Prepn. of di-acetal of sorbitol and aromatic aldehyde - using mineral acid catalyst, as polymer additive

摘要

A diacetal (I) of sorbitol and an aromatic aldehyde (II) is prepd. by (a) mixing D-sorbitol into an aq. soln. of a mineral acid to form a homogeneous mixt. contg. a catalytic amt. of the acid, (b) gradually adding (II) at a rate to give an immediate reaction and to form an aq. suspension contg. crude (I), the molar ratio of sorbitol:(II) being 1:0.75-1.75, (c) neutralising the suspension, (d) sepg. (I) from the liq. phase of the suspension, (e) washing (I) with water to remove monoacetal impurities, and (f) drying the washed (I). Pref. acids are HCl and H2SO4. The amt. is 10-75 (15-60), esp. 30-60wt.% w.r.t. the water. Claimed (II) are benzaldehyde (III), methylbenzaldehyde (IV), and benzaldehydes with 1-3 substits. which are less than 5C alkyl, methoxy, mono- or dialkylamino, NO2 or halogen. The molar ratio of sorbitol:II is esp. 1:1-1.5 (1:1.25-1.75). Neutralisation may be with NaOH, KOH or NaHCO3. (I) are polymer additives, e.g. dibenzylidene sorbitol improves the transparency of polyolefine films.