JP2004161898A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition enabling its foamed surface to tend to be exposed through thinning its nonfoamed skin layer in contact with a mold and capable of fully eliciting the performance of the resultant foamed rubber even with a short running-in travel distance, and to provide a pneumatic tire using the rubber composition. <P>SOLUTION: The rubber composition is obtained by compounding a synthetic rubber and/or natural rubber as the rubber component with a foaming agent and a foaming auxiliary comprising a hydrazide compound and/or a hydrazone compound. The pneumatic tire using this rubber composition is also provided. <P>COPYRIGHT: (C)2004,JPO

Description

【００３０】
＊１ 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
＊２ ＲＤ；２，２，４−トリメチル−１，２−ジヒドロキノリン重合体
＊３ 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
＊４ アゾジカルボンアミド
＊５ 尿素
＊６ ｐ−トルエンスルホニルセミカルバジド
＊７ ベンゼンスルホニルヒドラジド
＊８ ｐ−トルエンスルホニルヒドラジド
【００３１】
【発明の効果】
本発明によれば、金型に接する発泡していないスキン層を薄くし、発泡面を露出しやすくすることを可能とし、慣らし走行距離が少なくても発泡ゴムの性能を十分に引き出すことのできるタイヤ用トレッド用ゴムとして好適なゴム組成物が得られる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a foamable rubber composition, and particularly when used for a pneumatic tire, a rubber composition that provides an increase in frictional force between a tread surface and an ice and snow road surface of a tire that rolls on an ice and snow road surface, and The present invention relates to a pneumatic tire using the rubber composition.
[0002]
[Prior art]
Conventional techniques for increasing the frictional force on ice of the tread surface include increasing the surface roughness of the tread surface by mixing powder such as walnut shells and rice hulls in the tread rubber, and forming the tread rubber with foamed rubber. It is widely and generally known that in these tires, the frictional force on ice on the tread surface can be increased by taking in the ice-melt water generated by rolling of the tire into the recess on the tread surface.
[0003]
However, when these tires are new, the tread surface in contact with the molding surface of the vulcanizing mold generally has a small roughness, and it is difficult to immediately generate the required on-ice frictional force on those tires. .
[0004]
Also, other general tires, except snow tires and studless tires, have low roughness on the tread surface regardless of whether they are new or in use, so the tread surface and ice It was not possible to ensure a sufficient abrasion force between the surfaces.
[0005]
On the other hand, in recent years, it has been said that in such a case, it is effective to provide a long scratch extending in the circumferential direction on the surface of the tread, and in practice, the tread surface is provided on the molding surface of the vulcanizing mold. There has also been proposed a technique in which a long ridge for forming a long scratch is provided, thereby forming a large number of long scratches extending in the circumferential direction on the tread surface of a tire to be vulcanized and formed.
[0006]
However, since this technique forms a long scratch of a tire with a relatively thick ridge formed on a molding die, the skin layer of the foamed rubber itself still remains, and abrasion due to running occurs. It is inevitable that the performance on ice will improve as we proceed.
[0007]
[Problems to be solved by the invention]
In view of the above circumstances, the present invention makes it possible to reduce the thickness of a non-foamed skin layer in contact with a mold and to easily expose a foamed surface, and to sufficiently bring out the performance of foamed rubber even if the running-in distance is small. It is an object of the present invention to provide a rubber composition that can be used and a pneumatic tire using the rubber composition.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, at least one selected from a natural rubber and a synthetic rubber as a rubber component, a blowing agent, and at least one selected from a hydrazide compound and a hydrazone compound. It has been found that a rubber composition containing one kind of foaming aid and a pneumatic tire using the rubber composition can achieve the object. The present invention has been completed based on such findings.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Examples of the rubber component of the present invention include natural rubber, polyisoprene rubber, butadiene rubber, high cis and low cis polybutadiene rubber, diene rubbers such as emulsion-polymerized and solution-polymerized styrene-butadiene copolymer rubber, and the like. These can be used alone or as a blend.
[0010]
Examples of the foaming agent of the present invention include azodicarbonamide (ADCA), azobisisobutyronitrile, dinitrosopentamethylenetetramine (DPT), paratoluenesulfonitrile hydrazine, p, p'-oxybis (benzenesulfonylhydrazine) and the like. Among them, ADCA is particularly excellent in terms of effect, and is relatively safe to handle as a medicine, has excellent storage stability, and has a small amount of toxic safety that is certified as a food additive. And are particularly preferred blowing agents.
[0011]
The foaming aid used in combination with the foaming agent of the present invention must contain at least one selected from hydrazide compounds and hydrazone compounds. As the hydrazide compound, p-toluenesulfonylhydrazide, benzenesulfonylhydrazide, diphenylsulfone-3,3-disulfonylhydrazide, thiobisbenzenesulfonylhydrazide, and p-toluenesulfonylsemicarbazide are preferable. As the hydrazone compound, p-toluenesulfonylacetone Hydrazones are preferred. In the rubber composition of the present invention, it is preferable to blend a foaming aid containing at least one selected from these hydrazide compounds and hydrazone compounds.
These hydrazide compounds and hydrazone compounds themselves have a function as a foaming agent, but it is difficult to produce a useful foam by itself. However, by combining with a suitable foaming agent, especially ADCA, it functions as a foaming aid and achieves the effects of the present invention. Specifically, the foaming aid lowers the decomposition temperature of a foaming agent such as ADCA, and sharpens the gas generation behavior with respect to the temperature. Thereby, the portion of the skin layer that does not foam, which is in contact with the mold during vulcanization, can be made thinner, and the effects of the present invention can be achieved.
Further, it is preferable to add urea to at least one selected from the above-mentioned hydrazide compounds and hydrazone compounds as a foaming aid, and the effect of the present invention is further improved by adding urea.
[0012]
The amount of the foaming agent used in the present invention is preferably 1 to 20 parts by weight based on 100 parts by weight of the rubber component. This is because if the amount of the foaming agent is within this range, predetermined foaming is easily performed and bubbles are easily formed, and the bubble rate is moderate. This is because the tire also has excellent wear resistance. From the same viewpoint, the usage amount of the foaming agent is more preferably 3.5 to 8.5 parts by weight.
[0013]
The amount of the foaming aid is preferably 0.1 to 25 parts by weight based on 100 parts by weight of the rubber component. This is because if the amount of the foaming aid is within this range, the predetermined foaming is easily performed and the foaming rate becomes moderate, so the pneumatic tire using such a rubber for the tread is This is because it also has excellent wear resistance.
[0014]
The rubber composition of the present invention preferably contains a resin. The resin that can be used in the present invention may be formed from a crystalline polymer, may be formed from an amorphous polymer, or may include both of them. From the viewpoint of facilitating viscosity control of the composition, a crystalline polymer is preferable.
[0015]
Examples of the crystalline polymer include polyethylene, polypropylene, polybutylene, polybutylene succinate, polyethylene succinate, syndiotactic-1,2-polybutadiene, and copolymers thereof, among which general-purpose products are used. From the viewpoint of easy availability, polyethylene and polypropylene are preferred.
Examples of the non-crystalline polymer include polymethyl methacrylate, acrylonitrile butadiene styrene copolymer, and polystyrene.
Further, these resins are preferably long or plate-shaped.
[0016]
The content of the resin is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the rubber component in the rubber composition. Within this range, it is sufficient to take in the gas generated from the foaming agent, and the dispersibility of the resin in the rubber composition, the workability during rubber extrusion, and the like are improved. From these viewpoints, the content of the resin is more preferably 1.0 to 15 parts by weight, particularly preferably 1.0 to 10 parts by weight.
[0017]
In the foamed rubber composition of the present invention, carbon black, silica or the like can be blended as a filler. When these fillers are blended, the carbon black is HAF in a pneumatic tire for a passenger car. , ISAF or SAF is preferable, and in the case of a pneumatic tire for heavy load, ISAF or SAF is preferable. The amount of the filler is preferably 30 to 100 parts by weight based on 100 parts by weight of the rubber component. This is because, when this rubber composition is applied to a tire tread, good wear resistance can be obtained when it is within this range.
[0018]
In the foamed rubber composition of the present invention, in addition to the above foaming agent, foaming aid, carbon black, fillers such as silica, aroma oils, softeners such as spindle oil, antioxidants, vulcanization accelerators, Vulcanization accelerating aids such as stearic acid and zinc white, and rubber compounding agents such as vulcanizing agents can be appropriately compounded within the usual range.
[0019]
Further, the foamed rubber composition used in the present invention can be produced by a conventional method, using the rubber composition of the present invention as a tread rubber, according to a normal tire production method, by heating and pressurizing the desired use, A pneumatic tire of a size can be manufactured. In this case, by adjusting the amounts of the foaming agent and the foaming aid, the bubble ratio and the bubble diameter can be appropriately adjusted.
The pneumatic tire obtained by using the rubber composition of the present invention can be filled with an ordinary gas or an inert gas such as air or nitrogen having a changed oxygen partial pressure, or a mixture thereof.
[0020]
【Example】
Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
The performance on ice by actual vehicle running was evaluated by the following method. The manufactured tire was a radial tire for passenger cars (185 / 70R14) having the same max performance on ice, and was mounted on a 1600 cc class passenger car and tested.
(Performance test on ice)
On a test course (on an ice road surface, a road surface temperature of about -5 ° C.), a vehicle running at 20 km / h was braked to lock the tires, and the distance required for stopping was measured. Each index is shown. The larger the value, the better the performance on ice.
Here, INDEX = 0 means a so-called new tire having a mileage of 0, and INDEX = 100 indicates a mileage required for the tire of Comparative Example 1 or 2 to exhibit the best on-ice performance. It is indexed. Therefore, INDEX = 50 and INDEX = 150 mean tires that have traveled 50% and 150% of the travel distance corresponding to INDEX = 100, respectively.
[0021]
Example 1
For a rubber component consisting of 30 parts by weight of natural rubber and 70 parts by weight of polybutadiene rubber, 20 parts by weight of carbon black (SAF), 35 parts by weight of silica, 3 parts by weight of stearic acid, 3 parts by weight of zinc white, 1 part by weight of wax, As an antioxidant, 1 part by weight of 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine), RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) ) 0.2 parts by weight, 1 part by weight of CZ (N-cyclohexyl-2-benzothiazylsulfenamide) as a vulcanization accelerator, 1 part by weight of sulfur, 4 parts by weight of azodicarbonamide as a foaming agent, foaming aid Using a rubber composition containing 1 part by weight of urea and 2 parts by weight of p-toluenesulfonyl semicarbazide as an agent, a tire was manufactured by a usual method. The performance on ice is shown in Table 1.
[0022]
Example 2
A tire was produced in the same manner as in Example 1 except that 2.2 parts by weight of benzenesulfonyl hydrazide was added as a foaming aid instead of 2 parts by weight of p-toluenesulfonyl semicarbazide, and the performance on ice was evaluated. The results are shown in Table 1.
[0023]
Example 3
A tire was manufactured in the same manner as in Example 1 except that 1.5 parts by weight of p-toluenesulfonyl hydrazide was added instead of 2 parts by weight of p-toluenesulfonyl semicarbazide as a foaming aid, and the performance on ice was evaluated. The results are shown in Table 1.
[0024]
Example 4
After the tire was manufactured, the performance on ice was evaluated in the same manner as in Example 1 except that the tread portion of the tire was subjected to riblet processing. Table 1 shows the results.
[0025]
Example 5
A tire was manufactured in the same manner as in Example 4 except that 2.2 parts by weight of benzenesulfonyl hydrazide was added instead of 2 parts by weight of p-toluenesulfonyl semicarbazide as a foaming aid, and the performance on ice was evaluated. The results are shown in Table 1.
[0026]
Example 6
A tire was produced in the same manner as in Example 4 except that 1.5 parts by weight of p-toluenesulfonyl hydrazide was added instead of 2 parts by weight of p-toluenesulfonyl semicarbazide as a foaming aid, and the performance on ice was evaluated. The results are shown in Table 1.
It can be seen that the tire using the rubber composition according to the present invention exhibits performance on ice at a stage where the running-in distance is short.
[0027]
Comparative Example 1
A tire was manufactured in the same manner as in Example 1 except that only 3 parts by weight of urea was added as a foaming aid, and the performance on ice was evaluated.
[0028]
Comparative Example 2
After the tire was manufactured, the performance on ice was evaluated in the same manner as in Comparative Example 1 except that the tread portion of the tire was subjected to riblet processing. Table 1 shows the results.
[0029]
[Table 1]

[0030]
* 16C; N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine * 2 RD; 2,2,4-trimethyl-1,2-dihydroquinoline polymer * 3 CZ; N- Cyclohexyl-2-benzothiazylsulfenamide * 4 azodicarbonamide * 5 urea * 6 p-toluenesulfonylsemicarbazide * 7 benzenesulfonylhydrazide * 8 p-toluenesulfonylhydrazide
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the skin layer which does not foam in contact with a metal mold is made thin, and it becomes possible to make it easy to expose a foaming surface, and it is possible to sufficiently bring out the performance of foam rubber even if the running-in distance is small. A rubber composition suitable as a tire tread rubber is obtained.

Claims (7)

A rubber composition comprising, as a rubber component, at least one selected from natural rubber and synthetic rubber, and a foaming agent and a foaming aid containing at least one selected from hydrazide compounds and hydrazone compounds. The hydrazide compound is one selected from p-toluenesulfonylhydrazide, benzenesulfonylhydrazide, diphenylsulfone-3,3-disulfonylhydrazide, thiobisbenzenesulfonylhydrazide, p-toluenesulfonyl semicarbazide, and the hydrazone compound is p-toluenesulfonyl semicarbazide. The rubber composition according to claim 1, wherein the rubber composition is toluenesulfonylacetone hydrazone. 3. The rubber composition according to claim 1, wherein the blowing agent comprises azodicarbonamide. The rubber composition according to any one of claims 1 to 3, wherein the foaming aid further contains urea. The rubber composition according to any one of claims 1 to 4, wherein a resin is further added to the rubber composition. The rubber composition according to claim 5, wherein at least a part of the resin has a long shape or a plate shape. A pneumatic tire using the rubber composition according to claim 1.