Rubber composition for treads and pneumatic tire

• US 10,639,933 B2
• Filed: 10/18/2017
• Issued: 05/05/2020
• Est. Priority Date: 11/16/2016
• Status: Active Grant

• Current Assignee: Sumitomo Rubber Industries Limited
• Original Assignee: Sumitomo Rubber Industries Limited
• Inventors: Ikeda, Keiji
• Primary Examiner(s): Zemel, Irina S
• Assistant Examiner(s): Lenihan, Jeffrey S
• Application Number:
  US15/786,934
• Publication Number:
  US 20180134080A1
• Time in Patent Office: 930 Days
• CPC Class Codes: B60C 1/0016 Compositions of the tread
• CPC Class Codes: C08F 136/06 Butadiene
• CPC Class Codes: C08F 2500/04 Broad molecular weight distribution, i.e. Mw/Mn > 6
• CPC Class Codes: C08F 36/06 Butadiene
• CPC Class Codes: C08F 36/08 Isoprene
• CPC Class Codes: C08F 4/7096 Cobalt or compounds thereof
• CPC Class Codes: C08K 3/04 Carbon
• CPC Class Codes: C08K 3/36 Silica
• CPC Class Codes: C08K 5/548 containing sulfur C08K5/5477 takes precedence
• CPC Class Codes: C08L 2201/50 Aqueous dispersion, e.g. containing polymers with a glass transition temperature (Tg) above 20°C
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 7/00 Compositions of natural rubber
• CPC Class Codes: C08L 9/00 Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• CPC Class Codes: C08L 9/06 Copolymers with styrene
• CPC Class Codes: C08L 93/00 Compositions of natural resins; Compositions of derivatives thereof of polysaccharides C08L1/00 - C08L5/00; of natural rubber C08L7/00

Abstract

Provided are a rubber composition for treads which achieves a balanced improvement in fuel economy, abrasion resistance, and wet grip performance while offering good processability, and a pneumatic tire formed from the rubber composition. The present invention relates to a rubber composition for treads containing: a polybutadiene; and a terpene resin having a glass transition temperature (Tg) of 40° C. to 90° C., the polybutadiene satisfying the following conditions (A), (B) and (C): (A) a ratio (Tcp/ML₁₊₄, 100° C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML₁₊₄, 100° C.) is 0.9 to 2.3; (B) a stress relaxation time (T80) is 10.0 to 40.0 seconds, which is a time required for torque to decay by 80%, where 100% represents torque at the end of a ML₁₊₄, 100° C. measurement; and (C) a molecular weight distribution (Mw/Mn) is 2.50 to 4.00.

Claims

1. A pneumatic tire, comprising a tread formed from a rubber composition for treads, the rubber composition comprising:

a polybutadiene; and

a terpene resin having a glass transition temperature (Tg) of 50°

C. to 70°

C.,

the polybutadiene satisfying the following conditions (A), (B), and (C);

(A) a ratio (Tcp/ML₁₊₄, 100°

C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML₁₊₄, 100°

C.) is 0.9 to 2.3;

(B) a stress relaxation time (T80) is 10.0 to 40.0 seconds, which is a time required for torque to decay by 80%, where 100% represents torque at the end of a ML₁₊₄, 100°

C. measurement; and

(C) a molecular weight distribution (Mw/Mn) is 2.50 to 4.00,

wherein the rubber composition comprises the polybutadiene in an amount of 10% to 40% by mass based on 100% by mass of a rubber component in the rubber composition, and the terpene resin in an amount of 5 to 15 parts by mass per 100 parts by mass of the rubber component,

wherein the rubber composition further comprises silica in an amount of 50 to 90 parts by mass per 100 parts by mass of the rubber component,

wherein the rubber composition further comprises styrene-butadiene rubber terminally modified with N-methylpyrrolidone in an amount of 10% to 95% 60% to 90% by mass based on 100% by mass of the rubber component.

2. The pneumatic tire according to claim 1,

wherein the rubber composition comprises the polybutadiene in an amount of 15% to 40% by mass based on 100% by mass of the rubber component.

3. The pneumatic tire according to claim 1,

wherein the polybutadiene satisfies the following conditions (A), (B), and (C):

(A) a ratio (Tcp/ML₁₊₄, 100°

C.) of 5% by mass toluene solution viscosity (Tcp) to Mooney viscosity (ML₁₊₄, 100°

C.) is 1.4 to 1.7;

(B) a stress relaxation time (T80) is 12.0 to 20.0 seconds, which is a time required for torque to decay by 80%, where 100% represents torque at the end of a ML₁₊₄, 100°

C. measurement; and

(C) a molecular weight distribution (Mw/Mn) is 2.70 to 3.20.

4. The pneumatic tire according to claim 1,

wherein the terpene resin is at least one selected from the group consisting of polyterpene resin, aromatic modified terpene resin, and hydrogenated product thereof.