JPH11255962A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for tire, capable of suppressing the increase of viscosity at a mastication step of the rubber composition, excellent in mixing and kneading processability, having an improved temperature dependence of tan δ and further having a good abrasion resistance. SOLUTION: This rubber composition for tire is obtained by mixing and kneading 30-85 pts.wt. rubber component comprising a dienic rubber having (-120)-(-20) deg.C glass transition temperature (Tg), (b) 20-100 pts.wt. reinforcing filler and (c) 0.1-10 pts.wt. at least one kind of a compound having a radical selected from a nitroxyl radical, a hydrazyl radical and an allyloxyl radical and stably present at a room temperature in the presence of oxygen, and further mixing and kneading the mixed and kneaded product with (d) a dienic rubber having the glass transition temperature 5 deg.C higher than that of the before dienic rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a tire, and more particularly to a rubber composition having excellent kneading processability and improved temperature dependency of tan δ (tan δ value at 0 ° C. is relatively high, tan δ at 60 ° C.). Is relatively low) and also has good abrasion resistance.

[0002]

2. Description of the Related Art Various attempts have been made to improve the workability in tire manufacturing processes and the characteristics of tire products in tire rubber compositions. Among them, it is desired to reduce the viscosity of the rubber polymer in the mastication stage and solve the problem of poor dispersion of the intermediate mixture in the kneading stage due to the increase in viscosity.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress the increase in viscosity of a rubber composition during the mastication stage, solve the problem of poor dispersion of the compound at the kneading stage, and improve the kneading processability. It is an object of the present invention to provide a rubber composition for a tire which is excellent in tan δ, improves the temperature dependency of tan δ, and has good abrasion resistance.

[0004]

According to the present invention, (a)
30-85 parts by weight of a rubber component comprising a diene rubber having a glass transition temperature (Tg) of -120 ° C to -20 ° C,
(B) 20 to 100 parts by weight of a reinforcing filler and (c) at least one radical selected from nitroxyl radical, hydrazyl radical, allyloxyl radical and trityl radical, which is stably present at room temperature in the presence of oxygen. 0.1 to 10 parts by weight of a compound having the following formula: and then (d) a rubber for tires obtained by kneading (d) a diene rubber having a glass transition temperature (Tg) higher than that of the diene rubber by 5 ° C. or more. A composition is provided.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a rubber composition is first compounded with a diene rubber having a low glass transition temperature (Tg) and a reinforcing filler such as carbon black. The compound may be mixed with a diene rubber having a Tg higher than that of the diene rubber by 5 ° C. or more to prepare a rubber composition. In the first kneading step, nitroxyl radicals and hydra By compounding a compound having a stable radical at room temperature, such as a zyl radical, an allyloxyl radical, and / or a trityl radical, the viscosity of the intermediate product in the kneading intermediate stage is reduced, and the dispersion of the compounding components in the next kneading stage is poor. Can be solved. According to the estimations of the present inventors, it is considered that the compound having a stable radical at room temperature binds to the cut end of the polymer chain generated during rubber kneading and prevents recombination. Is shown. In order to obtain this effect, it is preferable that the compound having a radical stable at room temperature does not have a functional group that binds to a reinforcing filler such as carbon black or other components.

The rubber composition according to the present invention is blended as a first rubber component with a diene rubber having a Tg of -120 ° C to -20 ° C, preferably -100 ° C to -20 ° C, such as natural rubber (NR). ), Polyisoprene rubber (IR), various styrene-butanediene copolymer rubbers (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), etc. The diene rubber generally compounded in the composition can be used alone or as an arbitrary blend. Tg of this diene rubber is -120 ° C
If it is lower than -20 ° C, on the contrary, if it exceeds -20 ° C, it is not preferable because sufficient low-temperature flexibility as a compound for tires after kneading with high Tg rubber cannot be secured.

The rubber component of the present invention contains -C (= M) in the molecule.
-N = may be used. For example, rubber and-
The compound is reacted with a compound having a C (= M) -N = bond (where M represents an oxygen or sulfur atom) (hereinafter, sometimes referred to as a reactant). Examples of such compounds include N, N
Amides such as -diethylformamide, N, N-dimethylacetamide, N, N-dimethylbenzamide;
Ureas such as N, N'-dimethylurea, N, N'-dimethylethyleneurea, ε-caprolactam, N-methyl-
ε-caprolactam, N-methyl-2-pyrrolidone, N-
Lactams such as vinyl-2-pyrrolidone;
The compounds disclosed in JP-A-61-268702, such as the compounds disclosed in 1-1103904, 1,3-dimethyl-2-imidazolidinone, and 1,3-dimethylethylenethiourea, may be mentioned.

Examples of the reinforcing agent to be added to the rubber composition according to the present invention include, for example, carbon black, silica (or white carbon) and the like which have been generally added to rubber compositions for tires. The carbon black used in the rubber composition according to the present invention is not particularly limited, but preferably has a nitrogen specific surface area (N ₂ SA) of 2 or more.
0-200 m ² / g, DBP oil absorption 60-130 ml /
100 g. The silica used in the rubber composition according to the present invention is not particularly limited, but among silica (or white carbon) generally used for rubber compounding, preferably, N ₂ SA is 80 to 300 m ² /
g, DBP oil absorption is 100 to 300 ml / 100 g.

The rubber composition according to the present invention contains a compound containing a radical of a nitroxyl radical, a hydrazyl radical, an allyloxyl radical and / or a trityl radical, which is stably present at room temperature in the presence of oxygen at room temperature. I do. The following compounds that can be used in the present invention can be exemplified as compounds containing in their molecules radicals that are stably present at room temperature.

[0010]

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[0011]

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[0012]

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[0013]

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[0014]

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[0015]

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In the rubber composition according to the present invention, a diene rubber having a Tg higher than that of the diene rubber which is the first rubber component by 5 ° C. or more is blended as a second rubber component.
Except for Tg, the types of diene rubbers include those exemplified as the first rubber component. In an actual compounding, the first rubber component and the second rubber component satisfy the above conditions. As long as they are the same or different, they may be different. The first and second rubber components may be compatible or incompatible, but are more preferably incompatible rubber components.

As described above, the rubber composition for a tire according to the present invention comprises (a) a first rubber component (diene rubber) having a Tg of -120 ° C to -20 ° C, (b) a reinforcing filler, (C)
A compound having a specific room-temperature stable radical and (d)
Tg contains a second rubber component (diene rubber) as an essential component by 5 ° C. or more higher than the first rubber component, and the compounding amounts of the components (a), (b), (c) and (d) are as follows: (A) 30 to 85 parts by weight (preferably 35 to 75 parts by weight), and (b) 20 to 100 parts by weight (preferably 30 to 75 parts by weight).
95 parts by weight), (c) 0.1 to 10 parts by weight (preferably 0.5 to 5 parts by weight) and (d) preferably 15 to 70 parts by weight (more preferably 25 to 65 parts by weight). If the compounding amount of the component (c) having a stable radical at room temperature is too small, the desired effect cannot be obtained. On the other hand, if the compounding amount is too large, the necessary reinforcing properties of the rubber composition cannot be obtained, which is not preferable. .

In the rubber composition according to the present invention, in addition to the above-mentioned essential components, vulcanizing or cross-linking agents, vulcanizing or cross-linking accelerators, various oils, anti-aging agents, plasticizers, etc. Various additives generally compounded for rubber can be compounded, and such compounds can be kneaded and vulcanized into a composition by a general method, and used for vulcanization or crosslinking. it can. The compounding amounts of these additives can also be conventional general compounding amounts as long as they do not contradict the object of the present invention.

The compounding method of the rubber composition according to the present invention can be the same as the conventional method except that the second rubber component of the component (d) is kneaded in the second stage. However, a specific example will be described below.

[0020]

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

Examples 1 to 8 and Comparative Examples 1 to 6 1) Sample preparation In the formulations shown in Tables I and II, each component of rubber 1, compounding agent 1 and compounding agent 2 was mixed in a 1.4-liter closed mixer. The mixture was kneaded for 3 minutes and released when the temperature reached 150 ° C., thus completing the first mixing step. Next, the compound was cooled down to room temperature, then compounded with rubber 2 and kneaded for 2 minutes in the same manner. When the temperature reached 150 ° C., the compound was released, and the vulcanization system shown in Tables I and II (vulcanization acceleration) And sulfur) were kneaded with an open roll of 5 inches to obtain a rubber composition. The unvulcanized physical properties of the obtained rubber composition were measured. Next, this composition was press-vulcanized in a mold of 15 × 15 × 0.2 cm at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization properties were evaluated.

[0022]

[Table 1]

Table I Footnote a) Emulsion polymerization SBR (styrene content 23.5%, no oil extension): Nipol 1502 (manufactured by Nippon Zeon Co., Ltd.)
Tg = −52 ° C. b) Emulsion polymerization SBR (styrene content 23.5%, oil extension =
20 phr) Tg = -52 ° C c) Solution polymerization SBR (styrene content 15%, no oil extension):
Nipol NS112 (manufactured by Zeon Corporation) Tg
D) Emulsion polymerization SBR (styrene content 45%, oil extension = 50)
%): Nipol 9529 (manufactured by Zeon Corporation)
Tg = −20 ° C. e) Zinc-2-banzamidothiophe
mixture of nate, metal chelate compound carrier, etc .: Noctizer SZK (manufactured by Ouchi Shinko Chemical Co., Ltd.) f) TEMPO (molecular weight: 155) g) OH-TEMPO (molecular weight: 171) h) STE-TEMPO (molecular weight: 452) i) MDI- TEMPO (molecular weight 290) j) N339: Show Black N339 (manufactured by Showa Cabot Co., Ltd.) k) Nocrack 6C (manufactured by Ouchi Shinko Chemical Co., Ltd.) 1) Noxera NS-F (manufactured by Ouchi Shinko Chemical Co., Ltd.) 1) , 3) The blending amount (phr) is expressed as a pure rubber content excluding the oil extension. The oil extension was summed and displayed in the column of aroma oil. 2) The stable radical compound is 0.0
05 mol was blended.

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

2) Test Methods for Physical Properties The test methods for unvulcanized physical properties and vulcanized physical properties of the compositions obtained in the respective examples are as follows. Unvulcanized properties 1) Mooney viscosity: 10 based on JIS K 6300
It was measured at 0 ° C. Vulcanization properties 1) tan δ: Using a viscoelastic spectrometer (manufactured by Toyo Seiki Co., Ltd.) at a temperature of 0 ° C. and 60 ° C., respectively.
These values are measured under the conditions of an initial strain of 10%, a dynamic strain of ± 20%, and a frequency of 20 Hz. Tan δ at 0 ° C is a measure of grip on wet roads and tan δ at 60 ° C is a measure of grip on dry roads. In any case, the larger the tan δ value, the greater the grip force of the tire.

3) Abrasion resistance : Wear loss was measured at a temperature of 20 ° C. using a Lambourn type abrasion tester (manufactured by Iwamoto Seisakusho), and the wear loss was indicated as an index. Abrasion resistance (index) = [(weight loss of standard example) / (weight loss of sample)] × 100 (Note) The larger the index, the better the wear resistance.

4) Stable radical compound : The structure of the stable radical compound used in the rubber composition is as follows.

[0030]

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5) Evaluation Results (i) Results of Examples 1 to 4 and Comparative Examples 1 and 2 In Comparative Example 1, the first and second rubber components were kneaded together with carbon black without adding a stable radical compound. Example. Comparative Example 2 is an example in which the first rubber component was kneaded at the same time as carbon black without adding a stable radical compound, and then the second rubber component was kneaded. Examples 1 to 4 are examples in which a stable radical compound was added using the same kneading method as in Comparative Example 2. As is clear from these, Examples 1 to
No. 4 has a low Mooney viscosity after the end of the first mixing step and realizes a reduction in tan δ at 60 ° C.

(Ii) Results of Examples 5 to 6 and Comparative Examples 3 to 5 Comparative Examples 3, 4, and 5 and Examples 5 and 6 are examples in which experiments were performed using SBR-2. Comparative Example 3 is an example in which a stable radical compound was not added, and Comparative Examples 4 and 5 are examples in which a commercially available mastication accelerator was used. These results also show that the rubber composition of the present invention achieves excellent tan δ temperature dependency and processability (low Mooney viscosity).

(Iii) Results of Examples 7 and 8 and Comparative Example 6 Comparative Example 6, Examples 7 and 8 are examples using SBR-3 in the same manner. Again, it can be seen that the rubber composition of the present invention is superior to the comparative example in that it has both excellent tan δ temperature dependency and processability.

[0034]

As described above, in the present invention, a compound containing a stable radical at room temperature in the presence of specific oxygen is compounded in the rubber composition, so that the viscosity increase of the compound in the mastication step can be suppressed. In addition, a rubber composition for a tire having improved dispersibility in the next kneading step, excellent kneading processability, and good abrasion resistance can be obtained, and the tan δ temperature dependency (0
° C, 60 ° C) are not affected or improved.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fumi Yayanagi 2-1 Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory

Claims (4)

[Claims] (A) The glass transition temperature (Tg) is -12.
30 to 85 parts by weight of a rubber component containing a diene rubber having a temperature of 0 ° C to -20 ° C, and (b) a reinforcing filler of 20 to 100
0.1 to 10 parts by weight of (c) a compound having at least one kind selected from a nitroxyl radical, a hydrazyl radical, an allyloxyl radical and a trityl radical, which is stably present at room temperature in the presence of oxygen. , And (d) a diene rubber having a glass transition temperature (Tg) higher than that of the diene rubber by 5 ° C. or more. (A) a glass transition temperature (Tg) of -12;
30 to 85 parts by weight of a rubber component containing a diene rubber at 0 ° C to -20 ° C and (b) a reinforcing filler 20 to 1
2. The rubber composition according to claim 1, wherein 00 parts by weight are made into a wet master batch. 3. The glass transition temperature (Tg) is -12.
Rubber component 3 consisting of diene rubber at 0 ° C to -20 ° C
0 to 85 parts by weight, (b) 20 to 100 parts by weight of a reinforcing filler, and (c) at least one kind selected from a nitroxyl radical, a hydrazyl radical, an allyloxyl radical and a trityl radical. The rubber composition according to claim 1, wherein 0.1 to 10 parts by weight of a compound having a radical that is stably present in the form of a wet master batch. 4. (a) 30-85 parts by weight of a rubber component composed of a diene rubber having a Tg of -120 ° C. to −20 ° C. has —C (＝ M) —N = bond (where M The rubber composition according to claim 1, 2 or 3, further comprising a rubber component reacted with a compound having an oxygen or sulfur atom.