EP0014901B1 - Process for printing a substrate resistant to a heat of more than 220 degrees c - Google Patents

Description

For example, from DE-A-1 771 812.2 337 798, 2436 783 and 2 458 660, it is known to print on textile fabrics by the so-called transfer printing process, in that auxiliary substrates, in particular paper or aluminum foil, are printed with sublimable dyes using binders and the subcarriers printed in this way in turn are used for printing on the textiles. In this case, the auxiliary carriers are placed with the printed side on the textiles to be printed, after which the dyes are sublimed onto the textile material by heating the auxiliary carrier on the non-printed side to approximately 160 to 220 ° C. If the textile material consists of cotton fabric, according to the publications mentioned, special measures are used to bind the dyes on the cotton.

From DE-A-2 642 350 it is also already known to use heat-resistant sheet-like structures which, as such, do not accept the sublimable dyes, such as wood, metals, certain plastics, glass, ceramic materials, natural and plastic products or the like, by the transfer printing process to be printed by providing such substrates before or at the same time as the transfer printing with a surface layer made of a thermoplastic which bonds to the surface of the substrate and absorbs the sublimed disperse dyes. Thermoplastics have always been used as plastic coatings in these known processes, and there is no lower limit for the molecular weights of the dyes that can be used.

FR-A-2 230 794 also describes a method for printing heat-resistant sheet materials, such as metal sheets or ceramic tiles, using the transfer printing method, the substrate being coated with an epoxy resin in accordance with claim 1. This publication does not indicate the types of thermosets used in accordance with the invention, nor does it provide the knowledge that the disperse dyes must have certain molecular weights. The same applies to GB-A-1 517 832, in which a substrate according to claim 1 is coated with a hardened unsaturated polyester resin. This patent also does not give any indication of specific molecular weights of the dyestuffs which can be used; rather, the information on page 2, lines 18 to 29 suggests that the higher sublimation temperatures required for high-molecular dyestuffs lead to increased migration. ,

It has now been found that articles obtained in the transfer printing process, at least in certain applications, only have sufficient migration resistance if certain plastic coatings and dyes are selected. Inadequate migration resistance has the consequence that the dyes migrate in the surface layer on the substrate and blur the printed image or pattern. This disadvantage occurs particularly and particularly strongly when the printed substrate is exposed to short-term high temperatures or continuous heating during its later use. This is the case with many household items, such as stove tiles, heating cladding, floor coverings in rooms with underfloor heating, stoves, cooking pots, kitchen machines of all kinds, etc. Especially in such applications, the previously known transfer printing processes are not suitable because they do not produce clear print images or cause the initially clear images to blur with time.

The object underlying the invention was therefore to obtain a new method for printing on substrates resistant to heating above 220 ° C., which leads to flawlessly clear printed images, which do not change over time, not even with continuous heating or short-term heating by migration to become blurred or blurred and also not yellowing.

The method according to the invention for printing a substrate that is resistant to heating above 220 ° C. after the transfer printing process by coating the substrate with a plastic that is affine with the printing inks, placing an auxiliary carrier printed with sublimable dispersion dyes on the plastic coating and transferring the dispersion dyes by dry heat treatment into the plastic coating characterized in that at least one cross-linked thermoset from the group of phenoplasts, aminoplasts, polyesters, polyphenylene sulfide resins, silicone resins, acrylate resins, alkyl resins, polyethylene sulfide resins and / or unsaturated are used as dispersion dyes with high molecular weight dispersion dyes with molecular weights between 340 and 1000 and as plastics for coating the substrate Polyester resins used.

Surprisingly, it has been found that the migration tendency of the dyes becomes practically negligible with this process, even if the printed substrates are exposed to relatively high temperatures during printing or after printing. The reduction in the migration tendency is due on the one hand to the three-dimensional crosslinking of the thermosets and on the other hand to the unusually high molecular weights of the disperse dyes. There is also practically no discoloration or yellowing of the coating due to aging or heating.

Because of the surprisingly frozen migration tendency of the dyes according to the invention, the substrates printed by the process according to the invention can be exposed to shock temperature stresses above 220 ° C. and long-term permanent temperature stresses, for example to 150 ° C., without any dye migration being recognizable.

For this reason, you can find many household items, such as saucepans, frying pans, electric kitchens For the first time, use the halftone or halftone technique to print a photographic image on kitchen appliances, rechauds, waffle irons, grills, toasters, coffee machines, stove tiles, heating panels, ashtrays and many other objects without the image being blurred during the printing process or later.

The substrates can consist of metals such as aluminum or steel, glass, ceramic materials, natural or artificial stone products, heat-resistant plastic or the like. For example, ceramic tiles, which could previously only be decorated using the screen printing process, can now be printed using halftone technology with pictures that are true to the photograph, and such tiles can be used even in heated areas, such as on hot tables, as stove tiles or as floor tiles in rooms with underfloor heating, without using Migration of the photographic print would be blurred. The ceramic tiles can consist of conventional tile materials such as clay, earthenware, stoneware, porcelain, chamotte or the like. However, the substrates can also be slabs made of natural stones, such as granite, marble, slate, dolomite or any other natural stone, or of a plastic material made of wood or metal. Other substrates can be, for example, moldings made from phenolic resins reacted with organic di- and / or polyisocyanates, especially those made from foams according to DE-A-2 542 900.

Other substrates which can be printed by the process according to the invention are active substances in web form which can be coil-coated and printed in coil form. These can in turn consist of metal, plastic or the like.

The method is also particularly suitable for printing on a wide variety of household appliances which are exposed to elevated temperatures temporarily or in the long term, such as all types of cookware, toasters, hot plates, waffle irons, grills, thermos containers and heaters. All of these are coated at least on their visible sides with the thermosetting plastic or first with another plastic and finally with the thermosetting plastic before the decoration is printed on using the transfer printing process.

When we are talking about cookware, this includes all containers of any shape, with or without a handle or handle, as used in the home and kitchen. For example, there are saucepans, frying pans, pressure cookers, kettles, milk churns, roasting pans, saucepans, bowls, each with or without a lid, and other containers which serve to heat food or drinks. Such cookware is usually made of metal, such as steel, aluminum, enamelled steel, but can also consist of ceramic material or, above all, of fireproof glass. According to the invention, the heating plates can be printed with decor on their heating surface without this losing quality due to the heating. The thermal surface can be made of any thermally conductive material, such as steel or ceramic.

The thermos containers can be in the form of bottles, jugs, mugs, mugs or boxes or in other conventional forms for this purpose. They are generally used to store drinks or food in the home, but can also be used for technical purposes.

Various designs of heating devices to be printed according to the invention with a housing and at least one visible side are known. For example, it can be oil ovens, gas ovens, coal ovens, electric ovens or heat stores. It is essential that all of these heaters have a housing which is generally essentially cuboid with at least one visible side. This housing is generally made of metal, but can also be covered or supplemented in certain areas with ceramic plates, plastic plates, wooden plates or the like.

The thermosets used according to the invention can be crosslinked in different ways. Crosslinking agents are used which are capable of converting the linear molecular chains of the precursor of the crosslinked thermoset, which has reactive centers, onto the substrate by forming intermolecular bridges into networks of three-dimensional structure. The crosslinking agents can either themselves be built into the network as intermolecular bridges or activate a direct combination of reactive centers from chain to chain.

For example, the network can be formed by polyaddition reactions or polycondensation reactions, but also by radical, peroxide-catalyzed polymerization.

Accelerators such as cobalt octanoate, dimethylaniline or peroxides can be added to influence the hardening of the thermosets.

A particularly favorable group of thermosets is that of silicone resins, especially those with methyl, ethyl and phenyl substituents, such as methylphenyl silicone resins. Depending on the substituents, they are water-repellent and flame-retardant, show good dimensional stability at high temperatures and have good surface hardness in addition to excellent affinity for the disperse dyes to be used. Silicone polyester resins are also very suitable.

Another means of crosslinking the thermosets is by using crosslinking radiation such as infrared rays, ultraviolet rays or ionizing radiation such as gamma rays, X-rays or electron beams. This method is known per se and is described, for example, in “defazet Deutsche Farben-Zeitschrift” 1977, pages 257 to 264 and in “Maschinenmarkt”, Würzburg, 84 (1978), 64, pages 1249 to 1252. The advantages of this networking method are the very high production speed and the uniformity of the networking. The curing or crosslinking takes place at room temperature. Pigmented and unpigmented systems can be used equally.

During electron radiation, the wet paint film is covered with a protective gas. Good inerting combined with a high ionization density due to electron radiation leads to a high degree of cross-linking of the thermoset molecules. After a hardening time of approx. 0.2 seconds, the products are immediately stackable and can be processed further. This technology enables greater surface hardness, increased abrasion resistance, increased density, improved resistance to chemicals, good dye affinity, reduced flammability and high throughput speeds.

Unsaturated acrylate resins and unsaturated polyester resins, as described, for example, in the above article "defazet", the content of which is included here, are particularly suitable for this crosslinking method by radiation.

The process according to the invention is usually carried out by first providing the substrate with a precursor of the crosslinked thermosetting plastic at least on the surface to be printed. This can be done by dipping, brushing, spraying, brushing on or rolling on a solution or dispersion of the precursor of the thermoset. Instead, it can also be applied without solvent by extrusion, lamination or powder coating.

Certain substances such as pigments can already be added to the precursor of the thermoset. Instead, an intermediate layer, such as a pigmented intermediate layer, which is suitable for achieving color effects or for improving the surface quality, can also be applied under the precursor coating.

After the precursor of the thermoset has been applied, crosslinking or curing takes place in a manner known per se, a hard and resistant coating being obtained on the substrate. The printed subcarrier is now placed on this surface layer with the printed side facing this layer, whereupon the dispersion colors are transferred by sublimation onto and into the thermosetting surface coating of the substrate by heating from the unprinted side of the subcarrier.

The disperse dyes used are suitably those which sublime above 200, especially above 220 ° C. The disperse dyes used according to the invention expediently sublimate above 250 ° C., preferably above 300 ° C., particularly above 350 ° C. For reasons of equipment, however, it is expedient to select such dyes that do not first exceed 500 ° C., preferably not above 400 ° C. sublimate.

While the dyes previously used for transfer printing processes should not contain any ionic, highly water-solubilizing groups such as -S0 ₃ H or -COOH, such dyes can be used successfully in the process according to the invention. The number of non-ionic polar groups, such as -N0 ₂ , -CN, -S0 ₂ R (R = alkyl), -OH, -NH ₂ or -NHR (R = alkyl), can be higher than in the previously usable Dyes. In addition to alkyl-substituted amino groups, such as isobutylamino groups, linear residues can also be present, which has hitherto been avoided in the transfer printing process. For azo dyes, cyano groups are preferable to nitro groups, and fluorine atoms are more suitable than chlorine atoms. Trimethylsilyl groups can increase the vapor pressure in the azo dyes.

A preferred group of the disperse dyes used according to the invention are certain anthraquinone, monoazo and azomethine dyes, but the process according to the invention is not restricted to these groups of dyes.

Anthraquinone, monoazo and azomethine dyes are particularly preferred, the molecules of which are heavily occupied with amino, alkoxy, oxalkyl, nitro, halogen and cyano groups. These dye groups are defined in Color Index, Volume 1, pages 1655 to 1742.

Preferred examples of dyes used in the present invention are those of the following formulas.

Blue dyes:

Yellow dyes:

Orange dye:

Red dye:

The subcarrier can be printed with these dyes continuously in gravure printing or discontinuously in offset printing, with images or patterns having to be printed in reverse. You can use the finest screening. Printing can also be done using the classic screen printing process or on rotary film printing machines.

The auxiliary carriers, such as transfer papers, should have a weight of at least 60 g / m ² and a maximum of 120 g / m ² . The tear length should be at 5000 m, the burst pressure at 3 to 3.5 kg / cm ² , the absorption at 60 to 80 g of water per square meter in 60 seconds (according to Kobb) and the porosity at 40 ml / sec. lie. In addition to paper, metal foils and possibly elastic but not dye-affine plastic foils can also be used as auxiliary carriers, provided they can withstand the transfer printing temperatures above 220 ° C.

The process according to the invention can be used on continuous finishing lines for aluminum sheets at furnace temperatures of 250 ° C. When the cooling zone is switched off, the aluminum sheet can simultaneously be passed over a calender roll with transfer paper. The drying heat of 250 ° C. in the aluminum enables the transfer to the aluminum without further energy supply.

• Fig. 1 eine perspektivische Darstellung einer erfindungsgemäß bedruckten Fliese oder Platte aus Keramikmaterial oder Metall,
• Fig. 2 eine perspektivische Darstellung einer erfindungsgemäßen bedruckten Metallbahn,
• Fig. 3 einen weggebrochenen vergrößerten Ausschnitt aus dem Querschnitt der Fliese oder Platte gemäß Fig. 1 entlang der Linie III-III und
• Fig. 4 eine perspektivische Darstellung einer auf der Wärmefläche erfindungsgemäß bedruckten Wärmeplatte.

In the drawing, three application examples of the method according to the invention are shown. In the drawing shows

• 1 is a perspective view of a tile or plate printed according to the invention made of ceramic material or metal,
• 2 is a perspective view of a printed metal sheet according to the invention,
• Fig. 3 is a broken away enlarged section of the cross section of the tile or plate of FIG. 1 along the line III-III and
• Fig. 4 is a perspective view of a hot plate printed on the thermal surface according to the invention.

In Fig. 1, a tile or plate is shown in perspective, which can be coated and printed as a single plate. The coating can be carried out by dipping processes, spraying processes or other known coating processes. The tiles can be plastic-coated on one side on the visible side or on both sides.

2 shows a correspondingly printed strip-shaped metal web in roll form, which is suitable for being coated on a strip.

FIG. 3 of the drawing shows the cross section of an object printed according to the invention using the example of the tile or plate of FIG. 1. The substrate 1 made of metal or another material customary for tiles or plates, such as ceramic material, is on both sides with the plastic coating 4 and a thermosetting coating 2 provided. The thermosetting coating 2 lies on the visible side of the tile or plate and lies directly on the substrate 1. Dyes 3 are embedded in the thermosetting coating 2 in such a way that they adjoin the free surface thereof, but in the illustrated case only extend over a limited part of the thickness of the thermosetting coating, the latter being free of dyes in its area directly adjacent to the substrate 1 .

The heating plate 7 shown in FIG. 4 of the drawing has a grip strip 6 at each of its two ends, between which the heating part 5 with the printed heating surface is located.

example 1

An aluminum sheet was pretreated with an organic grease solvent to make its surface free of grease and other contaminants. Then the pre-cleaned aluminum sheet was first coated with a white primer layer with a layer thickness of 40 ± 10 µm using a spray process. This primer layer consisted of 43% by weight of a silicone-polyester resin with a polysiloxane content of 75% and a polyester content of 25%, 28% by weight of titanium dioxide, 10% by weight of xylene, 10% by weight of ethyl glycol acetate, 3% of BaysilonÖl M 40 (trademark from Bayer AG, 10% in xylene), 3% by weight lead octoate and 3% by weight butyl titanate (18% in ethyl glycol / xylene 1: 1). The coating was then dried in a continuous oven at 180 ° C. for 10 minutes. Then a colorless clear lacquer layer based on silicone polyester was also applied by spraying with a layer thickness of 15 ± 10 µm. This clearcoat consisted of 80% by weight of the silicone polyester resin contained in the primer layer, 4% by weight of xylene, 4% by weight of ethyl glycol acetate, 3% by weight of Baysilon oil M 40, 3% by weight of lead octoate and 6% by weight of butyl titanate in ethyl glycol / xylene. This drying took place at 250 "C. for 10 minutes.

The still hot coated sheets were brought into contact with a transfer printing paper which had been offset with offset printing inks, each of which was 16% by weight of Disperse-blue (CI No. DB 165-1, MG = 425) or disperse dye. Brilliant yellow (CI No. DY 201, MG = 413) or disperse red (CI No. DR 177, MG = 438) or disperse red violet (CI No. DV 26, MG = 422). The printing process was heated to 250 C for 30 seconds.

The printed aluminum sheets obtained in this way were distinguished by very good heat resistance and service temperatures above 150 ° C. and by high resistance against all burdens that occur, for example, in the household sector.

Example 2

Biscuit tiles were first sprayed with a barrier primer that was dry at room temperature because the tiles were very absorbent. This pretreatment agent consisted of 27% by weight epoxy resin (MW approx. 3800, OH content approx. 6.8%), 1% by weight nitrocellulose, 0.1% by weight Acronal 700 L (trademark of BASF, 10%) , 3.4% by weight Bentone (100 / big), 27% by weight titanium dioxide, 7.5% by weight xylene, 20% by weight ethyl glycol acetate and 20% by weight Desmodur N 75 (trademark of Bayer AG).

A plastic coating of aliphatic urethane acrylate, 42.5% by weight Ebecryl 264 (trademark of UCB S.A.) and 57.5% by weight hexanediol diacrylate was then applied in the casting process. The top coat layer was applied with a layer thickness of 50 ± 10 µm solvent-free. The crosslinking took place within fractions of a second at room temperature by electron beam curing. The coating had an exceptional scratch resistance and hardness for plastic surfaces.

The coated tiles were brought into contact with a transfer printing medium which had been printed using the high-pressure process with a high-pressure paste which contained 15% by weight of Disperse-red (C.I. No. DR 177, M.G. = 438). The transfer printing was carried out at 240 ° C. for a residence time of 70 seconds.

Example 3

Tinplate was coated without connection directly by roller coating with a coating system based on a saturated polyester and a self-crosslinking acrylic resin. First, a white primer based on a saturated polyester was applied as a base coat in a layer thickness corresponding to 20 to 30 g / m ² , after which it was dried at 160 ° C. for about 8 minutes. This consisted of 12% by weight Dynapol LH 812 (60%, trademark of Dynamit Nobel), 29.4% by weight titanium dioxide, 36.7% by weight Dynapol L 850 (35%, trademark of Dynamit Nobel), 11 % By weight Maprenol MF 980 (62%, trademark of Hoechst AG), 0.4% by weight Modaflow (10%, trademark of Monsanto), 0.5% by weight Epicote 834 (90%, trademark of Shell AG), 1.7% by weight of Paraplex G 54 (trademark of Rohm and Haas), 0.5% by weight of curing agent and 8.15 weight ⁰ / o solvent Solvesso 150 (trademark of Esso AG). A colorless clear lacquer layer based on a self-crosslinking acrylate resin was then applied in a layer thickness corresponding to 10 to 20 g / m ² . This consisted of 85% by weight of Larodur 150 (500%, trademark of BASF), 5% by weight of Shellsol AB (trademark of Shell AG), 6% by weight of terpene-containing hole solvent Depanol N IV (trademark of Hoechst AG) and 4% by weight -% 1,2,3,4-tetrahydronaphthalene. Drying took place within 10 minutes at 190 ° C.

The tinplate was later overprinted at 250 ° C. for 30 seconds using a transfer printing substrate which had been screen-printed. The screen printing pastes used when printing out the transfer printing medium contained the dyes specified in Example 1.

Example 4

Particle boards were first subjected to a sanding with a grain size of 80 to 120. The coating system was the same as that of Example 3.

A white primer layer as in Example 3 in an amount of 400 g / m ² was sprayed on both sides with a cup gun at an air pressure of 3 to 3.5 bar and a nozzle size of 2 to 3 mm. The drying was carried out at room temperature until it was sandable for 4 to 6 hours or at a temperature of about 80 ° C. for 20 minutes. Then the grit was sanded with grit 280 to 320 before the top coat.

Then a colorless clear lacquer layer of the same composition as in Example 3 was applied with the same cup gun in an amount of 150 to 300 g / m ² . The drying was carried out at room temperature for 8 to 10 hours or at a temperature of about 80 ° C for 10 to 15 minutes.

At a later point in time, the chipboard coated in this way was printed with a transfer printing medium at a temperature of 230 ° C. and with a residence time of 40 seconds, which had been printed with a gravure printing ink. This contained disperse brilliant yellow as the dye (C.J. No. DY 201, M.G. = 413).

The printed products obtained in all four examples had excellent image clarity even after prolonged use and with temporary heating to 200 ° C. and with long-term heating to 150 ° C for several hours. Migration of the dyes was not detectable despite the heating, and the printed images remained completely clear.

Claims (3)

1. Process for imprinting a substrate withstanding heating to above 220° C according to the transfer print method by coating the substrate with a plastic having affinity for the printing inks, applying an auxiliary support imprinted with sublimable dispersion dyes to the plastic coating, and transferring the dispersion dyes by dry heat treatment into the plastic coating, characterized in that as dispersions dyes high molecular dispersion dyes having molecular weights between 340 and 1000 and as plastic for the coating of the substrate at least one crosslinked duroplast selected from the group consisting of phenoplasts, aminoplasts, polyesters, polyphenylene sulfide resins, silicone resins, acrylate resins, alkyd resins, polyethylene sulfide resins and/or unsaturated polyester resins are used.

2. Process according to claim 1, characterized in that as dispersion dyes anthraquinone, monoazo and/or azomethine dyes are used.

3. Process according to claim 1 and 2, characterized in that as duroplasts at least one silicone resin or radiation-hardened unsaturated acrylate resin or polyester resin are used.

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