Note: Descriptions are shown in the official language in which they were submitted.
' 21987!~2
Herberts Gesellschaft mit beschrankter Haftung
A method of producing a binder vehicle component for aqueous two-component
co~tin~ media
This invention relates to a method of producing water-thinnable components, which are
stable on storage and which contain hydroxy-functional binder vehicles, for two-component coating media, and relates to the use of these components in two-component
coating media in multi-layer coatings for the coating of vehicles and for industrial
coating.
In recent years, the importance of aqueous lacquers and coatings has increased
considerably, on account of emission guidelines which are becoming more stringent as
regards the solvents released during lacquer application operations. Although aqueous
two-component systems have in the me~ntime already become available for many areas
of application, these do not yet attain, in all aspects, the high level of quality of
conventional, solvent-cont~ining two-component lacquers.
Meanwhile, there is a large number of water-thinnable, two-component systems based
on a hydroxy-functional component and a polyisocyanate component which have beendescribed. For example, isocyanate-crosslinking two-component systems based on
polyacrylate polyols are described in EP-A-0 358 979, WO-A-94/03516, EP-A-0 554
747 and EP-A-0 557 844, two-component systems based on polyurethane polyols are
described, for example, in EP-A-0 496 205, WO-A-94/03511 and EP-A-0 554 747, andthose based on polyester polyols are described, for example, in EP-A-0 537 568 and
WO-A-94/03513. Mixtures of the said polyols are described, for example, in EP-A-0
542 105 and EP-A-0 610 450.
A si~nific~nt disadvantage of all these cited two-component systems is that the finished
component, which contains an OH-functional binder vehicle and is in the form of a
water-thinnable dispersion, such as that which exists as the so-called master material in
a coating shop, for example, has an unsatisfactory storage stability. These water-
. 2l98~92
thinnable dispersions generally exhibit phase separation after a few weeks or months. In
areas of application such as these, such as that of vehicle coating for repair purposes for
example, in which a long-term stability of 1 to 3 years is required, the water-th;nnable
two-component systems which have been described hitherto can therefore only be used
5 to a limited extent.
Moreover, the processing times, i.e. the periods within which the final lacquer is still
processable after mixing the two components, are also too short in many cases.
10 The object of the present invention was therefore to provide water-thinnable components,
which contain hydroxy-functional binder vehicles, for water-thinnable two-component
coating media, which exhibit a satisfactory long-term storage stability. The object was
also that the final coating media should exhibit an increased processing time.
15 It has been shown that this object is achieved by the method, to which this invention
firstly relates, of producing an aqueous dispersion, which contains customary lacquer
additives and which can be used as a binder vehicle component for aqueous two-
component coating media or which is suitable for producing a binder vehicle component
of this type, of hydroxy-functional, customary lacquer binder vehicles which contain
20 ionic, non-ionic hydrophilic, and/or neutralisable acidic or basic groups, which is
characterised in that the hydroxy-functional binder vehicle, which may exist in the
presence of organic solvent, is mixed in non-aqueous phase with at least part of the
customary lacquer additives provided, acidic or basic groups which are present are at
least partially neutralised before, during or after mixing with the additives, the mixture
25 thus obtained is homogenised and is subsequently converted into the aqueous phase, and
if a residue of customary lacquer additives is present, this is added.
The dispersion which is provided by the method according to the invention is hereinafter
called the master component. The master component contains one or more hydroxy-
30 functional binder vehicles such as those described above, water, and customary lacqueradditives, and optionally contains one or more organic solvents and/or one or more
pigments and/or extenders.
}~f.,
In contrast to the procedure which is otherwise customary and in which addition of the
additives is always effected during and/or after the formation of the dispersion or
emulsion in the aqueous phase, it has surprisingly been found that a very good storage
stability of the master component is obtained, even over extended periods of time, by
5 the procedure according to the invention. Surprisingly, the processing time of coating
media which contain the binder vehicle component produced according to the invention
is improved by the procedure according to the invention.
In detail, the production of the aqueous master component can be effected as follows,
10 for example. The OH-functional binder vehicles are produced in non-aqueous form in
the usual manner by polymerisation, condensation polymerisation and/or addition
polymerisation. Solvent-based solutions, or dispersions or melts of the OH-functional
binder vehicles are thereby obtained in each case. In order to impart the requisite
hydrophilic character to the binder vehicles for their conversion into the aqueous phase,
15 they are modified ionically o'r non-ionically.
After the production of the OH-functional binder vehicles in non-aqueous form, at least
part of the customary lacquer additives contained in the final coating medium is added
to the solution, dispersion or melt. Addition of the additives can also be effected,
20 however, after the solvent present in the solution or dispersion has been completely or
partially removed. However, it is essential to the invention that the addition of at least
part of the additives is effected before the conversion of the OH-functional binder
vehicles into the aqueous phase. In this connection, the total amount of additives can also
be added before the conversion of the OH-functional binder vehicles into the aqueous
25 phase. If only part of the customary lacquer additives is added, this part may comprise
a partial amount of one or more special additives and/or may comprise different
additives, some of which are according to the invention in each case and others of which
are added to the final dispersion in the conventional manner. In this connection, it is
preferable not to add partial amounts of individual special additives, but to add the entire
30 amount of a special additive according to the invention in each case. After the addition
of the additives, all the components are homogenised. Homogenisation can be effected
21987~;~
by using customary homogenisers, for example (e.g. customary agitating units).
Homogenisation can be conducted at elevated temperature, for example at 40 to 60~C.
Binder vehicles modified with basic or acidic groups are neutralised before conversion
5 into the aqueous phase. In this respect, it is possible to add the corresponding
neutralising agent before, during or after the addition of the additives. The neutralising
agents are preferably added after the addition of the additives. This is followed by a
repeated homogenisation. Homogenisation can be effected as described above for the
addition of the additives, as before. Homogenisation at elevated temperature, for
10 example at 40 to 60~C, is possible here also.
After the addition of the additives and neutralising agents, formation of the dispersion
is then effected in aqueous phase. Dispersion is conducted in the usual manner, wherein
either the organic phase can be added to the aqueous phase or water can be added to the
15 organic phase. After the formation of the dispersion, organic solvents which originate
from the production process can be removed, provided that these have not already been
removed previously and that they are not wanted in the dispersion; removal can be
effected by distillation, for example. During and/or after the formation of the dispersion,
the rem~ining part of the additives which may optionally exist can be added; this part
20 of the additives may comprise one or more organic solvents, which are preferably
miscible with water. The solvents are added in the amounts f~mili~r to one skilled in the
art, in order to obtain desired rheological or viscosity properties for example.
If the master component thus obtained is to be used in pigmented coating media, it is
25 also possible to incorporate one or more pigments and/or extenders (which do not come
under the definition of the additives which can be incorporated according to theinvention) in the master component. This can be effected, for example, by incorporating
the pigments and/or extenders simultaneously with the rem~ining customary lacquer
additives or subsequent to the addition thereof. Homogenisation or comminution can be
30 effected in the usual manner for the incorporation of pigments and/or extenders, for
example. The procedure may, for example, be such that part or the whole amount of the
master component produced according to the invention is mixed with the pigments
~1J~
and/or extenders and optionally with solvents and optionally with the rem~ining
customary lacquer additives, and the mixture is ground in milling units. Thereafter, the
ground material is completed with the rem~ining amount of binder vehicle. However,
it is also possible firstly to grind the pigments in a paste resin and subsequently to
5 complete this batch with the master component produced according to the invention. The
paste resins may be the usual paste resins based on polyester, polyacrylate and/or
polyurethane resins, for example. The polyurethane paste resins which are preferably
used are described in EP-A-0 438 090, for example.
10 All customary lacquer pigments of an organic or inorganic nature are suitable as
pigments or extenders. Examples of inorganic or organic colour-imparting pigments and
extenders include titania, micronised titania, iron oxide pigments, zinc phosphate (anti-
corrosion pigment), azo pigments, phthalocyanine pigments, quinacridone or
pyrrolopyrrole pigments, carbon black, silica, barium sulphate, french chalk, aluminium
15 silicate and magnesium silicate.
The additives which can be added in the method according to the invention are the
customary additives which can be used in the lacquer industry. Additives of this type are
usually substances which can be added in relatively small amounts to coating media in
20 order to improve certain properties or to suppress unwanted properties. They are familiar
to one skilled in the art. The additives which can be used according to the invention may
comprise solid or liquid additives which can be added as such. However, it is also
possible, for example, to melt or dissolve solid additives before they are added. The
solvents which can be used for dissolution include those which are contained in the
25 binder vehicle component to be produced or which are to be added thereto, for example.
Examples of additives such as these include light stabilisers e.g. those based on
benztriazoles and HALS compounds, levelling agents e.g. those based on (meth)acrylic
homopolymers or silicone oils, rheology-influencing agents such as microdispersed
hydrated silica or polymeric urea compounds, thickeners such as crosslinked
30 polycarboxylic acid or polyurethanes, antifoaming agents, wetting agents, anti-
skinning agents, anti-settling agents, anti-flocculants, matting agents, bonding agents,
structure-forming additives, gloss-enhancing additives, catalysts e.g. curing accelerators
i 2
for the crosslinking reaction of the OH-functional binder vehicles, for example organic
salts of metals such as dibutyltin dilaurate or zinc naphthenate, and compounds
cont~ining tertiary amino groups, such as triethylamine, for the crosslinking reaction
with polyisocyanates for example. These additives are used in the customary amounts
5 f~mili~r to one skilled in the art. Depending on the additive, for example, these amounts
range from 0.005 to 5 % by weight with respect to the total finished coating medium.
Within the scope of the present invention, customary lacquer additives should also be
understood to include solvents which influence the industrial application properties of
coating media and which, provided that they are not already present during the
10 production of the binder vehicle component, can also be added within the scope of the
additive addition of the method according to the invention. Solvents of this type which
can be considered as additives can be added in larger amounts, for example up to 15 %
by weight with respect to the master component. Examples of solvents such as these are
given later.
The ionically and/or non-ionically modified, OH-functional binder vehicles are
customary hydroxy-functional polymers, such as those which are used, for example, for
the production of two-con~ponent lacquers, e.g. polyurethane lacquers. Examples of
hydroxy-functional polymers include those based on poly(meth)acrylates, polyurethanes,
20 polyurethane ureas, polyesters, polyethers or polycarbonates, which can be used
individually or in combination. The hydroxy-functional polymers preferably have an OH
number of 10 - 250 mg KOH/g.
Ionically modified hydroxy-functional polymers may contain anionic or cationic groups
25 or groups which can be converted into anionic or cationic groups, namely acidic or basic
groups. Amino groups are one example of basic groups which can be converted intocationic groups. Carboxyl and sulphonic acid groups are examples of acidic groups
which can be converted into anionic groups.
30 Examples of non-ionically stabilised hydroxy-functional polymers include those in which
water-thinnability is achieved by the incorporation of hydrophilic groups, e.g. of
polyether segments, particularly polyethylene oxide segments, into the resin molecule.
~ 2 1 9 ~
Examples of ionically and/or non-ionically modified OH-functional poly(meth)acrylates
are described in detail in EP-A-0 358 979, EP-A-0 554 747, WO-A-94/03516 and WO-A-95/02005. Examples of ionically and/or non-ionically modified OH-functional
polyesters which can be used are described in EP-A-0 554 747, EP-A-0 537 568, WO-
S A-94/03513 and EP-A-0 583 728, and examples of ionically and/or non-ionically
modified OH-functional polyurethanes are described in EP-A-0 496 205, EP-A-0 554747, WO-A-94/03511, WO-A-94/03512, EP-A-0 603 219 and EP-A-0 469 389.
Examples of polyurethanes also include acrylated polyurethanes such as those which are
cited in EP-A-0 657 483 for example. Examples of polyether polyols are cited in EP-A-0
554 747.
The OH-functional binder vehicles are preferably polyurethane polyols which may
optionally be modified with fatty acids. The polyurethane polyols are preferably modified
anionically, or anionically and non-ionically.
The preferred examples of ànionically or anionically and non-ionically modified
polyurethane polyols have an OH number of 25 - 250 mg KOH/g, preferably of 40 - 140
mg KOH/g, a content of urethane groups of 2 - 20 % by weight, preferably of 5 - 15
% by weight, with respect to the resin solids, a number average molecular weight (Mn)
of 1000 to 100,000, preferably from 1500 to 50,000, and an acid number which is
preferably 10 - 35 mg KOH/g, most preferably 15 - 25 mg KOH/g, with respect to 100
g resin solids in each case. The polyurethane polyols can have a content of ethylene
oxide units of less than 200 milliequivalents, preferably less than 150 milliequivalents,
most preferably less than 100 milliequivalents.
The preferred anionically or anionically and non-ionically modi~led polyurethane polyols
are produced by
I) preparing a preliminary addition compound, which contains NCO groups, from
a) one or more organic acids having a sterically hindered acid function and
two groups capable of reacting with isocyanate and/or one or more
- ' 219~ 2
compounds having at least one hydrophilic side chain cont~ining ethylene
oxide units and two groups capable of reacting with isocyanate, and from
- b) one or more aliphatic or cycloaliphatic diisocyanates, optionally together
with one or more aliphatic or cycloaliphatic diisocyanates having at least
one hydrophilic side chain cont~ining ethylene oxide units,
II) preparing a preliminary condensate, which contains OH groups, from
c) one or more polyalcohols,
d) optionally one or more fatty acids,
e) one or more dicarboxylic acids and
f) optionally one or more polyols having at least one hydrophilic side chain
cont~ining ethylene oxide units, and
15 III) the subsequent reaction of the products obtained as in I) and II), optionally in the
presence of one or more monoisocyanates having a hydrophilic chain cont~ining
ethylene oxide units, in quantitative proportions such that the OH groups of thepreliminary condensate obtained as in II) are present in excess in relation to the
NCO groups present.
Production of the preferred OH-functional polyurethanes or urethane alkyds is effected,
for example, by reacting polyalcohols II) with polyisocyanates I) in the melt or in non-
aqueous organic solvents which do not react with isocyanate groups, for example at
temperature of 60 - 160~C.
The preferred anionically or anionically and non-ionically modified OH-functional
polyurethanes and the production thereof are described in detail in WO-A-94/03511 and
WO-A-94/035 12. Polyurethane polyols without ethylene oxide units in hydrophilic chains
are preferably used.
2198t,~2
The preferred anionically or anionically and non-ionically modified OH-functional
polyurethanes may also be used in admixture with others of the ionically and/or non-
ionically modified hydroxy-functional polymers described above.
5 Small amounts of organic solvents, preferably not more than 15 % by weight with
respect to the total master component, may be present in the master component produced
according to the invention. As described above, these solvents may have been
incorporated completely or partially as additives according to the invention. However,
they may also originate completely or in part from the production of the binder vehicles
10 or may have been incorporated in the aqueous dispersion. These organic solvents are
preferably miscible with water. They may be customary solvents used in lacquer
technology, for example. Examples of solvents such as these include mono- or
polyhydric alcohols, e.g. propanol, butanol or hexanol; glycol ethers or esters, e.g.
diethylene glycol dialkyl ethers, dipropylene glycol dialkyl ethers, each cont~ining a
15 C1-6 alkyl, ethoxypropanol or butyl glycol; glycols e.g. ethylene glycol, propylene
glycol and oligomers thereof; N-methylpyrrolidone, as well as ketones such as methyl
ethyl ketone, acetone or cyclohexanone; aromatic or aliphatic hydrocarbons, e.g.toluene, xylene or linear or branched aliphatic C6-C12 hydrocarbons. The flow and
viscosity of the coating medium produced from the master component can be influenced
20 by the choice and amount of solvents.
The master component produced according to the invention contains neutralising agents
for the neutralisation of acidic or basic groups in order to obtain the anionically or
cationically modified binder vehicle. Anionically modified binder vehicles contain bases
25 as neutralising agents. Examples of these include ammonia or organic amines such as
triethylamine or N-methylmorpholine, amino alcohols such as dimethylisopropanolamine,
dimethylethanolamine or 2-amino-2-methylpropanol-1. Cationically modified bindervehicles contain acids as neutralising agents. Organic monocarboxylic acids, such as
formic acid and acetic acid for example, are preferred. Hydroxycarboxylic acids are also
30 quite suitable, such as lactic acid, glycolic acid, diglycolic acid, malic acid, citric acid,
mandelic acid, tartaric acid, hydroxypropionic acid and dimethylolpropionic acid, for
example.
21g8 ~;~2
In addition to the master component, the coating media which are prepared using the
master component produced according to the invention contain a further componentwhich contains functions which are reactive with hydroxyl groups. This is designated
here as the OH-reactive component. Polyisocyanates or binder vehicles which contain
S anhydride groups are examples of suitable OH-reactive components. Binder vehicles
which contain anhydride groups are produced, for example, by the copolymerisation of
maleic anhydride with other unsaturated monomers. Examples of anhydride-functional
binder vehicles which can be used according to the invention are described in EP-A-0
048 128, EP-A-0 304 817 and EP-A-0 353 899.
Polyisocyanates are preferably used as the OH-reactive component. These
polyisocyanates include any organic polyisocyanates which contain aliphatically,cycloaliphatically, araliphatically and/or aromatically bonded, free isocyanate groups,
such as those which are familiar to one skilled in the art in the lacquer sector. They are
liquid at room temperature, or are liquefied by the addition of organic solvents. The
polyisocyanates preferably have a viscosity at 23~C from 1 to 6000 mPa.s, most
preferably greater than 5 and less than 3000 mPa.s.
Polyisocyanates of this type are generally known and are described, for example, in DE-
A-38 29 587 or DE-A-42 26 243.
The polyisocyanates are preferably polyisocyanates or polyisocyanate mixtures which
solely contain aliphatically and/or cycloaliphatically bonded isocyanate groups with an
average NCO functionality of 1.5 to 5, preferably 2 to 3.
Examples of polyisocyanates which are particularly suitable include "lacquer
polyisocyanates" based on hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-
isocyanatomethane-cyclohexane (IPDI) and/or bis(isocyanatocyclohexyl)methane and the
derivatives of these diisocyanates which contain biuret, allophanate, urethane and/or
30 isocyanurate groups and which are known in the art, which after their production are
freed from surplus diisocyanate starting material, preferably by distillation, down to less
than 0.5 % by weight.
- 21~7~
11
Polyiso~;y~ates which are also very suitable are sterically hindered polyisocyanates of
general formula
Rl R,
S l l
OCN - C - A - C - NCO
R2 R2
10wherein Rl = H or R2, and R2 = CnH2"+l with n = 1 to 6.
The substituents R, and R2 are either linear or branched, identical or different. The basic
skeleton A may consist of a single bond, an aromatic or alicyclic ring, or of an aliphatic,
linear or branched C chain containing 1 to 12 C atoms.
Examples thereof include 1,1,6,6-tetramethyl-hexamethylene diisocyanate, 1,5-dibutyl-
pentamethyl diisocyanate, p- or m-tetramethylxylylene diisocyanate and their
corresponding hydrogenated homologues. These diisocyanates can likewise be converted
in a suitable manner into compounds of higher functionality, for example by
20 trimeri.~tion or by reaction with water or trimethylolpropane.
Aromatic polyisocyanates are also suitable, but are less prefelled. Examples thereof
include polyisocyanates based on 2,4-diisocyanatotoluene or mixtures thereof with 2,6-
diisocyanatotoluene, or based on 4,4'-diisocyanatophenylmethane and trimers thereof.
Shortly before application, the master component produced according to the invention
is thoroughly mixed, optionally with pigments and/or extenders, with the OH-reactive
component, preferably with the polyisocyanates. If need be, the batch can then be
adjusted to spraying viscosity with water or small amounts of organic solvents.
The coating media which are produced in this manner are particularly suitable for the
production of pigmçnted or transparent outer coats of an air-drying or force-dried multi-
layer coating. However, they can also be hardened at higher tempel~ les, of 80 -
.
~198 ~
140~C for example. They are suitable for the coating of vehicles and for industrialcoating operations, particularly for the coating of vehicles and vehicle parts for repair
purposes.
S The coating media are applied by known methods, such as spraying, dipping, by rollers
or by doctor blades for example. A transparent clear lacquer coat can be applied to
conventional or aqueous base lacquers by the wet-into-wet method, for example,
whereupon both coats are hardened together, e.g. for 15 - 20 minutes at 50 - 80~C for
example, or a pigmented covering lacquer coat can be applied to customary single-
10 component or two-component primer surfacer coats.
One significant advantage of the master component produced by the method according
to the invention is its very good storage stability, even over an extended period of 2 -
3 years for example. The two-component coating media which are produced using this
15 master component have a processing time of about 2 - 4 hours. Coatings which are
obtained from the coating med'ia exhibit an improvement in gloss and body compared
with conventionally produced coating media.
The invention is explained in more detail by way of the following examples. The
20 expression pts (parts) denotes parts by weight in each case.
Example 1
1.1 Production of a master component
A) 600 pts trimethylolpropane, 444 pts coconut oil acid and 421 pts
tetrahydrophthalic anhydride were mixed and carefully melted. The batch was
slowly heated, together with 100 pts xylene, to 170 - 230~C with st*ring and
under a nitrogen atmosphere, so that the water of reaction was steadily distilled
off azeotropically and the acid number fell to less than 0.3.
13
B) 212 pts dimethylolpropionic acid were suspended in 1000 pts acetone in a dry
reaction vessel, and after adding 704 pts isophorone diisocyanate were reacted
whilst increasing the temperature to 60~C.
500 pts of reaction product A) were mixed with 300 pts of reaction product B) and
carefully heated until the evolution of heat was observed. After the evolution of heat was
complete, the batch was subsequently stirred at 60~C until the NCO content was less
than 0.2 %. 14 pts dimethylethanolamine were then added. The following commercially
available lacquer additives were then added in the sequence given: 107 pts butyl glycol,
17 pts of a light stabiliser combination comprising a UV absorber of the benztriazole
type and a radical scavenger of the HALS type (HALS = hindered amine light
stabiliser), 4 pts of a polyurethane thickener and 7 pts of a polysiloxane-based levelling
agent. The mixture was homogenised for 30 minutes at 50~C. Thereafter it was diluted
with deionised water and the acetone was distilled off under vacuum, so that a free-
flowing dispersion was obtained (solids content: about 40 % by weight / 60 minutes at
150~C).
The master component produced in this manner exhibited no coagulation and/or settling
phenomena, even after a storage period of more than two years.
1.2 Production of a two-component clear lacquer
19 pts of a commercially available polyisocyanate based on a hexamethylene diisocyanate
trimer (NCO number: 17 ~) were homogeneously stirred into 100 pts of the master
component from Example 1. The viscosity was then adjusted to 20 seconds (DIN-4 cup
/ 23~C) with deionised water. The coating medium had a processing time of 4 hours.
2nd F,~ le (comparative)
2.1 Production of the binder vehicle
Components A) and B) were produced according to Example 1. 500 pts of reaction
product A) were mixed with 300 pts of reaction product B) and carefully heated until the
~19~7~2
14
evolution of heat was observed. After the evolution of heat was complete, the batch was
subsequently stirred at 60~C until the NCO content was less than 0.2 %. 14 pts
dimethylethanolamine and 100 pts deionised water were then added, followed after five
nlinu~es by a further 6Q0 pts deionised water. The batch was then stirred whilst being
5 heated to 70~C, and the acetone was then distilled off under vacuum. A free-flowing
dispersion was obtained which had a solids content of about 43 % by weight.
2.2 Production of a master component
10 The following commercially available lacquer additives were homogeneously
incolpor~led, in the sequence given, into 500 pts of the dispersion produced according
to co,.~pal~tive example 2.1: 13 pts butyl glycol, 2 pts of a light stabiliser combination
comprising a UV absorber of the benzotriazole type and a radical scavenger of the
HALS type, 0.6 pts of a polyurethane thickener and 0.8 pts of a polysiloxane-based
15 levelling agent. The solids content was adjusted to 40 5~ by weight with deionised water.
A perceptible settling behaviour of the particles of the dispersion was observed, even
after just a few months.
2.3 Production of a two-component clear lacquer
19 pts of a commercially available polyisocyanate based on a hexamethylene diisocyanate
trimer (NCO number: 17 %) were homogeneously stirred into 100 pts of the master
coll,ponent from comparative example 2.2. The viscosity was then adjusted to 20
seconds (DIN-4 cup / 23 ~C) with deionised water. The coating medium had a processing
25 time of only 2.5 hours.
