JP5448054B2 - Rubber for tire tread and tire using the same - Google Patents

Description

  The present invention relates to a tire tread rubber capable of exhibiting high wear resistance and excellent adhesion, and a tire having the same in a tread portion.

  In recent years, in response to the demand for lower fuel consumption of automobiles, development of tires that reduce the rolling resistance of the tires and suppress heat generation has been promoted. Among the tire members, an excellent low heat generation property is required for a tread having a high occupation ratio in the tire.

  Therefore, in the rubber composition for tire tread, carbon black, which has been conventionally used as a reinforcing agent, is partly replaced with silica to reduce rolling resistance and reduce fuel consumption.

  However, since silica has a lower affinity for the rubber component than carbon black, the reinforcing effect of the rubber is small.

  Therefore, in order to increase the silica reinforcing effect to the same level as that of carbon black, it is possible to increase the silica reinforcing effect by improving the dispersibility of silica or by chemically combining the rubber component and silica. A method of reducing rolling resistance has been proposed.

  In Patent Document 1, a tire tread is manufactured using a rubber composition for a tire tread to which a predetermined tin compound is added together with a diene rubber, silica, and a silane coupling agent, thereby reducing the fuel consumption of the vehicle. Technology is disclosed. Patent Document 2 discloses a technique for reducing fuel consumption of a vehicle by producing a tire tread using a rubber composition for a tire tread containing an emulsion polymerization rubber obtained by emulsion polymerization, silica, and a silane coupling agent. Is disclosed. These techniques can improve the rolling resistance of the tire, but further improvement in wear resistance is required.

  Patent Document 3 and Patent Document 4 disclose a technique for achieving both low fuel consumption performance and grip performance by blending acrylonitrile butadiene rubber. Although this technology can improve both the rolling resistance performance and wear resistance performance of the tire, since it uses a polar polymer such as acrylonitrile butadiene rubber, the adhesion to members other than the tire tread made of a nonpolar polymer deteriorates. There is a problem of doing.

Japanese Patent Laid-Open No. 11-181161 JP 2000-248120 A JP 2003-26860 A JP-A-2-114003

  An object of the present invention is to provide a tire tread rubber capable of realizing high wear resistance and having sufficient adhesion to members other than the tire tread, and a tire having excellent fuel efficiency using the same. It is to be.

  The present invention relates to a tire tread rubber comprising a cap rubber and a base rubber, wherein the cap rubber contains an acrylonitrile-butadiene copolymer rubber and an amino-terminated liquid rubber, and the base rubber contains a diene rubber and an epoxidized natural rubber. Rubber for tire tread.

  In the rubber for tire tread according to the present invention, the rubber component of the cap rubber contains 5 to 80% by mass of acrylonitrile-butadiene copolymer rubber, and 2 to 40 of the amino-terminated liquid rubber with respect to 100 parts by mass of the rubber component. It is preferable to include parts by mass.

Rubber tire tread according to the present invention, the cap rubber per 100 parts by mass of the rubber component, the nitrogen adsorption specific surface area by BET method is 50m ² / g~500m ² / g of silica containing 30 to 100 parts by weight It is preferable.

  In the tire tread rubber according to the present invention, the amino-terminated liquid rubber is preferably an amino-terminated liquid acrylonitrile-butadiene copolymer rubber.

  The present invention is a tire having the tire tread rubber in a tread portion.

  According to the present invention, a tire having excellent wear resistance performance by blending acrylonitrile-butadiene copolymer, low fuel consumption by blending silica, and sufficient adhesion performance to other tire members. A tread rubber and a tire using the same can be provided.

  The rubber for tire tread according to the present invention comprises a cap rubber on the ground surface side and a base rubber inside the tire, the cap rubber contains an acrylonitrile-butadiene copolymer rubber and an amino-terminated liquid rubber, and the base rubber is a diene rubber. Contains epoxidized natural rubber. In the rubber for tire tread of the present invention, since the cap rubber contains acrylonitrile-butadiene copolymer rubber, excellent wear resistance can be obtained. Further, the adhesion between the cap rubber and the base rubber is improved by the reaction between the amino-terminated liquid rubber of the cap rubber and the epoxidized natural rubber of the base rubber. Furthermore, since the diene rubber usually used for tires and the epoxidized natural rubber having good adhesion are used for the base rubber, the adhesion to members other than the tread is also improved.

<Cap rubber>
(Acrylonitrile-butadiene copolymer rubber)
The rubber component of the cap rubber of the tire tread rubber according to the present invention may contain a known acrylonitrile-butadiene copolymer rubber (hereinafter also referred to as “NBR”) obtained by polymerizing acrylonitrile and butadiene. The other rubber component may contain a diene rubber usually used in tires. As NBR, a carboxyl-modified acrylonitrile-butadiene copolymer rubber (hereinafter also referred to as “carboxyl-modified NBR”) obtained by copolymerizing a vinyl monomer having a carboxyl group, acrylonitrile and butadiene can be used. Further, hydrogenated acrylonitrile-butadiene copolymer rubber (hereinafter also referred to as “hydrogenated NBR”) or hydrogenated carboxyl-modified acrylonitrile-butadiene obtained by hydrogenating acrylonitrile-butadiene copolymer rubber or carboxyl-modified acrylonitrile-butadiene copolymer rubber. Copolymer rubber (hereinafter also referred to as “hydrogenated carboxyl-modified NBR”) can be used. The preferable amount of acrylonitrile copolymerization in NBR is 10 to 80% by mass from the viewpoint of improving the wear performance.

  The content of NBR is 5% by mass or more, preferably 10% by mass or more, and more preferably 20% by mass or more in the rubber component from the viewpoint of reducing rolling resistance and improving wear resistance. When the content of NBR is less than 5% by mass, there is no effect obtained by containing NBR. The NBR content is 80% by mass or less, preferably 75% by mass or less, and more preferably 70% by mass or less. If the NBR content exceeds 80% by mass, the adhesive strength with other rubbers decreases. Further, from the viewpoint of realizing higher wear resistance, the acrylonitrile copolymerization amount of NBR is preferably 20% by mass or more, and more preferably 25% by mass or more. The acrylonitrile copolymerization amount is the mass of acrylonitrile with respect to the total mass of NBR, and can be measured by a known method such as IR spectrum method, Kjeldahl method, or gas chromatograph method.

(Amino-terminated liquid rubber)
The tire tread rubber cap rubber according to the present invention contains an amino-terminated liquid rubber having amino groups at both ends of the molecule. Since this amino-terminated liquid rubber has a main chain of rubber and has reactive amino groups at both ends of the molecule, it can impart toughness (a property that does not break even when bent) to the thermosetting resin. . In addition, when press vulcanizing with the base rubber described later, the amino group in the amino-terminated liquid rubber reacts with the epoxy group in the epoxidized natural rubber of the base rubber, and the cap rubber and the base rubber are excellent. Adhesiveness can be realized.

  As the amino-terminated liquid rubber, amino-terminated liquid acrylonitrile-butadiene copolymer rubber is preferably used.

  The number average molecular weight of the amino-terminated liquid rubber is preferably 500 to 50,000. The content of the amino-terminated liquid rubber is preferably 2 to 40 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of improving adhesiveness.

  Examples of rubber other than NBR used for the rubber component of the cap rubber include natural rubber (NR), polyisoprene synthetic rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and chloroprene rubber. At least one selected from the group consisting of (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR) can be used. From the viewpoint of achieving sufficient tire strength and achieving excellent wear resistance, it is preferable to use a mixed rubber of NR / NBR, BR / NBR, SBR / NBR as the rubber component used in the present invention. . Here, as BR, NBR, and SBR, known ones can be used.

(silica)
The cap rubber of the tire tread rubber according to the present invention preferably contains silica. The cap rubber, nitrogen adsorption specific surface area by the BET method can be conventional silica of 50m ² / g~500m ² / g. For example, silica (anhydrous silicic acid) obtained by a dry method and / or silica (hydrous silicic acid) obtained by a wet method can be used. Among these, it is preferable to use silica obtained by a wet method.

  The content of silica in the cap rubber is preferably 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. Depending on the content, it is possible to obtain a tire tread rubber capable of realizing both low rolling resistance and high wear resistance.

Silica used in the cap rubber is preferably a nitrogen adsorption specific surface area by BET method is 50m ² / g~500m ² / g. When the nitrogen adsorption specific surface area of silica is less than 50 m ² / g, the fracture strength after vulcanization tends to decrease, and when it exceeds 500 m ² / g, the workability tends to deteriorate. In addition, the nitrogen adsorption specific surface area by the BET method of a silica can be measured by the method based on ASTM-D-4820-93.

(Silane coupling agent)
In the present invention, since silica is used, it is preferable to incorporate what is generally known as a silane coupling agent. Examples of coupling agents include: γ-aminopropyltriethoxysilane, vinyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltri Examples include methoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and bis- (3-triethoxysilylpropyl) -tetrasulfide. The compounding amount of the coupling agent is 5 to 20% of the silica compounding amount. If the amount of the coupling agent is small, the heat generation of the tire increases. Conversely, if the amount of the coupling agent is too large, the hardness of the rubber increases, and the rubber chipping performance on a rough road decreases. In addition, the cost becomes high and the practicality becomes poor.

(Other ingredients)
The cap rubber of the tire tread rubber according to the present invention includes a vulcanizing agent (for example, sulfur), a vulcanization accelerator, a vulcanization auxiliary (for example, stearic acid, zinc oxide, etc.), an anti-aging agent, a filler, and a softening agent. Plasticizers, tackifiers and the like can be added as necessary.

  Examples of vulcanization accelerators include sulfenamide (vulcanization accelerators NS, CZ, DZ, etc.), thiazonyl (vulcanization accelerator M, MZ, etc.), guanidine (vulcanization accelerators D, DT, etc.). ) Etc. can be used. In particular, a method in which a guanidine series and one of the former two are used in combination is exemplified.

<Base rubber>
(Epoxidized natural rubber)
The rubber component of the base rubber of the tire tread rubber according to the present invention contains a diene rubber and an epoxidized natural rubber. The epoxidation degree of the epoxidized natural rubber is preferably 3 to 50% mol. The content of the epoxidized natural rubber is preferably 2 to 20% by mass of the net epoxidized natural rubber content converted by the epoxidation rate in the rubber component of the base rubber. When the content of the epoxidized natural rubber is 2 to 20% by mass, the epoxy group in the epoxidized natural rubber reacts with the amino group of the amino-terminated liquid rubber, and good adhesiveness can be obtained.

  Epoxidized natural rubber is obtained by reaction of natural rubber latex with peracetic acid. This reaction epoxidizes the double bond present in the natural rubber molecule, and its structure is revealed by proton nuclear magnetic resonance spectrum (NMR) and infrared absorption spectrum (IR). In addition, the content of epoxy groups is measured from IR and elemental analysis. The epoxidized natural rubber used in the present invention has an epoxidation degree of 3 to 50 mol%, preferably 10 to 50 mol%. If the degree of epoxidation is less than 3 mol%, the effect of epoxidation does not appear, and if it exceeds 50 mol%, the glass transition point becomes too high and the durability at low temperatures is poor.

  Examples of the diene rubber used for the rubber component of the base rubber include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and styrene-isoprene-butadiene copolymer rubber (SIBR). ) Etc. can be used.

  The rubber other than the diene rubber and the epoxidized natural rubber used for the rubber component of the base rubber is, for example, at least selected from the group consisting of polyisoprene synthetic rubber (IR), chloroprene rubber (CR), and butyl rubber (IIR). One type can be used.

<Cap rubber, base rubber>
The cap rubber and the base rubber of the tire tread rubber according to the present invention preferably contain the following components in addition to the rubber component and the amino-terminated liquid rubber.

(Other ingredients)
The base rubber of the tire tread rubber according to the present invention includes a vulcanizing agent (for example, sulfur), a vulcanization accelerator, a vulcanization auxiliary (for example, stearic acid, zinc oxide, etc.), an anti-aging agent, silica, carbon black, Silane coupling agents, fillers, softeners, plasticizers, tackifiers and the like can be added as necessary. When silica is contained, the amount is preferably 20 to 100 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of balance between hardness and fuel efficiency for maintaining steering stability.

  Examples of vulcanization accelerators include sulfenamide (vulcanization accelerators NS, CZ, DZ, etc.), thiazonyl (vulcanization accelerator M, MZ, etc.), guanidine (vulcanization accelerators D, DT, etc.). ) Etc. can be used. In particular, a method in which a guanidine series and one of the former two are used in combination is exemplified.

<Examples 1-11, Comparative Examples 1-11>
(Production of tread rubber)
Using 1.7 L Banbury, rubber components, amino-terminated liquid NBR, silica, silane coupling agent, plasticizer, zinc oxide, stearic acid, aging as shown in the cap rubber and base rubber of Tables 1 and 2 An inhibitor was kneaded. Next, sulfur and a vulcanization accelerator were added to the kneaded material obtained using a roll and kneaded to obtain a cap rubber unvulcanized rubber composition and a base rubber unvulcanized rubber composition.

  The obtained cap rubber unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a cap rubber vulcanized rubber composition. An abrasion resistance test was conducted using the cap rubber vulcanized rubber composition.

  Further, a base rubber unvulcanized rubber composition was superimposed on a cap rubber unvulcanized rubber composition, and a rubber composition was obtained by press vulcanization at 170 ° C. for 15 minutes and vulcanized and bonded. At this time, vulcanization was performed with a cellophane sandwiched about 60 mm from the end in order to allow the tester to grip. An adhesion performance test was performed on the rubber composition obtained by vulcanizing and bonding the obtained cap rubber and base rubber.

(Abrasion resistance test)
Test pieces were prepared from rubber sheets of the vulcanized rubber compositions of the cap rubbers of Examples 1 to 11 and Comparative Examples 1 to 11, and the temperature was 20 ° C., the slip rate was 20%, and the test was performed using a lamborn abrasion tester. The amount of lamborn wear was measured under the condition of 5 minutes, and the volume loss was calculated. The wear index was calculated from the following formula using Comparative Example 1 for the formulation in Table 1 and the volume loss of Comparative Example 7 as the reference (100) for the formulation in Table 2. It shows that it is excellent in abrasion resistance, so that an abrasion index is large.

(Wear index (Table 1)) = (Volume loss amount of Comparative Example 1) / (Volume loss amounts of Examples 1 to 6 and Comparative Examples 1 to 6) × 100
(Wear Index (Table 2)) = (Volume Loss of Comparative Example 7) / (Volume Loss of Examples 7-11 and Comparative Examples 7-11) × 100
(Adhesion performance test)
The test was carried out according to JIS K6256 (peeling test of cloth and vulcanized rubber). A rubber sheet of a rubber composition obtained by vulcanizing and bonding cap rubber and base rubber was cut into a width of 25 mm to prepare a test piece. The test piece was peeled off at a speed of 50 mm / min for a peel test. The adhesive performance index was calculated from the following formula using Comparative Example 1 in the formulation of Table 1 and the adhesive strength of Comparative Example 7 as the reference (100) in the formulation of Table 2. The larger the adhesion performance index, the better the adhesion performance.

(Adhesive performance index (Table 1)) = (Adhesive strength of Examples 1-6 and Comparative Examples 1-6) / (Adhesive strength of Comparative Example 1) × 100
(Adhesive Performance Index (Table 2)) = (Each adhesive strength of Examples 7 to 11 and Comparative Examples 7 to 11) / (Adhesive strength of Comparative Example 7) × 100

NR: RSS # 3
NBR: NIPOL 1042 manufactured by Nippon Zeon Co., Ltd. (acrylonitrile-butadiene copolymer rubber, acrylonitrile copolymerization amount: 35% by mass)
Carboxyl-modified NBR: DN631 (carboxyl-modified acrylonitrile-butadiene copolymer rubber, acrylonitrile copolymerization amount: 33.5% by mass) manufactured by Nippon Zeon Co., Ltd.
Hydrogenated carboxyl-modified NBR: VPKA8889 manufactured by LANXESS (hydrogenated carboxyl-modified acrylonitrile-butadiene copolymer rubber, acrylonitrile copolymerization amount: 35% by mass)
Amino-terminated liquid NBR: Hycar ATBN 1300 × 16 (number average molecular weight: 5,500) manufactured by BF Goodrich
SBR: NS116 manufactured by JSR Corporation (vinyl content: 60%, styrene content: 20%)
ENR25: Epoxidized natural rubber (epoxidation rate: 25% mol) manufactured by Kumpulan Gatherie Berhad (Malaysia)
Silica: ULTRASIL VN3 manufactured by Degussa (nitrogen adsorption specific surface area: 175 m ² / g)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Tegusa
Plasticizer: DOP manufactured by Taoka Chemical Co., Ltd.
Zinc oxide: Zinc Hua 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Agate manufactured by Nippon Oil & Fats Co., Ltd. Anti-aging agent: Antigen 6C (N- (1,3-dimethylbutyl) manufactured by Sumitomo Chemical Co., Ltd. -N'-phenyl-p-phenylenediamine)
Sulfur: Tsurumi Chemical Co., Ltd. vulcanization accelerator NS: Nouchira NS (N-tert-butyl-2-benzothiazolylsulfanamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator D: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(Evaluation results)
In Examples 1 to 4 and 7 to 9, wear resistance performance was improved by using NBR as a cap rubber. Further, since the cap rubber contains amino-terminated liquid NBR and the base rubber contains epoxidized natural rubber (ENR25), the amino group and the epoxy group react during vulcanization to improve the adhesion. Examples 5, 6, 10, and 11 are the same as Examples 1 to 4 and 7 to 9 except that wear resistance is further improved using carboxy-modified NBR and hydrogenated carboxy-modified NBR.

  Comparative Examples 2 to 5 and 8 to 11 have good wear resistance, but the cap rubber does not contain an amino-terminated liquid NBR, so that the adhesion is very poor. Since Comparative Example 6 does not contain epoxidized natural rubber in the base rubber, the adhesion is very poor.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (2)

In rubber for tire tread consisting of cap rubber and base rubber,
The cap rubber contains 5 to 80% by mass of an acrylonitrile-butadiene copolymer rubber in a rubber component, and 2 to 40 parts by mass of an amino-terminated liquid acrylonitrile-butadiene copolymer rubber and BET with respect to 100 parts by mass of the rubber component. nitrogen adsorption specific surface area of 50m ² / g~500m ² / g of silica containing 30 to 100 parts by weight of law,
The base rubber contains a diene rubber and an epoxidized natural rubber;
Rubber for tire tread. Tire having a rubber claim 1 Symbol mounting of the tire tread to the tread portion.