GB2411880A - Label removable from article by hot washing - Google Patents

Abstract

A label is removable from an article under the action of a hot washing fluid, the label including an adhesive layer comprising a pressure sensitive adhesive material. The adhesive properties of the adhesive layer are reduced when the article is subjected to a hot washing liquid, so assisting the removal of the label from the article. The label comprises a backing layer which is a polymeric film. The pressure sensitive adhesive is a water-borne, permanent, pressure sensitive adhesive having a combination of polymer component and surfactant component which permit the label to be removed from an article within a period of 10 minutes using an aqueous wash at 80{C.

Description

241 1 880 - 1

A LABEL FOR AN ARTICLE

Field of the Invention

The invention relates to a label for an article, in particular for a reusable container, the backing material layer of the label being bondable onto the article by means of an adhesive layer and the label being removable from the article under the effect of hot washing fluid. The articles may be beverage bottles or medicine bottles of glass or plastic, test tubes, repeatedly reusable outer packagings for a multiplicity of individual containers, in particular beverage bottle crates, etc. The invention also relates to a method of making the label, an article to which the label has been applied and a method of removing the label from an article to which it has been applied by the application of a hot washing fluid.

Background of the Invention

For example, in the beverage industry, the containers used, for example bottles, are subject to a high quota of reuse. The containers are cleaned with each return before refilling, the labels also being detached during washing of the vessels. Then the vessels are refilled and relabelled corresponding to the beverage type filled. If the vessels are standardised for a particular product group, such as a beer bottle, the bottles returning to the brewery do not need to be resorted according to beer types, as would be the case with permanently pre-decorated bottles. The different labelling usually only occurs after filling. In the case of a direct printing of the bottle which cannot be washed off, large warehouse stocks of the appropriate pre-decorated bottles In the beverage tndustry the washing of the vessels, i.e. the bottles, is -I generally carried out with a hot washing liquid, such as dilute caustic soda, heated to j 60 to BLOC., without additional mechanical support in the form of brushes, high pressure nozzles etc. Often, paper labels with wet- glue adhesive are used for the labelling of reusable containers. In this case, the wet-glue adhesive is applied to the full surface or in strips, ! the adhesive only being applied to the paper immediately before labelling. The disadvantage is that the filler must work with wet glue, that is to say contamination of the machine occurs and the handling of these labels is more difficult than that of self- adhesive labels. - 2-

This disadvantage is avoided by self-adhesive labels, which are obtained from the label suppliers already provided with adhesive. Because of the standardised washing-off conditions in the beverage industry, it has previously only been possible to use paper-based labels. During washing off of the labels in the wash station, the water permeability of paper is exploited with the object that the adhesive comes relatively quickly into full-surface contact with the washing liquid, and is completely detached in the predetermined washing time-of the order of some minutes. In the case of wet glue applied labels, the adhesive usually goes into solution in the washing liquid. In the case of pre-coated self adhesive labels, water-borne emulsion acrylic adhesives are often used and the objective is that the adhesive is removed intact with the paper face to avoid contamination of the washing bath. This high permeability for washing liquid and water is not possessed by the thermoplastic films used for many labels-such as polyolefins, polycarbonates, polyesters, polyvinyl chlorides, polystyrenes, etc. Such films prevent the access of the washing liquid to the interface of the adhesive and container surface, so that the impermeable film labels can only be slowly detached from the label edge, which, without additional mechanical support, such as brushes, high-press nozzles, etc., does not permit complete removal of the labels within an economically justifiable time span. These mechanical means are undesirable because of the higher outlay.

In the case of a paper/wet-glue label, the adhesive swells and is then detached.

In the case of paper labels precoated with adhesive, redispersible adhesives are also used. In addition, there are particular paper types that quickly disintegrate.

In particular in the beverage industry, however, there is an increasing demand for film-based labels precoated with adhesive. Such film labels, in contrast to paper labels, can be decorated in an extremely wide range of ways. In contrast to paper, they are also available in transparent form, have wet strength and can be dispensed onto the containers at high speed in standardised machines, without the need to work with adhesives, as for example in the case of the wet-glue paper label. Their mechanical properties such as tensile strength and extensibility are greatly superior to those of paper labels. However, it should also be possible to readily wash off such film labels with existing washing systems as easily as the paper labels often used until now.

Broadly speaking adhesives that demonstrate wash-off properties can be categorized as follows: water wash; alkali sensitive and alkali soluble.

The characteristics of water wash adhesives is that in conjunction with an appropriate facestock, most typically paper due to its inherent water permeability, these adhesives can be removed from an article simply with cold or ambient temperature water. In ambient humidity conditions they retain their permanent adhesive characteristics, but when exposed to a sufficient level of water such as through immersion of the article in a water bath, hosing or spraying the adhesive quickly loses adhesion to the article and the label detaches. Whilst the facestock can be a paper with an appropriate level of wet strength so that it remains intact after the washing process, applications exist where the facestock may require a paper grade that is water dispersible. In addition, water soluble materials also exist for specific applications.

Water soluble pressure sensitive adhesives have been and continue to be an area of active development largely to facilitate the effectiveness of subsequent recycling processes. Research into 'environmentally benign' adhesive formulations in the area of pressure sensitive postage stamp adhesives has been necessary to eliminate the stickles' problem caused by pressure sensitive adhesives. In their simplest form water wash adhesives generally contain a given percentage of a water-soluble component such as derivatives of polyvinyl ethers, although water soluble polyacrylatebased pressure sensitive adhesives are also known.

The characteristics of alkali sensitive adhesives is that in conjunction with an appropriate facestock, most typically paper due its inherent water permeability, these adhesives cannot be removed easily with immersion of the labelled article in cold or ambient temperature water they can only be successfully removed from an article, in commercial application terms with hot alkaline solutions, typical of returnable bottle washing plants. This distinction from water wash adhesives is important for applications where a defined level of water resistance is required as part of the functionality of the label. A typical example is wine and champagne labelling, where a specified level of ice water resistance is required. These adhesives are generally I 25 modified acrylic dispersions. They contain within their formulations components which are balanced in ratio to impart the required level of water resistance, but when in full surface contact with an alkaline solution react and facilitate wash-off.

! The characteristics of alkali soluble adhesives category is that in conjunction with an appropriate facestock, most typically paper due to its inherent water j 30 permeability, these adhesives will be soluble in hot alkaline solution as against the previously described non-soluble adhesives. These adhesives have been specifically developed to support the paper recycling process. US-A-5229447 discloses an alkali soluble pressure sensitive adhesive which is described as comprising 100 parts by weight of a polymer obtained by polymerization of a carboxyl-group containing vinyl i: 35 monomer as an adhesive component and 50-500 parts by weight of a non-ionic surface a' active agent capable of endowing plasticity as a main additive component' Commercial j j - 4- applications for this particular type of adhesive are reported to be reducing due largely to cost.

A characteristic of pressure sensitive adhesives is that they are permanently tacky at the temperature of use, such as room temperature. Pressure sensitive adhesives adhere to a variety of substrates when applied with pressure, do not require activation by water, heat or solvents, and have sufficient cohesive strength to be handled with fingers, The primary bond for a pressure sensitive adhesive is not chemical or mechanical but rather a polar attraction to the substrate, and requires pressure to achieve sufficient "wet-out" onto the surface to provide adhesion. Further information regarding pressure sensitive adhesives can be found in the textbook Pressure-Sensitive Adhesives Technology by Istvan Benedek, Luc J. Heymans, Istran Benedek.

One would not normally associate permanent pressure sensitive adhesives as a usual' category within the scope of 'wash-off' adhesives. However, it has now surprisingly been found that successful wash-off is achieved with certain adhesives where permanent characteristics have been the main specification for the adhesive.

Summary of the Invention

According to a first aspect of the present invention, there is provided a label which is removable from an article under the action of a hot washing fluid, which label comprises a backing layer which is a polymeric film and a pressure sensitive adhesive layer for bonding the label onto the article, wherein the pressure sensitive adhesive is a water-borne, permanent, pressure sensitive adhesive having a combination of polymer component and surfactant component which permit the label to be removed from an article to which the label has been attached within a period of 10 minutes using an aqueous wash at 80 C. Preferably the label is removed from the article with the adhesive layer remaining captive on the label.

i, According to a second aspect of the present invention, there is provided an article, such as a glass or plastic bottle to which a label according to the first aspect of the present invention has been applied.

I According to a third aspect of the invention, there is provided a method of removing the label from the article of the third aspect of the present invention, I comprising the step of subjecting the label to the action of a hot washing fluid, for I | 35 example a hot caustic solution, for a time sufficient to remove the label. - 5-

According to a fourth aspect of the present invention, there is provided a method of reusing articles, such as bottles, to each of which a label according to the first aspect of the invention has been applied, said method comprising: providing a plurality of said bottles; subjecting said bottles to a hot water wash to remove the labels from the bottles; recovering the bottles from which the labels have been removed; and reusing the recovered bottles.

For example the method of the invention may be used in respect of at rates of least 1000 bottles per hour, preferably at least 10,000 bottles per hour. Commercial operations may be conducted at for example 50,000 to 70,000 bottles per hour, or even as high as 90,000 bottles per hour.

Detailed Description

Polymeric film The polymeric film of the label of the present invention may be any suitable polymer film from which labels may be made. For the avoidance of doubt, the polymeric film used in the invention is not a paper. Examples of polymer films are thermoplastic films such as polyolefins, polycarbonates, polyesters, polyvinyl chlorides and polystyrenes. Biopolymers such as cellophane or polylactic acid (PLA) may also be used. Particularly preferred are water-impermeable polyolefin films, most preferably polypropylene films, such as biaxially-oriented polypropylene (BOPP), which may have a water permeability of less than about 5 g/m2 per 24 hours at 38 C and 90% relative humidity, for example about 3 3 g/m2 per 24 hours at 38 C and 90% relative humidity.

A regenerated cellulose film may also be used, having for example a water permeability of from about 300 to 400 g/m2 per 24 hours at 38 C and 90% relative humidity.

The polymer film may be a laminate or a single layer. It may include additional non-polymer layers such as metallicized layers.

The polymer film is preferably transparent to provide a "no-label" look. It may or may not be coloured to match the colour of an article to which the label is to be attached.

The polymer film may have a thickness typical of films for labels, such as from 35 15,um to 100,um, preferably 40 to 50pm. - 6-

The polymer film may be treated by known methods in the art and may be coated in a manner which is known per se.

Pressure sensitive adhesive The adhesive used in the present invention is a water borne, permanent, pressure sensitive adhesive. By "water-borne" is meant that water is used as the carrier in which the polymers of the pressure sensitive adhesive are dispersed in the manufacture of the adhesive. Typically, water-borne pressure sensitive adhesives are made by a process in which the polymer component of the adhesive is dispersed in water as a solvent and surFactant(s), for example in amounts of about 50:50 by weight of the polymer to the solvent used. The solvent is subsequently removed. The pressure sensitive adhesive is also typically not one which is "resinatedn. By this is meant that the pressure sensitive adhesive has not had any additional resins added to it, i.e. tackifiers.

The pressure sensitive adhesive used in the present invention is one which has a combination of polymer component and surfactant component which permit the label to be removed from an article to which the label has been attached within a period of minutes using an aqueous wash at 80 C. More specifically, the pressure sensitive adhesive is preferably one which, when used as the adhesive for a label in which the facestock is a biaxially oriented polypropylene (BOPP) film layer (which may have a water permeability of about 3 3 g/m2 per 24 hours at 38 C and 90% relative humidity) having a thickness of 50'um, the label is removed from a glass substrate within 10 minutes or less under the action of a wash water at 80 C, wherein the wash water has | a 2% NaOH concentration and a 0.1% addition of a surfactant washing additive, such as P3 Stabilon Plus, available from Ecolab, Inc. Preferably in this test, the label should be removed from the glass substrate in less than 8 minutes, more preferably within 5 minutes and most preferably within 3 minutes.

| With other more water permeable facestock materials, such as regenerated | cellulose film (which may have a water transmission rate of around 370 g/m2 per 24 hours at 38 C and 90% relative humidity), the label will be removed in a shorter period of time than noted above. Such materials may have a thickness of about 45,um.

In the above noted test, the labelled article may be allowed a minimum of 24 hours and up to 7 days standing time at ambient conditions (23 C, 50% RH) prior to undertaking the washing test, to allow the associated cold creep of the pressure 35 sensitive adhesive and adhesion to the glass surface to fully develop. The glass article i i, may be, for example, a returnable glass bottle for a beer product. i. 1 i. - 7-

In the test, the label to be tested may be cut to dimensions of 50mm (width) x 70mm (height) and hand applied to the glass article using a wiper blade mechanism to simulate automatic application.

The washing test may be conducted in a stainless steel bath filled with 12 litres of hot washing fluid agitated at least 1 5cm in depth via an overhead stirrer at 250 rpm, simulating the conditions within the main soak of an industrial washing environment.

The bath is maintained at a temperature of 80 C, 2.0% NaOH concentration and with a 0.1% addition of P3 Stabilon Plus, a washing additive supplied commercially by Ecolab.

The pressure sensitive adhesive used in the present invention, when tested in accordance with the "water whitening" test method that is described on Page 558 of Pressure Sensitive Adhesive Technology, Istvan Benedek & Luc J Heymans, may have a performance that is classified as 'very good' i.e. the adhesive film does not show any signs of water whitening within 17 seconds. Indeed, for examples of pressure sensitive adhesives for use in the invention, whitening may not occur for 90 seconds and even up to 300 seconds.

The pressure sensitive adhesive used in the present invention, when tested in accordance with the "loss of transparency" test method that is described on Page 558 of Pressure Sensitive Adhesive Technology, Istvan Benedek & Luc J Heyrnans, may have a performance that is classified as 'fair' i.e. the adhesive film demonstrates a difference in transparency between wet and dry laminate of <8%.

The pressure sensitive adhesive used in the present invention, when tested in accordance with the "wet anchorage" test method that is described on Page 558 of Pressure Sensitive Adhesive Technology, Istvan Benedek & Luc J Heymans, may have a performance such that the adhesive layer does not rub off the intended substrate after immersion in distilled water for 7 minutes.

The pressure sensitive adhesive used in the present invention, when tested in accordance with the "wet adhesion on glass" test method that is described on Page 558 of Pressure Sensitive Adhesive Technology, Istvan Benedek & Luc J Heymans, may have adhesive recovery properties over time after immersion of the sample in distilled water for 7 minutes in excess of 60 minutes when coated onto a polypropylene material and between 30 minutes and 60 minutes on regenerated cellulose film.

I Good performance of the adhesive may be obtained if the shear value of the I adhesive is relatively high. A characteristic of a preferred adhesive would be that it demonstrates high cohesion when the labels are slowly removed from the glass article leaving no residues on the surface; however if the label is quickly removed the adhesive shears from the substrate ( - 8 - Good performance of the adhesive may be achieved if the Glass Transition Temperature of the adhesive is in the range of -25 C to-40 C.

A preferred pressure sensitive adhesive for use in the present invention is SE5279 available from HO Fuller Limited.

Preferably the adhesive is applied to the label material covering the full surface or in regions with gaps, if appropriate in patterns.

A cover or release layer may be provided over the outer surface of the pressure sensitive adhesive layer as is well known in the art.

Method for making the label of the invention The label of the present invention may be made by methods well known in the art by applying a layer of the desired pressure sensitive adhesive to a suitable facestock layer.

The pressure sensitive adhesive may be applied at a suitable coat weight to the facestock layer. For example, coat weights of up to 20 g/m2 may be used. However, beneficial results can be obtained with coat weights of between 8 to 16 g/m2, for | example at a coat weight of 8 to 12 9/m2 or 14 to 16 g/m2.

Reuse of labelled articles The present invention also provides a method of reusing articles, such as 4 bottles, to each of which a label according to the first aspect of the invention has been ' applied, said method comprising: i! providing a plurality of said bottles; 1 subjecting said bottles to a hot water wash to remove the labels from the 1 25 bottles; 3 recovering the bottles from which the labels have been removed; and 5' reusing the recovered bottles.

For example the method of the invention may be used in respect of at least 1000 bottles per hour, preferably at least 10,000 bottles per hour.

The method of this aspect of the invention may for example be used in respect , of used, labelled beer bottles, or bottles for other drink products. The labelled articles Hi, may be collected from a number of different sources and transported to a central J location where the labels are removed in the hot washing step, and the articles recovered. The plurality of recovered articles may be reused at the location the labels ! 35 have been removed or at a different location. Reuse of the articles would include re :1 i

Y

labelling the articles, preferably using a label of the present invention, refilling the articles, for example refilling a bottle for a drink, such as beer, and sealing the article.

The invention may be used with a variety of articles, but is preferably employed with glass articles such as returnable glass beer bottles, which may include conventional hot and cold end coatings.

The present invention may be used in conjunction with the invention of our co pending Application No. 0405271.8 filed 9 March 2004. The description of this co pending application is included below. The drawings of the copending application are also included herein.

Thus, in the label of the present invention the pressure sensitive adhesive layer may have an inner surface which faces towards the backing layer and an outer surface for adhering to the surface of the article, wherein the outer surface of the adhesive layer, prior to its application to an article, includes a plurality of micro-channels which extend to the periphery of the label.

Other features of the co-pending application which may be incorporated in the label of the present invention are as follows: the micro-channels extend all or part way across the label, when viewed in the plane of the label.

the channels only extend part way into the label.

the channels have a depth of no greater than about 15pm.

the channels have a depth of no greater than about 10'um.

the channels have a depth of at least 1,um.

the channels have a depth of at least 5,um.

the channels have a width of no greater than about 250,urn.

the channels have a width of no greater than about 150pm.

I the channels have a width of no less than about 10,um.

j the channels have a width no less than about 50,um.

! . the minimum distance between adjacent channels is about 10pm the maximum distance between adjacent channels is 10mm.

s the polymeric film of the label is s elected from thermoplastic films such as | polyolefins, polycarbonates, polyesters, polyvinyl chlorides and polystyrenes; and biopolymers such as cellophane or polylactic acid (PLA).

g go the polymeric film is a polypropylene film. to

the polymer film has a thickness of from 15,um to 100'um. al i s s -

The method of the co-pending application may be used to make labels of the present invention. This method comprises providing a composite structure comprising a backing layer which is a polymeric film and a pressure sensitive adhesive layer for bonding the label onto the article, the pressure sensitive adhesive layer having an inner surface which faces and adheres to the backing layer and an outer surface for adhering to the surface of the article; and forming micro-channels in the outer surface of the adhesive layer, which micro- channels extend to the periphery of the label.

In the method the micro-channels may be formed by embossing a surface of the composite structure.

The invention will now be illustrated by reference to the accompanying examples.

Example

A water-borne, permanent pressure sensitive adhesive available from HB Fuller as SE5279 was coated onto a permeable facestock material (Regenerated Cellulose Film of thickness 45 Bum) and a non-permeable facestock (Biaxially Oriented Polypropylene of thickness 50 Bum) The samples were cut to dimensions of 50mm (width) x 70mm (height) and hand applied to a returnable glass beer bottles using a wiper blade mechanism to simulate automatic application.

The labelled bottles were then allowed a minimum of 24 hours and up to 7 days standing time at ambient conditions (23 C, 50% RH) prior to undertaking the washing tests, to allow the associated cold creep of the PSA and adhesion to the glass surface to fully develop.

The washing tests were conducted in a stainless steel bath filled with 12 litres of i, hot washing fluid agitated via an overhead stirrer at 250 rpm, simulating the conditions I within the main soak of an industrial washing environment. The bath was maintained at a temperature of 80 C, 2. 0% NaOH concentration and with a 0.1% addition of P3 Stabilon Plus, a washing additive supplied commercially by Ecolab.

It was determined that in conjunction with the Regenerated Cellulose Film, the | wash-off performance of this adhesive was less than 180 seconds.

It was also determined that in conjunction with the BOPP film, the washoff performance of this adhesive was under 480 seconds. I' : ,. :: - 11

Description of cooendino Application No. 0405271.8 filed 9 March 2004 The invention relates to a label for an article, in particular for a reusable container, the backing material layer of the label being bondable onto the article by means of an adhesive layer and the label being removable from the article under the effect of hot washing fluid. The articles may be beverage bottles or medicine baffles of glass or plastic, test tubes, repeatedly reusable outerpackagings for a multiplicity of individual containers, in particular beverage bottle crates, etc. The invention also relates to a method of making the label, an article to which the label has been applied and a method of removing the label from an article to which it has been applied by the application of a hot washing fluid.

For example, in the beverage industry, the containers used, for example bottles, are subject to a high quota of reuse. The containers are cleaned with each return before refilling, the labels also being detached during washing of the vessels. Then the vessels are refilled and relabelled corresponding to the beverage type filled. If the vessels are standardized for a particular product group, such as a beer baffle, the baffles resuming to the brewery do not need to be resorted according to beer types, as would be the case with permanently pre-decorated baffles. The different labelling usually only occurs after filling. In the case of a direct printing of the baffle which cannot be washed off, large warehouse stocks of the appropriate pre-decorated baffles In the beverage industry the washing of the vessels, i.e. the baffles, is generally carried out with a hot washing liquid, such as dilute caustic soda, heated to to 90 C., without additional mechanical support in the form of brushes, high pressure nozzles etc. Often, paper labels with wet-glue adhesive are used for the labelling of reusable containers. In this case, the wet-g/ue adhesive is applied to the full surface or in strips, the adhesive only being applied to the paper immediately before labelling. The disadvantage is that the filler must work with wet glue, that is to say contamination of the machine occurs and the handling of these labels is more difficult than that of self- adhesive labels.

This disadvantage is avoided by self-adhesive labels, which are obtained from the label suppliers already provided with adhesive. Because of the standardized washing-off conditions in the beverage industry, it has previously only been possible to use paper-based labels. During washing off of the labels in the wash station, the water permeability of paper is exploited with the object that the adhesive comes relatively quickly into full-sufface contact with the washing liquid, and is completely detached in - 12 the predetermined washing time-of the order of some minutes. In the case of wet glue applied labels, the adhesive usually goes into solution in the washing liquid. In the case of pre-coated self adhesive labels, redispersible adhesives are often used and the objective is that the adhesive is removed intact with the paper face to avoid contamination of the washing bath. This high permeability for washing liquid and wateris not possessed by the thermoplastic films used for many labels-such as polyolefins, polycarbonates, polyesters, polyvinyl chlorides, polystyrenes, etc. Such films prevent the access of the washing liquid to the interface of the adhesive and container surface, so that the impermeable film labels can only be slowly detached from the label edge, which, without additional mechanical support, such as brushes, high-press nozzles, etc., does not permit complete remove/ of the labels within an economically justifiable time span. These mechanical means are undesirable because of the higher outlay.

In the case of a paper/wet-glue label, the adhesive swells and is then detached.

In the case of paper labels precoated with adhesive, redispersible adhesives are also used. In addition, there are particular paper types that quickly disintegrate.

In particular in the beverage industry, however, there is an increasing demand for film-based labels precoated with adhesive. Such film labels, in contrast to paper labels, can be decorated in an extremely wide range of ways. In contrast to paper, they are also available in transparent form, have wet strength and can be dispensed onto the containers at high speed in standardised machines, without the need to work with adhesives, as for example in the case of the wet-g/ue paper label. Their mechanical properties such as tensile strength and extensibility are greatly superior to those of paper labels. However, it should also be possible to readily wash off such film labels with existing washing systems as easily as the paper labels often used until now.

One solution to the problem outlined above is set forth in US Patent No. 6680097 (Steinbeis), the contents of which are hereby incorporated by reference, which provides a label is stated to be detachable from the article with little effort. This i is achieved by the use of a label in which the backing material layer comprises a plastic film layer that is stretched in at least one direction and shrinks back under the effect of heat, such as the temperature of the washing fluid or/and by thermal radiation, so as to overcome the retention force of the adhesive layer. By virtue of the effect of the heat, a | shrinking back of the plastic film occurs, while at the same time the adhesive loses | adhesive force. It is stated that by this means, the label detaches gradually from the article, for example from the edge or with the formation of channels, and can be easily removed within an extreme/yshorttime. r - 13

Anotherprior aft reference is W002/07474, the contents of which are hereby incorporated by reference, which discloses a label in which the film is a biopolymer such as cellulose.

US-A-2003/0150148, the contents of which are hereby incorporated by reference, discloses a label which has embossed or debossed porffions to correspond to indicia printed on the label.

According to a first aspect of the present invention, there is provided a label which is removable from an article under the action of a hot washing fluid, which label comprises a backing layer which is a polymeric film and a pressure sensitive adhesive layer for bonding the label onto the article, the pressure sensitive adhesive layer having an inner sufface which faces towards the backing layer and an outer sufface for adhering to the sufface of the article, wherein the outer sufface of the adhesive layer, prior to its application to an article, includes a plurality of micro-channels which extend to the periphery of the label.

According to a second aspect of the present invention, there is provided a method of making the label of the first aspect of the present invention comprising: providing a composite structure comprising a backing layer which is a polymeric film and a pressure sensitive adhesive layer for bonding the label onto the arfficle, the pressure sensitive adhesive layer having an inner sufface which faces and adheres to the backing layer and an outer sufface for adhering to the sufface of the article; and forming micro-channels in the outer sufface of the adhesive layer, which micro channels extend to the periphery of the label.

In the process aspect of the present invention, the micro-channels may be formed by embossing the sufface of the composite structure. The composite structure 25 may itself be the label, or may be a structure (such as web of material) from which a I label itself may be formed, for example by further processing steps including printing i steps and steps to cut the desired shape of label from the web of material. These i further steps are known per se.

The label of the present invention has been found to exhibit superior wash off 30 characteristics when washed in a hot washing fluid. It is presently believed that when J an arfficle to which the label is applied is contacted with a hot washing fluid, typically hot j water, the hot fluid causes expansion of the polymeric species in the pressure sensitive 1 adhesive at the periphery of the label and lifting of the label at the edges. This allows the hot fluid to travel along the channels in the adhesive layer, mobilizing components, 35 for example suffactants, within the adhesive and progressively lifting the label from the article and allowing rapid remove/ of the label from the arfficle. ] - 14

According to a third aspect of the present invention, there is provided an abide, such as a glass or plastic bottle to which a label according to the first aspect of the present invention has been applied.

According to a fourth aspect of the invention, there is provided a method of removing the label from the article of the third aspect of the present invention, comprising the step of subjecting the label to the action of a hot washing fluid, for example a hot caustic solution, for a time sufficient to remove the label.

For a better understanding of the present invention, and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings in which: Figure 1 represents the cross-sectional primary composite structure of a typical pressure sensitive label to which no mechanical treatment has been made and is typical of the structure using thermoplastic film facestock manufactured for non returnable applications; Figure 2 represents the cross-sectional primary composite structure of the pressure sensitive label herein described, where through the mechanical process of embossing and via the properties of the label material described herein, the print layer, face material and adhesive layer have been physically altered to replicate the paffem of the embossing tool used; and Figure 3 represents the front aspect of the label described herein demonstrating an example of the embossing structure.

As previously stated, the outer surface of the adhesive layer, prior to application to an article, includes a plurality of micro-channels which extend to the periphery of the label. Thus surface micro-channels are provided within the adhesive channels layer ! 25 which may extend all or part way across the label, when viewed in the plane of the label. In some embodiments of the invention, the channels may only extend part way into the label, it being sufficient for the invention that the channels extend to the edge of the label and permit the hot washing water to lift the outer edge of the label from the I article to which the label is affixed. Once the outer edges of the label have been lifted, this will expose the inner areas of the label to the hot water which, in some circumstances, will be sufficient to facilitate complete removal of the label from the article.

The size and density of the micro-channels in the adhesive layer may depend I; upon a number of factors, such as the elasticity of the face material and adhesive.

However, as a general guideline, the channels will normally have a depth of no greater than about 1 Bum, no less than 3,um and most preferably in the range of 5,um to 1 0,um. j, 2q2 : -

The channels will normally have a width of no greater than about 300,um and no less than about 10,um and preferably in the range of about 50,um to 150pm. At least some of the channels may cross each other to form a network of inter-linked channels, such as a regular grid. Altematively, a series of generally parallel channels may be provided which do not interlink. The arrangement of channels may be in the form of a regular pattern, but this is not essential and labels in which the channels are randomly arranged are also considered to be within the scope of the present application The distance between adjacent channels should be such that the label is removal under the action of the hot washing water. The precise number and disposition of such channels can be determined empirically by routine experimentation.

Normally, a minimum distance between the micro-channels will be about Mum, preferably about 250,um, to ensure a sufficient amount of exposed adhesive is provided to bond to the article satisfactorily. A maximum distance between adjacent channels may be of the order of up to about 10mm, and normally will be no more than 5mm.

In one presently preferred embodiment of the invention, the microchannels comprises two series of parallel channels which intersect each other substantially at 90 , with a spacing of from The cross-sectional shape of the channels is not critical. For example, the channels may each be defined by a base and a pair of generally parallel side walls which extend away from the base. Altematively, the channels may have a concave cross-sectional shape. This latter arrangement is typically obtained with most pressure sensitive adhesives.

The polymeric film of the label of the present invention may be any suitable polymer file, from which labels may be made. For the avoidance of doubt, the polymeric film used in the invention is not a paper. Examples of polymer films are thermoplastic films such as polyolefins, polycarbonates, polyesters, polyvinyl chlorides | and polystyrenes. Biopolymers such as cellophane or polylactic acid (PLA) may also be used. Particularly preferred are water-impermeable polyolefin films, most preferably polypropylene films, such as biaxially- oriented polypropylene (BAPP).

The polymer film may be a laminate or a single layer. It may include additional non-polymer layers such as metallicized layers.

3 The polymer film is preferably transparent to provide a "no-label" look. It may or may not be coloured to match the colour of an article to which the label is to be affached. The The polymer film may have a thickness typical of films for labels, such as from 15,um to 100,um, preferably 40 to 50,um l - 16 The polymer film may be treated by known methods in the aft and may be coated in a manner which is known per se.

The adhesive used in the present invention is a pressure sensitive adhesive. A characteristic of pressure sensitive adhesives is that they are permanently tacky at the temperature of use, such as room temperature. Pressure sensitive adhesives adhere to a variety of substrates when applied with pressure, do not require activation by water, heat or solvents, and have sufficient cohesive strength to be handled with fingers, The primary bond for a pressure sensitive adhesive is not chemical or mechanical but rather a polar attraction to the substrate, and requires pressure to achieve sufficient Wet-out" onto the surface to provide adhesion. Further information regarding pressure sensitive adhesives can be found in the textbook Pressure Sensitive Adhesives Technology by Istvan Benedek, Luc J. Heymans, Istran Benedek Whilst pressure sensitive adhesives are known for use with thermoplastic labels for a "no-label" look, such adhesives are water resistant and are not removable under a hot water wash.

The present invention permits the use of a wide variety of pressure sensitive adhesives, including those which are water resistant. The provision of the micro channels in the adhesive layer permits hot wash water to penetrate and detackify the adhesive so that it is removed from the article complete with the remainder of the label.

In order that the label of the present invention is not removable under the action of cold water, such as water which condenses on the article in a refrigerator or other cold environment, the pressure sensitive adhesive used should be one which is not readily soluble in water.

Examples of pressure sensitive adhesives which may be used in the present | 25 invention are ones that do not dissolve in water, at least until detachment of the label, in particular a redispersible adhesive such as a dispersion adhesive based on acrylate or copolymeric acrylate/polyurethane compounds and copolymers with an acrylate I proportion (e.g. rubber/acrylate).

Preferably the adhesive is applied to the label material covering the full surface 1 30 or in regions with gaps, if appropriate in patterns.

i The adhesive layer may also be a hot-melt adhesive or a glue or a radiation | curing or thermally melting adhesive applied to the article or to the label immediately before labelling.

l A cover or release layer may be provided over the outer surface of the pressure i 35 sensitive adhesive layer as is well known in the aft. : i, : - 1 7

The hot washing fluid by be in the form of a liquid, in particular water and contain suffactants and alkaline agents, in particular caustic soda.

The present invention also provides a method of making the label of the first aspect of the present invention comprising: providing a composite structure comprising a backing layer which is a polymeric film and a pressure sensitive adhesive layer for bonding the label onto the article, the pressure sensitive adhesive layer having an inner sufface which faces and adheres to the backing layer and an outer sufface for adhering to the sufface of the article; and forming micro-channels in the outer sufface of the adhesive layer, which micro channels extend to the periphery of the label.

The micro-channels in the outer sufface of the adhesive layer may be formed by a process in which the composite material is subjected to a mechanical forming step in which the desired paffem of channels is formed on a resilient sufface as a series of recessed areas on the block, which resilient sufface is then used to press the sufface of the composite to mechanically deform the layers of the composite. This process is otherwise referred to as "embossing". Embossing is a technique that produces raised or depressed sections on a sufface in accordance with the shape and contours of the desired design. Known embossing techniques typically utilize a pair of dies having the design to be embossed found in them, one die generally being the negative of the other. When the pair of dies are brought together under pressure, with a piece of work material between them, the design is transferred to the work material by deforming the material in the region of the design away from the original plane. Typically, in the present invention, the dies will be constituted by a pair of rollers, one of which has the desired pattern of channels provided on its sufface, and the other of which is a backing roller against which the embossing roller presses.

The embossing of the composite structure may be carried out so that the pattern is applied to the face material or to the adhesive layer sufface. It is preferred that the embossing is carried out so that the paffem is applied through the face material.

In the embossing method of the invention, the embossing roller may be formed of a mete/ in which the desired paffem of channels is etched. The depth of the channels, and their desired shape and disposition will correspond to the desired depth i and disposition of channels in the adhesive layer, as described above. When the composite structure is embossed, the pattern of channels is transferred directly to the composite layer. The backing layer of the structure is a polymeric film, and in some instances, for example where the film is a polyolefin film such as polypropylene, the : - 18 polymer film will deform elastically and shortly thereafter return to its original form, without any paffem of channels remaining in it. However, the material of the pressure sensitive adhesive has a very high viscosity and does not flow appreciably under the conditions under which the labels are made or used. Thus, the pattern of channels will remain in the surface of the adhesive layer for a prolonged period of time.

The invention will now be illustrated by reference to the following example

Example.

In one embodiment of the invention, samples of UCB Rayoface C50 (50,um bi axially oriented polypropylene) was transfer laminated with 20gsm of a water-borne pressure sensitive adhesive, described as a high tack, high cohesion, permanent adhesive suitable for paper and filmic facestocks, against a 30 micron siliconised transparent polyester liner, as outlined in Figure 1.

In another embodiment of the invention, samples of UCB Rayophane 645E721 (64.5gsm Regenerated Cellulose Film) was transfer laminated with 20gsm of the same water-borne pressure sensitive outlined above.

The samples were then embossed over their entire surface with a paffern appropriate to create a network of micro-channels with interlinking in both directions of the label and that would extend to the periphery of the cut labels. The depth of the embossing was 7-10,um and the width of the channels prior to application was 100 125/Jm as outlined in Figure 2.

The embossed material samples were cut to dimensions of 50mm (width) x 70mm (height) and hand applied to a returnable glass beer baffle using a wiper blade mechanism to simulate automatic application. l

The labelled bottles were then allowed a minimum of 24 hours standing time at ambient conditions (23 C, 50% RH) prior to undertaking the washing tests, to allow the associated cold creep of the PSA and adhesion to the glass surface to fully develop.

The washing tests were conducted in a stainless steel bath filled with 12 litres of hot washing fluid agitated via an overhead stirrer at 250 rpm, simulating the conditions within the main soak of an industrial washing environment. The bath was maintained at a temperature of 80 C, 2.0% NaOH concentration and with a 0.1 % addition of P3 Stabilon Plus, a washing additive supplied commercially by Ecolab.

The labelled bottles were partially filled with ambient temperature water and then immersed into the bath. The time taken for the label to completely detach from the bottle was measured.

35 The average of the results obtained for the polypropylene labels described above was 180 seconds. 1 - 19

The average of the results obtained for the regenerated cellulose labels described above was 60 seconds.

In both embodiments, the average wash-off time had been reduced by a factor of 50% as a consequence of the mechanical treatment described herein, compared to labels that had not been treated in this way.

I 3 - 20-

Claims (4)

1. Claims 1. A label which is removable from an article under the action of a

   hot washing fluid, which label comprises a backing layer which is a polymeric film and a pressure sensitive adhesive layer for bonding the label onto the article, wherein the pressure sensitive adhesive is a water-borne, permanent, pressure sensitive adhesive having a combination of polymer component and surfactant component which permit the label to be removed from an article to which the label has been attached within a period of 10 minutes using an aqueous wash at 80 C.
2. 2. An article, such as a glass or plastic bottle, to which a label according to claim 1 has been applied.
3. 3. A method of removing the label from the article of claim 1, comprising the step of subjecting the label to the action of a hot washing fluid for a time sufficient to remove the label.
4. 4. A method of reusing articles, such as bottles, according to claim 2, said method 1 5 comprising: providing a plurality of said bottles; subjecting said bottles to a hot water wash to remove the labels from the bottles; recovering the bottles from which the labels have been removed; and i 20 reusing the recovered bottles.