Soft films having enhanced physical properties

• US 5,376,439 A
• Filed: 03/29/1994
• Issued: 12/27/1994
• Est. Priority Date: 09/16/1992
• Status: Expired due to Term

• Current Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Original Assignee: Exxon Chemical Patents Inc. (Exxon Mobil Corporation)
• Inventors: Pierce, Charles L., Hodgson, William J., Halle, Richard W.
• Primary Examiner(s): Seccuro, Jr., Carman J.
• Application Number:
  US08/219,754
• Time in Patent Office: 273 Days
• Field of Search: 525/240, 525/221, 525/222, 525/227, 428/220
• US Class Current: 428/220
• CPC Class Codes: B32B 2250/242 All polymers belonging to those covered by group B32B27/32
• CPC Class Codes: B32B 2250/40 Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
• CPC Class Codes: B32B 2307/718 Weight, e.g. weight per square meter
• CPC Class Codes: B32B 2307/72 Density
• CPC Class Codes: B32B 2309/02 Temperature
• CPC Class Codes: B32B 2323/043 HDPE, i.e. high density polyethylene
• CPC Class Codes: B32B 2323/046 LDPE, i.e. low density polyethylene
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 27/322 comprising halogenated polyolefins, e.g. PTFE
• CPC Class Codes: C08J 2323/04 Homopolymers or copolymers of ethene
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08L 23/06 Polyethene
• CPC Class Codes: C08L 23/0815 Copolymers of ethene with aliphatic 1-olefins
• CPC Class Codes: C08L 2666/06 Homopolymers or copolymers of unsaturated hydrocarbons; Derivatives thereof
• CPC Class Codes: Y10S 526/943 Polymerization with metallocene catalysts
• CPC Class Codes: Y10T 428/31913 Monoolefin polymer

Abstract

The present invention provides for a polymer composition comprising a blend of from about 25 to about 90% by weight of a very low density ethylene polymer having a density on the range of from about 0.88 to 0.925 g/cm³, a melt index of from about 0.5 to about 7.5 dg/min, a molecular weight distribution not greater than about 3.5 and a compositional distribution breadth index greater than about 70%, and from about 10 to about 75% by weight of a low to medium density ethylene polymer having a density of from about 0.910 to about 0.935, a melt index of from about 0.5 to about 20, a molecular weight distribution greater than about 3.5 and a compositional breadth index less than about 70%.

The invention also provides for films prepared from this blend having single layer construction or having laminar ABA construction wherein the A or skin layers comprise the blend of this invention and the B or core layer comprises a different olefin polymer such as high density polyethylene.

Films of this invention exhibit excellent elongation, tensile and impact properties and also softness, feel and noise properties which render them eminently suitable for use as back sheet components in the fabrication of absorbent articles such as diapers, bed pads and like articles where such properties are desirable.

Claims

1. A soft film comprising a mixture of:

a) about 30 to about 90% by weight based on polymer content, of a copolymer of ethylene and a C₄ to C₂₀ alpha-olefin comonomer, said copolymer prepared with a metallocene catalyst system, having essentially a single melting point in the range of 60°

C. to 115°

C., having a density of from about 0.88 g/cm³ to about 0.91 g/cm³, a melt index of from about 0.5 to about 7.5 dg/min, a molecular weight distribution less than about 3.0 and a compositional breadth index greater than about 70 percent, and

(b) about 10 to about 70% by weight, based on polymer content, of a low density ethylene polymer prepared by a high pressure polymerization process having a density in the range of from about 0.91 to about 0.935 g/cm³, a melt index than that of (a) up to about 20-dg/min and a molecular weight distribution above about 3.5;

wherein said film has a secant modulus in the transverse direction of less than about 14,570 psi.

2. The film of claim 1 containing from about 50 to about 80% by weight of component (a) and from about 20 to about 50% by weight of component (b).

3. The film of claim 1 wherein component (a) comprises a copolymer of ethylene and a C₄ to C₁₀ alpha-monolefin.

4. The film of claim 3 wherein component (a) comprises a copolymer of ethylene and butene-1.

5. The film of claim 3 wherein component (a) comprises a copolymer of ethylene and hexene-1.

6. The film of claim 1 wherein component (b) is a low density ethylene polymer having a density of above about 0.915 g/cm3.

7. The film of claim 6 wherein said component (b) is an ethylene polymer having a melt index of from about 5 to about 15.

8. The film of claim 1 wherein said ethylene copolymer (a) contains from about 4 to about 15 mole percent of said comonomer.

9. The film of claim 1 wherein said component (a) is a terpolymer comprising said copolymer of ethylene and said C₄ to C₂₀ alpha-mono-olefin and an additional C₄ to C₂₀ alpha-olefin different from said alpha-mono-olefin.

10. A film prepared by melt extrusion and shaping the composition of claim 1.

11. The film of claim 10 having a thickness in the range of from about 0.5 to about 2 mil.

12. The film of claim 10 which is a monolayer film.

13. An article of manufacture made from the film of claim 10.

14. The film of claim 1 wherein said film is fabricated by melt extrusion at a line speed in excess of 600 ft/minute.

28. A diaper backsheet comprising a film according to claim 1.

29. The diaper backsheet of claim 28 wherein the film has a secant modulus in the machine direction of less than about 14,070 psi or a secant modulus in a transverse direction less than about 14,570 psi or both.

30. The diaper backsheet of claim 28 wherein said film comprises from about 50 to about 80% by weight of component (a) and from about 20 to about 50% by weight of component (b).

31. The film of claim 28 wherein said ethylene copolymer component (a) contains from about 4 to about 15 mole percent of said comonomer.

32. The film of claim 28 wherein said component (a) is a terpolymer comprising said copolymer of ethylene and said C₄ to C₂₀ alpha-mono-olefin comonomer and an additional C₄ to C₂₀ alpha-olefin different from said alpha-mono-olefin.

15. A film comprising a mixture of:

a) about 30 to about 90% by weight based on polymer content, of a copolymer of ethylene and a C₄ to C₂₀ alpha-mono-olefin comonomer, said copolymer prepared with a metallocene catalyst system, having essentially a single melting point in the range of 60°

C. to 115°

C., having a density of from about 0.88 g/cm³ to about 0.91 g/cm³, a melt index of from about 0.5 to about 7.5 dg/min, a molecular weight distribution less than about 3.0 and a compositional breadth index greater than about 70 percent, and

(b) about 10 to about 70% by weight, based on polymer content, of a low density ethylene polymer prepared by a high pressure polymerization process having a density in the range of from about 0.91 to about 0.935, a melt index higher than that of (a) up to about 20 dg/min and a molecular weight distribution above about 3.5;

wherein said film has a secant modulus in the machine direction of less than about 14,070 psi.

16. The film of claim 15 wherein said film comprises from about 50 to about 80% by weight of component (a) and from about 20 to about 50% by weight of component (b).

17. The film of claim 15 wherein said ethylene copolymer component (a) contains from about 4 to about 15 mole percent of said comonomer.

18. The film of claim 15 wherein said component (a) is a terpolymer comprising said copolymer of ethylene and said C₄ to C₂₀ alpha-mono-olefin comonomer and an additional C₄ to C₂₀ alpha-olefin different from said alpha-mono-olefin.

19. The film of claim 15 wherein said copolymer of ethylene and a C₄ to C₂₀ alpha-mono-olefin comonomer has a density in the range of 0.88 g/cm³ to about 0.90 g/cm³.

20. The film of claim 15 wherein the secant modulus in the machine direction is in the range of about 11,910 psi to about 14,070 psi.

27. The film of claim 15 wherein the secant modulus in the machine direction is in the range of about 11,910 psi to about 14,070 psi.

21. A film comprising a mixture of:

(a) about 30 to about 90% by weight based on polymer content, of a copolymer of ethylene and a C₄ to C₂₀ alpha-mono-olefin comonomer, said copolymer prepared with a metallocene catalyst system, having essentially a single melting point in the range of 60°

C. to 115°

C., having a density of from about 0.88 g/cm³ to about 0.91 g/cm³, a melt index of from about 0.5 to about 7.5 dg/min, a molecular weight distribution less than about 3.0 and a compositional breadth index greater than about 70 percent, and

(b) about 10 to about 70% by weight, based on polymer content, of a low density ethylene polymer prepared by a high pressure polymerization process having a density in the range of from about 0.91 to about 0.935 g/cm³ , a melt index higher than that of (a) up to about 20 dg/min and a molecular weight distribution above about 3.5;

wherein said film has a secant modulus in the machine direction of less than about 14,070 psi and a secant modulus in the transverse direction of less than 14,570 psi.

22. The film of claim 21 wherein said film comprises from about 50 to about 80% by weight of component (a) and from about 20 to about 50% by weight of component (b).

23. The film of claim 21 wherein said ethylene copolymer component (a) contains from about 4 to about 15 mole percent of said comonomer.

24. The film of claim 21 wherein said component (a) is a terpolymer comprising said copolymer of ethylene and said C₄ to C₂₀ alpha-mono-olefin comonomer and an additional C₄ to C₂₀ alpha-olefin different from said alpha-mono-olefin.

25. The film of claim 21 wherein said copolymer of ethylene and a C₄ to C₂₀ alpha-mono-olefin comonomer has a density in the range of 0.88 g/cm³ to about 0.90 g/cm³.

26. The film of claim 21 wherein the secant modulus in the transverse direction is in the range of about 12,430 psi to about 14,570 psi.