CHEMICALS

Arco to Buy Olin Plastics Unit: Olin Corp. plans to spin off its aerospace and ordnance operations, and sell its polyurethane business to Arco Chemical Co. for $565 million to boost profit margins and strengthen its balance sheet. The Norwalk, Conn.-based company also would split its common shares 2-for-1, repurchase as much as 10% of its stock and seek a buyer for a Kentucky business that makes chemicals used in household cleaners. The spun-off operations would be renamed Primex Technologies Inc. For Arco Chemical, a subsidiary of Los Angeles-based Atlantic Richfield Co., the purchase would give it a guaranteed outlet for the chemicals, known as isocyanates. Olin shares surged $4.375 to $88.50; Arco Chemical shares were unchanged at $49.125. Both trade on NYSE.