Zeon Corp. (TYO:4205) and Sumitomo Chemical Co. Ltd. (TYO:4005) have entered into a partnership contract to integrate their solution-styrene butadiene rubber (S-SBR) business operations under a joint venture firm to be established on Dec. 8. According to the contract, ZS Elastomers Co. Ltd. (ZSE) will be established as a wholly owned Zeon subsidiary using a capital investment of 450 million…