A useful method for thorough dehydrochlorination of Poly(vinylidene chloride-co-vinyl chloride) using Zinc(II) oxide

A poly(vinylidene chloride)-based polymer is a good material for food packaging as a barrier for oxygen and steam; however, there are problems related to chemical recycling due to low temperature degradation. To aid in developing a chemical recycling method without the evolution of harmful hydrochloric acid (HCl) and organochlorines, we have proposed a dehydrochlorination process at a low temperature (around 423 K) using zinc(II) oxide (ZnO). ZnO particles dispersed into the polymer matrix were found to be effective for thorough dehydrochlorination because the reaction promoters (zinc chloride [ZnCl2] and water) spontaneously penetrated the polymer via exothermic reactions. As a result, only a small percentage of chlorine atoms remained with a low amount of HCl. The efficiency of dehydrochlorination was a result of increasing the contact area with ZnO particles using a heat-kneading apparatus. The catalyst ZnCl2 was involved in the cross-linking reaction to form C–C single bond. Due to exothermic reaction, the scission or isomerization to polyene and aromatics also proceeded over a short period, leading to a microporous carbonaceous solid with a surface area of 5 × 102 m2/g. [Display omitted] •PVDC-PVC copolymer dehydrochlorinated at a low temperature (around 423 K) in the presence of ZnO.•Only a small percentage of chlorine atoms remained with a low amount of HCl.•ZnO particles dispersed into the polymer matrix were effective for thorough dehydrochlorination.•The efficiency of dehydrochlorination was a result of increasing the contact area with ZnO particles.•Scission or isomerization to polyene also proceeded over a short period, forming a microporous carbonaceous solid.