Claims
- 1. A process for making a cross-linked ethylene polymer foam structure, comprising:
- a) forming a foamable melt polymer material by blending and heating a decomposable chemical blowing agent and an ethylene polymer material comprising a blend of:
- 1) an ethylene polymer selected from the group consisting of an ethylene/vinyl acetate copolymer, a high density polyethylene, a medium density polyethylene, and an ethylene/ester copolymer, and a copolymer of ethylene and an ethylenically unsaturated carboxylic acid; and
- 2) a substantially linear ethylene polymer having:
- i) a melt flow ratio, I.sub.10 /I.sub.2, .gtoreq.5.63;
- ii) a molecular weight distribution, M.sub.w /M.sub.n, defined by the equation: M.sub.w /M.sub.n .ltoreq.(I.sub.10 /I.sub.2)-4.63; and
- iii) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having about the same I.sub.2 and M.sub.w /M.sub.n ;
- b) inducing cross-linking in the foamable melt polymer material; and
- c) expanding the foamable melt polymer material by exposing it to an elevated temperature to form the foam structure.
- 2. The process of claim 1, wherein the M.sub.w /M.sub.n is from about 1.5 to about 2.5.
- 3. The process of claim 1, wherein the substantially linear ethylene polymer having from about 0.01 to about 3 long chain branches/1000 carbons along the polymer backbone.
- 4. The process of claim 3, having about 0.01 to about 1 long chain branches/1000 carbons along the polymer backbone.
- 5. The process of claim 3, having about 0.05 to about 1 long chain branches/1000 carbons along the polymer backbone.
- 6. The process of claim 1, wherein the foam composition is 80 percent or more closed-cell.
- 7. The process of claim 1, wherein the foam composition has a density of less than 250 kilograms per cubic meter.
- 8. The process of claim 1, wherein the ethylene polymer material comprises greater than 70 percent by weight of ethylene monomeric units.
- 9. The process of claim 1, wherein the foam composition is an extruded foam composition.
- 10. The process of claim 1, wherein the I.sub.10 /I.sub.2 is about 8 or more.
- 11. The process of claim 1, wherein the I.sub.10 /I.sub.2 is about 9 or more.
- 12. The process of claim 1, wherein the rheological processing index is less than or equal to 70 percent of that of a linear ethylene polymer which lacks long-chain branching at about the same I.sub.2 and M.sub.w /M.sub.n.
- 13. The process of claim 1, wherein the process is a foam bead.
- 14. The process of claim 1, wherein cross-linking is induced by irradiating the foamable melt polymer material.
- 15. The process of claim 1, wherein cross-linking is induced by incorporating a cross-linking agent into the foamable melt polymer material and exposing it to an elevated temperature.
- 16. A process for making a cross-linked ethylene polymer foam structure, comprising:
- a) forming a foamable melt polymer material by blending and heating a decomposable chemical blowing agent and an ethylene polymer material comprising a blend of:
- 1) a polymer selected from the group consisting of a polystyrene, a high impact polystyrene, a styrene-butadiene block copolymer, and a polyisoprene; and
- 2) a substantially linear ethylene polymer having:
- i) a melt flow ratio, I.sub.10 /I.sub.2, .gtoreq.5.63;
- ii) a molecular weight distribution, M.sub.w /M.sub.n, defined by the equation: M.sub.w /M.sub.n .ltoreq.(I.sub.10 /I.sub.2)-4.63; and
- iii) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylene polymer having about the same I.sub.2 and M.sub.w /M.sub.n ;
- b) inducing cross-linking in the foamable melt polymer material; and
- c) expanding the foamable melt polymer material by exposing it to an elevated temperature to form the foam structure.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation from application U.S. Ser. No. 08/252,151, filed Jun. 1, 1994; which is a continuation from U.S. Ser. No. 08/148,711, filed Nov. 8, 1993, now abandoned; which is a continuation from U.S. Ser. No. 08/054,329, filed Apr. 28, 1993, now U.S. Pat. No. 5,288,762.
US Referenced Citations (10)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0206794A1 |
Dec 1986 |
EPX |
Continuations (3)
|
Number |
Date |
Country |
Parent |
252151 |
Jun 1994 |
|
Parent |
148711 |
Nov 1993 |
|
Parent |
54329 |
Apr 1993 |
|