Polybutylene terephthalate and process for production thereof

Abstract

Disclosed is a process for producing a polybutylene terephthalate continuously from terephthalic acid and 1,4-butanediol using a titanium compound and a compound of at least one metal selected from the metals belonging to Groups I and II on the periodic table as catalysts, the process satisfying the following conditions (a) to (c): (a) terephthalic acid and 1,4-butanediol are subjected to continuous esterification in the presence of a titanium catalyst in an amount of 460 [mu]mol or less in terms of a titanium atom per mol of a terephthalic acid unit, thereby producing an oligomer; (b) the oligomer is subjected to continuous polycondensation in the presence of a compound of at least one metal selected from the metals belonging to Groups I and II on the periodic table in an amount of 450 [mu]mol or less in terms of the metal atom per mol of a terephthalic acid unit; and (c) until the esterification rate of the oligomer reaches 90% or higher, the compound of the metal may be added in an amount of 300 [mu]mol or less in terms of the metal atom per mol of a terephthalic acid unit, and after the esterification rate of the oligomer reaches 90% or higher, the compound of the metal may be added in an amount of 10 [mu]mol or more in terms of the metal atom per mol of a terephthalic acid unit.

Description

technical field [0001] The present invention relates to polybutylene terephthalate and a method for producing the same. Specifically, it relates to suppressing the by-production of tetrahydrofuran without sacrificing productivity, color tone, hydrolysis resistance, thermal stability, transparency, molding, etc. Polybutylene terephthalate which is excellent in properties and has reduced impurities and can be applied to films, monofilaments, fibers, electrical and electronic parts, automobile parts, and the like, and a method for producing the same. Background technique [0002] Among thermoplastic polyester resins, polybutylene terephthalate is a representative engineering plastic due to its ease of molding and processing, mechanical properties, heat resistance, chemical resistance, fragrance retention (fragrance retention), and other It has excellent physical and chemical properties, so it is widely used in injection molding products such as automobile parts, electrical and ...

AI Technical Summary

Problems solved by technology

However, these methods cannot be said to have sufficiently solved the above-mentioned problems, and cannot be said to be satisfactory methods when the quality requirements for polybutylene terephthalate are increased.

[0007] As a method for producing polybutylene terephthalate, a transesterification method (DMT method) using dimethyl terephthalate and 1,4-butanediol as raw materials or using terephthalic acid and 1, the direct polymerization method of 4-butanediol, but because the transesterification method produces the methyl alcohol as reaction by-product, there is the problem of the recovery treatment of the low molecular weight material of by-product, therefore, in recent years, to raw material unit consumption (original unit ) The direct polymerization method that is advantageous has attracted attention. In addition, from the viewpoint of product quality stability, miniaturization of production equipment, energy efficiency, etc., the direct continuous polymerization method that continuously supplies raw materials and continuously obtains products has attracted attention.

[0008] However, there is a problem that part of the titanium catalyst used in the production of polybutylene terephthalate is deactivated in the middle of the production process of polybutylene terephthalate. It is more remarkable in the case of a direct continuous polymerization method in which dicarboxylic acid is used as a raw material (for example, refer to Patent Documents 4 and 5)

However, these methods have problems in that not only the effect of reducing impurities and haze is limited, but also the color tone of polybutylene terephthalate is deteriorated due to the addition of tin compounds

[0010] In addition, in the direct continuous polymerization method of polybutylene terephthalate, tetrahydrofuran is by-produced in the initial esterification reaction, and there is a problem that the unit consumption of 1,4-butanediol as a raw material is deteriorated.

In order to solve this problem, it has been proposed to set the molar ratio of 1,4-butanediol to terephthalic acid during the esterification reaction to be relatively low, and also to exist tin in addition to titanium (for example, refer to patent Document 6), but the solution haze of the polybutylene terephthalate that this method obtains is still high, and the problem of catalyst deactivation still does not get any solution

In addition, a method of performing esterification at a specific temperature and a specific pressure has also been proposed (for example, refer to Patent Document 8), but in these methods, the functions of suppressing the by-production of tetrahydrofuran and preventing catalyst deactivation cannot be combined.

Images