ES2349632T3 - STRENGTHENING AND DRYING OF VARNISHING SYSTEMS AND PRINTING INKS. - Google Patents

Abstract

Use of semiconductor materials in the form of scale or sphere, clear or transparent, or of substrates in the form of a sphere, needle or scale coated with semiconductor materials, clear or transparent, in amounts of 0.01-30% by weight for the hardening and / or drying of varnish layers and printing inks.

Description

The present invention relates to the use of clear or transparent semiconductor materials as drying or hardening additives in varnish systems and printing inks.

Currently many materials are varnished or stamped. In this way it is possible to improve properties such as color and strength of materials. The disadvantages are the partially long drying times or the high drying temperature. In varnishing cars, relatively long drying lines are needed to ensure that the varnish is dry before applying the next layer of varnish. If the drying time could be reduced, the energy demand and the length of these drying lines could be reduced, which would imply lower production costs.

Therefore, the objective of the present invention is to find a method to accelerate the hardening of varnishes and printing inks that at the same time can be applied in a simple manner. In addition, hardening accelerators should be easily integrated into the varnishing system or printing ink, have high transparency and be used only at low concentrations.

Surprisingly it was discovered that the hardening and / or drying of the varnish layers or printing inks can be accelerated by adding small amounts of finely dispersed clear or transparent semiconductor materials to the varnish or printing ink. By adding this hardening accelerator, the properties of the varnish and printing ink are unaffected or only irrelevant.

In addition, the hardening accelerator influences the thermal conductivity of the varnish or printing inks. Investigations have

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shown to clearly improve the distribution of heat in the varnish or in printing ink.

The use of electrically conductive charges, doped zinc oxide particles and electrically conductive pigments in application systems is known, for example, from public patent application DE 42 20 411 A and U.S. patents. 5,876,856 and U.S. 5,350,448. The use of semiconductor materials with a defined particle shape for the hardening and / or drying of varnish systems and printing inks has not been described according to the state of the art.

The object of the invention is the use of semiconductor materials in the form of a particle or of substrates in the form of a particle coated with clear or transparent semiconductor materials for the hardening and / or drying of varnishes and printing inks according to claim 1.

Suitable clear or transparent semiconductor materials are, for example, those that absorb in the IR range. Particle shaped semiconductor materials are preferably sphere or flake particles or flake, sphere or needle shaped substrates coated with semiconductor materials.

Semiconductor materials are homogeneously constituted from clear or transparent semiconductor materials or are applied as a coating on a particle-shaped substrate. Semiconductor materials are preferably based on oxides and / or sulfides, such as e.g. ex. indium oxide, antimony oxide, tin oxide, zinc oxide, zinc sulphide, tin sulfide or mixtures thereof.

Suitable semiconductor materials typically have a particle size of 0.01 to 2000 µm, preferably 0.1 to 100 µm, in particular 0.5 to 30 µm.

Semiconductor materials are homogeneously composed of so-called semiconductors, or they are substrates in

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particle form, preferably in the form of a sphere, needle or scale, which are coated with one or more layers of the so-called semiconductor materials. Preferably the substrates are only coated with one layer.

The substrates may have a sphere, scale or needle shape. The shape of the particle is not critical in itself. Normally the particles have a diameter of 0.01-2000 µm, preferably 5 -300 µm and in particular 5 -60 µm. Particularly preferred are substrates in the form of a sphere or scale. Suitable flake substrates have a thickness between 0.02 and 5 µm, in particular between 0.1 and 4.5 µm. The extension in the other two intervals is usually between 0.1 and 1000 µm, preferably between 1 and 500 µm and in particular between 1 and 60 µm.

The substrates are preferably natural or synthetic mica flakes, SiO2 flakes, Al2O3 flakes, glass flakes, aluminum flakes, BiOCI flakes, SiO2 spheres, glass spheres, hollow glass spheres, TiO2 spheres, spheres polymers, e.g. ex. of polystyrene or polyamide, or needles of TiO2 or mixtures of said substrates.

The coating of the substrates in the form of a particle with the semiconductor materials is known or can be carried out according to the procedures known to the specialist. Preferably the substrates are coated by hydrolysis of the corresponding metal salts, such as e.g. ex. metal chloride or metal sulfide, metal alkoxides or salts of carboxylic acid in aqueous or conventional solvent.

For both homogeneous semiconductors and substrates coated with one or more layers of semiconductor materials, preferably the semiconductor material is microcrystalline.

Especially preferred drying and / or hardening accelerators are tin oxide, antimony oxide, indium oxide and tin (ITO) in

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form of scale or sphere, as well as mica scales coated with ITO, tin oxide or antimony oxide or mixtures of said oxides.

Especially preferred drying and / or hardening accelerators are clear or transparent semiconductor materials with a dust resistance of <20 � · m, preferably <5 � · m.

A particularly preferred hardening accelerator is a tin oxide doped with antimony oxide or a substrate coated therewith, such as e.g. ex. Mica scales In addition, sphere-shaped SiO2 particles coated with tin oxide doped with antimony oxide are preferred.

In addition to antimony, preferably antimony oxide, elements of groups 3, 5 and 7, preferably halides, in particular chloride and fluoride, are suitable as doping agents.

Doping depends on the semiconductor material used and usually represents 0.01-30% by weight, preferably 2 -25% by weight, in particular 5-16% by weight with respect to the semiconductor material.

In addition, mixtures of hardening accelerators can be used in which no limits are set on the proportion of the mixture.

Preferred mixtures are indium and tin oxides with tin oxides doped with antimony and indium oxide and tin with doped zinc oxides.

Mixtures of two, three or more semiconductor materials can also be added to varnish systems or printing inks. The total concentration depends on the composition of the varnish or printing ink, but should not represent more than 35% by weight in the application system.

The accelerator (s) for hardening and / or drying are added to the varnishing system or the printing ink in an amount of 0.01-30% in

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weight, in particular 0.1-5% by weight, and amounts of 0.5-4% by weight are especially preferred.

Before application on an object, the hardening accelerator is mixed with varnish or printing ink. This is preferably carried out using a high speed stirrer or, in the case of hardening accelerators not sensitive to mechanical means and difficult to disperse, with the use of, for example, a pearl mill or a shaker. It is also possible to use other dispersion equipment known to the specialist. Finally, the varnish or printing ink is air dried by physical means or hardened by oxidation, condensation, thermally, preferably using IR radiation.

By means of the hardening and / or drying accelerator the hardening and / or drying times of the varnish layer or the printing ink are normally reduced by approx. 10-60% compared to the original drying time. In particular for printing inks and varnishing systems that are hardened or dried by IR radiation, clearly shorter drying times are observed.

In addition, surprisingly it was discovered that the acceleration of hardening also causes a very positive effect on the varnish layers arranged above. In addition, it improves the thermal conductivity within the varnish layers.

Suitable varnishing systems include in particular thermally hardened varnishes with aqueous or solvent base, IR varnishes, powder varnishes, melting varnishes, in addition to application in sheets and plastic welding, as well as solvent or aqueous printing inks for all types of normal prints, such as gravure printing, flexographic printing, typographic printing, tissue printing, offset printing, screen printing, security printing. The varnishes or printing inks can be white, colored, or transparent.

The following examples illustrate the invention without limiting it.

Examples

Example 1a (comparison)

In a clear polyester / commercial acrylate varnish that dries with

5 physical methods are introduced 10% by weight of TiO2 Kronos 2310 (TiO2 pigment of particle size of about 300 nm) with respect to the formulation of the varnish by dispersion with spheres of zirconium dioxide (diameter 3 mm). The dispersion is carried out in a Dispermat at a peripheral speed of 12.6 m / s for 1 hour at 20 ° C.

10 Example 1b

As in Example 1a, 8% by weight of TiO2 Kronos 2310 is introduced into a polyester / acrylate varnish that is dried by physical methods and

15 2% by weight of drying additive (a tin dioxide doped with antimony oxide with a particle size of approximately 1 µm) with respect to the formulation of the varnish by dispersion with zirconium dioxide spheres.

20 Example 1c: measurement results

Varnish samples from example 1a and 1b are applied on Q-Panel panels with a wet layer thickness of 200 µm. The dry layer thickness is 25 ± 2 µm.

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The varnished samples of Example 1a and Example 1b are steam dried for 5 min and exposed to radiation with IR radiators of total power 3 kW at a distance of 50 cm. The duration of irradiation varies between 5, 10 and 15 min. Drying / hardening control is performed

30 by means of a Fisherscope microhardness apparatus at room temperature immediately after irradiation with IR and using a diamond tip and a discharge force of 3 mN. Each measurement is carried out in triplicate and the average value is calculated from the individual measurement results.

35 The results of the microhardness measurements are shown numerically in Table 1 according to the different duration of the IR irradiation of the varnish samples.

Table 1:

Irradiation duration with IR min

Microhardness / varnish without additive N / mm2 Microhardness / varnish with additive N / mm2

5 10 15

24.0 ± 1.2 31.6 ± 1.6 32.2 ± 0.6 34.0 ± 5.8 37.0 ± 2.6 37.2 ± 2.4

From the microhardness measures it is clearly seen that the addition of the drying additive accelerates the drying / hardening of the varnish that is

15 dry with physical methods. Already after 5 minutes of IR irradiation of the varnish sample with the drying additive, the hardness value is greater than that of the sample without additive after 15 minutes of IR irradiation. By adding the drying additive, the time to obtain a dry powder product is clearly reduced, and

20 the complete hardening of the varnish that is dried by physical methods is also improved.

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Claims (7)

 Claims 1. Use of semiconductor materials in the form of scale or sphere, clear or transparent, or of substrates in the form of a sphere, needle or scale coated with semiconductor materials, clear or trans 5 parentes, in amounts of 0.01-30% by weight for the hardening and / or drying of varnish layers and printing inks. 2. Use of semiconductor materials according to claim 1, characterized in that the semiconductor material is obtained from 10 oxides or sulfides. 3. Use of semiconductor materials according to claim 1 or 2, characterized in that the semiconductor material is based on indium oxide, antimony oxide, tin oxide, zinc oxide, sulfide fifteen zinc, tin sulfide or a mixture of said materials. 4. Use of semiconductor materials according to claim 3, characterized in that the mixture is indium tin oxide (ITO). twenty 5. Use of semiconductor materials according to one or more of claims 1 to 4, characterized in that the substrate is chosen from the group of mica flakes, SiO2 flakes, Al2O3 flakes, glass flakes, aluminum flakes , BiOCI scales, SiO2 spheres, glass spheres, hollow glass spheres, 25 TiO2 spheres, polymer spheres, TiO2 needles or mixtures thereof. 6. Use of semiconductor materials according to one or more of claims 1 to 5, characterized in that the materials 30 semiconductors are doped. 7. Use of semiconductor materials according to one or more of claims 1 to 6, characterized in that the semiconductor material is structured in an amorphous, crystalline or microcrystalline manner. 35