Note: Descriptions are shown in the official language in which they were submitted.
CA 02393289 2002-06-03
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ACHROMATIC hACQUERS, A METHOD FOR PRODUCING
SALE AND THE USE THEREOF
The present invention relates to novel achromatic
paints, especially jet black paints. The present
invention further relates to a novel process for
preparing achromatic paints, especially jet black
paints. The present invention relates not least to the
use of the novel achromatic paints in automotive OEM
finishing and automotive refinish, in industrial
coating, including container coating and coil coating,
and in furniture coating.
Achromatic paints differ from the chromatics in that
they lack chroma and hue; they exhibit only lightness.
The achromatic colors include black and white and also
the gray shades which lie between them or can be mixed
from them (cf. Rompp Lexikon Lacke and Druckfarben,
Georg Thieme Verlag, Stuttgart, New York, 1998
"achromatic point", page 590). In the context of the
present invention, however, achromatic colors are
understood to embrace black and gray shades.
To produce jet black shades is a declared objective in
the paint industry. However, this causes great
difficulties particularly in the case of aqueous
paints. In general, an improvement in pigment wetting
is achieved by adding wetting agents and dispersants.
This raises the color strength, giving cleaner, deeper
shades. In the case of carbon black pigments, however,
which form the bases of achromatic paints, especially
jet black paints, this technique does not provide the
desired success.
The German patent DE-C-197 56 465 discloses jet black
conventional and aqueous paints which comprise carbon
black pigments. The carbon black pigments contain,
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based on their overall weight, from 0.1 to 30~ by
weight of silicon, calculated as silicon dioxide. These
carbon black pigments are obtained by adding suitable
silicon-containing compounds to the base carbon black
material. An alternative possibility which exists is to
supply the silicon-containing compounds to the feed
stream of the respective carbon black process, shortly
before or directly in the carbon black formation zone.
Suitable silicon-containing compounds are organosilicon
compounds such as organosilanes, organochlorosilanes,
siloxanes and silazanes. Particularly suitable are
silicon tetrachloride, siloxanes, and silazanes.
Preference is given to methyl or ethyl silicate,
siloxanes, and silazanes for the preparation of the
silicon-containing carbon blacks.
A disadvantage of this known technique is that the
carbon black pigments are modified as part of the
carbon black process, so that the properties. of the
respective carbon black pigments are decided as such by
the comparatively complex production process and not by
means of a simple, targeted modification of customary
and known commercial carbon black pigments as part of
the paint production process. The targeted preparation
of carbon black pigments possessing special suitability
for a given end application is therefore very complex.
A further factor is that, at the higher temperatures
employed in the production of carbon black, the
organosilicon compounds are altered in a way which is
difficult to predict, thereby making the targeted
production of modified carbon black pigments even more
difficult.
It is an object of the present invention to provide
novel achromatic paints, especially jet black paints,
which can be prepared in a simple yet targeted way and
whose carbon black pigments can be modified not as part
of the carbon black process but rather as part of the
paint production process, in a simple way, to give an
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improvement in the jetness without detriment to the
other essential performance properties of the
respective paints.
Found accordingly have been the novel achromatic paints
which comprise at least one binder, at least one carbon
black pigment, and at least one silicone.
In the text below, the novel achromatic paints are
referred to as "paints of the invention".
Also found has been the novel process for preparing the
paints of the invention, in which at least one binder,
at least one carbon black pigment, and at least one
silicone are mixed with one another, and which is
referred to below as "process of~the invention".
A further subject matter of the invention will emerge
from the following description.
In the light of the prior art it was surprising and
unforeseeable for the skilled worker that the object on
which the present invention is based could be achieved
by means of the process of the invention and the paints
of the invention. Put another way, it was surprising
that, by means of the usually accomplished measure of
adding an additive, it was possible to provide an
alternative, attractive in terms both of performance
and of economics, to the complex production process of
silicon-containing carbon black pigments. A very
particular surprise was that the addition of the
silicones does not lead to the well-known, unwanted
side effects of silicone additives such as foaming,
problems of wetting and adhesion on overcoating (cf.
the textbook "Lackadditive" [Additives for coatings] by
Johan Bieleman, Wiley-VCH, Weinheim, New York, 1998,
page 139) and/or to paint defects such as craters (on
this point, cf. Rompp Lexikon Lacke and Druckfarben,
Georg Thieme Verlag, Stuttgart, New York, 1998,
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"silicone additives", page 524).
The inventively essential constituent of the paints of
the invention is at least one silicone. Silicones are
also referred to by those in the art, as will be known,
as silicone oils, polysiloxanes, polyorganosiloxanes or
organosiloxanes. They are synthetic polymeric compounds
in which the silicon atoms are linked in the form of
chains and/or networks via oxygen atoms and the
remaining valences of the silicon are satisfied by
hydrocarbon radicals, preferably methyl, phenyl, ethyl
and/or propyl groups, especially methyl groups.
Depending on chain length, degree of branching, and
substituents, the silicones may be oils with a
viscosity ranging from low to high, or may be solid.
Furthermore, they may have been modified with
polyethers. For further details, refer to Rompp Lexikon
Lacke and Druckfarben, Georg Thieme Verlag, Stuttgart,
New York, 1998, "silicone additives", page 524,
"silicone copolymers", page 525, and "silicones",
page 525.
In accordance with the invention, linear liquid
silicones and silicone oils are used which contain from
10 to 100, preferably. from 11 to 80, more preferably
from 12 to 70, with particular preference from 13 to
60, with very particular preference from 14 to 55, and
in particular from 15 to 50 Si-0 units. It is preferred
to use silicone copolymers that have been modified with
polyethers, especially polyethylene oxide-co-propylene
oxide). Particularly preferred silicones are head-to-
head modified, with the polyether chains being linked
to the siloxane chains by way of allyl groups. Very
particularly preferred silicones contain polyether
chains composed of from 10 to 90 mol o, preferably from
15 to 85 mol%, of ethylene oxide units and from 90 to
10 molo, preferably from 85 to 15 mol%, of propylene
oxide units. The polyether chains preferably have a
number-average molecular weight Mn of from 500 to 3000,
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more preferably from 600 to 2500, with particular
preference from 800 to 2200, and in particular from 900
to 2000. The silicones overall preferably have a
number-average molecular weight Mn of from 2000 to
10,000, more preferably from 2100 to 9500, with
particular preference from 2200 to 9000, with very
particular preference from 2300 to 8500, and in
particular from 2400 to 8000.
Especially suitable silicones contain, for example,
chains having 18 Si-O units and 2 head-to-head-linked
polyether chains with a number-average molecular weight
Mn of 1250, containing 80 molo of ethylene oxide units
and 20 mold of propylene oxide units, or chains having
48 Si-O units and 2 head-to-head-linked polyether
chains with a number-average molecular weight Mn of
1860, containing 50 mol°s of ethylene oxide units and
50 mold of propylene oxide units.
The silicones of the type specified are customary and
known and are available on the market.
The silicone content of the paints of the invention may
vary very widely and is guided on the one hand by the
particular carbon black pigment used and on the other
hand by the compatibility of the other constituents of
the paints of the invention with the silicones. The
skilled worker is therefore easily able to determine
the amount on the basis of his or her general art
knowledge with the assistance, where appropriate, of
simple preliminary tests. The amount is preferably from
0.01 to 2.0~, more preferably from 0.02 to 1.50, with
particular preference from 0.03 to 1.2%, with very
particular preference from 0.03 to 1.0o, and in
particular from 0.04 to 0.8% by weight based in each
case on the overall amount of the paint of the
invention.
The further inventively essential constituent of the
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paint of the invention is at least one carbon black
pigment. Carbon black pigments are also referred to by
those in the art as pigment blacks, color blacks or
carbon pigments. They are normally prepared by the
furnace black, Degussa gas black and lamp black
process. In general they have primary particle sizes of
from 10 to 200 nm. For further details, refer to Rompp
Lexikon Lacke and Druckfarben, Georg Thieme Verlag,
Stuttgart, New York, 1998, "industrial carbon blacks",
pages 300 and 301, and "pigment blacks", pages 452 and
453. The choice of which carbon black pigment is
employed in the paint of the invention is guided
primarily by the desired shade or the desired depth of
color and by the particular end utility. The skilled
worker is therefore easily able to determine the carbon
blacks best suitable. in each case, on the basis of his
or her general art knowledge with the assistance, where
appropriate, of simple preliminary tests. The amount of
the carbon black pigments in the paints of the
invention may vary widely. It is preferably from 0.5 to
20%, more preferably from 1.0 to 18%, with particular
preference from 1.2 to 16%, with very particular
preference from 1.3 to 15%, and in particular from 1.4
to 14% by weight, based in each case on the paint of
the invention.
A further essential constituent of the paint of the
invention has at least one binder. Regarding the
definition, refer to Rompp Lexikon Lacke and
Druckfarben, Georg Thieme Verlag, Stuttgart, New York,
1998, "binders", pages 73 and 74).
Examples of suitable binders are oligomeric and
polymeric, thermally curable, linear and/or branched
and/or block, comb and/or random poly(meth)acrylates or
acrylic copolymers, especially those described in
patent DE-A-197 36 535, polyesters, especially those
described in patents DE-A-40 09 858 or DE-A-44 37 535,
alkyds, acrylated polyesters, polylactones, polycarbon-
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ates, polyethers, epoxy resin-amine ,adducts,
(meth)acrylatediols, partially hydrolyzed polyvinyl
esters, polyurethanes and acrylated polyurethanes, as
described in patents EP-A-0 521 928, EP-A-0 522 420,
EP-A-0 522 419, EP-A-0 730 613 or DE-A-44 37 535, or
polyureas.
The selection of the binders is guided in particular by
whether the paints of the invention are conventional
paints, comprising organic solvents, or aqueous paints,
or water- and solvent-free liquid paints (100
systems), solid pulverulent paints (powder coatings),
or water-dispersed powder coatings (powder slurries).
The selection of the binders is further guided by
whether the paints of the invention are physically
cured paints. As is known, physical curing takes place
by loss of solvent from the applied paint film and/or
with coalescence of binder . particles. For further
details, refer here to Rompp Lexikon Lacke and
Druckfarben, Georg Thieme Verlag, Stuttgart, New York,
1998, "curing", pages 274 and 275).
Additionally, the selection of the binders is guided by
whether the paints of the invention are self-
crosslinking paints or externally crosslinking paints.
As is known, the term "self-crosslinking" refers to the
capacity of a binder to undergo crosslinking reactions
with itself. A prerequisite for this is that the
binders already contain both kinds of complementary
reactive functional groups which are necessary for
crosslinking, such as hydroxyl groups and blocked
isocyanate groups or N-methylol groups. Externally
crosslinking paints, on the other hand, are those in
which one kind of the complementary reactive functional
groups, say the hydroxyl groups, are present in the
binder and the other kind, say the blocked isocyanate
groups or the N-methylol groups, are present in a
curing or crosslinking agent. For further details of
CA 02393289 2002-06-03
this, refer to Rompp Lexikon Lacke and Druckfarben,
Georg Thieme Verlag, Stuttgart, New York, 1998,
"curing", pages 274 to 276, particularly page 275,
bottom.
Moreover, the selection of the binders is guided by the
intended use. The paint of the invention is preferably
used in automotive OEM finishing and automotive
refinish as a surfacer, solid-color topcoat material or
as a basecoat material, especially an aqueous basecoat
material, as part of what is known as the wet-on-wet
technique (cf., for example, European patent EP-B-0 089
497) for producing multicoat color and/or effect paint
systems. In addition it is suitable for industrial
coating, including coil coating and container coating,
and also for furniture coating.
The skilled worker is therefore easily able to
determine the binders which are best suited in each
case, taking into account the requirements associated
with the form of the paint of the invention and/or with
its aggregate state and its particular intended use, on
the basis of his or her general art knowledge with the
assistance where appropriate of simple preliminary
tests. The same applies to the amount of the binders in
the paints of the invention, which may vary extremely
widely and is preferably from 1.0 to 99.499%, more
preferably from 2.0 to 98%, with particular preference
from 3.0 to 95%, with very particular preference from
4.0 to 92%, and in particular from 5.0 to 90% by weight
based in each case on the paint of the invention.
The paint of the invention may be a one-component (1K)
system.
For the purposes of the present invention a one-
component (1K) system is a thermosetting coating
material in which the binder and the crosslinking agent
are present alongside one another, i.e., in one
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component. A prerequisite for this is that the two
constituents crosslink with one another only at
relatively high temperatures.
The paint of the invention may also be a two-component
(2K) or multicomponent (3K, 4K) system.
For the purposes of the present invention, this means a
paint of the invention in which in particular the
binder and the crosslinking agent are present
separately from one another in at least two components
which are not combined until shortly before
application. This form is chosen when binder and
crosslinking agent react with one another even at room
temperature, which is the case, as is known, when using
hydroxyl groups on the one hand and isocyanate groups
on the other. Paints of the invention of this kind are
employed in particular for coating thermally sensitive
substrates, especially in automotive refinish.
Besides the inventively essential constituents
described above, the paints of the invention may
comprise additional pigments in customary and known
amounts.
The pigments in question are primarily white pigments,
especially when the paint of the invention is a gray
paint. Suitable white pigments are described, for
example, in Rompp Lexikon Lacke and Druckfarben, Georg
Thieme Verlag, 1998, "white pigments", page 629.
The paint. of the invention may further comprise
effective amounts of customary and known effect
pigments which do not per se induce any chromaticity.
Examples of suitable effect pigments are described, for
example, in Rompp Lexikon Lacke and Druckfarben, Georg
Thieme Verlag, 1998, page 176, "effect pigments"; or
pages 380 and 381 "metal oxide-mica pigments" to "metal
pigments".
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The paint of the invention, especially the externally
crosslinking paint of the invention, may further
comprise crosslinking agents in customary and known,
effective amounts.
Examples of suitable crosslinking agents are amino
resins, compounds or resins containing anhydride
groups, compounds or resins containing epoxide groups,
tris(alkoxycarbonylamino)triazines, compounds or resins
containing carbonate groups, blocked and/or nonblocked
polyisocyanates, beta-hydroxyalkylamides, and compounds
containing on average at least two groups capable of
transesterification, examples being reaction products
of malonic diesters and polyisocyanates or of esters
and partial esters of polyhydric alcohols of malonic
acid with monoisocyanates, such as described in
European patent EP-A-0 596 460.
Crosslinking agents of this kind are obtainable
commercially.
Not least, the paint of the invention may comprise
customary and known paint additives in effective
amounts.
Examples of suitable paint additives are organic and
inorganic fillers which do not per se induce' any
chromaticity, transparent pigments, thermally curable
reactive diluents, low-boiling and/or high-boiling
organic solvents ("long solvents"), UV absorbers, light
stabilizers, free-radical scavengers, thermal labile
free-radical initiators, crosslinking catalysts,
devolatilizers, slip additives, polymerization
inhibitors, defoamers, emulsifiers, wetting agents,
adhesion promoters, leveling agents, film-forming
auxiliaries, rheology control additives or flame
retardants. Further examples of suitable paint
additives are described in the textbook "Lackadditive"
[Additives for coatings] by Johan Bieleman, Wiley-VCH,
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Weinheim, New York, 1998.
The preparation of the paint of the invention has no
special features but instead takes place in a customary
and known way by mixing of the above-described
constituents in suitable mixing equipment such as
stirred tanks, dissolvers, stirrer mills or extruders
by the techniques suitable for preparing the respective
paints of the invention. Particular advantages result
if the carbon black pigments for use in accordance with
the invention are incorporated by way of pigment
pastes. These pastes may already contain the silicones
for use in accordance with the invention, or a portion
thereof.
The paint of the invention, especially the aqueous
basecoat material of the invention, is used for
producing the paint systems of the invention,
especially multicoat paint systems, on primed. or
unprimed substrates.
Suitable substrates include all surfaces intended for
painting; that is, for example, metals, plastics, wood,
ceramic, stone, textile, fiber composites, leather,
glass, glass fibers, glass wool and rock wool, mineral-
and resin-bound building materials, such as plaster-
board and cement slabs or roofing shingles, and
composites of these materials. Accordingly, the paint
system of the invention is also suitable for
applications outside of automobile finishing. In this
case it is suitable in particular for the painting of
furniture, for do-it-yourself painting, and for
industrial painting, including coil coating and
container coating. In the context of do-it-yourself
painting and industrial coating it is suitable for
coating and refinishing virtually all parts for private
or industrial use such as radiators, domestic
appliances, small metal parts such as nuts and bolts,
hubcaps, wheel rims or packaging.
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In the case of electrically conductive substrates it is
possible to use primers produced conventionally from
electrocoat materials. Both anodic and cathodic
electrocoat materials are suitable for this purpose,
but especially cathodics.
The paints of the invention may also be used to coat
primed or unprimed plastics such as, for example, ABS,
AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, PA,
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 (abbreviated codes in accordance with
DIN 7728P1). The plastics to be painted may of course
also be polymer blends, modified plastics or fiber-
reinforced plastics. It is also possible to employ the
plastics commonly used in vehicle construction,
especially motor vehicle construction.
Nonfunctionalized and/or apolar substrate surfaces may
be subjected prior to coating in a known manner to a
pretreatment, such as with a plasma or by flaming, or
may be provided with a hydroprimer.
The paint of the invention may be applied by any
customary application method, such as spraying, knife
coating, brushing, flow coating, dipping, impregnating,
trickling or rolling, for example . The substrate to be
coated may itself be at rest, with the application
equipment or unit being moved. Alternatively, the
substrate to be coated, in particular a coil, may be
moved, with the application unit being at rest relative
to the substrate or being moved appropriately.
Preference is given to employing spray application
methods, such as compressed air spraying, airless
spraying, high-speed rotation, electrostatic spray
application (ESTA), alone or in conjunction with hot
spray applications such as hot air spraying, for
example. The applications may be conducted at
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temperatures of max. 70 to 80°C, so that suitable
application viscosities are achieved without the brief
exposure to thermal loading being accompanied by any
changing or damage to the aqueous basecoat material or
its overspray, which may be intended for reprocessing.
Hot spraying, for instance, may be configured in such a
way that the paint is heated only very briefly in the
spray nozzle or shortly before the spray nozzle.
The spray booth used for the application may be
operated, for example, with a circulation system, which
may be temperature-controllable, and which is operated
with a suitable absorption medium for the overspray, an
example being the paint of the invention itself.
The paints of the invention are generally applied in a
wet film thickness such that curing thereof results in
coats having the thicknesses which are advantageous and
necessary f.or their functions. In the case of the
surfacer coat this thickness is from 10 to 150 um,
preferably from 10 to 120 um, with particular
preference from 10 to 100 pm, and in particular from 10
to 90 um, in the case of the basecoat it is from 5.0 to
50 um, preferably from 5.5 to 40 pm, with particular
preference from 6 to 30 um, and in particular from 10
to 25 ~zm, and in the case of the solid-color topcoat it
is from 5.0 to 100 um, preferably from 5.5. to 80 pm,
with particular preference from 6 to 70 ~zm, and in
particular from 10 to 60 um.
The applied paint films of the invention, especially
the surfacer films, basecoat films, and solid-color
topcoat films, are cured thermally.
In the case of the wet-on-wet technique, the basecoat
films of the invention, especially aqueous basecoat
films, are not cured thermally but instead are predried
and then overcoated with customary and known clearcoat
materials. After that, the basecoat films of the
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invention and the clearcoat films are thermally cured
together, using the methods described below. This
results in the multicoat paint systems of the
invention.
Curing may take place after a certain rest time. This
may have a duration of from 30 s to 2 h, preferably
from 1 min to 1 h, and in particular from 1 min to
45 min. The rest time serves, for example, for the
leveling and devolatilization of the paint films or for
the evaporation of volatile constituents such as
solvents. The rest time may be shortened and/or
assisted by the application of elevated temperatures up
to 90°C and/or by a reduced atmospheric humidity < 10 g
water/kg air, in particular < 5 g/kg air, provided this
does not entail any damage to or change in the paint
films, such as premature complete crosslinking.
Thermal curing has no special features in terms of its
method but instead takes place in accordance with the
customary and known methods such as heating in a forced
air oven or irradiation with IR lamps. Thermal curing
here may also take place in stages. Thermal curing
takes place advantageously at a temperature of from 50
to 100°C, with particular preference from 60 to 100°C,
and in particular from 80 to 100°C for a time of from
1 min up to 2 h, with particular preference 2 min up to
1 h, and in particular 3 min to 45 min. Where
substrates are used which can withstand high thermal
loads, thermal crosslinking may also be conducted at
temperatures above 100°C. In general it is advisable in
this case not to exceed temperatures of 180°C,
preferably 160°C, and especially 155°C.
The paint systems of the invention, especially the
multicoat paint systems of the invention, have an
outstanding profile of properties which is very well
balanced in terms of mechanics, optics, corrosion
resistance, and adhesion. In particular, the multicoat
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paint systems of the invention exhibit an outstanding
D.O.I. (distinctiveness of the reflected image) and an
outstanding surface smoothness.
Examples and comparative experiments
Preparation Example 1
The preparation of a grinding resin dispersion based on
polyurethane
In a reaction vessel equipped with a stirrer, a reflux
condenser, and 2 feed vessels, 63.5 parts by weight of
isophorone diisocyanate were added to a mixture of 77.6
parts by weight of a polyesterdiol having a number-
average molecular weight of 630 based on adipic acid,
hexanediol, and neopentyl glycol, 9.3 parts by weight
of neopentyl glycol, 3.0 parts by weight of
trimethylolpropane monoallyl ether, 0.1 part by weight
of dibutyltin dilaurate, and 110.2 parts by weight of
methyl isobutyl ketone. The resultant reaction mixture
was then heated at 105°C. At an isocyanate content of
1.8% by weight, 15.1 parts by weight of trimethylol-
propane were added to the reaction mixture and the
reaction was continued until free isocyanate groups
were no longer detectable.
To the resultant polyurethane solution there was added
at 105°C over the course of three hours a mixture of
69.6 parts by weight of n-butyl acrylate, 69.6 parts by
weight of methyl methacrylate, 16.6 parts by weight of
hydroxypropyl methacrylate, and 13.0 parts by weight of
acrylic acid. At the same time, 5.1 parts by weight of
tert-butyl perethylhexanoate, dissolved in 42.8 parts
by weight of methyl isobutyl ketone, were metered in
over the course of 3.5 hours. After a further 2.5 hours
at 105°C, the reaction mixture was cooled to 90°C. Then
10.6 parts by weight of dimethylethanolamine and 483.2
parts by weight of deionized water were added. Removal
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of the methyl isobutyl. ketone in vacuo gave a stable
polyurethane dispersion having a solids content of 43%
by weight and a pH of 7.9.
Preparation Example 2
Preparation of a binder dispersion
A 4 1 steel reactor suitable for free-radical
copolymerization, with metering attachments and reflux
condenser, was charged with 583 parts by weight of
propanol and this initial charge was heated to 95°C.
Over the course of 5 minutes, a mixture of 2.2 parts by
weight of Trigonox~ 421 (free-radical polymerization
initiator from Akzo) and 13 parts by weight of propanol
was added. At the same time, a mixture of 83.2 parts by
weight of acrylic acid, 240 parts by weight of styrene,
and 290 parts by weight of butyl acrylate was metered
in at a uniform rate over the course of 2 hours and
also 3.5% of a mixture of 181 parts by weight of
Trigonox~ and 181 parts by weight of propanol was
metered in over the course of 30 minutes. Subsequently,
the resultant reaction mixture was heated at 95°C for a
further 20 minutes.
After this time, a mixture of 86.2 parts by weight of
styrene and 115 parts by weight of n-butyl acrylate was
metered in at a uniform rate over the course of 2
hours, and, beginning at the same time, 6.2% of the
mixture of 181 parts by weight of Trigonox~ and 181
parts by weight of propanol was metered in over the
course of one hour. After the end of the two feed
streams, the reaction mixture was postpolymerized for
one hour.
Subsequently, after this time, a mixture of 180 parts
by weight of methyl methacrylate, 315 parts by weight
of styrene, and 495 parts by weight of n-butyl acrylate
was metered in at a uniform rate over the course of 4
CA 02393289 2002-06-03
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hours, and, beginning at the same time, 48.1$ of the
mixture of 181 parts by weight of Trigonox~ and 181
parts by weight of propanol was metered in over the
course of 4 hours.
Finally, 42.2% of the mixture of 181 parts by weight of
Trigonox~ and 181 parts by weight of propanol were
metered in over the course of 2 hours.
After the end of the feed streams, the temperature of
the reaction mixture was held at 95°C for 1.5 hours
more.
The resultant solution had a solids content of 70.6 by
1S weight (2 g initial mass + 2 g xylene; 1 hour at 130°C)
and an acid number of 41.8 mg KOH/g. The solution was
adjusted to a solids content of 37~ by weight using
75.6 parts by weight of 25$ aqueous ammonia and
isopropanol. The viscosity of the dilute solution was
4.4 dPas. The copolymer had a number-average molecular
weight Mn of 15.981 and a mass average molecular weight
Mw of 53.316 (determined by gel permeation
chromatography with polystyrene as internal standard).
Example 1 and comparative experiment Cl
The preparation of a jet black inventive paint (Example
1) and of a noninventive paint (comparative experiment
C1)
For Example 1, 30 parts by weight of the binder
dispersion of preparation Example 2 were introduced as
an initial charge. Added to this with stirring were 4.4
parts by weight of propanol, 0.4 part by weight of a
commercial wetting agent based on a phosphoric
monoester (Pigmentverteiler LR 8807 from BASF AG), and
0.4 part by weight of a technical-grade ammonia
solution, with stirring.
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0.3 part by weight of a commercial emulsifier
(Surfynol~ 104 E, 50o in ethylene glycol), 0.05 part by
weight of sodium nitrite and 6.45 parts by weight of
deionized water were mixed with one another and the
resultant mixture was added with stirring to the
mixture described above.
The resultant mixture was admixed, with vigorous
stirring, with 2.2 parts by weight of amorphous carbon
black (Printex U~ from Degussa), 0.7 part by weight of
pyrogenic silica (Aerosil~ 200 CV), 12 parts by weight
of precipitated barium sulfate (Blanc Fixe~ Micro from
Sachtleben) and 4 parts by weight of propanol.
The resultant mixture was ground on a horizontal
stirrer mill (grinding media SAZER; 1.6-2.5 mm
diameter, Si-Zr beads) at a maximum temperature of 50°C
to a Hegmann fineness of from 13 to 15 um (wedge
um) .
The stirrer mill was rinsed first with 10.5 parts by
weight of water and then with 10.5 parts by weight of
propanol. Subsequently, 18 parts by weight of the
binder dispersion of preparation Example 2 and also 0.1
part by weight of the silicone Tego Glide~ 410 (100 0)
from Tego Chemie GmbH were added to the mixture.
The pH of the resultant premix of the invention was
adjusted to 8.7-9.0 using ammonia. The viscosity of the
premix of the invention was adjusted to 40 s in the
DIN 4 flow cup using a mixture of propanol and water
(1:1) .
74.4 parts by weight of this premix were mixed with
53.9 of dimethyl ether and applied. The resultant paint
system was measured by colorimetric.
For comparative experiment C1, Example 1 was repeated
but without using any silicone. The resultant paint
,' CA 02393289 2002-06-03
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system was likewise measured by colorimetry. The values
obtained in this case were defined as the standard.
Table 1 indicates the deviations of the colorimetric
results obtained in the case of Example 1 from the
standard. A distinct shade shift relative to the
standard is evident, i.e., the shade becomes cleaner
and f etter .
Table 1: Color distances in the Cielab color space
(illuminant: D65)
Example dL* da* db* dC* dH* dE*
No.
1 0.2 -0.1 -0.3 0.3 -0.1 0.4
C1 Standard
Example 2 and comparative experiment C2
The preparation of a jet black inventive paint and
production of an inventive multicoat paint system
(Example 2 ) and preparation of a noninventive paint
and production of an noninventive multicoat paint
system (comparative experiment C2)
For Example 2 and comparative experiment C2, first of
all a black paste was prepared. This was done by
introducing 52 parts by weight of the grinding resin
dispersion from preparation Example 1 as an initial
charge. To this dispersion there were added, with
stirring, 13 parts by weight of a commercial dispersant
(Disperbyk~ 184 from Byk Chemie), 10 parts by weight of
a carbon black pigment (Monarch~ 1400), 7.0 parts by
weight of a loo strength diethanolamine solution, and
18 parts by weight of deionized water. The resultant
mixture was predispersed for 30 minutes. It was then
ground in a stirrer mill (grinding media: 1.0 mm;
charge: 750) until an energy input of 0.6 kilowatt
hour/kg was reached.
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For the preparation of the aqueous basecoat materials,
first of all a make-up mixture was prepared.
This was done by introducing 21.4 parts by weight of a
solution of a thixotropic agent based on a synthetic
phyllosilicate (3°s in deionized water) as an initial
charge and subjecting it to pretreatment with a
dissolver at maximum stirrer speed for ten minutes.
Thereafter, 39.0 parts by weight of the grinding resin
dispersion from preparation Example 1 and, after that,
0.6 part by weight of a commercial defoamer based on a
combination of liquid hydrocarbons, hydrophobic silica,
synthetic copolymers, and nonionic emulsifiers were
added. To the results of the mixture there were added
3.0 parts by weight of butyl diglycol, 1.5 parts by
weight of butyl glycol, 5.0 parts by weight of
Shellsol~ T, 5.0 parts by weight of
N-methylpyrrolidone, and 2.5 parts by weight of
ethylhexanol. Then 5.0 parts by weight of a commercial
wetting agent solution based on acetylenediol (12.5 in
butyl diglycol) and 2.5 parts by weight of
polypropylene glycols were added. In order to adjust
the pH to 7.8-8.5, an additional 3.0 parts by weight of
a 10% strength amine solution were added, after which
the desired solids content was set using 11.5 parts by
weight of deionized water, so giving the make-up
mixture.
61.5 parts by weight of the above-described make-up
mixture were introduced as an initial charge. To this
initial charge there were added, with stirring, 20.0
parts by weight of the above-described black paste and
0.1 part by weight of a commercial silicone oil (Tego
Glide~ 450 from Tego Chemie GmbH, 100%). The resultant
mixture was then admixed with 7.3 parts by weight of a
commercial melamine resin (Cymel~ 327, 90%) and with
11.1 parts by weight of deionized water, with stirring.
The resultant mixture was stirred at maximum stirrer
speed for 30 minutes and adjusted to a pH of 7.8 using
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10~ strength dimethylethanolamine solution. The spray
viscosity of the aqueous basecoat material was adjusted
to 28 s in the DIN 4 flow cup using deionized water.
For the preparation of the noninventive aqueous
basecoat material of comparative experiment C2,
Example 1 was repeated but without adding any silicone
oil.
For producing the inventive and the noninventive
multicoat paint system, first of all test panels were
produced. This was done by coating steel panels
(bodywork panels) that had been coated with a customary
and known, cathodically deposited and baked
electrocoat, with a commercial surfacer, after which
the resultant surfacer film was flashed off at 20°C and
a relative humidity of 65~ for 5 minutes and dried in a
forced air oven at 80°C for 5 minutes, and then baked
at 150°C. After that, the surfacer coat had a dry
thickness of from 30 to 35 um.
After the test panels had cooled to 20°C, the inventive
aqueous basecoat material of Example 1 and the
noninventive aqueous basecoat material of comparative
experiment C2 were applied, flashed off at 20°C and a
relative humidity of 65~ for 5 minutes, and dried in a
forced air oven at 80°C for l0 minutes, so that the dry
basecoat films had a dry film thickness of
approximately 15 um.
To the basecoat films of Example 2 and of comparative
experiment C2 there was applied a commercial two-
component clearcoat material, after which the basecoat
films and the clearcoat films of Example 2 and of
comparative experiment C2 were baked at 130°C for
30 minutes. The resultant multicoat paint systems were
measured by colorimetry. The results obtained can be
found in Table 2. They show that the multicoat paint
system of the invention exhibited a deeper black than
~.
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the noninventive paint system.
Table 2: Black measurement according to Lippok/Lohmer
(DIN 55979)
Example Black numbers according to DIN 55979:
No. M~
2 293 289
C2 277 279
