PAPER PACKAGING CONTAINERS AND PROCESS FOR MAKING THE SAME

Abstract: A paper material for forming soft three-dimensional packaging containers, characterised by consisting of a yieldable paper sheet (4) to which at least one impermeabilizing agent has been added.

Description: Paper packagi ng containers and process for maki ng the same. This invention relates to a paper material for forming threedimensional soft packaging containers for products in the solid, liquid, solidifiable liquid, granular or powder form, a method for forming said packaging containers and a container obtained by the method. Methods for packaging liquid, solidifiable liquid, granular or powder products in metered quantities for consumption are known. In one of these methods, half-casings of substantially rigid plastics material, for example polypropylene, are thermodeformed and joined together along their adges to form a cavity, which can then be filled by a traditional filling machine. If the product is to be used in the solid, liquid, granular or powder state, the package obtained in this manner is ready for marketing after sealing. If however the product is to be used in the solid state (for example ice-cream), after the filling operation the container filled with the solid or liquid product and then sealed is refrigerated and preserved under refrigerated conditions until its consumption. Independently of the nature of the packaged material, these known containers have the advantage of being formable in practically any shape, but also have certain drawbacks, and in particular: - a considerable cost, related to the cost of the plastics material used, - practically no ecological characteristics, given the non-biodegradable nature of the plastics used, - a certain weight, with consequent transport costs, - a space requirement after use, in that the container cannot be substantially reduced in volume after use compared with the full container. It is also known to package generally liquid products using a continuous tubular element of polythylene - or bipolyethylene - coated cardboard which is filled in portions separated by transverse welds, transverse cuts then being made through said welds. The package obtained is generally of tetrahedral, parallelepiped or cylindrical shape, depending on the manner in which the transverse welds are made and on the folding operations to which the package may be subjected after its separation from the continuous tubular element. This known method considerably accelerates the packaging operations but has certain limitations in terms of obtainable shapes, space requirement of the packaging container after its use, and cost. An object of the invention is to eliminate these drawbacks by providing a paper material for forming soft, but in some cases rigid, packaging containers of practically any shape for solid, granular, powder, liquid or solidifiable liquid products, which is of low costs. A further object of the invention is to provide a paper material for very light packaging containers such as to minimally impinge on packing and transport costs. A futher object of the invention is to provide a paper material which enables the containers to be reduced to minimum volume after use. A futher object of the invention is to provide a container which is biodegradable. A futher object of the invention is to provide a method which enables traditional commercially available packaging equipment to be used. These and further objects are attained according to the invention through a paper material as described in claim 1. According to the invention a method is also provided as claimed in claim 14. Some preferred embodiments of the present invention are described in detail hereinafter with reference to the accompanying drawings, in which: Figure 1 is an enlarged section showing a portion of paper material according to the invention; Figure 2 is a schematic representation of one embodiment of the method according to the invention; Figure 3 is a perspective view of the open mould of Figure 2, to a larger scale; Figure 4 is a vertical section through a closed mould during the stage preceding the introduction of pressurized fluid; Figure 5 shows the same view as Figure 4 in the stage following the introduction of pressurized fluid; Figure 6 is a perspective view of a packaging container extracted from the mould and awaiting filling; Figure 7 is a schematic cross-section through an open mould used for implementing a further embodiment of the method; Figure 8 shows a futher embodiment of the mould of Figure 7; Figure 9 shows a packaging container extracted from the mould and awaiting filling, and Figure 10 shows a different embodiment of a portion of paper material. As can be seen from the figures, the paper material 2 according to the invention consists of a yieldable paper sheet 4 to which during the preparation stage a food-suitable or other chemical additive of impermeabilizing, water- repellent and anti-grease characteristics is added. This additive can advantageously be a fluorinated compound, colophony, formaldehyde, titanium dioxide, a polymer mix, waxes, paraffins or substances having the property of reducing or nullifying the degree of porosity of the yieldable paper. In other cases the chemical additive is not added during the paper preparation stage but is sprayed onto the already prepared yieldable paper by traditional methods. The paper 4 has a degree of yieldability such as to enable it to be stretched permanently in a transverse and longitudinal direction by at least 10% and preferably 20%, and has an ultimate tensile strength not less than 4000 m so as to ensure that the final desired configuration can be obtained without tearing. The paper material is preferably prepared by traditional methods which do not form part of the invention and are not further described. In the embodiment shown in Figure 2, the paper material is wound onto a bobbin 8 and is folded longitudinally so that the two edges face each other. In the embodiment shown in Figures 2-4, the method of the invention also comprises the use of a mould formed from two half-moulds 10 movable relative to each other and each comprising a cavity 12 bounded by a rim 14 comprising an interruption 16. The cavities 12 of the half-moulds 10, the rims 14 which bound them and the interruptions 16 in the rims 14 perfectly mate when the two half-moulds 10 are brought into mutual contact. On the drawings the two half-moulds 10 are shown with a single impression for simplicity, whereas in practice it is preferable to use multi- impression moulds to accelerate the packaging operations. The cavity 12 of each half-mould 10 extends outwards in the form of a conduit 18 which opens at the interruption 16 provided in the rim 14 bounding the cavity 12, and which mates with the adjacent conduit in the other half- mould 10. In this embodiment, the method of the invention is as follows: the paper material is firstly treated with a preferably peelable, heat-softenable adhesive applied as a contour corresponding to the contour of the desired shape. After the sheet 2 has been folded longitudinally into two parts and has then been positioned folded in this manner between the two half-moulds 10, these latter are made to approach each other so as to retain it between them (see Figure 4). The two facing rims 14 are then pressed together and the adhesive softened, with consequent joining together of the two parts of the sheet included between them, with the obvious exception of the interruption 16. After this joint has been made, compressed air is fed through the conduit 18 to stretch the two sheets of paper material retained between the rims 14, so that they adhere to the surface of the respective cavity 12 (see Figure 5). On termination of this blowing stage the two half-moulds 10 are spaced apart to allow removal of an impermeabilized paper packaging container 20 having the configuration corresponding to the cavities of the half-moulds 10, the configuration being permanent because of the permanent deformation to which the paper material has been subjected (see Figure 6). This container can then be fed for filling, preferably carried out by automatic machines, followed by sealing the interruption 16, through which the product to be packaged was fed and which can be of liquid, paste, granular or powder form. Depending on the nature of this product, the packaging container 20, once sealed, can be subjected to further processing or transferred to storage. For example, if the product is to be used in the liquid (shampoo, detergent, milk, water, etc.), granular or powder state, it can be directly stored. If the product has been temporarily heated to be transformed into the liquid state, although being solid at ambient temperature (chocolate, cheese or soap), it is sufficient to await its cooling to cause it to assume the shape of the container 20, and maintain this shape even after this latter has been removed at the moment of consumption. If however the product is a liquid for preparing an ice¬ cream or water ice, after filling it must be frozen, which can be done just prior to consumption. In short, independently of the product to be packaged, this first embodiment of the method of the invention is based on the principle of using the impermeabilizing, water-repellent and anti-grease additive not only for its traditional purpose of impermeabilizing the yieldable paper against the liquid product during filling and during its storage, but also for impermeabilizing the paper against air and hence making a forming operation with paper possible which has never been able to be effected in the past without using pleats. A further purpose is to form the barrier necessary for the product to remain in the packaging container. In a second embodiment of the method according to the invention, after the edges of the paper material have been joined together, not air but the actual liquid product to be packaged is fed through the conduit 18 under pressure, to stretch the yieldable paper until it adheres to the walls of the half- mould 10. Again in this case, the treatment to which the paper is subjected can depend on the nature of the product to be packaged, but in all cases the invention provides for forming the packaging container within the mould by the action of the actual product to be packaged. If this product is solidifiable, ie if it is a solid at ambient temperature and has been previously heated to facilitate the filling, or if it is a liquid at ambient temperature but is to be refrigerated after filling, the invention involves mutual action between the liquid product forces the paper material to assume the form determined by the mould within which it is housed, whereas during solidification it is the container itself, previously been shaped by the liquid, which forms the mould for the liquid during its solidification. In both embodiments of the method of the invention, and in particular for packaging edible solidifiable liquid products, the filling stage can be preceded by the introduction into the mould of a traditional stick 21, for example of wood or plastic, which when the product has solidified remains embedded therein to form an essential part of packaged products hand-held during consumption. In a third embodiment of the method of the invention, the paper material 2 is made to face the cavity 22 of a mould 24 and is constrained thereto along the continuous edge of said cavity. The mould is then put under vacuum via suitable suction channels 26 provided in it so as to cause said material to stretch tangentially until it adheres to the surface of said cavity. To achieve a greater stretching effect a complementary punch 28 is made to face the cavity, to contribute mechanically in stretching the paper during suction. This mechanical effect is preferably combined with a pneumatic effect, for which purpose the punch 28 is provided with a plurality of channels 30, through which the paper material 2 can be exposed to a jet of possibly hot air. The tray-type packaging container 32 obtained in this manner can then be filled with the product to be packaged, and then be closed by sealing with a transparent film 34 or by applying a complementary inverted tray with the edges of both trays previously coated with a traditional adhesive. In any event independently of embodiment used, the paper material according to the invention and the method for forming the desired packaging containers therefrom have considerable advantages, and in particular: - they enable packaging containers to be obtained practically without any limit on their shape, - they enable traditional commercially available forming and filling equipment to be used, - they enable lightweight low-cost packaging containers to be formed which can be reduced to minimum bulk after use and which are biodegradable. In a further embodiment shown in Figure 10, an impermeabilizing film 5 of yieidability and strength compatible with those of the paper material is applied to a surface of the paper material. This impermeabilizing film is preferably a plastics film obtained from polyethylene or another thermoplastic material, or an aluminium alloy. By virtue of the presence of the impermeabilizing film, the paper material obtained in this manner has the further advantage of enabling the joint between the two sheets to be made by traditional thermowelding methods. In a further embodiment, to achieve a more robust structure two sheets of paper material are used, bonded together by an extrusion of polyethylene or of a traditional adhesive.

Claims: C L A I M S 1. A paper material for forming soft three-dimensional packaging containers, characterised by consisting of a yieldable paper sheet (4) to which at least one impermeabilizing agent has been added. 2. A paper material as claimed in claim 1, characterised in that the chemical additive has water-repellent characteristics. 3. A paper material as claimed in claim 1, characterised in that the chemical additive has anti-grease characteristics. 4. A paper material as claimed in claim 1 , characterised in that the sheet of yieldable paper has a degree of yieldabiiity of not less than 10% in any direction. 5. A paper material as claimed in claim 1, characterised in that the chemical additive is waxes and/or paraffins. 6. A paper material as claimed in claim 1, characterised in that the chemical additive is colophony, a polymer mix or formaldehyde. 7. A paper material as claimed in claim 1, characterised in that the chemical additive is a fluorinated compound. 8. A paper material as claimed in claim 1, characterised in that the chemical additive is titanium dioxide. 9. A paper material as claimed in claim 1 , characterised in that one of its surfaces is covered with a film of impermeabilizing material. 10. A paper material as claimed in claim 5, characterised in that the material consists of two yieldable sheets of paper bonded together by an extrusion of polyethylene or of a traditional adhesive. - - 11. A paper material as claimed in claim 6, characterised in that the impermeabilizing film consists of thermoformable and thermoweldable material. 12. A paper material as claimed in claim 6, characterised in that the impermeabilizing film is of polyethylene. 13. A paper material as claimed in claim 6, characterised in that the impermeabilizing film is of aluminium alloy. 14. A method for forming packaging containers from the paper material in accordance with one or more of claims 1 to 13, characterised in that a sheet (2) of paper material is made to face the cavity of at least one mould and is constrained thereto along the continuous edge which bounds said cavity, after which said sheet of paper material is caused to stretch tangentially until it adheres to the inner surface of said cavity to obtain a concave tray having the shape of said cavity, to be fed to subsequent filling and closure. 15. A method as claimed in claim 14, characterised in that the sheet of paper material is stretched by vacuum created between it and the inner wall of said cavity. 16. A method as claimed in claim 14, characterised in that the sheet of paper material is stretched by mechanically urging the sheet into the cavity by a punch having a shape substantially complementary to that of said cavity. 17. A method as claimed in claim 16, characterised in that the mechanical effect is supplemented by a pneumatic effect by feeding a compressed air jet onto the sheet of paper material through said punch. 18. A method as claimed in claim 15, characterised by using hot compressed air. 19. A method as claimed in claim 14, characterised in that after its filling, the concave tray is sealed with a material film applied to it along its edge. 20. A method as claimed in claim 14, characterised in that after its filling, the concave tray is closed by another, which is positioned inverted on the first and glued to it along their contacting edges. 21. A method as claimed in claim 14, characterised in that: - the surface of the paper material is treated with a heat-softenable adhesive applied in a pattern corresponding to the contour of the form of the container, - two sheets (2) of paper material are laid one on the other, - the two sheets (2) are subjected to softening of the adhesive along a perimetral line (14) of the predetermined pattern, comprising at least one interruption (16), to cause softening of the adhesive and subsequent joining together of the sheets, - a fluid is fed under pressure through said interruption (16) into the interspace bounded by said sheets (2) maintained between two cloased half-moulds (10) which form between them a cavity (12) bounded by said perimetral constraint line (14), to hence cause stretching of said sheets (2), which adhere to the walls of said cavities (12), - the volume bounded by said sheets (2) is filled with the product to be packaged, and - the perimetral line is closed in correspondence with said interruption (16). 22. A method as claimed in claim 21, characterised in that the two sheets (2) to be coupled together are obtained by longitudinal doubling of a continuous web (8). 23. A method as claimed in claim 21, characterised in that the two sheets (2) are joined together along said perimetral line by thermowelding. 24. A method as claimed in claim 21 , characterised in that the two sheets (2) are joined together along said perimetral line by ultrasonic welding. 25. A method as claimed in claim 21 , characterised in that said two sheets (2) are joined together while retained between said half-moulds (10). 26. A method as claimed in claim 21 , characterised in that the fluid is the actual product to be packaged. 27. A packaging container obtained by the method claimed in one or more of claims 14 to 26, characterised by consisting of at least one concave tray to the edge of which, after filling, there is applied a closure film. 28. A packaging container obtained by the method claimed in one or more of claims 14 to 26, characterised by consisting of two concave trays joined together along their adjacent edges.

Inventors: TRANI GIORGIO, TRANI, GIORGIO
Applicants: TRANI GIORGIO, TRANI, GIORGIO
Application year: 1997
Main classification: D21H27
IPC codes: B31D5, B31F1, B32B29, B65D1, D21H19, D21H27