Three of Japan’s chemical giants—Mitsui Chemicals, Idemitsu Kosan, and Sumitomo Chemical —are moving closer to reshaping the country’s polyolefin landscape after securing a key green light from regulators for a sweeping business integration.

 

The companies first announced on September 10, 2025, a basic agreement to integrate the polyolefin (PO) operations of Prime Polymer —the Mitsui–Idemitsu joint venture—with Sumitomo Chemical’s polypropylene (PP) and linear low-density polyethylene (LLDPE) businesses in Japan. The deal is aimed at strengthening competitiveness and building more resilient core materials businesses that underpin Japanese industry.

 

They stated the objective is “to realize resilient and essential businesses that support Japanese industries and to enhance the competitiveness of the PO business, including PP and polyethylene (PE), in Japan.”

 

Momentum behind the plan accelerated on December 24, 2025, when the companies formally concluded a business integration agreement and a joint venture agreement to move the deal forward.

 

The integration has since been under review by the Japan Fair Trade Commission after a formal notification was submitted under the Act on Prohibition of Private Monopolization and Maintenance of Fair Trade.

 

That process has now reached a major milestone. The companies confirmed they have received notice from the Japan Fair Trade Commission that it will not issue a cease-and-desist order, clearing a critical domestic regulatory checkpoint.

 

However, the deal is not yet fully cleared. Overseas merger reviews by relevant competition authorities are still underway, and the integration will proceed only after those approvals are completed.