. "A third group of suitable compounds are the polar vinyl polymers, e.g., polyvinyl pyridine, polyvinyl pyrrolidone, polyvinyl alcohol and cellulose derivatives, e.g.,carboxymethylcellulose (CMC).The comminuted rubber preferably has a mean particle size of between 90 .mu.m and 1200 .mu.m and more particularly a media" . . .