Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/02—Cellulose; Modified cellulose
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D101/00—Coating compositions based on cellulose, modified cellulose, or cellulose derivatives
  • C09D101/02—Cellulose; Modified cellulose
• • 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
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/001—Modification of pulp properties
  • D21C9/007—Modification of pulp properties by mechanical or physical means
• • 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
  • 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
  • D21H21/18—Reinforcing agents
• • 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
  • 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
  • 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
  • D21H19/12—Coatings without pigments applied as a solution using water as the only solvent, e.g. in the presence of acid or alkaline compounds

Definitions

• the present invention relates to a method of producing a three- dimensional cellulose-based structure by means of fiber molding.
• 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 to a forming 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.
• WSA wet strength agents
• Wet strength chemicals improve the strength properties of the paper both in wet and dry state by crosslinking the cellulose fibres with covalent bonds that do not break upon wetting. Wet strength agents also improve mechanical properties under humid conditions.
• a disadvantage associated with addition of WSA is that the repulpability of the material is decreased, i.e. the fraction of reusable fibers upon recycling is reduced, or harsher process condition than normally used at the mill is required.
• Another disadvantage with WSA is that the chemical retention in the sheet or substrate is important in order to achieve the effects.
• One way is to combine WSA with a specific retention chemical in order to increase the fixation.
• the harsh dewatering conditions in fiber molding present challenging conditions for obtaining good and efficient retention of the chemicals.
• the preferred technical solution is to inrease dosage of WSA and with higher dosage of retention chemicals. As a consequence, the use of higher concentration of WSA deteriorates disintregration of the molded product and hence reduces repulpability.
• the objects of the invention are obtained by means of a method for producing a three-dimensional molded article from cellulose fibers according to claim 1.
• Said method comprises at least the steps of: -providing an aqueous pulp molding composition; -wet molding a three-dimensional precursor structure from said composition, wherein said structure comprises a dry content between 15-80wt%;
• Said achieved three-dimensional molded article thus comprises a base substrate originating from the aqueous pulp molding composition, and a surface barrier layer (herein sometimes also referred to as “top layer” or “top barrier layer”) originating from the aqueous suspension.
• a surface barrier layer herein sometimes also referred to as "top layer” or “top barrier layer”
• the procedure of molding a three- dimensional precursor structure" in this context may include the steps of providing a forming tool having a three dimensional shape and comprising a forming portion; and bringing said forming portion into contact with the aqueous composition so that said forming portion is covered with a wet layer of pulp from the pulp molding composition.
• 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 or semi-wet state (dry content between 15-80wt%).
• recycling refers to the process of converting waste cellulose-based materials into new cellulose-based materials and products. The recyclability of a material depends on its ability to reacquire the properties it had in its virgin state.
• recyclability and repulpability means that preconsumer waste can be collected, disintegrated and reused for example when making new formed fiber products.
• Post-consumer waste can be collected and treated in various ways before being reused in e.g. molded pulp. The treatment before reuse depends on the packed product and level of contaminants. Repulpability can be determined according to the PTS standard (PTS R.H 021/97).
• said aqueous pulp molding composition used for molding the precursor structure is free from wet strength agent.
• a top barrier layer is formed on a surface of the molded article. It has surprisingly been found that a top layer comprising a mixture of MFC and WSA, which have been applied onto a wet precursor substrate as a pre-mixture leads to several advantages.
• One advantage is that the method allows for the use of significantly reduced dosages of WSA compared to known products, while still retaining enough wet strength of the endproduct. Lower amounts of WSA in its turn leads to increased repulpability of the material, i.e. to a lower reject rate of the material once it is being recycled.
• the present invention leads to that a majority, i.e. >90%, of the WSA is concentrated to one top layer of the article. Furthermore, applying the aqueous suspension onto a wet precursor substrate ensures better economy, better infiltration of MFC and chemicals into the base substrate, and significantly better chemical retention.
• the method according to the invention leads to advantageous properties of the molded end-product.
• the top barrier layer provides surprisingly good oil and grease resistance (OGR.) as well as water repellence measured as KIT and Cobb values.
• the MFC content of 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.
• Microfibrillated cellulose shall in the context of the patent application mean a nano scale cellulose particle fiber or fibril with at least one dimension less than 1000 nm. MFC comprises partly or totally fibrillated cellulose or lignocellulose fibers.
• the liberated fibrils have a diameter less than 1000 nm, whereas the actual fibril diameter or particle size distribution and/or aspect ratio (length/width) depends on the source and the manufacturing methods.
• the smallest fibril is called elementary fibril and has a diameter of approximately 2-4 nm (see e.g. Chinga-Carrasco, G., Cellulose fibres, nano fibrils and microfibrils, : The morphological sequence of MFC components from a plant physiology and fibre technology point of view, Nanoscale research letters 2011, 6:417 , while it is common that the aggregated form of the elementary fibrils, also defined as microfibril Fengel, D., Ultrastructural behavior of cell wall polysaccharides, Tappi J., March 1970, Vol 53, No. 3.), is the main product that is obtained when making MFC e.g. by using an extended refining process or pressure-drop disintegration process.
• the length of the fibrils can vary from around 1 to more than 10 micrometers.
• a coarse MFC grade might contain a substantial fraction of fibrillated fibers, i.e. protruding fibrils from the tracheid (cellulose fiber), and with a certain amount of fibrils liberated from the tracheid (cellulose fiber).
• MFC cellulose microfibrils, fibrillated cellulose, nanocellulose, fibril aggregates, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregrates and cellulose microfibril aggregates.
• MFC can also be characterized by various physical or physical-chemical properties such as large surface area or its ability to form a gel-like material at low solids (1-5 wt%) when dispersed in water.
• the cellulose fiber is preferably fibrillated to such an extent that the final specific surface area of the formed MFC is from about 1 to about 300 m 2 /g, such as from 1 to 200 m 2 /g or more preferably 50-200 m 2 /g when determined for a freeze-dried material with the BET method.
• the MFC should preferably be a mechanically fibrillated fiber from either non-mechanically pretreated 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 is fine fibrils derived from enzymatically treated and fluidized chemical pulp or homogenized pulp or disinegrated 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 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.
• 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 aqueous suspension comprises wet strength agent of an amount between 1- lOOkg/tn, more preferably 5-75kg/tn and most preferably 10- 50kg/tn (measured in dry weight of top layer).
• wet strength agent of an amount between 1- lOOkg/tn, more preferably 5-75kg/tn and most preferably 10- 50kg/tn (measured in dry weight of top layer).
• said wet strength agent is selected from the group comprising : polyamide epichlorohydrin, polyethylene imine, dialdehyde starch, polyacryl amides, glyoxal or melamine formaldehyde, polyamidoamineepichloro 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. 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 flocs.
• WSA is added together with additional functional chemicals such as retention agents to fiber before subjecting the resulting mixture to fibrillation treatment.
• said 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 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.
• said aqueous suspension further comprises dye and/or pigment to achieve a shaded/colored product providing possibilities of controlling the appearance of the final article.
• the viscosity of the 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.
• said aqueous suspension is applied onto the precursor structure by means of a non-contact application method, e.g. by spraying liquid droplets onto the surface of the precursor structure, or by means of curtain coating.
• Non-contact application onto the precursor structure may be repeated several times in order to reach the desired grammage of the top layer, preferable in at least two consecutive steps, or at least ten steps.
• Spraying of aqueous suspension can be carried out using methods known in the art.
• the spraying can for example be electrostatically assisted or ultrasound assisted. It can also be performed by a co-axial spray nozzle, as steam, high air pressure or by use of a rotary disk atomizer.
• aqueous suspension onto the precursor structure by means of contact applications, such as immersing the precursor structure into a bath of aqueous suspension comprising MFC and WSA or by means of pad printing technology (i.e. using a resilient pad for transferring the suspension onto the surface structure)
• the pulp molding composition for wet molding the precursor structure is an aqueous composition having a solid content between 0.05 - 10wt%, preferably between 0.2-1.5wt%.
• the pulp molding composition 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, R.MP, 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 - 500 gsm in dry weight.
• 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.
• dewatering and drying said molded precursor structure is performed as a onesided 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 WSA.
• the top barrier layer has a grammage between 5-50gsm, preferably 10-30gsm, preferably between 7-20gsm.
• the top barrier layer comprises ⁇ 10 pinholes/m 2 , preferably ⁇ 5 pinholes/m 2 , more preferably pinhole free according to standard EN13676:2001.
• the surface barrier side of the three-dimensional molded article has a water Cobbeo value (as determined according to standard ISO 535:2014 after 60 seconds) below 50 g/m 2 , preferably below 30 g/m 2 .
• the substrate comprises internal sizing such as AKD, and the three-dimensional molded article has a Cobbeo value below 30 g/m 2 .
• the three- dimensional molded article has an oil Cobbso value (as determined according to standard SCAN-P 37:77 after 30 seconds) below 9 g/m 2 , preferably below 5 g/m 2 .
• the three- dimensional molded article has a KIT barrier >5, preferably >10 such as 12 (TAPPI method 559, 3M KIT test).
• the three- dimensional molded article 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 three- dimensional molded article 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).
• said three-dimensional molded article has an average density between 350-1500 kg/m3, preferably 400-1200 kg/m3 or more preferably 500-900 kg/m3.
• said three-dimensional molded article 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 .
• said dried three-dimensional molded article has a repulpability characterized by a reject rate (as determined according to the PTS R.H 021/97 test method) below 10%, preferably below 5%.
• a reject rate as determined according to the PTS R.H 021/97 test method
• said three-dimensional molded article comprises a wet strength >1%, preferably between 2-10% (measured as percent wet strenght over dry strength).
• said three-dimensional molded article has a wet rub turbidity between 1- 25 Nephelometric Turbidity Units (NTU) measured with a nephelometer (ISO 7027) after 20s.
• NTU Nephelometric Turbidity Units
• the present invention further comprises a three-dimensional molded pulp article comprising more than one layer, whereof at least one layer is made by means of a method according to the invention, further where said top barrier layer is arranged as an outer layer of said multilayer article.
• the present description is directed to production of three- dimensional molded pulp articles with barrier properties and improved repulpability.
• three-dimensional molded pulp articles 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.
• concentrating wet strength agent only to a surface of a 3D molded fiber article, wherein said wet strength agent has been applied in an aqueous suspension together with MFC to create a surface barrier layer leads to a product with improved recyclability, yet having a good wet strength as well as barrier properties.
• the molded article is intended to contain foodstuff.
• the surface comprising the top barrier layer is arranged at the food-contact side of the product.
• a 3D molded fiber article comprising at least one outer surface, or a portion of an outer surface, which has been subjected to application (e.g. spraying, coating or immersion) of an aqueous suspension comprising a mixture of WSA and MFC.
• Said aqueous suspension is to be applied onto a substrate in wet state, whereafter the article is subjected to drying and dewatering under heat treatment, and preferably also applied pressure.
• a wet molding method for manufacturing a three-dimensional molded fiber article with barrier properties and improved/enhanced recyclability will be described in a non-limiting way.
• An aqueous pulp composition is provided with consistency between 0.05-10wt%.
• 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, R.MP, TMP, CMP, NSSC, dissolving pulp, and regenerated fibers or mixtures thereof.
• the pulp is CTMP.
• a 3D shaped forming tool comprising a forming portion is brought into contact with the pulp composition, for instance by immersing said tool into the slurry bath.
• Said forming portion is arranged to represent a 3D mirror image of the article to be formed.
• Pulp is drawn onto the forming portion e.g. by means of vacuum suction until a layer of desired thickness has been formed, whereupon the forming tool is removed from the slurry.
• the wet layer of pulp is dewatered to a dry content between 15-80wt%.
• an intermediate precursor structure has been obtained, which is still supported by the shape of the forming tool.
• an aqueous suspension comprising microfibrillated cellulose and wet strength agent mixed with each other to a homogenous mixture.
• the aqueous suspension is applied onto at least one face of said precursor structure e.g. by means of a non-contact application method to create a layer on said structure.
• An example of a non-contact application method is spraying liquid droplets onto the precursor structure.
• Application of the aqueous suspension can be performed in many consecutive sessions, e.g. spraying sessions, e.g. such as spraying at least two times on the same surface, or at least five times or at least twenty times, until a desired thickness of the sprayed layer is achieved.
• the top layer originating from the aqueous suspension will provide barrier properties, and the wet strength agent present in the suspension will contribute to make the article stable and rigid.
• the precursor structure having been covered with a top barrier layer of mixed WSA and MFC 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 is partially drawn into the substrate and gets somehow integrated therewith, and binding of the top surface components is improved.
• 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.
• 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 for 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 150-220 °C, with a press range between 1-10 bar. This way, a single layer 3D molded fiber article is formed, having a dry content of >88wt%, preferably >94wt%, more preferably >96%.
• multilayered molded fiber products can be accomplished for instance by applying more than one fibrous layer on top of each other in consecutive molding production steps.
• the various layers of a multilayered product may hereby provide different functions, such as rigidity, barrier properties, etc.
• the foodcontact layer of the end-product is arranged to comprise the top barrier layer described herein.
• Pulp - CTMP pulp was used with and without additives, i.e. internal sizing agent and/or wet strength agent (WSA).
• Fine fibril - This was a chemical pulp that was enzymatically treated and then fluidized.
• the characteristic properties of this material is high water retention value properties, but due to its fineness, it is difficult to retain on a wire. If blended with a furnish/pulp, it will pass through the wire or holes in the dewatering unit.
• the material is gel like at low solid contents 2-4 wt%.
• Coarse fibril - This is a fibrillated fiber prepared from a chemical pulp. The characteristic properties of this is that it is easier to retain mechanically in a fiber matrix or on a dewatering wire. On the other hand, it increases also drainage resistance.
• the preferred Shopper Riegler level is 50-95 and more pref. 60-93.
• the SR for fibril coarse used here was about 93.
• the internal sizing agent used was alkyl ketene dimer (AKD).
• the wet strength agent (WSA) used here was polyamide epichlorohydrin.
• a 300 gsm sheet was prepared on a 2D molding wire using vacuum suction.
• the wet sheets were dried using a hot plate (under pressure) at 180 C. No barrier properties were obtained.
• Base sheet with WSA and internal sizing (comparative example)
• Base sheet with integrated fine fibril top layer and WSA After wet forming the base, a 10 gsm (dry weight) wet layer of fine fibril pre-mixed with WSA was applied by spraying, and then the product was further dewatered and dried.
• This recipe shows a significant reduction in oil uptake (Oil Cobb).
• the amount of WSA corresponds to 0.86 kg/tn of the whole product, i.e. a reduction with more than 50% compared to #2.
• Base sheet with integrated top layer comprising fine fibril and sizing agent
• This sample shows the benefit of adding sizing agent to the integrated top layer instead of adding the chemical to the bulk furnish. Compared to the reference #1, an increased wet rub resistance is obtained.
• Base sheet with integrated top layer comprising fine fibril, AKD and WSA
• Base sheet with top layer comprising fine fibril, AKD and WSA
• Base sheet with top layer comprising fine fibril, AKD and WSA
• Base sheet with top layer comprising fine fibril, AKD and WSA and dispersing agent
• Base sheet with top layer comprising coarse fibril, AKD and WSA
• Base sheet with top layer comprising coarse fibril, AKD and WSA
• Base sheet with top layer comprising coarse fibril, AKD and WSA and dispersing agent
• top layer contains a dispersing agent (low molecular weight CMC).
• dispersing agent low molecular weight CMC

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