Multimodal polyethylene composition

Abstract

The present invention relates to a multimodal polyethylene composition, a polyethylene blend comprising the multimodal polyethylene composition, a film comprising the multimodal ethylene composition or the polyethylene blend, a method for preparing the film, a multilayer film comprising the film, and an article comprising the multilayer film.

Description

[Technical field]

[0001] The present invention relates to a multimodal polyethylene composition used to make an oriented film that can be stretched in one or two directions. The present invention further relates to a multilayer film comprising said film and an article comprising said multilayer film. [Background technology]

[0002] Global plastic packaging market trends are expected to grow the most in 2023. Manufacturers and brand owners are looking to move towards a circular economy where materials are not wasted and plastics are used multiple times. While there is growing concern about packaging and the environment, especially plastics, with brands and retailers setting themselves targets to ensure their packaging is recyclable, reusable or compostable, there is growing pressure on companies, including shareholders, from both the general public and initiatives such as CEFLEX to collect and redirect over 80% of all flexible packaging and recycled materials for valuable new markets and alternative uses for virgin materials by 2025.

[0003] Plastic flexible packaging is mainly composed of multi-material and multi-layer to enhance features such as barrier performance and product protection. Multi-layer packaging contains multiple film layers, each film layer is prepared from different types of polymers (i.e. PP, PE, PET, nylon, etc.) depending on the usefulness of use. For example, (a) inner or sealing layer, (b) tie layer, (c) barrier layer, and (d) outer or printing layer. The outer or printing layer is prepared from biaxially oriented polyamide film (BOPA film) or biaxially oriented polyethylene terephthalate film (BOPET film) depending on the packaging application. These materials are superior in terms of thermal stability and have less heat shrinkage during the printing process. However, the different types of polymers in the packaging cannot be used in mono-material packaging (fully PE packaging). They represent a challenge for the existing recycling system in facing the circular economy principle.

[0004] The printing layer products used for monomaterials in the market include biaxially oriented polypropylene film (BOPP film), biaxially oriented polyethylene film (BOPE film) and machine direction oriented film (MDOPE film). Various films are known in the art that can be applied as a single layer or to the core or surface of a multilayer film. Similarly, various polymer compositions, especially polyethylene compositions, for producing such films are described.

[0005] Common problems when using BOPE films in plastic flexible packaging are high levels of heat shrinkage during the printing process and poor seal appearance during the bag manufacturing process. Heat shrinkage occurs after the reheating process, which results in dimensional changes in the film due to amorphous migration, and the level of crystallinity is a critical point for the shrinking process.

[0006] Usually, the heat shrinkage was improved by increasing the final density of the polyethylene resin for film production. However, increasing the final density of the polyethylene resin for film production is in a trade-off relationship with stretchability and film transparency and haze and gloss properties. Therefore, the challenge of biaxially oriented high density polyethylene film (BO-HDPE film) is to achieve a balance between low heat shrinkage, high film transparency, and still good stretchability.

[0007] To achieve a balance between stretchability and heat shrinkage in high density polyethylene resins (HDPE resins), HDPE materials can be engineered using a multimodal process, which can provide better stretchability than bimodal and unimodal processes.

[0008] There are many prior art attempts to develop and disclose the following:

[0009] U.S. Patent Application Publication No. 2014 / 179873 discloses a denaturation coefficient of about 0.916 to about 0.936 g / cm 3Density: about 0.1 to about 2.0 g / 10 min, melt index (I2): about 32 to about 50, melt flow ratio (I 21 / I2), molecular weight distribution (Mw / Mn) of about 3.6 to about 6.5, inverted comonomer distribution profile determined by GPC-FTIR, multimodal TREF profile, composition distribution width index CDBI of about 45 wt% to about 75 wt% determined by TREF 50 and b) 5 to about 95% by weight of a low-density first polyethylene copolymer having a molecular weight of about 0.910 to about 0.940 g / cm3 and further satisfying the relationship: (Mw / Mn) is 72 or more; and 3 0.2 to 5.0 g / 10 min, and a melt flow ratio (I 21 and about 95 to about 5 weight percent of a second polyethylene copolymer having a copolymer ratio of 1:1 / I2).

[0010] US 2009 / 029182 discloses a multi-layer "barrier" film with excellent water vapor transmission rate (WVTR) performance prepared using a core layer comprising a blend of two different high density polyethylenes (HDPEs) and a nucleating agent. The film is suitable for preparing packages for dry foods such as crackers and breakfast cereals.

[0011] US 2005 / 170194 describes an essentially transparent high density polyethylene film having a haze of 20% or less, a gloss of 40% or more, and a density in the range of 0.935-0.948 g / cc. The film is prepared by a high stalk blown extrusion process and then uniaxially oriented in the machine direction, which includes converting polyethylene having a density in the range of 0.935-0.948 g / cc and an MI2 in the range of 0.03-0.15 dg / min into a film by high stalk blown extrusion, and then uniaxially orienting the film in the machine direction. The oriented film is essentially transparent and has a haze of 20% or less and a gloss of 40% or more.

[0012] However, in light of the above prior art, there remains a need to provide a multimodal polyethylene composition for preparing films, and films prepared by using such a multimodal polyethylene composition that overcomes the shortcomings of the prior art, in particular to provide a high density polyethylene composition for oriented films that can be used to prepare multi-layer packages and containers.

[0013] It is therefore an object to provide a high density polyethylene composition having improved polyethylene properties for producing biaxially oriented polyethylene (BOPE) or (machine direction oriented (MDO)) films having particularly good properties, which overcomes the drawbacks of the prior art. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] US Patent Application Publication No. 2014 / 179873 [Patent Document 2] US Patent Application Publication No. 2009 / 029182 [Patent Document 3] US Patent Application Publication No. 2005 / 170194 Summary of the Invention

[0015] Multimodal polyethylene composition In one aspect, the present invention provides a multimodal polyethylene composition comprising: (A) a low molecular weight polyethylene, which is 40% by weight to 52% by weight, preferably 40% by weight to 50% by weight, based on the total weight of the multimodal polyethylene composition, the low molecular weight polyethylene being a homopolymer, the low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol, as measured by gel permeation chromatography; (B) a first high molecular weight polyethylene, which is 10 to 28% by weight, preferably 10 to 26% by weight, based on the total weight of the multimodal polyethylene composition, the first high molecular weight polyethylene being a homopolymer or a copolymer, the first high molecular weight polyethylene having a weight average molecular weight (Mw) of 300,000 to 900,000 g / mol, preferably 300,000 to 850,000 g / mol, more preferably 350,000 to 800,000 g / mol, and most preferably 400,000 to 750,000 g / mol, as measured by gel permeation chromatography; (C) 25 to 50% by weight, preferably 26 to 50% by weight, of a second high molecular weight polyethylene, based on the total weight of the multimodal polyethylene composition, the second high molecular weight polyethylene being a homopolymer or a copolymer, the second high molecular weight polyethylene having a weight average molecular weight (Mw) of 130,000 to 500,000 g / mol, preferably 140,000 to 450,000 g / mol, as measured by gel permeation chromatography; the first high molecular weight polyethylene differs from the second high molecular weight polyethylene in terms of weight average molecular weight; The crystallinity of the multimodal polyethylene composition is 49% to 65%, preferably 50% to 65%, and more preferably 52% to 65%, as measured by differential scanning calorimetry; and The number average linear methylene sequence length (L n ) value is from 1.90 nm to 4.80 nm, preferably from 2.0 nm to 4.80 nm, and more preferably from 2.8 nm to 4.8 nm, and the weight average of the linear methylene sequence length (L w The present invention provides a multimodal polyethylene composition having a .DELTA.(.DELTA.) value, as measured by DSC sequential self-nucleation and annealing (SSA), of 2.5 nm to 5.6 nm, preferably 3.0 nm to 5.6 nm, and more preferably 3.3 nm to 5.6 nm.

[0016] The multimodal polyethylene composition according to the present invention may be a polyethylene composition for the production of biaxially oriented polyethylene (BOPE) films.

[0017] The multimodal polyethylene composition of the present invention is produced in a multi-stage process, with fractions (A), (B) and (C) being produced in subsequent stages. In such cases, the properties of the fractions produced in the second or third (or further) stages of the multi-stage process can be inferred from the polymer produced separately in a single stage by applying identical polymerization conditions (e.g., identical temperature, reactant / diluent partial pressures, suspension medium, reaction time) for the stage of the multi-stage process in which the fraction is produced, and by using a catalyst in which no previously produced polymer was present. Alternatively, the properties of the fractions produced in the higher stages of the multi-stage process can also be calculated, for example, according to B. Hagstrom, Conference on Polymer Processing (The Polymer Processing Society), Extended Abstracts and Final Programme, Gothenburg, August 19 to 21, 1997, 4:13.

[0018] Thus, the properties of fractions produced in higher stages of such multi-step processes, which cannot be measured directly in the multi-step process product, can be determined by applying either or both of the above methods. Those skilled in the art can select the appropriate method. One particular method of calculating properties such as molecular weight (such as Mw) is to apply a deconvolution method using Excel or other calculation programs. In the deconvolution method, subtraction of each signal is performed.

[0019] HDPE polymers produced in a multi-stage process are also called "in-situ" blends. The final product obtained consists of a homogeneous mixture of polymers from three or more reactors, whose different molecular weight distribution curves together form a molecular weight distribution curve with a broad maximum or two or more maxima.

[0020] The density of multimodal polyethylene is 0.935-0.960 g / cm, as measured by ASTM standard D1505. 3, more preferably 0.939 to 0.960 g / cm 3 , and even more preferably 0.943 to 0.960 g / cm 3 , and most preferably 0.943 to 0.956 g / cm 3 may be in the range.

[0021] The melt index / melt flow rate MI2 of the multimodal polyethylene may be in the range of 0.01 to 2.5 g / 10 min, preferably 0.02 to 1.8 g / 10 min, more preferably 0.02 to 1.6 g / 10 min, and most preferably 0.02 to 1.5 g / 10 min.

[0022] The polydispersity of the multimodal polyethylene composition may be from 12 to 40, preferably from 15 to 35, and most preferably from 16 to 33, as measured by gel permeation chromatography (GPC).

[0023] The multimodal polyethylene composition may have a weight average molecular weight of 130,000 to 400,000 g / mol, preferably 140,000 to 350,000 g / mol, more preferably 150,000 to 300,000, and / or a number average molecular weight of 5,000 to 15,000 g / mol, preferably 7,000 to 13,000 g / mol, and / or a Z average molecular weight of 1,000,000 to 3,000,000 g / mol, preferably 1,000,000 to 2,500,000 g / mol, each measured according to gel permeation chromatography (GPC).

[0024] The multimodal polyethylene composition may have an Fm / Fy of 1 or more, preferably 1 to 5, more preferably 1 to 3, and most preferably 1 to 2, where Fm is the tensile strength at break of the multimodal polyethylene composition and Fy is the tensile yield strength of the multimodal polyethylene composition, each measured in accordance with ISO standard 527-2.

[0025] The multimodal polyethylene composition according to the present invention may further comprise LLDPE, LDPE and, depending on its intended use, optionally added additives such as nucleating agents, processing aids, antioxidants and light stabilizers.

[0026] Polyethylene Mixture According to another aspect, the present invention relates to a polyethylene mixture (polyethylene blend) comprising a multimodal polyethylene composition according to the present invention and and a further component selected from the group consisting of linear low density polyethylene, low density polyethylene, very low density polyethylene, and mixtures of two or more thereof. The present invention provides a polyethylene mixture comprising:

[0027] The addition of LLDPE, LDPE, ULDPE or mixtures thereof to the multimodal polyethylene composition to prepare a polyethylene blend can be advantageous in producing a film for use as at least one layer of a multilayer film having a stretch ratio of 1.5 to 4.5, a longitudinal stretch ratio of 3 to 15 and a transverse stretch ratio of 3 to 12.

[0028] The polyethylene mixture may comprise the multimodal polyethylene composition according to the present invention in an amount of 50-90% by weight, preferably 55-80% by weight, preferably 60-70% by weight, most preferably about 65% by weight, relative to the total weight of the polyethylene mixture, and a further component selected from the group consisting of linear low density polyethylene, low density polyethylene, very low density polyethylene and mixtures of two or more thereof in an amount of 10-50% by weight, preferably 20-45% by weight, preferably 30-40% by weight, most preferably about 35% by weight, relative to the total weight of the polyethylene mixture.

[0029] In addition to LLDPE, LDPE and ULDPE, the polyethylene blend according to the invention may optionally further comprise further additives, such as nucleating agents, processing aids, antioxidants and light stabilizers, depending on its intended use.

[0030] film According to another aspect, the present invention provides a film comprising the multimodal polyethylene composition according to the invention or the polyethylene blend according to the invention.

[0031] That is, according to the present invention, there is provided a film comprising: (A) a low molecular weight polyethylene, which is 40 to 52 wt. % (by weight), based on the total weight of the multimodal polyethylene composition, the low molecular weight polyethylene being a homopolymer, and which has a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol, as measured by gel permeation chromatography; (B) a first high molecular weight polyethylene, the first high molecular weight polyethylene being 10% by weight to 28% by weight based on the total weight of the multimodal polyethylene composition, the first high molecular weight polyethylene being a homopolymer or a copolymer, the first high molecular weight polyethylene having a weight average molecular weight (Mw) of 300,000 to 900,000 g / mol, preferably 300,000 to 850,000 g / mol, more preferably 350,000 to 800,000 g / mol, and most preferably 400,000 g / mol to 750,000 g / mol, as measured by gel permeation chromatography; (C) a second high molecular weight polyethylene in an amount of 25% to 50% by weight, based on the total weight of the multimodal polyethylene composition, the second high molecular weight polyethylene being a homopolymer or a copolymer, the second high molecular weight polyethylene having a weight average molecular weight (Mw) of 130,000 to 500,000 g / mol, preferably 140,000 to 450,000 g / mol, as measured by gel permeation chromatography; The first high molecular weight polyethylene differs from the second high molecular weight polyethylene in terms of weight average molecular weight. The crystallinity of the multimodal polyethylene composition is 49% to 65%, as measured by differential scanning calorimetry; The number average linear methylene sequence length (L) of the multimodal polyethylene composition was measured by DSC sequential self-nucleation and annealing (SSA). n ) value is 1.90 nm to 4.8 nm, and the weight average of the linear methylene sequence length (L w ) value is 2.5nm to 5.6nm, The film optionally further comprises an additional component selected from the group consisting of linear low density polyethylene, low density polyethylene, very low density polyethylene, and mixtures of two or more thereof; The polyethylene mixture preferably comprises the multimodal polyethylene composition according to the present invention in an amount of preferably 50-90% by weight, preferably 55-80% by weight, preferably 60-70% by weight, most preferably about 65% by weight, relative to the total weight of the polyethylene mixture, and preferably comprises a further component selected from the group consisting of linear low density polyethylene, low density polyethylene, very low density polyethylene and mixtures of two or more thereof in an amount of 10-50% by weight, preferably 20-45% by weight, preferably 30-40% by weight, most preferably about 35% by weight, relative to the total weight of the polyethylene mixture, The film is provided.

[0032] The film according to the invention may be a homogeneous film. Alternatively, the film may be heterogeneous. When the film is heterogeneous, a film comprising two or more sublayers, for example three sublayers, may be provided.

[0033] The film of the present invention may be a film having three sublayers, i.e. two outer layers and one inner layer, the two outer layers being respectively arranged on opposite surfaces of the inner layer. In this regard, the inner layer may comprise (or consist of) a multimodal polyethylene composition according to the present invention or may comprise (or consist of) a polyethylene composition according to the present invention, and the two outer layers may comprise (or consist of) low density polyethylene or linear low density polyethylene, preferably linear low density polyethylene (LLDPE). Such films having more than two, for example three, sublayers may be produced by coextrusion, the inner layer acting as a substrate on which further polymeric components are applied by one or more extruders to form the outer layers.

[0034] In other words, the film (which can be used to form a printing layer in a multilayer film as described below) can be, for example, a multimodal polyethylene composition according to the invention or a homogeneous film prepared from 100% of the polyethylene composition according to the invention, or the film can be a coextruded film (more than one layer) in which the multimodal polyethylene composition according to the invention or a homogeneous film prepared from 100% of the polyethylene composition according to the invention is at least one sublayer of the film. For example, to improve the transparency of the film (low % haze), a film comprising (or consisting of) the polyethylene composition according to the invention or a coextruded film with LLDPE as a skin layer may be preferred. The process for preparing a coextruded film is a coextrusion coating process.

[0035] The films according to the invention comprising the multimodal polyethylene composition according to the invention may be blown or may be obtained by casting and even coextrusion. The films may be prepared by hot stretching the film by biaxial sequential orientation, by hot stretching the film by biaxial simultaneous orientation and by hot stretching the film in the machine direction.

[0036] The film may be a double bubble blown film or a triple bubble blown film.

[0037] There are various film stretching process options depending on the purpose of application / process design / machine owner design / end use. For example, there may be one-step uniaxial stretching process in machine direction (MD), there may be multi-step film stretching process, for example, biaxial sequential stretching process in machine direction (MD) and transverse direction (TD), and biaxial simultaneous stretching process in machine direction (MD) and transverse direction (TD). All film stretching process options have stretch ratios between 1.5 and 15.

[0038] Multilayer Film According to another aspect, the present invention provides a multilayer film comprising a film according to the present invention, i.e. a film comprising a multimodal polyethylene composition or comprising a polyethylene blend of the present invention.

[0039] In this regard, the multilayer film may comprise two or more layers laminated together, at least one of the layers being the film of the present invention. That is, the film comprising the multimodal polyethylene composition is at least one layer of the multilayer film. The layers constituting the multilayer film may be bonded together, optionally with an adhesive. The multilayer film may comprise or consist of the following layers: (a) an inner layer which may be (and may act as) a sealing layer; (b) a barrier layer, preferably having barrier properties against moisture and / or water (water vapor); (c) an outer layer which may be (and may act as) a printing layer, in this order, the outer layer being a film of the present invention comprising a film of the present invention.

[0040] The multilayer film may comprise or consist of the following layers, in that order: (a) an inner layer which may be (and may act as) a sealing layer; (b) a first adhesive layer which may be a first tie resin layer; (c) a barrier layer, preferably having barrier properties against moisture and / or water (water vapor); (d) a second adhesive layer which may be a second tie resin layer; (e) an outer layer which may be (and may act as) a printing layer, the outer layer being a film according to the present invention comprising a film according to the present invention.

[0041] The multilayer film may comprise the following layers, in that order: (a) an inner layer which may be (and may act as) a seal layer; (b) a first adhesive or tie layer which may be a first tie resin layer in direct contact with the inner layer; (c) a barrier layer which preferably has barrier properties against moisture and / or water (water vapor) and which is in direct contact with the first adhesive layer; (d) a second adhesive layer which may be a second tie resin layer in direct contact with the barrier layer; (e) an outer layer which may be (and may act as) a print layer in direct contact with the second adhesive layer, the outer layer being a film according to the invention comprising a film according to the invention.

[0042] The inner layer, the first adhesive layer, and the barrier layer may independently be prepared from low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), or a blend of two or more thereof.

[0043] The inner layer may be prepared from LDPE, LLDPE, MDPE, or a blend of two or more thereof.

[0044] The first adhesive layer and the second adhesive layer may independently be made of LDPE, LLDPE, HDPE, or a blend of two or more thereof, preferably LDPE, LLDPE, or a blend thereof. Alternatively, the adhesive layer may comprise a polyurethane-based resin, an acrylic-based resin, a polyvinyl-based resin, a rubber, or a mixture thereof.

[0045] The barrier layer may be prepared from HDPE or a blend of HDPE and ethylene vinyl alcohol (EVOH), the amount of EVOH being 3-5% (by weight) of the total weight of the multilayer. Alternatively, the adhesive layer may comprise a polyurethane-based resin, an acrylic-based resin, a polyvinyl-based resin, a rubber, or a mixture thereof.

[0046] The different layers of the multilayer film may be bonded together to form a laminate by a lamination process. If the layers to be bonded together are incompatible, i.e., do not bond together during the lamination process, a tie layer (adhesive layer) may be placed between them.

[0047] "Laminate" refers to a film structure that includes inner and outer layers attached to one another by lamination.

[0048] By using in the multilayers of the present invention, the films of the present invention comprising the multimodal polyethylene composition of the present invention, in particular in the print layer, by replacing art known materials for print layers such as PET or nylon (i.e. by using a "mono-material layer arrangement" based only on polyethylene), the recyclability and / or the thermal stability and / or the heat shrinkage behavior of the multilayer film can be improved.

[0049] The multilayer film may be a coextruded multilayer film. The multilayer film may be prepared by a dry lamination process. The printed layer may be coated with a barrier adhesive as a moisture barrier to prevent moisture, oxygen, aroma, and to allow bonding with other incompatible film layers. The coated printed layer with the barrier adhesive may then be laminated with a seal layer or inner layer that directly contacts the product contained inside the package prepared from the multilayer film. Each multilayer film that may be used to manufacture a flexible package (i.e., food package, personal care package, home care package, etc.) may be either a coextruded film or a laminate consisting of a combination of coextruded films.

[0050] Preferably, the film comprising multimodal polyethylene is at least one layer of a multilayer film prepared for packaging or containers, such as food packaging, personal care packaging, and home care packaging.

[0051] Preferably, a film comprising the multimodal polyethylene composition according to the invention or the polyethylene mixture according to the invention is at least one layer of a multilayer film according to the invention which may be used to prepare a package or container.

[0052] Goods According to another aspect, the present invention provides an article comprising a multilayer film according to the present invention, the article being a package or container.

[0053] The package or container may be for storing, transporting, etc., a consumer product, which may be, for example, a food package, a personal care package, or a personal and home care package. For example, the package may be used for storing, transporting, etc., vacuum processed foods, liquid softeners, detergents, etc.

[0054] Film Preparation Method According to another aspect, the present invention provides a process for preparing a film according to the present invention, comprising the steps of blowing or casting the film and further co-extruding the film.

[0055] The method of preparing the film may further comprise, preferably as a subsequent step, a step of heat-stretching the film by biaxial sequential orientation, and / or a step of heat-stretching the film by biaxial simultaneous orientation, and / or a step of heat-stretching the film with a machine direction orientation.

[0056] Process for preparing multimodal polyethylene compositions The multimodal polyethylene composition can be produced via a multimodal polyethylene polymerization reactor system comprising a first reactor, a second reactor, a third reactor, and a hydrogen removal unit disposed between the first and second reactors.

[0057] The hydrogen-deficient polyethylene from the first reactor influences the polymerization of higher molecular weights in subsequent reactors. In particular, higher molecular weights result in improved mechanical properties of the polyethylene.

[0058] The catalyst for producing the multimodal polyethylene resin of the present invention may be selected from Ziegler-Natta catalysts, single-site catalysts or chromium-based, including metallocene-based catalysts and non-metallocene-based catalysts, preferably conventional Ziegler-Natta catalysts or single-site catalysts are used. The catalysts are typically used together with co-catalysts well known in the art.

[0059] The polymerization in the first reactor, the second reactor and the third reactor may be carried out in the presence of an inert hydrocarbon. The inert hydrocarbon is preferably an aliphatic hydrocarbon such as hexane, isohexane, heptane, isobutane, etc. Hexane (most preferably n-hexane) is preferably used.

[0060] The coordination catalyst, ethylene, hydrogen and optionally an α-olefin comonomer are polymerized in the first reactor, and the entire product from the first reactor may then be transferred to a hydrogen removal unit to remove 98.0-99.8% (by weight) of hydrogen, unreacted gases and some volatile materials from the slurry from the first reactor before being fed to a second reactor to continue the polymerization.

[0061] The polyethylene obtained from the second reactor is a bimodal polyethylene, which is a combination of the product obtained from the first reactor and the product of the second reactor. This bimodal polyethylene is then fed to a third reactor to continue the polymerization. The final multimodal (trimodal) polyethylene obtained from the third reactor is a mixture of the polymers from the first, second and third reactors. The polyethylenes prepared in each of the first, second and third reactors (corresponding to components A to C of the multimodal polyethylene composition of the present invention) differ from each other, for example, in terms of their weight average molecular weights. The first high molecular weight polyethylene can be fed having a weight average molecular weight higher than that of the second high molecular weight polyethylene.

[0062] The polymerization in the first, second and third reactors may be carried out under different process conditions. As a result, the polyethylene obtained in each reactor (corresponding to components A-C) has different molecular weights. These may be variations in the concentration of ethylene and hydrogen in the gas phase, in the temperature or in the amount of comonomer fed to each reactor. The appropriate conditions for obtaining the respective homo- or copolymers of the desired properties, in particular of the target molecular weight, are well known in the art. The skilled person, based on his general knowledge, can choose the respective conditions accordingly. Preferably, the low molecular weight polyethylene is produced in the first reactor, the first high molecular weight polyethylene is produced in the second reactor and the second high molecular weight polyethylene is produced in the third reactor.

[0063] The term first reactor refers to the stage where low molecular weight polyethylene (LMW) is produced. The term second reactor refers to the stage where the first high molecular weight polyethylene (HMW1) is produced. The term third reactor refers to the stage where the second high molecular weight polyethylene (HMW2) is produced.

[0064] The term LMW refers to the low molecular weight polyethylene polymer polymerized in the first reactor having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol.

[0065] The term HMW1 refers to a first high molecular weight polyethylene polymer polymerized in the second reactor having a weight average molecular weight (Mw) of greater than 300,000 to 900,000 g / mol, preferably 300,000 to 850,000 g / mol, more preferably 350,000 to 800,000 g / mol, and most preferably 400,000 to 750,000 g / mol.

[0066] The term HMW2 refers to a second high molecular weight polyethylene polymer polymerized in the third reactor having a weight average molecular weight (Mw) of 130,000 to 500,000 g / mol, preferably 140,000 to 450,000 g / mol.

[0067] The LMW may be produced in the first reactor in the absence of comonomer to obtain a homopolymer.

[0068] Ethylene has a density of ≥ 0.965 g / cm for LMW. 3 The polyethylene may be polymerized in the first reactor in the absence of comonomer to obtain a high density LMW polyethylene having a MI2 in the range of 10-1000 g / 10 min and a density of 1000 g / 10 min. The polymerization conditions are controlled and adjusted to obtain the target density and MI in the first reactor. The temperature in the first reactor is in the range of 70-90°C, preferably 80-85°C. Hydrogen is fed to the first reactor to control the molecular weight of the polyethylene. The molar ratio of hydrogen to ethylene in the gas phase can vary depending on the target MI. However, the preferred molar ratio is in the range of 0.01-8.0, more preferably 0.01-6.0. The first reactor is operated at a pressure between 250-900 kPa, preferably 400-850 kPa. The amount of hydrogen present in the gas phase of the first reactor is in the range of 0.1-95 mol%, preferably 0.1-90 mol%.

[0069] The resulting slurry from the first reactor, preferably comprising LMW polyethylene in hexane, may be transferred to a hydrogen removal unit prior to being fed to the second reactor, which may have a flash drum connected to a pressure reducing device, preferably comprising one or a combination of a vacuum pump, a compressor, a blower and an ejector, whereby volatile unreacted gases and hydrogen are removed from the slurry stream as the pressure in the flash drum is reduced. The operating pressure of the hydrogen removal unit is typically in the range of 103-145 kPa (abs), preferably 104-130 kPa (abs), at which pressure 98.0-99.8 wt. %, preferably 98.0-99.5 wt. %, most preferably 98.0-99.1 wt. % of hydrogen can be removed from the slurry.

[0070] In the present invention, when 98.0-99.8 wt.% hydrogen is removed from the slurry and polymerization is carried out in the second reactor under conditions of this hydrogen content, a (very) high molecular weight polymer can be achieved. The polymerization conditions in the second reactor are significantly different from those in the first reactor. The temperature in the second reactor is in the range of 65-90°C, preferably 68-80°C. The molar ratio of hydrogen to ethylene is not controlled in this reactor, because no hydrogen is fed into the second reactor. The hydrogen in the second reactor is the residual hydrogen from the first reactor, which remains in the slurry stream after flashing in the hydrogen removal unit. The polymerization pressure in the second reactor is in the range of 100-3000 kPa, preferably 150-900 kPa, more preferably 150-400 kPa.

[0071] Hydrogen rejection is a comparison of the amount of hydrogen present in the slurry mixture before and after passing through the hydrogen rejection unit. Hydrogen rejection is calculated by measuring the gas composition in the first and second reactors by gas chromatography.

[0072] After a significant amount of hydrogen has been removed to achieve the above concentrations, the slurry from the hydrogen removal unit is transferred to a second reactor for continued polymerization, in which ethylene can be polymerized with or without an α-olefin comonomer in the presence of the LMW polyethylene from the first reactor to form HMW1 polyethylene. α-olefin comonomers useful for copolymerization include C 4-12 , preferably 1-butene or 1-hexene.

[0073] After polymerization in the second reactor, the resulting slurry is transferred to a third reactor for continuing the polymerization.

[0074] HMW2 is produced in a third reactor by polymerizing ethylene, optionally with an α-olefin comonomer, in the presence of the LMW and HMW1 obtained from the first and second reactors. Useful α-olefin comonomers for copolymerization include C 4-12, preferably 1-butene and 1-hexene.

[0075] The polymerization conditions may be controlled and adjusted, if desired, to obtain the desired density and MI2 in the third reactor. However, the polymerization conditions in the third reactor are significantly different from those in the first and second reactors. The temperature in the third reactor may be in the range of 68-90°C, preferably 68-80°C. Hydrogen is optionally fed to the third reactor to control the molecular weight of the polyethylene. The molar ratio of hydrogen to ethylene may vary depending on the target MI. However, the preferred molar ratio is in the range of 0.01-2.0. The polymerization pressure in the third reactor is in the range of 250-900 kPa, preferably 250-600 kPa, and is controlled by the addition of an inert gas such as nitrogen.

[0076] The final (free-flowing) multimodal polyethylene composition may be obtained by separating the hexane from the slurry exiting the third reactor.

[0077] The method of producing a multimodal polyethylene composition comprises: (a) polymerizing ethylene in an inert hydrocarbon medium in a first reactor in the presence of a catalyst system selected from a Ziegler-Natta catalyst or a metallocene, and hydrogen in an amount of 0.1 to 95 mol % relative to the total gas present in the gas phase in the first reactor, to obtain a low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol, wherein the low molecular weight polyethylene and the medium molecular weight polyethylene each have a density of at least 0.965 g / cm3, the low molecular weight polyethylene having a MI2 in the range of 10 to 1,000 g / 10 min, and the medium molecular weight polyethylene having a MI2 in the range of 0.1 to 10 g / 10 min; (b) removing, in a hydrogen removal unit, 98.0 to 99.8% by weight, for example 98.0 to 99.1% (by weight) of the hydrogen contained in the slurry mixture obtained from the first reactor having a pressure in the range of 103 to 145 kPa (abs) and transferring the resulting residual mixture to a second reactor; (c) polymerizing ethylene and optionally a C4 to C12 α-olefin comonomer in the second reactor in the presence of a catalyst system selected from a Ziegler-Natta catalyst or a metallocene and in the presence of the amount of hydrogen obtained in step (b) to obtain a first high molecular weight polyethylene in the form of a homopolymer or copolymer having a weight average molecular weight of more than 400,000 to 750,000 g / mol, and transferring the resulting mixture to a third reactor; (d) polymerizing ethylene and optionally a C4 to C12 α-olefin comonomer in a third reactor in the presence of a catalyst system selected from a Ziegler-Natta catalyst or a metallocene and hydrogen, wherein the amount of hydrogen in the third reactor is in the range of 0.1 to 70 mol %, preferably 0.1 to 60 mol %, based on the total gas present in the gas phase in the third reactor, or optionally in the substantial absence of hydrogen, to obtain a second high molecular weight polyethylene homopolymer or copolymer having a weight average molecular weight of 140,000 to 450,000 g / mole.

[0078] "In the substantial absence" in this context means that hydrogen is included in the third reactor only in amounts that cannot be avoided by technical means.

[0079] Technical effects Unlike methods known in the prior art, the method of the present invention does not require the use of multiple layers or blends of two or more resins.

[0080] In the present invention, the printing layer of the multi-layer film is prepared from PE, which has been developed to replace the existing printing layer (PET and nylon). It is targeted to be part of the circular economy initiative, as the list of major brands, retailers, packaging companies, and also resin manufacturers, is continuously growing, working towards the use of 100% reusable, recyclable, or compostable packaging by 2025 or even before. A full PE solution based on mono-material PE is one of the key challenges for flexible packaging, which is claimed to be efficient in terms of performance and acts as a 100% replacement for multi-material film solutions. The mono-material PE solution provides high stiffness with balanced dart impact and more efficient operation in MDO process, BOPE process, and other stretching processes itself, producing high quality film with increased thermal stability (low heat shrinkage) during conversion for packaging applications such as printing process, lamination, and stand-up pouches.

[0081] Therefore, the multimodal polyethylene composition according to the present invention for forming a film for a printing layer has been developed to solve this problem.

[0082] Although LLDPE or LDPE known in the art have been used to produce films that can be stretched in the machine direction or biaxial orientation direction, these compositions cannot be used as print layers for containers or packaging. The reason for this is that LLDPE or LDPE films cannot withstand high temperatures and exhibit shrinkage. These disadvantages are overcome by the multimodal polyethylene composition of the present invention.

[0083] Definition and Measurement Method As used herein, "comprising" can mean comprising in an amount of at least 50%, alternatively comprising in an amount of at least 80%, alternatively comprising in an amount of at least 90%, alternatively comprising in an amount of at least 95%, alternatively comprising in an amount of at least 98%, alternatively comprising in an amount of at least 99%, or "consisting of."

[0084] Resin Evaluation MI 2: The melt flow rate (MFR) and melt flow index (MI2) of polyethylene are measured in accordance with ASTM standard D1238, which measures the fluidity of a polymer under test conditions of a load of 2.16 kg and 190°C, and are expressed in units of g / 10 min.

[0085] density The density of polyethylene is measured by observing the level to which pellets sink in a liquid column gradient tube, compared to standards of known density. This method measures the solid plastic after annealing at 100 °C according to ASTM standard D1505.

[0086] Molecular weight and polydispersity index (PDI) : weight average molecular weight (Mw), number average molecular weight (Mn) and Z average molecular weight (M Z ) are analyzed by gel permeation chromatography (GPC). The polydispersity is calculated by Mw / Mn. Approximately 8 mg of sample was dissolved in 8 ml of 1,2,4-trichlorobenzene at 160°C for 90 minutes. Then 200 μl of the sample solution was injected into a high temperature GPC equipped with an IR5, infrared detector (Polymer Char, Spain) at a flow rate of 0.5 ml / min, column zone at 145°C, detector zone at 160°C. The data are processed by GPC One® software (Polymer Char, Spain).

[0087] The multimodal polyethylene composition of the present invention is produced in a multi-stage process, with fractions (A), (B) and (C) being produced in subsequent stages. In such cases, the properties of the fractions produced in the second or third (or further) stages of the multi-stage process can be inferred from the polymer produced separately in a single stage by applying identical polymerization conditions (e.g., identical temperature, reactant / diluent partial pressures, suspension medium, reaction time) for the stage of the multi-stage process in which the fraction is produced, and by using a catalyst in which no previously produced polymer was present. Alternatively, the properties of the fractions produced in the higher stages of the multi-stage process can also be calculated, for example, according to B. Hagstrom, Conference on Polymer Processing (The Polymer Processing Society), Extended Abstracts and Final Programme, Gothenburg, August 19 to 21, 1997, 4:13.

[0088] Thus, the properties of fractions produced in higher stages of such multi-step processes, which cannot be measured directly in the multi-step process product, can be determined by applying one or both of the above methods. Those skilled in the art can select the appropriate method. One particular method of calculating properties such as molecular weight (such as Mv) is to apply the deconvolution method using Excel or other calculation programs. In the deconvolution method, subtraction of each signal is performed.

[0089] HDPE polymers produced in a multi-stage process are also called "in-situ" blends. The final product obtained consists of a homogeneous mixture of polymers from three or more reactors, whose different molecular weight distribution curves together form a molecular weight distribution curve with a broad maximum or two or more maxima.

[0090] Crystallinity:Crystallization is determined by Differential Scanning Calorimetry (DSC) as follows: A sample of the polymer is pressed into a thin film at a temperature of 190°C. Approximately 5 + / - 0.5 mg of sample is weighed and placed in a DSC pan. The lid is crimped onto the pan to ensure a closed atmosphere. The sample pan is placed into a DSC (brand: Mettler Toledo) cell and then heated at a high rate of approximately 50 K / min from 50C to 200C with a N2 purge rate of 25 ml / min. The sample is held at this temperature, 200C, for 5 minutes. The sample is then cooled at a rate of 10 K / min with a N2 purge rate of 25 ml / min. to at least 50C. The sample is then heated at a rate of 10 K / min with a N2 purge rate of 25 ml / min until melting is complete. The sample is characterized by peak temperature and enthalpy, and the % crystallinity is calculated from the peak area.

[0091] DSC sequential self-nucleation and annealing (SSA) : The linear methylene sequence length is evaluated by differential scanning calorimetry (DSC) using the sequential self-nucleation and annealing (SSA) method reported in another paper [1]. The multi-peak thermogram obtained by the DSC-SSA measurement is first analyzed using Gaussian function fitting to separate the peaks. Using the Gibbs-Thomson equation, Eq. 1 [1,2]

number

[0092] The statistical mean value of l (l n ) and weighted average value (l w ) is calculated as shown in the following formula:[3]

number

[0093] References: 1.Rungswang, W.;Saendee, P.;Thitisuk, B.;Pathaweeisariyakul, T.;Cheevasrirungruang, WJ Appl. Polym. Sci. 2012, 128, 5, 3131. 2.Teng, HX;Shi, Y.;Jin, XG;J. Polym. Sci. Part B:Polym. Phy. 2002, 40, 2107. 3.Zhu, H,;Monrabal, B.;Han, CC;Wang, D.Macromolecules 2008, 41, 826.

[0094] Extension evaluation Tensile strength (uniaxial stretching evaluation) : Test specimens are prepared according to ISO standard 293. These test methods follow ISO standard 527-2. The tests use a constant grip separation speed of 50 mm / min at room temperature. The ratio of tensile strength at break (Fm) to tensile strength at yield (Fy) is calculated as Fm / Fy (ratio). The Fm / Fy ratio can be identified as: (a) good stretch ratio: Fm / Fy>,=1, and (b) poor stretch ratio: Fm / Fy<1.

[0095] KARO-IV (biaxial stretching evaluation) PE resin (pure multimodal polyethylene composition) prepared by compressing sheets at 190°C, pressure 5 MPa for 2 min and quenching sheets at 11°C for 2 min. The compressed sheets are then stretched at MD stretch ratio of 6 and TD stretch ratio of 6 using a Karo IV in simultaneous mode with a stretching speed of 100% / sec. The stretching temperatures in the machine direction (MD) and transverse direction (TD) were the same as the specified stretching temperatures (123-135°C). The stretch ratios at break are recorded and compared to evaluate the extensibility of each material.

[0096] KARO-IV (biaxial stretching evaluation) : Blends of multimodal polyethylene composition (HDPE) with LLDPE or LDPE are prepared by compressing sheets at 190°C and 5 MPa pressure for 2 min and quenching sheets at 11°C for 2 min. The compressed sheets are then stretched with a Karo IV in sequential mode with a stretch rate of 100% / sec at an MD stretch ratio of 4 and a TD stretch ratio of 7. The stretching temperatures in the machine direction (MD) and transverse direction (TD) were the same as the specified stretching temperature (123°C). The TD stretch ratios at break are recorded and compared to evaluate the extensibility of each material.

[0097] Film properties Heat shrinkage rate of oriented film : Measure the heat shrinkage (%) according to ASTM standard D-1204. Stretched film samples (film dimensions: 10 cm x 10 cm) obtained from KARO-IV are evaluated under the condition of 15 minutes of placement time in a hot air oven at 100°C. The stretched film is then allowed to cool at room temperature. The comparative ratio of the measured machine direction (MD) and transverse direction (TD) sizes, bidirectional sizes after heat shrinkage and bidirectional sizes in the former state is the heat shrinkage. The heat shrinkage level % can be specified as (a) low heat shrinkage: 4% or less and (b) high heat shrinkage: over 4%. EXAMPLES

[0098] Reference will now be made in detail to exemplary embodiments of the invention. Exemplary embodiments are described below to illustrate aspects of the invention, but do not necessarily limit the invention. Nevertheless, its particular aspects, together with the general aspects described herein for purposes of disclosure of the invention, may be material for implementing embodiments of the invention.

[0099] 1. Preparation and properties of multimodal resin compositions Inventive examples IE1-IE6 and comparative examples CE1-CE2 were prepared and run in a continuous process using three reactors connected in series. Ethylene, hydrogen, hexane, catalyst and cocatalyst were fed to the first reactor in the amounts shown in Table 1, with no comonomer present. A commercial Ziegler-Natta catalyst was used. Prior to feeding to the second reactor, the resulting slurry from the first reactor, preferably containing LMW polyethylene in hexane, may be transferred to a hydrogen removal unit to remove unreacted gases and a portion of the hexane from the polymer.

[0100] After removing a substantial amount of hydrogen, the slurry from the hydrogen removal unit was transferred to a second reactor to continue the polymerization, where ethylene could be polymerized with or without an α-olefin comonomer in the presence of the LMW polyethylene from the first reactor to form HMW1 polyethylene. The α-olefin comonomers that were useful for copolymerization were C 4-12 Of these, 1-butene and 1-hexene are preferred.

[0101] After polymerization in the second reactor, the resulting slurry was transferred to a third reactor to continue the polymerization. HMW2 was produced in the third reactor by polymerizing ethylene, optionally with an α-olefin comonomer, in the presence of LMW and HMW1 obtained from the first and second reactors. The α-olefin comonomers that were useful for copolymerization included C 4-12 , preferably 1-butene and 1-hexene.

[0102] The multimodal PE product from the third reactor was dried and the resulting powder was mixed with antioxidants and optional additives, then extruded and granulated into pellets. The pelletized resin was used to obtain density and MI.

[0103] In the comparative example from CE4, the polymerization was carried out in a 10 liter autoclave reactor using 6 liters of purified n-hexane as diluent. A commercially available Ziegler-Natta catalyst was used. A suitable catalyst preparation is described, for example, in Hungarian Patent Application No. 0800771R. The catalyst dosages shown in Table 1 were added. 6.0 mmoles of triethylaluminum were introduced. The temperature was then heated to the target value and the ethylene feed was started. Hydrogen was charged into the reactor to adjust the melt flow rate of the polymer produced in the first reactor. Ethylene was continuously fed while maintaining the total pressure of the reaction. Once the target amount of powder was prepared, the polymerization was stopped by releasing the pressure and cooling the slurry content. The second stage of the reaction was started by increasing the temperature to the target value. Butene-1 comonomer was added in this step to produce the copolymer in the second stage. Ethylene was continuously fed while maintaining the total pressure of the reaction. The polymerization was stopped once the blend ratio of the second stage was reached. The polymerization was stopped by releasing the pressure and cooling the slurry content. The third stage of the reaction was started by increasing the temperature to the target value. Butene-1 comonomer was added in this step to produce the copolymer in the third stage. Hydrogen was charged into the reactor to adjust the melt flow rate of the produced polymer in the third reactor. Ethylene was continuously fed while maintaining the total pressure of the reaction. Once the blend ratio of the third stage was reached, the polymerization was stopped. The polymerization was stopped by releasing the pressure and cooling the slurry content. The blend ratio can be calculated directly by comparing the ethylene uptake in the various stages of the polymerization as described, for example, in patent application EP 3293205.

[0104] Comparative Example 4 was synthesis from laboratory scale polymerization with multimodal polymer composition outside the claimed scope to compare with the inventive examples. However, it was some difference in different scale and polymerization conditions, such as continuous and batch polymerization, but it may be applicable to use for comparison with the inventive examples. This will be known to a person skilled in the art and applied based on his general knowledge to adjust the polymerization conditions for various reactor sizes in cliding the laboratory to commercial scale.

[0105] In Comparative Example 3, bimodal polyethylene resins were prepared from slurry polymerization in two reactors in parallel. CE3 was selected to compare the stretching performance compared with the polymer composition of the present invention. The polymerization conditions for CE3 are shown in Table 2.

[0106] Due to the uniqueness of the inventive polymer compositions in Table 1 and the characteristic properties of these multimodal polymers in Table 3, it has surprisingly been found that these compositions are advantageous when forming the inventive stretched films.

[0107] The polymerization conditions and resin properties of the inventive and comparative examples are shown in Tables 1, 2 and 3, respectively.

[0108] Example 1 of the present invention (IE1) The multimodal polyethylene composition (IE1) of the present invention was prepared by a process carried out in three reactors in series, resulting in amounts of polyethylene components within the claimed ranges (42 wt.% fraction (A), 18 wt.% fraction (B), and 40 wt.% fraction (C)) as set forth in Table 1. The final MI2 of IE1 was in the range of 0.20-0.35 g / 10 min, and the final density was 0.952-0.956 g / cm. 3 In the advantageous polymer composition shown in Table 3, the crystallinity % from DSC and Ln and Lw from DSC-SSA were within the range of the present invention. IE1 showed a good stretch ratio of 1.53 ("good" means greater than 1). As a result, the film obtained from IE1 showed good stretch properties.

[0109] Example 2 of the present invention (IE2) Inventive Example 2 (IE2) was carried out in the same manner as Inventive Example (IE1). As seen in Table 1, the polymer composition or weight percentage from each polymer composition of IE2 is the same as that of IE1, but the final MI2 of IE2 was lower than that of IE1. The characteristic properties of this multimodal polymer were shown in Table 3. The crystallinity % from DSC and Ln and Lw from DSC-SSA were within the range of the present invention. IE2 showed a good stretch ratio of 1.42 ("good" means greater than 1). As a result, the film obtained from IE2 showed good stretch properties.

[0110] Example 3 of the present invention (IE3) Inventive Example 3 (IE3) was carried out in the same manner as Inventive Example (IE1). Although the polymer composition or weight percentage from each polymer composition of IE3 was slightly different compared to that of IE1, the final density of IE3 was lower than that of IE1, resulting in a significant improvement in the stretch ratio. As a result, the film obtained from IE3 showed very good stretching properties (Fm / Fy>,=1.5).

[0111] Example 4 of the present invention (IE4) Inventive Example 4 (IE4) was carried out in the same manner as Inventive Example (IE1). The weight percentage of low molecular weight polyethylene in IE4 was the same as that in IE1, but other compositions were slightly different. The final MI2 of IE4 was higher than that of IE1, but the final density of IE4 was lower than that of IE1. As shown in Table 3, IE4 showed a good stretch ratio of 1.32 ("good" means greater than 1). As a result, the film obtained from IE4 showed good stretch properties.

[0112] Example 5 of the present invention (IE5) Inventive Example 5 (IE5) was carried out in the same manner as Inventive Example (IE5). The weight percentages of the low molecular weight polyethylene and the first high molecular weight polyethylene of IE5 were higher than those of IE1, but both the final MI2 and final density of IE5 were lower than those of IE1, resulting in a significant improvement in the stretch ratio. As a result, the film obtained from IE5 showed very good stretch properties (Fm / Fy>,=1.5).

[0113] Example 6 of the present invention (IE6) Inventive Example 6 (IE6) was carried out in the same manner as Inventive Example (IE1). Although the polymer composition or weight percentage from each polymer composition of IE6 was different compared to that of IE1, the final density of IE3 was almost the same as that of IE1. The characteristic properties of this multimodal polymer are shown in Table 3. IE6 showed a good stretch ratio of 1.32 ("good" means greater than 1). As a result, the film obtained from IE6 showed good stretching properties.

[0114] Comparative Example (CE1) Comparative Example 1 (CE1) was carried out in the same manner as Inventive Example (IE1). The multimodal polyethylene composition of Comparative Example CE1 was prepared using a split ratio in the preparation process, resulting in the amount of polyethylene components within the claimed range (45 wt% fraction (A), 10 wt% fraction (B), 45 wt% fraction (C)). However, the crystallinity from DSC and Ln and Lw from DSC-SSA were outside the ranges specified in the present invention. As a result, CE1 exhibited poor stretch ratio (Fm / Fy<1.0).

[0115] Comparative Example 2 (CE2) Comparative Example 2 (CE2) was carried out in the same manner as inventive example (IE1). The multimodal polyethylene composition of Comparative Example CE2 was prepared using a split ratio in the preparation process, which resulted in amounts of polyethylene components outside the claimed range (56 wt% of fraction (A), 18 wt% of fraction (B), and 26 wt% of fraction (C)). The crystallinity from DSC and Ln and Lw from DSC-SSA were outside the ranges specified in the present invention, resulting in poor stretch ratios (Fm / Fy<1.0).

[0116] Comparative Example (CE3) A bimodal polyethylene resin obtained by slurry polymerization in two reactors in parallel was used, with the properties shown in Table 2. In particular, CE3 has an MI of 7.5 g / 10 min and an M of 0.964 g / cm 3 However, the crystallinity from DSC and the Ln and Lw values ​​from DSC-SSA were outside the ranges specified in the present invention. As a result, CE3 exhibited poor stretching ratio (Fm / Fy<1.0).

[0117] Comparative Example 4 (CE4) Comparative Example 4 (CE4) was carried out in the same manner as Inventive Example (IE1). The multimodal polyethylene composition of Comparative Example CE4 was prepared using a split ratio in the preparation process, resulting in amounts of polyethylene components outside the claimed ranges (22.4 wt% of fraction (A), 47 wt% of fraction (B), 30.6 wt% of fraction (C)). Although the crystallinity from DSC and Ln and Lw from DSC-SSA were outside the ranges specified in the present invention, it was surprisingly found that CE4 exhibited good stretch ratios (Fm / Fy>,=1.5).

[0118] [Table 1A]

[0119] [Table 1B]

[0120] [Table 2]

[0121] [Table 3]

[0122] 2. Preparation and testing of biaxially stretched films (KARO-IV) As a result of Table 3, the multimodal polyethylene compositions of IE1-IE6 and CE4 exhibited good stretch ratios (Fm / Fy>1.0). Therefore, these compositions could be evaluated for biaxial stretching performance measured by KARO-IV.

[0123] The biaxially stretched films shown in Table 4 were produced by KARO-IV from multimodal polyethylene compositions IE1-IE6 and CE1-CE4. These biaxially stretched films were evaluated for heat shrinkage % according to ASTM standard D-1204. Surprisingly, it was found that the inventive compositions of multimodal polyethylene compositions IE1-IE6 were advantageous when forming the inventive biaxially stretched films and performed low heat shrinkage % (low heat shrinkage: equivalent to 4% or less).

[0124] Table 4. (a) Simultaneous stretching results evaluated on a laboratory scale tenter frame stretcher (Bruckner KARO IV) and (b) % heat shrinkage at 100 °C for 15 min of films retrieved from the KARO.

[0125] [Table 4]

[0126] 3.Polyethylene mixture The multimodal polyethylene compositions IE1 to IE6 may be selected as blend partners from the group consisting of linear low density polyethylene and low density polyethylene in an amount of 35% (by weight) with respect to the total weight of the polyethylene blend, and mixtures of the two.

[0127] The polyethylene blends of the multimodal polyethylene composition of the present invention were evaluated for both draw ratio (Fm / Fy) measured by KARO-IV and bidirectional stretch performance as shown in Table 5.

[0128] Table 5. Examples of blends of the multimodal polyethylene composition of the present invention (HDPE) with LLDPE or LDPE and their properties

[0129] [Table 5]

[0130] Example 7 of the present invention (IE7) IE7 is a polyethylene blend (polyethylene mixture) consisting of 65 wt.% of the multimodal polyethylene composition IE1 according to the present invention and 35 wt.% of LLDPE, the synthesized LLDPE resin had an MI2 of 3.5 g / 10 min and a density of 0.915 g / cm3.

[0131] Example 8 of the present invention (IE8) IE8 is a polyethylene blend (polyethylene mixture) consisting of 65% by weight of the multimodal polyethylene composition IE1 according to the invention and 35% by weight of LLDPE, the synthetic resin having an MI2 of 2.5 g / 10 min and a density of 0.918 g / cm 3 It was.

[0132] Example 9 of the present invention (IE9) IE9 is a polyethylene blend (polyethylene mixture) consisting of 65% by weight of the multimodal polyethylene composition IE1 according to the invention and 35% by weight of LDPE, the MI2 of the commercial resin (EL-Lene™ D777C) is 7.0 g / 10 min and the density is 0.920 g / cm 3It was.

[0133] As shown in Table 5, Examples 7, 8 and 9 showed Fm / Fy values ​​greater than 1, which were 1.67, 1.68 and 1.14, respectively. After all of the inventive Examples 7, 8, 9 could achieve a machine direction (MD) stretch ratio equal to 4, the transverse direction (TD) stretch ratio at break measured by KARO-IV (sequential mode) at a temperature of 123°C for the inventive Examples 7, 8 and 9 was greater than 6. This means that the multimodal HDPE composition according to the present invention was a good partner of the compound solution containing LLDPE or LDPE to produce stretched films.

[0134] The multimodal HDPE composition of Example (IE1) and the uniqueness of the first high molecular weight portion could increase the TD stretch ratio (greater than 5) in various LLDPE types and LDPE.

[0135] The features disclosed in the foregoing description and in the dependent claims may, both separately and in any combination thereof, be material for realizing the aspects of the disclosure made in the independent claims in diverse forms thereof.

[0136] The features disclosed in the foregoing description and in the dependent claims may, both separately and in any combination thereof, be material for realizing the aspects of the disclosure made in the independent claims in diverse forms thereof.

Claims

1. 1. A multimodal polyethylene composition comprising: (A) 40 to 52 wt. % of a low molecular weight polyethylene, based on the total weight of the multimodal polyethylene composition, the low molecular weight polyethylene being a homopolymer, the low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol, as measured by gel permeation chromatography; (B) 10 to 28 wt. % of a first high molecular weight polyethylene, based on the total weight of the multimodal polyethylene composition, the first high molecular weight polyethylene being a homopolymer or a copolymer, the first high molecular weight polyethylene having a weight average molecular weight (Mw) of 300,000 to 900,000 g / mol, as measured by gel permeation chromatography; (C) 25 to 50 wt. % of a second high molecular weight polyethylene, based on the total weight of the multimodal polyethylene composition, the second high molecular weight polyethylene being a homopolymer or a copolymer, the second high molecular weight polyethylene having a weight average molecular weight (Mw) of 130,000 to 500,000 g / mol, as measured by gel permeation chromatography; Including, the first high molecular weight polyethylene differs from the second high molecular weight polyethylene in terms of the weight average molecular weight; the crystallinity of the multimodal polyethylene composition is from 49% to 65%, as measured by differential scanning calorimetry; and the number average linear methylene sequence length (L) of the multimodal polyethylene composition as measured by DSC sequential self-nucleation and annealing (SSA); ｎ ) value of the multimodal polyethylene composition is 1.90 nm to 4.8 nm, and the weight average linear methylene sequence length (L ｗ ) value is 2.5 nm to 5.6 nm.

2. The density of the multimodal polyethylene is 0.935 to 0.960 g / cm, as measured according to ASTM standard D1505. ３ 2. The multimodal polyethylene composition of claim 1, wherein the polyvinyl alcohol is in the range of

3. Melt flow rate MI of multimodal polyethylene ２ 2. The multimodal polyethylene composition of claim 1, wherein the modulus of elasticity is in the range of 0.01 to 2.5 g / 10 min, as measured according to ASTM standard D1238.

4. 2. The multimodal polyethylene composition according to claim 1, wherein the polydispersity of the multimodal polyethylene composition is from 12 to 40, as measured by gel permeation chromatography.

5. 2. The multimodal polyethylene composition according to claim 1, wherein the multimodal polyethylene composition has a weight average molecular weight of 130,000 to 400,000 g / mol; and / or a number average molecular weight of 5,000 to 15,000 g / mol; and / or a Z average molecular weight of 1,000,000 to 3,000,000 g / mol, each measured by gel permeation chromatography.

6. 2. The multimodal polyethylene composition according to claim 1, wherein the multimodal polyethylene composition has an Fm / Fy of 1.0 to 1.9, where Fm is the tensile strength at break of the multimodal polyethylene composition, and Fy is the tensile strength at yield of the multimodal polyethylene composition, each measured in accordance with ISO standard 527-2.

7. 1. A polyethylene blend comprising: The multimodal polyethylene composition of claim 1; an additional component selected from the group consisting of linear low density polyethylene, low density polyethylene, medium density polyethylene, very low density polyethylene, and mixtures of two or more thereof, in an amount of 10 to 50 wt %, based on the total weight of the polyethylene blend; A polyethylene mixture comprising:

8. 8. A film comprising the multimodal polyethylene composition according to any one of claims 1 to 6 or the polyethylene blend according to claim 7.

9. 10. A method for producing the film of claim 8, comprising blowing or casting the film and further co-extruding the film.

10. 10. The method for producing a film according to claim 9, further comprising the subsequent step of heat-stretching the film by biaxial sequential orientation and / or heat-stretching the film by biaxial simultaneous orientation and / or heat-stretching the film in the machine direction.

11. A film as described in claim 8, wherein the film has a stretching ratio of 1.5 to 4.5; and / or a longitudinal stretching ratio of 3 to 15; and / or a transverse stretching ratio of 3 to 12.

12. A film obtainable by the method described in claim 9, wherein the film has a stretching ratio of 1.5 to 4.5; and / or a longitudinal stretching ratio of 3 to 15; and / or a transverse stretching ratio of 3 to 12.

13. A multilayer film comprising the film described in claim 8.

14. (a) inner layer; (b) a first adhesive layer; (c) a barrier layer; (d) a second adhesive layer; and (e) outer layer; Including, A multilayer film wherein the outer layer is the film of claim 8.

15. An article comprising the multilayer film of claim 13, the article being a package or container.

16. An article comprising the multilayer film of claim 14, the article being a package or container.