Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2000-09-13
2003-11-04
Maki, Steven D. (Department: 1733)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C156S215000, C156S273300, C156S275300, C156S275700, C156S331400, C156SDIG009
Reexamination Certificate
active
06641911
ABSTRACT:
This invention relates to the use of selected adhesive systems for bonding so-called wrap-around labels using an overlap adhesive in their application to blown plastic containers, more particularly plastic bottles.
The steadily increasing number of plastic bottles, particularly based on the PET (polyethylene terephthalate), in the beverage industry is attributable above all to three major advantages of plastic over glass bottles, namely: the considerably lighter weight, the fact that plastic bottles are unable to shatter and the reduction in the transport weight, particularly of so-called empties. Another advantage of plastic bottles is that they can be repeatedly reused. However, this does presuppose the complete and clean removal of all residues, not only inside the bottles but also on their outer surface. This means above all that the labels used to identify the contents of the bottles and the adhesives used to apply them or rather residues of the constituents in question should be able to be reliably removed.
The plastic bottles used in particular for soft drinks containing carbon dioxide were originally labelled with so-called shield labels. In their case, adhesive had to be directly applied between the label and the outer surface of the bottle. In order to reduce the disadvantages this involves, wrap-around labels are now also commonly used for cylindrical bottles. Wrap-around labels are labels which completely surround the circumference of the bottle. In this type of labelling, the labels first have to be fixed to the wall of the bottle which can be done, for example, by so-called pick-up adhesives but also by simply forming a layer of moisture on the outer surface of the bottle. Overlap bonding is then carried out, i.e. the end of the label is fixed to the beginning of the label using a suitable adhesive without establishing direct contact between the outer surface of the bottle and the adhesive region.
Foil labels of the type in question are now based predominantly on plastics. They are supplied as a foil roll and are only cut continuously into individual labels in the roll labelling machine. Modern plastic bottle labelling technology is characterized by high throughputs per unit of time so that, for example, 6 to 10 bottles per second are provided with wrap-around labels. It will be readily be appreciated that, under these conditions, the overlap adhesive to be applied to the end of the labels in strip form has to meet stringent and very diverse requirements. Rapid and uninterrupted machine application—without problems, such as stringing—coupled with adequate adhesion immediate after the two label ends to be joined have been fitted together are essential requirements. However, the overlap adhesive used has to meet a much broader range of requirements. The following problem areas are mentioned purely by way of example in this regard: the curing of the adhesive joint and its strength have to be able durably to withstand the forces acting on the wrap-around label. Adhesive systems of the type commonly used today as bottle labelling adhesives form undesirable ribbed or wavy adhesive joints in the dry state. However, one of the greatest problem areas lies in the fact that the pressure inside the bottle can vary significantly, particularly when the bottles are filled with beverages containing carbon dioxide. Unavoidable temperature variations during the storage and transportation of the filled and sealed bottles lead to corresponding variations in internal pressure. In contrast to the old glass bottle, the thin-walled plastic bottle is able to accommodate such variations to a certain extent by volume adaptation. It will readily be appreciated that very considerable tensile stresses are thus applied to the adhesive joint of the wrap-around label applied.
The outcome of such processes is often a partial displacement in the adhesively bonded label ends relative to one another, as a result of which parts of the adhesive are released onto the visible outer surface of the wrap-around label. These visible areas of the adhesive strip are particularly vulnerable to soiling and, accordingly, are undesirable.
Accordingly, the problem addressed by the present invention was to provide adhesives or adhesive systems which could be used with particular advantage as so-called overlap adhesives in the labelling of plastic bottles with wrap-around labels.
SUBJECT OF THE INVENTION
Accordingly, the present invention relates to the use of reactive adhesives reacting off in several steps based on curable polyfunctional macromonomer compounds—also referred to hereinafter as “polyfunctional macromers”—which contain moisture-curing isocyanate groups, at least partly together with olefinically unsaturated radically reactive groups, in their molecular structure as reactive binder components curable by different reaction mechanisms—referred to hereinafter as “binder components A”—in overlap adhesives for the application of wrap-around labels to plastic bottles.
More particularly, the present invention relates to the use of the multicomponent mixtures described in the following based on the binder components A in admixture with other binder components.
PARTICULARS OF THE TEACHING ACCORDING TO THE INVENTION
The use of selected adhesives or adhesive components from the field of so-called dual-cure adhesives has proved to be useful in providing an improved solution to the various problems discussed at the beginning in the field of application in question. The composition characterized as binder component A from the field of adhesive materials is distinguished by the fact that its curing mechanism on the one hand allows an increase in the size of the molecule through the reaction of radically reactive olefinically unsaturated groups in the macromer molecule, but on the other hand guarantees additional setting through an increase in the size of the molecule under the effect of moisture by virtue of the presence of free isocyanate groups in the polyfunctional macromer or macromer mixture.
DE-OS 29 13 676 describes a process for the production of laminated films using solventless adhesives. More particularly, this document describes an adhesive liquid at room temperature which consists of oligomeric and/or polymeric esters and/or ethers which contain both free isocyanate groups and free (meth)acrylate groups in one molecule. The teaching of EP-B1 0 564 483 relates to reactive contact adhesives, to processes for their production and to their use. The document in question describes urethane-based coating compositions curable in two stages which, through a content of UV-curable acrylate groups, can be cured in a first curing step to form a firm, but still formable or embossable material which is irreversibly hardened in a following second step. Monofunctional acrylates may be added to the adhesive to reduce its viscosity. The application envisaged for the contact adhesive described in the document in question is said to be the bonding of wood and/or plastic parts at temperatures of up to about 70° C. and preferably at room temperature. However, none of the literature references cited above discloses the use of these multifunctional macromer molecules reacting off in several stages in conjunction with their use as a reactive binder component in overlap adhesives of the type with which the present invention is concerned for applying wrap-around labels to plastic bottles. In particular, none of the references cited above describes the multicomponent mixtures disclosed in detail hereinafter and the mixture components preferably used in accordance with the invention as further constituents of the adhesive compositions for the field of application with which the invention is concerned.
Those parts of the reactive adhesives used which are referred to as “binder component A” in the present specification are generally multicomponent mixtures of the following two types of polyfunctional macromers. One type contains the olefinically unsaturated reactive groups reacting off by the radical mechanism together with moisture-c
Ferencz Andreas
Heemann Marcus
Huver Thomas
Onusseit Hermann
Puerkner Eckhard
Carmen Michael E.
Corcoran Gladys
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Maki Steven D.
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