Factors that must be considered prior to choosing a process for the cleaning of polyvinyl-chloride (PVC) reactors were discussed. The author used the decision making process from Air Products and Chemicals, Incorporated, Allentown, Pennsylvania, to illustrate the considerations. Air Products chose solvent cleaning of its PVC reactors as being the most suitable method for their purposes. The choice was made on the basis of a series of cost benefit decisions. These decisions included a detailed appraisal of the existing facility equipment, its products, its processes, and its location. Problems encountered by Air Products included closed reactor operation with high pressure jets that required the use of nozzles large enough for rotating heads. Such nozzles were not available. Polymer buildup inside the reactors was rapid due to the age of the reactors and poor condition of their inner surfaces. Reflux condensers used in a large part of the operation had to be kept free of buildup. The decision to use solvent cleaning was made after a study of antifouling methods and clean wall processes. The solvents ethylene-dichloride (107062), dimethyl-formamide (68122) (DMF), methyl-pyrrolidone (872504) (NMP), tetrahydrofuran (104803), and ketones were considered for material cost, solvent power, ease of recovery, and factors such as toxicity, volatility, and corrosive nature. Air Products chose DMF for solvent cleaning due to its good solvent power and their familiarity with its characteristics. The reactor cleaning and solvent regeneration systems were described. The systems were in use in facilities manufacturing homopolymer and copolymer and also in emulsion operations. Problems with commercialization included severe corrosion due to the formate- chloride combination. The author concludes that a byproduct of the technology, beyond the goal of reduced employee exposures and emissions, is improved equipment life.
Symposium Proceedings. Control Technology in the Plastics and Resins Industry, Division of Physical Sciences and Engineering, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, DHHS (NIOSH) Publication No. 81-107