Note: Descriptions are shown in the official language in which they were submitted.
" ` 21 73475
COATING COMPOSITION BASED ON A POLYACRYLATE
RESIN CONTAINING HYDROXYL GROUPS, AND ITS USE
IN PROCESSES FOR THE PRODUCTION OF COATINGS
BACKGROUND OF THE INVENTION
The present invention relates to a coating composition which
comprises
(A) at least one component which contains hydroxyl groups,
consisting of:
(A1) from 20 to 60% by weight of at least one polyester
and
(A2) from 40 to 80% by weight of at least one
polyacrylate resin which contains hydroxyl groups
and has been prepared, at least partially, in the
presence of component (A1),
and
(B) at least one crosslinking agent.
The present invention also relates to processses for the
production of a protective and/or decorative coating on
" ` 21 70475
.
a substrate surface and to the use of the coating com-
positions in the area of automotive refinishing.
DE-A-40 24 204 has already disclosed coating composi-
tions which contain, as binder, a polyacrylate resin
which contains hydroxyl groups and has been prepared in
the presence of a polyester which contains hydroxyl
~lOU~. However, especially when these coating composi-
tions are applied at low temperatures, from about 8 to
12C, the mas~ing resistance and solvent resistance of
the resulting coatings is in need of improvement.
In the area of the finishing of large-size vehicles,
for example the finis~ing of goods-vehicle bodies, the
masking resistance of the resulting coatings is of
particular importance. This is because large-size vehi-
cles are commonly provided with written characters,
whose application requires the adjacent area to be
masked off. If the masking resistance is inadequate,
the marks must be removed by hand, by laborious sanding
and polishing, which entails a considerable financial
outlay.
Furthermore, the coating compositions must also cure as
rapidly as possible, in order to avoid excessive
standing times between the individual operations.in the
coating plant. These coating compositions must also, of
course, possess good application properties and lead to
coatings having good mechanical properties.
" " 2170475
- 3 - `
In addition, DE-A-31 33 769 discloses that the curing
rate of one-component polyurethane coating compositions
based on amines and on compounds containing isocyanate
groups can be increased by the addition of benzoic
acid. These coating compositions known from
DE-A-31 33 769 differ from the coating compositions
according to the invention in that no description is
given of coating compositions based on polymers con-
taining hydroxyl groups and on crosslinking agents con-
taining isocyanate groups.
Furthermore, US-A-3,897,396 discloses that the curing
rate of molding compositions based on polyurethane-
ureas can be increased by the addition of alkyl- or
alkoxybenzoic acid, without thereby shortening the pot
life.
These compositions known from US-A-3,897,396 differ
from the coating compositions according to the inven-
~tion in that US-A-3,897,396 describes molding composi-
tions rather than coating compositions. Furthermore,
these molding compositions known from US-A-3,897,396
contain binders comprising prepolymers which contain
isocyanate groups and are based on the reaction product
of a polyetherpolyol, polyesterpolyol or hydrocarbon-
polyol with isocyanates and a crosslinking agent com-
prising polyamines. Compositions based on acrylate
copolymers containing hydroxyl groups and on compounds
21 704i`~i
--4--
containing isocyanate groups, on the other hand, are not described
in US-A-3,897,396.
Finally, German Patent Application P 44 07 409.3, which is not a
prior publication, discloses coating compositions containing a
polyacrylate resin, which contains hydroxyl groups and is based on
hydroxy-n-butyl acrylate, and a crosslinking agent. The
preparation of the polyacrylate resin in the presence of a
polyester resin, however, is not described in this application.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide coating
compositions based on polyesters containing hydroxyl groups and on
polyacrylate resins, which compositions exhibit rapid drying
coupled with a lot pot life, i.e. which can be processed in the
ready-to-use state over a long period. In particular, the coating
compositions should provide a masking resistance of the resulting
coatings which is improved in comparison with that of conventional
coating compositions. Furthermore, the coating compositions should
at least meet the requirements conventionally placed on a topcoat
or clearcoat. The coating compositions should therefore, for
:example, exhibit good spray-mist assimilation, good topcoat holdout
and good leveling. In addition, they should lead to coatings
having good solvent resistance and a high degree of surface
hardness. Furthermore, the coating compositions should cure at room
temperature or at slightly elevated
21 70~75
- 5 -
temperature, so that they can be employed in automotive
refinishing.
The tlacuna] invention is surprisingly achieved by the
coating compositions of the type mentioned initially,
which are characterized in that
1.) the polyester (Al) has an OH number of from 90 to
130 mg of KOH/g, an acid number of less than 10 mg
of KOH/g, a number-average molecular weight of
from 1300 to 3500 and a polydispersity of from 5
to 50,
2.) the polyacrylate resin (A2) contains one or more
monomers selected from the group consisting of
4-llydLoxy-n-butyl acrylate, 4 llyd~y-n-butyl
methacrylate, 3-hydroxy-n-butyl acrylate,
3-hydroxy-n-butyl methacrylate and/or hydroxyethyl
methacrylate, incorporated by polymerization,
3.) the polyacrylate resin (A2) has a hydroxyl number
of from 50 to 150 mg of KOH/g and an acid number
of from 0 to 10 mg of KOH/g, and
4.) from 0.1 to 1% by weight, based on the weight of
component (A) without solvent, of at least one
aromatic mono- and/or polycarboxylic acid and/or
an anhydride of an aromatic polycarboxylic acid
" 2 1 704 75
-- 6
are added to component (A) after its preparation
or to the coating composition.
The invention furthermore relates to a process for the
production of a protective and/or decorative coating on
a substrate surface, using these coating compositions,
and to the use of these coating compositions for
refini~h;ng, either as a pigmented or nonpigmented top-
coat.
It is surprising and was not foreseeable that the
coating compositions according to the invention, even
on curing at low temperatures, cure rapidly while at
the same time retaining long processibility (pot life).
A particular advantage is the masking resistance of the
resulting coatings, which is improved in comparison
with that of conventional coating compositions and is
of particular importance when the coating compositions
are used in the area of the finishing of large-size
vehicles.
An additional advantage is that the improvement of the
masking resistance of the coatings can surprisingly be
achieved without any impairment of the leveling, top-
coat holdout and pot life. Finally, an additional
advantage is that the resulting coatings possess good
solvent resistance and surface hardness.
21 70475
--7--
DETAILED DESCRIPTION OF THE INVENTION
The individual components of the coating composition according to
the invention are now described in more detail.
The coating composition according to the invention contains as
binder a component (A) which contains hydroxyl groups and
comprises:
(A1) from 20 to 60% by weight, preferably from 30 to 50% by weight,
of at least one polyester, and
(A2) from 40 to 80% by weight, preferably from 50 to 70% by weight,
of at least one polyacrylate resin which contains hydroxyl
groups and has been prepared at least partially in the
presence of components (A1).
The binder employed as component (A) preferably has a hydroxyl
number of from 80 to 150, particularly preferably from 85 to 105,
mg of KOH/g and an acid number of from 0.1 to 10, preferably from
4 to 8, mg of KOH/g.
It is essential to the invention that the polyester (Al) has an OH
number of from 90 to 130, preferably from 90 to 110, mg of KOH/g,
an acid number of less than 10 mg of KOG/g, preferably from 1 to 8
mg of KOG/g, a number-average molecular weight of from 1300 to
3500, preferably from 1350 to 2000, and a
`. " 21 70475
-- 8 --
polydispersity of from 5 to 50, preferably from 5 to
10. The polydispersity is in this context defined as
the ratio of the weight-average molecular weight to the
number-average molecular weight. The molecular weights
are in each case determined by gel permeation
chromatography against a polystyrene standard.
The polyesters (A1) are preferably obtainable by
reacting
- pl) polycarboxylic acids or their esterifiable deriva-
tives, together if desired with monocarboxylic
acids,
p2) polyols, together if desired with monools,
p3) if desired, other modifying components, and
p4) if desired, a component which is capable of reac-
tion with the reaction product of (pl), (p2) and,
if appropriate, (p3).
Examples of polycarboxylic acids which can be employed
as component (pl) are aromatic, alip~atic and
cycloaliphatic polycarboxylic acids. It is preferred to
employ aromatic and/or aliphatic polycarboxylic acids
as component (pl).
`` 21 7[)475
. _ g
Examples of suitable polycarboxylic acids are phthalic
acid, isophthalic acid, terephthalic acid, halophthalic
acids, such as tetrachloro- or tetrabromophthalic acid,
adipic acid, glutaric acid, acelaic tsic] acid, sebacic
acid, fumaric acid, maleic acid, trimellitic acid,
pyromellitic acid, tetrahydrophthalic acid, hexa-
hydrophthalic acid, 1,2-cyclohexanedicarboxylic acid,
1,3-cyclohexane-dicarboxylic acid, 1,4-cyclohexane-
dicarboxylic acid, 4-methylhexahydrophthalic acid,
endomethylenetetrahydrophthalic acid, tricyclodecane-
dicarboxylic acid, endoethylenehexahydrophthalic acid,
camphoric acid, cyclohexanetetracarboxylic acid,
cyclobutanetetracarboxylic acid etc. The cycloaliphatic
polycarboxylic acids may be employed either in their
cis or in their trans form or as a mixture of the two
forms. Also suitable are the esterifiable derivatives
of the abovementioned polycarboxylic acids, for example
their single or multiple esters with aliphatic alcohols
having 1 to 4 carbon atoms or hydroxy alcohols having 1
to 4 carbon atoms. In addition, it is also possible to
employ the anhydrides of the abovementioned acids,
where they exist.
If desired, monocarboxylic acids can also be employed
together with the polycarboxylic acids, examples being
benzoic acid, tert-butylbenzoic acid, lauric acid,
isononanoic acid and fatty acids of naturally occurring
oils. The monocarboxylic acid preferably employed is
isononanoic acid.
`` 21 70475
.
-- 1 o
Alcohol components (p2) suitable for the preparation of
the polyester or alkyd resin (A1) are polyhydric
alco,hols such as ethylene glycol, propanediols, butane-
diols, hexanediols, neopentylglycol, diethylene glycol,
cyclohexanediol, cyclohexanedimethanol, tri-
methylpentanediol, ethylbutyl-propanediol di-
trimethylolpropane, trimethylolethane, trimethylol-
propane, glycerol, pentaerythritol, dipenta-e'rythritol,
trishydroxyethyl isocyanate, polyethylene glycol,
polypropylene glycol, together if desired with mono-
hydric alcohols, for example butanol, octanol, lauryl
alcohol, and ethoxylated and propoxylated phenols.
Suitable components (p3) for the preparation of the
polyesters (Al) are in particular compounds which
contain a group which is reactive with respect to the
functional yL~u~ of the polyester, with the exception
of the compounds cited as component (p4). As the
modifying component (p3) it is preferred to use
polyisocyanates and/or diepoxide compounds, and also -
if desired - monoisocyanates and/or monoepoxide
compounds. Examples of suitable components (p3) are
described in DE-A-40 24 204 on page 4, lines 4 to 9.
Compounds which are suitable as components (p4) for the
preparation of the polyesters or alkyd resins (A1) are
those which also contain, in additaon to a group which
is reactive with respect to the functional groups of
the polyester (A1), a tertiary amino group, for example
`` ~ 21 70475
monoisocyanates having at least one tertiary amino
group or mercapto compounds having at least one
tertiary amino group. For details reference is made to
DE-A-40 24 204, page 4, lines 10 to 49.
The polyesters (A1) are prepared by the known methods
of esterification (cf. various standard works, for
example:
1. Temple C~ Patton, Alkyd Resin Technology,
Interscience Publishers John Wiley & Sons, New
York, London 1962;
2. Dr. Johannes Scheiber, Chemie und Technologie der
k~nstlichen Harze [Chemistry and Technology of
Synthetic Resins], Wissenschaftliche
Verlagsgesellschaft mbH, Stuttgart, 1943;
3. Hans Wagner + Hans-Friedrich Sarx, Lackkunstharze
tSynthetic Resins for Coatings], 4th edition, Karl
Hanser Verlag, Munich, 1959;
4. Ullmanns Encyklopadie der technischen Chemie
[Ullmann's Encyclopedia of Industrial Chemistry],
volume 14, pages 80 to 106 (1963)).
This reaction is conventionally carried out at
temperatures of between 180 and 280C, in the presence
if desired of an appropriate esterification catalyst,
`` 21 70475
- 12 -
for example lithium octanoate, dibutyltin oxide,
dibutyltin dilaurate, para-toluenesulfonic acid and the
like.
The preparation of the polyesters (A1) is conven-
tionally carried out in the presence of small quanti-
- ties of a suitable solvent as entraining agent.
Examples of the entraining agents employed are aromatic
hydrocarbons, in particular xylene and (cyclo)aliphatic
hydrocarbons, for example cyclohexane.
The polyacrylates employed as component (A2) in the
coating compositions according to the invention have OH
numbers of from 50 to 150 mg of KOH/g, preferably from
70 to 105 mg of KOH/g, and acid numbers of from O to
10 mg of KOH/g, preferably from 0 to 8 mg of KOH/g, the
OH numbers and acid numbers in each case being
calculated without taking into account the polyester
~raction. The number-average molecular weights of the
polyacrylate resins prepared in the presence of the
polyesters are generally between 1500 and 5000, pre-
ferably between 2000 and 4000, in each case measured by
GPC against a polystyrene standard.
It is essential to the invention that the polyacrylate
resin (A2) has been prepared at least partially in the
presence of the polyester resin (A1). Advantageously at
least 40% by weight and, particularly advantageously,
2~ 70475
~ - 13 -
from S0 to 70% by weight of component (A2) are prepared
in the presence of component (A1).
The possible residual quantity of component (A2) is
added to the binder solution or to the coating
composition subsequently. In this context it is
possible for this prepolymerized resin to have the same
monomer composition as the addition polymer resin built
up in the presence of the condensation polymer resin.
However, it is also possible for a condensation polymer
resin and/or addition polymer resin containing hydroxyl
groups and having a different monomer composition to be
added. Furthermore, it is possible to add a mixture of
different addition polymer resins and/or condensation
polymer resins, it being possible for a resin to have
the same monomer composition as the addition polymer
resin built up in the presence of the condensation
polymer resin.
It is also essential to the invention that the poly-
acrylate resin (A2) comprises one or more monomers
selected from the group consisting of 4-hydroxy-n-butyl
acrylate, 4-hydroxy-n-butyl methacrylate, 3-hydroxy-
n-butyl acrylate, 3-hydroxy-n-butyl methacrylate and/or
hydroxyethyl methacrylate, as monomer components which
are incorporated by polymerization. The acrylate resin
(A2) preferably contains one or more monomers selected
from the group consisting of 4-hydroxy-n-butyl
acrylate, 4-hydroxyl-n-butyl methacrylate, 3-hydroxy-
21 7047S
- 14 -
n-butyl acrylate and/or 3-hydroxy-n-butyl methacrylate,
together if desired with hydroxyethyl methacrylate.
The preparation of the polyacrylate resins which are
employed in accordance with the invention can be
carried out by polymerization methods which are
generally well known. Polymerization methods for the
preparation of polyacrylate resins are generally known
and have been described in numerous references (cf.
e.g.: Houben-Weyl, Methoden der organischen Chemie
lMethods in Organic Chemistry], 4th edition, volume
14/1, pages 24 to 255 (1961)).
The polyacrylate resins employed in accordance with the
invention are preferably prepared using the solution
polymerization method. In this method it is conven-
tional to take an organic solvent or solvent mixture
together with the polyester (Al) and to heat the
mixture to boiling. The monomer mixture to be
polymerized and one or more polymerization initiators
are then added continuously to this mixture of organic
solvent or solvent mixture and polyester resin (Al).
Polymerization takes place at temperatures of between
100 and 160C, preferably between 130 and 150C.
The polymerization is preferably carried out in a high-
boiling organic solvent which is inert with respect to
the monomers employed. Examples of suita~le solvents
are relatively highly substituted aromatics, for
example Solvent Naphtha, heavy benzene, various
21 70475
- 15 -
Solvesso grades, various Shellsol grades and Deasol and
relatively high-boiling aliphatic and cycloaliphatic
hydrocarbons, for example various white spirits,
mineral terpentine oil, tetralin and decalin and
various esters, for example ethylglycol acetate, butyl-
glycol acetate, ethyldiglycol acetate and the like.
The polymerization initiators preferably employed are
initiators which form free radicals. The nature and
quantity of initiator are usually selected such that,
at the temperature of polymerization, the supply of
free radicals is substantially constant during the feed
phase.
Cited examples o~ initiators which can be employed are
di-tert-butyl peroxide, tert-butyl hyd~aroxide, tert-
butyl peroxybenzoate, tert-butyl peroxypivalate, tert-
butyl peroxy-3,5,5trimethylhexanoate tsic], tert-butyl
peroxy-2-ethylhexanoate, dicumyl peroxide, cumyl
hydroperoxide, tert-amyl peroxybenzoate, tert-amyl
peroxy-2-ethylhexanoate, diacyl peroxides, for example
diacetyl peroxide, peroxyketals, 2,2-di(tert-amyl-
peroxy-)propane [sic], ethyl 3,3-di(tert-amyl-
peroxy-)butyrate [sic] and thermally labile highly sub-
stituted ethane derivatives, based for example on
silyl-substituted ethane derivatives and on benzo-
pinacol. Furthermore, it is also possible to empLo~
aliphatic azo compounds, for example azoisovalero-
nitrile and azobiscyclohexanenitrile.
21 70475
- 16 -
The initiators employed are primarily those containing
tert-butyl groups, for example di-tert-butyl peroxide,
tert-butyl hydroperoxide, 2,2-di-tert-butylperoxybutane
and 1,3-bis(tert-butylperoxyisopropyl)benzene, since
they promote grafting of the acrylate onto the
polyester.
The quantity of initiator is in most cases from 0.1 to
8% by weight, based on the quantity of monomer to be
processed, although it can be even higher if desired.
The initiator, dissolved in a portion of the solvent
employed for the polymerization, is metered in
gradually during the polymerization reaction. The
initiator feed preferably takes from about 0.5 to
2 hours longer than the monomer feed, so as to achieve
a good action during the after-polymerization phase as
well. In another preferred preparation variant the feed
of initiator is commenced about 15 minutes before the
addition of the monomers, so as to ensure a good supply
of free radicals at the beginning of the polymeriza-
tion. If initiators are employed which only have a low
rate of decomposition under the prevailing reaction
conditions, then it-is also possible to include the
initiator in the initial charge.
The polymerization conditions (reaction temperature,
feed time of- the monomer mixture, nature and quantity
of the organic solvents and polymerization initiators,
21 70475
- 17 -
possible use of molecular weight regulators, for
example mercaptans, thioglycolic esters and chlorine-
containing hydrogen compounds) are selected such that
the polyacrylate resins employed in accordance with the
invention have the desired molecular weight.
The acid number of the polyacrylate resins employed in
accordance with the invention can be adjusted by the
person skilled in the art via the use of appropriate
quantities of monomers which contain carboxyl groups.
Similar comments apply to the adjustment of the
hydroxyl number. It can be controlled via the quantity
of hydroxyl group-containing monomers which are
employed.
The polyacrylate resins which contain hydroxyl groups
and are preferably employed as component (A2) are
obtainable by polymerizing
(a) from 5 to 50% by weight, preferably from 10 to 35%
by weight, of one or more monomers selected from
the group consisting of 4-hydroxy-n-butyl
acrylate, 4-hydroxy-n-butyl methacrylate,
3-hydroxy-n-butyl acrylate, 3-hydroxy-n-butyl
methacrylate and/or hydroxyethyl methacrylate
(b) from 0 to 50~ by weight, preferably from 0 to 30%
by weight, of an ethylenically unsaturated,
copolymerizable monomer which is different from
~_ ~ 1 7~475 "
- 18 -
(a) and contains hydroxyl groups, or a mixture of
such monomers,
(c) from 5 to 95% by weight, preferably from 15 to 55%
by weight, of an aliphatic and/or cycloaliphatic
ester of methacrylic and/or acrylic acid which is
different from (a) and (b), or a mixture of such
monomers,
(d) from 0 to 30~ by weight, preferably from 5 to 15~
by weight, of a copolymerizable vinyl ester which
is different from (a), (b) and (c), or a mixture
of such monomers,
(e) from 0 to 85% by weight, preferably from 15 to 60%
by weight, of an aromatic vinyl hydrocarbon which
is different from (a), (b), (c) and (d), or a
mixture of such monomers, and
(f) from 0 to 10~ by weight, preferably from 0 to 8%
by weight, of a further ethylenically unsaturated
monomer which is different from (a), (b), (c), (d)
and (e), or a mixture of such monomers,
at least partially in the presence of component (A1),
- to give the polyacrylate resin (A2), the sum of the
proportions by weight of monomers (a) to (f) being in
each case 100% by weight.
, `` l9 2170475
As a further hydroxyl group-containing monomer
(component (b)) for the preparation of the acrylate
resin, it is also possible, if desired, to employ other
hydroxyl group-containing esters of acrylic and/or
methacrylic acid. Particular examples of hydroxyl
group-containing monomers which are suitable as com-
ponent (b) are the reaction pr~duct of 1 mol of
hydroxyethyl acrylate and/or hydroxyethyl methacrylate
and on average 2 mol of -caprolactone and/or the reac-
tion product of acrylic acid and/or methacrylic acidwith the glycidyl ester of a carboxylic acid having a
tertiary carbon atom. These glycidyl esters of
-branched carboxylic acids having 11 to 13 carbon atoms
(Versatic acid) are commercially available, for
example, from Shell under the name Cardura. The reac-
tion of the acrylic and/or methacrylic acid with the
glycidyl ester can be carried out before, during or
after the polymerization.
As component (b) it is also possible to employ,
however, alkyl esters of acrylic acid and/or
methacrylic acid, for example hydroxyethyl acrylate,
hydroxypropyl (meth)acrylate, hydroxypentyl
(meth)acrylates, hydroxyhexyl (meth)acrylates, hydroxy-
octyl (meth)acrylates etc., and/or the esters,
different from (a) and containing hydroxyl groups, of a
polymerizable, ethylenically unsaturated carboxylic
acid, ~or example the hydroxyl group-containing esters
of crotonic and isocrotonic acid.
` - 20 2 1 7 0 4 75
As component (c) it is possible in principle to employ
any aliphatic or cycloaliphatic esters of acrylic acid
or of methacrylic acid which are different from (a) and
(b), or a mixture of such monomers. Examples are
aliphatic esters of acrylic acid and of methacrylic
acid, for example methyl, ethyl, propyl, n-butyl,
isobutyl, tert-butyl, n-hexyl, 2-ethylhexyl, stearyl
and lauryl acrylate and methacrylates, and
cycloaliphatic esters of (meth)acrylic acid, for
example furfuryl, cyclohexyl, isobornyl and
t-butylcyclohexyl acrylate and methacrylate.
Vinyl esters of monocarboxylic acids are employed as
component (d). Preferably employed are vinyl esters of
-branched monocarboxylic acids having 5 to 15 carbon
atoms per 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 acidic catalyst; the olefins may be
products of the cracking of paraffinic hydrocarbons,
such as mineral oil fractions, and may contain both
branched and straight-chain acyclic and/or
cycloaliphatic olefins. In the reaction of such olefins
with formic acid or with carbon monoxide and water, a
mixture is formed of carboxylic acids in which the
carboxyl groups are located predominantly at a
quaternary carbon atom. Examples of other olefinic
starting materials are propylene trimer, propylene
- 21 - 217~'~75
tetramer and diisobutylene. The vinyl esters may also
be produced from the acids in a manner known per se,
for example by reacting the acids with acetylene.
Because of their ready availability, vinyl esters of
saturated aliphatic monocarboxylic acids having 9-11
~ carbon atoms and branched at the carbon atom are
particularly preferred.
Furthermore, particular preference is given to the
vinyl ester of p-tertiary-butyl benzoic acid. Examples
of other suitable vinyl esters are vinyl acetate and
vinyl propionate.
As component (e), aromatic vinyl hydrocarbons such as
styrene, -alkylstyrenes such as -methylstyrenes,
chlorostyrenes, o-, m- and p-methylstyrene,
2,5-dimethylstyrene, p-methoxystyrene, p-tert-butyl-
styrene, p-dimethylaminostyrene, p-acetamidostyrene and
vinyltoluene are employed, with preference being given
to the employment of vinyltoluenes and, in particular,
styrene.
The monomer employed as component (f) may in principle
be any ethyienically unsaturated monomer which is
different from (a), (b), (c), (d) and (e), or a mixture
of such monomers. ExampLes of monomers which can be
employed as component (f) are monomers containing
carboxyl groups, such as acrylic andlor methacrylic
2 1 704 75
- 22 -
acid; amides of acrylic acid and methacrylic acid, for
example methacrylamide and acrylamide; nitriles of
methacrylic acid and acrylic acid; vinyl ethers and
vinyl esters.
It is essential to the invention to add to the binder
component (A), after i~s preparation, from 0.1 to 1% by
weight, preferably from 0.4 to 0.9% by weight, of at
least one aromatic mono- and/or polycarboxylic acid
and/or at least one anhydride of an aromatic poly-
carboxylic acid. The quantity of acid or anhydride
added is in this context related to the weight of the
hydroxyl group-containing binder, calculated as solid
resin, i.e. without the solvent fraction. Preferred
additions in this context are phthalic anhydride,
benzoic acid and/or alkyl- and/or alkoxy-substituted
benzoic acid. It is particularly preferred to add
benzoic acid.
The acid is added preferably at a temperature of from
20 to 120C, particularly preferably at a temperature
of from 40 to 100C.
The anhydride is added preferably at a temperature of
from 100 to 180C, particularly preferably at a
temperature of from 130 to 170C.
In this respect the acid can be added to the finished
coating composition, i.e. after the addition of pig-
` ~ 2170475
23 -
ments, fillers, auxiliaries and crosslinking agents.
Preferably, however, the acid or the anhydride is added
to the acrylate resin (A2) and dispersed to give a
maximum degree of homogeneity.
The polyisocyanate component (B) comprises any organic
polyisocyanate which contains free isocyanate groups
which are attached to aliphatic, cycloaliphatic,
araliphatic and/or aromatic structures. The polyiso-
cyanate~ preferably employed are those containing 2 to
5 isocyanate groups per molecule. It is possible if
desired to add to the polyisocyanates small quantities
of organic solvent, preferably from 1 to 25% by weight,
based on pure polyisocyanate, so as to improve the ease
of incorporation of the i~ocyanate. Examples of
solvents which are suitable as additi~es for the poly-
isocyanates are ethoxyethyl propionate, butyl acetate
and the like.
Examples of suitable isocyanates are described in, for
example, "Methoden der organischen Chemie" [Methods in
Organic Chemistry], Houben-Weyl, volume 14~2, 4th
edition, Georg Thieme Verlag, Stuttgart 1963, page 61
to 70, and by W. Siefken, Liebigs Ann. Chem. S62, 75 to
136.
Suitable examples are 1,2-ethylene diisocyanate,
1,4-tetramethylene diisocyanate, 1,6-hexamethylene
diisocyanate, 2,2,4- or 2,4,4-trimethyl-1,6-
21 70475
- 24 -
hexamethylene diisocyanate, l,12-dodecane diisocyanate,
,'-diisocyanato-dipropyl ether, cyclobutane
1,3-diisocyanate, cyclohexane 1,3- and 1,4-diiso-
cyanate, 2,2- and 2,6-diisocyanato-l-methyl-cyclo-
hexane, 3-isocyanatomethyl-3,5,5-trimethyl-cyclo-hexyl
isocyanate ("isophorone diisocyanate"), 2,5- and
- 3,5-bis(isocyanatomethyl)-8-methyl-1,4-methano-deca-
hydro-naphthalene, 1,5-, 2,5-, 1,6- and
2,6-bis(i ocyanatomethyl)-4,7-meth-nQhexahydroindane,
1,5-, 2,5-, 1,6- and 2,6-bis(i60cyanato)-4,7-methano-
hexahydroindane, dicyclo-hexyl 2,4'- and 4,4'-diiso-
cyanate, 2,4- and 2,6-hexahydrotolylene diisocyanate,
perhydro-2,4'- and -4,4'-diphenylmethane diisocyanate,
,'-diisocyanato-1,4-diethylbenzene, 1,3- and
1,4-phenylene diisocyanate, 4,4'-diiso-cyanatobiphenyl,
4,4'-diisocyanato-3,3'-dichloro-biphenyl, 4,4'-diiso-
cyanato-3,3'-dimethoxybiphenyl, 4,4'- diisocyanato-
3,3'-dimethylbiphenyl, 4,4'-diiso-cyanato-3,3'-di-
phenylbiphenyl, 2,4'- and 4,4'-diisocyanato-
diphenylmethane, naphthylene 1,5-diisocyanate, tolylene
diisocyanates, such as 2,4- or 2,6-tolylene
diisocyanate, N,N'-(4,4'-dimethyl-3,3'-diisocyanato-
diphenyl)uretdione, m-xylylene diisocyanate, dicyclo-
hexylmethane diisocyanate, tetramethylxylylene diiso-
cyanate, and also triisocyanates, such as
2,4,4'-triisocyanatodiphenyl ether, and 4,4',4 " -tri-
isocyanatotriphenylme~hane. Th~ polyisocyanates
preferably employed, in combination if desired with the
abovementioned polyisocyanates, are those containing
` 21 70475
- 25 -
isocyanurate groups and/or biuret groups and/or
allophanate groups and/or urethane groups and/or urea
groups. Polyisocyanates containing urethane groups are
obtained, for example, by reacting some of the iso-
cyanate groups with polyols, for example trimethylol-
propane and glycerol.
It is preferred to employ aliphatic or cycloaliphatic
polyisocyanates, especially hexamethylene diisocyanate,
dimerized and trimerized hexamethylene diisocyanate,
isophorone diisocyanate, dicyclohexylmethane
2,4'-diisocyanate or dicyclohexylmethane 4,4'-diiso-
cyanate, or mixtures of these polyisocyanates. Very
particular preference is given to employing mixtures of
polyisocyanates which contain uretdione and/or
i~ocyanurate groups and/or allophanate groups and which
are based on hexamethylene diisocyanate, as are formed
by the catalytic oligomerization of hexamethylene
diisocyanate using appropriate catalysts. Otherwise,
the polyisocyanate component (B) can also consist of
any desired mixtures of the polyisocyanates mentioned
by way of example.
The quantity of the crosslinking agent employed is
selected such that the ratio of the isocyanate groups
of the crosslinking agent to the hydroxyl groups of the
binder component is in the range from 1:3 to 3:1. The
coating compositions according to the invention usually
contain from 15 to 50% by weight of the polyester-modi-
` - . . 21 7047~
- 26 -
fied acrylate resin, from o to 30% by weight o~ the
other binder component and from 7 to 50% by weight of
the crosslinking agent (B), based in each case on the
overall weight of the coating composition and on the
solids content of the binder and crosslinking com-
ponents.
The coating compositions according to the invention
also contain one or more organic solvents. These
~olvents are usually employed in quantities of from 20
to 70% by weight, preferably from 30 to 60% by weight,
based in each case on the overall weight of the coating
composition.
Examples of suitable solvents are relatively highly
substituted aromatic compounds, for example solvent
naphtha, heavy benzene, various Solvesso grades,
various Shellsol grades and Deasol, and relatively
high-boiling aliphatic and cycloaliphatic hydrocarbons,
for example various white spirits, mineral terpentine
oil, tetralin and decalin, and various esters, for
example ethylglycol acetate, butylglycol acetate,
ethyldiglycol acetate and the like.
The coating compositions according to the invention may
furthermore contain conventional auxiliaries and
additives in conventional quantities, preferably from
0.01 to 10% by weight based on the overall weight of
the coating composition. Examples of appropriate
` 21 7047~-`
- 27 -
auxiliaries and additives are leveling agents such as
silicone oils, plasticizers such as phosphoric esters
and phthalic esters, viscosity-controlling additives,
flatting agents, W absorbers, light stabilizers,
texturing agents and, if desired, fillers.
The coating compositions according to the invention may
also contain co~ventional pigments in conventional
quantities, preferably from 0 to 40% by weight based on
the overall weight of the coating composition. ~mrles
of suitable pigments are organic and inorganic color
pigment tsic] and metallic and/or special-effec~ pig-
ments.
The coating compositions are prepared in a known
manner, by mixing and - if desired - dispersing the
individual components.
These coating compositions may be applied to a sub-
strate, by spraying, flow coating, dipping, rolling,
knife coating or brushing, in the form of a film, the
film subsequently being cured to give a firmly adhering
coating.
The curing of these coating compositions is carried out
conventionally at room temperature or at slightly
elevated temperature, preferably at slightly elevated
temperature, advantageously at temperatures below 120C
and preferably at temperatures of between 800c and
~ ``` 21 7047`5
- 28 -
60-C. The coating compositions can, however, also be cured under
baking conditions, i.e. at temperatures of at least 120-C.
Particularly suitable substrates are metals and also wood, plastic,
glass and the like.
Because of the short curing times and low curing temperatures, the
coating compositions according to the invention are preferably
employed for automotive refinishing, and for the finishing of
large-size vehicles and goods-vehicle bodies. However, depending
on the crosslinking agent employed, they may also be used for the
production-line finishing of motor vehicles. Furthermore, they are
particularly suitable as solid-color topcoat. However, they can,
of course also be employed as clearcoat, in particular over a
metallic basecoat or a solid-color basecoat.
The present invention therefore also relates to a processes for the
production of a protective and/or decorative coating on a substrate
surface, which process is characterized in that the coating
composition according to the invention is applied.
PREFERRED EMBODIMENTS OF THE INVENTION
The invention is now illustrated in more detail with reference to
exemplary embodiments. All parts and percentages in these examples
are by weight, unless expessly stated otherwise.
21 70475
. .
- 29 -
I.l. Preparation of a ~olYester resin Al:
796 parts of trimethylolpropane, 540 parts of
isononanoic acid, 821 parts of phthalic anhydride and
83 parts of xylene are placed in a 4 liter condensation
polymerization vessel fitted with stirrer, steam-heated
column and water separator and are heated slowly.
Condensation is carried out at a temperature of max.
190C up to an acid number of 5 mg of KOH/g and a
viscosity of 8.0 dPas (60~ in xylene). The batch is
then cooled, diluted at 130C with 910 parts of
Shellsol A, and cooled further to room temperature.
The resulting polyester has a solids content of 66.5%,
an acid number of 5 mg of KOH/g, a (theoretical) OH
number of 97.2 mg of KOH/g and a viscosity of 70 dPas
(original). The number-average molecular weight Mn is
1493, the weight-average molecular weight Mw is 13,243
and the polydispersity Mw/Mn is 8.87 (each determined
by gel permeation chromatography against a polystyrene
standard).
~,e~,, . ,::. i
21 70475
_ - 30 -
I.2. PreParation of a polYester resin A2:
796 parts of trimethylolpropane, 540 parts of
isononanoic acid, 821 parts of phthalic anhydride and
83 parts of xylene are placed in a 4 liter condensation
polymerization vessel fitted with stirrer, steam-heated
column and water separator and are heated slowly.
Condensation is carried out at a temperature of max.
190C up to an acid number of 10 mg of KOH/g and a
viscosity of 7.2 dPas (60~ in xylene). The batch is
then cooled, diluted at 130C with 910 parts of
Shellsol A, and cooled further to room temperature.
The resulting polyester has a solids content of 65.4%,
an acid number of 8.9 mg of KOH/g, a (theoretical) OH
number of 101 mg of KOH/g and a viscosity of 50 dPas
(original). The number-average molecular weight Mn is
1350, the weight-average molecular weight Mw is 7830
and the polydispersity Mw/Mn is 5.8 (each determined by
gel permeation chromatography against a polystyrene
standard).
I.3. Preparation of a PolYester resin A3:
796 parts of trimethylolpropane, 540 parts of
isononanoic acid, 821 parts of phthalic anhydride and
83 parts of ~ylene are placed in a 4 liter condensation
polymerization vessel fitted with stirrer, steam-heated
column and water separator and are heated slowly.
21 70475
- 31
Condensation is carried out at a temperature of max.
190C up to an acid number of 15 mg of KOH/g and a
viscosity of 5.3 dPas (60% in xylene). The batch is
then cooled, diluted at 130C with 910 parts of
Shellsol A, and cooled further to room temperature.
The resulting polyester has a solids content of 66.5%,
an acid number of 13 mg of KOH/g, a (theoretical) OH
number of 104 mg of KOH/g and a viscosity of 22 dPas
(original). The number-average molecular weight Mn is
1241, the weight-average molecular weight Mw is 5843
and the polydispersity Mw/Mn is 4.71 (each determined
by gel permeation chromatography against a polystyrene
standard).
I.4. Preparation of a Polyester resin A4:
848 parts of trimethylolpropane, 444 parts of
isononanoic acid, 876 parts of phthalic anhydride and
83 parts of xylene are placed in a 4 liter condensation
polymerization vessel fitted with stirrer, steam-heated
column and water separator and are heated slowly.
Condensation is carried out at a temperature of max.
190C up to an acid number of 18 mg of KOH/g and a
viscosity of 80 dPas (60% in xylene). The batch is th~n
cooled, diluted at 130C-with 1200 parts of Shellsol A,
and cooled further to room temperature.
` `` 21 70475
32 -
The resulting polyester has a solids content of 66.5%,
an acid number of 16 mg of KOH/g, a theoretical OH
number of 114 mg of KOH/g and a viscosity of >90 dPas
(original). Because of the high viscosity of the
resulting polyester, no further reactions were carried
out.
II.1. Pre~aration of the hydroxYl qrouP-containinq
acrylate resins El to E5 and C1 to C6
The preparation of the acrylate copolymers was in each
case carried out in a 4 liter stainless steel poly-
merization vessel fitted with stirrer, reflux con-
denser, a monomer feed and an initiator feed. The com-
ponents, specified in each case in Table 1, are weighed
in and then the initial charge is heated to 165C.
All of the additions are commenced at the same time;
the monomer feed is metered in-at a uniform rate over
the course of 4 h, and the initiator feed is metered in
at a uniform rate over the course of 5 h. During the
polymerization the temperature in the vessel is held at
160-165C.
After this, polymerization is continued for a further
2 h.~ The resulting acrylate resin solution has a solids
content of 80%. The temperature is then lowered to
120C and the acrylate resin is diluted with butyl
acetate to a solids content of 6~%, and the quantity of
` 21 73475
__ - 33
benzoic acid indicated in Table 1, or the quantity of
tert-butyl benzoic acid or hydroxystearic acid
indicated in Table 1, is added.
The polyester resin A1 or A2 or A3 and the commercially
available vinyl ester of Versatic acid (commercial
product VeoVa 10 from Shell Chemie), in each case in
the quantities ~pecified in Table 1, are weighed into
the initial charge.
The quantities of styrene, OH monomer and methyl
methacrylate indicated in each case in Table 1 are
weighed into the monomer feed.
14 parts of di-tert-butyl peroxide,
44- parts of Shellsol A (commercially available
aromatic solvent mixture having a boiling range of 165
to 185C) and
parts of xylene
are weighed into the initiator feed. This composition
of the initiator feed is employed in the preparation of
all of the acrylate resins.
"` 2170475
- 34 -
II.2. Pre~aration of the hYdroxYl qrouP-containinq
acrylate resin E6
The preparation of the acrylate copolymer according to
the invention was carried out in each case in a 4 liter
stainless steel polymerization vessel fitted with
stirrer, reflux condenser, a monomer feed and an
initiator feed. The components, indicated in Table 1,
of the initial charge, of the monomer feed and of the
initiator feed are weighed in, and the initial charge
is then heated to 165C.
The additions are all commenced at the same time; the
monomer feed is metered in uniformly over the cou~e of
4 h, and the initiator feed is metered in uniformly-
over the course of 5 h. During the polymerization the
temperature in the vessel is held at 160-165C. After
this, polymerization is continued for a further 2 h.
The resulting acrylate resin solution has a solids con-
tent of 80%. 7.5 parts of phthalic anhydride are addedat 165C, and the temperature is held at 165C for
about a further 2 hours. The temperature is then
lowered to 120C and the acrylate resin is diluted with
butyl acetate to a solids content of 65%.
The polyacrylate resin obtained in this way has a
solids content of 64.4%, an acid number of 4.4 mg of
KOH/g, a viscosity of 3.0 dPas (55% in butyl acetate~
and a hydroxyl number of about 90.
2 1 70475
~_ - 35 -
II.3. PreParation of the hYdrox~l qroup-containinq
acrYlate resin C7
The preparation of the hydroxyl group-containing
acrylate resin C7 was carried out analogously to the
preparation of the acrylate resin E6, but adding 7.8
parts of hexahydrophthalic anhydride instead of
phthalic anhydride.
II.4. Preparation of the hydroxyl qroup-containing
acrYlate resin C 8
The preparation of the hydroxyl group-containing
acrylate resin C 8 is carried out analogously to the
preparation of the acrylate resin C 1, the acrylic acid
likewise being weighed into the monomer feed and added
with the other monomers.
II.5. Preparation of the hydroxyl group-containinq
acrylate resin C9
177 parts of Shellsol A and 113 parts of VeoVa 10 are
weighed into the initial charge.
565 parts of styrene
250 parts of hydroxy-n-~utyl acrylate and
201 parts of methyl methacrylate
" 21 70~75
- 36 -
are weighed into the monomer feed.
22.6 parts of di-tert-butyl peroxide,
71 parts of Shellsol A (commercially available
aromatic solvent mixture having a boiling range of 165
to 185C) and
40 parts of xylene
are weighed into the initiator feed.
The polymerization is carried out analogously to the
preparation of the polyacrylate resin C1, by heating
the initial charge at 165C. All of the additions are
commenced at the same time; the monomer feed is metered
in uniformly over the course of 4 h, and the initiator
feed is metered in uniformly ~ver the course of 5 h.
-During the polymerization the temperature in the vessel
is held at 160-165C. After this, polymerization is
continued for a further 2 h. The resulting acrylate
resin solution has a solids content of 80%. The
temperature is then lowered to 120C and the acrylate
resin is diluted with butyl acetate to a solids content
of 65%. 3.94 parts of benzoic acid are then added.
After this, 1133 parts of polyester resin A1 are added
to the polyacrylate resin solution.
21 70475
- 37 -
The polyacrylate resin/polyester mixture obtained in
this way has a solids content of 64.5%, an acid number
of 4.0 mg of KOH/g, a viscosity of 7.2 dPas (55% in
butyl acetate) and a hydroxyl number of a~out 90.
Because of the high viscosity of the polyacrylate
resin/polyester mixture, no coating composition was
prepared using this mixture.
III. Preparation of the coatinq compositions E1 to E6
and Cl to C8 (Comarative Exam~les~
III.l. Preparation of the curin~ agent solution
The curing agent solutions are prepared by mixing the
components ~pecified below:
4 parts of catalyst solutionl)
50.6 parts of Desmodur N 33902)
- 10.0 parts of Solvent naphtha
7.5 parts of xylene
1.5 parts of n-butyl acetate 98/100
0.6 part of Baysilon coating additive oL443)
14.0 parts of l-me.thoxypropyl 2-acetate
11.0 parts of butylglycol acetate
1) the cataIyst solution described in section
III.3.
` ` 21 7`3475
- 38 -
2) commercially available polyisocyanate from
Bayer AG, a 90% strength solution in butyl
acetate/solvent naphtha, 1:1, of a trimer
based on hexamethylene diisocyanate and
having a number-average molecular weight of
about 700, an average functionality of
between 3 and 4 and a content of uretdione
groups of not more than 5%;
3) commercially available leveling agent based
on a polyether-modified methylpolysiloxane
from Bayer AG
III.2. Preparation of an adiustment additive
An adjustment additive is prepared by mixing the
components specified below:
-Xylene 15.0 parts
Solvent naphtha 13.0 parts
Petroleum spirit 135/18010.0 parts
Butylglycol acetate 3.0 parts
n-Butyl acetate 98/100 50.0 parts
l-Methoxypropyl 2-acetate5.0 parts
Butoxyl 2.0 parts
Dipentenes 2.0 parts
`.` 217~4~5
- 39 -
III.3. Preparation of a catalyst solution
1.0 part of dibutyltin dilaurate is mixed with 50 parts
of butyl acetate 98/100 and 49 parts of xylene.
III.4. Preparation of topcoats El to E6 and Cl to C8
The topcoats are prepared by adding 5.5 parts of a
commercially available organic red pigment (commercial
product Novopermrot F2RK 70 from Hoechst) to 38.8 parts
of the respective acrylate resin solution together with
3.2 parts of butyl acetate 98/100. The batch is first
placed in a dissolver at 2000 revolutions/min for
10 min and then, with cooling, is ground to a Hegmann
particle fineness of c 10 m. After this a mixture of
3.4 parts of butyl acetate 981100, 20 parts of a
commercially available acrylate resin containing
hydroxyl groups and having an OH number of 150 mg of
KOH/g (commercial product Macrynal SM 510 N from
~oechst AG), 0.5 parts of a commercially available
light stabilizer based on a sterically hindered amine
(commercial product Tinuvin 292 from Ciba Geigy), 0.2
part of the catalyst solution described above and 28.4
parts of the respective acrylate resin solution is
added, and the mixture is homogenized using a stirrer
(1000 revolutions/min).
In order to prepare the topcoats, in each case 4 parts
by volume of the resulting mixture are mixed with 1
part by volume of the curing agent solution described
2 1 704 ~5
- 40 -
above and 1 part by volume of the adjustment additive
described above.
III.5. APPlication of the topcoats
The resulting topcoat is then applied to phosphatized
steel panels which have been treated with filler. The
phosphatized steel panels are for this purpose coated
with a commercially available, conventional filler
(commercial product Glasurit Grundf~ller tPrimer
surfacer] 283-1874 from Glasurit GmbH, M~nster) based
on a binder containing epoxide groups and on an amino-
functional curing agent, and are subjected to
intermediate drying at room temperature for 1 h. Then
the topcoat is applied in 2 spray passes, with a flash-
off time of 15 min in between, and dried at 20C for
16 h. The dry film thickness is from 50 to 60 m.
~The panels coated in this way are then subjected to
various tests. The test results are shown in Table 3.
41 - 21 7~75
`
~r
o~ u o ~ a~
~U o~ ' U~ o
o. o U~ o
U I I O U~ U7 1 1 1 ~ I I
oo U~
r oo u~
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n
oo u) u~ .
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` 21 704~75
.
- 42 -
Explanations for Table 1
A1, A2, A3 = polyester resin Al, A2 and A3 respectively
VeoVa = commercially available mixture of vinyl esters
of saturated aliphatic monocarboxylic acids having pre-
dominantly 10 carbon atoms and being branched at the
carbon atom
HBA = 4-hydroxy-n-butyl methacrylate
HEMA = hydroxyethyl methacrylate
HPMA = hydroxypropyl methacrylate
HEA = hydroxyethyl acrylate
MMA = methyl methacrylate
AA = acrylic acid
BA = benzoic acid
PA = phthalic anhydride
HSA = hydroxystearic acid
HPA = hexahydrophthalic anhydride
` . 21 70475
.
-- 43 --
tBBA = t-butylbenzoic acid
Table 2: Characteristics of the acrylate resins and acrylate resin/polyester mixture
1 Cl C2 C3, 2 C4 C5 3 4 S 6 C6 C7 C8 C9
SC ( ~ ) 65 65.8 65.5 65 66 65.4 64.6 64 65.2 64.6 64.4 64.2 66.1 64.3 64.5
AN 5.3 2.5 2.5 6 4.5 5.3 4.7 6.6 6.7 4.2 4.4 4.5 5.0 5.8 4
OHN 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90
Visc. 2.3 2.6 2.5 2.3 2.5 2.6 4.1 3.0 2.3 2.4 3.0 2.6 2.1 2.6 7.2
Mn 2282 1893 2102
Mw 11414 6267 9555
Mw/Mn 5.00 3.31 4.55
45- 2170475
-
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`` 21 70475
- 46 -
Summary of the test results:
The spray mist assimilation is equally good across all
the examples. A rating of > 3 or above tsic] for the
leveling is no longer acceptable in practice, so that
the coating compositions of Comparative Examples C1, C6
and C8 exhibit unacceptable results.
The solvent resistance of the resulting coatings is
only acceptable at a rating of 2 or better. Coatings
with a rating > 2 exhibit dulling phenomena and are no
longer acceptable. Therefore the coatings of Compara-
tive Examples C2, C3, C4 and C5 are not suitable with
respect to solvent resistance. All the coating composi-
tions show an adequate pot life of at least 3-4h.
For the most important criterion of the coatings, the
masking tape test, the rating ~or acceptable coatings
must be at least 2-3 or better. Therefore, the coatings
of Comparative Examples C2, C3, C4, C5 and C8 exhibit a
masking resistance which is completely inade~uate. The
best masking resistance is shown by the coating of
Example 1.
