JPH0580931B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing polyester, and more specifically, it relates to a method for producing polyester, and more specifically, a method for producing polyester with excellent color tone that exhibits high ultrathin viscosity in a short period of time, and in particular, polyester that has thermotropic liquid crystallinity. It's about how to do it. (Prior art) Polyester has been widely accepted for use as general molded products, but many polyesters have insufficient mechanical properties such as flexural strength and flexural modulus. Therefore, it was not suitable for fields requiring high physical properties. In recent years, there has been an increasing demand for materials with excellent strength, rigidity, heat resistance, chemical resistance, etc., regardless of whether they are fibers, films, or molded products. WJ Jackson has already reported a thermotropic liquid crystalline polyester made of polyethylene terephthalate and 4-hydroxybenzoic acid as a pioneer in polyesters with such high physical properties, and this thermotropic liquid crystalline polyester has attracted attention. It is worshiped. This thermotropic liquid crystalline polyester has mechanical properties that are several times higher than ordinary thermotropic polyesters that do not exhibit liquid crystalline properties, and we have discovered new possibilities for highly functional polymers. Generally, this thermotropic liquid-compatible polyester is produced by contacting polyethylene terephthalate and 4-acetoxybenzoic acid in the first step of production to depolymerize the polyethylene terephthalate through an acidolysis reaction, and then using the depolymerized product in the second step. It is produced by polycondensation. However, this manufacturing method has the following two drawbacks. That is, the polycondensation reaction rate in the second step is extremely slow, resulting in low productivity. Furthermore, it is difficult to produce thermotropic liquid crystalline polyesters with high intrinsic viscosity. Measures to solve these problems are currently being actively researched and many patents have been proposed. For example, JP-A No. 60-221412 discloses a method in which an aromatic oxycarboxylic acid and a polyalkylene terephthalate are brought into contact in the presence of an acetylating agent. This method also results in a reduction in the reaction rate, since it is only necessary to add an amount of acid anhydride sufficient to acetylate the hydroxyl group of the oxycarboxylic acid (the aromatic oxycarboxylic acid and the acid anhydride are used in equivalent amounts). The promoting effect was still insufficient. (Problems to be Solved by the Invention) As described above, in the conventional technology, even though productivity can be improved to some extent, productivity is still low, and the polyester that can be obtained has reached its limit. However, even if a polyester with a high intrinsic viscosity could be obtained, it would take an extremely long time to produce it, resulting in poor color tone of the resulting polyester. Therefore, the main object of the present invention is to produce polyester with high intrinsic viscosity and excellent color tone, which is especially suitable for fibers, films, and other molded products, and in particular, with thermotropic liquid crystallinity and excellent physical properties, in a short time. It lies in manufacturing. (Means for Solving the Problems) As a result of intensive research into a method for producing polyester that does not have the above-mentioned problems, the present inventors found that aromatic oxycarboxylic acid, polyalkylene terephthalate with a specific intrinsic viscosity, It has been found that it is extremely effective to mix the acid anhydrides of lower fatty acids in an amount that exceeds the sum of the number of equivalents of all hydroxyl groups and the number of equivalents of all glycol end groups, and then to complete the polycondensation. , arrived at the present invention. That is, the present invention, when producing a polyester from an aromatic oxycarboxylic acid component represented by the formula () and a polyalkylene terephthalate component, uses an aromatic oxycarboxylic acid and an intrinsic viscosity of 0.2.
polyalkylene terephthalate of dl/g or less,
Mixing an acid anhydride of a lower fatty acid in an amount exceeding the sum of the number of equivalents of all the hydroxyl groups of the aromatic oxycarboxylic acid and the number of equivalents of all the glycol end groups of the polyalkylene terephthalate, and then completing the polycondensation. The object of the present invention is to provide a method for producing a polyester having an intrinsic viscosity of at least 0.5 dl/g.

[In the formula, Ar represents a divalent aromatic group. However, the aromatic ring may be substituted with a substituent.] The intrinsic viscosity [η] of the polyester produced by the method of the present invention is: It is at least 0.5 dl/g, preferably 0.5-1.0 dl/g, optimally 0.6-0.8 dl/g. Unless the intrinsic viscosity is at least 0.5 dl/g, various physical properties such as the desired bending properties, etc.
Mechanical properties are poor. The polyalkylene terephthalate having an intrinsic viscosity of 0.2 dl/g or less used in the production of polyester in the present invention is, for example, any of various known homopolymers and copolymers such as polyethylene terephthalate, polybutylene terephthalate, etc. It includes monomers such as bis(β-hydroxyethyl) terephthalate, but polyethylene terephthalate is particularly suitable, and the intrinsic viscosity of such polyethylene terephthalate is 0.2 dl/g or less, preferably about 0.1 dl/g. It is. If the intrinsic viscosity becomes too high beyond these ranges, the resulting polyester tends to lose its randomness, and only the aromatic oxycarboxylic acid component locally constitutes the homopolyester, which precipitates from the melt as crystals. This may be undesirable as it may become a foreign substance. The aromatic oxycarboxylic acid used in the production of polyester in the present invention has the above formula ()
Any known aromatic oxycarboxylic acid represented by the above formula can be used, but in order to obtain a thermotropic liquid crystalline polyester, the para-oriented one is basically used because it plays the rigid part of the thermotropic liquid crystalline polyester to be produced. It is necessary that a compound with a neutral or amphi orientation is selected. Preferred specific examples include 4-hydroxybenzoic acid, 1-hydroxy-4-naphthoic acid, 4-hydroxy-3-
Examples include compounds such as methylbenzoic acid, 4-hydroxy-3-chlorobenzoic acid, and 2-hydroxy-6-naphthoic acid, but 4-hydroxybenzoic acid is most suitable. However, it is also possible to copolymerize compounds with ortho, meta, ana, shrimp, kata, peri, and pros orientations as long as the liquid crystallinity of the polyester to be produced is not impaired. Hereinafter, as an example to which the method of the present invention can be particularly suitably applied, a polyester obtained from polyethylene terephthalate as the first structural unit and 4-hydroxybenzoic acid as the second structural unit will be exemplified.
The manufacturing method of the present invention will be explained. The ratio of the first structural unit to the second structural unit is preferably 5:95 to 95:5 in molar ratio, particularly preferably 30:70 to 70:30, and in order to obtain a thermotropic liquid crystalline polyester, The ratio of the first structural unit to the second structural unit is preferably a molar ratio of 50:50 to 50:50.
It may be selected appropriately within the range of 70:30. In the production method of the present invention, the lower fatty acid anhydride is used in an amount exceeding the sum of the number of equivalents of all hydroxyl groups of 4-hydroxybenzoic acid and the number of equivalents of all glycol end groups of polyalkylene terephthalate, and
It is necessary to mix with hydroxybenzoic acid and polyalkylene terephthalate. Therefore, the number of hydroxyl groups in aromatic oxycarboxylic acid, that is, the number of moles of aromatic oxycarboxylic acid, and when polyethylene terephthalate (PET) is used as polyalkylene terephthalate, when the intrinsic viscosity is 0.1 dl/g, it is 1200. 〜1500 equivalents/ton−
When the intrinsic viscosity of PET is 0.2 dl/g, it is appropriate to use an acid anhydride of a lower fatty acid having a weight of 600 to 700 equivalents/ton-PET or more. Examples of the acid anhydrides of lower fatty acids include acid anhydrides of lower fatty acids having 1 to 8 carbon atoms, such as acetic anhydride, propionic anhydride, monochloroacetic anhydride, dichloroacetic anhydride, trichloroacetic anhydride, monobromoacetic anhydride, and dibromoanhydride. Acetic acid, tribromoacetic anhydride, monofluoroacetic anhydride, difluoroacetic anhydride, trifluoroacetic anhydride, bromoacetic anhydride, glutaric anhydride, maleic anhydride, succinic anhydride, β-bromopropionic anhydride, butyric anhydride,
Isobutyric anhydride, propyl acetic anhydride, valeric anhydride,
Examples include pivalic anhydride, but acetic anhydride is particularly preferably used in view of price and boiling point, and in the following description, acetic anhydride (Ac ₂ O) will be used as representative. In the present invention, 4-hydroxybenzoic acid,
It is particularly suitable to charge a polyester containing polyethylene terephthalate as a main component and acetic anhydride in the amount described above into a reactor, and to react according to the following reaction schedule. First, (a) react in an inert atmosphere at a temperature not exceeding 150°C for 30 minutes to 4 hours. If the temperature exceeds 150℃ or the reaction time exceeds 30℃
If it is less than 1 minute, the reaction will be insufficient and the reaction rate in the polycondensation step may become slow, which is not preferable. On the other hand, even if the reaction is allowed to take place for more than 4 hours, the effect will only reach a saturated state, which is also unfavorable from an economic point of view. Then (b) in an inert atmosphere,
React at a temperature of 150°C to 230°C for 30 minutes to 8 hours. If the temperature exceeds 230°C or the reaction time is less than 30 minutes, the reaction will be insufficient, and the intrinsic viscosity of the final polyester may not increase or 4-hydroxybenzoic acid may become homogeneous as described above. This is undesirable because polyester is formed, 4-hydroxybenzoic acid becomes 4-acetoxybenzoic acid and scatters, and Ac ₂ O scatters. on the other hand,
Even if the reaction is carried out for more than 8 hours, the effect not only reaches a saturated state but also only impairs the color tone of the obtained polyester, which is also not preferable. (c) 230℃ to 250℃ to 290℃ in an inert atmosphere;
When the temperature reaches 270° C. at the latest, depressurization is started using a depressurization schedule that takes at least 60 minutes, preferably 90 minutes, to reach fluvacium. If the temperature exceeds 290°C, this will only impair the color tone of the resulting polyester, while if the vacuum schedule is less than 60 minutes, 4-hydroxybenzoic acid may become 4-acetoxybenzoic acid and scatter. Both are undesirable. Then, (d) acetic acid (AcOH) is distilled out in the molten phase for a polycondensation reaction at a temperature of usually 250 to 290°C under a high vacuum of about 1 torr for several tens of minutes to several hours. , polyester can be produced. In the present invention, in addition to the above two structural units, for example, 2,2-bis(4'-hydroxyphenyl)propane, hydroquinone, resorcinol,
4,4'-dihydroxybiphenyl, 1,6-hexanediol, cyclohexanedimethanol, pentaerythritol, naphthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, 2,2
-bis(4'-carboxyphenyl)propane, bis(4-carboxyphenyl)methane, bis(4'-carboxyphenyl)propane, bis(4'-carboxyphenyl)methane,
-carboxyphenyl) ether, etc. are suitably used as the copolymerization component. Further, although a catalyst is usually used in the polycondensation reaction, when producing polyester 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. It will be done. Such metal compounds include antimony, titanium, germanium, tin, zinc, aluminum,
Compounds such as magnesium, calcium, manganese, sodium or cobalt are used, while organic sulfonic acid compounds include compounds such as sulfosalicylic acid, o-sulfobenzoic anhydride (OSB), and antimony trioxide (CS).
and OSB are particularly preferably used. The amount of the catalyst added is usually 0.1 x 10 ^-4 to 100 x 10 -4 mol, preferably 0.1 x 10 ^-4 mol per mol of polyester structural unit.
0.5×10 ^-4 ~50×10 ^-4 mol, optimally 1×10 ^-4 ~10
×10 ^-4 mol is used. Further, according to the method of the present invention, for example, thermal characteristic values include a melting point of 200°C or higher, a heat distortion temperature of 60°C or higher, preferably a melting point of 220°C or higher, and a heat distortion temperature of 100°C.
Above, optimal melting point is 220-250℃, heat distortion temperature is 100℃
A polyester having a temperature of up to 130° C. can be obtained, and such a polyester is preferable because it has both heat resistance and various physical and mechanical properties. (Function) The reason why polyester having high intrinsic viscosity and excellent color tone can be produced in a short time by the method of the present invention is not fully understood, but it is inferred as follows. Ru. Since the acid anhydride of a lower fatty acid is added in an amount exceeding the number of equivalents of all the glycol end groups of the polyalkylene terephthalate and reacted with the polyalkylene terephthalate, the glycol end of the polyalkylene terephthalate is effectively acetylated, resulting in polycondensation. The reaction rate increases significantly. At the same time, since the acid anhydride of lower fatty acid is added in an amount exceeding the number of equivalents of the total hydroxyl groups of the aromatic oxycarboxylic acid, there is no need to use expensive acyl aromatic oxycarboxylic acid, and The reaction rate during polycondensation is even faster than when using carboxylic acid. Since no acyl aromatic oxycarboxylic acid is used, the acyl aromatic oxycarboxylic acid does not form a homopolyester by itself, and there are extremely few foreign substances. (Examples) Hereinafter, the present invention will be explained in more detail by giving examples. In the examples, [η] of the polymer was determined from the solution viscosity measured at 20° C. in a mixed solvent of equal weights of phenol and tetrachloroethane. Further, the total glycol end groups of the polyalkylene terephthalate were determined by subtracting the number of carboxyl end groups described below from the total number of end groups calculated back from the intrinsic viscosity. Furthermore, the carboxyl terminal group was determined by titration with a 1/10 normal sodium hydroxide solution in benzyl alcohol. In addition, thermotropic liquid crystallinity was confirmed using a Leitz polarizing microscope equipped with a hot stage. Reference Example 1 Terephthalic acid and ethylene glycol were esterified by a conventional method to obtain bis-(β-hydroxyethyl) terephthalate and/or its low polymer (BHET) with an esterification reaction rate of 95%. Add CS to this BHET as the structural unit of polyester 1
By adding 2×10 ⁻⁴ mol based on the mole and appropriately selecting the polycondensation time, polyethylene terephthalate (PET) of various [η] shown in Table 1 was obtained. Reference Example 2 Dimethyl terephthalate and 1,4-butanediol were transesterified by a conventional method to distill methanol, and then tetrabutyl titanate was added as a catalyst in an amount of 5% per mole of polyester structural unit.
×10 ^-4 mole was added for preliminary polycondensation, and [η] was 0.15.
dl/g polybutylene terephthalate (PBT)
was manufactured. Example 1 PET obtained in Reference Example 1 with [η] of 0.1 dl/g, total glycol end group equivalent number of 1, and 123 equivalents/ton,
4-hydroxybenzoic acid (4HBA) in a molar ratio of 1:1.5 (the number of equivalents of hydroxyl group is 7500 for 1 ton of PET)
9000 equivalents/ton-PET of acetic anhydride were added, and the mixture was stirred and mixed at 150° C. for 1 hour. After that, 5
The temperature was gradually raised to 230°C over time, and the mixture was stirred and mixed for 2 hours. Then another 2 hours
The temperature was raised to 270°C, and then depressurization was started on a depressurization schedule that would take 90 minutes to reach fluvacium (1 torr). At a final temperature of 270℃,
As a result of a polycondensation reaction in the melt phase under reduced pressure of 0.3 torr for 3 hours, a thermotropic liquid crystal with an intrinsic viscosity of 0.75, an L value of 75.2, an a value of -1.1, and a b value of 8.9, with excellent color tone and no foreign substances was obtained. A polyester was obtained. Examples 2 to 4, Comparative Examples 1 to 5 Instead of the polyester used in Example 1, various [η] polyesters obtained in Reference Example 1 were used, and the amount of acetic anhydride added was variously changed. was reacted in substantially the same manner as in Example 1 to obtain a thermotropic liquid crystalline polyester. Results first
Shown in the table. Examples 5 to 8 Thermotropic liquid crystalline polyesters were obtained by reacting in substantially the same manner as in Example 1, except that the reaction conditions were changed. The results are shown in Table 2. Example 9 A polyester having no thermotropic liquid crystallinity was obtained by reacting in substantially the same manner as in Example 1 except that the molar ratio of PET and 4-hydroxybenzoic acid was 2:1. The results are shown in Table 2. Example 10 A reaction was carried out in almost the same manner as in Example 1 except that 4-hydroxybenzoic acid and 3-hydroxybenzoic acid were used as aromatic oxycarboxylic acids at a molar ratio of 7:3 to obtain a thermotropic liquid phase. Obtained polyester that does not. The results are shown in Table 2. Example 11 2-oxy-6 as aromatic oxycarboxylic acid
- A thermotropic liquid crystalline polyester was obtained by reacting in substantially the same manner as in Example 1 except that naphthoic acid was used. The results are shown in Table 2. Example 12 A thermotropic liquid crystalline polyester was obtained by reacting in substantially the same manner as in Example 3, except that the polybutylene terephthalate obtained in Reference Example 2 was used instead of PET. The results are shown in Table 2.

【table】

【table】

[Table] (Effects of the Invention) According to the present invention, (1) A polyester having a high intrinsic viscosity and excellent color tone and physical and mechanical strength can be obtained. (2) Sublimation of raw materials is minimal, polymerization time is short, and polyester free of foreign substances can be produced economically. (3) The thermotropic liquid crystalline polyester obtained by the present invention is extremely useful as a material used in applications requiring particularly high physical properties.

Claims (1)

[Scope of Claims] 1 When producing a polyester from an aromatic oxycarboxylic acid component represented by formula () and a polyalkylene terephthalate component, aromatic oxycarboxylic acid and a polyalkylene having an intrinsic viscosity of 0.2 dl/g or less are used. Mixing terephthalate and an acid anhydride of a lower fatty acid in an amount exceeding the sum of the number of equivalents of all hydroxyl groups of the aromatic oxycarboxylic acid and the number of equivalents of all glycol end groups of the polyalkylene terephthalate,
A method for producing a polyester having an intrinsic viscosity of at least 0.5 dl/g, characterized in that the polycondensation is then completed. [Formula] (In the formula, Ar represents a divalent aromatic group. However, the aromatic ring may be substituted with a substituent.) 2. A patent claim in which the resulting polyester is a thermotropic liquid crystalline polyester. A method for producing polyester according to scope 1. 3. The method for producing polyester according to claim 1 or 2, wherein the polyester production conditions include the following steps. (a) 30°C under an inert atmosphere at a temperature not exceeding 150°C;
Step (b) React for 30 minutes to 4 hours at a temperature of 150 to 230°C under an inert atmosphere.
Step (c) of reacting for 8 hours Under an inert atmosphere, raise the temperature from 230°C to 250°C to 290°C, and when it reaches 270°C at the latest, start reducing the pressure with a reduced pressure schedule that takes at least 60 minutes to reach fluvacium. Step (d) Step 4 of polycondensation under reduced pressure at a temperature of 250°C to 290°C for several tens of minutes to several hours The polyalkylene terephthalate is polyethylene terephthalate, the aromatic oxycarboxylic acid is 4-hydroxybenzoic acid, and the lower Claim 1, wherein the acid anhydride of fatty acid is acetic anhydride.
2. A method for producing a polyester according to item 2 or 3.