Note: Descriptions are shown in the official language in which they were submitted.
t~~ . .. . _.. ,..._.
CA 02377691 2001-12-28
,.
WO 01/01202 PCT/EP00/05481
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.
1
~~~ . . . . . b ....___
CA 02377691 2001-12-28
WO 01/01202 PCT/EP00/05481
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
2
_.
"' 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.
3
WO 01/01202 PCT/EP00/OS481
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
4
_ ,
,. _ . __._ . , ._. __
~t
CA 02377691 2001-12-28
WO 01/01202 PCT/EP00/05481
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
._
CA 02377691 2001-12-28
WO 01/01202 PCT/EP00/05481
- 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
6
., , _ ,..
. . ~~~
i
CA 02377691 2001-12-28
WO 01/01202 PCT/EP00/05481
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.
7
