Multilayered film

Details Multilayered film Multilayered film

2002-07-18

2004-04-06

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C428S412000, C428S476300, C428S483000, C428S520000, C428S522000

Reexamination Certificate

active

06716501

ABSTRACT:

TECHNICAL FIELD
This invention relates to multilayered films and, more particularly, to multilayered films which are useful in making in-mold labels. Labels of this type are referred to as “in-mold” labels because the labels are held in place within the mold which forms the container during the container-forming process.
BACKGROUND OF THE INVENTION
Polymeric in-mold labels offer many aesthetic and functional advantages over paper labels in the labeling of containers made from polymeric resins using blow-molding, injection-molding or injection-blow molding. When a plastic container such as a high density polyethylene (HDPE) squeeze bottle is used to package a product such as a hair shampoo, a package using a polymeric label is generally more appealing to consumers than a package using a paper label. In many applications the use of polymeric in-mold labels is required for reasons of appearance, handling, performance, moisture-resistance, conformability, durability and compatibility with the container to be labeled. Polymeric in-mold labels also enable clear or substantially transparent labels with only the label indicia being visible to the consumer.
A problem with polymeric in-mold labels is that they tend to shrink and increase in thickness or the “Z” direction during the container-forming process. This is believed to be due to increases in film thickness caused by foaming. This foaming is believed to be a result of air entrapment in cavitated regions in the film and heat applied to the film during blow molding. Biaxially oriented films tend to foam more than uniaxially or machine direction oriented films. As a result, these labels, when applied to a container, typically exhibit a surface roughness that detracts from the aesthetics of the graphic or printed image formed on the label.
The present invention provides a solution to this problem by providing a multilayered film that exhibits only minimal surface roughening after application as an in-mold label to a container. The labels made from this film, when applied to a container, typically exhibit a surface roughness on the print surface of about 100 microinches or less, as determined by test method ANSI B46.1. This compares to labels in the prior art which have been observed to exhibit a surface roughness that detracts from the aesthetics of the graphic or printed image formed on the label and have a surface roughness of about 200 microinches.
SUMMARY OF THE INVENTION
This invention relates to a multilayered film for use in making an in-mold label, comprising:
a core layer having a first surface and a second surface, the core layer being comprised of a polymeric material and particulate solids dispersed in the polymeric material, the polymeric material being a high density polyethylene, a polypropylene, a polystyrene, a polyester, a copolymer of ethylene and propylene, a polyester copolymer, a polyamide, a polycarbonate or a mixture of two or more thereof;
a first skin layer overlying the first surface of the core layer, the first skin layer being comprised of a thermoplastic copolymer or terpolymer derived from ethylene or propylene and a functional monomer selected from the group consisting of alkyl acrylate, acrylic acid, alkyl acrylic acid, vinyl acetate and combinations of two or more thereof;
the film being formed by co-extruding the core layer and the first skin layer to form the multilayered film, hot-stretching the film at a temperature above the expected service temperature of the label to provide the film with a machine direction orientation, and annealing the film at a temperature above the expected service temperature of the label;
the density of the film being reduced by about 5% to about 25% during hot-stretching;
the film having a machine direction Gurley stiffness value in the range of about 30 to about 120 after hot-stretching and annealing;
the film having a machine direction shrinkage of less than about 2% after hot-stretching and annealing;
the film having a machine direction shrink tension at 200° F. (93.3° C.) of less than about 100 pounds per square inch (psi) after hot-stretching and annealing.
In one embodiment, the inventive film further comprises a second skin layer overlying the second surface of the core layer.
In one embodiment, the inventive film further comprises a first opacifying layer positioned between the first surface of the core layer and the first skin layer.
In one embodiment, the inventive film further comprises a first tie layer positioned between the first surface of the core layer and the first skin layer.
In one embodiment, the inventive film further comprises a second skin layer overlying the second surface of the core layer, a first opacifying layer positioned between the first surface of the core layer and the first skin layer, and a second opacifying layer positioned between the second surface of the core layer and the second skin layer.
In one embodiment, the inventive film further comprises a second skin layer overlying the second surface of the core layer, a first tie layer positioned between the first surface of the core layer and the first skin layer, and a second tie layer positioned between the second surface of the core layer and the second skin layer.
In one embodiment, the inventive film further comprises a second skin layer overlying the second surface of the core layer, a first opacifying layer positioned between the first surface of the core layer and the first skin layer, a first tie layer positioned between the first opacifying layer and the first skin layer, a second opacifying layer positioned between the second surface of the core layer and the second skin layer, and a second tie layer positioned between the second opacifying layer and the second skin layer.
The invention also relates to in-mold labels made from the inventive film, and to polymeric containers having the in-mold labels adhered to their surface. The in-mold labels include relatively large labels (e.g., surface area of about 12 square inches or larger), and the polymeric containers include relatively large containers (e.g., volume of about 32 fluid ounces or larger). The labels, when applied to the polymeric containers, are characterized by a printed surface having a very smooth texture, that is, a printed surface that exhibits a surface roughness of up to about 100 microinches as measured by test method ANSI B46.1.


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