JPS6111248B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester, and particularly to a method for producing aromatic polyester having a high softening point and good color tone. Aromatic polyesters whose main components are difunctional aromatic carboxylic acids and glycols have excellent mechanical, physical, and chemical properties.
Widely used for fibers, films, and other molded products. Among aromatic polyesters, polyesters containing terephthalic acid as the main acid component and ethylene glycol, tetramethylene glycol, hexamethylene glycol, or cyclohexane-1,4-dimethylol as the main glycol component are particularly important. Such polyester, particularly polyethylene terephthalate, is produced by heating ethylene glycol ester of terephthalic acid and/or its low polymer under reduced pressure to cause a polycondensation reaction. This polycondensation reaction can proceed smoothly and produce products with commercial value only by using a catalyst, and the type of catalyst used will affect the reaction rate and the quality of the product obtained. is greatly influenced. Titanium compounds such as tetrabutyl titanate have been known to have excellent polycondensation catalytic ability. However, when such a titanium compound is used, the resulting polyester tends to be yellowish, and especially when used in an amount sufficient to achieve an industrial production rate, the resulting polyester exhibits a deep yellow color and has a low softening point. descend. Several methods have been proposed for preventing coloring when such titanium compounds are used. That is, Japanese Patent Publication No. 48-2229 discloses a method using titanium hydride, and Japanese Patent Publication No. 47-26597 discloses a method using α-titanic acid.
However, in the former method, it is not easy to powderize titanium hydride, and in the latter method, α-titanic acid is easily deteriorated, making it difficult to store and handle it, and therefore neither method is suitable for industrial use. It's not an appropriate method. Furthermore, Japanese Patent Publication No. 43-9759 discloses a method using a titanium salt of phosphorous acid, and Japanese Patent Publication No. 48-49893 discloses a method using a condensate of a titanium compound and phosphinic acid. It is shown. However, these titanium-phosphorus compounds do not result in a homogeneous and transparent catalyst solution, but instead result in a solution containing white to yellow precipitates. In order to produce high-quality polyester with a constant and uniform reaction rate, it is essential to quantitatively add a very small amount of catalyst, and making a uniform catalyst solution is extremely important when handling the catalyst. be. In particular, forming a catalyst into a homogeneous solution makes it possible to automatically measure and add the catalyst, which is extremely important industrially.
Moreover, when the above titanium-phosphorus compound is used,
When the polycondensation reaction temperature is raised to increase productivity, the resulting polyester exhibits a fairly strong yellow color and its commercial value is significantly reduced. In view of the above circumstances, the present inventor conducted extensive research on a titanium compound that can satisfy all of the requirements, including the preparation of a uniform and transparent catalyst solution, the stability of the catalyst solution, the activity of the catalyst, and the quality of the produced polyester. The heat-treated product obtained by reacting titanate and trimellitic acid and then heat-treating this product with tributyl phosphate satisfies all of the above conditions, and the resulting polyester has a high softening point and good color tone. I learned that. The present invention was completed as a result of further intensive research based on this knowledge. That is, the present invention provides polycondensation of at least one difunctional aromatic carboxylic acid glycol ester and/or its low polymer in the presence of a catalyst to produce a polyester. ) Ti(OR) ₄ ...() [In the formula, R is an alkyl group. ] Titanium compound represented by and the following general formula () [In the formula, n is an integer from 2 to 4, and at least 1
The COOH groups of the set are in positions that allow them to form anhydrides. ] The reaction product A with the aromatic polyhydric carboxylic acid or its anhydride represented by the following general formula () [In the formula, R ₁ , R ₂ and R ₃ are hydrogen atoms or alkyl groups, and at least one of R ₁ , R ₂ and R ₃ is an alkyl group. ] This is a method for producing polyester, characterized in that a heat-treated product obtained by heat-treating a phosphorus compound represented by the following is used in the form of a solution. The glycol ester of difunctional aromatic carboxylic acid used in the present invention may be produced by any method. It is usually produced by heating and reacting a difunctional aromatic carboxylic acid or its ester-forming derivative with a glycol or its ester-forming derivative. The difunctional aromatic carboxylic acid used here is mainly terephthalic acid, and its ester-forming derivatives are preferably alkyl esters having 1 to 4 carbon atoms, phenyl esters, and the like. In addition, difunctional aromatic carboxylic acids other than terephthalic acid, such as isophthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenylmethane dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenoxyethane dicarboxylic acid, acid, β-hydroxyethoxybenzoic acid, etc., or a part of the main component difunctional aromatic carboxylic acid may be substituted with other difunctional aromatic carboxylic acids and/or, for example, sebacic acid, adipic acid, etc. , a difunctional fatty carboxylic acid such as oxalic acid, a difunctional alicyclic carboxylic acid such as 1,4-cyclohexanedicarboxylic acid, or an ester-forming derivative thereof. Glycol mainly refers to ethylene glycol, and as its ester-forming derivative, ethylene oxide is particularly preferably used. Other aliphatic and alicyclic glycols such as tetramethylene glycol, trimethylene glycol, and cyclohexane-1,4-dimethanol may also be used. A method for producing a glycol ester/or a low polymer thereof from such an acid component and a glycol component is, for example, for an ethylene glycol ester of terephthalic acid and/or a low polymer thereof, which is a constituent raw material of polyethylene tetophthalate. Generally, a method is employed in which a direct esterification reaction is performed between terephthalic acid and ethylene glycol, a transesterification reaction is performed between a lower alkyl ester of terephthalic acid and ethylene glycol, or an addition reaction is performed between terephthalic acid and ethylene oxide. Although any catalyst can be used in these reactions, it is preferable to select and use a catalyst that does not adversely affect the color tone, taking into account the purpose of the present invention. The polycondensation reaction catalyst used in the method of the present invention is a reaction product obtained by further reacting a phosphorus compound with a reaction product A of a titanium compound and an aromatic polyhydric carboxylic acid or its anhydride. The titanium compound used here has the following general formula () Ti(OR) ₄ ...() However, R in the formula is an alkyl group, especially in the case of an alkyl group having 3 or 4 carbon atoms, that is, tetrapropyl titanate. , tetraisopropyl titanate or tetrabutyl titanate are preferred. Two or more such titanium compounds may be used in combination. The compound to be reacted with such a titanium compound is an aromatic polycarboxylic acid represented by the following general formula () or an anhydride thereof. [In the formula, n is an integer from 2 to 4, and at least 1
in a position that allows the formation of a set of COOH groups or anhydrides. ] Preferred examples of the aromatic polycarboxylic acid or anhydride thereof include phthalic acid, trimellitic acid, hemimellitic acid, pyromellitic acid, and anhydrides thereof. Further, the phosphorus compound to which the reaction product A of the titanium compound and the aromatic polyhydric carboxylic acid or its anhydride is heat-treated is a phosphorus compound represented by the following general formula (). However, R ₁ , R ₂ and R ₃ in the formula are hydrogen atoms or alkyl groups, and at least one of R ₁ , R ₂ and R ₃ is an alkyl group. Specifically, they are monoalkyl esters, dialkyl esters, trialkyl esters, or mixed alkyl esters of phosphoric acid, and esters with an alkyl group having 1 to 4 carbon atoms are particularly preferred. Moreover, these phosphorus compounds may be used alone or in combination of two or more. The reaction between the titanium compound and the aromatic polycarboxylic acid or its anhydride is carried out by dissolving part or all of the aromatic polycarboxylic acid or its anhydride in a solvent, adding the titanium compound dropwise to the solution, and raising the temperature to 0°C. The reaction may be carried out at a temperature of ~200°C for about 30 minutes or more. The reaction pressure at this time is not particularly limited, and normal pressure is sufficient. In addition,
As the solvent, any solvent that can dissolve part or all of the aromatic polycarboxylic acid or its anhydride can be used, but ethanol, ethylene glycol, benzene, etc. are particularly preferable, and in particular, the same glycol component as that of the polyester is preferred. Glycols are preferred. The molar ratio of the titanium compound and the aromatic polycarboxylic acid or its anhydride in this reaction can vary over a wide range, but if the titanium compound is too large, the color tone and softening point of the resulting polyester tend to deteriorate. On the other hand, if the amount of titanium compound is too small, the polycondensation reaction tends to be difficult to proceed sufficiently. Preferably, they are used in proportions. The reaction product A of the titanium compound and the aromatic polycarboxylic acid or its anhydride obtained in this way is
The solution may be used as it is for the next heat treatment with a phosphorus compound, or it may be re-purified with acetone or the like and then dissolved in a solvent and used for the next heat treatment with a phosphorus compound. Here, the infrared absorption chart (hereinafter referred to as
Here is an example of an IR chart (sometimes called an IR chart).
Shown in Figure c. In FIG. 1, a and b are IR charts of trimellitic anhydride and trimellitic acid, respectively, and c is a heat treatment of tetrabutyl titanate and trimellitic anhydride in ethylene glycol, and acetone is added to the resulting treatment solution. In addition, this is an IR chart of the precipitate. And the IR of trimellitic anhydride in Figure 1a
Comparing the chart with the IR chart in Figure 1c, we find that in Figure 1c, there is a characteristic characteristic of trimellitic anhydride.
No absorption was observed between 1800 and 1900 cm ^-1 , giving an absorption pattern similar to the IR chart of trimellitic acid shown in Figure 1b. On the other hand, in comparison with the IR chart of trimellitic acid shown in FIG. 1b, ^the IR chart of FIG ^.
Nearby absorption is small. This generally means that the carboxyl group (-
When COOH) and metal (M) react to form -COOM, absorption near 1700 cm ^-1 , which is unique to -COOH, occurs.
Since it shifts to around 1600cm ^-1 ,
The IR chart indicates that trimellitic anhydride and tetrabutyl titanate are reacting. Next, the heat treatment of the reaction product A and the phosphorus compound may be carried out by dropping the phosphorus compound into a solution of the reaction product A and heat-treating the solution at a temperature of 150 to 200° C. for about 30 minutes or more. There is no particular limit to the pressure at this time,
Normal pressure is sufficient. Furthermore, as a solvent, those used in the reaction of the titanium compound and the aromatic polyhydric carboxylic acid or its anhydride may be optionally used, but as in the above reaction, the same glycol component as the glycol component constituting the polyester can be used. The use of is particularly industrially advantageous because the heat-treated solution after heat treatment can be used as it is. The amount of phosphorus compound used in this heat treatment can vary over a wide range, but if the amount of phosphorus compound is too small, the color tone and softening point of the resulting polyester tend to worsen, while if the amount of phosphorus compound is too large, Since the condensation reaction tends to be difficult to proceed sufficiently, the phosphorus compound is added to 1/3 to 6 mol of the titanium atom in the reaction product A of the titanium compound and the aromatic polyhydric carboxylic acid or its anhydride. It is preferable to use it in a molar ratio, particularly preferably 1/2 to 3 molar. The amount of the heat-treated product of the reaction product A obtained in this manner and a phosphorus compound (hereinafter referred to as a phosphorus compound) is not particularly limited, but
If the amount is too small, sufficient polycondensation reaction rate cannot be obtained, and if the amount is too large, the resulting polyester tends to turn yellow. It is 0.001 to 0.05 mol%, preferably 0.005 to 0.03 mol%. The addition time may be any time before the completion of the polycondensation reaction, but it is preferably added between before and immediately after the start of the polycondensation reaction. Particularly when used as a transesterification catalyst, it is preferable to add the above amount between before and immediately after the start of the transesterification reaction. Note that other polycondensation reaction catalysts such as antimony compounds, germanilam compounds, etc. can also be used in combination without departing from the purpose of the present invention. It is not necessary to adopt special conditions for the polycondensation reaction in the present invention, and the conditions adopted when polycondensing the glycol ester of a difunctional carboxylic acid and/or its low polymer to form a polyester are arbitrary. will be adopted. In the case of polyethylene terephthalate, the glycol generated is generally produced by heating ethylene glycol ester of terephthalic acid and/or its low polymer to which the above-mentioned amount of a phosphorous compound has been added to a temperature above its melting point and below 300°C under reduced pressure. A method is adopted in which a polycondensation reaction is caused by distillation. In addition, when using the lintitanium-containing compound as a transesterification catalyst,
There is no need to adopt special conditions for the transesterification reaction. For example, in the case of polyethylene terephthalate, a reaction mixture (lower alkyl ester of terephthalic acid and ethylene glycol or the reaction product thereof) to which the above amount of a nitrous compound is added is used. (mixtures with substances) under normal pressure or slightly increased pressure (usually 10
Kg/cm ² or less) or under slight reduced pressure (usually 50mmHg
After the transesterification reaction is carried out by heating to 150 to 250°C and distilling off the alcohol generated, the polycondensation reaction is then completed. In carrying out the present invention, a monofunctional compound such as benzylbenzoic acid, phenolsulfonate, γ-hydroxypropanesulfonate, etc. may be bonded to the terminal end of the polyester obtained. A trifunctional or higher polyfunctional compound may be copolymerized in an amount that does not substantially cause the polyester to lose its thermoplasticity. Furthermore, optional additives such as colorants, matting agents, fluorescent whitening agents, stabilizers, ultraviolet absorbers, ether bond inhibitors, dye-facilitating agents, flame retardants,
Antistatic agents and the like may also be used. The present invention will be explained in further detail by giving examples below.
In the examples, parts are parts by weight, and [η] is the intrinsic viscosity determined from the viscosity measured at 35° C. using orthochlorophenol as a solvent. The color tone was expressed by the L value and b value obtained by heat-treating the polymer at 200°C for 20 minutes in a nitrogen stream to crystallize it, and then measuring the surface color with a Color Machine CM-20 model (manufactured by Color Machine Co., Ltd.). . The L value indicates brightness, and the higher the value, the higher the brightness.The higher the b value is on the (+) side, the more yellow it is, and the higher it is on the (-) side, the more blue it is. show. The softening point was measured by the penetration method. Example 1 (a) Preparation of catalyst Ethylene glycol 380 was added to a reactor equipped with a stirrer, a rectification column, and a butanol distillation condenser.
1 part, 35 parts of tetrabutyl titanate, and 39 parts of trimellitic anhydride (2 times the mole to trouble titanate), heated to 150 to 180°C under normal pressure, and the butyl alcohol and ethylene glycol monobutyl ether produced as a result of the reaction were removed from the system. The reaction was continued for 60 minutes while distilling, and when the amount of distillate reached 31 parts, the reaction was terminated and the mixture was cooled to room temperature. 187 parts of the resulting reaction solution was collected, and 22.2 parts of tributyl phosphate (2 times the molar ratio to the titanium atoms in the reaction solution) was added dropwise to the solution under stirring under normal pressure in air. After dropping, heat to an internal temperature of 170~
Ethylene glycol monobutyl ether was distilled out around 180°C. When the internal temperature reached 193°C, the heat treatment was stopped and the mixture was cooled to room temperature. A slightly yellow transparent catalyst solution was obtained. (b) Production of polyester 970 parts of dimethyl terephthalate, 640 parts of ethylene glycol, 0.18 parts of manganese acetate, and 0.12 parts of cobalt acetate were charged into a reactor equipped with a stirrer, a rectification column, and a methanol distillation condenser.
The mixture was heated from 140°C to 230°C to carry out a transesterification reaction while distilling methanol produced as a result of the reaction out of the system. Three hours after the start of the reaction, the internal temperature was
The temperature reached 230°C and 320 parts of methanol was distilled out. Here trimethyl phosphate as stabilizer
0.21 parts and 4.85 parts of titanium dioxide as a matting agent were added, and the catalyst solution obtained in (a) above was added in an amount such that the titanium atoms in the liquid were 0.015 mol% to dimethyl terephthalate, and then the reaction mixture was stirred with a stirrer. The mixture was transferred to a reactor equipped with an ethylene glycol distillation condenser, and a polycondensation reaction was carried out while gradually raising the temperature from 230°C to 285°C and lowering the pressure from normal pressure to a high vacuum of 1 mmHg. A polymer having [η] 0.642 was obtained in a total polycondensation reaction time of 3 hours and 30 minutes. The softening point of this polymer was 260.7°C, and the color tone was L value 82.6 and b value 2.3. For comparison, 0.26 parts of tetrabutyl titanate (as titanium atoms) was added instead of the catalyst solution obtained in (a) above.
The above (b) was reacted in the same manner, except that 0.015 mol % of dimethyl terephthalate was used. The [η] of the obtained polymer was 0.648, the color tone was L value 78.3,
The b value was 11.7 and the softening point was 259.1°C. Example 2 A transparent catalyst solution was obtained by carrying out the reaction in the same manner as in Example 1-(a), except that the amount of tributyl phosphate used in Example 1-(a) was varied as shown in Table 1. Ta. Polymers were obtained in the same manner as in Example 1-(b) using each solution in an amount such that titanium atoms in the solution were 0.015 mol % to dimethyl terephthalate. The results are shown in Table 1.

[Table] The moles of the amount of tributyl phosphate in the table indicate the molar ratio with respect to 1 mole of titanium atoms in the catalyst solution. Examples 3 and 4 Same as Example 1-(a) except that trimethyl phosphate and dibutyl phosphate were used in the amounts shown in Table 2 instead of the tributyl phosphate used in Example 1-(a). After the reaction, a slightly yellow transparent catalyst solution was obtained. Polymers were obtained in the same manner as in Example 1-(b) using each catalyst solution in an amount such that titanium atoms in the solution were 0.015 mol % to dimethyl terephthalate. The results are shown in Table 2.

[Table] The mole of the amount of phosphorus compound in the table indicates the molar ratio with respect to 1 mole of titanium atom in the catalyst solution.

[Brief explanation of the drawing]

In FIG. 1, a and b are IR charts of trimellitic anhydride and trimellitic acid, respectively, and c is tetrabutyl titanate and trimellitic anhydride heated in ethylene glycol.
This is an IR chart of the precipitate formed by adding acetone to the obtained treatment solution.

Claims (1)

[Scope of Claims] 1. When producing a polyester by subjecting at least one type of difunctional aromatic carboxylic acid glycol ester and/or its low polymer to a polycondensation reaction in the presence of a catalyst, the following general formula is used as a polycondensation catalyst: () Ti(OR) ₄ ... () [In the formula, R is an alkyl group. ] Titanium compound represented by and the following general formula () [In the formula, n is an integer from 2 to 4, and at least 1
The COOH groups of the set are in positions that allow them to form anhydrides. ] The reaction product A with the aromatic polyhydric carboxylic acid or its anhydride represented by the following general formula () [In the formula, R ₁ , R ₂ and R ₃ are hydrogen atoms or alkyl groups, and at least one of R ₁ , R ₂ and R ₃ is an alkyl group. ] A method for producing polyester, characterized in that a heat-treated product obtained by heat-treating a phosphorus compound represented by the formula is used in the form of a solution. 2. The reaction product A constituting the polycondensation catalyst has the following general formula () Ti(OR) ₄ ...() [wherein R is an alkyl group]. ] A titanium compound represented by the following general formula () in a proportion of 1/2 to 21/2 mol per 1 mol of titanium. [In the formula, n is an integer from 2 to 4, and at least 1
The COOH groups of the set are in positions that allow them to form anhydrides. ] The method for producing a polyester according to claim 1, which is a reaction product with an aromatic polycarboxylic acid represented by the following or an anhydride thereof. 3 The polycondensation catalyst is a reaction product A and the reaction product A
The following general formula () at a ratio of 1/3 to 6 moles per mole of titanium atoms in [In the formula, R ₁ , R ₂ and R ₃ are hydrogen atoms or alkyl groups, and at least one of R ₁ , R ₂ and R ₃ is an alkyl group. ] The method for producing polyester according to claim 1 or 2, which is a heat-treated product with a phosphorus compound represented by: 4. The titanium compound which is a reaction component constituting the polycondensation catalyst has the following general formula (') Ti(OR') ₄ ... (') [wherein R' is an alkyl group having 3 or 4 carbon atoms. ] The method for producing a polyester according to any one of claims 1 to 3, which is a titanium compound represented by the following. 5. The aromatic polycarboxylic acid or its anhydride, which is a reaction component constituting the polycondensation catalyst, is at least one compound selected from the group consisting of phthalic acid, trimellitic acid, hemimellitic acid, pyromellitic acid, and anhydrides thereof. A certain patent claim, item 1~
4. A method for producing polyester according to any one of item 4. 6 The phosphorus compound constituting the polycondensation catalyst has the following general formula (') [In the formula, R′ ₁ , R′ ₂ and R′ ₃ are hydrogen atoms or carbon atoms with 1
-4 alkyl groups, in which at least one of R' ₁ , R' ₂ and R' ₃ is an alkyl group having 1 to 4 carbon atoms. ] The method for producing a polyester according to any one of claims 1 to 5, which is a phosphorus compound represented by the following. 7. The method for producing a polyester according to any one of claims 1 to 6, wherein the glycol ester of difunctional aromatic carboxylic acid is a glycol ester of terephthalic acid. 8. The method for producing a polyester according to any one of claims 1 to 6, wherein the glycol ester of difunctional aromatic carboxylic acid is ethylene glycol of terephthalic acid.