Note: Descriptions are shown in the official language in which they were submitted.
CA 02394029 2002-06-10
1
AQUEOUS PRIMARY DISPERSIONS AND COATING MATTERS, A METHOD
FOR PRODUCING SAME AND THE USE THEREOF
The present invention relates to novel aqueous primary
dispersions and coating materials which comprise
dispersed and/or emulsified, solid and/or liquid
polymer particles and/or dispersed solid core-shell
particles having a diameter <_ 500 nm. The present
invention further relates to a novel process for
preparing the novel aqueous primary dispersions and
coating materials by means of controlled free-radical
microemulsion and miniemulsion polymerization. The
present invention relates, furthermore, to the use of
the novel aqueous primary dispersions and coating
materials for producing single-coat or multicoat
clearcoat systems and single-coat or multicoat color
and/or effect paint systems in automotive OEM finishing
and refinishing, industrial coating, including
container coating, coil coating and the coating of
electrical components, and furniture coating.
Microemulsions and miniemulsions are dispersions
comprising water, an oil phase and one or more surface-
active substances and having droplet sizes of from 5 to
50 nm (microemulsions) or from 50 to 500 nm.
Microemulsions are regarded as being thermodynamically
stable, whereas the miniemulsions are regarded as being
metastable (cf. Emulsion Polymerization and Emulsion
.. ' CA 02394029 2002-06-10
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Polymers, Editors: P.A. Lovell and Mohamed S. E1-
Aasser, John Wiley and Sons, Chichester, New York,
Weinheim, 1997, pages 700 et seq.; Mohamed S. E1-
Aasser, Advances in Emulsion Polymerization and Latex
Technology, 30th Annual Short Course, Volume 3, June 7-
11, 1999, Emulsion Polymers Institute, Lehigh
University, Bethlehem, Pennsylvania, USA). Both types
of dispersions find broad application in the art: for
example, in cleaning products, cosmetics or bodycare
products. They may, however, also be used for
polymerization reactions in place of the customary
macroemulsions, in which droplet sizes >1000 nm are
present.
The preparation of aqueous primary dispersions by means
of free-radical miniemulsion polymerization is known,
for example, from the international patent application
WO 98/02466 or from German patents DE-A-196 28 143 and
DE-A-196 28 142. In the case of these known processes,
the monomers may be copolymerized in the presence of
different low molecular mass, oligomeric or polymeric
hydrophobic substances, which are also referred to as
costabilizers. Furthermore, hydrophobic, organic
auxiliaries of low solubility in water, such as
plasticizers, enhancers of the tackiness of the
resulting film, film-forming auxiliaries or other,
unspecified organic additives, may be incorporated into
the monomer droplets of the miniemulsion. The use of
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the known aqueous primary dispersions for preparing
coating materials is not evident from the patents.
Aqueous coating materials based on aqueous primary
dispersions which comprise solid core-shell particles
and have been prepared by miniemulsion polymerization
of monomers in the presence of hydrophobic polymers are
known from the patents EP-A-0 401 565, WO 97/49739 or
EP-A-0 755 946. Although the known coating materials
already have numerous advantageous properties, problems
associated with inadequate distribution of the
crosslinking agents in the aqueous dispersions continue
to arise. One particular consequence of this is the
need to use a larger amount of crosslinking agents than
would be necessary theoretically. Unreacted cross-
linking agents may then, in certain circumstances,
impair the performance properties of the coatings
produced from the coating materials.
The microencapsulation of hydrophobic organic solvents
or of target materials such as biocides and herbicides
in water-insoluble core-shell particles, prepared by
miniemulsion polymerization, is known from the patents
EP-A-0 203 724 or US-A-4,&77,003. However, the
(co)polymerization is not conducted in the presence of
hydrophobic crosslinking agents for the (co)polymers
formed from the monomers.
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, - 4 -
Patents EP-A-0 622 389 or DE-A-43 14 297 disclose the
(co)polymerization of monomers in the presence of
blocked polyisocyanates and epoxy resins. The technique
used, however, is not that of miniemulsion
polymerization. A comparable process is evident from
patents EP-A-0 758 347 or WO 95/29944. The
corresponding known (co)polymers and their primary
dispersions are used to prepare coating materials. The
known coating materials likewise possess the problems
associated with inadequately fine distribution of the
crosslinking agents in the coating materials.
It is an object of the present invention to find new
aqueous primary dispersions and coating materials
comprising dispersed and/or emulsified, solid and/or
liquid polymer particles and/or dispersed solid core-
shell particles having a diameter <_ 500 nm which no
longer have the disadvantages of the prior art but
instead can be prepared in a simple manner.
Furthermore, the new aqueous primary dispersions and
coating materials ought to comprise very finely divided
crosslinking agents.
A further object of the present invention was to find a
new process for preparing aqueous primary dispersions
and coating materials by free-radical microemulsion or
miniemulsion polymerization which no longer has the
disadvantages of the prior art.
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Accordingly, we have found the novel aqueous primary
dispersions and coating materials comprising dispersed
and/or emulsified, solid and/or liquid polymer
particles and/or dispersed solid core-shell particles
having a diameter <_ 500 nm, preparable by free-radical
microemulsion or miniemulsion polymerization of at
least one olefinically unsaturated monomer (A) in the
presence of at least one hydrophobic crosslinking agent
for the (co)polymer resulting from the monomer or
monomers (A) , which are referred to below for short as
"primary dispersions of the invention" and,
respectively, "coating materials of the invention".
We have also found the novel process for preparing
aqueous primary dispersions and coating materials
comprising dispersed and/or emulsified, solid and/or
liquid polymer particles and/or dispersed solid core-
shell particles having a diameter < 500 nm which
comprises subjecting at least one olefinically
unsaturated monomer (A) to free-radical (co)polymer
ization in a microemulsion or miniemulsion in the
presence of at least one hydrophobic crosslinking agent
for the (co)polymer resulting from the monomer or
monomers (A), said process being referred to for short
below as "process of the invention".
Further subjects of the invention will emerge from the
following description.
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In the light of the prior art it was surprising and
unforeseeable for the skilled worker that the object on
which the present invention was based could be achieved
through the primary dispersions of the invention and
the coating materials of the invention and also through
the process of the invention. In particular it was
surprising that the (co)polymers present in the primary
dispersions of the invention have properties which make
them highly suitable for use in coating materials. It
was also surprising that the primary dispersions of the
invention can be used directly as coating materials,
requiring even less crosslinking agent than
conventional coating materials. Not least was it
surprising that the process of the invention yields, as
intended, the primary dispersions and coating materials
of the invention in a particularly simple manner
without the occurrence of the above-described problems
known from the prior art.
For the purposes of the present invention, the property
of being hydrophilic is understood as the
constitutional property of a molecule or functional
group to penetrate into the aqueous phase or to remain
therein. Accordingly, for the purposes of the present
invention, the property of being hydrophobic is
understood as the constitutional property of a molecule
or functional group to exhibit exophilic behavior with
respect to water; i.e., they display the tendency not
to penetrate into water, or to depart the aqueous
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phase. For further details refer to Rompp Lexikon Lacke
and Druckfarben, Georg Thieme Verlag, Stuttgart, New
York, 1998, "Hydrophilicity", "Hydrophobicity", pages
294 and 295.
In accordance with the invention, the primary
dispersions and coating materials comprise dispersed
and/or emulsified solid and/or liquid polymer particles
and/or dispersed solid core-shell particles. The size
of the polymer particles or of the dispersed core-shell
particles is a direct result of the process of the
invention described below. In this case the average
particle diameter is less than 500 nm. It is preferably
from 10 to 500 nm, more preferably from 50 to 400 nm,
and with very particular preference from 100 to 350 nm.
The primary dispersions and coating materials of the
invention have an advantageously high solids content
of, for example, more than 20~ by weight, preferably
more than 30~ by weight . It is , even possible to obtain
solids contents of more than 40~ by weight. The primary
dispersions and coating materials of the invention have
a low viscosity even at high solids content.
The core-shell particles for use in accordance with the
invention result from the graft copolymerization of
organic solids and the monomers (A) for use in
accordance with the invention, described below. Said
organic solids are preferably hydrophobic polymers, as
described, for example, in the patents EP-A-0 401 565,
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page 3, lines 5 to page 4, line 50, W0. 97/49739, page
4, lines 19 to page 5, line 3, or EP-A-0 755 946, page
3, line 26 to page 5, line 38. These hydrophobic
polymers may also be prepared by the process of the
invention.
The primary dispersions and coating materials of the
invention may also have a bimodal particle size
distribution in which from 0.1 to 80~ by weight, in
particular from 1.0 to 50~ by weight, of the
(co) polymer resulting from the monomer or monomers (A)
have a particle size, determined using an analytical
ultracentrifuge, of from 20 to 500 nm, in particular
from 50 to 300 nm, and from 20 to 99.9 by weight, in
particular from 50 to 99~ by weight, of the (co)polymer
have a particle size of from 200 to 1500 nm, in
particular from 300 to 900 nm, said particle sizes
differing by at least 50 nm, in particular by at least
100 nm, with very particular preference by at least
200 nm. Concerning the measurement method, reference
is made for further details to lines 5 to 9 of page 6
of German patent application DE-A-196 28 142.
The first starting compound essential to the invention
for the primary dispersions or coating materials of the
invention, and for the process of the invention, is at
least one olefinically unsaturated monomer (A).
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._ g ._
In this context it is preferred to use at least one
monomer (A) comprising reactive functional groups which
are able to enter into crosslinking reactions with the
complementary reactive functional groups of the
crosslinking agents. Examples of suitable complementary
reactive functional groups for use in accordance with
the invention are collated in the overview below. In
the overview, the variable R is an acyclic or cyclic
aliphatic radical, an aromatic radical and/or an
aromatic-aliphatic (araliphatic) radical; the variables
R' and R" are identical or different aliphatic radicals
or are linked to one another to form an aliphatic or
heteroaliphatic ring.
Overview: Examples of complementary functional groups
Monomer (A) and crosslinking agent (C)
or
Crosslinking agent (C) and monomer (A)
-SH -C(O)-OH
-NH2 -C (0) -O-C (O) -
-OH -NCO
-O- (CO) -NH- (CO) -NHZ -NH-C (O) -OR
-0- (CO) -NH2 -CH2-OH
~
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>NH -CHZ -O-CH3
-NH-C (O) -CH (-C (O) OR) 2
-NH-C (O) -CH (-C (O) OR) (-C (O) -R)
-NH-C (O) -NR' R"
15 -C (O) -OH
=Si (OR) 2
-CH-CHI
-CH-CHI
The selection of the respective complementary groups is
guided on the one hand by the consideration that,
during the storage of primary dispersions or coating
materials of the invention, these groups do not enter
into any unwanted reactions and/or, if appropriate, do
not inhibit or disrupt curing with actinic radiation,
and on the other hand by the temperature range within
which crosslinking is to take place.
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In the case of the coating materials of the invention,
it is preferred to use crosslinking temperatures of
from 100 to 180°C. For this reason it is preferred to
use monomers (A) containing thio, hydroxyl,
alkoxymethylamino, imino, carbamate, allophanate and/or
carboxyl groups, but in particular amino,
alkoxymethylamino or hydroxyl groups, especially
hydroxyl groups, on the one hand, and crosslinking
agents containing anhydride, carboxyl, epoxy, blocked
isocyanate, urethane, methylol, methylol ether,
siloxane, amino, hydroxyl and/or beta-hydroxyalkylamide
groups, but especially blocked isocyanate, urethane or
methylol ether groups, on the other.
Examples of suitable monomers (A) are
al) substantially acid-group-free (meth)acrylic esters
such as (meth)acrylic alkyl or cycloalkyl esters
having up to 20 carbon atoms in the alkyl radical,
especially methyl, ethyl, propyl, n-butyl, sec-
butyl, tert-butyl, hexyl, ethylhexyl, stearyl and
lauryl acrylate or methacrylate; cycloaliphatic
(meth)acrylic esters, especially cyclohexyl,
isobornyl, dicyclopentadienyl, octahydro-4,7-
methano-1H-indenemethanol acrylate or tert-
butylcyclohexyl (meth)acrylate; (meth)acrylic
oxaalkyl esters or oxacycloalkyl esters such as
ethyltriglycol (meth)acrylate and methoxy-
oligoglycol (meth)acrylate having a molecular
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weight Mn of preferably 550, or other ethoxylated
and/or propoxylated hydroxyl-free (meth)acrylic
acid derivatives. These may contain minor amounts
of (meth)acrylic alkyl or cycloalkyl esters of
higher functionality, such as the
di(meth)acrylates of ethylene glycol, propylene
glycol, diethylene glycol, dipropylene glycol,
butylene glycol, 1,5-pentanediol, 1,6-hexanediol,
octahydro-4,7-methano-1H-indenedimethanol or 1,2-,
1,3- or 1,4-cyclohexanediol; trimethylolpropane
di- or tri(meth)acrylate; or pentaerythritol di-,
tri- or tetra(meth)acrylate. For the purposes of
the present invention, minor amounts of monomers
of higher functionality in this case are to be
understood as amounts which do not lead to
crosslinking or gelling of the copolymers (A)
unless the specific intention is to prepare
crosslinked polymeric microparticles.
a2) Monomers which carry per molecule at least one
hydroxyl, thio, amino, alkoxymethylamino,
carbamate, allophanate or imino group, in
particular a hydroxyl, amino or alkoxymethylamino
group, and are substantially free from acid
groups, such as hydroxyalkyl esters of acrylic
acid, methacrylic acid or another alpha,beta-
olefinically unsaturated carboxylic acid, which
derive from an alkylene glycol esterified with the
acid, or which are obtainable by reacting the
~
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alpha, beta-olefinically unsaturated carboxylic
acid with an alkylene oxide, especially
hydroxyalkyl esters of acrylic acid, methacrylic
acid, ethacrylic acid, crotonic acid, malefic acid,
fumaric acid or itaconic acid in which the
hydroxyalkyl group contains up to 20 carbon atoms,
such as 2=hydroxyethyl, 2-hydroxypropyl,
3-hydroxypropyl, 3-hydroxybutyl, 4-hydroxybutyl
acrylate, methacrylate, ethacrylate, crotonate,
maleate, fumarate or itaconate; or hydroxycyclo-
alkyl esters such as 1,4-bis(hydroxymethyl)-
cyclohexane, octahydro-4,7-methano-1H-indene-
dimethanol or methylpropanediol monoacrylate,
monomethacrylate, monoethacrylate, monocrotonate,
monomaleate, monofurriarate or monoitaconate; or
reaction products of cyclic esters, such as
epsilon-caprolactone, for example, and these
hydroxyalkyl or hydroxycycloalkyl esters; or
olefinically unsaturated alcohols such as allyl
alcohol or polyols such as trimethylolpropane
monoallyl or diallyl ether or pentaerythritol
monoallyl, diallyl or triallyl ether (as far as
these monomers (a2) of higher functionality are
concerned, the comments made above relating to the
monomers (al) of higher functionality apply
analogously); N,N-dimethylaminoethyl acrylate,
N,N-diethylaminoethyl methacrylate, allylamine or
N-methyliminoethyl acrylate or N,N-
di(methoxymethyl)aminoethyl acrylate and
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methacrylate or N,N-di(butoxymethyl)aminopropyl
acrylate and methacrylate;
a3) monomers which carry per molecule at least one
acid group which can be converted into the
corresponding acid anion group, such as acrylic
acid, methacrylic acid, ethacrylic acid, crotonic
acid, malefic acid, fumaric acid or itaconic acid;
olefinically unsaturated sulfonic or phosphonic
acids or their partial esters; or
mono(meth)acryloyloxyethyl maleate, succinate or
phthalate. For the purposes of the present
invention the monomers (a3) are not used as the
sole monomers (A) but are always used in
conjunction with other monomers (A) and, moreover,
in amounts so small that the monomers (a3) do not
polymerize outside the droplets of the
miniemulsion.
a4) Vinyl esters of alpha-branched monocarboxylic
acids having 5 to 18 carbon atoms in the molecule.
The branched monocarboxylic acids can be obtained
by reacting formic acid or carbon monoxide and
water with olefins in the presence of a liquid,
strongly acidic catalyst; the olefins may be
cracking products of paraffinic hydrocarbons, such
as mineral oil fractions, and may comprise both
branched and straight-chain acyclic and/or
cycloaliphatic olefins. The reaction of such
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olefins with formic acid or, respectively, with
carbon monoxide and water produces a mixture of
carboxylic acids in which the carboxyl groups are
located predominantly on a quaternary carbon atom,
Examples of other olefinic starting materials are
propylene trimer, propylene tetramer and
diisobutylene. Alternatively, the vinyl esters
(a4) may be prepared in a conventional manner from
the acids, by reacting, for example, the acid with
acetylene. Particular preference, owing to their
ready availability, is given to using vinyl esters
of saturated aliphatic monocarboxylic acids having
9 to 11 carbon atoms that are branched on the
alpha carbon atom, especially Versatic~ acids.
a5) Reaction products of acrylic acid and/or
methacrylic acid with the glycidyl ester of an
alpha-branched monocarboxylic acid having 5 to 18
carbon atoms per molecule, in particular a
Versatic~ acid, or, instead of the reaction
product, an equivalent amount of acrylic and/or
methacrylic acid which is then reacted during or
after the polymerization reaction with the
glycidyl ester of an alpha-branched monocarboxylic
acid having 5 to 18 carbon atoms per molecule,
especially a Versatic~ acid.
a6) Cyclic and/or acyclic olefins such as ethylene,
propylene, 1-butene, 1-pentene, 1-hexene, cyclo-
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hexene, cyclopentene, norbornene, butadiene,
isoprene, cyclopentadiene and/or dicyclo-
pentadiene.
a7) (Meth)acrylamides such as (meth)acrylamide,
N-methyl-, N,N-dimethyl-, N-ethyl-, N,N-diethyl-,
N-propyl-, N,N-dipropyl-, N-butyl-, N,N-dibutyl-,
N-cyclohexyl-, N,N-cyclohexylmethyl-~ and/or
N-methylol-, N,N-dimethylol-, N-methoxymethyl-,
N,N-di(methoxymethyl)-, N-ethoxymethyl- and/or
N,N-di(ethoxyethyl)-(meth)acrylamide;
a8) monomers containing epoxide groups, such as the
glycidyl ester of acrylic acid, methacrylic acid,
ethacrylic acid, crotonic acid, malefic acid,
fumaric acid and/or itaconic acid.
a9) Vinylaromatic hydrocarbons such as styrene, alpha-
alkylstyrenes, especially alpha-methylstyrene,
and/or vinyltoluene; vinylbenzoic acid (all
isomers), N,N-diethylaminostyrene (all isomers),
alpha-methylvinylbenzoic acid (all isomers), N,N-
diethylamino-alpha-methylstyrene (all isomers)
and/or p-vinylbenzenesulfonic acid.
a10) nitrites such as acrylonitrile and/or methacrylo-
nitrite.
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all) Vinyl compounds, especially vinyl halides and/or
vinylidene dihalides such as vinyl chloride, vinyl
fluoride, vinylidene dichloride or vinylidene
difluoride; N-vinylamides such as vinyl-N-
methylformamide, N-vinylcaprolactam, 1-vinyl-
imidazole or N-vinylpyrrolidone; vinyl ethers such
as ethyl vinyl ether, n-propyl vinyl ether,
isopropyl vinyl ether, n-butyl vinyl ether,
isobutyl vinyl ether and/or vinyl cyclohexyl
ether; and/or vinyl esters such as vinyl acetate,
vinyl propionate, vinyl butyrate, vinyl pivalate
and/or the vinyl ester of 2-methyl-2-
ethylheptanoic acid.
a12) Allyl compounds, especially allyl ethers and allyl
esters such as allyl methyl, ethyl, propyl or
butyl ether or allyl acetate, propionate or
butyrate.
a13) Polysiloxane macromonomers having a number-average
molecular weight Mn o~ from 1000 to 40,000 and
having on average from 0.5 to 2.5 ethylenically
unsaturated double bonds per molecule; especially
polysiloxane macromonomers having a number-average
molecular weight Mn of from 2000 to 20,000, with
particular preference from 2500 to 10, 000 and, in
particular, from 3000 to 7000 and having on
average from 0.5 to 2.5, preferably from 0.5 to
1.5, ethylenically unsaturated double bonds per
~
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molecule, as are described in DE-A-38 07 571 on
pages 5 to 7, in DE-A-37 06 095 in columns 3 to 7,
in EP-B-0 358 153 on pages 3 to 6, in US-A-
4, 754, 014 in columns 5 to 9, in DE-A-44 21 823 or
in the international patent application WO
92/22615 on page 12, line 18 to page 18, line 10.
and/or
a14) Acryloyloxysilane-containing vinyl monomers,
preparable by reacting hydroxy-functional silanes
with epichlorohydrin and then reacting the
reaction product with (meth)acrylic acid and/or
hydroxyalkyl and/or hydroxycycloalkyl esters of
(meth)acrylic acid (cf. monomers a2).
Further examples of suitable monomers (A) are disclosed
in German patent application DE-A-196 28 142, page 2,
line 50 to page 3, line 7.
Each of the abovementioned monomers (A), with the
exception of the monomer (a3), can be polymerized alone
to give polymers. In accordance with the invention,
however, it is advantageous to use at least two
monomers (A), since by this means it is possible to
vary the profile of properties of the resulting
copolymers very widely, in a particularly advantageous
manner, and to tailor said profile of properties to the
particular intended use of the primary dispersions of
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the invention or of the coating materials of the
invention.
Preferably, the monomers (A) are selected so as to give
(meth)acrylate (co)polymers whose profile of properties
is determined primarily by the (meth)acrylates
described above. In that case it is preferred as
comonomers (A) to use vinylaromatic hydrocarbons (a9),
especially styrene.
The monomers (A) to be used in accordance with the
invention are reacted with one another to form
(co)polymers in the presence of at least one water-
soluble and/or oil-soluble initiator which forms free
radicals. Examples of initiators which can be used are:
dialkyl peroxides, such as di-tert-butyl peroxide or
dicumyl peroxide; hydroperoxides, such as cumene
hydroperoxide or tert-butyl hydroperoxide; per esters,
such as tert-butyl perbenzoate, tert-butyl perpivalate,
tert-butyl per-3,5,5-trimethylhexanoate or tert-butyl
per-2-ethylhexanoate; peroxodicarbonates; potassium,
sodium or ammonium peroxodisulfate; azo initiators,
examples being azodinitriles such as azobisisobutyro-
nitrile; C-C-cleaving initiators such as benzpinacol
silyl ethers; or a combination of a nonoxidizing
initiator with hydrogen peroxide. Combinations of the
initiators described above may also be used.
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Further examples of suitable initiators are described
in German patent application DE-A-196 28 142, page 3,
line 49 to page 4, line 6.
It is preferred to add comparatively large amounts of
free-radical initiator, the proportion of the initiator
in the reaction mixture being, based in each case on
the overall amount of the monomers (A) and of the
initiator, with particular preference from 0.2 to 20~
by weight, with very particular preference from 0.5 to
15~ by weight, and in particular from 1.0 to 10~s by
weight.
In accordance with the invention, the monomers (A) are
copolyme-rized in the presence of at least one
hydrophobic crosslinking agent. The hydrophobic
crosslinking agents preferably contain the above-
described reactive functional groups which enter into
crosslinking reactions with the complementary reactive
functional groups present in the resulting
(co) polymers .
Examples of particularly suitable crosslinking agents
are blocked polyisocyanates, tris(alkoxycarbonyl
amino)triazines or fully etherified amino resins.
Examples of suitable blocking agents for preparing the
blocked polyisocyanates are the blocking agents known
from the patent US-A-4,444,954:
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i) phenols such as phenol, cresol, xylenol,
nitrophenol, chlorophenol, ethylphenol, t-butyl-
phenol, hydroxybenzoic acid, esters of these
acids, or 2,5-di-tert-butyl-4-hydroxytoluene;
ii) lactams, such as E-caprolactam, 8-valerolactam,
y-butyrolactam or (3-propiolactam;
iii) active methylenic compounds, such as diethyl
malonate, dimethyl malonate, ethyl or methyl
acetoacetate, or acetylacetone;
iv) alcohols such as methanol, ethanol, n-propanol,
isopropanol, n-butanoJ., isobutanol, t-butanol,
n-amyl alcohol, t-amyl alcohol, lauryl alcohol,
ethylene glycol monomethyl ether, ethylene glycol
monoethyl ether, ethylene glycol monobutyl ether,
diethylene glycol monomethyl ether, diethylene
glycol monoethyl ether, propylene glycol
monomethyl ether, methoxymethanol, glycolic acid,
glycolic esters, lactic acid, lactic esters,
methylolurea, methylolmelamine, diacetone alcohol,
ethylenechlorohydrin, ethylenebromohydrin, 1,3
dichloro-2-propanol, 1,4-cyclohexyldimethanol or
acetocyanohydrin;
v) mercaptans such as butyl mercaptan, hexyl
mercaptan, t-butyl mercaptan, t-dodecylmercaptan,
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2-mercaptobenzothiazole, thiophenol, methylthio-
phenol or ethylthiophenol;
vi) acid amides such as acetoanilide, acetoanisidine
amide, acrylamide, methacrylamide, acetamide,
stearamide or benzamide;
..
vii) imides such as succinimide, phthalimide or
maleimide;
viii)amines such as diphenylamine, phenylnaphthylamine,
xylidine, N-phenylxylidine, carbazole, aniline,
naphthylamine, butylamine, dibutylamine or
butylphenylamine;
ix) imidazoles such as imidazole or 2-ethylimidazole;
x) ureas such as urea, thiourea, ethyleneurea,
ethylenethiourea or 1,3-diphenylurea;
xi) carbamates such as phenyl N-phenylcarbamate or
2-oxazolidone;
xii) imines such as ethyleneimine;
xiii)oximes such as acetone oxime, formaldoxime,
acetaldoxime, acetoxime, methyl ethyl ketoxime,
diisobutyl ketoxime, diacetyl monoxime, benzo-
phenone oxime or chlorohexanone oximes;
~~
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xiv) salts of sulfurous acid such as sodium bisulfate
or potassium bisulfate;
xv) hydroxamic esters such as benzyl methacrylo
hydroxamate (BMH) or allyl methacrylohydroxamate;
or
xvi) substituted pyrazoles, especially dimethyl-
pyrazole, or triazoles; and also
to
xvii)mixtures of these blocking agents, especially
dimethylpyrazole and triazoles, malonic esters and
acetoacetic esters or dimethylpyrazole and
succinimide.
Examples of suitable organic polyisocyanates for
blocking are in particular the so-called paint
polyisocyanates having isocyanate groups attached to
aliphatic, cycloaliphatic, araliphatic and/or aromatic
structures. Preference is given to polyisocyanates
having from 2 to 5 isocyanate groups per molecule and
having viscosities of from 100 to 10,000, preferably
from 100 to 5000.
Further examples of suitable polyisocyanates for
blocking are described in "Methoden der organischen
Chemie", Houben-Weyl, Volume 14/2, 4th edition, Georg
Thieme Verlag, Stuttgart 1963, pages 61 to 70, and by
W. Siefken, Liebigs Annalen der Chemie, Volume 562,
CA 02394029 2002-06-10
- 24 -
pages 75 to 136. Suitable examples are the polyurethane
prepolymers which contain isocyanate groups, can be
prepared by reacting polyols with an excess of
polyisocyanates and are preferably of low viscosity.
Further examples of suitable polyisocyanates for
blocking are polyisocyanates containing isocyanurate,
biuret, allophanate, iminooxadiazinedione, urethane,
urea and/or uretdione groups. Polyisocyanates
containing urethane groups, for example, are obtained
by reacting some of the isocyanate groups with polyols,
such as trimethylolpropane and glycerol, for example.
Preference is given to the use of aliphatic or
cycloaliphatic polyisocyanates, especially hexa-
methylene diisocyanate, dimerized and trimerized
hexamethylene diisocyanate, isophorone diisocyanate,
dicyclohexylmethane 2,4'-diisocyanate, dicyclohexyl-
methane 4,4'-diisocyanate, diisocyanates derived from
dimeric fatty acids, as marketed under the commercial
designation DDI 1410 by Henkel and described in patents
DO 97/49745 and WO 97/49747, especially 2-heptyl-3,4-
bis(9-isocyanatononyl)-1-pentylcyclohexane; or 1,2-,
1,4- or 1,3-bis(isocyanatomethyl)cyclohexane, 1,2-,
1,4- or 1,3-bis(2-isocyanatoeth-1-yl)cyclohexane, 1,3-
bis(3-isocyanatoprop-1-yl)cyclohexane or 1,2-, 1,4- or
1,3-bis(4-isocyanatobut-1-yl)cyclohexane, 1,8-diiso-
cyanato-4-isocyanatomethyloctane, 1,7-diisocyanato-4-
isocyanatomethylheptane or 1-isocyanato-2-(3-iso-
' CA 02394029 2002-06-10
- 25 -
cyanatopropyl)cyclohexane, or mixtures of these
polyisocyanates.
Very particular preference is given to the use of
mixtures of polyisocyanates containing uretdione and/or
isocyanurate groups and/or allophanate groups, which
are based on hexamethylene diisocyanate, as formed by
catalytic oligomerization of hexamethylene diisocyanate
using appropriate catalysts.
Examples of particularly suitable amino resins are
melamine resins, guanamine resins or urea resins. In
this context it is possible to use any amino resin that
is suitable for clearcoats, or a mixture of such amino
resins. For further details reference is made to Rompp
Lexikon Lacke and Druckfarben, Georg Thieme Verlag,
1998, page 29, "Amino resins", and the textbook
"Lackadditive" by Johan Bieleman, Wiley-VCH, Weinheim,
New York, 1998, pages 242 ff . , or to the book "Paints,
Coatings and Solvents", second completely revised
edition, editors: D. Stoye and W. Freitag, Wiley-VCH,
Weinheim, New York, 1998, pages 80 ff. Also suitable
are the customary and known amino resins some of whose
methylol and/or methoxymethyl groups have been
defunctionalized by means of carbamate or allophanate
groups. Crosslinking agents of this kind are described
in the patents US-A-4 710 542 and EP-B-0 245 700 and
also in the article by B. Singh and coworkers
"Carbamylmethylated Melamines, Novel Crosslinkers for
~
CA 02394029 2002-06-10
' - 26 -
the Coatings Industry" in Advanced Organic Coatings
Science and Technology Series, 1991, Volume 13, pages
193 to 207.
The particularly suitable tris(alkoxycarbonylamino)-
triazines had the following formula:
H
N N I
R 0 C J / ~C OR
II N ~N
0 .
N
H ~ ~'C OR
0
Examples of particularly suitable tris(alkoxy
carbonylamino)triazines are described in the patents
US-A-4,939,213, US-A-5,084,541 or EP-A-0 624 577. Use
is made in particular of the tris(methoxy-, tris
(butoxy- and/or tris(2-ethylhexoxycarbonylamino)
triazines (R = methyl, butyl or ethylhexyl).
The methyl butyl mixed esters, the butyl 2-ethylhexyl
mixed esters and the butyl esters are of advantage.
They have the advantage over the simple methyl ester of
better solubility in polymer melts and also have less
of a tendency to crystallize out.
CA 02394029 2002-06-10
- 27
Of the crosslinking agents described above, the blocked
polyisocyanates offer particular advantages and are
therefore used with very particular preference in
accordance with the invention.
In the process of the invention, the ratio of the
monomers (A) comprising complementary reactive
functional groups to the crosslinking agents may vary
very widely. In accordance with the invention it is of
advantage if the molar ratio of complementary reactive
functional groups in (A) to complementary reactive
functional groups in the crosslinking agents is from
5.0 . 1.0 to 1.0 . 5.0, preferably from 4.0 . 1.0 to
1.0 . 4.0, with particular preference from 3.0 . 1.0 to
1.0 . 3.0, and in particular from 2.0 . 1 to 1 . 2Ø
Particular advantages result if the molar ratio is
approximately or precisely 1.0 . 1Ø
The monomers (A) for use in accordance with the
invention are preferably copolymerized in the presence
of emulsifiers and/or protective colloids. Examples of
suitable emulsifiers and/or protective colloids, and
the amounts in which they are advantageously used, are
disclosed in German patent application DE-A-196 28 142,
page 3, lines 8 to 48.
In addition to the hydrophobic crosslinking agents
described above for use in accordance with the
invention, the (co)polymerization of the monomers (A)
~
CA 02394029 2002-06-10
- 2$ -
to be used in accordance with the invention may also be
accompanied by hydrophobic compounds which differ
materially from the crosslinking agents. These
hydrophobic compounds are also referred to by those in
the art as costabilizers.
The hydrophobic compounds comprise water-insoluble low
molecular mass, oligomeric or polymeric substances.
Examples of suitable hydrophobic compounds are esters
of alpha, beta-monoolefinically unsaturated carboxylic
acids, having 3 to 6 carbon atoms, with alcohols having
12 to 30 carbon atoms in the alkyl radical; esters of
vinyl alcohol and/or allyl alcohol with alkanemono-
carboxylic, -sulfonic and/or -phosphonic acids having
12 to 30 carbon atoms in the molecule; amides of
alpha, beta-monoolefinically unsaturated carboxylic
acids having 3 to 6 carbon atoms with alkylamines
having 12 to 30 carbon atoms in the alkyl radical;
macromonomers based on olefinically unsaturated
compounds having on average at least one olefinically
unsaturated group, in particular at least one terminal
olefinically unsaturated group, in the molecule;
polysiloxane macromonomers having on average at least
one olefinically unsaturated group, in particular at
least one terminal olefinical'ly unsaturated group, in
the molecule; oligomeric and/or polymeric products of
addition polymerization, polycondensation and/or
polyaddition; water.-insoluble molecular weight
regulators, especially mercaptans; aliphatic,
CA 02394029 2002-06-10
- 29 -
cycloaliphatic and/or aromatic halogenated and/or
nonhalogenated hydrocarbons; alkanols and/or
alkylamines having at least 12 carbon atoms in the
alkyl radical; organosilanes and/or organosiloxanes;
vegetable, animal, semisynthetic and/or synthetic oils;
hydrophobic dyes. Further examples of suitable
hydrophobic compounds, or costabilizers, and the
amounts in which they are advantageously used, are
disclosed in German patent application DE-A-196 28 142,
page 4, lines 37 to 59.
In terms of molecular weight and the molecular weight
distribution, the (co)polymers formed from the monomers
(A) are not subject to ar_y restrictions whatsoever.
Advantageously, however, the (co)polymerization is
conducted so as to result in a molecular weight
distribution Mw/Mn, measured by gel permeation
chromatography using polystyrene as standard, of 5 12,
with particular preference <_ 10, and in particular <_ 7.
Suitable reactors for the (co)polymerization processes
are the customary and known stirred tanks, stirred tank
cascades, tube reactors, loop reactors or Taylor
reactors, as described, for example, in the patents DE-
B-1 071 241 or EP-A-0 498 583 or in the article by K.
Kataoka in Chemical Engineering Science, Volume 50, No.
9, 1995, pages 1409 to 1416. The free-radical
(co)polymerization is preferably conducted in stirred
tanks or Taylor reactors, the Taylor reactors being
~
CA 02394029 2002-06-10
- 30 -
configured such that the conditions of Taylor flow are
met over the entire length of the reactor, even if the
kinematic viscosity of the reaction medium alters
greatly - in particular, increases - as a result of the
(co)polymerization.
In accordance with the invention, the
(co)polymerization is conducted in an aqueous medium.
The aqueous medium comprises essentially water. In
addition to the above-detailed crosslinking agents,
emulsifiers and/or protective colloids and/or
hydrophobic compounds, the aqueous medium may also
comprise customary and known additives and/or other
dissolved, solid, liquid or gaseous, organic and/or
inorganic, low and/or high molecular mass substances,
provided the latter do not adversely affect or even
inhibit the (co)polymerization. For the purposes of the
present invention, the term "minor amount" means an
amount which does not destroy the aqueous character of
the aqueous medium.
Alternatively, the aqueous medium may also comprise
straight water.
The (co)polymerization is advantageously conducted at
temperatures above room temperature, preference being
given to the choice of a temperature range of from 30
' CA 02394029 2002-06-10
- 31 -
to 95°C, with very particular preference from 5U to
90°C.
When using particularly volatile monomers (A) the
(co)polymerization may also be conducted under
pressure, preferably under from 1.5 to 3000 bar, with
particular preference from 5 to 1500 and, in
particular, from 10 to 1000 bar. In specific cases,
temperatures higher than 95°C may be used here. Use may
be made in this context of the regimes described in
German patent application DE-A-196 28 142, page 4,
lines 6 to 36.
In accordance with the invention, the (co)polymer-
ization is conducted in a microemulsion or
miniemulsion, in particular a miniemulsion. In this
case the average particle diameter of the emulsified
monomer droplets is below 500 nm. It is preferably from
10 to 500 nm, more preferably from 50 to 400 nm, and
with very particular preference from 100 to 300 nm.
Said particle diameter is the so-called z-average
particle diameter, which is determined by means of
photon correlation spectroscopy in accordance with the
principle of dynamic, quasielastic light scattering.
For this purpose use may be made, for example, of a
Coulter N4 Plus Particle Analyzer from Coulter
Scientific Instruments or a PCS Malvern Zetasizer 1000.
The measurement is normally made on an aqueous
emulsion containing 0.01% by weight of the emulsified
CA 02394029 2002-06-10
- 32 -
monomer droplets. The aqueous emulsion further
comprises, in the aqueous phase, the corresponding
monomers in dissolved form (up to saturation), so that
the emulsified monomer droplets do not break up.
The process of the invention may be performed so as to
give the bimodal particle size distribution described
above. Methods of producing bimodal particle size
distributions are customary and known in the
technological field in question here. It is preferred
to use the seed method described in German patent
application DE-A-196 28 142, page 5, lines 31 to 49.
The preparation of the miniemulsion as part of the
process of the invention has no particular features as
regards method, but instead takes place in accordance
with the customary and known methods of dispersing or
emulsifying in a high shear field. Examples of suitable
methods are described in the patents DE-A-196 28 142,
page 5, lines 1 to 30, DE-A-196 28 143, page 7, lines
to 58, or EP-A-0 401 565, lines 27 to 51.
An essential advantage of the primary dispersions of
the invention is that they can be used per se as
25 coating materials of the invention, preferably
surfacers, solid-color topcoat, aqueous basecoat and
clearcoat materials, in particular as clearcoat
materials. For these end uses, at least one
conventional and known additive in effective amounts
' CA 02394029 2002-06-10
- 33 -
may be added to the primary dispersions of the
invention before, during and/or after their
preparation. Before or during the preparation of the
primary dispersions of the invention, the only
additives added are those which do not disrupt, or even
totally inhibit, the miniemulsion polymerization. The
general technical knowledge of the skilled worker
allows him or her to identify such additives.
Preferably, said additives are added after the
preparation of the primary dispersions of the
invention.
Examples of suitable additives are pigments, as
described in Rompp Lexikon Lacke and Druckfarben, Georg
Thieme Verlag, 1998, pages 176, "Effect pigments";
pages 380 and 381 "Metal oxide-mica pigments" to "Metal
pigments"; pages 180 and 181, "Iron blue pigments" to
"Black iron oxide"; pages 451 to 453, "Pigments" to
"Pigment volume concentration"; page 563, "Thioindigo
pigments"; and page 567, "Titanium dioxide pigments".
Pigments are used when the coating materials of the
invention are used as surfacers, solid-color topcoat or
aqueous basecoat materials, but in particular as
aqueous basecoat materials in the context of the so-
called wet-on-wet technique (cf., for example, European
patent 0 089 497), to produce multicoat color and/or
effect paint systems.
~
CA 02394029 2002-06-10
_ 3g _
Further examples of suitable additives which can be
used both in the pigmented coating materials and in the
unpigmented coating materials are additional binders
such as oligomeric and polymeric, thermally curable,
linear and/or branched poly(meth)acrylates or acrylate
copolymers of block, comb and/or random structure,
especially those described in the patent DE-A-197 36
535, polyesters, especially those described in the
patents DE-A-40 09 858 or DE-A-44 37 535, alkyds,
acrylated polyesters, polylactones, polycarbonates,
polyethers, epoxy resin-amine adducts, (meth)acrylate
diols, partially hydrolyzed polyvinyl esters, poly-
urethanes and acrylated polyurethanes, as described in
the 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.
Further examples of suitable additives are customary
and known coating additives such as organic and
inorganic fillers, thermally curable reactive diluents,
low-boiling and/or high-boiling organic solvents ("long
solvents"), UV absorbers, light stabilizers, free-
radical scavengers, thermally 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
CA 02394029 2002-06-10
- 35 -
the textbook "Lackadditive" by Johan Bieleman, Wiley-
VCH, Weinheim, New York, 1998.
If the coating materials of the invention are to be
curable with actinic radiation as well (dual cure),
they comprise additives curable with actinic radiation.
Said actinic radiation may comprise electromagnetic
radiation such as near infrared (NIR), visible light,
W light or X-rays, or corpuscular radiation such as
electron beams. Examples of suitable additives curable
with actinic radiation are known from German patent
DE-C-197 09 467.
In terms of method, the application of the coating
materials of the invention has no special features, but
instead can be carried out by all customary application
methods, such as spraying, knife coating, brushing,
flow coating, dipping, trickle coating or roller
coating, for example. It is preferred to use spray
application methods, such as for example compressed air
spraying, airless spraying, high-speed rotation,
electrostatic spray application (ESTA), alone or in
conjunction with hot spray application such as hot air
spraying, for example.
Suitable substrates are all surfaces to be coated which
are not damaged by curing of the coatings present on
them with application of heat; examples include metals,
plastics, wood, ceramic, stone, textile, fiber
" CA 02394029 2002-06-10
- 36 -
composites, leather, glass, glass fibers, glasswool and
rockwool, mineral-bound and resin-bound building
materials, such as plasterboard and cement slabs or
roof shingles, and also assemblies of these materials.
Accordingly, the coating material of the invention is
also suitable for applications outside of automotive
..
finishing, especially for the coating of furniture and
for industrial coating, including coil coating,
container coating and the impregnation or coating of
electrical components. In the context of industrial
coatings, it is suitable for coating virtually- all
parts for private or industrial use, such as radiators,
domestic appliances, small metal parts such as nuts and
bolts, hub caps, wheel rims, packaging, or electrical
components such as motor windings or transformer
windings.
In the case of electrically conductive substrates it is
possible to use primers produced in a customary and
known manner from electrodeposition (ED) coating
materials. Suitable for this purpose are both anodic
(AED) and cathodic (CED) electrodeposition coating
materials, but especially CED. Unfunctionalized and/or
apolar plastic surfaces can be subjected to
conventional pretreatment before coating, such as with
a plasma or by flaming, or may be provided with an
aqueous primer.
CA 02394029 2002-06-10
The method of curing the applied coating materials of
the invention also has no special features, but instead
takes place in accordance with the customary and known
thermal methods such as heating in a forced air oven or
irradiation with IR lamps, which in the case of dual
cure may be supplemented by exposure to actinic
radiation. In this context it is possible to use
radiation sources such as high-pressure or low-pressure
mercury vapor lamps, which may be doped with lead in
order to open up a radiation window up to 405 nm; or
electron beam sources.
The resultant coatings of the invention, especially the
single-coat or multicoat color and/or effect paint
systems and clearcoats of the invention, are easy to
produce and have outstanding optical properties and
very high chemical resistance and weathering stability.
Accordingly, the substrates of the invention,
comprising at least one coating of the invention, are
of particularly high service value and have a
particularly long service life, which makes them
particularly attractive, economically and technically,
for producers and users.
Example 1
The preparation of a primary dispersion of the
invention and of a coating material of the invention by
the process of the invention
~
CA 02394029 2002-06-10
' - 38 -
For the implementation of example 1 an emulsifier was
first dissolved in water. Thereafter, the olefinically
unsaturated monomers (A), the blocked polyisocyanate,
and an oil-soluble initiator were mixed with one
another. The resulting organic solution and the
solution of the emulsifier were converted into a milky
emulsion over the course of 40 seconds using an
Ultraturrax, at room temperature. The resultant
preemulsion was stable for several minutes, i.e., did
not exhibit phase separation and could therefore be
processed further without problems to give the fine
miniemulsion, using a high-pressure homogenizer. To
prepare the miniemulsion the preemulsion was introduced
into the supply vessel of a pressure release
homogenizer and an emulsification was carried out in
circulation mode for 10 minutes under maximum pressure,
with cooling. Following emulsification, the
miniemulsion had particle sizes in the range from
100 nm to 500 nm and contained 40% by weight of monomer
mixture and polyisocyanate (in 100% form), based on the
total amount of the respective miniemulsion, and was
stable on storage for several weeks.
Table 1 gives an overview of the starting materials
used for the miniemulsions. of the amounts in which
they were used, and of the z-average particle diameter
of the monomer droplets, which was determined by means
of photon correlation spectroscopy in accordance with
CA 02394029 2002-06-10
_ 30 _
the principle of dynamic, qudsielastic light
scattering, using a PCS Malvern Zetasizer 1000.
The miniemulsion was transferred to a suitable steel
reactor and heated slowly to 80°C with stirring. At
this temperature the miniemulsion was stirred until the
solids content of the resultant primary dispersion of
the invention showed no further increase. The primary
dispersion of the invention was stable to sedimentation
over several weeks.
Table 1 gives an overview of the polymerization time,
the theoretical glass transition temperature Tg,
calculated by the method of Fox, of the (co)polymer
present in the primary dispersion of the invention, its
hydroxyl number, its molecular weight, and the
polydispersity of its molecular weight distribution,
and also the z-average particle diameter (measured
using a PCS Malvern Zetasizer 1000), the solids
content, and the pH of the primary dispersion of the
invention.
The primary dispersion of the invention was knife
coated onto glass plates, in a wet film thickness of
150 ~.m, and baked for 30 minutes at 145°C, 160°C and
180°C. The results set out in Table 1 for the methyl
ethyl ketone test demonstrate that the resultant
coating of the invention had a particularly high
solvent stability.
CA 02394029 2002-06-10
- 40 -
Table l: Material composition and properties of the
miniemulsion of the invention, polymerization
conditions, material composition and
properties of the primary dispersion of the
invention, and solvent stability of the
coating of the invention
Example 1
Miniemulsion:
Compositon (parts by weight):
Emulsifiera~ ~ 0.521
Methyl methacrylate 16.95
n-Butyl methacrylate 13.69
Styrene 16.29
Hydroxypropyl methacrylate 18.25
Blocked polyisocyanateb~ 34.29
OH NCO ratio 1:l
Particle diameter (nm) 146
Polymerization:
Initiator~ (parts by weight
per 100 parts by weight of
emulsifier, monomer mixture
and blocked polyisocyanate) 3.26
Polymerization time (h) 6.0
Primary dispersion:
Solids contentd~ (% by wt.) 39
Particle diameter (nm) 157
PH 6.0
Sediment, wet (g) 0
CA 02394029 2002-06-10
- 41 -
Copolymer:
Number-average molecular
weight Mne~ (daltons) 102.700
Mass-average molecular
weight
Mwe~ (daltons) ' 557.400
Polydispersity Mw/Mn 5.43
Glass transition
' temperature (theoretical,
acc. to Fox) (C) 74.55
Hydroxyl number (mg KOH/g) 109
Clearcoat:
MEK DSf~ (145/160/180C) 5/43/>200
a) Sodium lauryl sulfate, Texapon~ from Henkel;
b) dimethylpyrazole-blocked commercial polyiso-
cyanate;
c) tert-butyl peroxyethylhexanoate;
d) 130°C, one hour;
e) measured by gel permeation chromatography with
polystyrene as internal standard;
f) number of double strokes with a cotton pad soaked
with methyl ethyl ketone;
