MXPA99002101A - Method and apparatus for continuous polycondensation - Google Patents

Abstract

A continuous polyester manufacturing apparatus comprising an esterifier (first reactor), a prepolymerizer (second reactor) and a final polymerizer. At least one of the first and second reactors is a reactor which does not have a stirring function performed by an external power source, and the final polymerizer is a horizontal single-shaft low-revolution reactor. With this constitution, polyesters can be manufactured with the minimum number of reactors necessary for the reaction and with the least power consumption for the stirring necessary for the reaction. As a result, high-quality polyesters can be produced with high efficiency at a minimum energy cost.

Description

METHOD AND APPARATUS FOR CONTINUOUS POLYCONDENSATION TECHNICAL FIELD "The present invention relates to a process and apparatus for the continuous polycondensation of polymers of the polyester series, such as polyethylene terephthalate, polybutylene terephthalate, etc., of an aromatic dicarboxylic acid its derivative and a glycol .

PREVIOUS TECHNIQUE According to the conventional process for producing polymers of polyethylene terephthalate polycondensation series, etc., the raw materials, terephthalic acid and ethylene glycol, are fed to a mixing tank in an appropriate proportion for the esterification and the mixture is then fed to esterification reactor tanks through a pump. In the esterification step, 2 or 3 agitation tanks, each provided with stirring fins, are supplied in series and an effluent of water, as a by-product, is separated in a distillation column. A prepolymerization stage follows, where a plurality of vertical agitation tanks or horizontal agitation tanks are supplied, and a final stage of polymerization follows, where a horizontal agitation tank is provided. The tanks of these polymerization stages are each .provided with a condenser, to remove the ethylene glycol as a by-product, and operate in an atmosphere of reduced pressure. In the conventional process for producing polyesters, there are 4 to 6 reactor tanks, each of which is provided with stirring fins and its power source and provided additionally is a "distillation or condenser" column, to separate and remove Also, the polymerization steps are operated in a reduced pressure atmosphere and thus additional vacuum elements are required for the generation of a reduced pressure, that is, the operation of the apparatus requires a higher maintenance cost and a cost of An example of the related art is disclosed in Japanese Patent JP-A 7-207009, where each tank is provided with stirring fins and the vacuum is controlled, and thus its execution or operation is complicated. Improved apparatus and process, with greater efficiency of the apparatus and an economic operation based on energy savings through the apparatus, are highly suitable for the production of low molecular weight polyester.

EXHIBITION OF THE INVENTION An object of the present invention is to provide a process and an apparatus for continuous polycondensation, JTapaz to efficiently produce a high molecular weight polyester. - - Another object of the present invention is to provide a process and an apparatus for continuous polycondensation, capable of efficiently producing a polyester of high molecular weight, with a simple structure and arrangement of the apparatus. Another object of the present invention is to provide an apparatus for continuous polycondensation and a process for this continuous polycondensation, which can overcome the aforementioned problems of the prior art, and can lead a more efficient reaction to produce high quality polymers with a minimum energy, through the necessary structure and arrangement of the reactor. According to a first aspect of the present invention, a process is provided to produce continuously polyester, which comprises a first e-cap of reacting an aromatic dicarboxylic acid, or its derivative, with a glycol in a first reactor, thus producing an oligoester or a polyester, having an average polymerization degree of 3 to 7; a second step of polycondensing the oligoester or polyester of the first stage, in a second reactor, thereby producing a low molecular weight polyester, having an average degree of polymerization of 20 to 40; and a third step of further polycondensing the low molecular weight polyester of the second stage to an average degree of polymerization of 90 to 180, in a third reactor, thereby producing a high molecular weight polyester, wherein at least one of the first and second reactors is free of a stirring element of an external energy source; , or in which a reactor is used as the third reactor, which comprises a horizontal cylindrical vessel having an inlet for the low molecular weight polyester of the second stage in the lower part of one of its ends and an outlet for the polyester of high molecular weight in the lower part at its other end, in its longitudinal direction, an outlet for volatile matters in its upper part, and a stirring rotor that can rotate in 'the vicinity of the internal periphery of the container in the longitudinal direction of and inside the container, the rotor - of agitation within the container, comprises a plurality of agitation blocks, according to the level I have viscosity of the polyester, and the stirring rotor has stirring fins without some rotating shaft in the center of the stirring rotor; more preferably, in that a mixture of the aromatic dicarboxylic acid or its derivative and the glycol, in a molar ratio of 1: 1.05 to 1: 2.0 from the first to the last, is fed to a first reactor, maintained at a temperature of 240 to 285 ° C, under a pressure from atmospheric to 3 x 106 Pa; the oligoester or polyester of the first reactor is fed to the second reactor maintained at a temperature of 250 to 290 ° C, under a pressure from atmospheric to 13 Pa; and the low molecular weight polyester of the second reactor is fed to the third reactor, maintained at a temperature of 270 to 290 ° C, under a pressure of 200 to 13.3 Pa; more preferably, in that the stirring rotor is rotated from 0.5 to 10 rpm: and more preferably in that the total reaction time through the first reactor, the second reactor and the third reactor is from 4 to 8 hours. According to a second aspect of the present invention, there is provided an apparatus for continuously producing polyesters, which comprises a first reactor, for the reaction of aromatic dicarboxylic acid or its derivative, with a glycol, thus producing an oligoester or polyester , having an average degree of polymerization of 3 to 7, a second reactor for the polycondensation of an oligoester or polyester from the first reactor, thereby producing a low molecular weight polyester having an average polymerization degree of 20 to 40; and a third reactor for the further polycondensation of the low molecular weight polyester from the second reactor to an average degree of polymerization of 90 to 180, thereby producing a high molecular weight polyester, in which at least one of the first and second reactors is free from a stirring element of external energy source, or in which the third reactor comprises a horizontal cylindrical vessel that It has an entry for the low molecular weight polyester from the second reactor in the lower part of one of its ------ i --- ends, and an outlet for the high molecular weight polyester at the bottom at its other end, in its longitudinal direction, an outlet for the materials - volatile in its upper part, and a stirring rotor, which can rotate in the vicinity of the internal periphery of the container in the longitudinal direction of, and within, the The container, the stirring rotor, inside the container, comprises a plurality of stirring blocks,. according to him "viscosity level of the charge of the polyester and stirring rotor, which has stirring fins without some rotation shaft in the center of the stirring rotor, more preferably, in which in the first reactor the reaction is conducted at a temperature of 240 to 285 ° C, under a pressure from atmospheric pressure to 3 x 106 Pa, in the second reactor the polycondensation is carried out at a temperature of 250 to 290 ° C, under a pressure from atmospheric pressure up to 133 Pa, and a third reactor conducts the further polycondensation at a temperature of 270 to 290 ° C under a pressure of 200 to 13. Pa. The aforementioned objects of the present invention can be obtained using three simple reactors, each for an esterification step, a prepolymerization step and a final polymerization step, where a single reactor is used without any external power supply for at least one of the esterification step and the prepolymerization step, and one reactor of agitation, which requires power, is used for the final polymerization stage. The first reactor for the esterification step, according to the present invention, is, for example, a natural circulation type evaporator, comprising a vertical cylindrical vessel provided with an inlet and an outlet for a raw material charge, such as a mixture of an aromatic dicarboxylic acid, or its derivative, and a glycol and an oligoester or polyester at the bottom of the container and furthermore with a steam tube to discharge the values at the top of the container; a jacket of a heating means, which covers the outside of the container; and a helmet and tube type heat exchanger, inside the vessel, the outer tube of the heat exchanger is heated by the heating medium, while allowing the raw material charge to rise through the tubes without the need for power external It is convenient for the natural circulation-type evaporator to obtain the average speed of the liquid charge flowing downwards by the natural convection between the internal wall of the cylindrical vessel and the external wall of the helmet of the shell-tube heat exchanger, smaller than the average speed of the liquid load that rises through the tubes of the helmet and tube type heat exchanger, and also provide an entrance space at the bottom of the shell and tube type heat exchanger, to thus allowing the raw materials, which circulate internally, to enter uniformly inside the tubes. For the second reactor of the prepolymerization stage an apparatus is used comprising, for example, a substantially vertical cylindrical vessel, provided with an inlet for an oligopolyester or polyester charge from the first reactor, and an outlet for a polyester filler. of low molecular weight in the lower end and bottom in the center of the container, respectively, in the longitudinal direction of the container, and in addition in an outlet of volatile materials in the upper part of the -rec-ipiente, and covered with a jacket of a means of "heating on the outside of the container, whereby it does not need any external power." The second reactor can furthermore be provided with a heat exchange section in the lower part inside the container and a residence section with helical plates of deviation in the intermediate part, inside the container, in order to retain the liquid charge and transfer the charge of ¿-poJi ester successively from a lower stage to a higher stage, furthermore with a space for the separation of gas and liquid in the upper part, inside the container and a downward pipe in the vertical direction in the middle inside the container, so as to allow the Polyester load flow down like a thin film. For the third reactor for the final polymerization stage, an apparatus is used comprising, for example, a horizontal cylindrical vessel, provided with an inlet for charging low molecular weight polyester from the second reactor in the lower part at one end and an outlet for a high molecular weight polyester in the lower part at the other end, respectively, of the container in its longitudinal direction, and furthermore with an outlet for the volatile materials in the upper part of the container and a stirring motor, the which extends in the longitudinal direction of the container and rotates in the vicinity of the internal periphery of the container, the agitation rotor within the container is divided into a plurality of agitation blocks, according to the level of the viscosity of the container. the polyester loading, and the stirring rotor being without a rotation shaft, but with stirring fins in the central part of the stirring rotor.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow diagram, showing "an array of reactors for a process for continuously producing polyethylene terephthalate, according to one embodiment of the present invention," Figure 2 is a cross-sectional view, showing an evaporator according to an embodiment of the present invention; Figure 3 is a vertical front view, in cross section, showing an embodiment of the present invention, Figure 4 is a vertical front view, in cross section, showing another embodiment of the present invention; Figure 5 is a cross-sectional view along line A-A of Figure 4; Figure 6 is a cross-sectional view along line B-B of Figure 4; • * - - Figure 7 is a cross-sectional view, along line C- of Figure 4; X Figure 8 is a cross-sectional view along the line D-D of Figure 4; Figure 9 is a schematic view, showing the flow of a polyester filler in a low viscosity agitation block; Figure 10 is a schematic view showing the flow of a liquid charge around the thin hollow disk in a low viscosity agitation block; Figure 11 is a schematic view, showing the flow of a polyester filler around the hollow disk in an intermediate viscosity agitation block; Figure 12 is a schematic view, illustrating the flow of a polyester charge in the thin hollow disk in an intermediate viscosity agitation block; Figure 13 is a schematic view, showing the flow of a polyester filler in a high viscosity agitation block; Figure 14 is a cross-sectional view along the line E-E of Figure 4; and Figure 15 is a vertical front view, in cross section, showing another embodiment of the present invention.

BEST MODES FOR CARRYING OUT INVENTION X - Figure 1 shows one embodiment of the present 'invention, ie a flow diagram showing an arrangement of reactors for a process of continuously producing polyethylene terephthalate. An economically very advantageous industrial process for producing polyester is a direct esterification process, which has been used a lot recently. In Figure 1, number 31 shows a cargo mix tank, to mix and stir the TPA ( terephthalic acid) as an aromatic dicarboxylic acid and EG (ethylene glycol) as a glycol, in a molar ratio of 1: 1.05 to 1: 2.0 from the first to the last, both being raw materials to produce polyethylene terephthalate. In this step of etherifying the process, a polymerization catalyst of additives, such as a stabilizer, a color tone regulator, etc., can be used together, when required. "Polymerization catalysts include, for example, metal compounds derived from antimony, titanium, germanium, tin, zinc, etc. It is well known that not only the reaction rate, but also the dye and heat stability of the resulting polyester They depend on the type and combinations of the catalyst used, and the esterification reaction is carried out in the presence of a catalyst at a high temperature for a long time, which results in the occurrence of several side reactions, which discolor the polyester in yellow, increase the content of diethylene glycol (DEG) and the concentration of the terminal carboxy groups beyond appropriate levels and lower physical properties, such as the melting point and the "strength of the polyester. The development of new catalysts has gone far in an attempt to overcome these problems. Antimony compounds, now widely used in the industry, particularly antimony trioxide, are differentiated in cost and effect. However, the discoloration of the resulting polyester polymers is inevitable, even using these catalysts. To overcome this disadvantage, a phosphorus-based stabilizer (eg, trimethyl phosphate or triphenyl phosphate) is used together as a stabilizer. In another attempt, an inlet position of the polymerization catalyst or stabilizer is made to stabilize the quality. In the ordinary process, it is preferable to use 200 to 400 ppm of the catalyst and 50 to 200 ppm of the stabilizer. The raw materials, thus mixed, are taken to an esterification reactor 33, as a raw material charge through a feed line 32, which "supplies the raw material charge there." The esterification reactor (first reactor) 33 is provided with a jacket structure of the heating means (not shown in the drawing) on the outer periphery of the reactor, to maintain the charge of the raw material at a reaction temperature and also provided with a helmet heat exchanger 34 and tube, submerged in the charge of raw material, inside the first reactor, as a means to heat the load of raw material from a - source of external heat and circulate the charge of raw material inside the first reactor by natural circulation, proceeding thus with the reaction. The most convenient type of the first reactor is a type of calender, so the "- Esterification reaction will be carried out by the natural circulation of the raw material charge inside the reactor, based on the use of the evaporative action of the byproducts formed by the reaction.This type of reactor does not need a power source external for agitation, resulting in advantages in a simple reactor structure, does not need a sealant device of the agitation shaft and has a low manufacturing cost of the reactor.An example of such desired first reactor is shown in Figure 2. This figure 2 shows a modality of the first reactor 52. The raw material charge 52 flows in a vertical evaporator 51 through an inlet 53, provided at the bottom of the evaporator 51 and heated while passing through a plurality of transfer tubes of heat in a heat exchanger 54 of helmet and tube type, to go upwards by natural convection, where a portion of the components of eb Low pressure, in the raw material charge 52, evaporates, and is discharged from a steam tube 55 to the outside of the system. The remaining charge 52 of raw material flows down between the inner wall of the evaporator 51 and the outer shell wall of the shell and tube type heat exchanger 54, by natural convection and enters an inlet cylindrical space 56, provided in the bottom of the shell and tube type heat exchanger 54, where the flow of the charge and raw material can be rectified to a less turbulent state, and the average flow velocity through the pipes of the helmet-type heat exchanger 54 and tube, it becomes greater than the average flow velocity of the raw material charge, which flows downwards through natural convection, between the internal wall of the evaporator and the external wall of the hull. Thus, the raw material charge can enter a plurality of heat transfer tubes with a more uniform speed distribution and uniformly heated again to repeat the circulation by natural convection. In the course of circulation, the low-boiling components are evaporated and, after a suitable convection time, the resulting polyester or polyester 59 is taken out of the system by the outlet 60. To generate a uniform accelerated flow , the area of the space flow passage .-cylindrical inlet should be designed larger than the ~ total area of the flow passage of the heat transfer tubes and also the passage area of the "section of double tube, formed between the inner wall of the .-- evaporator 51 and the outer shell wall of heat exchanger 54 of helmet and tube type, becomes larger than the area of the flow passage of the inlet space. The number 57 shows an input of a heating means and 58 shows an output of the medium of ^ warming up. The outer periphery of the evaporator 51 is covered with a thermal insulator or a jacket of the heating means (not shown in the drawing). Thus, in the evaporator of this modality, the distribution of - uniform flow velocity in the axial direction of the heat exchanger, can ensure the uniform evaporation or esterification reaction of the raw material charge, and a better quality of the product can be obtained effectively in a shorter residence time. In case the raw material charge 52 is a mixture of "solid particles and a liquid (which will later be referred to as an aqueous paste), the raw material charge 52, which undergoes natural circulation, flows into the cylindrical space 56. of the inlet, provided at the bottom of the heat exchanger 54 of the hull-and-tube type and by a greater uniform elevation along a conical member 62, the solid particles are never precipitated in the background. Liquid is an aqueous paste, the solid particles contained in the aqueous paste can be prevented from precipitating, by the provision at the bottom of the evaporator of the conical member to raise the charge of the raw material to undergo internal circulation.

The conical member may have some curvature Thus, the evaporator of this embodiment is effective and more suitable for the natural circulation of an aqueous paste, and can produce a reliable polyester product of good quality The present invention is not limited to this type of evaporator and use of evaporator with stirring fins is not objectionable for process reasons.In the first reactor, the water formed by the reaction is in the form of vapor, and a gas phase "65 is obtained together with the vaporized EG. Recommended reaction conditions for the first reactor are conveniently a temperature of 240 to 285 ° C and a pressure from H- "atmospheric pressure to 3 x 106 Pa. The gases, in gas phase 65, are separated in water and EG by a "rectification" column (not shown in the drawing), and the water - discharge outside the system, as long as the EG is returned to the system. The advantages of the present invention are such that only a simple rectification column is satisfactory, because the esterification step is carried out in a single reactor, and thus not only the cost of the rectification column but also the cost of the rectification column. Also the number of pipes, valves, control units, etc., can be reduced, which results in a big reduction of the cost of the apparatus In Figure 1, the load of raw material, when it is retained in the reactor of esterification 33 (first Yeactor) for a predetermined reaction time, arrives at a predetermined esterification regime to produce an oligoester or polyester, which has an average degree of polymerization of 3 to 7, and then the resulting oligoester or polyester is supplied to a initial polymerization reactor (second reactor) 37 through a connecting tube 36, where the charge of the oligoester or polyester is heated to a predetermined reaction temperature by an in. heat exchanger 38, to undergo the polycondensation reaction, thus increasing the average degree of polymerization. The reaction conditions are a temperature of 250 to 290 ° C and a pressure from atmospheric pressure to 133 Pa, preferably 266 at 133 Pa, whereby the polycondensation reaction is proceeded to produce a low molecular weight polyester, which has an average polymerization degree of 20 to 40. The initial polymerization reactor, shown in this "Mode" is a reactor without stirring fins, but the invention is not limited to such a reactor.The initial polymerization step is such that the kinetics of the polymerization reaction is determinative of the regime and thus the reaction can proceed uniformly only by the supply of the necessary amount of heat for the polycondensation reaction completely, so there is no need for the charge of oligoester or polyester to have a stirring action by stirring fins and it is only necessary to discharge the EG formed by the polycondensation to the outside A second reactor more suitable for such an operation is conveniently the apparatus shown "in Figure 3. In Figure 3, the number 71 is a cylindrical vessel whose outer periphery is covered by a liner 72 of the heating means, having an inlet 80 for a heating means and an outlet 81 thereof, and •• "a down tube 73 having an open top end is provided in the longitudinal direction in the" "center of the vessel 71. A plurality of heat transfer tubes 74 are provided in the bottom inside the vessel 71, in parallel to the descending tube 73. A plurality of helical deflection plates 75 - are provided at different levels given at the outer periphery of the down tube 73, above the heat transfer tube 74. The deflection plates 75 each have a clearance 83 between its edge and the inner wall of the container 71, to allow the volatile materials to pass therethrough and divide the interior of the container 71 in the vertical direction, to form a plurality of residence compartments 84. There is a space 76 for separating the liquid charge from the volatile matter in the upper part of the vessel 71, i.e. - above the falling tube 73 and the upper extreme deflection load 75C. A plurality of tapered liquid receivers 88 are provided at different given levels in the inner wall of the down tube 73, through which the charges of the oligoester or polyester flow down as a thin film. The charge of the oligoester or -polyester, which flows down through the down tube 73, can be retained once in the individual liquid receivers and then successively moved downward and the polycondtion reaction can proceed, while minimizing the short path of the the charge of oligoester or polyester and effectively separates the vapors from the volatile matter. In the second reactor, the charge of the oligoester or polyester, continuously supplied through an inlet nozzle 77, enters the heat transfer tubes 74 and rises therethrough, while heating and reaches the chamber of heat transfer. extreme lower 84A residence. While the charge slowly rises through the residence compartment 84A, the polycondtion reaction proceeds and the resulting volatile matter, such as ethylene glycol, etc., moves upward through the gaps 83 at the outer edge of the chamber. the deflection plate 75. On the other hand, the load is raised by the helical configuration of the deflection plate 75 in a swirl current, in the residence compartment 84A and enters the next upper residence compartment 84B. Since the load can move smoothly in a swirl current in the next upper residence compartment 84B, the load can be raised successively through another upper residence compartment, without causing any backflow, and thus the polycondtion reaction proceeds effectively. The charge, which has reached the upper end residence compartment 84c, flows on the upper edge 82 of the down tube 73 and flows down along the inner periphery of the down tube 73 as a thin film, while separating the vapors from the volatile matters, which result from the reaction, and thus the polycondtion reaction may proceed further. Loading at an advanced stage of the polycondtion reaction, which has been separated from the "vapors of the volatile materials resulting from the reaction, is discharged to the exterior of the system through" an outlet nozzle 78, while the materials The resulting volatiles are separated from the charge drag (polyester) in an overhead space 76 in the container 71 and discharged to the outside of the system through the outlet nozzle 79 for volatile materials. At that time, the volatile materials are able to drag the load (polyesters), that is, a drag problem is likely to occur. In the present invention, the load and the volatile materials that are pumped upwards can be displaced towards the circumferential direction by the helical deflection plates 75, to suppress these trawls. The volatile materials generated in the second reactor, ie the EG, vaporize in the upper space (gas phase section) 76, maintained at a reduced pressure and discharged to the outside of the system after condtion, through a condr (not shown in the drawing), provided in the upper part of the vessel 71. The advantages of the present invention are such that only a single condr is satisfactory, because the initial polymerization step is carried out in a reactor simple and so not only the cost of "manufacture of the condr but also the number of pipes, valves, control devices, etc., can be reduced, resulting in a large decrease in the cost of the apparatus., .-- In Figure 1, the load retained in the initial polymerization reactor (second reactor) 37 for a predetermined reaction time, is supplied to a final polymerizer (third reactor) 41 through a connection pipe 40. In the final polymerizer, the polycondtion reaction also proceeds under a good surface renewal action of the agitation fins 42, without a stirring shaft in the center to raise the degree of polymerization, whereby a high molecular weight polyester, having an average degree of polymerization of 90 to 180 occurs. The right final polymerizer (third reactor) is shown in Figures 4 and 15, which has very different characteristics of the performance of "" surface renewal and energy consumption. Due to the wide viscosity range of the liquid charge, the conventional final polymerizer is divided into two apparatuses to conduct the final polymerization step, while, in the present invention, the step can be carried out "c-abo in a simple apparatus. , which results in a large reduction in the cost of the apparatus In Figure 1, the numbers 35 and 39 in the first ... - reactor 33 and second reactor 37, show liquid-gas phases, respectively, and number 44 in the third reactor is a pulse element to the stirring rotor. The present final polymerizer will be described below with reference to Figure 5, which shows a vertical front view, in cross section, of the present apparatus. In Figure 4, the number 1 shows a cylindrical container horizontally elongated, whose outer periphery is covered with a jacket of the heating means (not shown in the drawing), and at its both ends in the longitudinal direction the shafts 3a and 3b for the rotor support, respectively. A stirring rotor 4 is fixed to and supported between the shafts 3a and 3b for the support of the rotor, and the shaft 3a of the rotor is connected to a pulse element (not shown in FIG. 4, but shown at 44 in the FIG. 1), and the rotor support members, 2a and 2b, are connected to the connection support rods, 5a, 5b, 5c and 5d, as shown in Figures 4 and 5 (the number of support rods of connection depends on the size of the agitation motor 4, and is four in this mode) at both ends of the agitation rotor 4. This agitation motor 4 has a plurality of agitation blocks between the support members (end disks) 2a and 2b. The support member • fr 2a is a member for a low-viscosity polyester filler and support member 2b for a high-viscosity polyester filler. The support member 2b is smaller in the external diameter than the stirring rotor 4 and has scraping fins 13a and 13b on the side leading the end of the container forward to place the high molecular weight polyester on the inner wall of the container 1, in front of the output of the product of the container 1 by the rotation of the stirring rotor 4. Its detailed structure is shown in Figure 14, which is a cross-sectional view along the line EE of Figure 4. In the low viscosity zone of the stirring rotor 4 in the vicinity of the inlet nozzle 11 are provided with a plurality of low viscosity agitation blocks, each of which comprises a pair of hollow discs 8 with supports formed by scraping fins 6a and 6b and thin hollow discs 7a provided between a pair of hollow discs 8 and which are subjected to the charge of low molecular weight polyester, emptied from the supports (its detailed structure will be described with reference to Figures 5, 9 and 10). In the intermediate viscosity zone a plurality of intermediate viscosity agitation blocks are provided, each of which comprises a pair of hollow discs 8, a plurality of thin hollow discs 7b, which have the same external diameter and at equal distances between the a pair of hollow discs 8 and a plurality of scraping fins 6c, provided radially on the outer peripheral side of these discs (their detailed structure will be described with reference to Figures 6, 7, 11 and 12).

"Likewise, a high viscosity agitation block, which comprises a plurality of wheel-like discs 9, provided at appropriate distances from each other and the scraping fins 10, are provided on the outer peripheral side of the wheel-type discs 9. , said block is provided on the exit side of vessel 1 (its detailed structure will be described, with reference to Figures 3 and 13). An outlet nozzle 12 for discharging the high molecular weight polyester product (final polymer) is provided in the lower part at the other end of the container 1, and an outlet nozzle 14 for the materials,? Oltiles, is provided in the upper part of the container -1 and is connected to a condenser and a vacuum element through a pipe (not shown in the drawings). In the final polymerizer, as shown in Figure 4, a low viscosity low molecular weight polyester (prepolymer) filler, having a degree of polymerization, for example an average degree of polymerization of 20 to 40, is fed continuously through the inlet nozzle 11, is the first stirred in a plurality of low viscosity agitation blocks, by supports on the hollow discs, shown in Figure 5. At that time, the load has such low viscosity as that of a few Pascals to a few dozen Pascals. In the low viscosity agitation blocks, a pair of the scraping fins, 6a and 6b, forms a support on the outer peripheral side of the hollow disk 8, as shown in Figure 5, so .. • pick up the load inside the support by rotation, as shown in Figure 9. That is, Figures 9 and 10 -p- schematically show the load flow states. At the bottom of each basket of the scraping fins 6a and 6b, a small or light hole d is formed. With the rotation of the stirring rotor, the low viscosity load 91 is collected by the basket, as shown by the number 100. "in Figure 9, and the baskets are also tilted downward by the subsequent rotation, to allow the load to begin to leave the load inside, and, at the same time, begin to escape to the outside little by little, from the basket , through the small hole in the clearing, as shown by the number 102 in Figure 9, to form liquid films inside and out, 101 and 102, respectively, of the basket.The load 101, flowing towards down inside from the basket, it is emptied onto the thin hollow disk 7a, provided in the vicinity of the tip end on the side to the inside of the baskets, as shown by number 103 in Figure 10, to form liquid films on the surface of each thin hollow disc 7a and between the adjacent thin hollow discs 7a, at the same time, thus producing a larger surface area of evaporation.These actions are repeated for each rotation of the baskets to ensure an area s uperficial with sufficient evaporation and better surface renewal. The most satisfactory performance can be obtained in the viscosity agitation blocks, even at a low revolution per minute, such as at 0.5 rpm up to a few rpm (no greater than 10 rpm). and the effective reduction of agitation energy consumption can be obtained. Evaporated by-products of the charge pass through central holes 20a of the hollow discs and holes in the center of the thin hollow discs 7a, and discharged through the outlet nozzle 14. The charge treated in the agitation blocks of low viscosity for a predetermined residence time, has an increased viscosity, such as a few tens of Pascals, and enters a plurality of adjacent agitation blocks, of intermediate viscosity, which have a detailed structure shown in the Figures 6 and 7. The intermediate viscosity agitation blocks each comprise a pair of hollow discs 8, a plurality of thin hollow discs 7b, provided between them, and scraping fins 6c, provided through the peripheral sides of these discs holes 8 and 7b.

DI diameter of the central hole 20a of the hollow disk 8, as in Figure 6, and the diameter D3 of a central hole 20a The thin hollow disk 7b, as in Figure 7, is selected to be optimal, depending on the rate of vapor flow of the by-products developed from the charge by the subsequent polycondensation reaction.

Also, the diameter D2 of the circular holes Small of the thin hollow disk 7b, as shown in Figure 7, is selected to be optimal, depending on the viscosity of the charge and the rate of vapor flow of the byproducts developed from the charge by the polycondensation reaction. The load 92, which has an increased viscosity, such as a few tens of Pascals, is carried upwards by the scraping fins 6c by rotation, and flows downward by the gradual inclination of the scraping fins 6c by their subsequent rotation. , to form liquid films 104, as shown in Figure 11. The liquid films 104 flow down onto the connecting support rods 5a of the stirring rotor 4 and are retained there for a long time, as glued and - suspended below them, and in addition, the load carried upwards, is suspended downwards on the central hole 20a of the hollow disk 8, to form a liquid film 105, as shown in Figure 11. A film 107 of liquid is similarly formed on the central hole 20a of the thin hollow disk 7b and also the load is suspended downwards on the small circular holes 20b of the thin hollow disk 7b, to form liquid films 106, as shown in Figure 12. The charge is formed in such liquid films and "may have an increased degree of polymerization and viscosity, due to the greatly increased surface area of evaporation and renewal. When the viscosity of the charge reaches a few hundred Pascals, the charge is treated in a high viscosity agitation block.

- High viscosity comprises a plurality of wheel-like disks 9, having scraping fins 10 (Figure 4) on its outer peripheral side, as shown in Figure 8. The wheel-type disks 9 are connected to each other predetermined distances by the connection support rods 5a, 5b, 5c and 5d in the horizontal direction. The scraping fins 10 comprise front side flaps 10a and rear side scraping fins 10b, arranged alternately on a wheel-like disk 9 and on another wheel-like, adjacent disk 9, respectively, so the total length in the horizontal direction of the scraping fins on all discs 9 > : wheel type is such that the track of the scraping fin 10a on a wheel-type disc, may overlap that of a scraping fin 10b on another wheel-type disc, when rotated, to scrape the entire wall surface corresponding internal of the wheel 1. As shown in Figure 13, the load 93, which has a viscosity of a few hundred Pascals, is "carried upwards by the scraping fins 10a by the rotation of the stirring rotor 4 , and this load thus carried upwards flows downwards by the rotation of the wheel-like disk 9 and suspended to form a liquid film 108, and likewise, a liquid film 109 is also formed on the hollow parts of the wheel-like disk 9 , thus creating complicated surface configurations of liquid films.When the viscosity of the liquid charge is subsequently increased to reach a few thousand Pascals, the amount of the Charge, thus carried upwards by the scraping fins 10a is increased. When the revolutions per minute "H-the stirring rotor 4 increases in that state, occurs such retained phenomenon of charge circulation, to bring up the load retained by the shaving fins 10a, again without leaving the fins." Thus, the stirring rotor 4 It should be turned at no more than 10 rpm.When the viscosity of the liquid charge becomes greater, the optimal rotation should be made slower. '"" test of the inventors, the optimal rotation is in the range of 0.5 to 6 rpm. The agitation and surface renewal actions are repeated, as described above, to promote the polycondensation reaction. The volatile substances formed by the reaction pass through the hollow parts central holes and small holes of the hollow discs successively and move in the longitudinal direction through the container 1 and are discharged to the system to the outside through the discharge nozzle. 14 for volatile matters. The resulting high molecular weight final polyester, which has a high degree of polymerization, such as an average degree of polymerization of 90 to 180 and a high viscosity, such as a few thousand Pascals, thus obtained, is discharged to --- - system to the outside through the outlet nozzle 12. At that time, the final polyester, which has such J-aita viscosity, is bound to remain in the region "above the outlet nozzle 12, but the external diameter of the support member 2b of the stirring rotor 4 ~ is less than the eternal diameter of the stirring rotor 4, the final polyester never remains on the support member 2b. Also, the scraping fins 13a and 13b are provided on the support member 2b on the side facing the wall, the inner end of the container, as shown in Figures 4 and 14 to go forward to the final polyester, hence at the outlet 12 of the container 1 and as-iT the inner end wall surface of the container is always maintained in a self-cleaning, substantially complete state, to prevent the final polyester from depositing and remaining there. In the polycondensation of the polyethylene terephthalate in such a final polymerizer, a prepolymer charge from the second reactor is continuously supplied in the final polymerizer (third reactor) through the inlet nozzle 11, stirred by the stirring rotor 4, while renewing the loading surfaces of the prepolymer, and the evaporation and removal of the volatile materials results from the polycondensation reaction, such as ethylene glycol, etc., and as a result of the polycondensation reaction of the final polyester of a higher viscosity, can be obtained. The volatile materials separated during the polycondensation reaction, for example, ethylene glycol, etc., are discharged to the external system through the outlet nozzle 14. The operating conditions for the final polymerizer are a temperature of 260 to 300 ° C, preferably 270 to 290 ° C, a pressure of 10,000 to 10 Pa, preferably 200 to 13.3 Pa, and revolutions of the agitation motor from 1 to 10 rpm. The resulting final polymers are discharged to the external system through the outlet nozzle 12. The interior of the container 1 is agitated and maintained always in a state of self-cleaning, substantially complete, during the polycondensation reaction and the load is subjected to a better surface renewal, and thus the final polyester of good quality can be obtained efficiently, without any deterioration due to the permanence in the container 1. This type of current final polymerizer can be similarly applied to a continuous volume polymerization of resins of the polycondensation series, such as polyethylene naphthalate, plyliamide, polycarbonate, etc. - If the viscosity of the load to be supplied to the final polymerizer is relatively high, low viscosity agitation blocks can not be used. That is, the low viscosity agitation blocks can be omitted from the final polymerizer, as shown in Figure 4. Figure 15 shows one embodiment of such a final polymerizer, which is identical in structure with that of Figure 4, except that the low viscosity agitation blocks are omitted from that of Figure 4. In Figure 15, the high viscosity agitation block comprises a plurality of wheel-like disks 9, provided at appropriate distances from each other, the fins 200 of scraping being provided as connected between the outer peripheral flanks of a pair of adjacent wheel-type discs 9, but the position of the scraping fins 200 in a pair of adjacent wheel-like discs 9 is altered with that of the other pair of the following wheel-like adjacent discs 9. ~ In the structure of the apparatus, mentioned above, to produce polyethylene terephthalate, the number of reactors decreases, compared to the structure of the conventional apparatus and thus the cost of the apparatus can be , very reduced in the present invention. Not only the number of distillation or rectification columns and accessory capacitors can decrease due to the smaller number of reactors, but also ..J-a-s pipes there connected, instrumentation or control devices and values, can be saved greatly. The utility costs relative to the vacuum elements and the establishment of the heating medium can also greatly decrease, resulting in a lower operating cost, as an advantage. According to the present invention, an apparatus can be obtained to continuously produce polyester from only 3 reactors, each directed to the "esterification stage, the pre-polymerization stage and the final polymerization stage, and can be operated economically at increased efficiency through the apparatus, and energy savings through plant establishment The total reaction time through the first reactor, second reactor and third reactor is 4 to 8 hours.

Claims (3)

1. CLAIMS 1. A process for continuously producing polyester, which comprises a first reaction step of an aromatic dicarboxylic acid, or its derivative, with a glycol, in a first reactor, thus producing an oligoester or a polyester, which has an average degree PoXimerization from 3 to 7; a second step of polycondensation of the oligoester or polyester of the first stage in a second reactor, thus producing a low molecular weight polyester, having an average degree of "olimerization from 20 to 40, and a third stage of further polycondensation of the low molecular weight polyester of the second stage to an average degree of polymerization of 90 to 180, in a third reactor, thus producing a high molecular weight polyester, in that at least one of the first reactor and the second reactor is free of a stirring element of an external power source.
2. 2. A process for continuously producing polyester, which comprises a first step of reacting an aromatic dicarboxylic acid, or its derivative, with a glycol, in a first reactor, thus producing an oligoester or a polyester, having an average degree of polymerization from 3 to 7; a second stage of polycondensation of the oligoester or polyester of the first stage in a second reactor, thus producing a low molecular weight polyester having an average degree of polymerization of 20 to 40; and a third step of further polycondensation of the low molecular weight polyester of the second stage to an average degree of polymerization of 90 to 180, in a third reactor, thus producing a high molecular weight polyester, in which a reactor in the third reaction, which comprises -a horizontal cylindrical vessel, which has an entry for the low molecular weight polyester of the second '"Stage in the lower part of one of its ends and an outlet for the high molecular weight polyester in the lower part of its other end in its longitudinal direction, an outlet for the volatile materials in its upper part, and a rotor of agitation, which can rotate in the vicinity of the internal periphery of the container in the longitudinal direction of, and within, the container, the agitation rotor, inside the container, comprises a plurality of agitation blocks, according to the level of viscosity of the polyester, and the stirring rotor has stirring fins without any rotation shaft in the center of the stirring rotor. 3. A process, according to claim 1 6 XX, wherein the mixture of the aromatic dicarboxylic acid, or su-derivative, and the glycol, in a molar ratio of 1: 1.05 to 1: 2.0, of the aromatic dicarboxylic acid, or its derivatized, to glycol, is fed to the first reactor, maintained at a temperature of 240 to 285 ° C, under a pressure, from atmospheric pressure to 3 x 106 Pa; the oligoester or polyester of the first reactor is fed to the second reactor, maintained at a temperature of 250 to 2-90 ° C, under a pressure, from atmospheric pressure to 133 lPa; and the low molecular weight polyester of the second reactor, is fed to the third reactor, maintained at a temperature of 270 ° C to 290 ° C, under a pressure of 200 to 13.3 Pa. 4. A process, according to claim 2, wherein the agitation motor in the third reactor is rotated at 0.5 to 10 rpm. "5. A process, according to claim 1"~ or ~ 2, in which the total reaction time through the first reactor, the second reactor and the third reactor, is 4 to 8 hours . ~ "6Tr An apparatus for continuously producing polyester, which comprises a first reactor, to react an acid "aromatic dicarboxylic, or its derivative, with a glycol, thus producing an oligoester or polyester, having an average degree of polymerization of 3 to 7, a second reactor for the polycondensation of the oligoester or polyester of the first reactor, thus producing a polyester of low molecular weight, which has an average degree of polymerization of 20 to 40, and a third reactor for the further polycondensation of the low molecular weight polyester of the second reactor at an average degree of polymerization of 90 to 180, thus producing a high polyester molecular weight, in which at least one of the first reactor '* and * the second reactor are free of a stirring element from an external power source. 7. An apparatus for continuously producing a psester, which comprises a first reactor, for the reaction of an aromatic dicarboxylic acid, or its "derivative, with a glycol, thus producing an oligoester or polyester, having an average degree of polymerization of 3 to 7; a second reactor, for the polycondensation of the dligoester or polyester of the first reactor, thus producing a low molecular weight polyester, having a degree "Polymerization average of 20 to 40, and a third reactor, "Sara- the further polycondensation of the low molecular weight polyester of the second reactor at an average degree of polymerization of 90 to 180, thus producing a high molecular weight polyester, in which the third reactor comprises a horizontal cylindrical vessel, having an inlet - • the low molecular weight polyester of the second reactor, in the lower part of one of its ends, and a high molecular weight polyester outlet in the lower part in its other end, in its longitudinal direction, an outlet for materials volatile in its upper part, and a stirring rotor, which can rotate in the vicinity of the internal periphery of the container in the longitudinal direction of and inside the container, the stirring rotor, inside the container, comprises a plurality of stirring blocks , according to the viscosity level of the polyester filler, and a stirring rotor, which has stirring fins without any rotary shaft in the center of the stirring rotor. .r_- H 8. The apparatus, according to claim 6 6 7, in which the first reactor is for conducting the reaction of a mixture of the aromatic dicarboxylic acid, or its derivative, and the glycol, in a molar ratio of 1: 1.05 to 1: 2.0, from the first to the last, fed therein a temperature from 240 to 285 ° C, under a pressure from 'atmospheric pressure to 3 x 10s Pa; the second reactor is for conducting the polycondensation of the reaction product -Jaired there from the first reactor, at a temperature of 250 to 290 ° C, under a pressure from the pressure - "atmospheric up to 133 Pa, and the third reactor is for conducting the further polycondensation of the product fed there from the second reactor, at a temperature of 270 to 290 ° C, under a pressure of 200 to 13.
3. 3 Pa. : "^ r- = ~ - 9. A reactor for the continuous production of polyester, this reactor is for use in a stage of The final arc of a process for producing a high molecular weight polyester of an aromatic dicarboxylic acid, or its "derivative, and a glycol, which comprises a horizontal cylindrical vessel, having an inlet for a low weight polyester. molecular weight of the second reactor, in the lower part at one of its ends, and an outlet for a high molecular weight polyester in the lower part at its other end in its longitudinal direction, an outlet for volatile materials in its upper part, and a stirring rotor that can rotate in the vicinity of the internal periphery of the container in the longitudinal direction of, and within, the container, this stirring rotor, within the The container comprises a plurality of agitation blocks, according to the viscosity level of the polyester filler, and the agitation rotor has fins without a rotating shaft in the center of the agitation rotor. 10. A rotor, to produce continuously, this reactor is for use in the final stage of a process for producing a high molecular weight polyester from an aromatic dicarboxylic acid, or its derivative, and a glycol, which comprises a cylindrical container, substantially horizontal, which has an inlet for charging the low molecular weight polyester from a second reactor, at the bottom at one end, and an outlet for a high molecular weight polyester, at the bottom at its other end, in its horizontal direction, and - an outlet for volatile substances in its upper part, and a stirring rotor, which can rotate in the vicinity of the periphery of the container, in the longitudinal direction of, and inside, the container, this stirring rotor, inside the container , comprises a plurality of agitation blocks, according to the viscosity level of the - caxga of the polyester, and has stirring fins without any rotating shaft in the center of the stirring rotor, the outer diameter of the end discs, - which connect the power transmission shafts at both ends of the shaking rotor to this shaking rotor, are smaller than the eternal diameter of the shaking rotor. 11. A reactor, according to the claim 10, in which the agitating blocks comprise a plurality of low viscosity agitation blocks, connected to each other and provided on the inlet side of the container; these low viscosity agitation blocks each comprise a pair of hollow discs, provided at both ends of the block and the thin hollow discs, these hollow discs each having not a plurality of supports, each consisting of a pair of scraping fins in the outer peripheral part of the hollow disk, these supports serve to collect the polyester load, the thin hollow discs each being provided in the vicinity of the inner peripheral end side of the scraping fins, the polyester load collected in the supports by the rotary movement thereof, they are for emptying on the thin hollow discs, thus forming liquid films of the polyester filler along the thin hollow discs. 12. A reactor, according to claim 11, wherein a pair of scraping fins in the bottom part of each of the supports, has in the joint of the scraping fins a hole or a small clearing to allow the load Polyester collection flow out through it. 13. A reactor, according to claim 10, wherein the agitating blocks comprise a plurality of intermediate viscosity agitation blocks, connected together; these intermediate viscosity agitation blocks each comprise a pair of hollow discs provided at both ends of the block, and a plurality of thin hollow discs having the same external peripheral size as that of the hollow discs, provided between a pair of hollow discs These hollow discs each have a plurality of scraping fins, provided radially on the outer peripheral sides of each of the hollow discs, and the thin hollow discs each having a plurality of small circular holes. 14. A reactor, according to claim 10, wherein the agitating blocks comprise a high viscosity-agitating block, comprising a plurality of wheel-type disks, arranged in the horizontal direction and each provided with scraping fins, the positioning of the scraping fins on a wheel-type disc is alternated with that on another wheel-like adjacent disc. 15. A reactor, according to claim 10, wherein the outer diameter of the end disk on the side of higher viscosity, which is connected to the agitation rotor, is smaller than the outer diameter of the agitation rotor, the disk at the end has scraping fins on its side facing the end wall of the inner container, the scraping fins of the end disc can rotate in the vicinity of the end wall of the inner container and is capable of carrying forward the polyester. ato "" "molecular weight that remains in the inner end wall of the container in front of the outlet of the container by its rotation. 16- A reactor, according to the claim 14, in which the scraping fins are provided connected between the peripheral peripheral side of a pair of adjacent wheel-type disks. 17. A reactor for continuously producing polyester, this reactor is for use in the intermediate reaction stage of a process for producing a high molecular weight polyester from an aromatic dicarboxylic acid, or its derivative, and a glycol, the - which comprises a substantially vertical cylindrical vessel, having an inlet for a charge of an oligoester or polyester from the first reactor, in its lower side portion, and an outlet for a charge of low molecular weight polyester to a third reactor, in the background at its center in the longitudinal direction, an exit for "volatile matters in its upper part, a jacket of a heating means, provided around the outer periphery of the container, a heat exchange section in the lower part inside the container, a residence section with deflected helical plates, provided in the intermediate position inside the container, to retain and transfer successively the load of the oligoester "cf pbliester from top to bottom, a space for the separation of gas-liquid, provided in the upper position inside the container, and a down tube, provided in the center of the vertical direction of the container, for the downward flow of the load of polyester as a "Thin film through it. .__ ---- 18. A natural, circulation type evaporator for use in the initial reaction stage of a process for producing a high molecular weight polyester from an aromatic dicarboxylic acid, or its derivative, and a glycol, as raw materials, which comprises a vertical cylindrical vessel that has an inlet for the loading of raw materials and an outlet for the charges of an oligoester or polyester to a second reactor, a steam tube provided in its upper part, to discharge vapors , a jacket of a heating means, provided around the outer periphery of the container and a shell-and-tube type heat exchanger, provided inside the container, for exterior heating of the tube and allowing the loading of raw materials to rise to through the tubes, in which the average velocity of the charge of raw materials flowing downwards by the natural convection between the inner wall of the container and the external wall of the interchange The helmet and tube type heat exchanger is made smaller than the average speed of the raw material charge that rises through the tubes of the shell and tube type heat exchanger, and an inlet space is provided in the bottom of the shell and tube type heat exchanger, to allow the internal circulation of the raw material charge to enter uniformly in the tubes of the shell and tube type heat exchanger.