The investment group, BCP Crystal Acquisition GmbH & Co. KG, is offering 32.50 euros per share for Celanese in a bid valued at 3.1 billion euros ($3.8 billion).

In a separate announcement, Celanese said BASF AG would acquire the worldwide nylon 6,6 business of Celanese's Ticona business. Terms of that sale were not announced.

Celanese, based in Kronberg, Germany, was spun off in 1999 from the former Hoechst AG. The company is a manufacturer of basic and specialty chemicals, including a number of coatings raw materials. The product portfolio includes methanol, formaldehyde, polyols, acetic acid, acetic acid derivatives, vinyl acetate monomer, polyvinyl alcohol, emulsions, acrylic acid, acrylates, amines, esters, anydrides, alcohols, and others.