WO2022218772A1 - A cellulose fiber structure comprising a barrier layer - Google Patents

A cellulose fiber structure comprising a barrier layer Download PDF

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Publication number
WO2022218772A1
WO2022218772A1 PCT/EP2022/059097 EP2022059097W WO2022218772A1 WO 2022218772 A1 WO2022218772 A1 WO 2022218772A1 EP 2022059097 W EP2022059097 W EP 2022059097W WO 2022218772 A1 WO2022218772 A1 WO 2022218772A1
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WO
WIPO (PCT)
Prior art keywords
fiber product
molded fiber
product according
previous
barrier layer
Prior art date
Application number
PCT/EP2022/059097
Other languages
French (fr)
Inventor
Frank Peng
Sohrab KAZEMAHVAZI
Olga SIEVE
Matthias Hausmann
Original Assignee
Stora Enso Oyj
Kiefel Gmbh
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 Stora Enso Oyj, Kiefel Gmbh filed Critical Stora Enso Oyj
Publication of WO2022218772A1 publication Critical patent/WO2022218772A1/en

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J3/00—Manufacture of articles by pressing wet fibre pulp, or papier-mâché, between moulds
    • D21J3/10—Manufacture of articles by pressing wet fibre pulp, or papier-mâché, between moulds of hollow bodies
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J3/00—Manufacture of articles by pressing wet fibre pulp, or papier-mâché, between moulds
    • 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
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J5/00—Manufacture of hollow articles by transferring sheets, produced from fibres suspensions or papier-mâché by suction on wire-net moulds, to couch-moulds
    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J7/00—Manufacture of hollow articles from fibre suspensions or papier-mâché by deposition of fibres in or on a wire-net mould
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B29/00—Layered products comprising a layer of paper or cardboard
    • 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
    • D21H27/30—Multi-ply
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W90/00—Enabling technologies or technologies with a potential or indirect contribution to greenhouse gas [GHG] emissions mitigation
    • Y02W90/10—Bio-packaging, e.g. packing containers made from renewable resources or bio-plastics

Definitions

  • the present invention relates to a molded fiber product comprising a barrier layer.
  • Natural fibers include cellulose fibers of any natural origin, such as derived from wood pulp and/or plants.
  • Manufacturing molded fiber products and structures can be done by wet forming, wherein an aqueous pulp composition is applied onto a forming tool/molding tool to form a fiber matt followed by compression-molding performed under elevated temperatures, resulting in a dried fiber product having a shape complementary to the shape of the mold.
  • said tool is perforated or porous so that water can be removed from the suspension or wet pulp during forming, such as in a dewatering/drying step.
  • the desired barrier property can be achieved by adding barrier chemicals into the pulp suspension.
  • the object of the invention is obtained by means of a method for producing a molded product from cellulose fibers, and a molded fiber product as described in the claims.
  • a molded fiber product comprising at least a first molded base layer and a second molded top barrier layer, said product being produced by means of a method comprising the steps of:
  • a first aqueous pulp suspension i.e. a pulp slurry
  • a forming tool having a forming surface, and immersing said forming surface into the first aqueous pulp suspension under applied vacuum so that said forming surface is covered with a layer of pulp from said first aqueous pulp suspension, said layer representing a precursor structure comprising a dry content between 10-80wt%
  • the precursor structure comprises an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m 2 , preferably below 15 g/m 2 , preferably below 10 g/m 2 .
  • Said molded product thus comprises a base substrate originating from the first aqueous pulp molding composition, and a surface barrier layer (herein sometimes also referred to as “top layer” or “top barrier layer”) originating from the second aqueous suspension.
  • a surface barrier layer herein sometimes also referred to as “top layer” or “top barrier layer”
  • a top barrier layer is formed on a surface of the molded article.
  • the "barrier component” is microfibrillated cellulose (MFC).
  • MFC microfibrillated cellulose
  • the barrier component is highly refined cellulose.
  • the barrier component can also be carboxymethylcellulose (CMC).
  • the top barrier layer may also comprise a mixture of different barrier components, such as a mixture of MFC and/or CMC and/or highly refined cellulose.
  • a top barrier layer applied by means of vacuum-assisted wet molding onto a wet precursor molded fiber substrate, dried under pressure and heat provides a final product with a dense top layer having excellent grease barrier properties with a minimum of pin holes.
  • applying the aqueous barrier suspension onto a wet precursor substrate ensures better economy, better infiltration of MFC and chemicals into the base substrate, and significantly better chemical retention.
  • PFASs perfluorinated alkylated substances
  • Microfibrillated cellulose shall in the context of the patent application mean a cellulose particle, fiber or fibril having a width or diameter of from 20 nm to 1000 nm.
  • MFC Microfibrillated cellulose
  • Various methods exist to make MFC such as single or multiple pass refining, pre-hydrolysis followed by refining or high shear disintegration or liberation of fibrils.
  • One or several pre-treatment steps is usually required in order to make MFC manufacturing both energy efficient and sustainable.
  • the cellulose fibers of the pulp used when producing MFC may thus be native or pre-treated enzymatically or chemically, for example to reduce the quantity of hemicellulose or lignin.
  • the cellulose fibers may be chemically modified before fibrillation, wherein the cellulose molecules contain functional groups other (or more) than found in the original cellulose.
  • groups include, among others, carboxymethyl (CM), aldehyde and/or carboxyl groups (cellulose obtained by N-oxyl mediated oxidation, for example "TEMPO"), or quaternary ammonium (cationic cellulose).
  • CM carboxymethyl
  • TEMPO N-oxyl mediated oxidation
  • quaternary ammonium cationic cellulose
  • MFC can be produced from wood cellulose fibers, both from hardwood or softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It can be made from pulp, including pulp from virgin fiber, e.g. mechanical, chemical and/or thermomechanical pulps. It can also be made from broke or recycled paper.
  • MFC Middle-MediaCard
  • cellulose microfibrils fibrillated cellulose, nanocellulose, fibril aggregates, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregrates and cellulose microfibril aggregates.
  • the MFC used as barrier component should preferably be a mechanically fibrillated fiber from either non- mechanically pre-treated or mechanically pre-treated pulp.
  • the pulp can also be enzymatically pre-treated before fibrillation step.
  • the MFC should preferably have the following characteristics: FS5 fines should preferably lower than 100%, and preferably lower than 90% (as determined the Valmet FS5 fiber image analyzer). "FS5 fines" here refers to the projection area of particles with a size under 0.2mm of the total surface area of all measured objects x 100%.
  • FS5 fibrillation level (P14) should preferably be higher than 1.5% and more preferably higher than 1.8% and more preferably higher than 2%.
  • the MFC used as barrier component is fine fibrils derived from enzymatically treated and fluidized chemical pulp or homogenized pulp or disintegrated by Aqueous counter collision (ACC) or high pressure drop methods or treated in a high shear rotor stator mixer.
  • ACC Aqueous counter collision
  • the pulp can be mechanically activated or fibrillated in one or several steps.
  • the enzymatically treated pulp can be provided as never- dried, dewatered or dried before further subjecting to the activation and fibrillation step.
  • said MFC is coarse fibril, derived from fibrillated chemical pulp, said fibril coarse having a Shopper Riegler value between 50-95, more preferably between 60-93.
  • the Schopper-Riegler value can be determined through the standard method defined in EN ISO 5267-1.
  • the barrier component can be in the form of highly refined cellulose.
  • said highly refined cellulose is cellulose refined to an SR value in the range of 70-94, preferably in the range of 70- 90, and wherein the cellulose fibers have a length of ⁇ lmm.
  • the fiber length may be the length weighted mean fiber length as determined according to ISO 16065-2. This SR value is determined for a pulp, with or without additional chemicals, thus the fibers have not consolidated into a film or started any hornification or such.
  • the content of barrier component in the top barrier layer may be in the range of 70 to 99 weight%, in the range of 80 to 99 weight%, or in the range of from 90 to 99 weight% of the solids of the top barrier layer.
  • said second aqueous suspension further comprises a wet strength agent at a concentration between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the surface barrier layer.
  • the second aqueous suspension comprises a wet strength agent at a concentration such that the formed top barrier layer comprises between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the top barrier layer. It is within the scope of the present invention to mix fine and coarse MFC and apply together with wet strength agent (WSA) as said aqueous solution to form the top barrier layer.
  • WSA wet strength agent
  • said wet strength agent is selected from the group comprising: polyamide epichlorohydrin, polyethylene imine, dialdehyde starch, polyacryl amides, glyoxal or melamine formaldehyde, polyamidoamine- epichloro hydrin and urea formaldehyde melamine or a combination thereof.
  • said microfibrillated cellulose and WSA have been co-fibrillated and/or co-mixed before applied onto said precursor structure as an aqueous suspension. Co-fibrillation and/or co-mixing leads to facilitated preparation of the aqueous solution, e.g.
  • WSA is added together with additional functional chemicals such as retention agents to fiber before subjecting the resulting mixture to fibrillation treatment.
  • said second aqueous suspension further comprises a sizing agent, preferably selected from the group comprising: alkyl ketene dimer (AKD), rosin sizes such as soap or rosin emulsions, alkyl succinic anhydride (ASA), polyurethane or styrene maleic anhydrides.
  • the second aqueous suspension comprises a sizing agent at a concentration such that the formed top barrier layer comprises between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the top barrier layer.
  • the sizing agent is AKD.
  • the amount of AKD is between 0.05 -100 kg/tn, more preferably 0.1-50 kg/tn, and even more preferably 0.5-40 kg/tn and more preferably 2-20 kg/tn based on the dry content of the top layer.
  • the viscosity of the second aqueous suspension is 5-2000 mPas, such as 10-500 mPas as determined with Brookfield, i.e. Brookfield viscosity determined at 100 rpm according to standard SCAN-P 50:84.
  • the second aqueous suspension has a solid content between 0.1-3wt%.
  • the top barrier layer is created by means of immersing the precursor structure into a bath of the second aqueous suspension comprising barrier material, e.g. MFC, followed by vacuum suction.
  • Said second aqueous suspension is herein also sometimes referred to as "second aqueous mixture”.
  • the first aqueous suspension (i.e. the pulp slurry) comprises cellulose fibers or a mix or cellulose fibers selected from the group comprising: wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, NSSC, dissolving pulp, and regenerated fibers and mixtures thereof.
  • the pulp molding composition is based on CTMP.
  • CTMP comprise bulky and stiff fibers and provide more rigidity to the final structure.
  • CTMP pulp can also be deficient of fines e.g. by fractionation or washing. Less fines in the bulk layer leads to faster dewatering during production of the molded structure.
  • the grammage of the three-dimensional molded article is 50 - 1000 gsm in dry weight, preferably 50 - 500 gsm.
  • dewatering and drying the precursor structure comprising the top barrier layer is performed by pressing the wet fiber layer under applied heat, optionally with vacuum suction for removing water/steam.
  • dewatering and drying said molded precursor structure comprising the top barrier layer is performed as a one-sided dewatering.
  • one-sided dewatering is performed by applying the vacuum on the non-coated side of the structure. This leads to that the top barrier layer is to some extent drawn into the base substrate, leading to improved retention and integration of the MFC and optionally WSA.
  • the top barrier layer has a grammage between 5-50gsm, preferably 10-30gsm, preferably between 7-20gsm.
  • the molded fiber product has an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m 2 , preferably below 10 g/m 2 , preferably below 5 g/m 2 .
  • the molded fiber product has a water Cobb 6 o value (as determined according to standard ISO 535:2014 after 60 seconds) below 50 g/m 2 , preferably below 30 g/m 2 .
  • the molded fiber product has a KIT barrier >5, preferably >10 (TAPPI method 559, 3M KIT test).
  • the molded fiber product has an air permeance, L&W Code 168 air permeance tester (pm/Pa s at 20 kPa), less than 1000 and more preferably less than 500 and most preferably less than 210 (SCAN P26 or ISO 5636-1).
  • the molded fiber product has a Gurley Hill value (L&W Code 166) >20 000, more preferably >30 000 and most preferably >40 000 s/100 ml (determined according to the standard ISO 5636/6).
  • the molded fiber product has an oxygen transmission rate (OTR) below 1,000, preferably below 500, and even more preferably below 300 cc/m 2 /24h/atm, measured according to the standard ASTM F-1927 at 50% relative humidity and 23 °C.
  • OTR oxygen transmission rate
  • the top barrier layer comprises ⁇ 10 pinholes/m 2 , preferably ⁇ 5 pinholes/m 2 , more preferably pinhole free according to standard EN13676:2001.
  • said molded product has an average density between 350-1500 kg/m 3 , preferably 400-1200 kg/m 3 or more preferably 500-900 kg/m 3 .
  • said molded product comprises a top side comprising said top barrier layer, and a back side opposite to said top side.
  • the density at said top side is >800 kg/m 3 , more preferably > 850 kg/m 3
  • the density at said back side is 300 - 800 kg/m 3 .
  • one or all of said layers in the molded product has been subjected to coloring, i.e. a coloring substance has been added to the aqueous suspension.
  • a coloring substance has been added to the aqueous suspension.
  • the present invention further comprises a three-dimensional molded pulp article comprising more than one layer, whereof at least one layer corresponds to a product according to the invention, further where said top barrier layer is arranged as an outer layer of said multilayer article.
  • molded pulp products with barrier properties.
  • molded pulp products include in a non-limiting way bowls, cups, capsule, pots, containers, trays and packages.
  • the present description relates to the context of wet molding procedures.
  • a barrier compound is provided as an aqueous suspension and applied onto the surface of a wet molded fiber structure which comprises a dry content between 15-80wt%, whereafter the structure is dewatered under heat, leading to a product with good barrier properties, e.g. against grease.
  • the molded product is arranged to contain foodstuff.
  • the surface comprising the top barrier layer is arranged at the food-contact side of the product. It is thus within the ambit of the present invention to provide a molded fiber article comprising at least one outer surface, or a portion of an outer surface, which has been covered with a layer of an aqueous suspension comprising a barrier component such as MFC.
  • Said aqueous barrier suspension is to be applied onto a base substrate by vacuum-assisted dipping wherein the base structure is in wet state (i.e. said base substrate having a dry content between 15-80wt%), whereafter the product is subjected to drying and dewatering under heat treatment, preferably in combination with applied pressure.
  • a first aqueous pulp suspension is provided with consistency between 0.05-10wt%, preferably 0.2 - 1.5wt%.
  • the pulp may be any one of wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, NSSC, dissolving pulp, and regenerated fibers or mixtures thereof.
  • the pulp is CTMP.
  • the first aqueous pulp suspension may also comprise sizing agent/s such as alkyl ketene dimer (AKD), rosin sizes such as soap or rosin emulsions, alkyl succinic anhydride (ASA), polyurethane and/or styrene maleic anhydrides.
  • sizing agent/s such as alkyl ketene dimer (AKD), rosin sizes such as soap or rosin emulsions, alkyl succinic anhydride (ASA), polyurethane and/or styrene maleic anhydrides.
  • a forming tool comprising a forming portion is brought into contact with the first pulp suspension by immersing at least a part of the forming portion into the slurry bath.
  • Said forming portion is arranged to represent a mirror image of the article to be formed.
  • Pulp is drawn onto the forming portion by means of vacuum suction through the tool until a wet pulp layer of desired thickness has been formed, whereupon the forming tool is removed from the suspension.
  • a wet intermediate precursor structure has been obtained comprising a dry content between 15-80wt%, which is supported by the shape of the forming tool.
  • a second aqueous suspension comprising at least one component which provides barrier properties, so called “barrier component”.
  • the barrier component can be microfibrillated cellulose (MFC) or highly refined cellulose.
  • the barrier component can also be carboxymethylcellulose (CMC). It is of course conceivable to provide a mixture of different barrier components in said second aqueous suspension.
  • said second aqueous suspension has a dry content between 0.1-3wt%.
  • the wet intermediate precursor structure is immersed into the second aqueous suspension, and barrier component is drawn onto the surface thereof by means of vacuum suction so that a top layer providing barrier properties is formed.
  • the precursor structure having been covered with a top barrier layer is then to be further dewatered and dried.
  • dewatering of said molded precursor structure is performed as a one-sided dewatering by means of applying suction at the non- coated side of the structure. Sucking from the untreated side leads to that the top layer substances are partially drawn into the substrate and gets integrated therewith, and binding of the top surface components onto the substrate is improved.
  • the side of the structure comprising the barrier layer is pressed against a support arrangement, e.g. a mesh.
  • a multilayer molded fiber product can be achieved comprising several barrier layers.
  • Each barrier layer may comprise the same or different barrier component/s.
  • a first barrier layer may comprise MFC of a coarse type and a second barrier layer may comprise MFC of fine type.
  • the various layers of a multilayered product may hereby provide different functions, such as rigidity, barrier properties, etc.
  • Application of several barrier layers accomplished by means of consecutive vacuum-assisted immersion steps of a wet molded structure leads to a product with a dense and stable barrier, e.g. with lowered risk of cracks during drying.
  • Dewatering and/or drying can be done in various ways.
  • a wet curing procedure the wet layer is pressed under elevated temperatures to be compressed and dried to a certain thickness, thereby yielding a smooth external surface of the end structure.
  • a dry curing process the wet layer is subjected to heated air thereby removing moisture, which results in an end structure with a more textured finish.
  • the hot press temperature range for a wet molded procedure is between 100-220°C, with a press range between 1-10 bar. This way, a molded fiber product is formed, having a dry content of 388wt%, preferably 394wt%, more preferably 396%.
  • Said molded product comprises at least a base layer originating from the first pulp suspension, and a top barrier layer originating from the second aqueous mixture.
  • the base layer has a lower density compared to the barrier layer.
  • the base layer has a density ranging between 300 - 800 kg/m 3
  • the barrier layer has a density >800 kg/m 3 , more preferably > 850 kg/m 3 .
  • the barrier layer ensures a good grease resistance, with an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m 2 , preferably below 10 g/m 2 , preferably below 5 g/m 2 .
  • a first aqueous CTMP pulp slurry was provided with consistencies between 0.5-lwt%.
  • a second aqueous mixture was provided, comprising microfibrillated cellulose (MFC) at a consistency of 0.5wt%.
  • MFC microfibrillated cellulose
  • the MFC used in the second mixture was coarse fibril, derived from fibrillated chemical pulp, said fibril coarse having a Shopper Riegler value between 50-95, more preferably between 60- 93.
  • the Schopper-Riegler value can be determined through the standard method defined in EN ISO 5267-1.
  • a forming tool with venting holes coupled to a vacuum source was used for molding a fiber product as follows. A portion of the forming tool was immersed into the CTMP pulp slurry, and a layer of pulp was drawn onto the tool surface by means of vacuum. The forming tool and the wet pulp layer was removed from the CTMP pulp slurry, and brought to the second aqueous MFC mixture. The wet pulp layer on the forming tool was again immersed into the second aqueous MFC mixture, whereafter vacuum was activated resulting in that MFC was drawn onto the surface of the CTMP pulp layer, forming a top barrier layer. The tool which at this point supported a two-layer molded pulp structure was removed from the MFC mixture and further dried by means of pressing and heating said structure at 190°C.
  • the resulting end-product had good grease barrier properties with oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 15 g/m 2 , in some cases even below 10 g/m 2 .

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Abstract

The invention discloses a molded fiber product comprising at least a first base layer and a second top barrier layer.

Description

A CELLULOSE FIBER STRUCTURE COMPRISING A BARRIER LAYER
Technical field
The present invention relates to a molded fiber product comprising a barrier layer. Background
There is a growing interest for producing cellulose based products, e.g. for use as packaging applications for foodstuff, tableware, trays, technical products, electronic equipment and/or consumer goods. Several advantages are associated with the use of natural fibers for manufacturing packages. Being a renewable resource, natural fibers provide a sustainable alternative to other packaging materials such as aluminum and plastics, and furthermore natural fibers are both recyclable and biodegradable allowing for composting. Natural fibers include cellulose fibers of any natural origin, such as derived from wood pulp and/or plants.
Manufacturing molded fiber products and structures can be done by wet forming, wherein an aqueous pulp composition is applied onto a forming tool/molding tool to form a fiber matt followed by compression-molding performed under elevated temperatures, resulting in a dried fiber product having a shape complementary to the shape of the mold. Typically, said tool is perforated or porous so that water can be removed from the suspension or wet pulp during forming, such as in a dewatering/drying step. It is often desirable to provide a barrier layer on the molded product, to protect against e.g. grease and water, for instance in case the product is intended for food stuff. The desired barrier property can be achieved by adding barrier chemicals into the pulp suspension. In such case, the amounts of chemicals needed to achieve desired effect is high because of bulk charge. Another option is to apply surface treatment with barrier materials. As an example, in W02015019061 the surface of a molded fiber product is subjected to spraying of a coating providing barrier qualities. However, there is currently no working system with this technology due to limitations for instance in rheology control of the applied materials, and difficulty in achieving a uniform coverage of a 3D surface, leading to inadequate barrier function.
Thus, there is a need for improvements when it comes to producing molded fiber products having barrier properties.
Object of the invention
It is an object of the present invention to provide an improved method for manufacturing a cellulose-based, molded fiber article, resulting in a product having good barrier properties.
Summary
The object of the invention is obtained by means of a method for producing a molded product from cellulose fibers, and a molded fiber product as described in the claims.
According to the invention, there is provided a molded fiber product comprising at least a first molded base layer and a second molded top barrier layer, said product being produced by means of a method comprising the steps of:
-providing a first aqueous pulp suspension (i.e. a pulp slurry) having a dry content between 0.05-10wt%, or between 0.2- 1.5wt%; -providing a forming tool having a forming surface, and immersing said forming surface into the first aqueous pulp suspension under applied vacuum so that said forming surface is covered with a layer of pulp from said first aqueous pulp suspension, said layer representing a precursor structure comprising a dry content between 10-80wt%;
-providing a second aqueous suspension comprising a barrier component;
-immersing the precursor structure into the second aqueous suspension under applied vacuum so that a top barrier layer is formed on at least a portion of said precursor structure; and -dewatering and drying said precursor structure comprising the top barrier layer under elevated temperature >100°C to a dry content of ³88wt%, preferably ³94wt%, more preferably ³96% to achieve the molded fiber product, wherein the molded fiber product comprises an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m2, preferably below 15 g/m2, preferably below 10 g/m2.
Said molded product thus comprises a base substrate originating from the first aqueous pulp molding composition, and a surface barrier layer (herein sometimes also referred to as "top layer" or "top barrier layer") originating from the second aqueous suspension.
It is to be understood that said "precursor structure" refers to an intermediate, not-yet ready structure, that in the present case has been formed into a three-dimensional shape, and which is still in a wet state (dry content between 10-80wt%). According to the present invention, a top barrier layer is formed on a surface of the molded article. According to one aspect of the invention, the "barrier component" is microfibrillated cellulose (MFC). According to another aspect of the invention, the barrier component is highly refined cellulose. The barrier component can also be carboxymethylcellulose (CMC). The top barrier layer may also comprise a mixture of different barrier components, such as a mixture of MFC and/or CMC and/or highly refined cellulose. Other heat-resistant plant-fiber based barrier components are also conceivable for use in said top layer. It has surprisingly been found that a top barrier layer applied by means of vacuum-assisted wet molding onto a wet precursor molded fiber substrate, dried under pressure and heat, provides a final product with a dense top layer having excellent grease barrier properties with a minimum of pin holes. Furthermore, applying the aqueous barrier suspension onto a wet precursor substrate ensures better economy, better infiltration of MFC and chemicals into the base substrate, and significantly better chemical retention. Thanks to the invention, a fiber-based and biodegradable package product can be achieved with good grease barrier properties while being free from environmentally harmful perfluorinated alkylated substances (PFASs). Being heat resistant (i.e. no defined melting temperature), plant-based fibers used as barrier components provides the advantage of resistance against hot oil and grease.
Microfibrillated cellulose (MFC) shall in the context of the patent application mean a cellulose particle, fiber or fibril having a width or diameter of from 20 nm to 1000 nm. Various methods exist to make MFC, such as single or multiple pass refining, pre-hydrolysis followed by refining or high shear disintegration or liberation of fibrils. One or several pre-treatment steps is usually required in order to make MFC manufacturing both energy efficient and sustainable. The cellulose fibers of the pulp used when producing MFC may thus be native or pre-treated enzymatically or chemically, for example to reduce the quantity of hemicellulose or lignin. The cellulose fibers may be chemically modified before fibrillation, wherein the cellulose molecules contain functional groups other (or more) than found in the original cellulose. Such groups include, among others, carboxymethyl (CM), aldehyde and/or carboxyl groups (cellulose obtained by N-oxyl mediated oxidation, for example "TEMPO"), or quaternary ammonium (cationic cellulose). After being modified or oxidized in one of the above-described methods, it is easier to disintegrate the fibers into MFC.
MFC can be produced from wood cellulose fibers, both from hardwood or softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse, or other non-wood fiber sources. It can be made from pulp, including pulp from virgin fiber, e.g. mechanical, chemical and/or thermomechanical pulps. It can also be made from broke or recycled paper.
There are different acronyms for MFC such as cellulose microfibrils, fibrillated cellulose, nanocellulose, fibril aggregates, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregrates and cellulose microfibril aggregates.
According to the invention, the MFC used as barrier component should preferably be a mechanically fibrillated fiber from either non- mechanically pre-treated or mechanically pre-treated pulp. The pulp can also be enzymatically pre-treated before fibrillation step. Further, the MFC should preferably have the following characteristics: FS5 fines should preferably lower than 100%, and preferably lower than 90% (as determined the Valmet FS5 fiber image analyzer). "FS5 fines" here refers to the projection area of particles with a size under 0.2mm of the total surface area of all measured objects x 100%. FS5 fibrillation level (P14) should preferably be higher than 1.5% and more preferably higher than 1.8% and more preferably higher than 2%.
According to one aspect of the invention, the MFC used as barrier component is fine fibrils derived from enzymatically treated and fluidized chemical pulp or homogenized pulp or disintegrated by Aqueous counter collision (ACC) or high pressure drop methods or treated in a high shear rotor stator mixer. Before subjecting the enzymatically pre-treated pulp to high shear disintegration, the pulp can be mechanically activated or fibrillated in one or several steps. The enzymatically treated pulp can be provided as never- dried, dewatered or dried before further subjecting to the activation and fibrillation step.
According to another aspect of the present invention, said MFC is coarse fibril, derived from fibrillated chemical pulp, said fibril coarse having a Shopper Riegler value between 50-95, more preferably between 60-93. The Schopper-Riegler value can be determined through the standard method defined in EN ISO 5267-1.
The barrier component can be in the form of highly refined cellulose. Preferably, said highly refined cellulose is cellulose refined to an SR value in the range of 70-94, preferably in the range of 70- 90, and wherein the cellulose fibers have a length of <lmm. The fiber length may be the length weighted mean fiber length as determined according to ISO 16065-2. This SR value is determined for a pulp, with or without additional chemicals, thus the fibers have not consolidated into a film or started any hornification or such.
In one embodiment, the content of barrier component in the top barrier layer may be in the range of 70 to 99 weight%, in the range of 80 to 99 weight%, or in the range of from 90 to 99 weight% of the solids of the top barrier layer.
According to another aspect of the invention, said second aqueous suspension further comprises a wet strength agent at a concentration between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the surface barrier layer. In some embodiments, the second aqueous suspension comprises a wet strength agent at a concentration such that the formed top barrier layer comprises between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the top barrier layer. It is within the scope of the present invention to mix fine and coarse MFC and apply together with wet strength agent (WSA) as said aqueous solution to form the top barrier layer.
According to another aspect of the present invention, said wet strength agent is selected from the group comprising: polyamide epichlorohydrin, polyethylene imine, dialdehyde starch, polyacryl amides, glyoxal or melamine formaldehyde, polyamidoamine- epichloro hydrin and urea formaldehyde melamine or a combination thereof. According to another aspect of the present invention, said microfibrillated cellulose and WSA have been co-fibrillated and/or co-mixed before applied onto said precursor structure as an aqueous suspension. Co-fibrillation and/or co-mixing leads to facilitated preparation of the aqueous solution, e.g. due to that MFC alone is sometimes difficult to mix with water. The mixing is even more difficult if the WSA is added with a retention agent or if the WSA has cationic or cellulose fibril reactive sites since this can causes substantial increase in gel viscosity or formations or floes. Thus, in one aspect of the invention, WSA is added together with additional functional chemicals such as retention agents to fiber before subjecting the resulting mixture to fibrillation treatment. According to another aspect of the invention, said second aqueous suspension further comprises a sizing agent, preferably selected from the group comprising: alkyl ketene dimer (AKD), rosin sizes such as soap or rosin emulsions, alkyl succinic anhydride (ASA), polyurethane or styrene maleic anhydrides. In some embodiments, the second aqueous suspension comprises a sizing agent at a concentration such that the formed top barrier layer comprises between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the top barrier layer. In a preferred aspect, the sizing agent is AKD. Preferably, the amount of AKD is between 0.05 -100 kg/tn, more preferably 0.1-50 kg/tn, and even more preferably 0.5-40 kg/tn and more preferably 2-20 kg/tn based on the dry content of the top layer.
According to another aspect of the invention, the viscosity of the second aqueous suspension is 5-2000 mPas, such as 10-500 mPas as determined with Brookfield, i.e. Brookfield viscosity determined at 100 rpm according to standard SCAN-P 50:84.
According to another aspect of the present invention, the second aqueous suspension has a solid content between 0.1-3wt%.
The top barrier layer is created by means of immersing the precursor structure into a bath of the second aqueous suspension comprising barrier material, e.g. MFC, followed by vacuum suction. Said second aqueous suspension is herein also sometimes referred to as "second aqueous mixture".
According to another aspect of the present invention, the first aqueous suspension (i.e. the pulp slurry) comprises cellulose fibers or a mix or cellulose fibers selected from the group comprising: wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, NSSC, dissolving pulp, and regenerated fibers and mixtures thereof. In a preferred aspect, the pulp molding composition is based on CTMP. CTMP comprise bulky and stiff fibers and provide more rigidity to the final structure. CTMP pulp can also be deficient of fines e.g. by fractionation or washing. Less fines in the bulk layer leads to faster dewatering during production of the molded structure.
According to yet another aspect of the present invention, the grammage of the three-dimensional molded article is 50 - 1000 gsm in dry weight, preferably 50 - 500 gsm. Preferably, dewatering and drying the precursor structure comprising the top barrier layer is performed by pressing the wet fiber layer under applied heat, optionally with vacuum suction for removing water/steam.
According to another aspect of the present invention, dewatering and drying said molded precursor structure comprising the top barrier layer is performed as a one-sided dewatering. In case of dewatering and drying by means of vacuum suction, one-sided dewatering is performed by applying the vacuum on the non-coated side of the structure. This leads to that the top barrier layer is to some extent drawn into the base substrate, leading to improved retention and integration of the MFC and optionally WSA.
According to yet another aspect of the invention, the top barrier layer has a grammage between 5-50gsm, preferably 10-30gsm, preferably between 7-20gsm.
According to yet another aspect of the invention, the molded fiber product has an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m2, preferably below 10 g/m2, preferably below 5 g/m2.
According to yet another aspect of the invention, the molded fiber product has a water Cobb6o value (as determined according to standard ISO 535:2014 after 60 seconds) below 50 g/m2, preferably below 30 g/m2.
According to yet another aspect of the invention, the molded fiber product has a KIT barrier >5, preferably >10 (TAPPI method 559, 3M KIT test). According to yet another aspect of the invention, the molded fiber product has an air permeance, L&W Code 168 air permeance tester (pm/Pa s at 20 kPa), less than 1000 and more preferably less than 500 and most preferably less than 210 (SCAN P26 or ISO 5636-1).
According to yet another aspect of the invention, the molded fiber product has a Gurley Hill value (L&W Code 166) >20 000, more preferably >30 000 and most preferably >40 000 s/100 ml (determined according to the standard ISO 5636/6).
According to yet another aspect of the invention, the molded fiber product has an oxygen transmission rate (OTR) below 1,000, preferably below 500, and even more preferably below 300 cc/m2/24h/atm, measured according to the standard ASTM F-1927 at 50% relative humidity and 23 °C.
According to yet another aspect of the invention, the top barrier layer comprises <10 pinholes/m2, preferably <5 pinholes/m2, more preferably pinhole free according to standard EN13676:2001.
According to yet another aspect of the present invention, said molded product has an average density between 350-1500 kg/m3, preferably 400-1200 kg/m3 or more preferably 500-900 kg/m3.
According to yet another aspect of the present invention, said molded product comprises a top side comprising said top barrier layer, and a back side opposite to said top side. According to this aspect, the density at said top side is >800 kg/m3, more preferably > 850 kg/m3, and the density at said back side is 300 - 800 kg/m3. According to one aspect of the present invention, one or all of said layers in the molded product has been subjected to coloring, i.e. a coloring substance has been added to the aqueous suspension. Hereby, the apperance/color of the end-product can be controlled.
The present invention further comprises a three-dimensional molded pulp article comprising more than one layer, whereof at least one layer corresponds to a product according to the invention, further where said top barrier layer is arranged as an outer layer of said multilayer article.
Detailed description
The present description is directed to molded pulp products with barrier properties. Examples of molded pulp products include in a non-limiting way bowls, cups, capsule, pots, containers, trays and packages.
The present description relates to the context of wet molding procedures.
According to the invention, a barrier compound is provided as an aqueous suspension and applied onto the surface of a wet molded fiber structure which comprises a dry content between 15-80wt%, whereafter the structure is dewatered under heat, leading to a product with good barrier properties, e.g. against grease.
In one embodiment, the molded product is arranged to contain foodstuff. In such a variant, the surface comprising the top barrier layer is arranged at the food-contact side of the product. It is thus within the ambit of the present invention to provide a molded fiber article comprising at least one outer surface, or a portion of an outer surface, which has been covered with a layer of an aqueous suspension comprising a barrier component such as MFC. Said aqueous barrier suspension is to be applied onto a base substrate by vacuum-assisted dipping wherein the base structure is in wet state (i.e. said base substrate having a dry content between 15-80wt%), whereafter the product is subjected to drying and dewatering under heat treatment, preferably in combination with applied pressure.
In the following, vacuum-assisted wet molding according to the invention for manufacturing a molded fiber product with barrier properties will be described.
A first aqueous pulp suspension is provided with consistency between 0.05-10wt%, preferably 0.2 - 1.5wt%. The pulp may be any one of wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, NSSC, dissolving pulp, and regenerated fibers or mixtures thereof. Preferably, the pulp is CTMP. The first aqueous pulp suspension may also comprise sizing agent/s such as alkyl ketene dimer (AKD), rosin sizes such as soap or rosin emulsions, alkyl succinic anhydride (ASA), polyurethane and/or styrene maleic anhydrides.
A forming tool comprising a forming portion is brought into contact with the first pulp suspension by immersing at least a part of the forming portion into the slurry bath. Said forming portion is arranged to represent a mirror image of the article to be formed. Pulp is drawn onto the forming portion by means of vacuum suction through the tool until a wet pulp layer of desired thickness has been formed, whereupon the forming tool is removed from the suspension. Hereby, a wet intermediate precursor structure has been obtained comprising a dry content between 15-80wt%, which is supported by the shape of the forming tool.
In a next step, a second aqueous suspension is provided comprising at least one component which provides barrier properties, so called "barrier component". The barrier component can be microfibrillated cellulose (MFC) or highly refined cellulose. The barrier component can also be carboxymethylcellulose (CMC). It is of course conceivable to provide a mixture of different barrier components in said second aqueous suspension. According to one example of the present invention, said second aqueous suspension has a dry content between 0.1-3wt%. The wet intermediate precursor structure is immersed into the second aqueous suspension, and barrier component is drawn onto the surface thereof by means of vacuum suction so that a top layer providing barrier properties is formed.
The precursor structure having been covered with a top barrier layer is then to be further dewatered and dried. Preferably, dewatering of said molded precursor structure is performed as a one-sided dewatering by means of applying suction at the non- coated side of the structure. Sucking from the untreated side leads to that the top layer substances are partially drawn into the substrate and gets integrated therewith, and binding of the top surface components onto the substrate is improved. Preferably, the side of the structure comprising the barrier layer is pressed against a support arrangement, e.g. a mesh. As a result, a dense and stable top barrier layer is achieved with no cracks and a minimum of pin-holes.
In some applications, before drying the product, more than one barrier layer is applied on top of each other by means of repeated vacuum-assisted immersion into aqueous barrier suspension/s comprising barrier component/s, while the intermediate precursor structure is still in wet state. Hereby, a multilayer molded fiber product can be achieved comprising several barrier layers. Each barrier layer may comprise the same or different barrier component/s. As an example, a first barrier layer may comprise MFC of a coarse type and a second barrier layer may comprise MFC of fine type. The various layers of a multilayered product may hereby provide different functions, such as rigidity, barrier properties, etc. Application of several barrier layers accomplished by means of consecutive vacuum-assisted immersion steps of a wet molded structure leads to a product with a dense and stable barrier, e.g. with lowered risk of cracks during drying.
Dewatering and/or drying can be done in various ways. In a wet curing procedure, the wet layer is pressed under elevated temperatures to be compressed and dried to a certain thickness, thereby yielding a smooth external surface of the end structure. In a dry curing process, the wet layer is subjected to heated air thereby removing moisture, which results in an end structure with a more textured finish. According to the invention, the hot press temperature range for a wet molded procedure is between 100-220°C, with a press range between 1-10 bar. This way, a molded fiber product is formed, having a dry content of ³88wt%, preferably ³94wt%, more preferably ³96%. Said molded product comprises at least a base layer originating from the first pulp suspension, and a top barrier layer originating from the second aqueous mixture. The base layer has a lower density compared to the barrier layer. In a preferred embodiment, the base layer has a density ranging between 300 - 800 kg/m3, and the barrier layer has a density >800 kg/m3, more preferably > 850 kg/m3. The barrier layer ensures a good grease resistance, with an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m2, preferably below 10 g/m2, preferably below 5 g/m2.
The present invention has been described with regards to preferred embodiments. However, it will be obvious to a person skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as described herein.
Example
A first aqueous CTMP pulp slurry was provided with consistencies between 0.5-lwt%. A second aqueous mixture was provided, comprising microfibrillated cellulose (MFC) at a consistency of 0.5wt%. The MFC used in the second mixture was coarse fibril, derived from fibrillated chemical pulp, said fibril coarse having a Shopper Riegler value between 50-95, more preferably between 60- 93. The Schopper-Riegler value can be determined through the standard method defined in EN ISO 5267-1.
A forming tool with venting holes coupled to a vacuum source was used for molding a fiber product as follows. A portion of the forming tool was immersed into the CTMP pulp slurry, and a layer of pulp was drawn onto the tool surface by means of vacuum. The forming tool and the wet pulp layer was removed from the CTMP pulp slurry, and brought to the second aqueous MFC mixture. The wet pulp layer on the forming tool was again immersed into the second aqueous MFC mixture, whereafter vacuum was activated resulting in that MFC was drawn onto the surface of the CTMP pulp layer, forming a top barrier layer. The tool which at this point supported a two-layer molded pulp structure was removed from the MFC mixture and further dried by means of pressing and heating said structure at 190°C.
The resulting end-product had good grease barrier properties with oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 15 g/m2, in some cases even below 10 g/m2.

Claims

1. A molded fiber product comprising at least a first base layer and a second top barrier layer, said product being produced by means of a method comprising the steps of:
-providing a first aqueous pulp suspension with a dry content between 0.05-10wt%;
-providing a forming tool having a forming surface, and immersing at least a portion of said forming surface into the first aqueous pulp suspension under applied vacuum so that said forming surface is covered with a wet base layer of pulp from said first aqueous pulp suspension, said layer representing a precursor structure comprising a dry content between 10-80wt%; -providing a second aqueous suspension comprising a barrier component;
-immersing the precursor structure into the second aqueous suspension under applied vacuum so that a top barrier layer is formed on at least a portion of said precursor structure; and -dewatering and drying said precursor structure comprising the top barrier layer under elevated temperature >100°C to a dry content of ³88wt%, preferably ³94wt%, more preferably ³96% to achieve the molded fiber product.
2. A molded fiber product according to claim 1, wherein the barrier component is any one of microfibrillated cellulose (MFC), highly refined cellulose or CMC or a mixture thereof.
3. A molded fiber product according to claim 2, wherein said microfibrillated cellulose is fine fibril derived from enzymatically treated and fluidized chemical pulp or homogenized pulp or disintegrated by aqueous counter collision (ACC) or high pressure drop methods or treated in a high shear rotor stator mixer.
A molded fiber product according to claim 2, wherein said microfibrillated cellulose is coarse fibril, derived from fibrillated chemical pulp, said fibril coarse having a Shopper Riegler value between 50-95, more preferably between 60-93.
A molded fiber product according to any one of the previous claims, wherein the first aqueous pulp suspension has a dry content between 0.2-1.5wt%.
A molded fiber product according to any one of the previous claims, wherein dewatering and drying said precursor structure comprising the top barrier layer is performed under temperatures >150°C.
A molded fiber product according to any one of the previous claims, wherein the first aqueous pulp suspension comprises cellulose fibers or a mix of cellulose fibers selected from the group comprising wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, NSSC, dissolving pulp, and regenerated fibers and mixtures thereof.
8. A molded fiber product according to any one of the previous claims, having a grammage between 50 - lOOOgsm in dry weight.
9. A molded fiber product according to any one of the previous claims, wherein the dewatering and drying of said molded precursor structure is performed as a one-sided dewatering.
10. A molded fiber product according to any one of the previous claims, wherein the top barrier layer has a basis weight between 5-50gsm, preferably 10-30gsm, preferably between 7-20gsm.
11. A molded fiber product according to any one of the previous claims, having an average density between 350-1500 kg/m3, preferably 400-1200 kg/m3 or more preferably 500-900 kg/m3.
12. A molded fiber product according to any one of the previous claims, comprising a top side with the top barrier layer, and a back side opposite to said top side, wherein the density of said top side is >800 kg/m3, more preferably > 850 kg/m3, and the density of said back side is 300 - 800 kg/m3.
13. A molded fiber product according to any one of the previous claims, wherein said second aqueous suspension further comprises a wet strength agent at a concentration between 1- 100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the surface barrier layer.
14. A molded fiber product according to claim 13, wherein said wet strength agent is selected from the group comprising: polyamide epichlorohydrin, polyethylene imine, dialdehyde starch, polyacryl amides, glyoxal or melamine formaldehyde, and urea formaldehyde melamine or a combination thereof.
15. A molded fiber product according to any one of the previous claims, wherein the second aqueous suspension further comprises a sizing agent at a concentration between 1-100 kg/tn, more preferably 5-75 kg/tn, even more preferably 10-50 kg/tn based on the dry content of the surface barrier layer.
16. A molded fiber product according to claim 15, wherein said sizing agent is selected from the group comprising alkyl ketene dimer (AKD), rosin sizes such as soap or rosin emulsions, alkyl succinic anhydride (ASA), polyurethane and styrene maleic anhydrides.
17. A molded fiber product according to any one of the previous claims, further comprising an oil Cobb3o value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 30 g/m2, preferably below 10 g/m2, preferably below 5 g/m2.
18. A molded fiber product according to claim 17, comprising an oil- and grease resistance (OGR) against oil and grease having a temperature >60°C, preferably >100°C.
19. A molded fiber product according to any one of the previous claims, wherein the three-dimensional molded article has a water Cobb6o value (as determined according to standard ISO 535:2014 after 60 seconds) below 50 g/m2, preferably below 30 g/m2.
20. A molded fiber product according to any one of the previous claims, further comprising a KIT barrier >5, preferably >10 (TAPPI method 559, 3M KIT test).
21. A molded fiber product according to any one of the previous claims, further comprising an air permeance, L&W Code 168 air permeance tester (pm/Pa s at 20 kPa), less than 1000 and more preferably less than 500 and most preferably less than 210 (SCAN P26 or ISO 5636-1).
22. A molded fiber product according to any one of the previous claims, further comprising a Gurley Hill value (L&W Code 166) >20 000, more preferably >30 000 and most preferably
>40 000 s/100 ml (determined according to the standard ISO 5636/6).
23. A molded fiber product according to any one of the previous claims, comprising an oxygen transmission rate (OTR) below 1,000, preferably below 500, and even more preferably below 300 cc/m2/24h/atm, measured according to the standard ASTM F-1927 at 50% relative humidity and 23 °C.
24. A molded fiber product according to any one of the previous claims, wherein the top barrier layer comprises <10 pinholes/m2, preferably <5 pinholes/m2, more preferably pinhole free according to standard EN13676:2001.
25. A molded fiber product according to any one of the previous claims, comprising more than one layer, whereof at least two layers are made by means of vacuum-assisted suction from aqueous suspension comprising barrier components.
26. A method for producing a molded fiber product according to any one of claims 1-25, comprising the steps of:
-providing a first aqueous pulp suspension with a dry content between 0.05-10wt%;
-providing a forming tool having a forming surface, and immersing at least a portion of said forming surface into the first aqueous pulp suspension under applied vacuum so that said forming surface is covered with a wet base layer of pulp from said first aqueous pulp suspension, said layer representing a precursor structure comprising a dry content between 10-80wt%;
-providing a second aqueous suspension comprising a barrier component; -immersing the precursor structure into the second aqueous suspension under applied vacuum so that a top barrier layer is formed on at least a portion of said precursor structure; and -dewatering and drying said precursor structure comprising the top barrier layer under elevated temperature >100°C to a dry content of ³88wt%, preferably ³94wt%, more preferably
³96% to achieve the molded fiber product.
PCT/EP2022/059097 2021-04-12 2022-04-06 A cellulose fiber structure comprising a barrier layer WO2022218772A1 (en)

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Publication number Priority date Publication date Assignee Title
SE2330131A1 (en) * 2023-03-20 2024-05-30 Stora Enso Oyj A method for providing a barrier coating on a moulded article

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DE1436922A1 (en) * 1965-05-07 1969-03-13 Bankers Life And Casualty Comp Method and apparatus for forming pulps
WO2015019061A1 (en) 2013-08-07 2015-02-12 Hpc Healthline Uk Limited A method of manufacturing a moulded pulp object
WO2021038511A1 (en) * 2019-08-29 2021-03-04 Stora Enso Oyj Method of producing an imprintable cellulose fiber product and a fiber product
FR3112351A1 (en) * 2020-07-09 2022-01-14 Centre Technique Du Papier Process for manufacturing an article molded from cellulose fibers

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Publication number Priority date Publication date Assignee Title
DE1436922A1 (en) * 1965-05-07 1969-03-13 Bankers Life And Casualty Comp Method and apparatus for forming pulps
WO2015019061A1 (en) 2013-08-07 2015-02-12 Hpc Healthline Uk Limited A method of manufacturing a moulded pulp object
WO2021038511A1 (en) * 2019-08-29 2021-03-04 Stora Enso Oyj Method of producing an imprintable cellulose fiber product and a fiber product
FR3112351A1 (en) * 2020-07-09 2022-01-14 Centre Technique Du Papier Process for manufacturing an article molded from cellulose fibers

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Publication number Priority date Publication date Assignee Title
SE2330131A1 (en) * 2023-03-20 2024-05-30 Stora Enso Oyj A method for providing a barrier coating on a moulded article

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