JPH07276493A - Film width control device in molding of inflation film - Google Patents

Abstract

PURPOSE:To automatically enable the alteration of film width within a short time when the film width is altered in a case producing an inflation film by extrusion molding. CONSTITUTION:A first blower means (internal cooling air supply control part 7, internal cooling air supply blower part 8) supplying cooling air into a bubble and a second blower means (internal cooling air exhaust control part 10, internal cooling air exhaust blower part 11) discharging cooling air from the interior of the bubble on the basis of the air supply amt. of the first blower means are provided and the internal cooling air exhaust blower part 11 estimates the inner vol. of an inflation film from set film width and the set production speed of the inflation film. The inner vol. change rate of the inflation film is estimated from this inner vol. and set width altering speed and control is performed so as to allow the inner vol. change rate to coincide with the difference between the supply and discharge amts. of air with respect to the inflation film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film width control device for forming an inflation film by supplying and exhausting a cooling gas to and from an inflation film extruded by extrusion molding to set a film width.

[0002]

2. Description of the Related Art In blown film molding, the outside (outside of bubbles) of a blown film extruded from an extruder is forcibly cooled. At the same time, the inside of the inflation film (the inside of the bubble) is also forcibly cooled to improve the film formation rate of the inflation film. This blown film molding is disclosed in JP-A-58
-78725.

By forming such an inflation film, the production amount of the film per unit time can be improved. Also, with this inflation film molding,
It is possible to improve the transparency and quality stability of the film.

[0004]

The blown film molding described above has the following problems. In other words, this blown film molding
The blown film extruded from the extruder is forcibly cooled outside and inside. For this reason, a control device that keeps the film width constant by matching the supply amount and the exhaust amount of the cooling air is used in the extruder.

However, when changing the film width of the blown blown film to be produced, the operator of the extruder must manually adjust the balance of air supply and exhaust. By adjusting this air supply and exhaust, from the die outlet of the extruder,
The film width is controlled until the frost line of the blown inflation film is reached. Such work requires skill, and it takes time until the film width is changed, which may cause production loss.

The object of the present invention is to eliminate the above-mentioned drawbacks and to allow the film width to be changed automatically and in a short time when the film width is changed when an inflation film is produced by extrusion molding. An object is to provide a film width control device for film formation.

[0007]

In order to achieve the object, the present invention has a first blower means for supplying a cooling gas to the inside of an inflation film extruded by extrusion molding, and an air supply for the first blower means. Second, exhausting cooling air from the inside of the blown film based on the amount
A blower means for adjusting the amount of the cooling gas exhausted from the second blower means to a set film width, and a film width control apparatus for inflation film molding, wherein the second blower means is a set film The inner volume of the blown film is estimated from the width and the production rate of the blown film, and the inner volume change rate of the blown film is estimated from the inner volume and the set width change rate. It has a control means for controlling the difference between the supply and exhaust air amount for the film.

[0008]

With this configuration, the control means estimates the rate of change in the inner volume of the inflation film from the set film width and width changing speed and the inflation film production speed. After that, the control means controls the difference between the estimated internal volume change rate and the supply / exhaust flow rate for the inflation film to match.

As a result, the second blower means regulates the exhaust of the cooling gas. As a result, the second blower means
The film width can be quickly changed to the set value.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The film width control device for inflation film molding includes a setting unit 1, calculation units 2 and 3, an external cooling control unit 4, an external cooling blower unit 5, temperature detection units 6 and 9, and an internal cooling air supply control unit. 7, an internal cooling air supply blower unit 8, an internal cooling exhaust control unit 10, an internal cooling exhaust blower unit 11, and a film width detection unit 12.

In this embodiment, the first blower means comprises an internal cooling air supply control section 7 and an internal cooling air supply blower section 8, and the second blower means comprises an internal cooling exhaust control section 10 and an internal cooling exhaust blower. Part 11
With. The control means is the internal cooling exhaust control unit 10.

The setting unit 1 is for making various settings necessary for the production of blown film. In the setting unit 1, the temperature of the frost line of the blown inflation film to be produced, the film width, the width changing speed for changing the film width, and the like are set. The setting unit 1
The set frost line temperature a is output to the arithmetic units 2 and 3, and the film width b and the width change speed c are used as the internal cooling exhaust control unit 1.
Output to 0.

The temperature detection unit 6 detects the temperature outside the frost line of the inflation film extruded from the die of the extrusion molding machine and outputs the detected temperature to the calculation unit 2. The temperature detection unit 9 detects the temperature inside the frost line and outputs the detected temperature to the calculation unit 3.

The film width detection unit 12 detects the width of the blown film being produced and outputs the detected width to the internal cooling exhaust control unit 10 as a measured value.

The calculation unit 2 subtracts the temperature outside the frost line from the temperature detection unit 6 and the frost line temperature a from the setting unit 1 and outputs the subtraction result to the external cooling control unit 4. The calculation unit 3 calculates the temperature inside the frost line from the temperature detection unit 9 and the frost line temperature a from the setting unit 1.
And the subtraction result is output to the internal cooling air supply control unit 7.

The external cooling control unit 4 calculates the cooling air amount for cooling the vicinity of the frost line extruded from the extruder from the outside, that is, the external cooling air amount, based on the subtraction result of the calculation unit 2. To do. Then, the external cooling control unit 4 outputs the calculated external cooling air amount to the external cooling blower unit 5.

The internal cooling air supply control unit 7 determines the amount of cooling air for cooling the inflation film extruded from the extruder from the inside based on the subtraction result of the calculation unit 3, that is, the internal cooling air supply amount. Is calculated. Then, the internal cooling air supply control unit 7 uses the calculated internal cooling air supply amount as the internal cooling air supply blower unit 8.
And the internal cooling exhaust control unit 10.

The internal cooling / exhaust control unit 10 controls the film width b and the width changing speed c from the setting unit 1, the internal cooling air supply amount d from the internal cooling air supply control unit 7, and the film width detection unit 12. Based on the film width measurement value g, the line speed (production speed) e from the line speed detection unit (not shown), and the bubble internal pressure f from the internal pressure detection unit (not shown), the film is extruded from the extruder. The internal cooling exhaust amount exhausted from the inside of the blown inflation film is calculated. The internal cooling exhaust control unit 10
When calculating this internal cooling exhaust amount, it changes in unit time,
The bubble capacity change rate, which represents the capacity change of the inflation film, is made to match the difference between the internally cooled air supply amount and the internally cooled exhaust amount.

The bubble capacity change rate changes as shown in FIG. 3, for example, when the film width is expanded at a constant speed. Here, the line speed L of the blown film is 2.0 m / s, 1.0 m / s, 0.5 m / s, 0.
A bubble capacity change rate of 25 m / s is obtained by
2, 103 and 104 respectively. As shown in this graph, the bubble capacity change rate increases in order to increase the film width during the time period from zero to around 10 s. When the film width reaches the set width after about 10 seconds, the bubble capacity change rate sharply decreases to zero.

As described above, the internal-cooling exhaust control unit 10 sets the internal-cooling exhaust amount so that the difference between the internal-cooling air supply amount and the internal-cooling exhaust amount matches the curve of the bubble capacity change rate. Calculate An example of the internal cooling exhaust control unit 10 that performs this calculation is shown in FIG.

The internal cooling / exhaust control unit 10 includes calculation units 21 to 21.
27 is provided.

The calculation unit 27 performs a calculation to add the film width setting value b from the setting unit 1 to the width changing speed c from the setting unit 1 and outputs the width change setting value h.

The calculation unit 25 performs a calculation by subtracting the film width measurement value g of the film width detection unit 12 from the width change setting value h of the calculation unit 27 to obtain the width change deviation value j based on the film width currently produced. Output.

The calculation unit 21 calculates the exhaust amount k from the internal cooling air supply amount d of the internal cooling air supply control unit 7.

The calculation unit 22 calculates the displacement k from the calculation unit 21.
Is calculated with the width change deviation value j from the calculation unit 25. This exhaust amount n is a value required for control for maintaining the set film width, that is, control in a steady state.

The calculation unit 28 calculates the film width setting value b and the width changing speed c from the setting unit 1 and the line speed e from
The change in the inner volume of the blown film is estimated, and the estimation result is output as the estimated value m of the inner volume change rate.
At the time of this calculation, the calculation unit 28 determines that the film width setting value b
And the inner speed of the blown film is calculated based on the line velocity e. Then, based on the calculated internal volume and the width change speed c when the film width is changed, the estimated value m of the internal volume change rate of the blown film is calculated.

The calculation unit 26 uses the width change deviation value j from the calculation unit 25 and the estimated value m of the internal volume change rate from the calculation unit 28 to form a curve indicated by the estimated value m of the internal volume change rate, for example, The displacement ΔQ is calculated so as to match the curve shown in FIG. This displacement ΔQ is an excessive value required when the film width is reduced or expanded. Then, the calculation unit 26 outputs the calculated displacement ΔQ as the transient value p.

The calculation unit 24 calculates the displacement n from the calculation unit 22.
And the transient value p from the calculation unit 26, the internal cooling exhaust amount is calculated. When an abnormality occurs in the bubble internal pressure f, the calculation unit 24 calculates the internal cooling exhaust amount related to the control for dealing with the abnormality.

The internal cooling exhaust control unit 10 controls the internal cooling exhaust blower unit 11 based on the internal cooling exhaust amount calculated in this way so that the film width becomes a set value.

The outside cooling blower unit 5, the inside cooling air supply blower unit 8 and the inside cooling exhaust blower unit 11 are controlled by the outside cooling control unit 4, the inside cooling air supply blower unit 8 and the inside cooling exhaust control unit 10 to carry out inflation. Vary the amount of cooling air for the film.

Next, the operation of this embodiment will be described.

The following control is carried out in the steady state in which an inflation film is produced while maintaining a constant film width.

The temperature detection unit 6 detects the temperature of the blown film currently being produced outside the frost line. The calculation unit 2 calculates the difference between the temperature of the frost line measured by the temperature detection unit 6 and the temperature of the frost line set in the setting unit 1, and outputs the obtained difference to the external cooling control unit 4. The external cooling control unit 4 controls the external cooling blower unit 5 based on the difference from the calculation unit 2 so that the difference between the measured value of the frost line and the set value becomes zero.

The temperature detector 9 detects the temperature inside the frost line. The calculation unit 3 calculates the difference between the frost line temperature measured by the temperature detection unit 9 and the frost line temperature a set in the setting unit 1, and outputs the obtained difference to the internal cooling air supply control unit 7. To do. The internal cooling air supply control unit 7 controls the external cooling blower unit 5 based on the difference from the calculation unit 3 so that the difference between the measured value of the frost line and the set value becomes zero.

The film width detection unit 12 detects the width of the blown film currently being produced. In the internal cooling exhaust control unit 10, the calculation unit 25 calculates the difference between the film width actual measurement value g and the set film width b, and outputs it as the width change deviation value j.

On the other hand, the calculation unit 21 calculates the exhaust amount k based on the internal cooling air supply amount d from the internal cooling air supply control unit 7. The calculation unit 22 corrects the exhaust amount k with the width change deviation value j of the calculation unit 25 and outputs the exhaust amount n. The calculation unit 24 calculates the internal cooling exhaust amount from this exhaust amount n.

The internal cooling exhaust blower unit 11 controls the internal cooling exhaust blower unit 11 based on the internal cooling exhaust amount from the internal cooling exhaust control unit 10 so that the film width of the inflation film becomes constant.

As a result, steady-state control is performed.

When it is excessive to enlarge or reduce the film width of the blown film, the setting section 1 outputs the set width changing speed c to the internal cooling / exhaust control section 10. When the width change speed c is added, the calculation unit 28 of the inner cooling / exhaust control unit 10 receives the width change speed c, the film width b, and the line speed e.
With, the estimated value m of the internal volume change rate is calculated. The calculation unit 26 calculates the exhaust amount ΔQ so as to match the curve indicated by the estimated value m of the internal volume change rate, and outputs the calculation result as the transient value p. The calculator 24 calculates the internal cooling exhaust amount from the transient value p.

The internal cooling exhaust blower unit 11 is based on the internal cooling exhaust amount from the internal cooling exhaust control unit 10.
Control and quickly change the film width of blown film.

As described above, in this embodiment, when the film width is changed, the internal cooling is adjusted so that the difference between the internal cooling air supply amount and the internal cooling exhaust amount according to the change is matched with the bubble capacity change rate. Calculate the displacement. This allows the film width to be changed automatically.

Further, since the difference between the internal cooling air supply amount and the internal cooling exhaust amount is made to coincide with the bubble capacity change rate, a rapid change in the pressure inside the bubble is prevented, and production loss is prevented, and The film width can be changed in a short time.

[0044]

As described above, the present invention estimates the rate of change in the internal volume of an inflation film and cools the cooling film so as to match the difference between the rate of change in the internal volume and the supply / exhaust flow rate to the inflation film. Since the supply / exhaust of the gas is controlled, the film width can be changed automatically and in a short time.

Further, since the supply / exhaust of the cooling gas is controlled so that the difference between the internal volume change rate and the supply / exhaust amount becomes the same,
It is possible to prevent loss when changing the film width.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal cooling exhaust control unit.

FIG. 3 is a diagram showing a bubble capacity change rate.

[Explanation of symbols]

 7 Internal cooling air supply control unit 8 Internal cooling air supply blower unit 10 Internal cooling exhaust control unit 11 Internal cooling exhaust blower unit

Claims (1)

[Claims] 1. A first blower means for supplying a cooling gas to the inside of an inflation film extruded by extrusion molding, and cooling air is exhausted from the inside of the inflation film based on the amount of air supplied by the first blower means. Second
A blower means for adjusting the amount of cooling gas exhausted from the second blower means to achieve a set film width, wherein the second blower means is a set film width control device. The inner volume of the blown film is estimated from the width and the production rate of the blown film, and the inner volume change rate of the blown film is estimated from the inner volume and the set width change rate. A film width control device for inflation film molding, comprising control means for controlling the difference between the supply and exhaust air amounts for the film.