WO2017072694A2 - A process for coating polymeric substrates and paper - Google Patents

A process for coating polymeric substrates and paper Download PDF

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Publication number
WO2017072694A2
WO2017072694A2 PCT/IB2016/056473 IB2016056473W WO2017072694A2 WO 2017072694 A2 WO2017072694 A2 WO 2017072694A2 IB 2016056473 W IB2016056473 W IB 2016056473W WO 2017072694 A2 WO2017072694 A2 WO 2017072694A2
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WO
WIPO (PCT)
Prior art keywords
plasma
polymeric
composition
steps
paper
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PCT/IB2016/056473
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French (fr)
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WO2017072694A3 (en
Inventor
Claudia Riccardi
Stefano Zanini
Elisa Camilla DELL`ORTO
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Università Degli Studi Di Milano - Bicocca
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Publication of WO2017072694A2 publication Critical patent/WO2017072694A2/en
Publication of WO2017072694A3 publication Critical patent/WO2017072694A3/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/14—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by electrical means
    • B05D3/141—Plasma treatment
    • B05D3/142—Pretreatment
    • B05D3/144—Pretreatment of polymeric substrates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/14—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by electrical means
    • B05D3/141—Plasma treatment
    • B05D3/142—Pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/02—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to macromolecular substances, e.g. rubber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C59/00—Surface shaping of articles, e.g. embossing; Apparatus therefor
    • B29C59/14—Surface shaping of articles, e.g. embossing; Apparatus therefor by plasma treatment
    • 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
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/0427—Coating with only one layer of a composition containing a polymer binder
    • 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
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/043—Improving the adhesiveness of the coatings per se, e.g. forming primers
    • 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
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/048—Forming gas barrier coatings
    • 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
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/054—Forming anti-misting or drip-proofing coatings
    • 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
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/04—Coating
    • C08J7/056—Forming hydrophilic coatings
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
    • D21H17/24—Polysaccharides
    • D21H17/31—Gums
    • D21H17/32—Guar or other polygalactomannan gum
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
    • D21H17/20—Macromolecular organic compounds
    • D21H17/33—Synthetic macromolecular compounds
    • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H17/36—Polyalkenyalcohols; Polyalkenylethers; Polyalkenylesters
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/10—Coatings without pigments
    • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/10—Coatings without pigments
    • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/20—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H19/22—Polyalkenes, e.g. polystyrene
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H19/58—Polymers or oligomers of diolefins, aromatic vinyl monomers or unsaturated acids or derivatives thereof
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H19/00—Coated paper; Coating material
    • D21H19/36—Coatings with pigments
    • D21H19/44—Coatings with pigments characterised by the other ingredients, e.g. the binder or dispersing agent
    • D21H19/56—Macromolecular organic compounds or oligomers thereof obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D21H19/60—Polyalkenylalcohols; Polyalkenylethers; Polyalkenylesters
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
    • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
    • D21H23/22—Addition to the formed paper
    • D21H23/30—Pretreatment of the paper
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
    • D21H25/04—Physical treatment, e.g. heating, irradiating
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/10—Homopolymers or copolymers of propene
    • C08J2323/12—Polypropene
    • 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
    • C08J2401/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
    • C08J2401/08—Cellulose derivatives
    • C08J2401/26—Cellulose ethers
    • C08J2401/28—Alkyl ethers
    • 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
    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
    • C08J2405/04—Alginic acid; Derivatives thereof
    • 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
    • C08J2405/00—Characterised by the use of polysaccharides or of their derivatives not provided for in groups C08J2401/00 or C08J2403/00
    • C08J2405/08—Chitin; Chondroitin sulfate; Hyaluronic acid; Derivatives thereof
    • 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
    • C08J2429/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2429/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2429/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids

Definitions

  • the present invention concerns a method or process for coating with polymeric compositions applied by deposition on said polymeric substrates or paper through pre- and post- plasma treatments.
  • EP2431409 discloses a process for coating containers made of plastic material for food use with oxygen banier in which the activation is carried out with an oxyfluorination process, i.e. treatment with fluorine gas in mixture with inert gas, preferably air. This activation is followed by deposition of a coating of polyvinyl alcohol and a coating of polyvinyl acetal (polyvinyl butyral).
  • the activation step earned out by corona or plasma treatment, is followed by a deposition of a first inorganic coating by sol-gel technique, CVD (chemical vapour deposition) or PVD (physical vapour deposition), having the function both of a barrier coating and of a primer, for the subsequent application of a polymer having low permeability such as polyvinyl alcohol.
  • CVD chemical vapour deposition
  • PVD physical vapour deposition
  • the treatments known in the state of the art of activation of the surface of a substrate, on which the coating is applied are very wearisome since they require a whole series of treatments for the deposition of one or more layers of organic or inorganic primer or, as in the case of oxyfluorination, the use of very aggressive gases such as fluorine.
  • the organic primers are also applied in solution with organic solvents and must therefore be dried, with consequent consumption of energy, wasting of solvent and possible impact on the environment and human health.
  • a further drawback of the prior art is that, when in known coating processes polymerizable monomers are applied, other precursors are deposited in mixtures containing polymerization initiators that facilitate polymerization and increase the stability of the deposit.
  • the use of polymerization initiators becomes necessary, for example, for radical polymerization through UV systems and for ionic polymerization both through UV systems and through EB.
  • the amount of photoinitiator in the formulation can vary from 0.5 to 15 %. Besides being very expensive, photoinitiators are also very often toxic to human health, for which reason systems capable of polymerizing without them are highly desirable.
  • the Applicant has now unexpectedly found a coating process that allows the adhesion of the coating without the need for applications of primer or without the treatment with gases that are very aggressive and very dangerous for health and for the environment, like for example fluorine.
  • the subject of the present invention is therefore a method consisting of the following steps:
  • polymeric composition (A) comprising at least one polymer capable of adhering to said polymeric substrate or paper from step a) and selected from the group consisting of: polyvinyl alcohol, poly (meth)acrylic acid or relative partially or completely salified forms with alkaline metals, ethylene / (meth) acrylic acid copolymer or its related partially or completely salified forms with alkaline metals, poliurethanes, polyurethane-based polymeric compositions, polyalkylene glycols in which the alkylene chain is a C2-C4 alkylene, polysaccharides, preferably selected from chitosan, sodium carboxymethylcellulose, alginic acid or related forms completely or partially salified with alkaline metals or alkaline earth metals
  • polymeric composition (B) comprising:
  • a polymerizable monomer selected from an epoxy monomer, or a monomer containing at least one ethylenic unsaturation
  • primer layer is meant to indicate an intermediate layer of polymeric or even inorganic material, arranged between the substrate to be coated and the coating material, which, due to its physical and chemical nature, allows a more homogeneous distribution of the coating material on the substrate and a better adhesion of the aforementioned coating to the substrate.
  • polymeric substrate is meant to indicate a substrate in the form of a soft polymeric film or rigid film or a rigid three-dimensional polymeric material, or a polymeric material made of fabric or non- woven fabric.
  • soft polymeric film is meant to indicate a polymeric film conventionally used in packaging (for example in food packaging) like for example polyethylene, polypropylene, polyethylene terephthalate, biodegradable polymers, like for example: starch-based polymers, polylactic acid, polyglycolic acid, or lactic acid/glycolic acid copolymers.
  • rigid polymeric films is meant to indicate the films compounding the containers of liquid or solid foods and beverages. They preferably consist of polyethylene, polypropylene, polyethylene terephthalate, biodegradable polymers.
  • rigid polymeric material is meant to indicate materials consisting of polyethylene, ethylene/propylene copolymers, polycarbonates, polystyrene, polyesters, polyurethanes in general used in industry for example for components in the automotive industry.
  • polymeric materials made of fabric or non-woven fabric is meant to ndicate polyamides and/or polyesters in general used in the textile, sports, technical-textile and construction textiles industries.
  • Step (a) (plasma pre-treatment of the substrate to be coated) has the purpose of increasing the wettability of the substrate and/or the uniformity of the coating and the adhesion of the coating to the surface of the substrate on which the coating is applied.
  • antifog material is meant to indicate a material on which water does not condense in the form of small droplets, but rather condensing water forms a transparent film even at low temperatures.
  • step (a) and step (c) can be earned out using various types of plasma sources, like for example: sources of the dielectric barrier type (dielectric barrier discharge - DBD), surface dielectric barrier discharge (SDBD), plasma beam (Plasma Jet), remote plasmas (for which the plasma is generated in a given area, from which it is then extracted thanks to flows of directed gas and/or by pressure difference and/or magnetic fields and/or electromagnetic drifts).
  • sources of the dielectric barrier type dielectric barrier discharge - DBD
  • SDBD surface dielectric barrier discharge
  • Plasma beam Pasma Jet
  • remote plasmas for which the plasma is generated in a given area, from which it is then extracted thanks to flows of directed gas and/or by pressure difference and/or magnetic fields and/or electromagnetic drifts.
  • DBD is used as plasma source.
  • the plasma treatment temperatures of the coating method according to the present invention are those typical of cold plasmas.
  • the operating frequencies of the aforementioned types of plasma sources as stated above can vary from those typical of direct current (DC) up to microwaves, and thus can reach maximum values of up to 10 6 MHz. More preferably they are between 300 Hz and 10 MHz, even better between 10 Hz and 10 4 MHz.
  • the optimal frequencies range from 0.5 kHz to 1 MHz.
  • the direct current (DC) source can work in direct current or with pulsed current. In any case, according to the method of the invention in order to trigger the plasma it is also possible to use generators at the cyclotronic resonance frequencies.
  • the operating pressures vary from 0.5 atm up to 3 atm.
  • the ideal work conditions are comprised between 90% and 150% of atmospheric pressure.
  • the specific working energies are generally comprised between 10 Wxmin/m 2 and 1000 Wxmin/m 2 , preferably between 30 Wxmin/m 2 and 300 Wxmin/m 2 .
  • the work frequencies are comprised between DC and Radio Frequency.
  • the gases that can be used in step (a) of plasma pre-treatment are: air, nitrogen, noble gases, C0 2 , or mixtures thereof, possibly containing water vapour.
  • nitrogen plasmas or C0 2 are used or mixtures thereof.
  • the gases that can be used in step (c) of plasma cross-linking are: air, nitrogen, noble gases, C0 2 , or mixtures thereof possibly containing water vapour.
  • nitrogen plasmas are used in the case in which the composition (B) contains (ii) monomers with ethylenic unsaturation, and air plasmas in the case in which the composition (B) contains epoxy monomers (ii).
  • poly(meth)acrylic acid is meant to indicate polyacrylic acid, and/or polymethacrylic acid
  • ethylene / (meth) acrylic acid copolymer is meant to indicate acrylic acid/ethylene copolymer, and/or methacrylic acid copolymer
  • alkaline metals is meant to indicate sodium and potassium, preferably sodium
  • alkaline earth metals is meant to indicate magnesium and calcium, preferably calcium.
  • composition (A) and composition (B) are in liquid form, thus in the form of a solution or dispersion of polymer (or mixture of polymers) in suitable solvent.
  • the solvent must be sufficiently volatile, to allow the removal thereof by evaporation at the end of step b).
  • the polymer contained in formulation (A) or (B) is a hydrophilic polymer, such as polyvinyl alcohol or a polysaccharide, water is used as solvent, possibly combining the use of suitable surfactants.
  • the epoxy monomers for composition (B) are preferably selected from: glycidol, styrene oxide, butadiene oxide, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, glycidyl mefhacrylate, bisphenol A diglycidyl ether (and oligomers thereof), 1,2 epoxydodecane, glycerol diglycidyl ether, 1,4 butanediol diglycidyl ether, 1,3 diglycidyl glyceryl ether, glycidyl octafluoropentylether, propylene oxide, glycidyl methyl ether, glycidyl butyn-ate, cyclohexene oxide, epoxyoctane, glycidyl tosylate, diepoxyoctane, furfuryl glycidyl ether, (2,2, 3,3,4,4,5,5, 6,6,7,7
  • the monomers (ii) of composition (B) are preferably selected in the class consisting of acrylic acid and esters of acrylic and methacrylic acid possibly perhalogenated preferably perfluorinated, vinylesters possibly perhalogenated, preferably perfluorinated, vinylethers possibly perhalogenated preferably perfluorinated, vinyl halides.
  • a further advantage of the method object of the present invention is that polymerizable composition (B) is capable of polymerizing in the absence of catalysts.
  • polymeric composition (A) contains polyvinyl alcohol as polymer in the method of the invention
  • the coating obtained constitutes a gas barrier layer. This coating is thus very useful when the soft film is used in food packaging, since the aforementioned characteristic allows the shelf life of foods to be lengthened.
  • the polymeric composition (B) contains a polyvinyl alcohol as polymer, and it is applied on soft polymeric film, such as those used in food packaging.
  • the film obtained with the method of the invention besides constituting a barrier layer against gas and in particular against oxygen, it has excellent antifog properties. This is particularly advantageous, when the film is used in food packaging, since it allows perfect visibility of the food underneath even in the case of cryopreservation.
  • the coating gives the polymeric substrate an excellent barrier against moisture.
  • composition (A) or (B) can be carried out with a series of techniques such as: immersion, knife coating, brush application, spraying, electrostatic spraying, atomisation, vaporisation and reverse roll coating, electrophoresis.
  • All of the techniques can foresee the use of rolls or rotors and of squeezing and/or drying processes.
  • the deposition of the composition with all of the techniques listed above can be earned out at a different temperature from room temperature, for example at a temperature comprised between 0°C and 150°C, keeping the composition itself and/or the deposition apparatus at the preselected temperature.
  • the deposition of the composition can be carried out in many steps, for example using the techniques quoted above and/or combinations thereof in order to obtain different types of coating even with many layers.
  • the coating can be applied on a surface or on both surfaces with the method of the invention.
  • the coating using the polymeric composition (A) in which the polymer is polyvinyl alcohol on one surface with the method of the invention on the other hand applying a coating with the method according to the invention on the opposite surface using the polymerizable composition (B) in which the polymer (i) is polyvinylidene chloride or fluoride, a film is obtained that has a moisture barrier layer of the same type as that described in the aforementioned prior art document US5,512,338.
  • the method of the invention makes it possible in a few steps and selecting suitable polymers, to give the polymeric substrate or the paper the desired characteristics, without the need to apply primers or to activate the surface with very aggressive gases.
  • a further advantage of the method of the present invention is that, when composition (B) is used, radical (photo)catalysts or ionic (photo)catalysts are not any more necessary.
  • the polymeric composition (A) and the polymerizable composition (B) can contain, as further additives, organic substances like for example surfactants, dyes and, in the case in which the polymeric substrate coated with the method of the invention is not used in the food industry, it can also contain UV stabilizers, flame-retardant agents and inorganic fillers of the conventional type.
  • compositions (A) and (B) can also incorporate nano and/or micro particles consisting of at least one metallic or non-metallic oxide, or even of metals or non- metals, such as Si and C, or are organic nano and/or micro particles.
  • the particles that can be incorporated in the compositions (A) and (B) are preferably in the form of nanometric powders, with average particle diameter preferably comprised between 10 nm and 1 micron, or are in the form of micrometric particles, with diameter ranging from 1 micron to tens microns.
  • the particles can be solid, porous or capsules.
  • oxides are silica, titanium dioxide, zirconia, alumina, nickel oxide, clays and zeolites.
  • organic particles are: polypropylene or polyethylene microparticles or polystyrene microparticles or nanoparticles or a mixture thereof.
  • composition (A) or (B) used in the method of the invention comprises nanoparticles and/or microparticles, which are in turn capable of giving specific further properties to the coating.
  • the polymeric composition (A) can also comprise a conventional cross-linking agent to further improve both the adhesion to the polymeric or paper substrate, and resistance to a moist/aqueous environment.
  • a conventional cross-linking agent for example, in case a hydrophilic polymer is used, such as polyvinyl alcohol, the cross-linking agent is a melamine-formaldehyde or urea-formaldehyde resin, boric acid or borax.
  • the cross-linker can be of the epoxy type.
  • Two films of polypropylene (PP) each of 180 cm are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the pre- treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • Polyvinyl alcohol (PVA) is deposited on the two films, applying a solution of 25 g/1 of PVA in water through mayer bar.
  • the films are dried in an oven for 30 s at 90°C.
  • the treatment is carried but by passing the film under plasma once at a speed of 7 m/min and with a specific energy of 270 Wxmin/m 2 .
  • the characterisation of the films takes place through measurement of oxygen permeability according to the standard ASTM D 3985-05(2010)el. For comparison the permeability of a film of PP as such and that of a film of polypropylene not pre-treated with plasma and spread with PVA is also measured.
  • PP polypropylene
  • the pre- treatment is carried out by passing the films under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • a solution of polyvinyl alcohol 25 g/1 in water is applied through a mayer bar on the first and second film.
  • the films are then dried in an oven at 90°C for 30 s.
  • One of the two films is finally treated in air plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • a solution containing polyvinyl alcohol (PVA) 20 g/1, diethylene glycol diglycidyl ether (DEGDGE) 10 g/1 and polyethylene glycol (10) tridecyl ether 0.6 g/1 in water is applied through a mayer bar on the third and on the fourth film. These films are also dried in an oven at 90°C for 30 s.
  • a film is finally treated in air plasma at atmospheric pressure with a planar reactor of the DBD type for the cross-linking of the epoxy monomer. The treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • the two different coatings are applied with weight per square metre 0.03 g/m 2 .
  • the characterisation of the films of modified PP is earned out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films for 30 seconds over a beaker of hot water (80°C), at a distance from the surface of the water of 5 cm.
  • the pre-treatment and the post-treatment are carried out with a planar reactor of the DBD type, by passing the film under plasma once at a speed of 7 m/min and with a specific energy of 270 Wxmin/m 2 .
  • the four films are evaluated by applying a layer of ink Pluricel Base through a mayer bar, and evaluating the adhesion thereof through a tape test (ASTM F2252- 03).
  • EXAMPLE 4 Anti-fog property
  • Two films of polypropylene (PP) of 180 cm 2 are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The pre-treatment is earned out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • a solution containing diethylene glycol diglycidyl ether (DEGDGE) (30 g/1), chitosan (10 g/1) and polyethylene glycol (10) tridecyl ether (0.6 g/1) in water was applied on the films through a mayer bar. The films are then dried in an oven at 90°C for 30 s.
  • DEGDGE diethylene glycol diglycidyl ether
  • chitosan 10 g/1
  • polyethylene glycol (10) tridecyl ether 0.6 g/1
  • a film is then treated in air plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin m 2 .
  • a film that is not pre-treated is also prepared, applied with the same solution and treated in air plasma.
  • the characterisation of the films of modified PP is earned out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films above a beaker of hot water (80°C) for 30 seconds, at a distance from the surface of the water of 5 cm.
  • Two films of polypropylene (PP) of 180 cm 2 are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the pre-treatment is earned out with by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • a solution containing polyvinyl alcohol (10 g/1), diethylene glycol diglycidyl ether (DEGDGE) (5 g/1), chitosan (5 g/1) and polyethylene glycol (10) tridecyl ether (0.6 g/1) in water was applied on the films through a mayer bar. The films are then dried in an oven at 90°C for 30 s.
  • a film is then treated in air plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the treatment is earned out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin m 2 .
  • a film is also prepared that is not pre-treated, applied with the same solution and treated in air plasma.
  • the characterisation of the films of modified PP is carried out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films over a beaker of hot water (80°C) for 30 seconds, at a distance from the surface of the water of 5 cm.
  • a film of polypropylene (PP) of 180 cm 2 is pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the pre-treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m .
  • a solution containing diethylene glycol diglycidyl ether (DEGDGE) (5 g/1), chitosan (10 g/1) and polyethylene glycol (10) tridecyl ether (0.6 g/1) in water is applied on the film through a mayer bar.
  • the film is then dried in an oven at 90°C for 30 s and treated in air plasma at atmospheric pressure with a planar reactor of the DBD type.
  • the treatment is earned out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m 2 .
  • a film not pre-treated is also prepared, applied with the same solution, and one pre-treated in C0 2 plasma is also prepared, applied with the same solution and treated in air plasma.
  • the characterisation of the film of modified PP is carried out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films over a beaker of hot water (80°C) for 30 seconds, at a distance from the surface of the water of 5 cm.

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Abstract

Method for coating on a polymeric substrate or on paper consisting of the following steps: a) Plasma pre-treatment at a pressure comprised between 0,5 and 3 atmospheres of the aforementioned polymeric substrate or paper b) Deposition and drying on said polymeric substrate or paper from step (a) of one of the following polymeric compositions: • Polymeric composition (A) comprising at least one polymer capable of adhering to said polymeric substrate or paper from step (a), • Polymerizable composition (B) comprising: (i) at least one polymer of the type of those of the polymeric composition (A) and polyvinylidene chloride or fluoride, and (ii) a polymerizable monomer selected from an epoxy monomer, or a monomer containing at least one ethylenic unsaturation; c) plasma treatment of the material coming from step (b).

Description

A PROCESS FOR COATING POLYMERIC SUBSTRATES AND PAPER
FIELD OF THE INVENTION
The present invention concerns a method or process for coating with polymeric compositions applied by deposition on said polymeric substrates or paper through pre- and post- plasma treatments.
STATE OF THE ART
In the state of the art the application on polymeric substrates in film form, for example with gas banier properties, is preceded by various preparation steps of the surface to be coated, having the puipose of activating it, promoting the deposition and the surface adhesion thereof.
For example US5,512,338 describes a process for coating with films to be used in food packaging. The coating thus obtained forms a banier to gases and moisture that comprises the following steps:
1. Activation of the surface through flame, corona, or plasma treatment, 2. Application of the primer preferably a solution in alcohol solvent of polyethylenimine, or an epoxy resin preferably dispersed in aqueous emulsion with an acidified aminoethylated vinyl polymer on both surfaces of the film. In both cases, the application is followed by drying of the solvent,
3. Deposition of a coating of a polymer capable of providing a gas banier on a surface of the film, preferably polyvinyl alcohol in the presence of a cross-linking agent and drying the solvent,
4. Deposition of the second coating preferably of polyvinylidene chloride. on the other surface of the film.
EP2431409 discloses a process for coating containers made of plastic material for food use with oxygen banier in which the activation is carried out with an oxyfluorination process, i.e. treatment with fluorine gas in mixture with inert gas, preferably air. This activation is followed by deposition of a coating of polyvinyl alcohol and a coating of polyvinyl acetal (polyvinyl butyral).
In other cases, for example in WO201419571, EP2832537, US7811669, the activation step, earned out by corona or plasma treatment, is followed by a deposition of a first inorganic coating by sol-gel technique, CVD (chemical vapour deposition) or PVD (physical vapour deposition), having the function both of a barrier coating and of a primer, for the subsequent application of a polymer having low permeability such as polyvinyl alcohol.
Therefore, the treatments known in the state of the art of activation of the surface of a substrate, on which the coating is applied, are very wearisome since they require a whole series of treatments for the deposition of one or more layers of organic or inorganic primer or, as in the case of oxyfluorination, the use of very aggressive gases such as fluorine. The organic primers are also applied in solution with organic solvents and must therefore be dried, with consequent consumption of energy, wasting of solvent and possible impact on the environment and human health.
A further drawback of the prior art is that, when in known coating processes polymerizable monomers are applied, other precursors are deposited in mixtures containing polymerization initiators that facilitate polymerization and increase the stability of the deposit. The use of polymerization initiators becomes necessary, for example, for radical polymerization through UV systems and for ionic polymerization both through UV systems and through EB. The amount of photoinitiator in the formulation, depending on the system that is taken into consideration, can vary from 0.5 to 15 %. Besides being very expensive, photoinitiators are also very often toxic to human health, for which reason systems capable of polymerizing without them are highly desirable.
There is thus a need to have a process for coating a polymeric substrate that does not have the aforementioned drawbacks of the processes of the prior art.
SUMMARY OF THE INVENTION
The Applicant has now unexpectedly found a coating process that allows the adhesion of the coating without the need for applications of primer or without the treatment with gases that are very aggressive and very dangerous for health and for the environment, like for example fluorine.
The subject of the present invention is therefore a method consisting of the following steps:
a) Plasma pre-treatment at a pressure comprised between 0,5 and 3 atmospheres of the aforementioned polymeric substrate or paper b) Deposition and drying on said polymeric substrate or paper from step a) of one of the following polymeric compositions in liquid form:
• polymeric composition (A) comprising at least one polymer capable of adhering to said polymeric substrate or paper from step a) and selected from the group consisting of: polyvinyl alcohol, poly (meth)acrylic acid or relative partially or completely salified forms with alkaline metals, ethylene / (meth) acrylic acid copolymer or its related partially or completely salified forms with alkaline metals, poliurethanes, polyurethane-based polymeric compositions, polyalkylene glycols in which the alkylene chain is a C2-C4 alkylene, polysaccharides, preferably selected from chitosan, sodium carboxymethylcellulose, alginic acid or related forms completely or partially salified with alkaline metals or alkaline earth metals
• polymeric composition (B) comprising:
(i) at least one polymer selected from those of the polymeric composition (A) and polyvinylidene chloride or fluoride
(ii) a polymerizable monomer selected from an epoxy monomer, or a monomer containing at least one ethylenic unsaturation;
c) plasma treatment of the material from step b),
DETAILED DESCRIPTION OF THE INVENTION
For the purposes of the present invention, the term primer layer is meant to indicate an intermediate layer of polymeric or even inorganic material, arranged between the substrate to be coated and the coating material, which, due to its physical and chemical nature, allows a more homogeneous distribution of the coating material on the substrate and a better adhesion of the aforementioned coating to the substrate.
For the purposes of the present invention the term polymeric substrate is meant to indicate a substrate in the form of a soft polymeric film or rigid film or a rigid three-dimensional polymeric material, or a polymeric material made of fabric or non- woven fabric.
For the purposes of the present invention, the term soft polymeric film is meant to indicate a polymeric film conventionally used in packaging (for example in food packaging) like for example polyethylene, polypropylene, polyethylene terephthalate, biodegradable polymers, like for example: starch-based polymers, polylactic acid, polyglycolic acid, or lactic acid/glycolic acid copolymers.
For the purposes of the present invention the term rigid polymeric films is meant to indicate the films compounding the containers of liquid or solid foods and beverages. They preferably consist of polyethylene, polypropylene, polyethylene terephthalate, biodegradable polymers.
For the purposes of the present invention, the term rigid polymeric material is meant to indicate materials consisting of polyethylene, ethylene/propylene copolymers, polycarbonates, polystyrene, polyesters, polyurethanes in general used in industry for example for components in the automotive industry.
For the purposes of the present invention the term polymeric materials made of fabric or non-woven fabric is meant to ndicate polyamides and/or polyesters in general used in the textile, sports, technical-textile and construction textiles industries.
Step (a) (plasma pre-treatment of the substrate to be coated) has the purpose of increasing the wettability of the substrate and/or the uniformity of the coating and the adhesion of the coating to the surface of the substrate on which the coating is applied. The subsequent plasma treatment (c), after step (b), particularly when in the latter a polymeric composition (A) containing polyvinyl alcohol is used, increases the hydrophilicity of the coating transforming it into a discrete antifog material. The term antifog material is meant to indicate a material on which water does not condense in the form of small droplets, but rather condensing water forms a transparent film even at low temperatures.
Both step (a) and step (c) can be earned out using various types of plasma sources, like for example: sources of the dielectric barrier type (dielectric barrier discharge - DBD), surface dielectric barrier discharge (SDBD), plasma beam (Plasma Jet), remote plasmas (for which the plasma is generated in a given area, from which it is then extracted thanks to flows of directed gas and/or by pressure difference and/or magnetic fields and/or electromagnetic drifts).
Preferably DBD is used as plasma source. The plasma treatment temperatures of the coating method according to the present invention are those typical of cold plasmas. The operating frequencies of the aforementioned types of plasma sources as stated above, can vary from those typical of direct current (DC) up to microwaves, and thus can reach maximum values of up to 106 MHz. More preferably they are between 300 Hz and 10 MHz, even better between 10 Hz and 104 MHz. For DBD generators the optimal frequencies range from 0.5 kHz to 1 MHz. The direct current (DC) source can work in direct current or with pulsed current. In any case, according to the method of the invention in order to trigger the plasma it is also possible to use generators at the cyclotronic resonance frequencies. The operating pressures vary from 0.5 atm up to 3 atm. In particular the ideal work conditions are comprised between 90% and 150% of atmospheric pressure. Finally, the specific working energies are generally comprised between 10 Wxmin/m2 and 1000 Wxmin/m2, preferably between 30 Wxmin/m2 and 300 Wxmin/m2.
When the Plasma Jet type source is used, including plasma needle and plasma blaster, the work frequencies are comprised between DC and Radio Frequency. The gases that can be used in step (a) of plasma pre-treatment are: air, nitrogen, noble gases, C02, or mixtures thereof, possibly containing water vapour. Preferably, nitrogen plasmas or C02 are used or mixtures thereof. The gases that can be used in step (c) of plasma cross-linking are: air, nitrogen, noble gases, C02, or mixtures thereof possibly containing water vapour. Preferably nitrogen plasmas are used in the case in which the composition (B) contains (ii) monomers with ethylenic unsaturation, and air plasmas in the case in which the composition (B) contains epoxy monomers (ii).
For the purposes of the present invention the term poly(meth)acrylic acid is meant to indicate polyacrylic acid, and/or polymethacrylic acid, and the term ethylene / (meth) acrylic acid copolymer is meant to indicate acrylic acid/ethylene copolymer, and/or methacrylic acid copolymer. For the purposes of the present invention the term alkaline metals is meant to indicate sodium and potassium, preferably sodium, and the term alkaline earth metals is meant to indicate magnesium and calcium, preferably calcium.
Both composition (A) and composition (B) are in liquid form, thus in the form of a solution or dispersion of polymer (or mixture of polymers) in suitable solvent. The solvent must be sufficiently volatile, to allow the removal thereof by evaporation at the end of step b). Preferably, when the polymer contained in formulation (A) or (B) is a hydrophilic polymer, such as polyvinyl alcohol or a polysaccharide, water is used as solvent, possibly combining the use of suitable surfactants.
The epoxy monomers for composition (B) are preferably selected from: glycidol, styrene oxide, butadiene oxide, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, glycidyl mefhacrylate, bisphenol A diglycidyl ether (and oligomers thereof), 1,2 epoxydodecane, glycerol diglycidyl ether, 1,4 butanediol diglycidyl ether, 1,3 diglycidyl glyceryl ether, glycidyl octafluoropentylether, propylene oxide, glycidyl methyl ether, glycidyl butyn-ate, cyclohexene oxide, epoxyoctane, glycidyl tosylate, diepoxyoctane, furfuryl glycidyl ether, (2,2, 3,3,4,4,5,5, 6,6,7,7,8, 8, 9,9,9-eptadecafluorononyl) oxirane, epoxy silicones with high and low molecular weight and preferably with low viscosity, like for example 2-(3,4-epoxycyclohexyl)ethyltriethoxy silane. The monomers (ii) of composition (B) are preferably selected in the class consisting of acrylic acid and esters of acrylic and methacrylic acid possibly perhalogenated preferably perfluorinated, vinylesters possibly perhalogenated, preferably perfluorinated, vinylethers possibly perhalogenated preferably perfluorinated, vinyl halides.
A further advantage of the method object of the present invention is that polymerizable composition (B) is capable of polymerizing in the absence of catalysts.
When polymeric composition (A) contains polyvinyl alcohol as polymer in the method of the invention, the coating obtained constitutes a gas barrier layer. This coating is thus very useful when the soft film is used in food packaging, since the aforementioned characteristic allows the shelf life of foods to be lengthened. When the polymeric composition (B) contains a polyvinyl alcohol as polymer, and it is applied on soft polymeric film, such as those used in food packaging. The film obtained with the method of the invention besides constituting a barrier layer against gas and in particular against oxygen, it has excellent antifog properties. This is particularly advantageous, when the film is used in food packaging, since it allows perfect visibility of the food underneath even in the case of cryopreservation.
When the polymeric composition (B) contains polyvinylidene chloride or fluoride as polymer, the coating gives the polymeric substrate an excellent barrier against moisture.
The deposition of composition (A) or (B) can be carried out with a series of techniques such as: immersion, knife coating, brush application, spraying, electrostatic spraying, atomisation, vaporisation and reverse roll coating, electrophoresis.
All of the techniques can foresee the use of rolls or rotors and of squeezing and/or drying processes. The deposition of the composition with all of the techniques listed above can be earned out at a different temperature from room temperature, for example at a temperature comprised between 0°C and 150°C, keeping the composition itself and/or the deposition apparatus at the preselected temperature. The deposition of the composition can be carried out in many steps, for example using the techniques quoted above and/or combinations thereof in order to obtain different types of coating even with many layers.
When the polymeric substrate is a film, the coating can be applied on a surface or on both surfaces with the method of the invention.
In fact, by suitably applying the coating using the polymeric composition (A) in which the polymer is polyvinyl alcohol on one surface with the method of the invention, on the other hand applying a coating with the method according to the invention on the opposite surface using the polymerizable composition (B) in which the polymer (i) is polyvinylidene chloride or fluoride, a film is obtained that has a moisture barrier layer of the same type as that described in the aforementioned prior art document US5,512,338. The method of the invention makes it possible in a few steps and selecting suitable polymers, to give the polymeric substrate or the paper the desired characteristics, without the need to apply primers or to activate the surface with very aggressive gases.
A further advantage of the method of the present invention is that, when composition (B) is used, radical (photo)catalysts or ionic (photo)catalysts are not any more necessary.
The polymeric composition (A) and the polymerizable composition (B) can contain, as further additives, organic substances like for example surfactants, dyes and, in the case in which the polymeric substrate coated with the method of the invention is not used in the food industry, it can also contain UV stabilizers, flame-retardant agents and inorganic fillers of the conventional type.
The compositions (A) and (B) can also incorporate nano and/or micro particles consisting of at least one metallic or non-metallic oxide, or even of metals or non- metals, such as Si and C, or are organic nano and/or micro particles. The particles that can be incorporated in the compositions (A) and (B) are preferably in the form of nanometric powders, with average particle diameter preferably comprised between 10 nm and 1 micron, or are in the form of micrometric particles, with diameter ranging from 1 micron to tens microns. The particles can be solid, porous or capsules. Examples of oxides are silica, titanium dioxide, zirconia, alumina, nickel oxide, clays and zeolites. Examples of organic particles are: polypropylene or polyethylene microparticles or polystyrene microparticles or nanoparticles or a mixture thereof.
In this case the composition (A) or (B) used in the method of the invention comprises nanoparticles and/or microparticles, which are in turn capable of giving specific further properties to the coating.
Only exceptionally, the polymeric composition (A) can also comprise a conventional cross-linking agent to further improve both the adhesion to the polymeric or paper substrate, and resistance to a moist/aqueous environment. For example, in case a hydrophilic polymer is used, such as polyvinyl alcohol, the cross-linking agent is a melamine-formaldehyde or urea-formaldehyde resin, boric acid or borax. In the case in which a polymer with amminic functionality such as chitosan is used, the cross-linker can be of the epoxy type.
For illustrating but not limiting purposes, the following examples of the coating method according to he present invention are given.
EXAMPLE 1 - Barrier property
Two films of polypropylene (PP) each of 180 cm are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The pre- treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2. Polyvinyl alcohol (PVA) is deposited on the two films, applying a solution of 25 g/1 of PVA in water through mayer bar. The films are dried in an oven for 30 s at 90°C. On one of the two films another treatment is finally earned out with nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The treatment is carried but by passing the film under plasma once at a speed of 7 m/min and with a specific energy of 270 Wxmin/m2.
The characterisation of the films takes place through measurement of oxygen permeability according to the standard ASTM D 3985-05(2010)el. For comparison the permeability of a film of PP as such and that of a film of polypropylene not pre-treated with plasma and spread with PVA is also measured.
Figure imgf000010_0001
* non-uniform coating, in islands
EXAMPLE 2 - Anti-fog property
Four films of polypropylene (PP) each of 180 cm2 are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The pre- treatment is carried out by passing the films under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2. A solution of polyvinyl alcohol 25 g/1 in water is applied through a mayer bar on the first and second film. The films are then dried in an oven at 90°C for 30 s. One of the two films is finally treated in air plasma at atmospheric pressure with a planar reactor of the DBD type. The treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2.
A solution containing polyvinyl alcohol (PVA) 20 g/1, diethylene glycol diglycidyl ether (DEGDGE) 10 g/1 and polyethylene glycol (10) tridecyl ether 0.6 g/1 in water is applied through a mayer bar on the third and on the fourth film. These films are also dried in an oven at 90°C for 30 s. A film is finally treated in air plasma at atmospheric pressure with a planar reactor of the DBD type for the cross-linking of the epoxy monomer. The treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2.
The two different coatings are applied with weight per square metre 0.03 g/m2.
The characterisation of the films of modified PP is earned out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films for 30 seconds over a beaker of hot water (80°C), at a distance from the surface of the water of 5 cm.
Antifog
Sample Contact angle (°)
evaluation
PP not treated 81±5 Opacification
Formation of
PP+ PLASMA N2 + PVA 49±2 droplets,
opacification
Formation of
PP + PLASMA N2 + PVA + air
39±3 droplets, slight plasma
opacification
PP + PLASMA N2 + PVA + n.m.*
n.m.*
DEGDGE
PP + PLASMA N2 + PVA + Perfectly
21±1
DEGDGE + air plasma transparent * the sample applied with PVA + DEGDGE without subsequent plasma cross- linking was not evaluated since it was oily (due to the presence of the non-cross- linked epoxy monomer) and unusable for the purposes of application.
EXAMPLE 3 - Ink adhesion
Four films of polypropylene (PP) are prepared:
1. PP as such;
2. PP as such applied with PVA (0.4 g/m2), called PP + PVA;
3. PP pre-treated with nitrogen plasma at atmospheric pressure and applied with PVA (0.4 g/m2), called PP + nitrogen plasma + PVA.
4. PP pre-treated with nitrogen plasma at atmospheric pressure, applied with PVA (0.4 g/m2) and again treated with nitrogen plasma, called PP + nitrogen plasma + PVA + nitrogen plasma.
The pre-treatment and the post-treatment are carried out with a planar reactor of the DBD type, by passing the film under plasma once at a speed of 7 m/min and with a specific energy of 270 Wxmin/m2.
The four films are evaluated by applying a layer of ink Pluricel Base through a mayer bar, and evaluating the adhesion thereof through a tape test (ASTM F2252- 03).
Figure imgf000012_0001
EXAMPLE 4 - Anti-fog property Two films of polypropylene (PP) of 180 cm2 are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The pre-treatment is earned out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2. A solution containing diethylene glycol diglycidyl ether (DEGDGE) (30 g/1), chitosan (10 g/1) and polyethylene glycol (10) tridecyl ether (0.6 g/1) in water was applied on the films through a mayer bar. The films are then dried in an oven at 90°C for 30 s. A film is then treated in air plasma at atmospheric pressure with a planar reactor of the DBD type. The treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin m2. For comparison a film that is not pre-treated is also prepared, applied with the same solution and treated in air plasma.
The characterisation of the films of modified PP is earned out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films above a beaker of hot water (80°C) for 30 seconds, at a distance from the surface of the water of 5 cm.
Figure imgf000013_0001
* the sample applied with DEGDGE + CHIT without plasma pre-treatment was not evaluated since it was opaque and uneven.
** the sample applied with DEGDGE + CHIT with plasma pre-treatment but without subsequent plasma cross-linking was not evaluated since it was oily (due to the presence of the non-cross-linked epoxy monomer) and unusable for the purposes of application. EXAMPLE 5 - Anti-fog property
Two films of polypropylene (PP) of 180 cm2 are pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The pre-treatment is earned out with by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2. A solution containing polyvinyl alcohol (10 g/1), diethylene glycol diglycidyl ether (DEGDGE) (5 g/1), chitosan (5 g/1) and polyethylene glycol (10) tridecyl ether (0.6 g/1) in water was applied on the films through a mayer bar. The films are then dried in an oven at 90°C for 30 s. A film is then treated in air plasma at atmospheric pressure with a planar reactor of the DBD type. The treatment is earned out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin m2. For comparison a film is also prepared that is not pre-treated, applied with the same solution and treated in air plasma.
The characterisation of the films of modified PP is carried out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films over a beaker of hot water (80°C) for 30 seconds, at a distance from the surface of the water of 5 cm.
Figure imgf000014_0001
* the sample applied with PVA + DEGDGE + CHIT without plasma pre- treatment was not evaluated since it was opaque and uneven. EXAMPLE 6 - Anti-fog property
A film of polypropylene (PP) of 180 cm2 is pre-treated in nitrogen plasma at atmospheric pressure with a planar reactor of the DBD type. The pre-treatment is carried out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m . A solution containing diethylene glycol diglycidyl ether (DEGDGE) (5 g/1), chitosan (10 g/1) and polyethylene glycol (10) tridecyl ether (0.6 g/1) in water is applied on the film through a mayer bar. The film is then dried in an oven at 90°C for 30 s and treated in air plasma at atmospheric pressure with a planar reactor of the DBD type. The treatment is earned out by passing the film under plasma once at a speed of 7 m/min and at a specific energy of 270 Wxmin/m2. For comparison a film not pre-treated is also prepared, applied with the same solution, and one pre-treated in C02 plasma is also prepared, applied with the same solution and treated in air plasma.
The characterisation of the film of modified PP is carried out through measurement of the contact angle and evaluation of the anti-fog characteristics, placing the films over a beaker of hot water (80°C) for 30 seconds, at a distance from the surface of the water of 5 cm.
Figure imgf000015_0001
* the sample applied with DEGDGE + CHIT without plasma pre-treatment and subsequent plasma cross-linking was not evaluated since it was opaque and uneven.

Claims

1. Method for coating on a polymeric substrate or on paper consisting of the following steps: a) Plasma pre-treatment at a pressure comprised between 0.5 and 3 atmospheres of the aforesaid polymeric substrate or paper
b) Deposition and drying on said polymeric substrate or paper from step a) of one of the following polymeric compositions in liquid form (A) or (B):
• Polymeric composition (A) comprising at least one polymer capable of adhering to said polymeric substrate or paper selected from the group consisting of: polyvinyl alcohol, poly(meth)acrylic acid or its related partially or completely salified forms with alkaline metals, ethylene / (meth) acrylic acid copolymer or its related partially or completely salified forms with alkaline metals, polyurethanes or polyurethane-based polymeric compositions, polyalkylene glycols in which the alkylene chain is a C2-C4 alkylene, polysaccharides
• Polymeric composition (B) comprising:
(i) at least one polymer selected from those of the polymeric composition (A) and polyvinylidene chloride or fluoride and
(ii) a polymerizable monomer selected from an epoxy monomer, or a monomer containing at least one ethylenic unsaturation;
c) plasma treatment of the material from step b).
2. Method according to claim 1 wherein the polysaccharides are selected from chitosan, sodium carboxymethylcellulose, alginic acid or related forms completely or partially salified with alkali metals or alkaline earth metals
3. Method according to claim 1, wherein the steps (a) and (c) are earned out using types of plasma sources, selected from the group consisting of sources of the dielectric barrier type (dielectric barrier discharge DBD), surface dielectric barrier discharge (SDBD), plasma beam (Plasma Jet), remote plasmas.
4. Method according to claim 3, wherein in the steps (a) and (c) a dielectric barrier discharge DBD is used as a plasma source.
5. Method according to any one of claims 1-4, wherein in the steps (a) and (c) the operating temperatures are those of cold plasmas.
6. Method according to claim 3, wherein the operating frequencies to cany out steps (a) and (c) range from those of direct current (DC) up to microwaves, to maximum values of 106MHz more preferably between 300 Hz and 105MHz even better between 103 Hz and 104MHz.
7. Method according to claim 3 or 6, wherein the optimal operating frequencies of steps (a) and (c) are comprised between 300 Hz and 105MHz, preferably between
103 Hz and 104MHz.
8. Method according to any one of claims from 1 to 7 wherein the operating pressure in step (a) is comprised between 90 and 150% atmospheric pressure.
9. Method according to any one of claims 1-8, wherein the specific working energies of steps (a) and (c) are comprised between 10 Wxmin/m and 1000
2 2 2
Wxmin/m , preferably between 30 Wxmin/m and 300 Wxmin/m .
10. Method according to any one of claims 3 or 9 wherein when in steps (a) and (c) the source is of plasma jet type the operating frequencies are comprised between DC and radiofrequency.
11. Method according to any one of claims from 1 to 10 wherein the gases used in steps (a) and (c) are selected from air, nitrogen, noble gases, C02, steam, mixtures thereof possibly in admixture with water vapour, preferably they are selected from nitrogen plasmas or C02 or mixtures thereof.
12. Method according to claim 11 wherein the gases used in step (a) are selected from nitrogen or C02 plasmas or mixtures thereof, gases in step c) are selected from nitrogen plasmas in case the polymeric composition (B) contains monomers with ethylenic unsaturation and air plasmas in case the same composition contains epoxy monomers.
13. Method according to any one of claims from 1 to 12 wherein in step b) said composition in liquid form (A) or (B) is selected from a solution or a dispersion in a suitable solvent of polymer or polymer mixture in the case of the polymeric composition (A), of polymer or monomer, mixture of polymers and mixture of monomers in the case of composition (B).
14. Method according to any one of claims 1-13 wherein the epoxy monomer (i) in the composition (B) is selected in the class consisting of glycidol, styrene oxide, butadiene oxide, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, glycidyl methacrylate, bisphenol A diglycidyl ether (and oligomers thereof), 1,2 epoxydodecane, glycerol diglycidyl ether, 1,4 butanediol diglycidyl ether, 1,3 diglycidyl glyceryl ether, glycidyl octafluoropentylether, propylene oxide, glycidyl methyl ether, glycidyl butyrrate, cyclohexene oxide, epoxyoctane, glycidyl tosylate, diepoxyoctane, furfuryl glycidyl ether, (2,2,3,3,4,4,5, 5, 6,6,7,7,8, 8,9,9,9-eptadecafluorononyl) oxirane, epoxy silicones of high and low molecular weight and preferably with low viscosity, such as 2-(3,4- epoxycyclohexyl)ethyltriethoxy silane.
15. Method according to any one of claims from 1 to 13 wherein the monomers (ii) are selected in the class consisting of acrylic acid and esters of acrylic and methacrylic acid possibly perhalogenated preferably perfluorinated, vinylesters possibly perhalogenated, preferably perfluorinated, vinylefhers possibly perhalogenated preferably perfluorinated, vinyl halides.
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