Decoration and adornment methods for thermoformed pulp

Abstract

A method of forming a molded and printed product from pulp material including the steps of: forming a wet pulp pre-form mold; applying printing decoration to the wet pulp pre-form via an intermediate transfer surface: transferring printed pre-form to a final mold; and molding or re-molding the printed pre-form into a final shape.

Claims

1. A method of forming a molded and printed product from pulp material including the steps of: a) forming a wet pulp pre-form from the pulp material; b) applying a dry or cured printing decoration ink membrane bespoke coating to said wet pulp pre-form using an intermediate transfer surface, being separate and distinct from said pre-form, to form a printed pre-form; c) transferring the printed pre-form to a mold; and d) molding or re-molding said printed pre-form to form said molded and printed product.

2. The method of claim 1 in which the pulp material is a pulp slurry and the pre-form is formed by a pre-form mold, wherein the step of forming the wet pulp pre-form is by transferring the pulp slurry to the pre-form mold, the pre-form mold having one or more planar surfaces, compound conjoined planar surfaces and/or two-dimensional curved surfaces.

3. The method of claim 1, wherein the step of applying the printing decoration of step (b) is the step of applying the printing decoration to said planar and/or two-dimensional curved surfaces in a pre-distorted configuration so as to form a post distortion configuration on said molded and printed product.

4. The method according to claim 1 wherein said semi wet pulp pre-form is supplied in the form of a continuous planar sheet or continuous planar web of pulp fiber.

5. The method according to claim 1, wherein said application of said printing decoration to said wet pulp pre-form is assisted by the introduction of adhesives.

6. The method according to claim 1, wherein said intermediate transfer surface is any one of or a combination of a carrier web and/or an intermediate transfer roller.

7. The method according to claim 6, wherein the intermediate transfer surface is the intermediate transfer roller, wherein the intermediate transfer roller applies the printing decoration to said wet pulp.

8. The method according to claim 6, wherein said intermediate transfer roller controls the release of said printing decoration reducing the amount of release required for transfer of said printing decoration to said wet pulp pre-form.

9. The method according to claim 6, wherein said intermediate transfer surface is a carrier web of fiber material compatible with said wet pulp pre-form such that application of said printing and said intermediate transfer surface result in the melding and integration of said printing and said intermediate transfer surface with said wet pulp pre-form into a single integrated printed pulp mat.

10. The method according to claim 6 including a conveyer movement of said wet pulp pre-form at a speed commensurate with the speed of rotation of said intermediate transfer roller.

11. The method according to claim 7, wherein said printing decoration is applied to said intermediate transfer surface via one or a plurality of print heads co-operating with said transfer roller.

12. The method according to claim 11 including the step of curing printing ink from the print head on said transfer roller prior to application of said printed ink to said wet pulp pre-form.

13. The method according to claim 6, wherein said carrier web is fed from a feeder spool to a takeaway spool via a tensioning roller so as to co-operate with said intermediate transfer roller for delivery of said printing decoration to said wet pulp pre-form.

14. The method according to claim 2, wherein the step of forming a wet pulp pre-form comprises preparing a pulp slurry in a pulp holding tank having a forming mesh belt for moving across a suction head so as to deliver a continuous planar sheet of semi wet pulp pre-form to a station which performs the step of applying printing decoration.

Description

DETAILED DESCRIPTION OF INVENTION

(1) In order that the invention is more readily understood, embodiments thereof will now be described with reference to the accompanying drawings and legend wherein:

(2) FIG. 1 is a schematic illustration of one embodiment of the process of forming a moulded pulp product;

(3) FIG. 2 is a schematic illustration of another embodiment of the invention;

(4) FIG. 3 is a schematic illustration of a further embodiment of the invention;

(5) FIG. 4 is a schematic illustration of a still further embodiment of the invention;

(6) FIG. 5 is a perspective view of a printed pre-form of one embodiment of a product moulded from pulp material in accordance with an embodiment of the invention; and

(7) FIG. 6 is a perspective view of the final moulded product of FIG. 5;

(8) FIG. 7 shows the detailed packaging available from the invention when applied to a popular confectionery product;

(9) FIG. 8 shows another example of the invention;

(10) FIG. 9 shows the use of a carrier web to apply print to intermediate transfer surface;

(11) FIG. 10 shows the use of print heads to apply print;

(12) FIG. 11 shows an automated production line;

(13) FIG. 12 shows a transfer roller applying print to a batch run of pre-forms;

(14) FIG. 13 shows a transfer roller applying print to a continuous pulp sheet.

LEGEND

(15) 1 2 3 4 5 6 7 8 9 10 11 12 Product 13 14 Ribs 15 16 Slurry 17 Container 18 Mould 19 Mesh 20 Outer surface 21 Mat 22 Preform 23 Printing process 24 Final mould 25 26 Pre printed label or film 27 Lugs 28 Screen mesh 29 Pad 30 Vents 31 Anamorphic projection 32 33 Planar top 34 Conical surface 35 Printing 36 Intermediate transfer surface 37 Carrier web 38 Feeder spool 39 Take up spool 40 Tensioning roller 41 Transfer roller 42 Wet pulp 43 Conveyor belt 44 Print heads 45 UV light source 46 Wet pulp sheet continuous web 47 Forming mesh belt 48 Pulp holding tank 49 Suction head 50 Heated mandrel/rollers 51 Delivery belt 52 Forming station 53 Intermediate transfer roller(s) 54 Printed pulp sheet 55 Melded or integrated printed carrier web and substrate pulp

(16) Referring to FIG. 1, a product 12 moulded from pulp material is in the form of a cup having a complex outer surface shape with a plurality of ribs 14 which may be of different thicknesses and spacings to provide insulation, crush-resistance and other characteristics to the cup product 12.

(17) A slurry 16 of pulp material as hereinbefore defined is mixed in a container 17, and the desired additives to produce desired end-product characteristics are added to the slurry 16. Such additives may include chalk, fabric material, and the like known in the art of pulp moulding. The fibre content and moisture levels of the pulp slurry 16 are controlled so as to obtain maximum control over the deform characteristics of the pulp during the moulding processes and to thereby obtain control of the deformation profile and retention of the subsequently applied decoration or other printed material. Preferably, the moisture level of the slurry 16 in the container 17 is between 100% and 600% by weight (total weight/dry weight), more preferably between 200% and 450%, and, in some embodiments, between 300% and 400% by weight. It will be understood that the moisture content will depend to a large extent on the nature of the fibres in the slurry.

(18) A preliminary, or pre-form mould 18 is prepared so as to have planar and/or two dimensional curved surfaces, such as cylindrical or conical surfaces, to which printing or other coatings may be easily applied. In the illustrated embodiment, the pre-form mould 18 has a substantially conical form, to produce a pre-form with a conical outer surface 20. A framed mesh 19, which is in the form of the preliminary mould is dipped into the slurry 16 and lifts out a mat 21 of the pulp material from the slurry 16 in the container 17. The mat 21 is offered up to the matching part of the preliminary mould by the shaped mesh platen 19 where it is formed into the pre-form 22 using, air pressure, heat or other moulding processes which set the overall material parameters of the pulp product and the initial characteristics of the product shape. These characteristics include the volume of pulp material in the product, the uniformity of wall thickness, initial density and product size. The pre-form mould also removes a proportion of the liquid from the pulp mat 21 by applying a highly controlled amount of heat and pressure, and extracting steam through the mesh and through special vents 30 built into the opposing part of the preliminary mould (note, typically these vents are placed so as not to align with print areas as they cause a change in surface texture which interferes with the printing process) so that the pre-form is able to receive printed material thereon.

(19) When the pre-form 22 is released from the mould 18, it is not self-supporting because there is still a high moisture content within the pulp, to allow deformation at the final stage. It is held onto the preliminary mould by suction. At this point it has the shape of a hollow, frustroconical container matching the shape of the pre-form mould 18. The outer, conical surface 20 of the pre-form 22 is then able to be printed with appropriate printing and/or decoration using, for example, a dry, offset letterpress printing process schematically indicated at 23, or using offset photolithography, or other printing processes.

(20) The image printed onto the two dimensional conical surface of the pre-form 22 is an anamorphic projection which is designed so that, when the final product 12 is moulded, the printed indicia takes the desired form and shape required for the finished product. To create an accurate model for the distortion profile there are two distinct methods, the first is to utilise a printed grid with either uniform or otherwise predetermined pattern. A typical grid would use either an XY format or concentric circle. The product to be manufactured is then printed with the grid and the process of shaping and distorting is completed to create a finished product. The grid on the finished product will typically be distorted and mapping the final co-ordinates of this grid against the pre-deformed co-ordinates allows the creation of a distortion map. The other method is based on profiling the material to ascertain its deformation characteristics. This data would then be used to create a virtual distortion map which would then enable specific computer aided design software to predict the final level of distortion across any given shape. The mapping of the distortion across the surface, real or virtual, then enables the accurate pre-distortion of the original image/insignia/type/device so that it, the design, is faithfully reproduced in the finished form from the projection printed on the two dimensional surfaces. This form and shape may include the reproduction of lettering, barcodes, logos, images or any other design or decoration to be identified on the outer surface of the finished product 12.

(21) The printed pre-form 22 is then transferred to the final mould 24 where it is subjected to heat and/or pressure to cause the pre-form 22 to conform to the shape of the final mould 24. This shape includes the ribs 14 on the finished product 12, which ribs 14 have complex shapes. The transformation of the printing on the two dimensional surface of pre-form 22 to the three dimensional shapes formed in the final product 12 require the inks used during the printing process to be able to be deformed, stretched, compressed or otherwise transmuted to the desired form on the finished product 12.

(22) Referring to FIG. 2, this method is similar to that of FIG. 1 except that there are two separate preliminary mould processes before the final moulding. The first is where the shaped mesh platen lifts the pulp mat into the preliminary mould and a low heat (approx 50 degrees Celsius) and pressure is applied to create a loosely tamped version of the pre-form 22. As the pre-form mould opens, the pre-form is held onto the mould by suction, to give adequate support for the ensuing printing process. Then the indicia is applied to the pre-form 22 comprising a pre-printed label or film 26 which is applied to the pre-form. Appropriate tabs, or lugs 27 or other means, may be used to orient the label in the desired position within the pre-form mould 18. The pre-form mould then closes again, and heat and pressure are applied, under close parameters. The key here is to melt the heat release coating on the film, such that the ink is able to transfer to the wet pulp, and also to apply adequate pressure for the ink to bind and adhere to the pulp, whilst retaining enough moisture content within the pulp to allow for deformation inside the final moulding process. In one particular embodiment a temperature of 175 degrees Celsius, for one second combined with a pressure of 400 Kpa is sufficient.

(23) This process is the optimum one for this methodology, because it allows for a fast-moving semi-automated process. When the product is relatively flat, the film may be advanced over the pre-form 22 whilst being held on an opposing pair of rollers. As the process proceeds then each section of used film is advanced from one spool or roller onto the opposing spool or roller. In some cases, where the finished article has a deep recess, and it is not practical to lay the print film over the product, then the film is cut into pieces and positioned in the pre-form mould 18, thereafter the rest of the process remains the same.

(24) The label carrier film may either act as a laminate on the pre-form surface where it actually adheres to the surface, or may be ejected from the pre-form mould 18 on completion of the pre-form moulding process. The pre-form 22 is then transferred to the final mould 24 where the final product 12 is produced, with the shapes, texts and designs on the printed material transmuting to the desired appearance on the finished product 12. A higher heat is applied, typically 200 degrees Celsius, and all moisture extracted from the pulp by means of steam extraction vents, which are all placed on the opposing face of the pulp to the printed face.

(25) Where in-mould and release film methods are used, a stable film is used, such as a Garfilm ERC film (trademark), onto which is applied a Heat Release coating, typically at a coverage in the region of 2.7 gsm film weight. Then a specific high-draw ink is used to print on the images or text, using a system with an engraved gravure cylinder with a line screen ranging between 110 and 200 lines per inch. The ink contains the usual additives to increase scuff resistance and adhesion, flexibility and specifically draw (which is required because of the distortion during the re-form process). Heat is then applied to the rear of the film so that the release coating forms a film with the ink, partially bonding with it, which further increases the adhesion and transfer to the pulp. At this stage the printed film is stable and can be transported or stored if required. Once ready for use the film is used either in pre-cut pieces or direct from a roll. As the product emerges from the preliminary mould, it is retained on the male component of the mould by suction applied through the vents in the mould designed for this purpose, and for the purpose of steam extraction. The film is placed onto the planar surfaces designed to receive it. Then the female mould is re-applied and heat applied, typically 150 degrees Celsius, for one second combined with a pressure of 400 Kpa. Referring to FIG. 3, in this methodology, the printed design is applied to the conical outer surface of the pre-form 22 by a resilient pad 29, such as that known as a Tampo (trade mark) pad or similar, which is sufficiently malleable to facilitate printing onto uneven surfaces. Pad Printing is a relative of gravure printing. The inked image is created on an etched flat plate (clich) in a manner similar to gravure (in the surface rather than proud or in relief as in letterpress or flexographic printing). A large, resilient silicone rubber pillow (the pad) is pressed against the clich. The ink pattern is transferred to the pad, which is subsequently pressed against the substrate (in this case the pulp pre-form). Process (4 colour) printing can be accomplished by using several printing stations in sequence. The key feature of pad printing is the ability to print highly irregular surfaces. The resilient pad transferring the ink can conform intimately to surprisingly asymmetric and uneven surfaces. The resilient transfer pad lifts the image from the plate (clich) etched with the decorative image prior to engaging the pad with the outer surface 20 of the pre-form 22. The printed pre-form 22 is then moulded to the final product 12 as previously described.

(26) FIG. 4 illustrates a methodology wherein the pre-form 22 is printed using a screen printing technique. The screen mesh 28 is contacted by the surface of the pre-form 22 and the print is applied from the screen to the pre-form surface. The screen mesh 28 may be rotated around the axis of the pre-form 22 or the pre-form may be rotated and rolled along the planar surface of the screen mesh 28. Many forms of screen printing are known and may be adapted for use in embodiments of the present invention.

(27) As shown in FIGS. 5 and 6, a product 12, having a complex outer surface shape moulded from pulp material, in this case, a hemispherical bowl, can be printed or decorated in such a manner that decorative material in the form of letters, codes, logos or the like printed as an anamorphic projection 31 on the conical side surface 34 and planar top surface 33 of the pre-form 22 is recognisable and identifiable when the pre-form 22 is re-shaped to exhibit the complex curved surface 36. In the embodiment illustrated, the lettering 31 as an anamorphic projection is able to be printed by simple printing techniques on the flat top surface 33 and two dimensional side surface 34. The final moulding process causes the printed material to change shape to exhibit the desired properties.

(28) As previously discussed, these prior art techniques whilst providing some improvements on the earlier art are still subject to a range of limitations including reliance of the provision of the printing materials for application to the pre-moulds which take the form of silicon coated paper or various polymer webs. Moreover, these technologies are used for the application of substantially one off print runs. Whilst a degree of semi-automation can be applied the processes still essentially remain one step processes and are not well adapted for full automation and continuous batch lot productions as is commonly found in the general printing industry.

(29) A first embodiment of the invention will now be described with reference to FIGS. 9 to 12.

(30) In FIG. 9 the printed decoration is applied to an intermediate transfer surface 36. The intermediate transfer surface may be a carrier web (paper, film, etc) which is stored on a feeder spool 38. The feeder spool feeds the carrier web 37 to a take-up spool 39 via a tensioning roller 40. The tensioning roller 40 pushes the carrier web or film 37 tight and applies pressure onto the film and a transfer roller 41. The Transfer roller 41 is a large Teflon coated roller, which may contain small holes and is used to deliver the printing to the wet pulp 42. The rollers 40, 41 plus the spools 38, 39 are held in a frame in such a way that they can be moved together, so that the Transfer roller 41 can make contact with the wet pulp 42 with varying, designed, levels of pressure, without affecting the efficient transfer of decoration to the transfer roller itself from the carrier web. The Wet pulp 42 is itself on a conveyor belt 43 which moves in the direction shown, and at a speed which is in direct relation to the speed of the rotating transfer roller 41.

(31) In a further embodiment of this process as shown in FIG. 10 the transfer roller 41 can receive print directly via print heads 44. In a similar technique to dry offset letterpress which prints directly to a transfer cylinder then applies the ink to the final product. The ink is then typically cured by the use of a UV light source 45. However, the process of the invention can cure the inks on the transfer cylinder prior to contacting the now dry ink membrane to the surface of the wet pulp. The release layer would also be applied in this manner but would be activated by UV instead of heat, as illustrated in FIG. 10.

(32) In both the previously detailed embodiments the provision and delivery of the printing 35 by way of the intermediate transfer surface 36 is provided by a rotating transfer roller 41. The rotating transfer roller provides a highly efficient method of delivering the print 35 as a continuous and highly automated process where the rotation of the transfer roller continuously follows or co-ordinates with the movement of the wet pulp 42 so as to rapidly apply the print to the wet pulp in a continuous and highly automated fashion. In this manner, the speed of delivery is limited only by the ability of the transfer roller to accept print and deliver same to the wet pulp 42 which is being moved by a suitable conveying system.

(33) The rotating transfer roller therefore provides highly novel apparatus feature of the invention which allows the otherwise one by one application of printing to a pre-form to be highly automated as a continuous application of printing, not necessarily to the pre-form; but instead of using a pre-form, being applied directly to the wet pulp or pulp sheet material per se. The wet pulp can be printed either prior to preparation of the pre-form or after the preparation of the wet pulp into the pre-form stage. The additional advantage of the use of the transfer roller is shown in FIG. 10 where the print 35 can be applied directly to the transfer roller 41 by way of a plurality of print heads 44 positioned around the transfer roller. In this manner the print heads directly apply the print 35 to the transfer roller in a highly controlled manner including the ability to provide a variety or sequence of different prints which can be controlled from each separate print head.

(34) The ability to control the print can be further enhanced by the use of curing facilities including a UV curing lamp 45 such that the print can be applied to the transfer roller in a highly controlled and precise manner with a precise amount of release required to transfer the print from the print roller to the wet pulp or pre-form. In the instances where the print may require assistance with adhesion to the wet pulp an additional step can be incorporated including the application of appropriate adhesives to the wet pulp so as to ensure appropriate adhesion occurs.

(35) Continuous Sheet Pulp Moulding

(36) Further to the invention as so far described, a continuous sheet as shown in FIG. 11, typically referred within the industry as a continuous web 46, of pulp fibre is provided. The benefits in creating such a web include reducing the time spent in creating the initial pulp pre-form in the initial stage of the process which requires the cycle of forming be complete and the partly formed part forwarded on to the next stage prior to the forming tool returning to the tank to begin the manufacture of the next part. The deforming of semi wet pulp into new forms and increasing the level of deformation has characterised deformation parameters for different fibre types and blends; and level of deformation that could be achieved through the deformation of a planar web of semi wet pulp fibre. The method of manufacture provided by the invention reduces the need for the pre-forming tooling as used in the prior art. Printing onto the semi-wet web would then be discretionary. However, if printing was applied it would be applied prior to the secondary forming and drying stage as outlined in the prior art. The development of the current invention would therefore provide benefit from a reduction in costs due to increased line speed and no requirement for pre-moulds.

(37) Further to this development it is advantageous to review the design of the forming mesh upon which the web is created. Typically the pulp fibre is drawn onto a mesh forming tool through suction with the water being sucked through the mesh and the pulp fibres building up on the mesh, small fibres or fines are pulled through and typically removed through the use of a centrifuge system. FIG. 11 shows a forming mesh in the form of a belt 47 which is cycled through the pulp holding tank 48 and then over a suction head 49 with the time taken to cross this head being directly related to the build up of fibre on the web. As the web clears the tank it is then passed between a heated mandrel 50 and a further suction head (not shown) to reduce moisture content and through compression can set the dimensional tolerance and density of the pulp web 46. The pulp web 46 is now in a semi-wet form and has a degree of structural integrity such that the pulp having left the forming mesh can be propelled along the manufacturing path by the web forming behind and potentially assisted by delivery belts 51. The semi-wet pulp web can now be decorated by transferring the pre-printed ink membrane via the intermediate transfer surfaces 36 onto the planar pulp web. The decorated or undecorated semi-wet pulp web now enters the forming station 52. The forming station deforms the semi-wet pulp into its final form while also drying the pulp. The forming station can either have a rotary design or can have a straight press design as shown in FIG. 11 which would track with the movement of the web during the period of drying and deformation. The trimming of the product can occur either within this final forming tool or as a post forming stage. In this automated embodiment of the invention the design of the initial suction head 49 within the pulp holding tank 48 could also be modified to vary the suction on different parts of the web which would allow local control of pulp density which could be used to allow greater scope for deformation or for increasing localised pulp density which could be beneficial for product strength or to create a tactile difference to the finished pulp product.

(38) Referring now to FIGS. 12 and 13 a variation of the use of the transfer roller as previously described is shown with FIG. 12 showing the transfer roller 41 applying printing by way of the intermediate transfer surface 36 which is tensioned under tensioning rollers 40 and being applied to pre-forms 22 which are transferred by way of a conveyor belt.

(39) Alternatively, the transfer roller can be applied as shown in FIG. 13 where a continuous web of wet pulp sheet is drawn from a slurry pool 16 and in an analogous manner to that applied to the pre-form 22, the printing is applied by way of the intermediate transfer surface 36 in a continuously operating manner to the wet pulp sheet material 46 being drawn from the slurry 16 by way of a conveyor system.

(40) A further embodiment of the invention can be understood by combining FIGS. 11 and 13 where the constant pulp mat is fed from a slurry pool 16 to a conveyor belt with the printing decoration being delivered directly to the continuously formed pulp mat prior to the moulding stages. The carrier web is matched to the pulp fibre being used for the pulp mat. The carrier web carries the printing decoration and may also carry a dried, water activated adhesive on the side opposite the printing decoration.

(41) In one particularly preferred embodiment the carrier web is formed of a fibre material compatible with the substrate pulp mat wherein the printing being delivered and the carrier web per se are melded together into a single integrated pulp mat. The transfer roller 41 serves to assist in the controlled delivery of the carrier web/printing to the pulp mat to ensure faithful melding or integration there with.

(42) The use of a carrier web of compatible materials and construction to that of the substrate pulp, either as a continuously formed pulp mat or as pulp pre-forms mean that the print does not need to release from the carrier web and that the carrier web has limited waste. The fibre based carrier web would contact the wet pulp pre-form or continuously formed pulp mat and would adhere to the surface through a mixture of mechanical bonds and surface tension, further adhesion could also be applied through the use of spray adhesives applied at the point of contact or in dried adhesive coatings applied to the carrier web that are activated by moisture or other methods to bond to the underlying pulp pre-form or continuously formed pulp mat. The carrier web when applied to the pulp pre-form or continuously formed pulp mat would then be bonded more fully by the application of heat and or pressure into a singular surface. The now decorated pulp pre-form or continuously formed pulp mat would then be capable of being compressed and dried to a predetermined specification or of being deformed and dried to predetermined specifications.

(43) Further benefits of the embodiment of the invention include the ability of the fibre carrier web to add a high quality surface finish, higher gloss or matt finishes, tactile or visual properties, such as the by addition of metallic flecks or mica etc or be capable of adding specific physical properties, such as increased moisture barrier or anti-fungal properties.

(44) In this manner the intermediate transfer surface or carrier web is rolled out on top of the web pulp mat 46 with the adhesive if required touching the carrier mat and the printing facing up.

(45) Once the printing step is executed the pulp mat can then be formed directly with or without the use of an intermediate pre-form. The moulding process therefore creates the final shaped product and at the same time the fibres of the carrier web adhere to and meld with the fibres of the pulp mat. In this manner the printing decoration remains on the surface of the product and serves to decorate or print the final product in all three dimensions.

(46) The invention thus facilitates the manufacture of a multitude of moulded products using pulp material, the moulded products having complex shapes which, nonetheless, are able to be printed or decorated to produce attractive, aesthetically pleasing and/or informative products.

(47) It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.