JPH1135735A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the processibility of a rubber compsn. by a softening effect and to thereby obtain a rubber compsn. having an excellent tan δ balance and an improved abrasion resistance by compounding a diene rubber with a reinforcement and a specified amt. of an acid anhydride-modified polybutene obtd. by modifying an alkenyl-contg. polybutene with an acid anhydride. SOLUTION: A diene rubber of 100 pts.wt. is compounded with at least 20 pts.wt. reinforcement and 3-80 pts.wt. acid anhydride-modified polybutene obtd. by modifying an alkenyl-contg polybutene contg. 50 mol.% or higher polyisobutylene with an acid anhydride. An acid anhydride-modified polybutene mainly comprising a maleic anhydride-modified polyisobutylene typically represented by formulas I to IV (wherein R is a 4C hydrocarbon distillate; and (n) is 1-100) is used. Thus obtd. rubber compsn. is suitable for tire treads.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition,
More specifically, the present invention relates to a rubber composition having a softening effect, having an excellent tan δ balance and improved wear resistance, and particularly useful as a tire tread for a pneumatic tire.

[0002]

2. Description of the Related Art Conventionally, various developments have been made as rubber compositions for pneumatic tires, particularly for tire treads. Under such circumstances, a compounding method of adding an oil such as an aroma type at the time of rubber mixing is used for the purpose of cost reduction, improvement of processability (reduction of viscosity of a compound), improvement of physical properties (reduction of modulus, improvement of elongation), and the like. Are known. However, the addition of oil has problems such as that the compounded oil component is easily extracted from the vulcanized product and the properties of the vulcanized rubber (for example, tan δ balance and abrasion resistance) are reduced.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems in the conventional oil compounding, to improve workability by a softening effect, and to improve tan δ.
An object of the present invention is to provide a rubber composition having an excellent balance and improved abrasion resistance.

[0004]

According to the present invention, 100 parts by weight of at least one kind of diene-based raw rubber, 20 parts by weight or more of at least one kind of reinforcing agent, and 5 parts by weight of polyisobutylene are used.
Acid anhydride-modified polybutenes 3 to 8 obtained by modifying an alkenyl group-containing polybutene containing at least 0 mol% with an acid anhydride.
A rubber composition comprising 0 parts by weight is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition according to the present invention is a rubber composition suitable for use in tire treads comprising a diene rubber, a rubber reinforcing agent and an anhydride-modified polybutene as essential components. .

[0006] Examples of the rubber compounded in the rubber composition according to the present invention include diene rubbers generally compounded in rubber compositions, particularly rubber compositions for tires. Specifically, for example, natural rubber (NR),
Various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), polyisoprene rubbers (I
R), butyl rubber (IIR), acrylonitrile butadiene rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, etc., which can be used alone or in any desired form. It can be used as a blend.

[0007] The rubber composition of the present invention contains, as a rubber reinforcing agent, any carbon black and / or silica that is usually added to the rubber composition. Such silica is not particularly limited, such as wet silica, dry silica, or surface-treated silica, and any silica having silanol groups remaining can be used. Carbon black surface-treated with silica can also be used. The rubber reinforcing agent is used in an amount of 20 parts by weight or more, preferably 20 to 120 parts by weight, more preferably 40 to 100 parts by weight, based on 100 parts by weight of rubber. Silica can also be used as a rubber reinforcing agent.

The carbon black used in the present invention has a nitrogen adsorption specific surface area (N ₂ SA) of 10 to 200.
(M ² / g), dibutyl phthalate oil absorption (DBP)
Is preferably 50 to 200 (cc / 100 g),
More preferably, the N ₂ SA is 130 to 200 (m ² / g).
And DBP is 100 to 150 (cc / 100 g). The silica preferably has a specific surface area of 80 to 330 (m ² / g) and a DBP of 110 to 300 (cc / 100 g),
More preferably, the specific surface area is 150 to 250 (m ² /
g), DBP is 180-250 (cc / 100g).

The polybutene modified with maleic anhydride used in the present invention comprises polyisobutylene in an amount of 50 mol%.
The polybutene having an alkenyl group, which includes the above, is typically polyisobutylene and / or a polymer containing the same as a main component. Such polybutene is a C ₄ cut obtained in the petrochemical field (usually about 90% of isobutylene and the balance of 1,4).
In the present invention, polybutene obtained by polymerizing 2-butene, 2,3-butene, etc.) can be used as it is for maleic anhydride modification.

In the present invention, the acid anhydride-modified polybutene is compounded in an amount of 3 to 80 parts by weight, preferably 10 to 50 parts by weight, more preferably 15 to 40 parts by weight, per 100 parts by weight of rubber. If the compounding amount is too small, the softening effect is not remarkably exhibited, so that it is not preferable. On the other hand, if it is too large, kneading time is required at the time of processing, and the roll separation is deteriorated.

As described above, the rubber composition of the present invention is blended with an acid anhydride-modified polybutene containing at least 50 mol% of polyisobutylene and having an alkenyl group modified with an acid anhydride at the time of mixing the rubber. Typically, formula (I)
To (IV) maleic anhydride-modified polyisobutylene (existing chemical substance name: polybutene average molecular weight 200 to 20)
000) as the main component.

[0012]

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Here, polybutene means isobutylene, 1,2-butene, 2,3-butene obtained by naphtha decomposition or the like.
A liquid polymer obtained by polymerizing a C ₄ hydrocarbon fraction containing butene and the like in the presence of a Friedel-Crafts catalyst such as aluminum chloride, which is obtained by substantially hydrogenating the double bonds in polybutene Can also be used. -CH ₂ -C R in the formula (CH _{3) 2} - it was mainly a small amount of -CH ₂
-CH (C ₂ H ₅₎ - or _{-CH (CH 3) -CH (CH} 3) - , and the like.

The introduction of the maleic anhydride units of the formulas (I) to (IV) is carried out in a conventional manner, for example, by the Ene reaction, the terminal olefin reacts with maleic anhydride under heating and stirring conditions to give polyisobutylene. Can be introduced. By mixing the acid anhydride-modified polybutene thus obtained, the maleic anhydride unit reacts with, for example, a hydroxyl group or a carbonyl group on the carbon black and binds to the carbon black. On the other hand, the isobutylene unit is compatible with the diene polymer to exhibit a softening effect,
Improves nδ balance and wear resistance. If the amount of the acid anhydride-modified polybutene is too small, the softening effect is not exhibited, which is not preferable. On the other hand, if the amount is too large, there is a problem that the mixing property and the roll processability are deteriorated and tack is left on the vulcanized rubber.

When silica is compounded in the rubber composition according to the present invention, for example, 5 to 30% by weight of a silane coupling agent with respect to the silica compounding amount may be compounded as in the conventional case. In this case, furthermore, in this case, the silanol condensation catalyst may be used in an amount of 0.05 to less than the compounding amount of the silane coupling agent.
50% by weight can be blended. The silane coupling agent used in the silica-containing rubber composition according to the present invention can be any silane coupling agent conventionally used in combination as a silica filler, and as a typical example,
For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, N- (2-aminoethyl) 3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) 3-aminopropyltrisilane Methoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl)
Ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, bis- [3- (triethoxysilyl) -propyl]
Tetrasulfide and the like can be mentioned. Of these, bis- [3- (triethoxysilyl) -propyl]
Tetrasulfide is most preferred in terms of processability.

[0016] The rubber composition according to the present invention may further contain ordinary vulcanizing or crosslinking agents, vulcanizing or crosslinking accelerators, various oils, antioxidants, fillers, plasticizers, softeners, and other general rubbers. Various additives generally compounded for can be compounded, such a compound is kneaded by a general method,
The composition can be vulcanized and vulcanized or crosslinked. The amounts of these additives may be conventional general amounts as long as they do not contradict the purpose of the present invention.

[0017]

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

The following commercially available products were used for the components shown in Table I used in the following Examples and Comparative Examples. The method for measuring physical properties is also shown below.

BR: Nipol BR1220 (manufactured by Nippon Zeon) IR: Nipol IR2200 (manufactured by Zeon) Carbon black: HAF-HS Show Black N3
39 (manufactured by Showa Cabot) Silica: Nip Seal AQ (manufactured by Nippon Silica Kogyo Co., Ltd.) Silane coupling agent: Si69 (manufactured by DEGUSSA) Zinc flower: Ginmine zinc flower R (manufactured by Toho Zinc) Stearic acid: beads stearic acid Tung (manufactured by Nippon Oil & Fats) Anti-aging agent: Vulkanox 4020 (manufactured by Bayer) Sulfur: oil-treated sulfur (manufactured by Karuizawa Refinery) Vulcanization accelerator: Noxeller CZ-G (manufactured by Ouchi Shinko Chemical) Aroma oil: Desolex No. 3 (manufactured by Showa Shell Sekiyu) Polybutene : Nisseki polybutene HV-1900 (molecular weight 2)
900) Commercial polymer in which n-butene is partially copolymerized with polyisobutylene (manufactured by Nippon Oil Co., Ltd.) Maleic anhydride-modified polybutene: Prototype of Nisseki Chemical Co., Ltd. (manufactured by reaction of exomethylene polybutene with maleic anhydride) (Molecular weight 3000)

Measurement of physical properties Mooney viscosity: ML1 + 4, temperature 100 ° C., rotor L, 10 kg / cm M50: 50% modulus tan δ (0 ° C.) when pulling a No. 3 dumbbell at a tensile speed of 500 mm / min: 20 Hz, 10 ± 2% Stretching, 0 ° C. tan δ tan δ at 60 mm sample width (60 ° C.): 20 Hz, 10 ± 2% stretching, 60 ° C. tan δ tan δ balance at (sample width 5 mm): 0 ° C. tan δ value / 60 ° C. tan δ value Wear resistance ( (Index): Duplicate Lambourn test (slip ratio 2)
5%, load 5 kg, time 4 minutes, room temperature RT, using K-80 grindstone). In addition, the result was shown as an index with the value of Comparative Example 1 being 100. The larger the value, the better the wear resistance.

Preparation of Examples 1 to 5 and Comparative Examples 1 to 5 Among the formulations shown in Table I, the components excluding the vulcanization accelerator and sulfur were kneaded for 3 to 5 minutes in a 1.8 liter hermetic mixer. ,
The vulcanization accelerator and sulfur are kneaded with an 8-inch open roll into the master batch released when the temperature reaches 165 ± 5 ° C.
A rubber composition was obtained. The unvulcanized physical properties (Mooney viscosity) of the obtained rubber composition were measured. The results are shown in Table I.

Next, the composition was placed in a size of 15 × 15 × 0.2 cm.
A test specimen (rubber sheet) was prepared by press vulcanization at 160 ° C. for 20 minutes in a mold of No. 1, and the vulcanization physical properties 50% modulus, tan δ (0 ° C. and 60 ° C.) and abrasion resistance were evaluated. . The results are shown in Table I.

[0023]

[Table 1]

As is evident from the results in Table I, the rubber compositions of Examples 1 to 5 satisfying all the requirements specified in the present invention are compared with Comparative Examples 1 and 2 which do not contain maleic anhydride-modified polybutene. , Tan δ and abrasion resistance are improved. Comparative Example 4 also shows that a normal aroma oil softener reduces the balance of tan δ. Comparative Example 4 shows that the addition of ordinary polybutene was t
It shows that the balance of an δ and the wear resistance are reduced. In Comparative Example 5, 9 parts of maleic anhydride-modified polybutene were used.
This shows that the balance of tan δ and the abrasion resistance are reduced although the addition is as large as 0 parts by weight.

[0025]

As described above, according to the present invention, by mixing an acid anhydride-modified polybutene with a diene rubber,
The rubber compound is softened to improve processability, and
Since the nδ balance (that is, the grip performance of the tire when used as a tire tread material) is improved and the abrasion resistance is also improved, it is particularly useful as a rubber composition for a pneumatic tire.

Claims (3)

[Claims] 1. At least one kind of diene raw rubber 10
0 parts by weight, at least 20 parts by weight of at least one kind of reinforcing agent and at least 50 mol% of polyisobutylene, and 3 to 80 parts by weight of an acid anhydride-modified polybutene obtained by modifying polybutene having an alkenyl group with an acid anhydride. A rubber composition comprising: 2. An acid anhydride-modified polybutene having the formula (I)
At least one selected from (IV): The rubber composition according to claim 1, which comprises a maleic anhydride-modified polybutene as a main component. 3. A rubber composition for a pneumatic tire obtained by using the rubber composition according to claim 1 or 2.