JP2009221248A - Rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire exhibiting excellent long-term preservation stability that is prevented from deterioration in workability in a factory and suppressed in changes in the vulcanization speed and the molecular weight of a natural rubber of a natural rubber-based unvulcanized rubber composition, particularly an unvulcanized rubber containing no vulcanizing chemicals, after preserved for a long period of term, and also to provide a tire using the same. <P>SOLUTION: The rubber composition for a tire includes at least 0.1 pt.mass of a sulfur-containing phenolic antioxidant based on 100 pts.mass of a natural rubber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tire rubber composition having excellent long-term storage stability. More specifically, a rubber composition for tires with excellent long-term storage stability, which suppresses deterioration in factory workability after long-term storage of natural rubber-based unvulcanized rubber compositions and changes in the vulcanization speed and the molecular weight of natural rubber. The present invention relates to a thing and a tire using the same.

Normally, natural rubber has a high molecular weight, so there is a lot of entanglement between molecules, and in order to take an elastic behavior, it is mechanically cut using a roll or Banbury mixer, or chemically cleaved by adding a capping agent or the like. It is used to improve the plasticity (paste process).
Next, carbon black, oil, and other compounding materials are added to the natural rubber that has undergone the kneading process and kneaded (non-pro kneading process), and the rubber compound obtained in the non-pro kneading process is vulcanized and accelerated. A vulcanizable rubber composition is obtained by kneading with an agent or the like (professional kneading step).
In the professional kneading step, as described above, a vulcanizing agent, a vulcanization accelerator, and the like are blended, and therefore, the kneading is usually carried out at a low temperature of 110 ° C. or lower in order to prevent rubber from being burned.
In general, the pro-rubber obtained in the professional kneading process is not immediately subjected to vulcanization molding, but is vulcanized after storage to produce rubber products such as tires.
When storing the above-mentioned pro-rubber, the vulcanizing agent and vulcanization accelerator in the rubber composition are susceptible to chemical changes under the influence of other compounding components and atmosphere, and the vulcanization characteristics are likely to change. If the vulcanization characteristics of the vulcanizing agent or accelerator are changed, the fluidity and vulcanization time during vulcanization will be different from the original ones. It becomes impossible to mold rubber products.
For this reason, conventionally, a rubber composition containing a vulcanizing agent or a vulcanization accelerator needs to be stored carefully, and is usually stored in a storage kept at a low temperature and low humidity.

In order to solve the above-mentioned problems, a vulcanizing agent or a vulcanization accelerator and a thermoplastic resin are mixed, and the mixture is freeze-pulverized to form a granular material, thereby adding vulcanization in the pre-vulcanization process. There has been proposed a rubber composition that prevents the start of vulcanization and shortens the vulcanization time in the vulcanization process (see Patent Document 1).
In addition, a vulcanized component containing a vulcanizing agent and / or vulcanization accelerator is encapsulated with a film formed by an emulsion polymerization method or a suspension polymerization method to prevent chemical change of the vulcanized component during storage. It has been proposed to stably maintain the sulfur characteristics (see Patent Document 2).
However, these relate to the storage stability of the pro-rubber obtained in the professional kneading step, and in order to ensure the long-term storage stability of the non-pro rubber obtained in the non-pro kneading step, a vulcanizing agent and / or a vulcanization accelerator. However, further improvement is desired. Non-pro rubbers that do not contain vulcanized chemicals can be adjusted to some extent by adding kneading to moisture absorption and viscosity changes, and therefore tend to be stored longer and transported longer than pro rubber. Among these non-pro rubbers, when natural rubber is used as a rubber component, the degree of change in physical properties due to long-term storage is large. For example, a non-pro rubber after running out of sheets, a decrease in molecular weight, and storage for a long time can be used as a vulcanizing agent or a vulcanization accelerator. However, the pro-rubber kneaded with the above has problems such as a delay in the vulcanization speed.
Moreover, although the said change was relieve | moderated by mix | blending a phenylenediamine type | system | group antioxidant and a quinoline type | system | group antioxidant with non-pro rubber, the effect was not enough.

JP 2001-279026 A JP 2004-35723 A

  Under such circumstances, the present invention is a natural rubber-based unvulcanized rubber composition, particularly a decrease in factory workability after long-term storage of a non-pro rubber containing no vulcanized chemicals, a vulcanization speed, and a molecular weight of natural rubber. An object of the present invention is to provide a rubber composition for a tire excellent in long-term storage stability, in which the change in temperature is suppressed, and a tire using the same.

（式中ｎは６〜１８の整数を示す。）で表される化合物である上記（１）のタイヤ用ゴム組成物、
（３） さらに、前記天然ゴム１００質量部当りフェニレンジアミン系老化防止剤を０．１質量部以上含む請求項１又は２に記載のタイヤ用ゴム組成物、
（４） しゃっ解剤を含まない上記（１）〜（３）いずれかのタイヤ用ゴム組成物、
（５） 加硫系薬品を含まないノンプロゴムである上記（１）〜（４）いずれかのタイヤ用ゴム組成物、及び
（６） 請求項１〜５のいずれかに記載のゴム組成物を用いたタイヤ、
を提供するものである。 As a result of intensive studies to develop a rubber composition for tires having the above-mentioned preferable properties, the present inventors have found that a rubber composition containing a specific amount of a specific sulfur-containing phenolic antioxidant per 100 parts by mass of natural rubber. We have found that it can be adapted to that purpose. The present invention has been completed based on such findings.
That is, the present invention
(1) A rubber composition for tires containing 0.1 part by mass or more of a sulfur-containing phenolic antioxidant per 100 parts by mass of natural rubber,
(2) The sulfur-containing phenolic antioxidant is represented by the general formula (I)

(Wherein n represents an integer of 6 to 18), and the rubber composition for tire according to the above (1), which is a compound represented by:
(3) The tire rubber composition according to claim 1 or 2, further comprising 0.1 parts by mass or more of a phenylenediamine-based anti-aging agent per 100 parts by mass of the natural rubber.
(4) The rubber composition for tires according to any one of the above (1) to (3), which does not contain a peptizer.
(5) The rubber composition for a tire according to any one of the above (1) to (4), which is a non-pro rubber not containing a vulcanized chemical, and (6) the rubber composition according to any one of claims 1 to 5. Tires,
Is to provide.

  According to the present invention, natural rubber-based unvulcanized rubber composition, in particular, non-pro-rubber containing no vulcanized chemicals, reduced factory workability after long-term storage and changes in vulcanization speed, natural rubber molecular weight and the like were suppressed. A rubber composition for a tire excellent in long-term storage stability and a tire using the same can be provided.

[Rubber composition]
The rubber composition for tires of this invention needs to contain 0.1 mass part or more of sulfur containing phenolic antioxidants per 100 mass parts of natural rubber.
<Natural rubber>
Since natural rubber has a high molecular weight, there is a lot of entanglement between molecules, and in order to take an elastic behavior, it is chemically added using a roll or Banbury mixer or added with a capping agent (peptizer, peptizer). It is used by cleaving molecules to increase plasticity.
However, in order to obtain a rubber composition excellent in long-term storage stability, which is the object of the present invention, chemical molecular cleavage using a chelating agent is not preferred. When a peptizer is used, the molecular weight of natural rubber is significantly reduced during long-term storage, which causes a decrease in mechanical properties of the vulcanizate.
Accordingly, in the present invention, natural rubber mastication is preferably mechanical plasticization or thermoplasticization.

<Sulfur-containing phenolic antioxidant>
In the rubber composition of this invention, it is preferable to mix | blend 0.1 mass part or more of sulfur containing phenolic antioxidant as an essential component with respect to 100 mass parts of natural rubber. More preferably, it is 0.2 parts by mass or more. Although there is no restriction | limiting in particular about the upper limit, Usually, it is about 0.5 mass part. By making the compounding quantity of a sulfur containing phenolic antioxidant into the said range, while being able to suppress the fall of the molecular weight of a natural rubber, the delay of a vulcanization speed at the time of using it as a pro rubber can be improved compared with the former.
Moreover, although the said sulfur containing phenolic antioxidant can be mix | blended in any in a non-pro kneading process and a pro kneading process, it is preferable to mix | blend in a non-pro kneading process. As a result, the effects of the present invention can be maximized.

（式中ｎは６〜１８の整数を示す。）で表される４，６−ビス（ｎ−アルキルチオメチル）−ｏ−クレゾール類が好ましい。
上記一般式（Ｉ）で表される化合物としては、市販品として入手可能なものとして、例えば、４，６−ビス（オクチルチオメチル）−ｏ−クレゾール（商品名ＩＲＧＡＮＯＸ１５２０Ｌ、チバ・スペシャルティケミカルズ社製）、４，６−ビス（ドデシルチオメチル）−ｏ−クレゾール（商品名ＩＲＧＡＮＯＸ１７２６、チバ・スペシャルティケミカルズ社製）等が挙げられる。
また、上記４，４’−チオビスフェノール類としては、市販品として入手可能なものとして、例えば、４，４’−チオビス（６−ｔ−ブチル−３−メチルフェノール）（商品名ノクラック３００、大内新興社製）が挙げられ、その他の硫黄を含むフェノール系酸化防止剤として、ビス（３，５−ジ−ｔ−ブチル−４−ヒドロキシベンジル）サルファイド（商品名サンザント１０３、三新化学社製）等が挙げられる。 The sulfur-containing phenol-based antioxidant is not particularly limited as long as it is a sulfur-containing phenol-based antioxidant, and 4,4′-thiobisphenols in which a sulfur atom is bonded to phenols, 4,6-bis (n -Alkylthiomethyl) -o-cresols are preferably used.
Among the phenolic antioxidants containing sulfur, the general formula (I)

4,6-bis (n-alkylthiomethyl) -o-cresols represented by the formula (wherein n represents an integer of 6 to 18) is preferred.
As a compound represented by the said general formula (I), as what can be obtained as a commercial item, for example, 4, 6-bis (octyl thiomethyl) -o-cresol (brand name IRGANOX1520L, the product made by Ciba Specialty Chemicals) ), 4,6-bis (dodecylthiomethyl) -o-cresol (trade name IRGANOX 1726, manufactured by Ciba Specialty Chemicals) and the like.
Moreover, as said 4,4'- thiobisphenol, as what is obtained as a commercial item, for example, 4,4'-thiobis (6-t-butyl-3-methylphenol) (trade name NOCRACK 300, large As a phenolic antioxidant containing other sulfur, bis (3,5-di-t-butyl-4-hydroxybenzyl) sulfide (trade name: Sanzanto 103, manufactured by Sanshin Chemical Co., Ltd.) ) And the like.

<Phenylenediamine anti-aging agent>
The tire rubber composition of the present invention preferably further contains 0.1 parts by mass or more of a phenylenediamine-based anti-aging agent per 100 parts by mass of the natural rubber. More preferably, it is 0.2 parts by mass or more. Although there is no restriction | limiting in particular about the upper limit of content of this phenylenediamine type anti-aging agent, it is about 0.5 mass part.
By using the phenol-based antioxidant containing sulfur and the phenylenediamine-based antioxidant in combination, the effects of the present invention can be further achieved. Both are preferably used in a non-pro kneading step.
Specific examples of the phenylenediamine-based antioxidant include N, N′-diphenyl-p-phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, and N, N′-di-2-naphthyl. -P-phenylenediamine, N-phenyl-N '-(3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine, N, N'-bis (1-methylheptyl) -p-phenylenediamine, N, N′-bis (1,4-dimethylpentyl) -p-phenylenediamine, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, a mixture of diallyl-p-phenylenediamine, phenyl, And octyl-p-phenylenediamine. Of these, N-isopropyl-N′-phenyl-p-phenylenediamine and N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine are preferable.

<Other ingredients>
Furthermore, in the rubber composition according to the present invention, a reinforcing filler usually used in the rubber industry, for example, carbon black, silica, and various chemicals, for example, as long as the effects of the present invention are not impaired. Vulcanizing agents, vulcanization accelerators, process oils, anti-aging agents, anti-scorch agents, zinc white, stearic acid, and the like can be included.

(Preparation of rubber composition, production of pneumatic tire)
The rubber composition according to the present invention is obtained by kneading using a kneading machine such as a Banbury mixer, a roll, an internal mixer or the like according to the above-mentioned blending prescription, vulcanized after molding, and tire tread rubber It is used as various other tire member rubbers.
The tire of the present invention, as described above, the rubber composition according to the present invention containing various chemicals is processed into each member at an unvulcanized stage, and is pasted and molded by a normal method on a tire molding machine, A green tire is formed. The green tire is heated and pressed in a vulcanizer to obtain a tire.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Various characteristics were measured according to the following methods.
<Evaluation of non-professional rubber>
<Measurement of carbon gel>
After chopping the non-pro rubber and measuring its weight, it is placed in a sample basket made of a wire mesh (150 mesh) with a known tare weight, and immersed in toluene for 24 hours together with the basket. Thereafter, the basket was taken out, toluene-insoluble matter (carbon gel) was sufficiently dried, and its weight was measured. The ratio (%) of the natural rubber weight (weight obtained by removing toluene-insoluble matter such as carbon black from the insoluble matter) to the weight of the natural rubber in the non-pro rubber (weight obtained by multiplying the weight of the non-pro rubber by the natural rubber content). Asked.
<Measurement of weight average molecular weight of natural rubber>
The weight average molecule of natural rubber was measured by gel permeation chromatography. The measurement device is a gel permeation chromatograph HCL-8020 manufactured by Tosoh Corp., the column is GMHXL manufactured by Tosoh Corp., the standard polystyrene manufactured by Tosoh Corp. is calibrated, the solvent is THF, and the solution is 0.01 g sample. / 30 cm ³ of THF was used.

<Measurement of crosslinking reaction start point T0.1>
Vulcanization is possible by kneading the chemicals shown in Table 1 with the chemical composition shown in Table 1 (pro-kneading step) to each of the original rubbers of Examples 1 and 2 and Comparative Examples 1 to 4 and non-pro rubbers left at 40 ° C. for 20 days. Pro rubber was prepared, and the crosslinking reaction starting point T0.1 was measured at 145 ° C. using a rheometer.
As shown in FIG. 1, the cross-linking solution viewpoint T0.1 is the maximum torque Fmax. When the vulcanization curve is measured using a rheometer. This is the time (minutes) until the torque of 0.1 times is shown. The larger the value, the slower the vulcanization.

Examples 1-2 and Comparative Examples 1-4
First, a non-pro rubber was prepared by a conventional method by kneading using a Banbury mixer based on the above-mentioned six kinds of non-pro rubber compounding compositions shown in Table 1 (non-pro kneading step). Each non-pro rubber is divided into two. One is to immediately measure each characteristic (carbon gel, weight average molecular weight of natural rubber) of non-pro rubber and mix with non-pro rubber using Banbury mixer based on the composition composition for pro rubber shown in Table 1. Pro-rubber was prepared by a conventional method (pro-kneading step), and T0.1 of the vulcanization characteristic was measured.
The remaining non-pro rubber was stored for a long period of time (40 ° C., 20 days), then the same measurement as ORIGINAL was performed, and a pro rubber was prepared, and the crosslinking reaction start point T0.1 was measured. The respective evaluation results are shown in Table 1.

［注］
＊１．しゃっ解剤ＳＫ：商品名「ノクタイザーＳＫ」大内新興社製
＊２．カーボンブラックＮ１１０：商品名「旭＃９０」旭カーボン社製
＊３．フェニレンジアミン系老化防止剤：商品名「ノクラック６Ｃ」、Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン、大内新興社製
＊４．硫黄含有フェノール系酸化防止剤：商品名「ＩＲＧＡＮＯＸ１５２０Ｌ」 ４，６−ビス（オクチルチオメチル）−ｏ−クレゾール、チバ・スペシャルティケミカルズ社製
＊５．加硫促進剤ＣＺ：商品名「ノックセラーＣＺ」Ｎ−シクロヘキシル−２−ベンゾチアジルスルフェンアミド、大内新興社製
第１表のORIGINALと４０℃で２０日間放置したノンプロゴムの比較から次のようなことがわかる。
（１）本発明の硫黄含有フェノール系酸化防止剤を配合した実施例１及び２は放置による天然ゴムの分子量低下が各比較例に比べ少なく大幅に改良されている。また、素練りでしゃっ解剤を用いなかった効果も大きい。
（２）また、加硫時間に関するＴ０．１の結果でも本発明の実施例１及び２は加硫遅れが小さく大幅に改善されている。
（３）フェニレンジアミン系老化防止剤の併用は分子量低下を抑制することはできるが、加硫速度の遅れに対する改善効果は認められない。

[note]
* 1. Spooking agent SK: Trade name “Noctizer SK” manufactured by Ouchi Shinsei Co., Ltd. * 2. Carbon black N110: trade name “Asahi # 90” manufactured by Asahi Carbon Co., Ltd. * 3. Phenylenediamine-based anti-aging agent: Trade name “NOCRACK 6C”, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, manufactured by Ouchi Shinsei Co., Ltd. * 4. Sulfur-containing phenolic antioxidant: trade name “IRGANOX1520L” 4,6-bis (octylthiomethyl) -o-cresol, manufactured by Ciba Specialty Chemicals * 5. Vulcanization accelerator CZ: Trade name “Knock Cellar CZ” N-cyclohexyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinsei Co., Ltd. Comparison of ORIGINAL in Table 1 and non-pro-rubber left for 20 days at 40 ° C. I understand that.
(1) In Examples 1 and 2 in which the sulfur-containing phenolic antioxidant of the present invention was blended, the molecular weight of the natural rubber was decreased by leaving as compared with each of the comparative examples, and was greatly improved. Moreover, the effect which did not use a coughing agent by mastication is also great.
(2) Moreover, also in the result of T0.1 regarding the vulcanization time, Examples 1 and 2 of the present invention have a small vulcanization delay and are greatly improved.
(3) Although the combined use of a phenylenediamine-based anti-aging agent can suppress a decrease in molecular weight, no improvement effect on the delay of the vulcanization rate is observed.

  The rubber composition for tires of the present invention is a natural rubber-based unvulcanized rubber composition, particularly a decrease in factory workability after long-term storage of a non-pro rubber containing no vulcanized chemicals, vulcanization speed, and the molecular weight of natural rubber. It is possible to provide a tire rubber composition excellent in long-term storage stability, in which changes are suppressed, and a tire using the same.

This is a value defining T0.1 in the vulcanization characteristics of the rubber composition from the relationship between the vulcanization time and the torque measured by the rheometer.

Claims (6)

  A rubber composition for tires comprising 0.1 part by mass or more of a sulfur-containing phenolic antioxidant per 100 parts by mass of natural rubber. The sulfur-containing phenolic antioxidant is represented by the general formula (I)

The rubber composition for tires according to claim 1, wherein n is a compound represented by the formula (wherein n represents an integer of 6 to 18).   Furthermore, the rubber composition for tires of Claim 1 or 2 which contains 0.1 mass part or more of phenylenediamine type | system | group antioxidant for 100 mass parts of said natural rubbers.   The rubber composition for tires according to any one of claims 1 to 3, which does not contain a chelating agent.   The tire rubber composition according to any one of claims 1 to 4, which is a non-pro rubber containing no vulcanized chemicals. A tire using the rubber composition according to claim 1.

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