Method for producing a vacuum insulation panel

Abstract

The invention relates to a method for producing a vacuum insulation panel (12), wherein a film (5) is inserted into a cavity (7) of a molding tool (6) and an open-cell PUR mixture is applied. Protruding regions of the film are folded and the PUR mixture is completely surrounded by film. The molding tool closes, the PUR mixture foams and presses the film against the walls of the cavity. This results in the formation of an open-cell rigid PUR foam structure with a compact skin which is surrounded by film. A step of evacuating the open-cell (rigid) PUR foam structure creates a vacuum insulation panel. In order to improve the process integration and for efficient production of vacuum insulation panels, all the steps of the method can be carried out directly one after another.

Description

[0001] Description

[0002] Process for producing a vacuum insulation panel

[0003] Vacuum insulation panels (VIPs) are highly efficient thermal insulation materials that utilize the principle of vacuum insulation. They are often used for the thermal insulation of coolers and cold storage facilities. The principle of vacuum insulation is also increasingly being used in the manufacture of refrigerators and freezers.

[0004] Vacuum insulation panels typically consist of an open-pore support core and a highly dense, particularly gas- or vacuum-tight, shell system, often formed from coated foils. Open-cell rigid polyurethane foam is commonly used as the open-pore support core. The abbreviation "PUR" will be used below for the term "polyurethane."

[0005] The production of vacuum insulation panels with a PUR rigid foam typically takes place in several separate process and assembly steps. First, a block of open-cell PUR rigid foam is produced from a foamable PUR mixture. After curing and demolding, the closed skin that formed on the surface of the block during foaming is at least partially sawn off. This creates open cells on the outside of the block, which facilitates subsequent vacuum application. In a subsequent step, the block thus formed is wrapped in a suitable gas- or vacuum-tight film, and in a further downstream step, the film-coated block is evacuated.Based on this, the object of the invention is to provide a method for producing a vacuum insulation panel, which is characterized by improved process integration and enables efficient production of vacuum insulation panels.

[0006] This object is achieved by a method having the features of claim 1. Advantageous further developments and embodiments can be found in the dependent claims.

[0007] A basic idea of ​​the invention is to carry out as many process steps as possible for the production of a vacuum insulation panel in one pass, so that at the end of the method according to the invention a finished vacuum insulation panel is available.

[0008] Accordingly, the method according to the invention provides the following steps (a) to (i) as well as a step of creating a vacuum inside the film package:

[0009] (a) providing a gas-tight film whose area is larger than the surface of the finished vacuum insulation panels;

[0010] (b) inserting the film into the cavity of a lower part of a mold;

[0011] (c) Fixing those sections of the film which are located outside the cavity of the lower part of the tool,

[0012] (c) introducing an open-cell polyurethane mixture into the cavity of the lower part of the tool lined with the film,

[0013] (e) covering the polyurethane mixture and any areas of the film exposed in the cavity with those sections of the film which are located outside the cavity of the lower part of the tool, whereby the polyurethane mixture is completely enclosed by film and a film package is formed;

[0014] (f) moving an upper part of the molding tool towards the lower part of the mold and closing the cavity before the rise time of the polyurethane mixture has begun; (g) holding the molding tool closed for a period of time which corresponds at least to the rise time, whereby the polyurethane mixture foams in the cavity and thereby the film surrounding the polyurethane mixture is pressed against the walls of the cavity, whereby the polyurethane mixture penetrates between overlapping film regions and bonds them together in a vacuum-tight manner, whereby an open-cell PUR foam structure is formed with a compact skin layer covering the PUR foam structure and which is completely surrounded by film;

[0015] (h) allowing the PUR foam structure to cure until an open-cell PUR rigid foam structure is formed;

[0016] (i) Opening the forming tool and removing the finished film package.

[0017] There are various options for creating the vacuum inside the foil package, which are described in more detail below.

[0018] According to a first embodiment, a vacuum can be present around the molding tool to generate the vacuum, at least for the duration of step (d). For this purpose, a suitable and evacuable or evacuated cell can be provided. In particular, the molding tool can thus be located in a closed and evacuated cell. If necessary, other production elements relevant to the implementation of the method, such as a mixing head, can also be arranged in the cell. In such a cell, the polyurethane mixture can foam under negative pressure, and the negative pressure thus created is retained in the film package.

[0019] According to a second embodiment, a mixing head can be used to generate the vacuum, which is designed both for discharging the polyurethane mixture and for extracting air from the film package. For this purpose, the mixing head can in particular have a valve with which a connection can be established between a suitable vacuum pump and the mixing head outlet pipe in order to extract air from the film package by means of the vacuum pump until a predeterminable negative pressure is reached in the film package. According to a third embodiment, the film package can be designed with a closable film connection to generate the vacuum, via which a predeterminable negative pressure can be generated in the film package by means of a suitable vacuum pump.The foil connection can preferably be designed to be contour-neutral, so that the surface of the foil package has almost no elevations or depressions in the area of ​​the foil connection.

[0020] The film may preferably be a metallized plastic film, in particular an aluminum composite film.

[0021] Furthermore, it may be advantageous if the film is prefabricated according to the desired shape of the vacuum insulation panels or the cavity of the lower mold part. For this purpose, preforming corners and / or the formation of projections can be provided, which serve as those sections of the film that are located outside the cavity of the lower mold part before the PUR material is introduced.

[0022] The insertion of the film into the cavity of the lower part of the tool is preferably carried out in such a way that no wrinkles are formed and / or that overlapping areas are bonded by penetrating PUR mixture.

[0023] Finally, it is important to ensure that the cavity has sufficient time to vent before it is kept closed for the foaming process. Therefore, during step (f), the cavity is preferably closed or closed only after a predefined time for venting the cavity has elapsed. This time is preferably specified depending on the polyurethane mixture used.

[0024] In a further development of the invention and to improve process integration, step (a) of providing the film can be carried out by means of an extrusion system, in particular by means of a flat film extrusion system. Furthermore, a finishing device can be connected downstream of the extrusion system, to which the continuous film produced by the extrusion system is fed and by means of which the extruded continuous film is cut into a film of a predeterminable shape. The film thus produced can be inserted into the cavity of a lower tool part of a mold according to step (b). Between the exit of the continuous film from the extrusion system and the feeding of the continuous film to the finishing device, the continuous film can preferably be coated, in particular a coating with a metallic material, preferably with aluminum.A continuous film coated in this way ensures that the vacuum created in the film package is maintained, at least over a long period of time and at least as long as the film is not damaged. In this respect, such a film can also be described as a gas-tight or vacuum-tight film.

[0025] The invention will be described in more detail below using an exemplary embodiment and with reference to Figures 1 and 2. They show:

[0026] Figure 1 shows a schematic representation of essential elements of a production plant for carrying out the method according to the invention;

[0027] Figure 2 perspective view of the mold in a situation with inserted film.

[0028] Figure 1 shows a production plant for manufacturing a vacuum insulation panel using the method according to the invention. This production plant comprises a flat film extrusion plant 1 for producing and providing a continuous film 2, which is provided with a metal layer, in particular an aluminum layer, in a subsequent process step in a coating plant 3. The thus coated continuous film 2a is fed to a finishing device 4, in which the coated continuous film 2a is cut to size and individual films 5 are produced, which serve to enclose the vacuum insulation panels. The film 5 is thus pre-finished according to the desired shape of the vacuum insulation panels or the cavity of the lower tool part, in particular by preforming corners and / or by forming projections as those sections of the film that are located outside the cavity of the lower tool part.Such a film 5 has a total area that is larger than the surface of the finished vacuum insulation panel. The total area and the contour of the film 5 are such that a closed shell can be formed when folded. By means of a first robot 8, the film 5 is fed to a forming tool 6, which comprises a lower tool part 6a and an upper tool part 6b. The film 5 is inserted into the cavity 7 of the lower tool part 6a. This creates sections 5a to 5d that are located outside the cavity 7. These are fixed in a suitable manner. The insertion of the film 5 into the cavity 7 should be carried out in such a way that no wrinkles are formed, if possible. Furthermore, it can be provided that overlapping areas of the film can be bonded together using penetrating PUR material.Subsequently, using a mixing head (not shown here), an open-cell polyurethane mixture is introduced into the cavity 7 of the lower mold part 6a, which is lined with film 5, in a manner known per se. Once the required amount of PUR mixture has been deposited onto the film 5 located in the cavity, the PUR mixture and, if applicable, any areas of the film exposed in the cavity are covered with the sections 5a to 5d located outside the cavity. The PUR mixture is thus completely enclosed by film. This results in a film package with a PUR mixture inside. The upper mold part 6b of the molding tool 6 is now moved towards the lower mold part 6a and the cavity 7 is closed (see arrow in the upper mold part 6b). The closed state of the cavity must be achieved before the rising time of the PUR mixture begins.The mold 6 is kept closed for a period of time that corresponds at least to the rise time. During the rise time, the polyurethane mixture foams in the cavity. As a result, the film 5 surrounding the polyurethane mixture is pressed against the walls of the cavity 7. The polyurethane mixture penetrates between overlapping film areas and these are bonded together in a vacuum-tight manner by means of the PUR mixture. After the rise time has elapsed and the PUR foam structure has cured, an open-cell PUR rigid foam structure is created with a compact skin layer covering the PUR rigid foam structure and completely surrounded by film. After the mold 6 has been moved up, this film package is transferred by a second robot 9 into a vacuum device 10 which is connected to a vacuum pump 11.When a predeterminable negative pressure is reached, a finished vacuum insulation panel 12 can be removed from the vacuum device 10.

[0029] Figure 2 shows a perspective view of the molding tool 6 in the open state. It depicts a situation in which the film 5 has been inserted into the cavity 7 of the lower tool section 6a. As described above, sections 5a, 5b, 5c, and 5d of the film 5 remain outside the cavity 7. After the PUR mixture has been introduced into the cavity or onto the film located there, sections 5a to 5d are folded upwards and placed onto the PUR mixture and any exposed areas of the film. The result is a film package that completely encloses the PUR mixture. The upper tool section 6a is now lowered (see arrow in Figure 2), and the molding tool is closed. Subsequently, the polyurethane mixture foams up in the cavity 7 and presses the film 5 against the walls of the cavity 7. In the process, the PUR mixture also penetrates into overlapping film areas and bonds them together.After the PUR foam structure has hardened, an open-cell PUR rigid foam structure is created with a compact skin layer covering the PUR rigid foam structure, which is completely surrounded by film.

[0030] The production plant shown in Figure 1 can also be modified in such a way that the vacuum device 10 can be dispensed with.

[0031] Accordingly, according to a first variant, a vacuum can be generated and present around the mold 6. For example, the mold 6 can be located in a closed and evacuated cell which can be evacuated by means of a vacuum pump. In this way, the polyurethane mixture can foam under negative pressure and the negative pressure thus created is maintained in the film package. The vacuum should be present at least for the duration of step (d) of the method according to the invention, i.e. during the introduction of the open-cell polyurethane mixture into the cavity of the mold lower part lined with the film. According to a further variant, a mixing head can be used to generate the vacuum, which mixing head is designed both for discharging the polyurethane mixture into the cavity and for extracting air from the film package.In particular, such a mixing head can be equipped with a valve that can be used to establish a connection between a suitable vacuum pump and the mixing head outlet pipe. This allows the vacuum pump to extract the air from the film pack via the mixing head outlet pipe until a predefined negative pressure is reached in the film pack.

[0032] List of reference symbols

[0033] Flat film extrusion line

[0034] Continuous film a Coated continuous film

[0035] Coating system

[0036] Assembly facility

[0037] Slide a-5d Sections outside the cavity

[0038] Forming tool a Lower tool part b Upper tool part

[0039] cavity

[0040] First robot

[0041] Second robot 0 Vacuum device 1 Vacuum pump 2 Vacuum insulation panels

Claims

Claims 1. A method for producing a vacuum insulation panel (12), comprising the following steps (a) to (i): (a) providing a gas-tight film (5) whose area is larger than the surface of the finished vacuum insulation panels (12); (b) inserting the film (5) into the cavity (7) of a lower tool part (6a) of a mold (6); (c) fixing those sections (5a, 5b, 5c, 5d) of the film (5) which are located outside the cavity (7) of the lower part of the tool (6b), (d) introducing an open-cell polyurethane mixture into the film (5) designed cavity (7) of the lower tool part (6a), (e) covering the polyurethane mixture and any areas of the film (5) that may be exposed in the cavity (7) with those sections (5a, 5b, 5c, 5d) of the film (5) that are located outside the cavity (7) of the lower tool part (6a), the polyurethane mixture being completely enclosed by the film (5) and a film package being produced; (f) moving an upper mold part (6b) towards the lower mold part (6a) and closing the cavity (7) before the rise time of the polyurethane mixture has begun; (g) Holding the mold (6) closed for a period of time which corresponds at least to the rise time, whereby the polyurethane mixture foams in the cavity (7) and as a result the film (5) surrounding the polyurethane mixture is pressed against the walls of the cavity (7), whereby the polyurethane mixture penetrates between overlapping film regions and bonds them together in a vacuum-tight manner, whereby an open-cell PUR foam structure is formed with a compact skin layer covering the PUR foam structure and being completely surrounded by film; (h) allowing the PUR foam structure to cure until an open-cell PUR rigid foam structure is formed; (i) opening the forming tool (6) and removing the finished film package; and comprising a step of creating a vacuum inside the film package.

2. Method according to claim 1, characterized in that for generating the vacuum, at least during the duration of step (d) a vacuum is present around the molding tool (6), in particular in that the molding tool (6) is located in a closed and evacuated cell, wherein the polyurethane mixture foams under negative pressure and the negative pressure thus formed is maintained in the film package.

3. Method according to claim 1, characterized in that a mixing head is used to generate the vacuum, which is designed both for the discharge of the polyurethane mixture and for the extraction of air from the film package, in particular by establishing the connection between a suitable vacuum pump and the mixing head outlet pipe via a valve, the air being extracted from the film package by means of the vacuum pump until a predeterminable negative pressure is reached in the film package.

4. Method according to claim 1, characterized in that for generating the vacuum the film package is or will be formed with a closable, preferably contour-neutral, film connection, and that via this film connection by means of a suitable vacuum pump a predeterminable negative pressure is generated in the film package.

5. Method according to one of the preceding claims, characterized in that the film is a metallized plastic film, in particular an aluminum composite film.

6. Method according to one of the preceding claims, characterized in that that the film is prefabricated according to the desired shape of the vacuum insulation panels or the cavity of the lower tool part or is prefabricated in the desired manner by means of a prefabrication device, in particular by preforming corners and / or by forming projections as those sections of the film which are located outside the cavity of the lower tool part.

7. Method according to one of the preceding claims, characterized in that the insertion of the film into the cavity (7) of the lower tool part (6a) is carried out in such a way that no folds are formed and / or that overlapping areas of the film can be bonded by penetrating PUR mixture.

8. Method according to one of the preceding claims, characterized in that when carrying out step (f), the cavity (7) is only closed when a predeterminable time for venting the cavity (7) has elapsed, this time preferably being predetermined as a function of the polyurethane mixture used.

9. Method according to one of the preceding claims, characterized in that the step (a) of providing the film takes place by means of an extrusion system (1), in particular by means of a flat film extrusion system, that the extrusion system (1) is followed by a finishing device (4) to which the continuous film (2) produced by the extrusion system (1) is fed and by means of which the extruded continuous film (2) is cut to a film (5) of a predeterminable shape, and that this film (5) is inserted into the cavity (7) of a lower tool part (6a) of a molding tool (6) according to step (b).

10. Method according to claim 9, characterized in that between the exit of the continuous film (2) from the extrusion system (1) and the feeding of the continuous film (2) to the finishing device (4), a coating of the continuous film (2) is carried out by means of a coating system (3), in particular a coating with a metallic material, preferably with aluminum, so that a correspondingly coated continuous film (2a) is produced and fed to the finishing device (4).