Westlake Chemical Corp. is buying Vinnolit Holdings GmbH for €490 million (U.S. $668.5 million) from private equity firm Advent International.

Vinnolit, headquartered in Ismaning, Germany, manufactures polyvinyl chloride (PVC), a product used in the construction process. Boston-based Advent bought the company in 2000, and made several add-on acquisitions, including the 2007 deal for Ineos Paste PVC business, which increased the company's production capacity.

Houston-based Westlake manufactures petrochemicals, polymers and building products. Westlake expects the deal to expand its chlorvinyl business and add specialty PVC products.

Advent has about $31.8 billion in assets under management. The firm was founded in 1984 and has invested in more than 290 transactions in 39 countries. In December, the firm led a group that bought a minority interest in Oleoducto Centra SA, an oil transportation system in Colombia. Before that, in October, Advent announced a deal for P2 Equity Partners, which provides software, geospatial data and land-management tools to the oil and gas industry.

In another recent PVC deal, OpenGate Capital LLC bought Profalis, a PVC supplier to the construction industry.