Film with high stiffness and balance of stiffness and toughness

Abstract

The present invention relates to a film comprising a polyolefin composition comprising a polyethylene-based material and a polypropylene-based material and a method of forming a film.

Description

Technical Field

[0001] The present invention relates to films comprising a polyolefin composition comprising a polyethylene-based material and a polypropylene-based material and a method of forming the film. Background Art

[0002] In the production of polymer films, especially cast films, it is desirable to have a polymer with good processability to achieve commercial production volumes while maintaining sufficient toughness. In addition, the physical properties required for the final film product include stiffness, toughness and / or tear strength, etc.

[0003] Stiffness and toughness are key properties of polyethylene (PE) films. Examples of applications where stiffness and toughness of PE films are key properties include stand-up bags, sealed bags, heavy-duty bags, etc. Toughness can be characterized, for example, by dart impact resistance and needle puncture strength. Stiffness can be characterized, for example, by machine direction (MD) 1% secant modulus.

[0004] High-density polyethylene (HDPE) and polypropylene (PP) are two possible blending partners for polyethylene (PE) films to improve stiffness. However, the selection of PP as a blending partner is limited because PP and PE have different crystal phases and types, and there is little or no co-crystallization between PP and PE. Those skilled in the art generally believe that blending PP with PE can improve the stiffness of PE films, but will simultaneously reduce the toughness of PE films.

[0005] On the other hand, PP has many advantages over HDPE, such as lower density, higher stiffness, and higher heat resistance. If PP can be used in most PE formulations to improve the stiffness of the film while still maintaining toughness properties, it will show great value for industrial and food packaging thickness reduction of PP / PE film structures.

[0006] In addition, industrial packaging and food packaging require high stiffness, such as films with a 1% secant modulus greater than 410 MPa in the machine direction (MD). Self-supporting packaging, such as self-supporting bags, requires films with high stiffness. High-stiffness films provide the following advantages: self-supporting bags are not easy to tip over; it is conducive to more accurate printing patterns on the packaging surface; for packaging with multi-layer films, the layers are more closely attached and less prone to wrinkling.

[0007] Moreover, while having high stiffness, industrial packaging and food packaging also require the film to have a balance of stiffness and toughness.

[0008] Films having high stiffness, for example, a machine direction (MD) 1% secant modulus greater than 410 MPa, while having a balance of stiffness and toughness are a challenge in the art.

[0009] Relevant publications include, for example, WO 2017 / 068106 and WO 2021 / 040760. Summary of the invention

[0010] The inventors of the present invention unexpectedly found that by providing a polyolefin composition using homopolypropylene (hPP) instead of high-density polyethylene (HDPE), and subjecting a film comprising (or essentially consisting of, or consisting of) the polyolefin composition to machine direction orientation (MDO), the present invention successfully obtains a film having high stiffness, for example, a machine direction (MD) 1% secant modulus greater than 410 MPa, while having a balance of stiffness and toughness.

[0011] The present invention provides novel films comprising (or consisting essentially of, or consisting of) a polyolefin composition, wherein the polyolefin composition comprises (or consisting essentially of, or consisting of) one or more broad orthogonal composition distribution (BOCD) polyethylenes and one or more homopolypropylenes (hPPs).

[0012] The film of the present invention is manufactured by a casting process.The film of the present invention undergoes machine direction orientation (MDO) with a stretch ratio of 3X to 5X, such as 3X, 4X, 5X.

[0013] It is generally believed in the art that during machine direction orientation (MDO), as the draw ratio increases, the toughness of the film decreases.

[0014] However, contrary to the general understanding in the art, the inventors of the present invention unexpectedly found that by subjecting a film comprising (or essentially consisting of, or consisting of) the polyolefin composition of the present invention to machine direction orientation (MDO), as the stretch ratio increases, not only the stiffness of the film is significantly improved, but also the toughness of the film is improved accordingly, so that while achieving high stiffness, the film of the present invention also successfully obtains a beneficial balance between stiffness and toughness.

[0015] According to an embodiment of the present invention, the polyolefin composition comprises (or consists essentially of, or consists of) about 60 wt % to about 95 wt % BOCD polyethylene and about 5 wt % to about 40 wt % homopolypropylene, based on the weight of the polyolefin composition.

[0016] According to an embodiment of the present invention, the content of BOCD polyethylene can be, for example, about 60wt%, about 65wt%, about 70wt%, about 75wt%, about 80wt%, about 85wt%, about 90wt%, about 95wt% based on the weight of the polyolefin composition. The content range of BOCD polyethylene can be a combination of any two of the above content values, such as about 60wt% to about 95wt%, about 60wt% to about 90wt%, etc. based on the weight of the polyolefin composition.

[0017] According to an embodiment of the present invention, based on the weight of the polyolefin composition, the content of homopolypropylene can be, for example, about 5wt%, about 10wt%, about 15wt%, about 20wt%, about 25wt%, about 30wt%, about 35wt%, about 40wt%. Based on the weight of the polyolefin composition, the content range of homopolypropylene can be a combination of any two of the above content values, such as about 5wt% to about 40wt%, about 5wt% to about 35wt%, etc.

[0018] According to an embodiment of the present invention, the BOCD polyethylene contains about 70 mol% to about 99 mol% of polymer units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene, and a density of about 0.91 g / cm 3 To about 0.925g / cm 3 , which is measured according to ASTM D-792 or ASTM D-1505, and a melt index (MI, or I 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16kg).

[0019] According to an embodiment of the present invention, the BOCD polyethylene has a composition distribution breadth index (CDBI) from about 25 wt % to about 55 wt %.

[0020] According to an embodiment of the present invention, the homopolypropylene has a melt index of from about 1 g / 10 min to about 6 g / 10 min, as measured according to ASTM D1238-L (230° C. / 2.16 kg).

[0021] According to an embodiment of the present invention, the homopolymer polypropylene has a molecular weight of from about 0.8 g / cm 3 To about 0.98g / cm 3 The density of the composite is measured according to ASTM D792-13 method.

[0022] According to an embodiment of the present invention, the homopolypropylene has a tensile strength at yield of from about 20 MPa to about 100 MPa, as measured according to ASTM D638.

[0023] According to an embodiment of the present invention, a film comprising (or consisting essentially of, or consisting of) the polyolefin composition of the present invention has a thermal conductivity of from greater than about 410 MPa, greater than about 420 MPa, greater than about 430 MPa, greater than about 440 MPa, greater than about 450 MPa, greater than about 460 MPa, greater than about 500 MPa, greater than about 550 MPa, greater than about 600 MPa, greater than about 610 MPa, greater than about 620 MPa, greater than about 630 MPa, greater than about 640 MPa, greater than about 650 MPa, greater than about 700 MPa, greater than about 730 MPa, greater than about 740 MPa, greater than about 750 MPa, greater than about 760 MPa, or greater than about 770 MPa to less than about 780 MPa. or less than about 460 MPa, or less than about 450 MPa, in a machine direction (MD) 1% secant modulus, when a film comprising (or consisting essentially of, or consisting of) the polyolefin composition of the present invention has a thickness of about 25 μm, wherein the machine direction (MD) 1% secant modulus is measured according to ASTM D 882 method.

[0024] According to an embodiment of the present invention, a film comprising (or consisting essentially of, or consisting of) the polyolefin composition of the present invention has a needle punch strength / μm (mN / μm) from greater than about 90 mN / μm, greater than about 100 mN / μm, greater than about 110 mN / μm, greater than about 120 mN / μm, greater than about 130 mN / μm, or greater than about 140 mN / μm to less than about 150 mN / μm, less than about 140 mN / μm, less than about 130 mN / μm, or less than about 120 mN / μm, wherein the needle punch strength / μm (mN / μm) is measured according to the CEN 14477 method.

[0025] The film comprising (or consisting essentially of, or consisting of) the polyolefin composition of the present invention may be a monolayer film, or a multilayer film, wherein any layer of the multilayer film may comprise the polyolefin composition of the present invention.

[0026] The thickness of the film of the present invention can be selected and determined according to actual needs.

[0027] Films comprising (or consisting essentially of, or consisting of) the polyolefin composition of the present invention can be made using a casting process known in the art for making polyethylene (PE) films, and subsequently subjected to machine direction orientation (MDO), wherein the stretch ratio is 3X to 5X, such as 3X, 4X, 5X.

[0028] According to an embodiment of the present invention, the present invention provides a film comprising a polyolefin composition, wherein the polyolefin composition comprises from about 60 wt % to about 95 wt % of a BOCD polyethylene and from about 5 wt % to about 40 wt % of a homopolypropylene, based on the weight of the polyolefin composition,

[0029] wherein the BOCD polyethylene contains from about 70 mol % to about 99 mol % of polymer units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene, and has a density of about 0.918 g / cm 3 , which is measured according to ASTM D-792, and a melt index (MI, or I 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16 kg), and the BOCD polyethylene has a composition distribution breadth index (CDBI) of about 38.6 wt%, or

[0030] wherein the BOCD polyethylene contains from about 70 mol % to about 99 mol % of polymer units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene, and has a density of about 0.915 g / cm 3 , which is measured according to ASTM D-1505, and a melt index (MI, or I 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16kg), and the BOCD polyethylene has a composition distribution breadth index (CDBI) of about 43 wt%,

[0031] wherein the homopolypropylene has a melt index of 3.2 g / 10 min, as measured according to ASTM D1238-L (230° C. / 2.16 kg),

[0032] wherein the film is manufactured by a casting process, and subsequently the film is subjected to machine direction orientation (MDO) with a stretch ratio of 3X to 5X, and

[0033] wherein the film has a machine direction (MD) 1% secant modulus from greater than about 410 MPa to less than about 780 MPa, measured when the film has a thickness of about 25 μm, wherein the machine direction (MD) 1% secant modulus is measured according to ASTM D 882 method, or

[0034] Preferably, the homopolymer polypropylene has a density of 0.900 g / cm 3 The density of

[0035] Preferably, the film has a needle punch strength / μm (mN / μm) from greater than about 90 mN / μm to less than about 150 mN / μm, wherein the needle punch strength / μm (mN / μm) is measured according to the CEN 14477 method, or

[0036] Preferably, the homopolypropylene has a tensile strength at yield of from about 20 MPa to about 100 MPa, as measured according to ASTM D638.

[0037] The invention also relates to industrial packaging and food packaging comprising the film according to the invention.

[0038] According to an embodiment of the present invention, the films made by the present invention are suitable for use in upright, flexible packages or pouches. Such a package will be stiff enough to be formed into a shape that allows it to stand upright, for example, with a label on the front thereof, but soft enough to allow the user to bend and / or squeeze the package to force and / or pour out the liquid.

[0039] Broad Orthogonal Composition Distribution (BOCD) Polyethylene

[0040] The polyolefin compositions of the present invention include one or more broad orthogonal composition distributions (BOCD) polyethylenes. Broad orthogonal composition distributions (BOCD) polyethylenes are polyethylene homopolymers or polyethylene copolymers, in most cases polyethylene copolymers. It is desirable that polyethylene has a broad orthogonal composition distribution, which provides enhanced stiffness, toughness and processability (S / T / P) balance for polyethylene and compositions comprising these polymers. Considering that polymers are blends of molecules with different chain length distributions, polymers with BOCD are branched polymers, which have any branching that occurs on the high molecular weight molecules of the polymer, if not all, which makes them less crystalline. This microstructure has a trend of improving certain properties of products made from the BOCD type polymers (including polyolefin compositions as described herein).

[0041] Ziegler-Natta ("Zn") produced polyethylenes tend not to have a BOCD type structure, with most of the short chain branching occurring on the low molecular weight portion of the molecules so produced. On the other hand, some metallocene polyethylenes can often have a BOCD type structure. The value of BOCD polymers relative to conventional polymers is significant.

[0042] In embodiments of the present invention, the BOCD polyethylene may have a "broad orthogonal composition distribution" ("BOCD"). The broad orthogonal composition distribution may be determined using a fractionation technique, such as gel permeation chromatography-differential viscometer (GPC-DV), temperature rising elution fractionation-differential viscometer (TREF-DV), or a cross-fractionation technique. For example, WO 2015 / 123164A1 (which is incorporated herein by reference) discusses the TREF technique, providing a measurement of the bivariate mass distribution of the crystalline portion of a BOCD polyethylene.

[0043] The BOCD polyethylene of the present invention comprises about 70 mol% to about 99 mol% of units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene. Based on the total moles of polymer units of the BOCD polyethylene, the lower limit of the content range of units derived from ethylene can be 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, 92 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 98 mol% or 99 mol%. Based on the total moles of polymer units of the BOCD polyethylene, the upper limit of the content range of units derived from ethylene can be 80 mol%, 85 mol%, 90 mol%, 92 mol%, 94 mol%, 95 mol%, 96 mol%, 97 mol%, 98 mol%, 99 mol%, 99.5 mol% or 100 mol%. Any of the above upper limit contents can be combined with any of the above upper limit contents; any of the above upper limit contents can be combined with any of the above lower limit contents; and any of the above upper limit contents can be combined with any of the above lower limit contents.

[0044] The BOCD polyethylene of the present invention may have equal to or less than 30 mol% of polymer units derived from C3-C20 olefins, such as C3-C20 α-olefins, such as hexene or octene. Based on the total moles of polymer units of the BOCD polyethylene, the upper limit of the content range of polymer units derived from C3-C20 olefins may be 30 mol%, 25 mol%, 20 mol%, 15 mol%, 10 mol%, 8 mol%, 6 mol%, 5 mol%, 4 mol%, 3 mol%, 2 mol%, 1 mol% or 0.5 mol%. Based on the total moles of polymer units of the BOCD polyethylene, the lower limit of the content range of polymer units derived from C3-C20 olefins may be 0 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 8 mol%, 10 mol%, 15 mol%, 20 mol% or 25 mol%. Any of the above upper limits may be combined with any of the above upper limits; any of the above upper limits may be combined with any of the above lower limits; and any of the above upper limits may be combined with any of the above lower limits.

[0045] According to an embodiment of the present invention, the density of BOCD polyethylene measured according to ASTM D-792 or ASTM D-1505 may be 0.910 g / cm 3 Up to 0.925g / cm 3 , or 0.910g / cm 3 Up to 0.923g / cm 3 , 0.910g / cm 3 Up to 0.920g / cm 3 , 0.915g / cm 3 To 0.921g / cm 3 , 0.910g / cm 3 Up to 0.918g / cm 3 , 0.912g / cm 3 Up to 0.918g / cm 3 or 0.912 g / cm 3 To 0.917g / cm 3 .

[0046] According to an embodiment of the present invention, the BOCD polyethylene has a melt index (MI, or I) of about 0.5 g / 10 min to about 3.0 g / 10 min, preferably about 1.0 g / 10 min to about 2.0 g / 10 min. 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16kg).

[0047] The term "Composition Distribution Breadth Index (CDBI)" represents the weight percent of copolymer molecules having a comonomer content within 50% of the median molar content of all comonomers. The BOCD polyethylenes of the present invention typically have a broad composition distribution as measured by the Composition Distribution Breadth Index (CDBI).

[0048] The CDBI of a copolymer can be measured using techniques known in the art. The CDBI of a copolymer is easily 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. Generally, a high CDBI indicates that most components are washed out in a shorter period of time (smaller temperature range) and the comonomer distribution is narrow; a low CDBI indicates that most components are washed out in a longer period of time (larger temperature range), indicating that the comonomer distribution is wide.

[0049] Details on determining the CDBI of a copolymer are known to those skilled in the art, for example, see PCT patent application WO 1993 / 003093 published on February 18, 1993 (which is incorporated herein by reference), the content regarding CDBI in the specification, such as the fourth paragraph on page 13 of the specification, the transition paragraph on pages 14-15, the transition paragraph on pages 18-19, etc.

[0050] According to an embodiment of the present invention, the BOCD polyethylene is characterized as having a composition distribution breadth index (CDBI) from about 25 wt % to about 55 wt %.

[0051] Materials and methods for making BOCD polyethylene have been described in, for example, U.S. Patent No. 6,956,088, particularly Example 1; U.S. Patent Application Publication No. 2009 / 0297810, particularly Example 1; U.S. Patent Application Publication No. 2015 / 0291748, particularly PE1-PE5 in the examples; and WO 2014 / 099356, particularly PE3 mentioned on page 12 and in the examples, including the use of a silica-supported hafnium transition metallocene / methylaluminoxane catalyst system as described, for example, in U.S. Patent Nos. 6,242,545 and 6,248,845 (particularly Example 1).

[0052] Many BOCD polyethylenes are commercially available. One or more BOCD polyethylenes are commercially available from ExxonMobil Chemical Company, Houston, TX, and as Exceed TMXP metallocene polyethylene (mPE) sales. Exceed TM XPmPE offers advantageous properties such as dart impact strength, flex crack resistance and machine direction (MD) tear, as well as maintaining stiffness at lower density. TM XP mPE also offers a good balance of melt strength, toughness, stiffness and sealing capabilities, which makes this class of polymers well suited for example in blown film / sheet applications.

[0053] Other BOCD polyethylenes commercially available from ExxonMobil Chemical Company, Houston, TX include Exceed TM S 9333 series, EXP609CB CAST, EXT515, etc.

[0054] The following BOCD polyethylene was used in the examples of this application:

[0055] Exceed TM XP 8318 is a polyethylene available from ExxonMobil Chemical Company, Houston, TX, which is a copolymer of ethylene and 1-hexene with a molecular weight of 0.918 g / cm2 as measured according to ASTM D792. 3 A density of 1.0 g / 10 min and a melt index of 1.0 g / 10 min measured according to ASTM D1238-E (190° C. / 2.16 kg), and a composition distribution breadth index (CDBI) of about 38.6 wt %;

[0056] EXT515 is a polyethylene available from ExxonMobil Chemical Company, Houston, TX, which is a copolymer of ethylene and 1-hexene with a molecular weight of 0.915 g / cm2 as measured according to ASTM D1505. 3 and a melt index of 1.4 g / 10 min measured according to ASTM D1238-E (190° C. / 2.16 kg), and a composition distribution breadth index (CDBI) of about 43 wt %.

[0057] Homopolymer Polypropylene (hPP)

[0058] The polyolefin composition of the present invention comprises one or more homopolypropylenes.

[0059] According to an embodiment of the present invention, homopolypropylene (hPP) can have a melt index of from about 1 g / 10min, about 1.2 g / 10min, about 1.4 g / 10min, about 1.6 g / 10min or about 1.8 g / 10min to about 2 g / 10min, about 2.2 g / 10min, about 2.5 g / 10min, about 2.8 g / 10min, about 3 g / 10min, about 3.5 g / 10min, about 4 g / 10min, about 4.5 g / 10min, about 5 g / 10min, about 5.5 g / 10min or about 6 g / 10min, which is measured according to ASTM D1238-L (230°C / 2.16 kg). The combination of any upper limit and any lower limit mentioned above is also within the scope of the present invention.

[0060] According to an embodiment of the present invention, the homopolypropylene (hPP) may have a molecular weight from about 0.8 g / cm 3 , about 0.82g / cm 3 , about 0.84g / cm 3 , about 0.85g / cm 3 , about 0.86g / cm 3 or about 0.88g / cm 3 To about 0.9g / cm 3 , about 0.92g / cm 3 , about 0.95g / cm 3 or about 0.98g / cm 3 The density of the present invention is measured according to ASTM D792-13 method. The combination of any upper limit and any lower limit mentioned above is also within the scope of the present invention.

[0061] According to an embodiment of the present invention, the homopolypropylene (hPP) can have a yield tensile strength of from about 20 MPa, about 25 MPa, about 30 MPa, or about 35 MPa to about 40 MPa, about 45 MPa, about 50 MPa, about 60 MPa, about 80 MPa or about 100 MPa, as measured according to ASTM D638. The combination of any upper limit and any lower limit mentioned above is also within the scope of the present invention.

[0062] In the examples of the present invention, T30S from Maoming Petrochemical, ie, "PP PPH-T03 (T30S) Sinopec / Wire Drawing Grade" is used as homopolypropylene (hPP).

[0063] The polypropylene homopolymer of "PP PPH-T03 (T30S) Sinopec / Drawing Grade" has the following performance parameters:

[0064] Melt index: 3.2 g / 10 min, measured at 230 ° C and 2.16 kg;

[0065] Isotactic index: 97.2%;

[0066] Ash content: 0.02%;

[0067] Tensile break nominal strain: 498%;

[0068] Yield tensile strength: 31.5Mpa;

[0069] Density: 0.900g / cm 3 , which is measured according to ASTM D792-13 method.

[0070] High Density Polyethylene

[0071] The high density polyethylene (HDPE) according to the present invention has a thickness greater than 0.940 g / cm 3 and a melt index of about 0.5 g / 10 min to about 10 g / 10 min, wherein the density is measured according to ASTM D-1505 and the melt index is measured according to ASTM D1238-E (190° C. / 2.16 kg).

[0072] In the embodiments of the present invention, ExxonMobil TM HDPE HTA 108 was used as high density polyethylene, which was purchased from ExxonMobil Chemical Company, Houston, TX.

[0073] ExxonMobil TM HDPE HTA 108 has the following performance parameters:

[0074] Density: 0.961g / cm 3 , measured according to ASTM D-1505;

[0075] Melt index: 0.70 g / 10 min, which is measured according to ASTM D-1238-E (190° C. / 2.16 kg).

[0076] additive

[0077] According to embodiments of the present invention, other additives may also be present in the polyolefin compositions and films of the present invention.

[0078] These additives may include antioxidants (e.g., hindered phenols and phosphites), stabilizers such as lactones and vitamin E, nucleating agents (α-nucleating agents and β-nucleating agents), clarifying agents, colorants (dyes or pigments), fillers (silicon dioxide or talc), UV stabilizers, mold release agents, slip agents, tackifiers, antistatic agents, acid scavengers (e.g., calcium stearate), antiblocking agents, antiblooming agents, polymer processing aid masterbatch (PPA MB) additives / agents, hydrocarbon resins such as Oppera TM Resin or a combination thereof.

[0079] Machine Direction Orientation (MDO)

[0080] As is known in the art, the process of machine direction orientation (MDO) involves uniaxial stretching of a film or sheet to improve physical and barrier properties.

[0081] The MDO process is a process used to change and improve the following film properties: optical properties (haze and gloss), tensile properties, stiffness (secant modulus), dead folds and OTR, WTR, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 The MD tensile strength at break (MPa) of the following formulations is shown: Pure Exceed TM XP 8318, with 4X MDO draw ratio; 80wt% Exceed TM XP 8318 + 20wt% T30S, using 4X MDO stretch ratio; 80wt% Exceed TM XP 8318 + 20 wt% HTA 108 with 4X MDO draw ratio; and

[0083] Pure EXT 515 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% HTA 108 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% T30S uses an MDO stretch ratio of 3X, 4X or 5X respectively.

[0084] Figure 2 The MD elongation at break (%) of the following formulations is shown: Pure Exceed TM XP 8318, with 4X MDO draw ratio; 80wt% Exceed TM XP 8318 + 20wt% T30S, using 4X MDO stretch ratio; 80wt% Exceed TM XP 8318 + 20 wt% HTA 108 with 4X MDO draw ratio; and

[0085] Pure EXT 515 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% HTA 108 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% T30S uses an MDO stretch ratio of 3X, 4X or 5X respectively.

[0086] Figure 3 MD 1% Secant Modulus (MPa) for the following formulations are shown: Pure Exceed TM XP 8318, with 4X MDO draw ratio; 80wt% Exceed TM XP 8318 + 20wt% T30S, using 4X MDO stretch ratio; 80wt% Exceed TM XP 8318 + 20 wt% HTA 108 with 4X MDO draw ratio; and

[0087] Pure EXT 515 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% HTA 108 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% T30S uses an MDO stretch ratio of 3X, 4X or 5X respectively.

[0088] Figure 4 Shows the dart drop strength / thickness (g / μm) of the following formulations: Pure Exceed TM XP 8318, with 4X MDO draw ratio; 80wt% Exceed TM XP 8318 + 20wt% T30S, using 4X MDO stretch ratio; 80wt% Exceed TM XP 8318 + 20 wt% HTA 108 with 4X MDO draw ratio; and

[0089] Pure EXT 515 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% HTA 108 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% T30S uses an MDO stretch ratio of 3X, 4X or 5X respectively.

[0090] Figure 5 Shows the needle puncture strength / μm (mN / μm) of the following formulations: Pure Exceed TM XP 8318, with 4X MDO draw ratio; 80wt% Exceed TMXP 8318 + 20wt% T30S, using 4X MDO stretch ratio; 80wt% Exceed TM XP 8318 + 20 wt% HTA 108 with 4X MDO draw ratio; and

[0091] Pure EXT 515 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% HTA 108 uses an MDO stretch ratio of 3X, 4X or 5X respectively; 80wt% EXT 515+20wt% T30S uses an MDO stretch ratio of 3X, 4X or 5X respectively. DETAILED DESCRIPTION

[0092] In order to better understand the technical solution of the present invention, the applicant provides the following examples for illustration. The examples are only for the purpose of illustration and do not limit the scope of protection of the present invention.

[0093] Measurement method

[0094] The present invention uses the following measurement method.

[0095] Table 1

[0096]

[0097]

[0098] Example

[0099] Examples 1-2 are both single-layer films, and the thickness of the films is 25 μm. Examples 1-2 are both manufactured under the same casting process conditions as described below.

[0100] The tape casting process uses the following steps:

[0101] 1- Heating / preheating roller: (80-130℃)

[0102] The temperature of the film is raised to the temperature of machine direction (MD) orientation (hereinafter referred to as melting temperature). The temperature depends on the material properties (including density, Mw, LCB, etc.), line speed, draw ratio, coextrusion formulation, etc.

[0103] 2-Stretch ratio / stretch tension:

[0104] Stretch up to 10 times;

[0105] Controlling the tension at a certain stretch ratio: material properties.

[0106] 3- Annealing roller: (100-120℃):

[0107] Membrane properties obtained after heating fixation in MDO;

[0108] Control reactions that may be exposed to heat in the future, such as sealing.

[0109] 4-Cooling roller: (70-20℃):

[0110] The film was cooled and its temperature was allowed to cool to room temperature before being rewound.

[0111] Specifically, the following conditions were used:

[0112]

[0113] Example 1

[0114] In the MDO process, films with the following compositions were stretched at 3X, 4X and 5X stretch ratios, and the properties of each film were tested. All films were single-layer films with a film thickness of 25 μm:

[0115] (1) Pure EXT 515;

[0116] (2)80wt%EXT 515+20wt%HTA 108;

[0117] (3)80wt%EXT 515+20wt%T30S.

[0118] Table 2

[0119]

[0120] As shown in Table 2, the film of the present invention comprising 80wt% EXT 515 + 20wt% T30S polyolefin composition achieves high stiffness, i.e., a 1% secant modulus in the longitudinal direction (MD) of greater than 410MPa. Specifically, with a stretch ratio of 3X, 4X and 5X, the film of the present invention comprising 80wt% EXT 515 + 20wt% T30S polyolefin composition achieves a 1% secant modulus in the longitudinal direction (MD) of 442.0MPa, 634.0MPa and 774.0MPa, respectively. In particular, with a stretch ratio of 5X, the film of the present invention comprising 80wt% EXT 515 + 20wt% T30S polyolefin composition can achieve a 1% secant modulus in the longitudinal direction (MD) of up to 774.0MPa.

[0121] It is generally believed in the art that during machine direction orientation (MDO), as the draw ratio increases, the toughness of the film decreases.

[0122] However, surprisingly, the film of the present invention comprising 80wt% EXT 515 + 20wt% T30S polyolefin composition simultaneously obtains improved toughness with increasing stretch ratio. Specifically, with stretch ratios of 3X, 4X and 5X, the film of the present invention comprising 80wt% EXT 515 + 20wt% T30S polyolefin composition achieved needle punch strengths / μm (mN / μm) of 111.45mN / μm, 141.97mN / μm and 140.35mN / μm, respectively.

[0123] In particular, the film of the present invention comprising 80 wt% EXT 515 + 20 wt% T30S polyolefin composition unexpectedly has a 27.4% increased needle punch strength / μm when a stretch ratio of 4X is used compared to a stretch ratio of 3X. The film of the present invention comprising 80 wt% EXT 515 + 20 wt% T30S polyolefin composition unexpectedly has substantially the same needle punch strength / μm (mN / μm) at a stretch ratio of 4X and 5X, i.e., 141.97 mN / μm and 140.35 mN / μm.

[0124] It can be seen that the above examples illustrate that by providing a polyolefin composition using homopolypropylene instead of high-density polyethylene and orienting the film in the longitudinal direction, the film of the present invention has a beneficial balance of stiffness and toughness on the basis of high stiffness.

[0125] In addition, compared to a film comprising 80wt% EXT 515 + 20wt% HTA 108 polyolefin composition (wherein HTA108 is a high density polyethylene), when a stretch ratio of 3X, 4X and 5X is used, respectively, the film of the present invention comprising 80wt% EXT 515 + 20wt% T30S polyolefin composition unexpectedly has a machine direction (MD) 1% secant modulus that is increased by 60.7%, 86.5% and 58.3%, respectively.

[0126] Moreover, compared with a film comprising 80wt% EXT 515+20wt% HTA 108 polyolefin composition (wherein HTA108 is a high density polyethylene), when a stretch ratio of 3X, 4X and 5X is adopted, the film of the present invention comprising 80wt% EXT 515+20wt% T30S polyolefin composition unexpectedly has a needle punch strength / μm increased by 14.7%, 33.5% and 6.0%, respectively.

[0127] In addition, compared to a film comprising 80wt% EXT 515+20wt% HTA 108 polyolefin composition (wherein HTA108 is a high density polyethylene), when a stretch ratio of 3X, 4X and 5X is used, respectively, the film of the present invention comprising 80wt% EXT 515+20wt% T30S polyolefin composition unexpectedly has a dart drop strength / thickness (g / μm) that is increased by 8.7%, 47.4% and 35%, respectively.

[0128] It can be seen that the above embodiments illustrate that by providing a polyolefin composition using homopolymer polypropylene instead of high-density polyethylene and longitudinally orienting the film, compared with the film using high-density polyethylene in the prior art, the film of the present invention has significantly improved stiffness and also improved toughness, thereby successfully achieving a beneficial balance between stiffness and toughness.

[0129] Example 2

[0130] In the MDO process, films with the following compositions were stretched at a stretch ratio of 4X and the properties of each film were tested, where all films were single-layer films with a film thickness of 25 μm:

[0131] (1) Pure Exceed TM XP 8318;

[0132] (2) 80wt%Exceed TM XP 8318 + 20wt% HTA 108;

[0133] (3) 80wt%Exceed TM XP 8318 + 20wt% T30S.

[0134] Table 3

[0135]

[0136] It can be seen from Table 3 that when the stretching ratio is 4X, the TM Compared with the film of XP 8318 + 20wt% HTA 108 polyolefin composition, the film of the present invention containing 80wt% Exceed TM While the toughness of the film of XP 8318+20wt% T30S remains essentially unchanged, i.e., the needle punch strength / μm (mN / μm) is 109.04 mN / μm and 102.62 mN / μm, respectively, the film of the present invention achieves a significantly increased stiffness of 41.1%, i.e., the 1% secant modulus in the longitudinal direction (MD) is significantly increased by 41.1%.

[0137] All documents described herein, including any priority documents and / or test procedures are introduced for reference under all jurisdictions that do not conflict with the present invention. It is obvious from the above overview and specific embodiments that, although the form of the present disclosure has been illustrated and described, various modifications can be made without departing from the spirit and scope of the present disclosure. Therefore, it is not desired that the present disclosure be limited in this way. Similarly, the term "comprising" is considered to be synonymous with the term "including". Similarly, whenever a composition, element or element group is in front of the transitional term "comprising", it should be understood that it is also considered to have the transitional term "essentially consisting of", "consisting of", "selected from" or "being" in front of the listed composition, element or each element The same composition or element group, and vice versa.

[0138] For simplicity, only some numerical ranges are clearly disclosed herein. However, a certain lower limit can be used in combination with any other upper limit to limit the scope that is not clearly recorded. Similarly, a certain lower limit can be used in combination with any other lower limit to limit the scope that is not clearly recorded. Similarly, a certain upper limit can also be used in combination with any upper limit to limit the scope that is not clearly recorded. In addition, even if there is no clear description, each point or individual value between the two end points is also included in the scope. Therefore, each point or individual value itself can be used as a lower limit or upper limit in combination with other points or individual values ​​or other lower or upper limits to limit the scope that is not clearly recorded.

Claims

1. A film comprising a polyolefin composition, wherein the polyolefin composition comprises from about 60 wt % to about 95 wt % of BOCD polyethylene and from about 5 wt % to about 40 wt % of homopolypropylene, based on the weight of the polyolefin composition, wherein the BOCD polyethylene contains from about 70 mol % to about 99 mol % of polymer units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene, and has a density of about 0.91 g / cm 3 To about 0.925g / cm 3 , which is measured according to ASTM D-792 or ASTM D-1505, and a melt index (MI, or I 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16kg), and the BOCD polyethylene has a composition distribution breadth index (CDBI) from about 20 wt% to less than 50 wt%, wherein the homopolypropylene has a melt index of from about 1 g / 10 min to about 6 g / 10 min as measured according to ASTM D1238-L (230° C. / 2.16 kg), wherein the film is manufactured by a casting process, and subsequently the film is subjected to machine direction orientation (MDO) with a stretch ratio of 3X to 5X, wherein the film has a machine direction (MD) 1% secant modulus from greater than about 410 MPa to less than about 780 MPa, measured when the film has a thickness of about 25 μm, wherein the machine direction (MD) 1% secant modulus is measured according to ASTM D 882 method.

2. The film of claim 1, wherein the film has a needle punch strength / μm (mN / μm) from greater than about 90 mN / μm to less than about 150 mN / μm, wherein the needle punch strength / μm (mN / μm) is measured according to the CEN 14477 method.

3. The film according to any one of claims 1 to 2, wherein the homopolymer polypropylene has a molecular weight of from about 0.8 g / cm 3 To about 0.98g / cm 3 The density of the composite is measured according to ASTM D792-13 method.

4. The film of any one of claims 1 to 3, wherein the homopolypropylene has a tensile strength at yield of from about 20 MPa to about 100 MPa, as determined according to ASTM D638.

5. A film comprising a polyolefin composition, wherein the polyolefin composition comprises from about 60 wt % to about 95 wt % of BOCD polyethylene and from about 5 wt % to about 40 wt % of homopolypropylene, based on the weight of the polyolefin composition, wherein the BOCD polyethylene contains from about 70 mol % to about 99 mol % of polymer units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene, and has a density of about 0.918 g / cm 3 , which is measured according to ASTM D-792, and a melt index (MI, or I 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16 kg), and the BOCD polyethylene has a composition distribution breadth index (CDBI) of about 38.6 wt%, or wherein the BOCD polyethylene contains from about 70 mol % to about 99 mol % of polymer units derived from ethylene, based on the total moles of polymer units of the BOCD polyethylene, and has a density of about 0.915 g / cm 3 , which is measured according to ASTM D-1505, and a melt index (MI, or I 2.16 ), which is measured according to ASTM D-1238-E (190°C / 2.16kg), and the BOCD polyethylene has a composition distribution breadth index (CDBI) of about 43 wt%, wherein the homopolypropylene has a melt index of 3.2 g / 10 min, as measured according to ASTM D1238-L (230° C. / 2.16 kg), wherein the film is manufactured by a casting process, and subsequently the film is subjected to machine direction orientation (MDO) with a stretch ratio of 3X to 5X, and wherein the film has a machine direction (MD) 1% secant modulus from greater than about 410 MPa to less than about 780 MPa, measured when the film has a thickness of about 25 μm, wherein the machine direction (MD) 1% secant modulus is measured according to ASTM D 882 method.

6. The film of claim 5, wherein the homopolypropylene has a 3 A density of 200 MPa to 100 MPa as measured by ASTM D792-13; and / or, the homopolypropylene has a yield tensile strength of from about 20 MPa to about 100 MPa as measured by ASTM D638.

7. The film of claim 5 or 6, wherein the film has a needle punch strength / μm (mN / μm) from greater than about 90 mN / μm to less than about 150 mN / μm, wherein the needle punch strength / μm (mN / μm) is measured according to the CEN 14477 method.

8. Industrial packaging comprising the film according to any one of claims 1 to 7.

9. Food packaging comprising the film according to any one of claims 1 to 7.

10. The method for manufacturing a film according to any one of claims 1 to 7, wherein the polyolefin composition is manufactured into a film by a casting method, and subsequently the film is subjected to machine direction orientation (MDO) with a stretch ratio of 3X to 5X.

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