U.S. patent application number 12/447997 was filed with the patent office on 2010-07-01 for metal effect pigments for use in the cathodic electrodeposition painting, method for the production and use of the same, and electrodeposition paint.
This patent application is currently assigned to Eckart GMBH. Invention is credited to Carolin Heckel, Christian Schramm, Harald Weiss.
Application Number | 20100163420 12/447997 |
Document ID | / |
Family ID | 39264840 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100163420 |
Kind Code |
A1 |
Weiss; Harald ; et
al. |
July 1, 2010 |
METAL EFFECT PIGMENTS FOR USE IN THE CATHODIC ELECTRODEPOSITION
PAINTING, METHOD FOR THE PRODUCTION AND USE OF THE SAME, AND
ELECTRODEPOSITION PAINT
Abstract
The invention relates to electrocoat material pigments, said
electrocoat material pigments comprising metal effect pigment
platelets coated with at least one coating material, said coating
material comprising one or more functional groups for adhesion or
attachment to the pigment surface and at least one amino-functional
group, said amino-functional group being protonatable or positively
charged. The invention further relates to a process for producing
these electrocoat material pigments and to the use thereof, and to
a cathodic electrocoat material which comprises the inventive
pigments.
Inventors: |
Weiss; Harald; (Furth,
DE) ; Schramm; Christian; (Hersbruck, DE) ;
Heckel; Carolin; (Velden, DE) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
US
|
Assignee: |
Eckart GMBH
Furth
DE
|
Family ID: |
39264840 |
Appl. No.: |
12/447997 |
Filed: |
October 27, 2007 |
PCT Filed: |
October 27, 2007 |
PCT NO: |
PCT/EP2007/009351 |
371 Date: |
March 3, 2010 |
Current U.S.
Class: |
205/80 |
Current CPC
Class: |
C09D 5/36 20130101; C09C
1/62 20130101; C09C 1/66 20130101; C09D 5/4492 20130101; C09C 1/644
20130101; C09C 1/648 20130101 |
Class at
Publication: |
205/80 |
International
Class: |
C25D 3/00 20060101
C25D003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2006 |
DE |
10 2006 051 893.4 |
Claims
1. An electrocoat material pigment, said electrocoat material
pigment comprising metal effect pigment platelets coated with at
least one coating material, said coating material comprising a) one
or more functional groups for adhesion or attachment to the pigment
surface and b) at least one amino-functional group, said
amino-functional group being protonatable or positively
charged.
2. The electrocoat material pigment as claimed in claim 1, wherein
the metal effect pigments have a coating which inhibits corrosion
by aqueous systems or media.
3. The electrocoat material pigment as claimed in claim 1, wherein
the metal effect pigments are selected from the group comprising
metal effect pigments provided with at least one of inorganic and
organic coatings, metal effect pigments provided with
inorganic/organic mixed layers, metal effect pigments coated with
synthetic resin, surface-oxidized metal effect pigments and colored
metal effect pigments.
4. The electrocoat material pigment as claimed in claim 1, wherein
the metal effect pigment platelets consist of metals or alloys
which are selected from the group consisting of aluminum, copper,
zinc, tin, brass, iron, titanium, chromium, nickel, steel, silver
and alloys and mixtures thereof.
5. The electrocoat material pigment as claimed in claim 3, wherein
the synthetic resin coating of the metal effect pigment comprises
at least one of a polyacrylate, a polymethacrylate and a
combination thereof.
6. The electrocoat material pigment as claimed in claim 2, wherein
the corrosion-inhibiting coating consists essentially of a metal
oxide.
7. The electrocoat material pigment as claimed in claim 2, wherein
the corrosion-inhibiting coating is a surface oxide layer.
8. The electrocoat material pigment as claimed in claim 6 wherein
the oxide layer additionally comprises color pigments.
9. The electrocoat material pigment as claimed claim 1, wherein the
coating material has one or more functional groups for adhesion or
attachment to the metal effect pigment surface or to at least one
of a synthetic resin surface and an inorganic coating applied to
the metal effect pigment surface.
10. The electrocoat material pigment as claimed in claim 9, wherein
one or more functional groups of the coating material are selected
from the group consisting of phosphonic ester, phosphoric ester,
carboxylate, metallic ester, alkoxysilyl, silanol, sulfonate,
hydroxyl, polyol groups and mixtures thereof.
11. The electrocoat material pigment as claimed in claim 1, wherein
the coating material is applied to the pigment in an amount of 1 to
100% by weight based on the weight of the metallic component of the
metal effect pigment.
12. The electrocoat material pigment as claimed in claim 1, wherein
the coating material is a cathodic electrocoat material binder.
13. A process for producing electrocoat material pigments as
claimed in claim 1, wherein the process comprises the following
steps: (a) coating a metal effect pigment with the coating material
having an amino-functional group dissolved or dispersed in a
solvent, said amino-functional group being protonatable or
positively charged, (b) optionally drying the metal effect pigments
coated with the coating material in step (a), and (c) optionally
converting the metal effect pigments dried in step (b) to a
paste.
14. The process as claimed in claim 13, wherein steps (a) and (b)
are combined into a single step, by applying the coating material
as a solution or dispersion to metal effect pigments moving in a
gas stream.
15. A method of making a cathodic electrocoat material for use in
cathodic electrocoating, said method comprising incorporating into
said cathodic electrocoat material a plurality of electrocoat
material pigments as claimed in claim 1.
16. A cathodic electrocoat material comprising electrocoat material
pigments as claimed in claim 1.
17. The electrocoat material pigment as claimed in claim 6, wherein
the metal oxide is silicon dioxide.
Description
[0001] The invention relates to pigments based on metal effect
pigment platelets which can be deposited in the course of cathodic
electrocoating. The invention further relates to a process for
producing these electrocoat material pigments and to the use
thereof in a cathodic electrocoat material or in cathodic
electrocoating. The invention finally also relates to a cathodic
electrocoat material.
[0002] Electrocoating (EC) is a process for applying particular
water-soluble coating materials, so-called electrocoat materials,
to electrically conductive substrates, for example a workpiece.
Between a workpiece immersed into a coating bath and a
counterelectrode, an electrical direct current field is applied. A
distinction is drawn between anodic deposition, so-called anodic
electrocoating (AEC), in which the workpiece is connected as the
anode or plus pole, and cathodic deposition, so-called cathodic
electrocoating (CEC), in which the workpiece is connected as the
cathode or as the minus pole.
[0003] The coating material binder contains functional groups of
particular polarity, which are present in salt form due to
neutralization and as a result colloidally dissolved in water. In
the vicinity of the electrode (within the diffusion boundary
layer), owing to hydrolysis, hydroxide ions form in CEC or H.sup.+
ions in AEC. These ions react with the binder salt, causing the
functionalized binders to lose their salt form ("salting out"),
become insoluble and coagulate at the surface of the workpiece.
Later, the coagulated binder particles lose water owing to
electroosmosis procedures, which causes further compaction.
Finally, the workpiece is withdrawn from the immersion bath, freed
of noncoagulated coating material particles in a multistage rinsing
process and fired at temperatures of 150-190.degree. C. (Brock,
Groteklaes, Mischke, "Lehrbuch der Lacktechnologie" [Textbook of
coating technology] 2.sup.nd edition, Vincentz Verlag 1998, p. 288
ff.).
[0004] Electrocoating has several economic and ecological
advantages over conventional coating methods such as wet coating or
powder coating.
[0005] A primary factor which should be mentioned here is the
comparatively exactly adjustable layer thickness. Compared to
powder coatings, electrocoating also homogeneously coats
difficult-to-access parts of the workpiece. This results from the
following fact: first, the deposition of the binder takes place at
points of high field strength, such as corners and edges. However,
the film which forms has a high electrical resistance. The field
lines therefore shift to other regions of the workpiece and are
concentrated toward the end of the coating operation entirely on
the most inaccessible points, for example regions or points in the
interior of the workpiece (inner coating). The coating of
particularly difficult-to-access points of a workpiece can be
improved once more by the provision of auxiliary electrodes. With
electrocoating (EC) it is therefore possible to coat workpieces of
any shape, provided that they are electrically conductive. EC is
additionally associated advantageously with properties such as
minimal solvent emissions, optimal material yield and
noncombustibility. Droplet- and run-free paintwork is obtained.
Electrocoating is performed in an automated manner and is as a
result a very inexpensive coating method, especially since it can
be performed at comparatively low current densities of a few
mA/cm.sup.2.
[0006] Owing to the simple and highly inexpensive application
method, electrocoating at present finds use in numerous systems.
The most common are basecoats, for example in automotive OEM
finishing, and single-layer topcoats. Electrocoats are found, for
example, on radiators, control cabinets, office furniture, in
construction, in iron and household products, in storage technology
or in rack construction, in climate control and lighting
technology, and in apparatus construction and mechanical
engineering.
[0007] Compared to the older process, anodic electrocoating (AEC),
cathodic electrocoating (CEC) has become increasingly established
since the mid-1970s. It has various advantages: in addition to
improved corrosion protection, mention should be made of
homogeneous layer thickness distribution, and also better throwing
power and good edge coverage.
[0008] CEC finds use especially in chassis coating. This process
firstly achieves corrosion protection, and secondly protects the
coating from stonechipping. CEC can be used as a corrosion
protection coating for all metallic substrates; mention should be
made here, for example, of supports or racks for outside use. Owing
to the substantial absence of organic solvent, environmental
compatibility completes the advantages of cathodic electrocoating
as a highly efficient and attractive coating method.
[0009] Electrocoat materials in use to date have especially been
waterborne coating materials which usually comprise
self-crosslinking or extraneously crosslinking synthetic resins as
binders, which can be dispersed through protonation with acid in
water. Protonation of the functional groups present in the
synthetic resins forms ammonium, phosphonium or sulfonium groups.
The synthetic resins are, for example, polymerization, polyaddition
or polycondensation products containing primary or tertiary amino
groups, such as amino epoxy resins, amino poly(meth)acrylate resins
or amino polyurethane resins. The electrocoat materials may contain
conventional color pigments, which are generally organic and
inorganic color pigments. However, the range of color shades which
is actually used commercially is very limited. The use of effect
pigments in electrocoat material is commercially unknown to
date.
[0010] The CEC bath contains binder, pigment paste, water-miscible
organic solvent and water. The essential constituent of binder and
pigment paste is frequently epoxy resin. Binder and pigment paste
make up the majority of the about 20% solids content of the coating
material. The electrocoat material further consists to an extent of
about 80% by weight of water. There is additionally a small portion
of organic solvents (1-2%), acids (0.4%) and additives. The epoxy
resin is converted to a water-dispersible form by adding a
neutralizing agent. An organic acid is used for this purpose
(principally acetic acid). Often only a portion of the functional
groups is reacted with neutralizing agent. The molar ratio of acid
to functional group is referred to as the degree of neutralization.
A degree of neutralization of about 30% is sufficient to achieve
the desired water dispersibility. An organic acid is also used to
establish the slightly acidic pH in the CEC bath.
[0011] DE 10 2005 020 763.4, which was yet to be published at the
priority date of the present application, describes metal effect
pigments which can find use in anodic electrocoat materials.
[0012] EP 0 477 433 A1 discloses metal effect pigments coated with
synthetic resins, a very thin siloxane layer being applied as an
adhesion promoter between metal effect pigment surface and the
synthetic resin layer. This document does not make any reference to
electrocoating.
[0013] EP 0 393 579 B1 discloses a metal pigment-containing
waterborne coating material which is said to be applicable to a
substrate by means of electrocoating. EP 0 393 579 B1 does not
disclose any metal effect pigments suitable for cathodic
electrocoating.
[0014] It is an object of the present invention to provide metal
effect pigments which can be deposited in a coating material on a
workpiece in cathodic electrocoating.
[0015] The metal effect pigments must be corrosion-stable to the
aqueous electrocoat material medium and be depositable reproducibly
even after more than 60 days of bath time. Electrocoatings thus
produced should have a metallic effect whose optical quality
preferably corresponds to at least that of powder coatings.
[0016] It is a further object of the present invention to find a
process for producing such metal effect pigments.
[0017] The object is achieved by providing electrocoat material
pigments which are metal effect pigment platelets coated with at
least one coating material, said coating material comprising [0018]
(a) one or more functional groups for adhesion or attachment to the
pigment surface and [0019] (b) at least one amino-functional group,
said amino-functional group being protonatable or positively
charged.
[0020] Preferred developments of the electrocoat material pigments
are specified in subclaims 2 to 12.
[0021] The object is additionally achieved by providing a process
for producing electrocoat material pigments as claimed in one of
claims 1 to 12, wherein the process comprises the following steps:
[0022] (a) coating a metal effect pigment with the coating material
having an amino-functional group dissolved or dispersed in a
solvent, said amino-functional group being protonatable or
positively charged, [0023] (b) optionally drying the metal effect
pigments coated with the coating material in step (a), [0024] (c)
optionally converting the metal effect pigments dried in step (b)
to a paste.
[0025] A development of the process according to the invention is
specified in subclaim 14.
[0026] The object underlying the invention is also achieved by the
use of electrocoat material pigments as claimed in one of claims 1
to 12 in a cathodic electrocoat material or in cathodic
electrocoating.
[0027] The invention further relates to a cathodic electrocoat
material comprising electrocoat material pigments as claimed in one
of claims 1 to 12.
[0028] The metal effect pigments may consist of metals or alloys
which are selected from the group consisting of aluminum, copper,
zinc, tin, brass, iron, titanium, chromium, nickel, steel, silver
and alloys and mixtures thereof. Preference is given here to
aluminum pigments and brass pigments, particular preference being
given to aluminum pigments.
[0029] The metal effect pigments are always platelet-shaped in
nature. This is understood to mean pigments in which the
longitudinal dimension is at least ten times, preferably at least
twenty times and more preferably at least fifty times the mean
thickness. In the context of the invention, when metal effect
pigments are mentioned, what is meant is always metal effect
pigment platelets.
[0030] The metal effect pigments used in the inventive electrocoat
material possess mean longitudinal dimensions which are determined
as sphere equivalents by means of laser granulometry (Cilas 1064,
from Cilas) and are reported as the d.sub.50 value of the
corresponding cumulative undersize distribution. These d.sub.50
values are 2 to 100 .mu.m, preferably 4 to 35 .mu.m and more
preferably 5 to 25 .mu.m.
[0031] It has been found that, surprisingly, it is virtually no
longer possible to deposit very large pigment particles with a
d.sub.50 above 100 .mu.m. It appears that the migration and
deposition properties are considerably reduced for relatively large
particles. From such coarse pigment distributions, only the
fractions below approx. 100 .mu.m are now deposited (fines
fraction). However, this considerably reduces the size and size
distribution of the particles deposited compared to those used. For
this reason, smaller particles with a d.sub.50 of less than <100
.mu.m are preferred. From a d.sub.50 of approx. 2 to 35 .mu.m, the
inventive pigments are deposited over their entire size
distribution without any problems. In addition, pigments from this
size enable a bath time of more than 60 days.
[0032] Below a d.sub.50 of 4 .mu.m, the particles are too fine to
produce an appealing visual effect. Here too, owing to the very
high specific surface area of the fine pigments, gassing problems
can occasionally occur in the aqueous electrocoat medium.
[0033] The mean thickness of the inventive metal effect pigments,
in contrast, is preferably 40 to 5000 nm, more preferably 65 to 800
nm and most preferably 250 to 500 nm.
[0034] Electrocoat materials are always waterborne systems. For
this reason, metal effect pigments present in an electrocoat
material have to be stabilized for use in aqueous systems. For
example, they are provided with a protective layer in order to
prevent the corrosive influence of water on the metal effect
pigment. In addition, they must have suitable surface charges in
order to possess sufficient electrophoretic mobility in the
electrical field.
[0035] These properties are surprisingly provided when metal effect
pigments are coated with a coating material, said coating material
having one or more functional groups for adhesion or attachment to
the pigment surface and at least one protonatable or positively
charged amino-functional group.
[0036] In the context of the invention, the term "adhesion" is
understood to mean noncovalent interactions, for example
hydrophobic interactions, hydrogen bonds, ionic interactions, van
der Waals forces, etc., which lead to immobilization of the coating
material on the pigment surface.
[0037] In the context of the invention, the term "attachment" is
understood to mean covalent bonds which lead to covalent
immobilization of the coating material on the pigment surface.
[0038] It has been found, entirely surprisingly, that metal effect
pigments in cathodic electrocoating have outstanding
electrophoretic mobility when the metal effect pigments are
provided with a coating material which contains an amino-functional
group.
[0039] The protonatable or positively charged amino-functional
group, after introduction of the coated metal effect pigments into
the electrocoat medium, preferably projects into the electrocoat
medium. The protonatable or positively charged amino-functional
group is preferably arranged spaced apart from the metal effect
pigment surface by a spacer. The spacer is a preferably organic
structural element which is unreactive under electrocoating
conditions and binds the adhering or attaching group on the metal
effect pigment surface and the protonatable or positively charged
amino-functional group to one another.
[0040] The unreactive organic structural element may, for example,
be a linear or branched alkyl chain having 1 to 20 carbon atoms,
preferably having 2 to 10 carbon atoms, more preferably having 3 to
5 carbon atoms. Optionally, this linear or branched alkyl chain may
contain heteroatoms or heteroatom groups such as O, S or NH.
[0041] More preferably, the protonatable or positively charged
amino-functional group is a terminal, substituted or unsubstituted
amino group, i.e. an amino group arranged terminally on the spacer,
which is spaced apart to the maximum degree from the group which
provides attachment or adhesion to the metal effect pigment
surface.
[0042] The amino-functional group is preferably a protonatable
amino group or a positively charged amino group.
[0043] In one variant of the invention, the positively charged
amino-functional group is preferably a quaternary ammonium
compound. Such quaternary ammonium compounds are preferably
obtained by alkylating amine compounds.
[0044] In a further preferred compound, the charge state can be
controlled by lowering the pH, by adding acid to protonate the
amino-functional group(s).
[0045] In one variant of the present invention, the
amino-functional group is an --NH.sub.2 group arranged on the
spacer.
[0046] In a further variant, the amino-functional group is an
--NR.sup.1R.sup.2 group arranged on the spacer,
where R.sup.1 and R.sup.2 may be the same or different from one
another and may each independently be hydrogen, alkyl having 1 to
20 carbon atoms, preferably having 2 to 10 carbon atoms, more
preferably having 3 to 5 carbon atoms, or R.sup.1 and R.sup.2 may
be joined to one another and, together with the nitrogen atom, form
a heterocycle which preferably contains 4 or 5 carbon atoms.
[0047] In a further variant, the amino-functional group is an
--NR.sup.1R.sup.2R.sup.3 group arranged on the spacer,
where R.sup.1, R.sup.2 and R.sup.3 may be the same or different
from one another and may each independently be hydrogen, alkyl
having 1 to 20 carbon atoms, preferably having 2 to 10 carbon
atoms, more preferably having 3 to 5 carbon atoms.
[0048] In a preferred development of the invention, the metal
effect pigments are provided with an inorganic and/or organic
coating, optionally in the form of an inorganic/organic mixed
layer, coated with synthetic resin or surface oxidized so as to
inhibit corrosion (ALOXAL.RTM. product series from Eckart GmbH
& Co.) or colored metal effect pigments (for example
ALUCOLOR.RTM. product series from Eckart GmbH & Co.) and
treated with at least one coating material which contains binder
functionalities suitable for electrocoat materials.
[0049] The metal effect pigments coated with synthetic resins
contain a coating of polymers. These polymers are polymerized onto
the metal effect pigments proceeding from monomers. The synthetic
resins include polyacrylates, polymethacrylates, polyesters and/or
polyurethanes.
[0050] In a preferred embodiment, the coated metal effect pigment
is coated with at least one polymethacrylate and/or
polyacrylate.
[0051] Particular preference is given to using metal effect
pigments which have been produced according to the teaching of EP 0
477 433 A1, which is hereby incorporated by reference. Such
pigments preferably contain, between the metal effect pigment and
the synthetic resin coating, an organofunctional silane which
serves as an adhesion promoter. Particular preference is given here
to coatings composed of preferably multiply crosslinked
polyacrylates and/or polymethacrylates. Such coatings already
constitute a certain though not completely reliable
corrosion-inhibiting protection against the aqueous medium of
electrocoat materials. Similar pigments are described in DE 36 30
356 C2, an ethylenically unsaturated carboxylic acid and/or
phosphoric mono- or diester as an adhesion promoter being arranged
here between the metal effect pigment and the synthetic resin
coating.
[0052] Examples of such crosslinkers which can be used with
preference in the present invention are: tetraethylene glycol
diacrylate (TEGDA), triethylene glycol diacrylate (TIEGDA),
polyethylene glycol-400 diacrylate (PEG400DA),
2,2'-bis(4-acryloyloxyethoxyphenyl)propane, ethylene glycol
dimethacrylate (EGDMA), diethylene glycol dimethacrylate (DEGDMA),
triethylene glycol dimethacrylate (TRGDMA), tetraethylene glycol
dimethacrylate (TEGDMA), butyldiglycol methacrylate (BDGMA),
trimethylolpropane trimethacrylate (TMPTMA), 1,3-butanediol
dimethacrylate (1,3-BDDMA), 1,4-butanediol dimethacrylate
(1,4-BDDMA), 1,6-hexanediol dimethacrylate (1,6-HDMA),
1,6-hexanediol diacrylate (1,6-HDDA), 1,12-dodecanediol
dimethacrylate (1,12-DDDMA), neopentyl glycol dimethacrylate
(NPGDMA). Particular preference is given to trimethylolpropane
trimethacrylate (TMPTMA).
[0053] These compounds are commercially available from Elf Atochem
Deutschland GmbH, D-40474 Dusseldorf, Germany, or Rohm & Haas,
In der Kron 4, D-60489 Frankfurt/Main, Germany.
[0054] The thickness of the corrosion-inhibiting coating,
preferably organic coating or synthetic resin coating, is
preferably 2 to 50 nm, more preferably 4 to 30 nm and especially
preferably 5 to 20 nm. The proportion of organic coating or
synthetic resin coating, based in each case on the weight of the
uncoated metal effect pigment, depends in the individual case on
the size of the metal effect pigments and is preferably 1 to 25% by
weight, more preferably 2 to 15% by weight and especially
preferably 2.5 to 10% by weight.
[0055] The coating material is applied to the metal effect pigments
after the application of the organic coating or of the synthetic
resin layer and/or of another corrosion-inhibiting layer, for
example of an inorganic coating such as a metal oxide-containing
layer or metal oxide layer.
[0056] The corrosion-inhibiting coating may, for example, comprise
essentially metal oxide, especially silicon dioxide, or consist
thereof. A metal oxide layer can be applied using different
processes known to those skilled in the art. For example, a silicon
dioxide layer can be applied by means of sol-gel methods with
hydrolysis of tetraalkoxysilanes, where the alkoxy group may be
methoxy, ethoxy, propoxy or butoxy. However, it is also possible to
apply an SiO.sub.2 coating to the metal effect pigment surface
using waterglass.
[0057] The corrosion-inhibiting coating may also be a surface oxide
layer. For example, it is possible to provide aluminum effect
pigments with an impervious surface oxide layer which is
corrosion-inhibiting with respect to aqueous media.
[0058] In a preferred embodiment, the oxide layer may additionally
comprise color pigments. The color pigments can be introduced
during the application of the metal oxide layer, especially silicon
dioxide layer, or during the surface oxidation of the surface of
the metal oxide layer.
[0059] The corrosion-inhibiting coating, for example synthetic
resin layer, may completely surround the pigments, but it may also
be present in not entirely continuous form or have cracks. Use of
the coating material with protonatable or positively charged
amino-functional group and with functional groups for adhesion
and/or attachment to the pigment surface in the present invention
covers possible corrosion sites which can be caused by such cracks
or by an incomplete corrosion-inhibiting coating on the metal
effect pigment.
[0060] The coating material used in the present invention is
capable, especially when it attaches to the metallic pigment
surface, of penetrating into such gaps or cracks in the
corrosion-inhibiting coating, preferably synthetic resin coating,
thus bringing about the required corrosion stability.
[0061] Even though it has been found that, surprisingly, the
coating material used in the present invention also has
corrosion-inhibiting properties in the case of metal effect
pigments, this coating material is used primarily in order to make
the metal effect pigments cathodically depositable. The coating
material with protonatable or positively charged amino-functional
group makes the metal effect pigments electrophoretically mobile in
the electrocoating bath, i.e. they migrate in the direction of the
object to be coated which is connected as the cathode.
[0062] Metal effect pigments which are coated only with synthetic
resin or other corrosion-inhibiting coatings and have not been
treated with the coating material with amino-functional group used
in the present invention can be cathodically deposited only
insufficiently, or cannot be cathodically deposited effectively, in
cathodic electrocoating.
[0063] In electrocoating, conventional color pigments added to an
electrocoat material are deposited on the workpiece by a
comparatively random process. The electrocoat material is always
stirred vigorously here during the deposition. As a result,
essentially mass transfer toward the workpiece takes place
(convection). Only within the Nernst diffusion layer which forms
does electrophoretic migration of the charged binder particles
within the electrical field proceed. The concentration of the color
pigments in the deposition bath is very high (approx. 10% by
weight). The binder which is deposited entrains the color pigments.
There is no electrophoretic migration of the color pigments in the
electrical field.
[0064] Metal effect pigments are not usable per se in electrocoat
materials. Even if they are corrosion-stable to the aqueous medium
of the electrocoat material as a result of a suitable protective
layer, for example a metal oxide or a synthetic resin, they are
either not or are no longer deposited after a few hours to days
after an initial deposition, which is referred to as inadequate
bath stability.
[0065] It has been found that, surprisingly, the inventive metal
effect pigments can be deposited reliably and over long periods in
cathodic electrocoating, and the electrocoat material has a bath
stability of more than 60 days. The inventive metal effect pigments
present in the cathodic electrocoat material are therefore
deposited reliably on the workpiece even after 60 days, preferably
after 90 days. Moreover, they have sufficient corrosion stability,
such that no significant gassing (in the case of aluminum or iron
pigments) or release of metal ions (in the case of brass pigments)
occurs within this time in the electrocoat material.
[0066] It has been found that the coating material in this case
must have one or more amino-functional groups. These are at least
partly protonated in the electrocoat material. These protonated
amino groups are thought to impart sufficient positive surface
charges to the inventive electrocoat material pigment to be
well-dispersed in the predominantly aqueous medium of the
electrocoat material. Moreover, the inventive metal effect pigments
are thought to be positively charged at their surface such that
migration in the electrical field applied toward the cathode is
enabled within the Nernst diffusion layer. It is thought that the
surface of the inventive metal effect pigments is matched
chemically in this way to the binders of the cathodic electrocoat
material. This enables the effect that the metal effect pigments
can firstly migrate electrophoretically in the electrical field and
secondly take part in the deposition mechanism of the electrocoat
materials at the cathode.
[0067] Furthermore, the coating materials contain functional groups
which bring about or can bring about adhesion and/or attachment to
the surface of the metal effect pigment or the stabilizing coating
thereof. The pigment surface may directly be the metal effect
pigment surface. The pigment surface may, however, also be the
metal effect pigment surface coated with an inorganic or organic
coating, preferably with synthetic resin. In this way, the coating
materials can be anchored to the metal effect pigments reliably and
to a sufficient degree.
[0068] These functional groups for adhesion or attachment to the
coated or uncoated metal effect pigment surface are, for example,
phosphonic ester, phosphoric ester, carboxylate, metallic ester,
alkoxysilyl, silanol, sulfonate, hydroxyl, polyol groups, and
mixtures thereof. Particular preference is given to the alkoxysilyl
and/or silanol groups of suitable organofunctional silanes.
[0069] Such functionalized coating materials contribute to the
corrosion stability of the metal effect pigments in the aqueous
electrocoat material. For example, in the case of iron or aluminum
pigments, gassing, i.e. evolution of hydrogen, can surprisingly be
suppressed effectively.
[0070] It has been found to be essential that the coating material
must necessarily have at least one protonatable or positively
charged amino-functional group and at least one functional group
for adhesion or attachment to the pigment surface. For example,
aliphatic amines which lack the at least one functional group for
adhesion or attachment to the pigment surface are unsuitable for
providing metal effect pigments which are effectively cathodically
depositable in a cathodic electrocoat material system.
[0071] In the inventive electrocoat material pigments, preference
is given to using, as coating materials, amines which can be
protonated to ammonium salts. Particularly preferred coating
materials comprise amino-functional silanes of the formula
R.sup.1.sub.aR.sup.2.sub.bSi(OR').sub.(4-a-b) (I)
where R.sup.1 is an organofunctional group which contains at least
one amino-functional group, R.sup.2 is a further organofunctional
group which does not contain an amino-functional group, R' is
independently H or an alkyl group having 1 to 6 carbon atoms,
preferably having 1 to 3 carbon atoms, and where a and b are
integers, with the proviso that a may be 1 to 3 and b may be 0 to
3, where a and b in total are not more than 3. R' is preferably
ethyl or methyl. R.sup.2 is preferably substituted or unsubstituted
alkyl having preferably 1 to 6 carbon atoms, for example methyl or
ethyl. In addition, R.sup.2 may be substituted by functional
groups, for example acrylate, methacrylate, vinyl, isocyanato,
hydroxyl, carboxyl, thiol, cyano, epoxy or ureido groups.
[0072] In a preferred embodiment, b=0. In a particularly preferred
embodiment, a=1 and b=0.
[0073] The at least one protonatable or positively charged
amino-functional group which contains R.sup.1 is preferably a
primary, secondary, tertiary amine or an ammonium group. The
amino-functional group is preferably as defined above.
[0074] Such silanes are commercially available. For example, these
are many representatives of the products which are produced by
Degussa, Rheinfelden, Germany and are sold under the trade name
Dynasylan.RTM., or the Silquest.RTM. silanes produced by OSi
Specialties, or the GENOSIL.RTM. silanes produced by Wacker,
Burghausen, Germany.
[0075] Examples thereof are
N-benzyl-N-aminoethyl-3-aminopropyltrimethoxysilane (Dynasylan
1161), N-vinylbenzyl-N-(2-aminoethyl)-3-aminopropylpolysiloxane
(Dynasylan 1172),
N-vinylbenzyl-N-(aminoethyl)-3-aminopropylpolysiloxane (Dynasylan
1175), aminopropyltrimethoxysilane (Dynasylan AMMO; Silquest
A-1110), aminopropyltriethoxysilane (Dynasylan AMEO) or
N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (Dynasylan DAMO,
Silquest A-1120) or N-(2-aminoethyl)-3-aminopropyltriethoxysilane,
triamino-functional trimethoxysilane (Silquest A-1130),
bis-(gamma-trimethoxysilylpropyl)amine (Silquest A-1170),
N-ethyl-gamma-aminoisobutyltrimethoxysilane (Silquest A-link 15),
N-phenyl-gamma-aminopropyltrimethoxysilane (Silquest Y-9669),
4-amino-3,3-dimethylbutyltrimethoxy-silane (Silquest Y-11637),
N-cyclohexylaminomethyl-methyldiethoxysilane (GENIOSIL XL 924),
(N-cyclohexylaminomethyl) triethoxysilane (GENIOSIL XL 926),
(N-phenylaminomethyl)trimethoxysilane (GENIOSIL XL 973),
aminopropyldimethylethoxysilane, aminopropylmethyldiethoxysilane,
N-methylaminopropyl-dimethylethoxysilane,
N-methylaminopropylmethyl-diethoxysilane,
N-methylaminopropyltriethoxysilane,
N-ethylaminopropyldimethylethoxysilane,
N-ethylamino-propylmethyldiethoxysilane,
N-ethylaminopropyl-triethoxysilane,
N-cyclohexylaminopropyltriethoxy-silane,
N-cyclohexylaminopropylmethyldiethoxysilane,
N-phenylaminotriethoxysilane, N-phenylaminopropyl-triethoxysilane,
N,N-dimethylaminopropyldimethylethoxy-silane,
N,N-dimethylaminopropylmethyldiethoxysilane,
N,N-dimethylaminopropyltriethoxysilane,
N,N-diethyl-aminopropyldimethylethoxysilane,
N,N-diethylamino-propylmethyldiethoxysilane,
N,N-diethylaminopropyl-triethoxysilane,
N,N-dipropylaminopropyldimethyl-ethoxysilane,
N,N-dipropylaminopropylmethyl-triethoxysilane,
N,N-dipropylaminopropyltriethoxy-silane,
N,N-methylethylaminopropyldimethylethoxysilane,
N,N-methylethylaminopropylmethyldiethoxysilane,
N,N-methylethylaminopropyltriethoxysilane,
anilinopropyldimethylethoxysilane,
anilinopropylmethyldiethoxysilane, anilinopropyltriethoxysilane,
morpholinopropyldimethyl-ethoxysilane,
morpholinopropylmethyldiethoxysilane,
morpholinopropyltriethoxysilane,
N,N,N-trimethyl-ammoniumpropyldimethylethoxysilane,
N,N,N-trimethylammoniumpropylmethyldiethoxysilane,
N,N,N-trimethylammoniumpropyltriethoxysilane,
N,N,N-triethyl-ammoniumpropyldimethylethoxysilane,
N,N,N-triethylammoniumpropylmethyldiethoxysilane,
N,N,N-triethylammoniumpropyltriethoxysilane,
trimethoxysilylpropyl-substituted polyethyleneimine,
dimethoxymethylsilylpropyl-substituted polyethyleneimine and
mixtures thereof.
[0076] The coating materials with protonatable or positively
charged amino-functional group are preferably used in amounts of 1
to 100% by weight based on the weight of the uncoated metal effect
pigment. Below 1% by weight, the effect may be too minor, such that
the metal effect pigments can no longer be deposited reliably,
especially after more than 60 days of bath time. Above 100% by
weight, an unnecessarily large amount of coating material with
amino-functional group is used. In addition, excess coating
material with an amino-functional group can adversely affect the
properties of the electrocoat material. The coating material(s)
with an amino-functional group are preferably used in amounts of 5
to 70% by weight and especially preferably of 7 to 50% by weight,
more preferably of 10 to 30% by weight, based in each case on the
weight of the metal effect pigment uncoated with coating material.
These figures are based in each case on the coating material itself
and not on any solvent which is possibly present and in which the
coating material with an amino-functional group is supplied in its
commercially available administration form.
[0077] The coating material may, but need not, completely surround
the metal effect pigments.
[0078] A process for providing the inventive metal effect pigments
comprises the coverage of the metal effect pigment with the coating
material with an amino-functional group. It comprises the following
steps: [0079] (a) coating a metal effect pigment with the coating
material having an amino-functional group dissolved or dispersed in
a solvent, said amino-functional group being protonatable or
positively charged, [0080] (b) optionally drying the metal effect
pigments coated with the coating material in step (a), [0081] (c)
optionally converting the metal effect pigments dried in step (b)
to a paste.
[0082] The coverage can take place in many different ways. The
metal effect pigment can be initially charged, for example, in a
mixer or kneader in the form of a paste, for example in an organic
solvent or in a mixture of organic solvent and water. Subsequently,
the coating material with a protonatable or positively charged
amino-functional group is added and allowed to act on the metal
effect pigment preferably for at least 5 min. The coating material
is preferably added in the form of a solution or dispersion. This
may be an aqueous solution or a predominantly organic solution.
[0083] In addition, the metal effect pigment can first be dispersed
in a solvent. The coating material is then added thereto with
stirring. In this case, the solvent in which the coating material
is dissolved should preferably be miscible with that in which the
metal effect pigment is dispersed. If required, higher temperatures
up to the boiling point of the solvent or of the solvent mixture
can be established, but room temperature is usually sufficient to
apply the coating material effectively to the metal effect
pigment.
[0084] Thereafter, the pigment is freed from the solvent and either
dried to give the powder and/or optionally converted to a paste in
another solvent. Useful solvents include water, alcohols, for
example ethanol, isopropanol, n-butanol, or glycols, for example
butylglycol. The solvent should be miscible with water. The
inventive pigment is traded as a paste or powder. The pastes have a
nonvolatile component of 30 to 70% by weight based on the weight of
the overall paste. The paste preferably has a nonvolatile component
of 40 to 60% by weight and more preferably of 45 to 55% by
weight.
[0085] The paste form is a preferably dust-free and homogeneous
preparation form of the inventive electrocoat material pigments.
The inventive electrocoat material pigments may also be present in
dust-free and homogeneous form as pellets, sausages, tablets,
briquettes or granules. The aforementioned preparation forms can be
produced in the manner known to those skilled in the art by
pelletization, extrusion, tabletting, briquetting or granulation.
In these compacted preparation forms, the solvent has substantially
been removed. The residual solvent content is typically within a
range of less than 15% by weight, preferably less than 10% by
weight, more preferably between 0.5 and 5% by weight, based in each
case on the weight of the pigment preparation.
[0086] The coating material with a protonatable or positively
charged amino-functional group may, before the coating of the metal
effect pigment, be present in a neutralized or partly neutralized
form. However, it can also be neutralized after the coating
operation. The neutralization/partial neutralization can also not
be effected until the pH adjustment of the electrocoat
material.
[0087] Customary acids are suitable for neutralization of the basic
functionalities. Examples thereof are: formic acid, acetic acid,
hydrochloric acid, sulfuric acid or nitric acid, or mixtures of
these acids. A sufficient amount of acid should be used that at
least 25%, preferably 40%, of the basic groups of the metal effect
pigment covered with the coating material are present in neutral
form. In this context, basic groups also include functional groups
which may originate from the metal effect pigment itself.
[0088] It is also possible to combine steps (a) and (b) of the
process according to the invention to one step, by applying the
coating material as a solution or dispersion to metal effect
pigments moving in a gas stream.
[0089] In a particular embodiment, the inventive electrocoat
material pigments can be produced by a process with the following
steps: [0090] a) producing a solution or dispersion of the coating
material with protonatable or positively charged amino-functional
group in an organic solvent, [0091] b) coating the metal effect
pigment with the coating material by [0092] i) dispersing the metal
effect pigment in the solution or dispersion of a) and then
spraying or [0093] ii) spraying the solution or dispersion from a)
onto metal effect pigments fluidized in a gas stream, [0094] c)
optionally drying the metal effect pigments coated with binder in a
moving gas stream, [0095] d) optionally converting the pigment to
paste in water and/or an organic solvent, [0096] e) optionally
neutralizing with an acid.
[0097] The pigments can be neutralized and converted to paste as
described above.
[0098] Preference is given to combining steps b) and c) in one
process step, by performing the spraying and drying in a spray
drier.
[0099] Preference is given to using volatile solvents, for example
acetone and/or ethyl acetate.
[0100] The inventive electrocoat material pigments are used in
cathodic electrocoat materials or in cathodic electrocoating.
[0101] The invention further provides a cathodic electrocoat
material comprising the inventive electrocoat material pigments, a
binder and water. The binders are, for example, polymerization,
polyaddition or polycondensation products containing primary or
tertiary amino groups, for example amino epoxy resins, amino
poly(meth)acrylate resins or amino polyurethane resins. In
addition, further customary additions such as fillers, additives,
organic and/or inorganic color pigments, etc. may be present in the
electrocoat material.
[0102] By means of acids, the amino groups of the binders and
preferably the amino groups of the coating material of the
inventive electrocoat material pigments are at least partly
protonated. This has the effect that the binders and the inventive
electrocoat material pigments move toward the cathode in the
applied electrical field and take part in the deposition mechanism
of the cathodic electrocoating. The coatings obtained in this way
have an attractive metal effect which has been unknown to date in
cathodic electrocoat material and are exceptionally
abrasion-stable.
[0103] The inventive electrocoat material pigments can optionally
also be neutralized as early as after the coating with coating
material.
[0104] The examples which follow illustrate the invention in
detail, but without restricting it.
INVENTIVE EXAMPLE 1
[0105] 46.5 g of PCA 9155 (aluminum pigment coated with organic
polymers, with D.sub.50=18 .mu.m; from Eckart GmbH & Co. KG,
Furth, Germany) are mixed with a solution of 7 g of Dynasylan 1161
(N-benzyl-N-aminoethyl-3-aminopropyltrimethoxysilane from Degussa,
Germany) in 46.5 g of butylglycol to give a homogeneous pigment
paste.
INVENTIVE EXAMPLE 2
[0106] 46.5 g of PCA 9155 (aluminum pigment coated with organic
polymers, with D.sub.50=18 .mu.m; from Eckart GmbH & Co. KG,
Furth, Germany) are mixed with a solution of 7 g of Dynasylan 1172
(N-vinylbenzyl-N-(2-aminoethyl)-3-aminopropylpolysiloxane from
Degussa, Germany) in 46.5 g of butylglycol to give a homogeneous
pigment paste.
[0107] The paste is dried cautiously in a vacuum drying cabinet at
approx. 60.degree. C. to give the powder.
INVENTIVE EXAMPLE 3
[0108] 46.5 g of PCA 9155 (aluminum pigment coated with organic
polymers, with D.sub.50=18 .mu.m; from Eckart GmbH & Co. KG,
Furth, Germany) are mixed with a solution of 7 g of Dynasylan 1175
(N-vinylbenzyl-N-(aminoethyl)-3-aminopropylpolysiloxane from
Degussa, Germany) in 46.5 g of butylglycol to give a homogeneous
pigment paste.
INVENTIVE EXAMPLE 4
[0109] The preparation is effected as in Example 3, but with an
aluminum effect pigment of greater particle size D.sub.50=32 .mu.m,
PCA 214 (from Eckart GmbH & Co. KG).
Production of the Electrocoat Materials and Testing Thereof:
[0110] 27 g of the pastes from Examples 1, 3 or 4 are admixed with
27 g of butylglycol.
[0111] 15 g of the powder from Example 2 are admixed with 39 g of
butylglycol.
[0112] 10 g of VEK 40871-02 CEC binder (800 by weight epoxy resin
from Cytech, Austria) and 1.5 g of wetting agent (from FreiLacke,
Braunlingen, Germany), 465 g of VEK 40871-0-03 CEC binder (34.5% by
weight epoxy resin from Cytech, Austria) and 662 g of water are
added.
[0113] The dip-coating materials produced according to this
formulation for cathodic dip-coating feature a viscosity of 9.+-.1
seconds, measured at a temperature of 20.degree. C. in a DIN 4
flowcup. The electrocoat materials possess a solids content of 13
to 17% by weight based on the weight of the overall electrocoat
material. The proportion of the aluminum pigments is approx. 1% by
weight. The measured pH of the electrocoating baths at 25.degree.
C. is a pH of about 5.5 to 6.5.
COMPARATIVE EXAMPLE 1
[0114] PCA 9155 (from Eckart GmbH & Co. KG), a synthetic
resin-coated aluminum effect pigment of mean particle size
D.sub.50=18 .mu.m in paste form (solids 50% by weight) is used in
the electrocoat material without further coating. In contrast to
inventive example 1, 7 g of Dynasylan 1161 coating material are
introduced here into the electrocoating bath only on addition of
the commercial cathodic dip-coating material (from Frei Lacke).
COMPARATIVE EXAMPLE 2
[0115] PCA 9155 (from Eckart GmbH & Co. KG), a synthetic
resin-coated aluminum effect pigment of mean particle size
D.sub.50=18 .mu.m in paste form (solids 50% by weight) without
further coating.
[0116] Here, no further additive (coating material) is added to the
dip-coating material.
[0117] The electrochemical deposition operation is effected in an
electrically conductive vessel, a so-called tank, which consists of
an electrically conductive material and is connected as the anode
in the circuit. The workpiece to be coated, in the inventive
example a metal sheet of dimensions 7.5 cm.times.15.5 cm is
connected as the cathode and immersed into the electrocoating bath
for 2/3 of its length.
[0118] In order to prevent sedimentation and the formation of dead
spaces, the electrocoat material is moved with a mean flow rate of
approx. 0.1 m/s. Subsequently, a voltage of 100 V is applied over a
period of 120 seconds. The temperature of the electrocoating bath
is 30.degree. C. The workpiece thus coated is subsequently rinsed
off thoroughly with distilled water in order to remove residues of
uncoagulated resin. The workpiece is then left to vent for a period
of 10 minutes. Subsequently, the electrocoat material is
crosslinked and fired at 170.degree. C. for 20 minutes. The coating
layer thickness thus achieved is 30.+-.2 .mu.m.
[0119] The cathodic electrocoat materials produced with the
pigments from inventive examples 1 to 4 have an exceptionally high
storage and deposition stability in relation to the aluminum effect
pigments present therein. This is evident from Table 1. The coating
materials were stored at room temperature and, within a time
interval of 7 days, metal sheets as described above were
electrocoated. These tests were stopped after 60 days.
[0120] In addition, samples of inventive examples 1 to 4 were
stored at 40.degree. C. for 30 days. Subsequently, they were
incorporated into an electrocoating material as described above,
and metal sheets were electrocoated. With regard to the optical
properties of these applications, no difference from applications
with freshly produced samples were found.
[0121] Gassing tests were carried out with the electrocoat
materials produced using the pigments from inventive examples 1 to
4 and comparative examples 1 and 2. For this purpose, 250 g of the
electrocoat materials were heat treated at 40.degree. C. in a gas
bottle with a double chamber tube attachment, and the amount of gas
evolved (H.sub.2, which is formed by the reaction of the aluminum
effect pigments with water) is measured. The test is considered to
be passed when not more than 20 ml of hydrogen have evolved after
30 days.
[0122] The test results are compiled in Table 1.
TABLE-US-00001 TABLE 1 Performance of the cathodic dip-coating
materials which have been produced using the pigments from examples
1 to 4 and comparative examples 1 and 2. Deposition Gassing after
stability 30 days Sample (in d) (ml of H.sub.2) Example 1 >60 d
12 Example 2 >60 d 5 Example 3 >60 d 10 Example 4 >60 d 6
Comparative example 1 <7 d 12 Comparative example 2 <7 d
After 10 days >25 ml
[0123] For the electrocoat materials comprising pigments of
inventive examples 1 to 4, reproducible results with regard to the
visual appearance of the coated test sheets were obtained even
after more than 60 days of storage time at room temperature.
Moreover, they did not exhibit any significant gassing in the
aqueous electrocoat materials.
[0124] The electrocoat material comprising pigments of comparative
example 1 was likewise gassing-stable, but had virtually no
deposition stability. The aluminum effect pigments not provided
with a coating of comparative example 2 are neither gassing-stable
in the electrocoat material nor do they possess sufficient
deposition stability.
COMPARATIVE EXAMPLE 3
Metal Effect Pigment-Containing Powder Coating Material
[0125] 9 g of a commercial metal effect pigment for powder coating
material, Spezial PCA 214, d50=32 .mu.m (from Eckart GmbH & Co.
KG), are mixed intimately in a plastic bag with 291 g of a powder
clearcoat material, AL 96 Polyester PT 910 System (from DuPont) and
0.6 g of a "free-flow additive", Acematt OK 412 (from Degussa). The
contents are subsequently transferred directly into a mixing vessel
which approximates to a commercial kitchen mixer in terms of
construction and form (Thermomix from Vorwerk), and mixed at a
moderate stirrer speed level at 25.degree. C. for 4 minutes. This
procedure corresponds to the "dry-blend method" common in powder
coating materials. The powder coating material thus produced is
applied by means of the customary corona discharge technique (GEMA
electrostatic spray gun PG 1-B) to a customary test sheet ("Q
panel"). The application conditions of the powder coating technique
applied here corresponds to the following: powder hose connection:
2 bar; purge air connection: 1.3 bar; voltage: 60 kV; material flow
regulator: approx. 500; gun-sheet distance: approx. 30 cm.
[0126] This is followed by the firing and the crosslinking of the
powder coating material system in an oven. The firing time is 10
minutes at a temperature of 200.degree. C. The dry layer thickness
to be achieved in this process is 50-75 .mu.m.
COMPARATIVE EXAMPLE 4
Metal Effect Pigment-Containing Powder Coating Material
[0127] As comparative example 3, except that the metal effect
pigment used was Spezial PCA 9155, d50=16 .mu.m (from Eckart GmbH
& Co. KG).
[0128] The different applications in inventive examples 1 to 4 were
compared with the substrates of comparative examples 3 and 4 coated
by powder coating technology. For comparative assessment, as is
evident from inventive examples 1 to 4 and comparative examples 3
and 4, aluminum effect pigments of similar particle size and
coloristic properties were used.
[0129] Surprisingly, the applications in inventive examples 1 to 4
exhibit excellent covering capacity, which corresponds in terms of
goodness and quality to the powder coating material of comparative
examples 3 and 4.
[0130] The optical properties are compared via the visual
impression of the observer. It is found here that, surprisingly,
inventive examples 1 to 4 have no significant differences with
regard to brightness and metallic effect from the conventional
powder coating material application in comparative examples 3 and
4.
[0131] For the assessment of the optical properties, reference is
made to DIN 53230. In the testing of paints, coating materials and
similar coatings, the properties and/or changes therein often have
to be assessed subjectively. For this case, DIN 53 230 lays down a
homogeneous assessment system. This describes how test results
which cannot be reported by means of directly obtained measurements
should be assessed.
[0132] To assess the coating materials which have been obtained
with pigments according to inventive examples 1 to 4 and
comparative examples 1 to 4, reference is made to the "fixed rating
scale" explained under 2.1 in DIN 53 230. This fixed rating scale
constitutes a scale for assessing the degree of properties. In
this, the best possible value is designated with the index 0, the
lowest possible value with the index 5, the term "lowest possible
value" being understood to mean that a change or deterioration over
and above this value is no longer of interest in performance terms.
Tab. 2 reproduces the coloristic and optical properties determined
in relation to DIN 53 230 section 2.1. The indices are determined
by the subjective impression of several test subjects. In all
cases, an agreement of the subjective impression of the assessing
test subjects could be found.
TABLE-US-00002 TABLE 2 Visual comparison of the electrocoat
material applications of the pigments of inventive examples 1 to 4,
of comparative examples 1 to 2 and of the powder coating material
applications of comparative examples 3 and 4 Mean particle Covering
size D.sub.50 capacity Brightness General visual Sample [.mu.m]
[index] [index] impression Inventive 18 0 1 Very metallic, example
1 relatively minor "sparkling" effect Inventive 18 0 1 Very
metallic, example 2 relatively minor "sparkling" effect Inventive
18 0 1 Very metallic, example 3 relatively minor "sparkling" effect
Inventive 32 1 0 Very good metallic, example 4 "sparkling" effect
Comparative 18 3 3 Relatively minor example 1 metallic effect as a
result of lack of covering capacity Comparative 18 5 5 Virtually no
metal example 2 effect pigment deposited Comparative 32 0 1 Very
good metallic, example 3 "sparkling" effect Comparative 16 0 0 Very
metallic, example 4 relatively minor "sparkling" effect
[0133] It can be seen from the comparison displayed above that the
applications with the inventive electrocoat material pigments and
pigment preparations according to examples 1 to 4 are comparable
with regard to optical properties with the powder coating material
pigments and applications which have already been established on
the market for many years. From the comparison of the indices of
the electrocoatings which have been obtained using inventive
examples 1 to 4 with the powder coatings in comparative examples 3
and 4 shows clearly that the optical properties are virtually
identical to one another in relation to coverage, shine and
metallic effect.
[0134] The coatings in comparative example 1, in which the coating
material was only introduced directly into the electrocoat material
production in the last step thereof, have deviations. In these
variants, significant losses are found with regard to coverage,
shine and, associated with these, in the metallic effect.
[0135] A metal effect pigment treated without coating material
(comparative example 2) virtually cannot be deposited in the
cathodic electrocoat material or in the electrocoating, even though
the metal effect pigment has a synthetic resin shell.
[0136] It is suspected that it is necessary that the coating
material with protonatable or positively charged amino-functional
group has to be applied directly to the metal effect pigment and
cannot be added later to the electrocoat material. It is further
suspected that the coating material with its functional groups for
adhesion or attachment forms a physisorptive and/or chemisorptive
adhesion or attachment to the pigment surface, which then appears
to play a crucial key role in the deposition performance of the
pigment.
* * * * *