High performance polyethylene film with improved aging properties

Abstract

The present application relates to a high performance polyethylene film with improved aging properties. Specifically, the present application provides a machine oriented film comprising: at least one layer comprising: (a) from 60 to 99.95 wt% of polyethylene, based on the total weight of the layer, the polyethylene having: (i) a density of from 0.910 to 0.930 g / cm3; (ii) a melt index I2 at 190 DEG C and 2.16 kg from 0.1 to 3 g / 10 min; and optionally, (iii) an inflection point in the Van Gurp Palmen curve of the phase angle in degrees of polyethylene relative to the complex modulus in Pa, and (b) 0.05 to 3 wt% of an anti-aging additive, based on the total weight of the layer. The film is composed by longitudinal orientation, in combination with a specific film, achieving significantly improved aging properties.

Description

Technical Field

[0001] The present application relates to a high-performance polyethylene film with improved aging performance. Specifically, the present application provides a machine direction oriented (MDO) film, a method for preparing the machine direction oriented film, a use of the machine direction oriented film, and a method for improving the aging performance of the film. Background Art

[0002] With the continuous advancement of agricultural modernization, the application of agricultural films plays an increasingly important role in improving agricultural production efficiency and protecting the ecological environment. Among the many agricultural film products, greenhouse films and ground films are two common types. Greenhouse films are mainly used to cover greenhouses to regulate temperature, humidity and light, thereby providing a more ideal growth environment for crops. Ground films are widely used to cover the soil surface to inhibit weed growth, maintain soil moisture and increase crop yields.

[0003] However, agricultural films undergo oxidation reactions, chain crosslinking and chain degradation randomly during long-term use due to radiation (mainly ultraviolet radiation), heat, chemicals, etc. As a result, the film becomes brittle, discolored, cracked and damaged as internal stress develops, which significantly affects the integrity of the film and shortens the service life of the film. Therefore, aging / weathering performance has always been a key requirement for consumers and has also been an important aspect for solution design.

[0004] WO2016193186A1 discloses a film comprising a specific multimodal linear low density polyethylene and a tubular or autoclave low density polyethylene, which has been uniaxially stretched in the longitudinal direction. The application discloses that longitudinal stretching can improve dart drop and MD tear properties, but does not mention aging properties.

[0005] WO2018071250A1 discloses an oriented film comprising a linear low density polyethylene polymer and having an improved balance of properties, including improved MD tear strength. The application discloses that longitudinal stretching can improve dart drop and MD tear properties, but does not mention aging properties.

[0006] EP1941999B1 discloses a uniaxially oriented multilayer film comprising at least one of: (i) an outer layer (B) and (ii) an inner layer (C), wherein the layer (B) (i) comprises a multimodal linear low density polyethylene (LLDPE), the layer (C) (ii) comprises at least one polymer component having a Tm≤100°C, the multilayer film being in the form of a uniaxially stretched film in the longitudinal direction at a stretch ratio of at least 1:3. The application discloses that longitudinal stretching can improve mechanical properties, but does not mention aging properties.

[0007] It is therefore an object of the present invention to provide a novel polyethylene film having improved aging properties. Another object of the present invention is to provide a novel method for improving the aging properties of a film. Summary of the invention

[0008] In a first aspect, the present disclosure provides a longitudinally oriented film comprising: at least one layer comprising: (a) 60 to 99.95 weight percent polyethylene, based on the total weight of the layer, the polyethylene having: (i) 0.910 to 0.930 g / cm 3 % of an oxidizing agent, based on the total weight of the layer, wherein the polyethylene further comprises: (iii) an inflection point in the Van GurpPalmen curve of the phase angle in degrees relative to the complex modulus in Pa of the polyethylene; (iv) a shear thinning ratio of greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and (v) a MIR / MWD ratio of greater than or equal to 8, MIR being defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

[0009] In a second aspect, the present disclosure provides a method for preparing a film as described above and below, comprising: utilizing the components of the film to form a precursor film through a blow molding process or a casting process, and after cooling the precursor film to form a crystalline structure, stretching the precursor film in the longitudinal direction to produce the longitudinally oriented film.

[0010] In a third aspect, the present disclosure provides use of a machine direction oriented film as described above and below as an agricultural film.

[0011] In a fourth aspect, the present disclosure provides a method for improving the aging performance of a film, comprising: using the components of the film to form a precursor film through a blow molding process or a casting process, wherein the components of the film are such that the film comprises at least one layer, the layer comprising: (a) 60 to 99.95 weight percent of polyethylene, based on the total weight of the layer, the polyethylene having: (i) 0.910 to 0.930 g / cm 3% of an oriented film; and (ii) a melt index I2 at 190°C and 2.16 kg of 0.1 to 3 g / 10 min, and (b) 0.05 to 3 wt % of an anti-aging additive, based on the total weight of the layer, after cooling the precursor film to form a crystalline structure, stretching the precursor film in the machine direction to produce a machine direction oriented film, wherein the polyethylene also has one or more of the following properties: (iii) an inflection point in the Van Gurp Palmen curve of the phase angle in degrees relative to the complex modulus in Pa of the polyethylene; (iv) a shear thinning ratio greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and (v) a MIR / MWD ratio greater than or equal to 8, MIR being defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

[0012] Surprisingly, it is found that the film of the technical solution of the present application achieves significantly improved aging performance through longitudinal orientation combined with a specific film composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Van GurpPalmen plots of phase angle versus complex modulus are shown for the four polyethylenes used in the Examples.

[0014] Figure 2 The machine direction (MD) tensile strength at break retention after aging is shown for non-oriented monolayer films.

[0015] Figure 3 The machine direction (MD) tensile strength at break retention after aging is shown for machine direction oriented monolayer films.

[0016] Details

[0017] Definition and test methods

[0018] Unless otherwise indicated, room temperature is 25°C.

[0019] An "olefin" is a linear, branched or cyclic compound of carbon and hydrogen having at least one double bond.

[0020] "Polymer" has two or more identical or different monomer (mer) units. "Homopolymer" is a polymer having identical monomer units. The term "polymer" as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc. The term "polymer" as used herein also includes impact, block, graft, random and alternating copolymers. Unless otherwise specifically stated, the term "polymer" shall also include all possible geometric configurations. Such configurations may include isotactic, syndiotactic and random symmetries.

[0021] As used herein, unless otherwise specified, the term "copolymer" refers to a polymer formed by the polymerization of at least two different monomers (i.e., monomer units). For example, the term "copolymer" includes copolymerization products of propylene and α-olefins such as ethylene, 1-hexene. A "terpolymer" is a polymer having three monomer units that are different from each other. Therefore, the term "copolymer" also includes terpolymers and tetrapolymers such as copolymer products of mixtures of ethylene, propylene, 1-hexene and 1-octene.

[0022] As used herein, when a polymer is referred to as "comprising, consisting of, or consisting essentially of a monomer," the monomer is present in the polymer in the polymerized / derivative form of the monomer. For example, when a copolymer is said to have an "ethylene" content of 35% to 55% by weight, it is understood that the monomer units in the copolymer are derived from ethylene in the polymerization reaction, and the derived units are present at 35% to 55% by weight based on the weight of the copolymer. Thus, a polymer or copolymer said to have a 90% by weight "ethylene" content is equivalent to a polymer or copolymer said to have a 90% by weight "ethylene-derived" content or 90% by weight "units derived from ethylene," etc.

[0023] As used herein, "polyethylene" means an ethylene homopolymer or a copolymer comprising at least 50% by weight ethylene. The terms "polyethylene polymer", "polyethylene", "ethylene polymer", "ethylene copolymer" and "ethylene-based polymer" have the same meaning as polyethylene copolymers, except where otherwise indicated (e.g., when referring to a polyethylene homopolymer, this means a polymer formed from ethylene monomers without comonomer units, e.g., 100% by weight ethylene-derived units).

[0024] As used herein, "high density polyethylene (HDPE)" means a polyethylene produced in a gas phase and / or slurry phase polymerization and having a density of 0.940 g / cm 3 Up to 0.970g / cm 3 Ethylene homopolymers and ethylene copolymers having a range of densities.

[0025] As used herein, "low density polyethylene (LDPE)" means a polyethylene produced in high pressure free radical polymerization and having a density of 0.910 g / cm 3 Up to 0.940g / cm 3 Ethylene homopolymers and / or ethylene copolymers having a density within a certain range.

[0026] As used herein, "linear low density polyethylene (LLDPE)" means a polyethylene produced in a suspension, solution, slurry or gas phase polymerization process and having an average molecular weight of 0.910 g / cm 3 Up to 0.940g / cm 3 The LLDPE can be produced in a gas phase reactor, a high pressure tubular reactor and / or a slurry reactor and / or in a solution reactor using any of the disclosed catalysts. The LLDPE typically has a large number of short branches and is structurally different from conventional LDPE because the LLDPE typically has minimal long chain branching and more short chain branching than the LDPE.

[0027] As used herein, the term "metallocene-catalyzed linear low density polyethylene (m-LLDPE or mLLDPE) refers to a LLDPE composition prepared by a metallocene catalyst.

[0028] As used herein, the term "Ziegler-Natta catalyzed linear low density polyethylene (zn-LLDPE or znLLDPE) refers to a LLDPE composition prepared by a Ziegler-Natta catalyst.

[0029] Moment and distribution of molecular weight (Mw, Mn, Mz, Mw / Mn, Mz / Mn, etc.) and monomer / comonomer content (C2, C4, C6 and / or C8 and / or other, etc.) and g'(vis) were determined by using high temperature gel permeation chromatography (Polymer Char GPC-IR) equipped with a multi-channel bandpass filter based infrared detector IR5, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10 μm mixed-B LS columns were used to provide polymer separation. Detailed analysis principle and method for determination of molecular weight and g' visDescribed in paragraphs

[0044] -

[0051] of PCT Publication WO2019 / 246069A1, which is incorporated herein by reference (note that the equation c= / / / mentioned in paragraph

[0044] regarding the concentration (c) at each point in the chromatogram is c=βI, where β is the mass constant and I is the IR5 broadband signal intensity (I) minus the baseline). Unless specifically mentioned, all molecular weight moments used or mentioned in this disclosure are determined according to the absolute determination method (such as mentioned in paragraphs

[0044] -

[0051] of the just-mentioned publication), noting that for the equation in such paragraph

[0044] , a=0.695 and K=0.000579 (1-0.75Wt) are used, where Wt is the weight fraction of the comonomer, and further noting that the comonomer composition is determined by the ratio of the IR5 detector intensities corresponding to the CH2 and CH3 channels calibrated with a series of PE and PP homo / copolymer standards, the nominal values ​​of which are predetermined by NMR or FTIR as indicated in paragraph

[0045] of the just-mentioned PCT publication (providing methyl groups / 1000 total carbons (CH3 / 1000TC)). Other parameters required can be found in the paragraphs mentioned in the WO2019 / 246069A1 disclosure text, but for convenience, some are included here: TCB at 145°C n = 1.500; I = 665nm; dn / dc = 0.1048mL / mg.

[0030] Density values ​​of polymers were measured according to ASTM D1505.

[0031] Each melt flow index or melt index (MI) and high load melt index (HLMI) are measured on a Goettfert MI-4 melt indexer according to ASTM D1238-13, wherein the MI is measured at 190°C, 2.16 kg load (sometimes referred to as I2); and the HLMI is measured at 190°C, 21.6 kg load (sometimes referred to as I 21 ). Samples in an amount of 5 to 6 g were loaded into the barrel of the instrument at 190°C and compressed manually. Thereafter, the material was automatically compacted in the barrel by lowering all available weight onto the piston to remove all air bubbles. Data collection began after a 6 min pre-melting time. The melt flow index ratio or melt index ratio (equivalently MFR or MIR) is the ratio HLMI / MI (or I 21 / I2).

[0032] Details

[0033] The present disclosure provides a longitudinally oriented film comprising: at least one layer comprising: (a) 60 to 99.95 weight percent polyethylene, based on the total weight of the layer, the polyethylene having: (i) 0.910 to 0.930 g / cm3 % of an oxidizing agent, based on the total weight of the layer, wherein the polyethylene further comprises: (iii) an inflection point in a Van Gurp Palmen curve of phase angle in degrees versus complex modulus in Pa of the polyethylene; (iv) a shear thinning ratio of greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and (v) a MIR / MWD ratio of greater than or equal to 8, MIR being defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

[0034] Surprisingly, it is found that the film of the technical solution of the present application achieves significantly improved aging performance through longitudinal orientation combined with a specific film composition (including polyethylene and anti-aging additives).

[0035] Polyethylene

[0036] The polyethylene useful in the present invention may include or be a long chain branched metallocene linear low density polyethylene (LCB-mLLDPE).

[0037] LCB-mLLDPE are considered to be long chain branched compared to other linear low density polyethylenes, especially compared to other metallocene LLDPEs; however, their total long chain branching is still less than that of LDPE with a very high degree of long chain branching. This small amount of LCB can be achieved by, for example, a high melt index ratio (MIR) and / or specific rheological properties (e.g., η 20 ) as shown by data obtained by small angle oscillatory shear (SAOS) experiments. 0.01 / η 100 , the ratio of the complex viscosities recorded at angular frequencies of 0.01 and 100 rad / s) is confirmed. Another useful parameter indicating the presence of LCBs is the Van Gurp Palmen (VGP) plot. In particular, polyethylene copolymers (even LLDPE) with some LCBs will show an inflection point in their VGP curves, while LLDPE without any LCBs will not show such an inflection point.

[0038] Yet another useful parameter that indicates the presence of some LCB is the ratio of melt index ratio to molecular weight distribution, i.e., MIR / MWD. Melt index ratio (MIR) is the ratio of high load melt index (HLMI, ASTM D1238, at 190°C, 21.6 kg) to melt index (MI, ASTM D1238, at 190°C, 2.16 kg). Molecular weight distribution (MWD) is the ratio of weight average molecular weight Mw to number average molecular weight Mn.

[0039] Thus, LCB-mLLDPE useful in the present invention may have one or more of the following properties (the following properties may be useful indicators of a medium LCB):

[0040] (1) MIR is in the range of any low of 20, 25, 26, 27, 28, 29, 30 or 31 to any high of 40, 35, 34, 33, 32, 31 or 30, and ranges from any of the above lows to any of the above highs are contemplated herein, e.g., 25 to 40, 28 to 37, or 30 to 35.

[0041] (2) The ratio of MIR / MWD is greater than or equal to 8, greater than or equal to 9, greater than or equal to 10, or within the range of any low point of 8, 8.5, 9, 9.5 to any high point of 15, 14.5, 14, 13.5, 13, 12.5, 12, 11.5, 11, 10.5, and the range from any of the above low points to any of the above high points is contemplated herein, for example, 9 to 13, or 9.5 to 11.5.

[0042] (3) Complex shear viscosity (η) at 0.01 rad / s and 190°C * s, for example, 5000 to 25000 Pa·s, or 15000 to 20000 Pa·s.

[0043] (4) Complex shear viscosity (η) at 100 rad / s and 190 °C *s, or from any low point among 500, 600, 700, 800, 900, 1000, 1200, 1300 Pa.s to any high point among 3000, 1800, 2500, 2300, 2000, 1900, 1800, 1600, 1500, 1200, 1300, 1400, 1300 or 1200 Pa.s, and the range from any of the above low points to any of the above high points is encompassed herein, for example, 900 to 2000 Pa.s, or 1100 to 1600 Pa.s.

[0044] (5) a shear thinning ratio (the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C) of 11.5 or greater, 12 or greater, 12.5 or greater, or 13 or greater, or in the range of any low point of 11.5, 12, 12.5, 13 to any high point of 20, 19, 18, 17, 16, 15, 14, with ranges from any of the above low points to any of the above high points, for example, 13 to 17, or 13 to 15.

[0045] (6) There is an inflection point in the Van Gurp Palmen plot of phase angle (degrees) versus complex modulus (Pa) of LCB-mLLDPE.

[0046] (7) Less than or equal to 70 degrees at 190 degrees and 10 4 The phase angle at the complex modulus of Pa is, for example, less than or equal to 69 degrees, less than or equal to 68 degrees, less than or equal to 67 degrees, less than or equal to 66 degrees, or less than or equal to 65 degrees, or in the range of from any low point of 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60 degrees to any high point of 70, 69, 68, 67, 66, 65, 64, 63 degrees. The present invention covers the range from any of the above low points to any of the above high points, for example, 55 to 65 degrees, or 60 to 64 degrees.

[0047] (8) LCB index (g' or g' vis ) is less than 1, for example in the range of 0.9 to 0.99, or 0.94 to 0.98, but still significantly higher than the g' of heavy LCB polyethylene (such as LDPE made using free radical polymerization).

[0048] Suitable LCB-mLLDPE preferably comprises 80, 85, 88, 90, 92, 93, 94 or 95 to 96, 97, 98 or 99 weight percent ethylene, with the balance being one or more C3 to C 12That is, the LCB-mLLDPE may contain 80, 85, 88, 90, 92, 93, 94 or 95 to 96, 97, 98 or 99 weight percent of ethylene-derived units and 1, 2, 3, 4 or 5 to 6, 7, 8, 10, 12, 15, 20 weight percent of one or more C3 to C 12 α-olefin derived units. The C3 to C 12 The α-olefin is preferably one or more of butene, hexene, octene, preferably one of them, more preferably hexene. The weight % is based on the total weight of ethylene derived units plus comonomer derived units in the polyethylene.

[0049] Suitable LCB-mLLDPE may also have a CDBI greater than or equal to 60%, preferably greater than or equal to 70%, for example, within the range of any low point of 60, 70 or 75% to any high point of 80, 85, 90, 05 or 99%, and the range from any of the above low points to any of the above high points is encompassed herein. The CDBI of the copolymer can be measured using techniques known in the art. The CDBI of the copolymer is easily determined using techniques known to separate individual fractions of a copolymer sample. One such technique is temperature rising elution fractionation (TREF), as described in Wild et al., J. Poly. Sci., Poly. Phys. Ed., Vol. 20, pp. 441-455 (1982), which is incorporated herein by reference. Details on determining the CDBI of a copolymer are known to those skilled in the art, see, for example, PCT patent application WO 1993 / 003093, published on February 18, 1993, and the content of the specification regarding CDBI.

[0050] Suitable LCB-mLLDPE may also have an MWD (Mw / Mn) in the range of 2.5 to 5.5, and the MWD may be in the range of 3 or 3.5 to 4 or 4.5 or 5, for example.

[0051] Suitable LCB-mLLDPE can also have a number average molecular weight Mn of 20,000 to 55,000 g / mol. The number average molecular weight can be in the range of any low point from 20,000, 21,000, 22,000, 23,000, 24,000, 25,000 g / mol to any high point from 55,000, 50,000, 45,000, 40,000, 35,000, 30,000, 29,000, 28,000, 27,000 g / mol. The range from any of the above low points to any of the above high points is encompassed herein, for example, 22,000 to 40,000 g / mol.

[0052] Suitable LCB-mLLDPE can also have a weight average molecular weight Mw of 50,000 to 200,000 g / mol. The weight average molecular weight can be in the range of any low point from 50,000, 60,000, 70,000, 80,000, 85,000 g / mol to any high point from 200,000, 180,000, 150,000, 120,000, 100,000 g / mol. The present invention covers the range from any of the above low points to any of the above high points, for example, 70,000 to 120,000 g / mol.

[0053] Suitable LCB-mLLDPE can also have a melt index (MI, I2, measured according to ASTM D1238 at 190°C and 2.16 kg load) in the range of 0.1 to 3 g / 10 min. The melt index can be in the range of from any low point of 0.1, 0.15, 0.2, 0.22, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 g / 10 min to any high point of 3.0, 2.8, 2.5, 2.2, 2.0, 1.8, 1.5, 1.2, 1.0 g / 10 min. The range from any of the above low points to any of the above high points is encompassed herein, for example, 0.2 to 2.5 g / 10 min, 0.5 to 1.5 g / 10 min.

[0054] Suitable LCB-mLLDPE has a high load melt index (HLMI, I 21 The melt index may be in the range of from 10 to 75 g / 10 min, or from 20 to 50 g / 10 min, or from 25 to 45 g / 10 min, and the high load melt index may be in the range of from 10 to 75 g / 10 min, or from 25 to 45 g / 10 min, or from 30 to 50 g / 10 min, or from 30 to 50 g / 10 min, or from 30 to 50 g / 10 min,

[0055] Suitable LCB-mLLDPE may have a density of 0.900 to 0.940 g / cm 3 range, for example, from 0.905, 0.910, 0.920 or 0.925 g / cm 3 Any low point to 0.930, 0.932, 0.933, 0.934, 0.935 or 0.940 g / cm 3 The present invention covers the range from any of the above low points to any of the above high points, for example, 0.910 to 0.935 g / cm 3 .

[0056] Suitable LCB-mLLDPE may have a "broad orthogonal comonomer distribution". "Broad orthogonal comonomer distribution" or BOCD means that there is a significantly higher degree of short chain branching on the longer molecular weight polymer chains than on the shorter molecular weight polymer chains in the copolymer. Suitable LCB-mLLDPE may have a T of 5 to 10. 75 -T 25 value, or 5.5 to 10 T 75 -T 25 value, or 5.5 to 8 T 75 -T 25 value, or a T of 6 to 10 75 -T 25 value, or a T of 6 to 8 75 -T 25 Value, where T 25 is the temperature in degrees Celsius at which 25% of the eluted polymer is obtained and T 75 is the temperature in degrees Celsius at which 75% of the eluted polymer is obtained (by temperature rising elution fractionation (TREF)).

[0057] In addition to those discussed above, polyethylenes useful in the present invention include copolymers commercially available from ExxonMobil Product Solutions, such as those sold under the trade name Enable TM Those sold, including but not limited to those sold under the trade name Enable TM Those sold in 2010.

[0058] Enable TM 2010 is a LCB-mLLDPE, ethylene 1-hexene copolymer, with a density of 0.920 g / cm 3 The material has a density of 1.0 g / 10 min, a melt index (190°C / 2.16 kg), a melting peak temperature of 114°C and a Vicat softening temperature of 106°C.

[0059] Anti-aging additives

[0060] The anti-aging additives useful in the present invention may include or be a light stabilizer, a heat stabilizer, an antioxidant, or a combination thereof.

[0061] Light stabilizers may also be referred to as UV stabilizers. UV stabilizers are chemical agents that absorb or shield light radiation with frequencies higher than the frequency of violet light in the visible spectrum to prevent light radiation catalytic reactions that cause plastic degradation. Specific UV absorbers include benzophenone, benzotriazole (including hydroxyphenylbenzotriazole), substituted acrylonitrile, salicylic acid derivatives and nickel complexes thereof. Commercially available benzotriazoles may include "Tinuven 1130" (from Ciba-Geigy), "UV5411" (from Cytec) and "Mixxim BB / 200" (from Fairmont). Commercially available benzophenones may include "Uvinul 3048" (from BASF) and "Syntase230" (from Great Lakes Chemical). Another commercially available UV absorber is N, N'-diphenyloxalamide, available from Sandoz under the name "VP Sanduvor VSU". UV absorbers are often used in combination with free radical scavengers that can prevent any UV catalytic reactions.

[0062] Hindered amine light stabilizers (HALS) are a particularly useful class of light stabilizers, which can be used alone or in combination with UV absorbers as free radical scavengers. Preferred examples of such light stabilizers are derivatives of 2,2,4,4-tetramethylpiperidine, such as N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, poly[2-N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-hexanediamine-4-(1-amino-1,1,3,3-tetramethylbutane)-s-triazine]. Commercially available hindered amine light stabilizers may include "Tinuven 123", "Tinuvin 770", "Tinuvin 622LD" (from Ciba-Geigy), "Uvasil 299" (from Enichem), "BLS 1770" (from Mayzo), "Chimassorb 944LD" (from BASF) and HS-625.

[0063] Heat stabilizers can include lead salt heat stabilizers, metal soap heat stabilizers and organotin heat stabilizers. Examples of lead salt heat stabilizers include tribasic lead sulfate, dibasic lead stearate, dibasic lead phosphite, etc. Examples of metal soap heat stabilizers include higher fatty acid salts of metals such as calcium, magnesium, cadmium, lead, particularly stearates and laurates. Examples of organotin heat stabilizers include methyl tin, butyl tin, octyl tin, tin dilaurate, dibutyl tin maleate, organotin mercaptan esters, organotin sulfonamides, etc.

[0064] Antioxidants can include organic phosphites and phenolic antioxidants. Non-limiting examples of suitable organic phosphites are tris (2,4-di-tert-butylphenyl) phosphite (IRGAFOS 168) and di (2,4-di-tert-butylphenyl) pentaerythritol diphosphite (ULTRANOX 626). Non-limiting examples of phenolic antioxidants (e.g., sterically hindered phenols) include octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (IRGANOX-1076); pentaerythritol tetrakis (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (IRGANOX 1010); and 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl-isocyanurate (IRGANOX 3114).

[0065] Anti-aging additives can be introduced into the composition as part of a masterbatch. For example, one or more anti-aging additives can be pre-blended into a masterbatch together with polyethylene, wherein the masterbatch can include at least 5 wt %, or at least 7 wt %, or at least 10 wt %, or at least 12 wt %, or at least 15 wt % of an anti-aging additive, and / or at most 60 wt %, at most 50 wt %, at most 40 wt %, at most 30 wt %, at most 25 wt % of an anti-aging additive, based on the gross weight of the masterbatch. Then, the antioxidant masterbatch can form at least 0.5 wt %, at least 1 wt %, at least 5 wt %, or at least 7 wt %, or at least 10 wt %, or at least 15 wt %, and / or at most 30 wt %, at most 20 wt %, at most 15 wt %, at most 10 wt %, at most 5 wt %, or at most 3 wt % of the film layer composition.

[0066] Preferably, the anti-aging additive used in the present invention comprises or is a light stabilizer, preferably comprises or is a hindered amine light stabilizer.

[0067] membrane

[0068] The term "film" may refer to a monolayer film or a multilayer film. The film may be formed by any suitable means (e.g., extrusion molding, cast or blown film technology). When used in a multilayer film, the polymer described herein may be used in any layer of the film unless otherwise noted. The multilayer film may be prepared by such a method, wherein each layer is prepared individually or individually; that is, the layer formed by the polymer composition or the layer comprising the polymer composition may have the same or different chemical composition, density, melt index, thickness, etc., depending on the desired film properties. Similarly, orientation may be applied individually to a single layer or to a combined multilayer film.

[0069] To facilitate discussion of the different film structures of the present invention, the following notation is used herein. Each layer of the film is denoted "A" or "B", where "A" indicates one film layer, preferably an inner film layer, and "B" indicates a different film layer. In the case where the film includes more than one A layer or more than 1 B layer, one or more prime symbols (', ", ", ", etc.) are attached to the A or B symbols to indicate the same type of layers (conventional or inventive), which may be the same or may differ in one or more properties (such as chemical composition, density, melt index, thickness, etc.). Finally, the symbols of adjacent layers are separated by a slash ( / ). Using this notation, a layer structure of a three-layer film having an inner layer (also referred to herein as a "core layer") arranged between two outer film layers can be expressed as A / B / A'. Similarly, a five-layer film of alternating layers can be represented as A / B / A' / B' / A". Unless otherwise indicated, for purposes of the present invention, the order of the layers from left to right or right to left is not significant, nor is the order of the prime symbols; for example, an A / B film is equivalent to a B / A film, and an A / A' / B / A" film is equivalent to an A / B / A' / A" film. The relative thicknesses of the individual film layers are also represented similarly, with the thickness of each layer being represented numerically and separated by slashes relative to the total film thickness of 100 (dimensionless); for example, the relative thicknesses of an A / B / A' film having A and A' layers each 10 μm thick and a B layer having a 30 μm thick layer are represented as 20 / 60 / 20.

[0070] The layer containing polyethylene and anti-aging additives as described above and below can be referred to as layer A. The film of the present invention can contain at least one layer A, such as one A, two A, A', three A, A', A", etc. As mentioned above, A, A', A" can be the same or can be different in one or more properties (such as chemical composition, density, melt index, thickness, etc.). In addition, the film of the present invention can also contain one or more layers different from layer A. When the film of the present invention is a single-layer film, that is, it contains only one layer A, the composition of the film is the same as the composition of layer A.

[0071] Based on the total weight of layer A, the content of polyethylene as described above and below in layer A can be 60 to 99.95 weight%, for example, in the range of any low point from 60, 65, 70, 75, 80, 85, 90, 95 weight% to any high point from 80, 85, 90, 95, 96, 97, 98, 99, 99.5, 99.8, 99.9, 99.95 weight%, and the range from any of the above low points to any of the above high points is encompassed herein.

[0072] In one embodiment, layer A contains only polyethylene as described above and below as the only polymer, that is, such that the content of polyethylene as described above and below is 100 weight percent based on the total weight of polymers in layer A. In this embodiment, the content of polyethylene as described above and below can be 90 to 99.95 weight percent, based on the total weight of layer A, for example, in the range of from any low point of 90, 91, 92, 93, 94, 95, 96, 97 weight percent to any high point of 95, 96, 97, 98, 99, 99.5, 99.8, 99.9, 99.95 weight percent, and the range from any of the above low points to any of the above high points is encompassed herein.

[0073] In another embodiment, in addition to the polyethylene as described in the context, layer A can also contain other polymers, such as polyolefins, such as polypropylene or polyethylene. Other polyethylene can be one or more of high-density polyethylene (HDPE), low-density polyethylene (LDPE), medium-density polyethylene (MDPE), linear low-density polyethylene (LLDPE). In this embodiment, based on the gross weight of layer A, the content of polyethylene as described in the context can be 60 to 90 weight %, for example, in the range of any low point from 60,65,70,75,80 weight % to any high point from 70,75,80,85,90 weight %, and the scope from any of the above low points to any of the above high points is covered herein. The content of other polymers (such as other polyethylene) can be 5 to 40 weight %, for example, in the range of any low point from 5,10,15,20,25,30 weight % to any of the high points from 10,15,20,25,30,35,40 weight %, and the scope from any of the above low points to any of the above high points is covered herein.

[0074] Based on the total weight of layer A, the content of the anti-aging additive as described above and below in layer A can be 0.05 to 3 weight %, for example, in the range of any low point from 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1 weight % to any high point from 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3 weight %, and the range from any of the above low points to any of the above high points is encompassed herein.

[0075] The unaged MD tensile strength at break of the longitudinally oriented film according to the present invention is ≥140MPa, preferably ≥150MPa, preferably ≥155MPa; the MD tensile strength at break after 1000 hours of xenon lamp aging is ≥140MPa, preferably ≥150MPa, preferably ≥155MPa; the MD tensile strength at break retention rate (MD tensile strength at break after 1000 hours of xenon lamp aging / MD tensile strength at break without aging) is ≥98%, preferably ≥99%, preferably about 100%.

[0076] Method for preparing longitudinally oriented film

[0077] The present disclosure also provides a method of making a machine direction oriented film as described above and below, comprising stretching the film in the machine direction as an additional step after the film has been formed, to produce a machine direction (MD) uniaxially oriented film.

[0078] Some methods of producing polymer films suitable for MD orientation after film preparation may be blown and cast film methods. A specific blown film method comprises extruding a polyethylene composition through an annular die to form an extruded tube of molten material to provide a tube having a tube diameter substantially equal to the diameter of the annular die. At the same time, the tube is continuously extruded, and the tube is expanded downstream of the annular die to thin its tube wall, so that the tube of molten material forms a bubble film having a bubble diameter greater than (i) the diameter of the annular die and (ii) the diameter of the tube. The bubble film has a frost line, which comprises a boundary between the molten material and the crystallized film.

[0079] Some films suitable for MD orientation described herein are prepared by cast film methods. Typically, in cast film methods, forming the composition into a film comprises extruding the composition through a flat die or a slot die to form an extrudate, which is continuously moved on a polished turning roll and quenched from one side on the turning roll. The speed of the roll controls the draw ratio and the final film thickness. Increasing the speed / draw ratio reduces the film thickness. The film can then be sent to a second roll to cool on the other side. Typically, although not necessarily, the film is passed through a roller system and wound onto the roller. Most flat dies are T-slit or coat hanger designs, containing a manifold for spreading the flowing polymer along the width of the die, with alternating narrow slits and slits downstream to produce desired flow distribution and pressure drop.

[0080] Suitable blown film and cast film processes are described in detail in "Plastics Films", John H. Briston, Longman Scientific and Technical, 1986, which is incorporated herein by reference in its entirety.

[0081] Films suitable for MD orientation have a film thickness (or thickness as defined above) of 10 to 120 μm before MD orientation. The lower limit of the film thickness before MD orientation may be 10, 15, 20, 25, 30, 40, 45, 50, 60, 70 or 80 μm. The upper limit of the film thickness before MD orientation may be 120, 110, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25 or 20 μm.

[0082] Any combination of the lower limit and the upper limit (wherein the upper limit>the lower limit) should be deemed to be disclosed by the above upper and lower limits, for example, 10 to 120 μm, 20 to 120 μm, 30 to 120 μm, 50 to 120 μm, 40 to 110 μm, 40 to 100 μm, etc. In certain exemplary embodiments, the film has a film thickness of 50 to 120 μm before MD orientation.

[0083] The present application relates to the orientation of polymer films formed by casting or blowing processes after the film polymer is no longer in a molten state and has solidified to have a crystalline structure. MD orientation can be achieved by any known MD orientation method in-line or off-line during cast or blown film extrusion. That is, the film produced by the blowing or casting process can be temporarily stored (off-line) before MD orientation or can be directly (on-line) fed to the MD orientation equipment.

[0084] The orientation process can be heated or unheated. Cold drawing or cold stretching is a suitable process. When heating the film, do not heat the polymer above its melting temperature.

[0085] A preferred MD orientation process may include heating the film to an orientation temperature, preferably using a set of temperature-controlled rollers. The orientation temperature may be as high as the melting temperature of the polymer. The heated film is then fed into a slow stretching roller with a nip roller having the same rolling speed as the heated roller. The film then enters a fast stretching roller, for example 1.5 to 12 times the speed of the slow stretching roller, which effectively orients (stretches) the film in a continuous manner. The oriented film then enters an annealing hot roller, which allows stress release by keeping the film at an elevated temperature for a period of time. The annealing temperature is preferably in the same temperature range used for stretching or slightly below the temperature range (e.g., 10 to 20°C lower than the temperature range used for stretching but not lower than room temperature, where room temperature is 23°C). Finally, the film is cooled to ambient temperature by a cooling roller to produce a longitudinally oriented (MDO) film.

[0086] In an exemplary embodiment, the MDO substrate of the multilayer film described herein is formed using a draw ratio of about 3 to about 7, more preferably about 4 to about 6, and most preferably about 5.

[0087] The MDO substrate may have a film thickness of 10-110 μm after MD orientation. The lower limit of the film thickness after MD orientation may be 10, 15, 20, 25, 30, 40, 50, 60, 70, or 80 μm. The upper limit of the film thickness after MD orientation may be 110, 100, 80, 70, 60, 50, 40, 30, 25, or 20 μm. Any combination of the lower limit and the upper limit (where the upper limit is greater than the lower limit) should be deemed to be disclosed by the above upper and lower limits, such as 10-100 μm, 10-50 μm, 15-40 μm, 20-30 μm, 30-90 μm, 40-110 μm, 40-100 μm, etc. In certain exemplary embodiments, the film has a film thickness of 15-40 μm after MD orientation.

[0088] Unless otherwise indicated, all numerical values ​​used in this specification and the related claims expressing the amount of ingredients, properties such as molecular weight, reaction conditions, etc. should be understood as being modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters listed in the following specification and the appended claims are approximate values, which may vary depending on the desired properties sought to be obtained by the embodiment of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0089] One or more illustrative embodiments including one or more inventive elements are proposed herein. For the sake of clarity, all features of physical implementation are not described or shown in this application. It should be understood that in the development of physical implementations including one or more elements of the present invention, in order to achieve the developer's goal, many specific decisions must be made to achieve, for example, system-related, business-related, government-related and other constraints are observed, which change from time to time with the implementation. Although the developer's efforts may be time-consuming, such efforts are routine tasks for those of ordinary skill in the art who benefit from the present disclosure.

[0090] Although compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. In the context of compositions, consisting essentially of allows for 25 ppm or less (of each) of impurities.

[0091] Additional embodiments

[0092] The present invention also relates to the following embodiments.

[0093] 1. Longitudinally oriented film, comprising:

[0094] At least one layer, the layer comprising:

[0095] (a) 60 to 99.95 wt. % polyethylene, based on the total weight of the layer,

[0096] The polyethylene has:

[0097] (i) 0.910 to 0.930 g / cm 3 density; and

[0098] (ii) a melt index I2 at 190°C and 2.16 kg of 0.1 to 3 g / 10 min, and

[0099] (b) 0.05 to 3 wt. % of an anti-aging additive, based on the total weight of the layer,

[0100] The polyethylene also has one or more of the following characteristics:

[0101] (iii) the inflection point in the Van GurpPalmen plot of phase angle in degrees versus complex modulus in Pa for polyethylene;

[0102] (iv) a shear thinning ratio greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and

[0103] (v) a MIR / MWD ratio greater than or equal to 8, where MIR is defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

[0104] 2. The longitudinally oriented film according to embodiment 1, wherein the polyethylene further has:

[0105] Less than or equal to 70 degrees at 190°C and 10 4 The phase angle under the complex modulus of Pa.

[0106] 3. The longitudinally oriented film according to embodiment 1 or 2, wherein the polyethylene has one or more of the following properties:

[0107] 55 to 65 degrees at 190°C and 10 4 The phase angle under the complex modulus of Pa;

[0108] A shear thinning ratio of 13 to 17, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190° C. to the complex shear viscosity at 100 rad / s and 190° C.; and

[0109] MIR / MWD ratio of 9 to 13, MIR is defined as the high load melt index I at 190°C and 21.6 kg 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

[0110] 4. The longitudinally oriented film according to embodiment 1 or 2, wherein the polyethylene has one or more of the following properties:

[0111] Complex shear viscosity η at 0.01 rad / s and 190°C of 5000 to 25000 Pa·s 0.01 ;

[0112] Complex shear viscosity η at 100 rad / s and 190°C from 900 to 2000 Pa·s 100 ;

[0113] A melt index I2 at 190°C and 2.16 kg of 0.2 to 2.5 g / 10 min;

[0114] High load melt index I at 190°C and 21.6 kg of 10 to 75 g / 10 min 21 ;

[0115] MIR of 25 to 40, MIR is defined as the high load melt index I at 190°C and 21.6 kg 21 Ratio to the melt index I2 at 190°C and 2.16 kg;

[0116] A number average molecular weight Mn of 20,000 to 55,000 g / mol;

[0117] A weight average molecular weight Mw of 50,000 to 200,000 g / mol;

[0118] MWD of 2.5 to 5.5, MWD being defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn;

[0119] 5 to 10 T 75 -T 25 , T 25 is the temperature in degrees Celsius at which 25% of the polyethylene is eluted, and T 75 It is the temperature in degrees Celsius at which 75% of the polyethylene is eluted, as measured by Temperature Rising Elution Fractionation TREF.

[0120] 5. The longitudinally oriented film according to embodiment 1 or 2, wherein the polyethylene has one or more of the following properties:

[0121] Contains 80 to 99 wt% of ethylene-derived units and 1 to 20 wt% of C3-C 12 α-olefin derived units;

[0122] is an ethylene-hexene copolymer; and

[0123] It is a long-chain branched metallocene linear low-density polyethylene, namely LCB-mLLDPE.

[0124] 6. The longitudinally oriented film according to embodiment 1 or 2, wherein

[0125] The longitudinally oriented film is a single-layer film; and / or

[0126] The longitudinally oriented film is a uniaxially longitudinally oriented film; and / or

[0127] The layer comprises 80 to 99 wt % of the polyethylene, based on the total weight of the layer; and / or

[0128] The layer contains 0.1 to 1 wt % of the anti-aging additive, based on the total weight of the layer.

[0129] 7. A longitudinally oriented film according to embodiment 1 or 2, wherein:

[0130] The anti-aging additives include light stabilizers, heat stabilizers, antioxidants or a combination thereof.

[0131] 8. The longitudinally oriented film according to embodiment 1 or 2, wherein:

[0132] The anti-aging additives include hindered amine light stabilizers.

[0133] 9. A longitudinally oriented monolayer film comprising:

[0134] (a) 99% by weight of polyethylene, based on the total weight of the film,

[0135] The polyethylene has:

[0136] (i) 0.920 g / cm 3 density; and

[0137] (ii) a melt index of 1 g / 10 min at 190°C and 2.16 kg, and

[0138] (b) 0.2 wt % of a hindered amine light stabilizer, based on the total weight of the film,

[0139] The polyethylene also has one or more of the following characteristics:

[0140] (iii) the inflection point in the Van GurpPalmen plot of phase angle in degrees versus complex modulus in Pa for polyethylene;

[0141] (iv) a shear thinning ratio of 13 to 15, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190° C. to the complex shear viscosity at 100 rad / s and 190° C.;

[0142] (v) a MIR / MWD ratio of 9 to 11, MIR being defined as the high load melt index I at 190°C and 21.6 kg 21 The ratio of the melt index I2 at 190°C and 2.16 kg, MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn; and

[0143] (iv) 60 to 65 degrees at 190°C and 10 4 The phase angle under the complex modulus of Pa.

[0144] 10. The method for preparing a longitudinally oriented film according to any one of embodiments 1 to 9, comprising:

[0145] Using the components of the film to prepare a precursor film through a blow molding process or a casting process,

[0146] After the precursor film is cooled to form a crystalline structure, the precursor film is stretched in a machine direction to produce the machine direction oriented film.

[0147] 11. Use of the longitudinally oriented film according to any one of embodiments 1 to 9 as an agricultural film.

[0148] 12. The use according to embodiment 11, wherein the agricultural film is a greenhouse film or a mulch film.

[0149] 13. A method for improving the aging performance of a membrane, comprising:

[0150] The precursor film is made by using the components of the film through a blow molding process or a casting process,

[0151] The composition of the film is such that the film comprises at least one layer comprising:

[0152] (a) 60 to 99.95 wt. % polyethylene, based on the total weight of the layer,

[0153] The polyethylene has:

[0154] (i) 0.910 to 0.930 g / cm 3 density; and

[0155] (ii) a melt index I2 at 190°C and 2.16 kg of 0.1 to 3 g / 10 min, and

[0156] (b) 0.05 to 3 wt. % of an anti-aging additive, based on the total weight of the layer,

[0157] After cooling the precursor film to form a crystalline structure, stretching the precursor film in a longitudinal direction to produce a longitudinally oriented film,

[0158] The polyethylene also has one or more of the following characteristics:

[0159] (iii) the inflection point in the Van GurpPalmen plot of phase angle in degrees versus complex modulus in Pa for polyethylene;

[0160] (iv) a shear thinning ratio greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and

[0161] (v) a MIR / MWD ratio greater than or equal to 8, where MIR is defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg. DETAILED DESCRIPTION

[0162] In order to facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. The following examples should in no way be construed as limiting or defining the scope of the present invention.

[0163] Example

[0164] Test Method

[0165] Dynamic Shear Melt Rheology Test: Rheological data including complex modulus, complex viscosity and phase angle were determined using SAOS (Small Amplitude Oscillatory Shear) testing. SAOS experiments were performed at 190°C using a 25 mm parallel plate configuration on an ARES-G2 (TA Instruments). Sample test discs (25 mm diameter, 2 mm thickness) were prepared at 190°C using a Carver Laboratory press. The samples were placed without pressure for approximately 3 minutes to melt, and then typically held under pressure for 3 minutes to compression mold the samples. The disc-shaped samples were first equilibrated between the parallel plates of the rheometer at 190°C for approximately 10 minutes to eliminate any previous thermal and crystallization history. Next, an angular frequency sweep was performed with a typical measurement gap of 1.5 mm, from 398 rad / s to 0.01 rad / s angular frequency, using 5 points / decade, and strain values ​​in the linear viscoelastic region determined by strain sweep experiments (see CW Macosko, Rheology Principles, Measurements and Applications, Wiley-VCH, New York, 1994). All experiments were performed in a nitrogen atmosphere to minimize any degradation of the sample during the rheological testing process.

[0166] From the storage (G') and loss (G") dynamic moduli (CW Macosko, Rheology Principles, Measurements and Applications (Wiley-VCH, New York, 1994)), the loss tangent (tan δ) at each angular frequency (where δ is the phase (loss) angle, which is a measure of the elasticity of the melt) is defined as follows:

[0167]

[0168] The Van Gurp-Palmen plot (van Gurp, M., Palmen, J. "Time temperature superposition for polymeric blends", 67 (1) Rheol. Bull. 5-7 (1998)) is a plot of the measured phase angle δ (as defined by equation (1)) versus the complex shear modulus |G * Plot of (ω)| (which is calculated for each angular frequency according to equation (2):

[0169] |G * (ω)|= ( G' 2 +G” 2 ) 1 / 2 (2).

[0170] The modulus of complex viscosity as a function of frequency ω is calculated from G' and G" as follows * | Or referred to as complex viscosity η* (CW Macosko, Rheology Principles, Measurements and Applications (Wiley-VCH, New York, 1994)):

[0171]

[0172] The Van-Gurp Palmen plot (VGP-plot) can be used to extract some information about molecular properties, such as linear vs. (long) chain branching, type of long chain branching, polydispersity, etc. (Dealy, MJ, Larson, RG, "Structure and Rheology of Molten Polymers", Carl Hanser Verlag, Munich 182-183 (2006)). It has been suggested that the VGP-plot is related to the polydispersity of linear polymers (Trinkle, S., Friedrich, C. "Van Gurp-Palmenplot: A way to characterize polydispersity of linear polymers", 40 Rheol. Acta 322-328 (2001)). It has also been suggested that the VGP-plot can be used to reveal the presence of long chain branching in polyethylene (Trinkle, S., Walter, P., Friedrich, C. "Van Gurp-Palmen plot II-Classification of long chain branched polymers by their topology", 41 Rheol. Acta 103-113 (2002)].

[0173] Melt Index Ratio: Each melt flow index or melt index (MI) and high load melt index (HLMI) are measured on a Goettfert MI-4 melt indexer according to ASTM D1238-13, wherein the MI is measured at 190°C, 2.16 kg load (sometimes referred to as I2); and the HLMI is measured at 190°C, 21.6 kg load (sometimes referred to as I 21 ). Samples in an amount of 5 to 6 g were loaded into the barrel of the instrument at 190°C and compressed manually. Thereafter, the material was automatically compacted in the barrel by lowering all available weight onto the piston to remove all air bubbles. Data collection began after a 6 min pre-melting time. The melt index ratio (MIR) is the ratio HLMI / MI (or I21 / I2).

[0174] Molecular weight distribution: Moment and distribution of molecular weight (Mw, Mn, Mz, Mw / Mn, Mz / Mn, etc.) and monomer / comonomer content (C2, C4, C6 and / or C8 and / or other, etc.) and g'(vis) were determined by using high temperature gel permeation chromatography (Polymer Char GPC-IR) equipped with a multi-channel bandpass filter based infrared detector IR5, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10 μm mixed-B LS columns were used to provide polymer separation. Detailed analysis principle and method for molecular weight determination and g' vis Described in paragraphs

[0044] -

[0051] of PCT Publication WO2019 / 246069A1, which is incorporated herein by reference (note that the equation c= / / / mentioned in paragraph

[0044] regarding the concentration (c) at each point in the chromatogram is c=βI, where β is the mass constant and I is the IR5 broadband signal intensity (I) minus the baseline). Unless specifically mentioned, all molecular weight moments used or mentioned in this disclosure are determined according to the absolute determination method (such as mentioned in paragraphs

[0044] -

[0051] of the just-mentioned publication), noting that for the equation in such paragraph

[0044] , a=0.695 and K=0.000579 (1-0.75Wt) are used, where Wt is the weight fraction of the comonomer, and further noting that the comonomer composition is determined by the ratio of the IR5 detector intensities corresponding to the CH2 and CH3 channels calibrated with a series of PE and PP homo / copolymer standards, the nominal values ​​of which are predetermined by NMR or FTIR as indicated in paragraph

[0045] of the just-mentioned PCT publication (providing methyl groups / 1000 total carbons (CH3 / 1000TC)). Other parameters required can be found in the paragraphs mentioned in the WO2019 / 246069A1 disclosure text, but for convenience, some are included here: TCB at 145°C n = 1.500; I = 665nm; dn / dc = 0.1048mL / mg.

[0175] Composition distribution width: The width of the composition distribution of a polymer can be expressed as T 75 -T 25To characterize. TREF is measured using an analytical size TREF instrument (Polymerchar, Spain) with a column having the following dimensions: inner diameter (ID) 7.8 mm, outer diameter (OD) 9.53 mm, and a column length of 150 mm. The column can be filled with steel beads. 0.5 mL of a 4 mg / ml polymer solution in o-dichlorobenzene (ODCB) containing 2 g BHT / 4 L is loaded into the column and cooled from 140 ° C to -15 ° C at a constant cooling rate of 1.0 ° C / min. Subsequently, ODCB can be pumped through the column at a flow rate of 1.0 ml / min, and the column temperature can be increased at a constant heating rate of 2 ° C / min to elute the polymer. The polymer concentration in the eluted liquid can then be measured using an infrared detector at 2941 cm -1 The concentration of the ethylene-α-olefin copolymer in the eluted liquid can be calculated from the absorbance and plotted as a function of temperature. As used herein, T 75 -T 25 The value is where T 25 is the temperature in degrees Celsius at which 25% of the eluted polymer is obtained and T 75 is the temperature in degrees Celsius at which 75% of the eluted polymer is obtained (by TREF analysis).

[0176] Tensile strength at break: The tensile strength at break was measured using Zwick Roell according to ASTM-D882. A 25 mm*50 mm specimen was prepared and placed in a fixture, a force of 0.65 MPa was applied, and the specimen was stretched at a speed of 500 mm / min until it broke.

[0177] Xenon lamp aging: Xenon lamp aging was performed using the Altas-4400 xenon lamp aging chamber according to ISO 4892-2. 25mm*50mm specimens were prepared and placed in the aging chamber (irradiance: 0.5W / m 2 Aging was performed at 340 nm).

[0178] Table 1 shows information and analytical data of the polyethylene used in the examples.

[0179] Table 1 Information and analytical data of polyethylene used in the examples

[0180]

[0181]

[0182] Figure 1The Van Gurp Palmen plot of phase angle versus complex modulus of the above four polyethylenes is shown. As can be seen from the figure, among the four polyethylenes, only Enable 2010 has an inflection point in the Van Gurp Palmen plot, indicating that it has long chain branching, while the Van Gurp Palmen plots of the other three polyethylenes do not have an inflection point, indicating that there is no long chain branching. In addition, the MIR / MWD value of Enable 2010 is higher than that of the other three polyethylenes, which is also a reflection of long chain branching. In addition, from Figure 1 As can be seen from the results in Table 1, Enable 2010 has the lowest phase angle, indicating that it has higher melt elasticity.

[0183] Ten film samples were prepared with the formulations shown in Tables 2 and 3, wherein the film samples in Table 2 were unoriented and the film samples in Table 3 were longitudinally oriented. The unoriented film samples with a thickness of 20 μm in Table 2 and 100 μm in Table 3 were prepared using a film blowing device Hosokawa Alpine according to the conditions in Table 4. The 100 μm thick film sample in Table 3 was then stretched 5 times using an offline longitudinal stretching device SML-offline MDO to obtain a 20 μm thick longitudinally oriented film sample.

[0184] Table 2 Unoriented single layer film formulation

[0185]

[0186]

[0187] * The UV-resistant masterbatch contains 20 wt% HALS and 80 wt% polyethylene carrier resin. HALS is a hindered amine light stabilizer. HS-625.

[0188] Table 3 Single-layer film formulation after longitudinal orientation

[0189]

[0190] Table 4 Preparation conditions of unstretched film samples

[0191] Die head diameter (mm) 160(single layer) Die diameter (mm) 1.5 Fog line height (mm) ～550 Blowing ratio 2.5 Output (kg / h) 120 Online thickness measurement yes

[0192] The MD tensile strength at break of the above 10 film samples before and after aging was tested. The results are shown in Tables 5 and 6, and Figure 2 and Figure 3 The retention rate of MD tensile strength at break after aging (MD tensile strength at break after aging / MD tensile strength at break before aging) can be used to reflect the anti-UV aging performance of the film sample.

[0193] Table 5 MD tensile strength at break of unoriented monolayer films before and after aging

[0194]

[0195]

[0196] Table 6 MD tensile strength at break of longitudinally oriented monolayer films before and after aging

[0197]

[0198] From Table 5 and Figure 2 The results show that the addition of UV stabilizers can significantly improve the aging performance compared to pure Enable 2010 without UV stabilizers. When 1 wt% of UV stabilizer masterbatch is added, the tensile strength at break retention rate of the material is 44%. Compared with other systems, the retention rate of Enable 2010 + UV stabilizer system is at a relatively low level.

[0199] From Table 6 and Figure 3 As can be seen from the results, compared with the corresponding unoriented monolayer films, the tensile strength retention rate of the longitudinally oriented monolayer films is improved, which indicates that longitudinal orientation can improve the aging performance of the film. Surprisingly, after longitudinal orientation, the tensile strength retention rate of the system based on Enable 2010 is improved most significantly, and even the retention rate of the Enable 2010+UV stabilizer system reaches about 100%, which means that under 1000 hours of UV exposure, the tensile strength at break of the material has almost no degradation. It is believed that this is due to the presence of long chain branching in Enable2010 as reflected in the above test. During the longitudinal stretching process, the presence of long chain branching is conducive to producing more orientation, improving the regularity of the molecular chain arrangement, and thus improving the aging performance of the material. In addition, although the LLDPE LL1001 system also shows a relatively high retention rate, its absolute value of tensile strength at break is always at a low level. This is believed to be due to the fact that LLDPE LL1001 has an uneven microcrystalline structure due to a slightly wider molecular weight and uneven comonomer distribution compared to, for example, Enable 2010 and Exceed 1018, resulting in a relatively lower absolute value of tensile strength at break.

[0200] In summary, the present disclosure provides a new polyethylene film and a new method for improving the aging performance of the film, by which significantly improved aging performance is achieved through longitudinal orientation combined with a specific film composition (including polyethylene and anti-aging additives).

[0201] Therefore, the present invention is well adapted to obtain the results and advantages mentioned and inherent therein. The specific embodiments and configurations disclosed above are illustrative only, as it is apparent to those skilled in the art having the benefit of the teachings herein that different but equivalent means may be employed to modify and implement the present invention. In addition, except as described in the following claims, it is not intended to limit the details of the construction or design shown herein. It is therefore apparent that the specific illustrative embodiments disclosed above may be changed, combined or modified, and all such changes are considered to be within the scope and spirit of the present invention. The invention disclosed illustratively herein may be suitably implemented in the absence of any element not specifically disclosed herein and / or any optional element disclosed herein.

[0202] Although compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. All numerical values ​​and ranges disclosed above may be varied to some extent.

[0203] Whenever a numerical range with a lower limit and an upper limit is disclosed, any numerical value and any included range falling within the range are specifically disclosed. In particular, the range of each value disclosed herein (having the following form "from about a to about b", or equivalently "from about a to b", or equivalently "from about ab") should be understood to enumerate each numerical value and range contained within the wider range of values. Similarly, when multiple ranges (e.g., 1-100 or 10-90, e.g., 30 to 75) are disclosed, the range from any disclosed lower end to any disclosed upper end (e.g., 10-75) is specifically covered.

[0204] Furthermore, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Furthermore, the indefinite articles "a" or "an" as used in the claims are defined herein to mean one or more than one of the element it introduces.

Claims

1. Longitudinally oriented film, comprising: At least one layer, the layer comprising: (a) 60 to 99.95 wt. % polyethylene, based on the total weight of the layer, The polyethylene has: (i) 0.910 to 0.930 g / cm 3 density; and (ii) a melt index I2 at 190°C and 2.16 kg of 0.1 to 3 g / 10 min, and (b) 0.05 to 3 wt. % of an anti-aging additive, based on the total weight of the layer, The polyethylene also has one or more of the following characteristics: (iii) the inflection point in the Van GurpPalmen plot of phase angle in degrees versus complex modulus in Pa for polyethylene; (iv) a shear thinning ratio greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and (v) a MIR / MWD ratio greater than or equal to 8, where MIR is defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

2. The longitudinally oriented film according to claim 1, wherein the polyethylene further has: Less than or equal to 70 degrees at 190°C and 10 4 The phase angle under the complex modulus of Pa.

3. The longitudinally oriented film according to claim 1 or 2, wherein the polyethylene has one or more of the following properties: 55 to 65 degrees at 190°C and 10 4 The phase angle under the complex modulus of Pa; A shear thinning ratio of 13 to 17, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190° C. to the complex shear viscosity at 100 rad / s and 190° C.; and MIR / MWD ratio of 9 to 13, MIR is defined as the high load melt index I at 190°C and 21.6 kg 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

4. The longitudinally oriented film according to claim 1 or 2, wherein the polyethylene has one or more of the following properties: Complex shear viscosity η at 0.01 rad / s and 190°C of 5000 to 25000 Pa·s 0.01 ; Complex shear viscosity η at 100 rad / s and 190°C from 900 to 2000 Pa·s 100 ; A melt index I2 at 190°C and 2.16 kg of 0.2 to 2.5 g / 10 min; High load melt index I at 190°C and 21.6 kg of 10 to 75 g / 10 min 21 ; MIR of 25 to 40, MIR is defined as the high load melt index I at 190°C and 21.6 kg 21 Ratio to the melt index I2 at 190°C and 2.16 kg; A number average molecular weight Mn of 20,000 to 55,000 g / mol; A weight average molecular weight Mw of 50,000 to 200,000 g / mol; MWD of 2.5 to 5.5, MWD being defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn; 5 to 10 T 75 -T 25 , T 25 is the temperature in degrees Celsius at which 25% of the polyethylene is eluted, and T 75 It is the temperature in degrees Celsius at which 75% of the polyethylene is eluted, as measured by Temperature Rising Elution Fractionation TREF.

5. The longitudinally oriented film according to claim 1 or 2, wherein the polyethylene has one or more of the following properties: Contains 80 to 99 wt% of ethylene-derived units and 1 to 20 wt% of C3-C 12 α-olefin derived units; is an ethylene-hexene copolymer; and It is a long-chain branched metallocene linear low-density polyethylene, namely LCB-mLLDPE.

6. The longitudinally oriented film according to claim 1 or 2, wherein The longitudinally oriented film is a single-layer film; and / or The longitudinally oriented film is a uniaxially longitudinally oriented film; and / or The layer comprises 80 to 99 wt % of the polyethylene, based on the total weight of the layer; and / or The layer contains 0.1 to 1 wt % of the anti-aging additive, based on the total weight of the layer.

7. The longitudinally oriented film according to claim 1 or 2, wherein: The anti-aging additives include light stabilizers, heat stabilizers, antioxidants or a combination thereof.

8. The longitudinally oriented film according to claim 1 or 2, wherein: The anti-aging additives include hindered amine light stabilizers.

9. A longitudinally oriented monolayer film comprising: (a) 99% by weight of polyethylene, based on the total weight of the film, The polyethylene has: (i) 0.920 g / cm 3 density; and (ii) a melt index of 1 g / 10 min at 190°C and 2.16 kg, and (b) 0.2 wt % of a hindered amine light stabilizer, based on the total weight of the film, The polyethylene also has one or more of the following characteristics: (iii) the inflection point in the Van GurpPalmen plot of phase angle in degrees versus complex modulus in Pa for polyethylene; (iv) a shear thinning ratio of 13 to 15, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190° C. to the complex shear viscosity at 100 rad / s and 190° C.; (v) a MIR / MWD ratio of 9 to 11, MIR being defined as the high load melt index I at 190°C and 21.6 kg 21 The ratio of the melt index I2 at 190°C and 2.16 kg, MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn; and (iv) 60 to 65 degrees at 190°C and 10 4 The phase angle under the complex modulus of Pa.

10. The method for preparing a longitudinally oriented film according to any one of claims 1 to 9, comprising: Using the components of the film to prepare a precursor film through a blow molding process or a casting process, After the precursor film is cooled to form a crystalline structure, the precursor film is stretched in a machine direction to produce the machine direction oriented film.

11. Use of the longitudinally oriented film according to any one of claims 1 to 9 as an agricultural film.

12. The use according to claim 11, wherein the agricultural film is a greenhouse film or a ground film.

13. A method for improving the aging performance of a membrane, comprising: The precursor film is made by using the components of the film through a blow molding process or a casting process, The composition of the film is such that the film comprises at least one layer comprising: (a) 60 to 99.95 wt. % polyethylene, based on the total weight of the layer, The polyethylene has: (i) 0.910 to 0.930 g / cm 3 density; and (ii) a melt index I2 at 190°C and 2.16 kg of 0.1 to 3 g / 10 min, and (b) 0.05 to 3 wt. % of an anti-aging additive, based on the total weight of the layer, After cooling the precursor film to form a crystalline structure, stretching the precursor film in a longitudinal direction to produce a longitudinally oriented film, The polyethylene also has one or more of the following characteristics: (iii) the inflection point in the Van GurpPalmen plot of phase angle in degrees versus complex modulus in Pa for polyethylene; (iv) a shear thinning ratio greater than or equal to 12, the shear thinning ratio being defined as the ratio of the complex shear viscosity at 0.01 rad / s and 190°C to the complex shear viscosity at 100 rad / s and 190°C; and (v) a MIR / MWD ratio greater than or equal to 8, where MIR is defined as the high load melt index I at 190°C and 21.6 kg. 21 MWD is defined as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn, as compared to the melt index I2 at 190°C and 2.16 kg.

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