After hydrolyzing a phospholipid bonded to a molecular end of a natural rubber, a compound having a polar group reacting with a hydroxyl group is condensed with a hydroxyl group contained in the phospholipid-hydrolyzed natural rubber to thereby obtain a modified natural rubber in which a polar group is present at a molecular end. The modified natural rubber thus obtained in which a polar group is present at a molecular end is used for a rubber component of a rubber composition, whereby a rubber composition in which carbon black and silica as fillers are bonded to the rubber component to enhance a reinforcing effect and which is excellent in a low hysteresis loss property and abrasion resistance to a large extent is obtained. An enzyme or an alkali is used for hydrolyzing the phospholipid, and a condensing agent is used for condensing the polar group-containing compound.
在
水解与
天然橡胶分子末端结合的
磷脂后,具有与羟基反应的极性基团的化合物与
水解
磷脂的
天然橡胶中所含的羟基缩合,从而获得分子末端含有极性基团的改性
天然橡胶。由此获得的分子末端含有极性基团的改性
天然橡胶可用作橡胶组合物的橡胶成分,从而获得一种橡胶组合物,其中
炭黑和
白炭黑作为填料被粘合到橡胶成分中以增强补强效果,并在很大程度上具有优异的低滞后损失特性和耐磨性。使用酶或碱
水解
磷脂,使用
缩合剂缩合含极性基团的化合物。