WO2015004313A1 - A thermally shrinkable plastic film and an item comprising the same - Google Patents

A thermally shrinkable plastic film and an item comprising the same Download PDF

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Publication number
WO2015004313A1
WO2015004313A1 PCT/FI2013/050758 FI2013050758W WO2015004313A1 WO 2015004313 A1 WO2015004313 A1 WO 2015004313A1 FI 2013050758 W FI2013050758 W FI 2013050758W WO 2015004313 A1 WO2015004313 A1 WO 2015004313A1
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WO
WIPO (PCT)
Prior art keywords
plastic film
shrinkable plastic
temperature
thermally shrinkable
film
Prior art date
Application number
PCT/FI2013/050758
Other languages
French (fr)
Inventor
Noel Mitchell
Matti Manner
Original Assignee
Upm Raflatac Oy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Upm Raflatac Oy filed Critical Upm Raflatac Oy
Priority to PCT/FI2013/050758 priority Critical patent/WO2015004313A1/en
Publication of WO2015004313A1 publication Critical patent/WO2015004313A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B32B27/325—Layered products comprising a layer of synthetic resin comprising polyolefins comprising polycycloolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/514—Oriented
    • B32B2307/516—Oriented mono-axially
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/732—Dimensional properties
    • B32B2307/734—Dimensional stability
    • B32B2307/736—Shrinkable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2519/00—Labels, badges

Definitions

  • the application relates to a film of a label. Especially to a heat shrink film for labelling applications. Further the application concerns a body having been labelled with the film.
  • Shrink sleeves may be provided by forming a tube of plastic film, which may be dropped over a body to be labelled and subsequently fed the item through a shrink-tunnel at elevated temperature causing the film to shrink and fit the shape of the item.
  • the film has such shrinkage properties that are beneficial in the overall labelling process, considering the transportation of the material, and the large variation is the shapes of the bodies to be labelled. Moreover, other properties of the film makes the overall process, e.g. in term of recycling, more efficient.
  • the structure and composition of the film which allow for the aforementioned properties, will also be discussed.
  • thermoly shrinkable plastic film According to an aspect of the invention there is provided a thermally shrinkable plastic film
  • ⁇ (98 °C) is less than -0.35, optionally at most -0.85;
  • ⁇ (65 °C) is greater than -0.10, preferably greater than -0.07; optionally at most 0;
  • thermoly shrinkable plastic film According to another aspect of the invention, there is provided a thermally shrinkable plastic film
  • MDO machine direction oriented
  • TDO transverse direction oriented
  • the thermally shrinkable plastic film may have been stretched in the one direction with a ratio of unstretched film thickness to stretched film thickness between 2 and 10.
  • the thermally shrinkable plastic film may have been stretched in the one direction with a stretching ratio of between 2:1 and 10:1 .
  • Fig. 1 shows, in a cross sectional view, an example embodiment of a multilayer thermally shrinkable plastic film suitable for a label
  • Fig. 2 shows, in a perspective view, the film of Fig. 1 ,
  • Fig. 3 shows, in a perspective view, an example embodiment of a label comprising thermally shrinkable plastic film
  • Fig. 4a shows, in a perspective view, an example embodiment of a thermally shrinkable plastic film before shrinking
  • Fig. 4b shows, in a perspective view, a shrunk film, wherein the shrunk film has been made by shrinking the film of Fig. 4a by thermal treatment
  • Fig. 5 shows an example embodiment of a label around a part of a body
  • labelled item shows examples for shrinkage as function of temperature for some known heat shrink label films; shows examples for relative shrinkage as function of temperature for some known heat shrink label films; shows examples for shrinkage as function of temperature for embodiments of thermally shrinkable plastic films according to the present invention; and shows examples for relative shrinkage as function of temperature for embodiments of thermally shrinkable plastic films according to the present invention.
  • l_o a length of a film (e.g. the film 1 , Fig. 4a), in a first direction, before heat treatment, wherein the first direction is in the plane of the film,
  • the length L(T) refers to a length of the shrunk film 1 1 (cf. Fig. 4b),
  • ⁇ ⁇ ( ⁇ ) relative shrinkage of a film defined as ⁇ ( ⁇ )/ ⁇ (98 °C)
  • Lpo a length of a film, in a second direction, before heat treatment, wherein the second direction is perpendicular to the first direction and is in the plane of the film,
  • a b i an area between a label and a body
  • DIR2 another direction (cf. e.g. Fig. 5), 1 a thermally shrinkable plastic film, i.e. a label film,
  • label refers to a piece of material, which is used for labelling of a body. Label may be used to identify something. Label may be attached to a body thereby forming an item, such as an article. In other words, label is suitable to be applied to a surface of a body to provide decoration, and/or to display information about the product being sold, such as content information, a trade name, a logo, a barcode, or any other graphics.
  • the body may be also called as an article, or a substrate.
  • the label comprises a thermally shrinkable plastic film and at least some graphics on a surface of the thermally shrinkable plastic film.
  • a thermally shrinkable plastic film may also be referred to as a label film.
  • the graphics may comprise, for example, printed information and/or decoration.
  • Figure 1 shows, in a side view a thermally shrinkable plastic film 1 .
  • the film 1 comprises a first layer (i.e. a first skin layer 3 or front surface layer 3) and a second layer 5 (i.e. an intermediate layer 5, i.e. a core layer 5).
  • the film 1 may comprise a third layer 7 such as another skin layer 7.
  • Figure 2 shows the film 1 in a perspective view.
  • a label 2 comprises a thermally shrinkable plastic film 1 .
  • At least one surface of the thermally shrinkable plastic film may comprise graphics MRK1 .
  • the thermally shrinkable plastic film may comprise or consist of a multilayer plastic film structure comprising e.g. three layers.
  • the label may comprise adhesive.
  • the adhesive may be used to enable the label to be attached to a body, an article or a container.
  • label refers to an object having length, width and thickness.
  • the object may be a plastic film or it may be derived from a plastic film.
  • a label comprises a first surface portion.
  • the first surface portion is intended to be attached to a second surface portion different from the first surface portion.
  • the second surface portion may be a surface portion of the label different from the first surface portion, or a surface portion of another object.
  • the first and second surface portions may be adjoined to each other by various means, such as by using an adhesive or heat, for example by welding.
  • Term “shrinkable” refers to a property of a plastic film or a label made thereof to shrink under exposure to external energy.
  • thermally shrinkable refers to the ability to shrink under exposure to heat.
  • plastic refers to a body comprising polymer or polymers, or consisting of polymer material or materials.
  • film refers to a body, of which one dimension is significantly smaller than the other two dimensions. Referring to Fig. 4a, typically in a film the thickness is less than one twentieth of the length and the width, i.e. d1 ⁇ 0.05*w1 and d1 ⁇ 0.05*h1 .
  • a thermally shrinkable plastic film 1 such as a thermally shrinkable plastic film 1 of a label 2, may shrink when exposured to an elevated temperature.
  • Heat may be applied via suitable heat transfer medium, such as hot air, steam, or water.
  • radiation such as infrared radiation can be used.
  • the thermally shrinkable plastic film 1 or a label 2 comprising said plastic film 1 is arranged to shrink.
  • Film shrinkage may be focused on a local area or to the whole plastic film area.
  • Thermally shrinkable plastic film refers to a film that shrinks at least 35 per cent, preferably at least 45 or at least 50 per cent upon heating to 98 °C in stress free conditions.
  • such a film may shrink at most 85 per cent or at most 80 per cent.
  • a heat shrink label 2 comprises a multilayer thermally shrinkable plastic film 1 (label film) comprising or consisting of thermally shrinkable layer(s).
  • the shrink label 2 comprises at least some graphics MRK1 on a surface of the thermally shrinkable plastic film 1 .
  • the thermally shrinkable label 2 may comprise adhesive.
  • the adhesive may be applied only in a joint area of cylindrical label, wherein the opposite edges of the thermally shrinkable plastic film 1 are overlapping.
  • the adhesive may be applied between the overlapping edges (cf. Fig. 5).
  • the adhesive may be applied between the thermally shrinkable plastic film and surface of a body to be labelled. Shrinkage of label may be focused on a local area or to the whole label area.
  • Local shrinkage may be focused on required areas, for example on an edge area of a label.
  • Whole label may be shrunk in a direction extending circumferentially around a container to conform to the outside (external) shape of the container.
  • Local shrinkage may be focused on required areas, for example on an edge area of an article.
  • machine direction MD refers to the running direction of the plastic film or continuous label web during label manufacturing.
  • Transverse direction TD or cross direction CD refers to the direction perpendicular to the running direction MD of the film or label web. Both machine direction and the transverse direction are in the plane of the thermally shrinkable plastic film.
  • the thermally shrinkable plastic film may be drawn (stretched) at least in one direction. The film may be drawn in a machine direction, in a transverse direction, or both. The resulting film is thus monoaxially (uniaxially) oriented (MO) or biaxially oriented (BO).
  • a monoaxially oriented film may be either machine direction oriented (MDO) or transverse direction oriented (TDO) in accordance to the direction of the orientation (of stretching), but not in both directions.
  • a biaxially oriented (BO) film is both machine direction oriented (MDO) and transverse direction oriented (TDO) in accordance to the direction of the orientation (stretching).
  • the present invention relates to films for labelling, whereby dimensional stability is preferable in one direction. Therefore, the present invention relates, in particular, to monoaxially (uniaxially) oriented films; either MDO or TDO, but not both.
  • the roll has an axis of rotation, around which the roll is rotated during said rolling.
  • the transverse direction (TD) is parallel to the axis of rotation, and thus also in plane of the film.
  • the machine direction on the other hand, is also in the plane of the film, and perpendicular to the transverse direction.
  • the length of the rolled film, in the MD may be from tens of meters upwards.
  • the width of the rolled film, in the TD is less, such as a few meters.
  • the whole roll may be cut to narrower label bands according to use.
  • the narrower rolls comprise film having the same, relatively long, length; only the width decreases in this kind of cutting.
  • the MD oriented and the TD oriented films are typically used in different ways, as will be detailed later under the terms RFS and HS.
  • the MD oriented RFS labels are generally cut in narrower strips and applied as single labels.
  • the TD oriented HS labels are slit generally wider so that tubes can be formed from the film, and thereafter, these tubes are applied onto bodies, such as bottles.
  • a ratio of total film thickness before and after stretching is called a "draw ratio” or “drawing ratio” (DR). It may also be referred to as a stretching ratio or orientation ratio.
  • draw ratio is a non-oriented (undrawn) film thickness in relation to the oriented (drawn) film thickness.
  • the non-oriented film thickness is the thickness after extrusion and subsequent chilling of the film.
  • the thickness of the film may diminish in the same ratio as the film stretches or elongates. For example, a film having thickness of 100 micrometres before uniaxial orientation is stretched by a draw ratio of 5. After the uniaxial orientation the film may have a fivefold diminished thickness of 20 micrometres.
  • the randomly oriented polymer chains of the extruded films are oriented in the direction of stretching (drawing).
  • Orientation under uniaxial stress provides orientation of polymer chains of the plastic film in the direction of stress provided.
  • the polymer chains are oriented at least partially in the direction of stretching (drawing).
  • machine direction (MD) refers to the running direction of the film during manufacturing.
  • 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.
  • the orientation like orientation direction, amount and ratio, may have effect on properties of the film, and/or the label comprising the film.
  • 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. Upon application of energy, such as heat, the drawn films shrinks in the opposite direction(s) relative to the deformations due to the drawing.
  • Haze is a property used to describe transparency of a plastic film or a face stock of label consisting of the plastic film. Haze relates to scattering of light by a film that results in a cloudy appearance of the film. Haze corresponds to the percentage of light transmitted through a film that is deflected from the direction of the incoming light. Haze may be measured according to standard ASTM D1003.
  • Thermally shrinkable films are, in general used to label items.
  • Such labeled item 1 10 comprises a body 100, and a loop 22 of a plastic film, which loop encircles a part of the body, wherein the plastic film 22 has been made by thermally treating the thermally shrinkable plastic film 1 as discussed in this document.
  • an area A b i is left in between the loop 22 of the plastic film and the body 100.
  • Term "roll-fed shrink film” (RFS) refers to labelling process, where a ready cut (MDO) label is rolled over a part, and the edges of the cut label are attached to each other to form a loop. Two alternatives can be distinguished.
  • the part may be a container (i.e.
  • the part may be a separate part, such as a cylinder, onto which the ready cut label is rolled, and the edges attached to each other. Thereafter the sleeve thus formed may be arranged onto the body 100.
  • Label is supplied from a reel, cut into individual labels and applied around the cylinder. The cylinder is thereafter applied around a part of a body and shrunk onto it.
  • adhesive e.g. hot melt adhesive
  • the adhesive may be supplied onto the body 100, e.g. by spraying onto the surface of the body, such as container, or bottle.
  • the adhesive may comprise or consist of e.g. hot melt adhesive.
  • the adhesive may be applied on those locations of the surface of the body that have the largest cross section.
  • the adhesive may be applied on the label 2.
  • the adhesive is preferably applied only on the label, since the container, in general, has a curved surface.
  • the adhesive may be applied at a trailing edge 23 and at a leading edge 25 of the label 2 (cf. Fig. 5).
  • the trailing and leading edges When rolled over to the body 100, the trailing and leading edges may overlap and form a seam 24.
  • the width of the seam may be e.g. at most 12 mm.
  • the first adhesive on the body
  • a second adhesive on the trailing edge 25
  • the second adhesive may comprise e.g. UV hot melt adhesive.
  • Subsequent shrinking process at high temperatures enables tight fitting of the label around the body. Heat shrinking may occur at a shrink tunnel, where for example hot steam may be blown towards passing items.
  • the label 2 may be rolled over the body 100.
  • an item 1 10, formed by RFS labelling body 100 directly comprises some adhesive in between the loop 22 and the body 100.
  • some adhesive is arranged between the loop 22 of the plastic film and the body 100.
  • the area A b i (Fig. 5) comprises some adhesive.
  • the item comprises a seam, and the adhesive located in between the body 100 and the loop 22 is located radially at the same location as the seam.
  • the adhesive that is arranged between the loop 22 of the plastic film and the body 100 may be located, as viewed from the seam 24 in the direction of a surface normal of the loop 22 and towards to body 100.
  • the adhesive may be let to cure or may be cured e.g. by using ultrasound or a hot-bar.
  • RFS labeling may be used e.g. with films having a reasonably low shrinkage, e.g. ⁇ (98 °C) more than about -0.4; wherein the value ⁇ (98 °C) will be defined in more detail later.
  • the film is rolled on a piece, such as a cylinder, which is not the body 100.
  • the edges of the label are attached to each other.
  • the edges may be attached to each other e.g. by laser welding techniques, ultrasound meltable adhesive in connection with ultrasound, a hot-bar, or solvent.
  • the trailing and leading edges may overlap and form a seam, and thereby a loop of the label.
  • the width of the seam may be e.g. at most 12 mm.
  • the loop of the film may be taken away from the cylinder, and arranged onto the body 100 or a part of the body 100. Heat shrinking may occur at a shrink tunnel, where for example hot steam may be blown towards passing items.
  • an item 1 10 formed by labelling a body using this type of RFS does not (necessarily) comprise some adhesive in between the loop 22 and the body 100. In such an item, the area A b i is free from adhesive.
  • This type of RFS labeling may be used e.g. with films having a reasonably high shrinkage, e.g. their ⁇ (98 °C) value is e.g. less than -0.45, such as less than -0.50.
  • Roll-fed shrink films may be uniaxially oriented in machine direction (MD).
  • MD machine direction
  • a label consists of a MDO shrink film as a face stock, and the machine direction of the label extends circumferentially around the body, the label is arranged to shrink primarily in the orientation direction when heated.
  • Term “shrink-sleeve” or “heat shrinkable sleeve film” (HS) refers to a labelling process, where a preformed (TDO) label tube (or sleeve) is introduced around a body.
  • Shrink sleeve label comprises or consists of transverse direction oriented (TDO) shrink film. The film is seamed by using solvent into a continuous tube label around the axis extending to the machine direction.
  • the formed continuous tube (or sleeve) is cut into predetermined lengths and supplied as a form of individual tube label around a body.
  • the label 2 may be a preformed label tube that is introduced around the body 100.
  • the body or container may be warmed before a cylindrical tube label is introduced over it.
  • Tube around a body is heated in order to shrink the tube label around the body.
  • the transverse direction orientation of the tube label extends circumferentially around the body. Thus, label primarily shrink in the transverse direction.
  • an item 1 10, formed by HS labelling a body does not (necessarily) comprise some adhesive in between the loop 22 and the body 100.
  • the area A b i is free from adhesive.
  • HS labeling may be used e.g. with films having a reasonably high shrinkage, e.g. their ⁇ (98 °C) value is less than -0.45, such as less than -0.50.
  • a label film may have a monolayer structure.
  • the label film may have a multilayer structure comprising two or more plastic film layers.
  • a thermally shrinkable plastic film of a label consists of a multilayer plastic film structure.
  • the multilayer label film structure 1 may comprise a first layer 3, a second layer 5 and a third layer 7.
  • the second layer 5 is between the first 3 layer and the third 7 layer.
  • the second layer 5 is an intermediate layer.
  • the intermediate layer may also be referred to as a core layer.
  • the first layer 3 and the third layer 7 may be also referred to as skin layers, i.e. a first skin layer and a second skin layer, respectively.
  • the first skin layer and the second skin layer may also be referred to as a front surface layer and a back surface layer, respectively.
  • the front surface layer may be an outermost layer of the multilayer structure when labelled to a surface of a body. However, the front surface may further be over coated.
  • the back surface layer may be the layer adjacent to a surface of a body.
  • a label may be attached to a body via adhesive on its front surface.
  • back surface may be the outermost layer of the labelled item.
  • the back surface may be covered, varnished or over-coated.
  • the multilayer structure has symmetric structure.
  • symmetric three layer structure comprises identical skin layers on opposite sides of the core layer.
  • the multilayer structure may be asymmetrical.
  • one skin layer may have more or less additives, e.g. anti-block or slip-agent, than the other skin layer.
  • the film structure may also comprise additional layers, such as tie layers or protective layers.
  • the multilayer structure may be laminated or coextruded.
  • the core layer 5 may form major portion of the multilayer film structure.
  • the core layer may have a monolayer or multilayer structure.
  • the core layer may be thicker than the first skin layer and the second skin layer.
  • the core may form 60 % of the total thickness of the multilayer structure.
  • the core may have thickness of 40 % of the total thickness of the multilayer film.
  • Thickness of the core layer may be from 15 to 50 microns (i.e. micro meters, ⁇ ), or from 20 to 50 microns, preferably around 30 or 25 microns.
  • Thickness of skin layers may be 40 % (such as from 35 % to 45 %) of the total thickness of the multilayer structure.
  • thickness of skin layers may be 60 % (such as from 55 % to 65 %) of the total thickness.
  • the thickness of a skin layer may be less than 20 microns, preferably around 10 or 7.5 microns or less.
  • the overall thickness of the multilayer film may be from 20 to 70 microns or from 25 to 60 microns, preferably around 50 microns or around 40 microns or less.
  • the multilayer film has uniform overall thickness. Uniform thickness refers to a homogeneous thickness of a film, wherein a thickness variation along the film is small.
  • the variation of the film thickness (here defined as the standard deviation divided by the average) is less than 10%, preferably between 0.1 and 5.0%.
  • Uniform thickness of the film provides better quality labels, for example, labels having good visual appearance. Uniform film thickness may have effect on the register control and image quality of the printing.
  • the multilayer plastic film structure may comprise or consist of layers having different compositions.
  • skin layer(s) may have different composition when compared to the composition of the core layer.
  • first and second skin layers may have different compositions.
  • the first and second skin layers may have similar compositions.
  • An embodiment the thermally shrinkable plastic film 1 (Fig. 1 ) comprises
  • the skin layer (3, 7) is located within a distance from the core layer 5 in the dimension of the surface normal S z of the thermally shrinkable plastic film 1 , and
  • the material of the core layer 5 is different from the material of the skin layer (3, 7).
  • thermoly shrinkable plastic film further comprises - a second skin layer (7, 3), such that
  • the core layer 5 is arranged in between the skin layer (3, 7) and the second skin layer (7, 3).
  • the second skin layer (i.e. the third layer 7) is made of the same material or materials as the skin layer (i.e. the first layer 3). In an embodiment, the second skin layer has the same thickness as the skin layer.
  • the thermally shrinkable plastic film 1 is planar symmetric, wherein the plane of symmetry is the central plane of the core layer 5 in the direction S z of the surface normal of the thermally shrinkable plastic film 1 (Fig. 1 ).
  • a skin layer may comprise a first cyclic olefin copolymer COCi and a second cyclic olefin copolymer COC 2 .
  • the cyclic olefin copolymer contains polymerized units derived from at least one cyclic and at least one acyclic olefin.
  • the acyclic olefin may be an alpha olefin having two or more carbon atoms.
  • Cyclic olefin copolymers may be based on cyclic monomers, such as norbornene and/or tetracyclododecene.
  • Cyclic mononner(s) may be chain copolymerized with ethene (ethylene).
  • cyclic olefin copolymer may be comprise monomers of norbornene and ethene.
  • cyclic olefin copolymer may comprise monomers of tetracyclododecene and ethene.
  • Cyclic olefin copolymer may also consists of monomers of norbornene, tetracyclododecene and ethene.
  • the first cyclic olefin is different from the second cyclic olefin.
  • a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C.
  • a difference in the glass transition temperature of the first cyclic olefin copolymer and the second cyclic olefin copolymer may be at most 40 °C, preferably at most 30°C.
  • the difference in the glass transition temperature of the first cyclic olefin copolymer and the second cyclic olefin copolymer may be at least 5 °C, preferably at least 10°C.
  • the glass transition temperature of the first cyclic olefin copolymer may be below 70°C and the glass transition of the second cyclic olefin may be above 70°C.
  • the first cyclic olefin copolymer COCi may have glass transition temperature of 65°C measured according to standard ISO 1 1357-1 , -2,-3 with heating rate of 10°C/min.
  • the second cyclic olefin copolymer may have a glass transition temperature of 78°C.
  • Melt volume rate tested according to standard ISO 1 133 at 230°C with test load of 2.16 kg of COCi may be 6.0 cm 3 /10min.
  • Melt volume rate of COC 2 may be 1 1 .0 cm 3 /10 min.
  • Density of COCi and COC 2 may be 1010 kg/m 3 , when measured according to standard ISO 1 183.
  • At least one skin layer may comprise equal amounts of the first cyclic olefin copolymer and the second cyclic olefin copolymer.
  • a ratio of the first cyclic olefin copolymer to the second cyclic olefin copolymer COC 1 /COC 2 may be between 1 .5 and 8.
  • Amount of cyclic olefin copolymer(s) in skin layer(s) may be at least 50 wt.%, or at least 60 wt.%.
  • Amount of cyclic olefin copolymer(s) may be at most 98 wt.% or at most 90 wt.%.
  • an amount of cyclic olefin copolymer(s) may be between 50 and 90 wt.%, or between 60 and 90 wt.%.
  • the skin layer (3, 7) comprises first cyclic olefin copolymer. In an embodiment, the skin layer (3, 7) further comprises second cyclic olefin copolymer, wherein the first cyclic olefin copolymer is different from the second cyclic olefin copolymer.
  • the first cyclic olefin copolymer (of the skin layer) has a first glass transition temperature and the second cyclic olefin copolymer (of the skin layer) has a second glass transition temperature, such that the second glass transition temperature is different from the first glass transition temperature, optionally the second glass transition temperature is greater than the first glass transition temperature by at least 5 °C or at least 10 °C .
  • the first glass transition temperature is below 70 °C, such as below 67 °C , such as 65 °C and
  • the second glass transition temperature is above 70 °C, such as above 75 °C, such as 78 °C.
  • the glass transition temperature may be measured as discussed above.
  • the first and second cyclic olefin copolymers according to embodiments may have effect on the shrinking behaviour of the film. For example, a specific shrinkage curve may be achieved with the at least some/all embodiments.
  • skin layer(s) may comprise linear low density polyethylene (LLDPE).
  • Skin layer(s) may comprise Ziegler-Natta catalyst based LLDPE.
  • Skin layer(s) may comprise metallocene LLDPE (m-LLDPE).
  • LLDPE may be a copolymer of ethylene and 1 -octene. Density of LLDPE may be 0.916 g/cm 3 , when measured according to standard ASTM D792.
  • Melt Index may be 2.0 g/10min, when measured according to standard ASTM D1238 at 190°C/2.16 kg.
  • an amount of linear low density polyethylene may be at most 30 wt.%, or at most 20 wt.%, or at most 10 wt.% of the total weight of the skin layer.
  • minimum amount of LLDPE may be between 5 and 10 wt.%.
  • An amount of LLDPE may be between 0 and 30 wt.%, or between 5 and 20 wt.%, or between 10 and 20 wt.%.
  • LLDPE has effect of reducing or avoiding the finger marking effect of the film.
  • LLDPE may have effect of reducing un-wanted visual appearance, for example due to reducing or avoiding the finger marking effect of the film.
  • LLDPE may have an effect of providing good interlayer attachment.
  • the skin layer comprises or further comprises linear low density polyethylene (LLDPE).
  • skin layer(s) may contain additives.
  • the skin layer comprises or further comprises at least one additive selected from the group comprising inorganic fillers, pigments, antioxidants, ultraviolet absorbers, anti-blocking agents, slip additives, antistatic additives, cavitating agents.
  • the first skin layer may comprise anti-blocking agent.
  • An amount of anti-blocking agent may be between 0.5 and 5 wt.%, preferably between 1 and 3 wt.% or between 2 and 3 wt.%.
  • the amount of each additive is less than 5 wt.%; however the total amount of different additives may be higher. In an embodiment, the total amount of different additives is less than 5 wt.%.
  • An intermediate layer 5 may contain at least one terpolymer.
  • the core layer 5 comprises at least one terpolymer.
  • the core layer 5 comprises at least one of the following propylenes: 1 -butene/propylene/ethylene, propylene/ethylene/1 -hexene and propylene/ethylene/1 -butene.
  • Propylene terpolymer may have a density of 0.90 g/cm 3 , when measured according to standard ISO 1 183.
  • Melt flow rate may be 5.5 g/10min, when measured according to standard ISO 1 133 at 230°C/2.16 kg. Alternatively the melt flow rate may be 0.9 g/10min.
  • the total amount of terpolymer or terpolymers is between 20 wt.% and 95 wt.%, preferably between 40 wt.% and 90 wt.%, more preferably between 50 wt.% and 80 wt.%.
  • Terpolymer(s) may have effect on the orientation behaviour of the film.
  • Terpolymer(s) may reduce the softening point of the film thus improving the stretching of the film.
  • films comprising terpolymer(s) may be stretched at a lower temperature.
  • higher orientation ratios may be achieved, which may have effect on the shrinkage potential of the film.
  • terpolymer(s) may have an effect on increasing the heat resistance of the film.
  • terpolymer(s) may have an effect on providing more stability for the film, which is advantageous during orientation process e.g. in avoiding the film tearing away from the grippers holding the film.
  • the intermediate layer 5 may contain polyolefin plastomer and/or polyolefin elastomer.
  • the intermediate layer may comprise at least one of the following: propylene/ethylene plastomer, ethylene/octene elastomer and ethylene/butene elastomer.
  • the core layer further comprises, in addition to terpolymer(s), polyolefin plastomer and/or polyolefin elastomer, such as at least one of the following: propylene/ethylene plastomer, ethylene/octene elastomer and ethylene/butene elastomer.
  • Polyolefin elastomer may have density of 0.863 g/cm 3 , when measured according to standard ASTM D729. Alternatively, density may be 0.867 g/cm 3 . Melt flow rate may be 8.0 g/10min, when measured according to standard ASTM D1238 at 230°C/2.16 kg. Polyolefin plastomer may have a density of 0.867 g/cm 3 and melt flow rate of 8.0 g/10min. An amount of polyolefin plastomer and/or elastomer may be between 2 and 50 wt.%, preferably between 5 and 35 wt.% and more preferably between 10 and 30 wt.%.
  • the core layer may comprise for example, total amount of 10, 15, 20, 25 or 30 wt.% polyolefin elastomer and/or polyolefin plastomer.
  • Polyolefin elastomer(s) and/or plastomer(s) may have an effect on the ability of the film to be stretched (oriented) and thus on the shrinkage potential of the film.
  • the intermediate layer may contain cyclic olefin copolymer.
  • An amount of cyclic olefin copolymer may be 5 wt.%, 10 wt.%, or 20 wt.%, preferably less than 30 wt.%. For example, between 0 and 30 wt.%, or between 5 and 20 wt.%, or between 10 and 20 wt.%.
  • the cyclic olefin copolymer in the intermediate layer may have effect on achieving good adhesion between the intermediate layer with skin layer(s).
  • the cyclic olefin copolymer contained in the intermediate layer may have effect of increasing the overall shrinkage of the film.
  • the intermediate layer according to embodiment may not resist shrinking of the film.
  • the multilayer film comprising at least a core layer, a first skin layer and a second skin layer is monoaxially, i.e. uniaxially, oriented, i.e. stretched only in one direction.
  • a film may be oriented in machine direction (MD).
  • MD machine direction
  • TD transverse direction
  • the films may be oriented in transverse direction (TD), so as to provide uniaxially in transverse direction oriented films having controlled shrinkage in transverse direction.
  • Unoriented multilayer films may be manufactured by using either a cast or blown-film extrusion process.
  • a shrinkable multilayer film may be obtained by stretching (drawing) the extruded multilayer film to an extent several times its original dimension to orient the film. Stretching may be designated also as orienting.
  • the stretching may be performed by using heated draw rolls with gradually increasing speed.
  • the stretching may be performed below the melting temperature of the polymer and/or at or near the glass transition temperature of the polymer.
  • the film stretching temperature is between 50°C and 120°C, preferably between 60°C and 1 10 °C or between 60°C and 100 °C.
  • the film may be cooled with a cooling roll having temperature of around 25°C. Stretching and subsequent cooling may provide suitable shrink potential for the film. Due to the shrink potential, the oriented films are able to shrink under elevated temperature towards the non-oriented (initial) state of the film.
  • the stretching is performed 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.
  • MDO films the polymer chains are oriented uniaxially in said machine direction.
  • Machine direction oriented films may be used for roll-fed labelling (RFS, as discussed above), i.e. in a labelling process where the label film is supplied from a reel, cut into separate labels, after which labels are mounted around a piece (directly onto the body 100 or first onto a separate cylinder, and thereafter transferred around a part of the body 100) and seamed during labelling step using adhesive, such as UV-acrylic hot- melt adhesive.
  • seam may be formed by solvent seaming, hot- bar (heat-sealing), laser-welding or ultrasonic radiation.
  • the label around the body may be shrunk in order to form a tight attachment and/or to conform the shape of the body.
  • some adhesive may be used between the label and the surface of the body 100 in order to keep the label in specified place.
  • the film may be stretched in transverse direction (TD), which means the direction perpendicular to machine direction of the film.
  • Transverse direction (TD) may be referred also to as cross direction (CD).
  • Transverse oriented films may be used for shrink-sleeve type of labels, which films are seamed into a form of a tube prior to labelling.
  • the tube is cut into tubes of predetermined lengths and supplied as in a form of tube around a body.
  • the labelled item may be heated in order to provide shrinking of the film around the body and/or to provide tight fitting of the label around the body and/or to conform the shape of the body with the label.
  • the stretched (oriented) structure 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.
  • the film may be uniaxially oriented approximately from 2 to 10 times, preferably 3 to 9 times, and most preferably from 3 to 8 times.
  • the film may be uniaxially oriented in machine direction.
  • Draw ratio (or orientation ratio) of the MD film is from 2 to 10 (from 2:1 to 10:1 ) , preferably from 3 to 9 (from 3:1 to 9:1 ), most preferably from 3 to 8 (from 3:1 to 8:1 ), correspondingly.
  • the film may be uniaxially oriented in transverse direction, for example, from 2 to 10 times, preferably 3 to 9 times, and most preferably from 3 to 8 times.
  • the films may be oriented at least 3 times at least in one direction, i.e. the draw ratio (stretching ratio) of the film is at least 3 in one direction of the film.
  • the orientation ratio at least in one direction may be at least 4.
  • the draw ratio may be between 3 and 7, preferably between 4 and 6.
  • first cooling roll(s) may have a temperature of around 90 °C, for example between 80°C and 90°C.
  • Subsequent cooling roll(s) may have temperature between 10 and 20°C, or around 25°C. Consequently, subsequent application of heat causes the oriented film to relax and the oriented film may return towards or substantially back to its original unstretched dimensions.
  • machine direction oriented films primarily shrink in the machine direction and transverse oriented films in the transverse direction.
  • a uniaxially oriented thermally shrinkable plastic film 1 having dimensions of a first length w1 , a second length width hi and thickness d1 , is arranged to shrink under application of heat so as to form a shrunk thermally shrinkable plastic film 1 1 .
  • Uniaxial orientation direction S x of the film is parallel to the first length w1 .
  • Uniaxial orientation direction may be, for example, the machine direction MD.
  • uniaxial direction may be the transverse direction TD.
  • the uniaxially oriented film 1 is capable of shrinking in the direction of the orientation S x . In other words, the length of the film reduces, when heat is applied.
  • the dimension hi remains substantially constant, as will be later defined in more detail. Same applies to the labels 2 comprising uniaxially oriented thermally shrinkable plastic film.
  • the thermally shrinkable plastic films 1 may be printed in order to provide visual effect and/or to display information. Printing may be performed by using traditional printing processes, for example, flexographic, gravure offset, and digital printing methods, such as liquid-toner, dry-toner or ink-jet processes.
  • the multilayer film may comprise printing on an outer surface of a first skin layer 3.
  • the reverse side of the multilayer structure may be printed, i.e. a third layer 7 may comprise the printing.
  • the graphic patterns may be printed on at least one of the skin layers of the multi-layered film.
  • the film When printing the second skin layer 5 of the film, the film may be referred to as reverse-printed.
  • the printing is in direct contact with a surface of a body to which the film is applied. The print is viewed through the multilayer film. With these kind of films no further layers are needed to protect the printing e.g. from abrasion or scratching during handling of the labelled items.
  • the multilayer films are suitable for printing.
  • the films enable high printing quality.
  • the films have excellent ink adhesion and register control, allowing for example gravure printing.
  • the printability of a surface can be characterized by the surface tension of the surface.
  • the surface tension can be measured as described in the standard ISO 8296 (e.g. the latest version available on 1 st , July 2013).
  • the surface tension of a printable surface may be e.g. from 36 mlM/m to 46 mlM/m, preferably from 38 mlM/m to 44 mlM/m. Quite commonly the surface tension is expressed in units dynes/cm.
  • the print receiving skin layer may have a surface tension at least 36 dynes/cm, preferably at least 38 dynes/cm or at least 44 dynes/cm measured according to the standard ASTM D-2578 (e.g. the latest version available on 1 st , July 2013).
  • the surface tension may be between 36 and 60 dynes/cm, preferably between 38 and 56 dynes/cm or between 44 and 50 dynes/cm.
  • the surface 2 may be apolar and may have a low surface tension. Low surface tension may lead to poor retaining capability of printing ink or other coating material, which may be applied to the skin layer surface.
  • the skin layer may be surface treated by e.g. by flame treatment, corona treatment, plasma treatment in order to enhance the surface tension of the surface of the skin layer and to enhance, for example, adhesion of the printed graphics.
  • the treatment increasing the surface tension may not be permanent, and the level of surface tension may decrease from the obtained treatment level as a function of time.
  • the treatment may later be repeated to restore the level of surface tension obtained in a previous treatment.
  • the multilayer plastic film is clear i.e. transparent to visible light.
  • Clear multilayer shrink films and labels comprising said films have good visual appearance.
  • said films may provide no-label look or appearance, when attached to the surface of a body.
  • the clear no-label look allows the objects beneath such label, i.e. the bottle or contents, to be visible through such label.
  • Clarity of the film and a label comprising said film can be measured and evaluated by the haze values.
  • the overall haze of the multilayer film and label consisting of said multilayer film may be less than 25%, preferably less than 15%, and most preferably less than 10% when measured according to the standard ASTM D1003.
  • the haze of the thermally shrinkable plastic film may be between 2 and 10%, or between 5 and 10%.
  • initially clear thermally shrinkable plastic film of a label may be printed on the reverse side of the thermally shrinkable plastic film and the printing is visible through the thermally shrinkable plastic film.
  • the printing is adjacent to the surface of the labelled item and as such protected, for example, from scuffing.
  • the printing may be two-layered, e.g. colour printing at the film surface covered (overprinted) with a white or some other colour printing.
  • the overprinting is next to the surface of the body. Through this kind of label the object beneath is not visible.
  • the multilayer films and labels comprising said films have controlled shrinkage, i.e. specific amount of shrinkage at specific temperature range.
  • the films have an ability to shrink upon exposure to external energy, e.g. some level of heat.
  • Shrinkage of the film is activated when the film is treated e.g. at elevated temperatures, such as passed through a hot air or steam- tunnel.
  • the shrink performance, i.e. shrinking capacity (potential) of the films in the stretching direction is very high at elevated temperatures.
  • Shrinkage may be measured.
  • shrinkage is defined with reference to the method; however, it is evident, and has been noticed, that the same shrinkage properties apply regardless of the method, provided that the same temperatures are used. I.e. the composition of heat transfer medium (air, steam, water) is not critical for shrinkage behaviour in the shrinkage test.
  • a steam tunnel provides for uniform heating, and thus uniform shrinkage.
  • a thermally shrinkable plastic film 1 stored at a temperature TO has a first length w1 in a first direction S x and a second length hi in a second direction S y , wherein the second direction S y is perpendicular to the first direction S x . Both directions S x and S y are in the plane of the film 1 .
  • the temperature TO may be e.g. from -50 °C to +50 °C, what is important is that the manufactured film does not shrink at the temperature TO.
  • TO may be e.g. +25 °C.
  • the dimensions of a part A00 of the (not shrunk) film 1 are measured before heating.
  • the shrinkage of a thermally shrinkable plastic film is determined as follows:
  • the area AOO has a first length L 0 in the first direction S x and a second length L p0 in the second direction S y .
  • the area is 100 mm ⁇ 100 mm.
  • L 0 100 mm
  • L p0 100 mm.
  • a sufficiently large piece of film is used, i.e. w1 >L 0 and h1 >L p0 .
  • the sample i.e. the film 1
  • the sample is placed for 15 seconds to a water bath having a temperature T.
  • T a temperature of the whole (shrunk) film 1 1
  • Some weight, such as rivets, may be applied to the film 1 (or 1 1 ) to let it sink in to the water bath. Otherwise, the film (1 , 1 1 ) could float, as will be discussed in detail later.
  • the length of the marked area, in the first direction S x , after the thermal treatment wherein the temperature has been T, and after the cooling back to the temperature TO is denoted by L(T).
  • the length of the marked area, in the second direction S y , after the thermal treatment wherein the temperature has been T, and after the cooling back to the temperature TO is denoted by L P (T).
  • temperatures T are used in the experiment, that are critical for transportation temperatures (i.e. reasonably hot water is used), and which temperature is achievable with the (unpressurized) water bath.
  • the length is measured from three different points of the sample (i .e. the area A00 or AO).
  • at least two similar samples are used to further improve the statistical accuracy, either by drawing two different areas A00 onto the same piece of film 1 , or by using two different pieces of film having the same composition.
  • the numerical value of shrinkage is negative, while the numerical value of strain would be positive.
  • a "better" shrinkage is, in terms of numbers, a more negative (i.e. a smaller) value.
  • a thermally shrinkable film 1 can be shrunk using different heat sources such as hot air, hot gas, steam, and/or radiation. Thus, in practice, drying is not necessarily needed.
  • a thermally shrinkable film 1 having the shrinkage ⁇ ( ⁇ ) is configured to shrink, at the temperature T, - ⁇ ( ⁇ ) ⁇ 100 %.
  • a film used as a label is preferably only monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO). As discussed above, this kind of a film shrinks primarily in only one direction, i.e. in the "first direction” discussed above. This type of a film
  • ⁇ ⁇ ( ⁇ ) is less than 7 % (i.e. ⁇ ⁇ ( ⁇ ) is from -0.07 to 0.07 not including the limits) for temperatures 0 °C ⁇ T ⁇ 100 °C; preferably the absolute value of ⁇ ⁇ ( ⁇ ) is less than 5 % for temperatures 0 °C ⁇ T ⁇ 100 °C more preferably the absolute value of ⁇ ⁇ ( ⁇ ) is less than 3 % for temperatures 0 °C ⁇ T ⁇ 100 °C.
  • the subscripts p refer to perpendicular (cf. Figs 4a and 4b). This has the technical effect that the markings (MRK1 , Fig. 3) do not significantly shrink in the second direction, whereby the markings are easy to design.
  • a residual shrink force can also be used to characterize the force by which the label sticks to a body.
  • the residual shrink force is determined in a test according to the standard DIN 53369 (latest version available on 1 st July, 2013).
  • a sample of the thermally shrinkable film 1 having the length 100 mm is placed in between two objects being separated apart from each other by the distance 100 mm.
  • the film can be oriented in any direction in between these objects, however, typically, the film is oriented such that either the machine direction or the transverse direction is oriented from the first object to the second object, depending on which property is to be measured.
  • the distance between these object is arranged fixed, and the sample is clamped to the objects.
  • At least one of the objects is arranged to measure or coupled to a device arranged to measure the force, by which the film pulls the objects towards each other.
  • the sample width is 15 mm, whereby the result of the test is given in units of force per 15mm.
  • the heating rate is 120 °C/h, whereby a heating of 70 degrees takes 35 minutes.
  • the cooling of 70 degrees takes another 35 minutes.
  • the force, by which the film pulls the objects towards each other at the end of the test is defined as the residual shrink force.
  • the film does not shrink, as its dimension is fixed by the objects.
  • the selection of materials and the thickness of the film affect the residual shrink force.
  • the shrink force may be measured as function of time and/or temperature during the test; however, the residual shrink force is defined as discussed above, at the final stage of the test.
  • the composition of the multilayer thermally shrinkable plastic film 1 has effect of providing adequate shrinkage for use as a heat shrink label 2.
  • the thermally shrinkable plastic film 1 may have tensile strength in the orientation direction of the film between 90 MPa and 170 MPa. As for the strength, the ultimate strain in orientation direction of the film may be between 20 % and 50 %. Bending resistance (L&W 5mm, 15°) may be between 10 mN and 20 mN. 1 % secant modulus may be at least 500 MPa, or between 1200 MPa and 2000 MPa, or between 1200 MPa and 1800 MPa, when measured according to standard ISO 527-3. Stiffness (1 % secant modulus) may be between 0.008 and 0.015. Preferable values for the shrinkage of the thermally shrinkable plastic film
  • the thermally shrinkable plastic film 1 is, in some cases, used to label bodies 100 having uneven cross section.
  • the film shrinks rapidly, i.e. when the film starts to shrink (referring here to temperature), the film shrinks a lot.
  • the label will be fitted also to the areas having small cross section without the need for excessive heating.
  • a thermally shrinkable plastic film 1 having a first size w1 in a first direction S x ,
  • the length L(T) refers to the length after cooling and drying or after drying and cooling. Heat treatment can be done in a dry atmosphere, whereby drying is optional. Drying merely refers to the test method, not to the practical applications of the film.
  • the shrinkage of the thermally shrinkable plastic film is generally large, tens of per cents, in order to be applicable in the application.
  • the value may be at most -0.85; and typically at most -0.80.
  • the film is configured to shrink, at this temperature, more than 35 per cent; which is characteristic for a thermally shrinkable plastic film.
  • FIG. 9a shows examples of prior at films, as denoted by the reference numbers 010 and 020.
  • the films cannot be freely transported.
  • the temperature in vehicles may rise to reasonably high temperatures, whereby such films may start to shrink already during transportation, i.e. prior to use.
  • shrinkage during transportation would cause blocking in the rolls.
  • the roll having some shrunk film would be too tightly wound, and not industrially applicable
  • this is the case for a film having a temperature dependent shrinkage as shown in Fig. 9a by the reference number 010.
  • the prior art shrink labels of Fig. 9a and 9b are not necessarily oriented in the machine direction.
  • the density of the shrink labels of Fig. 9a and 9b is not such that the label floats, in particular on water.
  • the films should shrink a reasonable amount already for only slightly higher temperatures. When the films shrink at such temperatures, the attaching of the film to the body becomes faster, since the films can be heated more rapidly. This is particularly the case for bodies 100 having uneven cross section (cf. e.g. Fig. 8).
  • ⁇ ⁇ ( ⁇ ) ⁇ [L(T)-L 0 ]/L 0 ⁇ /s(98 °C).
  • the value of ⁇ ⁇ ( ⁇ ) will be given in percentages.
  • the reason for selecting the reference temperature of 98 °C is that such a temperature is achievable using hot water or unpressurized (pressure equals 1 atm) steam.
  • the film may shrink also for temperatures above 98 °C, however these are of little practical interest, since the films are commonly heated by water and/or steam.
  • water is used in a typical shrinkage test, while steam is typically used in a labeling process. So, the value ⁇ (98 °C) is not a maximum shrinkage, only a reference value.
  • the relative shrinkage s r first, at low temperatures, the relative shrinkage should be reasonably low. This is because the temperature during transportation may rise such that, provided that the shrinkage at the corresponding temperature would not be small, some shrinkage would occur. However, as discussed above, shrinkage during transportation would cause blocking in the rolls. Thus, the roll having the shrunk film would be too tightly wound, and not industrially applicable.
  • the shrinkage ⁇ at the transportation temperatures needs to be low, preferably negligible or zero.
  • the relative shrinkage ⁇ ⁇ at the transportation temperatures is low, in order to further reduce the shrinkage during transportation at hot conditions. Still further, with a low relative shrinkage at these temperatures, the shrinkage potential after transportation of the film is high, regardless of the shrinkage ⁇ . As for an example of a transportation temperature, typically these are at most 65°C.
  • the relative shrinkage should be reasonably high. This is because films that are purposely heat treated have preferably used most of their shrinkage potential. For example, when the crushed film floats on water, e.g. hot water, the crushed pieces are preferably not further shrunk on the water. For example, the crushed pieces may be collected using a sieve having a size, and further shrinking of the pieces might make the smaller than the sieve size. Thus their collection might become hard. Furthermore, the further shrinking, as discussed, might curve or bend the crushed pieces, and the further utilization of such curved pieces might be more problematic than the utilization of planar pieces. The heat shrunk label would not have too much residual shrinkage potential left.
  • High shrinkage potential of the label may be harmful for example if heated liquid (having a temperature around 80 °C) is used during the separation process, which will cause e.g. curling of the label into tight tubes blocking the apparatus wherein the parts are separated.
  • Such an apparatus may be simultaneously arranged to wash the pieces.
  • the film should use most of its shrinkage potential for a reasonable small temperature change.
  • the lower of the two temperatures, Ti may be 65 °C, whereby ⁇ ⁇ (80 °C)-s r (65 °C) is more than 50 pp.
  • the lower of the two temperatures, Ti may be 70 °C, whereby ⁇ ⁇ (85 ° ⁇ )- ⁇ ⁇ (70 °C) is more than 50 pp.
  • the thermally shrinkable plastic film is monoaxially oriented; in the MD or the TD.
  • a value "greater than -0.1 " may be e.g. -0.05. Because the value is negative by definition, a greater value means less shrinkage.
  • a value "less than -0.25" may be e.g. -0.3. Because the value is negative by definition, a lesser value means more shrinkage.
  • ⁇ (70 °C) is greater than -0.18, or more preferably greater than -0.16.
  • ⁇ (75 °C) is less than -0.16 or more preferably less than -0.17.
  • the shrinkage decreases with increasing temperature relatively rapidly. This kind of rapid decrement can be described with a function.
  • the film floats on water (for reasons discussed above), and for ease of manufacturing, preferably the film is oriented only in the machine direction.
  • the thermally shrinkable plastic film is monoaxially oriented in the machine direction (MD) or the transverse direction (TD),
  • the thermally shrinkable plastic film is monoaxially oriented, either in the machine direction (MDO) or transverse oriented (TDO),
  • the value of the function fi 2 (T) is depicted in Fig. 10a.
  • These functions provide for a reasonable limit for temperature behavior of the shrinkage.
  • the more specific values, that were discussed above, can be used to describe the shrinkage behavior.
  • the shrinkage behavior can be described using the relative shrinkage ⁇ ⁇ ( ⁇ ) as defined above.
  • the relative shrinkage ⁇ ⁇ ( ⁇ ) is preferably above some limiting values in some specific temperatures, as will be discussed later.
  • the relative shrinkage ⁇ ⁇ ( ⁇ ) may be between some limiting values in some specific temperatures, as will be discussed later.
  • thermoly shrinkable plastic film Because of these reasons, in some embodiments of the thermally shrinkable plastic film
  • the values of relative shrinkage of different samples manufactured as described earlier are shown in Fig. 10b with the reference "Samples”. In total 21 samples were manufactured and measured as describe above. For the aforementioned reasons, the behavior of the relative shrinkage is particularly important in the temperature range 70 °C ⁇ T ⁇ 85 °C.
  • ⁇ ⁇ may also be lower than another limiting function.
  • the shrink properties in particular ⁇ ( ⁇ ) and ⁇ ⁇ ( ⁇ ) can be affected by selection of materials, their composition, and/or the thicknesses and number of different layers, as well as by the draw ratio.
  • All the 21 samples of Figs. 10a and 10b have a three layered structure as shown in Fig. 1 , the composition as discussed above, and manufactured as discussed above.
  • Roll-fed shrink labels may be applied to a body with a combination of steps including: rolling over, seaming and shrink technique.
  • Labels may be provided in a roll of continuous label stock and cut into individual labels.
  • a label 2 cut from a continuous label stock and comprising or consisting of a multilayer plastic film 1 is mounted around the outer surface of a body 100.
  • orientation direction of the label film (S x in Fig. 4a and 4b) extends circumferentially around the body 100 in direction DIR1 .
  • Main shrinking direction of the film is indicated by the Sx corresponding to direction DIR1 , as shown in Fig. 5.
  • S x may correspond to the orientation direction of the film, for example machine direction MD.
  • the opposite edges of the label, leading edge 23 and trailing edge 25, may overlap and form a seam 24.
  • the seam 24 may comprise an adhesive layer, such as a hot melt or UV-curable adhesive. Alternatively, it may comprise solvent dissolving the film materials and thus provide a joint.
  • the adhesive may be provided as a continuous strip or separate adhesive patterns. Alternatively, the seaming may be performed using other methods such as laser welding, heat sealing, or ultrasonic bonding.
  • the body 100 having a label 2 wrapped around it is subsequently heated. The heating causes the label 2 to shrink to a shrunk label 22 and to conform to the surface of the body.
  • a shrunk, tight fitting label 22 for the body 100 is shown in Fig. 6.
  • the shrunk label 22 provides a smooth and consistent coating for the body.
  • the heating temperature of the film may be between 80 °C and 150 °C, preferably between 120 °C and 130 °C in hot-air tunnels or between 80 °C and 90°C in steam tunnels. As discussed, heating in a steam tunnel may be more uniform than in another tunnel. This issue further clarifies, why the film should shrink preferably a lot already at the temperature 80 °C, but at the temperature 90 °C the latest.
  • Labels comprising oriented films in this embodiment shrink in the machine direction, the machine direction is extending circumferentially around the body.
  • the heat that induces shrinkage may be provided by conventional heat sources, such as hot steam, heated air, infrared radiation, or any other suitable heat source.
  • the label may consist of a thermally shrinkable plastic film having transversal orientation direction (TD).
  • transverse oriented films Prior to labelling, transverse oriented films may be solvent seamed into a form of a continuous tube. The continuous tube is then cut into shorter, predetermined lengths and supplied as a separate tube around a body. The labelled item is transferred to the following process step of heating so as to provide shrinking of the label around the body.
  • TD transversal orientation direction
  • An embodiment of such labeled item 1 10 comprises
  • the plastic film 22 has been made by thermally treating the thermally shrinkable plastic film 1 as discussed in this document.
  • a loop may be made of the label 2 comprising the film 1 by joining one edge 25 of a band of the film to the opposite edge 23 of the band of the film. Thus a seam 24 is formed between these ends.
  • the loop is arranged around at least a part of the body 100. After the application of heat, the loop shrinks to a shrunk loop 22 onto the part of the body 100.
  • the aforementioned first direction of the film in which direction the film shrinks, as denoted by S x in Fig. 4a, is aligned circumferentially with the body 100, as depicted by the direction DIR1 in Fig. 5.
  • the part of the body 100 that is encircled by the loop 22 has a cross sectional area of at least 4 (cm) 2 ; preferably at least 8 (cm) 2 or at least 12 (cm) 2 .
  • the part of the body that is encircled by the loop may have a cross sectional area of at most 1000 (cm) 2 , such as at most 660 (cm) 2 or at most 330 (cm) 2 .
  • the body 100 to be labelled may be highly contoured container, such as shampoo or detergent bottle, or drink container having e.g. recesses and/or protrusions at the outer surface.
  • a diameter of the bottle may alternate.
  • a container may comprise different diameters.
  • Difference between the diameters to be labelled in a container may be up to 30 %, or up to 20 %, or 2-30 %, or 5-20 %, or 8-15 %.
  • the difference between the smallest diameter and the largest diameter of the body to be labelled may be up to 30 %, or up to 40 %, or up to 50 %, or up to 60 %, or up to 70 %, or 2-70 %, or 5-60%, or 10-35%.
  • the body may also be recyclable.
  • the body 100 needs not be circular. In this case the contour may be described with a cross sectional area the label 22 encircles.
  • the shrinkable plastic film is used to label a body 100, wherein the body has a varying shape. In the embodiment,
  • the part of the body 100 that is encircled by the loop 22 has, at a first location, a first cross sectional area Ai,
  • the part of the body 100 that is encircled by the loop 22 has, at a second location, a second cross sectional area A 2 , and
  • the first cross sectional area Ai is different from the second cross sectional area A 2 .
  • the ratio of the second cross sectional area to the first cross sectional area, A 2 /Ai, is at least 1 .5, at least 2 or at least 4.
  • the ratio of the linear sizes, such as diameters, at the first and the second location is at least about 1 .2.
  • the film should shrink at least about 20 % to fit also to the smaller parts of the body, even if the larger parts could be labeled with a film having only a small shrinkage.
  • the film should be reasonably flexible for smooth manufacturing process. This is achieved by proper thickness, since it is well known that thickness increases the stiffness.
  • the thickness if the film is from 10 ⁇ to 80 ⁇ , preferably from 15 ⁇ to 50 ⁇ .
  • the film thickens. If the film can freely shrink, the shrinkage may be e.g. as good as -0.75 (length decreases to one quarter), whereby the thickness could increase by a factor of four.
  • the thickness of the plastic film forming the loop is from 15 ⁇ to 150 ⁇ , preferably from 20 ⁇ to 50 ⁇ .
  • the multilayer plastic films 1 of the invention are suitable for labels and use for labelling of bodies 100.
  • the multilayer plastic films may be used for a thermally shrinkable plastic film of a label.
  • the films described above are suitable for a label film.
  • the films are suitable for labelling of a wide range of product designs and particularly suitable for highly contoured containers and products comprising curved sections, recesses and/or protrusions at the outer surface.
  • the labels comprising heat shrink multilayer thermally shrinkable plastic film are suitable for bodies of glass, plastic, ceramics, glass, and metal . Shrinkage properties of films and/or labels enable labels to be used in highly contoured containers.
  • the body 100 may comprise or consist of polyethylene terephthalate (PET).
  • PET polyethylene terephthalate
  • the body 100 may have a shape of a container.
  • the body 100 may have a shape of a bottle.
  • the shape and/or the material of the body 100 ensures proper rigidity for the body 100, whereby the shrinking of the label 2 (Fig. 5) to the shrunk label 22 does not deform the body 100 (cf. Fig. 6). This happens at least, when the film thickness and/or shrinkage of the film 1 has the aforementioned values.
  • This issue can also be described using a film having a residual shrink force from 1 N/15 mm to 10 N/15 mm; preferably from 2 N/15 mm to 6 N/15 mm.
  • the residual shrink force is affected by the thickness of the film; whereby the thickness affects several aspects of the process.
  • Sufficient rigidity of the body is affected by the density of the material of the body. In some embodiments, the density of the body is at least 1 100 kg/m 3 , preferably at least 1200 kg/m 3 or 1300 kg/m 3 . These density values have also a surprising effect is recycling the item, as will be discussed later.
  • the label may be a full body label, i.e. the shrunk label 22 may cover substantially the whole outer surface of the body 100, as shown in Fig. 7.
  • the label may cover the body only partially, as shown in Figs. 6 8.
  • a neck of a bottle 104 may be left without a label, or a separate and/or different label may be used for the bottle neck part than for the bottle volume part.
  • the item may be recycled. Typically during recycling the item is crushed into pieces.
  • the area A b i (Figs. 5 and 6) in between the loop of the plastic film and the body is free from adhesive, the film separates from the body during this crushing.
  • the pieces of the body are separated from the pieces of the film based on the difference in their densities.
  • the pieces of the film may float on a liquid having a special density.
  • - the body 100 has a first density pi ,
  • the plastic film forming the loop 22 has a second density p 2 .
  • the ratio of the second density to the first density, P 2 /P 1 at most 0.9; preferably at most 0.8 or at most 0.7 at a temperature, such as at the temperature 80 °C.
  • an item may comprise a body 100 comprising polyethylene terephthalate (PET; having the density of about 1380 kg/m 3 ), and a film 22 having the density of about 920 kg/m 3 , whereby the ratio of these densities is as low as 0.67.
  • PET polyethylene terephthalate
  • a film 22 having the density of about 920 kg/m 3 , whereby the ratio of these densities is as low as 0.67.
  • These densities are typically measured near room temperature, such as 25 °C, however, increasing temperature up to e.g. 80 °C does not affect the ratio much.
  • the composition of the multilayer structure has effect of providing the overall film density less than 1 g/cm 3 (note: 1 g/cm 3 equals 1000 kg/m 3 ).
  • the density is less than 1 g/cm 3 also after printing of the film.
  • the density may be, for example between 0.90 g/cm 3 and 0.98 g/cm 3 , or between 0.90 g/cm 3 and 0.95 g/cm 3 .
  • the multilayer plastic film contains less than 20 wt.%, preferably less than 10 wt.% or less than 5 wt.% polymeric material having density above 1 .3 g/cm 3 or 1 .25 g/cm 3 or 1 .1 g/cm 3 .
  • the thermally shrinkable plastic film 1 (and/or the shrunk film 1 1 of the item 1 10) has a density p 2 of less than 1000 kg/m 3 , preferably less than 960 kg/m 3 , such as less than 920 kg/m 3 . As the density may be dependent on temperature, these values are given at the at the temperature 80 °C.
  • the aforementioned special density for the liquid is between 960 kg/m 3 and 1000 kg/m 3 .
  • water has a temperature dependent density that is between 958 kg/m 3 (for 100 °C) and 999.97 kg/m 3 (for 4 °C).
  • the crushed pieces of plastic are cleaned in water having a temperature of about 80 °C. At 80 °C, the density of water is 972 kg/m 3 .
  • the density of the cleaning liquid can be affected by ingredients (e.g. salts) added to the cleaning liquid.
  • the second density p 2 (of the film) is less than 1000 kg/m 3 ; preferably less than 950 kg/m 3 at the temperature 80 °C.
  • the first density pi (of the body) is more than 1000 kg/m 3 at the temperature 80 °C.
  • Low density of the film has effect of enabling the film and label comprising said film to be more easily separated from the substrates having higher density, such as PET bottles.
  • Said film density allows the films to be separated from the substrate material during recycling process, for example in the normally used washing process of the bottles, i.e. flotation separation process, of the bottles or other containers.
  • the separated labels may also be further recycled.
  • the strength of the film should be reasonable.
  • the strength of the film is affected, among other things, by the density of the film.
  • the thermally shrinkable plastic film has a density of more than 700 kg/m 3 , preferably more than 800 kg/m 3 , such as more than 870 kg/m 3 .
  • the thermally shrinkable film comprises a printable face 2, such as a printable surface 2 (Fig. 3).
  • the printable face is typically arranged on a skin layer (3, 7) of the plastic film.
  • Multilayer plastic film structure has effect of providing a heat shrinkable label which can be easily separated in re-cycling process from the body it is mounted.
  • a thermally shrinkable label comprising
  • the thermally shrinkable plastic film is oriented in one direction
  • the thermally shrinkable plastic film comprises at least a first layer and a second layer, wherein
  • the first layer of the thermally shrinkable plastic film comprises first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C.
  • a heat shrink label film wherein the heat shrink label film is oriented in one direction, and includes a layer comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C.
  • a method for providing a heat shrink label comprising: - providing a thermally shrinkable plastic film comprising at least one layer comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C ;
  • a method for labelling of a body wherein the label comprises an oriented thermally shrinkable plastic film comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C , the method comprising:
  • a combination of a label and a body wherein the label comprises a continuous thermally shrinkable plastic film around an external surface of the body, wherein the continuous thermally shrinkable plastic film is oriented in one direction, and comprises a layer comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C, and wherein a leading end of the label and a trailing end of the label are overlapped on the surface of the body, and wherein the label between the leading edge and the trailing edge is next to the surface of the body.
  • a difference between the smallest diameter and the largest diameter of the body is between 20 % and 80 %, preferably between 30 % and 70 %.

Abstract

A monoaxially oriented thermally shrinkable plastic film, having a temperature dependent shrinkage E(~0, wherein the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=98 °C is less than -0.35. Moreover, the shrinkage, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=65 °C is greater than -0.10. The film has a relative temperature dependent shrinkage ErO~) such that the difference between the values of the relative temperature dependent shrinkage for at least one pair of temperatures T2 and Ti having a difference T2-Ti=15 °C is more than 50 percentage points; wherein the lower of the two temperatures of the pair, T1( is from 65°C to 70 °C. An item comprising a body (100) and a loop (22) of a plastic film, which loop (22) encircles a part of the body, wherein the plastic film has been made by thermally treating the thermally shrinkable plastic film.

Description

A THERMALLY SHRINKABLE PLASTIC FILM AND AN ITEM COMPRISING THE SAME
Field of the Invention
The application relates to a film of a label. Especially to a heat shrink film for labelling applications. Further the application concerns a body having been labelled with the film. Background of the Invention
It is general practice to apply a label to a surface of a body to provide decoration, and/or to display information about the product being sold, such as the content of the item, a trade name, or a logo. In addition to pressure- sensitive, wet glue, and wrap around labels other labelling technologies are available, for example shrink sleeves. Shrink sleeves may be provided by forming a tube of plastic film, which may be dropped over a body to be labelled and subsequently fed the item through a shrink-tunnel at elevated temperature causing the film to shrink and fit the shape of the item.
Summary of the Invention
It is an object of this application to provide a thermally shrinkable plastic film and a heat shrink label comprising said heat shrinkable plastic film. Another object is to provide an item, i.e. a combination of a heat shrink label and a body. The film has such shrinkage properties that are beneficial in the overall labelling process, considering the transportation of the material, and the large variation is the shapes of the bodies to be labelled. Moreover, other properties of the film makes the overall process, e.g. in term of recycling, more efficient. The structure and composition of the film, which allow for the aforementioned properties, will also be discussed.
According to an aspect of the invention there is provided a thermally shrinkable plastic film,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO), - having a first length L0 in a first direction before heat treatment and a second length L(T) in the first direction after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo, wherein
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), wherein
- the value of ε(98 °C) is less than -0.35, optionally at most -0.85;
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=65 °C, is ε(65 °C), wherein
- the value of ε(65 °C) is greater than -0.10, preferably greater than -0.07; optionally at most 0;
and
- the thermally shrinkable plastic film has a relative temperature dependent shrinkage εΓ(Τ)={[ί(Τ)-ί0]/ί0}/ε(98 °C), wherein
- the difference between the values of the relative temperature dependent shrinkage εΓ(Τ) for at least one pair of temperatures T2 and Ti having a difference T2-Ti=15 °C, i.e. εΓ(Τ2)-εΓ(Τι), is more than 50 percentage points; wherein the lower of the two temperatures of the pair, Ti, is from 65 °C to 70 °C.
According to another aspect of the invention, there is provided a thermally shrinkable plastic film,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO),
- having a first length L0 in a first direction before heat treatment and a second length in the first direction L(T) after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage ε(Τ)=[Ι_(Τ)-Ι_ο]/Ι_ο, wherein
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is greater than -0.10, and
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=80 °C is less than -0.25. According to another aspect of the invention, there is provided an item comprising
- a body, and
- a loop of a plastic film, which loop encircles a part of the body, wherein - the plastic film has been made by thermally treating the thermally shrinkable plastic film according to an embodiment.
During manufacturing, the thermally shrinkable plastic film may have been stretched in the one direction with a ratio of unstretched film thickness to stretched film thickness between 2 and 10. In other words, the thermally shrinkable plastic film may have been stretched in the one direction with a stretching ratio of between 2:1 and 10:1 .
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 multilayer thermally shrinkable plastic film suitable for a label,
Fig. 2 shows, in a perspective view, the film of Fig. 1 ,
Fig. 3 shows, in a perspective view, an example embodiment of a label comprising thermally shrinkable plastic film,
Fig. 4a shows, in a perspective view, an example embodiment of a thermally shrinkable plastic film before shrinking, Fig. 4b shows, in a perspective view, a shrunk film, wherein the shrunk film has been made by shrinking the film of Fig. 4a by thermal treatment,
Fig. 5 shows an example embodiment of a label around a part of a body, shows an example embodiment of a label shrunk and fitted on a surface of a body i.e. a labelled item, shows another example embodiment of a label around a part of a body and fitted on a surface of a body i.e. a labelled item, shows another example embodiment of a label around a part of a body and fitted on a surface of a body i.e. labelled item; shows examples for shrinkage as function of temperature for some known heat shrink label films; shows examples for relative shrinkage as function of temperature for some known heat shrink label films; shows examples for shrinkage as function of temperature for embodiments of thermally shrinkable plastic films according to the present invention; and shows examples for relative shrinkage as function of temperature for embodiments of thermally shrinkable plastic films according to the present invention.
Detailed Description of the Invention
In this description and claims, the percentage values relating to an amount of raw materials are percentages by weight (wt.%) unless otherwise indicated. The following reference numbers and denotations are used in this application: micron micro meter, μητι, 1 10"6 m,
TD transverse direction,
TDO transverse direction oriented
CD cross direction,
MD machine direction,
MDO machine direction oriented,
DR draw ratio, MRK1 graphics,
hi a first length of a label film prior to shrinking,
w1 a second length of a label film prior to shrinking,
d1 thickness of a label film prior to shrinking,
Sx a first direction of the film, in the plane of the film,
l_o a length of a film (e.g. the film 1 , Fig. 4a), in a first direction, before heat treatment, wherein the first direction is in the plane of the film,
L(T) the length of the part of the film having the length L0 in the first direction before heat treatment, after a heat treatment, in which the temperature of the thermally shrinkable plastic film has been T, and cooled back to the temperature before the heat treatment. Thus, the length L(T) refers to a length of the shrunk film 1 1 (cf. Fig. 4b),
ε strain (when positive) or shrinkage (when negative),
ε(Τ) shrinkage of a film, after a heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, defined as ε(Τ)=[Ι_(Τ)-Ι_]/Ι_. For thermally shrunk materials ε(Τ)<0; in addition ε(Τ) > -1 ,
ε(98 °C) shrinkage of a film, after a heat treatment wherein the temperature of the thermally shrinkable plastic film has been 98 °C,
εΓ(Τ) relative shrinkage of a film, defined as ε(Τ)/ε(98 °C),
a, b, c constants,
f functions,
Sy a second direction of the film, in the plane of the film, and perpendicular to Sx,
Lpo a length of a film, in a second direction, before heat treatment, wherein the second direction is perpendicular to the first direction and is in the plane of the film,
Lp(T) the length of the a part of the film in the second direction after a heat treatment, in which the temperature of the thermally shrinkable plastic film is T, the part of the film having the length Lp in the second direction before heat treatment,
ερ(Τ) shrinkage or strain of a film in the second direction, after a heat treatment, in which the temperature of the thermally shrinkable plastic film has been T, after cooling the sample back to the temperature before the heat treatment, defined as
Figure imgf000007_0001
pp percentage point, i.e. the absolute difference of relative values given in per cents,
A2, Ai cross sectional areas of a part that is encircled by a loop formed from the film,
pi density of a body that has been labeled or is to be labeled,
P2 density of a label,
Abi an area between a label and a body,
Sz the direction of the thickness of the film, perpendicular to Sx and
Sy,
DIR1 a direction, (cf. e.g. Fig. 5),
DIR2 another direction (cf. e.g. Fig. 5), 1 a thermally shrinkable plastic film, i.e. a label film,
2 a label,
3 a first layer (a first skin layer or front surface layer),
5 a second layer (a core or intermediate layer),
7 a third layer (a second skin layer or back surface layer),
1 1 a shrunk plastic film,
22 a shrunk plastic label,
23 a leading edge of a label,
24 a seam,
25 a trailing edge of a label,
100 a body,
104 a neck of a bottle.
1 10 a labelled item,
In this application term "label" refers to a piece of material, which is used for labelling of a body. Label may be used to identify something. Label may be attached to a body thereby forming an item, such as an article. In other words, label is suitable to be applied to a surface of a body to provide decoration, and/or to display information about the product being sold, such as content information, a trade name, a logo, a barcode, or any other graphics. The body may be also called as an article, or a substrate. Preferably, the label comprises a thermally shrinkable plastic film and at least some graphics on a surface of the thermally shrinkable plastic film. A thermally shrinkable plastic film may also be referred to as a label film. The graphics may comprise, for example, printed information and/or decoration.
Figure 1 shows, in a side view a thermally shrinkable plastic film 1 . The film 1 comprises a first layer (i.e. a first skin layer 3 or front surface layer 3) and a second layer 5 (i.e. an intermediate layer 5, i.e. a core layer 5). The film 1 may comprise a third layer 7 such as another skin layer 7. Figure 2 shows the film 1 in a perspective view. Referring to Fig. 3, a label 2 comprises a thermally shrinkable plastic film 1 . At least one surface of the thermally shrinkable plastic film may comprise graphics MRK1 . The thermally shrinkable plastic film may comprise or consist of a multilayer plastic film structure comprising e.g. three layers. In addition, the label may comprise adhesive. The adhesive may be used to enable the label to be attached to a body, an article or a container. In other words, "label" refers to an object having length, width and thickness. The object may be a plastic film or it may be derived from a plastic film. A label comprises a first surface portion. The first surface portion is intended to be attached to a second surface portion different from the first surface portion. The second surface portion may be a surface portion of the label different from the first surface portion, or a surface portion of another object. The first and second surface portions may be adjoined to each other by various means, such as by using an adhesive or heat, for example by welding. Term "shrinkable" refers to a property of a plastic film or a label made thereof to shrink under exposure to external energy. The shrinking is irreversible in the sense, that after the exposure to energy, the shrunk film does not elongate to the initial size. The term "thermally shrinkable" refers to the ability to shrink under exposure to heat. The term "plastic" refers to a body comprising polymer or polymers, or consisting of polymer material or materials. The term "film" refers to a body, of which one dimension is significantly smaller than the other two dimensions. Referring to Fig. 4a, typically in a film the thickness is less than one twentieth of the length and the width, i.e. d1 <0.05*w1 and d1 <0.05*h1 . Some uses of thermally shnnkable plastic films
Referring to Fig. 4a, a thermally shrinkable plastic film 1 , such as a thermally shrinkable plastic film 1 of a label 2, may shrink when exposured to an elevated temperature. Heat may be applied via suitable heat transfer medium, such as hot air, steam, or water. Moreover, radiation, such as infrared radiation can be used. In response to application of heat, the thermally shrinkable plastic film 1 or a label 2 comprising said plastic film 1 is arranged to shrink. Film shrinkage may be focused on a local area or to the whole plastic film area. Thermally shrinkable plastic film refers to a film that shrinks at least 35 per cent, preferably at least 45 or at least 50 per cent upon heating to 98 °C in stress free conditions. Optionally such a film may shrink at most 85 per cent or at most 80 per cent.
Preferably, a heat shrink label 2 comprises a multilayer thermally shrinkable plastic film 1 (label film) comprising or consisting of thermally shrinkable layer(s). In addition, the shrink label 2 comprises at least some graphics MRK1 on a surface of the thermally shrinkable plastic film 1 . In addition, the thermally shrinkable label 2 may comprise adhesive. The adhesive may be applied only in a joint area of cylindrical label, wherein the opposite edges of the thermally shrinkable plastic film 1 are overlapping. For example, the adhesive may be applied between the overlapping edges (cf. Fig. 5). Alternatively or in addition, the adhesive may be applied between the thermally shrinkable plastic film and surface of a body to be labelled. Shrinkage of label may be focused on a local area or to the whole label area. Local shrinkage may be focused on required areas, for example on an edge area of a label. Whole label may be shrunk in a direction extending circumferentially around a container to conform to the outside (external) shape of the container. Local shrinkage may be focused on required areas, for example on an edge area of an article.
Term "machine direction" MD refers to the running direction of the plastic film or continuous label web during label manufacturing. "Transverse direction" TD or "cross direction" CD refers to the direction perpendicular to the running direction MD of the film or label web. Both machine direction and the transverse direction are in the plane of the thermally shrinkable plastic film. During manufacturing, the thermally shrinkable plastic film may be drawn (stretched) at least in one direction. The film may be drawn in a machine direction, in a transverse direction, or both. The resulting film is thus monoaxially (uniaxially) oriented (MO) or biaxially oriented (BO). A monoaxially oriented film may be either machine direction oriented (MDO) or transverse direction oriented (TDO) in accordance to the direction of the orientation (of stretching), but not in both directions. A biaxially oriented (BO) film is both machine direction oriented (MDO) and transverse direction oriented (TDO) in accordance to the direction of the orientation (stretching). The present invention relates to films for labelling, whereby dimensional stability is preferable in one direction. Therefore, the present invention relates, in particular, to monoaxially (uniaxially) oriented films; either MDO or TDO, but not both.
A film, when manufactured and coming out of the machine, is typically rolled to form a roll. As known, the roll has an axis of rotation, around which the roll is rotated during said rolling. The transverse direction (TD) is parallel to the axis of rotation, and thus also in plane of the film. The machine direction, on the other hand, is also in the plane of the film, and perpendicular to the transverse direction. The length of the rolled film, in the MD, may be from tens of meters upwards. The width of the rolled film, in the TD, is less, such as a few meters. The whole roll may be cut to narrower label bands according to use. After such cutting, also the narrower rolls comprise film having the same, relatively long, length; only the width decreases in this kind of cutting. The MD oriented and the TD oriented films are typically used in different ways, as will be detailed later under the terms RFS and HS. The MD oriented RFS labels are generally cut in narrower strips and applied as single labels. The TD oriented HS labels are slit generally wider so that tubes can be formed from the film, and thereafter, these tubes are applied onto bodies, such as bottles.
A ratio of total film thickness before and after stretching is called a "draw ratio" or "drawing ratio" (DR). It may also be referred to as a stretching ratio or orientation ratio. In other words, draw ratio is a non-oriented (undrawn) film thickness in relation 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 film, the thickness of the film may diminish in the same ratio as the film stretches or elongates. For example, a film having thickness of 100 micrometres before uniaxial orientation is stretched by a draw ratio of 5. After the uniaxial orientation the film may have a fivefold diminished thickness of 20 micrometres.
During stretching the randomly oriented polymer chains of the extruded films are oriented in the direction of stretching (drawing). Orientation under uniaxial stress provides orientation of 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 of the film during manufacturing. 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. The orientation, like orientation direction, amount and ratio, may have effect on properties of the film, and/or the label comprising the film. 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. Upon application of energy, such as heat, the drawn films shrinks in the opposite direction(s) relative to the deformations due to the drawing. Haze is a property used to describe transparency of a plastic film or a face stock of label consisting of the plastic film. Haze relates to scattering of light by a film that results in a cloudy appearance of the film. Haze corresponds to the percentage of light transmitted through a film that is deflected from the direction of the incoming light. Haze may be measured according to standard ASTM D1003.
Thermally shrinkable films are, in general used to label items. Such labeled item 1 10 comprises a body 100, and a loop 22 of a plastic film, which loop encircles a part of the body, wherein the plastic film 22 has been made by thermally treating the thermally shrinkable plastic film 1 as discussed in this document. As will be shown, an area Abi is left in between the loop 22 of the plastic film and the body 100. Term "roll-fed shrink film" (RFS) refers to labelling process, where a ready cut (MDO) label is rolled over a part, and the edges of the cut label are attached to each other to form a loop. Two alternatives can be distinguished. The part may be a container (i.e. the body 100) and then the label is shrunk onto the body in order to conform shape and size of the body. In the alternative, the part may be a separate part, such as a cylinder, onto which the ready cut label is rolled, and the edges attached to each other. Thereafter the sleeve thus formed may be arranged onto the body 100. Label is supplied from a reel, cut into individual labels and applied around the cylinder. The cylinder is thereafter applied around a part of a body and shrunk onto it.
In the first RFS case, adhesive (e.g. hot melt adhesive) is used to hold the label on the surface of the body 100. The adhesive may be supplied onto the body 100, e.g. by spraying onto the surface of the body, such as container, or bottle. The adhesive may comprise or consist of e.g. hot melt adhesive. The adhesive may be applied on those locations of the surface of the body that have the largest cross section. In addition or alternatively, the adhesive may be applied on the label 2. The adhesive is preferably applied only on the label, since the container, in general, has a curved surface. The adhesive may be applied at a trailing edge 23 and at a leading edge 25 of the label 2 (cf. Fig. 5). When rolled over to the body 100, the trailing and leading edges may overlap and form a seam 24. The width of the seam may be e.g. at most 12 mm. Even if the adhesive is applied onto the body 100, some adhesive is applied on a part of the label, in particular on the trailing edge 25. Thus, the first adhesive (on the body) keeps the label in its position before thermal shrinking, and a second adhesive (on the trailing edge 25) closes the seam 24. The second adhesive may comprise e.g. UV hot melt adhesive. Subsequent shrinking process at high temperatures enables tight fitting of the label around the body. Heat shrinking may occur at a shrink tunnel, where for example hot steam may be blown towards passing items. Alternatively, hot air or infrared radiation could be used to heat and shrink the labels. However, in practice, a steam tunnel provides for more uniform shrinkage than other means for heating. The described process may be called as on-line labelling process. Referring to Fig. 5, the label 2 may be rolled over the body 100. Referring to Fig. 5, an item 1 10, formed by RFS labelling body 100 directly comprises some adhesive in between the loop 22 and the body 100. In such an item some adhesive is arranged between the loop 22 of the plastic film and the body 100. Thus, the area Abi (Fig. 5) comprises some adhesive. In some cases the item comprises a seam, and the adhesive located in between the body 100 and the loop 22 is located radially at the same location as the seam. Thus, the adhesive that is arranged between the loop 22 of the plastic film and the body 100 may be located, as viewed from the seam 24 in the direction of a surface normal of the loop 22 and towards to body 100. The adhesive may be let to cure or may be cured e.g. by using ultrasound or a hot-bar. RFS labeling may be used e.g. with films having a reasonably low shrinkage, e.g. ε(98 °C) more than about -0.4; wherein the value ε(98 °C) will be defined in more detail later.
In the second RFS case, the film is rolled on a piece, such as a cylinder, which is not the body 100. The edges of the label are attached to each other. The edges may be attached to each other e.g. by laser welding techniques, ultrasound meltable adhesive in connection with ultrasound, a hot-bar, or solvent. The trailing and leading edges may overlap and form a seam, and thereby a loop of the label. The width of the seam may be e.g. at most 12 mm. After forming the seam, the loop of the film may be taken away from the cylinder, and arranged onto the body 100 or a part of the body 100. Heat shrinking may occur at a shrink tunnel, where for example hot steam may be blown towards passing items. Alternatively, hot air or infrared radiation could be used to heat and shrink the labels. However, in practice, a steam tunnel provides for more uniform shrinkage than other means for heating. Referring to Fig. 5, an item 1 10, formed by labelling a body using this type of RFS does not (necessarily) comprise some adhesive in between the loop 22 and the body 100. In such an item, the area Abi is free from adhesive. This type of RFS labeling may be used e.g. with films having a reasonably high shrinkage, e.g. their ε(98 °C) value is e.g. less than -0.45, such as less than -0.50.
Roll-fed shrink films may be uniaxially oriented in machine direction (MD). When a label consists of a MDO shrink film as a face stock, and the machine direction of the label extends circumferentially around the body, the label is arranged to shrink primarily in the orientation direction when heated. Term "shrink-sleeve" or "heat shrinkable sleeve film" (HS) refers to a labelling process, where a preformed (TDO) label tube (or sleeve) is introduced around a body. Shrink sleeve label comprises or consists of transverse direction oriented (TDO) shrink film. The film is seamed by using solvent into a continuous tube label around the axis extending to the machine direction. Typically a solvent is used to partly dissolve the film itself, whereby an edge of the film can be attach onto another edge of the film. The formed continuous tube (or sleeve) is cut into predetermined lengths and supplied as a form of individual tube label around a body. Referring to Fig. 5, the label 2 may be a preformed label tube that is introduced around the body 100. The body or container may be warmed before a cylindrical tube label is introduced over it. Tube around a body is heated in order to shrink the tube label around the body. The transverse direction orientation of the tube label extends circumferentially around the body. Thus, label primarily shrink in the transverse direction. Referring to Fig. 5, an item 1 10, formed by HS labelling a body does not (necessarily) comprise some adhesive in between the loop 22 and the body 100. In such an item, the area Abi is free from adhesive. HS labeling may be used e.g. with films having a reasonably high shrinkage, e.g. their ε(98 °C) value is less than -0.45, such as less than -0.50.
A label film (thermally shrinkable plastic film) may have a monolayer structure. Referring to Fig. 1 , the label film may have a multilayer structure comprising two or more plastic film layers. Preferably, a thermally shrinkable plastic film of a label consists of a multilayer plastic film structure.
Structure and composition of a thermally shrinkable plastic film
Referring to Fig. 1 , the multilayer label film structure 1 may comprise a first layer 3, a second layer 5 and a third layer 7. Preferably the second layer 5 is between the first 3 layer and the third 7 layer. In a three layer structure, the second layer 5 is an intermediate layer. The intermediate layer may also be referred to as a core layer. The first layer 3 and the third layer 7 may be also referred to as skin layers, i.e. a first skin layer and a second skin layer, respectively. The first skin layer and the second skin layer may also be referred to as a front surface layer and a back surface layer, respectively. The front surface layer may be an outermost layer of the multilayer structure when labelled to a surface of a body. However, the front surface may further be over coated. For example, in order to protect the printed graphics. The back surface layer may be the layer adjacent to a surface of a body. Alternatively, a label may be attached to a body via adhesive on its front surface. In this alternative, back surface may be the outermost layer of the labelled item. Alternatively the back surface may be covered, varnished or over-coated. Preferably the multilayer structure has symmetric structure. For example, symmetric three layer structure comprises identical skin layers on opposite sides of the core layer. Alternatively, the multilayer structure may be asymmetrical. For example, one skin layer may have more or less additives, e.g. anti-block or slip-agent, than the other skin layer. The film structure may also comprise additional layers, such as tie layers or protective layers. The multilayer structure may be laminated or coextruded.
The core layer 5 may form major portion of the multilayer film structure. The core layer may have a monolayer or multilayer structure. The core layer may be thicker than the first skin layer and the second skin layer. For example, the core may form 60 % of the total thickness of the multilayer structure. Alternatively, the core may have thickness of 40 % of the total thickness of the multilayer film. In a three layer symmetric film, the core layer having thickness of 40 % of the total thickness of the film still forms major portion of the film, since the skin surfaces may have thickness of up to 30 % of the label thickness each. Thickness of the core layer may be from 15 to 50 microns (i.e. micro meters, μηη), or from 20 to 50 microns, preferably around 30 or 25 microns. Thickness of skin layers may be 40 % (such as from 35 % to 45 %) of the total thickness of the multilayer structure. Alternatively, thickness of skin layers may be 60 % (such as from 55 % to 65 %) of the total thickness. The thickness of a skin layer may be less than 20 microns, preferably around 10 or 7.5 microns or less. The overall thickness of the multilayer film may be from 20 to 70 microns or from 25 to 60 microns, preferably around 50 microns or around 40 microns or less. Preferably the multilayer film has uniform overall thickness. Uniform thickness refers to a homogeneous thickness of a film, wherein a thickness variation along the film is small. For example in a film area of 100 mm χ 100 mm the variation of the film thickness (here defined as the standard deviation divided by the average) is less than 10%, preferably between 0.1 and 5.0%. Uniform thickness of the film provides better quality labels, for example, labels having good visual appearance. Uniform film thickness may have effect on the register control and image quality of the printing.
The multilayer plastic film structure may comprise or consist of layers having different compositions. For example, skin layer(s) may have different composition when compared to the composition of the core layer. Also first and second skin layers may have different compositions. Alternatively, the first and second skin layers may have similar compositions. An embodiment the thermally shrinkable plastic film 1 (Fig. 1 ) comprises
- a core layer 5 and
- a skin layer (3 or 7), such that
- the skin layer (3, 7) is located within a distance from the core layer 5 in the dimension of the surface normal Sz of the thermally shrinkable plastic film 1 , and
- the material of the core layer 5 is different from the material of the skin layer (3, 7).
An embodiment of the thermally shrinkable plastic film further comprises - a second skin layer (7, 3), such that
- the core layer 5 is arranged in between the skin layer (3, 7) and the second skin layer (7, 3).
In an embodiment, the second skin layer (i.e. the third layer 7) is made of the same material or materials as the skin layer (i.e. the first layer 3). In an embodiment, the second skin layer has the same thickness as the skin layer. In an embodiment, the thermally shrinkable plastic film 1 is planar symmetric, wherein the plane of symmetry is the central plane of the core layer 5 in the direction Sz of the surface normal of the thermally shrinkable plastic film 1 (Fig. 1 ).
According to an embodiment, a skin layer (or skin layers) may comprise a first cyclic olefin copolymer COCi and a second cyclic olefin copolymer COC2. The cyclic olefin copolymer contains polymerized units derived from at least one cyclic and at least one acyclic olefin. The acyclic olefin may be an alpha olefin having two or more carbon atoms. Cyclic olefin copolymers may be based on cyclic monomers, such as norbornene and/or tetracyclododecene. Cyclic mononner(s) may be chain copolymerized with ethene (ethylene). For example, cyclic olefin copolymer may be comprise monomers of norbornene and ethene. Alternatively, cyclic olefin copolymer may comprise monomers of tetracyclododecene and ethene. Cyclic olefin copolymer may also consists of monomers of norbornene, tetracyclododecene and ethene. Preferably, the first cyclic olefin is different from the second cyclic olefin. A glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C. A difference in the glass transition temperature of the first cyclic olefin copolymer and the second cyclic olefin copolymer may be at most 40 °C, preferably at most 30°C. The difference in the glass transition temperature of the first cyclic olefin copolymer and the second cyclic olefin copolymer may be at least 5 °C, preferably at least 10°C. The glass transition temperature of the first cyclic olefin copolymer may be below 70°C and the glass transition of the second cyclic olefin may be above 70°C. For example, the first cyclic olefin copolymer COCi may have glass transition temperature of 65°C measured according to standard ISO 1 1357-1 , -2,-3 with heating rate of 10°C/min. The second cyclic olefin copolymer may have a glass transition temperature of 78°C. Melt volume rate tested according to standard ISO 1 133 at 230°C with test load of 2.16 kg of COCi may be 6.0 cm3/10min. Melt volume rate of COC2 may be 1 1 .0 cm3/10 min. Density of COCi and COC2 may be 1010 kg/m3, when measured according to standard ISO 1 183. At least one skin layer may comprise equal amounts of the first cyclic olefin copolymer and the second cyclic olefin copolymer. For example, a ratio of the first cyclic olefin copolymer to the second cyclic olefin copolymer COC1/COC2 may be between 1 .5 and 8. Amount of cyclic olefin copolymer(s) in skin layer(s) may be at least 50 wt.%, or at least 60 wt.%. Amount of cyclic olefin copolymer(s) may be at most 98 wt.% or at most 90 wt.%. For example, an amount of cyclic olefin copolymer(s) may be between 50 and 90 wt.%, or between 60 and 90 wt.%.
In an embodiment, the skin layer (3, 7) comprises first cyclic olefin copolymer. In an embodiment, the skin layer (3, 7) further comprises second cyclic olefin copolymer, wherein the first cyclic olefin copolymer is different from the second cyclic olefin copolymer. In an embodiment the first cyclic olefin copolymer (of the skin layer) has a first glass transition temperature and the second cyclic olefin copolymer (of the skin layer) has a second glass transition temperature, such that the second glass transition temperature is different from the first glass transition temperature, optionally the second glass transition temperature is greater than the first glass transition temperature by at least 5 °C or at least 10 °C .
In an embodiment the
- the first glass transition temperature is below 70 °C, such as below 67 °C , such as 65 °C and
- the second glass transition temperature is above 70 °C, such as above 75 °C, such as 78 °C.
The glass transition temperature may be measured as discussed above. The first and second cyclic olefin copolymers according to embodiments may have effect on the shrinking behaviour of the film. For example, a specific shrinkage curve may be achieved with the at least some/all embodiments. In addition, skin layer(s) may comprise linear low density polyethylene (LLDPE). Skin layer(s) may comprise Ziegler-Natta catalyst based LLDPE. In addition or alternative, Skin layer(s) may comprise metallocene LLDPE (m-LLDPE). For example, LLDPE may be a copolymer of ethylene and 1 -octene. Density of LLDPE may be 0.916 g/cm3, when measured according to standard ASTM D792. Melt Index may be 2.0 g/10min, when measured according to standard ASTM D1238 at 190°C/2.16 kg. For example, an amount of linear low density polyethylene may be at most 30 wt.%, or at most 20 wt.%, or at most 10 wt.% of the total weight of the skin layer. As an example, minimum amount of LLDPE may be between 5 and 10 wt.%. An amount of LLDPE may be between 0 and 30 wt.%, or between 5 and 20 wt.%, or between 10 and 20 wt.%. LLDPE has effect of reducing or avoiding the finger marking effect of the film. LLDPE may have effect of reducing un-wanted visual appearance, for example due to reducing or avoiding the finger marking effect of the film. LLDPE may have an effect of providing good interlayer attachment. In an embodiment, the skin layer comprises or further comprises linear low density polyethylene (LLDPE).
Further, skin layer(s) may contain additives. In an embodiment, the skin layer comprises or further comprises at least one additive selected from the group comprising inorganic fillers, pigments, antioxidants, ultraviolet absorbers, anti-blocking agents, slip additives, antistatic additives, cavitating agents. For example, the first skin layer may comprise anti-blocking agent. An amount of anti-blocking agent may be between 0.5 and 5 wt.%, preferably between 1 and 3 wt.% or between 2 and 3 wt.%.
In an embodiment, the amount of each additive is less than 5 wt.%; however the total amount of different additives may be higher. In an embodiment, the total amount of different additives is less than 5 wt.%.
An intermediate layer 5 may contain at least one terpolymer. In an embodiment, the core layer 5 comprises at least one terpolymer. In an embodiment, the core layer 5 comprises at least one of the following propylenes: 1 -butene/propylene/ethylene, propylene/ethylene/1 -hexene and propylene/ethylene/1 -butene. Propylene terpolymer may have a density of 0.90 g/cm3, when measured according to standard ISO 1 183. Melt flow rate may be 5.5 g/10min, when measured according to standard ISO 1 133 at 230°C/2.16 kg. Alternatively the melt flow rate may be 0.9 g/10min. In an embodiment, the total amount of terpolymer or terpolymers is between 20 wt.% and 95 wt.%, preferably between 40 wt.% and 90 wt.%, more preferably between 50 wt.% and 80 wt.%. For example 50, 55, 60, 65, 70, 75 or 80 wt.%. Terpolymer(s) may have effect on the orientation behaviour of the film. Terpolymer(s) may reduce the softening point of the film thus improving the stretching of the film. For example, films comprising terpolymer(s) may be stretched at a lower temperature. In addition, higher orientation ratios may be achieved, which may have effect on the shrinkage potential of the film. In a core layer of the film terpolymer(s) may have an effect on increasing the heat resistance of the film. In addition, terpolymer(s) may have an effect on providing more stability for the film, which is advantageous during orientation process e.g. in avoiding the film tearing away from the grippers holding the film.
In addition, the intermediate layer 5 may contain polyolefin plastomer and/or polyolefin elastomer. The intermediate layer may comprise at least one of the following: propylene/ethylene plastomer, ethylene/octene elastomer and ethylene/butene elastomer. In an embodiment, the core layer further comprises, in addition to terpolymer(s), polyolefin plastomer and/or polyolefin elastomer, such as at least one of the following: propylene/ethylene plastomer, ethylene/octene elastomer and ethylene/butene elastomer. Polyolefin elastomer may have density of 0.863 g/cm3, when measured according to standard ASTM D729. Alternatively, density may be 0.867 g/cm3. Melt flow rate may be 8.0 g/10min, when measured according to standard ASTM D1238 at 230°C/2.16 kg. Polyolefin plastomer may have a density of 0.867 g/cm3 and melt flow rate of 8.0 g/10min. An amount of polyolefin plastomer and/or elastomer may be between 2 and 50 wt.%, preferably between 5 and 35 wt.% and more preferably between 10 and 30 wt.%. The core layer may comprise for example, total amount of 10, 15, 20, 25 or 30 wt.% polyolefin elastomer and/or polyolefin plastomer. Polyolefin elastomer(s) and/or plastomer(s) may have an effect on the ability of the film to be stretched (oriented) and thus on the shrinkage potential of the film.
According to an embodiment, the intermediate layer may contain cyclic olefin copolymer. An amount of cyclic olefin copolymer may be 5 wt.%, 10 wt.%, or 20 wt.%, preferably less than 30 wt.%. For example, between 0 and 30 wt.%, or between 5 and 20 wt.%, or between 10 and 20 wt.%. The cyclic olefin copolymer in the intermediate layer may have effect on achieving good adhesion between the intermediate layer with skin layer(s). In addition, the cyclic olefin copolymer contained in the intermediate layer may have effect of increasing the overall shrinkage of the film. The intermediate layer according to embodiment may not resist shrinking of the film.
According to an embodiment, the multilayer film comprising at least a core layer, a first skin layer and a second skin layer is monoaxially, i.e. uniaxially, oriented, i.e. stretched only in one direction. A film may be oriented in machine direction (MD). A film oriented in a machine direction provides controlled shrinkage of the film in MD direction during subsequent shrinking process. Alternatively, the films may be oriented in transverse direction (TD), so as to provide uniaxially in transverse direction oriented films having controlled shrinkage in transverse direction.
Unoriented multilayer films may be manufactured by using either a cast or blown-film extrusion process. A shrinkable multilayer film may be obtained by stretching (drawing) the extruded multilayer film to an extent several times its original dimension to orient the film. Stretching may be designated also as orienting. The stretching may be performed by using heated draw rolls with gradually increasing speed. The stretching may be performed below the melting temperature of the polymer and/or at or near the glass transition temperature of the polymer. Preferably the film stretching temperature is between 50°C and 120°C, preferably between 60°C and 1 10 °C or between 60°C and 100 °C. After stretching, the film may be cooled with a cooling roll having temperature of around 25°C. Stretching and subsequent cooling may provide suitable shrink potential for the film. Due to the shrink potential, the oriented films are able to shrink under elevated temperature towards the non-oriented (initial) state of the film.
According to an embodiment, the stretching is performed 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 said machine direction. Machine direction oriented films may be used for roll-fed labelling (RFS, as discussed above), i.e. in a labelling process where the label film is supplied from a reel, cut into separate labels, after which labels are mounted around a piece (directly onto the body 100 or first onto a separate cylinder, and thereafter transferred around a part of the body 100) and seamed during labelling step using adhesive, such as UV-acrylic hot- melt adhesive. Alternatively seam may be formed by solvent seaming, hot- bar (heat-sealing), laser-welding or ultrasonic radiation. The label around the body may be shrunk in order to form a tight attachment and/or to conform the shape of the body. In case the label is rolled directly onto the body 100, some adhesive may be used between the label and the surface of the body 100 in order to keep the label in specified place.
Alternatively, the film may be stretched in transverse direction (TD), which means the direction perpendicular to machine direction of the film. Transverse direction (TD) may be referred also to as cross direction (CD). Transverse oriented films may be used for shrink-sleeve type of labels, which films are seamed into a form of a tube prior to labelling. The tube is cut into tubes of predetermined lengths and supplied as in a form of tube around a body. The labelled item may be heated in order to provide shrinking of the film around the body and/or to provide tight fitting of the label around the body and/or to conform the shape of the body with the label.
The stretched (oriented) structure 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.
The film may be uniaxially oriented approximately from 2 to 10 times, preferably 3 to 9 times, and most preferably from 3 to 8 times. The film may be uniaxially oriented in machine direction. Draw ratio (or orientation ratio) of the MD film is from 2 to 10 (from 2:1 to 10:1 ) , preferably from 3 to 9 (from 3:1 to 9:1 ), most preferably from 3 to 8 (from 3:1 to 8:1 ), correspondingly. Alternatively, the film may be uniaxially oriented in transverse direction, for example, from 2 to 10 times, preferably 3 to 9 times, and most preferably from 3 to 8 times.
For example, the films may be oriented at least 3 times at least in one direction, i.e. the draw ratio (stretching ratio) of the film is at least 3 in one direction of the film. Alternatively, the orientation ratio at least in one direction may be at least 4. For example, the draw ratio may be between 3 and 7, preferably between 4 and 6.
After the stretching the film is not heat set, i.e. not annealed, to provide maximum shrinkage for the multilayer shrink film. After stretching at elevated temperature the oriented film is immediately cooled by passing the film through cooling rolls. Cooling of the film may be gradual, for example first cooling roll(s) may have a temperature of around 90 °C, for example between 80°C and 90°C. Subsequent cooling roll(s) may have temperature between 10 and 20°C, or around 25°C. Consequently, subsequent application of heat causes the oriented film to relax and the oriented film may return towards or substantially back to its original unstretched dimensions. Thus, machine direction oriented films primarily shrink in the machine direction and transverse oriented films in the transverse direction.
Referring to Fig. 4a, a uniaxially oriented thermally shrinkable plastic film 1 having dimensions of a first length w1 , a second length width hi and thickness d1 , is arranged to shrink under application of heat so as to form a shrunk thermally shrinkable plastic film 1 1 . Uniaxial orientation direction Sx, of the film is parallel to the first length w1 . Uniaxial orientation direction may be, for example, the machine direction MD. Alternatively, uniaxial direction may be the transverse direction TD. Under heating, the uniaxially oriented film 1 is capable of shrinking in the direction of the orientation Sx. In other words, the length of the film reduces, when heat is applied. If the film is oriented only in one direction Sx, in the perpendicular direction Sy, the dimension hi remains substantially constant, as will be later defined in more detail. Same applies to the labels 2 comprising uniaxially oriented thermally shrinkable plastic film.
The thermally shrinkable plastic films 1 may be printed in order to provide visual effect and/or to display information. Printing may be performed by using traditional printing processes, for example, flexographic, gravure offset, and digital printing methods, such as liquid-toner, dry-toner or ink-jet processes. The multilayer film may comprise printing on an outer surface of a first skin layer 3. Alternatively the reverse side of the multilayer structure may be printed, i.e. a third layer 7 may comprise the printing. Thus the graphic patterns may be printed on at least one of the skin layers of the multi-layered film. When printing the second skin layer 5 of the film, the film may be referred to as reverse-printed. During labelling the reverse-printed film the printing is in direct contact with a surface of a body to which the film is applied. The print is viewed through the multilayer film. With these kind of films no further layers are needed to protect the printing e.g. from abrasion or scratching during handling of the labelled items.
The multilayer films are suitable for printing. Preferably the films enable high printing quality. The films have excellent ink adhesion and register control, allowing for example gravure printing. The printability of a surface can be characterized by the surface tension of the surface. The surface tension can be measured as described in the standard ISO 8296 (e.g. the latest version available on 1 st, July 2013). The surface tension of a printable surface may be e.g. from 36 mlM/m to 46 mlM/m, preferably from 38 mlM/m to 44 mlM/m. Quite commonly the surface tension is expressed in units dynes/cm. For example, the print receiving skin layer may have a surface tension at least 36 dynes/cm, preferably at least 38 dynes/cm or at least 44 dynes/cm measured according to the standard ASTM D-2578 (e.g. the latest version available on 1 st, July 2013). The surface tension may be between 36 and 60 dynes/cm, preferably between 38 and 56 dynes/cm or between 44 and 50 dynes/cm. Due to the polymer composition of the skin layer surface 2, the surface 2 may be apolar and may have a low surface tension. Low surface tension may lead to poor retaining capability of printing ink or other coating material, which may be applied to the skin layer surface. After the orientation the skin layer(s) of the facestock, the skin layer may be surface treated by e.g. by flame treatment, corona treatment, plasma treatment in order to enhance the surface tension of the surface of the skin layer and to enhance, for example, adhesion of the printed graphics.
The treatment increasing the surface tension may not be permanent, and the level of surface tension may decrease from the obtained treatment level as a function of time. The treatment may later be repeated to restore the level of surface tension obtained in a previous treatment.
According to an embodiment, the multilayer plastic film is clear i.e. transparent to visible light. Clear multilayer shrink films and labels comprising said films have good visual appearance. For example, said films may provide no-label look or appearance, when attached to the surface of a body. The clear no-label look allows the objects beneath such label, i.e. the bottle or contents, to be visible through such label. Clarity of the film and a label comprising said film can be measured and evaluated by the haze values. The overall haze of the multilayer film and label consisting of said multilayer film may be less than 25%, preferably less than 15%, and most preferably less than 10% when measured according to the standard ASTM D1003. For example, the haze of the thermally shrinkable plastic film may be between 2 and 10%, or between 5 and 10%.
According to another embodiment, initially clear thermally shrinkable plastic film of a label may be printed on the reverse side of the thermally shrinkable plastic film and the printing is visible through the thermally shrinkable plastic film. Thus, the printing is adjacent to the surface of the labelled item and as such protected, for example, from scuffing. The printing may be two-layered, e.g. colour printing at the film surface covered (overprinted) with a white or some other colour printing. Thus, the overprinting is next to the surface of the body. Through this kind of label the object beneath is not visible.
Shrinkage of the thermally shrinkable plastic film
The multilayer films and labels comprising said films have controlled shrinkage, i.e. specific amount of shrinkage at specific temperature range. The films have an ability to shrink upon exposure to external energy, e.g. some level of heat. Shrinkage of the film is activated when the film is treated e.g. at elevated temperatures, such as passed through a hot air or steam- tunnel. The shrink performance, i.e. shrinking capacity (potential) of the films in the stretching direction is very high at elevated temperatures.
Shrinkage may be measured. The term "shrinkage" is defined with reference to the method; however, it is evident, and has been noticed, that the same shrinkage properties apply regardless of the method, provided that the same temperatures are used. I.e. the composition of heat transfer medium (air, steam, water) is not critical for shrinkage behaviour in the shrinkage test. However, as discussed above, in the labelling process, a steam tunnel provides for uniform heating, and thus uniform shrinkage.
Referring to Figs. 4a and 4b, a thermally shrinkable plastic film 1 , stored at a temperature TO has a first length w1 in a first direction Sx and a second length hi in a second direction Sy, wherein the second direction Sy is perpendicular to the first direction Sx. Both directions Sx and Sy are in the plane of the film 1 . The temperature TO may be e.g. from -50 °C to +50 °C, what is important is that the manufactured film does not shrink at the temperature TO. TO may be e.g. +25 °C. The dimensions of a part A00 of the (not shrunk) film 1 , are measured before heating.
When heat is applied to the film 1 , the temperature of the film 1 rises. After sufficient heating, the film 1 shrinks to a shrunk film 1 1 . The dimensions of a part AO of the shrunk film 1 1 , the part AO of the shrunk film 1 1 corresponding to the part A00 of the not shrunk film 1 , after cooling back to TO, are measured, and the shrinkage is determined as the relative change of the dimension. More precisely, the shrinkage of a thermally shrinkable plastic film is determined as follows:
- An area A00 is drawn onto a surface of the thermally shrinkable plastic film 1 at the temperature TO. The area AOO has a first length L0 in the first direction Sx and a second length Lp0 in the second direction Sy. Typically the area is 100 mm χ 100 mm. Thereby, in a typical measurement, L0 = 100 mm and Lp0 = 100 mm. Moreover, as is clear, a sufficiently large piece of film is used, i.e. w1 >L0 and h1 >Lp0. Thereafter,
- the sample (i.e. the film 1 ) is placed for 15 seconds to a water bath having a temperature T. As the film 1 is thin, 15 seconds is a time in which the temperature of the whole (shrunk) film 1 1 is practically equal to T. Some weight, such as rivets, may be applied to the film 1 (or 1 1 ) to let it sink in to the water bath. Otherwise, the film (1 , 1 1 ) could float, as will be discussed in detail later. Thereafter
- cooling the sample back to the temperature TO. This may be done by using a second water bath having the temperature TO.
- Drying the sample. After cooling and drying
- measuring the size of the marked area AO, which was the area A00 before the thermal treatment. In particular, the length of the marked area, in the first direction Sx, after the thermal treatment wherein the temperature has been T, and after the cooling back to the temperature TO, is denoted by L(T). In particular, the length of the marked area, in the second direction Sy, after the thermal treatment wherein the temperature has been T, and after the cooling back to the temperature TO, is denoted by LP(T).
In practice, such temperatures T are used in the experiment, that are critical for transportation temperatures (i.e. reasonably hot water is used), and which temperature is achievable with the (unpressurized) water bath. In practice, measurements are done at temperatures T = 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, 85 °C, 90 °C, 95 °C, and 98 °C for all samples. To improve statistical accuracy, the length (at least one, such as all, of L0, L(T), Lp0, or Lp(T)) is measured from three different points of the sample (i .e. the area A00 or AO). Moreover, at least two similar samples are used to further improve the statistical accuracy, either by drawing two different areas A00 onto the same piece of film 1 , or by using two different pieces of film having the same composition.
The shrinkage ε(Τ) for the temperature T is defined as the relative change in length in the first direction; i.e. s(T)=(L(T)-L0)/L0. In a similar way, in the second direction, another shrinkage ερ(Τ)=(Ι_ρ(Τ)-Ι_ρ0)/Ι-ρο, can be defined. It is noted that by this definition, the numerical value of shrinkage is negative, while the numerical value of strain would be positive. Thus a "better" shrinkage is, in terms of numbers, a more negative (i.e. a smaller) value. As is implicitly clear, in practical applications a thermally shrinkable film 1 can be shrunk using different heat sources such as hot air, hot gas, steam, and/or radiation. Thus, in practice, drying is not necessarily needed.
The shrinkage of the film is defined as ε(Τ)=[Ι_(Τ)-Ι_]/Ι_. Thus a thermally shrinkable film 1 having the shrinkage ε(Τ) is configured to shrink, at the temperature T, -ε(Τ) χ 100 %. The following examples probably clarify the issue: (A) a thermally shrinkable film 1 having the shrinkage ε(70 °C) = -0.15 is configured to shrink, at the temperature T, -ε(Τ) χ 100 % = 15 %. (B) a thermally shrinkable film 1 having the shrinkage ε(98 °C) = -0.60 is configured to shrink, at the temperature T=98 °C, -ε(Τ) 100 % = 60 %.
A film used as a label is preferably only monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO). As discussed above, this kind of a film shrinks primarily in only one direction, i.e. in the "first direction" discussed above. This type of a film
- has a third length Lp0 in the second direction before heat treatment and a fourth length LP(T) in the second direction after heat treatment, in wherein the temperature of the thermally shrinkable plastic film has been T, wherein
- the second direction is perpendicular to the first direction, whereby
- the thermally shrinkable plastic film has another temperature dependent shrinkage ερ(Τ)=[Ι_ρ(Τ)-Ι_ρ0]/Ι-ρο, wherein
- the absolute value of ερ(Τ) is less than 7 % (i.e. ερ(Τ) is from -0.07 to 0.07 not including the limits) for temperatures 0 °C < T < 100 °C; preferably the absolute value of ερ(Τ) is less than 5 % for temperatures 0 °C < T < 100 °C more preferably the absolute value of ερ(Τ) is less than 3 % for temperatures 0 °C≤T < 100 °C. Here the subscripts p refer to perpendicular (cf. Figs 4a and 4b). This has the technical effect that the markings (MRK1 , Fig. 3) do not significantly shrink in the second direction, whereby the markings are easy to design. Moreover, when a film is applied onto a whole body (Fig. 7), preferably the film shrinks only in one dimension.
In addition to the shrinkage, as measured in the stress free test, as discussed above, a residual shrink force can also be used to characterize the force by which the label sticks to a body. The residual shrink force is determined in a test according to the standard DIN 53369 (latest version available on 1st July, 2013). In the test, a sample of the thermally shrinkable film 1 having the length 100 mm is placed in between two objects being separated apart from each other by the distance 100 mm. In principle, the film can be oriented in any direction in between these objects, however, typically, the film is oriented such that either the machine direction or the transverse direction is oriented from the first object to the second object, depending on which property is to be measured. The distance between these object is arranged fixed, and the sample is clamped to the objects. At least one of the objects is arranged to measure or coupled to a device arranged to measure the force, by which the film pulls the objects towards each other. The sample width is 15 mm, whereby the result of the test is given in units of force per 15mm. In this test the film, initially at the temperature TO = 30 °C, as discussed above, is heated to a temperature T = 100 °C and cooled (or let to cool) back to the temperature TO. The heating rate is 120 °C/h, whereby a heating of 70 degrees takes 35 minutes. Thus also the cooling of 70 degrees takes another 35 minutes. The force, by which the film pulls the objects towards each other at the end of the test is defined as the residual shrink force. In this test, however, the film does not shrink, as its dimension is fixed by the objects. The selection of materials and the thickness of the film affect the residual shrink force. Naturally the shrink force may be measured as function of time and/or temperature during the test; however, the residual shrink force is defined as discussed above, at the final stage of the test.
The composition of the multilayer thermally shrinkable plastic film 1 according to embodiments has effect of providing adequate shrinkage for use as a heat shrink label 2. The thermally shrinkable plastic film 1 according to at least some/all embodiments may have tensile strength in the orientation direction of the film between 90 MPa and 170 MPa. As for the strength, the ultimate strain in orientation direction of the film may be between 20 % and 50 %. Bending resistance (L&W 5mm, 15°) may be between 10 mN and 20 mN. 1 % secant modulus may be at least 500 MPa, or between 1200 MPa and 2000 MPa, or between 1200 MPa and 1800 MPa, when measured according to standard ISO 527-3. Stiffness (1 % secant modulus) may be between 0.008 and 0.015. Preferable values for the shrinkage of the thermally shrinkable plastic film
As will be discussed below, the thermally shrinkable plastic film 1 is, in some cases, used to label bodies 100 having uneven cross section. Thus, it is preferable that the film shrinks rapidly, i.e. when the film starts to shrink (referring here to temperature), the film shrinks a lot. Thus, the label will be fitted also to the areas having small cross section without the need for excessive heating.
Referring to Figs. 4a and 4b, a thermally shrinkable plastic film 1 , having a first size w1 in a first direction Sx,
- has a part (the area A00) having a first length L0 in a first direction Sx before heat treatment and, wherein the part has a second length L(T) in the first direction Sx after such a heat treatment wherein the temperature of the thermally shrinkable plastic film has been T and after cooling to a temperature that equals the temperature before the thermal treatment, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo in the first direction. Quite generally, the part of the film 1 having the area A00 could be considered as the film. Therefore, a thermally shrinkable plastic film
- has a first length L0 in a first direction before heat treatment and a second length L(T) in the first direction after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo in the first direction. As discussed above, the length L(T) refers to the length after cooling and drying or after drying and cooling. Heat treatment can be done in a dry atmosphere, whereby drying is optional. Drying merely refers to the test method, not to the practical applications of the film.
The shrinkage of the thermally shrinkable plastic film is generally large, tens of per cents, in order to be applicable in the application. In general, the shrinkage of the thermally shrinkable plastic film, after a thermal treatment wherein that the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), wherein the value of ε(98 °C) is less than -0.35, preferably less than -0.45, more typically less than -0.5. Optionally the value may be at most -0.85; and typically at most -0.80. When the value of ε(98 °C) is less than -0.35, the film is configured to shrink, at this temperature, more than 35 per cent; which is characteristic for a thermally shrinkable plastic film.
The dependence of the shrinkage of the film on the temperature is, for practical reasons critical for the use of the film. Figure 9a shows examples of prior at films, as denoted by the reference numbers 010 and 020. In case the film starts to shrink already at low temperatures, such as 65 °C, the films cannot be freely transported. For example, the temperature in vehicles may rise to reasonably high temperatures, whereby such films may start to shrink already during transportation, i.e. prior to use. However, shrinkage during transportation would cause blocking in the rolls. Thus, the roll having some shrunk film would be too tightly wound, and not industrially applicable For example, this is the case for a film having a temperature dependent shrinkage as shown in Fig. 9a by the reference number 010. It is noted that the prior art shrink labels of Fig. 9a and 9b are not necessarily oriented in the machine direction. It is noted that the density of the shrink labels of Fig. 9a and 9b is not such that the label floats, in particular on water.
As discussed above, the film should not shrink, at least significantly, at low temperatures. Therefore, in an embodiment, the shrinkage of the thermally shrinkable plastic film, after a thermal treatment wherein the temperature of the thermally shrinkable plastic film has been T=65 °C, is ε(65 °C), wherein the value of ε(65 °C) is greater than -0.10, preferably greater than -0.07 and more preferably at least -0.05. Optionally, this value may be at most 0. On the other hand, the films should shrink a reasonable amount already for only slightly higher temperatures. When the films shrink at such temperatures, the attaching of the film to the body becomes faster, since the films can be heated more rapidly. This is particularly the case for bodies 100 having uneven cross section (cf. e.g. Fig. 8).
Because of these two factors, the film should use most of its shrinkage potential for a reasonable small temperature change. To more precisely define the shrinkage potential, a relative temperature dependent shrinkage 8r(T) is herein defined as εΓ(Τ) = εΓ(Τ)/ε(98 °C) = {[L(T)-L0]/L0}/s(98 °C). In this description, the value of εΓ(Τ) will be given in percentages. The reason for selecting the reference temperature of 98 °C is that such a temperature is achievable using hot water or unpressurized (pressure equals 1 atm) steam. It is noted that the film may shrink also for temperatures above 98 °C, however these are of little practical interest, since the films are commonly heated by water and/or steam. As discussed, water is used in a typical shrinkage test, while steam is typically used in a labeling process. So, the value ε(98 °C) is not a maximum shrinkage, only a reference value.
As for the relative shrinkage sr; first, at low temperatures, the relative shrinkage should be reasonably low. This is because the temperature during transportation may rise such that, provided that the shrinkage at the corresponding temperature would not be small, some shrinkage would occur. However, as discussed above, shrinkage during transportation would cause blocking in the rolls. Thus, the roll having the shrunk film would be too tightly wound, and not industrially applicable. Thus, the shrinkage ε at the transportation temperatures needs to be low, preferably negligible or zero. Moreover, preferably also the relative shrinkage εΓ at the transportation temperatures is low, in order to further reduce the shrinkage during transportation at hot conditions. Still further, with a low relative shrinkage at these temperatures, the shrinkage potential after transportation of the film is high, regardless of the shrinkage ε. As for an example of a transportation temperature, typically these are at most 65°C.
Second, at high temperatures, the relative shrinkage should be reasonably high. This is because films that are purposely heat treated have preferably used most of their shrinkage potential. For example, when the crushed film floats on water, e.g. hot water, the crushed pieces are preferably not further shrunk on the water. For example, the crushed pieces may be collected using a sieve having a size, and further shrinking of the pieces might make the smaller than the sieve size. Thus their collection might become hard. Furthermore, the further shrinking, as discussed, might curve or bend the crushed pieces, and the further utilization of such curved pieces might be more problematic than the utilization of planar pieces. The heat shrunk label would not have too much residual shrinkage potential left. High shrinkage potential of the label may be harmful for example if heated liquid (having a temperature around 80 °C) is used during the separation process, which will cause e.g. curling of the label into tight tubes blocking the apparatus wherein the parts are separated. Such an apparatus may be simultaneously arranged to wash the pieces.
Moreover, as already discussed this has the benefit that a film rapidly shrinks to fit also uneven surfaces (Fig. 8).
Because of the aforementioned two factors, the film should use most of its shrinkage potential for a reasonable small temperature change. When the film uses most of its shrinkage potential for a reasonable small temperature change, the difference εΓ(Τ2)-εΓ(Τι), between the values of the relative temperature dependent shrinkage εΓ(Τ) for at least one pair of two temperatures T2 and Ti, the temperatures having a difference T2-Ti=15 °C, is more than 50 percentage points (pp); wherein the lower of the two temperatures, Ti, is from 65 °C to 70 °C. For example, the lower of the two temperatures, Ti, may be 65 °C, whereby εΓ(80 °C)-sr(65 °C) is more than 50 pp. For example, the lower of the two temperatures, Ti, may be 70 °C, whereby εΓ(85 °Ο)-εΓ(70 °C) is more than 50 pp. Preferably, for a slightly wider temperature range, the difference between the values of the relative temperature dependent shrinkage εΓ(Τ) for at least the pair of temperatures T2 = 85 °C and Ti = 65 °C, i.e. εΓ(Τ2)-εΓ(Τι), is more than 65 pp; preferably more than 70 pp. In a preferred embodiment the thermally shrinkable plastic film has a density that is less than 970 kg/m3 or less than 950 kg/m3 at the temperature T=80 °C. As discussed above, in a preferred embodiment the thermally shrinkable plastic film is monoaxially oriented; in the MD or the TD.
Regarding the values of the shrinkage ε(Τ) itself, as defined above, because of the aforementioned two factors, in an embodiment
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is greater than -0.10, and
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=80 °C is less than -0.25.
A value "greater than -0.1 " may be e.g. -0.05. Because the value is negative by definition, a greater value means less shrinkage. Preferably the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is e.g. greater than -0.08, or greater than -0.05.
A value "less than -0.25" may be e.g. -0.3. Because the value is negative by definition, a lesser value means more shrinkage. Preferably the value of the temperature dependent shrinkage ε(Τ) for the temperature T=80 °C is less than -0.27 or less than -0.30.
As for other temperatures, and for storing the film without significant shrinkage, in an embodiment of a thermally shrinkable plastic film the value of the temperature dependent shrinkage ε(Τ) for the temperature T=70 °C, ε(70 °C), is greater than -0.20. Preferably ε(70 °C) is greater than -0.18, or more preferably greater than -0.16. In addition or alternatively, the value of the temperature dependent shrinkage ε(Τ) for the temperature T=75 °C may be more than -0.40.
As for other temperatures, and for attaching a loop to a body in a reasonably low temperature, in an embodiment of a thermally shrinkable plastic film the value of the temperature dependent shrinkage ε(Τ) for the for the temperature T=75 °C, ε(75 °C), is less than -0.15. Preferably ε(75 °C) is less than -0.16 or more preferably less than -0.17. Preferably, the shrinkage (the numerical value thereof) decreases with increasing temperature relatively rapidly. This kind of rapid decrement can be described with a function. Moreover, preferably the film floats on water (for reasons discussed above), and for ease of manufacturing, preferably the film is oriented only in the machine direction. In an embodiment
- the thermally shrinkable plastic film is monoaxially oriented in the machine direction (MD) or the transverse direction (TD),
- the density of the shrinkable plastic film is less than 970 kg/m3 (preferably less than 950 kg/m3) at the temperature T=80 °C, and
- the value of the temperature dependent shrinkage ε(Τ) for the temperatures 75 °C < T < 90 °C is less than the value of the function fn(T)=aiiT2+biiT+Cn, wherein a = -0.00001667 (°C)"2, bn = -0.01821 (°C)"1, e = 1 .406, and T is the temperature in degrees of Celsius, including the unit °C.
The value of the function fn(T) is depicted in Fig. 10a. It is noted that unlike conventionally, in Figs. 2 and 4, the value of the shrinkage decreases towards the top of the page. In Fig. 10a, also the shrinkage curves of different samples manufactured as described earlier are shown; with the reference "Samples". In total 21 samples were manufactured and measured as describe above. Preferably, also in this case the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is more than -0.10. Preferably, the shrinkage decreases somewhat more rapidly with temperature. In an embodiment
- the thermally shrinkable plastic film is monoaxially oriented, either in the machine direction (MDO) or transverse oriented (TDO),
- the density of the shrinkable plastic film is less than 970 kg/m3 (preferably less than 950 kg/m3) at the temperature T=80 °C,
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is more than -0.10 and
- the value of the temperature dependent shrinkage ε(Τ) for the temperatures 70 °C < T < 80 °C is less than the value of the function fi2(T)=ai2T2+bi2T+Ci2, wherein ai2 = -0.000876(°C)"2, bi2 = 0.1 132(°C)"1, Ci2 = -3.66, and T is the temperature in degrees of Celsius, including the unit °C.
Also the value of the function fi2(T) is depicted in Fig. 10a. These functions provide for a reasonable limit for temperature behavior of the shrinkage. In addition or alternatively, the more specific values, that were discussed above, can be used to describe the shrinkage behavior. In addition or alternatively to the shrinkage ε(Τ), the shrinkage behavior can be described using the relative shrinkage εΓ(Τ) as defined above. In addition or alternatively to the shrinkage ε(Τ), as discussed above, the relative shrinkage εΓ(Τ) is preferably above some limiting values in some specific temperatures, as will be discussed later. Also preferably, the relative shrinkage εΓ(Τ) may be between some limiting values in some specific temperatures, as will be discussed later.
The relative shrinkage properties of some known films are shown in Fig. 9b. These are the same materials (010, 020) as in Fig. 9a. Clearly, by definition, at the temperature T=98 °C, the relative shrinkage is 100 %, increasing thereto with increasing temperature.
Because of these reasons, in some embodiments of the thermally shrinkable plastic film
- the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=65 °C is less than 10 %, and
- the value of the temperature dependent shrinkage εΓ(Τ) for the temperature T=80 °C is more than 45 %.
Preferably the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=65 °C is less than 7.5 %. In addition or alternative, preferably the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=80 °C is more than 50 % or more than 55 %.
To further characterize the properties at the low temperature side, in an embodiment the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=70 °C is less than 29 %; preferably less than 27 % or less than 26 %. In an embodiment the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=75 °C is more than 26 %; preferably more than 30 % or more than 33 %.
To further characterize the properties at the high temperature side, in an embodiment the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=85 °C is more than 65 %; preferably more than 67 % or more than 70 %. The values of relative shrinkage of different samples manufactured as described earlier are shown in Fig. 10b with the reference "Samples". In total 21 samples were manufactured and measured as describe above. For the aforementioned reasons, the behavior of the relative shrinkage is particularly important in the temperature range 70 °C < T < 85 °C. In an embodiment the value of the relative temperature dependent shrinkage εΓ(Τ), at the temperature range 70 °C < T < 85 °C is at least the value of a limiting function f2(T), wherein, f2(T)=a2T2+b2T+C2, wherein a2 = 0.00127(°C)"2, b2 = - 0.1577(°C)"1, C2 = 4.837, and T is the temperature in degrees of Celsius, including the unit °C. These functions are shown in Fig. 10b.
The value of εΓ may also be lower than another limiting function. In an embodiment the value of the relative temperature dependent shrinkage εΓ(Τ), at the temperature range 70 °C < T < 85 °C is at most the value of another limiting function fs(T), wherein f3(T)=a3T2+b3T+C3, wherein a3 = - 0.002013(°C)"2, b3 = 0.3417(°C)"1, c3 = -13.59, and T is the temperature in degrees of Celsius, including the unit °C. These functions are shown in Fig. 10b.
As is implicitly clear, the shrink properties, in particular ε(Τ) and εΓ(Τ) can be affected by selection of materials, their composition, and/or the thicknesses and number of different layers, as well as by the draw ratio. All the 21 samples of Figs. 10a and 10b have a three layered structure as shown in Fig. 1 , the composition as discussed above, and manufactured as discussed above.
Labelling at least a part of a body Roll-fed shrink labels may be applied to a body with a combination of steps including: rolling over, seaming and shrink technique. Labels may be provided in a roll of continuous label stock and cut into individual labels. Referring to Fig. 5, a label 2 cut from a continuous label stock and comprising or consisting of a multilayer plastic film 1 is mounted around the outer surface of a body 100. Preferably, orientation direction of the label film (Sx in Fig. 4a and 4b) extends circumferentially around the body 100 in direction DIR1 . Thus it is possible to provide 360°C decoration for the body. Main shrinking direction of the film is indicated by the Sx corresponding to direction DIR1 , as shown in Fig. 5. Sx may correspond to the orientation direction of the film, for example machine direction MD. Referring to Fig. 5, the opposite edges of the label, leading edge 23 and trailing edge 25, may overlap and form a seam 24. The seam 24 may comprise an adhesive layer, such as a hot melt or UV-curable adhesive. Alternatively, it may comprise solvent dissolving the film materials and thus provide a joint. The adhesive may be provided as a continuous strip or separate adhesive patterns. Alternatively, the seaming may be performed using other methods such as laser welding, heat sealing, or ultrasonic bonding. The body 100 having a label 2 wrapped around it is subsequently heated. The heating causes the label 2 to shrink to a shrunk label 22 and to conform to the surface of the body. A shrunk, tight fitting label 22 for the body 100 is shown in Fig. 6. The shrunk label 22 provides a smooth and consistent coating for the body. The heating temperature of the film may be between 80 °C and 150 °C, preferably between 120 °C and 130 °C in hot-air tunnels or between 80 °C and 90°C in steam tunnels. As discussed, heating in a steam tunnel may be more uniform than in another tunnel. This issue further clarifies, why the film should shrink preferably a lot already at the temperature 80 °C, but at the temperature 90 °C the latest. Labels comprising oriented films in this embodiment shrink in the machine direction, the machine direction is extending circumferentially around the body. The heat that induces shrinkage may be provided by conventional heat sources, such as hot steam, heated air, infrared radiation, or any other suitable heat source.
According to an embodiment, the label may consist of a thermally shrinkable plastic film having transversal orientation direction (TD). Prior to labelling, transverse oriented films may be solvent seamed into a form of a continuous tube. The continuous tube is then cut into shorter, predetermined lengths and supplied as a separate tube around a body. The labelled item is transferred to the following process step of heating so as to provide shrinking of the label around the body. A labelled item
Such films are, in general user to label items, as discussed above. With reference to Fig. 6, An embodiment of such labeled item 1 10 comprises
- a body 100, and
- a loop 22 of a plastic film, which loop encircles a part of the body, wherein
- the plastic film 22 has been made by thermally treating the thermally shrinkable plastic film 1 as discussed in this document.
For example, referring to Fig. 5, a loop may be made of the label 2 comprising the film 1 by joining one edge 25 of a band of the film to the opposite edge 23 of the band of the film. Thus a seam 24 is formed between these ends. The loop is arranged around at least a part of the body 100. After the application of heat, the loop shrinks to a shrunk loop 22 onto the part of the body 100. Referring to Figs. 5 and 6 the aforementioned first direction of the film, in which direction the film shrinks, as denoted by Sx in Fig. 4a, is aligned circumferentially with the body 100, as depicted by the direction DIR1 in Fig. 5.
Referring to Figs. 5 and 6, in an embodiment,
- an area Abi is left in between the loop 22 of the plastic film and the body 100, wherein
- at most 10 % of the area Abi is covered by adhesive.
This reduces the amount of adhesive deeded to attach a label to a body. For example the area is free from adhesive. This helps the recirculation of materials, as the loop 22, when broken, detaches from the body 100. In an embodiment,
- the part of the body 100 that is encircled by the loop 22 has a cross sectional area of at least 4 (cm)2; preferably at least 8 (cm)2 or at least 12 (cm)2. The part of the body that is encircled by the loop may have a cross sectional area of at most 1000 (cm)2, such as at most 660 (cm)2 or at most 330 (cm)2. The body 100 to be labelled may be highly contoured container, such as shampoo or detergent bottle, or drink container having e.g. recesses and/or protrusions at the outer surface. Thus, for example, a diameter of the bottle may alternate. A container may comprise different diameters. Difference between the diameters to be labelled in a container may be up to 30 %, or up to 20 %, or 2-30 %, or 5-20 %, or 8-15 %. According to an example, the difference between the smallest diameter and the largest diameter of the body to be labelled may be up to 30 %, or up to 40 %, or up to 50 %, or up to 60 %, or up to 70 %, or 2-70 %, or 5-60%, or 10-35%. The body may also be recyclable.
However, the body 100 needs not be circular. In this case the contour may be described with a cross sectional area the label 22 encircles. Referring to Fig. 8, in an embodiment, the shrinkable plastic film is used to label a body 100, wherein the body has a varying shape. In the embodiment,
- the part of the body 100 that is encircled by the loop 22 has, at a first location, a first cross sectional area Ai,
- the part of the body 100 that is encircled by the loop 22 has, at a second location, a second cross sectional area A2, and
- the first cross sectional area Ai is different from the second cross sectional area A2.
In an embodiment,
- the ratio of the second cross sectional area to the first cross sectional area, A2/Ai, is at least 1 .5, at least 2 or at least 4.
When the ratio is e.g. at least 2, the ratio of the linear sizes, such as diameters, at the first and the second location is at least about 1 .2. Thus, when the film is arranged around the body and thermally shrunk onto the body, the film should shrink at least about 20 % to fit also to the smaller parts of the body, even if the larger parts could be labeled with a film having only a small shrinkage.
When the film is used to label the items having an uneven size, as described above, the film should be reasonably flexible for smooth manufacturing process. This is achieved by proper thickness, since it is well known that thickness increases the stiffness. In an embodiment, before shrinking the film by said thermal treatment, the thickness if the film is from 10 μηη to 80 μητι, preferably from 15 μηη to 50 μηη. However, during the shrinking process, the film thickens. If the film can freely shrink, the shrinkage may be e.g. as good as -0.75 (length decreases to one quarter), whereby the thickness could increase by a factor of four. However, when the film is attached to a body 100, the size of the body 100 limits the shrinkage. Thereby the films does not thicken as much in practical use. Thus, in an embodiment the thickness of the plastic film forming the loop is from 15 μηη to 150 μητι, preferably from 20 μηη to 50 μηη.
The multilayer plastic films 1 of the invention are suitable for labels and use for labelling of bodies 100. Especially the multilayer plastic films may be used for a thermally shrinkable plastic film of a label. In other words, the films described above are suitable for a label film. The films are suitable for labelling of a wide range of product designs and particularly suitable for highly contoured containers and products comprising curved sections, recesses and/or protrusions at the outer surface. The labels comprising heat shrink multilayer thermally shrinkable plastic film are suitable for bodies of glass, plastic, ceramics, glass, and metal . Shrinkage properties of films and/or labels enable labels to be used in highly contoured containers.
The body 100 may comprise or consist of polyethylene terephthalate (PET). The body 100 may have a shape of a container. The body 100 may have a shape of a bottle. The shape and/or the material of the body 100 ensures proper rigidity for the body 100, whereby the shrinking of the label 2 (Fig. 5) to the shrunk label 22 does not deform the body 100 (cf. Fig. 6). This happens at least, when the film thickness and/or shrinkage of the film 1 has the aforementioned values. This issue can also be described using a film having a residual shrink force from 1 N/15 mm to 10 N/15 mm; preferably from 2 N/15 mm to 6 N/15 mm. In addition, adequate residual shrink force is needed for the proper fitting of the label around a body when heat is applied. As discussed above, the also the residual shrink force is affected by the thickness of the film; whereby the thickness affects several aspects of the process. Sufficient rigidity of the body is affected by the density of the material of the body. In some embodiments, the density of the body is at least 1 100 kg/m3, preferably at least 1200 kg/m3 or 1300 kg/m3. These density values have also a surprising effect is recycling the item, as will be discussed later.
The label may be a full body label, i.e. the shrunk label 22 may cover substantially the whole outer surface of the body 100, as shown in Fig. 7. Alternatively, the label may cover the body only partially, as shown in Figs. 6 8. Referring to Fig. 8, for example a neck of a bottle 104 may be left without a label, or a separate and/or different label may be used for the bottle neck part than for the bottle volume part.
Recycling the item
After the item has been used, the item may be recycled. Typically during recycling the item is crushed into pieces. In particular, when the area Abi (Figs. 5 and 6) in between the loop of the plastic film and the body is free from adhesive, the film separates from the body during this crushing. In a preferred embodiment, the pieces of the body are separated from the pieces of the film based on the difference in their densities. For example, the pieces of the film may float on a liquid having a special density. In an embodiment, - the body 100 has a first density pi ,
- the plastic film forming the loop 22 has a second density p2, and
- the ratio of the second density to the first density, P2/P1, at most 0.9; preferably at most 0.8 or at most 0.7 at a temperature, such as at the temperature 80 °C.
Thereby, when the liquid has a special density that is more than p2 and less than pi, the pieces of the body 100 sink into the liquid, while the pieces of the shrunk film 22 float on the liquid. For example, an item may comprise a body 100 comprising polyethylene terephthalate (PET; having the density of about 1380 kg/m3), and a film 22 having the density of about 920 kg/m3, whereby the ratio of these densities is as low as 0.67. These densities are typically measured near room temperature, such as 25 °C, however, increasing temperature up to e.g. 80 °C does not affect the ratio much. The composition of the multilayer structure according to embodiments has effect of providing the overall film density less than 1 g/cm3 (note: 1 g/cm3 equals 1000 kg/m3). Preferably the density is less than 1 g/cm3 also after printing of the film. The density may be, for example between 0.90 g/cm3 and 0.98 g/cm3, or between 0.90 g/cm3 and 0.95 g/cm3. According to an embodiment, the multilayer plastic film contains less than 20 wt.%, preferably less than 10 wt.% or less than 5 wt.% polymeric material having density above 1 .3 g/cm3 or 1 .25 g/cm3 or 1 .1 g/cm3.
During shrinking, the volume of the film changes only a little. The shrinking thus affects the thickness. Moreover, the density of the film may change during shrinking. However, the issues relating to the density of the film are equally applicable to the density of the film 1 before shrinking and to the density of the shrunk film 1 1 (cf. Fig. 4a and 4b). In an embodiment, the thermally shrinkable plastic film 1 (and/or the shrunk film 1 1 of the item 1 10) has a density p2 of less than 1000 kg/m3, preferably less than 960 kg/m3, such as less than 920 kg/m3. As the density may be dependent on temperature, these values are given at the at the temperature 80 °C.
When the second density p2 (of the film) is less than 960 kg/m3 (for temperatures from 0 °C to 98 °C) and the first density pi (of the body) is more than 1000 kg/m3 (for temperatures from 0 °C to 98 °C), the aforementioned special density for the liquid is between 960 kg/m3 and 1000 kg/m3. This is a very appealing embodiment, since water has a temperature dependent density that is between 958 kg/m3 (for 100 °C) and 999.97 kg/m3 (for 4 °C). In practice, the crushed pieces of plastic are cleaned in water having a temperature of about 80 °C. At 80 °C, the density of water is 972 kg/m3. However, the density of the cleaning liquid can be affected by ingredients (e.g. salts) added to the cleaning liquid. Thus, in a preferred embodiment, the second density p2 (of the film) is less than 1000 kg/m3; preferably less than 950 kg/m3 at the temperature 80 °C. Moreover, preferably in addition, the first density pi (of the body) is more than 1000 kg/m3 at the temperature 80 °C.
Low density of the film has effect of enabling the film and label comprising said film to be more easily separated from the substrates having higher density, such as PET bottles. Said film density allows the films to be separated from the substrate material during recycling process, for example in the normally used washing process of the bottles, i.e. flotation separation process, of the bottles or other containers. The separated labels may also be further recycled.
However, to ensure sufficient tension force for the film forming the label around a part of the body, the strength of the film should be reasonable. The strength of the film is affected, among other things, by the density of the film. In an embodiment, the thermally shrinkable plastic film has a density of more than 700 kg/m3, preferably more than 800 kg/m3, such as more than 870 kg/m3.
Still further, as the film is used to label the body (to form the item), the thermally shrinkable film comprises a printable face 2, such as a printable surface 2 (Fig. 3). The printable face is typically arranged on a skin layer (3, 7) of the plastic film.
Multilayer plastic film structure according to embodiments has effect of providing a heat shrinkable label which can be easily separated in re-cycling process from the body it is mounted. Some properties related to the structure and composition of a thermally shrinkable plastic film are summarized below
1 .1 . A thermally shrinkable label comprising
- a thermally shrinkable plastic film, wherein
- the thermally shrinkable plastic film is oriented in one direction
- the thermally shrinkable plastic film comprises at least a first layer and a second layer, wherein
- the first layer of the thermally shrinkable plastic film comprises first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C.
1 .2. The label according to example 1 .1 , wherein the first cyclic olefin copolymer is different from the second cyclic olefin copolymer. 1 .3. The label according to example 1 .1 or 1 .2, wherein the glass transition of the first cyclic olefin copolymer is different from the glass transition temperature of the second cyclic olefin copolymer. 1 .4. The label according to example 1 .3, wherein a difference in the glass transition temperature of the first cyclic olefin copolymer and the second cyclic olefin copolymer is at most 40 °C, preferably at most 30°C.
1 .5. The label according to any of the examples 1 .1 to 1 .4, wherein the difference in the glass transition temperature of the first cyclic olefin copolymer and the second cyclic olefin copolymer is at least 5 °C, preferably at least 10°C.
1 .6. The label according to any of the examples 1 .1 to 1 .5, wherein the glass transition temperature of the first cyclic olefin copolymer is below 70 °C and the glass transition of the second cyclic olefin is above 70°C.
1 .7. The label according to any of the examples 1 .1 to 1 .6, wherein the at least one layer comprises equal amounts of the first cyclic olefin copolymer and the second cyclic olefin copolymer.
1 .8. The label according to any of the examples 1 .1 to 1 .6, wherein a ratio of the first cyclic olefin copolymer to the second cyclic olefin copolymer in a layer is between 1 .5 and 8.
1 .9. The label according to any of the examples 1 .1 to 1 .8, wherein the at least one layer further comprises linear low density polyethylene.
1 .10. The label according to example 1 .9, wherein an amount of linear low density polyethylene is at most 20 wt.% or at most 10 wt.% of the total weight of the at least one layer.
1 .1 1 . The label according to any of the examples 1 .1 to 1 .10, wherein the multilayer thermally shrinkable plastic film has a density between 0.90 g/cm3 and 0.98 g/cm3. 1 .12. The label according to any of the examples 1 .1 to 1 .1 1 , wherein the label is configured to shrink in the direction of the orientation of the thermally shrinkable plastic film between 15 % and 85 % at a temperature range between 65 % and 85°C and wherein the label shrinks less than 10% at temperature below 65 °C.
1 .13. The label according to the example 1 .12, wherein the label is configured to shrink between 25 % and 50% at a temperature range between 65 °C and 85 °C.
1 .14 The label according to the example 1 .12, wherein the label is configured to shrink between 45 % and 75 % at a temperature range between 65 °C and 85 °C. 1 .15 The label according to any of the examples 1 .1 to 1 .12, wherein the thermally shrinkable plastic film is oriented in machine direction.
1 .16 The label according to any of the example 1 .1 to 1 .14, wherein the thermally shrinkable plastic film is oriented in transverse direction.
1 .17 A heat shrink label film, wherein the heat shrink label film is oriented in one direction, and includes a layer comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C.
The following examples summarize the manufacturing process
2.1 . A method for providing a heat shrink label, the method comprising: - providing a thermally shrinkable plastic film comprising at least one layer comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C ;
- stretching said thermally shrinkable plastic film in one direction; and
- cooling the stretched thermally shrinkable plastic film so as to provide shrink potential for the thermally shrinkable plastic film in said one direction. 2.2 The method according to example 2.1 , wherein the thermally shrinkable plastic film is stretched in said one direction with a ratio of unstretched film thickness to stretched film thickness between 2 and 10. 2.3. The method according to example 2.1 or 2.2, wherein the thermally shrinkable plastic film is stretched in machine direction of the film.
2.4. The method according to example 2.1 or 2.2, wherein the thermally shrinkable plastic film is stretched in transverse direction of the film.
The following examples summarize use of such a film
3.1 . A use of a label according to any of the example 1 .1 to 1 .17 for labelling of a container comprising an uneven surface, wherein a difference between the smallest diameter and the largest diameter of the container is between 20 % and 80 %, preferably between 30 % and 70 %.
3.2 A method for labelling of a body, wherein the label comprises an oriented thermally shrinkable plastic film comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C , the method comprising:
- wrapping the label around the body, wherein the orientation direction of the plastic film is extending circumferentially around the body;
- seaming said label by gluing, laser welding, heat sealing, or unltrasonic bonding;
- heating the label at temperature between 65 °C and 80 °C so as to for a tight fitting label for the body.
3.3. A combination of a label and a body, wherein the label comprises a continuous thermally shrinkable plastic film around an external surface of the body, wherein the continuous thermally shrinkable plastic film is oriented in one direction, and comprises a layer comprising first cyclic olefin copolymer and second cyclic olefin copolymer, wherein a glass transition of the first cyclic olefin copolymer and the second cyclic olefin copolymer is between 50 and 90 °C, and wherein a leading end of the label and a trailing end of the label are overlapped on the surface of the body, and wherein the label between the leading edge and the trailing edge is next to the surface of the body. 3.4. The combination according to the example 3.3, wherein a difference between the smallest diameter and the largest diameter of the body is between 20 % and 80 %, preferably between 30 % and 70 %.
For the person skilled in the art, it will be clear that modifications and variations of the products and the methods according to the present invention are perceivable. The drawings are schematic. The particular embodiments described above with reference to the accompanying drawings are illustrative only and not meant to limit the scope of the invention, which is defined by the appended claims.

Claims

Claims:
1 . A thermally shrinkable plastic film,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO),
- having a first length L0 in a first direction before heat treatment and a second length L(T) in the first direction after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-l_o]/Lo, wherein
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), wherein
- the value of ε(98 °C) is less than -0.35, optionally at most -0.85;
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=65 °C, is ε(65 °C), wherein
- the value of ε(65 °C) is greater than -0.10, preferably greater than -0.07; optionally at most 0;
and
- the thermally shrinkable plastic film has a relative temperature dependent shrinkage εΓ(Τ)={[ί(Τ)-ί0]/ί0}/ε(98 °C), wherein
- the difference between the values of the relative temperature dependent shrinkage εΓ(Τ) for at least one pair of temperatures T2 and Ti having a difference T2-Ti=15 °C, i.e. εΓ(Τ2)-εΓ(Τι), is more than 50 percentage points; wherein the lower of the two temperatures of the pair, Ti, is from 65 °C to 70 °C.
2. The thermally shrinkable plastic film of claim 1
- having a density that is less than 950 kg/m3 at the temperature T=80 °C.
3. The thermally shrinkable plastic film of claim 1 or 2,
- being oriented in the machine direction.
4. The thermally shrinkable plastic film of any of the claims 1 to 3, wherein
- wherein the lower of the two temperatures, Ti, is 65 °C.
5. The thermally shrinkable plastic film of any of the claims 1 to 4
- the difference between the values of the relative temperature dependent shrinkage εΓ(Τ) for at least the pair of temperatures T2 = 85 °C and Ti = 65 °C, i.e. Sr(T2)-Sr(Ti), is more than 65 percentage points, preferably more than 70 percentage points.
6. The thermally shrinkable plastic film of any of the claims 1 to 5, wherein
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=80 °C is less than -0.25.
7. A thermally shrinkable plastic film,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO),
- having a first length L0 in a first direction before heat treatment and a second length in the first direction L(T) after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo, wherein
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is greater than -0.10, and
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=80 °C is less than -0.25.
8. The thermally shrinkable plastic film of any of the claims 1 to 7, wherein - the shrinkage of the thermally shrinkable plastic film, after a thermal treatment wherein the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), and
- the thermally shrinkable plastic film has a relative temperature dependent shrinkage sr(T)={[L(T)-L0]/L0}/s(98 °C), wherein
- the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=65 °C is less than 10 % and
- the value of the temperature dependent shrinkage εΓ(Τ) for the temperature T=80 °C is more than 45 %.
9. A thermally shrinkable plastic film,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO), - having a first length L0 in a first direction before heat treatment and a second length L(T) in the first direction after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo, wherein
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment wherein the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), wherein
- the value of ε(98 °C) is less than -0.35, optionally at most -0.85; and
- the thermally shrinkable plastic film has a relative temperature dependent shrinkage sr(T)={[L(T)-L0]/L0}/s(98 °C), wherein
- the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=65 °C is less than 10 % and
- the value of the temperature dependent shrinkage εΓ(Τ) for the temperature T=80 °C is more than 45 %.
10. The thermally shrinkable plastic film of any of the claims 1 to 9, wherein
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=70 °C is greater than -0.20.
1 1 . The thermally shrinkable plastic film of any of the claims 1 to 10, wherein
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=75 °C is greater than -0.40.
12. The thermally shrinkable plastic film of any of the claims 1 to 1 1 , wherein
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=75 °C is less than -0.15; preferably less than -0.16 or less than -0.17.
13. The thermally shrinkable plastic film of any of the claims 1 to 12, wherein - the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=70 °C is less than 29 %.
14. The thermally shrinkable plastic film of any of the claims 1 to 13, wherein
- the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=85 °C is more than 65 %.
15. The thermally shrinkable plastic film of any of the claims 1 to 14, wherein - the value of the relative temperature dependent shrinkage εΓ(Τ) for the temperature T=75 °C is more than 26 %.
16. A thermally shrinkable plastic film, or the thermally shrinkable plastic film of any of the claims 1 to 15,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO),
- having a first length L0 in a first direction before heat treatment and a second length in the first direction L(T) after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo, wherein
- the density of the shrinkable plastic film is less than 970 kg/m3 at the temperature T=80 °C,
- the value of the temperature dependent shrinkage ε(Τ) for the temperatures 75 °C < T < 90 °C is less than the value of the function fn(T)=aiiT2+biiT+Cn , wherein a = -0.00001667 (°C)"2, bn = -0.01821 (°C)"1, e = 1 .406, and T is the temperature in degrees of Celsius, including the unit °C.
17. A thermally shrinkable plastic film, or the thermally shrinkable plastic film of any of the claims 1 to 16,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO),
- having a first length L0 in a first direction before heat treatment and a second length in the first direction L(T) after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage s(T)=[L(T)-Lo]/Lo, wherein
- the density of the shrinkable plastic film is less than 970 kg/m3 at the temperature T=80 °C,
- the value of the temperature dependent shrinkage ε(Τ) for the temperature T=65 °C is more than -0.10 and
- the value of the temperature dependent shrinkage ε(Τ) for the temperatures 70 °C < T < 80 °C is less than the value of the function fi2(T)=ai2T2+bi2T+Ci2, wherein ai2 = -0.000876(°C)"2, bi2 = 0.1 132(°C)"1, Ci2 = -3.66, and T is the temperature in degrees of Celsius, including the unit °C.
18. A thermally shrinkable plastic film or the thermally shrinkable plastic film of any of the claims 1 to 17,
- being monoaxially oriented, either machine direction oriented (MDO) or transverse direction oriented (TDO),
- having a first length L0 in a first direction before heat treatment and a second length L(T) in the first direction after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, whereby
- the thermally shrinkable plastic film has a temperature dependent shrinkage e(T)=[L(T)-Lo]/L0> wherein
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), wherein
- the value of ε(98 °C) is less than -0.35, optionally at most -0.85;
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=65 °C, is ε(65 °C), wherein
- the value of ε(65 °C) is greater than -0.10, preferably greater than -0.07; optionally at most 0;
and
- the thermally shrinkable plastic film has a relative temperature dependent shrinkage εΓ(Τ)={[ί(Τ)-ί0]/ί0}/ε(98 °C), wherein
- the value of the relative temperature dependent shrinkage εΓ(Τ), at the temperature range 70 °C < T < 85 °C is at least the value of a function f2(T), wherein, f2(T)=a2T2+b2T+C2, wherein a2 = 0.00127(°C)"2, b2 = -0.1577(°C)"1, C2 = 4.837, and T is the temperature in degrees of Celsius, including the unit °C.
19. The thermally shrinkable plastic film of the claim 18, wherein
- the value of the relative temperature dependent shrinkage εΓ(Τ), at the temperature range 70 °C < T < 85 °C is at most the value of a function f3(T), wherein, f3(T)=a3T2+b3T+C3, wherein a3 = -0.002013(°C)"2, b3 = 0.3417(°C)"1, C3 = -13.59, and T is the temperature in degrees of Celsius, including the unit °C.
20. The thermally shrinkable plastic film of any of the claims 1 to 19, wherein
- the shrinkage of the thermally shrinkable plastic film, after a thermal treatment such that the temperature of the thermally shrinkable plastic film has been T=98 °C, is ε(98 °C), wherein
- the value of ε(98 °C) is less than -0.45 or less than -0.50.
21 . The thermally shrinkable plastic film of any of the claims 1 to 20, the film
- having a third length Lp0 in a second direction before heat treatment and a fourth length LP(T) in the second direction after heat treatment wherein the temperature of the thermally shrinkable plastic film has been T, wherein
- the second direction is perpendicular to the first direction, whereby
- the thermally shrinkable plastic film has another temperature dependent shrinkage sp(T)=[Lp(T)-Lpo]/Lp0, wherein
- the absolute value of ερ(Τ) is less than 0.07 for temperatures 0 °C < T < 100 °C; preferably the absolute value of ερ(Τ) is less than 0.05 or less than 0.03 for temperatures 0 °C < T < 100 °C
22. The thermally shrinkable plastic film of any of the claims 1 to 21 , wherein the thermally shrinkable plastic film
- is monoaxially oriented, either in the machine direction (MD) or in the transverse direction (TD),
and
- is arranged to impose a residual shrink force to an object, when the shrinkable plastic film is first fixed to the object and a second object such that the length of the plastic film correspond to the distance between the object and the second object at a first temperature that is less than 40 °C, thereafter heated to a temperature T, thereafter further cooled or let to cool back to the first temperature, such that
- the residual shrink force is from 1 N/15 mm to 10 N/15 mm; preferably from 2 N/15 mm to 6 N/15 mm.
23. The thermally shrinkable plastic film of any of the claims 1 to 22 comprising
- a core layer and
- a skin layer, such that - the skin layer is located within a distance from the core layer in the dimension of the surface normal of the thermally shrinkable plastic film, and
- the material of the core layer is different from the material of the skin layer.
24. The thermally shrinkable plastic film of the claim 23 wherein
- the core layer comprises at least one terpolymer.
25. The thermally shrinkable plastic film of the claim 24 wherein
- the core layer comprises at least one of the following propylenes:
o 1 -butene/propylene/ethylene,
o propylene/ethylene/1 -hexene, and
o propylene/ethylene/1 -butene.
26. The thermally shrinkable plastic film of the claim 24 or 25 wherein
- the total amount of terpolymer or terpolymers is be between 20 wt.% and 95 wt.%, preferably between 40 wt.% and 90 wt.%, more preferably between 50 wt.% and 80 wt.%.
27. The thermally shrinkable plastic film of any of the claims 24 to 26, wherein
- the core layer further comprises polyolefin plastomer and/or polyolefin elastomer, such as at least one of the following: propylene/ethylene plastomer, ethylene/octene elastomer and ethylene/butene elastomer.
28. The thermally shrinkable plastic film of any of the claims 23 to 27 wherein
- the skin layer comprises first cyclic olefin copolymer.
29. The thermally shrinkable plastic film of claim 28 wherein
- the skin layer comprises further comprises second cyclic olefin copolymer, wherein
- the first cyclic olefin copolymer is different from the second cyclic olefin copolymer.
30. The thermally shrinkable plastic film of claim 29 wherein
- the first cyclic olefin copolymer has a first glass transition temperature and - the second cyclic olefin copolymer has a second glass transition temperature, such that
- the second glass transition temperature is different from the first glass transition temperature, optionally the second glass transition temperature is greater than the first glass transition temperature by at least 5 °C or at least 10 °C .
31 . The thermally shrinkable plastic film of claim 30 wherein
- the first glass transition temperature is below 70 °C, such as below 67 °C , such as 65 °C and
- the second glass transition temperature is above 70 °C, such as above 75 °C, such as 78 °C.
32. The thermally shrinkable plastic film of any of the claims 23 to 31 wherein - the skin layer comprises or further comprises linear low density polyethylene (LLDPE); such as at least one of Ziegler-Natta catalyst based LLDPE and metallocene LLDPE (m-LLDPE)..
33. The thermally shrinkable plastic film of any of the claims 23 to 32 wherein - the skin layer comprises or further comprises at least one additive selected from the group comprising inorganic fillers, pigments, antioxidants, ultraviolet absorbers, anti-blocking agents, slip additives, antistatic additives, cavitating agents.
34. The thermally shrinkable plastic film of claim 33 wherein
- the amount of each additive is less than 5 wt.%; however the total amount of different additives may be higher.
35. The thermally shrinkable plastic film of claim 34 wherein
- the total amount of different additives is less than 5 wt.%.
36. The thermally shrinkable plastic film of any of the claims 23 to 35, further comprising
- a second skin layer, such that
- the core layer is arranged in between the skin layer and the second skin layer.
37. The thernnally shrinkable plastic film of claim 36, wherein
- the second skin layer is made of the same material or materials as the skin layer.
38. The thermally shrinkable plastic film of claim 36 or 37, wherein
- the second skin layer has the same thickness as the skin layer.
39. The thermally shrinkable plastic film of any of the claims 36 to 38, wherein
- the thermally shrinkable plastic film is planar symmetric, wherein the plane of symmetry is the central plane of the core layer in the direction of the surface normal of the thermally shrinkable plastic film.
40. The thermally shrinkable plastic film of any of the claims 1 to 39, characterized by having density of less than 1000 kg/m3, preferably less than
970 kg/m3, such as less than 920 kg/m3 at the temperature 80 °C.
41 . The thermally shrinkable plastic film of any of the claims 1 to 40, characterized by having density of more than 700 kg/m3, preferably more than 800 kg/m3, such as more than 870 kg/m3 at the temperature 80 °C.
42. The thermally shrinkable plastic film of any of the claims 1 to 41 , comprising a printable face, optionally arranged on a face of a skin layer.
43. The thermally shrinkable plastic film of claim 42, wherein the printable face has a surface tension from 36 mN/m to 46 mN/m, preferably from 38 mN/m to 44 mN/m, as measured according to the standard ISO 8296.
44. The thermally shrinkable plastic film of any of the claims 1 to 43, having - the thickness from 20 μηη to 70 μητι, preferably from 25 μηη to 60 μηη.
45. An item comprising
- a body, and
- a loop of a plastic film, which loop encircles a part of the body, wherein - the plastic film has been made by thermally treating the thermally shrinkable plastic film of any of the claims 1 to 44.
46. The item of claim 45, wherein
- an area is left in between the loop of the plastic film and the body, wherein
- at most 10 % of the area is covered by adhesive.
47. The item of claim 46, wherein
- some adhesive is arranged between the loop of the plastic film and the body.
48. The item of claim 47, wherein
- the loop comprises a seam, and
- some adhesive is arranged between the loop of the plastic film and the body, radially at the same location as the seam.
49. The item of claim 46, wherein
- the area that is left in between the loop of the plastic film and the body is free from adhesive.
50. The item of any of the claims 45 to 49, wherein
- the part of the body that is encircled by the loop has a cross sectional area of at least 4 (cm)2; preferably at least 8 (cm)2 or at least 12 (cm)2
51 . The item of any of the claims 45 to 50, wherein
- the part of the body that is encircled by the loop has a cross sectional area of at most 1000 (cm)2, such as at most 660 (cm)2 or at most 330 (cm)2.
52. The item of any of the claims 45 to 51 , wherein
- the part of the body that is encircled by the loop has, at a first location, a first cross sectional area Ai,
- the part of the body that is encircled by the loop has, at a second location, a second cross sectional area A2, and
- the first cross sectional area Ai is different from the second cross sectional area A2.
53. The item of the claim 52, wherein
- the ratio of the second cross sectional area to the first cross sectional area, A2/Ai, is at least 1 .5, at least 2 or at least 4.
54. The item of any of the claims 45 to 53, wherein
- the thickness of the plastic film forming the loop is from 20 μηη to 300 μητι, preferably from 25 μηη to 200 μηη.
55. The item of any of the claims 45 to 54 wherein
- the body comprises polyethylene terephthalate (PET).
56. The item of any of the claims 45 to 55, wherein
- the density of the body is at least 1 100 kg/m3, preferably at least 1200 kg/m3 or 1300 kg/m3, at the temperature 80 °C.
57. The item of any of the claims 45 to 57, wherein
- the body forms a container.
58. The item of any of the claims 57, wherein
- the body has the shape of a bottle.
59. The item of any of the claims 45 to 58, wherein
- the body has a first density pi ,
- the plastic film forming the loop has a second density p2, and
- the second density p2 is less than 1000 kg/m3; preferably less than 950 kg/m3 at the temperature 80 °C.
60. The item of the claim 59, wherein
- the first density pi is more than 1000 kg/m3; preferably more than 1 100 kg/m3 at the temperature 80 °C.
61 . The item of any of the claims 45 to 60, wherein
- the body has a first density pi ,
- the plastic film forming the loop has a second density p2, and
- the ratio of the second density to the first density, p2/pi , at most 0.9, preferably at most 0.8 or at most 0.7 at a temperature, such as at the temperature 80 °C.
62. The item of any of the claim 61 , wherein
- the first density pi is more than 1000 kg/m3 at the temperature 80 °C and
- the second density p2 is less than 950 kg/m3 at the temperature 80 °C.
PCT/FI2013/050758 2013-07-12 2013-07-12 A thermally shrinkable plastic film and an item comprising the same WO2015004313A1 (en)

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WO2016102781A1 (en) * 2014-12-23 2016-06-30 Upm Raflatac Oy A shrinkable label film, a shrinkable label and a method for providing a shrinkable film and a label
WO2019101480A3 (en) * 2017-11-27 2019-07-18 Sleever International Company Portable shrink device and associated method
US10858504B2 (en) 2017-07-06 2020-12-08 Exxonmobil Chemical Patents Inc. Polyethylene compositions comprising cyclic-olefin copolymers
US11141961B2 (en) 2017-05-19 2021-10-12 Exxonmobil Chemical Patents Inc. Shrink films comprising a cyclic-olefin copolymer core
US11441023B2 (en) 2018-04-27 2022-09-13 Exxonmobil Chemical Patents Inc. Polyethylene films and methods of making the same

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WO2016102781A1 (en) * 2014-12-23 2016-06-30 Upm Raflatac Oy A shrinkable label film, a shrinkable label and a method for providing a shrinkable film and a label
US10703078B2 (en) 2014-12-23 2020-07-07 Upm Raflatac Oy Shrinkable label film, a shrinkable label and a method for providing a shrinkable film and a label
US10981363B2 (en) 2014-12-23 2021-04-20 Upm Raflatac Oy Shrinkable label film, a shrinkable label and a method for providing a shrinkable film and a label
US11141961B2 (en) 2017-05-19 2021-10-12 Exxonmobil Chemical Patents Inc. Shrink films comprising a cyclic-olefin copolymer core
US10858504B2 (en) 2017-07-06 2020-12-08 Exxonmobil Chemical Patents Inc. Polyethylene compositions comprising cyclic-olefin copolymers
WO2019101480A3 (en) * 2017-11-27 2019-07-18 Sleever International Company Portable shrink device and associated method
US11441023B2 (en) 2018-04-27 2022-09-13 Exxonmobil Chemical Patents Inc. Polyethylene films and methods of making the same

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