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WO2020222916A1 - Films de polyoléfine contenant des structures de polyoléfine allongées formées in situ - Google Patents

Films de polyoléfine contenant des structures de polyoléfine allongées formées in situ Download PDF

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Publication number
WO2020222916A1
WO2020222916A1 PCT/US2020/022267 US2020022267W WO2020222916A1 WO 2020222916 A1 WO2020222916 A1 WO 2020222916A1 US 2020022267 W US2020022267 W US 2020022267W WO 2020222916 A1 WO2020222916 A1 WO 2020222916A1
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Prior art keywords
polyolefin
film
polymer
stretching
density
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Inventor
Nino RUOCCO
Joseph A. THROCKMORTON
Tamara L. BLANTON
Brian J. ROHDE
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ExxonMobil Chemical Patents Inc
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ExxonMobil Chemical Patents Inc
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/92—Measuring, controlling or regulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92704—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed

Definitions

  • TITLE POLYOLEFIN FILMS HAYING IN-SITU FORMED ELONGATED
  • This invention relates to films with elongated reinforcing structures therein.
  • elongated reinforcing structures e.g., structures having an aspect ratio of 3 or greater
  • elongated reinforcing structures include cellulose, clay, and pre-formed elongated polymer structures.
  • Forming films containing aligned elongated reinforcing structures involves combining a polymer with the elongated reinforcing structures and extruding the polymer composition into a film. Extrusion typically mechanically aligns the elongated reinforcing structures in the polymer matrix.
  • the improvement in strength and stiffness can be negatively impacted by incompatibility or poor compatibility between the polymer matrix and the elongated reinforcing structures.
  • the polymer matrix and the elongated reinforcing structures are not compatible at their interface, there can be poor interaction between and poor load transfer from the polymer matrix to the elongated reinforcing structures.
  • references of interest include: (a) Ruland W. (1969)“Small-Angle Scattering Studies on Carbonized Cellulose Fiberts,” J. Polymer Sci. Part C. No. 28, pp. 143-151; (b) Stribeck N. (2007) X-Ray Scattering of Soft Matter, Springer; (c) Liang, S. et al. (2008) “Unique Crystal Morphology and Tensile Properties of Injection-Molded Bar of LLDPE by Adding HDPE with Different Molecular Weights, Acta Materialia, v.56(l) pp.
  • the present disclosure relates to film and methods of forming films that comprise elongated polyolefin structures that are formed in-situ. More specifically, the compositions and methods described herein use a two-polyolefin blend where each polyolefin has a similar molecular weight but different density. A film produced therefrom can then be heated and stretched to form elongated polyolefin structures therein.
  • the present disclosure includes a method comprising: extruding a film from a polymer melt comprising a first polyolefin and 0.1 wt% to 30 wt% of a second polyolefin, wherein the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin, wherein a melt flow index of the first polyolefin is within 25% of a melt flow index of the second polyolefin, and wherein a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film has a multimodal, typically bimodal, differential scanning calorimetry melting profile above 40°C; and stretching the film while the film is at a temperature from 25 °C to below the melting point of the second polyolefin to form elongated polyolefin structures in-situ in the film.
  • reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film refers to a blend of the same first polyolefin and the same second polyolefin used in the polymer melt to make the film, where the first polyolefin is present in the reference polymer blend at the same wt% the first polyolefin is present in the polymer melt used to make the film and the second polyolefin is present in the reference polymer blend at the same wt% the second polyolefin is present in polymer melt used to make the film.
  • this relationship is specific to a layer and is not generalized across multiple layers.
  • first and second polyolefin in the polymer melt and the film are considered to be the same as in the polymer blend used to make the polymer melt.
  • the polymer blend of first and second polyolefins used to make the polymer melt is preferably used as the "reference polymer blend.”
  • the present disclosure also includes a film comprising a first polyolefin and 0.1 wt% to 30 wt% of a second polyolefin, wherein the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin, wherein a melt flow index of the first polyolefin is within 25% of a melt flow index of the second polyolefin, and wherein a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film has a multimodal, typically bimodal, differential scanning calorimetry melting profile at temperatures above 40°C.
  • FIGS. 1A-1C illustrate x-ray scattering patterns with a circular shape, an oblong shape, and a streaked shape, respectively.
  • FIG. 2 illustrates a non-limiting example of a system suitable for forming the films of the present disclosure having in-situ elongated polyolefin structures therein.
  • FIG. 3 is the DSC melting and crystallization profiles for the individual PolyA and PolyB and a blend of PolyA:PolyB at a weight ratio of 90: 10.
  • FIG. 4 is a photograph of the final stretched specimen for the 90: 10 specimen at the three temperatures investigated.
  • FIG. 5 includes a plot of the stress as a function of time during stretching of the specimen for the 90:10 specimen at 80°C along with SAXS scattering pattern data corresponding to five time points during the stretching, during cooling, and after cooling.
  • FIG. 6 is a plot of the stress as a function of time during stretching of the specimen for the 90: 10 specimen at the three stretching temperatures.
  • FIG. 7A includes representative 2-D and 3-D phase 2 AFM scans of the 25°C stretched specimen.
  • FIG. 7B includes representative 2-D and 3-D phase 2 AFM scans of the 70°C stretched specimen.
  • FIG. 7C includes representative 2-D and 3-D phase 2 AFM scans of the 80°C stretched specimen.
  • compositions and methods described herein use a two-polyolefin blend where each polyolefin has a similar molecular weight but different density.
  • a film produced therefrom can then be heated and stretched to form elongated polyolefin structures therein.
  • the first polyolefin (the major component) is a lower density polyolefin than the second polyolefin (the minor component).
  • the higher density for the second polyolefin should be such that the polymer melt of the first and second polyolefins has a multimodal, typically bimodal, differential scanning calorimetry (DSC) melting profile at temperatures above 40°C.
  • DSC differential scanning calorimetry
  • the second, higher density polyolefin remains crystalline while the first, lower density polyethylene softens.
  • the crystalline, second, higher density polyolefin then is thought to act as a nucleation and/or growth site where, as the first, lower density polyethylene cools, it crystallizes around the crystalline, second, higher density polyolefin to form elongated polyolefin structures in the film in-situ.
  • the size and orientation of the elongated polyolefin structures depend on the temperature during stretching and degree of stretching.
  • the elongated polyolefin structures impart strength to the film much like an elongated filler particle would if included in the original polymer melt.
  • the size, orientation, and other properties of the elongated polyolefin structures can be tailored based on the properties of the two polyolefins, the temperature of stretching, and the degree of stretching. Therefore, advantageously, a variety of fillers to include in the polymer melt are not needed, instead, commercial film stretching machines can be modified to tailor the elongated polyolefin structures and film property.
  • room temperature is 25 °C.
  • An“olefin,” alternatively referred to as“alkene,” is a linear, branched, or cyclic compound of carbon and hydrogen having at least one double bond.
  • A“polymer” has two or more of the same or different mer units.
  • A“homopolymer” is a polymer having mer units that are the same.
  • the term“polymer” as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc.
  • the term“polymer” as used herein also includes impact, block, graft, random, and alternating copolymers.
  • the term “polymer” shall further include all possible geometrical configurations unless otherwise specifically stated. Such configurations may include isotactic, syndiotactic, and random symmetries.
  • the term“copolymer(s)” refers to polymers formed by the polymerization of at least two different monomers (i.e., mer units).
  • the term“copolymer” includes the copolymerization reaction product of propylene and an alpha-olefin, such as ethylene, 1 -hexene.
  • A“terpolymer” is a polymer having three mer units that are different from each other.
  • the term“copolymer” is also inclusive terpolymers and tetrapolymers, such as, for example, the copolymerization product of a mixture of ethylene, propylene, 1 -hexene, and 1-octene.
  • “Different” as used to refer to monomer mer units indicates that the mer units differ from each other by at least one atom or are different isomerically.
  • An "ethylene polymer” or “ethylene copolymer” is a polymer or copolymer comprising at least 50 mole% ethylene derived units
  • a "propylene polymer” or “propylene copolymer” is a polymer or copolymer comprising at least 50 mole% propylene derived units, and so on.
  • a polymer when referred to as "comprising, consisting of, or consisting essentially of" a monomer, the monomer is present in the polymer in the polymerized form of the monomer or is the derivative form of the monomer.
  • a copolymer when a copolymer is said to have an "ethylene" content of 35 wt% to 55 wt%, it is understood that the mer unit in the copolymer is derived from ethylene in the polymerization reaction and said derived units are present at 35 wt% to 55 wt%, based upon the weight of the copolymer.
  • Density in g/cm 3 is determined in accordance with ASTM 1505-10 and molded based on ASTM D4703-10a, procedure C, plaque preparation. A plaque is made and conditioned for at least forty hours at 23 °C to approach equilibrium crystallinity, measurement for density is then made in a density gradient column.
  • Mn is number average molecular weight
  • Mw is weight average molecular weight
  • Mz is z- average molecular weight.
  • Polydispersity index (PDI) is defined to be Mw divided by Mn. Unless otherwise noted, all molecular weights (e.g., Mw, Mn, Mz) are reported in units of g/mol. Molecular weight distribution is a graph of the concentration of polymer as a function of molecular weight.
  • GPC is a liquid chromatography technique widely used to measure the molecular weight, molecular weight distribution, and polydispersity) of polymers. This is a common and well-known technique. Such characteristics, as described here, can be measured using the techniques described below.
  • the distribution and the moments of molecular weight (e.g., Mw, Mn, Mz, Mw/Mn) and the comonomer content (e.g., C2, C3, Ce) can be determined by using a high temperature Gel Permeation Chromatography (Polymer Char GPC-IR) equipped with a multiple-channel band-filter based Infrared detector IR5, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10-pm Mixed-B LS columns can be used to provide polymer separation.
  • TCB Aldrich reagent grade 1,2,4-trichlorobenzene
  • BHT butylated hydroxytoluene
  • the TCB mixture can be filtered through a 0. 1 -pm Teflon filter and degassed with an online degasser before entering the GPC instrument.
  • the nominal flow rate can be 1.0 mL/min, and the nominal injection volume can be 200 qL.
  • the whole system including transfer lines, columns, and detectors can be contained in an oven maintained at 145°C.
  • the polymer sample can be weighed and sealed in a standard vial with 80-pL flow marker (heptane) added to it.
  • polymer After loading the vial in the autosampler, polymer can be automatically dissolved in the instrument with 8 mL added TCB solvent.
  • the polymer can be dissolved at 160°C with continuous shaking for about 1 hour for most polyethylene samples or 2 hour for polypropylene samples.
  • the TCB densities used in concentration calculation can be 1.463 g/ml at room temperature and 1.284 g/mL at 145°C.
  • the sample solution concentration can be from 0.2 to 2.0 mg/mL, with lower concentrations being used for higher molecular weight samples.
  • the mass recovery can be calculated from the ratio of the integrated area of the concentration chromatography over elution volume and the injection mass, which is equal to the pre-determined concentration multiplied by injection loop volume.
  • the conventional molecular weight can be determined by combining universal calibration relationship with the column calibration, which can be performed with a series of monodispersed polystyrene (PS) standards ranging from 700 to 10,000,000 gm/mole.
  • PS monodispersed polystyrene
  • the molecular weight at each elution volume can be calculated with (1):
  • a 0.695 and K is 0.000579*(l-0.0087*w2b+0.000018*(w2b) /v 2) for ethylene-butene copolymer where w2b is a bulk weight percent of butene comonomer
  • a 0.695 and K is 0.000579*(l-0.0075*w2b) for ethylene-hexene copolymer where w2b is a bulk weight percent of hexene comonomer
  • a 0.695 and K is 0.000579*(l-0.0077*w2b) for ethylene-octene copolymer where w2b is a bulk
  • the comonomer composition can be determined by the ratio of the IR5 detector intensity corresponding to CPE and CPE channel calibrated with a series of polyethylene and propylene homo/copolymer standards whose nominal value are predetermined by NMR or FTIR. In particular, this provides the methyls per 1,000 total carbons (CPE/IOOOTC) as a function of molecular weight.
  • the short-chain branch (SCB) content per lOOOTC (SCB/1000TC) can be then computed as a function of molecular weight by applying a chain- end correction to the CPE/IOOOTC function, assuming each chain to be linear and terminated by a methyl group at each end.
  • the weight % comonomer can be then obtained from the following expression in which / is 0.3, 0.4, 0.6, 0.8, and so on for C3, C4, Ce, Cs, and so on co monomers, respectively:
  • the bulk composition of the polymer from the GPC-IR and GPC-4D analyses can be obtained by considering the entire signals of the CPE and CPE channels between the integration limits of the concentration chromatogram. First, the following ratio is obtained.
  • Bulk IR ratio Area of CH2 signal within integration limits EQ. 3 [0036] Then the same calibration of the CH3 and CH2 signal ratio, as mentioned previously in obtaining the CH3/IOOOTC as a function of molecular weight, can be applied to obtain the bulk CH3/IOOOTC.
  • a bulk methyl chain ends per lOOOTC (bulk CH 3 end/1000TC) can be obtained by weight- averaging the chain-end correction over the molecular- weight range.
  • w2b f * bulk CH3/1000TC EQ. 4
  • bulk SCB/1000TC bulk CH3/1000TC - bulk CH3end/1000TC EQ. 5 and bulk SCB/1000TC can be converted to bulk w2 in the same manner as described above.
  • the LS detector can be the 18-angle Wyatt Technology High Temperature DAWN HELEOSII.
  • the LS molecular weight (M) at each point in the chromatogram can be determined by analyzing the LS output using the Zimm model for static light scattering ( Light Scattering from Polymer Solutions, Huglin, M. B., Ed.; Academic Press, 1972.):
  • AR(0) is the measured excess Rayleigh scattering intensity at scattering angle Q
  • c is the polymer concentration determined from the IR5 analysis
  • A2 is the second virial coefficient
  • R(q) is the form factor for a monodisperse random coil
  • K 0 is the optical constant for the system:
  • NA is Avogadro’s number
  • (dn/dc) is the refractive index increment for the system.
  • a high temperature Viscotek Corporation viscometer which has four capillaries arranged in a Wheatstone bridge configuration with two pressure transducers, can be used to determine specific viscosity.
  • One transducer measures the total pressure drop across the detector, and the other, positioned between the two sides of the bridge, measures a differential pressure.
  • the specific viscosity, h s for the solution flowing through the viscometer is calculated from their outputs.
  • the intrinsic viscosity, [h] at each point in the chromatogram is calculated from the following equation:
  • the branching index (g' v is) is calculated using the output of the GPC-DRI-LS-VIS method as follows.
  • the average intrinsic viscosity, [h] av g of the sample is calculated by:
  • the branching index g’ vjs is defined as: g'vis [hL g
  • M v is the viscosity-average molecular weight based on molecular weights determined by LS analysis.
  • a high temperature viscometer such as those made by Technologies, Inc. or
  • Viscotek Corporation which has four capillaries arranged in a Wheatstone bridge configuration with two pressure transducers, can be used to determine specific viscosity.
  • One transducer measures the total pressure drop across the detector, and the other, positioned between the two sides of the bridge, measures a differential pressure.
  • the specific viscosity, , for the solution flowing through the viscometer can be calculated from their outputs.
  • the intrinsic viscosity, [h], at each point in the chromatogram can be calculated from the equation
  • /c, where c is concentration and is determined from the IR5 broadband channel output.
  • a“peak” occurs where the first derivative of the corresponding curve changes sign from positive value to negative value.
  • a“valley” occurs where the first derivative of the corresponding curve changes from a negative value to a positive value.
  • a“mode” is a local minimum or local maximum depending on the measurement and plotting.
  • Molecular weights are plotted as molecular weight (g/mol or kg/mol) (x-axis) versus number of molecules (y-axis). Accordingly, modes for molecular weight are peaks.
  • Differential scanning calorimetry (DSC) measurements from which melting point or melting temperature (Tm) and crystallization temperature (Tc) are derived, are plotted as temperature (x-axis) versus heat flow (W/g) (y-axis). Because melting temperatures occur at reductions in heat flow during heating, melting temperature modes are valleys on the DSC plot. Because crystallization temperature occur at higher heat flow during cooling, crystallization temperature modes are peaks on the DSC plot.
  • Modes for molecular weight plots are identified above a molecular weight of 5,000 g/mol.
  • Modes for DSC plots are identified above a temperature of 40°C.
  • multimodal is a plot having two or more modes.
  • “monomodal” is a plot having one mode.
  • “bimodal” is a plot having two modes.
  • Melt flow index (MFI) or was measured according on a Goettfert MI-4 Melt Indexer. Testing conditions were set at 190°C and 2.16 kg load. An amount of 5 g to 6 g of sample was loaded into the barrel of the instrument at 190°C and manually compressed. Afterwards, the material was automatically compacted into the barrel by lowering all available weights onto the piston to remove all air bubbles. Data acquisition was started after a 6 min pre-melting time. Also, the sample was pressed through a die of 8 mm length and 2.095 mm diameter.
  • Heavy load melt flow index (HLMFI) or hi is determined according to ASTM D-1238-E (190°C/21.6 kg).
  • Melt index ratio is the ratio of I21/I2.
  • DSC differential scanning calorimetry
  • the melting temperature (T m ) and crystallization temperature (T c ) were calculated by integrating the melting and crystallization peaks (area below the curves).
  • T m melting temperature
  • T c crystallization temperature
  • SAXS Small angle x-ray scattering
  • the azimuthally distributed scans of intensities at different scattering vector (q) values are analyzed using the Lorentz function to yield the average width of the angular distribution.
  • the width of the equatorial streaks in the reciprocal space can be related to obtain the length of the elongated polyolefin structures.
  • the relationship between the L and B f can be approximated as EQ. 8
  • the elongated polyolefin structures’ length (L) and degree of misorientation (B f ) are determined by the linear least square fitting (XPolar software, available from Precision Works) applied to the data.
  • XPolar software available from Precision Works
  • q 4p s me (where Q is the scattering angle, q is the scattering vector, and l is the wavelength).
  • a“continuous phase” of a film is the portion of the material phase in which a“discontinuous phase” is dispersed.
  • the term“extruding” and grammatical variations thereof refer to processes that includes forming a polymer and/or polymer blend into a melt, such as by heating and/or sheer forces, and then forcing the melt out of a die in a desirable form or shape such as in a film.
  • Most any type of apparatus will be appropriate to effect extrusion such as a single or twin-screw extruder, or other melt-blending device as is known in the art and that can be fitted with a suitable die.
  • the films described herein comprise (1) a continuous phase that comprises a first polyolefin and (2) a discontinuous phase of elongated polyolefin structures that comprise a second polyolefin.
  • the second polyolefin can be present in the film at about 0.1 wt % to about 30 wt %, or about 1 wt% to about 20 wt%, or about 5 wt% to about 15 wt%, or about 0.1 wt% to about 15 wt% based on the total weight of the first polyolefin and the second polyolefin.
  • the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin; a melt flow index (190°C, 2.16 kg) of the first polyolefin is within 25% of a melt flow index (190°C, 2.16 kg) of the second polyolefin; and a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film has a multimodal, such as bimodal, DSC melting profile above 40°C.
  • Methods of producing such films can comprise: extruding a film from a polymer melt comprising the first polyolefin and 0.1 wt% to 30 wt% of the second polyolefin; and stretching the film while the film is at a temperature from 25 °C to below the melting point of the second polyolefin to form the elongated polyolefin structures in-situ in the film.
  • the first polyolefin described herein is a major component of the polymeric composition of the film.
  • the first polyolefin can be present at about 70 wt% to about 99.9 wt% or about 99 wt% to about 80 wt%, or about 95 wt% to about 85 wt%, or about 99.9 wt% to about 85 wt% relative to the combined first and second polyolefin weight of the polymeric composition.
  • the second polyolefin described herein is a minor component of the polymeric composition of the film.
  • the second polyolefin can be present at about 0.1 wt% to about 30 wt%, or about 1 wt% to about 20 wt%, or about 5 wt% to about 15 wt%, or about 0.1 wt% to about 15 wt% relative to the combined first and second polyolefin weight of the polymeric composition.
  • the first and second polyolefins are preferably similar in molecular weight. Without being limited by theory, it is believed that having the MFIs of the two polyolefins within 25% (or within 20%, or within 15%, or within 10%, or within 5%) provides a similar enough molecular weight that the two polyolefins blend homogeneously.
  • a “homogeneous” blend refers to a blend of polymers that do not phase separate when mixing the molten polymers and during the initial extrusion at film forming conditions.
  • melt flow index provides an indication of molecular weight of a polyolefin.
  • the melt flow index of the first polyolefin (MFTpi) is within 25% of the melt flow index of the second polyolefin (MFfe) as described in EQ. 9.
  • An alternative way to characterize the molecular weight of the two polyolefins is by molecular weight distribution of the blend of the two polyolefins.
  • the blend of the two polyolefins at the relative concentrations as in the film can optionally have a monomodal plot of molecular weight (or a monomodal molecular weight distribution).
  • the lower concentration of the second polyolefin and similar molecular weights of the first and second polyolefins provide a good dispersion of the second polyolefin throughout the polymer melt so that individual elongated polyolefin structures can be formed.
  • first polyolefins include, but are not limited to, ethylene homopolymers, propylene homopolymers, ethylene copolymers, propylene copolymers, and the like, and any combination thereof that comport with the prescribed density, melt flow index, and multimodal, preferably bimodal, DSC melting profile.
  • second polyolefins include, but are not limited to, ethylene homopolymers, propylene homopolymers, ethylene copolymers, propylene copolymers, and the like, and any combination thereof that comport with the prescribed density, melt flow index, and multimodal, preferably bimodal, DSC melting profile.
  • Ethylene copolymers typically comprises 51 wt% to 98 wt% (or 51 wt% to 70 wt%, or 60 wt% to 80 wt%, or 75 wt% to 95 wt%, or 90 wt% to 98 w%) of polymer units derived from ethylene, 2 wt% to 49 wt% (or 2 wt% to 10 wt%, or 5 wt% to 25 wt%, or 20 wt% to 40 wt%, or 30 wt% to 49 wt%) of polymer units derived from one or more C3 to C20 alpha-olefin comonomers, and 0 wt% to 10 wt% (or 0 wt%, or 0 wt% to 5 wt%, or 1 wt% to 6 wt%, or 3 wt% to 8 wt%, or 5 wt% to 10 wt%) polymer
  • Propylene copolymers typically comprise 51 wt% to 98 wt% (or 51 wt% to 70 wt%, or 60 wt% to 80 wt%, or 75 wt% to 95 wt%, or 90 wt% to 98 w%) of polymer units derived from propylene, 2 wt% to 49 wt% (or 2 wt% to 10 wt%, or 5 wt% to 25 wt%, or 20 wt% to 40 wt%, or 30 wt% to 49 wt%) of polymer units derived from one or more ethylene and/or C4 to C20 alpha-olefin comonomers, and 0 wt% to 10 wt% (or 0 wt%, or 0 wt% to 5 wt%, or 1 wt% to 6 wt%, or 3 wt% to 8 wt%, or 5 wt% to 10 wt%
  • the diene may be any hydrocarbon structure having at least two unsaturated bonds wherein at least one of the unsaturated bonds is readily incorporated into a polymer.
  • dienes include, but are not limited to, straight chain acyclic olefins such as 1,4-hexadiene and 1,6-octadiene; branched chain acyclic olefins such as 5 -methyl- 1,4-hexadiene, 3,7- dimethyl-l,6-octadiene, and 3,7-dimethyl-l,7-octadiene; single ring alicyclic olefins such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, and 1,7-cyclododecadiene; multi-ring alicyclic fused and bridged ring olefins such as tetrahydroindene, norbornadiene, methyl-tetrahydroindene, di
  • the first and second polyolefins are the same type of polyolefin.
  • the first and second polyolefins may both be ethylene homopolymers that each comport with the prescribed density, melt flow index, and multimodal, such as bimodal, DSC melting profile.
  • the first and second polyolefins may both be propylene homopolymers that each comport with the prescribed density, melt flow index, and multimodal, such as bimodal, DSC melting profile.
  • the first and second polyolefins may be different types of polyolefins.
  • the first polyolefin may be an ethylene homopolymer or an ethylene copolymer
  • the second polyolefin may be a propylene homopolymer or a propylene copolymer (or vice versa)
  • each of the first and second polyolefins comport with the prescribed density, melt flow index, and multimodal, such as bimodal, DSC melting profile
  • the first polyolefin may be an ethylene homopolymer
  • the second polyolefin may be an ethylene copolymer (or vice versa), where each of the first and second polyolefins comport with the prescribed density, melt flow index, and multimodal, such as bimodal, DSC melting profile.
  • the first polyolefin may be a propylene homopolymer
  • the second polyolefin may be a propylene copolymer (or vice versa)
  • each of the first and second polyolefins comport with the prescribed density, melt flow index, and multimodal, such as bimodal, DSC melting profile.
  • the first and second polyolefins are compatible so that a homogenous blend is achieved before casting the film.
  • both the first and second polyolefin are ethylene polymers.
  • both the first and second polyolefin are propylene polymers.
  • the ethylene polymers useful herein are selected from ethylene homopolymers and ethylene copolymers.
  • the method of making the ethylene polymers is not critical, as it can be made by slurry, solution, gas phase, high pressure, or other suitable processes, and by using catalyst systems appropriate for the polymerization of polyethylenes, such as Ziegler-Natta-type catalysts, chromium catalysts, metallocene-type catalysts, other appropriate catalyst systems, or combinations thereof, or by free-radical polymerization.
  • the ethylene polymers are made by the catalysts, activators, and processes described in US Patent Nos.
  • the ethylene polymers are metallocene polyethylenes (mPEs).
  • the ethylene copolymer comprises one or more mPEs, such as those described in US Patent Application Publication No. 2007/0260016, US Patent No. 6,476,171, and US Patent No. 6,255,426.
  • the ethylene polymer comprises a Ziegler-Natta polyethylene.
  • the ethylene polymer is produced using chrome based catalysts, such as, for example, in US Patent No. 7,491,776, including that fluorocarbon does not have to be used in the production.
  • chrome based catalysts such as, for example, in US Patent No. 7,491,776, including that fluorocarbon does not have to be used in the production.
  • Commercial examples of polymers produced by chromium include the PAXONTM grades of polyethylene produced by ExxonMobil Chemical Company, Houston Texas.
  • the ethylene polymer comprises substantially linear and linear ethylene polymers (SLEPs).
  • SEPs substantially linear and linear ethylene polymers
  • Substantially linear ethylene polymers and linear ethylene polymers and their method of preparation are fully described in US Patent Nos. 5,272,236; 5,278,272; 3,645,992; 4,937,299; 4,701,432; 4,937,301; 4,935,397; 5,055,438; EP 129,368; EP 260,999; and WO 1990/007526, which are fully incorporated herein by reference.
  • a linear or substantially linear ethylene polymer means a homopolymer of ethylene or a copolymer of ethylene and one or more alpha-olefin comonomers having a linear backbone (i.e. no cross linking), a specific and limited amount of long-chain branching or no long-chain branching, a narrow molecular weight distribution, a narrow composition distribution (e.g., for alpha-olefin copolymers) or a combination thereof. More explanation of such polymers is discussed in US Patent No. 6,403,692, which is incorporated herein by reference for all purposes.
  • the ethylene polymers is produced by gas-phase polymerization of ethylene and, optionally, an C3 to C20 alpha-olefin using transition metal catalyst(s), such as traditional Ziegler-Natta catalysts or metallocene catalysts, useful examples include bis(n-C3-4 alkyl cyclopentadienyl) hafniumX2, or(cyclopentadienyl)(propyl,tetramethyl- cyclopentadienyl)hafniumX2, where X is a leaving group, such as halogen or Ci to C2oalkyl.
  • transition metal catalyst(s) such as traditional Ziegler-Natta catalysts or metallocene catalysts
  • useful examples include bis(n-C3-4 alkyl cyclopentadienyl) hafniumX2, or(cyclopentadienyl)(propyl,tetramethyl- cyclopentadienyl)hafniumX2, where X is a leaving group,
  • metalocene catalyst refers to a catalyst having at least one transition metal compound containing one or more substituted or unsubstituted Cp moiety (typically two Cp moieties) in combination with a Group 4, 5, or 6 transition metal.
  • Preferred ethylene polymers and copolymers that are useful in this invention include those sold by ExxonMobil Chemical Company in Houston Texas, including those sold as EXXONMOBILTM HDPE, EXXONMOBILTM LLDPE, and EXXONMOBILTM LDPE; and those sold under the ENABLETM , EXACTTM, EXCEEDTM, ESCORENETM, EXXCOTM, ESCORTM, PAXONTM, and OPTEMATM tradenames.
  • Particularly useful grades include EXCEEDTM 1018 LLDPE, ENABLETM 2010 polyethylene, and the LDPETM 103 series.
  • the first polyolefin may have a density of 0.850 g/cm 3 to 0.930 g/cm 3 , or 0.860 g/cm 3 to 0.910 g/cm 3 , or 0.880 g/cm 3 to 0.900 g/cm 3 .
  • the second polyolefin may have a density of 0.890 g/cm 3 to 0.970 g/cm 3 , or 0.910 g/cm 3 to 0.970 g/cm 3 , or 0.930 g/cm 3 to 0.960 g/cm 3 .
  • the foregoing densities should be chosen such that the second polyolefin has a density of at least 0.04 g/cm 3 , or at least 0.055 g/cm 3 , or 0.04 g/cm 3 to 0.12 g/cm 3 , or 0.05 g/cm 3 to 0.10 g/cm 3 greater than a density of the first polyolefin.
  • the first and second polyolefins may independently have a melt flow index of 0.2 g/10 min to 10 g/10 min, or of 0.4 g/10 min to 6 g/10 min, or of 0.5 g/10 min to 3 g/10 min such that the melt flow index of the first polyolefin is within 25%, or within 0% to 25%, (0% meaning the melt flow indices are the same), or within 0.01% to 25%, or within 1% to 20%, or within 10% to 15%or within 5% to 10%, preferably within 0% to 5% of a melt flow index of the second polyolefin.
  • the polymer blend used to make the melt e.g., a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film
  • the lower melting temperature (Tm) of the bimodal DSC melting profile is above 40°C, or above 50°C, or above 60°C, or above 70°C, or above 80°C.
  • Tm melting temperature
  • a melting peak corresponding to the first polyolefin may be at about 50°C to about 180°C, or about 60°C to about 175 °C, or about 70°C to about 170°C; and a melting peak corresponding to the second polyolefin may be at about 80°C to about 200°C, or about 90°C to about 190°C, or about 100°C to about 185°C.
  • the melting peak of the second polyolefin minus the melting peak of the first polyolefin may be about 25°C to about 100°C, or about 35°C to about 85°C, or about 45°C to about 65°C.
  • the lower melting temperature (Tm) of the bimodal DSC melting profile is above 40°C, or above 50°C, or above 60°C, or above 70°C, or above 80°C.
  • Tm melting temperature
  • a melting peak corresponding to the first polyethylene may be at about 50°C to about 100°C, or about 60°C to about 95 °C, or about 70°C to about 90°C; and a melting peak corresponding to the second polyethylene may be at about 80°C to about 150°C, or about 90°C to about 145°C, or about 100°C to about 140°C.
  • the melting peak of the second polyethylene minus the melting peak of the first polyethylene may be about 25 °C to about 100°C, or about 35°C to about 85°C, or about 45°C to about 65°C.
  • the lower melting temperature (Tm) of the bimodal DSC melting profile is above 70°C, or above 90°C, or above 110°C.
  • Tm melting temperature
  • a melting peak corresponding to the first polypropylene may be at about 70°C to about 180°C, or about 90°C to about 175°C, or about 100°C to about 170°C; and a melting peak corresponding to the second polypropylene may be at about 100°C to about 200°C, or about 120°C to about 190°C, or about 140°C to about 185°C.
  • the melting peak of the second polypropylene minus the melting peak of the first polypropylene may be about 25 °C to about 100°C, or about 35°C to about 85°C, or about 45°C to about 65 °C.
  • the polyolefin film and/or polyolefin melt can further comprise additives.
  • additives include, but are not limited to, stabilization agents (e.g., antioxidants or other heat or light stabilizers), anti-static agents, crosslink agents or co-agents, crosslink promoters, release agents, adhesion promoters, plasticizers, anti-agglomeration agents (e.g., oleamide, stearamide, emcamide or other derivatives with the same activity), and fillers (e.g., substantially spherical fillers having an aspect ratio of 1 to 3 like silica particle and titania particles).
  • stabilization agents e.g., antioxidants or other heat or light stabilizers
  • anti-static agents e.g., crosslink agents or co-agents
  • crosslink promoters e.g., release agents, adhesion promoters, plasticizers
  • anti-agglomeration agents e.g., oleamide, stearamide
  • the polyolefin film and/or polyolefin melt have an absence of particles or compositions having an aspect ratio greater than 3 aside from the in-situ formed elongated polyolefin structures of the film.
  • the absence is an absence of material added relative to the manufactured polyolefin.
  • the first and second polyolefins, as manufactured may have up to 2 wt% of particulates therein without any filler being added. The size and shape of such particulates depends on the manufacturing materials and process parameters.
  • the polyolefin film and/or polyolefin melt contains less than 1 wt% of additives cumulatively, based on the total weight of the first and second polyolefins.
  • the amount of the additives cumulatively may range from a 0.01 wt% to 1 wt%, or 0.02 wt% to 0.5 wt%, or 0.05 wt% to 0.1 wt%.
  • the polyolefin film and/or polyolefin melt contains less than 1 wt% of added filler, based on the total weight of the first and second polyolefins.
  • the amount of added filler is less than 0.5 wt%, or less than 0.1 wt%, or less than 0.05 wt%, or less than 0.01 wt%.
  • added filler is present at 0 wt%.
  • the films produced herein are typically initially formed by extrusion (such as cast extrusion) of a polymer melt comprising the first and second polyolefins. Then, the film is stretched at a temperature from 25 °C to below the melting point of the second polyolefin to form the elongated polyolefin structures in-situ in the film. Between forming and stretching the film, the film may be cooled (or quenched) or it may be maintained at elevated temperatures. Without being limited by theory, it is believed that cooling below the crystallization temperature of the second polyolefin after forming the film and before stretching may allow for the second polyolefin to crystallize and create nucleation/growth sites for the elongated polyolefin structures.
  • FIG. 2 illustrates a non-limiting example of a system 100 suitable for forming the films of the present disclosure having in-situ elongated polyolefin structures therein.
  • An extruder 104 having a hopper 102 for adding a mixture of the first and second polyolefins as well as any optional additive included in the formulation.
  • the extruder 104 illustrated has four temperature zones 104a- 104d that may be at different temperatures suitable for melting and blending the first and second polyolefins.
  • the resultant melt is extruded through a die 108, which is typically at an elevated temperature, and passed through a series of rollers 109-122 and 126-136.
  • the extruded melt is cooled and stretched to form a film.
  • the film is reheated with heating element 124 to a temperature from 25 °C to below the melting point of the second polyolefin and stretched using the rollers to form the elongated polyolefin structures in-situ in the film 138b.
  • the heating element 124 is positioned between rollers 122 and 126.
  • rollers may be heated to different temperatures to provide the film heating and cooling steps.
  • a system 100 may be operated at the polymer/film temperatures and roller speeds provided in Table 1. Because roller 122 and prior rollers 110-120 are all at the same speed and the following rollers 126-130 are at higher speed, the film stretches between rollers 122 and 126. Again, this is a non-limiting example and the stretching location, polymer/film temperatures, roller speeds, and other aspects of this example can be changed.
  • FIG. 2 illustrates a system 100 that incorporates the in-situ formation of the elongated polyolefin structures with the extrusion and film forming.
  • Other systems and methods can be implemented including forming the film on one system and then using rollers and heating elements in another system to form the elongated polyolefin structures in the film.
  • the film can be stretched while the film is at a temperature from 25°C to below the melting point of the second polyolefin to form the elongated polyolefin structures in-situ in the film.
  • the temperature may also be above 40 °C and below the melting point of the second polyolefin, or above 50°C and below the melting point of the second polyolefin, or above 60°C and below the melting point of the second polyolefin, or above 40°C and below 5°C below the melting point of the second polyolefin, or above 50 °C and below 5°C below the melting point of the second polyolefin, or above 60 °C and below 5°C below the melting point of the second polyolefin, or above 40°C and below 10°C below the melting point of the second polyolefin, or above 50°C and below 10°C below the melting point of the second polyolefin, or above 60°C and below 10°C below the melting point of the second polyolefin.
  • the temperature of stretching influences the length and the degree of misorientation of the elongated polyolefin structures in the film. For example, low temperatures may not allow the first polyolefin to soften enough to give the second polyolefins enough freedom of movement to orient in the stretch direction. Conversely, approaching the melting point of the second polyolefin may soften the second polyolefin such that its crystallinity is disrupted and it deforms, which may disrupt the orientation of the second polyolefin molecules in the stretch direction.
  • the film Before stretching, the film can be heated to the stretching temperature at a rate of 15°C/min to 100°C/min, or 30°C/min to 85°C/min, or 50°C/min to 75°C/min.
  • the stretching rate can be 25 microns per second (pm/s) to 200 pm/s, or 50 pm/s to 150 pm/s, or 75 pm/s to 125 pm/s.
  • the rate at which the film is heated before stretching, stretching rate, and the rate of quenching the film after heating and stretching may each also influence the length and the degree of misorientation of the elongated polyolefin structures in the film.
  • the films are stretched in the machine direction (MD) at up to 800%, preferably from 100% to 800%, or 100% to 500%, or 100% and 300%, or 140 to 250%, or 175% to 225%.
  • the film can be cooled (or quenched) to a temperature of 0°C to 40°C, or 10°C to 35°C, or 20°C to 30°C, or room temperature.
  • the film can be cooled at a rate of 15°C/min to 100°C/min, or 30°C/min to 85°C/min, or 50°C/min to 75°C/min. Cooling can be with a cooled gas like air, liquid nitrogen, or other cryogenic gas.
  • the film having the elongated polyolefin structures therein may have a thickness of 10 microns to 150 microns, or 15 microns to 100 microns, or 25 microns to 75 microns.
  • the film may contain one or more layers of the composition described herein, each of which may have a thickness of 10 microns to 150 microns, or 15 microns to 100 microns, or 25 microns to 75 microns.
  • the presence of the elongated polyolefin structures can be observed using small angle x-ray scattering (SAXS).
  • SAXS small angle x-ray scattering
  • the film before stretching has a circular scattering pattern, also referred to as an isotropic scattering pattern, (FIG. 1A), which indicates a homogenous film having randomly oriented lamellar structures.
  • FIG. 1A the appearance and growth of an equatorial streak
  • FWHM full width at half max
  • these structures are elongated polyolefin structures and not voids, which was confirmed with atomic force microscopy.
  • the equatorial streak from streaked SAXS patterns can be analyzed using the Ruland streak method.
  • the elongated polyolefin structures may have a length (L) per the Ruland streak method analysis of the SAXS scattering patterns of 0.1 microns to 10 microns, or 0.25 microns to 8 microns, or 0.5 microns to 5 microns, or 0.25 microns to 3 microns, or 0.5 microns to 3.5 microns, or 1 micron to 5 microns.
  • the elongated polyolefin structures may have a degree of misorientation (B f ) per the Ruland streak method analysis of the SAXS scattering patterns of 0.05 to 0.5, or 0.075 to 0.15, or 0.1 to 0.25, or 0.2 to 0.3. Lower values for the degree of misorientation indicates that the elongated polyolefin structures are more oriented in the machine direction.
  • the films described herein having elongated polyolefin structures therein formed by in-situ methods may be used as formed or may be laminated to other films or structures.
  • the films may be used as is or in other films/structures in a similar fashion to highly oriented films.
  • Examples of applications where the films described herein having elongated polyolefin structures therein formed by in-situ methods may be useful may include, but are not limited to, packaging, agriculture films, construction films, bubble wrap, trash bags, and the like.
  • one or more layers may be modified by corona treatment, electron beam irradiation, gamma irradiation, flame treatment, or microwave.
  • one or both of the surface layers is modified by corona treatment.
  • a non-limiting example embodiment is a method comprising: extruding a film from a polymer melt comprising a first polyolefin and 0.1 wt% to 30 wt% of a second polyolefin, wherein the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin, wherein a melt flow index of the first polyolefin is within 25% of a melt flow index of the second polyolefin, and wherein a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film has a multimodal (e.g., biomodal) differential scanning calorimetry melting profile above 40°C; and stretching the film while the film is at a temperature from 25 °C to below the melting point of the second polyolefin to form elongated polyolefin structures in-situ in the film.
  • multimodal e.g., biomodal
  • This embodiment can further include one or more of the following: Element 1: wherein the second polyolefin is present at 0.1 wt% to 15 wt%; Element 2: the method further comprising: cooling the film after extruding and before stretching to below a crystallization temperature of the second polyolefin; Element 3: Element 2 and heating the film after cooling and before stretching at a rate of 30°C/min to 90°C/min up to the temperature from 25 °C to below the melting point of the second polyolefin; Element 4: the method further comprising: cooling the film after stretching to a temperature of 0°C to 40°C; Element 5: Element 4 and wherein cooling is at a rate of 15°C/min to 100°C/min; Element 6: wherein the stretching is at a stretching rate of 50 microns per second (pm/s) to 200 pm/s; Element 7: wherein the first polyolefin is a first ethylene polymer (homopolymer or copo
  • combinations include, but are not limited to, Element 1 in combination with one or more of Elements 2-12; Element 2 and optionally Element 3 in combination with Element 4 and optionally Element 5 ; one or more of Elements 2-5 in combination with one or more of Elements 7-12; and two or more of Elements 7-12 in combination.
  • Another non-limiting example embodiment is a film comprising a first polyolefin and 0.1 wt% to 30 wt% of a second polyolefin, wherein the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin, wherein a melt flow index of the first polyolefin is within 25% of a melt flow index of the second polyolefin, and wherein a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film has a multimodal (e.g., biomodal) differential scanning calorimetry melting profile above 40°C.
  • multimodal e.g., biomodal
  • This embodiment can further include one or more of the following: Element 1; Element 7; Element 8; Element 9; Element 10; Element 11; and Element 13: wherein the film further comprises one or more additives selected from the group consisting of: a stabilization agent, an anti-static agent, a crosslink agent, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti-agglomeration agent.
  • a stabilization agent an anti-static agent
  • a crosslink agent e.g., a crosslink promoter, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti-agglomeration agent.
  • combinations include, but are not limited to, Element 1 in combination with one or more of Elements 7-11 and 13 ; and two or more of Elements 7-11 and 13 in combination.
  • compositions and methods are described herein in terms of “comprising” various components or steps, the compositions and methods can also“consist essentially of’ or“consist of’ the various components and steps.
  • compositions comprising two or more polyolefins, optionally formed in to films, where the composition comprises:
  • melt flow index of 0.2 g/10 min to 10 g/10 min (or 0.4 to 6 g/10 min, or of 0.5 to 3 g/10 min), and
  • Tm melting temperature
  • a density of 0.890 g/cm 3 to 0.970 g/cm3 (or 0.910 g/cm 3 to 0.970 g/cm 3 , or 0.930 g/cm 3 to 0.960 g/cm 3 ), wherein the density of the second polyolefin is at least 0.04 g/cm 3 (or at least 0.055 g/cm 3 , or 0.04 g/cm 3 to 0.12 g/cm 3 , or 0.05 g/cm 3 to 0.10 g/cm 3 ) greater than the density of the first polyolefin, ii) a melt flow index of 0.2 g/10 min to 10 g/10 min (or 0.4 to 6 g/10 min, or 0.5 to 3 g/10 min)
  • a Tm of 80°C to about 200°C (or about 90°C to about 190°C, or about 100°C to about 185°C, or about 80°C to about 150°C, or about 90°C to about 145°C, or about 100°C to about 140°C, or about 100°C to about 200°C, or about 120°C to about 190°C, or about 140°C to about 185°C); and
  • melt flow index of the first polyolefin is within 25% (preferably within 20%, (preferably within 0.01% to 25%, or within 1% to 20%, or within 10% to 15% or within 5% to 10%, preferably within 0% to 5%) of the melt flow index of the second polyolefin,
  • a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the composition has a multimodal (e.g., bimodal) differential scanning calorimetry melting profile above 40°C (or above 50°C, or above 60°C, or above 70°C, or above 80°C),
  • the Tm of the second polyolefin minus the Tm of the first polyolefin is about 25°C to about 100°C (or about 35°C to about 85°C, or about 45°C to about 65 °C),
  • the composition is preferably present in a molten or solid state
  • the composition contains less than 1 wt% of added filler, based on the total weight of the first and second polyolefins.
  • This invention also relates to a method to form a film comprising:
  • composition comprising two or more polyolefins into a film, where the composition comprises:
  • a first polyolefin having: i) a density of 0.850 g/cm 3 to 0.930 g/cm 3 (or 0.860 g/cm 3 to 0.910 g/cm 3 , or 0.880 g/cm 3 to 0.900 g/cm 3 ),
  • melt flow index of 0.2 g/10 min to 10 g/10 min (or 0.4 to 6 g/10 min, or of 0.5 to 3 g/10 min), and
  • Tm melting temperature
  • a second polyolefin having: i) a density of 0.890 g/cm 3 to 0.970 g/cm3 (or 0.910 g/cm 3 to 0.970 g/cm 3 , or 0.930 g/cm 3 to 0.960 g/cm 3 ), wherein the density of the second polyolefin is at least 0.04 g/cm 3 (or at least 0.055 g/cm 3 , or 0.04 g/cm 3 to 0.12 g/cm 3 , or 0.05 g/cm 3 to 0.10 g/cm 3 ) greater than the density of the first polyolefin,
  • melt flow index of 0.2 g/10 min to 10 g/10 min (or 0.4 to 6 g/10 min, or 0.5 to 3 g/10 min)
  • a Tm of 80°C to about 200°C (or about 90°C to about 190°C, or about 100°C to about 185°C, or about 80°C to about 150°C, or about 90°C to about 145°C, or about 100°C to about 140°C, or about 100°C to about 200°C, or about 120°C to about 190°C, or about 140°C to about 185°C); and
  • the melt flow index of the first polyolefin is within 25% (preferably within 20%, (preferably within 0.01% to 25%, or within 1% to 20%, or within 10% to 15% or within 5% to 10%, preferably within 0% to 5%) of the melt flow index of the second polyolefin,
  • a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the composition has a multimodal (e.g., bimodal) differential scanning calorimetry melting profile above 40°C (or above 50°C, or above 60°C, or above 70°C, or above 80°C),
  • the Tm of the second polyolefin minus the Tm of the first polyolefin is about 25°C to about 100°C (or about 35°C to about 85°C, or about 45 °C to about 65 °C),
  • the composition is preferably present in a molten or solid state
  • the composition contains less than 1 wt% of added filler, based on the total weight of the first and second polyolefins.
  • the film can be heated to the stretching temperature at a rate of 15°C/min to 100°C/min, or 30°C/min to 85°C/min, or 50°C/min to 75°C/min;
  • the film can be cooled or quenched to a temperature of 0°C to 40°C (or 10°C to 35 °C, or 20°C to 30°C, or room temperature) at a rate of 15°C/min to 100°C/min (or 30°C/min to 85°C/min, or 50°C/min to 75°C/min);
  • Embodiment Al which is a method comprising:
  • Embodiment A2 which is the method of Embodiment Al, wherein the second polyolefin is present at 0.1 wt% to 15 wt%.
  • Embodiment A3 is the method of Embodiment Al or A2 further comprising: a) cooling the film after extruding in step 1) and before stretching in step 2) to below the crystallization temperature of the second polyolefin.
  • Embodiment A4 which is the method of Embodiment A3 further comprising: heating the film, after cooling in step la) and before stretching in step 2), at a rate of 30°C/min to 90°C/min up to the temperature above 25°C and below the melting point of the second polyolefin.
  • Embodiment A5 which is the method of any of Embodiments A1-A4 further comprising: cooling the film after stretching in step 2) to a temperature of 0°C to 40°C.
  • Embodiment A6 which is the method of Embodiment A5, wherein cooling is at a rate of 15°C/min to 100°C/min.
  • Embodiment A7 which is the method of any of Embodiments A1-A6, wherein the stretching is at a stretching rate of 50 microns per second (pm/s) to 200 pm/s.
  • Embodiment A8 is the method of any of Embodiments A1-A7, wherein the film is stretch up to 800% in a machine direction.
  • Embodiment A9 which is the method of any of Embodiments A1-A8, wherein the first polyolefin is a first ethylene polymer and the second polyolefin is a second ethylene polymer.
  • Embodiment A10 which is the method of any of Embodiments A1-A9, wherein the reference blend has a monomodal molecular weight distribution.
  • Embodiment Al l which is the method of any of Embodiments A1-A10, wherein the elongated polyolefin structures have a length of 0.1 microns to 10 microns according to a Ruland streak method analysis of SAXS scattering data.
  • Embodiment A 12 is the method of any of Embodiments Al-Al 1, wherein the film has a degree of misorientation of 0.05 to 0.5 according to a Ruland streak method analysis of SAXS scattering data.
  • Embodiment A13 which is the method of any of Embodiments A1-A12, wherein the polymer melt further comprises one or more additives selected from the group consisting of: a stabilization agent, an anti-static agent, a crosslink agent, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti agglomeration agent.
  • Embodiment Bl is a composition comprising: a film comprising a first polyolefin and 0.1 wt% to 30 wt% of a second polyolefin, wherein the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin, wherein a melt flow index of the first polyolefin is within 25% of a melt flow index of the second polyolefin, and wherein a polymer blend consisting of the first and second polyolefins in the corresponding relative amounts as in the film, reference blend, has a multimodal differential scanning calorimetry melting profile above 40°C, wherein elongated polyolefin structures are present in the film.
  • Embodiment B2 which is the composition of Embodiment Bl, wherein the first polyolefin is a first ethylene polymer and the second polyolefin is a second ethylene polymer.
  • Embodiment B3 is the composition of Embodiment Bl or B2, wherein the reference blend has a monomodal molecular weight distribution.
  • Embodiment B4 is the composition of any of Embodiments B1-B3, wherein the elongated polyolefin structures have a length of 0.1 microns to 10 microns according to a Ruland streak method analysis of SAXS scattering data.
  • Embodiment B5 is the composition of any of Embodiments B 1-B34 wherein the film has a degree of misorientation of 0.05 to 0.5 according to a Ruland streak method analysis of SAXS scattering data.
  • Embodiment B6 which is the composition of any of Embodiments B1-B5, wherein the film further comprises one or more additives selected from the group consisting of: a stabilization agent, an anti-static agent, a crosslink agent, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti- agglomeration agent.
  • This invention further relates to:
  • a method comprising:
  • step 2 heating the film, after cooling in step la) and before stretching in step 2), at a rate of 30°C/min to 90°C/min up to the temperature from 25°C to below the melting point of the second polyolefin.
  • step 2 cooling the film after stretching in step 2) to a temperature of 0°C to 40°C.
  • first polyolefin is a first ethylene polymer and the second polyolefin is a second ethylene polymer.
  • the polymer melt further comprises one or more additives selected from the group consisting of: a stabilization agent, an anti-static agent, a crosslink agent, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti-agglomeration agent.
  • a stabilization agent selected from the group consisting of: a stabilization agent, an anti-static agent, a crosslink agent, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti-agglomeration agent.
  • composition comprising:
  • a film comprising a first polyolefin and 0.1 wt% to 30 wt% of a second polyolefin, wherein the second polyolefin has a density of at least 0.04 g/cm 3 greater than a density of the first polyolefin, wherein a melt flow index of the first polyolefin is within 25% of a melt flow index of the second polyolefin, and wherein a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the film, reference blend, has a multimodal differential scanning calorimetry melting profile above 40°C, wherein elongated polyolefin structures are present in the film.
  • composition of paragraph 14 wherein the first polyolefin is a first ethylene polymer and the second polyolefin is a second ethylene polymer.
  • composition of paragraph 14 or 15, wherein the reference blend has a monomodal molecular weight distribution.
  • a stabilization agent selected from the group consisting of: a stabilization agent, an anti-static agent, a crosslink agent, a crosslink promoter, a release agent, an adhesion promoter, a plasticizer, and an anti-agglomeration agent.
  • a method to form a film comprising:
  • a density of 0.850 g/cm 3 to 0.930 g/cm 3 ii) a melt flow index of 0.2 g/10 min to 10 g/10 min, and iii) a melting temperatureTM of about 50°C to about 100°C;
  • melt flow index of the first polyolefin is within 25% of the melt flow index of the second polyolefin
  • a reference polymer blend consisting of the same first and second polyolefins in the same relative amounts as in the composition has a multimodal differential scanning calorimetry melting profile where all peaks are above 40°C, III) a melting temperature of the second polyolefin minus a melting temperature of the first polyolefin is about 25 °C to about 100°C,
  • the polymer melt contains less than 1 wt % of added filler, based on the total weight of the first and second polyolefins;
  • the film can be heated to the stretching temperature at a rate of 15°C/min to 100°C/min;
  • the film can be cooled or quenched to a temperature of 0°C to 40°C at a rate of 15°C/min to 100°C/min;
  • PolyA is an ethylene-hexene copolymer (MI 1.03 g/10 min, density 0.895 g/cm 3 , Tm 81.7°C)
  • PolyB is an ethylene-hexene copolymer(MI 0.85 g/10 min, a density 0.952 g/cm 3 , Tm 135.8°C).
  • FIG. 3 is the DSC melting and crystallization profiles for the individual PolyA and PolyB and a blend of PolyA:PolyB at a weight ratio of 90:10.
  • Table 2 Blend properties
  • the dog-bone specimens were then heated and stretched while rheology and SAXS data was collected to identify the in-situ formation of elongated polyethylene structures.
  • a Linkam tensile stage was used to stretch the dog-bone specimens. More specifically, the specimens were loaded in the Linkam stage between two clamps, pre-stretched at 10 pm/s until the axial force became positive but below 0.5 N. While still in the stage, the pre-stretched specimens were then preheated for 30 seconds at a target temperature (25°C, 70°C, and 80°C.). Then, a constant stretching rate of 100 pm/s was applied until a final strain of 200% was achieved.
  • FIG. 4 is a photograph of the final stretched specimen for the 90: 10 specimen at the three temperatures investigated. Stretching at higher temperatures yield a longer, thinner stretched section.
  • FIG. 5 includes a plot of the stress as a function of time during stretching of the specimen for the 90:10 specimen at 80°C along with SAXS scattering pattern data corresponding to five time points during the stretching, during cooling, and after cooling.
  • the plot indicates that the specimen undergoes strain hardening.
  • SAXS Scan A is at the beginning and illustrates a circular scattering pattern.
  • an oblong scattering pattern forms.
  • SAXS Scans D and E With further stretching and cooling through SAXS Scans D and E, a streaked scattering pattern forms and becomes better defined.
  • the progression of the SAXS scattering patterns indicates that elongated structures are forming in- situ as the specimen is being stretched. Further, the progression to a clear, streaked scattering pattern indicates that the elongated structures have a lower degree of misorientation.
  • the Ruland streak method was used to analyze SAXS Scans D and E.
  • the Ruland streak method analysis SAXS Scan D (during strain hardening) yields a 2.0 pm length of the elongated polyethylene structures and a 0.11 degree of misorientation.
  • the Ruland streak method analysis SAXS Scan D (during cooling) yields a 3.7 mhi length of the elongated polyethylene structures and a 0.11 degree of misorientation.
  • the growth in length may be due to additional polymer molecules crystallizing around the already formed elongated polyethylene structures during the cooling.
  • FIG. 6 is a plot of the stress as a function of time during stretching of the specimen for the 90:10 specimen at the three stretching temperatures. This illustrates that each sample undergoes strain hardening during stretching.
  • Table 4 provides the Ruland streak method analysis SAXS scans for these temperatures and 80°C at similar data points to Scans D and E of the 80°C stretched specimen. This analysis illustrates that elongated polyethylene structures are formed at various stretching temperatures. Further, higher temperatures produce longer, more aligned elongated polyethylene structures.
  • phase 2 data are provided.
  • Phase 2 data is a measure of the hardness of a surface where darker portions are harder. Without being limited by theory, it is believed that the harder portions of the phase 2 data are the elongated polyethylene structures. Samples were prepared for AFM by cryo-microtoming the specimen.
  • FIG. 7 A includes representative 2-D and 3-D phase 2 AFM scans of the 25 °C stretched specimen.
  • FIG. 7B includes representative 2-D and 3-D phase 2 AFM scans of the 70°C stretched specimen.
  • FIG. 7C includes representative 2-D and 3-D phase 2 AFM scans of the 80°C stretched specimen.
  • the AFM data further supports the SAXS data that with higher temperatures, the elongated polyethylene structures become longer, more aligned. Further, the AFM data confirms that the equatorial streaks are a result of elongated polyethylene structure formation and not void formation.
  • compositions and methods are described in terms of“comprising,”“containing,” or“including” various components or steps, the compositions and methods can also“consist essentially of’ or“consist of’ the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form,“from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values.

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Abstract

La présente invention concerne un procédé de formation d'un film comprenant l'extrusion du film à partir d'une masse polymère fondue comprenant une première polyoléfine et de 0,1 % en pds à 30 % en pds d'une seconde polyoléfine, la seconde polyoléfine ayant une densité d'au moins 0,04 g/cm3 supérieure à une densité de la première polyoléfine, un indice d'écoulement de la masse fondue de la première polyoléfine s'inscrivant à l'intérieur de 25 % d'un indice d'écoulement de la masse fondue de la seconde polyoléfine, et un mélange de polymères constitué de la première et de la seconde polyoléfine en les mêmes quantités relatives que dans le film présentant un profil de fusion par calorimétrie différentielle à balayage multimodal supérieur à 40 °C ; et l'étirage du film lorsque le film se trouve à une température supérieure à 25 °C et inférieure au point de fusion de la seconde polyoléfine pour former des structures de polyoléfine allongées in situ dans le film.
PCT/US2020/022267 2019-05-01 2020-03-12 Films de polyoléfine contenant des structures de polyoléfine allongées formées in situ Ceased WO2020222916A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030096128A1 (en) * 2001-07-19 2003-05-22 Farley James Mcleod Polyethylene films with improved physical properties
US20090192270A1 (en) * 2008-01-28 2009-07-30 Malakoff Alan M Ethylene-Based Polymers And Articles Made Therefrom
US20090297810A1 (en) * 2008-05-30 2009-12-03 Fiscus David M Polyethylene Films and Process for Production Thereof
US20100298508A1 (en) * 2008-01-29 2010-11-25 William Michie Polyethylene compositions, method of producing the same, articles made therefrom, and method of making the same
US20150368415A1 (en) * 2012-12-18 2015-12-24 Exxonmobil Chemical Patents Inc. Polyethylene Films and Method of Making Same

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030096128A1 (en) * 2001-07-19 2003-05-22 Farley James Mcleod Polyethylene films with improved physical properties
US20090192270A1 (en) * 2008-01-28 2009-07-30 Malakoff Alan M Ethylene-Based Polymers And Articles Made Therefrom
US20100298508A1 (en) * 2008-01-29 2010-11-25 William Michie Polyethylene compositions, method of producing the same, articles made therefrom, and method of making the same
US20090297810A1 (en) * 2008-05-30 2009-12-03 Fiscus David M Polyethylene Films and Process for Production Thereof
US20150368415A1 (en) * 2012-12-18 2015-12-24 Exxonmobil Chemical Patents Inc. Polyethylene Films and Method of Making Same

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