JPH0610255B2 - Method for producing liquid crystalline polyester - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a thermotropic liquid crystalline polyester, and more specifically, to a thermotropic liquid crystalline compound having a high intrinsic viscosity in a short time and having an excellent color tone. The present invention relates to a method for producing polyester.

(Prior Art) In recent years, there has been an increasing demand for materials excellent in strength, rigidity, heat resistance, chemical resistance, etc., regardless of whether they are fibers, films or molded products.

Polyester has been widely accepted as a general molded product, but many polyesters have
Since various mechanical properties such as flexural modulus were insufficient, it was not suitable for fields requiring high physical properties.

Therefore, as a polyester suitable for applications requiring high strength, WJ Jackson published in Journal of Polymer Science Polymer Chemistry Edition, Volume 14 (1976), p. 2043, polyethylene terephthalate and 4-hydroxybenzoic acid. Since the thermotropic liquid crystalline polyester consisting of and has been reported, such thermotropic liquid crystalline polyester has been attracting attention. In this reference, Jackson reported that this thermotropic liquid crystalline polyester has a rigidity of 5 times or more, a strength of 4 times or more, and an impact strength of 25 times or more of polyethylene terephthalate, and a new possibility for highly functional polymers. Showed sex.

However, it has been found that the method for producing the thermotropic liquid crystalline polyester has the following drawbacks. That is, a polyester fragment is prepared by contacting polyalkylene terephthalate and acetoxy aromatic carboxylic acid in the first step of production, and the intrinsic viscosity of this polyester fragment is increased in the second step, but the reaction rate at that time is increased. Since it is extremely slow, the productivity is low, and at the same time, it is difficult to produce a thermotropic liquid crystalline polyester having a high intrinsic viscosity.

Measures for solving these problems are still being actively researched and various patents have been proposed. For example, Japanese Patent Application Laid-Open No. 60-221422 discloses a method of contacting an oxyaromatic carboxylic acid and a polyalkylene terephthalate in the presence of an acetylating agent, but this proposal is also basically theoretical. As expected, the contact ratio between the oxyaromatic carboxylic acid and the acetylating agent is basically equivalent, and as a result, this method was still insufficient in terms of the effect of promoting the reaction rate.

(Problems to be Solved by the Invention) As described above, in the prior art, although the productivity can be improved to some extent, the productivity is still low, and the limit of the obtained polyester is the same. Even if a polyester having an insufficient viscosity or a high intrinsic viscosity is obtained, it takes an extremely long time to produce the polyester, so that the color tone of the obtained polyester is inferior.

Therefore, the main object of the present invention is to
It is an object of the present invention to provide a method for producing a polyester having a thermotropic liquid crystallinity having a high intrinsic viscosity and an excellent color tone, which is particularly suitable for other molded articles in a short time.

(Means for Solving Problems) As a result of earnest research on a method for producing a polyester having thermotropic liquid crystallinity which does not have the above problems, the present inventors have found that oxyaromatic carboxylic acid and a specific amount of low-grade It has been found that it is extremely effective to mix an acid anhydride of a fatty acid with a polyalkylene terephthalate having a specific intrinsic viscosity and then complete polycondensation.
The present invention has been reached.

That is, the present invention relates to an oxyaromatic carboxylic acid represented by the formula (I) and 1.05 to 1.50 times the equivalent of 2 carbon atoms.
At least 0 to 5 are mixed with an acid anhydride of a lower fatty acid and a polyester having alkylene terephthalate as a main constituent and having an intrinsic viscosity of at least 0.3 dl / g, and then polycondensation is completed. .5 dl
The gist is a method for producing a thermotropic liquid crystalline polyester having an intrinsic viscosity of / g.

(In the formula, Ar represents a divalent aromatic group. However, the aromatic ring may be substituted with a substituent.) The main constituent component of alkylene terephthalate used in the production of the thermotropic liquid crystalline polyester in the present invention. Examples of the polyester to be used include polyethylene terephthalate, polybutylene terephthalate, and various copolymers thereof. Of these, polyethylene terephthalate is particularly preferable. As the polyester, those having an intrinsic viscosity of 0.3 dl / g or more are used, and those having an intrinsic viscosity of 1.4 dl / g or less are also preferable, and particularly preferable ones have an intrinsic viscosity of 0.5 to 1.0 dl / g.
g. If the intrinsic viscosity is less than 0.3 dl / g, the concentration of all glycol unterminated groups will be high, and the water produced by the condensation reaction will increase the reaction-inactive phenolic-OH groups, slowing down the reaction rate and increasing the It becomes difficult to obtain a polymer having a degree of polymerization.

Examples of the oxyaromatic carboxylic acid used for producing the polyester in the present invention include any known oxyaromatic carboxylic acid represented by the above formula (I). Aromatic compounds having a substantially para-orientation are often selected because they are responsible for the rigid portion, and preferred specific examples include 4-hydroxybenzoic acid, 1-hydroxy-4-naphthoic acid, and 4-hydroxy-3-methylbenzoic acid. , 4-hydroxy-3-chlorobenzoic acid, 2-hydroxy-6-naphthoic acid and the like, and a mixture of these may be used as necessary. 4-hydroxybenzoic acid, 2-hydroxy-6- Naphthoic acid is particularly preferred. However, an ortho- or meta-orienting compound can be copolymerized as long as it does not impair the liquid crystallinity of the resulting polyester. Examples of the acid anhydride of lower fatty acid used for producing the polyester in the present invention include acid anhydrides of lower fatty acid having 2 to 5 carbon atoms, such as acetic anhydride, propionic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroanhydride. Acetic acid, monobromoacetic anhydride,
Dibromoacetic anhydride, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, pivalic anhydride, etc. are mentioned, but acetic anhydride, pyropionic acid anhydride, anhydrous Trichloroacetic acid is particularly preferably used.

In the present invention, the amount of the oxyaromatic carboxylic acid used is preferably 5 to 95 mol% with respect to the number of moles of the polyester having alkylene terephthalate as a main constituent,
It is particularly preferably 30 to 70 mol%, and may be appropriately selected so as to obtain a so-called thermotropic liquid crystalline polyester.

In the production method of the present invention, the amount of the acid anhydride of lower fatty acid to be used is 1.05 to 1.50 times equivalent, preferably 1.1 to 1.2 times equivalent to the oxyaromatic carboxylic acid.

In the production method of the present invention, first, a polyester containing oxyaromatic carboxylic acid, acid anhydride of lower fatty acid and alkylene terephthalate as main constituents in an inert atmosphere, preferably 300 ° C. or lower, particularly preferably 100 to 250.
Mix at 100 ° C, more preferably 100-150 ° C. In the present invention, the mixture is then heated and melted in an inert atmosphere until the mixture becomes uniform. Heating and melting is usually 210-300 ℃
Tens of minutes to several hours, preferably 5 to 120 at 250 to 300 ° C
Min, optimally 250 to 280 ° C for 30 to 60 minutes. That is, after mixing the three at 100 to 150 ° C, stir and mix at 100 to 150 ° C for at least 30 minutes, then raise the temperature to 250 to 280 ° C for at least 5 hours and heat to dissolve until uniform. Is particularly preferable. If the heating time from 250 to 280 ° C. exceeds 5 hours, the production of a homopolymer of oxyaromatic carboxylic acid is preferentially performed, which may cause a problem that it remains as a foreign substance in the polymer, which is not preferable.

Polycondensation reaction is usually 200-300 ℃, preferably 250-300 ℃
The temperature may be gradually reduced under the temperature of 10 to 10 torr, preferably less than 1.0 torr for several tens of minutes to several hours. A catalyst is usually used in the polycondensation reaction, but when the polyester is produced by the method of the present invention, for example, one or more compounds selected from various metal compounds or organic sulfonic acid compounds are used. To be As such metal compounds, compounds such as antimony, titanium, germanium, tin, zinc, aluminum, magnesium, calcium, manganese, sodium or cobalt are used, while as organic sulfonic acid compounds, sulfosalicylic acid, o-sulfoanhydride are used. Benzoic acid (OSB)
Compounds such as are used, but antimony trioxide (CS) and OS
B is particularly preferably used. The amount of the catalyst added is usually 0.1 × with respect to 1 mol of the constitutional unit of polyester.
10 ^{−4 to} 100 × 10 ⁻⁴ mol, preferably 0.5 × 10 ⁻⁴ to 50 × 1
0 ^-4 mol, optimally 1 x 10 ^-4 to 10 x 10 ^-4 mol, is used.

(Function) The reason why the thermotropic liquid crystalline polyester having high intrinsic viscosity and color tone can be produced in a short time by the method of the present invention is not fully understood, but Is speculated as.

The acid anhydride of the lower fatty acid reacts with the water contained in the raw material to form the lower fatty acid, which is distilled out of the system. Therefore,
The hydrolysis of the polyester containing alkylene terephthalate as the main constituent does not lower the degree of polymerization, and the hydrolysis of the oxyaromatic carboxylic acid does not generate a reaction-inactive phenolic-OH group.

Since the glycolic end group in the polyester mainly composed of alkylene terephthalate is esterified by the acid anhydride of the lower fatty acid, the reaction of the glycolic end group with the acyloxyaromatic carboxylic acid is inactive phenolic- No formation of OH groups occurs.

(Examples) Hereinafter, the present invention will be described more specifically with reference to Examples.

In addition, in the examples, the intrinsic viscosity [η] of the polymer was determined from the solution viscosity measured at 20 ° C. in a mixed solvent by weight such as phenol-ethane tetrachloride. The thermotrobic liquid crystallinity was confirmed with a Leitz polarization microscope with a hot stage. The composition of the polymer was confirmed by quantitative analysis by gas chromatography after methanolysis.

Example 1 Terephthalic acid and ethylene glycol were esterified by a conventional method to obtain an esterified product having an esterification reaction rate of 95%. This esterified product was charged into a polycondensation reactor, and 2 × 10 ^-4 mol of antimony trioxide was added to 1 mol of the acid component,
The polycondensation reaction was carried out for 3 hours under stirring at 270 ° C. under reduced pressure. When a part of the produced polyester was sampled and the intrinsic viscosity was measured, it was 0.63 dl / g.

The polyester in the molten state, 4-hydroxybenzoic acid in an equimolar amount to the polyester, and 1.2 times the equivalent of acetic anhydride to 4-hydroxybenzoic acid were mixed and stirred at 270 ° C. for 1 hour in a nitrogen atmosphere. However, the reaction mixture became a uniform solution state. Then, the pressure was gradually reduced, and finally the polycondensation reaction was carried out at 1.0 torr for 5 hours.

The polymer obtained had an intrinsic viscosity of 0.69 dl / g and a color tone of L value 7
The values were 4.9, a-value-1.3, and b-value 12.0, showing thermotropic liquid crystallinity. The composition of the obtained polymer was 50 mol% of the polyethylene terephthalate component and 50 mol% of the paraoxybenzoic acid component, which were in agreement with the charged composition. The solution for viscosity measurement was completely transparent, and no insoluble matter was found.

Examples 2 to 11 Except that the intrinsic viscosity of polyethylene terephthalate, the molar ratio of 4-hydroxybenzoic acid and acetic anhydride, and the mixing temperature of polyethylene terephthalate, 4-hydroxybenzoic acid and acetic anhydride were changed as shown in Table 1. In the same manner as in Example 1, a thermotropic liquid crystalline polyester was obtained.

The results of Examples 1 to 11 are shown in Table 1.

Example 12 Terephthalic acid and ethylene glycol were esterified by a conventional method to obtain an esterified product having an esterification reaction rate of 95%. This esterified product was charged into a polycondensation reactor, 2 × 10 ⁻⁴ mol of antimony trioxide was added to 1 mol of the acid component, and the polycondensation reaction was carried out under reduced pressure at 270 ° C. for 3 hours with stirring. This was dispensed into chips by a conventional method. When the intrinsic viscosity of the obtained polyester was measured, it was 0.64 dl / g.

In a separate polycondensation reactor, the polyester chips, 4-hydroxybenzoic acid equimolar to the polyester, 4-
1.2 times the equivalent of acetic anhydride to hydroxybenzoic acid
After charging at 140 ° C. and stirring at 140 ° C. for 1 hour under a nitrogen atmosphere, the temperature was raised to 270 ° C. over 3 hours while stirring, and the reaction mixture became a uniform solution state. Then, the pressure was gradually reduced, and finally the polycondensation reaction was carried out at 1.0 torr for 5 hours.

The obtained polymer has an intrinsic viscosity of 0.68 dl / g and a color tone of L value 7
The values were 4.3, a-value 1.2, and b-value 9.0, showing thermotropic liquid crystallinity. The composition of the obtained polymer was 50 mol% of polyethylene terephthalate component and 50 mol% of paraoxybenzoic acid component, which was in agreement with the charged composition.
The solution for viscosity measurement was safe and transparent, and no insoluble matter was found.

Examples 13 to 22 The molar ratio of 4-hydroxybenzoic acid and acetic anhydride, the mixing temperature of polyethylene terephthalate, 4-hydroxybenzoic acid and acetic anhydride, and the heating time to 270 ° C. were changed as shown in Table 2. A thermotropic liquid crystalline polyester was obtained in the same manner as in Example 12 except for the above.

The results of Examples 12 to 22 are shown in Table 2.

Example 23 Instead of using 4-hydroxybenzoic acid alone, 3-
A thermotropic liquid crystalline polyester was obtained by the same reaction as in Example 1 except that hydroxybenzoic acid and 4-hydroxybenzoic acid were used in a molar ratio of 2: 8.

The results are shown in Table 3.

Example 24 A thermotropic liquid crystalline polyester was obtained by the same reaction as in Example 1 except that 2-hydroxy-6-naphthoic acid was used as the oxyaromatic carboxylic acid. The results are shown in Table 3.

Example 25 Transesterification reactor with dimethyl ester of TPA and 1,4
After charging butanediol and carrying out a transesterification reaction at a temperature of 220 ° C. to distill off methanol, the reaction product was charged into a batch type polymerization reaction device, and TBT (tetrabutyl titanate) was used as a catalyst to form a polyester structural unit 1. Add 5 × 10 ^-4 mol to mol and under reduced pressure of 1.0 torr, 240 ℃
The polycondensation reaction was carried out for 3 hours. When a part of the produced polyester was sampled and the intrinsic viscosity was measured, it was 0.82dl
It was / g.

This polyester and 4-molar equivalent of polyester
Hydroxybenzoic acid and 1.2 times the equivalent of acetic anhydride to 4-hydroxybenzoic acid were mixed, and the mixture was heated under a nitrogen atmosphere to give 270
After stirring for 1 hour at ℃, the reaction mixture became a homogeneous solution state. Then, gradually reduce the pressure, and finally 1.0
The polycondensation reaction was performed for 5 hours at torr.

The polymer obtained had an intrinsic viscosity of 0.69 dl / g and a color tone of L value 7
The value was 4.3, the value a was -1.2, and the value b was 9.3, indicating thermotropic liquid crystallinity. The composition of the obtained polymer was 50 mol% of the polyethylene terephthalate component and 50 mol% of the paraoxybenzoic acid component, which were in agreement with the charged composition.
The solution for viscosity measurement was completely transparent, and no insoluble matter was found.

Comparative Example 1 A thermotropic liquid crystalline polyester was obtained in the same manner as in Example 1 except that acetic anhydride was not used. The obtained polyester has an intrinsic viscosity of 0.42 dl / g and a color tone of L value 71.1, a
The value was -1.8 and the b value was 18.3.

Comparative Example 2 The amount of acetic anhydride used was 1.
A thermotropic liquid crystalline polyester was obtained in the same manner as in Example 1 except that the amount was 0 times equivalent. The obtained polyester had an intrinsic viscosity of 0.36 dl / g, a color tone of L value of 69.9 and an a value of -2.
The 0 and b values were 19.1.

Comparative Example 3 A thermotropic liquid crystalline polyester was obtained in the same manner as in Example 1 except that only 4-acetoxybenzoic acid was used instead of using 4-hydroxybenzoic acid and acetic anhydride. The polyester obtained had an intrinsic viscosity of 0.37 l / g and a color tone of L value 73.2, a value -1.5, and b value 14.2.

Comparative Example 4 The amount of acetic anhydride used was 1.
A thermotropic liquid crystalline polyester was obtained in the same manner as in Example 12 except that the amount was 0 equivalent. The obtained polyester had an extreme extreme of 0.39 dl / g, color tone of L value 73.1, a value of -1.3,
The b value was 13.9.

(Effect of the Invention) According to the method of the present invention, it is possible to produce a thermotropic liquid crystalline polyester having an excellent color tone in a short time.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-55-94930 (JP, A) JP-A-62-277427 (JP, A)

Claims (4)

[Claims] 1. An oxyaromatic carboxylic acid represented by the formula (I), an acid anhydride of a lower fatty acid having 2 to 5 carbon atoms in an amount of 1.05 to 1.50 times equivalent thereto, and an alkylene terephthalate as a main constituent component. A method for producing a thermotropic liquid crystalline polyester having an intrinsic viscosity of at least 0.5 dl / g, which comprises mixing with a polyester having an intrinsic viscosity of at least 0.3 dl / g, and then completing polycondensation. . (In the formula, Ar represents a divalent aromatic group.
The aromatic ring may be substituted with a substituent. ) 2. An oxyaromatic carboxylic acid, an acid anhydride of a lower fatty acid, and a polyester containing alkylene terephthalate as a main constituent are mixed at 150 ° C. or lower, and then 100
The method for producing a polyester according to claim 1, wherein the mixture is heated and stirred at ˜150 ° C. for at least 30 minutes, then the mixture is uniformly heated and dissolved within at least 5 hours, and then the polycondensation reaction is completed. 3. A polyester having an alkylene terephthalate as a main constituent, which has an intrinsic viscosity of at least 0.5 dl / g.
The method for producing a polyester according to the item. 4. The production of a polyester according to claim 1, 2 or 3 wherein the oxyaromatic carboxylic acid is 4-hydroxybenzoic acid and the acid anhydride of the lower fatty acid is acetic anhydride. Method.