EP2799243B1 - Direct printing method for printing on containers with a cover layer - Google Patents

Description

The invention relates to a direct printing method for printing on containers, such as bottles, with different layers.

State of the art

The printing of containers, such as bottles, is well known in the art. The use of multiple print layers is eg in DE 10 2010 044 243 A1 discloses, wherein here an intermediate or base layer is provided, which is first applied to the container surface, after which then the print layer is applied to this base layer. Physical properties such as adhesion and migration properties are determined by the corresponding parameters between the print layer and the intermediate layer on the one hand and the intermediate layer and the container surface on the other hand.

Direct printing method for applying a plurality of, even superposed printing layers are from WO 2009/018892 A1 known. Here, several layers of printing ink can be applied either one above the other or side by side in successive process steps.

From the WO 2005/025873 A2 Also, a method of printing on containers is known. Here too, printed layers can be applied to different, predetermined areas.

The WO 2012/003186 A1 shows further an apparatus and a method for applying recyclable printing layers, which in particular comprise hydrophilic monomers, which can come loose on contact with appropriate cleaning solutions from the container.

From the US 2010/0281833 A1 a printing method is known with which initially a permanent print layer can be applied to a container. This permanent print layer is excellent in that it does not dissolve in cleaning solutions from the container. Furthermore, a second, temporary print layer can be applied to the permanent print layer, wherein this temporary print layer can be detached from the container surface during cleaning processes of the container, so that, for example, the permanent print layer can be provided with a new print image.

task

The invention is based on the prior art, the task to improve existing direct printing process, in particular with regard to the recyclability of the products produced by this method.

solution

This object is achieved by the direct printing method according to claim 1. Advantageous embodiments of the invention are covered in the subclaims.

The direct printing method according to the invention for printing on containers such as bottles by means of a direct printing machine is characterized in that in a first step, the container is printed at least in a first specific area with a printing layer in a first device and, in a second step, in a second device, a cover layer is applied to the container, wherein the cover layer is applied to a second specific area, which comprises the first specific area and whose area is greater than that of the first predetermined area, wherein the cover layer has a first connection with the ink in the first predetermined area, wherein the cover layer undergoes a second connection with the container in different from the first specific area parts of the second specific area, wherein the first and second compounds insoluble in aqueous solutions having a pH between 3 and 10 and readily soluble in aqueous solutions having a pH in a range of less than 3 and / or greater than 10. By this cover layer, the ink is fixed on the one hand on the surface of the container, without even have to adhere strongly to this and on the other hand, the print layer is so protected from environmental influences, such as from scratching or the like. Furthermore, the recyclability of the printed containers is improved because the solubility of the topcoat in basic solutions facilitates the release of the underlying print layer from the container.

In one embodiment, the direct printing method is characterized in that the cover layer is applied to the second region by means of a rolling device or a baffle device or a spray device or a dipping device or a direct printing device or a plasma coating device or a flame pyrolysis device. These versatile possibilities of applying the cover layer make flexible methods for applying the cover layer available, in particular with regard to the form that can be produced and certain properties of the cover layer.

In a further embodiment, the direct printing method is characterized in that the covering layer is readily soluble in the aqueous solutions at a temperature of at least 70 ° C. By solubility of the topcoat, especially at high temperatures, the recyclability of a so-printed container is significantly improved because in common washing solutions on the one hand, the pH is significantly less than 3 or greater than 10 and on the other hand, the temperature is often in the range of 70 to 100 ° C is located. It is advantageous here that only the cover layer has to have these properties with respect to solubility. The print layer or layers need not have these properties, which makes it easier to provide the materials used for the print layers.

Furthermore, it can be provided that the printing layer is readily soluble in the aqueous solutions. This ensures that not only the cover layer can be dissolved during a recycling process, but also the print layer can be removed in the aqueous solution used.

In addition, the second specific region may be geometrically similar to the first specific region. A cover layer applied in such a targeted manner reduces material costs and is more environmentally friendly and ecological.

In one embodiment, the distance of a point on the edge of the first particular region from the edge of the second particular region is the same for each point on the edge of the first particular region. This ensures that the print layer is uniformly surrounded on all sides by the cover layer and weak points that could already occur during production are thus avoided.

Furthermore, it can be provided that the material from which the cover layer is irradiated with radiation of a specific wavelength with change of at least one of the properties adhesion, color, barrier properties, migration properties reacts and wherein the container with the aid of an arranged in the transport direction to the second device irradiation unit Radiation of this particular wavelength is irradiated. Thus, containers that have been printed on can be provided with cover layers with specific properties that go beyond the improved recyclability. For example, the cover layer may thus have certain optical properties or certain degrees of hardness.

In one embodiment, the cover layer is applied to the container in response to sensor data indicative of the geometric shape of the print layer. By using appropriate sensor data, the cover layers for each container can be custom-applied, which can contribute to further savings and more environmentally friendly and ecological recycling.

In a further embodiment, between the first step and the second step at least one further printing layer is applied in a third specific area, wherein the third specific area coincides at least partially with the first specific area, or the third specific area is different from the first specific area wherein the first and third designated areas form a printed area and wherein the second designated area comprises the printed area and the area of the second designated area is greater than the printed area. A direct printing machine designed in this way can apply a cover layer to an already printed container, wherein this cover layer can protect the printing layer from environmental influences.

Furthermore, a direct printing machine is provided for printing on containers such as bottles, the direct printing machine comprising a transport device for conveying the containers through the printing press along a transport direction, a first device for applying a printing layer in a first specific region of the container and a second device for applying a cover layer in a second specific area of the container, wherein the first device is arranged in the transport direction in front of the second device characterized in that the second device is adapted to apply the cover layer in the second specific region, the second specific region comprising the first specific region and the second specific region being larger than the first specific region. The use of one or more of these devices for applying the cover layer may be advantageous depending on the process parameters and requirements for the cover layer. Corresponding printing presses can be designed as linear rotors, but also as rotary machines.

In the direct printing machine, the second device may include a rolling device or a baffle device or a spray device or a dipping device or a direct printing device or a plasma coating device or a flame pyrolysis device that can apply the cover layer. The use of one or more of these devices for applying the cover layer may be advantageous depending on the process parameters and requirements for the cover layer.

Furthermore, it can be provided that the direct printing machine comprises an irradiation unit in the transport direction after the second device, wherein the irradiation unit can emit radiation in a certain wavelength range and wherein the material of which the cover layer consists responds to irradiation with radiation in this particular wavelength range. A correspondingly carried out irradiation of the cover layer allows the cover layer to be provided with special properties, such as, for example, a certain degree of hardness / degree of drying or optical properties.

In a further embodiment, the direct printing press is characterized in that the direct printing press in the transport direction after the first device and before the second device comprises a sensor which measure the geometric shape of the print layer and a signal indicative of the geometric shape of the print layer a data processing device can forward, wherein the data processing device can generate a signal for controlling the second device, which is indicative of the second specific area and the second device is controllable in response to the signal. The provision of corresponding sensors and control units for controlling the cover layer applying second device allow an ecological and effective application of the cover layer.

Furthermore, in the transport direction after the first and before the second device, means which are suitable for applying at least one further print layer in a third region can be used. be arranged. The application of multiple print layers below the cover layer allows the creation of very diverse print images, which can also be multi-layered.

Brief description of the figures

Fig. 1

Schematic representation of a printing press.

Fig. 2

Schematic representation of the printing process.

Fig. 3

Schematic representation of various embodiments of the print layers and cover layer.

Detailed description

Fig. 1 shows a schematic representation of a direct printing machine 100. This includes, for example, a feed conveyor 104, are transported on the unprinted containers, such as bottles 130 to the device 100. The containers can in principle consist of any materials. For example, it may be containers or bottles made of glass or plastics. Preferably, it is PET containers. In the apparatus 100, printing units 111 are arranged. In principle, at least one printing unit is provided. But it can also be provided a variety of printing units. The printing units 111 together form the first device in which the unprinted containers 130 are printed with printing layers. For this purpose, the printing units 111 of the first device 101 are connected, for example, via lines 113 to ink reservoirs 112. The different printing units 111 can be designed as a direct printing device according to the prior art and be suitable for applying printed images of certain shape and color. In this case, the individual printing units 111 can each apply different printing inks and printed images or the same printing inks at different locations or in several layers on the same areas of the container. The thus printed container 131 then leaves the first device 111 and is passed for example via a further conveyor 103 to the second device 102.

In this device, the outer layer is applied over further treatment units 121. Since the cover layer may not be a substance or a mixture of conventional printing inks, the treatment units 121 are especially suitable for applying the materials used for the cover layer. Also for this purpose, the treatment units 121 of the second device 102 are connected via lines 123 to storage containers 122, in which the material or mixtures of substances for the cover layer are stored. In the second device 102, the cover layer is applied via the treatment units 121 at least in regions that were previously printed in the first device 101, so that the print layer or the print layers are completely covered by the cover layer. The thus printed and provided with the cover layer container 133 then leave the second device 102 via a further conveyor.

Before the printing is finally completed, an irradiation unit 104 can be provided, in which the printed and capped containers 133 are retracted and irradiated. This irradiation can for example change the chemical properties or physical properties of the applied topcoat. Thus, it can be used, for example, for the eventual curing of the cover layer. The irradiation unit 104 preferably emits radiation or light of a specific wavelength for this purpose. This may be radiation in the visible range (light) or in the non-visible range, such as IR radiation or UV radiation. After completion of the irradiation, the container 132 can be supplied to further devices.

Regardless of the specific embodiment of the printing machine or direct printing machine 100 described here, it should be mentioned that this can basically be designed as a linear or as a rotary machine.

Fig. 2 shows a schematic representation of the printing process of a container. This will be done in Fig. 2 considered only a section 230 of the container, which serves as a substrate here. In the first step, a print layer 251 is applied to the substrate 230. The print layer is shown here considerably enlarged in comparison to the extension of the substrate for illustrative purposes. Typical layer thicknesses range from a few microns to tens of microns. The print layer 251 can be applied from nozzles 211, for example, via drop-on-demand methods. Other printing methods are conceivable here, such as, for example, rolling or spraying and dipping. The pressure layer thus applied preferably adheres to the substrate or the container surface 230 itself. However, since a cover layer is applied in the further course, this adhesion need not be so permanently formed as in the case of previous direct printing methods.

In a next step will be in the in Fig. 1 shown second device, the cover layer 253 applied. This can likewise take place via one or more nozzles 221 and also according to the treatment method described with reference to FIG. 2a. As can be seen, the cover layer 253 completely covers the print layer 251 and moreover covers parts of the substrate 230 that are directly adjacent to the edges of the print layer. This will be a complete one Encapsulation of the print layer 251 and the entire print image achieved, which protects the printed image from environmental influences, such as contact with water. Likewise, this encapsulation leads to a further fixation of the print layer, which is why the adhesion of the print layer 251 on the substrate 230 is thereby reinforced. Preferably, the cover layer adheres very well to the substrate 230. Basically, it is intended that the cover layer consists of a transparent and colorless material. It is therefore less used to produce certain optical properties, but serves to coat and encapsulate the printing inks. However, it may have certain material properties, such as a certain surface roughness, hardness or optical effects.

In a further method step, irradiation 241 of the substrate 230 with the print layer 251 and the cover layer 253 can then take place. This irradiation can be, for example, an entry of thermal energy or light energy, such as UV radiation or even visible light. Such an irradiation 241 can be used if the cover layer 253 applied in the previous step does not yet have the required properties directly after application. For example, if the topcoat is applied by inkjet or screen printing or by plasma coating or by flame pyrolysis, for example, subsequent treatment may be necessary. In order to compensate, for example, unevenness of the cover layer in a controlled manner, the heat treatment can be used, whereby a smoother surface is achieved by superficial melting of the cover layer and subsequent hardening. This also ensures that the print layer 251 is preferably covered by a film of the cover layer 253 of the same thickness everywhere. Furthermore, the degree of hardness of the cover layer can be changed by irradiation, for example with UV light, after application, so that certain requirements for the cover layer can be met.

Fig. 3 shows the schematic embodiment of the direct printing method according to the invention. It should be noted that, although here always at least two designated as different printed images are provided on the container, they can each also consist of the same color. The overprinting of different print layers is still not in contradiction to the explanations below Fig. 2 because the in Fig. 2 shown print layer 251 according to the comments to Fig. 2 may consist of a plurality of printing layers, which were applied by the printing units 111. Furthermore, it is possible to apply only one printing layer.

In Fig. 3a is a printed image consisting of two rectangular printed images 301 and 302 on the surface of a container 300 shown. Due to the rectangular structure, it is technically possible without difficulty to apply the cover layer in such a way that it encloses the complete resulting print image, in particular the overlap of the print layers 301 and 302. As already in Fig. 2 described, an overhang of the cover layer 303 is provided, which extends beyond the edges of the printed image and is in direct contact with the surface of the container 300. To achieve this, the second device is according to Fig. 1 is formed so that it prints on a larger area on the container than occupied by the print images 301 and 302, this larger area comprising at least the surface of the printed images and, as shown, is slightly larger.

In Fig. 3b 2 schematically shows a combination of two print images 301 and 302, which in this case have an irregular shape on the container 300. In order to provide such an irregular printed image with a cover layer, it may be provided to coat the entire container or a large area of the container surface 300 with the cover layer 303, wherein the print images 301 and 302 are completely encapsulated in this area. Although this implementation is not very effective from an environmental point of view, it certainly guarantees the complete encapsulation of the print layers 301 and 302. Moreover, especially with complete application of the cover layer to the container, no further devices are necessary to ensure that the print layers are completely encapsulated by the cover layer.

Fig. 3c shows a further embodiment for covering a print layer 301 and a print layer 302 with a cover layer 303. Again, the print layers 301 and 302 each have an irregular shape. Since it is ecologically and economically advantageous if as little as possible of material is used for the cover layer, it is provided in this embodiment that the cover layer is applied so that only the printed images 301 and 302 are covered and a narrow area of the cover layer, over the Edges of the print layers 301 and 302, is in direct contact with the substrate or container 300. However, this is technically more difficult with irregular print images. In particular, when printing methods are used which produce different print images from container to container, this can be difficult. For this purpose, it is provided that the device, for example according to Fig. 1 , has sensors that can measure the positions and dimensions of the print images 301 and 302, in particular when using irregular print images. On the basis of these measured values, it can then be provided that a control unit controls the second device, which applies the cover layer 303, in such a way that the cover layer only in the region of Printing images 301 and 302 is applied and an edge of the cover layer is provided, wherein the distance of a point on the edge of the print image 301 or 302 is equal to the edge of the cover layer for each point on the edge of the print image 301 and 302. For example, it may be provided that this in Fig. 3c shown strip is about 1 mm, preferably 0.5 mm, more preferably 0.25 mm wide.

Since the cover layer is designed so that it should be soluble in aqueous solutions having a pH of less than 3 and / or greater than 10, for which, for example, polymers are suitable, such a printed container can be recycled particularly easily. In particular, if the printing layers or the printing inks used for this purpose do not hold well on the container and are encapsulated by the overlying cover layer and fixed on the container, the cover layer can be divided into a corresponding basic solution when the container is divided into plastic flakes, as is usual in recycling processes and the printing layers underneath are very easily removed from the plastic flakes, since dividing the container into plastic flakes and in particular by the use of a basic solution, the cover layer is dissolved or at least broken, whereby a dissolution of the printing layers takes place in the aqueous solution. It is also envisaged that the cover layer adheres very well to the print layer, which is why a detachment of the cover layer from the container allows entrainment of the print layer, which further increases the effectiveness of the recycling process. For this purpose, the cover layer may preferably consist of UV inks or water and solvent-based paints. Hot-melt inks can also be used here. Also known primer materials, such as from the DE 10 2010 044 243 A1 , may be considered as a topcoat. Flame pyrolytic layers, which preferably consist of silicon oxide layers, are also advantageous. Depending on the material used, the barrier properties of the container or at least the region in which the cover layer is provided can thus also be improved. This concerns in particular the diffusion of gases such as oxygen or carbon dioxide or other substances which should not penetrate into the contents of the container.

Claims (9)

1. A direct printing method for printing on containers, such as bottles, with the aid of a direct printing machine (100), wherein a print layer (251) is printed onto the container, at least in a first predefined area thereof, in a first device (101) in a first step and a cover layer (253) is applied to the container in a second device (102) in a second step, the cover layer (253) being applied to a second predefined area, which comprises the first predefined area and the surface area of which is larger than that of the first predefined area, characterized in that the cover layer (253) coalescing with the printing ink in the first predefined area thus creating a first connection, the cover layer (253) coalescing with the container in parts of the second predefined area which differ from the first predefined area thus creating a second connection, and the first and second connections being insoluble in aqueous solutions having a pH value between 3 and 10 and easily soluble in aqueous solutions having a pH value in a range of less than 3 and/or higher than 10, wherein the second connection between the cover layer (253) and the container is stronger than the connection of the print layer (251) and the container and the first connection is stronger than the connection of the print layer (251) and the container.
2. The direct printing method according to claim 1, characterized in that the cover layer (253) is applied to the second area with the aid of a rolling device or a flushing device or a spraying device or a dipping device or a direct printing device or a plasma coating device or a flame pyrolysis device.
3. The direct printing method according to claim 1 or 2, characterized in that the cover layer (253) is easily soluble in the aqueous solutions at a temperature of at least 75°C.
4. The direct printing method according to one of the claims 1 to 3, characterized in that the print layer (251) can easily be separated from the container in the aqueous solutions.
5. The direct printing method according to one of the claims 1 to 4, characterized in that the second predefined area and the first predefined area are geometrically similar.
6. The direct printing method according to claim 5, characterized in that the distance of a point on the edge of the first predefined area to the edge of the second predefined area is identical for any point on the edge of the first predefined area.
7. The direct printing method according to one of the claims 1 to 6, characterized in that, when exposed to radiation of a specific wavelength, the material of the cover layer (253) reacts with a change of at least one of the properties adhesion strength, color, barrier properties, migration properties, and wherein the container is irradiated with radiation of this specific wavelength with the aid of an irradiation unit (104) arranged downstream of the second device (102) when seen in the conveying direction.
8. The direct printing method according to one of the claims 1 to 7, characterized in that the cover layer (253) is applied to the container depending on sensor data indicative of the geometrical shape of the print layer (251).
9. The direct printing method according to one of the claims 1 to 8, characterized in that, between the first step and the second step, at least one further print layer is applied to a third predefined area, the third predefined area being at least partially congruent with the first predefined area, or the third predefined area being different from the first predefined area, the first and the third predefined areas defining a printed region and the second predefined area comprising the printed region and the surface area of the second predefined area being larger than the printed region.

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