Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1998-12-14
2001-10-02
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C524S801000, C523S223000, C521S056000, C521S060000, C521S063000, C521S064000, C442S151000, C428S3550RA, C428S3550CN, C428S402000
Reexamination Certificate
active
06296932
ABSTRACT:
FIELD OF INVENTION
This invention relates to adhesive coated articles and in particular to microsphere adhesives coated onto a substrate particularly useful on coated paper.
BACKGROUND OF THE INVENTION
Repositionable notes, flags and markers have become a readily recognizable part of the office and home. Repositionable notes and flags, such as those manufactured by 3M under the tradename of POST-IT® Notes and POST-IT® Flags are used to mark documents for reproduction, for ready reference, to communicate comments or concerns to another reader, your favorite recipe, a well-loved passage in a book and so on. These products are convenient, easy to use and easy to reposition from one portion of a document to another.
Coated or “glossy” paper, as it is sometimes called, is used in the printing of covers, magazines, sales pieces, direct mail, reply cards, and brochures. The most distinguishing feature of coated paper is that printing inks will sit on top of the coating (ink tends to soak into a sheet of uncoated stock). The result is a clean, sharp image. For this reason, coated papers are used when precise color matches, extremely clear detail, or the faithful reproduction of photography (both color and black-and-white) is desired. Although coated stock is generally more expensive than uncoated, it is the paper of choice for fine quality printing.
There are two basic categories of paper finishes commonly used today: uncoated and coated. All paper starts out uncoated, and it is commonly used in this form. The non-glare surface of uncoated paper makes it suitable for all types of reading material, and so it is used extensively in paperbacks, newsletters and newer textbooks. Generally, the term “coated paper” refers to paper and paperboard, of which the surface has been treated with clay or some other pigment and adhesive mixture, or other suitable material, to improve the finish with respect to printing quality, color, smoothness, opacity or other surface properties. The term is also applied to lacquered and varnished papers.
However, with coated papers, the repositionable adhesive that allows a repositionable note or flag to be used, lifted and reused, has a tendency to build adhesion and form a more permanent bond between the note or flag and the paper upon which you are attaching the note or flag. Hence when marking magazines or catalogues or even older textbooks (use of coated papers) with notes or flags, there is the possibility that the repositionable note or flag may become more permanently attached. Such behavior is generally referred to as “adhesion build” and is not generally observed with uncoated papers.
Thus, there is a need to produce a repositionable adhesive coated article that retains the repositionability characteristic of the adhesive when used on coated papers.
SUMMARY OF THE INVENTION
Briefly, in one aspect of this invention an adhesive coated article is provided comprising a layer of microsphere adhesive onto a portion of at least one major surface of a substrate. The microspheres in the adhesive are obtained as the reaction product of (a) at least one alkyl (meth)acrylate ester wherein the alkyl group contains four to about 14 carbon atoms, preferably four to about 10 carbon atoms and (b) a comonomer(s). The comonomer may be a nonpolar, ionic, polar comonomer or mixtures of such monomers. This microsphere adhesive exhibits a lower than expected adhesion to coated papers without sacrificing the adhesion to standard uncoated (bond) papers. Preferably, the 90° peel adhesion, as measured on Kromkote® paper (used as an industry standard) is in the range of 20 to 250 grams/inch.
Advantageously, the microsphere adhesive used in the present invention can either contain microspheres that have been formulated with a (meth)acrylamide containing comonomer (“in situ”) or a polyacrylamide material can be added to a microsphere adhesive (“post-add”), even if the microspheres do not contain a (meth)acrylamide comonomer.
In another aspect of this invention microspheres are made as described in U.S. Pat. No. 3,691,140 (Silver). The resultant microspheres are coagulated and redispersed in solvent. To this organic solvent dispersion an aqueous polyacrylamide material is added and mixed into the dispersion at a loading of 1-10% by weight. This material is then coated onto a suitable backing. With this aspect of the invention other microspheres made by such methods as described in U.S. Pat. No. 5,571,617 (Cooprider et al.); U.S. Pat. No. 5,714,237 (Cooprider et al); U.S. Pat. No. 5,118,750 (Silver et al); U.S. Pat. No. 5,045,569 (Delgado); U.S. Pat. No. 5,824,748 (Kesti et al); U.S. Pat. No. 4,786,696 (Bohnel); and U.S. Pat. No. 5,756,625 (Crandall et al) may be used in combination with the polyacrylamide, either in solvent or aqueous form, to form adhesive combinations with lower adhesion to coated paper without sacrificing the adhesion to uncoated (bond) papers.
As used in this application:
“adhesive coated article” refers to an article having at least a portion of a substrate coated with an adhesive;
“coated paper” refers to paper and paperboard, of which the surface has been treated with clay or some other pigment and adhesive mixture, or other suitable material, to improve the finish with respect to printing quality, color, smoothness, opacity or other surface properties and term is also applied to lacquered and varnished papers.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Useful alkyl (meth)acrylate monomers are those monofunctional unsaturated (meth)acrylate esters, the alkyl groups of which have from 4 to 14 carbons atoms. Such (meth)acrylates are oleophilic, water dispersible, and are essentially water insoluble. Furthermore, useful (meth)acrylates are those that as homopolymers, generally have a glass transition temperature below about −20° C., or if a combination of monomers is used, such a combination would produce a copolymer or terpolymer generally having a glass transition temperature below about −20° C. Nonlimiting examples of such (meth)acrylates included but are not limited to, isooctyl acrylate, 4-methyl-2-pentyl acrylate, 2-methylbutyl acrylate, isoamyl acrylate, sec-butyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isodecyl methacrylate, t-butyl acrylate, t-butyl methacrylate, isobornyl acrylate, methylmethacrylate, isononyl acrylate, isodecyl acrylate and the like, and the combination thereof.
Preferred alkyl (meth)acrylate monomers include isooctyl acrylate, isononyl acrylate, isoamyl acrylate, isodecyl acrylate, 2-ethylhexyl acrylate, n-butyl acrylate, sec-butyl acrylate and mixtures thereof.
Vinyl ester monomers suitable for use in the present invention include but are not limited to: vinyl 2-ethylhexanoate, vinyl caprate, vinyl laurate, vinyl pelargonate, vinyl hexanoate, vinyl propionate, vinyl decanoate, vinyl octanoate, and other monofunctional unsaturated vinyl esters of linear or branched carboxylic acids comprising 1 to 14 carbon atoms, which as homopolymers have glass transition temperatures below about −10° C. Preferred vinyl ester monomers include vinyl laurate, vinyl caprate, vinyl 2-ethylhexanoate, and mixtures thereof.
Additional other vinyl monomers which, as homopolymers, have glass transition temperatures higher than about −10° C. to 0° C., such as vinyl acetate, acrylonitrile, mixtures thereof and the like, may optionally be utilized in conjunction with one or more of the acrylate, methacrylate and vinyl ester monomers provided the glass transition temperature of the resultant polymer is below about −10° C.
Suitable comonomers include nonpolar, ionic, polar monomers and mixtures thereof. In addition to using one or more acrylate monomers as a comonomer, as described above, the following are non-limiting examples of comonomers:
(1) ionic comonomers, such as sodium methacrylate, ammonium acrylate, sodium acrylate, (I) trimethylamine p-vinyl benzimide, (II) 4,4,9-trimethyl-4-azonia-7-oxo-8-oxa-dec-9-ene-1-sulphonate, (III) N,N-dimethyl-N-&bgr;-methacryloxyethyl) ammonium propionate betaine, (IV) trimethylamin
Cooprider Terrence E.
Crandall Michael D.
3M Innovative Properties Company
Peters Carolyn V.
Zirker Daniel
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