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多元酸与多元醇的三向聚酯反应,象单元酸与单元醇的酯化反应一样,是氢离子催化机构,并且,动力学方程与酸基和醇基的起始克分子比有密切关系。我们首先用严格的动力学方程处理三向聚酯反应的实验数据。当酸基与醇基以等克分子比起反应,在无外酸存在时,三向聚酯反应是2(1/2)级反应。若有外酸作催化剂,如氢离子由外酸和多元两方面供给,三向聚酯反应不是二级反应,只有当外酸的量加到适当多,多元酸本身供给的氢离子可以忽略不计时,才是二级反应。当酸基与酸基以不等克分子比反应,我们的实验结果亦与理论一致。根据我们的实验结果,丙三醇中的伯羟基和仲羟基的反应能力相差很小,可以用同一反应速度常数处理实验数据。不论酸基与醇基是等或不等克分子比的丁二酸与异戊四醇,己二酸与异戊四醇,癸二酸与异戊四醇,以及己二酸与丙三醇在不同温度,有无外酸作催化剂,和有无间甲酚作溶剂时的三向聚酯反应,实测的凝膠点,都与计算值很相近(在±1%范国内)。并且,用实验证明凝膠点只与起始的多元酸的羧基与多元醇的羟基的克分子比,以及与其官能团的数目有关,与反应温度,有无催化剂和溶剂存在,催化剂的量,以及酸和醇的种类无关。同时也指出 Stockmayer 和 Flory 等实测的凝膠点与理论计算值所以不相符合的可能原因。
The tri-to-polyester reaction of polybasic acids with polyhydric alcohols, like monoester acids, is a hydrogen ion catalysis, as with the esterification of monovalent alcohols, and the kinetic equation is closely related to the initial molar ratio of acid groups to alcohol groups . We first used rigorous kinetic equations to treat the experimental data for the three-way polyester reaction. When the acid group and the alcohol group react in equimolar proportions, the tri-to-polyester reaction is in the absence of external acid in the 2 (½) order reaction. If external acid as a catalyst, such as hydrogen ions from the external acid and multiple supply, the three-way polyester reaction is not a secondary reaction, only when the amount of external acid added properly, the hydrogen ion supplied by the polyacid itself is negligible Timing, is the secondary reaction. When the acid and acid groups react at unequal molar ratios, our experimental results are also consistent with the theory. According to our experimental results, the primary and secondary hydroxyl groups in glycerol have little difference in reaction ability, and experimental data can be processed with the same reaction rate constant. Regardless of whether the acid group and the alcohol group are equal or unequal molar ratios of succinic acid to isopentyl alcohol, adipic acid to isopentyl alcohol, sebacic acid to isopentyl alcohol, and adipic acid to glycerol At different temperatures, with or without external acid as a catalyst, and with or without m-cresol as a solvent when the three-way polyester reaction, the measured gel point, are very similar with the calculated value (within ± 1% Fan national). Moreover, it is experimentally demonstrated that the gel point is only related to the molar ratio of the carboxyl groups of the starting polybasic acid to the hydroxyl groups of the polyhydric alcohol, as well as to the number of functional groups thereof, depending on the reaction temperature, presence or absence of catalyst and solvent, amount of catalyst, Acid and alcohol type has nothing to do. Also pointed out that Stockmayer and Flory and other measured gel points and theoretical calculations so do not coincide with the possible reasons.