LAMINATED MONOMATERIAL POLYETHYLENE FILM

Abstract

The present invention relates to a laminated polyethylene film comprising: (a) a first film; and (b) a second film; wherein the first and the second film are adhering to one another to form a laminate; wherein the first film is a bi-directionally oriented film; and the second film is a blown film; wherein the first film comprises or consists of polyethylene, and the second film comprises or consists of polyethylene; wherein the second film comprises one or more film layers, and comprises a sealing layer so that the sealing layer forms a surface layer of the laminated film; wherein the sealing layer comprises a polyethylene copolymer (I) comprising moieties derived from 1-octene, having: a density of 855 kg/m3 and 910 kg/m3, as determined in accordance with ASTM D792 (2008); a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg. Such laminated film, constituting a mono-material, mechanically recyclable packaging film solution, demonstrates a desirably low sealing temperature whilst ensuring good seal strength. This enables use in thermally sealed food packages, with reduced sealing energy consumption and reduced exposing of package contents to high temperatures, leading to increase of shelf life of the packed foodstuff. Moreover, the mechanical properties of the laminate are of desirably high level.

Claims

1. Laminated polyethylene film comprising: (a) a first film; and (b) a second film; wherein the first and the second film are adhering to one another to form a laminate; wherein the first film is a bi-directionally oriented film; and the second film is a blown film; wherein the first film comprises or consists of polyethylene, and the second film comprises or consists of polyethylene; wherein the second film comprises one or more film layers, and comprises a sealing layer so that the sealing layer forms a surface layer of the laminated film; wherein the sealing layer comprises a polyethylene copolymer (I) comprising moieties derived from 1-hexene or 1-octene having: a density of 855 kg/m.sup.3 and 910 kg/m.sup.3, as determined in accordance with ASTM D792 (2008); a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg.

2. Laminate polyethylene film according to claim 1, wherein the polyethylene that is present in the first film is: a linear low-density polyethylene having a density of 910 and 940 kg/m.sup.3; or a high-density polyethylene having a density of >940 and 975 kg/m.sup.3.

3. Laminate polyethylene film according to claim 1, wherein the first film is oriented in both machine and transverse direction in the solid state.

4. Laminate polyethylene film according to claim 1, wherein the second film is a single-layer or a multi-layer film obtained by multi-layer melt co-extrusion.

5. Laminate polyethylene film according to claim 1, wherein the sealing layer comprised in the second film comprises the polyethylene copolymer (I), linear low-density polyethylene (LLDPE) (II).

6. Laminate polyethylene film according to claim 1, wherein the second film is a multi-layer film comprising a first layer, optionally a second layer, and a sealing layer.

7. Laminate polyethylene film according to claim 6, wherein the second film is adhered to the first film with that surface of the second film formed by the first layer.

8. Laminate polyethylene film according to claim 6, wherein the first layer and/or the second layer comprises LLDPE (II).

9. Laminate polyethylene film according claim 8, wherein the LLDPE (II) in the first layer and LLDPE (II) in the sealing layer are the same or different, and/or wherein LDPE (III) in the first layer and LDPE (III) in the sealing layer are the same or different.

10. Laminate polyethylene film according to claim 5, wherein the LLDPE (II) is a polyethylene copolymer comprising moieties derived from ethylene and moieties derived from one or more of 1-butene, 1-hexene and 1-octene, with 75.0 wt % of moieties derived from ethylene and/or 25.0 wt % of moieties derived from one or more of 1-butene, 1-hexene and 1-octene, with regard to the total weight of the LLDPE (II), and wherein the LLDPE (II) has a density of 910 and 940 kg/m.sup.3 and a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg.

11. Laminate polyethylene film according to claim 5, wherein the LDPE (III) is an ethylene polymer obtained by free-radical polymerisation, and/or high-pressure free-radical polymerisation, and has a density of 910 and 940 kg/m.sup.3 and a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg.

12. Laminate polyethylene film according to claim 1,wherein the first and the second film of the laminate polyethylene film comprise no polymer materials other than polymers comprising only polymer moieties derived from ethylene and mono-olefins comprising 3 and 12 carbon atoms.

13. Package comprising the laminate polyethylene film according to claim 1.

14. Package according to claim 14 wherein the package is a heat-sealed bag.

15. Process for manufacturing a sealed bag, the process involving subjecting an assembly comprising a first and a second part of the laminate polyethylene film assembled so that both sealing layers face each other, and subjecting at least a part of the assembly to an energy treatment and/or a heat treatment, whilst pressing the parts together so that, termination of the energy treatment, a seal is formed closing the assembly so as to form a sealed bag.

16. Laminate polyethylene film according to claim 1, wherein the sealing layer comprises a polyethylene copolymer (I) comprising moieties derived from 1-octene.

17. Laminate polyethylene film according to claim 1, wherein the first film is oriented in both machine and transverse direction in the solid state, and wherein the first film is oriented at a drawing ratio of 3.0 in the machine direction, and wherein the first film is oriented at a drawing ratio of 3.0 in the transverse direction, wherein the drawing ratio is defined as the dimension of the film in the particular direction after being subjected to the orientation step, divided by the dimension of the film in the particular direction prior being subjected to the orientation step.

18. Laminate polyethylene film according to claim 1, wherein the first film is oriented in both machine and transverse direction in the solid state, and wherein the first film is oriented at a drawing ratio of 3.0 and 15.0 in the machine direction, and wherein the first film is oriented at a drawing ratio of 3.0 and 15.0 in the transverse direction, wherein the drawing ratio is defined as the dimension of the film in the particular direction after being subjected to the orientation step, divided by the dimension of the film in the particular direction prior being subjected to the orientation step.

19. Laminate polyethylene film according to claim 1, wherein the sealing layer comprised in the second film comprises the polyethylene copolymer (I), linear low-density polyethylene (LLDPE) (II) and low-density polyethylene (LPDE) (III), and wherein the sealing layer comprises 10.0 wt %, or 20.0 wt %, or 40.0 wt %, of the polyethylene copolymer (I).

20. Laminate polyethylene film according to claim 6, wherein the first layer and/or the second layer comprises LLDPE (II) and LDPE (III), and comprises 80.0 wt % of the LLDPE (II), with regard to the total weight of the first layer, or wherein the first layer comprises the LLDPE (II) and the LDPE (III) as the only polymer materials in the particular layer.

Description

[0005] Hence, there is a desire to provide objects comprising thermoplastic materials, such as plastic packages, of such nature that the thermoplastic materials used in such object belong to the same family of thermoplastics, i.e. the materials allow for mechanical recycling via melt processing of the thermoplastics with minimised down-cycling, allowing for manufacture of products of similar value and quality as the original object. Such objects are commonly referred to as mono-material objects or articles.

[0006] It is now by the present invention achieved to provide a laminated polyethylene mono-material film that is suitable for a variety of packaging applications, in that the invention provides for a laminated polyethylene film comprising: [0007] (a) a first film; and [0008] (b) a second film; [0009] wherein the first and the second film are adhering to one another to form a laminate; wherein [0010] the first film is a bi-directionally oriented film; and [0011] the second film is a blown film; [0012] wherein the first film comprises or consists of polyethylene, and the second film comprises or consists of polyethylene; [0013] wherein the second film comprises one or more film layers, and comprises a sealing layer so that the sealing layer forms a surface layer of the laminated film; [0014] wherein the sealing layer comprises a polyethylene copolymer (I) comprising moieties derived from 1-hexene or 1-octene, preferably from 1-octene, having: [0015] a density of 855 kg/m.sup.3 and 910 kg/m.sup.3, as determined in accordance with ASTM D792 (2008); [0016] a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg.

[0017] Such laminated film, constituting a mono-material, mechanically recyclable packaging film solution, demonstrates a desirably low sealing temperature whilst ensuring good seal strength. This enables use in thermally sealed food packages, with reduced sealing energy consumption and reduced exposing of package contents to high temperatures, leading to increase of shelf life of the packed foodstuff. Moreover, the mechanical properties of the laminate are of desirably high level.

[0018] The polyethylene that is present in the first film may for example be a linear low-density polyethylene having a density of 910 and 940 kg/m.sup.3, preferably 910 and 930 kg/m.sup.3, more preferably 910 and 925 kg/m.sup.3, even more preferably 915 and 925 kg/m.sup.3. Alternatively, the polyethylene that is present in the first film may for example be a high-density polyethylene having a density of >940 and 975 kg/m.sup.3, preferably 945 and 970 kg/m.sup.3, more preferably 945 and 960 kg/m.sup.3. Preferably, the polyethylene that is present in the first film is a linear low-density polyethylene.

[0019] The linear low-density polyethylene in the first film may for example be a polyethylene comprising moieties derived from ethylene and moieties derived from an olefin selected from 1-butene, 1-hexene and 1-octene. For example, the linear-low density polyethylene in the first film may comprise 80.0 and 95.0 wt % of moieties derived from ethylene, with regard to the total weight of the linear low-density polyethylene, preferably 85.0 wt % and 95.0 wt %. For example, the linear-low density polyethylene in the first film may comprise 5.0 and 20.0 wt % of moieties derived from an olefin selected from 1-butene, 1-hexene and 1-octene, with regard to the total weight of the linear low-density polyethylene, preferably 5.0 wt % and 15.0 wt %. It is preferred that the olefin is 1-hexene.

[0020] The linear low-density polyethylene in the first film may for example have a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg, preferably 0.5 and 5.0 g/10 min, preferably 0.5 and 3.0 g/10 min, more preferably 0.8 and 3.0 g/10 min, even more preferably 1.0 and 3.0 g/10 min, even more preferably 1.0 and 2.5 g/10 min.

[0021] The linear low-density polyethylene in the first film may be characterised by its a-TREF fingerprint, that is, i a particular distribution of the fractions of polymer that in a-TREF are eluted in particular defined temperature ranges in which the fractionation is performed. The linear low-density polyethylene in the first film may for example have a fraction eluted in a-TREF at a temperature >94.0 C. of 20.0 wt %, with regard to the total weight of the polyethylene. More preferably, the linear low-density polyethylene in the first film has a fraction eluted >94.0 C. of 25.0 wt %, even more preferably 30.0 wt %, yet even more preferably 35.0 wt %. In the field of polyethylenes, the fraction of polymer that is eluted in a-TREF at a temperature of >94.0 C. reflects the quantity of linear polymeric material that is present in the particular polymer. In the present polymer, having a particular quantity of the material in this fraction, this indicates that a certain amount of linear polymeric material is to be present.

[0022] Further, the linear low-density polyethylene in the first film may for example have a fraction that is eluted in a-TREF at a temperature 30.0 C. of 8.0 wt %, with regard to the total weight of the polyethylene. The fraction that is eluted at a temperature of 30 C. may in the context of the present invention be calculated by subtracting the sum of the fraction eluted >94 C. and the fraction eluted >30 C. and 94 C. from 100%, thus the total of the fraction eluted 30 C., the fraction eluted >30 C. and 94 C. and the fraction eluted >94 C. to add up to 100.0 wt %. The fraction eluted 30 C. preferably is 9.0 wt %, more preferably 10.0 wt %, even more preferably 11.0 wt %. Preferably, the fraction that is eluted in a-TREF at a temperature 30.0 C. is 8.0 and 16.0 wt %, more preferably 9.0 and 14.0 wt %, even more preferably 10.0 and 14.0 wt % with regard to the total weight of the polymer; and/or preferably, the fraction that is eluted in a-TREF at a temperature >94.0 C. is 20.0 and 50.0 wt %, more preferably 25.0 and 45.0 wt %, even more preferably 30.0 and 40.0 wt %, with regard to the total weight of the polymer; and/or preferably, the fraction that is eluted in a-TREF at a temperature >30.0 and 94.0 C. is 40.0 and 64.0 wt %, more preferably 45.0 and 60.0 wt %, even more preferably is 45.0 and 55.0 wt %.

[0023] According to the invention, analytical temperature rising elution fractionation, also referred to as a-TREF, may be carried out using a Polymer Char Crystaf-TREF 300 with a solution containing 4 mg/ml of sample prepared in 1,2-dichlorobenzene stabilised with 1 g/l Topanol CA (1,1,3-tri(3-tert-butyl-4-hydroxy-6-methylphenyl)butane) and 1 g/l Irgafos 168 (tri(2,4-di-tert-butylphenyl) phosphite) at a temperature of 150 C. for 1 hour. The solution may be further stabilised for 45 minutes at 95 C. under continuous stirring at 200 rpm before analyses. For analyses, the solution was crystallised from 95 C. to 30 C. using a cooling rate of 0.1 C./min. Elution was performed with a heating rate of 1 C./min from 30 C. to 140 C. The set-up was cleaned at 150 C. Particularly, a-TREF may be carried out using a Polymer Char Crystaf-TREF 300 using a solution containing 4 mg/ml of the polymer in 1,2-dichlorobenzene, wherein the solution is stabilised with 1 g/l 1,1,3-tri(3-tert-butyl-4-hydroxy-6-methylphenyl)butane and 1 g/l tri(2,4-di-tert-butylphenyl) phosphite) at a temperature of 150 C. for 1 hour, and optionally further stabilised for 45 minutes at 95 C. under continuous stirring at 200 rpm, wherein the prior to analyses the solution is crystallised from 95 C. to 30 C. using a cooling rate of 0.1 C./min, and elution is performed at a heating rate of 1 C./min from 30 C. to 140 C., and wherein the equipment has been cleaned at 150 C.

[0024] The linear low-density polyethylene in the first film may for example have an M.sub.w/M.sub.n ratio of >4.0, preferably >4.0 and <10.0, more preferably >5.0 and <8.0. For example, the linear low-density polyethylene in the first film may have an M.sub.z/M.sub.n ratio of >15.0, preferably >15.0 and <40.0, preferably >20.0 and <30.0, wherein M.sub.n is the number average molecular weight, M.sub.w is the weight average molecular weight, and M.sub.z is the z-average molecular weight, as determined in accordance with ASTM D6474 (2012). For example, the linear low-density polyethylene in the first film may for example have an M.sub.w/M.sub.n ratio of >4.0, preferably >4.0 and <10.0 and an M.sub.z/M.sub.n ratio of >15.0, preferably >15.0 and <40.0. It is preferred that in the range of log(M.sub.w) between 4.0 and 5.5, the slope of the curve of the number of CH.sub.3 branches per 1000 C atoms versus the log(M.sub.w) is negative, wherein the number of CH.sub.3 branches is determined via SEC-DV with and IR5 infrared detector, in accordance with ASTM D6474 (2012). The linear low-density polyethylene in the first film may have an M.sub.w of for example >75 kg/mol, preferably >100 kg/mol, such as >75 and <200 kg/mol, preferably >100 and <150 kg/mol. The linear low-density polyethylene in the first film may have an M.sub.n of for example >15 kg/mol, preferably >20 kg/mol, such as for example >15 and <40 kg/mol, preferably >20 and <30 kg/mol. The linear low-density polyethylene in the first film may have an M.sub.z of >300 kg/mol, preferably >400 kg/mol, such as >300 and <700 kg/mol, preferably >400 and <650 kg/mol. Such characteristics of M.sub.w, M.sub.z and/or M.sub.n may contribute to the improved stretchability of the film.

[0025] The high-density polyethylene in the first film may for example have a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg, preferably 0.5 and 5.0 g/10 min, preferably 0.5 and 3.0 g/10 min, more preferably 0.8 and 3.0 g/10 min, even more preferably 1.0 and 3.0 g/10 min, even more preferably 1.0 and 2.5 g/10 min.

[0026] The first film may for example comprise 80.0 wt %, preferably 90.0 wt %, more preferably 95.0 wt %, even more preferably 98.0 wt %, of the polyethylene.

[0027] The polyethylene copolymer (I) preferably has a density of 870 and910 kg/m.sup.3, preferably of 880 and 910 kg/m.sup.3, more preferably of 890 and 910 kg/m.sup.3, even more preferably of 895 and 905 kg/m.sup.3. The use of a polyethylene copolymer having such density contributes to improved sealing.

[0028] The polyethylene copolymer (I) preferably has a fraction of material that is eluted in a-TREF at a temperature of 30.0 C. of 5.0 wt % with regard to the total weight of the polyethylene, preferably 7.5 wt %, more preferably 10.0 wt %, even more preferably 11.5 wt %. Preferably, the polyethylene copolymer (I) has a fraction of material that is eluted in a-TREF at a temperature of 30.0 C. of 5.0 wt % and 25.0 wt %, more preferably 7.5 wt % and 20.0 wt %, even more preferably 10.0 wt % and 20.0 wt %, even more preferably 11.0 wt % and 15.0 wt %, with regard to the total weight of the polyethylene. The use of a polyethylene copolymer having such a fraction of material that is eluted in a-TREF at a temperature of 30.0 C. contributes to a reduction of the seal initiation temperature.

[0029] The polyethylene copolymer (I) preferably has a shear storage modulus G determined at a shear loss modulus G=5000 Pa of >1000 Pa, preferably >1100 Pa, more preferably >1200 Pa, even more preferably >1300 Pa. The use of a polyethylene copolymer having such shear storage modulus G at a shear loss modulus of 5000 Pa contributes to improved processability of the film.

[0030] For determination of the shear storage modulus G and the shear loss modulus G, specimens may be used as prepared in accordance with ISO 17855-2 (2016). The DMS measurements were carried out according to ISO 6721-10 (2015) at 190 C. Determination of G at G=5000 Pa may be done by preparation of a double-logarithmic Cole-Cole plot of G and G, where above and below G=5000 Pa, each 2 data points are to be selected, so in total 4 data points, and a first order line may be determined, where from this line G at G=5000 Pa is determined.

[0031] The polyethylene copolymer (I) preferably has a melt mass-flow rate, determined at 190 C. under a load of 2.16 kg (MFR2), in accordance with ASTM D1238 (2013), of 0.2 and 4.0 g/10 min, preferably 0.5 and 3.0 g/10 min, more preferably 0.5 and 2.5 g/10 min. Such polyethylene copolymer allows for manufacturing of films with appropriate melt stability and processability.

[0032] The polyethylene copolymer (I) may for example have a chemical composition distribution broadness (CCDB) of 15.0, preferably 20.0, wherein the CCDB is determined according to formula I:

[00001]$\begin{array}{cc}\mathrm{CCDB}=\frac{T_{z+2}-T_{n-2}}{T_{n-2}}*100& \mathrm{formula}I\end{array}$ [0033] wherein [0034] T.sub.n2 is the moment calculated according to the formula II:

[00002]$\begin{array}{cc}{T}_{n-2}=\frac{.Math.\frac{w\left(i\right)}{{T\left(i\right)}^2}}{.Math.\frac{w\left(i\right)}{{T\left(i\right)}^3}}& \mathrm{formula}\mathrm{II}\end{array}$ [0035] and [0036] T.sub.z+2 is the moment calculated according to the formula III:

[00003]$\begin{array}{cc}{T}_{z+2}=\frac{.Math.w\left(i\right).Math.{T\left(i\right)}^4}{.Math.w\left(i\right).Math.{T\left(i\right)}^3}& \mathrm{formula}\mathrm{III}\end{array}$ [0037] wherein [0038] w(i) is the sampled weight fraction in wt % with regard to the total sample weight in a-TREF analysis of a sample (i) taken at temperature T(i), where T(i) >30 C., the area under the a-TREF curve being normalised to surface area=1 for T(i)>30 C.; and [0039] T(i) is the temperature at which sample (i) is taken in a-TREF analysis, in C.

[0040] The polyethylene copolymer (i) may for example have a CCDB of 15.0, preferably 17.5, more preferably 20.0. For example, the polyethylene copolymer (I) may have a CCDB of 15.0 and 30.0, preferably 17.5 and 25.0, more preferably 20.0 and 25.0, or 20.0 and 30.0. The use of a polyethylene copolymer having such CCDB contributes to an improved seal strength.

[0041] It is preferred that the first film is oriented is both machine and transverse direction in the solid state, preferably wherein the first film is oriented at a drawing ratio of 3.0, preferably 3.0 and 15.0 in the machine direction, and/or at a drawing ratio of 3.0, preferably 3.0 and 15.0 in the transverse direction, wherein the drawing ratio is defined as the dimension of the film in the particular direction after being subjected to the orientation step, divided by the dimension of the film in the particular direction prior being subjected to the orientation step.

[0042] In the laminate polyethylene film according to the present invention, the second film may for example be a single-layer or a multi-layer film obtained by multi-layer melt co-extrusion.

[0043] The sealing layer comprised in the second film may for example comprise the polyethylene copolymer (I), linear low-density polyethylene (LLDPE) (II) and optionally low-density polyethylene (LPDE) (Ill), preferably wherein the sealing layer comprises 10.0 wt %, preferably 20.0 wt %, more preferably 40.0 wt %, of the polyethylene copolymer (I). It is preferred that the sealing layer comprises 20.0 wt % and 80.0 wt % of the polyethylene copolymer (I), 10.0 wt % and 70.0 wt % of the LLDPE (II), and 20.0 wt % of the LDPE (III), with regard to the total weight of the sealing layer. More preferably, the sealing layer comprises 30.0 wt % and 80.0 wt % of the polyethylene copolymer (I), 10.0 wt % and 70.0 wt % of the LLDPE (II), and 15.0 wt % of the LDPE (III), with regard to the total weight of the sealing layer. Even more preferably, the sealing layer comprises 50.0 wt % and 80.0 wt % of the polyethylene copolymer (I), 10.0 wt % and 50.0 wt % of the LLDPE (II), and 15.0 wt % of the LDPE (III), with regard to the total weight of the sealing layer. Yet even more preferably, the sealing layer comprises 50.0 wt % and 80.0 wt % of the polyethylene copolymer (I), 10.0 wt % and 45.0 wt % of the LLDPE (II), and 5.0 and 15.0 wt % of the LDPE (III), with regard to the total weight of the sealing layer. Yet even more preferably, the sealing layer comprises 60.0 wt % and 80.0 wt % of the polyethylene copolymer (I),10.0 wt % and 35.0 wt % of the LLDPE (II), and 5.0 and 15.0 wt % of the LDPE (III), with regard to the total weight of the sealing layer.

[0044] In such embodiments of the invention wherein the second film is a multi-layer film, the second film may for example comprise a first layer, optionally a second layer, and a sealing layer. It is preferred that the second film is adhered to the first film with that surface of the second film formed by the first layer. The first layer and/or the second layer may for example comprise LLDPE (II) and optionally LDPE (III), preferably 80.0 wt % of the LLDPE (II), with regard to the total weight of the first layer, more preferably the first layer comprises the LLDPE (II) and the optional LDPE (III) as the only polymer materials in the particular layer. The LLDPE (II) in the first layer and the LLDPE (II) in the sealing layer may be the same or different, and/or the LDPE (III) in the first layer and the LDPE (III) in the sealing layer may be the same or different.

[0045] The LLDPE (II) may for example be a polyethylene copolymer comprising moieties derived from ethylene and moieties derived from one or more of 1-butene, 1-hexene and 1-octene, preferably 75.0 wt % of moieties derived from ethylene and/or 25.0 wt % of moieties derived from one or more of 1-butene, 1-hexene and 1-octene, with regard to the total weight of the LLDPE (II), preferably wherein the LLDPE (II) has a density of 910 and 940 kg/m.sup.3 and a melt mass-flow rate of 0.2 and 5.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg.

[0046] The LDPE (III) may for example be an ethylene polymer obtained by free-radical polymerisation, preferably high-pressure free-radical polymerisation, and has a density of 910 and 940 kg/m.sup.3, preferably of 920 and 930 kg/m.sup.3, and a melt mass-flow rate of 0.2 and 15 5.0 g/10 min, preferably of 0.4 and 2.0 g/10 min, as determined in accordance with ASTM D1238 (2013) at a temperature of 190 C. under a load of 2.16 kg.

[0047] It is also preferred that the first and the second film of the laminate polyethylene film comprise no polymer materials other than polymers comprising only polymer moieties derived from ethylene and mono-olefins comprising 3 and 12 carbon atoms.

[0048] The first film may for example have a thickness of 10 and 150 m, preferably of 10 and 100 m, more preferably 20 and 70 m. The second film may for example have a thickness of 10 and 150 m, preferably 10 and 100 m, more preferably 20 and 70 m. The laminated polyethylene film may for example have a thickness of 20 and 300 m, preferably of 40 and 200 m, more preferably 60 and 150 m.

[0049] The present invention, in a certain embodiment, also relates to a package comprising the laminate polyethylene film. For example, the package may be a heat-sealed bag.

[0050] The invention also relates in certain of its embodiments to a process for manufacturing a sealed bag, the process involving subjecting an assembly comprising a first and a second part of the laminate polyethylene film assembled so that both sealing layers face each other, and subjecting at least a part the assembly to an energy treatment, such as a heat treatment, whilst pressing the parts together so that, termination of the energy treatment, a seal is formed closing the assembly so as to form a sealed bag.

[0051] The invention will now be illustrated by the following non-limiting examples.

[0052] The following materials were used in the examples demonstrating the present invention:

TABLE-US-00001 BOPE SABIC LLDPE BX202, MFR2: 2.1 g/10 min; density: 921 kg/m.sup.3 Polyethylene SABIC COHERE S100L, MFR2: 1.0 g/10 min; copolymer density 900 kg/m.sup.3 (Co-PE) (I) LLDPE (II) SABIC 118WJ, MFR2: 1.0 g/10 min; density 918 kg/m.sup.3 LDPE (III) SABIC HP0823, MFR2: 0.8 g/10 min; density 923 kg/m.sup.3 Wherein the MFR2 is the melt mass flow rate as determined in accordance with ASTM D1238
(2013) ata temperature of 190 C. under a load of 2.16 kg, and the density is as determined in accordance with ASTM D792 (2008).

[0053] First film: A bi-directionally oriented (BOPE) film was produced as 3-layer film using the BOPE material as above. The bi-directionally oriented film was produced in a cast film production line with subsequent sequential biaxial orientation. A set-up comprising three melt extruders was used, where an extruder A supplied material for a first skin layer A, an extruder B supplied material for inner layer B, and an extruder C supplied the material for the second skin layer C. The extruders were positioned such that the molten material was forced through a t-shaped die with a die gap of 3.0 mm, so that the arrangement of the layers in the obtained cast film was A/B/C. Each of the extruders A, B and C was operated such to supply molten polymer material at a temperature of 260 C. The die temperature was 260 C.

[0054] The film as extruder through the t-shaped die was cast onto a chill roll to form a cast film having a thickness of about 840 m.

[0055] The chilled cast film was subjected to stretching in the machine direction using a set of stretching rolls at a temperature of 98 C., followed by an annealing at 80 C., to induce a degree of stretching in the machine direction of 4.6.

[0056] Subsequently, the film was stretched in the transverse direction to a degree of stretching of 9.0 by subjecting the film to heat whilst applying a stretching force, wherein the film was passed through an oven through which the film was continuously transported, wherein the temperature was 140 C. at the entering zone of the oven, decreasing to 100 C. towards the exit of the oven. The skin layer C was subsequently subjected to a corona treatment of 25 W.Math.min/m.sup.2. Bi-directionally oriented 3-layer films having a thickness of 30 m were obtained.

[0057] Second film: 3-layer blown films were produced according to the layer formulations as exhibited in the table below. The films were produced using a Wuhan Jingji blown film line. The obtained film has a thickness of 50 m, and a layer distribution A/B/C of 1/2/1 (weight ratio). Layer A was the first layer, layer B the second layer, and layer C the sealing layer. The layer A was subjected to a corona treatment. The blow-up ratio was 2.5 for all blown films as produced. The line was operated at a line speed of 17 m/min, using an extruder temperature profile for each of the zones and a speed in RPM as indicated below:

TABLE-US-00002 Extruder Zone temperature ( C.) speed Extruder I II III IV V VI RPM A 175 190 190 190 190 185 50 B 175 190 190 190 190 185 53 C 175 190 190 190 190 185 60

[0058] Formulations for blown films:

TABLE-US-00003 Formulation (in wt % w.r.t. weight of layer) Blown Film Layer Co-PE (I) LLDPE (II) LDPE (III) B1 A 80 20 B 80 20 C 90 10 B2 A 80 20 B 80 20 C 20 70 10 B3 A 80 20 B 80 20 C 40 50 10 B4 A 80 20 B 80 20 C 70 20 10

[0059] Using the BOPE films and the above produced blown films B1-B4, laminates were produced using a Nordmeccanica simplex solventless laminator, using Henkel Loctite Liofol LA7758/LA6011 as solventless adhesive. Laminates were formed by adhering layer A of the second film to the BOPE film. Properties of the obtained laminates were determined, the results of which are presented below.

TABLE-US-00004 Sample L1 L2 L3 L4 Structure BOPE/B1 BOPE/B2 BOPE/B3 BOPE/B4 Secant modulus 1% 296 308 297 284 (MD) (MPa) Tensile strength at 30.7 29.9 29.8 29.9 break (MD) (N/mm.sup.2) Elongation at break 254 257 273 251 (MD) (%) Puncture force at 191 187 187 203 break (N) Puncture energy at 3.1 3.1 3.1 3.3 break (J) Dart impact resistance 6.9 7.6 8.1 7.3 (g/m) Tear resistance (MD) 1.6 1.4 1.4 1.2 (g/m) Tear resistance (TD) 1.4 1.3 1.2 1.2 (g/m) Flex crack resistance 4.5 6.8 6.5 5.5

[0060] Wherein: [0061] The secant modulus is the 1% secant modulus as determined in accordance with ASTM D882 (2012); [0062] The tensile strength at break is determined in accordance with ASTM D882 (2012) at room temperature using an initial sample length of 50 mm and a testing speed of 500 mm/min; [0063] The elongation at break is determine in accordance with ASTM D882 (2012) at room temperature using an initial sample length of 50 mm and a testing speed of 500 mm/min; [0064] The puncture force at break and puncture energy at break were determined in accordance with ASTM D5748-95 (2012); [0065] The dart impact resistance is determined as impact failure weight in accordance with ASTM D1709 (2016), method B, at room temperature, expressed in grams per unit of film thickness; [0066] The tear resistance is determined as Elmendorf tear resistance in accordance with ASTM D1922 (2015); [0067] The flex crack resistance is presented as the pinhole count occurring on a sample per 300 cm.sup.3 after 21600 cycles when tested in accordance with ASTM F392-93 (2004); [0068] MD indicates machine direction, i.e. the direction in which the film is extruded in the cast film extrusion process, TD indicates transverse direction, i.e. the direction perpendicular to the machine direction.

[0069] Furthermore, a number of sealing properties were determined as set out below.

[0070] The heat seal strength was determined in accordance with ASTM F88, using method A, on specimens of 15 mm width. Fin-seals were prepared according to ASTM F2029 at different temperatures. Two samples of the same film were compressed together, with layer C of the first film sample contacting layer C of the second film sample. Seals were produced by applying a force of 3.0 bar for 0.5 sec, wherein the films were protected with a 12 m BOPET sheet. The press used for preparing the seal was heated to various temperatures to identify the strength of the seal when produced at different temperatures.

[0071] The seal strength was tested using a tensile testing machine with a testing speed of 200 mm/min, and a grip distance of 10 mm. The maximum load was recorded as the seal strength.

[0072] The results of seal strength testing of films of the various above examples, sealed at varying temperatures, are presented in the table below.

TABLE-US-00005 Seal strength at Example 80 C. 85 C. 90 C. 95 C. 100 C. 105 C. 110 C. 115 C. 120 C. L1 0 0 0 0 0 2 4 22 26 L2 0 0 1 2 4 19 23 24 29 L3 0 1 2 6 18 21 23 25 31 L4 4 10 17 18 22 24 27 31 32

[0073] Further, the hot tack strength of the films was determined. Determination thereof was conducted in accordance with ASTM F1921, method B on 15 mm width specimens, with layer C against layer C. The seal pressure was 0.3 N/mm.sup.2, and the dwell time 0.5 sec. The delay time was 300 ms and the clamp separation rate was 200 mm/s. The hot tack strength is expressed in N/15 mm width.

TABLE-US-00006 Hot tack strength at Example 70 C. 80 C. 90 C. 100 C. 110 C. 120 C. 130 C. 140 L1 0.2 0.6 1.5 2.7 2.0 1.3 L2 0.3 2.2 2.4 2.8 2.1 1.5 1.1 L3 0.5 2.4 2.3 2.4 2.5 1.8 1.3 L4 0.4 2.5 3.3 3.7 3.4 3.1 1.9 1.3