MANUFACTURE OF ALLYL DIGLYCOL CARBONATE

Alkyl-diglycol carbonates R2OOC-(OR')n-OOC-R2 (I) (where R' is an aliphatic di-radical, e.g. -C2H4- or -C3H6-; R2 is an unsatd. aliphatic radical, e.g. allyl or methallyl and n is 1-3) are prepd. continuously by first reacting a bischloroformate Cl-CO-(OR')n-OOC-Cl (II) with an alcohol R2OH (III) in the presence of an alkali metal hydroxide in >=2 intense mixing zones connected in series at -5 to +60 degrees C at pH >7. The first reaction zone is kept in the lower- and the 2nd and subsequent zones in the higher part of the temp. range. The prod.(I) is recovered continuously by (1) passing the reaction mixt. directly from the last reaction-zone through a liq.-liq. sepg. zone; (2) countercurrently gas-stripping the prods. stream of the liq.-liq. sepg. zone, in a zone kept at 50-150 degrees C under pressure 5 mm Hg to atmospheric, and removing the prod. from the bottom of the stripping zone; (3) removing and condensing the gas-stream from the stripping-zone, condensing and distilling the condensate to recover the allyl alcohol; and (4) continuously introducing (II) aq. alkali metal hydroxides and part of recovered- or pure allyl alcohol to first reaction zone, to replace spent materials. Allyl-diglycolcarbonate (CH2-CH-COO-CO-CH2CH2)2O (Ia) is used as monomer in the prodn. of hard safety lenses and of scratch-resistant, tough plastic sheets.