SIMULTANEOUS STATISTICAL SUSPENSION COPOLYMERIZATION OF VINYL-CHLORIDE WITH BUTYL ACRYLATE AND GRAFTING ON POLY(BUTYL ACRYLATE)

An intrinsically softened poly(vinyl chloride-butyl acrylate) was prep ared by the suspension statistical polymerization of vinyl chloride (V C) with butyl acrylate (BA) using oil-soluble initiators, dispersants, and a buffer agent, at the temperature 59 +/- 1 degrees C (procedure A). The polymer obtained was sufficiently soft and elastic, depending on the ratio of VC and BA; however, the polymer was hard to process. i t stuck to metal parts of an assembly line. The properties of the poly mer were slightly modified, mainly by addition of crosslinking agents, and improved treatability was obtained in this way. Acceptable treata bility was obtained only after preplastification. Similar features wer e exhibited by a polymer prepared by grafting of a fine dispersion of polybutyl acrylate (PBA) with VC (procedure B). The dispersion of PBA was prepared separately via the emulsion polymerization of BA. at 75 /- 1 degrees C (the weight ratio H2O : BA = 2; a mixture of sodium alk ane sulfonates 0.95 w/w % and K2S2O8 0.4 w/w % with respect to BA). An intrinsically softened polymer with elasticity derived from the amoun t of incorporated BA was obtained; unfortunately, as with case A, the polymer was difficult to work up, and preplastification was necessary. The best procedure for the preparation of intrinsically softened poly (vinyl chloride-butyl acrylate) proved to be simultaneous statistical copolymerization of VC and BA, and grafting on PBA (procedure C). The principle consists of gradual addition of VC and BA to the fine disper sion of PBA. A shape stable, aesthetic looking, and well readily proce ssible material was obtained. The ductility of foils prepared from the polymer increases with the increasing amount of BA, while the tempera ture stability, hardness, and mechanical strength decrease. A hypothes is expressing the morphology of a polymer with good propel ties has be en proposed. Significantly different values of copolymerization parame ters of BA (approx. 5) and VC (approx. 0.1) are responsible for irregu larities in a copolymer when all amounts of monomers are added at the start of the reaction. The rate of addition of monomers to the polymer ic reaction mixture ought to be at such a rate as to allow the formati on of relatively regular alternated chains of homopolymers and copolym ers of BA. and VC that start to grow mainly from the core represented by PBA chains. At the end of copolymerization, an excess of VC is usef ul for making a PVC hydrophobic cover of particles, and, in consequenc e, low stickiness to metal surfaces. This may be used for the descript ion of a good polymer, as well as to account for bad properties of oth er copolymers of BA and VC. (C) 1998 John Wiley & Sons, Inc.