A. Schulman Inc. is continuing its buying spree and also has reached an agreement to sell an Ohio plant. The Fairlawn-based compounder and distributor said Aug. 20 it has signed a definitive agreement to acquire ECM Plastics Inc., a privately owned plastics compounder in Worcester, Mass., for $36.5 million. It also announced the sale of its PVC compounding plant in Bellevue, Ohio, to a subsidiary of Mitsubishi Chemical Corp. ECM employs 140 and generates about $40 million in annual sales. The firm operates nine twin-screw extrusion lines and one single-screw line at a 120,000-square-foot plant, making custom compounds and color and additive concentrates based on most major commodity and engineering resins. The transaction is expected to close in early September. The ECM deal is the sixth acquisition in less than three years for Schulman, which ranks as one of North America’s 30 largest compounders and concentrate makers. Most recently, Schulman in January paid $63 million for specialty color concentrate maker Elian SAS of Oyonnax, France.