JP2007023295A - Method for producing rubber composition for tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a silica-compounded rubber composition for tread, having a low electric resistance, and also having low rolling resistance, abrasion resistance and good wet properties in good balance. <P>SOLUTION: The method for producing the rubber composition for the tread, obtained by compounding 40-90 pts.wt. silica and 5-40 pts.wt. adipic acid diester with 100 pts.wt. diene rubber comprises previously kneading the silica with the adipic acid diester, and further kneading the resultant mixture with other components. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a rubber composition for use in a tire tread.

  In recent years, due to the increasing social demand for low fuel consumption of vehicles, in the development of low fuel consumption tires with reduced rolling resistance, it has been common practice to reduce the hysteresis loss of rubber compositions for treads. As a method of reducing hysteresis loss, it is known that it is effective to reduce the amount of carbon black in the tread rubber composition and use silica as a filler.

  However, since the electrical resistance of the tread rubber composition increases as the carbon black content decreases, the electrical resistance of the tire obtained using the tread rubber composition also increases, and static electricity accumulates in the car and tire. However, there is a problem that it causes radio noise and sparks (ignition) when refueling gasoline. Therefore, it is important how to reduce the electrical resistance of a silica-blended rubber composition with a small amount of carbon black.

  Therefore, the present inventors have found that when a specific adipic acid diester is blended with a rubber composition comprising silica, the electrical resistance can be effectively reduced, and the present invention has been completed. It was.

For example, Patent Documents 1 to 5 describe a technique for blending an adipic acid ester as a plasticizer into a rubber composition, but since only carbon black is used as a filler, electric resistance is reduced. No problem is found, and there is no disclosure or suggestion about using adipic acid diesters to reduce electrical resistance.
JP-A-60-223840 JP-A-61-66733 Japanese Unexamined Patent Publication No. 63-43937 JP-A-1-242644 JP 7-292154 A

  That is, an object of the present invention is to obtain a rubber composition for silica-containing tread having a low electric resistance. Furthermore, an object of the present invention is to obtain a rubber composition for a silica-blended tread having a well-balanced low rolling resistance, wear resistance, and good wet performance.

  The present invention relates to a method for producing a rubber composition for a tread comprising 40 to 90 parts by weight of silica and 5 to 40 parts by weight of adipic acid diester based on 100 parts by weight of a diene rubber. The present invention relates to a method for producing a rubber composition for a tread, in which adipic acid diester is kneaded in advance and then kneaded with other components.

  According to the present invention, it is possible to obtain a rubber composition for a silica-blended tread having a low electrical resistance, and further to provide a rubber composition for a silica-blended tread having a good balance of low rolling resistance, wear resistance, and good wet performance Can be obtained.

  The diene rubber used in the present invention is not particularly limited as long as it is conventionally used in the tire field. For example, natural rubber (NR), styrene butadiene rubber (SBR), isoprene rubber (IR), Examples include ethylene propylene diene rubber (EPDM), isoprene butadiene rubber (IBR), butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and these are used alone or in any combination. be able to. Of these, NR, BR, SBR, and IR are preferably used from the viewpoint of general-purpose rubber generally used for tires.

Next, the silica used in the present invention is not particularly limited as long as it is conventionally used in the field of tires. However, for example, a BET specific surface area of 150 to from the point of reinforcing effect on rubber and rubber processability. It is preferably 250 m ² / g and a DBP oil absorption of 190 to 280 ml / 100 g.

  Examples of commercially available silicas include NIPSIL VN3 and NIPSIL AQ manufactured by Nippon Silica Co., Ltd., Z1165MP and Z165Gr manufactured by Rhone-Poulenc, and Degussa's Ultra Seal VN3.

  The compounding amount of silica in the present invention may be 40 to 90 parts by weight with respect to 100 parts by weight of the diene rubber, but is preferably 60 to 90 parts by weight from the viewpoint of ensuring wet performance. .

  Next, in this invention, the electrical resistance of the rubber composition for treads obtained is reduced by mix | blending adipic acid diester. It is considered that this is because the electric resistance of the obtained tire tread rubber composition can be reduced because free electrons exist in the oxygen atom of the ester bond portion.

As such adipic acid diester, for example, formula (1): HO— (CH ₂ —CH ₂ —O) _m —OOC— (CH ₂ ) ₄ —COO— (O—CH ₂ CH ₂ ) _m —OH (wherein , M is an integer of 10 to 20, and adipic acid (polyethylene glycol) diester (a reaction product of adipic acid and polyethylene glycol), formula (2): C _n H _{2n + 1} —O—C ₂ H ₄ —O—C ₂ H ₄ —OOC— (CH ₂ ) ₄ —COO—C ₂ H ₄ —O—C ₂ H ₄ —O—C _n H _{2n + 1} (where n is 1, 2 or 4) Adipic acid (diethylene glycol monoalkyl ether) diester (reaction product of adipic acid and ether) represented by formula (1) is preferable, but it is preferable to use the compound represented by formula (1) from the viewpoint of high conductivity. .

  The blending amount of the adipic acid diester may be 5 to 40 parts by weight with respect to 100 parts by weight of the diene rubber, but is 15 to 30 parts by weight from the viewpoint of a balance between electric resistance and wear resistance. Is preferred.

  Moreover, the adipic acid diester used in this invention can be manufactured by a conventional method from polyethyleneglycol and adipic acid, for example.

  Furthermore, in this invention, it is preferable to mix | blend a metal salt, especially a metal perchlorate. This is because, in the obtained tread rubber composition, metal ions can form a network with oxygen atoms in the adipic acid diester molecule and ion conduction can reduce the electrical resistance of the obtained tread rubber composition. is there.

Any metal salt may be used as long as it can provide a metal ion in the rubber composition of the present invention. Examples thereof include perchlorates such as LiClO ₄ , KClO ₄ , NaClO ₄ , and Mg (ClO ₄ ) _2. In particular, lithium salts are preferable. Among them, it is preferable to use LiClO ₄ from the viewpoint that there is no risk of explosion and there is safety, and the wear resistance of the obtained tread is improved.

  The compounding amount of the metal salt may be 1 to 5 parts by weight with respect to 100 parts by weight of the adipic acid diester, but it is preferably 3 to 5 parts by weight from the viewpoint of high conductivity.

  In the present invention, a silane coupling agent is preferably further blended. This, when a silane coupling agent is blended, the adipic acid diester and the diene rubber are chemically bonded via the silane coupling agent, can further reduce rolling resistance and improve wet performance, This is because the temperature dependence of hardness is reduced.

  The silane coupling agent is not particularly limited as long as it is conventionally used in the tire field. For example, vinyltrimethoxysilane, vinyltriethoxysilane, N- (2-aminoethyl) -3-amino Examples include propylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, and 3-glycidoxypropylmethyldimethoxysilane.

  The blending amount of the silane coupling agent may be a minimum amount necessary for reducing rolling resistance and improving wet performance, and can be appropriately selected by those skilled in the art.

  In addition to the above components, the rubber composition of the present invention includes, for example, fillers such as talc, clay and carbon black, softeners such as paraffinic, aromatic and naphthenic process oils, coumarone indene resins, The present invention includes tackifiers such as rosin resins and cyclopentadiene resins, vulcanizing agents such as sulfur and peroxides, vulcanization accelerators, vulcanization aids such as stearic acid and zinc oxide, and antiaging agents. In the range which does not impair the effect, it can mix | blend suitably as needed.

  Next, a method for producing the tread rubber composition of the present invention will be described.

  The rubber composition for a tread of the present invention can be obtained by kneading the above components at once in a conventional manner, but adipic acid diester and silica are kneaded in advance from the viewpoint that adipic acid diester is attached to the silica surface. It is preferred that the adipic acid diester is physically or chemically supported on the silica surface and then kneaded with other components.

  In addition, when a metal salt is blended, it is preferably used by kneading with adipic acid diester in advance from the viewpoint of forming an ion conductive network.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

  First, Table 1 summarizes each component used in the examples.

Comparative Examples 1-3
According to the blending ratio shown in Table 1 and Table 2, using a 1.7 liter Banbury mixer manufactured by Kobe Steel, all components except sulfur and vulcanization accelerator were kneaded at about 150 ° C. for 4 minutes. A kneaded product was obtained. Next, 1.5 parts by weight of sulfur and 3.0 parts by weight of a vulcanization accelerator are added to the obtained kneaded product, kneaded at 80 ° C. for about 4 minutes using a biaxial roller, and further vulcanized at 170 ° C. for 10 minutes. Thus, comparative rubber compositions 1 to 3 after vulcanization were obtained.

  The obtained rubber composition for a tread after vulcanization was tested by the following method. The results are shown in Table 2.

[Test method]
(1) Volume resistivity (log δV): A sample having a size of 15 cm × 15 cm × 2 mm was prepared from the rubber composition for tread after vulcanization, and an applied voltage of 1000 V using an ADVANTESTER 8340A electric resistance measuring instrument manufactured by Advantest Corporation. The volume resistivity value was measured under the conditions of a temperature of 25 ° C. and a humidity of 50%. The volume resistivity value is preferably less than 11.

(2) Rolling resistance: Using a test machine manufactured by Kobe Machine Co., Ltd., the rolling resistance was measured by running at a load of 345 kg, an internal pressure of 200 kPa, and a speed of 80 km / h. The rolling resistance was evaluated. The larger the index, the lower the rolling resistance.

(3) Abrasion resistance: A tire of 175 / 70R13 size having a tread made of a rubber composition for a tread before vulcanization is prepared by a conventional method, and a general road and a highway are used by using a vehicle equipped with the tire. The depth of the remaining groove of the tread after traveling 30,000 km in combination was measured, and the wear resistance was evaluated by an index with the case of Comparative Example 6 described later as 100. The larger the index, the better the wear resistance.

(4) Wet performance: In the car used in the test of (3) above, measure the maximum speed when the car turns and slips on a test course in which low-μ tiles are spread and water is sprayed, In the case of Comparative Example 6 described later, the wet performance was evaluated with an index of 100. The larger the index, the better the wet performance.

(5) Electric resistance of tire: For the tire used in the test of (3) above, using a megohm meter, the center of the rim under the conditions of an internal pressure of 200 kPa, a load of 2.94 kN, an applied voltage of 1000 V, a temperature of 25 ° C., and a humidity of 50% The resistance value between the part and the conductor plate on which the tire was grounded was measured. The electrical resistance is preferably less than 9.

Comparative Examples 4 and 5
According to the blending ratios shown in Tables 1 and 2, comparative rubber compositions 4 and 5 after vulcanization were obtained and tested in the same manner as in Comparative Example 1 except that lithium salt was previously mixed with adipic acid diester. The results are shown in Table 2.

Example 1
Using the blending ratio shown in Table 1 and Table 2, except that silica and adipic acid diester were mixed in advance, the rubber composition 1 for tread of the present invention after vulcanization was obtained in the same manner as in Comparative Example 1, and the test was performed. I did it. The results are shown in Table 2.

Comparative Examples 6-8
Comparative rubber compositions 6 to 8 were obtained in the same manner as in Comparative Example 1, except that the blending ratio shown in Table 2 was changed, and the same test as in Comparative Example 1 was performed. The results are shown in Table 2.

Comparative Examples 9 and 10
Comparative rubber compositions 9 and 10 after vulcanization were obtained and tested in the same manner as in Comparative Examples 4 and 5, except that the type of adipic acid diester was changed. The results are shown in Table 2.

Example 2
Except for changing the type of adipic acid diester, the rubber composition 2 for tread of the present invention after vulcanization was obtained and tested in the same manner as in Example 1. The results are shown in Table 2.

  From the evaluation results of Comparative Example 1 and Comparative Examples 6 and 7, it can be seen that the electrical resistance is not reduced when the amount of adipic acid diester is less than 5 parts by weight.

  In addition, the evaluation results of Comparative Example 3 and Comparative Example 8 show that the wear resistance is reduced when the blending amount of adipic acid diester exceeds 40 parts by weight.

Claims (1)

A method for producing a rubber composition for a tread comprising 40 to 90 parts by weight of silica and 5 to 40 parts by weight of an adipic acid diester based on 100 parts by weight of a diene rubber, the silica and the adipic acid diester Is kneaded in advance, and then kneaded with other components.