Alternatively, a backing sheet may be made from a thermoplastic olefin such as polypropylene or polyethylene, in which case the size coat is made from a thermoplastic chlorinated polyolefin (CPO), preferably a chlorinated polypropylene or chlorinated polyethylene, in which the coating composition contains about 10% to about 60% by weight of CPO, and correspondingly, about 50% to about 90% by weigh