JP2006307007A - Method for producing aromatic polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an aromatic polyester with which sticking materials sticking to a wall surface of a vapor-phase part of a polycondensation vessel are reduced and foreign materials in products can resultantly be reduced to simultaneously reduce both clogging frequency of a take-out nozzle of the polycondensation vessel and washing frequency of the polycondensation vessel in the method for producing the aromatic polyester by heating an acetylation reaction solution obtained by acetylating raw material monomers of the aromatic polyester with acetic anhydride and carrying out the polycondensation. <P>SOLUTION: The method for producing the aromatic polyester is characterized as follows. The temperature of the sidewall and upper lid in the vapor-phase part of the polycondensation vessel are heated to a temperature not lower than (liquid temperature in the polycondensation vessel-20°C) during heating and carrying out of the polycondensation reaction in the method for transferring the acetylation reaction solution obtained by acetylating the raw material monomers of the aromatic polyester with the acetic anhydride in an acetylation reaction vessel to the polycondensation vessel, heating the reaction solution and conducting the polycondensation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an aromatic polyester. More specifically, the present invention relates to a method for producing an aromatic polyester capable of reducing deposits on the inner wall of a gas phase portion of a condensation polymerization tank when the aromatic polyester is produced by condensation polymerization.

A method for producing an aromatic polyester by polycondensing a reaction product obtained by acetylating a raw material monomer selected from aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids and aromatic diols with acetic anhydride is well known. In this case, the low-boiling product distilled from the condensation polymerization tank includes low-molecular compounds such as raw material monomers or acetylated monomers.
Distillation of these low molecular weight compounds leads to a decrease in product yield, product quality fluctuations, and clogging due to adhesion of low molecular weight compounds to the condenser. A method for recovering low molecular weight compounds and the like by controlling the temperature of the low boilers distilled from the partial condenser to 80 to 150 ° C. while the recovered amount of the product is 50 to 90% of the theoretical amount ( (See Patent Document 1).

However, in the method described in Patent Document 1, it is impossible to prevent sublimates such as low molecular compounds from adhering to the wall surface of the gas phase portion of the condensation polymerization tank, and it grows as the batch reaction is repeated, and eventually becomes a reaction solution. Drop off and mix in product. Since the adhering matter is colored or altered by the heat history, it becomes a foreign matter when mixed in the product. Moreover, when the lump of deposits falls off, the extraction nozzle of the condensation polymerization tank is closed. Therefore, the operation must be stopped and periodic chemical cleaning must be performed, leading to a reduction in productivity.
JP 2000-212264 A

  An object of the present invention is to reduce deposits on the gas phase inner wall of a condensation polymerization tank in a method for producing an aromatic polyester, to improve product quality and at the same time to reduce the frequency of washing the condensation polymerization tank. The object is to provide a method for producing an aromatic polyester.

  In order to solve such problems, the present inventors have intensively studied a method for producing an aromatic polyester by condensation polymerization. As a result, by controlling the temperature of the gas phase wall of the condensation polymerization tank, the deposits on the wall The present invention has been completed.

  That is, the present invention is to transfer an acetylation reaction solution obtained by acetylating aromatic polyester raw monomers and acetic anhydride in an acetylation reaction tank to a condensation polymerization tank, and subjecting the aromatic polyester to condensation polymerization by heating. In the production method, the temperature of the side wall and the upper lid of the gas phase portion of the condensation polymerization tank is heated to (the liquid temperature in the condensation polymerization tank −20 ° C.) or higher while the condensation polymerization reaction is performed by heating. This is a method for producing an aromatic polyester.

  According to the present invention, in the method for producing an aromatic polyester, the amount of deposits on the inner wall of the gas phase portion of the condensation polymerization tank is reduced, and the deposits are prevented from being mixed into the product to become foreign matters, thereby improving the quality. In addition, since the frequency of washing the condensation polymerization tank can be reduced, productivity is improved.

  Examples of the raw material monomers for the aromatic polyester used in the present invention include aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids, and aromatic diols.

As aromatic hydroxycarboxylic acids, for example, the following general formula (1),
HO-X-COOR ¹ (1)
(Wherein R ¹ represents hydrogen, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 16 carbon atoms, and X represents a divalent aromatic group).

  Specific examples of the aromatic hydroxyloxycarboxylic acids include p-hydroxybenzoic acid, p-hydroxybenzoic acid methyl, p-hydroxybenzoic acid propyl, p-hydroxybenzoic acid phenyl, p-hydroxybenzoic acid benzyl, p- (4 -Hydroxyphenyl) benzoic acid, methyl p- (4-hydroxyphenyl) benzoate, 2-hydroxy-6-naphthoic acid, methyl 2-hydroxy-6-naphthoate and phenyl 2-hydroxy-6-naphthoate Is done. Of these, p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid and the like are preferable.

As aromatic dicarboxylic acids, for example, the following general formula (2),
R ² —O—CO—Y—CO—O—R ² (2)
(Wherein R ² represents hydrogen, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 16 carbon atoms, or an aryl group having 6 to 16 carbon atoms, and Y represents a divalent aromatic group.) The thing shown by is mentioned.

  Specific examples of the aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4′-dicarboxydiphenyl, 1,2-bis (4-carboxyphenoxy) ethane, 2,5-dicarboxynaphthalene, 2,6 -Carboxynaphthalene, 1,4-dicarboxynaphthalene, 1,5-dicarboxynaphthalene, dimethyl terephthalate, dimethyl isophthalate, diphenyl terephthalate, diphenyl isophthalate, 4,4'-dimethoxycarbonyldiphenyl, 2,6-dimethoxy Examples thereof include carbonylnaphthalene, 1,4-dichlorocarbonylnaphthalene and 1,5-diphenoxycarbonylnaphthalene. Of these, terephthalic acid, isophthalic acid, 2,6-dicarboxynaphthalene, and the like are preferable.

As aromatic diols, for example, the following general formula (3),
HO-Z-OH (3)
(Wherein Z represents a divalent aromatic group).

  Specific examples of the aromatic diols include hydroquinone, resorcin, catechol, 4,4′-dihydroxydiphenyl, 4,4′-hydroxybenzophenone, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenylethane, 4,4'-dihydroxydiphenyl ether, 2,2-bis (4-hydroxyphenyl) propane, 4,4'-hydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, 2,6-dihydroxynaphthalene and 1,5- Examples thereof include hydroxynaphthalene. Of these, hydroquinone, resorcin, 4,4'-dihydroxydiphenyl, 2,2-bis (4-hydroxyphenyl) propane, 4,4'-dihydroxydiphenylsulfone, and the like are preferable.

  The use ratio of the aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids and aromatic diols is not particularly limited, but the aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids and aromatic diols are usually added to a total of 100 moles. An aromatic hydroxycarboxylic acid is selected in the range of 30 to 80 mol, an aromatic dicarboxylic acid in an amount of 10 to 35 mol, and an aromatic diol in an amount of 10 to 35 mol.

FIG. 1 is a schematic view of an example of an apparatus used in the present invention. Aromatic polyester raw material monomers and acetic anhydride are supplied to the acetylation reaction tank 1, and an acetylation reaction is carried out under heating and reflux. The acetylation reaction solution obtained by acetylation is transferred to the condensation polymerization tank 2 through the transfer pipe 3 and heated by the jacket 10 for condensation polymerization. During the condensation polymerization reaction, most of the low-boiling substances distilled from the condensation polymerization tank are cooled and condensed by the condenser 5 via the partial condenser 4, and the condensate 8 is recovered and contained in the low-boiling substances. Most of the low molecular weight compounds are condensed in the partial condenser and collected in the condensation polymerization tank, and the uncondensed gas 9 is discharged from the condenser. Heating / cooling means are attached to the side wall and the upper lid of the gas phase portion of the condensation polymerization tank. The means is cooled when the acetylation reaction solution is received, and is heated during the condensation polymerization by heating. After completion of the condensation polymerization reaction, the aromatic polyester 7 is extracted from the condensation polymerization tank 2.
In addition, the side wall and upper cover of the gas phase part of the condensation polymerization tank are portions that are not covered with a jacket at the upper part of the condensation polymerization tank.

The acetylation reaction is carried out under reflux, and the temperature and pressure are not particularly limited, but are usually carried out at 140 to 150 ° C. under normal pressure. The acetylation reaction is carried out for 0.5 to 5 hours after the start of reflux. The acetylation reaction solution obtained by acetylation usually contains unreacted raw material monomers, acetylation reaction products, acetic acid, unreacted acetic anhydride, and the like.
As the material for the acetylation reaction tank, the acetylation reaction solution preferably has corrosion resistance, and GL or the like is usually used.

The acetylation reaction solution is transferred to a condensation polymerization tank and heated to carry out a condensation polymerization reaction.
In the present invention, the acetylation reaction solution may be a solution in which raw material monomers in which some raw material monomers are acetylated in advance are dissolved in acetic acid as a solvent.
Examples of the acetylated raw material monomers include p-acetoxybenzoic acid and 4,4′-diacetoxydiphenyl.

The material of the condensation polymerization tank is preferably resistant to corrosion with respect to the acetylation reaction solution. Specifically, SUS316, SUS316L, duplex stainless steel, nickel-molybdenum alloy, impervious graphite, titanium, zirconium, GL And tantalum and the like. Specific examples of the nickel-molybdenum-based alloy include Hastelloy-B (registered trademark of Mitsubishi Materials Corporation), Hastelloy-C (registered trademark of Mitsubishi Materials Corporation), and the like.
The condensation polymerization tank and its blade shape may be of a known type. Specifically, in the case of a vertical stirring tank, etc., multistage paddle blades, turbine blades, double helicam blades, saddle blades, comb blades, etc. Is used.

  As described above, the acetylation reaction is performed at 140 to 150 ° C., and after completion of the reaction, the acetylation reaction solution is transferred from the acetylation reaction tank to the condensation polymerization tank at substantially the same temperature. During the transfer, the condensation polymerization tank is heated so that the temperature of the reaction solution transferred to the condensation polymerization tank is maintained at 140 ° C to 250 ° C.

  While the acetylation reaction solution is transferred to the condensation polymerization tank, low boiling point vapor is generated from the liquid surface of the condensation polymerization tank. A part of the low-boiling substances is cooled and refluxed on the wall surface of the gas phase portion of the condensation polymerization tank, that is, the side wall and the upper lid surface. By setting the temperature of the wall surface of the gas phase part to 100 ° C. or lower, preferably 80 ° C. or lower, it is preferable to increase the reflux amount and wash the deposits on the inner wall generated by the previous batch reaction.

The polycondensation reaction is usually carried out by gradually heating the solution in the polycondensation tank to 350 ° C. under normal pressure while distilling low boiling substances. Depending on the type of aromatic polyester, it is further maintained for about 0.5 to 5 hours while maintaining the same temperature.
If the final temperature of the polycondensation solution is maintained below 270 ° C., the polycondensation tends to be slow, and if maintained above 350 ° C., side reactions such as decomposition of the resulting aromatic polyester tend to occur. It is in.

  Examples of the low boilers distilled from the condensation polymerization tank include low molecular weight compounds, acetic acid and unreacted acetic anhydride. The low molecular compound is specifically a constituent component of an aromatic polyester such as raw material monomers such as aromatic carboxylic acids and acetylated monomers. In addition, water, alcohols and phenols generated by the polymerization reaction may be included.

  While conducting the condensation polymerization reaction by heating, the heating is carried out so that the temperature of the side wall and the upper lid of the gas phase portion of the condensation polymerization tank becomes equal to or higher than the liquid temperature in the condensation polymerization tank -20 ° C. The temperature is preferably in the range of 150 ° C to 350 ° C. When the temperature of the side wall and the upper lid is lower than (the liquid temperature in the condensation polymerization tank −20 ° C.), the low molecular weight compound contained in the low boiling point vapor is deposited on the inner wall surface of the gas phase portion and adheres. Even when the temperature of the side wall and the upper lid exceeds 350 ° C., there is an effect of preventing adhesion, but it is preferable to carry out at 350 ° C. or lower because it is restricted by the type of heat source and the energy cost increases.

Since the liquid temperature is low during the transfer from the acetylation reaction tank to the condensation polymerization tank, the low boiling substances are almost all acetic acid and acetic anhydride, and low molecular compounds are not included. As the liquid temperature rises, the amount of low-molecular compounds contained in the low boiling point increases, particularly at 240 ° C. or higher, and a large amount of low-molecular compounds adhere to the inner wall surface of the gas phase. However, adhesion can be reduced by heating the temperature of the side wall and the upper lid to a temperature equal to or higher than (the liquid temperature in the condensation polymerization tank-20 ° C). Furthermore, it is preferable to heat the temperature of the side wall and the upper lid to be equal to or higher than the melting point of the low molecular weight compound distilled from the condensation polymerization tank. As a result, the low molecular weight compound melts and adhesion is unlikely to occur. Specific examples of the low molecular weight compound that easily adheres during the polycondensation reaction include p-hydroxybenzoic acid (melting point: 216 ° C.), 4,4-dihydroxydiphenyl (melting point: 280 ° C.), and acetylated monomers. Monomers such as p-acetoxybenzoic acid (melting point: 194 ° C.), 4,4-diacetoxydiphenyl (melting point: 160 ° C.) and the like, and the temperature of the side wall and the lid is above these melting points, specifically about 300 ° C. It is preferable to heat above.
In addition, the temperature of the side wall and the upper lid may be increased in accordance with the temperature increase of the solution in the condensation polymerization tank, or may be set to a high temperature in advance.

  Oil, an electric heater, steam, water, or the like is used as a heating / cooling means for the side wall and upper lid of the condensation polymerization tank. A method of fixing a tube through which a heat medium or refrigerant flows or a heat transfer tube of an electric heater to the outer wall surface with a metal fitting or the like is common, but a method of making the outer wall into a jacket structure is also effective. Cover the top of the tube or heat transfer tube with heat transfer cement, heat insulating material, etc. In addition, it is more preferable if the nozzle attached to the upper lid is similarly formed.

The temperature of the side wall and upper lid of the condensation polymerization tank is usually measured by a temperature sensor brought into contact with the outer wall surface.
The position of the temperature sensor is attached to a location that represents the surface temperature. It is preferable to install a plurality of them in order to increase the temperature measurement accuracy.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these.

Example 1
Aromatic polyester was produced using the apparatus shown in FIG.
1,000 kg (7,240 mol) of p-hydroxybenzoic acid, 435 kg (2,336 mol) of 4,4′-dihydroxydiphenyl, 300 kg (1,806 mol) of terephthalic acid, 100 kg (602 mol) of isophthalic acid and acetic anhydride 1347 kg (13,194 mol) was charged into a 4 m ³ acetylation reactor equipped with a vertical stirrer. The mixture was heated with stirring in a nitrogen gas atmosphere, and the reaction was carried out at a solution temperature of 145 ° C. for 3 hours in a total reflux state to complete the acetylation reaction.

The condensation polymerization tank was a 4.5 m ³ tank having a vertical stirrer, and a heat medium tube was wound around the side surface other than the jacket surface and the upper lid surface and covered with a heat insulating material. A temperature sensor was attached to the upper lid at one location so that the surface temperature could be measured.
The acetylation reaction solution was transferred to the condensation polymerization tank over about 20 minutes. During the transfer, the jacket temperature of the condensation polymerization tank was set to 200 ° C. The solution temperature was 145 ° C. During the transfer, the temperature of the heat medium tube was controlled so that the temperature of the upper lid surface was 80 to 100 ° C. After completing the transfer of the acetylation reaction solution, the temperature of the heat medium tube was set to 320 ° C. Thereafter, the solution in the condensation polymerization tank was heated to 300 ° C. The temperature of the upper lid was 200 ° C. at the start of temperature rise, but increased with the inner solution, reached 310 ° C. when the inner solution was 250 ° C., and thereafter maintained at about 310 ° C. until the end of extraction. In this process, the temperature of the upper lid was always higher than (liquid temperature in the condensation polymerization tank −20 ° C.). After keeping the inner solution at 300 ° C. for 5 hours, the aromatic polyester was extracted while cooling with a belt cooler.

  The batch condensation polymerization reaction was repeated 30 times in the same manner as described above. Then, when the condensation polymerization tank was opened and inspected, adhesion was observed in about 20% of the upper lid area. Further, during the batch condensation polymerization reaction of 30 to 35 times, the extraction nozzle was not clogged.

Comparative Example 1
This was carried out in the same manner as in Example 1 except that the temperature of the upper lid of the condensation polymerization tank was not controlled. The temperature of the upper lid of the condensation polymerization tank was always lower than (the liquid temperature in the condensation polymerization tank −20 ° C.) and increased from 100 ° C. to 200 ° C. as the liquid temperature increased.

  After repeating the batch condensation polymerization reaction 10 times in the same manner as described above, when the opening of the partial condenser was inspected, adhesion was observed on almost the entire upper lid. Further, when the batch condensation polymerization reaction was performed 10 to 15 times, the extraction nozzle was clogged, and the condensation polymerization tank was chemically washed.

It is the schematic of an example of the apparatus used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Acetylation reaction tank 2 Condensation polymerization tank 3 Transfer pipe 4 Condenser 5 Condenser 6 Sight glass 7 Aromatic polyester 8 Condensate 9 Uncondensed gas 10 Jacket 11 Heating / cooling means

Claims (5)

  In a method for producing an aromatic polyester by transferring an acetylation reaction solution obtained by acetylating raw material monomers and acetic anhydride of an aromatic polyester in an acetylation reaction tank to a condensation polymerization tank and heating and condensation polymerization, While performing the condensation polymerization reaction by heating, the temperature of the side wall and the upper lid of the gas phase portion of the condensation polymerization tank is heated to (liquid temperature in the condensation polymerization tank-20 ° C) or more. Production method.   2. The aromatic polyester according to claim 1, wherein the temperature of the wall surface and upper lid of the gas phase portion of the condensation polymerization tank is set to 100 ° C. or lower during the transfer of the acetylation reaction solution from the acetylation reaction tank to the condensation polymerization tank. Manufacturing method.   While conducting the condensation polymerization reaction by heating the condensation polymerization tank, the temperature of the wall surface and upper lid of the gas phase portion of the condensation polymerization tank is in the range of 150 ° C. to 350 ° C. (liquid temperature in the condensation polymerization tank −20 ° C.) or more. The method for producing an aromatic polyester according to claim 1, wherein the aromatic polyester is heated to a high temperature.   While performing the condensation polymerization reaction by heating the condensation polymerization tank, the temperature of the wall surface and the upper lid of the gas phase portion of the condensation polymerization tank is heated to the melting point of the low molecular weight compound distilled from the condensation polymerization tank. The manufacturing method of the aromatic polyester of Claim 1. 2. The process for producing an aromatic polyester according to claim 1, wherein the raw material monomers are aromatic hydroxylcarboxylic acids, aromatic dicarboxylic acids and aromatic diols.

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