Engineering polymers maker Celanese is buying Italy’s SO.F.TER. Group, a privately owned compounder of engineering plastics and thermoplastic elastomers. Terms of the deal weren’t disclosed. SO.F.TER. employs 550 people and operates eight plants across Brazil, Italy, Mexico, and the U.S. Celanese has been expanding its polymer compounding business, recently adding materials such as nylon and polyether ether ketone.