Advanced Powder Technol., Vol. 16, No. 1, pp. 27–34 (2005)  VSP and Society of Powder Technology, Japan 2005. Also available online - www.vsppub.com Original paper Dechlorination of polyvinyl chloride by its grinding with KOH and NaOH TSUYOSHI INOUE 1,∗ , MIYUKI MIYAZAKI 1 , MASATAKA KAMITANI 1 , JUNYA KANO 2 and FUMIO SAITO 2 1 Sekisui Chemical Co., Ltd., 2-2 Kamichoshi-cho Kamitoba Minami-ku, Kyoto 601-8105, Japan 2 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira Aoba-ku, Sendai 980-8577, Japan Received 8 July 2003; accepted 21 January 2004 Abstract—Polyvinyl chloride (PVC) powder was ground with one of two dried alkaline additives, i.e. KOH and NaOH, pellets in air by a planetary ball mill to investigate the dechlorination reaction during the grinding. Grinding of the mixture causes the size reduction of PVC, with causing its mechanochemical reaction with the additive to form partially dechlorinated PVC and chloride (KCl or NaCl), respectively. In both reaction systems, the dechlorination yield increases with an increase in grinding time and amount of additive. The C C bonds in the PVC ingredient are created in its structure with decreasing molecular weight (MW). The MW of the polymer ground with KOH is higher than that ground with NaOH. The dechlorination speed of the polymer ground with KOH is faster than that ground with NaOH in the initial stage of grinding, but this is reversed during prolonged grinding. Keywords: Dechlorination; grinding; PVC; mechanochemistry; KOH; NaOH. 1. INTRODUCTION Polyvinyl chloride (PVC, [ (CH 2 CHCl) n ], n = polymerization degree) is a material that plays a significant role in our daily life, due to its excellent chemical and physical properties. There have been many PVC products; however, they are fated to be wastes after their usage or even in their production process when they are of insufficient quality. To dispose of such PVC wastes, reclamation and combustion have been conducted since last few decades. Reclamation needs a huge area, so that a limitation exists in any case. Combustion brings about emission of harmful ∗ Correspondence to T. Inoue, Shiga Ritto Plant, Sekisui Chemical Co., Ltd., 75 Noziri, Ritto shi, Shiga 520-3081, Japan. E-mail: inoue042@sekisui.jp