A preparing method for polyester composition

Abstract

The invention discloses a preparing method for a polyester composition. An esterification reaction between aromatic dicarboxylic acid and aliphatic dihydric alcohol is firstly performed in the method;an antimony compound, an inorganic acid containing phosphorus, or an organic compound containing phosphorus and phosphoric acid alkali metal salt are added to the reaction system from the end of esterification reaction to the beginning of a polymerization reaction to begin the polymerization reaction; in the time period from the inherent viscosity of the polymerized reactant reaching 0.5dl/g to the end of the polymerization reaction, a manganese compound is added to the reaction system to the continue the polymerization reaction until the end of the polymerization reaction. The gel fraction of the polyester composition prepared through the method is under 5wt% in a N2/O2 gas mixture (oxygen concentration is 1 vol%) after thermal treatment of 300DEG C * 6hr and the polyester composition can be used for preparing thin films and fibers with little foreign material.

Description

technical field [0001] The invention relates to a preparation method of a polyester composition with low gel rate and few foreign substances. Background technique [0002] Polyesters, especially polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, etc., are widely used due to their excellent mechanical, physical and chemical properties Production of fibers, films and other molded products. However, most polyesters will undergo thermal oxygen degradation and thermal decomposition under high temperature conditions. In the thermal oxygen degradation reaction, oxygen radicals attack the hydrogen on the benzene ring of polyester to generate peroxide functional groups, which are unstable. It will also decompose to generate free radicals, and the generated free radicals serve as bridging points and the products of polyester thermal decomposition to form bridging structures, that is, cross-linking reactions occur to form infusible gels, which are ...

AI Technical Summary

Problems solved by technology

For example, Japanese Patent Laid-Open 2005-314643 and Japanese Patent Laid-Open 2006-225621 describe that gelation can be suppressed to some extent by adding titanium compounds in processes such as transesterification, but the heat resistance of polyester itself is reduced. Thermal cracking will occur during long-term film production, so gel formation cannot be sufficiently suppressed

At the same time, a stabilizer phosphorus compound is generally added during the polymerization process, and after the added phosphorus compound reacts with the metal co-catalyst, it is easy to form insoluble matter in the polyester and form particles, which will cause the filter pressure of the filter to rise during the molding process. It is easy to break during spinning, which will affect the spinning performance, or cause the filter pressure of the filter to increase during the membrane production process, and the filter will be replaced frequently, resulting in waste of raw materials and an increase in cost

In addition, the occurrence of gel defects on the film leads to a decrease in the quality of the film and limits its use

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