Method for treating a surface of a cellulosic substrate
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-05
- Publication Date
- 2026-08-13
Smart Images
Figure FI2026050056_13082026_PF_FP_ABST
Abstract
Description
Method for treating a surface of a cellulosic substrateFIELD
[0001] The present invention belongs to the field of material technology. More specifically, the present invention relates to methods for treating surfaces of cellulosic substrates.BACKGROUND
[0002] Cellulosic materials are used widely in a range of packaging applications, for example for packaging food, medicines, clothes and other consumer products. The surface of cellulosic materials is characterized by significant porosity and roughness that adversely impact the barrier properties of the packaging material, thus causing the material to permit the passage of gases and liquids. This is not acceptable for packaging of products that are sensitive to ambient air exposure. Furthermore, products comprising water or oil may adversely impact the structural integrity of the package as the water or oil seeps through the packaging material.
[0003] Low density fibrous materials may shed fibres and dust, which may impair the use of such packaging material for example for white goods.
[0004] It is known that a coating, such as a polyethylene or a dispersion barrier coating, may be applied to provide barrier properties to a cellulosic substrate. However, the coating needs to fill the porous surface of the cellulosic substrate in a sufficient manner, requiring more coating material to be applied to achieve the required barrier properties. In some cases, the porous surface may not be adequately or uniformly filled, leaving pinholes in the coating, which leads to poor barrier properties.
[0005] Some coating materials used to provide the barrier properties are fossil based and / or may not be biodegradable, thus making the packaging less sustainable.
[0006] There is thus a need to avoid or reduce the use of coating materials in cellulosic packaging materials. Furthermore, there is a need to reduce the shedding of fibres and dust from low density fibrous materials.
[0007] WO2022157651 describes a coating method, wherein a cellulose-based substrate is coated by bringing a cellulose solution onto the substrate and subsequently regenerating the cellulose. The obtained cellulosic coating comprising the regenerated cellulose is subsequently hydrophobized. The process thus requires preparation of a coating solution (the cellulose solution) and additionally a hydrophobization treatment, which increase the complexity of the overall process.
[0008] It is an object of the present invention to overcome or alleviate at least some of the above-mentioned problems.SUMMARY OF THE INVENTION
[0009] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
[0010] According to a first aspect of the present invention, there is provided a method comprising the following steps:a) applying a cellulose solubilizing agent onto a surface of a cellulosic substrate,b) allowing the cellulose solubilizing agent to solubilize an amount of structural polysaccharides from the cellulosic substrate to generate solubilized structural polysaccharides onto said surface,c) removing at least a part of the cellulose solubilizing agent, whereby the solubilised structural polysaccharides become deposited on said surface of the cellulosic substrate.
[0011] Various embodiments of the first aspect may comprise one or more features from the following bulleted list:• In step a), the cellulose solubilizing is applied onto the surface of the cellulosic substrate by brushing, coating, bar coating, curtain coating, dipping, sprinkling or spraying, preferably by brushing or by spraying.The structural polysaccharides are selected from the group consisting of cellulose, hemicellulose and a combination thereof.In step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in a flowable form, such as in the form of a liquid, a liquid mixture, a solution, a dispersion or a suspension.• In step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in the form of a liquid mixture with water, preferably wherein the molar ratio of the cellulose solubilizing agent to water in the liquid mixture is from 1 :3 to 9:1, more preferably from 1 :2 to 2: 1.• In step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in solid form, preferably in the form of granules or powder.• The method comprises applying at least 10 g / m2, such as 20 to 200 g / m2of the cellulose solubilising agent on said surface.• In step a), the cellulose solubilizing agent is applied to one or both sides of the cellulosic substrate.• In step a), the cellulose solubilizing agent to be applied is free from cellulosic material and / or structural polysaccharides, such as cellulose and hemicellulose.• Before step a), the cellulose solubilizing agent is pre-heated above the melting point of the cellulose solubilizing agent.• Before step a), the cellulosic substrate is pre-heated above the melting point of the cellulose solubilizing agent.• In step b), a layer comprising the solubilized structural polysaccharides is formed onto the surface of the cellulosic substrate.• In step b), the temperature is 20 to 200 °C, preferably 50 to 120 °C, more preferably 60 to 90 °C.• In step b), solubilized structural polysaccharides are allowed to be generated for a period of at least 0.1 seconds, preferably for 0.1 seconds to 10 minutes,such as for 0.1 to 120 seconds, more preferably for 0.1 to 60 seconds, even more preferably for 1 to 10 seconds.• In step b), a pressure of at least 5 bar, such as at least 10 bar, such as at least 20 bar, such as at least 25 bar is applied to the cellulosic substrate.• In step b), a pressure of up to 60 bar, such as up to 50 bar, such as up to 45 bar, such as up to 40 bar is applied to the cellulosic substrate.• In step b), a pressure ranging from 5 to 60 bar, preferably 10 to 50 bar, more preferably from 20 to 45 bar, most preferably 25 to 40 bar, is applied to the cellulosic substrate.• In step b), the cellulosic substrate is calendered, preferably in a hot nip calender.• The cellulose solubilizing agent is removed by washing the surface of the cellulosic substrate with an antisolvent.• The surface of the cellulosic substrate is washed with an antisolvent, and optionally steam and / or suction is applied to the surface.• The antisolvent is water or an aqueous solution.• In step c), the removal of the cellulose solubilizing agent is facilitated by applying steam and / or suction to said surface.• After step c), the method further comprises: d) drying the cellulosic substrate.• In step d) the temperature is at least to 50 °C , such as 50 to 120 °C.• The cellulose solubilizing agent is a cellulose solvent, such as a non- derivatizing cellulose solvent.• The cellulose solubilizing agent is an aqueous solution comprising sodium hydroxide and urea.• The cellulose solubilizing agent is an ionic liquid.• The ionic liquid is selected from 7-methyl-l,5,7-triazabicyclo(4.4.0)dec-5- enium acetate ([mTBDH]OAc), l-ethyl-3-methylimidazolium acetate ([EMIM]OAc), l-butyl-3-methylimidazolium chloride ([BMIM]C1) and 1- methyl-3-(2,3-dihydroxypropyl)-imidazolium chloride ([DPmim]Cl).• The cellulose solubilizing agent is N-methylmorpholine N-oxide (NMMO).• The cellulosic substrate is a multi-layered cellulosic substrate, preferably a three-layered cellulosic substrate.• The cellulosic substrate is a multi-layered cellulosic substrate comprising at least 2 fibrous layers, such as at least 3 fibrous layers.• The cellulosic substrate is a multi-layered cellulosic substrate, and the method comprises applying the cellulose solubilizing agent onto a surface of an outermost fibrous layer of the multi-layered cellulosic substrate.• The cellulosic substrate, or at least one fibrous layer of the multi-layered cellulosic substrate comprises chemical pulp, mechanical pulp, chemi- thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), non-wood pulp, semi-chemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp, preferably hydrophobized pulp.• The solubilized structural polysaccharides consist of structural polysaccharides originating from the cellulosic substrate or from an outermost fibrous layer and / or the fibrous layer immediately below the outermost fibrous layer of a multi-layered cellulosic substrate.• The cellulosic substrate or at least one fibrous layer thereof comprises paper or tissue paper or paperboard, such as folding boxboard or carton board, or a moulded fibre material or a low-density fibrous material or a thermoformed fibrous material or a vacuum-formed fibrous material or a non-woven web or sheet.The cellulosic substrate is a multi-layered cellulosic substrate; wherein an outermost fibrous layer of the multi-layered cellulosic substrate comprises atissue paper; and wherein the method comprises applying the cellulose solubilizing agent onto a surface of the tissue paper.• The cellulosic substrate is paperboard, and the method comprises applying the cellulose solubilizing agent onto a surface of the paperboard.• The cellulosic substrate comprises a non-woven web or sheet; and wherein the method comprises applying the cellulose solubilizing agent onto a surface of the non-woven web or sheet.• The non-woven web or sheet comprises cellulosic fibres and bi-component fibres, and wherein the non-woven web or sheet has been obtained by an air-laid process.• The cellulosic substrate comprises or consists of a fibrous layer made of a thermoformed fibrous material; and the method comprises applying the cellulose solubilizing agent onto a surface of said fibrous layer made of the thermoformed fibrous material.• The cellulosic substrate comprises a fibrous layer made of a vacuum-formed fibrous material; and the method comprises applying the cellulose solubilizing agent onto a surface of said fibrous layer made of the vacuum- formed fibrous material.• Before step a), the air permeance of the cellulosic substrate is at least 200 ml / min, preferably at least 400 ml / min, most preferably at least 600 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013).• Before step a), the water absorption capacity of the cellulosic substrate is at least 40 g / m2, preferably at least 100 g / m2according to Cobb 60 test (ISO 535:2023), or the cellulosic substrate fails the Cobb 60 test.• Before step a) the oil absorption capacity of the cellulosic substrate is at least 60 g / m2, such as at least 80 g / m2, such as at least 120 g / m2, according to Cobb-Unger test (Scan-P 37:77), or the cellulosic substrate fails the Cobb- Unger test.The method further comprises: after step c) or after step d), applying one or more coating layers onto the surface of the cellulosic substrate, to obtain a coated cellulosic substrate.• Said one or more coating layers are selected from the following group:hydrophobic coating layers, oleophobic coating layers, and any combinations thereof.• As a result of executing the steps a) to c), the air permeance of the cellulosic substrate is decreased by at least 10%, for example by at least 10% and at most by 99%, for example by 10 to 25%, preferably by 10 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Sheffield air permeance test (ISO 5636-4:2013).• As a result of executing the steps a) to c), the water absorption capacity of the cellulosic substrate is decreased by at least 10%, for example by at least 10% and at most 99%, for example by 10 to 25%, preferably by 30 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Cobb 60 test (ISO 535:2023),• As a result of executing the steps a) to c), the oil absorption capacity of the cellulosic substrate is decreased by at least 10%, for example by at least 10% and at most 90%, for example by 10 to 25%, preferably by 20 to 80%, more preferably by 30 to 80%, most preferably by 50 to 80%, according to Cobb-Unger test (Scan-P 37:77).
[0012] According to a second aspect of the present invention, there is provided a cellulosic substrate obtained by the method according to the first aspect of the present invention.
[0013] Various embodiments of the second aspect may comprise one or more features from the following bulleted list:• The air permeance of the cellulosic substrate is less than 50ml / min, preferably less than 20 ml / min, more preferably less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013).• The water absorption capacity of the cellulosic substrate is less than 100 g / m2, preferably less than 60 g / m2, more preferably less than 5 g / m2according to Cobb 60 test (ISO 535:2023).• The oil absorption capacity of the cellulosic substrate is less than 60 g / m2, preferably less than 50 g / m2according to Cobb-Unger test (Scan-P 37:77),• the profilometer average roughness of the cellulosic substrate is less than 3 pm, such as less than 2 pm.
[0014] According to a third aspect of the present invention, there is provided a cellulosic substrate comprising or consisting of a fibrous layer made of a thermoformed fibrous material, wherein: the air permeance of the cellulosic substrate is less than 50 ml / min, preferably less than 20 ml / min, more preferably less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013); the water absorption capacity of the cellulosic substrate is less than 100 g / m2, preferably less than 60 g / m2, more preferably less than 5 g / m2according to Cobb 60 test (ISO 535:2023); the oil absorption capacity of the cellulosic substrate is less than 60 g / m2, preferably less than 50 g / m2according to Cobb-Unger test (Scan-P 37:77); and preferably the profilometer average roughness of the cellulosic substrate is less than 3 pm, such as less than 2 pm.
[0015] According to a fourth aspect of the present invention, there is provided a coated cellulosic substrate.
[0016] The present invention may provide many advantages.
[0017] A simplified process for improving barrier properties of a cellulosic substrate may be provided.
[0018] Application of coating layers, such as barrier coating layers, may be avoided, or the required amounts of barrier coating materials to be applied may be decreased. Barrier material savings may be achieved.BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIGURES 1 A and IB show reference SEM images of an untreated cellulosic substrate.
[0020] FIGURES 1C and ID show SEM images of a cellulosic substrate treated according to an embodiment of the present invention.
[0021] FIGURE 2 shows air permeance of a cellulosic substrate treated with NMMO in various treatment conditions according to some embodiments of the present invention.
[0022] FIGURE 3 shows air permeance of a cellulosic substrate treated with [mTBDH]OAc in various treatment conditions according to some embodiments of the present invention.
[0023] FIGURE 4 shows air permeance of a cellulosic substrate treated with NMMO and calendering in various treatment conditions according to some embodiments of the present invention.
[0024] FIGURE 5 shows air permeance of a cellulosic substrate treated with [mTBDH]OAc and calendering in various treatment conditions according to some embodiments of the present invention.EMBODIMENTS
[0025] DEFINITIONS
[0026] Unless otherwise stated herein or clear from the context, any percentages referred to herein are expressed as percent by weight based on a total weight of the respective composition.
[0027] In the present context, the term “structural polysaccharides” refers to non-water-soluble polysaccharides having a structural role in plant cell walls, such as cellulose and hemicellulose, which are present in cellulosic material derived from plants.
[0028] In the present context, the term “hemicellulose” is used as a common term for all hemicelluloses contained in cellulosic material, such as in a cellulosic substrate comprising pulp. In some embodiments, the amount of hemicellulose is generally less than 40 wt-%, in particular less than 20 wt-% of the dry weight of the cellulosic substrate. In contrast to cellulose, hemicelluloses may have a branched structure.
[0029] In the present context, the term “cellulose solvent” or “cellulose-dissolving solvent” refers to a solvent or a mixture of solvents which is capable of directly dissolving cellulose, without derivatizing the cellulose.
[0030] In the present context, the term “antisolvent” refers to a solvent in which the solubilized structural polysaccharides are less soluble, in particular in which the structural polysaccharides are non-soluble. The antisolvent can thereby precipitate or coagulate the solubilized polysaccharides for example by essentially diluting and / or removing the cellulose solubilizing agent in which the structural polysaccharides are solubilized.
[0031] In the present context, the term “barrier properties” refers to for example oil resistance, grease resistance, moisture resistance, water vapour resistance, gas resistance, flavour resistance and / or oxygen resistance.
[0032] In the present context, the term “thermoformed fibrous material” refers to a cellulosic fibrous material, wherein the cellulosic fibrous material has been heat-treated in a substantially dry state on or against a mould by applying heat and optionally also pressure, into a pre-determined three-dimensional or a substantially flat shape.
[0033] In the present context, the term “an outermost fibrous layer of a cellulosic substrate” refers to the outermost fibrous layer on either side of a multi-layered cellulosic substrate.
[0034] “Profilometer average roughness” can be measured by any suitable profilometer, for example by Bruker Dektak XT profilometer.
[0035] The inventors have herein found that a layer of solubilized structural polysaccharides may be generated onto a cellulosic substrate by solubilizing with a cellulose solubilizing agent an amount of the structural polysaccharides that form part of a surface of the cellulosic substrate. The solubilized structural polysaccharides may then be deposited, or coagulated back, onto the same surface of the cellulosic substrate by removing the cellulose solubilizing agent.
[0036] It was observed that a cellulosic substrate treated in this way may exhibit improved barrier properties even without any hydrophobization of the surface or of the deposited structural polysaccharides. The barrier properties may be further improved by treating the cellulosic substrate for example by calendering while the structural polysaccharides are still in a dissolved state.
[0037] Some embodiments of the present invention provide a method for in situ deposition of a layer comprising regenerated structural polysaccharides on a porous cellulosic substrate.
[0038] In some embodiments, the present invention provides a novel method of forming a solubilized layer of structural polysaccharides onto a cellulosic substrate by partly solubilizing the structural polysaccharides at the surface of the cellulosic substrate with a cellulose solubilizing agent and subsequently depositing a layer of regenerated structural polysaccharides by removing the cellulose solubilizing agent from the cellulosic substrate. The obtained cellulosic substrate may exhibit a smoother and less porous surface, improving the barrier properties of the cellulosic substrate.
[0039] In an embodiment, the method comprises the following steps:a) applying a cellulose solubilizing agent onto a surface of a cellulosic substrate, b) allowing the cellulose solubilizing agent to solubilize an amount of structural polysaccharides from the cellulosic substrate to generate solubilized structural polysaccharides onto said surface, andc) removing the cellulose solubilizing agent, whereby the solubilised structural polysaccharides become deposited on said surface of the cellulosic substrate.
[0040] In an embodiment, one or both sides of the cellulosic substrate may be treated by applying a cellulose solubilizing agent onto one or both sides of the cellulosic substrate.
[0041] In an embodiment, in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate by brushing, coating, bar coating, curtain coating, dipping, sprinkling or spraying. Preferably, the cellulose solubilizing agent is applied by brushing or by spraying.
[0042] In some embodiments, in step b), the cellulose solubilizing agent solubilizes structural polysaccharides only from a surface part or surface parts of the cellulosic substrate. In an embodiment, said surface part or surface parts constitute less than 50 vol-%, such as less than 20 vol-% of the total volume of the cellulosic substrate.
[0043] In some embodiments, in step b), the cellulose solubilizing agent does not penetrate through the entire thickness of the cellulosic substrate.
[0044] In some embodiments, in step b), the cellulose solubilizing agent penetrates into the cellulosic substrate by less than 30%, such as by less than 10% of the thickness of the cellulosic substrate.
[0045] In an embodiment, the structural polysaccharides are selected from the group consisting of cellulose, hemicellulose and a combination thereof.
[0046] In preferred embodiments, the method comprises the following steps:a) applying a cellulose solubilizing agent onto a surface of a cellulosic substrate,b) allowing the cellulose solubilizing agent to solubilize an amount of cellulose and / or hemicellulose from the cellulosic substrate to generate solubilized cellulose and / or hemicellulose, respectively, onto said surface, andc) removing the cellulose solubilizing agent, whereby the solubilised cellulose and / or hemicellulose become deposited on said surface of the cellulosic substrate.
[0047] In an embodiment, in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in a flowable form, such as in the form of a liquid, a liquid mixture, a solution, a dispersion or a suspension. The cellulose solubilizing agent in flowable form may be applied by brushing, coating, roll coating, bar coating, curtain coating, dipping or spraying or by any combination of two or more of said application methods. Preferably, the cellulose solubilizing agent is applied by brushing, by roll coating or by spraying or by any combination thereof. Alternatively, the cellulose solubilizing agent may be applied by any other suitable application method.
[0048] In some embodiments, before step a), the cellulose solubilizing agent is preheated to a temperature above the melting point of the cellulose solubilizing agent.
[0049] In some embodiments, in step a), the cellulosic substrate is pre-heated to a temperature above the melting point of the cellulose solubilizing agent.
[0050] In some embodiments, during step a), the temperature of the cellulose solubilizing agent and / or the temperature of the cellulosic substrate is higher than the melting point of the cellulose solubilizing agent.
[0051] In an embodiment, in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in a solid form, for example in the form of granules or in the form of powder.
[0052] In an embodiment, in step a), the cellulose solubilizing agent in a solid form is applied by sprinkling, powder coating, dipping or brushing or by any combination of said application methods. Alternatively, the cellulose solubilizing agent in a solid form may be applied by any other suitable application method.
[0053] In an embodiment, the cellulose solubilizing agent to be applied in step a) is substantially free from cellulosic material. Particularly, the cellulose solubilizing agent to be applied in step a) is preferably substantially free from structural polysaccharides, such as cellulose and hemicellulose. Thereby the cellulose solubilizing agent to be applied has a simple and preferably non-cellulosic composition. Hence, the generation of solubilized structural polysaccharides onto the cellulosic substrate may be considered to occur in situ.
[0054] In an embodiment, in step b), a layer comprising solubilized structural polysaccharides is generated onto the surface of the cellulosic substrate.
[0055] The generated layer may comprise the cellulose solubilising agent and cellulose dissolved in said cellulose solubilising agent. For example, the generated layer may comprise a cellulose solvent and cellulose dissolved in said cellulose solvent.
[0056] In an embodiment, in step b), the temperature is at least 20 °C, for example 20 to 200 °C, preferably 50 to 120 °C, more preferably 60 to 90 °C.
[0057] In an embodiment, in step b), the temperature is at least 20 °C, for example at least 50 °C, such as at least 60 °C.
[0058] In an embodiment, in step b), the temperature is less than 200 °C, for example less than 120 °C, such as less than 90 °C.
[0059] In some embodiments, in step b) the temperature is above the melting point of the cellulose solubilizing agent.
[0060] Certain ionic liquids, such as [mTBDH]OAc, may tend to stay supercooled. Therefore, step b) of the method may even be performed in a temperature below themelting point of the cellulose solubilizing agent, although crystallization of the cellulose solubilizing agent may occur especially with treatment times longer than 10 seconds.
[0061] In an embodiment, in step b), the solubilized structural polysaccharides are allowed to be generated on the cellulosic substrate for 1 to 10 minutes, to generate solubilized structural polysaccharides onto the cellulosic substrate.
[0062] In an embodiment, in step b), the solubilized structural polysaccharides are allowed to be generated at least for a period of 0.1 seconds, preferably for 0.1 second to 10 minutes, more preferably for 0.1 to 60 seconds, even more preferably for 1 to 10 seconds.
[0063] In an embodiment, the cellulose solubilizing agent is applied in a solid form and in step b) it is allowed to stay on the cellulosic substrate for a sufficient period of time to enable melting of the cellulose solubilizing agent, preferably completely, on the cellulosic substrate. For example, the solubilized structural polysaccharides are allowed to be generated on the cellulosic substrate for at least for a period of 0.1 seconds, such as for 0.1 seconds to 10 minutes, preferably for 1 to 120 seconds, more preferably for 5 to 120 seconds, even more preferably for 5 to 60 seconds.
[0064] The time required to form a layer comprising solubilized structural polysaccharides may depend on the temperature and the pressure applied to the cellulosic substrate in step b). For example, if the cellulosic substrate is calendered in step b), the solubilized structural polysaccharides may be allowed to be generated for a period of 0.1 to 120 seconds, preferably for 0.1 to 60 seconds, more preferably for 0.1 to 10 seconds.
[0065] In an embodiment, in step b), a pressure ranging from 5 to 60 bar, preferably from 10 to 50 bar, more preferably from 20 to 45 bar, most preferably from 25 to 40 bar, is applied to the cellulosic substrate. For example, the pressure may be applied by a roll press, a calender, a blade or a static press.
[0066] It was observed that, in step b), by applying pressure to the cellulosic substrate while the cellulose solubilizing agent is solubilizing an amount of structural polysaccharides from the cellulosic substrate, a less porous layer or film comprising solubilized polysaccharides may be deposited on the surface of the cellulosic substrate in step c).
[0067] In an embodiment, in step b), the cellulosic substrate is calendered, preferably in a hot nip calender. For example, the temperature during the calendering may be in the range of 20 to 200 °C, or 50 to 120 °C, or 60 to 90 °C. In this embodiment, the pressure applied to the cellulosic substrate during the calendering may be in the range of 5 to 60 bar, or 10 to 50 bar, or 20 to 45 bar, or 25 to 40 bar.
[0068] In an embodiment, in step b), when employing calendering, the treatment time of the cellulosic substrate may be reduced dramatically.
[0069] Also, calendering may enable a further reduction in air permeance, water absorption and / or oil absorption capacity of the cellulosic substrate.
[0070] In an embodiment, the layer comprising solubilized structural polysaccharides is subjected to a wash step c) by washing the cellulose solubilizing agent from the surface of the cellulosic substrate with an antisolvent. As the cellulose solubilizing agent is removed from the surface of the cellulosic substrate, regenerated structural polysaccharides are deposited on the surface of the cellulosic substrate.
[0071] In some embodiments, in step c), the cellulosic substrate is washed with water or an aqueous solution. In an embodiment, the cellulosic substrate is washed with deionized water, which may allow monitoring of the quantity and / or presence of the cellulose solubilizing agent from the effluent wash water by determining the conductivity of the effluent water. Other suitable means for determining the efficiency of the removal of cellulose solubilizing agent, such as FTIR andNMR measurements from the washed cellulosic substrate, may be employed as well.
[0072] In some embodiments, the antisolvent is an acidic aqueous solution.
[0073] In some embodiments, the antisolvent comprises or consists of reused effluent water from other process streams.
[0074] In an embodiment, the removal of the cellulose solubilizing agent is facilitated by applying steam or suction onto the surface of the cellulosic substrate.
[0075] In an embodiment, the method further comprises, as step d), drying the cellulosic substrate.
[0076] In an embodiment, the temperature in step d) is from 50 to 120 °C.
[0077] In an embodiment, as a result of step c), a surface layer of deposited structural polysaccharides is formed onto the cellulosic substrate.
[0078] In an embodiment, after step c) or after step d), the method further comprises applying a coating layer onto the surface of the cellulosic substrate. Preferably the coating layer is applied on the deposited structural polysaccharides. The coating layer may comprise a hydrophobic coating layer or an oleophobic coating layer.
[0079] Cellulose solubilizing agent
[0080] In an embodiment, the cellulose solubilizing agent is capable of dissolving at least cellulose and hemicellulose.
[0081] In an embodiment, the cellulose solubilizing agent is an ionic liquid capable of dissolving at least cellulose and hemicellulose.
[0082] The ionic liquid typically comprises a cation and an anion.
[0083] The cation may be selected from the group consisting of: imidazolium, pyridinium, pyrrolidinium, ammonium, phosphonium, sulphonium, or 7-methyl-l,5,7-triazabicyclo(4.4.0)dec-5-enium, and any derivative thereof. For example, the cation may be alkyl-imidazolium, such as l-ethyl-3 -methyl -imidazolium, l-butyl-3-methylimidazolium or l-methyl-3-(2,3-dihydroxypropyl)-imidazolium, or allylpyridinium.
[0084] The anion may be selected from the group consisting of: carboxylate, halide, tetrafluoroborate, hexafluorophosphate, nitrate, sulphonate, phosphate, trifluoromethanesulphonate. Preferably the anion is carboxylate, such as acetate, or halide, such as chloride.
[0085] In an embodiment, the ionic liquid is selected from imidazolium-based ionic liquids.
[0086] In an embodiment, the ionic liquid is selected from superbase-based ionic liquids, such as ionic liquids based on acyclic or cyclic guanidine or amidine derivatives, in particular superbases such as 1,1, 3, 3 -tetramethylguanidine (TMG), 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN).
[0087] In an embodiment, the ionic liquid is selected from ionic liquids having acetate as the anion.
[0088] In an embodiment, the ionic liquid is selected from the group consisting of; 7-methyl-l,5,7-triazabicyclo(4.4.0)dec-5-enium acetate ([mTBDH]OAc), l-ethyl-3-methylimidazolium acetate ([EMIM]OAc), l-butyl-3-methylimidazolium chloride ([BMIM]C1) and l-methyl-3-(2,3-dihydroxypropyl)-imidazolium chloride ([DPmim]Cl), N-allylpyridinium chloride ([APy]Cl), l-ethyl-3-methylimidazolium diethylphosphonate ([EMIM]DEP).
[0089] In an embodiment, the ionic liquid is 7-methyl-l,5,7-triazabicyclo(4.4.0)dec-5-enium acetate ([mTBDH]OAc).
[0090] In an embodiment, the cellulose solubilizing agent is N-methylmorpholine N-oxide (NMMO).
[0091] In an embodiment, the cellulose solubilizing agent is an aqueous solution comprising sodium hydroxide and urea, or an aqueous solution comprising sodium hydroxide and thiourea.
[0092] In some embodiments, the addition of water to the cellulose solubilizing agent decreases the viscosity of the resulting mixture, allowing easier application of the cellulose solubilizing agent to the surface of the cellulosic substrate. However, the addition of water to at least some cellulose solubilizing agents may decrease the solubility of structural polysaccharides, such as cellulose and hemicellulose. In some embodiments it may be possible to find a balance between the solubilization efficiency and the viscosity of the cellulose solubilizing agent, allowing fine-tuning of the properties of the cellulose solubilizing agent for a wide range of application methods, for example allowing the cellulose solubilizing agent to be applied by spraying.
[0093] In an embodiment, in step a), the cellulose solubilizing agent is applied by spraying, for example by using an ultrasonic sprayer. The viscosity of the cellulose solubilizing agent is preferably less than 2000 mPa-s.
[0094] In some embodiments, in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in the form of a liquid mixture with water.Preferably the molar ratio of the cellulose solubilizing agent to water in the liquid mixture is from 1 :3 to 9:1, more preferably from 1 :2 to 2: 1.
[0095] In an embodiment, the cellulose solubilizing agent is NMMO, and the NMMO is applied onto the surface of the cellulosic substrate in the form of a liquid mixture with water. Preferably the molar ratio of NMMO to water is from 1:3 to 9:1, preferably from 1 :2 to 3 : 1, more preferably from 1 :2 to 1:1.
[0096] In an embodiment, the cellulose solubilizing agent is [mTBDH]OAc, and the [mTBDH]OAc is applied onto the surface of the cellulosic substrate in the form of a liquid mixture with water. Preferably the molar ratio of [mTBDH]OAc to water is 1:3 to 9:1, preferably from 1 :2 to 3 : 1, more preferably from 1 :2 to 2: 1.
[0097] In some embodiments, the cellulose solubilizing agent consists of one or more solvents, for example a cellulose-dissolving solvent and optionally water.
[0098] Cellulosic substrate
[0099] In an embodiment, the cellulosic substrate, before step a), has at least one property, preferably at least two properties, more preferably all of the properties selected from the following bulleted list:• air permeance of the cellulosic substrate is at least 200 ml / min, preferably at least 400 ml / min, most preferably at least 600 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013),• water absorption capacity of the cellulosic substrate is at least 35 g / m2, preferably at least 100 g / m2according to Cobb 60 test (ISO 535:2023), or the cellulosic substrate fails the test,• oil absorption capacity of the cellulosic substrate is at least 60 g / m2, preferably at least 80 g / m2, according to Cobb-Unger test (Scan-P 37:77), or the cellulosic substrate fails the test,• the profilometer average roughness of the cellulosic substrate is at least 3 pm.
[0100] In an embodiment, the cellulosic substrate comprises chemical pulp, mechanical pulp, chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), non-wood pulp, semi-chemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp.
[0101] In some embodiments, the pulp may be made from any broad-leaved tree such as a tree from the betulaceae family, for example birch or aspen, from the salicaceae family, from eucalyptus, mixed tropical hardwood or pines or from any combination of the aforementioned. The pulp may be also made from any conifer such as spruce or pine or from any combination thereof. The pulp may also be made from a combination of broadleaved trees and conifers. In another embodiment, the pulp may be made from any annuals such as straw, common reed, reed canary grass, bamboo, sugarcane, bagasse or any grass plant.
[0102] In an embodiment, the cellulosic material of the cellulosic substrate is wood-derived material, preferably wood derived pulp. Being renewable, wood derived materials are a sustainable alternative to fossil-based materials.
[0103] In some embodiments, the cellulosic substrate or at least one fibrous layer thereof comprises cellulosic and / or lignocellulosic fibres in an amount of at least 60 wt-%, such as at least 70 wt-%, such as at least 75 wt-%, such as at least 80 wt-%, such as at least 85 wt-% calculated from the dry weight of the cellulosic substrate.
[0104] In an embodiment, the cellulosic substrate or at least one fibrous layer thereof comprises structural polysaccharides, such as cellulose and / or hemicellulose.
[0105] In an embodiment, structural polysaccharides, such as cellulose and hemicellulose, are present at the surface of the cellulosic substrate, for example in an outermost fibrous layer of the cellulosic substrate.
[0106] In an embodiment, the cellulosic substrate or at least one fibrous layer thereof comprises paper or tissue paper or paperboard, such as folding boxboard or carton board, or a moulded fibre material or a low-density fibrous material or a thermoformed fibrous material or a vacuum-formed fibrous material or a non-woven web or sheet.
[0107] In an embodiment, the cellulosic substrate is paperboard, and the method comprises applying the cellulose solubilizing agent onto a surface of the paperboard.
[0108] In an embodiment, the cellulosic substrate is folding box board or a carton board.
[0109] In an embodiment, the cellulosic substrate or at least one fibrous layer thereof is a low-density fibrous material, preferably a moulded fibre product.
[0110] In an embodiment, the density of the low-density fibrous material is less than 220 kg / m3, such as from 25 to 200 kg / m3.
[0111] In an embodiment, the cellulosic substrate or at least one fibrous layer thereof comprises a thermoformed fibrous material.
[0112] In an embodiment, the cellulosic substrate or at least one fibrous layer thereof comprises a vacuum-formed fibrous material.
[0113] In an embodiment, the cellulosic substrate comprises a non-woven web or sheet; and the method comprises applying the cellulose solubilizing agent onto a surface of the non-woven web or sheet.
[0114] In an embodiment, the non-woven web or sheet comprises cellulosic fibres and bi-component fibres, and the non-woven web or sheet has been obtained by an air-laid process.
[0115] In some embodiments, the method may be used to treat a cellulosic substrate already having some or substantial barrier properties, such as a thermoformed fibrous material, which may have an air permeance of less than 50 ml / min according to Sheffield air permeance test (ISO 5636-4:2013). By treating such a cellulosic substrate according to some embodiments of the present method, a cellulosic substrate having a smoother surface may be obtained. For example, the profilometer average roughness of a cellulosic substrate which comprises or consists of a layer of a thermoformed fibrous material may become lowered to less than 3 pm, such as less than 2 pm, as a result of executing the present method. Advantageously, in this embodiment, the air permeance of the cellulosic substrate may be lowered to even less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013).
[0116] In an embodiment, as a result of executing the steps a) to c), the air permeance of the cellulosic substrate is decreased by at least 10% and at most by 99%, for example by 10 to 25%, preferably by 10 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Sheffield air permeance test (ISO 5636-4:2013).
[0117] In an embodiment, as a result of executing the steps a) to c), the water absorption capacity of the cellulosic substrate is decreased by at least 10% and at most 99%, for example by 10 to 25%, preferably by 30 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Cobb 60 test (ISO 535:2023).
[0118] In an embodiment, as a result of executing the steps a) to c), the oil absorption capacity of the cellulosic substrate is decreased by at least 10% and at most 90%, for example by 10 to 25%, preferably by 20 to 80%, more preferably by 30 to 80%, most preferably by 50 to 80%, according to Cobb-Unger test (Scan-P 37:77).
[0119] In an embodiment, as a result of executing the steps a) to c), the profilometer average roughness of the cellulosic substrate is decreased by at least 10%.
[0120] For example, as a result of executing the steps a) to c), the profilometer average roughness of the cellulosic substrate is less than 3 pm, such as less than 2 pm.
[0121] In an embodiment, the cellulosic substrate comprises cellulose and hemicellulose and optionally lignin.
[0122] The cellulosic substrate may be substantially planar and comprise two sides or surfaces.
[0123] The cellulosic substrate may be substantially planar and have a thickness, which is the smallest dimension of the cellulosic substrate.
[0124] In some embodiments, the cellulosic substrate may have a substantially flat or planar shape, for example the cellulosic substrate may be in the form of a sheet.
[0125] In some embodiments, the cellulosic substrate undergoes the method in a continuous or semi-continuous form, such as in the form of a web.
[0126] In some embodiments, the cellulosic substrate may be a three-dimensional article, for example the cellulosic substrate may be a moulded or folded three-dimensional article. In some embodiments the cellulosic substrate may for example function as a container or as a part thereof.
[0127] Multi-layered cellulosic substrate
[0128] In an embodiment, the cellulosic substrate is a multi-layered cellulosic substrate.
[0129] In an embodiment, the multi-layered cellulosic substrate comprises at least two fibrous layers, for example at least three fibrous layers. Preferably all layers of the multi-layered cellulosic substrate are cellulosic fibrous layers.
[0130] In some embodiments, the cellulosic substrate may comprise or consist of 1 to 20 cellulosic fibrous layers, such as at least two cellulosic fibrous layers, such as at least three cellulosic fibrous layers.
[0131] In an embodiment, the cellulosic substrate is a multi-layered cellulosic substrate, and the method comprises applying the cellulose solubilizing agent onto a surface of an outermost fibrous layer of the multi-layered cellulosic substrate.
[0132] In an embodiment, a cellulose solubilizing agent solubilizes an amount of structural polysaccharides from the outermost fibrous layer of the multi-layered cellulosic substrate.
[0133] In an embodiment, the solubilised structural polysaccharides become deposited on the surface of the outermost fibrous layer of the multi-layered cellulosic substrate.
[0134] In an embodiment, a layer comprising the solubilized structural polysaccharides is formed onto the surface of the outermost fibrous layer of the multilayered cellulosic substrate. In a preferred embodiment, the solubilized structural polysaccharides in said layer consist of polysaccharides originating from the outermost fibrous layer of the multi-layered cellulosic substrate.
[0135] In an embodiment, the cellulosic substrate, before step a), has at least one property selected from the following bulleted list:• air permeance of the cellulosic substrate is at least 200 ml / min, preferably at least 400 ml / min, most preferably at least 600 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013),water absorption capacity of the cellulosic substrate is at least 35 g / m2, preferably at least 100 g / m2according to Cobb 60 test (ISO 535:2023), or the cellulosic substrate fails the test,• oil absorption capacity of the cellulosic substrate is at least 60 g / m2, preferably at least 80 g / m2, according to Cobb-Unger test (Scan-P 37:77), or the cellulosic substrate fails the test.
[0136] In some embodiments, at least one layer of the multi-layered cellulosic substrate comprises cellulosic and / or lignocellulosic fibres in an amount of at least 60 wt-%, such as at least 70 wt-%, such as at least 75 wt-%, such as at least 80 wt-%, such as at least 85 wt-% calculated from the dry weight of the cellulosic substrate.
[0137] In an embodiment, the cellulosic substrate, or at least one fibrous layer of the multi-layered cellulosic substrate comprises chemical pulp, mechanical pulp, chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), nonwood pulp, semi-chemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp.
[0138] In an embodiment, at least the outermost fibrous layer of the multi-layered cellulosic substrate comprises chemical pulp, mechanical pulp, chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), non-wood pulp, semichemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp.
[0139] In an embodiment, at least the outermost layer and the layer immediately below the outermost layer of a multi-layered cellulosic substrate comprise chemical pulp, mechanical pulp, chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), non-wood pulp, semi-chemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp.
[0140] In an embodiment, at least the outermost fibrous layer and / or the fibrous layer immediately below the outermost fibrous layer of the cellulosic substrate comprises hydrophobized pulp.
[0141] In an embodiment, the layer comprising solubilized structural polysaccharides is formed onto the surface of a multi-layered cellulosic substrate, and the solubilized structural polysaccharides consist of structural polysaccharides originatingfrom an outermost fibrous layer and possibly also from the fibrous layer immediately below the outermost fibrous layer of the multi-layered cellulosic substrate.
[0142] In an embodiment, the outermost fibrous layer of the multi-layered cellulosic substrate comprises one or more sub-layers capable of absorbing and permitting passage of the cellulose solubilizing agent through the outermost fibrous layer and into contact with a fibrous layer immediately below the outermost fibrous layer. An amount of the structural polysaccharides in the outermost layer may dissolve in the cellulose solubilizing agent and form a fused layer together with solubilized structural polysaccharides originating from the fibrous layer immediately below the outermost fibrous layer. Thus, as a result, the multilayered cellulosic substrate may receive on the surface of its outermost fibrous layer a layer comprising regenerated structural polysaccharides originating from the outermost fibrous layer and from the fibrous layer immediately below the outermost fibrous layer of the multi-layered cellulosic substrate.
[0143] In an embodiment, a layer comprising solubilized structural polysaccharides is formed onto an outermost fibrous layer of a multi-layered cellulosic substrate. The layer comprising solubilized structural polysaccharides may consist of polysaccharides originating from the outermost fibrous layer of the multi-layered cellulosic substrate and from the fibrous layer immediately below the outermost fibrous layer of the multi-layered cellulosic substrate, and the cellulose solubilising agent.
[0144] In an embodiment, the multi-layered cellulosic substrate or at least one fibrous layer thereof comprises paper or tissue paper or paperboard, such as folding boxboard or carton board, or a moulded fibre material or a low-density fibrous material or a thermoformed fibrous material or a vacuum-formed fibrous material or a non-woven web or sheet.
[0145] In an embodiment, the multi-layered cellulosic substrate or at least one fibrous layer thereof comprises paper or paperboard.
[0146] In an embodiment, the multi-layered cellulosic substrate or at least one fibrous layer thereof is folding box board.
[0147] In an embodiment, the multi-layered cellulosic substrate or at least one fibrous layer thereof is a low-density fibrous material, preferably a moulded fibre product.
[0148] In an embodiment, the multi-layered cellulosic substrate or at least one fibrous layer thereof is a thermoformed fibrous material layer.
[0149] In an embodiment, the multi-layered cellulosic substrate, or at least one fibrous layer thereof comprises or consists of a non-woven web or sheet.
[0150] In an embodiment, the non-woven web or sheet comprises cellulosic fibres and bi-component fibres, and the non-woven web or sheet has been obtained by an air-laid process.
[0151] In an embodiment, the cellulosic substrate is a multi-layered cellulosic substrate; and an outermost fibrous layer of the multi-layered cellulosic substrate comprises a tissue paper; and the method comprises applying the cellulose solubilizing agent onto a surface of the tissue paper.
[0152] In an embodiment, the outermost fibrous layer of a multi-layered cellulosic substrate comprises or consists of one or more plies each made of the same cellulosic material, such as a single-ply or multi-ply tissue paper.
[0153] The outermost fibrous layer may comprise fibrous sub-layers, such as plies of tissue paper.
[0154] In an embodiment, as a result of executing the steps a) to c), the air permeance of the multi-layered cellulosic substrate is decreased by at least 10% and at most by 99%, for example by 10 to 25%, preferably by 10 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Sheffield air permeance test (ISO 5636-4:2013).
[0155] In an embodiment, as a result of executing the steps a) to c), the water absorption capacity of the multi-layered cellulosic substrate is decreased by at least 10% and at most 99%, for example by 10 to 25%, preferably by 30 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Cobb 60 test (ISO 535:2023).
[0156] In an embodiment, as a result of executing the steps a) to c), the oil absorption capacity of the multi-layered cellulosic substrate is decreased by at least 10% and at most 90%, for example by 10 to 25%, preferably by 20 to 80%, more preferably by 30 to 80%, most preferably by 50 to 80%, according to Cobb-Unger test (Scan-P 37:77).
[0157] Hydrophobized pulp
[0158] In an embodiment, the cellulosic substrate comprises pulp that has been treated with a hydrophobization agent.
[0159] In some embodiments, the hydrophobization agent is selected from the following group: fatty acids, rosins, waxes, such as alkyl ketene dimer (AKD) or paraffin wax, oils, such as alkenyl succinic anhydride (ASA), fatty alcohols, fatty acid esters, biopolymers, cationic polyamines, cationic polyethyleneimines (PEI), cationic or non-ionic polyacrylamides, polydimethyldiallylammonium chloride (pDADMAC), maleic anhydride (MA), maleic anhydride grafted polypropylene (MAPP), silanes, alkoxysilanes, organosilanes, betulin, betulinic acid, and derivatives and combinations thereof.
[0160] In some embodiments, the hydrophobization agent is selected from the following group: fatty acids, alkyl ketene dimer (AKD), fatty alcohols, fatty acid esters, biopolymers, cationic polyamines, cationic polyethyleneimines (PEI), cationic or non-ionic polyacrylamides, polydimethyldiallylammonium chloride (pDADMAC), maleic anhydride (MA), maleic anhydride grafted polypropylene (MAPP), silanes, alkoxysilanes, and derivatives and combinations thereof.
[0161] Cellulosic substrate obtained by the method
[0162] In the present disclosure, the cellulosic substrate obtained by the present method may be referred to as “the treated cellulosic substrate” or “the cellulosic substrate treated by the present method” or “the obtained cellulosic substrate”.
[0163] It was surprisingly discovered that by depositing a layer comprising regenerated structural polysaccharides on a cellulosic substrate, the barrier properties of the cellulosic substrate may be improved significantly even without introducing any coating layer onto the cellulosic substrate. It is believed that the layer comprising regenerated structural polysaccharides may reduce the porosity of the surface of the cellulosic substrate and / or pinholes present at the surface, providing improved barrier properties to the cellulosic substrate.
[0164] In an embodiment, the obtained cellulosic substrate comprises chemical pulp, mechanical pulp, chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), non-wood pulp, semi-chemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp, preferably hydrophobized pulp.
[0165] In an embodiment, the air permeance, water absorptivity and / or oil absorptivity of the obtained cellulosic substrate is less than what the cellulosic substrate had before undergoing the present method.
[0166] In an embodiment, the air permeance of the obtained cellulosic substrate is less than 50ml / min, preferably less than 20 ml / min, more preferably less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013).
[0167] In an embodiment, the water absorption capacity of the obtained cellulosic substrate is less than 100 g / m2, preferably less than 60 g / m2, more preferably less than 5 g / m2according to Cobb 60 test (ISO 535:2023).
[0168] In an embodiment, the oil absorption capacity of the obtained cellulosic substrate is less than 60 g / m2, preferably less than 50 g / m2according to Cobb-Unger test (Scan-P 37:77).
[0169] The obtained cellulosic substrate may be used in food contact materials and articles.
[0170] Also many other application areas, such as non-food applications, can be envisioned for the obtained cellulosic substrate.
[0171] Coating layer
[0172] While the present method may avoid application of any coating layers, in some embodiments the obtained cellulosic substrate may additionally be coated by a coating layer or several coating layers. Advantageously, the grammage of such coating layers may be lower than what is used in conventional coating layers.
[0173] In some embodiments, after step c) or after step d), one or more coating layers are applied onto the surface of the obtained cellulosic substrate.
[0174] To ensure sealing of any remaining pinholes and pores at a surface of the obtained cellulosic substrate, a sufficient amount of a coating material may need to be applied onto a surface of the obtained cellulosic substrate. The surface of the obtained cellulosic substrate having solubilized structural polysaccharides deposited onto saidsurface may exhibit a low porosity and contain relatively few pinholes. Therefore, less coating material may be required to cover said surface by a coating layer.
[0175] In an embodiment, one or more coating layers, preferably one or more hydrophobic layers, one or more oleophobic coating layers, or any combination thereof, may be applied on the obtained cellulosic substrate. As a result, a coated cellulosic substrate is obtained.
[0176] In an embodiment, the coated cellulosic substrate has air permeance of less than 20 ml / min, preferably less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013),
[0177] In an embodiment, the coated cellulosic substrate has water absorption capacity of less than less than 60 g / m2, preferably less than 5 g / m2according to Cobb 60 test (ISO 535:2023),
[0178] In an embodiment, the coated cellulosic substrate has oil absorption capacity of less than less than 50 g / m2according to Cobb-Unger test (Scan-P 37:77).
[0179] Typically, the coating is a non-fibrous layer and comprises or consists of a thermoplastic polymer material or a thermoset polymer material, such as polyolefin, polyester, copolyester elastomer, PET, nylon, polyhydroxyalkanoate or polylactic acid. The polyolefin may comprise polyethylene and / or polypropylene.
[0180] In some embodiments, the coating is a non-fibrous layer and comprises or consists of a thermoplastic biodegradable polymer material.
[0181] In some embodiments, the coating is a non-fibrous layer and comprises or consists of a thermoplastic bio-based or non-fossil-based polymer material.
[0182] In one embodiment, the coating layer comprises at least 50 wt-%, such as at least 80 wt-%, such as at least 90 wt-% of a thermoplastic polymer material or a thermoset polymer material.
[0183] The coating may comprise a functional layer adapted to alter functional properties of the surface, such as barrier properties, optical properties, print quality, visual properties and / or haptic properties.
[0184] The coating may be adapted to increase barrier properties of the surface of the cellulosic substrate. The barrier properties may include one or more of the following: oil and grease resistance, liquid resistance, water resistance, water vapour resistance, aroma resistance, gas resistance, oxygen resistance, flavour barrier.
[0185] In some embodiments, the coating layer is generated on said surface of the obtained cellulosic substrate by spraying.
[0186] In one embodiment, the thickness of the coating layer on the obtained cellulosic substrate is at least 1 pm, such as in the range 2 to 20 pm, for example 5 to 10 pm.
[0187] In an embodiment, the required thickness of the coating layer applied on the surface of the obtained cellulosic substrate may be reduced after step c) or step d).
[0188] In some embodiments, the coating layer or a part of it may impart first-type of barrier properties, and the treated cellulosic substrate below the coating layer may impart second-type of barrier properties which differ from the first-type of barrier properties. For example, the coating layer or a part of it may impart water barrier properties, and the treated cellulosic substrate below the coating layer may impart oil and grease barrier properties.
[0189] The coated cellulosic substrate may be used in food contact materials and articles.
[0190] Also many other application areas can be envisioned for the coated cellulosic substrate.
[0191] Examples
[0192] Measurement methods
[0193] Air permeance of the dried samples was measured as an average of 5 measurements with a L&W Air Permeance Tester (model 985107). The samples were not conditioned before the measurements. For air permeance measurement, the reference sample was once soaked in water and fully dried.
[0194] Scanning electron microscope (SEM) was used to image board surfaces and cross-sections. The samples were put onto aluminium SEM sample stubs with double-sidedcarbon tape. The samples were sputter coated (EM ACE200, Leica, Germany) with 3 nm of Au / Pd prior to SEM imaging. Secondary electron images with in-lens detector were taken with Zeiss Merlin field emission SEM (Zeiss International) with 2 keV acceleration voltage and 60 pA probe current with original magnification of 100, 300 and 500X. The cross-section samples were cut with a surgical knife starting from the treated side. The cut samples were attached with double-sided carbon tape and treated like the other samples. The cross-section images were taken with original magnification of 100, 200 and 300X.
[0195] Example 1.
[0196] N-methylmorpholine N-oxide (NMMO) monohydrate was obtained from ABCR and Sigma-Aldrich. NMMO solutions were heated in an oven at 90 °C. 1 % (w / w), and propyl gallate was added as a stabilizer to NMMO before heating. Ionic liquid 7-methyl-l,5,7-triazabicyclo[4.4.0]dec-5-enium acetate ([mTBDH]OAc) was obtained from Liuotin Group.
[0197] 90 to 140 g / m2of the cellulose solubilising agent, as a mixture with water having a water : cellulose solubilizing agent molar ratio of 1:1 and 2:1 for NMMO and 1.5:1 for [mTBDH]OAc, was applied onto the samples (Prime Folding Boxboard Bright sheet in A5 format, 235 g / m2) by brushing, using a conventional paint brush. The samples were then heated in an oven at temperatures ranging from 20 to 80 °C for 2 to 200 minutes, after which the samples were rinsed with water for 5 minutes. The washed samples were dewatered with paper towels and subsequently dried in an oven at 80 °C. The obtained samples were characterized by the measurement methods described above.
[0198] Figures 2 and 3 show a significant decrease in air permeance of the samples, the most drastic improvements being achieved for the sample treated at 80 °C with NMMO and for the sample treated at 60 °C with [mTBDH]OAc.
[0199] Example 2.
[0200] The cellulose solubilizing agents were prepared and applied to similar samples as in Example 1 and the samples were treated as in Example 1. In addition to washing with water, the samples were first treated with a conventional steam vacuum device (Karcher SV 7, settings: suction at level 1; steam outflow at level 4), swiping the sample 10 times from one end to the opposite end for each side of the sample. The treated samples were characterized by the measurement methods described above.
[0201] Example s.
[0202] The cellulose solubilizing agents were prepared and applied to similar samples as in Example 1, with water : cellulose solubilizing agent molar ratios of 1:1 and 2:1 for NMMO, and with molar ratios of 1:2, 1:1, 1.5:1 and 2:1 for [mTBDH]OAc, immediately after which the samples were calendered for 1 to 120 seconds. The calendering parameters were as follows:• calendering speed: 2.8 m / min,• nip temperature: 40, 60, 80, 100 °C,• line pressure: 10 or 40 bar.
[0203] After the calendering, the sample was immediately washed with water to remove the cellulose solubilizing agent, and the sample was dewatered and dried as in Example 1. The treated samples were characterized by the measurement methods described above.
[0204] SEM images show clear changes in the surface of the treated samples. After the treatment, the surface appears smoother, has fewer craters and is less porous as seen in Figures 1C and ID compared to the reference surface of Figures 1 A and IB.
[0205] Figures 4 and 5 show a significant decrease in air permeance of the sample treated according to Example 3, the most drastic improvement being observed by employing hot nip calendering at temperature of 100 °C and pressure of 40 bar for NMMO and at 80 °C and pressure of 40 bar for [mTBDH]OAc. Furthermore, a dramatic decrease in the treatment time is achieved by employing hot nip calendering.
[0206] Example 4.
[0207] Dynamic sheet samples (grammage 180 g / m2, thickness 380 pm) in A5 format were prepared from hydrophobized softwood pulp. NMMO in 1:1 molar ratio with water was applied as in Example 1 after which the sheet was fed through a soft hot nip calender (pressure 40, temperature 80 °C). After the treatment the sheet samples were washed with water and dried at 80 °C for 1 hour.
[0208] The treated sheet samples had the following properties against an untreated reference sheet consisting of softwood pulp:• Air permeance according to ISO 5636-4:2013 was decreased by 98% from -410 ml / min to 9 ml / min,• Water absorption according to ISO 535:2023 was improved from failed test (defined as water passing completely through the structure) to 60 g / m2,• Oil absorption according to Scan-P 37:77 was improved from failed test (oil passing completely through the structure) to 35 g / m2.
[0209] Example 5.
[0210] Sample sheets in A5 format were prepared from softwood pulp, and treated with NMMO in 1:1 molar ratio with water as in Example 1. After the treatment, the samples were washed and dried as in Example 4.
[0211] The air permeance according to ISO 5636-4:2013 decreased from 408 ml / min of the untreated reference to 10 ml / min of the treated sample, and the oil absorption according to Scan-P 37:77 decreased from untreated reference failing the test to treated sample having a value of 45 ml / m2.INDUSTRIAL APPLICABILITY
[0212] The present method and the obtained cellulosic substrates are industrially applicable at least in manufacturing of cellulosic products having barrier properties.ACRONYMS LIST AKD alkyl ketene dimerASA alkenyl succinic anhydrideBCTMP bleached chemi-thermomechanical pulpCTMP chemi-thermomechanical pulp[BMIM]C1 1 -butyl-3 -methylimidazolium chloride[DPmim]Cl l-methyl-3-(2,3-dihydroxypropyl)-imidazolium chloride[EMIM]0Ac 1 -ethyl-3 -methylimidazolium acetateFTIR Fourier-Transform Infrared SpectroscopyMA maleic anhydrideMAPP maleic anhydride grafted polypropyleneNMMO N-methylmorpholine N-oxideNMR Nuclear Magnetic Resonance[mTBDH]OAc 7-methyl-l,5,7-triazabicyclo(4.4.0)dec-5-enium acetate pDADMAC polydimethyldiallylammonium chloridePEI cationic polyethyleneiminesPET polyethylene terephthalateSEM Scanning Electron Microscope
Claims
CLAIMS:
1. A method comprising the following steps:a) applying a cellulose solubilizing agent onto a surface of a cellulosic substrate, b) allowing the cellulose solubilizing agent to solubilize an amount of structural polysaccharides from the cellulosic substrate to generate solubilized structural polysaccharides onto said surface,c) removing at least a part of the cellulose solubilizing agent, whereby the solubilised structural polysaccharides become deposited on said surface of the cellulosic substrate.
2. The method according to claim 1, wherein in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate by brushing or by spraying.
3. The method according to claim 1 or 2, wherein the structural polysaccharides are selected from the group consisting of cellulose, hemicellulose and a combination thereof.
4. The method according to any of the preceding claims, wherein in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in a flowable form, such as in the form of a liquid, a liquid mixture, a solution, a dispersion or a suspension.
5. The method according to claim 4, wherein in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in the form of a liquid mixture with water, preferably wherein the molar ratio of the cellulose solubilizing agent to water in the liquid mixture is from 1:3 to 9: 1, more preferably from 1 :2 to 2: 1.
6. The method according to any of claims 1-3, wherein in step a), the cellulose solubilizing agent is applied onto the surface of the cellulosic substrate in solid form, preferably in the form of granules or powder.
7. The method according to any of the preceding claims, wherein in step b), the cellulose solubilizing agent solubilizes structural polysaccharides only from a surfacepart or surface parts of the cellulosic substrate, and said surface part or surface parts constitute less than 50 vol-%, such as less than 20 vol-% of the total volume of the cellulosic substrate.
8. The method according to any of the preceding claims, wherein in step b), the cellulose solubilizing agent penetrates into the cellulosic substrate by less than 30%, such as by less than 10% of the thickness of the cellulosic substrate.
9. The method according to any of the preceding claims, wherein, in step b), a layer comprising the solubilized structural polysaccharides is formed onto the surface of the cellulosic substrate.
10. The method according to any of the preceding claims, wherein in step b), the temperature is 20 to 200 °C, preferably 50 to 120 °C, more preferably 60 to 90 °C.
11. The method according to any of the preceding claims, wherein in step b), solubilized structural polysaccharides are allowed to be generated for a period of at least 0.1 seconds, preferably for 0.1 seconds to 10 minutes, such as for 0.1 to 120 seconds, more preferably for 0.1 to 60 seconds, even more preferably for 1 to 10 seconds.
12. The method according to any of the preceding claims, wherein in step b), a pressure ranging from 5 to 60 bar, preferably 10 to 50 bar, more preferably from 20 to 45 bar, most preferably 25 to 40 bar, is applied to the cellulosic substrate.
13. The method according to any of the preceding claims, wherein in step b), the cellulosic substrate is calendered, preferably in a hot nip calender.
14. The method according to any of the preceding claims, wherein the cellulose solubilizing agent is removed by washing the surface of the cellulosic substrate with an antisolvent, wherein the antisolvent is preferably water or an aqueous solution.
15. The method according to any of the preceding claims, wherein in step c), the removal of the cellulose solubilizing agent is facilitated by applying steam and / or suction onto said surface.
16. The method according to any of preceding claims, further comprising: d) drying the cellulosic substrate.
17. The method according to claim 16, wherein in the step d) the temperature is 50 to 120 °C.
18. The method according to any of the preceding claims, wherein the cellulose solubilizing agent is an ionic liquid, preferably selected from 7-methyl-l,5,7-triazabicyclo(4.4.0)dec-5-enium acetate ([mTBDH]OAc), l-ethyl-3-methylimidazolium acetate ([EMIM]0Ac), l-butyl-3-methylimidazolium chloride ([BMIM]C1) and l-methyl-3-(2,3-dihydroxypropyl)-imidazolium chloride ([DPmim]Cl).
19. The method according to any of the preceding claims, wherein the cellulose solubilizing agent is N-methylmorpholine N-oxide (NMMO).
20. The method according to any of the preceding claims, wherein the cellulose solubilizing agent is an aqueous solution comprising sodium hydroxide and urea.
21. The method according to any of the preceding claims, wherein the cellulosic substrate is a multi-layered cellulosic substrate, preferably a three-layered cellulosic substrate.
22. The method according to any of the preceding claims, wherein the cellulosic substrate is a multi-layered cellulosic substrate, and the method comprises applying the cellulose solubilizing agent onto a surface of an outermost fibrous layer of the multilayered cellulosic substrate.
23. The method according to any of the preceding claims, wherein the cellulosic substrate, or at least one fibrous layer of the multi-layered cellulosic substratecomprises chemical pulp, mechanical pulp, chemi-thermomechanical pulp (CTMP), bleached chemi-thermomechanical pulp (BCTMP), non-wood pulp, semi-chemical pulp, thermomechanical pulp, hydrophobized pulp or recycled pulp, preferably hydrophobized pulp.
24. The method according to any of the preceding claims, wherein the solubilized structural polysaccharides consist of structural polysaccharides originating from the cellulosic substrate or from an outermost fibrous layer and / or the fibrous layer immediately below the outermost fibrous layer of a multi-layered cellulosic substrate.
25. The method according to any of the preceding claims, wherein the cellulosic substrate or at least one fibrous layer thereof comprises paper or tissue paper or paperboard, such as folding boxboard or carton board, or a moulded fibre material or a low-density fibrous material or a thermoformed fibrous material or a vacuum-formed fibrous material or a non-woven web or sheet.
26. The method according to any of the preceding claims, wherein the cellulosic substrate is a multi-layered cellulosic substrate; wherein an outermost fibrous layer of the multi-layered cellulosic substrate comprises a tissue paper; and wherein the method comprises applying the cellulose solubilizing agent onto a surface of the tissue paper.
27. The method according to any of the preceding claims, wherein the cellulosic substrate is paperboard, and the method comprises applying the cellulose solubilizing agent onto a surface of the paperboard.
28. The method according to any of the preceding claims, wherein the cellulosic substrate comprises a non-woven web or sheet; and wherein the method comprises applying the cellulose solubilizing agent onto a surface of the non-woven web or sheet.
29. The method according to claim 28, wherein the non-woven web or sheet comprises cellulosic fibres and bi-component fibres, and wherein the non-woven web or sheet has been obtained by an air-laid process.
30. The method according to any of the preceding claims, wherein the cellulosic substrate comprises or consists of a fibrous layer made of a thermoformed fibrous material; and wherein the method comprises applying the cellulose solubilizing agent onto a surface of said fibrous layer made of the thermoformed fibrous material.
31. The method according to any of the preceding claims, wherein the cellulosic substrate comprises a fibrous layer made of a vacuum-formed fibrous material; and wherein the method comprises applying the cellulose solubilizing agent onto a surface of said fibrous layer made of the vacuum -formed fibrous material.
32. The method according to any of the previous claims, wherein before step a), the air permeance of the cellulosic substrate is at least 200 ml / min, such as at least 400 ml / min, such as at least 600 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013).
33. The method according to any of the previous claims, wherein before step a), the water absorption capacity of the cellulosic substrate is at least 40 g / m2, such as at least 100 g / m2according to Cobb 60 test (ISO 535:2023), or the cellulosic substrate fails the Cobb 60 test.
34. The method according to any of the previous claims, wherein before step a), the oil absorption capacity of the cellulosic substrate is at least 60 g / m2, such as at least 80 g / m2, such as at least 120 g / m2, according to Cobb-Unger test (Scan-P 37:77), or the cellulosic substrate fails the Cobb-Unger test.
35. The method according to any of the preceding claims, further comprising: after step c) or after step d), applying one or more coating layers onto the surface of the cellulosic substrate, to obtain a coated cellulosic substrate.
36. The method according to any of the preceding claims, wherein said one or more coating layers are selected from the following group: hydrophobic coating layers, oleophobic coating layers, and any combinations thereof.
37. The method according to any of the preceding claims, wherein as a result of executing the steps a) to c), the air permeance of the cellulosic substrate is decreased by at least 10% and at most by 99%, for example by 10 to 25%, preferably by 10 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Sheffield air permeance test (ISO 5636-4:2013).
38. The method according to any of the preceding claims, wherein as a result of executing the steps a) to c), the water absorption capacity of the cellulosic substrate is decreased by at least 10% and at most 99%, for example by 10 to 25%, preferably by 30 to 95%, more preferably by 50 to 95%, most preferably by 60 to 95%, according to Cobb 60 test (ISO 535:2023).
39. The method according to any of the preceding claims, wherein as a result of executing the steps a) to c), the oil absorption capacity of the cellulosic substrate is decreased by at least 10% and at most 90%, for example by 10 to 25%, preferably by 20 to 80%, more preferably by 30-80%, most preferably by 50 to 80%, according to Cobb-Unger test (Scan-P 37:77).
40. A cellulosic substrate obtained by the method according to any of the preceding claims.
41. The cellulosic substrate according to claim 40, wherein the air permeance of the cellulosic substrate is less than 50 ml / min, preferably less than 20 ml / min, more preferably less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013).
42. The cellulosic substrate according to any of claims 40 to 41, wherein the water absorption capacity of the cellulosic substrate is less than 100 g / m2, preferably less than 60 g / m2, more preferably less than 5 g / m2according to Cobb 60 test (ISO 535:2023).
43. The cellulosic substrate according to any of claims 40 to 42, wherein the oil absorption capacity of the cellulosic substrate is less than 60 g / m2, preferably less than 50 g / m2according to Cobb-Unger test (Scan-P 37:77).
44. A cellulosic substrate comprising or consisting of a fibrous layer made of a thermoformed fibrous material, wherein:the air permeance of the cellulosic substrate is less than 50 ml / min, preferably less than 20 ml / min, more preferably less than 10 ml / min, according to Sheffield air permeance test (ISO 5636-4:2013),the water absorption capacity of the cellulosic substrate is less than 100 g / m2, preferably less than 60 g / m2, more preferably less than 5 g / m2according to Cobb 60 test (ISO 535:2023),the oil absorption capacity of the cellulosic substrate is less than 60 g / m2, preferably less than 50 g / m2according to Cobb-Unger test (Scan-P 37:77), andthe profilometer average roughness of the cellulosic substrate is less than 3 pm, such as less than 2 pm.
45. A coated cellulosic substrate obtained by the method according to any of claims 35