JP5289890B2 - Rubber composition and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition capable of improving heat build-up, and a pneumatic tire using the rubber composition.

  In recent years, the demand for lower fuel consumption of automobiles has been increasing, and there is a strong demand for reducing the rolling resistance of tires. It is known that the rolling resistance is related to the exothermic property of the rubber composition. Therefore, reducing the hysteresis loss of the rubber composition, that is, suppressing the loss factor (tan δ) to be low is effective in reducing fuel consumption.

  In order to meet such a requirement, it is known that a modified polymer is prepared by adding a modifying group to a diene synthetic rubber such as styrene-butadiene rubber at the time of polymer production. The modified diene rubber can improve the affinity with an unmodified diene rubber with a filler such as carbon black or silica, and can increase the reactivity. Therefore, heat generation can be suppressed and fuel efficiency can be improved. However, this technique can generally only be carried out under anionic polymerization, so that the polymer species are limited to styrene-butadiene rubber and butadiene rubber with a low cis content. Therefore, although the fuel efficiency can be improved, there is a demerit that the reinforcing property is lowered.

  In Patent Documents 1 and 2 below, in order to improve the dispersibility of the filler in the natural rubber composition, a modified natural rubber obtained by graft polymerization of a polar group-containing monomer on a natural rubber latex, and a styrene-butadiene rubber or It is disclosed that a butadiene rubber is blended with a modified diene-based synthetic rubber obtained by modifying a tertiary amino group. In these documents, various types of polar groups are listed, but the actual amino acids used in the examples are tertiary amino groups. Therefore, modified natural rubbers and tertiary amino groups modified with tertiary amino groups are used. Only a combination with a modified diene-based synthetic rubber modified with a group is disclosed. Patent Document 3 below discloses that a diene rubber having an amino group introduced therein is blended with a diene rubber having a hydroxyl group and / or an epoxy group introduced therein.

  However, these documents merely disclosed the use of a blend of a modified diene rubber having a functional group that interacts with the filler in order to improve the dispersibility of the filler such as silica or carbon black. There is nothing.

On the other hand, Patent Document 4 below discloses blending epoxidized natural rubber and chlorosulfonated polyethylene as a rubber composition having self-crosslinkability, but is not a combination of diene rubber polymers, Also, it is silent about the point of achieving both low heat generation and reinforcement.
JP 2006-15211 A JP 2006-152212 A JP 2006-036822 A JP 2001-329119 A

  In view of the above points, the present invention provides a rubber composition comprising a diene rubber polymer capable of improving low heat buildup without impairing reinforcing properties, and a pneumatic tire using the rubber composition. With the goal.

The rubber composition according to the present invention includes 20 to 80 parts by weight of a diene rubber polymer (A) having a carboxyl group introduced therein, and a diene rubber polymer (B) 80 to 20 having at least one amino group and hydroxyl group introduced therein. containing 100 parts by weight of a rubber component comprising a weight section, wherein the diene rubber polymer (a) and the diene rubber polymer (B) are each a styrene - is at least one selected from butadiene rubber and polybutadiene rubber The tire rubber composition .

  The pneumatic tire according to the present invention is obtained by using the rubber composition as at least a part of the tire.

  According to the present invention, the low exothermic property can be improved without impairing the reinforcing property by using the diene rubber polymer having the specific functional group in combination as the rubber component. This is because the carboxyl group of the diene rubber polymer (A) and the amino group and / or hydroxyl group of the diene rubber polymer (B) react together with the effect of improving the dispersibility of the filler by each functional group, It is considered that both the polymers are cross-linked to compensate for the above-described decrease in the conventional reinforcing property due to the use of the modified polymer. Thus, since low exothermic property can be improved without impairing the reinforcing property, when used in a tire, the rolling resistance can be reduced and the fuel efficiency can be improved while maintaining the reinforcing property.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition according to the present invention uses, as a rubber component, a diene rubber polymer (A) having a carboxyl group introduced therein and a diene rubber polymer (B) having at least one amino group and hydroxyl group introduced therein. It will be.

  In these diene rubber polymers (A) and (B), the type of polymer used as a base is not particularly limited as long as it is a diene polymer. Examples of the diene polymer include a polymer of a conjugated diene monomer, or a copolymer of a conjugated diene monomer and an aromatic vinyl monomer. Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, and 1,3-butadiene and isoprene are particularly preferable. Examples of the aromatic vinyl monomer include styrene, o-, m- or p-methylstyrene, p-tert-butylstyrene, vinylnaphthalene and the like, and styrene is particularly preferable. Specific examples of the polymer include styrene-butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and the like. More preferred are SBR and BR.

  The diene rubber polymer (A) is a modified diene polymer containing a carboxyl group (—COOH). Such a diene polymer containing a carboxyl group is known per se, and such a known modified diene polymer can be used. The method for producing the modified diene polymer is not limited. For example, a carboxyl group may be introduced by modifying a polymer synthesized by anionic polymerization with a modifying agent, or a polymer synthesized by emulsion polymerization may be modified. The monomer having a carboxyl group may be introduced into the polymer chain by copolymerizing with the monomer of the base polymer. More specifically, for example, as disclosed in JP-A-5-255408, a conjugated diene monomer is polymerized in a hydrocarbon solvent using an alkyllithium catalyst as an initiator, and an active living end and a dioxide. By reacting carbon, a carboxyl group can be introduced into the polymer terminal. Further, a carboxyl group may be introduced into the polymer main chain by adding thioglycolic acid to polybutadiene having a 1,2-double bond.

  The diene rubber polymer (B) is a modified diene polymer containing an amino group and / or a hydroxyl group. By combining the diene rubber polymer (B) introduced with such an amino group or hydroxyl group having reactivity to the carboxyl group with the diene rubber polymer (A), low exothermicity is obtained without impairing the reinforcing property. It can be improved. The diene rubber polymer (B) contains an amino group in addition to a diene polymer containing an amino group, a diene polymer containing a hydroxyl group, a diene polymer containing an amino group and a hydroxyl group alone. A diene polymer and a diene polymer containing a hydroxyl group may be used in combination.

  A diene polymer itself containing an amino group or a hydroxyl group is known, and its production method and the like are not limited. For example, an amino group or a hydroxyl group may be introduced by modifying a polymer synthesized by anionic polymerization with a modifying agent, or a polymer synthesized by emulsion polymerization may be modified. You may introduce | transduce into a polymer chain by copolymerizing with the monomer of a base polymer using the monomer which has a group and a hydroxyl group.

  The amino group may be not only a primary amino group but also a secondary or tertiary amino group. The production method of the amino group-modified diene rubber is not particularly limited, and examples thereof include methods disclosed in WO 03/029299 and JP-A-9-71687. The production method of the hydroxyl group-modified diene rubber is not particularly limited, and examples thereof include a method disclosed in WO96 / 23027 and the like.

  The diene rubber polymer (A) and (B) are 20 to 80 parts by weight of the diene rubber polymer (A) and 80 to 20 parts by weight of the diene rubber polymer (B) in 100 parts by weight of the rubber component. Is preferred. When the blending amount of any one of the polymers is less than 20 parts by weight, the effect of improving the reinforcing property due to the reaction with the other polymer becomes small.

  In the rubber composition of the present invention, a diene rubber other than the diene rubber polymers (A) and (B) may be blended as a rubber component within a range not impairing the effects of the present invention. Examples of such other diene rubbers include various unmodified diene rubbers such as natural rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, styrene-isoprene copolymer rubber, butadiene-isoprene. Copolymer rubber and the like.

  You may mix | blend the filler which consists of a silica and / or carbon black with the rubber composition of this invention. Silica and carbon black may be used alone or in combination. Although the compounding quantity of a filler is not specifically limited, It is preferable that it is 20-200 weight part with respect to 100 weight part of rubber components, More preferably, it is 50-100 weight part.

The carbon black is not particularly limited, and for example, carbon black having colloidal characteristics having a nitrogen adsorption specific surface area (BET) of 25 to 160 m ² / g can be used. Here, the nitrogen adsorption specific surface area of carbon black is a value measured according to JIS K6217-2. Examples of such carbon black include various grades such as ASTM numbers N110, N220, N330, N550, and N660.

Examples of silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like. Among them, wet silica having both fracture characteristics and low rolling resistance is used. It is also preferable from the viewpoint of excellent productivity. Although it does not specifically limit as a colloidal characteristic, For example, it is preferable that nitrogen adsorption specific surface area (BET) is 100-300 m < ² > / g. The BET of silica is measured according to the method described in the BET method described in ISO 5794.

  When using silica, it is preferable to use 2-20 weight% of silane coupling agents with respect to the amount of silica, more preferably 5-15 weight%. The silane coupling agent is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetra Examples include sulfide silanes such as sulfide, and protected mercaptosilanes such as 3-octanoylthio-1-propyltriethoxysilane and 3-propionylthiopropyltrimethoxysilane.

  In addition to the above components, the rubber composition of the present invention generally includes a process oil, zinc white, stearic acid, wax, anti-aging agent, vulcanizing agent, vulcanization accelerator, vulcanizing aid, resins and the like. Various additives used in the composition can be used without limitation as long as the effects of the present invention are not impaired. The rubber composition can be prepared by kneading using a commonly used Banbury mixer, a mixer such as a roll or a kneader.

  The use of the rubber composition is not particularly limited, and examples thereof include various uses such as treads and sidewalls, belts and ply topping rubbers, tires such as bead fillers and rim strips, conveyor belts, and vibration-proof rubbers. When the rubber composition is used for a tire, rubber portions (tread rubber and the like) of various pneumatic tires can be constituted by vulcanization molding at, for example, 140 to 200 ° C. according to a conventional method.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a closed banbury mixer with a capacity of 1.7 liters, rubber compositions for tire treads of Examples and Comparative Examples were prepared according to the formulations shown in Tables 1 to 4 below. The detail of each component in Tables 1-4 is as follows.

Unmodified SBR1: Unmodified styrene-butadiene rubber synthesized by anionic polymerization, “VSL5025-2HM” manufactured by LANXESS (styrene content = 24 wt%, vinyl content = 63 wt%),
Modified SBR1: modified styrene-butadiene rubber having a carboxyl group synthesized by anionic polymerization, “PBR4003” manufactured by LANXESS (styrene content = 24 wt%, vinyl content = 63 wt%),
Unmodified SBR2: Unmodified styrene-butadiene rubber, “SBR1721” manufactured by Nippon Zeon Co., Ltd. (styrene content = 40 wt%, vinyl content = 18 wt%),
Modified SBR2: modified styrene-butadiene rubber having amino group, “# 9590” manufactured by Nippon Zeon Co., Ltd. (styrene content = 40 wt%, vinyl content = 18 wt%),
Unmodified BR1: Unmodified polybutadiene rubber synthesized by anionic polymerization, “Diene NF35R” (cis 1,4 content = 32 wt%) manufactured by Asahi Kasei Corporation,
Modified BR1: Modified polybutadiene rubber having a hydroxyl group synthesized by anionic polymerization, “Tuffden E40” (cis 1,4 content = 32 wt%) manufactured by Asahi Kasei Corporation.

  The unmodified SBR1 and the modified SBR1, the unmodified SBR2 and the modified SBR2, and the unmodified BR1 and the modified BR1 are polymers that are substantially different only in the presence or absence of modification.

In each rubber composition, as a common formulation, 75 parts by weight of silica (“Ultrasil 7000GR” manufactured by Evonik, BET = 170 m ² / g) is added to 100 parts by weight of the rubber component, and a silane coupling agent (Evonik “ Si69 ") 5.6 parts by weight, mineral oil (aromatic oil," X-140 "manufactured by JOMO) 30 parts by weight, anti-aging agent (N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylene Diamine, 2 parts by weight of “Nocrack 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd., 2 parts by weight of stearic acid (“industrial stearic acid” manufactured by Kao Corporation), zinc oxide (“No. 1 zinc manufactured by Mitsui Kinzoku Mining Co., Ltd.) "Hana") 3 parts by weight, paraffin wax (Nippon Seiwa Co., Ltd. "Ozoace 0355") 2 parts by weight, vulcanization accelerator (N-tert-butyl-2-benzothiazolylsulfur) N'amido, Ouchi Shinko Chemical Industrial Co., Ltd. "NOCCELER NS-P"), 1.5 parts by weight of sulfur (Tsurumi Chemical Industry Co., Ltd. "5% oil treated powder sulfur") was blended 2 weight parts.

  Each rubber composition obtained was vulcanized at 160 ° C. for 30 minutes to prepare a test piece having a predetermined shape. Using the obtained test piece, tan δ as a low heat generation index and a reinforcing index The breaking strength was measured by the following method.

Tan δ: According to JIS K6394, tan δ was measured under the conditions of frequency 10 Hz, dynamic strain 2%, 70 ° C., Table 1 shows the values of Comparative Example 1, Table 2 shows the values of Comparative Example 4, and Table 3 shows the values. The values of Comparative Example 7 are shown in Table 4 as indices with the value of Comparative Example 10 as 100. The smaller the numerical value, the smaller the tan δ.

-Breaking strength: According to JIS K6251, a tensile test (dumbbell shape No. 3) was carried out to measure the tensile strength. Table 1 shows the values of Comparative Example 1, Table 2 shows the values of Comparative Example 4, In Table 3, the value of Comparative Example 7 is displayed as an index, and in Table 4, the value of Comparative Example 10 is displayed as an index of 100. The larger the value, the greater the breaking strength and the better the reinforcement.

The results are as shown in Tables 1 to 4. In Comparative Examples 2, 3, 5, 6, 8, 9, 11, and 12, in which one of the modified rubbers is a modified rubber, compared to Comparative Examples 1, 4, 7, and 10 in which unmodified rubbers are combined, low exothermic property Was improved, but the reinforcement was reduced. On the other hand, in Examples 1 to 4 in which modified rubbers are combined, the low exothermic property is greatly improved while maintaining or improving the reinforcing property as compared with Comparative Examples 1, 4, 7, and 10. It was.

Claims (5)

Rubber component 100 comprising 20 to 80 parts by weight of a diene rubber polymer (A) having a carboxyl group introduced therein and 80 to 20 parts by weight of a diene rubber polymer (B) having at least one amino group and hydroxyl group introduced thereto Parts by weight ,
The diene rubber polymer (A) and the diene rubber polymer (B) are at least one selected from styrene-butadiene rubber and polybutadiene rubber, respectively.
Rubber composition for tires . The rubber composition according to claim 1 , which contains sulfur as a vulcanizing agent .   The rubber composition according to claim 1 or 2, comprising a filler composed of silica and / or carbon black. It is an object for tire treads, The rubber composition of any one of Claims 1-3.   The pneumatic tire which used the rubber composition of any one of Claims 1-4 for at least one part of a tire.