The Synthesis Of Nucleating Agents MDBS And DMDBS

(1,3:2,4)-di-(p-methylbenzylidene)sorbitol(MDBS) and (1,3:2,4)-di- (3,4-dimethylbenzylidene)sorbitol(DMDBS) were prepared from sorbitol and p-methylbenzaldehyde and 3,4-dimethylbenzaldehyde in the presence of a acid catalyst, respectively. On optimizing the synthetic process, the yields were up to 99% more than the ones reported in the previous literatures. The industrialization of process in this paper had been accomplished.In the process of preparing MDBS with toluene/methanol system as solvent, the suitable acid catalyst was C12 alkyl benzenesulfonic acid. Toluene was more advantage to converting the gel state to wet powder than cyclohexane and the lower speed of removing the mixture of methanol and resultant water was in favor of reaction. The addition of toluene/methanol resulted in high yields. The p-methylbenzaldehyde was preferably used in an amount of 2.3 moles per mole of sorbitol. The presence of DMF and DMSO were adverse to condensation reaction of sorbitol and p-methylbenzaldehyde.The study of work-up process indicated that toluene, methanol, cyclohexane, acetone and the recovered mixture of methanol and water were suitable solvents for the purification of the products after neutralization and washing with water. The presence of a certain amount of water in the work-up procedure did not affect the quality of the product. Some additives such as stearate, trialkylamine and some antioxidants could improve the applying properties by improving melt point of MDBS up to 250℃, trialkylamine with a single long carbon chain was especially favor of improving the properties of products. The industrialized yield could be up to 90%.For the process of preparing DMDBS, suitable solvent was cyclohexane/methanol system, and the suitable acid catalyst was C12 alkyl benzenesulfonic acid. The 3,4-dimethyl benzaldehyde was preferably used in an amount of 2.1 to 2.3 moles per mole of sorbitol. The portionwise addition of 3,4-dimethylbenzaldehyde was helpful to converting the gel state to wet powder. Additionally feeding cyclohenane/methanol and maintaining at a high temperature for a certain reaction time could achieve high yields. The product yields in the laboratory experiments were up to 99%.The solution of trialkylamine in toluene was most effective solvent capable for the purifying products in work-up procedure. The melt points of DMDBS were up to 261℃ and the yields were not less than 95%. The quality of DMDBS was identical with the imported products'.Nucleating agents MDBS and DMDBS synthesized according to the present method were tested through injection molding and granulation and their applying properties were the same as first-class products in the world.