JP3598018B2 - Polyester continuous production method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for continuously producing polyester, especially polyethylene terephthalate.
[0002]
[Prior art]
Polyesters represented by polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate have excellent physical and chemical properties and are therefore widely used for various applications. 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]
Generally, polyester used for such various uses is 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 between 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 in which a lower alkyl ester of an acid component is transesterified with a diol to form a polyester precursor, and then the polyester precursor is subjected to polycondensation under normal pressure or reduced pressure to produce the polyester precursor. It is.
[0004]
Conventionally, the polymerization of the above-mentioned polyesters has often been carried out by a batch method.However, in order to take advantage of scale and to produce polyester at a 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 adoption are extremely large.
[0005]
In general, many continuous polyester production methods are performed 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 out of the polyester transesterification reactor, esterification reactor, or polycondensation reactor is generally recovered and reused as a part of the raw material due to economic advantages.
[0006]
By the way, in the polyester high polymer finally obtained by the polycondensation reaction, there are so-called solid substances, degraded substances, carbides, gel-modified polymers, aggregates of additives, and inclusion of metals contained in the raw materials. However, there is concern about the presence of “foreign matter”. The presence of such “foreign matter” causes various problems in a post-process such as a thread-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, thereby lowering the product yield. In order to prevent this, an operation is generally performed to remove "foreign matter" through a polymer obtained by finally completing the polycondensation reaction in a polymer filter provided after the final polycondensation reactor.
[0007]
FIG. 3 illustrates a flow chart of the conventional continuous production process for 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.
[0008]
Here, the conventional polyester continuous polymerization method will be briefly described. Terephthalic acid and ethylene glycol as raw materials are continuously supplied as a slurry to the esterification reactor 1 to produce an oligomer. 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, it 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 finally obtained polyethylene terephthalate high polymer is discharged by a pump 7 and supplied to a double polymer filter 8 which is used by switching two polymer filters alternately 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.
[0009]
As a conventional technique in which a polymer filter is provided on the output side of the final polycondensation reaction as in the above-described continuous polymerization process of polyester, for example, a patent of Dupont is cited in “Chemical Engineering Vol. 24, No. 12, 1960”. Can be mentioned. In addition, “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. I have. Further, in “Piping and Apparatus Vol. 36, No. 10 P. 22-32 1996”, it is the same that a polymer filter is provided on the outlet side of the final polycondensation reaction, but two polymer filters are switched and used. A continuous system is described. 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.
[0010]
By the way, in order to remove the “foreign matter” from the polymer, the requirements for the polymer filter include (1) the ability to efficiently and stably remove “foreign matter” in the polymer, and (2) the resistance when the polymer passes. (3) high strength, durability and corrosion resistance, (4) easy to clean, reproducible and economical, (5) excellent workability, and (6) ) When switching the clogged filter, there is little shock and little intrusion of retained matter.
[0011]
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 the cost increases in terms of equipment cost and operation cost. Furthermore, in such a conventional technology, when switching a clogged polymer filter, a polymer residue is mixed in, a pressure fluctuation occurs, or air bubbles are caught, and a shock at the time of switching is caused by a tip. There is a serious problem that it has a large direct influence on post-processes such as forming, spinning, film forming, kneading and the like.
[0012]
[Problems to be solved by the invention]
In view of the above-described problems, the problem to be solved by the present invention is to suppress shock due to switching of a polymer filter, and to significantly reduce energy consumption when passing through the polymer filter. It is an object of the present invention to provide a continuous method for producing polyester, which is excellent in the above and can significantly improve the product yield of polyester.
[0013]
[Means for Solving the Problems]
The present inventors have conducted intensive studies and found that, in a method for continuously producing a polyester polymer, melting between a final polycondensation reactor and a polycondensation reactor immediately before the final polycondensation reactor. By filtering the polymer through a polymer filter and not providing a polymer filter at the outlet of the final polycondensation reactor, it is possible to suppress the shock at the time of switching the polymer filter, and further reduce the energy consumption required for filtration. They have found that they can be significantly reduced, and have completed the present invention.
[0014]
That is, according to the present invention,
(Claim 1) In a method for continuously producing a polyester polymer through a plurality of polycondensation reactors, a polymer filter provided between the final polycondensation reactor and the immediately preceding polycondensation reactor has an intrinsic viscosity. There 0.2 or more, 0.55 filtered through a is melted polymer less, continuous production method of the polyester, characterized in that the outlet side of the final polycondensation reactor without the polymer filter,
(Claim 2) In the continuous production method of polyester according to claim 1, 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. Continuous production method of polyester characterized by comprising
(Claim 3) The continuous polyester production method according to claim 1 or 2, wherein the polyester is polyethylene terephthalate.
(Claim 4) according to claim having a shaft at both ends of the reactor, in the middle of the reactor, characterized in that the production of polyester by the final polycondensation reactor consisting of horizontal uniaxial reactor without a shaft Continuous production method of the polyester according to any one of 1 to 3 , and,
(Claim 5) The continuous production method for polyester according to any one of claims 1 to 4, wherein a plurality of polymer filters are alternately used.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
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 terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, and 1,5-naphthalenedicarboxylic acid. Examples thereof include acids, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and / or lower alkyl esters thereof (the alkyl group usually has 1 to 4 carbon atoms). Furthermore, examples of the alicyclic dicarboxylic acid component or its ester-forming derivative include cyclohexanedicarboxylic acid, and 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 preferably include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid and / or their dimethyl esters. In addition, these aromatic dicarboxylic acid components, alicyclic dicarboxylic acid components, and aliphatic dicarboxylic acid components may be used alone or in combination of two or more.
[0016]
Next, as the diol component, ethylene glycol, neopentyl glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, propylene glycol and the like can be exemplified. Preferably, ethylene glycol, 1,4-butanediol, and diethylene glycol are main components. Here, “main” refers to 50 mol% or more, preferably 80 mol% or more based on all diol components. These diol components may be used alone or in combination of two or more.
[0017]
As the polyester composed of these dicarboxylic acids and diols, preferably, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polybutylene naphthalate, copolymers of these polyesters, and the like can be given.
[0018]
In addition, a compound such as a trifunctional or higher polyfunctional compound such as trimellitic acid, pyromellitic acid, and glycerol, and a monofunctional compound such as benzoic acid and phenyl isocyanate can be copolymerized with the polyester.
[0019]
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, antimony compounds, manganese compounds, titanium compounds, tin compounds, zinc compounds, magnesium compounds, germanium compounds and the like are used. Further, as additives, known antioxidants, antistatic agents, flame retardants such as brominated polycarbonate and brominated epoxy compounds, flame retardant aids such as antimony trioxide and antimony pentoxide, plasticizers, lubricants, and 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, titanium oxide, iron oxide, antimony oxide, metal compounds such as alumina, potassium, alkali metal compounds such as sodium and the like. It may be added in any manner.
[0020]
Next, the polymer filter used in the present invention will be exemplified. The “polymer filter” in the present invention means a polymer filter used in a polymerization step, and does not mean a filter provided for filtering a 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.
[0021]
In addition, from the viewpoint of heat resistance and durability of the polymer filter, examples of the filter medium include wire mesh, sintered metal powder, felt, sintered metal laminated wire mesh, sintered metal fiber, and the like. Sintered bodies are preferred. 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. Further, 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 thus, in order to perform sufficient filtration in a state where the filtration resistance is reduced, a replacement operation and a cleaning operation of the polymer filter are necessary. .
[0022]
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 denote oligomer or polymer liquid supply pumps, 5 denotes an oligomer filter, and 8 denotes a double 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.
[0023]
First, a slurry in which terephthalic acid and ethylene glycol as raw materials are mixed is continuously supplied to the esterification reactor 1, and an oligomer is generated 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 to a double-type polymer filter 8 which is used alternately through a pump 6, and after the “foreign matter” is filtered, the polymer is supplied to the final polycondensation reactor 3. Is done. At that time, the polycondensation reaction proceeds while generating ethylene glycol vapor in the initial polycondensation reactor 2 and the final polycondensation reactor 3.
[0024]
Here, in the present invention, the intrinsic viscosity of polyethylene terephthalate supplied to the polymer filter 8 is preferably 0.2 or more and 0.55 or less. This is because when the intrinsic viscosity is lower than 0.2, 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.
[0025]
The polyethylene terephthalate high polymer finally obtained as described above is discharged from the final polycondensation reactor 3 in which the polymer filter is not provided on the output side by the pump 7, and is formed into chips, spinning, film forming, and kneading. And so on. 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, 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, and direct cooling of at least a portion of the polyester polymer to a subsequent step (the spinning step is illustrated in the embodiment of FIG. 2) without forming a cooling chip. 2) illustrates a flow for transferring to (1). In FIG. 2, since the flow until the polyester high polymer leaves the final polycondensation reactor is the same as that in FIG. 1, the description up to this point will be omitted to avoid duplication. Therefore, the description will be made from the point where the polyester high polymer comes out from the final polycondensation reactor 3.
[0026]
The polyester high polymer coming out of the final polycondensation reactor 3 by the process as shown in FIG. 1 is discharged by the pump 7 while maintaining the same state, and sent directly to the distributor 9 and the spinning gear pump 10. . 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.
[0027]
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. Is characterized in that no polymer filter is provided. Thus, rather than filtering the high viscosity polymer exiting the final polycondensation reactor, it will filter the relatively low viscosity polymer prior to entering the final polycondensation reactor. For this reason, the flow resistance (filtration resistance) when passing through the polymer filter is reduced, thereby making it possible to reduce the power cost, suppress the drift in the polymer filter, and reduce the pressure resistance of pipes and filters.
[0028]
Furthermore, depending on the conditions, usually, even when a switching shock (for example, pressure fluctuation or air bubble entrapment) occurs when periodically switching the clogged polymer filter in several weeks to several months, The final polycondensation reactor located on the outlet side of the polymer filter acts as a cushion and does not directly affect the outlet of the final polycondensation reactor. Also, 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. In particular, in a direct spinning method in which at least a part of the polyester polymer is directly spun without forming a cooling chip, pressure fluctuation, thread breakage, generation of fluff, and the like due to switching of a polymer filter can be suppressed.
[0029]
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 and 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 a shaft at both ends and no shaft at the middle part, long-term adhesion and stagnation of oligomers and polymers in the gas phase in the polycondensation reactor are reduced, thereby reducing the "foreign matter" It is more preferable to suppress the occurrence of the above.
[0030]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the manufacturing method of this invention, the shock by switching of a polymer filter can be suppressed, and also a relatively low-viscosity polyester polymer can be passed through a 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. Furthermore, 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 continuous polymerization of polyester.
[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

Claims (5)

In the method for continuously producing a polyester polymer through a plurality of polycondensation reactors, the polymer filter provided between the final polycondensation reactor and the immediately preceding polycondensation reactor has an intrinsic viscosity of 0.2 or more . 0. 55 filtered through a is melted polymer less, continuous process for producing a polyester, characterized in that the outlet side of the final polycondensation reactor without the polymer filter. The method for continuously producing polyester according to claim 1, 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. Continuous production method of polyester. 3. The method according to claim 1, wherein the polyester is polyethylene terephthalate. Has a shaft at both ends of the reactor, any of claims 1 to 3 in the middle of the reactor, characterized in that the production of polyester by the final polycondensation reactor consisting of horizontal uniaxial reactor without a shaft A method for continuously producing a polyester according to claim 1. The method for continuously producing a polyester according to any one of claims 1 to 4, wherein a plurality of polymer filters are alternately used.

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