A molded three-dimensional packaging product

Abstract

The invention relates to a three-dimensional packaging product, such as a tray, made of molded fiber, said product comprising a lower base portion (2) and side walls (3) extending from said base, wherein said base portion (2) and side walls (3) enclose at least one inner compartment (6); wherein the upper portions of said side walls (3) transition into a circumferential rim (7) comprising an inner wall (70), a top portion (71) and a downwardly deflected outer wall (72) defining a continuous inner space (73); wherein said rim (7) comprises destacking knobs (4) for preventing the outside of said product (1) touching the inside of another, identical product when stacked therein, said knobs being arranged / positioned at said downwardly deflected outer wall (72).

Description

[0001] A MOLDED THREE-DIMENSIONAL PACKAGING PRODUCT

[0002] Technical field

[0003] The present invention relates to a three-dimensional packaging product made from molded fiber.

[0004] There is a growing interest in producing cellulose based products, e.g. for use as packaging applications for plants and foodstuff, tableware, trays, bowls, technical products, electronic equipment and / or consumer goods. Several advantages are associated with the use of natural fibers for manufacturing packages. Being a renewable resource, natural fibers provide a sustainable alternative to other packaging materials such as aluminum and plastics, and furthermore natural fibers are both recyclable and biodegradable allowing for composting. Natural fibers include cellulose fibers of any natural origin, such as derived from wood pulp and / or plants.

[0005] Trays for plants is an example of a single-use packaging product where there is a strong interest in providing alternatives to plastic material. An example of a tray for pot plants made from molded cellulose pulp is disclosed in WO2023047295A1.

[0006] Whereas plastic is a material which is easy to use for producing three-dimensional products with complicated shapes, e.g. by means of injection molding, pulp molding has proven to be challenging, especially when it comes to designs requiring narrow sections such as e.g. cavities, recesses and / or portions with small draft angles. During manufacturing, wet pulp material can easily be trapped at narrow sections of the mold unintentionally building up thick bulbs and / or bridges that destroy the end product and leads to undesirable discard.

[0007] There is a need for improvements in the molded pulp field facilitating production of three-dimensional products such as trays, containers and pots. of the invention

[0008] It is an object of the present invention to provide a molded fiber packaging product and related production method solving or at least alleviating problems associated with producing a uniform and compact molded product by providing an improved method leading to minimized discard rate. Another object is to improve the yield of molded fiber products comprising small draft angles. of the invention

[0009] The object of the invention is obtained by means of a fiber-based three-dimensional structure according to the appended claims.

[0010] Thus, according to the invention, there is provided a three- dimensional packaging product, such as a tray, made of molded fiber, said product comprising a lower base portion and side walls extending from said base, wherein said base portion and side walls enclose at least one inner compartment. Said side walls are preferably tapered outwardly. The upper portions of the side walls transition into a circumferential rim, said rim comprising an inner wall, a top portion and a downwardly deflected outer wall defining a continuous inner space. The rim comprises destacking knobs for preventing the outside of said product touching the inner compartment of another, identical product when stacked therein, said knobs being arranged / positioned at said downwardly deflected outer wall.

[0011] The outline of the molded fiber product presented above is the result of careful development and design optimization, and many advantages are associated with the specifically chosen features. The circumferential rim has been given an outermost, downwardly deflected wall leading to increased mechanical strength compared to e.g. a tray with a horizontal, flat rim. Thus, the packaging product according to the invention be able to carry heavier loads without breaking. Moreover, placing of the destacking knobs at the outer rim wall leads to that they can be made larger both in volume and numbers than if positioned at the inner rim wall where they would compete with the space intended for the items / content to be carried by the packaging product. Furthermore, it has been found that trays according to the invention, where destacking knobs are located at the outer rim wall, can be destacked more easily compared to trays with no knobs and / or trays with knobs placed elsewhere on the product. Trays according to the invention that are superimposed are also more stable and have better position locking. This is especially advantageous for trays that are large sized and have higher weight. Heavier trays that are stacked run the risk of getting locked into each other, and becoming difficult to separate, e.g. after having been transported to the destination point where the trays are to be unpacked for further use.

[0012] According to one aspect of the present invention, said destacking knobs have a density of at least 4 g / mm3. This means that the destacking knobs are compact and robust, and thus mechanically stable with very low risk of breaking and / or cracking upon use. Also, the positioning of the knobs as described above leads to notable production-related advantages. As stated above, a circumferential rim with downwardly deflected outer wall is preferred due to improved mechanical properties of the product / tray. However, wet molding of pulp which includes pressing is difficult when the mold shape comprises sections that include e.g. narrow cavities and recessed portions such as said rim and the resulting continuous inner space. These difficulties are due to the significant risk that a surplus of wet pulp will get stuck in these narrow / tight sections during the forming, causing so-called "bridging". Such bridging leads to uneven wall thickness of the endproduct, and thereby to inferior product quality and increased discard rate. Bridging also leads to a risk that the product cracks during further pressing&drying steps of manufacturing. However, the inventors have realized that by creating a space adjacent to such narrow section / s whereto excess pulp can go during pressing, accumulation of pulp and resulting bridging are avoided. According to the invention, this phenomenon is taken advantage of by creating destacking knobs at the outer rim, i.e. creating a space in the form of knobs adjacent to the narrow section created by the circumferential rim with downwardly deflected outer wall. That is, the destacking knobs constitute the extra space whereto excess pulp is squeezed out from the continuous inner space during pressing the wet pulp into a product.

[0013] In summary, the packaging product (i.e. a tray) made of molded pulp can be designed with a deflected, outer rim for enhanced mechanical stiffness, where said tray comprises destacking knobs which, thanks to their position on the outer rim wall, are not in the way of content to be carried, and wherein the knobs are allowing for surplus pulp to be accumulated during pressing step in manufacturing thereby avoiding unwanted bridging during production and therefore contributing to lowered discard rate. As a result, waste is reduced and product quality is improved, where trays according to the invention are of uniform and compact material made by means of a predictable and efficient manufacturing method.

[0014] According to one aspect of the invention, said destacking knobs are three-dimensional, solid molded pulp structures.

[0015] According to another aspect of the invention, the packaging product is unitarily molded in fiber-based material such as cellulose based material. Preferably, said molding includes heat and pressure in a so-called thermoforming procedure.

[0016] According to another aspect of the invention, said downwardly deflected outer rim wall is a sloping wall with a draft angle (0) between 0-10°, preferably between 5-10° or between 5-8°. The skilled person understands that a "draft angle" refers to the degree of taper of the side wall of a mold or a product, or the angle of clearance designed to aid removal from a mold. It is calculated as a degree of draft from the vertical axis of the mold or product. It is also understood that a draft angle of zero degrees means a perfectly straight sidewall with no taper. The combination of a downwardly sloping outer rim wall and destacking knobs placed on said outer rim wall leads to easy destacking of superimposed trays, with low risk of trays getting locked to each other. According to one aspect of the present invention, the packaging product has a total weight between 100 - 150g.

[0017] According to the present invention, the packaging product has a load capacity between 8 - 20kg, or between 10 - 17kg.

[0018] According to another aspect of the invention, at least a section of the top portion of said rim has a width between 8 - 12mm.

[0019] According to another aspect of the invention, said destacking knobs are positioned with their lowermost portions at the level corresponding to the outer, lower edge of said downwardly deflected outer wall.

[0020] According to another aspect of the invention, a top portion of said knobs comprises a horizontal abutment surface providing a resting surface for another identical stacked product. Thanks to this feature, a distance is created between stacked trays which promotes easier separation after storage.

[0021] The present invention also relates to a method of producing a product according to the invention, comprising the steps of: a. providing an aqueous fiber pulp slurry; b. providing a molding tool with a three-dimensional forming surface, said forming surface comprising at least one recess defined by inner and outer side walls and a connecting wall that spans said inner and outer walls, said recess having a draft angle between 0-10°, and wherein said recess comprises at least one indentation located at said outer walls; c. immersing the forming surface into the pulp slurry and forming a wet fiber layer thereon; d. press-drying said wet fiber layer, during which step excess pulp present in said recess is squeezed into said indentation, to form a dried packaging product complementary to the contour of said forming surface, where said dried product has a dry content of at least 60wt%.

[0022] According to the invention, step d) comprises heating of said product in a thermoforming process.

[0023] Advantageous embodiments according to aspects of the present disclosure are described in the appended claims.

[0024] Brief description of the figures

[0025] By way of non-limiting examples only, embodiments of aspects of the present disclosure will now be described with reference to the accompanying figures in which:

[0026] Figs, la-c show perspective views of a product according to one embodiment of the invention;

[0027] Fig. 2 shows a cross sectional view of a product according to Fig. la; and

[0028] Fig. 3 shows another cross sectional view of a product according to Fig. la, illustrating the phenomenon of bridging of pulp.

[0029] The fiber-based three-dimensional packaging product 1 according to the invention will now be described with reference to the appended figures. According to the invention, the fiber-based three-dimensional product 1 is a tray for carrying a plurality of items. An example of such a tray is seen in Fig. la. Other types of trays and / or bowls for carrying cups, mugs, plants etc. are also conceivable. In the following, the term "tray" is used to denote the fiber-based three- dimensional product 1.

[0030] According to the invention, the tray 1 is unitarily moulded in fiberbased material such as cellulose based material. Fibers used can be, for example, lignocellulose fibers derived from wood or agriculture sources. It can also be recycled fibers such as deinked pulp. Other examples of pulps included are kraft pulp, dissolving pulp, CTMP, TMP, NSSC, reinforcement pulps, cellulose fines, sulphite pulps, pulps obtained from e.g. organosolv processes. The pulp can further be unbleached or bleached or even colored.

[0031] The pulp used for molding the tray 1 according to the invention may further contain process and performance chemicals. Examples of process-chemicals are e.g. drainage chemicals, slip or lubricants, wet strength chemicals, and fillers. Example, of performance chemicals are such that affects the final end product properties such as hydrophobicity (AKD, ASA, Rosin size, SMA, waxes), wet strength (various resins e.g. PAE), strength (polysaccharides such as starches or cellulose derivatives), rub resistance, oil and grease resistance (barrier chemicals esp. PVOH of derivatives thereof, cellulose derivatives), electrostaticity (metal salts), printability (Metal salts, cationic polymers, pigments), etc. Some of the additives can improve both process and performance. The tray 1 according to the invention may further comprise a barrier layer to protect against e.g. water and moisture. The desired barrier property can be achieved by adding barrier chemicals into the pulp suspension before wet moulding. Another option is to apply surface treatment with barrier materials on a ready formed product.

[0032] In the remaining part of the description, longitudinal, vertical and transverse axes will be referred to, in a non-limiting way, as shown by the "L,V,T" trihedron in Fig. la. As commonly understood, the plane defined between the transverse T and longitudinal L axis is a horizontal plane. The skilled person further understands that the "longitudinal side" may be referred to as the "long side" and that the "transversal side" may be referred to as the "short side" of the tray 1 in this example.

[0033] Now referring to the example of Fig. la, the three-dimensional packaging product is a rectangular open-top, multi-compartment tray 1 made of molded fiber. The tray 1 comprises a lower, horizontal base portion 2 and side walls 3 surrounding said base and extending from said base 2. The base portion 2 and side walls 3 enclose at least one receiving compartment 6. In the example of Fig. la the tray has six compartments 6. The compartments are intended for receiving products to be carried, such as flower pots, coffe cups or other items. As depicted in the cross-sectional view of Fig. 2, the upper portions of said side walls 3 transition into a continuous, circumferential rim 7. The tray 1 in Fig. la is shown from below in Fig. lc, exposing the base portion 2. As seen herein, the tray has a long side X and a short side Y. The long side X of the tray 1 is at least 35cm and the short side Y is at least 25cm. For instance, the long side X of the tray 1 can be between 35 - 60cm, and the short side Y of the tray can be between 25 - 35cm.

[0034] Turning now to the cross sectional views of Figs. 2-3, the rim 7 comprises an inner wall 70, a top portion 71 and a downwardly deflected outer wall 72 provided around an outer periphery of the tray 1 to give additional rigidity and mechanical strength to the tray 1. It will be appreciated that said substantially downwardly extending wall portion 72 may extend in a vertical plane, or preferably may slope to some extent, i.e. it can be angled (0) between 1 degrees and 10 degrees (i.e. the draft angle), for instance to ease release of the thermoformed container from a mold or mold part. Together, the inner wall 70, the top portion 71 and the outer wall 72 define a continuous inner space 73 seen in Fig. 2. The top portion 71 of the rim 7 has a width w, depicted in Fig. 3, which at its most narrow sections may be between 8 - 12 mm.

[0035] The rim 7 comprises solid destacking knobs 4 for preventing the outside of said product 1 touching the inside of another, identical product when stacked therein. The knobs 4 are arranged / positioned at said downwardly deflected outer wall 72 of said rim 7. The example of Fig. la has a plurality of destacking knobs 4 evenly distributed along the circumference of the tray 1, preferably with a C-C distance between two knobs 4 of 60-80 mm. Preferably, the tray comprises at least destacking knobs 4 at the four corners to provide stability during stacking. The detailed view of Fig. lb shows an example of a destacking knob 4 according to the invention. Herein is seen that the destacking knobs 4 are formed as bulging protrusions protruding from the rim wall 72 and terminating in the lower edge 74 of said rim. The top portion 40 of said knobs 4 comprises a horizontal abutment surface 41 arranged to create a distance between stacked trays. Moreover, said destacking knobs 4 are three-dimensional, solid molded pulp structures and have a density of at least 4 g / mm3. This is achieved by means of a production procedure which will be described later.

[0036] The method of producing the molded packaging product 1 according to the invention, e.g. a tray, will now be described. According to the present invention, the tray is preferably made in a wet molding process wherein an aqueous pulp slurry is applied by vacuum suction onto a porous forming tool / mold to form a 3D fiber layer followed by compression-molding performed under elevated temperatures, resulting in a dried fiber product having a shape complementary to the shape of the mold. In accordance herewith, the method of the invention comprises the steps of providing an aqueous fiber pulp slurry and a molding tool with a three- dimensional forming surface. The forming surface of the molding tool is complementary to the product to be produced, in this case, the tray 1 of Fig. la. The forming surface according to the invention comprises at least one recess intended for forming the rim 7. The recess of the tool is thus defined by inner and outer side walls and a connecting wall that spans said inner and outer walls, said recess having a draft angle (0) between 0-10° depending on which draft angle to be assigned to the rim 7. In order to create the destacking knobs 4, the recess also comprises at least one indentation located at said outer mold wall, where said indentation is complementary to the 3D shape of said destacking knob. The molding tool is immersed into the pulp slurry and a wet fiber layer is formed on said forming surface including said indentation. This means that the full volume of the indentation is now filled with wet pulp. At this stage of the process, i.e. after the first forming of the wet pulp on the forming surface, the narrow section defined by said recess will contain a certain amount of accumulated excess pulp 8. For better understanding, this phenomenon of accumulated excess pulp 8 is illustrated in Fig. 3, showing a cross sectional view of the wet fiber layer at the rim 7 of the tray 1 (the molding tool is not shown herein) after the first forming step of the method according to the invention. Next, the wet fiber layer is to be press-dried. According to the invention, the presence of said indentation provides a way to remove the excess pulp 8 from the bottom of the rim, and at the same time make use of it in the form of pressing said excess pulp into the indentations of the tool, thereby also adding pulp material to the destacking knobs 4 and increase their density. Thus, during the press-drying step, the excess pulp 8 accumulated in said recess due to bridging is pressed into said at least one indentation of the molding tool. This means that the indentation is filled with pulp material at least twice: firstly at the forming when pulp is vacuum sucked from the pulp slurry, and secondly when the excess pulp is forced by means of applied pressure into the indentation during press-drying. Press-drying may also comprise application of heat. After press-drying, a dried packaging product such as a tray has been formed which is complementary to the contour of said forming surface of the molding tool.

[0037] The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to restrict the invention to the variants described. Many modifications and variations will obviously be apparent to one skilled in the art, for instance the packaging product may be circular or having other shapes than the rectangular tray in the figures. The embodiments have been chosen and described in order best to explain the principles of the invention and its practical applications and hence make it possible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims

CLAIMS1. A three-dimensional packaging product, such as a tray, made of molded fiber, said product comprising a lower base portion (2) and side walls (3) extending from said base, wherein said base portion (2) and side walls (3) enclose at least one inner compartment (6); wherein the upper portions of said side walls (3) transition into a circumferential rim (7) comprising an inner wall (70), a top portion (71) and a downwardly deflected outer wall (72) defining a continuous inner space (73); wherein said rim (7) comprises destacking knobs (4) for preventing the outside of said product (1) touching the inner compartment of another, identical product when stacked therein, said knobs being positioned at said downwardly deflected outer wall (72).

2. The product according to claim 1, wherein the destacking knobs (4) are three-dimensional, solid molded pulp structures.

3. The product according to claim 1, wherein the packaging product (1) is unitarily moulded in fiber-based material such as cellulose based material.

4. The product according to claim 1, wherein said a downwardly deflected outer wall (72) is a sloping wall with a draft angle (e) between 0-10°, preferably between 5-8°.

5. The product according to claim 1, wherein at least a section of the top portion of said rim (7) has a width (w) between 8 - 12 mm.

6. The product according to claim 1, wherein the distance (d) between two adjacent destacking knobs is between 60-80 cm.

7. The product according to claim 1, wherein said destacking knobs (4) are positioned with their lowermost portions (42) at the level corresponding to the outer, lower edge (74) of said outer rim wall (72).

8. The product according to claim 1, wherein a top portion (40) of said knobs (4) comprises a horizontal abutment surface (41) arranged to create a distance between stacked products.

9. The product according to claim 1, having a total weight between 100 - 150g.

10. The product according to claim 1, having a load capacity between 8 - 20kg, such as between 10 - 17kg.

11. The product according to claim 1 having a rectangular shape comprising a long side (X) and a short side (Y), wherein the long side (X) of the tray 1 is between 35 - 60cm, and the short side Y of the tray is between 25 - 35cm.

12. A method of producing a molded packaging product such as a tray according to any one of claims 1-11, comprising the steps of: a. providing an aqueous fiber pulp slurry;b. providing a molding tool with a three-dimensional forming surface, said forming surface comprising at least one recess defined by inner and outer side walls and a connecting wall that spans said inner and outer walls, said recess having a draft angle (0) between 0- 10°, and wherein said recess comprises at least one indentation located at said outer wall, said indentation arranged to form said destacking knob of said packaging product; c. immersing the forming surface into the pulp slurry and forming a wet fiber layer on said forming surface including said indentation; d. press-drying said wet fiber layer, during which step excess pulp accumulated in said recess is pressed into said at least one indentation, thereby forming a dried packaging product complementary to the contour of said forming surface, where said dried product has a dry content of at least 60wt%, and wherein the pulp that has been squeezed into the at least one indentation form at least one destacking knob on said packaging product.

13. The method according to claim 12, wherein step d) comprises heating of said product in a thermoforming process.

14. The method according to claim 12, wherein at least a portion of the connecting wall has a width between 8 - 12 mm.

Images