JP5407305B2 - Rubber composition for tire tread - Google Patents

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 that is effectively used for forming a tread portion of a racing tire.

  One of the performances required for racing tires is excellent wear resistance in addition to good grip performance. One way to improve grip performance is to use SBR with a high glass transition point Tg and a high styrene content, but this is a very useful method because wear resistance deteriorates and thermal sag is large. I can't say that.

A rubber composition for tire treads with excellent tire workability and tire workability, in which diene rubber is blended with (hydrogenated) terpene resin, has been proposed. Rubber is used, preferably SBR polymerized with a Li-based polymerization initiator, and a specific SBR having a bound styrene content of 10 to 50% by weight and a vinyl bond content of butadiene part of 20 to 70% is used. .
JP 2004-18760 A

In addition, as a rubber composition for tire treads that improves the initial grip and running stability of the tire, the rubber component has a hydrogenated terpene resin with a softening point of 130 ° C or higher, a softening point of 130 to 190 ° C, and contains indene C ₉ and resin has been proposed that is blended to a nitrogen adsorption specific surface area in the rubber composition (N ₂ SA) of about 80~280m ² / g carbon black, for example HAF, ISAF, and SAF carbon black It is said that 60 to 200 parts by mass is preferably compounded with respect to 100 parts by mass of the rubber component. Although natural rubber or synthetic rubber is said to be used as the rubber component, it is preferably SBR, and when the indene-containing C ₉ resin is not used in combination, the initial grip performance is good, It is said that the running stability is low because the grip reduction during running is large.
JP 2008-169296 A

In addition, natural rubber, polyisoprene rubber, SBR, polybutadiene rubber, and NBR at least one diene rubber are blended with heat-expandable microcapsules and terpene resin with a softening point of 50-90 ° C. A rubber composition for a tire that suppresses a decrease in performance has been proposed by the present applicant, and the nitrogen adsorption specific surface area (N ₂ SA) of this rubber composition is preferably 70 m ² / g or more, more preferably 80 to Although 200 m ² / g of carbon black can be blended, as a diene rubber, a blend rubber having a weight ratio of natural rubber to polybutadiene rubber of 50:50 is used in all of the examples.
Japanese Patent No. 3955565

The present applicant also stated that the diene rubber has a copolymer weight of α-pinene or a copolymer of β-pinene and aromatic vinyl, α-pinene, β-pinene, dipentene and aromatic vinyl. A rubber composition containing at least one of a coalescence and a hydrogenated product of these copolymers has been proposed, and this rubber composition improves the wet grip without deteriorating the rolling resistance of the tire. In this rubber composition, it is said that carbon black or the like can be further contained, and in that example, carbon black N339 (corresponding to HAF carbon black, and its N ₂ SA is 100 m ² / g or less) Is used.
JP-A-9-309978

  An object of the present invention is a rubber composition for tire tread mainly composed of natural rubber, which generates high heat at high temperature without impairing strength and improves wear resistance. It is to provide what can be used effectively.

The object of the present invention is to provide 85 to 150 parts by weight of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 120 to 320 m ² / g based on 100 parts by weight of a diene rubber containing 80 to 100% by weight of natural rubber. And a rubber composition for a tire tread comprising 80 to 150 parts by weight of a terpene resin .

The tread portion formed from a rubber composition for tire treads containing a large amount of natural rubber-rich, small particle size carbon black and terpene resin according to the present invention has high heat generation at high temperatures without impairing strength, and wear resistance. Therefore, it is effectively used for forming a tread portion of a racing tire. Pneumatic tires (size 245 / 40R18) with a tread part with these characteristics are mounted on a vehicle, and the grip performance (driver feeling) and resistance against running 20 laps at a speed of 200 km / h or more on the circuit When the wearability was evaluated, it was confirmed that the tire exhibited sufficient performance as a racing tire with an increased ratio of non-oil resources. In particular, the actual tire performance is particularly high after gripping, and the wear resistance is longer than that of a normal racing tire.

  As the rubber component, a diene rubber containing 80 to 100% by weight of natural rubber is used. As the diene rubber used by blending with natural rubber in a proportion of 20% by weight or less, any synthetic rubber can be used, but SBR is preferably used. If the blending ratio of the natural rubber is lower than this, not only the ratio of non-oil resources but also the desired exothermic property and wear resistance cannot be improved.

  Such diene rubber is blended with 85 to 150 parts by weight, preferably 100 to 120 parts by weight of carbon black and 80 to 150 parts by weight, preferably 90 to 120 parts by weight of tackifier resin per 100 parts by weight. The

Carbon black having a nitrogen adsorption specific surface area (N ₂ SA; JIS K6217-2 compliant) of 120 to 320 m ² / g, preferably 180 to 280 m ² / g is used. If a N ₂ SA value smaller than this is used, heat generation is low and improvement in grip performance cannot be expected. If the blending amount is less than 85 parts by weight, improvement in grip performance cannot be expected. On the other hand, if the blending amount is more than 150 parts by weight, mixing becomes difficult, and deterioration of wear resistance due to poor dispersion is inevitable.

The terpene resin as the tackifier resin is used in the above ratio. If the blending amount of the terpene resin is less than 80 parts by weight, the improvement in grip performance cannot be expected.

  As the terpene resin, a terpene resin, a hydrogenated terpene resin, a terpene phenol resin, an aromatic modified terpene resin or the like is used, and an aromatic modified terpene resin is preferably used. Aromatically modified terpene resins are terpene resins synthesized by cation polymerization from citrus α-pinene, β-pinene, α-limonene and dipentene, and benzene, toluene, xylene, styrene, phenol, cresol, A modified resin obtained by coexisting an aromatic compound such as benzoic acid. In fact, commercial products such as Yasuha Chemical U-115 (phenol-modified terpene resin; softening point 115 ° C), TO-125 (aromatically modified terpene resin; softening point 125 ° C), TO-8585 Terpene resin (softening point 85 ° C.) or the like is used as it is.

These terpene resins have a softening point of about 80 to 160 ° C, preferably about 100 to 140 ° C. If a softening point lower than this is used, the grip performance becomes insufficient, while if a softening point higher than this is used, the warming property of the rubber is adversely affected.

  In the diene rubber composition containing the above components as essential components, a compounding agent generally used as a compounding agent for rubber, for example, a vulcanizing agent such as sulfur depending on the type of diene rubber, thiazole , Sulfenamide, guanidine, thiuram and other vulcanization accelerators, reinforcing agents and fillers such as talc, clay, graphite and calcium silicate, processing aids such as stearic acid, paraffin wax and aroma oil, oxidation Zinc, an anti-aging agent, a plasticizer and the like are appropriately blended and used as necessary.

  The composition was prepared by kneading by a general method using a kneader such as a kneader, a Banbury mixer, and an open roll, and the obtained composition was a diene rubber, a vulcanizing agent, Vulcanization is carried out at a vulcanization temperature corresponding to the type of vulcanization accelerator and its blending ratio to form a tread portion. Such a tread portion forms a tread portion of a pneumatic tire, particularly a racing tire.

  Next, the present invention will be described with reference to examples.

Comparative example 1 (standard example)
70 parts by weight of natural rubber
SBR (Nippon ZEON product Nipol 9526; 50% oil spread) 45 〃
Carbon Black A (Nippon Nidec Carbon Products 415UD; N ₂ SA 220m ² / g) 100 〃
Carbon black B (Tokai carbon product seast 7HM; N ₂ SA 118m ² / g) −
Aromatic modified terpene resin (Yasuha Chemical product TO-125) 85 〃
Zinc oxide (Zondox Chemical Products Zinc Oxide 3 types) 3 〃
Stearic acid (Japanese oil and fat product beads stearic acid) 2 〃
Anti-aging agent (SANYOFLEX 6PPD, product of Flexis) 2 〃
Vulcanization accelerator (Ouchi Emerging Chemical Industry Noxeller CZ-G) 2
Sulfur (Tsurumi Chemical Co., Ltd., Jinhua Ink Fine Powdered Sulfur) 2 〃
The above components were kneaded using a kneader to prepare a rubber composition.

This rubber composition was subjected to press vulcanization at 165 ° C. for 20 minutes, and the strength (modulus at 300% elongation, 100 ° C.) and tan δ (60 ° C.) of the vulcanized product were measured. Evaluation of an actual vehicle equipped with a pneumatic tire having the formed tread portion was performed.
Strength (modulus at 300% elongation, 100 ° C): JIS K6251 compliant
Displayed as an index with a standard example of 100
The larger the index, the higher the strength.
tanδ (60 ° C): Tensile deformation strain rate of 10 ± using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho
Measured under the conditions of 2%, frequency 20Hz, temperature 60 ° C.
Display as a number
The higher the index, the higher the fever and the better the grip performance. Actual car evaluation: Wear a pneumatic tire of size 245 / 40R18 on the vehicle, run on the circuit
, Evaluation of grip performance when running 20 laps on the circuit (for the driver
5 to 1 where 5 is the best one
(Evaluation in 5 stages) and wear resistance measurement (measure the tire remaining groove depth after running,
Displayed as an index with a standard example of 100; higher index indicates better wear resistance
Did)

Comparative Examples 2-6, Examples 1-2
In Comparative Example 1, the types and amounts (parts by weight) of diene rubber, carbon black and aromatic modified terpene resin were changed as shown in the following table. In Comparative Example 6, silica (Degussa product 7000GR) was used instead of carbon black.

The measurement results obtained in the above comparative examples and examples are shown in the following table together with the types and amounts of use of diene rubber, carbon black, silica and aromatic modified terpene resins.
table
Comparative Example
1 2 3 4 5 6 1 2
(Rubber composition)
Natural rubber (part) 70 100 100 100 100 100 100 90
SBR (50% oil spread) (part) 45 15
Carbon black A (part) 100 100 100 80 100 100
Carbon black B (part) 100
Silica (part) 100
Aromatic modification 80 100 70 160 100 100 100 100
Terpene resin (part)
〔Measurement result〕
300% modulus 100 102 95 80 105 98 120 112
tanδ (60 ° C) 100 110 122 125 95 90 130 133
Actual vehicle evaluation
Grip performance 3 4 2 5 2 1 4 5
Abrasion resistance 100 103 101 90 107 95 140 125

From the above results, the following can be said.
(1) If the natural rubber is less than 80% by weight in the diene rubber, the desired heat build-up and wear resistance cannot be improved. In addition, when the amount of natural rubber is 80% by weight or more, the ratio of non-oil resources increases.
(2) If the N ₂ SA value of carbon black is less than 120 m ² / g, heat generation is low, and improvement in grip performance cannot be expected. Even when the blending amount is less than 85 parts by weight, improvement in grip performance cannot be expected. On the other hand, when the blending amount is more than 150 parts by weight, mixing becomes difficult, and deterioration of wear resistance due to poor dispersion is inevitable.
(3) When less than 85 parts by weight of carbon black is used, heat generation is low and grip performance is poor.
(4) When the blending amount of the aromatic modified terpene resin is less than 80 parts by weight, improvement in grip performance cannot be expected. On the other hand, when the blending amount is more than 150 parts by weight, the mixing processability deteriorates and comes into close contact.
(5) When silica is used instead of carbon black, heat generation is low and grip performance is lowered.

Claims (5)

100 to 100 parts by weight of diene rubber containing 80 to 100% by weight of natural rubber, 85 to 150 parts by weight of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 120 to 320 m ² / g and 80 to 150 terpene resins A rubber composition for a tire tread formed by blending parts by weight.   The rubber composition for a tire tread according to claim 1, wherein a diene rubber in which 20% by weight or less of SBR is blended with natural rubber is used. The rubber composition for a tire tread according to claim 1, wherein the terpene resin is an aromatic modified terpene resin. The pneumatic tire which has a tread part formed from the rubber composition for tire treads of Claim 1, 2, or 3. The pneumatic tire according to claim 4, which is used as a racing tire.