JP2000212263A - Production of copolyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for reusing distillate glycol to be generated in each step as a part or the entire of the feedstock and, in addition, industrially advantageously producing a high quality copolyester. SOLUTION: This process for producing a copolyester comprises spraying a distillate liquid having, as the major component, a glycol to be discharged form polycondensation reaction equipment and/or esterification reaction equipment 3 and 4 and containing a copolymerization component as a condensation cooling liquid for the gas formed in the esterification reaction in a partial condenser 5, filtering the resulting partially condensed fluid to separate undissolved substances, and then reusing the partially condensed liquid thus obtained as a part or the entire of the feedstock, In this instance, while substantially continuously measuring the concentration of the copolymerization component in the partially condensed liquid, the amount of the copolymerization component to be introduced is adjusted on the basis of the result of this operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a copolymerized polyester, and more particularly, to terephthalic acid (hereinafter, referred to as TPA), ethylene glycol (hereinafter, referred to as EG), and 1,4. The present invention relates to a method for producing a copolyester having a minimum amount of glycol such as butanediol (hereinafter referred to as BD) and having stable quality.

[0002]

2. Description of the Related Art In the case of polyester, for example, polyethylene terephthalate (hereinafter referred to as PET), TPA and EG slurried in a slurry mixing tank are sent to an esterification reactor, which undergoes an esterification reaction to form a polyester low polymer. After that, it is sent to a polycondensation reaction apparatus and is produced by a polycondensation reaction.

[0003] In recent years, for the purpose of expanding the use of PET and modifying it to be suitable for various uses, it is manufactured by adding a copolymer component such as diethylene glycol (hereinafter referred to as DEG) or by adding other additives. The method of doing so is also widely practiced.

[0004] In the case of producing a polyester such as PET, in order to improve the reactivity, EG is usually supplied in an amount of 1.1 to 2.0 mole times with respect to TPA and a catalyst added in each reaction. Most of the components and additives are also used after being dissolved in EG, so that in the process, EG is present in excess of the theoretical amount of EG contained in the polyester. As a result, it is necessary to extract a part of the EG from the esterification reactor or the polycondensation reactor, and to co-exist this EG with water, low-boiling substances, polyester low polymer accompanied by droplets, and DEG added as a copolymer component. The distillate containing the polymerization component is discharged out of the system.

[0005] In addition, a polyester polymerization facility usually includes a distillate EG generated from the process and an EG that is additionally supplied.
Is collectively purified into high-purity EG, and the high-purity EG purified here is reused as a raw material. However, it is practically impossible to make the yield in the recovery step 100%, and the amount of EG used increases,
This is one of the causes of cost increase.

[0006] Furthermore, the substances removed in the recovery of EG are mainly water, low-boiling substances and low-polyester polymers, as well as high-melting polymers, catalysts, and some copolymer components. Disposal of coalescence and copolymers is
Similarly, the use amount of other copolymer components of TPA and EG is greatly increased, which is a major cause of cost increase.

Until now, various studies have been made to solve the above-mentioned cost increase factors. One of the solutions is a method in which a distillate generated from an esterification reaction apparatus or a polycondensation reaction apparatus is directly reused as a raw material without going through a recovery / purification step (JP-A-53-126096,
JP-B-59-48058).

According to this method, it is possible to solve the cost problem described above. However, the above-mentioned distillate contains solid or semi-solid high-melting components (hereinafter, referred to as high-melting substances), and these components are reacted in an esterification reactor or a polycondensation reactor. The polyester does not dissolve therein and becomes a foreign substance, which deteriorates the quality of the polyester, and further, the quality of the polyester, which is produced as a raw material, because the polyester is present as a foreign substance. There is also a method of removing these solids with a filter before entering the reactor, but those below the filtration accuracy are not removed,
Further, if the filtration accuracy is made fine, clogging of the filter tends to occur due to a large amount of the low polymer, which causes a problem in terms of maintenance.

As a method for solving this problem, Japanese Patent Application Laid-Open
No. 241368 proposes a method for separating a solid or semi-solid in a distillate by utilizing a specific gravity difference. However, this method has a problem that the amount of TPA or EG cannot be significantly reduced because undissolved low polymer present in a large amount in the distillate is also separated and removed. Further, when the concentration of a copolymer component such as DEG in the distillate changes,
There is a problem that the quality of the polyester is not stable because the concentration in the product also changes.

[0010]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and recycles the distillate glycol generated from each step as a part or the whole of the raw material, and furthermore, provides a stable and high-quality copolyester. It is an object of the present invention to provide a method for industrially advantageously producing a compound.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, the distillate glycol generated from each step is directly converted into a raw material without passing through a distillation purification step, and is significantly reduced. Along with reducing the cost, the low polymer contained in the generated distillate is dissolved by the heat of condensation of the high-temperature esterification reaction gas. By adjusting the amount of the raw material to be newly added according to the concentration of the copolymer component in the condensed liquid, it has been found that the quality of the copolymerized polyester produced can always be stabilized, and the present invention has been completed. .

That is, the present invention provides a distillate containing mainly a glycol discharged from a polycondensation reaction apparatus and / or an esterification reaction apparatus and condensing a distillate containing a copolymer component for cooling a gas produced by the esterification reaction. Sprayed as a liquid in the condensator, and after filtering the obtained condensed liquid to separate undissolved substances,
In the method for producing a copolymerized polyester to be reused as a part or the whole amount of the raw material, while the concentration of the copolymerized component in the condensed liquid is substantially continuously measured, the copolymerized component is charged based on the calculation result. The gist of the present invention is a method for producing a copolymerized polyester, characterized in that the amount is adjusted.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, TPA is used as a dicarboxylic acid component,
It is intended for copolymerized polyesters containing G, BD, DEG, etc. as glycol components, and preferably contains ethylene terephthalate units or butylene terephthalate units as main components.

As a part of the acid component, for example, dicarboxylic acids such as isophthalic acid, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid and sebacic acid are used. Alternatively, copolymerization may be carried out using trimethylene glycol, hexamethylene glycol, triethylene glycol, polyethylene glycol, 1,4-cyclohexanedimethanol, an ethylene oxide adduct of bisphenol II, or the like as a part of the glycol component. Further, the method for producing the copolymerized polyester of the present invention may be a continuous type or a batch type.

Next, a method for producing the copolymerized polyester of the present invention will be described with reference to the drawings. FIG. 1 is a schematic process diagram showing one embodiment of the present invention. In FIG. 1, TPA and EG are supplied to a slurry mixing tank 1 at a constant molar ratio to form a slurry. This slurry is sent to the esterification reactor 3 by the slurry supply pump 2.

In the method shown in FIG. 1, TPA and EG are slurried.
A and EG may be separately supplied to the esterification reactor 3. In the esterification reactor 3, preferably 2
The reaction is carried out at a temperature of 30 to 270 ° C. and a pressure of 100 kPa to 400 kPa to a predetermined reaction rate, and then sent to the second-stage esterification reactor 4 to perform the esterification reaction until the reaction rate reaches the predetermined reaction rate.

The gas generated in the esterification reactors 3 and 4 enters the separator 5 and is cooled and condensed by the polycondensation step distillate sprayed from the shower nozzle 6. The distillate of the polycondensation step is usually supplied as a liquid at a temperature of 30 ° C. or lower.
Because it is sprayed inside and receives heat from the gas generated during the esterification reaction and is heated to about 130 ° C. to 230 ° C.,
The low boiling components and water contained therein are gasified and enter the rectification column 9 together with the uncondensed esterification reaction product gas. In the rectification column 9, low-boiling substances and water are separated and discharged from the top of the column, and EG (hereinafter referred to as recovered EG) is extracted from the bottom of the column. The recovered EG is supplied to the slurry mixing tank 1 as a part of the raw material by the recovered EG supply pump 10.

On the other hand, in the condensing device 5, the low polymer is completely dissolved by the high-temperature EG, extracted as a condensed liquid together with the EG and the copolymer component, and is pumped by the condensed liquid supply pump 7 to be compressed. After passing through the contraction filter 8, the concentration of the copolymer component is measured by the concentration analyzer 11 and supplied to the slurry mixing tank 1 as a part of the raw material. At this time, the high melting point components such as the unmelted polyester high melting point polymer, the catalyst, and the modified polymer of the additives which are present in the split EG are completely separated and removed by the splitting liquid filter 8.

The object of the fractionated liquid filter 8 used here is EG whose temperature is as high as 130 ° C. to 230 ° C.
The self-cleaning regenerative filter type is the most suitable in consideration of the danger of burns during clogging removal work and maintenance. Specifically, SUPER-Z manufactured by Yak Filter Systems Co., Ltd. and # 200 manufactured by IM Co., Ltd.
-50A can be used. In addition, the filtration accuracy of the filter is selected in consideration of the allowable size of the undissolved material and the cost of equipment, but is generally 50 to 500 μm.
m is preferred.

Further, as the concentration analyzer 11, an industrial analysis type gas chromatograph is practical in terms of operational stability and accuracy. Specifically, process gas chromatography (SAG-600) manufactured by Yanagimoto Seisakusho Co., Ltd. or process gas chromatography (GC8) manufactured by Yokogawa Electric Corporation can be used.

When the temperature of the shrinkage EG is lower than 130 ° C., a part of the low polymer is not dissolved, and when the temperature exceeds 230 ° C., a side reaction such as formation of a large amount of glycol dimer is caused, which is not preferable. . Further, the temperature of the divided EG can be adjusted by the spray amount of the distilling EG liquid supplied to the divided unit 5 or the pressure of the divided unit 5.

As described above, the high-melting point component is completely removed from the reduced EG, so that the high-melting point component is not charged into the slurry mixing tank 1 or the esterification reactors 3 to 4 as a part of the raw material. Is obtained.

Here, the description has been made using a device for directly extracting the condensed liquid from the condensing device 5, but it is also possible to use a device for circulating the condensed liquid to the condensing device 5 and extracting a part thereof. Good. Alternatively, the distillate from the polycondensation step may be directly added to the condensed liquid circulated to the condensator 5 and sprayed onto the condensate 5.

The low polymer thus obtained is sent to polycondensation reactors 14 to 16 in the next step. The copolymer component is
The low-polymer just before being supplied to the polycondensation reactors 14 to 16 is constantly supplied and added from the copolymer component supply pump 13. At this time, the optimum addition amount is calculated by the arithmetic unit 12 in accordance with the copolymer component concentration measured by the concentration analyzer 11, and the addition amount is controlled by changing the rotation speed of the copolymer component supply pump 13.

If the position where the copolymerization component is supplied and added is located in the slurry mixing tank 1, it takes a long time to change the concentration of the copolymerization component to the target concentration when producing a brand in which the concentration of the copolymerization component is largely changed. However, if the reaction is carried out immediately before the polycondensation reactors 14 to 16, the concentration can be adjusted to the target concentration in a short time, so that the generation of products whose concentration of the copolymer component is out of the standard can be suppressed.

In the polycondensation reactors 14 to 16, the polyester is synthesized when the temperature and the degree of vacuum are gradually increased, preferably in the range of 250 to 295 ° C. and 0.05 to 10 kPa. The polycondensation reactors 14 to 16 are provided with wet condensers 17 to 19, respectively, which contain EG generated by the polycondensation reaction, as well as moisture, low-boiling substances, and entrained polyester low polymers and copolymers. The distillate components such as the components are condensed here to form a distillate, and each of the distillate is circulated in the circulating EG tank
22 and is sent again to each of the wet condensers 17 to 19 as a circulation EG to be used as a spray liquid for condensing distillate components. Each of the wet condensers 17 to 19 is connected to a vacuum generator by a pipe.

Here, the pressure loss caused by the vapor pressure of low boiling components such as water contained in the distillate in the distillate in the wet condenser 19 attached to the polycondensation reaction device 16 requiring a high degree of vacuum is particularly required. In order to prevent the increase and prevent the adhesion of the low polymer generated by entrainment to each device and piping, a new EG is used.
Preferably, it is added to the circulation EG storage tank 22.

In the circulating EG storage tank 22, a part is extracted so as to keep the liquid level constant, and sent to the circulating EG storage tank 21. The distillate sent to the circulation EG storage tank 21 is used as a spray liquid for the wet condenser 18. In addition, a part is drawn out so that the liquid level of the circulation EG storage tank 21 becomes constant, and sent to the circulation EG storage tank 20. The distillate sent to the circulation EG storage tank 20 is used as a spray for the wet condenser 17. A part of the liquid level of the circulating EG storage tank 20 is also withdrawn so that the height is constant, and the liquid level is supplied to the condensing device 5 in the esterification step by the distillate transfer pump 23 and the shower nozzle 6
, And the gas generated in the esterification reactors 3 and 4 is cooled and condensed.

In FIG. 1, the transfer destination from the distillate transfer pump 23 is shown by a single series of condensers, but may be transferred to a plurality of series of condensers. Further, a part of this can be transferred to a conventional distillation purification step.

[0030]

Next, the present invention will be described specifically with reference to examples. In Examples and Comparative Examples, a polyester continuous production apparatus was used in both the esterification step and the polycondensation step. In addition, the measuring method is as follows. (A) Intrinsic viscosity ([η]) Measured at a temperature of 20 ° C. using an equal weight mixture of phenol and tetrachloroethylene as a solvent. (B) Diethylene glycol content (DEG) The polyester was hydrolyzed with an aqueous potassium hydroxide solution, and then measured using a GC-14B gas chromatograph manufactured by Shimadzu Corporation. (C) Foreign matter 20 g of polyester was formed into a film having a thickness of 100 μm, and the number of foreign matter having a size of 0.5 mm or more was visually measured.

Example 1 Using the manufacturing apparatus shown in FIG. 1, a copolymerized PET obtained by copolymerizing DEG with 3.0 mol% was produced. The total amount of the EG, the recovered EG and the added EG in the partially condensed liquid is controlled to be always 22 kg / h, and is supplied to the slurry mixing tank 1 together with TPA 36 kg / h to be slurried, and then esterified via the pump 2. It was supplied to the reactor 3. Then, an esterification reaction and a polycondensation reaction were performed under the conditions shown in Table 1.

The distillate generated in the polycondensation reaction step is supplied to the total amount of the condensing device 5, and the condensed liquid filter 8 is a self-cleaning regenerative filter having a filtration accuracy of 100 μm (SUPER- manufactured by Yak Filter Systems, Ltd.). Z) was used. At this time, the concentration of the copolymer component in the split solution was measured using a concentration analyzer 11.
(Using a SAG-600 manufactured by Yanagimoto Mfg. Co., Ltd.), and this signal was sent to the arithmetic unit 12 to calculate the optimum addition amount to control the rotation speed of the copolymer component supply pump 13.
As a result, the amount of DEG added was 0.5 kg / h.
The pressure of the separator 5 was 100 kPa, and the temperature of the separator was 170 ° C.

[0033]

[Table 1]

Operation was continued under these conditions for one month, but the process was stable. Further, the intrinsic viscosity, DEG component concentration, and foreign substances of the obtained copolymerized polyester were measured every day. As a result, good quality as shown in Table 2 was obtained.

[0035]

[Table 2]

COMPARATIVE EXAMPLE 1 The distillate EG solution from the polycondensation reaction was directly supplied to the slurry mixing tank 1, and the DEG supply amount was 0.5 kg / kg without measuring the DEG concentration in the separation liquid. The operation was performed under the same reaction conditions using the same production equipment as in Example 1 except that the rotation speed of the copolymer component supply pump 13 was fixed so as to be h. Note that a wire mesh filter having a filtration accuracy of 800 µm was used for filtering the polymerization distillate.

Under these conditions, the operation was continued for one month. During that time, the polymerization distillate EG liquid filter was clogged 32 times, and it took much time to replace and clean the filter. Other steps were stable. The results of daily measurements of the intrinsic viscosity, DEG component concentration, and foreign substances of the obtained copolymerized polyester are shown in Table 2, which were inferior to those of Example 1.

[0038]

According to the present invention, the distilled glycol can be reused without being purified by distillation, and a high-quality copolymerized polyester can be stably produced for a long period of time. .

[Brief description of the drawings]

FIG. 1 is a schematic process chart showing one embodiment of a method for producing a copolymerized polyester of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slurry mixing tank 2 Slurry supply pump 3-4 Esterification reaction apparatus 5 Separator 6 Shower nozzle 7 Minute condensate supply pump 8 Minute condensate liquid filter 9 Rectification tower 10 Recovery EG supply pump 11 Concentration analyzer 12 Arithmetic unit 13 Copolymerization component supply pump 14-16 Polycondensation reactor 17-19 Wet condenser 20-22 Circulating EG storage tank 23 Distillate transfer pump

Claims (4)

[Claims] 1. A distillate mainly composed of glycol discharged from a polycondensation reaction apparatus and / or an esterification reaction apparatus, and a distillate containing a copolymer component is condensed as a cooling liquid for condensing a gas produced by the esterification reaction. In a method for producing a copolymerized polyester, which is sprayed into a vessel, and the obtained fractionated liquid is filtered to separate undissolved substances, and then reused as a part or the whole amount of the raw material, a copolymer component in the divided liquid is used. A method for producing a copolymerized polyester, characterized in that the amount of the copolymerized component is adjusted based on the result of the calculation while measuring the concentration of the copolymer substantially continuously. 2. The method for producing a copolymerized polyester according to claim 1, wherein the copolymerized component is diethylene glycol. 3. The method for producing a copolymerized polyester according to claim 1, wherein the concentration of the copolymerized component is measured by an industrial analytical gas chromatograph. 4. The method for producing a copolymerized polyester according to claim 1, wherein the introduction of the copolymerization component is performed immediately before the polycondensation reaction.