JP2007284507A - Rubber composition for tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for treads, which can improve the reaction efficiency of a silane coupling agent, when kneaded, can control the production of ethanol to prevent the formation of bubbles, and can improve the rolling resistance and abrasion resistance of the treads. <P>SOLUTION: This rubber composition for the treads, comprising a rubber component and silica, is characterized by containing boron oxide, and a silane coupling agent in an amount of 3 to 15 pts.wt. per 100 pts.wt. of the silica. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tread.

  In recent years, there has been a strong demand for lower fuel consumption of tires, and in order to satisfy the demand, silica is mixed with a tread that can reduce rolling resistance. However, since sufficient reinforcement cannot be obtained with silica alone, a silane coupling agent is used in combination with silica. For tires, silane coupling agents containing alkoxyl groups are generally used. However, the reaction of the silane coupling agent cannot be sufficiently completed in the rubber kneading step, and in order to obtain sufficient reinforcement, the silane coupling agent has to be blended more than necessary. Also, the silane coupling agent that could not react during kneading (hereinafter referred to as unreacted coupling agent) reacts in the extrusion process to generate alcohol (such as ethanol), and in the extruded unvulcanized tread There was a problem in the process of generating bubbles.

  Patent Document 1 includes a predetermined amount of a predetermined rubber component, silica, a silane coupling agent, and a predetermined basic aqueous solution, thereby providing excellent wear resistance, low fuel consumption, wet performance, workability, and workability. A rubber composition is disclosed. However, the rubber composition can improve the reaction efficiency of the silane coupling agent, but the improvement effect is not sufficient, and the generation of bubbles is not completely suppressed, so there is still room for improvement. There is.

JP 2000-219779 A

  The present invention increases the reaction efficiency of the silane coupling agent during kneading, suppresses the generation of bubbles by suppressing the amount of ethanol generated, and can further improve both rolling resistance characteristics and wear resistance. It aims at providing the rubber composition for treads.

  The present invention relates to a rubber composition for a tread containing a rubber component and silica, and the rubber composition for a tread containing 3 to 15 parts by weight of a silane coupling agent and boron oxide with respect to 100 parts by weight of the silica. About.

  The content of boron oxide is preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the rubber component.

  The present invention contains a rubber component and boron oxide, and further contains silica and a silane coupling agent at a predetermined ratio, thereby increasing the reaction efficiency of the silane coupling agent during kneading and suppressing the amount of ethanol generated. Thus, it is possible to provide a rubber composition for a tread that can improve both rolling resistance characteristics and wear resistance.

  The rubber composition for a tread of the present invention contains a rubber component, silica, a silane coupling agent, and boron oxide.

  Examples of the rubber component include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber ( NBR) and butyl rubber (IIR). These rubber components may be used alone or in combination of two or more. Among these, a diene rubber is preferable and SBR is more preferable because wet grip performance and wear resistance can be improved.

  Silica includes silica produced by a wet method or a dry method, but is not particularly limited.

Silica has a BET specific surface area (BET) of preferably 45 m ² / g or more, and more preferably 70 m ² / g or more. If the BET of silica is less than 45 m ² / g, the reinforcing property tends not to be improved. Further, BET of silica is 500m or less preferably ² / g, more preferably at most 450 m ² / g. If the BET of silica exceeds 500 m ² / g, it tends to be difficult to disperse in the rubber.

  The content of silica is preferably 10 parts by weight or more and more preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of silica is less than 10 parts by weight, there is a tendency that almost no improvement effect such as rolling resistance characteristics and wet grip performance due to the inclusion of silica is observed. The silica content is preferably 120 parts by weight or less, and more preferably 100 parts by weight or less. When the content of silica exceeds 120 parts by weight, the hardness is excessively increased and sufficient wet grip performance tends not to be obtained.

  As the silane coupling agent, a silane coupling agent that has been conventionally used together with silica can be used. Specifically, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) can be used. ) Tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetra Sulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, Screw (2-to Rimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) ) Disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl Tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl- , N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate Sulfide series such as monosulfide, mercapto series such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltriethoxysilane, vinyltri Vinyl type such as methoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) a Amino compounds such as nopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl Glycidoxy type such as methyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloro Examples include chloro-based compounds such as propyltriethoxysilane, 2-chloroethyltrimethoxysilane, and 2-chloroethyltriethoxysilane. These may be used alone or in combination of two or more.

  The content of the silane coupling agent is 3 parts by weight or more, preferably 4 parts by weight or more with respect to 100 parts by weight of silica. If content of a silane coupling agent is less than 3 weight part, the improvement effect of the reinforcement improvement by containing a silane coupling agent will not be seen. The content of the silane coupling agent is 15 parts by weight or less, preferably 12 parts by weight or less. When the content of the silane coupling agent exceeds 15 parts by weight, the hardness increases and the wet grip performance decreases.

  Examples of boron oxide include diboron trioxide, boron trioxide, diboron dioxide, tetraboron trioxide, tetraboron pentoxide, etc., but it is said to be excellent in improving the reaction efficiency of the silane coupling agent. For reasons, diboron trioxide is preferred.

  The content of boron oxide is preferably 0.2 parts by weight or more and more preferably 0.5 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of boron oxide is less than 0.2 parts by weight, the effect of improving the reaction efficiency of the silane coupling agent tends to be hardly observed. Further, the content of boron oxide is preferably 5 parts by weight or less, and more preferably 2.5 parts by weight or less. When the content of boron oxide exceeds 5 parts by weight, the reaction of the silane coupling agent is promoted too much, and the aggregation reaction between the silane coupling agents tends to increase.

  The rubber composition for a tread of the present invention contains the rubber component and boron oxide, and further contains silica and a silane coupling agent at a predetermined ratio, thereby increasing the reaction efficiency of the silane coupling agent during kneading. Further, by suppressing the generation amount of ethanol, it is possible to suppress the generation of bubbles, and to improve both the rolling resistance characteristics and the wear resistance.

  In addition, the rubber composition for treads of the present invention may contain carbon black.

  When carbon black is contained, the content of carbon black is preferably 5 parts by weight or more and more preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component. When the carbon black content is less than 5 parts by weight, the effect of improving the dry grip performance tends to be small. The carbon black content is preferably 100 parts by weight or less, and more preferably 80 parts by weight or less. When the content of carbon black exceeds 100 parts by weight, it becomes too hard and the grip performance tends to be lowered.

  In addition to the rubber component, silica, silane coupling agent and boron trioxide, the rubber composition for tread of the present invention includes compounding agents conventionally used in the rubber industry, for example, softeners such as aroma oil, various aging An inhibitor, a vulcanizing agent such as stearic acid, zinc oxide and sulfur, various vulcanization accelerators and the like can be appropriately blended as necessary.

  A tire using the rubber composition for a tread of the present invention is produced by a usual method. That is, if necessary, the rubber composition for a tread of the present invention blended with the above-mentioned compounding agent is extruded in accordance with the shape of the tire tread at an unvulcanized stage, and a normal method is performed on a tire molding machine. An unvulcanized tire is formed by molding with. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Next, various chemicals used in Examples and Comparative Examples will be described together.
Styrene butadiene rubber (SBR): SBR NS210 manufactured by Nippon Zeon Co., Ltd.
Carbon black: Diamond Black I (N220) manufactured by Mitsubishi Chemical Corporation
Silica: Ultrazil VN3 manufactured by Degussa (BET: 175 m ² / g)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Diboron trioxide: Reagent potassium tetraborate tetrahydrate: Aroma oil manufactured by Wako Pure Chemical Industries, Ltd .: X140 manufactured by Japan Energy Co., Ltd.
Anti-aging agent: Nocrack 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Nippon Oil & Fats Co., Ltd. Zinc oxide: Mitsui Metal Mining Co., Ltd. Sulfur: Tsurumi Chemical Industry Co., Ltd. Vulcanization Accelerator (1): Nouchira NS (N -Tert-butyl-2-benzothiazolylsulfenamide)
Vulcanization accelerator (2): Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Co., Ltd.

Examples 1-5 and Comparative Examples 1-3
In accordance with the formulation of Table 1, using a 1.7 L Banbury mixer, knead the chemicals other than the antioxidant, stearic acid, zinc oxide, sulfur and vulcanization accelerator for 3 minutes at 150 ° C. A kneaded product 1 was obtained (step 1). Subsequently, after discharging, an anti-aging agent, stearic acid and zinc oxide are added to the kneaded material 1 obtained in step 1 using a Banbury mixer, kneaded for 2 minutes at 130 ° C., and mixed. A kneaded product 2 was obtained (step 2). Next, using an open roll, sulfur and a vulcanization accelerator were added to the kneaded material 2 obtained in step 2, and kneaded for 4 minutes at 60 ° C. to obtain an unvulcanized rubber sheet ( Step 3). Furthermore, the unvulcanized rubber sheet obtained in Step 3 was press vulcanized for 20 minutes under the condition of 170 ° C. to prepare vulcanized rubber sheets of Examples 1 to 5 and Comparative Examples 1 to 3.

(Unreacted coupling agent amount)
The unvulcanized rubber sheet was cut into small pieces and subjected to an extraction test using ethanol for 24 hours. Then, the amount of unreacted silane coupling agent extracted in the extract is measured with a gas chromatograph, and the weight ratio (% by weight) of the amount of unreacted silane coupling agent to the total amount of silane coupling agent is calculated. did. The smaller the weight ratio, the smaller the amount of unreacted silane coupling agent, and the better.

(Ethanol generation amount)
Create a test piece from the unvulcanized rubber sheet, using a head space gas chromatograph, heated for 10 minutes at 150 ° C. to drive off volatile components (ethanol), measure the amount of ethanol generated at that time, The ethanol generation index of Comparative Example 1 was set to 100, and the amount of ethanol generated for each formulation was displayed as an index according to the following formula. In addition, it shows that the smaller the ethanol generation index is, the smaller the amount of ethanol generated and the less bubbles are generated.
(Ethanol generation index) = (Ethanol generation amount of each formulation)
÷ (Amount of ethanol generated in Comparative Example 1) × 100

(Viscoelasticity test)
Loss tangent (tan δ) of vulcanized rubber sheet at 70 ° C. using viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under conditions of frequency 10 Hz, initial strain 10%, dynamic strain 2%. The rolling resistance index of Comparative Example 1 was set to 100, and tan δ of each formulation was indicated by an index according to the following calculation formula. In addition, it shows that rolling resistance is reduced and it is excellent, so that a rolling resistance index | exponent is large.
(Rolling resistance index) = (tan δ of Comparative Example 1)
÷ (tan δ of each formulation) × 100

(Abrasion resistance)
Using a Lambourn wear tester, the Lambourn wear amount was measured under the conditions of a load of 2.5 kgf, a slip rate of 40% and a test time of 3 minutes. Further, the volume loss amount was calculated from the measured lamborn wear amount, the lamborn wear index of Comparative Example 1 was set to 100, and the volume loss amount of each formulation was displayed as an index according to the following formula. In addition, it shows that it is excellent in abrasion resistance, so that a Lambourn abrasion index is large.
(Lambourn wear index) = (volume loss amount of Comparative Example 1)
÷ (volume loss of each compound) x 100

  The evaluation results of the above test are shown in Table 1.

  In Comparative Example 1, boron trioxide is not blended, the amount of unreacted coupling agent is large, and generation of ethanol cannot be suppressed, so generation of bubbles cannot be suppressed, and both rolling resistance characteristics and wear resistance are insufficient. This is a conventional tread rubber composition.

  In Examples 1 to 5, by adding boron trioxide, the amount of unreacted coupling agent is reduced compared to Comparative Example 1 in which boron trioxide is not added, and generation of bubbles is suppressed by suppressing the generation of ethanol. The rolling resistance index and the lamborn wear index are both improved.

  Further, in Comparative Example 3 in which 5 parts by weight or more of boron trioxide is blended, the wear resistance and rolling resistance characteristics are lowered.

Claims (2)

A rubber composition for a tread containing a rubber component and silica,
For 100 parts by weight of the silica,
A rubber composition for a tread containing 3 to 15 parts by weight of a silane coupling agent and boron oxide. The rubber composition for a tread according to claim 1, wherein the content of boron oxide is 0.2 to 5 parts by weight with respect to 100 parts by weight of the rubber component.