1. Field of the Invention
The present invention relates to a process for preparing unsaturated, cyclic orthoesters.
2. Discussion of the Background
The unsaturated, cyclic orthoesters find use in the preparation of various polymer blends which comprise polymers which are generally regarded as immiscible with one another, for example polyesters and polyolefins (EP 0 496 116 A1, EP 0 499 717 A1). EP 0 519 642 describes the use of a copolymer of unsaturated, cyclic orthoesters in a polymeric blend consisting of polyphenylene ether and polyester. These copolymers based on unsaturated, cyclic orthoesters enable compatibility between these two polymer types.
The unsaturated, cyclic orthoesters are prepared according to previously described processes by first cyclizing glycerol with an orthoester (see reaction 1) and reacting the resulting hydroxy orthoester with acryloyl chloride or methacryloyl chloride in the presence of a base to give the target compound (see reaction 2). 4-Acryloyloxymethyl-2-methoxy-2-methyl-1,3-dioxolane ((2-methoxy-2-methyl-1,3-dioxolan-4-yl)methyl acrylate, MMDA) can, for example, be prepared in this way when the substituent R of the acid chloride is a hydrogen atom.

EP 0 471 222, EP 0 475 039 and EP 0 475 040 describe, for example, the reaction of glycerol (1,2,3-propanetriol) with methyl orthoacetate in methylene chloride in the presence of p toluenesulfonic acid according to reaction 1.
The reaction of the cyclized orthoester with acryloyl chloride or methacryloyl chloride in methylene chloride and in the presence of triethylamine according to reaction 2 is described, inter alia, by EP 0 496 116, EP 0 499 717, EP 0 519 642 and EP 0 731 141.