JPH02158621A - Production of aromatic copolyester - Google Patents

Abstract

PURPOSE:To obtain the title polymer having a little discoloration and excellent heat stability by adding a specific amount of isophthalic acid to a dicarboxylic acid adjusting concentration of acetic acid of ester derivative and subjecting the ester derivative to polycondensation. CONSTITUTION:(A) A dicarboxylic acid containing >=5wt.% isophthalic acid, (B) hydroxybenozoic acid and (C) a dihydroxy compound such as hydroquinone are esterified with (D) acetic anhydride and acetic anhydride prepared as a by-product is reduced to <=15wt.% to give an ester derivative. Then the derivative is subjected to polycondensation to give the aimed polymer.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing aromatic copolyester (prior art) In recent years, demands for higher performance of plastics have been increasing, and various high-performance plastics have been developed. has been developed and supplied to the market. Among them, thermotropic liquid crystal polymers, which are composed of particularly rigid molecular chains and exhibit optical anisotropy when melted, are attracting attention because they have low melt viscosity, good processability, and excellent mechanical properties.

Aromatic copolyesters are known as such liquid crystal polymers, and the polymerization method includes, for example, reacting hydroxybenzoic acid and dihydroxy compounds with acetic anhydride to prepare ester derivatives, and then carrying out a polycondensation reaction with dicarboxylic acids. There is a law. In this method, since acetic acid is produced as a by-product during ester preparation, the surface of the reactor material is soaked, and the eluted metal adversely affects the coloring and thermal stability of the polymer.

(Problems to be Solved by the Invention) The purpose of the present invention is to provide a method for producing an aromatic copolyester with excellent thermal stability and less blue color when producing the aromatic copolyester by dissolution polycondensation. It is about providing.

(Means for Solving the Problems) The present inventors have completed the present invention as a result of intensive study on a method for obtaining a hexaaromatic copolyester having excellent thermal stability with less blue color.

That is, the present invention provides an aromatic copolyester consisting of hydroxybenzoic acid, dicarboxylic acid, and a dihydroxy compound, in which at least one of the dicarboxylic acids is isophthalic acid, and the aromatic copolyester contains isophthalic acid in an amount of 5% or more relative to the total dicarboxylic acids. A method for producing an aromatic copolyester, the method comprising: reducing the acetic acid concentration in the reaction mixture after the esterification reaction to 15% by weight or less, and then carrying out a polycondensation reaction. Regarding.

The present invention will be explained in detail below.

The reaction of esterifying acetic anhydride and raw materials while stirring is generally a very fast reaction that is completed in less than 5 minutes in the presence of sulfuric acid, and an example of this is Organic Synthesis (ORGAN I C3YNTHESES) Vol.
, m page 452. In the present invention, it has been found that during the esterification reaction, acetic acid is produced as a by-product at the same time as acetic anhydride is consumed, and that when the reaction is carried out while removing this by-product acetic acid, the hue and thermal stability of the resulting polymer are significantly improved. . Moreover, when the ester derivative was prepared in this way, the esterification reaction was completed in a short time.

Should the by-product acetic acid be removed under normal pressure or reduced pressure?
It is necessary to carry out the reaction at a temperature at which acetic anhydride, which is the I material, does not distill off, or to install an acetic anhydride reflux device.

The acetic acid concentration in the reaction mixture after the esterification reaction is 15
Weight percentage or less is preferable. When the acetic acid concentration exceeds 15 nee percent, the amount of acetic acid removed at high temperatures during polycondensation increases, which adversely affects the coloration and thermal stability of the polymer due to corrosion of the reactor material. There is also a problem in durability due to reactor corrosion.

The esterification reaction time is preferably 30 minutes or more and 5 hours or less. 3
If it is less than 0 minutes, the esterification rate will be low, making it impossible to obtain a polymer with a sufficient molecular weight. If the time exceeds 5 hours, the esterification rate is sufficient, but the coloring and thermal stability of the polymer are adversely affected due to corrosion of the reactor material.

In the polycondensation reaction, the reaction temperature is gradually raised over 1 to 10 hours, and the final temperature is 240 to 350°C, preferably 280 to 350°C.
The temperature was raised to 350°C to proceed with polycondensation.

Further, in order to speed up the reaction rate, the reaction may be carried out under a reduced pressure atmosphere.

In this production method, it is possible to obtain a final molecular weight polymer by the method described below, or it is also possible to increase the molecular weight by solid phase polymerization after producing a prepolymer.

The target polymer of the present invention is hydroxybenzoic acid (■)
, dihydroxy compound (■), dicarboxylic acid (III)
It is a copolymer formed by polycondensation of

Examples of the structural unit (1) of this copolymer include P-hydroxybenzoic acid, m-hydroxybenzoic acid, θ, 6-acid, P-(4-hydroxyphenoxy)benzoic acid, 2-hydroxy-6-naphthoic acid, 1 -Hydroxy-4-naphthoic acid, 1-hydroxy-5-naphthoic acid, etc., and one or more of these can be used.

Examples of the structural unit (■) include hydroquinone, chlorohydroquinone, methylhydroquinone, phenylhydroquinone, resorcinol, 4,4°-dihydroxydiphenyl, 4,4'-dihydrobinzophenone, 4,4
° -dihydroxydiphenylmethane, 4,4° -dihydroxydiphenyl ether, 4,4° -dihydroxydiphenyl sulfone, 4.4゛ -dihydroxydiphenyl sulfide, 2,2'-bis(4-hydroxyphenyl)propane, 2,6-dihydroxy Examples include naphthalene, 2°7-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, and 1,4-dihydroxynaphthalene, and one or more of these can be used.

At least one of the structural units (II[) is isophthalic acid, which is contained in an amount of 5% by weight or more based on the total dicarboxylic acids. If the isophthalic acid is less than 5% by weight based on the total dicarboxylic acids, the esterification reaction will be different when the reaction is carried out while removing the by-product acetic acid and when the reaction is carried out without removing the by-product acetic acid. Although a slight effect on coloring and thermal stability is observed in the latter case, it is not significant. Examples of dicarboxylic acids other than isophthalic acid include terephthalic acid, 4,4°-dicarboxydiphenyl, 2,6-dicarboxynaphthalene, 27-dicarboxynaphthalene, 1,5-dicarboxynaphthalene,
1,2-bis(4-carboxyphenoxy)ethane, 1
．． 4-dicarboxynaphthalene, etc., and one of these
A species or two or more species can be used.

(Effect of the invention) The present invention improves coloring and thermal stability by preparing an ester derivative while removing by-product acetic acid during the esterification reaction in the polycondensation reaction for producing an aromatic copolyester. Excellent polymers can be obtained.

(Examples) The present invention will be explained in more detail by Examples, but the present invention is not limited to these Examples.

Example I P-hydroxybenzoic acid 10.21Icg4.4°
-Biphenol 4.65kg terephthalic acid
3.32kg isophthalic acid
0.91kg acetic anhydride 15.29
Icg The above raw materials were charged into a 501 reaction tank, heated to 150° C. with stirring, and then reacted for 3 hours while removing by-product acetic acid from the system. The acetic acid concentration in the reaction mixture at that time was 10% by weight.

Subsequently, the temperature was raised to 300° C. over 4 hours while removing by-product acetic acid, and the reaction was continued at that temperature for 1 hour.

The polycondensation reaction was stopped when the stirring torque increased by 2.5 kgm, and the mixture was cooled while stirring to obtain 18 Ic g of prepolymer. Next, the temperature of the prepolymer was raised from room temperature to 310° C. over 10 hours, and solid phase polymerization was further performed using the warm melon for 6 hours.

The melt viscosity of the resulting polymer was 1800 poise at a temperature of 340°C and a shear rate of 1.0'5 ec-'.

It was. At this time, by-product acetic acid was not removed from the system.

The temperature was further increased to 300° C. over 4 hours while removing by-product acetic acid, and the reaction was continued at that temperature for 1 hour.

The polycondensation reaction was stopped when the stirring torque increased by 2.5 kgm, and the mixture was cooled while stirring to obtain 9.18 kg of prepolymer. Next, the temperature of the prepolymer was raised from room temperature to 310° C. over 10 hours, and solid phase synthesis was further performed at that temperature for 6 hours.

The melt viscosity of the resulting polymer was 2000 poise at a temperature of 340 DEG C. and a shear rate of 10'5 ec-'.

Comparative example 1 P-hydroxybenzoic acid 10.21 kg 4.4°
-Biphenol 4.65kg terephthalic acid
3.32kg isophthalic acid
0.91kg Acetic anhydride 15.29k
gThe above raw materials were charged into a 501 reaction tank, and heated for 15 minutes while stirring.
Reflux at 0°C for 3 hours to perform esterification Comparative Example 2 P-hydroxybenzoic acid 9.36kg4.4'
-Biphenol 6.31kg terephthalic acid
5.82kg isophthalic acid
200g acetic anhydride 15.20Ic
gThe above raw materials were charged into a 501 reaction tank, and heated for 15 minutes while stirring.
After heating to 0℃, while removing by-product acetic acid from the system,
A time reaction was performed. The acetic acid concentration in the reaction mixture at that time was 13% by weight.

Subsequently, the temperature was raised to 300° C. over 4 hours while removing by-product acetic acid, and the reaction was continued at that temperature for 1 hour.

The polycondensation reaction was stopped when the stirring torque increased by 0.5 kgm, and the mixture was cooled while stirring to obtain 18 kg of prepolymer.

Next, the temperature of the prepolymer was raised from room temperature to 330° C. over 13 hours, and solid phase polymerization was further performed at that temperature for 6 hours.

The melt viscosity of the resulting polymer was 650 poise at a temperature of 390 DEG C. and a shear rate of 10'5 ec-'.

The mixture was refluxed at 150°C for 3 hours to perform an esterification reaction.

At this time, by-product acetic acid was not removed from the system.

The temperature was further increased to 300° C. over 4 hours while removing by-product acetic acid, and the reaction was continued at that temperature for 1 hour.

When the stirring torque increased by 0.5 kgm, the polycondensation reaction was stopped and the mixture was cooled while stirring to obtain 18 kg of prepolymer.

Next, the temperature of the prepolymer was raised from room temperature to 330° C. over 13 hours, and solid phase polymerization was further performed at that temperature for 6 hours.

The melt viscosity of the grated polymer was 700 poise at a temperature of 390°C and a shear rate of 10'secml.

Comparative Example 3 9, 36 kg 6.311 cg 5, 82 kg 00 g 15.201 cg P-hydroxybenzoic acid 4,4'-biphenol terephthalic acid isophthalic acid acetic anhydride The above raw materials were charged in a reaction tank and stirred. Table 1 shows the coloration and thermal decomposition temperature of the polymer prepared in Comparative Example 1.2.3. In Comparative Example 1, the by-product acetic acid was not removed from the system during the esterification reaction, so the hue was poor and the thermal decomposition temperature, which is one of the indicators of thermal stability, was 13°C lower. . In Comparative Examples 2 and 3, the content of isophthalic acid is 3.3% by weight based on the total dicarboxylic acids, and even if the by-product acetic acid is removed from the system during the esterification reaction (Comparative Example 2), Even if it is not removed (Comparative Example 3), no significant difference is observed in hue and thermal decomposition temperature. Therefore, in the polycondensation reaction for producing an aromatic copolyester of the present invention, a polymer with excellent coloring and thermal stability can be obtained by preparing an ester derivative while removing by-product acetic acid during the esterification reaction. The gains are clear. The hue is 5M-4-2 manufactured by Suga Test Instruments.
The whiteness (W) and yellowness (Y) were determined by Δp1 using a model color computer, and the thermal decomposition temperature was determined using a DS manufactured by Seiko Electronics Co., Ltd.
Illumination at 40°C/min under nitrogen atmosphere using C-200 type
? J was decided.

Part 1 table

Claims (1)

[Claims] (1) An aromatic copolyester consisting of hydroxybenzoic acid, dicarboxylic acid, and a dihydroxy compound, in which at least one of the dicarboxylic acids is isophthalic acid, and the aromatic copolyester contains 5% by weight or more of isophthalic acid based on the total dicarboxylic acid. 1. A method for producing an aromatic copolyester by an esterification method, which comprises reducing the acetic acid concentration in the reaction mixture after the esterification reaction to 15% by weight or less, and then carrying out a polycondensation reaction.