Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2000-02-29
2003-11-18
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S335000, C428S035600, C428S349000, C428S347000, C428S034900, C428S035100, C428S035200, C428S035500, C264S497000, C264S460000, C264S662000, C522S100000, C522S110000, C522S111000, C522S112000, C522S104000, C522S170000, C522S182000
Reexamination Certificate
active
06649259
ABSTRACT:
FIELD OF INVENTION
This invention relates to radiation curable adhesives for use with thermally-shrinkable films or labels.
BACKGROUND OF INVENTION
This invention is directed to the thermally shrinkable films or labels coated with radiation curable adhesive compositions and to a process for applying such films or labels to containers wherein they are adhered to the container surface.
There has been a trend in the packaging industry, and particularly in the beverage segment of such industry, to replace lithographically preprinted cans with blank cans which can be filled as desired. The labeling of these cans is carried out by applying to the container a printed label formed from a heat shrink film some time soon before or after the filling operation.
This method of labeling is particularly attractive, for example, to breweries which often bottle and package their products under a variety of trade names. By utilizing a thermally shrinkable labeling process, these breweries are no longer required to stock a large inventory of pre-printed containers for each brand and could, instead, stock only unprinted containers together with a supply of the appropriate thermally shrinkable printed film labels. Moreover, the presence of the film label around the container would provide additional protection against the printed containers rubbing together during transport.
Initially these labeling operations were carried out using processes and methods such as described in U.S. Pat. No. 3,822,459 issued Jul. 9, 1974, to Aveberg et al. These earlier processes required the formation of a tube or sleeve of thermally shrinkable film which was then placed over the container and heated in order to shrink the film to conform to the size and shape of the container. Recently Hoffman, in U.S. Pat. Nos. 3,765,991; 3,834,963; 4,108,710; 4,704,173; and 4,844,957, has proposed a process which does not require a preformed sleeve and permits the application of the film directly from a continuous roll of film material onto the container.
Both techniques, but especially the high speed continuous operation such as described by Hoffman, require the use of an adhesive which will form an adequate bond between the container and the label. More specifically, the bond must be such that it will not shrink and separate at the seam during the heat shrinking step. The bond should also form a smooth coating which will not bubble or cause creasing of the film during curing.
Moreover, in many applications, the containers are subjected to heating either during hot filling (e.g., fruit juice processing) or after filling as when a separate pasteurization step is required, these processes put additional stress on the adhesive bond. When used in these processes, conventional adhesives do not have adequate heat strength.
To provide the desirable properties required of an adhesive for use with thermally shrinkable films or labels, the prior art teaches the use of hot melt adhesives. Heretofore, curable adhesives for thermally shrinkable films or labels has not been considered.
SUMMARY OF INVENTION
We have found that radiation curable adhesive compositions permit satisfactory application of thermally shrinkable films or labels onto containers even at the high speeds involved in continuous processes and where such radiation curable adhesive composition gains instant high heat resistance after curing. The resultant bond is strong, and retains its configuration even after the heat shrinking operation and any additional pasteurization operations so that the “shoulder seams” formed at the ends of the container as well as the seam joint formed at the interface of the leading and trailing edge of the film remain in the desired configuration with no distortion of the label or undesirable exposure of the container at the seam lap.
Thus, the present invention is directed to thermally shrinkable films or labels having coated thereon a radiation curable adhesive and to a process for applying thermally shrinkable films or labels to containers comprising the steps of a) coating at least a portion of a thermally shrinkable but unshrunken film or label segment with a radiation curable adhesive; b) applying the film or label to the longitudinal surface of the container; c) subjecting the radiation curable adhesive to a radiation source to effect curing thereof and, d) subjecting the container to heat to shrink the film or label onto the container so as to permanently affix it thereto.
With some adhesive compositions it is possible, and may be desirable, to reverse steps b) and c). Such adhesives undergo initiation and partial polymerization under UV light, but continue and eventually complete their cure after removal from the UV light source. These adhesives complete their cure some time after exposure in what is commonly known as the dark-cure process. Cationic curing systems typically exhibit dark cure behavior, whereas free-radical curing systems typically do not.
In a preferred embodiment, the radiation curable adhesive is applied to a narrow region of the container or at the leading end of the film segment to secure the leading end of the film to the container, the film wrapped around the container and the film segment secured to the container by overlapping the trailing end, a narrow region of which has been coated with the radiation curable adhesive.
Also disclosed herein are shrink labeled containers wherein the labels are affixed to the container utilizing radiation curable adhesive having an epoxidized block copolymer or a cycloaliphatic epoxide as the base resin. The term “solid hydrogenated tackifier” as used herein, is intended to mean any composition which is solid at room temperature and which is useful to impart tack to the radiation curable adhesive composition. ASTM D-1878-61T defines tack as “the property of a material which enables it to form a bond of measurable strength immediately on contact with another surface”.
The term “base resin” as used herein is intended to mean a polymer which undergoes curing upon UV exposure. Radiation curable adhesives as used herein is intended to mean adhesives that generally comprise one or more of the following:
(a) a base resin, such as epoxidized block copolymer (as described in U.S. Pat. No. 5,516,824 and U.S. Pat. No. 5,776,998); and/or a cycloaliphatic epoxy (such as CYRACURE UVI6110 available from UNION CARBIDE); an olefin (including that having a Carbon-Carbon double bond pendant to the backbone or on ends—such materials may be oligomeric, polymeric or monomeric and the backbone may vary in polarity ranging from aliphatic, urethane, polyester and polyether);
(b) a photoinitiator, the type of which is dependent on the type of chemistry of the base resin e.g. cationic photoinitiator suitable for curing epoxidized block copolymer, cycloaliphatic epoxies, and vinyl ether olefins which includes sulfonium or iodonium salts such as SARCAT CD1010, SARCAT CD 1011 AND SARCAT CD 1012 (available from SARTOMER) (note: SARCAT CD1010 is also available under the trade name CYRACURE UVI 6974 from UNION CARBIDE). For free-radical curing systems such as olefinic or thiolene curing systems the following photoinitiators may be suitable: IRGACURE 651, 184 and 1700 and DAROCUR 1173, available from CIBA-GEIGY; as well as GENOCURE LBP available from RAHN; and ESACURE KIP150 available from SARTOMER. Other examples of photoinitiators which may be used include one or more of the following: Benzophenone, Benzyldimethyl ketal, Isopropylthioxanthone, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl) phosphineoxide, 2-hydroxy-2-methyl-1 -phenyl-1 -propanone, Diphenyl(2,4,6-trimethybenzoyl)phosphine oxides, 1-hydroxycyclohexyl phenyl ketone, 2-benzyl-2-(dimethylamino)-1-4-(4-morpholinyl)phenyl-1 -butanone, alpha,alpha.-dimethoxy-alpha-phenylacetophenone, 2,2-diethoxyacetophenone, 2-methyl-1 -4-(methylthio)phenyl-2-(4-morpholinyl)-1 -propanone, 2-hydroxy-1 -4-(hydroxyethoxy)phenyl-2-methyl-1 -propanone;
(c) a tackifier, such as the C
5
/C
9
hydrocarbon resins, synthetic polyterpenes, rosin, rosin esters, natural terpenes,
Hu Ziyi
Paul Charles W.
Pierce Peter D.
Foulke Cynthia L.
McClendon Sanza L
National Starch and Chemical Investment Holding Corporation
Seidleck James J.
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