WO2014177754A1

WO2014177754A1 - A film for a label, a label laminate and a method for manufacturing a label laminate

Info

Publication number: WO2014177754A1
Application number: PCT/FI2013/050481
Authority: WO
Inventors: Noel Mitchell; Matti Manner
Original assignee: Upm Raflatac Oy
Priority date: 2013-04-30
Filing date: 2013-04-30
Publication date: 2014-11-06
Also published as: DE112013007014T5

Abstract

The invention relates to a plastic film of a label laminate. According to an embodiment the plastic film may comprise at least polyethylene, polypropylene or copolymer of propylene, and silicone particles at least 0.01 wt.%. The plastic film may be oriented at least in one direction with a draw ratio at least 4. According to an embodiment the plastic film may be a release liner of a label laminate. Further the invention relates to a manufacturing of the plastic film.

Description

A FILM FOR A LABEL, A LABEL LAMINATE AND A METHOD FOR MANUFACTURING A LABEL LAMINATE

Field of the Invention

The application relates to plastic films and especially to a release liner for labels, and to a label laminate comprising a face layer and a release liner. Further the application concerns a method for manufacturing a label laminate.

Background of the Invention

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. The label comprises at least a face layer. Usually the label comprises also an adhesive layer and a release liner. The face layer and release liner are typically laminated together having an adhesive layer in between, which laminated structure is referred to as a label laminate. The release liner is used to protect the adhesive layer but also to allow easier handling of the label to up to the point where the label face layer is dispensed and adhered to a surface of an item.

The release liner may comprise, for example, glassine or kraft paper, or polymeric film as a backing material. Further the backing material is coated with a release agent, such as silicone.

Summary of the Invention It is an object of this application to provide a plastic film for a label laminate. Another object is to provide a release liner and a label laminate comprising a release liner and a face layer. Still another object is to provide a method for manufacturing a release liner. According to an embodiment a label laminate is provided. A label laminate comprises a plastic film having a first surface and a second surface, and an adhesive layer. The plastic film comprises at least one of the following polymers: polyethylene, polypropylene and copolymer of propylene, and silicone particles at least 0.01 wt.%. Further the plastic film is oriented at least in one direction and has a draw ratio at least 4 in said direction. According to an embodiment a release liner for labels is provided. The release liner comprises a plastic film substrate comprising at least one of the following polymers: polyethylene, polypropylene and copolymer of propylene, and silicone particles at least 0.01 . The plastic film substrate is oriented at least in one direction and has a draw ratio in said one direction at least 4. Further the release liner comprises a release layer consisting of a release agent on one surface of the plastic film substrate.

A use of a release liner according to embodiments, wherein the release liner is used in adhesive label laminates suitable for attaching onto a surface of an article is provided.

According to an embodiment a plastic film in a label laminate is provided.

According to an embodiment a method for manufacturing a release liner is provided. The method comprises heating the polymer material comprising silicone particles to a melt state so as to form a mixture, forming a plastic film from the mixture, stretching the plastic film in one direction with draw ratio at least 4, and applying a release layer consisting of a release agent on one surface of the stretched plastic film.

Further embodiments are presented in the dependent claims.

The plastic film may comprise between 0.01 and 10 wt.% or between 0.15 and 0.7 wt.%. silicone particles. The silicone particles may have at least one dimension less than 2 microns.

The draw ratio of the plastic film may be at least 6. The plastic film may be oriented in a machine direction. The film may be further oriented in transverse direction with a draw ratio under 8, under 6, or under 2.

The plastic film may comprise or consist mainly of polypropylene, copolymer of propylene or combination thereof. The plastic film may have a multilayer structure further comprising at least one skin layer. The skin layer may have a thickness between 1 and 30% from the total thickness of the plastic film. The plastic film may have 1 % secant at least 2000 MPa, at least 2200 or at least 2500 in machine direction of the film.

The plastic film may be a at least part of at least one of the following: a release liner and a facestock.

The plastic film may include a layer of release agent between the plastic film and the adhesive layer. The adhesive layer may consists of a pressure sensitive adhesive. The method may further comprise a step of grinding at least part of the polymer raw material before heating. The polymer raw material comprising silicone particles may be grinded from at least one of the following materials a spent release liner and a label laminate waste material comprising silicone coating layer.

The polymer raw material for a plastic film may include recycled material, such as between 2 and 80 wt.% grinded polymer material comprising silicone particles. The recycled material may be grinded from at least one of the following a spent release liner and a label laminate waste material comprising silicone coating layer.

Description of the Drawings In the following some examples and embodiments of the invention will be described in more detail with reference to appended drawings, in which,

Fig. 1 shows, in a cross sectional view, an example embodiment of a laminated structure for labels,

Fig. 2 shows, in a cross sectional view, an example embodiment of a release liner, shows, in a cross-sectional view, an example embodiment of a laminated structure comprising die-cut labels, shows, in a cross-sectional view, separating a label from a release liner, shows, in a cross sectional view, an example embodiment of a multilayer backing structure of a release liner, shows a perspective view of a multilayer structure of a plastic film, shows a perspective view of a label laminate structure, shows a label on a surface of an article, shows a diagram on the effect of silicone content on the haze of the film, shows a diagram on the effect of silicone content on the tear resistance of the film.

Detailed Description of the Invention

In this description and claims, the percentage values relating to an amount of a material are percentages by weight (wt.%) unless otherwise indicated. The following reference numbers and denotations are used in this application:

Sx, S_y, Sz orthogonal directions,

TD transverse direction,

CD cross direction,

MD machine direction,

DR draw ratio,

MRK1 printed information, 1 a label,

2 a face layer,

4 an adhesive layer,

6 a release liner,

8 a label laminate web,

10 a backing material layer (substrate)

12 a release coating layer,

14 a core layer,

16 a first skin layer,

18 a second skin layer.

In this application term "label" 1 refers to a product that comprises at least a face layer 2 and an adhesive layer 4. Advantageously, the face layer 2 is laminated together with a release liner 6 having an adhesive layer 4 in between so as to provide a label laminate. During manufacturing of a label 1 , the adhesive layer may be added onto the face layer 2, and/or onto the release liner 6 prior to lamination step. Term "label laminate web" 8 refers to a continuous structure for labels comprising a face layer 2, an adhesive layer 4 and a release liner 6 from which the individual labels may be die-cut. When the label is used i.e. labelled to an item 100, the face layer is attached to the surface of an item through an adhesive layer. The release liner is removed prior to labelling. The term "face layer" 2 refers to a top layer of the label, also called as a facestock, or a face material layer. The face layer 2 is the layer that is adhered to the surface of an item during labelling through an adhesive layer. The face layer may comprise e.g. printing in order to provide information and/or visual effect, such as information of the content of the item labelled. The printing may exist on a top surface, reverse side or both top and reverse side of the facestock. A label consisting of a face layer and printing layer may be referred to as a printed label. The face layer may have a monolayer or multilayer film structure comprising at least two layers. The multilayer structure may be co-extruded or it may comprise several layers laminated together. The term "release liner" 6 refers to a structure comprising a backing material layer 10 as a substrate and a release coating layer 12 on the surface. In the other words, the backing material 10 is usually coated with a thin layer of release agent, such as silicone. The backing material will also be referred to as a substrate film or a backing film hereinafter. The release agent provides a low release force and ensures the separation of the label 1 containing a face layer 2 and an adhesive layer 4 from the release liner 6. In other words, the release layer allows easy delamination of the label laminate and easy application of the label 1 onto the article to be labelled.

A haze is a property used to describe transparency of a film. Haze is the scattering of light by a film that results in a cloudy appearance of film and is the percentage of light transmitted through a film that is deflected from the direction of the incoming light. Haze is measured according to standard ASTM D1003.

Fig. 1 presents an example embodiment of a laminated label web structure 8. The label web 8 may comprise a face layer 2, a release liner 6 and an adhesive layer 4. The adhesive layer may be applied on the face layer 2 and/or onto the release liner 6 during the label laminate web manufacturing. Referring to Fig. 1 , the adhesive layer 4 is between the release layer 12 of the liner 6 and the face layer 2. Referring to Fig. 7, the laminated label structure may further comprise printing MRK1 . A top surface of the facestock 2 may be printed. The printing may be subsequently top coated in order to protect the printing. Alternatively or in addition, the reverse side of the facestock adjacent to the adhesive layer 4 may be printed.

Thanks to the adhesive layer 4 the label 1 can be affixed to the substrate, i.e. to the surface of an item (article), such as a surface of a bottle, as shown in Fig. 8. The adhesive layer may consist of a pressure sensitive adhesive (PSA). The labels consisting of PSA 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. The PSA forms a bond when pressure is applied onto the label at room temperature, adhering the label to the product to be labelled. The label comprising pressure sensitive adhesive may be referred to as a pressure sensitive adhesive (PSA) label. Pressure sensitive adhesive labels may also be referred to as a self-adhesive labels. The adhesive layer may consist of at least one of the following, a water based adhesive, a solvent based adhesive and a hot melt adhesive. If the adhesive layer is to be applied onto the face layer 2, the adhesive layer may consists of, for example, UV-curable hot melt which is cured by UV light after coating. Chemical composition of the adhesive may be based on acrylic polymers, e.g. acrylic polymers can be used as pressure sensitive adhesives. Tackifiers may be used in order to improve adhesion properties of acrylic adhesives. Alternatively, the adhesive may be a rubber based adhesive made of a synthetic or natural rubber. Rubber based adhesives contain, in addition, tackifier resin(s). According to an example, a heat activatable adhesive(s) may be used. With activatable adhesive no release liner need to be applied. The labels consisting of activatable adhesives may be referred to as linerless labels. Fig. 2 presents an example embodiment of a release liner 6 having a release coating layer 12 on top of the backing material 10. Further, the release liner may comprise at least one adhesive layer on top of the release coating layer 12. The release liner 6 is used to protect the adhesive layer 4 and to allow easier handling of the label web 8 up to the point where the labels 1 are die cut, dispensed and adhered to a surface of an item.

The backing material (substrate) 10 of the release liner 6 may consist of a polymeric (plastic) film, such as a polyester (PET) film. The polyester film may biaxially oriented in both machine and transverse (cross) directions. Alternatively, the substrate of release liner may be polyolefin based, such as polyethylene (PE) or polypropylene (PP). For example, monoaxially or biaxially oriented polypropylene film (BOPP). The substrate may be a single layer plastic film (monolayer) or it may comprise several layers (multilayer). Preferably, the substrate consists of a multilayer structure having at least 2 plastic film layers. Alternatively, the substrate consists of a multilayer structure having three or five layers. A release coating layer 12 may consists of a material having high repellency properties towards the adjacent adhesive layer. The release coating may consists of silicone, for example, crosslinkable silicone which can be applied to the substrate film and cured into a cross-linked silicone, i.e. into a polydimethylsiloxane network (PDMS). In order to achieve a silicone release coating layer a solvent-based, emulsion-based or solventless silicone systems may be used. The silicone may be cured, for example, by heat, UV radiation, LED or electron beam. UV curable silicone may be preferred if low melting plastic film substrates are used, such as low density polyethylene.

The release coating layer may consists of silicone. Silicone content may be less than 2 g/m², less than 1 .5 g/m² or less than 1 g/m² (dry grammage). The amount of silicone may be at least 0.01 , 0.02 or 0.1 g/m². The amount of silicone may be between 0.4 and 1 .5 g/m² or between 0.6 and 1 g/m², for example 1 g/m². Due to the release agent, such as silicone, the release liner 6 can be easily removed from the adhesive layer 4 of the face layer 2 during labelling i.e. prior to application of the label to the surface of an item, as shown in Fig. 4. Plastic films are preferably used for the substrate of release liner in order to achieve good evenness, such as smooth surface.

Referring to Fig. 3, individual labels 1 may be cut from laminated label web structure 8. In particular, the labels 1 may be die-cut from the web 8. After the cutting, the labels may be attached to a common liner 6, which remains uncut. Thus, a plurality of labels may remain attached to a common continuous liner 6. Alternatively, the labels 1 may be completely separate, i.e. also the liner 6 may be cut. Referring to Fig. 4, the label 1 may be separated from the liner 6 e.g. by pulling the liner 6 in the direction -S_z with respect to the label 1 . Thus, a surface of the adhesive layer 4 may be exposed so that said surface can be attached to an item.

Laminated layers of a label, such as a facestock and a substrate of a release liner, may have a monolayer structure. Alternatively, these may have multilayer structure comprising several plastic film layers, for example at least three plastic film layers. The multilayer structure may be e.g. a three layer structure consisting of three plastic film layers or a five layer structure.

Referring to Fig. 5, the substrate 10 of release liner may have a multilayer structure consisting of a core layer 14, a first skin layer 16 and a second skin layer 18. The multilayer structures can be made by co-extrusion, coating, or any other laminating process. In co-extrusion the layers of the multilayer structure are formed simultaneously by using a suitable co-extrusion die. The layers are adhered to each other to provide a unitary co-extrudate. The multilayer films may be co-extruded through blown film extrusion technology. Alternatively, the films may be cast, i.e. produced by cast extrusion technology.

In a multilayer structure the compositions of layers may be different. Alternatively, layers may have same composition. For example, the plastic film may be based on polyolefin, such as polyethylene (PE) and/or polypropylene (PP). According to an embodiment, main polymer component of the plastic film(s) is polypropylene, i.e. the film consists mainly of polypropylene. Thanks to the polypropylene stiffness of the film may be increased. In addition, tear resistance of the polypropylene based film may be decreased when compared e.g. to the polyethylene based film. Decrease in tear resistance may be advantageous, for example, in the re-cycling process and grinding of the plastic film, such as a release liner. Preferably the polypropylene is homopolymer consisting of only propylene units. According to an embodiment, the core layer of a multilayer film structure may comprise or consist mainly of propylene block copolymers. Alternatively or in addition, skin layer(s) of a multilayer structure may comprise or consist mainly of propylene copolymer(s), such as propylene block copolymer and/or propylene random copolymer which are copolymers of propylene with co- monomers, such ethylene, butene, hexene or octene. For example, propylene copolymers may be used in a skin layer which further receives a silicone coating layer (release agent). Thanks to propylene copolymer(s) better anchorage of silicone may be achieved. Thanks to propylene block copolymers in both the skin and core layers improved tear resistance and compressibility of the film may be achieved. In addition to polypropylene, the plastic film may include minor component(s), such as hydrocarbon (HC) resin(s). An amount of hydrocarbon resin(s) may be, for example, from 3 to 20 wt.%. Hydrocarbon resins are low molecular weight compounds (polymers/oligomers) consisting of only hydrogen and carbon. Hydrocarbon resins may have amorphous structure and they may be derived from synthetic or natural monomers. For example, petroleum based resins may be used. Hydrocarbon resins may be partially or fully hydrogenated. Saturated hydrocarbons are composed entirely of single bonds and are saturated with hydrogen (fully hydrogenated). The hydrocarbon resin may be aromatic, i.e. having at least one aromatic ring. Alternatively, it may be an acyclic or cyclic aliphatic resin. The number average molecular weight (M_n) of the HC may be below 2000 g/mol. For example, the M_n may be between 400 and 500 g/mol and the M_w (weight average molecular weight) between 600 and 700 g/mol, when measured via gel permeation chromatography using PS standards. The softening point according to ASTM E 28 may be below 140 °C, preferably between 90 and 140 °C.

Instead of hydrocarbon resin(s), the plastic film may comprise polyolefin elastomer(s) and/or polyolefin plastomer(s). Suitable elastomers and plastomers may be based on copolymers of ethylene or propylene with hexene, octene or butylene (1 -butene). For example butene based ethylene alpha olefin plastomers may be used, such as Exact 3024, 401 1 and/or 4049. Alternatively, or in addition, octane based plastomers may be used, such as Exact 0203, 0210, 0230, 8203, 8210 and/or 8230. Densities of plastomers may range from 0.86 to 0.91 kg/m3. Propylene based elastomers include, for example, Vistamaxx range from Exxon Mobil, such as Vistamaxx L330, 3020FL or 3980FL. Propylene based plastomers may include Koattro range of butylene (1 -butene) based copolymers from LyondellBasell. For example, Koattro KTAR 05.

In addition, the polypropylene film layer(s) may also include other minor ingredients. For example, skin layer(s) may comprise antiblocking agent, such as synthetic silica, creating some surface roughness. The content of the antiblocking agent may be between 0.05 and 0.2%, between 0.2 and 0.5%.

Further, the film may include fillers, such as T1O2. Due to the fillers, e.g. white plastic liners may be achieved. Other fillers may be, for example, talc, calcium carbonate and silicates.

According to an embodiment, the plastic film composition includes particles of silicone. Advantageously, at least 90 wt.% and more preferably at least 95 wt.% of the silicone particles are cured having cross-linked network structure. Thus, the plastic film comprises under 10 wt.% or preferably under 5 wt.% silicone which is non-cured, i.e. monomers of silicone. The amount of silicone is at most 20 wt.% or 10 wt.%, advantageously at most 8 wt.% or 5 wt.%, more preferably at most 2 or 1 wt.%. Advantageously, the amount of silicone is under 2%, or under 1 .5%, preferably under 1 %. The amount of silicone may be between 0.01 and 20 wt.% or between 0.01 and 10 wt.%. Advantageously, the amount of silicone may be between 0.01 and 1 %, or between 0.1 and 1 %, preferably between 0.1 and 0.8%, or between 0.15 and 0.7%.

In a multilayer plastic film structure, the silicone particles preferably exists only in the core layer. Referring to Fig. 5, the core layer 14 may comprise silicone particles and the skin layers 16 and 18 are films without silicone particles. The plastic film layer containing silicone particles may at least partially be based on the re-cycled material. For example, at least part of the material in a core layer may be based on re-cycled material, such as spent release liner or other label laminate waste material comprising silicone coating layer. A content of re-cycled material, also referred to as a reclaim, may be 100% or at most 80%, preferably at most 60% or 40%, more preferably at most 30% or 20%. Advantageously, the reclaim content is above 2% or above 5%. The reclaim content may be, for example between 2 and 60% or between 5 and 40%.

In a plastic film composition the silicone is in the form of particles and dispersed in a polymer matrix. Preferably, the silicone particles are evenly distributed in the polymer matrix. Alternatively, the particles may be randomly distributed. The particles have at least one dimension under 2 microns or under 1 microns. For example, a thickness of the particle may be between 1 and 2 microns. In addition, at least one other dimension of the particle may be 2-10 times larger than thickness of the particle. The silicone particles may be, for example, in a flake form. For example, the length of the flake like particle may be 2 or 3 times larger than thickness of the particle. At least part of the particles included in the film may be in a flake form, for example, at least 10 wt.% or 20 wt.%, preferably at least 50 wt.%. Small particle size of the silicone, i.e. particles having at least one dimension less than 2 microns, may provide optimum haze for the film. Small silicone particles may enable, for example, uniform haze throughout the film. In addition, small particle size may enable effective manufacturing of the films. For example, small particles may be fed more easily to the extruder. Small particle size i.e. small average diameter of particles enable also manufacturing of thin plastic film layers.

With reference to Fig. 6, during film manufacturing, such as extrusion, the silicone particles may be aligned in a core layer 14 so that the longest dimension of the particle is along the melt flow direction i.e. along the machine direction of the film (S_x). Advantageously the smallest dimension of the particle, such as thickness of 1 microns, is parallel to the thickness (S_z) of the film. Further, during stretching of the extruded film, the cavities may be formed around the silicone particles. The cavities may be formed along the stretching direction. For example the cavities are, at least partly, parallel to the stretching direction e.g. machine direction (S_x) of the film. Alternatively or in addition, cavities may be aligned in TD direction (S_y). According to an embodiment, the plastic film comprising silicone particles and polyolefin, such as polypropylene, as a main polymeric component (polymer matrix) is used as a substrate of a release liner. Advantageously, the plastic film containing silicone particles is a core layer of a multilayer substrate structure and the skin layer(s) are plastic films without silicone particles. Preferably at least the most outer layer(s) of the structure are films without silicone particles. For example, in 5-layer structure the three layers in the middle of the structure includes silicone particles and the outermost layers are silicone free. Alternatively, in the 5-layer structure at least one of the middle layers contains silicone particles. The film including silicone particles may also be used in a facestock of label, e.g. in a core layer of a multilayer facestock structure.

According to an embodiment, a multilayer film may comprise re-cycled material in a core layer and virgin polymers in skin layer(s). It is also possible that the core layer includes both virgin material and re-cycled material. The core layer of the multilayer structure may comprise up to 50 wt.%, preferably up to 30 wt.% of re-cycled material, such as re-cycled release liner containing polypropylene and silicone. The total content of re-cycled material in a plastic film, such as a core layer of a multilayer structure, may be at least 1 wt.%, preferably at least 5 wt.% or at least 10 wt.%, for example between 1 and 50 wt.%, between 5 and 50 wt.%, preferably between 5 and 30 wt.% or between 10 and 30 wt.%. Due to the use of re-cycled material the lower cost release liner may be provided.

In a multilayer structure, such as a multilayer substrate of a release liner, the thicknesses of separate layers may be different. In other words, the thickness of the core layer may be greater than the thickness of the first skin layer and/or the second skin layer. The total thickness of the substrate may be between 10 and 40 microns, for example, between 15 and 35 or between 15 and 25 microns. For example, the thickness of three-layer structure may be 30 microns.

According to an embodiment, the multilayer film structure is symmetric, i.e. the first skin layer and the second skin layer are of the same thickness.

Preferably, the core layer may be relatively thick compared to skin layer(s). The thickness of the skin layer(s) may be 15-20% and the core layer 60-70% from the total thickness of the film. The thickness for the three layered film

(1 ^st skin%:core%:2^nd skin%=total100%), as shown in Fig. 5, may be 15:70:15.

Preferably the multilayer structure contains thin skin layer(s), e.g. having thickness from 1 to 3 microns after extrusion. The thickness of the skin layer(s) may be between 1 % and 30%, between 1 .5-15%, or between 2.5 and 10% from the total thickness of the multilayer structure. In biaxially oriented film, the thickness of the skin layer may be 2% of the total thickness of the film. Due to the thick core layer comprising silicone particles, the high haze of the film may be limited to the core layer. Further, through skin layer(s) consisting of virgin material without silicone particles, the haze of the film at the surface may be reduced. Thin skin layer consisting of virgin material without silicone may also be beneficial in providing smooth film surface. Smooth surface may further allow e.g. cutting the amount of release agent needed for providing the release surface. According to an embodiment, the film, such as a substrate of a release liner, may be monoaxially (uniaxially) oriented, e.g. machine direction oriented (MDO). For example, the film comprising polypropylene (PP) and silicone particles may be after extrusion oriented (stretched) in one direction, such as machine direction. Referring to Fig. 6, the plastic film may be uniaxially oriented, for example, either in direction S_x or in direction S_y. Orientation under uniaxial stress provides orientation of the polymer chains of the plastic film in the direction of stress provided. In other words, the polymer chains are oriented at least partially in the direction of stretching (drawing). In this application, machine direction (MD) refers to the running direction (S_x) of the film during manufacturing, as shown in Fig. 6. Alternatively, the plastic film may oriented in transverse direction (TD) in direction S_y or it may be oriented biaxially, i.e. in both machine direction and transverse direction.

The ratio of total film thickness before and after stretching is called a "draw ratio" or "drawing ratio" (DR). In other words, draw ratio is a ratio of non- oriented (undrawn) film thickness to the oriented (drawn) film thickness. The non-oriented film thickness is the thickness after extrusion and subsequent chilling of the film. When stretching the facestock, the thickness of the facestock may diminish in the same ratio as the facestock stretches or elongates. For example, a facestock having thickness of 100 micrometres before machine direction orientation (MDO) is stretched by a draw ratio of 5. After the machine direction orientation the facestock has a fivefold diminished thickness of 20 micrometers.

During stretching the randomly oriented polymer chains of the extruded films are oriented in the direction of stretching (drawing). The degree of orientation of the polymer chains depends on the drawing ratio of the film. In other words, the polymer chains in the film stretched with a higher draw ratio are more oriented when compared to the films stretched with lower draw ratio. A plastic film which is oriented at least in one direction and has a specific draw ratio refers to a plastic film oriented at least in one direction with the specific draw ratio.

According to an embodiment, the stretching may be performed at least in one direction of the film, e.g. in machine direction, i.e. in longitudinal direction of the film. Films stretched in machine direction may be referred to as machine direction oriented (MDO) films. In MDO films the polymer chains are oriented uniaxially in one direction. Alternatively, the film may be stretched in transverse direction (TD), which means the direction perpendicular to machine direction of the film. TD may be referred also to as cross direction (CD). If the films are stretched both in MD and CD, the polymer chains are oriented biaxially. The stretching of the film and orientation of the polymer chains may be observed microscopically. Further, the orientation is detectable e.g. from the mechanical properties of the films, such as values of modulus and/or tensile strength.

According to an embodiment, the films are oriented at least in one direction. The films may be oriented in machine direction (MD). For example, the films may be oriented at least 4 times at least in one direction, i.e. the draw ratio of the film is at least 4 in one direction of the film. Alternatively, the orientation ratio at least in one direction may be at least 4.5, or 5, preferably at least 6 or 7. The maximum for the orientation ratio may be 8, 10, or 12. For example, the draw ratio may be between 4.5 and 12, between 5 and 10, between 6 and 8, or between 4.5 and 8. Thanks to the adequate draw ratio in machine direction, e.g. at least 4.5, further film stretching in the machine direction during subsequent labeling may be avoided. For example, providing a release liner which doesn't stretch is important while dispensing the labels. If the liner would stretch while dispensing the labels, a gap between two labels would vary leading to miss-positioning of the labels and making labeling process much less robust.

Alternatively or in addition, the films may be oriented in transverse direction, so as to provide transverse direction oriented films or biaxially oriented films. The draw ratio in transverse direction (TD) may be less than 8, or less than 6, or less than 2. For example, the draw ratio of the film in TD (if any) may be between 1 .5 and 8, or between 2 and 6.

As an example, polypropylene (PP) film comprising silicone mixed within the polypropylene matrix is oriented only in machine direction. In the film the silicone is in particulate form and the silicone particles are cured, i.e. have cross-linked network structure. The silicone content of the film may be e.g. 1 1 wt.%. An orientation ration in MDO the film may be at least 4 or 5, preferably at least 6 or 7. The draw ratio in machine direction may be between 4.5 and 8. Thanks to the machine direction orientation specific mechanical properties of the film, such as sufficient modulus in machine direction and/or elongation in both machine direction and in cross direction, may be achieved providing efficient printing and subsequent application of the label. For example, 1 % secant modulus of the machine direction oriented PP film comprising silicone particles between 0.01 and 10 wt.% may be below 4500 MPa, 4000 MPa or 3000 MPa. The secant modulus may be at least 2000 or 2200 MPa, preferably at least 2500 MPa. For example, between 2000 and 4000 MPa, or between 2500 and 4000 MPa in the machine direction of the film. Elongation of the films in machine direction may be between 20 and 100%. Elongation may be preferably below 100%, advantageously below 40% or 35%, and more preferably between 20 and 40% or between 20 and 35%.

Table 1 shows example values of mechanical properties of plastic films suitable for liner. 1 % secant modulus and elongation values are measured according to standard ISO 527-3 (specimen 2).

Samples 1 -4 are machine direction oriented films consisting of polypropylene (PP) and reclaim containing silicone particles. The amount of reclaim 5, 10, 20 and 30 wt.% corresponds to the silicone particle content of around 0.12, 0.24, 0.48 and 0.78 wt.%, respectively. The thickness of the films is around 40 microns and the orientation ratio in machine direction is 6. Comparative samples 5-7 are biaxially oriented PET films (BOPET).

Table 1 .

Sample Material Stretching Amount Thickness 1 % Elongation no ratio (DR) of (urn) secant (%) in MD in MD reclaim modulus

(%) (MPa) in

MD

1 PP 6 5 39 3082 32

2 PP 6 10 38 3066 31

3 PP 6 20 38 3166 31

4 PP 6 30 40 3018 31

5 PET - 14 4342 96 6 PET - 21 4692 96

7 PET - 24 4947 99

Table 2 shows example values of haze of non-oriented and machine direction oriented plastic films comprising polypropylene. Samples 1 -5 are non-oriented polypropylene films comprising 0, 5, 10, 20 and 30 wt.% reclaim material containing silicone. Thus samples 1 -5 contain 0, 0.12, 0.24, 0.48 and 0.78 wt.% silicone particles, respectively. Samples 6-9 are polypropylene films oriented (stretched) in machine direction with a draw ratio 6. Samples 6- 9 contain 5, 10, 20 and 30 wt.% reclaim material, i.e. the content of silicone particles is 0.12, 0.24, 0.48 and 0.78 wt.%, respectively. In addition, a film oriented in machine direction with draw ratio 6.8 and having thickness 35 microns is provided. Haze of the film is 14.6. Haze values are reported for D65/10⁰, referring to CIE standard llluminant D65 for outdoor daylight entering the observer in an angle of 10°.

Table 2.

For example, the non-oriented plastic film having thickness around 200 microns and wherein the film consists mainly of PP without silicone particles may have haze around 35%. With increasing silicone content the haze of non-oriented PP film may be increased. As an example, haze of the film including silicone may be at least 5% or 8% higher than the haze of the film without silicone. For example, haze may be at least 15 or 30% higher when the film contains silicone particles. Haze of the polypropylene based film having drawing ratio 6 (in MD) and thickness around 40 microns may also increase with increasing silicone content. As an example, haze of the oriented film including silicone may be at least 10%, 30% or 40% higher than the haze of the film without silicone. Haze of machine direction oriented film including silicone particles may be 160 or even 240% higher than the oriented film without silicone. Thus, by varying the silicone content and/or the drawing ratio optical properties of the films may be controlled. Thanks to the silicone particles haze of the oriented plastic films may be increased, for example, between 10 and 250 %. Table 3 and Fig. 9 present haze (%) of the films relative to thickness (μιτι) of the film. Amount of reclaim containing silicone 5, 10, 20 and 30 wt.% corresponds to the silicone particle content of around 0.12, 0.24, 0.48 and 0.78 wt.%, respectively. It can be clearly observed that the orientation with draw ratio 6 further increases the haze of the films which contain silicone particles. The increase in haze is also more pronounced with oriented films containing silicone when compared to the non-oriented films. For example, difference between haze of the oriented films and non-oriented films comprising silicone particles between 0.12 and 0.78% may be between 200 and 500%. Based on previous, it is advantageous to provide oriented films comprising silicone particles if increased haze of the film is preferred.

Table 3.

Haze (%) / thickness of the film (μιτι)

Amount of reclaim (%) Non-oriented film Oriented film (DR 6)

0 0.16 0.42

5 0.17 0.52

10 0.18 0.68

20 0.19 1

30 0.2 1 .23 According to an embodiment, haze of the non-oriented polypropylene based film further comprising between 0.01 and 10 wt.% silicone particles and having thickness between 100 and 250 microns may be under 60% or under 55%. For example, haze of the non-oriented films comprising between 0.01 and 10 wt.% silicone particles may be between 30 and 60%, between 30 and 55% or between 34 and 45%.

According to an embodiment, haze of propylene based films oriented at least in one direction and comprising silicone particles between 0.01 and 10 wt.% and having thickness between 10 and 40 microns may be above 20% or 45%, preferably above 30% or 40%, more preferably above 45 or 50%. For example, haze of the oriented films comprising between 0.01 and 10 wt.% silicone particles may be between 20 and 70%, between 30 and 60% or between 35 and 50%. Preferably the drawing ratio in at least one direction of the film is above 4, for example at least 4.5 or 5. Due to the increase in orientation (drawing ratio) the haze of the silicone containing films may be additionally increased.

Thanks to the orientation of the film at least in one direction, e.g. in machine direction, the haze of the silicone containing films may be increased and films having milky or cloudy appearance may be achieved. Milky appearance may be advantageous, for example, during detection of the label laminate. Thanks to the milky or cloudy appearance the detection of the label laminate may be possible with the optical detection equipment without the use of separate dispensing marks printed on the release liner.

According to an embodiment, the plastic films are suitable for re-cycling and re-use. For example, release liner may be subsequently re-cycled and reused after removing from the face layer of the label. For example, the removed liner comprising backing material containing a release coating layer consisting of silicone may be reprocessed and reused, i.e. the removed liner or label laminate waste comprising release liner may be fed back into further plastic film production, such as producing new plastic films e.g. for a release liner. For example, a closed loop system may be used for re-cycling, i.e. a product, such as a plastic liner may be recycled back into the same type of product. Thanks to the oriented films comprising silicone particles the re-cycling process of the film may also become easier. For example, the reduced tear resistance of the film makes the grinding of the film to smaller particles, such as flakes, more easy. Grinded material may be further granulated prior to further use. The grinded and granulated material is easy to be reclaimed, inter alia, in plastic film manufacturing process where the flakes and/or granulates are fed through an extruder and formed into a new film. The film can be made entirely from the re-cycled film or in combination with virgin polymers.

According to an embodiment, the tear resistance in machine direction of MDO polypropylene based liner with reclaim may be lower than either non- oriented polypropylene based film's or BOPP film's tear resistance in machine direction. Lower tear resistance may be advantageous while recycling the liner as then the liner is easier to cut to smaller pieces before re-grinding pieces to reclaim.

Referring to Fig. 10, a tear resistance of the film as a function of silicone content is presented. The amount of reclaim 5, 10, 20 and 30 wt.% corresponds to the silicone particle content of around 0.12, 0.24, 0.48 and 0.78 wt.%, respectively. The tear resistance measurements are based on Elmendorf test method and standard ISO 6383/2-1983 E. With increasing silicone content the tear resistance of the film may be reduced. For example, tear resistance of the MD oriented film having drawing ratio 6 and comprising silicone particles embedded in polymer matrix may be between 10% and 70%, or 20 and 45% smaller than tear resistance of the film without silicone. For example, the tear resistance of the oriented film comprising silicone particles may be between 50 and 75% of the tear resistance of the film without silicone.

Claims

Claims:

A label laminate comprising a plastic film having a first surface and a second surface, and an adhesive layer, the plastic film comprising:

- at least one of the following polymers: polyethylene, polypropylene and copolymer of propylene, and said plastic film further comprising silicone particles at least 0.01 wt.%,

- and which plastic film is oriented at least in one direction and has a draw ratio at least 4 in said direction.

The label laminate according to claim 1 , wherein the content of silicone particles is between 0.01 and 10 wt.%.

The label laminate according to claim 1 , wherein the content of silicone particles is between 0.15 and 0.7 wt.%.

The label laminate according to any of the preceding claims, wherein the draw ratio of the plastic film is at least 6.

The label laminate according to any of the preceding claims, wherein the polymer of the plastic film is polypropylene, copolymer of propylene or combination thereof.

The label laminate according to any of the preceding claims, wherein the silicone particles have at least one dimension less than 2 microns.

The label laminate according to any of the preceding claims, wherein the plastic film is oriented in a machine direction.

The label laminate according to any of the preceding claims, wherein the plastic film is further oriented in transverse direction having a draw ratio in transverse direction under 8, under 6, or under 2.

9. The label laminate according to any of the preceding claims, wherein the plastic film has a multilayer structure further comprising at least one skin layer.

10. The label laminate according to claim 9, wherein the skin layer has a thickness between 1 and 30% from the total thickness of the plastic film. 1 1 . The label laminate according to any of the preceding claims, wherein the plastic film comprises a layer of a release agent between the plastic film and the adhesive layer.

12. The label laminate according to any of the preceding claims, wherein the adhesive layer consists of a pressure sensitive adhesive.

13. The label laminate according to any of the preceding claims, wherein 1 % secant modulus of the plastic film is at least 2000 MPa, at least 2200 or at least 2500 in machine direction.

14. A release liner for labels, the release liner comprising:

- a plastic film comprising at least one of the following polymers: polyethylene, polypropylene and copolymer of propylene, and silicone particles at least 0.01 , and which plastic film is oriented at least in one direction and has a draw ratio in said direction at least 4,

- a release layer consisting of a release agent on one surface of the plastic film.

15. The release liner according to claim 14, wherein the content of silicone particles is between 0.01 and 10 wt.%.

16. The release liner according to claim 14, wherein the content of silicone particles is between 0.15 and 0.7 wt.%. 17. The release liner according to any of claims 14-16, wherein the draw ratio of the plastic film is at least 6.

18. The release liner according to any of claims 14-17, wherein the polymer of the plastic film is polypropylene, copolymer of propylene or combination thereof.

19. The release liner according to any of claims 14-18, wherein the silicone particles have at least one dimension less than 2 microns.

20. The release liner according to any claims 14-19, wherein the plastic film is oriented in machine direction.

21 .The release liner according to any of claims 14-20, wherein the plastic film is further oriented in transverse direction having a draw ratio in transverse direction under 8, under 6, or under 2.

22. The release liner according to any of claims 14-21 , wherein the plastic film has a multilayer structure further comprising at least one skin layer.

23. The release liner according to claim 22, wherein the skin layer has a thickness between 1 and 30% from the total thickness of the plastic film.

24. The release liner according to any of claims 14-23, wherein the plastic film further comprises an adhesive layer on a surface of the release agent layer for adhering the release liner to a facestock of a label.

25. The release liner according to claim 24, wherein the adhesive layer consists of a pressure sensitive adhesive.

26. The release liner according to any of claims 14-25, wherein 1 % secant modulus of the plastic film is at least 2000 MPa, at least 2200 or at least 2500 in machine direction.

27. Use of a release liner according to any of claims 14 to 26 in adhesive label laminates.

28. A plastic film on a label laminate, the plastic film comprising:

at least one of the following polymers: polyethylene, polypropylene and copolymer of propylene, and said plastic film further comprising silicone particles at least 0.01 wt.%; and which plastic film is oriented in at least one direction having a draw ratio in said one direction at least 4.

29. The plastic film on a label laminate according to claim 28, wherein the plastic film is at least part of at least one of the following a release liner and a facestock.

30. A method for manufacturing a release liner according to any of claims 14-26, the method comprising:

- heating the polymer material comprising silicone particles to a melt state so as to form a mixture;

- forming a plastic film from the mixture;

- stretching the plastic film in one direction with draw ratio at least 4;

- applying a release layer consisting of a release agent on one surface of the stretched plastic film.

31 . The method according to claim 30, further comprising a step of grinding at least part of the polymer material comprising silicone particles before heating from at least one of the following materials a spent release liner and a label laminate waste material comprising silicone coating layer.

32. The method according to claims 30, wherein the polymer material comprises at least between 2 and 80 wt.% grinded polymer comprising silicone particles based on at least one of the following a spent release liner and a label laminate waste material comprising silicone coating layer.