JP2010248421A - Rubber composition and pneumatic tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition improving break strength of tire by eliminating the dispersion defect of softening components having high softening point. <P>SOLUTION: The rubber composition is prepared by mixing a plurality of the softening components each having different softening point in a rubber component. The softening components contain a resin (A) having 120-190°C softening point and the resin (A) has ≤1,000 μm particle diameter. The softening components preferably contain a softening agent (B) having ≥70°C and ≤120°C softening point and in such a case, it is further preferable that the softening components have respectively different molecular structure (including a structure originating in monomer molecule). <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 to a rubber composition capable of improving grip performance and breaking strength on a dry road surface of the tire.

  In the tread of a tire, particularly a tread of a high-performance passenger car tire, it is desired to ensure excellent driving stability (for example, grip performance on a dry road surface) on the dry road surface from the beginning of travel to the end of travel. . Various techniques have been studied in the past in order to impart high grip performance on dry road surfaces to tires, for example, a method of applying a rubber composition containing a softening component such as resin or oil to a tread rubber. Are known.

  JP-A-2006-249230 (Patent Document 1) describes a grip performance excellent in tires over a wide temperature range by applying a rubber composition using softening components having different softening points to a tread rubber. A technique for expressing the above is disclosed. A softening component with a low softening point is used from the viewpoint of improving grip performance at the beginning of driving, but when only a softening component with a low softening point is used, the gripping performance decreases as the temperature of the tire tread increases during driving. For this reason, a combination with a softening component having a high softening point is required.

JP 2006-249230 A

  However, when softening components having different softening points are blended in the rubber component, softening components having a high softening point are less soluble in the rubber component than those having a low softening point and may cause poor dispersion. In this case, the softened component that remains undissolved serves as a fracture nucleus, thereby reducing the durability of the rubber composition. In order to solve this problem, a method of increasing the kneading temperature when mixing the softening component in the rubber component is conceivable. In this case, however, physical properties of the rubber composition may be deteriorated.

  Accordingly, an object of the present invention is to provide a rubber composition capable of improving the breaking strength of a tire by eliminating poor dispersion of a softening component having a high softening point as well as grip performance on a dry road surface. . Another object of the present invention is to provide a pneumatic tire using the rubber composition in a tread and having excellent breaking strength and grip performance on a dry road surface.

  As a result of diligent study to achieve the above-mentioned object, the present inventor, as a result of blending a rubber component with a plurality of softening components having different softening points, a particle size of a certain value or less as a softening component having a high softening point. It has been found that the use of a resin having an improved breaking strength as well as grip performance on the dry road surface of the tire has led to the completion of the present invention.

  That is, the rubber composition of the present invention is obtained by blending a rubber component with a plurality of softening components having different softening points, and the softening component includes a resin (A) having a softening point of 120 to 190 ° C. The particle size of (A) is 1000 μm or less. In this case, the resin (A) can be completely dissolved in the rubber component and the breaking strength can be improved.

  For example, the softening point of the softening component can be measured according to the ring and ball method defined in JIS K2207.

  In a preferred embodiment of the rubber composition of the present invention, the softening component contains a softening agent (B) having a softening point of 70 ° C or higher and lower than 120 ° C. In this case, both the grip performance and the breaking strength on the dry road surface can be reliably improved.

  In another preferred embodiment of the rubber composition of the present invention, the softening components preferably have different molecular structures (including structures derived from monomer molecules). In this case, the grip performance on the dry road surface can be reliably improved.

  The pneumatic tire of the present invention is characterized by using the rubber composition as a tread rubber.

  According to the present invention, in a rubber composition in which a plurality of softening components having different softening points are blended in a rubber component, a resin having a particle size of a certain value or less is used as a softening component having a high softening point. It is possible to provide a rubber composition capable of improving the breaking strength of a tire together with the grip performance. Moreover, the pneumatic tire which was excellent in breaking strength and the grip performance on a dry road surface using this rubber composition as tread rubber can be provided.

  The present invention is described in detail below. The rubber composition of the present invention comprises a rubber component containing a plurality of softening components having different softening points, and the softening component contains a resin (A) having a softening point of 120 to 190 ° C. ) Has a particle size of 1000 μm or less. Thus, a rubber composition using a plurality of softening components having different softening points can exhibit excellent grip performance in a tire over a wide temperature range. The softening component used in the rubber composition of the present invention contains a resin (A) having a high softening point, that is, a softening point of 120 to 190 ° C., in order to improve the grip performance of the tire over a wide temperature range. However, when the particle diameter of the resin (A) is 1000 μm or less, the dispersibility of the resin (A) at the time of rubber kneading is improved, and the resin (A) is sufficiently dissolved in the rubber component. For this reason, the breaking strength of the vulcanized rubber obtained by vulcanizing such a rubber composition can be improved.

  In the rubber composition of the present invention, the resin (A) needs to have a particle size of 1000 μm or less, and is preferably less than 600 μm. If the particle diameter of the resin (A) is 1000 μm or less, the resin (A) can be sufficiently dissolved in the rubber component without increasing the kneading temperature when the softening component is mixed into the rubber component. Further, the smaller the particle size of the resin (A), the more effective the improvement of dispersibility. However, from the viewpoint of workability, workability, etc., the particle size of the resin (A) is preferably 50 μm or more. In addition, as a method of adjusting the particle diameter of the resin, for example, the resin is pulverized using a pulverizer such as Quick Mill QMY manufactured by Seishin Enterprise Co., Ltd., and the pulverized resin has a specific opening size (for example, And a method of sorting with a sieve having 1000 μm, 600 μm, 300 μm, 90 μm, etc.).

  In the rubber composition of the present invention, the resin (A) needs to have a high softening point and 120 to 190 ° C. When the softening point of the resin (A) used is less than 120 ° C., it is difficult to ensure sufficient hysteresis loss at a high temperature of the rubber composition, and it becomes difficult to develop excellent grip performance in the tire in a high temperature region. . On the other hand, if the softening point of the resin (A) used exceeds 190 ° C., it is necessary to increase the kneading temperature in order to dissolve the resin, and the rubber component may be burnt.

Specific examples of the resin (A) include an aromatic petroleum resin obtained by (co) polymerizing a phenol resin and / or a C ₉ fraction. Among these, a phenol resin is used. preferable. Among phenolic resins, alkyl-substituted phenol resins and long-chain alkyl-modified phenol resins are preferable. Examples of the alkyl-substituted phenol resin include pt-butylphenol / formaldehyde resin, pt-butylphenol / acetaldehyde resin, pt-octylphenol / formaldehyde resin, and styrene-modified phenol / formaldehyde resin. Examples of the alkyl-modified phenol resin include terpene-modified phenol resins. On the other hand, the aromatic petroleum resin obtained by (co) polymerizing the C ₉ fraction is generally an aromatic fraction having 9 carbon atoms mainly containing vinyltoluene and indene obtained by thermal decomposition of naphtha. It is a resin obtained by polymerizing components. Here, other examples of the C ₉ fraction include styrene homologues such as α-methylstyrene and β-methylstyrene. The aromatic petroleum resin may contain a coumarone unit or the like. As a trade name of the above-mentioned aromatic petroleum resin, Neo Nippon Petrochemical's neopolymer and the like can be mentioned. In addition, it is preferable that the compounding quantity of resin (A) is 5-50 mass parts with respect to 100 mass parts of rubber components.

  Since the rubber composition of the present invention contains a plurality of softening components having different softening points, the grip performance can be expressed over a wide temperature range, but as a softening component that further improves the grip performance in a low temperature range. By using the softening agent (B) having a softening point of 70 ° C. or higher and lower than 120 ° C., grip performance on a dry road surface can be reliably ensured from the beginning of traveling to the end of traveling. If the softening point of the softening agent (B) is less than 70 ° C, the grip performance at the beginning of running may not be ensured. On the other hand, if it is 120 ° C or higher, the difference in softening point from the resin (A) is insufficient. Therefore, it may be difficult to develop excellent grip performance for the tire over a wide temperature range.

  Further, as the softening agent (B), specifically, a high vinyl polybutadiene having a vinyl bond content of 50% or more is preferable, and a liquid high vinyl having a vinyl bond content of 50% or more and a molecular weight of 3000 to 30000. More preferred is polybutadiene. Here, the liquid state means a liquid state at room temperature (25 ° C.). In addition, it is preferable that the compounding quantity of a softener (B) is 5-50 mass parts with respect to 100 mass parts of rubber components.

  In the rubber composition of the present invention, when softening components having different softening points such as the same structure of repeating units and different molecular weights are used, even if a plurality of softening components having different softening points are used in combination, the softening components can be easily combined. May result in substantially the same results as when using a single softening component having an intermediate softening point. Accordingly, the softening components used in the rubber composition of the present invention preferably have different molecular structures (including structures derived from monomer molecules when the softening component is a polymer).

  In addition, as a softening component used for the rubber composition of this invention, you may use other softening agents, plasticizers, etc. other than the said resin (A) and a softening agent (B). Examples of the process oil include paraffin oil, naphthenic oil, and aroma oil. Further, the plasticizer is preferably an ester plasticizer, and specifically, a phthalic acid derivative, a long-chain fatty acid derivative, a phosphoric acid derivative, a sebacic acid derivative and an adipic acid derivative are preferred.

  The rubber component used in the rubber composition of the present invention is not particularly limited. In addition to natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR) ), Ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), halogenated butyl rubber, acrylonitrile-butadiene rubber (NBR), etc., and these rubber components can be used alone. Alternatively, two or more kinds may be blended and used.

  The rubber composition of the present invention usually contains a filler. The filler is not particularly limited, and carbon black and various inorganic fillers can be used. These fillers may be used alone or in combination of two or more. The blending amount of the filler is preferably in the range of 30 to 200 parts by mass with respect to 100 parts by mass of the rubber component, and more preferably in the range of 50 to 150 parts by mass from the viewpoint of reinforcing properties and the effect of improving various physical properties thereby. . If the blending amount of the filler is less than 30 parts by mass, sufficient grip performance of the tire cannot be ensured, and if it exceeds 200 parts by mass, the processability of the rubber composition tends to decrease.

The carbon black is not particularly limited, and grades such as SRF, GPF, FEF, HAF, ISAF, and SAF can be used. The iodine adsorption amount (IA) is 60 mg / g or more, and dibutyl phthalate (DBP). ) Carbon black having an oil absorption of 80 mL / 100 g or more is preferred. By using carbon black, the improvement effect of the grip performance and fracture resistance of the tire can be improved. In order to further improve the wear resistance of the tire, it is particularly preferable to use HAF, ISAF, or SAF grades. Moreover, the external surface area by the cetyltrimethylammonium bromide (CTAB) adsorption method is in the range of 130 to 200 m ² / g, and the 24M4DBP oil absorption is preferably 80 mL / 100 g or more. The 24M4 DBP oil absorption is the DBP oil absorption after four times of compression at a pressure of 24,000 psi.

  The rubber composition of the present invention contains, in addition to the softening component and filler, a compounding agent usually used in the rubber industry, such as stearic acid, anti-aging agent, zinc white, vulcanization accelerator, A vulcanizing agent or the like can be produced by appropriately selecting and blending the vulcanizing agent and the like within a range not impairing the object of the present invention, and kneading, heating, extruding or the like.

  The pneumatic tire of the present invention is characterized by using the rubber composition as a tread rubber. Since the pneumatic tire of the present invention uses the rubber composition as a tread rubber, it is excellent in breaking strength and grip performance on a dry road surface. The pneumatic tire of the present invention is not particularly limited except that the above rubber composition is used for the tread rubber, and can be produced according to a conventional method. Further, as the gas filled in the pneumatic tire, an inert gas such as nitrogen, argon, helium, or the like can be used in addition to normal or air whose oxygen partial pressure is adjusted.

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

A rubber composition was prepared using a Banbury mixer according to the formulation shown in Table 1, and the resin dispersibility, breaking strength (tensile strength; T _B ), and grip were applied to the rubber composition by the following methods. The performance was measured and evaluated. The results are shown in Table 1.

(1) Dispersibility of resin The rubber composition was processed into a sheet-like rubber having a thickness of 3 mm, and resin aggregates exceeding 1 mm in diameter present in the sheet-like rubber of 900 cm ² were counted as poor resin dispersion points. The reciprocal of the number of defective resin dispersion points in Comparative Example 1 is shown as an index, with 100 being the inverse. It shows that it is excellent in the dispersibility of resin, so that an index value is large.

(2) Fracture strength Tensile strength (T _B ) was measured for the vulcanized rubber obtained by vulcanizing the above sheet rubber at 160 ° C. for 15 minutes, and the tensile strength of Comparative Example 1 was taken as 100. displayed. It shows that it is excellent in fracture strength, so that an index value is large.

(3) Grip performance Using a Rheometrics mechanical spectrometer, tan δ was measured at a shear strain of 5%, a frequency of 15 Hz, a temperature of 80 ° C. (high temperature), and 20 ° C. (low temperature). The index was displayed. The larger the index value, the greater the hysteresis loss and the better the grip performance.

* 1 Styrene-butadiene copolymer rubber [E-SBR, "1712" manufactured by JSR Corporation, aroma oil oil extension: 37.5 parts by mass, styrene content: 23.5% by mass].
* 2 Tokai Carbon Co., Ltd., Seast 9H, Nitrogen adsorption specific surface area (N ₂ SA) = 142 m ² / g, Dibutyl phthalate oil absorption = 130 ml / 100 g.
* 3 A / O MIX manufactured by Mitsui Yuka Kogyo Co., Ltd.
* 4 Resin A: Nippon Petrochemical Co., Ltd., Neopolymer 170S, softening point = 160 ° C. The particle size of A-1 exceeds 1000 μm, the particle size of A-2 is 1000 μm or less, and the particle size of A-3 is less than 600 μm.
* 5 Resin B: manufactured by Mitsui Chemicals, α-methylstyrene homopolymer resin, softening point = 140 ° C. The particle size of B-1 exceeds 1000μm, the particle size of B-2 is less than 1000μm, and the particle size of B-3 is less than 600μm.
* 6 Resin C: manufactured by Nippon Petrochemical Co., Ltd., Neopolymer L90, softening point = 90 ° C. The particle size of C-1 exceeds 1000μm, the particle size of C-2 is 1000μm or less, and the particle size of C-3 is less than 600μm.
* 7 Microcrystalline wax manufactured by Seiko Chemical Co., Ltd.
* 8 Bis (4-methyldibenzothiazolyl-2) -disulfide manufactured by Sanshin Chemical Industry Co., Ltd.

  From Table 1, the rubber compositions of Examples 1 to 4 using a resin having a softening point of 120 to 190 ° C. and a particle size of 1000 μm or less as the softening component are superior to the rubber compositions of Comparative Examples 1 to 5. The resin dispersibility is shown, and it can be seen that the breaking strength and the grip performance are improved.

Claims (4)

A plurality of softening components having different softening points are blended with the rubber component,
The rubber composition, wherein the softening component includes a resin (A) having a softening point of 120 to 190 ° C., and the particle size of the resin (A) is 1000 μm or less.   The rubber composition according to claim 1, wherein the softening component contains a softening agent (B) having a softening point of 70 ° C or higher and lower than 120 ° C.   The rubber composition according to claim 1 or 2, wherein the softening components have different molecular structures (including structures derived from monomer molecules).   A pneumatic tire using the rubber composition according to claim 1 as a tread rubber.