Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/08—Copolymers of ethene
  • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
  • C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/10—Homopolymers or copolymers of propene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/06—Polyethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2314/00—Polymer mixtures characterised by way of preparation
  • C08L2314/06—Metallocene or single site catalysts
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L91/00—Compositions of oils, fats or waxes; Compositions of derivatives thereof
  • C08L91/06—Waxes

Definitions

• TITLE Improved Processability of Metallocene-Catalyzed Polyolefins
• This invention relates generally to materials added to metallocene-catalyzed narrow molecular weight polyolefin polymers made with metallocene catalyst systems to improve their melt processing properties. More specifically, this invention relates to solid solvents to improve the melt processability of metallocene-catalyzed polyolefins and polyolefin blends containing one or more metallocene-catalyzed polyolefins, while physical properties of articles fabricated with these polyolefins and solvents are substantially the same as those of articles fabricated from the linear polyolefin itself.
• LLDPE linear low density polyethylene
• the LLDPE polymer's higher melt viscosity at typical processing conditions made the then existing extrusion and molding equipment less efficient as a polymer pumping apparatus, for instance as measured by pounds per hour per inch of die (lb./hr/in of die) (kg/hr/cm of die) when used to process linear low density Ziegler-Natta catalyzed polyolefin polymers.
• metallocene-catalyzed linear polymers have, in certain instances, once again brought similar melt processing difficulties, probably due at least in part to the comparatively narrow molecular weight distribution and narrow composition distribution of these metallocene-catalyzed materials when compared for example to traditional Ziegler-Natta catalyzed polyolefin polymers, solution polymerized mono-cyclopentadienyl catalyzed polyolefins, or especially to free radical initiated polyolefins. Due to the newness of the metallocene-catalyzed polyolefin polymers and their relatively low current commercial volume of sales, fabricators and converters of polyolefin polymers have not been compelled to push the processing envelope of these polymers.
• metallocene-catalyzed polyolefin polymers reach commercially significant sales and use, their relative difficulty of processing of certain of these metallocene-catalyzed polymers will become more important as converters of these resins attempt to maximize the output on a given machine while using these new polymers.
• Polyolefins (hereinafter "metallocene-catalyzed polyolefins") made from metallocene based catalyst systems (which include mono-cyclopentadienyl and bis(cyclopentadienyl) metallocene catalyst systems as described in U.S. Patents 5,026,798 and 5,324,800 incorporated herein by reference for purposes of U.S.
• more energy may be used to pump the same amount of polymer (at a constant output based on weight/unit of die circumference/unit of time) if the machine is not power limited.
• attempts many of them successful, to improve the processability of various kinds of polymers. These attempts have included adding lubricants, or plasticizers, use of other viscosity reduction techniques, and other methods of improving processing.
• these solutions have had deleterious effects on other important aspects of polymer melt processing, fabrication, and fabricated articles made from these polymers. Some examples of such detrimental effects include that the materials intended to improve processability tend to reduce physical properties, and that others have drawbacks such as increasing solvent extractables (limited for food law compliance).
• EP 0 279 573 A2 suggests that the melt viscosity of vinylidene chloride polymers is purportedly reduced by introducing a solid solvent such as dimethyl sulfone into the polymer.
• the sulfone may be compatible with vinylidene chloride polymers at a processing temperature above the solid solvent melting point and will reduce the melt viscosity and improve processing of the vinylidene chloride polymer.
• the solid solvent Upon cooling below the solid solvent melting point, the solid solvent is said to become micro dispersed in the vinylidene chloride polymer with little or no solid solvent remaining dissolved in the vinylidene chloride polymer.
• EP 0 324 264 A2 suggests that the extrudability of linear polymers of ethylene such as low density copolymers of ethylene of a C4 to CIO olefins (LLDPE) into thin films is improved by adding small amounts, for example, of 0.02 to 2 weight percent ethylene vinyl polymer to reduce melt fracture, head pressure and to obtain having excellent anti-blocking characteristics.
• diatomaceous earth is added to further reduce blocking.
• EP 0 308 090 A2 suggests that head pressure and extruder torque in the extrusion of linear ethylene polymers such as linear low density polyethylene (LLDPE) are reduced by adding a small amount (less than 3 weight percent) of a thermoplastic polyamide polymer. Films extruded from the blend purportedly exhibit better surface appearance by reduction of melt fracture.
• linear ethylene polymers such as linear low density polyethylene (LLDPE)
• LLDPE linear low density polyethylene
• EP 0 308 089 A2 suggests that head pressure and extruder torque in the extrusion of linear ethylene polymers such as linear low density polyethylene (LLDPE) are purportedly reduced by adding a small amount (less than 5 weight percent) of a thermoplastic polyurethane. Films extruded from the blend are said to exhibit better surface appearance by reduction of melt fracture.
• linear ethylene polymers such as linear low density polyethylene (LLDPE)
• LLDPE linear low density polyethylene
• metallocene-catalyzed polyolefins with a solid solvent can provide advantages in melt processing of metallocene-catalyzed polyolefins.
• the advantages include, but are not limited to; lower extruder torque, lower extruder back-pressures, lower power requirements and/or improved maximum outputs at substantially the same specific extruder output, and with generally little smoking and/or plate-out. Additionally, these advantages can be realized generally without loss of physical properties of an article fabricated from the combination. I have thus found that the above discussed disadvantages associated with metallocene- catalyzed polyolefins can generally be solved by the material combinations of various embodiments of my invention.
• a solid solvent is used in a metallocene-catalyzed polyolefin
• the result is a combination which has a polyolefin or polyolefins (majority component) selected from a group consisting of polyethylene, polypropylene, ethylene homopolymers, ethylene-alpha-olefin copolymers, ethylene alpha-olefin terpolymers, propylene homopolymers, propylene-ethylene copolymers, propylene-alpha-olefin copolymers or terpolymers and mixtures (combinations) and blends thereof, where the polyolefin is made from the group of catalysts or initiators consisting of a metallocene or single site catalyzed polymerization products, a traditional Ziegler-Natta catalyzed system, and a Chromium based catalyst system.
• the majority component can also contain an additional polymer or polymers.
• the majority component has a density in the range
• the combination may also include in the range of 0.5 to 10 parts per hundred parts of the majority component, generally a metallocene-catalyzed polyolefin.
• solid solvent means a material which is dispersed in the polymer in an associated state (crystal, micel, or cluster, for example) at temperatures below the processing temperature of the polymer.
• the solid solvent may dissociate somewhat below the (melt) processing temperature of the majority component and should have sufficiently low molecular weight to enhance extrudability, but sufficiently high molecular weight to prevent substantial screw slippage (in an extruder), smoking, or fuming during melt processing, solvent extractability (food law compliance), and plate-out.
• the solid solvent should preferably reassociate during or somewhat before solidification of a fabricated article based on the combination, to form a separate phase within the polymer article.
• the minority or solid solvent component has: (a) a disassociation temperature (T ⁇ ) at or below the processing temperature of the blend; (b) an association temperature (T equal to or above the crystallization temperature of the polyolefin; (c) a solubility index in the range of from 15 to 20 (MPa) ; (d) optionally a degree of crystallinity exceeding 80%; (e) a viscosity not exceeding 2000 MPa at 170°C; (f) an extractability in n-hexane at 50°C not exceeding 5.5 weight percent based on the total weight of the combination with the majority component; (g) a degradation temperature in excess of 250°C; and (h) a refractive index within ⁇ 10% of the polyolefin majority component.
• One embodiment of the present invention is directed to a combination of a polyolefin and a solid solvent, as well as articles fabricated based on this combination.
• These polyolefin compositions have improved melt processability properties which make them unique and particularly well suited for use in most melt processing operations used for fabrication of metallocene-catalyzed polyolefins.
• the metallocene-catalyzed polyolefin/solid solvent combinations of various embodiments of the present invention will contain at least these two components. Such combinations can be achieved by schemes including but not limited to, melt compounding, dry blending, or other schemes which will be well known to those of ordinary skill in the art.
• the majority component of the combination of the present invention is generally a melt processable polymer or polymer blend selected from the group consisting of: polyethylene, polypropylene, copolymers and te ⁇ olymers of ethylene and propylene, ethylene propylene rubber, ethylene propylene diene monomer rubber (EPDM), styrene isoprene styrene, styrene butadiene styrene, and combinations thereof.
• EPDM ethylene propylene diene monomer rubber
• styrene isoprene styrene, styrene butadiene styrene, and combinations thereof are becoming available commercially and may be prepared or polymerized by metallocene and or single site catalyst systems, however other constituents of the "majority" component may be polyolefins catalyzed or initiated with other types of catalysts or initiators or other types of catalyst mixtures.
• free radical, high pressure polyethylenes and ethylene copolymers include but are not limited to homopolymer polyethylene, ethylene vinyl acetate, ethylene ethyl acrylate, ethylene methyl acrylate, ethylene n-butyl acrylate, ethylene acrylic acid, ethylene methacrylic acid, ionomers of the acid co or te ⁇ olymers, combinations thereof and the like.
• the majority component polyolefin may be an ethylene homopolymer or an ethylene-alpha-olefin copolymer where the polymer contains one or more alpha-olefins.
• the alpha-olefins will have from 3 to 20 carbon atoms.
• the polyolefin may also be a polypropylene, either a homopolymer polypropylene or a copolymer or te ⁇ olymer of propylene and ethylene and/or an alpha-olefin having 4 to 20 carbon atoms.
• the preferred alpha-olefins in either the polyethylene or the polypropylene copolymers or te ⁇ olymers are olefins having 4 to 8 carbon atoms.
• Non-limiting examples of these alpha-olefins are butene-1, 4-methyl pentene-1, hexene-1, and octene-1.
• the use of te ⁇ olymers and tetrapolymers of the ethylene or propylene using alpha-olefins are also contemplated, as are blends of the polyolefin with other polyolefin copolymers or other thermoplastics.
• the use or inclusion into either the majority component, or for instance into the article fabricated from the combination of majority components and solid solvent include additives, such as for instance antioxidants, acid neutralizers, antiozonants, UV inhibitors or absorbers, colors, fillers, combinations thereof and the like are also contemplated.
• the alpha-olefin or alpha-olefins are present in the ethylene copolymer in the range of from 0.2 to 20 mole percent based on the total moles of copolymer, preferably in the range of from 0.5 to 15 mole percent, more preferably in the range of from 1 to 10 mole percent.
• the melt index of the ethylene copolymers will be in the range of from 0.01 dg/min to 100 dg/min, preferably in the range of from 0.25 to 10 dg/min, more preferably 0.5 dg/min to 10 dg min (as measured by ASTM D 1238 condition E 190° C 2.16 kg).
• the density of the polymers is in the range of from 0.85 to 0.96 g cc, preferably in the range of from 0.89 to 0.93 g cc.
• the choice of a specific density and melt index will be driven mainly by the end use article property requirements.
• the molecular weight distribution of the ethylene-alpha-olefin copolymers will generally be below 2.8 (M ⁇ M preferably below 2.5.
• composition breadth distribution index (CDBI) of the ethylene-alpha-olefin copolymer is greater than 50%, preferably more than 65.
• CDBI composition breadth distribution index
• the propylene polymers contemplated are also catalyzed by metallocene based catalysts systems. These polymers may be propylene homopolymers or propylene or copolymers or te ⁇ olymers.
• a propylene copolymer, te ⁇ olymer, or tetrapolymer may also be propylene where the monomers may be selected from the group consisting of ethylene and/or alpha-olefins where the alpha-olefins have a carbon number in the range of 4 to 20, more preferably the carbon number is from 4 to 10, most preferably from 4 to 8.
• Comonomer or comonomers will be present in the copolymer in the range of from 0.2 to 8 mole percent based on the total mole of the copolymer, preferably from 0.5 to 6 mole percent, more preferably from 1 to 3 mole percent.
• the melt flow rate of any of these propylene polymers will be in the range of from 0.1 to 5000 g/10 min. (as measured by ASTM D-1238 Condition L (230°C/2.6 Kg)).
• the melt flow rate is more preferably in the range of from 0.5 to 10 g/10 min. If the end use or the melt process used to convert the propylene polymer resin into a useful fabricated article is fiber spinning or extrusion, the melt flow rate is preferably in the range of from 10 to 3000 g/10 min, more preferably in the range of from 100 to 1500 g 10 min.
• the composition distribution of the propylene copolymers is generally narrow.
• the molecular weight distribution of the propylene copolymers demonstrated by the Mw Mn is in the range of up to 2.8, preferably up to 2.5, and most preferably to 2.
• the solid solvents contemplated by the present invention include a broad range of materials that can most generally be described as those materials whose molecules disassociate in the melt, where the solid solvent will act as a viscosity modifier, but then will reassociate (through crystallization, micel formation, ionic bonding and the like) before or simultaneously with the recrystallization of the majority component polyolefin.
• the solid solvent will have a disassociation temperature ( & ) less than the normal processing temperature or melt processing temperature of the majority component, preferably more than 10° C below the melt processing temperature, more preferably more than 20° C below the melt processing temperature.
• the association temperature (T of the solid solvent will be equal to or greater than crystallization temperature of the majority component, preferably 10° C greater than the crystallization temperature, preferably 20° C greater than the crystallization temperature. It will be understood by those of ordinary skill in the art that regardless of the crystallization temperature of the majority component, the crystallization temperature of the solid solvent will preferably be at or above the crystallization temperature of the majority component polyolefin.
• the T a and the T ⁇ can be measured utilizing techniques well known to those of ordinary skill in the art, such as Dynamic Mechanical Thermal Analysis (DMT A), differential scanning calorimeter (DSC), or hot stage microscopy.
• DMT A Dynamic Mechanical Thermal Analysis
• DSC differential scanning calorimeter
• the solid solvent is generally non-crystalline in nature, before or simultaneously with the crystallization temperature of the majority component, the solid solvent will reassociate with the majority component. Likewise the material will disassociate at a temperature of less than the typical processing temperatures for the majority component polyolefin.
• the solid solvent (either crystalline, non-crystalline or partially crystalline) selected will act as a viscosity modifier in the melt phase of the majority component polyolefin and will be disassociated from the polyolefin.
• the solid solvent will be sufficiently reassociated with the majority component that the extractability of the combination of solid solvent, majority component, and additives will not be greater than 5.5 weight percent, preferably less than 4 weight percent, more preferably less than 3 weight percent, most preferably less than 2.6 weight percent(of the total combination) in n-hexane, as measured by a standard test of the US Food and Drug Administration noted 21 CFR ⁇ 177.1520.
• the solid solvent should reassociate with the majority component such that the physical properties of an article made from the combination should not have substantially lower values than that of the majority component without the solid solvent added.
• Solid Solvents may be selected from the group consisting of C20 to C70 hydrocarbons, monofunctional C20 to C70 hydrocarbons, and multifunctional C20 to C70 hydrocarbons, wherein said functionality is selected from the group consisting of alcohols, acids, esters, sulfonates, aldehydes, ketones, ethers acid amides, amines and combinations thereof. Additionally, the solid solvent should have a number average molecular weight in the range of from 250 to 5000. Non-limiting examples of such solid solvent materials are shown below in table I. Each of the materials are available from at least one commercial source, and one of those sources is indicated in the table. Additionally Chemical Abstracts numbers (CAS#), are included for clarity. TABLE 1
• the solubility index (p) of the solid solvent should be 16.5 MPa , preferably in the range of from 15 to 20, more preferably in the range of from 15 to 19.5 MPa . It will be understood that the solubility index is a measure of compatibility with the polyolefin material.
• the degradation temperature or T d of the solid solvent should be greater than 250° C, preferably greater than 275° C and more preferably greater than 300° C. It will be well understood by those of ordinary skill in the art that the degradation temperature of the solid solvent should be chosen such that degradation during normal extrusion conditions of the majority component polyolefin be avoided. To determine a satisfactory degradation temperature limit for a solid solvent, weight loss may be kept below 2.5 weight percent, preferably below 1.5, more preferably below 1 weight percent. Such weight loss may be determined by for instance Thermo-Gravimetric Analysis (TGA).
• TGA Thermo-Gravimetric Analysis
• the refractive index of the polyolefin/solid solvent combination should be as close as possible to the refractive index of the majority component polyolefin preferably in the range of ⁇ 10% of the refractive index of the majority component, where the clarity of the end product of the melt processable polyolefin is of importance.
• the volatility of the solids solvent should be minimal. Those of ordinary skill in the art will appreciate that the volatility should be kept at or below the level of volatility, at normal processing temperatures, of the majority component melt processable polyolefin to avoid smoking, die build-up, and buildup on other parts around the die and extrusion zone.
• the solid solvent should preferably be food law compliant.
• Extrusion and molding are two broad categories of melt processing that take in substantially all of the shear and heat conversion processes encountered by polyethylenes or polypropylenes.
• Extruded products can be made into films having a thickness in the range of from 5 microns to 200 microns or a sheet having a thickness in the range of from 200 micron to 4000 microns, or fibers having a broad range of fiber deniers.
• the films may be blown films or cast films.
• polyolefin/solid solvent melt processable blends include: blown and cast films, oriented films, fibers (melt blown and spun bonded), fabrics made from said fibers, sheets and molded articles (injection molding, compression molding, extrusion blow molding, and extrusion stretch blow molding).
• extruded materials find use in trash bags, can liners, t-shirt bags, stretch films, heavy duty shipping sacks, retail bags, meat, cheese and produce packaging, snack foods packaging, food containers, diaper back sheets, diaper liners, diaper fillers, medical drapes and gowns, medical devices (e.g. syringes, IV tubing, and the like ), bottles, and pails.
• An ethylene butene copolymer (EXACT® 3028, available from Exxon Chemical Company) made utilizing a metallocene catalyst is blown into a mono-layer film on a in the blown film application on a 2.5 in (64 mm) Egan extruder (24: 1 L:D) with a 60 mil (1.5 mm) die gap.
• the same resin was used for all three Samples.
• the gauge of the film made from the polymer is 1.25 mils (31.75 microns).
• the butene copolymer has a density of approximately 0.90 g cc and a melt index of a nominal 1.2 dg min.
• Sample 1 (control) is Exact 3028 extruded without additives, save for anti- oxidants, acid neutralizers, and the like, and Viton® A to substantially eliminate melt fracture.
• the additives included are 500 ppm Viton® A.
• Viton A can be obtained from E. I. DuPont and is one of a family of fluoroelastomers
• Such fluoroelastomers are generally useful as processing aids that generally act to eliminate melt fracture.
• Sample 2 has 500 ppm Viton A, and 4 weight percent of a solid solvent, a low molecular weight polypropylene wax PP 230, (available from Hoechst Celanese).
• Sample 3 has 500 ppm Viton A and 7.5 weight percent of LD-200.48 (a nominal 8 dg min melt index free radical initiated low density polyethylene material with 0.917 g/cc density from Exxon Chemical Company).
• Sample 3 represents previously suggested materials (highly branched LDPE) to improve processability.
• Table II the control (Sample 1) exhibited a motor load
• inventive Sample 2 shows dramatic property improvements in Elmendorf tear, puncture force, and puncture energy when compared to Sample 1. Specifically over 18% improvement in both MD and TD tear values over the reference (Sample 1).
• a blend of propylene-ethylene and propylene-hexene copolymers are extruded into a film.
• the motor load in KVA for the two controls when compared to those of the same additives as added in Example 1 are diminished at least by 10%.
• the same order of magnitude reduction is seen in back pressure.

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• 1996
  • 1996-04-10 WO PCT/US1996/005039 patent/WO1996032441A1/en not_active Application Discontinuation
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