JPH02208318A - Production of high-mw polyester - Google Patents

Abstract

PURPOSE:To make it possible to obtain a high-MW polyester by recovering a heating medium by a simple process and using the recovered heating medium by polymerizing a specified linear oligoester or polyester in a heating medium of a limited content of cyclooligoesters. CONSTITUTION:In the production of a high-MW polyester by polymerizing a linear oligoester or polyester derived from an aromatic dicarboxylic acid or its derivative and a glycol in a heating medium while blowing an inert gas into the system and using the heating medium again, the polymerization is performed in the heating medium of a content of cyclooligoesters <=30wt.% to obtain the purpose high-MW polyester of an intrinsic viscosity >=1.5. The above heating medium is a thermally stable organic compound which can be handled in the form of a fluid below the reaction temperature and which can swell the polyester but does not dissolve it. As the heating medium, hydrogenated terphenyl or an alkyldiphenyl is particularly desirable.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention further improves the polymerization method in a heating medium previously proposed by the applicant, and reuses the heating medium used for polymerization. The present invention relates to a method for producing high molecular weight polyester.

(Prior art) Polyesters, represented by polyethylene terephthalate, are now widely used not only as fibers but also as materials for films and various plastic molded products, and are becoming a part of general-purpose plastics. In particular, with the aim of further improving mechanical strength, various studies are being carried out on increasing the molecular weight.

Conventional general-purpose polyester (intrinsic viscosity 0.5-0,
8) and aromatic dicarboxylic acid and glycol, or transesterify the alkyl ester of aromatic dicarboxylic acid and glycol to obtain glycol ester and/or its low polymer (including oligomer), It is then produced by a melt polymerization method in which this is heated and stirred under high vacuum to cause polycondensation.

On the other hand, the performance requirements, especially the mechanical properties, for polyester for industrial materials such as tire cords are becoming more sophisticated.
In order to meet these demands, it is desirable to further increase the molecular weight of polyester.

However, in the conventional melt polymerization method as mentioned above, as the polymer increases, the viscosity of the melt becomes extremely high, making it difficult to stir or remove the polymer from the reaction vessel, which naturally limits the ability to increase the molecular weight. be.

As a method for increasing the molecular weight of polyester, there is also known a method in which a polymer obtained by melt polycondensation is subjected to solid phase polymerization for an extended period of time in an inert gas stream or under reduced pressure. However, even if this method is adopted, the limit is usually that the intrinsic viscosity can only be increased to about 1.0 to 1.5 at most, and furthermore, the product polyester is thought to have partially undergone a crosslinking reaction, and the solvent The solubility in the compound clearly decreases.

In view of the above-mentioned drawbacks, the present inventors conducted intensive research in an attempt to develop a new manufacturing method that can prevent the simultaneous occurrence of crosslinking reactions and obtain a high molecular weight polyester with excellent solubility in solvents. Developed a new polymerization method called polymerization (Japanese Unexamined Patent Publication No. 61157524, No. 61-15)
(See Publication No. 7525, etc.).

Polymerization in a heating medium is a process in which linear oligoesters or polyesters obtained from aromatic dicarboxylic acids or derivatives thereof and glycols are heated and stirred in the presence of a liquid heating medium at the polycondensation temperature while blowing inert gas. This method involves a polycondensation reaction.

In addition, the glycol that is produced as a by-product during the polycondensation reaction and migrates into the heating medium is removed from the system in sequence by being accompanied by an inert gas, and this action causes the polycondensation reaction to proceed, yielding a high-molecular-weight polyester. be. During this time, the crosslinking reaction is also suppressed as much as possible, making it possible to obtain products with excellent solubility in solvents.

(Problems to be Solved by the Invention) However, as the present inventors proceeded with research on the practical application of the polymerization method in a heat medium, the following drawbacks of this method became apparent.

In other words, in the conventional method, vacuum distillation is used to recover the heating medium, which increases the recovery cost.

Furthermore, as a result of intensive research by the present inventors, it was discovered that during thermal polymerization, about 10% of the low molecular weight cyclic oligoester of the polyester is produced based on the polymer and extracted into the heating medium. . That is, in order to recover the heating medium by the above method, the process must be performed after this low molecular weight cyclic oligoester is removed from the heating medium. Therefore, there has been a strong demand for the development of a simpler method for recovering and reusing the heat medium without vacuum distillation.

(Means for Solving the Problems) In order to solve the above problems, the present inventors conducted extensive research and finally completed the present invention.

That is, the present invention polymerizes a linear oligoester or polyester derived from an aromatic dicarboxylic acid or a derivative thereof and a glycol in a heating medium while blowing an inert gas, and then reuses the heating medium to produce a high molecular weight polyester. This is a method for producing a high molecular weight polyester having an intrinsic viscosity of 1.5 or more, characterized in that the content of the cyclic oligoester in the heating medium is 30% by weight or less.

Aromatic dicarboxylic acids or derivatives thereof used in the present invention include terephthalic acid, isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-dicarboxyldiphenyl, 4,4' ~ Dicarboxybenzophenone, bis(4-carboxyphenyl)ethane pentasodium sulfoisophthalic acid, or alkyl esters thereof such as methyl, ethyl, propyl, etc., and glycols include ethylene glycol, propylene glycol, butanediol, neo Examples include pentyl glycol, diethylene glycol, cyclohexane dimetatool, and ethylene oxide adduct of bisphenol A.

In the present invention, the heat medium means a thermally stable organic compound that can be treated as a fluid within the reaction temperature, and is a compound selected from aromatic hydrocarbons, aliphatic hydrocarbons, and alicyclic hydrocarbons. The polyester swells the polyester but does not dissolve it, and it is one kind or a mixture of two or more thereof.

Specifically, they include paraffin, alkyldiphenyl, hydrogenated terphenyl, alkylnaphthalene, cyclohexylbiphenyl, etc., and hydrogenated terphenyl and alkyldiphenyl are particularly preferred. These heat carriers may be purified by known methods such as distillation before use.

Next, to specifically describe the method of the present invention for producing polyester, an aromatic dicarboxylic acid or its derivative and a glycol are subjected to an esterification reaction or transesterification reaction by a known method, and then a polycondensation reaction is performed to form a line. obtained oligoester or polyester. At this time, it is preferable to carry out the reaction in the presence of a known polycondensation catalyst such as antimony, titanium, germanium, or tin.

The above-mentioned linear oligoester or polyester is molded into chips or pulverized, and heated together with a heating medium at about 150 to 250° C., preferably at 210° C. under normal pressure, reduced pressure, or pressurization.
Polymerization in a heat medium is carried out at ~240° C. by heating and stirring for about 10 to 50 hours while blowing an inert gas such as nitrogen gas, helium, carbon dioxide gas, etc.

The polyester obtained by the above method has an angle of 100 to 200°
It is filtered while hot at C and separated from the heating medium. However, as a result of intensive research by the present inventors, when reusing the heating medium, as mentioned above, about 10% of the low molecular weight cyclic oligoester of the polyester is generated based on the polymer, and We found that it was extracted to.

In view of this, the inventors of the present invention have taken the following steps:
Alternatively, it has been found that it can be reused with some of the low molecular weight cyclic oligoester removed by centrifugal filtration, glass filter filtration, or a conventional filtration method using commercially available filter paper.

The cyclic oligoester contained in the heat medium in the present invention is mostly a cyclic trimer, tetramer, gelamer, or more, and the linear oligoester used as a starting material is They are distinct.

The amount of cyclic oligoester contained in the heat medium is preferably 30% by weight or less, preferably 20% by weight or less, based on the heat medium; if it exceeds this amount, a polyester with a high degree of polymerization may not be obtained or the polymer may become colored. This is not preferable because it has drawbacks such as burning and clogging the inert gas blowing pipe.

(Examples) Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

In addition, the intrinsic viscosity in the examples was measured at 30°C using a mixed solution of phenol/tetrachloroethane-3/2 (volume ratio).

The amount of cyclic oligoester contained in the heating medium was calculated by cooling the heating medium to precipitate the oligoester, filtering it with a glass filter, removing the heating medium with acetone, drying, and then measuring the weight.

Moreover, all "parts" indicate parts by weight.

Example 1 Polyethylene terephthalate with an average particle size of 1.7 m (terephthalic acid as a catalyst 1,500 parts of antimony and 8,000 parts of hydrogenated terphenyl purified by distillation were added as a heating medium, and nitrogen gas was blown at 2001 parts per hour. Raise the temperature while blowing at 215°C for 6 hours, then 240°C'': 1
The mixture was heated and stirred for 6 hours. During this time, some of the waste gas and heat medium were discharged from the waste gas outlet, so new heat medium was added to keep the liquid level constant.

Both the exhaust heat medium and the additional heat medium were 500 parts.

After the completion of the reaction, the slurry was cooled to 150°C, extracted from the outlet as a slurry, and filtered through a 30-mesh filter to recover the polymer. After washing the polymer with acetone and drying under reduced pressure, the intrinsic viscosity was measured to be 2.42.

Next, the mother liquor after polymer filtration was used again as it was to carry out polymerization in a heat medium in the same manner as described above. This mother liquor contains approximately 5
% of cyclic oligoester, resulting in a high molecular weight polyester with an intrinsic viscosity of 2.21.

Example 2 Approximately 15% cyclic oligoester was added in the same manner as in Example 1.
Polymerization in a heat medium was carried out using a heat medium containing the following. As a result, a high molecular weight polyester with an intrinsic viscosity of 2.08 was obtained.

Example 3 Approximately 25% cyclic oligoester was added in the same manner as in Example 1.
Polymerization in a heat medium was carried out using a heat medium containing the following. As a result, a high molecular weight polyester having an intrinsic viscosity of 1.90 was obtained.

Comparative Example 1 Approximately 35% cyclic oligoester was added in the same manner as in Example 1.
Polymerization in a heat medium was carried out using a heat medium containing the following. As a result, the nitrogen gas blowing pipe became clogged after 4 hours, making it impossible to continue.

(Effect of the invention) When producing a high molecular weight polyester by polymerizing a linear oligoester or polyester derived from an aromatic dicarboxylic acid or a derivative thereof and glycols in a heat medium while blowing an inert gas, it is possible to By adopting the method of the present invention that uses a heating medium containing an ester, the heating medium containing the cyclic oligoester used for polymerization can be reused as is for polymerization, or the low molecular weight oligomer can be purified by centrifugal filtration etc. This has many advantages, such as being able to reuse it with some of it removed, and will greatly contribute to industry.

Claims (1)

[Claims] A linear oligoester or polyester derived from an aromatic dicarboxylic acid or a derivative thereof and a glycol is polymerized in a heating medium while blowing an inert gas, and the heating medium is reused to obtain a polymer having a high molecular weight. A method for producing a high molecular weight polyester having an intrinsic viscosity of 1.5 or more, which comprises carrying out polymerization at a content of cyclic oligoester in the heat medium of 30% by weight or less when producing the polyester.