Study On Synthesis Of Sorbitol-Typed Clarifying Nucleating Agent

Polypropylene(PP) has been one of the five widest applied resin because of its excellent performance. But the faulty sheen and transparence restrict its application. At present, adding clarifying nucleating agent is the simplest method to modify the transparence of PP. The sorbitol-typed nucleating agent is the most popular at home and abroad.The synthesis of the third generation sorbitol-typed nucleating agent 1,3-2,4-di(3,4-dimethy- benzylidene)sorbitol(DMDBS) was researched thoroughly, and the effects of putting the materials into reactor, raw materials ratio, and the category and mass of catalyst, etc on the yield of DMDBS were studied in this thesis. According to the data of the conditional experiment, the optimal condition of synthesis is: under the protection of N2, the materials are put into reactor in one time, the ratio of aldehyde to sorbitol is 2.0:1.0, paratoluenesulfonic acid is the catalyst, the catalyst, solvent and accelerating agent are 1.5%, 627% and 447% of raw materials by weight respectively, temperature is elevated slowly, reacting time is 6 hours. The reaction is terminated by neutralization, the raw product is washed and cyclohexane is recycled by evaporation. The raw product is refined with acetone and the average yield of DMDBS is 74.7%. The refined DMDBS is white and odorless. The craft is rational and repetitional. The melting point of the refined DMDBS is about 265℃which reaches the demand of this type nucleating agent at home and abroad. The haze of T30S PP is minished from 36.3% to 17.6% when the addition of DMDBS is 0.1% of PP by weight. The nucleating capability of DMDBS is as the same as Millad3988.The synthesis of 1,3-2,4-di(3,4-benzylidene)xylitol (DMDBX) was studied in this thesis. DMDBX is similar to DMDBS, and both them are the product of acetalization. The effects of solvent system, raw material ratio, and the mass of catalyst and accelerating agent on the yield of DMDBX were studied. The optimal condition is: in the system of cyclohexane and methanol, the ratio of aldehyde to sorbitol is 2.4:1.0, the catalyst and accelerating agent are 4.0%wt and 430%wt of raw materials by weight respectively, and the other condition is as the same as the synthesis condition of DMDBS. The raw product is refined with acetone and the average yield of DMDBX is up to 92.55%. The craft is rational and repetitional. The melting point of the refined DMDBX is about 240℃. The haze of T30S PP is 19.1% when the addition of DMDBX is 0.1% of PP by weight. This proves the good nucleating capability of DMDBX and proves that the dihydric structure is not the crucial factor of nucleating capability of sorbitol-typed nucleating agents, which is just one of the factors that accelerate the nucleating function. Besides the nucleating capability, DMDBX also has some good effects on the impact strength and tensile strength of PP and has no bad effect on the thermal performance of PP.