Patent Description:
Nowadays, the attempt of using polymers obtained from waste materials for the manufacturing of new products is of increasing interest and importance for ecological reasons and for reducing costs. Due to the growing environmental problems caused by plastics, the focus today is on the recycling of these plastics.

Secondary packagings, like collation shrink films, do not require a food approval and a large amount of recycled material is resulting from flexible applications. Due to the original material design the best use of this material would be in a flexible application. Therefore, secondary packagings are a perfect fit application for using recycled plastics. Nevertheless, the use of recycled materials is limited due to their lower performances. However, multilayer collation shrink films comprising recycled plastics are also known in the prior art.

<CIT> relates to the use of multilayer heat shrinkable film for advantageous high shrinkage but low shrinkage force is combined with the use of recycle scrap of such film to provide a multilayer heat shrinkable film retaining these advantageous properties. Exemplary of the film is a core of a blend of certain linear low density polyethylene with certain highly branched low density polyethylene sandwiched between two relatively thin outer layers of propylene/ethylene copolymer, with the core also containing recycle scrap of the multilayer film.

<CIT> refers to a packaging for bottles or cans with the following components; <NUM>) an outer packaging for at least partially repackaging bottles or cans consisting of a heat-shrinkable plastic film and <NUM>) a carrying handle fastened to the outer packaging with a carrying handle additional component, wherein all components of the packaging consist of at least one recyclable plastic and wherein the carrying handle additional component consists of a printable plastic and has an imprint.

In most of the multilayer collation shrink films the use of more than <NUM> % of recycled material is not possible without significant deterioration of the mechanical properties. Inhomogeneities originating from contaminants from the original use, collection and recycling of flexible materials increase the risk for hole formation in an oven, for example a shrink oven. LDPE is the most sensitive material for hole formation due to inhomogeneities.

<CIT> relates to a multilayer film which comprises a core layer (C) and two outer layers (O-<NUM>, O-<NUM>) sandwiching the core layer, and its use for packaging, especially for frozen food packaging. The core layer (C) comprises a bimodal ethylene/<NUM>-butene/C<NUM>-C<NUM>-α-olefin terpolymer, One outer layer (O-<NUM>) comprises a low density polyethylene or the bimodal terpolymer as defined for the core layer (C) or a metallocene produced linear low density polyethylene and optionally a low density polyethylene. The other outer layer (O-<NUM>) comprises a metallocene produced linear low density polyethylene and optionally a low density polyethylene.

Based on this it was one objective of the present invention to provide a multilayer collation shrink film allowing the use of bigger amounts of recycled LDPE with low or no hole formation. It was another objective of the present invention that the multilayer collation shrink film shows very good mechanical properties without increasing the film thickness. Furthermore, it was the objective of the present invention that the multilayer collation shrink film has good optical surface layer properties, a good shrink behaviour and a good balance between holding force and cold shrink properties.

This objective is satisfied by a multilayer collation shrink film in accordance with claim <NUM> comprising at least the following layers:.

Advantageous embodiments of the multilayer collation shrink film in accordance with the present invention are specified in the dependent claims <NUM> to <NUM>.

The present invention further relates in accordance with claim <NUM> to a method for manufacturing the collation shrink film. Claim <NUM> relates to the use of the film according to the present invention for secondary packaging and claim <NUM> refers to the use of multimodal terpolymer b2) as defined above in a layer of a multilayer collation shrink film comprising in the same layer at least <NUM> wt. -% of recycled LDPE b1).

In the present invention the term "multimodal" can mean multimodal with respect to molecular weight distribution and includes also therefore bimodal polymers. However, as explained in the detailed description of the components, the components can also be multimodal with respect to other properties, like the MFR or the density.

Usually, a polymer composition, comprising at least two polyethylene fractions, which have been produced under different polymerisation conditions resulting in different (weight average) molecular weights and molecular weight distributions for the fractions, is referred to as "multimodal". The prefix "multi" relates to the number of different polymer fractions present in the polymer. Thus, for example, the term multimodal polymer includes so called "bimodal" polymers consisting of two fractions. The form of the molecular weight distribution curve, i.e. the appearance of the graph of the polymer weight fraction as a function of its molecular weight, of a multimodal polymer, e.g. LLDPE, will show two or more maxima or at least be distinctly broadened in comparison with the curves for the individual fractions.

Ideally, the molecular weight distribution curve for multimodal polymers of the invention will show two distinction maxima. For example, if a polymer is produced in a sequential multistage process, utilising reactors coupled in series and using different conditions in each reactor, the polymer fractions produced in the different reactors will each have their own molecular weight distribution and weight average molecular weight. When the molecular weight distribution curve of such a polymer is recorded, the individual curves from these fractions are superimposed into the molecular weight distribution curve for the total resulting polymer product, usually yielding a curve with two or more distinct maxima.

In any multimodal polymer, there is by definition a lower molecular weight component (LMW) and a higher molecular weight component (HMW). The LMW component has a lower molecular weight than the higher molecular weight component. This difference is preferably at least <NUM>/mol.

In the sense of the present invention it is preferred that all olefins are alpha olefins.

The meaning of low density polyethylene (LDPE) is well known and documented in the literature. Although the term LDPE is an abbreviation for low density polyethylene, the term is understood not to limit the density range, but covers the LDPE-like HP polyethylenes, which are produced by free-radical polymerization in a high-pressure process, with low, medium and higher densities. The term LDPE describes and distinguishes only the nature of HP polyethylene with typical features, such as different branching architecture, compared to the polyethylene produced in the presence of an olefin polymerization catalyst. Moreover, said low density polyethylene (LDPE) homopolymer, may be unsaturated.

In the present invention "collation shrink films" are films that are wrapped around an object to be packaged and shrunk to keep the units within the object together. The most common use of these films is in the packaging of multiple containers (items), such as bottles or cans which might contain food, beverages and so on. The collation shrink film is wrapped around a number of the containers, perhaps a <NUM>-pack of drinks or <NUM>-pack of food cans optionally held in a cardboard tray or pad and shrunk around the containers. The wrapping process typically involves a shrink oven or shrink tunnel in which the film and object covered by the film is briefly heated to cause the collation shrink wrapping to occur. The plastic film then collapses around the multiple containers and holds the units in place.

For the purposes of the present description and of the subsequent claims, the term "recycled LDPE" is used to indicate that the material is recovered from post-consumer waste and/or industrial waste. Namely, post-consumer waste refers to objects having completed at least a first use cycle (or life cycle), i.e. having already served their first purpose; while industrial waste refers to the manufacturing scrap which does normally not reach a consumer. In the gist of the present invention "recycled LDPE" may also comprise up to <NUM> wt. -%, preferably up to <NUM> wt. -%, more preferably up to <NUM> wt. -% and even more preferably up to <NUM> wt. -% based on the overall weight of component b1) of other components like for example LLDPE, MDPE, HDPE. Respectively, the term "virgin" denotes the newly produced materials and/or objects prior to first use and not being recycled. In case that the origin of the polymer is not explicitly mentioned the polymer is a "virgin" polymer.

The "density" of the materials described in the present description and claims means the density determined according to ISO <NUM>.

The "melt flow rate" (= MFR) of the polymers described in the present description and claims means the MFR determined according to ISO <NUM>.

The "melting temperature" of the polymers described in the present description and claims may be measured with a TA Instrument Q200 differential scanning calorimetry (DSC) on <NUM> to <NUM> samples. Crystallization temperature (Tc) and crystallization enthalpy (Hcryst) are determined from the cooling step, while melting temperature (Tm) and heat of fusion (Hfusion) are determined from the second heating step. The crystallinity is calculated from the heat of fusion by assuming an Hfusion-value of <NUM> J/g for a fully crystalline polypropylene (see <NPL>).

Layer A) of the multilayer collation shrink film in accordance with the present invention comprises components a1), a2), a3) and these components optionally contain additives and/or admixtures and layer B) comprises components b1), b2) and these components optionally contain additives and/or admixtures. The requirement applies here that the components a1), a2), a3) and if present including the additives add up to <NUM> wt. -% in sum and that components b1), b2) and if present including the additives add up to <NUM> wt. The fixed ranges of the indications of quantity for the individual components a1), a2), a3) or b1), b2) respectively and optionally the additives and/or admixtures are to be understood such that an arbitrary quantity for each of the individual components can be selected within the specified ranges provided that the strict provision is satisfied that the sum of all the components a1), a2) a3) or b1), b2) respectively and optionally the additives and/or admixtures add up to <NUM> wt.

Where the term "comprising" is used in the present description and claims, it does not exclude other non-specified elements of major or minor functional importance. For the purposes of the present invention, the term "consisting of" is considered to be a preferred embodiment of the term "comprising of". If hereinafter a group is defined to comprise at least a certain number of embodiments, this is also to be understood to disclose a group, which preferably consists only of these embodiments.

Layer A) of the multilayer collation shrink film in accordance with the present invention comprises as component a1) a multimodal polymer of ethylene with at least two different comonomers selected from alpha-olefins having from <NUM> to <NUM> carbon atoms, which multimodal polymer of ethylene has a density in the range from <NUM> to <NUM>/m<NUM>, and a Mw/Mn of <NUM> to <NUM>.

Preferred embodiments of component a1) will be discussed in the following.

According to one preferred embodiment of the present invention the content of component a1) in layer A) is from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% and most preferably from <NUM> to <NUM> wt. -% based on the overall weight of layer A.

Another preferred embodiment of the present invention stipulates that component a1) comprises at least two comonomers (i) and (ii), preferably selected from the group consisting of <NUM>-butene, <NUM>-hexene and <NUM>-octene, more preferably <NUM>-butene and <NUM>-hexene and even more preferably comprises an ethylene butene copolymer component (i) and an ethylene hexene copolymer component (ii), where butene and hexene are the only comonomers present in the respective component. More preferably the copolymers (i) and (ii) have different MFR values and/or different densities. It is furthermore preferred that copolymer (i) has a higher density than copolymer (ii).

According to another preferred embodiment component a1) is a terpolymer comprising an ethylene butene copolymer (i) and an ethylene hexene copolymer (ii).

According to still a further preferred embodiment of the present invention component a1) has a MFR<NUM> in the range from <NUM> to <NUM>/<NUM>, preferably in the range from <NUM> to <NUM>/<NUM> and more preferably in the range from <NUM> to <NUM>/<NUM> determined according to ISO <NUM> at <NUM> under <NUM> load.

In addition, another preferred embodiment stipulates that the MFR<NUM>/ MFR<NUM> of component a1) is in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM> and more preferably in the range from <NUM> to <NUM> (MFR<NUM> determined at <NUM> under <NUM> load).

Still another preferred embodiment stipulates that the MWD (molecular weight distribution) of component a1) is in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM> and more preferably in the range from <NUM> to <NUM>.

In a preferred embodiment, the multimodal polymer of ethylene (A) has one or more of the features:.

According to a further preferred embodiment the multimodal polymer of ethylene a1) is preferably a linear low density polyethylene (LLDPE). Even more preferably the density of the multimodal polymer of ethylene a1) is in the range from <NUM> to <NUM>/m<NUM> and more preferably in the range from <NUM> to <NUM>/m<NUM>.

Still another preferred embodiment of the present invention stipulates that The Mw of the multimodal polymer of ethylene a1) is in the range from <NUM>,<NUM> to <NUM>,<NUM> and preferably in the range from <NUM>,<NUM> to <NUM>,<NUM>.

Another preferred embodiment of the present invention stipulates that the multimodal polymer of ethylene a1) preferably comprises a minimum of <NUM> wt. -% eluting in TREF (Temperature Rising Elution Fractionation) in the temperature range of <NUM> to <NUM>, preferably at least <NUM> wt. -%, and more preferable in the range from <NUM> to <NUM> wt.

According to another preferred embodiment of the present invention the multimodal polymer of ethylene a1) comprises the ethylene polymer comonomer (i) in an amount in the range from <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and the ethylene copolymer (ii) in an amount in the range from <NUM> to <NUM> wt. -%, preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -%, based on the total amount (<NUM> wt. -%) of the multimodal polymer of ethylene a1).

A further preferred embodiment of the present invention stipulates that the multimodal polymer of ethylene a1) consists of the ethylene copolymers (i) and (ii) as the sole polymer components. Accordingly, the split between ethylene copolymer (i) to ethylene copolymer (ii) is of (<NUM> to <NUM>):(<NUM> to <NUM>) preferably of (<NUM> to <NUM>):(<NUM> to <NUM>), more preferably of (<NUM> to <NUM>):(<NUM> to <NUM>), more preferably of (<NUM> to <NUM>):(<NUM> to <NUM>), wt.

According to a further preferred embodiment the multimodal polymer of ethylene (a1) preferably comprises a lower Mw copolymer (i) and a higher molecular weight copolymer (ii).

Another preferred embodiment of the present invention stipulates that copolymer (i) has a MFR<NUM> of <NUM> to <NUM>/<NUM>, preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, even more preferably of <NUM> to <NUM>/<NUM>. More preferably, the ethylene copolymer (i) has higher MFR<NUM> than ethylene copolymer (ii). Even more preferably, the ratio of the MFR<NUM> of ethylene copolymer (i) to the MFR<NUM> of the final multimodal polymer of ethylene (a1) is of <NUM> to <NUM>, preferably of <NUM> to <NUM>, preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>, more preferably of <NUM> to <NUM>.

If the MFR<NUM> of ethylene polymer copolymer, e.g. copolymer (ii), cannot be measured, because it cannot be isolated from the mixture of at least ethylene copolymers (i) and (ii), then it can be calculated using a log mixing rule.

Naturally, in addition to multimodality with respect to, i.e. difference between, the MFR of the ethylene copolymers (i) and (ii), the polymer of ethylene (a1) can also be multimodal e.g. with respect to one or both of the two further properties:.

Preferably, the multimodal polymer of ethylene (a1) of the polymer composition is further multimodal with respect to comonomer type and/or comonomer content (mol-%), preferably wherein the alpha-olefin comonomer having from <NUM> to <NUM> carbon atoms of ethylene copolymer (i) is different from the alpha-olefin comonomer having from <NUM> to <NUM> carbon atoms of ethylene copolymer (ii), preferably wherein the alpha-olefin comonomer having from <NUM> to <NUM> carbon atoms of ethylene copolymer (i) is <NUM>-butene and the alpha-olefin comonomer having from <NUM> to <NUM> carbon atoms of ethylene copolymer (ii) is <NUM> -hexene.

Preferably, the ratio of [the amount (mol-%) of alpha-olefin comonomer having from <NUM> to <NUM> carbon atoms comonomer present in ethylene copolymer (i)] to [the amount (mol%) of at least two alpha-olefin comonomers having from <NUM> to <NUM> carbon atoms of the final multimodal polymer of ethylene a1)] is of <NUM> to <NUM>, preferably of <NUM> to <NUM>, more preferably the ethylene copolymer (i) has a lower amount (mol%) of comonomer than the ethylene copolymer (ii).

The comonomer content of copolymers (i) and (ii) can be measured, or, in case, and preferably, one of the components is produced first and the other thereafter in the presence of the first produced in so called multistage process, then the comonomer content of the first produced copolymer, e.g. copolymer (i), can be measured and the comonomer content of the other copolymer, e.g. copolymer (ii), can be calculated according to following formula: <MAT>.

Copolymers (i) and (ii) can be produced in the same or different reactors.

According to another preferred embodiment of the present invention the amount (mol-%) of alpha-olefin comonomer having from <NUM> to <NUM> carbon atoms present in the ethylene copolymer (i) is in the range from <NUM> to <NUM> mol-%, preferably in the range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-%, even more preferably in the range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-% and even more preferably in the range from <NUM> to <NUM> mol%.

More preferably, the total amount of comonomers present in the multimodal polymer of ethylene (a1) is in the range from <NUM> to <NUM> mol-%, preferably the in range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-% and more preferably in the range from <NUM> to <NUM> mol-%.

According to a further preferred embodiment the multimodal polymer of ethylene (a1) of the polymer composition is further multimodal with respect to difference in density between the ethylene copolymer (i) and ethylene copolymer (ii). Preferably, the density of ethylene copolymer (i) is different, preferably higher, than the density of the ethylene copolymer (ii). More preferably the density of the ethylene copolymer (i) is in the range from <NUM> to <NUM> and preferably in the range from <NUM> to <NUM>/m<NUM>.

In a preferred embodiment the multimodal polymer of ethylene (a1) comprises at least.

Another preferred embodiment of the present invention stipulates that the density of the multimodal polymer of ethylene a1) is in the range from <NUM> to <NUM>/m<NUM> and an MFR<NUM> in the range from <NUM> to <NUM>/<NUM>.

In another preferred embodiment the multimodal polymer of ethylene a1) is produced using a single site catalyst, preferably the ethylene copolymers are produced using the same single site catalyst.

It is furthermore preferred that the multimodal polymer a1) is bimodal.

A further preferred embodiment of the present invention stipulates that multimodal polymer a1) is a virgin polymer.

Layer A) of the multilayer collation shrink film in accordance with the present invention comprises as component a2) a multimodal terpolymer of ethylene and two alpha olefin comonomers wherein the multimodal terpolymer has a density in the range from <NUM> to <NUM>/m<NUM> and a Mw/Mn of <NUM> to <NUM>.

A preferred embodiment stipulates that the multimodal terpolymer a2) has a density in the range from <NUM> to <NUM>/m<NUM> and a Mw/Mn of <NUM> to <NUM>.

Layer B) of the multilayer collation shrink film in accordance with the present invention comprises as component b2) a multimodal terpolymer of ethylene and two alpha olefin comonomers wherein the multimodal terpolymer has a density in the range from <NUM> to <NUM>/m<NUM> and a Mw/Mn of <NUM> to <NUM>.

A preferred embodiment stipulates that the multimodal terpolymer b2) has a density in the range from <NUM> to <NUM>/m<NUM> and a Mw/Mn of <NUM> to <NUM>.

A preferred embodiment of the present invention stipulates that components a2) and b2) are identical. However, it is within the scope of the present invention that components a2) and b2) are different.

Preferred embodiments of component a2) and b2) will be discussed in the following. According to a preferred embodiment of the present invention the content of component a2) in layer A) is in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and most preferably in the range from <NUM> to <NUM> wt. -% based on the overall weight of layer A).

A further preferred embodiment of the present invention stipulates that the content of component b2) in layer B) is in the range from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and most preferably in the range from <NUM> to <NUM> wt. -% based on the overall weight of layer B).

The polyethylene terpolymer(s) a2) and/or b2) according to the present invention are multimodal, such as bimodal, i.e. its molecular weight profile does not comprise a single peak but instead comprises the combination of two or more peaks (which may or may not be distinguishable) centred about different average molecular weights as a result of the fact that the polymer comprises two separately produced components.

Alternatively, the multimodal terpolymer(s) a2) and/or b2) of the present invention can be multimodal in view of its comonomer content or in view of the nature of the comonomers. It is preferred if the multimodal terpolymer is multimodal with respect to molecular weight distribution.

Multimodal polyethylene terpolymer(s) a2) and/or b2) are typically made in more than one reactor, each having different conditions. The components of the multimodal terpolymers a2) and b2) are typically so different that they show more than one peak or shoulder in the diagram given as result of its GPC (gel permeation chromatograph) curve, where d(log(MW)) is plotted as ordinate vs log(MW), where MW is molecular weight.

According to a preferred embodiment of the present invention the multimodal polyethylene terpolymer(s) a2) and/or b2) may comprise at least two C4-<NUM> alpha-olefin comonomers. Ideally, the multimodal polyethylene terpolymer(s) a2) and/or b2) contain <NUM> comonomers only. These comonomers are especially selected from the group consisting of <NUM>-butene, <NUM>-hexene or <NUM>-octene. The amount of comonomers present in the multimodal terpolymers a2) and b2) is preferably in the range from <NUM> to <NUM> mol-%, more preferably <NUM> to <NUM> mol-% and more preferably <NUM> to <NUM> mol-%.

The multimodal polyethylene terpolymer(s) a2) and/or b2) suitable for use in the multilayer collation shrink films of the present invention can comprise a lower molecular weight fraction being a polyethylene homopolymer and a higher molecular weight fraction being a terpolymer of ethylene and at least two alpha olefin comonomers having <NUM> to <NUM> carbon atoms.

The multimodal polyethylene terpolymer(s) a2) and/or b2) suitable for use in the multilayer collation shrink films of the present invention can preferably comprise.

Preferably the comonomer of the higher molecular weight component is a C6-C12-alpha-olefin selected from the group consisting of <NUM>-hexene, <NUM>-methyl-<NUM>-pentene, <NUM>-octene and <NUM>-decene, especially <NUM>-hexene or <NUM>-octene.

More preferably the multimodal polyethylene terpolymer(s) a2) and/or b2) comprises lower and higher molecular weight components as defined in (A-<NUM>) and (A-<NUM>).

The multimodal polyethylene composition may be produced by polymerisation using conditions which create a multimodal (e.g. bimodal) polymer product ideally using a Ziegler Natta catalyst system. Typically, a two or more stage, i.e. multistage, polymerisation process is used with different process conditions in the different stages or zones (e.g. different temperatures, pressures, polymerisation media, hydrogen partial pressures, etc). Preferably, the multimodal (e.g. bimodal) composition is produced by a multistage polymerisation, e.g. using a series of reactors, with optional comonomer addition preferably in only the reactor(s) used for production of the higher/highest molecular weight component(s). A multistage process is defined to be a polymerisation process in which a polymer comprising two or more fractions is produced by producing each or at least two polymer fraction(s) in a separate reaction stage, usually with different reaction conditions in each stage, in the presence of the reaction product of the previous stage which comprises a polymerisation catalyst. The polymerisation reactions used in each stage may involve conventional ethylene homopolymerisation or copolymerisation reactions, e.g. gas-phase, slurry phase, liquid phase polymerisations, using conventional reactors, e.g. loop reactors, gas phase reactors, batch reactors etc. (see for example <CIT> and <CIT>). Terpolymers meeting the requirements of the invention are known and can be bought from suppliers such as Borealis and Borouge, e.g. FX1002.

A preferred embodiment of the present invention stipulates that the multimodal terpolymer(s) a2) and/or b2) have a density in the range from <NUM> to <NUM>/m<NUM>, more preferably from <NUM> to <NUM>/m<NUM>, even more preferably in the range from <NUM> to <NUM>/m<NUM> and most preferably in the range from <NUM> to <NUM>/m<NUM>. Ideally, the multimodal terpolymer has a density in the range from <NUM> to <NUM>/m<NUM>. Alternatively, the density may be in the range from <NUM> to <NUM>/m<NUM>.

The melt flow rate <NUM>/<NUM> according to ISO1133 (i.e. MFR5) of the multimodal terpolymer(s) a2) and/or b2) is preferably in the range from <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM> and even more preferably in the range from <NUM> to <NUM>/<NUM>. The MFR5 is highly preferably in the range from <NUM> to <NUM>/<NUM>.

The MFR21 of the multimodal terpolymer(s) a2) and/or b2) may be in the range from <NUM> to <NUM>/<NUM>, preferably in the range from <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>, even more preferably in the range from <NUM> to <NUM>/<NUM> and most preferably in the range from <NUM> to <NUM>/<NUM>.

The ratio of MFR21 to MFR5 is an indication on molecular weight distribution and to a certain extent also to the processability. The ratio of MFR21 to MFR5 is understood as FRR <NUM>/<NUM>.

According to a preferred embodiment of the present invention the FRR21/<NUM> of multimodal terpolymers a2) and/or b2) is at least <NUM> or higher, preferably <NUM> or higher, more preferably in the range from <NUM> or <NUM>. The FRR21/<NUM> is usually <NUM> or below, preferably <NUM> or lower and more preferably in the range from <NUM> or <NUM>. It is thus preferred that the FRR21/<NUM> of the multimodal terpolymer(s) a2) and/or b2) is in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM> and more preferably in the range from <NUM> to <NUM>. It is preferred, if the multimodal polyethylene terpolymer(s) a2) and/or b2) of the present invention has a MFR21 in the range from <NUM> to <NUM>/<NUM> and a FRR21/<NUM> of at least <NUM>.

The Mw of the multimodal terpolymer(s) a2) and/or b2) may be in the range from <NUM>,<NUM> to <NUM>,<NUM>, preferably in the range from <NUM>,<NUM> to <NUM>,<NUM> and more preferably in the range from <NUM>,<NUM> to <NUM>,<NUM>. The Mw/Mn of the multimodal terpolymer(s) a2) and/or b2) may be in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM> and most preferably in the range from <NUM> to <NUM>.

According to a further preferred embodiment of the present invention the lower molecular weight fraction of the multimodal polyethylene terpolymer(s) a2) and/or b2) may have a MFR<NUM> of at least <NUM>, preferably in the range from <NUM> to <NUM>/<NUM> and more preferably at least <NUM>/<NUM>. The molecular weight of the lower molecular weight component should preferably range from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

Still another preferred embodiment of the present invention stipulates that the density of the lower molecular weight component may range from <NUM> to <NUM>/m<NUM>, preferably from <NUM> to <NUM>/m<NUM>, more preferably from <NUM> to <NUM>/m<NUM> in the case of copolymer and from <NUM> to <NUM>/m<NUM>, preferably from <NUM> to <NUM>/m<NUM> in the case of homopolymer.

The lower molecular weight component preferably forms from <NUM> to <NUM> wt. -% and more preferably <NUM> to <NUM> wt. -% of the multimodal terpolymer(s) a2) and/or b2) with the higher molecular weight component forming <NUM> to <NUM> wt. -% and preferably <NUM> to <NUM>% wt.

According to still another preferred embodiment of the present invention the higher molecular weight component of the multimodal polyethylene terpolymer(s) a2) and/or b2) has a lower MFR<NUM> and a lower density than the lower molecular weight component.

Another preferred embodiment stipulates that the higher molecular weight component has an MFR<NUM> of less than <NUM>/<NUM>, preferably less than <NUM>/<NUM>, more preferably less than <NUM>/<NUM>.

According to another preferred embodiment of the present invention the higher molecular weight component has a density of less than <NUM>/m<NUM>, preferably less than <NUM>/m<NUM> and more preferably less than <NUM>/m<NUM>. The Mw of the higher molecular weight component may range from <NUM>,<NUM> to <NUM>,<NUM>,<NUM> and preferably from <NUM>,<NUM> to <NUM>,<NUM>.

A further preferred embodiment of the present invention stipulates that component(s) a2) and/or b2) are virgin polymers.

Layer A) of the multilayer collation shrink film in accordance with the present invention comprises as component a3) a LDPE.

Preferred embodiments of component a3) will be discussed in the following.

According to one preferred embodiment of the present invention the content of component a3) in layer A) is from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% and most preferably from <NUM> to <NUM> wt. -% based on the overall weight of layer A).

Another preferred embodiment of the present invention stipulates that component a3) is a homopolymer.

According to still another preferred embodiment of the present invention LDPE a3) has a MFR<NUM> in the range from <NUM> to <NUM>/<NUM>, preferably in the range from <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>, even more preferably in the range from <NUM> to <NUM>/<NUM>, still more preferably in the range from <NUM> to <NUM>/<NUM> and most preferable in the range from <NUM> to <NUM>/<NUM>.

In a further preferred embodiment of the present invention component a) has a density in the range from <NUM> to <NUM>/m<NUM>, preferably in the range from <NUM> to <NUM>/m<NUM>, more preferably in the range from <NUM> to <NUM>/m<NUM> more preferably in the range from <NUM> to <NUM>/m<NUM>.

Another preferred embodiment of the present invention stipulates that component a3) is a virgin polymer.

Layer B) of the multilayer collation shrink film in accordance with the present invention comprises as component b1) a recycled LDPE.

Preferred embodiments of component b1) will be discussed in the following.

A preferred embodiment in accordance with the present invention stipulates that the content of component b1) in layer B) is from <NUM> to <NUM> wt. -%, preferably from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% and most preferably from <NUM> to <NUM> wt. -% based on the overall weight of layer B).

In a further embodiment of the present invention component b1) originates from post consumer waste.

As already mentioned component b1) can comprise up to <NUM> wt. -% of constituents originating from the first use. Type and amount of these constituents influence the physical properties of component b1). The properties given below refer to the main component.

Still a further preferred embodiment of the present invention stipulates that component b1) has a MFR<NUM> in the range from <NUM> to <NUM>/<NUM>, preferably in the range from <NUM> to <NUM>/<NUM> and more preferably in the range from <NUM> to <NUM>/ <NUM>.

According to a further preferred embodiment of the present invention component b1) has a density in the range from <NUM> to <NUM>/m<NUM>, preferably <NUM> to <NUM>/m<NUM>, more preferably in the range from <NUM> to <NUM>/m<NUM> and even more preferably in the range from <NUM> to <NUM>/m<NUM>.

In a further preferred embodiment component a1) has a melting point (second melting) in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM> and more preferably in the range from <NUM> to <NUM>.

Recyled LDPE's meeting the requirements of the invention are known and can be bought from suppliers such as Ecoplast, e.g. ecoplast NAV <NUM>.

Preferred embodiments of the multilayer collation shrink film will be discussed in the following.

A preferred embodiment of the present invention stipulates that the multilayer film contains at least <NUM> layers and preferably consists of <NUM> layers. It is furthermore preferred that layer B) forms the core layer and is sandwiched by two outer layers A), more preferably both outer layers A) consist of identical components and are most preferably the same. In this context "being the same" means that the outer layers A) consist not only of the same components (amount and chemical composition), but also have the same layer thickness, so that the multilayer film is symmetric.

In one preferred embodiment of the present invention layer A) consists of components a1), a2), a3), optionally one or more of these components can contain additives. The content of component a1) in layer A) is in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and most preferably in the range from <NUM> to <NUM> wt. -% based on the overall weight of layer A), the content of component a2) in layer A) is in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and most preferably in the range from <NUM> to <NUM> wt. -% based on the overall weight of layer A) and the content of component a3) in layer A) is in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and most preferably in the range from <NUM> to <NUM> wt. -% based on the overall weight of layer A), wherein the weight proportions of components (a1) to (a3) add up to <NUM> wt.

In another preferred embodiment of the present invention layer B) consists of components b1), b2), optionally one or both of these components can contain additives. The content of component b1) in layer B) is from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% and most preferably from <NUM> to <NUM> wt. -% based on the overall weight of layer B); and the content of component b2) in layer B) is from <NUM> to <NUM> wt. -%, more preferably from <NUM> to <NUM> wt. -% and most preferably from <NUM> to <NUM> wt. -% based on the overall weight of layer B), wherein the weight proportions of components (b1) and (b2) add up to <NUM> wt.

As mentioned above components a1), a2), a3), b1) and b2) may contain additives and/or admixtures.

Additives are preferably selected from the group consisting of slip agents, UV-stabiliser, antioxidants, nucleating agents and mixtures thereof, preferably these additives are contained in an the range from <NUM> to <NUM> ppm, preferably in the range from <NUM> to <NUM> ppm and more preferably in the range from <NUM> to <NUM> ppm based on the overall weight of the respective layer.

Admixtures are preferably selected from the group consisting of pigments, fillers, antiblocking agents and mixtures thereof, preferably these additives are contained in an the range from <NUM> to <NUM> wt. -% ppm, preferably in the range from <NUM> to <NUM> wt. -%, more preferably in the range from <NUM> to <NUM> wt. -% and most preferably from <NUM> to <NUM> wt. -% based on the overall weight of the respective layer.

According to still a further preferred embodiment of the present invention the multilayer collation shrink film according to the present invention has a tensile stress at <NUM> % strain in the range from <NUM> to <NUM> MPa, preferably from <NUM> to <NUM> MPa and more preferably from <NUM> to <NUM> MPa.

Still another preferred embodiment of the present invention stipulates that the multilayer collation shrink film has a shrinkage in machine direction in the range from <NUM> to <NUM> %, preferably from <NUM> to <NUM> % and more preferably from <NUM> to <NUM> %.

In a further preferred embodiment of the present invention the multilayer collation shrink film has a shrinkage in cross direction in the range from <NUM> to <NUM> %, preferably from <NUM> to <NUM> % and more preferably from <NUM> to <NUM> %.

Another preferred embodiment of the present invention stipulates that the multilayer collation shrink film has a retraction force in the range from <NUM> to <NUM>/cm<NUM>, preferably from <NUM> to <NUM>/cm<NUM> and more preferably from <NUM> to <NUM>/cm<NUM>.

According to a further preferred embodiment of the present invention the multilayer collation shrink film has a contraction force in the range from <NUM> to <NUM>/cm<NUM>, preferably from <NUM> to <NUM>/cm<NUM> and more preferably from <NUM> to <NUM>/cm<NUM>.

Still a further preferred embodiment of the present invention stipulates layer A) of the multilayer collation shrink film has a thickness in the range from <NUM> to <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

According to a further preferred embodiment of the present invention layer B) has a thickness in the range from <NUM> to <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

In a further embodiment of the present invention the overall film thickness is in the range from <NUM> to <NUM>, preferably from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

A preferred multilayer collation shrink film consists of a core layer B) sandwiched by two outer layers A), wherein.

Another preferred multilayer collation shrink film consists of a core layer B) sandwiched by two outer layers A), wherein.

A further preferred multilayer collation shrink film consists of a core layer B) sandwiched by two outer layers A), wherein.

The present invention further relates to a method for manufacturing the multilayer collation shrink film according to the present invention. According to one preferred embodiment the multilayer collation shrink film is manufactured by a one-step blown film coextrusion process.

The film according to the present invention can be used for secondary packaging, preferably for bottles and cans more preferably bottles and cans in the field of household products, food, healthcare products, beverage products and bottles.

The present invention further refers to the use of the multimodal terpolymer b2) as defined above for improving the mechanical properties and shrink behaviour of a multilayer film.

In accordance with the present invention the mechanical properties and shrink behaviour of the multilayer collation shrink film can be improved by incorporation of <NUM> to <NUM> wt. -% and preferably of <NUM> to <NUM> wt. -% of the multimodal terpolymer b2) in a layer of a multilayer collation shrink film comprising in the same layer at least <NUM> wt. -%, preferably <NUM> to <NUM> wt. -% and more preferably <NUM> to <NUM> wt. -% of recycled LDPE b1) as defined above, wherein the weight indications are based on the overall weight of the layer comprising b1) and b2).

In a preferred embodiment of the present invention the multimodal terpolymer b2) is used in a symmetrical film having the layer sequence A/B/A.

In addition, a monolayer film comprising components b1) and b2) as defined above is described herein. Said film can be produced by a step blown film extrusion processes.

According to a further preferred embodiment of the present invention the monolayer film has a thickness in the range from <NUM> to <NUM>, preferably in the range from <NUM> to <NUM> and more preferably from <NUM> to <NUM>.

A preferred monolayer film consists of components b1) and b2) and more preferably consists of.

A further preferred monolayer film consists of.

Tensile tests were performed on an Instron apparatus according to ISO <NUM>-<NUM>.

Determination of shrinkage was performed in oil according to ISO <NUM>.

<NUM> x <NUM> samples are placed in oil (Polydimethylsiloxan) at <NUM> for <NUM> seconds. After this the samples are removed, and conditioned at room temperature for <NUM> hour. Finally the shrinkage, i.e. change in dimension is measured. Shrinkage values are calculated as: <MAT> wherein Lo is the original length (i.e. <NUM>), and Lm is the length measured after thermal exposure. If the measured value increases (e.g. in the TD direction), then shrinkage is negative.

The retraction force and contraction force were determined according to ISO <NUM> using a shrinkage film tester (Retratech) at <NUM> and a residence time in the oven for <NUM> seconds.

FX1002: multimodal alpha olefin terpolymer commercially available by Borealis AG, density <NUM>/m<NUM> (determined according to ISO <NUM>), Melt Flow Rate (<NUM>/<NUM>) of <NUM>/<NUM> and a Melt Flow Rate (<NUM>/<NUM>) of <NUM>/<NUM> (according to ISO <NUM>).

FK1820: Anteo™ FK1820 is a bimodal terpolymer commercially available by Borealis AG, density <NUM>/m<NUM> (determined according to ASTM D792), Melt Flow Rate (<NUM>/<NUM>) of <NUM>/<NUM>.

LDPE: low density polyethylene, grade FT3200 available by Borealis.

FB1350: Borstar® FB1350 is a linear medium density polyethylene, density <NUM>/m<NUM> (determined according to ISO1183), Melt Flow Rate (<NUM>/<NUM>) of <NUM>/<NUM>.

NAV <NUM>: recycled LDPE, commercially available by Ecoplast under the tradename Ecoplast NAV <NUM>, density: <NUM>±<NUM>/cm<NUM> (determined according to ISO <NUM>), Melt Flow Rate (<NUM>/<NUM>) of <NUM>±<NUM>/<NUM>, origin: household and commercial waste collection.

The films were produced on a commercial scale <NUM>-layer extrusion blown film line with three extruders (extruder temperature setting <NUM> to <NUM>, die diameter <NUM>, blow up ratio (BUR) <NUM>:<NUM>, die gap <NUM>, with internal bubble cooling).

The distribution for the ABA films was <NUM>%/<NUM>%/<NUM>% and the overall film thickness was <NUM> for Inventive Example <NUM> and <NUM> for Inventive Example <NUM> and Comparative Example <NUM>.

The film according to Inventive Example <NUM> has the following composition.

The film according to Comparative Example <NUM> has the following composition.

Below Table <NUM> summarizes the mechanical data measured for above films.

Claim 1:
A multilayer collation shrink film comprising at least the following layers:
A) a layer comprising at least the following components:
a1) a multimodal polymer of ethylene with at least two different comonomers selected from alpha-olefins having from <NUM> to <NUM> carbon atoms, which multimodal polymer of ethylene has a density in the range from <NUM> to <NUM>/m<NUM>, and a Mw/Mn of <NUM> to <NUM>;
a2) a multimodal terpolymer of ethylene and two alpha olefin comonomers wherein the multimodal terpolymer has a density in the range from <NUM> to <NUM>/m<NUM> and a Mw/Mn of <NUM> to <NUM>; and
a3) LDPE;
B) a layer comprising at least the following components:
b1) recycled LDPE; and
b2) a multimodal terpolymer of ethylene and two alpha olefin comonomers wherein the multimodal terpolymer has a density in the range from <NUM> to <NUM>/m<NUM> and a Mw/Mn of <NUM> to <NUM>.