WO2016192901A1

WO2016192901A1 - Multi-layer shrink film, label and container

Info

Publication number: WO2016192901A1
Application number: PCT/EP2016/059226
Authority: WO
Inventors: Nao Yoshida; Christopher Holmes
Original assignee: Fuji Seal International, Inc.
Priority date: 2015-06-02
Filing date: 2016-04-26
Publication date: 2016-12-08
Also published as: GB201509558D0; GB2539186B; GB2539186A

Abstract

A multi-layer shrink film (10) including a skin layer (13) and a core layer (11) is disclosed. The skin layer comprises at least 50% by weight of a cyclic olefin copolymer and the core layer comprises from 5% by weight to 50% by weight of a propylene based elastomer, from 20% by weight to 50% by weight of a propylene based plastomer, from 1% by weight to 20% by weight of a hydrocarbon resin and from 5% by weight to 30% by weight of a cyclic olefin copolymer. The multi-layer shrink film (10) exhibits a density of below 0.96 g/cm³and has excellent shrinkage and stiffness.

Description

MULTI-LAYER SHRINK FILM, LABEL AND CONTAINER

FIELD OF THE INVENTION

The present invention relates to a multi-layer shrink film including at least one skin layer and a core layer.

The present invention further relates to a shrink sleeve comprising such a multi-layer shrink film.

The present invention yet further relates to a container comprising such a multi-layer shrink film or shrink sleeve.

BACKGROUND OF THE INVENTION

The packaging and presentation of goods is recognised by product manufacturers to play an extremely important role in selling goods to consumers. One method of packaging which is becoming increasingly popular is to package a product in a plain, non-decorated container, to place a shrinkable label such as a heat-shrinkable label around the container, and then to shrink the sleeve so that it becomes tightly wrapped around the container. This technology is dependent on the properties of the shrinkable sleeve, which is generally made out of a decorated shrinkable film.

This technology is appealing to product manufacturers because it can give an attractive finish to the packaging of a product at low cost. This attractive appearance is complimented by an added lustre derived from a potential full 360° decoration of the packaging. In addition, because these labels are shrunk in a controlled manner around a container, they are extremely versatile and may be easily fitted onto attractive, ergonomically-shaped packaging.

Multi-layer shrink films are often used because the presence of multiple layers, e.g. one or more skin layers contacting a skin layer, to gain benefit from the advantageous properties of more than one material. By careful selection of the materials for each layer, it is possible for the disadvantageous properties of one material to be compensated for and their effect marginalized by the advantageous properties of the materials in the other layers. Another reason for the increasing popularity of this type of labelling is its ability to aid recycling. The label may be fitted around a container made out of recyclable material, such as plastic like polyethylene terephthalate (PET), which for instance may be reclaimed in the form of flakes and pellets. To this end, collected PET containers are ground into pieces of from a few to ten millimeters square, and then the ground pieces of the labels and caps having a specific gravity of lower than 1 g/cm³ are removed with a gravity separator. The gravity separator is a device such that the ground pieces are placed in water and those floating on water, e.g. the label, and those sinking in water having a specific gravity of 1 g/cm³ or higher, e.g. the PET flakes and pellets are separated. Gravity separators are popular as they can produce a much higher throughput compared to alternative separation techniques, e.g. air separators.

The provision of multi-layer shrink films having a density below 1 g/cm³ to facilitate gravity separator-based recycling and having desirable film properties such as sufficient shrinkability and strength, as well as high transparency (low haze) is far from trivial. For example, polystyrene labels and polyester labels are desirable because of their favourable shrinkage and glossiness characteristics. However, the specific gravity of polystyrene labels and polyester labels is higher than 1 g/cm³, such that these labels cannot be separated from the ground PET using a gravity separator. On the other hand, polyolefin labels, while having a specific gravity of lower than 1 g/cm³, have inferior shrinkage and glossiness characteristics. The density of the multi-layer shrink film should be well below 1 g/cm³, e.g. 0.97 g/cm³ or less, such that impregnating the multi-layer shrink film with decoration, e.g. inks or the like, does not increase the density of the decorated multi-layer shrink film to 1 g/cm³ or above, as this would preclude harvesting the multi-layer shrink film with a gravity separator during recycling.

EP 1 632 343 B1 addresses this problem by providing a multi-layered heat-shrinkable film composed of at least three layers including front and back film layers each composed of a resin composition having cyclic olefin-based resin of from 55 to 95 mass % and linear low-density polyethylene of from 45 to 5 mass % and an intermediate film layer composed of a resin composition having propylene-a-olefin random copolymer of from 95 to 55 mass % and cyclic olefin- based resin of from 5 to 45 mass %. When immersed in water of 90° C for 10 seconds, the multi-layered heat-shrinkable film exhibits a heat shrinkage in a lateral direction of 50 % or higher. However, such polyolefin-based heat- shrinkable films may suffer from unsatisfactory stiffness and insufficient shrinkage.

SUMMARY OF THE INVENTION

The present invention seeks to provide a low-density multi-layer shrink film with improved properties.

The present invention further seeks to provide a shrink sleeve comprising such a multi-layer shrink film.

The present invention yet further seeks to provide a container comprising such a multi-layer shrink film or shrink sleeve.

It has been found that combining a polypropylene based elastomer, a polypropylene based plastomer, a hydrocarbon resin and a cyclic olefin copolymer in the appropriate weight ratios in the core layer of a multi-layer shrink film, a multi-layer shrink film can be provided that exhibits excellent stiffness at densities well below 1 g/cm³, i.e. below 0.945 g/cm³. Moreover, such films routinely exhibit shrinkage in excess of 60%.

Accordingly, there is provided a multi-layer shrink film including a skin layer and a core layer, wherein the skin layer comprises at least 50% by weight of a cyclic olefin copolymer and the core layer comprises from 5% by weight to 50% by weight of a propylene based elastomer; from 20% by weight to 50% by weight of a propylene based plastomer; from 1 % by weight to 20% by weight of a hydrocarbon resin; and from 5% by weight to 30% by weight of a cyclic olefin copolymer.

The core layer may comprise from 10% by weight to 40% by weight of a propylene based elastomer; from 25% by weight to 45% by weight of a propylene based plastomer; from 5% by weight to 18% by weight of a hydrocarbon resin; and from 5% by weight to 25% by weight of a cyclic olefin copolymer.

The multi-layer shrink film preferably further comprises a further skin layer, wherein the core layer is sandwiched between the skin layer and the further skin layer.

The core layer may further comprise up to 5% by weight of a linear low- density polyethylene.

The hydrocarbon resin may be selected from rosin resins or derivates thereof, resin acid dimers, terpene resins, petroleum resins or combinations thereof.

The hydrocarbon resin preferably consists of one or more petroleum resins.

The hydrocarbon resin may have a softening point in the range of from 100°C to 150°C, preferably from 120°C to 145°C when measured in accordance with the ISO 4625 standard.

Each skin layer may comprise from 70% by weight to 100% by weight of the cyclic olefin copolymer and further comprises up to 30% by weight of a linear low density polyethylene.

The thickness of the skin layers present in the multi-layer shrink film may be such that the overall volume of the skin layers present corresponds to 15-35% of the total volume of multi-layer shrink film and the core layer has a thickness such that the volume of the core layer corresponds to 65-85% of the total volume of multi-layer shrink film. That is, in case of a single skin layer, the overall volume of the single skin layer corresponds to 15-35% of the total volume of multi-layer shrink film, whereas in case of a pair of skin layers the combined overall volume of the skin layers corresponds to 15-35% of the total volume of multi-layer shrink film.

The layers of the multi-layer shrink film may be mainly monoaxially oriented in the transverse direction. The multi-layer shrink film may exhibit shrinkage in excess of 60% in a main orientation direction of the multi-layer shrink film when immersed in water of 90°C for 10 seconds without applying a load.

The multi-layer shrink film may have a haze of less than 10% when measured in accordance with the ISO 14782 standard.

The multi-layer shrink film may have a density of less than 0.945 g/cm³ when measured in accordance with the ISO 1 183-A standard.

The multi-layer shrink film may be shrunk by applying any suitable stimulus, e.g. by the application of heat. The multi-layer shrink film may be a multi-layer heat shrink film.

According to another aspect, there is provided a shrink sleeve comprising the multi-layer shrink film of any of the above embodiments. Such a shrink sleeve exhibits excellent shrink properties, which makes the sleeve particularly suitable as a sleeve for containers, e.g. food or beverage containers.

According to yet another aspect, there is provided a container comprising the multi-layer shrink film or the shrink sleeve of any of the above embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail and by way of non-limiting examples with reference to the accompanying drawings, wherein:

FIG. 1 schematically depicts a multi-layer shrink film according to an embodiment;

FIG. 2 schematically depicts a multi-layer shrink film according to another embodiment;

FIG. 3 schematically depicts a container carrying a multi-layer shrink film according to an embodiment; and

FIG. 4 schematically depicts another container carrying a multi-layer shrink film according to an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

In the present application, unless specifically specified otherwise, the term 'polymer' can refer to homopolymers, copolymers, block copolymers, graft copolymers, random copolymers, interpolymers, terpolymers, and so on.

The propylene based elastomers (PBEs) as used in the present application may be produced by different types of single site catalysts such as bridged metallocenes (see WO 199907788), pyridine amines (see WO03/040201 ) and unbridged metallocenes (see US5969070), preferably in a solution process. The propylene based elastomers may incorporate one or more units derived from a co-monomer of a C-2 or C₄-C-2o alpha-olefin and optionally diene-derived units. Such propylene-alpha-olefin elastomers can comprise between 6 to 25 wt.% alpha-olefin and more preferably more than 7 wt.% alpha- olefin. Polypropylene-based elastomers comprising from 8 to 12 wt% ethylene are particularly suitable. The propylene-based elastomers preferably have a density of 0.80 - 0.90 g/cm³, more preferably of 0.85 - 0.89 g/cm³ determined according to ISO 1 183 in order to ensure that the multi-layer shrink film has sufficiently low density. The propylene-based elastomers preferably have a melt flow rate (as per ISO 1 133) at 230°C and a load of 2.13 kg of 0.1 - 10 grams per 10 minutes and more preferably of 1 -5 grams per 10 minutes for controlling the melting behaviour of the multi-layer shrink film. The propylene-based elastomers preferably have a flexural modulus in the range of 10-200 MPa. Propylene-based elastomers that may be useful in accordance with this application are commercially available from ExxonMobil Chemical Company under the trade name of Vistamaxx™.

The propylene based plastomers (PBPs) as used in the present application have a density between 0.88 g/cm³ to 0.93 g/cm³, more preferably between 0.90 g/cm³ to 0.92 g/cm³ determined according to ISO 1 183. The propylene based plastomers are not particularly limited, as long as being a polymer containing propylene as a constitutional monomer, and can be either a propylene homopolymer or a copolymer containing a copolymerization component such as an a-olefin (propylene-a-olefin copolymer). Preferably, for such polypropylene based plastomers, preferred are polypropylenes prepared through polymerization in the presence of a metallocene catalyst (metallocene- catalyzed polypropylenes) and propylene-a-olefin random copolymers. Each of different polypropylene based plastomers can be used alone or in combination.

Exemplary a-olefins for use as copolymerization components in the propylene-a-olefin copolymers include ethylene; and a-olefins having about 4 to about 20 carbon atoms, such as 1 -butene, 1 -pentene, 4-methyl-1 -pentene, 1 - hexene, 1 -heptene, 1 -octene, 1 -nonene, and 1 -decene. Each of different copolymerization components can be used alone or in combination. Among such propylene-a-olefin copolymers, ethylene-propylene random copolymers using ethylene as a copolymerization component are especially preferred. In the ethylene-propylene random copolymers, the ratio (by weight) of ethylene to propylene can be selected within the range of from about 2:98 to about 5:95, and preferably from about 3:97 to about 4.5:95.5.

Preferably, the ethylene-propylene random copolymers are copolymers copolymerized in the presence of a metallocene catalyst, for allowing the shrink film to have further excellent shrinkability at low temperatures of about 60°C to about 80°C and to have further higher fittability to a container upon (thermal) shrinkage. Those having isotactic indices of 90% or more are preferred for further excellent shrinkability at low temperatures and further satisfactory toughness of the film. The metallocene catalyst can be a known or common metallocene catalyst adopted to polymerization of olefins. A process for the copolymerization is not limited and can be selected, for example, from known polymerization processes such as slurry polymerization, solution polymerization, and vapour phase polymerization.

The weight-average molecular weight of the propylene based plastomers is preferably 100,000 to 500,000, and more preferably 200,000 to 400,000, for controlling the melting behaviour within a preferred range. The melting point of the propylene based plastomers is preferably 100°C to 150°C, and more preferably 120°C to 140°C.

The melt flow rate (MFR) as per ISO 1 133 at a temperature of 230°C under a load of 2.16 kg of the propylene based plastomers is preferably 0.1 to 10 grams per 10 minutes, and more preferably 1 to 5 grams per 10 minutes, for controlling the melting behaviour. Such plastomers are for instance commercialized by LyondellBasell Polymers under the trade name Clyrell™, by Total under the trade name PPR™ and by the Japan Polychem Corporation under the trade name Wintec™.

The hydrocarbon (HC) resins as used in the present application may be used to modify the properties of polyolefin polymers, e.g. to tackify or plasticize such polymers. The hydrocarbon resin may refer to a petroleum resin such as an aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, alicyclic hydrocarbon resin and hydrogenated products thereof, as well as to rosin resins, resin acid dimers and terpene resins and/or derivates thereof, or to combinations of such resins. Petroleum resins are particularly preferred. The hydrocarbon resins may have a softening point in the range of from 100°C to 150°C, preferably from 120°C to 145°C when measured in accordance with the ISO 4625 standard. The hydrocarbon resins may have a number average molecular weight (M_n) in the range of from 500 to 10,000 as determined by the GPC method. The hydrocarbon resins may have a density in the range of from 0.95 to 1.00 g/cm³. Suitable hydrocarbon resins are for instance commercialized by Arakawa Europe under the trade name Arkon™, by the Eastman Chemical Company under the trade name Plastolyn™, by Yasuhara Chemical Co. Ltd. under the trade name Clearon™ and by Idemitsu Kosan co. Ltd. under the trade name l-MARV™.

The cyclic olefin copolymers (COCs) used in the present application may be:

a) random copolymers of ethylene or propylene and a cyclic olefin, such as, norbornene and/or its derivatives and tetracyclododecene and/or its derivatives; b) ring-opened polymers of the cyclic olefin, copolymers of the cyclic olefin and a-olefin;

c) hydrogenated copolymers of the copolymers in b); or

d) graft modifications of a) to c) modified with unsaturated carboxylic acid. The glass transition temperature of the COC used according to the present application is usually from 60°C to 120°C, more preferably from 70°C to 80°C to achieve low natural shrinkage. COC with lower glass transition temperature, for example with a glass transition temperature as low as 50°C, may be used for films which shrink at very low temperature but those films could have higher natural shrinkage and could require transportation and/or storage under controlled conditions. The density of the COC according to ISO 1 183 is preferably in the range of from 1.00 to 1.06 g/cm³, more preferably from 1.00 to 1.03 g/cm³. The number average molecular weight (M_n) measured by GPC is typically from 1 ,000 to 1 ,000,000. Commercially available suitable COCs for instance include Topas™ products available from Topas Advanced Polymers.

The linear low-density polyethylene (LLDPE) as used in the present application may be a Ziegler-Natta catalyst-based LLDPE, which is formed by polymerization using Ziegler-Natta catalyst. Preferably, metallocene catalyst- based LLDPE, which is formed by polymerization using metallocene catalyst is used, as this improves transparency without having to add petroleum resin as is the case for Ziegler-Natta catalyst-based LLDPE, and eliminates the occurrence of blocking caused by addition of petroleum resin. Metallocene catalyst-based LLDPE further shows a significantly small increase in its viscosity when heated compared with Ziegler-Natta catalyst-based LLDPE. The term Ziegler-Natta catalyst is intended to mean the catalysts described by Komatsu et al. on pages 14 to 22 of "New Polymer Made Using Metallocene Catalyst," Kogyo Chosakai Publishing Inc., 1999. The term metallocene catalyst is intended to mean the catalysts described on pages 22 to 36 of this book. The low-density polyethylene as used in the present specification preferably has a density of from 0.910 to 0.935 g/cm³. Commercially available suitable LLDPEs are for instance available from the ExxonMobil Chemical Company under the trade name Exceed™ and Enable™.

According to at least some embodiments, a multi-layer shrink film 10 as schematically shown in FIG. 1 is provided that comprises a core layer 1 1 having its major surface covered by a skin layer 13. The skin layer 13 typically is exposed when the film 10 is applied to a container such as a PET bottle, with the core layer 1 1 located in between the skin layer 13 and the container.

The core layer 1 1 contains from 5% by weight to 50% by weight of a propylene based elastomer, from 20% by weight to 50% by weight of a propylene based plastomer, from 1 % by weight to 20% by weight of a hydrocarbon resin; and from 5% by weight to 30% by weight of a cyclic olefin copolymer based on the total weight of the core layer. In an embodiment, the sum of the weight fractions of the propylene based elastomer, the propylene based plastomer, the hydrocarbon resin and the cyclic olefin copolymer fractions is at least 80% of the total weight of the core layer, preferably at least 90% and more preferably at least 95% of the total weight of the core layer. If the formulation of the core layer 1 1 is in the above range, recycled material can be used in the core layer in order to achieve the desired properties of the core layer.

As used herein, the term "recycled material" refers to a recycling material including non-product portions such as films residues upstream and downstream from product films, and film edges; and film scraps and polymer scraps, such as residual portions of intermediate products from which product films have been cut, and substandard articles. It should be noted, however, that the recycled material should be formed in the production of a multi-layer shrink film according to the present invention.

It has been found that the addition of at least 1 wt% of a hydrocarbon resin to the polyolefin-based core layer 1 1 improves the shrinkage characteristics of the core layer. If the fraction of the hydrocarbon resin in the core layer 1 1 exceeds 20 wt%, it becomes difficult to produce a core layer 1 1 having even thickness. If the fraction of the hydrocarbon resin in the core layer 1 1 is below 1 wt%, the core layer 1 1 may exhibit insufficient shrinkage. The hydrocarbon resin preferably has a softening point in the range of from 100°C to 150°C, more preferably from 120°C to 145°C when measured in accordance with the ISO 4625 standard. If the hydrocarbon resin has a softening point below this temperature range, the core layer 1 1 may become thermally unstable, whereas if the hydrocarbon resin has a softening point above this temperature range, the core layer 1 1 may become too unresponsive at typical processing temperatures.

The addition of the cyclic olefin copolymer to the core layer 1 1 further improves the shrinkage characteristics of the core layer. However, where the fraction of the cyclic olefin copolymer in the core layer 1 1 exceeds 30 wt%, the density the core layer 1 1 may become too high. Furthermore, the haze of the core layer 1 1 may become too high, which is detrimental if the multi-layer shrink film 10 desirably is transparent.

Similarly, the propylene based elastomer is added to the core layer 1 1 to lower the density of the core layer and improve its shrinkage. If the fraction of the propylene based elastomer is below 5 wt%, the density of the core layer 1 1 may become too high and the shrinkage may become too low. On the other hand, if the fraction of the propylene based elastomer is above 50 wt%, the core layer 1 1 may exhibit insufficient stiffness.

Similarly, the propylene based plastomer is added to the core layer 1 1 to improve the stiffness of the core layer 1 1 whilst maintaining a low density. If the fraction of the propylene based plastomer is below 20 wt%, the core layer 1 1 may have insufficient stiffness. On the other hand, if the fraction of the propylene based plastomer is above 50 wt%, the core layer 1 1 may exhibit insufficient shrinkage.

In a particularly advantageous embodiment, the core layer 1 1 contains from 10% by weight to 40% by weight of a propylene based elastomer.

In a particularly advantageous embodiment, the core layer 1 1 contains from 25% by weight to 45% by weight of a propylene based plastomer

In a particularly advantageous embodiment, the core layer 1 1 contains from 5% by weight to 18% by weight of a hydrocarbon resin. In a particularly advantageous embodiment, the core layer 1 1 contains from 5% by weight to 25% by weight of a cyclic olefin copolymer.

The above particularly advantageous embodiments may be combined into a single embodiment or one or more of the above particularly advantageous embodiments may be combined instead.

In an embodiment, the core layer 1 1 may further include up to 5% by weight of a linear low-density polyethylene in order to lower the density of the core layer 1 1 whilst maintaining shrinkage characteristics. Above 5% by weight, the core layer 1 1 may exhibit excessive natural shrinkage and be too soft.

The core layer 1 1 may further contain other additives such as inorganic fillers, pigments, antioxidants, acid scavengers, ultraviolet absorbers, processing aids such as zinc stearate, extrusion aids, slip additives, permeability modifiers, antistatic additives, cavitating agents such as calcium carbonate and β- nucleating agents. Such additives are typically present in small amounts, e.g. less than 5 wt% or even less than 3 wt% based on the total weight of the core layer 1 1.

The skin layer 13 contains at least 50% by weight of a cyclic olefin copolymer and preferably contains from 70% by weight to 100% by weight of the cyclic olefin copolymer and further comprises up to 30% by weight of a linear low density polyethylene based on the total weight of the skin layer. The addition of the LLDPE to the skin layer 13 reduces the density of the skin layer and improves its transparency. Furthermore, a metallocene catalyst-based LLDPE effectively prevents whitening of the skin layer 13 by fingerprints. However, if more than 30 wt% LLDPE is added to the skin layer 13, the stiffness of the skin layer 13 may deteriorate.

The skin layer 13 may further comprise other additives such as pigment, antioxidants, acid scavengers, ultraviolet absorbers, processing aids such as zinc stearate, extrusion aids, antiblock, slip additives or antistatic additives. Such additives are typically present in small amounts, e.g. less than 10 wt% or even less than 5 wt% based on the total weight of the first skin layer 13. In a preferred embodiment schematically depicted in FIG. 2 of the multilayer shrink film 10, the core layer 1 1 sandwiched between the first skin layer 13 and a second skin layer 15. The second skin layer 15 contains at least 50% by weight of a cyclic olefin copolymer and preferably contains from 70% by weight to 100% by weight of the cyclic olefin copolymer and further comprises up to 30% by weight of a linear low density polyethylene based on the total weight of the skin layer. In an embodiment, the first skin layer 13 and the second skin layer 15 have the same composition although it should be understood that the first skin layer 13 and the second skin layer 15 may have different compositions.

The second skin layer 15 may further comprise other additives such as pigment, antioxidants, acid scavengers, ultraviolet absorbers, processing aids such as zinc stearate, extrusion aids, antiblock, slip additives or antistatic additives. Such additives are typically present in small amounts, e.g. less than 10 wt% or even less than 5 wt% based on the total weight of the second skin layer 15.

The multi-layer shrink film 10 according to embodiments of the present invention exhibits shrinkage in excess of 60% in a main orientation direction of the multi-layer shrink film when immersed in water of 90°C for 10 seconds without applying a load. The multi-layer shrink film 10 according to preferred embodiments of the present invention further exhibits shrinkage in a direction orthogonal to the main orientation of 1 % to 10%.

The multi-layer shrink film 10 according to embodiments of the present invention exhibits a haze of less than 10% when measured in accordance with the ISO 14782 standard. Such a transparent film is preferable as this facilitates printing on an inner layer of the film such that the print is protected by the multilayer shrink film, e.g. on a layer facing a container on which the multi-layer shrink film is placed.

The multi-layer shrink film 10 according to embodiments of the present invention exhibits a density of less than 0.945 g/cm³ when measured in accordance with the ISO 1 183-A standard. In order to obtain the desired density, the core layer 1 1 may have a thickness such that the volume of the core layer corresponds to 65-85% of the total volume of multi-layer shrink film, with the remainder of the volume formed by the one or more skin layers (and optional tie layers between the skin layers and the core layers to improve inter-layer adhesion, e.g. a-olefin polymer tie layers although it is preferable that the skin layer(s) contact the core layer directly), e.g. the first skin layer 13 and the optional skin layer 15. In other words, the first skin layer 13 and if present the second skin layer 15 have respective thicknesses such that the overall volume of the skin layers present in the multi-layer shrink film 10 corresponds to 15-35% of the total volume of multi-layer shrink film.

The films of the present disclosure can be produced by any known method. The films may be obtained by extrusion or co-extrusion through cast die or annular die. The core layer 1 1 , first skin layer 13 and optional second skin layer 15 preferably are mainly monoaxially oriented in the transverse direction but it should be understood that these layers alternatively may be oriented in the machine direction or in both the machine and transverse directions.

For example, the multi-layer shrink film 10 according to FIG. 2 may be manufactured as per the general manufacturing example below to obtain a multilayer shrink film 10 that is mainly monoaxially oriented in the transverse direction.

The multi-layer shrink film 10 disclosed in this application may be shrunk using any suitable stimulus. A particularly suitable stimulus is heat, such that the multi-layer shrink film 10 is a multi-layer heat shrink film although other stimuli may also be contemplated.

The multi-layer shrink film 10 according to embodiments of the present invention are useful in many shrink film applications for packaging containers including without limitations, batteries, aluminium can containers, aerosol cans, plastic liquid beverage containers such as PET bottles, glass containers and irregular shaped containers. FIG. 3 schematically depicts an example embodiment of a container 1 having a body in between a bottom and a neck with a lid on the neck, in which substantially the entire outer surface of the body of the container 1 is covered by the multi-layer shrink film 10 according to an embodiment, whereas FIG. 4 schematically depicts an example embodiment of a container 1 in which the multi-layer shrink film 10 according to an embodiment covers part of the outer surface of the body of the container 1 , e.g. forms a label or band around the container 1. In FIG. 3, the multi-layer shrink film 10 defines the overall appearance of the container 1 whereas in FIG. 4 the multi-layer shrink film 10 is more clearly recognizable as a separate entity on the container 1 , e.g. recognizable as a sleeve label.

Embodiments of the multi-layer shrink film 10 may be converted into a sleeve label by subjecting the shrink film to printing by a suitable method such as gravure or offset printing on the film surface subjected to corona discharge treatment, e.g. on the first skin layer 13 and/or on the second skin layer 15. To obtain a tubular label from the printed planar multi-layer shrink film thus prepared, seaming may be carried out with the use of an organic solvent as described from example in EP 1 632 343 and cut into appropriate lengths thereby obtaining labels as sleeve form. The organic solvent is not particularly limited insofar as it dissolves or swells the front back film layers of the film. Organic solvents comprising tetrahydrofuran (THF), cyclohexane or methyl ethyl ketone (MEK) are preferred and more preferably blends of these solvents. Multi-layer shrink films 10 and labels formed therefrom may optionally include perforations through the film or label. Perforations are most desirably carried out immediately before sealing the film or label.

The present invention will now be explained in more detail with the aid of the following examples. It should be understood that these examples serve as an illustration of embodiments of the present invention only and should not be in any way construed as limiting the present invention.

In the following examples, multi-layer shrink films according to FIG. 2, i.e. having a core layer 1 1 sandwiched in between a first skin layer 13 and a second skin layer 15 were produced. The first skin layer 13 and the second skin layer 15 have the same composition in these examples by way of non-limiting example only. General manufacturing example

The resin compositions for skin and core layers were placed in a main extruder heated at 210°C and a sub-extruder heated at 190°C respectively, followed by melting and extrusion using the two extruders. The resins were merged with a feed block merging system such that the resin extruded from the main extruder constitutes a core layer 1 1 and the resin extruded from the sub- extruder forms the first skin layer 13 and the second skin layer 15 on opposite major surfaces of the core layer 1 1 (obviously one of the skin layers may be omitted to form a film comprising a single skin layer 13). The merged resins were extruded through a T-die (1 mm of lip opening), and quenched on a casting drum cooled to 25° C to give a three-layer unstretched shrink film 10. Next, the unstretched film was stretched by a factor 1.02 at 85°C in the machine direction and subsequently stretched by a factor 5.5 at 76°C in the transverse direction after preheating to give a multi-layer shrink film 10 that is shrinkable mainly in a uniaxial direction. The shrink film was adjusted to have a total thickness of 50 μηη by controlling the film-forming speed.

In accordance with the general manufacturing example, multi-layer shrink films according to examples 1 -10 and comparative examples 1 -5 were formed with the following compositions.

The properties of the raw materials used in these examples are given in Tables 1 -4. TABLE 1

MFR Flexural Density

(g/10 min) modulus (g/cm³)

(Mpa)

PBE Vistamaxx 1.4 12.3 0.862

6102FL™

(Exxon Mobil) Vistamaxx 1.1 59.7 0.874

3020FL™

(Exxon Mobil)

MFR determined at 190°C. 2.16 kg as per ISO 1 133 standard

Flexural modulus determined as per ISO 1 178 standard Density determined as per ISO 1 183 standard

TABLE 2

Tensile modulus determined as per ISO 527-2 standard Density determined as per ISO 1 183 standard

TABLE 3

Softening point determined as per ISO 1 183 standard TABLE 4

Tensile modulus determined as per ISO 527-2 standard. Example 1

Skin layer resins: 85 wt% of TOPAS 9506F04™ was used as a COC and 15 wt% of Exceed 3518CB™ was used as a LLDPE.

Core layer resins: 29 wt% of Vistamaxx 6102FL™ was used as a PBE, 37 wt% of Clyrel RC1890™ was used as a PBP, 12 wt% of Arkon P125™ was used as HC resin was used as HC resin, 20 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

The thickness ratio in the unstretched film was adjusted to be (skin layer):(core layer):(skin layer) = 1 :5:1 to yield a layer volume ratio of 14.0%:72.0%:14.0%.

Example 2

Core layer resins: 29 wt% of Vistamaxx 6102FL™ was used as a PBE, 44 wt% of Clyrel RC1890™ was used as a PBP, 15 wt% of Arkon P125™ was used as HC resin, 10 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE. The thickness ratio in the unstretched film was adjusted to be (skin layer):(core layer):(skin layer) = 1 :5:1 to yield a layer volume ratio of 14.0%:72.0%:14.0%. Example 3

Core layer resins: 20 wt% of Vistamaxx 3020FL™ was used as a PBE, 42 wt% of Clyrel RC1890™ was used as a PBP, 14 wt% of Arkon P125™ was used as HC resin, 22 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

The thickness ratio in the unstretched film was adjusted to be (skin layer):(core layer):(skin layer) = 1 :8.5:1 to yield a layer volume ratio of 9.5%:81.0%:9.5%.

Example 4

Core layer resins: 26 wt% of Vistamaxx 3020FL™ was used as a PBE, 38 wt% of Clyrel RC1890™ was used as a PBP, 12 wt% of Arkon P125™ was used as HC resin, 22 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

Example 5

Skin layer resins: 85 wt% of TOPAS 9506F500™ was used as a COC and 15 wt% of Exceed 3518CB™ was used as a LLDPE.

Core layer resins: 26 wt% of Vistamaxx 3020FL™ was used as a PBE, 38 wt% of Clyrel RC1890™ was used as a PBP, 12 wt% of Arkon P125™ was used as HC resin, 22 wt% of TOPAS 9506F500 '^M was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

Example 6

Core layer resins: 26 wt% of Vistamaxx 3020FL™ was used as a PBE, 38 wt% of Wintec WFX6™ was used as a PBP, 12 wt% of Arkon P125™ was used as HC resin, 22 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

Example 7

Core layer resins: 26 wt% of Vistamaxx 3020FL™ was used as a PBE, 38 wt% of Clyrel RC1890™ was used as a PBP, 12 wt% of Plastolyn r1 140™ was used as HC resin, 22 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

Example 8

Skin layer resins: 85 wt% of TOPAS 9506F04™ was used as a COC and

15 wt% of Exceed 3518CB™ was used as a LLDPE. Core layer resins: 16 wt% of Vistamaxx 3020FL '^M was used as a PBE, 24 wt% of Clyrel RC1890™ was used as a PBP, 8 wt% of Arkon P125™ was used as HC resin, 6 wt% of TOPAS 9506F04™ was used as a COC and 46 wt% of an article recycled from itself that has the same composition of the film of Example 4 was added as a regrind.

The thickness ratio in the unstretched film was adjusted to be (skin layer):(core layer):(skin layer) = 1 :8.5:1 to yield a layer volume ratio of 9.5%:81.0%:9.5%. Example 9

Skin layer resin: 100 wt% of TOPAS 9506F04™ was used as a COC. Core layer resins: 26 wt% of Vistamaxx 3020FL™ was used as a PBE, 40 wt% of Clyrel RC1890™ was used as a PBP, 12 wt% of Arkon P125™ was used as HC resin and 22 wt% of TOPAS 9506F04™ was used as a COC.

Example 10

Skin layer resins: 85 wt% of TOPAS 9506F04™ was used as a COC and

15 wt% of Exceed 3518CB™ was used as a LLDPE.

Core layer resins: 38 wt% of Vistamaxx 3020FL™ was used as a PBE, 33 wt% of PPR 3321™ was used as a PBP, 7 wt% of Arkon P125™ was used as HC resin, 20 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

The thickness ratio in the unstretched film was adjusted to be (skin layer):(core layer):(skin layer) = 1 :8.5:1 to yield a layer volume ratio of 9.5%:81.0%:9.5%. Comparative Example 1 (core without PBP) Skin layer resins: 85 wt% of TOPAS 9506F04 '^M was used as a COC and 15 wt% of Exceed 3518CB™ was used as a LLDPE.

Core layer resins: 38 wt% of Vistamaxx 3020FL™ was used as a PBE, 40 wt% of PPR 3321™ was used as a PBP, 20 wt% of TOPAS 9506F04™ was used as a COC and 2 wt% of Exceed 31518 3518CB™ from Exxon Mobil was used as a LLDPE.

Comparative Example 2 (core without HC/COC)

Skin layer resin: 100 wt% of TOPAS 9506F04™ was used as a COC.

Core layer resins: 80 wt% of Vistamaxx 3020FL™ was used as a PBE and

20 wt% of Clyrel RC1890™ was used as a PBP.

The thickness ratio in the unstretched film was adjusted to be (skin layer):(core layer):(skin layer) = 1 :8.5:1 to yield a layer volume ratio of

9.5%:81.0%:9.5%.

Comparative Example 3 (core without PBE)

Skin layer resin: 100 wt% of TOPAS 9506F04™ was used as a COC.

Core layer resins: 72 wt% of Clyrel RC1890™ was used as a PBP, 8 wt% of Arkon P125™ was used as HC resin and 20 wt% of TOPAS 9506F04™ was used as a COC.

Comparative Example 4 (core with excess COC)

Skin layer resin: 100 wt% of TOPAS 9506F04™ was used as a COC. Core layer resins: 25 wt% of Vistamaxx 3020FL '^M was used as a PBE, 25 wt% of Clyrel RC1890™ was used as a PBP, 10 wt% of Arkon P125™ was used as HC resin and 40 wt% of TOPAS 9506F04™ was used as a COC.

Comparative Example 5 (core with excess HC)

Skin layer resin: 100 wt% of TOPAS 9506F04™ was used as a COC. Core layer resins: 25 wt% of Vistamaxx 3020FL™ was used as a PBE, 25 wt% of Clyrel RC1890™ was used as a PBP, 40 wt% of Arkon P125™ was used as HC resin and 10 wt% of TOPAS 9506F04™ was used as a COC.

The multi-layer shrink films obtained in the above examples were subjected to the following tests to determine properties of interest of each multilayer shrink film.

Thermal shrinkage in the main orientation direction of each example multilayer shrink film was determined in warm water of 90°C by immersing the film in the water for 10 seconds without application of a load. Shrinkage was determined along a film having dimensions of 120mm in the main orientation and a width of 5 mm. Each film was marked with lines at 10 mm intervals in the main orientation direction of the film. Thermal shrinkage was calculated as the difference between the standard line interval before and after the heat treatment in accordance with the following equation:

Thermal shrinkage (90°C, 10 seconds) (%) = (L₀ -l_i) / L₀ x 100, wherein l_o is the marked line spacing in the main orientation direction prior to heat treatment and l_i is the marked line spacing in the main orientation direction after the heat treatment.

Density (specific gravity) was measured in accordance with the ISO 1 183- A standard.

Haze was measured in accordance with the ISO 14782 standard.

Compressive strength or stiffness of the films was measured prior to thermal shrinkage using the well-known ring test method based on the principles of the ISO 12192:2002 standard. The test speed was 13 mm/min. The measurement direction is the longitudinal direction of the films. An AGS-50G Autograph by the Shimadzu Co., Ltd with a load cell type 500N was used for the measurements on a film sample size of 15 mm in the longitudinal direction by 152.4 mm in the main orientation direction (width direction). The test was repeated 5 times for each sample and averaged results are presented below.

The test results from Examples 1 -10 and comparative examples 1 -5 are presented in Table 5.

TABLE 5

Shrinkage (%) Density Stiffness (N) Haze

(g/cm³)

Example 1 69 0.939 5.9 9.2

Example 2 60 0.931 4.9 8.3

Example 3 64 0.939 8.0 12.7

Example 4 67 0.938 7.4 9.2

Example 5 65 0.939 7.6 8. 9

Example 6 67 0.938 7.4 9.2

Example 7 64 0.939 7.0 9.3

Example 8 67 0.939 7.4 9.0 Example 9 66 0.938 7.5 9.2

Example 10 61 0.936 8.2 9.5

Comparative 56 0.933 7.8 9.7

Example 1

Comparative 43 0.90 4.0 7.0

Example 2

Comparative 58 0.98 10.0 13.0

Example 3

Comparative 63 0.95 1 1.5 23.0

Example 4

Comparative N/A N/A N/A N/A

Example 5

As can be seen from Table 5, the multi-layer shrink films according to Examples 1 -10 exhibit a density of less than 0.945 g/cm³ whilst maintaining excellent shrinkage, stiffness and haze properties. In comparison, when excluding PBP, HC and COC or PBE from the core layer as per comparative examples 1 -3, the multi-layer shrink film has inferior shrinkage characteristics, whereas an increase in the COC content of the core layer leads to inferior haze characteristics as demonstrated by Comparative Example 4. Moreover, when increasing the HC content to beyond 20 wt% in the core layer, no stable multi- layer shrink film could be obtained. Consequently, it is demonstrated that the multi-layer shrink film according to embodiments of the present invention can be easily recycled in a gravity separator owing to its low density whilst maintaining excellent film characteristics in terms of shrinkage and haze, for example.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A multi-layer shrink film (10) including a skin layer (13) and a core layer (1 1 ), wherein the skin layer comprises at least 50% by weight of a cyclic olefin copolymer and the core layer comprises:

from 5% by weight to 50% by weight of a propylene based elastomer; from 20% by weight to 50% by weight of a propylene based plastomer; from 1 % by weight to 20% by weight of a hydrocarbon resin; and from 5% by weight to 30% by weight of a cyclic olefin copolymer.

2. The multi-layer shrink film (10) of claim 1 , wherein the core layer comprises:

from 10% by weight to 40% by weight of a propylene based elastomer; from 25% by weight to 45% by weight of a propylene based plastomer; from 5% by weight to 18% by weight of a hydrocarbon resin; and from 5% by weight to 25% by weight of a cyclic olefin copolymer.

3. The multi-layer shrink film (10) of claim 1 or 2, further comprising a further skin layer (15), wherein the core layer (1 1 ) is sandwiched between the skin layer (13) and the further skin layer.

4. The multi-layer shrink film (10) of any of claims 1 -3, wherein the core layer (1 1 ) further comprises up to 5% by weight of a linear low-density polyethylene.

5. The multi-layer shrink film (10) of any of claims 1 -4, wherein the hydrocarbon resin is selected from rosin resins or derivates thereof, resin acid dimers, terpene resins, petroleum resins or combinations thereof.

6. The multi-layer shrink film (10) of claim 5, wherein the hydrocarbon resin consists of one or more petroleum resins.

7. The multi-layer shrink film (10) of claim any of claims 1 -6, wherein the hydrocarbon resin has a softening point in the range of from 100°C to 150°C, preferably from 120°C to 145°C when measured in accordance with the ISO 4625 standard.

8. The multi-layer shrink film (10) of any of claims 1 -7, wherein each skin layer (13, 15) comprises from 70% by weight to 100% by weight of the cyclic olefin copolymer and further comprises up to 30% by weight of a linear low density polyethylene.

9. The multi-layer shrink film (10) of any of claims 1 -8, wherein the thickness of the skin layers (13, 15) present in the multi-layer shrink film is such that the overall volume of the skin layers present corresponds to 15-35% of the total volume of multi-layer shrink film and the core layer (1 1 ) has a thickness such that the volume of the core layer corresponds to 65-85% of the total volume of the multi-layer shrink film.

10. The multi-layer shrink film (10) of any of claims 1 -9, wherein the layers of the film are mainly monoaxially oriented in the transverse direction.

1 1 . The multi-layer shrink film (10) of any of claims 1 -10, wherein the multilayer shrink film exhibits shrinkage in excess of 60% in a main orientation direction of the multi-layer shrink film when immersed in water of 90°C for 10 seconds without applying a load.

12. The multi-layer shrink film (10) of any of claims 1 -1 1 , wherein the multilayer shrink film has a haze of less than 10% when measured in accordance with the ISO 14782 standard.

13. The multi-layer shrink film (10) of any of claims 1 -12, wherein the multilayer shrink film has a density of less than 0.945 g/cm³ when measured in accordance with the ISO 1 183-A standard.

14. A shrink sleeve comprising the multi-layer shrink film (10) of any of claims 1 -13.

15. A container (1 ) comprising the multi-layer shrink film (10) of any of claims 1 -13 or the shrink sleeve of claim 14.