Heat sealable composition and use thereof

Abstract

This application relates to a heat-sealable composition and its uses. The composition, based on the total weight of the composition, comprises: 20 wt% to 65 wt% of a first polyethylene, the first polyethylene comprising 70.0 wt% to 100.0 wt% of units derived from ethylene and 0 wt% to 30.0 wt% of units derived from C3-C 20 α-olefins and having a density of 0.905 to 0.926 g / cm 3 and a melt index of 12 to 35 g / 10 min at 2.16 kg / 190 °C; and 5 wt% to 50 wt% of a polyolefin plastomer having a density of 0.890 to 0.910 g / cm 3 and a melt index of 5 to 20 g / 10 min at 2.16 kg / 190 °C; wherein the composition has a density of 0.902 to 0.922 g / cm 3 . The heat-sealable composition can achieve a reduced heat-sealing start temperature, an increased peak heat tack, and an increased heat-sealing window width when used as a heat-sealable film or as a heat-sealable layer in a heat-sealable packaging structure.

Description

Technical Field

[0001] The present application relates to a heat-sealable composition and uses thereof, in particular, to a heat-sealable composition, a heat-sealable film formed from the heat-sealable composition, a method for preparing the heat-sealable film, a heat-sealable packaging structure comprising the heat-sealable composition, and use of the heat-sealable composition for improving the heat-sealability of a heat-sealable film or a heat-sealable packaging structure. Background Art

[0002] Aseptic packaging is a packaging technology that ensures that products remain sterile during storage and transportation. This packaging technology is widely used in the packaging of products such as medicines, food and cosmetics, aiming to prevent contamination and growth of microorganisms, thereby extending the shelf life and safety of products. As consumers' requirements for product safety and quality continue to increase, manufacturers are seeking more efficient and reliable packaging solutions. Among them, form-fill-seal (FFS) packaging technology is favored due to its high and excellent heat sealing performance.

[0003] FFS packaging technology achieves an integrated packaging process by completing product forming, filling and heat sealing on the same equipment. This technology not only improves production efficiency, but also effectively reduces the risk of manual intervention, thereby minimizing the chance of product contamination by contact with the external environment during the packaging process.

[0004] The structure of aseptic packaging is usually a multi-layer composite film, for example, including a polymer layer, a cardboard layer, an aluminum foil layer, etc. The cardboard layer serves as the main structural support for the packaging, providing strength and toughness for the packaging. The function of the aluminum foil layer is to block oxygen and light, etc., to protect the product from oxidation and light. There are usually multiple polymer layers (usually polyethylene layers), and because the polymer layers play different roles in different positions, there are also different requirements for their material selection. The polymer layer located on the outside (in contact with the external environment) plays a role in blocking moisture and microorganisms, protecting the internal products from the influence of the external environment. The polymer layer located between the layers plays a bonding role, ensuring that the layers are tightly combined to form a whole. The polymer layer located on the inside (in contact with the product) plays a heat sealing role, usually called a heat sealing layer.

[0005] As part of the overall packaging structure, the requirements for heat-sealing layers are getting higher and higher. For example, it is expected that the heat-sealing layer has a high melt index (for example, higher than 15g / 10min) to cater to the trend of faster speeds of packaging production lines (for example, high-speed FFS packaging production lines). At the same time, it is expected that the heat-sealing layer can have heat-sealing properties that meet the requirements, especially a lower heat-sealing starting temperature, a higher hot tack strength, and a wider heat-sealing window, etc. However, there is often a compromise between the properties of the heat-sealing layer. For example, a polymer layer with a high melt index may have poor heat-sealing properties, or a decrease in the heat-sealing starting temperature is often accompanied by a decrease in hot tack strength, and so on.

[0006] Therefore, the object of the present invention is to provide a novel heat-sealable composition which can meet all the requirements mentioned above, has a high melt index to meet the requirements of high-speed processing, and has excellent heat-seal properties, such as reduced heat-seal initiation temperature, increased hot tack strength and a widened heat-seal window, etc. The composition can be used as a heat-sealable film or as a heat-sealable layer in a heat-sealable packaging structure, providing improved heat-sealability, processing performance and cost advantages. Summary of the invention

[0007] In a first aspect, the present disclosure provides a composition comprising, based on the total weight of the composition, 20 wt % to 65 wt % of a first polyethylene, the first polyethylene comprising 70.0 wt % to 100.0 wt % of units derived from ethylene and 0 wt % to 30.0 wt % of units derived from C 3 -C 20 α-olefin units and have a value of 0.905 to 0.926 g / cm 3 A density of 12 to 35 g / 10 min and a melt index at 2.16 kg / 190° C.; and 5 to 50% by weight of a polyolefin plastomer having a molecular weight of 0.890 to 0.910 g / cm 3 and a melt index at 2.16 kg / 190° C. of 5 to 20 g / 10 min; wherein the composition has a density of 0.902 to 0.922 g / cm 3 density.

[0008] In a second aspect, the present disclosure provides a film comprising the composition as described above and below.

[0009] In a third aspect, the present disclosure provides a method for preparing a film as described above and below, comprising extrusion coating a composition as described above and below to form the film.

[0010] In a fourth aspect, the present disclosure provides a packaging structure comprising at least one layer formed from a composition as described above and below.

[0011] In a fifth aspect, the present disclosure provides use of a composition as described above and below as a heat sealable film or as a heat sealable layer in a packaging structure.

[0012] Surprisingly, it is found that the heat-sealable composition of the technical solution of the present application has a high melt index to meet the requirements of high-speed processing, and at the same time has excellent heat-sealing properties, such as reduced heat-sealing initiation temperature, increased hot tack strength and a widened heat-sealing window, etc. The composition can be used as a heat-sealable film or as a heat-sealable layer in a heat-sealable packaging structure, providing improved heat-sealing properties, processing properties and cost advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The heat seal strength curves of Example 2, Comparative Example 1, Reference Example 1 and Reference Example 2 as a function of temperature are shown.

[0014] Figure 2 The hot tack curves of Example 2, Comparative Example 1, Reference Example 1 and Reference Example 2 as a function of temperature are shown.

[0015] Figure 3 The heat seal strength curves of Examples 1-4, Comparative Example 1 and Reference Example 1 as a function of temperature are shown.

[0016] Figure 4 The hot tack curves of Examples 1-4, Comparative Example 1 and Reference Example 1 as a function of temperature are shown.

[0017] Details

[0018] Definition and test methods

[0019] Unless otherwise indicated, room temperature is 25°C.

[0020] An "olefin" is a linear, branched or cyclic compound of carbon and hydrogen having at least one double bond.

[0021] "Polymer" has two or more identical or different monomer (mer) units. "Homopolymer" is a polymer having identical monomer units. The term "polymer" as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc. The term "polymer" as used herein also includes impact, block, graft, random and alternating copolymers. Unless otherwise specifically stated, the term "polymer" shall also include all possible geometric configurations. Such configurations may include isotactic, syndiotactic and random symmetries.

[0022] As used herein, unless otherwise specified, the term "copolymer" refers to a polymer formed by the polymerization of at least two different monomers (i.e., monomer units). For example, the term "copolymer" includes copolymerization products of propylene and α-olefins such as ethylene, 1-hexene. A "terpolymer" is a polymer having three monomer units that are different from each other. Therefore, the term "copolymer" also includes terpolymers and tetrapolymers such as copolymer products of mixtures of ethylene, propylene, 1-hexene and 1-octene.

[0023] "Different" as used to refer to monomeric monomeric units means that the monomeric units differ from each other by at least one atom or are isomerically different. An "ethylene polymer" or "ethylene copolymer" is a polymer or copolymer comprising at least 50 mole % ethylene derived units, a "propylene polymer" or "propylene copolymer" is a polymer or copolymer comprising at least 50 mole % propylene derived units, and so forth. For purposes of the present invention, polyethylene is an ethylene polymer.

[0024] As used herein, when a polymer is referred to as "comprising, consisting of, or consisting essentially of a monomer," the monomer is present in the polymer in the polymerized / derivative form of the monomer. For example, when a copolymer is said to have an "ethylene" content of 35% to 55% by weight, it is understood that the monomer units in the copolymer are derived from ethylene in the polymerization reaction, and the derived units are present at 35% to 55% by weight based on the weight of the copolymer. Thus, a polymer or copolymer said to have a 90% by weight "ethylene" content is equivalent to a polymer or copolymer said to have a 90% by weight "ethylene-derived" content or 90% by weight "units derived from ethylene," etc.

[0025] As used herein, "polyethylene" means an ethylene homopolymer or a copolymer comprising at least 79 wt.% ethylene. The terms "polyethylene polymer", "polyethylene", "ethylene polymer", "ethylene copolymer" and "ethylene-based polymer" have the same meaning as polyethylene copolymers, except where otherwise indicated (e.g., when referring to polyethylene homopolymers, this means polymers formed from ethylene monomers that do not contain comonomer units, e.g., 100 wt.% ethylene-derived units).

[0026] As used herein, "high density polyethylene (HDPE)" means a polyethylene produced in a gas phase and / or slurry phase polymerization and having a density of 0.940 g / cm 3 Up to 0.970g / cm 3 Ethylene homopolymers and ethylene copolymers having a range of densities.

[0027] As used herein, "low density polyethylene (LDPE)" means a polyethylene produced in high pressure free radical polymerization and having a density of 0.910 g / cm 3Up to 0.940g / cm 3 Ethylene homopolymers and / or ethylene copolymers having a density within a certain range.

[0028] As used herein, "linear low density polyethylene (LLDPE)" means a polyethylene produced in a suspension, solution, slurry or gas phase polymerization process and having an average molecular weight of 0.910 g / cm 3 Up to 0.940g / cm 3 The LLDPE can be produced in a gas phase reactor, a high pressure tubular reactor and / or a slurry reactor and / or in a solution reactor with any of the disclosed catalysts. The LLDPE has a large number of short branches and is structurally different from conventional LDPE because LLDPE generally has minimal long chain branching and more short chain branching than LDPE.

[0029] As used herein, the term "metallocene-catalyzed linear low density polyethylene (m-LLDPE) refers to a LLDPE composition prepared by a metallocene catalyst.

[0030] Moment and distribution of molecular weight (Mw, Mn, Mz, Mw / Mn, Mz / Mn, etc.) and monomer / comonomer content (C2, C4, C6 and / or C8 and / or other, etc.) and g'(vis) were determined by using high temperature gel permeation chromatography (Polymer Char GPC-IR) equipped with a multi-channel bandpass filter based infrared detector IR5, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10 μm Mixed-B LS columns were used to provide polymer separation. Detailed analysis principle and method for determination of molecular weight and g' vis Described in paragraphs

[0044] -

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

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

[0044] -

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

[0044] , a=0.695 and K=0.000579 (1-0.75Wt) are used, where Wt is the weight fraction of the comonomer, and further noting that the weight fraction of the comonomer is calculated by corresponding to CH calibrated with a series of PE and PP homo / copolymer standards. 2 and CH 3The ratio of the IR5 detector intensities of the channels determines the comonomer composition, the nominal value of the standard being predetermined by NMR or FTIR as indicated in paragraph

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

[0031] The density values ​​of polymers are measured by following ASTM D1505.

[0032] Each melt flow index or melt index (MI) and high load melt index (HLMI) are measured on a Goetfert MI-4 melt indexer according to ASTM D1238-13, wherein the MI (sometimes referred to as I 2 ); and HLMI (sometimes referred to as I 21 ). Samples in an amount of 5 to 6 g were loaded into the barrel of the instrument at 190°C and compressed manually. Thereafter, the material was automatically compacted in the barrel by lowering all available weight onto the piston to remove all air bubbles. Data acquisition started after a 6 min pre-melting time.

[0033] The melt flow index ratio or melt index ratio (equivalently MFR or MIR) is the ratio HLMI / MI (or I 21 / I 2 ).

[0034] The "Heat Seal Initiation Temperature" is the temperature at which a heat seal (custom force value) is formed immediately after the heat sealing operation. The strength of the heat seal is measured at specified time intervals (milliseconds) after the heat sealing cycle is completed and after the heat seal has cooled to ambient temperature and reached maximum strength. The strength of a heat seal is usually specified, for example, the heat seal initiation temperature at 1N refers to the temperature at which such a heat seal is formed, and the heat seal will have a strength of 1N force. The heat seal initiation temperature can be measured by ASTM F1921.

[0035] "Hot tack strength" refers to the peel force of the heat-sealed area when it has not been completely cooled. "Heat seal strength" refers to the peel force when the heat-sealed area has been completely cooled. The hot tack strength and heat seal strength of the same material are usually different from each other.

[0036] To characterize the overall heat-sealing performance of the material, the parameter "heat-sealing index" is defined in this article. The heat-sealing index is (peak heat adhesion force × heat-sealing window width at 2N - heat-sealing start temperature at 1N) / density of the composition, where the peak heat adhesion force, heat-sealing window width, heat-sealing start temperature, and density are defined and measured as in this application.

[0037] First polyethylene

[0038] The first polyethylene may comprise or be linear low density polyethylene (LLDPE), and the linear low density polyethylene comprises a copolymer derived from ethylene and one or more C 3 -C 20 α-olefin comonomers. In various embodiments, the first polyethylene has one or more of the following properties:

[0039] (a) The density (ASTM D4703 / D1505) is about 0.905 to about 0.926 g / cm 3 , or about 0.912 to about 0.922 g / cm 3 , or about 0.915 to about 0.925 g / cm 3 , or about 0.915 to about 0.920 g / cm 3 , or about 0.916 to about 0.920 g / cm 3 , or about 0.918 to about 0.920 g / cm 3 ;

[0040] (b) The melt index ("MI", ASTM D-1238, 2.16 kg, 190 °C) is about 12 to about 35 g / 10 min, about 15 to about 35 g / 10 min, or about 15 to about 25 g / 10 min, or about 17 to about 25 g / 10 min, or about 18 to about 20 g / 10 min;

[0041] (c) a composition distribution breadth index ("CDBI") of about 60% to about 85%, or about 65% to about 85%. "CDBI" refers to the weight percentage of copolymer molecules having a comonomer content within 50% of the median total molar comonomer content. The CDBI of a copolymer can be measured using techniques known in the art. The CDBI of a copolymer is readily determined using well-known techniques for isolating individual fractions of a copolymer sample. One such technique is temperature rising elution fractionation (TREF), as described in Wild et al., J. Poly. Sci., Poly. Phys. Ed., Vol. 20, pp. 441-455 (1982), which is incorporated herein by reference. Details regarding determining the CDBI of a copolymer are known to those skilled in the art, see, for example, PCT patent application WO 1993 / 003093, published on February 18, 1993, regarding CDBI;

[0042] (d) a weight average molecular weight (Mw) of about 15,000 to about 400,000 g / mol, about 20,000 to about 250,000 g / mol, about 20,000 to about 200,000 g / mol, about 25,000 to about 150,000 g / mol, about 150,000 to about 400,000 g / mol, about 200,000 to about 400,000 g / mol, or about 250,000 to about 350,000 g / mol;

[0043] (e) a molecular weight distribution ("MWD", "Mw / Mn") of about 1.5 to about 5.0, or about 2.0 to about 3.5. Techniques for determining molecular weight ("Mw" and "Mn") and molecular weight distribution ("MWD", "Mw / Mn") can be found in U.S. Pat. No. 4,540,753 to Cozewit et al. and references cited therein, and in VerStrate et al., Macromolecules, Vol. 21, p. 3360 (1986) and references cited therein, the foregoing documents being incorporated herein by reference; and

[0044] (f) Branching Index (as defined herein) g' vis is greater than about 0.85, or greater than about 0.9, or greater than about 0.95, or greater than about 0.97, or greater than about 0.98, indicating a substantially linear structure of the molecular chain.

[0045] The first polyethylene comprises about 70.0 wt % to about 100.0 wt % of units derived from ethylene. The lower limit of the ethylene content range of the first polyethylene can be about 70.0 wt %, about 75.0 wt %, about 80.0 wt %, about 85.0 wt %, about 90.0 wt %, about 92.0 wt %, about 94.0 wt %, about 95.0 wt %, about 96.0 wt %, about 97.0 wt %, about 98.0 wt % or about 99.0 wt %. The upper limit of the ethylene content range of the first polyethylene can be about 80.0 wt %, about 85.0 wt %, about 90.0 wt %, about 92.0 wt %, about 94.0 wt %, about 95.0 wt %, about 96.0 wt %, about 97.0 wt %, about 98.0 wt %, about 99.0 wt %, about 99.5 wt % or about 100.0 wt %. Therefore, the first polyethylene can have less than 30.0 wt % of units derived from C 3 -C 20 Polymer units of olefins (preferably α-olefins, such as hexene or octene). 3 -C 20 The lower end of the olefin content range may be about 25.0 wt%, about 20.0 wt%, about 15.0 wt%, about 10.0 wt%, about 8.0 wt%, about 6.0 wt%, about 5.0 wt%, about 4.0 wt%, about 3.0 wt%, about 2.0 wt%, about 1.0 wt%, or about 0.5 wt%. 3 -C 20 The upper limit of the olefin content range can be about 20.0 wt %, about 15.0 wt %, about 10.0 wt %, about 8.0 wt %, about 6.0 wt %, about 5.0 wt %, about 4.0 wt %, about 3.0 wt %, about 2.0 wt % or about 1.0 wt %. Any lower limit can be combined with any upper limit to form a range. The comonomer content is based on the total content of all monomers in the first polyethylene.

[0046] C 3 -C 20 The α-olefin comonomers may be linear or branched, and two or more comonomers may be used if desired. Examples of suitable α-olefin comonomers include propylene, butene, 1-pentene; 1-pentene with one or more methyl, ethyl or propyl substituents; 1-hexene; 1-hexene with one or more methyl, ethyl or propyl substituents; 1-heptene; 1-heptene with one or more methyl, ethyl or propyl substituents; 1-octene; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene; 1-nonene with one or more methyl, ethyl or propyl substituents; 1-decene substituted with ethyl, methyl or dimethyl; 1-dodecene and styrene. Preferred α-olefins may include pentene, hexene, heptene, octene or a combination thereof.

[0047] In various embodiments, the first polyethylene is polymerized in the presence of a single-site catalyst. In a specific embodiment, the single-site catalyst is a metallocene. For example, the first polyethylene may include or be a metallocene-catalyzed linear low-density polyethylene (m-LLDPE). Useful metallocene catalysts, resins, and manufacturing methods are described in U.S. Patent No. 6,932,592, entitled "Very Low Density Polyethylene Produced by Metallocenes" (Farley et al.), which is incorporated herein by reference.

[0048] The first polyethylene described herein is not limited to any particular method of preparation.In various embodiments, the ethylene derived resin is prepared by gas phase polymerization of a supported catalyst containing a bridged bis(alkyl-substituted dicyclopentadienyl) zirconium dichloride transition metal component and a methylaluminoxane cocatalyst.

[0049] In addition to those discussed above, first polyethylenes useful in the present invention include copolymers commercially available from ExxonMobil Chemical Company, such as those sold under the tradename EXCEED TM Those sold, including but not limited to those sold under the brand name EXCEED TM 0019XC and EXCEED TM Those sold by 0015XC.

[0050] EXCEED TM 0019XC is a m-LLDPE, ethylene 1-hexene copolymer, with a viscosity of 0.918 g / cm 3 density, a melt index of 19 g / 10 min (190°C / 2.16 kg), a melting peak temperature of 113°C and a Vicat softening temperature of 95.0°C. TM 0019XC has a 1-hexene content of 9.34 wt%, a Mw / Mn of 2.9, and a CDBI of 77%.

[0051] EXCEED TM 0015XC is a m-LLDPE, ethylene 1-hexene copolymer, with a viscosity of 0.918 g / cm 3 The material has a density of 15 g / 10 min, a melt index (190°C / 2.16 kg), a melting peak temperature of 113°C and a Vicat softening temperature of 96.0°C.

[0052] Polyolefin plastomers

[0053] The polyolefin plastomer can include or be based on ethylene plastomer. In various embodiments, the polyolefin plastomer has one or more of the following properties:

[0054] (a) Density: 0.860 g / cm 3 Up to 0.910g / cm 3 , or 0.880g / cm 3 Up to 0.910g / cm 3 , or 0.890 g / cm 3 Up to 0.910g / cm 3 , or 0.895 g / cm 3 Up to 0.905g / cm 3 , or 0.880g / cm 3 Up to 0.900g / cm 3 ;

[0055] (b) a melt index ("MI", ASTM D-1238, 2.16 kg, 190°C) of about 5 to about 30 g / 10 min, about 5 to about 20 g / 10 min, or about 7 to about 17 g / 10 min, or about 5 to about 10 g / 10 min, or about 10 to about 20 g / 10 min;

[0056] (c) a melting temperature of about 75 to about 125°C, or about 80 to about 120°C, or about 85 to about 115°C, or about 90 to about 110°C;

[0057] (d) a Vicat softening temperature of about 55 to about 105°C, or about 60 to about 100°C, or about 65 to about 95°C, or about 70 to about 90°C.

[0058] Suitable ethylene-based plastomers are preferably homopolymers of ethylene or contain at least 50 wt%, preferably 65-99 wt%, even more preferably 94-99 wt% ethylene (or units derived from ethylene) and have up to 50 wt%, preferably 1-35 wt%, even more preferably 1-6 wt% C 3 -C 20 Comonomer (or derived from C 3 -C 20 The polyethylene copolymer preferably has a composition distribution breadth index (CDBI) of 90% or more, more preferably greater than 95%, even more preferably 95% to 99%.

[0059] C of the above ethylene-based plastomer 3 -C 20The comonomer can be any polymerizable olefin monomer and is preferably a linear, branched or cyclic olefin, and even more preferably an alpha-olefin. Suitable examples of olefins include propylene, butylene, isobutylene, pentene, isopentene, cyclopentene, hexene, isohexene, cyclohexene, heptene, isoheptene, cycloheptene, octene, isooctene, cyclooctene, nonene, cyclononene, decene, isodecenes, dodecene, isodecenes, 4-methyl-pentene-1, 3-methyl-pentene-1, 3,5,5-trimethylhexene-1. Suitable comonomers also include dienes, trienes and styrene monomers. Preferred examples include styrene, alpha-methylstyrene, p-alkylstyrene (such as p-methylstyrene), hexadiene, norbornene, vinyl norbornene, ethylidene norbornene, butadiene, isoprene, heptadiene, octadiene and cyclopentadiene. Preferred comonomers for ethylene-based plastomers are propylene, butene, hexene and / or octene.

[0060] The above-mentioned ethylene-based plastomers may also include trimers and tetramers, which may be the above-mentioned C 3 -C 20 Olefins, any C 4 -C 20 One or more of linear, cyclic or branched dienes or trienes and any styrenic monomers such as styrene, α-methylstyrene or p-methylstyrene. Preferred examples include butadiene, pentadiene, cyclopentadiene, hexadiene, cyclohexadiene, heptadiene, octadiene, nonadiene, norbornene, vinyl norbornene, ethylidene norbornene, isoprene and heptadiene.

[0061] In a preferred embodiment, the ethylene-based plastomer is a metallocene polyethylene (mPE). The mPE homopolymer or copolymer can be prepared in solution, slurry, high pressure or gas phase using a mono- or di-cyclopentadienyl transition metal catalyst in combination with an aluminoxane and / or a non-coordinating anion activator. The catalyst and activator can be supported or unsupported and the cyclopentadienyl ring can be substituted or unsubstituted. Some commercial products prepared using such catalyst / activator combinations are available from ExxonMobile Chemical Company under the trade name EXACT TM Commercially available, including but not limited to, under the brand name EXACT TM 3139 and EXACT TM Those sold at 3040.

[0062] EXACT TM 3139 is a mPE, ethylene hexene copolymer, with a density of 0.900 g / cm 3 The material has a density of 1.5 g / 10 min, a melt index (190°C / 2.16 kg) of 7.5 g / 10 min, a melting peak temperature of 95°C and a Vicat softening temperature of 79.9°C.

[0063] EXACT TM 3040 is a kind of mPE, which is an ethylene hexene copolymer with a hardness of 0.900g / cm 3 The material has a density of 17 g / 10 min, a melt index (190°C / 2.16 kg), a melting peak temperature of 96°C and a Vicat softening temperature of 75.7°C.

[0064] Second polyethylene

[0065] In a preferred embodiment, the heat-sealable composition of the present invention further comprises a second polyethylene.

[0066] The second polyethylene may include or be LDPE. In various embodiments, the second polyethylene has one or more of the following properties:

[0067] (a) Density is about 0.910 g / cm 3 To about 0.930g / cm 3 , or about 0.910g / cm 3 About 0.920g / cm 3 , or about 0.916g / cm 3 To about 0.930g / cm 3 , or about 0.918g / cm 3 to about 0.926g / cm 3 , or about 0.915g / cm 3 About 0.920g / cm 3 , or about 0.915g / cm 3 to about 0.919 g / cm 3

[0068] (b) a melt index (ASTM D-1238, 190°C, 2.16 kg) of from about 5 g / 10 min to about 35 g / 10 min, or from about 5 g / 10 min to about 25 g / 10 min, or from about 6 g / 10 min to about 16 g / 10 min, or from about 7 g / 10 min to about 15 g / 10 min, or from about 8 g / 10 min to about 12 g / 10 min;

[0069] (c) a melting temperature of about 80 to about 130°C, or about 85 to about 125°C, or about 90 to about 120°C, or about 95 to about 115°C, or about 103°C to 107°C;

[0070] (d) a molecular weight distribution (MWD=Mw / Mn) of from about 5 to about 70, or from about 5 to about 11, from about 8 to about 10.5, or from about 8.5 to about 11, or from about 25 to about 70;

[0071] (e) a weight average molecular weight (Mw) of about 630,000 to about 1,400,000 g / mol;

[0072] (f) a number average molecular weight (Mn) of about 16,500 to about 24,500 g / mol.

[0073] LDPE can be a polyethylene homopolymer. Alternatively, LDPE can be an ethylene copolymer containing C3-C20 α-olefins. Examples of comonomers include propylene, 1-butene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, 1-pentene, 1-pentene containing one or more methyl, ethyl or propyl substituents, 1-hexene, 1-hexene containing one or more methyl, ethyl or propyl substituents, 1-heptene, 1-heptene containing one or more methyl, ethyl or propyl substituents, 1-octene, 1-octene containing one or more methyl, ethyl or propyl substituents, 1-nonene, 1-nonene containing one or more methyl, ethyl or propyl substituents, 1-decene substituted with ethyl, methyl or dimethyl, 1-dodecene and styrene. Exemplary combinations of ethylene and comonomers include: ethylene 1-butene, ethylene 1-pentene, ethylene 4-methyl-1-pentene, ethylene 1-hexene, ethylene 1-octene, ethylene decene, ethylene dodecene, ethylene 1-butene 1-hexene, ethylene 1-butene 1-pentene, ethylene 1-butene 4-methyl-1-pentene, ethylene 1-butene 1-octene, ethylene 1-hexene 1-pentene, ethylene 1-hexene 4-methyl-1-pentene, ethylene 1-hexene 1-octene, ethylene 1-hexene decene, ethylene 1-hexene dodecene, ethylene propylene 1-octene, ethylene 1-octene 1-butene, ethylene 1-octene 1-pentene, ethylene 1-octene 4-methyl-1-pentene, ethylene 1-octene 1-hexene, ethylene 1-octene decene, ethylene 1-octene dodecene, and combinations thereof. It goes without saying that the above list of comonomers and comonomer combinations is merely exemplary and is not intended to be limiting. Preferably, the comonomer is 1-butene, 1-hexene or 1-octene. Most preferably, the comonomer is 1-hexene.

[0074] In the copolymer, the ethylene derived units may comprise 65 wt% to 99.9 wt%, or 70 wt% to 99 wt%, or 85 wt% to 95 wt% of the LDPE, and the comonomer may comprise 0.1 wt% to 35 wt%, or 5 wt% to 15 wt% of the LDPE.

[0075] LDPE is not limited to any particular method of preparation and can be formed using any method known in the art. For example, LDPE can be formed by a high pressure autoclave or tubular reactor process.

[0076] LDPE that can be used in the present invention includes LDPE that can be used under the trade name Dow TMLDPE is commercially available from Dow, including but not limited to LDPE 722; also includes LDPE available under the trade name ExxonMobil TM LDPE's are those commercially available from ExxonMobile Chemical Company, including but not limited to LD258 and LD259.

[0077] Dow TM LDPE 722 is a broad molecular weight distribution polyethylene homopolymer with a molecular weight of 0.918 g / cm 3 The density is 8.0 g / 10 min, the melt index is 8.0 g / 10 min, the melting temperature is 107° C., and the Vicat softening temperature is 87.8° C.

[0078] ExxonMobil TM LDPE LD 258 is a low density polyethylene extrusion coating grade with a density of 0.919 g / cm 3 A density of 1.3 g / 10 min, a melt index of 8.2 g / 10 min, and a peak melting temperature of 105°C.

[0079] ExxonMobil TM LDPE LD 259 is a low density polyethylene extrusion coating grade with a density of 0.915 g / cm 3 A density of 100 g / 10 min, a melt index of 12 g / 10 min, and a peak melting temperature of 103°C.

[0080] Composition

[0081] Composition of the present invention can comprise the first polyethylene of 20 wt % to 65 wt % and the polyolefin plastomer of 5 wt % to 50 wt %, based on the gross weight of described composition.For example, the content of the first polyethylene can be in the range of from 20 wt %, 25 wt %, 30 wt %, 35 wt %, 40 wt %, 45 wt %, 50 wt %, 55 wt %, or the lower limit of 60 wt % to 65 wt %, 60 wt %, 55 wt %, 50 wt %, 45 wt %, 40 wt %, 35 wt %, 30 wt %, or the upper limit of 25 wt %, including the scope that above any two values ​​constitute, as long as the lower limit is less than the upper limit. The content of polyolefin plastomer can be in the range of from a lower limit of 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, or 45 wt% to an upper limit of 50 wt%, 45 wt%, 40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt%, 10 wt%, including ranges consisting of any two of the above values, as long as the lower limit is less than the upper limit.

[0082] In a preferred embodiment, the composition comprises 25 to 60 weight percent of the first polyethylene and 10 to 45 weight percent of the polyolefin plastomer, based on the total weight of the composition.

[0083] In a more preferred embodiment, wherein the composition comprises 35 wt% to 50 wt% of the first polyethylene and 20 wt% to 35 wt% of the polyolefin plastomer, based on the total weight of the composition.

[0084] In a preferred embodiment, the first polyethylene is selected from EXCEED TM 0019XC and EXCEED TM 0015XC, preferably EXCEED TM 0019XC.

[0085] In a preferred embodiment, the polyolefin plastomer is selected from EXACT TM 3139 and EXACT TM 3040, preferably EXACT TM 3139.

[0086] High melt index high performance polyethylene such as EXCEED TM 0019XC and EXCEED TM 0015XC offers the advantages of high line speeds and good drawdown properties. At the same time, the higher density of this high-performance polyethylene provides a lower coefficient of friction (COF), which facilitates machinability on packaging lines.

[0087] The inventors surprisingly found that by blending a polyolefin elastomer with the high-performance polyethylene, the heat sealing performance can be significantly improved while maintaining excellent processing performance, such as significantly reducing the heat sealing starting temperature, increasing the hot tack strength and widening the heat sealing window. Therefore, the composition is particularly suitable for use as a heat-sealable film or as a heat-sealable layer in a packaging structure, providing improved heat sealing performance, processing performance and cost advantages.

[0088] The composition of the present invention can also include 15% to 45% by weight of the second polyethylene, based on the gross weight of the composition. For example, the content of the second polyethylene can be in the range of from 15% by weight, 20% by weight, 25% by weight, 30% by weight, 35% by weight, or a lower limit of 40% by weight to 45% by weight, 40% by weight, 35% by weight, 30% by weight, 25% by weight, or an upper limit of 20% by weight, including the range formed by any two of the above values, as long as the lower limit is less than the upper limit.

[0089] In a preferred embodiment, the composition comprises 20 wt% to 40 wt% of the second polyethylene, based on the total weight of the composition.

[0090] In a more preferred embodiment, the composition comprises 25 wt% to 35 wt% of the second polyethylene, based on the total weight of the composition.

[0091] In a preferred embodiment, the second polyethylene is selected from Dow TM LDPE 722, ExxonMobil TM LDPELD 258 and ExxonMobil TM LDPE LD 259, preferably Dow TM LDPE 722.

[0092] The composition has a thickness of 0.902 to 0.922 g / cm 3 Preferably, the composition has a density of 0.910 to 0.920 g / cm 3 More preferably, the composition has a density of 0.910 to 0.918 g / cm 3 More preferably, 0.910 to 0.916 g / cm 3 Most preferably, 0.912 to 0.914 g / cm 3 density.

[0093] The composition has a melt index of 5 to 20 g / 10 min at 2.16 kg / 190° C. Preferably, the composition has a melt index of 7 to 20 g / 10 min at 2.16 kg / 190° C. More preferably, the composition has a melt index of 7 to 15 g / 10 min at 2.16 kg / 190° C.

[0094] Compared with the comparative composition, the heat seal initiation temperature at 1 N of the composition is reduced by at least 3°C, preferably at least 5°C, at least 6°C, at least 7°C, at least 8°C, at least 9°C, at least 10°C.

[0095] Compared with the comparative composition, the peak hot tack of the composition is increased by at least 1N, preferably by at least 1.1N, at least 1.2N, at least 1.3N, at least 1.4N, at least 1.5N.

[0096] Compared with the comparative composition, the heat seal window width at 2N of the composition increases by at least 5°C, preferably by at least 6°C, at least 7°C, at least 8°C, at least 9°C, at least 10°C.

[0097] The comparative composition refers to a composition that is the same as the composition except that the polyolefin plastomer is replaced with the first polyethylene.

[0098] The heat seal initiation temperature of the composition at 1 N is at most 100°C, preferably at most 95°C, at most 90°C, at most 85°C, at most 80°C.

[0099] The peak hot tack of the composition is at least 5N, preferably at least 5.5N, at least 6N, at least 6.5N, at least 7N.

[0100] The heat sealing window width of the composition at 2N is at least 40°C, preferably at least 45°C, at least 50°C, at least 55°C, at least 60°C, at least 65°C.

[0101] The inventors also surprisingly found that the composition of the present invention has a significantly higher heat sealing index than the comparative composition, for example, greater than 200, preferably greater than 210, greater than 220, greater than 230. The heat sealing index is defined as (hot tack peak value×heat sealing window width at 2N-heat sealing starting temperature at 1N) / density of the composition. The heat sealing index can be used as a representation of the overall heat sealing performance of the material. The higher the heat sealing index, the better the heat sealing performance of the material.

[0102] The composition can be formed in any common manner, such as melt blending, dry blending or online mixing. In melt blending, the components are first mixed and then extruded in a compounding extruder to obtain a pellet containing the combination of these materials. In dry blending, the components (preferably in granulated form) are mixed together and then directly added to the extruder for producing the film. Optionally, slip additives, anti-blocking additives, antioxidants, UV stabilizers, pigments, fillers and other processing aids can be introduced into the melt blend or dry blend.

[0103] Film and packaging structures

[0104] The composition of the present disclosure can be used to produce a heat-sealable film. In one embodiment, the present disclosure provides a film, i.e., a heat-sealable film, comprising a composition of the present disclosure. The film can be a monolayer film or a multilayer film, when it is a monolayer film, the film is formed by the composition of the present disclosure, when it is a multilayer film, the film comprises at least one layer formed by the composition of the present disclosure. In a preferred embodiment, the film is a monolayer film formed by the composition of the present disclosure.

[0105] The thickness of the film may be 20 μm to 500 μm, for example 20 μm to 200 μm, 20 μm to 100 μm, 20 μm to 50 μm, 25 μm to 100 μm, 25 μm to 50 μm.

[0106] The film can be made by any conventional method, including bubble extrusion, (uniaxial / biaxial) orientation methods (such as tenter frame, air bubble method or double bubble method), extrusion, coextrusion, casting, lamination, extrusion casting, extrusion lamination, extrusion coating, and blow molding, etc. In a preferred embodiment, wherein the film is used as a heat seal layer in a packaging structure, the film is combined with other layers by extrusion coating to form the desired packaging structure.

[0107] In one embodiment, the present disclosure provides a packaging structure, ie, a heat-sealable packaging structure, comprising at least one layer formed from a composition of the present disclosure, preferably one layer formed from a composition of the present disclosure.

[0108] In a preferred embodiment, the packaging structure is a sterile packaging structure.

[0109] In a preferred embodiment, in addition to the layer formed by the present disclosure, the packaging structure further comprises at least one layer selected from the following: polymer layer, paper layer, metal layer. When used as a layer that mainly plays a barrier role, the polymer can be polyethylene, polypropylene, polyester (such as polyethylene terephthalate), or polyether ester. Preferably, the polymer is polyethylene, preferably low-density polyethylene. When used as a layer that mainly plays an adhesive role, the polymer can be ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, or ethylene maleic anhydride copolymer. Preferably, the polymer is ethylene acrylic acid copolymer. The paper can be paper or paperboard, preferably paperboard. The metal can be aluminum foil.

[0110] In a preferred embodiment, the packaging structure has the following layers arranged in order: (a) a first polymer; (b) paperboard; (c) a second polymer; (d) aluminum foil; (e) a third polymer; and (f) a composition of the present disclosure. The first polymer and the second polymer may be the same or different. The third polymer is typically different from the first polymer and the second polymer.

[0111] In a more preferred embodiment, the packaging structure has the following layers arranged in order: (a) a first low-density polyethylene; (b) paperboard; (c) a second low-density polyethylene; (d) aluminum foil; (e) ethylene acrylic acid copolymer; and (f) a composition of the present disclosure. The first low-density polyethylene and the second low-density polyethylene may be the same or different.

[0112] The layer formed from the composition of the present disclosure as a heat-sealable layer in a packaging structure may have a thickness of 20 μm to 100 μm, such as 20 μm to 50 μm, 25 μm to 100 μm, or 25 μm to 50 μm.

[0113] The packaging structure can be manufactured by any conventional method. Generally, the individual layers are produced by a method predetermined according to the layer composition, and the individual layers are combined together to form the packaging structure.

[0114] Unless otherwise indicated, all numerical values ​​used in this specification and the related claims expressing the amount of ingredients, properties such as molecular weight, reaction conditions, etc. should be understood as being modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters listed in the following specification and the appended claims are approximate values, which may vary depending on the desired properties sought to be obtained by the embodiment of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0115] One or more illustrative embodiments including one or more inventive elements are proposed herein. For the sake of clarity, all features of physical implementation are not described or shown in this application. It should be understood that in the development of physical implementations including one or more elements of the present invention, in order to achieve the developer's goal, many specific decisions must be made to achieve, for example, system-related, business-related, government-related and other constraints are observed, which change from time to time with the implementation. Although the developer's efforts may be time-consuming, such efforts are routine tasks for those of ordinary skill in the art who benefit from the present disclosure.

[0116] Although compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. In the context of compositions, consisting essentially of allows for 25 ppm or less (of each) of impurities.

[0117] Additional embodiments

[0118] The present invention also relates to the following embodiments.

[0119] 1. A composition, based on the total weight of the composition, comprising:

[0120] 20 to 65 wt% of a first polyethylene comprising 70.0 to 100.0 wt% of units derived from ethylene and 0 to 30.0 wt% of units derived from C 3 -C 20 α-olefin units and have a value of 0.905 to 0.926 g / cm 3 and a melt index at 2.16 kg / 190° C. of 12 to 35 g / 10 min; and

[0121] 5 to 50 wt% of a polyolefin plastomer having a molecular weight of 0.890 to 0.910 g / cm 3 A density of 5 to 20 g / 10 min and a melt index at 2.16 kg / 190° C.;

[0122] The composition has a g / cm 3 density.

[0123] 2. A composition according to embodiment 1, wherein:

[0124] The heat seal index of the composition is greater than 200,

[0125] The heat seal index is defined as (hot tack peak value×heat seal window width at 2N−heat seal initiation temperature at 1N) / density of the composition.

[0126] 3. A composition according to embodiment 1, wherein:

[0127] The difference in density between the first polyethylene and the polyolefin plastomer is less than 0.05 g / cm 3 .

[0128] 4. The composition of any one of embodiments 1-3, wherein the first polyethylene:

[0129] With 0.912 to 0.922 g / cm 3 density; and / or

[0130] having a melt index at 2.16 kg / 190°C of 15 to 25 g / 10 min; and / or

[0131] having a molecular weight distribution Mw / Mn of 2.0 to 3.5; and / or

[0132] having a composition distribution breadth index (CDBI) of 65% to 85%; and / or

[0133] Contains derivatives of C 3 -C 20 The α-olefin units are units derived from hexene; and / or

[0134] It is linear low density polyethylene.

[0135] 5. The composition according to any one of embodiments 1-3, wherein the polyolefin plastomer:

[0136] With 0.895 to 0.905 g / cm 3 density; and / or

[0137] having a melt index at 2.16 kg / 190°C of 7 to 17 g / 10 min; and / or

[0138] It is an ethylene-based plastomer.

[0139] 6. The composition according to any one of embodiments 1-3, wherein the composition:

[0140] With 0.910 to 0.920 g / cm 3 density; and / or

[0141] Having a melt index at 2.16 kg / 190°C of 7 to 20 g / 10 min.

[0142] 7. The composition of any one of embodiments 1-3, wherein the composition comprises 25 to 60 wt% of the first polyethylene, and 10 to 45 wt% of the polyolefin plastomer, based on the total weight of the composition.

[0143] 8. The composition according to any one of embodiments 1-3, wherein compared to a comparative composition:

[0144] The heat seal initiation temperature of the composition at 1 N is reduced by at least 3°C; and / or

[0145] The peak hot tack of the composition is increased by at least 1 N; and / or

[0146] The heat seal window width of the composition at 2N is increased by at least 5°C;

[0147] The comparative composition refers to a composition that is the same as the composition except that the polyolefin plastomer is replaced with the first polyethylene.

[0148] 9. The composition of any one of embodiments 1-3, wherein the composition further comprises 15% to 45% by weight of a second polyethylene, wherein the second polyethylene:

[0149] With 0.910 to 0.930 g / cm 3 density; and / or

[0150] having a melt index at 2.16 kg / 190°C of 7 to 15 g / 10 min; and / or

[0151] It is low density polyethylene.

[0152] 10. The composition according to any one of embodiments 1 to 4, comprising, based on the total weight of the composition:

[0153] 35 wt % to 50 wt % of a first polyethylene comprising 88 wt % to 92 wt % of units derived from ethylene and 8 wt % to 12 wt % of units derived from hexene and having a molecular weight of 0.918 g / cm 3 A density of 1.5 g / 10 min, a melt index at 2.16 kg / 190° C. of 19 g / 10 min, a molecular weight distribution Mw / Mn of 2.9, and a composition distribution breadth index CDBI of 77%; and

[0154] 20 to 35 weight percent of an ethylene-based plastomer having a molecular weight of 0.900 g / cm 3 A density of 2.5 g / 10 min and a melt index of 1.5 g / 10 min at 2.16 kg / 190 °C;

[0155] The composition has a g / cm 3 density.

[0156] 11. A film comprising the composition according to any one of embodiments 1-10.

[0157] 12. A method for preparing a film according to embodiment 11, comprising extrusion coating the composition according to any one of embodiments 1 to 10 to form the film.

[0158] 13. A packaging structure comprising at least one layer formed from the composition according to any one of embodiments 1 to 10.

[0159] 14. The packaging structure according to embodiment 13, wherein the packaging structure further comprises at least one layer selected from the group consisting of: a polymer layer, a paper layer, a metal layer.

[0160] 15. The packaging structure according to embodiment 13 or 14, wherein the packaging structure has the following layers arranged in order:

[0161] (a) a first low density polyethylene;

[0162] (b) Paperboard;

[0163] (c) a second low density polyethylene;

[0164] (d) Aluminium foil;

[0165] (e) ethylene acrylic acid copolymer; and

[0166] (f) a composition according to any one of embodiments 1-10;

[0167] The first low-density polyethylene and the second low-density polyethylene may be the same or different.

[0168] 16. Use of the composition according to any one of embodiments 1 to 10 as a heat sealable film or as a heat sealable layer in a packaging structure.

[0169] 17. The composition of any one of embodiments 1-10, wherein:

[0170] The density of the first polyethylene is higher than the density of the polyolefin plastomer; and / or

[0171] The melt index of the first polyethylene is higher than the melt index of the polyolefin plastomer; and / or

[0172] The difference in density between the first polyethylene and the polyolefin plastomer is less than 0.05 g / cm 3 , preferably less than 0.04 g / cm 3 , preferably 0.01-0.02 g / cm 3 ; and / or

[0173] The difference between the melt index of the first polyethylene and the polyolefin plastomer is less than 20 g / 10 min, preferably less than 15 g / 10 min, preferably 2-12 g / 10 min.

[0174] 18. The composition according to any one of embodiments 1-10, comprising, based on the total weight of the composition:

[0175] 35 wt% of a first polyethylene comprising 88 wt% to 92 wt% of units derived from ethylene and 8 wt% to 12 wt% of units derived from hexene and having a molecular weight of 0.918 g / cm 3 A density of 1.5 g / 10 min, a melt index at 2.16 kg / 190° C. of 19 g / 10 min, a molecular weight distribution Mw / Mn of 2.9, and a composition distribution breadth index CDBI of 77%; and

[0176] 35 wt% of an ethylene-based plastomer having a 0.900 g / cm 3 A density of 2.5 g / 10 min and a melt index of 1.5 g / 10 min at 2.16 kg / 190 °C;

[0177] The composition has a thickness of 0.912 g / cm 3 density.

[0178] 19. The composition according to any one of embodiments 1-10, comprising, based on the total weight of the composition:

[0179] 50 wt% of a first polyethylene comprising 88 wt% to 92 wt% of units derived from ethylene and 8 wt% to 12 wt% of units derived from hexene and having a molecular weight of 0.918 g / cm 3 A density of 1.5 g / 10 min, a melt index at 2.16 kg / 190° C. of 19 g / 10 min, a molecular weight distribution Mw / Mn of 2.9, and a composition distribution breadth index CDBI of 77%; and

[0180] 20 wt% of an ethylene-based plastomer having a density of 0.900 g / cm 3 A density of 2.5 g / 10 min and a melt index of 1.5 g / 10 min at 2.16 kg / 190 °C;

[0181] The composition has a g / cm 3 density. DETAILED DESCRIPTION

[0182] In order to facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. The following examples should in no way be construed as limiting or defining the scope of the present invention.

[0183] Example

[0184] Test Method

[0185] The hot adhesive strength (N / 30mm) test was conducted using a hot adhesive strength instrument supplied by J&B Instruments. The test conditions were: 30mm wide strip, 0.5N / mm 2 Heat seal pressure, 0.5 second heat seal time, 50mmx5mm heat seal area, and 200mm / s peel speed. Hot tack strength is measured after 0.4 second cooling time. Four samples are measured at each temperature point, and the average hot tack strength at each temperature point is recorded to generate a hot tack strength curve.

[0186] The peak hot tack strength is the hot tack strength value at the highest point in the hot tack strength curve.

[0187] The heat sealing window width is determined as follows: a straight line is drawn parallel to the horizontal axis with a hot tack force of 2N (custom force value), and the temperature difference between the two points intersecting the hot tack strength curve is defined as the heat sealing window temperature.

[0188] The heat seal strength (N / 15mm) test is carried out according to the following procedure. Prepare the heat seal parts under the same sample preparation conditions as the above-mentioned hot adhesive strength test, but after preparing the heat seal parts, cut the samples into 15mm strips. After conditioning the samples at 23℃±2℃ and 50% humidity±10% humidity for at least 40 hours, use a Zwick tensile tester to measure the heat seal strength of 15mm wide samples under the following conditions: 200N force sensor, and 50mm clamping distance, place the sample between the clamps and stretch at a speed of 500mm / min. Measure four samples and record the maximum force and take the average value. The heat seal strength is the maximum force when the sample fails. Failure refers to instantaneous tearing, tearing after stretching, edge tearing, etc.

[0189] The heat seal starting temperature is the temperature when the heat seal strength reaches 1N (custom force value).

[0190] Table 1 shows the polyethylenes used in the examples.

[0191] Table 1 Description of polyethylene used in the examples

[0192]

[0193]

[0194] Seven film samples were prepared with the formula shown in Table 2, of which Eli 5815+LDPE 722 and El tex1320+LDPE 722 were used as reference examples. Both are heat-sealing layer formulas in packaging structures currently recognized on the market. The film samples were prepared using the SML 7-layer co-extrusion casting processing line as follows: the above raw materials were fed into the extruder for melt blending, extruded through the die head, then stretched through the casting roller, and cooled and shaped to obtain the film samples. The process conditions were: extruder temperature 265°C, die head temperature 280°C, line speed 100m / min, film thickness 25mm, and winding sample width 500mm.

[0195] Table 2: Formula of samples in the examples

[0196] Example No. formula Comparative Example 1 70%0019+LD722 Reference Example 1 70%5815+LD722 Reference Example 2 70%1320+LD722 Example 1 25%0019+45%3139+LD722 Example 2 35%0019+35%3139+LD722 Example 3 50%0019+20%3139+LD722 Example 4 60%0019+10%3139+LD722

[0197] The density and heat sealing properties of the above 7 film samples were tested. The results are shown in Table 3 and Figure 1-4 shown.

[0198] Table 3 Density and heat sealing properties of samples in the examples

[0199]

[0200]

[0201] * As there are no data points above 140°C for the heat sealing windows of Examples 3 and 4, only >46 and >43 are indicated.

[0202] **Heat seal index = (hot tack peak value × heat seal window width at 2N - heat seal starting temperature at 1N) / total density

[0203] From Table 3 and Figure 1 It can be seen from the results that compared with the sample of Exceed 0019+LDPE 722 (Comparative Example 1), the heat-sealing initiation temperature of Elite 5815+LDPE 722 (Reference Example 1) and Eltex1320+LDPE 722 (Reference Example 2) is about 4°C lower. Compared with Comparative Example 1, the 35% Exceed 0019+35% Exact 3139 blending scheme (Example 2) reduces the heat-sealing initiation temperature of the Exceed 0019 system by about 8°C, even lower than Reference Examples 1 and 2. This shows that blending with polyolefin plastomers can significantly reduce the heat-sealing initiation temperature.

[0204] From Table 3 and Figure 2 It can be seen from the results that compared with the sample of Exceed 0019+LDPE 722 (Comparative Example 1), the peak value of hot tack of Elite 5815+LDPE 722 (Reference Example 1) is lower, and the peak value of hot tack of Eltex 1320+LDPE 722 (Reference Example 2) is slightly higher. In addition, the heat sealing window temperatures of Reference Examples 1 and 2 are wider than that of Comparative Example 1. Surprisingly, the 35% Exceed 0019+35% Exact 3139 blending scheme (Example 2) significantly improves the peak value of hot tack of the Exceed0019 system, reaching 6.5N at 110°C, which is even much higher than that of the Eltex 1320 system. At the same time, the blending scheme also greatly broadens the heat sealing window temperature of the Exceed 0019 system, that is, it improves the heat sealing strength and heat sealing window width at the same time.

[0205] From Table 3 and Figure 3 The results show that for the Exceed 0019+Exact 3139 blending solution, as the content of Exact 3139 increases, the heat seal initiation temperature decreases gradually. When the content of Exact 3139 is 10%, the heat seal initiation temperature has dropped by about 3°C. When the content of Exact 3139 is 20%, the heat seal initiation temperature is close to that of the Eli te 5815 system and the El tex 1320 system.

[0206] From Table 3 and Figure 4The results show that for the Exceed 0019+Exact 3139 blending scheme, as the Exact3139 content increases, the heat seal window width gradually widens. In addition, all blending schemes show a significant increase in the peak value of hot tack. Considering the heat seal performance and cost, 35% Exceed 0019+35% Exact 3139 and 50% Exceed0019+20% Exact 3139 are the best implementation schemes.

[0207] In addition, it can be seen from the results in Table 3 that the heat sealing indexes of Examples 1-4 are all greater than 200, which are much higher than those of the comparative example and reference examples 1 and 2, which is consistent with the results of the excellent comprehensive heat sealing performance of Examples 1-4 in terms of heat sealing strength, heat sealing starting temperature, heat sealing window width, etc.

[0208] In summary, the inventors of the present application surprisingly found that by blending high MI polyolefin plastomers with high MI high-performance polyethylene, significant improvements in heat sealing performance can be achieved while maintaining good processability. This blending scheme provides an excellent solution for demanding packaging applications (including high-speed form-fill-heat-seal packaging). This discovery brings great commercial and technical value to the market, and suppliers with both high MI polyolefin plastomers and polyethylene in their product portfolios can provide an integrated solution to meet demanding industry needs.

[0209] Therefore, the present invention is well adapted to obtain the results and advantages mentioned and inherent therein. The specific embodiments and configurations disclosed above are illustrative only, as it is apparent to those skilled in the art having the benefit of the teachings herein that different but equivalent means may be employed to modify and implement the present invention. In addition, except as described in the following claims, it is not intended to limit the details of the construction or design shown herein. It is therefore apparent that the specific illustrative embodiments disclosed above may be changed, combined or modified, and all such changes are considered to be within the scope and spirit of the present invention. The invention disclosed illustratively herein may be suitably implemented in the absence of any element not specifically disclosed herein and / or any optional element disclosed herein.

[0210] Although compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. All numerical values ​​and ranges disclosed above may be varied to some extent.

[0211] Whenever a numerical range with a lower limit and an upper limit is disclosed, any numerical value and any included range falling within the range are specifically disclosed. In particular, the range of each value disclosed herein (having the following form "from about a to about b", or equivalently "from about a to b", or equivalently "from about ab") should be understood to enumerate each numerical value and range contained within the wider range of values. Similarly, when multiple ranges (e.g., 1-100 or 10-90, e.g., 30 to 75) are disclosed, the range from any disclosed lower end to any disclosed upper end (e.g., 10-75) is specifically covered.

[0212] Furthermore, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Furthermore, the indefinite articles "a" or "an" as used in the claims are defined herein to mean one or more than one of the element it introduces.

Claims

1. A composition, based on the total weight of the composition, comprising: 25 wt % to 60 wt % of a first polyethylene, the first polyethylene being an ethylene-hexene copolymer and comprising 75 wt % to 95 wt % of units derived from ethylene and 5 wt % to 25 wt % of units derived from hexene and having a molecular weight of 0.905 to 0.926 g / cm 3 A density of 100 g / min, a melt index at 2.16 kg / 190° C. of 12 to 35 g / 10 min, a molecular weight distribution Mw / Mn of 2.0 to 3.5, and a composition distribution breadth index CDBI of 65% to 85%, and the first polyethylene is a linear low density polyethylene; 10 to 45 wt% of a polyolefin plastomer, the polyolefin plastomer being an ethylene-hexene copolymer and having a molecular weight of 0.895 to 0.910 g / cm 3 and a melt index at 2.16 kg / 190° C. of 7 to 20 g / 10 min; and 15 wt % to 45 wt % of a second polyethylene, the second polyethylene being a polyethylene homopolymer and having a molecular weight of 0.910 to 0.930 g / cm 3 A density of 2.16 kg / 190° C. and a melt index of 7 to 15 g / 10 min at 2.16 kg / 190° C.; The difference between the density of the first polyethylene and the density of the polyolefin plastomer is less than 0.05 g / cm 3 ; The composition has a thickness of 0.902 to 0.922 g / cm 3 density.

2. The composition according to claim 1, wherein: The heat seal index of the composition is greater than 200, The heat seal index is defined as (hot tack peak value×heat seal window width at 2N−heat seal initiation temperature at 1N) / density of the composition.

3. The composition according to claim 1, wherein: The difference in density between the first polyethylene and the polyolefin plastomer is less than 0.04 g / cm 3 ; and / or The difference between the melt index of the first polyethylene and the polyolefin plastomer is less than 15 g / 10 min.

4. The composition according to any one of claims 1 to 3, wherein the first polyethylene: With 0.912 to 0.922 g / cm 3 density; and / or Having a melt index at 2.16 kg / 190°C of 15 to 25 g / 10 min.

5. The composition according to any one of claims 1 to 3, wherein the polyolefin plastomer: With 0.895 to 0.905 g / cm 3 density; and / or having a melt index at 2.16 kg / 190° C. of 7 to 17 g / 10 min; and / or It is an ethylene-based plastomer.

6. The composition according to any one of claims 1 to 3, wherein the composition: With 0.910 to 0.920 g / cm 3 density; and / or Having a melt index at 2.16 kg / 190°C of 7 to 20 g / 10 min.

7. The composition of any one of claims 1-3, wherein the composition comprises 35 wt% to 50 wt% of the first polyethylene, and 20 wt% to 35 wt% of the polyolefin plastomer, based on the total weight of the composition.

8. The composition according to any one of claims 1 to 3, wherein compared to a comparative composition: The heat seal initiation temperature of the composition at 1 N is reduced by at least 3°C; and / or The peak hot tack of the composition is increased by at least 1 N; and / or The heat seal window width of the composition at 2N is increased by at least 5°C; The comparative composition refers to a composition that is the same as the composition except that the polyolefin plastomer is replaced with the first polyethylene.

9. The composition according to any one of claims 1 to 3, wherein the second polyethylene It is low density polyethylene.

10. The composition according to any one of claims 1 to 3, comprising, based on the total weight of the composition: 35 wt % to 50 wt % of a first polyethylene comprising 88 wt % to 92 wt % of units derived from ethylene and 8 wt % to 12 wt % of units derived from hexene and having a molecular weight of 0.918 g / cm 3 A density of 1.5 g / 10 min, a melt index at 2.16 kg / 190° C. of 19 g / 10 min, a molecular weight distribution Mw / Mn of 2.9, and a composition distribution breadth index CDBI of 77%; and 20 wt % to 35 wt % of an ethylene-based plastomer having a molecular weight of 0.900 g / cm 3 A density of 2.5 g / 10 min and a melt index of 1.5 g / 10 min at 2.16 kg / 190 °C; The composition has a g / cm 3 density.

11. A film comprising the composition according to any one of claims 1 to 10.

12. A method for preparing a film according to claim 11, comprising extrusion coating the composition according to any one of claims 1 to 10 to form the film.

13. A packaging structure comprising at least one layer formed from the composition according to any one of claims 1 to 10.

14. The packaging structure of claim 13, wherein the packaging structure further comprises at least one layer selected from the group consisting of: a polymer layer, a paper layer, a metal layer.

15. The packaging structure according to claim 13 or 14, wherein the packaging structure has the following layers arranged in order: (a) a first low density polyethylene; (b) Paperboard; (c) a second low density polyethylene; (d) Aluminium foil; (e) ethylene acrylic acid copolymer; and (f) a composition according to any one of claims 1 to 10; The first low-density polyethylene and the second low-density polyethylene are the same or different.

16. Use of the composition according to any one of claims 1 to 10 as a heat sealable film or as a heat sealable layer in a packaging structure.

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