JPH11300827A - Auxiliary air ring, and thickness accuracy improvement system for inflation molding using auxiliary air ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the thickness accuracy even when production parameters are changed by forming plural air feed paths on a disc-like plate and controlling the individual temperatures of auxiliary cooling air streams ejected from the air supply paths for performing the auxiliary cooling of a molten resin to be extruded from a die lip. SOLUTION: An auxiliary air ring 1 is of a disc-like shape with a cavity formed in the center part as viewed from above and a die lip is positioned in the cavity part. Inside the auxiliary air ring 1, a cluster of air feed paths 11 for performing the auxiliary cooling of a molten resin to be extruded in a tubular form are radially provided from the center part of an air ring 1 holder. Further, a heater 12 as a means for controlling the temperature of an auxiliary cooling air is installed halfway through the air feed paths 11 respectively. In addition, the turning ON/OFF of the heater 12 for heat generation and the setting of a heat temperature at a low or a high level are performed by a temperature sensor and a controller which supplies an electric power to the heater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auxiliary air ring having a function of improving the thickness accuracy of a tubular film when forming the tubular film, and
The present invention relates to a thickness accuracy improving system for inflation molding using the auxiliary air ring.

[0002]

2. Description of the Related Art As means for forming a synthetic resin into a film,
The inflation method is often used. This method has an advantage that it can be produced with relatively simple equipment and is therefore cost-effective. In this method, the thickness unevenness of the film is adjusted by adjusting the gap between the die lips. However, this adjustment requires skill, and even if the adjustment is performed over a long time, there is a limit in the thickness accuracy.

[0003] Many attempts have been made to solve such problems. For example, there is a method in which the thickness of a film extruded into a tube and solidified is measured over the entire circumference, and the gap between the die lips is automatically adjusted based on the data. However, this method
The mechanism for adjusting the gap of the die lip is complicated and costly, and the mechanism for adjusting the gap of the die lip needs to be provided directly on the circular die. there were.

On the other hand, in the same manner as described above, the thickness of a film extruded into a tube and solidified is measured over the entire circumference, and then the temperature of a cooling air flow blown from an air ring is adjusted based on the data. There is a way. In this method, when cooling air is blown onto the molten resin discharged from the die lip into a tube, if the temperature of the cooling air is lowered, the synthetic resin in that part solidifies more quickly and the thickness increases, and conversely, the temperature of the cooling air The higher the value, the slower the solidification of the synthetic resin, the more the blow-up progresses, resulting in a reduction in thickness. This is effective in improving the thickness accuracy. However, this method directly controls the temperature of the cooling air blown from the air ring, which is the main means for cooling the molten resin. Therefore, the temperature of the cooling air blown to the molten resin extruded into a tubular shape is controlled at each location, from the state where a tubular film with good thickness accuracy is obtained, increase or decrease of the extrusion amount, increase or decrease of the take-up speed, If the total amount of cooling air supplied from the air ring is increased or decreased due to a change in manufacturing conditions such as an increase or decrease in the blow ratio, the well-controlled state will collapse, and it will take a considerable time for the control to stabilize again. There was a problem that required. Therefore, these methods are not suitable for use in situations where production conditions change. Furthermore, in these methods, the air ring bears most of the capacity for cooling the molten resin, and since the cooling capacity of the air ring is directly controlled, there is also a disadvantage that the control fluctuation tends to be large. there were.

Further, in the production of a synthetic resin film using an actual inflation molding method, even when the same circular die is used, air is produced in accordance with the standard of the film to be produced or the type of raw material. It is common sense to use different rings, and it has not been realistic in terms of cost to update all the air rings attached to the same circular die to one having such a mechanism.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and the control is hardly disturbed even when the production conditions are changed. It is an object of the present invention to provide an auxiliary air ring having a function of improving thickness accuracy that can be used. It is another object of the present invention to provide a thickness accuracy improving system for inflation molding using the auxiliary air ring.

[0007]

Means for Solving the Problems The present inventors have intensively studied. As a result, the present inventors have found that the above-mentioned problem can be solved by providing a function of auxiliary cooling the molten resin to an auxiliary air ring located between the circular die and the air ring, and reached the present invention. Further, the present inventors have found that by combining the auxiliary air ring, a thickness measuring device for a tubular film, and an arithmetic device, it is possible to automate the improvement of the thickness accuracy in inflation molding, and have reached the present invention.

That is, according to the present invention, first, there is provided a disk-shaped plate provided between the circular die and the air ring and having a hollow center portion capable of supporting the air ring. Has a plurality of independent air supply passages formed along a line extending radially from the center point of the plate, and discharges from the air supply passages for auxiliary cooling of the molten resin extruded from the die lip into a tube shape. An auxiliary air ring is provided, which is provided with means for separately controlling the temperature of the auxiliary cooling air to be supplied.

Further, the above-mentioned auxiliary air ring is provided, wherein the auxiliary cooling air outlet at the tip of the air supply path is extendable.

A disk-shaped plate provided between the circular die and the air ring and having a hollow center portion capable of supporting the air ring; A plurality of independent air supply paths are formed along a line extending radially from the center point, and auxiliary cooling air discharged from the air supply path to auxiliary cool the molten resin extruded from the die lip into a tube shape Auxiliary air ring equipped with a means for controlling the temperature of the tube, ・ Thickness measurement to measure the thickness of the tubular film formed by cooling and solidifying the molten resin extruded into a tube from the die lip, over the entire circumference The thickness of the tubular film by means of auxiliary cooling of the molten resin extruded from the die lip into a tubular shape A device for outputting a signal for performing a positive operation, the operation of which feeds back the thickness data of the tubular film obtained by the thickness measuring device, and furthermore, the output signal is provided in the auxiliary air ring. An arithmetic unit capable of controlling the temperature of the auxiliary cooling air discharged from the plurality of air supply paths provided in each of the air supply paths for each of the air supply paths, the thickness accuracy for inflation molding. An improved system is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The most important feature of the present invention is that the mechanism for improving the thickness accuracy is not integrated with the air ring, but is configured in the auxiliary air ring separately from the air ring. In this way, the main cooling of the molten resin is assigned to the air ring, and the auxiliary cooling of the molten resin is assigned to the auxiliary air ring, and the temperature of the auxiliary cooling air discharged from the cooling air supply path provided in the auxiliary air ring is controlled. By doing so, the thickness accuracy control system can be separated and independent from the main cooling system using the air ring.
As a result, even if the situation changes in the main cooling system using the air ring, the control system for the thickness accuracy is hardly affected, and the stability is hardly lost. Further, for the same reason, in the thickness accuracy control, the fluctuation of the control can be kept small.

Further, the auxiliary air ring of the present invention has a feature that if one auxiliary air ring is provided on the same circular die, it can be used for any air ring and the thickness accuracy of the tubular film can be improved.

FIG. 1 is a schematic view showing a form of an auxiliary air ring according to the first aspect of the present invention, and is a plan view (A).
Is a disassembled state, front view (B) is a- of plan view (A).
It is a schematic diagram showing the cross section along line a '.

As is apparent from FIG. 1, the auxiliary air ring 1 of the present invention has a disk shape with a hollow center when viewed from above. The die lip is located in this cavity. Inside the auxiliary air ring 1, a group of air supply paths 11 for auxiliary cooling of the molten resin extruded in a tube shape is provided along a line extending radially from the center of the air rig holder 1. Means for controlling the temperature of the auxiliary cooling air is provided in the middle of the air supply path 11. In the example of this figure, a heater 12 is provided in the middle of the air supply path 11 as a heating means. The on / off or strength of the heat generated by the heater 12 is determined by a temperature sensor (not shown) and a controller 13 that supplies power to the heater based on a signal from the temperature sensor. The setting of the controller 13 may be manually set based on the thickness data of the tubular film, or an operation is performed based on the thickness data of the tubular film as described later, and the result is sent to the controller 13. It may be set automatically by outputting.

The greater the number of air supply paths provided inside the above-described auxiliary air ring, the more preferable the effect of improving the accuracy of thickness accuracy is desired. However, there is also a problem that the apparatus becomes complicated. Therefore, the number of air supply paths is 4
It is preferably in the range of 156 to 156.

Although the representative embodiment of the auxiliary air ring according to the present invention has been described with reference to FIG. 1, the present invention further provides an auxiliary cooling air outlet at the tip of an air supply path provided in the auxiliary air ring. Can be configured to be extendable. When an auxiliary air ring having such a structure is used, the same auxiliary air ring can be combined with circular dies of various sizes, and the effect of the present invention is more remarkably exhibited. In order for the auxiliary air ring to have such a structure, the end of the air supply path has a telescopic structure, the end of the air supply path has a bellows structure, or the air supply path has a bellows structure. For example, there is a means having a structure in which a distal end portion can be connected to a hollow threaded joint. FIG. 2 is a schematic diagram showing an example in which the air supply path has such a structure. It can be seen that the hollow threaded joint 14 is screwed to the tip of the air supply path 11. It is apparent from comparison with FIG. 1 that the present invention can be applied to a die having a smaller die lip diameter.

Next, a description will be given of a thickness accuracy improving system for inflation molding using the auxiliary air ring of the present invention described above. The system includes the above-mentioned "auxiliary air ring", a "thickness measuring device" for measuring the thickness of a tubular film formed by cooling and solidifying a molten resin extruded from a die lip into a tube shape, over the entire circumference thereof, A device for outputting a signal for correcting the thickness of the tubular film by means of auxiliary cooling of the molten resin extruded into a tubular shape from the means, the calculation of the tubular film obtained by the thickness measurement device It feeds back the thickness data,
In addition, the output signal can control the amount or temperature of air supplied to the plurality of air supply paths provided in the auxiliary air ring for each air supply path. It consists of

Next, the above will be described. First, the “thickness measuring device” has the function of measuring the thickness of the cooled and solidified tubular film after the molten resin extruded into a tube shape from the die lip of the circular die is blown up, over the entire circumference. . As the measuring mechanism, an infrared type, a β-ray type, a capacitance type, or the like is used. This thickness measuring device may be mounted around the tubular film by the number of thickness control points provided by the air supply path provided in the auxiliary air ring, but one thickness measuring device moves around the tubular film. Then, the thickness over the entire circumference of the tubular film may be measured. Rather, this method not only simplifies the structure of the apparatus but also is advantageous in terms of cost. The thickness data measured by the thickness measuring device is transmitted to a later-described "arithmetic device" by means of a cable or a means using electromagnetic waves such as infrared rays.

Next, the "arithmetic device" will be described. The arithmetic unit is based on the thickness data over the entire circumference of the tubular film transmitted from the thickness measuring device, and the auxiliary for auxiliary cooling of the molten resin from the air supply path group provided inside the auxiliary air ring. It has a function to calculate the optimum amount or temperature of the cooling air. For this calculation method, a known control method such as PID control is used. Then, a signal corresponding to the calculated optimal amount or temperature of the auxiliary cooling air is sent to the auxiliary air ring.

By controlling the temperature of the auxiliary cooling air discharged from the air supply path provided in the auxiliary air ring by this signal, the thickness data of the tubular film is fed back, and the accuracy of the thickness of the tubular film is improved. It will be improved.

Next, a system for automatically improving thickness accuracy in inflation molding will be described more specifically with reference to the drawings.

FIG. 3 is a schematic diagram of a system for improving the thickness accuracy of a tubular film by controlling the temperature of auxiliary cooling air supplied to an air supply passage provided in an auxiliary air ring. In addition, the line shown by the broken arrow in FIG. 3 means that connection to other similar parts (air supply path, air intake hole of the air ring) not shown is made.

In this figure, a molten resin 71 is discharged from the die lip 51 of the circular die 5 into a tube, blown up by the air blown into the tube, and cooled and solidified by the cooling air blown from the air ring 6. While being picked up by a pinch roll (not shown) installed above the molding apparatus. Thus, a tubular film is formed.

After the molten resin 71 is blown up, the thickness of the cooled and solidified tubular film 72 is measured by the thickness measuring device 2 over the entire circumference. The thickness data obtained in this manner is transmitted to the arithmetic unit 3, and the optimum temperature of the auxiliary cooling air supplied to each air supply path 11 provided in the auxiliary air ring 1 is calculated. In addition, a signal corresponding to this result is output to the controller 13, and an optimal temperature value is set in the controller 13. The controller 13 and a sensor (not shown) provided in the air supply path 11 in the auxiliary air ring 1 determine whether the power supply to the heater 12 located in the air supply path 11 is turned on or off, or whether the power supply is strong or weak. Controlled. In addition, auxiliary cooling air for auxiliary cooling the molten resin 71 is supplied to the group of air supply paths 11 provided in the auxiliary air ring 1, and the air volume at this time may be kept constant. In this way, the thickness accuracy of the tubular film is automatically improved.

[0025]

As described above, according to the present invention, the control is not easily disturbed even if the production conditions change, and the thickness can be adapted to any air ring if one is mounted on the same circular die. An auxiliary air ring having an effect of improving accuracy is provided. Claim 3 of the present invention
According to the technique described in the above, an auxiliary air ring having a thickness accuracy improving effect that can be used without changing even if the size of the circular die is changed is provided. Furthermore, by combining the auxiliary air ring of the present invention with the above-described thickness measuring device and arithmetic device, it is possible to automate the improvement of thickness accuracy in inflation molding. Thus, it can be said that the present invention is very useful in providing a tubular film having good thickness accuracy at low cost in inflation molding.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of the invention according to claim 1 of the present invention.

FIG. 2 is a schematic diagram showing an embodiment of the invention according to claim 2 of the present invention.

FIG. 3 is a schematic view showing an embodiment of the invention according to claim 3 of the present invention.

[Explanation of Codes] Auxiliary air ring 11. Air supply path 12. Heater 13. Controller 14. Screw joint 2. 2. Thickness measuring device Arithmetic unit 4. Air supply device 5. Circular dice 51. Die lip 6. Air ring 71. Molten resin 72. 7. tubular film Air supply device for air ring

Claims (3)

[Claims] 1. A disc-shaped plate, which is provided between a circular die and an air ring and has a hollow center portion capable of supporting the air ring, wherein a center point of the plate is provided inside the plate. A plurality of independent air supply passages are formed along a line extending radially from the surface, and the temperature of the auxiliary cooling air discharged from the air supply passages for auxiliary cooling the molten resin extruded from the die lip into a tube shape. An auxiliary air ring characterized by being provided with a means for separately controlling the auxiliary air ring. 2. The auxiliary air ring according to claim 1, wherein an auxiliary cooling air outlet at a tip end of the air supply path is configured to be extendable. 3. The auxiliary air ring according to claim 1, wherein the thickness of the tubular film formed by cooling and solidifying the molten resin extruded into a tubular shape from the die lip is measured over the entire circumference. A thickness measuring device that outputs a signal for correcting the thickness of the tubular film by means of auxiliary cooling of the molten resin extruded from the die lip into a tubular shape, the calculation of which is performed by the thickness measuring device. It feeds back the thickness data of the obtained tubular film,
In addition, the output signal comprises an arithmetic unit capable of controlling the temperature of the auxiliary cooling air discharged from the plurality of air supply paths provided in the auxiliary air ring for each of the air supply paths. Thickness improvement system for inflation molding characterized by the following.