Highly loaded coalesced foam

• US 4,801,484 A
• Filed: 01/13/1988
• Issued: 01/31/1989
• Est. Priority Date: 01/13/1988
• Status: Expired due to Term

• Current Assignee: The Dow Chemical Company (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Malone, Bruce A., Yao, Peter C.
• Primary Examiner(s): Foelak, Morton
• Application Number:
  US07/143,430
• Time in Patent Office: 384 Days
• Field of Search: 428/294, 428/398, 264/46.1, 264/45.1, 264/45.9, 521/79, 521/81, 521/134, 521/143, 521/146, 521/149
• US Class Current: 428/398
• CPC Class Codes: B29C 44/468 in a plurality of parallel streams which unite during the foaming
• CPC Class Codes: B29K 2023/00 Use of polyalkenes or derivatives thereof as moulding material
• CPC Class Codes: B29K 2025/00 Use of polymers of vinyl-aromatic compounds or derivatives thereof as moulding material
• CPC Class Codes: B29K 2105/043 Skinned foam
• CPC Class Codes: C08J 9/14 organic
• CPC Class Codes: Y10S 264/05 Use of one or more blowing agents together
• CPC Class Codes: Y10S 264/18 Cross-linking a thermoplastic linear foam during molding
• CPC Class Codes: Y10T 428/2975 Tubular or cellular

Abstract

Highly loaded improved closed cell foams comprising a plurality of coalesced strands or profiles of an alkenyl aromatic thermoplastic synthetic resin or mixture of an olefin polymer resin and a copolymer of ethylene with one or more copolymerizable comonomers having a lower melting point than the olefin polymer resin. The loading of the nucleating additive is in a range of about 0.5 to about 50 weight percent, based on total resin weight. When highly loaded with carbon black these foams are electroconductive foams.

Claims

1. A highly loaded closed cell foam structure comprising a plurality of coalesced extruded strands or profiles of a mixture comprising:

(a) a thermoplastic resin selected from the group consisting of;

(1) an olefin resin blend of

(a) an olefin polymer selected from the group consisting of homopolymers of ethylene or propylene, copolymers of ethylene or propylene with one or more C4-8 α

-olefins and mixtures thereof; and

(b) an interpolymer of ethylene and at least one comonomer, said interpolymer having a melting point less than the melting point of olefin polymer (a);

and

(2) an alkenyl aromatic synthetic resinous material; and

(b) a nucleating additive in a range of about 0.5 to about 50 percent, based on the total weight of the thermoplastic resin;

provided further that the foam structure has a density from about 0.5 to about 5.0 lbs/ft³ and the strands or profiles are disposed in substantially parallel arrangement to the longitudinal axis of the foam.

2. A foam according to claim 1, wherein the foam structure has a minimal cross-sectional area of at least 12 square inches and a minimal cross-sectional dimension of at least one quarter inch.

3. A foam according to claim 1, wherein the foam structure has a minimal cross-sectional area of at least 18 square inches and a minimal cross-sectional dimension of at least one half inch.

4. A foam according to claim 1, wherein the nucleating additive is carbon black.

5. A foam according to claim 4, wherein the carbon black is present in a range of about 5 to about 50 percent.

6. A foam according to claim 1 having a density of from about 0.5 to about 3.0 lb/ft³.

7. A foam according to claim 1 having a density of from about 1.0 to about 2.8 lb/ft³.

8. A foam according to claim 4 having a density from about 1.2 to about 2.0 lb/ft³.

9. A foam according to claim 1, wherein the thermoplastic resin is:

an olefin resin blend of

(a) an olefin polymer selected from the group consisting of homopolymers of ethylene or propylene, copolymers of ethylene or propylene with one or more C_4-8 α

-olefins and mixtures thereof; and

(b) an interpolymer of ethylene and at least one comonomer, said interpolymer having a melting point less than the melting point of olefin polymer (a).

10. A foam according to claim 9, wherein component (b) is a copolymer of ethylene and acrylic acid or ethylene and vinyl acetate.

11. A foam according to claim 10, wherein component (b) comprises from about 85 to about 98 percent by weight ethylene.

12. A foam according to claim 11, wherein component (b) is a homogeneous random copolymer of ethylene and acrylic acid.

13. A foam according to claim 1, wherein the thermoplastic resin is an alkenyl aromatic synthetic resinous material.

14. A foam according to claim 13, wherein the alkenyl aromatic synthetic resinous material is polystyrene.

15. A foam according to claim 1, wherein the strands are each approximately 0.5 to about 10.0 mm in the largest cross-sectional dimension, or the profiles are each approximately 0.5 to about 10.0 mm in cross-sectional thickness.

16. A foam according to claim 15, wherein the strands are each about 1.0 to 5.0 mm in the largest cross-sectional dimension, or the profiles are each approximately 1.0 to about 5.0 mm in cross-sectional thickness.

17. A foam according to claim 1 additionally comprising a crosslinking agent.

18. A foam according to claim 1, wherein the strands have a circular cross-sectional shape.

19. A foam according to claim 1, wherein the strand'"'"'s cross-sectional shape is that of a star, cross or X.

20. A foam according to claim 1 wherein the profiles when coalesced describe in cross-section a repeating structure containing voids.