Pre-treatment and/or pre-coating of non-adsorbent substrates and/or non-adsorbent support materials

ES 2 477 992 T3

DESCRIPTION

Pretreatment and / or precoating of non-absorbent substrates and / or non-absorbent substrates.

The present invention relates to a pre-treatment and / or a pre-coating of non-absorbent substrates and / or non-absorbent substrates for ink printing, ink-jet printing with water-based ink with a pre-treatment solution and / or coating.

At present, low viscosity printing inks are used for ink printing and ink jet printing which are essentially manufactured as water-based printing inks. Its leveling is controlled by the quality of the substrate or support. In this respect, it is often disadvantageous that in case of changing substrates and supports, in case of changing printing speeds and in case of changing ink compositions, the printing ink or ink spreads or flows differently and the inscription fades, does not adhere sufficiently, and the character or print becomes blurry due to flow behavior. Conventional ink jet printing is a form of non-contact digital printing, in which the printing inks are divided into individual volume units or drops and applied as a function of time and position on any substrate or support.

Inkjet printing also includes, among others, continuous ink jet (CIJ) printing, discontinuous ink printing, thermally or piezoelectrically activated (Drop on Demand, DoD, drop on demand) as well as electronically controlled spraying techniques, eg Air Brush.

For inkjet printing, printing inks of different colors are printed side by side within a screen depending on the color arrangement system, with the screen determining the resolution of the print. In this case, the ink printed on the substrate or the support spreads depending on the interfacial tension generated between the applied ink and the support, as well as depending on the structure of the support or substrate itself. The leveling speed is determined by the fluidity of the printed ink in the film formation process.

The leveling of the ink or printing ink, on the other hand, determines the degree of surface coating and the distribution of the ink, so that the ink moistens the surface of the substrate or support as much as possible in the sense of a high degree surface coating and is distributed as evenly as possible in the sense of uniform ink distribution, without causing any bleeding or unwanted mixing in the sense of a defined distribution of the ink.

Low-viscosity inks for inkjet printing, whose film formation is temporarily determined by the evaporation of the solvent, require a control of the decisive influence parameters for the leveling of the ink in the sense of good print quality. such as interfacial tension and fluidity. This control has been insufficiently fixed.

The print quality is usually controlled, in the sense of a suitable interfacial tension, by a previous chemical treatment (cleaning, pickling, chrome plating, phosphating, varnish removal, oxyfluorination), a physical pre-treatment (flame application, corona discharge , plasma treatment) or a permanent coating or pre-coating) that guarantees a surface tension of wetting power in the sense of a high degree of surface coating and a uniform distribution of the ink. Conventional procedures for controlling interfacial tension cannot be used universally, but are largely substrate specific.

On the other hand, the printing quality is usually controlled, in the sense of proper leveling behavior, by accelerating the reduction in flowability of the applied low-viscosity printing ink in the physical film-forming process. (drying by heat, drying by convection) or photophysically (drying by ultraviolet radiation) in order to prevent in the sense of a uniform distribution of the ink that the ink runs and mixes with each other. This generally involves a high technical effort.

DE10204143A1 discloses ink absorbing layers and absorbed inks. The formulas of the ink absorbing layers and the inks are coordinated with each other so that a chemical crosslinking of the ink absorbing layers and the ink occurs. Document DE10204143A1 therefore refers to a pre-treatment in the form of a permanent absorption layer which chemically crosslinks with the ink.

EP0480362A refers to a coating medium that contains a starch and is used as an absorption pre-treatment on non-absorbent substrates yet. This pre-treatment produces an absorption layer that sucks up and absorbs the ink applied on it.

The object of the invention is to create pre-treatments or pre-coatings for non-absorbent substrates or supports, such as plastics, metals and glass, that can be used universally and that in case

ES 2 477 992 T3 necessary to guarantee interfacial tensions of wetting power in the sense of a high degree of surface coating and a homogeneous distribution of the ink, and to create inks that, applied over such previous treatments or previous coatings, prevent in the sense of a defined ink distribution a bleed or a mixture of the applied volume units. These pre-treatments or pre-coatings must universally make it possible to precisely control the fluidity of the inks, the film formation, the mobility of the pigments and, if necessary, the interfacial tension, without high technical effort.

This objective is achieved by the features of claim 1.

According to the invention it has been found that non-absorbent substrates can be printed with ink if they have been previously treated with an initiator. According to the invention, the initiator physically and chemically reduces the fluidity of the ink applied to the substrate by reducing the solubility of at least one component of the ink.

In contrast to the state of the art mentioned, a permanent absorption layer is therefore not provided, which is cross-linked with the ink. Rather, the non-absorbent substrate is pre-treated with a layer of a chemical that does not necessarily absorb the ink and varies the fluidity of the ink. This layer does not necessarily have to cross-link with the ink. The initiator can here be a temporary or permanent chemical.

The claimed instruction then relates to an initiator that actively varies the fluidity of the ink. However, the initiator does not necessarily have to be bound to an ink absorbing layer or pretreatment. Furthermore, the initiator itself does not have to have absorption properties.

In the present invention, it has been found to be particularly advantageous to apply a temporary or permanent pre-treatment, in particular a coating, on a non-absorbent substrate or support before applying the ink, which is suitable to sufficiently reduce the flowability of the applied ink, for for example, by flocculation or agglomeration, and / or to activate a hardening or a polymerization of the applied ink.

Furthermore, the colorants present in the ink, which give coloration, must be permanently fixed on the coating or on the support or substrate.

It has been particularly advantageous to select a coating which has at least one initiator and, if necessary, at least one surfactant. The initiator is preferably a monomeric, oligomeric or polymeric acid or a polyvalent metal salt, for example CaCl2 or Ca (OH) 2.

The surfactant is preferably a monomeric, oligomeric or polymeric surfactant or a hydrocolloid. By this we also understand emulsifying, wetting and dispersing agents.

Precisely the pKa value of the coating or the pKa value of the initiator makes it possible to control the flow behavior of the ink applied on the pretreated substrate and / or on the coating if acrylates, for example polyacrylates and / or polymethacrylates, have been added to the ink, whose solubility depends on the pH value. The acidic effect of the initiator can be further used to control the flowability of the applied ink in order to cause further cure, in particular further thermal cure, which causes crosslinking of the applied ink. The amino resins together with the co-binders, also the low molecular weight co-binders, have given good results in the cross-linking reaction.

In this way an exact control of the leveling / behavior of the ink is possible. The applied ink thickens immediately under the influence of acid.

Consequently, in correspondence with the pKa value of the initiator, the flow behavior of the applied ink and the hardening of the film that is formed can be influenced.

Other details, advantages and characteristics of the invention are derived from the following description of preferred embodiments, as well as from the drawing. They show:

FIG. 1 a side view, represented schematically, of a substrate and / or a support which is provided with a pre-coating according to the invention and can be printed by means of ink printing or ink jet printing; Y

Fig. 2 a side view, represented schematically, of a pre-treatment of a substrate and / or a support which is provided with a coating according to the invention and on which it is printed by means of ink printing or ink jet printing, as another example of realization.

According to figure 1, a substrate 1 and / or a support 2 is provided in the present invention with a coating 3, according to the invention, which can be applied with the substrate 1 or the support 2 in any coating process.

ES 2 477 992 T3

The coating 3 according to the invention is used to influence the flow behavior and / or curing of a water-based ink 4 which has been applied by ink printing or ink jet printing.

The ink 4 is applied on the coating 3 or on the substrate 1 and / or the support 2 with the aid of conventional methods, ink printers and ink jet printers.

As substrate 1 or support 2, any non-absorbent material can be used, such as plastics, metals, composites, sheets, glass or the like.

The coating 3 is also arranged or applied on the substrate 1 and / or the support 4 by coating processes, such as dipping, laminating, casting, flooding and printing as non-atomized coating processes. However, other coating processes are also possible, such as injection coating processes, spraying liquid coatings, injection of compressed air, airless or high pressure injection processes, as well as electrostatic spraying or powder coating processes for join cladding 3 to support 2.

Within the framework of the present invention, it should be considered that the ink 4 of the inkjet printing or ink printing is applied on the coating 3 in dependence of time or space before the ink 4 (inline) is applied on the substrate. 1 or bracket 2. However, within the framework of the present invention, it should also be considered that the ink 4 is applied independently of the time before the coating 3 is applied on the substrate 1 or the support 2, the ink 4 applied on the substrate can be heat treated. coating 3 or substrate 1 by means of a thermal conditioning device 5.

In the present invention it has been particularly advantageous for the coating 3 to be manufactured or formed from at least one initiator and at least one surfactant. In this way, a sufficiently rapid reduction in the fluidity of the ink 4, applied on the coating 3 and / or the substrate 1 or the support 2, in the sense of a defined ink distribution, must be produced or chemically induced. The coating 3, composed of the initiator and the surfactant, can be partially or completely volatile here or it can be soluble in the applied printing ink. The ink 4 is bonded to the coating 3 applied on the substrate 1 or on the support 2.

In this regard, it has proven advantageous to use as a component of coating 3 as surfactant a monomeric, oligomeric or polymeric surfactant, preferably anionic surfactants, cationic surfactants, amphoteric surfactants or myosurfactants. Hydrocolloids can also be used as surfactant.

The surfactants can here be emulsifying, wetting and dispersing agents. Hydrocolloids can also be dispersing agents.

The essential component of the present coating is the acid-configured initiator, in particular as a monomeric, oligomeric or polymeric acid. As initiator, a mono or polyfunctional carboxylic acid is preferably used which has a pKa value of -6 to 15. The initiator, which preferably remains acidic, causes a decrease in the solubility of at least one component of the ink 4 applied to the substrate. 1 or the support 2, in particular on the coating 3. The coating 3 or the acid initiator can cause a flocculation of a polymeric component or a coloring component or the agglomeration of pigments and, therefore, immobilization of the ink 4 applied on the substrate 1.

Furthermore, the initiator can activate at least partially or completely a polymerization of the ink 4 applied on the coating 3 or the substrate 1 and / or the support 2.

In the case of the present invention, it has also been advantageous to use an ink 4 which has, in addition to the volatile components, an at least partially polymerizable composition. This ink 4, according to the invention, has a composition which, with the coating, enables an optimized control of the leveling behavior or the flow behavior. The coating initiator 3 allows a corresponding control of the leveling behavior of the ink 4.

To this end, it has been particularly advantageous to use an ink 4 which contains acrylates, preferably polyacrylates and / or polymethacrylates, as components. Acrylates, in particular polyacrylates and / or polymethacrylates, can be present in an amount of up to 15% by weight as a component of the aqueous ink 4. In principle, all polymers whose solubility depends on the pH value are suitable in this regard.

Furthermore, the acid initiator as a component of the coating 3 acts as a setting accelerator.

The composition can be the following here:

- solvent 10-98% by weight

- amino resin, in particular melamine-formaldehyde resin 0.1-50% by weight

- co-binding agents, also low-molecular-weight co-binding agents,

ES 2 477 992 T3 as bifunctional, trifunctional, oligofunctional or polyfunctional alcohols, including and / or glycols or glycol ethers

- surfactants, such as monomeric, oligomeric or polymeric surfactants

- biocides, such as bactericides or fungicides

- pH value stabilizers

- acrylates, in particular polyacrylates and / or polymethacrylates

- dispersing agents

- wetting agents

- coloring agents, in particular coloring pigments

0-25% by weight

0-5% by weight

0-5% by weight

0-5% by weight

0-15% by weight

0-10% by weight

0-20% by weight

1-10% by weight

This preferred composition of ink 4 acts particularly advantageously with the coating resulting from the previous treatment with a solution 3 having the following composition:

- dissolving agents, water and / or alcohol 80-100% by weight

- initiators, in particular inorganic and / or organic acids, for example monomeric, oligomeric or polymeric acids, in particular mono or polyfunctional carboxylic acids 1-50% by weight

- surfactants, such as monomeric, oligomeric or polymeric surfactants, in particular anionic surfactants, cationic surfactants, amphoteric surfactants or non-surfactants 0-25% by weight

The acid initiator polymerizes the amino resin, in particular the melamine-formaldehyde resin, which is present in the ink 4, the ink 4 bonding to the coating 3 and / or to the substrate 1 and / or to the support 2, optionally also by thermal acceleration, being able to control the leveling behavior and quickly reduce the fluidity of the ink 4. As a result of this, ink markings or prints 4 with very high stability, high adhesion and resistance and high light fastness are possible on any substrate 1 or support 2 by coating 3, in particular pre-treatment.

Reference character list

Substratum

Medium

Pretreatment and / or coating solution

ink

Thermal conditioning device