GB2411881A

GB2411881A - Label with adhesive containing surfactant

Info

Publication number: GB2411881A
Application number: GB0406047A
Authority: GB
Inventors: Darren Hammonds
Original assignee: Spear Group Holdings Ltd
Current assignee: Spear Group Holdings Ltd
Priority date: 2004-03-12
Filing date: 2004-03-17
Publication date: 2005-09-14
Also published as: GB2411879A; GB0405688D0; GB0406047D0

Abstract

A label, removable with the assistance of a hot liquid, comprises a polymeric film backing layer and a pressure sensitive adhesive layer. The pressure-sensitive adhesive layer comprises a water-borne pressure-sensitive adhesive including a combination of a polymer component and a surfactant component. The adhesive layer permits the label to be removed from a surface within a period of ten minutes using an aqueous wash at 80{C. The label may be applied to an article such as a glass or plastics bottle. A method of removing a label, comprising subjecting the label to the action of a hot washing fluid for a time sufficient to remove the label, is also claimed. A method of reusing articles such as bottles is also claimed, and comprises providing a plurality of bottles, subjecting the bottles to a hot water wash to remove their labels, and recovering and reusing the bottles.

Description

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.

Backaround 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 industry the washing of the vessels, i.e. the bottles, is generally carried out with a hot washing liquid, such as dilute caustic soda, heated to 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 dimcuit 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 - 3- 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 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 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 monomer as an adhesive component and 50-500 parts by weight of a non-ionic surface active agent capable of endowing plasticity as a main additive component' Commercial - 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, stuck 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 SAC. 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.

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, 6 comprising the step of subjecting the label to the action of a hot washing fluid, for 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 15'um to 100pm, 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 "resinated". 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 Ecoiab, 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 sensitive adhesive and adhesion to the glass surface to fully develop. The glass article may be, for example, a returnable glass bottle for a beer product. I, : :

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 15cm 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 Heymans, 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.

Good performance of the adhesive may be obtained if the shear value of the 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 l 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 g/m2 or 14 to 16 g/m2.

Reuse of labelled articles The present invention also provides 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.

l 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 j of used, labelled beer bottles, or bottles for other drink products. The labelled articles may be collected from a number of different sources and transported to a central 3 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 have been removed or at a different location. Reuse of the articles would include re - 9 - labelling the articles, preferably using a label of the present invention, refilling the articles, for example refliling 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 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 m) 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 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 25 Stabilon Plus, a washing additive supplied commercially by Ecolab.

I, 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; i,!. -

Claims

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. An article, such as a glass or plastic bottle, to which a label according to claim 1 has been applied.
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. 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 reusing the recovered bottles.