INDIANAPOLIS -- Materials firm ATC Plastics LLC has bought its Houston plant site and building for an undisclosed price. The firm also soon will add a new concentrate production line.

Indianapolis-based ATC bought the 171,000-square-foot building in a deal that closed Dec. 31, co-owner Tom Stevning said in a Feb. 20 phone interview. The firm bought the site from the Heller family, which had owned ATC before selling the business to Stevning and co-owner Rich Mejia in early 2010.

Buying the building "allows us to do other things," Stevning said. "We can make some changes if we need to."

The new production line is expected to be in place by the end of the first quarter. It is needed because of increased demand for black color concentrates used in pipe, film, injection molding and other markets, according to Stevning. ATC also operates a smaller plant making flexible PVC compounds in Visalia, Calif.

ATC employs 25-30 in Houston, with that total expected to increase when the new line is in place. The firm generates most of its sales from proprietary products, with the remainder coming from tolling work.