Molded mixed plastics, applications

Rigid slabs, pipe sections, beveled lags, molded products and as a dry mix for wet plastic application. 

Secondary recycling is the recycle of plastic resins into new products with less demanding physical and chemical characteristics than the original application. Mixed plastics are applied most easily in the secondary recycling market because less separation of resin types and less complicated production methods are necessary to achieve a finished product. The most readily recognized secondary plastic product is "plastic lumber" (thick extrusion molded slabs of resin in which some types of resins act as fillers). Plastic lumber is used to make park benches, fence posts, boat docks, playground equipment and the like. The fabrication of mixed plastic lumber is discussed in Part II of the book. 

Union Carbide (34) and in particular Dow adopted the continuous mass polymerization process. Credit goes to Dow (35) for improving the old BASF process in such a way that good quality impact-resistant polystyrenes became accessible. The result was that impact-resistant polystyrene outstripped unmodified crystal polystyrene. Today, some 60% of polystyrene is of the impact-resistant type. The technical improvement involved numerous details it was necessary to learn how to handle highly viscous polymer melts, how to construct reactors for optimum removal of the reaction heat, how to remove residual monomer and solvents, and how to convey and meter melts and mix them with auxiliaries (antioxidants, antistatics, mold-release agents and colorants). All this was necessary to obtain not only an efficiently operating process but also uniform quality products differentiated to meet the requirements of various fields of application. In the meantime this process has attained technical maturity over the years it has been modified a number of times (Shell in 1966 (36), BASF in 1968 (37), Granada Plastics in 1970 (38) and Monsanto in 1975 (39)) but the basic concept has been retained. 

Another important application of butyraldehyde is in the production of oxo-alcohols for use as plasticizers used to improve mixing of solid compounds that must be molded or extruded into specific shapes. The hydrogenation catalyst is Ni/Al203. 

---