The invention relates to a transfer label comprising a backing layer and a transfer layer releasably attached thereto, which transfer layer can be detached from the backing layer for transfer to a container. The invention also relates to a container, in particular to a plastic crate, comprising such a transfer layer and to a method of removing such a transfer layer from a container.
It is known in the packaging technology art to label containers such as plastic crates by providing a non-removable permanent image by a silk screen method. Such labels offer a highly durable finish with two or three color availability. This technique however offers limited colors, lacks the improved graphics that other labelling techniques offer, is not flexible in its ability to have graphic changes to meet market strategies leading to large inventories of obsolete units, and tends to show signs of wear after about four trips.
When removable inks are to be applied to re-usable plastic crates by a screen printing or a tampon printing process, the inks have to be applied in the bottling plant, such as a brewery, which may lead to problems with respect to registration. Upon removal from the crates by means of crate washers, the inks will be dissolved in the washing liquid and in this way contaminate the crate washers. Furthermore the speed of application is limited, and curing of the inks requires a lot of space and long storage times prior to delivery.
A second way of labelling containers encompasses gluing printed paper labels to containers such as plastic crates or bottles at the time of filling and sealing. This type of labels however offer little resistance to label damage from handling and exposure to moisture (wrinkling). Furthermore, paper labels are difficult to remove from crates, and tend to clog the crate washers available today. Upon removal of paper labels from plastic crates, a glue residue may be left on the crates.
A third technique for labelling containers, in particular glass bottles is based on the principles as described in WO 90/05088. In this publication, a method of labelling bottles is described which provides a durable, highly impact resistant label and yet permits high definition label printing. A transfer label comprising a removable backing layer is provided which backing layer is reverse printed with a vinyl or acrylic ink which is cured and overprinted with adhesive. The label is applied to the container with its adhesive surface in contact therewith. The backing layer is separated from the transfer layer of the label for instance by the application of heat to either the container, the label or to both. The labelled container is then applied with a coating which is subsequently cured. The cured coating provides the required degree of impact resistance and durability. The disadvantage of permanently attached labels, is that when these labels get scratched or otherwise damaged, they cannot be easily removed from the bottles. Also, it is not possible to provide the same containers each time with new and/or different labels, which is desirable for promotional activities.
It is an object of the present invention to provide a transfer label which comprises a transfer layer that has good adherence to a container during storage and use, but which can also easily be removed from the container for replacing the label by a new and/or different labels.
It is another object of the present invention to provide a transfer label with an attractive appearance, which can be printed in a large variety of designs and colors and which can be removed from the container in an environmentally friendly manner.
It is a further object to provide a returnable crate system which can be provided with attractive labels, that can be easily and economically be removed and re-applied. The labels should be applied and removed at relatively high speeds.
These and other objects are achieved by the transfer label according to the present invention which is characterized in that the transfer layer, after attachment to a container and under turbulent soaking conditions in an aqueous liquid of a temperature not more than 100xc2x0 C., preferably not more than 70xc2x0 C., breaks up in at least 4 parts, each part not smaller than 5 micrometers and is detached from the container within a soaking time of not more than 20 minutes, preferably not more than 20 seconds. Surprisingly it was found that the advantageous properties of good adherence of the transfer layer to the container during storage and use, and easy removability for re-labelling purposes was provided by labels which break up during soaking conditions without dissolving in the soaking solution. Without wishing to be bound by any theory, it is supposed that the breaking up of the transfer layer during removal by soaking, provides for an increase in the number of positions of the label where the soaking solution can penetrate and attack the interface of the container and the label and can hence detach the label from the container. Hereby a very rapid removal of the label from the container is achieved at modest temperatures. As the label disintegrates into smaller fragments, these fragments can be removed from the soaking solution by a simple sieving process without the labels dissolving in the soaking solution. Hereby no contamination of the wash solution occurs, and effluents to the surroundings of ink and other label parts can be prevented.
During the wet removal process, not more than 10% by weight of the ink in a transfer layer is dissolved in an alkaline wash solution. Hereby it is prevented that the containers are discolored by the inks. Furthermore, the ink levels in the wash solution remain low enough to not effect the aerobic and anaerobic treatment in the waste water treatment plants. The low concentrations of inks in the wash water prevent accumulation of metals in the sludge of the waste water treatment plants, such that this sludge will not have to be treated as chemical waste under government regulations.
Surprisingly it was found that the transfer labels which break up into pieces in the soaking solution according to the present invention can be very rapidly removed using conventional crate washing apparatus, which normally is used to remove dirt and/or paper labels from re-usable plastic crates for containing bottles. A transfer label according to the present invention can for instance be removed from a plastic crate within ten (10) seconds, compared to a removal time of several minutes or more for conventional paper labels. Still the adherence of the transfer label according to the invention to a container, preferably to a re-usable plastic crate for bottles during in-use conditions and its scratch resistance are very good compared to conventional paper labels.
Although it is preferred to use the transfer layer according to the present invention on re-usable plastic crates, the label can also be used in combination with plastic bottles, such as PET-bottles, plastic food trays, glass bottles and the like.
A preferred transfer label according to the present invention comprises a transfer layer which is permeable for the soaking liquids.
With xe2x80x9cpermeablexe2x80x9d it is meant that a transfer layer has a water uptake value after 3 hours between 0.0 and 100 g/m2, preferably about 5 g/m2, in water at room temperature. Such labels have a water vapor transmission rate between 50 and 750 g/m2, preferably about 600 g/m2 after 24 hours for water at room temperature.
The transfer layer may comprise a cover layer overlaying the ink pattern, which cover layer forms the outwardly facing surface upon attachment of the transfer layer to a container. The cover layer may for instance be formed by an acrylic wax coating. The cover layer may be a continuous layer, or may be discontinuous and printed in register with the ink pattern. The acrylic wax cover layer can very advantageously be penetrated by for instances a 0.5% NaOH-solution, while providing a sufficient barrier to penetration of moisture during storage and use-conditions of the label on a container. Labels according to the present invention which combine sufficient durability with quick and economic removal have a pencil hardness between 1N and 7N in the dry state and a pencil hardness less than 0.5 N after a soaking time between 1 minute and 15 minutes in water at 20xc2x0 C.
In a further embodiment of the transfer label according to the present invention, the ink pattern is discontinuous such that areas of reduced thickness are formed in the transfer layer. In the washing process, these areas of reduced thickness, for instance between separate zones of the ink pattern, can form natural lines of weakening such that break-up of the label in these areas can more easily occur.
The transfer layer preferably comprises an adhesive layer, the tack of which is at least reduced by contact with the soaking liquid. According to a preferred embodiment, the adhesive is dissolved by the soaking liquid. Preferably this adhesive layer is discontinuous and is printed in register with the ink pattern.
A suitable transfer label has a transfer layer with a thickness of not more than 30 micrometers, preferably not more than 20 micrometers.
The adhesive layer lay down weight is not higher than 10 g/m2, preferably around 3-6 g/m2. These weights provide good adhering of the label during use and allow for break-up of the label in parts during the wash process.
In one embodiment the labels according to the invention are applied to returnable crates. The need for returnable crates is a direct result of industry preference and government legislation with regard to returnable (refillable) containers in various parts in the world instead of one way packaging. In this type of recycling environment a whole new market has been created for the handling of packaged beverage containers. This is presently true for both refillable PET and glass bottle containers. By use of the transfer label according to the present invention a single, blank crate can be used which can in an easy and inexpensive way be provided with an image imprint which can also easily be removed after the crate is returned to the bottle line for refilling.
Containers being provided with a transfer layer according to the present invention can be xe2x80x9ccleanedxe2x80x9d very rapidly in a conventional crate washing station with cleaning times per container below 1 minute, preferably below 10 seconds at temperatures below 100xc2x0 C., preferably below 70xc2x0 C. The soaking solution is pumped through a sieve which collects the pieces of the broken up labels. The sieves are periodically cleaned and the label pieces are removed from the sieves of the washing station.
According to a preferred embodiment a transparent protective cover layer is attached over the transfer layer upon or after attaching the transfer layer to the container. This cover layer or coating improves the resistance of the label against environmental influences without impairing its break-up properties during wash conditions. A preferred material for the protective coating is compatible with the material of the ink used in the transfer layer. More preferably all materials, adhesive, ink and protective coating are based on acrylate polymers. In order to improve the durability of the label further, without impairing its break-up properties during wash conditions, one or more heat treatments may be given after application of the label to cause a shrinking of at least parts of the transfer layer, to provide a coalescence of the materials of the various layers. This results in an improved service life without deteriorating the wash-off behaviour of the transfer layer.
A label according to the present invention that combines sufficient durability during storage and use with quick and economic removal has preferably been heat treated after application to the container at a temperature between 40xc2x0 C. and 100xc2x0 C., preferably between 50xc2x0 C. and 90xc2x0 C.
By carefully selecting the composition of the label, the use of a protective coating and the nature of the post treatment (heat treatment) it is possible to steer the properties of the transfer layer, especially with respect to the behaviour during washing.
The selection of the adhesive to be used in adhering the label image to the container surface will influence the wash-off properties. The adhesive must have been activated prior to or during application of the transfer layer to the container. An easy and generally preferred method of applying the image is through the use of heat activatable adhesives that have been applied to the image in the form of a reverse printed label. Other methods include the use of adhesive that can be activated through radiation, chemicals, electron-beam, micro-wave, UV and the like. It is also possible to use adhesives that can be activated through photo initiation, humidity, enzymatic action, pressure or ultra-sonic treatment.
A preferred adhesive has a low tack temperature, preferably between 60xc2x0 C. and 90xc2x0 C., more preferably between 80xc2x0 C. and 90xc2x0 C. Instead of a separate layer of adhesive it is also possible to use in the transfer layer an ink which in itself has adhesive properties upon activation.