Film for silage packaging

Abstract

The present invention relates to a multi-layer blown film comprising at least three layers, being: (a) a first outer layer; (b) a core layer; and (c) a second outer layer; wherein the layers are present in this order; wherein the layer (a) comprises an ethylene-based polymer (A) having a density of ≤ 890 kg / m3, preferably of ≥ 850 and ≤ 890 kg / m3, as determined in accordance with ASTM D792 (2013), and a melt mass-flow rate of ≥ 0.5 and ≤ 8.0 g / 10 min, preferably of ≥ 0.5 and ≤ 5.0 g / 10 min, as determined in accordance with ASTM D1238 (2013) at 190°C and 2.16 kg load; wherein the layer (b) comprises or consists of a linear low-density polyethylene (LLDPE); and wherein the layer (c) comprises or consist of a low-density polyethylene (LDPE). Such film provides a mono-material solution for silage packaging having low noise generation during unwinding of reels, low peel off force, high ultimate elongation, good puncture resistance, and high cling force.

Description

24POLYOQ88-WO-ORD 1Film for silage packaging.

[0001] The present invention relates to a film for silage packaging.

[0002] In the realm of agricultural preservation, polyethylene films have emerged as a pivotal player in the silage packaging industry. These films, meticulously engineered from linear low- density polyethylene (LLDPE), high-density polyethylene (HDPE) or low-density polyethylene (LDPE) polymers, possess a unique set of properties that make them indispensable for optimizing the conservation and longevity of silage.

[0003] A function of polyethylene films in silage packaging is to create an airtight seal, thereby minimizing the entry of atmospheric oxygen into the silage mass. Oxygen, a notorious enemy of silage, facilitates the growth of spoilage microorganisms, which can drastically decrease the nutritional value and palatability of the silage. By obstructing oxygen intrusion, polyethylene films contribute significantly to maintaining the desired anaerobic conditions within the silage.

[0004] Additionally, these films offer remarkable resistance to UV radiation and water penetration. UV radiation can cause polymer degradation and thus compromise the film's integrity, leading to potential leaks and premature aging. Water penetration can dilute the silage, potentially leading to clumping and uneven feeding. Polyethylene films effectively shield the silage from these external factors, ensuring optimal preservation conditions.

[0005] Furthermore, their flexibility, strength, and adaptability to various silage densities and volumes make polyethylene films a versatile and cost-effective solution for silage packaging. The films can be manufactured in various thicknesses and sizes, catering to the specific needs of different agricultural operations.

[0006] Accordingly, the use of polyethylene films in silage packaging provides an airtight seal, resistance to UV radiation and water penetration, and adaptability to different silage densities and volumes, all of which are crucial factors in preserving the quality and nutritional value of silage for livestock feed.

[0007] Polyethylene films for silage packaging, herein also referred to as silage films, may be produced by blown film production technology.24POLYOQ88-WO-ORD 2

[0008] For use in silage packaging applications, polymer films are to deliver a certain balance of properties, including low noise generation during unwinding of reels, low peel off force, high ultimate elongation, good puncture resistance, and high cling force. In addition, it is beneficial that such films are so-called mono-material films; that is, they desirably are to contain no other polymers than polymer materials from a single genus of polymers, such as polyethylene-type polymers. Such mono-material film solutions are much easier to recycle than films comprising polymer materials of very different nature, such as when polyesters, polyamides and polyolefins are combined in a single film solution.

[0009] According to the present invention, such objective is now achieved by multi-layer blown film comprising at least three layers, being:(a) a first outer layer;(b) a core layer; and(c) a second outer layer; wherein the layers are present in this order; wherein the layer (a) comprises an ethylene-based polymer (A) having a density of < 890 kg / m3, preferably of > 850 and < 890 kg / m3, as determined in accordance with ASTM D792 (2013), and a melt mass-flow rate of > 0.5 and < 8.0 g / 10 min, preferably of > 0.5 and < 5.0 g / 10 min, as determined in accordance with ASTM D1238 (2013) at 190°C and 2.16 kg load; wherein the layer (b) comprises or consists of a linear low-density polyethylene (LLDPE); and wherein the layer (c) comprises or consist of a low-density polyethylene (LDPE).

[0010] The ethylene-based polymer (A) may for example be a copolymer of ethylene and a comonomer selected from 1 -butene, 1 -hexene and 1 -octene, preferably wherein the comonomer is 1-butene or 1-octene; and preferably wherein the ethylene-based comprises > 20.0 and < 45.0 wt% of moieties derived from the comonomer, more preferably > 25.0 wt% and < 40.0 wt%, even more preferably > 30.0 and < 40.0 wt%.

[0011] The ethylene-based polymer (A) may for example have a melt mass-flow rate of > 0.5 and < 3.0 g / 10 min, preferably of > 0.5 and < 2.0 g / 10 min, more preferably of > 0.5 and < 1.5 g / 10 min, as determined in accordance with ASTM D1238 (2013) at 190°C and 2.16 kg load. Alternatively, the ethylene-based polymer (A) may for example have a melt mass-flow rate of >24POLYOQ88-WO-ORD 33.5 and < 8.0 g / 10 min, preferably of > 4.0 and < 7.0 g / 10 min, more preferably of > 4.0 and < 6.0 g / 10 min, as determined in accordance with ASTM D1238 (2013) at 190°C and 2.16 kg load.

[0012] The ethylene-based polymer (A) may for example have a fraction eluting in a-TREF at < 30°C of > 95.0 wt%.

[0013] The layer (a) may for example comprise > 40 wt%, preferably > 40.0 and < 90.0 wt% of the ethylene-based polymer (A), preferably > 50.0 and < 80.0 wt%, more preferably > 50.0 and < 70.0 wt%, with regard to the total weight of the layer (a), or the layer (a) may consists of the ethylene-based polymer (A).

[0014] The layer (a) may for example comprise an ethylene-based polymer (B), wherein the ethylene-based polymer (B) has a density of < 905 kg / m3, preferably of > 870 and < 905 kg / m3, more preferably of > 890 and < 905 kg / m3, and a melt mass-flow rate of > 0.5 and < 5.0 g / 10 min; preferably, wherein the ethylene-based polymer (A) and the ethylene-based polymer (B) are different.

[0015] The ethylene-based polymer (B) may for example have a melt mass-flow rate of > 0.5 and < 3.0 g / 10 min, preferably of > 0.5 and < 2.0 g / 10 min, even more preferably of > 0.5 and < 1.8 g / 10 min.

[0016] The ethylene-based polymer (B) may for example have has a fraction eluting in a-TREF at < 30°C of < 15.0 wt%, preferably of > 8.0 wt% and < 15.0 wt%, more preferably of > 11.0 wt% and < 15.0 wt%.

[0017] The layer (a) may for example comprise > 10.0 and < 60.0 wt% of the ethylene-based polymer (B), preferably > 20.0 and < 50.0 wt%, more preferably > 30.0 and < 50.0 wt%, with regard to the total weight of or the layer (a).

[0018] Alternatively, the layer (a) may comprise, or consist of, > 75.0 and < 95.0 wt% of the ethylene-based polymer (A) and > 5.0 and < 25.0 wt% of the ethylene-based polymer (B), with regard to the total weight of the layer (a); preferably, > 75.0 and < 90.0 wt% of the ethylenebased polymer (A) and > 10.0 and < 25.0 wt% of the ethylene-based polymer (B); more preferably, > 75.0 and < 85.0 wt% of the ethylene-based polymer (A) and > 15.0 and < 25.0 wt% of the ethylene-based polymer (B).24POLYOQ88-WO-ORD 4

[0019] In an embodiment, the ethylene-based polymer (A) may have a density of > 850 and < 870 kg / m3and the ethylene-based polymer (B) may have a density of > 890 and < 905 kg / m3, preferably of > 895 and < 905 kg / m3.

[0020] In an embodiment, the ethylene-based polymer (A) may have a melt mass-flow rate of > 2.0 and < 8.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 2.0 g / 10 min; preferably, the ethylene-based polymer (A) has a melt mass-flow rate of > 3.0 and < 8.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 2.0 g / 10 min; more preferably, the ethylene-based polymer (A) has a melt mass-flow rate of > 3.0 and < 6.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 1.8 g / 10 min; even more preferably, the ethylenebased polymer (A) has a melt mass-flow rate of > 4.0 and < 6.0 g / 10 min, and the ethylenebased polymer (B) of > 0.5 and < 1 .8 g / 10 min.

[0021] In an embodiment, the layer (a) may comprise, or consist of, > 75.0 and < 95.0 wt% of the ethylene-based polymer (A) and > 5.0 and < 25.0 wt% of the ethylene-based polymer (B), with regard to the total weight of the layer (a); preferably, > 75.0 and < 90.0 wt% of the ethylenebased polymer (A) and > 10.0 and < 25.0 wt% of the ethylene-based polymer (B); more preferably, > 75.0 and < 85.0 wt% of the ethylene-based polymer (A) and > 15.0 and < 25.0 wt% of the ethylene-based polymer (B); wherein the ethylene-based polymer (A) may have a density of > 850 and < 870 kg / m3and the ethylene-based polymer (B) may have a density of > 890 and < 905 kg / m3, preferably of > 895 and < 905 kg / m3; wherein the ethylene-based polymer (A) may have a melt mass-flow rate of > 2.0 and < 8.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 2.0 g / 10 min; preferably, the ethylene-based polymer (A) has a melt mass-flow rate of > 3.0 and < 8.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 2.0 g / 10 min; more preferably, the ethylene-based polymer (A) has a melt mass-flow rate of > 3.0 and < 6.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 1.8 g / 10 min; even more preferably, the ethylene-based polymer (A) has a melt mass-flow rate of > 4.0 and < 6.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 1.8 g / 10 min.

[0022] In a particular embodiment, the layer (a) may comprise, or consist of, > 75.0 and < 85.0 wt% of the ethylene-based polymer (A) and > 15.0 and < 25.0 wt% of the ethylene-based polymer (B), with regard to the total weight of the layer (a), wherein the ethylene-based polymer (A) may have a density of > 850 and < 870 kg / m3and the ethylene-based polymer (B) may have a density of > 895 and < 905 kg / m3, and wherein the ethylene-based polymer (A) has a melt24POLYOQ88-WO-ORD 5 mass-flow rate of > 4.0 and < 6.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 1.8 g / 10 min.

[0023] The LLDPE may for example have a density of > 910 and < 930 kg / m3and a melt massflow rate at 190°C / 2.16 kg of > 0.5 and < 2.0 g / 10 min.

[0024] The LLDPE may for example be a copolymer of ethylene and a comonomer selected from 1-butene, 1-hexene and 1-octene, preferably 1-hexene; preferably wherein the LLDPE comprises > 5.0 and < 20.0 wt% of moieties derived from the comonomer, more preferably > 5.0 and < 15.0 wt%, with regard to the total weight of the LLDPE.

[0025] The LDPE may for example have a density of > 915 and < 930 kg / m3and a melt massflow rate of > 0.5 and < 5.0 g / 10 min, preferably of > 1.0 and < 3.0 g / 10 min.

[0026] The LDPE may for example have an Mw / Mnof > 8.0, preferably of > 8.0 and < 15.0, more preferably of > 8.0 and < 11.0.

[0027] In an embodiment of the invention, the film consists of the three layers (a), (b) and (c).

[0028] The film may for example have a thickness of > 5 and < 250 pm, preferably of > 10 and < 200 pm, more preferably of > 10 and < 100 pm, even more preferably of > 10 and < 50 pm.

[0029] In an embodiment, the film comprises:• > 5.0 and < 25.0 wt%, preferably > 10.0 and < 20.0 wt%, of the layer (a);• > 50.0 and < 90.0 wt%, preferably > 60.0 and < 80.0 wt%, of the layer (b); and / or• > 5.0 and < 25.0 wt%, preferably > 10.0 and < 20.0 wt%, of the layer (c); with regard to the total weight of the film.

[0030] The invention also relates to a package comprising goods, wherein the goods are wrapped with the film according to the invention. In an embodiment, the package comprises silage.

[0031] The invention also related to the use of the film according to the invention to improve the puncture resistance and / or the cling force and / or the peel-off force of a silage package.24PGLY0088-WG-ORD 6

[0032] 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 equipped with stainless steel columns having a length of 15 cm and an internal diameter of 7.8 mm, 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 may be performed with a heating rate of 1°C / min from 30°C to 140°C. The set-up may be cleaned at 150°C. The sample injection volume may be 300 pl, and the pump flow rate during elution 0.5 ml / min. The volume between the column and the detector may be 313 pl. The fraction that is eluted at a temperature of <30.0°C may in the context of the present invention be calculated by subtracting the sum of the fraction eluted >30.0°C from 100%, thus the total of the fraction eluted < 30.0°C, and the fraction eluted >30.0°C to add up to 100.0 wt%.

[0033] 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 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.

[0034] In the context of the present invention, the SCB quantity is determined via infrareddetection gel permeation chromatography (GPC-IR). GPC-IR analysis may for example be performed using a chromatographer, such as a Polymer Char GPC-IR system, equipped with three columns of internal diameter 7.5 mm and 300 mm length, packed with of particles of 13 pm average particle size, such as Polymer Laboratories 13pm PLgel Olexis, operating at 160°C, equipped with an MCT IR detector, wherein 1 ,2,4-trichlorobenzene stabilised with 1 g / l butylhydroxytoluene may be used as eluent at a flow rate of 1 ml / min, with a sample concentration of 0.7 mg / ml and an injection volume of 200 pl, with molar mass being determined based on the universal GPC principle using a calibration made with PE narrow and broad standards in the range of 0.5-2800 kg / mol, Mw / Mn - 4 to 15 in combination with known Mark24POLY0088-WO-ORD 7Houwink constants of PE-calibrant alfa = 0.725 and log K = -3.721. Short chain branching content was determined via IR determination of the intensity ratio of CH3 (ICHS) to CH2 (ICH2) coupled with a calibration curve. The calibration curve is a plot of SCB content (XSCB) as a function of the intensity ratio of ICH3 / ICH2- TO obtain a calibration curve, a group of polyethylene resins (no less than 5) (SCB Standards) were used. All these SCB Standards have known SCB levels and flat SCBD profiles. Using SCB calibration curves thus established, profiles of short chain branching distribution across the molecular weight distribution can be obtained for resins fractionated by the IR5-GPC system under exactly the same chromatographic conditions as for these SCB standards. A relationship between the intensity ratio and the elution volume is converted into SCB distribution as a function of MWD using a predetermined SCB calibration curve (i.e., intensity ratio of ICH3 / ICH2 VS. SCB content) and MW calibration curve (i.e., molecular weight vs. elution time) to convert the intensity ratio of ICH3 / ICH2 and the elution time into SCB content and the molecular weight, respectively.

[0035] The invention will now be illustrated by the following non-limiting examples.

[0036] In the context of the present invention, the below materials were used in the experiments.Table 1 : Materials used.24POLY0088-WO-ORD 8Table 2: Properties of materials

[0037] The Mnis the number-average molecular weight, the Mwis the weight-average molecular weight, and the Mzis the z-average molecular weight, as determined in accordance with ASTM D6474 (2012), expressed in kg / mol.

[0038] The IVWis the weight-average intrinsic viscosity, expressed in dl / g, determined via SizeExclusion Chromatography coupled to differential viscometry (SEC-DV), following ASTM D6474 (2012). The intrinsic viscosity as function of elution volume is determined by using differential viscosity detector in combination with a concentration detector.

[0039] The soluble fraction is the fraction eluting in a-TREF, when performed in accordance with the method of the description, at temperatures < 30°C, in wt%.

[0040] Defining the comonomer, C6 indicates the comonomer to be 1-hexene, C8 it to be 1- octene. The comonomer content was determined via13C-NMR.24POLY0088-WO-ORD 9

[0041] The SCB is the content of short chain branches as determined via the method of the description, expressed in branches per 1000 carbon atoms of the polymer molecules ( / 1000C). The CH3 end group content was determined via SEC-DV with and IR5 infrared detector, in accordance with ASTM D6474 (2012), expressed in groups per 1000 carbon atoms of the polymer molecules ( / 1000C).

[0042] Using the above materials, a number of blown 3-layer films were produced according to the film structure on the table below. Table 3: Film Structure

[0043] In a first trial, a number of films of above structure were produced using a multilayer Colin blown film pilot line, equipped with single screw extruders between 35 and 45 mm and an L / D of 30. The extrusion was run at a throughput of 20 kg / h and a blow-up ratio of 3.0. The coextruded film samples had a thickness of 25 pm. The formulation of the cling layer for each of the experimental films was as per below.Table 4: Formulation of cling layers, experiments 1-1124POLY0088-WO-ORD 10

[0044] The films as produced per above were tested to evaluate the achievement of appropriate cling properties at 0% stretch and at 200% stretch. Cling force was tested according to ASTM D5458 - 95 (Re 2012). From these tests, it appeared that the cling force of the films 1-5 was not sufficient at both stretch conditions.

[0045] Subsequently, a number of trials were performed on a commercial-scale multilayer blown film extrusion line, running at a throughput of 300 kg / h and 68 m / min. The line was equipped with an internal bubble cooling, operating at 10°C. Again, 3-layer films were produced having the cling / core / release structure as presented in the table above, wherein the formulation of the cling layer for each film was as in the next table.Table 5: Formulation of cling layers, experiments 12-23

[0046] Of the films produced as per above, a number of film properties were tested as in the table below.Table 6: Film properties.24POLY0088-WO-ORD 11

[0047] The above tests were performed using an ESTL FTP-750 testing machine. The cling force is expressed in N, at 0% strain and at 100% strain; the unwind force is expressed in N; the puncture energy is expressed in J; the peel off force is expressed in N; the ultimate elongation force is expressed %; the sound is the sound level in dB on peel-off. Some selected samples were also tested after conditioning at 30°C for 6 hours for sound level and peel-off force.

[0048] From the above, it can be observed that all films as produced exhibited a desirable low sound level of below 100 dB, even after conditioning at increased temperature.

Claims

24POLYOQ88-WO-ORD 12Claims1. Multi-layer blown film comprising at least three layers, being:(a) a first outer layer;(b) a core layer; and(c) a second outer layer; wherein the layers are present in this order; wherein the layer (a) comprises an ethylene-based polymer (A) having a density of < 890 kg / m3, preferably of > 850 and < 890 kg / m3, as determined in accordance with ASTM D792 (2013), and a melt mass-flow rate of > 0.5 and < 8.0 g / 10 min, preferably of > 0.5 and < 5.0 g / 10 min, as determined in accordance with ASTM D1238 (2013) at 190°C and 2.16 kg load; wherein the layer (b) comprises or consists of a linear low-density polyethylene (LLDPE); and wherein the layer (c) comprises or consist of a low-density polyethylene (LDPE).

2. Film according to claim 1 , wherein the ethylene-based polymer (A) is a copolymer of ethylene and a comonomer selected from 1 -butene, 1 -hexene and 1 -octene, preferably wherein the comonomer is 1 -butene or 1 -octene; and preferably wherein the ethylenebased comprises > 20.0 and < 45.0 wt% of moieties derived from the comonomer, more preferably > 25.0 wt% and < 40.0 wt%, even more preferably > 30.0 and < 40.0 wt%.

3. Film according to any one of claims 1-2, wherein the ethylene-based polymer (A) has a fraction eluting in a-TREF at < 30°C of > 95.0 wt%.

4. Film according to any one of claims 1-3, wherein the layer (a) comprises an ethylenebased polymer (B), wherein the ethylene-based polymer (B) has a density of < 905 kg / m3, preferably of > 870 and < 905 kg / m3, more preferably of > 890 and < 905 kg / m3, and a melt mass-flow rate of > 0.5 and < 5.0 g / 10 min; preferably, wherein the ethylene-based polymer (A) and the ethylene-based polymer (B) are different.24POLYOQ88-WO-ORD 135. Film according to claim 4, wherein the ethylene-based polymer (B) has a fraction eluting in a-TREF at < 30°C of < 15.0 wt%, preferably of > 8.0 wt% and < 15.0 wt%, more preferably of > 11.0 wt% and < 15.0 wt%.

6. Film according to any one of claims 4-5, wherein the layer (a) comprises, or consists of, > 75.0 and < 85.0 wt% of the ethylene-based polymer (A) and > 15.0 and < 25.0 wt% of the ethylene-based polymer (B), with regard to the total weight of the layer (a), wherein the ethylene-based polymer (A) has a density of > 850 and < 870 kg / m3and the ethylenebased polymer (B) has a density of > 895 and < 905 kg / m3, and wherein the ethylenebased polymer (A) has a melt mass-flow rate of > 4.0 and < 6.0 g / 10 min, and the ethylene-based polymer (B) of > 0.5 and < 1.8 g / 10 min.

7. Film according to any one of claims 1-6, wherein the LLDPE has a density of > 910 and < 930 kg / m3and a melt mass-flow rate at 190°C / 2.16 kg of > 0.5 and < 2.0 g / 10 min.

8. Film according to any one of claims 1-7, wherein the LLDPE is a copolymer of ethylene and a comonomer selected from 1-butene, 1-hexene and 1-octene, preferably 1-hexene; preferably wherein the LLDPE comprises > 5.0 and < 20.0 wt% of moieties derived from the comonomer, more preferably > 5.0 and < 15.0 wt%, with regard to the total weight of the LLDPE.

9. Film according to any one of claims 1-8, wherein the LDPE has a density of > 915 and < 930 kg / m3and a melt mass-flow rate of > 0.5 and < 5.0 g / 10 min, preferably of > 1.0 and < 3.0 g / 10 min.

10. Film according to any one of claims 1-9, wherein the LDPE has an Mw / Mn, as determined in accordance with ASTM D6474 (2012), of > 8.0, preferably of > 8.0 and < 15.0, more preferably of > 8.0 and < 11.0.11 . Film according to any one of claims 1-10, wherein the film has a thickness of > 5 and < 250 pm, preferably of > 10 and < 200 pm, more preferably of > 10 and < 100 pm, even more preferably of > 10 and < 50 pm.

12. Film according to any one of claims 1-11 , wherein the film comprises:• > 5.0 and < 25.0 wt%, preferably > 10.0 and < 20.0 wt%, of the layer (a);24POLYOQ88-WO-ORD 14• > 50.0 and < 90.0 wt%, preferably > 60.0 and < 80.0 wt%, of the layer (b); and / or• > 5.0 and < 25.0 wt%, preferably > 10.0 and < 20.0 wt%, of the layer (c); with regard to the total weight of the film.

13. Package comprising goods, wherein the goods are wrapped with the film according to any one of the claims 1-12 to form the package, preferably wherein the package comprises silage.

14. Use of the film according to any one of the claims 1-12 to improve the puncture resistance and / or the cling force and / or the peel-off force of a silage package.

Images