JP2010265431A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition appropriate for tire treads which overcomes a problem of the combination of wear resistance and heat evolution resistance, and greatly enhances wear resistance without damaging rubber performances such as heat evolution resistance, and a pneumatic tire using the same. <P>SOLUTION: The rubber composition comprises at least a rubber component, sulfur, zinc oxide, a fatty acid, and/or a fatty acid zinc salt wherein an average melting point per weight of the fatty acid zinc salt contained in a vulcanized rubber when the rubber composition is vulcanized is not higher than 105°C. The rubber composition is used as a tire tread for the pneumatic tire. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and more particularly, a rubber composition suitable for a tire tread having greatly improved wear resistance without impairing rubber performance such as heat generation. And a pneumatic tire using the same, and more particularly, to a pneumatic tire suitable for high loads.

  Conventionally, as rubber compositions for tire treads, blends of rubber components such as natural rubber (NR) and styrene-butadiene copolymer rubber (SBR) and carbon black as a reinforcing filler have been widely used. It is coming. The processability of the rubber composition for tire treads by appropriately selecting the types and molecular weights of these rubbers, the types, characteristics and blending amounts of the carbon black, and the types and blending amounts of softeners and plasticizers. Improvements in properties such as rubber elasticity, heat generation and wear resistance have been made.

  By the way, conventionally, as a method for improving the wear resistance of a rubber composition for a tire tread, there are many known methods such as using carbon black having a small particle size and a large specific surface area, and increasing the amount of carbon black. However, these methods have a problem that the viscosity of the rubber composition is increased, the workability is remarkably lowered, and the exothermic property of the rubber composition is further increased.

Therefore, many improvements have been made to solve the problem of compatibility between wear resistance and heat generation in the rubber composition for a tire tread.
For example, (A) natural rubber and diene-based rubber containing 60% or more of natural rubber and cis-1,4 isoprene (IR) in the total rubber content and containing 20% by weight or more of the total rubber content. A rubber composition comprising (B) 30 to 70 parts by weight of carbon black having specific physical properties and (c) 5 to 9 parts by weight of stearic acid with respect to 100 parts by weight of synthetic rubber, and the rubber composition There is known a heavy-duty pneumatic tire using a rubber tread rubber (for example, see Patent Document 1).
However, even with a rubber composition comprising a combination of a specific type of rubber component described in Patent Document 1, carbon black having specific physical properties, and stearic acid, the improvement in wear resistance is still insufficient. For heavy duty pneumatic tires for trucks, buses, construction, aircraft, etc., it overcomes the problem of further compatibility between wear resistance and heat generation, and without impairing rubber performance such as heat generation. A rubber composition suitable for a tire tread with greatly improved wear and a pneumatic tire suitable for a high load using the rubber composition are currently desired.

On the other hand, as a proximity technique of the present invention, for example, 1) A processing aid is added to a rubber composition for a tire tread to improve the workability by lowering the viscosity of the unvulcanized rubber, and the rolling resistance of the vulcanized rubber. As an improvement in the control and the wear resistance, at least 70 parts by weight of a solution-polymerized styrene-butadiene copolymer rubber having a specific molecular weight, a specific range of styrene bond content, and a vinyl bond content of a butadiene moiety are included. A rubber composition for a tire tread comprising 1 to 10 parts by weight of a processing aid comprising a fatty acid zinc salt per 100 parts by weight of a diene rubber (for example, see Patent Document 2), 2) natural rubber And / or a rubber composition comprising 40 parts by weight or more of polyisoprene rubber, 10 to 30 parts by weight of halogenated butyl rubber, and the remainder of other diene rubber. Relative to 100 parts by weight, the nitrogen adsorption specific surface area of 70~160m ² / g and 35 to 65 parts by weight of carbon black as a tire tread rubber composition containing 0.5 to 5 parts by weight of fatty acid zinc salts (e.g. 3) natural rubber and / or polyisoprene rubber 40 parts by weight or more, halogenated butyl rubber 10-30 parts by weight, and other diene rubber remaining 100 parts by weight of rubber component On the other hand, a rubber composition for a tire tread, comprising 35 to 65 parts by weight of carbon black having a nitrogen adsorption specific surface area of 70 to 160 m ² / g and 0.5 to 5 parts by weight of a fatty acid zinc salt. (See, for example, Patent Document 4) 4) A pneumatic tire characterized by using a rubber composition in which a high-molecular fatty acid zinc salt is blended with a vulcanizable rubber component ( In example, it is known see Patent Document 5).

However, the rubber composition for tire tread and the pneumatic tire described in Patent Documents 1 to 5 are mainly intended to improve workability by adding fatty acid zinc. It is not intended to improve wear resistance.
In contrast, the present invention aims to positively improve fracture resistance and abrasion resistance by replacing stearic acid used conventionally with the fatty acid and fatty acid zinc of the present invention. The above Patent Documents 1 to 5 are different from each other in the purpose and technical idea (configuration and operational effects thereof).

Japanese Patent Laid-Open No. 11-1575 (Claims, Examples, etc.) JP-A-6-248114 (Claims, Examples, etc.) JP 2002-338736 A (Claims, Examples, etc.) JP 2002-97304 A (Claims, Examples, etc.) JP 2008-201827 A (Claims, Examples, etc.)

  The present invention is to solve this problem in view of the above-mentioned problems of the prior art and the current situation, overcomes the problem of achieving both wear resistance and heat generation, and without damaging the rubber performance such as heat generation. It is an object of the present invention to provide a rubber composition suitable for a tire tread having greatly improved wear characteristics, and a pneumatic tire using the rubber composition, particularly a pneumatic tire suitable for high loads.

  As a result of intensive studies on the above-mentioned conventional problems and the like, the present inventors have found that rubbers for tire treads and the like are blended with stearic acid as a conventional softener and plasticizer and zinc oxide (zinc white) as a vulcanization accelerator. The composition and the pneumatic tire using this rubber composition were found to be inferior in wear resistance by tests and the like to be described later, and in particular, this compounding composition has high performance for trucks, buses, construction, aircraft, etc. It was confirmed by tests that the wear resistance of weighted pneumatic tires gradually deteriorates over time, and when intensive investigations were made based on the results of these tests, a formulation that does not use stearic acid was formulated. In the composition containing zinc oxide at least with respect to the rubber component, a rubber composition containing fatty acid and / or fatty acid zinc is used, and at least zinc oxide is added to the rubber component. In the composition that does not have, a rubber composition containing fatty acid zinc, and when these rubber compositions are vulcanized, the average melting point per weight of fatty acid zinc contained in the vulcanized rubber shall be a specific temperature or less. Thus, the inventors have found that the above rubber composition and a pneumatic tire using the rubber composition can be obtained, thereby completing the present invention.

That is, this invention exists in following (1)-(11).
(1) A rubber composition containing at least a rubber component, sulfur, zinc oxide, fatty acid and / or fatty acid zinc, and fatty acid contained in the vulcanized rubber when the rubber composition is vulcanized A rubber composition having an average melting point per weight of zinc of 105 ° C. or less.
(2) A rubber composition containing at least a rubber component, sulfur and fatty acid zinc, and having an average melting point per weight of fatty acid zinc contained in the vulcanized rubber when the rubber composition is vulcanized A rubber composition having a temperature of 105 ° C. or lower.
(3) The rubber composition as described in (1) or (2) above, wherein the content of fatty acid and / or fatty acid zinc is 4 parts by mass or less with respect to 100 parts by mass of the rubber component.
(4) In the above (1) or (3), the fatty acid is at least one selected from caprylic acid, pelargonic acid, capric acid, lauric acid, mytilic acid, oleic acid, linoleic acid, and vaccenic acid The rubber composition as described.
(5) The fatty acid zinc is at least one selected from zinc caprylate, zinc pelargonate, zinc caprate, zinc laurate, zinc myristylate, zinc oleate, zinc linoleate, and zinc vaccenate. The rubber composition according to any one of (1) to (3) above.
(6) The rubber composition according to any one of (1) to (5) above, wherein carbon black is contained in an amount of 20 to 60 parts by mass with respect to 100 parts by mass of the rubber component.
(7) The rubber composition according to (6), wherein the natural rubber and carbon black are composed of a master batch.
(8) The rubber composition according to any one of (1) to (7), wherein silica is contained in an amount of 25 parts by mass or less with respect to 100 parts by mass of the rubber component.
(9) A rubber composition, wherein the rubber composition according to any one of (1) to (8) is a tire tread composition.
(10) A pneumatic tire using the rubber composition according to any one of (1) to (9) above.
(11) The pneumatic tire according to (10), wherein the pneumatic tire is a heavy duty pneumatic tire.
The “average melting point per weight of fatty acid zinc contained in the vulcanized rubber” defined in the present invention means that the fatty acid zinc contained in the vulcanized rubber is extracted with chloroform, and the extract is methylated with hydrochloric acid, The average melting point referred to in the present invention is obtained by performing differential scanning calorimetry (DSC measurement) of the fatty acid zinc component quantified as a fatty acid ester by gas chromatography.

  According to the present invention, a rubber composition suitable for a tire tread that overcomes the problem of achieving both wear resistance and heat generation and has greatly improved wear resistance without impairing rubber performance such as heat resistance. And a pneumatic tire using the same, particularly a pneumatic tire suitable for high loads.

Hereinafter, embodiments of the present invention will be described in detail.
The rubber composition of the present invention contains at least a rubber component, sulfur, zinc oxide, fatty acid and / or fatty acid zinc, or contains at least a rubber component, sulfur and fatty acid zinc. The rubber composition is characterized in that when the rubber composition is vulcanized, an average melting point per weight of fatty acid zinc contained in the vulcanized rubber is 105 ° C. or less.

The rubber component used in the present invention is not particularly limited as long as it is used for a pneumatic tire such as a tire tread or a rubber article such as a belt member, as long as it has a double bond in the main chain (diene rubber). Vulcanization such as sulfur crosslinking is possible. For example, natural rubber and / or diene synthetic rubber is used. Specifically, natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene copolymer (SBR), polybutadiene rubber, isoprene rubber, ethylene-propylene-diene copolymer, chloroprene rubber, halogenated butyl rubber, At least one of acrylonitrile-butadiene rubber and the like can be used.
Preferably, from the viewpoint of breaking strength, it is preferable that 80 parts by mass or more of natural rubber and / or styrene-butadiene copolymer (SBR) is contained in 100 parts by mass of the rubber component.

Zinc oxide (zinc flower) used in the present invention is used as a vulcanization acceleration aid, and in a composition containing zinc oxide with respect to at least the rubber component, a rubber composition containing fatty acid and / or fatty acid zinc. In addition, at least a composition not containing zinc oxide with respect to the rubber component is a rubber composition containing fatty acid zinc.
In the composition using zinc oxide, it is desirable to contain 0.5 to 10 parts by mass, preferably 1 to 5 parts by mass of zinc oxide with respect to at least 100 parts by mass of the rubber component from the viewpoint of promoting vulcanization.

In the present invention, a rubber composition (rubber composition that contains zinc stearate by kneading) using stearic acid as a conventional softening agent / plasticizer and zinc oxide as a vulcanization acceleration aid, and In the pneumatic tire using this rubber composition, the problem of inferior wear resistance arises, and in order to solve this, when zinc oxide is used, it is contained in the vulcanized rubber instead of stearic acid. When the specific fatty acid and / or fatty acid zinc is used so that the average melting point per weight of the fatty acid zinc is 105 ° C. or less, and when zinc oxide is not used as a vulcanization accelerator, vulcanization is performed. At least a specific fatty acid zinc having an average melting point of 105 ° C. or less per weight of the fatty acid zinc contained in the rubber is used.
The fatty acid that can be used in the rubber composition of the present invention has an average melting point per weight of fatty acid zinc (by reaction of fatty acid and zinc oxide) contained in the vulcanized rubber when the rubber composition is vulcanized. For example, at least one kind of saturated fatty acids such as caprylic acid, pelargonic acid, capric acid, lauric acid, myristylic acid, and unsaturated fatty acids such as oleic acid, linoleic acid, and vaccenic acid ( Each alone or a mixture of two or more thereof.

The fatty acid zinc that can be used in the rubber composition of the present invention is such that when the rubber composition is vulcanized, the average melting point per weight of the fatty acid zinc contained in the vulcanized rubber is 105 ° C. or less. For example, saturated fatty acid zinc such as zinc caprylate, zinc pelargonate, zinc caprate, zinc laurate, zinc myristylate, and unsaturated fatty acid zinc such as zinc oleate, zinc linoleate, zinc vaccenate, etc. There may be mentioned at least one (each alone or a mixture of two or more thereof).
Preferably, from the viewpoint of fracture resistance and abrasion resistance, the average melting point per weight of fatty acid zinc (by reaction of fatty acid and zinc oxide) contained in the vulcanized rubber when the rubber composition is vulcanized is 105 ° C. Hereinafter, more preferable examples include those having a temperature of 70 to 105 ° C. Specifically, oleic acid (zinc oleate: average melting point 81 ° C.), lauric acid (zinc laurate: average melting point 101 ° C.) and the like are suitable. Can be used.
In the present invention, when the average melting point per weight of the fatty acid zinc contained in the vulcanized rubber exceeds 105 ° C. when the rubber composition is vulcanized (for example, 117 ° C. for zinc stearate). Thus, no improvement in fracture resistance and wear resistance is observed, and the intended rubber composition and pneumatic tire cannot be obtained.

The (total) content of these fatty acids and / or fatty acid zinc is preferably 4 parts by mass or less, more preferably 1.5 to 3.5 parts by mass with respect to 100 parts by mass of the rubber component. It is desirable.
When the content of the fatty acid and / or the fatty acid zinc exceeds 4 parts by mass, improvement in fracture resistance and wear resistance is not observed, which is not preferable.

  In addition to the rubber component, zinc oxide, fatty acid and / or fatty acid zinc, the rubber composition of the present invention can contain a filler usually used in rubber compositions for tire treads, for example, An inorganic filler such as carbon black or silica can be contained.

There is no restriction | limiting in particular as carbon black to be used, Arbitrary things can be selected and used from what is conventionally used as a filler for reinforcement of rubber | gum. Examples of carbon black include GPF (N660), FEF (N550), SRF (N774), HAF (N330), ISAF (N220), ISAF-HS (N234), and SAF (N110). Preferably, the nitrogen adsorption specific surface area (N ₂ SA) of 30 to 150 m ² / g, and a dibutyl phthalate (DBP) oil absorption of 80~140cm ³ / 100g of carbon black (e.g., N234, N110, N220) is. By using these carbon blacks, the effect of improving various physical properties is increased.
The content of these carbon blacks is desirably 20 to 60 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of heat generation and wear resistance.

When natural rubber is used as the carbon black and rubber component, it is preferable to use natural rubber and carbon black composed of a natural rubber masterbatch from the viewpoint of workability and heat generation.
As the natural rubber masterbatch, either a dry masterbatch or a wet masterbatch may be used.
Here, the dry masterbatch is a masterbatch obtained by kneading natural rubber and carbon black with a kneading machine such as a Banbury mixer, an internal mixer, or a roll.
Further, the wet masterbatch is a masterbatch obtained by mixing natural rubber latex and carbon black, and it is preferable to mix after making a slurry solution in which carbon black is dispersed in water in advance. In order to improve the dispersibility of carbon black, it is desirable to uniformly mix using a rotor / stator type high shear mixer, high pressure homogenizer, ultrasonic homogenizer, colloid mill, or the like.
Moreover, in order to improve the dispersibility of carbon black, it is preferable to dry a wet masterbatch using a continuous kneader, and it is more preferable to use a biaxial kneading extruder as the continuous kneader. In order to further enjoy the effects of the present invention, a wet masterbatch is more preferable.
If the natural rubber carbon black masterbatch is used, even when natural rubber and a synthetic rubber such as a diene are used in combination, it is possible to prevent the carbon black from being unevenly distributed in the synthetic rubber.

The silica that can be used is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. preferable. Moreover, it can use together with the said carbon black.
The total content of these silicas is preferably 25 parts by mass or less, more preferably 0 to 15 parts by mass, particularly preferably from 100 parts by mass of the rubber component from the viewpoint of workability and heat generation. It is desirable to contain 0.1-15 mass parts.
In addition, when content of a silica exceeds 25 mass parts, workability | operativity and exothermic property will deteriorate, and it is unpreferable.

  When silica is used as the filler, a silane coupling agent can be contained as desired. The silane coupling agent is not particularly limited, and known ones conventionally used in rubber compositions such as bis (3-triethoxysilylpropyl) polysulfide, γ-mercaptopropyltriethoxysilane, γ-amino Propyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, and the like can be used. The content of the silane coupling agent used as desired is usually selected in the range of 1 to 20% by mass with respect to silica. By setting the amount of the silane coupling agent within the above range, the effect as a coupling agent is sufficiently exhibited, and the rubber component is not gelled. In view of the effect as a coupling agent and the prevention of gelation, the preferable content of the silane coupling agent is in the range of 5 to 15% by mass.

Although there is no restriction | limiting in particular as sulfur used for the rubber composition of this invention, Usually powder is used.
The sulfur content is preferably in the range of 0.3 to 10 parts by mass and more preferably in the range of 3 to 8 parts by mass with respect to 100 parts by mass of the rubber component.

  Furthermore, in the rubber composition of the present invention, the rubber component, zinc oxide, fatty acid and / or fatty acid zinc, filler, sulfur serving as a vulcanizing agent, vulcanization accelerator (thiazole type, sulfenamide type, Additives usually used in the rubber industry such as dithioate type), anti-aging agents, workability improving agents and the like can be used with the intent of not impairing the effects of the present invention. As these compounding agents, commercially available products can be suitably used.

  In the rubber composition configured as above, a rubber composition containing at least a rubber component, sulfur, zinc oxide, fatty acid and / or fatty acid zinc, or at least a rubber component, sulfur, and fatty acid zinc An average melting point per unit weight of fatty acid zinc contained in the vulcanized rubber when the rubber composition is vulcanized, thereby improving the fracture resistance. As a result, a rubber composition capable of overcoming the problem of compatibility between wear resistance and heat build-up and greatly improving wear resistance without impairing rubber performance such as heat build-up can be obtained. It will be a thing.

  The rubber composition of the present invention is prepared by kneading the above rubber component, zinc oxide, fatty acid and / or fatty acid zinc, filler, vulcanizing agent, vulcanization accelerator, anti-aging agent, etc. Since it can be manufactured and has the above characteristics, it can be suitably used as a rubber composition for tire treads. In addition, tire members other than tire treads, belt members such as conveyor belts, wear resistance It can be suitably used for hose products having excellent properties.

  The pneumatic tire according to the present invention uses the rubber composition having the above characteristics as a tire member such as a tire tread, thereby overcoming the problem of compatibility between wear resistance and heat generation, and heat generation. A pneumatic tire with greatly improved wear resistance can be obtained without impairing the rubber performance.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, when the rubber composition of the present invention is used as a tire tread member that requires the most wear resistance, for example, a rubber composition containing the above-mentioned various fillers and compounding agents as required is not yet available. At the vulcanization stage, it is extruded into a tire tread and pasted and molded by a usual method on a tire molding machine to form a raw tire. The green tire is heated and pressurized in a vulcanizer to obtain a desired pneumatic tire.
In particular, when the pneumatic tire according to the present invention is applied to heavy-duty pneumatic tires for trucks, buses, construction, aircrafts, etc., the conventional pneumatic tires containing stearic acid (zinc stearate) are time-lapsed. However, the wear resistance of the pneumatic tire of the present invention has been gradually deteriorated. However, the pneumatic tire of the present invention maintains a high degree of compatibility between wear resistance and heat generation, and improves rubber performance such as heat generation. A pneumatic tire suitable for heavy loads with significantly improved wear resistance can be obtained without loss.
The heavy-duty pneumatic tire of the present invention can be suitably used for heavy loads or for applications in which the thickness of the tread layer is 100 mm or more for OR (off-the-road) applications.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to the following Example etc.

[Examples 1 to 17 and Comparative Examples 1 to 7]
The compounding prescription shown in following Table 1-Table 3 was knead | mixed with the Banbury mixer, and the rubber composition was prepared.
This rubber composition was vulcanized (vulcanization temperature: 145 ° C., vulcanization time: 30 minutes), and the average melting point per weight of fatty acid zinc contained in the vulcanized rubber was measured by the following method.
Further, tires having a size of 2400R35 were made using each of the obtained rubber compositions as a tread, and the heat resistance, tear resistance, and wear resistance of the tires were evaluated by the following methods.
These results are shown in Tables 1 to 3 below.

<Measurement of average melting point per weight of fatty acid zinc contained in vulcanized rubber>
Fatty acid zinc contained in the vulcanized rubber was extracted with chloroform, the extract was methylated with hydrochloric acid, and quantified as a fatty acid ester by gas chromatography (manufactured by Ajident Co., 689ON).
The average melting point was measured by DSC measurement (Q1000, manufactured by TA Instruments Inc.) of the quantified fatty acid zinc component.
In Table 1, in terms of the average melting point per weight of fatty acid zinc contained in the vulcanized rubber, the average melting point of zinc caprate and zinc caprylate 101 ° C. “below”, the average melting point of zinc linoleate and zinc vaccenate The notation of “below” at 81 ° C. is presumed that capric acid, which has a lower molecular weight than lauric acid and has a low melting point, and zinc salt of caprylic acid, have a lower melting point than zinc laurate, and more than oleic acid. This is based on the assumption that zinc salts of linoleic acid and vaccenic acid having many heavy bonds and having a low melting point have a lower melting point than zinc oleate.

<Evaluation of heat generation>
The tread portion of the test tire was taken out, and resilience (RES,%) was measured according to JIS K 6301. In Tables 1 and 2, Comparative Example 1 was set to 100, and Table 3 was set to Comparative Example 6. The index is shown as 100. It shows that it is excellent in exothermic property, so that a numerical value is high.

<Evaluation of tear resistance>
The number of scratches generated in the tire tread when the test tire was mounted on a vehicle and traveled for 50,000 km was measured. Tables 1 and 2 show the number of scratches on the tire of Comparative Example 1. In Table 3, the reciprocal number of the tires in Comparative Example 6 was set as 100, and the reciprocal number of the tires in Table 3 was represented as an index. It shows that it is excellent in tear resistance, so that an index value is large.

<Evaluation of wear resistance>
Measure the depth of the tire groove when the test tire is mounted on a vehicle and run for 50,000 km, and travel distance / (groove depth of the tire before running−groove depth of the tire after running) In Tables 1 and 2, the value of the tire of Comparative Example 1 was set to 100, and in Table 3, the value of the tire of Comparative Example 6 was set to 100, and the index was displayed. It shows that it is excellent in abrasion resistance, so that an index value is large.

* 1 to * 5 in Tables 1 to 3 are as follows.
* 1: Nipsil AQ manufactured by Nippon Silica Kogyo Co., Ltd.
* 2: Si75, manufactured by Degussa
* 3: Actiplast PP (main component: zinc oleate, zinc palmitate) manufactured by Rhein Chemie
* 4: N-phenyl-N′-1,3-dimethylbutyl-p-phenylenediamine (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller 6C)
* 5: N-cyclohexyl-2-benzothiazylsulfenamide (Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller CZ)

As is clear from the results of Tables 1 to 3, Examples 1 to 17 that are within the scope of the present invention are more resistant to heat and tear than Comparative Examples 1 to 7 that are outside the scope of the present invention. It was also found to be excellent in wear resistance.
Looking at the examples individually, Examples 1 to 8 and 11 to 13 are rubber compositions containing natural rubber, sulfur, zinc oxide, and various fatty acids as rubber components, and vulcanized. The average melting point per weight of the fatty acid zinc contained in the vulcanized rubber is 105 ° C. or less. Examples 9 and 10 are wet masterbatches (natural rubber + carbon black) and sulfur as rubber components. And a rubber composition containing zinc oxide and oleic acid, wherein the average melting point per weight of zinc oleate contained in the vulcanized rubber when vulcanized is a combination of 105 ° C. or less, Examples 14 to 17 are rubber compositions containing SBR, sulfur, zinc oxide, and various fatty acids as rubber components per weight of fatty acid zinc contained in the vulcanized rubber when vulcanized. Average melting There is a combination of a 105 ° C. or less, in these cases, excellent 耐発 heat, tear resistance and abrasion resistance, it has been found that can exhibit the effect of the present invention.
On the other hand, when comparative examples are viewed individually, Comparative Examples 1 to 4 are rubber compositions containing natural rubber, sulfur, zinc oxide, and various fatty acids as rubber components, and are vulcanized. The average melting point per weight of the fatty acid zinc contained in the vulcanized rubber exceeds 105 ° C., and Comparative Examples 5 to 7 are SBR, sulfur, zinc oxide and various fatty acids as rubber components. In which the average melting point per weight of fatty acid zinc contained in the vulcanized rubber exceeds 105 ° C., and in these cases, the desired heat resistance, It has been found that the tear resistance and the wear resistance cannot be exhibited and the effects of the present invention cannot be exhibited.

  In the present invention, since it is a rubber composition that overcomes the problem of achieving both wear resistance and heat resistance, and has greatly improved wear resistance without impairing rubber performance such as heat resistance, it can be used for passenger cars. In addition, it can be suitably applied to high-load pneumatic tires, particularly for trucks, buses, construction, and aircraft.

Claims (11)

  A rubber composition containing at least a rubber component, sulfur, zinc oxide, fatty acid and / or fatty acid zinc, and the weight of fatty acid zinc contained in the vulcanized rubber when the rubber composition is vulcanized A rubber composition having an average melting point of 105 ° C. or less.   A rubber composition containing at least a rubber component, sulfur, and fatty acid zinc, and an average melting point per weight of fatty acid zinc contained in the vulcanized rubber when the rubber composition is vulcanized is 105 ° C. or less. A rubber composition characterized in that   The rubber composition according to claim 1 or 2, wherein the content of fatty acid and / or fatty acid zinc is 4 parts by mass or less with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 1 or 3, wherein the fatty acid is at least one selected from caprylic acid, pelargonic acid, capric acid, lauric acid, mytilic acid, oleic acid, linoleic acid, and vaccenic acid.   The fatty acid zinc is at least one selected from zinc caprylate, zinc pelargonate, zinc caprate, zinc laurate, zinc myristylate, zinc oleate, zinc linoleate, and zinc vaccenate. The rubber composition as described in any one of -3.   The rubber composition according to any one of claims 1 to 5, comprising 20 to 60 parts by mass of carbon black with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 6, wherein the rubber component and the carbon black comprise a master batch.   The rubber composition according to any one of claims 1 to 7, comprising 25 parts by mass or less of silica with respect to 100 parts by mass of the rubber component.   A rubber composition according to any one of claims 1 to 8, wherein the rubber composition is a tire tread composition.   A pneumatic tire using the rubber composition according to any one of claims 1 to 9.   The pneumatic tire according to claim 10, wherein the pneumatic tire is a heavy duty pneumatic tire.