WO2012072889A1

WO2012072889A1 - Removable label

Info

Publication number: WO2012072889A1
Application number: PCT/FI2011/051075
Authority: WO
Inventors: Noel Mitchell; Markus KIVELÄ
Original assignee: Upm Raflatac Oy
Priority date: 2010-12-03
Filing date: 2011-12-02
Publication date: 2012-06-07
Also published as: EP2646240A1; EP2646240A4

Abstract

The invention relates to a label which is removable from surface of an item, wherein the label comprises an adhesive layer which is water absorbable and includes an acrylic block copolymer. The invention also relates to a method for manufacturing such labels and to use of labels for labelling recyclable or reusable items. The invention further relates to a combination of an item and a label, wherein the label has been attached to a surface of the item and to a method for removing a label from a surface of an item.

Description

Removable label Field of the Invention The present invention relates to adhesive laminate webs and labels made thereof being removable in a washing process. More specifically, the invention relates to an adhesive layer.

Background of the Invention

It is general practice to apply labels to the surface of containers, like bottles made of polymer or glass, to provide decoration, identification, and/or information for example on the contents of the container. Plastic labels, in contrast to paper labels, are increasingly preferred, for example due to their more appealing appearance (for example transparency) and better mechanical properties. The containers, like bottles in the beverage industry, are generally reused many times and thus there is a need for plastic labels which are easily and completely removed from the surface of the container during conventional washing processes such as heated dilute caustic soda. Thus, removable labels are an important topic, for example, in beverage industry.

Wash-off labels, known from prior art, have been based on paper materials, which may become easily disintegrated into the washing liquid. Another known approach, which is typically used in combination with paper labels, has been to select adhesives which are soluble into water- based washing liquid and thus lead to the removal of the labels. The use of such adhesives requires that the label material allows the washing liquid to penetrate into the adhesive layer so that rapid loosening of the label is possible. Even if these approaches may facilitate quick and effective removal of the labels in the washing process without leaving markings or residues on the container, they may suffer from the major drawback that the washing liquid quickly becomes contaminated by the label material and/or the dissolved adhesive components. Yet another approach is that the label structure comprises a heat-shrinkable plastic film layer(s) causing the label to curl and detach the label from the surface of an item under typical washing conditions at 80-85 °C in an alkaline solution. Typically these labels consist of a release liner, for example a polyester film, coated with silicone which is then further coated with a pressure-sensitive adhesive and dried under heat in an oven. This adhesive layer is then laminated further with a monoaxially oriented heat-shrinkable polyester (PET) or polyvinylchloride film (PVC), in which case the adhesive preferentially transfers to the PVC or PET filmic surface. The major deficiencies of these types of constructions are that they are rather costly and in addition, in some cases they are using environmentally unfriendly PVC solutions.

It would be desirable to produce wash-off labels which are economical but also environmentally friendly, totally removable from a surface of an item without leaving deposits or remnants of adhesive on the surface of the item. It would be further desired that the washing liquid is not contaminated with the adhesive. Summary of the Invention

It is an object of the present invention to provide a label, which is easy to wash off during conventional washing processes. It is an object of the present invention to provide a laminated structure for removable labels used in labelling of reusable items, like glass or plastic bottles or other reusable containers.

According to one aspect of the present invention there is provided a laminated label structure comprising a facestock and an adhesive layer. The label is removable from surface of an item during a washing process of the item. The adhesive layer comprises an acrylic block copolymer and is water absorbable.

According to a second aspect of the invention a method for producing a label is provided. The method may comprise combining an adhesive layer, wherein the adhesive layer comprises an acrylic block copolymer and is water absorbable, to one side of a release liner and to one side of a facestock so as to form laminated label structure. The laminated label structure may be further cut so as to form labels.

According to a third aspect of the invention a use of a label for labelling recyclable or reusable items is provided.

According to a fourth aspect of the invention a use of an acrylic block copolymer comprising PMMA based end blocks together with hydrophilic acrylic co-monomers mid block for labels removable from surface of an item during a washing process of the item is provided. The acrylic block copolymer may be at least partly in nanostructured and cohesive form and it may provide a swelling adhesive for the label. Washing liquid may comprise an alkaline washing liquid.

According to a fifth aspect of the invention a method for removing a label from a surface of an item is provided. The method may comprise at least exposing the adhesive layer to alkaline washing liquid at a temperature in the range of from 60 to 90 °C.

According to a sixth aspect of the invention a combination of an item and a label, wherein the label has been attached to a surface of the item, is provided. The label comprises at least an adhesive layer which is water absorbable and includes an acrylic block copolymer. The item may be a recyclable or reusable item, such as a glass or plastic bottle, or other container.

Further embodiments of the invention are presented in the dependent claims.

The acrylic block copolymer comprises PMMA based end blocks and hydrophilic acrylic co-monomer mid block. The acrylic block copolymer may be at least partly nanostructured. The hydrophilic acrylic co-monomer of the acrylic block copolymer may have a glass transition temperature of approximately -30°C to -50 °C. The adhesive layer of a label may also retain its cohesion even when water is absorbed into the adhesive structure. The adhesive layer may absorb 40- 200% or more water when exposed to alkaline washing liquid during the washing process. The adhesive layer may swell when it is exposed to alkaline washing liquid during the washing process. The water absorption of the adhesive layer may be dependent on the pH of the washing liquid. The alkaline washing liquid of the washing process may contain 1 -4% caustic soda. pH of the alkaline washing liquid is above 7.

Description of the Drawings

Fig. 1 shows, in a cross-sectional view, a laminate web for labels,

Fig. 2 shows, in a cross-sectional view, a laminate web comprising die-cut labels,

Fig. 3 shows, in a cross-sectional view, individual labels released from the release liner,

Fig. 4 shows, in a side view, a label attached to the surface of an item, Fig. 5 shows, in a side view, a label removed from an item.

Detailed Description of the Invention

According to one aspect of the present invention there is provided a laminated label structure comprising a facestock and a swellable adhesive layer. The adhesive layer may consist of an acrylic block copolymer. The label may be pressure-sensitive adhesive (PSA) label. The invention is not limited only to self-adhesive type labels but covers also labels that may require activation by heat or other activation method in order to become tacky and thereafter attachable with pressure. According to one embodiment of the invention, the facestock of the label is a monolayer or a multilayer polymer film. The polymer film(s) may be oriented or non-oriented. In an embodiment, the facestock comprises plastic films which are not heat-shrinkable. Advantageously all materials of the label have heat-shrinkability substantially less than 5% at temperatures between 60 to 90^°C, even in wet conditions. Heat-shrinkability means a dimensional change of a material in at least one direction when the temperature of the material is increased from 25 to 90 ^°C. Film(s) of the facestock may be non moisture penetrable. Alternatively the plastic film(s) may absorb moisture. In an embodiment, the facestock may comprise plastic film(s) having minor or more pronounced heat-shrinkability.

A wide variety of polymer film materials are useful in preparing the polymer film(s) of facestock. Polymer film may include homopolymers, copolymers or it may be a polymer blend. For example film(s) may comprise polyethylene, polystyrene, polyester, or mixtures thereof. Polymer film(s) may also be degradable and/or derived from renewable sources, such as cellulose or lactic acid based polymer. According to an example embodiment of the invention, the facestock may include biaxially oriented polypropylene (BOPP). According to another embodiment of the invention, the facestock is a paper material.

According to one embodiment of the invention, the adhesive layer comprises an acrylic block copolymer. An acrylic block copolymer adhesive may be a solvent based or a hot melt. The acrylic block copolymer may comprise poly(methyl methacrylate) (PMMA) blocks and hydrophilic acrylic co- monomer blocks. The PMMA blocks may be located as end blocks and hydrophilic acrylic co-monomer as mid block of the copolymer chain. The one part of the block copolymer chain, such as PMMA blocks, may have a relatively high glass transition temperature which imparts excellent cohesion to the polymer. The another part of the block copolymer, such as hydrophilic co-monomer blocks, may be relatively soft with a glass transition temperature of approximately -30 ^°C to -50 ^°C which imparts good tack properties to the adhesive and high water absorption when the adhesive is subjected to aqueous conditions like during the washing processes. In a preferred embodiment, the acrylic block copolymer is such that the water absorption capability and/or rate is strongly pH dependent. Using washing solution pH values from neutral to alkaline the water absorption is thus significantly increased. This preferred behaviour can be obtained using copolymers with PMMA based end blocks together with hydrophilic acrylic co-monomer mid block. Such a combination with certain non-compatibility between the end and mid blocks leads to a degree of nanostructuration of the polymer, i.e. formation of three-dimensionally organized structures deviating from typical purely amorphous structures that do not contain any longer- range order characteristics of a crystalline structure. This nanostructuration provides the capability of the structure to absorb and hold significant amount water without losing cohesion but instead leading to swelling of the structure. According to one embodiment of the invention, the water absorption and thus swelling of an acrylic adhesive may be increased by the addition of small amounts of basic components to the adhesive, e.g. potassium hydroxide (KOH) or any other alkaline components. It is observed that the water absorption (weight gain) of the adhesive may be of approximately 40 to 200% at pH 7 without losing the cohesive properties of the adhesive. In more alkaline environment, like alkaline washing liquid containing 1 -4% caustic soda, the water absorption may be even significantly more pronounced. Cohesive properties of the adhesive is important factor when trying to avoid the dissolving of the adhesive into the washing liquid and the contamination of the liquid.

According to one embodiment of the invention, the label laminate structure may consists of only one adhesive layer comprising acrylic block copolymer which is applied against the facestock and which adhesive layer bonds the label to the surface of an item.

According to another embodiment of the invention, the laminate structure may have a multilayer adhesive structure including additional adhesive layer(s). These additional adhesive layer(s) may comprise other adhesive compositions than acrylic block copolymer. These additional layer(s) may be used to bond the label to the surface of the item. Additional adhesive layers may also be sublayers between an adhesive layer comprising an acrylic block copolymer and facestock.

In wash off process, the adhesive layer with acrylic block copolymer according to the invention intakes significant amounts of water and alkalines, whereupon the strong swelling of this adhesive layer aids to lift of the label from the surface and allows the wash off liquid to deaden the adhesive causing the label to lift of and become removed.

According to another aspect of the present invention there is provided a method for producing a pressure-sensitive laminated structure for labels. The manufacturing comprises at least the following steps: coating a release liner with a releasing agent e.g. silicone, coating a facestock with adhesive layer(s), laminating the facestock layer and the release liner together with the adhesive layer(s) in between. Alternatively adhesive layer(s) may be coated on top of the release agent layer of the release liner. According to further aspect of the present invention there is provided a use of the label for labelling of reusable or recyclable items like glass or plastic bottles or other containers. The label may be attached to a surface of an item, e.g. to a glass or plastic bottle or other container and the swellable adhesive is in contact with the surface of the item.

According to still further aspect of the present invention there is provided a method for removing the label from a surface of an item. The label is a wash- off label i.e. it is easily removed from the surface of an item labelled. The method comprises exposing the label to an alkaline washing liquid at temperature which is in the range of 60-90 ^°C. The alkaline washing liquid may contain 1 -4% caustic soda (by weight). When the adhesive layer is exposed to a washing liquid the adhesive layer starts to absorb water which facilitates and allows the fast removal of the label from the surface of an item. The label is removed through swelling i.e. expanding of the adhesive layer. Due to the swelling of the adhesive, it may lose at least partially a contact with the surface of the item causing at least the edges of the label to lift. The washing liquid may further penetrate into the gap between the adhesive layer and the surface of the item. The adhesive force of the adhesive layer will be reduced causing the label to be removed cleanly from the surface so that it will not leave residues on the surface. During wash-off process the adhesive layer maintains it cohesive properties and stays on the facestock film layer of the label thus the washing liquid is not contaminated with the adhesive.

Referring to the Fig. 1 , a laminate web structure 1 for labels comprises a facestock layer 2, also referred as a face layer, or a facing material, an adhesive layer 4, and a release liner 6. The release liner may be a polymeric film, such as a polyester or polypropylene film, or a paper based, such as a glassine or kraft paper. The thickness of the liner may be, for example, 25 microns. The release liner may be coated with a thin layer of releasing agent, such as a silicone polymer, in order to ease the subsequent removal of the release liner from the label structure before the label is adhered to the surface of an item. During the manufacture of a label laminate web structure 1 , the release liner 6 may be coated with an adhesive layer 4, such as a pressure-sensitive adhesive, and dried under heat in an oven. Subsequently the release liner with an adhesive layer may be combined (laminated) with a facestock layer 2 in order to form a laminated web structure. Alternatively, the adhesive layer may be applied on the facestock prior to combining with the release liner. One purpose of a release liner of the label laminate structure is to protect the adhesive layer of the label and allow efficient handling until the label is ready to be used and adhered to another surface, such as the surface of a bottle.

Referring to the Fig. 2, individual labels 3 may be cut from the laminate web structure 1 . After cutting, a number of individual labels 3 may be attached to a liner 6, which remains uncut and continuous. Thus, a release liner may provide also a die-cutting base. Alternatively, the individual labels 3 may be completely separate, i.e. also the liner 6 may be cut. A label refers to a product which comprises at least a face layer 2 and an adhesive layer 4. Prior to the application the label comprises also a release liner 6. Referring to the Fig. 3, the label 3 may be separated from the liner 6 prior to the application of the label. Thus, when using the label, i.e. when attaching a label to another surface, a surface of the adhesive layer 4 is exposed so that said label can be attached to an item 5, as shown in Fig. 4. The adhesive layer 4 may be in direct contact with a surface 7 of the item 5, such as a bottle or another container.

According to one embodiment of the invention, the facestock 2 of the label is a monolayer film. Alternatively, a multilayer polymer film may be used as a facestock layer. The polymer film(s) may be oriented or non-oriented. In an embodiment, the facestock comprises plastic films which are not heat- shrinkable. Advantageously all materials of the label have heat-shrinkability substantially less than 5% at temperatures between 60 to 85 °C, even in wet conditions. Heat-shrinkability means a dimensional change of a material in at least one direction when the temperature of the material is increased from 25 to 85 °C. Film(s) of the facestock may be non-moisture penetrable. Alternatively, the plastic film(s) may absorb moisture. If the facestock of the label is able to absorb moisture it may facilitate the label removal during the washing process from the surface to which it is attached. In an embodiment, the facestock may comprise plastic film(s) having minor or more pronounced heat-shrinkability. The heat-shrinkage of the film may also promote the label removal during washing process. The thickness of the facestock layer may be from 30 to 60 microns, preferably from 40 to 50 microns. The facestock is preferably clear, i.e. substantially transparent to visible light. The clear facestock layer is preferred, as it allows the objects beneath such layer, i.e. the bottle or its contents, to be seen through such layer. The facestock has a haze less than 25%, preferably less than 15%, and most preferably less than 10% (according to standard ASTM D1003).

The facestock layer 2 of a label may also comprise graphic patterns, in order to provide visual effect and/or in order to display information. The facestock layer may be printed by any known printing methods, such as gravure or flexographic processes. Graphic patterns may be printed either on the first or second surface of the facestock layer, or alternatively on both surfaces. The second side of the face layer is subsequently contacting the adhesive layer 4.

The label laminate may also comprise other layers, such as additional adhesive layers, print layers or protective layers, in order to improve the label properties, functionality or appearance.

A wide variety of polymer film materials are useful in preparing the polymer film(s) of facestock. Polymer film may include homopolymers, copolymers or it may be a polymer blend. For example film(s) may comprise polyethylene, polystyrene, polyester, or mixtures thereof. Polymer film(s) may also be degradable and/or derived from renewable sources, such as cellulose or lactic acid based polymer. According to an example embodiment of the invention, the facestock may include biaxially oriented polypropylene (BOPP).

The label may be a pressure-sensitive adhesive (PSA) label, i.e. the adhesive layer comprises a pressure sensitive adhesive. PSA labels are adhered to the surface of an item through said adhesive layer forming a bond when pressure is applied on the label at room temperature. PSA labels may also be called as self-adhesive labels or self-stick labels. The present invention is not limited only to self-adhesive type labels, but covers also labels that may require activation by heat or other activation method in order to become tacky and thereafter attachable with pressure. For example, certain types of hot melt adhesives that are not significantly tacky at room temperature and require heat or other activation to become tacky and attachable with pressure may be used.

According to the invention, the adhesive layer comprises an acrylic block copolymer. An acrylic block copolymer adhesive may be a solvent based or a hot melt adhesive. The acrylic block copolymer may comprise poly(methyl methacrylate) (PMMA) blocks and hydrophilic acrylic co-monomer blocks. The PMMA blocks may be located as end blocks and hydrophilic acrylic co- monomer as mid block of the copolymer chain. The one part of the block copolymer chain, such as PMMA blocks, may have a relatively high glass transition temperature which imparts excellent cohesion to the polymer. The another part of the block copolymer, such as hydrophilic co-monomer blocks, may be relatively soft with a glass transition temperature of approximately from -30 °C to -50 °C which imparts good tack properties to the adhesive and high water absorption when the adhesive is subjected to aqueous conditions for example during washing processes.

The adhesive layer may be transparent, thus allowing its use in label applications where clear labels enabling objects to be visible beneath the label are preferred.

In an embodiment, the adhesive layer is water absorbable, i.e. the adhesive layer is able to absorb water or aqueous liquid, such as an alkaline washing liquid in a washing process during the removal of the label from a surface upon which the label is applied. Alkaline washing liquid may also be called as an alkaline solution or alkaline water. The water absorption capability and/or rate of the adhesive layer may be adjusted. Preferably, the water absorption capability and/or rate is pH dependent and may be controlled through the adhesive layer composition comprising an acrylic block copolymer. By using washing solution pH values from neutral to alkaline the water absorption of the adhesive layer may be significantly increased. For example at pH 4 the water absorption may be from 10 to 80 % and at pH 7 from 40 to 200 %.

Controlled water absorption and/or rate can be obtained using copolymers with PMMA based end blocks together with a hydrophilic acrylic co-monomer mid block. Such combination has certain non-compatibility between the end and mid blocks which leads to a degree of nanostructuration of the polymer, i.e. formation of three-dimensionally organized structures deviating from typical purely amorphous structures that do not contain any longer-range order characteristics of a crystalline structure.

Due to this specific adhesive layer comprising acrylic block copolymer wherein the hydrophilic co-monomers in the mid-block are structured in an organized manner, i.e. the copolymer has nanostructured polymer structure, the adhesive layer is capable of absorbing water, such as alkaline washing liquid, which further causes swelling of the adhesive layer. Thus, it may be the specific adhesive layer composition and its nanostructuration which provides the capability of the adhesive structure to absorb and hold a significant amount of water without losing cohesion but instead leading to the swelling of the structure. Nanostructured polymer structure may be achieved, for example, during process of controlled radical polymerization.

An acrylic block copolymer comprising PMMA based end blocks together with hydrophilic acrylic co-monomers mid block and having at least partly nanostructured and cohesive form may be used to provide a swelling adhesive layer for labels removable from surface of an item during a washing process of the item in an alkaline washing liquid. The act of using an adhesive layer which is able to swell is beneficial especially in label applications wherein subsequent label removal, i.e. detachment of the label, in washing processes is desired. The swelling of the adhesive layer may cause the edges of the labels to lift thereby allowing the alkaline washing solution to reach the adhesive, and subsequently to deaden it, causing the label to fall off from the surface to which it is attached. Further, an ability of the adhesive layer to retain its cohesion may prevent the washing liquid to be contaminated with the adhesive.

Thanks to the present invention, it is possible to achieve a label structure having a single-layer facestock, i.e. the facestock layer of the label may comprise a single-layer film, such as a normal BOPP film or cellulosic film. Thus, the use of facestock comprising shrinkable films or laminated multilayered structures may be avoided. The act of using single-layer facestock results in a great simplification of the manufacturing process of the label. It may also result in reduction in the material costs of the label. Another effect of the invention is that during the removing process of the labels, i.e. an industrial washing process, the labels remain relatively flat after removal from the article and do not curl up into tight shapes, such as "needlelike" shapes, which can block-up the washing apparatus and are difficult to remove from the apparatus. The labels also exhibit fast washing times. Fast washing time being on the average less than 45 seconds, preferably 30 seconds or less.

According to one embodiment of the invention, the water absorption and thus the swelling of an acrylic adhesive may be increased by the addition of small amounts of basic components to the adhesive layer, e.g. potassium hydroxide (KOH) or any other alkaline components. The adhesive layer may also comprise other components, such as a plasticizer, a tackifier, or a filler. Other components may be used in order to affect adhesive properties and/or performance, such as to reduce melt viscosity, to adjust the tack and adhesion properties and to reduce the costs. For example, in addition to the acrylic block copolymer, polyvinyl methylether resin, polyethylene glycol, and amine (2- amino 2 methyl propanol as a pH adjusting agent may be included to the formulation of adhesive layer .

It is observed that the water absorption of the adhesive layer may be approximately from 40 to 200% at pH 7 without losing the cohesive properties of the adhesive. Water absorption is measured as a weight gain of the adhesive layer. Preferably, the water absorption of the adhesive layer is approximately 200% at pH 7. The increased water absorption provides more pronounced swelling of the label, thus helping the subsequent label removal in a washing process. In more alkaline environment, for example in an alkaline washing liquid containing 1 -4% caustic soda, the water absorption may be even significantly more pronounced. Cohesive properties of the adhesive are important factors when trying to avoid the dissolving of the adhesive into the washing liquid and the contamination of the liquid. Thus, with the adhesive having cohesive properties, the washing does not become contaminated by the dissolved adhesive components. According to an embodiment, the label laminate structure may consists of only one adhesive layer comprising an acrylic block copolymer which is applied against the facestock and which adhesive layer bonds the label to the surface of an item. Alternatively, the laminate structure may have a multilayer adhesive structure including additional adhesive layer(s). These additional adhesive layer(s) may comprise other adhesive compositions than the acrylic block copolymer. These additional layer(s) may be used to bond the label to the surface of the item. Additional adhesive layers may also be used as sublayers between an adhesive layer comprising an acrylic block copolymer and facestock. By using multi-layered adhesive structure, for example, the properties and performance of the adhesive layer, such as bond properties (adhesion to variety of substrates), migration of adhesive components to the facestock and environmental resistance can be modified, thus providing tailor-made labels for specific applications.

In the wash-off process of the label from the surface upon which the label is applied, the adhesive layer comprising an acrylic block copolymer intakes significant amounts of alkaline water, whereupon the strong swelling of this adhesive layer aids to lift of the adhesive layer of the label from the surface at least partially and consequently allows the wash-off liquid to deaden the adhesive causing the whole label to lift off and become removed from the surface of an item upon which the label is applied

According to another aspect of the present invention, there is provided a method for producing a pressure-sensitive laminated structure for labels. The manufacturing process comprises at least the following steps: coating a release liner with a releasing agent e.g. silicone, coating a facestock with adhesive layer(s), wherein at least one adhesive layer comprises an acrylic block copolymer and is water absorbable, laminating the facestock layer and the release liner together with the adhesive layer(s) in between. Alternatively, adhesive layer(s) may be coated on top of the release agent layer of the release liner. Laminated label structure may be further cut so as to form labels.

According to a further aspect of the present invention there is provided a use of the label for labelling of reusable or recyclable items like glass or plastic bottles or other containers. The label may be attached to a surface of an item, e.g. to a glass or plastic bottle or other container and the swellable adhesive, such as an acrylic block copolymer comprising poly(methyl methacrylate) (PMMA) blocks and hydrophilic acrylic co-monomer blocks, is in contact with the surface of the item. Alternatively, the swellable adhesive may be a part of a multilayer adhesive structure, wherein another adhesive is used to bond the label to the surface of an item.

According to still another aspect of the present invention there is provided a method for removing the label from a surface of an item during a washing process of the labelled article, i.e. in standard bottle washing conditions. As defined herein, the removability or wash-off capability of a label refers to the capability of the label to be removed from the surface of an article upon which the label is adhered in a solution, e.g. warm caustic washing solution during the re-using process of the labelled article. According to the invention, the label is a wash-off label, i.e. it is easily removed from the surface of an item labelled as shown in Fig. 5. Ideally, the label 3 of an article is completely removed during a washing process with no residue being left on the surface 7 of the article. Additionally, the short amount of time the labelled article must remain in the washing solution before the label is removed is preferred. The removal of the label within less than 50 seconds, preferably within less than 30 seconds is considered as a good wash-off result. The washing process comprises a washing liquid, e.g. an alkaline washing solution.

The method for removing the label from a surface of an item comprises exposing the label to an alkaline washing liquid at a temperature which is in the range of 60-90 °C. The alkaline washing liquid may contain e.g. from 0.5 to 10%, in particular from 1 to 4% caustic soda (by weight). The pH of the alkaline washing liquid is above 7. The temperature of the washing liquid may be e.g. higher than or equal to 60 °C, preferably in the range of 80-85 °C. During the washing process the label is exposed to the washing liquid and the adhesive layer 4 loses its adhesive force, and the label is subsequently detached from the surface 7. When the adhesive layer is exposed to a washing liquid the adhesive layer starts to absorb water which facilitates and allows the fast removal of the label from the surface of an item. The label is removed through swelling i.e. expanding of the adhesive layer. Due to the swelling of the adhesive, it may lose at least partially the contact with the surface of the item, causing at least the edges of the label to lift. The washing liquid may further penetrate into the gap between the adhesive layer and the surface of the item. The adhesive force of the adhesive layer will be reduced, causing the label to be removed cleanly from the surface so that it will not leave residues on the surface. During the wash-off process the adhesive layer maintains it cohesive properties and stays on the facestock film layer of the label, and thus the washing liquid is not contaminated with the adhesive.

Example A

Labels having a facestock layer comprising a regenerated cellulose film and an adhesive layer comprising: an acrylic block copolymer (Arkema Nanostrength CRPH), polyvinyl methylether resin ( Lutonal M40 - BASF ), polyethylene glycol ( Pluriol E600 - BASF ) and amine ( 2- amino 2 methyl propanol) as a pH adjusting agent were produced. The labels were applied to surface of bottles and conditioned for 24 hours at 55 °C. Subsequently, the labelled bottles were washed by immersing the bottles in 1 ,5% caustic soda solution having temperature of 80 °C During washing the labels were observed to be washed off of the bottle surface within average of 27 seconds.

For the person skilled in the art, it will be clear that modifications and variations of the products and the methods according to the present invention are perceivable.

The various aspects of the invention are also illustrated by the following examples. Example 1 . A wash off label comprising:

- a facestock;

- an adhesive layer,

wherein the adhesive layer comprises an acrylic block copolymer with pH dependent water absorption. Example 2. The label according to example 1 , wherein the acrylic block copolymer comprises PMMA based end blocks together with hydrophilic acrylic co-monomer mid block. Example 3. The label according to example 1 , wherein the acrylic block copolymer is at least partly nanostructured.

Example 4. The label according to any of the examples 1 to 3, wherein the acrylic block copolymer retains cohesion even with water absorbed into the structure.

Example 5. The label according to example 2, wherein the hydrophilic acrylic co-monomer has a glass transition temperature of approximately -30 °C to - 50 0.

Example 6. The label according to any of the examples 1 to 5, wherein the adhesive absorbs 40-200% or more water when exposed to alkaline washing liquid. Example 7. The label according to any of the examples 1 to 6, wherein the adhesive layer swells when exposed to alkaline washing liquid.

Example 8. The use of a label according to any of the examples 1 -7 for labelling recyclable or reusable items.

Example 9. A method for removing a label from a surface of an item, the label comprising a facestock, an adhesive layer, wherein the adhesive layer comprises an acrylic block copolymer, the method comprising exposing the adhesive layer to alkaline washing liquid at a temperature in the range of 60- 90 °C.

Example 10. The method according to example 9, wherein the alkaline washing liquid contains 1 -4% caustic soda. Example 1 1 . The method according to example 9 or 10, wherein the pH of the alkaline washing liquid is above 7.

Example 12. The use of acrylic block copolymer comprising PMMA based end blocks together with hydrophilic acrylic co-monomers mid block in a at least partly nanostructured and cohesive form as swelling adhesive for labels removable in alkaline washing liquid.

The embodiments described above are only example embodiments of the invention and a person skilled in the art recognizes readily that they may be combined in various ways to generate further embodiments without deviating from the basic underlying invention.

Claims

Claims:

1 . A label which is removable from surface of an item during a washing process of the item, the label comprising:

- a facestock and

- an adhesive layer,

wherein the adhesive layer comprises an acrylic block copolymer and is water absorbable.

2. The label according to claim 1 , wherein the acrylic block copolymer comprises PMMA based end blocks and hydrophilic acrylic co-monomer mid block.

3. The label according to claim 1 or 2, wherein the acrylic block copolymer is at least partly nanostructured.

4. The label according to any of the claims 1 to 3, wherein the hydrophilic acrylic co-monomer of the acrylic block copolymer has a glass transition temperature of approximately -30 °C to -50 °C.

5. The label according to any of the claims 1 to 4, wherein the adhesive layer retains cohesion even with water absorbed into the structure.

6. The label according to any of the claims 1 to 5, wherein the adhesive layer absorbs 40-200% or more water when exposed to alkaline washing liquid during the washing process.

7. The label according to any of the claims 1 to 6, wherein the adhesive layer swells when exposed to alkaline washing liquid during the washing process.

8. The label according to claim 6 or 7, wherein the water absorption of the adhesive layer is dependent on the pH of the washing liquid.

9. The label according to claims 8, wherein the alkaline washing liquid contains 1 -4% caustic soda.

10. The use of a label according to any of the claims 1 to 9 for labelling recyclable or reusable items.

1 1 . A method for removing a label from a surface of an item, the label comprising a facestock, an adhesive layer, wherein the adhesive layer comprises an acrylic block copolymer and is water absorbable, the method comprising exposing the adhesive layer to alkaline washing liquid at a temperature in the range of from 60 to 90 °C.

12. The method according to claim 1 1 , wherein the alkaline washing liquid contains 1 -4% caustic soda.

13. The method according to claim1 1 or 12, wherein the pH of the alkaline washing liquid is above 7.

14. The use of acrylic block copolymer comprising PMMA based end blocks together with hydrophilic acrylic co-monomers mid block in a at least partly nanostructured and cohesive form as swelling adhesive for labels removable from surface of an item during a washing process of the item in an alkaline washing liquid.

15. A combination of an item and a label, wherein the label has been attached to a surface of the item, the label comprising

- a facestock and

- an adhesive layer,

16. A method for producing a label, the method comprising:

combining an adhesive layer, wherein the adhesive layer comprises an acrylic block copolymer and is water absorbable, to one side of a release liner and to one side of a facestock so as to form laminated label structure, cutting the laminated label structure so as to form labels.