CA2377691A1

CA2377691A1 - Coating material and method for producing a coating material

Info

Publication number: CA2377691A1
Application number: CA002377691A
Authority: CA
Inventors: Michael Zimmer; Waldemar Weinberg; Horst Stedron; Inka Henze
Original assignee: Individual
Current assignee: Schott AG
Priority date: 1999-06-28
Filing date: 2000-06-15
Publication date: 2001-01-04
Also published as: DE19929523A1; WO2001001202A1; JP2003503758A; EP1203267A1

Abstract

The invention relates to a coating material for an electrostatic printing method with material particles. The aim of the invention is to produce surfa ce coatings that exhibit a high surface quality, especially a good scratch resistance, on nearly any materials. To this end, the invention provides tha t at least a portion of the material particles comprises the duromer constituents consisting of a resin and of a hardener. The invention also relates to method for producing such a coating material.

Description

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Coating Material and Method for Producing a Coating Material The invention relates to a coating material for an electrostatic printing method with material particles.
Morcover, the invention also relates to a method for producing a coating material, wherein a basic plastic material is mixed in a mixing device with the application of heat to foam a raw toner material, and wherein the raw toner material is comminuted, for examplc granulated, downstream of the mixing device to form toner particles.
A toner which is used for printing on ceramic and glass products is known from EP
0 647 885 Al . The toner particles of the toner have a pigment core consisting of ceramic pigments.
The pigment core is surrounded by a binder resin shell. Charge control agents ate connected to the binder resin shell. With the aid of an electrostatic copying process the toner is placed on a paper coated with gum arabic. A clear lacquer is applied to the coated paper for fixing. Thereafter, the paper can be placed on the ceramic or glass product to be coated and can be wetted. The paper can then be pulled off, while the gum arabic layer and the colvrcd coating applied to it adhere to the ceramic or glass product. The latter is subsequently fired, so that the color pigments melt together with the surface of the product. Such a toner can only be employed in connection with ceramic and glass products.

~~~ . . . . . b ....___ Toners are also lrnown, which have a thermoplastic material as the basic material.
The toner is mixed with color pigment and charge control agents, The toner is applied by means of an electrostatic printing process to a paper to be coated. Thereafter the coated support is fixed at a temperature between 90 ° C and 170 ° C.
These toners are not suitable for coating materials in connection with which high demands are made on the surface resistance, in particular scratching resistance.
It is the object of the invention to create a coating material of the type mentioned at the outset, by means of which surface coatings of a high surface quality can be produced on almost any arbitrary materials, It is furthczznore an object of the invention to make available a method for producing such a coating material.
These objects are attained in that at least a portion of the material particles has the duromer components of resin and hardener.
Thus, a coating material is made available by the invention, which forms a duromer coating on the workpiece to be coated. In this case the properties of the duromer are used for creating good surface qualities, in particular scratch- and heat- resistant surfaces, The coating can be a colored coating, for example, by means of which the surface of a workpiece can be designed in colors, It is also conceivable that the coating is used for affecting the surface properties of a workpiece. In this case the wear or corrosion properties, but also the _.
"' CA 02377691 2001-12-28 WO 01 /01202 PCTlEP00/05481 coefficient of friction, can be affected. By means of electrostatic processes it is possible to apply the coating material specifically at places of the workpieces where the surface is intended to be affected.
Coloring agents are added to the coating material so that it is possible to design the surfaces in colors. Pigments or dyestuffs can be used as coloring agents.
Sulfides are particularly suitable when using pigments. Zinc sulfide pigments in particular should also be mentioned, which are distinguished by a high degree of whiteness and great fade resistance.
Because of their low hardness they generate almost no tool wear and no impairment of the mechanical properties of the plastic material. The ZnS portion of these zinc sulfide pigments acts as a dry lubricant. The use of inorganic colored pigments is also conceivable. These are particularly distinguished by a high degree of covering capacity. Chromium oxide pigments should also be mentioned in this connection, which arc particularly light-, weather- and temperature-resistant. Among the metallizcd pigments, the naphthol-AS pigments are distinguished by color intensity, fade resistance and chemical resistance.
The diazo- condensation pigments among the metahized pigments are furthermore also suitable, if the material is intended to be used undo rough surrounding wnditions. In this connection the diazo-condensation pigments are greatly distinguished mainly by solvent- and migration-resistance, temperature resistance and color intensity. These pigments are also light- and weather-resistant.
So that the material particles can be applied to the workpiece to be coated by means of the electrostatic printing process, it is provided in accordance with an embodiment variation of the invention that the material particles are provided with charge-control particles, for example zinc atoms.

It is intended here for the charge control particles to be electrostatically charged or to make it possible for them to be electrostatically chargeable.
In accordance with the invention, an acid hardener or a peroxide can be used as the resin.
To a~'ect the properties of the material it can be provided that a portion of the material particles is designed as a filler, for example in the form of wood fiber, cellulose powder, shell flour, meal, aluminum trinitrate, ,fused corundum, cryolite, barite, fixed white, barium ferrite, calcium carbonate, dolomite, carbon, graphite, andalusite, feldspar, mica, kaoline, diatomaceous earth, massive micro-spheres, hollow micro-spheres, mullite, olivine, sihimanite, nepheline, talcum, quartz sand, quartz powder, slate flour, silicon carbide and/or wollastonite.
By means of the fillers it is possible to affect the density, the modulus of elasticity, the pressure and bending resistance, the hardness, the plastic yield in heat, the surface quality and -depending on the type of filler - the antistatic properties or the flamo-resistance effects of the coating.
Moreover, the tensile and shear strengths, as well as the heat resistance can be improved when using fibrous materials, A phenolic resin, a urea resin, a melamine resin, a forn~aldehyde resin, an epoxy resin or a non-saturated polyester resin, for example, can be used as the resin.
Because of their high degree of cross-linking, the phcnolic resins are distinguished by great strength, rigidity and hardness. Moreover, they have a small creeping tendency and have, depending on the added filler, great toughness, great plastic yield in heat, a low linear expansion _ , ,. _ . __._ . , ._. __ ~t coefficient, great resistance to glow heat, great resistance to organic solvcnts and neutral chemicals, as well as to weak acids and lyes, are resistant to stress cracking and they are highly non-flermmabIe.
The urea resins are distinguished by the following properties:
- great mechanical strength, rigidity and hardness, - great surface gloss, - very good electrical properties.
The melamine/formaldehyde resins can be preferably employed when great surface strength and scratch resistance, as well as great surface gloss, are demanded.
Moreover, these resins can be used for producing foodstuff resistant object.
The unsaturated polyesters are primarily distinguished by the following properties:
- great strength, rigidity and hardness, - great plastic yield in heat, - good electrical insulating properties, - capability of being electrostatically charged, - great weather resistance, The epoxy resins are primarily distinguished by the following properties:
- no great tendency for stress cracking, - good adherence to almost all materials, - great resistance to chemicals, - good damping capability, S

._ - grEat plastic yield in heat, - good dimensional stability, - great plastic yield in heat and heat stability, - good aging properties, - good electrical and dielectric properties, - low combustibility, - absence of smell and taste.
In accordance with a further possible embodiment variation of the invention it can be provided that at least a portion of the material particles have a thernnoplastic material as a basic constituent, whose melting temperature is Beater than 170°C. It has been shown that these thermoplastic materials in particular can be used for producing scratch-resistant surface coatings.
A PEEK, an SPS, a PAl', a PSU or a PSE material can be used as the thermoplastic material. The employment of a thermoplastic material on the basis of polystyrene or epoxy bisphenol A thermoplastic material is also conceivable, For producing the above described coating material, an extruder can be used as the mixing device, for example. Resin and a hardener can be placed into this extruder and can be heated in it to a temperature which is higher than the melting temperature of the resin and hardener, but less than the duromer cross-linking temperature. The color pigments and the charge control particles can be placed into the extruder, so that a complete and uniform mixing of resin, hardener, color pigments and charge control particles can take place. When mixing is completed, the raw toner material is ., , _ ,..

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i removed from the mixing device and cooled. Thereafter it can be comminuted, for example ganulated, in order to produce the individual material particles in this way.

Claims

1. A coating material for an electrostatic printing process with material particles, wherein at least a portion of the material particles has the duromer components resin and hardener characterized in that the resin is a phenolic resin, a urea resin, a melamine resin, a formaldehyde resin, an epoxy resin or a non-saturated polyester resin, and that the hardener is an

2. The coating material in accordance with claim 1, characterised in that at least a portion of the material particles is made of coloring agents or contains coloring agents.

3. The coating material in accordance with claim 2, characterized in that the coloring agent is an inorganic pigment, for example an oxide, a sulfide, a chromate, or an organic pigment, an azo pigment, metal-complex pigment, a phthalocyanine pigment or a polycyclic pigment, a metal-effect pigment, a nacreous-luster pigment, a day-glow pigment, a phosphorescent coloring agent or an optical brightener.

4. The coating material in accordance with one of claims 1 to 3, characterized in that the material particles are provided with charge control particles, for example zinc atoms.

5. The coating material in accordance with claim 4, characterized in that the charge control particles are electrostatically charged or can be electrostatically charged.

6. The coating material in accordance with one of claims 1 to 5, characterized in that the hardener is a hydroperoxide, an alkyl peroxide, an acrylic peroxide, an acetyl peroxide, a ketal peroxide or a ketone peroxide, or a per-ester.

7. The coating material in accordance with one of claims 1 to 6, characterized in that a portion of the material particles is designed as a filler, for example in the form of wood fiber, cellulose powder, shell flour, meal, aluminum trinitrate, fused corundum, cryolite, barite, fixed white, barium ferrite, calcium carbonate, dolomite, carbon, graphite, andalusite, feldspar, mica, kaoline, diatomaceous earth, massive micro-spheres, hollow micro-spheres, mullite, olivine, sillimanite, nepheline, talcum, quartz sand, quartz powder, slate flour, silicon carbide and/or wollastonite.

8. The coating material in accordance with one of claims 1 to 7, characterized in that the duromer is a heat-curing, UV curing and/or IR curing plastic material.

9. A coating material for an electrostatic printing process with material particles, characterized in that at least a portion of the material particles has as its basic component an thermoplastic material, whose melting temperature is higher than 170°C.

10. The coating material in accordance with claim 9, characterized in that the melting temperature of the thermoplastic material lies in the range between 170°C
and 300°C.

11. The coating material in accordance with claim 9 or 10, characterized in that the thermoplastic material is a PEEK, an SPS, a PAJ, a PSU or a PSE material or epoxy bisphenol A.

12. A method for producing a coating material in accordance with one of claims 1 to 8, wherein a basic plastic material is mixed in a mixing device with the application of heat to form a raw toner material, and wherein the raw toner material is comminuted, for example granulated, characterized in that the duromer components resin and hardener are introduced into the mixing device as the basic plastic material.

13. The method in accordance with claim 12, characterized in that in this mixing device the resin and a hardener is heated to or maintained at a temperature which is equal to or higher than the melting temperature of the resin and hardener, but less than the duromer cross-linking temperature, and following the mixing process the raw toner material is cooled and comminuted.

14. The method in accordance with claim 12 or 13, characterized in that color pigments and/or charge control particles are introduced into the mixing device.