Oxy plans to buy Tenneco’s polyvinyl chloride unit.

The acquisition, for undisclosed terms, will nearly double Occidental Petroleum’s annual PVC resin production capacity to 1.35 billion pounds from 700 million pounds. PVC is used to make pipe, siding, floor and wall covering, wire insulation and window frames. Houston-based Tenneco said the business, which will have revenue of about $250 million this year, consists of two manufacturing plants located in Pasadena, Tex., and Burlington, N.J. Los Angeles-based Oxy said the deal would be closed during the first three months of 1986.