U.S. patent application number 14/234851 was filed with the patent office on 2014-08-21 for methods for substrate coating and use of additive-containing powdered coating materials in such methods.
This patent application is currently assigned to Eckart GmbH. The applicant listed for this patent is Marco Greb, Sebastian Hofener, Andreas Reis, Markus Rupprecht, Christian Wolfrum. Invention is credited to Marco Greb, Sebastian Hofener, Andreas Reis, Markus Rupprecht, Christian Wolfrum.
Application Number | 20140230692 14/234851 |
Document ID | / |
Family ID | 46601799 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140230692 |
Kind Code |
A1 |
Hofener; Sebastian ; et
al. |
August 21, 2014 |
Methods for Substrate Coating and Use of Additive-Containing
Powdered Coating Materials in Such Methods
Abstract
The present invention relates to the use of a
particle-containing powdered coating material, wherein an additive
has been at least partially applied to the surface of the
particles, in coating methods, in particular in cold gas spraying,
flame spraying, high-speed flame spraying, thermal plasma spraying
and non-thermal plasma spraying. Furthermore, the present invention
relates to coating methods, in particular the above-named methods,
using the powdered coating material according to the invention.
Inventors: |
Hofener; Sebastian;
(Nurnberg, DE) ; Rupprecht; Markus; (Edelsfeld,
DE) ; Wolfrum; Christian; (Erlangen, DE) ;
Greb; Marco; (Linsengericht, DE) ; Reis; Andreas;
(Nurnberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hofener; Sebastian
Rupprecht; Markus
Wolfrum; Christian
Greb; Marco
Reis; Andreas |
Nurnberg
Edelsfeld
Erlangen
Linsengericht
Nurnberg |
|
DE
DE
DE
DE
DE |
|
|
Assignee: |
Eckart GmbH
Hartenstein
DE
|
Family ID: |
46601799 |
Appl. No.: |
14/234851 |
Filed: |
July 25, 2012 |
PCT Filed: |
July 25, 2012 |
PCT NO: |
PCT/EP2012/064638 |
371 Date: |
April 10, 2014 |
Current U.S.
Class: |
106/204.01 ;
106/287.1; 106/287.24; 106/287.26; 427/180; 427/447; 524/441 |
Current CPC
Class: |
C23C 4/067 20160101;
C23C 4/123 20160101; C23C 4/129 20160101; C23C 4/134 20160101; C23C
24/04 20130101; C23C 4/12 20130101; C23C 4/04 20130101; C23C 30/00
20130101 |
Class at
Publication: |
106/204.01 ;
427/447; 427/180; 524/441; 106/287.24; 106/287.26; 106/287.1 |
International
Class: |
C23C 30/00 20060101
C23C030/00; C23C 4/06 20060101 C23C004/06; C23C 4/12 20060101
C23C004/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2011 |
DE |
10 2011 052 119.4 |
Jul 25, 2011 |
DE |
10 2011 052 120.8 |
Claims
1. A process for producing a coating, comprising: introducing a
particle-containing powdered coating material into a coating method
selected from the group consisting of cold gas spraying, flame
spraying, high-speed flame spraying, thermal plasma spraying and
non-thermal plasma spraying, wherein the particles of the powdered
coating material comprise at least one additive.
2. The process according to claim 1, wherein the weight proportion
of the at least one additive is at most 32 wt.-%, relative to the
total weight of the coating material and the additive.
3. The process according to claim 1, wherein the carbon content of
the powdered coating material comprising the at least one additive
is from 0.01 wt.-% to 15 wt.-%, relative to the total weight of the
coating material and the additive.
4. The process according to claim 1, wherein the weight proportion
of the at least one additive is at least 0.02 wt.-%, relative to
the total weight of the coating material and the at least one
additive.
5. The process according to claim 1, wherein the at least one
additive has at least 6 carbon atoms.
6. The process according to claim 1, wherein the particles comprise
metal particles, and the metal is selected from the group
consisting of silver, gold, platinum, palladium, vanadium,
chromium, manganese, cobalt, germanium, antimony, aluminum, zinc,
tin, iron, copper, nickel, titanium, silicon, alloys and mixtures
thereof.
7. The process according to claim 1, wherein the coating method is
selected from the group consisting of flame spraying and
non-thermal plasma spraying.
8. The process according to claim 1, wherein the at least one
additive is free of stearic acid and/or oleic acid.
9. The process according to claim 1, wherein the at least one
additive is selected from the group consisting of polymers,
monomers, silanes, waxes, oxidized waxes, carboxylic acids,
phosphonic acids, derivatives and mixtures thereof.
10. The process according to claim 1, wherein the at least one
additive can be removed from the coated particles using organic
and/or aqueous solvent.
11. The process according to claim 1, wherein the powdered coating
material has a particle-size distribution with a D.sub.50 value
ranging from 1.5 to 53 .mu.m.
12. A method for coating a substrate selected from the group
consisting of cold gas spraying, flame spraying, high-speed flame
spraying, thermal plasma spraying and non-thermal plasma spraying,
the method comprising: (a) introducing a particle-containing
powdered coating material into a medium directed onto a substrate
to be coated by cold gas spraying, flame spraying, high-speed flame
spraying, thermal plasma spraying or non-thermal plasma spraying,
wherein the particles comprise least one additive; and (b)
depositing the powdered coating material onto the substrate.
13. The method according to claim 12, wherein the coating method is
selected from the group consisting of flame spraying and
non-thermal plasma spraying.
14. The method according to claim 12, wherein the powdered coating
material is conveyed as an aerosol.
15. The method according to claim 12, wherein the medium directed
onto the substrate is air or has been produced from air.
16. The process according to claim 1, wherein the coating method is
non-thermal plasma spraying.
17. The method according to claim 12, wherein the coating method is
non-thermal plasma spraying.
18. The process of claim 9, wherein the waxes comprise natural
waxes and synthetic waxes.
19. The process of claim 1, wherein the powdered coating material
has a span value according to formula I Span = D 90 - D 10 D 50 ( I
) ##EQU00004## in the range of from 0.4 to 2.9.
20. The process of claim 1, wherein at most 70% of the surface of
the particles of the powdered coating material is covered with the
additive.
21. A coating produced according to the process of claim 1.
22. A coated substrate produced according to the method of claim
12.
Description
[0001] The present invention relates to the use of powdered coating
materials for coating substrates. Furthermore, the present
invention comprises methods for substrate coating using such
powdered coating materials. Furthermore, the present invention
comprises powdered coating materials which are suitable for the
above-named uses and/or methods.
[0002] A large number of coating methods for different substrates
are already known. For example, metals or precursors thereof are
deposited on a substrate surface from the gas phase, see e.g. PVD
or CVD methods. Furthermore, corresponding substances can be
deposited for example from a solution by means of galvanic methods.
In addition, it is possible to apply coatings for example in the
form of varnishes to the surface. However, all the methods have
specific advantages and disadvantages. For example, in the case of
deposition in the form of varnishes, large amounts of water and/or
organic solvents are required, a drying time is needed, the coating
material to be applied must be compatible with the base varnish,
and a residue of the base varnish likewise remains on the
substrate. For example, application by means of PVD methods
requires large amounts of energy in order to bring non-volatile
substances into the gas phase.
[0003] In view of the above-named limitations, a large number of
coating methods have been developed to provide the properties
desired for the respective intended use. Known methods use, for
example, kinetic energy, thermal energy or mixtures thereof to
produce the coatings, wherein the thermal energy can originate for
example from a conventional combustion flame or a plasma flame. The
latter are further divided into thermal and non-thermal plasmas, by
which is meant that a gas has been partially or completely
separated into free charge carriers such as ions or electrons.
[0004] In the case of cold gas spraying, the coating is formed by
applying a powder to a substrate surface, wherein the powder
particles are greatly accelerated. For this, a heated process gas
is accelerated to ultrasonic speed by expansion in a de Laval
nozzle and then the powder is injected. As a result of the high
kinetic energy, the particles form a dense layer when they strike
the substrate surface.
[0005] For example, WO 2010/003396 A1 discloses the use of cold gas
spraying as a coating method for applying wear-protection coatings.
Furthermore, disclosures of the cold gas spraying method are found
for example in EP 1 363 811 A1, EP 0 911 425 B1 and U.S. Pat. No.
7,740,905 B2.
[0006] Flame spraying belongs to the group of thermal coating
methods. Here, a powdered coating material is introduced into the
flame of a fuel gas/oxygen mixture. Here, temperatures of up to
approximately 3200.degree. C. can be reached for example with
oxyacetylene flames. Details of the method can be learned from
publications such as e.g. EP 830 464 B1 and U.S. Pat. No. 5,207,382
A.
[0007] In the case of thermal plasma spraying, a powdered coating
material is injected into a thermal plasma. In the typically used
thermal plasma, temperatures of up to approx. 20,000 K are reached,
whereby the injected powder is melted and deposited on a substrate
as coating.
[0008] The method of thermal plasma spraying and specific
embodiments, as well as method parameters are known to a person
skilled in the art. By way of example, reference is made to WO
2004/016821, which describes the use of thermal plasma spraying to
apply an amorphous coating. Furthermore, EP 0 344 781 for example
discloses the use of flame spraying and thermal plasma spraying as
coating methods using a tungsten carbide powder mixture. Specific
devices for use in plasma spraying methods are described multiple
times in the literature, such as for example in EP 0 342 428 A2,
U.S. Pat. No. 7,678,428 B2, U.S. Pat. No. 7,928,338 B2 and EP 1 287
898 A2.
[0009] In the case of high-speed flame spraying, a fuel is
combusted under high pressure, wherein fuel gases, liquid fuels and
mixtures thereof can all be used as fuel. A powdered coating
material is injected into the highly accelerated flame. This method
is known for being characterized by relatively dense spray
coatings. High-speed flame spraying is also well known to a person
skilled in the art and has already been described in numerous
publications. For example, EP 0 825 272 A2 discloses a substrate
coating with a copper alloy using high-speed flame spraying.
Furthermore, WO 2010/037548 A1 and EP 0 492 384 A1 for example
disclose the method of high-speed flame spraying and devices to be
used therein.
[0010] Non-thermal plasma spraying is carried out largely
analogously to thermal plasma spraying and flame spraying. A
powdered coating material is injected into a non-thermal plasma and
deposited with it onto a substrate surface. As can be learned for
example from EP 1 675 971 B1, this method is characterized by a
particularly low thermal load of the coated substrate. This method,
particular embodiments and corresponding method parameters are also
known to a person skilled in the art from different publications.
For example, EP 2 104 750 A2 describes the use of this method and a
device for carrying it out. For example, DE 103 20 379 A1 describes
the production of an electrically heatable element using this
method.
[0011] Further disclosures in respect of the method or devices for
non-thermal plasma spraying are found for example in EP 1 675 971
B1, DE 10 2006 061 435 A1, WO 03/064061 A1, WO 2005/031026 A1, DE
198 07 086 A1, DE 101 16 502 A1, WO 01/32949 A1, EP 0 254 424 B1,
EP 1 024 222 A2, DE 195 32 412 A1, DE 199 55 880 A1 and DE 198 56
307 01.
[0012] A general problem of coating methods using a powdered
coating material is the conveying of the powders. A very uniform
feeding in of the powdered coating material is necessary in
particular to produce particularly thin layers for example. For
this reason, various specially designed conveyor devices are
additionally to be found as the subject of separate patent
applications. Examples are found in WO 03/029762 A1 and WO
2011/032807 A1.
[0013] The object of the present invention is to make it possible
to produce novel coatings or to improve the production of known
coatings. Furthermore, an object of the present invention is to
make it possible to produce particularly thin coatings of high
quality. Furthermore, an object of the present invention is to
solve existing problems with respect to the conveyability of the
powdered coating material used in a coating method.
[0014] A further object of the present invention is to provide
methods for substrate coating which are characterized by novel
coatings or an improved quality of the coating.
[0015] A further object of the present invention is to provide a
powdered coating material which is particularly suitable for one of
the above-named uses in coating methods.
[0016] The present invention relates to the use of a
particle-containing powdered coating material in a coating method,
wherein the particles of the powdered coating material are at least
partially provided with at least one additive and wherein the
coating method is selected from the group consisting of cold gas
spraying, flame spraying, high-speed flame spraying, thermal plasma
spraying and non-thermal plasma spraying.
[0017] In particular embodiments of the above-named use, the weight
proportion of the additive or additives is at most 32 wt.-%,
relative to the total weight of the coating material and the
additive.
[0018] In particular embodiments of the above-named uses, the
weight proportion of the additive or additives is between 0.02% and
32 wt.-%, in each case relative to the total weight of the coating
material and the additive.
[0019] In particular embodiments of the above-named uses, the
carbon content of the additive-containing particles of the powdered
coating material is from 0.01 wt.-% to 15 wt.-%, in each case
relative to the total weight of the coating material and the
additive.
[0020] In particular embodiments of the above-named uses, the
weight proportion of the additive or additives is at least 0.02
wt.-%, relative to the total weight of the coating material and the
additive.
[0021] In particular embodiments of the above-named uses, the
compound used as additive has, or the compounds used as additive
have, at least 6 carbon atoms.
[0022] In particular embodiments of the above-named uses, the
particles of the powdered coating material comprise or are metal
particles, and the metal is selected from the group consisting of
silver, gold, platinum, palladium, vanadium, chromium, manganese,
cobalt, germanium, antimony, aluminum, zinc, tin, iron, copper,
nickel, titanium, silicon, alloys and mixtures thereof.
[0023] In particular embodiments of the above-named uses, the
coating method is selected from the group consisting of flame
spraying and non-thermal plasma spraying. Non-thermal plasma
spraying is particularly preferred.
[0024] In particular embodiments of the above-named uses, the at
least one additive comprises no stearic acid and/or oleic acid and
preferably no saturated or unsaturated C18 carboxylic acids, more
preferably no saturated or unsaturated C14 to C18 carboxylic acids,
still more preferably no saturated or unsaturated C12 to C18
carboxylic acids and most preferably no saturated or unsaturated
C10 to C20 carboxylic acids.
[0025] In particular embodiments of the above-named uses, the
additive is, or the additives are, selected from the group
consisting of polymers, monomers, silanes, waxes, oxidized waxes,
carboxylic acids, phosphonic acids, derivatives of the above-named
and mixtures thereof.
[0026] In particular embodiments of the above-named uses, the
powdered coating material has a span value in the range of from 0.4
to 2.9, which is defined as follows:
Span = D 90 - D 10 D 50 ##EQU00001##
[0027] In particular embodiments of the above-named uses, the
additive, or the additives, can be removed from the coated
particles using organic and/or aqueous solvent.
[0028] In particular embodiments of the above-named uses, the
powdered coating material has a particle-size distribution with a
D.sub.50 value in the range of from 1.5 to 53 .mu.m.
[0029] In particular embodiments of the above-named uses, the
powdered coating material has a particle-size distribution with a
D.sub.90 value in the range of from 9 to 103 .mu.m.
[0030] In particular embodiments of the above-named uses, the
powdered coating material has a particle-size distribution with a
D.sub.10 value in the range of from 0.2 to 5 .mu.m.
[0031] Furthermore, the present invention relates to methods for
coating a substrate selected from the group consisting of cold gas
spraying, flame spraying, high-speed flame spraying, thermal plasma
spraying and non-thermal plasma spraying, wherein a powdered
coating material is used the particles of which are provided at
least partially with at least one additive.
[0032] In particular embodiments of the above-named method, the
method is is selected from the group consisting of flame spraying
and non-thermal plasma spraying. The method is preferably
non-thermal plasma spraying in particular ones of the above-named
embodiments.
[0033] In particular embodiments of the above-named methods, the
powdered coating material is conveyed as an aerosol.
[0034] In particular embodiments of the above-named methods, the
medium directed onto the substrate is air or has been produced from
air. The above-named air can be taken from the surrounding
atmosphere. In particular embodiments, in which for example a
particularly high purity of the coating is desired, the air is
purified before it is used, wherein for example dust and/or water
vapor is separated off. It can likewise be preferred that the
gaseous constituents of the air, other than nitrogen and oxygen,
are also largely separated off completely, wherein the total amount
of the impurities is preferably <0.01 vol.-%, further preferably
<0.001 vol.-%.
[0035] The term "powdered coating material" within the meaning of
the present invention relates to a particle mixture which is
applied to the substrate as coating. The provision of the surface
of the particles of the powdered coating material with the
additive, or the additives, need not be complete here in order to
make the use according to the invention possible. Without being
understood as limiting the invention, the inventors are of the view
that the effect of the applied additives is caused, among other
things, by an effect as spacers between the individual particles,
wherein an application to or a coverage of the surface beyond a
particular extent is not associated with a markedly improved
conveyability, but requires an increased use of the additive, or
the additives, which therefore only gives rise to costs and thus is
not economically worthwhile. In particular embodiments, therefore,
it is preferred that at most 90%, preferably at most 85%, more
preferably at most 80%, still more preferably at most 75% and most
preferably at most 70% of the surface of the particles is covered
with the additive, or the additives. At the same time, however, as
complete as possible a coverage of the surface of the particles
provides a certain protective effect for example against oxidizing
influences from the environment. In certain particularly preferred
embodiments of the invention, therefore, it is preferred that at
least 20%, preferably at least 25%, more preferably at least 30%
and still more preferably at least 35% of the surface of the
particles is covered with the additive, or the additives. In
particular ones of the above-named embodiments, it is preferred in
particular that at least 40%, preferably at least 50%, more
preferably at least 55% and still more preferably at least 60% of
the surface of the particles is covered with the additive, or the
additives. A determination of the surface coverage of the powdered
coating materials according to the invention is carried out by
means of SEM, wherein 30 randomly selected particles are
examined.
[0036] The inventors have surprisingly found that the conveyability
of a powdered coating material is significantly increased by at
least partially covering the surface of the particles with at least
one additive. This is of great importance in coating methods, in
particular in those in which a thin layer is to be applied, in
order to obtain high-quality and reproducible results. An increase
in the reproducibility of the method and more uniform feeding in of
the powdered coating material furthermore makes it possible to
produce much more homogeneous coatings with few defects and a very
high degree of cross-linking of the particles. Such features are
important in particular for the production of particularly thin
coatings. In addition, a conveyability improved in this way results
in a greatly simplified feeding in of the powdered coating material
and a dramatic reduction in the outlay on equipment.
[0037] Methods according to the invention which can be used to
build up coatings are for example cold gas spraying, thermal plasma
spraying, non-thermal plasma spraying, flame spraying and
high-speed flame spraying. An improved conveyability has proved to
be of particularly great importance in particular in coating
methods in which as low as possible a thermal load of the substrate
is to be effected and no, or almost no, thermal component is used
to apply the coating. In particular embodiments, therefore, the use
of the powdered coating material according to the invention in
flame spraying, non-thermal plasma spraying, cold gas spraying and
high-speed flame spraying is preferred. In particular cases, it is
desired in addition to be able also to coat delicate substrates
with the method according to the invention, which is why the
powdered coating material may be coated with only limited kinetic
energy. In particular ones of the above-named embodiments, the
method is therefore preferably selected from the group consisting
of flame spraying and non-thermal plasma spraying. However, the
industrial use of flame spraying requires the use and, to guarantee
a continuous operation, the storage of large amounts of the gas
used. As combustible gases are necessary to generate the flame in
flame spraying, their storage is associated with a corresponding
safety risk and therefore requires special safety regulations. A
plasma, in contrast, can also be produced using non-combustible
gases, with the result that the storage of corresponding amounts of
gas is associated with lower safety standards and therefore reduced
costs. In particular ones of the above-named embodiments,
therefore, it is quite particularly preferred that non-thermal
plasma spraying is used as coating method.
[0038] The term "additive" within the meaning of the present
invention relates to substances which are present, not
cross-linked, i.e. they have not been cross-linked, on the surface
of the particles of the powdered coating material. In particular,
the term "additive" relates, in preferred embodiments of the
present invention, to carbon-containing compounds which have not
been cross-linked on the surface of the particles of the powdered
coating material. Within the meaning of the present invention, by
"not cross-linked on the surface" is meant that no covalent bonds
between the individual additive molecules are built up during or
after the application of the additive to the particles of the
powdered coating material, consequently no post-cross-linking takes
place on the pigment surface. In particular, by the term "additive"
is not meant cross-linked polymers such as are disclosed for
example in EP 2115075 A1.
[0039] In particular embodiments, it is preferred in particular
that the additives are only bound to the particles of the powdered
coating material by means of physical bonds, for example by means
of van der Waals interactions, dipole-dipole interactions or
hydrogen bridges. However, it is also possible that the additives
are additionally or alternatively bound to the surface of the
particles of the powdered coating material by means of chemical
bonds, such as for example covalent or ionic bonds.
[0040] In general, it is preferred that the additives according to
the invention can be removed from the particles again through the
use of organic and/or aqueous solvents. Such additives have in
particular the advantage that they are easy and inexpensive to
apply. In particular embodiments, particular preferred additives
can be dispersed for example in a solvent and applied to the powder
particles by mechanical forces. Additionally or alternatively, in
particular embodiments, the additives can be dissolved in a
suitable solvent, then mixed with the powder particles and applied
by evaporation of the solvent onto the powder particles.
[0041] Without being understood as limiting the invention, the
inventors are of the view that the additives according to the
invention reduce the interactions between the particles and thereby
increase the conveyability.
[0042] Substances which as additives within the meaning of the
present invention are in particular carbon-containing compounds
which are chemically and/or physically bound to the surface of the
particles of the powdered coating material.
[0043] Without being understood as limiting the present invention,
the inventors are of the view that a particularly strong
improvement in the coatings produced according to the invention is
brought about in the use of additives with a high carbon content in
a combustion flame or a plasma flame by combusting the additive in
the flame and applying agglomerates of the powdered coating
material present here. In particular embodiments, therefore, it is
preferred that the weight proportion of the carbon atoms in the
additive-covered powdered coating material is at least 0.01 wt.-%,
preferably at least 0.05 wt.-%, more preferably at least 0.1 wt.-%
and still more preferably at least 0.17 wt.-%. In particular
embodiments, it is preferred in particular that the weight
proportion of the carbon atoms in the additive-covered powdered
coating material is at least 0.22 wt.-%, preferably at least 0.28
wt.-%, more preferably at least 0.34 wt.-% and still more
preferably at least 0.4 wt.-%. The above-named wt.-% are based on
the total weight of the coating material and the additive.
[0044] On the other hand, in particular embodiments, it is
preferred that the weight proportion of the carbon atoms in the
additive-covered powdered coating material is at most 15 wt.-%,
preferably at most 10 wt.-%, more preferably at most 7 wt.-% and
still more preferably at most 5 wt.-%. In particular ones of the
above-named embodiments, it is preferred in particular that the
carbon content is at most 4 wt.-%, preferably at most 3 wt.-%, more
preferably at most 2 wt.-% and still more preferably at most 1
wt.-%. The above-named wt.-% are based on the total weight of the
coating material and the additive.
[0045] In particular embodiments, it is preferred in particular
that the weight proportion of the carbon atoms in the
additive-covered powdered coating material lies in the range of
between 0.01 wt.-% and 15 wt.-%, preferably in the range of between
0.05 wt.-% and 10 wt.-%, more preferably in the range of between
0.1 wt.-% and 7 wt.-% and still more preferably in the range of
between 0.17 wt.-% and 5 wt.-%. In particular ones of the
above-named embodiments, it is preferred in particular that the
weight proportion of the carbon atoms in the additive-covered
powdered coating material lies in the range of between 0.22 wt.-%
and 4 wt.-%, preferably in the range of between 0.28 wt.-% and 3
wt.-%, more preferably in the range of between 0.34 wt.-% and 2
wt.-% and still more preferably in the range of between 0.4 wt.-%
and 1 wt.-%. The above-named wt.-% are based on the total weight of
the coating material and the additive. The weight proportion of the
carbon atoms to the total weight of the coating material and the
additive is determined for example with a CS 200 device from Leco
Instruments GmbH.
[0046] In particular embodiments, furthermore, it is preferred that
the compounds used as additive contain at least 6 carbon atoms,
preferably at least 7 carbon atoms, more preferably at least 8
carbon atoms and still more preferably at least 9 carbon atoms. In
particular ones of the above-named embodiments, it is preferred in
particular that the compounds used as additive contain at least 10
carbon atoms, preferably at least 11 carbon atoms, more preferably
at least 12 carbon atoms and still more preferably at least 13
carbon atoms. The number of carbon atoms contained in the additive
according to the invention can be determined for example by
determining the respective additive. All methods known to a person
skilled in the art for determining a substance can be used here.
For example, an additive can be removed from the particles of the
powdered coating material using organic and/or aqueous solvents and
then identified by means of HPLC, GCMS, NMR, CHN or combinations of
the above-named with each other or with other routinely used
methods.
[0047] In particular embodiments, it is furthermore preferred that
the weight proportion of the additive, or additives, is at least
0.02 wt.-%, preferably at least 0.08 wt.-%, more preferably at
least 0.17 wt.-% and still more preferably at least 0.30 wt.-%. In
particular ones of the above-named embodiments, it is preferred in
particular that the C content of the coating material and the
additive is at least 0.35 wt.-%, preferably at least 0.42 wt.-%,
more preferably at least 0.54 wt.-% and still more preferably at
least 0.62 wt.-%. The above-named wt.-% are based on the total
weight of the coating material and the additive.
[0048] In further particular embodiments, it is furthermore
preferred that the weight proportion of the additive is at most 32
wt.-%, preferably at most 18 wt.-%, more preferably at most 13
wt.-% and still more preferably at most 9 wt.-%. In particular ones
of the above-named embodiments, it is preferred in particular that
the C content of the coating material and the additive is at most 7
wt.-%, preferably at most 6 wt.-%, more preferably at most 4.5
wt.-% and still more preferably at most 2.3 wt.-%. The above-named
wt.-% are based on the total weight of the coating material and the
additive.
[0049] In further particular embodiments, it is furthermore
preferred that the weight proportion of the additive lies in the
range of between 0.02 wt.-% and 32 wt.-%, preferably in the range
of between 0.08 wt.-% and 18 wt.-%, more preferably in the range of
between 0.17 wt.-% and 13 wt.-% and still more preferably in the
range of between 0.30 wt.-% and 9 wt.-%. In particular ones of the
above-named embodiments, it is preferred in particular that the
weight proportion of the carbon atoms in the coating material and
the additive lies in the range of between 0.35 wt.-% and 7 wt.-%,
preferably in the range of between 0.42 wt.-% and 6 wt.-%, more
preferably in the range of between 0.54 wt.-% and 4.5 wt.-% and
still more preferably in the range of between 0.62 wt.-% and 2.3
wt.-%. The above-named wt.-% are based on the total weight of the
coating material and the additive.
[0050] Examples of substances which can be used as additives,
within the meaning of the present invention are:
polymers (e.g. polysaccharides, plastics), monomers, silanes,
waxes, oxidized waxes, carboxylic acids (e.g. fatty acids),
phosphonic acids, derivatives of the above-named (in particular
carboxylic acid derivatives and phosphoric acid derivatives) and
mixtures thereof. In particular embodiments, it is preferred that
polysaccharides, plastics, silanes, waxes, oxidized waxes,
carboxylic acids (e.g. fatty acids) carboxylic acid derivatives,
phosphonic acids, phosphoric acid derivatives or mixtures thereof,
preferably polysaccharides, silanes, waxes, oxidized waxes,
carboxylic acids (e.g. fatty acids) carboxylic acid derivatives,
phosphonic acids, phosphoric acid derivatives or mixtures thereof,
more preferably polysaccharides, silanes, waxes, oxidized waxes,
phosphonic acids, phosphoric acid derivatives or mixtures thereof,
are used as additive.
[0051] The above-named waxes comprise both natural waxes and
synthetic waxes. Examples of such waxes are paraffin waxes,
petroleum waxes, montan waxes, animal waxes (e.g. beeswax, shellac,
wool wax), vegetable waxes (e.g. carnauba wax, candelilla wax, rice
bran wax), fatty acid amide waxes (such as e.g. erucamide),
polyolefin waxes (such as e.g. polyethylene waxes, polypropylene
waxes), grafted polyolefin waxes, Fischer-Tropsch waxes, and
oxidized polyethylene waxes and modified polyethylene and
polypropylene waxes (e.g. metallocene waxes). The waxes according
to the invention are preferably bound via physical bonds in
particular embodiments. However, it is not ruled out that in
further particular embodiments the waxes have functional groups
which alternatively or additionally make an ionic and/or covalent
bond possible.
[0052] The term "polymer" within the meaning of the present
invention also comprises oligomers. In particular preferred
embodiments, the polymers used according to the invention are,
however, preferably built up of at least 25 monomer units, more
preferably of at least 35 monomer units, still more preferably of
at least 45 monomer units and most preferably of at least 50
monomer units. The polymers can be bound here to the particles of
the powdered coating material without covalent or ionic bonds being
formed. In particular embodiments, however, it is preferred that
the additive according to the invention can form at least one ionic
or covalent bond with the particles of the powdered coating
material. In particular ones of the above-named embodiments, such a
binding preferably takes place via a phosphoric acid, carboxylic
acid, silane or sulfonic acid group contained in the polymer.
[0053] The term "polysaccharide" within the meaning of the present
invention also comprises oligosaccharides. In particular preferred
embodiments, the polysaccharides used according to the invention
are, however, preferably built up of at least 4 monomer units, more
preferably of at least 8 monomer units, still more preferably of at
least 10 monomer units and most preferably of at least 12 monomer
units. In particular embodiments, particularly preferred
polysaccharides are cellulose, cellulose derivatives such as e.g.
methyl cellulose, ethyl cellulose, carboxymethyl celluose,
hydroxyethyl cellulose, hydroxypropyl methylcellulose,
nitrocellulose (e.g. ethocel, or methocel from Dow Wolff
Cellulosics), cellulose esters (e.g. cellulose acetate, cellulose
acetobutyrate, and cellulose propionate), starches such as e.g.
corn starch, potato starch and wheat starch and modified
starches.
[0054] The term "plastic" within the meaning of the present
invention comprises thermoplastic, thermosetting or elastomeric
plastics. Thermoplastic plastics are particularly preferred here,
wherein all thermoplastics known to a person skilled in the art
come into consideration. A summary of corresponding thermoplastics
is found e.g. in the Kunststoff-Taschenbuch, ed. Saechtling, 25th
edition, Hanser-Verlag, Munich, 1992, in particular chapter 4, as
well as references cited therein, and in the Kunststoff-Handbuch,
ed. G. Becker and D. Braun, volumes 1 to 11, Hanser-Verlag, Munich,
1966 to 1996. Without being limited to this, the following
thermoplastics are to be named by way of example for illustration:
polyoxyalkylenes, polycarbonates (PC), polyesters such as
polybutylene terephthalate (PBT) or polyethylene terephthalate
(PET), polyolefins such as polyethylene or polypropylene (PP),
poly(meth)acrylates, polyamides, vinylaromatic (co)polymers such as
polystyrene, impact-modified polystyrene such as HIPS, or ASA, ABS
or AES polymers, polyarylene ethers such as polyphenylene ether
(PPE), polysulfones, polyurethanes, polylactides,
halogen-containing polymers, polymers containing imide groups,
cellulose esters, silicone polymers and thermoplastic elastomers.
Mixtures of different thermoplastics can also be used in the form
of single- or multi-phase polymer blends.
[0055] Polyoxyalkylene homo- or copolymers, in particular
(co)polyoxymethylenes (POM), and methods for the production thereof
are known per se to a person skilled in the art and described in
the literature. The polymer main chain of these polymers has at
least 50 mol.-% recurring units of --CH.sub.2O--. The homopolymers
are generally produced, preferably catalytically, by polymerization
of formaldehyde or trioxane. Polyoxymethylene copolymers and
polyoxymethylene terpolymers are examples.
[0056] Suitable polycarbonates are known per se and can be obtained
e.g. according to DE 1 300 266 B1 by means of interfacial
polycondensation or according to DE 14 95 730 A1 by reacting
biphenyl carbonate with bisphenols.
[0057] Suitable polyesters are also known per se and described in
the literature. The polyesters can be produced by reacting aromatic
dicarboxylic acids, esters thereof or other ester-forming
derivatives of same with aliphatic dihydroxy compounds in a manner
known per se. In particular embodiments, naphthalene dicarboxylic
acid, terephthalic acid and isophthalic acid or mixtures thereof
are used as dicarboxylic acids. Up to 10 mol.-% of the aromatic
dicarboxylic acids can be replaced by aliphatic or cycloaliphatic
dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid,
dodecane diacids and cyclohexane dicarboxylic acids. Examples of
aliphatic dihydroxy compounds are diols with 2 to 6 carbon atoms,
in particular 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol,
1,4-hexanediol, 1,4-cyclohexanediol and neopentyl glycol or
mixtures thereof.
[0058] Examples of the above-named polyolefins are polyethylene and
polypropylene as well as copolymers based on ethylene or propylene,
optionally also with higher .alpha.-olefins. The term "polyolefin"
within the meaning of the present invention also comprises
ethylene-propylene elastomers and ethylene-propylene
terpolymers.
[0059] Examples of the above-named poly(meth)acrylates are
polymethyl methacrylate (PMMA) and copolymers based on methyl
methacrylate with up to 40 wt.-% further copolymerizable monomers,
such as e.g. n-butyl acrylate, t-butyl acrylate or 2-ethylhexyl
acrylate.
[0060] The above-named polyamides also comprise polyetheramides
such as polyether block amides and are described for example in the
disclosures of U.S. Pat. No. 2,071,250, U.S. Pat. No. 2,071,251,
U.S. Pat. No. 2,130,523, U.S. Pat. No. 2,130,948, U.S. Pat. No.
2,241,322, U.S. Pat. No. 2,312,966, U.S. Pat. No. 2,512,606 and
U.S. Pat. No. 3,393,210. Furthermore, the above-named polyamides
comprise for example polycaprolactams, polycapryllactams,
polylaurolactams and polyamides, which are obtained by reacting
dicarboxylic acids with diamines. Examples of dicarboxylic acids
suitable for this are alkanedicarboxylic acids with 6 to 12, in
particular 6 to 10 carbon atoms and aromatic dicarboxylic acids can
be used. Examples of suitable diamines are alkanediamines with 6 to
12, in particular 6 to 8 carbon atoms, as well as
m-xylylenediamine, di-(4-aminophenyl)methane,
di-(4-aminocyclohexyl)methane, 2,2-di-(4-aminophenyl)propane or
2,2-di-(4-aminocyclohexyl)propane.
[0061] Examples of the above-named vinylaromatic (co)polymers are
polystyrene, styrene-acrytnitrile copolymers (SAN) and
impact-modified polystyrene (HIPS=High Impact Polystyrene). The
production of such vinylaromatic (co)polymers is known to a person
skilled in the art and is found for example in EP-A-302 485.
Further examples are ASA, ABS and AES polymers
(ASA=acrylonitrile-styrene-acrylester,
ABS=acrylonitrile-butadiene-styrene, AES=acrylonitrile-EPDM
rubber-styrene). The production of ABS polymers is found for
example in DE 197 28 629 A1 and the production of ASA polymers is
found for example in EP 99 532 A2. Details on the production of AES
polymers is furthermore found for example in U.S. Pat. No.
3,055,859 or in U.S. Pat. No. 4,224,419.
[0062] Examples of the above-named polyarylene ethers are
polyarylene ethers per se, polyarylene ether sulfides, polyarylene
ether sulfones and polyarylene ether ketones. The arylene groups
thereof can be the same or different, and independently of each
other can be for example an aromatic radical with 6 to 18 C atoms.
Examples of suitable arylene radicals are phenylene, bisphenylene,
terphenylene, 1,5-naphthylene, 1,6-naphthylene, 1,5-anthrylene,
9,10-anthrylene or 2,6-anthrylene. Examples of production details
for polyarylene ether sulfones are found in EP 113 112 A1 and EP
135 130 A2.
[0063] Further examples of plastics which can be used as additives
in particular embodiments are polyurethanes, polyisocyanurates and
polyureas.
[0064] Examples of the polymers of lactic acid, polylactides, as
well as methods for the production thereof are known to a person
skilled in the art. In particular embodiments, it is preferred in
particular to use copolymers or block copolymers based on lactic
acid and further monomers.
[0065] Examples of halogen-containing polymers are polymers of
vinyl chloride, such as polyvinyl chloride (PVC) (e.g. hard PVC and
soft PVC), and copolymers of vinyl chloride (e.g. PVC-U molding
compounds).
[0066] Further examples of plastics which can be used as additives
in particular embodiments are fluorine-containing polymers such as
polytetrafluoroethylene (PTFE),
tetrafluoroethylene-perfluoropropylene copolymers (FEP), copolymers
of tetrafluoroethylene with perfluoroalkyl vinyl ether,
ethylene-tetrafluoroethylene copolymers (ETFE), polyvinylidene
fluoride (PVDF), polyvinyl fluoride (PVF),
polychlorotrifluoroethylene (PCTFE) and
ethylene-chlorotrifluoroethylene copolymers (ECTFE).
[0067] Examples of the above-named polymers containing imide groups
are polyimides, polyetherimides, and polyamide-imides. Such
polymers are described for example in Rompp Chemie Lexikon, CD-ROM
version 1.0, Thieme Verlag Stuttgart 1995.
[0068] The above-named thermoplastic elastomers (TPE) are
characterized in that they can be processed like thermoplastics but
have rubber-elastic properties. More detailed information is found
for example in G. Holden et al., Thermoplastic Elastomers, 2nd
edition, Hanser Verlag, Munich 1996. Examples are thermoplastic
polyurethane elastomers (TPE-U or TPU), styrene oligoblock
copolymers (TPE-S) such as SBS (styrene-butadiene-styrene-o.times.y
block copolymer) and SEES (styrene-ethylene-butylene-styrene block
copolymer, obtainable by hydrogenation of SBS), thermoplastic
polyolefin elastomers (TPE-O), thermoplastic polyester elastomers
(TPE-E), thermoplastic polyamide elastomers (TPE-A) and
thermoplastic vulcanisates (TPE-V).
[0069] Examples of the above-named polyacrylates are
poly(meth)acrylates, which are preferably present as homopolymers
or as block polymers. Such polymers are sold for example by Evonik
under the trade name Degalan.
[0070] In particular embodiments, it is preferred that the
additives are selected from the group consisting of the products of
the copolymerization of PE or PP with maleic acid (anhydride) or
acrylic acid.
[0071] In particular embodiments, it is preferred that the polymers
used as additives have a molecular weight of at most 200,000,
preferably of at most 170,000, more preferably of at most 150,000
and still more preferably at most 130,000. In particular ones of
the above-named embodiments, it is preferred in particular that the
compounds used as additives have a molecular weight of at most
110,000, preferably of at most 90,000, more preferably of at most
70,000 and still more preferably of at most 50,000.
[0072] The above-named carboxylic acids also comprise in particular
dicarboxylic acids, tricarboxylic acids and tetracarboxylic acids
in particular embodiments. Examples of dicarboxylic acids are
succinic acid, glutaric acid, adipic acid, pimelic acid, suberic
acid, azelaic acid and sebacic acid.
[0073] In particular preferred embodiments, the above-named
carboxylic acid derivatives are directed in particular towards
carboxylic acid esters.
[0074] Examples of the above-named fatty acids are capric acid,
undecanoic acid, lauric acid, tridecanoic acid, myristic acid,
pentadecanoic acid, palmitic acid, margaric acid, nonadecanoic
acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid,
melissic acid, undecylenic acid, palmitoleic acid, elaidic acid,
vaccenic acid, eicosenoic acid, cetoleic acid, erucic acid,
nervonic acid, sorbic acid, linoleic acid, linolenic acid,
eleostearic acid, arachidonic acid, timnodonic acid, clupanodonic
acid, docosahexaenoic acid, stearic acid and oleic acid. In
particular quite particularly preferred embodiments of the present
invention, the additives comprise no stearic acid or oleic acid and
preferably no saturated or unsaturated C18 carboxylic acids, more
preferably no saturated or unsaturated C14 to C18 carboxylic acids,
still more preferably no saturated or unsaturated C12 to C18
carboxylic acids and most preferably no saturated or unsaturated
C10 to C20 carboxylic acids. The term "C" followed by a number
relates within the meaning of the present invention to the carbon
atoms contained in a molecule or molecule constituent, wherein the
number expresses the quantity of carbon atoms.
[0075] The above-named phosphonic acids are expressed by Formula
(I):
(X).sub.mP(=0)Y.sub.nR.sub.(3-m) (I),
wherein m is 0, 1 or 2, n is 0 or 1, X can be the same or different
and is hydrogen, hydroxy, halogen or --NR'.sub.2, R' can be the
same or different and is hydrogen, a substituted or unsubstituted
C1-C9 alkyl group or a substituted or unsubstituted aryl group, Y
can be the same or different and is --O--, --S--, --NH-- or --NR--
and R can be the same or different and is selected from the group
consisting of C1-C30 alkyl groups, C2-C30 alkenyl groups, C2-C30
alkinyl groups, C5-C30 aryl groups, C6-C30 arylalkyl groups, C4-C30
heteroaryl groups, C5-C30 heteroarylalkyl groups, C3-C30 cycloalkyl
groups, C4-C30 cycloalkylalkyl groups, C2-C30 heterocycloalkyl
groups, C3-C30 heterocycloalkylalkyl groups, C1-C30 ester groups,
C1-C30 alkyl ether groups, C1-C30 cycloalkyl ether groups, C1-C30
cycloalkenyl ether groups, C6-C30 aryl ether groups, C7-C30
arylalkyl ether groups, wherein the above-named groups can be
substituted or unsubstituted and optionally straight-chained or
branched.
[0076] The term "substituted" within the meaning of the present
invention describes that at least one hydrogen atom of the relevant
group by a halogen, hydroxy, cyano, C1-C8 alkyl, C2-C8 alkenyl,
C2-C8 alkinyl, C1-C5 alkanoyl, C3-C8 cycloalkyl, heterocyclic,
aryl, heteroaryl, C1-C7 alkylcarbonyl, C1-C7 alkoxy, C2-C7
alkenyloxy, C2-C7 alkinyloxy, aryloxy, acyl, C1-C7 acryloxy, C1-C7
methacryloxy, C1-C7 epoxy, C1-C7 vinyl, C1-C5 alkoxycarbonyl,
aroyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl,
amincarbonyloxy, C1-C7 alkylaminocarbonyloxy, C1-C7
dialkylamincarbonyloxy, C1-C7 alkanoylamine, C1-C7
alkoxycarbonylamine, C1-C7 alkylsulfonylamine, aminosulfonyl, C1-C7
alkylaminosulfonyl, C1-C7 dialkylaminsulfonyl, carboxy, cyano,
trifluoromethyl, trifluoromethoxy, nitro, sulfonic acid, phosphoric
acid, amine, amide (wherein the nitrogen atom is optionally,
independently of each other, substituted once or twice with C1-C5
alkyl or aryl groups), ureido (wherein the nitrogen atoms is
optionally, independently of each other, substituted once or twice
with C1-C5 alkyl or aryl groups) or C1-C5 alkylthio group.
[0077] The terms "cycloalkyl group" and "heterocycloalkyl group"
within the meaning of the present invention comprise saturated,
partially saturated and unsaturated systems, apart from aromatic
systems, which are called "aryl groups" or "heteroaryl groups".
[0078] The term "alkyl" within the meaning of the present
invention, unless otherwise indicated, preferably represents
straight or branched C1 to C27, more preferably straight or
branched C1 to C25 and still more preferably straight or branched
C1 to C20 carbon chains. The terms "alkenyl" and "alkinyl" within
the meaning of the present invention, unless otherwise indicated,
preferably represent straight or branched C2 to C27, more
preferably straight or branched C2 to C25 and still more preferably
straight or branched C2 to C20 carbon chains. The term "aryl"
within the meaning of the present invention represents aromatic
carbon rings, preferably aromatic carbon rings with at most 7
carbon atoms, more preferably the phenyl ring, wherein the
above-named aromatic carbon rings can be a constituent of a
condensed ring system. Examples of aryl groups are phenyl,
hydroxyphenyl, biphenyl and naphthyl. The term "heteroaryl" within
the meaning of the present invention represents aromatic rings, in
which a carbon atom of an analogous aryl ring has formally been
replaced by a heteroatom, preferably by an atom selected from the
group consisting of O, S and N.
[0079] The above-named silanes are characterized by a structure
according to Formula (II):
R.sub.pSiX.sub.(4-p) (II),
wherein p is 0, 1, 2 or 3, X can be the same or different and is
hydrogen, hydroxy, halogen or --NR'2, R' can be the same or
different and is hydrogen, a substituted or unsubstituted C1-C9
alkyl group or a substituted or unsubstituted aryl group and R can
be the same or different and is selected from the group consisting
of C1-C30 alkyl groups, C2-C30 alkenyl groups, C2-C30 alkinyl
groups, C5-C30 aryl groups, C6-C30 arylalkyl groups, C4-C30
heteroaryl groups, C5-C30 heteroarylalkyl groups, C3-C30 cycloalkyl
groups, C4-C30 cycloalkylalkyl groups, C2-C30 heterocycloalkyl
groups, C3-C30 heterocycloalkylalkyl groups, C1-C30 ester groups,
C1-C30 alkyl ether groups, C1-C30 cycloalkyl ether groups, C1-C30
cycloalkenyl ether groups, C6-C30 aryl ether groups, C7-C30
arylalkyl ether groups, wherein the above-named groups can be
substituted or unsubstituted and optionally straight-chained or
branched.
[0080] The additive can be bound for example chemically or
physically to the surface of the particles of the powdered coating
material. It is not necessary here that an unbroken surface
coverage of the particles is carried out, even if this is preferred
in particular embodiments of the present invention.
[0081] In particular embodiments, it is preferred that the
additives are bound as weakly as possible to the surface of the
particles of the powdered coating material. For example, in
particular ones of the above-named embodiments, it is preferred
that the additives used according to the invention carry no
functional groups. The term "functional group" within the meaning
of the present invention denotes molecular groups in molecules
which decisively influence the substance properties and the
reaction behavior of the molecules. Examples of such functional
groups are: carboxylic acid groups, sulfonic acid groups,
phosphoric acid groups, silane groups, carbonyl groups, hydroxyl
groups, amine groups, hydrazine groups, halogen groups and nitro
groups.
[0082] In particular other embodiments, in contrast, it is
preferred that the additives cannot be removed from the surface too
easily, for example as a result of friction. In particular ones of
the above-named embodiments, it is preferred in particular that the
additives used according to the invention carry at least one
functional group, preferably at least two functional groups, more
preferably at least three functional groups.
[0083] The inventors have surprisingly found that when the powdered
coating materials covered with an additive according to the
invention are used, the use of coating materials with an
unexpectedly high melting point also allowed. Without being
understood as limiting the invention, the inventors are of the view
that the more uniform conveying of the particles with reduced
tendency to agglomerate allows the particles to strike the
substrate surface individually and the kinetic energy present to be
able to be utilized fully to shape the particle. In the case of a
non-uniform, thus localized, application of agglomerates, some of
the kinetic energy is apparently used up by the breakup of the
agglomerate and particles that strike later are cushioned by
coating material already present at this site, but not yet
solidified. If the powdered coating material is passed through a
flame beforehand, the thermal energy is furthermore probably better
transferred to the particles in the case of uniformly fed-in
particles without agglomerates.
[0084] For example, in particular embodiments, according to the
invention powdered coating materials covered with at least one
additive can also be used to produce homogeneous layers if the
melting point, measured in [K], of the coating material is up to
50%, preferably up to 60%, more preferably up to 65% and still more
preferably up to 70% of the temperature, measured in [K], of the
medium used in the coating method directed onto the substrate, for
example the gas stream, the combustion flame and/or the plasma
flame. In particular ones of the above-named embodiments
furthermore according to the invention powdered coating materials
covered with at least one additive can also be used to produce
homogeneous layers if the melting point, measured in [K], of the
coating material is up to 75%, preferably up to 80%, more
preferably up to 85% and still more preferably up to 90% of the
temperature, measured in [K], of the medium used in the coating
method directed onto the substrate, for example the gas stream, the
combustion flame and/or the plasma flame. The above-named
percentages relate to the ratio of the melting temperature of the
coating material to the temperature of the gas stream in cold gas
spraying, the combustion flame in flame spraying and high-speed
flame spraying or the plasma flame in non-thermal or thermal plasma
spraying in [K].
[0085] The term "homogeneous layer" within the meaning of the
present invention describes that the relevant coating has less than
10%, preferably less than 5%, more preferably less than 3%, still
more preferably less than 1% and most preferably less than 0.1%
cavities. In particular, it is preferred that no cavities at all
are recognizable. The above-named term "cavity" within the meaning
of the present invention describes the proportion of holes,
incorporated in the coating, on the two-dimensional surface of a
cross-section of the coated substrate, relative to the coating
contained in the two-dimensional surface. A determination of this
proportion is carried out by means of SEM at 30 randomly selected
sites on the coating produced according to the invention, wherein
for example a length of 100 .mu.m of the substrate coating is
examined.
[0086] It was surprisingly found that not only is there an improved
conveyability of powdered coating materials through the use of the
coating material and the additive, but even previously unconveyable
powdered coating materials can be conveyed easily and can be used
to produce high-quality coatings.
[0087] The size distribution of the particles is preferably
determined by means of laser granulometry. In this method, the
particles can be measured in the form of a powder. The scattering
of the irradiated laser light is detected in different spatial
directions and evaluated according to the Fraunhofer diffraction
theory. The particles are treated computationally as spheres. Thus,
the determined diameters always relate to the equivalent spherical
diameter determined over all spatial directions, irrespective of
the actual shape of the particles. The size distribution is
determined, calculated in the form of a volume average relative to
the equivalent spherical diameter. This volume-averaged size
distribution can be represented as a cumulative frequency
distribution. The cumulative frequency distribution is
characterized in a simplified manner by different characteristic
values, for example the D.sub.10, D.sub.50 or D.sub.90 value.
[0088] The measurements can be carried out for example with the
particle-size analyzer HELOS from Sympatec GmbH,
Clausthal-Zellerfeld, Germany. Here, a dry powder can be dispersed
using a dispersing unit of the Rodos T4.1 type at a primary
pressure of for example 4 bar. Alternatively, a size distribution
curve of the particles can be measured, for example, with a device
from Quantachrome (device: Cilas 1064) according to the
manufacturer's instructions. For this, 1.5 g of the powdered
coating material is suspended in approx. 100 ml isopropanol,
treated for 300 seconds in an ultrasound bath (device: Sonorex IK
52, Bandelin) and then introduced by means of a Pasteur pipette
into the sample preparation cell of the measuring device and
measured several times. The resultant average values are formed
from the individual measurement results. The scattered light
signals are evaluated according to the Fraunhofer method.
[0089] In particular embodiments of the invention, it is preferred
that the powdered coating material has a particle-size distribution
with a D.sub.50 value of at most 53 .mu.m, preferably at most 51
.mu.m, more preferably at most 50 .mu.m and still more preferably
at most 49 .mu.m. In particular ones of the above-named
embodiments, it is preferred in particular that the powdered
coating material has a particle-size distribution with a D.sub.50
value of at most 48 .mu.m, preferably at most 47 .mu.m, more
preferably at most 46 .mu.m and still more preferably at most 45
.mu.m.
[0090] The term "D.sub.50" within the meaning of the present
invention denotes the particle size at which 50% of the above-named
particle-size distribution volume-averaged by means of laser
granulometry lies below the indicated value. The measurements can
be carried out for example according to the above-named measurement
method with a particle-size analyzer HELOS from Sympatec GmbH,
Clausthal-Zellerfeld, Germany.
[0091] In particular embodiments of the invention, it is preferred
in particular that the powdered coating material has a
particle-size distribution with a D.sub.50 value of at least 1.5
.mu.m, preferably at least 2 .mu.m, more preferably at least 4
.mu.m and still more preferably at least 6 .mu.m. In particular
ones of the above-named embodiments, it is preferred in particular
that the powdered coating material has a particle-size distribution
with a D.sub.50 value of at least 7 .mu.m, preferably at least 9
.mu.m, more preferably at least 11 .mu.m and still more preferably
at least 13 .mu.m.
[0092] In particular embodiments, it is furthermore preferred that
the powder has a particle-size distribution with a D.sub.50 value
in the range of from 1.5 to 53 .mu.m, preferably in the range of
from 2 to 51 .mu.m, more preferably in the range of from 4 to 50
.mu.m and still more preferably in the range of from 6 to 49 .mu.m.
In particular ones of the above-named embodiments, it is preferred
in particular that the powder has a particle-size distribution with
a D.sub.50 value in the range of from 7 to 48 .mu.m, preferably in
the range of from 9 to 47 .mu.m, more preferably in the range of
from 11 to 46 .mu.m and still more preferably in the range of from
13 to 45 .mu.m.
[0093] In other embodiments, it is preferred for example that the
powder has a particle-size distribution with a D.sub.50 value in
the range of from 1.5 to 45 .mu.m, preferably in the range of from
2 to 43 .mu.m, more preferably in the range of from 2.5 to 41 .mu.m
and still more preferably in the range of from 3 to 40 .mu.m. In
particular ones of the above-named embodiments, it is preferred in
particular that the powder has a particle-size distribution with a
D.sub.50 value in the range of from 3.5 to 38 .mu.m, preferably in
the range of from 4 to 36 .mu.m, more preferably in the range of
from 4.5 to 34 .mu.m and still more preferably in the range of from
5 to 32 .mu.m.
[0094] In still other embodiments, in contrast, it is preferred for
example that the powder has a particle-size distribution with a
D.sub.50 value in the range of from 9 to 53 .mu.m, preferably in
the range of from 12 to 51 .mu.m, more preferably in the range of
from 15 to 50 .mu.m, still more preferably in the range of from 17
to 49 .mu.m. In particular ones of the above-named embodiments, it
is preferred in particular that the powder has a particle-size
distribution with a D.sub.50 value in the range of from 19 to 48
.mu.m, preferably in the range of from 21 to 47 .mu.m, more
preferably in the range of from 23 to 46 .mu.m and still more
preferably in the range of from 25 to 45 .mu.m.
[0095] In further particular embodiments of the invention, it is
preferred that the powdered coating material has a particle-size
distribution with a D.sub.90 value of at most 103 .mu.m, preferably
at most 99 .mu.m, more preferably at most 95 .mu.m, still more
preferably at most 91 .mu.m and most preferably at most 87 .mu.m.
In particular ones of the above-named embodiments, it is preferred
in particular that the powdered coating material has a D.sub.90
value of at most 83 .mu.m, preferably at most 79 .mu.m, more
preferably at most 75 .mu.m and still more preferably at most 71
.mu.m.
[0096] The term "D.sub.90" within the meaning of the present
invention denotes the particle size at which 90% of the above-named
particle-size distribution volume-averaged by means of laser
granulometry lies below the indicated value. The measurements can
be carried out for example according to the above-named measurement
method with a particle-size analyzer HELOS from Sympatec GmbH,
Clausthal-Zellerfeld, Germany.
[0097] In particular embodiments, it is therefore preferred that
the powdered coating material has a particle-size distribution with
a D.sub.90 value of at least 9 .mu.m, preferably at least 11 .mu.m,
more preferably at least 13 .mu.m and still more preferably at
least 15 .mu.m. In particular ones of the above-named embodiments,
it is preferred in particular that the powdered coating material
has a particle-size distribution with a D.sub.90 value of at least
17 .mu.m, preferably at least 19 .mu.m, more preferably at least 21
.mu.m and still more preferably at least 22 .mu.m.
[0098] According to particular preferred embodiments, the powdered
coating materials have a particle-size distribution with a D.sub.90
value in the range of from 42 to 103 .mu.m, preferably in the range
of from 45 to 99 .mu.m, more preferably in the range of from 48 to
95 .mu.m and still more preferably in the range of from 50 to 91
.mu.m. In particular ones of the above-named embodiments, it is
preferred in particular that the powdered coating material has a
D.sub.90 value in the range of from 52 to 87 .mu.m, preferably in
the range of from 54 to 81 .mu.m, more preferably in the range of
from 56 to 75 .mu.m and still more preferably in the range of from
57 to 71 .mu.m.
[0099] Furthermore, it was surprisingly found that a clear
improvement in the conveyability of fine particle sizes is achieved
by an additive covering. This provides the advantage that powdered
coating materials with a larger proportion of fines and therefore
better activatability in non-thermal plasma spraying can also be
used. In further particular embodiments of the invention, it is
preferred that the powdered coating material has a particle-size
distribution with a D.sub.10 value of at most 5 .mu.m, preferably
at most 4 .mu.m, more preferably at most 3 .mu.m and still more
preferably at most 2.5 .mu.m. In particular ones of the above-named
embodiments, it is preferred in particular that the powdered
coating material has a particle-size distribution with a D.sub.10
value of at most 2.2 .mu.m, preferably at most 2 .mu.m, more
preferably at most 1.8 .mu.m and still more preferably at most 1.7
.mu.m.
[0100] The term "D.sub.10" within the meaning of the present
invention denotes the particle size at which 10% of the above-named
particle-size distribution volume-averaged by means of laser
granulometry lies below the indicated value. The measurements can
be carried out for example according to the above-named measurement
method with a particle-size analyzer HELOS from Sympatec GmbH,
Clausthal-Zellerfeld, Germany.
[0101] On the other hand, the additive-covered powdered coating
materials with a high fines proportion also still have a strong
tendency to form fine dusts, which makes the handling of
corresponding powders much more difficult. In particular
embodiments, therefore, it is preferred that the additive-covered,
powdered coating material has a particle-size distribution with a
D.sub.10 value of at least 0.2 .mu.m, preferably at least 0.4
.mu.m, more preferably at least 0.5 .mu.m and still more preferably
at least 0.6 .mu.m. In particular ones of the above-named
embodiments, it is preferred in particular that the
additive-covered, powdered coating material has a particle-size
distribution with a D.sub.10 value of at least 0.7 .mu.m,
preferably 0.8 .mu.m, more preferably 0.9 .mu.m and still more
preferably at least 1.0 .mu.m.
[0102] In particular preferred embodiments, the additive-covered,
powdered coating material is characterized in that it have a
particle-size distribution with a D.sub.10 value from a range of
from 0.2 to 5 .mu.m, preferably from a range of from 0.4 to 4
.mu.m, more preferably from a range of from 0.5 to 3 .mu.m and
still more preferably from a range of from 0.6 to 2.5 .mu.m. In
particular ones of the above-named embodiments, it is preferred in
particular that the additive-covered, powdered coating material has
a particle-size distribution with a D.sub.10 value from a range of
from 0.7 to 2.2 .mu.m, preferably from a range of from 0.8 to 2.1
.mu.m, more preferably from a range of from 0.9 to 2.0 .mu.m and
still more preferably from a range of from 1.0 to 1.9 .mu.m.
[0103] For example, in particular embodiments, it is preferred in
particular that the powdered coating material has a particle-size
distribution with a D.sub.10 value of from 3.7 to 26 .mu.m, a
D.sub.50 value of from 6 to 49 .mu.m and a D.sub.90 value of from
12 to 86 .mu.m. In particular ones of the above-named embodiments,
it is particularly preferred that the powdered coating material has
a particle-size distribution with a D.sub.10 value of from 5.8 to
26 .mu.m, a D.sub.50 value of from 11 to 46 .mu.m and a D.sub.90
value of from 16 to 83 .mu.m. In particular ones of the above-named
embodiments, it is still more preferred that the powdered coating
material has a particle-size distribution with a D.sub.10 value of
from 9 to 19 .mu.m, a D.sub.50 value of from 16 to 35 .mu.m and a
D.sub.90 value of from 23 to 72 .mu.m.
[0104] In further particular embodiments, it is preferred for
example that the powdered coating material has a particle-size
distribution with a D.sub.10 value of from 0.8 to 28 .mu.m, a
D.sub.50 value of from 1.5 to 45 .mu.m and a D.sub.90 value of from
2.5 to 81 .mu.m. In particular ones of the above-named embodiments,
it is particularly preferred that the powdered coating material has
a particle-size distribution with a D.sub.10 value of from 2.2 to
22 .mu.m, a D.sub.50 value of from 4 to 36 .mu.m and a D.sub.90
value of from 4 to 62 .mu.m. In particular ones of the above-named
embodiments, it is still more preferred that the powdered coating
material has a particle-size distribution with a D.sub.10 value of
from 2.8 to 17 .mu.m, a D.sub.50 value of from 6 to 28 .mu.m and a
D.sub.90 value of from 9 to 49 .mu.m.
[0105] In further particular embodiments, it is preferred for
example that the powdered coating material has a particle-size
distribution with a D.sub.10 value of from 4.8 to 29 .mu.m, a
D.sub.50 value of from 9 to 53 .mu.m and a D.sub.90 value of from
13 to 97 .mu.m. In particular ones of the above-named embodiments,
it is particularly preferred that the powdered coating material has
a particle-size distribution with a D.sub.10 value of from 12 to 26
.mu.m, a D.sub.50 value of from 23 to 46 .mu.m and a D.sub.90 value
of from 35 to 87 .mu.m. In particular ones of the above-named
embodiments, it is still more preferred that the powdered coating
material has a particle-size distribution with a D.sub.10 value of
from 15 to 24 .mu.m, a D.sub.50 value of from 28 to 44 .mu.m and a
D.sub.90 value of from 41 to 78 .mu.m.
[0106] Furthermore, it was observed that the conveyability of the
additive-covered, powdered coating material is dependent on the
width of the particle-size distribution. This width can be
calculated by indicating the so-called span value, which is defined
as follows:
Span = D 90 - D 10 D 50 ##EQU00002##
[0107] The inventors have found that in particular embodiments, for
example, a still more uniform conveyability of the powdered coating
material is achieved through the use of a powdered coating material
with a smaller span, which further simplifies the formation of a
more homogeneous and higher-quality layer. In particular
embodiments, therefore, it is preferred that the span of the
powdered coating material is at most 2.9, preferably at most 2.6,
more preferably at most 2.4 and still more preferably at most 2.1.
In particular ones of the above-named embodiments, it is preferred
in particular that the span of the powdered coating material is at
most 1.9, preferably at most 1.8, more preferably at most 1.7 and
still more preferably at most 1.6.
[0108] On the other hand, the inventors have found that a very
narrow span is not necessarily required to provide the sought
conveyability, which makes the production of the powdered coating
material easier. In particular embodiments, therefore, it is
preferred that the span value of the powdered coating material is
at least 0.4, preferably at least 0.5, more preferably at least 0.6
and still more preferably at least 0.7. In particular embodiments,
it is preferred in particular that the span value of the powdered
coating material is at least 0.8, preferably at least 0.9, more
preferably at least 1.0 and still more preferably at least 1.1.
[0109] On the basis of the teaching disclosed herein, a person
skilled in the art can select any combination, in particular of the
above-named limit values of the span value, in order to provide the
desired combination of properties. In particular embodiments, it is
preferred for example that the powdered coating material has a span
value in the range of from 0.4 to 2.9, preferably in the range of
from 0.5 to 2.6, more preferably in the range of from 0.6 to 2.4
and still more preferably in the range of from 0.7 to 2.1. In
particular ones of the above-named embodiments, it is preferred in
particular that the powdered coating material has a span value in
the range of from 0.8 to 1.9, preferably in the range of from 0.9
to 1.8, more preferably in the range of from 1.0 to 1.7 and still
more preferably in the range of from 1.1 to 1.6.
[0110] A person skilled in the art is aware that, on the basis of
the teaching disclosed herein, particular combinations of the span
limit values or value ranges with the above-named preferred
D.sub.50 value ranges are preferred depending on the desired
combination of advantages. For example, in particular preferred
embodiments the powdered coating material has a particle-size
distribution with a span in the range of from 0.4 to 2.9 and a
D.sub.50 value in the range of from 1.5 to 53 .mu.m, preferably in
the range of from 2 to 51 .mu.m, more preferably in the range of
from 4 to 50 .mu.m, still more preferably in the range of from 6 to
49 .mu.m and most preferably in the range of from 7 to 48 .mu.m. In
particular preferred ones of the above-named embodiments, the
powdered coating material has a particle-size distribution with a
span in the range of from 0.5 to 2.6 and a D.sub.50 value in the
range of from 1.5 to 53 .mu.m, preferably in the range of from 2 to
51 .mu.m, more preferably in the range of from 4 to 50 .mu.m, still
more preferably in the range of from 6 to 49 .mu.m and most
preferably in the range of from 7 to 48 .mu.m. In particular
further preferred embodiments, the powdered coating material has a
particle-size distribution with a span in the range of from 0.6 to
2.4 and a D.sub.50 value in the range of from 1.5 to 53 .mu.m,
preferably in the range of from 2 to 51 .mu.m, more preferably in
the range of from 4 to 50 .mu.m, still more preferably in the range
of from 6 to 49 .mu.m and most preferably in the range of from 7 to
48 .mu.m. In particular still further preferred embodiments, the
powdered coating material has a particle-size distribution with a
span in the range of from 0.7 to 2.1 and a D.sub.50 value in the
range of from 1.5 to 53 .mu.m, preferably in the range of from 2 to
51 .mu.m, more preferably in the range of from 4 to 50 .mu.m, still
more preferably in the range of from 6 to 49 .mu.m and most
preferably in the range of from 7 to 48 .mu.m.
[0111] Furthermore, it was found that the density of the powdered
coating material can influence the conveying of such powders in the
form of an aerosol. Without being understood as limiting the
invention, the inventors are of the view that the differences in
inertia of particles that are the same size but have different
densities lead to a different behavior of the aerosol streams of
powdered coating materials with identical particle-size
distribution. It can therefore prove to be difficult to transfer
conveying methods which have been optimized for a specific D.sub.50
to powdered coating materials with other densities. In particular
embodiments, therefore, it is preferred that the upper limit of the
span value is corrected dependent on the density of the powdered
coating material used.
Span UC = Span U ( .rho. Alu .rho. X ) 1 3 ##EQU00003##
[0112] Here, Span.sub.UC is the corrected upper span value,
Span.sub.O is the upper span value, p.sub.Alu is the density of
aluminum (2.7 g/cm.sup.3) and .rho..sub.X is the density of the
powdered coating material used. However, it was furthermore found
that the differences in the case of powdered coating materials with
a lower density than aluminum are only slight, and a selection,
optimized in this respect, of the powdered coating material does
not result in a noticeable improvement in the conveyability. A
powdered coating material with an uncorrected upper span value is
therefore used for powdered coating materials with a density lower
than the density of aluminum.
[0113] Coating methods that can be used according to the invention
are known to a person skilled in the art under the names cold gas
spraying, thermal plasma spraying, non-thermal plasma spraying,
flame spraying and high-speed flame spraying.
[0114] Cold gas spraying is characterized in that the powder to be
applied is not melted in the gas jet, but the particles are greatly
accelerated and, as a result of their kinetic energy, form a
coating on the surface of the substrate. Here, various gases known
to a person skilled in the art can be used as carrier gas, such as
nitrogen, helium, argon, air, krypton, neon, xenon, carbon dioxide,
oxygen or mixtures thereof. In particular variants, it is preferred
in particular that air, helium or mixtures thereof are used as
gas.
[0115] Gas speeds of up to 3000 m/s are achieved through a
controlled expansion of the above-named gases in a corresponding
nozzle. The particles can be accelerated here to up to 2000 m/s.
However, in particular variants of cold gas spraying, it is
preferred that the particles achieve speeds for example of between
300 m/s and 1600 m/s, preferably between 1000 m/s and 1600 m/s,
more preferably between 1250 m/s and 1600 m/s.
[0116] A disadvantage is, for example, the strong generation of
noise which is brought about by the high speeds of the gas streams
used.
[0117] In flame spraying, for example, a powder is converted to the
liquid or plastic state by means of a flame and then applied to a
substrate as coating. Here, e.g. a mixture of oxygen and a
combustible gas such as acetylene or hydrogen is combusted. In
particular variants of flame spraying, some of the oxygen is used
to transport the powdered coating material into the combustion
flame. The particles achieve speeds of between 24 and 31 m/s in
customary variants of this method.
[0118] Similarly to flame spraying, in high-speed flame spraying,
for example, a powder is also converted to a liquid or plastic
state by means of a flame. However, the particles are accelerated
to significantly higher speeds compared with the above-named
method. In specific examples of the above-named method, for
example, a speed of the gas stream of from 1220 to 1525 m/s with a
speed of the particles of from approx. 550 to 795 m/s is named. In
further variants of this method, however, gas speeds of over 2000
m/s are also achieved. In general, in customary variants of the
previous method, it is preferred that the speed of the flame lies
between 1000 and 2500 m/s. Furthermore, in customary variants, it
is preferred that the flame temperature lies between 2200.degree.
C. and 3000.degree. C. The temperature of the flame is thus
comparable to the temperature in flame spraying. This is achieved
by combusting the gases under a pressure of from approx. 515 to 621
kPa, followed by expansion of the combustion gases in a nozzle. In
general, the view is taken that coatings produced here have a
higher density than, for example, coatings obtained by the flame
spraying method.
[0119] Detonation/explosive flame spraying can be viewed as a
subtype of high-speed flame spraying. Here, the powdered coating
material is strongly accelerated by repeated detonations of a gas
mixture such as acetylene/oxygen, wherein for example particle
speeds of approx. 730 m/s are achieved. The detonation frequency of
the method here lies for example between approx. 4 and 10 Hz. In
variants such as the so-called high frequency gas detonation
spraying, however, detonation frequencies of around approx. 100 Hz
are also chosen.
[0120] The layers obtained are usually supposed to have a
particularly high hardness, strength, density and good binding to
the substrate surface. A disadvantage in the above-named methods is
the increased safety costs, as well as for example the high noise
load because of the high gas speeds.
[0121] In thermal plasma spraying, for example, a direct current
arc furnace is passed through by a primary gas such as argon at a
speed of 40 l/min and a secondary gas such as hydrogen at a speed
of 2.5 l/min, wherein a thermal plasma is generated. Then, for
example, 40 g/min of the powdered coating material is fed in with
the aid of a carrier gas stream, which is passed into the plasma
flame at a speed of 4 l/min. In usual variants of thermal plasma
spraying, the conveying rate of the powdered coating material is
between 5 g/min and 60 g/min, more preferably between 10 g/min and
40 g/min.
[0122] In particular variants of the method, it is preferred to use
argon, helium or mixtures thereof as ionizable gas. The whole gas
stream is furthermore preferably 30 to 150 SLPM (standard liters
per minute) in particular variants. The electrical power used to
ionize the gas stream, without the heat energy dissipated as a
result of cooling, can be selected for example between 5 and 100
kW, preferably between 40 and 80 kW. Here, plasma temperatures of
between 4000 K and a few 10000 K can be achieved.
[0123] In non-thermal plasma spraying, a non-thermal plasma is used
to activate the powdered coating material. The plasma used here is
generated for example with a barrier discharge or corona discharge
with a frequency of from 50 Hz to 1 MHz. In particular variants of
non-thermal plasma spraying, it is preferred that work is done at a
frequency of from 10 kHz to 100 kHz. The temperature of the plasma
here is preferably less than 3000 K, preferably less than 2500 K
and still more preferably less than 2000 K. This minimizes the
technical outlay and keeps the input of energy into the coating
material to be applied as low as possible, which in turn allows a
gentle coating of the substrate. The order of magnitude of the
temperature of the plasma flame is thus preferably comparable to
that of flame spraying or of high-speed flame spraying. Non-thermal
plasmas the core temperature of which is below 1173 K or even below
773 K in the core region can also be generated by targeted choice
of the parameters. The temperature in the core region is measured
here, for example, using an NiCr/Ni thermocouple and a spray
diameter of 3 mm at a distance of 10 mm from the nozzle outlet in
the core of the emerging plasma jet at ambient pressure. Such
non-thermal plasmas are suitable in particular for coatings of very
temperature-sensitive substrates.
[0124] To produce coatings with sharp boundaries without the need
to cover areas in a targeted manner, it has proved to be
advantageous to design, in particular, the outlet opening for the
plasma flame such that the track widths of the coatings produced
lie between 0.2 mm and 10 mm. This makes a very precise, flexible,
energy-efficient coating possible while making the best possible
use of the coating material used. For example, a distance of 1 mm
is chosen as the distance from the spray lance to the substrate.
This makes possible as great a flexibility as possible of the
coatings and, at the same time, guarantees high-quality coatings.
The distance between spray lance and substrate expediently lies
between 1 mm and 35 mm.
[0125] Various gases known to a person skilled in the art and
mixtures thereof can be used as ionizable gas in the non-thermal
plasma method. Examples of these are helium, argon, xenon,
nitrogen, oxygen, hydrogen or air, preferably argon or air. A
particularly preferred ionizable gas is air.
[0126] For example to reduce the noise load, it can also be
preferred here that the speed of the plasma stream lies below 200
m/s. For example, a value of between 0.01 m/s and 100 m/s,
preferably between 0.2 m/s and 10 m/s, can be chosen as the flow
rate. In particular embodiments, it is preferred in particular for
example that the volume flow of the carrier gas lies between 10 and
25 l/min, more preferably between 15 and 19 l/min.
[0127] According to a preferred embodiment, the particles of the
powdered coating material are preferably metallic particles or
metal-containing particles. It is preferred in particular that the
metal content of the metallic particles or metal-containing
particles is at least 95 wt.-%, preferably at least 99 wt.-%, still
more preferably at least 99.9 wt.-%. In particular preferred
embodiments, the metal is, or the metals are, selected from the
group consisting of silver, gold, platinum, palladium, vanadium,
chromium, manganese, cobalt, germanium, antimony, aluminum, zinc,
tin, iron, copper, nickel, titanium, silicon, alloys and mixtures
thereof. In particular ones of the above-named embodiments, it is
preferred in particular that the metal is, or the metals are,
selected from the group consisting of silver, gold, aluminum, zinc,
tin, iron, copper, nickel, titanium, silicon, alloys and mixtures
thereof, preferably from the group consisting of silver, gold,
aluminum, zinc, tin, iron, nickel, titanium, silicon, alloys and
mixtures thereof.
[0128] According to further preferred embodiments of the method
according to the invention, the metal or the metals of the
particles of the powdered coating material is or are selected from
the group consisting of silver, aluminum, zinc, tin, copper, alloys
and mixtures thereof. In particular, metallic particles or
metal-containing particles in which the metal is, or the metals
are, selected from the group consisting of silver, aluminum and tin
have proved to be particularly suitable particles in specific
embodiments.
[0129] In further embodiments of the invention, the powdered
coating material consists of inorganic particles which are
preferably selected from the group consisting of carbonates,
oxides, hydroxides, carbides, halides, nitrides and mixtures
thereof. Mineral and/or metal-oxide particles are particularly
suitable.
[0130] In other embodiments, the inorganic particles are
alternatively or additionally selected from the group consisting of
carbonaceous particles or graphite particles.
[0131] A further possibility is the use of mixtures of the metallic
particles and the above-named inorganic particles, such as for
example mineral and/or metal-oxide particles, and/or the particles
which are selected from the group consisting of carbonates, oxides,
hydroxides, carbides, halides, nitrides and mixtures thereof.
[0132] Furthermore, the powdered coating material can comprise or
consist of glass particles. In particular embodiments, it is
preferred in particular that the powdered coating material
comprises or consists of coated glass particles.
[0133] In addition, in particular embodiments, the powdered coating
material comprises or consists of organic and/or inorganic
salts.
[0134] In still other embodiments of the present invention, the
powdered coating material comprises or consists of plastic
particles. The above-named plastic particles are formed for example
from pure or mixed homo-, co-, block or pre-polymers or mixtures
thereof. Here, the plastic particles can be pure crystals or be
mixed crystals or have amorphous phases. The plastic particles can
be obtained for example by mechanical comminution of plastics.
[0135] In particular embodiments of the method according to the
invention, the powdered coating material comprises or consists of
mixtures of particles of different materials. In particular
preferred embodiments, the powdered coating material consists in
particular of at least two, preferably three, different particles
of different materials.
[0136] The particles can be produced via different methods. For
example, the metal particles can be obtained by spraying or
atomizing molten metals. Glass particles can be produced by
mechanical comminution of glass or else from the melt. In the
latter case, the glass melt can likewise be atomized or nebulized.
Alternatively, melted glass can also be comminuted on rotating
elements, for example a drum.
[0137] Mineral particles, metal-oxide particles and inorganic
particles which are selected from the group which consists of
oxides, hydroxides, carbonates, carbides, nitrides, halides and
mixtures thereof can be obtained by comminuting the naturally
occurring minerals, stones, etc. and then screening them by
size.
[0138] The screening by size can be carried out for example by
means of cyclones, air separators, screens, etc.
[0139] In particular embodiments of the present invention, the
particles of the powdered coating material have been provided with
a coating before they were covered with the additive.
[0140] In particular preferred embodiments of the present
invention, the above-named coating can comprise a metal or consist
of a metal. Such a coating of a particle can be formed closed or
particulate, wherein coatings with a closed structure are
preferred. The layer thickness of such a metallic coating
preferably lies below 1 .mu.m, more preferably below 0.8 .mu.m and
still more preferably below 0.5 .mu.m. In particular embodiments,
such coatings have a thickness of at least 0.05 .mu.m, more
preferably of at least 0.1 .mu.m. Metals that are particularly
preferred in particular embodiments for use in one of the
above-named coatings, preferably as main constituents, are selected
from the group consisting of copper, titanium, gold, silver, tin,
zinc, iron, silicon, nickel and aluminum, preferably from the group
consisting of gold, silver, tin and zinc, further preferably from
the group consisting of silver, tin and zinc. The term main
constituent within the meaning of the above-named coating denotes
that the relevant metal or a mixture of the above-named metals
represents at least 90 wt.-%, preferably 95 wt.-%, further
preferably 99 wt.-% of the metal content of the coating. It must be
understood that, in the case of a partial oxidation, the oxygen
proportion of the corresponding oxide layer is not taken into
account. Such metallic coatings can be produced for example by
means of gas-phase synthesis or wet-chemical methods.
[0141] In further particular embodiments, the particles according
to the invention of the powdered coating material are additionally
or alternatively coated with a metal oxide layer. Preferably, this
metal oxide layer substantially consists of silicon oxide, aluminum
oxide, boron oxide, zirconium oxide, cerium oxide, iron oxide,
titanium oxide, chromium oxide, tin oxide, molybdenum oxide, oxide
hydrates thereof, hydroxides thereof and mixtures thereof. In
particular preferred embodiments, the metal oxide layer
substantially consists of silicon oxide. The above-mentioned term,
"substantially consists of", within the meaning of the present
invention means that at least 90%, preferably at least 95%, more
preferably at least 98%, still more preferably at least 99% and
most preferably at least 99.9% of the metal oxide layer consists of
the above-named metal oxides, in each case relative to the number
of particles of the metal oxide layer, wherein any water contained
is not factored in. The composition of the metal oxide layer can be
determined by means of methods known to a person skilled in the
art, such as for example sputtering in combination with XPS or
TOF-SIMS. In particular ones of the above-named embodiments, it is
preferred in particular that the metal oxide layer does not
represent an oxidation product of a metal core located underneath
it. Such a metal oxide layer can be applied for example using the
sol-gel method.
[0142] In particular preferred embodiments, the substrate is
selected from the group consisting of plastic substrates, inorganic
substrates, cellulose-containing substrates and mixtures
thereof.
[0143] The plastic substrates can be for example plastic films or
shaped bodies made of plastics. The shaped bodies can have
geometrically simple or complex shapes. The plastic shaped body can
be for example a component from the automotive industry or the
construction industry.
[0144] The cellulose-containing substrates can be cardboard, paper,
wood, wood-containing substrates, etc.
[0145] The inorganic substrates can be for example metallic
substrates, such as metal sheets or metallic shaped bodies or
ceramic or mineral substrates or shaped bodies. The inorganic
substrates can also be solar cells or silicon wavers, to which for
example electrically conductive coatings or contacts are
applied.
[0146] Substrates made of glass, such as for example glass panes,
can also be used as inorganic substrates. The glass, in particular
glass panes, can be provided for example with electrochromic
coatings using the method according to the invention.
[0147] The substrates coated by means of the method according to
the invention are suitable for very different uses.
[0148] In particular embodiments, the coatings have optical and/or
electromagnetic effects. Here, the coatings can bring about
reflections or absorptions. Furthermore, the coatings can be
electrically conductive, semi-conductive or non-conductive.
[0149] Electrically conductive layers can be applied for example in
the form of strip conductors to components. This can be used for
example to make current-carrying possible within the framework of
the on-board power supply in an automobile component. Furthermore,
such a strip conductor can, however, also be formed for example as
an antenna, as a shield, as an electrical contact, etc. This is
particularly advantageous for example for RFID applications (radio
frequency identification). Furthermore, coatings according to the
invention can be used for example for heating purposes or for the
targeted heating of specific components or specific parts of larger
components.
[0150] In further particular embodiments, the coatings produced act
as sliding layers, diffusion barriers for gases and liquids, wear
and/or corrosion protection layers.
[0151] Furthermore, the coatings produced can influence the surface
tension of liquids or have adhesion-promoting properties.
[0152] The coatings produced according to the invention can
furthermore be used as sensor surfaces, for example as
human-machine interface (HMI), for example in the form of a
touchscreen. The coatings can likewise be used to shield from
electromagnetic interferences (EMI) or to protect against
electrostatic discharges (ESD). The coatings can also be used to
bring about electromagnetic compatibility (EMC).
[0153] Furthermore, through the use of the particles according to
the invention, layers can be applied which are applied for example
to increase the stability of corresponding components after repair.
An example is repairs in the aviation sector, wherein for example a
loss of material as a result of processing steps must be
compensated for, or a coating is to be applied for example for
stabilization. This proves to be difficult for aluminum components
for example, and normally requires post-processing steps such as
sintering. In contrast, by means of the methods according to the
invention, firmly adhering coatings can be applied under very
gentle conditions, without post-processing steps such as sintering
even being required.
[0154] In still other embodiments, the coatings act as electrical
contacts and allow an electrical connection between different
materials.
[0155] A person skilled in the art is aware that the specifications
indicated above with regard to the method according to the
invention in respect of the powdered coating material and the
particles contained therein also apply correspondingly to the use
of the powdered coating material and the particles contained
therein, and vice versa.
FIGURES
[0156] FIGS. 1 and 2 show a wafer, coated with solar contact paste,
which has been coated with a powdered coating material according to
the invention using non-thermal plasma spraying according to
Example 14.
EXAMPLES
Materials and Methods Used
[0157] The size distribution of the particles of the powdered
coating materials used was determined by means of a HELOS device
(Sympatec, Germany). For the measurement, 3 g of the powdered
coating material was introduced into the measuring device and
treated, before the measurement, with ultrasound for 30 seconds.
For the dispersion, a Rodos T4.1 dispersing unit was used, wherein
the primary pressure was 4 bar. The evaluation was carried out with
the device's standard software.
[0158] The method according to the invention is now explained in
more detail with reference to the following examples, without being
limited to the examples.
Example 1
Powdered Coating Materials Covered with Acrylic Polymer
(Poly(Isobutyl Methacrylate)
[0159] 0.3 g of an acrylic polymer based on isobutyl methacrylate
(Degalan P 675, from Evonik) was used as additive and dissolved in
50 g ethyl acetate. This mixture was then introduced, together with
240 g aluminum particles (D.sub.50=17.5 .mu.m), into a kneader
(Duplex kneader from IKA) and kneaded for 30 min at RT (20.degree.
C.). A temperature of 40.degree. C. and a vacuum of 250 mbar were
then set. Drying was carried out for 1 h and then the
additive-containing particles were removed from the kneader and
then screened (71 .mu.m).
Example 2
Powdered Coating Materials Covered with Ethyl Cellulose
[0160] The application of the additive was carried out analogously
to Example 1. 1 g ethyl cellulose (Ethocel Standard 10, from Dow
Wolff Cellulosics) was used as additive.
Example 3
Powdered Coating Materials Covered with Acrylic Polymer (Methyl
Methacrylate)
[0161] The application of the additive was carried out analogously
to Example 1. 2 g of an acrylic polymer based on methyl
methacrylate and n-butyl methacrylate (Degalan LP AL 23, from
Evonik) was used as additive.
Example 4
Powdered Coating Materials Covered with 1,10-Decanedicarboxylic
Acid
[0162] 3 g of 1,10-decanedicarboxylic acid was used as coating
excipient and dissolved in 50 g ethyl acetate. This mixture was
then introduced, together with 240 g aluminum particles (D.sub.50=2
.mu.m), into a kneader (Duplex kneader from IKA) and kneaded for 30
min at RT (20.degree. C.). A temperature of 40.degree. C. and a
vacuum of 250 mbar were then set. Drying was carried out for 1 h
and then the particles covered with the coating excipient were
removed from the kneader and then screened (71 .mu.m).
Example 5
Powdered Coating Materials Covered with Monoethyl Fumarate
[0163] The application of the coating excipient was carried out
analogously to Example 4. 3 g monoethyl fumarate was used as
coating excipient.
Example 6
Powdered Coating Materials Covered with Adipic Acid Monoethyl
Ester
[0164] The application of the coating excipient was carried out
analogously to Example 4. 3 g adipic acid monoethyl ester was used
as coating excipient.
Example 7
Powdered Coating Materials Covered with Methyl Triglycol
[0165] The application of the coating excipient was carried out
analogously to Example 4. 3 g methyl triglycol was used as coating
excipient.
Example 8
Powdered Coating Materials Covered with Adipic Acid Monoethyl
Ester
[0166] The application of the coating excipient was carried out
analogously to Example 4. However, copper particles with a D.sub.50
of 34 .mu.m were used here. 3 g adipic acid monoethyl ester was
used as coating excipient.
Example 9
Powdered Coating Materials Covered with Methyl Triglycol
[0167] The application of the coating excipient was carried out
analogously to Example 4. However, a copper particle with a
D.sub.50 of 34 .mu.m was used here. 3 g methyl triglycol was used
as coating excipient.
Example 10
Powdered Coating Materials Covered with Ethocel
[0168] The application of the coating excipient was carried out
analogously to Example 4. A copper particle with a D.sub.50 value
of 34 .mu.m was used here. 3 g ethyl cellulose (Ethocel Standard
10, from Dow Wolff Cellulosics) was used as coating excipient.
Example 11
Powdered Coating Materials Covered with Monoethyl Fumarate
[0169] The application of the coating excipient was carried out
analogously to Example 4. A copper particle with a D.sub.50 value
of 34 .mu.m was used here. 3 g DEGALAN PM 381 (copolymer from
methyl methacrylate and isobutyl methacrylate, from Evonik) was
used as coating excipient.
Example 12
Powdered Coating Materials Covered with Aerosil 200
[0170] The additive was applied analogously to Example 4. 100 g
spherical tin particles with a D.sub.50 of 28 .mu.m were used here.
3 g Aerosil 200 (pyrogenic silicic acid, from Evonik) was used as
additive.
Example 13
Determination of the Conveyability
[0171] In order to determine an improvement in the conveyability of
the powdered coating material covered with an additive according to
the invention, an AS 100 fluidimeter from Sames was used. There,
250 g of the respective particles according to Examples 1 to 3 were
poured in and fluidized with a gas. Nitrogen was used here as gas.
A calibrated bore was then opened for 30 seconds and the weight (W)
of the material that flowed out in this time was recorded as the
measured variable.
TABLE-US-00001 Sample Weight Standard alu grit WA 25 5 g Example 1
12 g Example 2 28 g Example 3 16 g
Example 14
Non-Thermal Plasma Spraying of Tin Particles
[0172] The powdered coating material was applied by means of a
Plasmatron system from Inocon, Attnang-Puchheim, Austria. Nitrogen
was used as ionizable gas. Standard process parameters were used
here. Wafers coated with a solar contact paste were used as
substrate. Additive-covered tin particles according to Example 12
and analogous tin particles without additive served as powdered
coating materials.
[0173] The conveying of the tin particles without additive was not
possible in the consistency required for the coating. The conveying
failed rapidly and the small amount conveyed was apparently fed
into the flame intermittently. In contrast, the powdered coating
material according to Example 12 was able to be conveyed without
trouble and a first visual evaluation of the obtained coatings
showed a uniform application. SEM photographs of the obtained
coatings are found in FIGS. 1 and 2.
Example 15
Flame Spraying of Powdered Coating Materials According to Examples
4 to 11
[0174] Using a flame spraying system from CASTOLIN, aluminum
particles with a D.sub.50 value of 2 .mu.m without coating
excipient, as well as the aluminum particles according to Examples
4 to 7, were applied to a metal sheet by means of an oxyacetylene
flame. Furthermore, copper particles with a D.sub.50 value of 34
.mu.m without coating excipient, as well as the copper particles
according to Examples 8 to 11, were applied analogously. The
obtained metal sheets were examined by means of SEM.
[0175] The metal sheets coated according to the invention were much
more homogeneous in relation to their optics as well as their
haptics. SEM photographs of the surfaces demonstrate the formation
of larger uniform areas of the coating, while the surface of the
comparison examples is characterized by a large number of isolated
particles. Furthermore, the cross-section shows that cavities
contained in the coating of the metal sheet according to the
invention are significantly smaller.
* * * * *