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Title:
METHOD OF MANUFACTURING A CARDBOARD-BASED SHAPED PIECE AND A MOULD SUITABLE FOR THE MANUFACTURE
Document Type and Number:
WIPO Patent Application WO/2010/000945
Kind Code:
A1
Abstract:
The invention relates to a method of manufacturing a cardboard-based shaped piece and to a mould used in the manufacture. The shaped pieced is formed from a cardboard-based blank A by compression moulding under injection moulding conditions, wherein a spot between its bottom and side wall is bent to form the shaped piece. For the moulding, a mould is used, which helps to decrease the friction between the cardboard blank and the mould. This decrease in friction is provided by first roughening and then coating the surfaces of the mould that come into contact with the cardboard blank.

Inventors:
MAEAETTAE PAEIVI (FI)
KINISJAERVI REETTA (FI)
JAERVINEN JALLIINA (FI)
KARHU TEEMU (FI)
Application Number:
PCT/FI2009/050601
Publication Date:
January 07, 2010
Filing Date:
July 02, 2009
Export Citation:
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Assignee:
STORA ENSO OYJ (FI)
MAEAETTAE PAEIVI (FI)
KINISJAERVI REETTA (FI)
JAERVINEN JALLIINA (FI)
KARHU TEEMU (FI)
International Classes:
B29C33/42; B29C33/56; B29C43/36; B29C45/37; B31B50/59; B31F1/00; B32B29/00; B65D1/28; B65D1/34
Foreign References:
US20020068108A12002-06-06
US4026458A1977-05-31
GB2238266A1991-05-29
DE19938452A12001-02-15
Attorney, Agent or Firm:
BERGGREN OY AB (Helsinki, FI)
Download PDF:
Claims:
CLAIMS:

1. A method of manufacturing a cardboard-based shaped piece, wherein the shaped piece is formed from a cardboard-based blank A by compression moulding under injection moulding conditions, the piece comprising at least a bottom 1c and a side wall 1d, which extends upwards from the bottom, and a spot 1e between the bottom and the side wall that is bent to form the shaped piece, characterized in that, for the moulding, an at least two-piece mould is used, by means of which the friction between the cardboard blank and the mould is decreased, so that the surface of at least one part of the mould, which comes against the cardboard- based blank, the mould cavity 1a, is first roughened and then coated with a coating.

2. A method according to Claim 1 , characterized in that the surface roughness Ra of the roughened mould part is 0.1 μm or more, more preferably 0.1-0.9 μm.

3. A method according to Claim 1 or 2, characterized in that the surface against the front mould that comes against the cardboard-based blank, i.e., the printed surface, is roughened and coated.

4. A method according to any of the preceding Claims 1-3, characterized in that the coating of the cardboard-based blank that reduces friction comprises a material, which is selected from a group of silicon oxide-based coatings; metal ni- tride coatings; carbon-based coatings, more preferably diamond-coatings, metal carbide coatings, other carbon-based metal alloys; metal oxide coatings; and multilayer coatings made of these.

5. A method according to any of the preceding Claims 1-4, characterized in that the cardboard-based blank is coated with a coating, which is selected from a group of plastic materials, colouring materials, clay materials, minerals, lacquers and combinations thereof.

6. A method according to any of the preceding Claims 1-5, characterized in that the plastic material is selected from a group of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) or glass fibre-reinforced PET, polybu- tylene terephthalate (PBT), bioplastic, polyamide (PA) and ethylene vinyl alcohol (EVOH).

7. A method according to any of the preceding Claims 1-6, characterized in that the colouring material is printing ink.

8. A method according to any of the preceding Claims 1-7, characterized in that the temperature of at least one part of the mould that comes into contact with the cardboard-based blank during moulding is 55-95 0C.

9. A method according to any of the preceding Claims 1-8, characterized in that, under the injection moulding conditions, all parts of the mould that come into contact with the cardboard-based blank are at the same temperature.

10. A mould for forming a cardboard-based shaped piece from a flat cardboard- based blank by compression moulding under injection moulding conditions, characterized in that the mould comprises at least two parts and that the surface of at least one part that comes into contact with the cardboard-based blank is first roughened and then coated with a coating.

11. A mould according to Claim 10, characterized in that the coating is made at a temperature, where the production material of the mould is neither hardened nor annealed.

12. A mould according to Claim 10 or 11 , characterized in that the thickness of the coating is below 10 μrn.

13. A mould according to Claim 10-12, characterized in that the roughened and coated surface is the part of the mould that causes the greatest stretching tension in the cardboard-based blank.

Description:
METHOD OF MANUFACTURING A CARDBOARD-BASED SHAPED PIECE AND A MOULD SUITABLE FOR THE MANUFACTURE

Field of the invention

The invention relates to a method of manufacturing a cardboard-based shaped piece from a cardboard-based blank by compression moulding under injection moulding conditions. The invention further relates to a mould used in the manufacture of the cardboard-based shaped piece in question.

Background of the invention

Cardboard packages, wherein the package with the shape of a container can be formed from a flat cardboard blank, can be used as so-called tray packages, generally, for storing food products. Generally, good tightness is required of food product packages; no gas, humidity or, e.g., fat, depending on the quality of the food product, is allowed to leak through. The package should have good so-called barrier properties. Furthermore, in addition to the technical properties, the aesthetic and marketing values of the packages are increased by a possibility to use colours and text information on the outer surface of the package to optimize its appearance and informative quality.

The package is usually formed from the flat blank by pressing it to shape in a mould. The previous application FI20070973 of the applicant describes the manufacture of cardboard packages from cardboard blanks by compression moulding and casting, whereby in connection with the compression moulding, an edge flange is cast on the upper edge of the package for attaching a lid; and the equipment used in the manufacture and its operation.

The flat, straight cardboard blank preferably already has the layers and materials needed in the final product package before it is shaped. However, the compatibility and the plasticity properties of the different materials may deviate considerably from each other. This makes it challenging to select suitable parameters to be used in the moulding.

The mould that is used under the injection moulding conditions is at the same temperature on both sides, whereas in conventional tray pressing or tray compression moulding, the side that comes against the cardboard surface of the blank can be at a higher temperature, and the side that comes against plastic can be at a lower temperature.

A high temperature is preferable for forming the cardboard, as then the moisture in the cardboard evaporates and it is easier to shape the blank. A low temperature, again, is preferable for plastic, as then the coating neither softens nor becomes sticky and will thus not stick to the mould. As the temperature of the mould should be optimized between various materials, the end result is that, typically, the cardboard-based blank is shaped at a temperature that is not optimal for any of its individual components.

High plasticity and sliding with respect to the plastic material is required of the cardboard product, particularly in those places of formation, which are subjected to considerable shaping, e.g, bending, such as sharp turns, so that no mechanically or qualitatively weak spots, thin, cracking, or even breaking spots are created due to an excessive stretching of the said spot.

WO03078012 discloses a container, which can be hermetically sealed and which comprises a rim that is shaped from an injection-moulded material or coated with the same. Typically, the material used is plastic, such as polyolefin, nylon or polyethylene. The patent application further describes a method of making the rim and the equipment required for it.

The previous application FI20070973 of the applicant describes a method of forming a package from a cardboard blank, wherein the package with the shape of a container is formed by compression moulding, comprising a bottom and side walls extending upwards from the bottom. At the end stage of the compression moulding, a rim of the moulding material extending sideways is moulded to the upper part of the side walls, when the mould is kept closed in such a way that a mould cavity corresponding to the rim is formed by moving a counter surface inside the mould backwards from a surface opposite to it, after which the moulding material is introduced into the mould cavity.

Another previous application FI20061319 of the applicant describes a method of closing a package that contains a product. The lid part and the bottom part of the package are attached to each other by means of a plastic material. The lid part and the bottom part are attached to each other by means of an injection moulding closure by casting the plastic material on both sides of the seam between the bot- torn part and the lid part, so that the plastic material covers the seam on the outside and attaches the bottom part and the lid part to each other.

Efforts have been made to change the surface properties of tools by adding various coating materials to the surfaces. In the patent specification US 4 992 153, various coatings, such as carbon-containing wolfram, boron and silicon, which increase the hardness and wear resistance, are applied on a tool surface by a sputter DC-CVD process. An optimum hardness and sliding quality are obtained at a positive bias of the material, which is to be coated, relative to the plasma used. In the patent specification US2005242156, a bearing material of copper or a copper- containing alloy is at least partly coated with a DLC (Diamond Like Carbon) hard coating to increase the sliding quality.

The object of the present invention is to disclose a method of forming a cardboard product by using a mould suitable for injection moulding, so that the above- descried problems caused by sharp bending points are avoided.

Short description of the invention

The method according to the invention for forming a cardboard-based shaped piece is characterized in that, which is disclosed in the independent Claim 1. Another aspect of the invention discloses a mould, which is used in the manufacture of this cardboard-based shaped piece and which is defined in the independent Claim 11.

Surprisingly, it has been observed that by roughening the closing surface of the mould that is suitable for compression moulding and injection moulding and that is brought into contact with the cardboard-based blank, and by coating the surface in question, after roughening, by a coating that suitably improves the sliding quality and decreases friction, a shaped piece, such as a package is provided, which no longer exhibits mechanically or otherwise qualitatively weak spots in its pressed and creased, sharp angular bends or corners, which spots are a result of forming the cardboard-based blank.

The invention is described in detail below with reference to the following figures, wherein

Figs. 1-4 show the formation of the package by means of a forming tool at different stages, starting from the flat cardboard-based blank; and Fig. 5 shows a compression-moulded cardboard blank, which is coated with printing ink and on the corner of which a fracture can be observed; and

Fig. 6 shows the corners of the compression-moulded cardboard blank.

Detailed description of the invention

According to the first aspect of the invention, it provides a method of manufacturing a cardboard-based shaped piece, such as a package, wherein, according to Fig. 4, e.g., a package with the form of a container is formed from the cardboard- based blank A by compression moulding under injection moulding conditions, the package comprising at least a bottom 1c and a side wall 1d that extends upwards from the bottom, a spot 1e between the bottom and the side wall being bent to form the shaped piece and at least a two-piece mould being used for the forming. The invention is characterized in that the surface of at least one mould, such as the recess of the mould, essentially 1a, which comes against the cardboard-based blank and, in particular, contains a contact point with the spot 1e of the cardboard- based blank that is subjected to the greatest stretching tension, is first roughened and then coated with a coating that decreases the friction between the cardboard- based blank and the mould.

In the manufacture of the cardboard-based package, raw materials are used, which are commonly known in tray packages and plastic casting. The cardboard- based blank A (Fig. 1), from which the cardboard portion of the shaped piece is made, can comprise coated or uncoated cardboards, preferably coated cardboards. The coating can be one or two-sided, preferably one-sided. The object is a one-sided coating; however, in some products, it is not sufficient. These include, e.g., packages that are subjected to moist conditions, those that endure great mechanical stresses and those that require the ink to be protected. As coating materials, any appropriate coatings can be used, which fulfil the regulations and quality requirements that are applied to end use, preferably the use of food products. The food product in this connection refers to any food intended for human or animal consumption. The product packed in the package manufactured by the method according to the invention is preferably a food product.

The coating method of the cardboard may comprise dispersion coating, sol gel coating, extrusion coating, thermal coating or any other suitable known method. The cardboard refers to a fibre-based product, the basis weight of which may vary, which is suitable for packaging purposes and which can be compression-moulded. The coating layer or coating of the cardboard, which in Fig. 4 constitutes the inner and/or outer surface of the possible container T that is presented, preferably com- prises, particularly regarding food product use, a known barrier material, which prevents the substances from going from the food product to the outside of the package or from outside the package into the food product.

The coating materials can be selected from a group of plastic materials, colouring agents, clay materials, minerals, lacquers or combinations thereof. Typically, the coating contains plastic material for improving the strength properties and colouring agent for improving aesthetics and the informative quality. A clay surface or mineral coating provides a better printing surface, as the colour does not then penetrate deep into the pores of the cardboard. Thus, the end result is a visually better tray.

The plastic material coating can either be made in connection with or after manufacturing the cardboard. The plastic coating should be compatible with the possible injection-moulded flange material to achieve a tight seam between the coating and the flange that is to be cast. The plastic coating and the flange material can be of a different or the same material, preferably the same material. The plastic material coating comprises a polymer material, e.g., thermoplast or thermoplastic elastomer. It is essential that it can be moulded as solid or suitably soft coating material in the mould, and that it can also preferably be cast in liquid or fluid state so as to form a flange 8 on the edges of the shaped package (Fig. 4), and solidified into a shape that tightly joints the possible lid portion L (Fig. 4) and bottom portion 7 (Fig. 4) of the final package to each other. The tight joint of the lid and the flange is achieved in connection with seaming the lid.

The preferable plastic materials used comprise polymers, such as polyolefins, polyesters and polyamides or similar materials, which in the end use withstand sufficiently high temperatures, such as 225 0 C in the oven, or are suitable for use in the microwave oven. Below 100 0 C is preferably an adequate thermal resistance of the polymer used, as long as it withstands use in the microwave oven. Typically, polyolefins do not withstand normal use in the oven and, e.g., polyethylene (PE) hardly withstands use in the microwave oven. Therefore, these materials generally have other uses, such as microwave meal trays for polypropylene (PP). Polyethyl- ene is often used as part of the barrier coating, e.g., in protective gas packages together with ethyl vinyl alcohol (EVOH). The plastic material can be polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) or glass fibre- reinforced PET. The plastic material is preferably environmental-friendly, biodegradable plastic, which can be, e.g., polylactide (PLA), biodegradable polyester, starch-based plastic, polyhydroxyalkanoate (PHA) or polyhydroxybutyrate (PHB). The plastic material is most preferably selected from a group of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) or glass fibre-reinforced PET, polybutylene terephthalate (PBT), bioplastic, polyamide (PA) or ethylene vinyl alcohol (EVOH).

Considering the use according to the present invention, the plastic material can also be suitably modified. Furthermore, it is possible that the plastic material used is coloured in a suitable manner to enhance the appearance of the package, and it is further possible to use a mixture of plastics or laminates formed by several layers of plastic.

The colouring material used in the coating is preferably a commercial colouring agent suitable for food product packages, such as a pigment-based colouring agent or ink. The coating plastic is preferably ready coloured, whereby the product on the side of the coating is of one colour. The colouring material is most preferably a printing ink, which can be printed on the surface of the cardboard-based blank by known methods.

Furthermore, clay-based coatings, preferably kaolin or talc, which are known from paper coating, can be used in the coating. However, the use of clay-based coating is hard on the mould, as is well known.

The lacquer used in the coating should be suitable for the applications of the package. The lacquer is preferably ovenproof and/or it has good moisture resis- tance properties. The finished lacquer coat can preferably contribute to lowering the friction in the compression moulding of the cardboard blank.

Furthermore, the plastic coating materials mentioned above can also be used in the flange materials that are made by injection moulding, or in other parts that are essential to the package. In the flange material, the plastic can be blended with, e.g., talc to decrease the shrinkage or a pigment for a visual effect.

In the method according to the invention, the flat cardboard-based blank is rendered its final coated structural composition before shaping it to its final mechanical shape by means of the compression moulding and casting tools. In the method according to the invention, the cardboard, preferably coated cardboard is shaped by using, in the mould, a temperature optimal for each cardboard- based blank composition, at which temperature the plastic does not soften or melt so that it would cause sticking but, on the other hand, the cardboard material slides and moulds sufficiently, so that no breaking caused by stretching, as illustrated, e.g., in Fig. 5, or other unwanted mechanical or visual deformation takes place in demanding places of formation, such as sharp angles, in particular; especially when the bending radius is small. The smaller the radius, the easier the tray breaks. The tray comprises two effective radii, i.e., the radius of the "corners" of the bottom, such as R10 in Fig. 6A, and the bending radius between the bottom and the side wall, such as the bending radius of 99° in Fig. 6B.

When pressing to shape in an injection mould and under injection conditions, the essential changeable parameter is the retention pressure of the blank, as the temperatures must be selected on terms of the injection moulding. In particular, the magnitude of the retention pressure depends on the compressed air cylinders and pressure area used.

Using plastic coating as coating in the cardboard-based blank, especially on the side of the blank that remains outside the product, increases friction between the blank and the mould. Printing coloured figures or tones on the surface of the blank, or a clay coating may further increase this friction.

According to a preferred embodiment, the temperature of the mould is within 55- 95 0 C. Under the injection moulding conditions, all parts of the mould are preferably at the same temperature. Depending on the coatings, it would be optimal, if the different parts could be at different temperatures, but this is extremely challenging due to thermal expansion and moving (with respect to each other) of the parts. The temperatures presented above are extremely well-suited to be used, when the mould is coated with CrN or sol gel, and/or a cardboard-based blank that is coated with plastic material and/or printing ink is being moulded.

Fig. 1 shows the cross section of a moulding and casting tool, which can be used in the method according to the invention and which is intended for forming the package, starting from moulding the package and ending in a possible casting of a rim. The tool is a kind of a compression moulding and casting mould, which is intended, at a first stage, for moulding from the essentially straight, flat and uniform cardboard-based blank A, a package with the shape of a container formed by the mould, which can also be called a tray. A casting function can also be integrated into the tool for casting a material on the edges of the compression-moulded package.

The tool comprises a first force side part 1 or "front mould", which comprises a mould cavity 1a, against which the flat blank A is moulded and which defines the general form of the package. The tray thus generated comprises at least a bottom 1c, the shape of side walls 1d extending from the bottom, and inclination and roundings 1e of the walls, at which stretching very easily occurs. The tool also comprises a second force side part 2, "bottom mould", which presses the blank A into the said mould cavity 1a. For this, the bottom mould comprises a so-called shaping kernel 2a, which fits into the cavity 1a mentioned above, so that the blank is pressed between the kernel and the cavity, getting its final shape. The force side parts, i.e., the front mould and the bottom mould, are arranged to be movable with respect to each other to close and open the mould by arrangements, which are not described herein in detail. In the mould shown in the figures, the front mould 1 is a stationary part and the bottom mould 2 is a moving part.

The bottom mould 2 has, in an annular manner around the kernel 2a, a closing surface 2b, which is opposite to the corresponding surface 1 b that surrounds the cavity 1a of the front mould 1. When the mould closes, so that the force side parts 1 , 2 come together, the surfaces come against each other. This closing surface 2b also functions as an ejection surface in the ejection part, which is movable with respect to the kernel 2a in its depth direction. The ejection part thus moves between a front position (shown in Fig. 1) and a posterior position (shown in Figs. 2 and 3). The holding power of the closing surface 2b can be controlled by means of an actuator 3 that operates on a pressure medium and is attached to the bottom mould 2. This actuator 3 is most preferably a compressed air cylinder.

In the manufacture, compression moulding and casting of the cardboard blank, it is essential that the cardboard blank neither sticks to the front or bottom mould nor the kernels in them, but can be detached therefrom when the desired shape is achieved. Furthermore, it is essential that the cardboard-based blank A moves and/or slides enough with respect to the front and/or bottom moulds, i.e., the friction between the mould and the cardboard-based blank is sufficiently small, so that smooth, mechanically strong, high-quality and visually flawless shaped surfaces are formed in the rounded spots 1e, in particular. If the tray formed from cardboard-based blank sticks to one or both moulds or does not slide well with respect to the mould, a quality mutation, possibly a mechanically weaker spot, even a fracture or a visually deviating spot, is generated in the problematic spot. The surface roughening according to the invention and the subsequent coating reduce or even eliminate these problems. Another advantage is a decrease in or prevention of mould contamination, as the ink no longer sticks to the mould as easily as when not treated and does not thus shift to the next cardboard blank that is formed by the same mould.

Fig. 1 shows the position before closing the mould. The blank A that is to be pressed to shape is brought by a robot to the small holders (not shown) provided in the front mould 1. After this, the mould is closed, the kernel 2a settles into the cavity 1a, and the blank remaining between them is formed into a container with the shape of a tray. The stage, at which the kernel 2a begins to shape the blank after settling into the mould cavity 1a, is shown in Fig. 2. The closing surface 2b, including the face of the flange ring 4, leans forward by the force of the actuator 3, preferably compressed air, and retains the blank A at its edges between the closing surface 2b and the corresponding closing surface 1 b of the front mould 1 at the moulding stage. Fig. 3 shows a position, wherein the mould is completely closed and the blank A is formed into a tray, so that its outermost edge (the upper edge of the side walls of the tray) is flush with the face of the flange ring 4 or slightly in front of it. The last holding power on the blank edges is caused by the face of the flange ring 4, against which the closing surface of the front mould that surrounds the cavity 1 a of the front mould lies.

The holding power prevents too quick, easy or uncontrolled sliding of the blank into the mould cavity. The power should be great enough, so that the blank forms regular creases at its corners instead of creating irregular folds and/or creases. If the power is too great, the blank breaks at its corners.

The mould, such as the front mould, which is used in shaping the cardboard-based blank and which is preferably a steel mould, or the cavity of the front mould, the closing surface 1a, in particular, is roughened preferably to a roughness of 0.1 μm or more, more preferably to a roughness of 0.1-0.9 μm. The roughening can be made by machining or grinding or by some other method, preferably by machining or grinding. In particular, the spots of the mould, which expose the cardboard- based blank to the highest stretching tension, are preferably roughened and coated. The surface that is against the front mould and comes against the cardboard blank, i.e., the printed surface is most preferably roughened and coated.

In an embodiment according to the invention, both surfaces that come against the cardboard-based blank or all surfaces of the mould parts are roughened. After roughening, the roughened surface of the mould that comes against the blank is coated with a coating that decreases friction and enhances sliding. The coating is preferably carried out at a low temperature of below 220 0 C, more preferably below 200 0 C. When using the steel mould, the purpose is neither to harden nor anneal the mould, so the temperature used should be selected accordingly by an appropriate selection of the materials or the method of coating them, or both. The injection mould is often hardened before coating to increase its hardness, and this hardening should not be annealed, i.e., softened in connection with possible coating.

When needed, the surface(s) of the kernel coming against the cardboard blank can also be roughened and coated.

The coating methods used can be any known methods that are suitable for the purpose and work at low temperatures, such as the CVD (Chemical Vapor Deposition) or CVD-type methods, such as PACVD, PVD (Physical Vapour Deposition), arc discharge or arc steaming. The coating layer should be harder than the mould material, such as steel, and very wear-resisting, especially if the coating of the cardboard comprises clay materials, and chemically as inert as possible. A functioning coating layer can be very thin, the thickness of the coating is preferably below 10 μm, more preferably below 5 μm.

The coating materials on the roughened surface of the mould can comprise any known materials, which are known to increase the slippiness of the surface or sliding on the surface and, thus, to decrease the friction between the blank and the closing surface of the different parts of the mould, but which, however, adhere well enough to the surface of the mould. Typically, the known materials decrease fric- tion in contact with metal surfaces; however, the requirement in this invention is to decrease the friction, when dealing with the contact of the mould with the cardboard-based material, particularly the coated cardboard-based material at a raised temperature.

The coating material is preferably selected from a group of silicon oxide-based coatings, more preferably sol gel coatings; metal nitride coatings, more preferably CrN, TiN, AIN or mixtures thereof; carbon-based coatings, more preferably diamond-coatings, such as DLC (Diamond Like Carbon), t-aC, a-C:H, more preferably metal carbide coatings, such as TiC or WC, more preferably other carbon- based metal alloys, such as C+Cr, B, N, Ti or W; metal oxide coatings, more pref- erably Al, Ti, Cr, Si and Zr oxides; or multilayer coatings made of these. After pressing to shape and/or making the possible flange part of the tray, when the molten plastic materials have solidified, the mould can again be opened to its open position. The ejection part is now still in its posterior position. When the ejection part is pushed to its front position by the ejection rod 6, it removes the finished container T from the bottom mould 2 and, at the same time, the flange ring 4 can again be moved to the front position, i.e., returned to the position shown in Fig. 1. After this, the robot takes the finished container out and replaces it with a new blank A, after which the working phases are repeated as described above. It should be noticed that all the detailed figures that show the cross sections show the position throughout the circumference of the package.

The above-described tool and method according to the invention provide a shaped piece, a package that shows, even in the sharp folds of the package, no traces of stretching or fractures in the cardboard-based material or the coating layers on the same. When using the roughened and coated mould surface according to the in- vention, the cardboard-based blank slides suitably at a low friction with respect to the mould and is moulded into its desired shape that can even be strongly rounded.

According to another aspect of the invention, the invention thus provides a mould for forming a cardboard-based shaped piece from a flat cardboard-based blank by compression moulding under injection moulding conditions. This mould comprises at least two parts, the surface of at least one of them that comes into contact with the cardboard-based blank being first roughened and then coated with a coating that decreases friction.

According to a preferred embodiment of the invention, the method and the tool ac- cording to the invention can be used to manufacture a package, wherein the package that is formed from the cardboard-based blank by compression moulding comprises an edge flange, which is connected to the upper edge of the side walls of the package at an angle and which extends directly sidewards therefrom, the edge flange consisting of casting material and the seam of the casting material and the cardboard part of the package being also able to extend inside the side walls of the package.

The packages provided by the method according to the invention are typically polygons, such as rectangles, ellipses or round, according to the bottom, i.e., the horizontal section. Furthermore, the bottom part of the package can also comprise, e.g., separating shapes. As needed, the packages may also have other shapes, such as cup-like, a package with a round or square horizontal section, the relation of its height to its width being greater than in tray packages, i. e., a so-called cup. It is obvious to those skilled in the art that by modifying the shape of the tool, pieces with desired shapes can be made.

The following examples illustrate the method according to the invention in detail, however, without limiting the invention thereto.

Example 1

The surface of the mould made of steel that comes into contact with the cardboard blank, essentially at least 1a and part of the 1b surface, possibly the whole piece, which is technically an easier solution, is roughened to a surface roughness of 0.2 μm. The temperature of the mould is adjusted within 23 °C-200 0 C. Cardboard- based plastic-coated (PET) flat blanks are brought into the mould to be moulded, whereby the mould, the surface 1a and part of the surface 1b, which the blank covers, comprises as coatings

a. nothing (i.e. a reference) b. sol gel, SiO 2 , and a blank, which has no prints c. CrN, and a blank, which has no prints d. sol gel, SiO 2 , and a blank, on which ink prints have been made e. CrN, and a blank, on which ink prints have been made.

The samples are measured for dynamic friction in the direction of fibres (KS) and in the direction against the fibre direction (PS). The measuring results are shown in Table 1.

Even with this roughening, the sol gel coating without prints show a decrease in friction. With the CrN coating, the friction does not decrease until at temperatures high enough for the plastic coating to begin to soften. The printing increases the friction, even if the surface is roughened by 0.2 μm and coated with sol gel of CrN.

Example 2

The surface of the mould made of steel that comes into contact with the cardboard blank is roughened to a surface roughness of 0.6 μm. The temperature of the mould is adjusted within 23 °C-200 0 C. Cardboard-based, plastic-coated (PET) flat blanks are brought into the mould to be moulded, whereby the moulds comprise as coatings

f. nothing (i.e., a reference) g. sol gel, SiO 2 , and a blank, which has no prints h. CrN, and a blank, which has no prints i. sol gel, Siθ 2 , and a blank, on which ink prints have been made j. CrN, and a blank, on which ink prints have been made.

The samples are measured for dynamic friction in the direction of fibres (KS) and in the direction against the fibre direction (PS). The measuring results are shown in Table 2.

Now, a decrease in friction is observed on each coating type tested, both with and without prints. The hotter the mould, the more the friction coefficient decreases.