A thread wound golf ball is generally produced by winding thread rubber around a center in a highly drawn condition to form a thread wound core and then providing a covering on the cover. The thread rubber requires a high strength sufficient for tightly winding it on a center and also a high impact rubber resilience at a highly drawn condition sufficient for enhancing the flight distance.
In order to satisfy the above mentioned requirement for thread rubber, the thread rubber is conventionally formed from a mixture of natural rubber or a high-cis polyisoprene rubber with a low-cis polyisoprene rubber, because the natural rubber or high-cis polyisoprene rubber provides a high strength and the low-cis polyisoprene rubber a high impact resilience.
Japanese Kokoku Publication 54 (1979)-4733 proposes that a disulfide compound is mixed with natural rubber, because the disulfide compound improves the impact resilience of the natural rubber while maintaining the strength of the natural rubber.
The above publication considerably improves strength and impact resilience, but further improvement is desired.