Method for producing a protective packaging insert comprising a solid cellulose foam

Abstract

The invention relates to a method for producing a protective packaging insert, the method comprising the steps of: providing a solid cellulose foam; and forming at least one cavity in the solid cellulose foam, the at least one cavity extending from a first surface of the cellulose foam, and wherein at least one dimension of the cavity in the width and / or length direction is chosen such that it is smaller than the respective dimension of an object to be placed in the cavity.

Description

Technical Field

[0001] This invention relates to a method for producing a protective packaging insert comprising solid cellulose foam, and a protective packaging insert comprising solid cellulose foam. Background Technology

[0002] In fact, almost all consumer goods require protective packaging to cushion the items during storage and transportation. It is recognized that numerous solutions exist for packaging and cushioning a wide variety of items, depending on the physical properties of the item to be protected and the required level of protection associated with its application. Examples of these protective packaging materials are polymeric foam materials used for packaging, such as polyurethane foam (PU), polyethylene foam (PE), expanded polystyrene (EPS), or expanded polypropylene (EPP). Porous materials used for this type of application must be stable, lightweight, and easy to manufacture. Due to the growing recognition of the necessity of using renewable materials, there is a strong incentive to replace petroleum-based polymers with polymers derived from renewable resources.

[0003] Finding foam materials from renewable sources presents numerous challenges. Many bio-based foams have higher production costs and lower mechanical properties compared to established petroleum-based sources. Bio-based protective materials need to possess the same characteristics and properties as petroleum-based protective materials to become the preferred alternative.

[0004] The low weight and good shock absorption of bio-based foams are examples of key properties. Cellulose, as the most abundant renewable natural polymer on Earth, has shown particular potential due to its crystalline structure and the availability of methods for preparing large-volume materials on an industrial scale. Cellulose-based foams, such as those described in WO2023119215A1, possess excellent cushioning properties, making them a suitable choice for use in protective packaging applications.

[0005] Importantly, it is also possible to customize the shape and form of the foam in the protective packaging to the shape and form of the item to be protected. Further important is the ability to hold the item in place within the packaging. Using petroleum-based foam, highly resilient foam can be obtained that adapts its shape to the shape of the item to be protected, thus tightly conforming to the item and holding it in place within the packaging.

[0006] Compared to petroleum-based foams, some cellulose foams are typically more rigid by nature, meaning they have lower flexibility and resilience. This means that it can be difficult to achieve a tight fit around the item being protected when using such cellulose foams. This, in turn, means that the item is not always held in place within the protective packaging, increasing the risk of damage. Holding objects with smooth and slippery surfaces in place can be particularly challenging due to the low level of friction between the object and the foam.

[0007] Therefore, there is still a need for a protective packaging insert that is natural, bio-based, and recyclable, and that can be adjusted to fit snugly around the item it protects, thereby holding the item in place within the packaging. Summary of the Invention

[0008] One object of the present invention is to provide a protective packaging insert that is recyclable and made from renewable sources, and that eliminates or mitigates at least some of the disadvantages of prior art materials.

[0009] A further object of the present invention is to provide a method for producing a protective packaging insert comprising solid cellulose foam, such that the insert can be used in packaging applications in which holding the article to be protected in position within the packaging is critical.

[0010] The above objectives, as well as other objectives that a person skilled in the art will recognize from this disclosure, are achieved through various aspects of this disclosure.

[0011] According to a first aspect, the present invention relates to a method for producing protective packaging inserts, the method comprising the following steps:

[0012] - Provides solid cellulose foam; and

[0013] - Forming at least one cavity in a solid cellulose foam, the at least one cavity extending from a first surface of the cellulose foam, and wherein at least one dimension of the cavity is selected in the width and / or length directions such that it is smaller than the corresponding dimension of the object to be placed in the cavity.

[0014] Surprisingly, by selecting at least one dimension of the width and / or length of the at least one cavity such that the cavity is slightly smaller than the object to be placed in the cavity, the cellulose foam will tightly adhere to the object and hold it in position. When the cellulose foam tightly adheres to the object, the forces and friction between the foam and the object increase, thereby preventing the object from moving around within the cavity, for example, during impact or transport. Preferably, the cavity is slightly smaller than the object to be placed in the cavity in both the width and length directions.

[0015] According to a second aspect, the present invention relates to a protective packaging insert comprising a solid cellulose foam, wherein the solid cellulose foam includes at least one cavity extending from a first surface of the solid cellulose foam into the foam, and wherein at least one dimension of the cavity is selected in the width and / or length direction such that it is smaller than the corresponding dimension of an object to be placed in the cavity. The protective packaging insert according to the second aspect can be obtained by the method according to the first aspect.

[0016] Solid cellulose foam is made from renewable resources and can be redispersed in water, thus enabling recycling in conventional paper recycling processes. Preferably, the entire protective packaging insert is made of solid cellulose foam, making the protective packaging insert recyclable.

[0017] The object is held securely in position within the cavity of the protective packaging insert, making it suitable for fragile and / or easily breakable objects, where holding the object securely in position is important, for example, during transport. Furthermore, objects with smooth and slippery surfaces can be protected by the protective packaging insert of this invention. Detailed Implementation

[0018] As used in this article, the term "foam" refers to a substance created 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. Three requirements must be met for foam to form. First, mechanical work is needed to increase the surface area. This can be achieved by agitation, dispersing a large amount of gas into a liquid, or injecting gas into a liquid. Second, a foaming agent must be present, typically an amphiphilic substance, surfactant, or surface-active component, to reduce surface tension. Finally, foam formation must be faster than its collapse.

[0019] As used herein, the term "cellulose foam" refers to a foam containing cellulose as well as other components such as thickeners, surfactants, and additives. The primary component of cellulose foam is cellulose, such that cellulose constitutes at least 70 wt% of the dry content of the cellulose foam. Cellulose is in fibrous form; therefore, the foam can also be defined as fibrous foam or cellulose fiber foam. The cellulose foam can be wet or solid.

[0020] As used herein, the term "wet foam" or "wet cellulose foam" refers to a wet foam containing cellulose and other components such as thickeners, surfactants, and additives. Wet foam contains gas bubbles. It is self-supporting and behaves as a viscoelastic solid. This means that wet foam possesses both viscous and elastic properties. Unless a sufficiently large force is applied to cause it to begin flowing and become a viscous material, wet foam will behave as a solid and thus be self-supporting. Depending on the magnitude and timescale of any shear stress applied, wet foam can exhibit primarily viscous or elastic behavior.

[0021] As used herein, the term "solid cellulose foam" or "solid foam" refers to a dried porous cellulose material formed from wet cellulose foam, i.e., a foam forming material. During the drying process, the closed wet cellulose foam transforms into an open solid cellulose foam. The collapse of the cellulose fiber network is prevented during drying. Therefore, the solid cellulose foam will have a shape that largely corresponds to the shape of the wet cellulose foam. Based on the total weight of the solid cellulose foam, the dry content of the solid cellulose foam is at least 95 wt%. The shape and density of the solid cellulose foam are also maintained in an unconstrained state. Solid cellulose foam has an open-cell structure, allowing air to occupy the pores within the foam. Solid cellulose foam can also be described as a porous material or a low-density material.

[0022] Cellulose foam, which is preferably used as a starting material in the method according to the invention, will now be described in detail.

[0023] The cellulose foam used in this invention may contain cellulose fibers in the range of 71 to 95 wt%, for example 75 to 95 wt%, based on the total dry weight of the cellulose foam.

[0024] Cellulose fibers suitable for use in this invention may be derived from wood (e.g., coniferous or hardwood), leaves, or fiber crops (including cotton, flax, and hemp). Cellulose fibers suitable for use in this invention may also be derived from regenerated cellulose, such as rayon and lyocell. Cellulose fibers suitable for use in this 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; more preferably, the cellulose fibers are pulp fibers obtained through a pulping process that releases fibers from a wood matrix. Pulp fibers can be released by mechanical pulping to obtain mechanical pulps such as thermomechanical pulp (TMP) or chemithermomechanical pulp (CTMP), or by chemical pulping, such as sulfate (Kraft) pulp or pulp obtained through sulfite, caustic soda, or organic solvent pulping processes. More preferably, the cellulose fibers are pulp fibers released through a chemical pulping process. The different characteristics of each cellulose fiber will affect the properties of the final cellulose foam. The length of the cellulose fiber is significantly greater than its width. Cellulose fibers can have an average width of 0.01 to 0.05 mm. The fiber length of coniferous wood can be 2.5 to 4.5 mm, while that of hardwood can be 0.7 to 1.6 mm, and that of eucalyptus can be 0.7 to 1.5 mm. However, fiber length can vary significantly depending on factors such as the growing location. The cellulose fibers in the cellulose foam disclosed herein can have lengths 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. Fiber length can provide different mechanical properties to the foam. Due to the fiber length, the fibers can entangle with each other, giving the fiber-to-fiber bond, which contributes to the strength of the foam. The aspect ratio of the cellulose fibers in the cellulose foam according to the invention, i.e., the ratio of fiber length to fiber width, can be at least 10, at least 25, at least 50, at least 75, or at least 100. This provides retention and stability of the foam structure during the drying process, allowing the wet cellulose foam to be dried while maintaining its shape. The aspect ratio can be up to 6500, or preferably up to 2000.

[0025] Cellulose fibers can be modified to impart different properties to the final cellulose foam. For example, phosphorylated fibers or periodate oxidized fibers can also be used in the production of cellulose foam according to the invention.

[0026] Preferably, the cellulose fibers are selected from wood pulp, such as bleached softwood sulfate pulp, hardwood pulp, chemithermomechanical pulp, and dissolving pulp, or a combination of one or more of these. More preferably, the cellulose pulp fibers are derived from softwood pulp, chemithermomechanical pulp, or dissolving pulp. Most preferably, the cellulose pulp fibers are derived from softwood pulp, such as bleached softwood sulfate pulp.

[0027] The cellulose foam used in this invention preferably comprises cellulose fibers in the range of 71 to 95 wt%, for example 75 to 95 wt%, based on the total dry weight of the cellulose foam, a water-soluble thickener in the range of 4 to 24 wt%, for example 5 to 20 wt%, based on the total dry weight of the cellulose foam, and at least two surfactants.

[0028] Water-soluble thickeners 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. The fact that the thickener is water-soluble facilitates the recycling of cellulose foam.

[0029] Water-soluble thickeners improve the fiber-to-fiber bond strength in cellulose foam, primarily through hydrogen bonding. Therefore, the amount of water-soluble thickener will affect the mechanical properties of cellulose foam, and especially the bulk of the material. Higher amounts of water-soluble thickener provide a stiffer material. Thus, water-soluble thickeners allow for the customization of mechanical properties.

[0030] The cellulose foam may also contain a mixture of at least two surfactants. One of these at least two surfactants is preferably a fast-acting surfactant, and an anionic surfactant is suitable for this purpose, preferably a low molecular weight anionic surfactant. The anionic surfactant may have an apparent pKa of 3.2 to 3.8, preferably 3.4 to 3.6, or 3.5, in a solution with a pH of 7 to 9, preferably pH 8. The low molecular weight anionic surfactant may be selected from sodium dodecyl sulfate (SDS); potassium dodecyl sulfate; sodium lauryl ether sulfate (SLES); sodium dodecylbenzene sulfonate; sodium cocoyl sarcosinate; and 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.

[0031] Another of the at least two surfactants is preferably a co-surfactant. The co-surfactant may be selected from the group consisting of: surfactants having an apparent pKa of at least 8 or at least 9 in a surfactant solution at pH 7 to 9, preferably pH 8; and amphoteric betaine. The co-surfactant may have a maximum apparent pKa of 10. The co-surfactant preferably has a long carbon chain, more preferably a carbon chain having 14 carbon atoms (C14). Co-surfactants can be selected from high pKa fatty acids, such as plant-derived raw materials, such as tetradecanoic acid (myristic acid), sodium oleate, lauric acid, palmitic acid, and stearic acid; glucose-based co-surfactants with aliphatic carbon tails, such as alkyl glycosides, alkyl polyglucosides, alkyl thioglycosides, and alkyl maltodextrins; amphoteric betaines, such as cocamidopropyl betaine (CAPB) and sodium coiminodipropionate (CADP); polyethylene glycol sorbitan monolaurate, namely Tween® (e.g., Tween® 20, Tween® 80, and Tween® 85); and polyoxyethylene lauryl ethers, such as polyethylene glycol dodecyl ether, pentaethylene glycol monododecyl ether, and octaethylene glycol monododecyl ether.

[0032] Therefore, the at least two surfactants used in the cellulose foam preferably comprise a mixture of anionic surfactant and co-surfactant. The molar ratio between the anionic surfactant and the co-surfactant can be from 0.2:1 to 3:1, preferably from 0.5:1 to 2:1. Based on the total weight of the cellulose foam, the total amount of the at least two surfactants in the cellulose foam can be 0.6-5 wt% or 0.8-2.0 wt%.

[0033] Solid cellulose foam can be redispersed in water, thus enabling its recycling in conventional paper recycling processes.

[0034] Wet cellulose foam can be prepared using a method comprising the following steps:

[0035] - Disintegrate cellulose fibers in water to obtain a cellulose fiber slurry;

[0036] - Add a water-soluble thickener to the slurry to obtain a mixture of thickener and cellulose fibers in water;

[0037] - Add at least two surfactants to the mixture to obtain a fiber suspension; and

[0038] - The fiber suspension is aerated to obtain wet foam, wherein, based on the total weight of the wet foam, the wet cellulose foam contains 10-38 wt% cellulose fibers, 0.5-10 wt% water-soluble thickener, and 0.1-2 wt% surfactant, and wherein the wet cellulose foam has a density of 120-500 kg / m³. 3Or 120-400 kg / m 3 The density and yield stress of at least 80 Pa.

[0039] Adding a water-soluble thickener increases the viscosity of the slurry and enables sufficient air to be incorporated during aeration to create a densely packed foam. Because the cellulose fibers are mixed in at a high concentration, a draining step is unnecessary, allowing for the use of water-soluble bio-based thickeners at high concentrations.

[0040] Adding a fast-acting surfactant will facilitate the formation of cellulose foam with high density and high viscosity, as it will rapidly localize at the air-water interface during inflation. This enables self-supporting wet cellulose foam. Adding a co-surfactant along with the fast-acting surfactant will further improve the properties of the cellulose foam, as it will enhance the action of the fast-acting surfactant. Co-surfactants with suitable pKa and long carbon chains further contribute to the stabilization of cellulose suspensions and the stability of wet cellulose foam.

[0041] During inflation, a composition comprising cellulose fibers, a thickener, and at least two surfactants forms a highly stable wet cellulose foam. Inflation can be achieved through mechanical agitation, and a large amount of air is incorporated into the material. The surfactant promotes foam formation. By using a combination of thickener and surfactant to regulate the stability of the wet foam, self-supporting cellulose foams can be produced without the use of crosslinking agents or fibrillated cellulose. The good stability of the foam prevents curing, i.e., changes in bubble size, and leakage. The resulting wet foam is self-supporting and does not require molds or forming fabrics to maintain its shape during drying. Therefore, the wet foam can form a self-supporting foam that is stable enough to dry without collapsing in the absence of a supporting mold.

[0042] The bubble size in the wet foam is typically less than 100 µm. This provides a homogeneous wet foam with good stability that does not flocculate during processing. The average bubble size is largely maintained during processing and subsequent drying steps, and the cellulose fibers remain well dispersed. The resulting solid cellulose foam obtained by drying the wet foam is structurally homogeneous, robust, has good mechanical properties, a smooth surface, and is free of defects.

[0043] In contrast, wet cellulose foams with low stability have a larger average bubble size (typically greater than 100 µm), and the bubbles coalesce more rapidly during processing and drying, resulting in larger bubbles. Additionally, 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 homogeneous structure and will also contain defects in the form of cavities created by the coalescing bubbles in the wet foam. Due to these defects, this solid cellulose foam is weak and has a rough surface.

[0044] In some embodiments, the yield stress of the wet cellulose foam used in this invention may be at least 80 Pa, or at least 100 Pa, or at least 150 Pa, or 80 to 500 Pa, or 100 to 500 Pa, or 150 to 500 Pa.

[0045] In some embodiments, the density of the wet cellulose foam used in this invention can be 70-600 kg / m³. 3 or 100-500 kg / m 3 or 100-400 kg / m 3 or 125-375 kg / m 3 or 140-375 kg / m 3 .

[0046] In some embodiments, the wet cellulose foam used in this invention contains at least 10 wt% cellulose, calculated based on the total weight of the wet cellulose foam. In some embodiments, the wet cellulose foam may contain 10-40 wt%, 11-40 wt%, 10-30 wt%, 11-30 wt%, 10-20 wt%, or 11-20 wt% cellulose fibers, calculated based on the total weight of the wet cellulose foam.

[0047] Due to its high solids content, the wet foam does not need to be dehydrated before drying. The foam can be dried by evaporation at room temperature or at elevated temperatures, such as between 40°C and 140°C.

[0048] After drying, solid cellulose foam can have a density of 10 to 80 kg / m³. 3 or 10 to 60 kg / m 3 or 20 to 50 kg / m 3 The density. In a preferred embodiment, the cellulose foam comprises cellulose fibers in the range of 71 to 95 wt%, for example 75 to 95 wt%, based on the total dry weight of the cellulose foam; a water-soluble thickener in the range of 4 to 24 wt%, for example 5 to 20 wt%, based on the total dry weight of the cellulose foam; and at least two surfactants. The wet cellulose foam having this composition is structurally homogeneous and has good stability, as described above. This wet cellulose foam can also be dried without pre-dehydration.

[0049] After drying, the solid cellulose foam can have a solid content in the range of 90 to 100 wt%, preferably 95 to 100 wt%, based on the total weight of the solid cellulose foam.

[0050] During drying, a densification layer is formed on the outer surface of the wet cellulose foam, and this densification layer remains on the outer surface of the dried cellulose foam. Compared to the bulk, the densification layer comprises more densely packed and partially disoriented cellulose fibers. Compared to the core of the cellulose foam, the densification layer provides improved mechanical stability and strength. The core of the cellulose foam comprises a homogeneous network of open-cell fibers. The core is highly porous, and although the densification layer has a denser structure than the core, it is still porous. The densification layer provides increased stability and mechanical strength to the cellulose foam.

[0051] Cellulose foam can be prepared by a two-step deposition process, as described, for example, in WO2023119215 A1. In the first deposition, wet foam is deposited as discrete units on a surface and dried at least partially. During drying, a densification layer is formed on the outer surface of the discrete units. In the second deposition, wet foam, preferably having the same composition as the wet foam in the first deposition, is deposited such that it fills the space around the discrete units deposited in the first deposition. After drying, a solid cellulose foam containing discrete units of foam embedded in a foam matrix is ​​obtained. Cellulose foam can also be prepared by assembling separately formed complementary dry cellulose foam pieces. For example, dry foam pieces with complementary shapes formed from individual wet foams can be assembled to form a foam substrate with any desired shape (e.g., a plank).

[0052] The cellulose foam described above is a preferred solid cellulose foam used in the method of the present invention, and is further described in WO2023119213 A1. Alternatively, other cellulose foams may be used, such as those disclosed in WO2016068771A1, WO2016068787 A1 and WO2020011587 A1.

[0053] According to a first aspect, the first invention relates to a method for producing protective packaging inserts. The provided solid cellulose foam is solid, i.e., dry, and may have any suitable properties. The solid cellulose foam may be rigid or resilient. The term "resilient" as used herein refers to a cellulose foam that can recover its shape after bending or compression. After any applied pressure is removed, a resilient cellulose foam is able to recover 90-100% of its thickness, regardless of compressive strain. The term "rigid" as used herein refers to a solid cellulose foam that is substantially hard and non-flexible and cannot be bent significantly without tearing and / or wrinkling the foam. When a rigid cellulose foam is compressed, it does not recover its original shape, or only to a very small extent, and only when compressed at a low degree of compression.

[0054] Resilient cellulose foam can be obtained by compressing rigid cellulose foam below a certain threshold. The open-cell structure of the rigid cellulose foam deforms upon compression, resulting in a more compact resilient cellulose foam. The use of resilient cellulose foam in this invention is advantageous because the foam's resilient properties ensure a tighter fit of the foam around the object to be protected within the cavity of the insert. However, rigid cellulose foam has better cushioning properties than resilient cellulose foam, therefore, rigid cellulose foam is preferred in applications where cushioning is critical.

[0055] The density of solid cellulose foam is 10-80 kg / m³. 3 Within the defined range. Due to its more compact structure, the density of resilient cellulose foam is typically higher than that of rigid cellulose foam, but still within the defined range.

[0056] The solid cellulose foam provided according to the method of the first aspect can have any shape, such as a block, cube, cylinder, or any irregular shape. Preferably, the solid cellulose foam has at least one flat surface. As used herein, the term "flat" means a smooth surface without depressions or protrusions.

[0057] In one embodiment, the solid cellulose foam is provided in the form of a sheet having a thickness ranging from 1 to 20 cm, preferably 1 to 10 cm, and more preferably 2 to 6 cm. The length and width dimensions of the sheet are typically in the range of 100 to 300 cm. The sheet can be cut into smaller pieces, but it is preferred that the same thickness be maintained after cutting. In embodiments where the foam is provided in sheet form, the foam will have a top surface, a bottom surface, and side surfaces.

[0058] In a preferred embodiment, the solid cellulose foam has a top surface, a bottom surface, and side surfaces. The top surface and / or bottom surface is preferably flat. Preferably, the provided solid cellulose foam has a uniform thickness throughout the entire foam.

[0059] In some embodiments, the provided solid cellulose foam includes a densification layer on at least one outer surface. In embodiments where the cellulose foam is provided in sheet form, the solid cellulose foam may include a densification layer on at least the top and bottom surfaces, and optionally on the side surfaces. The densification layer provides the cellulose foam with improved mechanical properties, such as strength and stability.

[0060] The method according to the first aspect also relates to forming at least one cavity in a solid cellulose foam, said at least one cavity extending from a first surface of the solid cellulose foam into the foam. The first surface is preferably the top surface of the cellulose foam. The at least one cavity extends from the first surface of the cellulose foam toward a second surface of the cellulose foam. Preferably, the first surface is the top surface of the cellulose foam, and the second surface is the bottom surface of the cellulose foam.

[0061] The at least one cavity has a height, width, and length. The height, width, and length may be uniform or may vary along the cavity. The cavity includes a wall extending from a first surface of the cellulose foam and also includes a bottom portion. In an embodiment where the bottom portion is flat, the height of the cavity corresponds to the height of the cavity wall. The cavity wall extends along the periphery of the cavity and is primarily formed by a core of cellulose foam.

[0062] The cavity can have any desired shape. The shape and size of the cavity are chosen so that the object to be protected fits snugly within it. Depending on the object, placing the bottom portion of the object within the cellulose foam cavity may suffice. Therefore, the shape of the cavity corresponds to the shape of the bottom portion of the object. Alternatively, the entire object can be placed inside the cavity. This is particularly suitable when the object is fragile and brittle.

[0063] The cavity is selected in at least one dimension in its width and / or length directions such that it is smaller than the corresponding size of the object to be placed in the cavity. The object placed in the cavity is protected by a protective packaging insert. The smaller size of the cavity ensures that the object is held in position within the cavity, and that foam will tightly wrap around the object. Preferably, the dimensions of the cavity in both its width and length directions are selected such that they are smaller than the corresponding size of the object to be placed in the cavity.

[0064] If the object to be protected has an irregular shape, the shape of the cavity can also be made irregular. Preferably, the shape of the cavity closely corresponds to the shape of the object to be protected, but the size is slightly smaller.

[0065] For example, the cavity can be sized in the width and / or length directions such that it is 0.5 to 5 mm smaller than the object to be protected. If the cavity is made too small, it may be difficult to insert the object to be protected without damaging the foam.

[0066] The cavity can be formed using any suitable method, such as by cutting or milling. Preferably, the cavity is formed by cutting, such as using die cutting, waterjet cutting, or an oscillating cutter.

[0067] If a resilient cellulose foam is desired, the cellulose foam can be compressed after forming the at least one cavity. Depending on the forming method used, it may be easier to form cavities in the solid cellulose foam before compression because the stiffness of rigid solid cellulose foam is higher than that of resilient cellulose foam obtained after compression.

[0068] In some embodiments, the at least one cavity is formed while the cellulose foam is compressed. When die-cutting is used to form the at least one cavity, the cellulose foam is compressed by the die-cutting tool, thereby obtaining a resilient foam while forming the at least one cavity within the foam.

[0069] In some embodiments, the at least one cavity is formed after compressing a rigid solid cellulose foam. Therefore, in such embodiments, the cavity is formed within a resilient cellulose foam.

[0070] Regardless of when the cavity is formed, the properties of the at least one cavity are the same. Cellulose foam is cut in a similar manner, whether the foam is rigid or resilient. Therefore, in the following discussion, the foam may be rigid, uncompressed cellulose foam, or resilient, compressed cellulose foam, or cellulose foam that can be compressed during cutting. The cellulose foam is always solid cellulose foam, i.e., it is dry.

[0071] In some embodiments, the solid cellulose foam is cut along a direction perpendicular to the first surface of the solid cellulose foam, such that at least a portion of the cavity wall is perpendicular to the first surface. All portions of the cavity wall may be perpendicular to the first surface, or only some portions may be perpendicular to the first surface. Cutting along a perpendicular direction is typically easier than cutting at an angle relative to the first surface, thus simplifying manufacturing.

[0072] In some embodiments, the cavity wall is cut at an angle relative to the first surface of the solid cellulose foam, such that at least a portion of the cavity wall is inclined. All portions of the cavity wall may be inclined, or only some portions may be inclined. Preferably, the wall is inclined such that the width and / or length of the cavity is greater at the bottom portion of the cavity than at the top portion. The top portion of the cavity is located at the first surface of the cellulose foam, and the bottom portion of the cavity is located at the bottom of the cavity, i.e., on the side opposite to the top portion. In such embodiments, the angle between the first surface of the cellulose foam and the cavity wall is less than 90°, for example, less than 80°, or less than 70°, or less than 60°, or less than 50°. The angle may also vary at different portions of the cavity wall. The inclined cavity wall facilitates holding an object in position within the cavity. In embodiments where the width and / or length of the cavity varies along the height of the cavity, such as in embodiments with inclined cavity walls, at at least one point along the height of the cavity wall, at least one dimension of the width and / or length is smaller than the corresponding dimension of the object to be protected. Preferably, at the top portion of the cavity, the width and / or length of the cavity is smaller than the corresponding dimensions of the object to be protected. This secures the object within the cavity.

[0073] In some embodiments, the cavity wall is first cut perpendicular to the first surface and then angled relative to the first surface, such that the cavity wall is perpendicular to the first surface at the top portion of the cavity but slopes downwards further into the cavity. The vertical portion of the cavity wall preferably does not extend deep into the cavity but exists only at the top portion. For example, the vertical portion may be less than 20 mm, less than 10 mm, or less than 5 mm when measured from the first surface of the cellulose foam. The vertical portion provides a robust lid to the cavity, resulting in improved protective properties because the cavity will be less fragile and less prone to breakage.

[0074] The cavity can extend through the entire thickness of the cellulose foam, cutting through it along its full thickness when forming the cavity. Alternatively, the cavity can extend only partially through the thickness of the cellulose foam, leaving a portion of the foam intact to form the bottom portion of the cavity. Depending on the object to be placed in the cavity, this bottom portion can be flat or have any other suitable shape. In such an embodiment, the cellulose foam within the cavity can be removed by cutting along the bottom portion of the cavity, or the foam can be further compressed and retained at the bottom portion of the cavity. Any object placed within the cavity will keep the foam compressed.

[0075] In some implementations, more than one cavity is formed within the solid cellulose foam. The cavities may have the same shape or may have different shapes.

[0076] According to a second aspect, the present invention relates to a protective packaging insert comprising solid cellulose foam, wherein the solid cellulose foam comprises at least one cavity extending from a first surface of the solid cellulose foam into the foam, and wherein at least one dimension of the cavity is selected in the width and / or length direction such that it is smaller than the corresponding dimension of an object to be placed in the cavity.

[0077] Preferably, the protective packaging insert is made entirely of solid cellulose foam. Alternatively, the protective packaging insert may include an additional substrate attached to the solid cellulose foam. The protective packaging insert may also include an additional solid cellulose foam substrate.

[0078] The at least one cavity extends from a first surface of the solid cellulose foam toward a second surface of the solid cellulose foam. Preferably, the first surface is the top surface of the foam, and the second surface is the bottom surface of the foam. The cavity may extend through the foam to the bottom surface of the foam, such that the cavity has no bottom portion. Alternatively, the cavity may extend partially through the foam, such that the bottom portion of the cavity is formed by the foam. The cavity can have any suitable shape as long as at least one dimension is smaller than the corresponding dimension of the object to be protected. Therefore, the shape is selected according to the object to be placed in the cavity.

[0079] In some embodiments, at least a portion of the cavity wall is perpendicular to the first surface of the solid cellulose foam. In some embodiments, all the cavity walls are perpendicular.

[0080] In some embodiments, at least a portion of the cavity wall is arranged such that the angle between the first surface of the solid cellulose foam and the cavity wall is less than 90°, for example less than 80°, or less than 70°, or less than 60°, or less than 50°. The angle may also vary at different portions of the cavity wall. In such embodiments, at least some portions of the cavity wall will be sloped. In such embodiments, the width and / or length of the cavity is greater at the bottom portion of the cavity than at the top portion. The sloped walls facilitate securing the object to be protected within the cavity.

[0081] In some embodiments, at least a portion of the top of the cavity wall is arranged perpendicular to the first surface of the solid cellulose foam. Below the top portion, the cavity wall is arranged at an angle relative to the first surface, such that the cavity wall slopes towards the bottom portion of the cavity. In such embodiments, the vertical portion of the cavity wall preferably does not extend deep into the cavity, but exists only at the top portion. For example, the vertical portion may be less than 5 mm when measured from the first surface of the cellulose foam.

[0082] The cavity can extend throughout the entire solid cellulose foam, such that it is cut through the entire thickness of the foam when the cavity is formed. In such an embodiment, the bottom portion can be provided by placing the solid cellulose foam on a substrate (e.g., a cardboard substrate or another cellulose foam substrate). Thus, the cavity is provided with a bottom portion. The solid cellulose foam can be bonded to the substrate. The bottom portion can also be formed by the walls of a box in which protective packaging inserts are placed.

[0083] At least one of the width and length of the cavity is smaller than the corresponding size of the object to be placed in the cavity. Therefore, the width and / or length of the object to be protected by the solid cellulose foam is larger than the corresponding size of the cavity in the solid cellulose foam. When the object is placed in the cavity, the foam will be pushed outwards by the object from the cavity. Because the foam is soft and has at least some resilience, it will tend to return to its original shape and thus exert a force on the object, holding it in place within the cavity. This effect is more pronounced when using resilient cellulose foam, but even in rigid cellulose foam, the foam core, which exists mostly along the cavity wall, is quite soft and has a relatively low degree of flexibility.

[0084] The second type of protective packaging insert is suitable for, for example, protecting objects during transportation. It can be placed inside a box or other type of packaging to hold the object in place inside the packaging.

[0085] In view of the above detailed description of the invention, those skilled in the art will understand other modifications and variations. However, it should be understood that these other modifications and variations can be made without departing from the spirit and scope of the invention.

Claims

1. A method for producing protective packaging inserts, the method comprising the following steps: - Provides solid cellulose foam; as well as - Forming at least one cavity in a solid cellulose foam, the at least one cavity extending from a first surface of the cellulose foam into the foam, and wherein at least one dimension of the cavity is selected in the width and / or length direction such that it is smaller than the corresponding dimension of the object to be placed in the cavity.

2. The method of claim 1, wherein the provided solid cellulose foam has a density of 10 to 80 kg / m³. 3 The density within the range.

3. The method according to any one of claims 1 or 2, wherein the solid cellulose foam comprises cellulose fibers in the range of 71 to 95 wt% based on the total dry weight of the solid cellulose foam.

4. The method according to any one of the preceding claims, wherein the solid cellulose foam comprises cellulose fibers in the range of 71 to 95 wt% of the total dry weight of the solid cellulose foam, a water-soluble thickener in the range of 4 to 24 wt% of the total dry weight of the solid cellulose foam, and at least two surfactants.

5. The method of claim 4, wherein the step of forming the at least one cavity involves cutting a solid cellulose foam to obtain the at least one cavity.

6. The method of claim 5, wherein the cutting is performed along a direction perpendicular to the first surface of the solid cellulose foam, such that at least a portion of the wall of the cavity is perpendicular to the first surface.

7. The method according to any one of claims 5 or 6, wherein the first surface of the solid cellulose foam is cut at an angle such that at least a portion of the wall of the cavity is inclined.

8. The method of claim 7, wherein the cutting is performed such that the width and / or length of the cavity is greater at the bottom portion of the cavity than at the top portion of the cavity, and wherein the top portion of the cavity is located at the first surface of the solid cellulose foam.

9. The method according to any one of claims 5-8, wherein the cavity is first cut at the top portion in a direction perpendicular to the first surface of the solid cellulose foam, and then cut at an angle relative to the first surface at a lower portion within the cavity.

10. A protective packaging insert comprising solid cellulose foam, wherein the solid cellulose foam includes at least one cavity extending from a first surface of the solid cellulose foam into the foam, and wherein at least one dimension of the cavity is selected in the width and / or length direction such that it is smaller than the corresponding dimension of an object to be placed in the cavity.

11. The insert of claim 10, wherein the solid cellulose foam comprises cellulose fibers in the range of 71 to 95 wt% based on the total dry weight of the solid cellulose foam.

12. The insert according to any one of claims 10 or 11, wherein the solid cellulose foam comprises cellulose fibers in the range of 71 to 95 wt% of the total dry weight of the solid cellulose foam, a water-soluble thickener in the range of 4 to 24 wt% of the total dry weight of the solid cellulose foam, and at least two surfactants.

13. The insert according to any one of claims 10-12, wherein at least a portion of the wall of the cavity is arranged perpendicular to the first surface of the solid cellulose foam.

14. The insert according to any one of claims 10-13, wherein at least a portion of the wall of the cavity is arranged such that the angle between the first surface of the solid cellulose foam and the wall of the cavity is less than 90°.

15. The insert of claim 14, wherein at least one of the width and length of the cavity is greater at the bottom portion of the cavity than at the top portion of the cavity, wherein the top portion is located at the first surface of the solid cellulose foam.