Rubber composition for sidewalls, and pneumatic tire using same
The present technology provides a rubber composition for sidewalls containing, a diene rubber, from 10 to 120 parts by mass of a carbon black, and from 3 to 30 parts by mass of an acid-modified polyolefin having a melting point of from 100 to 150° C. per 100 parts by mass of the diene rubber, a main chain of the acid-modified polyolefin being a homopolymer of an olefin; and a pneumatic tire using the same in sidewalls thereof.
1. A rubber composition for sidewalls comprising:
a diene rubber containing natural rubber and butadiene rubber, a content of the butadiene rubber being not less than 30 parts by mass per 100 parts by mass of the diene rubber and a total content of both of the natural rubber and the butadiene rubber being greater than 50 mass % of the diene rubber;
from 10 to 120 parts by mass of a carbon black; and
from 3 to 30 parts by mass of an acid-modified polyolefin having a melting point of from 100 to 150° C. per 100 parts by mass of the diene rubber, a main chain of the acid-modified polyolefin being a homopolymer of an olefin.
2. The rubber composition for sidewalls according to claim 1 , wherein a main chain of the acid-modified polyolefin is a polyethylene, polypropylene, or polybutene.
3. The rubber composition for sidewalls according to claim 1 , wherein the acid-modified polyolefin is a polyolefin modified with a carboxylic acid or an acid anhydride.
4. The rubber composition for sidewalls according to claim 1 , wherein a melt mass flow rate of the acid-modified polyolefin at 190° C. is from 1.0 to 8.0 g/10 min.
5. A pneumatic tire using the rubber composition for sidewalls according to claim 1 as a sidewall.
6. The rubber composition for sidewalls according to claim 2 , wherein the acid-modified polyolefin is a polyolefin modified with a carboxylic acid or an acid anhydride.
7. The rubber composition for sidewalls according to claim 6 , wherein a melt mass flow rate of the acid-modified polyolefin at 190° C. is from 1.0 to 8.0 g/10 min.
8. A pneumatic tire using the rubber composition for sidewalls according to claim 7 as a sidewall.