MULTILAYER FOAMS

• US 20020026977A1
• Filed: 11/12/1998
• Published: 03/07/2002
• Est. Priority Date: 12/08/1997
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: Dow Global Technologies, Inc. (Dow, Inc.)
• Inventors: VO, CHAU VAN, ESCHENLAER, GEORGES, MASON, JEFFFREY JOHN
• Granted Patent: US 6,440,241 B1
• Time in Patent Office: Days
• US Class Current: 156/78
• CPC Class Codes: B29C 44/24 Making multilayered articles
• CPC Class Codes: B29C 44/468 in a plurality of parallel streams which unite during the foaming

Abstract

The present invention concerns foamed products having a plurality of coalesced extruded layers or layers of coalesced strands of a foamed thermoplastic composition having a low density.

Claims

1. A method for producing a polymer or copolymer multilayer foam, comprising the steps of:

(a) providing at least one foamable composition comprising at least one polymer or copolymer and a blowing agent formulation,

(b) extruding the composition through a die having a plurality of orifices,

(c) foaming the extruded composition at a foaming temperature which is above the glass-transition temperature or the melting temperature of the polymer composition,

(d) maintaining the foaming product at an elevated temperature for a sufficient period of time to obtain adhesion between individual foam layers, and

(e) allowing the foamed product to cool, characterized in that a foamed product is obtained comprising a plurality of adherent foam layers, wherein at least one of these foam layers extends across the whole breadth of the foamed product.

2. The method of claim 1, wherein the polymer or copolymer composition is selected from alkylene aromatic polymers or copolymers and olefinic polymers or copolymers and mixtures thereof.

3. The method of claim 1 wherein the blowing agent is selected from hydrocarbons, ethers, lower alcohols, partially halogenated hydrocarbons, water, carbon dioxide, nitrous oxides, nitrogen, ammonia, air, noble gases and mixtures thereof.

4. The method of claim 1, wherein the multilayer foam comprises at least three foam layers.

5. The method of claim 4, where the blowing agent formulation exhibits a low evaporative cooling capacity during the foaming process, and step (e) includes an accelerated cooling of the foamed product.

6. The method of claim 4, where the blowing agent formulation exhibits a high evaporative cooling capacity during the foaming process, and step (d) includes a transfer of additional heat to the foaming product.

7. The method of claim 1, wherein the polymer or copolymer composition is substantially free from adhesive additives.

8. The method of claim 1, wherein the foaming temperature is 1°

C. to 50°

C. above the glass-transition temperature or melting temperature of the polymer or copolymer.

9. The method of claim 1, further comprising co-extruding a first polymer or copolymer composition through at least one first opening of the multiorifice die, and a second polymer or copolymer composition through at least one second opening of the multiorifice die, wherein the first composition is different from the second composition, and whereby a multilayer foam is produced comprising at least one layer of the first polymer or copolymer foam and at least one layer of the second polymer or copolymer foam.

10. The method of claim 9, wherein the first composition comprises polypropylene and the second composition comprises polystyrene.

11. A polymer or copolymer multilayer foam, obtainable by the method of claim 1.