Buyout groups AGIC Capital and AEA Investors as well as a Chinese peer are expected to hand in final offers worth up to 500 million euros (441.76 million pounds), including debt, for the operations by an end-July deadline, they added.

Other bidders, such as private equity firm Bridgepoint, have dropped out of the race for the business, which is expected to post earnings before interest, tax, depreciation and amortisation (EBITDA) of just below 40 million euros this year.

Lanxess and AGIC declined to comment. The other groups were not immediately available for comment.

Lanxess, a former unit of Bayer making products including pesticide ingredients, construction pigments and leather chemicals, has said that more strategic steps could be in the offing following recent acquisitions.

Having wrapped up the sale of 50 percent of its synthetic rubber business to Saudi Aramco in 2016 to reduce exposure to harsh competition in the sector, Lanxess branched out with the purchase of Chemours' hygiene product ingredients business and of Chemtura, a U.S. maker of additives for lubricants and flame retardants.

Lanxess' Liquid Purification Technologies business unit makes ion exchange resins and reverse osmosis membrane elements with productions sites in Leverkusen and Bitterfeld, Germany, and in Jhagadia, India.

($1 = 0.8579 euros)

(Additional reporting by Matthias Inverardi; Editing by Maria Sheahan)

By Arno Schuetze