JP5180506B2 - Method for producing aromatic polyester - Google Patents

Description

  The present invention relates to a method for producing an aromatic polyester that is an LCP prepolymer.

  The aromatic polyester can be obtained by polycondensation using dicarboxylic acid, diol, and hydroxycarboxylic acid as raw materials. The raw material has at least one aromatic ring. Generally, in the polycondensation reaction process of an aromatic polyester, when polycondensation proceeds while stirring, the viscosity of the reaction system increases, the stirring load increases, and further stirring becomes difficult. Therefore, in many cases, the reaction product is extracted from the polymerization tank in the middle of the reaction, cooled and solidified, then pulverized as necessary, and heated again to complete the polycondensation reaction.

  At this time, it is preferable in terms of quality that the aromatic polyester in the middle of the polycondensation reaction extracted from the polymerization tank is cooled and solidified not only to the surface but also to the inside, and used for the next step. For example, when a thick polymer is cooled, a temperature difference occurs between the surface and the interior, and even if the polycondensation reaction stops on the surface, the interior is still hot and the reaction proceeds. A tribe polyester cannot be obtained.

Therefore, in Patent Document 1, the aromatic polyester in the middle of the polycondensation reaction is passed from the polymerization tank through a fixed-quantity supply device having a flow-squeezing type feeder, and supplied to a double belt type cooler while maintaining a constant flow rate. A method for solidification is disclosed.
JP-A-6-256485

  As disclosed in Patent Document 1, in a method of supplying an aromatic polyester in the middle of a polycondensation reaction to a double belt cooler, a ball valve is usually used for flow rate control. The ball valve has the advantages of low resistance when fully open, reliable shut-off when fully closed, operation to increase / decrease the flow rate over a wide range, and easy maintenance such as cleaning. On the other hand, the flow rate varies greatly even with a slight valve operation due to the structure, and therefore it is not suitable for flow rate adjustment. For this reason, if the flow rate of the aromatic polyester is excessive, the double belt type cooler breaks out from the end of the roller on the inlet side of the double belt type cooler in the lateral direction and is solidified. On the other hand, if the flow rate is too small, the monomer remaining in the polymerization tank without being discharged is polymerized in the polymerization tank and solidified in the tank.

The causes of fluctuations in the flow rate are the generation of resin solidified products and the mixing of sublimates in the polymerization tank, fluctuations in viscosity, pressure fluctuations in the polymerization tank, and differences in grades of aromatic polyester (ease of polymerization, solidification) The difference in ease of use etc.) can be considered.
In particular, the aromatic polyester extracted from the polymerization tank has a property that it tends to harden when the movement stops. Therefore, if there is a delay in extraction, solidification is promoted inside the feeder supplied to the belt cooler or in the discharge section, and the generated solidified product is likely to reduce the extraction flow rate, become clogged, or scatter.

  The present invention has been made in view of the above problems, and when the aromatic polyester in the course of the polymerization reaction is extracted from the polymerization tank and supplied to the belt cooler, it is easy to cope with fluctuations in the flow rate of the extracted aromatic polyester. It is an object of the present invention to provide a method capable of following the above and stably producing an aromatic polyester.

  The method for producing an aromatic polyester according to the present invention comprises the step of pouring the aromatic polyester in the middle of the polycondensation reaction drawn out from the polymerization tank onto a belt cooler through a ball valve, and cooling and solidifying the aromatic polyester in the width direction of the belt. (1) When the spread in the width direction is within a predetermined range, the opening degree of the ball valve is automatically controlled by PID control, and (2) the spread in the width direction is detected. When it is out of the predetermined range, the opening degree of the ball valve is automatically operated by a sequence.

  In such a method of the present invention, the aromatic polyester to be poured is detected as a thermal image by a camera, and the area of the image of the aromatic polyester within a predetermined frame on the monitor screen is determined, and (1) the image area Is automatically controlled by PID control when (2) is within a predetermined range, and (2) when the image area is outside the predetermined range, the opening of the ball valve is automatically operated by a sequence. Is preferred.

  In that case, the frame may be a range including the entire aromatic polyester extending in the width direction of the roller, or the frame may be a small section near the left and right ends in the width direction of the roller. .

  In the present invention, it is preferable that the dynamic control by the PID control of the ball valve is performed with a small proportional gain.

  In the method for producing an aromatic polyester according to the present invention, the aromatic polyester is extracted from the polymerization tank through a ball valve and poured onto the belt cooler. As described above, the ball valve has a drawback in that it is not suitable for adjusting the flow rate because the flow rate fluctuates greatly even with a slight valve operation.

  On the other hand, the aromatic polyester withdrawn from the polymerization tank is easy to solidify in the polymerization tank, the resin solidified product in the polymerization tank and the mixing of sublimation, viscosity fluctuation, pressure fluctuation in the polymerization tank, aromatic polyester Sudden flow rate fluctuations are likely to occur suddenly due to differences in the ease of polymerization and solidification.

  Therefore, in the present invention, the spread in the belt width direction of the aromatic polyester poured into the belt cooler through the ball valve is detected by a thermal image, and when stable (that is, when the spread in the width direction is within a predetermined range). In addition, the ball valve opening is automatically controlled by PID control, and at the time of abnormality (that is, when the spread in the width direction (that is, when the flow rate increases or decreases outside the predetermined range)), automatic operation by a sequence is performed. Thus, the opening degree of the ball valve is adjusted promptly. Thus, using a ball valve that is generally considered not suitable for flow rate adjustment, it is possible to respond quickly to fluctuations in the flow rate of the aromatic polyester and to stabilize the production.

  Specifically, since the spread in the width direction can be represented as a thermal image by the area of the image of the aromatic polyester, it is easy to determine whether the image area of the aromatic polyester is within a predetermined range and Judgment can be made quickly.

  In that case, since the state of the whole aromatic polyester can be monitored when the frame is in a range including the whole liquid spreading in the width direction of the roller, relatively stable control is possible. On the other hand, when the frame is a small section near the left and right ends in the width direction of the roller, it can be detected quickly. Further, in the case of such a method, it is possible to more reliably detect the presence or absence of protrusion from the end portion that has a fatal effect on the belt.

  Hereinafter, the manufacturing method of the aromatic polyester which concerns on this invention, and the extraction cooling device used for this are demonstrated, referring drawings. FIG. 1 is a schematic explanatory view showing an embodiment of an extraction cooling apparatus to which the method of the present invention is applied, FIG. 2 is a perspective view of a main part of a belt cooler used in the polymer extraction cooling apparatus, and FIG. 3 is a liquid of FIG. FIG. 4 is a block diagram showing an extraction cooling method by the extraction cooling device of FIG. 1.

  The extraction cooling apparatus 10 shown in FIG. 1 controls the flow rates of the prepolymerization tanks (hereinafter simply referred to as polymerization tanks) 11a and 11b and the aromatic polyester 12 in the middle of the polycondensation reaction extracted from the lower ends of the polymerization tanks. A flow rate control ball valve 13, a double belt cooler (hereinafter simply referred to as a belt cooler) 14 disposed below the ball valve 13, a camera 15 for capturing a thermal image of the inlet side of the belt cooler 14, A monitor 17 that displays analysis data of the captured thermal image, and a control means 16 that includes a DCS (distribution control system) to which the analysis data is sent and adjusts the opening degree of the flow control valve 13 are provided.

  The aromatic polyester in the present invention is an aromatic polyester such as polyethylene terephthalate, polybutylene terephthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, poly 1,4-cyclohexanedimethylene terephthalate; p-hydroxybenzoic acid Liquid crystal polyesters obtained from aromatic hydroxycarboxylic acids such as 2-hydroxy-6-naphthoic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, hydroquinone, resorcin, 4 , 4′-dihydroxydiphenyl, liquid crystalline polyesters obtained from aromatic dihydroxy compounds such as 2,6-dihydroxynaphthalene, and the like.

In particular, it is preferably applied to a liquid crystal polyester having a relatively high flow temperature. Specifically, the flow temperature is a temperature higher than the ambient temperature (usually a temperature higher by 30 ° C. or more than the ambient temperature). For example, it is preferably applied to an aromatic polyester having a temperature of 200 ° C. or more. Here, the flow temperature means that when a resin heated and melted at a heating rate of 4 ° C./min is extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm under a load of 100 kg / cm ² , the melt viscosity is 48000 poise. It is the temperature at the point indicated.

  In this embodiment, two polymerization tanks 11a and 11b are provided, and one polymerization tank 11a is arranged directly above the inlet side of the belt cooler 14 so that the aromatic polyester is dropped straight. The other polymerization tank 11 b is disposed at a position away from the inlet side of the belt cooler 14. Therefore, in the other polymerization tank 11b, an inclined pipe line 18 for transferring the aromatic polyester is provided from the outlet at the lower end to the vicinity of the inlet of the belt cooler 14. On the lower end side of the inclined pipe line 18, a contact plate 19 for dropping the flowing liquid aromatic polyester downward is provided.

  The two polymerization tanks 11a and 11b are normally used alternately. That is, while opening the ball valve 13 of one polymerization tank 11a and taking out the aromatic polyester 12 from the polymerization tank 11a, the ball valve 13 of the other polymerization tank 11b is closed, The polymerization tank 11b is filled and pre-polymerization is performed. When the removal of the aromatic polyester 12 from one polymerization tank 11a is completed, the ball valve 13 of the one polymerization tank 11a is closed and the aromatic polyester is taken out from the other polymerization tank 11b. As described above, by performing the treatment alternately in the polymerization tanks 11a and 11b, efficient polymerization / removal / cooling treatment can be performed.

  In addition, the inclined pipe line 18 includes a jacket 20 so that the transfer distance of the aromatic polyester 12 becomes longer, so that the temperature of the aromatic polyester flowing therein does not decrease and solidify. Each of the polymerization tanks 11a and 11b is also provided with a jacket 21 in order to maintain the temperature in the tank at a predetermined temperature. A pipe line 22a for pouring the monomer from the previous acetylation reaction tank is connected to the lid body 22 of each polymerization tank 11a, 11b. In addition, acetic acid by-produced during the reaction is taken out via the pipe line 22b.

  A ball valve 13 provided at an outlet at the lower end of the polymerization tanks 11a and 11b performs an opening / closing operation and an opening degree adjustment. As a result, there is little resistance when fully open, and high shut-off when fully closed. Further, the opening can be adjusted in a wide range, and cleaning is easy. The opening degree of the ball valve can be adjusted by, for example, motor driving or air driving.

The belt cooler 14 has an upper belt 24 and a lower belt 25 made of metal endless belts each having corrosion resistance such as a steel belt, which are arranged in close contact with each other in the middle, and a polycondensation reaction is in progress between the upper and lower belts 24 and 25 It is an apparatus that cools while sandwiching and transporting an aromatic polyester. The upper and lower belts 24 and 25 are cooled by cooling water. The inlet side and the outlet side of the upper belt 24 are wound around an inlet side roller 26 and an outlet side roller 27, respectively, and are stretched between them. The lower belt 25 is stretched in a substantially triangular shape by a guide roller 30 in addition to the inlet side roller 28 and the outlet side roller 29. The upper belt 24 circulates counterclockwise in FIG. 1, and the lower belt 25 is driven by a motor so as to circulate clockwise.
The clearance between the belts 24 and 25 is usually about 1 to 2 mm, and the lengths and moving speeds of the belts 24 and 25 are set to be optimal for lowering the temperature of the liquid material to a desired temperature. .

  The liquid aromatic polyester during the polycondensation reaction is supplied between the rollers 26 and 28 on the inlet side of the belt cooler 14 (more precisely, between the belts). A pulverizer 31 for coarsely pulverizing the cooled and solidified aromatic polyester is disposed on the outlet side of the belt cooler 14, and is further sent from the pulverizer 31 to a pulverizer for fine pulverization (not shown). .

  As shown in FIG. 2, the camera 15 captures a thermal image of the liquid aromatic polyester 12 that is poured between the rollers 26 and 28 on the inlet side of the belt cooler 14. The aromatic polyester 12 that has fallen to the substantially central position in the left-right direction between the rollers 26 and 28 on the inlet side has a high viscosity and is further cooled by the belts 24 and 25, so that the viscosity is further increased. It flows while expanding in the width direction in a substantially triangular groove 32 formed between the belts 24 and 25 wound around. In the middle of the process, the aromatic polyester 12 is drawn from the gap between the belts 24 and 25 so as to be sandwiched between the belts as the belts 24 and 25 move. The rollers 26 and 28 are cylindrical, and the contacting portions are grooves 32 having a substantially triangular cross section. However, the lower roller 28 is positioned below the upper roller 26 as shown in FIG. Therefore, the groove 32 is shallow.

  When the flow rate of the aromatic polyester 12 flowing down from above and the flow rate (conveyance amount) of the aromatic polyester 12 flowing in and being drawn between the belts 24 and 25 are balanced, for example, they accumulate in the region R1 indicated by the solid line. It is stable in the state. From this state, when the flow rate of the falling aromatic polyester 12 increases, the region where the aromatic polyester 12 is accumulated expands in the width direction as indicated by a two-dot chain line R2.

  However, if the falling aromatic polyester 12 rapidly increases and the balance with the flow rate drawn into the belts 24 and 25 is greatly lost, the end of the region R1 where the aromatic polyester 12 is accumulated becomes the width of the belts 24 and 25. For example, it adheres to the drive mechanism and solidifies there, and the double belt cooler 14 is damaged. In this extraction cooling device 10, the region R1 of the aromatic polyester 12 accumulated on the belts 24, 25 is detected by the camera 15, and when the spread state is within a predetermined range, the flow rate fluctuation is shown in FIG. The control means 16 performs feedback control by reducing or expanding the opening of the ball valve 13.

  The thermal image detected by the camera 15 is, for example, a vertically long image 33 of aromatic polyester falling from above and a horizontally long image of aromatic polyester spreading on the belts 24 and 25 as shown in the image of the monitor 17 in FIG. 34, that is, the image 34 having a predetermined temperature or higher (for example, 200 ° C. or higher) is only seen in a plane, and the low temperature rollers 26 and 28 and the belts 24 and 25 do not appear as images. Therefore, the outline of the aromatic polyester 12 is clear, and image processing (digital processing) of a thermal image is easy. That is, in a simple image, the contrast between the aromatic polyester 12 and the belts 24, 25, etc. is not clear and may be mistaken. However, by making a thermal image, for example, the aromatic polyester 12 having a temperature of 200 ° C. A clear contour based on the temperature difference from 25 is obtained.

  When the magnitude of the spread of the aromatic polyester 12 is digitized based on a thermal image, for example, the area of the aromatic polyester 12 in the frame 35 can be used as it is as a numerical value for control or discrimination. Or the rectangular frame (target area | region) 35 which shows a detection object area | region in the image in the monitor 17 can be set, and the area of the polymer in the frame can be digitized. Such processing includes a central processing unit (CPU) for data processing provided in the control means 16 having the DCS, a random access memory (RAM) for temporarily storing data, and a read-only memory for storing programs and the like ( (ROM) or the like.

  The size of the frame (target region) can be set freely. For example, as shown by a two-dot chain line in FIG. 3, small frames 36 and 37 are set near the ends of the spread of the aromatic polyester 12 in the left-right direction. The area value of the aromatic polyester in the frame can be used, or the ratio of the area of the aromatic polyester 12 in the frame to the area of the frames 36 and 37 can be calculated. Here, the area can be specified by the number of pixels (pixels) of the image. Moreover, the presence or absence of the detection of the aromatic polyester 12 can also be detected as an alarm. Based on the numerical value obtained from the larger frame 35 and the numerical value obtained from the small-compartment frames 36 and 37, or the numerical value obtained from the width of the falling aromatic polyester, the entire sum is taken or weighted. By taking an average value, a numerical value for unique control or determination may be calculated.

  When the control numerical value is obtained based on the thermal image, as shown in FIG. 4, the comparator calculates the deviation e between the numerical value X and the preset target value P so that the deviation becomes zero. The opening of the ball valve 13 is sequentially changed. That is, in the case of FIG. 4, the control unit multiplies the deviation e, an integral term obtained by integrating the deviation by time and dividing by the predetermined integration time constant Ti, and the deviation time by differentiating the deviation by time. A value obtained by calculating the sum with the differential term and multiplying by the proportional gain K is defined as a control amount y, and proportional integral differential control (PID control) is used in which the valve opening is determined by the control amount y.

  At this time, if the PID control becomes sharp (that is, if the proportional gain K is increased), the flow rate fluctuation becomes large and the ball valve 13 cannot be controlled. Therefore, the PID control is slowed down (that is, the proportional gain K is decreased), and when the image area of the aromatic polyester is out of a predetermined range, the opening degree of the ball valve 13 is automatically operated by a sequence. This makes it possible to safely cope with sudden fluctuations peculiar to the polycondensation reaction of aromatic polyester.

That is, when the flow rate of the aromatic polyester increases and the image area exceeds a predetermined range, the automatic operation is performed according to the sequence as follows.
(a) When the flow rate increases, the opening of the ball valve 13 is closed by a certain amount.
(b) When the flow rate decreases, the ball valve 13 is opened by a certain amount.
(c) When the flow rate increases abnormally, the ball valve 13 is once completely closed by the constantly monitored interlock sequence and returned to the beginning of extraction. The reason for this is to prevent delay in operation due to other sequence operations, in addition to having no effect even if the opening degree is reduced when the ball valve 13 is opened by 50% or more.
(d) If the flow rate decreases abnormally, once the opening degree of the ball valve 13 is increased (for example, after opening 10 times or more of the opening degree to be increased instantaneously), the opening degree is immediately increased. Perform the operation of returning. For example, when the opening degree is increased from 20.0% to 0.3%, the opening degree is increased from 20.0% to 30.3% and then returned to 20.3%. At this time, it is preferable to open instantaneously (for example, 1 second) until the opening degree is 30.3%. This is because if the solid is released only by 0.3%, the flow rate is increased abnormally when the solid matter that seems to have been caught can be removed, and even if the valve is slightly throttled, it cannot be stopped. Although the overflow is stopped by the interlock sequence, the same operation is repeated many times, and the process does not proceed.
In addition, in the automatic operation by the sequence, it is desirable not to make the valve opening less than a certain valve opening (for example, opening 18% or less). As a result, a state where the flow rate is low is suppressed to the shortest time, and consolidation in the flow path is minimized.

  Next, FIG. 5 shows an example of the flow rate control using both the automatic control by the PID control and the automatic control by the sequence. FIG. 5 shows the behavior of the image area (pixel) of the aromatic polyester from the start to the end of the pouring of the aromatic polyester from the polymerization tank to the double belt cooler 14, and the opening degree of the control valve 13 corresponding thereto. Yes. In this example, the trade name “Thermopics” manufactured by Chino Co., Ltd. was used as the thermal image measurement device. Further, the PID for automatic control of the ball valve 13 makes the sensitivity dull and suppresses large fluctuations. Furthermore, the automatic control setting range is set to 2500 to 5000 pixels within the area of the frame 35 shown in FIG. 3, and the ball valve 13 is opened and closed by automatic operation when it is outside this range.

As a result, sudden flow fluctuations occurred after minutes A and B from the start of extraction of the aromatic polyester from the polymerization tank, but other than that, it was stably operated by automatic valve control based on thermal images. I understand.
Note that the sudden flow rate fluctuation, which occurred suddenly after A minute from the start of extraction, was an image area of the aromatic polyester exceeding 5000 pixels, so at that time, from the automatic control by PID control, depending on the sequence Switching to operation, the valve opening was lowered, the flow rate was within the set range, and the original automatic control was restored.
Furthermore, the sudden flow rate fluctuation after B minutes was that the image area of the aromatic polyester was less than 2500 pixels. At that time, switching from automatic control to operation again, increasing the valve opening and setting the flow rate Returned to the original automatic control.

  The above-described setting range for automatic control is merely an example, and varies greatly depending on the grade of the aromatic polyester, the distance and angle at which the camera 15 is installed, and it is necessary to set each time. That is, it is necessary to set the automatic control setting range while comparing the monitor image with the actual state (real image).

  Further, the cooling means is not limited to the double belt type cooler 14, but may be a single belt type cooler, that is, a cooler of a type that cools and solidifies while placing and conveying a liquid material on the belt. The invention is applicable, and the spread in the width direction of the aromatic polyester poured on one end of the single belt cooler is detected by a thermal image.

It is a schematic side view which shows one Embodiment of the extraction cooling device of this invention. It is a fragmentary perspective view which shows the principal part of the extraction cooling device. It is a front view which shows the thermal image of the aromatic polyester extracted from the polymerization tank. It is a block diagram which shows the control method of the extraction amount of aromatic polyester. It is a graph which shows the relationship between the behavior of the image area (pixel) of aromatic polyester, and the opening degree of the ball valve 13 with respect to it.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Extraction cooling device, 11a, 11b: Polymerization tank, 12: Aromatic polyester, 13: Ball valve, 14: Double belt type cooler, 15: Camera, 16: Control means, 17: Monitor, 18: Inclined pipe line , 19: patch plate, 20: jacket, 21: jacket, 22: lid, 24: upper belt, 25: lower belt, 26: inlet side roller, 27: outlet side roller, 28: inlet side roller, 29: outlet Side roller, 30: guide roller, 31: pulverizer, 32: groove, 33: portrait image of (aromatic polyester), 34: landscape image of (aromatic polyester), 35: frame, 36, 37: small Parcel frame

Claims (10)

When the aromatic polyester in the middle of the polycondensation reaction extracted from the polymerization tank is poured onto a belt cooler through a ball valve and cooled and solidified,
The thermal polyester detects the spread of the aromatic polyester in the width direction of the belt, and (1) when the spread in the width direction is within a predetermined range, the opening degree of the ball valve is automatically controlled by PID control, (2) A method for producing an aromatic polyester, wherein when the spread in the width direction is out of a predetermined range, the opening of the ball valve is automatically operated by a sequence.   The aromatic polyester to be poured is detected as a thermal image with a camera, and the area of the image of the aromatic polyester in a predetermined frame on the monitor screen is determined. (1) When the image area is within a predetermined range, 2. The aromatic polyester according to claim 1, wherein the opening of the ball valve is automatically controlled by PID control, and (2) when the image area is out of a predetermined range, the opening of the ball valve is automatically operated by a sequence. Production method.   The method for producing an aromatic polyester according to claim 2, wherein the frame is in a range including the whole of the aromatic polyester spreading in the width direction of the belt cooler.   The method for producing an aromatic polyester according to claim 2, wherein the frame is a small section near the left and right end portions in the width direction of the belt cooler.   The method for producing an aromatic polyester according to any one of claims 1 to 4, wherein automatic control by PID control of the ball valve is performed with a small proportional gain.   6. The automatic operation by the sequence is such that when the flow rate increases, the ball valve opening is closed by a certain amount, and when the flow rate decreases, the ball valve opening is opened by a certain amount. A process for producing the aromatic polyester according to claim 1.   The method for producing an aromatic polyester according to any one of claims 1 to 6, wherein in the automatic operation by the sequence, when the flow rate is abnormally increased, the ball valve is once completely closed and then returned to the initial extraction state.   The aromatic according to any one of claims 1 to 7, wherein in the automatic operation by the sequence, when the flow rate is abnormally reduced, the opening degree of the ball valve is once increased and then immediately returned to the opening degree at which the desired flow rate is obtained. A method for producing polyester.   The method for producing an aromatic polyester according to claim 8, wherein the ball valve is instantaneously opened to 10 times or more of an opening degree at which a desired flow rate is obtained, and then immediately returned to the opening degree at which the desired flow rate is obtained.   The method for producing an aromatic polyester according to any one of claims 1 to 9, wherein in the automatic operation by the sequence, the ball valve is not set below a certain degree of opening so as to minimize the caking of the aromatic polyester in the flow path. .

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