Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1999-10-26
2001-04-03
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S343000, C428S3550RA, C428S040100, C428S040200, C428S146000, C428S147000, C428S149000, C428S349000, C428S3550RA, C428S3550BL, C428S3550AC, C428S3550EN, C283S081000
Reexamination Certificate
active
06210795
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to adhesive coatings. More specifically, the invention relates to heat-sealable adhesive coatings containing spacer particles, and methods for making and using the same.
BACKGROUND OF THE INVENTION
In-mold labeling is a process in which a heat-sealable label is applied to a blow molded article during the molding process. The resulting label, if properly applied, appears to be not a label at all, but an integral part of the bottle itself. Examples of such labeled articles include, among others, food and beverage containers, liquid detergent containers, motor oil containers, and bleach and other household cleaning product containers.
In-mold labeling eliminates a separate labeling step after an article is formed. Typically, in-mold labels are cut to size from a sheet of substrate coated with an adhesive, then stacked in a feeding magazine for the mold. One or more labels are fed into the mold and positioned against the sidewalls of the mold cavity by a mechanical or vacuum operated device. Vacuum pressure often is used to maintain the proper position of the label during this stage of the labeling process.
The mold then typically is closed, and a parison or molten plastic balloon is blown into the closed mold cavity. The parison typically is a balloon of molten thermoplastic resin, such as high density polyethylene, polypropylene, or polyethyleneterephthalate (PET). As the parison contacts the adhesive side of the label, the heat from the parison activates the heat-sealable adhesive layer which causes the label to adhere to the blown article as the pressure of the parison against the label increases. Typically, the mold sidewalls are cooled, and thus, the molten plastic article is hardened by cooling. Subsequently, the labeled article is removed from the mold.
One general problem encountered with in-mold labeling is that the substrate film used for the labels typically is not porous. Without permitting the escape of air or volatiles from between the label and the bottle, the air or volatiles may be trapped between the label and the article which results in air pockets or blisters.
Another general problem encountered with adhesive labels, whether for in-mold or other applications, is that in feeding the adhesive labels from a stack of labels from, for example, a feed magazine, the labels may tend to stick together. This problem generally is referred to as “blocking.” Blocking also can be a problem in feeding labels from a roll of labels when the transfer of adhesive from the adhesive side of one layer of labels to the print side of the successive layer of labels causes the layers to stick together. Blocking is particularly problematic in commercial labeling processes where labeling is carried out at high speeds and each piece of apparatus along a production line, including the feed magazine, must be accurately synchronized and reliable. Blocking may create downtime for the line and/or an increase in defective articles.
SUMMARY OF THE INVENTION
An adhesive label has been developed which provides improved feeding properties as well as improvements in the appearance of the adhesive label after application to an article. The adhesive label of the present invention generally includes spacer materials in the adhesive layer to provide these improved properties. The adhesive label of the present invention minimizes blocking, double feeding, and wrinkling of labels during feeding and application of labels, for example, in an in-mold labeling process. Furthermore, the adhesive label of the present invention minimizes or eliminates the formation of air pockets behind the applied label which can cause wrinkling and/or blistering. Also, the adhesive label of the present invention generally reduces or eliminates any transfer of adhesive from the adhesive coating of the labels to the labeling and/or printing equipment or to the print side of adjacent labels.
The adhesive label of the present invention generally includes a substrate having a first surface and a second surface and an adhesive coating disposed on the first surface of the substrate. The adhesive coating includes an adhesive and a plurality of spacer particles that impart roughness to the adhesive coating. In one embodiment, the spacer particles have an average particle size of between about 8 microns and about 60 microns. In another embodiment the density of the spacer particles is from about 0.5 g/cm
3
to about 2.0 g/cm
3
. In yet another embodiment, the spacer particles are spheroidal.
In certain embodiments, the spacer particles may be plastic particles including polyethylene particles, acrylic particles and polystyrene particles, starch particles including unmodified potato starch, corn starch and wheat starch, and/or glass particles. Spacer particles of the invention also may be fibrous. In certain embodiments, an adhesive may be selected from the group consisting of ethylene copolymers including ethylene-vinyl acetates, polyvinyl acetates, styrene-butadiene copolymers, polystyrenes, acrylics including ethylene acrylates, methacrylics, ethylene methacrylates, polyurethanes and combinations of these adhesives.
An adhesive label can be manufactured economically using methods of the invention. In a broad form of the method, a substrate having a first surface and a second surface is provided. An adhesive coating then is applied to the first surface of the substrate. The adhesive coating includes an adhesive and a plurality of spacer particles that imparts roughness to the adhesive coating.
In one embodiment, the adhesive coating is applied by dispersing the plurality of spacer particles in an aqueous dispersion including an adhesive to form an adhesive coating mixture. The adhesive coating mixture then is coated onto the first surface of the substrate. The adhesive coating mixture then is dried to form the adhesive coating. In another embodiment, the adhesive may be a liquid, e.g. melted, and mixed with a plurality of spacer particles to form an adhesive coating mixture, and then applied to the first surface of the substrate. The adhesive coating mixture then may be solidified, e.g., by allowing the adhesive coating mixture to cool to form an adhesive coating or by curing the adhesive. In yet another alternative embodiment, an adhesive first may be applied to the first surface of the substrate and then a plurality of spacer particles added to the adhesive to form an adhesive coating mixture. The adhesive coating mixture may then be solidified to form an adhesive coating.
An adhesive label of the present invention can be used in accordance with methods of the present invention. In a broad sense, a plurality of adhesive labels of the present invention is stacked, e.g., in a feed magazine. An individual adhesive label is fed from the stack of adhesive labels and then applied to an article to be labeled, e.g., in a commercial labeling process.
It should be understood that the order of the steps of the methods of the invention is immaterial so long as the invention remains operable, i.e., a substrate must be provided prior to applying an adhesive coating to the substrate.
The invention will be understood further upon consideration of the following drawings, description and claims.
DETAILED DESCRIPTION OF THE INVENTION
The present invention broadly is directed to a heat-sealable adhesive label having a plurality of spacer particles in its adhesive coating. The label of the present invention reduces the formation of blisters and/or air pockets which may cause wrinkling and blistering of the applied label, particularly in in-mold applications. The present invention further is directed to providing heat-sealable adhesive labels which reduce the amount of blocking, double feeding, and wrinkling of the labels when stacked and fed using commercial labeling equipment. Also the label of the present invention generally reduces or eliminates any transfer of adhesive from the adhesive coating of the labels to the labeling and/or printing equipment. Although the invention will be described wit
Avison David W.
Messinger Mark R.
Nelson Richard A.
Dean Frederick G.
Nashua Corporation
Testa Hurwitz & Thibeault LLP
Zirker Daniel
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