JPH05271395A - Production of copolyester - Google Patents

Abstract

PURPOSE:To obtain the subject high-quality liquid crystalline polymer by carrying out a specific multi-stage reaction and using an inexpensive low sublimable hydroxy aromatic carboxylic acid without causing formation of block component and side reactions. CONSTITUTION:First, a polyester (e.g. polyester terephthalate) having a unit of formula I (R1 is aromatic group; R2 is aliphatic group or alicyclic group) is blended with a hydroxy aromatic monocarboxylic acid (e.g. p-hydroxybenzoic acid) of formula II in a molar ratio of 90/10-40/60, subjected to acidolysis reaction by heating and melting to give a prepolymer. Then, the compound of formula II in an amount deficient to form the objective polymer is gradually added to the reaction system and an acetylating agent (preferably acetic anhydride) is added to the reaction system to carry out acetylation and acidolysis. Finally the reaction system is evacuated to reduced pressure and polycondensation reaction is carried out to give the objective polymer having the unit of formula I and the compound of formula II in a molar ratio of 5/95-30/70.

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 a copolyester capable of producing a thermotropic liquid crystalline copolyester having excellent heat resistance and improved melt processability at low cost.

[0002]

2. Description of the Related Art In recent years, thermotropic liquid crystalline polyesters have attracted attention as high performance resins, and various liquid crystalline polyesters have been proposed. In particular, polyalkylene terephthalates such as polyethylene terephthalate and p-hydroxybenzoic acid have been proposed. The liquid crystalline polyester obtained from such a hydroxyaromatic carboxylic acid component has been attracting attention as having good fluidity and excellent moldability.

Conventionally, polyethylene terephthalate and p-
A liquid crystalline polyester composed of a hydroxybenzoic acid component is prepared by first heating and melting polyethylene terephthalate and p-acetoxybenzoic acid to carry out an acidolysis reaction.
After the prepolymer (polyester fragment) was formed, the polycondensation reaction was carried out under reduced pressure. However, when a liquid crystalline polyester having a large proportion of p-hydroxybenzoic acid component is produced by this method, a component having a high block property generated by the self-condensation reaction of the p-hydroxybenzoic acid component is generated in the copolymer. However, there is a problem that the surface gloss, flow characteristics, impact strength, etc. of the polymer are significantly reduced.

Therefore, as a method for solving this problem,
Part of polyethylene terephthalate and p-acetoxybenzoic acid are heated and melted to perform an acidolysis reaction, and p-
After forming a polyester in which the content of the hydroxybenzoic acid component is less than the target ratio, p-acetoxybenzoic acid in an amount insufficient to obtain the target polyester is added to perform an acidolysis reaction, Then, a method has been proposed in which the pressure is reduced and the polycondensation reaction is carried out (Japanese Patent Laid-Open No. S60-12065).
64-26632). However, in this method, p-acetoxybenzoic acid used as a raw material is produced by acetylating p-hydroxybenzoic acid, so that it is more expensive than p-hydroxybenzoic acid. Furthermore, p-acetoxybenzoic acid is sublimated. Since the property (vaporization) is high, there arises a problem that the piping of the device is closed to reduce the production efficiency.

On the other hand, a method using p-hydroxybenzoic acid, which is inexpensive and has a low sublimation property, in place of p-acetoxybenzoic acid has also been proposed (JP-A-60-186525). But,
p-Hydroxybenzoic acid is very thermally unstable [JOURNA
L OF POLYMERSCIENCE: Polymer Cheistry Edition, VOL.
14, 2207 to 2224 (1976)], and when it is kept in a molten state at a high temperature of 250 ° C. or higher or at a temperature of 250 ° C. or lower for a long time, dehydration between hydroxyl groups of p-hydroxybenzoic acid in addition to the esterification reaction. The reaction causes a side reaction of forming an ether bond. When the component having an ether bond is introduced into the polymer main chain, the thermotropic liquid crystallinity is remarkably relaxed and the heat resistance properties such as melting point and heat distortion temperature are remarkably lowered. In addition to this side reaction, phenol is generated by decarboxylation reaction of p-hydroxybenzoic acid to cause remarkable coloring of the polymer, and further, the generation of this phenol causes a molar balance of the raw material composition of the polymer. And the target copolyester cannot be obtained.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a liquid crystalline polyester having a large proportion of a hydroxyaromatic carboxylic acid component from a polyester such as polyalkylene terephthalate and a hydroxyaromatic carboxylic acid component. As a carboxylic acid component, a hydroxyaromatic carboxylic acid that is cheaper and less sublimable than acetoxyaromatic carboxylic acid is used, and there is little block component formation or side reaction due to self-condensation of the hydroxyaromatic carboxylic acid component, and high quality. Another object of the present invention is to provide a method for producing a copolyester capable of obtaining the above polymer.

[0007]

[R ₁ represents an aromatic group, R ₂ represents an aliphatic group or an alicyclic group, and R ₃ represents an aromatic group. ]

First step: a polyester having a unit represented by the formula (I) and a hydroxyaromatic carboxylic acid represented by the formula (II) are combined with a unit of the formula (I) and a hydroxyaromatic carboxylic acid represented by the formula (II). Mixed in a molar ratio of 90/10 to 40/60,
It is heated and melted to carry out an acidolysis reaction to form a prepolymer. Second step: A quantity of the hydroxyaromatic carboxylic acid of the formula (II) which is insufficient to form a polyester having a desired copolymerization molar ratio is gradually added to the reaction system at atmospheric pressure. Third stage: An acetylating agent is added to carry out an acetylation reaction and an acidolysis reaction. Fourth stage: The reaction system is depressurized to carry out a polycondensation reaction.

The present invention will be described in detail below. First, the raw material polyester used in the present invention has the formula (I)
Specifically, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene-4,4'-diphenyl dicarboxylate, polycyclohexane dimethylene terephthalate and the like can be mentioned. Be done. The degree of polymerization of the raw material polyester is not particularly limited, and oligomers may be used, but those having a high terminal hydroxyl group concentration are not suitable because ether bond compounds are easily formed.

Further, the hydroxyaromatic carboxylic acid used in the present invention is represented by the formula (II), but since it bears the rigidity of the produced polyester, a para-oriented one is used. Include p-hydroxybenzoic acid, 2-
Hydroxy-6-naphthoic acid, 1-hydroxy-5-naphthoic acid, 1-hydroxy-4-naphthoic acid and the like can be mentioned. Further, acetic anhydride is preferably used as the acetylating agent.

The copolyesters produced by the process of the invention have a molar ratio of units of formula (I) to residual units of hydroxyaromatic carboxylic acid of formula (II) of 5/95 to 30/70, preferably Is from 15/85 to 30/70.

The method of the present invention is performed in four steps as follows. First, as a first step, polyester and hydroxyaromatic carboxylic acid are mixed in a molar ratio of 90/10 to 40/60, preferably 50/50, put into a reaction vessel, heated and melted to carry out an acidolysis reaction, Form a prepolymer. The heating temperature is selected in the range of 150 to 350 ° C, preferably 200 to 250 ° C. If it exceeds 350 ° C, the polyester may be thermally decomposed, and if it is less than 150 ° C, the reaction rate is remarkably slow and the reaction requires a long time, which is not preferable.
The acidolysis reaction in the first step can be carried out under normal pressure, but it is preferable to carry out it under pressure because side reactions can be further reduced. It is desirable to carry out the reaction under a pressure of preferably 0.1 to 8 kg / cm ² , more preferably 1 to 4 kg / cm ² .

Then, in the second step, when the first step is carried out under pressure, the system is returned to normal pressure with nitrogen gas or the like, and then it is insufficient to form a polyester having a desired copolymerization molar ratio. The amount of hydroxyaromatic carboxylic acid is gradually added to the reaction system at atmospheric pressure. The rate of addition depends on the amount of hydroxyaromatic carboxylic acid added per minute.
It is suitable to set it to 0.1 to 5 mol%, preferably 1 to 2 mol%. The reason why the hydroxyaromatic carboxylic acid is gradually added is that if this is added all at once, the temperature of the reaction system will drop rapidly and stirring will become difficult.

Next, as a third step, an acetylating agent (acetic anhydride) is added to the reaction system to carry out an acetylation reaction and an acidolysis reaction.

Finally, in the fourth step, the pressure inside the reaction system is reduced to accelerate the distillation of by-product acetic acid, and the temperature inside the system is appropriately raised to carry out the polycondensation reaction to obtain a copolymer with a high degree of polymerization. A polymerized polyester is obtained.

In order to carry out the above reaction efficiently, it is desirable to use a suitable catalyst. In particular, in the acidolysis reaction in the first step, the use of a transesterification catalyst allows the reaction to proceed more efficiently. As the transesterification catalyst, an organic metal catalyst such as zinc acetate or stannous acetate is more effective. The amount of the catalyst added is, relative to the polymer produced, 100 to 5000 ppm, preferably,
An amount of 200 to 2000 ppm is suitable.

[0016]

In the present invention, since hydroxyaromatic carboxylic acid, which is cheaper and less sublimable than acetoxy aromatic carboxylic acid, is used, it is not only advantageous in the raw material cost, but also clogging of the piping of the manufacturing apparatus is prevented. Since it does not occur, the production efficiency is remarkably improved, and since there is no sublimation, a copolyester having the same composition ratio as the charged composition ratio can be obtained.

Further, in the present invention, since hydroxyaromatic carboxylic acid is used, unlike the case of acetoxy aromatic carboxylic acid, self-condensation does not occur during melting,
Residue units of hydroxyaromatic carboxylic acid are likely to be relatively randomly incorporated into the copolymer chain, so that a polymer having a uniform property in which a component having a high block property does not exist can be obtained.

Further, the hydroxyaromatic carboxylic acid is thermally unstable, and when it is excessively present in the reaction system, it causes a side reaction such as an etherification reaction or a decarboxylation reaction. However, in the present invention, Since the hydroxyaromatic carboxylic acid is divided and added, such side reaction is suppressed.
In particular, when the acidolysis reaction of the first stage is carried out under pressure, the effect of suppressing side reactions becomes remarkable. This is a side reaction, etherification reaction and decarboxylation reaction are equilibrium reactions,
This is because the water and carbon dioxide produced are gases at the reaction temperature, so that the side reaction is suppressed by applying pressure to the reaction system. Further, when the acidolysis reaction is carried out under pressure, the frequency of collisions between the hydroxyaromatic carboxylic acid and the polyester increases due to the increase in pressure, and the effect of increasing the reaction rate can also be expected.

[0019]

EXAMPLES Next, the present invention will be specifically described with reference to examples. The measuring method of the characteristic value in the examples is as follows. Using a differential scanning calorimeter DSC-2 type manufactured by Perkin Elmer Co.,
The measurement was performed at a temperature rising rate of 20 ° C / min. Intrinsic viscosity [η] It was measured at 25 ° C. using a mixed solvent of equal weight of phenol and tetrachloroethane. Apparent melt viscosity (μ) 300 using Shimadzu's advanced flow tester CFT-500
The polymer was discharged at 0 ° C., and the apparent melt viscosity (μ) was calculated from the discharge amount Q (ml / sec) by the following formula. μ = πR ⁴ P / 8IQ However, I: nozzle length (cm), R: nozzle radius (cm)
P: Pressure when extruded from nozzle (dyne / cm ² ) The pressure P extruded from the nozzle for each sample is changed to find the relationship between the apparent shear rate and the apparent melt viscosity. Then, the calculated value of the apparent melt viscosity when the apparent shear rate was 10 ⁻³ was used as the representative value. Amount of ether bond 1H-NMR measurement was carried out using VXR 300 manufactured by Varian as a measuring device with a measuring nucleus of 1H, a resonance main wave number of 300 MHz, a solvent of trifluoroacetic acid, and a measuring temperature of room temperature. In the measurement of the diphenyl ether component, the peak at 7.2 to 7.25 ppm was defined as protons (for four) in the ortho position of the phenyl group with respect to the oxygen position of the ether bond. For the ethyl phenyl ether group, 4.75 to 4.8 ppm of ether-side protons (two) of the ethyl group were measured, and the ratio was calculated. (The amount of ether bond shown in the table is the sum of the measured values of both components.) Judgment of liquid crystallinity When a Leitz polarizing microscope with a hot stage was used and each polymer was heated up to the molding temperature, crossed Nicols were observed. It was judged whether or not to allow polarized light to pass therethrough. The heat distortion temperature was measured according to ASTM D-648, and the measured value at 18.6 kg / cm ² was shown. Flexural modulus was measured according to ASTM D-790. Izod impact strength Measured according to ASTM D-256.

Example 1 A copolymerized polyester was produced using 20 parts by mole of polyethylene terephthalate (PET) of [η] 0.71 and 80 parts by mole of p-hydroxybenzoic acid (POB) as raw materials. First, PET chips
20 parts by mol (38.4 kg), 20 parts by mass of powdered POB (27.6 kg) and 200 ppm (0.027 kg) of stannous acetate were charged in a reactor and sufficiently dried under reduced pressure, then 220- 230
The temperature was raised to 0 ° C, and after all the raw materials were melted, the temperature was maintained for 40 minutes to carry out an acidolysis reaction to obtain a prepolymer. Then, 60 parts by mole of POB (82.8 k
g) was gradually charged into the reaction system at a rate of 1.656 kg per minute. After the POB was added, the temperature in the reaction system was lowered to 140 ° C over 1 hour, 1.3 times mol of acetic anhydride was added to the total amount of POB, and the acetylation reaction was performed for about 1 hour, followed by 3 hours.
The temperature was raised to 270 ° C. and the acidolysis reaction was performed for 20 minutes. Then, the temperature was raised sequentially and finally the polycondensation reaction was carried out in the melt phase at 300 ° C. under a reduced pressure of 0.3 torr for 3 hours. The resulting copolyester was a polyester having a thermotropic liquid crystallinity with a melting point of 280 ° C., and the yield was 96%. The results of injection molding and evaluation of this copolyester are shown in Table 1.

Example 2 The first stage acidolysis reaction was performed with nitrogen gas at a pressure of 4
A copolyester was produced in the same manner as in Example 1 except that the pressure was up to 6 kg / cm ² . The obtained copolyester was a polyester having a thermotropic liquid crystallinity and a melting point of 284 ° C., and the yield was 96%. The results of injection molding and evaluation of this copolyester are shown in Table 1.
Shown in.

Example 3 A copolymerized polyester was produced using 17 parts by mole of polyethylene terephthalate (PET) of [η] 0.71 and 83 parts by mole of p-hydroxybenzoic acid (POB) as raw materials. First, PET chips
17 parts by mol (32.6 kg), 17 parts by mol of powdered POB (23.5 kg) and 200 ppm stannous acetate (0.027 kg) were charged in a reactor and sufficiently dried under reduced pressure, then 220 to 220 with a slight flow of nitrogen gas. 230
The temperature was raised to 0 ° C, and after all the raw materials were melted, the temperature was maintained for 40 minutes to carry out an acidolysis reaction to obtain a prepolymer. Next, 66 parts by mole of POB (91.08k) was added to the prepolymer.
g) was gradually charged into the reaction system at a rate of 1.82 kg per minute. After the POB is charged, the temperature in the reaction system is set to 1 hour over 1 hour.
The temperature was lowered to 40 ° C., and acetic anhydride was added in an amount 1.3 times the total amount of POB.
Acetylation reaction is performed for about 1 hour and then 270 over 3 hours.
The temperature was raised to ° C and the acidolysis reaction was performed for 20 minutes. After that, the temperature is raised sequentially and finally at 320 ° C. under a reduced pressure of 0.3 torr.
The polycondensation reaction was carried out in the melt phase for a period of time. The obtained copolyester was a polyester having a thermotropic liquid crystallinity with a melting point of 300 ° C., and the yield was 96%. The results of injection molding and evaluation of this copolyester are shown in Table 1.
Shown in.

Example 4 A copolymerized polyester was produced using 20 parts by mole of polyethylene terephthalate (PET) of [η] 0.71 and 80 parts by mole of 6-hydroxy-2-naphthoic acid (6H2N) as raw materials. First,
PET chip 20 parts (38.4 kg), powdered 6H2N 20 parts
(37.6 kg) and stannous acetate 200 ppm (0.038 kg) were charged in a reactor and sufficiently dried under reduced pressure, then heated to 220 to 230 ° C while flowing a small amount of nitrogen gas, and all raw materials were melted. From
The temperature was maintained for 40 minutes to carry out an acidolysis reaction to obtain a prepolymer. This prepolymer was then added to 6H2N 60
The molar part (82.8 kg) was gradually charged into the reaction system at a rate of 2.256 kg per minute. After the completion of charging 6H2N, the temperature in the reaction system was lowered to 140 ° C over 1 hour, 1.3 times mol of acetic anhydride was added to the total amount of 6H2N, and the acetylation reaction was performed for about 1 hour, and then over 3 hours. The temperature was raised to ° C and the acidolysis reaction was performed for 20 minutes. After that, the temperature is raised sequentially and finally at 320 ℃
The polycondensation reaction was performed in the melt phase for 2 hours under a reduced pressure of 0.3 torr. The copolyester obtained was a polyester having a thermotropic liquid crystallinity with a melting point of 305 ° C., and the yield was 90%. The results of injection molding and evaluation of this copolyester are shown in Table 1.

Comparative Example 1 A copolymerized polyester was produced using 20 parts by mole of polyethylene terephthalate (PET) of [η] 0.71 and 80 parts by mole of p-hydroxybenzoic acid (POB) as raw materials. First, PET chips
Charge 20 parts by mole (38.4 kg), 80 parts by weight of POB (110.4 kg) and 200 ppm stannous acetate (0.027 kg) into the reactor, and sufficiently dry under reduced pressure, then 220- 2
The temperature was raised to 30 ° C., and all the raw materials were melted, and the temperature was maintained for 2 hours to carry out the acidolysis reaction. Then, the temperature in the reaction system was lowered to 140 ° C over 1 hour to completely remove acetic anhydride.
After 1.3 times the molar amount of POB was added and the acetylation reaction was carried out for about 1 hour, the temperature was raised to 270 ° C. over 3 hours and the acidolysis reaction was carried out for 20 minutes. After that, the temperature is raised sequentially and finally 29
The polycondensation reaction was performed in the melt phase at 0 ° C. under a reduced pressure of 0.3 torr for 3 hours. The obtained copolyester has a melting point of 254 ° C.
Is a polyester showing thermotropic liquid crystallinity of
The yield was 95%. The results of injection molding and evaluation of this copolyester are shown in Table 1.

[0025]

[Table 1]

[0026]

According to the present invention, when a liquid crystalline polyester having a high proportion of a hydroxyaromatic carboxylic acid component is produced from a polyester such as polyalkylene terephthalate and a hydroxyaromatic carboxylic acid component, a hydroxyaromatic carboxylic acid is used. As a component, a hydroxyaromatic carboxylic acid that is cheaper and less sublimable than acetoxy aromatic carboxylic acid is used, and there is little block component generation or side reaction due to self-condensation of the hydroxyaromatic carboxylic acid component, and a high-quality polymer Can be obtained. And, the copolyester obtained by the method of the present invention is excellent in heat resistance and has good melt processability without any foreign matter, infusible matter or microcrystals, and various extrusion molding of fibers, films, sheets, pipes, etc. It is preferably used for the production of articles and injection-molded articles.

Claims (3)

[Claims] 1. A polyester having a unit of the formula (I) and a hydroxyaromatic carboxylic acid of the formula (II)
In producing a copolyester having a molar ratio of 5 units to a residue unit of the hydroxyaromatic carboxylic acid of the formula (II) of 5/95 to 30/70, the following four steps are sequentially performed. A method for producing a copolyester. (I) —OC—R ₁ —CO—O—R ₂ —O— (II) HO—R ₃ —COOH [R ₁ is an aromatic group, R ₂ is an aliphatic group or an alicyclic group, and R ₃ is Represents an aromatic group. 1st step; a polyester having a unit represented by the formula (I) and a hydroxyaromatic carboxylic acid represented by the formula (II) are combined with a unit of the formula (I) and a hydroxyaromatic carboxylic acid represented by the formula (II). And a molar ratio of 90/10 to 40/60 are mixed,
It is heated and melted to carry out an acidolysis reaction to form a prepolymer. Second step: A quantity of the hydroxyaromatic carboxylic acid of the formula (II) which is insufficient to form a polyester having a desired copolymerization molar ratio is gradually added to the reaction system at atmospheric pressure. Third stage: An acetylating agent is added to carry out an acetylation reaction and an acidolysis reaction. Fourth stage: The reaction system is depressurized to carry out a polycondensation reaction. 2. The polyester having units of formula (I) is polyethylene terephthalate, and the hydroxyaromatic carboxylic acid of formula (II) is p-hydroxybenzoic acid or 6
The method according to claim 1, which is -hydroxy-2-naphthoic acid. 3. The method according to claim 1, wherein the acidolysis reaction in the first step is carried out under pressure.