三组分共聚酯数均聚合度和数均分子量的计算方程

为便于生产控制以制得预定分子量的产物，根据直接酯化法合成聚对苯二甲酯乙二酯（ＰＥＴ）共聚酯的特点，综合考虑各种主、副反应，从统计观点出发，对三组分ＰＥＴ共聚酯体系的齐聚物和缩聚物，分别建立了其数均聚合度Ｘｎ和数均分子量Ｍｎ的简化和非简化计算方程．将简化Ｘｎ方程与Ｃａｒｏｔｈｅｒｓ方程进行计算比较，其结果完全相同；将简化Ｘｎ方程应用于二组分聚酯体系，其形式与传统的二组分线型缩聚物Ｘｎ方程形式相同，各Ｘｎ和Ｍｎ方程可推广应用于二组分聚酯体系和三组分以上的多组分共聚酯体系．

THE CALCULATION EQUATIONS FOR NUMBER AVERAGE DEGREE OF POLYMERIZATION AND NUMBER AVERAGE MOLECULAR WEIGHTS OF TRICOMPONENT COPOLYESTER

In the synthesis of tricomponent poly(ethylene terephthalate) copolyesters through the direct esterification route, in order to control process of production to obtain the desired molecular weights of polymers, the simplified and nonsimplified calculation equations for the number average degree of polymerization n and the number average molecular weights n of oligomers and polycondensates were given, respectively. The calculation equations, derived on the basis of reaction mechanism and technological characteristics, relate n and n to the extent of reaction of carboxyl groups and the amounts of small molecules produced. The various main reactions and important side reactions were all considered for the nonsimplified calculation equations, but for the simplified calculation equations, the various side reactions were neglected. The simplified n calculation equations were compared with carothers equation by calculation, the results are the same. Applied to the dicomponent polyester systems, the simplified n equations are the same as that used conventionally for the dicomponent linear polycondensates. The simplified and nonsimplified calculation equations for n and n of tricomponent poly(ethylene terephthalate) copolyesters can be extended and applied to the dicomponent polyester systems and multicomponent copolyester systems over three components.