WO1995016555A1

WO1995016555A1 - Printing components

Info

Publication number: WO1995016555A1
Application number: PCT/GB1994/002706
Authority: WO
Inventors: Cyril Miles Prince; Ettore Bruno
Original assignee: Ams Packaging S.A.
Priority date: 1993-12-15
Filing date: 1994-12-12
Publication date: 1995-06-22
Also published as: ZA9410045B

Abstract

An apparatus for and method of printing components of polymeric materials by thermoforming a thermoplastic sheet (10) to which a layer of material (15) which carries a thermally diffusable dyestuff has been applied. The heat of thermoforming is used to cause the dyestuff to diffuse from the carrier layer onto the thermoplastic sheet. In an alternative embodiment the invention uses the heat of injection moulding in order to transfer sublimable dyestuffs from a support layer placed within an injection mould onto the injection moulding component. The operation enables three dimensional decoration to be applied to a component and also allows a dual use of energy resources to be made.

Description

PRINTING COMPONENTS

This invention relates to an apparatus for and method of printing components of polymeric materials.

Printing of plastics components is well-known and includes such processes as offset lithography,, for example. However, known techniques pose problems in printing the finished component, due to its three dimensional and often complex form and are also very costly in terms of energy usage.

Processes are already known for carrying out the decoration of fabrics with the so-called transfer decoration system, which in practice is based on the use of a support layer on which are provided decorations or similar which are realised by means of inks or sublimable dyestuffs.

The transfer of decoration or similar from the support layer to the fabric is obtained by heating by means of a plate brought to a temperature of 170/220°C.

Similar processes are already used for the transfer of decorations obtained on a support layer with sublimable lacquers, when the transfer has to be carried out on flat surfaces.

At present, however, the problem of forming moulded surfaces with the direct application of decorations obtained through sublimable lacquers has not been solved and in particular it has not been possible to carry out the transfer of the decorations onto articles obtained by means of injection moulding.

Such problems derive from the difficulty of prearranging a support which is simultaneously deformable, so as to follow the shape of the mould, and in the degree of withstanding the injection temperature of the plastics material without being damaged.

The invention aims to overcome the above problems by means of a process for applying a decoration onto thermoformed or injection moulded articles.

According to the present invention, there is provided a method of producing a printed plastics component comprising: providing a layer of material which carries a thermally diffusable dyestuff; heating a thermoplastic to moulding temperature and combining the thermoplastic and carrier layer, whereby the dyestuff is transferred from the carrier layer to the thermoplastic; and moulding the thermoplastic to form the printed component.

In one embodiment of the present invention, there is provided a method of producing a printed plastics component comprising: combining a sheet of thermoplastics material with a layer of material which carries a thermally diffusable dyestuff; heating the combination to the temperature required for thermoforming the sheet so that the dyestuff is transferred from the carrier to the sheet; and thermoforming the thermoplastics material to form the printed component.

Preferably, the method further comprises the step of separating the carrier layer from the sheet. This step may take place prior to, during or after the thermoforming step.

According to a further aspect of the present invention, there is provided an apparatus for producing a printed plastics component, comprising: means for combining a sheet of thermoplastics material with a layer of material which carries a thermally diffusable dyestuff; heating means for heating the combination to the temperature required for thermoforming and for transferring the dyestuff from the carrier layer to the sheet; and a thermoformer for producing a formed component.

In another embodiment of the present invention, there is provided a method of applying a decoration to an injection moulded component made of plastics material, characterised by applying, onto a support layer, a decoration comprising thermally diffusable dyestuff; positioning the support layer on the die of an injection mould with the decoration directed towards the injection zone; coupling a mandrel of the mould to the die for partial deep drawing of the support layer; injecting plastics material to complete deep drawing of the support layer; cooling the moulded component; extracting the component from the mould; and separating the moulded component from the support layer.

The invention thus utilises the heat required for thermoforming or injection moulding in order to diffuse (sublime) the dyestuff to produce the desired printing and/or decoration.

The transfer of the decoration takes place directly during the thermoforming or injection moulding stage, thus obtaining an article in which the decoration forms an integral part.

A particular advantage of the invention is that the decoration improves the anti-scratch characteristics of the surface of the object made of plastics material. In addition, the method of the present invention is able to give the most ample guarantees of reliability and safety in use.

Not only do the method and apparatus of the invention enable a dual use of energy resources to be made, ie for both sublimation and thermoforming or injection moulding, but they also enable a component to be manufactured which has an all-round three dimensional printed finish. Such decoration is very difficult to obtain by sublimation after the moulding or thermoforming operation has taken place, since the heat required for sublimation tends to distort the component, rendering it useless. Furthermore, it is very difficult to obtain continuity of printing around any corners or complex shapes of the component. In one embodiment the layer of material, or web, comprises paper which is readily removed from the sheet prior to thermoforming. Alternatively, the web may comprise a dissimilar thermoformed plastic web, which may be removed from the formed sheet before or after thermoforming has taken place. Removal after thermoforming has the advantage of providing a high quality decoration but the web is less readily strippable from the formed product than from an unformed planar sheet. Whilst it is possible to deform the web after moulding, it is preferable for very large deformations to form the web prior to injecting a thermoplastic material onto the web. This leads to better accuracy and reproducibility.

The web may be combined with the sheet at the sublimation/diffusion stage or, alternatively, the combination may take place prior to diffusion of the dyestuffs as a discrete step. Preferably, the web and sheet are held together during diffusion so that there is little or no relative movement. Thus a single stage combination and diffusion operation is advantageously carried out between nip rolls to which heat may be applied. A two stage operation preferably comprises combining the web and sheet by prelaminating with low level heating to hold the web and sheet together, followed by boosting the heat applied so as to diffuse the dyestuffs.

The method preferably further comprises injection moulding additional thermoplastic material onto the articles formed in the sheet to produce a desired internal shape, screwthreads, ribbing or the like for the final component or container. The formed sheet may then be trimmed to provide individual components or containers. Alternatively, the trimming may take place prior to injection moulding. Usually, the majority of material for the final product is injection moulded. Alternatively, injection moulding may be omitted if the trimmed articles are usable as finished products without the need for additional material.

The web may be applied to either or both sides of the sheet, depending on where decoration is desired. If decoration is applied to the side which is to become the inside of the finished articles then the thermoplastic sheet is preferably transparent so that the decoration is visible from the outside of the formed products.

The temperature of moulding is preferably selected according to the particular polymeric sheet which is to be decorated and also according to the dyestuffs which should diffuse at the moulding temperature.

In another thermoforming embodiment, the dyestuff may be registered on the support web so that decoration is only applied to the areas which are to be thermoformed. In this way, material removed by trimming of the thermoformed sheet can be recycled, without problems which would otherwise arise when recycling print-contaminated sheet.

Typical materials for carrying out the invention may include non-cystalline or partially crystalline thermoplastics, such as styrene polymers, acrylic polymers, vinyl polymers, polyamides, polyolefins or thermoplastic polyester. Particularly preferred materials include styrene polymers and acrylic polymers.

Preferred embodiments of printing apparatus/method will now be described, by way of example only, with reference to the drawings, in which:

Figure 1 is a schematic of a first embodiment of printing and thermoforming line;

Figure 2 is a second embodiment of printing and thermoforming line;

Figure.3 is a cup formed by either of the processes of figures 1 and 2;

Figure 4 is the cup of figure 3, after injection moulding;

Figure 5 is a side section of an injection moulding apparatus showing positioning of a support layer on a mould, prior to injection moulding;

Figure 6 is the side section of figure 5 showing coupling of an injection moulding mandrel to the die of the mould with partial deep drawing of the support layer; and

Figure 7 is the side section of figures 5 and 6 showing the injection stage.

Figure 1 shows a sheet 10 passed along a conveyor 20 to a roller 22 for application of thermally diffusable dyestuff. The sheet 10 is passed through a heater, such as an infra-red heater 30, in order to preheat the sheet to the temperature required for thermoforming. This heat is also used to transfer the dyestuffs which are applied by introduction of paper 15 coated with dyestuffs. The paper is brought into contact with the underside of the sheet 10 between roller 22 and nip rolls 24.

The paper is then removed from the heated sheet before the sheet passes through thermoformer 40. The cupped sheet 12 which emerges from the thermoformer is trimmed into individual cups. Alternatively, it may be trimmed in the thermoform mould. If desired, each cup may thereafter be formed with a lining of thermoplastics material formed by injection-moulding onto the cup as an insert in the mould cavity.

Figure 2 shows a similar process to that of figure 1 but in which the material which supports the dyestuff comprises a dissimilar plastic web to that of the sheet 10. In this embodiment, the web 15, here shown applied to the upper side of sheet 10, passes together with the sheet through the thermoformer 40 and is only removed thereafter.

The use of either paper or dissimilar plastic support web enables the web to be released cleanly from the sheet. Whilst the paper is removed from the sheet which is heated for thermoforming, it is possible to cool the plastic web prior to removal if this is desired for any reason. It is not, however, necessary to cool the support web prior to removal in order to produce a sharp image or decoration. The decoration may be a defined image or may be an abstract design, such as a marbled finish. If the image is to be defined, then the initial image registered on the support web will need to be distorted so as to allow for the stretching which takes place during thermoforming which then corrects the image to the desired final design.

Figure 3 shows a trimmed cup 50 after thermoforming, having an abstract design 52 thereon.

Figure 4 shows a typical finished container 54, having an injection-moulded insert 56 with ribs 58 defined therein.

Figures 5 to 7 represent a further embodiment of the invention in which the heat of injection moulding is used to transfer dyestuffs. This process comprises applying a decoration onto a support layer using sublimable dyestuffs. The support layer comprises a film of mylar or polyester, in the case of simple mouldings, or possibly in polypropylene for more complex mouldings. The film advantageously has a thickness of between 20 and 40 microns.

A decoration is applied onto the film using sublimable dyestuffs with a thickness of around 20 microns. The dyestuffs have been printed by means of rotogravure, flexography, lithography or other printing techniques, with the addition of other materials to increase the anchorage of the sublimable dyestuffs to the support layer.

The support layer 60, which can be a single sheet or a continuous web 62, as illustrated in figure 5, is positioned on the die 70 of the injection mould. The positioning is advantageously obtained through retaining means under vacuum which act in correspondence with the periphery of the die.

To the die can be coupled a mould mandrel 71 so as to define the mould cavity in the desidered conformation.

When coupled to the die, as shown in figure 6, the mould mandrel 71 carries out a partial deep drawing of the support layer 60. The deep drawing of the support layer is completed during the stage of injection of the plastics material as shown in figure 7. The plastics material enters via the mould mandrel, in such a way as to make the support layer adhere to the die 70, thus obtaining the desired moulding.

The support layer is positioned in the mould with the decoration formed with sublimable dyestuffs turned towards the injection chamber and for this purpose it is necessary that the sublimable dyestuffs are particularly well anchored to the support layer in order to prevent them from being displaced during the injection stage.

The plastics material used can be, for example, ABS acrylonitrile butadiene styrene, SAN styrene acrylonitrile, Pmma polymethyl methacrylate, PA polyamide, PET polythylene terepthalate and PBT polybutylene terephthalate.

The injection temperature is normally between 160°C and 250°C, depending on the type of plastics material used.

The injection pressures are particularly high and are normally between 1000 and 2000 kg/cm², thus causing the support layer to be moulded perfectly on the mould defined by the die.

In order to prevent the support layer of mylar, polyester or polyropylene from suffering damage due to the high temperature, the die is kept cold at a temperature of about 50°C so that the support layer does not deteriorate since it is in contact with a cold surface.

In the injection stage the sublimable dyestuffs migrate into the plastics material which is injected, creating an anti-scratch surface on the object, since the decoration which is obtained is integrated directly into the plastics material. This anti-scratch surface is also obtained when using a thermoforming moulding operation as described with reference to figures 1 to 4. Sublimable dyestuffs having atoxic focus are used, which do not produce solvent vaporisations, thus simplifying the moulding stage.

After the injection there typically follows compacting cooling of the article and subsequent opening of the mould with extraction of the moulded object obtained, separating it from the support layer of sublimable dyestuffs.

From the above examples it can be seen that the invention enables decorated articles to be obtained by means of support layers on which are provided sublimable dyestuffs and deep drawing of the support layer is realised. Damage to the support layer itself is prevented by means of the adoption of cold dies which, when contacting the plastics film which comprises the support layer, do not allow the film itself to reach temperatures which could cause damage.

As illustrated above, it can be seen that the invention enables the application of decorations to be made onto the surface of any moulding whatsoever. The invention has been described above by way of example only and changes may be made without departing from the scope of the invention as defined by the claims. For example, in practice, the materials used, as well as the dimensions and the contingent shapes may be varied according to the particular requirements.

Claims

1. A method of producing a printed plastics component comprising: providing a layer of material which carries a thermally diffusable dyestuff; heating a thermoplastic to moulding temperature and combining the thermoplastic and carrier layer, whereby the dyestuff is transferred from the carrier layer to the thermoplastic; and moulding the thermoplastic to form the printed component.

2. A method of applying a decoration to an injection moulded component made of plastics material, comprising: providing a support layer carrying thermally diffusable dyestuffs; positioning the support layer on the die of an injection mould with said decoration directed towards the injection zone; coupling the mandrel of the mould to the die for partial deep drawing of the support layer; injecting plastics material to complete deep drawing of the support layer; cooling the moulded component; extracting the component from the mould; and separating the moulded component from the support layer.

3. A method according to claim 2, in which the support layer comprises a film made of mylar, or a film of polypropylene, or polyester.

4. A method according to claim 3, in which the film has a thickness of between 20 and 40 microns.

5. A method according to one or more of claims 2 to 4, in which the layer of sublimable dyestuffs has a thickness of approximately 20 microns.

6. A method according to one or more of claims 2 to 5, in which the injection of the plastics material is carried out at a pressure of between 100 to 2000 kg/cm² and at a temperature of between 160°C to 250°C, as a function of the type of plastics material used.

7. A method according to one or more of claims 2 to 6, in which the die is kept at a temperature of about 50°C.

8. A method according to one to more of claims 2 to 7, in which the dyestuffs are applied to the support layer with the addition of materials suitable for increasing anchorage to the support layer.

9. A method according to one or more of claims 2 to 8 in which the support layer comprises a continuous film and is positioned on the die by means of positioning devices under vacuum.

10. A method of producing a printed plastics component comprising: combining a sheet of thermoplastics material with a layer of material which carried a thermally diffusable dyestuff; heating the combination to the temperature required for thermoforming the sheet so that the dyestuff is transferred from the carrier layer to the sheet; and thermoforming the thermoplastic material to form the printed component.

11. A method according to claim 10, further comprising separating the carrier layer from the sheet.

12. A method according to claim 11, in which the carrier layer comprises paper which is separated from the sheet prior to thermoforming.

13. A method according to claim 10 or claim 11, in which the carrier layer comprises a web of plastics material which is different from that of the sheet.

14. A method according to any one of claims 10 to 13, in which the carrier layer is applied to either or both sides of the sheet.

15. A method according to any one of claims 10 to 14, in which the combining and heating take place as a single step.

16. A method according to anyone of claims 10 to 14 , in which the combining comprises prelaminating the sheet and carrier layer together and is followed by the heating step.

17. A method according to any one of claims 10 to 16, further comprising injection moulding onto the formed component.

18. A printed plastics component with surface decorations comprising a moulded body made of plastics material having, on at least one of its surface portions, decorations or similar obtained by means of sublimable dyestuffs transferred from a support layer and having migrated into the plastics material at the time of moulding.

19. An apparatus for producing a printed plastics component, comprising: means for combining a sheet of thermoplastics material with a layer of material which carries a thermally diffusable dyestuff; heating means for heating the combination to the temperature required for moulding and for transferring the dyestuff layer to the sheet, and moulding means for producing a formed component.