EP4471207A1 - Papierverpackungsmaterial mit niedriger opazität - Google Patents

Papierverpackungsmaterial mit niedriger opazität Download PDF

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Publication number
EP4471207A1
EP4471207A1 EP23177036.3A EP23177036A EP4471207A1 EP 4471207 A1 EP4471207 A1 EP 4471207A1 EP 23177036 A EP23177036 A EP 23177036A EP 4471207 A1 EP4471207 A1 EP 4471207A1
Authority
EP
European Patent Office
Prior art keywords
coating
paper product
less
fibrous web
heat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23177036.3A
Other languages
English (en)
French (fr)
Inventor
Armin NIEDERHUBER
Martha Birnkhammer
Oxana CHERKAS
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Neenah Gessner GmbH
Mativ Luxembourg SARL
Original Assignee
Neenah Gessner GmbH
Mativ Luxembourg SARL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Neenah Gessner GmbH, Mativ Luxembourg SARL filed Critical Neenah Gessner GmbH
Priority to EP23177036.3A priority Critical patent/EP4471207A1/de
Priority to PCT/EP2024/064735 priority patent/WO2024246108A1/en
Priority to AU2024281027A priority patent/AU2024281027A1/en
Priority to EP24730292.0A priority patent/EP4720407A1/de
Priority to CN202480033798.1A priority patent/CN121175464A/zh
Priority to KR1020257043484A priority patent/KR20260018903A/ko
Publication of EP4471207A1 publication Critical patent/EP4471207A1/de
Pending legal-status Critical Current

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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
    • D21H19/10—Coatings without pigments
    • D21H19/14—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12
    • D21H19/18—Coatings without pigments applied in a form other than the aqueous solution defined in group D21H19/12 comprising waxes
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
    • D21C7/00—Digesters
    • 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
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • 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
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/16—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only modified by a particular after-treatment
    • D21H11/18—Highly hydrated, swollen or fibrillatable fibres
    • 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
    • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
    • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
    • D21H21/26—Agents rendering paper transparent or translucent
    • 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
    • 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
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/06—Vegetable or imitation parchment; Glassine 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
    • D21H27/00—Special paper not otherwise provided for, e.g. made by multi-step processes
    • D21H27/10—Packing paper

Definitions

  • Transparent or translucent materials are used in all different types of applications. Transparency, for instance, is a highly desirable quality in packaging materials. For example, although packaging materials are necessary to protect products during shipping and sales, consumers prefer to be able to view the product through the packaging.
  • plastic materials such as polyester polymers and polyolefin polymers.
  • plastic materials are derived from non-renewable, fossil resources, including petroleum-based resources. These resources are not sustainable, are not renewable, and produce polymer products that do not readily degrade. Thus, efforts have been made in the past in an attempt to produce transparent or translucent materials from renewable resources, such as cellulose materials.
  • non-renewable resources or components that do not readily biodegrade were combined with the paper.
  • one type of paper produced in the past was manufactured from wood pulp fibers that may have been combined with an enzyme, such as xylanase. These substrates typically had a relatively high basis weight in order to provide sufficient strength or other mechanical properties.
  • the paper was combined with petroleum-based chemicals or synthesized resins and then fed through a supercalendering process. As used herein, during supercalendering, a paper is first calendered by pressing it between metal cylinders or rollers.
  • the paper is sent through an additional set of calenders to produce an even smoother and glossier paper, referred to as a supercalendered paper.
  • the supercalender includes several cylinders alternating between polished metal and soft resilient surfaces. The supercalender applies pressure, heat, and friction to glaze both surfaces of the paper to make the paper smooth and/or glossy.
  • Transparent or translucent papers made in the past as described above have various drawbacks and deficiencies.
  • the fibers used to produce the paper are obtained from renewable resources and are biodegradable and compostable, the papers are typically combined with petroleum-based chemicals or other synthetic resins that can frustrate the goal of producing biodegradable materials.
  • supercalendering can be very effective at changing the properties of the paper, the process is very energy intensive.
  • the above papers fail to include heat-seal characteristics.
  • Barrier properties to water, water vapor, and grease are important for packaging materials. Usually, these properties are also achieved with petroleum-sourced materials.
  • the present disclosure is directed to a low opacity paper that can be made at relatively low basis weights, without containing any petroleum-based resources, and without having to supercalender the paper, thus reducing the energy requirements needed to make the product.
  • the low opacity paper of the present disclosure can also be formulated to be completely biodegradable and compostable.
  • the low opacity paper can have an excellent balance of properties including high transparency and low permeability for providing high barrier properties, good mechanical properties for converting and handling, and excellent heat-seal properties.
  • the present disclosure is directed to a paper product with low opacity characteristics.
  • the paper product comprises a fibrous web containing cellulose fibers.
  • the cellulose fibers contained in the web can be refined to a relatively high degree as may be measured according to a freeness value.
  • the freeness value (° SR) measures generally the rate at which a dilute suspension of refined fibers may be drained.
  • the freeness is measured by the Schopper Riegler Method for drainability. As used herein, freeness can be measured according to DIN EN ISO 5267-1 :2000.
  • the cellulose fibers contained in the web can have a degree of refining of greater than about 60° SR, such as greater than about 70° SR.
  • the fibers generally have a freeness value of less than about 100° SR, such as less than about 90° SR.
  • the fibrous web in one aspect, can also have a relatively low basis weight for enhancing transparency.
  • the basis weight of the web can be less than about 38 g/m 2 , such as less than about 35 g/m 2 , such as less than about 33 g/m 2 , such as less than about 30 g/m 2 , such as less than about 28 g/m 2 , such as less than about 25 g/m 2 , such as less than about 23 g/m 2 , and generally greater than about 10 g/m 2 , such as greater than about 12 g/m 2 .
  • the basis weight of the fibrous web is in the range of 10 to 24 g/m 2 and preferably 10 to 18 g/m 2 .
  • the fibrous web defines a first surface and a second surface.
  • the first surface and the second surface are the main surfaces of the fibrous web, which may also be referred to as "upper" and lower" surface and are located opposite to each other.
  • At least two different coating compositions can be applied to a surface of the fibrous web.
  • the first coating comprises a transparency agent, such as a bio-based wax or oil for lowering opacity.
  • the second coating composition can form a heat-sealable coating that can be applied over the transparency agent coating on the first surface and/or the second surface of the fibrous web, and preferably on just one of the first surface and the second surface of the fibrous web.
  • the first and the second coating compositions can be applied to opposite surfaces of the fibrous web, namely, the first and the second surface thereof, as is the case in feature (ii) in claim 2.
  • the second coating composition can be combined with the transparency agent coating composition and applied to the web as a single coating. This is the subject of claim 1.
  • the heat-sealable coating composition also when combined with the transparency agent coating composition, can form an exterior surface of the paper product.
  • the heat-sealable coating can comprise a polymer, such as a thermoplastic polymer or a protein.
  • the polymer can be a polyester, a protein, a polysaccharide, a polysaccharide ester, a polysaccharide ether, or a polysaccharide ether ester.
  • the protein can be casein, whey, or the like.
  • Paper products made in accordance with the present disclosure can display an opacity of less than about 45% when tested according to ISO 2471 :2008. For example, the opacity can be less than about 40%, such as less than about 35%.
  • the amount of the transparency agent incorporated into the product can depend on various factors.
  • the basis weight (dry) of the transparency agent coating can be from about 0.5 g/m 2 to about 18 g/m 2 , including all increments of 0.5 g/m 2 therebetween.
  • the transparency agent coating can have a basis weight of greater than about 2 g/m 2 , such as greater than about 4 g/m 2 , such as greater than about 5 g/m 2 , such as greater than about 6 g/m 2 , such as greater than about 7 g/m 2 , such as greater than about 8 g/m 2 .
  • the basis weight of the transparency agent coating can be less than about 20 g/m 2 , such as less than about 15 g/m 2 , such as less than about 12 g/m 2 , such as less than about 10 g/m 2 , such as less than about 8 g/m 2 .
  • the transparency agent can be water miscible and applied to the fibrous web as an aqueous composition.
  • the heat-sealable coating can comprise a polymer.
  • the polymer can be a thermoplastic starch or a protein.
  • the heat-sealable coating can be applied to the cellulose layer so as to have a dry basis weight of greater than about 1 g/m 2 , such as greater than about 3 g/m 2 , such as greater than about 4 g/m 2 , such as greater than about 5 g/m 2 , and generally less than about 20 g/m 2 , such as less than about 15 g/m 2 , such as less than about 10 g/m 2 , such as less than about 8 g/m 2 .
  • the basis weight of the coating can be greater than about 3 g/m 2 , such as greater than about 5 g/m 2 , such as greater than about 8 g/m 2 , such as greater than about 12 g/m 2 , and generally less than about 35 g/m 2 , such as less than about 30 g/m 2 , such as less than about 25 g/m 2 , such as less than about 20 g/m 2
  • the fibrous web can comprise a wetlaid web.
  • the fibrous web can contain wood pulp fibers alone or in combination with bast fibers.
  • the wood pulp fibers for instance, can be softwood fibers, hardwood fibers, or combinations thereof.
  • the paper product can be produced without containing any paraffins, mineral oils, or hydrocarbon oils.
  • the paper product can be repulpable and compostable.
  • the fibrous web (prior to applying any coatings) can contain cellulose fibers generally in an amount greater than about 65% by weight, such as in an amount greater than about 75% by weight, such as in an amount greater than about 80% by weight, such as in an amount greater than about 85% by weight, such as in an amount greater than about 90% by weight, such as in an amount greater than about 95% by weight.
  • Cellulose fibers are generally present in the fibrous web in an amount of 100% by weight, or in an amount of less than about 99% by weight, such as in an amount less than about 98% by weight.
  • the fibrous web can contain first cellulose fibers blended with second cellulose fibers.
  • the first cellulose fibers can have an average fiber length that is shorter than the average fiber length of the second cellulose products.
  • the first cellulose fibers for instance, can be contained in the fibrous web in an amount from about 30% to about 70% by weight and the second cellulose fibers can be present in the fibrous web in an amount from about 70% to about 30% by weight based upon the total weight of fibers contained in the web.
  • the first cellulose fibers for instance, can have an average fiber length of from about 2.5 mm to about 5 mm.
  • the paper product of the present disclosure can have a combination of beneficial properties.
  • the paper product can be relatively thin having a thickness of less than about 80 ⁇ m, such as less than about 70 ⁇ m, such as less than about 60 ⁇ m, and generally greater than about 30 ⁇ m according to EN ISO 534:2011.
  • the paper product can also have a Gurley air permeability according to ISO 5636:2003 of less than about 45,200 seconds, such as less than about 20,000 seconds, such as less than about 10,000 seconds, such as less than about 1000 seconds, and generally greater than about 600 seconds.
  • the paper product can also have a water drop resistance greater than 5 min according to TAPPI T 432 cm-09 (2 ⁇ L of water volume is used in test).
  • the paper product can have a water vapor barrier at 23°C and 50%HR of less than 80 g/m 2 /day, such as less than 50 g/m 2 /day and greater than about 0.1 g/m 2 /day according to ASTM E96/E96M - 15:2014 (coated side on top, measurement made during 3 days).
  • the present disclosure is also directed to a packaging formed from the coated paper.
  • the packaging can define a hollow enclosure or interior volume that is formed between two layers of the coated paper.
  • the coated paper can be heat-sealed together along the margins of the product.
  • paper can be used as a packaging material for food, tobacco, cosmetics, pharmaceutical products, and other products.
  • the present disclosure in another aspect, is also directed to a method for producing a low opacity paper product as described above.
  • the method includes coating a fibrous web with an aqueous composition containing a bio-based wax or oil, such as a coconut-based wax or oil, a rice-based wax, a palm-based wax or oil and/or a soy-based wax or oil.
  • a second coating is then applied to the fibrous web that forms a heat-sealable coating on the web.
  • the heat-sealable coating can be applied over the first coating.
  • the heat sealable composition can be combined with the transparency agent composition to form a single coating on the web that has heat sealable properties.
  • the method can further include calendering the coated fibrous web.
  • the coated fibrous web can be calendered after the first coating has been applied and/or after the heat-sealable coating has been applied.
  • the coating comprising the heat-sealable composition is sometimes referred to as "heat-sealable coating".
  • the aqueous composition containing the transparency agent is coated on the fibrous web using a size press.
  • the heat-sealable coating on the other hand, can also be applied by a size press or can be applied in an offline process using, for instance, a knife coating technique.
  • Figure 1 is a cross-sectional view of one embodiment of a low opacity paper made in accordance with the present disclosure.
  • a "coating" (provided) on the surface(s) of the fibrous web can be obtained by applying a generally liquid coating agent on the surface(s) of the fibrous web by means of any suitable coating, impregnation or saturation technique, such as for example air knife coating, roll-to-roll coating, blade coating, spray coating, Mayer rod coating, direct gravure printing, offset gravure printing, reverse gravure printing, smooth roll coating, curtain coating, bead coating, slot coating, fill press coating or impregnation via a size press.
  • the coating can be a continuous coating or a discontinuous coating. Accordingly, along the lateral dimension of the fibrous web, the coating can be present in a part of or the complete fibrous web.
  • the coating composition When applying the coating composition to the fibrous web, it will penetrate into some of the internal spaces and pores between the fibers of the fibrous web resulting in saturation and/or impregnation of the fibrous web with the coating (composition). That is, in the present invention the coating will permeate into the fibrous web, in particular internal spaces and pores therein, and apart from this it can cover and preferably does cover at least part of the first and/or the second surface of the fibrous web in the form of a surface coating.
  • a "coating" (provided) on the fibrous web as understood herein covers the saturation and impregnation of the fibrous web.
  • low opacity means transparent or translucent.
  • a product is considered to have low opacity when the product displays an opacity of, e.g., less than about 45% when tested according to ISO 2471:2008.
  • Low opacity characteristics refer to the characteristics which provide a paper product with transparency or translucency, such as the presence of a transparency agent.
  • the term "transparency agent” refers to an agent which decreases the opacity of fibrous web when applied inside or on the fibrous web.
  • examples include plant or animal derived waxes or oils, such as a coconut-based wax, a palm-based wax, and/or a soy-based wax. Plant or animal derived components as understood herein can be obtained from biomass.
  • the transparency agent can be a bio-based wax or oil.
  • biomass is broadly understood as encompassing all kinds of plant and animal material and material derived from the same. Biomass does not include petroleum or petroleum-derived products.
  • the biomass for use in the present invention may comprise macromolecular compounds, examples of which are lignin and polysaccharides, such as starch, proteins, cellulose, hemicellulose.
  • biomass may include both plant and animal-derived material.
  • manure (dung), night soil and sewage sludge can be mentioned.
  • the biomass for use in the present invention is preferably plant biomass, i.e. biomass of or derived from plants, certain contents of animal biomass (i.e. biomass of or derived from animals) may be present therein.
  • the biomass may contain up to 30 % of animal biomass.
  • the biomass for use in the present disclosure which is preferably plant biomass, contains more than 70 wt%, most preferably more than 90 wt%, of polysaccharides and lignines in terms of the solid contents of the biomass.
  • the plant biomass may be agricultural plant material (e.g. agricultural wastes) or all kinds of wood material.
  • biomass examples include crop, agricultural food and waste, feed crop residues, wood (such as wood flour, wood waste, scrap wood, sawdust, chips and discards), straw (including rice straw), grass, leaves, chaff, and bagasse.
  • wood such as wood flour, wood waste, scrap wood, sawdust, chips and discards
  • straw including rice straw
  • grass leaves, chaff, and bagasse.
  • industrial and municipal wastes, including waste paper can be exemplified.
  • Biomass also encompasses oils and waxes obtained or derived from plant or animal materials.
  • a “biodegradable” component is a component that is capable of being decomposed by living organisms, such as bacteria or fungi.
  • a biodegradable component can thus be decomposed by the action of microorganisms such as bacteria or fungi with or without oxygen.
  • a biodegradable component fulfills the requirements of at least one of the international industrial standards ISO 14855:2018, ISO 14853:2017, and ASTM D5338:2015.
  • the term "compostable” refers to components that can disintegrate into non-toxic, natural elements. Compostable components, for instance, can degrade at a rate consistent with similar organic materials. Compostable components degrade when exposed to microorganisms, humidity, and/or heat to yield a finished compost product. Coated papers made according to the present disclosure can be formulated to meet international industrial standards ISO 17088:2021, DIN EN 13432:2007, DIN EN 14995:2007, and/or ASTM 6400:2021 defines the requirements for industrially compostable components.
  • Pulp refers to fibers from natural sources such as woody and non-woody plants.
  • Woody plants include, for example, deciduous and coniferous trees.
  • Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse.
  • Pulp fibers can include hardwood fibers, softwood fibers, and mixtures thereof.
  • opacity is measured according to ISO 2471:2008. Opacity is a measure of the ability of the paper product to obstruct the passage of light through it. The lower is the level of opacity, the higher is the level of translucency/transparency.
  • fibrous web refers to sheet made from the pulp by a wetlaid process without coating.
  • bio-based wax or oil refers to wax or oil which have a bio-based content more than 90%. Examples include coconut-based wax, a palm-based wax and/or a soy-based wax.
  • the term "repulpable” means that the paper disintegrates during the pulping process in water.
  • the present disclosure is directed to a low opacity paper with heat-seal properties.
  • the paper can be transparent.
  • the paper can be formulated to be translucent.
  • the low opacity paper of the present disclosure can be formed exclusively from sustainable resources that meets all of the requirements for entering the paper recycle stream after use.
  • transparent papers typically contained components derived from fossil-based resources, such as petroleum-derived products.
  • the low opacity paper of the present disclosure can be produced without containing any mineral oils or hydrocarbons, including mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons.
  • the low opacity paper can be formulated to be paraffin-free.
  • the low opacity paper can be constructed in order to meet all of the requirements for food contact and food handling.
  • the low opacity paper of the present disclosure can have excellent barrier and heat-seal properties.
  • a heat-seal coating for instance, can form an exterior surface of the paper product.
  • the heat-seal coating not only facilitates the formation of thermal bonds between the coated paper and an adjacent surface, such as another layer of the coated paper, but can also be made entirely from sustainable, biodegradable, and compostable materials.
  • the low opacity paper of the present disclosure can be developed so as to minimize the use of materials while still having sufficient mechanical properties for handling, processing, and end use applications.
  • the low opacity paper of the present disclosure can be manufactured at relatively low basis weights and at relatively low thicknesses.
  • the low opacity paper of the present disclosure is formed from a fibrous web containing cellulose fibers that have been refined to a relatively high degree.
  • the fibrous web is combined with a transparency agent, which can be a bio-based wax or oil.
  • the transparency agent not only increases the barrier characteristics of the paper but also lowers the opacity characteristics of the paper.
  • a paper can be produced that has an opacity of less than about 45%.
  • the opacity of the paper products can be less than about 40%, such as less than about 38%, such as less than about 35%.
  • the actual opacity can depend upon various factors and is generally greater than 5%, such as greater than about 10%.
  • FIG. 1 represents a schematic cross-sectional view of the product 10.
  • the low opacity paper 10 includes a paper base sheet 12 which is a fibrous web formed from cellulose fibers.
  • the fibrous web 12 can be a wetlaid paper web. In other embodiments, however, the fibrous web 12 can be made using any suitable papermaking technique.
  • the fibrous web 12 includes a first surface opposite a second surface. Applied to the first surface of the fibrous web 12 is a first coating 14 and a second coating 16.
  • the first coating 14 contains a transparency agent that lowers the opacity of the paper product 10.
  • the first coating 14 is shown as a separate layer in FIG. 1 but will also become impregnated into the fibrous web 12 as explained above.
  • the first coating 14 can be made from a bio-based oil or wax.
  • the first coating 14 is formed from a coconut-based wax, a soy-based wax, a rice-based wax, and/or a palm-based wax.
  • the second or heat-sealable coating 16 is applied over the first coating 14 .
  • the heat-sealable coating 16 further improves the barrier properties of the overall product.
  • the heat-sealable coating 16 is also heat-sealable and therefore can be used to bond the coated paper to an adjacent coated paper for producing packages or other items where a hollow enclosure is desired.
  • the heat-sealable coating 16 can contain, for instance, a plant or animal derived wax alone or in combination with other components, such as a polymer.
  • the polymer combined with the plant or animal derived wax for instance, can be a polyester polymer, a protein such as casein, a polysaccharide, a polysaccharide ester, a polysaccharide ether, a polysaccharide ether ester, or combinations thereof.
  • the transparency agent coating 14 and the heat-sealable coating 16 can be applied to one side of the cellulose layer or to different sides of the cellulose layer.
  • the composition used to form the first coating can be combined with the composition used to form the second coating and applied to the web as a single coating that lowers opacity and provides heat seal properties.
  • the low opacity paper 10 can be made exclusively from a single layer of a fibrous web in combination with the first coating 14 and the second coating 16 (or a single coating that combines the first coating components with the second coating components).
  • the coated paper 10 defines an exterior surface 18 as shown in FIG. 1 that is a heat-sealable surface.
  • the surface 18 can be formulated to not be sticky at room temperature.
  • the surface 18 or heat-sealable coating 16 can produce a heat seal at a temperature of greater than about 100°C, such as greater than about 110°C, such as greater than about 120°C, such as greater than about 130°C, such as greater than about 140°C, such as greater than about 150°C, such as greater than about 160°C, such as greater than about 170°C, such as greater than about 180°C, and less than about 250°C, such as less than about 230°C, such as less than about 220°C, such as less than about 210°C, such as less than about 200°C, such as less than about 190°C, such as less than about 180°C.
  • the coating displays excellent heat-sealability even at relatively low basis weights.
  • the coated paper 10 as shown in FIG. 1 can be used to form various different packages using different techniques and processes.
  • the fibrous web 12 can be a wetlaid paper web formed from cellulose fibers.
  • the fibrous web can be formed from an aqueous suspension of fibers.
  • the cellulose fibers contained in the fibrous web can be pulp fibers including wood pulp fibers, plant waste fibers, or other plant fibers.
  • the aqueous suspension of fibers can be deposited onto a porous forming surface that allows water to drain thereby forming the fibrous web. As the web is formed and dried, the paper can be calendered.
  • the fibrous web is made primarily from plant derived or natural fibers.
  • Natural (plant derived) fibers may be selected from chemical pulp, such as sulphate and sulphite pulp, organosolv pulp, recycled fibers, and/or mechanical pulp including e.g.
  • RMP refiner mechanical pulp
  • PRMP pressurized refiner mechanical pulp
  • P-RC APMP pretreatment refiner chemical alkaline peroxide mechanical pulp
  • thermomechanical pulp TMP
  • TMCP thermomechanical chemical pulp
  • HT-TMP high-temperature TMP
  • APP alkaline peroxide mechanical pulp
  • APMP alkaline peroxide mechanical pulp
  • APIMP alkaline peroxide thermomechanical pulp
  • CMP chemirefinermechanical pulp
  • CMP chemithermomechanical pulp
  • CTMP chemirefinermechanical pulp
  • CTMPR sulphite-modified thermomechanical pulp
  • SC semichemical pulp
  • the pulp may be a bleached or non-bleached pulp.
  • the pulp may originate from hardwood or softwood, including birch, beech, aspen such as European aspen, alder, eucalyptus, maple, acacia, mixed tropical hardwood, pine such as loblolly pine, fir, hemlock, larch, spruce such as Black spruce or Norway spruce, and mixtures thereof.
  • Non-wood plant fibers can also be used, such as seed hair fibers, leaf fibers, and bast fibers.
  • Plant fibers can be provided from e.g. straws of grain crops, wheat straw, reed canary grass, reeds, flax, hemp, kenaf, jute, ramie, seed, sisal, abaca, coir, bamboo, bagasse, cotton kapok, milkweed, pineapple, cotton, rice, reed, esparto grass, Phalaris arundinacea, or combinations thereof.
  • the fibrous web can be primarily formed from the cellulose fibers without being combined with other components, such as fillers.
  • the fibrous web (prior to coating) can contain cellulose fibers in an amount greater than about 90% by weight, such as in an amount greater than about 95% by weight.
  • Particular cellulose fibers well suited to producing the fibrous web include softwood fibers, hardwood fibers, birch fibers, hemp fibers, or mixtures thereof.
  • the fibrous web can be made exclusively from softwood fibers alone or in combination with hardwood fibers.
  • the fibrous web can be made from a blend of wood pulp fibers, such as softwood fibers, with bast fibers, such as hemp fibers.
  • the cellulose fibers can be selected, for instance, in order to produce a web that can be efficiently drained from aqueous fluids during formation and that can produce a relatively low opacity paper at lower basis weights while still retaining mechanical properties needed for processing and handling.
  • the fibers used to form the web can optionally be fed through a refining process in order to increase freeness as measured by the Schopper Riegler Method for drainability (ISO 5267-1:2000).
  • refining the cellulose fibers is different than producing pulp fibers.
  • pulping the lignin is removed from the cellulose fibers.
  • the nap of individual fibrils making up the outer surface or wall of the fiber is raised which is sometimes referred to as defibrillation.
  • Refining is the mechanical and/or chemical action which causes defibrillation.
  • the fibers in preparing the fibers for producing the fibrous web, can first go through a suitable pretreatment, such as washing, and can also be chopped especially if using bast fibers.
  • a suitable pretreatment such as washing
  • the fibers can be fed through a hammermill or subjected to various different chemical treatments.
  • the cellulose fibers can be mixed with an aqueous solution or solvent which can occur in a refiner, such as a twin screw machine. If desired, wetting agents, acids, or alkalis can also be added in order to soften the cellulose fibers. In addition, one or more alcohols can also be added to the fibers including methyl alcohol, ethyl alcohol, or mixtures thereof.
  • the aqueous suspension can be fed to or formed in a refiner and subjected to a mechanical refining action.
  • the consistency of the fibers in the refiner can be from about 1% to about 30% solids content.
  • the pulp suspension is subjected to mechanical action that produces the formation of greater fibrils within each fiber.
  • any suitable refining device may be used in order to increase the freeness value of the fibers and that a twin screw refiner merely represents one instrument, process or technique that may be used.
  • the cellulose fibers After exiting one or more refiners, in accordance with the present disclosure, the cellulose fibers have a freeness value of greater than about 60° SR, such as greater than about 65° SR, such as greater than about 70° SR. In one aspect, the cellulose fibers have been refined to greater than about 73° SR, such as greater than about 75° SR, such as greater than about 78° SR, such as greater than about 80° SR, such as greater than about 82° SR. The freeness value of the fibers is less than about 95° SR, such as less than about 90° SR, such as less than about 85° SR, such as less than about 80° SR.
  • refining the fibers to the extent described above not only can improve drainage of the web during production but can also lower the opacity characteristics of the paper.
  • Refining the cellulose fibers can also allow for a reduction in the thickness of the sheet while still providing good mechanical properties. Reduction in thickness for a given basis weight, for instance, has been found to unexpectedly improve transparency while still maintaining an excellent balance of mechanical properties.
  • Adjusting the level of refining of the cellulose fibers can also allow for adjustments to the barrier properties of the low opacity paper. For instance, refining of the fibers can be used to adjust air permeability and to develop air barrier properties, water barrier properties, oil barrier properties, or the like.
  • the basis weight of the web is relatively low.
  • the basis weight of the fibrous web can be less than about 38 g/m 2 , such as less than about 36 g/m 2 , such as less than about 34 g/m 2 , such as less than about 32 g/m 2 , such as less than about 30 g/m 2 , such as less than about 28 g/m 2 , such as less than about 25 g/m 2 , such as less than about 23 g/m 2 .
  • the basis weight is generally greater than about 10 g/m 2 , such as greater than about 12 g/m 2 .
  • the basis weight of the fibrous web is from about 10 g/m 2 to about 24 g/m 2 , preferably from about 10 g/m 2 to about 18 g/m 2 including all increments of 1 g/m 2 therebetween.
  • two coating compositions or a combined coating composition are applied to the fibrous web.
  • the first coating is applied to the fibrous web in order to lower the opacity of the final product.
  • the second coating can be a heat-sealable coating for providing the paper product with heat-sealable characteristics.
  • both coatings can synergistically function together to provide excellent barrier properties.
  • the paper product can have excellent aesthetic and functional qualities that makes the product well suited for packaging applications.
  • the first coating can form a layer on one side of the fibrous web, which will also imply impregnation into the web.
  • the second coating can form a surface layer underlying first coating.
  • the first coating comprises a transparency agent.
  • the transparency agent can comprise a bio-based wax or oil.
  • the bio-based wax or oil for instance, can be derived from animal or plant biomass.
  • the transparency agent can be a bio-based wax derived from at least 80% by weight vegetable oils, such as at least about 90% by weight vegetable oils, such as up to 100% by weight vegetable oils.
  • the bio-based wax can be paraffin-free and can be free of mineral oil saturated hydrocarbons and mineral oil aromatic hydrocarbons.
  • the transparency agent can meet all government requirements for food contact and food handling.
  • the coating compositions can meet all of the requirements of FDA 21 CFR ⁇ 176.180 which is directed to components of paper and paperboard that are in contact with dry food.
  • the transparency agent and the low opacity paper can also meet all of the requirements of European Commission Regulation No. 1935/2004 regarding materials and articles intended to come in contact with food.
  • the bio-based wax in one embodiment, can have a melting point of from about 25°C to about 75°C, including all increments of 1°C therebetween.
  • the melting point of the bio-based wax can be less than about 70°C, such as less than about 65°C, such as less than about 60°C, such as less than about 55°C, such as less than about 50°C, such as less than about 45°C, such as less than about 40°C.
  • the melting point of the bio-based wax can be greater than about 25°C, such as greater than about 30°C, such as greater than about 35°C, such as greater than about 40°C, such as greater than about 45°C, such as greater than about 50°C.
  • a bio-based wax can be selected having a particular melting point that is well suited for a particular application.
  • the transparency agent comprises a bio-based wax that is a coconut-based wax, a rice-based wax, a palm-based wax, a soy-based wax or mixtures thereof.
  • the transparency agent is a coconut-based wax or oil.
  • the coconut-based wax can have a melting point of from about 25 degrees C to about 45 degrees C, such as from about 30 degrees C to about 40 degrees C.
  • the coconut-based wax can be applied to the fibrous web as an anionic, aqueous dispersion.
  • the transparency agent can be a palm-based wax or oil.
  • the palm-based wax can have a melting point of from about 50 degrees C to about 70 degrees C, such as from about 55 degrees C to about 65 degrees C.
  • the palm-based wax can be applied to the fibrous web as an anionic, aqueous dispersion.
  • the transparency agent can be a soy-based wax that may be applied to the fibrous web as an aqueous cationic emulsion having a melting point of from about 55 degrees C to about 80 degrees C, such as from about 63 degrees C to about 72 degrees C.
  • the bio-based wax can be water dispersible or water miscible.
  • the transparency agent can be incorporated into an aqueous composition for application to the fibrous web in producing the low opacity paper.
  • the amount of the transparency agent incorporated into the product can depend on various factors.
  • the basis weight (dry) of the transparency agent coating can be from about 0.5 g/m 2 to about 18 g/m 2 , including all increments of 0.5 g/m 2 therebetween.
  • the transparency agent coating can have a basis weight of greater than about 2 g/m 2 , such as greater than about 4 g/m 2 , such as greater than about 5 g/m 2 , such as greater than about 6 g/m 2 , such as greater than about 7 g/m 2 , such as greater than about 8 g/m 2 .
  • the basis weight of the transparency agent coating can be less than about 20 g/m 2 , such as less than about 15 g/m 2 , such as less than about 12 g/m 2 , such as less than about 10 g/m 2 , such as less than about 8 g/m 2 .
  • the transparency agent can be present in the paper product in an amount greater than about 2% by weight, such as in an amount greater than about 3% by weight, such as in an amount greater than about 4% by weight, such as in an amount greater than about 5% by weight, such as in an amount greater than about 10% by weight, such as in an amount greater than about 13% by weight.
  • the transparency agent is present in the paper product generally in an amount less than about 35% by weight, such as in an amount less than about 25% by weight, such as in an amount less than about 20% by weight, such as in an amount less than about 15% by weight, such as in an amount less than about 10% by weight, such as in an amount less than about 8% by weight, such as in an amount less than about 6% by weight.
  • the transparency agent can improve various properties and characteristics of the coated paper. For instance, the transparency agent can increase the transparency and/or decrease the opacity of the final product. The transparency agent can also reduce the permeability of the low opacity paper and increase the barrier properties of the paper.
  • the first coating applied to the fibrous web can be covered with a second or heat-sealable coating or can be combined with a heat-sealable coating composition.
  • the heat-sealable coating can be applied directly to the transparency agent coating and can be applied to the coated paper without any type of adhesive or tie layer between the transparency agent coating and the heat-sealable coating.
  • the coated paper of the present disclosure can be made without any adhesive layers between any of the coatings or between the fibrous web and the coating.
  • the first coating containing the transparency agent can be combined with the heat sealable coating composition and applied to the web as a single coating.
  • the heat-sealable (second) coating can be applied to the fibrous web on a side that is the opposite side to the side coated with the first coating containing the transparency agent, so as to provide a first coating on the first surface and a second coating on the second surface of the fibrous web.
  • the heat-sealable coating can contain a polymer and various other components.
  • the polymer can be a polymer selected from the group consisting of proteins, polysaccharides, polysaccharide ethers, polysaccharide esters and polysaccharide ether esters.
  • the above polymers can completely replace petroleum-derived heat-sealable polymers used in the past.
  • the polymers above, for instance, can be produced from biomass.
  • the polymers can be sustainable and environmentally friendly, just like the plant or animal derived wax or oil and exhibit excellent heat-sealable properties.
  • the polymer is preferably a protein and/or thermoplastic polymer that improves the heat-sealability.
  • the polymer can be a thermoplastic polymer with a melting point in the range of 60 to 200°C, more preferably 100 to 180°C, and most preferably 110 to 180°C.
  • the heat-sealable coating of the coated paper (paper product) of the present disclosure comprises a thermoplastic polymer having a melting point in the range of 60 to 200°C, the heat-sealability of the coated paper is improved.
  • the polymer is preferably a biomass-based polymer, so that the coated paper is more sustainable and environmentally friendly.
  • the polymer can be a polyester polymer that may be selected from the group consisting of polyhydroxyalkanoate, polylactic acid, polyglycolic acid, polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate, and polylactic acid-polyethylene glycol.
  • Polyhydroxyalkanoates are polyesters of hydroxyalkanoic acids.
  • Polyhydroxyalkanoates are thermoplastic. They may be homopolyesters or copolyesters and differ in their properties according to their chemical composition, namely the contained hydroxyalkanoic acid(s).
  • the PHA may be one or more polyesters selected from the group consisting of poly(3-hydroxypropionate), poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3-hydroxynonanoate), poly(3-hydroxydecanoate), poly(3-hydroxyundecanoate), poly(3-hydroxydodecanoate), poly(3-hydroxytetradecanoate), poly(3-hydroxypentadecanoate),and poly(3-hydroxyhexadecanoate).
  • polyesters selected from the group consisting of poly(3-hydroxypropionate), poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate), poly(3-hydroxyoctanoate), poly(3
  • the PHA may also be one or more copolyester obtained from copolymerization of two or more hydroxyalkanoic acids. More particularly, the PHA copolyester may be one or more selected from the group consisting of poly(3-hydroxypropionate-co-3-hydroxybutyrate), poly(3-hydroxypropionate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-3-hydroxyhexanoate).
  • the PHA copolyester may be one or more selected from the group consisting of poly(3-hydroxypropionate-co-3-hydroxybutyrate), poly(3-hydroxypropionate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-co-3-
  • the PHA is preferably one or more polyesters selected from the group consisting of poly(3-hydroxypropionate), poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(3-hydroxybutyrate-3-hydroxyhexanoate), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate).
  • the PHA is most preferably poly(3-hydroxybutyrate).
  • the polybutylene adipate terephthalate is preferably a block copolymer.
  • the polylactic acid-polyethylene glycol is preferably a block copolymer.
  • the polysaccharide may be one or more polymers selected from the group consisting of starch, cellulose, arabinoxylan, chitin, and pectin.
  • the polysaccharide is preferably starch or cellulose, such as a cellulose derivative.
  • thermoplastic polysaccharide comprising a polysaccharide and a plasticizer is obtained.
  • the plasticizer may be one or more compound(s) selected from the group consisting of polyhydric alcohols, diols, esters of polyhydric alcohols and aliphatic esters of mono-, di- or polycarboxylic acids.
  • the plasticizer is preferably a polyhydric alcohol or a diol and most preferably one or more compound(s) selected from glycerol, glycol, and sorbitol.
  • the glycerin may be vegetable glycerin (VG). Vegetable glycerin is glycerin obtained from plant oils such as soybean oil, coconut oil or palm oil.
  • thermoplastic polysaccharide preferably comprises at least one of starch and cellulose.
  • the thermoplastic polysaccharide is preferably thermoplastic starch, thermoplastic cellulose or a combination thereof, and more preferably thermoplastic starch.
  • the thermoplastic starch preferably comprises one or more plasticizer selected from the group consisting of glycerol, glycol, and sorbitol.
  • thermoplastic polysaccharide is derived from agricultural waste from corn.
  • the polymer used in the present disclosure may also be a polysaccharide ether, a polysaccharide ester or a polysaccharide ether ester.
  • the polysaccharide ether is preferably a cellulose ether.
  • the polysaccharide ether is more preferably carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, ethyl methyl cellulose, and hydroxypropyl methyl cellulose.
  • the polysaccharide ether is most preferably carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose.
  • the polysaccharide ester may be a cellulose ester such as cellulose acetate.
  • the polysaccharide ether ester may be a cellulose ether ester such as hydroxypropyl methyl cellulose acetate succinate and carboxymethyl cellulose acetate butyrate.
  • the polymer is most preferably one or more selected from the group consisting of poly(3-hydroxybutyrate), poly(4-hydroxybutyrate), polylactic acid, polylactic acid-polyethylene glycol block copolymer, polybutylene adipate terephthalate and thermoplastic starch.
  • the polymer can also be a protein, especially plant sourced proteins.
  • proteins include soybean protein isolate, whey protein isolate, or casein.
  • the heat-sealable coating used in the present disclosure may comprise one or more additives.
  • Each additive can be present in the coating in an amount of from about 0.01% by weight to about 7% by weight, such as from about 0.1% by weight to about 3% by weight.
  • the additive may be at least one compound selected from the group consisting of a rheology modifier and a softener.
  • the rheology modifier can be one or more compounds selected from the group consisting of cellulose, starch or a derivative thereof.
  • the rheology modifier can be a microcrystalline cellulose and/or a nanocellulose.
  • the rheology modifier is preferably water-soluble or water-dispersible.
  • the rheology modifier is more preferably biomass-based and/or biodegradable. The rheology modifier allows to thicken the emulsion and to improve emulsion stability. Thus, dripping during application of the coating can be avoided.
  • the heat-sealable coating of the present disclosure may also contain a softener.
  • the softener may be one or more compound(s) selected from the group consisting of polyhydric alcohols, diols, esters of polyhydric alcohols and aliphatic esters of mono-, di- or polycarboxylic acids.
  • the softener is preferably a polyhydric alcohol or a diol and most preferably one or more compound(s) selected from bio-based glycerin or glycerol, glycol, and sorbitol.
  • the coating comprises up to 90 wt.-% of the polymer, 0 to 3 wt.-% of rheology modifier, and 0 to 7 wt.-% of softener based on the total weight of the coating.
  • the heat-sealable coating used in the present invention can be mixed with the transparency agent in ratio of from about 10 to 90 wt.-% of the wax and about 10 to 90 wt.-% of the polymer and may more preferably comprise 10 to 40 wt.-% of the wax and 60 to 90 wt.-% of the polymer, based on the total weight of the coating mixture.
  • a paper coated with a coating comprising 10 to 90 wt.-% of the wax and 10 to 90 wt.-% of the polymer, based on the total weight of the coating combines a paper-like look and feel with a workability and heat-sealability comparable to a plastic film.
  • the heat-sealability of the coated paper can be improved when the coating comprises 10 to 40 wt.-% of the wax and 60 to 90 wt.-% of the polymer, based on the total weight of the coating.
  • a coated paper with a coating comprises 10 to 40 wt.-% of the wax and 60 to 90 wt.-% of the polymer, based on the total weight of the coating, exhibits improved water-vapor barrier properties.
  • the coating comprises 20 to 40 wt.-% of the wax and 60 to 80 wt.-% of the polymer, based on the total weight of the coating. In such coating, the best compromise between water vapor barrier properties and heat-sealability is achieved.
  • the basis weight of the heat-sealable coating can vary depending upon the particular application and the end use of the coated paper.
  • the basis weight of the heat-sealable coating can be from about 1 g/m 2 to about 20 g/m 2 , including all increments of 1 g/m 2 therebetween.
  • the heat-sealable coating can have a basis weight of greater than about 1 g/m 2 , such as greater than about 3 g/m 2 .
  • the basis weight of the heat-sealable coating can be less than about 20g/m 2 , such as less than about 18 g/m 2 , such as less than about 15 g/m 2 , such as less than about 13 g/m 2 , such as less than about 10 g/m 2 , such as less than about 8 g/m 2 .
  • the basis weight of the resulting coating can be from about 3 g/m 2 to about 35 g/m 2 , including all increments of 1 g/m 2 therebetween.
  • the combined coating can have a basis weight of greater than about 5 g/m 2 , such as greater than about 8 g/m 2 .
  • the basis weight of the combined coating can be less than about 30 g/m 2 , such as less than about 25 g/m 2 , such as less than about 20 g/m 2 , such as less than about 18 g/m 2 , such as less than about 15 g/m 2 .
  • the coating compositions can be applied to the fibrous web using any suitable method or technique.
  • an aqueous composition containing the transparency agent can be applied to the fibrous web using a size press either at the wet end of the papermaking machine or after the web has been dried.
  • the fibrous web can be formed and then later coated with a composition containing the transparency agent.
  • Coating can be performed using any suitable method including air knife coating, roll-to-roll coating, blade coating, spray coating, Mayer rod coating, direct gravure printing, offset gravure printing, reverse gravure printing, smooth roll coating, curtain coating, bead coating, slot coating, fill press coating, and the like.
  • the heat-sealable coating can be formed by applying a coating composition over the transparency agent coating by spraying, brushing, or rolling. Upon application to the surface, the surface coating composition undergoes film formation.
  • the heat-sealable coating may be formed by coalescence-based film formation.
  • Coalescence-based film formation takes place with polymer particles dispersed in a liquid phase, preferably with latex polymers, and most preferably with water-dispersed polymers selected from the group consisting of polyester, polysaccharide, polysaccharide ester, polysaccharide ether and polysaccharide ether ester in combination with a plant or animal derived wax.
  • the heat-sealable coating composition can be an aqueous dispersion or emulsion comprising the wax and/or polymer.
  • the wax is preferably a wax as defined in the first aspect of the present invention.
  • the wax is preferably a plant wax or an animal wax and is more preferably a plant wax.
  • the wax comprised in the heat-sealable coating compositions is most preferably one or more selected from the group consisting of coconut wax, soy wax, palm wax, rice bran wax, and mixtures thereof.
  • the wax has preferably a dropping point in the range of 60°C to 120°C.
  • the coatings are dried to form a coated paper.
  • the first coating composition can be applied and dried followed by application of the second coating composition followed by drying.
  • the first and second coating compositions can be combined together and then applied to the fibrous web followed by drying.
  • Drying may be carried out by blowing hot dry air onto the coating, thus raising the coating temperature to a point where water is evaporated from the coated paper, leaving a relatively dry coated paper.
  • the web temperature i.e. the temperature of the fibrous web
  • the web temperature during drying is preferably less than 120°C.
  • the web temperature of the paper can be determined by means of non-contact temperature measurement using an infrared, non-contact thermometer.
  • the coated fibrous web can be calendered without being supercalendered.
  • a plain filigree press may be used for a glazing effect on the surface of the product.
  • the calender rolls can include a hard roll opposite a soft roll.
  • the pressure applied to the coated paper can be greater than about 200 kPa (2 bar), such as greater than about 400 kPa (4 bar), such as greater than about 500 kPa (5 bar), and generally less than about 1200 kPa (12 bar), such as less than about 1000 KPa (10 bar), such as less than about 800 kPa (8 bar), such as less than about 700 kPa (7 bar).
  • Calendering can occur at ambient temperature or, alternatively, one or both of the calender rolls can be heated.
  • the transparency agent can be applied to the fibrous web and the fibrous web can be calendered. After being calendered, the heat-sealable coating can be applied to the web.
  • the coated fibrous web can be calendered after both coatings have been applied to the web, i.e. after the heat-sealable coating has been applied and formed on the web.
  • the coated fibrous web can be calendered multiple times. For instance, in one aspect, the transparency agent can be applied to the fibrous web and the fibrous web can undergo a first calendering process. Next, the heat-sealable coating can be applied and formed on the fibrous web and the coated web can be calendered again.
  • the coated paper of the present disclosure can have a relatively low thickness.
  • the thickness of the paper can be less than about 80 ⁇ m, such as less than about 70 ⁇ m, such as less than about 60 ⁇ m.
  • the paper generally has a thickness of greater than about 20 ⁇ m, such as greater than about 25 ⁇ m, such as greater than about 30 ⁇ m.
  • Low opacity papers made according to the present disclosure not only display low opacity and heat sealability but also display a beneficial blend of other properties.
  • the low opacity paper can have a Gurley air permeability of less than about 45,200 seconds, such as less than about 20,000 seconds, such as less than about 10,000 seconds, such as less than about 1000 seconds, and generally greater than about 600 seconds.
  • the low opacity and heat-sealable paper can also have a water drop resistance greater than 10 min according to TAPPI T 432 cm-09 (2 ⁇ L of water volume is used in test).
  • the paper product can have a water vapor barrier at 23°C and 50%HR less than 80 g/m 2 /day, such as less than 50 g/m 2 /day according to ASTM E96/E96M - 15:2014.
  • the low opacity and heat-sealable paper of the present disclosure has numerous uses and applications.
  • the low opacity and heat-sealable paper can be used as a packaging material.
  • the low opacity and heat-sealable paper for instance, can be made to be flexible or semirigid making the product well suited for constructing packages.
  • the present disclosure is also directed to a method for producing a low opacity and heat-sealable paper.
  • the method includes forming a fibrous web from a fiber furnish.
  • the fibrous web for instance, can be a wetlaid web.
  • the fibrous web is then coated with an aqueous composition containing the transparency agent as described above.
  • Any suitable technique can be used to coat the fibrous web.
  • the fibrous web can be coated using a size press.
  • the coating applied to the fibrous web can be dried and then optionally calendered.
  • a second coating can be applied to the fibrous web containing heat-sealable components.
  • the coating can be dried to form the heat-sealable coating and the coated and dried web can optionally be calendered.
  • the heat-sealable composition or components can be combined with the transparency agent composition or components and the resulting heat-sealable and transparency composition can be applied to the web to form a single coating that reduces opacity and is heat sealable.
  • the coating can be dried and then optionally calendered.
  • Each sample included a fibrous web, also called or base web.
  • the basis weight of the fibrous web in Sample No. 1 was 14 g/m 2 and it had a Schopper-Riegler freeness value of 86° SR.
  • the basis weight of the fibrous web in Sample No. 2 and No. 3 was 22 g/m 2 and it had a Schopper-Riegler freeness value of 82° SR.
  • Each fibrous web was made from pulp fibers, particularly refined softwood fibers.
  • Sample No. 1 and Sample No. 2 were coated with a mix of a transparency agent composition comprising a soy-based wax and a heat-sealable coating composition that contained a polysaccharide derived from agricultural corn waste.
  • the heat-sealable and transparency agent coating had a basis weight of 11 g/m 2 .
  • Sample No. 3 was first coated with transparency agent composition comprising a coconut-based wax and secondly with a heat-sealable coating composition that contained a casein protein, having a sealing temperature between 130 and 220°C.
  • the coating weight of the two layers was 11 g/m 2 .
  • the coated paper samples had very low opacity characteristics while also including excellent mechanical strength properties and barrier properties.
  • the described samples displayed sealable properties at 150°C.

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EP23177036.3A 2023-06-02 2023-06-02 Papierverpackungsmaterial mit niedriger opazität Pending EP4471207A1 (de)

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EP23177036.3A EP4471207A1 (de) 2023-06-02 2023-06-02 Papierverpackungsmaterial mit niedriger opazität
PCT/EP2024/064735 WO2024246108A1 (en) 2023-06-02 2024-05-29 Low opacity paper packaging material
AU2024281027A AU2024281027A1 (en) 2023-06-02 2024-05-29 Low opacity paper packaging material
EP24730292.0A EP4720407A1 (de) 2023-06-02 2024-05-29 Papierverpackungsmaterial mit niedriger opazität
CN202480033798.1A CN121175464A (zh) 2023-06-02 2024-05-29 低不透明度纸包装材料
KR1020257043484A KR20260018903A (ko) 2023-06-02 2024-05-29 저 불투명도 종이 패키지 재료

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WO (1) WO2024246108A1 (de)

Citations (6)

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Publication number Priority date Publication date Assignee Title
EP3483337A1 (de) * 2017-11-14 2019-05-15 Arjo Wiggins Fine Papers Limited Recycelbares und repulpierbares transluzentes oder transparentes papier verwendung für verpackungsanwendungen
WO2020209781A1 (en) * 2019-04-12 2020-10-15 Fernandi Musik Sealed package comprising parchment paper and a polysaccharide-based coating
WO2021224839A1 (en) * 2020-05-07 2021-11-11 Stora Enso Oyj Coated paper substrate suitable for metallization
US11371189B2 (en) * 2018-02-13 2022-06-28 Mitsubishi Hitec Paper Europe Gmbh Heat-sealable barrier paper
WO2022243445A1 (en) * 2021-05-21 2022-11-24 Neenah Gessner Gmbh Coated paper for use as packaging material
WO2023073544A1 (en) * 2021-10-29 2023-05-04 Stora Enso Oyj Food or liquid packaging laminate comprising fibers obtained from used beverage cartons (ubc)

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3483337A1 (de) * 2017-11-14 2019-05-15 Arjo Wiggins Fine Papers Limited Recycelbares und repulpierbares transluzentes oder transparentes papier verwendung für verpackungsanwendungen
US11371189B2 (en) * 2018-02-13 2022-06-28 Mitsubishi Hitec Paper Europe Gmbh Heat-sealable barrier paper
WO2020209781A1 (en) * 2019-04-12 2020-10-15 Fernandi Musik Sealed package comprising parchment paper and a polysaccharide-based coating
WO2021224839A1 (en) * 2020-05-07 2021-11-11 Stora Enso Oyj Coated paper substrate suitable for metallization
WO2022243445A1 (en) * 2021-05-21 2022-11-24 Neenah Gessner Gmbh Coated paper for use as packaging material
WO2023073544A1 (en) * 2021-10-29 2023-05-04 Stora Enso Oyj Food or liquid packaging laminate comprising fibers obtained from used beverage cartons (ubc)

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EP4720407A1 (de) 2026-04-08
WO2024246108A1 (en) 2024-12-05
KR20260018903A (ko) 2026-02-09
CN121175464A (zh) 2025-12-19
AU2024281027A1 (en) 2025-11-27

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