Nonoriented stiff packaging film with superior tear properties

• US 20030054161A1
• Filed: 04/17/2002
• Published: 03/20/2003
• Est. Priority Date: 04/17/2001
• Status: Active Grant

• Current Assignee: Pliant Corporation (Berry Global Group Inc.)
• Original Assignee: Pliant Corporation (Berry Global Group Inc.)
• Inventors: Forte, Nicholas F., Korp, Sharon L.
• Granted Patent: US 6,825,276 B2
• Time in Patent Office: Days
• US Class Current: 428/332
• CPC Class Codes: B32B 2307/582 Tearability
• CPC Class Codes: B32B 2323/10 Polypropylene
• CPC Class Codes: B32B 2439/70 Food packaging
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/18 characterised by the use of special additives
• CPC Class Codes: B32B 27/20 using fillers, pigments, thixotroping agents
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: C08J 2323/12 Polypropene
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08K 5/0083 Nucleating agents promoting the crystallisation of the polymer matrix
• CPC Class Codes: C08L 23/10 Homopolymers or copolymers of propene
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/258 Alkali metal or alkaline earth metal or compound thereof
• CPC Class Codes: Y10T 428/259 Silicic material
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/264 Up to 3 mils
• CPC Class Codes: Y10T 428/31855 Of addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31909 Next to second addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31913 : Monoolefin polymer
• CPC Class Codes: Y10T 428/31938 : Polymer of monoethylenically unsaturated hydrocarbon

Abstract

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.

Claims

1. A nonoriented film comprising:

highly crystalline homopolymer polypropylene with a melt flow greater than 30 g/10 minutes,

a nucleating agent, and

polypropylene.

2. The film as recited in claim 1, wherein the amount of the highly crystalline polypropylene and the amount of nucleating agent are sufficient to enable the film to have requisite memory, modulus, and tearability, such that the film is able to hold a shape and to be easily torn, and wherein the requisite memory, modulus and tearability are achieved without orienting the film.

3. The film as recited in claim 1, wherein the amount of the highly crystalline polypropylene and the amount of the nucleating agent are sufficient to enable the film to break at an elongation of less than about 350% as measured by ASTM D 882 and to enable the film to have a secant modulus of greater than about 200,000 psi as measured in one direction by ASTM D 882, and wherein the film achieves the secant modulus of greater than about 200,000 psi and the ability to break at an elongation of less than 350% without orienting the film.

4. The film as recited in claim 1, wherein the amount of the highly crystalline polypropylene is at least 15% by weight of the film.

5. The film as recited in claim 1, wherein the amount of the highly crystalline polypropylene is in a range from about 30% to about 90% by weight of the film.

6. The film as recited in claim 1, wherein the amount of the highly crystalline polypropylene is in a range from about 40% to about 50% by weight of the film.

7. The film as recited in claim 1, wherein the highly crystalline polypropylene has a melt flow from about 30 g/10 minutes to about 50 g/10 minutes.

8. The film as recited in claim 1, wherein the highly crystalline polypropylene has a melt flow of about 40 g/10 minutes.

9. The film as recited in claim 1, wherein the amount of the nucleating agent is less than about 5% by weight of the film.

10. The film as recited in claim 1, wherein the polypropylene is homopolymer polypropylene with a melt flow of about 8 to about 20 g/10 minutes.

11. The film as recited in claim 1, wherein the film breaks at an elongation of less than about 350% as measured by ASTM D 882.

12. The film as recited in claim 1, wherein the film breaks at an elongation of less than about 100% as measured by ASTM D 882.

13. A nonoriented film comprising:

a core layer containing highly crystalline homopolymer polypropylene, polypropylene and a nucleating agent, wherein the highly crystalline homopolymer polypropylene has a melt flow of at least 20 g/10 minutes and

two skin layers containing polypropylene and highly crystalline homopolymer polypropylene having a melt flow of at least 20 g/10 minutes

14. The film as recited in claim 13, wherein the amount of the highly homopolymer crystalline polypropylene is at least about 15% by weight of the film.

15. The film as recited in claim 13, wherein the amount of the nucleating agent ranges from about 0.1% to about 2% by weight of the film.

16. The film as recited in claim 13, wherein at least one of the skin layers further contains highly homopolymer crystalline polypropylene with a melt flow of at least 20 g/10 minutes.

17. The film as recited in claim 13, wherein the core layer contains a colorant.

18. A package comprising:

a film that has been shaped to hold a product;

wherein the film is formed from highly crystalline polypropylene with 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 sufficient memory and stiffness to retain a shape around the product contained in the package.

19. The film as recited in claim 18, wherein the amount of the highly crystalline polypropylene is at least 15% by weight of the film.

20. The film as recited in claim 18, wherein the amount of the highly crystalline polypropylene ranges from about 30% to about 90% by weight of the film.

21. The film as recited in claim 18, wherein the film breaks at an elongation of less than about 100% as measured by ASTM D 882.

22. The film as recited in claim 18, wherein the film has a thickness ranging from about 0.4 mil to about 2 mil.

23. The film as recited in claim 18, wherein the film has a thickness ranging from about 1 mil to about 2 mil.