JP2000336162A - Continuous production of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously producing a polyester, designed to suppress a shock in polymer filter changeover operation, capable of cutting both installation cost and running cost and of improving product yields as well. SOLUTION: This method for continuously producing a polyester polymer through a plurality of polycondensation reactors comprises filtering a molten polymer through a polymer filter 8 set up between the final reactor 3 and the preceding reactor 2; wherein the outlet side of the final reactor 3 is not provided with such a filter 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for continuously producing polyester, especially polyethylene terephthalate.

[0002]

2. Description of the Related Art Polyesters represented by polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate have excellent physical and chemical properties and are therefore widely used for various purposes. In particular, fibers, films, and other molded articles are widely used in clothing, industrial fibers such as tire cords, engineering plastics, and the like because of their excellent mechanical properties such as strength and elastic modulus and heat resistance.

[0003] In general, polyesters used for such various uses are produced by a direct polymerization method or a transesterification method. Here, the former direct polymerization method is a method in which a polyester precursor is formed by a direct esterification reaction of an acid component and a diol component, and then the polyester precursor is subjected to polycondensation under normal pressure or reduced pressure. . On the other hand, the latter transesterification method is a method of producing a polyester precursor by subjecting a lower alkyl ester of an acid component to a transesterification reaction with a diol, and then subjecting the polyester precursor to polycondensation under normal pressure or reduced pressure. It is.

Conventionally, the above-mentioned polymerization of polyester has been often carried out by a batch method. However, in order to take advantage of economies of scale and to produce polyester at low cost, switching to a continuous method has been promoted. The merits such as improvement of yield and quality, uniformity of quality, improvement of operability, and cost reduction by adopting the continuous method are extremely large.

In general, many continuous polyester production processes are carried out by a process in which a plurality of esterification reactors or transesterification reactors and a polycondensation reactor are combined. For example, the raw material is supplied to a transesterification reactor or an esterification reactor to produce a monomer or an oligomer, filtered through a monomer filter or an oligomer filter, and subsequently supplied to an initial polycondensation reactor and reacted under reduced pressure. To produce an intermediate polymer and / or a final polycondensation reactor under reduced pressure to obtain an intermediate polymer and / or a high polymer. ing. At that time, the diol component distilled from the polyester transesterification reactor, esterification reactor, or polycondensation reactor is generally recovered and reused as a part of the raw material, because of economic advantages.

[0006] Incidentally, in the polyester high polymer finally obtained by the polycondensation reaction, solid matter, degraded matter, carbide, gel-modified polymer, aggregate of additives, and inclusion of metals contained in the raw material are included. The so-called “foreign matter” is concerned. The presence of such “foreign matter” causes various problems in a post-process such as a yarn forming process and a film forming process.
For example, in the spinning process, there is a concern that the frequency of replacement of the spinning pack may be increased, the thread may be broken, and fluff may be generated, resulting in a decrease in product yield. To prevent this,
In the polymer filter provided after the final polycondensation reactor,
An operation of removing "foreign matter" through a polymer obtained by finally completing the polycondensation reaction is generally performed.

FIG. 3 is a flowchart illustrating the above-mentioned conventional continuous production process of polyester. In the figure, 1 is an esterification reactor, 2 is an initial polycondensation reactor, and 3 is a final polycondensation reactor. Reference numerals 4, 6, and 7 denote oligomer or polymer pumps, 5 denotes an oligomer filter, and 8 denotes a polymer filter. Such a conventional polyester continuous polymerization method is characterized in that the polymer filter 3 is provided on the outlet side of the final polycondensation reactor as shown in FIG.

Here, the conventional polyester continuous polymerization method will be briefly explained. Terephthalic acid and ethylene glycol as raw materials are converted into a slurry in an esterification reactor 1.
To produce oligomers. Then, the obtained oligomer is supplied to the initial polycondensation reactor 2 via the pump 4. On the way, the mixture is filtered through an oligomer filter 5, and a polymerization catalyst and various agents are added.
Subsequently, the solution is supplied to the final polycondensation reactor 3 via the pump 6. The polycondensation reaction proceeds while generating ethylene glycol vapor in the initial polycondensation reactor 2 and the final polycondensation reactor 3. The polyethylene terephthalate high polymer finally obtained is discharged by a pump 7 and supplied to a double polymer filter 8 which is used by alternately switching two polymer filters by operating a valve or a cock, and the “foreign matter” in the polymer is removed. And then sent to the next step such as chipping, spinning, film forming, kneading and the like.

As a conventional technique for providing a polymer filter on the output side of the final polycondensation reaction as in the above-described continuous polymerization process of polyester, for example, "Chemical Engineering No. 24"
Vol. 12, No. 1960, which is shown in the schematic drawing cited from the Dupont patent. Also,
"Piping and Apparatus Vol.27, No.2, P.20-26 1987" generally describes that a double polymer filter is provided after the final polycondensation reactor as a measure against clogging of the filter. Furthermore, `` Piping and equipment Vol.36, No.10 P.
22-32 1996 "describes a continuous system in which a polymer filter is provided at the output of the final polycondensation reaction, but uses two polymer filters switched. Such prior art is a preferred embodiment in terms of finally removing "foreign matter" generated in the final polycondensation reactor. Therefore, in these prior arts, the output of the final polycondensation reactor is reduced. It is essential to provide a polymer filter on the side.

By the way, in order to remove “foreign matter” from the polymer, the requirements for the polymer filter include (1) that “foreign matter” in the polymer can be efficiently and stably removed, and (2) when the polymer passes through (3) High strength, durability and corrosion resistance, (4) Easy cleaning, renewable and economical, (5) Excellent workability, and (6) When switching the clogged filter, there is little mixing of shocks and accumulated substances.

However, the polymer on the outlet side of the final polycondensation reactor has a high degree of polymerization and therefore has a high viscosity. If a polymer filter is installed on the outlet side of the final polycondensation reactor, the above requirements cannot be sufficiently satisfied. . That is, the filtration resistance when passing through the polymer filter is increased, and the pressure loss is inevitably increased, so that filtration under high pressure is required. Therefore, it is necessary to increase the power cost, cause a drift in the polymer filter, and increase the pressure resistance of the piping and the filter. Therefore, in order to solve these problems, the equipment is increased, a large amount of operating energy is required, and costs are increased in terms of equipment cost and operation cost. Furthermore, in such a conventional technology, when switching a clogged polymer filter,
It is said that the shock at the time of the switching directly affects the subsequent processes such as chipping, spinning, film formation, kneading etc. by mixing in polymer residue, causing pressure fluctuations, and catching bubbles. There is a serious problem.

[0012]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the problem to be solved by the present invention is to suppress the shock caused by switching the polymer filter and to significantly reduce the energy consumption when passing through the polymer filter. , Which makes facilities and operation costs excellent,
Another object of the present invention is to provide a continuous production method of polyester that can significantly improve the product yield of polyester.

[0013]

As a result of intensive studies, the present inventors have found that in a method for continuously producing a polyester polymer, a final polycondensation reactor and one before the final polycondensation reactor are provided. The molten polymer is filtered through a polymer filter between the polycondensation reactor and the polymer filter is not provided on the outlet side of the final polycondensation reactor, so that the shock when switching the polymer filter can be suppressed. Further, they have found that the energy consumption required for filtration can be significantly reduced, and have completed the present invention.

That is, according to the present invention, there is provided a method for continuously producing a polyester polymer through a plurality of polycondensation reactors. 2. A method for continuous production of polyester, characterized in that the molten polymer is filtered through a polymer filter provided between the polyester and the polymer filter, and no polymer filter is provided on the outlet side of the final polycondensation reactor. The method for continuous production of a polyester according to the above, further comprising a step of directly supplying at least a part of the polyester polymer obtained from the final polycondensation reactor to a subsequent step without forming a cooling chip. (3) The polyester according to (1) or (2), wherein the polyester is polyethylene terephthalate. Way continuous production, upon entering the (Claim 4) according to claim 3 polymer filter of polyethylene terephthalate according to claim 1, wherein,
4. The method for continuous production of polyester according to claim 3, wherein the intrinsic viscosity of the polyethylene terephthalate is not less than 0.2 and not more than 0.55. The polyester production method according to any one of claims 1 to 4, wherein the polyester is produced by a final polycondensation reactor comprising a horizontal single-screw reactor having no axis at an intermediate portion of the reactor. And (Claim 6) The continuous production method of polyester according to any one of claims 1 to 5, wherein a plurality of polymer filters are alternately used.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described. The polyester produced by the method of the present invention is obtained by reacting a dicarboxylic acid and / or an ester-forming derivative thereof with a diol. Examples of the dicarboxylic acid having an aromatic dicarboxylic acid component as a main component thereof or an ester-forming derivative thereof include, for example, terephthalic acid, isophthalic acid,
Phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and / or their lower alkyl esters (the carbon number of the alkyl group is Usually 1 to 4) and the like. Examples of the alicyclic dicarboxylic acid component or its ester-forming derivative include, for example, cyclohexanedicarboxylic acid. Examples of the aliphatic dicarboxylic acid component or its ester-forming derivative include adipic acid, sebacic acid, and suberic acid. Is mentioned. These dicarboxylic acids are preferably terephthalic acid, 2,6-naphthalenedicarboxylic acid,
Isophthalic acid and / or their dimethyl esters. In addition, these aromatic dicarboxylic acid component, alicyclic dicarboxylic acid component, and aliphatic dicarboxylic acid component may be used alone or in combination of two or more.

Next, diol components include ethylene glycol, neopentyl glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-butanediol. Examples thereof include pentadiol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, and propylene glycol. Among them, ethylene glycol, 1,4-butanediol and diethylene glycol are preferred as main components. Here, “main” means 50 mol% or more, preferably 80 mol%, of all diol components.
Say more. These diol components may be used alone or in combination of two or more.

The polyester comprising a dicarboxylic acid and a diol preferably includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polybutylene naphthalate, and copolymers of these polyesters.

The polyester may be copolymerized with compounds such as trifunctional or higher polyfunctional compounds such as trimellitic acid, pyromellitic acid and glycerol, and monofunctional compounds such as benzoic acid and phenyl isocyanate.

The production of the polyester in the present invention may be carried out in the presence or absence of a catalyst. When a catalyst is used, a known catalyst can be used. For example, an antimony compound, a manganese compound, a titanium compound, a tin compound, a zinc compound, a magnesium compound, a germanium compound, and the like are used. Further, as additives, known antioxidants, antistatic agents, flame retardants such as brominated polycarbonates and brominated epoxy compounds, flame retardant aids such as antimony trioxide and antimony pentoxide, plasticizers, lubricants, release agents A molding agent, a coloring agent, a crystal nucleating agent and the like may be added.
Also, if necessary, as an inorganic filler, talc, silica, alumina, clay, carbon black, kaolin,
Metal compounds such as titanium oxide, iron oxide, antimony oxide and alumina, and alkali metal compounds such as potassium and sodium may be added by any method.

Next, the polymer filter used in the present invention will be exemplified. "Polymer filter" in the present invention
Means a polymer filter used in the polymerization step,
It does not mean a filter provided for filtering the polymer in a later step such as a spinning step or a film forming step.
Therefore, it goes without saying that a dedicated filter may be provided in a post-process such as a spinning process or a film-forming process.

From the viewpoint of heat resistance and durability of the polymer filter, a wire mesh, a sintered metal powder,
Felt, sintered metal laminated wire mesh, sintered metal fiber, and the like can be exemplified, and among them, a nonwoven fabric sintered body made of stainless steel long fiber is preferable. The shape is preferably processed into a three-dimensional structure, and examples thereof include those processed into a cylindrical candle shape, a cylindrical disk shape, a leaf disk shape, and the like. In addition, such a polymer filter may be a filter of a type in which a filter clogged by long-term use is washed and used repeatedly. In addition, when these polymer filters become clogged, the filtration resistance increases, and therefore, in order to perform sufficient filtration with the filtration resistance reduced, a replacement operation and a cleaning operation of the polymer filter are necessary. .

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. FIG. 1 illustrates a flow chart of the continuous production process of the polyester of the present invention. In the figure, 1 is an esterification reactor, 2
Is an initial polycondensation reactor, and 3 is a final polycondensation reactor. Reference numerals 4, 6, and 7 are pumps for feeding an oligomer or polymer, 5 is an oligomer filter, and 8 is a compound polymer filter. In the continuous production process of the polyester of the present invention configured as described above, the polyester is continuously produced as described below.

First, a slurry in which terephthalic acid and ethylene glycol as raw materials are mixed is continuously supplied to the esterification reactor 1 to produce an oligomer by an esterification reaction. The oligomer thus obtained is supplied to the initial polycondensation reactor 2 via the pump 4. On the way,
The mixture is filtered through an oligomer filter 5, and a polymerization catalyst and / or various additives are added. Subsequently, the oligomer supplied to the initial polycondensation reactor 2 undergoes an initial polycondensation reaction and becomes a polymer having a relatively low viscosity. Thereafter, the polymer having a relatively low viscosity is supplied via a pump 6 to a double-type polymer filter 8 which is used alternately and alternately.
Supplied to. At that time, the polycondensation reaction proceeds while generating ethylene glycol vapor in the initial polycondensation reactor 2 and the final polycondensation reactor 3.

Here, in the present invention, the intrinsic viscosity of the polyethylene terephthalate supplied to the polymer filter 8 is preferably 0.2 or more and 0.55 or less. Because if the intrinsic viscosity is lower than 0.2,
This is because the filtration by the oligomer filter 5 can be used instead, and it is not necessary to provide the polymer filter 8. On the other hand, when the intrinsic viscosity exceeds 0.55, the melt viscosity of the polymer becomes high, causing various problems as described in the section of the prior art. The intrinsic viscosity of polyethylene terephthalate was determined from the viscosity measured at 35 ° C. using orthochlorophenol as a solvent.

The polyethylene terephthalate high polymer finally obtained as described above is discharged by the pump 7 from the final polycondensation reactor 3 having no polymer filter on the outlet side, and formed into chips, spinning, and film formation. , Kneading, and the like. Needless to say, a pipe for transporting the polymer to the subsequent step is provided with a polymer viscosity measuring device, a polymer cooler, a mixer, a ruder, a pump, and the like as necessary. The present invention is useful in such a post-process, and in this regard, FIG.
An embodiment of the present invention will be described in detail with reference to FIG.
FIG. 2 illustrates the continuous production of a polyester polymer without directly cooling at least a portion of the polyester polymer into a cooling chip (the embodiment of FIG. 2 illustrates a spinning process). 3) illustrates a flow for transferring to (a). In FIG. 2, the flow until the high polyester polymer exits from the final polycondensation reactor is the same as that in FIG. 1, and the description up to this point will be omitted to avoid duplication. Therefore, description will be made from the point where the polyester high polymer comes out from the final polycondensation reactor 3.

The polyester high polymer coming out of the final polycondensation reactor 3 by the process as shown in FIG.
The water is discharged by the pump 7 while being kept as it is, and is directly sent to the distributor 9 and the gear pump 10 for spinning. Then, it is extruded from the spinneret pack 11 via the distributor 9 and the spinning gear pump 10 to become a fiber product. The method of the present invention can be expected to have a great effect particularly in such a direct spinning method.

In the method of the present invention described above, the molten polymer is filtered through a polymer filter provided between the final polycondensation reactor and the immediately preceding polycondensation reactor.
A major feature is that no polymer filter is provided on the outlet side of the final polycondensation reactor. Thus, rather than filtering the high viscosity polymer exiting the final polycondensation reactor,
The relatively low viscosity polymer will be filtered prior to entering the final polycondensation reactor. Therefore, the flow resistance (filtration resistance) when passing through the polymer filter is reduced,
As a result, it is possible to reduce the power cost, suppress the drift in the polymer filter, and reduce the pressure resistance of pipes and filters.

Furthermore, depending on the conditions, a shock (for example, pressure fluctuation or air bubble entrapment) occurs when switching the polymer filter which is clogged periodically in several weeks to several months. Even so, the final polycondensation reactor located on the outlet side of the polymer filter acts as a cushion, so that there is no direct adverse effect after the outlet of the final polycondensation reactor. In addition, even if a small amount of defective retentate is mixed in the production line when switching the polymer filter, the concentration will be reduced by the high polymer produced in large quantities in the final polycondensation reactor, and the effect will be affected. The level is negligible, and the reduction in product yield due to switching is eliminated. Therefore, it is possible to prevent the shock at the time of switching the polymer filter from having a large direct influence on the subsequent steps such as chipping, spinning, film formation, kneading and the like. Particularly, in a direct spinning method in which at least a part of a polyester polymer is directly spun without forming a cooling chip,
There is an effect that pressure fluctuation, thread breakage, fluff generation, and the like due to switching of the polymer filter can be suppressed.

In the present invention, since no polymer filter is provided on the outlet side of the final polycondensation reactor, even if "foreign matter" is generated in the final polycondensation reactor, it cannot be removed. However, these "foreign matter" can be removed by a filter provided exclusively in a spinning step, a film forming step or the like. However, in order to suppress the generation of “foreign matter” in the final polycondensation reactor, it is a preferable embodiment to use a thin-film type polycondensation reactor having self-cleaning properties as the final polycondensation reactor. In this case, it is particularly preferable that the final polycondensation reactor be a horizontal single-screw reactor, as described in JP-B-40-3964, JP-B-49-16555, and the like. By having a structure with shafts at both ends and no shaft in the middle part, long-term adhesion and retention of oligomers and polymers in the gas phase in the polycondensation reactor are reduced,
Thus, it is more preferable to suppress the generation of “foreign matter”.

[0030]

According to the production method of the present invention, the shock caused by switching the polymer filter can be suppressed,
Further, a relatively low viscosity polyester polymer can be passed through the polymer filter under low filtration pressure. Therefore, the energy consumption when the polyester polymer is passed through the polymer filter can be significantly reduced, whereby the costs such as equipment costs and operation costs can be reduced. Further, there is a remarkable effect that the product yield of the produced polyester can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an embodiment of a continuous production method of a polyester of the present invention.

FIG. 2 is a flowchart illustrating an embodiment of another continuous production method of polyester.

FIG. 3 illustrates a flow chart of a conventional polyester continuous polymerization.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Esterification reactor 2 Initial polycondensation reactor 3 Final polycondensation reactor 4, 6, 7 Pump 8 Polymer filter 9 Distributor 10 Spinning gear pump 11 Spinning pack

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[Procedure amendment]

[Submission date] July 12, 1999 (1999.7.1)
2)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

FIG. 3

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J029 AA03 AB04 AB05 BA03 BA04 BA07 BA09 BA10 BD06A BD07A BF09 BF18 BF25 CA02 CA06 CB04A CB05A CB06A CC05A CC06A CD03 KE05 KE07 KH03 KH05 LA05 LA10 LB05 LB06 LB06 LB10

Claims (6)

[Claims] 1. A method for continuously producing a polyester polymer through a plurality of polycondensation reactors, wherein a polymer filter provided between the final polycondensation reactor and the immediately preceding polycondensation reactor has a molten polymer. A process for continuous production of polyester, characterized by filtering through coalescence and not providing a polymer filter at the outlet of the final polycondensation reactor. 2. The method for continuously producing a polyester according to claim 1, wherein at least a part of the polyester polymer obtained from the final polycondensation reactor is directly supplied to a subsequent step without forming a cooling chip. A method for continuous production of polyester, comprising: 3. The continuous polyester production method according to claim 1, wherein the polyester is polyethylene terephthalate. 4. The polyethylene terephthalate according to claim 3, wherein said polyethylene terephthalate has an intrinsic viscosity of 0.2 or more and 0.55 or less when flowing into said polymer filter. 3. The continuous production method of the polyester according to 3. 5. The polyester is produced in a final polycondensation reactor comprising a horizontal single-screw reactor having a shaft at both ends of the reactor and no shaft in the middle of the reactor. The continuous production method of the polyester according to any one of claims 1 to 4. 6. The continuous polyester production method according to claim 1, wherein a plurality of polymer filters are alternately used.