JP4967385B2 - Cleaning method for aromatic polyester production equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an effective cleaning method for effectively washing away such an extraneous matter as polyester, etc., adhered to an aromatic polyester production apparatus comprised of a condensation polymerization tank having a partial condenser. <P>SOLUTION: The method for cleaning an aromatic polyester production apparatus comprised of a condensation polymerization tank having a partial condenser using a mixture of glycols and primary or secondary amines as a washing solvent while heating and refluxing the solvent comprises controlling an amount of vapor generated in the condensation polymerization tank and/or a temperature of a heat medium at inlet of the partial condenser so as to keep an outlet gas temperature of the partial condenser at not higher than the temperature of the partial condenser at the inlet of the heating medium at the first half of the washing operation, and to keep an outlet gas temperature of the partial condenser at not lower than the temperature of the heating medium at the inlet of the partial condenser at the second half of the washing operation. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a method for cleaning an aromatic polyester production apparatus.

Aromatic polyesters are used in various electronic parts and industrial parts because they are excellent in heat resistance and solvent resistance.
Aromatic polyester is obtained by condensing a reaction product obtained by acetylating raw material monomers of aromatic polyester with acetic anhydride, or a raw material monomer that has been partially acetylated in advance. An aromatic polyester is produced while heating and condensation using a polymerization tank, fractionating the distillate and collecting the condensate in the condensation polymerization tank (for example, Patent Document 1).
These polyesters remained attached to the apparatus and were not easy to remove. In order to remove the adhered polyester, a method of washing and removing by heating, total refluxing using glycols or using primary or secondary amines in combination with glycols is known (Patent Document 2). reference.).

However, the polyester blockage adhering to the partial condenser cannot be removed sufficiently, and since it is repeatedly subjected to a condensation polymerization reaction, it cannot be removed only by washing the solvent, and the equipment must be opened and physically removed. There wasn't. Not only does it take time to remove the attached polyester, but also the productivity is reduced due to the stoppage of equipment, so an effective cleaning method for an aromatic polyester production apparatus comprising a condensation polymerization tank equipped with a partial condenser is desired. ing.
JP 2004-331829 A JP-A-5-295392

  The objective of this invention is providing the method of wash | cleaning effectively deposits, such as polyester adhering to the aromatic polyester manufacturing apparatus which consists of a condensation polymerization tank provided with the partial condenser.

  As a result of intensive studies on a method for washing an aromatic polyester production apparatus comprising a condensation polymerization tank provided with a partial condenser, the present inventors have heated using a mixture of glycols and primary or secondary amines as a washing solvent, When washing while refluxing, the amount of steam generated in the condensation polymerization tank and / or the inlet temperature of the heat medium to the condenser is adjusted, and in the first half of the washing, the gas temperature at the outlet of the condenser is reduced. It is possible to easily remove the polyester adhering to the condenser by setting the gas temperature at the outlet of the condenser to be equal to or lower than the inlet temperature to the condenser in the latter half. The headline, the present invention has been reached.

  That is, the present invention provides a method for reducing the amount of condensation when an aromatic polyester production apparatus comprising a condensation polymerization tank equipped with a partial condenser is heated and refluxed using a mixture of glycols and primary or secondary amines as a cleaning solvent. By adjusting the amount of steam generated in the polymerization tank and / or the inlet temperature of the heating medium to the condenser, the outlet gas temperature in the first half of the washing should be lower than the inlet temperature of the heating medium of the condenser, and in the latter half Is a method for cleaning an aromatic polyester production apparatus, characterized in that the temperature of the gas at the outlet of the condenser is equal to or higher than the temperature at the inlet of the heat medium to the condenser.

  By this invention, the polyester etc. which have adhered to the aromatic polyester manufacturing apparatus which consists of a condensation polymerization tank which provided the partial condenser can be removed easily.

Hereinafter, the present invention will be described in detail.
Examples of the aromatic polyester in the present invention include polyesters such as polyethylene terephthalate, polybutylene terephthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, poly-1,4-cyclohexanedimethylene terephthalate, and p-hydroxybenzoic acid. And polyesters obtained from aromatic hydroxycarboxylic acids such as 2-hydroxy-6-naphthoic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid Examples thereof include liquid crystalline polyesters obtained from aromatic dihydroxy compounds such as hydroquinone, resorcin, 4,4′-dihydroxydiphenyl, and 2,6-dihydroxynaphthalene.

  The aromatic polyester is produced, for example, using aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids and aromatic diols as raw material monomers.

  Examples of aromatic hydroxyl carboxylic acids include p-hydroxybenzoic acid, methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, phenyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p- (4-hydroxy). And phenyl) benzoic acid, methyl p- (4-hydroxyphenyl) benzoate, 2-hydroxy-6-naphthoic acid, methyl 2-hydroxy-6-naphthoate and phenyl 2-hydroxy-6-naphthoate. . Of these, p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid and the like are preferably used.

  Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 4,4′-dicarboxydiphenyl, 1,2-bis (4-carboxyphenoxy) ethane, 2,5-dicarboxynaphthalene, and 2,6-carboxyl. Naphthalene, 1,4-dicarboxynaphthalene, 1,5-dicarboxynaphthalene, dimethyl terephthalate, dimethyl isophthalate, diphenyl terephthalate, diphenyl isophthalate, 4,4′-dimethoxycarbonyldiphenyl, 2,6-dimethoxycarbonylnaphthalene 1,4-dichlorocarbonylnaphthalene, 1,5-diphenoxycarbonylnaphthalene and the like. Of these, terephthalic acid, isophthalic acid, 2,6-dicarboxynaphthalene and the like are preferably used.

  Examples of 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-hydroxynaphthalene Etc. are exemplified. Of these, hydroquinone, resorcin, 4,4'-dihydroxydiphenyl, 2,2-bis (4-hydroxyphenyl) propane, 4,4'-dihydroxydiphenylsulfone and the like are preferably used.

  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. The range is selected from about 30 to 80 mol of the aromatic hydroxycarboxylic acid, about 10 to 35 mol of the aromatic dicarboxylic acid, and about 10 to 35 mol of the aromatic diol.

First, raw material monomers and acetic anhydride are reacted under reflux to obtain an acetylation reaction product. The temperature and pressure in the acetylation reaction are not particularly limited as long as the acetylation reaction solution is refluxed. Usually, the reaction is performed at about 140 to 150 ° C. under normal pressure. If the reaction temperature does not reach the reflux temperature, the reaction time tends to be longer. The acetylation reaction is carried out for about 1 to 5 hours after the start of reflux. The reaction solution obtained by acetylation usually contains unreacted raw material monomers, acetylated raw material monomers, acetic acid, unreacted acetic anhydride and the like.
As the material of the acetylation reaction tank, the acetylation reaction product preferably has corrosion resistance, and GL or the like is usually used.

The reaction product obtained by acetylation is charged into a condensation polymerization tank, and condensation polymerization is carried out. There may be a case of condensation polymerization using raw material monomers in which some raw material monomers are acetylated in advance. Examples of the acetylated raw material monomers include p-acetoxybenzoic acid and 4,4′-diacetoxydiphenyl.
A catalyst may be used to increase the reaction rate of the condensation polymerization. As a catalyst, for example,
Examples thereof include metal oxides and organic metal salts. Specific examples include germanium, tin, titanium, antimony, cobalt, manganese, and other oxides, acetates, oxalates, and the like.

The material of the condensation polymerization tank is preferably resistant to corrosion with respect to acetylation reaction products and the like. Specifically, SUS316, SUS316L, two-phase stainless steel, nickel-molybdenum alloy, impervious graphite, titanium, zirconium, GL and tantalum are used. Examples of commercially available nickel-molybdenum alloys include Hastelloy (R) B and Hastelloy (R) C.
In the case of a vertical stirring tank or the like, the condensation polymerization tank and its blades are formed using multistage paddle blades, turbine blades, double helicam blades, saddle blades, comb blades, and the like.
Note that the same tank may be used for the condensation polymerization tank and the acetylation reaction tank.

  The condensation polymerization is usually carried out by gradually raising the solution in the condensation polymerization tank to about 270 ° C. to 350 ° C. under normal pressure while distilling a low boiling point. 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 solution in the condensation polymerization tank is maintained below 270 ° C., the condensation polymerization tends to be slow, and if maintained above 350 ° C., side reactions such as decomposition of the resulting aromatic polyester may occur. Tend to occur.

  Low-boiling components distilled off from the condensation polymerization tank include low molecular weight compounds, acetic acid, unreacted acetic anhydride, etc. Of course, acetic acid, water, alcohol, phenol, etc. produced by the condensation polymerization reaction are also included. Yes. Among these, the low molecular weight compound is specifically a constituent component of an aromatic polyester such as raw material monomers such as aromatic carboxylic acids and acetylated monomers. If a large amount of the low molecular weight compound is distilled off from the condensation polymerization tank, the yield of the desired aromatic polyester may be reduced, or a product with a composition ratio of raw material monomers may not be obtained. Is not preferred because of problems such as not being stabilized.

The partial condenser is installed between the condensation polymerization tank and the condenser that cools the low boiling point. Most of the low boiling point is cooled and condensed by the condenser via the partial condenser, and is recovered outside the condensation polymerization tank. However, the low molecular weight compound in the low boiling part is almost completely condensed by the partial condenser. It is condensed and recovered in the condensation polymerization tank.
At this time, the temperature of the heat medium supplied to the partial condenser is controlled so that the temperature of the low boiling point distilled from the partial condenser is 115 ° C. to 145 ° C., preferably 120 ° C. to 135 ° C. To do. As a result, adhesion of a low molecular compound or the like to the partial condenser is reduced. Note that the temperature of the low boiling point is set in consideration of the types of raw material monomers and the charged composition. Note that the outlet of the partial condenser is slightly depressurized in order to condense low-boiling substances in the condenser.
When the temperature is lower than 115 ° C., the condensation in the partial condenser is increased, the amount of reflux increases, the temperature rise in the condensation polymerization tank is delayed, and the condensation polymerization reaction is delayed. Further, when the liquid is cooled and refluxed, the polyester may be locally hardened. In addition, the low molecular weight compound, which is a constituent component of aromatic polyester such as 145 ° C. and monomers, is distilled off from the condensation polymerization tank, resulting in a decrease in the yield of the desired aromatic polyester, The product cannot be obtained, which is not preferable.

  The liquid contact surface material of the voltage divider is a nickel-molybdenum alloy or nickel-molybdenum-chromium alloy. When represented by the alloy symbols described in JIS H4551, they are NiMo30Fe5, NiMo28, and NiMo16Cr15Fe6W4. Specific examples of commercially available products include Hastelloy (R) B and Hastelloy (R) C.

FIG. 1 is a view showing an outline of one embodiment of an aromatic polyester production apparatus comprising a condensation polymerization tank provided with a partial condenser.
An inert gas (usually nitrogen gas) 12 is supplied to the condensation polymerization tank 1 to replace the inside of the reaction system. A reaction product 11 obtained by acetylation is supplied to the condensation polymerization tank 1 and heated by a jacket to carry out a condensation polymerization reaction. The produced aromatic polyester 13 is taken out from the bottom of the condensation polymerization tank. In addition, the low boiling point produced is partially condensed by the partial condenser 2 and refluxed to the condensation polymerization tank. Uncondensed low-boiling substances are distilled from the condenser, condensed in the condenser 3 (the refrigerant is not shown), the recovered acetic acid 14 is taken out, and the exhaust gas 15 is discharged.

  In the partial condenser 2, the low boiling point thermometer 7 at the outlet of the partial condenser is used to measure the temperature of the low boiling point, and a predetermined temperature within the range of 115 ° C. to 145 ° C. (for example, 125 ° C.) The heating medium thermometer 6 measures and controls the heating medium temperature. In this example, the heat medium 16 circulates in the partial condenser through the heat medium circulation pump 4. A part of the new heat medium is supplied to the circulating heat medium via the heat medium control valve 9, and the return heat medium 17 corresponding to the new heat medium is taken out. The circulating heat medium is controlled by the heat medium control valve 8, a part of which is cooled by the heat medium cooler, and mixed with the remaining heat medium to adjust the temperature. The heating medium temperature supplied to the partial condenser 2 measured by the heating medium thermometer 6 is adjusted by the heating medium control valve 8 so that the temperature of the low boiling substance measured by the low boiling point thermometer 7 becomes a predetermined temperature. , So-called cascade control.

  The blockage state of the partial condenser is judged from the difference between the temperature of the low boiling point distilled from the partial condenser and the temperature of the heat medium supplied to the partial condenser. Specifically, when the difference between the temperature of the low boiling point distilled from the partial condenser and the temperature of the heat medium supplied to the partial condenser is 30 ° C. or more, polyester, low molecular weight compounds, etc. The adherence increases and is closing, so the divider is cleaned. Since the internal pressure rises rapidly due to clogging, it is difficult to grasp the clogging situation only by measuring the internal pressure, but when the internal pressure of the condensation polymerization tank exceeds 0.01 MPa (gauge pressure), the internal pressure tends to rise rapidly. Confirm that the difference between the temperature of the low boiling point distilled from the partial condenser and the temperature of the heat medium supplied to the partial condenser is 30 ° C. or more and that the internal pressure of the condensation polymerization tank is 0.01 MPa or more. The contractor may be washed.

  The aromatic polyester production apparatus of the present invention is washed while heating and refluxing using a mixture of glycols and primary or secondary amines to remove deposits such as polyester and low molecular weight compounds.

  Examples of glycols include trimethylene glycol, ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol. Among these, triethylene glycol (boiling point 287 ° C.) having a moderately high boiling point, inexpensive and easily available is preferable.

  Examples of the primary or secondary amines include alkyl monoamines such as diethylamine, propylamine, dipropylamine, butylamine, dibutylamine, and hexylamine, alkylpolyamines such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, and diethylenetriamine. , Aromatic amines such as aniline and benzylamine, and alkanolamines such as monoethanolamine, diethanolamine and triethanolamine. Among these amines, monoethanolamine (boiling point 171 ° C.) is preferable in consideration of the boiling point and price.

  A higher temperature at the time of washing is preferable because the washing effect is large. The washing time is 1 to 10 hours, preferably 2 to 8 hours.

  Regarding the quantitative relationship between amine and glycol, the amine concentration is suitably 5 to 50% by weight, preferably 7 to 30% by weight. If the amine concentration is less than 5% by weight, the effect of adding the amine is small, and if it exceeds 50% by weight, the reflux temperature cannot be increased, so the cleaning effect is rather deteriorated.

When washed in this manner, the polyester and the like adhering to the condensation polymerization tank are removed, but removal of the polyester and the like adhering to the partial condenser is insufficient, so in the present invention, it is generated in the condensation polymerization tank. By adjusting the amount of steam and / or the inlet temperature of the heat exchanger of the partial condenser, the temperature of the partial condenser outlet gas is set to be equal to or lower than the inlet temperature of the partial condenser heat medium in the first half of cleaning, and in the latter half, the partial condenser outlet gas The temperature is set to be equal to or higher than the temperature at the inlet of the heat medium divider.
In the first half of washing, the amount of evaporation from the condensation polymerization tank is suppressed and / or the temperature of the inlet of the heating medium to the condenser is lowered, and the temperature of the outlet of the condenser is less than the inlet temperature of the heating medium of the condenser. And Gradually increase the amount of evaporation from the condensation polymerization tank and / or increase the inlet temperature to the heat medium partial condenser, and in the latter half, set the partial outlet gas temperature to be higher than the inlet temperature to the heat medium partial condenser. Then, a part of the steam is distilled from the condenser.
Increasing the amount of evaporation from the condensation polymerization tank and / or raising the temperature of the inlet of the heat medium into the partial condenser is performed continuously or stepwise. When the heat medium is circulated through the partial condenser, the heat medium may not be sufficiently cooled, and may be performed by a method of gradually increasing the temperature of the heat medium by latent heat of condensation.

  The higher the temperature, the greater the cleaning effect, so it is preferable to carry out under pressure. In particular, since a mixture of glycols and primary or secondary amines is repeatedly used, the decomposed resin dissolves, the cleaning property is deteriorated, and the boiling point is lowered. Preferably.

  Hereinafter, a description will be given based on FIG. An inert gas (usually nitrogen gas) 12 is supplied to the condensation polymerization tank 1 to replace the inside of the system. A mixture 11 of glycols and primary or secondary amines is supplied to the condensation polymerization tank 1 and heated by the jacket, and the generated steam is partially condensed by the partial condenser 2 and refluxed to the condensation polymerization tank 1 to be uncondensed. The fraction is distilled from the condenser, condensed in the condenser 3 (the refrigerant is not shown), refluxed to the condensation polymerization tank 1, and the exhaust gas 15 is discharged.

  In the partial condenser 2, the heat medium temperature is measured and controlled by the heat medium thermometer 6. In this example, the heat medium 16 circulates in the partial condenser via the heat medium circulation pump 4. A part of the new heat medium is supplied to the circulating heat medium via the heat medium control valve 9, and the return heat medium 17 corresponding to the new heat medium is taken out. The circulating heat medium is controlled by the heat medium control valve 8, a part of which is cooled by the heat medium cooler 5, and mixed with the remaining heat medium to adjust the temperature.

In the first half of the washing, the amount of evaporation from the condensation polymerization tank is suppressed and / or the inlet temperature to the heat medium partial condenser is lowered, and the partial condenser outlet gas temperature is made lower than the inlet temperature of the partial heat exchanger. To do. At this time, normally, the inlet temperature (heat medium thermometer 6) of the heat medium to the partial condenser is about 40 to 110 ° C., and the partial gas outlet gas temperature (low boiling point thermometer 7) is room temperature to about 100 ° C. To do. Gradually increase the amount of evaporation from the condensation polymerization tank and / or increase the inlet temperature to the heat medium partial condenser, and in the latter half, set the partial outlet gas temperature to be higher than the inlet temperature to the heat medium partial condenser. Then, a part of the steam is distilled from the condenser. At this time, the inlet temperature (heat medium thermometer 6) of the heat medium to the partial condenser is usually about 90 to 160 ° C., and the partial gas outlet gas temperature (low boiling point thermometer 7) is about 110 to 180 ° C. To do.
In the method of increasing the temperature of the inlet of the heat medium to the partial condenser, when the heat medium is circulated to the partial condenser, the heat medium is not sufficiently cooled in the heat medium cooler 5, and the temperature of the heat medium is caused by the latent heat of condensation. It is sufficient to gradually increase the value.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Reference example 1
Production of polyester (acetylation reaction)
An acetylation reaction tank was charged with 1,250 kg of p-hydroxybenzoic acid, 544 kg of 4,4′-dihydroxydiphenyl, 375 kg of terephthalic acid, 125 kg of isophthalic acid, and 1,684 kg of acetic anhydride, and the liquid temperature was 145 with stirring in a nitrogen atmosphere. Reaction was carried out at reflux for 3 hours to obtain an acetylation reaction solution.
(Condensation polymerization reaction)
The acetylation reaction liquid is charged into a condensation polymerization tank having a vertical stirrer, and the temperature is raised at a rate of about 1.5 ° C./min while stirring in a nitrogen gas atmosphere. The reaction was carried out while partial condensation was performed and refluxed to the condensation polymerization tank, and the remainder (mainly acetic acid) was condensed and recovered by a condenser. The temperature was raised to 300 ° C., and further maintained at 300 ° C. for 60 minutes to complete the reaction.

Example 1
After the reaction shown in Reference Example 1 was repeatedly carried out for about 20 batches, washing was carried out because adhesion of polyester and low molecular compounds increased in the condensation polymerization tank.
1350 kg of triethylene glycol and 200 kg of monoethanolamine were charged into a condensation polymerization tank and washed for 6 hours while refluxing under atmospheric pressure.
At the initial stage of washing, the inlet temperature of the heating medium to the partial condenser was about 60 ° C., and the partial outlet gas temperature was about 40 ° C. Thereafter, the amount of heating is increased to increase the amount of evaporation from the condensation polymerization tank, and the cooling of the heat medium is decreased to raise the temperature of the inlet to the heat medium partial condenser, and after 3 hours, the heat medium is partially condensed. The inlet temperature to the vessel was about 123 ° C., the gas outlet gas temperature was about 138 ° C., and washing was continued for 3 hours.
The boiling point of this solution composition is 213 ° C., and the vapor condensation temperature is 174 ° C.
The reaction was repeated about 20 batches until the equipment was opened and washed, and then the cycle for washing as described above was carried out for about 15 cycles.

Comparative Example 1
At the initial stage of washing, the inlet temperature of the heat medium to the partial condenser was about 58 ° C., and the partial outlet gas temperature was about 37 ° C. After 3 hours, the same operation as in Example 1 was performed except that the inlet temperature of the heat medium to the partial condenser was about 92 ° C., the partial outlet gas temperature was about 88 ° C., and washing was continued for 3 hours.
The reaction was repeated about 20 batches until the equipment was opened and washed, and then the above washing cycle was carried out about 11 cycles.

It is a figure which shows the outline | summary of one embodiment of the aromatic polyester manufacturing apparatus which consists of a condensation polymerization tank provided with the partial condenser.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Condensation polymerization tank 2 Partial condenser 3 Condenser 4 Heat medium circulation pump 5 Heat medium cooler 6 Heat medium thermometer 7 Low boiling point thermometer 8 Heat medium control valve 9 Heat medium control valve 11 Acetylation reaction product / glycol And mixtures of primary and secondary amines 12 inert gas 13 aromatic polyester 14 acetic acid 15 exhaust gas 16 heating medium 17 return heating medium

Claims (5)

  When an aromatic polyester production apparatus comprising a condensation polymerization tank equipped with a partial condenser is heated and refluxed using a mixture of glycols and primary or secondary amines as a washing solvent, it is generated in the condensation polymerization tank. By adjusting the steam volume and / or the inlet temperature of the heat medium to the condenser, the outlet gas temperature in the first half of the cleaning is set to be lower than the inlet temperature of the heat exchanger of the condenser, and in the latter half, the outlet of the condenser A method for cleaning an aromatic polyester production apparatus, characterized in that the gas temperature is set to be equal to or higher than the temperature at the inlet to the heat medium partial condenser.   2. The vaporizer outlet gas temperature is increased by gradually increasing the amount of steam generated in the condensation polymerization tank and / or gradually increasing the inlet temperature of the heating medium to the divider. Cleaning method. In the first half of the washing, the inlet temperature to the heat medium partial condenser is set to 40 to 110 ° C., and the gas temperature at the outlet of the partial condenser is set to room temperature to 100 ° C. In the second half, the inlet temperature to the partial condenser of the heat medium is set to 90 ° C. The cleaning method according to claim 1 or 2, wherein the temperature of the gas at the outlet of the condenser is set to 110 to 180 ° C.   The washing method according to any one of claims 1 to 3, wherein the glycol is triethylene glycol.   The cleaning method according to any one of claims 1 to 4, wherein the amine is monoethanolamine.

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