Method for producing thermoplastic foam panels by means of at least two heating elements offset in parallel with each other

Patent metadata

Field	Value
Publication number	US-10000014-B2
Application number	US-201414906938-A
Country	US
Kind code	B2
Filing date	Jul 17, 2014
Priority date	Jul 24, 2013
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

The present invention relates to a process for the production of at least two-layer thermoplastic foam sheets via thermal welding of at least two thinner thermoplastic foam sheets. In the process of the invention, at least two heating elements are conducted on mutually offset planes between the surfaces to be welded of the thinner thermoplastic foam sheets, and the foam sheets here do not touch the heating elements. The number of layers of the thermoplastic foam sheet is per se a result of the number of thinner thermoplastic foam sheets that are thermally welded to one another. If by way of example three thinner thermoplastic foam sheets are thermally welded to one another, a three-layer thermoplastic foam sheet is per se obtained, and if there are four thinner thermoplastic foam sheets the result is accordingly per se a four-layer thermoplastic foam sheet.

First claim

The invention claimed is:

1. A process for the production of an at least two-layer thermoplastic foam sheet via thermal welding of at least two thinner thermoplastic foam sheets, comprising the following steps a) to e):
a) two thinner thermoplastic foam sheets are oriented parallel to one another with a separation a, in such a way that they form an intermediate space,
b) at least two heating elements are introduced on parallel-offset planes, and parallel to the two thinner thermoplastic foam sheets, into the intermediate space, and the surfaces of the two thinner thermoplastic foam sheets here do not touch the heating elements,
c) the heating elements are introduced between the two thinner thermoplastic foam sheets to an extent such that, in relation to every location on the respective surface of the two thinner thermoplastic foam sheets, at least one of the heating elements has been present at least temporarily between the two thinner thermoplastic foam sheets,
d) the heating elements are removed completely from the intermediate space,
e) at least one of the two thinner thermoplastic foam sheets is forced against the surface of the respective other thinner thermoplastic foam sheet
where, in step b), two heating elements are introduced from, in each case, mutually opposite directions into the intermediate space or, in step d), two heating elements are in turn removed in, in each case, mutually opposite directions from the intermediate space.

2. The process according to claim 1 , wherein the thickness of the weld formed via the thermal welding process is from 30 to 200 μm.

3. The process according to claim 2 , wherein the thickness is from 80 to 100 μm.

4. The process according to claim 1 , wherein the thinner thermoplastic foam sheet is a molded foam or an extruded foam.

5. The process according to claim 4 , wherein the thinner thermoplastic foam sheet is an extruded foam made of polystyrene or made of a copolymer produced from styrene.

6. The process according to claim 1 , wherein the thermoplastic foam sheet comprises at least one flame retardant.

7. The process according to claim 6 , wherein the flame retardant is selected from a phosphate, a phosphite, a phosphonate, a polyphosphonate, melamine, an aluminum oxide hydrate, or a halogenated organic compound.

8. The process according to claim 1 , wherein two heating elements are used, or the heating elements are heating plates.

9. The process according to claim 8 , wherein the two heating elements are IR sources with surface temperature from 200 to 1000° C.

10. The process according to claim 1 , wherein, in each sheet pair to be welded, at least one and preferably both of the surfaces to be thermally welded of the thinner thermoplastic foam sheets are foaming-skin-free.

11. The process according to claim 1 , wherein the thermal welding process is carried out at temperatures which are from 50 to 300° C. above the glass transition temperature in the case of amorphous thermoplastic foams, or which are from 50 to 100° C. above the melting point in the case of semicrystalline thermoplastic foams.

12. The process according to claim 1 , wherein the heating elements in the steps b) and d) are moved with a velocity of from 0.1 to 5 m/s.

13. The process according to claim 1 , wherein, in step b), two heating elements are introduced from respectively mutually opposite directions into the intermediate space, and, in step d), two heating elements are removed in respectively mutually opposite directions from the intermediate space.

14. The process according to claim 1 , wherein the total duration of the steps b) to e) is at most 20 seconds.

15. The process according to claim 1 , wherein, in step a), the length (x-direction) of the two thinner thermoplastic foam sheets is respectively from 500 to 2800 mm, and their width (y-direction) is from 500 to 1250 mm, and their thickness (z-direction) is from 20 to 200 mm.

16. The process according to claim 1 , wherein the length (x-direction) of the heating elements is respectively the same as or at most 10% greater than the corresponding lengths (x-direction) of the two thinner thermoplastic foam sheets, and the width (y-direction) of the heating elements is from 30 to 100% of the corresponding width (y-direction) of the two thinner thermoplastic foam sheets.

17. The process according to claim 1 , wherein the heating elements are moved parallel to the xy-plane and along the y-direction (width) of the two thinner thermoplastic foam sheets.

18. The process according to claim 1 , wherein the density of the thermoplastic foam sheets is from 10 to 500 g/l.

19. The process according to claim 1 , wherein the process is carried out in a thermally insulated enclosure, and a temperature that is constant within +/−10° C. is maintained in the range from 40 to 200° C. in the thermal enclosure.

20. The process according to claim 1 , wherein, in the steps b) to d), the separation between the surface of each of the two thinner thermoplastic foam sheets and the surface of the respective heating element that is respectively spatially closest thereto is from 0.5 to 25 mm.

21. The process according to claim 1 , wherein in step b), two heating elements are introduced from, in each case, mutually opposite directions into the intermediate space and, in step d), two heating elements are in turn removed in, in each case, mutually opposite directions from the intermediate space.

Assignees

• Basf Se

Inventors

• Scherzer Dietrich
• Diehlmann Tim
• Dietzen Franz-Josef
• Sandner Carsten
• Schall Herbert

Classifications

• B29C66/727

  being porous, e.g. foam · CPC title

• B29C66/71

  characterised by the composition of the plastics material of the parts to be joined (welding bar compositions B29C65/125) · CPC title

• B29C65/1432

  direct heating of the surfaces to be joined · CPC title

• B29C66/735

  characterised by the extensive physical properties of the parts to be joined · CPC title

• B29C65/7847

  using vacuum to hold at least one of the parts to be joined (vacuum work holders in general B25B11/005) · CPC title