Sealable multi-layer opaque film

1. A sealable multi-layer opaque film comprising a core layer and at least one sealable skin layer,

wherein said core layer comprises an orientation-enhancing polymer, a polypropylene homopolymer and at least one beta crystal nucleator of polypropylene,

wherein said orientation-enhancing polymer comprises an (isotactic propylene)-ethylene heterophasic copolymer and at least one polymer selected from the group consisting of:

an impact polypropylene polymer;

an impact polypropylene copolymer;

an ethylene-(isotactic propylene) rubber;

a metallocene isotactic polypropylene;

an isotactic polypropylene grafted with elastomer;

a maleated-isotactic polypropylene;

a blend of an isotactic polypropylene and a syndiotactic polypropylene;

a blend of an isotactic polypropylene and an atactic polypropylene;

a blend of an isotactic polypropylene and an acrylic elastomer;

a blend of an isotactic polypropylene and an alkenic elastomer;

a blend of an isotactic polypropylene, a polyethylene, and an ethylene-propylene rubber;

a blend of an isotactic polypropylene and a polyisobutylene;

a blend of an isotactic polypropylene and a styrenic elastomer,

a blend of an isotactic polypropylene and a metallocene isotactic polypropylene copolymer; and

a blend of an isotactic polypropylene and an isotactic propylene copolymer, and

wherein said orientation-enhancing polymer does not comprise an ethylene-propylene block copolymer.

2. The sealable multi-layer opaque film of claim 1 , wherein said polypropylene homopolymer is an isotactic polypropylene.

3. The sealable multi-layer opaque film of claim 2 , wherein said isotactic polypropylene has m-pentad greater than 85% by NMR spectroscopy measurement.

4. The sealable multi-layer opaque film of claim 3 , wherein said isotactic polypropylene comprises a mixture of at least two polypropylene polymers having different m-pentads.

5. The sealable multi-layer opaque film of claim 1 , wherein said beta crystal nucleator of polypropylene comprises a mixture of an organic dibasic acid and an oxide, a hydroxide, or an acid salt of a Group II metal.

6. The sealable multi-layer opaque film of claim 1 , further comprising an outer skin layer on the side of the core layer opposite to the sealable skin layer.

7. The sealable multi-layer opaque film of claim 6 , wherein said outer skin layer comprises:

at least one polymer selected from the group consisting of an impact polypropylene polymer, a polypropylene homopolymer, polypropylene copolymer, a metallocene polypropylene, a metallocene isotactic propylene copolymer and an (isotactic propylene)-ethylene heterophasic copolymer; and

optionally, a beta crystal nucleator of polypropylene.

8. The sealable multi-layer opaque film of claim 6 , wherein said outer skin layer comprises a material selected from the group consisting of:

i) an impact polypropylene polymer and a beta crystal nucleator of polypropylene;

ii) an (isotactic propylene)-ethylene heterophasic copolymer and a beta crystal nucleator of polypropylene;

iii) a blend which is the same as the core layer; and

iii) an impact polypropylene masterbatch with a beta crystal nucleator of polypropylene.

9. The sealable multi-layer opaque film of claim 6 , further comprising at least one intermediate layer.

10. The sealable multi-layer opaque film of claim 6 , further comprising at least two intermediate layers.

11. The sealable multi-layer opaque film of claim 1 , wherein said sealable skin layer comprises a polymer selected from the group consisting of an ethylene-propylene-butene-1 terpolymer, an (isotactic propylene)-alpha olefin copolymer, a (syndiotactic propylene)-alpha olefin copolymer, an ethylene vinylacetate copolymer, an ethylene methacrylic acid copolymer, an ethylene acrylic acid copolymer, an ethylene methylacrylate acrylic acid terpolymer, an ethylene alkyl acrylate copolymer, an ionomer, a metallocene plastomer, a very low density polyethylene, an ethylene-(methyl acrylate)-(glycidyl methacrylate) terpolymer, and ethylene-(glycidyl methacrylate) copolymer.

12. The sealable multi-layer opaque film of claim 1 , wherein said sealable skin layer comprises a material selected from the group consisting of:

i) an ethylene-propylene-butene-1 terpolymer,

ii) an ethylene-vinylacetate copolymer, and

iii) a metallocene catalyzed plastomer.

13. The sealable multi-layer opaque film of claim 1 , wherein said core layer comprises 1 to 99 wt. % of the polypropylene homopolymer, 99 to 1 wt. % of the orientation-enhancing polymer (based on total polymers) and 0.005 to 2 wt. % of the beta crystal nucleator for polypropylene.

14. The sealable multi-layer opaque film of claim 13 , wherein said core layer comprises 10 to 90 wt. % of the polypropylene homopolymer, 90 to 10 wt. % of the orientation-enhancing polymer (based on total polymers) and 0.005 to 2 wt. % of the beta crystal nucleator for polypropylene.

15. The sealable multi-layer opaque film of claim 13 , wherein said core layer comprises 30 to 70 wt. % of the polypropylene homopolymer, 70 to 30 wt. % of the orientation-enhancing polymer (based on total polymers) and 0.005 to 2 wt. % of the beta crystal nucleator for polypropylene.

16. The sealable multi-layer opaque film of claim 1 , wherein said core layer thickness is at least 70% of the whole film thickness.

17. The sealable multi-layer opaque film of claim 1 , wherein the sealable multi-layer opaque film is uniaxially oriented at from 3 to 10 times of orientation ratio.

18. The sealable multi-layer opaque film of claim 1 , wherein the sealable multi-layer opaque film is biaxially oriented from 3 to 6 times of orientation ratio in the machine direction and 4 to 10 times of orientation ratio in the transverse direction.

19. The sealable multi-layer opaque film of claim 1 , wherein the sealable multi-layer opaque film is made by coextrusion of the layers.

20. The sealable multi-layer opaque film of claim 1 , further comprising an inorganic filler selected from the group consisting of CaCO 3 , BaCO 3 , clay, talc, silica, mica and TiO 2 .

21. The sealable multi-layer opaque film of claim 1 , wherein the core layer further comprises an organic filler selected from the group consisting of a polybutylene terephthalate, a polyamide, a polyethylene terephthalate, a cyclic olefin copolymer, a polystyrene, and a syndiotactic polystyrene.

22. The sealable multi-layer opaque film of claim 1 , wherein said film has a light transmission of less than 35%.

23. The sealable multi-layer opaque film of claim 1 , wherein said film has a light transmission of less than 30%.

24. The sealable multi-layer opaque film of claim 1 , wherein said film has a light transmission of less than 25%.

25. The sealable multi-layer opaque film of claim 1 , wherein said film has a water vapor transmission rate of greater than 4.0 g/m 2 /day.

26. The sealable multi-layer opaque film of claim 1 , wherein said film has a water vapor transmission rate of greater than 15.0 g/m 2 /day.

27. The sealable multi-layer opaque film of claim 1 , wherein said film has a water vapor transmission rate of greater than 50.0 g/m 2 /day.

28. The sealable multi-layer opaque film of claim 1 , wherein the sealable multi-layer opaque film has a heat seal strength greater than 200 g/in at a heat seat temperature below 82° C.

29. A packaged article, wherein the package comprises the sealable multi-layer opaque film of claim 1 .

30. The sealable multi-layer opaque film of claim 1 , wherein the beta crystal nucleator of polypropylene is not a red dye and the core layer has voids formed therein by the beta crystal nucleator of polypropylene.