JP2007099932A - Tire tread rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire tread rubber composition comprising natural rubber (NR) as the major component which has good wet grip, abrasion resistance, and breaking properties after vulcanization. <P>SOLUTION: The tire tread rubber composition comprises a diene rubber component containing natural rubber (NR) and a phenol-modified rosin, and the compounding amount of the natural rubber (NR) based on 100 pts.wt. the above rubber component is 50-100 pts.wt., and the compounding amount of the phenol-modified rosin based on 100 pts.wt. the rubber component is 5-50 pts.wt., and the above phenol-modified rosin has a softening point of 60-200°C and a hydroxyl value of 10-150 KOHmg/g. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition for a tire tread. More specifically, the present invention relates to a rubber composition for a tire tread comprising a rubber component mainly composed of natural rubber (NR), which has good wet grip properties, abrasion resistance, and breaking properties after vulcanization. About.

  In recent years, due to increasing interest in environmental protection, the use of non-petroleum materials as tire raw materials has been studied, but styrene-butadiene copolymers commonly used in rubber components of rubber compositions for tire treads have been studied. It is known that when the polymer rubber (SBR) is replaced with natural rubber (NR), there is a problem that the wet grip property is lowered.

  Thus, although it has been proposed to increase the amount of aroma oil or resin component in the rubber composition for tire treads as a countermeasure against the above problem, such a countermeasure has a drawback of a decrease in wear resistance.

  Prior art document information related to the invention of this application includes the following.

JP-A-10-287768 JP 2000-154302 A JP 2001-288296 A

  An object of the present invention is to provide a rubber composition for a tire tread comprising a rubber component mainly composed of natural rubber (NR), which has good wet grip properties, wear resistance, and breaking properties after vulcanization. That is.

The above purpose is
A tire tread rubber composition comprising a phenol-modified rosin blended with a diene rubber component comprising natural rubber (NR),
The blending amount of the natural rubber (NR) is 50 to 100 parts by weight with respect to 100 parts by weight of the rubber component;
The amount of the phenol-modified rosin is 5 to 50 parts by weight based on 100 parts by weight of the rubber component, and the phenol-modified rosin has a softening point of 60 to 200 ° C. and a hydroxyl value of 10 to 150 KOHmg / g. Having
A rubber composition for a tire tread, characterized by
Achieved by:

  According to the present invention, from the viewpoint of environmental protection, even when a rubber component mainly composed of natural rubber (NR) is used, the tire tread exhibits good wet grip properties, wear resistance, and rupture characteristics after vulcanization. A rubber composition can be provided.

  The present invention blends a specific amount of a specific phenol-modified rosin with a rubber component mainly composed of natural rubber (NR), thereby satisfying the recent social demands for environmental protection and good wet grip. This is based on the finding that a rubber composition for a tire tread that exhibits properties, wear resistance, and fracture characteristics after vulcanization can be provided.

  The mechanism for obtaining the desired effect as described above has not been elucidated in detail. However, when a specific phenol-modified rosin having a relatively strong polarity is blended with a relatively weak natural rubber (NR), a half-phase is obtained. Due to the contribution of this semi-compatible state, the viscosity of the rubber composition before vulcanization is reduced, and the rupture characteristics and wear resistance are maintained at a good level in the rubber composition after vulcanization. It is estimated that tan δ at a low temperature can be increased.

  That is, the rubber composition according to the present invention is a rubber composition for a tire tread obtained by blending a phenol-modified rosin with a diene rubber component containing natural rubber (NR). ) Is 50 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and the compounding amount of the phenol-modified rosin is 5 to 50 parts by weight with respect to 100 parts by weight of the rubber component. And the said phenol modified rosin has the softening point of 60-200 degreeC, and the hydroxyl value of 10-150 KOHmg / g, It is a rubber composition for tire treads characterized by the above-mentioned.

  As described above, the present invention considers the use of a non-petroleum-based material as a tire raw material from the viewpoint of environmental protection. Therefore, the rubber component used in the rubber composition for a tire tread according to the present invention. Is not mainly composed of diene-based synthetic rubber such as styrene-butadiene copolymer rubber (SBR) like the rubber component in the conventional rubber composition for tire tread, but is composed mainly of natural rubber (NR). It is what. Specifically, the rubber component used in the rubber composition according to the present invention comprises 50 to 100 parts by weight, preferably 55 to 100 parts by weight of natural rubber (NR) per 100 parts by weight of the rubber component. Is desirable.

  In the rubber composition according to the present invention, when other rubber components are added and used in addition to the natural rubber (NR), the other rubber components are not particularly limited. For example, various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), polyisoprene rubber (IR), butyl rubber (IIR), acrylonitrile-butadiene rubber, chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer Examples thereof include diene-based synthetic rubbers such as polymer rubber, styrene-isoprene-butadiene copolymer rubber, and isoprene-butadiene copolymer rubber, and mixed systems thereof.

  In the rubber composition according to the present invention, 5 to 50 parts by weight, preferably 5 to 45 parts by weight of phenol-modified rosin is blended with respect to 100 parts by weight of the rubber component. When the blending amount of the phenol-modified rosin is less than 5 parts by weight with respect to 100 parts by weight of the rubber component, the desired improvement effect accompanying the blending of the phenol-modified rosin (that is, resistance to resistance in the rubber composition after vulcanization). It is not preferable because maintenance of wearability and improvement of wet grip properties cannot be obtained. On the contrary, when the compounding amount of the phenol-modified rosin exceeds 50 parts by weight with respect to 100 parts by weight of the rubber component, the temperature dependence of the physical properties of the rubber composition after vulcanization becomes extremely large, This is not preferable because it adversely affects the physical properties of the vulcanized material, such as a decrease in wear.

  Moreover, the said phenol modified rosin mix | blended in the rubber composition which concerns on this invention has a softening point of 60-200 degreeC, Preferably it is 80-190 degreeC. When the softening point is less than 60 ° C., workability deteriorates, which is not preferable. On the contrary, when the softening point exceeds 200 ° C., the dispersibility at the time of mixing the resin components deteriorates, and the physical properties of the rubber composition after vulcanization are lowered, which is not preferable. The softening point is measured according to JIS K 2207.

  Furthermore, the phenol-modified rosin blended in the rubber composition according to the present invention has a hydroxyl value of 10 to 150 KOHmg / g, preferably 15 to 100 KOHmg / g. When the hydroxyl value is less than 10 KOH mg / g, since a partially compatible system is not formed, improvement in physical properties is not exhibited, which is not preferable. Conversely, when the hydroxyl value exceeds 150 KOHmg / g, the resin aggregates in the matrix, which is not preferable because the physical properties are lowered.

  The phenol-modified rosin used in the rubber composition according to the present invention can be easily obtained by adding an appropriate amount of phenol to various rosins including abietic acid.

  A vulcanizing agent such as sulfur is also added to the rubber composition according to the present invention. When sulfur is used as the vulcanizing agent, for example, powder sulfur or the like, which is well known in the rubber compounding technical field, can be used. It can be a general blending amount.

  Further, the rubber composition according to the present invention includes a filler (carbon black, silica, etc.), a plasticizer, a softener, a vulcanization aid, a vulcanization accelerator, a vulcanization retarder, a vulcanization activator, and aging. Various other additives generally used in the field of rubber compounding technology and the like can be blended. The blending amount of these additives can also be a conventional general blending amount as long as the object of the present invention is not violated.

  The rubber composition according to the present invention can be produced by mixing the above components using a known rubber kneading machine (for example, a roll, a Banbury mixer, a kneader, etc.).

  Although the present invention will be described in more detail with reference to comparative examples and examples described below, the technical scope of the present invention is not limited to these examples.

Comparative Examples 1-4 and Examples 1-3
Compounding Components Various compounding components used in the preparation of various rubber compositions and various test pieces to be described later are listed below.

Natural rubber (NR): RSS No. 3 Carbon black (CB): “Show Black N220” (ISAF) manufactured by Showa Cabot Corporation
Zinc oxide: Zinc Oxide Industrial Co., Ltd. “Zinc oxide 3 types”
Stearic acid: Nippon Oil & Fats Co., Ltd. “Bead stearic acid paulownia”
Sulfur: Tsurumi Chemical Co., Ltd. “Jinhua seal oil-filled fine powder sulfur”
Vulcanization accelerator (TBBS): “SANTOCURE TBBS” manufactured by FLEXSYS (N-tert-butyl-2-benzothiazolyl-sulfenamide)

Aroma oil: “Process X140” manufactured by Japan Energy Co., Ltd.
Phenol-modified rosin (Rosin 1): “Neotor 125P” manufactured by Harima Kasei Co., Ltd.
Phenol-modified rosin (Rosin 2): “Hariphenol P-600” manufactured by Harima Kasei Co., Ltd.
Unmodified rosin (Rosin 3): “Chinese gum rosin” manufactured by Harima Chemicals Co., Ltd.
Maleic acid-modified rosin ester (rosin 4): “Harimak R-100” manufactured by Harima Chemical Co., Ltd.

  The details and various physical properties of the various rosins (Rosin 1 to 4) are as described in Table I below. Among these, the phenol-modified rosins according to the present invention are rosins 1 and 2.

Preparation of various rubber compositions and various test pieces The components other than sulfur and vulcanization accelerator (TBBS) shown in Table II below were mixed in a 1.8 L hermetic Banbury mixer at a compounding amount shown in Table II below. Mixing and kneading for ˜5 minutes, the master batch was released when 150 ± 5 ° C. was reached. To this master batch, sulfur and a vulcanization accelerator (TBBS) having the compounding amounts shown in Table II below were added and kneaded with an 8-inch open roll, and rubbers of Comparative Examples 1 to 4 and Examples 1 to 3 were used. A composition was obtained. This measured the Mooney viscosity. Next, various rubber compositions were press vulcanized at 160 ° C. for 20 minutes in a 15 cm × 15 cm × 0.2 cm mold to prepare various target test pieces.

Measurement of physical properties of various rubber compositions and various test pieces Various physical properties of the various rubber compositions and various test pieces were measured according to the following test methods.

1) Mooney viscosity:
The Mooney viscosity (ML1 + 4, 100 ° C.) of each of the above unvulcanized rubber compositions was measured according to JIS K6300. Higher Mooney viscosity means higher viscosity of the unvulcanized rubber composition and lower processability.

2) Breaking strength:
With respect to the above various test pieces (dumbbell-shaped No. 3 type), the breaking strength [MPa] was measured in accordance with JIS K6251 (former JIS K6301). Higher breaking strength means better breaking physical properties.

3) Loss tangent (tan δ):
With respect to the above various test pieces, loss tangent (tan δ) was measured using a viscoelastic spectrometer under the conditions of frequency 20 Hz, static strain 10%, dynamic strain ± 2%, and temperature 0 ° C. A larger loss tangent (tan δ) means higher wet grip properties of the rubber composition after vulcanization.

4) Abrasion resistance:
About each said test piece, based on JISK6264, the wear loss was measured at room temperature using the Lambone abrasion tester, and the reciprocal number of the measured value was displayed with the index which made Comparative Example 1 100. The larger this index, the better the wear resistance of the rubber composition after vulcanization.

Evaluation of Physical Properties of Various Rubber Compositions and Various Test Pieces Results of various physical property measurements of the above 1) to 4) for the various rubber compositions and various test pieces are also shown in Table II. As shown in Table II above, in all examples, the blending amounts of all components other than aroma oil and various rosins are the same.

  The rubber composition of Comparative Example 1 is a rubber composition that serves as a reference standard, and in the evaluation of various physical properties, the rubber composition and test piece of Comparative Example 1 were used as a reference.

  The rubber composition of Comparative Example 2 was compared except that the amount of aroma oil was increased from 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the rubber component for the purpose of further improving wet grip properties. 2 is a comparative rubber composition having the same composition as the rubber composition of Example 1. As a result of increasing the blending amount of the aroma oil, the Mooney viscosity was greatly reduced and tan δ, which is a measure of wet grip, was slightly increased, but the wear resistance was greatly deteriorated.

  The rubber composition of Example 1 was the same as that of Comparative Example 1 except that 10 parts by weight of the phenol-modified rosin (Rosin 1) according to the present invention was blended with 100 parts by weight of the rubber component instead of the aroma oil. The rubber composition according to the present invention has the same composition as the product. As a result of blending the phenol-modified rosin (Rosin 1) according to the present invention in an amount that satisfies the provisions of the present invention, tan δ, which is a measure of wet grip, is increased, and at the same time, the wear resistance is greatly improved. did.

  The rubber composition of Example 2 has the same composition as the rubber composition of Example 1 except that the compounding amount of the phenol-modified rosin (Rosin 1) according to the present invention is increased from 10 parts by weight to 15 parts by weight. The rubber composition according to the present invention. The blending amount of the phenol-modified rosin (Rosin 1) in this example also satisfies the provisions of the present invention. As a result, although the abrasion resistance is slightly deteriorated as compared with Example 1, Comparative Example 1 and While maintaining a sufficiently good level, tan δ, which is a measure of wet grip properties, could be further increased.

  The rubber composition of Example 3 has the same composition as the rubber composition of Example 2 except that the second phenol-modified rosin (Rosin 2) according to the present invention is used. It is. As a result, various physical properties could be improved.

  The rubber composition of Comparative Example 3 was the same as that of Comparative Example 1 except that 10 parts by weight of a comparative unmodified rosin (Rosin 3) was blended with 100 parts by weight of the rubber component instead of the aroma oil. A comparative rubber composition having the same composition as. Although the blending amount of rosin (rosin 3) for comparison satisfies the provisions of the present invention, the hydroxyl value deviates from the provisions of the present invention. As a result, compared with Comparative Example 1, the wet grip Although tan δ, which is a measure of property, slightly increased, the wear resistance decreased.

  The rubber composition of Comparative Example 4 was the same as that of Comparative Example 1 except that 10 parts by weight of maleic acid-modified rosin (rosin 4) for comparison was blended with 100 parts by weight of the rubber component instead of the aroma oil. It is a comparative rubber composition having the same composition as the product. Similar to Comparative Example 3 above, the amount of this comparative rosin (Rosin 4) satisfies the provisions of the present invention, but its hydroxyl value deviates from the provisions of the present invention. As a result, tan δ, which is a measure of wet grip properties, was slightly increased as compared with Comparative Example 1, but the wear resistance was greatly reduced.

  From the above evaluation results, even when a rubber component mainly composed of natural rubber (NR) is used from the viewpoint of environmental protection, a specific amount of a specific phenol-modified rosin that satisfies the provisions of the present invention is blended. It has been clarified that a rubber composition for a tire tread exhibiting good wet grip properties, wear resistance, and breaking properties after vulcanization can be provided.

Claims (1)

A tire tread rubber composition comprising a phenol-modified rosin blended with a diene rubber component comprising natural rubber,
The blending amount of the natural rubber is 50 to 100 parts by weight with respect to 100 parts by weight of the rubber component;
The amount of the phenol-modified rosin is 5 to 50 parts by weight based on 100 parts by weight of the rubber component, and the phenol-modified rosin has a softening point of 60 to 200 ° C. and a hydroxyl value of 10 to 150 KOHmg / g. Having
A rubber composition for a tire tread characterized by the above.