Thread-wound golf ball

DETAILED DESCRIPTION OF THE INVENTION The thread-wound golf ball according to this invention comprises a ball core, a rubber thread layer and an outer skin layer or cover in which the rubber material constituting the rubber thread of the rubber thread layer and/or the core ball contains an isoprene-butadiene random copolymer.
The content of the isoprene-butadiene random copolymer in the rubber constituting the rubber thread and/or ball core is more than 30 parts by weight and, preferably, more than 50 parts by weight based on 100 parts by weight of the total rubber ingredient in view of the impact resiliency and the flying performance of the ball.
If the content of the isoprene-butadiene random copolymer is lower than 30 parts by weight, the impact resiliency and the flying performance of the ball are insufficient, failing to attain the object of this invention.
The isoprene-butadiene random copolymer suitably used in this invention comprises from 5 to 90% by weight and, particularly, from 10 to 50% by weight of a butadiene component and from 10 to 95% by weight and, particularly, from 50 to 90% by weight of an isoprene component.
If the butadiene component is less than 5% by weight, it may sometimes only give an insufficient effect of decreasing the energy loss upon great stretching of the rubber thread and thus less effect of improving the impact resiliency.
While on the other hand, if the content is more than 90% by weight, the strength of the rubber may sometimes be decreased.
Further, in view of the microstructure of the isoprene-butadiene random copolymer, it is desired that more than 80%, preferably, more than 90% and, more preferably, more than 95% of cis-1,4 structure.
If the cis-1,4 structure is less than 80%, the strength of the rubber may sometimes be poor.
Furthermore, those isoprene-butadiene random copolymers with Mooney viscosity from 30 to 100 and, particularly, from 40 to 70 can be used preferably.
If the Mooney viscosity is lower than 30, the rubber may possibly flow even under the room temperature resulting in problems both in storage and in fabrication