Claims
- 1. A process for making an ethylene polymer foam structure, comprising:
- a) heating an ethylene polymer material to form a melt polymer material, the ethylene polymer material comprising 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 olefin polymer having about the same I.sub.2 and M.sub.w /M.sub.n ;
- b) incorporating into the melt polymer material at an elevated pressure a blowing agent; and
- e) expanding the foamable gel at a reduced pressure to form the foam structure.
- 2. The process of claim 1, wherein the M.sub.w /M.sub.n is about 3.5 or less.
- 3. The process of claim 1, wherein the M.sub.w /M.sub.n is from about 1.5 to about 2.5.
- 4. 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.
- 5. The process of claim 4, having about 0.01 to about 1 long chain branches/1000 carbons along the polymer backbone.
- 6. The process of claim 4, having about 0.05 to about 1 long chain branches/1000 carbons along the polymer backbone.
- 7. The process of claim 1, wherein the substantially linear ethylene polymer is an ethylene/alpha-olefinic copolymer.
- 8. The process of claim 7, wherein the substantially linear ethylene polymer is a copolymer of ethylene monomer and a comonomer selected from the group consisting of 1-octene, 1 -butene, 1 -hexene, and 4-methyl- 1 -pentene.
- 9. The process of claim 1, wherein the substantially linear ethylene polymer is an ethylene homopolymer.
- 10. The process of claim 1, wherein the foam composition is 80 percent or more closed-cell.
- 11. The process of claim 1, wherein the foam composition has a density of less than 250 kilograms per cubic meter.
- 12. The process of claim 1, wherein the ethylene polymer material comprises greater than 70 percent by weight of ethylenic ethylene monomeric units.
- 13. The process of claim 1, wherein the foam composition is an extruded foam composition.
- 14. The process of claim 1, wherein the I.sub.10 /I.sub.2 is about 8 or more.
- 15. The process of claim 1, wherein the I.sub.10 /I.sub.2 is about 9 or more.
- 16. 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.
- 17. The process of claim 1, wherein the ethylene polymer material further comprises a low density polyethylene.
- 18. The process of claim 1, wherein the ethylene polymer material further comprises a linear low density polyethylene.
- 19. The process of claim 1, wherein the ethylene polymer material further comprises an ethylene/acrylic acid copolymer.
- 20. The process of claim 1, wherein the foam structure comprises a blowing agent selected from the group consisting of isobutane, 1,1-difluoroethane, and mixtures of the foregoing.
- 21. The process of claim 1, wherein the ethylene polymer material comprises greater than 50 percent by weight ethylene monomeric units.
- 22. The process of claim 1, wherein the foam structure is in the form of a foam bead.
- 23. A process for making an ethylene polymer foam structure in the form of a foam bead, comprising:
- a) forming a suspension of discrete particles of an ethylene polymer material in a liquid in which it is substantially insoluble and at an elevated temperature and pressure, the ethylene polymer material comprising 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 olefin polymer having about the same I.sub.2 and M.sub.w /M.sub.n ;
- b) impregnating a blowing agent into the discrete particles at an elevated temperature and pressure;
- e) discharging the discrete particles into an atmosphere of reduced pressure to form the foam beads.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Ser. No. 08/032,917, filed Mar. 18, 1993, now abandoned. Related applications include U.S. Ser. Nos. 07/939,281, filed Sep. 2, 1992 and 07/776,130, filed Oct. 15, 1991.
US Referenced Citations (8)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0206794A1 |
Dec 1986 |
EPX |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
32917 |
Mar 1993 |
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