JP2000212329A - Rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition useful as rubber for a pneumatic tire or the like by adding an organic compound including a specified radical and so preventing viscosity rise in e.g. storage time and improving abrasion resistance after vulcanization. SOLUTION: This composition is obtained by adding an organic compound including at least one free radical of formula I or formula II in a mixing step after a compounding and mixing step of at least one compounding agent except vulcanizing agents wherein the free radical is stably existing at room temperature in the presence of oxygen. It is preferable that the raw material rubber is at least a kind of diene-based one, the radical sealing compound is selected from a group of a nitroxy radical, a hydroxyl radical, an allyloxy radical, a trityl radical and their analogs and the blending quantity is 0.01-10 pts.wt. based on 100 pts.wt. diene-based raw material rubber.

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 which prevents an increase in viscosity during storage of an unvulcanized rubber and has improved abrasion resistance.

[0002]

2. Description of the Related Art Various attempts have been made to improve the processability of rubber compositions, particularly rubber compositions for pneumatic tires, and the characteristics of products such as tires. There is a need for improved rubber compositions. Among them, there is a problem that the viscosity of the unvulcanized rubber composition after kneading increases during storage, for example. In mixing the rubber, a peptizer (peptizer) etc. is added to accelerate the plasticization of the raw unvulcanized rubber and accelerate the reduction of the viscosity of the rubber to shorten the mastication work time. There is the problem of increasing the viscosity of the rubber during the storage of the obtained unvulcanized rubber. Therefore, when the kneaded unvulcanized rubber is subjected to processing such as rolling, the viscosity of the rubber is high, so that it is necessary to knead the rubber again to reduce the viscosity.

[0003] A rubber composition in which a diene raw rubber is compounded with a reinforcing agent and a compound containing a nitroxide radical, a hydrazyl radical, an allyloxyl radical and / or a trityl radical and stably existing at room temperature and in the presence of oxygen. Is described in Japanese Patent Application Laid-Open No. 10-182881, which is characterized in that the above compound is added together with the raw rubber to provide excellent workability, an excellent balance of high grip / low heat generation, and an improvement in wear resistance. There is no description of blending the radical-containing compound in a masterbatch at or after the mastication and mixing stage of the raw rubber.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent an increase in the viscosity of an unvulcanized rubber composition during the storage period, which is a problem of the above-mentioned prior art, and to further improve the resistance to vulcanization after vulcanization. An object of the present invention is to provide a rubber composition having improved abrasion properties.

[0005]

According to the present invention, formulas (I) and (II) which are stably present in rubber at ordinary temperature and in the presence of oxygen:

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[0006]

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[0007] A rubber composition characterized by adding at least one radical-containing compound containing free radicals in a mixing step after the step of compounding and mixing at least one compounding agent other than the vulcanizing compounding agent. Provided.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted studies to solve the above-mentioned problems of the prior art, and as a result, more specific examples including free radicals represented by the above formulas (I) and (II) have been described. A mixing step after compounding a compounding agent other than a vulcanizing compounding compound with at least one compound selected from the group consisting of a nitroxy radical, a hydrazyl radical, an allyloxyl radical, a trityl radical and analogs thereof. By adding to the mixture, it is possible to trap radicals remaining after the completion of kneading, prevent the viscosity of the rubber from increasing during the storage period of the unvulcanized rubber composition, and also trap the radicals generated when the rubber product is worn. I found that I can do it.

The rubber compounded in the rubber composition according to the present invention can be any rubber conventionally compounded generally in various rubber compositions, especially a diene rubber, for example, natural rubber (NR) Diene rubbers such as polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR) alone or It can be used as any blend.

Examples of the compounding agents other than the vulcanizing compound such as the vulcanizing agent and the vulcanization accelerator of the present invention include various compounding agents generally compounded for rubber.
Mention may be made of peptizers, softeners, antioxidants, plasticizers, lubricants, fillers and the like.

[0011] Examples of the reinforcing agent include carbon black and silica. From the viewpoint of reinforcing properties, preferably 40 parts by weight or more, more preferably 50 to 120 parts by weight, based on 100 parts by weight of the diene rubber. Is done.

As a peptizing agent, aromatic mercaptan compounds, disulfide compounds and zinc salts thereof,
Organic peroxides, nitro compounds, nitroso compounds and the like can be preferably mentioned, and the compounding amount is preferably 0.01 to 5 parts by weight based on 100 parts by weight of rubber. If the amount is too small, the desired effect may not be obtained. If the amount is too large, the mechanical properties deteriorate.

The radical compound used in the present invention is preferably used in an amount of 0.01 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, per 100 parts by weight of the diene raw rubber. If the amount is too small, the desired effect may not be obtained. Conversely, if the amount is too large, there is a possibility that the reinforcing property and other aspects may be adversely affected.

Examples of the compound containing a radical stably present at room temperature and in the presence of oxygen in the molecule of the above formula (I) and / or (II) which can be used in the present invention include, for example, the following compounds. be able to.

[0015]

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[0016]

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(In the above formulas (1) to (6), R represents C ₁ to C which may include O, N, S, P, Cl, Br, l)
A C ₃₀ hydrocarbon group is shown. )

[0018]

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[0019]

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Other examples are as follows.

[0021]

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[0022]

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Hydrazyl radical

[0024]

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Allyloxy radical

[0026]

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Trityl radical

[0028]

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[0029]

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. Preparation of Samples of Standard Example 1, Examples 1-2 and Comparative Examples 1-4 Rubber compositions were prepared based on the formulations (parts by weight) shown in Table I. In the first step, the components shown in the first step are kneaded for 3 to 5 minutes with a 1.5-liter closed mixer, and the contents are discharged when the temperature of the contents reaches 165 ± 5 ° C. (NP1) was obtained.

Next, in the second step, the master batch NP1 obtained in the first step is kneaded together with the stable radical compound in Examples 1 and 2 in the same closed mixer for 3 to 5 minutes. When the temperature reached 165 ± 5 ° C., the contents were released to obtain a master batch (NP2). (note:
The second step was performed also in Examples 1 and 2. )

Finally, in the third step, the master batch NP2 obtained in the second step and the vulcanization system (sulfur and vulcanization accelerator) are kneaded with an 8-inch open roll for 2 to 4 minutes to obtain each rubber composition. Was.

[0032]

[Table 1]

Evaluation of physical properties The obtained unvulcanized rubber was used as a test piece, and the vulcanized rubber was press-vulcanized at 160 ° C. for 15 minutes in a mold to obtain the target test piece. Prepared and evaluated physical properties. The results are shown in Table I. The measuring method of the physical properties is as follows.

Mooney viscosity 100 ° C. of unvulcanized rubber according to JIS K6300
Was measured for Mooney viscosity (ML _{1 + 4} ). Abrasion resistance The wear loss was measured using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) at a temperature of 20 ° C. and a slip ratio of 50%. The larger the value, the better the wear resistance.

Preparation of Standard Example 2, Example 3 and Comparative Examples 5 to 8 Samples A rubber composition was prepared based on the formulation (parts by weight) shown in Table II. In the first step, the mixture was kneaded with a 1.5-liter closed mixer for 3 to 5 minutes and released when the temperature reached 165 ± 5 ° C. to obtain a master batch (NP1). Next, in the second step, NP1 obtained in the first step (and TEMPO) is
The mixture was kneaded for 5 minutes and released when the temperature reached 165 ± 5 ° C. to obtain a master batch (NP2). Finally, in the third step, the NP2 obtained in the second step and the vulcanization system were kneaded with an 8-inch open roll to obtain a rubber composition. The unvulcanized rubber was used as a test piece, and the vulcanized rubber was press-vulcanized in a mold at 160 ° C. for 15 minutes to prepare a target test piece, and the Mooney viscosity was measured by the above method. The results are shown in Table II.

[0036]

[Table 2]

[0037]

As described above, according to the present invention, kneading is performed by adding the above-mentioned radical-sealing compound to the master batch in a step after the kneading step of the compounding agent other than the vulcanizing compounding agent of the raw rubber. When the unvulcanized rubber after storage is stored for a long period of time, an increase in viscosity can be prevented, and the wear resistance of the vulcanized rubber can be improved. This is because the radicals generated from the compound trap the radicals in the rubber composition after the completion of the kneading of the rubber, and effectively suppress the increase in the viscosity during storage of the unvulcanized rubber composition which is considered to be derived from the radicals. In addition to this, it is considered that radicals generated when the rubber product of the vulcanized rubber is worn are also trapped, so that the wear resistance of the vulcanized rubber can be improved.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Katsuhiro Igawa 2-1 Oiwake, Hiratsuka-shi, Kanagawa F-term in Hiratsuka Factory of Yokohama Rubber Co., Ltd. (Reference) 4J002 AC011 AC031 AC061 AC071 AC081 BB181 BC051 BG101 EA066 EE026 EL066 EQ006 EU076 FD010 FD206 GN01

Claims (4)

[Claims] 1. Formulas (I) and (II) which are stably present in a rubber at normal temperature and in the presence of oxygen: Embedded image A rubber composition characterized in that a radical-containing compound containing at least one free radical is added in a mixing step after the step of mixing and mixing at least one compounding agent other than the vulcanizing compounding agent. 2. The raw material rubber is at least one kind of diene-based raw material rubber, and the radical-sealing compound is selected from the group consisting of nitroxy radical, hydrazyl radical, allyloxyl radical, trityl radical and analogs thereof. The rubber composition according to claim 1, which is at least one compound selected from the group consisting of 0.01 to 10 parts by weight per 100 parts by weight of the diene-based raw rubber. 3. The rubber composition according to claim 1, wherein the compounding agent other than the vulcanizing compounding agent is a peptizing agent. 4. The method according to claim 1, wherein the amount of the peptizing agent is 100%.
The rubber composition according to any one of claims 1 to 3, wherein the amount is 0.01 to 5 parts by weight based on parts by weight.