Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/06—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent
  • C08J9/08—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a chemical blowing agent developing carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2201/00—Foams characterised by the foaming process
  • C08J2201/02—Foams characterised by the foaming process characterised by mechanical pre- or post-treatments
  • C08J2201/03—Extrusion of the foamable blend
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/02—CO2-releasing, e.g. NaHCO3 and citric acid
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/06—CO2, N2 or noble gases
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/08—Supercritical fluid
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2203/00—Foams characterized by the expanding agent
  • C08J2203/18—Binary blends of expanding agents
  • C08J2203/184—Binary blends of expanding agents of chemical foaming agent and physical blowing agent, e.g. azodicarbonamide and fluorocarbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/04—Homopolymers or copolymers of ethene
  • C08J2323/06—Polyethene

Definitions

• the present disclosure relates generally to methods of forming talc-free polymeric foam films with dual blowing agents and the resultant talc-free polymeric foam films. More specifically, but without limitation, the disclosure relates to methods of forming talc-free polymeric foam films by employing dual blowing agents (a physical blowing agent and a chemical blowing agent) in a mixture that is extruded at a temperature above a decomposition temperature of the chemical blowing agent.
• dual blowing agents a physical blowing agent and a chemical blowing agent
• Polymeric foams include a plurality of cells (or voids) formed within a polymer matrix.
• Microcellular foams are polymeric foams which have small cell sizes and high cell densities. By replacing solid plastic with voids, polymeric foams use less raw material than solid plastics for a given volume. Thus, raw material savings may increase as the density of a foam decreases.
• Polymeric foamed films can be made in the form of monolayer or coextruded films with multiple layers, where one or more of the layers are foamed. The polymeric foamed films can be further bonded/laminated to other substrates including, foil, paper, other plastics, or they can be post stretched in one or two directions, among other possibilities.
• Polymeric foam films can be formed as a cast film via a casting process or as a blown film via a blown film extrusion process.
• a blown film extrusion process may involve extruding a tube of molten polymer through an annular die and inflating the tube of molten polymer to several times its initial diameter (as measured by a blow-up ratio and draw down ratio) to form a thin film bubble. The resultant bubble may then be collapsed and formed into a blown polymeric foam film.
• a casting process may involve extruding a tube of molten polymer through a flat die that can then be cooled via a quench roller to form a cast polymeric foam film.
• Blowing agents can be employed in cast and/or blown film processes to produce polymeric foam films.
• a physical blowing agent and/or a chemical blowing agent can be employed in a cast and/or blown film process.
• physical blowing agents include hydrocarbons, chlorofluorocarbons, nitrogen, and carbon dioxide, among other physical blowing agents.
• nucleating agent i.e., nucleant
• nucleating agents include talc and calcium carbonate.
• WO Publication 2002/026,485 describes use of talc as a nucleant. However, having talc-free polymeric foam films may be desirable.
• talc may contain carcinogens such as asbestos among other shortcomings associated with use of talc as detailed herein.
• the present disclosure provides a method of forming a talc-free polymeric foam film with dual blowing agents comprising:
• the method of forming a talc-free polymeric foam film with dual blowing agents employed at a temperature above a decomposition temperature of a chemical blowing agent surprisingly provides talc-free polymeric foam films with improved porosity and desired mechanical/physical properties.
• advantages of the methods and resultant talc-free polymeric foam films of this disclosure over other polymeric foam films may include being talc-free, improved porosity, and/or exhibiting desired mechanical properties such as a desired puncture resistance, puncture break load, normalized Spencer Impact resistance, and/or a MD/CD tensile strength.
• composition refers to a mixture of materials which comprises the composition, as well as reaction products and decomposition products formed from the materials of the composition.
• Polymer and“polymeric material” mean a polymeric compound prepared by polymerizing monomers, whether of the same or a different type.
• the generic term polymer thus embraces the term homopolymer as defined hereafter, and the term interpolymer as defined hereinafter. Trace amounts of impurities (for example, catalyst residues) may be incorporated into and/or within the polymer.
• a polymer may be a single polymer, a polymer blend or a polymer mixture, including mixtures of polymers that are formed in situ during polymerization.
• homopolymer refers to polymers prepared from only one type of monomer with the understanding that trace amounts of impurities can be incorporated into the polymer structure.
• interpolymer refers to polymers prepared by the polymerization of at least two different types of monomers.
• the generic term interpolymer thus includes copolymers (employed to refer to polymers prepared from two different types of monomers), and polymers prepared from more than two different types of monomers.
• olefin-based polymer or“polyolefin”, as used herein, refer to a polymer that comprises, in polymerized form, a majority amount of olefin monomer, for example ethylene or propylene (based on the weight of the polymer), and optionally may comprise one or more comonomers.
• ethylene/a-olefm interpolymer refers to an interpolymer that comprises, in polymerized form, a majority amount (>50 mol %) of units derived from ethylene monomer, and the remaining units derived from one or more a-olefms.
• Typical a-olefms used in forming ethylene/a-olefm interpolymers are C3-C10 alkenes.
• ethylene/a-olefm copolymer refers to a copolymer that comprises, in polymerized form, a majority amount (>50 mol%) of ethylene monomer, and an a-olefm, as the only two monomer types.
• a-olefm refers to an alkene having a double bond at the primary or alpha (a) position.
• Polyethylene or“ethylene-based polymer” shall mean polymers comprising a majority amount (>50 mol %) of units which have been derived from ethylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers).
• LDPE Low Density Polyethylene
• LLDPE Linear Low Density Polyethylene
• ULDPE Ultra Low Density Polyethylene
• VLDPE Very Low Density Polyethylene
• m-LLDPE linear low density resins
• POP ethylene-based plastomers
• POE ethylene-based elastomers
• MDPE Medium Density Polyethylene
• HDPE High Density Polyethylene
• LDPE low density polyethylene polymer
• “highly branched polyethylene” is defined to mean that the polymer is partly or entirely homo-polymerized or copolymerized in autoclave or tubular reactors at pressures above 14,500 psi (100 MPa) with the use of free-radical initiators, such as peroxides (see for example US 4,599,392, which is hereby incorporated by reference).
• LDPE resins typically have a density in the range of 0.916 to 0.935 g/cm 3 .
• LLCPE includes both resin made using the traditional
• Ziegler-Natta catalyst systems and chromium-based catalyst systems as well as single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts & polyvalent aryloxy ether catalysts (typically referred to as bisphenyl phenoxy), and includes linear, substantially linear or heterogeneous polyethylene copolymers or homopolymers.
• LLDPEs contain less long chain branching than LDPEs and includes the substantially linear ethylene polymers which are further defined in U.S. Patent 5,272,236, U.S. Patent 5,278,272, U.S.
• Patent 5,582,923 and US Patent 5,733,155 the homogeneously branched linear ethylene polymer compositions such as those in U.S. Patent No. 3,645,992; the heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Patent No. 4,076,698; and/or blends thereof (such as those disclosed in US 3,914,342 or US
• the LLDPEs can be made via gas-phase, solution-phase or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art.
• MDPE refers to polyethylenes having densities from 0.926 to
• MDPE is typically made using chromium or Ziegler-Natta catalysts or using single-site catalysts including, but not limited to, substituted mono- or bis- cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts & polyvalent aryloxy ether catalysts (typically referred to as bisphenyl phenoxy), and typically have a molecular weight distribution (“MWD”) greater than 2.5.
• MWD molecular weight distribution
• HDPE refers to polyethylenes having densities greater than about 0.935 g/cm 3 and up to about 0.980 g/cm 3 , which are generally prepared with Ziegler-Natta catalysts, chrome catalysts or single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts & polyvalent aryloxyether catalysts (typically referred to as bisphenyl phenoxy).
• ULDPE refers to polyethylenes having densities of 0.855 to
• ULDPEs include, but are not limited to, polyethylene
• Polyethylene (ethylene-based) elastomers plastomers generally have densities of 0.855 to 0.912 g/cm 3 .
• Blends mean a composition of two or more polymers. Such a blend may or may not be miscible. Such a blend may or may not be phase separated. Such a blend may or may not contain one or more domain configurations, as determined from transmission electron spectroscopy, light scattering, x-ray scattering, and any other method known in the art. Blends are not laminates, but one or more layers of a laminate may contain a blend. Such blends can be prepared as dry blends, formed in situ (e.g., in a reactor), melt blends, or using other techniques known to those of skill in the art.
• compositions claimed through use of the term“comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary.
• the term,“consisting essentially of’ excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability.
• the term“consisting of’ excludes any component, step or procedure not specifically delineated or listed.
• the terms“a,”“an,”“the,” “at least one,” and“one or more” are used interchangeably.
• the present disclosure provides a method of forming a talc-free polymeric foam film with dual blowing agents comprising:
• being“talc-free” refers to a talc content of less than 5 percent talc, less than 4 percent talc, less than 3 percent talc, less than 2 percent talc, less than 1 percent talc, less than 0.5 percent talc, or 0.0 percent talc by weight of a total weight of a mixture/a total weight of a resultant talc-free polymeric foam film.
• a mixture (including i), ii) and iii)) and the resultant talc-free polymeric foam film each have less than 5 percent talc, preferably less than 4 percent talc, more preferably less than 3 percent talc, more preferably still less than 2 percent talc, yet more preferred less than 1 percent talc, even more preferably less than 0.5 percent talc, even more preferably less than 0.1 weight percent or most preferred 0.0 percent talc by weight of a total weight of the mixture and of a total weight of the talc- free polymeric foam film.
• a mixture (including i), ii) and iii) and the resultant talc-free polymeric foam film have less than 0.1 percent weight or less talc by a total weight of the mixture/a total weight of the resultant talc-free polymeric foam film. In some embodiments a mixture (including i), ii) and iii) and the resultant talc-free polymeric foam film have 0.0 percent weight talc by a total weight of the mixture/a total weight of the resultant talc-free polymeric foam film.
• being“talc- free” can desirably avoid/mitigate carcinogens, permit a desired density of a talc-free polymeric foam film, permit greater amount of polymeric material to be present in the resultant talc-free polymeric foam film, and/or permit the presence/higher amounts of pigment in the resultant talc-free polymeric foam film, among other advantages,
• the polymeric material used in the methods of forming talc-free polymeric foam films and resultant talc-free polymeric foam films of this disclosure may be formed of any suitable polymeric material.
• Suitable polymeric materials include polyolefins and, in particular, polyethylene.
• Blends of more than one polymeric material, such as blends of poly ethyl enes, may be suitable.
• polymeric material can be a low density polyethylene (LDPE) with a density of 0.918 to 0.935 gram/cubic centimeter as measured by ASTM D-792 and a melt index in a range from 0.25 to 8.0 gram/10 minutes as determined in accordance with as measured by ASTM D-1238 (190° C./2.16 kilogram (kg)), a linear low density polyethylene (LLDPE) having a density of 0.917 to 0.937 gram/cubic centimeter as measured by ASTM D-792 and a melt index in a range from 0.4 to 6.0 gram/10 minutes as determined in accordance with as measured by ASTM D-1238 (190° C./2.16 kg), or a combination thereof.
• LDPE low density polyethylene
• LLDPE linear low density polyethylene
• the polymeric materials can include ethylene/a- olefin copolymers having a density in a range of from 0.917 to 0.937 gram/cubic centimeter.
• suitable ethylene/a-olefm copolymers include LLDPE such as those available under the tradename INNATETM.
• Suitable ethylene/a-olefm copolymers include LDPE such as those available under the tradename AGILITYTM.
• the polymeric material can include a LDPE having density in a range of from 0.918 to 0.935 gram/cubic centimeter. All individual values and subranges from 0.918 to 0.935 are included; for example, the density can be from a lower limit of 0.918 or 0.925 to an upper limit of 0.935 or 0.930.
• the LDPE can have a melt index in a range from 0.25 to 8.0 gram/10 minutes.
• melt index can be from a lower limit of 0.25, 0.50, or 1.00 to an upper limit of 8.00, 3.50, 3.00, or 2.00.
• melt index of the LDPE can be a value in a range of from 1.0 to 8.0 gram/10 minutes.
• the ethyl ene/a-olefm copolymers can include LLDPE.
• the LLDPE can have density in a range of from 0.917 to 0.0937gram/cubic centimeter. All individual values and subranges from 0.917 to 0.937 are included; for example, the density can be from a lower limit of 0.917 or 0.925 to an upper limit of 0.937 or 0.930.
• the LLDPE can have a melt index in a range from 0.40 to 6.0 gram/10 minutes.
• melt index can be from a lower limit of 0.40, 0.75, or 1.00 to an upper limit of 6.00, 5.00 4.00, 3.00, or 2.00.
• melt index of the LLDPE can be a value in a range of from 2.0 to 6.0 gram/ 10 minutes.
• suitable physical blowing agents include hydrocarbons, chlorofluorocarbons, nitrogen, and carbon dioxide, among other physical blowing agents.
• the physical blowing agents can be in a supercritical state.
• a substance being in a“super critical” state refers to the substance being at a temperature and pressure above a critical point of the substance such that distinct liquid and gas phases do not exist.
• a physical blowing agent such as nitrogen and/or carbon dioxide be employed that are in the supercritical state in an extruder.
• that physical blowing agent can be supercritical nitrogen.
• the chemical blowing agent can be citric acid (CeFLCh), sodium bicarbonate (NaHCCh) and/or sodium citrate (NasCeFLCh).
• the dual blowing agents can include nitrogen as the physical blowing agent and citric acid can be included as the chemical blowing agent, among other possibilities.
• the chemical and/or physical blowing agent alone or in combination with the polymeric material can be introduced via a port or otherwise into an extruder.
• the chemical blowing agent can be present in an amount of from 0.5 percent to 5.0 percent by weight of a total weight of a mixture of i), ii), and iii), as detailed herein.
• the chemical blowing agent can be present in a range from 0.1 percent to 5.0 percent by weight, in a range from 0.5 to 5.0 percent by weight, or in a range from 0.5 to 2.0 by weight of a total weight of the mixture.
• the chemical blowing agent can be present in an amount of from 0.5 percent to 2.0 percent or from 0.5 to 1.0 by weight of a total weight of a mixture of i), ii), and iii), as detailed herein.
• the chemical blowing agent can be present at a numerical value of 1.0 or 0.5 percent by weight of a total weight of a mixture of i), ii), and iii), as detailed herein.
• the physical blowing agent can be present in an amount that is less than 10 percent, less than 5 percent, less than 2.5 percent, less than 1 percent, or less than 0.1 percent by weight of a total weight of a mixture of i), ii), and iii), as detailed herein. All individual values and subranges from less than 10 percent are included; for example, the physical blowing agent can be present in a range from 0.01 percent to 1.0 percent by weight, in a range from 0.05 to 0.1 percent by weight, or in a range from 0.04 to 0.06 by weight of a total weight of a mixture of i), ii), and iii).
• the physical blowing agent can be present at a numerical value of 0.05 percent or 0.06 by weight of a total weight of a mixture of i), ii), and iii), as detailed herein.
• a physical blowing agent when nitrogen is employed as a physical blowing agent, it may be possible in some embodiments to use very low amounts of blowing agent such as less than 1.0 percent, less than 0.5 percent, or less than 0.1 percent based on a total weight of the mixture of i), ii), and iii).
• the physical blowing agent can be provided to an extruder (or otherwise placed in thermal contact with a mixture including a chemical blowing agent) at a temperature well above a decomposition temperature of a chemical blowing agent.
• the physical blowing agent can be provided at a temperature above 200° C. All individual values and subranges above 200° C are included; for example, the physical blowing agent can be provided at a temperature in a range from 200° C to 250° C.
• the physical blowing agent can include nitrogen provided at a temperature of 215° C to an extruder having a mixture including citric acid compounds as a chemical blowing agent in the mixture.
• talc-free polymeric foam films are produced.
• overall density of the extruded/coextruded polyethylene structure can be reduced from typically 0.925 to 0.945 gram/cubic centimeter for a solid film to 0.620 to 0.850 gram/cubic centimeter for a talc-free polymeric foam film.
• a core layer and/or the skin layers can be formed of talc-free polymeric foam film.
• a core layer can formed of a talc-free polymeric foam film while a skin layer can formed from LDPE, LLDPE, or combination thereof. That is, in such embodiments provide for coextrusion of unfoamed skin layers around the foamed talc- free core layer formed with dual blowing agents (chemical and physical blowing agents) at a temperature above a decomposition temperature of the chemical blowing agent.
• the resultant thin talc-free polymeric foam films can have a film thickness of less than 100 microns for blown films and/or less than 300 microns for cast films.
• the methods of forming talc-free polymeric foam films herein can include extruding the heated mixture through the die to form a polymeric foam film precursor and processing the polymeric foam film precursor to form the talc-free polymeric foam film.
• a polymeric foam precursor refers to extruding from an extruder that can be subjected to processing for form a polymeric foam film.
• processing the polymeric foam film precursor can include i) blowing the polymeric foam film precursor with air to form a blown polymeric foam film or ii) cooling the polymeric foam film precursor on a quench roller to form a cast polymer foam film.
• further processing methods/steps can be employed to form the blown polymeric foam film and/or the cast polymeric foam films.
• a mixture of i), ii), and iii) can be heated to a temperature above a decomposition temperature of a chemical blowing agent.
• a mixture of i), ii), and iii) can be heated to a temperature in a range from 180° C to 230° C or in a range from 190° C to 230° C.
• the mixture of i), ii) and iii) can be heated to a temperature of 180° C, 182° C, 190° C, 193° C, or 216° C, among other possibilities.
• a suitable pressure to maintain the physical blowing agent in a supercritical state at a given temperature is employed. For instance, pressures above approximately 1000 PSI can be employed.
• heating to a temperature above a decomposition temperature of the chemical blowing agent can occur while i), ii), and/or iii) are present in an extruder.
• a mixture of i), ii), and iii) can be heated within a barrel, at a die, and/or other component of an extruder to a temperature above a decomposition temperature of the chemical blowing agent.
• Heating of the mixture above the decomposition temperature of the chemical blowing agent can cause the decomposition of the chemical blowing agent (e.g., partially into its constituent parts, such as CO2 due to being heated above a
• the decomposition temperature of the chemical blowing agent to provide chemical foaming in the polymer(s) being extruded, while the physical blowing agent provides a desired degree of physical foaming of the polymer(s) being extruded. Further, it is believed that at least some of the chemical blowing agent remains present as inorganic particles to function as nucleation sites (e.g., for N2 physical foaming).
• the resultant talc-free polymeric foam films can have an improved porosity in a range from 20 percent to 45 percent, as compared to other approaches that do not employ dual blowing agents (a physical blowing agent and a chemical blowing agent) in a mixture that is extruded at a temperature above a decomposition temperature of the chemical blowing agent.
• the resultant talc-free polymeric foam films can have a density reduction of from 20 percent to 45 percent. That is, the resultant talc-free foams, as detailed herein have a density reduction of less than 50 percent, in contrast to other approaches that may employ chemical blowing agents solely when seeking a density reduction of greater than 50 percent.
• the resultant talc-free polymeric foam films can have an improved porosity (i.e., density reduction) of from 25 percent to 45 percent, from 30 percent to 45 percent, or from 35 to 45 percent.
• the resultant talc-free polymeric foam films have improved physical/mechanical properties including at least a puncture resistance of at least 5.7 foot pound/cubic inches, a puncture break load of at least 16.9 pound-force, a normalized Spencer Impact resistance of at least 198 gram-force, a MD tensile @ break of at least 1686 pounds per square inch (PSI), and/or a CD tensile at break of at least 998 PSI, as compared to other approaches that do not employ dual blowing agents (a physical blowing agent and a chemical blowing agent) in a mixture that is extruded at a temperature above a decomposition temperature of the chemical blowing agent.
• dual blowing agents a physical blowing agent and a chemical blowing agent
• the puncture resistance of at least 5.7 foot-pound/cubic inches. All individual values and subranges above at least 5.7 are included; for example, in some embodiments the puncture resistance can be a value in a range of from 5.7 to 6.2, from 5.7 to 16.6, or from 5.7 to 18.2 foot-pound/cubic inches.
• a puncture break load is at least 16.9 pound-force.
• the puncture break load can be a value in a range of from 16.9 to 19.0, from 16.9 to 22.9, or from 16.9 to 24.6 pound-force.
• a normalized Spencer Impact resistance is at least
• a MD tensile @ break is at least 1686 PSI. All individual values and subranges above at least 1686 are included; for example, in some embodiments the MD tensile @ break can be a value in a range of from 1686 to 1864, from 1686 to 1902, or from 1686 to 1907 PSI.
• a CD tensile at break is at least 998 PSI. All individual values and subranges above at least 998 are included; for example, in some embodiments the CD tensile @ break can be a value in a range of from 998 to 1010, from 998 to 1016, or from 1686 to 1395 PSI.
• Talc is available from Dow Coming (Multibase ME 50024 (64% talc in
• a talc-free citric Acid compound is available from CLAMANTTM under the tradename HYDROCEROLTM CF 40E (40% active, having a decomposition temperature of approximately 160° C) and HYDROCEROLTM 1622 (40% active, having a decomposition temperature of approximately 150° C), as detailed in Table 4.
• LDPE has a density in a range from 0.918 to 0.935 gram/cubic centimeter and a melt index in a range from 0.25 to 8.0 gram/10 minutes.
• suitable LDPE include those available from The DOW Chemical Company such as those under the Tradename AGILITYTM, among other suitable LDPE.
• the LDPE employed is LDPE 722 which has a density of 0.918 g/cc and a MI of 8.0 gram / 10 minutes or LDPE 6621 which as a density of 0.919 g/cc and a MI of 0.47 gram/10 minutes.
• the ethylene/a-olefm has a density in a range from 0.917 to 0.937 gram/cubic centimeter and a melt index in a range from 0.4 to 6.0 gram/10 minutes.
• a suitable ethylene/a-olefm include LLDPE such as those available from The DOW Chemical Company under the Tradename INNATETM’ among other suitable ethylene/a-olefms.
• the ethylene/a-olefm employed is INNATETM ST50 (referred to in the tables below as“PE”) which as a density of 0.918 g/cc and a MI of 0.85 gram / 10 minutes.
• Nitrogen is available from Air Gas Company in high purity grade.
• CE 1-5 were prepared by procuring competitive chemical blowing agents as described in Tables 1 and 2 from the sources as detailed above and performed testing as detailed herein.
• CE 1 and CE 3 corresponds to 15 percent talc master batch (64% talc in LDPE with density 1.6 g/cc) by weight of a total weight of a mixture of the talc and a polymeric material (LDPE), while CE 2 corresponds to the 2 percent HYDROCEROLTM CF 40E (40% active) by weight of a total mixture including the chemical blowing agent and a polymeric material (LDPE).
• CE 1 - 3 are physical blowing only examples.
• CE 4 -5 are each conducted in the absence of a physical blowing agent (e.g., supercritical Nitrogen) and these are chemical blowing only examples.
• a MLP-10 unit from MuCell Extrusion, LLC was set up on a cast coextrusion line.
• the MuCell unit was designed to continuously deliver a controllable amount of N2 in a supercritical state to an extruder at a controllable pressure.
• the cast coextrusion line is composed of three 1.5-inch single-screw extruders (extruder A, extruder B, and skin extruder) and each extruder is coupled with a gear pump for flow control. This line was originally designed to coextrude microlayer film samples where two core extruders, extruder A and extruder B, feed an A/B/A three layer feedblock.
• LDPE low density polyethylene
• MI melt index
• Puncture resistance (ft lb./in3) and Puncture Break Load (lbf) were determined by a modified method based on ASTM D5748 as follows.
• the Puncture test determines the resistance of a film to the penetration of a probe at a standard low rate, single test velocity.
• the film is conditioned for at least 40 hours after film production at 23°C (+/- 2°C) and 50% R.H (+/- 10) as per ASTM standards.
• Standard testing conditions are 23°C (+/- 2°C) and 50% R.H (+/- 10) as per ASTM standards. Puncture is measured on a tensile testing machine. Square specimens are cut from a sheet to a size of 6 inches by 6 inches.
• the specimen is clamped in a 4 inch diameter circular specimen holder and a puncture probe is pushed into the center of the clamped film at a cross head speed of 10 inches/minute.
• the Dow test method deviates from the ASTM standard in that the probe used is a 0.5 inch diameter polished steel ball on a 0.25 inch diameter support rod.
• the ASTM test method uses the 0.75 inch diameter, pear shaped Teflon coated probe specified in D5748. There is an approximate 12 inch maximum travel length to prevent damage to the test fixture. There is no gauge length; prior to testing the probe is as close as possible to, but not touching, the specimen. A single thickness measurement is made in the center of the specimen.
• CE 1 and CE 2 are Comparative Examples of physical foaming only (no chemical foaming) where CE 1 is using 15% talc Multibase as a nucleating agent vs.
• CE 2 is using 2% HYDROCEROLTM CF 40E as a nucleating agent at temperature 138 °C below the decomposition, both in LDPE 722 (core and skins).
• IE 1 and IE 2 are Inventive Examples of physical and chemical foaming.
• IE 1 is LDPE 6621 using 0.5% HydrocerolTM CF-40E as a nucleating agent and a chemical blowing agent (due to being heated above a decomposition temperature of CF- 40E)
• IE 2 is LDPE 6621 using 1% HydrocerolTM CF-40E as a nucleating agent and a chemical blowing agent (due to being heated above a decomposition temperature of CF- 40E).
• IE 3 and IE 4 are Inventive Examples of physical and chemical foaming.
• IE 3 is a blend of INNATETM ST 50 and LDPE 6621 using 0.5% HydrocerolTM
• CF-40E as a nucleating agent and a chemical blowing agent and IE 2 is a blend of
• CE3 is a Comparative Examples of physical foaming only (no chemical foaming) using 15% talc MB as a nucleating agent (i.e., a nucleant) in LDPE 6621 (core and skins).
• IE 5 - 7 are Inventive Examples of physical and chemical foaming in all cases using 1% talc-free nucleating agent and chemical blowing agent run at a temperature above a decomposition temperature. That is, notably each of IE 5, IE 6, and IE 7 have both physical and chemical foaming due to heating of the HydrocerolTM 1622/HydrocerolTM CF-40E above a decomposition temperature of the HydrocerolTM
• IE 4 and IE 5 are Comparative Examples of chemical foaming only
• CE 4 is a blend of INNATETM ST
• IE 8 and IE 9 are Inventive Examples of physical and chemical foaming.
• IE 8 is a blend of INNATETM ST 50 and LDPE 6621 using 0.5% HydrocerolTM
• CF-40E as a nucleating agent and a chemical blowing agent
• IE 9 is a blend of
• Multibase ME 50024 or HydrocerolTM CF 40-E Multibase ME 50024 or HydrocerolTM CF 40-E.
• CE 3 was performed with talc containing nucleating agent (ME 50024)
• CE 4, and CE 5 were both conducted in an absence of a physical blowing agent.
• the above examples are directed to cast films.
• the disclosure is not so limited and can include blown films.
• each of the polymeric foam films in IE 1-9 was talc-free, in contrast to CE 1 and CE 3 which each contained talc.
• Talc-free polymeric foam films are desirable as described above.
• talc is generally present in relatively high amounts ( See e.g., CE 1 and CE 3 having talc present at 15 percent by weight). Such high amounts of talc can negatively impact end product properties of a polymeric foam film such as a density given the relatively high density of talc (-1.6 gram/cubic centimeter).
• the presence and/or amount of another components e.g., pigment
• the presence and/or amount of another components e.g., pigment
• the shape of the pigment (sphere) vs. talc (lamellae) can affect the quality of the foamed film.
• the talc-free polymeric foam films of IE 1-9 desirably have porosities of 27.0, 30.0, 37.0, 40.0, 36.0, 44.0 35.0, 41.0, and 39.0, respectively. That is, IE 1-9 desirably and surprisingly exhibited improved (higher) porosity than the porosities of CE 1 and 3-5 that have porosities of 23, 22.0, 3.0, and 15.0, respectively. For instance, talc-free IE 1 (27.0 percent porosity) exhibited - 17% percent increase in porosity as compared CE 1 (23 percent porosity). Further still, talc-free IE 1 also desirably and unexpectedly exhibited improved mechanical/physical properties.
• IE 1 exhibited improved (higher values) in puncture resistance (-38 percent higher), puncture break load (-20 percent higher), and MD Tensile @ break ( ⁇ 5 percent higher), as compared to CE 1, and yet again had improved porosity (- 17 percent higher).
• IE 1 (along with IE 2-9) exhibited talc-free polymeric foam films that desirable and surprisingly had improved porosity while providing similar and/or improved mechanical properties as compared to CE 1-5.
• the combination of improved porosity and similar and/or improved mechanical properties realized by IE 1-9 is believed to be attributable to the combination of a particular chemical blowing agent (e.g., citric acid compound) in the presence of a physical blowing agent (e.g., N2) when the extrusion temperature of the mixture is greater than a decomposition temperature of the particular chemical blowing agent.
• a particular chemical blowing agent e.g., citric acid compound
• a physical blowing agent e.g., N2
• the decomposition of the chemical blowing agent (e.g., at least partially into its constituent parts due to being heated above a decomposition temperature of the chemical blowing agent) provides a desired degree of chemical foaming in the polymer(s) being extruded, while the physical blowing agent provides a desired degree of physical foaming of the polymer(s) being extruded. Further, it is believed that at least some of the chemical blowing agent remains present as inorganic particles to function as nucleating agent by providing nucleation sites (e.g., for N2) for physical foaming).
• nucleation sites e.g., for N2
• a chemical blowing agent e.g., citric acid compound
• a physical blowing agent e.g., N2
• a synergist benefit e.g., higher porosity and/or improved/similar mechanical properties
• CE 2 results in improved porosity of 30.1 (relative to the porosity of 23 in CE 1), but also undesirably results in a significant decrease in at least some physical/mechanical properties as compared to the values of the physical/mechanical properties in each of IE 1-9 which employ the combination of physical blowing agent and chemical blowing agent in a mixture heated above a decomposition temperature of the chemical blowing agent.
• each of CE 1, CE 2 and IE 2 employ LDPE.
• IE 2 (1%) utilizes half of the agent of CE 2 (2%) and yet IE 2 realizes higher porosity along with improved/similar mechanical properties as CE 2.
• IE 2 (1%) utilizes far less nucleating agent than CE 1 (15%) and yet IE 2 realizes higher porosity along with improved/similar mechanical properties as CE 1.

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