Multi-layer film

Abstract

A multilayer film comprising a skin layer (A) and a core layer (B), wherein: - The skin layer (A) contains a polyolefin composition (I) comprising (a) a propylene copolymer containing 70% to 95% by weight of a propylene copolymer containing 10.0% by weight or less of units derived from an α-olefin and having a xylene-soluble fraction at 25°C in the range of 10% to 20% by weight, and (b) 5% to 30% by weight of a butene-1 polymer, where the amounts of (a) and (b) are based on the total weight of (a) + (b); - The core layer (B) contains a copolymer of propylene and 25% by weight or less of an α-olefin.

Description

Technical Field

[0001] The present invention relates to a heat-sealable multilayer film, preferably an inflation multilayer film or a cast multilayer film, having good sealing properties and optical properties.

Background Art

[0002] Heat-sealable films of polypropylene are used in many common packaging applications such as tobacco, candy, snacks, food wraps, etc. Polypropylene can also be used for shrink packaging, sanitary products, and sterilization wraps for medical applications.

[0003] Generally, the heat-sealing properties of polypropylene are not sufficient for high-speed packaging systems. To improve the heat-sealing properties of polypropylene, it is known in the art to add polybutene-1 to polypropylene. Therefore, multilayer films containing a mixture of polypropylene and polybutene-1 in the outer seal layer are known in the art.

[0004] International Patent Application No. 2004 / 048424 discloses a multilayer film with a low seal start temperature, and this seal layer is composed of a combination of polybutene-1 containing 2.1 mol% ethylene and a propylene-butene-ethylene terpolymer.

[0005] International Patent Application No. 2011 / 064131 discloses using polybutene-1 having a low flexural modulus in combination with a heterophasic propylene polymer to provide a seal layer with a low seal start temperature.

[0006] International Patent Application No. 2012 / 031953 discloses using butene-1 homo- or copolymer to lower the seal start temperature of a seal layer containing a propylene copolymer and hexene-1. In this film, the number of fish eyes is also reduced.

[0007] International Patent Application No. 2018 / 211107 discloses using polybutene-1 with an Mw in the range of 100,000 to 300,000 and an MWD of less than 6.0 to lower the sealing start temperature and hot tack of a propylene random copolymer with a comonomer content of 1.0 to 10% by weight. The optical properties of a multilayer film containing a mixture of polypropylene and polybutene-1 are not significantly affected by the presence of polybutene-1.

[0008] In this framework, there remains a need to provide a propylene polymer composition that combines improved heat-sealing properties and optical properties with good mechanical properties.

Summary of the Invention

[0009] The present invention is a multilayer film comprising a skin layer (A) and a core layer (B), - The skin layer (A) contains a polyolefin composition (I), and the polyolefin composition (I) is (a) 70% to 95% by weight of a copolymer of propylene and at least one α-olefin of the formula CHCH 2 =CHR (wherein R is hydrogen or a linear or branched C2-C8 alkyl), containing 10.0% by weight or less of units derived from the α-olefin based on the weight of (a), and the xylene-soluble fraction of the propylene copolymer at 25 °C is in the range of 10% to 20% by weight, the copolymer, and (b) 5% to 30% by weight of a butene-1 polymer selected from a butene-1 homopolymer, a butene-1 copolymer containing 5.0% by weight or less of units derived from ethylene and / or propylene based on the weight of (b), and mixtures thereof, The amounts of (a) and (b) are based on the total weight of (a) + (b), - The core layer (B) contains propylene and, based on the weight of the copolymer, 25% by weight or less of the formula CH 2A multilayer film is provided that contains a copolymer (c) with at least one α-olefin of =CHR (wherein R is hydrogen or linear or branched C2-C8 alkyl).

[0010] The multilayer film of the present invention has good sealing properties, namely, a low seal initiation temperature (SIT) and a high hot tack. In particular, when compared with a multilayer film in which the skin layer does not contain component (b), the SIT is lower and the hot tack is higher.

[0011] The good sealing properties are combined with an improvement in optical properties, particularly an increase in gloss and a decrease in haze, when compared with a multilayer film in which the skin layer does not contain component (b).

[0012] Furthermore, the mechanical properties of the multilayer film of the present invention are suitable for the production of cast films and inflation films.

[0013] Although multiple embodiments are disclosed, from the following detailed description, other embodiments will become apparent to those skilled in the art. As is apparent, the specific embodiments disclosed herein can be modified in various obvious ways without departing from the spirit and scope of the claims presented herein. Accordingly, the following detailed description is to be regarded as illustrative in nature and not restrictive.

Embodiments for Carrying Out the Invention

[0014] In the context of the present disclosure, - Unless otherwise specified, percentages are expressed by weight.

[0015] - Unless otherwise specified, the total weight of the composition is 100%.

[0016] - The term "comprising" when referring to a polymer, plastic material, polymer composition, mixture or blend should be construed to mean "consisting essentially of or composed of".

[0017] - The term "consisting essentially of" means that in addition to the essential components, other components may also be present in the material as long as the essential properties of the material are not substantially affected by their presence. Examples of components that, when present in normal amounts, do not substantially affect the properties of a polymer or polyolefin composition, mixture, or blend include catalyst residues, antistatic agents, processing aids, melt stabilizers, light stabilizers, antioxidants, and antacids.

[0018] - The term "copolymer" refers to a polymer obtained from the polymerization of at least two comonomers, i.e., the term "copolymer" includes dimer polymers and trimer polymers.

[0019] - The term "skin layer" refers to the outermost layer of a multilayer film.

[0020] - The term "core layer" refers to the innermost layer of a multilayer film.

[0021] The polyolefin composition (I) of the skin layer (A) preferably contains 75% to 90% by weight of a propylene copolymer (a) and 10% to 25% by weight of a butene-1 polymer (b), and the amounts of (a) and (b) are based on the total weight of (a)+(b).

[0022] Hereinafter, the individual components of the polyolefin composition (I) contained in the skin layer (A) and the propylene copolymer contained in the core layer (B) will be described in more detail. The individual components can be included in each layer in any combination.

[0023] The polyolefin composition (I) preferably contains a copolymer of propylene (a) containing 0.5% to 10.0% by weight of units derived from an α-olefin, preferably ethylene, based on the weight of component (a), and a butene-1 copolymer (b) containing 0.5 to 5.0% by weight of ethylene and / or propylene, preferably units derived from ethylene, based on the weight of component (b).

[0024] In a preferred embodiment, the propylene copolymer (a) contained in the polypropylene composition (I) is a propylene-ethylene copolymer, that is, a copolymer composed of repeating units derived from propylene and ethylene, and has at least one, preferably all, of the following characteristics.

[0025] - Based on the weight of the propylene copolymer (a), it contains 2.0 wt% to 10.0 wt%, preferably 2.2 wt% to 9.8 wt%, more preferably 3.0 wt% to 8.0 wt%, still more preferably 4.5 wt% to 7.2 wt% of units derived from ethylene, and / or

[0026] The melt flow rate MFR(a) measured according to ISO 1133-1:2011 (230 °C / 2.16 kg) is 0.1 to 10.0 g / 10 min, preferably 0.3 to 7.0 g / 10 min, more preferably 0.5 to 3.0 g / 10 min, and / or - Based on the weight of the propylene copolymer (a), it contains the xylene-soluble fraction XS(a) at 25 °C measured according to the method reported in the experimental section in the range of 12 wt% to 20 wt%, preferably 14 wt% to 18 wt%.

[0027] In addition to one or more of the above characteristics, the propylene-ethylene copolymer (a) preferably has a melting point measured by DSC according to the ISO 11357-3:2018 method in the range of 130 °C to 142 °C, more preferably 131 °C to 140 °C, still more preferably 132 °C to 137 °C.

[0028] In one embodiment, the propylene copolymer (a) contains at least one additive selected from the group consisting of an antistatic agent, an antioxidant, a light stabilizer, a lubricant, an antacid, a melt stabilizer, and combinations thereof in an amount of 5.0 wt% or less, more preferably 0.01 wt% to 5.0 wt%, and the amount of the additive is based on the total weight (100% of the total weight) of the copolymer (a) containing the additive.

[0029] Propylene copolymer (a) is obtained by polymerizing the relevant monomers in the presence of a highly stereospecific Ziegler-Natta catalyst system containing the following components.

[0030] (1) A solid catalyst component containing a magnesium halide carrier in which a Ti compound having at least a Ti-halogen bond is present and a stereoregulating internal donor; (2) Optionally, preferably, an Al-containing cocatalyst, and (3) Optionally, preferably, a further electron-donating compound (external donor).

[0031] The solid catalyst component (1) preferably contains TiCl in an amount that ensures that 0.5 to 10% by weight of Ti is present based on the total weight of the solid catalyst component (1). 4 Including.

[0032] The solid catalyst component (1) contains at least one stereoregulating internal electron-donating compound selected from monodentate or bidentate organic Lewis bases, which is preferably selected from esters, ketones, amines, amides, carbamates, carbonates, ethers, nitriles, alkoxysilanes and combinations thereof.

[0033] Preferred donors are phthalic acid esters as described in European Patent Application No. 45977A2 and European Patent Application No. 395083A2, in particular diisobutyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, diphenyl phthalate, benzyl butyl phthalate, and combinations thereof.

[0034] The fatty acid ester can also be selected from malonic acid esters as described in International Patent Application No. 98 / 056830, International Patent Application No. 98 / 056833, International Patent Application No. 98 / 056834, glutaric acid esters as disclosed in International Patent Application No. 00 / 55215, and succinic acid esters as disclosed in International Patent Application No. 00 / 63261.

[0035] Certain types of diesters are obtained from the esterification of aliphatic or aromatic diols as described in International Patent Application No. 2010 / 078494 and US Patent Application No. P7,388,061.

[0036] In some embodiments, the internal donor is selected from 1,3 - diethers such as those described in European Patent Application No. 361493, European Patent Application No. 728769, and International Patent Application No. 02 / 100904.

[0037] As the internal donor, a specific mixture of aliphatic or aromatic mono - or dicarboxylic acid esters and 1,3 - diethers disclosed in International Patent Application No. 07 / 57160 and International Patent Application No. 2011 / 061134 can be used.

[0038] A preferred magnesium halide carrier is magnesium dihalide.

[0039] The amount of the internal donor remaining fixed on the solid catalyst component (1) is 5 - 20 mol% with respect to magnesium dihalide.

[0040] A preferred method for producing the solid catalyst component (1) is described in European Patent Application No. 395083A2.

[0041] The preparation of the catalyst component by a general method is described, for example, in US Patent Application No. 4,399,054, US Patent Application No. 4,469,648, International Patent Application No. 98 / 44009A1, and European Patent Application No. 395083A2.

[0042] The catalyst system preferably includes an Al - containing cocatalyst (2) selected from Al - trialkyls, preferably selected from the group consisting of Al - triethyl, Al - triisobutyl, and Al - tri - n - butyl. The Al / Ti weight ratio in the catalyst system is 1 - 1000, preferably 20 - 800.

[0043] In a preferred embodiment, the catalyst system comprises a further electron donor compound (3) (external electron donor) selected from silicon compounds, ethers, esters, amines, heterocyclic compounds, in particular 2,2,6,6-tetramethylpiperidine, and ketones.

[0044] Preferred silicon compounds are selected from methylcyclohexyldimethoxysilane (C-donor), dicyclopentyldimethoxysilane (D-donor) and mixtures thereof.

[0045] The polymerization process for obtaining the propylene copolymer (a) can be carried out continuously or batchwise, either in the liquid phase or in the gas phase.

[0046] The liquid phase polymerization can be carried out either in slurry, solution or bulk (liquid monomer). The latter technique is most preferred and can be carried out in various types of reactors such as continuous stirred tank reactors, loop reactors, plug flow reactors.

[0047] The gas phase polymerization can be carried out in a fluidized bed or a fixed bed reactor with a stirred bed, but preferably in a multi-zone circulation reactor (MZCR) as shown in European Patent Application No. 1012195 B1.

[0048] The polymerization process described in detail in European Patent No. 1012195B1 has been shown to be particularly useful for producing olefin polymers with a wide range of molecular weights, especially multimodal olefin polymers in a single reactor, where the term multimodal refers to the modes of the molecular weight distribution. As used in the art and herein, multimodal shall include bimodal. Such polymers can be obtained by polymerizing olefins in a cascade of two or more polymerization reactors or in different zones of an MZCR reactor under different reaction conditions. Thus, "modality" refers to the number of different polymerization conditions used to prepare the polymer, regardless of whether this modality of the molecular weight distribution can be recognized as a separated maximum of the gel permeation chromatography (GPC) curve. In addition to the molecular weight distribution, olefin polymers can also be multimodal, i.e., bimodal, in the comonomer distribution. In one embodiment, the average comonomer content of polymer chains with higher molecular weight is higher than that of polymer chains with lower molecular weight. However, it is also possible to employ the same or very similar reaction conditions in all polymerization reactors of the reaction cascade to prepare narrow molecular weight or single-mode olefin polymers.

[0049] The polymerization temperature is preferably in the range of 40°C to 90°C, and the polymerization pressure is preferably 3.3 to 4.3 MPa in the case of a liquid phase process and 0.5 to 3.0 MPa in the case of a gas phase process.

[0050] Propylene copolymer (a) is commercially available, for example, from LyondellBasell under the trade names Adstif, Clyrell, Moplen, and Purell.

[0051] Preferably, the butene-1 polymer (b) contained in the polyolefin composition (I) is a copolymer of butene-1 and ethylene having at least one, preferably all, of the following characteristics.

[0052] - Based on the weight of (b), the content of ethylene-derived units is in the range of 1.0 wt% to 4.5 wt%, preferably 1.5 wt% to 4.5 wt%, more preferably 2.0 wt% to 4.0 wt%, still more preferably 2.5 wt% to 3.5 wt%, and / or - The melting point Tm(I) of Form I measured by DSC according to Method ISO 11357-3:2018 is less than 100 °C, preferably in the range of 80 °C to less than 100 °C, more preferably 90 °C to 97 °C, and / or - The melt flow rate measured according to ISO 1133-1:2011 (190 °C / 2.16 kg) is in the range of 1.0 to 6.0 g / 10 min, preferably 2.0 to 5.0 g / 10 min, still more preferably 3.0 to 4.5 g / 10 min, and / or - The flexural modulus measured according to ISO 178:2010 is 80 MPa or more, preferably in the range of 80 to 250 MPa, more preferably 100 to 210 MPa.

[0053] In a preferred embodiment, in addition to one or more of the above characteristics, the butene-1 copolymer (b) has a molecular weight distribution Mw / Mn in the range of 4.0 to 9.0, preferably 4.0 to 8.0, more preferably 4.0 to 7.0, still more preferably greater than 4.5 to less than 6.0.

[0054] In one embodiment, the butene-1 polymer (b) contains at least one additive selected from the group consisting of an antistatic agent, an antioxidant, a light stabilizer, a lubricant, an antacid, a melt stabilizer, and combinations thereof, in an amount of 5.0 wt% or less, more preferably 0.01 wt% to 5.0 wt%, and the amount of the additive is based on the total weight of the butene-1 polymer (b) containing the additive, and the total weight is 100%.

[0055] In some embodiments, the butene-1 polymer (b) is obtained using a metallocene-based catalyst system.

[0056] The butene-1 polymer (b) is preferably obtained by polymerizing the relevant monomers in the presence of a Ziegler-Natta catalyst system as described above.

[0057] The polymerization process can be carried out according to known techniques, for example, slurry polymerization using a liquid inert hydrocarbon as a diluent, or solution polymerization using, for example, liquid butene-1 as a reaction medium. Further, it can be operated in one or more fluidized bed reactors or mechanically stirred bed reactors to carry out the polymerization process in the gas phase. It is highly preferred to carry out the polymerization in liquid butene-1 as the reaction medium.

[0058] The polymerization is generally carried out at a temperature of 20°C to 120°C, preferably at a temperature of 40°C to 90°C. The polymerization can be carried out in one or more reactors that can operate under the same or different reaction conditions, such as the concentration of the molecular weight regulator, the concentration of the comonomer, temperature, pressure, etc.

[0059] A suitable catalyst system and polymerization process for obtaining the butene-1 polymer (b) are disclosed in International Patent Application No. 2004 / 048424A1.

[0060] The butene-1 polymer (b) is commercially available, for example, sold under the trade name Toppyl by LyondellBasell.

[0061] In one embodiment, the polyolefin composition (I) is composed of the above components (a) and (b), and optionally contains additives.

[0062] In one embodiment, the skin layer (A) is composed of the above polyolefin composition (I).

[0063] The core layer (B) is composed of propylene and 25% by weight or less, preferably 10% to 25% by weight of the formula CH 2It contains a copolymer (c) with at least one α-olefin of =CHR (wherein R is hydrogen or linear or branched C2-C8 alkyl). In a preferred embodiment, the α-olefin is ethylene.

[0064] The copolymer (c) of propylene contained in the core layer (B) is preferably selected from the group consisting of a propylene random copolymer, a heterophasic propylene polymer, a recycled propylene polymer, and combinations thereof, and the heterophasic propylene polymer is particularly preferred.

[0065] In a preferred embodiment, the copolymer (c) of propylene contained in the core layer (B) is - a polymer fraction (i) of 20% to 40% by weight, which is a propylene homopolymer, 6.0% by weight or less, preferably 0.1% to 6.0% by weight based on the weight of the fraction (i), of the formula CH 2 =CHR (wherein R is hydrogen or linear or branched C2-C8 alkyl) of at least one α-olefin, and a propylene polymer selected from the group consisting of combinations thereof, the polymer fraction (i), and - a polymer fraction (ii) of 60% to 80% by weight, based on the weight of the fraction (ii), 35.0% by weight or less, preferably 20% to 35.0% of at least one formula CH 2 =CHR of α-olefin (wherein R is hydrogen or linear or branched C2-C8 alkyl), and based on the weight of the fraction (ii), a propylene copolymer having a solubility in xylene at 25 °C in the range of 45.0% to 75.0% by weight, the polymer fraction (ii), and is a heterophasic propylene polymer, The amounts of the (i) and the (ii) are based on the total weight of the (i) + the (ii).

[0066] In a more preferred embodiment, the heterophasic propylene polymer is - Based on the weight of fraction (i), a propylene-ethylene copolymer containing 6.0 wt% or less, preferably 0.1 wt% to 6.0 wt%, more preferably 1.5 wt% to 4.5 wt% of ethylene-derived units, and 20 wt% to 40 wt%, preferably 25 wt% to 35 wt% of polymer fraction (i), - Based on the weight of fraction (ii), a propylene-ethylene copolymer containing 35.0 wt% or less, preferably 20.0 wt% to 35.0 wt%, more preferably 23.0 wt% to 30.0 wt% of ethylene-derived units, and fraction (ii) having a solubility in xylene at 25 °C in the range of 55.0 wt% to 75.0 wt%, preferably 60.0 wt% to 70.0 wt% based on the weight of fraction (ii), and 60 wt% to 80 wt%, preferably 65 wt% to 75 wt% of fraction (ii), The amounts of the above (i) and (ii) are based on the total weight of (i) + (ii).

[0067] The heterophasic propylene polymer preferably has at least one, more preferably all of the following properties.

[0068] - The melt flow rate measured according to ISO 1133-1:2011 method (230 °C / 2.16 kg) is in the range of 0.1 to 5 g / 10 min, preferably 0.2 to 3.0 g / 10 min, more preferably 0.3 to 1.2 g / 10 min, even more preferably 0.3 to 0.8 g / 10 min, and / or - The melting point measured by DSC according to ISO 11357-3 method is in the range of 135 °C to 148 °C, and / or - The flexural modulus measured according to method ISO 178:2010 is 250 MPa or less, preferably 150 MPa or less, and the lower limit is preferably 50 MPa with respect to each upper limit.

[0069] In one embodiment, the propylene copolymer (c) contains at least one additive selected from the group consisting of a nucleating agent, an antistatic agent, an antioxidant, a light stabilizer, a lubricant, an antacid, a melt stabilizer, and combinations thereof, in a conventional amount, preferably 5.0% by weight or less, more preferably 0.01% to 5.0% by weight, based on the total weight of the copolymer (c) (100% total weight).

[0070] The propylene copolymer (c) is preferably obtained by polymerizing the relevant comonomer using the polymerization process as described above in the presence of a highly stereospecific Ziegler-Natta catalyst system.

[0071] The heterophasic propylene polymer is obtained by melt blending fractions (i) and (ii) or, preferably, by polymerizing the relevant monomers in the gas phase in at least two polymerization stages, where the second and each subsequent polymerization stage is carried out in the presence of the polymer produced and the catalyst used in the immediately preceding polymerization stage or in a multizone circulation reactor as disclosed in International Patent Application No. 2011 / 144489 and International Patent Application No. 2018 / 177701. The polymerization temperature and pressure are as described above.

[0072] When the heterophasic propylene polymer is a reactor blend produced by sequential polymerization, the amounts of fractions (i) and (ii) correspond to the split between reactors, and when the heterophasic propylene polymer is produced in a multizone circulation reactor, the amounts of fractions (i) and (ii) correspond to the split between the riser and the downcomer.

[0073] The propylene copolymer (c) is commercially available, for example, under the trade names Adflex and Hiflex sold by LyondellBasell.

[0074] In one embodiment, the core layer (B) is composed of the above propylene copolymer (c).

[0075] The multilayer film of the present invention preferably has a total film thickness in the range of 10 to 200 microns, preferably 20 to 140 microns.

[0076] In a preferred embodiment, in the multilayer film, the ratio of the thickness of the skin layer (A) to the thickness of the core layer (B) is in the range of 1:1 to 1:12, preferably 1:2 to 1:6.

[0077] According to a preferred embodiment, the multilayer film includes a second skin layer (C), and the second skin layer (C) contains the above polyolefin composition (I). Optionally, at least one intermediate layer D can be interposed between the skin layer A and / or the skin layer C and the core layer B.

[0078] In a more preferred embodiment, the skin layer (A) and the skin layer (C) contain the same polyolefin composition (I). More preferably, the skin layer (A) and the skin layer (C) are equal, and the multilayer film has an A / B / A structure.

[0079] In the most preferred embodiment, the multilayer film of the present disclosure has a structure A / B / A, - The skin layer (A) and the second skin layer (C) are, (a) a propylene-ethylene copolymer of 70% to 95% by weight, preferably 75% to 90% by weight, and the propylene-ethylene copolymer is, Based on the weight of the propylene copolymer (a), it contains 10.0% by weight or less, preferably 2.0% to 10.0% by weight, more preferably 2.2% to 9.8% by weight, more preferably 3.0% to 8.0% by weight, and still more preferably 4.5% to 7.2% by weight of ethylene, - Based on the weight of the propylene copolymer (a), the xylene-soluble fraction at 25°C is in the range of 10% to 20% by weight, preferably 12% to 20% by weight, more preferably 14% to 18% by weight. The propylene-ethylene copolymer has a melt flow rate measured in accordance with ISO 1133-1:2011 (230 °C / 2.16 kg) of 0.1 to 10.0 g / 10 min, preferably 0.3 to 7.0 g / 10 min, more preferably 0.5 to 3.0 g / 10 min. and

[0080] (b) A copolymer of butene-1 and ethylene in an amount of 5 to 30% by weight, preferably 10 to 25% by weight, wherein the copolymer of butene-1 and ethylene - contains units derived from ethylene in the range of 5.0% by weight or less, preferably 1.0% to 4.5% by weight, preferably 1.5% to 4.5% by weight, more preferably 2.0% to 4.0% by weight, even more preferably 2.5% to 3.5% by weight, based on the weight of (b), and / or - has a melting point Tm(I) measured in accordance with Method ISO 11357-3:2018 of less than 100 °C, preferably less than 80 °C to 100 °C, more preferably 90 °C to 97 °C, and / or - has a melt flow rate measured in accordance with ISO 1133-1:2011 (190 °C / 2.16 kg) in the range of 1.0 to 6.0 g / 10 min, preferably 2.0 to 5.0 g / 10 min, even more preferably 2.5 to 4.5 g / 10 min, - and contains or is composed of a polyolefin composition (I) containing or composed of a copolymer of butene-1 and ethylene having a flexural modulus measured in accordance with ISO 178:2010 in the range of 80 MPa or more, preferably 80 to 250 MPa, more preferably 100 to 210 MPa. Here, the amounts of (a) and (b) are based on the total weight of (a) + (b). Also - The core layer (B) is - Based on the weight of fraction (i), a propylene-ethylene copolymer containing 6.0 wt% or less, preferably 0.1 wt% to 6.0 wt%, more preferably 1.5 wt% to 4.5 wt% of units derived from ethylene, 20 wt% to 40 wt%, preferably 25 wt% to 35 wt% of polymer fraction (i), and - Based on the weight of fraction (ii), a propylene-ethylene copolymer containing 35.0 wt% or less, preferably 20.0 wt% to 35.0 wt%, more preferably 23.0 wt% to 30.0 wt% of units derived from ethylene, 60 wt% to 80 wt%, preferably 65 wt% to 75 wt% of fraction (ii), and the solubility in xylene at 25 °C is in the range of 55.0 wt% to 75.0 wt%, preferably 60.0 wt% to 70.0 wt% based on the weight of fraction (ii). Fraction (ii) and, comprising or consisting of a heterophasic propylene polymer, Here, the heterophasic propylene polymer has a total ethylene content of 25 wt% or less based on the weight of the heterophasic propylene composition, and the amounts of (i) and (ii) are based on the total weight of (i) + (ii).

[0081] The multilayer film of the present disclosure optionally includes an additional layer interposed between the core layer (B) and the skin layer (A) and / or any skin layer (C) if present.

[0082] The multilayer film of the present invention is obtained by known methods such as coextrusion or lamination. In coextrusion, the components contained in different layers are supplied to a plurality of extruders.

[0083] In a preferred embodiment, the multilayer film of the present disclosure is an unoriented film, more preferably a cast film or an inflation film.

[0084] In one embodiment, the multilayer film of the present disclosure, preferably a multilayer cast film or an inflation film, has at least one, preferably all, of the following characteristics.

[0085] - The seal start temperature (SIT) is in the range of 125°C or lower, preferably 90°C to 125°C, more preferably 100°C to 125°C, and even more preferably 110°C to 120°C, and / or

[0086] - The hot tack at 110°C is in the range of 1.0 to 6.0 N, preferably 1.5 to 4.0 N.

[0087] The features that describe the subject matter of this disclosure are not necessarily closely related to each other. Thus, a preferred range of one function can be combined with a more preferred or less preferred range of another function, regardless of the level of preference.

[0088]

Examples

[0089] The following examples are for illustrative purposes only and are not intended to limit the scope of the disclosure in any way.

[0090] Characteristic evaluation method: The following method is used to determine the characteristics shown in the specification, claims, and examples.

[0091] Melt flow rate: Measured according to the DISO 1133-1:2011 method (230°C / 2.16 kg for propylene polymers and 190°C / 2.16 kg for butene-1 copolymers).

[0092] Solubility of the propylene polymer in xylene at 25°C: A 2.5 g polymer sample and 250 ml of xylene are placed in a glass flask equipped with a refrigerator and a magnetic stirrer. The temperature is raised to 135°C in 30 minutes. The resulting clear solution is stirred for an additional 30 minutes while refluxing. The solution is cooled in two steps. In the first step, the temperature is lowered to 100°C in 10 - 15 minutes in air while stirring. In the second step, the flask is transferred to a temperature - controlled water bath at 25°C for 30 minutes. The temperature is lowered to 25°C without stirring for the first 20 minutes and maintained at 25°C with stirring for the last 10 minutes. The formed solid is filtered through a fast - drying filter paper (e.g., Whatman filter paper grade 4 or 541). 100 ml of the filtered solution (S1) is poured into a pre - weighed aluminum container and heated to 140°C on a heating plate under a nitrogen stream to evaporate and remove the solvent. Next, the container is stored in an oven at 80°C under vacuum until a constant weight is reached. Next, the amount of polymer dissolved in xylene at 25°C is calculated. The XS(I) and XS A values were determined experimentally. The proportion (XS B ) of component (B) dissolved in xylene at 25°C can be calculated by the following formula. XS = W(A)×(XS A ) + W(B)×(XS B ) Here, W(A) and W(B) are the relative amounts of component (A) and (B) respectively, and W(A)+W(B)=1.

[0093] Comonomer content: 13 The 13C NMR spectrum is acquired with a Bruker AV - 600 spectrometer equipped with a cryoprobe and operates in Fourier - transform mode at 120°C. Comonomer content: 13The 13C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with a cryoprobe and operated at 120 °C in Fourier transform mode. The sample was dissolved in 1,1,2,2-tetrachloroethane-d2 at 120 °C to a concentration of 8% wt / v. Each spectrum was acquired with a 90° pulse and a 15 s delay was provided between the pulse and CPD to remove 1H-13C coupling. The spectrometer was operated at 160.91 MHz. The peak of Sδδ carbon (nomenclature: “Monomer sequence distribution of ethylene-propylene rubber measured by 13C NMR. 3. Use of reaction probability mode” by C. J. Carman, R. A. Harrington, and C. E. Wilkes, Polymer, 1977, 10, 536) was used as an internal reference at 29.9 ppm. 512 transients were stored at 32K data points using a spectral window of 9000 Hz.

[0094] Propylene copolymer : The spectral assignment, evaluation of the ternary distribution, and composition were carried out according to Kakugo (“Carbon-13 NMR measurement of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethylaluminum chloride” by M. Kakugo, Y. Naito, K. Mizunuma, and T. Miyatake, Polymer, 1982, 15, 1150) using the following equations. PPP = 100T ββ / SPPE = 100T βδ / SEPE = 100T δδ / S PEP = 100S ββ / SPEE = 100S βδ / SEEE = 100(0.25S γδ + 0.5S δδ ) / S S = T ββ + T βδ + T δδ + S ββ + S βδ + 0.25S γδ + 0.5S δδ The molar contents of ethylene and propylene are calculated from the triads using the following equations. [E]mol = EEE + PEE + PEP [P]mol = PPP + PPE + EPE The weight percentage of ethylene content (E%wt) is calculated using the following equation. [Eq.] where [P]mol = molar percentage of propylene content MWE = molecular weight of ethylene MWP = molecular weight of propylene.

[0095] The total ethylene content C2(tot) and the ethylene content C2(A) of component (A) were measured, and the ethylene content C2(B) of component (B) was calculated by the following equation. C2(tot) = W(A) × C2(A) + W(B) × C2(B) where W(A) and W(B) are the relative amounts of components (A) and (B) (W(A) + W(B) = 1).

[0096] 1-Butene copolymer: The spectral assignments, evaluation of the triad distribution, and composition are determined using the following, according to Kakugo [M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 16, 4, 1160 (1982)] and Randall [J. C. Randall, Macromol. Chem Phys., C30, 211 (1989)]. BBB = 100T ββ / S BBE = 100T βδ / S EBE = 100P δδ / S BEB = 100S ββ / S BEE = 100S (( / S EEE = 100(0.25S γδ + 0.5S δδ ) / S S = Tββ +T βδ +P δδ +S ββ +S (( +0.25S γδ +0.5S δδ

[0097] The total amount (mole percent) of 1-butene and ethylene is calculated from the triplets using the following relational expressions. [E] = EEE + BEE + BEB [B] = BBB + BBE + EBE

[0098] The weight percentage (E%wt) of the ethylene content is calculated using the following formula. [Number] Here, [B]mol = mole percentage of 1-butene content MWE = molecular weight of ethylene MWB = molecular weight of 1-butene.

[0099] Molecular weight distribution Mw / Mn: The measurements of the average Mn and Mw, and the Mw / Mn obtained therefrom were carried out using a Waters GPCV 2000 apparatus equipped with a column set of four PLgel Olexis mixed gels (Polymer Laboratories) and an IR4 infrared detector (PolymerChar). The column dimensions were 300×7.5 mm and the particle size was 13 μm. 1-2-4-Trichlorobenzene (TCB) was used as the mobile phase, the flow rate was maintained at 1.0 ml / min, and all measurements were carried out at 150 °C. The solution concentration was 0.1 g / dl in TCB, and 0.1 g / l of 2,6-di-tert-butyl-p-cresol was added to prevent decomposition. In the GPC calculation, a universal calibration curve was obtained using 10 polystyrene (PS) standard samples (the range of peak molecular weights was 580 - 8500000) provided by Polymer Laboratories. A cubic polynomial approximation was used to interpolate the experimental data and obtain the relevant calibration curve. The data acquisition and processing were performed using Empower (Waters). The Mark-Houwink equation was used to determine the molecular weight distribution and the related average molecular weights. The K value was KPS = 1.21×10⁻⁴ dL / g for PS and KPB = 1.78×10⁻⁴ dL / g for PB, and the Mark-Houwink exponent was α = 0.706 for PS and α = 0.725 for PB. For the butene-1 / ethylene copolymer, regarding data evaluation, it was assumed that the composition was constant over the entire range of molecular weights, and the K value of the Mark-Houwink relationship was calculated using a linear combination as shown below. K EB =x E K PE +x p K PB Here, K EB is the copolymer constant, K PE (4.06×10 (4 , dL / g) and PB (1.78×10 (4(dl / g) are constants for polyethylene and polybutene, and xE and xB are the weight % contents of ethylene and butene-1. The Mark-Houwink exponent (= 0.725 is used independently for all butene-1 / ethylene copolymers.

[0100] Melting point: Measured according to the method of ISO 11357-3:2018. To measure the melting point (Tm(I)) of polybutene-1 crystalline form I, the sample was melted, held at 200 °C for 5 minutes, and then cooled to 20 °C at a cooling rate of 10 °C / min. Then, the sample was stored at room temperature for 10 days. After 10 days, the sample was subjected to DSC, cooled to -20 °C, and then heated to 200 °C at a scan rate of 10 °C / min. In this heating, the first peak temperature from the low-temperature side of the thermogram was taken as the melting point Tm(I).

[0101] Flexural modulus: Measured according to the method of ISO 178:2010 for injection-molded test specimens (80 × 10 × 4 mm) obtained according to the method of ISO 1873-2:2007 for propylene polymers or for compression-molded test specimens for butene-1 polymers. Test specimens of butene-1 copolymers were conditioned at 23 °C for 10 days before testing.

[0102] Seal initiation temperature (SIT): A 6 × 35 cm film strip was cut out from the cast film, and two film strips were overlapped. The strips were sealed using a Brugger Feinmechanik Sealer, model HSG-ETK745, under the following conditions: Teflon TMA smooth metal sealing bar coated with , and both bars are heated. The sealing time is 5 seconds, the sealing pressure is 0.14 MPa (20 psi), and the initial sealing temperature is 90 °C. Six test pieces with a width of 15 mm and a length that fits into the grips of a tensile testing machine were cut from each seal strip. The seal strength at a given temperature was tested with a load cell capacity of 100 N, a cross speed of 100 mm / min, and a grip distance of 50 mm. The value of the seal strength is the average of the results of measuring the same test piece six times. The test was repeated by increasing the temperature by 5 °C each time. When the difference in seal strength at three temperatures is less than 3 N, a plateau is reached, and the average plateau strength is calculated. The seal initiation temperature (SIT) was calculated as the temperature corresponding to half of the seal strength at the plateau on the seal plot (force / temperature).

[0103] Determination of hot tack The hot tack was measured after sealing the test piece for 5 seconds at a pressure of 0.12 MPa (18 psi) using a Brugger HSG heat sealer (equipped with a hot tack kit). The film was cut to a minimum length of 15 × 200 mm and sealed by overlapping at various temperatures starting from 80 °C and increasing the seal temperature by 5 °C each time. Immediately after sealing, the test piece was pulled onto a mandrel by a pulley to split the hot seal seam. For each seal temperature, the force (hot tack) required to split the still-hot sealed joint at half of its length was determined using various drop weights created to impact the test piece.

[0104] Haze: ASTM D1003

[0105] Gloss: ASTM D2457 (angle 45°)

[0106] Raw materials:

[0107] PP(a): A propylene-ethylene copolymer obtained by the gas-phase polymerization process described in Example 44 of European Patent Application No. 1012195 B1, containing 6.0% by weight of units derived from ethylene, having a solubility in xylene at 25 °C of 16.0% by weight based on the weight of PP(a), and an MFR(a) of 0.8 g / 10 min (230 °C / 2.16 kg).

[0108] PB1(b): A copolymer of butene-1 and ethylene, with an ethylene content of 3.6% by weight, a Tm(I) of 94 °C, a molecular weight distribution Mw / Mn of 5.6, a melt flow rate of 3.5 g / 10 min (190 °C / 2.16 kg), and a flexural modulus of 120 MPa. The butene-1 copolymer was obtained by sequentially polymerizing in two reactors using a Ziegler-Natta catalyst system according to Example 11 of International Patent Application No. 2004 / 048424 with butene-1 as the liquid medium. The polymerization conditions in the first reactor were a temperature of 75 °C and a hydrogen / butene feed ratio of 1000 ppmV. After 2.5 hours, the polymerization contents of the first reactor were transferred to the second reactor, and copolymerization was continued under the same conditions except that the supply of ethylene was stopped. Polymerization was stopped after 2 hours.

[0109] PP(c): A heterophasic propylene copolymer containing 32% by weight of a propylene-ethylene copolymer (i) containing 3.2% by weight of units derived from ethylene based on the weight of (i), and 68% by weight of a propylene-ethylene copolymer (ii) containing 27.0% by weight of units derived from ethylene and having a solubility in xylene at 25 °C of 64% by weight based on the weight of (ii). The amounts of (i) and (ii) are based on the total weight of (i)+(ii). The melt flow rate of the heterophasic propylene polymer is 0.6 g / 10 min (230 °C / 2.16 kg), the melting point measured by DSC is 142 °C, and the flexural modulus is 100 MPa. The heterophasic propylene polymer was prepared in the presence of a Ziegler-Natta catalyst system described in Example 4 of International Patent Application No. 2012 / 139897 in at least two reactors connected in series (H 2 / C 3 GPR1: 0.03 mol, C 2 / C3 It is produced by a gas-phase polymerization process carried out within GPR2: 0.17 mol. The amounts of (i) and (ii) correspond to the split between reactors.

[0110] PP45NP : A premix containing 10% by weight of Silica Sylobloc 45H manufactured by Grace and 90% by weight of Moplen RP310M manufactured by LyondellBasell as a carrier resin (a slightly modified propylene-ethylene copolymer with a melt flow rate of 8.5 g / 10 min (230 °C / 2.16 kg)).

[0111] Examples E1 - E2 and Comparative Example CE3

[0112] An inflation film having a structure A / B / A and a total film thickness of 100 microns (layer distribution A = 20% / B = 60% / A = 20%) was produced on a co-rotating coextrusion inflation film line. Here, the diameter of the extruder for layer A is 30 mm, and the diameter of the extruder for the core layer B is 45 mm. The ABA flow is supplied to an annular die with a diameter of 80 mm and a die gap (lip open) of 1.2 mm. Total output: 12 Kg / h. Next, the annular melt flow is expanded by air to a diameter of 200 mm, with an expansion ratio (BUR = diameter of the inflated film / diameter of the annular die) of 2.5:1, and then cooled by cold air at the outlet of a distribution ring located outside the annular die and coaxial with the annular die. The cooled tubular film was folded by nip rolls and collected on a reel by a winding unit.

[0113] The components contained in the single layer are shown in Table 1. The mechanical, thermal, and optical properties of the inflation film are shown in Table 2.

Table 1

Table 2

Claims

1. A multilayer film comprising a skin layer (A) and a core layer (B), wherein the skin layer (A) contains a polyolefin composition (I), and the polyolefin composition (I) contains (a) 70% to 95% by weight of a copolymer of propylene and at least one α-olefin of the formula CH ２ =CHR, where R is hydrogen or a linear or branched C2-C8 alkyl, containing, based on the weight of (a), up to 10.0% by weight of units derived from said α-olefin, and the xylene-soluble fraction of said propylene copolymer at 25 °C being in the range of 10% to 20% by weight, said copolymer, and 5% to 30% by weight of a butene-1 polymer selected from (b) a butene-1 homopolymer, (b) a butene-1 copolymer containing 5.0% by weight or less of units derived from ethylene and / or propylene based on the weight of (b), and mixtures thereof, wherein the amounts of (a) and (b) are based on the total weight of (a)+(b), - The core layer (B) is a multilayer film containing a copolymer (c) of propylene and at least one α-olefin of the formula CH ２ =CHR (wherein R is hydrogen or a linear or branched C2-C8 alkyl) in an amount of 25% by weight or less based on the weight of the copolymer.

2. The multilayer film according to claim 1, wherein the polyolefin composition (I) contains 75% to 90% by weight of a propylene copolymer (a) and 10% to 25% by weight of a butene-1 polymer (b), and the amounts of (a) and (b) are based on the total weight of (a)+(b).

3. The multilayer film according to claim 1 or 2, wherein the polyolefin composition (I) contains a copolymer of propylene (a) containing 0.5% to 10.0% by weight of units derived from an α-olefin, preferably ethylene, based on the weight of (a), and a butene-1 copolymer (b) containing 0.5 to 5.0% by weight of ethylene and / or propylene, preferably units derived from ethylene, based on the weight of (b).

4. The propylene copolymer (a) is a propylene-ethylene copolymer having at least one of the following characteristics: - containing 2.0% to 10.0% by weight, preferably 2.2% to 9.8% by weight, more preferably 3.0% to 8.0% by weight, still more preferably 4.5% to 7.2% by weight of units derived from ethylene based on the weight of the propylene copolymer (a), and / or - having a melt flow rate measured according to ISO 1133-1:2011 (230 °C, 2.16 Kg) of 0.1 to 10.0 g / 10 min, preferably 0.3 to 7.0 g / 10 min, more preferably 0.5 to 3.0 g / 10 min, and / or - having a xylene soluble fraction XS(a) at 25 °C in the range of 12 to 20% by weight, preferably 14 to 18% by weight based on the weight of the propylene copolymer (a), the multilayer film according to any one of claims 1 to 3.

5. The butene-1 polymer (b) is a copolymer of butene-1 and ethylene having at least one of the following characteristics, - Based on the weight of the (b), the content of units derived from ethylene is in the range of 1.0% by weight to 4.5% by weight, preferably 1.5% by weight to 4.5% by weight, more preferably 2.0% by weight to 4.0% by weight, still more preferably 2.5% by weight to 3.5% by weight, and / or - The melting point Tm(I) measured according to DSC method ISO 11357-3:2018 is less than 100 °C, preferably 80 °C to less than 100 °C, more preferably 90 °C to 97 °C, and / or - The melt flow rate measured according to ISO 1133-1:2011 (190 °C / 2.16 kg) is in the range of 1.0 to 6.0 g / 10 min, preferably 2.0 to 5.0 g / 10 min, still more preferably 3.0 to 4.5 g / 10 min, and / or - The flexural modulus measured according to ISO 178:2010 is 80 MPa or more, preferably 80 to 250 MPa, more preferably 100 to 210 MPa. The multilayer film according to any one of claims 1 to 4.

6. The propylene copolymer (c) is - The polymer fraction (i) is 20% to 40% by weight and comprises a propylene homopolymer, at most 6.0% by weight, preferably 0.1% to 6.0% by weight based on the weight of the fraction (i), of a propylene copolymer with at least one α-olefin of the formula CH ２ =CHR, where R is hydrogen or a linear or branched C2-C8 alkyl, and combinations thereof, and the polymer fraction (i) as selected from the group consisting of these, - The polymer fraction (ii) is 60% to 80% by weight, and based on the weight of the fraction (ii), at least one type of formula CH ２ =CHR α-olefin (wherein R is hydrogen or linear or branched C2-C8 alkyl), and based on the weight of the fraction (ii), the solubility in xylene at 25 ° C is in the range of 45.0% to 75.0% by weight. A heterophasic propylene polymer comprising the propylene copolymer and the polymer fraction (ii). The amounts of the (i) and the (ii) are based on the total weight of the (i) + the (ii). The multilayer film according to any one of claims 1 to 5.

7. The propylene copolymer (c) is a heterophasic propylene polymer. - 20% to 40% by weight, preferably 25% to 35% by weight of a polymer fraction (i) containing a propylene-ethylene copolymer containing 6.0% by weight or less, preferably 0.1% by weight to 6.0% by weight, more preferably 1.5% by weight to 4.5% by weight of units derived from ethylene based on the weight of the fraction (i), and - 60% to 80% by weight, preferably 65% to 75% by weight of a fraction (ii) containing a propylene-ethylene copolymer containing 35.0% by weight or less, preferably 20.0% by weight to 35.0% by weight, more preferably 23.0% by weight to 30.0% by weight of units derived from ethylene based on the weight of the fraction (ii), and having a solubility in xylene at 25 °C in the range of 55.0% by weight to 75.0% by weight, preferably 60.0% by weight to 70.0% by weight based on the weight of the fraction (ii). The multilayer film according to claim 6, wherein the amounts of the above (i) and the above (ii) are based on the total weight of the above (i) + the above (ii).

8. The multilayer film according to any one of claims 1 to 7, wherein the thickness of the entire film ranges from 10 to 200 μm, preferably from 20 to 140 μm.

9. The multilayer film according to any one of claims 1 to 8, wherein the ratio of the thickness of the skin layer (A) to the thickness of the core layer (B) is 1:1 to 1:12, preferably 1:2 to 1:

6.

10. The multilayer film according to any one of claims 1 to 9, comprising a second skin layer (C), wherein the second skin layer (C) comprises the polyolefin composition according to any one of claims 1 to 5.

11. The multilayer film according to claim 10, wherein the skin layer (A) and the second skin layer (C) comprise the same polyolefin composition (I).

12. The multilayer film according to claim 10 or 11, wherein the skin layer (A) and the second skin layer (C) are equal, and the multilayer film has an A / B / A structure.

13. The multilayer film according to any one of claims 1 to 12, wherein the film is unoriented.

14. The multilayer film according to claim 13, wherein the film is a cast film or an inflation film.

15. Having at least one of the following characteristics: - The seal initiation temperature (SIT) ranges from 125°C or lower, preferably from 90°C to 125°C, more preferably from 100°C to 125°C, still more preferably from 110°C to 120°C, and / or - The hot tack at 110°C ranges from 1.0 to 6.0 N, preferably from 1.5 to 4.0 N. The multilayer film according to claim 13 or 14.

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