EP0121179B1 - Backing for decalcomanias of the pull-off or the slide-off type - Google Patents

Description

The invention relates to a support for decals or decals made of absorbent paper with an applied barrier layer and a water-soluble separating layer for receiving a print and / or lacquer layer.

Carriers for decals or decals are known (DE-OS 25 51 860 corresponding to US-PS 4,049,860 or also US-PS 2,970,076). They contain a water- or heat-soluble separating layer, on which the decoration picture is printed by screen printing or offset printing. When transferring the decor image to the desired surface, either manually or mechanically, depending on the procedure, a residual amount of separating layer components is always transferred. Components of the separating layer are usually gum arabic, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl acetate, polyglycols or oligosaccharides or polysaccharides.

An important feature of such transferred transfer layer components is their residue-free burning when the decor image is subsequently burned in, which usually consists of mixtures of inorganic pigments and a paint mask.

On substrates made of glass or ceramics with underglaze, the usual procedure in the presence of water-soluble separating layer components and a high firing temperature means that the quality is perfect, i.e. receive absolutely free, decorative end products.

If larger amounts of water-soluble separating layer constituents are also transferred, these prove to be a hindrance, especially when transferring to unglazed ceramic pieces, but also when using critical firing processes, such as rapid firing, or when using low baking temperatures. In such cases, carried-along separating layer components leave permanently visible, undesirable residues after baking.

Decals or decals are also known which are used outside the ceramic area. These images are transferred to glass, metal, enamel, plastic etc. at temperatures up to max. Fixed at 250 ° C on the base, while the paint mask surrounding the decor image is retained. A major disadvantage of the known separating layers is that the components of the separating layer which are also transferred dissolve again when water is attacked on the base and reduce or eliminate the adhesion of the decorative image. Of course, such images can also be produced in reverse printing, with the advantage that a heat-activatable adhesive is applied in the last working step. Such images then adhere permanently to the base after the heat treatment. However, it is disadvantageous that the image can no longer be positioned manually after the transfer, since the water-soluble, lubricious separating layer is missing between the decorative image and the base. This is particularly important for irregularly shaped documents.

It is also known (US Pat. No. 3,128,197) to use materials for decals for underglaze processing which have a water-soluble separating layer between the paper support and the image system to be transferred. The separating layer is disproportionately thick and consists of a low molecular weight carboxy group-bearing polyvinyl compound, such as polyacrylic acid or its alkali salt.

The disadvantage of this is that the water-soluble layer on the one hand is strongly transferred to the object to be decorated and on the other hand the soaking water is undesirably quickly concentrated. The presence of salt constituents also entails the risk of a residue-free combustion during the baking process. Finally, only the underglaze transfer is possible with such a material, but not use on objects to be decorated, such as glass or plastic surfaces.

It was an object of the present invention to provide a support for decals or decals with a water-soluble separating layer, which is used both for applying a decorative image to objects such as enamel, glass, stainless steel, porous ceramics, in which baking at low baking temperatures or can be carried out in rapid firing, and is also suitable for applying a decorative image to, for example, plastic surfaces in which only the decorative image is fixed.

The solution to this problem is based on a support for decals or decals of the type mentioned at the outset, and it is characterized in that the separating layer contains or consists of a copolymer of acrylic acid and / or a copolymer of alkyl vinyl ether and maleic anhydride. The separating layer preferably consists of a mixture of a copolymer of acrylic acid or a copolymer of methyl vinyl ether and maleic anhydride and a polysaccharide, in particular dextrin.

This ensures that the transfer of the decorative image from its carrier to porous ceramic substrates, for example with the following application of critical firing processes or to documents that are only subjected to a subsequent fixing process, no longer has a detrimental effect on the appearance of the end product and the final liability of the decorative image will. The resulting decorative images on the documents do not show any signs of toner, nor are they easily removable by moisture or water attack. After transferring, for example, to unglazed ceramic pieces and after baking, in which the lacquer mask burns, clean decorative images result, even if a large proportion of separating layer components have also been transferred. In the event that the decorative image is transferred to a base on which it is only fixed, ie while maintaining the paint mask, in which there is normally a risk that the decorative image will become detached due to aqueous attack, since water-soluble components of the separating layer have also been transferred this effect according to the invention be prevented.

Copolymers of acrylic acid have proven to be suitable as materials for the separating layer. The copolymers have molecular weights of 2,000 to 250,000. Examples of suitable copolymers are those composed of acrylic acid / acrylic acid esters or methacrylic acid esters. Their molecular weights are in the range from 30,000 to 260,000. These products are commercially available.

It has been shown that the copolymers of acrylic acid have excellent burning properties and primarily burn or decompose even in low temperature ranges, without the combustion taking place with excessive deposition of soot.

The copolymers are preferably used in a mixture with customary substances known and suitable for the separating layer. These include the substances described at the beginning. Mixtures with polysaccharides, in particular dextrin, are very particularly preferably used. For the optimal embodiment of the invention, it has proven to be advantageous if the separating layer contains at least 50 percent by weight of copolymer. Separating layers consisting of copolymers of acrylic acid mixed with dextrin can be used to decorate unglazed ceramic substrates. After baking in the rapid firing process, no residues are visible in the non-image areas.

Copolymers of alkyl vinyl ether and maleic anhydride, in particular of methyl vinyl ether and maleic anhydride, have also proven to be very suitable as materials for the separating layer according to the invention.

These products are commercially available. They have molecular weights in the range from approximately 50,000 to 200,000 and are water-soluble. They are suitable in a mixture with substances which carry reactive groups, such as oligosaccharides or polysaccharides, vinylpyrrolidone-containing polymers, polyvinyl alcohol, alkylamine, polyalkylpolyamine or other substances with polyfunctional groups, and are outstandingly suitable for separating layers with applied decorative images which are transferred in aqueous solution to documents that cannot be subjected to a subsequent baking process. It has been shown that the transferred separating layer components cross-link with one another at the prevailing fixing temperatures and bring about a water-insoluble or poorly soluble state. As a result, the decor image on the base is insensitive to moisture or water attack. Mixtures with at least 50 percent by weight of the copolymer according to the invention for the separating layer have proven particularly useful.

Mixtures of copolymers of acrylic acid and of copolymers of alkyl vinyl ether and maleic anhydride can also be used for the separating layer according to the invention. In this way, depending on the mixing ratio, in connection with preferably dextrin, different dissolving and floating times of the images are achieved, which is particularly important in the case of machine application. In this way, simple and relatively inexpensive separating layers can be achieved, which can be used for a wide variety of applications.

Overall, the invention achieves that a support for decals or decals can be made available, which meets the requirements for decor images for residue-free decorations, as well as can be used for a water-soluble coating, with subsequent fixing of the decor image, under Conversion of the residual separating layer components into a water-insoluble state.

The invention is explained in more detail with reference to the attached figure. It shows schematically a cross section of a carrier according to the invention for decals or decals. Position 1 indicates the paper carrier, with an average basis weight in the range of approximately 100 to 200 g / m ^2. The paper carrier contains a barrier layer 2, which makes one surface of the paper carrier less porous. It can consist of surface sizing or a sealable spread, for example starch, casein, glue, alkali metal silicate or water glass with and without clay filler. The presence of the barrier layer 2 prevents excessive penetration and absorption of the material according to the invention to be applied for the separating layer 3.

The separation layer 3 made of the materials described is applied over the barrier layer 2 by means of a suitable application method. The dry weight to be applied is 6 to 15 g / m ² . Drying takes place in a drying tunnel at approx. 80 ° C.

To prepare the interface solution, the individual components are first dissolved in water.

Dextrin is sprinkled in cold water and dissolved with moderate stirring.

The copolymer of acrylic acid and acrylic acid ester (PAS / PAE) is dissolved in water at 70 ° C. by neutralization, for example by adding 23 parts of triethanolamine to 100 parts of copolymer.

• In 70 Teile kochendes Wasser werden 15 Teile des Copolymerisates mit einem Molekulargewicht von etwa 125.000 und einer spezifischen Viskosität von 0,1 bis 0,5 mPa s (Gantrez ^® AN 119 der GAF, USA) bei großer Geschwindigkeit eingerührt. Die vollständige Auflösung zeigt sich im plötzlichen Aufklaren der milchigen Aufschlämmung. Parallel erfolgt ein Absinken der Viskosität. Zur abgekühlten Lösung gibt man unter Rühren 15 Teile Dextringranulat und rührt bis zum völligen Auflösen. Die so erhaltene Lösung kann nun mit den üblichen Auftragsverfahren auf den Papierträger aufgebracht werden, wobei ein Auftrag von mindestens 6 g/m² bis etwa 15 g/m² angebracht ist. Vorzugsweise beträgt das Trockenschichtgewicht 8 bis 12 g/m^2.

The copolymer of methyl vinyl ether and maleic anhydride (PVE / MA) is dissolved in hot water at 95 ° C. with stirring. The procedure is as follows:

• In 70 parts of boiling water 15 parts of the copolymer having a molecular weight of about 125,000 and an intrinsic viscosity of 0.1 to 0.5 mPa s (Gantrez ^® AN 119 GAF, USA) are stirred at high speed. Complete dissolution is shown by the sudden clearing of the milky slurry. At the same time, the viscosity drops. 15 parts of dextrin granules are added to the cooled solution with stirring and the mixture is stirred until completely dissolved. The solution thus obtained can now be applied to the paper support using the customary application methods, with an application of at least 6 g / m ² to about 15 g / m ^{2 being} appropriate. The dry layer weight is preferably 8 to 12 g / m ^2.

The aforementioned components can now be mixed with one another as desired.

Since dextrin can impair residue-free combustion, according to the invention a proportion of 50 percent by weight in the formulation should not be exceeded. On the other hand, dextrin is also useful to the extent that its presence has a positive influence on the floating and peeling properties with regard to the separating layer and the decor. When using a decal to be fixed by heat, dextrin is suitable as a reaction partner to PVE / MA.

The formulations listed in the table below are applied to a paper support provided with a barrier layer at 10 g / m ² (dry weight) and dried.

Using the examples, the influences of the various components on the cleanliness of the decor or its heat fixability are shown.

The paper supports provided with the separating layers 1 to 6 are coated with a commercially available, residue-free burning acrylic varnish (varnish 83450 from Degussa) as a varnish mask and air-dried.

For the test, the test specimens prepared in this way are briefly placed on the back with water. The peeling paint film is pushed onto unglazed ceramic pieces after 1 minute and spread using a rubber squeegee. The air-dry pieces are then heated to 550 ° C., the paint mask being completely burned, and then cooled again.

Recipe 1 clearly shows traces of unburned interface. Recipes 2 to 6, on the other hand, show no traces of clays, i.e. Even at a relatively low firing temperature, the residues of the separating layer that are also transferred are burned without residue, without leaving soot particles.

A paint mask applied to the separating layer according to recipe 2 instead of an applied decorative image with a paint mask is transferred in the usual way to a plastic container (bottle) as a base and exposed to a temperature of approximately 200 ° C. for 15 minutes. For comparison, a plastic container is treated accordingly, a material according to recipe 1 being used as the separating layer.

After cooling, both containers are exposed to water containing surfactants as a test solution. While the paint mask, transferred with the help of recipe 2, withstands the action of water for 20 minutes, the paint mask, which was transferred with the help of recipe 1 for the separating layer, floats after the same time.

Claims (5)

1. Support for transfer images or slide-off images, composed of absorbent paper with an applied barrier layer and a watersoluble separation layer for receiving a print layer and/or lacquer layer, wherein the separation layer is constituted by or contains a copolymer of acrylic acid and/or a copolymer of alkylvinyl ether and maleic acid anhydride.

2. Paper support as claimed in Claim 1, wherein the separation layer is comprised of a mixture of a copolymer of acrylic acid and a polysaccharide.

3. Paper support as claimed in Claim 1, wherein the separation layer is comprised of a mixture of a methylvinyl ether/maleic acid anhydride copolymer and a polysaccharide.

4. Paper support as claimed in Claims 2 and 3, wherein the polysaccharide is dextrin.

5. Paper support as claimed in Claims 1 to 4, wherein the separation layer contains at least 50 percent by weight of copolymer.

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