JP2001048968A - Production of polybutylene terephtahlate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain polybutylene terephthalate excellent in quality and capable of being used in various kinds of uses as fiber, film and injection molded products by conducting esterification reaction and polycondensation reaction of 1,4-butylene glycol containing 2-(4'-hydroxybutoxy)tetrahydrofuran and terephthalic acid containing acetic acid as raw materials by a direct polymerization method. SOLUTION: By conducting esterification reaction and polycondensation reaction of a glycol comprising 1,4-butylene glycol as a principal ingredient and 0.05 to 0.5 wt.% 2-(4'-hydroxybutoxy)tetrahydrofuran and a dicarboxylic acid comprising terephthalic acid as a principal ingredient and 0.003 to 0.2 wt.% acetic acid, polybutylene terephthalate is obtained. The esterification reaction is conducted preferably at a reaction temperature of 180 to 250 deg.C, a pressure of 100 to 600 mmHg and a polybutylene terephthalate oligomer conversion of >=97%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for efficiently producing polybutylene terephthalate having excellent quality.

[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter referred to as PB)
T) has excellent moldability, heat resistance, mechanical properties, chemical resistance, etc., so it can be used as a molding material for electrical parts and automobile parts, and for fibers using its softness and stretchability. Also widely used.

One of the methods for producing such a PBT is as follows.
Direct polymerization comprising an esterification step for producing a PBT oligomer from terephthalic acid (hereinafter referred to as TPA) and 1,4-butylene glycol (hereinafter referred to as BG), and a polycondensation step for increasing the degree of polymerization of the generated PBT oligomer. There is legal.

The raw material BG used in this direct polymerization method
Is produced by various methods, and usually contains various impurities. Among them, 2- (4′-hydroxybutoxy) tetrahydrofuran (hereinafter referred to as HTHF) is particularly large. For example, Japanese Patent Application Laid-Open No. 10-265418 discloses that when a PBT is produced using BG containing HTHF by a DMT method using dimethyl terephthalic acid (DMT), which is an ester derivative of terephthalic acid, as a starting material, It is described that the polycondensation reaction is delayed. HTHF in direct polymerization
Is used, the carboxylic acid, which is a functional group useful for the reaction, reacts and is blocked from the initial stage of the esterification reaction, so that further reaction delay occurs.

[0005] Another raw material, TPA, is produced by a method of aerial oxidation of p-xylene. In this TPA, acetic acid used as a solvent in the production process contains about 0.003 to 0.003 even after purification. 0.3% by weight (30 to 3000
ppm) in some cases. When PBT is produced using this TPA containing acetic acid, acetic acid easily reacts with BG to be converted into a glycol ester of acetic acid. For example, JP-A-61-233015 and JP-A-61-233016 disclose that the esterification reaction and the subsequent polycondensation reaction are delayed by the presence of acetic acid and a glycol ester of acetic acid in the reaction system. It is described.

[0006] Therefore, it has been considered that when PBT is produced using BG containing HTHF and TPA containing acetic acid, further polymerization delay is caused.

On the other hand, in the process of producing PBT, from the economic viewpoint, there is a method of recovering and reusing the BG distilled off in the polycondensation reaction as it is from the economical viewpoint. When PBT is produced using TPA containing acetic acid and acetic acid, HT is contained in the recovered BG.
Impurities such as HF, acetic acid, and glycol ester of acetic acid are included.

However, the boiling points of HTHF and glycol esters of acetic acid are difficult to separate because they are close to the boiling point of BG, and as a result, H
THF and glycol esters of acetic acid are accumulated, and the concentration is increased. When such a BG containing HTHF or a glycol ester of acetic acid is used as a part of the raw material, the esterification reaction and the subsequent polycondensation reaction are delayed, and in an extreme case, the esterification reaction and the subsequent polycondensation reaction are performed. It may not be completed and may significantly impair the economics of PBT production.

Further, in order to further increase the degree of polymerization of PBT and to keep the carboxyl end group concentration lower,
It is known that it is effective to carry out solid-phase polymerization of the PBT obtained from the above-mentioned polycondensation reaction. However, the solid-state polymerization also has a problem that the reactivity is greatly reduced.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to use the above BG containing HTHF and TPA containing acetic acid as raw materials, and carry out an esterification reaction, a subsequent polycondensation reaction, and a solid phase polymerization reaction. It is a main object of the present invention to provide a PBT production method by a direct polymerization method that can be carried out smoothly, and to provide a PBT with higher quality than before.

[0011]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have reached the present invention.

That is, the present invention provides: A glycol based on 1,4-butylene glycol containing 0.05 to 0.5% by weight of 2- (4'-hydroxybutoxy) tetrahydrofuran;
1. A method for producing polybutylene terephthalate, comprising esterifying a dicarboxylic acid containing terephthalic acid as a main component and containing 0.3 to 0.2% by weight of acetic acid, followed by polycondensation; The content of 2- (4′-hydroxybutoxy) tetrahydrofuran in 1,4-butylene glycol is 0.1
2. The method for producing polybutylene terephthalate as described in 1 above, wherein the acetic acid content in terephthalic acid is 0.03 to 0.15% by weight. 3. The method for producing polybutylene terephthalate as described in 1 or 2 above, wherein part or all of the distillate from the polycondensation is reused in the esterification reaction. As a terminal group of polybutylene terephthalate, 1 to 10 equivalents of a 2- (4'-hydroxybutoxy) tetrahydrofuran hydroxyl group per 1 ton of a polymer has a structure in which a hydroxyl group of polybutylene terephthalate is reacted with a carboxyl group of polybutylene terephthalate, and 1 per ton
Polybutylene terephthalate produced by the method according to any one of the above 1 to 3, wherein the carboxyl group of acetic acid has a terminal group having a structure reacted with the hydroxyl group of polybutylene terephthalate, and 5. A method for producing polybutylene terephthalate, which further comprises solid-phase polymerization of polybutylene terephthalate obtained by using the method for producing PBT described in the above 1 to 3.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The PBT in the present invention refers to a high-molecular-weight thermoplastic polyester having an ester bond in the main chain, using BG as a main glycol component and TPA as a main dicarboxylic acid component.

The BG used in the present invention contains 0.05 to 0.5% by weight of HTHF based on the glycol component, and preferably contains 0.1 to 0.4% by weight of HTHF. Can be used, and as other glycol components, ethylene glycol, propylene glyco-
, 1,6-hexanediol, 1,4-cyclohexanedimethanol, bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can also be used. The above other glycol components are 10 mol% based on all glycol components.
The following is preferred.

The TPA used in the present invention contains 0.003 to 0.2% by weight of acetic acid, preferably 0.03 to 0.15% by weight, based on the dicarboxylic acid component.
Can be used.Other acid components include aromatic, aliphatic, and fatty acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, oxalic acid, adipic acid, and 1,4-cyclohexanedicarboxylic acid. Cyclic dicarboxylic acids can also be used. The content of the other acidic components is preferably 10 mol% or less based on all dicarboxylic acid components.

The ratio of the acid component to the glycol component is B
In order to suppress a side reaction such as by-product of tetrahydrofuran due to decomposition of G, the molar ratio (P) of the glycol component to the acid component is preferably 1.1 to 3.0, and more preferably 1.1 to 2.0. .0 is preferred.

In the present invention, polybutylene terephthalate is produced by esterifying the above glycol component and the above dicarboxylic acid, followed by polycondensation.

As a method for adding glycol to the reaction system, in order to suppress a side reaction such as decomposition of BG, the reaction from the point at which distillation of the water produced from the esterification reaction starts to the point at which the esterification reaction ends is stopped. It is preferable to continuously add an equal amount to the mixture.

The esterification in the present invention is carried out at a reaction temperature of 180 to 250 ° C., preferably 200 to 240 ° C.
The pressure is more preferably 760 mmHg or less, and it is more preferably performed under reduced pressure of 100 to 600 mmHg from the viewpoint of removing acetic acid, which is considered to be an impurity causing a delay in the reaction, to the outside of the reaction system. (1 mmHg = 1.333
(22 × 10 ² Pa) Further, the reaction rate of the PBT oligomer obtained after the esterification reaction is preferably 97% or more.

In the esterification reaction, catalysts generally used for effectively proceeding the reaction, for example, an organic zirconia compound such as zirconium tetra-n-butoxide, an organic titanium compound such as titanium tetra-n-butoxide, 0.001 to 0.15% by weight of a tin compound such as monobutylhydroxytin oxide with respect to PBT,
Furthermore, it is preferable to add in the range of 0.02 to 0.1% by weight. One of these catalysts may be used alone, or two or more of them may be used in combination. The timing of adding the esterification catalyst is not particularly limited, and may be added immediately before the reaction or at any stage from the beginning of the reaction to the end of the reaction.

In the present invention, part or all of the BG distilled off from the polycondensation step may be reused as a raw material. The distilled BG can be used as it is, but it may be purified by rectification or the like before being supplied to the esterification reaction step, or HTH contained in the polycondensation distillate may be used.
It is also possible to use one obtained by appropriately removing the glycol ester of F or acetic acid by hydrogenation or saponification, and adjusting the amount of the glycol ester of HTHF or acetic acid.

The PBT oligomer is then subjected to a polycondensation reaction, but the method is not particularly limited, and may be a batch method or a continuous method, and the polymerization conditions used in the production of ordinary PBT can be applied as it is. For example, the reaction temperature is preferably from 230 to 260 ° C, and from 240 to 255 ° C.
C is more preferred.

Further, in the polycondensation reaction, a necessary catalyst can be separately added and used at the time of the polycondensation reaction, and in order to effectively carry out the reaction, a commonly used catalyst such as antimony trioxide, acetic acid is used. Antimony compounds such as antimony; organic zirconia compounds such as zirconium tetra-n-butoxide; organic titanium compounds such as titanium tetra-n-butoxide;
It is preferable to add in the range of 0.15% by weight, and it is particularly preferable to use an organic titanium compound.

In order to further increase the degree of polymerization of PBT and further reduce the concentration of carboxyl terminal groups, it is effective to carry out solid-phase polymerization of PBT obtained from the above polycondensation reaction. There is no particular limitation on the solid-state polymerization method of the present invention,
As long as the reaction temperature is equal to or lower than the melting point of PBT, the reaction may be carried out under an inert gas stream or under vacuum, may be carried out continuously or batchwise, and the production method may be a packed tower system, a horizontal clinker system, a tumbler system, or the like.

In producing PBT by the method of the present invention,
As long as the object of the present invention is not impaired, it is possible to add one or more ordinary additives such as an ultraviolet absorber, a heat stabilizer, a lubricant, a release agent, and a coloring agent including a dye and a pigment. it can. In particular, in the present invention, phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, phosphoric acid triamide, monoammonium phosphate, trimethyl phosphate, dimethyl phosphate, diphenyl phosphate, triphenyl phosphate, diphenyl phosphite Addition of a phosphorus compound such as triphenyl phosphite or dimethylphenyl phosphonate has a remarkable effect on the improvement of the color tone of the polymer.

When the amount of HTHF in BG and the amount of acetic acid in TPA are both within the scope of the present invention, the reaction is carried out in the same polymerization time as in the case where each impurity is contained alone. At the same time, a polymer having excellent heat stability can be obtained.

The PBT obtained by the production method of the present invention is PB
As a terminal group of T, a terminal group having a structure in which a hydroxyl group of HTHF is reacted with a carboxyl group of PBT in an amount of 1 to 10 equivalents per ton of polymer, and a carboxyl group of acetic acid in 1 to 6 equivalents per ton of polymer is It is characterized by containing a terminal group having a structure reacted with a hydroxyl group of PBT. When the amount of the terminal group is within this range, PBT having a high degree of polymerization and excellent quality can be produced without lowering the solid phase polymerization reactivity.

The PBT obtained by the production method of the present invention can be used for various uses as a fiber, a film, or an injection molded product.

[0030]

The present invention will be described in detail with reference to the following examples.

In the examples, the reaction rate of the obtained oligomer was determined from the acid value and saponification value of the reaction product according to the following formula. Reaction rate = {(saponification value−acid value) / saponification value} × 100
(%) Acid value: The value obtained by dissolving the reaction product in o-cresol / chloroform solvent and titrating with ethanolic potassium hydroxide. Saponification value: The value obtained by alkaline hydrolysis of the reaction product and back titration with an acid.

The intrinsic viscosity was calculated from the solution viscosity measured at 25 ° C. using o-chlorophenol as a solvent.

The carboxyl terminal group concentration was measured by dissolving the polymer in an o-cresol / chloroform solvent and titrating with ethanolic potassium hydroxide.

The concentration of the terminal group of the structure in which the hydroxyl group of HTHF has reacted with the carboxyl group of PBT depends on the concentration of HTHF in the distillate from the esterification and polycondensation steps.
The amount was determined by gas chromatography, and H
It was calculated from the difference from the amount of THF, and it was regarded as the concentration of the terminal group of the structure in which the hydroxyl group of HTHF reacted with the carboxyl group of PBT.

The concentration of the terminal group in the structure in which the carboxyl group of acetic acid has reacted with the hydroxyl group of PBT is determined by gas chromatography using the amounts of acetic acid and the reactants of acetic acid and BG in the distillate from the esterification reaction step and the polycondensation step. And the difference between the amount of acetic acid at the time of reaction preparation and the amount of acetic acid and BG reactant is calculated.
Was considered as the concentration of the end group of the structure which reacted with the hydroxyl group of.

Example 1 B containing 0.4% by weight of HTHF based on BG
G1104g, acetic acid content is 0.14 with respect to TPA
An esterification reaction and then a polycondensation reaction were carried out using 1132 g of TPA (weight ratio of BG / TPA: 1.8) which was a weight%.

First, the total amount of TPA, 750 g of BG, 0.8 g of titanium tetra-n-butoxide and 0.7 g of monobutylhydroxytin oxide were charged into a reactor equipped with a rectification column, and esterified at 190 ° C. and 400 mmHg. After the reaction was started, the temperature was gradually raised, and the remaining BG
Was added continuously.

To this reaction product, 0.08 g of titanium tetra-n-butoxide and 0.01 g of phosphoric acid were added, and the mixture was heated at 250 ° C.
The polycondensation reaction was performed at 0.5 mmHg.

The resulting polymer fine particles were charged into a rotary reaction vessel and subjected to solid-state polymerization at 190 ° C. under a reduced pressure of 0.5 mmHg for 8 hours to obtain a high polymerization degree PBT.

The obtained PBT was placed in a nitrogen stream at 250 ° C. for 1 hour.
After holding for a time, the carboxyl end group concentration was measured.

Example 2 B having a HTHF content of 0.1% by weight with respect to BG
The same procedure was performed as in Example 1 except that TPA having a G and acetic acid content of 0.05% by weight based on TPA was used.

Example 3 The procedure was the same as in Example 1 except that the distillate distilled off during the polycondensation of Example 1 was completely reused in the esterification reaction step.

Comparative Example 1 B containing 0.4% by weight of HTHF based on BG
The same procedure was performed as in Example 1 except that TPA having a G and acetic acid content of 0.002% by weight based on TPA was used.

COMPARATIVE EXAMPLE 2 Except for using BG having a HTHF content of 0.03% by weight with respect to BG and TPA having an acetic acid content of 0.14% by weight with respect to TPA, all examples were used. Performed similarly to 1.

Comparative Example 3 The content of HTHF was 0.03% by weight based on BG and the content of acetic acid was 0.002% by weight based on TPA.
The procedure was the same as in Example 1 except that TPA was used.

Comparative Example 4 B containing 0.6% by weight of HTHF based on BG
The same procedure was performed as in Example 1 except that TPA containing 0.3% by weight of G and acetic acid based on TPA was used.

Comparative Example 5 The same procedure as in Comparative Example 1 was carried out except that the distillate distilled off during the polycondensation of Comparative Example 4 was completely reused in the esterification reaction step.

Table 1 shows a comparison of the esterification reaction time and the reaction rate, the polymerization time, the intrinsic viscosity of the polymer and the terminal group concentration in the above Examples and Comparative Examples.

[0049]

[Table 1]

[0050]

According to the present invention, B containing HTHF
In a method for producing PBT using a glycol containing G as a main component and a dicarboxylic acid containing TPA containing acetic acid as a main component, the esterification reaction and the subsequent polycondensation reaction are not delayed, and the quality is further improved. PBT can be obtained.

Continuation of the front page F term (reference) 4J029 AA03 AB04 AC01 AD10 BA05 CB06A FA12 FB03 JB163 JB303 KD02 KD07 KE03 KE05 KE06 KE07 KE12 KF00 KJ02

Claims (5)

[Claims] (1) 0.05-0.5% by weight of 2- (4′-
(Hydroxybutoxy) 1,4-butylene glycol containing tetrahydrofuran as a main component and a dicarboxylic acid containing terephthalic acid as a main component containing 0.003 to 0.2% by weight of acetic acid are esterified. A method for producing polybutylene terephthalate, comprising condensation. 2. The compound of claim 1, wherein 2-
The (4'-hydroxybutoxy) tetrahydrofuran content is 0.1 to 0.4% by weight, and the acetic acid content in terephthalic acid is 0.03 to 0.15% by weight. A method for producing the polybutylene terephthalate described above. 3. The method according to claim 1, wherein part or all of the distillate from the polycondensation is reused in the esterification reaction.
Or the method for producing polybutylene terephthalate according to 2. 4. The terminal group of polybutylene terephthalate has 1 to 10 equivalents of 2- (4 ′) per ton of polymer.
-Hydroxybutoxy) tetrahydrofuran contains end groups of structures in which the hydroxyl groups have reacted with the carboxyl groups of polybutylene terephthalate, and 1 to 6 equivalents of acetic acid per ton of the polymer have reacted with the hydroxyl groups of polybutylene terephthalate. The polybutylene terephthalate produced by the method according to any one of claims 1 to 3, which contains a terminal group of a structure. 5. A method for producing polybutylene terephthalate, which further comprises solid-phase polymerization of polybutylene terephthalate obtained by using the production method according to claim 1.