Nonoriented stiff packaging film with superior tear properties
A nonoriented film containing highly crystalline polypropylene, standard polypropylene and nucleating agents. The film has physical properties that are desirable for applications such as food wrappers and tampon overwrap, including good tearability, stiffness and memory. In addition, the nonoriented film is cost effective because the film achieves these physical properties without the step of stretching or orienting the film, as required for conventional polypropylene films used in food wrappers and tampon overwrap.
1 . A package comprising:
a film that has been shaped to hold a product wherein the film contains highly-crystalline polypropylene having a melt flow of at least 20 g/10 minutes, a nucleating agent, and polypropylene;
wherein the film has not been oriented before being shaped into the package; and
wherein the package may be easily torn open and has sufficent memory and stiffness to retain a shape around the product contained in the package.
2 . The package of claim 1 , wherein said highly-crystalline polypropylene comprises at least about 15% by weight of said film.
3 . The package of claim 1 , wherein said nucleating agent comprises from about 0.1% to about 2% by weight of said film.
4 . The package of claim 1 , wherein at least one of said skin layers further comprises highly-crystalline polypropylene having a melt flow of at least 30 g/10 minutes.
5 . The package of claim 1 , wherein said core layer further comprises a colorant.
6 . The package of claim 1 , said highly-crystalline polypropylene comprising from about 30% to about 90% by weight of said film.
7 . The package of claim 1 , said highly-crystalline polypropylene comprising from about 40% to about 50% by weight of said film.
8 . The package of claim 1 , said highly-crystalline polypropylene having a melt flow of from about 30 g/10 minutes to about 50 g/10 minutes.
9 . The package of claim 1 , said highly-crystalline polypropylene having a melt flow of from about 40 g/10 minutes.
10 . The package of claim 1 , wherein said nucleating agent comprises less than 5% by weight of said film.
11 . The package of claim 1 , wherein said polypropylene is a homopolymer polypropylene having a melt flow of from about 8 g/10 minutes to about 20 g/10 minutes.
12 . The package of claim 1 , wherein said film breaks at an elongation of less than 350% as measured by ASTM D 882.
13 . The package of claim 1 , wherein said film breaks at an elongation of less than about 100% as measured by ASTM D 882.
14 . The package of claim 1 , wherein said film breaks at an elongation of less than about 200% as measured by ASTM D 882.
15 . The package of claim 1 , wherein said film breaks at an elongation of less than 15% as measured by ASTM D 882.
16 . The package of claim 1 , said film further comprising a trouser tear.
17 . The package of claim 16 , said trouser tear comprising less than about 100 grams.
18 . The package of claim 1 , said film having a secant modulus value of greater than or equal to about 200,000 psi.
19 . The package of claim 1 , said highly-crystalline homopolymer polypropylene comprising from about 35-65% by weight of said film.
20 . The package of claim 1 , said highly-crystalline homopolymer polypropylene having a xylene-soluble content of from about 0.5% to about 1% by weight.
21 . The package of claim 1 , said polypropylene having a xylene-soluble content of from about 2% to about 4% by weight.
22 . The package of claim 1 , said polypropylene having a melt flow of from about 2 g/10 minutes to about 20 g/10 minutes.
23 . The package of claim 1 , said polypropylene having a melt flow of from about 8 g/10 minutes to about 18 g/10 minutes.
24 . The package of claim 1 , said polypropylene comprising up to about 85% by weight of said film.
25 . The package of claim 1 , said polypropylene comprising from about 15% to about 70% by weight of said film.
26 . The package of claim 1 wherein said polypropylene is a polypropylene copolymer.
27 . The package of claim 26 wherein said polypropylene copolymer is a random copolymer polypropylene.
28 . The package of claim 1 further comprising at least one additive selected from the group consisting of antiblock compounds, antistatics, lubricants, stabilizers and mixtures thereof.
29 . The package of claim 1 , said nucleating agent comprising from about 0.1% to about 4% by weight of said film.
30 . The package of claim 1 , said nucleating agent being selected from the group consisting of talc, silica, carbon black, kaolin, salts of aliphatic monobasic acids and free acids thereof, salts of aliphatic dibasic acids and free acids thereof, salts of arylalkyl acids and free acids thereof, alkali metals of aromatic carboxylic acids, alkali metals of alicyclic carboxylic acids, aluminum salts of aromatic carboxylic acids and free acids thereof, aluminum salts of alicyclic carboxylic acids and free acids thereof, bis-benzylidene sorbitol, benzoate salts and free acids thereof, sodium salts of organic phosphates and free acids thereof, and mixtures thereof.
31 . The package of claim 1 wherein said nucleating agent is in a form selected from the group consisting of powders, powder mixtures, suspensions, solutions, master batches, or mixtures thereof.
32 . The package of claim 31 wherein said nucleating agent is predispersed.
33 . The package of claim 1 further comprising up to about 30% by weight of a CaCO 3 additive.
34 . The package of claim 33 wherein said CaCO 3 additive is a 60% calcium carbonate/propylene blend.
35 . The package of claim 28 , said antiblock compound being selected from the group consisting of silicon dioxide, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate, polyamides, polyesters, polycarbonates, and mixtures thereof.
36 . The package of claim 35 , said film comprising from about 0.1% to about 5% by weight of said antiblock compound.
37 . The package of claim 28 , said lubricants being selected from the group consisting of polyethylene wax, erucamide, ethylene bis-oleamide, stearic acid, calcium/zinc heat-stabilizer soaps, slip compounds, and mixtures thereof.
38 . The package of claim 37 , said colorants being selected from the group consisting of titanium dioxide, calcium carbonate, and mixtures thereof.
39 . The package of claim 38 , said film comprising up to about 30% by weight of said colorants.
40 . The package of claim 1 wherein said highly-crystalline polypropylene is a homopolymer.
41 . The package of claim 1 wherein said highly-crystalline polypropylene is a copolymer.
42 . The package of claim 41 wherein said copolymer comprises propylene and an α-olefin.
43 . The package of claim 42 wherein said α-olefin is ethylene.
44 . The package of claim 1 wherein said film has a thickness of from about 0.4-2.0 mils.
45 . The package of claim 1 wherein said film has a thickness of from about 1.0-2.0 mils.