Recyclable cellulose-based substrate comprising cellulosic fibers and non-fibrous cellulosic material

Abstract

The present invention relates to a cellulose-based substrate comprising natural cellulosic fibers and a non-fibrous cellulosic material wherein the substrate is recyclable by repulping wherein at least 50 wt% of the substrate is recoverable according to EN13430; a method for preparing a cellulose-based substrate; a method for processing the cellulose-based substrate; and a use of the cellulose-based substrate for packaging.

Description

Technical Field

[0001] The present invention relates to a recyclable cellulose-based substrate that can be used as a packaging material. Another aspect of the present invention relates to methods for preparing the cellulose-based substrate and its derived products. Background Art

[0002] Packaging materials create a large amount of waste, and many countries are currently trying to reduce such waste through recycling. Recyclable materials are advantageous because they extend the lifespan of raw materials. In the case of recycling cellulose-based materials (e.g., by repulping), this can reduce the need for further cultivation and harvesting of natural cellulose sources. Therefore, recycling through repulping is expected to bring economic and ecological benefits.

[0003] Parchment paper offers several advantages as a packaging material, such as providing oil and water resistance, providing gas barrier, and biodegradability and / or compostability. In addition, parchment paper-based products are generally considered safe for food contact and have long been used by consumers for packaging and / or preparing food. Parchment paper-based products can also be processed in various ways, such as printing labels on the products.

[0004] Although they are generally biodegradable and / or compostable, parchment paper-based materials are usually not recyclable because the fibers are bound too strongly in an amorphous gel-like state. In other words, the advantageous properties of parchment paper-based food materials are accompanied by a reduction in recyclability and lower economic and ecological benefits. Alternatively, laminated products (e.g., products where a polymer film is glued to a cellulose-based substrate) require further compounds and processing steps, which also have negative environmental and economic impacts.

[0005] EP 3 819 426 discloses a highly parchmentized cellulose-based paper with a very low oxygen transmission rate. Although the material is compostable and / or biodegradable, the repulpability of this material may be affected due to the fact that the fibers are embedded in a continuous cellulose fiber matrix containing non-fiber cellulose materials.

[0006] US2,023,711 discloses an attempt to prepare a partially parchmentized paper substrate, where some cellulose fibers are dissolved while others are unaffected. This is achieved by first passing the paper through a solution that protects the fibers from parchmentization, such that only the uncoated fibers can react with the parchmentizing acid. However, initially coating the protective solution will further limit the recyclability and repulpability of the paper substrate.

[0007] Therefore, there is still room for improvement, and there is a need for a cellulose-based packaging product that has improved recyclability through repulping while still providing the beneficial properties of parchment paper. Summary of the Invention

[0008] The present invention solves the problems of the prior art in the following manner.

[0009] In a first aspect, the present invention relates to a cellulose-based substrate comprising natural cellulose fibers and non-fibrous cellulose material, wherein the substrate is recyclable by repulping, and wherein at least 50 wt% of the substrate is recyclable according to EN13430.

[0010] In a second aspect, the present invention relates to a method for preparing the substrate according to the first aspect, wherein the method comprises the following steps:

[0011] (i) providing a cellulose-based substrate precursor material comprising natural cellulose fibers,

[0012] (ii) partially impregnating the cellulose-based substrate precursor material with a gelling agent, thereby subjecting the cellulose-based substrate precursor material to a reaction with the gelling agent to dissolve the natural cellulose fibers to obtain a partially treated cellulose-based substrate precursor material; and

[0013] (iii) subjecting the partially treated cellulose-based substrate precursor material to a reprecipitating agent.

[0014] According to a third aspect, the present invention relates to a method for processing the cellulose-based substrate according to the first aspect, wherein the processing comprises any one of the following: printing, laminating, coating, painting, spraying, bonding, gluing, varnishing, impregnating, soaking, and / or adhering.

[0015] In a fourth aspect, the present invention relates to the use of the cellulose-based substrate according to the first aspect for packaging. Description of the Drawings

[0016] Figure 1 A scanning electron micrograph of the sample of Example 1 is shown, in which a parchmentized portion containing non-fibrous cellulose material can be observed at the surface. The remaining fibers in the core region remain unchanged from the untreated fibers. The inset in Region A further shows that the thickness of the parchmentized portion containing non-fibrous cellulose material in the surface region is approximately 5 - 10 μm.

[0017] Figure 2Shows the results of the grease resistance test on the sample of Example 1. Region A shows the treated area, which is more transparent as the dye has not been absorbed. Region B is untreated and is darker in color as the dye has been absorbed. The right-hand picture shows the other side of the plate. Region C is the treated area where the dye has not penetrated. Region D is untreated and thus the dye has penetrated.

[0018] Figure 3 Shows a scanning electron micrograph of the sample of Example 2, in which parchmentized portions containing non-fibrous cellulose material can be observed at the top and bottom surfaces. The remaining fibers in the core region remain unchanged.

[0019] Figure 4 Shows the results of the grease resistance test on the sample of Example 2. Above the blue line, the sample was subjected to a gelling agent. Region A shows the treated area, which is more transparent as the dye has not been absorbed. Region B is untreated and is darker in color as the dye has been absorbed. The right-hand picture shows the other side of the plate. Region C is the treated area where the dye has not penetrated. Region D is untreated and thus the dye has penetrated.

[0020] Figure 5 Shows a photograph of the sample of Example 3, in which the blotting paper portion covers the substrate plate. The top portion of the plate is not covered by the blotting paper layer.

[0021] Figure 6 Shows a scanning electron micrograph of the sample of Example 3. As can be seen, the parchmentized portions containing non-fibrous cellulose material are located on the layer that was previously the blotting paper, while the denser plate substrate material remains substantially unchanged. The inset in Region A further shows the parchmentized portion of the surface region containing non-fibrous cellulose material.

[0022] Figure 7 Shows the results of the grease resistance test on the sample of Example 3. Region A shows the treated area, which is more transparent as the dye has not been absorbed. Region B is untreated and is darker in color as the dye has been absorbed. The right-hand picture shows the other side of the plate. Region C is the treated area where the dye has not penetrated. Region D is untreated and thus the dye has penetrated. Detailed Description

[0023] The present invention relates to a substrate comprising natural cellulose fibers and non-fibrous cellulose material, wherein the substrate is recyclable by repulping, and wherein at least 50 wt% of the substrate is recyclable according to EN13430.

[0024] Definitions

[0025] In the context of the present invention, the following definitions and test methods apply.

[0026] As used herein, the term "fiber" refers to a form of material characterized by an extremely high length-to-diameter ratio. Generally, depending on the fiber type and the source of the fiber, cellulose fibers have a very wide range of diameters and lengths. The average length of the wood pulp fibers preferably used in the present invention is generally in the range of 0.3 mm to 3.5 mm, preferably 0.3 mm to 3.0 mm, more preferably 0.8 mm to 2.5 mm, and even more preferably 1.0 mm to 2.0 mm. The diameter of the wood pulp fibers is generally in the range of 10 μm to 40 μm, preferably 15 μm to 35 μm, and more preferably 20 μm to 30 μm. Thus, the aspect ratio (the ratio of fiber length to fiber diameter) of the wood pulp fibers is generally in the range of 7.5 to 350, preferably 7.5 to 300, more preferably 10 to 200, and even more preferably 20 to 150. Unless otherwise specifically stated, the terms "fiber" and "filament" can be used interchangeably for the purposes of the present invention.

[0027] The term "cellulose-based" describes a substrate and / or material and / or article that mainly contains cellulose. The material can be a fiber or a film. The cellulose material is derived from man-made sources, such as regenerated cellulose fibers or films, or from natural sources, such as fibers or pulp from woody or non-woody plants. The cellulose-based material can include woven or non-woven cellulose. The non-woven cellulose-based material can be formed by many processes, for example, spunbonding, carding, knitting, air-laying, and wet-laying processes. The basis weight of the cellulose-based material is usually expressed in weight per unit area, for example, in grams per square meter (gsm = g / m 2 ) or ounces per square foot (osf). The cellulose-based material can include natural cellulose fibers and / or non-fiber cellulose materials.

[0028] The term "natural cellulose fiber" refers to cellulose fibers from natural sources such as: woody plants, including deciduous trees and conifers; or non-woody plants, including cotton, flax, reed grass, kenaf, sisal, abaca, milkweed, straw, jute, hemp, and bagasse. Preferably, the natural cellulose fibers are suitable for being dissolved by a gelling agent. For example, fibers suitable for dissolution are, for example, hardwood fibers, softwood fibers, or annual plant fibers. Natural cellulose fibers form a crystalline material that contains a crystalline fraction, in which the crystal form of cellulose I contains all parallel-oriented cellulose chains. The natural cellulose fibers may have undergone a pulping step.

[0029] The term "non-fibrous cellulose material" designates a material obtained by subjecting natural cellulose fibers to a reaction with a gelling agent, thereby at least partially dissolving the natural cellulose fibers, wherein the natural cellulose fibers disintegrate and form a gel-like viscous material, and subsequently the gelling agent is removed by washing with a reprecipitating agent, whereby the gel-like material precipitates to form a solid material. A process of dissolving and reprecipitating natural cellulose fibers is called the parchmentization process. The solid material herein called non-fibrous cellulose material is mainly amorphous and may contain other forms of crystalline fractions, such as a crystalline fraction having the crystal form of cellulose II containing antiparallel cellulose chains. The non-fibrous cellulose material is preferably a reprecipitated gelled cellulose material.

[0030] The term "re-pulping" describes a process whereby a material that has previously been subjected to or has been formed by at least one pulping step is subjected to a further pulping step.

[0031] The term "recyclable by re-pulping" describes a material that can be at least partially recovered and converted into a new material or object during a re-pulping step. The material may be a waste product. The term "recyclable" is generally described in accordance with EN13430. Thus, the expression "recyclable by re-pulping, wherein at least 50 wt% is recyclable according to EN13430" describes a material that has been formed by or otherwise subjected to at least one pulping step and from which at least 50 wt% of the substrate can be recovered after being subjected to a further pulping step.

[0032] For ease of reference, unless further specified, the term "substrate" refers to the cellulose-based substrate according to the first aspect of the present invention.

[0033] Cellulose-based substrate

[0034] As mentioned above, in a first aspect, the present invention relates to a cellulose-based substrate comprising natural cellulose fibers and non-fibrous cellulose materials, wherein the substrate is recyclable by re-pulping, wherein at least 50 wt% of the substrate is recyclable according to EN13430.

[0035] In one embodiment of the first aspect, the substrate can be recycled by repulping, wherein at least 55 wt% of the substrate is recyclable according to EN13430, more preferably, wherein at least 60 wt% of the substrate is recyclable according to EN13430, more preferably, wherein at least 65 wt% of the substrate is recyclable according to EN13430, more preferably, wherein at least 70 wt% of the substrate is recyclable according to EN13430, more preferably, wherein at least 75 wt% of the substrate is recyclable according to EN13430, more preferably, wherein at least 80 wt% of the substrate is recyclable according to EN13430, more preferably, wherein at least 85 wt% of the substrate is recyclable according to EN13430, and even more preferably, wherein at least 90 wt% of the substrate is recyclable according to EN13430.

[0036] In one embodiment, the natural cellulose fibers contained in the substrate are recycled by repulping. In one embodiment, the wt% amount of the substrate that can be recycled during recycling by repulping is at most the amount of the natural cellulose fibers in the substrate. That is, in the sense of the present invention, all or most of the non-gelatinized cellulose fiber materials that can be recycled during recycling by repulping can be regarded as recyclable natural cellulose materials. Therefore, natural cellulose materials also include fibers that have not undergone a reaction with a gelling agent or have preferably partially undergone a reaction with a gelling agent. In this sense, "partial" reaction defines a situation that allows the fibers to substantially maintain their fibrous state.

[0037] In one embodiment, the substrate comprises a composite material, the composite material comprising natural cellulose fibers and non-fibrous cellulose materials. The substrate can be an article and / or a material.

[0038] In one embodiment, the natural cellulose fibers and non-fibrous cellulose materials are contained in a continuous cellulose fiber matrix. The term "continuous cellulose fiber matrix" refers to a cellulose material comprising natural cellulose fibers and non-fibrous cellulose materials, wherein the natural cellulose fibers are embedded in the non-fibrous cellulose materials, whereby the pores of the fiber skeleton are blocked. Therefore, the continuous cellulose fiber matrix represents a dense material that provides a cellulose continuum between the natural cellulose fibers and the non-fibrous cellulose materials, avoiding any voids at the interface between the natural cellulose fibers and the non-fibrous cellulose materials. Therefore, the continuous cellulose fiber matrix is a continuous pore-free material. The continuous cellulose fiber matrix can have high gas barrier properties, especially against oxygen.

[0039] In one embodiment, the continuous cellulose fiber matrix further comprises de-structured cellulose fibers. The expression "de-structured cellulose fibers" describes the periphery of natural cellulose fibers that have been partially dissolved with a gelling agent, thereby creating a progressive structural change from natural cellulose to precipitated cellulose. Such a progressive structural change means that the structure of the continuous cellulose fiber matrix contains a structural gradient, where the crystalline structure of the natural cellulose fibers is slowly transformed into a mostly amorphous structure of non-fibrous cellulose material by forming de-structured cellulose fibers on the surface of the natural cellulose fibers. Thus, the de-structured cellulose fibers surround the natural cellulose fibers and are inserted between the natural cellulose fibers and the non-fibrous cellulose material. Preferably, the continuous cellulose fiber matrix can consist of natural cellulose fibers, de-structured cellulose fibers, and non-fibrous cellulose material. De-structured cellulose fibers that substantially retain their fibrous state and are only minimally subjected to reaction with the gelling agent can also be considered natural cellulose fibers.

[0040] In one embodiment, the substrate can be a substantially 2D-formed article (e.g., a sheet) or a 3D-formed article. A formed article is an article that is at least partially prepared by at least one forming step. A substantially 2D-formed article is an article having length and width dimensions that are significantly greater than the thickness dimension. For the purposes of this application, a 2D-formed article (e.g., a butter wrapper, or one that is not self-supporting) that wraps around a 3D-formed object and thus presents the appearance of a 3D-formed article will also be considered a 2D-formed article.

[0041] In a preferred embodiment of the first aspect, the substrate can be obtained by a method comprising the following steps:

[0042] (i) providing a cellulose-based substrate precursor material comprising natural cellulose fibers,

[0043] (ii) partially impregnating the cellulose-based substrate precursor material with a gelling agent, thereby subjecting the cellulose-based substrate precursor material to a reaction with the gelling agent to dissolve the natural cellulose fibers to obtain a partially treated cellulose-based substrate precursor material; and

[0044] (iii) subjecting the partially treated cellulose-based substrate precursor material to a reprecipitating agent.

[0045] In step (i) of the preferred embodiment of the first aspect of the present invention, a cellulose-based substrate precursor material comprising natural cellulose fibers is provided. The cellulose-based substrate has been formed by or otherwise subjected to at least one pulping step. For ease of reference, the terms "precursor material" and "cellulose-based substrate precursor material" are used synonymously herein. The precursor material may comprise at least 50 wt% of natural cellulose fibers, preferably at least 55 wt% of natural cellulose fibers, more preferably at least 60 wt% of natural cellulose fibers, more preferably at least 65 wt% of natural cellulose fibers, more preferably at least 70 wt% of natural cellulose fibers, more preferably at least 75 wt% of natural cellulose fibers, more preferably at least 80 wt% of natural cellulose fibers, more preferably at least 85 wt% of natural cellulose fibers, more preferably at least 90 wt% of natural cellulose fibers, and even more preferably at least 95 wt% of natural cellulose fibers. In one embodiment, the precursor material consists essentially or entirely of natural cellulose fibers. Preferably, the precursor material comprises less than 1 wt% of non-fibrous cellulose material.

[0046] In one embodiment, the precursor material may be any of the following: cardboard, blotting paper, absorbent paper, filter paper, cellulose tissue paper.

[0047] In step (ii) of the preferred embodiment of the first aspect, the precursor material is partially impregnated with a gelling agent. "Partially impregnated" herein means that only a part of the natural cellulose fibers in the precursor material provided in step (i) are in contact with the gelling agent, and the contact is carried out by impregnation. In one embodiment, 0.1 mass%-99 mass% of the natural cellulose fibers in the precursor material are in contact with the gelling agent, more preferably 0.1 mass%-50 mass%, more preferably 0.1 mass%-40 mass%, more preferably 0.1 mass%-30 mass%, more preferably 0.1 mass%-20 mass%, more preferably 0.1 mass%-10 mass%, more preferably 0.1 mass%-5 mass%, and even more preferably 0.1 mass%-2 mass%.

[0048] In one embodiment, the gelling agent is provided in liquid form (e.g., in solution form). The gelling agent comprises at least one cellulose solvent selected from the group consisting of: inorganic acids comprising sulfuric acid and phosphoric acid, Lewis acids comprising ZnCl2 and Ca(SCN)2, inorganic bases comprising NaOH, organic bases comprising N-methylmorpholine N-oxide, and ionic liquids comprising tetraalkylammonium salts. Preferably, the gelling agent comprises sulfuric acid.

[0049] In one embodiment, the precursor material is porous and capable of absorbing the gelling agent, thereby causing impregnation when the precursor material comes into contact with the gelling agent. The degree of impregnation can be controlled by controlling the porosity of the precursor material, controlling the thickness of the precursor material, controlling the basis weight of the precursor material, controlling the pressure of contact with the gelling agent (e.g., by embossing with a roller), controlling the contact time between the precursor material and the gelling agent (e.g., by immersing the precursor material in the gelling agent for a predetermined time), adding an anti-reprecipitation agent, and the like. Preferably, the degree of impregnation is controlled by controlling the porosity and thickness of the precursor material, as further described below.

[0050] In step (ii) of the preferred embodiment of the first aspect of the present invention, the precursor material provided in step (i) is partially impregnated with the gelling agent, and the precursor material is subjected to a reaction with the gelling agent to dissolve the natural cellulose fibers to obtain a partially treated cellulose-based substrate precursor material. The reaction may be a chemical reaction. The degree to which the gelling agent dissolves the natural cellulose fibers depends on the degree of impregnation, since the gelling agent dissolves the fibers with which it is in direct contact. In addition, the degree to which the reaction occurs depends on the nature and concentration of the gelling agent. For example, if 10 wt% of the precursor material is impregnated with the gelling agent, the gelling agent may dissolve 10 wt% or less of the natural cellulose fibers in the precursor material. In one embodiment, the gelling agent reacts with substantially all of the natural cellulose fibers with which it is in direct contact, thereby dissolving all of the natural cellulose fibers with which it is in direct contact. The reaction with the gelling agent and thus the dissolution of the natural cellulose fibers produces a partially treated cellulose-based substrate precursor material. Thus, the partially treated cellulose-based substrate precursor material contains natural cellulose fibers and dissolved cellulose fibers, and the dissolved cellulose fibers are a gel-like viscous material. Preferably, the partially treated cellulose-based substrate precursor material further contains de-structured cellulose fibers.

[0051] In step (iii) of the preferred embodiment of the first aspect of the present invention, the partially treated cellulose-based substrate precursor material is subjected to an anti-reprecipitation agent. In one embodiment, all of the dissolved cellulose fibers are subjected to the anti-reprecipitation agent. In another embodiment, only a portion of the dissolved cellulose fibers are subjected to the anti-reprecipitation agent. Preferably, at least the dissolved cellulose fibers are subjected to the anti-reprecipitation agent.

[0052] The anti-reprecipitation agent interrupts the reaction between the gelling agent and the natural cellulose fibers by eliminating the gelling agent. Thus, the gel-like viscous material containing the dissolved cellulose fibers precipitates into a solid material. This solid material is referred to herein as "non-fibrous cellulose material". The non-fibrous cellulose material may be dry or wet. Preferably, the non-fibrous cellulose material, together with the de-structured cellulose fibers and the natural cellulose fibers, forms a continuous cellulose fiber matrix.

[0053] In one embodiment, the reprecipitating agent is water. In such embodiments, "removing the gelling agent" means diluting and washing away the gelling agent. Other reprecipitating agents that remove the gelling agent (e.g., by neutralizing or inactivating it) can be used.

[0054] Preferred embodiments of the first aspect of the present invention may include an additional step (iv), wherein the substrate is consolidated by a drying step. Optionally, step (iv) may include an additional separate washing step before the drying step.

[0055] In one embodiment, the precursor material provided in step (i) is provided in the form of a substrate precursor article. For ease of reference, the terms "substrate precursor article" and "precursor article" are used synonymously herein. The precursor article can be a substantially 2D-formed article (e.g., a sheet) or a 3D-formed article. In one embodiment, the forming step can occur during step (ii) or (iii), or before the substrate is consolidated. In another embodiment, the forming step can occur after the substrate is consolidated.

[0056] In one embodiment, the cellulose-based substrate precursor material provided in step (i) is provided in the form of a substrate precursor article having at least one surface region and a core region, and wherein in step (ii), the gelling agent penetrates the at least one surface region. After penetrating the at least one surface region, the precursor article is subjected to a reprecipitating agent such that the at least one surface region contains non-fibrous cellulose material. Preferably, after being subjected to the reprecipitating agent, the at least one surface region contains a continuous cellulose fiber matrix.

[0057] In one embodiment, the gelling agent does not penetrate the core region. In this case, the native cellulose fibers in the core region remain intact and do not dissolve.

[0058] The at least one surface region is substantially located at the surface of the article, and the core region is substantially located in the body of the article.

[0059] In one embodiment, relative to the total thickness of the article, the surface region penetrates at most 50%, more preferably at most 40%, more preferably at most 30%, more preferably at most 20%, more preferably at most 10%, more preferably at most 5%, more preferably at most 3%, and even more preferably at most 1%.

[0060] In one embodiment, the surface region penetrates into the article at most 5 cm, more preferably at most 3 cm, more preferably at most 1 cm, more preferably at most 0.1, more preferably at most 1 mm, more preferably at most 100 μm, more preferably at most 50 μm, and even more preferably at most 10 μm.

[0061] The surface region may cover the entire surface of the precursor article or only a part thereof. The part of the surface not covered by the surface region is referred to herein as the "remaining surface". For example, in one embodiment, the precursor article is a substantially 2D shaped article, such as a sheet, where the surface region covers only one side and the other side is the remaining surface. In another embodiment, the precursor article is a concave 3D shaped article, where the surface region covers only the inner surface of the concave article. Thus, the outer surface of the concave article is the remaining surface. In another embodiment, the precursor article is a cube-shaped article, such as a box, and the surface region covers only one face. Thus, the other five faces constitute the remaining surface.

[0062] The penetration of the gelling agent into at least one surface region can be controlled by any suitable method. For example, the gelling agent is in contact only with the surface region and the remaining surface is not. For example, this can be achieved by immersing the surface region in a solution containing the gelling agent. Alternatively, the gelling agent can be surface-applied only on one side of the sheet, for example by rolling, spraying, kiss coating, transfer coating, and / or size press. The degree of penetration can be controlled by controlling the porosity of the precursor article, controlling the thickness of the precursor article, controlling the basis weight of the precursor article, controlling the pressure of contact with the gelling agent (e.g., by embossing with a roller), controlling the contact time between the precursor material and the gelling agent (e.g., by immersing the precursor material in the gelling agent for a predetermined time), adding a reprecipitation inhibitor, etc. Preferably, the degree of penetration is controlled by controlling the porosity and thickness of the precursor article, as further described below.

[0063] In one embodiment, the precursor material provided in step (i) is provided in the form of a precursor article for a multi-layer or single-layer article. The multi-layer article can be a multi-layer sheet comprising several layers stacked vertically on top of each other.

[0064] In one embodiment, the multi-layer precursor article can comprise a first layer and a second layer, the first layer being located at the surface of the article and wherein the first layer is more permeable to the gelling agent than the second layer. Preferably, at least the first layer and the second layer are composed of a cellulose-based material. For example, the permeability of the layer may depend on the basis weight / density of the layer and / or the Bendtsen porosity of the layer. Thus, the gelling agent penetrates deeper into the first layer and reacts more strongly with the native cellulose fibers. Thus, when the multi-layer precursor article is subjected to a reprecipitation agent, the first layer contains more non-fibrous cellulose material than the second layer. Preferably, the first layer comprises a more continuous cellulose fiber matrix.

[0065] In one embodiment, the second layer is substantially impermeable to the gelling agent. Thus, after step (iii), the second layer does not contain non-fibrous cellulose material and / or a continuous cellulose fiber matrix. Preferably, the first layer comprises more than 90 wt% of a continuous cellulose fiber matrix, while the second layer comprises less than 10 wt% of a continuous cellulose fiber matrix.

[0066] In one embodiment, the second layer is positioned at the surface of the preform. In another embodiment, the second layer is positioned below the first layer, substantially within the body of the article. The preform may comprise additional layers which may be more permeable, less permeable or equally permeable to the gelling agent compared to the second layer.

[0067] In one embodiment, the precursor material provided in step (i) has a basis weight of at least 100 gsm, preferably at least 120 gsm, more preferably at least 140 gsm, more preferably at least 160 gsm, more preferably at least 180 gsm, more preferably at least 200 gsm, more preferably at least 220 gsm, more preferably at least 240 gsm, more preferably at least 260 gsm, and even more preferably at least 270 gsm. The precursor material may have a basis weight below 100 gsm (e.g., 70 gsm), but the barrier properties and / or the recovery rate may be affected. The preform may have the same basis weight. The basis weight is preferably determined according to ISO 536:1995.

[0068] In one embodiment, the precursor material provided in step (i) is provided in the form of a preform for a multi-layer article, the multi-layer article comprising a first layer and a second layer, the first layer being positioned at the surface of the article and having a basis weight of at most 270 gsm, more preferably at most 260 gsm, more preferably at most 240 gsm, more preferably at most 220 gsm, more preferably at most 200 gsm, more preferably at most 180 gsm, more preferably at most 160 gsm, more preferably at most 140 gsm, more preferably at most 120 gsm, more preferably at most 100 gsm, more preferably at most 80 gsm, more preferably at most 60 gsm, more preferably at most 40 gsm, and even more preferably at most 20 gsm. The basis weight of the first layer may be as low as 6 gsm.

[0069] In one embodiment, the precursor material provided in step (i) has a Bendtsen porosity of 2000 ml / min or lower, preferably 1500 ml / min or lower, more preferably 1000 ml / min or lower, more preferably 900 ml / min or lower, more preferably 800 ml / min or lower, more preferably 700 ml / min or lower, more preferably 600 ml / min or lower, more preferably 500 ml / min or lower, more preferably 400 ml / min or lower, more preferably 300 ml / min or lower, more preferably 200 ml / min or lower, and even more preferably 100 ml / min or lower. The precursor article can have the same Bendtsen porosity. The Bendtsen porosity is preferably measured according to ISO 5636-3:2013.

[0070] In one embodiment, the precursor material provided in step (i) has a thickness of 1200 μm or lower, more preferably 1000 μm or lower, and even more preferably 800 μm or lower. The precursor material provided in step (i) preferably has a thickness of at least 10 μm. More preferably, the precursor material provided in step (i) has a thickness of at least 50 μm, more preferably at least 100 μm, more preferably at least 200 μm, and even more preferably at least 300 μm. The precursor article can have the same thickness. The thickness is preferably measured according to TAPPI T 411.

[0071] The Bendtsen porosity and thickness can be used in combination to control the degree of penetration of the gelling agent. It is believed that a substrate prepared from a precursor material and / or article having a relatively high Bendtsen porosity will be more difficult to recycle (while having relatively high barrier properties) than a substrate prepared from a less porous precursor material and / or article. It is also believed that a substrate prepared from a precursor material and / or article having a relatively high thickness will be more recyclable than a substrate having a lower thickness. Preferably, therefore, the Bendtsen porosity and thickness of the substrate material and / or article are configured in a manner that achieves optimal barrier and / or recyclability performance.

[0072] In one embodiment, the precursor material has a Bendtsen porosity of 2000 ml / min or lower and a thickness of 10 - 1500 μm, preferably a Bendtsen porosity of 1500 ml / min or lower and a thickness of 50 - 1000 μm, and even more preferably a Bendtsen porosity of 1000 ml / min or lower and a thickness of 100 - 800 μm. In a particularly preferred embodiment, the precursor material has a Bendtsen porosity of 200 - 1000 ml / min and a thickness of 300 - 800 μm. The precursor article can have the same combination of porosity and thickness.

[0073] In one embodiment, the precursor material provided in step (i) is provided in the form of a precursor article for a multi-layer article, the multi-layer article comprising a first layer and a second layer, the first layer being positioned at the surface of the article, and the first layer having a Bentzen porosity of at least 100 ml / min, more preferably at least 200 ml / min, more preferably at least 300 ml / min, more preferably at least 400 ml / min, more preferably at least 500 ml / min, more preferably at least 600 ml / min, more preferably at least 700 ml / min, more preferably at least 800 ml / min, more preferably at least 900 ml / min, and even more preferably at least 1000 ml. In one embodiment, the second layer has a Bentzen porosity of at most 500 ml / min, more preferably at most 400 ml / min, more preferably at most 300 ml / min, more preferably at most 200 ml / min, more preferably at most 100 ml / min, more preferably at most 50 ml / min, and even more preferably at most 30 ml / min. The permeability of these layers is related to their porosity. Preferably, therefore, the porosity of the first and second layers is configured such that the first layer has a higher Bentzen porosity than the second layer. Preferably, the first layer also has a lower thickness than the second layer, preferably the thickness of the first layer is at least 10 μm. In one embodiment, the thickness of the first layer is less than 50% of the total thickness of the first and second layers. Preferably, the thickness of the first layer is less than 40% of the total thickness of the first and second layers, more preferably less than 30%, more preferably less than 20%, more preferably less than 10%, more preferably less than 5%, more preferably less than 3%, and even more preferably less than 1%. The thickness of the first layer is preferably at least 0.0001% of the thickness of the first and second layers.

[0074] In one embodiment, the substrate is at least 90 wt%, preferably at least 95 wt%, and more preferably 100 wt% compostable according to EN13432 and / or ASTM D6400. The expression "compostable" is generally defined in accordance with the EN13432 standard. The term "compostable substrate" refers to a substrate in which at least 90% of the material must decompose biologically within 6 months under the conditions of a standard test method, thereby complying with EN13432. When applied to a material or product, the expression "compostable" means that the material or the entire product will be biodegradable and disintegrate. "Biodegradation" means the decomposition of a chemical structure or material under the action of microorganisms, while "disintegration" means that the material or the product made from it will physically break down into small fragments that are visually indistinguishable at the end of a typical composting cycle. In order to be considered a compostable polymer material, the polymer chains must decompose under the action of microorganisms so that complete mineralization (i.e., the conversion of the material into CO2, water, inorganic compounds, and biomass under aerobic conditions) is achieved at a high rate compatible with the normal composting process of vegetable waste.

[0075] In one embodiment, the substrate is fully compostable. In one embodiment, according to EN13432 and / or ASTM D6400, the portion of the substrate that cannot be recycled by repulping is at least 90 wt% compostable.

[0076] In one embodiment, the 3D-formed substrate is plastic-free.

[0077] In one embodiment, the 3D-formed substrate is approved for food contact according to any of the following: EU1935 / 2004, BfR 36, BfR 36-1, BfR 36-2, FDA21CFR§176-170 and 176-180.

[0078] In one embodiment, the substrate is oil-resistant according to TAPPI T454.

[0079] In one embodiment, the substrate is waterproof as determined according to TAPPI T441, where there is no water leakage for 30 seconds, preferably no water leakage for 60 seconds, more preferably no water leakage for 180 seconds, more preferably no water leakage for 300 seconds, more preferably no water leakage for 600 seconds, and even more preferably no water leakage for 1800 seconds.

[0080] In one embodiment, the substrate has less than 200 cm 3 / (m 2 × day), more preferably less than 180 cm 3 / (m 2 × day), more preferably less than 160 cm 3 / (m 2× days), more preferably less than 140 cm 3 / (m 2 × days), more preferably less than 120 cm 3 / (m 2 × days), more preferably less than 120 cm 3 / (m 2 × days), more preferably less than 100 cm 3 / (m 2 × days), more preferably less than 80 cm 3 / (m 2 × days), more preferably less than 60 cm 3 / (m 2 × days), more preferably less than 40 cm 3 / (m 2 × days), and even more preferably less than 20 cm 3 / (m 2 × days). The oxygen transmission rate is measured at 23 °C and 50% relative humidity according to ASTM D3985 and ASTM F 1927.

[0081] In one embodiment, the substrate comprises only natural polymers. In the context of the present invention, natural polymers are naturally occurring non - petroleum - based polymers such as rayon and hyaluronic acid, starch or modified starch. The natural polymers may have been formed and extracted by biological organisms or they can be chemically or physically modified by subsequent processes to convert them into the desired shape or form. In a preferred embodiment, the substrate does not contain petroleum - based synthetic polymer binders or glues.

[0082] In one embodiment, the substrate is a packaging article. A packaging article is an article configured to package a second article. The packaging article is not particularly limited in size and / or shape.

[0083] In one embodiment, the substrate is a food packaging article. In a food packaging article, the second article is food or a food ingredient. The food packaging is not particularly limited and can be used for preserving food, such as oxygen - sensitive food. The food packaging article can be a substantially 2D - shaped article (such as a butter wrapper) or a 3D - shaped article (such as an egg carton or a soup bowl). The packaging article can be selected, for example, from any of the following: beverage containers, coffee capsules, coffee pods, chocolate wrappers, and cookie wrappers.

[0084] In one embodiment, the packaging article can be selected from any of the following: cosmetic packaging articles, medical packaging articles, or electronic device packaging articles.

[0085] Method for preparing a cellulose - based substrate

[0086] In a second aspect, the present invention relates to a method for preparing a substrate according to the first aspect of the present invention, the method comprising the following steps:

[0087] (i) providing a cellulose-based substrate precursor material comprising natural cellulose fibers,

[0088] (ii) partially impregnating the cellulose-based substrate precursor material with a gelling agent, thereby subjecting the cellulose-based substrate precursor material to a reaction with the gelling agent to dissolve the natural cellulose fibers to obtain a partially treated cellulose-based substrate precursor material; and

[0089] (iii) subjecting the partially treated cellulose-based substrate precursor material to a reprecipitating agent.

[0090] In one embodiment, any one of steps (i)-(iii) may be further characterized in an embodiment related to steps (i)-(iii) disclosed above. Additionally, the method of the second aspect of the present invention may comprise an additional step (iv), wherein the substrate is consolidated by a drying step. Optionally, step (iv) may comprise an additional separate washing step before the drying step.

[0091] Processing a cellulose-based substrate

[0092] In a third aspect, the present invention relates to a method for processing a substrate according to the first aspect of the present invention.

[0093] In one embodiment, the processing comprises any one of the following: printing, laminating, painting, spraying, bonding, gluing, varnishing, impregnating, soaking, and / or adhering.

[0094] In a preferred embodiment, the substrate is a food packaging product, and the processing comprises printing a label on the food packaging product.

[0095] Use of a cellulose-based substrate

[0096] In a fourth aspect, the present invention relates to a use for packaging a substrate according to the first aspect of the present invention.

[0097] In one embodiment, such use may relate to any one of transportation, storage, protection, preservation, and / or display of a packaged article (such as gift packaging).

[0098] In one embodiment, the use for packaging relates to packaging food, such as single-serve beverage capsules, packaged cosmetics, packaged medical products, and / or packaged electronic devices.

[0099] Based on the foregoing discussion, the following examples, and without wishing to be bound by theory, the inventors believe that the problem of providing a substrate for packaging that has improved recyclability without compromising the advantageous properties of parchment-based materials has been solved.

[0100] Examples

[0101] In the examples, the following standard chemicals and conditions were used.

[0102] The material properties of the sheet-like precursor articles are given in the table below (Table 1)

[0103] Characteristic Average value Thickness (μm) 566 <![CDATA[Grammage (g / m 2 )]]> 271 Bekk smoothness (s) 1.5 Bendtsen porosity (ml / min) 456

[0104] Table 1 | Material properties of the sheet-like precursor articles

[0105] Absorbent paper layer: A highly porous sheet having a thickness of approximately 50 μm and a Bentzen porosity of 1980 ml / min.

[0106] Gelling agent: Sulfuric acid having a concentration of 70% to 75%.

[0107] Method of impregnation: In one example, the cellulose substrate was immersed in a sulfuric acid bath, and in another example, sulfuric acid was deposited at one corner of the sample, and a silicone roller was used to disperse the acid over the surface of the sample on the same side.

[0108] Imaging method: Scanning electron microscopy (SEM) and / or digital photography.

[0109] The Bentzen porosity was measured according to ISO 5636-3:2013.

[0110] The Bekk smoothness was measured according to ISO 5627:1995.

[0111] The thickness was measured according to TAPPI T 411.

[0112] The basis weight was determined according to ISO 536:1995.

[0113] The grease resistance was tested according to Tappi T-454:2015.

[0114] The recyclability was tested according to EN 13430. The given sample was cut into small pieces of about 25 cm 2 and repulped in a pulper. The repulped sample was screened on a Somerville-type apparatus using a 0.15 mm slotted plate according to the test method TAPPI / ANSI T 275sp-18. Different recovered fractions were used to calculate the recyclable portion.

[0115] Example 1

[0116] Sulfuric acid was deposited at one corner of the plate-shaped precursor, and the acid was dispersed over the surface of the sample on the same side using a silicone roller. The sample was then rinsed under running water and dried. Figure 1 Scanning electron micrographs showing cross-sectional views of the samples are presented. As can be seen, only the surface region was sueded, while the core region remained substantially unchanged.

[0117] The sample was then subjected to a grease resistance test. An oil-based dye was dispersed on the treated side, and the back side was observed. As can be seen in Figure 2 what follows, the dye only penetrated the untreated areas.

[0118] Example 2

[0119] The plate-shaped precursor article was immersed in a sulfuric acid bath. The sample was then rinsed under running water and dried. During this process, both sides of the plate were treated.

[0120] The recyclability of the substrate was then tested and compared with industrial samples. The results for these samples are shown in Table 2 below.

[0121]

[0122] Table 2|Recyclability test according to EN13430

[0123] Figures 3 - 4 Cross-sectional SEM and oil resistance tests of the samples of Example 2 are shown respectively.

[0124] Example 3

[0125] A double-layer precursor article was prepared by placing a layer of blotting paper on one face of the plate-shaped precursor article such that the blotting paper layer covered only approximately 80% of the plate-shaped precursor article. The total thickness of the precursor article was approximately 616 μm where covered by the blotting paper and 566 μm where not covered.

[0126] Sulfuric acid was deposited on the face of the plate-shaped precursor, including the blotting paper layer on the side of the sample that included only the plate. A silicone roller was then used to disperse the acid towards the opposite side of the sample by rolling the acid over the blotting paper and simultaneously pressing the gel. The sample was then rinsed under running water and dried.

[0127] Figures 5 - 7 Photographs, cross-sectional SEM and oil resistance tests of the samples of Example 3 are shown respectively.

Claims

1. A cellulose-based substrate, said cellulose-based substrate comprising natural cellulose fibers and non-fibrous cellulose material, wherein the substrate is capable of being recycled by repulping, and wherein according to EN13430, at least 50 wt% of the substrate is recyclable.

2. The cellulose-based substrate according to claim 1, wherein the substrate can be obtained by a method comprising the following steps: (i) providing a cellulose-based substrate precursor material comprising natural cellulose fibers; (ii) partially impregnating the cellulose-based substrate precursor material with a gelling agent, thereby subjecting the cellulose-based substrate precursor material to a reaction with the gelling agent to dissolve the natural cellulose fibers to obtain a partially treated cellulose-based substrate precursor material; (iii) subjecting the partially treated cellulose-based substrate precursor material to a reprecipitating agent.

3. The cellulose-based substrate according to claim 2, wherein the cellulose-based substrate precursor material provided in step (i) is provided in the form of a substrate precursor article having at least one surface region and a core region, and wherein the gelling agent impregnates the at least one surface region.

4. The cellulose-based substrate according to claim 2 or 3, wherein the cellulose-based substrate precursor material provided in step (i) is provided in the form of a substrate precursor article for a multi-layer or single-layer article.

5. The cellulose-based substrate according to claim 4, wherein the substrate precursor article is a multi-layer article comprising a first layer and a second layer, the first layer being located at the surface of the article, and wherein the first layer is more permeable to the gelling agent than the second layer.

6. The cellulose-based substrate according to any one of claims 2 to 5, wherein the cellulose-based substrate precursor material provided in step (i) - has a basis weight of at least 100 gsm, and / or - has a Bendtsen porosity of 2000 ml / min or less.

7. The cellulose-based substrate according to any one of claims 1 to 6, wherein the substrate is capable of being recycled by repulping, and wherein according to EN13430, at least 75 wt% of the substrate is recyclable, more preferably, wherein according to EN13430, at least 90 wt% of the substrate is recyclable.

8. The cellulose-based substrate according to any one of claims 1 to 7, wherein the substrate - is at least 90 wt% compostable according to EN13432, and / or - is approved for food contact according to any of the following: EU 1935 / 2004, BfR 36, BfR 36-1, BfR 36-2, FDA21CFA§176-170 and 176-180.

9. The cellulose-based substrate according to any one of claims 1 to 8, wherein the substrate - is oil-proof according to TAPPI T454, and / or - is waterproof as determined according to TAPPI T441, with no water leakage in 60 seconds, and / or - Having an oxygen transmission rate of less than 200 cm3 / (m2×day) when determined at 23 °C and 50% relative humidity.

10. The cellulose-based substrate according to any one of claims 1 to 9, wherein the substrate comprises only natural polymers.

11. The cellulose-based substrate according to any one of claims 1 to 10, wherein the substrate is a packaging article, and further optionally, wherein the substrate is any one of the following: a food packaging article, a cosmetic packaging article, a medical packaging article, or an electronic device packaging article.

12. A method for preparing a cellulose-based substrate according to any one of claims 1 to 11, the method comprising the following steps: (iv) Providing a cellulose-based substrate precursor material comprising natural cellulose fibers, (v) Partially impregnating the cellulose-based substrate precursor material with a gelling agent, thereby subjecting the cellulose-based substrate precursor material to a reaction with the gelling agent to dissolve the natural cellulose fibers to obtain a partially treated cellulose-based substrate precursor material; (vi) Subjecting the partially treated cellulose-based substrate precursor material to a reprecipitating agent.

13. The method according to claim 12, wherein the reprecipitating agent in step (iii) is water.

14. A method for processing a cellulose-based substrate according to any one of claims 1 to 11, wherein the processing comprises any one of the following: printing, laminating, coating, painting, spraying, bonding, gluing, varnishing, impregnating, soaking, and / or adhering.

15. Use of a cellulose-based substrate according to any one of claims 1 to 11 for packaging, preferably for packaging food, electronic devices, cosmetics, and / or medical products.

Images