DE102021212286A1 - Process and device for the production of a flat product - Google Patents

Abstract

Method for producing a flat product with at least one flat plastic layer (4), the method having the following:- applying at least one flat plastic layer (4) to a carrier material (2) to form a preliminary product (5);- heating the preliminary product (5) to achieve a change in the state of the material of the at least one plastic layer (4), the heating comprising at least one heating step under the influence of a high-frequency alternating electric field, the heating step comprising the following:- providing a high-frequency alternating electric field with a predetermined fixed frequency in a heating area (6 );- Introduction of the preliminary product (5) into the heating area (6) and adaptation of a process impedance to a system impedance of a source of the high-frequency electric alternating field.

Description

The present invention relates to a method and a device for producing a flat product with at least one flat plastic layer, for example coated foam foils or artificial leather.

In the manufacture of such planar products, typically at least one, often several, planar plastic layers are brushed or applied in some other way to a carrier material and then heated. The purpose of heating is to dry, harden, crosslink and/or gel the material of the plastic layer by evaporating solvent, or to bring about a similar type of change in state. Continuous furnaces are used for heating, which heat the preliminary product created by applying at least one flat plastic layer to a carrier material in a continuous process using convection heat.

This procedure has the disadvantage that it is relatively time-consuming and energy-consuming, in particular because of the temperatures of, for example, over 200° C. required for certain materials.

From the WO 2006/125411 A1 it is known to heat food homogeneously by means of high-frequency alternating electric fields in order to preserve it. However, in such a heating process, there is no change in the state of the heated material that would result in changed material parameters and thus changed behavior in the high-frequency alternating electric field, and only low heating temperatures are aimed for.

The use of infrared radiation for heating plastic layers is sometimes known. The problem here, however, is that the infrared radiation has only a very small depth of penetration into the material to be heated and thus mainly superficial heating can be achieved. This can lead to undesirable effects such as skin formation on the surface. Such problems can also arise when using a convective heating method.

It is therefore an object of the present invention to specify a method and a device for producing a flat product with at least one flat plastic layer, in which a required change in the state of at least one plastic layer is carried out as energy-efficiently, gently and evenly as possible.

This object is solved by the subject matter of the independent claims. Advantageous embodiments and developments are the subject of the dependent claims.

According to one aspect of the invention, a method for producing a flat product with at least one flat plastic layer is specified, the method of applying at least one flat plastic layer to a carrier material to form a preliminary product and heating the preliminary product to achieve a change in the state of the material of the at least one plastic layer has, wherein the heating comprises at least one heating step under the influence of a high-frequency alternating electric field. The heating step includes the provision of a high-frequency alternating electric field with a predetermined fixed frequency in a heating area and the introduction of the preliminary product into the heating area and the adaptation of a process impedance to a system impedance of a source of the high-frequency alternating electric field.

Here and in the following, a change in the state of the material of the plastic layer is understood to mean, in particular, drying by evaporation of solvent, gelling, hardening and/or crosslinking of the material by the action of heat. The heating step thus causes a transition of the material of the flat plastic layer from a first state in which the material can be easily applied to the substrate, for example by brushing or, in the case of varnishing, by application by means of a pressure roller, to a second state in which the Plastic material is in its permanent rigid but typically flexible state.

The method thus includes, in particular, high-frequency electrical heating of the plastic material in the field of one or more capacitors. So that the heating step can take place as energy-efficiently as possible, the aim is for the heating process of the plastic layer to absorb the highest possible proportion of the electrical energy introduced and reflect only the smallest possible proportion. For this purpose, the adaptation of the process impedance, ie the impedance of the capacitor cell with the material provided in the heating area, is adapted to the system impedance of the source of the high-frequency electric alternating field. The matching takes place in particular by means of a matching network which, for example, can have at least one resonant transformer with variable capacitors in a known manner. At the source of the high fre quent electric field, it can in particular be a semiconductor-based high-frequency generator. A radio frequency approved for industrial processes, for example 13.56 MHz, 27.12 MHz or 40.86 MHz, is advantageously selected as the frequency of the alternating electric field.

Multi-layer flat products are often produced, which require the application and subsequent heating of several layers of plastic one on top of the other. The method can thus comprise several steps of applying a flat plastic layer, with a first plastic layer being applied to a carrier material and further plastic layers to underlying plastic layers. Furthermore, the method can have several heating steps if a flat plastic layer that has just been applied is first to be converted into a different state before a subsequent plastic layer is applied.

The method has the advantage that the heating step required to bring about the change in state is carried out in a particularly energy-efficient and gentle manner. Heating in a high-frequency alternating electric field enables the material to be heated relatively quickly, evenly and deeply. The impedance adjustment made enables the use of semiconductor-based high-frequency generators, which specify fixed frequencies, with a high level of energy efficiency. In addition, the heating in the high-frequency electrical alternating field has a particularly flexible controllability of the heating process. The quality of the adaptation can be directly inferred from the proportion of the power absorbed by the material. If the adjustment is not optimally selected or if, for example, the process impedance changes during the heating process, for example because the physical parameters of the material change as a result of the change in state, the adjustment can be readjusted immediately.

Due to the volumetric energy input, in contrast to an input via the surface, such as in the case of convective heating, the heating takes place more quickly, as a result of which the drying section can be shortened and/or passed through more quickly.

According to one embodiment, the source of the high-frequency alternating electric field comprises at least two electrodes which are arranged above and/or below the carrier material.

For example, the preliminary product can be introduced into the heating area in a continuous process. In particular, the carrier material can be taken from a roll and initially provided with a plastic layer, for example in a coating process, in order to then continuously pass through the heating area. The electrodes can then be arranged above and/or below the carrier material in relation to the direction of movement of the flat preliminary product and its surface area. An arrangement of both electrodes above or both electrodes below the carrier material has the advantage that the structure is particularly simple. However, such stray field heating is often not as homogeneous as heating, for example in a through field, in which the material to be heated is placed between the electrodes and the electrodes are therefore arranged above and below the carrier material or the preliminary product.

According to one embodiment, a sequence of high-frequency electrical alternating fields is generated along a direction of movement of the preliminary product.

This embodiment has the advantage that the material runs through different, possibly graded, alternating electrical fields in the continuous process. In particular, the adjustment can be coordinated with the degree of the change in state of the material that has already taken place. In this case, the alternating fields are typically generated and regulated independently of one another; in particular, the adaptation takes place individually in each case.

According to one embodiment, process impedance matching parameters are monitored to examine material properties of the precursor.

This embodiment utilizes the fact that by monitoring the parameters of the matching network, conclusions can be drawn about the material behavior of the material to be heated, for example its degree of drying. In particular, the status parameters of the adjustment network can also be used by comparing them with those of a reference process in order to identify deviations in the production of the materials at an early stage and thus reduce rejects.

According to one embodiment, the preliminary product is also subjected to at least one heating step by means of convective heating and/or heating by means of infrared radiation. In this embodiment, a combination of different types of heating is used in order to work in a particularly energy- and time-efficient manner if necessary, to achieve relatively high heating temperatures. In this case, the primary product can, in particular, pass through several spatially separate heating areas one after the other, with the heating taking place in different ways in the heating areas. This embodiment can also be advantageous if the dielectric heating is to be used as a supplement in an already existing system for convective heating.

According to a further aspect of the invention, a device for producing a flat product with at least one flat plastic layer is specified, the device having means for applying at least one flat plastic layer to a carrier material to form a preliminary product and at least one source for generating a high-frequency electrical alternating field for heating of the preliminary product to achieve a change in the state of the material of the at least one plastic layer. Furthermore, the device includes a matching network for matching a process impedance to a system impedance of the source of the high-frequency electric alternating field.

The device has the advantages already described in connection with the method.

According to one embodiment, the source of the high-frequency alternating electric field comprises two electrodes which are arranged above and/or below the carrier material. The preliminary product can be introduced into the heating area in particular in a continuous process and the device can have means for transporting the preliminary product through the high-frequency alternating electric field, for example rollers or rollers or conveyor belts.

According to one embodiment, the device has a number of sources for generating a sequence of high-frequency electrical alternating fields along a transport path of the preliminary product.

The device can also have at least one continuous furnace and/or at least one source of infrared radiation for heating the preliminary product. The material to be heated is heated in a continuous furnace by means of convective heat.

Embodiments of the invention are described below by way of example using schematic drawings.

The single figure shows schematically a device for producing a flat product with at least one flat plastic layer according to an embodiment of the invention.

The device 1 according to 1 comprises a transport device 3 for transporting a carrier material 2 and further layers applied thereto in a continuous process. As in 1 is shown, a plastic layer 4 is applied to the carrier material 2 by means of a device not shown in detail, for example by means of a calender, a pressure roller or a similar device. Typically, this only takes place on one side of the carrier material 2, which is understood here as the upper side.

After the plastic layer 4 has been applied, it is heated in order to achieve a change in the state of the material of the plastic layer 4 . For this purpose, the preliminary product 5 formed by the application of the plastic layer 4 to the carrier material 2 is transported through a first heating area 6 and a second heating area 7 adjoining it.

The first heating area 6 is a spatial area in which a high-frequency alternating electric field heats the material of the plastic layer 4 . The high-frequency alternating electric field is provided by a device 8 which, in particular, has a semiconductor-based generator 9 and a matching network 10 as well as electrodes 11 . In the embodiment shown, the electrodes 11 are arranged above and below the carrier material 2 and thus also above and below the preliminary product 5 .

In the first heating area 6, the preliminary product 5 is heated up to an intermediate temperature. According to an example in which a change of state of polyurethane is to be brought about at temperatures of 150°C, heating to 80-120°C is achieved in the first heating zone 6 . The rest of the temperature rise to 150° C. takes place in the second heating area 7 by means of convective heating.

Such a structure is particularly advantageous when existing systems for convective heating of the preliminary product 5 are only to be supplemented by the device 8 for heating by means of an alternating electric field in order to make them more efficient. In another embodiment, not shown, the second heating area 7, which is provided by a conventional continuous furnace, for example, can be dispensed with. Alternatively or additionally, in other embodiments, an Erwär tion area are provided by the precursor 5 is heated by infrared radiation.

The temperature up to which the preliminary product 5 is heated depends on the material of the plastic layer 4 . If it is a paint, relatively low temperatures of 80-160 °C are aimed for, while temperatures in the range of 210 °C are typically to be achieved for PVC.

reference list

1

contraption

2

carrier material

3

transport device

4

plastic layer

5

preliminary product

6

heating area

7

heating area

8th

Furnishings

9

generator

10

adaptation network

11

electrode

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• WO 2006/125411 A1 [0004]

Claims (11)

Method for producing a flat product with at least one flat plastic layer (4), the method having the following: - Applying at least one flat plastic layer (4) to a carrier material (2) to form a preliminary product (5); - Heating the preliminary product (5) to achieve a change in the state of the material of the at least one plastic layer (4), the heating comprising at least one heating step under the influence of a high-frequency alternating electric field, the heating step comprising the following: - Providing a high-frequency electric alternating field with a predetermined fixed frequency in a heating area (6); - Introduction of the preliminary product (5) in the heating area (6) and adaptation of a process impedance to a system impedance of a source of the high-frequency electric alternating field. procedure after claim 1 , wherein the source of the high-frequency electric alternating field comprises at least two electrodes (11) which are arranged above and/or below the carrier material (2). procedure after claim 1 or 2 , wherein the introduction of the preliminary product (5) into the heating area (6) takes place in a continuous process. procedure after claim 3 , A sequence of high-frequency electrical alternating fields being generated along a direction of movement of the preliminary product (5). Procedure according to one of Claims 1 until 4 , wherein process impedance matching parameters are monitored to check material properties of the precursor (5). Procedure according to one of Claims 1 until 5 , wherein the preliminary product (5) is further subjected to at least one heating step by means of convective heating and/or heating by means of infrared radiation. Device (1) for producing a flat product with at least one flat plastic layer (4), the device (1) having the following: - Means for applying at least one flat plastic layer (4) to a carrier material (2) to form a preliminary product (5); - At least one source for generating a high-frequency electrical alternating field for heating the preliminary product (5) to achieve a change in the state of the material of the at least one plastic layer (4); - a matching network for matching a process impedance to a system impedance of the source of the high-frequency alternating electric field. Device (1) after claim 7 , wherein the source of the high-frequency electric alternating field comprises at least two electrodes (11) which are arranged above and/or below the carrier material (2). Device (1) after claim 7 or 8th , wherein the introduction of the preliminary product (5) into the heating area (6) takes place in a continuous process and the device (1) has means (3) for transporting the preliminary product (5) through the high-frequency alternating electric field. Device (1) after claim 9 , wherein the device (1) has a plurality of sources for generating a sequence of high-frequency electric alternating fields along a transport path of the preliminary product (5). Device (1) according to one of Claims 7 until 10 , further comprising at least one continuous furnace and/or at least one source of infrared radiation for heating the preliminary product (5).

Images