from 200°C to 320°C. After being left at a predetermined temperature for about 20 minutes, it was taken out from the furnace and cut in half, and the lower limit temperature at which bubbles were observed to be generated inside was measured as the blowout temperature.

[Effects of the Invention] As is clear from the above, the rubber composition according to the present invention can provide a rubber composition that maintains sufficient breaking strength and heat resistance while having a high modulus of elasticity at high temperatures.

Claims (1)

[Scope of Claims] 100 parts by weight of at least one rubbery polymer selected from the group consisting of natural rubber and/or synthetic rubber contains (A) general formula (I) ▲ mathematical formula, chemical formula, table, etc. ▼(I) [In the formula, R represents a divalent group of a substituted or unsubstituted aliphatic hydrocarbon. ] 0.1 to 1 lactam compound represented by
0 parts by weight (B) General formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) [In the formula, X is -(CH_2)n-, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ , chemical formulas, tables, etc.▼,
Or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (Here, R is a hydrogen atom, a chlorine atom, or an alkyl group,
Y is -O-, -CH_2-, -S-, -SO_2-,
n represents an integer from 2 to 12. 1. A rubber composition comprising 0.1 to 5 parts by weight or more of a bismaleimide compound represented by (A) to (B).