Paper label

Abstract

The invention relates to a method for manufacturing a paper label (2) comprising a face (1) and a pressure sensitive adhesive layer (4) for adhering the paper label (2) to a surface of an item to be labelled, wherein the face (1) comprises a paper, wherein the method comprises: applying an acrylic adhesive onto a surface, wherein the acrylic adhesive comprises a wash-off additive, the wash-off additive comprising a resinous material and a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, and drying the acrylic adhesive in order to form an acrylic pressure sensitive adhesive onto the surface, thereby obtaining the paper label The invention relates to a use of a wash-off additive for an acrylic pressure sensitive adhesive of a direct thermal wash-off paper label. The invention further relates to a paper label (2).

Description

[0001] PAPER LABEL

[0002] Technical field

[0003] The application relates to paper labels. The application particularly relates to pressure-sensitive wash-off paper labels. The application further relates to a method for manufacturing a paper label. The application relates to use of a wash-off additive for paper labels.

[0004] Background

[0005] It is general practice to apply a label to a surface of an item to provide decoration, and / or to display information about the product being sold, such as the content of the item, a trade name or logo. Alternative type of labelling technologies and labels are available, such as pressure-sensitive, wet glue, wrap around and shrink sleeve labels.

[0006] Containers, such as bottles in the beverage industry, are generally re-used or recycled. Therefore, there is a need for labels which are easily removed from the surface of the container during washing processes. Thus, removable labels are an important topic, for example, in beverage industry.

[0007] Summary

[0008] It is an object of this application to provide a paper label. Another object is to provide a combination of a label and an item, wherein the item is afterwards recycled or reused. Yet another object is to provide a method for manufacturing a paper label. Still another object is to provide a use of a wash-off additive for paper labels for improving washability of paper labels.

[0009] Aspects of the invention are characterized by what is stated in the independent claims. Some preferred embodiments of the invention are disclosed in the dependent claims. These and other embodiments of the invention are disclosed in the description and figures. Nowadays, producers and end users are looking for environmentally friendly solutions. The paper label according to this specification can be used in various applications for avoiding plastic based labels.

[0010] Advantageously, the paper label according to this specification is a plastic film free as well as a metal foil free. Thus, preferably, the paper label does not contain, for example, a layer made of a plastic. Technical effect is to provide environmentally friendly product.

[0011] Conventionally, washing temperatures of wash-off processes have been around +85°C. Due to environmental and cost reasons, nowadays a new target is to decrease washing temperature to +40°C. However, washing temperatures below 50°C have been challenging for PSA labels.

[0012] Surprisingly, the novel paper label can be washed efficiently during recycling process of plastic bottles. The novel paper label can be efficiently washed in plain water by using temperatures down to 40°C. Thus, the paper labels do not need alkaline conditions for the washing process. Further, thanks to the novel solution, wash-off time of paper labels can be substantially decreased. Particularly, the wash-off time of the paper labels can be substantially decreased at 40°C in plain water, compared to solutions without the wash-off additive.

[0013] Thanks to the novel paper label, desired properties for labels can be obtained in more environmentally friendly way than with plastic based wash-off labels. Further, as discussed, the paper label can be recycled at 40°C by using plain water. The reduced temperature and wash-off time, as well as a washing process without an alkaline agent, is advantageous for the environment.

[0014] The paper label according to this specification is typically a wash-off paper label. In an advantageous embodiment, the paper label is a direct thermal wash-off paper label, most preferably a direct thermal linerless wash-off paper label.

[0015] A paper label according to this specification comprises a face and a pressure sensitive adhesive layer for adhering the paper label to a surface of an item to be labelled. The face according to this specification comprises a paper. The pressure sensitive adhesive layer of the paper label can comprise an acrylic pressure sensitive adhesive which comprises a wash-off additive. The wash-off additive can comprise a resinous material, preferably selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof, and a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol. The capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether, preferably the capped polyalkylene glycol is a methyl ether capped polyethylene glycol. Technical effect of the wash-off additive is that washability of the paper label comprising an acrylic adhesive is substantially improved. Surprisingly, the novel paper label comprising the modified adhesive comprising the acrylic adhesive and the wash-off additive clearly improved acrylic polymer wash-off properties in low temperature washing processes at +40°C in water, without an alkaline agent.

[0016] For improving efficiency of the wash-off additive, an amount of the wash-off additive can be more than 0.5 wt.%. The wash-off additive can start to improve washability of the paper label even when a very small amount of more than 0.5 wt.% is used. The effect of the wash-off additive can start to decrease when the amount of the wash-off additive exceeds 3 wt.%. The amount of the wash- off adhesive can be equal to or less than 3 wt.%, preferably the amount of the wash-off adhesive is from equal to or more than 1 wt.% to equal to or less than 3 wt.%, calculated from total dry weight of the acrylic adhesive. In an advantageous example, the amount of the wash-off additive is in a range between 1 .5 wt.% and 2.7 wt.%, calculated from total dry weight of the acrylic adhesive.

[0017] For improving washability of the paper label, a molar ratio between the rosin ester and the capped polyalkylene glycol can be 0.05:1 to 1 :1 , preferably at least 0.4:1 , and most preferably from 0.7:1 to 0.9:1 .

[0018] In order to further improve washability of the paper label, an amount of the grafted rosin ester with respect to the resinous material can be from about 1 wt.% to about 8 wt.%. In an advantageous embodiment, the resinous material comprises or is the rosin resin. Furthermore, for the improved washability, the preferred polyalkylene glycol is a polyethylene glycol, and the alkyl ether is preferably a methyl ether. Most preferably, the capped polyalkylene glycol is a methyl ether capped polyethylene glycol for efficient and fast washing process of the paper label.

[0019] In an embodiment, the paper label has high wet strength so that the paper is not broken during the washing process. In this embodiment, the PSA can be configured to be attached to the face during the washing process. Technical effect is that the PSA can protect the paper during the washing process. The acrylic wash-off adhesive comprising the acrylic adhesive and the wash-off additive can cause adhesion of the pressure sensitive adhesive to the labelled item to be efficiently decreased during a washing process so that the PSA can still remain attached to the face.

[0020] Preferably, the acrylic adhesive comprises 2-ethylhexyl acrylate (2-EHA) and / or butyl acrylate as the wash-off adhesive can efficiently improve washability of the acrylic adhesive comprising 2-ethylhexyl acrylate and / or butyl acrylate. In an advantageous embodiment, the acrylic adhesive comprises 2-ethylhexyl acrylate (2-EHA).

[0021] Technical effects of the paper label include good mechanical properties which can facilitate the processability and handling of the labels in the labeling process while the washing additive improves washability in the washing processes.

[0022] A method for manufacturing a paper label comprising a face and a pressure sensitive adhesive layer for adhering the paper label to a surface of an item to be labelled, can comprise the steps of A or B as follows:

[0023] A) applying an acrylic adhesive onto a first surface of the face, wherein the acrylic adhesive comprises a wash-off additive, the wash-off additive comprising o preferably, an aqueous phase, o a resinous material, preferably selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof, and o a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether, preferably the capped polyalkylene glycol is a methyl ether capped polyethylene glycol, and

[0024] -drying the acrylic adhesive in order to form an acrylic pressure sensitive adhesive onto the first surface of the face, or

[0025] B) applying an acrylic adhesive onto a carrier material, wherein the acrylic adhesive comprises a wash-off additive, the wash-off additive comprising o preferably, an aqueous phase, o a resinous material, preferably selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof, and o a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether, preferably the capped polyalkylene glycol is a methyl ether capped polyethylene glycol, drying the acrylic adhesive in the carrier material in order to form an acrylic pressure sensitive adhesive onto the carrier material, and transferring the acrylic pressure sensitive adhesive to the first surface of the face, thereby obtaining the paper label.

[0026] The carrier material, if used, may be a belt, for example a silicone belt, a plastic belt, such as a nylon belt, or a metal belt, such as a steel belt. Alternatively, the carrier material may be a batch of a web material.

[0027] A polymer gel content of the water-based acrylic adhesive can be at least 20%, preferably in a range between 60% and 75%. This polymer gel content, and particularly the range from 60% to 75%, can improve adhesion performance of the acrylic adhesive. A mean particle size of the water-based acrylic adhesive can be at least 100 nm and 800 nm at the most, measured as a mean particle diameter. Thanks to said range, properties of the acrylic adhesive, such as a solid content and a viscosity level of the acrylic adhesive, can be controlled and adjusted to a desired level.

[0028] The paper label according to this specification can be adhered to a surface of an article, such as a beverage bottle. Thus, the paper label according to this specification can be used for labelling a beverage bottle.

[0029] In the washing process, the pressure sensitive adhesive comprising the wash- off adhesive, which is sensitive to the washing conditions, is efficiently detached from the labelled item. Thanks to the novel solution, adhesion of the adhesive efficiently decreases at the washing process, providing a technical effect of detaching the paper label efficiently from the item.

[0030] Thanks to the novel solution, the pressure sensitive adhesive can be easily and fast deactivatable at a temperature at 40°C in water, typically without alkaline conditions. The alkaline conditions refer to an aqueous solution containing alkaline agent, such as NaOH, KOH, LiOH, MgOH, CaOH, or combination thereof. Probably the most common alkaline agent is sodium hydroxide NaOH, which is also called caustic soda. The alkaline liquid generally contains about 0.5-4% (w / w) of the alkaline agent(s). However, thanks to the novel solution using the acrylic adhesive comprising the wash- off additive, alkaline conditions are not needed at the washing temperature of 40°C for obtaining suitable washing conditions for efficiently washing off the paper label according to this specification.

[0031] Therefore, thanks to the novel paper label according to this specification, washing conditions can be more environmentally friendly than conventionally and, furthermore, the paper label can be recycled cost-efficiently.

[0032] The adhesives according to this specification can be designed to have approval for direct or indirect food contact (food-safety), which is a requirement in certain food related label end use areas. For example, many HDPE bottles require labels having approval for food contact. The novel paper label can be good, cost efficient, and environmentally friendly product that is recyclable after usage. The adhesive that is water-based polymer emulsion can be suitable and approved for direct food contact. Furthermore, the paper label according to this specification can be suitable for use in food applications.

[0033] Brief of the

[0034] In the following, the invention will be described in more detail with reference to the appended drawings, in which:

[0035] Fig. 1 shows, in a perspective view, an example embodiment of a paper label,

[0036] Fig. 2 shows a cross section of a paper label laminate comprising diecut labels, and

[0037] Fig. 3 shows a labelled item comprising a paper label.

[0038] The Figures are intended to illustrate the general principles of the disclosed solution. Therefore, the illustrations in the Figures are not necessarily in scale or suggestive of precise layout of system components.

[0039] Detailed

[0040] The solution is described in the following in more detail with reference to some embodiments, which shall not be regarded as limiting.

[0041] The following reference numbers and denotations are used in this application:

[0042] Sx, Sy, Sz orthogonal directions

[0043] MRK1 marking, such as a printing,

[0044] DIR1 first direction,

[0045] DIR2 second direction,

[0046] 1 a face,

[0047] 2 a paper label,

[0048] 4 an adhesive layer,

[0049] 5 a release liner,

[0050] 6 a release layer of the release liner, 7 a substrate,

[0051] 8 a label laminate,

[0052] 100 an item, and

[0053] 101 a labelled item.

[0054] The embodiments and examples recited in the claims and in the specification are mutually freely combinable unless otherwise explicitly stated.

[0055] In this specification, the term “comprising” may be used as an open term, but it also comprises the closed term “consisting of.” Thus, unless otherwise indicated, the word “comprising” can be read as “comprising or consisting of’.

[0056] For the purpose of the present description and the claims, unless otherwise indicated, all ranges include any combination of the maximum and minimum points disclosed, and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

[0057] Percentage values relating to an amount of a material are percentages by dry weight (wt.%) unless otherwise indicated.

[0058] Term “web” refers to a continuous sheet of material. The web is generally processed by moving over rollers. Between processing stages, webs may be stored and / or transported as rolls.

[0059] Term “machine direction” (MD) refers to manufacturing direction of a web, i.e., running direction of the face or continuous label laminate during label manufacturing. In case of a rolled web, machine direction refers to a circumferential direction of the roll. Further, longitudinal direction of a web refers to the machine direction. MD may be equal to direction DIR1 of the label attached on the surface of an item.

[0060] Terms “cross direction” (CD) and “transverse direction" TD refer to a direction that is transversal to the machine direction. Thus, "transverse direction" TD and "cross direction" CD refer to the direction perpendicular to the running direction of the face or label laminate.

[0061] Term “gsm” refers to g / m2. Term “HDPE” refers to high density polyethylene. HDPE preferably has a density from 0.93 to 0.97 g / cm3.

[0062] Term “PP” refers to polypropylene. PP preferably has a density from 0.90 to 0.93 g / cm3.

[0063] Term “polyolefin bottle” refers to a polyolefin bottle, i.e., a bottle made of polyolefin(s).

[0064] Term “PET” refers to polyethylene terephthalate.

[0065] In this specification term "label" refers to a piece of material, which is used for labelling of an item. Label may be used to identify something. Label may be attached to an article. An article may be a package, such as a bottle. In other words, label is suitable to be applied to a surface of an item to provide decoration, and / or to display information about the product being sold, such as content information, a trade name, a logo, a barcode, or any other graphics.

[0066] The label according to this specification is a paper label.

[0067] Labels include, for example, labels used for packaging of beverages, food products, health and personal care products, pharmaceuticals, industrial chemicals, household chemicals or retail products.

[0068] Some example classes of labels are repositionable labels, removable labels, (washable) wash-off labels, resealable labels, no-look labels, deep freezer labels and security labels. It is to be noted that each class requires different properties for the label.

[0069] Containers, such as bottles, in the beverage industry are generally re-used or recycled. Therefore, there is a need for labels which are easily attached on to a surface of a container as well as removed from the surface of the container during washing processes. Thus, wash-off labels are an important topic, for example, in beverage industry. The present specification particularly relates to pressure-sensitive wash-off paper labels that can be washed off from an article. Thus, the paper label 2 according to this specification is preferably a wash-off label.

[0070] Term "wash-off label", also referred to as a washable label, refers to a label removable (detachable) from the surface of the item attached during subsequent washing process. At washing conditions having a temperature of 40°C, the adhesive bond between the label and the item the label is adhered to is weakened. A paper label 2 can comprise an adhesive layer sensitive to washing conditions. Paper labels can be used in labelling of beverage bottles. The paper label 2 according to this specification can be suitable for polyethylene terephthalate (PET) bottles. The paper label 2 according to this specification can be particularly suitable for polyolefin bottles, such as HDPE and PP bottles.

[0071] Term “face” refers to a substrate of the label, also called as a face stock or a face material.

[0072] In this specification, the term “adhesive coating” refers to a coating comprising an acrylic adhesive.

[0073] Term “PSA” refers to pressure sensitive adhesive(s). PSA according to this specification is an acrylic pressure sensitive adhesive.

[0074] Term “PEG” refers to polyethylene glycol(s).

[0075] Polymer gel content can be measured by using Dionex ASE 150 Solvent Extractor according to the following method:

[0076] Dionex ASE 150 Solvent Extractor has the following settings: Temperature - 100°C, Static Time - 30 min, Rinse Volume - 10%, Purge time - 60 seconds, Cell volume - 66 mL.

[0077] Equipment: 66 mL cell, 80 mm x 25 mm cellulose thimble, and acetone.

[0078] The method has the following steps:

[0079] 1 ) Weight dry thimble

[0080] 2) Add ~1 -1 .5 g wet adhesive to thimble by coating the inside in a thin film

[0081] 3) Dry in oven until no moisture left

[0082] 4) Weigh thimble + dry adhesive and insert into the 66 mL cell 5) Run through extractor process

[0083] 6) Remove thimble and dry in the oven until all the acetone is gone

[0084] 7) Repeat steps 5 and 6 two more times for a total of 3 cycles

[0085] 8) Dry the thimble one final time and measure weight

[0086] 9) With the values from steps 1 , 4 and 8, calculate polymer gel content percent as follows:

[0087] Polymer gel content = 100* (TAB - T) / (TAA- T) in which

[0088] Thimble dry weight = T

[0089] Thimble + adhesive before extraction dry weight = TAB

[0090] Thimble + adhesive after extraction dry weight = TAA

[0091] Adhesive before extraction weight = TAB - T Adhesive after extraction weight = TAA- T.

[0092] PAPER LABEL

[0093] As discussed, the paper label 2 is preferably a wash-off label. The wash-off label can also be referred to as a washable label, referring to a label removable (detachable) from the surface of the item attached to during subsequent washing process. A paper label 2 can comprise a pressure sensitive adhesive layer 4 sensitive to washing conditions.

[0094] The paper label 2 according to this specification can be washable at a washing temperature of 40°C, wherein washing liquid is water. Preferably, the washing liquid does not comprise an alkaline agent.

[0095] Referring to Figs 1 -2, a paper label 2 can comprise a face 1 and an adhesive layer 4 on the face 1 for adhering the label to the surface of an item to be labelled.

[0096] The paper label 2 can comprise at least the following layers: the face 1 , the acrylic PSA layer 4, and a print layer MRK1 .

[0097] Individual labels 2 can be die-cut from a continuous label web. Referring to Fig. 2, the paper label 2 can be a label laminate comprising a release liner 5. The release liner can protect the adhesive layer before the label is adhered to a surface of an item.

[0098] Alternatively, and referring to Fig. 1 , the paper label 2 can be a linerless label without the release liner 5. Elimination of release liners reduces the material costs of the labels but also avoids the disposal of the release liner after the labelling. Moreover, the exclusion of the release liner decreases the thickness in a roll of labels and more labels can be provided per roll. Thus, the paper label 2 can be a linerless paper label, such as a printed linerless paper label.

[0099] If the paper label 2 is the linerless label without the release liner 5, there is preferably a release layer on top of the face 1 for preventing adjacent layers of a linerless label roll for attaching to each other. The release layer is preferably a layer which does not cause problems for the washing process, such as a silicone based layer.

[0100] The paper label 2 can comprise the following layers, preferably in the following order:

[0101] - optionally, a release layer comprising a release agent, such as a silicone,

[0102] - a face 1 comprising a paper, and

[0103] - an adhesive layer comprising a wash-off additive and an acrylic pressure sensitive adhesive capable of forming a bond when pressure is applied at a room temperature.

[0104] The paper label 2 can be a printed paper label. The printing MRK1 may be subsequently top coated or laminated in order to protect the printing. Alternatively or in addition to the top coating and / or laminating, the reverse side of the face 1 adjacent to the adhesive layer 4 can be printed. Print layer is to be understood to include also decorations made by, for example, metallic or metallic like layers if such decorations are used in the label.

[0105] Thus, the paper label 2 comprises at least the face 1 comprising a paper, at least one adhesive layer 4, and optionally a release liner 5. The adhesive layer 4 comprises PSA. The PSA is used to enable the label to be attached to an item, an article, or a container. Preferably, the paper label 2 comprises only one layer of a paper. Further, preferably, the paper label 2 does not comprise a plastic layer. Thus, the paper label 2 preferably does not comprise, e.g., a thermoplastic film. Technical effect is to provide cost efficiently environmentally friendly wash-off label.

[0106] The paper label 2 may further comprise one or more additional layers, such as a primer layer. The primer layer may be arranged in between the face 1 and the adhesive layer. The primer layer may be arranged to increase the adherence of the adhesive layer to the face 1 .

[0107] FACE

[0108] The face 1 is adhered to the surface of an item during labelling through an adhesive layer 4. The face 1 comprises a first surface and a second surface. The first surface can refer to an adhesive side while the second surface can refer to a top side. The top side (i.e., the second surface of the paper label 2) can be printable e.g. by using heat.

[0109] The face 1 comprises a paper. The labels comprising a paper-based face 1 are typically environmentally friendlier material for labeling articles, such as e.g. bottles, than thermoplastic labels.

[0110] The paper can be calendered with a calender or a supercalender to obtain a high-density surface.

[0111] Preferably, for environmental reasons as well as for improving cost efficiency, the face 1 has only one layer of paper. Furthermore, the face 1 can have a paper substrate manufactured from FSC™ - certified (mix credit) pulp. Thus, the face 1 can comprise or consist of environmentally friendly materials. Thus, the paper label 2 can be better for the environment than some other kind of face materials.

[0112] The face 1 can comprise a paper comprising natural fibres as its main raw material. Natural fibres refer to any plant material that contains cellulose. The natural fibres are preferably wood based natural fibers. The wood based natural fibre may be from softwood trees, such as spruce, pine, fir, larch, douglas-fir or hemlock, and / or from hardwood trees, such as birch, aspen, poplar, alder, eucalyptus or acacia, or from a mixture of softwoods and hardwoods.

[0113] The face 1 can comprise cellulose fibers from both hardwood and softwood. Technical effect of the mixture of hardwood and softwood is to improve the internal bond strength of the face 1 . This can be particularly advantageous for the novel paper label 2, at least if it is used as a direct thermal paper label 2.

[0114] The paper of the paper label 2 is preferably so-called wood-free paper. Wood- free refers to chemical pulp, such as Kraft pulp. In accordance with an embodiment, a pulp used for making the face does not contain any kind of mechanical pulp due to high quality requirements of the face. Thus, the face 1 can be a wood-free paper comprising fibers, e.g., from softwoods and / or hardwoods.

[0115] The paper can have a fiber content of equal to or more than 50 wt.%, preferably at least 60 wt.%, and more preferably at least 70 wt.% in order to improve strength of the paper label 2. Further, increased content of natural fibres can decrease dusting of the paper label, if the paper is cut e.g. in on-demand printers.

[0116] The face 1 can further comprise, for example, at least one filler, such as a mineral filler. The at least one filler can be selected from a group consisting of clay, calcined clay, kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and titanium dioxide. A total amount of the fillers in the face 1 is preferably less than 10 weight-%, more preferably less than 5 weight-%, and most preferably less than 3 weight-%, for example between 0.5 and 5 wt.-%, or between 0 wt.-% and 3 wt.-%, based on the total dry weight of the face 1 . The fillers can decrease costs of the manufactured product. Further, as the fillers can decrease wet strength properties of the face, the fillers can improve recyclability of a paper label.

[0117] The mineral fillers can also decrease strength properties of the face 1. If the face 1 comprises too much mineral fillers, some properties of the face 1 can be compromised. Thus, in an example, the face 1 does not comprise mineral fillers.

[0118] The face 1 can comprise a paper which is coated with one or more coatings. For coated papers, a total coat weight in the range of 1 to 12 g / m2per side (on one or both sides) can be used. The coating layer(s) can comprise at least one pigment selected from a group consisting of clay, calcined clay, kaolin, natural ground calcium carbonate, precipitated calcium carbonate, talc, calcium sulphate, and titanium dioxide. Further, said coating layer(s) can comprise binders. For environmental reasons and for improving properties of paper labels, the binders can comprise or consists of starch and / or polyvinyl alcohol.

[0119] A face 1 comprising the paper can be calendered with a calender, for example with a supercalender, to obtain a high-density surface.

[0120] A grammage of the face 1 is preferably at least 50 g / m2, more preferably at least 60 g / m2. Further, the grammage of the face 1 is preferably less than 85 g / m2, more preferably equal to or less than 80 g / m2. Grammage can be, for example, in a range between 50 g / m2and 82 g / m2or in a range between 70 and 80 g / m2. Said grammage can be particularly suitable for paper labels used for on demand printers and afterwards for washing processes. The grammage can be measured according to standard ISO536.

[0121] The face 1 can have a caliper in a range between 50 pm and 95 pm, measured according to ISO534. If the face it is too thin, the paper label 2 can be difficult to handle. For example, if the face is very thin, a stiffness of the paper label can go too low causing the paper label to be too sloppy. Thus, the paper label can be difficult to manufacture and / or the paper label can cause problems when used in labelling processes.

[0122] For improving printability and / or for providing desired look, the top side of the paper label 2 can have a smoothness at least in a range between 350 sec and 550 sec (Beck), measured according to standard ISO5627. For example, a silicon layer on top of the face will smooth the paper label. Thus, in an embodiment, the top side of the paper label can have a smoothness of equal to or more than 1000 sec (Beck), measured according to standard ISO5627. The paper label 2 can have a brightness higher than 85% (R457) when measured according to standard ISO2469. Therefore, the paper label can look nice. Further, high brightness can create a contrast between the symbols / letters. Thus, if the letters comprise some machine-readable letters, the letters can be easily read thanks to said brightness. This can be particularly advantageous when using the paper labels for recyclable bottles.

[0123] The paper label 2 can have an opacity higher than 80%, such as in a range between 80 and 90, when measured according to standard ISO2471 . Thanks to said opacity, the surface of the paper label cannot be too transparent for a machine to read. This can be particularly advantageous when using the paper labels for recyclable bottles.

[0124] The face 1 and / or the paper label 2 can have a tensile strength in the machine direction higher than 40 N / 15mm, preferably higher than 45 N / 15 mm, when measured according to standard ISO1924 / 2. Technical effect is to improve dimensional stability of the paper label. The improved dimensional stability has a positive effect on manufacturing process and printing process as well as on some washing processes.

[0125] The face 1 and / or the paper label 2 can have a tensile strength in the cross direction higher than 10 N / 15mm, when measured according to standard ISO1924 / 2. Technical effect is to improve dimensional stability of the paper label. The improved dimensional stability has a positive effect on manufacturing process and printing process as well as on some washing processes.

[0126] In an advantageous embodiment, the paper label 2 is attached to a bottle, and the label and the labelled bottle have such densities wherein one has a density of more than water and the other has a density of less than water. Technical effect is to improve recyclability of the paper label.

[0127] In an embodiment, density of the paper label 2 is adjusted to a total average density of more than 1 .0 g / cm3. Technical effect is to provide a label that sinks during the washing process. For example, in a case of PP and HDPE bottles wherein recycling methods include crushing or shredding of plastic bottles, pieces of bottles float in water while the paper labels sink, thus allowing for efficient recovery and recycling of the PP and HDPE flakes. Therefore, as pieces of shredded plastic bottles floats, this can allow the labels to be separated from the bottles easily, particularly when using said total average density together with the wash-off adhesive allowing the PSA to separate from bottles efficiently at 40°C in water. Further technical effect is to provide particularly environmentally friendly product, wherein plastics and cellulosic fibers can be collected separately.

[0128] Paper labels can be recycled either in a fiber loss system, wherein the paper is fully broken into small pieces, or in a non-fiber loss system, wherein the paper does not break in wet conditions. Preferably, the paper label breaks fully into washing water.

[0129] The paper can be handled with washing water. The paper can be recycled, for example, in a system comprising a cyclone cleaning device. The cyclone cleaning device can be used to remove the paper label from the system.

[0130] Thus, as discussed, the paper label according to this specification can be particularly environmentally friendly wash-off label, which can be recycled together with labelled articles.

[0131] DIRECT THERMAL PAPER LABEL

[0132] The paper label 2 according to this specification may be a direct thermal paper label, such as a direct thermal linerless paper label. Technical effect of this embodiment is to provide paper label 2 that is thermally printable while improving washability of the paper label.

[0133] The face 1 of the direct thermal paper label has at least two layers. The face 1 can comprise or consist of

[0134] - a paper,

[0135] - a direct thermal coating layer,

[0136] - optionally, an intermediate layer left in between the direct thermal coating layer and the paper, and

[0137] - preferably, a top coating on the direct thermal coating layer. Thus, the paper label 2 can be a direct thermal paper label, such as a direct thermal linerless paper label, comprising or consisting of

[0138] - the face 1 comprising a paper, direct thermal printable coating, optionally, a top coating on the direct thermal printable coating, and optionally, an intermediate layer disposed between the base layer and the direct thermal printable coating,

[0139] - optionally, a release coating on the face 1 , and

[0140] - pressure sensitive adhesive coating.

[0141] If the paper label 2 is the direct thermal paper label, the face 1 can have a static sensitivity below 100 degrees C, preferably in a range between 75°C and 95°C. The static sensitivity, as well as dynamic sensitivity, needs to be low enough so that the product is not darkening before printing, for example during transportation. However, the static and dynamic sensitivities should be high enough so that the paper label is thermally printable.

[0142] As discussed, the face 1 may further comprise a top coating on the direct thermal printable coating. The top coating preferably has a grammage in a range between 0.5 g / m2and 3 g / m2. The top coating may protect the top surface and / or print of the face 1 against rubbing or other external stress.

[0143] The top coating, if used, may comprise at least one of: starch, polyvinyl alcohol (PVA), latex, and wax. Preferably, the top coating comprises polyvinyl alcohol (PVA) and / or wax. These coatings may provide improved protection for the direct thermal printable coating. Furthermore, wax may improve friction properties of the paper label. The top coating may further help to decrease dusting of the paper label during a usage of the paper label.

[0144] The direct thermal printable coating can be arranged to provide thermal printability for the face 1. The direct thermal printable coating is arranged to form a thermal sensitive, reactive layer changing color during the thermal printing. The thermal coating can comprise reactive components. The thermal coating may comprise a matrix. The matrix may comprise a dye and a developer. Preferably, in order to improve printing quality cost efficiently, the direct thermal printable coating has a grammage in a range between 1 g / m2and 5 g / m2.

[0145] Typically, the thermal coating matrix in a solid state is heated by a thermal print head above its activation point and / or melting point. The dye of the thermal coating may comprise a leuco type dye. The leuco type dye is arranged to react with an acid and change into a colored form.

[0146] Thermal coating may comprise a dye, a developer, a sensitizer, a binder, and a stabilizer.

[0147] The developer can be arranged to co-react with the dye above activation temperature during thermal printing. Reaction of the dye with the developer is arranged to trigger color formation. Developer may comprise sulfonyl ureas, zinc salts of substituted salicylic acids or phenols, for example Bisphenol S (BPS). The thermal coating may preferably be BPA free, Bisphenol (BP) free and / or Phenol free for increased chemical safety.

[0148] Sensitizer may be used in a thermal coating to decrease melting point of a dye and / or a developer. Dye and developer are arranged to react when heated above melting point of matrix of the thermal coating. The melting point of the matrix may depend on melting point values of its components. Thermal threshold of the thermal coating is melting point of the component of the thermal coating having the lowest melting point. Sensitizer of the thermal coating may be arranged to decrease melting point of dye and / or developer. This has effect of proving accuracy to the melting point and / or optimizing temperature of color change and / or facilitating mixing of dye and developer.

[0149] Optionally, the thermal coating may comprise stabilizers. Dyes in thermally sensitive paper may be unstable tending to return to their original colorless crystalline form. The thermal paper may be sensitive, for example, to hot and humid external conditions. In order to stabilize the metastable glass formed by leuco dye, developer and sensitizer, a stabilizer may be added to the mixture. Stabilizers may affect inhibiting recrystallization of the dye and developer and / or stabilizing the print.

[0150] Binder of the thermal coating may have an effect of facilitating the thermal coating to adhere to a base substrate or to a pre-coat. Binder may comprise double bonds. The binder may comprise polyvinyl alcohol (PVA) or latex, for example a styrene butadiene latex (SB) or a styrene acrylic (SA).

[0151] Sensitivity of the thermal coating refers to the degree to which it reacts to a given amount of heat or energy. Sensitivity is a decisive factor in the selection of the right thermal coating or thermal paper. It may be depicted in graphs plotting a curve of image density or optical density (OD) against the amount of heat or energy transferred. Optical density is a measure of a relationship between incident and reflected light. An optical density of approximately 1.1 is usually a full black to the human eye. Lower optical densities thus correspond to varying shades of grey. Thermal coatings and thermal papers are typically characterized by using static and dynamic sensitivity.

[0152] Static sensitivity indicates the temperature at which a thermal paper will begin imaging, i.e. changing color. Thermal papers with low static sensitivity only begin imaging at high temperatures, for example at above 90 degrees C. Thermal papers with medium static sensitivity on the other hand begin imaging at lower temperatures, for example at between 80 and 90 degrees C. High static sensitivity thermal papers start to react even at lower temperatures, for example at 65-80 degrees C, or at 70-80 degrees C. As discussed, if the paper label 2 is the direct thermal paper label, the face 1 of the paper label preferably has a static sensitivity below 100 degrees C, more preferably in a range between 75°C and 95°C.

[0153] RELEASE COATING LAYER ON THE FACE

[0154] The paper label 2 can comprise a release coating layer on top of the face 1 , i.e., on the second surface of the face 1 . The release coating layer on top of the face is an optional layer, particularly advantageous for linerless paper labels. If the paper label 2 is the direct thermal paper label, the release coating layer can be on top of the direct thermal coating. Thermal printing of the paper label can be made through the release coating layer.

[0155] In an embodiment, the paper label 2 is a linerless paper label, such as a direct thermal linerless paper label. Thus, the paper label 2 with pressure sensitive adhesive on its one side (bottom side) and release coating layer on its other side (top side) can be self-wound around itself without tendency of blocking the adjacent layers of the paper label web to each other. Thanks to the release coating layer on top of the face, the adhesion may be low enough so that the adhesive layer can be readily released from the face 1 material upon unwinding the linerless label roll.

[0156] The release coating layer may be a silicone-based or non-silicone-based release coating layer. Preferably, the release coating layer comprises or consists of silicone-based release coating.

[0157] Non-thermally curable release coatings, such as UV curable silicone, are preferable, at least when the paper label is the direct thermal paper label. Technical effect is that curing of such layers is not heating the thermally sensitive material of the direct thermal paper label. Thus, the release coating may be UV curable silicon having the benefit of being curable on top of thermal face 1 without heat.

[0158] Further technical effect of the release coating layer on top of the face is to lower friction against a print head of a printer and minimize wear of the print head. Furthermore, due to the lowered friction and minimized wear of the print head, a printing quality of the paper label can be improved.

[0159] Further, surprisingly, the silicone based release coating did not cause problems to the washing process during experimental tests.

[0160] ADHESIVE COMPOSITION

[0161] The paper label 2 comprises a modified adhesive composition comprising an acrylic adhesive and a wash-off additive. The wash-off additive added into the acrylic adhesive can be in a form of an aqueous dispersion. The acrylic adhesive composition comprising the wash-off additive can be prepared by blending an acrylic adhesive and the wash-off additive.

[0162] An amount of the wash-off additive is at least 0.5 wt.%, preferably at least 0.7 wt.% calculated from total dry weight of the acrylic adhesive. For further improving efficiency of the wash-off additive, an amount of the wash-off additive can be at least 1 wt.%, more preferably at least 1 .5 wt.%, and most preferably at least 1.7 wt.%. The wash-off additive can start to improve washability of the paper label even when a small amount of more than 0.5 wt.% is used. Further, the effect of the wash-off additive on the washability of the label can improve as the amount of the wash-off additive increases, at least up to 3 wt.%.

[0163] The effect of the wash-off additive can decrease when the amount of the wash- off additive exceeds 3 wt.%. Thus, the wash-off additive can be the most efficient when the amount of the wash-off adhesive does not exceed 3 wt.%. Thus, an amount of the wash-off additive can be equal to or less than 3 wt.%, preferably equal to or less than 2.7 wt.%, and more preferably equal to or less 2.5 wt.%, calculated from total dry weight of the acrylic adhesive. In an advantageous example, the amount of the wash-off additive is from 0.5 wt.% to up to 2.5 wt.%, calculated from total dry weight of the acrylic adhesive.

[0164] Thanks to the wash-off additive in the acrylic adhesive, washability of the PSA at 40°C can be substantially improved.

[0165] As discussed, the adhesive according to this specification is an acrylic adhesive. Acrylic adhesives have many advantages. Acrylics are a type of synthetic polymer which fall into the thermoplastic resin family. Acrylics provide strong, durable adhesion at normal temperatures and conditions. Acrylic adhesives are based on acrylic polymers, also called acrylate polymers. Acrylate monomers, used to form acrylate polymers, are based on the structure of acrylic acid, which comprises a vinyl group and a carboxylic acid terminus. Acrylic polymers are characteristically tacky, and they can be used as pressure sensitive adhesives without any modification. In general, acrylic adhesives have good aging and UV-resistance properties. They are polar in nature and therefore give good adhesion to polar substrates. The acrylic adhesive can be in a form of an aqueous dispersion of acrylates having a solids content in a range between 40% and 60%. The higher solids content can provide an easier drying process.

[0166] Preferably, the acrylic adhesive coating comprises

[0167] - butyl acrylate, or

[0168] - 2-ethylhexyl acrylate (2-EHA), or

[0169] - butyl acrylate and 2-ethylhexyl acrylate.

[0170] Total content of the butyl acrylate and 2-hydroxyethyl acrylate can be at least 50 wt.%, more preferably at least 70 wt.%, more preferably at least 80 wt.%, and most preferably at least 85 wt.%, calculated from the dry weight of the acrylic adhesive. These acrylic adhesives can be particularly advantageous for paper labels.

[0171] In an embodiment, the acrylic adhesive comprises at least 80 wt.% (by dry weight) 2-ethylhexyl acrylate (2-EHA), calculated from the dry weight of the acrylic adhesive. This kind of the adhesive can be particularly useful for wash- off adhesives. Further, the acrylate dispersion may not have strong effect on color of the layer, hence, visual appearance can be easily controlled.

[0172] The acrylic adhesive may further comprise one or more than one crosslinker. The one or more than one crosslinker can be selected from a group consisting of: allyl methacrylate (AMA), ethylene glycol dimethacrylate (eGDMA), triethyleneglycol dimethacrylate (TRGDMA), polyethyleneglycol 200 dimethacrylate (PeG200DMA), 1 ,3-butanediol dimethacrylate (1 ,3-BDDMA), 1 ,4-butanediol dimethacrylate (1 ,4-BDDMA), 1 ,6-hexanediol dimethacrylate (1 ,6-HDDMA), glycerol dimethacrylate (GDMA), trimethylolpropane trimethacrylate (TMPTMA), and diurethane dimethacrylate (HEMATMDI).

[0173] Particle size (nm) of the acrylic adhesive composition, measured as a mean particle diameter, can be in a range from 100 nm to 800 nm, preferably from 120 nm to 600 nm, more preferably from 140 nm to 500 nm, and most preferably from 150 nm to 400 nm. Particle size can affect to a behavior of the acrylic adhesive composition. With said range of 100 to 800 nm, and particularly with the most desired range from 150 nm to 400 nm, properties of the acrylic adhesive, such as solid content and viscosity levels, can be easily adjusted to a desired level. Polymer gel content of the acrylic adhesive composition can be used for determining crosslinking level of the adhesive. Polymer gel content of the acrylic adhesive composition can be in a range from 20% to 90%, preferably from 45% to 85%, more preferably from 55% to 80% and most preferably from 60% to 75%, or from 65% to 75%. Thanks to said polymer gel contents, and particularly the preferred ranges, adhesion performance can be controlled to an improved level. Too high gel content can decrease adhesion performance, while too low gel content can increase adhesion performance too much.

[0174] In order to improve washability of the acrylic adhesive, the acrylic adhesive according to this specification comprises a wash-off additive comprising a grafted rosin ester. The wash-off additive can comprise an aqueous phase and resin particles dispersed in the aqueous phase.

[0175] The resin particles can comprise resinous material, which can be selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof. Preferably, the resinous material comprises or is the rosin resin. In an embodiment, an amount of the rosin resin is at least 50 wt.%, preferably at least 65 wt.%, such as at least 80 wt.%, and more preferably at least 90 wt.%, such as 100 wt.%, with respect to the resinous material. Said resinous material and particularly the rosin resin can improve performance of the wash-off additive.

[0176] An amount of the grafted rosin ester with respect to the resinous material in the wash-off additive can be at least 1 wt.%, for example, from about 1 wt.% to about 8 wt.%, preferably from about 2 wt.% to about 6 wt.%, such as from about 3 wt.% to about 5 wt.%. Thus, the effect of the wash-off additive in the acrylic adhesive can be improved.

[0177] The dispersion can further comprise e.g. an anionic emulsifier from 0.1 wt.% up to 3 wt.%.

[0178] The total amount of the resinous material, the grafted rosin ester, the optional anionic emulsifier, and water in the wash-off additive can be at least 95 wt.%, preferably at least 97 wt.%, such as at least 98 wt.%, and more preferably at least 99 wt.%, such as 100 wt.%, with respect to the total weight of the wash- off additive.

[0179] In an embodiment, resin particles of the wash-off additive have a mean particle diameter d50 of less than 1.2 microns, preferably less than 0.9 microns, wherein d50 means the mean particle diameter for the 50 wt.% fraction of the particles starting from the smallest particles.

[0180] Thus, as discussed, the wash-off additive can be an aqueous dispersion comprising the grafted rosin ester. The grafted rosin ester according to this specification is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a poly(alkylene glycol) alkyl ether.

[0181] The polyalkylene glycol can be selected from the group consisting of C2-C5 polyalkylene glycols and mixtures thereof. In an advantageous embodiment, the polyalkylene glycol is or comprises polyethylene glycol. The polyethylene glycol can be particularly suitable for improving washability properties of the wash-off additive.

[0182] The alkyl ether can have 1 to 18 carbon atoms, preferably 1 to 4 carbon atoms. Most preferably, for improving washability properties of the wash-off additive, the alkyl ether is a methyl ether.

[0183] Therefore, in an advantageous embodiment, the capped polyalkylene glycol is a methyl ether capped polyethylene glycol. This can particularly improve washability of the wash-off label comprising an acrylic adhesive in low temperature washing processes at +40°C, in water. Further, by using a wash off additive comprising the rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is the methyl ether capped polyethylene glycol, the PSA can be remained attached to the paper face 1 .

[0184] Therefore, in an advantageous embodiment, the wash-off additive comprises a rosin ester grafted with a methyl ether capped polyethylene glycol. This kind of wash-off additive can substantially improve washability of paper labels.

[0185] The capped polyalkylene glycol may have a Mw in a range between 1000 and 10000, preferably from 1000 to 8000. The average molecular weight of the end-capped polyalkylene glycol can be determined, e.g., by hydroxyl number analysis.

[0186] The molar ratio between the rosin ester and the capped polyalkylene glycol can be 0.05:1 to 1 :1 , preferably from 0.2:1 to 1 :1 , more preferably from 0.4:1 to 1 :1 , and most preferably from 0.7:1 to 0.9:1. Said molar ratio can improve washability of the paper label.

[0187] Surprisingly, by using the wash-off additive comprising the grafted rosin ester in the acrylic adhesive, washability of the paper labels can be substantially improved. During experimental tests, this kind of effect was not seen with conventional rosin ester surfactant, nor with conventional polyalkylene glycols, such as polyethylene glycols.

[0188] The acrylic adhesive comprising a dispersion of acrylates and the wash-off additive can be extremely sensitive to washing conditions comprising a temperature of 40°C and water. Further, the adhesion of the adhesive to the labelled item can decrease more than the adhesion to the face 1 so that the adhesive remains attached to the face 1 .

[0189] The adhesive comprising the wash-off additive can be environmentally friendly solution, which can be used e.g. with food materials. Further, the acrylic waterbased adhesive may have a longer open time than some other pressure sensitive adhesives, hence, the paper label comprising water-based acrylic PSA may be removed after some seconds or minutes, if needed.

[0190] PRESSURE SENSITIVE ADHESIVE LAYER

[0191] The paper label can be affixed to the surface of an item (article) 100 through an adhesive layer 4 so as to form a labelled item 101. The paper label can comprise an adhesive layer sensitive to washing conditions.

[0192] An adhesive sensitive to washing conditions refers to such adhesives, wherein the adhesion of the adhesive decreases at washing conditions. The washing conditions comprise increased temperature. The increased temperature can be 40°C. The alkaline conditions refer to an aqueous solution containing alkaline agent, such as NaOH, KOH or combination thereof. The novel paper label can be washed by using water, without the alkaline agent.

[0193] The adhesive layer of the label should have a suitable adhesion i.e. tack (stickiness) in order to stick to an item during labelling process. Tack is the property of adhesive that allows the immediate formation of a bond on contact with another surface. The tackiness is needed at the point the label is attached to an item. The optimum adhesion between two materials depends on, for example, the wetting and surface energy of the materials.

[0194] The adhesive layer 4 can be a continuous coating covering 100% of the face surface (referring to the first surface of the face 1 ). Alternatively, the adhesive layer 4 can be applied discontinuously as spots or strips covering less than 100% of the first surface of the face 1 . For example, the adhesive can cover between 10 to 90% of the total area of the first surface of the face 1 . Reduced amount of adhesive can have effect on reducing the time needed for the subsequent removal of the label during washing process from the surface of the item attached. Thus, in an advantageous embodiment, the adhesive layer 4 covers less than 90%, more preferably less than 80% of the first surface of the face 1 .

[0195] An adhesive layer can have a thickness in the range of about 5-40 pm, or in the range of about 8-20 pm. For further improving efficiently of the washing, the thickness of the adhesive layer can be in the range of about 5-15 pm or 5- 12 pm.

[0196] The amount of the adhesive layer, in dry weight, can be in the range of about 5-40 g / m2, or 8-20 g / m2. For improving efficiently of the washing, the amount of the adhesive can preferably be less than 20 gsm, such as equal to or less than 15 g / m2. For example, for improving efficiently of the washing, the amount of the adhesive layer can be between 5 and 20 g / m2or between 5 and 15 g / m2.

[0197] The paper label comprises the acrylic pressure sensitive adhesive (PSA). Labels having a PSA layer can be adhered to most surfaces through an adhesive layer without the use of a secondary agent, such as a solvent, or heat to strengthen the bond. Generally, the pressure sensitive adhesives can be divided into the following groups: water based (water-borne) PSA, solvent based PSA and solid PSA. Solid PSAs are melted during application to the surface to be coated and may also be referred to as a hot-melt PSAs. Within context of this specification, the pressure sensitive adhesive is preferably water-based PSA. Furthermore, water based adhesives can be efficiently blended with the wash-off additive.

[0198] The adhesive (PSA) according to this specification is acrylic-based. Thanks to the acrylic-based adhesive, the adhesive remains predominantly adhered to the face 1 during the washing process. Thus, the adhesive according to this specification can be a water-based acrylic adhesive. The water-based acrylic adhesive can have many advantages over other kinds of PSAs. For example, tackiness of the product can be in an improved level thanks to the water-based acrylic adhesive. Further, the water-based acrylic adhesive can be environmentally friendly. Furthermore, the water based acrylic adhesive can be efficiently blended with the wash-off additive. Furthermore, wash-off label comprising the paper-based face 1 can be particularly environmentally friendly product.

[0199] The pressure sensitive adhesive according to this specification can exhibit reduction in its adhesion force in aqueous conditions at a temperature of 40°C.

[0200] RELEASE LINER

[0201] Referring to Fig.2, the label 2 may comprise a release liner 5. The release liner 5 is an optional feature.

[0202] The release liner 5 has a substrate 7 onto which a release coating layer 6, such as silicone, is applied.

[0203] Term "release liner" refers to a structure comprising a backing material layer as a substrate and a release coating layer on a surface of the substrate. In other words, the backing material is usually coated with a thin layer of release agent, such as silicone. The substrate of the release liner may be a paper based or film based substrate. The release coating layer provides a nonadherent surface i.e. low adhesion and release effect against the adhesive layer. The release liner protects the adhesive layer during shipment and storage. It further allows for efficient handling of individual labels after the labels are die-cut and the surrounding matrix is stripped up to the point wherein the individual labels are dispensed on a labelling line.

[0204] In labelling, the release liner is removed and disposed of, and the label is attached onto the surface to be labelled through the adhesive layer. Thus, release liners of the label laminates serve one or more useful functions: they are used as a carrier sheet onto which the adhesive may be coated; they protect the adhesive layer during storage and transportation; they provide a support for labels during die-cutting and printing, and ultimately, they release from the adhesive leaving it undamaged.

[0205] The face 1 and the release liner are typically laminated together having an adhesive layer in between, which laminated structure is referred to as a label laminate.

[0206] If the paper label is a paper label without the release liner, the paper label preferably has a release coating layer, such as a silicone layer, on top of the face 1 (i.e., on the second surface of the face 1 ).

[0207] ARTICLE

[0208] One embodiment provides a combination of a paper label and an article. The article may be a package. In an advantageous embodiment, the article is a bottle.

[0209] The paper labels may be in a form of a continuous label web having a plurality of individual labels wound into a roll. An automatic label dispensing machine can be configured to separate the individual labels from the label web and feed the labels onto a surface of a product to be labelled.

[0210] Labels can be used in wide variety of labelling applications and end-use areas, such as beverage labelling, food labelling, home, and personal care product labelling, and labelling of industrial products. The surface of the labelled article may be for example plastic, glass, metal, or paper based. The labelled article can be for example a container, such as a bottle, jar, canister, can, tin or the like. The label can also be applied to semi-rigid or flexible packages used for e.g. packaging of food.

[0211] An advantageous embodiment provides a use of a paper label for labelling of a beverage bottle. Examples of the beverage bottles include glass bottles, metal bottles, polyethylene terephthalate (PET) bottles, and bottles made of polyolefin, such as high density polyethylene (HDPE) and polypropylene (PP). The label can surround the labelled article, such as the beverage bottle, completely or partially. The beverage bottle is preferably a polyolefin bottle, polyethylene terephthalate (PET) bottle, or a glass bottle, most preferably the beverage bottle is the polyolefin bottle. The beverage bottle can be a plastic bottle exhibiting heat shrinkage during wash.

[0212] LABEL REMOVAL IN RECYCLING PROCESS

[0213] Removing the adhesive label can be implemented by washing said label off from the surface it has been adhered to. The item may be a recyclable container, such as a glass container or a polymer container.

[0214] Preferably, the item is a beverage bottle that can be a plastic bottle exhibiting heat shrinkage during wash.

[0215] Labelled items, such as bottles, are generally reused or recycled several times. Thus, there is a need for an improved label and face structures so as to would an efficient and cost-effective recycling process of the labelled items.

[0216] In the washing process the label is detached from the labelled item, for example from the surface of the bottle. During washing process, the label is exposed to a heated washing liquid. In washing process comprising heated aqueous washing solution, adhesion force of the adhesive layer is weakened thus detaching the adhesive label from the surface of the item attached. In addition, the adhesive layer 4 may lose its adhesion to at least some extent under the influence of washing conditions enabling and / or enhancing removal of the label from the surface of the item labelled.

[0217] In an example, the adhesive layer may not dissolve in the washing liquid. On the contrary, the adhesive layer may be adhered to the face 1 after removal of the label from the surface of an item. Thus, lifetime of the washing solution can be prolonged.

[0218] Conventional washing conditions of recyclable containers, such as glass containers, can comprise temperatures above 77°C in aqueous solution. For polyester or plastic containers, conventional washing temperature has been 70-75 °C, or even higher such as about 80 °C.

[0219] The novel paper label can have an improved washability already at 40°C, in water. Thus, thanks to the paper label according to this specification, washability of labels can be improved so that washing at a temperature of 40°C can show superior results compared to conventional wash-off labels.

[0220] EXPERIMENTAL TESTS

[0221] Example 1: HDPE bottle recycling at +40°C

[0222] Wash-off adhesive according to this specification, which comprised the grafted rosin ester comprising PEG, was blended with different water-based acrylic adhesives, and tested in wash-off tests at +40°C in plain water.

[0223] The test points included the following amounts of the wash-off additive: 0%, 0.5%, 0.7%, 1.0%, 1.5%, 2.2%, 2.5%, 3%, 4%, 4.5% and 6% (by dry weight) from a total dry weight of the acrylic adhesive.

[0224] An addition of the wash-off additive of more than 0.5 wt.%, to 3 wt.% (by dry weight) clearly improved washability at +40°C in water. The best efficiency was found at about 1 -3% concentration (by dry weight), after which the efficiency decreased with increased wash-off additive concentration.

[0225] According to the test results, an addition of the wash-off additive of equal to or more than 4 wt.% (by dry weight) was not as good for improving washability of the acrylic adhesive as the addition of equal to or less than 3 wt.%. Further, when amount of the wash-off additive was above 3 wt.% (by dry weight), washed adhesive particles were smaller. According to the test results, addition of more than 0.5 wt. (by dry weight) of the wash-off additive into the acrylic adhesive improved washability of the labels compared to the test point of 0 wt.%. With the addition of 0.7%, improvement in the washability was even more significant.

[0226] The best washability results were shown with the wash-off additive addition from 1 to 3%, and particularly with the wash-off additive addition from 1 .5% to 3%. For example, addition of 1 .5% (by dry weight) of the wash-off additive into acrylic adhesives improved washability up to 170%.

[0227] The addition of the wash-off additive up to 3 wt.% either improved or did not affect to the wet anchorage level of the acrylic adhesive (i.e., adhesive anchorage to the face after washing). Typically, the wet anchorage level was 100% during the experimental tests. Thus, the adhesive was always able to stay together with the face.

[0228] Example 2: HDPE bottle recycling at +40°C, comparative examples

[0229] Conventional rosin ester dispersion without the wash-off additive was blended with different water-based acrylic adhesives and tested in wash-off tests at +40°C by using the same concentration range as in the Example 1 .

[0230] Further, conventional PEG-solution was blended with different water-based acrylic adhesives and tested in wash-off tests at +40°C by using the same concentration range as in the Example 1 .

[0231] An addition of the conventional rosin ester dispersion did not improved washability at +40C. On the contrary, the conventional rosin ester dispersion decreased the washability, and the adhesive was poorly washable, or not at all washable.

[0232] Further, an addition of the PEG-solution did not improved washability at +40C, and the adhesive was poorly washable, or not at all washable. Further, in some test points, the addition of the PEG-solution decreased significantly wet anchorage of the adhesive during washing, hence, the adhesive was not always able to stay together with the face. In some test points, wet anchorage level was as poor as about 0%. Example 3: Tackification

[0233] The wash-off additive was formulated with different water-based acrylic adhesives and tested for tackification.

[0234] The wash-off additive according to this specification did not have any effect on the tackification. Thus, the wash-off additive was not able to work as a tackifier for the acrylic adhesive.

[0235] Further, comparative samples were manufactured by blending conventional rosin ester dispersion with different water-based acrylic adhesives. The conventional rosin ester dispersion was able to work as a tackifier.

[0236] Example 4: Hydrophobicity

[0237] The wash-off additive was formulated with different water-based acrylic adhesives and tested for hydrophobicity.

[0238] According to the test results, the wash-off additive clearly increased hydrophobicity, further improving washability of acrylic adhesives comprising the wash-off adhesive and improving delamination of labels from polyolefin bottles.

[0239] The novel wash-off additive had many advantages over conventional solutions during the experimental tests. Conventional rosin ester dispersions were not able to work as a wash-off additive. Further, PEG solution was not improving wash-off properties of acrylic adhesives at all. Surprisingly, the wash-off additive according to this specification comprising the grafted rosin ester was able to efficiently improve acrylic polymer wash-off properties in low temperature washing processes at +40°C in water, and was able to improve delamination during washing process.

[0240] The invention has been described with the aid of illustrations and examples. The invention is not limited solely to the above presented embodiments but may be modified within the scope of the appended claims.

Claims

Claims:1 . A method for manufacturing a paper label (2) comprising a face (1 ) and a pressure sensitive adhesive layer (4) for adhering the paper label (2) to a surface of an item to be labelled, wherein the face (1 ) comprises a paper, wherein the method comprises:A) applying an acrylic adhesive onto a first surface of the face (1 ), wherein the acrylic adhesive comprises a wash-off additive, the wash-off additive comprising o preferably, an aqueous phase, o a resinous material, preferably selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof, and o a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether, preferably the capped polyalkylene glycol is a methyl ether capped polyethylene glycol, and drying the acrylic adhesive in order to form an acrylic pressure sensitive adhesive onto the first surface of the face (1 ), orB) applying an acrylic adhesive onto a carrier material, wherein the acrylic adhesive comprises a wash-off additive, the wash-off additive comprising o preferably, an aqueous phase, o a resinous material, preferably selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof, and o a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether,preferably the capped polyalkylene glycol is a methyl ether capped polyethylene glycol, drying the acrylic adhesive in order to form an acrylic pressure sensitive adhesive onto the carrier material, and transferring the acrylic pressure sensitive adhesive to the first surface of the face (1 ), thereby obtaining the paper label.

2. The method according to claim 1 , wherein a polymer gel content of the acrylic adhesive is at least 60% and 75% at the most.

3. The method according to claim 1 or 2, wherein a mean particle size of the acrylic adhesive is at least 100 nm and 800 nm at the most, measured as a mean particle diameter.

4. A paper label (2) comprising a face (1 ) and a pressure sensitive adhesive layer (4) for adhering the label (2) to a surface of an item to be labelled, wherein the face (1 ) comprises a paper, and the pressure sensitive adhesive layer (4) comprises an acrylic pressure sensitive adhesive comprising a wash-off additive, the wash-off additive comprising o a resinous material, preferably selected from a group consisting of a hydrocarbon resin, an alkyd resin, a polyamide resin, a rosin resin, and mixtures thereof, and o a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether, preferably the capped polyalkylene glycol is a methyl ether capped polyethylene glycol.

5. The method or the paper label (2) according to any of the preceding claims, wherein an amount of the wash-off additive is equal to or more than 0.5 wt.%, preferably equal to or more than 1 wt.%, calculated from total dry weight of the acrylic adhesive.

6. The method or the paper label (2) according to any of the preceding claims, wherein an / the amount of the wash-off additive is equal to or less than 3 wt.%, calculated from total dry weight of the acrylic adhesive.

7. The method or the paper label (2) according to any of the preceding claims, wherein an amount of the grafted rosin ester with respect to the resinous material is from 1 wt.% to 8 wt.%.

8. The method or the paper label (2) according to any of the preceding claims, wherein the polyalkylene glycol is a polyethylene glycol.

9. The method or the paper label (2) according to any of the preceding claims, wherein the acrylic adhesive comprises 2-ethylhexyl acrylate (2-EHA).

10. The method or the paper label (2) according to any of the preceding claims, wherein the resinous material comprises or consists of the rosin resin.

11. The method or the paper label (2) according to any of the preceding claims, wherein a molar ratio between the rosin ester and the capped polyalkylene glycol is 0.05:1 to 1 :1 , preferably at least 0.4:1 , and most preferably from 0.7:1 to 0.9:1 .

12. The method or the paper label (2) according to any of the preceding claims, wherein the alkyl ether is a methyl ether.

13. The method or the paper label (2) according to any of the preceding claims, wherein the paper label is a direct thermal paper label.

14. The method or the paper label (2) according to any of the preceding claims, wherein the paper label is a linerless paper label.

15. The method or the paper label (2) according to any of the preceding claims 1 to 13, wherein the paper label is a paper label laminate comprising a release liner.

16. The method or the paper label (2) according to any of the preceding claims, wherein the paper label (2) is a wash-off paper label.

17. An article, preferably a beverage bottle, such as a polyolefin bottle, comprising the paper label (2) according to any of the claims 4-16 adhered to a surface of the article.

18. A use of a wash-off additive comprising a resinous material and a grafted rosin ester which is a rosin ester grafted with a capped polyalkylene glycol, wherein the capped polyalkylene glycol is a polyalkylene glycol end-capped by an alkyl ether, for an acrylic pressure sensitive adhesive of a direct thermal wash-off paper label.

19. A use of the paper label (2) according to any of the claims 4-16 for labelling of a beverage bottle.

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