DE102020131010A1 - BLOWED FILM PLANT AND METHOD FOR MANUFACTURING A BLOWED FILM - Google Patents

Abstract

The invention relates to a method (100) for regulating a temperature of a plastic melt provided by an extruder (2) as well as a device (20) for carrying out this method (100) and a blown film system (1) with such a device (20) comprising the steps determining (110) an actual temperature (T) of the plastic melt with a determining means (14); comparing (120) the actual temperature (T) with a target temperature (TS) by means of an evaluation unit (16); and adjusting (130) at least one actuator (15) for influencing the actual temperature (T) of the plastic melt.

Description

The invention relates to a method for regulating a temperature of a plastic melt provided by an extruder as well as a device for carrying out this method and a blown film plant with such a device.

Blown film lines are known. The plants are supplied with plastics in granulated form, which are then plasticized into a viscous mass in extruders under the action of high pressure. This mass is formed in a blow head and escapes from the blow head through an annular nozzle or a slot nozzle. As soon as it leaves the ring nozzle or slot nozzle, the mass already forms a sheet of film as a tube or sheet. The film web is then pulled off upwards, for example. In the case of tubular films using the example of a ring nozzle, compressed air is introduced into the interior of the film tube. This leads to a transverse stretching of the film tube. An active coolant for the rising film tube cools the melt at a tolerable distance from the ring nozzle. On its way up, the film tube passes through a calibration basket and then a flattening that flattens the tube. The lay-flat unit feeds the double-layer film web to a pre-squeeze. This is followed by squeezing, in which a double-layer film web, practically free of air, is finally formed from the film tube. From there on, at the latest, even from the preliminary squeezing off, a double-layer film web is present. In film production, the temperature of the plastic melt is an important parameter in order to produce film webs from a plastic melt reliably and with stable, good quality.

The present invention is based on the object of providing a method with which film webs can be produced from a plastic melt reliably and with stable, good quality.

• - Bestimmen einer Ist-Temperatur der Kunststoffschmelze mit einem Bestimmungsmittel;
• - Abgleichen der Ist-Temperatur mit einer Soll-Temperatur mittels einer Auswerteeinheit; und
• - Einstellen mindestens eines Stellglieds zum Einflussnehmen auf die Ist-Temperatur der Kunststoffschmelze.

The object is achieved by a method for regulating a temperature of a plastic melt provided by an extruder, preferably in a blown film plant, comprising the steps

• - Determining an actual temperature of the plastic melt with a determination means;
• - comparing the actual temperature with a target temperature by means of an evaluation unit; and
• - Setting at least one actuator to influence the actual temperature of the plastic melt.

The “actual temperature” refers to the temperature of the plastic melt that is actually present. Here, the actual temperature can be measured at different positions at one or more measuring points, whereby the respective measurements can be direct temperature measurements or indirect measurements. In the case of indirect measurements, the actual temperature is calculated or deduced from the respective actually measured variables. The “target temperature” denotes the temperature that the plastic melt should have at least at the measuring point, preferably at the die head ”, so that the film webs can be produced particularly reliably and with particularly stable and good quality. Small deviations from the target temperature nevertheless enable the reliable production of film webs from the plastic melt with stable, good quality.

The "plastic melt" refers to the viscous mass that leaves the extruder after the input materials have been plasticized. The film tube is produced from the plastic melt in the blow head. The plastic melt can have different compositions depending on the starting materials, which are usually fed to the extruder in granulated form from a metering system.

The "film web" is a tubular film web, with the cylindrical film tube produced by means of the blow head being cut open on one or both sides after being laid flat to form a double-sided film web or left in the form of a tube. The film web can be single-layer or multilayer.

The "extruder" describes the component in which plastics are fed in granulated form and plasticized under high pressure to form a viscous mass, the plastic melt. For this purpose, the granulated materials are melted by means of a screw using frictional and shear forces and transported along the screw to the exit of the extruder.

The "machine direction" is the designated path of the film web, starting from the extrusion at the nozzle to the winder. The machine direction therefore varies because it runs around a plurality of rollers and possibly also turning bars.

With the method according to the invention, film webs can be produced reliably and with stable, good quality from a plastic melt. In one embodiment, the method is carried out on a blown film line.

In one embodiment, the method comprises the further step of adjusting the actual temperature to the setpoint temperature with the Evaluation unit data-connected to the determination means and operatively connected to the actuator.

In a further embodiment, the step of determining takes place mathematically. In this case, the steps of determining can be carried out by means of one or more algorithms that use current settings of the actuators to calculate the actual temperature on the basis of training data on actual temperatures under analogous conditions of the actuators. For this purpose, the evaluation unit can comprise a processor on which the algorithm or algorithms are executed and a storage medium for storing the measurement and training data. The algorithms in machine learning build a statistical model that is based on training data and that is able to derive or calculate actual temperatures from the existing settings of the actuators. The training data here denote data that were obtained for training purposes and / or data from the production history that can be assigned to specific actual temperatures.

In a further embodiment, the method comprises the further step of training the algorithm or algorithms on the basis of the training data.

In a further embodiment, the step of setting uses one or more actuators from a group of heating bands around the extruder, extruder heating, screw temperature, speed of the screw, conveying rate of the screw, material mixture in the extruder, movement parameters of an axially movable screw, control of separate devices afterwards the extruder, variably adjustable extruder geometry.

The invention also relates to a device for regulating a melting temperature of a plastic melt according to the method according to the invention, comprising an extruder for providing the plastic melt, a means for determining the actual temperature, at least one actuator for influencing the actual temperature and an evaluation unit data-linked to the determining means and operatively connected to the actuator for balancing, preferably for balancing and adjusting, the actual temperature with the target temperature.

In one embodiment, the actuator is at least one element of a group of heating bands around the extruder, extruder heating, screw temperature (can be influenced by cooling, for example), screw speed, screw feed rate, material mixture in the extruder, movement parameters of an axially movable screw, control of separate devices in the Connection to the extruder (for example a heat exchanger), variably adjustable extruder geometry (for example by means of a temperature-dependent expansion or shrinkage of the extruder components or by utilizing the material expansion of the material of the extruder and its components).

The invention further relates to a blown film system for producing a film tube from a plastic melt, comprising a device according to the invention, the plastic melt being conveyed to a blow head with an actual temperature adjusted to a target temperature.

In one embodiment, the determination means is a temperature sensor. This temperature sensor can be arranged on the blow head or in the plastic melt.

It should be expressly pointed out that in the context of the present patent application, indefinite articles and figures such as “one”, “two” etc. should generally be understood as “at least” information, i.e. as “at least one ...”, "At least two ..." etc., unless it is explicitly stated in the respective context or it is obvious or technically imperative for a person skilled in the art that only "exactly one ...", "exactly two ..." etc. can be meant.

The embodiments listed above can be used individually or in any combination with one another to design the device according to the invention and the method according to the invention.

• 1: einer Ausführungsform einer Blasfolienanlage zur Ausführung des erfindungsgemäßen Verfahrens;
• 2: eine Ausführungsform des erfindungsgemäßen Verfahrens.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawings. There shows

• 1 : an embodiment of a blown film plant for carrying out the method according to the invention;
• 2 : an embodiment of the method according to the invention.

1 shows a blown film line according to the invention 1 , with which the method according to the invention can be carried out, comprising in this embodiment five extruders 2 each with an assigned dosing station 2a showing a blow head 3rd with plastic melt (melt flow) feed which in the extruders 2 made of plastic granulate received from the respective dosing station 2a has been generated. The extruder 2 delivers the plastic melt to the die with an adjustable throughput 3rd . The blow head 3rd blows in an extrusion direction 4th , here vertically upwards, a film tube from an annular slot nozzle 5 out. After laying flat 6th the film tube runs through 5 a pair of take-off rollers 7th (not in detail shown). About the rotation frequency of the pair of take-off rollers 7th can reduce the take-off speed of the film tube 5 can be set. The film tube then runs 5 as an endless sheet of film laid flat 8th two ply in the machine direction 9 through the rest of the blown film line 1 up to a winder 10 . On the way from the take-off, defined by the pair of take-off rollers 7th , to the winder 10 runs through the film web 8th first a longitudinal stretching device 11 (not shown in detail). The film web runs over it 8th a reversal 12th , then a downlink 13th towards the winder 10 . The blown film line 1 also includes an apparatus 20th for regulating a melting temperature of a plastic melt having the extruder 2 for providing the plastic melt, a determination means 14th for the actual temperature T , at least one actuator 15th to influence the actual temperature T and an evaluation unit 16 data connected to the means of determination 14th and operatively connected to the actuator 15th for balancing, preferably for balancing and matching, the actual temperature T with the target temperature TS which then causes the plastic melt to have an actual temperature T adjusted to a target temperature TS to a blow head 3rd is promoted. The means of determination 14th can be a temperature sensor, preferably arranged on the blow head 3rd or in the plastic melt.

2 shows an embodiment of the method according to the invention 100 for controlling a temperature of a plastic melt provided by an extruder 2 , preferably in a blown film line 10 comprising the steps of determining 110 an actual temperature T the plastic melt with a determining agent 14th ; of matching 120 the actual temperature T with a target temperature TS by means of an evaluation unit 16 ; and setting 130 at least one actuator 15th to influence the actual temperature T the plastic melt. The step of hiring 130 can be one or more actuators 15th from a group of heating bands around the extruder 2 , Extruder heating, screw temperature, screw speed, screw feed rate, material mixture in the extruder 2 , Movement parameters of an axially movable screw, control of separate devices connected to the extruder 2 , use variably adjustable extruder geometry. The method here includes the further step of adjusting 140 the actual temperature T to the target temperature TS with the evaluation unit 16 data connected to the means of determination 14th and operatively connected to the actuator 15th . The steps of determining 110 take place mathematically, which is carried out by means of one or more algorithms that calculate 150 the actual temperature on the basis of training data on actual temperatures under analog conditions of the actuators based on current settings of the actuators. The method here includes the further step of training 160 of the algorithm or algorithms based on the training data.

The embodiments shown here only represent examples of the present invention and must therefore not be understood as restrictive. Alternative embodiments contemplated by those skilled in the art are equally encompassed by the scope of the present invention.

List of reference symbols

1

Blown film line

2

Extruder

2a

Dosing system

3

Blow head

4th

Direction of extrusion

5

Film tube

6th

Flattening

7th

Pair of take-off rollers

8th

Film web

9

Machine direction

10

Winder

11

Longitudinal stretching device

12th

Reversing

13th

Downlink

14th

Determination unit, for example a temperature sensor

15th

Actuator

16

Evaluation unit

20th

Device for regulating a melting temperature of a plastic melt

100

Method according to the invention

110

Determining an actual temperature of the plastic melt

120

Comparison of the actual temperature with a target temperature

130

Adjusting at least one actuator for influencing the actual temperature of the plastic melt

140

Adjustment of the actual temperature to the target temperature

150

Calculation of the actual temperature based on training data

160

Training the algorithms for calculating the actual temperature

T

Actual temperature

TS

Target temperature

Claims (10)

A method (100) for regulating a temperature of a plastic melt provided by an extruder (2), preferably in a blown film plant (10), comprising the steps - Determining (110) an actual temperature (T) of the plastic melt with a determining means (14); - Matching (120) the actual temperature (T) with a target temperature (TS) by means of an evaluation unit (16); and - Setting (130) at least one actuator (15) for influencing the actual temperature (T) of the plastic melt. The method (100) according to Claim 1 , comprising the further step of adjusting (140) the actual temperature (T) to the target temperature (TS) with the evaluation unit (16), data-connected to the determining means (14) and operatively connected to the actuator (15). The method (100) according to Claim 1 or 2 , wherein the step of determining (110) occurs mathematically. The method (100) according to Claim 3 wherein the step of determining (110) is carried out by means of one or more algorithms which, on the basis of current settings of the actuators, calculate the actual temperature on the basis of training data on actual temperatures under analogous conditions of the actuators (150). The method (100) according to Claim 4 , comprising the further step of training (160) the algorithm or algorithms using the training data. The method (100) according to one of the preceding claims, wherein the step of setting (130) one or more actuators (15) from a group of heating bands around the extruder (2), extruder heating, screw temperature, speed of the screw, feed rate of the screw, Material mixing in the extruder (2), movement parameters of an axially movable screw, control of separate devices connected to the extruder (2), variably adjustable extruder geometry used. A device (20) for regulating a melting temperature of a plastic melt according to a method (100) according to one of the preceding claims, comprising an extruder (2) for providing the plastic melt, a means (14) for determining the actual temperature (T), at least one actuator (15) for influencing the actual temperature (T) and an evaluation unit (16) data-connected to the determining means (14) and operatively connected to the actuator (15) for adjusting, preferably for adjusting and adjusting, the actual temperature (T) with the target temperature (TS). The device (20) after Claim 7 , the actuator (15) at least one element of a group of heating bands around the extruder (2), extruder heating, screw temperature, speed of the screw, conveying rate of the screw, material mixture in the extruder (2), movement parameters of an axially movable screw, control of separate devices in Connection to the extruder (2), variably adjustable extruder geometry is. A blown film system (1) for producing a film tube (5) from a plastic melt, comprising a device (20) according to Claim 7 or 8th , the plastic melt being conveyed to a blow head (3) with an actual temperature (T) matched to a target temperature (TS). The blown film line (1) after Claim 9 , wherein the determining means (14) is a temperature sensor, preferably arranged on the blow head (3) or in the plastic melt.

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