Flexible solid cellulose foam

Abstract

A flexible solid cellulose foam, wherein the flexible 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 flexible 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 flexible solid cellulose foam.

Description

Technical Field

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

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

[0003] In a society striving to reduce plastic use and waste and move towards renewable materials, plastic packaging materials such as fossil-based foams appear increasingly out of place. With regulators now pushing for policies that trend towards restricting or banning fossil-based foam materials in packaging, new solutions are needed.

[0004] There are many challenges in finding foams from renewable resources. Many bio-based foams have higher production costs and lower mechanical properties, as well as poor stability in water or high temperatures compared to long-established foams from oil-based sources. Bio-based and recyclable protective materials need to have the same excellent properties and performance as petroleum-based protective materials to be preferred over petroleum-based materials.

[0005] The low weight and good shock absorption of bio-based foams are examples of critically important properties. Furthermore, the ability to tailor the shape and form of the bio-based foam to the shape and form of the goods to be shielded by the protective material is extremely important. As the most abundant renewable natural polymer on earth, cellulose has been shown to have particular potential due to its crystalline structure and the availability of methods for its preparation in large quantities on an industrial scale.

[0006] Several bio-based foams containing cellulose have been described. WO20200011587A1 describes a porous material prepared by aerating a paste containing cellulose fibers and gluten and depositing the aerated paste in a mold where the paste 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 into a mold where the cellulosic foam is dried to produce a dry cellulosic product.

[0007] In packaging applications, the goods to be shielded may often have protruding parts or complex three-dimensional (3D) shapes that require additional protection by the packaging material during storage and transportation. In addition, the goods may be made of susceptible materials (e.g., glass, porcelain) that require protection due to their fragility. In such applications, solid cellulose foams may be an interesting alternative. 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 for protruding parts or complex 3D shapes. It is often impossible to bend 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 goods of any shape and protect every part of the goods. The goods need to be well shielded so that any impact generated during storage and transportation will be absorbed by the surrounding cellulose foam and thus, the impact will not damage the goods.

[0009] Furthermore, solid cellulose foams need to be renewable, biodegradable, and fully recyclable in the stream of ordinary paper and board, allowing them to become part of the circular material stream in the existing packaging waste management system. To be a competitive option, the production cost of producing the foam and customizing the shape of the foam into any product shape must be moderate.

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

[0011] Furthermore, there is a need for protective packaging materials that can be easily transported to where the goods are to be packaged in the protective packaging materials, provide three-dimensional customized protection for the goods, and 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 flexible solid cellulose foam.

[0013] The solid cellulose foam provides flexibility such that the foam can be wrapped around the curved shape of the goods to be protected due to the solution as defined in claim 1. The solid cellulose foam can further be stretched, bent and twisted without any risk of cracking and breaking.

[0014] Another advantage is that the flexible solid cellulose foam is a flat material that takes up very little space when stored or during transport to the point of use. Furthermore, since the solid cellulose foam can be stretched, bent, folded and / or twisted, the foam can be customized around three-dimensional objects, even with complex shapes.

[0015] Another advantage is that the predetermined cutting depth DC is less than the thickness T of the cellulose foam, thereby allowing the foam to remain in one piece. No waste material is cut away.

[0016] A further advantage is that the direction of the cut into the foam is chosen according to the shape of the goods to be shielded by the foam, which means that there is a very good possibility to tailor the shape of the flexible foam to the shape of the goods.

[0017] The method for producing the flexible solid cellulose foam is cost-effective to be implemented in existing production lines.

[0018] The method may further lead to cheaper and easier manufacturing and improved product quality.

[0019] The process is also easy to carry out in large-scale equipment.

[0020] Further aspects and embodiments are defined in the appended claims, which are specifically incorporated herein by reference. DETAILED DESCRIPTION

[0021] Before the present invention is disclosed and described 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.

[0022] 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.

[0023] 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 this invention belongs.

[0024] As used herein, the expression "flat object" means an object having a height, a width and a length. The width and the length define two surfaces, and the height defines at least one side wall. The height is so small relative to the length and the width that the object is considered to be a flat object. Examples of flat objects are boards, tabletops, wall mirrors, door panels, glass panes, solar panels. The expression "flat" refers to an object having a horizontal surface without any protrusions or depressions.

[0025] As used herein, "plate" refers to an object that is flat and has an upper surface and a lower surface. Most often, the surfaces are parallel surfaces.

[0026] As used herein, "flexible" means capable of bending, stretching, twisting, and / or flexing.

[0027] As used herein, "flexible material" refers to a material that can be bent, stretched, twisted, and / or flexed.

[0028] As used herein, "rigid" means inflexible. A rigid material cannot be bent, stretched, twisted, and / or flexed without cracking and / or breaking into pieces.

[0029] As used herein, "predetermined depth of cut" means that the depth of a cut is predetermined prior to placing or making the cut.

[0030] 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 larger 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 stirring, dispersing a large amount of gas into the liquid, or injecting the gas into the liquid. The second requirement is that a foam former (typically an amphiphilic substance), a surfactant, or a surface-active component must be present to reduce surface tension. Finally, the foam must form more quickly than the foam bursts.

[0031] 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. Cellulose has the form of fibers, and therefore, the foam may also be defined as a cellulosic foam or a cellulose fiber foam. The cellulose foam may be wet or solid.

[0032] As used herein, the term "wet foam" or "wet cellulose foam" refers to a wet foam that contains cellulose and other components (such as thickeners, surfactants, and additives). Air bubbles are present within the wet foam. The wet foam is self-standing and behaves as a viscoelastic solid. This means that the wet foam has both viscosity and elasticity. The wet foam will behave as a solid and is thus self-standing, unless a large enough force is applied to cause it to start flowing and instead behave as a viscous material. Depending on the magnitude and time scale of any applied shear stress, the wet foam can exhibit predominantly viscous or elastic behavior.

[0033] As used herein, the term "solid cellulose foam" or "dry cellulose foam" refers to a dry, porous cellulose material that has been formed from a wet cellulose foam (i.e., the foam-forming material). During the drying process, the closed-cell wet cellulose foam is converted into an open-cell solid cellulose foam. During drying, the network of cellulose fibers is prevented from collapsing. Thus, the solid cellulose foam will have a shape that largely corresponds to the shape of the wet cellulose foam. The dry content of the solid cellulose foam can 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 kept unrestricted. The solid cellulose foam has an open-cell structure that allows air to occupy the pores within the foam. The solid cellulose foam can also be described as a porous material or a low-density material.

[0034] 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.

[0035] In a first aspect, the present invention relates to a flexible solid cellulose foam.

[0036] In a second aspect, the present invention provides a method for producing the flexible solid cellulose foam.

[0037] The solid cellulose foam can preferably be prepared from a cellulose foam composition comprising:

[0038] a) 71 - 95 wt% of cellulose fibers, calculated based on the total weight of the solid content of the composition,

[0039] b) 4 - 24 wt% of a water-soluble thickener, calculated based on the total weight of the solid content of the composition, and

[0040] c) at least two surfactants.

[0041] Cellulosic fibers suitable for use in the present invention may be derived from wood (e.g., softwood or hardwood), from leaves, or from fiber crops (including cotton, flax, and hemp). Cellulosic fibers suitable for use in the present invention may also be derived from regenerated cellulose, such as rayon and Lyocell. Cellulosic 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 in which the fibers are released from a wood matrix. The pulp fibers may be released as follows: by mechanical pulping to obtain mechanical pulp, such as thermomechanical pulp (TMP) or chemical thermomechanical pulp (CTMP); or, 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 a chemical pulping process. The different characteristics of each cellulose fiber will affect the properties of the final cellulose foam. Compared to the width of the cellulose fibers, it is significantly longer. The cellulose fibers may have an average width of 0.01-0.05 mm. The fiber length of softwood can be 2.5-4.5mm, while hardwood can have a fiber length of 0.7-1.6mm, and eucalyptus is 0.7-1.5mm. However, the fiber length can vary considerably with different growing locations, etc. The cellulose fibers in the cellulose foam disclosed herein can have a length of 0.1mm-65mm, or 0.1mm-10mm, or 0.5mm-65mm, or 0.5mm-10mm, or 0.5mm-7mm. The fiber length can provide different mechanical properties for the foam. Due to the length of the fibers, they can entangle with each other and give the mutual combination of fibers to fibers (which brings strength to the foam). The aspect ratio (i.e., the ratio of fiber length to fiber width) of the cellulose fibers 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 retention and stability of the foam structure during the drying procedure, making it possible to dry the wet cellulose foam in a retained shape. The aspect ratio can be up to 6500, or preferably up to 2000.

[0042] 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.

[0043] 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.

[0044] Preferably, the cellulosic fibers are selected from: wood pulp, such as softwood pulp, hardwood pulp, chemithermomechanical pulp; and dissolving pulp; or a combination of one or more of these.

[0045] More preferably, the cellulosic pulp fibers are selected from softwood pulp, chemithermomechanical pulp, or dissolving pulp.

[0046] Most preferably, the cellulosic pulp fibers are selected from softwood pulps, such as softwood kraft bleached pulp.

[0047] The water-soluble thickener can be present in an amount of 4-24wt% or 5-20wt%, calculated by the total weight of the solid content of the foam. The thickener can have a molecular weight of 80000-250000g / mol or 83000-197000g / 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.

[0048] 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 stirring during the preparation of the foam, which helps to form a foam with high density and high viscosity and is therefore able to become a self-standing foam. Suitable surfactants for this purpose are anionic surfactants, preferably low molecular weight anionic surfactants. Low molecular weight anionic surfactants can be selected from: sodium dodecyl sulfate (SDS); potassium dodecyl sulfate, sodium laureth sulfate (SLES); sodium dodecylbenzene sulfonate; sodium cocoyl sarcosinate; sodium lauroyl sarcosinate. Low molecular weight anionic surfactants are preferably selected from: sodium dodecyl sulfate (SDS); sodium p-n-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.

[0049] The other of the at least two surfactants is preferably a cosurfactant. The cosurfactant may be selected from: high pKa fatty acids, such as raw materials of plant origin, 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 thioglycosides, 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.

[0050] The foam composition can preferably be prepared by a method comprising the following steps:

[0051] a) decomposing cellulose fibers in water to obtain a slurry of cellulose fibers;

[0052] b) adding a thickener to the slurry obtained in a) to obtain a mixture of thickener and cellulose fibers in water;

[0053] c) adding the at least two surfactants to the mixture obtained in b) to obtain a fiber suspension;

[0054] d) aerating the suspension obtained in c) to obtain a wet foam,

[0055] The wet foam comprises 10-38 wt% of cellulose fibers, 0.5-10 wt% of a water-soluble thickener, and 0.1-2 wt% of a surfactant, calculated based on the total weight of the wet foam, and the wet foam has a density of 140-500 kg / m 3 Density and yield stress of 40-400Pa;

[0056] e) drying the wet foam obtained in d) to obtain a dry cellulose foam.

[0057] 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.

[0058] 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 is homogeneous and has good stability. The wet foam does not flocculate during processing. During any subsequent processing or drying steps, the average bubble size remains unchanged to a large extent, 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 merge faster during processing and drying, so that larger bubbles are formed. 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 generated by the merged bubbles in the wet foam. Due to the defects, such solid cellulose foam is not firm and has a rough surface.

[0059] The dried cellulose foam obtained in step e) can be used as solid cellulose foam.

[0060] The dried cellulose foam obtained in step e) may be obtained by a process comprising:

[0061] depositing discrete cells of cellulose foam on a surface to obtain a first foam deposition,

[0062] depositing wet cellulose foam between said discrete cells to obtain subsequent foam deposition, and,

[0063] The wet foam is dried to obtain a solid foam wherein discrete cells 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.

[0064] 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 means may be used, such as a mold or a frame.

[0065] The solid cellulosic foam material can be prepared, for example, by depositing the foam composition onto the forming section of a conventional papermaking machine for forming foam webs or onto a papermaking machine suitably adapted for this purpose.

[0066] 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 with different properties from the body part of the foam, which comprises a more uniform and porous open-cell fiber network. The outer layer has a higher density than the density of the body part because the fibers are more closely packed and partly oriented differently. The outer layer is called a "densification layer" or "densified outer layer". The densification layer will provide improved mechanical stability and improved strength for the foam.

[0067] Because 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.

[0068] The improved properties of the densified layer are used in various locations of the product where they can contribute to the protective properties of the product.Despite having a higher density, the densified layer is still highly porous and breathable.

[0069] The first aspect: the flexible solid cellulose foam will now be described in detail.

[0070] The flexible solid cellulose foam comprises an upper surface and a lower surface.

[0071] The flexible solid cellulose foam further comprises at least one side surface having a height H. Preferably, the height H corresponds to a thickness T of the solid cellulose foam.

[0072] At least one of the upper surface and the lower surface of the flexible 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 cut partially through the cellulose foam.

[0073] The cutting line is arranged not to be a through cut of the foam. This means that the predetermined cutting depth DC is smaller than the thickness T of the cellulose foam.

[0074] The predetermined cutting depth DC of the at least one cutting line is 99% or less, preferably 95% or less, and more preferably 90% or less of the thickness T of the cellulose foam.

[0075] The at least one cutting line is arranged to cut into the cellulose foam at a cutting angle CA to the at least one of the upper and lower surfaces. The angle chosen depends on the circumstances, for example on the shape of the object to be protected by the flexible solid cellulose foam.

[0076] In some embodiments, the at least one cutting line is arranged to cut into the cellulose foam in a direction perpendicular to the at least one of the upper surface and the lower surface.

[0077] In other embodiments, the at least one cutting line is arranged to cut into the material at a cutting angle CA that is not perpendicular to the upper surface or the lower surface. The cutting angle CA may be less than 90° or greater than 90° in these embodiments.

[0078] Embodiments are envisioned wherein the cutting angle CA may be in the interval 30-80° or 100-150°.

[0079] It should be understood that in embodiments wherein the at least one cutting line is arranged obliquely into the at least one of the upper surface and the lower surface and further into the foam, the predetermined cutting depth DC is a component of the vector of the cutting length of the inclined cutting line and thereby this component has the same direction as the thickness T (and most often the height H) of the foam.

[0080] The at least one cutting line may further be arranged on at least one of the upper or lower surface in a vertical direction, or a horizontal direction, or a direction between the vertical direction and the horizontal direction. The direction to be selected depends on the shape of the object to be protected by the flexible solid cellulose foam.

[0081] The direction between the vertical direction or the horizontal direction on the at least one of the upper surface or the lower surface may be, for example, a diagonal direction, ie, 45°.

[0082] In other words, the at least one cutting line is arranged to extend in a direction from one edge E of at least one of the upper surface and the lower surface to an opposite edge E, wherein the edge E is an edge E formed by at least one side surface and the upper surface or the lower surface.

[0083] The at least one cutting line is arranged to intersect the edge at an edge angle EA; the edge angle EA is in the interval of 10-170°.

[0084] In some embodiments, the at least one cutting line is arranged to intersect the edge at an edge angle EA of 90°, ie, the at least one cutting line intersects the edge E perpendicularly.

[0085] The flexible solid cellulose foam may contain 0.1-5 cutting lines per centimeter, preferably, 0.5-2 cutting lines per centimeter. In some embodiments, the flexible solid cellulose foam may contain 0.1-10 cutting lines per centimeter.

[0086] In some embodiments, the flexible solid cellulose foam may comprise 0.2-5 cut lines per centimeter, for example, 0.2-2, or 0.5-5 cut lines per centimeter.

[0087] Thus, the spacing between adjacent cut lines in the solid cellulose foam may be 1 mm to 10 cm, or 2 mm to 10 cm, or 5 mm to 2 cm, or 5 mm to 5 cm, or 2 mm to 2 cm.

[0088] The flexibility of the solid cellulose foam can be controlled by the number of cut lines per centimeter and can be customized for a specific application. When the number of cut lines per centimeter is high, the flexibility is high. However, the stability of the foam can be negatively affected by the high number of cut lines per centimeter, so that the integrity of the foam is reduced, which can affect the cushioning properties. Therefore, there is a compromise between high flexibility and good structural integrity of the foam. In a preferred embodiment, the solid cellulose foam contains 0.5-2 cut lines per centimeter. In such a range, good flexibility is obtained while maintaining the good cushioning properties of the foam.

[0089] Preferably, the flexible solid cellulose foam comprises a plurality of cut lines, for example, at least three cut lines, or at least four cut lines, or at least five cut lines.

[0090] In some embodiments, two or more cutting lines may be evenly distributed on at least one of the upper surface and the lower surface.

[0091] In other embodiments, the two or more cutting lines are unevenly distributed on at least one of the upper surface and the lower surface.

[0092] The number, spacing, orientation and / or distribution of the cutting lines depends on the intended use of the solid cellulose foam. A narrow spacing of the cutting lines may result in improved flexibility of the flexible solid cellulose foam. Providing cutting lines on both the upper surface and the lower surface may also improve flexibility. In embodiments in which cutting lines are provided on both the upper surface and the lower surface of the flexible solid cellulose foam, the number, spacing, orientation and / or distribution of the cutting lines may be the same on the upper surface and the lower surface, or may be different on both surfaces.

[0093] The flexible solid cellulose foam may comprise a flat surface.

[0094] Preferably, at least one of the upper surface and the lower surface is a flat surface, wherein the at least one cutting line is arranged on the flat surface.

[0095] It should be understood that since the at least one cutting line is arranged to extend in a direction from one edge E of at least one of the upper surface and the lower surface to the opposite edge E, the at least one cutting line also cuts the at least one side surface.

[0096] As previously mentioned, the height H of the at least one side surface may be related to the thickness T of the foam.

[0097] The height of the at least one side surface may be very small relative to the upper and lower surfaces.An example of a foam material having a small height relative to the upper and lower surfaces is a cellulose foam board.

[0098] An example of a flat surface may be the surface of the solid cellulose foam board.

[0099] In some embodiments, both the upper surface and the lower surface of the foam material comprise at least one cut line having a predetermined cut depth.

[0100] The at least one cutting line of the upper surface and the at least one cutting line of the lower surface may have the same direction.

[0101] The at least one cutting line of the upper surface and the at least one cutting line of the lower surface may have different directions.

[0102] Furthermore, it is conceivable that at least one of the upper surface and the lower surface includes at least two cutting lines in different directions.

[0103] In one embodiment, at least one of the upper surface and the lower surface may include diagonally arranged cutting lines. At least one cutting line may be arranged at an edge angle EA of 45°, while at least one other cutting line may be arranged at an angle EA of 135°; i.e., on the other diagonal of the at least one of the upper surface and the lower surface.

[0104] In other embodiments, at least one of the upper surface and the lower surface may include at least one horizontally arranged cutting line and at least one vertically arranged cutting line, wherein the two cutting lines in different directions together form a grid.

[0105] Furthermore, it is contemplated that the cutting angle CA may vary on the at least one of the upper surface and the lower surface.

[0106] Furthermore, it is contemplated that in embodiments where both the upper and lower surfaces include at least one cut line, the cut angle CA may be different on different surfaces.

[0107] In a preferred embodiment, at least one of the upper surface and the lower surface of the solid cellulose foam comprises a densified outer layer.

[0108] Preferably, both said upper surface and said lower surface comprise said densified outer layer.

[0109] In a preferred embodiment, at least one of the upper surface and the lower surface comprising the at least one cutting line further comprises the densified outer layer.

[0110] The at least one cutting line is arranged to cut through the densified outer layer and into at least one of the upper surface and the lower surface and further into the core of the solid cellulose foam material until the predetermined cutting depth DC is reached.

[0111] The predetermined cutting depth DC may be 99% or less, more preferably 90% or less, and most preferably 80% or less of the thickness T of the cellulose foam material.

[0112] In some embodiments, the at least one cutting line is arranged to cut through the densified outer layer of at least one of the upper surface and the lower surface and further into the core, and up to but not through the densified outer layer of the other of at least one of the upper surface and the lower surface. In these embodiments, the predetermined cutting depth is less than the thickness of the densified outer layer, so that the predetermined cutting depth can be expressed as the thickness T of the foam minus the thickness of the densified outer layer of the other of at least one of the upper surface and the lower surface.

[0113] It is conceivable that the densified outer layer has a different thickness depending on which surface the densified outer layer is arranged on.

[0114] Furthermore, it is contemplated that the densified outer layer may have the same thickness regardless of which surface the densified outer layer is disposed on.

[0115] Embodiments are conceivable in which the at least one cutting line is arranged into at least one of the upper and lower surfaces not comprising the densified outer layer.

[0116] The second aspect: the method for producing the flexible solid cellulose foam material will now be described in detail.

[0117] The method comprises the following steps:

[0118] - providing said cellulose foam material comprising said upper surface and said lower surface;

[0119] - arranging the at least one cutting line having the predetermined cutting depth DC into at least one of the upper surface and the lower surface, thereby further arranging the at least one cutting line to partially cut through the cellulose foam material.

[0120] The method further includes arranging the at least one cutting line to cut partially through the cellulose foam material such that the predetermined cutting depth DC is less than the thickness T of the cellulose foam material.

[0121] 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 and the lower surface. The cutting tool is then forced into the at least one of the upper surface and the lower surface and further into the core of the cellulose foam material, thereby arranging the at least one cutting line to partially cut through the cellulose foam material.

[0122] The predetermined cutting depth DC of the at least one cutting line is preferably 99% or less, more preferably 90% or less, and most preferably 80% or less of the thickness T of the cellulose foam.

[0123] In some embodiments, the method further includes arranging the at least one cutting line to partially cut into the cellulose foam material in a direction perpendicular to at least one of the upper surface and the lower surface.

[0124] In other embodiments of the method, the at least one cutting line is arranged to cut into the material obliquely. The at least one cutting line cuts into the material at a cutting angle CA with the upper surface or the lower surface, wherein the cutting angle is less than 90° or greater than 90°.

[0125] The at least one cutting line is arranged to extend in a direction from one edge E to the opposite edge E of the respective upper or lower surface; the at least one cutting line thereby forms an angle EA with the edge E.

[0126] The angle EA may be 90°, so that the at least one cutting line intersects the edge E perpendicularly, or the angle EA may be less than 90° or greater than 90°.

[0127] Alternatively, restating the foregoing aspect regarding the angle EA, the method further comprises arranging the at least one cutting line on at least one of the upper surface or the lower surface in a vertical direction, a horizontal direction, or a direction between the vertical direction and the horizontal direction.

[0128] According to the method, the flexible solid cellulose foam is arranged to contain 0.1-5 cutting lines per centimeter, preferably 0.5-2 cutting lines per centimeter. In some embodiments, the flexible solid cellulose foam may contain 0.1-10 cutting lines per centimeter.

[0129] In some embodiments, the flexible solid cellulose foam may include 0.2-5 cut lines per centimeter, for example, 0.2-2, 0.5-5 cut lines per centimeter.

[0130] Preferably, the flexible solid cellulose foam comprises a plurality of cut lines, for example, at least three cut lines, or at least four cut lines, or at least five cut lines.

[0131] Preferably, the method further comprises arranging at least one cutting line having a predetermined cutting depth into both the upper surface and the lower surface.

[0132] It will be appreciated that the predetermined cutting depth DC may be the same on both sides or may be different on different surfaces of the foam.

[0133] Furthermore, it should be understood that the at least one cutting line of the upper surface and the at least one cutting line of the lower surface may be arranged to have the same direction or to have different directions.

[0134] The method further comprises arranging at least one of the upper surface or the lower surface of the solid cellulose foam to include the densified outer layer; and preferably arranging both of the at least one of the upper surface or the lower surface to include the densified outer layer.

[0135] Materials and material properties

[0136] The cellulose fibers contained 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.

[0137] The solid cellulose foam preferably comprises:

[0138] d) 71-95 wt% of cellulose fibers, calculated on the total weight of the solid content of the foam,

[0139] e) 4 to 24 wt% of a water-soluble thickener, calculated on the total weight of the solid content of the foam, and

[0140] f) at least two surfactants.

[0141] The density of the solid cellulose foam can be between 10 and 80 kg / m 3 , preferably 10-60kg / m3 , and more preferably 20-50kg / m 3 within the range.

[0142] 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.

[0143] The cellulose foam may have a thickness in the interval of 5-200 mm, more preferably 10-100 mm, or 10-50 mm.

[0144] An example of conceivable dimensions is a solid cellulose foam board having a thickness of 40-60 mm, preferably about 50 mm.

[0145] 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.

[0146] Example

[0147] Example 1

[0148] A flexible solid cellulose foam sheet comprising vertically arranged cut lines on a top surface and horizontally arranged cut lines on a bottom surface so that the foam material can be wrapped around an object while still maintaining the protective properties of the foam material.

[0149] Example 2

[0150] A flexible solid cellulose foam sheet comprising cut lines arranged diagonally in one direction on the top surface and cut lines arranged diagonally in another direction on the bottom surface so that the foam material can be bent and twisted.

[0151] Example 3

[0152] A flexible solid cellulose foam sheet comprising cut lines arranged vertically or horizontally on the top surface and cut lines arranged diagonally on the bottom surface, thereby allowing bending and stretching of the foam material.

[0153] Example 4

[0154] A flexible solid cellulose foam comprising vertically arranged cut lines on the top surface and horizontally arranged cut lines on the bottom surface. The foam according to this embodiment can be wrapped around an object to be protected, for example around a bottle.

[0155] In all Examples 1-4, a solid cellulose foam board having a thickness of 5 cm was cut manually using a knife. The cutting lines were arranged to cut through the cellulose foam material to a depth corresponding to 2 / 3 of the thickness of the foam. The distance between adjacent cutting lines was in the range of 1-2 cm.

[0156] The cellulose foam board is dry and has a density of 32-35 kg / m 3 The invention discloses a foamed product having a density within the range of 1000 wt % and comprising 83-88 wt % cellulose fiber (softwood bleached kraft pulp), 10-15 wt % thickener (CMC) and about 2 wt % surfactant (a mixture of myristic acid and sodium cocoyl sarcosinate).

[0157] The top and bottom surfaces of the flexible solid cellulose foam in the aforementioned embodiments comprise the densified outer layer.

[0158] As will be appreciated by those skilled in the art, many changes and modifications may be made to the above-described embodiments and other embodiments of the present invention without departing from the scope of the present invention as defined by the appended claims. For example, the at least one cutting line may be in a form other than a straight line. The cutting line may, for example, be a curved cutting line, a zigzag-shaped cutting line, etc.

[0159] The flexible solid cellulose foam may comprise compressed regions.

[0160] At least one of the upper surface and the lower surface may be a curved surface.

[0161] It should be noted that the above described aspects may be the subject of their own protection in a separate divisional application. Therefore, 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 of the present application.

Claims

1. A flexible solid cellulose foam, wherein the flexible 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 flexible 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. 2 . The flexible solid cellulose foam according to claim 1 , wherein the predetermined cutting depth DC is less than a thickness T of the cellulose foam.

3. The flexible solid cellulose foam according to the preceding claim, wherein the predetermined cutting depth DC of the at least one cutting line is 99% or less, preferably 90% or less, and more preferably 80% or less of the thickness T of the cellulose foam.

4. The flexible solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line is arranged to cut partially into the cellulose foam in a direction perpendicular to the at least one of the upper surface and the lower surface.

5. The flexible solid cellulose foam according to any one of claims 1-4, wherein the at least one cutting line is arranged to partially cut into the material at an angle to the at least one of the upper surface or the lower surface, wherein the angle is less than 90° or greater than 90°.

6. The flexible solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line is arranged on the at least one of the upper surface or the lower surface in a vertical direction, or a horizontal direction, or a direction therebetween.

7. A flexible solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line is arranged to extend in a direction from one edge E of at least one of the upper surface and the lower surface to the opposite edge E; the at least one cutting line is thereby arranged to form an angle EA with the edge E.

8. The flexible solid cellulose foam according to any one of the preceding claims, wherein the at least one cutting line is arranged on a flat surface.

9. A flexible solid cellulose foam according to any one of the preceding claims, wherein the solid cellulose foam is a solid cellulose foam board.

10. A flexible solid cellulose foam according to any one of the preceding claims, wherein both the upper surface and the lower surface of the foam comprise at least one cut line having a predetermined cut depth DC.

11. The flexible solid cellulose foam of claim 10, wherein at least one cut line of the upper surface and at least one cut line of the lower surface have the same direction.

12. The flexible solid cellulose foam of claim 10, wherein at least one cut line of the upper surface and at least one cut line of the lower surface have different directions.

13. The flexible solid cellulose foam according to any one of the preceding claims, wherein the flexible solid cellulose foam comprises 0.1 to 5 cut lines per centimeter.

14. The flexible solid cellulose foam of any one of the preceding claims, wherein at least one of the upper surface and the lower surface of the solid cellulose foam comprises a densified outer layer.

15. A flexible solid cellulose foam according to any one of the preceding claims, wherein the density of the solid cellulose foam material is in the range of 10-80 kg / m 3 , preferably 10-60kg / m 3 , and more preferably 20-50kg / m 3 within the range.

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

17. A flexible solid cellulose foam according to any one of the preceding claims, wherein the cellulose fibers are 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.

18. A method for producing a flexible solid cellulose foam, the method The following steps are involved: - providing a solid cellulose foam comprising an upper surface and a lower surface; - arranging at least one cutting line having a predetermined cutting depth DC into at least one of said upper surface and said lower surface, whereby at least one cutting line is further arranged to cut partially through said solid cellulose foam.

19. The method according to claim 18, whereby the at least one cutting line is arranged to cut partially through the solid cellulose foam such that the predetermined cutting depth DC is less than the thickness T of the cellulose foam.

20. The method according to any one of claims 18-19, wherein the predetermined cutting depth DC of the at least one cutting line is 99% or less, preferably 90% or less, and more preferably 80% or less of the thickness T of the solid cellulose foam.

21. A method according to any one of claims 18 to 20, whereby the at least one cutting line is arranged to cut partially into the solid cellulose foam in a direction perpendicular to at least one of the upper surface and the lower surface.

22. A method according to any one of claims 18-20, whereby the at least one cutting line is arranged to cut partially into the solid cellulose foam at an angle to the upper surface or the lower surface, wherein the angle is less than 90° or greater than 90°.

23. The method according to any one of claims 18 to 22, whereby the at least one cutting line is arranged on at least one of the upper surface or the lower surface in a vertical direction, or in a horizontal direction, or in a direction therebetween.

24. A method according to any one of claims 18 to 23, whereby the flexible solid cellulose foam is arranged to contain 0.1 to 5 cut lines per centimetre.

25. Method according to any of claims 18-24, whereby at least one cutting line having a predetermined cutting depth DC is arranged into both the upper surface and the lower surface.

26. The method according to any one of claims 18-25, whereby the at least one cutting line of the upper surface and the at least one cutting line of the lower surface are arranged to have the same direction or to have different directions.

27. A method according to any one of claims 18 to 25, whereby at least one of the upper surface or the lower surface of the solid cellulose foam is arranged to comprise a densified outer layer.

28. The method according to any one of claims 18 to 28, wherein the density of the solid cellulose foam is in the range of 10 to 80 kg / m 3 , preferably 10-60kg / m 3 , and more preferably 20-50kg / m 3 within the range.

29. The method according to any one of claims 18 to 28, wherein the solid cellulose foam material (1) comprises: a) 71-95 wt% of cellulose fibers, calculated on the total weight of the solid content of the foam, b) 4 to 24 wt% of a water-soluble thickener, calculated on the total weight of the solid content of the foam, and c) at least two surfactants.

30. The method according to any one of claims 18 to 29, wherein the cellulose fibers are 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.