多元醇缩醛类PP成核剂的应用研究进展

Progress in Research of Application of Nucleating Agents for Polyalcohol Acetal Polypropylene

综述了包括山梨醇和木糖醇在内的多元醇缩醛类聚丙烯(PP)成核剂的应用研究进展,比较了三代山梨醇缩醛类成核剂DBS、MDBS和DMSBS在PP中的应用性能,DBS熔点低,对PP增透效果差,使用过程中醛味大;MDBS对PP增透效果好,但使用过程中仍然会产生醛味;DMDBS熔点高,增透效果好,使用中无异味,但加工温度高;以混合醛合成的非对称成核剂PP增透效果好,成本低,使用过程不产生异味;不同代成核剂的物理复配有利于降低成本,提高应用效果;该类成核剂也可用于聚乙烯及其他聚合物的成核改性。对该类成核剂的改进集中在两方面,一方面是对成核剂本身进行改性,如山梨醇与混合醛缩合直接合成具有不对称结构的缩醛,或者将不同品种的缩醛进行物理共混、或者与其他类成核剂进行物理混合,再或者与其他助剂进行复合,目的都是为了发挥不同成分的协同效应,提高成核剂的综合性能;另一方面是对成核剂的加入方式如釜内与釜外,成核剂的分散方式如母粒形式、配成液体形式和成核剂与PP的加工工艺进行研究。在可预见的将来,还没有更好的成核剂可以取代山梨醇成核剂。

This article describes the progress in the research on the application of nucleating agents for polyalcohol（including sorbitol and xylitol） acetal polypropylene（PP） and compares the performance of three generations of sorbital acetal nucleating agents — DBS,MDBS and DMSBS — when used in PP.DBS has a relatively low melting point,is not very effective in improving the transparency of PP and has a strong odor of aldehyde.MDBS can significantly improve PP′s transparency but also has a strong odor of aldehyde.DMDBS has a high melting point,is effective in improving PP transparency and has no special odor but requires very high processing temperatures.Asymmetrical nucleating agents synthesized with mixed aldehyde can effectively improve PP′s transparency,are cheap and have no special odor.The physical blending of different generations of nucleating agents can reduce cost and improve the performance of the agents in applications.These nucleating agents can also be used in the nucleating modification for polyethylene and other polymers.The efforts to improve the performance of these nucleating agents are focused on two areas.Efforts in the first area are to modify the nucleating agents themselves,such as condensing sorbitol and mixed aldehyde to directly synthesize acetal with an asymmetrical structure,or physically blending different types of acetals,or physically blending these nucleating agents with other types of nucleating agents,or adding compounding chemicals into these nucleating agents.All these methods are aimed to achieve synergy of different constituents to enhance the nucleating agents′ overall performance.Efforts in the other area are to study the pros and cons of different methods of adding nucleating agents（adding inside or outside the kettle,e.g.）,the forms in which nucleating agents are distributed（in the form of agglomerate or liquid,e.g.） and the technologies for producing nucleating agents and PP.In the foreseeable future,no better nucleating agent is expected to be able to replace sorbitol nucleating agents.