Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
21684~
PAT 93 376
~ L ~ L . ~
09.08.1993 ~ tr~
BASF Lacke + Farben Aktiengesellschaft, ~unst-r
Coating composition comprt~ing at lea~t on~ polyester
which contains hydroxyl y~ r ~ 8 for ~ts
preparation, and its u~e a~ h~ oat and in proce~ses
for th- product~on of a multicoat protoctive and/or
decorative coat$ng
The present invention relates to a coating composition,
in particular a basecoat, comprising at least one
polyester which contains hydroxyl groups.
The present invention also relates to a proce~s for the
preparation of the coating compositions and to pro-
cesses for the production of a multicoat protective
and/or decorative coating on a substrate ~urface.
Finally, the invention alfio relates to the use of the
coating compositions as ba~ecoat and to the use of the
coating compositions in the refinishing of, in
particular, motor vehicle bodies.
Especially in the finishing of motor vehicles, but also
in other sectors where coatings which combine a good
decorative effect with good protection against
corrosion are desired, it is known to provide sub-
strates with a plurality of ~uperposed coats. In this
context, great importance has become attached to multi-
coat finishes in which the substrate is first coated
5 ~
with a pigmented basecoat and subsequently a clearcoatis applied.
The preferred procedure here is the so-called wet-on-
wet method, in which the basecoat is flashed off
briefly without a hAki ng step, then the clearcoat i8
applied, and subsequently basecoat and clearcoat are
cured together.
In the basecoat it i8 common to use metallic pigments
which lead to the so-called metallic fini~hes. In order
to achieve a good metallic effect it is of paramount
importance to ensure a good disposition and fixing of
the metallic pigments in the paint film. For this
purpose it is necessary for the incipient dissolution
undergone by the basecoat when the clearcoat is applied
to the predried but not cured basecoat film to be very
slight, or in some cases even nonexistent. On the other
hand, a certain degree of incipient dissolution of the
basecoat when the clearcoat i~ applied is wholly
desirable, for reason~ of adhesion between ba~ecoat and
clearcoat.
For the production of the multicoat coatings, both con-
ventional (i.e. solvent-containing) basecoats and
clearcoats and water-dilutable systems are employed.
For example, DE-A-40 24 204 and the International
Patent Application bearing the Publication
2~ 6~5~
No. WO 88/02010 disclose multicoat coatings in which
the conventional basecoat used is based on polyester
resin, melamine resin, cellulose acetobutyrate and
aluminum flakes. However, more detailed information on
the polye~ter resin used and the type of cellulose
acetobutyrate are contained in neither of the two
documents.
In addition, DE-C-28 18 093 discloses multicoat
coatings in which the ba~ecoat used is based on a
polyester resin as film-forminq component, but in which
no information is present on the molecular weight of
the polyester in DE-C-28 18 093. As a component essen-
tial to the invention, these basecoats described in
DE-C-28 18 093 comprise polymer microparticles. These
polymer microparticles are intended to lead to an
improvement in the spray properties of the basecoat6.
The object of the present invention is therefore to
provide coating compositions, especially basecoats,
which have properties which are improved with respect
to the known coating compositions. In particular, the
coating compositions, when used as basecoats, should
ensure both a good metallic effect of the multicoat
finish and good adhesion to the clearcoat disposed on
the basecoat. Furthermore, the coating compositions
should cure at room temperature or slightly elevated
temperature, so that they can be employed in automotive
refinishing. They should also fulfill the requirements
- 2 16~5 1
which are commonly placed on a basecoat. The coating
compositions should therefore, for example, dry
rapidly, be stable on storage and ~Yhihit over-
coatability, good flop (a good metallic effect) and
good adhesion to the clearcoat.
This object is surprisingly achieved by a coating com-
po~ition, especially a basecoat, compri~ing at least
one polyester which contains hydroxyl group~, the ~aid
coating composition being characterized in that
1. the hydroxyl group-contA i n i~g polyester has a
weight-average molecular weight Mw of
40,000-200,000 and a polydisper~ity Mw/Mn > 8, and
2. at least 50% by weight of aromatic dicarboxylic
acids or their esterifiable derivatives have been
employed for the preparation of the polye~ter, but
with the maximum content of phthalic anhydride
being 80~ by weight and the percentages by weight
being based in each ca~e on the overall weight of
the acid components employed for the preparation
of the polyester.
The present invention also relates to a process for the
preparation of these coating compositions.
In addition, the present invention also relates to a
process for the production of a multicoat protective
and/or decorative coating on a substrate surface, in
84~1
which
1. a basecoat i~ applied,
2. from the composition applied in step (1) a polymer
film i8 formed on the surface
3. a transparent topcoat iB applied to the resulting
basecoat, and
4. the topcoat i~ cured together with the basecoat,
which proces~ iB characterized in that the ba~ecoat
employed in step (1) is the coating composition accor-
ding to the invention.
Finally, the pre6ent invention also relates to the use
of the coating compofiitions a~ ba~ecoat and to the use
of the coating compositions for refinishing, in
particular for the refinishing of motor vehicle bodie~.
It is surprising and was not foreseeable that the
coating compositions obtained with the polyesters u~ed
in accordance with the invention ensure both a good
metallic effect of the multicoat fini~h and good
adhesion to the clearcoat which is disposed on the
basecoat. Moreover, the coating composition~ have the
advantage that they cure at room temperature or
slightly elevated temperature and can thus be employed
in automotive refinishing. A further advantage is that
- 21684S~
the coating composition~ according to the invention
fulfill the re~uirements conventionally placed on a
basecoat. For example, the coating composition~ dry
rapidly, are stable on ~torage and exhibit over-
coatability, good flop and good adhe~ion to theclearcoat. Furthermore, they display good color
uniformity even when mixed with basecoats based on
other polyesters having different molecular weights and
degrees of branching.
In the text below, then, the individual components of
the coating composition according to the invention are
described in more detail.
It iB essential to the invention that the coating
compositions comprise as binder a hydroxyl y~u~
containing polyester having a weight-average molecular
weight of 40,000-200,000, preferably from 50,000 to
120,000, and a polydispersity (the polydispersity is
defined as the quotient of the weight-average molecular
weight Mw and the number-average molecular weight Mn)
of ~ 8, preferably > 8 to 200 and particularly
preferably from 10 to 100. The weight-average and the
number-average molecular weight in this context are
determined by gel permeation chromatography against a
polystyrene standard.
The hydroxyl group-cont~;ni ng polyesters preferably
have OH nl~mher~ of 20-150 mg of KOHtg, preferably
- 216~
60-110 mg of KO~/g. Moreover, these polyesters pre-
ferably have acid numbers of 5-20 mg of KOH/g,
particularly preferably 10-15 mg of KO~/g, and/or amine
numbers of 0-40 mg of KOH/g.
Also essential to the invention is that, for the pre-
paration of these hydroxyl group-cont~i n; ng polyesters,
at least 50~ by weight of aromatic dicarboxylic acids
are employed, but with the maximu~ content of phthalic
anhydride being 80% by weight. It i6 further preferred
for less than 20% by weight of cycloaliphatic
dicar~oxylic acids to be employed. In this context the
percentages by weight are based in each case on the
overall weight of the acid components employed for the
preparation of the polyesters. It is only this combina-
tion of high weight-average molecular weight with broad
molecular weight distribution and the use of a minimum
proportion of aromatic dicarboxylic acids as structural
component that ensures that the coating compositions
have the good properties re~uired, and in particular
good adhesion coupled with a good metallic effect.
The polyester employed in accordance with the invention
are obtainable by reaction of
a) polycarboxylic acids or their esterifiable deriva-
tive~, together if de~ired with monocarboxylic
acids,
- ~168~51
b) polyols, together if desired with monools,
c) if desired, further modifying components, and
d) if desired, a component which is reactive with the
reaction product of a), b) and, if appropriate,
c ) .
It is essential to the invention that the acid com-
ponent (a) employed for the preparation of the
polye~ters comprises at least 50~ by weight of aromatic
dicarboxylic acids or their esterifiable derivatives,
based on the overall weight of the carboxylic acids
employed for the preparation of the polyesters.
Inasmuch as phthalic anhydride is employed for the
preparation of the polyesters, a maximum of 80% by
weight of the acid component may comprise phthalic
anhydride. Together with the aromatic dicarboxylic
acids up to 50% by weight of ~lirh~tic and/or
cycloaliphatic polycarboxylic acids may be employed. In
this context it is preferred to employ less than 20% by
weight, and particularly preferred to employ no
cycloaliphatic di- or polycarboxylic acid~.
Example~ of aromatic dicarboxylic acids which are
suitable for the preparation of the hydroxyl group-con-
taining polyesters according to the invention are
phthalic acid, isophthalic acid, terephthalic acid,
halophthalic acids such as tetrachloro- and
2`~ s ~-
tetrabromophthalic acid, and the like.
Examples of aliphatic dicarboxylic acids which are
suitable for the preparation of the hydroxyl group-con-
5 tA i n i~g polyesters according to the invention areadipic acid, glutaric acid, acelaic tsic] acid, sebacic
acid, fumaric acid, maleic acid, succinic acid, muconic
acid, itaconic acid and the like.
Other suitable compounds are the esterifiable deriva-
tives of the abovementioned polycarboxylic acid~, for
example their monoesters or multiple esters with
aliphatic alcohols having 1-4 carbon atoms or hydroxy
alcohols having 1-4 carbon atoms. Moreover, it i~ also
possible to employ the anhydrides of the acids men-
tioned above, provided they exist.
If desired, it is also possible - together with the
polycarboxylic acids - to employ monocarboxylic acids
such as, for example, benzoic acid, tert-butylbenzoic
acid, lauric acid, isononanoic acid and fatty acids of
naturally occurring oils. The preferred monocarboxylic
acid employed is isononanoic acid. The proportion of
monocarboxylic acids is advantageously less than 20% by
weight based on the overall weight of the carboxylic
acids employed for the preparation of the polyester~.
It is preferred for the component (a) which is employed
to comprise less than 20% by weight of and, in
- 216~4~ 1
-- 10 --
particular, no cycloaliphatic dicarboxylic acids, for
example tetrahydrophthalic acid, hexahydrophthalic
acid, cyclohexanedicarboxylic acids, 4-methylhexa-
hydrophthalic acid, endomethylenetetrahydrophthalic
acid, tricyclodecanedicarboxylic acid, endomethylene-
hexahydrophthalic acid, camphoric acid, cyclo-
hexanetetracarboxylic acid, cyclobutanetetracarboxylic
acid etc.
Alcohol component~ (b~ which are ~uitable for the
preparation of the polyester are polyhydric alcohols
such as ethylene glycol, propanediols, butanediols,
hexanediols, neopentyl glycol, diethylene glycol,
cyclohexanediol, cyclohexanedimethanol, trimethyl-
pentanediol, ethylbutylpropanediol, ditrimethylol-
propane, trimethylolethane, trimethylolpropane,
glycerol, pentaerythritol, dipentaerythritol,
trishydroxyethyl isocyanate, polyethylene glycol,
polypropylene glycol, together if desired with
monohydric alcohols such as, for example, butanol,
octanol, lauryl alcohol, and ethoxylated and/or
propyoxylated t 8iC ] phenol.
Compounds which are suitable as component (c) for the
preparation of the polyesters are in particular tho~e
which have a group which iB reactive toward the func-
tional groups of the polyester, with the exception of
the compounds stated as component (d). As modifying
component (c) it is preferred to use polyisocyanates
- 2 ~ 3~ 8 ~
and/or diepoxide compounds, and also, if desired,
monoisocyanates and/or monoepoxide compo~n~.
Examples of suitable polyisocyanates are tolylene
diisocyanates, hexamethylene diisocyanates and
isophorone diisocyanate. DiepoYi~e compounds are to be
understood as epoxy resins contA i ni ng on average
approximately 2 epoYi~e group~ per molecule. Examples
of suitable monoepoxide compound6 are olefin oxides,
such as octylene oxide, butyl glycidyl ether, allyl
glycidyl ether, phenyl glycidyl ether, p-butylphenol
glycidyl ether, cresyl glycidyl ether, styrene oxide,
glycidyl methacrylate, glycidylhexanevinyl monoxide,
dipentene monoxide, ~-pinene oxide and glycidyl esters
of tertiary carboxylic acids.
Suitable examples of component (d) for the preparation
of the polyesters are compounds which contain not only
a group which is reactive towards the functional groups
of the polyester but also a tertiary amino group.
As components ~d) which are reactive with the reaction
product of (a), (b) and, if appropriate, Ic), pre-
ference is given to the use of monoisocyanates con-
tA i n ing at least one tertiary amino group. These com-
pounds can be prepared, for example, by reactingsuitable diisocyanates, such as isophorone diiso-
cyanate, with amino alcohols cont~ining a tertiary
amino group, for example hydroxyethylpyridine or
dimethylaminoethanol, or with polyamines cont~ining at
- 2 ~ 4 j l
least one tertiary and at least one secondary or
primary amino group. The monoisocyanate~ are attached
to the binder ~y6tem by reaction with free hydroxyl
groups of the polyester, accompanied by the formation
of a urethane formation [8iC]- As component (d) it is
also possible to u~e polyamines contAin;ng at least one
tertiary and at least one primary or secondary amino
group. A corresponding example which may be mentioned
is dimethylaminopropylamine.
Apart from by the use of component (d) (polymer-analo-
gous reaction), the tertiary ~mino groups can also be
introduced into the polyester by using polycarboxylic
acids and/or polyo~s which contain amino groups.
As component (a), together with the polycarboxylic
acids, it is pos6ible to use aminocarboxylic acids con-
taining at least one tertiary amino group. Examples of
these are pyridine-2-carboxylic acid, pyridine-
3-carboxylic acid, pyridine-4-carboxylic acid and
pyridine-2,6-dicarboxylic acid. Moreover, it is
possible to u6e the reaction product of an amino
alcohol containing at lea~t one tertiary amino group
and a polycarboxylic anhydride, and the reaction pro-
duct of a polyamine containing at least one tertiaryand at least one primary or secondary amino group and a
polycarboxylic anhydride.
A8 alcohol component (b) it is possible to use amino
2 ~ S ~
alcohols contAining at least one tertiary amino group.
Examples of these are 2-hydroxyethylpyridine,
dimethylaminopropanol, methyldiethanolamine, methyl-
dipropanolamine and dihydroxyethylaniline.
As alcohol component (b) it is also possible to employ
reaction product~ of epoxy resins with carboxylic acids
and/or amines. Thus, the reaction product of low
molecular weight epoxy resins with polycarboxylic acids
and/or polycarboxylic anhydrides and aminocarboxylic
acid~ cont~ining at least one tertiary amino group can
be used as alcohol component (b), the product sub-
sequently, if desired, being esterified with the acid
component and the alcohol component and, if desired,
modified with polyisocyanates. Low molecular weight
epoxy resins are understood as epoxy resins having a
molecular weight of less than approximately 2000. When
epoxy resins are used, low-chlorine grades should be
employed, since otherwise severe di6coloration of the
products may occur.
The polyesters can be prepared by the known and conven-
tional methods as are described, for example, in
various stAn~rd works, for example
1. Temple C. Patton, Alkyd Resin Technology,
Interscience Publishers John Wiley & Sons, New
York, London 1962;
~6~5 1
- 14 -
2. Dr. Johanne~ Schreiber, Chemie und Technologie der
kunstlichen ~arze [Chemistry and Technology of
Synthetic Resins], Wissenschaftliche
Verlagsge~ellschaft mb~, Stuttgart, 1943
s
3. Hans Wagner und Hans-Friedrich Sarx,
Lackkunstharze tSynthetic Resin~ for Coatings],
4th edition, Karl-Hanser-Verlag, Mllnich~ 1959
0 4. Ullmanns Encyklopadie der Techni~-hen Chemie
[Ullmann's Encyclopedia of Industrial Chemistry~,
volume 14, pages ~0 to 106 (1963).
During the preparation of the polyester~ the water of
reaction which is liberated or the Al~nols which are
liberated are removed continuously. The esterification
is virtually quantitative and can be monitored by
deterr; ni ng the acid numbers and the O~ numbers. In
this reaction the molecular weight and the degree of
branching of the polyester can be regulated in a simple
manner, familiar to the person skilled in the art, via
the ratio in which the alcohol component~ (diol and
polyol) and the di- and/or polycarboxylic acids are
employed. For instance, the weight-average molecular
weight Mw and the polydispersity Mw/Mn of the polyester
is higher the closer the ratio of O~ to acid groups is
to 1 and the higher the degree of branching. This is
achieved by employing only a small excess of polyols
and by continuing the conden~ation to a high conversion
21684~l
- 15 -
of > 98~. The degree of branching is controlled by the
proportion of compounds of relatively high
functionality. The degree of branching, degree of con-
densation and molar ratios of the polyols must be care-
fully matched to one another to avoid gelation of thecondensation resin. The degree of branching of the
polyester is higher the higher the proportion of struc-
tural components having a functionality of 3 or more.
The smaller the degree of branching, the les6 the
degree to which shifts in color occur if the coating
compo~itions according to the invention are blended
with basecoats based on other polyesters having
different molecular weights and degrees of branching.
The degree of branching is preferably from 0.6 to 1.2
branches per 1000 g of polyester resin (solid).
In general the esterification conditions are selected
such that the reaction is as complete as possible. In
other words, reaction is continued until the desired
acid number~ have been reached.
This reaction is conventionally carried out at tempera-
tures of between 180 and 280C in the presence, if
desired, of an appropriate esterification catalyst such
as, for example, lithium octanoate, dibutyltin oxide,
dibutyltin dilaurate, p-toluenesulfonic acid and the
like.
Conventionally, the preparation of the polye~ters is
2~ ~4~1
- 16 -
carried out in the presence of small amounts of a
suitable solvent as entraining agent. Examples of
entraining agents employed are aromatic hydrocarbons
such as, in particular, xylene, and cycloaliphatic
hydrocarbons, for example cyclohexane.
If the reaction is carried out in the presence of an
esterification catalyst, the latter is conventionally
employed in a quantity of from 0.01 to 0.5% by weight,
based on the solids content of polyester re6in solution
and on the solids content of the cataly~t solution.
The coating composition~ according to the invention
generally contain up to 20% by weight, preferably from
6 to 9% by weight, based in each case on the overall
weight of the coating composition and on the solids
content of the polyester re6in solution, of the
hydroxyl group-containing polyester.
As further component, the coating composition6 accor-
ding to the invention preferably contain at least one
cellulo~e ester, preferably in quantities of 10-40~ by
weight, particularly preferably from 15 to 30% by
weight, ba~ed in each case on the content of film-
forming solids and on the solid6 content of thecellulose eater solution. Example6 of 6uitable
cellulose ester6 are cellulo6e nitrate, cellulose
propionate, cellulo6e butyrate, cellulose aceto-
butyrate, cellulose acetopropionate, mixture6 thereof
~. 6~ 15 ~
- 17 -
and the like. Cellulose acetobutyrate i8 preferably
employed.
Especially if the coating compo~itions according to the
invention are employed as metallic baQecoat, it is pre-
ferred to employ a cellulose ester having a content of
acetyl groups of 12-16% by weight, a content of buturyl
~sic] groups of 35-43% by weight and a content of
hydroxyl groups of 1-2.5% by weight, and a weight-
average molecular weight of 100,000-250,000 (number-
average molecular weight 35,000-65,000). In the
following text this cellulose acetobutyrate is called
CABl for short.
If desired, another cellulo~e acetobutyrate - called
CAB2 for short below - can al~o be employed for the
preparation of metallic basecoat~. Thi~ CAB2 has a con-
tent of acetyl groups of 1-5% by weight, a content of
buturyl [8iC] group~ of 4~-52% by weight, a content of
hydroxyl groups of 1-2.5~ by weight and a weight-
average molecular weight of 100,000 to 250,000. For the
preparation of the metallic basecoats it is pos~ible to
employ mixtures of CAB1 and CAB2 in which the content
of CAB1 is preferably at least 60% by weight based on
the overall content of CABs. For the preparation of
pigmented solid-color basecoats it is likewise pre-
ferred to employ the CAB1 type or a mixture of CABl and
CAB2 as cellulose esters. However, besides this it is
al80 possible to use CAB2 alone.
Moreover, the coating compositions according to the
4~ ~
- 18 -
invention conventionally contain 60-90~ by weight,
preferably 70-85~ by weight, based in each case on the
overall weight of the coating composition, of at least
one solvent.
Examples of ~uitable solvent~ are the solvents already
mentioned for the preparation of the polyesters, and
also ketones ~uch as acetone, methyl isobutyl ketone
and the like.
The solvents preferably employed are esters, for
example butyl acetate, l-methoxypropyl acetate,
ethylene glycol diacetate, 2-ethoxyethyl acetate,
butylglycol acetate, ethyldiglycol acetate and the
like. Also suitable are aromatic compounds with
relatively high degrees of substitution, for example
Solvent Naphtha~, heavy benzole, various Solvesso~
grades, variou~ Shellsol~ grades and Dea~ol~, and
higher-boiling aliphatic and cycloaliphatic
hydrocarbons, for example various white spirits,
mineral turpentine oil, tetralin, decalin, Depanol and
the like.
The criteria for the selection of the solvent are,
among other desired properties, that it should not
react with the film-forming material and that it can be
easily removed in the application and curing procedure.
The quantity of ~olvent i~ controlled such that the
coating composition i~ rendered able to close the
coating, or to let it flow, to give a smooth ~urface,
8 ~ ~ ~
-- 19 --
thus en~uring an acceptable application. In spray
application methods involving viscosity, the
consistency of the coatings is controlled by the
addition of a sufficient quantity of solvent such that
the composition can be handled and can be applied to
form an appropriate coating without the deficiencies
which are known to occur in the spray method.
If desired, the coating compositions may also contain a
crosslinking agent which is reactive toward the
hydroxyl groups of the polyester. However, the formula-
tion of physically drying coating compositions, i.e.
coating compositions free from crosslin~inq agent, is
also possible. Should the coating compositions contain
a crosslinking agent, it is conventionally employed in
quantities of from 5 to 20% by weight based on the
overall weight of the coating composition.
Examples of crosslinking agent~ which can be employed
are polyisocyanates, for example aromatic isocyanates
such as 2,4- and 2,6-tolylene diisocynate and mixtures
thereof, 4,4'-diphenylmethane diisocyanate,
m-phenylene, p-phenylene, 4,4-diphenyl, 1,5-naph-
thalene, 1,4-naphthalene, 4,4-toluidine and xylylene
dii~ocyanate and substituted aromatic systems such as
dianisidine diisocyanates, 4,4 diphenyl ether
diisocyanates or chlorodiphenylene diisocyanates and
aromatic isocyanates of higher functionality, for
exsmple 1, 3, 5-trii~ocyanatobenzene [~ic],
~ :~ 6 ~
- 20 -
4,4',4''-triisocyanatotriphenylmethane, 2,4,6-tri-
isocyanatotoluene and 4,4'-diphenyldimethylmethane
2,2',5,5'-tetraisocyanate; cycloaliphatic isocyanates
such as 1,3-cyclopentane, 1,4-cyclohexane, 1,2-cyclo-
hexane and isophorone diisocyanate; and aliphaticisocyanates such as trimethylene, tetramethylene,
pentamethylene, hexamethylene and trimethylhexa-
methylene 1,6-diisocyanate, and tris-hexamethylene
triisocyanate.
Furthermore, however, the polyisocyanates may also be
linked to give prepolymers of higher molecular mass.
Compounds which can be mentioned in this context are
adducts of tolylene dii~ocyanate and trimethylol-
propane, a biuret formed from 3 molecules of hexa-
methylene diisocyanate, and the trimer~ of hexamethy-
lene diisocyanate and 3,5,5-trimethyl-1-isocyanato-
3-isocyanatomethylcyclohexane.
However, it is also possible to employ the isocyanates
described above which have been reacted with conven-
tional capping agent~, for example phenols, alcohols,
acetoacetic esters, ketoxime- and ~-caprolactam. These
combinations are stable at room temperature and in
general cure only at temperature~ above 100C. In
particular cases, for example when acetoacetic esters
are used for capping, it i6 al~o pofifiible for
crosslinking to occur below 100.
~ 5~tl~
The quantity of crosslinking agent employed iB
generally selected such that the ratio of the
isocyanate groups of the crosslinking agent to the
hydroxyl groups of the polyester is within the range
from 1:3 to 3:1.
Combinations with polyisocyanates and/or resin~ bearing
isocyanate group~ crosslink rapidly even at room tem-
perature.
Amino resins can also be employed as crosslinking
agents, examples being melamine/formaldehyde condensa-
tion product~, benzoguanamine/formaldehyde condensation
products, urea resins and the like. Examples of appro-
priate ~m; no resins are, for example, the commerciallyavailable melamine resins Maprenal MF 600, MF650,
MF 800 from Hoechst AG.
The quantity to be employed of these optionally
employed amino resins is conventionally between 3 and
8% by weight, based on the weight of the coating compo-
sition.
Furthermore, the coating compositions according to the
invention may also, if desired, contain other resins
such as polyurethane resins. Appropriate polyurethane
resin~ generally have number-average molecular weight~
of from 3000 to 7000.
It is po~si~le, for example, to employ the polyurethane
re~ins described in EP-A-355 433, DE-A-35 45 618 and
- 22 -
DE-A 38 13 866. In addition to this, however, the
employment of other polyurethane resins conventionally
employed in basecoats is possible. The quantity to be
employed of these polyurethane resins which are added
if desired is conventionally between 15 and 40% by
weight, based on the weight of the coating composition
and on solid polyurethane resin.
Furthermore, the coating compositions according to the
invention may also contain epoxy-ester resins, for
example reaction products of epoxy resins and
carboxylic acids, epoxide-modified acrylates and
epoxide-modified polyesters. For example, the
commercial epoxide-modified fatty acid polyester Uralac
AB733X-90 from DSM Kunstharze GmbH can be employed.
The quantities to be employed of the~e optionally
added, epoxide-modified resins is conventionally
between 0 and 4% by weight, based on the weight of the
coating composition.
If the coating compositions according to the invention
are employed as basecoats, then they contain as further
component pigments which are conventional in coating
technology. Such pigments may have particle sizes in
the range of 1-50 ~m and may be of inorganic nature,
for example titanium dioxide, iron oxide, chromium
oxide, lead chromate or carbon black, or of organic
nature, for example phthalocyanine blue, phthalocyanine
- ~16~l~5~
- 23 -
green, carbazol violet, anthrapyrimidine yellow,
vlavanthrone tsic] yellow, isoindoline yellow,
indanthrone blue, quinagrindone [sic] violet and
pherylene [ 8iC ~ red. Of particular interest in this
connection are metal pigments con~isting of flat flakes
of aluminum, copper, tin, nickel or stainles~ steel,
specifically because these can be used to obtain so-
called metallic effects by means of which a
differentiation is at~Ai n~ in the reflection of light
in dependence on the angle of viewing. The quantity of
these pigments employed i8 conventionally between 1 and
40% by weight, based on the overall weight of the
coating composition.
In addition, the coating compositions may also contain
conventionally employed fillers, for example silicic
acid, talc, ~aolin, metallic oxides, silicates,
~ulfides and the like. These filler~ are conventionally
employed in a quantity of between 0 and 10% by weight,
based on the weight of the coating compo~ition. The
coating compositions according to the invention may
also contain conventional auxiliaries and additives in
conventional quantitie~, preferably 0.01-10% by weight
based on the overall weight of the coating composition.
Examples of suitable auxiliaries and additives are
leveling agents such as silicone oils, plasticizers
such as phosphates and phthalate6, viscosity-con-
trolling additives, flatting agent~, W ab~orbers,
light stabilizer~ and the like.
- 2~6~
The coating compositions preferably al~o contain, in
addition, a crosslinking catalyst, conventionally in a
quantity of up to 10% by weight based on the weight of
the coating composition.
It is generally possible to dispense with the use of a
crosslin~ing catalyst if the polyester already contain~
tertiary amino groups.
Examples of suitable cross1i~king catalysts are, for
example, phosphoric acid, p-toluenesulfonic acid, tin
dibutyl dilaurate, tin dioctyl dilaurate, amines, for
example aliphatic diamines such as ethylenediamine and
hexanediamine, and aliphatic polyamines such as
diethylenetriamine, triethylenetetraamine and
tetraethylenepentamine, and alicyclic amines such as
piperidine, piperazine, aromatic amines, ethanolamine,
triethylamine, diazabicyclooctane, amidines such as
diazabicyclononene, diazabicycloundecene and low
molecular weight basic siloxanes. Advantageously, from
l to lO parts by weight of catalyst (solid) are used
per lO0 parts by weight of polye~ter.
The coating compositions are prepared in a known manner
by mixing and, if appropriate, di~persing the
individual components. The coating compositions accord-
ing to the invention can be applied to a sub~trate in
the form of a film by spraying, flow coating, dipping,
rolling, knife coating or brushing, the films
~ S~.J I
subsequently beinq cured to give a firmly adhering
coating.
These coating compositions are cured conventionally at
room temperature or slightly elevated temperature,
advantageously at temperatures below 100C and pre-
ferably at t~r~ratures below 80C. However, it is also
possible for the coating composition6 to be cured under
baking conditions, i.e. at temperatures of at least
100C.
Particularly suitable sub6trate~ are metals and al~o
wood, plastic, glass and the like.
Because of the short curing time and low curing tem-
perature6, the coating compositions according to the
invention are preferably employed for automotive
refinishing. However, depending on the crosslinking
agent employed, they may al60 be employed for the pro-
duction-line finishing of motor vehicles.
The coating composition~ according to the invention are
also suitable a~ the ~ase color of a mixer sy6tem, in
particular a mixer sy~tem in the area of refinishing.
It is particularly preferred for the coating composi-
tions according to the invention to be employed in a
2S mixer system for the production of conventional coating
compositions. Such mixer systems are de~cribed in, for
example, the as yet unpublished German Application
P 42 32 721Ø These mixer systems described therein
are characterized in that they contain
~6~43 ~
- 26 -
A) various base color~ A which contain less than 5%
by weight of water, at least one pigment which
provides color and/or effect, organic solvent, at
least one water-dilutable or water-di~persible
binder, and - if desired - auxiliaries and
additives,
B) at least one solvent-contAin;ng, binder-con-
t~;ning, pigment-free component B which may con-
tain up to 5% by weight of water, and if de~ired
C) a component C contAini~g at least one crosslinking
agent, and
D) a component D which contains organic solvent,
water if desired and, if desired, additives and
catalysts.
The coating compositions according to the invention
based on hydroxyl group-contAining polyesters and
cellulose acetobutyrate are in this context employed
for the preparation of component B. A particular advan-
tage in thi~ ca~e is the good color uniformity of the
resulting coating compo~ition~, especially if
polyesters according to the in~ention and contAi~i ng
hydroxyl groups, having a degree of branching of from
0.6 to 1.2 branches per 1000 g of polyester resin
~olid), are employed.
- 27 -
The crosslinking agents (C) employed are, for example,
the crosslinking agents already mentioned. However, it
i8 also possible to prepare physically drying coating
composition~ using this mixer system, in which case
component (C) can then be omitted.
The coating compositions according to the invention are
preferably employed as basecoat for a multicoat finish
of the basecoat/clearcoat type.
This mixer system has the special advantage, in
particular from an economic viewpoint, that the base
colors A contA; n; ng water-dilutsble or water-dis-
persible binders provide the possibility of using only
one series of base pastes both for aqueous systems and
for tho~e dissolved in organic solvents. The use, in
accordance with the invention, of essentially water-
free and preferably completely water-free base colors
offers the additional advantage that the containers
which can be u~ed for the ~torage of these base colors
do not have to be protected (for example by an appro-
priate internal coating) against corrosion by water.
Furthermore, it is also possible, with certain pre-
conditions, to employ water-sensitive pigments for the
formulation of the base colors, resulting in a con-
siderable increase in the selection of pigment~
available.
The individual components of the mixer sy~tem according
216~
- 28 -
to the invention will now be described below in more
detail.
Component A of the mixer system may contain any
pigments conventional for paint~, with the proviso that
they do not react with wster within a short period (the
period between combining components A and B and the
application of the coatings) and that they are
insoluble in water. In this context component A may
contain effect pigments and/or color-providing pigments
based on inorganic or organic compounds. In order to
ensure a scope for application which i6 as near
universal as possible and to maximize the number of
colors which can be produced, it is preferred to con-
struct a mixer system on the basis of components Awhich contain only color-providing pigments and com-
ponents A which contain only effect pigments.
For the preparation of component A, it is possible to
employ all effect pigments which are conventionally
employed in the formulation of aqueous coating composi-
tions. Examples of appropriate effect pigments are com-
mercially available aluminum bronzes, the chromatized
aluminum bronze~ according to DE-A 3636183, commer-
cially available stainless-steel bronzes, and other
conventional metal flakes and metal flake pigments.
Other pigments suitable for the preparation of com-
ponent A are nonmetallic effect pigments, for example
pearlescent and interference pigments. Examples of
- '~ 1 6 ~
- 29 -
suitable color-providing pigments based on inorganics
are titanium dioxide, iron oxides, carbon black and the
like. Examples of suitable color-providing pigments
based on organic co~rolln~ are indanthrene blue,
cromophthal red, Irgazin orange, Sicotrans yellow,
Heliogen green and the like.
Suitable binders for use in component A are all water-
dilutable or water-dispersible binders which are con-
ventionally employed in aqueous coating compositionsand which can be prepared in the form of organic
solutions. The water-dilutability or water-dispersi-
bility of the resins can also be adju~ted by the use of
corresponding solubilizers as cosolvent or solvent.
Critical factors for the selection of the binders are,
on the one hand, the good storage stability in organic
solution, and in particular the ability to avoid
settling of the pigments, and on the other hand the
ability to incorporate the ba~e color into component B
without problems or to incorporate component s into the
base color without problems.
The binders employed for component A are in particular
water-dilutable and water-dispersible polyurethane
resins, polyacrylate resins, polyester resins and amino
resins, and mixture~ thereof, which can be prepared in
organic solution.
The polyurethane resin~ employed as binders in the base
- 2~
- 30 -
colors are known in principle. Suitable examples are
the polyurethane resins described in the literature for
use in water-based coatings, provided these
polyurethane re6ins can be prepared - in modification
of the preparation described in the respective
literature - in the form of organic solutions.
Examples of suitable polyurethane resins are the resins
described in the following documents: EP-A-355433,
DE-A 3545618, DE-A 3813866 and DE-A 4005961.
Examples of suitable polyacrylate resins are, for
example, the resins described in DE-A 38 32 826. Other
suitable binders for component A are the polyester
resins and amino resins which are dilutable or dis-
persible in water and can be prepared in the form of
organic solutions.
The present invention therefore also relates to a pro-
cess for the production of a multicoat protectiveand/or decorative coating on a substrate surface, in
which
1. a basecoat is applied,
2. a polymer film is formed on the surface from the
composition applied in step (lJ,
3. a transparent topcoat is applied to the resulting
- 2163~
basecoat, and
4. the topcoat is cured together with the basecoat,
which i8 characterized in that the basecoat employed in
step (1) is a coating composition according to the
invention.
In this process, therefore, a transparent topcoat com-
position i9 applied directly after the application ofthe basecoat composition, preferably after a short
flush-off time without a baking step. Subsequently, the
basecoat is baked together with the topcoat (wet-on-wet
method). This curing of the basecoat and the topcoat is
conventionally carried out at a temperature below
100C, preferably below 80C in the case of automotive
refinishing. Otherwise, curing is carried out conven-
tionally at a temperature of between 100 and 150~C and
for a time between 15 and 30 minutes. The dry film
thicknesses of the resulting basecoat are in general
between 8 and 20 ~m, with those of the topcoat conven-
tionally being between 20 and 60 ~m.
Examples of a suitable clearcoat for this process are
the clearcoats described in EP-A-379 598 and based on
hydroxyl-cont~; n; ng components, cellulose esters and
isocyanates. Also suitable as clearcoat are the
clearcoats described in DE-A-39 42 803 and based on
polymers containing silyl groups, and the clearcoats
2~g4S~
described in DE-A-40 24 204 and based on hydroxyl
group-cont~in;~g products of condensation and addition
polymerization.
The invention i8 illu~trated in more detail in the
following examples. All part~ and percentages are by
weight, unless expre~sly stated otherwise.
1.1 Preparation of a hydroxyl group-cont~; n i ng
polyester 1
The following raw materials are weighed into a 4 1
stainless steel vessel fitted with stirrer, steam-
heated column with head temperature detector, and water
~eparator:
Neopentylglycol1,038.0 part~
Trimethylolpropane611.2 parts
Phthalic anhydride1,264.6 parts
20 Adipic acid 831.7 parts
Xylene 145.8 part~
The mixture is heated over the course of 1 hour to a
temperature of 135C, at which the beginning of distil-
lation can be observed. While maintA; n; ng a column headtemperature of below 100C, heating is continued slowly
to a maximum product temperature of 210C. The water
formed i8 removed continuously by azeotropic distilla-
tion. After an acid number of from 12 to 14 mg of KO~/g
8~
- 33 -
and a vi~cosity from 18 to 19 dPa. 8 ( 60% in xylene,
plate/cone viscometer at 23C) has been reached, the
mixture is cooled and diluted with butyl acetate to a
solids content of 80%. The resulting polyester resin 1
has a viscosity (measured using a plate/cone viscometer
at 23C, 60% in xylene) of 14.2 dPa.s and a number-
average molecular weight of 3000, as well as a weight-
average molecular weight of 105,000 (determined by gel
permeation chromatography against polystyrene as
st~n~Ard). The polydispersity Mw/Mn is 35 and the 0
number is 96.5 mg of KOH/g.
1.2 Preparation of a hydroxyl group-cont~ining
polyester 2
Example 2 corresponds to a re~in of the compo~ition of
Example 1 with the exception that 0.05% of dibutyltin
oxide is employed as catalyst (based on solid starting
materials). The preparation process is identical. After
an acid number of from 12 to 14 mg of RO~/g and a
viscosity of from 13 to 15 dPa.~ (60% in xylene,
plate/cone viscometer at 23C) have been reached, the
mixture is cooled, diluted with 6% of xylene and, after
a temperature of below 120C has been reached, is dis-
solved further using butyl acetate to a solid6 contentof 65%. The resulting polyester resin 2 has a viscosity
(measured with a platetcone viscometer at 23C, 60% in
butyl acetate) of 13.5 dPa.s and a number-average
molecular weight of 3100, and al~o a weight-average
- ~16845~
- 34 -
molecular weight of 155,000 (determined by gel
permeation chromatography against poly~tyrene as
stAn~rd). The polydispersity Mw/Mn is 52 and the OH
number is 96 mg of ROH/g.
1.3 Preparation of a hydroxyl group-cont~i~ing
polyester 3
The following raw materials are weighed into a 4 l
stainless steel vessel fitted with stirrer, steam-
heated column with head temperature detector, and water
separator:
198 parts of trimethylolpropane
892 part~ of neopentylglycol
437 parts of phthalic anhydride
490 parts of isophthalic acid
1.15 parts of dibutyltin oxide
The components are mixed and ~lowly melted under inert
gas. Distillation commences at 140C. Samples are then
taken hourly and a visual check iB made as to whether a
clear melt is obtained. At an acid number of about
45 mg of KOH/g the melt became clear. Then the
following further components are added to the melt:
575 parts of adipic acid
24 parts of xylene.
2 ~ 6 8 ~ ~ ~
- 35 -
Thereafter, heating i8 continued for 8-12 hourQ to
220C, while maintA; ni ng a column head temperature of
not more than 100C. Condensation is effected up to an
acid number of below 15 mg of KOH/g, at which point the
viscosity i8 about 9.8 dPa.s (measured 60~ in xylene).
After the acid number has been reached, the resin is
diluted with xylene to a theoretical solids content of
90% and with butyl acetate to a solids content of
theoretically 65~. The polyester resin solution, in a
60% dilution with butyl acetate, has a viscosity of
9.8 dPa.s tICI plate/cone viscometer at 23C) and an
acid number of 11.6 mg of ROH/g (based on solid~). The
resulting polyester has a number-average molecular
weight of 4500 g/mol, a weight-average molecular weight
of 65,500 g/mol (measured by GPC against polystyrene a~
stAn~Ard), an OH number of 57 mg of KOH/g and a poly-
dispersity Mw/Mn of 15.
1.4 Preparation of a hydroxyl group-containing
polyester Cl
The following raw materials are weighed into a 4 l
stainless steel vessel fitted with stirrer, steam-
heated column with head temperature detector, and water
separator:
Neopentylglycol 730.3 parts
Trimethylolpropane 537.4 parts
Phthalic anhydride 890.0 parts
2 1 6 ~ Ll ~ ~
- 36 -
Adipic acid 585.0 parts
Xylene 114.3 parts
The mixture is heated over the course of 1 hour to a
temperature of 135C, at which the beginning of distil-
lation can be observed. While maintAi~ing a column head
temperature of below 100C, heating is continued slowly
to a maximum product t~mrerature of 210C. The water
formed is removed continuously by azeotropic distilla-
tion. After an acid number of from 12 to 14 mg of KOH/gand a viscosity of 6.1 dPa.s (60~ in 1-methoxypropyl
acetate, plate/cone viscometer at 23C) have been
reached, the mixture is cooled and diluted with butyl
acetate to a solids content of 60%. The resulting
polyester resin C1 has a viscosity (measured using a
plate/cone viscometer at 23C) of 2.6 dPa.s and a
number-average molecular weight of 2050, and also a
weight-average molecular weight of 9100 (determined by
gel permeation chromatography against polystyrene as
standard). The polydispersity Mw/Mn is 5, the OH number
is 146 mg of KOH/g.
1.5 Preparation of a hydroxyl group-cont~i n ing
polyester C2
The following raw materials are weighed into a 4 1
stainless ~teel vessel fitted with stirrer, steam-
heated column with head temperature detector, and water
separator:
- ~ 6~15~
- 37 -
Trimethylolpropane 992.8 parts
Isononanoic acid 365.8 parts
Benzoic acid 282.9 parts
Hexahydrophthalic anhydride 528.1 parts
5 Cyclohexanedicarboxylic acid 589.8 parts
Xylene 115 parts
The components are mixed and slowly melted under inert
gas. Distillation commences at 140C. Thereafter,
heating is continued to 220C over the course of from 5
to 7 hours, while maint~i n; ng a column head temperature
of not more than 100C. Condensation i~ effected up to
an acid number of less than lS mg of ROH/g, at which
point the viscosity is 8.5 dPa. B (mea~ured 55% in butyl
acetate, plate/cone viscometer at 23~C). After the acid
number has been reached, the resin is run off as a
melt. Processible solutions of the resin can be pre-
pared by melting and dilution with the desired solvent.
The viscosity in xylene at a solids content of 55% is
9.1 dPa.s (plate/cone viscometer at 23C). The resul-
ting polyester C2 has a number-average molecular weight
of 2250 and a weight-average molecular weight of
247,000 (measured by gel permeation chromatography
against polystyrene as st~n~rd). The polydispersity
Mw/Mn is 110, the OH number is 111 mg of KOH/g.
- 2~6~
- 38 -
1.6 Preparation of a hydroxyl group-contA i n ing
polye6ter C3
The following raw material6 are weighed into a 4 1
stainless steel vessel fitted with stirrer,
steam-heated column with head temperature detector, and
water separator:
Neopentylglycol 1006.1 parts
10 Trimethylolpropane 356.3 parts
Adipic acid 1763.4 parts
Dibutyltin oxide 0.675 part
Xylene 112.5 parts
The component~ are mixed and slowly melted. Distilla-
tion commences at 135C. Thereafter heating is con-
tinued to 220 over the cour~e of from 5 to 7 hour~,
while maintA;n;ng a column head temperature of not more
than 100C. Condensation is effected up to an acid
number of 16 mg of ROH/g, at which point the viscosity
is 8.5 dPa. 8 (measured 60% in xylene, plate/cone Vi9-
cometer at 23C). After the de~ired values have been
reached the mixture is cooled, diluted with xylene to a
~olids content of 90~ and diluted further with butyl
acetate to a ~olids content of 65%. The vi~c06ity of
the resin solution is 17.8 dPa.s (plate/cone viscometer
at 23C), the acid num~er i~ 15.5 mg of RO~/g. The
resulting polyester C3 ha~ a number-average molecular
weight of 3294 and a weight-average molecular weight of
'~ 68 1~ ~
- 39 -
260,000 (measured by gel permeation chromatography
against polystyrene as ~tAnAArd). The polydispersity
Mw/Mn is 79, the OH number i6 75 mg of KOH/g.
1.7 Preparation of a hydroxyl group-contA;n;ng
polyester C4
The following raw materials are weighed into a 4 1
stainless steel ve~sel fitted with stirrer, steam-
heated column with head temperature detector, and waterseparator:
188.0 parts of trimethylolpropane
829.0 parts of neopentylglycol
151443.0 parts of hexahydrophthalic anhydride
96.0 parts of xylene.
Also added to the mixture iB 0.05%, based on solid
6tarting materials, of a tin catalyst (hydrogenated
monbutyltin ~sic] oxide, trade name Fascat 4100 from
Atochem Nederland).
The components are mixed and melted slowly under inert
gas. Distillation commence~ at 140C. Thereafter
heating i8 continued to 220C over the course of 5-7
hours, while maintA; n; ng a column head temperature of
not more than 100C. Condensation is effected up to an
acid number of below 10 mg of KO~/g, at which point the
visco~ity is about 14.5 dPa.s (measured 60% in xylene).
~ ~ 6 ~
- 40 -
After the acid number has been reached the resin i6
diluted with xylene to a theoretical solids content of
90% and with butyl acetate to a solids content of
theoretically 65%. In a 60% dilution with butyl
acetate, the polyester resin solution has a viscosity
of 8.8 dPa.s (ICI plate/cone viscometer at 23C) and an
acid number of 8.0 mg of KOH/g (based on solids).
The resulting polyester has a number-average molecular
weight of 3250 g/mol, a weight-average molecular weight
of 61,000 g/mol. (measured by GPC again~t polystyrene
as stAn~Ard), a polydispersity MM[sic3/Mn of 19 and an
OH number of 46 mg of KOH/g.
2.1 Cellulose acetobutyrate solution 1
A cellulose acetobutyrate solution contA;ning 15% CAB
and 85% butyl acetate was employed. The cellulose
acetobutyrate used has a content of acetyl groups of
from 13 to 16%, a content of butyryl groups of from 36
to 42%, a content of hydroxyl groups of from 1 to 2%
and a weight-average molecular weight of approximately
40,000.
2.2 Cellulose acetobutyrate solution 2
The cellulose acetobutyrate solution 2 used has a
cellulose acetobutyrate content of 15% and a butyl
acetate content of 85%. The cellulose acetobutyrate has
a content of from 2.5 to 4% of acetyl groups, a content
216~
of butyryl groups of from 36 to 42~ and a content of
hydroxyl groups of from 1 to 2%. The weight-average
molecular weight of the cellulose acetobutyrate is
approximately 40,000.
3. Preparation of basecoats 1 to 4 and Cl to C5
The preparation of the coating compositions according
to the invention is carried out by the conventional
methods by first pre-stirring the wax precipitation
until the wax precipitation is free from inhomo-
geneities. The cellulose acetobutyrate solution is then
added with rapid stirring. After this the remaining
components, except for the aluminum pigment and the
solvent, are added. The aluminum pigment is first made
into a paste with 5 parts of butyl acetate and this
paste is added to the other components while stirring.
Then the remaining quantities of solvent are also
added. The composition of basecoats 1 to 4 and Cl to C5
is indicated in Table 1. The ba6ecoats are applied to
sheet metal panels 40 x 60 cm in size. The primer used
was a commercially available, conventional filler
(commercial product Glasurit Grundfuller [primer
~urfacer] EP AC 01-1492 from Glasurit GmbH, Munster,
with an epoxy-functional binder and an amino-functional
curing agent). The filler was applied by spraying and,
after a flash-off time of 10 min, was then dried at
80C for 20 min. The dry film thickness of the filler
is from 50 to 80 ~m. After this the respective basecoat
- 21G~
- 42 -
was applied by spray application, applying 1 spray pass
first and, after a flash-off time of 5 min, a 2nd spray
pass. After a flash-off time of 20 min, likewise at
room temperature, the clearcoat was applied.
The clearcoat used for o~ercoating was the commercially
available clearcoat Gla~urit AF 23-0185 from Glasurit
GmbH based on a polyacrylate (similar to Macrynal~
SM 513 from Hoechst AG), mixed in a ratio of 2:1 with
the curing agent SC 29-0173 from Glasurit Gmb~ based on
isocyanate (mixture of a trimerized isocyanate which
contains isocyanurate groups and i~ based on hexamethy-
lene dii~ocyanate and isophorone diisocyanate). The
clearcoat was applied by spraying, carrying out one
6pray pas~ and, after a flash-off time of 2 min, a
second spray pass. After a flash-off time of 10 min at
ambient temperature the panel is then dried at 60C for
30 min. The film thickness of the basecoat is 20-25 ~m,
while that of the clearcoat is 60-80 ~m.
The test results of the coating~ are compiled in Table
2.
-- 43 --
o o oo o o o o a~ ~ o
..... . .
o o o o o o o o a~ ~ o
.................. ... -
U~ ~ --I N
O O O O O O O ~ ~lO
. . . . .
U~ O O O O O O O O CO ~ O
O O~ ~ --I
_l
o o o o o o o o a~ ~ o
O O O O O O O O C~ ~ O
o . . .....
C: O O O O O O O O 00 N O
o
o
O O O O O O IS~ O
rl O O O O O O O O CO ~ O
O ~ t`~ N
o
C O
O Q~ ~rl
O
O ~O C
O r~l r~l r~ r~l r~1 ^ 11 r~l ~rl ~
O O~ --
.rl Ll ~ ~ I U r~
- ---- u a~
rl O~ Il) ~ O
rl ~ r~l r~
m ~ x ,~
O ~ r~
E~ U ~ X m m u~ ~
- ~63 151
1) Cellulose acetobutyrate solution 1 (see above)
2) Cellulose acetobutyrate solution 2 (see above)
3~ Wax precipitation 1
The wax precipitation was prepared by heating an
initial charge of 44 parts of xylene to 80-100C.
Then 6 part~ were added of a commercially
available ethyl-vinyl acetate copolymer
(commercial product EVA l-Wachs BASF~ from BASF
AG, Ludwigshafen; polyethylene wax based on an
ethlyene tsic]/vinyl acetate copolymer having a
melting point of 87-92C, a Hoppler hardness at
23C of 110-140 bar and a molar mas~ of
approximately 6500 g/mol) and the resulting solu-
tion was stirred until a clear solution formed.
Then 50 parts of butyl acetate 98 were added and
the solution wa~ left to cool.
0 4) Commercially available melamine resin having a
solids content of 55%, dissolved in isobutanol,
and a viscosity DIN 4 of from 90 to 130 8, and
isobutanol as etherification alcohol (commercial
product Maprenal MF 650 from ~oechst AG)
5) Commercially available aluminum pigment (non-
leafing type) with a content of white ~pirit of
18% and of aromatic solvents of 20% and with an
average particle size of 9 microns (commercial
~ ~ 6 ~
- 45 -
product Sparkle Silver 7005 AR from Silberline
Ltd., Scotland).
6) A commercially available paint diluent was
employed consisting of 20% xylene, 5% butylglycol
acetate, 60% butyl acetate 98 and 15%
l-methoxypropyl 2-acetate.
7) Solution of 1 part of a commercially available
silicone oil (commercial product Baysilone OL44
from Bayer AG) in 99 parts of xylene
8) Solution of 10 parts of diazabicyclooctane (DABCO)
in 45 parts of butyl acetate and 45 parts of
butanol
~6~51
-- 46 --
O ~ ~ ~ W
Cl . L
r O~ O
~ ~ O1` ~ 0
~1~ 0 ~ ~ ~ Ll
C~ ~ ~ o o ~ O
Ll ~ ~ ~-- ~ Ll
U ~ ,1 0
C ~ o ~ _
0 U --~ ~ I I I I
m
'~ e" O U~ O O
Ei o
U ~ O O . ~
c
O ~ O O r~ _
.c o~
o o ~ --'
o m
O
U~ tO
~r _ r~
u ~r u~
Z ,~ d'
L ~ L
r ~ ~ _ _
0 ~ ~ N
_
o o o
u~ u~ o
a a L ~ ~ U U ~p
- 216~15~
1) Adhe~ion test
The adhesion te~t is carried out using a high-
pressure cleaner at 80 bar pressure and a flow
rate of 800 l/h at a cold temperature. The
distance of the nozzle from the test panel was
5 cm. For te~ting the adhesion the coated steel
panels (~ee above) were stored at room temperature
for 7 day~ and thus dried. A knife is then used to
cut a triangle with side~ 10 cm long through the
coating film~. The cut must extend down to the
substrate. Subsequently the ~ide~ of the triangle
are exposed to the high-pre~sure cleaner jet for
10 sec each.
Evaluation:
A metal lattice cut into squares with a mesh size
of 1/2" and a total edge length of 6" ~144
squares) is laid over the triangle. Each square in
which there is a loss of adhesion between the
clearcoat and basecoat is counted.
2) The colors are measured by DIN 6174, stAn~Ard
lighting D, using the three-angle mea~urement
in~trument MMX 111 from Datacolor, Weichenheim,
Germany. Each color was measured on a mixture of
80 parts by weight of coating compo~itions 1 to 3
and C2 to C5 with 20 parts by weight of coating
composition Cl. The mixture was adjusted to spray
visco~ity, from 18 to 20 s efflux time in the
- 21G~
- 48 -
DIN 4 cup, with the paint diluent indicated above.
The parameter measured in each case was the DC*
value in compari60n to coating compo6ition Cl
(C1 = stAn~Ard). Measurement was carried out in
each case at an angle to the vertical of 25, 45
and 70.
DC* po6itive: sample is more colored in comparison
with stA~rd Cl (in this case more
blue)
DC* negative: sample is les~ colored in comparison
with ~tAn~Ard C1 (in this case more
metallic)
3) StAn~Ard: coating composition C1 (see above)
4) Visual as6e6sment wa6 carried out at angles of 25,
45 and 70 to the vertical under an O~ram~ white-
univer6al neon tube.
