Technical Field

The present application relates to a method and apparatus for manufacturing a linerless label, and a linerless label.

Background

A label laminate is a self-adhesive label. Typically adhesive is applied on a release liner, which is laminated to a face stock of the label. Using release liners poses cost and manufacturing phases for label laminates. During labelling the release liner is removed. It may require separate collection, treatment lines and/or it may form waste.

Summary

Aim of the application is to provide linerless label. Another aim of the application is to enable use of water based adhesive with a linerless label laminate.

According to an embodiment a method for manufacturing a linerless label comprises a face stock and water based adhesive. The linerless label comprises a heat sensitive part. The method comprises applying the water based adhesive on a belt, drying the water based adhesive on the belt, unwinding the face stock and attaching the dried water based adhesive to the face stock. An embodiment comprises a linerless label laminate obtainable by the method.

According to an embodiment an apparatus for manufacturing a linerless label comprises a face stock and water based adhesive. The linerless label comprises a heat sensitive part. The apparatus comprises a coating unit arranged to apply the water based adhesive on a belt, a dryer arranged to dry the water based adhesive on the belt, a roll arranged to unwind the face stock and a nip arranged to attach the dried water based adhesive to the face stock. According to an embodiment an apparatus for manufacturing a linerless label comprises a face stock and water based adhesive. The linerless label comprises a heat sensitive part. The apparatus comprises means for applying the water based adhesive on a belt, means for drying the water based adhesive on the belt, means for unwinding the face stock and means for attaching the dried water based adhesive to the face stock.

According to an embodiment a linerless label comprises a face stock and water based adhesive. The linerless label comprises a heat sensitive part. The face stock may comprise polymer(s) and the water based adhesive layer may comprise heat activatable water based adhesive layer. Alternatively, the face stock may comprise paper and the water based adhesive may comprise heat activatable water based adhesive. Alternatively the face stock may comprise thermal paper.

Description of the Figures

The following figures illustrate some examples and embodiments of the invention.

Figure 1 illustrates a method according to an embodiment of the invention.

Figure 2 illustrates an apparatus according to an embodiment of the invention.

Figure 3 illustrates adhesive according to an embodiment of the invention.

Figure 4 illustrates a face stock according to an embodiment of the invention.

Figure 5 illustrates a face stock according to an embodiment of the invention. Figure 6a illustrates a face stock according to an embodiment of the invention.

Figure 6b illustrates a face stock according to an embodiment of the invention.

Figure 7 illustrates a linerless label according to an embodiment of the invention.

Detailed Description of Embodiments

The following description describes some embodiments of the invention in further detail with the accompanying figures.

Heat sensitive layers or parts of a label have prevented utilizing water based adhesive with a linerless label. The water based adhesive is typically dried in order to evaporate water after the adhesive has been applied on a face stock of a label. Use of water based adhesive necessitates drying, while any heat sensitive layer or part of a label may prohibit drying or heating. Drying with really low temperatures might be possible, but would in turn cause ineffectiveness due to long drying times.

A problem with face stock of a label comprising thermal paper arises from heat sensitivity of the thermal paper. Thermal coating of a thermal paper is activated using heat. This may prevent drying and/or heating water adhesive paper on a thermal paper, since heating may lead to activation and the thermal paper becoming blackish. The activated, black thermal paper surface prevents providing a visible print on it. Water based adhesive applied on a face stock comprising paper may penetrate onto the face stock, and soften the face stock, or weaken hydrogen bonds in it. Thus the paper face stock may lose its qualities, which in turn may prevent further steps of label process, like printing or die cutting. In case of a plastic face stock, drying water based adhesive applied on face stock has not been possible or has posed problems. For example polypropylene or polyethylene have not been suitable label face stock materials with a water based adhesive. The plastic face stock may shrink in response to increased temperature during drying of water based adhesive.

According to embodiments of the invention water based adhesive is dried separately, before attaching the adhesive onto a face stock of a label . This avoids problems arising from heat sensitivity. The embodiments enable to use environmentally friendly water based adhesive in linerless labels.

Method

Figure 1 illustrates a method according to an embodiment of the invention. Water based adhesive is applied on a belt 101 . The belt may be a silicone belt, a plastic belt, such as a nylon belt, or a metal belt, such as a steel belt. The belt may comprise at least one release coating layer. The release coating layer may have effect of increasing release effect of the belt. The release coating layer on the belt may enable to easily release the water based adhesive from the belt. The water based adhesive may be dried before detaching the adhesive from the belt. The adhesive is detached from the belt in order to apply and attach the water based adhesive on a face stock of a label. The water based adhesive may comprise a single adhesive layer or multilayer of adhesive.

The water based adhesive is dried 102 on the belt. The water based adhesive on a belt may be dried 102 in order to evaporate water from the water based adhesive. The water based adhesive may be dried using at least one of induction energy, infrared energy, microwave energy or air blow. The water based adhesive may be dried on one or both sides of the belt. The water based adhesive may be dried directly and/or indirectly. Drying 102 may be implemented indirectly by heating the belt. Drying 102 may comprise utilizing air blow. Drying 102 may comprise utilizing air blow and another type of drying. The another type of drying may comprise infrared energy and/or induction energy. Drying 102 may comprise heating. Heating may be implemented by at least one or more of induction heating, infrared heating, air blow or microwave heating. The dried water based adhesive is applied on a face stock of a label 103. The face stock may comprise a single layer or multilayers. The face stock may comprise plastic and/or paper. The linerless label web comprising the face stock and the water based adhesive is wound up on a roll 104. This may be enabled by heat activated, pressure sensitive adhesive, which is arranged in a non-activated state when wound up to a roll. The adhesive in non- activated state is non-tacky. When activated, the adhesive becomes tacky.

Apparatus

Figure 2 illustrates an apparatus according to an embodiment of the invention. The apparatus comprises a belt 210. Water based adhesive is applied on a belt by a coating unit 215. The coating unit 215 is arranged to apply the water based adhesive on the belt 210. Coating may comprise curtain coating, roll coating, foam coating or spray coating. The coating may contain a multilayer curtain coating. The least one water based adhesive layer may be applied on the belt 210 by a contactless method, preferably by a curtain coating. The curtain coating, as well as other contactless coating methods, have effect of providing non-static coating process. The contactless coating method substantially lacks pressure. The adhesive layer is arranged to adjust contour of a belt surface. Thickness of the contactless coating layer may remain stable, unaltered. Water based adhesive on the belt 210 is dried in order to evaporate water from the water based adhesive. Drying may be implemented by a one or more drying device 221 , 220. A drying device may utilize induction energy, infrared energy, microwave energy or air blow, for example. A drying device may comprise an induction heating device, an infrared heating device, a microwave heating device or an air dryer. Infrared heating device and/or induction heating device 220 may be situated under the belt 210, or on a side of the belt opposite to the side of the belt on which the water based adhesive is applied. Air dryer or air jets 221 may be over the belt 210, or on a side of the belt on which the water based adhesive is applied. The side of the belt 210, to which the water based adhesive is applied, is pointed with an arrow in the Figure 2.

The apparatus of the Figure 2 may comprise means for direct drying of the adhesive on the belt 210. The apparatus may comprise means for indirect drying of the adhesive on the belt 210. The apparatus may comprise both direct and indirect drying means. Indirect drying means may comprise means for heating the belt. Drying the water based adhesive on the belt may comprise air blower or air blow drying means. Drying the water based adhesive on the belt may comprise air blow dryer or -means, and another type of dryer or drying means. Dryer may comprise air blow dryer and infrared energy dryer, or means for drying by air blow and means for drying by infrared energy. The dryer may comprise air blow dryer and induction energy dryer, or means for drying by air blow and means for drying by induction energy. Drying may comprise heating. Drying means may comprise at least one or more of induction heater, infrared heater, air blower or microwave heater.

The apparatus comprises an unwinder 212 for a face stock of a label. The face stock label comprises a web wound to a roll. The face stock may be unwind 212 from the roll. After dried, the water based adhesive is attached to the face stock. The unwind face stock 212 and the dried water based adhesive are attached in a nip. A linerless label is formed. The formed linerless label 231 is wound up to a roll 232. The label roll 232 may be stored and/or transported for later processing. Label roll 232 may be printed and/or die-cut. Label roll 232 may be further processed in other location. The apparatus of the Figure 2 may further comprise a cooling cylinder. The cooling cylinder may situate before the point wherein the dried water based adhesive layer is attached to the face stock. Speed of the rolls in the apparatus of the Figure 2 is preferably substantially the same in order to avoid damaging the face stock web, for example stretching of a plastic face stock web or tearing of a paper face stock web. Speed difference between the rolls of the apparatus is preferably less than 0.5%.

The belt may comprise silicone, plastic, for example nylon, or metal, for example steel. The belt may be solid and/or non-porous and/or non- permeable. The belt may be non-permeable to adhesive. Adhesive may not penetrate to belt material. The belt may comprise a closed surface. An external surface of the belt may comprise roughness of 0.2-3.0 μιτι, preferably 0.4-1 .0 μηη, according to PPS 10 of ISO 8791 . The belt may comprise at least one release coating layer. The release coating layer has effect of increasing the release effects of the belt. The release coating layer may comprise at least one or two, or exactly one or two release layers. The at least one release coating layer may comprise at least one silicone coating layer or at least one fluoropolymer based coating layer, for example polytetrafluoroethylene (PTFE) coating layer and/or fluorinated ethylene propylene (FEP) coating layer and/or perfluroalkoxy (PFA) coating layer. The at least one release coating layer may be non-permeable to adhesive.

Length of the belt and/or speed of the belt and/or temperature of the belt are controllable. The belt length, speed and temperature have at least partly effect on drying the water based adhesive layer on the belt. The length of the belt may be at least 10 m, or at least 20 m, and not greater than 50 m or 40 m, or not greater than 35 m or 30 m. The speed of the belt may be 200-1200 m/min. Drying temperature of the water based adhesive on a belt may be less than 60-80 ^° C, preferably less than 70 ^° C, or less than 60 ^° C, or less than 55 ^° C. The at least one adhesive layer is in contact with the belt for at least 1 s, or 1 .5 s, preferably at least 1 .8 s, or at least 2.0 s, and not longer than 8 s, preferably no longer than 7 s or 6 s. Thickness of a metal belt may be for example 0.2-4.0 mm, preferably 1 -2 mm. The density of the metal belt at the temperature of 20 ^° C may be 7500-8500 kg/m ³ , preferably 7700-8050 kg/m ³ . Roughness of the belt coating may be 0.2-3.0 μιτι, preferably 0.4-1 .0 μιτι, according to PPS 10 of ISO 8791 . The thermal conductivity of the metal belt at the temperature of 20 ^° C may be for example 13-21 W/mK, or 14-15 W/mK. The thermal conductivity of the metal belt at the temperature of 100 ^° C may be for example 14-22 W/mK, or 15-16 W/mK. Temperature of a belt during the drying process is dependent on adhesive. Temperature may be adjusted according to the adhesive. For example, temperature of the belt may be at most 50-65 ^° C or at most 70-80 ^° C; or the temperature of the belt may be at least 75 ^° C, and not higher than 125 ^° C, or 120 ^° C, preferably no higher than 1 15 ^° C. Speed of the belt may be at least 280 m/min, more preferably at least 200 m/min, or at least 300 m/min, most preferably at least 350 m/min, or at least 370 m/min.

Dryer or drying device(s) arranged to evaporate water from the water based adhesive may comprise an induction energy dryer, an infrared energy dryer, a microwave energy dryer or an air dryer. Other dryers or drying means are possible and may be utilized. A dryer or a drying device may dry, for example heat, the water based adhesive directly or indirectly. The water based adhesive may be dried directly. Drying means may be arranged to heat the water based adhesive on a belt, for example provide heat straight towards or onto the water based adhesive. In addition or alternatively drying means may be arranged to heat the belt and conduct or transfer the heat via the belt to the water based adhesive on the belt. The water based adhesive is thus dried (or heated) indirectly, though the belt. Heating the belt may be implemented at least partly with induction heating or infrared heating. Drying has effect of removing moisture from the water based adhesive on a belt.

In embodiments, where a metal belt is used, the water based adhesive may be dried from a first side or both sides of the metal belt. The first side may be the belt side, so that the water based adhesive is heated via the belt. In these embodiments induction energy or infrared energy may be utilized. Infrared energy may be gas infrared energy or electrical infrared energy. Alternatively or in addition the water based adhesive may be dried from the second side of the metal belt. The second side refers to the belt side, on which the water based adhesive is applied. On the second side, for example infrared energy or air blow may be utilized. Microwave energy may be utilized on the side of the belt, to which the water based adhesive is applied. Microwave energy may be used to dry the water based adhesive on a belt directly. In addition or alternatively air blow may be used to dry and/or remove moisture from said at least one water based adhesive layer. Both direct and indirect drying of water based adhesive layer may enable having a desired temperature profile in relation to drying time. This may have effect of saving time and energy during drying of the water based adhesive. The induction energy may be utilized for drying. Induction drying may comprise a high frequency electrical heating. It may enable targeted drying or heating of the water based adhesive. An electrically conducting belt, for example a metal belt, may be heated by induction. Heat may be induced to the belt by circulating electrical currents. The frequency of an electromagnetic field used for heating may depend at least partly on belt size, belt material, coupling efficiency and electromagnetic field penetration depth. The induction heating may provide efficient combination of speed, consistency and control. Induction heating may provide repeatable and controllable heating process. The induction heating process may be controlled for example by choice of induction frequency, power density and interaction time. The induction heating may provide very accurate temperature control, which enables maximizing the used temperature with low tolerance. Higher temperature may speed up the drying process significantly. Adhesive performance of the water based adhesive layer may be improved due to less if any skinning of the adhesive during drying, compared to direct or sole direct drying. Since the belt is heated instead of ambient air or air only, energy used during drying process may be significantly decreased.

An infrared energy process may comprise an infrared gas heating process. The infrared gas heating device may use, for example, natural gas or propane as fuel gas. The infrared heating may be used instead or together with the induction heating. The infrared heating may be used instead or together with air blow. The infrared heater transfers energy through electromagnetic radiation. The infrared heater may dry the water based adhesive layer both directly and indirectly. The efficiency of the infrared heater may depend on matching the emitted wavelength and the absorption spectrum of the material or substance to be dried. The wavelength used for infrared heating comprises medium wave infrared range, for example 2-4 micrometers. Air blow or air jets may be used to remove moisture from the water based adhesive layer(s). The air jets are preferably placed on, or directed towards, the side of the belt, on which the at least one water based adhesive layer is applied. Adhesive

Figure 3 illustrates an embodiment, wherein water based adhesive 302 is applied on a belt 301 . Water based adhesives comprising no solvents are preferred for many applications. Using the water based adhesive has effect of providing environmentally friendly label. The label may be recycled and/or reused. A face stock according to at least some/all embodiments is coated with at least one water based adhesive layer. The number of water based adhesive layers may vary. There may be 1 -6 water based adhesive layers, more preferably 1 -3 water based adhesive layers on a face stock. Each adhesive layer may be formed using curtain coating. The total amount of adhesive on a face stock may be 5-40 g/m ² , preferably 10-30 g/m ² , more preferably 10-20 g/m ² . The water based adhesive may comprise polymers. Polymers may comprise polyacrylates based on polymerisation of monomers of methacrylate, methyl acrylate, 2-ethylhexyl acrylate, butyl acrylate, butyl methacrylate, ethyl acrylate co-polymer of vinyl acetate ethylene, natural rubber, non- carboxylated or carboxylated styrene, butadiene or acrylic ester, styrene copolymer or a combination of the previous. The water based adhesive may comprise tackifying agent, for example rosin acid, rosin ester, aliphatic hydrocarbon, aromatic hydrocarbon resin, terpene resin or a combination of the previous. The water based adhesive may comprise surfactants, thickeners and/or rheological modifiers. The water based adhesive may comprise acrylate polymer. The water based adhesive may comprise an amount of polymer of at least 50 wt-%, preferably 70-100 wt-%. Drying temperature of the water based adhesive on a belt may vary. When the drying temperature is lower, a longer drying time may be required. Before the water based adhesive is dried, it may comprise dry content of over 50 wt-%, preferably 50-80 wt-%, more preferably over 60 wt-%. If the dry content is lower than the mentioned, the process efficiency may be reduced, for example due to excessive water removal. The water based adhesive may comprise heat activatable water based adhesive. The heat activatable water based adhesive may be used with any kind of face stock in order to form a label. The heat activatable water based adhesive may comprise at least one or more than one polymer. The heat activatable water based adhesive may comprise heat activatable components. Heat activatable components may be at least partly based on solid plasticizer and/or core shell and/or hydrophilic-hydrophobic components. For instance, Solid plasticizer may comprise dicyclohexyl phthalategluceryl tribenzoate, sucrose benzoate and/or other suitable plasticizer(s). The heat activatable water based adhesive may comprise at least two different polymers.

Water based adhesive may be in a non-tacky state and be activated into a tacky state. Heat may activate the heat activatable water based adhesive. Before heat activation, for example in previous process phases, temperature is arranged below an activation temperature. Water based adhesive in the tacky state may be pressure sensitive. Process temperature may be adjusted according to application. Heat activatable component(s) of used adhesive may start to activate in order to change a state of the adhesive at certain temperature. Process temperature may be dependent on the activation temperature of heat activatable adhesive. Heat activation temperature may refer to activation temperature of heat activatable component(s), for example. Process temperature may be 5- 25 ^° C, preferably 10-20 ^° C lower than the activation temperature of heat activatable adhesive. Process temperature may be for example 15 ^° C lower compared to the activation temperature of heat activatable component(s) of the used adhesive. This avoids activation of adhesive during process phases. Activation temperatures of heat activatable adhesive may vary, for example from 70 ^° C to 1 10 ^° C. Other activation temperatures are possible. The process temperature may be adjusted accordingly. The heat activatable adhesive may be activated by exposing it to a temperature at or above the activation temperature. The activation temperature may be above or equal to 65 ^° C, or above or equal to 70 ^° C, or from 70 ^° C to 1 10 ^° C. The heat activatable adhesive may be activated by exposing it to infrared radiation. Other means for heat activation are possible. After the water based adhesive is dried, it may comprise dry content of over 80 wt-%, preferably 80-99 wt-%, more preferably over 95 wt-%.

The adhesive of the label may have (total) thickness of at least 10 or 12 micrometers, preferably at least 14 or 16 micrometers, and not greater than 40 or 35 micrometers, preferably not greater than 30, 25 or 20 micrometers. The thickness of the adhesive layer may be 16-20 micrometers. The amount of water based adhesive may comprise 16-22 g/m ² dry grammage.

A label may comprise a single adhesive layer, or multilayers of adhesive. The adhesive may comprise pressure sensitive adhesive. The adhesive may comprise pressure sensitive, heat activatable adhesive. The heat activatable adhesive may be activated to become tacky via heating. Heat activatable adhesive may be onto the belt, in touch with the belt. A heat activatable adhesive may be in a form of a film, when applied onto a belt. The heat activatable adhesive may be dried on a belt. The heat activatable and/or pressure sensitive adhesive may be applied on a face stock in a nip. Any of the adhesive layers may comprise line(s) or other suitable patterns of adhesive, or a continuous layer of adhesive. The belt may be fully or partly covered, or for example pattern coated by adhesive. The belt may be pattern coated with adhesive such that the belt comprises adhesive areas and adhesive-free areas. The adhesive areas may comprise continuous lines along a movement direction of the belt. Adhesive-free areas between two parallel adhesive lines in the movement direction of the belt may comprise 1 - 25 mm, preferably 2-6 mm or 10-15 mm. Face stock

Figure 4 illustrates an embodiment comprising a face stock. The face stock may comprise three layers 401 , 402, 403. Layers of the Figure 4 are illustrative and not in scale. The layers may be plastic layers. A face stock may comprise or consist of a monolayer film or a multilayer film. Face stock may comprise paper or plastic polymer layer(s). The face layer may be printable. The monolayer film may be blown or cast. The multilayer film may be coextruded, or at least two films may be laminated together. The face stock film may comprise polymer. The polymer film may comprise homopolymers, copolymers or polymer blend. The face stock layer(s) may comprise polyethylene (PE), polypropylene (PP), polystyrene, polyester, or any mixture thereof. The polymer film(s) may be degradable and /or derived from renewable sources, such as cellulose or lactic acid based polymer. A face stock may comprise PP, PE or both. Amount of PP and/or PE of the total weight of the face stock may be at least 50 wt-%, preferably at least 60 wt-%, more preferably at least 70 wt-%, most preferably at least 80 wt-%, or at least 90 wt-%.

The face stock may comprise odd number of polymer layers. The face stock may comprise at least one, at least three, at least five or at least seven layers, and at most nine, at most seven, at most five or at most three layers. The layers may comprise films of different polymers. Multilayer face stock comprising layers of different polymers may provide desired properties to the face stock and label. A face stock may have thickness of at least 20 micrometers, for example at least 30 or 40 micrometers, and preferably at the most 100 micrometers, more preferably at the most 90 or 85 or 80 micrometers. Thickness of a face stock may be 20-90 micrometers.

The face stock may comprise a clear plastic film. The clear plastic film provides a non-label look. The clear plastic film structure is substantially transparent to visible light. Haze of the face stock is preferably at the most 25% or at the most 20%, more preferably at the most 15%, at the most 10% or at the most 8%. Haze is tested according to standard ASTM D1003. Clear non-label look enables to see through the label, making the objects beneath the label visible through the label.

The face stock comprising plastic compound(s) may stretch in high temperatures. During manufacturing process the temperature of the plastic face stock is preferably less than 80 ^° C, more preferably less than 70 ^° C or less than 60 ^° C, most preferably less than 50 ^° C or less than 40 ^° C.

A layer of a face stock may be non-oriented or oriented in one or two directions. The directions refer to web manufacturing/running directions being longitudinal machine direction (MD) and transversal cross direction (CD). The face stock may be partially or totally oriented biaxially or monoaxially in the machine direction or in the cross direction. For example polypropylene may be biaxially oriented polypropylene (BOPP). The face stock may comprise at least one plastic film that is oriented 5-8 times in the machine direction. The machine direction oriented films primarily shrink in the machine direction. Shrink films may be applied to an article. A machine direction of the oriented film may extend circumferentially around a labelled item. A shrinkable film refers to a film which is arranged to shrink in response to exposure to elevated temperature. A first shrinkable uniaxially oriented film may be non-annealed or annealed to a very low extent. A second shrinkable uniaxially oriented film may be non- annealed or annealed to a very low extent. This may allow the film(s) to be shrinkable. At least one of the films may be non-annealed. Annealing refers to a thermal treatment involving heating a material to above its critical temperature, maintaining a suitable temperature, and then cooling. This may be called heat-setting, which may be used to anneal the internal stresses generated to a film during stretching process. Annealing may decrease the modulus and stiffness of the film(s).

Areal shrinkage of the first shrinkable uniaxially oriented film in the direction of the orientation may be at least 5% at 80°C, for example at least 10%, such as in the range of 5-80% or in the range of 10-80%. The areal shrinkage may be in the range of 40-80%. The areal shrinkage may be in the range of 50-70%. The areal shrinkage of the second shrinkable uniaxially oriented film in the direction of the orientation may be at least 5% at 80°C, for example at least 10%, such as in the range of 5-80% or in the range of 10-80%. The areal shrinkage may be in the range of 40-80%. The areal shrinkage may be in the range of 50-70%. The areal shrinkage may be defined for example by using standards AST D1204 or ASTM D2732, for example using liquid, such as water, as the heating medium at 80°C for at least 3 minutes, or using air as the heating medium at 80°C for at least 3 minutes. The tensile modulus (ASTM D882) of the first shrinkable uniaxially oriented film in the direction of the orientation may be 0.8-3.0 GPa after immersion in water at 80°C for at least 3 minutes. The second uniaxially oriented film may be annealed. It may have an areal shrinkage of less than 5%, for example less than 2% or less than 1 %.

A ratio of total film thickness before and after stretching is called a stretch ratio or a draw ratio. The stretch ratio is a ratio between the non-oriented (undrawn) film thickness and the oriented (stretched) film thickness. The non- oriented film thickness is the thickness after extrusion and subsequent chilling of the film. When stretching the face stock, the thickness of the face stock may diminish in the same ratio as the face stock stretches or elongates. For example, a face stock having thickness of 100 micrometres before machine direction orientation (MDO) may be stretched by a stretch ratio of 5. After the machine direction orientation the face stock may have a fivefold diminished thickness of 20 micrometers. The stretch ratio of a film in cross direction may be in the range of 2-7. The stretch ratio of a film in cross direction may be in the range of 3-6, for example 4-5. The stretch ratio of a film in a machine direction may be little higher compared to the stretch ratio of the film in a cross direction. The stretch ratio of a film in machine direction may be in the range of 2-10. The stretch ratio of a film in cross direction may be in the range of 3-8.

According to an embodiment heat activatable water based adhesive is dried on a belt, before applying it on a face stock comprising plastic polymer. The face stock web, which is arranged to be unwind from a roll, may be printable. The dried heat activatable, pressure sensitive water based adhesive is transferred from the belt to a surface of the unwind face stock web in a nip. The heat activatable, pressure sensitive water based adhesive is attached to the face stock. The formed linerless label web comprising the face stock and heat activatable, pressure sensitive water based adhesive is wound to a roll.

Base paper

Figure 5 illustrates an embodiment comprising coated paper. Base paper 501 is coated with coating 502. A base paper refers to a paper comprising natural fibres as its main raw material. Further, the base paper may comprise, for example, one or more fillers and/or additives. The base paper may be uncoated paper. The base paper may comprise natural fibre. Natural fibre refers to any plant material that contains cellulose. The natural fibre may be wood-based. The wood may be softwood, such as spruce, pine, silver fir, larch, Douglas fir, or Canadian hemlock; or hardwood, such as birch, aspen, poplar, alder, eucalyptus, or acacia; or a mixture of softwood and hardwood. Other than wood-based raw materials may include agricultural waste, grasses or other plant materials, such as straw, leaves, bark, seeds, legumes, flowers, tops, or fruit, which have been obtained from cotton, corn, wheat, oat, rye, barley, rice, flax, hemp, Manila hemp, sisal hemp, jute, ramee, kenaf hemp, bagasse, bamboo, or reed. Preferably, the natural fibre comprises chemically pulped natural fibre, that is, pulp made in a chemical pulping process.

A base paper may comprise raw material originating from a chemical pulp or a chemithermomechanical pulp (CTMP). The formed mass may be bleached. Content of fibres originated from a chemical pulp or a chemithermomechanical pulp may comprise at least 50-60 percentage of weight (wt-%) of base paper fibers. Amount of chemical pulp and/or CTMP originated fibers of all the base paper fibers may be up to 80-90 wt-%. Most natural fibres, for example 95 wt-%, used in the base paper may be chemically or chemithermomechanically pulped natural fibres. Alternatively or additionally, mass may originate at least partly from mechanical- or thermomechanical pulp. The diameter of the natural fibres may be 15 to 25 μιτι and the length more than 500 m, or for example 1 -1 .5 mm. The present application and embodiments are not limited to fiber size.

A base paper may comprise basis weight of 20-200 g/m ² . The base paper may comprise short and/or long fibres. Typically long fibres yield from softwood pulping, and short fibres from hardwood pulping. Long fibres of the softwood may provide strength to a base paper and enhance runnability on a paper machine. Short fibres of the hardwood may have effect on the end-use of the base paper, for example enhance the printability of the paper.

The base paper may comprises a filler. Content of a filler in a base paper may be 5-30 wt-%; advantageously 5-20 wt-%. The content of the filler in a base paper may depend on utilization and/or end use of the base paper. For example a base paper to be siliconized may comprise 0-15 wt-% filler; while a base paper used in a label product may comprise up to 15 wt-% filler. A filler may comprise clay. A filler may be used to fill spaces between fibres in a base paper. A filler may provide more weight to a base paper. In an end product an effect of a filler may be enhancing weight properties, smoothening a surface and/or decreasing opacity.

A base paper has such strength properties that it is suitable to be coated. A base paper may have such strength properties that it is suitable for finishing at a coating stage. The base paper withstands the amount of the used coating. The coated paper withstands printing phase. The fibers of the base paper may be oriented so that the base paper has required strength to both machine direction and the direction perpendicular to it. Depending on end use, even three dimensional strength properties may be desired. For example packing material, which may be used for forming a bag or a wrapper for a product, may need to have strength in 3-dimensions. A packing material may withstand customer process of making a bag or a wrapper, and end use of filling and using the bag or the wrapper. For label products strength of paper may withstand a die cutting phase, which comprises finalizing labels to obtain their final form by pressing with a metal frame and extracting extra portions at a process speed. According to an embodiment heat activatable water based adhesive is dried on a belt, before applying it on a face stock comprising paper. The face stock may comprise coated or non-coated base paper. The face stock web, which is arranged to be unwind from a roll, may be printable. The dried heat activatable, pressure sensitive water based adhesive is transferred from the belt to a surface of the unwind face stock web in a nip. The heat activatable, pressure sensitive water based adhesive is attached to the face stock. The formed linerless label web comprising the face stock and heat activatable, pressure sensitive water based adhesive is wound to a roll.

Coating

The paper may be coated. Coating may enhance property or quality of the paper, or make the paper face suitable for certain use. The coating may change surface properties of the base paper. The coating paste may penetrate to the paper. Coating may be applied as contour type coating, spray or curtain coating, or a film transfer coating. A coating may comprise binders and pigments, and optionally additives. The coating may comprise an additive, like carboxymethyl cellulose. Amount of an additive may be minor compared to the other ingredients. The pigments may be for example a calcium carbonate (CaCos) and clay. The coating may comprise amount of calcium carbonate in relation to the amount of clay 1 :1 . It is possible to employ more clay, or even only clay in a coating. Amount of clay in a coating may be 10-100 wt-%; or at least 10 wt-%; or preferably at least 15 wt-%; or more preferably at least 20 wt-%. In order to achieve light (-white), optical surface, a pigment(s) may be added. Clay may comprise plate like pigments, which provide a compact, tight surface. The coating has effect of providing good anchorage of printing ink and/or pigments of the printing ink to the surface. A binder may comprise double bonds. The binder may be latex, for example a styrene butadiene latex (SB) or a styrene acrylic (SA). Amount of binder in the coating may be 10-30 wt-%. Amount of binder in the coating may be 15-20 wt-%, or 20-30 wt-%, or 20-25 wt-%, or 25-30 wt-%, or preferably 25 wt-%. Latex used as a binder may enable coating on a paper machine. Latex has effect on later printing process. As an example, latex may have dominating effect for printability of the paper. Latex binds the pigments used in printing to the paper. Coating of a paper may enhance surface properties, for example smoothness, of the paper. Smoothness may have positive effect on printability of the surface. Amount of roughness in the printable surface may worsen the printing result correspondingly.

Latex may bind mineral pigments used in coating to each other and to the surface of the paper. Latex may have effect of providing a good base for printing. Latex may provide a compact and flexible structure. Latex may have effect of providing good bonding strength. For example if starch is used and the same bonding strength is desired, the amount of starch shall be two times the amount of latex. Thus less latex may be enough for the same quality. Latex may provide a moisture resistant surface. A runnability is good with latex, when compared to a coating comprising starch, for example. Starch is a dry component, thus may require lot of additional water during coating process. Amount of water in a starch leads to an end result, where the amount of starch in the coated paper is quite modest, for example 2-3 wt- % of the coated paper. Whereas amount of coating comprising latex may be for example 10 wt-% of the coated paper. Adding amount of coating may provide durability and strength to the coated paper.

The coating may comprise binder(s) and pigment(s) 70-90 wt-%; preferably at least 70 wt-%; more preferably at least 80 wt-%; most preferably at least 90 wt-%. It is possible to utilize other pigment(s) instead of, or in combination with, carbonate. For example, titanium may be utilized.

The coating may be added on a surface of a paper at the end phase of the papermaking machine or off-line, during some later phase, after the papermaking machine. The coating process may be of a batch type or continuous. Coating may be applied on at least one surface of the paper in order to enhance the printing performance of the paper. The coating may be added to one surface of the paper only. The other surface of the paper may comprise surface adhesive paste or starch, for example. When the end product is a label, the other side may comprise an adhesive.

Coating may comprise two or more coating layers. Sometimes better quality end results may be achieved, and/or properties of the coating increased, when at least two coatings are applied. It is possible to apply a pre-coating before applying the surface coating onto the paper. Content of a pre-coating may comprise 2-9 g/m ² ; preferably 4-6 g/m ² , and the content of a surface coating may comprise 6-12 g/m ² . The coatings may comprise 22-24 parts binder, for example polyvinyl alcohol (PVA). The coating layers may be similar layers, comprising the same components. A pre-coating may be different from the surface layer coating. The pre-coating and the surface coating together may form a coating.

Coating may comprise curtain coating, roll coating, foam coating or spray coating. The coating may comprise curtain coating. The coating may comprise a multilayer curtain coating.

Water based adhesive, dried on a belt, is applied to a face stock comprising paper. The dried water based adhesive may be attached to a non-coated side of a paper face stock. The water based adhesive is attached to the paper in a nip. Drying the water based adhesive on the belt before applying it on the paper face enables using paper face stock in a linerless label with water based adhesive.

A thermal coating

Figure 6a illustrates a thermal paper according to an embodiment. The thermal paper comprises a base paper 601 coated with a thermal coating 603. A thermal coating 603 is applied on the base paper 601 . The thermal coating 603 is arranged to form a thermal sensitive, reactive layer. The thermal coating 603 comprises reactive components. The thermal coating 603 may comprise a matrix. The matrix may comprise dye and developer. The dye may comprise leuco type dye. The developer may comprise acid. The thermal coating matrix in a solid state is heated above its activation- or melting point. The leuco dye is arranged to react with acid and change to a coloured form. Thermal coating may comprise dye, developer, sensitizer, binder.

Dye of the thermal coating may comprise leuco dye. Leuco dye is arranged to change colour in response to change in temperature. Crystalline and/or pH neutral leuco dye is in colourless leuco form. When dissolved in a melt form and/or exposed to acid environment, the leuco dye changes to a coloured form. Leuco dye may comprise for example triaryl methane phthalide dyes, fluoran dyes or crystal violet lactone. Developer of the thermal coating may comprise acid. Developer is arranged to co-react with dye. Reaction of dye with the developer is arranged to trigger colour formation. Developer may comprise sulfonyl ureas, zinc salts of substituted salicylic acids or phenols, for example Bisphenol A (BPA) or Bisphenol S (BPS).

Sensitizer may be used in a thermal coating to decrease melting point of dye and/or developer. Dye and developer 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 is 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 colour change and/or facilitating mixing of dye and developer. Sensitizer may comprise low viscosity solvent(s) or simple ether molecules, such as 1 ,2-bis-(3- methylphenoxy)ethane or 2-benzyloxynapthalene.

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

Binder of the thermal coating may have effect of facilitating a thermal coating to adhere to a base paper 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).

In the Figure 6a the thermal paper 601 may comprise coating layer(s) in addition the thermal coating 603. The coating layer(s) are optional. According to the embodiment of the Figure 6 a base coat or a pre-coat 602 is applied on a base paper 601 . The pre-coat 602 is arranged between the base paper 601 and the thermal coating 603. The pre-coat 602 may comprise pigments and binders. The pre-coat may comprise similar substances than paper coat, as discussed in the previous. The pre-coat may have effect of reducing heat transfer from a thermal coating to a base paper. This may enable enhanced or high resolution print to be formed. The pre-coat may have effect of providing smoothness to the thermal paper. Smoothness of the paper has positive effect on printing, for example resolution. The pre-coat may have positive effect on printing quality.

Figure 6b illustrates an embodiment comprising a thermal paper. According to the embodiment of the Figure 6b a thermal paper comprises a base paper 601 , a pre-coat 602, a thermal coating 603 and a top coat 604. The top coat 604 is applied on a thermal coating 603. The top coat 604 is arranged on top of the thermal coating 603. The top coat 604 may form the topmost layer of the thermal paper. Top coat may comprise polyvinyl alcohol. Top coat may comprise substances and/or agents, which may enhance printability of the paper and/or compatibility with the printing head and the paper. The top coat is arranged to form a protective coat. The top coat may have effect of protecting the thermal paper from mechanical stress and/or chemical reactions. For example, a top coat may reduce fading of print. Fading of print on a thermal paper may be due to thermal paper exposure to external conditions, like heat, humidity, UV light, water, oil, grease, fat, plasticizer or alike. Top coat may have effect of focusing heat from print head on the desired area(s) or point(s) of a thermal coating. The top coat may provide better anchorage of print. The thermal paper may comprises a back coat 605. The back coat is applied on a base paper 601 surface, which is opposite to the base paper surface 601 on which a pre-coat 602 and/or a thermal coating 603 is applied. The back coat 605 is arranged on the base paper 601 . The back coat 605 may form the lowermost layer of the thermal paper. Back coat may comprise polyvinyl alcohol. The back coat may provide protection for the thermal paper during lamination, printing or other mechanical processes. The back coat may protect thermal paper from external influences, for example from external chemical influences, like adhesive. Top and back coats of thermal paper are optional. For example thermal paper may lack the top coat and/or the back coat. Thermal paper is used for thermal printing. The digital printing process is arranged to selectively heat a thermal paper. Thermal printing press comprises a thermal printing head. The printing head exposes thermal paper to heat, which is arranged to initiate reactions in the thermal reactive layer for changing colour of the dye. The colour is changed due to change in temperature. Multicolour thermal paper is arranged to react to two or more different temperatures. Multicolour thermal paper may comprise multi thermal coating of separate colorizing layers. Two or more different colours are formed according to the temperature.

Thermal paper label

According to an embodiment a linerless label comprises thermal paper. Due to thermal sensitivity of the thermal paper, adhesive cannot be dried with the thermal paper. When activated or exposed to heat, the thermal paper blackens. Thus after this no print is visible. Using water based adhesive with thermal paper has not been possible due to need to evaporate the water from the adhesive after applied onto the paper. According to at least some embodiments at least one water based adhesive layer is dried separately before it is attached to a face stock comprising thermal paper. According to an embodiment a belt is used for drying at least one adhesive layer. The at least one adhesive layer is formed on a belt and dried on a belt, before the water based adhesive layer is attached to a surface of a face stock of a label.

Silicone

Figure 7 illustrates an embodiment of the invention. The face stock 702 may comprise paper, for example thermal paper. Water based adhesive 701 is attached on the face stock 702. A silicone layer 703 is applied on the face stock surface of linerless label. The silicone layer 703 is non-tacky with the adhesive layer 701 . Silicone may comprise UV curable silicone, for example UV free radical silicone or cationic UV silicone. When non-activatable water based adhesive is used, the silicone layer applied on opposing surface of the face stock enables winding the label on a roll. The adhesive does not stick or penetrate to the face stock, when rolled next to each other. The roll of label may be stored and/or transported. Roll of label may be used for labelling.

Embodiments and description of this application are not intended to limit the scope of this application or the following claims. Embodiments, examples and parts may be exchanged and replaced, for example with each other or partly. Obvious modifications may be made without departing from the scope.