JPH01197522A - Preparation of polyester - Google Patents

Abstract

PURPOSE:To make it possible to polymerize a polyester cyclic oligomer at a relatively low temp. without using any catalyst and to obtain a polyester being colorless, transparent and having high purity, by heating the polyester cyclic oligomer in the presence of a heating medium. CONSTITUTION:A purpose polyester is obtd. by feeding a polyester cyclic oligomer which is 2-10-mers derived from arom. dicarboxylic acids (homolog) and glycols, being ground, if necessary, in a reaction vessel, adding thereto a heating medium such as hydrogenated triphenyl or alkyldiphenyl and heating and melting it with stirring under N2 flow at, e.g., 280 deg.C for 1hr. Then, the heating medium in the obtd. polymer is extracted with acetone and removed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing a colorless, transparent and impurity-free polyester, which is characterized in that the polymerization of a cyclic polyester oligomer is carried out in the presence of a heat medium. It is related to.

(Prior Art) Conventionally, when polyester cyclic oligomers are polymerized, the polyester cyclic oligomers alone have been heated at high temperatures.

(Problem M to be solved by the invention) When polymerizing a polyester cyclic oligomer alone in conventional birch, the melting point of the cyclic oligomer is 300"C or higher, so the polymerization must be carried out at a high temperature, and as a result, the polyester The drawback was that decomposition and coloration occurred, making it impossible to obtain high-quality polyester.

(Means for solving the yA problem) The present inventors solved the i! ! In order to solve this problem, as a result of intensive research, we have finally completed the present invention.

That is, the present invention is a method for producing polyester, which is characterized by heating a polyester cyclic oligomer in the presence of a heat medium.

In the present invention, the heat medium refers to a thermally stable organic compound that can be treated as a fluid within the reaction temperature and is inert to polyester, including aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, etc. It is one kind or a mixture of two or more kinds of compounds selected from group hydrocarbons. Specifically, paraffin,
Alkylphenyl, dimethylbiphenyl, tetraethylbiphenyl, diethylbiphenyl, trimethylbiphenyl, triethylbiphenyl, triprobylbiphenyl, cyclohexylhenzene, hydrogenated triphenyl, alkylnaphthalene, cyclohexylbiphenyl, etc., and in the present invention, A heating medium that does not cause the polyester to swell is preferable, and hydrogenated triphenyl and alkyldiphenyl are particularly preferable. These heat carriers may be used after being purified by known methods such as distillation.

The polyester cyclic oligomer used in the present invention is derived from an aromatic dicarboxylic acid or its homologue and glycols, and is usually a dimer to a decamer, most of which is a dimer to a pentamer, Among them, trimers account for the majority. Examples of the aromatic dicarboxylic acid or its analog component include terephthalic acid, isophthalic 1M2.6-naphthalene dicarboxylic acid, or alkyl esters thereof such as methyl, ethyl, propyl, etc.
Examples of the glycol component include ethylene glycol, propylene glycol, butylene glycol, and the like.

Next, to specifically describe the method of the present invention for producing polyester from a polyester cyclic oligomer, first, a polyester cyclic oligomer obtained by a known method is
1 g of this polyester cyclic oligomer crushed to less than μ
0.1 to 1. Oml, preferably 0
．． Polymerization is carried out by placing the mixture in a reaction vessel at a ratio of 2 to 0.8 ml and heating it at about 200 to 300 °C under normal pressure, reduced pressure, or increased pressure in a stream of inert gas such as nitrogen gas, helium, or carbon dioxide gas. Polyester is obtained. Although one of the features of the method of the present invention is that it can be polymerized without a catalyst, there is no problem even if a conventionally known catalyst is present. The polyester obtained by the above method contains a heat medium, which can be extracted with an organic solvent such as acetone or benzene.

(effect) The action of the heat medium in the present invention is as follows.

By adding a heating medium to the polymerization reaction system, stirring can be performed uniformly at a relatively low temperature, and even when the polymerization has progressed and the viscosity has increased, stirring can be performed easily. It is thought that decomposition and discoloration of the particles can be suppressed.

(Examples) Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. Note that the intrinsic viscosity was measured at 30°C using a mixed solvent of phenol/tetrachloroethane-3/2.

Example 1 A polyethylene terephthalate cyclic oligomer (purity of 98% or more) obtained by a known method was pulverized to 500μ or less, 10 g of this polyethylene terephthalate 1!2 oligomer was charged into a reaction vessel, and a hydrogenated triglyceride was added as a heat medium. Phenyl 5d was added. By purging the system with nitrogen gas and heating, melting and stirring at 280° C. for 1 hour under a nitrogen stream, colorless and transparent polyethylene terephthalate was obtained. Hydrogenated triphenyl in the obtained polymer was extracted with acetone, and the intrinsic viscosity of the obtained polymer was measured and found to be 0.83.

Example 2 10 g of polyethylene terephthalate oligomer pulverized in the same manner as in Example 1 was charged into a reaction vessel, and 10 ml of triethyl biphenyl was further charged as a heat medium. By purging the system with nitrogen gas and heating, melting and stirring at 280° C. for 1 hour under a nitrogen stream, colorless and transparent polyethylene terephthalate was obtained. Triethyl biphenyl in the obtained polymer was extracted with acetone, and the intrinsic viscosity of the obtained polymer was measured and found to be 0.75.

Comparative Example 1 10 g of polyethylene terephthalate cyclic oligomer crushed in the same manner as in Example 1 was charged into a reaction vessel, the inside of the system was replaced with nitrogen gas, and the mixture was heated and melted and stirred at 280°C for 2 hours under a nitrogen stream. A brown, cloudy polyethylene terephthalate was obtained. The intrinsic viscosity was measured and found to be 0.46.

(Effects of the Invention) By employing the method of the present invention having the above configuration, polymerization can be performed at a relatively low temperature and without a catalyst, so that the obtained polyester is colorless and transparent and completely free of impurities such as metal compounds. This is a groundbreaking product that can dramatically expand its application to food applications and other fields, and will greatly contribute to industry.

Patent applicant: Toyobo Co., Ltd.

Claims (1)

[Claims] (1) A method for producing polyester, which comprises heating a polyester cyclic oligomer in the presence of a heat medium.