WO1997037861A2

WO1997037861A2 - Method for producing decorations on tiles and similar items, and apparatus for carrying out said method

Info

Publication number: WO1997037861A2
Application number: PCT/EP1997/001627
Authority: WO
Inventors: Fabio Primaio
Original assignee: Fabio Primaio
Priority date: 1996-04-03
Filing date: 1997-04-01
Publication date: 1997-10-16
Also published as: IT1289641B1; WO1997037861A3; ITFO960008A1; AU2507597A; ITFO960008A0

Abstract

A method for producing decorations on tiles (10) and similar items which comprises the step of applying, on one side of a film (1) made of plastic material, a layer (2) of at least one heat-activated mix (20) of ceramic pigments and binders, related to a preset color, in order to obtain a pigmented film (12). The ceramic pigments are then hot transferred, according to a programmed pattern, from the pigmented film (12) to a surface which is treated with an additional heat-activated binder (4).

Description

METHOD FOR PRODUCING DECORATIONS ON TILES AND SIMILAR ITEMS, AND APPARATUS FOR CARRYING OUT SAID METHOD Technical Field

The present invention relates to a method for producing decorations on ceramic tiles and similar items having a glazed or vitrified surface and to an apparatus conceived specifically for carrying out said method. Background Art It is known that the decoration of tiles with ceramic pigments in the industrial field is currently generally performed by means of printing methods such as direct screen printing or with the aid of transfers produced by screen printing. The decoration is fixed by melting the ceramic pigments in a kiln.

Screen printing entails the use of complicated and expensive equipment which is economically compatible only with industrial production but not with sample tests, which are required for example to prepare new product ranges, or with the production of customized decorations requested by customers. Use of screen printing also forces to work in environments wherein, unless expensive conditioning systems are used, one is far from being in a desirable condition offering environmental comfort. Another drawback of the use of screen printing resides in the fact that this method does not allow to have colors composed by superimposing colors produced by individual ceramic pigments.

The transfers used in the specified sector are constituted by a sort of sandwich wherein the screen printing of the decoration is inserted between a paper backing and a protective layer of collodion. The transfer backing paper has, on one side, a water-soluble layer, for example made of dextrin, which facilitates separation of the decoration, together with the protective layer of collodion, when immersed in water. The spreading of the water-soluble substance produces microscopic wrinkles in the transfer backing paper which prevent the uniform spreading of the ceramic pigments.

Another drawback of these transfers is constituted by the fact that they cannot be stored for long periods. DISCLOSURE OF THE INVENTION

A principal aim of the present invention is to solve the above problems, by providing a method which allows to produce decorations on tiles and similar items without resorting to complicated and expensive equipment, both for industrial production and for sample tests or for preparing customized decorations.

Within the scope of this aim, another object of the present invention is to provide means conceived specifically for performing said method, which allow optimum production of decorations on tiles and similar items, and can, in particular, be stored even for relatively long periods until use.

This aim and this object and others which will become apparent hereinafter are achieved, according to the present invention, by a method for producing decorations on tiles and similar items, characterized in that it entails applying, on one side of a film made of plastic material, a layer of at least one heat-activated mix of ceramic pigments and binders, related to a preset color, in order to obtain a pigmented film, and performing a hot transfer of said ceramic pigments, according to a programmed pattern, from said pigmented film to a surface which is treated with an additional heat-activated binder. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the present invention will become apparent from the detailed description of a preferred embodiment of means for producing decorations on tiles and similar items, illustrated only by way of non- limitative example in the accompanying drawings, wherein: figure 1 is a schematic view of a first step of the method according to the present invention for preparing a pigmented film; figure 2 is an identical schematic view of a second embodiment of the first step of the method according to the present invention; figure 3 is a schematic view of a second step of the method for the surface treatment of a transfer backing paper meant to receive the ceramic pigments; figure 4 is a schematic longitudinal sectional view of an apparatus meant to perform the transfer of the ceramic pigments, according to the present invention; figure 5 is a view of a second embodiment of the apparatus meant to transfer the ceramic pigments; figures 6, 7, 8 and 9 are schematic views of successive steps of the method according to the present invention for providing decorations on a corresponding item; figures 10 and 11 are, respectively, schematic views of further apparatuses meant to transfer said ceramic pigments directly onto the items to be decorated. WAYS OF CARRYING OUT THE INVENTION

With particular reference to the above figures, the reference numeral 1 designates a film made of plastic material which is meant to receive ceramic pigments for producing decorations on tiles 10 and similar items. The film 1, preferably made of neutral polyester, has a low thickness, in practice between 4 and 12 microns; however, it is possible to use films made of polyester, polypropylene or polyamide which are neutral or tensilized (i.e., subjected to a longitudinal yielding process) which are thicker, between 12 and 25 microns, particularly for direct printing with flat or rotating pads, as specified hereinafter.

In the method according to the present invention, a layer 2 of a heat-activated mix of ceramic pigments and binders, related to a preset color, is uniformly applied on one face of the film 1. It is also possible to apply in different regions of the film 1 respective mixes of ceramic pigments and binders related to different colors.

The ceramic pigments are supplied in powder form, with a particle size between 5 and 20 microns. It is also possible to use ceramic gold, lustre and silver, provided that in powder form. Said ceramic pigments have a melting temperature between 400°C and 950°C depending on the use for which they are meant. In particular, pigments having lower melting temperatures are meant for the decoration of glass items, whilst pigments having higher melting temperatures are meant for the decoration of ceramic items by third firing.

In practice, the binders are mainly water- or solvent- based disperse systems of polymers and copolymers of the vinyl acetate, ethyl vinyl acetate, ketone, acrylic, carboxylate, urethane, amide groups with one or two components or mixes thereof. There are also polyethylene waxes having low and high relative molecular mass, carnauba wax, microcrystalline wax and montan wax in a smaller amount with respect to the composition if hot spreading is performed using a solid mix.

The amount of heat-activated mix which is spread is, by way of indication, between 7 and 20 grams per square meter. The layer 2 of heat-activated mix is spread in different manners according to the purposes and method of fluidifying the binder mix with the ceramic pigments. In spreading with a water or solvent base it is possible to equally use rotogravure, flexographic, or contrarotating screen roller printing systems, always applying a release agent between the film and the mix.

More particularly, according to the solution shown schematically in figure 1, a mix 20 of ceramic pigments and binders is liquefied and kept liquid inside an open-top tank 21; the mix is kept agitated inside the tank to prevent the sedimentation of the ceramic pigments.

The film 1 unwinds from a roll 11, in the direction indicated by the arrow A, and is guided by a pair of free rollers 13 between two contrarotating rollers 14, 15 in the direction of the arrows B; a spreader roller 15 is partially immersed in the tank 21 so as to be wet by the mix 20 of ceramic pigments and binders.

Before being rewound onto a roll, the pigmented film 12 passes through a hot-air drying chamber, which is not shown. The particle size of the ceramic pigments is at the highest values among those specified.

Obviously, it is possible to apply to the film regions of ceramic pigments related to different colors during a plurality of subsequent printing cycles, similar to the one described. Before spreading the mix or mixes of ceramic pigments and binders on one face of the film, an adapted liquid release agent is spread on that face.

The release agent operates at a lower temperature than the binder mix and acts as a common cold matrix, avoiding some incompatibilities between the film and elements of the mix of ceramic pigments and binders. The release agent is in the form of an aqueous emulsion based on polyethylene wax with a high or low relative molecular mass, carnauba wax, montan wax, microcrystalline wax. The presence of small amounts of hydrophilic alcohols facilitates drying and reduces surface tension during spreading on the film. In certain mixes, anionic and cationic surfactants can also considerably reduce surface tension.

Figure 2 illustrates a second embodiment of the spreader unit for the hot spreading of the layer 2 of heat- activated mix on the film 1. In this case, the mix 20, which is in a substantially solid state, is fluidified and hot- spread onto the film 1 by means of a screen roller 16 which rotates in the opposite direction with respect to the advancement of the film, in the direction indicated by the arrow C, the screen roller 16 having between 30 and 50 screen recesses per centimeter.

The screen roller 16 is arranged between two idle rollers 17. The screen roller 16 picks up the heat-activated _miχ from the tank 21 and spreads it on the film 1; the excess mix on the surface of the roller 16 is removed by means of an adapted doctor 18.

In hot spreading, the heat is the agent which fluidifies the mix, which is in the solid state. In this solution, the release agent is not applied and, in order to compensate for its omission, the waxy component is predominant in the mix. The particle size of the ceramic pigments is at the lowest values among those indicated.

The transfer backing paper 3 meant to be associated with the pigmented film 12 is conveniently subjected to a surface treatment with a corresponding heat-activated mix 4 which is in practice constituted by polyethylene waxes and ethyl vinyl acetate copolymers.

As shown in figure 3, the transfer backing paper 3, which has a water-soluble layer for example of dextrin on one side, is passed through the idle rollers 41 and 42 of a calender 40 adapted to make the mix 4 perfectly smooth and uniform. The paper 3 receives the mix 4, which is supplied by a dispenser 43, from the first roller 41 of the calender 40, the second roller 42 whereof is clamped against the first roller 41; the rollers 41 and 42 are interposed between an input roller 44, which is adapted to cause the yielding of the paper 3, and an output roller 45, which is adapted to flatten and smooth the mix 4. The transfer backing paper 3 thus treated, in addition to being smooth, is also thermally active and opens out in its heated regions, thus including the ceramic pigments transferred thereonto and protecting them during the advancement of said paper. A heat-activated mix constituted by polyethylene waxes and ethyl vinyl acetate copolymers, followed by collodion, is instead spread on dextrin-free paper.

Another type of dextrin-free paper which can be used entails inserting a layer of silicone before receiving the heat-activated mix of polyethylene waxes and ethyl vinyl acetate copolymers.

In order to transfer the ceramic pigments onto the transfer backing paper 3 treated as described above, it is possible to use a thermal printer 30 controlled by a computer 9, as shown in figure 4.

The thermal printer 30, of the plotter type, has a heated stylus 33 movable in perpendicular directions and driven by the computer 9 according to a programmed pattern. The stylus 33 moves against the back of the pigmented film 12 so as to reproduce the pattern, on the opposite side, on the transfer backing paper 3; through the melting of the binders provided in the heat-activated mix of the pigmented film 12, the ceramic pigments are transferred to the film region which is in contact with the paper 3 in each instance.

The transfer backing paper 3, supplied in sheets, is fed to the thermal printer 30 by means of a belt conveyor 34 which is conveniently motorized in the direction of the arrow D. The sheets of paper 3, taken from a magazine 35, are conveyed at the region where the stylus 33 acts, below the pigmented film 12 which unwinds from a first reel 36 and rewinds onto a second reel 37.

The printer uses every time a portion of pigmented film 12 which comprises as many pigmented regions as there are colors to be reproduced in sequence in order to compose the decoration. It is possible to pass two or more times over a same point of the paper with different ceramic pigments in order to create a secondary color.

The thermal printer 30 may also be provided with a device for adjusting the operating temperature according to the temperature at which the ceramic pigments separate from the film.

Once the transfer of the ceramic pigments has been completed according to the intended pattern, the transfer backing paper decorated with said ceramic pigments, designated by the reference numeral 32 for the sake of clarity, is carried by the conveyor 34 at a conventional screen-printing system 50, wherein the decorated surface is covered with a protective layer of collodion 5. The screen-printing system 50 has a frame 51 which can be raised, along a vertical axis, above the decorated paper 32 under the actuation of adapted actuators 52. A doctor 53 is associated with the frame 51 and is movable transversely by means of further actuator elements 54. The resulting transfer elements are substantially constituted by a sandwich in which the decoration made of ceramic pigments in one or more colors is arranged between the transfer backing paper 3 and the collodion layer 5. An appropriate drying step, optionally accelerated by ventilation at room temperature or with heat, is adapted to give the collodion the consistency of a film. These transfer elements can be handled freely and stored until use.

Figure 5 illustrates a second embodiment of the transfer of the ceramic pigments, wherein the transfer backing paper 3 is provided in ribbon form and is fed continuously from a reel 31 to the thermal printer.

The thermal printer is provided with a plurality of heated bars 38 having hot regions formed by adapted 5 microresistors, which are meant to transfer the ceramic pigments from respective pigmented films 12 to the ribbon of transfer backing paper 3. The heated bars 38, appropriately loaded by elastic means, act in abutment against corresponding cylinders 39 which have a rubber covering and ₀ rotate in the direction of advancement of the paper ribbon.

Each heated bar 38, driven by the computer, transfers the pigments of a given color to the transfer backing paper

3. Once the pattern has been completed, the decorated paper is covered with a protective layer of collodion, as 5 described above.

As an alternative, it is possible to use a single heated bar 38 which operates in successive steps on magazines of different pigmented films, again to achieve decorations in a plurality of colors. o The conventional wet method illustrated in figures 6, 7, 8, and 9 is employed in order to use these transfer elements. The method entails first immersing the transfer elements 32 in an open-top water tank 6 (figure 6), in order to separate the transfer backing paper 3 from the collodion 5 film which supports the pigments of the decoration, designated by the reference numeral 25 (figure 7) . The pigmented collodion film 25, while still wet, is made to adhere by means of adapted tools 7 to the item to be decorated, for example the tile 10, placing the pigments of 0 the decoration in contact therewith (figure 8). The tile 10, after appropriate drying, is placed in a kiln 8 where, at a temperature of approximately 700-900°C, the pigments melt and the collodion volatilizes without leaving traces (figure

9). if pre-treated papers are used which are dextrin-free from the very beginning, as described above, the collodion is not applied, since the decorations can be transferred onto the items by heat.

In the method according to the present invention it is also possible to transfer the ceramic pigments from the pigmented film 12 directly onto the items to be decorated.

For this purpose, the items to be decorated are first subjected to an adapted surface treatment which is meant to achieve the characteristics already described for treating the transfer backing paper. This surface treatment consists, in the case of already-glazed tiles, in depositing, for example by spraying, a binding mix formed by waxes, polymers and copolymers onto the surface to be decorated. In the case of unfired tiles, the surface to be decorated is instead sprayed with alginates or with vinyl emulsions.

The direct printing of the items is performed by means of flat or rotating pads, using the thicker polyester or polypropylene films which are between 12 and 25 microns thick. These films are treated as described above, in order to obtain pigmented films in one color or with multicolored regions. However, it is also possible to print decorations by flexography, by means of mixes of ceramic pigments, binders, and nitrocellulose.

The transfer of the ceramic pigments onto the items to be decorated is performed by heat, as shown in figure 10, by means of a printing unit 60 having an appropriately heated pad 61. The pad 61 can move vertically under the actuation of an adapted actuator 62 which is supported by a fixed frame 63. The pad 61, provided with a silicone coating, is adapted to press the film 1 provided with the layer 2 of heat-activated mix onto the item to be decorated, for example the tile 10: the pigmented film unwinds from a first reel 64 and rewinds onto a second reel 65, engaging guiding rollers 66. As an alternative, it is possible to use printing units having a hot roller 67 which can rotate appropriately in the winding direction of the pigmented film, as shown by the arrow E (figure 11). The roller 67, provided with a silicone coating, is pressed elastically onto the pigmented film. The pads 61 and the rollers 67 bear, in relief, the pattern to be impressed on the tiles 10. By using monochrome films it is possible to provide monochrome decorations which can assume a plurality of colors by passing through subsequent printing units. If smooth pads or rollers are used instead, the tiles 10 are colored completely according to the pattern optionally provided on the pigmented film by flexographic printing.

In this case, too, the tiles 10 are subsequently placed in a kiln, where the pigments melt. In summary, the described method allows to provide in an optimum manner decorations on tiles and similar items, overcoming the drawbacks linked to conventional screen- printing methods. In particular, it is not necessary to resort to complicated and expensive equipment and it becomes possible to use secondary colors, and work is performed in satisfactory environmental conditions.

A specific advantage of the method according to the present invention is that it allows both industrial production and production for sample tests or for providing customized decorations. The means conceived specifically for carrying out the method according to the present invention, particularly the transfer backing papers 32 decorated with the ceramic pigments, can in fact be produced according to previously stored patterns or to patterns prepared on the spot, for example by modifying already-available decorations.

In practice, for example, in order to ensure the production of new decorations included in a catalog it is not necessary to prepare the corresponding expensive screen- printing unit but it is sufficient to store the corresponding pattern.

It is also possible to provide customized decorations, particularly at the customer's request, without additional costs. Transfer backing papers produced with the described method, in addition to being perfectly smooth and enhancing print sharpness, can also be handled freely and stored even for relatively long periods until use.

The described method and means can be advantageously used to provide decorations on items made of ceramic, glass, porcelain, majolica, gres, enamelled metals or in any case on all glazed or vitrified surfaces.

In the practical embodiment of the invention, the materials employed, as well as the shapes and the dimensions, may be any according to requirements.

Claims

1. A method for producing decorations on tiles and similar items, characterized in that it entails applying, on one side of a film (1) made of plastic material, a layer (2) of at least one heat-activated mix (20) of ceramic pigments and binders, related to a preset color, in order to obtain a pigmented film (12), and performing a hot transfer of said ceramic pigments, according to a programmed pattern, from said pigmented film (12) to a surface which is treated with an additional heat-activated binder (4).

2. A method according to claim 1, characterized in that it entails applying said layer (2) of heat-activated mix (20) on one side of said film (1) by means of contrarotating rollers (14, 15), with the interposition of a liquid release agent between said layer (2) and said film (1).

3. A method according to claim 1, characterized in that it entails a hot-spreading of said layer (2) of heat- activated mix on said film (1) by means of a screen roller (16) which rotates in an opposite direction with respect to the advancement direction of said film (1).

4. A method according to claim 1, characterized in that it entails a hot-transfer of said ceramic pigments from said pigmented film (12) onto a transfer backing paper (3) the surface whereof is treated with saic idditional heat- activated substance (4) by means of a the ^ιal printer (30) controlled by a computer (9) in order to obtain a transfer backing paper (32) provided with said ceramic pigments.

5. A method according to claim 4, characterized in that it entails covering the surface of said decorated transfer backing paper (32) with a protective layer (5) of collodion applied at a screen printing unit (50).

6. A method according to claim 5, characterized in that it entails immersing said transfer backing paper (32) in order to separate from the paper (3) a film (25) of collodion which bears the pigments of the decoration; making said pigmented collodion film (25) adhere while still wet to the item (10) to be decorated; placing said pigments of the decoration in contact therewith; and placing said item (10) in a kiln (8) after drying in order to melt said pigments and cause the volatilization of said collodion and of the hot-melting mixes without leaving traces.

7. A method according to claim 4, characterized in that it entails driving a hot stylus (33) of said thermal printer (30) which can move in perpendicular directions according to a programmed pattern against the back of said pigmented film (12) so as to melt the binders which are present in a heat- activated layer (2) of said pigmented film (12) and transfer said ceramic pigments onto the region in contact with said transfer backing paper (3).

8. A method according to claim 4, characterized in that it entails continuously feeding a ribbon of said transfer backing paper (3) to at least one heated bar (38) of said printer (30), which is adapted to transfer said ceramic pigments of a respective color from a corresponding pigmented film (12) to said ribbon of transfer backing paper (3).

9. A method according to claim 1, characterized in that it entails performing the hot transfer of said ceramic pigments from said pigmented film (12) to the items (10) to be decorated, which are treated on their surface with said additional heat-activated substance (4), with heated pad means (61, 67) which are adapted to press said film (12₎ against said items (10).

10. An apparatus for providing decorations on tiles and similar items, characterized in that they comprise a film (l) made of plastics on a face whereof a layer (2) of at least one heat-activated mix (20) of ceramic pigments and binders, related to a preset color, is applied so as to form a pigmented film (12) meant for the hot transfer of said ceramic pigments, according to a programmed pattern.

11. An apparatus according to claim 10, characterized in that said film (1) is made of polyester, polypropylene, or polyamide.

12. An apparatus according to claim 10, characterized in that said binders are constituted by water- or solvent- based disperse systems of polymers and copolymers of the vinyl acetate, ethyl vinyl acetate, ketone, acrylic, carboxylate, urethane, isocyanate, amide groups with one and two components or mixes thereof.

13. An apparatus according to claim 10, characterized in that said binders contain polyethylene waxes having high and low relative molecular mass, carnauba wax, microcrystalline wax, and montan wax, with the optional addition of resins or silicones.

14. An apparatus according to claim 10, characterized in that a release agent is interposed between said film (1) and said layer (2) of heat-activated mix, said agent being in the form of an aqueous emulsion based on polyethylene wax having a high or low relative molecular mass, carnauba wax, montan wax, microcrystalline wax.

15. An apparatus according to claim 10, characterized in that the surface of a transfer backing paper (3) is treated with an additional heat-activated binder (4) adapted to be associated with said pigmented film (12) for the hot transfer of said ceramic pigments.

16. An apparatus according to claim 15, characterized in that said additional heat-activated binder (4) provides for the presence of waxes and polymers or copolymers, preferably polyethylene waxes and ethyl vinyl acetate copolymers.

17. An apparatus according to claim 15, characterized in that said transfer backing paper (3) has, after the transfer of said ceramic pigments from said film (12), a decorated surface which is covered with a protective layer of collodion (5) adapted to provide a pigmented collodion film (25) which can be separated from said paper (3).

18. An apparatus according to claim 10, characterized in that said ceramic pigments are provided in powder form, with a particle size between 5 and 20 microns and with a melting temperature between 400°C and 950°C.

19. An apparatus according to claim 10, characterized in that the amount of said layer (2) of at least one heat- activated mix is between 7 and 20 grams per square meter.

20. An apparatus according to claim 10, characterized in that the thickness of said film (1) made of plastics is between 4 and 25 microns.