Classifications

• • 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
• • 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
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/385—Oxides, hydroxides or carbonates
• • 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
  • D21H19/38—Coatings with pigments characterised by the pigments
  • D21H19/40—Coatings with pigments characterised by the pigments siliceous, e.g. clays
• • 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
  • D21H19/46—Non-macromolecular organic compounds
  • D21H19/48—Diolefins, e.g. butadiene; Aromatic vinyl monomers, e.g. styrene; Polymerisable unsaturated acids or derivatives thereof, e.g. acrylic acid
• • 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
  • D21H19/50—Proteins
• • 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
  • D21H19/54—Starch
• • 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
  • D21H19/80—Paper comprising more than one coating
  • D21H19/82—Paper comprising more than one coating superposed
• • 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
  • D21H19/80—Paper comprising more than one coating
  • D21H19/84—Paper comprising more than one coating on both sides of the substrate

Definitions

• the present disclosure relates to coated paper materials for use in packages adapted for shelf-life extending heat treatment, e.g. with steam as a heat medium.
• print quality is often a desired property.
• the printing surface of paper or paperboard may be improved by applying a pigment coating onto the surface to be printed.
• a pigment coating often comprises a binder.
• An alternative or complementary way of improving the printing surface is calendering.
• Heat treatment at a temperature below 100 °C is sometimes referred to as pasteurization.
• Pigment coatings are normally sensitive to sterilization with steam.
• the coatings may absorb water during the harsh sterilization conditions.
• WO 2010/114467 addresses the problem of providing producing pigment coated paperboard that can withstand steam sterilization.
• the suggested solution to the problem is a hydrophobized paperboard coated with a composition comprising calcium carbonate pigment, a binder and a rheology modifier.
• a coated paperboard material for use in packages adapted for shelf-life extending heat treatment, e.g. with steam as a heat medium comprising a base board having a top side provided with a pigment coating to form a surface for printing, which pigment coating comprises a pigment mixture, at least one binder and a zirconium-based compound, wherein the pigment mixture comprises at least 40 wt.% calcium carbonate and at least 10 wt.% clay, such as kaolin clay, such as delaminated kaolin clay.
• top paper layer of the base board is bleached and optionally comprises titanium dioxide.
• top layer is formed from Kraft pulp, such as bleached Kraft pulp.
• the grammage (ISO 536) of the base board is between 120 and 290 g/m 2 , such as between 160 and 290 g/m 2 , such as between 190 and 250 g/m 2 , such as between 210 and 250 g/m 2 .
• the thickness (ISO 534) of the base board is between 230 and 390 ⁇ , such as between 255 and 325 ⁇ .
• the density (ISO 534) of the base board is between 600 and 900 kg/m3, such as between 650 and 850 kg/m3, such as between 680 and 810 kg/m3, such as between 700 and 780 kg/m3.
• coated paperboard according to any one of the previous items having a grammage (ISO 536) between 150 and 300 g/m 2 , such as between 200 and 300 g/m 2 , such as between 220 and 270 g/m 2 .
• coated paperboard according to any one of the previous items having a thickness (ISO 534) between 230 and 400 ⁇ , such as between 255 and 325 ⁇ .
• the coated paperboard according to any one of the previous items having a density (ISO 534) between 700 and 950 kg/m3, such as between 800 and 920 kg/m3,, such as between 800 and 880 kg/m3, such as between 820 and 890 kg/m3, such as between 820 and 860 kg/m3.
• the coated paperboard according to item 19 wherein the at least one rheology modifier amounts to 0.05-2.0 %, such as 0.1-1.0 %, of the dry weight of the pigment coating.
• 21 The coated paperboard according to item 19 or 20, wherein the at least one rheology modifier is CMC or an acrylic co-polymer, such as an alkali-swellable acrylate polymer.
• the base board is hydrophobized from a sizing agent treatment, such as treatment with alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) or a combination thereof.
• a sizing agent treatment such as treatment with alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) or a combination thereof.
• the pigment mixture comprises at least 50 wt.% calcium carbonate and at least 15 wt.% clay.
• zirconium-based compound is a zirconium-based cross-linker, e.g. a zirconium carbonate, such as ammonium zirconium carbonate or potassium zirconium carbonate.
• the at least one binder is/are selected from the group consisting of co-polymers, acrylic resins, polyvinyl acetate, polyvinyl alcohol, proteins, and polysaccharides, such as starches.
• synthetic co-polymers such as acrylic copolymers, styrene-butadiene co-polymers and methyl methacrylate- butadiene co-polymers.
• a method of producing a coated paperboard comprising applying a pigment coating composition on a top side of a base board, which top side is optionally coated with a pre-coating, characterized in that the pigment coating composition comprises the components defined in anyone of items 1- 30.
• 32. A package comprising the coated paperboard according to any one of items 1-30, wherein the package is a tray, a pod or a capsule.
• a package according to claim 32 characterized in that it is adapted for pre- or post printing in for example flexography, offset and lithography.
• Fig 1 shows a coated paperboard according to two embodiments of the present disclosure comprising a base paper and coatings.
• the present disclosure provides a coated paperboard material for use in packages adapted for shelf-life extending heat treatment.
• the heat treatment is preferably carried out with steam as a heat medium, but other heat mediums, such as hot air or hot water are also possible.
• Examples such shelf- life extending heat treatments with steam as a heat medium are retort and steam autoclave treatments.
• the treatment is normally carried out at an overpressure and a temperature above too °C, such as above no or 121 °C, such as 121-140 °C.
• packages adapted for shelf-life extending heat treatment with steam as a heat medium are those marketed under the name Tetra Recart.
• the shelf-life extending heat treatment comprises filling a package with a product having a temperature of at least 80 °C, but below 100 °C. The package is then closed and sealed. Finally, the filled and sealed package is kept at a temperature of at least 80 °C, but below 100 °C for a predetermined period, such as 1-30 min, by contact with a heat medium, such as steam or a hot gas, such as hot air.
• a heat medium such as steam or a hot gas, such as hot air.
• the heat treatment may for example co-sterilize the package and package content, such a foodstuff.
• the coated paperboard of the first aspect comprises a base board.
• the baseboard is a paperboard.
• the base board has a top side provided with a pigment coating forming a surface for printing.
• a pre- coating layer may be provided between the top side of the base board and the pigment coating forming the surface for printing.
• the coated paperboard is adapted for printing, such as printing by flexography, offset and lithography. Accordingly, in one the surface for printing may be printed. Further, the printed side may be covered by a barrier coating, such as a plastic coating.
• a plastic coating may for example comprise
• polyethylene polyethylene, polypropylene or polyester.
• the base board may for example comprise at least two paper layers, such as two, three, four or five layers.
• the top paper layer of the base board is provided with the pigment coating.
• the top paper layer of the base board is bleached. It may also comprise titanium dioxide for additional whitening.
• the bleached board is preferably formed from bleached Kraft pulp, such as a mixture of bleached hardwood sulphate pulp and bleached softwood sulphate pulp.
• the top layer may however be unbleached and obtained from, for example, unbleached Kraft pulp.
• the base board is solid, which means that it is composed of only one paper layer.
• the bottom layer may be formed from unbleached pulp. However, the bottom layer may also be bleached. In a package, the reverse side normally faces the inside of the package.
• the base board may be hydrophobized from a sizing agent treatment, such as treatment with alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) or a combination thereof.
• a sizing agent treatment such as treatment with alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA) or a combination thereof.
• ASA alkenyl succinic anhydride
• rosin size is another example of a hydrophobic sizing agent. If the base board comprises more than one layer, each layer may be hydrophobized from the sizing agent treatment.
• ISO 534 thickness between 230 and 390 ⁇ , such as between 255 and 325 ⁇ ;
• ISO 534 density between 600 and 900 kg/m3, such as between 650 and 850 kg/rri3, such as between 680 and 810 kg/m3, preferably between 700 and 780
• the pigment coating of the present disclosure may also be used in a material intended for pouches. Such a material typically is typically thinner and more flexible than the material intended for Tetra Recart. Accordingly, the base board may also have the following characteristics:
• ISO 534 thickness between 80 and 125 ⁇ , such as between 85 and 120 ⁇ ;
• This thinner base board typically consists of one or two layers. Further, at least one of the layers of the thinner base board is preferably formed from bleached pulp, such as bleached Kraft pulp.
• the base board of the present disclosure comprises at least one paper layer that is formed from a paper material having a
• stretchability (ISO 1924/3) of at least 5 % in both the machine direction (MD) and the cross direction (CD), such as at least 7 % in both the machine direction (MD) and the cross direction (CD).
• all paper layers of the base board may be formed from such a stretchable paper material. The stretchability enables packages of more complex shapes.
• the pigment coating of the first aspect comprises:
• the pigment mixture comprises calcium carbonate and clay.
• the clay may be kaolin clay, such as delaminated kaolin clay.
• Calcium carbonate amounts to at least 40 %, preferably at least 50 %, such as at least 60 %, of the dry weight of the pigment mixture.
• Clay amounts to at least 10 %, preferably at least 15 %, of the dry weight of the weight of the pigment mixture.
• Clay and calcium carbonate together preferably amounts to at least 80 %, such as at least 90 %, of the dry weight of the pigment mixture.
• the pigment mixture may for example amount to 75-95 %, such as 80-88 %, of the dry weight of the pigment coating.
• the at least one binder may for example amount to 10-20 %, such as 12-18 %, of the dry weight of the pigment coating.
• the zirconium-based compound may for example amount to 0.3-3 %, such as 0.6-1.5 %, such as 0.75-1.0 %, of the dry weight of the pigment coating.
• the presence of zirconium in a coating layer may for example be detected using X-ray Photoelectron Spectroscopy (XPS).
• XPS X-ray Photoelectron Spectroscopy
• the presence of the zirconium-based compound in the pigment coating is particularly important when the pigment coating layer is to be printed and the resulting coated and printed paperboard is for use in a package that is heat treated with steam as the heat medium, in particular when the steam condenses on the package during the heat treatment.
• the pigment mixture may consist of calcium carbonate and clay only.
• the pigment mixture can also, in addition to calcium carbonate and clay, comprise layered silicate mineral, hydrated magnesium silicate, titanium dioxide or satin white.
• the at least one binder is/are for example selected from the group consisting of co-polymers, acrylic resins, polyvinyl acetate, polyvinyl alcohol, proteins, and polysaccharides, such as starches.
• the at least one binder is/are selected from synthetic co-polymers, such as acrylic co-polymers, styrene-butadiene co-polymers and methyl methacrylate-butadiene copolymers.
• the at least one binder is a styrene/acrylate co- polymer. When the pigment coating composition is prepared, such a binder is added in the form of styrene/ acrylate latex.
• the zirconium-based compound may for instance be a zirconium-based cross-linker, e.g. a zirconium carbonate, such as ammonium zirconium carbonate or potassium zirconium carbonate.
• a zirconium-based cross-linker e.g. a zirconium carbonate, such as ammonium zirconium carbonate or potassium zirconium carbonate.
• the pigment coating may further comprise at least one rheology modifier.
• the purpose of such an addition would be to adjust the viscosity of the pigment coating composition.
• the at least one rheology modifier may for example amount to 0.05-2.0 %, such as 0.1- 1.0 %, of the dry weight of the pigment coating.
• the at least one rheology modifier may for example be CMC and/or an acrylic polymer, such as an alkali-swellable acrylate polymer or an hydrophobically modified alkali-swellable acrylate polymer. If the rheology modifier is CMC, it typically amounts to 0.5-2 % of the dry weight of the pigment composition. If the rheology modifier is an acrylic polymer, it typically amounts to 0.05-0.5 % of the dry weight of the pigment composition. Other examples of rheology modifiers are starch and polyvinyl alcohol.
• One or more pre-coating layers may be provided between the top side of the base board and pigment coating forming the printing surface. It is not necessary that such a pre-coating layer includes the zirconium-based cross-linker and the above-mentioned pigment mixture.
• a pre-coating layer preferably comprises:
• a pigment or a pigment mixture such as a mixture of 40-90 wt.% calcium carbonate and 10-60 wt.% clay;
• At least one binder such as any one of the binders discussed above, preferably a styrene/acrylate co-polymer;
• the pigment or pigment mixture may for example amount to 75-95 %, such as 80-88 %, of the dry weight of the pre-coating layer.
• the at least one binder may for example amount to 10-20 %, such as 12-18 %, of the dry weight of the pre-coating layer.
• the zirconium-based compound may for example amount to 0.3-3 %, such as 0.6-1.5 %, such as 0.75-1.0 %, of the dry weight of the pre-coating layer.
• the at least one rheology modifier may for example amount to 0.05-2.0 %, such as 0.1-1.0 %, of the dry weight of the pre-coating layer.
• the coat weight of the pigment coating forming the surface for printing may for example be 5-30 g/m 2 , such as 8-30 m 2 , such as 10-30 m 2 , such as 17-23 g/m 2 .
• the coat weight of the pigment coating forming the printing surface is preferably 5-15 g/m 2 .
• the coat weight of the pre-coating layer is preferably 5-15 g/m 2 .
• the reverse side of the base board may also be provided with a coating.
• the reverse side coating may have the same composition as the above-mention pigment coating, which comprises the pigment mixture, the binder, the zirconium-based compound and optionally the rheology modifier. However, as the reverse side is normally not printed, it may also be a coating lacking the zirconium-based compound. Accordingly, in one embodiment the reverse side coating may comprise the pigment mixture, the binder and optionally the rheology modifier, but no zirconium-based compound. In one
• the reverse side coating has the same composition as the pre- coating layer.
• the coat weight of the coating on the reverse side may for example be of 1-30 g/m 2 , such as 1-9 g/m 2 , such as 3-8 g/m 2 .
• the coated paperboard of the first aspect may for example have a grammage (ISO 536) of 150-320 g/m 2 , such as 200-300 g/m 2 , such as 220-270 g/m 2 . Further, the coated paperboard may have a thickness (ISO 534) of 200-400 ⁇ , 230-400 ⁇ , such as 255-325 ⁇ and/or a density (ISO 534) of 700-950 kg/m3, such as 800-920 kg/m3, such as 800-880 kg/m3, such as 820-890 kg/m3, such as
• a method of producing a coated paperboard comprising applying a pigment coating composition on a top side of a base board.
• the pigment coating composition of the second aspect is preferably water-based and comprises a pigment mixture, at least one binder, a zirconium-based compound and optionally a rheology modifier.
• the components of the coating composition are discussed and exemplified above in connection with the first aspect. Accordingly, the embodiments of the first aspect apply mutatis mutandis to the second aspect.
• the viscosity of the pigment coating composition is preferably 200-2000 mPa*s, such as 270-1800 mPa*s, measured at 23°C with a rheometer, such as the Paar Physica UDS 200 in cup-bob C25 geometry at 25S-1 constant shea.
• the pigment coating composition may be applied directly on the top side of the base board. Alternatively, the pigment coating composition is applied on top of a previously applied coating layer, which may lack the zirconium-based compound, as discussed above.
• the method of the second aspect may further comprise the step of applying a coating on a reverse side of the base board. Such a reverse side coating may also lack the zirconium- based compound, as discussed above.
• a package comprising the coated paperboard according to any one of items 1-30.
• the package of the third aspect may for example be a tray, a pod or a capsule.
• the base board may comprise at least one layer of a paper material that is stretchable by at least 5 %, such as at least 7 %, in the machine direction (MD) and by at least 5 %, such as at least 7 %, in the cross direction (CD).
• the base board of such a package is a laminate wherein all paper layers are formed from paper material that is stretchable by at least 5 %, such as at least 7 %, in the machine direction (MD) and by at least 5 %, such as at least 7 %, in the cross direction (CD).
• the stretchability is measured according to ISO 1924/3.
• the package of the third aspect may for example be adapted for pre- or post printing, e.g. in flexography, offset and lithography.
• a first configuration of a fourth aspect of the present disclosure there is provided a use of a coated paperboard according to the first aspect for producing a package adapted for sterilization.
• the sterilization or co-sterilization is preferably carried our using steam as the heating medium.
• a coated paperboard according to the first aspect for producing a package adapted for shelf-life extending heat treatment, e.g. with steam as a heat medium.
• FIG. la shows a non-limiting embodiment of a coated paperboard 1 according to the present disclosure.
• the coated paperboard 1 comprises a base board 10 composed of a top layer 11 and a bottom layer 12.
• the top layer 11 is made from bleached Kraft pulp.
• the bottom layer 12 is made from unbleached pulp.
• a top side of the base board 10 is provided with a top pigment coating layer 13 comprising a pigment mixture of CaCO 3 and clay, a styrene/acrylate co-polymer acting as a binder, an acrylic rheology modifier (thickener) and ammonium zirconium carbonate acting as a cross-linking agent.
• a top pigment coating layer 13 comprising a pigment mixture of CaCO 3 and clay, a styrene/acrylate co-polymer acting as a binder, an acrylic rheology modifier (thickener) and ammonium zirconium carbonate acting as a cross-linking agent.
• a bottom side of the base board 10 is provided with a bottom pigment coating layer 14, which also comprises the pigment mixture, the binder and the thickener, but lacks cross-linking agent.
• the top pigment coating layer 13 is adapted to maintain the quality of a print on its top surface 15 during retort.
• FIG lb shows another non-limiting embodiment of a coated paperboard 2 according to the present disclosure.
• the coated paperboard 2 comprises a base board 20 composed of a top layer 21 and a bottom layer 22.
• the top layer 21 is made from bleached Kraft pulp.
• the bottom layer 22 is made from of unbleached pulp.
• a top side of the base board 20 is provided with a top pigment coating layer 23, which comprises two sub-layers; a pre-coating layer 23a and a top layer 23b.
• the top layer 23b comprises a pigment mixture of CaC0 3 and clay, a styrene/acrylate co-polymer acting as a binder, an acrylic rheology modifier (thickener) and ammonium zirconium carbonate acting as a cross-linking agent.
• the base layer 23a comprises the pigment mixture, the binder and the thickener, but lacks cross-linking agent.
• a bottom side of the base board 20 is provided with a bottom pigment coating layer 24, which comprises the same components as the base layer 23a.
• the top layer 23b is adapted to maintain the quality of a print on its top surface 25 during retort.
• Thickness (ISO 534) 290-320 ⁇
• the top layer was formed from a mixture of bleached hardwood sulphate pulp and bleached softwood sulphate pulp and the bottom layer was formed from a mixture of unbleached softwood sulphate pulp and pulped broke.
• the fibers of the pulps were mechanically treated with high consistency-refining (HC-refining) and/or low consistency-refining (LC-refining).
• the board was internally sized with AKD.
• Other paper chemicals used in board production was TiO 2 , alum, bicarbonate, starch and BMA.
• the pilot coating trials were carried out in a pilot coating machine and the uncoated base board used was commercial uncoated board with the above characteristics intended for packages for heat sterilisation.
• the base board was pigment coated in two layers, 10 g/m 2 (pre-coating layer) + 10 g/m 2 (top coating layer for printing), on the print/top side and also pigment coated in one layer, 5-8 g/m 2 , on the reverse side.
• the various pigment coating compositions comprised a pigment mixture, a binder and a thickener/rheology modifier.
• the pigment mixture amounted to 85-87 % of the dry weight of the coating composition.
• the binder amounted to 12-14 % of the dry weight of the coating composition.
• the coating composition applied to the top/printing side further comprised an additive.
• the additive amounted to 0.8-0.9 % of the dry weight of the coating composition.
• the additive was either polyvinyl alcohol (PvOH) or ammonium zirconium carbonate (AZC).
• PvOH polyvinyl alcohol
• AAC ammonium zirconium carbonate
• Kuraray Poval 6-98 also known as Mowiol 6/98 from Kuraray Europe Nordic AB Oy and the specific AZC product was Zirlink from Brenntag Nordic AB. Although the trials in this case were performed with the ammonium
• zirconium carbonate product Zirlink other chemistries based on the zirconium metal ion could have been used instead.
• Such other chemistries include, i.a., potassium zirconium carbonate products.
• the pigment mixture in the trials comprised 5-40 wt.% delaminated kaolin clay ("Clay") and 60-95 wt.% calcium carbonate (“CaCO3")
• the binder was either styrene-butadiene copolymer (“SB”) provided as styrene-butadiene latex (Styron SB 94378) when the coating composition was prepared or styrene/acrylate co-polymer (SA) provided as styrene/acrylate latex (Styron SA 95085.01) when the composition was prepared.
• the thickener was either an acrylate polymer (Coatex RheocoatTM 66, "ASE") provided as an alkali swellable acrylate polymer emulsion when the coating composition was prepared or carboxy methylated cellulose (Finnfix 10 from CP Kelco Oy, "CMC").
• acrylate polymer Coatex RheocoatTM 66, "ASE”
• carboxy methylated cellulose Frazier 10 from CP Kelco Oy, "CMC”
• Full scale trials The full scale trials were carried out on a two layer paper machine with one bleached top layer and one unbleached bottom layer according to the characteristics above.
• the base board was pigment coated on both sides in a coating section of the paper machine.
• a pre-coating layer (10 g/m 2 ) and a top coating layer (10 g/m 2 ) were applied to the print/top side and one layer of a lower coat weight (5-8 g/m 2 ) was provided on the reverse side.
• compositions comprised the pigment mixture, the binder and one of the thickeners described above in connection with the pilot trials.
• the pigment mixture amounted to 85-86 % of the dry weight of the coating compositions.
• the binder amounted to 13-14 % of the dry weight of the coating
• the top coating composition further comprised the additive AZC in an amount corresponding to 0.9 % of the dry weight of the coating composition.
• the print quality before lamination was determined in accordance with the Tetra Pak global standard criteria for print quality evaluation in all packaging material production, including parameters such as dot gain, colour density etc.
• sample material was laminated and packages were prepared and retorted.
• the coated and printed paperboard was laminated to an aluminium foil of 9 ⁇ thickness by melt extrusion lamination with an interjacent layer of polypropylene.
• the surface weight of the interjacent layer was about 25 g/m 2 .
• the paperboard was further laminated by melt extrusion coating with an outer, heat-resistant and transparent layer of a polypropylene polymer layer on the printed side, and further with an outer, heat-resistant and transparent layer of a polypropylene polymer layer on the other side (the package inside) of the aluminium foil.
• the polypropylene layer on the inside was applied by co-extrusion coating onto the aluminium foil, together with an interjacent, about 4 g/m 2 thick, layer of an adhesive polymer, or a so- called "tie" layer of a polyolefin-based polymer having maleic anhydride functional binding groups.
• the outer, heat-resistant and transparent layer of polypropylene polymer on the printed side was applied by means of extrusion coating at an average temperature of 275 °C at a web speed of about 300-400 m/ min, and at a surface weight of about 30 g/m 2 .
• the outer layer of polypropylene applied on the other side, the inside, of the packaging material was applied at a surface weight of about 35 g/m 2 .
• Packaging containers were formed from the laminated packaging material, thermo-sealed, filled with water and sealed as described above. The packaging containers were then subjected to maximal severe retort treatment at an over-pressure of up to 4 bar with a total process time of up to about 2 hours. Steam and a steam-water mixture were used for heating the packages during the retort cycle, and water was used for cooling the packages.

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• 2016
  • 2016-06-23 EP EP16175942.8A patent/EP3260598A1/de not_active Withdrawn
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