LONDON (Sept. 4)—British polymer compounder British Vita P.L.C. plans to sell its shareholding in Spartech Corp., a St. Louis-based engineered thermoplastics processor, saying the 46-percent stake no longer serves its shareholders' interests. The stake is worth about $270 million at current market prices, British Vita Managing Director David Campbell said. British Vita disclosed the plan alongside releasing first half results. Details of the disposal are still being worked out, Campbell told shareholders, but the company hopes to make progress during the current quarter. British Vita has built its stake in Spartech over a period of 12 years; Spartech reports more than a billion dollars in annual sales, with 50 plants throughout North America and one in Europe. In North America, British Vita will still be active in polyurethane foams and other polymer products through its Vita Inc. subsidiary.