JP2006307006A - Method for manufacturing aromatic polyester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an aromatic polyester by using a reaction vessel for acetylation and a vessel for condensation, wherein the amount of a substance adhered to a partial condenser installed to the condensation vessel and consequently the number of operations for blocking the tube of the partial condenser is reduced and the frequency required to clean the partial condenser is reduced. <P>SOLUTION: The method comprises: transforming an acetylated reaction solution prepared by acetylating an aromatic polyester monomer with acetic anhydride in a reaction vessel; and subjecting the solution to polycondensation by heating to obtain an aromatic polyester. The method is characterized by refluxing a substance, which has low boiling point and effuses from the condensation vessel, by maintaining the temperature of a cooling medium in the partial condenser, which is installed to the condensation vessel, lower than the boiling point of the substance while the acetylated reaction solution is transported from the acetylation reaction vessel to the condensation vessel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an aromatic polyester. Specifically, the present invention relates to a method for producing an aromatic polyester capable of reducing deposits adhering to a partial condenser installed in a condensation polymerization tank when producing an aromatic polyester 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, the method described in Patent Document 1 cannot completely prevent deposits such as low-molecular compounds from adhering to the tube of the condenser, and the heat transfer capability decreases as the batch reaction is repeated. Over time, it will cause tube obstruction. In that case, the operation was stopped and regular chemical cleaning was performed, leading to a decrease in productivity.
JP 2000-212264 A

  The object of the present invention is to reduce the deposits adhering to the partial condenser installed in the polycondensation tank in the method for producing an aromatic polyester using the acetylation reaction tank and the condensation polymerization tank. It is an object of the present invention to provide a method for producing an aromatic polyester that can reduce clogging and reduce the frequency of cleaning of a partial condenser.

  In order to solve such problems, the present inventors diligently studied a method for producing an aromatic polyester by condensation polymerization. As a result, the acetylation reaction solution obtained by acetylation is transferred from the acetylation reaction tank to the condensation polymerization tank. During this time, the temperature of the refrigerant in the partial condenser installed in the condensation polymerization tank is set to be equal to or lower than the boiling point of the low boiling substance distilled from the condensation polymerization tank, so that the low-boiling substances are refluxed. The present invention has been completed by finding out that it can be reduced.

  That is, the present invention produces an aromatic polyester by transferring 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 heating to cause condensation polymerization. In this method, while the acetylation reaction solution is transferred from the acetylation reaction tank to the condensation polymerization tank, the temperature of the refrigerant of the partial condenser installed in the condensation polymerization tank is equal to or lower than the boiling point of the low boiling point distilled from the condensation polymerization tank. And a method for producing an aromatic polyester, characterized by refluxing low-boiling substances.

  According to the present invention, in the method for producing an aromatic polyester using an acetylation reaction tank and a condensation polymerization tank, the deposits attached to the partial condenser installed in the condensation polymerization tank are reduced, and as a result, the tube of the partial condenser is reduced. Since the blockage can be reduced and the frequency of cleaning the reducer can be reduced, the productivity can be 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)
(In the formula, 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 and the like. 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 is heated to cause 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. After completion of the condensation polymerization reaction, the aromatic polyester 7 is extracted from the condensation polymerization tank 2.

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.

  In the condensation polymerization tank, a partial condenser is installed between the condensers that cool and condense the low-boiling substances. Conventionally, during the transfer of the acetylation reaction solution, the condensation polymerization reaction proceeds as well. Most of the low-boiling substances are cooled and condensed by the condenser via the partial condenser, but in the present invention, the low-boiling substances are distilled from the condensation polymerization tank at the temperature of the refrigerant of the partial condenser. The low boiling point is refluxed at a temperature not higher than that, preferably not higher than 80 ° C. As a result, the low-boiling substances are totally refluxed, the partial condenser is washed, and the deposits adhering to the partial condenser are reduced. Instead of the refrigerant temperature of the partial condenser, the gas temperature at the outlet of the partial condenser may be controlled to 100 ° C. or lower, whereby the low-boiling substances are similarly totally refluxed.

  During the transfer of the acetylation reaction solution to the condensation polymerization tank, if the temperature of the reaction solution transferred to the condensation polymerization tank is less than 140 ° C., the amount of low-boiling substances to be refluxed tends to decrease. If the cleaning effect is reduced and the temperature exceeds 250 ° C., low molecular weight compounds increase in the low boiling point, which is not preferable.

  The transfer time of the acetylation reaction solution is usually 5 to 30 minutes. If the transfer time is lengthened or the total reflux is continued after completion of the transfer, the cleaning effect of the partial condenser is increased, but this is not preferable because the batch reaction cycle is extended and the productivity is lowered. The polycondensation reaction is carried out while distilling low boilers.

  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.

  Since the temperature of the solution is low during the transfer of the acetylation reaction solution to the condensation polymerization tank, the low molecular weight compound contained in the low boiling point product is small. Distilled at this stage is mainly acetic acid produced by acetylation reaction and unreacted acetic anhydride. Therefore, the low-boiling substance distilled during the transfer is refluxed by the partial condenser, so that the adhering substance adhering to the partial condenser can be washed and reduced.

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.

  During the condensation polymerization reaction, a portion of the low-boiling product distilled out is condensed and refluxed by the partial condenser, and most of the low-boiling product is cooled and condensed by the condenser via the partial condenser. Collected in a tank or the like. Most of the low molecular compounds contained in the low-boiling substances are condensed in the partial condenser and recovered in the condensation polymerization tank. Low boiling product distilled from the condenser to the condenser until the low boiling product recovered by the condenser reaches 50 to 90% by weight with respect to the theoretical recovery of low boiling product Is preferably controlled within a temperature range of about 80 to 150 ° C, preferably 100 to 150 ° C. Here, the theoretically recovered amount of low-boilers is the weight of acetic acid, the weight of unreacted acetic anhydride, and the ester groups of raw material monomers, all obtained by condensation polymerization. It represents the total weight of alcohol, phenol, etc. obtained on the assumption.

  When the solution temperature in the condensation polymerization tank reaches 250 ° C. or more and the end of the reaction is reached, the amount of low molecular compounds in the low-boiling product distilled from the condensation polymerization tank increases, but the amount of acetic acid produced by the reaction decreases. This leads to a decrease in the amount of reflux in the partial condenser, and the low molecular weight compound tends to adhere to the partial condenser tube. The adhering material remains as it is, and gradually closes the condenser while repeating the batch reaction. While transferring the acetylation reaction solution from the acetylation reaction tank to the condensation polymerization tank, the refrigerant of the condenser installed in the condensation polymerization tank. By reducing the boiling point of the low-boiling product to the boiling point of the low-boiling product distilled from the condensation polymerization tank, washing the deposits, reducing the amount of deposits, and reducing the blockage of the partial condenser Can do.

  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 acetylation reaction solution was transferred to a 4.5 m ³ condensation polymerization tank equipped with a vertical stirrer over about 20 minutes. During the transfer, the jacket temperature of the condensation polymerization tank was 200 ° C., and the solution temperature was 145 ° C. In the condensation polymerization tank, a vertical multi-tube heat exchanger was installed as a partial condenser, and the refrigerant temperature of the partial condenser being transferred was set to 80 ° C. The outlet gas temperature of the partial condenser changed at 80 to 100 ° C.
The sight glass at the bottom of the condenser confirmed that no condensate had come out. That is, it was confirmed that the low boiling product distilled from the condensation polymerization tank was totally refluxed by the partial condenser.
After completion of the transfer, the temperature of the refrigerant in the partial condenser was changed to 110 ° C., and while stirring, the solution was heated to 300 ° C. while distilling out low-boiling substances, and held at 300 ° C. for 60 minutes. Thereafter, the condensation polymerization tank was sealed, pressurized to 0.1 MPa with nitrogen, and the aromatic polyester was removed while cooling with a belt cooler in this state.

  After repeating the batch condensation polymerization reaction 30 times in the same manner as described above, when the opening of the partial condenser was checked, 3 (2%) of 130 tubes showed a tendency to block.

Comparative Example 1
The same procedure as in Example 1 was performed except that the refrigerant temperature of the partial condenser during the transfer of the acetylation reaction liquid to the condensation polymerization tank was set to 110 ° C. During the transfer, the outlet gas temperature of the partial condenser was about 120 ° C., and it was confirmed with a sight glass that a part of acetic acid distilled from the condensation polymerization tank was condensed in the condenser.

  After repeating the batch condensation polymerization reaction 30 times in the same manner as described above, when the opening of the partial condenser was checked, 46 (35%) of 130 tubes showed a tendency to block.

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 Partial condenser 5 Condenser 6 Sight glass 7 Aromatic polyester 8 Condensate 9 Uncondensed gas

Claims (5)

  In the method of producing an aromatic polyester by transferring an acetylation reaction solution obtained by acetylating aromatic polyester raw material monomers and acetic anhydride in an acetylation reaction tank to a condensation polymerization tank and heating the condensation polymerization, During the transfer of the acetylation reaction solution from the acetylation reaction tank to the condensation polymerization tank, the temperature of the refrigerant in the partial condenser installed in the condensation polymerization tank is reduced below the boiling point of the low boiling substance distilled from the condensation polymerization tank. A process for producing an aromatic polyester, characterized in that the process is refluxed.   The method for producing an aromatic polyester according to claim 1, wherein the temperature of the refrigerant in the partial condenser is 80 ° C or lower.   2. The method for producing an aromatic polyester according to claim 1, wherein the low-boiling substances are totally refluxed.   The method for producing an aromatic polyester according to claim 1, wherein the outlet gas temperature of the partial condenser is 100 ° C or lower. 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.

Images