High-resilience ionomeric compositions for golf ball covers

DETAILED DESCRIPTION OF THE INVENTION In the following disclosure the term `direct copolymer` means a copolymer made by polymerization of monomers together, at the same time, as distinct from a graft copolymer where a monomer is polymerized on an existing polymer chain.
The compositions of this invention are blends of ionomers derived from direct copolymers of ethylene and methacrylic acid or acrylic acid (or both) by neutralization with metal ions.
Methods of preparing such ionomers are well known and are described in U.
S.
Pat.
No.
3,264,272 which is herein incorporated by reference.
Preparation of these direct acid copolymers on which the ionomers are based is described in U.
S.
Pat.
No.
4,351,931 which is also incorporated by reference herein.
Acid copolymers with high levels of acid are difficult to prepare in continuous polymerizers because of monomer-polymer phase separation.
This difficulty can be avoided however by use of `cosolvent technology` as described in U.
S.
Pat.
No.
5,028,674 which is also incorporated herein by reference or by employing somewhat higher pressures than those at which copolymers with lower acid can be prepared.
Coefficient of restitution (COR) is a measure of resilience.
It is measured by a number of methods which are not always comparable.
For example, it is sometimes measured on finished golf balls where the material of special interest is, for example, the cover material of the golf ball.
In this case the COR measured is that of the golf ball itself.
Alternatively, it may be measured on solid spheres of the material under consideration, in which case the COR is characteristic of the material alone.
In either case more than one set of test conditions for its measurement can be used.
In comparing golf ball cover materials, there are two approaches.
One approach is to take a specific golf ball core and put on a cover of the material to be tested, then measure a COR for the golf ball.
The other is to measure a COR on a sphere of the material itself.
This is the method of testing used in this disclosure