Collapsible solid cellulose foam

Abstract

A collapsible solid cellulose foam, wherein the collapsible solid cellulose foam comprises an upper surface and a lower surface; wherein at least one of the upper surface and the lower surface of the collapsible solid cellulose foam comprises at least one cutting line having a predetermined cutting depth DC; wherein the at least one cutting line is arranged to partially cut through the cellulosic foam. The invention also provides a method for producing the foldable solid cellulose foam.

Description

Technical Field

[0001] The present invention relates to the field of cellulose foams for packaging, and more particularly to collapsible solid cellulose foams.

[0002] The invention further relates to a method for producing a collapsible solid cellulose foam. Background Art

[0003] Plastic packaging materials such as fossil-based foams appear increasingly obsolete in a society striving to reduce plastic use and waste and move towards renewable materials. With regulators now pushing for policies that restrict or ban fossil-based foam materials in packaging, new solutions are needed.

[0004] There are many challenges in finding foams from renewable sources. Many bio-based foams have higher production costs and lower mechanical properties, as well as poor stability in water or high temperatures, compared to established foams from petroleum-based sources. Bio-based and recyclable protective materials need to have the same excellent characteristics and properties as petroleum-based protective materials to become the first choice relative to petroleum-based materials.

[0005] The low weight and good shock absorption of bio-based foams are examples of key properties. Furthermore, the ability to tailor the shape and form of the bio-based foam to that of the item to be shielded by the protective material is of primary importance. As the most abundant renewable natural polymer on earth, cellulose has been shown to have particular potential, with its crystalline structure, and the availability of processes for preparing large quantities on an industrial scale.

[0006] Several bio-based foams containing cellulose have been described. WO20200011587 A1 describes a porous material prepared by aerating a paste containing cellulose fibers and gluten and depositing the aerated paste in a mold where it is dried. WO2015036659A1 describes a molded cellulosic product prepared by foaming an aqueous suspension of natural fibers combined with synthetic fibers and a surfactant, feeding the cellulosic foam to a mold where it is dried to produce a dry cellulosic product.

[0007] In packaging applications, the items to be shielded may often have protruding parts, such as corners and edges, or have complex three-dimensional (3D) shapes, which require additional protection of the packaging material during storage and transportation. In addition, the items may be made of sensitive materials (such as glass or porcelain) that require protection due to their fragile nature. Solid cellulose foams may be an interesting alternative in such applications. However, due to the rigidity, inflexibility and stiffness of bio-based foams, solid cellulose foams on the market most often fail to provide the necessary protection of protruding parts (such as corners and edges) or complex 3D shapes. It is usually impossible to bend or fold solid foam around an object without cracking and breaking the bio-based foam.

[0008] There still exists a need for a solid cellulose foam that can be customized around any shaped article and protect every part of the article. The article needs to be well shielded so that any shocks generated during storage and transportation will be absorbed by the surrounding cellulose foam and thus the shocks will not damage the article.

[0009] Furthermore, solid cellulose foams need to be renewable, biodegradable and fully recyclable in conventional paper and paperboard streams, allowing them to become part of the circular material stream in existing packaging waste management systems. The production costs of producing the foams and customizing the shape of the foams to any product shape must be modest in order to be a competitive option.

[0010] In order to save raw materials, there is also a need to reduce the amount of protective materials used in protective packaging, as well as to minimize waste materials.

[0011] There is a further need for protective packaging materials that can be easily transported to a location where the items are packaged inside the protective packaging materials. The protective packaging materials need to provide three-dimensional customized protection of the items, but also take up as little space as possible during transportation to the packaging location. Summary of the invention

[0012] It is an object of the present invention to obviate at least some of the disadvantages of the prior art and to provide a foldable solid cellulose foam.

[0013] Due to the solution as defined in claim 1, wherein the foldable solid cellulose foam comprises an upper surface and a lower surface and wherein at least one of the upper surface and the lower surface of the foldable solid cellulose foam comprises at least one cutting line with a predetermined cutting depth DC, and wherein the at least one cutting line is arranged to partially cut through the cellulose foam, the foldable solid cellulose foam is provided with at least one hinge for the cellulose foam to fold around, so that the foam can be easily folded around angular shapes (such as corners and edges) of the item to be protected, thereby providing cushioning for the item.

[0014] Another advantage is that the foldable solid cellulose foam is a flat material that takes up very little space when stored or during transport to the place of use. Still - due to the possibility of folding the solid cellulose foam - the foam can be tailored around three-dimensional objects even with complex shapes and protect the objects due to the cushioning properties of the foam.

[0015] Another advantage is that the predetermined cutting depth is smaller than the thickness of the cellulose foam and is arranged in the direction of the thickness, thereby allowing the foam to remain in one piece. No waste material is cut.

[0016] Yet another advantage is that the direction of the cut into the foam is chosen according to the shape of the item to be sheltered by the foam, meaning that there is a very good possibility to tailor the shape of the foldable foam to the shape of the item.

[0017] Another advantage is that the at least one cutting line can be a straight cutting line, a curved cutting line, an angled cutting line comprising at least one angle, an irregularly shaped cutting line or any combination thereof, again meaning that there is a very good possibility to customize the shape of the foldable foam to the shape of the article.

[0018] Yet another advantage is that the at least one cutting line can be arranged to include at least one portion having a predetermined cutting depth less than the thickness of the cellulose foam and at least one portion having a predetermined cutting depth equal to the thickness of the cellulose foam. The portion having a predetermined cutting depth equal to the thickness of the cellulose foam means that the cutting line portion completely cuts through the foam, which can provide many design opportunities for the foam. For example, a through cut provides a portion of the cellulose foam that can be taken away, thereby leaving a gap that can contribute to a receiving chamber for enclosing an item.

[0019] The method for producing the flexible solid cellulose foam is cost-effective to be implemented in existing production lines.

[0020] The method may further result in cheaper and easier manufacturing and improved product quality.

[0021] The method is also easy to carry out in a large-scale setup.

[0022] Further aspects and embodiments are defined in the appended claims, which are specifically incorporated herein by reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The foregoing aspects and many of the attendant advantages of the present invention will become more readily understood as they become better appreciated by reference to the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0024] The present invention will be described in more detail with reference to the accompanying drawings, in which:

[0025] Figure 1a-1b shows a solid cellulose-based foam in respective unfolded and folded states, and

[0026] Figure 2a-2c Different views of an unfolded and folded solid cellulose-based foam are shown. DETAILED DESCRIPTION

[0027] Before disclosing and describing the present invention in detail, it should be understood that the present invention is not limited to the specific compounds, configurations, method steps, substrates and materials disclosed herein, because such compounds, configurations, method steps, substrates and materials may vary slightly. It should also be understood that the terminology employed herein is only for the purpose of describing specific embodiments and is not intended to be limiting, because the scope of the present invention is limited only by the appended claims and their equivalents.

[0028] It must be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0029] Unless otherwise defined, any terms and scientific terms used herein are intended to have the meaning commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0030] As used herein, a "plate" refers to an object that is flat and has an upper surface and a lower surface. Most typically, the surfaces are parallel surfaces, meaning that the plate has a uniform or at least substantially uniform thickness.

[0031] As used herein, "flexible" means curvable, stretchable, twistable, bendable, and / or foldable.

[0032] As used herein, "flexible material" refers to a material that can be curved, stretched, twisted, bent, and / or folded. The difference between folding and bending is that folding has a sharp angle that occurs in a narrow hinge area; whereas bending is a global deformation that results in a smoother curvature. Folding can be interpreted as a well-defined and precise form of bending that occurs about a folding axis.

[0033] As used herein, "rigid" means inflexible. A rigid material cannot be bent, stretched, twisted, bent, and / or folded without cracking and / or breaking into pieces.

[0034] As used herein, "predetermined depth of cut" means that the depth of a cut is predetermined prior to arranging or making the cut.

[0035] As used herein, the term "foam" refers to a substance made by trapping air or gas bubbles inside a solid or liquid. Typically, the volume of the gas is much greater than the volume of the liquid or solid, with a thin film separating the gas pockets. In order to form a foam, three requirements must be met. Mechanical work is required to increase the surface area. This can occur by agitation, dispersing large amounts of gas into the liquid, or injecting the gas into the liquid. The second requirement is that a foam former must be present, typically an amphiphilic substance, a surfactant, or a surface-active component, to reduce the surface tension. Finally, the foam must form faster than it decomposes.

[0036] As used herein, the term "cellulose foam" refers to a foam comprising cellulose and other components such as thickeners, surfactants and additives. The main component of the cellulose foam is cellulose, such that cellulose constitutes at least 70 wt % of the dry content of the cellulose foam. The cellulose is in the form of fibers, so the foam may also be defined as a cellulosic foam or a cellulose fiber foam. The cellulose foam may be wet or solid.

[0037] As used herein, the term "wet foam" or "wet cellulose foam" refers to a wet foam comprising cellulose and other components such as thickeners, surfactants, and additives. Gas bubbles are present within the wet foam. The wet foam is free-standing and behaves as a viscoelastic solid. This means that the wet foam has both viscous and elastic properties. The wet foam will behave as a solid, and therefore free-standing, unless a force large enough is applied that it begins to flow and behaves instead as a viscous material. Depending on the magnitude and time scale of any applied shear stress, the wet foam may exhibit predominantly viscous or elastic behavior.

[0038] As used herein, the term "solid cellulose foam" or "dry cellulose foam" refers to a dry porous cellulose material, i.e., a foam-formed material, that has been formed from a wet cellulose foam. During the drying process, the closed wet cellulose foam is converted into an open solid cellulose foam. The network of cellulose fibers is prevented from collapsing during drying. Therefore, the solid cellulose foam will have a shape that corresponds to the shape of the wet cellulose foam to a large extent. The dry content of the solid cellulose foam may be at least 95 wt %, calculated based on the total weight of the solid cellulose foam. The shape and density of the solid cellulose foam are also maintained in an unrestricted state. The solid cellulose foam has an open cell structure, allowing air to occupy the pores within the foam. The solid cellulose foam may also be described as a porous material or a low density material.

[0039] The following detailed description and the examples contained therein are provided only for the purpose of describing and illustrating certain embodiments of the present invention and are not intended to limit the scope of the present invention in any way.

[0040] In a first aspect, the present invention relates to a collapsible solid cellulose foam.

[0041] In a second aspect, the present invention provides a method for producing the collapsible solid cellulose foam.

[0042] The solid cellulose foam may preferably be prepared from a cellulose foam composition comprising:

[0043] a) 71 to 95 wt% of cellulose fibers, calculated based on the total weight of the solid content of the composition,

[0044] b) 4 to 24 wt% of a water-soluble thickener, based on the total weight of the solid content of the composition, and

[0045] c) at least two surfactants.

[0046] Cellulose fibers suitable for use in the present invention may be derived from wood, such as softwood or hardwood, from leaves or from fiber crops (including cotton, flax and hemp). Cellulose fibers suitable for use in the present invention may also be derived from regenerated cellulose such as rayon and lyocell. Cellulose fibers suitable for use in the present invention may include lignin or hemicellulose or both, or the cellulose fibers may be free of lignin and hemicellulose. Preferably, the cellulose fibers are derived from wood, and more preferably, the cellulose fibers are pulp fibers obtained by a pulping process that releases fibers from a wood matrix. Pulp fibers may be released by mechanical pulping to obtain mechanical pulp, such as thermomechanical pulp (TMP) or chemical thermomechanical pulp (CTMP), or released by chemical pulping, such as Kraft pulp or pulp obtained by sulfite process, soda process or organic solvent pulping process. More preferably, the cellulose fibers are pulp fibers released by chemical pulping processes. The different characteristics of each cellulose fiber will affect the properties of the final cellulose foam. The length of the cellulose fibers is significantly greater than their width. The cellulose fibers may have an average width of 0.01 to 0.05 mm. The fiber length of softwood can be 2.5 to 4.5 mm, while hardwood can have a fiber length of 0.7 to 1.6 mm, and eucalyptus can have a fiber length of 0.7 to 1.5 mm. However, the fiber length can vary significantly with different growing locations, etc. The cellulose fibers in the cellulose foam disclosed herein can have a length of 0.1 mm to 65 mm, or 0.1 mm to 10 mm, or 0.5 mm to 65 mm, or 0.5 mm to 10 mm, or 0.5 mm to 7 mm. The fiber length can provide different mechanical properties for the foam. Due to the length of the fiber, they can be entangled with each other and give the mutual combination of fiber and fiber, which brings strength to the foam. The aspect ratio (i.e., the ratio of fiber length to fiber width) of the cellulose fiber in the cellulose foam according to the present invention can be at least 10, at least 25, at least 50, at least 75 or at least 100, which provides the preservation and stability of the foam structure during the drying procedure, so that the wet cellulose foam with a shape retention can be dried. The aspect ratio may be up to 6500, or preferably up to 2000.

[0047] The cellulose fibers may be modified to provide different properties to the final cellulose foam. For example, phosphorylated fibers or periodate-oxidized fibers may also be used when producing cellulose foams according to the present invention.

[0048] The cellulosic fibers of the cellulosic foam composition may be selected from wood pulp; regenerated cellulose fibers; and plant fibers, such as fibers from bamboo, cotton, hemp, flax, and jute.

[0049] Preferably, the cellulosic fibers are selected from wood pulp, such as softwood pulp, hardwood pulp, chemi-thermomechanical pulp, and from dissolving pulp, or a combination of one or more of these.

[0050] More preferably, the cellulosic pulp fibers are selected from softwood pulp, chemi-thermomechanical pulp or dissolving pulp.

[0051] Most preferably, the cellulosic pulp fibers are selected from softwood pulp, such as softwood bleached kraft pulp.

[0052] The water-soluble thickener may be present in an amount of 4-24 wt % or 5-20 wt %, calculated based on the total weight of the solid content of the foam. The thickener may have a molecular weight of 80 000-250 000 g / mol, or 83 000-197 000 g / mol. Exemplary water-soluble thickeners are selected from carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxyethyl cellulose (HEC), ethyl hydroxyethyl cellulose (EHEC), methyl hydroxypropyl cellulose (MHPC), starch, xanthan gum, guar gum and xyloglucan or mixtures thereof.

[0053] The foam preferably comprises a mixture of at least two surfactants. One of the at least two surfactants is preferably a fast-acting surfactant that settles rapidly at the air-water interface during mechanical agitation during the preparation of the foam, which helps to form a foam with high density and high viscosity, and thus achieves a self-standing foam. Suitable surfactants for this purpose are anionic surfactants, preferably low molecular weight anionic surfactants. The low molecular weight anionic surfactant can be selected from sodium dodecyl sulfate (SDS); potassium dodecyl sulfate, sodium laureth sulfate (SLES); sodium dodecylbenzene sulfonate; sodium cocoyl sarcosinate; sodium lauroyl sarcosinate. The low molecular weight anionic surfactant is preferably selected from sodium dodecyl sulfate (SDS); sodium p-dodecylbenzene sulfonate; sodium cocoyl sarcosinate; and sodium lauroyl sarcosinate. More preferably, the low molecular weight anionic surfactant is sodium cocoyl sarcosinate. The anionic surfactant may be biodegradable.

[0054] The other of the at least two surfactants is preferably a cosurfactant. The cosurfactant may be selected from high pKa fatty acids, for example, selected from plant-derived raw materials, such as myristic acid, sodium oleate, lauric acid, palmitic acid and stearic acid; glucose-based cosurfactants with aliphatic carbon tails, such as alkyl glycosides, alkyl polyglucosides, alkyl thio-glycosides and alkyl maltosides; amphoteric betaines, such as cocamidopropyl betaine (CAPB) and sodium cocoimidodipropionate (CADP); polyethylene glycol sorbitan monolaurate, i.e. (For example 20. 80 and 85); and polyoxyethylene lauryl ethers, such as polyethylene glycol lauryl ether, pentaethylene glycol monododecyl ether and octaethylene glycol monododecyl ether.

[0055] The foam composition can preferably be prepared by a process comprising the following steps:

[0056] a) disintegrating cellulose fibers in water to obtain a pulp of cellulose fibers;

[0057] b) adding a thickener to the pulp obtained in a) to obtain a mixture of thickener and cellulose fibers in water;

[0058] c) adding the at least two surfactants to the mixture obtained in b) to obtain a fiber suspension;

[0059] d) aerating the suspension obtained in c) to obtain a wet foam,

[0060] The wet foam comprises 10-38 wt% of cellulose fibers, 0.5-10 wt% of the water-soluble thickener and 0.1-2 wt% of a surfactant, based on the total weight of the wet foam.

[0061] And wherein the wet foam has 140-500kg / m 3 density and yield stress of 40 to 400 Pa;

[0062] e) Drying the wet foam obtained in d) to obtain a dry cellulose foam.

[0063] The wet foam can be dried without the use of a mold, ie, the wet foam is free-standing and retains its shape during drying without the need for a mold.

[0064] The wet foam is uniform and has good stability due to the small bubble size (typically below 100 μm) obtained when the mixture of cellulose fibers, thickeners and surfactants is aerated. The wet foam does not flocculate during processing. During any subsequent processing or drying steps, the average bubble size is largely maintained, and the cellulose fibers remain well dispersed. The resulting solid cellulose foam obtained by drying the wet foam will be uniform, firm, have good mechanical properties, smooth surface and no defects in structure. In contrast, the wet cellulose foam with low stability has a larger average bubble size (i.e., typically above 100 μm) and the bubbles will coalesce faster during processing and drying to form larger bubbles. In addition, the cellulose fibers will form clusters during processing and drying. This causes the wet foam to collapse during drying. The resulting solid cellulose foam will not have a uniform structure and will also contain defects in the form of cavities produced by the coalesced bubbles in the wet foam. Due to the defects, such solid cellulose foam is weak and has a rough surface.

[0065] The dried cellulose foam obtained in step e) can be used as the solid cellulose foam in the present invention.

[0066] The dried cellulose foam obtained in step e) can be obtained by a process comprising the following steps:

[0067] Depositing discrete units of cellulose foam on a surface to obtain a first foam deposit, depositing wet cellulose foam between the discrete units to obtain subsequent foam deposits, and drying the wet foam to obtain a solid foam wherein the discrete units of foam are embedded in a foam matrix. The solid cellulose foam can then be used as the solid cellulose foam of claim 1 and its dependent claims.

[0068] However, without departing from the scope of the present invention, the solid cellulose foam may be prepared by other methods than those described above. For example, the solid cellulose foam may be prepared by a single deposition of wet foam into any desired shape. Optionally, any suitable confinement device may be used, such as a mold or a frame.

[0069] The solid cellulosic foam material can be prepared, for example, by depositing the foam composition on the forming section of a conventional papermaking machine for forming foam webs or a papermaking machine suitably modified for the purpose.

[0070] The production of solid cellulose foam comprises different production steps, one of which is a drying step. During the drying step, the outer surfaces of the foam (top surface, lower surface, side surfaces) will obtain an outer layer, which has different properties from the main part of the foam comprising a more uniform and porous open-cell fiber network. The outer layer has a higher density than the density of the main part, because the fibers are more closely packed and partly oriented differently. The main body is highly porous, and even if the densification layer has a denser structure than the core, it is still porous. The outer layer is called a "densification layer" or "densified outer layer". The densification layer will provide improved mechanical stability and improved strength to the foam.

[0071] The densification layer is a very thin layer that forms on the very outer surface of the cellulose foam during drying. The densification layer consists of cellulose fibers oriented primarily in a two-dimensional plane (xy plane), whereas the fibers in the bulk of the cellulose foam contain fiber clusters oriented in three-dimensional space with more empty spaces between the clusters. The two-dimensional structure of the cellulose fibers in the densification layer quickly but gradually transforms into the three-dimensional structure found in the bulk of the cellulose foam. The thin thickness of the densification layer means that it does not substantially affect the overall density of the cellulose foam.

[0072] Since the densified layer has improved mechanical stability and provides strength to the foam, it may be preferred to orient the surface comprising the densified layer towards a direction where additional stability may be required.

[0073] The improved properties of the densified layer are used in the location of the product where they can contribute to the protective properties of the product. Despite the higher density, the densified layer is still highly porous and breathable.

[0074] The first aspect will now be described in detail with reference to the accompanying drawings, the foldable solid cellulose foam comprising an upper surface and a lower surface, wherein at least one of the upper surface and the lower surface of the foldable solid cellulose foam comprises at least one cutting line having a predetermined cutting depth DC, wherein the at least one cutting line is arranged to partially cut through the cellulose foam.

[0075] Figure 1a and Figure 1b The first embodiment of the foldable solid cellulose-based foam 1 is shown in an oblique side view from above. Figure 1a In the figure, the cellulose foam is shown in an expanded state, while in Figure 1b In the figure, the cellulose foam 1 is shown in a folded state.

[0076] The foldable solid cellulose foam has a plate shape, and includes an upper surface 11 and a lower surface 12 , two long side surfaces 16 and two short side surfaces 17 .

[0077] The side surfaces 16, 17 have a height h. Preferably, the height h corresponds to the thickness T of the solid cellulose foam 1. The long side surfaces 16 and the short side surfaces 17 are rectangular surfaces 16, 17 defined by respective lengths L16, L17 and the height h, and wherein the respective lengths L16, L17 are longer than the height h.

[0078] According to the present invention, the cellulose foam 1 comprises at least one cutting line 2 having a predetermined cutting depth DC, and wherein the at least one cutting line 2 is arranged in the direction of the thickness T.

[0079] exist Figure 1a In the embodiment shown, the upper surface 11 comprises two cutting lines 2; a first cutting line 21 and a second cutting line 22 having respective predetermined cutting depths DC1 , DC2 , wherein the two cutting lines are arranged to cut partially through the cellulose foam 1 .

[0080] In the illustrated embodiment, the cutting lines 21, 22 are arranged to extend from one long side surface 16 to the other long side surface 16. The cutting lines 21, 22 are further arranged parallel to the short side surface 17 of the cellulose foam 1. The cutting lines 21, 22 have respective cutting lengths LC1, LC2 equal to the length L17 of the short side surface 17, so that the cutting lines 21, 22 also partially cut through the long side surface 16 and cut to the same predetermined cutting depths DC1, DC2.

[0081] The cutting lines 21 , 22 are arranged not as through cuts of the foam 1 . This means that the predetermined cutting depth DC1 , DC2 is smaller than the thickness T of the cellulose foam 1 .

[0082] The cutting lines 21 , 22 are arranged in the cellulose foam 1 such that they cut through the upper surface 11 and further into the core C of the foam, in a direction towards the lower surface 12 and, as previously described, in the thickness direction of the foam 1 .

[0083] exist Figure 1a In FIG. 2 , it is shown that the cutting lines 21 , 22 are arranged to extend in the Y / Z plane of the X / Y / Z space. The cutting lines 21 , 22 are straight cutting lines that each produce a flat cut in the foam 1 .

[0084] The cutting lines 21, 22 divide the cellulose foam 1 into three parts P1, P2, P3, wherein the first part P1 is formed by the first cutting line 21 and one of the short side surfaces 17. The second part P2 is formed by the second cutting line 22 and the other of the short side surfaces 17, and the third part P3 is formed between the first cutting line 21 and the second cutting line 22.

[0085] Since the cutting lines 21, 22 are arranged not to cut through the cellulose foam 1 but to terminate before reaching the lower surface 12, the two remaining uncut portions RUP1, RUP2 (eg Figure 1b ) remain in the cellulose foam 1. The two remaining uncut portions RUP1, RUP2 are located between the position where each of the cutting lines 21, 22 ends and the lower surface 12, and extend in the Y / Z plane.

[0086] Each of the remaining uncut portions RUP1 , RUP2 has a thickness TRUP1 , TRUP2 (not shown) in the Y direction which is equal to the thickness T of the cellulose foam minus the predetermined cutting depth DC1 , DC2 of the cutting lines 21 , 22 .

[0087] Furthermore, each of the remaining uncut portions RUP1 , RUP2 has an extension parallel to the cutting lengths LC1 , LC2 , and extends from one of the long side surfaces 16 to the other of the long side surfaces 16 .

[0088] Since the cutting lines 21, 22 are arranged not to cut through the cellulose foam 1 but to terminate before reaching the lower surface 12, the remaining uncut portions RUP1, RUP2 are left, which form respective first and second hinges H1, H2 for the cellulose foam 1 to be folded around.

[0089] The first portion P1 may be folded around the first hinge H1 , and the second portion P2 may be folded around the second hinge H2 .

[0090] Each of the hinges H1, H2 comprises a respective folding axis FA1, FA2 about which the cellulose foam 1 can be folded. The folding axes FA1, FA2 extend in the cellulose foam 1 in the Z direction. Figure 1a In the embodiment shown, the folding axes FA1 , FA2 are parallel to the short side surfaces 16 , 17 and to the length direction of the cutting lines 21 , 22 .

[0091] Preferably, the predetermined cutting depth DC of the at least one cutting line is 99% or less of the thickness T of the cellulose foam; preferably 80% or more of the thickness T of the cellulose foam, more preferably 90% or more and most preferably 90-99%.

[0092] As mentioned above, in Figure 1b , the cellulose foam 1 is shown in a folded state. The first portion P1 is folded around the first hinge H1 toward the lower surface 12, and the second portion P2 is folded around the second hinge H2 toward the lower surface 12. The third portion P3 forms the bottom of the folded cellulose foam 1, and the first portion P1 and the second portion P2 form the top of the folded cellulose foam 1.

[0093] In the folded state, the cutting lines 21, 22 form two cutting surfaces, a first cutting surface 210 and a second cutting surface 220. The cutting surfaces 210, 220 form new short side surfaces 17. For the sake of accuracy, it must be pointed out that due to the folding of the cellulose foam 1, the short side surfaces 17 may now be longer than the folded long side surfaces 16.

[0094] For embodiments of the invention comprising two or more cutting lines, the cutting lines may have equal predetermined cutting depths DC or different predetermined cutting depths DC. Figure 1a In the embodiment shown, the two cutting lines 21 , 22 have equal predetermined cutting depths DC1 , DC2 .

[0095] The at least one cutting line is arranged to cut into the cellulose foam 1 at a cutting angle CA to the at least one of the upper surface 11 and the lower surface 12. Which angle is chosen depends on the circumstances, for example on the shape of the object to be protected by the foldable solid cellulose foam. Figure 1a-1b In the embodiment, the cutting lines 21, 22 are arranged to cut into the cellulose foam 1 at a perpendicular cutting angle.

[0096] Preferably, at least the lower surface 12 comprises a densified outer layer 120. Then, the two cutting lines 21, 22 are arranged not to cut through the densified outer layer 120, or at least to cut through only a small part of the densified outer layer 120, so that the two remaining uncut parts RUP1, RUP2 comprise the densified outer layer forming the at least one hinge H (i.e. the two hinges H1, H2 in this embodiment).

[0097] In some embodiments, there is no clear, well-defined limit between the core C and the densified outer layer 110, 120. Instead, there is a gradual transition from the core C to the densified outer layer 110, 120, such that the core C gradually transitions to the densified outer layer 110, 120. For these embodiments, the at least one cutting line 2 may possibly cut through only a portion of the transition from the core C toward the densified outer layer 110, 120, but is arranged not to cut through the densified outer layer 110, 120; or at least cut through only a small portion of the densified outer layer 110, 120.

[0098] In some embodiments, it may be preferred that not only the lower surface 12 comprises the densified outer layer 120, but also the upper surface 11 comprises the densified outer layer 110. In such an embodiment, the cutting lines 21, 22 will cut through the densified outer layer 110 on the upper surface 11, but not through the densified outer layer 120 on the lower surface 12.

[0099] Figure 2a A second embodiment of the foldable solid cellulose-based foam 1 is shown in an oblique side view. The cellulose foam 1 is shown in an unfolded state.

[0100] Already about Figure 1a to Figure 1b The description also applies to Figure 2a to Figure 2c , and will not necessarily be repeated hereinafter.

[0101] Figure 2a The cutting line 2 shown in FIG. 1 is arranged in the upper surface 11 and enters into the core C and further towards the lower surface 12. It can be seen that the cutting line 2 is an angled cutting line 2 comprising eight vertical corners C1-C8.

[0102] The cutting line 2 divides the cellulose foam 1 into two parts P1, P2, wherein the first part P1 is formed by the first cutting line 2 and one of the long side surfaces 16. The second part P2 is formed between the cutting line 2 and the other of the long side surfaces 16. The words "long side surface" and "short side surface" may not necessarily mean that the long side surface is always longer than the short side surface. Depending on the size of the cellulose foam 1, it may also be the opposite.

[0103] The cutting line 2 comprises six cutting line portions 23. All six cutting line portions 23 have a predetermined cutting depth DC equal to the thickness T of the cellulose foam. This means that the six cutting line portions 23 are through-cutting lines 23. Three of the six through-cutting lines 23 form a first protruding portion PP1 contained in the first portion P1, while the other three of the six through-cutting lines 23 form a second protruding portion PP2 contained in the second portion P2. Each pair of the through-cutting lines 23 separates the protruding portions PP1, PP2 from the cellulose foam 1, so that the protruding portions P1, P2 can be removable, as will be discussed further below.

[0104] The cutting line 2 further comprises three cutting line portions 21 arranged to partially cut through the cellulose foam 1 such that the three cutting line portions 21 have a predetermined cutting depth DC that is less than the thickness T of the cellulose foam 1. Three remaining uncut portions RUP1, RUP2, RUP3 are thereby formed between the three cutting line portions 21 and the lower surface 12. Each of the three remaining uncut portions RUP1, RUP2, RUP3 forms a respective hinge H1, H2, H3 comprising a common folding axis FA for the cellulose foam 1 to fold around.

[0105] In some embodiments, the lower surface 12 includes a densified outer layer 120. In these embodiments, the three cutting line portions 21 arranged to partially cut through the cellulose foam 1 are arranged to extend from the upper surface 11 and in a direction toward the lower surface 12 into the core C between the upper surface 11 and the lower surface 12 and toward the densified outer layer 120 on the lower surface 12. The three cutting line portions 21 are further arranged not to cut through the densified layer 120 but to terminate before the densified outer layer 120, so that the three remaining uncut portions RUP1, RUP2, RUP3 include the densified outer layer 120, wherein the three remaining uncut portions RUP1, RUP2, RUP3 and the densified outer layer 120 form the three hinges H1, H2, H3.

[0106] Due to the combination of the hinges H1 , H2 , H3 and the removable protrusions PP1 , PP2 , the cellulose foam 1 is made foldable.

[0107] The folding of the cellulose foam 1 is performed by folding any one of the two parts P1, P2 around the folding axis FA using the hinges H1, H2, H3. As described above, since the protruding parts PP1, PP2 are removably arranged by the through-cut line 23, when any one of the two parts P1, P2 is folded around the folding axis FA, the first protruding part PP1 will be removed from the second part P2, and the second protruding part PP2 will be removed from the first part P1.

[0108] Figure 2b The folded state of the foldable cellulose foam 1 is shown. One or both of the first portion P1 and the second portion P2 of the cellulose foam 1 have been folded to a folding angle A. In the embodiment shown, the folding angle A is 90°, and the first portion P1 and the second portion P2 together form a vertical corner that can be used, for example, as a corner protector.

[0109] In the folded state of the cellulose foam 1, the first protruding portion PP1 and the second protruding portion PP2 form the outer side of the corner (at Figure 2c ). The corner comprises two edges, a first edge E1 and a second edge E2, wherein the first edge E1 is part of the first protruding portion PP1 and the second edge E2 is part of the second protruding portion PP2. Due to this aspect, the protruding portions PP1, PP2 and their respective edges E1, E2 help stabilize the corner and improve the mechanical properties of the corner, such as impact resistance.

[0110] This structural design of the corners allows the use of the entire foldable cellulose foam with no waste material in between.

[0111] As in Figure 2b-2c As can be seen in FIG. 1 , when the cellulose foam 1 is in its folded state, the first protruding portions PP1 form corresponding voids V2 in the second portion P2 of the foam 1 , while the second protruding portions PP2 form corresponding voids V1 in the first portion P1 .

[0112] The protruding portions PP1 , PP2 each include a surface S1 , S2 formed by a through-cut line 23 .

[0113] The lower surface 12 of the cellulose foam 1 forms the inner side of the corner and will face the corner of the product to be protected. The outer surface of the corner is formed by the upper surface 11 and the surfaces S1 , S2 of the protruding parts PP1 , PP2.

[0114] In a preferred embodiment of the present invention, at least one of said upper surface 11 and said lower surface 12 of said solid cellulose foam comprises a densified outer layer 110 , 120 .

[0115] In some embodiments, the at least one cutting line 2 is arranged to cut through one of the upper surface 11 and the lower surface 12 into the core C and up to - but not through - the densified outer layer 110, 120 of the other of the at least one of the upper surface 11 and the lower surface 12, so that the at least one remaining uncut portion RUP is the densified outer layer 110, 120 forming the at least one hinge H. In these embodiments, the predetermined cutting depth DC can be expressed as the thickness T of the cellulose foam 1 minus the thickness of the densified outer layer 110, 120 of the other of the at least one of the upper surface 11 and the lower surface 12.

[0116] Preferably, both the upper surface 11 and the lower surface 12 comprise the densified outer layer 110 , 120 .

[0117] Can think of such embodiment, wherein said at least one cutting line 2 is arranged to cut into said material at a cutting angle CA, and this cutting angle CA is not perpendicular to said upper surface or said lower surface, but is arranged to cut obliquely.In these embodiments, said cutting angle CA can be less than 90 ° or greater than 90 °.

[0118] It should be understood that in an embodiment in which the at least one cutting line 2 is arranged obliquely into at least one of the upper surface 11 and the lower surface 12 and further obliquely into the foam 1, the predetermined cutting depth DC is a component of the vector of the cutting length of the inclined cutting line, and wherein this component has the same direction as the thickness T (and most commonly the height h) of the foam.

[0119] The at least one cutting line 2 may further be arranged in a vertical direction, or a horizontal direction, or a direction between the vertical direction and the horizontal direction on at least one of the upper surface 11 or the lower surface 12. The direction to be selected depends on the shape of the object to be protected by the foldable solid cellulose foam 1.

[0120] It should also be understood that the at least one cutting line 2 is arranged to cut through at least one of the upper surface 11 and the lower surface 12 from one of the long side surfaces 16 to the other of the long side surfaces 16 or from one of the short side surfaces 17 to the other of the short side surfaces 17, so that the relevant side surfaces 16, 17 are also cut through to a predetermined cutting depth DC that is the same as the predetermined cutting depth through the upper surface 11 and / or the lower surface 12.

[0121] The at least one cutting line 2 is arranged to extend from one side surface 16, 17 to the opposite side surface 16, 17 and cut through the upper surface 11 or the lower surface 12 and at least one of the one side surface 16, 17 and the opposite side surface 16, 17, but does not cut through the other of the upper surface 11 or the lower surface 12, providing the cellulose foam 1 with at least one remaining uncut portion RUP, which extends from the one side surface 16, 17 to the opposite side surface 16, 17, thereby providing the cellulose foam 1 with at least one hinge portion H. The cellulose foam 1 is thereby foldable around the at least one hinge portion H.

[0122] For embodiments in which the at least one cutting line 2 is arranged to extend from one long side surface 16 to another long side surface 16 , the at least one cutting line 2 is preferably arranged parallel to the short side surface 17 and has a cutting length LC equal to the length L17 of the short side surface 17 .

[0123] For embodiments in which the at least one cutting line 2 is arranged to extend from one short side surface 17 to another short side surface 17 , the at least one cutting line 2 is preferably arranged parallel to the long side surface 16 and has a cutting length LC equal to the length L16 of the long side surface 16 .

[0124] When the at least one cutting line 2 is arranged in parallel with any one of the long side surface 16 and the short side surface 17 , the at least one cutting line 2 is perpendicular to the corner between the upper surface 11 or the lower surface 12 and the long side surface 16 or the short side surface 17 .

[0125] In some embodiments, two or more cutting lines 2 are arranged on at least one of the upper surface 11 and the lower surface 12 .

[0126] The foldable solid cellulose foam 1 may preferably comprise a flat surface.

[0127] Preferably, at least one of the upper surface 11 and the lower surface 12 is a flat surface, wherein the at least one cutting line 2 is arranged on the flat surface.

[0128] It should be understood that since the at least one cutting line 2 is arranged to extend in a direction from one edge to the opposite edge of at least one of the upper surface 11 and the lower surface 12 , the at least one cutting line 2 also cuts the at least one side surface 16 , 17 .

[0129] As previously mentioned, the height h of the at least one lateral surface 16 , 17 may be related to the thickness T of the foam 1 .

[0130] The height of the at least one side surface 16, 17 may be very small relative to the upper surface 11 and the lower surface 12. An example of a cellulose foam 1 having a small height relative to the upper surface 11 and the lower surface 12 is a cellulose foam board.

[0131] An example of a flat surface may be the surface of the solid cellulose foam board.

[0132] In some embodiments, both the upper surface 11 and the lower surface 12 of the cellulose foam 1 comprise at least one cutting line 2 having a predetermined cutting depth DC.

[0133] The at least one cutting line 2 of the upper surface 11 and the at least one cutting line 2 of the lower surface 12 may have the same direction or different directions.

[0134] It is also conceivable that at least one of the upper surface 11 and the lower surface 12 comprises at least two cutting lines 2 of different directions.

[0135] It is contemplated that the densified outer layers 110, 120 have different thicknesses depending on which surface the densified outer layers 110, 120 are disposed on. It is also contemplated that the densified outer layers 110, 120 may have the same thickness regardless of which surface the densified outer layers 110, 120 are disposed on.

[0136] The second aspect, a method for producing the foldable solid cellulose foam 1 material will now be described.

[0137] The method comprises the following steps:

[0138] - providing a solid cellulose foam 1 comprising an upper surface 11 and a lower surface 12;

[0139] - arranging at least one cutting line 2 having a predetermined cutting depth DC into at least one of said upper surface 11 and said lower surface 12 , whereby said at least one cutting line 2 is further arranged to cut partially through said solid cellulose foam 1 .

[0140] The cutting is performed by providing a cutting tool and arranging the cutting tool in contact with the at least one of the upper surface 11 and the lower surface 12. The cutting tool is then forced into the at least one of the upper surface 11 and the lower surface 12 and further into the core C of the cellulose foam 1, thereby arranging the at least one cutting line 2, 21, 22 to partially cut through the cellulose foam 1.

[0141] The cutting operation ends when the at least one cutting line 2 partially cuts through the solid cellulose foam 1, so that the predetermined cutting depth DC is less than the thickness T of the cellulose foam, thereby arranging at least one remaining uncut portion RUP between the at least one cutting line 2 and the other of the upper surface 11 and the lower surface 12.

[0142] The at least one remaining uncut portion RUP has a thickness TRUP equal to the thickness T of the cellulose foam 1 minus the predetermined cutting depth DC of the cutting line 2, wherein the at least one remaining uncut portion RUP forms at least one hinge H for the cellulose foam 1 to fold around.

[0143] The predetermined cutting depth DC of the at least one cutting line is arranged to be 99% or less, preferably 80% or more, more preferably 90% or more, and most preferably 90-99% of the thickness T of the cellulose foam 1 .

[0144] Preferably, at least one of the upper surface 11 or the lower surface 12 of the solid cellulose foam 1 is arranged to comprise a densified outer layer 110 , 120 .

[0145] The cutting tool further arranges the at least one cutting line 2 to extend from one of the upper surface 11 and the lower surface 12 into the core C between the upper surface 11 and the lower surface 12 and toward the densified outer layer 110, 120 on the other of the upper surface 11 and the lower surface 12; and arranges the at least one cutting line 2 to not cut through the densified layers 110, 120, but to terminate before the densified layers 110, 120, so that the at least one remaining uncut portion RUP includes the densified outer layer 110, 120. The at least one remaining uncut portion RUP and the densified outer layer 110, 120 thereby form the at least one hinge H.

[0146] The at least one cutting line 2 is arranged as a straight cutting line, a curved cutting line, an angled cutting line comprising at least one angle, an irregularly shaped cutting line or any combination thereof.

[0147] The at least one cutting line 2 may further be arranged to include at least one portion having a predetermined cutting depth DC less than the thickness T of the cellulose foam 1 , and at least one portion having a predetermined cutting depth DC equal to the thickness T of the cellulose foam 1 .

[0148] The foldable solid cellulose foam 1 may be arranged to comprise at least one cutting line 2 having a predetermined cutting depth DC equal to the thickness T of the cellulose foam.

[0149] The at least one cutting line 2 arranged to cut through the foam 1 may be arranged as a straight cutting line, a curved cutting line, an angled cutting line comprising at least one angle, a cutting line forming a closed loop, an irregularly shaped cutting line or any combination thereof.

[0150] The method further comprises arranging the at least one cutting line 2 to partially cut into the solid cellulose foam 1 in a direction perpendicular to at least one of the upper surface 11 and the lower surface 12 .

[0151] In some embodiments, the at least one cutting line 2 is arranged to partially cut into the solid cellulose foam 1 at an angle to the upper surface 11 or the lower surface 12, wherein the angle is less than 90° or greater than 90°.

[0152] In other embodiments of the method, the at least one cutting line 2 is arranged to cut obliquely into the foam 1. The at least one cutting line 2 cuts into the foam 1 at a cutting angle CA with the upper surface or the lower surface, wherein the cutting angle CA is less than 90° or greater than 90°.

[0153] The at least one cutting line 2 is arranged to extend in a direction from one edge to the opposite edge of the respective upper surface 11 or lower surface 12; the at least one cutting line thereby forms an angle EA with the edge.

[0154] In some embodiments, the method further comprises arranging at least one cutting line 2 having a predetermined cutting depth DC into both the upper surface 11 and the lower surface 12. It should be understood that the predetermined cutting depth DC may be the same on both sides or may be different on different surfaces 11, 12 of the foam 1. It should also be understood that the at least one cutting line 2 of the upper surface 11 and the at least one cutting line 2 of the lower surface 12 may be arranged to have the same direction or to have different directions.

[0155] The method further comprises arranging at least one of the upper surface 11 or the lower surface 12 of the solid cellulose foam 1 to comprise the densified outer layer 110 , 120 ; and preferably arranging the at least one of the upper surface 11 or the lower surface 12 to comprise the densified outer layer 110 , 120 .

[0156] In some embodiments, the method includes arranging the at least one cutting line 2 to cut through one of the upper surface 11 and the lower surface 12 into the core C and up to - but not through - the densified outer layer 110, 120 of the other of at least one of the upper surface 11 and the lower surface 12, so that the at least one remaining uncut portion RUP is the densified outer layer 110, 120 forming the at least one hinge H. In these embodiments, the predetermined cutting depth DC can be expressed as the thickness T of the cellulose foam 1 minus the thickness of the densified outer layer 110, 120 of the other of at least one of the upper surface 11 and the lower surface 12.

[0157] Materials and material properties

[0158] The cellulose fibers comprised in the solid cellulose foam are preferably selected from wood pulp; regenerated cellulose fibers; and plant fibers; preferably selected from softwood pulp, chemithermomechanical pulp (CTMP) and dissolving pulp or a combination thereof.

[0159] The solid cellulose foam preferably comprises:

[0160] a) 71 to 95 wt% of cellulose fibers, calculated based on the total weight of the solid content of the foam,

[0161] b) 4 to 24 wt% of a water-soluble thickener, based on the total weight of the solids content of the foam, and

[0162] c) at least two surfactants.

[0163] The density of the solid cellulose foam can be between 10 and 80 kg / m 3 , preferably 10-60kg / m 3 And more preferably 20-50kg / m 3 within the range.

[0164] At least one of the upper surface or the lower surface of the solid cellulose foam comprises a densified outer layer.Preferably, both the upper surface and the lower surface comprise the densified outer layer.

[0165] The cellulose foam may have a thickness in the interval of 5-200 mm, more preferably 10-100 mm or 10-50 mm.

[0166] An example of conceivable dimensions is a solid cellulose foam board having a thickness of 40-60 mm, preferably about 50 mm.

[0167] The dimensions described are used as examples only and should not be considered to limit the products of the present invention to the described dimensions.

[0168] The collapsible solid cellulose foam may comprise compressed areas and through cuts creating through pores.

[0169] The volume of the through cut contributes to the receiving chamber for enclosing the product, while the partial cut defines a surface which is then pressed, thereby forming a compressed area. The volume of the compressed area also contributes to the receiving chamber for the item to be packaged and protected. Therefore, the arrangement of the receiving chamber in the solid cellulose foam does not result in waste material.

[0170] The partial cutouts allow the product to be perfectly positioned and add crucial extra protection in the packaging. The pressed details of the solid cellulose foam ensure correct positioning of the heaviest and / or most fragile parts of the item and ensure they are held in place.

[0171] Compressing well-defined portions of the solid cellulose foam to a higher density compressed material increases the stiffness and resilience of the solid cellulose foam in these portions. This provides a means for maintaining the product in position within the protective packaging insert.

[0172] Portions of the cellulose foam sheet can be folded toward the product so that the cut or compressed portion of the solid cellulose foam sheet is in direct contact with the product. The very good cushioning capacity of the solid cellulose foam sheet effectively shields the product; the cut or compressed portion fixedly arranged on the substrate helps to position the item during insertion and provides additional protection.

[0173] At least one of the upper surface and the lower surface may be a curved surface.

[0174] The terms "long side surface" and "short side surface" are merely exemplary terms used with respect to the drawings. It should be understood that the at least one cutting line may be arranged in a direction parallel or substantially parallel to or at an angle to any one of the long side surface and the short side surface.

[0175] As will be appreciated by those skilled in the art, numerous changes and modifications may be made to the above-described and other embodiments of the invention without departing from the scope of the invention as defined in the appended claims.

[0176] It should be noted that the above aspects may be the subject of their own protection, for example in a separate divisional application. Thus, it is foreseeable that this aspect of the invention may require its own protection, for example because it may also be applicable to other concepts than those defined by the independent claims in this application.

Claims

1. A foldable solid cellulose foam, wherein the foldable solid cellulose foam comprises an upper surface (11) and a lower surface (12); wherein at least one of the upper surface (11) and the lower surface (12) of the foldable solid cellulose foam (1) comprises at least one cutting line (2) having a predetermined cutting depth (DC); wherein the at least one cutting line (2) is arranged to partially cut through the cellulose foam (1).

2. The foldable solid cellulose foam according to claim 1, wherein the predetermined cutting depth (DC) is smaller than the thickness (T) of the cellulose foam (1) between the upper surface and the lower surface (11, 12).

3. A foldable solid cellulose foam according to any one of the preceding claims, wherein the cellulose foam (1) further comprises two long side surfaces (16) and two short side surfaces (17), and wherein the at least one cutting line (2) is arranged to also cut the two long side surfaces (16) or the two short side surfaces (17).

4. A foldable solid cellulose foam according to any one of the preceding claims, wherein at least one remaining uncut portion (RUP) is located between the at least one cutting line (2) and another surface of at least one of the upper surface (11) and the lower surface (12) comprising the at least one cutting line, and wherein the at least one remaining uncut portion (RUP) forms at least one hinge (H) for the cellulose foam (1) to be folded around.

5. A foldable solid cellulose foam according to any one of the preceding claims, wherein the predetermined cutting depth (DC) of the at least one cutting line is 99% or less of the thickness (T) of the cellulose foam (1); preferably 80% or more of the thickness (T) of the cellulose foam (1), more preferably 90% or more, and most preferably 90%-99%.

6. A foldable solid cellulose foam according to any one of the preceding claims, wherein at least one of the upper surface (11) and the lower surface (12) of the solid cellulose foam (1) comprises a densified outer layer (110, 120).

7. A foldable solid cellulose foam according to claim 6, wherein the at least one cutting line (2) is arranged to extend from one of the upper surface (11) and the lower surface (12) into the core (C) between the upper surface and the lower surface (11, 12) and extend toward the densified outer layer (110, 120) on the other of the upper surface and the lower surface (11, 12); the at least one cutting line (2) is arranged not to cut through the densified layer (110, 120), so that the at least one remaining uncut portion (RUP) contains the densified outer layer (110, 120).

8. The collapsible solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line (2) is a straight cutting line, a curved cutting line, an angled cutting line comprising at least one angle, an irregularly shaped cutting line or any combination thereof.

9. A foldable solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line (2) comprises at least one portion (21, 22) having a predetermined cutting depth (DC1, DC2) less than the thickness (T) of the cellulose foam and at least one portion (23) having a predetermined cutting depth equal to the thickness (T) of the cellulose foam (1).

10. A foldable solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line (2) is arranged to partially cut into the cellulose foam in a direction perpendicular to the at least one of the upper surface (11) and the lower surface (12).

11. A foldable solid cellulose foam according to any one of the preceding claims, wherein the solid cellulose foam (1) has a density of 10-80 kg / m 3 , preferably 10-60kg / m 3 within the range.

12. A collapsible solid cellulose foam according to any one of the preceding claims, wherein the solid cellulose foam comprises: a) 71 to 95 wt% of cellulose fibers, calculated based on the total weight of the solid content of the foam, b) 4 to 24 wt% of a water-soluble thickener, based on the total weight of the solids content of the foam, and c) at least two surfactants.

13. A method for producing a foldable solid cellulose foam, the method comprising the steps of: - providing a solid cellulose foam (1) comprising an upper surface (11) and a lower surface (12); - arranging at least one cutting line (2) having a predetermined cutting depth (DC) into at least one of the upper surface (11) and the lower surface (12), whereby the at least one cutting line (2) is further arranged to cut partially through the solid cellulose foam (1).

14. The method according to claim 13, wherein the at least one cutting line (2) is arranged to cut partially through the solid cellulose foam (1) so that the predetermined cutting depth (DC) is less than the thickness (T) of the cellulose foam (1) between the upper surface and the lower surface (11, 12).

15. The method according to claim 13 or 14, wherein at least one remaining uncut portion (RUP) is arranged between the at least one cutting line (2) and the other surface of at least one of the upper surface (11) and the lower surface (12) of the foldable solid cellulose foam (1) containing the at least one cutting line (2); the at least one remaining uncut portion (RUP) forms at least one hinge (H) for the cellulose foam (1) to be folded around.

16. The method according to any one of claims 13-15, wherein the predetermined cutting depth (DC) of the at least one cutting line (2) is 99% or less of the thickness T of the cellulose foam, preferably 80% or more of the thickness T of the cellulose foam (1), more preferably 90% or more, and most preferably 90-99%.

17. A method according to any one of claims 13 to 16, wherein at least one of the upper surface (11) or the lower surface (12) of the solid cellulose foam (1) is arranged to comprise a densified outer layer (110, 120).

18. The method according to claim 17, wherein the at least one cutting line (2) is arranged to extend from one of the upper surface (11) and the lower surface (12) into the core (C) between the upper surface and the lower surface (11, 12), and extends toward the densified outer layer (110, 120) on the other of the upper surface (11) and the lower surface (12); and the at least one cutting line (2) is arranged not to cut through the densified outer layer (110, 120), so that the at least one remaining uncut portion (RUP) includes the densified outer layer (110, 120).

19. The method according to any one of claims 13-18, wherein the at least one cutting line (2) is arranged as a straight cutting line, a curved cutting line, an angled cutting line comprising at least one angle, an irregularly shaped cutting line or any combination thereof.

20. The method according to any one of claims 13 to 19, wherein the at least one cutting line (2) is arranged to include at least one portion having a predetermined cutting depth (DC) less than the thickness (T) of the cellulose foam, and at least one portion having a predetermined cutting depth (DC) equal to the thickness (T) of the cellulose foam.

21. Method according to any one of claims 13-20, wherein the at least one cutting line (2) is arranged to cut partially into the solid cellulose foam (1) in a direction perpendicular to at least one of the upper surface (11) and the lower surface (12).

22. The method according to any one of claims 13 to 21, wherein the at least one cutting line (2) is arranged to partially cut into the solid cellulose foam (1) at a certain angle to the upper surface (11) or the lower surface (12), wherein the angle is less than 90° or greater than 90°.

23. The method according to any one of claims 13 to 22, wherein the density of the solid cellulose foam (81) is between 10 and 80 kg / m 3 , preferably 10-60kg / m 3 within the range.

24. The method according to any one of claims 13 to 23, wherein the solid cellulose foam material (1) comprises: a) 71 to 95 wt% of cellulose fibers, calculated based on the total weight of the solid content of the foam, b) 4 to 24 wt% of a water-soluble thickener, based on the total weight of the solids content of the foam, and c) at least two surfactants.

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