forms of the composition the waterborne resin dispersion used in the primer may be an acrylic emulsion or lacquer for example a material sold by zeneca resins division of imperial chemical industries plc of wilmington del under the trademark neocryl particular materials of this type include neocryl a 601 and neocryl b 723 among others the waterborne resin dispersion used in the primer may instead be a polyurethane prepolymer emulsion for example a material sold by zeneca under the trademark neorez a specific neorez dispersion useful herein is neorez r 960 emulsion another material which may be used is witcobond w 234 supplied by witco organics division chicago ill combinations of acrylic and polyurethane dispersions are also contemplated within the scope of the present invention the water borne dispersions contemplated herein contain from about 5 to about 90 solids preferably from about 20 to about 40 solids one of ordinary skill in the art is readily able to select a resin dispersion which is useful in a primer for the ball cover materials specified above the polyfunctional aziridine crosslinker materials useful herein are preferably tri or more highly functional compounds the preferred materials include pentaerythritol tris u03b2 n aziridinyl propionate trimethylol propane tris u03b2 n aziridinyl propionate mixtures of different.