JP4977175B2 - Vent-up detection method and extruder for an extruder equipped with a vent - Google Patents

Description

  The present invention relates to an extruder composed of a cylinder having a predetermined length provided with a vent for degassing and a screw that is driven to rotate in the cylinder, and is kneaded in the cylinder. The present invention relates to a vent-up detection method and an extruder for detecting a vent-up in which the molten resin that rises in the vent.

  The synthetic resin produced by the synthesis reaction may be inhomogeneous or may not have the necessary physical properties. Further, since it is not formed in a granular form, it is difficult to use as it is as a resin material. Therefore, the raw synthetic resin is melted, and a predetermined additive is added and kneaded so as to have predetermined physical properties. That is, it is reformed and homogenized. And it is granulated and provided as a pellet-shaped resin material. Such a pellet-shaped resin material is manufactured by a conventionally known pellet manufacturing apparatus including an extruder and a granulating apparatus. The extruder is composed of a cylinder of a predetermined length and a screw that can be driven in the direction of rotation in the cylinder. The granulator is a die provided in front of the cylinder and a plurality of cutters rotating while being pressed against the die. When the screw is rotated by supplying raw synthetic resin and additives from a hopper provided behind the cylinder of the extruder, the screw is melted and kneaded by frictional heat due to the shearing of the screw. Sent to the front of the cylinder. Since the molten resin is extruded from the die in a strand shape, a pellet-shaped resin material can be obtained by cutting with a cutter. By the way, since the raw synthetic resin also contains volatile components as impurities, it is necessary to degas the volatile components. Therefore, the cylinder of the extruder is provided with an opening at a predetermined portion and a vent is provided at the opening, and a predetermined negative pressure connected to the vent by natural exhaust or as necessary. Volatile components are degassed by being forced to exhaust by the source.

  The extruder is designed so that the pressure of the molten resin in the cylinder is kept low in the vicinity of the vent, and the molten resin in the cylinder does not rise from the opening. However, when abnormalities such as clogging of dies occur and the pressure of the molten resin in the cylinder increases, so-called vent up occurs in which the molten resin in the cylinder rises from the opening and rises in the vent. Even if vent-up occurs, the vent-up can be eliminated by detecting it promptly and taking necessary measures such as adjusting the supply of raw materials and adjusting the rotational speed of the screw. However, if the vent-up cannot be detected or the detection is delayed, the necessary treatment cannot be performed, and the vent is blocked by the molten resin. If it does so, it will not only become unable to deaerate but will also be unable to operate an extruder, and a big damage will occur. In addition, since a great deal of work is required to resume operation, the cost required for recovery also increases. Therefore, various detection methods for detecting vent-up have been proposed.

JP 2000-280239 A Japanese Examined Patent Publication 62-54655 Japanese Patent Publication No. 07-29363 Japanese Patent Laid-Open No. 02-286314 Japanese Patent Laid-Open No. 06-254945 Japanese Patent Laid-Open No. 05-147094

  Patent Document 1 describes a detection method for detecting vent-up by a monitoring camera provided in a vent. The vent is filled with vapors of evacuated volatile components and additives, but the surveillance camera is placed in the vent and placed in the vent, and the guard is heated by a predetermined heating means. Therefore, volatile components and evaporated additives are difficult to adhere to the surveillance camera lens. Therefore, a relatively clear image can be taken. The image is processed and it is determined whether vent-up has occurred.

Patent Document 2 describes a detection method in which vent-up is detected by three temperature sensors. Specifically, the first temperature sensor is always provided in the cylinder in contact with the molten resin, the second temperature sensor is provided at a low position in the vent, and the third temperature sensor is provided at a high position in the vent. The temperature difference of each temperature measured by the sensor is monitored. When vent-up occurs, the molten resin comes into contact with the second temperature sensor, so that the difference in temperature detected by the first and second temperature sensors is reduced, and the difference in temperature detected by the second and third temperature sensors. Becomes larger. This temperature difference is monitored to detect vent up.
Patent Document 3 describes a detection method in which vent-up is detected by two temperature detectors provided in the vent. Specifically, only one temperature detector is constantly heated by a heater so that a temperature higher than the temperature measured by the other temperature detector is measured. When vent-up occurs and the molten resin comes into contact with both temperature detectors, the difference in measured temperature is reduced, so that vent-up can be detected.
Patent Document 4 describes a detection method in which vent-up is detected by a temperature sensor provided in the vent and heated to a temperature higher than the temperature of the molten resin by a heater. When vent-up occurs and the molten resin comes into contact with the temperature sensor, the measured temperature decreases, so that vent-up can be detected.

Patent Document 5 describes a detection method in which vent-up is detected by a single pressure sensor provided at a predetermined position in a cylinder. According to this method, the molten resin and the volatilized gas are mixed in the cylinder, the pressure of the molten resin portion is high, and the pressure of the gas portion is low. Accordingly, the pressure measured by the pressure sensor is high when it is in contact with the molten resin, and is low when it is in contact with the gas. The minimum value of the pressure that fluctuates in this way is monitored, and when it is greater than a predetermined threshold value, it is determined that this is an indication that vent-up occurs.
Patent Document 6 describes a detection method in which vent-up is detected by a single pressure sensor provided downstream from the vent and in the vicinity of the vent. According to the detection method described in Patent Document 6, the pressure of the molten resin measured by the pressure sensor is monitored to detect the occurrence of vent-up. Alternatively, a sign of vent up can be detected.

  Since any method described in Patent Documents 1 to 6 can detect the vent-up, if a necessary measure is taken after the vent-up is detected, an accident that the vent portion is blocked by the molten resin is prevented to some extent. I can. However, there are also problems to be solved. In the vent-up detection methods described in Patent Documents 1 to 4, it is only possible to detect a vent-up that has already occurred, and it is not possible to detect or predict the occurrence of a vent-up in advance. Therefore, there is a possibility that the vent is blocked without taking necessary measures. In addition, other problems are recognized in these detection methods. For example, in the method described in Patent Document 1, measures are taken to prevent fogging of the lens of the surveillance camera, but since it is not possible to completely prevent fogging, operation is performed for a long time without performing maintenance. Then, the lens may become cloudy and it may become impossible to detect vent-up. In the methods described in Patent Documents 2 to 4, since the molten resin comes into contact with the temperature sensor to detect the vent-up, it cannot be detected unless the molten resin is sufficiently raised in the vent. In other words, since it cannot be detected until after the vent-up has progressed to some extent, there may be no time for taking necessary measures. Furthermore, these temperature sensors are designed to be able to remove the molten resin to some extent by heating with the heating means even once the molten resin has adhered, but it is considered difficult to completely remove it. It is done. Then, if the molten resin adhered without neglecting maintenance of the sensor is left, the sensitivity of the temperature sensor will decrease, and the adhered molten resin will deteriorate and enter the cylinder, resulting in high quality. There is a problem that a resin material cannot be obtained.

  According to the detection method described in Patent Literature 5 or Patent Literature 6, since a sign of vent-up can be detected, occurrence of vent-up can be predicted. Therefore, compared with the detection methods described in Patent Documents 1 to 4, there is a time margin for taking necessary measures. However, since the measurement point of the pressure of the molten resin is in the vicinity of the vent, the vent up occurs immediately after the sign of the vent up is detected. In other words, the time margin for taking necessary measures is not so large. Then, even if measures such as adjustment of the supply of raw materials and adjustment of the rotational speed of the screw are taken, it becomes difficult to sufficiently suppress the vent-up, and the operation of the extruder may have to be stopped. In addition, in the detection method described in Patent Document 5, when there is no volatilized gas in the cylinder, the minimum value of the pressure to be measured becomes high. It may be judged that it is a sign of vent-up, and the maximum pressure value is not taken into consideration, so it may not be detected even if vent-up occurs. There is also sex.

  The present invention aims to provide a vent-up detection method that solves the above-described problems and an extruder that can carry out such a detection method. Specifically, it is necessary to frequently maintain the sensor. The signs of vent-up can be reliably detected, and the detection of vent-up signs can be made sufficiently earlier than the occurrence of vent-up. It is an object of the present invention to provide a vent-up detection method capable of reliably suppressing or eliminating vent-up and an extruder capable of performing such a detection method.

  In order to achieve the above object, the present invention comprises a cylinder having a predetermined length provided with a vent for venting and a screw adapted to be driven to rotate within the cylinder. In an extruder provided with a granulator at the tip, in order to measure the pressure of the molten resin in the cylinder, the first pressure sensor is in the vicinity of the granulator and the second pressure sensor is the granulator and vent. The third pressure sensors are respectively provided in the vicinity of the vent near the granulator at predetermined positions between the two. And it is comprised so that the pressure of the molten resin in a vent may be estimated from the pressure measured with a 1st, 2nd pressure sensor, and the sign of vent up may be detected. Further, the vent pressure is detected by monitoring the pressure measured by the third pressure sensor.

Thus, in order to achieve the above object, the invention described in claim 1 is a cylinder having a predetermined length provided with a vent for deaeration, and a screw that is rotationally driven in the cylinder. In the extruder provided with a granulating device at the tip of the cylinder, a detection method for detecting a sign of vent up in which the molten resin kneaded in the cylinder rises in the vent, In the cylinder, the pressure of the molten resin is measured at a first position near the granulator and a second position which is a predetermined position between the granulator and the vent. , to obtain a pressure of 2, from said first and second pressure, to predict the pressure of the molten resin in the vent, pressure was the predicted vent up Once beyond the first threshold value set in advance signs der It is configured to determine that.
According to a second aspect of the present invention, in the method of the first aspect, the pressure of the molten resin in the cylinder between the granulator and the vent increases in proportion to the distance from the vent. Assuming that, the pressure of the molten resin in the vent is predicted from the first and second pressures, the first and second positions, and the position of the vent.
According to a third aspect of the present invention, in the method according to the first or second aspect, the pressure of the molten resin is measured in a third position near the vent near the granulator in the cylinder. When the third pressure exceeds a preset second threshold value , it is determined that vent-up has occurred .

According to a fourth aspect of the present invention, there is provided a cylinder having a predetermined length provided with a vent for degassing, and a screw adapted to be driven to rotate in the cylinder, and at the tip of the cylinder. In the extruder provided with the granulating device, a first pressure sensor is provided in the cylinder in the vicinity of the granulating device, and a second pressure sensor is provided at a predetermined position between the granulating device and the vent. There is provided, respectively, the first and second pressure sensors are connected to a predetermined controller, the pressure of the molten resin in the vent from the pressure of the first and second measured molten resin pressure sensor is predicted, the predicted When the measured pressure exceeds a first threshold value preset in the controller, it is determined that it is a sign of vent-up .
According to a fifth aspect of the present invention, in the extruder according to the fourth aspect, the screw is configured to be formed from a flight having the same shape from a portion corresponding to the vent to a tip portion.
According to a sixth aspect of the present invention, in the extruder according to the fourth or fifth aspect, a third pressure sensor is provided in the cylinder near the vent near the granulator, and the third pressure sensor is provided. The pressure sensor is connected to the controller, and it is determined that vent-up has occurred when the pressure of the molten resin measured by the third pressure sensor exceeds a second threshold value preset in the controller. It is comprised so that.

As described above, according to the present invention, a cylinder having a predetermined length provided with a vent for deaeration and a screw that is rotationally driven in the cylinder are provided at the tip of the cylinder. In an extruder provided with a granulator, the pressure of the molten resin in a cylinder at a first position near the granulator and a second position, which is a predetermined position between the granulator and the vent. , Respectively, to obtain first and second pressures, and from the first and second pressures, the pressure of the molten resin in the vent is predicted, and the predicted pressure is set to a first threshold value. Since it is configured to determine that it is a sign of vent-up if it exceeds, it can detect the sign of vent-up reliably and can detect the sign sufficiently earlier than the occurrence of vent-up . Therefore, necessary measures can be taken with a margin, and vent-up can be reliably suppressed or eliminated. Further, according to another invention, assuming that the pressure of the molten resin in the cylinder between the granulator and the vent increases in proportion to the distance from the vent, Since it is configured to predict the pressure of the molten resin in the vent from the first and second positions and the position of the vent, the calculation logic of pressure prediction is simple, and software that realizes such calculation logic The wear can be provided at low cost, and therefore the extruder can be provided at low cost. According to another invention, in the cylinder, the pressure of the molten resin is measured at a third position in the vicinity of the vent near the granulator to obtain a third pressure, and a preset second threshold value is obtained. When it exceeds the value , it is configured to judge that vent-up has occurred, so even if vent-up occurs, it can quickly detect and respond to the vent-up, and the vent is molten resin. It is possible to reliably prevent an accident that is blocked by. Furthermore, according to another invention, these pressures are configured to be measured by the first to third pressure sensors provided in the cylinder, that is, the molten resin adheres and the measurement accuracy is improved. Since it is different from a temperature sensor that decreases, stable measurement accuracy can be obtained and vent-up can be reliably detected without frequent maintenance of the sensor.

It is side surface sectional drawing which shows the pellet manufacturing apparatus provided with the extruder which concerns on embodiment of this invention. It is a graph which shows distribution of the pressure of the molten resin in the cylinder of the extruder which concerns on embodiment of this invention, The (a) is the normal operation, The (i)-(d) is the pressure of the molten resin. It is a graph which shows distribution of each pressure at the time of abnormality.

  Embodiments of the present invention will be described below. As shown in FIG. 1, the pellet manufacturing apparatus 1 according to the present embodiment is also composed of an extruder 2 positioned on the left side and a granulating apparatus 3 positioned on the right side thereof. The extruder 2 is composed of a cylinder 5 and a screw 6 provided inside the cylinder 5 so as to be rotationally driven. The cylinder 5 is composed of a plurality of cylinder blocks 7a, 7b,... Having a predetermined length, and the cylinder blocks 7a, 7b,... Are connected to each other by flanges provided at respective end portions. Although not shown in FIG. 1, a hopper is provided at a rear portion of the cylinder 5, that is, a predetermined portion on the left side in FIG. 1, so that a synthetic resin or additive as a raw material can be supplied into the cylinder 5. It has become. A granulating device 3 is provided at the tip of the cylinder 5. The granulating device 3 is composed of a die connected to the cylinder 5, a plurality of cutters rotating in contact with the die, and a casing storing these. FIG. Only is shown schematically. In such a predetermined portion of the cylinder 5, an opening 9 including a predetermined hole that communicates the outer peripheral surface of the cylinder 5 and the cylinder bore is provided, and a vent 10 is provided in the opening 9. Accordingly, impurities composed of volatile components contained in the molten resin melted and kneaded in the cylinder 5 are vaporized and degassed from the vent 10.

  In the extruder 2 according to the present embodiment, three pressure sensors, that is, first to third pressure sensors 12, 13, and 14 are provided in the cylinder 5 so that the pressure of the molten resin in the cylinder 5 can be measured. It has become. The first pressure sensor 12 is provided in the tip of the cylinder 5, that is, in the vicinity of the da granulator 3, and measures the pressure of the molten resin at the tip of the screw 6. The second pressure sensor 13 is provided between the tip of the cylinder and the vent 10, that is, between the granulator 3 and the vent 10, and the third pressure sensor 14 is immediately after the downstream side of the vent 10, in other words, It is provided in the vicinity of the vent 10 near the granulator 3. The first to third pressure sensors 12, 13, and 14 are connected to the controller 19 by signal lines 16, 17, and 18, respectively.

  In the present embodiment, the screw 6 is appropriately provided with, for example, a kneading disk, a reverse flight, etc. in order to efficiently melt and knead the synthetic resin as a raw material. The part is composed of a single type of screw such as a full flight screw. Therefore, the pressure of the molten resin from the vent 10 in the cylinder 5 to the tip portion increases uniformly in proportion to the distance from the vent 10. The screw 6 is composed of one axis in the present embodiment, but may be composed of two axes.

  The operation of the pellet granulating apparatus 1 according to the present embodiment will be described. The screw 6 is driven at a predetermined rotational speed. A raw synthetic resin and predetermined additives are supplied from a hopper. Then, the synthetic resin is melted in the cylinder 5 by frictional heat caused by the shearing of the screw and kneaded with the additive. The molten resin is sent to the screw 6 and sent forward in the cylinder 5. Impurities consisting of volatile components contained in the molten resin are volatilized in the vent 10 and the impurities are deaerated. After deaeration, the molten resin is fed forward by the screw 6 and extruded from the die of the granulator 3 in a strand shape. In the present embodiment, water is supplied to the granulator 3 and the die is submerged in water, so that the extruded molten resin is solidified in water. The resin solidified by the rotating cutter is cut to obtain a pellet-shaped resin material.

  The graph of FIG. 2A shows the pressure distribution of the molten resin in the cylinder 5 during normal operation of the pellet granulator 1. The horizontal axis represents the position in the cylinder, and the vertical axis represents the pressure of the molten resin. The first to third pressures 21a, 22a of the molten resin measured by the first to third pressure sensors are respectively shown. 23a is plotted. As shown in the graph of FIG. 2A, the pressure of the molten resin from the vent 10 to the tip portion increases in proportion to the distance from the vent 10. That is, the pressure distribution curve 24 of the pressure of the molten resin in the cylinder 5 is linear. When a straight line 25a passing through the first and second pressures 21a and 22a is drawn and the resin pressure at the position of the vent 10 is read, an expected resin pressure 26a at the vent 10 is obtained. As shown in FIG. 2A, the expected resin pressure 26a is substantially zero. The expected resin pressure 26a is substantially equal to the actual pressure of the molten resin near the vent 10 during normal operation, and the pressure is substantially equal to atmospheric pressure. Since the pressure of the molten resin is substantially zero, the so-called vent up in which the molten resin swells in the vent 10 does not occur during normal operation. In the graph of FIG. 2A, the pressure distribution curve 24a is substantially the same straight line as the straight line 25a, and the third pressure 23a is also almost on the straight line 24.

  When an abnormality such as clogging of the die occurs, the pressure of the molten resin in the cylinder 5 first increases in the vicinity of the tip, that is, in the vicinity of the die. As shown in the graph of FIG. 2A, the first pressure 21b measured by the first pressure sensor 12 increases. The pressure distribution curve 24b of the molten resin in the cylinder 5 rises rapidly in the vicinity of the first pressure sensor position. In addition, since the inclination of the straight line 25b passing through the first and second pressures 21b and 22b temporarily increases, the expected resin pressure is negative although it is not shown in the graph of FIG.

  When a predetermined time has elapsed since the occurrence of the abnormality, the second pressure 22c measured by the second pressure sensor 13 also increases. FIG. 2C shows the pressure distribution of the molten resin in the cylinder 5 in such a state. The pressure distribution curve 24 c in the cylinder 5 is greatly curved between the positions of the second and third pressure sensors 13 and 14. The predicted resin pressure 26c at the vent, which is obtained from the straight line 25c passing through the first and second pressures 21c and 22c, increases as shown in FIG. The controller 19 compares the preset first threshold value with the predicted resin pressure 26c. If it is detected that the predicted resin pressure 26c exceeds the first threshold value, it is determined that it is a sign of vent-up. Then, the controller 19 outputs an alarm. The operator changes the operating conditions by suppressing the supply amount of the raw synthetic resin to the extruder 2 or increasing the rotational speed of the screw 6. Then, after a predetermined time has elapsed, the pressure of the molten resin in the cylinder 5 returns to a normal state as shown in FIG. Vent up can be suppressed without stopping the extruder 2.

  When the operator's response is delayed or an abnormality that cannot be taken occurs, as shown in FIG. 2 (d), the third pressure sensor 14 measures the first. No. 3 pressure 23d also increases. The controller 19 compares the second threshold value set in advance with the third pressure 23d. When it is detected that the third pressure 23d exceeds the second threshold value, it is determined that vent-up has occurred, an alarm is output, and the extruder 2 is stopped. Since the extruder 2 is stopped immediately after the occurrence of vent-up, the vent 10 is not filled with the molten resin. Therefore, the operation of the extruder 2 can be restarted promptly after the abnormal part is recovered.

  The embodiment of the present invention can be variously modified. For example, it is explained that the controller only outputs an alarm when a sign of vent-up is detected, but according to the command of the controller, the supply amount of the synthetic resin of the raw material directly to the extruder can be suppressed, You may control so that the rotational speed of a screw may be raised. In this way, since there is no delay due to the operator's response, it is possible to more reliably suppress vent-up. In the present embodiment, it is described that a die is directly provided on the cylinder. However, a die may be provided on the tip of the cylinder via a filtration device such as a screen changer. Such a filtering device can also be regarded as a part of the granulating device, and according to the present invention, it is also possible to detect a sign of vent-up caused by an abnormal clogging of the filtering device. Furthermore, although the screw is described as being composed of a single type of screw such as a full flight screw from the portion corresponding to the vent toward the tip, the kneading disc or the like is different in the middle. A screw may be provided. As a result, the pressure distribution of the molten resin between the vent and the tip in the cylinder does not become linear, but becomes a curve of a predetermined shape, but the controller stores such a curve of the predetermined shape in advance. If so, the predicted resin pressure at the vent can be calculated.

  The extruder according to the present invention can be applied not only to a pellet manufacturing apparatus but also to an extruder used for other purposes.

DESCRIPTION OF SYMBOLS 1 Pellet production apparatus 2 Extruder 3 Granulation apparatus 5 Cylinder 6 Screw 10 Vent 12, 13, 14 1st-3rd pressure sensor 19 Controller

Claims (6)

Extrusion comprising a cylinder of a predetermined length provided with a vent for deaeration and a screw adapted to be driven to rotate in the cylinder, and provided with a granulating device at the tip of the cylinder In the machine, a detection method for detecting signs of vent up in which the molten resin kneaded in the cylinder rises in the vent,
In the cylinder, the pressure of the molten resin is measured at a first position near the granulator and a second position which is a predetermined position between the granulator and the vent. 2 pressure,
Predicting the pressure of the molten resin in the vent from the first and second pressures and determining that the predicted pressure exceeds a preset first threshold is a sign of venting up A vent-up detection method characterized by   The method of claim 1, wherein the pressure of the molten resin in the cylinder between the granulator and the vent is increased in proportion to the distance from the vent, the first, 2. A vent-up detection method, wherein the pressure of the molten resin in the vent is predicted from the second pressure, the first and second positions, and the position of the vent. The method according to claim 1 or 2, wherein in the cylinder, the pressure of the molten resin is measured at a third position near the vent near the granulator to obtain a third pressure,
A vent-up detection method , wherein when the third pressure exceeds a preset second threshold value , it is determined that a vent-up has occurred . Extrusion comprising a cylinder of a predetermined length provided with a vent for deaeration and a screw adapted to be driven to rotate in the cylinder, and provided with a granulating device at the tip of the cylinder In the machine
In the cylinder, a first pressure sensor is provided in the vicinity of the granulator, and a second pressure sensor is provided at a predetermined position between the granulator and the vent.
The first and second pressure sensors are connected to a predetermined controller;
When the pressure of the molten resin in the vent is predicted from the pressure of the molten resin measured by the first and second pressure sensors , and the predicted pressure exceeds a first threshold value preset in the controller An extruder characterized by being determined to be a sign of vent-up .   5. The extruder according to claim 4, wherein the screw is formed from a flight having the same shape from a portion corresponding to the vent to a tip portion. The extruder according to claim 4 or 5, wherein a third pressure sensor is provided in the cylinder near the vent near the granulator, and the third pressure sensor is connected to the controller. When the pressure of the molten resin measured by the third pressure sensor exceeds a second threshold value preset in the controller, it is determined that vent-up has occurred. Extruder.

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