Recently, the three major chemical giants in Japan, Mitsubishi Chemical, Asahi Kasei, and Mitsui Chemicals, announced the establishment of a limited liability partnership called "Setouchi Ethylene LLP". The new entity will focus on two ethylene production facilities shared by the three companies in western Japan and will complete related research work by 2030.

In May and November 2024, the three companies respectively released two related announcements, stating that they had conducted in-depth discussions on specific measures to promote carbon neutrality in ethylene manufacturing facilities. For example, they planned to gradually shift raw materials from traditional petroleum resources to biomass based raw materials, while introducing low-carbon fuels to reduce carbon emissions from the source and researching and optimizing the production framework, such as potential capacity reduction plans for the future.

After discussion, the three companies decided to establish a limited partnership company and further accelerate the research pace to deepen cooperation and enter the execution stage.
Setouchi Ethylene was established on August 19, 2025, with a registered capital of 1.5 million yen. Asahi Kasei, Mitsui Chemicals, and Mitsubishi Chemicals maintain a balanced capital ratio of 1:1:1, fully reflecting the equality and closeness of cooperation.

The main tasks of Setouchi Ethylene include conducting research on achieving carbon neutrality goals and production frameworks, and studying how to establish a joint operating entity to optimize the ethylene production facilities of the three companies in western Japan.

The steam cracking units of three companies located in western Japan include the Mizushima plant, a joint venture between Asahi Kasei and Mitsubishi Chemical, and the Osaka plant wholly owned by Mitsui Chemicals.