Note: Descriptions are shown in the official language in which they were submitted.
CA 02247959 1998-09-02
PAT 96 635 FI~ r. ,..~ ~ , "n ~Y rns ~ r 5 . 03 . 1996
BASF Lacke + Farben Aktien esellschif °'
g .i.~ , ....~.~ ~',~':~an'
Aqueous tv~o-component polyurethane coating composition,
process for its preparation and its use as a topcoat,
as a clearcoat and for the coating of plastics
The present invention relates to an aqueous two-
' component polyurethane coating composition comprising
I.) a component (I) which contains as binder (A)
(A1) at least one water-soluble or water-
dispersible polyester resin (A1) which contains
hydroxyl groups and acid groups which can be
converted into the corresponding acid anion groups
and has an OH number of from 30 to 250 mg of KOH/g
and an acid number of from 5 to 150 mg of KOH/g,
and
(A2) at least one water-soluble or water-
dispersible polyurethane resin (A2) which contains
hydroxyl groups and acid groups which can be
converted into the corresponding acid anion groups
and has an OH number of from 20 to 200 mg of KOH/g
and an acid number of from 5 to 150 mg of KOH/g,
and
(A3) at least one water-soluble or water-
dispersible acrylate copolymer which contains
hydroxyl groups and acid groups which can be
CA 02247959 1998-09-02
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converted into the corresponding acid anion
groups, and/or an acrylated polyester and/or an
acrylated polyurethane, which has an OH number of
from 40 to 200 mg of KOH/g and an acid number of
from 5 to 150 mg of KOH/g, and
(A4) if desired, at least one further polymer (A4)
and
II.) a component (II) which contains a polyisocyanate
component (F1) as crosslinking agent.
The present invention also relates to a process for
preparing these aqueous coating compositions and to
their use as a clearcoat or as a topcoat and to their
use for coating plastics.
For ecological and economic reasons, the paint industry
is seeking to replace the amount of organic solvents
used in paints as far as possible by water. Aqueous
coating compositions are already in use not only in the
area of automotive line coating but also in the area of
automotive repair finishes. In the area of plastic
coating, too, it is increasingly desirable to use
aqueous systems, not only in the area of primers but
also in the area of topcoats.
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Topcoats are understood to mean paints which are used
for producing the uppermost paint coat. The uppermost
paint coat can be a single-coat or multicoat system, in
particular a two-coat system. Two-coat topcoats
consist of a pigmented basecoat layer and a clearcoat
layer applied on top of the basecoat layer, which
clearcoat layer is unpigmented or pigmented only with
transparent pigments. Nowadays two-coat paints are
produced by the wet-in-wet method in which a pigmented
basecoat is precoated and the resulting basecoat layer,
without being subjected to a baking step, is overcoated
with a clearcoat, and basecoat layer and clearcoat
layer are then jointly cured. This method is very
advantageous in terms of economics, but it makes high
demands on the basecoat and the clearcoat. The
clearcoat applied on top of the not yet cured basecoat
must not dissolve the basecoat layer on the surface or
interfere in any other way since this would lead to
paints having poor appearance. This is in particular
true of paints in which basecoats containing effect
pigments (for example metallic pigments, in particular
aluminum flakes, or nacreous pigments) are used.
In the area of plastic coating an additional
requirement is that the resulting coatings should have
high flexibility while exhibiting high moisture
resistance (for example low permeability).
Furthermore, the coatings should have good appearance.
This means that the coatings exhibit, for example, high
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gloss and that the coating compositions show good flow
properties. Furthermore the coatings should possess
good adhesion. In addition, component (I) of the
coating composition should have a long shelf life.
In the area of plastic coating, an additional
requirement is that the coating compositions used can
be cured at low temperatures (in general below 100°C)
and give films having the desired properties even when
cured at these low temperatures.
DE-A-4,421,823 discloses aqueous polyurethane coating
compositions consisting of at least three components
where the component (I) contains at least one binder
dissolved in organic solvent, which binder is selected
from the group consisting of polyester resins,
polyurethane resins, polyacrylate resins and, if
desired, of further binders; component (II) contains at
least one uncapped polyisocyanate as crosslinking
agent; and component (III) is essentially free of
binder and contains water. The coating compositions
are prepared by mixing the three components a short
time before applying the coating compositions. These
coating compositions are used, in particular, in the
area of automotive repair finishes.
However, these coating compositions disclosed in
DE-A-4,421,823 have the disadvantage that their
preparation is quite expensive since three different
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components have to be stored and mixed with one another
a short time before applying the coating compositions.
Furthermore, this coating composition contains a binder
component which has been predissolved in an organic
solvent, this solvent being also present in the coating
composition prepared from the three components.
Furthermore, DE-A-4,326,670 discloses aqueous two-
component polyurethane coating compositions based on an
aqueous dispersion of at least one binder having a
number-average molecular weight of 1000 to 100,000 and
containing groups which are reactive towards isocyanate
groups, calculated on the basis of an OH number of 20
to 250 and an acid number of 10 to 100, the acid
functions of which are at least in part neutralized,
and of a polyisocyanate as crosslinking agent.
Examples of suitable binders include polyacrylate
resins, polyester resins, polyurethane resins or
(meth)acrylated polyester resins or (meth)acrylated
polyurethane resins.
DE-A-4,326,670 does not describe the use of a mixture
of at least one polyester and at least one polyurethane
resin and of at least one polyacrylate resin or an
acrylated polyester and/or an acrylated polyurethane as
binder. The coating compositions disclosed in
DE-A-4,326,670 have the disadvantage that their shelf
life is not sufficiently long.
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The present invention provides aqueous two-component polyurethane
coating compositions which are suitable for coating plastic
substrates, in particular in the area of~ the production
of topcoats. The resulting coatings should hake, in
particular, high elasticity while exhibiting high
moisture resistance (for example low permeability).
Furthermore, the coating compositions should meet the
requirements usually demanded of coating compositions
~10 which are used for coating plastic substrates.
Accordingly, thecoating compositions should, for
example, also give coatings having good appearance
(good gloss-, good flow properties, and the like) and
good adhesion. Furthermore, component (I) of the
coating composition should have a long shelf life.
Finally, the coating compositions should be curable at
low temperatures (in general below 100°C) and should
give films having. the desired properties even when
cured at these low temperatures:
Surprisingly, this is achieved by means of the
coating compositions of the type mentioned at the
beginning, wherein the mixing ratio of the polyester
resin (A1) to the polyurethane resin (A2) is between 95,
parts by weight of polyester resin ~. 5 parts by weight
of polyurethane resin and 5 parts by weight of
polyester resin . 95 parts by weight of polyurethane
resin.
CA 02247959 1998-09-02
The present invention also provides a process for
preparing these coating compositions and relates to the
use of the coating compositions as topcoat or clearcoat
and to their use for coating plastics.
It is surprising and was not foreseeable that the use
of a mixture of at least one polyacrylate resin and/or
acrylated polyester and/or acrylated polyurethane resin
and at least one polyester resin and at least one
polyurethane resin as binder would result in aqueous
two-component polyurethane coating compositions which
give coatings which, not only with respect to
flexibility but also simultaneously with respect to
moisture resistance, have improved properties compared
with coatings prepared by using at least one
polyacrylate resin and/or acrylated polyester and/or
acrylated polyurethane resin and either at least one
polyester resin or at least one polyurethane resin.
An additional advantage is that the coating
compositions according to the invention result in
coatings having good appearance and good adhesion.
Furthermore, component (I) of the coating composition
exhibits a long shelf life, and the coating
compositions show good application performance.
Finally, the coating compositions are curable at low
temperatures (in general below 100°C) and lead to films
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having the desired properties even when cured at these
low temperatures.
Below, first the individual components of the coating
compositions according to the invention are described
in more detail.
It is essential to the invention that the coating
composition contains as binder a mixture of at least
one polyacrylate resin and/or one acrylated polyester
and/or one acrylated polyurethane resin and at least
one water-soluble or water-dispersible polyester resin
(A1) and at least one water-soluble or water-
dispersible polyurethane resin (A2), the mixing ratio
of the polyester resin (A1) to the polyurethane resin
(A2) being between 95 parts by weight of polyester
resin . 5 parts by weight of polyurethane resin and 5
parts by weight of polyester resin . 95 parts by weight
of polyurethane resin. Preferred coating compositions
are obtained if the mixing ratio of polyester resin
(A1) to polyurethane resin (A2) is between 90 parts by
weight of polyester resin . 10 parts by weight of
polyurethane resin and 30 parts by weight of polyester
resin . 70 parts by weight of polyurethane resin,
particularly preferably between 75 parts by weight of
polyester resin . 25 parts by weight of polyurethane
resin and 50 parts by weight of polyester resin . 50
parts by weight of polyurethane resin.
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Suitable polyester resins (A1) for preparing the
coating compositions according to the invention are all
water-soluble or water-dispersible polyester resins
(A1) which contain hydroxyl groups and acid groups
which can be converted into the corresponding acid
anion groups, which polyester resins have an OH number
of from 30 to 250 mg of KOH/g, particularly preferably
of from 60 to 200 mg of KOH/g, and an acid number of
from 5 to 150 mg of KOH/g, preferably of from 15 to 75
mg of KOH/g, and particularly preferably of from 20 to
50 mg of KOH/g. Polyester resins (Al) preferably have
number-average molecular weights Mn of between 500 and
30,000 Dalton, preferably of between 1000 and 10,000
Dalton, and particularly preferably of between 1000 and
5000 Dalton, in each case measured against a
polystyrene standard. It is preferred to use branched
polyesters.
Preferably, those polyesters are used which are
obtainable by reacting
pl) di- and/or polycarboxylic acids or esterifiable
derivatives thereof, if desired together with
monocarboxylic acids,
p2) diols,
p3) polyolols, if desired together with monools, and
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p4) if desired further modifying components.
Of these, polyesters which have been prepared without
using monools and monocarboxylic acids are particularly
preferably used. Polyesters which are free of
unsaturated fatty acids are also particularly
preferred.
Examples of polycarboxylic acids which can be used as
component (pl) include aromatic, aliphatic and
cycloaliphatic polycarboxylic acids. Preferably,
aromatic and/or aliphatic polycarboxylic acids are used
as component (pl).
Examples of suitable polycarboxylic acids are phthalic
acid, isophthalic acid, terephthalic acid, halophthalic
acid, such as tetrachloro- or tetrabromophthalic acid,
adipic acid, glutaric acid, azelaic acid, sebacic acid,
fumaric acid, malefic acid, trimellitic acid,
pyromellitic acid, tetrahydrophthalic acid, hexahydro-
phthalic acid, 1,2-cyclohexanedicarboxylic acid,
1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexane-
dicarboxylic acid, 4-methylhexahydrophthalic acid,
endomethylenetetrahydrophthalic acid, tricyclodecane-
dicarboxylic acid, endoethylenehexahydrophthalic acid,
camphoric acid, cyclohexanetetracarboxylic acid,
cyclobutanetetracarboxylic acid and others. The
cycloaliphatic polycarboxylic acids can be used
either in their cis or in their traps form and as a
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mixture of both forms. The esterifiable derivatives of
the abovementioned polycarboxylic acids, such as, for
example, mono- or polyesters thereof with aliphatic
alcohols having 1 to 4 carbon atoms or hydroxyalcohols
having 1 to 4 carbon atoms, are also suitable. In
addition, the anhydrides of the abovementioned acids,
if they exist, can also be used.
Examples of monocarboxylic acids which, if desired, can
be used together with the polycarboxylic acids, are
benzoic acid, tert-butylbenzoic acid, lauric acid,
isononanoic acid and hydrogenated fatty acids of
naturally occurring oils, preferably isononanoic acid.
Examples of suitable diols (p2) for preparing the
polyester (A2) are ethylene glycol, propanediols,
butanediols, hexanediols, neopentylglycol hydroxy-
pivalate, neopentylglycol, diethylene glycol, cyclo-
hexanediol, cyclohexanedimethanol, trimethylpentanediol
and ethylbutylpropanediol. Furthermore, aliphatic
polyether diols, such as linear or branched
poly(oxyethylene) glycols, poly(oxypropylene) glycols
and/or poly(oxybutylene) glycols, and mixed polyether
diols, such as poly(oxyethyleneoxypropylene) glycols,
are also suitable. The polyether diols usually have a
molecular weight Mn of 400 to 3000.
Furthermore, the diols used can also be aromatic or
alkylaromatic diols, such as, for example, 2-alkyl-
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2-phenylpropane-1,3-diol, bisphenol derivatives having
ether functionality, and the like.
Further suitable diols include esters of
hydroxycarboxylic acids with diols where the
abovementioned diols can be used as the diol. Examples
of hydroxycarboxylic acids are hydroxypivalic acid or
dimethylolpropanoic acid.
Examples of polyols which are suitable as component
(p3) are ditrimethylolpropane, trimethylolethane,
trimethylolpropane, glycerol, pentaerythritol,
homopentaerythritol, dipentaerythritol, tris(hydroxy-
ethyl) isocyanate, 1,2,4 butanetriol [sic], propane-
and hexanetriols, trihydroxycarboxylic acids, such as
tris(hydroxymethyl)(ethyl)ethanoic acids. Polyols
having at least 3 OH groups can be used on their own or
as a mixture. If desired, the triols can be used
together with monohydric alcohols, such as, for
example, butanol, octanol, lauryl alcohol, cyclo-
hexanol, tert-butylcyclohexanol, ethoxylated and
propoxylated phenols.
Suitable components (p4) for preparing the polyesters
(A1) are in particular compounds containing a group
which is capable of reacting with the functional groups
of the polyester. Their modifying components (p4) used
can be diepoxide compounds, if desired also monoepoxide
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compounds. Examples of suitable components (p4) are
described in DE-A-4,024,204 on page 4, lines 4 to 9.
Suitable components (p4) for preparing the polyesters
(A1) include compounds which also contain, in addition
to a group which is capable of reacting with the
functional groups of the polyester (A1), a tertiary
amino group, for example monoisocyanates containing at
least one tertiary amino group or mercapto compounds
containing at least one tertiary amino group. For
details, see DE-A-4,024,204, page 4, lines 10 to 49.
Polyesters (A1) are prepared by the known
esterification methods, such as described, for example,
in DE-A-4,024,204, page 4, lines 50 to 65.
This reaction is usually carried out at temperatures of
between 180 and 280°C, if desired in the presence of a
suitable esterification catalyst, such as, for example,
lithium octoate, dibutyltin oxide, dibutyltin
dilaurate, para-toluenesulfonic acid, and the like.
The preparation of the polyesters (A1) is usually
carried out in the presence of small amounts of a
suitable solvent which is used as entrainer. Examples
of the entrainer used are aromatic hydrocarbons, such
as, in particular, xylene and (cyclo)aliphatic
hydrocarbons, for example cyclohexane. However,
another alternative is to prepare the polyesters in the
absence of solvents (solvent-free reaction).
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Particularly preferably, the components (Al) used are
polyesters which have been prepared by a two-step
process by first preparing a hydroxyl-containing
polyester having an OH number of from 100 to 400 mg of
KOH/g, preferably of from 150 to 350 mg of KOH/g, and
an acid number of less than 10 mg of KOH/g and a
number-average molecular weight Mn of from 500 to 2000
Dalton which is then reacted in a second step with
carboxylic anhydrides to give the desired polyester
(A1). The amount of carboxylic anhydrides is selected
such that the polyester obtained has the desired acid
number. Suitable acid anhydrides are those which are
usually used for this reaction, such as, for example,
hexahydrophthalic anhydride, trimellitic anhydride,
pyromellitic anhydride, phthalic anhydride, camphoric
anhydride, tetrahydrophthalic anhydride, succinic
anhydride and mixtures of these and/or other anhydrides
and, in particular, anhydrides of aromatic
polycarboxylic acids, such as trimellitic anhydride.
Apart from being reacted with carboxylic anhydrides,
the acid groups can furthermore also be incorporated in
the polyester by using dimethylolpropionic acid and the
like.
The polyurethane resins (A2) used for preparing the
coating compositions according to the invention include
any polyurethane resins (A2) which contain water-
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soluble or water-dispersible hydroxyl groups and acid
groups which can be converted into the corresponding
acid anion groups and have an OH number of from 20 to
200 mg of KOH/g, preferably of from 80 to 180 mg of
KOH/g, and an acid number of from 5 to 150 mg of KOH/g,
in each case relative to the solid resin. Preferably,
the polyurethane resins used are those having a number-
average molecular weight Mn of between 1000 and 30,000
Dalton, preferably of between 1000 and 15,000 Dalton,
and particularly preferably of between 1000 and 7500
Dalton, in each case measured against a polystyrene
standard.
Suitable polyurethane resins are described, for
example, in the following publications: EP-A-355,433,
DE-A-3,545,618, DE-A-3,813,866, DE-A-3,210,051,
DE-A-2,624,442, DE-A-3,739,332, US-A-4,719,132,
EP-A-89,497, US-A-4,558,090, US-A-4,489,135,
DE-A-3,628,124, EP-A-158,099, DE-A-2,926,584,
EP-A-195,931, DE-A-3,321,180 and DE-A-4,005,961.
The polyurethane resins which can be used in component
(I) are those which are preparable by reacting
isocyanato-containing prepolymers with compounds which
are capable of reacting with isocyanate groups.
The isocyanato-containing prepolymers can be prepared
by reacting polyols having a hydroxyl number of from 10
to 1800, preferably from 50 to 1200, mg of KOH/g with
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excess polyisocyanates at temperatures of up to 150°C,
preferably 50 to 130°C, in organic solvents which are
incapable of reacting with isocyanates. The equivalent
ratio of NCO to OH groups is between 2.0:1.0 and
> 1.0:1.0, preferably between 1.4:1 and 1.1:1.
The polyols used for preparing the prepolymer can be of
low molecular weight and/or of high molecular weight
and contain inert anionic groups or groups capable of
forming anions or cationic groups or groups which are
capable of forming cations. The additional use of low-
molecular-weight polyols having a molecular weight of
from 60 to 400 Dalton for preparing the isocyanato-
containing prepolymers is also possible. The amounts
of polyols used can be up to 30% by weight, preferably
about 2 to 20 o by weight, relative to the total amount
of polyol components.
To obtain an NCO prepolymer of high flexibility, a
large amount of a predominantly linear polyol having a
preferred OH number of from 30 to 150 mg of KOH/g
should be added. Up to 97o by weight of the total
amount of polyol can consist of saturated and
unsaturated polyesters and/or polyethers having a
number-average molecular weight Mn of from 400 to 5000
Dalton. The polyether diols selected should not
introduce excessive amounts of ether groups since
otherwise the polymers formed will be subject to
swelling in water. Polyester diols are prepared by
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esterifying organic dicarboxylic acids or anhydrides
thereof with organic diols or are derived from a
hydroxycarboxylic acid or from a lactone. Branched
polyester polyols can be prepared by using small
amounts of polyols or polycarboxylic acids having a
relatively high number of hydroxyl or carboxyl groups.
The NCO prepolymer contains at least about 0.5% by
weight of isocyanate groups, preferably at least 1% by
weight of NCO, relative to solids. The upper limit is
about 15o by weight, preferably loo by weight,
particularly preferably 5% by weight of NCO.
However, the compounds which are preferably used are
polyurethane resins (A2) which are available by
reacting in a first reaction step
(a) at least one organic di- and/or polyisocyanate
with
(b) at least one compound containing at least one
group which is capable of reacting with isocyanate
groups and at least one group which ensures water
dispersibility, preferably one group which is capable
of forming anions,
to give a reaction product having free isocyanate
groups which is then reacted with
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18
(c) a polycondensation product comprising
(kl) l0 to 45 mol% of at least one diol,
(k2) 5 to 50 mol% of at least one polyol having at
least 3 OH groups per molecule,
(k3) 35 to 47 mol% of at least one di- ;and/or
polycarboxlic acid, if desired together with a
monocarboxylic acid, and
(k4) 0 to 20 mol% of at least one monool, the sum of
the mol% of the components (kl) to (k4) being in each
case 100 mol%, and
(d) 0 to 20 mol%, relative to component c, of further
alcohol components
to give the polyurethane resin (A2), the amounts of
components (a) to (d) being selected such that the
polyurethane resin has the desired OH numbers and acid
numbers and, if desired, the desired molecular weights.
Particularly preferred polyurethane resins are obtained
by using components (kl), (k2), (k3) and (k4) in such
molar ratios that the sum of the OH building blocks
(kl), (k2) and (k4) combined and the sum of the COON
building blocks (k3) are used in the ratio of
0.8:1 to 1.6:1.
The relative amounts of components (a) to (d) can be
selected to vary over wide ranges and as a function of
the reaction components. If polyester component (c)
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does not contain any hydrophilic segments, such as
polyether portions, it is preferred to react up to
1.1 mol of polyester (c) per mole of NCO equivalent to
give an OH/NCO ratio of >_ 1. If a polymeric polyester
containing hydrophilic segments is used, it is also
possible to use more than 1.1 mol of polyester (c) per
NCO equivalent.
Suitable multifunctional isocyanates for preparing the
polyurethane resins include aliphatic, cycloaliphatic
and/or aromatic polyisocyanates containing at least two
isocyanate groups per molecule. Preference is given to
isomers or mixtures of isomers of organic
diisocyanates. Owing to their good resistance to W
light, (cyclo)aliphatic diisocyanates yield products of
low tendency to yellowing. The polyisocyanate
component needed for forming the polyurethane resin can
also contain a proportion of polyisocyanates of higher
valence, provided this does not lead to gel formation.
Triisocyanates which have successfully been employed
are those products which are obtained by trimerization
or oligomerization of diisocyanates or by reaction of
diisocyanates with polyfunctional compounds containing
OH or NH groups. If desired, the average functionality
can be lowered by adding monoisocyanates.
Examples of polyisocyanates which can be used are
phenylene diisocyanate, toluylene diisocyanate,
xylylene diisocyanate, bisphenylene diisocyanate,
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naphthylene diisocyanate, diphenylmethane diisocyanate,
isophorone diisocyanate, cyclobutane diisocyanate,
cyclopentylene diisocyanate, cyclohexylene
diisocyanate, methylcyclohexylene diisocyanate,
dicyclohexylmethane diisocyanate, ethylene diiso-
cyanate, trimethylene diisocyanate, tetramethylene
diisocyanate, pentamethylene diisocyanate, hexa-
methylene diisocyanate, propylene diisocyanate, ethyl-
ethylene diisocyanate and trimethylhexane diisocyanate.
High-solid polyurethane resin solutions are prepared by
using, in particular, diisocyanates of the general
formula (III')
R1 R1
f 1
OCN - C - X - C - NCO (III')
R2 R2
where X is a divalent aromatic hydrocarbon radical,
preferably an unsubstituted or halo-, methyl- or
methoxy-substituted naphthylene, diphenylene or 1,2-,
1,3- or 1,4-phenylene radical, particularly preferably
a 1,3-phenylene radical, and R1 and RZ are an alkyl
radical having 1 - 4 carbon atoms, preferably a methyl
radical. Diisocyanates of the formula (III') are known
(their preparation is described, for example, in
EP-A-101,832, US Patent Specification 3,290,350, US
Patent Specification 4,130,577 and US Patent
Specification 4,439,616), and are in part commercially
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available (1,3-bis)1-isocyanatoprop-2-yl)benzene is
sold, for example, by the American Cyanamid
Company under the trade name TMXDI (META)~).
Further preferred polyisocyanate components are
diisocyanates of the formula (IV'):
~ ~~NCO .
C'~~ R'-NCO ( IV' )
~/ 1
R H
where R is a divalent alkyl or'aralkyl radical having 3
to 20 carbon atoms and R' is a divalent alkyl or
aralkyl radical having 1 to 20 carbon atoms.
In general, polyurethanes are not compatible with water
unless specific components have been incorporated
during the synthesis and/or specific preparative steps
have been carried out. Thus, the compounds used for
preparing not only the preferred polyurethane resins
prepared by the abovementioned two-step process but
also for preparing other polyurethane resins used as
component (A2) are those containing at least one group
which is capable of reacting with isocyanate groups and
at least one group which ensures water dispersibility.
Suitable groups of this type are non-ionic groups (e. g.
polyethers), anionic groups, mixtures of these two
groups or cationic groups.
Thus, it is preferred to incorporate in the
polyurethane resin an acid number sufficient for
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dispersing the neutralized product in water to give a
stable dispersion. The compounds used for this purpose
are those containing at least one group which is
capable of reacting with isocyanate groups and at least
one group which is capable of forming anions. Suitable
groups which are capable of reacting with isocyanate
groups are in particular hydroxyl groups and primary
and/or secondary amino groups. Groups which are
capable of forming anions are carboxyl, sulfonic acid
and/or phosphonic acid groups. Preferably, alkanoic
acids containing two substituents on the alpha-carbon
atom are used. The substituent can be a hydroxyl
group, an alkyl group or an alkylol group. These
polyols one, contain at least usually 1 to 3, carboxyl
groups per molecule. They contain two to about 25,
preferably 3 to 10, carbon atoms. Very particular
preference is given to using dimethylolpropanoic acid.
The carboxyl-containing polyol can make up to 1 to 250
by weight, preferably 1 to 20% by weight, of the total
amount of polyol components in the polyurethane resin
( A2 ) .
The amount of ionizable carboxyl groups available in
salt form as a result of the neutralization of the
carboxyl groups is usually at least 0.4o by weight,
preferably at least 0.7% by weight, relative to solids.
The upper limit is about 12% by weight . The amount of
dihydroxyalkanoic acids in the unneutralized prepolymer
gives an acid number of at least 5 mg of KOH/g,
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preferably at least 10 mg of KOH/g. If the acid
numbers are very low, further measures for achieving
water dispersibility are usually necessary. The upper
limit of the acid number is 150 mg of KOH/g, preferably
40 mg of KOH/g, relative to solids. The acid number is
preferably in the range of from 20 to 40 mg of KOH/g.
As for the compounds (kl) to (k4) which are suitable
for preparing the polycondensation product (c) and as
for the reaction conditions used in their preparation,
see the description of the polyester resins (A1).
The polycondensation products (c) which are preferably
used are those having an OH number of from 100 to
400 mg of KOH/g, preferably of from 150 to 300 mg of
KOH/g, an acid number of from 0 to 50 mg of KOH/g,
preferably of from 0 to 30 mg of KOH/g, and
particularly preferably of 1 to 20 mg of KOH/g, in each
case relative to the solid resin, and a number-average
molecular weight Mn of between 500 and 15,000 Dalton,
preferably of between 1000 and 10,000 Dalton, in each
case measured against a polystyrene standard.
Examples of alcohol components which are suitable as
further modifying components (d) are monoalcohols, such
as nonanol and decanol, and reaction products of
monocarboxylic acids with epoxides. Preferably, the
components (d) are compounds having on average more
than 1 OH group per molecule.
CA 02247959 1998-09-02
- 24 -
The polyurethane resins can be prepared by the known
methods (e.g. acetone method). Alternatively, the
components can also be reacted in ethoxyethyl
propionate (EEP) as solvent. The amount of ethoxyethyl
propionate can var~~ over a wide range and should be
sufficient for obtaining a prepolymer solution of
suitable viscosity. In general, up to 70% by weight,
preferably 5 to 50% by weight, and particularly
preferably less than 20o by weight, of solvent,
relative to solids, are used. Thus, for example, it is
particularly preferred to carry out the reaction at a
solvent content of 10 - 15% by weight of EEP, relative
to solids.
If desired, the reaction of the components can be
carried out in the presence of a catalyst, such as
organotin compounds and/or tertiary amines.
The coating compositions according to the invention
contain as component (A3) at least one water-soluble or
water-dispersible acrylate copolymer which contains
hydroxyl groups and acid groups which can be converted
into the corresponding acid anion groups and/or one
acrylated polyester and/or one acrylated polyurethane
having an OH number of from 40 to 200 mg of KOH/g and
an acid number of from 5 to 150 mg of KOH/g.
CA 02247959 1998-09-02
- 25 -
The acrylate copolymers used as component (A3)
preferably have number-average molecular weights of
between 1000 and 30,000 Dalton, preferably of between
1000 and 15,000 Dalton, in each case measured against a
polystyrene standard.
Acrylate copolymers which are suitable as acrylate
copolymer (A3) containing hydroxyl groups and acid
groups include all those having the OH numbers, acid
numbers and molecular weights mentioned.
Acrylate copolymers which are preferably used as
component (A3) are those which are obtainable by
polymerization of
al) a (meth)acrylate which is different from (a2),
(a3), (a4), (a5) and (a6), copolymerizable with (a2),
(a3), (a4), (a5) and (a6) and substantially free of
acid groups or a mixture of such monomers,
a2) an ethylenically unsaturated monomer which is
copolymerizable with (al), (a3), (a4), (a5) and (a6),
different from (a5) and carries at least one hydroxyl
group per molecule and is substantially free of acid
groups, or a mixture of such monomers,
a3) an ethylenically unsaturated monomer which
carries, per molecule, at least one acid group which
can be converted into the corresponding acid anion
CA 02247959 1998-09-02
- 26 -
group, and is copolymerizable with (al), (a2), (a4),
(a5) and (a6), or a mixture of such monomers, and
a4) if desired one or more vinyl esters of alpha
s branched monocarboxylic acids having 5 to 18 carbon
atoms per molecule, and/or
a5) if desired at least one reaction product of
acrylic acid and/or methacrylic acid with the glycidyl
ester of an alpha-branched monocarboxylic acid having 5
to 18 carbon atoms per molecule or, instead of the
reaction product, an equivalent amount of acrylic
and/or methacrylic acid which is then reacted, during
or after the polymerization reaction, with the glycidyl
ester of an alpha-branched monocarboxylic acid having 5
to 18 carbon atoms per molecule,
a6) if desired an ethylenically unsaturated monomer
which is copolymerizable with (al), (a2), (a3), (a4)
and (a5), is different from (al), (a2), (a4) and (a5)
and is substantially free of acid groups, or a mixture
of such monomers
in an organic solvent or a solvent mixture and in the
presence of at least one polymerization initiator,
type and amount of (al), (a2), (a3), (a4), (a5) and
(a6) being selected such that polyacrylate resin (A3)
has the desired OH number, acid number and the desired
molecular weight.
CA OI2247959 2005-02-25
29018-33
- 27 -
I,n order to prepare the polyacrylate resins used
according to the invention, the component (al) used can
be any (meth)acrylic ester which is coplymerizable .with
(a2), (a3), (a4). (a5) and (a6) and is substantially
free of acid groups or a mixture of such (meth)acrylic
esters. Examples include alkyl acrylates and alkyl
.methacrylates having up to 20 carbon atoms in the alkyl
radical, such. as, for example, methyl acrylate and
l0 methacrylate, ethyl acrylate and methacrylate, propyl
acrylate and methacryhate, butyl acrylate and
methacrylate, hexyl acrylate and methacrylate,
ethylhexyl acrylate and methacrylate, stearyl acrylate
and methacrylate and lauryl acrylate and methacrylate,
and cycloaliphatic (meth)acrylic esters, such as, for
example, cyclohexyl (meth)acrylate, isobornyl
(meth)acrylate, dicyclopentane (meth)acrylate
and tert-butylcyclohexyl (meth)acrylate.
The component (al) used can also be ethyltriglycol
(meth)acrylate and methoxyoligoglycol (meth)acrylate
having a number-average molecular weight Mn of,.
preferably, 550 Dalton or other ethoxylated and/or
propoxylated hydroxyl-free (meth)acrylic acrd
derivatives.
The compounds which are used as component (a2) can be
ethylenically unsaturated monomers which are
copolymerizable with (al), (a2), (a3), (a4), (a5) and
CA 02247959 1998-09-02
- 28 -
(a6), are different from (a5), carry at least one
hydroxyl group per molecule and are substantially free
of acid groups, or can be a mixture of such monomers.
Examples include hydroxyalkyl esters of acrylic acid,
methacrylic acid or any other alpha, beta-ethylenically
unsaturated carboxylic acid. These esters can be
derived from an alkylene glycol which is esterified
with the acid or they can be obtained by reacting the
acid with an alkylene oxide. The compounds which are
used as component (a2) are preferably hydroxyalkyl
esters of acrylic acid or methacrylic acid in which the
hydroxyalkyl group contains up to 20 carbon atoms,
reaction products of cyclic esters, such as, for
example, epsilon-caprolactone, with these hydroxyalkyl
esters, or mixtures of these hydroxyalkyl esters or of
hydroxyalkyl esters modified with epsilon-caprolactone.
Examples of such hydroxyalkyl esters include
2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
3-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,
3-hydroxypropyl methacrylate, 2-hydroxyethyl
methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl
methacrylate, hydroxystearyl acrylate and
hydroxystearyl methacrylate. The corresponding esters
of other unsaturated acids, such as, for example,
ethacrylic acid, crotonic acid and similar acids having
up to about 6 carbon atoms per molecule, can also be
used.
CA 02247959 1998-09-02
- 29 -
Furthermore olefinically unsaturated polyols can also
be used as component (a2). Preferred polyacrylate
resins (A3) are obtained by using trimethylolpropane
monoallyl ether at least in part as component (a2).
The proportion of trimethylolpropane monoallyl ether is
usually 2 to 10% by weight, relative to the total
weight of the monomers (al) to (a6) used for preparing
the polyacrylate resin. However, in addition to this,
it is also possible to add 2 to loo by weight of
trimethylolpropane monoallyl ether, relative to the
total weight of the monomers used for preparing the
polyacrylate resin, to the finished polyacrylate resin.
The olefinically unsaturated polyols, such as, in
particular, trimethylolpropane monoallyl ether, can be
used as the only hydroxyl-containing monomers, but are
used in particular proportionately in a combination
with others of the hydroxyl-containing monomers
mentioned.
The component (a3) used can be any ethylenically
unsaturated monomer which carries at least one acid
group, preferably a carboxyl group, per molecule and is
copolymerizable with (al), (a2), (a4), (a5) and (a6),
or a mixture of such monomers. The component (a3) used
is particularly preferably acrylic acid and/or
methacrylic acid. However, other ethylenically
unsaturated carboxylic acids having up to 6 carbon
atoms in the molecule can also be used. Examples of
such acids include ethacrylic acid, crotonic acid,
CA 02247959 1998-09-02
- 30 -
malefic acid, fumaric acid and itaconic acid.
Furthermore, for example, ethylenically unsaturated
sulfonic or phosphonic acids or partial esters thereof
can be used as component (a3). Mono(meth)acryloyloxy-
ethyl maleate, mono(meth)acryloyloxyethyl succinate and
mono(meth)acryloyloxyethyl phthalate can also be used
as component (a3).
The component (a4) used includes one or more vinyl
esters of alpha-branched monocarboxylic acids having 5
to 18 carbon atoms in the molecule. The branched
monocarboxylic acids can be obtained by reacting formic
acid or carbon monoxide and water with olefins in the
presence of a liquid, strongly acid catalyst. The
olefins can be products obtained by cracking paraffinic
hydrocarbons, such as mineral oil fractions, and can
contain not only branched but also straight-chain
acyclic and/or cylcoaliphatic olefins. The reaction of
such olefins with formic acid or with carbon monoxide
and water produces a mixture of carboxylic acids in
which the carboxyl groups are predominantly attached to
a quaternary carbon atom. Examples of other olefinic
starting materials are propylene trimer, propylene
tetramer and diisobutylene. However, the vinyl esters
can also be prepared from the acids in the manner known
per se, for example by reacting the acid with
acetylene.
CA 02247959 1998-09-02
- 31 -
Owing to their ready availability, it is particularly
preferred to use vinyl esters of saturated aliphatic
monocarboxylic acids which contain 9 to 11 carbon atoms
and are branched on the alpha-carbon atom.
The compound which is used as component (a5) is the
reaction product of acrylic acid and/or methacrylic
acid with the glycidyl ester of an alpha-branched
monocarboxylic acid having 5 to 18 carbon atoms per
molecule. Glycidyl esters of highly branched
monocarboxylic acids are available under the trade name
"Cardura". The reaction of the acrylic or methacrylic
acid with the glycidyl ester of a carboxylic acid
having a tertiary alpha-carbon atom can take place
before, during or after the polymerization reaction.
Preferably, the component (a5) used is the reaction
product of acrylic and/or methacrylic acid with the
glycidyl ester of versatic acid. This glycidyl ester
is commercially available under the name "Cardura E10".
The compounds which can be used as component (a6)
include any ethylenically unsaturated monomers which
are copolymerizable with (al), (a2), (a3), (a4) and
(a5), are different from (al), (a2), (a3) and (a4) and
are substantially free of acid groups, or mixtures of
such monomers. Preferably, vinylaromatic hydrocarbons,
such as styrene, alpha-alkylstyrenes and vinyltoluene,
are used as component (a6).
CA 02247959 1998-09-02
- 32 -
The compounds which can be used as component (a6)
include polysiloxane macromonomers in combination with
other monomers mentioned as being suitable as component
(a6). Suitable polysiloxane macromonomers are those
having a number-average molecular weight Mn of from
1000 to 40,000, preferably of from 2000 to l0,OC0
Dalton and on average 0.5 to 2.5, preferably 0.5 to
1.5, of ethylenically unsaturated double bonds per
molecule. Examples of suitable polysiloxane
macromonomers are those described in DE-A 3,807,571 on
pages 5 to 7 , in DE-A 3 , 706 , 0 95 in columns 3 to 7 , in
EP-B 358, 153 on pages 3 to 6 and in US-A 4, 754, 014 in
columns 5 to 9. Furthermore, other vinyl monomers
containing acryloxysilane and having the abovementioned
molecular weights and contents of ethylenically
unsaturated double bonds, for example compounds
obtainable by reacting hydroxy functional silanes with
epichlorohydrin, followed by reacting the reaction
product with methacrylic acid and/or hydroxyalkyl
esters of (meth)acrylic acid, are also suitable.
Preferably, the polysiloxane macromonomers mentioned in
DE-A 4,421,823 are used as component (a6).
Examples of polysiloxane macromonomers which are
suitable as component (a6) include the compounds
mentioned in the international patent application,
application number WO 92/22615 on page 12, line 18, to
page 18, line 10.
CA 02247959 1998-09-02
- 33 -
The amount of the polysiloxane macromonomer(s) (a6)
used for modifying the acrylate copolymers (A1) is less
than 5% by weight, preferably 0.05 to 2.5% by weight,
particularly preferably 0.05 to 0.8% by weight, in each
case relative to the total weight of the monomers used
for preparing copolymer (A3).
By using such polysiloxane macromonomers, the slip of
the aqueous coating compositions according to the
invention is improved.
Particularly preferably used acrylate resins are
obtained by polymerization of
(al) 20 to 60% by weight, preferably 30 to 50% by
weight, of component (al),
(a2) 10 to 40% by weight, preferably 15 to 35o by
weight, of component (a2),
(a3) 1 to 15% by weight, preferably 2 to 8 o by weight,
of component (a3),
(a4) 0 to 25o by weight, preferably 5 to 15% by weight,
of component (a4),
(a5) 0 to 25% by weight, preferably 5 to 15o by weight,
of component (a5), and
CA 02247959 1998-09-02
- 34 -
(a6) 5 to 30% by weight, preferably 10 to 20% by
weight, of component (a6),
the sum of the weight proportions of components (al) to
(a6) being in each case 100% by weight.
The preparation of the polyacrylate resins (A3) used
according to the invention is carried out in an organic
solvent or solvent mixture and in the presence of at
least one polymerization initiator. The organic
solvents and polymerization initiators used are the
solvents and polymerization initiators customary for
preparing polyacrylate resins and suitable for
preparing aqueous dispersions. The solvents used can
participate in the reaction with the crosslinking
component (II) and thus act as reactive diluent.
Examples of useful solvents are butylglycol,
2-methoxypropanol, n-butanol, methoxybutanol, n-
propanol, ethylene glycol monomethyl ether, ethylene
glycol monoethyl ether, ethylene glycol monobutyl
ether, diethylene glycol monomethyl ether, diethylene
glycol monoethyl ether, diethylene glycol diethyl
ether, diethylene glycol monobutyl ether,
trimethylolpropane, ethyl 2-hydroxypropionate and 3-
methyl-3-methoxybutanol and derivatives based on
propylene glycol, for example ethyl ethoxypropionate,
isopropoxypropanol, methoxypropyl acetate and the like.
CA 02247959 1998-09-02
- 35 -
Alternatively, the polyacrylate resins (A3) can also be
prepared first in a solvent which is not water-
dilutable and then, if desired, to replace this solvent
after polymerization in part by a water-dilutable
solvent.
Examples of useful polymerization initiators include
free-radical initiators, such as, for example, tert-
butylperoxyethyl hexanoate, benzoyl peroxide,
azobisisobutyronitrile and tert-butyl perbenzoate.
Preferably, the initiators are used in an amount of 2
to 25% by weight, particularly preferably in an amount
of 4 to 10% by weight, relative to the total weight of
the monomers.
Polymerization is advantageously carried out at a
temperature of from 80 to 160°C, preferably from 110 to
160°C. Preferably, the solvents used are n-butanol,
ethoxyethyl propionate and isopropoxypropanol.
Polyacrylate resin (A3) is preferably prepared by a
two-step process since in this way the resulting
aqueous coating compositions exhibit better
processability. Accordingly, it is preferred to use
polyacrylate resins which are obtainable by
CA 02247959 1998-09-02
- 36 -
1. polymerizing a mixture of (al), (a2), (a4), (a5)
and (a6) or a mixture of portions of components (al),
(a2), (a4), (a5) and (a6) in an organic solvent,
2. adding, after at least 60% by weight of the
mixture comprising (al), (a2), (a4), (a5) and, if
present, (a6) have been added, (a3) and any remainder
of components (al), (a2), (a4), (a5) and (a6) and
continuing polymerization, and
3. after completion of the polymerization,
neutralizing the resulting polyacrylate resin, if
desired, at least in part, i.e. converting the acid
groups into the corresponding acid anion groups.
However, it is also possible to introduce first
components (a4) and/or (a5) together with at least a
portion of the solvent and then to meter in the
remaining components. Another possibility is to
introduce components (a4) and/or (a5) only in part
together with at least a portion of the solvent into
the reaction vessel and to add the remainder of these
components as described above. It is preferred to
introduce first, for example, at least 20o by weight of
the solvent and about 10% by weight of components (a4)
and (a5) and, if desired, portions of components (al)
and (a6). Preference is also given to preparing the
polyacrylate resins (A3) used according to the
invention by a two-step process in which step (I) has a
CA 02247959 1998-09-02
- 37 -
duration of 1 to 8 hours, preferably of 1.5 to 4 hours,
and the mixture comprising (a3) and any remainder of
components (al), (a2), (a4), (a5) and (a6) is added
over a period of 20 to 120 minutes, preferably over a
period of 30 to 90 minutes. After addition of the
mixture comprising (a3) and any remainder of components
(al), (a2), (a4), (a5) and (a6) is complete,
polymerization is continued until conversion of all
monomers used is essentially complete.
The amount and rate of addition of the initiator is
preferably selected such that a polyacrylate resin (A3)
having the desired number-average molecular weight is
obtained. It is preferred to start the initiator feed
some time, in general about 15 minutes, before the
monomer feed. Preference is furthermore given to a
process in which addition of the initiator is started
at the same time as addition of the monomers and is
completed about half an hour after addition of the
monomers has been completed. The initiator is
preferably added in a constant amount per unit of time.
After addition of the initiator is complete, the
reaction mixture is maintained at the polymerization
temperature for a time (usually 1.5 hours) sufficient
for essentially complete conversion of all monomers
used. "Essentially complete conversion" is understood
as meaning that preferably 100% by weight of monomers
used have been converted and that, however, it is also
possible that a small residual monomer content of not
CA 02247959 1998-09-02
- 38 -
more than about 0.5% by weight, relative to the weight
of the reaction mixture, may remain unconverted.
Preferably, the monomers for preparing polyacrylate
resins (A3) are polymerized at a polymerization solids
content which is not excessively high, preferably at a
polymerization solids content of 80 to 50% by weight,
and the solvents are then in part removed by
distillation to give polyacrylate resin solutions
having a solids content of, preferably, 80 to 60% by
weight.
Suitable components (A3) are furthermore acrylated
polyesters having an OH number of from 40 to 200 mg of
KOH/g, particularly preferably of from 60 to 160 mg of
KOH/g, and an acid number of from 5 to 150 mg of KOH/g,
preferably of from 15 to 75 mg of KOH/g, and
particularly preferably of from 20 to 50 mg of KOH/g.
The acrylated polyesters (A3) preferably have number-
average molecular weights Mn of between 1000 and 50,000
Dalton, preferably of between 1000 and 15,000 Dalton,
in each case measured against a polystyrene standard.
The acrylated polyesters which are used as component
(A3) are known. Suitable acrylated polyesters (A3) can
be prepared by various processes known to one skilled
in the art, for example by incorporating
trimethylolpropane monoallyl ether or malefic anhydride
or other reactive anhydrides which are polymerizable
CA 02247959 1998-09-02
- 39 -
with styrene and/or (meth)acrylates, followed by
acrylation (organic or aqueous).
Suitable components (A3) furthermore include acrylated
polyurethanes having an OH number of from 40 to 200 mg
of KOH/g, particularly preferably of from 60 to 160 mg
of KOH/g, and an acid number of from 5 to 150 mg of
KOH/g, preferably of from 15 to 75 mg of KOH/g, and
particularly preferably of from 20 to 50 mg of KOH/g.
The acrylated polyurethanes (A3) preferably have
number-average molecular weights Mn of between 1000 and
50,000 Dalton, preferably of between 1000 and 15,000
Dalton, in each case measured against a polystyrene
standard. The acrylated polyurethanes which are used
as component (A3) are also known. Examples of suitable
acrylated polyurethanes are described, for example, in
DE-A-4,122,265, page 2, line 15, to page 5, line 44, in
DE-A-4,010,176, page 2, line 41, to page 6, line 64, in
EP-A-308,115, page 2, line 29, to page 5, line 21, in
EP-A-510,572, page 3, line 21, to page 5, line 42, and
in US-A-4,496,708, column 4, line 5, to column 12, line
46.
Suitable components (A4) include any polymers which are
compatible with the remaining constituents of component
(I). For example, the di- and/or polyisocyanates
mentioned as examples of suitable crosslinking agents
can be used in capped form as (A4). Illustrative
examples of capping agents for the di- and/or
CA 02247959 1998-09-02
- 40 -
polyisocyanates mentioned include aliphatic,
cycloaliphatic or aralipatic monoalcohols, such as, for
example, methyl alcohol, butyl alcohol, octyl alcohol,
lauryl alcohol, cyclohexanol or phenylcarbinol,
hydroxylamines, such as ethanolamine, oximes, such as
methyl ethyl ketone oxime, acetone oxime or
cyclohexanone oxime, amines, such as dibutylamine or
diisopropylamine, malonic diesters, ethyl acetoacetate
and/or epsilon-caprolactam.
Component (I) preferably contains as binder (A) a
mixture of
10 to 50% by weight of the mixture of at least one
polyester (A1) and at least one polyurethane resin
( A2 ) ,
50 to 90% by weight of at least one polyacrylate resin
(A3) and/or of at least one acrylated polyester resin
and/or of at least one acrylated polyurethane resin and
0 to loo by weight of at least one further polymer
(A4 ) ,
the sum of the weight proportions of the components
being in each case 100% by weight.
Furthermore, it is preferable to use binders (A) (i.e.
the mixture of components (A1) to (A4)) which have an
CA 02247959 1998-09-02
- 41 -
OH number of from 50 to 200, preferably of from 80 to
180, mg of KOH/g.
The component (I) can contain as further constituent
(B) any pigments customary for paints in amounts of 0
to 60% by weight, relative to component I. The
pigments can be composed of inorganic or organic
compounds and can be effect pigments and/or coloring
pigments.
Effect pigments which can be used include metal flake
pigments, such as commercially available aluminum
bronzes, aluminum bronzes chromated in accordance with
DE-A-3,363,183, and commercially available stainless
steel bronzes and non-metallic effect pigments, such
as, for example, nacreous or interference pigments.
Examples of suitable inorganic coloring pigments are
titanium dioxide, iron oxides, Sicotrans yellow and
carbon black. Examples of suitable organic coloring
pigments are indanthrene blue, Cromophtal red, Irgazine
orange and Heliogene green.
Component (I) and also the binder can contain as
further constituent (C) at least one organic partially
or completely water-soluble solvent. Such solvents can
also participate in the reaction with crosslinking
component (II) and thus act as reactive diluent.
Examples of suitable solvents are the compounds already
mentioned for the preparation of the polyacrylate
CA 02247959 1998-09-02
- 42 -
resins (A3) (see above). Further suitable solvents are
esters, ketones, keto esters, glycol ether esters and
glycol ethers, for example ethylene glycol and 1,2- and
1,3-propylene glycol.
Furthermore, solvents (C) can entirely or in part
consist of lower-molecular-weight oligomeric compounds
which may be capable of reacting with crosslinking
component (II) or else may also be incapable of
reacting with them. Solvents (C) are usually used in
an amount of 0 to 20o by weight, preferably in an
amount of less than 15% by weight, relative to the
total weight of component (I).
Component (I) usually contains as constituent (D) at
least one neutralizing agent. Examples of suitable
neutralizing agents are ammonia, ammonium salts, such
as, for example, ammonium carbonate or ammonium
bicarbonate, and amines, preferably tertiary amines,
such as, for example, trimethylamine, triethylamine,
tributylamine, dimethylaniline, diethylaniline,
triphenylamine, dimethylethanolamine, diethylethanol-
amine, methyldiethanolamine, triethanolamine, and the
like. The neutralizaing agent used is particularly
preferably dimethylethanolamine.
The overall amount of neutralizing agent used in the
coating composition according to the invention is
selected such that 1 .to 100 equivalents, preferably 50
CA 02247959 1998-09-02
- 43 -
to 90 equivalents, of acid groups of the binder (A) are
neutralized.
Component (I) can contain as constituent (E) at least
one rheology-regulating additive. Examples of
rheolcgy-regulating additives include crosslinked
polymer microparticles, such as disclosed, for example,
in EP-A-38,127, inorganic layer silicates, such as, for
example, aluminum magnesium silicates, sodium magnesium
layer silicates and sodium magnesium fluorine lithium
layer silicates of the montmorillonite type, and
synthetic polymers containing ionic and/or associative
groups, such as polyvinyl alcohol, poly(meth)acryl-
amide, poly(meth)acrylic acid, polyvinylpyrrolidone,
styrene/maleic anhydride copolymers or ethylene/maleic
anhydride copolymers and derivatives thereof or else
hydrophobically modified ethoxylated urethanes or
polyacrylates. Preferably, the rheology-regulating
additives used are polyurethanes. Component (I)
preferably contains 0 to 2.Oo by weight of the
rheology-regulating additive, relative to the total
weight of component ( I ) .
In addition, component (I) can contain at least one
further customary paint additive. Examples of such
additives are defoamers, dispersing aids, emulsifiers
and flow-control agents.
Finally, component (I) additionally contains water.
CA 02247959 2005-02-25
29028-33'
- 44
Paint component~(II) contains as crosslinking agent at
., least one di- and/or polyisocyanate (F1) which may or
may not be dissolved in one or more organic solvent or
may or may not be dispersed in water-dilutabla solvents
and is preferably uncapped.
.The' polyisocyanate component (F1) can. be any organic
polyisocyanate containing aliphati~cally, cyclo-
aliphatically, araliphatically and/or aromatically
bonded free isocyanate groups. Preferably, the
polyisocyanates used have 2 to 5 isocyanate groups per
molecule and viscosities of from 100 to 2000 mPas (at
23°C). If desired, small amounts of organic solvent,
preferably 1 to 25% by weight, relative to the pure
polyisocyanate, can be added to the polyisocyanates to
improve the incorporability of the isocyanate and, if
desired, to lower the viscosity of the polyisocyanate
to a value within the abovementioned ranges. ~xamples .
of solvents for the polyisocyanates which are suitable
as additives are ethoxyether propionate, butyl acetate, .
and the like.
Examples of suitable isocyanates are described, for
example, in "Methoden der organischen Chemie " (Methods
of organic chemistry), Fiouben-Weyl, Volume 14/2, 4th
Edition, Georg Thieme Verlag, Stuttgart 1963, pp. 61 to
70, and by W. Siefken, Liebigs Ann. Chem., Volume 562, 1947,
pp. 75 to 136. Suitable isocyanates are, for exa~npl.e, the
CA 02247959 1998-09-02
- 45 -
isocyanates mentioned in the description of the
polyurethane resins (A2) and/or isocyanato-containing
polyurethane prepolymers which can be obtained by
reaction of polyols with excess polyisocyanate and are
preferably of low viscosity.
It is also possible to use polyisocyanates which
contain isocyanurate groups and/or biuret groups and/or
allophanate groups and/or urethane groups and/or urea
groups and/or uretdione groups. Polyisocyanates which
contain urethane groups are obtained, for example, by
reacting a portion of the isocyanate groups with
polyols, such as, for example, trimethylolpropane and
glycerol.
Preferably, the isocyanates used are aliphatic or
cycloaliphatic polyisocyanates, in particular
hexamethylene diisocyanate, dimerized and trimerized
hexamethylene diisocyanate, isophorone diisocyanate,
2-isocyanatopropylcyclohexyl isocyanate, dicyclohexyl-
methane 2,4'-diisocyanate or dicyclohexylmethane 4,4'-
diisocyanate or mixtures of these polyisocyanates.
Very particular preference is given to using mixtures
of polyisocyanates which are based on hexamethylene
diisocyanate and contain uretdione and/or isocyanurate
groups and/or allophanate groups, as obtained by
catalytic oligomerization of hexamethylene diisocyanate
in the presence of suitable catalysts. Incidentally,
the polyisocyanate component (F1) can also comprise any
CA 02247959 1998-09-02
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desired mixtures of the polyisocyanates mentioned by
way of example.
Advantageously, polyisocyanate component (F1) is used
in the coating compositions according to the invention
in such an amount that the ratio of the hydroxyl groups
of binder (A) to the isocyanate groups of crosslinking
agent (F1) is between 1 . 2 and 2 . 1, particularly
preferably between 1 . 1 and 1 . 1.5.
The two components (I) and (II) of the coating
composition according to the invention are prepared
from the individual constituents with stirring using
customary methods. The preparation of the coating
composition from these two components (I) and (II) is
likewise effected by stirring or dispersing using the
customarily used apparatuses, for example using
dissolvers or the like or using the likewise
customarily used 2-component metering and blending unit
or using the method for preparing aqueous 2-component
polyurethane coatings described in DE-A-19,510,651,
page 2, line 62, to page 4, line 5.
The aqueous coatings prepared using the binders
according to the invention usually contain in their
ready-to-use state 30 to 80, preferably 45 to 70, o by
weight of water, 0 to 50, preferably 0 to 20, o by
weight of organic solvents, 6 to 70, preferably 15 to
70, o by weight of binder (A) according to the
CA 02247959 1998-09-02
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invention, preferably 0 to 25% by weight of pigments
and/or fillers and 0 to loo by weight of other
additives, such as, for example, catalysts, thickeners,
flow-control agents, and the like, their percentages by
weight given being based on the entire formulation of
the coatings in the ready-to-use state (i.e., for
example with respect to their spray viscosity).
The aqueous coatings prepared using the binders
according to the invention can be used for coating
primed or unprimed plastics, such as, for example, ABS,
AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA,
PC, PE, HDPE, LDPE, LLDPE, UHMWPE, PET, PMMA, PP, PS,
SB, PUR, PVC, RF, SAN, PBT, PPE, POM, PUR-RIM, SMC,
BMC, PP-EPDM and UP (abbreviations in accordance with
DIN 7728T1). The plastics to be coated can of course
also be polymer blends, modified plastics or fiber-
reinforced plastics. The coating compositions
according to the invention are preferably used for
coating PPE/PA blends, polycarbonate blends (e. g.
PC/ASA, PC/PBT) and polypropylene blends. The coating
compositions according to the invention are used in
particular for plastics customarily used in the
construction of vehicles, in particular in the
construction of motorized vehicles.
Non-functionalized and/or non-polar substrate surfaces
have to be subjected to a pretreatment, such as plasma
or flame, prior to coating.
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Suitable primers include any customary primers, not
only conventional primers but also aqueous primers. It
is of course also possible to use radiation-curable
primers and radiation-curable aqueous primers.
The coating compositions according to the invention are
used for producing a single-layer or mufti-layer
coating and preferably as topcoats. However, they can
also be used as a clearcoat on top of a basecoat, for
example as a clearcoat of a mufti-layer coating
prepared by the wet-in-wet method. It is of course
also possible to coat the plastics or the other
substrates directly with the clearcoat or the topcoat.
Finally, the coating compositions can also be applied
to other substrates, such as, for example, metal, wood
or paper. They are applied by customary methods, for
example spraying, knife-coating, dipping or brushing.
The coating compositions according to the invention are
usually cured at temperatures of below 120°C,
preferably at temperatures of at most 100°C. In
special application forms of the coating compositions
according to the invention, it is also possible to
employ higher curing temperatures.
The coating compositions according to the invention are
preferably used for producing topcoats. The coating
CA 02247959 1998-09-02
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compositions according to the invention can be used not
only in line coating but also in repair finishes of
automotive bodies. However, they are preferably used
in the area of repair finishes and very particularly
preferably in the coating of plastic parts.
Below, the invention is illustrated in more detail by
means of exemplary embodiments. All parts given are
parts by weight unless expressly stated otherwise.
1 1 Preparation of a dispersion of a polyester resin
A1
7.43 kg of hexanediol, 25.72 kg of neopentyl glycol
hydroxypivalate, 4.23 kg of trimethylolpropane,
16.99 kg of hexahydrophthalic anhydride, 0.016 kg of
hydrated tin oxide and 2.529 kg of cyclohexane are
weighed into a steel vessel suitable for
polycondensation reactions, and the mixture is heated
at a maximum product temperature of 220°C for a time
sufficiently long to reach an acid number of from 6 to
8 and an OH number of about 276. After the acid number
has been reached, the mixture was cooled to 120°C, and
9.06 kg of trimellitic anhydride are added. Heating to
no more than 160°C is continued until reaching an acid
number of 35. The mixture was then cooled to 80°C, and
8.15 kg of isopropoxypropanol were added. This was
followed by adding at this temperature 2.62 kg of
dimethylethanolamine. Finally, a dispersion was
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prepared having an acid number .of 35 and a solids
content of 35%, a dimethylethanolamine content of 1.83%
and a solvent content of 6.29% by adding deivnized
water. The polyester resin (A1) had an OH number of
'5 143 mg and an acid number of 36.4 mg of KOH/g, in each
case relative to the solid resin.
1.2. Preparation of a dispersion of pol~rurethane resin
A2
Polyester precursor
To prepare 1 kg of polyester, 12 8.9 g of neopentyl
glycol, 318.9 g of neopentyl glycol hydroxypivalate,
166.0 g of trimethylolpropane; 205.5 g of isophthalic
acid, 40 g of xylene and 254.3 g of hexahydrophthalic
anhydride were weighed into a steel vessel
suitable for polycondensation reactions, the mixture
was continually heated up, and the water of
condensation was removed continuously. As,soon as the
product had reached an acid number of 3, the reaction
was stopped, and the mixture was cooled to 100°O and
partially dissolved with methyl ethyl ketone (MEK)
until reaching a solids content of 80% (viscosity of
the 50% solution in MEK 0.2 Pas.). The condensation
product thus obtained had an OH number of 202_mg of
KOH/g and an acid number of 3.5 mg of KOH/g, in each
case relative to the solid resin.
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Urethane-modified bolyester dispersion 1-
488.4 g of meta-tetramethylxylylene diisocyanate,
134.1 g of dimethylolpropionic acid and 568.0 ~
of methyl ethyl ketone are weighed into a steel vessel
suitable for polyaddition reactions, and the mixture
was heated to 80°C. At a constant isocyanate content
of 7.4%, relative to the mixture used, the batch was
cooled to 50°C, and 2110 g of the polyester solution
were added. This was followed by heating to 80°C. At
an isocyanate content of < 0.1% and a, viscosity of
3.6 dPas (10.3 in N-methylpyrrolidone, the
mixture was neutralized with 71.2 g of N,N-
dimethylethanolamine. It is then diluted with water,
and the organic solvent is removed in vacuo. Finally,
it is brought to a solids content of 43% by adding
deionized water. The pH of the dispersion was 6.8.
The dispersion:was speckle-free, homogenous and had a
shelf life of at least 8 weeks at 50°C. The DMEA
content was 1.42% and the solvent content 0.5%. The
polyurethane resin had an OH number of 98 mg of KOH/g,
an acid number of 26 mg of KOH/g and a number-average
molecular weight of 1713, measured against a
polystyrene standard and based on the solid resin.
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1 3 Preparation of a dispersion of an acrylate resin
A3
A 4 1 steel reactor equipped with two monomer feeds,
initiator feed, stirrer and reflux condenser was
charged with 470 parts by weight of n-butanol as
solvent component (B2) (water solubility WS: 9.0,
evaporation rate ER: 33, boiling point b.p.. 118°C),
and the mixture is heated to 110°C. This was followed
by addition of a solution of 36 parts by weight of
tert-butylperoxyethyl hexanoate in 92.4 parts by weight
of n-butanol (B2) at such a rate that addition is
complete after 5.5 hours. At the same time at which
addition of the tert-butylperoxyethyl hexanoate
solution is started, addition of the mixture comprising
(al) to (a6)
(al): 240 parts by weight of n-butyl methacrylate,
209 parts by weight of methyl methacrylate,
120 parts by weight of lauryl methacrylate
(methacrylic ester 13 from
Rohm GmbH),
(a2): 270 parts by weight of hydroxyethyl methacrylate
and
(a6): 180 parts by weight of styrene
is also started. The mixture comprising (al), (a2) and
(a6) is added at such a rate that addition is complete
after 5 hours.
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3.5 hours after the first monomer feed was started, a
second monomer feed is started which is completed
jointly with the first monomer feed and consists of a
mixture of monomer components (a2) and (a5):
(a2): 120 parts by weight of hydroxyethyl methacrylate
and
(a5): 61 parts by weight of acrylic acid.
After addition of the tert-butylperoxyethyl hexanoate
solution is complete, the reaction mixture is
maintained at 120°C for another 2 h. The resin
solution is then cooled to 80°C and neutralized with 63
parts by weight of dimethylethanolamine in 1379 parts
by weight [lacuna] to a degree of neutralization of 85%
within about 30 minutes.
The solvent (B) n-butanol is then removed by azeotropic
distillation until not more than to by weight of (B),
relative to the dispersion, can be detected by gas
chromatography.
After distillation is complete, the dispersion is
adjusted to the following final characteristic values
by addition of deionized water:
acid number of the entire solid: 37.2 mg of KOH/g,
solids content (1 hour, 130°C): 38.3%, pH: 7.40.
Dimethylethanolamine content: 2.11%
Solvent content: 0.52%
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The acrylate resin (A3) thus prepared had a number-
average molecular weight of 7772 Dalton and a weight-
average molecular weight of 26,651, measured against a
polystyrene standard, an OH number of about 140 mg of
KOH/g and an acid number of 37.2 mg of KOH/g, in each
case relative to the solid resin.
2 Preparation of the coating compositions from
Examples 1 to 3 and from Comparative Examples 1 and 2
The coating compositions are prepared from the
components listed in Table 1 by preparing first
component (I) from components (K-I-1) through (K-I-15)
and component (II) from components (K-II-1) through
(K-II-2) in each case by mixing using a laboratory
stirrer, then mixing components (I) and (II), and
finally bringing the mixture to the viscosity mentioned
by addition of water.
The coating compositions thus prepared are applied
pneumatically to PP panels (dry film thickness 30 - 35
micrometers). The panels thus coated are baked at 90°C
for 45 minutes and then aged at 22°C and 50% of
relative humidity of air for 8 days. The free
clearcoat films are then subjected to various tests.
The test results of the coatings are summarized in
Tables 2 and 3.
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Furthermore, the coating compositions of Examples l to
3 are distinguished by very good optical properties
(appearance). Moreover, components (I) of Examples~l
to 3 have a long shelf life .of at least half a year at
23°C or of at least 8 weeks at 40°C:
Summary of the test results
Examples 1 to 3 show that using a mixture of
polyester resin and polyurethane resin as further
binder results in coatings having high elasticity
(high elongation at break values at a relatively high
breaking force) while exhibiting low permeability.
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Table 1: Composition of the coating compositions of
Examples 1 to 3 and of Comparative Examples 1 and 2 in
parts by weight
Ex. Ex. 2 Ex. Comp. Comp.
1 3 1 2
PES (A1) K-I-1 12.16 9.12 6.08 18.24 -
PUR (A2) K-I-2 4.95 7.42 9.90 - 14.85
PAC (A3) K-I-3 64.7 64.7 64.7 65.21 65.21
BGA K-I-4 4.899 4.899 4.899 4.899 4.899
IPP K-I-5 0.868 1.059 1.251 0.769 1.633
PnB K-I-6 3.267 3.267 3.267 3.267 3.267
Water K-I-7 5.452 5.827 6.200 3.909 6.439
Dil. K-I-8 1.955 1.955 1.955 1.955 1.955
Emul. K-I-9 0.652 0.652 0.652 0.652 0.652
Wett. 1 K-I-10 0.938 0.938 0.938 0.938 0.938
Wett. 2 K-I-11 0.078 0.078 0.078 0.078 0.078
Flow-c. K-I-12 0.078 0.078 0.078 0.078 0.078
Light s. K-I-13 0.155 0.155 0.155 0.155 0.155
1
Light s. K-I-15 0.271 0.271 0.271 0.271 0.271
2
Sum - 100 100 100 100 100
SC BI - 31.17 31.17 31.17 31.17 31.17
SC (A1)/ - 2.000 1.000 0.500 - -
SC (A2)
Isocyan. K-II-1 21.60 21.38 21.16 21.96 20.73
EEP K-II-2 5.40 5.34 5.29 5.49 5.18
Water K-III 15.00 15.00 15.00 15.00 15.00
viscos.
OH (SC)/ - 0.717 0.717 0.717 0.717 0.717
NCO (mol)
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Explanation of Table 1
PES (A1): Polyester dispersion (A1) described in 1.1
PUR (A2): Polyurethane dispersion (A2) described in
1.2
PAC (A3): Polyacrylate dispersion (A3) described in
1.3
BGA: 2-Butoxyethyl acetate
IPP: 1(2)-Isopropoxy-2(1)-propanol
PnB : 1 ( 2 ) -Butoxy- 2 ( 1 ) -propanol
Dil.: 10% solution of a commercially available
thickener based on polyglycol dialkyl ether
in water
Emul.: Commercially available emulsifier based on
polyglycol octylphenol ether
Wett. 1: Commercially available polyether-modified
dimethyloligosiloxane
Wett. 2: Commercially available polyether-modified
dimethylpolysiloxane
Flow-c.: Commercially available flow-control agent
based on a polyether-modified polysiloxane
Light s. 1: Commercially available light stabilizer
based on a sterically hindered amine (HALS)
Light s. 2: Commercially available light stabilizer
based on benzotriazole
Isocyan.: Commercially available 100% pure isocyanate
based on a hexamethylene diisocyanate
allophanate having an NCO content of 20%
SC(BI): Solids content of the binder, sum of
(A1)+(A2)+(A3)
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EEP: Ethoxyethyl propionate
Water vise : Water added for adjusting the viscosity
OH(SC)/NCO (mol): Ratio of the OH groups of the binder
(sum of (Al) + (A2) + (A3)) to the NCO groups of the
crosslinking agent
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Table 2: Test results of permeability (100 micrometers
x g x ni Z x d'1) to water vapor
40C
Comparative Ex. 1 121
Example 1 ' 61
Example 2 68.8
Example 3 63.5
S
Comparative Ex. 2 74.5
Table 3: Test results of the mechanical properties
Comp. 1 Ex. 1 Ex. 2 Ex. 3 Gomp.
2
Breaking 5.4 6.7 8.4 . 7 8.7
force (N)
Elong. at 19 20 22 13 9
break ( %
)
Elong. 10 8 5.5 5 4.5
Fmax (%)
Explanation of Tables 2 and 3:
The permeability to water vapor was determined on
water-saturated foams at 40°C using the carrier gas
method.
Furthermore, characteristic values of the free films
,~
were determined in a ZWICK universal testing apparatus
CA 02247959 1998-09-02
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by subjecting them to a tensile/elongation test. The
values given are the breaking force in N, the
elongation at break in % and the elongation at Fmax in
o.
