Tosoh Corporation has decided to acquire the remaining 50 percent stake in Nanyo Kasei Co., Ltd. from Asahi Kasei Corporation, turning the joint venture into a wholly owned subsidiary. The move aims to secure a stable supply of HDI monomer for Tosoh’s HDI derivatives business and its new plant that began commercial operations in September 2026.

Nanyo Kasei was set up in 1980 through equal investment by Nippon Polyurethane Industry Co., Ltd., now part of Tosoh, and Asahi Kasei. The company was created to manufacture hexamethylene diisocyanate, known as HDI monomer. At present, both Tosoh and Asahi Kasei provide raw materials and other inputs to Nanyo Kasei. The joint venture produces the HDI monomer, which each partner then buys for its own use.

By taking full ownership, Tosoh seeks to ensure reliable access to HDI monomer. This step will support the steady running of its existing HDI derivatives operations. It will also help guarantee consistent procurement of the monomer for the company’s newly opened HDI derivatives plant.

The acquisition strengthens Tosoh’s control over a key intermediate used in its specialty chemical activities. Nanyo Kasei will continue its role in HDI monomer production under sole ownership by Tosoh following completion of the share transfer from Asahi Kasei.