JPH0529730U - Vent extruder - Google Patents

Abstract

(57) [Summary] [Purpose] Vent extruder vent up temperature sensor
To detect vent up early without touching the temperature sensing part of the resin. [Structure] A vent hole 3 is provided in the barrel 2, and an infrared detection type temperature sensor is provided above an exhaust chamber 4 communicating with the vent hole 3.
7 is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a vent extruder having a function of detecting a resin temperature of a vent hole.

[0002]

[Prior Art]

 Bent extruders are often used when attempting to remove water and volatiles in the synthetic resin of the material during the extrusion process. The vent extruder is equipped with one or more vent holes in the middle of the barrel and reduces the pressure in the screw groove and exhaust chamber around the vent hole. By making the transport capacity larger than the transport capacity of the screw on the root side of the vent hole, while extruding without screw filling the screw groove just below the vent hole, water and volatile components in the synthetic resin Has the function of removing.

However, when the operation is continued for a long time, the screen installed at the tip of the extruder is clogged with dust or the like to increase the flow resistance, and the pressure to overcome this resistance is increased. -The length of the groove filled with molten resin, measured from the screw tip as the starting point) gradually increases, until the screw groove immediately below the vent hole is also filled with molten resin, and the vent hole and exhaust chamber Also, the resin overflows and the vent is blocked. This phenomenon is called bent up.

In such a bent-up state, the ability to remove water and volatile components from the resin, which is the basic function of the vent extruder, is lost, which is a very problem. Further, after such a phenomenon occurs, not only the extruder needs to be stopped and the screen needs to be replaced, but it also takes a long time to clean the blocked vent hole and the exhaust chamber. The problem is big.

In Japanese Utility Model Publication No. 55-102523, a contact type thermometer such as a bimetal type, a platinum resistance type, a thermistor type, and a thermocouple type is used, and the exhaust chamber is overflowed at the time of venting. A device has been proposed that measures the temperature of the molten resin, detects the temperature change from normal extrusion, and issues an alarm. According to this device, it is possible to know that the vent up has occurred even if the operator does not constantly monitor. However, knowing the vent up after the contact between the molten resin and the temperature-sensitive part is a late timing, and it takes a long time to remove the resin adhered to the temperature-sensitive part.

In order to avoid such a problem, in this device, the proximity of the molten resin is detected by the temperature, and the vent-up is detected by a non-contact method by a method of detecting at a desired temperature by appropriately setting the detection temperature. Insists that you can also do.

However, what is measured by such a method is the vapor temperature of the volatile matter generated from the resin, not the temperature of the vented resin. Further, the vapor temperature of the volatile components gradually decreases by coming into contact with the vent hole and the wall of the exhaust chamber. Therefore, the temperature being measured is lower than the temperature of the vented resin. Furthermore, the difference between the resin temperature during normal extrusion and the resin temperature during vent up is not so large. Under these conditions, in order to measure the resin temperature with the contact type temperature sensing part in the non-contact state with the required accuracy, it is necessary that the temperature sensing part and the vented resin be very close. is there.

From the above, it was very difficult for this device to detect at least the initial state of vent up.

[0009]

[Problems to be solved by the device]

 As described above, the method using the contact-type temperature sensing part has a problem that the timing of detecting the occurrence of vent up is late and that it takes a long time to remove the resin adhered to the temperature sensing part. On the other hand, it was very difficult to detect the initial state of vent up without contact using such a contact type temperature sensing part.

For these reasons, it has been desired that the occurrence of vent-up can be reliably detected from the initial state by a non-contact method.

[0011]

[Means for Solving the Problems]

 As a result of various studies on the above points, the inventor of the present invention has found that the above problems can be solved by using an infrared detection type temperature sensor.

That is, in the vent extruder of the present invention, a vent hole is provided in the barrel, an exhaust chamber communicating with the vent hole is provided, and an infrared detecting temperature sensor is provided above the exhaust chamber. Is characterized by.

[0013]

[Action]

 The temperature of the resin existing on the bottom surface of the screw groove immediately below the vent hole or its portion is measured in a non-contact manner by the infrared detection type temperature sensor above the exhaust chamber.

Therefore, in the case of normal extrusion, the screw groove just below the vent hole is not filled with resin, and once the vent up starts, the screw groove immediately below the vent hole is first heated by the vent up. Since it begins to be covered with molten resin having a high temperature, the temperature change is immediately detected, and the early stage of vent up can be quickly known.

[0015]

【Example】

 FIG. 1 is a cross-sectional view showing the vicinity of the vent section of the vent extruder of the present invention. In FIG. 1, 1 is a screw, 2 is a barrel, 3 is a vent hole, and 4 is an exhaust chamber.

An infrared detection temperature sensor-7 is attached to a top plate above the exhaust chamber 4. A peephole 8 is also provided on the top plate. With this infrared detection type temperature sensor-7, the temperature of the resin existing on the bottom surface of the screw groove immediately below the vent hole 3 or its portion can be remotely measured without contacting the resin.

An exhaust hole is formed in the side wall of the exhaust chamber 4, and an exhaust pipe 5 connected to a vacuum pump is connected to the exhaust hole. As a result, the pressure inside the exhaust chamber 4 is reduced, so that water and volatile components in the synthetic resin of the material are removed.

The temperature change signal detected by the infrared detection type temperature sensor-7 is sent to a temperature display device / controller (not shown) so that an alarm signal is issued when a bend-up state is detected. By doing so, it is possible to take countermeasures early, such as changing the extrusion conditions early. In addition, it becomes possible to send the detected temperature change signal to the controller of the screw rotation speed, and return from the vent-up state to the normal state by increasing the screw rotation speed. This control method can be applied to an extruder in which the screw rotation speed and the resin feed amount control are independently performed. Furthermore, the detected temperature change signal can be sent to the screen changer system to automatically perform the screen change. This method enables unattended and fully automatic detection of vent up → return to normal operation.

Next, an extruding experiment example by this vent extruder will be described. As the resin used for extrusion, a hard PVC compound was used. In addition, a die equipped with a throttle valve was attached to the front end of the extruder to adjust the pressure inside the extruder.

In the range where this pressure takes a value corresponding to the case where the production mold is attached, normal vent extrusion is performed, and the temperature measured by the temperature sensor-7 is in the temperature range of 140 to 170 ° C. Had detected. However, as the throttle valve was closed and the resin pressure was increased, the melt length gradually became longer, and finally vent up occurred. At the beginning of venting up, the situation where the screw groove was gradually covered with molten resin was observed from the peephole 8 provided near the sensor 7. The temperature measured by the infrared temperature sensor at this time was 180 to 200 ° C.

According to the results of this experiment, it was confirmed that the temperature detection value by the infrared detection type temperature sensor provided in the vent extruder of the present invention can surely detect the early stage of vent up.

In this embodiment, the temperature sensor is installed on the ceiling of the exhaust chamber 4. However, the effect of the wall surface of the exhaust chamber does not change. The applicable resin is not limited to hard PVC, but can be applied to various synthetic resins.

[0023]

[Effect of the device]

 According to the present invention, since the temperature change at the time of venting up can be detected without contacting the resin, there is no problem of the resin sticking to the measuring portion as in the conventional case. Therefore, this eliminates the problem of deterioration of the detection capability and the problem of removing the adhered resin to the measuring part.

Moreover, since the infrared type remote measurement is used, it is possible to detect the initial temperature change of the vent up without delay. As in the conventional vent-up detection method, in order to know the vent-up only after the resin rises from the vent hole, for example, when replacing the clogged screen that is the cause of the vent-up, do it in parallel. The cleaning around the vent hole, which was necessary, is completely unnecessary.

As described above, the necessity of cleaning around the vent hole at the time of venting up is completely eliminated, which further enhances the value of the present invention. That is, according to the present invention, not only it is possible to detect a bent-up and issue an alarm, but also the possibility of returning to normal operation unattended and fully automatically occurs.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the periphery of a vent section of an embodiment of a vent extruder of the present invention.

[Explanation of symbols]

 1 Screw 2 Barrel 3 Vent Hole 4 Exhaust Chamber 5 Exhaust Pipe 6 Vacuum Pump 7 Infrared Temperature Sensor-

Claims (1)

[Scope of utility model registration request] 1. A vent extruder, wherein a vent hole is provided in a barrel, an exhaust chamber communicating with the vent hole is provided, and an infrared detecting temperature sensor is provided in an upper portion of the exhaust chamber.