Process for making PVC resin having improved initial color and clarity

Abstract

This invention discloses methods of polymerization in the field of PVC dispersion resins, in particular, dispersion PVC, made by the emulsion or microsuspension process with or without monomer metering. The invention achieves improved initial plastisol color without destroying blush resistance by employing techniques which entail at least two air evacuation steps. In the preferred embodiment a specified amount of a metabisulfite reducing agent is incorporated into the polymerization medium and/or monomer mixture followed by polymerization initiaton and further processing. Another disclosure of the invention is a simple method for reducing the haze of dispersion resin plastisol films thereby improving their clarity by the addition of a small amount of non-copolymerizable polybasic carboxylic acid to the dispersion resin or monomer dispersion prior to isolating the resin. The preferred poly basic acids are non-ethylenic unsaturated, di- or tri-carboxylic acids like citric acid and tartaric acid.

Dependencies are inferred from the claim text.