DE102024106679B3 - Process for producing a vacuum insulation panel - Google Patents

Abstract

A method for producing a vacuum insulation panel is described, wherein a film is inserted into a mold cavity and an open-cell PUR mixture is applied. Excessive areas of the film are folded together, and the PUR mixture is completely surrounded by film. The mold closes, the PUR mixture expands, and presses the film against the cavity walls. This results in the formation of an open-cell PUR rigid foam structure with a compact skin surrounded by film. A vacuum insulation panel is produced by evacuating the open-cell PUR (rigid) foam structure. To improve process integration and ensure efficient production of vacuum insulation panels, all steps of the method can be carried out directly one after the other.

Description

The invention relates to a method for producing vacuum insulation panels. Vacuum insulation panels (VIPs for short) are highly efficient thermal insulation materials that utilize the principle of vacuum insulation. They are frequently used for the thermal insulation of refrigerators and cold storage facilities. The principle of vacuum insulation is also increasingly being used in the manufacture of refrigerators and freezers.

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."

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 subsequent step, the film-coated block is evacuated. Methods of the aforementioned type are known from the documents DE 699 00 806 T2 and DE 44 18 507 A1 .

From the documents DE 10 2010 119 479 A1 and WO 2015 / 007 874 A1 The backfoaming of film wrappings is known, but no folding of the films after the introduction of the foam material and no vacuum application inside the film package is described.

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.

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.

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.

1. (a) Bereitstellen einer gasdichten Folie, deren Fläche größer ist als die Oberfläche der fertigen Vakuum-Isolationspaneele;
2. (b) Einlegen der Folie in die Kavität eines Unterteil eines Formwerkzeugs;
3. (c) Fixieren derjenigen Abschnitte der Folie, welche sich außerhalb der Kavität des Werkzeugunterteils befinden,
4. (c) Eintragen eines offenzelligen Polyurethan-Gemischs in die mit der Folie ausgelegte Kavität des Werkzeugunterteils,
5. (e) Überdecken des Polyurethan-Gemischs und von gegebenenfalls in der Kavität freiliegenden Bereichen der Folie mit denjenigen Abschnitten der Folie, welche sich außerhalb der Kavität des Werkzeugunterteils befinden, wobei das Polyurethan-Gemisch vollständig von Folie umschlossen wird und sich ein Folienpaket ergibt;
6. (f) Bewegen eines Werkzeugoberteils des Formwerkzeugs in Richtung des Werkzeugunterteils und Verschließen der Kavität, bevor die Steigzeit des Polyurethan-Gemischs begonnen hat;
7. (g) Zuhalten des Formwerkzeugs für eine Zeitdauer, welche mindestens der Steigzeit entspricht, wobei das Polyurethan-Gemisch in der Kavität aufschäumt und dadurch die das Polyurethan-Gemisch umgebende Folie an die Wandungen der Kavität gepresst wird, wobei Polyurethan-Gemisch zwischen sich überlappende Folienbereiche eindringt und diese vakuumdicht miteinander verklebt, wobei eine offenzellige PUR-Schaumstruktur mit einer kompakten die PUR-Schaumstruktur überdeckende Hautschicht gebildet wird, welche vollständig von Folie umgeben ist;
8. (h) Aushärtenlassen der PUR-Schaumstruktur bis zur Ausbildung einer offenzelligen PUR-Hartschaumstruktur;
9. (i) Öffnen des Formwerkzeugs und Entnahme des fertigen Folienpakets; und umfassend einen Schritt des Erzeugens eines Vakuums im Innern des Folienpakets.

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:

1. (a) providing a gas-tight film whose area is larger than the surface of the finished vacuum insulation panels;
2. (b) inserting the film into the cavity of a lower part of a mold;
3. (c) Fixing those sections of the film which are outside the cavity of the lower part of the tool,
4. (c) Introducing an open-cell polyurethane mixture into the cavity of the lower part of the tool lined with the film,
5. (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;
6. (f) moving an upper part of the mold towards the lower part of the mold and closing the cavity before the rise time of the polyurethane mixture has begun;
7. (g) holding the mold 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 areas 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;
8. (h) allowing the PUR foam structure to cure until an open-cell PUR rigid foam structure is formed;
9. (i) opening the forming tool and removing the finished film package; and comprising a step of creating a vacuum inside the film package.

There are various options for creating the vacuum inside the film package, which are described in more detail below.

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 maintained in the film package.

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 using the vacuum pump until a predeterminable negative pressure is reached in the film package.

According to a third embodiment, the foil package can be designed with a closable foil connection for generating the vacuum, via which a predeterminable negative pressure can be generated in the foil package using a suitable vacuum pump. The foil connection can preferably be designed to be contour-neutral, so that the surface of the foil package has virtually no elevations or depressions in the area of the foil connection.

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

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 forming projections may 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.

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 folds are formed and/or that overlapping areas are bonded by penetrating PUR mixture.

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.

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, the extrusion system can be followed by a finishing device, 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 aluminum. A continuous film coated in this way ensures that a 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 referred to as a gas-tight or vacuum-tight film.

• 1 schematische Darstellung wesentlicher Elemente einer Produktionsanlage zur Durchführung des erfindungsgemäßen Verfahrens;
• 2 perspektivische Darstellung des Formwerkzeugs in einer Situation mit eingelegter Folie.

In the following, the invention will be explained using an embodiment and with reference to the 1 and 2 are described in more detail. They show:

• 1 schematic representation of essential elements of a production plant for carrying out the method according to the invention;
• 2 Perspective view of the mold in a situation with inserted film.

The 1 shows a production plant for producing a vacuum insulation panel using the method according to the invention. This production plant comprises a flat film extrusion line 1 for producing and providing a continuous film 2, which in a subsequent process step is provided with a metal layer, in particular with an aluminum layer, in a coating system 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 created, which serve to enclose the vacuum insulation panels. The film 5 is therefore pre-finished according to the desired shape of the vacuum insulation panels or the cavity of the lower tool part, in particular by pre-forming corners and/or by forming projections as those sections of the film which are located outside the cavity of the lower tool part. Such a film 5 has an overall area which is larger than the surface of the finished vacuum insulation panels. The overall area and the contour of the film 5 are such that a closed envelope 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 a tool upper 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 by means of penetrating PUR material. Subsequently, by means of a mixing head (not shown here) in a conventional manner, an open-cell polyurethane mixture is introduced into the cavity 7 of the lower tool part 6a, which is lined with the film 5. Once the required amount of PUR mixture has been deposited onto the film 5 located in the cavity, the PUR mixture and any exposed areas of the film 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 tool part 6b of the mold 6 is now moved towards the lower tool part 6a and the cavity 7 is closed (see arrow in the upper tool part 6b). The closed state of the cavity must be achieved before the rise 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. This presses the film 5 surrounding the polyurethane mixture 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 using 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 forming tool 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. Once a predetermined negative pressure is reached, a finished vacuum insulation panel 12 can be removed from the vacuum device 10.

The 2 shows a perspective view of the mold 6 in the opened state. This shows a situation in which the film 5 has been inserted into the cavity 7 of the lower tool part 6a. As described above, sections 5a, 5b, 5c, and 5d of the film 5 remain, which are located outside the cavity 7. After the PUR mixture has been introduced into the cavity or onto the film located there, the 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 part 6b is now lowered (see arrow in 2 ) and the mold is closed. Subsequently, the polyurethane mixture foams in cavity 7 and presses film 5 against the walls of cavity 7. In the process, the polyurethane mixture also penetrates overlapping film areas and bonds them together. After the polyurethane foam structure has cured, an open-cell polyurethane rigid foam structure is created with a compact skin layer covering the polyurethane rigid foam structure and completely surrounded by film.

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

Accordingly, according to a first variant, a vacuum can be generated and maintained around the molding tool 6. For example, the molding tool 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 maintained at least during 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 lower mold part lined with the film.

According to a further variant, a mixing head can be used to generate the vacuum, which 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 have a valve that can be used to establish the connection between a suitable vacuum pump and the mixing head outlet pipe. Thus, the air can be extracted from the film package via the mixing head outlet pipe using the vacuum pump until a predefined negative pressure is reached in the film package.

List of reference symbols

1

Flat film extrusion line

2

Continuous film

2a

Coated continuous film

3

Coating system

4

Assembly facility

5

film

5a-5d

Sections outside the cavity

6

mold tool

6a

Tool base

6b

Tool upper part

7

cavity

8

First robot

9

Second robot

10

Vacuum device

11

vacuum pump

12

Vacuum insulation panels

Claims (9)

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 panel (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) that are located outside the cavity (7) of the lower mold part (6a), (d) Introducing an open-cell polyurethane mixture into the cavity (7) of the lower mold part (6a) lined with the film (5), (e) Covering the polyurethane mixture and any exposed areas of the film (5) 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 mold part (6a), whereby the polyurethane mixture is completely enclosed by the film (5), resulting in a film package; (f) Moving an upper mold part (6b) toward 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 at least equal to the rise time, whereby the polyurethane mixture foams in the cavity (7) and thereby presses the film (5) surrounding the polyurethane mixture 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, forming an open-cell PUR foam structure with a compact skin layer covering the PUR foam structure and 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 mold (6) and removing the finished film package; and comprising a step of creating a vacuum inside the film package. Procedure 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. Procedure 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. Procedure according to Claim 1 , characterized in that for generating the vacuum the film package is or will be designed with a closable, preferably contour-neutral, film connection, and that via this film connection a predeterminable negative pressure is generated in the film package by means of a suitable vacuum pump. Method according to one of the preceding claims, characterized in that the film is a metallized plastic film, in particular an aluminum composite film. Method according to one of the preceding claims, characterized in 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 prefabricating 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. 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. 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). Procedure according to Claim 8 , 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).

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