JPH10330468A - Production of polybutylene terephthalate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polybutylene terephthalate excellent in quality by a method using a continuous direct esterification while suppressing side reactions. SOLUTION: This method for producing a polybutylene terephthalate obtained by performing the esterification of dicarboxylic acids consisting mainly of terephthalic acid with diols consisting mainly of 1,4-butane diol, and then performing a polycondensation reaction of the obtained ester, is to perform a first step of the esterification reaction in the presence of an organic tin compound and substantially without the presence of an organic titanium compound until attaining >=80% rate of the esterification reaction, then a second step of the esterification reaction by adding an organic titanium compound and then the polycondensation reaction of the obtained ester.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polybutylene terephthalate having excellent quality while suppressing side reactions by continuously direct esterification and polycondensation.

[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.
There is a direct polymerization method comprising an esterification step of producing a PBT oligomer from terephthalic acid and 1,4-butanediol, and a polycondensation step of increasing the degree of polymerization of the produced PBT oligomer. The presence of a catalyst is indispensable for the esterification step in the direct PBT polymerization method, and an organic titanium compound is most commonly used as the catalyst.

However, organic titanium compounds (for example, titanates) exhibit excellent catalytic activity as an esterification reaction catalyst, while water produced as a by-product of the reaction and decomposition of 1,4-butanediol (dehydration cyclization). As a result, it is liable to be hydrolyzed to generate insoluble foreign matters and to reduce the activity as a catalyst.

In order to solve the problem of insolubilization and deactivation of such an organic titanium compound, an esterification reaction rate of 50% was applied to the organic titanium compound.
%, The addition method is improved in each of the first half and the second half (for example, JP-A-49-57092), and means for using a combination of a polyhydric alcohol compound and an alkali metal compound (for example, JP-A-62-1987) JP-A-225524), a method using an alkanolamine titanate compound as a catalyst (for example, JP-A-62-14022), and a method of using an organic titanium compound and an alkanolamine compound in combination (for example, JP-A-62-199617). ), A method of adding a hindered phenol compound at the esterification stage (for example, JP-A-1-282215), and the like, the catalyst activity is improved to some extent by these means.

[0006] However, the above improvement is effective when the PBT oligomer is produced by a batch method, but is not so effective when produced by a continuous method, and a large amount of insoluble foreign matter is generated. This is considered to be because, when a PBT oligomer is produced by a continuous method, the organotitanium compound not only reacts with water but also reacts with terephthalic acid in the system to form a metal salt, insolubilize and deactivate. .

[0007] The problems of the formation of insoluble contaminants and the reduction of the catalytic activity in the esterification stage not only become an inhibitory factor for shortening the reaction time, but also significantly reduce the transparency of the reaction product. As a result, a desired degree of polymerization cannot be obtained due to a decrease in polymerization reactivity. Further, in the process of forming the polymer, problems such as a decrease in moldability due to insoluble foreign matters and a decrease in quality of a molded article occur.

On the other hand, as an effective catalyst other than the organic titanium compound, an organic tin compound is disclosed in JP-B-53-9796. However, when the esterification reaction is carried out by a continuous method using an organotin compound as a catalyst, the reaction is slow and therefore the generation of by-products increases.On the other hand, if a large amount of catalyst is added to speed up the reaction, the reaction after polymerization may occur. Problems such as deterioration of color tone and heat resistance of PBT newly arise.

JP-A-62-195017 discloses a continuous direct polymerization method in which the molar ratio of 1,4-butanediol / terephthalic acid is 2 or more and either a titanium catalyst or a tin catalyst is used. It has been disclosed.

[0010]

However, continuous esterification at a high molar ratio has a problem that an ether bond is likely to be introduced into a molecular chain. Therefore, it is desirable that the molar ratio be as small as possible. It was difficult to reduce the molar ratio by the continuous direct esterification method.

Accordingly, an object of the present invention is to provide a method for producing PBT which is excellent in quality while suppressing side reactions, by continuous direct esterification and polycondensation.

[0012]

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. The PBT production method of the present invention comprises terephthalic acid as a main component. Dicarboxylic acid and diol having 1,4-butanediol as a main component are continuously esterified,
Then, in producing PBT by a polycondensation reaction, the esterification reaction is carried out in the presence of an organotin compound and in the substantial absence of an organotitanium compound until the esterification reaction rate reaches 80% or more. It is characterized in that a step of esterification reaction is performed, then an organic titanium compound is added, a second step of esterification reaction is performed, and then a polycondensation reaction is performed.

The organic tin compound is preferably a monoalkyltin compound and / or an alkylstannoic acid, and the molar ratio (P) of the diol to the dicarboxylic acid is preferably 1.1 to 1.6.

The first stage esterification reaction is carried out at a reaction temperature of 1
The reaction is carried out at a temperature of 80 to 240 ° C. and a pressure of 760 mmHg or less, and the esterification reaction of the second stage is carried out at a reaction temperature of 190 to 2
The reaction is preferably carried out at 50 ° C. and a pressure of 760 mmHg or less.
Performed at 0 to 230 ° C and a pressure of 100 to 600 mmHg,
And the esterification reaction of the second stage is carried out at a reaction temperature of 200 to
It is preferable to carry out at 240 ° C. and a pressure of 100 to 550 mmHg.

The amount of the organotin compound to be added is preferably 0.02 to 0.15 parts by weight based on 100 parts by weight of the PBT to be produced. The amount of PBT to be added
It is preferably 0.005 to 0.3 parts by weight based on 100 parts by weight.

[0016]

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

The polybutylene terephthalate (PBT) used in the present invention is a high molecular weight polymer having an ester bond in the main chain using terephthalic acid as a main dicarboxylic acid component and 1,4-butanediol as a main glycol component. Although refers to thermoplastic polyester, as the other acid components, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, oxalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, and the like, and other glycol components, ethylene glycol, Propylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can also be used as a copolymer component. Each of these copolymer components is preferably 40 mol% or less based on terephthalic acid or 1,4-butanediol.

The ratio of the acid component to the glycol component is not particularly limited. However, from the viewpoint of suppressing the by-product of tetrahydrofuran (hereinafter referred to as THF) generated by cyclization of 1,4-butanediol, the acid of the glycol component is suppressed. The molar ratio to the components is preferably from 1.1 to 1.6.

The organotin compound used in the present invention has the following general formula:

Embedded image (Where R is an alkyl group or an aryl group, X _{1 to} X
₄ is a monovalent group containing an alkyl group, an aryl group, an allyloxy group, a cyclohexyl group, a hydroxy group, a halogen, etc., which may be the same or different. Also, X
₅ represents a sulfur or oxygen atom. )).

Specific examples include dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexyldistin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyltin hydroxide, triisobutyl Examples include tin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, dibutyltin dichloride, tributyltin chloride, dibutyltin sulfide, and butylhydroxytin oxide. Among them, monoalkyl compounds are preferable.

As the other organotin compound, stannoxane can also be used, and alkylstannoic acids such as methylstannoic acid, ethylstannoic acid and butylstannoic acid are preferable. These organotin compounds are 1
They may be used alone or in combination of two or more.

In the present invention, the amount of the organotin compound to be added is 0.02 to 0.1 with respect to 100 parts by weight of the produced PBT.
It is preferably 5 parts by weight, more preferably 0.03 to 0.1 part by weight.

The organotin compound is preferably added in its entirety from the initial stage of the esterification reaction in the first stage, but it is also possible to add a part thereof in the initial stage of the esterification reaction and add the remainder in the middle. Good. And the esterification rate is 80
%, It is necessary to continue the esterification reaction in the substantial absence of the organic titanium compound. In the present invention, this step is referred to as a first-step esterification reaction.

The organotitanium compound used in the present invention is (R ₁ O) _n Ti (OR ₂ ) _4-n (where R _{1 and} R ₂ are aliphatic, alicyclic or aromatic having _{1 to 10} carbon atoms). Group, and n is a number from 0 to 4 (including a decimal number).

Specifically, methyl ester of titanic acid,
Examples thereof include tetra-n-propyl ester, tetra-n-butyl ester, tetraisopropyl ester, tetraisobutyl ester, tetra-tert-butyl ester, cyclohexyl ester, phenyl ester, benzyl ester, tolyl ester, and mixed esters thereof. Among them, particularly preferred are tetra-n-propyl ester, tetra-n-butyl ester, tetraisopropyl ester and the like. These organic titanium compounds can be used alone or in combination of two or more.

The addition amount of the organic titanium compound is in the range of 0.005 to 0.3 parts by weight, preferably 0.01 to 0.1 parts by weight, based on 100 parts by weight of the PBT to be produced.

The above-mentioned organotitanium compound needs to be added at a stage where the esterification reaction has progressed to some extent, that is, at a stage where the reaction rate has reached 80% or more. Otherwise, the amount of foreign matter in the polymer increases, and the object of the present invention cannot be achieved. In the present invention, this stage is referred to as a second stage esterification reaction.

The continuous esterification apparatus used in the practice of the present invention is not particularly limited, but is preferably a complete mixing tank type ester reactor. The first stage of the esterification reaction is carried out at a reaction temperature of 180 to 240 ° C., preferably 200 ° C.
~ 230 ° C, pressure 760mmHg or less, preferably 1
It is desirable to carry out the reaction under a reduced pressure of 00 to 600 mmHg so that the reaction rate becomes 80% or more. (1 mmHg =
(1.33322 × 10 ² Pa) The esterification reaction in the second stage is performed at a reaction temperature of 190 to 250 ° C., preferably 200 ° C.
~ 240 ° C, pressure 760mmHg or less, preferably 1
It is desirable to carry out under a reduced pressure of 00 to 550 mmHg. The esterification rate after the second stage esterification reaction is 9
It is preferably at least 7%.

The PBT oligomer produced by the continuous esterification reaction is then subjected to a polycondensation reaction, but the method is not particularly limited, and a conventional PBT oligomer may be used in either a batch method or a continuous method.
The polymerization conditions used for the production of BT can be applied as they are. For example, the reaction temperature is preferably 230 to 260 ° C, more preferably 240 to 255 ° C.

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 PBT is produced by the present production method, PBT having better resin toughness can be obtained than when PBT is produced by a conventional method. For example, it is possible to obtain a PBT having a temperature falling crystallization temperature measured by a differential scanning calorimeter (DSC) of 170 ° C. to 180 ° C. and a solution haze of 20% or less. Further, when a molded article is formed by injection molding, a molded article having a smaller average spherulite radius (for example, 4 μm or less) can be provided than when a PBT produced by a conventional method is molded.

The molded article obtained from the PBT according to the method of the present invention is characterized by having excellent toughness, in particular, toughness when heated for a long time, and thus can be usefully used for various automobile parts and electric / electronic parts.

[0033]

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 amount of by-produced tetrahydrofuran (THF) was determined by gas chromatography.

Solution haze: 5.4 g of the sample polymer was heated and dissolved in 40 mL of a mixed solvent of phenol and ethane tetrachloride (60:40 wt%), and the solution was placed in a 30 mm cell, and an integral haze meter (manufactured by Nippon Seimitsu Optical Co., Ltd.) ). It can be said that the larger this value is, the more foreign matter is.

Example 1 A continuous esterification reaction was carried out using a two-tank complete mixing tank type reactor. That is, a PBT with a reaction rate of 90% in advance
In the first esterification reaction tank filled with the oligomer, terephthalic acid and 1,4-butanediol were added at a molar ratio (P) of 1,4-butanediol to terephthalic acid of 1.4.
And supplied continuously in the form of slurry. At the same time, butylhydroxytin oxide was continuously supplied to the first esterification tank so as to be 0.04 parts by weight based on 100 parts by weight of PBT to be produced. The first esterification tank was controlled so that the reaction temperature was 220 ° C. and the pressure was 300 mmHg.

The PBT oligomer in the first esterification tank was continuously taken out and supplied to a second esterification tank previously filled with a PBT oligomer having a conversion of 98%. The second esterification tank was controlled so that the reaction temperature was 230 ° C. and the pressure was 200 mmHg. Tetrabutoxytitanate was added to the second esterification tank so as to be 0.08 parts by weight based on 100 parts by weight of the PBT to be produced. The PBT oligomer in the second esterification tank was continuously taken out and pulverized into flakes.

The slurry supply and oligomer take-out speeds were determined as follows: the residence time in the first esterification tank was 120 minutes;
It was adjusted so that the residence time in the esterification tank was 90 minutes.

After reaching a steady state 8 hours after the start of the reaction,
The distillate of the PBT oligomer was sampled for 6 hours, and the reaction rate and the amount of by-product THF were measured.
As a result, the reaction rate in the first esterification tank was 85%,
The reaction rate in the esterification tank is 99%, the amount of by-product THF is 1k
25 g per g of oligomer produced.

Further, tetrabutoxytitanate was added to the oligomer taken out from the second esterification tank in an amount of 0.03% by weight based on the produced polymer, and the mixture was subjected to a batch method at 250 ° C. under reduced pressure (1 mmHg or less) for 3 hours. The condensation reaction was carried out to obtain a PBT polymer, and the solution haze was measured to be 6%.

COMPARATIVE EXAMPLE 1 Instead of butylhydroxytin oxide, tetrabutoxytitanate was added to the first esterification tank so as to be 0.03 parts by weight based on PBT to be produced.
Continuous esterification and polycondensation were performed in the same manner as in Example 1.
As a result, the reaction rate of the first esterification tank was 88%, the reaction rate of the second esterification tank was 97%, and the amount of by-product THF was 1%.
The solution haze of the polymer was as high as 53% per kg of produced oligomer and 53%.

Comparative Example 2 Continuous esterification and polycondensation were carried out in the same manner as in Example 1 except that tetrabutoxytitanate added to the second esterification tank was added to the first esterification tank simultaneously with butylhydroxytin oxide. Was performed. As a result, the reaction rate of the first esterification tank was 79%, the reaction rate of the second esterification tank was 98%, the amount of by-product THF was 33 g per 1 kg of the produced oligomer, and the solution haze of the polymer was as high as 28%. Was.

Comparative Example 3 The amount of butylhydroxytin oxide added to the first esterification tank was 0.20 parts by weight with respect to the PBT to be produced, and no tetrabutoxytitanate was added to the second esterification tank. Other than that, continuous esterification and polycondensation were performed in the same manner as in Example 1. As a result, the reaction rate of the first esterification tank was 85%, and the reaction rate of the second esterification tank was 96%.
The amount of by-product THF was 32 g per 1 kg of the produced oligomer, and the solution haze of the polymer was 25%.

Comparative Example 4 Except that the residence time in the first esterification tank was adjusted to 90 minutes and the residence time in the second esterification tank was adjusted to 120 minutes.
Continuous esterification and polycondensation were performed in the same manner as in Example 1. As a result, the reaction rate of the first esterification tank was as low as 75%, the reaction rate of the second esterification tank was 96%, and the by-product T
The amount of HF was 40 g per kg of the produced oligomer, and the solution haze of the polymer was as high as 23%.

[0045]

According to the production method of the present invention, the production of foreign substances can be suppressed while suppressing the production of by-products, so that PBT with little foreign substance production and excellent toughness can be produced by a continuous direct esterification method.

Claims (7)

[Claims] 1. A polybutylene terephthalate is produced by a continuous esterification reaction of a dicarboxylic acid containing terephthalic acid as a main component and a diol containing 1,4-butanediol as a main component, followed by a polycondensation reaction. In this case, the esterification reaction is carried out in the first stage until the esterification reaction rate becomes 80% or more in the presence of the organotin compound and in the substantial absence of the organotitanium compound. A method for producing polybutylene terephthalate, comprising adding a compound, performing a second-stage esterification reaction, and then performing a polycondensation reaction. 2. The method for producing polybutylene terephthalate according to claim 1, wherein the organotin compound is a monoalkyltin compound and / or an alkylstannoic acid. 3. The method for producing polybutylene terephthalate according to claim 1, wherein the molar ratio (P) of the diol to the dicarboxylic acid is from 1.1 to 1.6. 4. The first stage esterification reaction is carried out at a reaction temperature of 180 to 240 ° C. and a pressure of 760 mmHg or less,
In addition, the esterification reaction of the second step is performed at a reaction temperature of 190
The process for producing polybutylene terephthalate according to any one of claims 1 to 3, wherein the process is performed at 250 ° C and a pressure of 760 mmHg or less. 5. The esterification reaction of the first stage is carried out at a reaction temperature of 200 to 230 ° C. and a pressure of 100 to 600 mmHg, and the esterification reaction of the second stage is carried out at a reaction temperature of 20 to 230 ° C.
5. The process for producing polybutylene terephthalate according to claim 4, wherein the process is carried out at 0 to 240 [deg.] C. and at a pressure of 100 to 550 mmHg. 6. The amount of the organotin compound added is 0.0 to 100 parts by weight of the resulting polybutylene terephthalate.
2 to 0.15 parts by weight.
5. The method for producing polybutylene terephthalate according to any one of 5. 7. The amount of the organic titanium compound to be added in the second stage esterification reaction is 0.005 to 0.3 parts by weight based on 100 parts by weight of the produced polybutylene terephthalate. A method for producing the polybutylene terephthalate according to claim 1.