Polyethylene compositions for film applications with improved toughness and stiffness

Abstract

This invention relates to a polyethylene composition comprising a multimodal linear low-density ethylene copolymer, an article comprising said polyethylene composition, such as a film, and the use of said polyethylene composition in the production of blown films for greenhouse film applications, heavy-duty shipping bag applications, laminated film applications, combined shrink film applications, stand-up pouch applications, or pool lining applications, wherein the linear low-density ethylene copolymer comprises fractions with different lamellar thicknesses, and the ratio of the amount of fractions with a lamellar thickness not exceeding 11.8 nm to the amount of fractions with a lamellar thickness exceeding 11.8 nm but not exceeding 21.7 nm is in the range of 1.30 to 1.60.

Description

Technical Field

[0001] This invention relates to a polyethylene composition comprising a multimodal linear low-density ethylene copolymer having a specific pattern of fractions with varying lamellar thickness, an article comprising the polyethylene composition, such as a film, and the use of the polyethylene composition in the production of blown films for several heavy-duty applications. Background Technology

[0002] Polyethylene compositions containing linear low-density ethylene copolymers (LLDPEs) are particularly suitable for film applications, such as films for packaging or greenhouse applications.

[0003] The packaging industry is trending towards thinner materials. To achieve packaging materials with reduced thickness but identical performance, innovative resins with improved performance balance are needed, particularly in terms of stiffness and toughness. This improved balance of stiffness and toughness contributes to thinner membrane structures and supports the industry's overall sustainability goals. While increased toughness necessitates lower density in packaging materials, lower density leads to lower stiffness; therefore, higher-density MDPE and HDPE products are increasingly used in packaging applications.

[0004] Another way to improve the balance between stiffness and toughness is to use higher levels of α-olefin comonomers (such as 1-hexene and 1-octene) in the polyethylene resin.

[0005] In greenhouse applications, in addition to the improved balance of stiffness and toughness, another performance characteristic that has shown significant benefits is haze. High haze leads to better light diffraction, which has been shown to improve crop yield performance. Typically, LLDPE products and highly branched high-pressure low-density polyethylene (LDPE) products are used for greenhouse applications.

[0006] LLDPE films with a high haze and improved stiffness-toughness balance, using 1-butene comonomers as a cost-effective alternative to those using higher α-olefin comonomers, are not readily available on the market. To date, the desired toughness properties of films designed for certain applications, such as high dart impact strength (DDI), have not been achieved using 1-butene comonomers.

[0007] WO 2004 / 000902 A1 discloses a polyethylene composition comprising bimodal LLDPE having a 1-butene comonomer, which exhibits sufficient stiffness but poor toughness.

[0008] Therefore, there is a need in the art for polyethylene compositions comprising linear low-density polyethylene that can be produced cost-effectively and offer an improved balance of performance in terms of high stiffness, high toughness, and high haze.

[0009] Surprisingly, it has been found that when the molecular design of the multimodal linear low-density ethylene copolymer is carefully tuned to give the copolymer a specific lamellar thickness distribution, polyethylene compositions exhibiting an improved balance of properties can be obtained, such as high stiffness as shown in good tensile properties, high toughness as shown in high puncture resistance, and especially high dart impact strength and high haze. Furthermore, the polyethylene compositions of the present invention exhibit good processability, as shown in high melt flow rate and rheological properties. Summary of the Invention

[0010] The present invention relates to a polyethylene composition comprising a multimodal linear low-density ethylene copolymer, wherein the linear low-density ethylene copolymer comprises fractions with different lamellar thicknesses, and the ratio of the amount of fractions with a lamellar thickness not exceeding 11.8 nm to the amount of fractions with a lamellar thickness exceeding 11.8 nm but not exceeding 21.7 nm is in the range of 1.30 to 1.60, more preferably in the range of 1.35 to 1.55, and most preferably in the range of 1.40 to 1.50.

[0011] Furthermore, the present invention relates to articles comprising polyethylene compositions as described above or below, preferably films, more preferably multilayer films, and even more preferably multilayer blown films.

[0012] Furthermore, the present invention relates to the use of the polyethylene compositions described above or below for the production of blown films for greenhouse film applications, heavy-duty shipping bag applications, laminated film applications, combined shrink film applications, stand-up pouch applications, or pool lining applications.

[0013] definition

[0014] The polyethylene composition according to the invention refers to a polymer derived from more than 50 mol% ethylene monomer units and optionally additional comonomer units.

[0015] The term "copolymer" refers to a polymer derived from ethylene monomer units and additional comonomer units in amounts exceeding 0.05 mol%.

[0016] A polyethylene composition or base resin that includes more than one fraction that differs from each other in at least one property (such as weight-average molecular weight or comonomer content) is called "multimodal". If a multimodal polyethylene composition or base resin includes two different fractions, it is called "bimodal", and correspondingly, if it includes three different fractions, it is called "trimodal". The form of the molecular weight distribution curve of such a multimodal polyethylene composition or base resin, that is, the appearance of the curve of polymer weight fraction as a function of its molecular weight, will, depending on the morphology, show two or more maximum values, or be at least significantly wider than the curve of a single fraction. (See also: ...) Figure 3 ).

[0017] In this invention, the two ethylene-1-butene copolymer fractions are preferably different not only in their molecular weight, as can be seen in the curves of their melt flow rate MFR2 and polymer weight fraction as a function of their molecular weight, but also in their 1-butene content.

[0018] Unless otherwise stated, percentages are typically given in this document as weight % (wt%). Attached Figure Description

[0019] Figure 1 The DSC melt profiles of the compositions of Examples CE1, CE2, IE1 and IE2 after the samples were subjected to the SSA process are shown.

[0020] Figure 2 The amounts of different lamellar thickness fractions of the compositions of Examples IE1, IE2, CE1 and CE2 are shown.

[0021] Figure 3 The GPC data (solid line) of the composition of CE2, IE1 and IE2 relative to molecular weight and the amount of short-chain branched SCBs (dashed line) relative to molecular weight / 1000C are shown. Detailed Implementation

[0022] Polyethylene composition

[0023] The present invention relates to a polyethylene composition comprising a multimodal linear low-density ethylene copolymer, wherein the linear low-density ethylene copolymer comprises fractions with different lamellar thicknesses, and the ratio of the amount of fractions with a lamellar thickness not exceeding 11.8 nm to the amount of fractions with a lamellar thickness exceeding 11.8 nm but not exceeding 21.7 nm is in the range of 1.30 to 1.60, more preferably in the range of 1.35 to 1.55, and most preferably in the range of 1.40 to 1.50.

[0024] Further, the amount of the fraction with a lamellar thickness of more than 11.8 nm to no more than 21.7 nm is preferably 35.0 to 60.0 mol% of the total amount of the linear low-density ethylene copolymer, more preferably 37.5 to 50.0 mol%, and most preferably 40.0 to 44.0 mol%.

[0025] Furthermore, the amount of the fraction with a lamellar thickness not exceeding 5.0 nm is preferably 17.0 to 30.0 mol% of the total amount of the linear low-density ethylene copolymer, more preferably 17.5 to 25.0 mol%, and most preferably 18.0 to 20.0 mol%.

[0026] Furthermore, the amount of the fraction with a lamellar thickness not exceeding 4.2 nm is preferably at least 8.5 mol% of the total amount of the linear low-density ethylene copolymer, more preferably 8.5 to 15.0 mol%, even more preferably 9.0 to 13.5 mol%, and most preferably 10.0 to 12.5 mol%.

[0027] In addition, the ratio of the amount of the linear low-density ethylene copolymer fraction with a lamellar thickness of no more than 4.2 nm to the amount of the fraction with a lamellar thickness of more than 11.8 nm to no more than 21.7 nm is preferably in the range of 0.20 to 0.30, more preferably in the range of 0.22 to 0.29, and most preferably in the range of 0.24 to 0.28.

[0028] Furthermore, the ratio of the amount of the fraction with a lamellar thickness of no more than 4.2 nm to the amount of the fraction with a lamellar thickness of more than 5.0 nm to no more than 6.1 nm is preferably in the range of 0.85 to 1.15, more preferably in the range of 0.90 to 1.10, and most preferably in the range of 0.95 to 1.05.

[0029] The amounts of fractions with different lamellar thicknesses are given in weight percent (wt%).

[0030] The amount of fractions with different lamellar thicknesses is typically measured using a continuous self-nucleation and annealing (SSA) thermal grading technique, which can be run on a differential scanning calorimeter (DSC), as described below in the Measurement Methods section.

[0031] SSA (Self-Nucleation and Annealing) technique consists of sequentially applying self-nucleation and annealing steps to a polymer sample. Following thermal conditioning (multiple heating and cooling cycles), the final DSC (Digital Subtraction and Coagulation) heating run reveals the melt temperature distribution induced by the SSA heat treatment due to the multiphase nature of the polymer's chain structure. SSA is particularly useful for studying the extent and distribution of short-chain branching produced by the copolymerization of ethylene and α-olefins.

[0032] The polyethylene composition comprises a linear low-density ethylene copolymer.

[0033] In one embodiment, the polyethylene composition may also contain other polymers different from the linear low-density ethylene copolymer. Based on the total weight of the polyethylene composition, the amount of said other polymer (if present) is preferably in the range of 0.5 to 15.0% by weight, more preferably in the range of 1.0 to 10.0% by weight.

[0034] However, it is preferred that the linear low-density ethylene copolymer is the only polymer component of the polyethylene composition.

[0035] Preferably, the linear low-density ethylene copolymer is present in the polyethylene composition in an amount of 90.00 to 100% by weight, more preferably 92.50 to 99.99% by weight, and most preferably 99.00% to 99.90% by weight, based on the total weight of the polyethylene composition.

[0036] The polyethylene composition may also contain additives and / or fillers. It should be noted herein that additives may be present in the polymer (a) of ethylene and / or mixed with one or more polymer components in the compounding step to produce the polyethylene composition. Examples of such additives include, in particular, antioxidants, processing stabilizers, UV stabilizers, pigments, fillers, antistatic additives, anti-caking agents, nucleating agents, acid scavengers, slip agents, and polymer processing agents (PPA). Preferably, the total amount of these additives is 1.0% by weight or less of the polyethylene composition, more preferably 0.5% by weight or less, and most preferably 0.25% by weight or less.

[0037] It should be understood in this document that any additives and / or fillers may optionally be added to a so-called masterbatch, which comprises one or more of the respective additives and a carrier polymer. In this case, the carrier polymer is not counted in the amount of one or more polymer components of the polyethylene composition, but rather in the amount of the respective additives, based on the total amount of the polyethylene composition.

[0038] The linear low-density ethylene copolymer is a multi-peak linear low-density ethylene copolymer, preferably a bi-peak linear low-density ethylene copolymer.

[0039] The linear low-density ethylene copolymer preferably comprises two ethylene copolymer fractions with different molecular weights, more preferably composed of two ethylene copolymer fractions with different molecular weights, namely a low molecular weight ethylene copolymer fraction and a high molecular weight ethylene copolymer fraction, wherein the low molecular weight ethylene copolymer fraction has a lower molecular weight than the high molecular weight ethylene copolymer fraction.

[0040] Lower molecular weight can be observed, for example, in the higher melt flow rate of low molecular weight ethylene copolymer fractions compared to high molecular weight ethylene copolymer fractions, or, based on morphology, in two or more maximum values ​​in the GPC curve, or in a GPC curve that is at least significantly wider than the GPC curve of a single fraction (e.g., Figure 3 As shown in the figure.

[0041] The low molecular weight ethylene copolymer fraction preferably has a melt flow rate MFR2 (190°C, 2.16 kg load) of 200 to 500 g / 10 min, more preferably 225 to 400 g / 10 min, and most preferably 250 to 350 g / 10 min.

[0042] The linear low-density ethylene copolymer preferably has a melt flow rate MFR5 (5 kg, 190 °C) of 0.40 to 0.85 g / 10 min, more preferably 0.50 to 0.80 g / 10 min, and most preferably 0.55 to 0.70 g / 10 min.

[0043] The weight ratio of the low molecular weight ethylene copolymer fraction to the high molecular weight ethylene copolymer fraction in the linear low-density ethylene copolymer is preferably 25.0:75.0 to 44.0:56.0, more preferably 30.0:70.0 to 42.0:58.0, even more preferably 35.0:65.0 to 40.5:59.5, and most preferably 37.5:62.5 to 40.0:60.0.

[0044] Furthermore, the weight of the high molecular weight ethylene copolymer fraction is preferably in the range of 56.0 to 75.0% by weight of the total weight of the linear low-density ethylene copolymer, more preferably in the range of 58.0 to 70.0% by weight, even more preferably in the range of 59.5 to 65.0% by weight, and most preferably in the range of 60.0 to 62.5% by weight.

[0045] In addition, the ratio of short-chain branch number to 1000 carbon atoms (SCB / 1000C) in the polymer chain of the high molecular weight ethylene copolymer fraction is preferably in the range of 15.0 to 35.0%, more preferably in the range of 16.0 to 32.5%, and most preferably in the range of 17.5 to 30.0%.

[0046] The ratio of short-chain branch number to 1000 carbon atoms (SCB / 1000C) indicates the comonomer content of the polymer fraction.

[0047] Preferably, the high molecular weight ethylene copolymer fraction has a higher comonomer content than the low molecular weight ethylene copolymer fraction.

[0048] The comonomer of the linear copolymer is preferably selected from α-olefins having 3 to 12 carbon atoms, more preferably 4 to 8 carbon atoms, such as 1-butene, 1-hexene, or 1-octene. 1-Butene is the most preferred.

[0049] Preferably, the low molecular weight ethylene copolymer fraction and the high molecular weight ethylene copolymer fraction contain the same comonomer.

[0050] The lower comonomer content of low molecular weight ethylene copolymer fractions can be seen from their higher density compared to linear low-density ethylene copolymers.

[0051] Preferably, the low molecular weight ethylene copolymer fraction has a molecular weight of 935 to 960 kg / m³. 3 More preferably 940 to 957 kg / m3 And the optimal value is 945 to 955 kg / m³. 3 The density.

[0052] Preferably, the linear low-density ethylene copolymer has a content of 915.0 to 925.0 kg / m³. 3 More preferably 917.0 to 923.5 kg / m 3 And the most preferred value is 919.0 to 922.0 kg / m³ 3 The density.

[0053] The polyethylene composition is characterized by the following properties:

[0054] MFR2

[0055] The polyethylene composition preferably has a melt flow rate MFR2 (190°C, 2.16 kg) as determined according to ISO 1133, which is 0.05 to 0.22 g / 10 min, more preferably 0.10 to 0.20 g / 10 min, and most preferably 0.12 to 0.18 g / 10 min.

[0056] MFR5

[0057] The polyethylene composition preferably has a melt flow rate MFR5 (190°C, 5 kg) as determined according to ISO 1133, which is 0.40 to 0.85 g / 10 min, more preferably 0.50 to 0.80 g / 10 min, and most preferably 0.55 to 0.70 g / 10 min.

[0058] MFR 21

[0059] The polyethylene composition preferably has a melt flow rate (MFR) of 10.0 to 20.0 g / 10 min, more preferably 12.0 to 18.0 g / 10 min, and most preferably 13.5 to 17.0 g / 10 min as determined according to ISO 1133. 21 (190℃, 21.6kg).

[0060] FRR 21 / 2

[0061] The polyethylene composition preferably has a flow rate ratio of 70 to 125, more preferably 80 to 110, and most preferably 90 to 100, compared to the FRR. 21 / 2 MFR 21 Compared to MFR2.

[0062] FRR 21 / 5

[0063] The polyethylene composition preferably has a flow rate ratio (FRR) of 10.0 to 20.0, more preferably 12.5 to 17.5, and most preferably 13.5 to 16.5. 21 / 5 MFR 21 Compared to MFR5.

[0064] Weight-average molecular weight Mw

[0065] The polyethylene composition preferably has a weight-average molecular weight Mw of 185,000 to 250,000 g / mol, more preferably 190,000 to 235,000 g / mol, and most preferably 195,000 to 220,000 g / mol.

[0066] z-average molecular weight Mz

[0067] The polyethylene composition preferably has a z-average molecular weight Mz of 1,000,000 to 1,500,000 g / mol, more preferably 1,050,000 to 1,400,000 g / mol, and most preferably 1,100,000 to 1,300,000 g / mol.

[0068] Molecular weight distribution Mw / Mn

[0069] The polyethylene composition has a polydispersity index (PDI) in the range of 10.0 to 20.0, more preferably in the range of 12.0 to 18.0, and most preferably in the range of 13.0 to 17.0, which is the ratio of weight-average molecular weight Mw to number-average molecular weight Mn, Mw / Mn.

[0070] Molecular weight distribution Mz / Mw

[0071] The polyethylene composition has a polydispersity index (PDI) in the range of 3.0 to 8.0, more preferably in the range of 3.5 to 7.5, and most preferably in the range of 4.0 to 6.0, which is the ratio of z-average molecular weight Mz to weight-average molecular weight Mw, Mw / Mw.

[0072] density

[0073] The polyethylene composition preferably has a content of 915.0 to 925.0 kg / m³. 3 More preferably 917.0 to 923.5 kg / m 3 And the most preferred value is 919.0 to 922.0 kg / m³ 3 The density is determined according to ISO 1183-1:2004.

[0074] The density of the base resin is primarily affected by the quantity and type of comonomers. In addition, the properties of the polymer, mainly derived from the catalyst used, and the melt flow rate also play a role.

[0075] The polyethylene composition is also characterized by specific rheological properties.

[0076] eta 0.05

[0077] The polyethylene composition preferably has a complex viscosity eta at 0.05 rad / s of 50,000 to 100,000 Pa·s, more preferably 55,000 to 85,000 Pa·s, and most preferably 60,000 to 75,000 Pa·s. 0.05 .

[0078] Viscosity eta 0.05 It is measured at low frequency and therefore under low shear stress, and is proportional to the molecular weight of the composition. Therefore, it can be regarded as a measure of the molecular weight of the polyethylene composition.

[0079] eta 300

[0080] The polyethylene composition preferably has a complex viscosity eta at 300 rad / s of 925 to 1250 Pa·s, more preferably 950 to 1200 Pa·s, and most preferably 975 to 1100 Pa·s. 300 .

[0081] Viscosity eta 300 It is measured at high frequencies and therefore under high shear stress, and is inversely proportional to the flowability of the composition. Therefore, it can be regarded as a measure of the processability of the polyethylene composition.

[0082] Viscosity eta under constant shear stress of 747 Pa 747

[0083] The polyethylene composition preferably has a viscosity eta at a constant shear stress of 747 Pa, which is 70 to 150 kPa·s, more preferably 80 to 135 kPa·s, and most preferably 85 to 125 kPa·s. 747 .

[0084] Viscosity eta under constant shear stress of 747 Pa 747 Influenced by weight-average molecular weight.

[0085] Shear thinning index SHI 2.7 / 210

[0086] The polyethylene composition preferably has a shear thinning index (SHI) of 10 to 20, more preferably 11 to 19, and most preferably 12 to 18. 2.7 / 210 That is, the ratio of the complex shear modulus at 2.7 kPa to the complex shear modulus at 210 kPa.

[0087] Shear thinning index SHI5 / 200

[0088] The polyethylene composition preferably has a shear thinning index (SHI) of 15.0 to 35.0, more preferably 17.5 to 32.5, and most preferably 20.0 to 30.0. 5 / 200 That is, the ratio of the complex shear modulus at 5 kPa to the complex shear modulus at 200 kPa.

[0089] Shear thinning index SHI 2.7 / 210

[0090] The polyethylene composition preferably has a shear thinning index (SHI) of 20.0 to 40.0, more preferably 22.5 to 37.5, and most preferably 25.0 to 35.0. 2.7 / 210 That is, the ratio of the complex shear modulus at 2.7 kPa to the complex shear modulus at 210 kPa.

[0091] The shear thinning index is the ratio of the upper complex shear modulus to the lower complex shear modulus and the ratio of the rheological frequency curve, and therefore can be regarded as a rheological measurement for polydispersity.

[0092] The rheological properties described above (such as SHI) 2.7 / 210 SHI 5 / 200 eta 0.05 eta 300 and eta 747 The rheological properties have been measured on polyethylene compositions that differ from polymeric compositions by including additional components (such as additives), preferably linear low-density ethylene copolymers. However, these properties can also be measured on polymeric compositions that have been stabilized with a stabilizer package, preferably linear low-density ethylene copolymers. The rheological properties measured on the polymeric composition (preferably a linear low-density ethylene copolymer) are preferably within the same range as those measured on the polyethylene composition.

[0093] Products

[0094] In another respect, the present invention relates to articles comprising, preferably composed of, a polyethylene composition as described above or below.

[0095] Preferably, the article is a film or a blown product.

[0096] Particularly preferred is that the article is a film, such as a blown film or a cast film, preferably a multilayer film, such as a multilayer blown film or a multilayer cast film, especially a multilayer blown film. In the multilayer film, the polyethylene composition is preferably contained in one or more or all of the layers of the multilayer film. Particularly preferred is that all or more or all of the layers of the multilayer film are composed of the polyethylene composition as described above or below.

[0097] This product (preferred film) is particularly suitable for heavy-duty applications, such as greenhouse film applications, heavy-duty shipping bag applications, laminated film applications, combined shrink film applications, stand-up pouch applications, or pool lining applications.

[0098] The membrane preferably has a thickness of 10 μm to 100 μm, more preferably 20 to 75 μm, and most preferably 30 to 50 μm.

[0099] In some embodiments, the thickness of the membrane can be up to 500 μm, more preferably up to 350 μm, and most preferably up to 250 μm.

[0100] Surprisingly, articles (preferably films) comprising polyethylene compositions as described above or below, preferably composed of polyethylene compositions as described above or below, exhibit an improved balance of properties in terms of stiffness (in terms of tensile properties), toughness (especially, for example, in terms of dart strength), optical properties (especially in terms of haze), and processability (in terms of the rheological properties of the polyethylene composition).

[0101] Preferably, the film comprising the polyethylene composition according to the invention is characterized by the following properties:

[0102] Longitudinal tensile modulus (TM-MD)

[0103] The film comprising the polyethylene composition according to the invention preferably has a longitudinal tensile modulus (TM-MD) of at least 275 MPa, more preferably at least 300 MPa, and most preferably at least 315 MPa, as measured according to ASTM D882 on a 40 μm blown film at a test speed of 5 mm / min and a strain of 1%. The upper limit of the longitudinal tensile modulus is generally not higher than 500 MPa, preferably not higher than 400 MPa.

[0104] Transverse tensile modulus (TM-TD)

[0105] The film comprising the polyethylene composition according to the invention preferably has a transverse tensile modulus (TM-TD) of at least 350 MPa, more preferably at least 375 MPa, and most preferably at least 400 MPa, as measured according to ASTM D882 on a 40 μm blown film at a test speed of 5 mm / min and a strain of 1%. The upper limit of the transverse tensile modulus is generally not higher than 500 MPa, preferably not higher than 450 MPa.

[0106] Longitudinal tensile stress at break (TSB-MD)

[0107] The film comprising the polyethylene composition according to the invention preferably has a longitudinal tensile stress at break (TSB-MD) of at least 50 MPa, more preferably at least 55 MPa, and most preferably at least 60 MPa, as measured on a 40 μm blown film at a test speed of 500 mm / min according to ISO 527-3:1996. The upper limit of the longitudinal tensile stress at break is generally not higher than 100 MPa, preferably not higher than 80 MPa.

[0108] Transverse tensile stress at break (TSB-TD)

[0109] The film comprising the polyethylene composition according to the invention preferably has a transverse tensile stress at break (TSB-TD) of at least 30 MPa, more preferably at least 35 MPa, and most preferably at least 402 MPa, as measured on a 40 μm blown film at a test speed of 500 mm / min according to ISO 527-3:1996. The upper limit of the transverse tensile stress at break is generally not higher than 75 MPa, preferably not higher than 60 MPa.

[0110] Longitudinal yield tensile stress (TSY-MD)

[0111] According to ISO 527-3:1996, when measured at a test speed of 500 mm / min on a 40 μm blown film, the film containing the polyethylene composition according to the present invention preferably does not have longitudinal yield tensile stress (TSY-MD).

[0112] Transverse yield tensile stress (TSY-TD)

[0113] The film comprising the polyethylene composition according to the invention preferably has a transverse yield tensile stress (TSY-TD) of at least 8.0 MPa, more preferably at least 9.0 MPa, and most preferably at least 10.0 MPa, measured on a 40 μm blown film at a test speed of 500 mm / min according to ISO 527-3:1996. The upper limit of the transverse yield tensile stress is generally not higher than 30 MPa, preferably not higher than 20 MPa.

[0114] Longitudinal elongation at break (EB-MD)

[0115] The film comprising the polyethylene composition according to the invention preferably has at least 300%, more preferably at least 350%, and most preferably at least 400% of the longitudinal elongation at break (EB-MD) measured on a 40 μm blown film at a test speed of 500 mm / min according to ISO 527-3:1996. The upper limit of the longitudinal elongation at break is generally not higher than 600%, preferably not higher than 500%.

[0116] Transverse elongation at break (EB-TD)

[0117] The film comprising the polyethylene composition according to the invention preferably has at least 600%, more preferably at least 650%, and most preferably at least 700% of the transverse elongation at break (EB-TD) measured on a 40 μm blown film at a test speed of 500 mm / min according to ISO 527-3:1996. The upper limit of the transverse elongation at break is generally not higher than 900%, preferably not higher than 800%.

[0118] Longitudinal Elmendorf tear strength (TS-MD)

[0119] The film comprising the polyethylene composition according to the invention preferably has a longitudinal Elmendorf tear strength (TS-MD) of at least 2.0 N, more preferably at least 3.0 N, and most preferably at least 5.0 N, as measured on a 40 μm blown film according to ISO 6383-2:1983. The upper limit of the longitudinal Elmendorf tear strength is generally not higher than 10.0 N, preferably not higher than 7.5 N.

[0120] Transverse Elmendorf tear strength (TS-TD)

[0121] The film comprising the polyethylene composition according to the invention preferably has a transverse Elmendorf tear strength (TS-TD) of at least 7.0 N, more preferably at least 8.5 N, and most preferably at least 10.0 N on a 40 μm blown film according to ISO 6383-2:1983. The upper limit of the transverse Elmendorf tear strength is generally not higher than 20.0 N, preferably not higher than 15.0 N.

[0122] Puncture resistance – force (PRF)

[0123] The film comprising the polyethylene composition according to the invention preferably has a puncture resistance force (PRF) of at least 30 N, more preferably at least 35 N, and most preferably at least 40 N when measured on a 40 μm blown film. The upper limit of the puncture resistance force (PRF) is generally no higher than 60 N, preferably no higher than 55 N.

[0124] Puncture resistance – energy (PRE)

[0125] The film comprising the polyethylene composition according to the invention preferably has a puncture resistance energy (PRE) of at least 1.2 J, more preferably at least 1.5 J, and most preferably at least 1.8 J when measured on a 40 μm blown film. The upper limit of the puncture resistance energy (PRE) is generally not higher than 5.0 J, preferably not higher than 3.5 J.

[0126] Dart Impact Intensity (DDI)

[0127] The film comprising the polyethylene composition according to the invention preferably has a dart impact strength (DDI) of at least 250 g, preferably at least 300 g, and most preferably at least 400 g when measured on a 40 μm blown film. The upper limit of the dart impact strength is generally no more than 500 g, preferably no more than 450 g.

[0128] Haze

[0129] The film comprising the polyethylene composition according to the invention preferably has a haze of at least 75.0%, preferably at least 80.0%, and most preferably at least 84.0% when measured on a 40 μm blown film. The upper limit of the dart impact strength is generally not more than 92.0%, preferably not more than 90.0%.

[0130] gloss

[0131] The film comprising the polyethylene composition according to the invention preferably has a gloss at 20° when measured on a 40 μm blown film of at least 0.2%, preferably at least 0.4%, and most preferably at least 0.5%. The upper limit of the dart impact strength is generally no more than 1.5%, preferably no more than 1.0%.

[0132] The film comprising the polyethylene composition according to the invention preferably has a gloss at 60° when measured on a 40 μm blown film of at least 5.0%, preferably at least 6.0%, and most preferably at least 7.5%. The upper limit of the dart impact strength is generally not more than 20.0%, preferably not more than 15.0%.

[0133] Films comprising the polyethylene composition according to the invention preferably have a gloss of at 85° when measured on a 40 μm blown film of at least 25.0%, preferably at least 30.0%, and most preferably at least 35.0%. The upper limit of the dart impact strength is generally no more than 60.0%, preferably no more than 50.0%.

[0134] method

[0135] The multimodal linear low-density ethylene copolymer of the polyethylene composition is preferably produced in a method wherein at least two linear low-density ethylene copolymer fractions are polymerized in any order in at least two sequential reactor stages in a multi-stage manner in the presence of a polymerization catalyst, preferably a Ziegler-Natta polymerization catalyst.

[0136] Polymerization catalyst

[0137] The preferred polymerization catalyst is a Ziegler-Natta polymerization catalyst, which preferably contains magnesium compounds, aluminum compounds and titanium compounds supported on a particulate support.

[0138] The particle support can be an inorganic oxide support, such as silicon dioxide, alumina, titanium dioxide, silicon dioxide-alumina, and silicon dioxide-titanium dioxide. Preferably, the support is silicon dioxide.

[0139] The average particle size of the silica support can typically be from 10 to 100 μm. However, it has been shown that if the support has an average particle size of 15 to 30 μm, preferably 18 to 25 μm, particular advantages can be obtained. In particular, it has been found that the average particle size of the polymer produced in the method of the present invention is the same regardless of whether the catalyst is prepared on a 20 μm or 40 μm support. In fact, it has been found that if a support with an average particle size of 20 μm is used, the fraction of fine polymer particles is lower. The reduction in fine polymers reduces the risk of clogging and thus contributes to stable process operation. On the other hand, this contributes to the production of polymer films with good uniformity. Examples of suitable support materials are, for example, ES747JR manufactured and sold by Ineos Silicas (formerly Crossfield) and SP9-491 manufactured and sold by Grace.

[0140] The magnesium compound is a reaction product of dialkyl magnesium and an alcohol. The alcohol is a straight-chain or branched aliphatic monohydric alcohol. Preferably, the alcohol has 6 to 16 carbon atoms. Branched alcohols are particularly preferred; 2-ethyl-1-hexanol is an example of a preferred alcohol. The dialkyl magnesium can be any compound in which magnesium is bonded to two alkyl groups, which can be the same or different. Butyl-octyl magnesium is an example of a preferred dialkyl magnesium.

[0141] The aluminum compounds are chlorinated alkyl aluminum compounds. Particularly preferred compounds are alkyl aluminum dichloride and alkyl sesquichloride.

[0142] The titanium compound is a halogenated titanium compound, preferably a chlorine-containing titanium compound. A particularly preferred titanium compound is titanium tetrachloride.

[0143] As described in EP-A-688794, the catalyst can be prepared by sequentially contacting the support with the aforementioned compound. Alternatively, as described in WO-A-01 / 55230, it can be prepared by first preparing a solution from the components and then contacting the solution with the support.

[0144] Other suitable catalysts are described in EP 2 799 456.

[0145] The aforementioned solid catalyst component is contacted with an alkylaluminum co-catalyst, preferably a trialkylaluminum compound, which can then be used for polymerization. The contact between the solid catalyst component and the alkylaluminum co-catalyst can be carried out before the catalyst is introduced into the polymerization reactor, or it can be carried out by introducing the two components separately into the polymerization reactor.

[0146] Method details:

[0147] Preferably, the method for producing the polyethylene composition according to the invention comprises the following steps:

[0148] a) In a first polymerization reactor, in the presence of a polymerization catalyst, ethylene and at least one comonomer selected from α-olefins having 3 to 12 carbon atoms are polymerized to produce a first intermediate material comprising a low molecular weight ethylene copolymer fraction.

[0149] b) Transfer the first intermediate material to the second polymerization reactor;

[0150] c) In the presence of a first intermediate material, polymerize ethylene and at least one comonomer selected from α-olefins having 3 to 12 carbon atoms to produce a high molecular weight ethylene copolymer fraction.

[0151] d) Obtain a multimodal linear low-density ethylene copolymer containing low-molecular-weight ethylene copolymer fractions and high-molecular-weight ethylene copolymer fractions from the final polymerization reactor;

[0152] e) Blend base resins to obtain a polyethylene composition.

[0153] Preferably, the first intermediate material comprises a low molecular weight ethylene copolymer fraction as defined above or below.

[0154] The preferred α-olefin comonomer used in the two polymerization reactors is 1-butene.

[0155] The linear low-density ethylene copolymer preferably comprises low molecular weight ethylene copolymer fractions and high molecular weight ethylene copolymer fractions as defined above or below.

[0156] The multimodal linear low-density ethylene copolymer and polyethylene composition is preferably defined by the properties of the base resin and polyethylene composition described above or in the claims.

[0157] The temperature in the first reactor, preferably a first slurry-phase reactor, and more preferably a first loop reactor, is typically 50 to 115°C, preferably 60 to 110°C, and particularly 70 to 100°C. The pressure is typically 1 to 150 bar, preferably 1 to 100 bar.

[0158] Slurry-phase polymerization can be carried out in any known reactor used for slurry-phase polymerization. Such reactors include continuous stirred tank reactors and loop reactors. Polymerization is particularly preferred in a loop reactor. In such a reactor, the slurry is circulated at high speed along a closed pipe using a circulation pump. Loop reactors are well known in the art and examples are given, for example, in US-A-4,582,816, US-A-3,405,109, US-A-3,324,093, EP-A-479,186, and US-A-5,391,654.

[0159] Slurry-phase polymerization is sometimes advantageous above the critical temperature and pressure of the fluid mixture. Such an operation is described in US-A-5,391,654. In this operation, the temperature is typically at least 85°C, preferably at least 90°C. Furthermore, the temperature is typically not higher than 110°C, preferably not higher than 105°C. The pressure under these conditions is typically at least 40 bar, preferably at least 50 bar. Furthermore, the pressure is typically not higher than 150 bar, preferably not higher than 100 bar. In a preferred embodiment, the slurry-phase polymerization step is carried out under supercritical conditions, whereby the reaction temperature and pressure are above the equivalent critical point of the mixture formed from the hydrocarbon medium, monomer, hydrogen, and comonomer, and the polymerization temperature is below the melting temperature of the formed polymer.

[0160] Slurry can be extracted from the slurry phase reactor continuously or intermittently. A preferred method for intermittent extraction is to use a settling leg, where the slurry is concentrated, followed by extraction of a batch of concentrated slurry from the reactor. The use of a settling leg is disclosed in particular in US-A-3,374,211, US-A-3,242,150, and EP-A-1,310,295. Continuous extraction is disclosed in particular in EP-A-891,990, EP-A-1415,999, EP-A-1,591,460, and WO-A-2007 / 025640. Continuous extraction is advantageously combined with suitable concentration methods as disclosed in EP-A-1415,999, and EP-A-1,591,460.

[0161] Settling legs are used to concentrate the slurry drawn from the reactor. Therefore, the drawn-out stream contains, on average, more polymer per volume than the slurry within the reactor. This results in less liquid needing to be recycled back to the reactor, thus reducing equipment costs. In commercial-scale systems, the fluid drawn out along with the polymer is evaporated in a flash tank, and from there compressed and recycled back to the slurry phase reactor.

[0162] However, the settling legs extract polymer intermittently. This causes pressure and other variables in the reactor to fluctuate with the extraction cycle. Furthermore, the extraction capacity is limited and depends on the size and number of settling legs. To overcome these drawbacks, continuous extraction is generally preferred.

[0163] On the other hand, the problem with continuous extraction is that it typically extracts the polymer at the same concentration as that present in the reactor. To reduce the amount of hydrocarbons to be compressed, continuous outlet is advantageously combined with a suitable concentration device, such as a hydrocyclone or sieve, as disclosed in EP-A-1 415 999 and EP-A-1 591 460. The polymer-rich stream is then directed to a flash evaporator, while the polymer-lean stream is returned directly to the reactor.

[0164] To adjust the melt flow rate of the polyethylene fraction polymerized in the slurry phase reactor, hydrogen is preferably introduced into the reactor.

[0165] Preferably, the hydrogen feed in the first reaction stage is adjusted according to the ethylene feed to achieve a hydrogen to ethylene ratio of 250 to 500 mol / kmol, more preferably 300 to 400 mol / kmol, in the first slurry phase reactor.

[0166] To adjust the content and density of comonomers in the polyethylene fraction polymerized in the slurry phase reactor, it is preferable to introduce α-olefin comonomers, preferably 1-butene, into the reactor.

[0167] Preferably, the hydrogen feed in the first reaction stage is adjusted according to the ethylene feed to achieve a comonomer to ethylene ratio of 575 to 750 mol / kmol, more preferably 600 to 700 mol / kmol, and more preferably a 1-butene to ethylene ratio in the first slurry phase reactor.

[0168] The polyethylene fraction produced in the first slurry phase reactor is typically an ethylene copolymer fraction.

[0169] The residence time and polymerization temperature in the first slurry phase reactor are adjusted so that the amount of the polymerized ethylene copolymer fraction is typically 25.0 to 44.0% by weight of the linear low-density ethylene copolymer, preferably 30.0 to 42.0% by weight, more preferably 35.0 to 40.0% by weight, and most preferably 37.5 to 40.0% by weight.

[0170] Before introducing the polymer slurry into the second polymerization reactor, a purging step can be performed to substantially remove hydrocarbons from the polymer slurry. The purging step is preferably carried out in a flash evaporator, operated at a pressure of 2 to 10 bar and a temperature of 50 to 100°C. After the purging step, the first intermediate material produced in the first slurry reactor is preferably transferred to the second reactor, preferably a gas-phase reactor, more preferably a fluidized bed gas-phase reactor.

[0171] In a fluidized bed gas-phase reactor, olefins are polymerized in an upward-moving gas stream in the presence of a polymerization catalyst. The reactor typically comprises a fluidized bed consisting of growing polymer particles containing an active catalyst positioned above a fluidized grid.

[0172] The polymer bed is fluidized with the aid of a fluidizing gas comprising an olefin monomer, one or more final comonomers, a final chain growth control agent or chain transfer agent such as hydrogen, and a final inert gas. Therefore, the inert gas may be the same as or different from the inert gas used in a slurry-phase reactor. The fluidizing gas is introduced into an inlet chamber at the bottom of the reactor. To ensure uniform gas flow distribution across the cross-sectional surface area of ​​the inlet chamber, the inlet pipe may be equipped with flow-splitting elements known in the art, such as US-A-4,933,149 and EP-A-684 871.

[0173] The gas flow enters the fluidized bed from the inlet chamber through a fluidizing grid. The purpose of the fluidizing grid is to uniformly distribute the gas flow across the cross-sectional area of ​​the bed. Sometimes, the fluidizing grid can be arranged to establish a gas flow to purge along the reactor wall, as disclosed in WO-A-2005 / 087261. Other types of fluidizing grids are disclosed, in particular, in US-A-4,578,879, EP 600 414, and EP-A-721 798. An overview is given in Geldart and Bayens: The Design of Distributors for Gas-fluidised Beds, Powder Technology, Vol. 42, 1985.

[0174] The fluidizing gas passes through the fluidized bed. The apparent velocity of the fluidizing gas must be higher than the minimum fluidizing velocity of the particles contained in the fluidized bed; otherwise, fluidization will not occur. On the other hand, the gas velocity should be lower than the initial velocity of the pneumatic transport; otherwise, the entire bed will be entrained by the fluidizing gas. When the particle characteristics are known, the minimum fluidizing velocity and the initial velocity of the pneumatic transport can be calculated using common engineering practices. An overview is given in particular in Geldart: Gas Fluidisation Technology, J. Wiley & Sons, 1996.

[0175] When fluidized gas comes into contact with a bed containing an active catalyst, the active components of the gas (such as monomers and chain transfer agents) react in the presence of the catalyst to produce polymer products. Simultaneously, the gas is heated by the heat of reaction.

[0176] The unreacted fluidizing gas is then removed from the top of the reactor, compressed, and recirculated to the reactor's inlet chamber. Fresh reactants are introduced into the fluidizing gas stream before entering the reactor to compensate for losses caused by the reaction and product extraction. It is well known to analyze the composition of the fluidizing gas and introduce gas components to maintain a constant composition. The actual composition is determined by the desired product properties and the catalyst used in the polymerization.

[0177] The gas is then cooled in a heat exchanger to remove the heat of reaction. The gas is cooled to a temperature below that of the bed to prevent the bed from being heated by the reaction. The gas can be cooled to a temperature at which some of the gas condenses. When droplets enter the reaction zone, they are vaporized. The heat of vaporization then helps to remove the heat of reaction. This operation is called condensation mode, and variations thereof are disclosed in particular in WO-A-2007 / 025640, US-A-4,543,399, EP-A-699 213, and WO-A-94 / 25495. A condensing agent can also be added to the circulating gas stream, as disclosed in EP-A-696 293. The condensing agent is a non-polymerizable component, such as propane, n-pentane, isopentane, n-butane, or isobutane, which condenses at least partially in the cooler.

[0178] The polymer product can be extracted from the gas-phase reactor continuously or intermittently. Combinations of these methods are also possible. Continuous extraction is disclosed in particular in WO-A-00 / 29452. Intermittent extraction is disclosed in particular in US-A-4,621,952, EP-A-188125, EP-A-250 169 and EP-A-579 426.

[0179] The top of at least one gas-phase reactor may include a so-called separation zone. In such a zone, the reactor diameter is increased to reduce the gas velocity and allow particles carried out of the bed by the fluidizing gas to settle back into the bed.

[0180] Bed levels can be observed using various techniques known in the art. For example, the pressure difference between the bottom of the reactor and a specific height of the bed can be recorded along the entire length of the reactor, and the bed level can be calculated based on the pressure difference value. Such a calculation produces a time-averaged level. Ultrasonic sensors or radioactive sensors can also be used. Instantaneous levels can be obtained using these methods, and these levels can then be averaged over a period of time to obtain a time-averaged bed level.

[0181] If desired, one or more antistatic agents may be introduced into at least one gas-phase reactor. Suitable antistatic agents and methods of using them are disclosed in particular in US-A-5,026,795, US-A-4,803,251, US-A-4,532,311, US-A-4,855,370, and EP-A-560 035. They are generally polar compounds and include, in particular, water, ketones, aldehydes, and alcohols.

[0182] The reactor may include a mechanical agitator to further promote mixing within the fluidized bed. Examples of suitable agitator designs are given in EP-A-707 513.

[0183] The temperature for gas-phase polymerization in the gas-phase reactor is typically at least 70°C, preferably at least 75°C. The temperature typically does not exceed 105°C, preferably not exceeding 95°C. The pressure is typically at least 10 bar, preferably at least 15 bar, but typically does not exceed 30 bar, preferably not exceeding 25 bar.

[0184] Hydrogen is introduced into the reactor to adjust the melt flow rate of the polyethylene fraction polymerized in the first gas phase reactor.

[0185] Preferably, the hydrogen feed is adjusted according to the ethylene feed to achieve a hydrogen to ethylene ratio of 2.5 to 10.0 mol / kmol in the gas phase reactor, more preferably 3.5 to 9.0 mol / kmol, and most preferably 5.0 to 7.5 mol / kmol.

[0186] In the gas-phase reactor, ethylene copolymer fractions are preferably produced. Therefore, the fluidized gas stream contains a comonomer, preferably 1-butene. The comonomer used in the first gas-phase reactor may be the same as or different from the comonomer used in the slurry-phase reactor, preferably the same. Preferably, the comonomer feed is adjusted according to the ethylene feed to achieve a comonomer to ethylene ratio of at least 750 mol / kmol, more preferably 750 to 850 mol / kmol, most preferably 760 to 800 mol / kmol, and preferably a 1-butene to ethylene ratio.

[0187] The residence time and polymerization temperature in the gas-phase reactor are adjusted so that the amount of the polymerized ethylene copolymer fraction is typically 56.0 to 75.0 wt%, more preferably 58.0 to 70.0 wt%, even more preferably 59.5 to 65.0 wt%, and most preferably 60.0 to 62.5 wt% of the linear low-density ethylene copolymer.

[0188] Furthermore, the linear low-density ethylene copolymer produced from the gas-phase reactor, preferably composed of low-molecular-weight ethylene copolymer fractions and high-molecular-weight ethylene copolymer fractions, preferably has a molecular weight distribution of 915.0 to 925.0 kg / m³. 3More preferably 917.0 to 923.5 kg / m 3 And the most preferred value is 919.0 to 922.0 kg / m³ 3 The density.

[0189] A prepolymerization step can be performed prior to the polymerization of the low-molecular-weight ethylene copolymer fraction and the high-molecular-weight ethylene copolymer fraction in the first and second polymerization regions. The purpose of prepolymerization is to polymerize a small amount of polymer onto the catalyst at low temperature and / or low monomer concentration. Prepolymerization can improve the performance of the catalyst in the slurry and / or alter the properties of the final polymer. The prepolymerization step can be carried out in the slurry or the gas phase. Preferably, prepolymerization is carried out in the slurry, and more preferably in a loop reactor. Prepolymerization is then preferably carried out in an inert diluent, preferably a low-boiling-point hydrocarbon or a mixture of such hydrocarbons having 1 to 4 carbon atoms.

[0190] The temperature in the prepolymerization step is typically 0 to 90°C, preferably 20 to 80°C, and more preferably 50 to 75°C.

[0191] Pressure is not critical and is typically between 1 and 150 bar, preferably between 10 and 100 bar.

[0192] The polymerization catalyst can be fed to any polymerization stage, but is preferably fed to the first polymerization stage or the prepolymerization stage (if present). Preferably, all catalyst components are introduced into the prepolymerization step. Then, preferably, the reaction products of the prepolymerization step are introduced into the first polymerization reactor. The prepolymer component is included in the amount of components produced in the first actual polymerization step following the prepolymerization step, preferably in the amount of the low molecular weight ethylene polymer component.

[0193] Mixing

[0194] The polyethylene compositions of the present invention are preferably produced in a multi-stage process, which further includes a compounding step in which a multi-peak linear low-density ethylene copolymer, typically obtained as a powder from a reactor, is extruded in an extruder and then granulated into polymer pellets in a manner known in the art to form the polyolefin compositions of the present invention.

[0195] Optionally, additives or other polymeric components may be added to the composition in the amounts described above during the compounding step. Preferably, the multimodal linear low-density ethylene copolymer obtained from the reactor is compounded with the additives in an extruder in a manner known in the art.

[0196] For example, the extruder can be any conventionally used extruder. Examples of extruders used in the compounding step of this invention can be those supplied by Japan Steelworks, Kobe Steel, or Farrel-Pomini, such as the JSW 460P or JSW CIM90P.

[0197] Membrane production

[0198] Polymer films are typically produced by blown film extrusion or cast film extrusion.

[0199] In the case of multilayer films, several layers of the film can be co-extruded or laminated during blown film extrusion or cast film extrusion.

[0200] These methods are well known in the art and are readily adaptable for the production of films comprising polyethylene compositions according to the invention.

[0201] use

[0202] The present invention further relates to the use of the polyethylene compositions described above or below for the production of blown films for greenhouse film applications, heavy-duty shipping bag applications, laminated film applications, combined shrink film applications, stand-up pouch applications, or pool lining applications.

[0203] Example

[0204] 1. Measurement Method

[0205] a) Melt flow rate

[0206] Melt flow rate (MFR) is determined according to ISO 1133 and expressed in g / 10 min. MFR indicates the flowability of a polymer and therefore its processability. A higher melt flow rate generally indicates a lower polymer viscosity. The MFR5 for polyethylene was measured at 190°C and a load of 5 kg, and the MFR2 for polyethylene was measured at 190°C and a load of 2.16 kg. 21 The measurement was taken at a temperature of 190℃ and a load of 21.6 kg. The flow rate ratio (FRR) refers to the ratio of flow rates under different loads. Therefore, FRR... 21 / 5 It refers to MFR 21 The value of / MFR5.

[0207] The MFR2 of the high molecular weight ethylene polymer component polymerized in the second polymerization reactor is calculated from the MFR2 of the low molecular weight ethylene polymer component polymerized in the first polymerization reactor and the MFR2 of the base resin as follows:

[0208] LogMFR最终 = weight% 第一 ×LogMFR 第一 +weight% 第二 ×LogMFR 第二

[0209] in

[0210] - "Finally" refers to "polyethylene resin".

[0211] - "First" refers to "the polymer component produced in the first reactor".

[0212] - "Second" refers to "the polymer component produced in the second reactor".

[0213] b) Density

[0214] The density of the polymer was measured according to ISO 1183-1:2004, Method A, on compression-molded specimens prepared according to EN ISO 1872-2 (February 2007), and expressed in kg / m³. 3 Provided.

[0215] c) Comonomer content

[0216] Recorded on a Bruker 400MHz spectrometer at 130°C from a sample dissolved in 1,2,4-trichlorobenzene / benzene-d6 (90 / 10 w / w). 13 C-NMR spectra. The conversion between % weight and % mole can be performed by calculation.

[0217] d) Rheological parameters

[0218] Characterization of the polymer melt by dynamic shear measurements conformed to ISO standards 6721-1 and 6721-10. Measurements were performed on an Anton Paar MCR301 stress-controlled rotational rheometer equipped with a 25 mm parallel plate geometry. Measurements were taken on a compression plate using a nitrogen atmosphere and with strain set within the linear viscoelastic range. Oscillatory shear tests were conducted at 190 °C with a frequency range between 0.01 and 600 rad / s and a gap of 1.2 mm.

[0219] In dynamic shear experiments, the probe undergoes uniform deformation under sinusoidally varying shear strain or shear stress (strain-controlled mode and stress-controlled mode, respectively). In controlled strain experiments, the probe is subjected to sinusoidal strain that can be expressed by the following equation:

[0220] γ(t)=γ0 sin(ωt) (1)

[0221] If the applied strain is within the linear viscoelastic range, the resulting sinusoidal stress response can be given by the following equation:

[0222] σ(t)=σ0 sin (ωt+δ) (2)

[0223] Where σ0 and γ0 are the stress and strain amplitudes, respectively; ω is the angular frequency; δ is the phase shift (the loss angle between the applied strain and the stress response); and t is time.

[0224] Dynamic test results are typically represented by several different rheological functions, namely shear storage modulus G', shear loss modulus G”, complex shear modulus G*, complex shear viscosity η*, dynamic shear viscosity η', the heterogeneous component of complex shear viscosity η”, and loss tangent tanη, which can be expressed as follows:

[0225]

[0226]

[0227] G* = G' + iG“ [Pa] (5)

[0228] η* = η' - iη" [Pa·s] (6)

[0229]

[0230]

[0231] The determination of the so-called shear thinning index, which is related to MWD but independent of Mw, is carried out as described in Equation 9.

[0232]

[0233] For example, SHI (2.7 / 210) SHI is defined as the complex viscosity (in Pa·s) determined by dividing the complex viscosity (in Pa·s) determined by the G* value equal to 2.7 kPa by the complex viscosity (in Pa·s) determined by the G* value equal to 210 kPa. (5 / 200) The complex viscosity is defined by dividing the value of the complex viscosity (in Pa·s) determined by the G* value equal to 5 kPa by the value of the complex viscosity (in Pa·s) determined by the G* value equal to 200 kPa.

[0234] As a function of frequency (ω), the values ​​of storage modulus (G'), loss modulus (G"), complex modulus (G*), and complex viscosity (η*) were obtained.

[0235] Therefore, for example, η* 300rad / s (eta* 300rad / s η* is used as an abbreviation for complex viscosity at a frequency of 300 rad / s. 0.05rad / s(eta* 0.05rad / s It is used as an abbreviation for complex viscosity at a frequency of 0.05 rad / s.

[0236] The loss tangent tan(δ) is defined as the ratio of the loss modulus (G") to the storage modulus (G') at a given frequency. Therefore, for example, tan... 0.05 Tandem is used as an abbreviation for the ratio of loss modulus (G') to storage modulus (G') at 0.05 rad / s. 300 It is used as an abbreviation for the ratio of loss modulus (G") to storage modulus (G') at 300 rad / s.

[0237] Elastic balance tan 0.05 / tan 300 Defined as the loss tangent tan 0.05 tan and loss angle 300 than.

[0238] In addition to the rheological functions mentioned above, other rheological parameters can be determined, such as the so-called elasticity index EI(x). The elasticity index Ei(x) is the value of the storage modulus (G') determined by the value of the loss modulus (G'') for x kPa, and can be described by Equation 10.

[0239] For (G″=x kPa), EI(x)=G′[Pa] (10)

[0240] For example, EI(5kPa) is defined by the value of the energy storage modulus (G') determined by the value of G” equal to 5kPa.

[0241] The multidispersion index PI is defined by Equation 11.

[0242] For (G'=G''), ω COP =ω (11)

[0243] Where ω COP It is the cross angular frequency, which is determined to be the angular frequency when the energy storage modulus G' is equal to the loss modulus G".

[0244] These values ​​were determined using a single-point interpolation procedure as defined by the Rheoplus software. In cases where the experiment did not reach a given G* value, the value was determined by extrapolation, using the same procedure as before. In both cases (interpolation or extrapolation), the options "Interpolate y-values ​​to x-values ​​from parameters" and "Logarithmic interpolation type" in Rheoplus were applied.

[0245] References:

[0246] [1]"Rheological characterization of polyethylene fractions",Heino,EL,Lehtinen,A.,Tanner J., J., Neste Oy, Porvoo, Finland, Theor.Appl.Rheol., Proc.Int.Congr.Rheol, 11th (1992), 1, 360-362.

[0247] [2] "The influence of molecular structure on some rheological properties of polyethylene", Heino, EL, Borealis Polymers Oy, Porvoo, Finland, Annual Transactions of the Nordic Rheology Society, 1995.

[0248] [3] "Definition of terms relating to the non-ultimate mechanicalproperties of polymers",Pure&Appl.Chem.,Vol.70,No.3,pp.701-754,1998.

[0249] e) Viscosity eta 747

[0250] One method used in this invention relates to the rheology of polymers and is based on the determination of polymer viscosity under very low constant shear stress. The shear stress chosen for this method is 747 Pa. The viscosity of the polymer at this shear stress is determined at a temperature of 190°C and has been found to be inversely proportional to the polymer's gravitational fluidity; that is, the higher the viscosity, the lower the gravitational fluidity.

[0251] Viscosity at a shear stress of 747 Pa was determined using a rotational rheometer, which can be a constant-stress rheometer, such as the Anton Paar MCR series rheometer. The rheometer and its functions are described in the "Encyclopedia of Polymer Science and Engineering," 2nd edition, Volume 14, pp. 492-509. Measurements were performed between two 25 mm diameter plates under constant shear stress (constant rotation direction). The gap between the plates was 1.2 mm. A 1.5 mm thick polymer sample was inserted between the plates.

[0252] The sample temperature was conditioned for 2 minutes before the measurement. The measurement was performed at 190°C. After temperature conditioning, the measurement was initiated by applying a predetermined stress. The stress was maintained for 1800 seconds to bring the system close to steady-state conditions. Afterward, the viscosity was measured and calculated.

[0253] The measurement principle involves applying a specific torque to a plate shaft using a precision motor. This torque is then converted into shear stress in the sample. This shear stress remains constant. The rotational speed generated by the shear stress is recorded and used to calculate the sample's viscosity.

[0254] f) Average molecular weight and molecular weight distribution (Mn, Mw, Mz, MWD)

[0255] According to ASTM D 6474-12, the mean molecular weight (Mz, Mw, and Mn), molecular weight distribution (MWD), and width described by polydispersity index PDI = Mw / Mn (where Mn is the number-average molecular weight and Mw is the weight-average molecular weight) are determined by gel permeation chromatography (GPC) using the following formula:

[0256]

[0257]

[0258]

[0259] For a constant elution volume interval ΔV i A i and M i These are respectively related to the elution volume V i The associated chromatographic peak slice area and polyolefin molecular weight (MW), where N equals the number of data points obtained from the chromatogram between the integration limits.

[0260] A high-temperature GPC instrument was used, equipped with a multi-band infrared detector model IR5 (PolymerChar, Valencia, Spain) and guard columns consisting of 3 x Agilent-PLgel Olexis and 1 x Agilent-PLgel Olexis. 1,2,4-trichlorobenzene (TCB), stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol, was used as both solvent and mobile phase. The chromatographic system was operated at a constant flow rate of 1 mL / min at 160 °C. 200 μL of sample solution was injected for each analysis. Data collection was performed using PolymerChar GPC-one software.

[0261] The column assembly was calibrated using a universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards ranging from 0.5 kg / mol to 11500 kg / mol. The PS standards were dissolved at room temperature for several hours. The conversion of the peak molecular weight of polystyrene to that of polyolefins was accomplished using the Mark Houwink equation and the following Mark Houwink constant:

[0262] K PS =19 x 10 -3 mL / g, α PS =0.655

[0263] K PE =39 x 10 -3 mL / g, α PE =0.725

[0264] K PP =19 x 10 -3 mL / g, α PP =0.725

[0265] Third-order polynomial fitting was used to fit the calibration data.

[0266] All samples were prepared in concentrations ranging from 0.5 to 1 mg / ml and dissolved at 160°C for 2.5 hours for PP and at 160°C for 3 hours under continuous gentle shaking.

[0267] g) Determine SCB / 1000TC along the molecular weight (logM).

[0268] The IR 5 detector provides different detector signals, which are designated as concentration signals (covering 2800 cm⁻¹). -1 Up to 3000cm -1 (broad spectral band in the spectral region), methyl (CH3) (at 2959 cm⁻¹) -1(centered narrowband filter) and methylene (CH2) (at 2928cm) -1 The signal is centered on methyl groups. The ratio of methyl to methylene detector signals is related to the total amount of methylene (CH3) per 1000 carbon atoms (CH3 / 1000TC) (A. Ortin, B. Monrabal, J. Montesinos, P. del Hierro, Macromol. Symp. 2009, 282, 65-70). The determination of CH3 / 1000TC using an IR5 detector can be performed by calibrating the CH3 / CH2 ratio against the nominal CH3 / 1000 main chain carbon content. Linear fitting was used for this purpose.

[0269] As described in K. Klimke, M. Parkinson, C. Piel, W. Kaminsky, H.W.S. piess, M. Wilhelm, Macromol. Chem. and Phys., 2006, 207, 382; M. Parkinson, K. Klimke, H.W.S. piess, M. Wilhelm, Macromol. Chem. and Phys., 2007, 208, 2128, via 13 The degree of branching of all calibration group samples was determined by 10⁻⁶ molten NMR. The calibration group used for this method included 17 different short-chain branched polyethylene fractions, including those catalyzed by a single active site as well as those catalyzed by Ziegler-Natta, such as polyethylene-co-butene, polyethylene-co-hexene, and polyethylene-co-octene, covering a total branching level of up to 80 methyl groups per 1000 carbons (CH₃ / 1000C).

[0270] Short-chain branching was defined as methyl branching per 1000 total carbons, and corrections were made for up to two methyl chain end groups per polymer chain.

[0271] h) Laminar thickness

[0272] Continuous self-nucleation / annealing (SSA) enhances the potential molecular fractionation that may occur during crystallization by amplifying the effects of annealing unmelted crystals at each stage of the process. General references and additional information can be found in the review article by Müller and Arnal [AJ Müller, M.L. Arnal, Thermal fractionation of polymers, Prog. Polym. Sci. 30 (2005) 559–603]. SSA was performed on an indium and tin-calibrated TA Instruments Q2000 differential scanning calorimeter equipped with an RCS90 cooling system. Sample masses of 5 to 10 mg from the compression-molded sheet were used. All samples were encapsulated in Tzero aluminum trays. Ultra-high purity dry nitrogen was used as the inert atmosphere. The experimental protocol is as follows:

[0273] (a) The previous thermal history was eliminated by heating the sample from room temperature to 180°C at 20°C / min and holding it isothermally for 5 minutes.

[0274] (b) In this method, eight subsequent cooling / heating cycles were performed at a rate of 10 °C / min, with the first isothermal crystallization temperature chosen to be 126 °C. Each isothermal crystallization step lasted for 5 minutes. After each isothermal crystallization step, the sample was cooled to 30 °C and held isothermally for 5 minutes.

[0275] (c) The subsequent isothermal temperature is always kept 5°C lower than the previous step, i.e., the second isothermal crystallization temperature at which the sample is heated from 30°C to 121°C.

[0276] (d) After the final isothermal crystallization step at 91 °C, the sample was cooled to 0 °C and the cooled sample was heated to 180 °C at a heating rate of 10 °C / min to obtain the melt profile.

[0277] The final heating run after SSA treatment exhibits a series of melting peaks, corresponding to the number of SSA cycles that promote annealing. The Gibbs-Thomson equation can then be used to establish the relationship between melting temperature and lamellar thickness:

[0278]

[0279] in It is the equilibrium melting point of an infinitely thick crystal, σ e It is specific surface energy. It is the enthalpy of fusion per unit mass, L c It is the thickness of the lamellar crystal, T m It is the melting temperature of lamellar crystals. σ e and The values ​​are 415K and 93×10 respectively. -3 J / m 3 and 3×10 8 J / m 3 [L.Mandelkern, RGAlamo, Thermodynamic quantities governing melting, in: Phys.Prop.Polym.Handb., Springer, 2007: pp.165–186.].

[0280] As described in ISO 11357-3, the enthalpy of fusion is calculated by dividing the extrapolated heat flux volume between the start and end of melting by the initial weight of the sample. A fixed integral method with a step size of 10 °C is used for quantification of melt profiles to determine the lamellar thickness distribution.

[0281] i) Tensile properties of the membrane

[0282] Tensile properties of a film were measured at 23°C using a 40 μm thick three-layer blown film of specimen type 2, according to ISO 527-3. The three-layer blown film was prepared as described in the Examples section below. The longitudinal tensile modulus (TM-MD) and transverse tensile modulus (TM-TD) were measured as 1% secant modulus according to ASTM D882 at a test speed of 5 mm / min and a measurement length of 50 mm.

[0283] According to ISO 527-3 specimen type 2, the tensile stress at break (TSB-MD and TSB-TD), tensile stress at yield (TSY-MD and TSY-TD), elongation at break (EB-MD), and elongation at yield (EY-MD and EY-TD) are measured with a measurement length of 50 mm and a test speed of 500 mm / min.

[0284] j) Tear strength

[0285] The tear test was performed according to ASTM 1922 on a 40 μm thick three-layer blown film prepared as described in the Examples section below. The Elmendorf tear strength is the Newtonian force required to propagate a tear on the film specimen. It is measured using a precisely calibrated pendulum device. Under the influence of gravity, the pendulum swings in an arc, tearing the specimen through a pre-cut slit. One side of the specimen is fixed by the pendulum, and the other side by a fixing component. The energy loss of the pendulum is indicated by a pointer. The scale indication is a function of the force required to tear the specimen. The pendulum weight is chosen based on the energy absorbed by the specimen, preferably between 20% and 80% of the pendulum capacity. There is no direct linear relationship between tear force and specimen thickness. Therefore, data should only be compared within the same thickness range.

[0286] k) Puncture resistance

[0287] A puncture resistance test was performed on a 40 μm thick three-layer blown film prepared according to the description in the Examples section below, in accordance with ASTM D5748. This test method determined the film sample's resistance to penetration by a pear-shaped TFE fluorocarbon-coated probe of a specific size with a diameter of 19 mm at a standard low rate, single test speed (250 mm / min). The test was conducted under standard conditions, with biaxial stress loading applied. The film sample was cut to 150 mm × 150 mm to fit the fixture and conditioned at 23 ± 2 °C and 50 ± 5% relative humidity.

[0288] Puncture resistance (N) is the maximum or highest force observed during the test, and puncture resistance energy (J) is the energy used before the probe breaks the specimen. Both are measured using a high-precision 500N force sensor and a crosshead position sensor.

[0289] l) Impact strength of the dart

[0290] The dart impact strength was measured according to ISO 7765-1, Method A (alternative test technique) on a 40 μm thick three-layer blown film prepared as described in the Examples section below. A dart with a hemispherical head of 38 mm diameter was dropped from a height of 0.66 m onto the film clamped in a hole. Groups of 20 specimens were tested consecutively. One weight was used for each group, and the weight was increased (or decreased) in uniform increments for each group. The weight that caused 50% of the specimens to fail was calculated and reported.

[0291] m) Optical properties

[0292] The haze was measured according to ASTM D 1003 on a 40 μm thick three-layer blown film prepared as described in the Examples section below.

[0293] The gloss was measured at angles of 20°, 60° and 85° on a 40 μm thick three-layer blown film, prepared according to the description in the Examples section below, in accordance with DIN 67530 / ISO 2813.

[0294] 2. Example

[0295] a) Catalyst

[0296] The polymerization catalyst for polymerizing Example 1 of the present invention, IE1, was prepared according to Example 1 of EP 1 378 528 A1.

[0297] b) Polymerization of Embodiments IE1 and IE2 of the present invention and Comparative Example CE2

[0298] During the prepolymerization stage, the volume was 50 dm³. 3 The first loop reactor was operated at 70°C and 64 bar. Ethylene, 1-butene, and hydrogen were added to produce the prepolymer fraction. Furthermore, the polymerization catalyst prepared according to the above description and the triethylaluminum (TEA) co-catalyst were introduced into the reactor. The reactor conditions are shown in Table 1.

[0299] The polymer slurry was extracted from the first loop reactor and transferred to a 500 dm³ volumetric reactor. 3 The second loop reactor was operated at 85°C and 64 bar. Ethylene, 1-butene, and hydrogen were introduced into the reactor. No additional catalyst was introduced into the reactor. The reactor conditions are shown in Table 1.

[0300] The polymer slurry was drawn from the second loop reactor and transferred to a flash evaporator operating at 3 bar and 70°C, where hydrocarbons were substantially removed from the polymer. The polymer was then introduced into a gas-phase reactor operating at 78.5°C and 19.6 bar. Ethylene, 1-butene, and hydrogen were also introduced into the reactor. The conditions are shown in Table 1.

[0301] The resulting polymer was purged with nitrogen (approximately 50 kg / h) for 1 hour, stabilized with 1000 ppm of Irganox 1010 and Irgafos 168 and 1000 ppm of calcium stearate, and then extruded into pellets in a counter-rotating twin-screw extruder CIM90P (manufactured by Japan Steel Works) to achieve a production rate of 223 kg / h and a screw speed of 323 rpm.

[0302] Table 1: Aggregation conditions of IE1 in embodiment of the present invention

[0303] IE1 / IE2 CE2 Prepolymerization: temperature ℃ 70 70 pressure -bar 64 64 Split ratio weight% 1.4 1.4 H2 / C3 feed ratio kg / t C3 0.2 0.2 C4 / C2 feed ratio kg / t C2 40 40 Ring pipe: temperature ℃ 85 85 pressure -bar 64 64 C2 concentration mole% 2.43 2.70 H2 / C2 molar ratio moles / kilomoles 350 390 C4 / C2 molar ratio moles / kilomoles 641 570 C4 / C2 feed ratio kg / t C2 47-48 46 Flow split ratio weight% 37.6 39.3 <![CDATA[MFR2]]> g / 10min 270-340 300-330 density <![CDATA[kg / m 3 ]]> 950.5-951.5 951.0-952.0 Gas phase: temperature ℃ 78.5 80.0 pressure -bar 19.6 19.6 C2 concentration mole% 3.6 3.8 H2 / C2 molar ratio moles / kilomoles 5.8-6.1 10.5-11.2 C4 / C2 molar ratio moles / kilomoles 765 743 C4 / C2 feed ratio kg / t C2 139-140 136 Flow split ratio weight% 61.0 59.3 Density (Base Resin) <![CDATA[kg / m 3 ]]> 920.0-921.2 923.0 <![CDATA[MFR5 (Base resin)]]> g / 10min 0.60-0.74 0.9-1.0

[0304] c) Comparative Example CE1

[0305] CE1 is a unimodal LLDPE resin with a density of 918 kg / m³. 3 The melt flow rate (MFR2, 190°C, 2.16 kg) is 1.0 g / 10 min. It is produced using the Unipol gas-phase polymerization process and can be commercially available from SABIC as Sabic 118W.

[0306] d) Properties of polyethylene compositions of IE1, IE2, CE1 and CE2

[0307] The polyethylene compositions of Examples IE1, IE2, CE1 and CE2 have the properties shown in Table 2 below.

[0308] Table 2: Properties of polyethylene compositions of IE1, IE2, CE1 and CE2

[0309] CE1 CE2 IE1 IE2 density <![CDATA[kg / m 3 ]]> 921.9 922.6 921.0 920.2 <![CDATA[MFR2]]> g / 10min 1.15 0.25 0.16 0.15 <![CDATA[MFR5]]> g / 10min 3.19 0.99 0.65 0.61 <![CDATA[MFR 21 ]]> g / 10min 28 22.2 15.2 14.2 <![CDATA[FRR 21 / 5 ]]> 8.8 22.4 23.4 23.4 <![CDATA[FRR 21 / 2 ]]> 24.3 88.8 95.0 94.7 Mn g / mol nm 12800 13450 13450 Mw g / mol nm 180000 199000 209500 Mz g / mol nm 1015000 1135000 1225000 Mw / Mn nm 14.04 14.82 15.58 Mz / Mw nm 5.6 5.7 5.8 <![CDATA[eta 747 ]]> kPa·s nm 59 96 102 <![CDATA[eta 0.05 ]]> Pa·s 8122 46186 65936 71162 <![CDATA[eta 300 ]]> Pa·s 1073 897 1006 1031 <![CDATA[SHI 2.7 / 210 ]]> 4.3 29.7 31.1 31.8 <![CDATA[SHI 5 / 200 ]]> 3.9 22.9 23.7 24.3

[0310] nm = Not measured

[0311] Furthermore, the lamellar thickness of the compositions of Examples IE1, IE2, CE1, and CE2 was measured by continuous self-nucleation and annealing (SSA) thermal grading as described above.

[0312] Figure 1 The DSC melt profiles of the compositions after SSA treatment are shown. Multi-peak melt profiles of the CE and IE materials are observed, indicating independently molten crystallites formed in each successive self-nucleation and annealing sequence. Each of these peaks in the melt profile is attributed to molecules or molecular fragments at specific distances between branches. In subsequent SSA cycles, the crystals initially formed at higher temperatures at each peak undergo lamellar thickening over time (5 minutes) and with temperature decreasing by 5°C for each subsequent step, due to the distribution of branches.

[0313] For each LLDPE material, the DSC melt profile of the sample subjected to the SSA protocol is unique: the effect of the catalyst, polymerization process / conditions, comonomer type, and comonomer content. By increasing the amount of comonomer and / or making the comonomer more uniformly distributed along the polymer chain, the area of ​​the melt peak at higher temperatures decreases (compare the single peak CE1 with the bimodal peaks IE1 and IE2).

[0314] The differences in the distribution of short-chain branches can be determined based on the amount of material melted between different temperature ranges.

[0315] The amounts of different lamellar thickness fractions in the compositions of Examples IE1, IE2, CE1, and CE2 are in Figure 2 As shown in the diagram. Therefore, the fractions of different lamellar thicknesses are divided into the following groups in the columns from left to right:

[0316] The lamellar thickness is no more than 4.2 nm (≤4.2 nm).

[0317] The lamellar thickness ranges from 4.2 nm to 5.0 nm (>4.2 nm to ≤5.0 nm).

[0318] The lamellar thickness ranges from 5.0 nm to 6.1 nm (>5.0 nm to ≤6.1 nm).

[0319] The lamellar thickness ranges from 6.1 nm to 8.1 nm (>6.1 nm to ≤8.1 nm).

[0320] The lamellar thickness ranges from 8.1 nm to 11.8 nm (>5.0 nm to ≤11.8 nm).

[0321] The lamellar thickness ranges from 11.8 nm to 21.7 nm (>11.8 nm to ≤21.7 nm), and

[0322] The fraction with a lamellar thickness exceeding 21.7 nm (>21.7 nm)

[0323] Table 3 also outlines the fractions of different lamellar thicknesses.

[0324] Table 3: Amount and Ratio of Different Lamellar Thicknesses

[0325] Grading CE1 CE2 IE1 IE2 ≤4.2nm 8.2% by weight 8.1% by weight 10.7% by weight 10.8% by weight >4.2 to ≤5.0 nm 7.9% by weight 7.1% by weight 7.5% by weight 7.8% by weight ≤5.0nm 16.1% by weight 15.2% by weight 18.2% by weight 18.6% by weight >5.0 to ≤6.1nm 13.3% by weight 10.1% by weight 10.4% by weight 10.7% by weight >6.1 to ≤8.1nm 20.3% by weight 13.0% by weight 13.0% by weight 13.4% by weight >5.0 to ≤8.1nm 33.6% by weight 23.1% by weight 23.5% by weight 16.1% by weight >8.1 to ≤11.8nm 24.6% by weight 16.9% by weight 16.8% by weight 16.9% by weight ≤11.8nm 74.3% by weight 55.2% by weight 58.4% by weight 59.6% by weight >11.8 to ≤21.7nm 25.8% by weight 44.6% by weight 41.0% by weight 40.2% by weight >8.1 to ≤21.7nm 50.3% by weight 61.5% by weight 57.9% by weight 57.0% by weight >21.7nm 0% by weight 0.3% by weight 0.5% by weight 0.3% by weight The ratio of ≤11.8nm to ≤21.7nm 2.88 1.24 1.42 1.48 The ratio of ≤4.2nm / >11.8 to ≤21.7nm 0.32 0.18 0.26 0.27 The ratio of ≤4.2nm to 5.0 to ≤6.1nm 0.62 0.80 1.03 1.01

[0326] It can be seen that, compared with the bimodal compositions of CE2, IE1 and IE2, the unimodal composition of CE1 shows a completely different pattern in terms of the amount of fractions with different lamellar thicknesses.

[0327] When comparing the bimodal compositions of CE2, IE1, and IE2, the most significant difference is that, for the compositions of the present invention IE1 and IE2, the amount of the fraction with a lamellar thickness of more than 11.8 nm to 21.7 nm (>11.8 nm to ≤21.7 nm) is significantly lower than that of the fraction with a lamellar thickness of more than 11.8 nm to 21.7 nm (>11.8 nm to ≤21.7 nm) in CE2, while the amount of the fraction with a lamellar thickness of no more than 4.2 nm (≤4.2 nm) is significantly higher than that of the fraction with a lamellar thickness of no more than 4.2 nm (≤4.2 nm) in CE2.

[0328] Without being bound by theory, these differences between IE1 / IE2 and CE2 are thought to be due to the higher amounts of the higher molecular weight ethylene-1-butene copolymer fraction produced in the gas-phase reactor (61.0 wt% for IE1 / IE2, 59.3 wt% for CE2) and the higher amounts of 1-butene comonomers in the higher molecular weight ethylene-1-butene copolymer fraction produced in the gas-phase reactor (765 mol C4 / kmol C2 for IE1 / IE2, 743 mol C4 / kmol C2 for CE2). These measures result in a higher and more uniform distribution of 1-butene comonomers in the longer polymer chains of the higher molecular weight ethylene-1-butene copolymer fraction. This is achieved by manipulating the process design to alter the polymer molecular structure. For example, polymerization in the gas-phase reactor is promoted by reducing the H2 concentration and increasing the comonomer content compared to Reference Example CE2. This, in turn, increases comonomer bonding. Specifically, comonomer bonding is promoted in the high molecular weight region of the polymer composition.

[0329] The findings are in Figure 3 This has been confirmed. Figure 3 The GPC data (solid line) of the composition of CE2, IE1 and IE2 relative to molecular weight and the amount of short-chain branched SCB / 1000C relative to molecular weight are shown.

[0330] In the GPC data, for all compositions, a shoulder peak is observed from ~LogM 5.0 for the high molecular weight ethylene-1-butene fraction, indicating a bimodal composition; however, this is more pronounced for IE1 and IE2. Furthermore, compared to CE2, the short-chain branched curves in the same molecular weight region for IE1 and IE2 show a higher SCB / 1000C content.

[0331] e) Membrane sample preparation

[0332] Test films (single-material three-layer blown films) with a thickness of 40 μm, consisting of three layers of each composition as described above, were prepared using a large-scale three-layer co-extrusion blown film production line (Polyrema Machinery).

[0333] The die head width is 400mm, the die gap is 1.8mm, and the total film thickness is 40μm.

[0334] The neck height and blow-up ratio (BUR) are 3.0.

[0335] Extrusion conditions and membrane properties are listed in Table 4.

[0336] All samples were easy to process and exhibited good bubble stability.

[0337] Table 4: Extrusion conditions and properties of blown films of CE1, CE2, IE1 and IE2

[0338] unit CE1 CE2 IE1 IE2 Extrusion conditions: motor load ampere 23.6 20.8 24.2 22.1 Extruder production volume kg / h 75.3 69.8 71.1 70.0 Melt pressure -bar 289 312 359 359 melt temperature ℃ 200 219 222 222 Mechanical properties: Tensile modulus (MD) MPa 266 355 337 323 Tensile modulus (TD) MPa 323 496 422 422 TSY-MD MPa No yielding No yielding No yielding No yielding TSY-TD MPa 12.6 13.3 13.0 12.0 TSB-MD MPa 53.2 63.6 66.0 70.8 TSB-TD MPa 28.0 42.4 44.0 47.1 EB-MD ％ 497 462 419 432 EB-TD ％ 708 749 727 736 EY-MD No yielding No yielding No yielding No yielding EY-TD 4.7 8.3 9.0 8.8 Tear strength (MD) N 1.5 4.7 5.4 3.3 Tear strength (TD) N 4.7 11.1 10.2 11.6 Puncture resistance, force N 28.5 45.3 46.0 43.0 Puncture resistance, energy J 1.1 2.3 2.3 2.0 DDI g 150 228 300 468 Optical performance: Haze ％ 33.6 82.4 86.5 84.7 Gloss at 20° ％ nm 0.7 0.6 0.6 Gloss at 60° ％ 47.7 8.7 7.8 7.9 Gloss at 85° ％ nm 46.2 40.6 39.9

[0339] nm = Not measured

[0340] Compared to CE1 and CE2, embodiments IE1 and IE2 of the present invention exhibit an improved performance balance, with comparable tensile properties and improved dart impact strength (DDI) as well as higher haze.

[0341] Despite the use of 1-butene as a comonomer in the linear low-density copolymer, surprisingly high dart impact strength (DDI) was observed for Examples IE1 and IE2 of the present invention.

[0342] High haze leads to better light diffraction, which suggests that when used as a greenhouse film, it improves the crop yield performance of the film.

Claims

1. A polyethylene composition comprising a multimodal linear low-density ethylene copolymer, wherein the multimodal linear low-density ethylene copolymer comprises fractions with different lamellar thicknesses, and the ratio of the amount of fractions with a lamellar thickness not exceeding 11.8 nm to the amount of fractions with a lamellar thickness exceeding 11.8 nm but not exceeding 21.7 nm is in the range of 1.30 to 1.

60.

2. The polyethylene composition according to claim 1, wherein the amount of the fraction with a lamellar thickness of more than 11.8 nm to no more than 21.7 nm is 35.0 to 60.0 mol of the total amount of the multimodal linear low-density ethylene copolymer.

3. The polyethylene composition according to claim 1, wherein the fraction with a lamellar thickness not exceeding 5.0 nm is present in an amount of 17.0 to 30.0 mol of the total amount of the multimodal linear low-density ethylene copolymer.

4. The polyethylene composition according to claim 1, wherein the amount of the fraction with a lamellar thickness not exceeding 4.2 nm is at least 8.5 mol% of the total amount of the multimodal linear low-density ethylene copolymer.

5. The polyethylene composition according to claim 1, wherein the ratio of the amount of the fraction with a lamellar thickness not exceeding 4.2 nm to the amount of the fraction with a lamellar thickness exceeding 11.8 nm to not exceeding 21.7 nm is in the range of 0.20 to 0.

30.

6. The polyethylene composition according to claim 1, wherein the ratio of the amount of the fraction with a lamellar thickness of not more than 4.2 nm to the amount of the fraction with a lamellar thickness of more than 5.0 nm to not more than 6.1 nm is in the range of 0.85 to 1.

15.

7. The polyethylene composition according to claim 1, wherein the multimodal linear low-density ethylene copolymer is a copolymer of ethylene and 1-butene.

8. The polyethylene composition according to claim 1, wherein the multimodal linear low-density ethylene copolymer has a content of 915.0 to 925.0 kg / m³. 3 The density.

9. The polyethylene composition according to claim 1, wherein the multimodal linear low-density ethylene copolymer comprises two ethylene copolymer fractions with different molecular weights, wherein the weight ratio of the low molecular weight ethylene copolymer fraction to the high molecular weight ethylene copolymer fraction in the multimodal linear low-density ethylene copolymer is from 25.0:75.0 to 44.0:56.

0.

10. The polyethylene composition according to claim 9, wherein the ratio of short-chain branch number to 1000 carbon atoms (SCB / 1000C) in the polymer chain of the high molecular weight ethylene copolymer fraction is in the range of 15.0 to 35.0%.

11. The polyethylene composition according to claim 1, wherein the polyethylene composition has a melt flow rate MFR5 of 0.40 to 0.85 g / 10 min measured at 190°C under a 5 kg load.

12. An article comprising the polyethylene composition according to any one of claims 1 to 11.

13. The article of claim 12, wherein the article is a film having a dart impact strength (DDI) of at least 250 g when measured on a 40 μm blown film according to ISO 7765-1.

14. The article of claim 12, wherein the article is a film having a 1% secant transverse tensile modulus of at least 275 MPa when measured on a 40 μm blown film according to ISO 527-3.

15. Use of the polyethylene composition according to any one of claims 1 to 11 for the production of blown films for greenhouse film applications, heavy-duty shipping bag applications, laminated film applications, combined shrink film applications, stand-up pouch applications, or pool lining applications.

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