WO2017114614A1 - Process for the production of modified polyethylene materials with inherent anti-fog properties - Google Patents

Process for the production of modified polyethylene materials with inherent anti-fog properties Download PDF

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Publication number
WO2017114614A1
WO2017114614A1 PCT/EP2016/078975 EP2016078975W WO2017114614A1 WO 2017114614 A1 WO2017114614 A1 WO 2017114614A1 EP 2016078975 W EP2016078975 W EP 2016078975W WO 2017114614 A1 WO2017114614 A1 WO 2017114614A1
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tert
polyethylene material
polyethylene
density
free radical
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PCT/EP2016/078975
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French (fr)
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Franciscus Petrus Hermanus SCHREURS
Jan Nicolaas Eddy DUCHATEAU
Ana Luisa VAZ
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Sabic Global Technologies B.V.
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Publication of WO2017114614A1 publication Critical patent/WO2017114614A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F255/00—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00
    • C08F255/02—Macromolecular compounds obtained by polymerising monomers on to polymers of hydrocarbons as defined in group C08F10/00 on to polymers of olefins having two or three carbon atoms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F8/00—Chemical modification by after-treatment
    • C08F8/46—Reaction with unsaturated dicarboxylic acids or anhydrides thereof, e.g. maleinisation
    • 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
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/18—Manufacture of films or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
    • B32B2307/21—Anti-static
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/40—Properties of the layers or laminate having particular optical properties
    • B32B2307/402—Coloured
    • B32B2307/4026—Coloured within the layer by addition of a colorant, e.g. pigments, dyes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/71—Resistive to light or to UV
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/75—Printability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2410/00—Agriculture-related articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging
    • 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
    • C08J2323/26—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers modified by chemical after-treatment

Definitions

  • the present invention relates to a process for the production of modified polyethylene materials having inherent anti-fog properties.
  • the invention also relates to modified polyethylene materials obtained via such process, and to films comprising such modified polyethylene materials as well as to the use of such modified polyethylene materials.
  • Polyethylene is a well known material for the production of a wide variety of products, such as for example film and sheet products, especially also for packaging and/or food packaging applications.
  • water that may come from the food contained in the package can condense against the packaging, forming droplets of water thereon.
  • droplets are unattractive to potential customers for packaged food and can prevent customers from buying leading to food waste. Moreover, the droplets can also reduce visibility through the packaging, so that the food inside the packaging cannot be seen and checked from the outside anymore. This may further reduce the appeal of the packaged good for potential customers.
  • anti-fog agents described in WO2002070597 may be added to the polyethylene, especially linear low density polyethylene (LLDPE) used for packaging film applications to obtain so called anti-fog properties by avoiding the formation of so called "fog” by condensed water droplets on the inside of the packaging films.
  • Anti-fog agents currently used are especially glycerol esters. These agents can migrate to the surface of packaging films and form a more polar layer at the film surface. This in turn will reduce surface energy and contribute to having condensed water more spread out.
  • anti-fog agents can be washed away with the water, so that they have only a limited effect.
  • the agents need some time to migrate to the surface, so that film producers need to store the produced films for some time to allow for the migration before they are actually used for food packaging applications.
  • anti-fog agents may also migrate to other layers of multi-layer films and influence or even degrade the properties of these other layers, which may be for example tie layers and/or barrier layers. This may lead to delamination and/or degradation of barrier properties.
  • a process for obtaining modified polyethylene materials wherein a polyethylene material is subjected to extrusion in the presence of a free radical initiator composition and at a polar monomer characterized in that the polar monomer may be added in quantities of 0.5 wt% to 20 wt% compared to the total weight of the polyethylene material and that the free radical initiator composition is added in an amount, so that no polar monomer remains detectable by IR and/or Raman spectroscopy for the modified polyethylene material, wherein the polar monomer is according to Formula 1 below:
  • R1 may be selected from -H or -CH3;
  • R2 may be selected from -0-, -(CO)-(NH)- or -(CO)-O-;
  • R3 may be an organic group, especially for example a linear or branched alkane or -CH2-CHR4-[0-CH 2 -CHR4] q -, wherein q ⁇ 1 and ⁇ 10 comprising 1-30 oms;
  • R4 is -OH, -IMH2, -N(CH 3 ) 2 , -N(CH 2 -CH 3 ) 2 , -N[CH(CH 3 ) 2 ] 2 , -NH[C(CH 3 ) 3 ]
  • n 0 or 1 ; and n ⁇ 1 and ⁇ 10; and p ⁇ 1 and ⁇ 10 or a mixture of two or more of these compounds above.
  • polyethylene materials are to be understood to be materials that comprise at least 50wt % of polyethylene or polyethylene copolymers, preferably at least 51 wt% polyethylene or polyethylene copolymers, preferably at least 60 wt% polyethylene or polyethylene copolymers, preferably at least 70 wt% polyethylene or
  • polyethylene copolymers preferably at least 80 wt% polyethylene or polyethylene copolymers, preferably at least 90 wt% polyethylene or polyethylene copolymers, preferably at least 95 wt% polyethylene or polyethylene copolymers, preferably at least 99 wt% polyethylene or
  • a polyethylene copolymer may thereby be a copolymer of ethylene and one or more other oolefin(s).
  • Polyethylene and/or polyethylene copolymers may be for example low-density
  • Polyethylenes linear low-density polyethylenes and/or high-density polyethylenes.
  • Polyethylene materials may thus especially for example comprise low-density polyethylenes, linear low- density polyethylenes and/or high-density polyethylenes.
  • Low-density polyethylenes also referred to as LDPE, may for example have a density as determined according to ISO 1 183-1 (2012), method A of ⁇ 900 and ⁇ 930 kg/m 3 .
  • Low-density polyethylenes may for example be produced via high-pressure radical polymerization processes.
  • Such high-pressure radical polymerization processes may for example be autoclave processes or tubular processes. Such processes are for example described in Nexant PERP report 2013-2 'Low Density Polyethylene'.
  • such high-pressure free radical polymerisation process comprise more than one of said autoclave reactors and/or said tubular reactors, for example positioned in series.
  • such high-pressure free radical polymerisation process comprise two reactors in series.
  • the process may comprise a first polymerisation in an autoclave reactor and a further polymerisation in a tubular reactor.
  • the process may comprise a first polymerisation in a tubular reactor and a further polymerisation in an autoclave reactor.
  • the process may comprise a first polymerisation in a tubular reactor and a further polymerisation in a further tubular reactor.
  • the process may comprise a first polymerisation in an autoclave reactor and a further polymerisation in an autoclave reactor.
  • Linear low-density polyethylenes may for example be obtained by polymerizing ethylene as monomer, optionally in the presence of one or more comonomers.
  • comonomers may include 1 -butene, 1 -pentene, 4-methyl-1-pentene, 1-hexene, 1 -heptene and/or 1 -octene.
  • such comonomers may be present in quantities of ⁇ 40.0 % by weight, alternatively ⁇ 30.0 % by weight, alternatively ⁇ 15.0 % by weight, alternatively ⁇ 10.0 % by weight, alternatively ⁇ 5.0% by weight, alternatively ⁇ 3.0 % by weight, compared to the total weight of the low-density polyethylene.
  • such comonomers may be present in quantities of ⁇ 0.01 % by weight , alternatively ⁇ 0.05 % by weight, alternatively ⁇ 0.10 % by weight, alternatively ⁇ 0.30 % by weight, alternatively ⁇ 0.50 % by weight, alternatively ⁇ 1.00% by weight, compared to the total weight of the low-density polyethylene.
  • such comonomers may be present in quantities of ⁇ 0.05 % and ⁇ 40.0 by weight, alternatively ⁇ 0.10 % and ⁇ 10.0 %by weight, alternatively ⁇ 0.30 % and ⁇ 3.0 % by weight, compared to the total weight of the low-density polyethylene.
  • Linear low-density polyethylenes also referred to as LLDPE, may for example have a density as determined according to ISO 1 183-1 (2012), method A of ⁇ 910 kg/m 3 and ⁇ 940 kg/m 3 .
  • High-density polyethylenes also referred to as HDPE
  • HDPE may for example have a density as determined according to ISO 1 183-1 (2012), method A of ⁇ 940 kg/m 3 and ⁇ 970 kg/m 3 .
  • the present invention relates to a process wherein the polyethylene material may comprise for example one or more of a low-density polyethylene, a linear low- density polyethylene or a high-density polyethylene, or mixtures thereof.
  • the invention relates to a process wherein the polyethylene material may comprise for example one or more of a linear low-density polyethylene having a density of ⁇ 905 kg/m 3 and ⁇ 935 kg/m 3 , a low-density polyethylene having a density of ⁇ 915 kg/m 3 and ⁇ 935 kg/m 3 , a high-density polyethylene having a density of ⁇ 936 kg/m 3 and ⁇ 970 kg/m 3 , or mixtures thereof, the density determined according to ISO 1 183-1 (2012), method A.
  • a linear low-density polyethylene having a density of ⁇ 905 kg/m 3 and ⁇ 935 kg/m 3
  • a low-density polyethylene having a density of ⁇ 915 kg/m 3 and ⁇ 935 kg/m 3
  • a high-density polyethylene having a density of ⁇ 936 kg/m 3 and ⁇ 970 kg/m 3 , or mixtures thereof, the density determined according to ISO 1 183-1 (2012)
  • the invention relates to a process wherein the polyethylene material may comprise for example ⁇ 10.0% by weight, alternatively ⁇ 50.0% by weight, alternatively ⁇ 60.0% by weight, alternatively ⁇ 80.0% by weight, alternatively ⁇ 90.0% by weight, alternatively ⁇ 95.0% by weight, of a low-density polyethylene, a linear low-density polyethylene or a high-density polyethylene, or mixtures thereof, compared to the total weight of the polyethylene material.
  • Linear low-density polyethylenes and/or high-density polyethylenes may for example be obtained by polymerizing ethylene as monomer, optionally in the presence of one or more comonomers, in a slurry polymerization process, a gas phase polymerization process or a solution polymerization process, or combinations thereof.
  • the slurry, gas phase and solution polymerization processes may be catalytic polymerization processes. Such catalytic
  • the catalytic polymerization processes are commonly operated at reaction pressures of up to 1 MPa.
  • the catalytic polymerization processes may be operated using for example Ziegler-Natta catalyst systems, chromium-based Phillips type catalyst systems, metallocene catalysts systems, or any other catalyst system known in the art of ethylene homo- or copolymer production.
  • Such catalyst systems are described in for example Lloyd, L, Olefin Polymerization Catalysts', in 'Handbook of Industrial Catalysts', p. 31 1 -350, ISBN: 978-0-387-24682-6, 201 1.
  • one or more a-olefins may be used.
  • the one or more o olefin comonomers may for example be one or more selected from the group of ⁇ -olefins having ⁇ 3 and ⁇ 10 carbon atoms.
  • the one or more a-olefin comonomers may comprise for example an acyclic a-olefin.
  • the one or more a-olefin comonomers may be one or more selected from 1 -butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and/or 1 - octene.
  • the one or more a-olefin comonomers may for example be present in an amount of ⁇ 10.0 % by weight, alternatively ⁇ 8.0 % by weight, alternatively ⁇ 5.0 % by weight, alternatively ⁇ 4.0 % by weight, alternatively ⁇ 3.0 % by weight, alternatively ⁇ 2.0 % by weight, alternatively ⁇ 1 .0 % by weight, alternatively ⁇ 0.5 % by weight, compared to the total weight of the monomers.
  • the one or more a-olefin comonomers may for example be present in an amount of ⁇ 0.01 % by weight, alternatively ⁇ 0.05 % by weight, alternatively ⁇ 0.10 % by weight, compared to the total weight of the monomers.
  • the one or more ⁇ -olefin comonomers may be present in an amount of for example ⁇ 0.01 % and ⁇ 10.0 % by weight, alternatively ⁇ 0.05 and ⁇ 5.0 % by weight, compared to the total weight of the monomers.
  • the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a solution polymerisation process.
  • a solution polymerisation process for the production of linear low-density polyethylenes in accordance with the present invention is to be understood to be a process in which the polymerisation is performed at for example a temperature in the range of 50-300°C, at for example a pressure in the range of 2.0- 15.0 MPa, in which the reaction takes place in a an inert solvent, in which the inert solvent for example has a boiling point below the reaction temperature.
  • said solution polymerisation process is a continuous process.
  • the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a slurry polymerisation process.
  • a slurry polymerisation process for the production of linear low-density polyethylenes in accordance with the present invention is to be understood to be a process in which the polymerisation is performed at for example a temperature in the range of 70-90°C, at for example a pressure in the range of 0.3-5.0 MPa, in which the reaction takes place in an inert diluent, in which said diluent is for example a hydrocarbon which is inert during the polymerisation process and which is in a liquid phase under the conditions occurring in the polymerisation process.
  • said diluent may be hexane.
  • said slurry polymerisation process is a continuous process.
  • the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a gas-phase polymerisation process.
  • the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a gas- phase fluidized bed polymerisation process.
  • a gas-phase polymerisation process for the production of linear low-density polyethylenes or high-density polyethylenes in accordance with the present invention is to be understood to be a process in which the polymerisation is performed in a reactor in which the polymerisation reaction takes place in a gaseous phase.
  • Modified polyethylene materials obtained with the process according to the present invention may for example be used for the production of films or sheets.
  • the production of films from modified polyethylene materials may for example be conducted using blown film production and/or cast film production. Both processes are known in the art and described in e.g. the Handbook of Plastic Films, E.M Abdel-Bary (ed.), Rapra Technology Ltd., 2003, in sections 2.3 and 2.4.
  • the film according to the present invention may be produced via blown film production. Alternatively, the film according to the present invention may be produced via cast film production.
  • additives may for example be added during the extrusion.
  • suitable additives include but are not limited to the additives usually used for polyethylene materials, for example antioxidants, nucleating agents, acid scavengers, processing aids, lubricants, surfactants, blowing agents, ultraviolet light absorbers, antistatic agents, slip agents, anti-blocking agents, pigments, dyes and fillers.
  • the additives may added present in the typically effective amounts, such as for example between 0.001 weight % to 10 weight % based on the total weight of polyethylene material.
  • Suitable antioxidants may for example include one or more of phenolic antioxidants, phosphites or phosphonites.
  • Phenolic antioxidants may for example include one or more of octadecyl 3 ,5-d i-t-butyl-4- hydroxyhydrocinnamate, 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionic acid methyl ester, 3-(3,5-di- t-butyl-4-hydroxyphenyl)propionic acid, 2,4,6-tris-t-butyl phenol, 1 ,6-hexamethylene bis(3,5-di-t- butyl-4-hydroxyhydrocinnamate), pentaerythritol tetrakis(3,5-di-t-butyl-4- hydroxyphenyl)propionate, ethylenebis(oxyethylene)bis(3-t-butyl-4-hydroxy-5- methylhydrocinnamate), hexamethylenebis(3,5-di-t-butyl-4-hydroxycinnamate), thiodiethyl bis(
  • Phosphites or phosphonites may for example include one or more of triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert- butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bisisodecyloxy-pentaerythritol diphos
  • Suitable acid scavengers may for example include one or more of zinc oxide,
  • hydrotalcites such as calcium stearate, zinc stearate, sodium stearate.
  • a free radical initiator composition is to be understood to be a composition comprising at least compound that is capable of forming free radicals when subjected to conditions occurring in the extrusion unit.
  • a free radical initiator composition according to the present invention may for example be solid, liquid or a solution of at least one free radical initiator, especially for example at least one organic or inorganic peroxide, azide or azo compound, in at least one solvent, especially an organic solvent.
  • solvents examples include organic solvents such as non-polar organic solvents including pentane, cyclopentane, hexane, cyclohexane, decane, benzene, toluene and/or polar organic solvents including tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, propylene carbonate, formic acid, n-butanol, isopropanol, n-propanol, ethanol, methanol, acetic acid and/or mixtures of two or more thereof.
  • the free radical initiator composition may thereby for example comprise one or more selected from organic peroxides, azides or azo compounds.
  • the present invention relates to a process wherein the free radical initiator composition may for example comprise at least one organic or inorganic peroxide and/or preferably at least one peroxide selected from:
  • dialkyl peroxides including dicumyl peroxide, di(tert- butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne, di-tert- butyl peroxide;
  • cyclic peroxides including 3,6,9-triethyl-3,6,9-trimethyl-1 ,4,7-triperoxononane, 3,3,5,7,7-pentamethyl- ⁇ 1 ,2,4-trioxepane; or
  • hydroperoxides including isopropylcumyl hydroperoxide, 1 ,1 ,3,3- tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide;
  • At least one of dicumyl peroxide, di(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5- di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexyne or di-tert-butyl peroxide may thereby be especially preferred.
  • Suitable organic peroxides may for example include diacyl peroxides, dialkyl peroxides, peroxymonocarbonates, peroxydicarbonates, peroxyketals, peroxyesters, cyclic peroxides, hydroperoxides.
  • Suitable azo compounds may for example include 2,2'-azodi(isobutyronitrile), 2,2'-azodi(2-methylbutyronitrile), 1 ,1 '-azodi(hexahydrobenzonitrile).
  • Suitable azides may for example include organic azides such as 4-acetamidobenzene sulfonyl azide, 1 - azidoadamantane, 4-azidoaniline, azidomethyl phenyl sulfide, 2-azido-4-octadecene-1.3-diol, 5- azidopentanoic acid, 3-azido-l -propanamine, 3-azido-1-propanol, 2,6-bis-(4-azidobenziliden)-4- methylcyclohexanone, ethyl azidoacetate, 4-methoxybenzyloxycarbonyl azide.
  • organic azides such as 4-acetamidobenzene sulfonyl azide, 1 - azidoadamantane, 4-azidoaniline, azidomethyl phenyl sulfide, 2-azido-4-octadecene-1.3
  • diacyl peroxides examples include diisobutyryl peroxide, di(3,5,5- trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, dibenzoyl peroxide.
  • dialkyl peroxides examples include dicumyl peroxide, di(tert- butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne, di-tert-butyl peroxide, di-isononanoyl peroxide, di-tert-amyl peroxide, didecanoyl peroxide.
  • the free radical initiator composition may for example comprise 2,5- dimethyl-2,5-di(tert-butylperoxy)hexane.
  • peroxymonocarbonates examples include tert-amylperoxy 2-ethylhexyl carbonate, tert-butylperoxy isopropyl carbonate, tert-butylperoxy 2-ethylhexyl carbonate.
  • peroxydicarbonates examples include di(3-methoxybutyl)peroxydicarbonate, di- sec-butyl peroxydi carbon ate, diisopropyl peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, dibutyl peroxydicarbonate, diacetyl peroxy dicarbonate, dimyristyl peroxydicarbonate, dicyclohexyl peroxydicarbonate.
  • peroxyketals examples include 1 ,1-di(tert-butyl peroxy)-3,5,5-trimethylcyclohexane, 1 ,1 -di(tert-amyl peroxy)cyclohexane, 1 ,1-di(tert-butyl peroxy)cyclohexane, 2,2-di(tert-butyl peroxy)butane, butyl 4,4-di(tert-butyl peroxy)valerate, n-ethyl-4,4-di-(tert-butylperoxy)valerate, ethyl-3,3-di(tert-butylperoxy)butyrate, ethyl-3,3-di(tert-amylperoxy)butyrate.
  • peroxyesters examples include cumyl peroxyneodecanoate, 1 ,1 ,3,3,- tetramethylbutylperoxyneodecanoate, cumyl peroxyneoheptanoate, tert-amyl
  • Suitable cyclic peroxides are 3,6,9-triethyl-3,6,9-trimethyl-1 ,4,7- triperoxononane, 3,3,5,7,7-pentamethyl-1 ,2,4-trioxepane, 3,3,6,6,9,9,-hexamethyl-1 ,2,4,5- tetraoxacyclononane.
  • hydroperoxides examples include isopropylcumyl hydroperoxide, 1 ,1 ,3,3- tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide, methyl isobutyl ketone hydroperoxide, di-isopropyl hydroxyperoxide, hydrogen peroxide.
  • the free radical initiator composition may for example comprise a free radical initiator that has a half-life time at 190°C of between 3.0 s and 45.0 s, alternatively between 5.0 s and 30.0 s, alternatively between 10.0 s and 20.0 s.
  • Free radical initiators having such half-life time may be well mixed with the polar monomer and/or the polyethylene material, while reducing the likeness of cross-linking.
  • the half-life time is determined according to the formula I:
  • A is the Arrhenius frequency factor in s "1 ;
  • E a is the activation energy for the dissociation of the initiator in J/mol; R is the universal gas constant 8.3142 J/mol-K; T is the temperature in K.
  • the half-life time presents the time by which at least half of the molecules of the free radical initiator have decomposed.
  • Examples of such free radical initiators having such half-life time at 190°C include dialkyl peroxides such as for example dicumyl peroxide, di(tert-butylperoxyisopropyl)benzene, 2,5- dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexyne, di-tert-butyl peroxide; cyclic peroxides such as for example 3,6,9-triethyl- 3,6, 9-tri methyl- 1 ,4,7-triperoxononane, 3,3,5,7,7-pentamethyl- ⁇ 1 ,2,4-trioxepane; hydroperoxides such as for example isopropylcumyl hydroperoxide, 1 ,1 ,3,3-tetramethylbutyl hydroperoxide, cumyl hydro
  • the free radical initiator composition may for example be fed to the extrusion unit of the polyethylene material at a single feed inlet.
  • the free radical initiator composition may for example be fed to the extrusion unit of the polyethylene material at multiple feed inlets.
  • the composition of the free radical initiator composition of the first feed inlet may for example be the same as the composition of the free radical initiator composition of the second and further feed inlets.
  • the composition of the free radical initiator composition may for example at each feed inlet be the same or different than the composition of the free radical initiator composition at each of the other inlets.
  • the free radical initiator composition may for example be fed in a liquid form or in a solid form, optionally under pressure.
  • the free radical composition may for example comprise between 5 w% and 100 w% alternatively between 10 w% and 95 w%, alternatively between 25 w% and 92 w%, alternatively between 30 w% and 91 w%, alternatively between 35 w% and 90 w%, alternatively between 40 w% and 70 w%, alternatively between 45 w% and 60 w% by weight of free radical initiator, compared to the total weight of the free radical initiator composition.
  • the free radical initiator composition may for example be added in quantities so as to add to the polyethylene material between 0.01 wt% and 20 wt% of at least one free radical initiator compared to the total weight of the polyethylene material.
  • the free radical initiator composition may for example be added to the polyethylene material in quantities of between 0.1 wt% and 15 wt%, alternatively of between 0.5 wt% and 10 wt%, alternatively of between 0.5 wt% and 9.5 wt%, alternatively of between 0.5 wt% and 9 wt%, alternatively of between > 0.5 wt% and 8.5 wt%, compared to the total weight of the polyethylene material.
  • the free radical initiator composition may be added to the extrusion unit in a stage where the polyethylene material is molten or in a solid state.
  • the free radical initiator composition may be added in an amount, so that no polar monomer remains detectable by IR and/or Raman spectroscopy for the modified polyethylene material. This may mean that substantially all, especially for example more than 60 wt%, more than 80 wt%, more than 95 wt%, more than 97 wt% or even more than 99 wt%, of polar monomer added should preferably have reacted at the outlet, preferably the main outlet, of the extrusion unit.
  • the main outlet of the extrusion unit may thereby be the outlet where the modified polyethylene material according to the invention is collected for further use and/or that has the highest throughput.
  • IR and/or Raman measurement can be for example performed with a Sentronic transmission measurement equipment for NIR, and/or a Bruker Equinox 55 for FTIR and/or WITEC alpha 300R for Raman with the parameters and under the conditions for example mentioned below in Table 1 .
  • a polar monomer to be added to the polyethylene material according to the invention may for example be according to Formula 1 below:
  • R1 may be selected from -H or -CH3;
  • R2 may be selected from -0-, -(CO)-(NH)- or -(CO)-O-;
  • R3 may be an organic group, especially for example a linear or branched alkane or -CH 2 - CHR4-[0-CH 2 -CHR4] q -, wherein q ⁇ 1 and ⁇ 10 comprising 1-30 carbon atoms;
  • R4 is -OH, -IMH2, -N(CH 3 ) 2 , -N(CH 2 -CH 3 ) 2 , -N[CH(CH 3 ) 2 ] 2 , -NH[C(CH 3 ) 3 ], o , -NCO, - CF 3 , -CH(CF 3 ) 2 , -(CF 2 )p-CF 3 , -Si[OSi(CH 3 ) 3 ] 3 and -OSi(CH 3 ) 3 ,
  • n 0 or 1 ; and n ⁇ 1 and ⁇ 10; and p ⁇ 1 and ⁇ 10
  • R3 in Formula 1 above may thereby especially for example be selected from the group consisting of:
  • each R4 individually may be selected from CH 3 and H; and -CH 2 -CH(OH)-CH 2 -.
  • a polar monomer may for example also be an ⁇ , ⁇ -unsaturated-carboxylic acid with 3 to 8 carbon atoms, in particular maleic acid, fumaric acid, itaconic acid, acrylic acid, methacrylic acid and crotonic acid or an anhydrides, in particular methacrylic anhydride, maleic anhydride or itaconic anhydride or a mixture of two or more thereof.
  • a polar monomer to be added to the polyethylene material according to the invention may be at least one or more acrylate(s) and/or methacrylate(s) preferably comprising at least 3 heteroatoms selected from O, N or S.
  • a polar monomer to be added to the polyethylene material according to the invention may be at least a mixture of two or more acrylates and/or methacrylates, preferably comprising at least 3 heteroatoms selected from O, N or S.
  • a polar monomer to be added to the polyethylene material according to the invention may preferably comprise at least one or more thiol, alcohol, acid or amine function, which may optionally have been deprotonated and/or converted to a salt.
  • a polar monomer may for example especially be selected from: 2-hydroxyethyl acrylate, 2- hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2- hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2,3-dihydroxypropyl acrylate, 2,3- dihydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate,
  • a polar monomer may for example preferably be selected from: 2-(dimethylamino)ethyl methacrylate, 2-(Diethylamino)ethyl methacrylate, 2-(Diethylamino)ethyl acrylate, 2- (Dimethylamino)ethyl acrylate, 2-Aminoethyl methacrylate hydrochloride, 2-Aminoethyl acrylate hydrochloride, N-[3-(Dimethylamino)propyl]methacrylamide, N-[3- (Dimethylamino)propyl]acrylamide, 2-(Diisopropylamino)ethyl methacrylate, 2- (Diisopropylamino)ethyl acrylate, 2-(tert-Butylamino)ethyl methacrylate, 2-(tert-Butylamino)ethyl acrylate, 3-(Dimethylamino)propyl acrylate
  • a polar monomer may for example particularly be 2-(dimethylamino)ethyl methacrylate.
  • the polar monomer may for example be added in quantities between 0.5 wt% and 20 wt% compared to the total weight of the polyethylene material.
  • the polar monomer may for example be added to the polyethylene material in quantities of between 0.2 wt% and 12 wt%, alternatively of between 0.12 wt% and 12 wt%, alternatively of between 0.15 wt% and 10 wt%, alternatively of between 0.17 wt% and 7 wt%, alternatively of between 0.19 wt% and 5 wt%, alternatively of between 0.2 wt% and 3.5 wt%, compared to the total weight of the polyethylene material.
  • the polar monomer may be added as a gas and/or solid and/or as a liquid and/or as a solution, optionally under pressure.
  • the polar monomer may be added to the extrusion unit in a stage where the polyethylene material is molten or in a solid state.
  • the polar monomer may be added together with the polyethylene material or separately, preferably for example in the lowest temperature zone (the zone with the lowest temperature setting) of an extrusion unit.
  • the polar monomer and/or the free radical initiator composition may be added to an extrusion unit, like an extruder, preferably in the melt zone.
  • the melt zone is a zone in the melt extruding unit may follow the feed zone starting from the inlet of the polyethylene material in the extrusion unit and may be the zone of the extrusion unit in which the polyethylene material may preferably be molten.
  • the melt zone may thus be further away from the inlet of polyethylene material compared to the feed zone, which may be the zone of the extrusion unit which is the closest to the inlet of the polyethylene material and/or where the temperature is not sufficient to melt the polyethylene material.
  • the polar monomer and/or the free radical initiator composition may for example be added to an extrusion unit, like an extruder, in the feed zone, preferably for example either together with or separately from the polyethylene material.
  • the feed zone of the extrusion unit may thereby be the first zone in the extrusion unit starting from the inlet of the polyethylene material in the extrusion unit and/or in which the polyethylene material may preferably not yet be molten and/or that has the lowest temperature setting of the extrusion unit
  • the polar monomer may be added to an extrusion unit, like an extruder, preferably at a temperature > 130 °C, further preferred between 140 °C and 165 °C.
  • the free radical initiator composition may be added to an extrusion unit, like an extruder, preferably at a temperature > 150 °C, further preferred between 170 °C and 250 °C.
  • the polar monomer may thereby for example be fed to the extrusion unit at an inlet that is different from the inlet used to feed the free radical initiator composition.
  • the polar monomer is thereby fed to the extrusion unit before feeding the free radical initiator composition, preferably at an inlet of the extrusion unit located closer to the inlet of the polyethylene material.
  • extrusion is to be understood to be a method of processing of a polyethylene material by bringing the material in a molten condition, allowing the material to be mixed, preferably homogenously, and allowing further ingredients to be mixed into the polyethylene material whilst that polyethylene material is in molten condition.
  • the processed polyethylene material is solidified and may for example be shaped into small granules to be used in further processing steps into applications, like for example the manufacturing of films.
  • extrusion may for example be performed in an extrusion unit, especially for example in an extruder.
  • the polyethylene material is fed to the extrusion unit under an atmosphere that is free from oxygen, for example under an atmosphere that contains ⁇ 0.1 % by weight of oxygen, compared to the total weight of the atmosphere.
  • an atmosphere that is free from oxygen for example under an atmosphere that contains ⁇ 0.1 % by weight of oxygen, compared to the total weight of the atmosphere.
  • polyethylene material is fed to the extrusion unit under a nitrogen atmosphere.
  • the invention relates to a process wherein the extrusion may for example be conducted in a melt extruder at a temperature higher than the melting temperature of the polyethylene material, preferably between 35 °C and 350°C, preferably at least > 130°C.
  • Extrusion may for example be conducted at a temperature of between 40 °C and 250°C, alternatively at a temperature of between 45 °C and 240°C, alternatively at a temperature of between 50 °C and 230°C, alternatively at a temperature of between 45 °C and 215 °C, alternatively at a temperature of between 50 °C and 210°C, alternatively at a temperature of between 45 °C and 195 °C, alternatively at a temperature of between 50 °C and 190 °C.
  • the temperature may be selected as a function of the MFI of the modified polyethylene material one wants to obtain represented by the corresponding melt mass flow rate as measured according to ISO 1 131-1 (201 1 ). A lower temperature can reduce the MFI drop during the process according to the invention, while a higher temperature may increase that MFI drop.
  • Extrusion may thereby be for example be carried out in an extrusion unit comprising at least 2 zones, preferably least 3 zones, preferably at least 6 zones ,with individual temperature settings, whereby the temperature in the first zone may be not sufficient to melt the polyethylene material, preferably between 30 °C and 120 °C, the temperature in the second zone may be sufficient to melt the polyethylene material preferably between > 120 °C and 350 °C, further preferred between > 120 °C and 250 °C, further preferred between > 120 °C and 150 °C.
  • the temperature in the third zone or any further zone may be between > 120 °C and 350 °C, whereby the temperature of the third or any further zone may be higher or equal to the temperature of the second zone and the zones of the extrusion unit are preferably counted starting from the from the inlet of the polyethylene material in the extrusion unit.
  • the second as well as any third and/or subsequent zone may form the melt zone.
  • the first zone may form the feed zone
  • a polar monomer and/or a free radical initiator composition may be added in the second zone of the extrusion unit.
  • a polar monomer may be added in the second zone and/or a free radical initiator may be added in a third and/or in a subsequent zone of the extrusion unit.
  • extrusion may for example be performed in an extrusion unit such as an extruder.
  • an extruder may for example be a single-screw extruder.
  • Such an extruder may for example be a twin-screw extruder.
  • Such extrusion unit may comprise multiple extruders positioned in series.
  • Extrusion may for example be performed for example with a screw speed of between 25 RPM and 400 RPM, especially between 50 RPM and 350 RPM, especially between 100 RPM and 250 RPM.
  • the present invention further relates to a modified polyethylene material obtained via a process according to the present invention, whereby the modified polyethylene material may preferably be a polyethylene copolymer, especially comprising at least ethylene units and/or monomer units from at least one oolefin and/or monomer units of at least one polar monomer.
  • a modified polyethylene material according to the invention may preferably comprise for example between 0.01 w% and 20w%, preferably between 0.1 w% and 15 w%, further preferred between 0.5 w% and 10 w%, further preferred 1 w% and 9 w%, further preferred 2 w% and 8 w%, further preferred 3 w% and 7 w% of polymerized polar monomer, preferably for example as polymer grafts of the polyethylene material.
  • a modified polyethylene material according to the invention may thereby be used for example to achieve increased adhesion and/or increased paintability/printabilty and/or to reduce statics and/or to increase compatibility with polar materials.
  • a modified polyethylene material according to the invention may especially also be used as a tie layer to other more polar materials like nylon or EVOH.
  • the present invention further relates to films comprising and/or consisting of modified polyethylene material according to the invention.
  • Films according to the present invention may for example be used for packaging, such as in flexible packaging, for example food packaging, or as extrusion-coated films.
  • Such films may for example be flexible films.
  • Such films or each layer of such films may for example have a thickness of between 0.1 ⁇ and 1000 ⁇ , alternatively between 0.2 ⁇ and 500 ⁇ , alternatively between 0.5 ⁇ and 200 ⁇ , alternatively between 0.7 ⁇ and 100 ⁇ , alternatively between 1 ⁇ and 50 ⁇ , alternatively between 1 .5 ⁇ and 25 ⁇ .
  • Films according to the invention material may also be multilayer films comprising two or more layers, preferably of different polymer/polyolefin materials, especially multilayer films where at least one outer layer comprises and/or consists of a modified polyethylene material according to the invention.
  • the other layer(s) of such a multi-layer film may comprise and/or consist of polyethylene materials, especially HDPE, LDPE and/or LLDPE.
  • At least one layer of polyethylene material according to the invention may thereby be combined to one or more layers comprising or comprising substantially, for example especially more than 60 wt% or more than 80 wt%, or consisting of HDPE, LDPE or LLDPE.
  • Films according to the invention may preferably have at least one side and/or outer layer with a surface energy of at least one of their outer surface of between 30 dynes/cm and 100 dynes/cm, preferably between 35 dynes/cm and 60 dynes/cm, preferably between 40 dynes/cm and 55 dynes/cm, between > 42 dynes/cm and 55 dynes/cm.
  • Films according to the invention may preferably have at least one side and/or outer layer with a contact angle of water of at least one of their outer surface of between 75 °and 30°, preferably between 70 °and 30, preferably between 60 °and 32°, preferably between 55 °and 30°, preferably between 45 °and 30°.
  • the present invention also concerns the use of modified polyethylene material according to the invention for film applications, especially film applications for food packaging and/or green house films.
  • the present invention also concerns the use of modified polyethylene material according to the invention for achieving so called anti-fog properties especially for film application, further preferred for film applications for food packaging and/or green house films.
  • the present invention also concerns the use of modified polyethylene material according to the invention for improving the visibility through films, especially multi-layer film comprising and/or consisting of polyethylene materials, especially for food packaging and/or green house films.
  • the present invention also concerns the use of modified polyethylene material according to the invention for reducing the contact angle of water on films, especially multi-layer films, comprising and/or consisting of polyethylene materials, especially for food packaging and/or green house films.
  • Contact angle and surface energy may thereby be measured by a Pocketgoniometer PG- according to ISO 1872-2:2007 and/or ASTM D5946-09(2009) for example with the parameters and under the conditions mentioned below in Table 2.
  • Table 2 determination of contact angle and surface energy
  • the extruder is equipped with two dosing points were liquids can be injected via a pumps.
  • the polyethylene material was added to the extruder first before di-methyl-amino-ethyl- methacrylate (DMAEMA), as a polar monomer, was added as a liquid via a pump in the melt zone of the extruder at a temperature of 130 °C.
  • DMAEMA di-methyl-amino-ethyl- methacrylate
  • the free radical initiator composition was added as a solution of a peroxide in decane to the extruder through an inlet that is further away from the inlet of the polyethylene material compared to the inlet used for adding the polar monomer at a temperature of 170 °C.
  • the extruder was operated at a screw speed of 175 RPM, and fed with such quantities of polyethylene material feed to ensure a throughput of 12 kg/h.
  • the free radical initiator composition that was used was a commercially available peroxide having the chemical name 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in solution in decane (used in the quantities listed below in Table 4).
  • I R measurements by NIR and Raman spectroscopy was performed on the modified polyolefin material obtained both NIR and Raman with the equipment, the parameters and under the conditions for example mentioned above in Table 1.
  • the temperature profiles used for the 4 zones of the extruder that had an independent temperature setting can be found below in Table 3.
  • IR measurement were performed on the modified polyethylene with the Sentronic NIR equipment as described in Table 1 .
  • Contact angle and surface energy of the samples obtained according to the invention have been measured by a Pocketgoniometer PG- according to ISO 1872-2:2007 for example with the parameters and under the conditions mentioned below in Table 2.
  • homopolymerization of a polar monomer occurs to lead to modified polyethylene material according to the invention.

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Abstract

The present invention relates to a process for the production of modified polyethylene materials having inherent anti-fog properties. The invention also relates to modified polyethylene materials obtained via such process, and to films comprising such modified polyethylene materials as well as to the use of such modified polyethylene materials.

Description

Process for the production of modified polyethylene materials with inherent anti-fog properties
The present invention relates to a process for the production of modified polyethylene materials having inherent anti-fog properties. The invention also relates to modified polyethylene materials obtained via such process, and to films comprising such modified polyethylene materials as well as to the use of such modified polyethylene materials.
Polyethylene is a well known material for the production of a wide variety of products, such as for example film and sheet products, especially also for packaging and/or food packaging applications.
In food packaging, water that may come from the food contained in the package can condense against the packaging, forming droplets of water thereon.
These droplets are unattractive to potential customers for packaged food and can prevent customers from buying leading to food waste. Moreover, the droplets can also reduce visibility through the packaging, so that the food inside the packaging cannot be seen and checked from the outside anymore. This may further reduce the appeal of the packaged good for potential customers.
Currently so called anti-fog agents described in WO2002070597 may be added to the polyethylene, especially linear low density polyethylene (LLDPE) used for packaging film applications to obtain so called anti-fog properties by avoiding the formation of so called "fog" by condensed water droplets on the inside of the packaging films. Anti-fog agents currently used are especially glycerol esters. These agents can migrate to the surface of packaging films and form a more polar layer at the film surface. This in turn will reduce surface energy and contribute to having condensed water more spread out.
However, there are several disadvantages when using these agents. For instance, the anti-fog agents can be washed away with the water, so that they have only a limited effect. Moreover, the agents need some time to migrate to the surface, so that film producers need to store the produced films for some time to allow for the migration before they are actually used for food packaging applications. Finally, anti-fog agents may also migrate to other layers of multi-layer films and influence or even degrade the properties of these other layers, which may be for example tie layers and/or barrier layers. This may lead to delamination and/or degradation of barrier properties.
There is thus a need for materials with good anti-fog properties without the problems related to the use and addition of anti-fog agents.
This objective has now been achieved according to the present invention by a process for obtaining modified polyethylene materials, wherein a polyethylene material is subjected to extrusion in the presence of a free radical initiator composition and at a polar monomer characterized in that the polar monomer may be added in quantities of 0.5 wt% to 20 wt% compared to the total weight of the polyethylene material and that the free radical initiator composition is added in an amount, so that no polar monomer remains detectable by IR and/or Raman spectroscopy for the modified polyethylene material, wherein the polar monomer is according to Formula 1 below:
Formula 1
Figure imgf000004_0001
wherein
R1 may be selected from -H or -CH3;
R2 may be selected from -0-, -(CO)-(NH)- or -(CO)-O-;
R3 may be an organic group, especially for example a linear or branched alkane or -CH2-CHR4-[0-CH2-CHR4]q-, wherein q≥ 1 and < 10 comprising 1-30 oms;
R4 is -OH, -IMH2, -N(CH3)2, -N(CH2-CH3)2, -N[CH(CH3)2]2, -NH[C(CH3)3]
Figure imgf000004_0002
-CF3, -CH(CF3)2, -(CF2)p-CF3, -Si[OSi(CH3)3]3 and -OSi(CH3)3,
m = 0 or 1 ; and n≥ 1 and < 10; and p≥ 1 and < 10 or a mixture of two or more of these compounds above.
In the context of the present invention, polyethylene materials are to be understood to be materials that comprise at least 50wt % of polyethylene or polyethylene copolymers, preferably at least 51 wt% polyethylene or polyethylene copolymers, preferably at least 60 wt% polyethylene or polyethylene copolymers, preferably at least 70 wt% polyethylene or
polyethylene copolymers, preferably at least 80 wt% polyethylene or polyethylene copolymers, preferably at least 90 wt% polyethylene or polyethylene copolymers, preferably at least 95 wt% polyethylene or polyethylene copolymers, preferably at least 99 wt% polyethylene or
polyethylene copolymers. A polyethylene copolymer, may thereby be a copolymer of ethylene and one or more other oolefin(s).
Polyethylene and/or polyethylene copolymers may be for example low-density
polyethylenes, linear low-density polyethylenes and/or high-density polyethylenes. Polyethylene materials may thus especially for example comprise low-density polyethylenes, linear low- density polyethylenes and/or high-density polyethylenes.
Low-density polyethylenes, also referred to as LDPE, may for example have a density as determined according to ISO 1 183-1 (2012), method A of≥ 900 and < 930 kg/m3. Low-density polyethylenes may for example be produced via high-pressure radical polymerization processes. Such high-pressure radical polymerization processes may for example be autoclave processes or tubular processes. Such processes are for example described in Nexant PERP report 2013-2 'Low Density Polyethylene'.
For example, such high-pressure free radical polymerisation process comprise more than one of said autoclave reactors and/or said tubular reactors, for example positioned in series. For example, such high-pressure free radical polymerisation process comprise two reactors in series. For example, the process may comprise a first polymerisation in an autoclave reactor and a further polymerisation in a tubular reactor. Alternatively, the process may comprise a first polymerisation in a tubular reactor and a further polymerisation in an autoclave reactor.
Alternatively, the process may comprise a first polymerisation in a tubular reactor and a further polymerisation in a further tubular reactor. Alternatively, the process may comprise a first polymerisation in an autoclave reactor and a further polymerisation in an autoclave reactor.
Linear low-density polyethylenes may for example be obtained by polymerizing ethylene as monomer, optionally in the presence of one or more comonomers. For example, such comonomers may include 1 -butene, 1 -pentene, 4-methyl-1-pentene, 1-hexene, 1 -heptene and/or 1 -octene.
For example, such comonomers may be present in quantities of < 40.0 % by weight, alternatively < 30.0 % by weight, alternatively < 15.0 % by weight, alternatively < 10.0 % by weight, alternatively < 5.0% by weight, alternatively < 3.0 % by weight, compared to the total weight of the low-density polyethylene.
For example, such comonomers may be present in quantities of≥ 0.01 % by weight , alternatively≥ 0.05 % by weight, alternatively≥ 0.10 % by weight, alternatively≥ 0.30 % by weight, alternatively≥ 0.50 % by weight, alternatively≥ 1.00% by weight, compared to the total weight of the low-density polyethylene.
For example, such comonomers may be present in quantities of≥ 0.05 % and < 40.0 by weight, alternatively≥ 0.10 % and < 10.0 %by weight, alternatively≥ 0.30 % and < 3.0 % by weight, compared to the total weight of the low-density polyethylene.
Linear low-density polyethylenes, also referred to as LLDPE, may for example have a density as determined according to ISO 1 183-1 (2012), method A of≥ 910 kg/m3 and < 940 kg/m3.
High-density polyethylenes, also referred to as HDPE, may for example have a density as determined according to ISO 1 183-1 (2012), method A of≥ 940 kg/m3 and < 970 kg/m3.
In an embodiment, the present invention relates to a process wherein the polyethylene material may comprise for example one or more of a low-density polyethylene, a linear low- density polyethylene or a high-density polyethylene, or mixtures thereof.
In a further embodiment, the invention relates to a process wherein the polyethylene material may comprise for example one or more of a linear low-density polyethylene having a density of≥ 905 kg/m3 and < 935 kg/m3, a low-density polyethylene having a density of≥ 915 kg/m3 and < 935 kg/m3, a high-density polyethylene having a density of≥ 936 kg/m3 and < 970 kg/m3, or mixtures thereof, the density determined according to ISO 1 183-1 (2012), method A.
In another embodiment, the invention relates to a process wherein the polyethylene material may comprise for example≥ 10.0% by weight, alternatively≥ 50.0% by weight, alternatively≥ 60.0% by weight, alternatively≥ 80.0% by weight, alternatively≥ 90.0% by weight, alternatively≥ 95.0% by weight, of a low-density polyethylene, a linear low-density polyethylene or a high-density polyethylene, or mixtures thereof, compared to the total weight of the polyethylene material.
Linear low-density polyethylenes and/or high-density polyethylenes may for example be obtained by polymerizing ethylene as monomer, optionally in the presence of one or more comonomers, in a slurry polymerization process, a gas phase polymerization process or a solution polymerization process, or combinations thereof. The slurry, gas phase and solution polymerization processes may be catalytic polymerization processes. Such catalytic
polymerization processes are commonly operated at reaction pressures of up to 1 MPa. The catalytic polymerization processes may be operated using for example Ziegler-Natta catalyst systems, chromium-based Phillips type catalyst systems, metallocene catalysts systems, or any other catalyst system known in the art of ethylene homo- or copolymer production. Such catalyst systems are described in for example Lloyd, L, Olefin Polymerization Catalysts', in 'Handbook of Industrial Catalysts', p. 31 1 -350, ISBN: 978-0-387-24682-6, 201 1.
As comonomers, for example one or more a-olefins may be used. The one or more o olefin comonomers may for example be one or more selected from the group of α-olefins having ≥ 3 and < 10 carbon atoms. Preferably the one or more a-olefin comonomers may comprise for example an acyclic a-olefin. For example, the one or more a-olefin comonomers may be one or more selected from 1 -butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and/or 1 - octene.
In case an α-olefin comonomer is used in the polymerisation, the one or more a-olefin comonomers may for example be present in an amount of < 10.0 % by weight, alternatively < 8.0 % by weight, alternatively < 5.0 % by weight, alternatively < 4.0 % by weight, alternatively < 3.0 % by weight, alternatively < 2.0 % by weight, alternatively < 1 .0 % by weight, alternatively < 0.5 % by weight, compared to the total weight of the monomers.
In case an α-olefin comonomer is used in the polymerisation, the one or more a-olefin comonomers may for example be present in an amount of≥ 0.01 % by weight, alternatively≥ 0.05 % by weight, alternatively≥ 0.10 % by weight, compared to the total weight of the monomers.
For example, in case an α-olefin comonomer is used in the polymerisation, the one or more α-olefin comonomers may be present in an amount of for example≥ 0.01 % and < 10.0 % by weight, alternatively≥ 0.05 and < 5.0 % by weight, compared to the total weight of the monomers.
In an embodiment, the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a solution polymerisation process. A solution polymerisation process for the production of linear low-density polyethylenes in accordance with the present invention is to be understood to be a process in which the polymerisation is performed at for example a temperature in the range of 50-300°C, at for example a pressure in the range of 2.0- 15.0 MPa, in which the reaction takes place in a an inert solvent, in which the inert solvent for example has a boiling point below the reaction temperature. For example, said solution polymerisation process is a continuous process.
In an embodiment, the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a slurry polymerisation process. A slurry polymerisation process for the production of linear low-density polyethylenes in accordance with the present invention is to be understood to be a process in which the polymerisation is performed at for example a temperature in the range of 70-90°C, at for example a pressure in the range of 0.3-5.0 MPa, in which the reaction takes place in an inert diluent, in which said diluent is for example a hydrocarbon which is inert during the polymerisation process and which is in a liquid phase under the conditions occurring in the polymerisation process. For example, said diluent may be hexane. For example, said slurry polymerisation process is a continuous process.
In an embodiment, the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a gas-phase polymerisation process. In an embodiment, the linear low-density polyethylenes or high-density polyethylenes may for example be produced in a gas- phase fluidized bed polymerisation process. A gas-phase polymerisation process for the production of linear low-density polyethylenes or high-density polyethylenes in accordance with the present invention is to be understood to be a process in which the polymerisation is performed in a reactor in which the polymerisation reaction takes place in a gaseous phase.
Modified polyethylene materials obtained with the process according to the present invention may for example be used for the production of films or sheets. The production of films from modified polyethylene materials may for example be conducted using blown film production and/or cast film production. Both processes are known in the art and described in e.g. the Handbook of Plastic Films, E.M Abdel-Bary (ed.), Rapra Technology Ltd., 2003, in sections 2.3 and 2.4. The film according to the present invention may be produced via blown film production. Alternatively, the film according to the present invention may be produced via cast film production.
According to the invention, additives may for example be added during the extrusion. Examples of suitable additives include but are not limited to the additives usually used for polyethylene materials, for example antioxidants, nucleating agents, acid scavengers, processing aids, lubricants, surfactants, blowing agents, ultraviolet light absorbers, antistatic agents, slip agents, anti-blocking agents, pigments, dyes and fillers. The additives may added present in the typically effective amounts, such as for example between 0.001 weight % to 10 weight % based on the total weight of polyethylene material.
Suitable antioxidants may for example include one or more of phenolic antioxidants, phosphites or phosphonites.
Phenolic antioxidants may for example include one or more of octadecyl 3 ,5-d i-t-butyl-4- hydroxyhydrocinnamate, 3-(3,5-di-t-butyl-4-hydroxyphenyl)propionic acid methyl ester, 3-(3,5-di- t-butyl-4-hydroxyphenyl)propionic acid, 2,4,6-tris-t-butyl phenol, 1 ,6-hexamethylene bis(3,5-di-t- butyl-4-hydroxyhydrocinnamate), pentaerythritol tetrakis(3,5-di-t-butyl-4- hydroxyphenyl)propionate, ethylenebis(oxyethylene)bis(3-t-butyl-4-hydroxy-5- methylhydrocinnamate), hexamethylenebis(3,5-di-t-butyl-4-hydroxycinnamate), thiodiethyl bis(3,5-di-t-butyl-4-hydroxyphenyl)propionate, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, (3-(3,5-di-t-butyl-4-hydroxyphenyl)propionic-1 ,3,5-tris(2-hydroxyethyl))isocyanurate ester, 1 ,3,5- trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxyphenyl)benzene, 3-(3,5-dt-t-butyl-4- hydroxyphenyl)propionic acid methyl ester.
Phosphites or phosphonites may for example include one or more of triphenyl phosphite, diphenyl alkyl phosphites, phenyl dialkyl phosphites, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert- butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bisisodecyloxy-pentaerythritol diphosphite, bis(2,4-di-tert-butyl- 6-methylphenyl) pentaerythritol diphosphite, bis(2,4,6-tri-tert-butylphenyl) pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl) 4,4'- biphenylenediphosphonite, 6-isooctyloxy- 2,4,8,10-tetra-tert-butyl-12H-dibenzo[d,g]-1 ,3,2-dioxaphosphocin, 6-fluoro-2,4,8,10-tetra-tert- butyl-12-methyldibenzo[d,g]-1 ,3,2-dioxaphosphocin, bis(2,4-di-tert-butyl-6-methylphenyl) methyl phosphite, bis(2,4-di-tert-butyl- 6-methylphenyl) ethyl phosphite
Suitable acid scavengers may for example include one or more of zinc oxide,
hydrotalcites, hydroalumites, and/or metallic stearates such as calcium stearate, zinc stearate, sodium stearate.
In the context of the present invention, a free radical initiator composition is to be understood to be a composition comprising at least compound that is capable of forming free radicals when subjected to conditions occurring in the extrusion unit. A free radical initiator composition according to the present invention may for example be solid, liquid or a solution of at least one free radical initiator, especially for example at least one organic or inorganic peroxide, azide or azo compound, in at least one solvent, especially an organic solvent.
Examples of solvents that may be used are organic solvents such as non-polar organic solvents including pentane, cyclopentane, hexane, cyclohexane, decane, benzene, toluene and/or polar organic solvents including tetrahydrofuran, ethyl acetate, acetone, dimethylformamide, acetonitrile, propylene carbonate, formic acid, n-butanol, isopropanol, n-propanol, ethanol, methanol, acetic acid and/or mixtures of two or more thereof. The free radical initiator composition may thereby for example comprise one or more selected from organic peroxides, azides or azo compounds.
The present invention relates to a process wherein the free radical initiator composition may for example comprise at least one organic or inorganic peroxide and/or preferably at least one peroxide selected from:
• dialkyl peroxides including dicumyl peroxide, di(tert- butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne, di-tert- butyl peroxide;
• cyclic peroxides including 3,6,9-triethyl-3,6,9-trimethyl-1 ,4,7-triperoxononane, 3,3,5,7,7-pentamethyl-≥1 ,2,4-trioxepane; or
• hydroperoxides including isopropylcumyl hydroperoxide, 1 ,1 ,3,3- tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide;
• and/or mixtures thereof.
At least one of dicumyl peroxide, di(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5- di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexyne or di-tert-butyl peroxide may thereby be especially preferred.
Suitable organic peroxides may for example include diacyl peroxides, dialkyl peroxides, peroxymonocarbonates, peroxydicarbonates, peroxyketals, peroxyesters, cyclic peroxides, hydroperoxides. Suitable azo compounds may for example include 2,2'-azodi(isobutyronitrile), 2,2'-azodi(2-methylbutyronitrile), 1 ,1 '-azodi(hexahydrobenzonitrile). Suitable azides may for example include organic azides such as 4-acetamidobenzene sulfonyl azide, 1 - azidoadamantane, 4-azidoaniline, azidomethyl phenyl sulfide, 2-azido-4-octadecene-1.3-diol, 5- azidopentanoic acid, 3-azido-l -propanamine, 3-azido-1-propanol, 2,6-bis-(4-azidobenziliden)-4- methylcyclohexanone, ethyl azidoacetate, 4-methoxybenzyloxycarbonyl azide.
Examples of suitable diacyl peroxides are diisobutyryl peroxide, di(3,5,5- trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, dibenzoyl peroxide.
Examples of suitable dialkyl peroxides are dicumyl peroxide, di(tert- butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne, di-tert-butyl peroxide, di-isononanoyl peroxide, di-tert-amyl peroxide, didecanoyl peroxide.
In an embodiment, the free radical initiator composition may for example comprise 2,5- dimethyl-2,5-di(tert-butylperoxy)hexane.
Examples of suitable peroxymonocarbonates are tert-amylperoxy 2-ethylhexyl carbonate, tert-butylperoxy isopropyl carbonate, tert-butylperoxy 2-ethylhexyl carbonate.
Examples of suitable peroxydicarbonates are di(3-methoxybutyl)peroxydicarbonate, di- sec-butyl peroxydi carbon ate, diisopropyl peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, dibutyl peroxydicarbonate, diacetyl peroxy dicarbonate, dimyristyl peroxydicarbonate, dicyclohexyl peroxydicarbonate.
Examples of suitable peroxyketals are 1 ,1-di(tert-butyl peroxy)-3,5,5-trimethylcyclohexane, 1 ,1 -di(tert-amyl peroxy)cyclohexane, 1 ,1-di(tert-butyl peroxy)cyclohexane, 2,2-di(tert-butyl peroxy)butane, butyl 4,4-di(tert-butyl peroxy)valerate, n-ethyl-4,4-di-(tert-butylperoxy)valerate, ethyl-3,3-di(tert-butylperoxy)butyrate, ethyl-3,3-di(tert-amylperoxy)butyrate.
Examples of suitable peroxyesters are cumyl peroxyneodecanoate, 1 ,1 ,3,3,- tetramethylbutylperoxyneodecanoate, cumyl peroxyneoheptanoate, tert-amyl
peroxyneodecanoate, tert-butyl peroxyneodecanoate, tert-butyl peroxyisononanoate, tert-butyl permaleate, tert-butyl peroxydiethylisobutyrate, 1 ,1 ,3,3-tetramethylbutyl peroxypivalate, tert- butyl peroxyneoheptanoate, tert-amyl peroxypivalate, tert-butyl peroxypivalate, 2,5-dimethyl-2,5- di(2-ethylhexanoylperoxy)hexane, 1 ,1 ,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxydiethylacetate, tert-butyl peroxyisobutyrate, tert-amyl peroxyacetate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-amyl peroxybenzoate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate. Examples of suitable cyclic peroxides are 3,6,9-triethyl-3,6,9-trimethyl-1 ,4,7- triperoxononane, 3,3,5,7,7-pentamethyl-1 ,2,4-trioxepane, 3,3,6,6,9,9,-hexamethyl-1 ,2,4,5- tetraoxacyclononane.
Examples of suitable hydroperoxides are isopropylcumyl hydroperoxide, 1 ,1 ,3,3- tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide, methyl isobutyl ketone hydroperoxide, di-isopropyl hydroxyperoxide, hydrogen peroxide.
In an embodiment, the free radical initiator composition may for example comprise a free radical initiator that has a half-life time at 190°C of between 3.0 s and 45.0 s, alternatively between 5.0 s and 30.0 s, alternatively between 10.0 s and 20.0 s. Free radical initiators having such half-life time may be well mixed with the polar monomer and/or the polyethylene material, while reducing the likeness of cross-linking.
The half-life time is determined according to the formula I:
ln2
A - e R-T
Formula I In which: ti/2 is the half-life time in s;
A is the Arrhenius frequency factor in s"1;
Ea is the activation energy for the dissociation of the initiator in J/mol; R is the universal gas constant 8.3142 J/mol-K; T is the temperature in K.
The half-life time presents the time by which at least half of the molecules of the free radical initiator have decomposed.
Examples of such free radical initiators having such half-life time at 190°C include dialkyl peroxides such as for example dicumyl peroxide, di(tert-butylperoxyisopropyl)benzene, 2,5- dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert- butylperoxy)hexyne, di-tert-butyl peroxide; cyclic peroxides such as for example 3,6,9-triethyl- 3,6, 9-tri methyl- 1 ,4,7-triperoxononane, 3,3,5,7,7-pentamethyl-≥1 ,2,4-trioxepane; hydroperoxides such as for example isopropylcumyl hydroperoxide, 1 ,1 ,3,3-tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl hydroperoxide, tert-amyl hydroperoxide.
The free radical initiator composition may for example be fed to the extrusion unit of the polyethylene material at a single feed inlet. Alternatively, the free radical initiator composition may for example be fed to the extrusion unit of the polyethylene material at multiple feed inlets. In case multiple feed inlets are used, the composition of the free radical initiator composition of the first feed inlet may for example be the same as the composition of the free radical initiator composition of the second and further feed inlets. Alternatively, the composition of the free radical initiator composition may for example at each feed inlet be the same or different than the composition of the free radical initiator composition at each of the other inlets.
The free radical initiator composition may for example be fed in a liquid form or in a solid form, optionally under pressure.
The free radical composition may for example comprise between 5 w% and 100 w% alternatively between 10 w% and 95 w%, alternatively between 25 w% and 92 w%, alternatively between 30 w% and 91 w%, alternatively between 35 w% and 90 w%, alternatively between 40 w% and 70 w%, alternatively between 45 w% and 60 w% by weight of free radical initiator, compared to the total weight of the free radical initiator composition.
The free radical initiator composition may for example be added in quantities so as to add to the polyethylene material between 0.01 wt% and 20 wt% of at least one free radical initiator compared to the total weight of the polyethylene material. Preferably, the free radical initiator composition may for example be added to the polyethylene material in quantities of between 0.1 wt% and 15 wt%, alternatively of between 0.5 wt% and 10 wt%, alternatively of between 0.5 wt% and 9.5 wt%, alternatively of between 0.5 wt% and 9 wt%, alternatively of between > 0.5 wt% and 8.5 wt%, compared to the total weight of the polyethylene material.
The free radical initiator composition may be added to the extrusion unit in a stage where the polyethylene material is molten or in a solid state.
The free radical initiator composition may be added in an amount, so that no polar monomer remains detectable by IR and/or Raman spectroscopy for the modified polyethylene material. This may mean that substantially all, especially for example more than 60 wt%, more than 80 wt%, more than 95 wt%, more than 97 wt% or even more than 99 wt%, of polar monomer added should preferably have reacted at the outlet, preferably the main outlet, of the extrusion unit. The main outlet of the extrusion unit may thereby be the outlet where the modified polyethylene material according to the invention is collected for further use and/or that has the highest throughput. Remaining unreacted polar monomer may thereby detected by IR and/or Raman spectroscopy by one or more band(s) characteristic of the C=C double bonds. The amount of free radical initiator composition may thereby especially be selected, so as to make the band(s) of the C=C double bond(s) of the polar monomer, which can be observed by IR and/or Raman spectroscopy for the material, especially the polymer material, that leaves an extrusion unit without the addition of any free radical initiator composition, for example for acrylates and/or methacrylates at around 1630 cm-1, substantially disappear. This means that the free radical initiator composition may be added in an amount, preferably so that no band(s) of the C=C double bond(s) of the polar monomer, can be observed by IR and/or Raman spectroscopy for the modified polyethylene material, for example for acrylates and/or methacrylates especially at around 1630 cm"1. Adding a higher amount of polar monomer may thus lead to add a higher amount of free radical initiator composition.
IR and/or Raman measurement can be for example performed with a Sentronic transmission measurement equipment for NIR, and/or a Bruker Equinox 55 for FTIR and/or WITEC alpha 300R for Raman with the parameters and under the conditions for example mentioned below in Table 1 .
Table 1 : IR measurements
NIR Sentronic Transmission measurement
Path length: 4mm
Integration time: 0.0007s
Scans: 500
Reference: Air or PE material
Raman WITEC alpha 300R Measurement on granulates
Laser power: 5 mW
0.5 s
Integration time:
200
Accumulations:
Objective: 20x Bruker Equinox 55 Transmission
measurement
Melting film, thickness: 500μηι
Scans: 100
Reference: Air or PE material
Resolution: 4 cm-1
A polar monomer to be added to the polyethylene material according to the invention may for example be according to Formula 1 below:
Formula 1
Figure imgf000015_0001
wherein
R1 may be selected from -H or -CH3;
R2 may be selected from -0-, -(CO)-(NH)- or -(CO)-O-;
R3 may be an organic group, especially for example a linear or branched alkane or -CH2- CHR4-[0-CH2-CHR4]q-, wherein q≥ 1 and < 10 comprising 1-30 carbon atoms;
R4 is -OH, -IMH2, -N(CH3)2, -N(CH2-CH3)2, -N[CH(CH3)2]2, -NH[C(CH3)3], o , -NCO, - CF3, -CH(CF3)2, -(CF2)p-CF3, -Si[OSi(CH3)3]3 and -OSi(CH3)3,
m = 0 or 1 ; and n≥ 1 and < 10; and p≥ 1 and < 10
or mixtures of two or more of such compounds.
R3 in Formula 1 above may thereby especially for example be selected from the group consisting of:
* linear or branched alkane;
* -CH2-CHR4-[0-CH2-CHR4]q-, wherein q≥ 1 and < 10,
and each R4 individually may be selected from CH3 and H; and -CH2-CH(OH)-CH2-. Alternatively, a polar monomer may for example also be an α,β-unsaturated-carboxylic acid with 3 to 8 carbon atoms, in particular maleic acid, fumaric acid, itaconic acid, acrylic acid, methacrylic acid and crotonic acid or an anhydrides, in particular methacrylic anhydride, maleic anhydride or itaconic anhydride or a mixture of two or more thereof.
A polar monomer to be added to the polyethylene material according to the invention may be at least one or more acrylate(s) and/or methacrylate(s) preferably comprising at least 3 heteroatoms selected from O, N or S. A polar monomer to be added to the polyethylene material according to the invention may be at least a mixture of two or more acrylates and/or methacrylates, preferably comprising at least 3 heteroatoms selected from O, N or S.
A polar monomer to be added to the polyethylene material according to the invention may preferably comprise at least one or more thiol, alcohol, acid or amine function, which may optionally have been deprotonated and/or converted to a salt.
A polar monomer may for example especially be selected from: 2-hydroxyethyl acrylate, 2- hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 2- hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2,3-dihydroxypropyl acrylate, 2,3- dihydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate,
poly(propylene glycol) monoacrylate, poly(propyleneglycol) monomethacrylate, poly(ethylene glycol) monoacrylate, poly(ethylene glycol) monomethacrylate, poly(ethylenepropyleneglycol) monomethacrylate, 2-hydroxyethyl vinyl ether, 2-(dimethylamino)ethyl methacrylate, 2- (Diethylamino)ethyl methacrylate, 2-(Diethylamino)ethyl acrylate, 2-(Dimethylamino)ethyl acrylate, 2-Aminoethyl methacrylate hydrochloride, 2-Aminoethyl acrylate hydrochloride, N-[3- (Dimethylamino)propyl]methacrylamide, N-[3-(Dimethylamino)propyl]acrylamide, 2- (Diisopropylamino)ethyl methacrylate, 2-(Diisopropylamino)ethyl acrylate, 2-(tert- Butylamino)ethyl methacrylate, 2-(tert-Butylamino)ethyl acrylate, 3-(Dimethylamino)propyl acrylate and 3-(Dimethylamino)propyl methacrylate or mixtures of two or more thereof.
A polar monomer may for example preferably be selected from: 2-(dimethylamino)ethyl methacrylate, 2-(Diethylamino)ethyl methacrylate, 2-(Diethylamino)ethyl acrylate, 2- (Dimethylamino)ethyl acrylate, 2-Aminoethyl methacrylate hydrochloride, 2-Aminoethyl acrylate hydrochloride, N-[3-(Dimethylamino)propyl]methacrylamide, N-[3- (Dimethylamino)propyl]acrylamide, 2-(Diisopropylamino)ethyl methacrylate, 2- (Diisopropylamino)ethyl acrylate, 2-(tert-Butylamino)ethyl methacrylate, 2-(tert-Butylamino)ethyl acrylate, 3-(Dimethylamino)propyl acrylate and 3-(Dimethylamino)propyl methacrylate or mixtures of two or more thereof.
A polar monomer may for example particularly be 2-(dimethylamino)ethyl methacrylate.
The polar monomer may for example be added in quantities between 0.5 wt% and 20 wt% compared to the total weight of the polyethylene material. Preferably, the polar monomer may for example be added to the polyethylene material in quantities of between 0.2 wt% and 12 wt%, alternatively of between 0.12 wt% and 12 wt%, alternatively of between 0.15 wt% and 10 wt%, alternatively of between 0.17 wt% and 7 wt%, alternatively of between 0.19 wt% and 5 wt%, alternatively of between 0.2 wt% and 3.5 wt%, compared to the total weight of the polyethylene material.
The polar monomer may be added as a gas and/or solid and/or as a liquid and/or as a solution, optionally under pressure.
The polar monomer may be added to the extrusion unit in a stage where the polyethylene material is molten or in a solid state.
The polar monomer may be added together with the polyethylene material or separately, preferably for example in the lowest temperature zone (the zone with the lowest temperature setting) of an extrusion unit.
The polar monomer and/or the free radical initiator composition may be added to an extrusion unit, like an extruder, preferably in the melt zone. The melt zone is a zone in the melt extruding unit may follow the feed zone starting from the inlet of the polyethylene material in the extrusion unit and may be the zone of the extrusion unit in which the polyethylene material may preferably be molten. The melt zone may thus be further away from the inlet of polyethylene material compared to the feed zone, which may be the zone of the extrusion unit which is the closest to the inlet of the polyethylene material and/or where the temperature is not sufficient to melt the polyethylene material. Alternatively, the polar monomer and/or the free radical initiator composition may for example be added to an extrusion unit, like an extruder, in the feed zone, preferably for example either together with or separately from the polyethylene material. The feed zone of the extrusion unit may thereby be the first zone in the extrusion unit starting from the inlet of the polyethylene material in the extrusion unit and/or in which the polyethylene material may preferably not yet be molten and/or that has the lowest temperature setting of the extrusion unit
The polar monomer may be added to an extrusion unit, like an extruder, preferably at a temperature > 130 °C, further preferred between 140 °C and 165 °C.
The free radical initiator composition may be added to an extrusion unit, like an extruder, preferably at a temperature > 150 °C, further preferred between 170 °C and 250 °C.
The polar monomer may thereby for example be fed to the extrusion unit at an inlet that is different from the inlet used to feed the free radical initiator composition. Preferably the polar monomer is thereby fed to the extrusion unit before feeding the free radical initiator composition, preferably at an inlet of the extrusion unit located closer to the inlet of the polyethylene material.
In the context of the present invention, extrusion is to be understood to be a method of processing of a polyethylene material by bringing the material in a molten condition, allowing the material to be mixed, preferably homogenously, and allowing further ingredients to be mixed into the polyethylene material whilst that polyethylene material is in molten condition. After extrusion, the processed polyethylene material is solidified and may for example be shaped into small granules to be used in further processing steps into applications, like for example the manufacturing of films. Such extrusion may for example be performed in an extrusion unit, especially for example in an extruder.
In an embodiment, the polyethylene material is fed to the extrusion unit under an atmosphere that is free from oxygen, for example under an atmosphere that contains < 0.1 % by weight of oxygen, compared to the total weight of the atmosphere. For example, the
polyethylene material is fed to the extrusion unit under a nitrogen atmosphere.
In an embodiment, the invention relates to a process wherein the extrusion may for example be conducted in a melt extruder at a temperature higher than the melting temperature of the polyethylene material, preferably between 35 °C and 350°C, preferably at least > 130°C. Extrusion may for example be conducted at a temperature of between 40 °C and 250°C, alternatively at a temperature of between 45 °C and 240°C, alternatively at a temperature of between 50 °C and 230°C, alternatively at a temperature of between 45 °C and 215 °C, alternatively at a temperature of between 50 °C and 210°C, alternatively at a temperature of between 45 °C and 195 °C, alternatively at a temperature of between 50 °C and 190 °C. The temperature may be selected as a function of the MFI of the modified polyethylene material one wants to obtain represented by the corresponding melt mass flow rate as measured according to ISO 1 131-1 (201 1 ). A lower temperature can reduce the MFI drop during the process according to the invention, while a higher temperature may increase that MFI drop.
Extrusion may thereby be for example be carried out in an extrusion unit comprising at least 2 zones, preferably least 3 zones, preferably at least 6 zones ,with individual temperature settings, whereby the temperature in the first zone may be not sufficient to melt the polyethylene material, preferably between 30 °C and 120 °C, the temperature in the second zone may be sufficient to melt the polyethylene material preferably between > 120 °C and 350 °C, further preferred between > 120 °C and 250 °C, further preferred between > 120 °C and 150 °C. The temperature in the third zone or any further zone may be between > 120 °C and 350 °C, whereby the temperature of the third or any further zone may be higher or equal to the temperature of the second zone and the zones of the extrusion unit are preferably counted starting from the from the inlet of the polyethylene material in the extrusion unit. The second as well as any third and/or subsequent zone may form the melt zone. The first zone may form the feed zone
According to the inventor, a polar monomer and/or a free radical initiator composition may be added in the second zone of the extrusion unit. Alternatively, a polar monomer may be added in the second zone and/or a free radical initiator may be added in a third and/or in a subsequent zone of the extrusion unit.
Such extrusion may for example be performed in an extrusion unit such as an extruder. Such an extruder may for example be a single-screw extruder. Such an extruder may for example be a twin-screw extruder. Such extrusion unit may comprise multiple extruders positioned in series.
Extrusion may for example be performed for example with a screw speed of between 25 RPM and 400 RPM, especially between 50 RPM and 350 RPM, especially between 100 RPM and 250 RPM. The present invention further relates to a modified polyethylene material obtained via a process according to the present invention, whereby the modified polyethylene material may preferably be a polyethylene copolymer, especially comprising at least ethylene units and/or monomer units from at least one oolefin and/or monomer units of at least one polar monomer.
A modified polyethylene material according to the invention may preferably comprise for example between 0.01 w% and 20w%, preferably between 0.1 w% and 15 w%, further preferred between 0.5 w% and 10 w%, further preferred 1 w% and 9 w%, further preferred 2 w% and 8 w%, further preferred 3 w% and 7 w% of polymerized polar monomer, preferably for example as polymer grafts of the polyethylene material.
A modified polyethylene material according to the invention may thereby be used for example to achieve increased adhesion and/or increased paintability/printabilty and/or to reduce statics and/or to increase compatibility with polar materials. A modified polyethylene material according to the invention may especially also be used as a tie layer to other more polar materials like nylon or EVOH.
The present invention further relates to films comprising and/or consisting of modified polyethylene material according to the invention.
Films according to the present invention may for example be used for packaging, such as in flexible packaging, for example food packaging, or as extrusion-coated films. Such films may for example be flexible films. Such films or each layer of such films may for example have a thickness of between 0.1 μηη and 1000 μηη, alternatively between 0.2 μηη and 500 μηη, alternatively between 0.5 μηη and 200 μηη, alternatively between 0.7 μηη and 100 μηη, alternatively between 1 μηη and 50 μηη, alternatively between 1 .5 μηη and 25 μηη.
Films according to the invention material may also be multilayer films comprising two or more layers, preferably of different polymer/polyolefin materials, especially multilayer films where at least one outer layer comprises and/or consists of a modified polyethylene material according to the invention. The other layer(s) of such a multi-layer film may comprise and/or consist of polyethylene materials, especially HDPE, LDPE and/or LLDPE. At least one layer of polyethylene material according to the invention may thereby be combined to one or more layers comprising or comprising substantially, for example especially more than 60 wt% or more than 80 wt%, or consisting of HDPE, LDPE or LLDPE.
Films according to the invention may preferably have at least one side and/or outer layer with a surface energy of at least one of their outer surface of between 30 dynes/cm and 100 dynes/cm, preferably between 35 dynes/cm and 60 dynes/cm, preferably between 40 dynes/cm and 55 dynes/cm, between > 42 dynes/cm and 55 dynes/cm.
Films according to the invention may preferably have at least one side and/or outer layer with a contact angle of water of at least one of their outer surface of between 75 °and 30°, preferably between 70 °and 30, preferably between 60 °and 32°, preferably between 55 °and 30°, preferably between 45 °and 30°.
The present invention also concerns the use of modified polyethylene material according to the invention for film applications, especially film applications for food packaging and/or green house films.
The present invention also concerns the use of modified polyethylene material according to the invention for achieving so called anti-fog properties especially for film application, further preferred for film applications for food packaging and/or green house films.
The present invention also concerns the use of modified polyethylene material according to the invention for improving the visibility through films, especially multi-layer film comprising and/or consisting of polyethylene materials, especially for food packaging and/or green house films.
The present invention also concerns the use of modified polyethylene material according to the invention for reducing the contact angle of water on films, especially multi-layer films, comprising and/or consisting of polyethylene materials, especially for food packaging and/or green house films.
Contact angle and surface energy may thereby be measured by a Pocketgoniometer PG- according to ISO 1872-2:2007 and/or ASTM D5946-09(2009) for example with the parameters and under the conditions mentioned below in Table 2. Table 2: determination of contact angle and surface energy
Figure imgf000022_0001
The invention will now be illustrated by the following non-limiting examples.
Experiment I: Modification of the polyethylenes with free radical initiator.
In a Leistritz micro twin screw extruder with a screw diameter of 27 mm, a quantity of LLDPE (SABIC LLDPE M200024, with a MFIi9o°c 2.i6kg = 20 and density 924 kg/m3), as the polyethylene material, was fed under a nitrogen atmosphere.
The extruder is equipped with two dosing points were liquids can be injected via a pumps.
The polyethylene material was added to the extruder first before di-methyl-amino-ethyl- methacrylate (DMAEMA), as a polar monomer, was added as a liquid via a pump in the melt zone of the extruder at a temperature of 130 °C. The polyethylene material and the polar monomer were mixed.
The free radical initiator composition was added as a solution of a peroxide in decane to the extruder through an inlet that is further away from the inlet of the polyethylene material compared to the inlet used for adding the polar monomer at a temperature of 170 °C. The extruder was operated at a screw speed of 175 RPM, and fed with such quantities of polyethylene material feed to ensure a throughput of 12 kg/h.
The free radical initiator composition that was used was a commercially available peroxide having the chemical name 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane in solution in decane (used in the quantities listed below in Table 4). I R measurements by NIR and Raman spectroscopy was performed on the modified polyolefin material obtained both NIR and Raman with the equipment, the parameters and under the conditions for example mentioned above in Table 1. The temperature profiles used for the 4 zones of the extruder that had an independent temperature setting can be found below in Table 3.
Table 3: temperature profile
Figure imgf000023_0001
Table 4: conditions for the production of modified polyethylene material according to the invention
Figure imgf000023_0002
As can be seen blanks were produced without peroxide and monomer, as comparative example.
IR measurement were performed on the modified polyethylene with the Sentronic NIR equipment as described in Table 1 . Contact angle and surface energy of the samples obtained according to the invention have been measured by a Pocketgoniometer PG- according to ISO 1872-2:2007 for example with the parameters and under the conditions mentioned below in Table 2.
Table 2: determination of contact angle and surface energy
Figure imgf000024_0001
One can see that surface energy increases and contact angle decreases with an increasing amount of polar monomer added as shown in Fig. 1.
Moreover, one can see that when both a free radical initiator composition and a polar monomer are added, as in the process according to the invention the MFI represented by the melt mass flow rate as measured according to ISO 1 131-1 (201 1 ) of the polyethylene material decreases much less, than when only the same amount a free radical initiator composition is added to the same polyethylene material. This indicates that some grafting and/or
homopolymerization of a polar monomer occurs to lead to modified polyethylene material according to the invention.

Claims

Claims
1 . Process for obtaining modified polyethylene materials wherein a polyethylene
material is subjected to extrusion in the presence of a free radical initiator composition characterized in that in that the polar monomer may be added in quantities of 0.5 wt% to 20 wt% compared to the total weight of the polyethylene material and that the free radical initiator composition is added in an amount, so that no polar monomer remains detectable by IR and/or Raman spectroscopy for the modified polyethylene material, wherein the polar monomer is according to Formula 1 below:
Formula 1
Figure imgf000025_0001
wherein
R1 may be selected from -H or -CH3;
R2 may be selected from -0-, -(CO)-(NH)- or -(CO)-O-;
R3 may be an organic group, especially for example a linear or branched alkane or -CH2-CHR4-[0-CH2-CHR4]q-, wherein q≥ 1 and < 10 comprising 1-30 oms;
R4 is -OH, -IMH2, -N(CH3)2, -N(CH2-CH3)2, -N[CH(CH3)2]2, -NH[C(CH3)3]
Figure imgf000025_0002
-CF3, -CH(CF3)2, -(CF2)p-CF3, -Si[OSi(CH3)3]3 and -OSi(CH3)3,
m = 0 or 1 ; and n≥ 1 and < 10; and p≥ 1 and < 10 or a mixture of two or more of these compounds above.
2. Process according to claim 1 wherein the free radical initiator composition comprises at least one free radical initiator selected from: a. dialkyl peroxides including dicumyl peroxide, di(tert- butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, tert-butyl cumyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne, di-tert- butyl peroxide;
b. cyclic peroxides including 3,6,9-triethyl-3,6,9-trimethyl-1 ,4,7-triperoxononane, 3,3,5,7,7-pentamethyl-≥1 ,2,4-trioxepane; or
c. hydroperoxides including isopropylcumyl hydroperoxide, 1 ,1 ,3,3- tetramethylbutyl hydroperoxide, cumyl hydroperoxide, tert-butyl
hydroperoxide, tert-amyl hydroperoxide;
d. and/or mixtures thereof.
Process according to any one of claims 1 or 2 wherein the polar monomer is added in quantities between 0.5 wt% and 20 wt% compared to the total weight of the polyethylene material.
Process according to any one of claims 1 -3 wherein the extrusion is performed in an extrusion unit, wherein the polar monomer is added to the extrusion unit in a stage where the polyethylene material is in molten.
Process according to any one of claims 1 -4 wherein the extrusion is performed in an extrusion unit, wherein the free radical initiator composition is added to the extrusion unit in a stage where the polyethylene material is molten.
Process according to any one of claims 1 -5 wherein the polyethylene material comprises one or more of a low-density polyethylene, a linear low-density
polyethylene or a high-density polyethylene, or mixtures thereof.
Process according to claim 6 wherein the polyethylene material comprises one or more of a linear low-density polyethylene having a density of≥ 905 kg/m3 and < 935 kg/m3, a low-density polyethylene having a density of≥ 915 kg/m3 and < 935 kg/m3, a high-density polyethylene having a density of≥ 936 kg/m3 and < 970 kg/m3, or mixtures thereof, the density determined according to ISO 1 183-1 (2012), method A.
8. Process according to any one of claims 1 -8 wherein the polyethylene material comprises at least 50wt % of polyethylene or polyethylene copolymers.
9. Process according to any one of claims 1 -8 wherein the extrusion is conducted in a melt extruder at a temperature higher than the melting temperature of the
polyethylene material and preferably between 35 and 350°C.
10. Modified polyethylene material obtained via a process according to any one of claims 1 -9.
1 1. Film comprising and/or consisting of a modified polyethylene material according claim 10.
12. Film according to claim 1 1 , whereby at least one side of the film has a surface
energy between 30 dynes/cm and 100 dynes/cm and/or a contact angle of water between 75° and 30°.
13. Film according to one or more of the claim 1 1 or 12, whereby the film is a multi-layer film, which comprises at least one outer layer comprising and/or consisting of modified polyethylene material according to claim 1 1.
14. Use of a modified polyethylene material obtained via a process according to any one of claims 1 -9 for film applications, especially film applications for food packaging and/or green house films.
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