DEVELOPMENT OF A NEW ADVANCED PROCESS FOR MANUFACTURING POLYACETAL RESINS .3. END-CAPPING DURING POLYMERIZATION FOR MANUFACTURING ACETAL HOMOPOLYMER AND COPOLYMER

Conventionally, acetal homopolymer or copolymer is obtained by the pol ymerization of formaldehyde or trioxane, following the end-capping usi ng acetic anhydride or unzipping of the unstable polymer end fraction. First, Asahi Chemical developed a new process to obtain an end-capped polymer during polymerization of highly purified formaldehyde using a cetic anhydride as the chain-transfer agent. Use of highly purified fo rmaldehyde and end-capping during polymerization using acetic anhydrid e as a chain-transfer agent or an end-capping agent will provide a sim ple process for manufacturing acetal homopolymer. The polymerization m echanism was confirmed by infrared spectroscopy analysis and proton NM R analysis of the polymer obtained. Second, for the acetal copolymer, purified trioxane was copolymerized with ethylene oxide in the presenc e of methylal, which gave an end-capped polymer with high thermal stab ility. Two new intermediates from the initiation reaction of the copol ymerization, 1,3,5,7-tetraoxacyclononane (TOCN) and 1,3,5,7,10-pentaox acyclododecane (POCD), were isolated and a new initiation mechanism wa s proposed. (c) 1993 John Wiley & Sons, Inc.