DE102021105890A1 - Foam molding and method for producing a foam molding - Google Patents

Abstract

In order to create a recyclable foam molding, the invention provides a foam molding (3, 4) with at least a first layer (1, 10) made of polyethylene and a second layer (2) made of polyethylene, the second layer (2) being a cover layer forms, which closes the foam molding (3, 4) on one of its sides (S) to the outside, the second layer (2) comprising non-crosslinked polyethylene and preferably consisting of non-crosslinked polyethylene.

Description

The invention relates to a foam molding which is intended in particular for use as a foam insert in suitcases, containers or drawers. The invention also relates to a method for producing a foam molding.

Foam inserts are inserts made of foam to accommodate components. They are often specially made for the respective application. They are used for order and clarity in suitcases, containers or drawers and ensure that the individual parts fit perfectly. This ensures safe storage or packaging of the components, which is particularly important for surface-treated, painted and sensitive parts. In particular, the foam material is used for shock absorption. Such foam inserts are widely used in the tool or automotive industry, medical technology, in aerospace and also for everyday objects.

Foam inserts are designed in two colors for a better overview. The substructure and the top layer are designed in different colors. If one of the components inserted in the foam insert is missing, this is immediately apparent to the user, since the differently colored substructure is visible at the corresponding point.

While the base layer or the substructure bears the main load of the inserted component and is intended to protect it from bumps and scratches, the top layer serves to protect the substructure against dirt. Therefore, the base layer and top layer are made of different materials whose properties are adapted to these tasks.

Polyethylene foam (PE foam) is a closed-cell material with excellent properties such as low density, excellent weather and aging resistance, good sound and heat insulation and very good resistance to commercially available acids, alkalis and other chemicals. PE foams are mainly used in packaging, sound insulation, for seals, for transport protection and for thermal insulation. In the production of PE foams, molten polyethylene is mixed with blowing gas under high pressure in the extruder. A distinction is made between crosslinked and non-crosslinked PE foams.

In the case of crosslinked PE foams, the polymer chains are chemically or physically connected to one another at certain points and form a three-dimensional network. Cross-linked PE foams have a fine, regular and closed cell structure, so that no gases or liquids can flow in or out of the cells.

To date, the applicant has produced molded foam parts with a cover layer made of crosslinked polyethylene, which offers good protection for the base layer. However, molded foam parts with crosslinked polyethylene are not recyclable. Chemically crosslinked materials also emit gases during use and react with precious metals, which can lead to surface corrosion of the inserted components, and they have a very strong inherent odor (like ammonia).

It is therefore an object of the invention to create an improved foam molding. In particular, it is an object of the invention to provide a recyclable foam molding. In addition, it is an object of the invention to provide a foam molding which does not outgas during use. In addition, surface corrosion of inserted components made of precious metals should be avoided.

The invention achieves these objects in a surprisingly simple manner with a foam molding according to claim 1. Advantageous further developments are the subject matter of the dependent claims.

The invention provides a foam molding available with at least a first layer made of polyethylene and a second layer made of polyethylene, the second layer forming a cover layer which closes the foam molding on one of its sides to the outside, the second layer comprising non-crosslinked polyethylene and preferably made of non-crosslinked polyethylene, in particular non-crosslinked LDPE.

In the case of non-crosslinked PE foam, the polymers are present as long chains that are not connected to one another. As a result, uncrosslinked foams have a limited melting point at which the polymer chains separate. Uncrosslinked PE foams can be recycled.

They are currently used as shock absorbers and for impact sound insulation.

Surprisingly, it turned out that a cover layer for a molded foam part can be produced from an uncrosslinked polyethylene foam. The top coat is on first Layer, which is also referred to as the base layer, glued or laminated on, in particular by thermal lamination.

Uncrosslinked polyethylene foams have a rough surface. Within the scope of the invention, however, the surface of the second layer made of non-crosslinked polyethylene could be produced in such a way that a user cannot distinguish it from a known cover layer made of crosslinked polyethylene, both visually and in terms of feel. This can be achieved, for example, by targeted compression of the second layer.

The material according to the invention is odorless and does not outgas. This means that it is also suitable in critical areas such as medical technology, toys, when used with inserts for parts made of precious metal, etc.

In addition, the new combination of layers with at least one top layer made of non-crosslinked polyethylene is not only more environmentally friendly, but also cheaper to buy. As a result, the insole can be offered more cheaply.

In a preferred development of the invention, the second layer has a density in the range from 50 kg/m ³ to 350 kg/m ³ , preferably in the range from 100 kg/m ³ to 300 kg/m ³ , particularly preferably in the range of 150 kg /m ³ to 250 kg/m ³ . The significantly higher density compared to the material previously used for the second layer according to the invention makes it possible to manufacture the second layer with a lower thickness and still achieve sufficient stability and protective effect with a corresponding saving in material. The person skilled in the art can set the density, for example, by selecting the parameters for the extrusion of a foam from granulated starting material with the addition of a blowing agent. Such a high density as provided according to the invention for the second layer has hitherto not been used to the best of the applicant's knowledge.

In a development of the invention, it is therefore provided that the second layer of the foam molding has a thickness in the range from 2 mm to 7 mm, preferably in the range from 3 mm to 5 mm.

Furthermore, it has surprisingly been shown for the applicant that the foam molding has a higher inherent stability compared to previous products, which the user can feel during handling, especially haptically, but which is also evident during milling. Furthermore, due to the higher density and the non-crosslinked material, the second layer as a TOP layer is significantly more resistant to external "injuries" such as scratches and damage from sharp-edged objects.

In a further development of the invention, the first layer has a density in the range from 20 kg/m ³ to 200 kg/m ³ , preferably in the range from 24 kg/m ³ to 120 kg/m ³ , particularly preferably 24 kg/m ³ up to 70 kg/ ^m3 . Compared to previous products, according to the invention, particularly given the relatively high density of the second layer described above, the density of the material of the first layer can be reduced by 25% or more. This saves costs and PE material and is therefore more sustainable. In a preferred embodiment of the invention, therefore, the first layer consists of non-crosslinked polyethylene.

In particular, it is provided within the scope of the invention that the molded foam part consists entirely of non-crosslinked polyethylene. Due to the use of a uniform material, namely non-crosslinked PE, in particular LDPE, the foam molding according to the invention enables the production of a two- or multi-layer composite by lamination, which has sufficient adhesive strength and is completely recyclable.

For use as an insert, the invention provides that the foam molding has at least one pocket which extends through the second layer into the first layer. The second layer can in particular be colored in a contrasting color to the color of the underlying layer. According to the experience of the applicant, the color combinations black for the top layer and another color or white or gray for the layer underneath have proven successful. A contrasting color design promotes the "shadow" effect, which is explained in more detail elsewhere. However, it is also possible to make the first layer black.

In a structurally simple manner, the at least one pocket can be milled into the foam molding and/or the outer contour of the foam molding can be produced at least in regions by milling from a blank. It has been shown that the material in the combination of both or all layers (first layer and second layer and possibly further layers) with or made of non-crosslinked polyethylene has a stability that leads to the milling speed being reduced by 50% and more compared to processing of previously used materials, in particular made of cross-linked PE, can be increased, while the partitions between the individual pockets are still more stable and stiffer are. This effect leads to a lower reject rate in processing.

With the advantages according to the invention, such as high stability, recyclability and corrosion resistance, a wide field of application is opened up for the use of the foam molding. In particular, the invention provides that the molded foam part is selected from the group comprising tool inserts, case inserts, reusable packaging, presentation packaging, foam trays, contoured parts, small load carriers, seat cushions and knee cushions.

From a completely different area of application, a material has surprisingly proven to be suitable for use for the second layer. Here, in one embodiment, the invention can use a material for impact sound insulation as the material for the second layer. This enables used materials from the impact sound insulation to be recycled for further use as the starting material for a foam molded part according to the invention.

1. a) Bereitstellen einer ersten Schicht aus Polyethylen aus einem ersten Ausgangsmaterial,
2. b) Bereitstellen einer zweiten Schicht aus Polyethylen aus einem zweiten Ausgangsmaterial,
3. c) Verbinden der ersten Schicht und der zweiten Schicht zu einem Schaumstoffformteil,

wobei unvernetztes Polyethylen, bevorzugt unvernetztes recyceltes Polyethylen, besonders bevorzugt unvernetztes recyceltes LD-Polyethlyen, zumindest als Bestandteil des ersten Ausgangsmaterials und/oder des zweiten Ausgangsmaterials eingesetzt wird.The invention also provides a method for producing a foam molding, in particular a foam molding as described above, which comprises the following steps:

1. a) providing a first layer of polyethylene from a first starting material,
2. b) providing a second layer of polyethylene from a second starting material,
3. c) connecting the first layer and the second layer to form a foam molded part,

wherein non-crosslinked polyethylene, preferably non-crosslinked recycled polyethylene, particularly preferably non-crosslinked recycled LD polyethylene, is used at least as a component of the first starting material and/or the second starting material.

The method can be carried out in a particularly simple manner in that the first starting material and the second starting material are identical.

Due to the above-described advantages of the material selection according to the invention, a preferred embodiment of the method provides that the first starting material and/or the second starting material consists of recycled polyethylene, preferably non-crosslinked recycled polyethylene, in particular non-crosslinked recycled low-density polyethylene.

The invention thus enables a significant increase in sustainability, in particular by also using all production waste for the starting material of the second and/or the first layer. For this purpose, they can be processed, for example, in a regranulation plant to form PE granules, in particular LDPE granules, which are fed to the extrusion for producing the starting material of the first layer and/or the starting material of the second layer. In a further development of the invention, it is provided that foam moldings that are no longer required are returned and also recovered as starting material.

The invention is explained in more detail below with reference to the accompanying figures and exemplary embodiments.

• 1 einen Ausschnitt aus einer Fotografie aus Richtung schräg von oben auf eine bisherige Schaumstoffeinlage der Anmelderin,
• 2 eine schematische perspektivische Darstellung eines erfindungsgemäßen Schaumstoffformteils ausgebildet als Rohling,
• 3 eine schematische perspektivische Darstellung einer weiteren Ausführungsform des erfindungsgemäßen Schaumstoffformteils mit Tasche,
• 4 eine schematische Darstellung im Längsschnitt entlang der Ebene AA der in 3 dargestellten Ausführungsform des erfindungsgemäßen Schaumstoffformteils mit Tasche,
• 5 einen Ausschnitt aus einer Fotografie aus einer Richtung schräg von oben auf eine erste erfindungsgemäße Schaumstoffeinlage der Anmelderin,
• 6 einen Ausschnitt aus einer Fotografie aus Richtung schräg von oben auf eine zweite erfindungsgemäße Schaumstoffeinlage der Anmelderin,
• 7 einen Ausschnitt aus einer Fotografie aus Richtung schräg von oben auf eine dritte erfindungsgemäße Schaumstoffeinlage der Anmelderin,
• 8 eine schematische Darstellung im Längsschnitt einer weiteren Ausführungsform des erfindungsgemäßen Schaumstoffformteils mit Tasche,
• 9 eine schematische Darstellung im Längsschnitt einer weiteren Ausführungsform des erfindungsgemäßen Schaumstoffformteils mit Tasche.

Show it:

• 1 a detail from a photograph from the direction diagonally from above of a previous foam insert of the applicant,
• 2 a schematic perspective view of a foam molding according to the invention designed as a blank,
• 3 a schematic perspective view of a further embodiment of the foam molding according to the invention with a pocket,
• 4 a schematic representation in longitudinal section along the plane AA of FIG 3 illustrated embodiment of the foam molding according to the invention with pocket,
• 5 a section of a photograph from a direction diagonally from above of a first foam insert according to the invention by the applicant,
• 6 a section of a photograph from the direction diagonally from above of a second foam insert according to the invention by the applicant,
• 7 a section of a photograph from the direction diagonally from above of a third foam insert according to the invention by the applicant,
• 8th a schematic representation in longitudinal section of a further embodiment of the foam molding according to the invention with a pocket,
• 9 a schematic representation in longitudinal section of a further embodiment of the foam molding according to the invention with a pocket.

In 1 shows a detail from a photograph from a direction obliquely from above onto a previous foam insert from the applicant. the Foam insert comprises two layers, a cover layer 200 is applied to a base layer 100 . The cover layer 200 is made of crosslinked LDPE and is colored black. As the top layer of the foam insert, it serves to protect the base layer 100 from contamination and mechanical damage. The top layer has a thickness DD, which is 5 mm in the example shown.

The base layer 100 is colored in a contrasting color to the cover layer 200 . In the figure in 1 Recesses, also referred to below as pockets, can be seen in the color of the base layer 100. Tools, cooking utensils, medical equipment and much more can be stored clearly and compactly in the pockets of such a foam tray.

In the exemplary embodiment shown, the molded foam part is designed as a so-called “shadowboard”. The two colors serve to improve the overview for the user. The substructure and the top layer are designed in different colors. If a piece is missing, this is immediately noticeable due to the resulting "shadow". At the same time, the foam offers the desired protection against scratches and other damage. "Shadowboards" can be made, for example, as suitcase inserts that allow easy transport

It can be seen that the cover layer 200 has a structure consisting essentially of closed cells.

In 2 a foam molding according to the invention is shown. In a simple embodiment, this has no pockets. It can be provided as a blank 4 for further processing, but can also be used itself. The foam molding has a first layer 1 and a second layer 2. Both layers are made of polyethylene. The second layer 2 forms a cover layer, which closes the foam molded part 4 on one of its sides S, here the upper side, to the outside. The second layer 2 comprises uncrosslinked polyethylene. In the context of the invention, it is preferred that the second layer consists of non-crosslinked polyethylene. In particular, LDPE is used as the polyethylene within the scope of the invention.

The second layer 2 follows the first layer 1 . Further layers can follow the first layer 1 . Likewise, a composite of the first layer—and possibly further layers—and the second layer can be provided with a second layer on more than one side S. In particular, a foam molding according to the invention can be completely surrounded by a second layer. This applies to all embodiments within the scope of the invention.

In accordance with a blank 4 2 a relief-like structure can be introduced, for example by milling. Such a structure can in particular be a negative of components that are to be inserted into the foam molded part when it is used. In 3 a foam molding 3 according to the invention with a pocket 5 is shown. The pocket 5 serves as an example of such a structure. The pocket 5 is introduced into the base layer 1 through the cover layer 2 . The color of the base layer 1 can be seen when looking at the molded foam part 3 through the opening of the pocket 5 in the top layer 2 .

In 4 is a longitudinal section along the plane AA of 3 shown embodiment of the foam molding 3 with pocket 5 shown. The thickness D of the second layer 2 is thinner in comparison to previously manufactured foam inserts made of cross-linked polyethylene and is preferably only 2 to 3 mm, while a thickness of 3 to 5 mm was usual up to now.

5 shows a section of a photograph from a direction obliquely from above of a first inventive foam molding 3 of the applicant. This is designed as a foam insert. The second layer 2 as the top layer can be seen flat and black. This is made of non-crosslinked LDPE. The base layer 1 is also made from non-crosslinked LDPE.

In the second layer 2 letter-number combinations are lasered (deep engraving). These are used by the user to identify the bag. Pockets 5 are introduced through the cover layer 2 into the first layer 1 adjoining the second layer 2 . Different pockets can be seen, which are identified uniformly with the reference number 5 for the sake of simplicity. The first layer 1 is colored blue here.

Compared to the figure in 1 one can see that the surface structure of the second layer 2 is optically very similar to the previously manufactured top layer 200. The second layer 2 is made from non-crosslinked LDPE and accordingly gives the human eye essentially the same optical impression as a top layer made from crosslinked LDPE. This is a surprising result of the invention, since the crosslinked materials can be adjusted significantly better to optical criteria in the production process.

In the 6 and 7 are excerpts from a photograph from an oblique direction from above from a smaller distance than in 5 shown on a second foam insert according to the invention by the applicant. The choice of material in the 6 and 7 foam inserts shown corresponds to the in 5 embodiment shown. In comparison with 1 In relation to the order of magnitude of the pocket dimensions, the relatively small thickness D of the second layer and the very fine-celled structure of its surface can be seen. The thickness D of the second layer in the shown embodiments of the invention is 2 mm.

8th shows a further embodiment of the foam molded part 3 according to the invention with pocket 5. The substructure of this embodiment has a two-layer structure consisting of a first layer 1 and a further layer 10. Functionally, this means that the base layer has a two-layer structure. The top layer 2 connects to the base layer. Within the scope of the invention, the base layer can also be made up of more than two layers. The second layer 2 itself can also have a multi-layer structure. This applies regardless of whether pockets are introduced into the foam molding or not.

In the illustrated embodiment of the invention in 8th a pocket 5 is introduced through the cover layer 2 into the foam molding 3 so deeply that the bottom of the pocket 5 is formed by material of the further layer 10 . This can also be achieved in that, in a first production step, a composite of layers 1 and 2 is provided with a through hole, the wall of which forms the wall of pocket 5 in the end product, which is essentially perpendicular to the main direction of extension of layers 1, 2 and 10 extends. In a second step, the further layer 10 is then connected to the layer 1 and the pocket 5 is thus provided with a bottom and closed from the top layer 2 as seen from below.

As in 9 is shown on the basis of a further embodiment of the foam molding 3 according to the invention with pocket 5, the pocket can also be manufactured through all layers 2, 1, 10 in the case of a multi-layer composite 2, 1, 10.

Within the scope of the invention, it is preferred to produce all layers 2, 1, 10 from non-crosslinked polyethylene, in particular from non-crosslinked LDPE. For the sustainability of their products, the applicant creates 100% recyclability, so that all production waste can be fed back into the foam production cycle, and the products used by customers of the applicant can be returned and recycled.

Another goal of the applicant is CO2 neutrality. Another advantage of the invention is that the CO2 consumption in the extrusion process for producing a foam from a non-crosslinked material is significantly lower than in the case of a chemically and/or physically crosslinked material. The applicant also delivers its products 100% CO2-neutral.

It is obvious to the person skilled in the art that the invention is not limited to the examples described above, but rather can be varied in many ways. In particular, the features of the individually illustrated examples can also be combined with one another or exchanged for one another.

Reference List

1, 10, 100

first layer, base material, substructure

2, 200

second layer, top layer

3

Foam molding, in particular foam molding with pockets, insert

4

Blank, foam molding

5

pocket

D

Thickness of the second layer

S

Side of foam molding or blank

Claims (13)

Foam molding (3, 4) with at least a first layer (1, 10) made of polyethylene and a second layer (2) made of polyethylene, the second layer (2) forming a cover layer which the foam molding (3, 4) has on one of its Sides (S) outwards, characterized in that the second layer (2) comprises non-crosslinked polyethylene and preferably consists of non-crosslinked polyethylene. Foam molding (3, 4) after claim 1 characterized in that the second layer (2) has a density in the range from 50 kg/m ³ to 350 kg/m ³ , preferably in the range from 100 kg/m ³ to 300 kg/m ³ , particularly preferably in the range of 150 kg /m ³ to 250 kg/m ³ . Foam molding (3, 4) after claim 1 or 2 , characterized in that the second layer (2) has a thickness (D) in the range from 2 mm to 7 mm, preferably in the range from 3 mm to 5 mm. Foam molding (3, 4) according to one of the preceding claims, characterized in that the first layer (1, 10) has a density in the range from 20 kg/m ³ to 200 kg/m ³ , preferably in the range from 24 kg/m ³ to 120 kg/m ³ , particularly preferably from 24 kg/m ³ to 70 kg/m ³ . Foam molding (3, 4) according to one of the preceding claims, characterized in that the first layer (1) consists of non-crosslinked polyethylene. Foam molding (3, 4) according to one of the preceding claims, characterized in that the foam molding (3, 4) consists entirely of non-crosslinked polyethylene. Foam molding (3, 4) according to one of the preceding claims, characterized in that the foam molding (3, 4) has at least one pocket (5) which extends through the second layer (2) into the first layer (1). . Foam molding (3, 4) after claim 7 , characterized in that the at least one pocket (5) is milled into the foam molding (3, 4) and/or that the outer contour of the foam molding is produced at least in regions by milling from a blank (4). Foam molding (3, 4) according to one of the preceding claims, characterized in that the foam molding (3, 4) is selected from the group comprising tool inserts, case inserts, reusable packaging, presentation packaging, foam trays, contour parts, small load carriers, seat cushions and knee cushions. Foam molding (3, 4) according to one of the preceding claims, characterized in that a material for impact sound insulation is used as the material for the second layer (2). Method for producing a foam molding (3, 4), in particular a foam molding according to one of Claims 1 until 10 , with the following steps a) providing a first layer (1) made of polyethylene from a first starting material, b) providing a second layer (2) made of polyethylene from a second starting material, c) connecting the first layer (1) and the second layer ( 2) to form a foam molding (3, 4), characterized in that non-crosslinked polyethylene, preferably non-crosslinked recycled polyethylene, particularly preferably non-crosslinked recycled LD polyethylene, is used at least as a component of the first starting material and/or the second starting material. procedure after claim 11 , characterized in that the first starting material and the second starting material are identical. procedure after claim 11 or 12 , characterized in that the first starting material and/or the second starting material consists of recycled polyethylene, preferably uncrosslinked recycled polyethylene, in particular uncrosslinked recycled low-density polyethylene.

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