Note: Descriptions are shown in the official language in which they were submitted.
T e A 30 984-US /Ecklklu/S-P 217 0 9 ~ 9
I
DISPERSING AGENTS FOR AQUEOUS COATING COMPOSITIONS
BACKGROUND OF THE INVENTION
5 Field of the Invention
The present invention relates to the use of water-soluble polyisocyanate addition
products based on selected starting materials as (1i~pPrsing agents for the incorpo-
ration of solids into aqueous lacquer or coating compositions.
Description of the Prior Art
10 A high amount of l,lecl~ ical power is are n~ss~ry in order to incorporate solids
into aqueous media. The amount of mecll~nical power depends to a large extent
on the wettability of the solid by the ~ulloullding medium and on its affinity with
this lllediulll. In order to reduce these dispersion forces, it is ~;U~Lolllw ~ to employ
di~ h~g agents which make incorporation easier. These are for the most part
15 surface-active m~t~ri~ which are also termed s~ ct~nt~, having an anion- or
cation-active structure or a nonionic structure. These materials are added in
relatively small amounts either directly to the solid or to the dispersion medium.
The energy required for dispersion is significantly reduced by these sl~rfact~nt~
It is also known that these solids tend to re-agglomerate after ~lisper~ion~ which
20 results in a waste of the dispersion energy previously employed and leads to
serious problems. This phenomenon is explained by London/van der Waals
forces, due to which the solids are mutually attracted. In order to overcome these
forces of attraction, adsorption layers have to be deposited on the solids. This is
effected by the use of surfactants.
25 During and after dispersion, however, an interaction occurs between the sur-
rounding medium and the solid particle, and desorption of the s~rfactant occurs in
exchange for the surrounding medium, which is present at a higher concentration.However, this surrounding medium is in most cases not capable of forming stable
adsorption layers which causes the whole system to break down. This becomes
30 ~1iccernible, for example, by an increase in viscosity in liquid systems, by loss of
gloss and by shifts of hue in lacquers and coatings.
Le A 30 984-US 2 170!1 4g
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Accordingly, there have been many efforts aimed at providing effective dispersing
agents for solids, particularly pigmçl t~, which facilitate in particular the in-
corporation of solids into coating compositions CO..~ g known solvents and
which result in coating compositions which are stable towards sedimentation. Dis-
5 persing agents, which are well suited for this purpose, are described, for exarnple,in EP-A-0,154,678, EP-A-0,205,510 and EP-A-0 335,197.
An object of the present invention is to provide suitable dispersing agents for
solids, particularly pi~m~.ntc, during the incorporation of the latter into aqueous
lacquer and coating compositions. It should be understood that conclusions re-
10 garding aqueous ~ itt;lllS cannot be drawn from observations associated withsolvent-based coating compositions because coating these two types of
compositions are fundal~lelltally di~lellt with regard to the dispersibility of solids,
particularly pigm~nt~
This object has been surprising achieved with the dispersing agents according to15 the invention which are described in detail below.
SUMMARY OF THE INVENTION
The present invention relates to an aqueous composition con~ ing dispersed
solids and, as dispersing agent, a water soluble polyisocyanate addition productco~ ing hydrophilic polyether chains, having a ~ in...i-- isocyanate group
20 content of 1.0% by weight and an ethylene oxide content (molecular weight 44) of
30 to 80% by weight, in which the polyisocyanate addition product is the reaction
product of
A) a polyisocyanate component having an average NCO functionality of at
least 2.5 and an NCO content of S to 50% by weight with
25 B) S to 100 equivalent %, based on the equivalents of isocyanate groups
present in component A), of one or more monohydric polyether alcohols
having a molecular weight of 150 to 5000 and an ethylene oxide content
of 50 to 99.5% by weight,
Le A 30 984-US 2170~9
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C) 0 to 20 equivalent %, based on the equivalents of isocyanate groups
present in component A), of one or more monohydric alcohols having a
molecular weight of 32 to 5000 other than component B),
D) 0 to 50 equivalent %, based on the equivalents of isocyanate groups
present in component A), of an amine component con~i~ting of at least one
tertiary amine having a molecular weight of 88 to 250 which contains an
isocyanate-reactive group and
E) 0 to 20 equivalent %, based on the equivalents of isocyanate groups
present in conlpollent A), of one or more compounds having a molecular
weight of 32 to 3000 and at least two isocyanate-reactive groups,
at an isocyanate index of 100 to 200, to form urethane groups and optionally urea
groups, in which any excess NCO groups have been reduced down to a ~
residual content of 1.0% by weight by secondary reactions taking place simul-
taneously with or subsequently to the reaction of components A) to E).
DESCRIPTION OF TT-TF PRTOR.AT~T
The polyisocyanate addition products, which are essçnti~l to the invention, are
plcpal~,d by reacting polyisocyanates A) with monohydric alcohols B) and
optionally other starting components C), D) and/or E) to form urethane and
optionally urea groups. The addition products are optionally freed from
20 isocyanate groups present after the formation of the urethane and optionally urea
groups by a simultaneous or subsequent secondary reaction.
The addition products have a content of ethylene oxide units (molecular weight
44), incorporated via component B), of 30 to 80% by weight, preferably 40 to
75% by weight. The content of free isocyanate groups is less than 1% by weight
25 and preferably cannot be ~letecte~l
Polyisocyanate component A) has an average NCO functionality of at least 2.5,
preferably at least 3.0, and an NCO content of 5 to 50% by weight, preferably 7
to 30% by weight. Polyisocyanate component A) is selected from organic poly-
isocyanates, such as unmodified polyisocyanates of higher functionality, or
r e A 30 984-US 2170 9 ~ ~
~_ - 4 -
modification products of known polyisocyanates, preferably diisocyanates, which
have the l~uir~d NCO content and functionality.
Exalllples of unmodified polyisocyanates include the higher functional polyiso-
cyanates of the diphenylmethane series, which are produced during the phos-
5 genation of aniline/formaldehyde con(lP~l~les, or other known higher functional
polyiso-;yal~t~s, such as 4,4',4"-triisocyanato-triphenylmethane.
The polyisocyanates of collll,ol~ent A) are preferably modification products or
derivatives of monomeric polyisocyanates, i.e., polyisocyanates cQ!~tr.;..i~ biuret,
~,ll~ne, alloph~nA~ and/or isocy~-ul~t~ groups. Examples of diisocyanates
10 which can be used to prepare these derivatives include hPY~m~thylene diiso-
cyanate, cycloh- ~ne-1,3- and/or -1,4-diisocyanate, 1-isocyanato-3,3,5-l~ilr,~thyl-5-
isocyanatomethyl-cyclohPY~ne, hexahydrotoluene 2,4- and/or 2,6-diisocyanate, per-
hydro- 2,4'- and/or 4,4'~1iph~;n~ lhalle diisocyanate, toluene 2,4- and/or 2,6-diisocyanate, dil)henyllllclhalle 2,4'- and/or 4,4'-diisocyanate and naphthalene15 1,5-diiso~ ~te.
More preferably, coll,ll.ercially available diisocyanates are used for plGl,a,lng the
modified polyisocyanates. Examples include 2,4-diisocyanatotoluene and mi~l~c s
thereof with up to 35% by weight, based on the weight of the Ir, ~ , of 2,6-
diisocyanatotoluene; 4,4'-diisocyanato-diphenylmethane and mixtures thereof
20 with 2,4'- and 2,2'-diisocyanato-diph~ P,th~nP, hPx~methylene diisocyanate
and Illix~ s of these diisocyanates. Most In~ir~lably polyisocyanate component
A) is a modification product cOI~ isocya~ lale groups and pl~,p~ed from
2,4-diisocyanatotoluene or nlixlu~es thereof co..~ g up to 35% by weight, based
on the weight of the Ini~ e, of 2,6-diisocyanatotoluene. These most plefell~,d
polyisocyanates preferably have an NCO content of 7 to 30% by weight and an
NCO functionality of 3 to 6. Polyisocyanate component A) may be used in the
form of a solution in an inert solvent, such as butyl acetate.
Monohydric alcohol coll,ponent B) is selected from monohydric alcohols having a
number average molecular weight (which may be calculated from the content of
hydroxyl groups) of 150 to 5000, preferably 500 to 3000, and cont~ining 50 to
99.5% by weight, preferably 70 to 99.5% by weight, based on the total weight of
monohydric alcohol, of ethylene oxide units incorporated within polyether chains.
E ~ A 30 984-US
217094~
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Examples include the known alkoxylation products of monovalent starter
molecules which contain an average of at least 3, preferably 7 to 100 alkylene
oxide units per molecule, and contain at least 50% by weight, preferably 70 to
100% by weight, of ethylene oxide units.
5 The monohydric alcohols do not have to exclusively contain alkoxylation products
of monovalent starter molecules. The previously described monoalcohols may be
further modified by the addition of, e.g., ~-caprolactone in a ring-opening reaction
with ester forn~tion These modified monohydric alcohols may contain up to
40% by weight of t~-...;nAl ~-caprolactone units (calculated as C6H~0O2; molecular
10 weight 114), based on the weight of the monoalcohols.
Monohydric alcohols, phenols and carboxylic acids may be used as starter
molecules for the pl~p~tion of the monohydric polyether alcohols. The starter
molecules generally contain 1 to 30, preferably 1 to 10 and more preferably 1 to 4
carbon atoms. Ex~llples include alcohols such as methanol, ethanol, n-propanol,
15 n-butanol, l-pentanol, l-hexanol, l-octanol, oleyl alcohol and benzyl alcohol;
phenols such as phenol, cresols, methylphenols, nonylphenols and dode~ ylpllenols;
acids, which can be alkoxylated, such as acetic acid, butyric acid, capric acid,lauric acid, palmitic acid, stearic acids and cyclohexane carboxylic acid. The
pl~,felled starter molecules are monohydric alcohols co~ g 1 to 4 carbon
20 atoms.
Ethylene oxide, or combinations of ethylene oxide with up to 50% by weight,
preferably up to 30% by weight, based on the total amount of alkylene oxides, ofother alkylene oxides (preferably propylene oxide) may be used for the
alkoxylation reaction, which is known. If other alkylene oxides are also used in25 addition to ethylene oxide, they be used in admixture with ethylene oxide to form
random chains or they may be added succes~ively to form blocks.
Component B) may be used in an amount of 5 to 100 equivalent %, preferably 50
to 90 equivalent %, based on the equivalents of isocyanate groups present in
component A).
30 Optional component C) is selected from at least one monohydric alcohol other
than those suitable for use as component B). Examples include monohydric ester
~ ~ A 30 984-US
._ 2170999
alcohols having a molecular weight of 94 to 350, such as methyl hydroxybutyrate,ethylene glycol mo~o~cet~te' 2,2-dimethylhydroxypropionic acid methyl ester and
propyl lactate (~D-hydroxycal)loic acid ethyl ester); and monohydric alcohols
having a molecular weight of 130 to 2000 which have been obtained by the
5 known addition of ~-caprolactone to the previously described monohydric
alcohols.
Mixtures of the ester alcohols prepared from ~-caprolactone and the monohydric
ester alcohols may also be used. Co,l,pone"l C) is used, if it is used at all, in an
amount of up to 20 equivalent %, preferably up to 10 equivalent %, based on the
10 equivalents of isocyanate groups present in component A). Pl~f~l~bly, component
C) is not used.
Optionally col,lpo~ l D) is selecte~l from organic compounds which contain at
least one tertiary amine group and also contain a group which is capable of
,~a,ting with isocyanate groups in an iso~ t~ addition reaction, preferably a
15 hydroxyl or amino group. These compounds preferably have a molecular weight
of 88 to 250, more pler~...bly 88 to 150.
Examples include amino alcohols such as N,N-diethylethanol-amine, N,N-
dhl~c~lylethanolamine, N,N-dimethyliso~lop~lolamine, 2-dibutylamino-ethanol, 3-
(dimethylamino)- 1 -propanol, 1 -methyl-4-piperidinol, 2-morpholinoethanol, 2-
piperidinoethanol, 2-1,i~,~;hlo-ethanol, 3-(diethylamino)-1-propanol, N-methyl-3-
pyrrolidinol and 2-(hydlv~ylll~,lhyl)-N-methylpiperidine. Also suitable are poly-
amines co..~ g at least one tertiary amine group and a primary or secondary
amino group, such as N,N-dimethyl-1,3-pl~alle~i~mine, N,N-diethylethylenedi-
amine N,N-dimethylethylene~iamine, 2-pipel~illo-ethylamine, 3-morpholino-
25 propylamine, N,N-dibutyl-trimethylenerliamine, N,N-diethyl-1,4-blltane~liamine and
N-methyl-pipel~i.le.
Plcfclled compounds for use as component D) include 4-(2-hydroxyethyl)-
pyridine, 2-hydroxyethylmorpholine, N,N-dimethyl-1,3-propane~iiamine~ N,N-
diethyl-1,4-b~lt~n~ tnin~, N,N-dimethylamino- ethanol and N,N-dimethylamino-
30 propylamine.
~e A 30 984-US 21709~9
- 7 --
Component D) is used in an amount of 0 to 50 equivalent %, preferably 10 to 50
. equivalent %, based on the equivalents of isocyanate groups present in component
A). Component D) is preferably used in an amount such that 0 to 200, preferably
2 to 200, and more preferably 5 to 100, milliequivalents of tertiary amino groups
5 solids are present per 100 g of the addition products according to the invention.
Optional component E) is selected from organic compounds having a molecular
weight of 32 to 3000, prefcldbly 118 to 2000, and CO~ g two groups which
are capable of reacting with isocyanate groups, pl~,felal)ly two alcoholic hydroxyl
groups. F~ ..ples include the known polyester or polyether diols, which have therequired molecular weight. C~lllpoll~nl E) is used in the plepa~&lion of the
addition compounds in an amount of up to 20 equivalent %, preferably up to 10
equivalent %, based on the equivalents of isocyanate groups present in colllpo
A). ~lc~,.al)ly, colllpollcnl E) is not used.
Various methods can be employed for the plepa~lion of the addition products
accol.iing to the invention from starting materials A) to E). In general, the
reaction is con~ cte~1 in the melt at tcnl~lalu,es of 20 to 250C, preferably 60 to
140C. In acco~ ce with one embodiment isocyanate component A) is reacted
with a Illi~ of component B) and optionally C), D) and/or E). Alternatively,
an NCO prepolymer may initially be formed from component A) and a portion of
collll,onellls B) to E), and subsequently reacted in a second step with the re-
m~in-l~r of the rç~-t~nt~ CO,.~ g groups capable of reacting with isocyanate
groups.
If, during the reaction, an excess of NCO is used with respect to isocyanate-re-active components B) to E), this excess is generally reduced by means of
secondary reactions down to a maximum residual content of 1.0% by weight,
preferably 0% by weight. These secondary reactions include the formation of
allophanate groups, biuret groups or isocyanulale groups, for example, through
addition or polymerization reactions of the excess NCO groups. Reactions of thistype are often catalyzed by the nitrogen atoms present and can be accomplished
by heating for 0.1 to 24 hours at 60 to 250C.
Although the reaction is preferably carried out in the melt apart from the smallamounts of solvents which are optionally employed in order to dissolve
Le A 30 984-US 21709~9
~_ - 8 -
component A), it is also possible to use inert solvents, e.g., to reduce the viscosity.
Examples of suitable solvents include dimethylformamide, N-methylpyrrolidone,
dimethyl~cet~mide, acetone, 2-butanone, ethyl acetate, butyl acetate, methoxypro-
pyl acetate, toluene and mixtures of solvents of this type. The solvents are
5 generally removed during the reaction or ~ul~se~luent to the reaction, for example,
by rli~till~tion.
Catalysts that accelerate the isocyanate addition reaction may also optionally be
used. These catalysts are known and include triethylamine, N,N-dimethylbenzyl-
amine and tin compounds, such as tin(II) octoate or dibutyltin dilaurate.
10 The polyisocyanate addition products which are essential to the invention
col~lilule dispersing agents for solids, particularly pigments or fillers, in the pro-
duction of co~ ,~nding aqueous lac~uc;~ or coating compositions. The polyiso-
cyanate addition products are employed in an amount of 0.1 to 100% by weight,
p,efe..~bly 0.5 to 40% by weight and more preferably 1 to 15% by weight, based
15 on the weight of the solids to be dispersed. The addition products can either be
pre-mixed with the solids to be dispersed, or dissolved directly in the dispersion
medium (water) before or ~imnlt~neously with the addition of the solids. It is
generally preferable, however, to deposit the polyisocyanate addition compounds
on the solids to be dispersed by intensive mixing before the dispersion process.
20 The dispersing agents according to the invention are suitable for f~ilit~tin~ the
dispersion of any solids, particularly pigme~t~ and fillers.
Examples of pigm~ntc include inorganic or organic pigments, and also carbon
blacks. Examples of inorganic pigments include titanium dioxides, iron oxides
and spinels. Examples of organic pigments include azo pigments, e.g. pigments of25 the monoazo series, 2ceto~cetic acid derivatives, derivatives of 2,3-oxynaphtholic
acid, 2,3-oxynaphtholic acid-ar,vl amide derivatives, pigments of the diazo series,
derivatives of 3,3dichlorobenzidine, diaryl yellow types, condensed diazo pig-
ments, metal complex pi~ment~, anthraquinone pigments, phthalocyanine pig-
ments, and polycyclic pi~m~nt~, particularly those- of the anthraquininone, thio-
30 indigo, quinacridone, dioxazine, pyrrolo-pyrrole, n~phth~lene tetracarboxylic acid,
pterylene, isoamidolin(one), fla~llhlone, p~ lLhlolle or isoviolanthrone series.
Le A 30 9g4-US
21709~9
g
Preferred pi~m~nt~ are ~B- and r-crystal modifications of unsubstituted linear
quinacridone, and mixed crystals of 2,9-dimethyl-quinacridones and unsubstiluledquinacridones.
Most preferably, the dispersing agents according to the invention are suitable for
5 the ~ p~r~ion of carbon black in aqueous coating compositions.
Exarnples of fillers which can be dispersed in aqueous lacquers accoldhlg to theinvention include those based on kaolin, french chalk, other silicates, chalk, glass
fibers, glass beads and metal powders.
Coating coml)o~ilions in which the solids can be fli~per~ed according to the
10 invention include any aqueous one-component or two-component lacquers.
E~l.ples include those based on alkyd, acrylate, epoxy, polyvinyl acetate, poly-ester or pol~ e resins, or aqueous two-col~,pol~nl co..~silions based on (i)polyacrylate or polyester resins co..'S~i..;n~ llydlo~yl groups and (ii~ eresins or optionally blocked polyisoc~la,.d~e resins as crosslinking agents. Aqueous
15 coating compositions based on polyepoxide resins are also suitable.
In addition, the polyisocyanate addition products according to the invention mayalso be used as wetting or dispersing agents during the inco~G.d1ion of solids,
particularly pi~m~nt~, in plastics forrnulations.
The following examples serve to further illustrate the present invention.
IeA30984-US
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EX~MPLES
The ffillowing starting materials were used in ple~dldlion examples 1 to 5 detailed
below:
Component A)
5 A 51% by weight solution in n-butyl acetate of a trimer prepared from 2,4-diiso-
- c~ldtot~luene and co~ g isocy~ululate groups; the NCO content of the
solution was 8% by weight (Desmodur IL, m~mlf~r,tllred by Bayer AG).
Component B)
A monohydric polyether alcohol having an average molecular weight of 2250 and
10 an ethylene oxide content of 87.5% by weight, which is prel)al-ed by the
alkoxylation of n-butanol using a Illixlule of ethylene oxide with a small amount
of propylene oxide.
Con~ponen~ D)
N,N-dh"~lylethanolamine.
15 FY~n~?les 1 to 5 - Plep~alion of polyisocyanate addition products to be
used accol.ihlg to the invention)
The amount of component B) set forth in Table 1 was placed in a three-necked
flask fitted with an internal thermometer, a mechanical stirrer and a ~ till~tion
offtake and dehydrated for 2 hours at 120C under a plCS~ of 10 mbar. The
20 amount of polyisocyanate co~ onelll A) set forth in Table I was added at 70C.
The tellll,c-~ e was then hlc.~,ased to 100C, and the mixlllle was stirred for a
further 2 hours at this telll~ dlu~. During this period all of the volatile sub-stances were removed via the ~ till~tion offtake under a ples~ule of 10 mbar.
The amount of amine component D) set forth in Table 1 was then added, and the
25 mixture was stirred for a further hour. A solvent-free, water soluble addition
product was obtained, which could be used for the dispersion of pigments and forthe dispersion and surface treatment of fillers. Due to the secondary reactions
Le A 30 984-US 21709~9
~ 11 -
which were promoted by the heat treatment in the presence of tertiary nitrogen
atoms, the final NCO content in all cases was less than 1.0% by weight.
Table I
Example Component A)~) Component Col~lponelll D)2) Isocyanate content of content of inert
B)2) index 3) utnhtys14e)ne oxide amino groups5)
0.143 0.093 0.05 100 72 19.65
2 0.157 0.093 0.05 105 71 19.49
3 0.1573 0.093 0.05 110 71 19.34
4 0.1716 0.093 0.05 120 70 19.04
0.2145 0.093 0.05 150 67 18.19
I) moles of NCO
2) data in moles
3) isocyanate index = (number of NCO groups) (number of groups capable of reacting with isocyanate groups)xlOO
4) % by weight '~
5) milliequivalents per 100 g of the addition products according to the invention
T e A 30 984-US
2170~49
'`~ - 13 -
Example 6 to 10 Coating compositions accordil1g to the invention
Preparation of ~ ti ~ ~nt solutions
5 The water soluble addition products from Table 1 were dissolved in the amount of
water set forth in Table 2 by heating to 65 to 70C. Clear solutions were obtained
having a solids content of 40% by weight, which could be used as wetting agents
for the production of aqueous coating compositions.
Preparation of pi~nent pastes
15.0 g of black pigment (Farbru~ FW 200, a co~ . ;ial product m~nllf~r,hlred by
Degussa), 0.2 g of anti-foaming agent (Nopco 8034E, a eo~ rcial product
m~nl-f~chlred by Munzig Chemie), 0.7 g of propylene glycol, 28.6 g of wetting
agent (see Table 2) and 150 g of glass beads ( li~mçt~.r = 3 mm) were placed in a
round glass bottle and were ~ pçrse~l by ~h~l~ing in a commercially available
dispersing unit for 90 lui~ le.s The glass beads were subsequently filtered off.
Lacquer pr~pqraffon, application and assesslaç~
5.0 g of pigment paste, 0.3 g of antioxidant (Ascinin R concenl~dt~, a commercial
product m~mlf~ch~red by Bayer AG), 45.0 g of an aqueous alkyd resin (Resydrol
AY 586W, a commercial product m~nuf~r,tllred by Hoechst AG) and 0.3 g of a
drier (Octa Soligen Co 7 aqua, a commercial product m~nuf~ctllred by Borchers
GmbH) were homogeniæd with 20 g of glass beads in a 100 ml round glass bottle
is a dispersing unit for 30 ,,.i~ es After a ~ lion period of about 12 hours, a
100 llm wet film was applied to a degreased glass plate. After storage for 1 dayat room tell~ ;, the haæ gloss and the Gardner gloss (20 angle) were
measured according to DIN 67530, ISO 2813, ASTM D 523.
T e A 30 984-US
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Table 2
Example Addition Water Solids 20 gloss Haze
product fromin ml gloss
Example
6 1 380 40% 80.9 11.4
7 2 380 40% 80.5 12.9
8 3 380 40% 80.9 10.0
9 4 395 40% 81.7 9.9
410 40% 81.6 11.5
11 C~ ol-* - 40% 80.9 30.7
* - wetting and .1;~,, i;,~g agent co~ il.;..g solvent, according to
EP-A-0 154 678 (U.S. Patents 4,647,647 and 4,762,752)
Although the invention has been described in detail in the folegoillg for the~ -
purpose of illustration, it is to be understood that such detail is solely for that
purpose and that variations can be made therein by those skilled in the art without
departing from the spirit and scope of the invention except as it may be limited by
15 the claims.
