JPH01178538A - Rubber composition - Google Patents

Abstract

PURPOSE:To improve the partial abrasion resistance without detriment to high speed durability, rib tear resistance, etc., by mixing a stock rubber with a specified reinforcing carbon black, a polyolefin resin, a bismaleimide compound and sulfur. CONSTITUTION:A polyolelfin resin (C) is obtained by copolymerizing a 5- methyl-1,4-hexadiene monomer unit bonded in the foam of a structure of formula I (wherein R is H or methyl, and m is 5-100) with at least one kind of a monoolefin monomer unit selected from ethylene and propylene and, optionally, other unsaturated monomer units in the presence of an olefin polymerization catalyst. 100pts.wt. at least one stock rubber (A) selected from among natural rubber, synthetic isoprene rubber and synthetic butadiene rubber is mixed with 40-60pts.wt. resinforcing carbon black (B) of a specific surface area (by nitrogen adsorption method) of 110-160m<2>/g, 1-15pts.wt. component C, 0.5-3pts.wt. bismaleimide compound (D) of formula II (wherein Z is a 2-10C bivalent group such as a 2-10C alkylene, a phenylene, an alkylphenylene or a combination thereof) and 0.4-2pts.wt. sulfur (E).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a rubber composition, and more specifically, the present invention relates to a rubber composition, and more specifically, the present invention relates to a rubber composition that can withstand running on good roads without impairing rubber durability such as high-speed running durability and rib tear resistance. The present invention relates to a rubber composition for treads such as pneumatic tires for heavy vehicles, which can significantly improve wear properties, particularly uneven wear resistance.

(Prior art) Tires that require excellent high-speed running durability in their tire treads, rubber durability related to rib tear resistance, wear resistance, etc. include truck and bus tires for running on good roads.
Therefore, various improvements have been made to rubber compositions for the treads of these tires.

For example, techniques for improving wear resistance are described on pages 115 to 121 of the publication entitled ``Points for Selection of Rubber Materials J'' (1979, published by the Japanese Standards Association). Under such conditions, techniques are known in which a blend of styrene-butadiene rubber or butadiene rubber is used in the tire tread, or a certain amount of highly reinforcing carbon black is used to improve wear resistance.

Further, attempts have also been made to improve the physical properties of rubber by incorporating bismaleimide compounds into rubber compositions. For example, according to JP-A No. 61-238501, 0.1 to 1.5 parts by weight of bismaleimide and 0.3 to 3 parts by weight of an accelerator are blended with 100 parts by weight of rubber, and sulfur is It is disclosed that a tread rubber having a specified weight ratio of tread and accelerator improves heat blowout resistance, abrasion resistance, and grip.

Attempts have also been made to improve the physical properties of rubber by incorporating into rubber compositions a resin component containing polypropylene chains as a main component. For example, JP-A-57-10632, JP-A-58-74733, and JP-A-58-16.
No. 8638 and Japanese Unexamined Patent Publication No. 59-4632 disclose a rubber composition that has a high modulus of elasticity and excellent fracture properties such as cut resistance and fracture energy by blending a resin component containing a specific polypropylene chain as a main component into a rubber composition. It is disclosed that a rubber composition is obtained.

(Problems to be solved by the invention) In recent years, the requirements for pneumatic tires for heavy vehicles, such as safety, high-speed running performance, durability, abrasion resistance, uneven wear resistance, etc., have become more and more severe. However, with the above-mentioned conventional techniques, it has become impossible to simultaneously obtain sufficiently satisfactory high-speed running performance, tread rubber durability such as rib tear resistance, abrasion resistance, and uneven wear resistance at a high level.

For example, when using a blend of butadiene rubber, there is a limit to the durability of trending rubbers such as rib tear resistance, when using a blend of styrene-butadiene rubber or when using highly reinforcing carbon black, there is a limit to high-speed running durability. There is a limit to rib tear resistance, and there is a limit to high-speed running durability when using a blend of resin components mainly composed of polypropylene chains, and these conventional technologies do not have sufficient high-speed running durability under the recent confusing tire usage conditions. , trend rubber durability such as rib tear resistance, abrasion resistance and uneven wear resistance can no longer be simultaneously obtained at a high level.

That is, an object of the present invention is to solve the above-mentioned conventional problems, and to improve the durability characteristics required of pneumatic tires for heavy vehicles when driving on good roads under recent severe tire usage conditions. The object of the present invention is to provide a rubber composition suitable for use as a tread rubber that has significantly improved properties.

(Means for Solving the Problems) The present inventors have discovered that while maintaining a high level of rubber durability and abrasion resistance such as high-speed running durability and rib tear resistance that could not be obtained with conventional rubber compositions, At the same time, as a result of intensive studies to find a method to provide a rubber composition suitable for pneumatic tire treads for heavy vehicles that has significantly improved uneven wear resistance, we found that natural rubber, isoprene-based synthetic rubber, butadiene-based rubber compositions, etc. A polyolefin resin component having a specific polyolefin chain, a specific bismaleimide compound, a specific carbon black, and sulfur are blended into raw rubber made of synthetic rubber or a combination thereof, and the blending amounts of each are within a predetermined range. The present inventors have discovered that by selecting the specified combination 1, the intended purpose as a rubber composition for pneumatic tire treads for heavy vehicles for running on good roads can be achieved, and the present invention has been completed. .

That is, if a resin component containing polypropylene chains as a main component is simply blended, cut resistance and uneven wear resistance will be improved, but there will be problems in that heat generation will increase and the high-speed running durability of the tire will be reduced. Furthermore, if a bismaleimide compound is simply added, heat resistance, heat oxidation resistance and uneven abrasion resistance are slightly improved, but there remains the problem that cut resistance is reduced.

However, it has been discovered that when a resin component having a polypropylene chain is combined with a bismaleimide compound, an unexpectedly large synergistic improvement effect on uneven wear resistance can be obtained. By taking advantage of this effect and selecting the amount of sulfur and carbon black, the desired objective can be achieved, while maintaining low heat build-up, resistance to thermal oxidative deterioration, and cut resistance. We were able to complete a rubber composition of the present invention that can significantly improve uneven wear resistance while maintaining tread rubber durability such as rib tear properties and abrasion resistance.

That is, the present invention provides a rubber having a specific surface area (NZSA value) of 110 to 160 as measured by a nitrogen adsorption method with respect to 100 parts by weight of raw rubber made of natural rubber, isoprene-based synthetic rubber, butadiene-based synthetic rubber, or a combination thereof. m”/
40 to 60 parts by weight of reinforcing carbon black within the range of
Indicates an integer of 100. ) The main components are 5-methyl-1,4-hexadiene monomer units bonded in the structure represented by Polyolefin resin 1~
15 parts by weight, and the following general formula ((■) in which Z is an alkylene group having 2 to 10 carbon atoms, a phenylene group, an alkyl-phenylene group, or a combination of two or more thereof having 2 carbon atoms) Bismaleimide compound 0 represented by ~10 divalent groups)
．． The present invention relates to a rubber composition suitable for a tread for a pneumatic tire for a heavy vehicle for running on good roads, characterized in that it contains 5 to 3 parts by weight of sulfur and 0.4 to 2 parts by weight of sulfur.

The raw material rubber used in the present invention is a sulfur-vulcanizable rubber, and specifically, natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, isoprene-isobutylene copolymer rubber, etc. Combined rubber and its halides, ethylene-propylene-diene copolymer rubber (EPDM), butadiene-propylene copolymer rubber, butadiene-ethylene copolymer rubber, butadiene-isoprene copolymer rubber, and blends thereof, etc. be. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, and blends thereof are particularly suitable because of their high versatility.

The polyolefin resin used in the present invention is
Although it can be produced by various methods, for example, 5-methyl-1,
4-Hexanene, propylene and/or ethylene, and optionally small amounts of other unsaturated monomers are supplied in suitable monomer ratios and copolymerized in the presence of a known suitable olefin polymerization catalyst. The copolymer obtained by this method can be manufactured as follows.

Specifically, as the polyolefin resin of the present invention, commercially available products ROP3D and ROP32 manufactured by Mitsubishi Yuka Co., Ltd.
1) (All are product names). Copolymers of these resins have the following properties.

As the bismaleimide compound used in the present invention,
Specifically, in the general formula (II), Z is phenylene, tolylene, xylylene, ethylphenylene, ethylmethylphenylene, isopropylphenylene, isobutylphenylene, isopropylmethylphenylene, diethylphenylene, n-propylphenylene, n-butylphenylene, tert-butylphenylene, ethylene, propylene, isopropylene, butylene, isobutylene,
Examples include compounds that are groups such as amidino, isobutylene, hexamethylene, pencumethylene, octamethylene, nonamethylene, and decamethylene.

The carbon black used in the present invention has a specific surface area (N!S^ value) of 110 =
It is a reinforcing carbon black within the range of 160 m''/g, and specific examples include carbon blacks shown in the following table.

The rubber composition of the present invention may contain various compounding agents in addition to the raw material rubber, polyolefin resin component, bismaleimide compound, reinforcing carbon black, and sulfur depending on the purpose. These various compounding agents include other types of reinforcing agents and fillers such as silica and calcium carbonate, softeners such as aroma oil, vulcanization accelerators, vulcanization accelerators, and anti-aging agents, which are commonly used in the rubber industry. The distribution used,
The mixture can be blended within the usual range of blending amounts as appropriate and necessary.

(Function) In the present invention, the polyolefin resin component contained in the rubber composition is preferably a resin in which propylene monomer units account for 50 mol% or more of the total olefin monomer units. The amount used is within the range of 1 to 15 parts by weight, preferably 3 to 9 parts by weight, per 100 parts by weight of the raw rubber. If it is less than 1 part by weight, no effect will be observed, while if it exceeds 15 parts by weight, the exothermic properties and elastic modulus will significantly increase, which is not preferable.

As the bismaleimide compound, phenylene bismaleimide, tolylene bismaleimide, ethylene bismaleimide, butylene bismaleimide, and hexamethylene bismaleimide are preferred. The amount of bismaleimide compound used is
The amount is 0.5 to 3 parts by weight per 100 parts by weight of the raw rubber, and if it is less than 0.5 parts by weight, there is almost no effect of improving uneven wear resistance, while if it exceeds 3 parts by weight, the cut resistance will decrease. , undesirable.

The blending amount of sulfur is 0.4 per 100 parts by weight of raw rubber.
-2 parts by weight; if it is less than 0.4 parts by weight, the vulcanization reaction will not proceed sufficiently, while if it exceeds 2 parts by weight, resistance to thermal oxidative deterioration will decrease, and in either case, wear resistance will decrease. Therefore, it is not desirable.

The blending ratio of the bismaleimide compound to sulfur is preferably 1 to 4 (weight ratio), more preferably 1.5 to 4.
It is 3.

The amount of carbon black to be used is 40 to 60 parts by weight per 100 parts by weight of the raw material rubber; if it is less than 40 parts by weight, the reinforcing effect is insufficient, and if it exceeds 60 parts by weight, there are disadvantages such as increased heat generation. occurs.

(Examples) Hereinafter, the rubber composition for tires according to the present invention will be explained in more detail with reference to Examples and Comparative Examples.

A 1000R20 pneumatic radial tire for trucks and buses was manufactured using the rubber compositions obtained with the formulations shown in the Examples and Comparative Examples as a tread, and this tire was mounted on the front wheels of a truck to determine the total mileage. After the vehicle was driven 80,000 times on a paved road with many curves, including approximately 10% unpaved roads, the wear resistance and uneven wear resistance of these running tires were evaluated. For abrasion resistance, the depth of the remaining groove in the tire pattern after running was measured at 20 points as above, and the average value was expressed as an index for each rubber composition. The larger the index value, the better the wear resistance. The uneven wear resistance was similarly measured by visually inspecting the tread surface after running, using the measurement points at areas with a large degree of wear on the circumference, and using the maximum level difference on the surface as a measure of uneven wear resistance, and displaying it as an index for each rubber composition. .

The larger the index value, the better the uneven wear resistance.

(2) Provisional subject matter Low heat generation was evaluated as a measure of high-speed running durability.

The low heat build-up of the rubber composition was evaluated by the rebound modulus (%) measured using a Dunlop resilience tester and expressed as an index. The larger the index value, the better the low heat generation property.

(3) Heat oxidation deterioration resistance was evaluated as a measure of rubber durability, such as resistance to dullness and rib tearing. The thermal oxidative deterioration resistance of the rubber composition is
Based on the "progressive aging test" described in JIS-6301,
After thermal oxidative deterioration treatment for 124 hours at 100'C in air, the fracture energy measured in a tensile test at 100'C was evaluated and expressed as an index.The larger the index value, the better the thermal oxidative deterioration resistance. shows.

(4) The tread performance of Sarasho Tires is greatly influenced by the modulus of elasticity. The elastic modulus of the rubber composition was evaluated based on the elastic modulus measured as the tensile stress at 300% elongation in accordance with "Tensile strength/elongation" described in JIS-6301, and expressed as an index. The larger the index value, the higher the elastic modulus.

-・111~3, 7111~6 100 parts by weight of natural rubber, N220 carbon black (^
N2SAAl2 measured according to STM-D3037
O2 m"/g) 50 parts by weight, 2 parts by weight of stearic acid, 1 part by weight of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, 4 parts by weight of zinc white.
Various rubber compositions were prepared by combining 0.9 parts by weight of N-oxydiethylene-2-benzothiazolesulfenamide with the compounding agents shown in Table 1 below and kneading them in a Banbury mixer.

In addition, ROP3D (product name) manufactured by Mitsubishi Yuka Co., Ltd.
was used as the olefin resin of the present invention.

The obtained rubber composition was evaluated for its abrasion resistance and uneven abrasion resistance using a tire, and its elastic modulus, low heat generation property, and thermal oxidation resistance were evaluated using a slab sheet. The obtained results are also listed in Table 1.

In addition, the abbreviations of compounding agents, etc. in Table 1 shall indicate the following contents.

phr: Part by weight based on 100 parts by weight of rubber S: Sulfur PBM: N, N'-m-phenylene bismaleimide HBM: N, N'-hexamethylene bismaleimide TBM: N, N'-) rylene bismaleimide PP
: rROP3D J propylene resin oil manufactured by Mitsubishi Yuka Co., Ltd. Aromatic oil 4 f-7~8 Styrene-butadiene rubber (5BR1500 (trade name) manufactured by Japan Synthetic Rubber Co., Ltd.) 45 parts by weight, natural 5 rubber 5
5 parts by weight, N220 carbon black (N22SAAl
2O2m"/g) 50 parts by weight, 2 parts by weight of stearic acid, 1 part by weight of N-(1,3-dimethylbutyl)-N'-phenyl-P-phenylenediamine, 4 parts by weight of zinc white, N-oxy Various rubber compositions were prepared by combining 1.2 parts by weight of diethylene-2-benzothiazolesulfenamide with the compounding agents shown in Table 2 below and kneading the mixture in a Banbury mixer.

Table 2 shows the results of evaluation of the obtained rubber composition.

Table 2 As is clear from Tables 1 and 2 above, the rubber composition of the present invention has excellent rubber durability such as high-speed running durability (low heat generation) and rib tear resistance (heat oxidation resistance). While ensuring this, wear resistance, especially uneven wear resistance, has been improved.

(Effects of the Invention) As detailed above, the rubber composition of the present invention is suitable for improving the wear resistance, particularly the uneven wear resistance, of pneumatic tire treads for heavy vehicles such as buses and trucks that run on good roads. However, it can also be applied to the treads of other types of pneumatic tires, as well as industrial products that require wear resistance.

Claims (1)

[Claims] 1. Specific surface area (N_
2SA value) is in the range of 110 to 160 m^2/g and 40 to 60 parts by weight of reinforcing carbon black, and the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (I) (In the formula (I) R is a hydrogen atom or a methyl group, m is 5
Indicates an integer between ~100. ) The main components are 5-methyl-1,4-hexadiene monomer units bonded in the structure represented by Polyolefin resin 1~
15 parts by weight and the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (II) (Z in formula (II) is an alkylene group, phenylene group, alkyl-phenylene group having 2 to 10 carbon atoms, or Bismaleimide compound 0 represented by (represents a divalent group having 2 to 10 carbon atoms, which is a combination of two or more of them)
．． A rubber composition comprising 5 to 3 parts by weight of sulfur and 0.4 to 2 parts by weight of sulfur.