| 摘要 |
Polyoxymethylenes are produced by polymerizing formaldehyde or trioxan in the presence of an ionic catalyst and of blocked oligomers of the formula R1-(-OCH2-)-nR2 wherein R1 and R2 are alkly, aryl, alkaryl, aralkyl or acyl, and n=2 to 12. Preferred amounts of catalyst are 10-4 to 10-1 mole per litre of reaction mixture, and the oligomers are present in less than 10% by weight of trioxan or, using formaldehyde, less than 10% by weight of polymerization medium. Formaldehyde is suitably polymerized using an inert organic solvent medium, anionic or cationic catalysts, and temperatures of -110 DEG to +100 DEG C., while trioxan is suitably polymerized as a melt, in the solid phase, or in an inert organic solvent medium using cationic catalysts, at temperatures of 0 DEG to 110 DEG C. for the solid phase and 70 DEG to 90 DEG C. for the melt or solvent polymerization. Exemplified oligomers and catalysts are (1), (4), (8) the dimethyl ether of pentaoxymethylene glycol (DEPG) and BF3 ether, (2), (5) DEPG and SnCl4, (3), (6) DEPG and H2SO4, (7) dimethyl ether of dioxymethylene glycol and BF3 ether, (9) DEPG and SnCl4, (10) dimethyl ether of dioxymethylene glycol and SnCl4, (11) dimethyl ether of heptaoxymethylene glycol and SnCl4, and (12) dimethyl ether of dioxymethylene glycol and SnCl4. |
