Note: Descriptions are shown in the official language in which they were submitted.
1~3829~
A~UEOUS COMPOSITIONS FOR USE IN THE
PRODUCTION OF CROSSLINKED POLYURETHANES
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to a.queously
dispersed, heat-curable coating compositions containing
water dispersible blocked polyisocyanates, water
dispersible hydroxyl-terminated prepolymers and epoxy
resins, and to coatings prepared from these
co~positions.
Description of the Prior Art
Mixtures of blocked polyisocyanates and
coreactants such as polyhydroxyl compounds are known in
the art. For example, U.S. Patent 4,098,933 is directed
to the preparation of water dispersible blocked polyiso-
cyanates and to their use as crosslinking agents for
other water dispersible coreactants such as polyhydrox.yl
compounds. U.S. Patent 4,284,544 is directed to
compositions containing water dispersible blocked poly-
isocyanates and polyhydroxyl coreactants which are not
dispersible in water. Finally, U.S. Patent, 4,608,413
is directed to mixtures of water dispersible blocked
polyisocyanate prepolymers and water dispersible
polyhydroxyl prepolymers.
Tt has not been possible to prepare coatings
from the above-described aqueous compositions which have
good solvent resistance and high hardness values, and
yet maintain good impact strength, flexibility and
hydrolytic stability. To a.chieve good solvent
resistance and high hardness values, it is necessary for
the coatings to have a high crosslink density; however,
to achieve the necessary crosslink density, the impact
strength and flexibility generally decrease. In order
to provide water dispersible blockéd polyisoc`yanate
prepolymers and water dispersible hydroxyl-terminated
Mo-3018 ~
1338294
-
prepolymers suitable for preparing coatings with high
crosslink densities, it is necessary to incorporate
relatively large amounts of internal emulsifiers which
results in coatings with reduced hydrolytic stability.
Accordingly, it is an object of the present
invention to provide storage stable aqueous compositions
which can be used to prepare coatings having excellent
solvent resistance and high hardness as well as good
impact strength, flexibility and hydrolytic stability.
This object may be achieved according to the present
invention which is described hereinafter.
SUMMARY OF THE INVENTION
The present invention is directed to an
~queously dispersed, heat-curable coating composition
comprising
a) a water dispersible, blocked polyisocyanate
containing chemicallv ~ncorporated anionic
hydrophilic groups, at least a portion of which
are neutralized with volatile organic compounds,
b) a water dispersible, hydroxyl-terminated
polyurethane prepolymer containing chemically
incorporated anionic hydrophilic groups, at
least a portion of which are neutralized with
volatile organic compounds and
c) an epoxy resin which remains stably dispersed in
said coating composition.
The present invention is also directed to
coatings prepared from the above coating composition.
DETAILED DESCRIPTION OF THE INVENTION
The water dispersible, blocked polyisocyanates
used in conjunction with the water dispersible
polyhydroxyl resins and the epoxy resins in the
compositions of the present invention preferably contain
an average of about 1.1 to 8, preferably about 2 to 6
and most preferably about 2.5 to 4 blocked isocyanate
groups per molecule and may be prepared from virtually
Mo-3018 - 2 -
zny organic polyisocyanate, lpr3e~e8rably from monomeric
diisocyanates or polyisocyanates containing 2 to 4
isocyanate groups. Especially preferred are
polyisocyanates having aliphatically- and/or
cycloaliphatically-bound isocyanate groups, although
polyisocyanates having aromatically-bound isocyanate
groups are not excluded and may be used.
The polyisocyanates used for preparing the
water dispersible blocked polyisocyanates may be
monomeric in nature or adducts prepared from organic
diisocyanates and containing carbodiimide, uretdione,
biuret, allophanate, urea or urethane groups or
isocyanurate rings. Suitable polyisocyanates which may
be used as such or as intermediates for preparing
polyisocyar.ate adducts include ethvlene diis~cyanate,
1,4-tetramethylene diisocyanate, 1,6-hexamethylene
diisocyanate, 2,4,4-trimethyl-1,6-hexamethylene
diisocyanate, 1,12-dodecane diisocyanate, cyclo-
butane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-
diisocyanate and mixtures of these isomers,l-isocyanato-2-isGcyanatomethyl cyclopentane,
l-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclo-
hexane, 2,4- and 2,6-hexahydrotoluylene diisocyanate and
mixtures of these isomers, 2,4'- and/or
4,4'-dicyclohexylmethane diisocyanate,~ ,~',a ,~'-
tetramethyl-1,3- and/or -1,4-xylylene diisocyanate, 1,3-
and l,4-xylylene diisocyanate, l-isocyanato-l-methyl-
4(3)-isocyanatomethyl-cyclohexane, 1,3- and
1,4-phenylene diisocyanate, 2,4- and 2,6-toluylene
diisocyanate and mixtures of these isomers, diphenyl
methane-2,4'- and/or -4,4'-diisocyanate, naphth-
alene-1,5-diisocyarate, triphenyl methane-4,
4',4"-triisocyanate, polyphenyl polymethylene
polyisocyanates of the type obtained by condensing
aniline with formaldehyde followed by phosgenation, and
mixtures of the above-mentioned polyisocyanates.
Mo-3018 - 3 -
1338294
Polyisocyanate adducts containing biuret groups
may be prepared from the previously mentioned
diisocyanates according to the processes disclosed in
U.S. Patents 3,124,605; 3,358,010; 3,644,490; 3,862,973;
3,903,126; 3,903,127; 4,051,165; 4,147,714; or 4,220,749
by using coreactants such as water, tertiary alcohols,
primary and secondary monoamines, and primary and/or
secondary diamines. The preferred diisocyanate to be
used in these processes is l,6-hexamethylene
diisocyanate.
Polyisocyanate adducts containing allophanate
groups may be prepared by reacting the previously
mentioned diisocyanates according to the process
disclosed in U.S. Patents 3,769,318 and 4,160,080,
British Patent 994,89C and German Offenlegungsschrift
2,040,645.
Polyisocyanate adducts containing isocyanurate
groups may be prepared by trimerizing the previously
mentioned diisocyanates in accordance with the processes
disclosed in U.S. Patents 3,487,080; 3,919,218;
4,Q40,9g2; 4,288,586; and 4,324,879; German Auslege-
schrift 1,150,080; German Offenlegungsschrift 2,325,826;
and British Patent 1,465,812. The preferred diiso-
cyanates to be used are 2,4-toiuylene diisocyanate
and/or 2,6-toluylene diisocyanate, 1,6-hexamethylene
diisocyanate, isophorone diisocyanate and any mixtures
of these diisocyanates.
Polyisocyanate adducts containing urea or
preferably urethane groups and based on the reaction
product of the previously mentioned diisocyanates and
compounds having a molecular weight of less than 400 and
containing 2 or more isocyanate-reactive groups may be
prepared according to the process disclosed in U.S.
Patent 3,183,112. W~len preparing polyisocyanate adducts
using a large excess of diisocyanate, the average
isocyanate functionality is determined from the
Mo-3018 - 4 -
1338294
functionality of the compounds containing isocyanate-
reactive hydrogens. For example, when an excess of a
diisocyanate is reacted with a diol, a polyisocyanate
with a functionality of 2 will be produced, while a triol
coreactant will result in a polyisocyanate functionality
of 3. By using mixtures of compounds containing
isocyanate-reactive hydrogens, various functionalities
can be obtained. The preferred isocyanate-reactive
hydrogens are provided by hydroxyl groups, although amino
groups are not excluded. Suitable compounds containing
isocyanate-reactive hydrogens are disclosed in U.S.
Patent 3,183,112 and include ethylene glycol, 1,2- and
1,3-propylene glycol, 1,3- and 1,4-butanediol,
1,6-hexanediol, 1,8-octanediol, neopentyl glycol,
diethylene glycol, 2-methyl-1,3-propylene glycol,
2,2-dimethyl-1,3-propylene glycol, the various isomeric
bis-hydroxy-methyl cyclohexanes, 2,2,4-trimethyl-1,3-
pentanediol, glycerine, trimethylol propane, ethylene
diamine, diethylene triamine, triethylene tetraamine,
1,6-hexanediamine, piperazine, 2,5-dimethyl piperazine,
l-amino-3-aminomethyl-3,5,5-trimethylcyclohexane,
bis(4-aminocyclohexyl)methane, bis(4-amino-3-
methylcyclohexyl)methane, 1,4-cyclohexanediamine,
1,2-propanediamine, hydrazine, aminoacid hydrazides,
hydrazides of semicarbazido carboxylic acids,
bis-hydrazides and bis-semicarbazides. 1,3- and
1,4-butanediol, 2,2,4-trimethyl-1,3-pentanediol,
trimethylol propane and mixtures thereof are particularly
preferred. Preferred diisocyanates are 2,4-toluylene
diisocyanate and/or 2,6-toluylene diisocyanate,
1,6-hexamethylene diisocyanate, isophorone diisocyanate
and mixtures of these diisocyanates.
It is also possible to use any of the previously
described polyisocyanate adducts for the
Mk-3018 -5-
- 133829~
urther preparation of polyisocyanate adducts containing
urethane or urea groups. Finally, it is possible to
prepare the polyisocyanate adducts containing urea or
urethane groups from the high molecular weight
isocyanate-reactive compounds, preferably polyols, known
from polyurethane chemistry and having molecular weights
of 400 to about 6,000, preferably 400 to about 3,000.
Examples of the high molecular weight compounds include
1) polyhydroxyl polyesters which are obtained from
polyhydric, preferably dihydric alcohols to which
trihydric alcohols may be added and polybasic,
preferably dibasic carboxylic acids. Instead of
these polycarboxylic acids, the corresponding
carboxylic acid anhydrides or polycarboxylic acid
esters of lower alcohols or mixtures thereof may be
used for preparing the polyesters. The poly-
carboxylic acids may be aliphatic, cyclo-
cycloaliphatic, aromatic and/or heterocyclic and
they may be unsaturated and/or substituted, e.g. by
halogen atoms. Examples of these acids include
succinic acid, adipic acid, suberic acid, azelaic
acid, sebacic acid, phthalic acid, isophthalic acid,
trimellitic acid, phthalic acid anhydride,
tetrahydropthalic acid anhydride, hexahydrophthalic
acid anhydride, tetrachlorophthalic acid anhydride,
endomethylene tetrahydrophthalic acid anhydride,
glutaric acid anhydride, maleic acid, maleic acid
anhydride, fumaric acid, dimeric and trimeric fatty
acids such as oleic acid, which may be mixed with
monomeric fatty acids, dimethyl terephthalate and
bis-glycol terephthalate. Suitable polyhydric
alcohols include the polyhydric &lcohols previously
set forth for preparing the polyisocyanate adducts
containing urea or urethane groups.
2) Polylactones generally known from polyurethane
chemistry, e.g., polymers of caprolactone initiated
with the above-mentioned polyhydric alcohols.
Mo-3018 - 6 -
1~3829~
3) Polycarbonates containing hydroxyl groups such as
the products obtained from reaction of the
polyhydric alcohols previously set forth for
preparing the polyisocyanate adducts containing urea
or urethane groups, preferably dihydric alcohols
such as 1,3-propanediol, 1,4-butanediol,
1,4-dimethylol cyclohexane, 1,6-hexanediol,
diethylene glycol, triethylene glycol or
tetraethylene glycol wi.th phosgene, diaryl
carbonates such as diphenyl carbonate or cyclic
carbonates such as ethylene or propylene carbonate.
Also suitable are polyester carbonates obtained from
the reaction of lower molecular weight oligomers of
the above-mentioned polyesters or polylactones with
phosgene, diaryl carbonates or cyclic carbonates.
4) Polyethers include the polymers obtained by the
reaction of starting compounds which contain
reactive hydrogen atoms with alkylene oxides such as
propylene oxide, butylene oxide, styrene oxide,
tetrahydrofuran, epichlorohydrin or mixtures of
the~e alkylene oxides. Certain proportions of
ethylene oxide may also be included, provided the
polyether does not contain more than about 10% by
weight o~ ethylene cxide; however, polyethers which
do not contain ethyl.ene oxide are generally used.
Suitable starting compounds containing at least one
reactive hydrogen atom include the polyols set forth
as suitable for preparing the polyisocyanate adducts
containing urethane or urea groups and, in addition,
water, methanol, ethanol, 1,2,6-hexanetriol,
1,2,4-butanetriol, trimethylol ethane,
pentaerythritol, mannitol, sorbitol, methyl
glycoside, sucrose, phenol, isononyl phenol,
resorcinol, hydroquinone and 1,1,1- or 1,1,2-tris-
(hydroxylphenyl)ethane. Polyethers which have been
obtained by the reaction of starting compounds
Mo-3018 - 7 -
- 133829~
containing amino groups can also be used, but are
less preferred for use in the present invention.
Suitable amine starting compounds include those set
forth as suitable for preparing the polyisocyanate
adducts containing urethane or urea groups and also
ammonia, methylamine, tetramethylenediamine,
ethanolamine, diethanolamine, triethanolamine,
aniline, phenylenediamine, ~,4- and 2,6-toluylene-
diamine, polyphenylene polymethylene polyamines of
the kind obtained by the aniline/formaldehyde
condensation reaction and mixtures thereof.
Resinous mate ials such as phenol and cresol resins
may also be usèd as the starting materials. The
preferred starting compounds for the polyethers are
those compounds which exclusively contain hydroxyl
groups, while compounds containing tertiary amine
groups are less preferred and compounds containing
isocyanate-reactive NH groups are much less
preferred.
Polyethers modified by vinyl polymers are also
suitable for the process according to the invention.
Products of this kind may be obtained by
polymerizing, e.g., styrene and acrylonitrile in the
presence of polyethers (U.S. Patent Nos. 3,383,351;
3,304,~3; 3,523,095; and 3,110,695; and German
Patent No. 1,152,536). Also suitable as polyethers
are amino polyethers wherein at least a portion of
the hydroxyl groups of the previously described
polyethers are converted to amino groups.
~) Polythioethers such as the condensation products
obtained from thiodiglycol on its own and/or with
other glycols, dicarboxylic acids, formaldehyde,
amino carboxylic acids or amino alcohols. The
products are either polythio mixed ethers, polythio
ether esters, or polythioether ester amides,
depending on the co-components.
Mo-3018 - 8 -
- 1~38294
6) Polyacetals including those obtained from the above
mentioned polyhydric alcohols, especially diethylene
glycol, triethylene glycol, 4,4'-dioxyethoxy-di-
phenyldimethylene, 1,6-hexanediol and formaldehyde.
Polyacetals suitable for use in the invention may
also be prepared by the polymerization o cyclic
acetals.
7) Polyether esters containing isocyanate-reactive
groups and known in the art.
10 8) Polyester amides and polyamides including the
predominantly linear condensates obtained from
polyvalent saturated and unsaturated carboxylic
acids or their anhydrides and polyvalent saturated
and unsaturated amino alcohols, diamines,
polyamines, or mixtures thereof.
The preferred high molecular weight isocyanate-
reacti~e compounds .or use in the process according to
the invention are the dihydroxy polyesters, dihydroxy
polylactones, dihydroxy polycarbonates and dihydroxy
20 polyester carbonates.
The blocking agents which are suitable for
preparing the blocked polyisocyanates are compounds with
preferably one isocyanate-reactive group which enter
into an addition reaction with an isocyanate group at
temperatures above about 50C, preferably at
temperatures in the range of about 60C to 100C, and
wherein the resulting addition product liberates the
blocking agent at temperatures in the range of about
100C to 250C. Suitable blocking agents of this type
include secondary or tertiary alcohols such as
isopropanol or tert-butanol; C-H-acidic compounds such
as malonic acid dialkyl esters, acetylacetone or
acetoacetic acid alkyl esters; oximes such as formal-
doxime, acetaldoxime, methyl ethyl ketoxime, cyclo-
35 hexanone oxime, acetophenone oxime, benzophenone oximeor diethyl glyoxime; lactams such as~ -caprolactam or
Mo-3018 - 9 -
1~38~9~
~-valerolactam; phenols such as phenol, cresol or nonyl
phenol; N-alkyl amides such as N-methyl acetamide; imides
such as phthalimide; imidazoles such as benzimidazole;
triazoles such as benzotriazole and tolyltriazole; or
5 alkali metal bisulphites.
In order to make the polyisocyanates water
dispersible, it is necessary to chemically incorporate
hydrophilic groups, i.e., anionic groups, potential
anionic groups or optionally nonionic hydrophilic
10 groups, into the polyisocyanate component. Suitable
hydrophilic components contain at least one isocyanate
reactive group and at least one hydrophilic group or
potential hydrophilic group. Examples include aliphatic
hydroxy carboxylic acids, aliphatic or aromatic amino-
15 carboxylic acids with primary or secondary amino groups,aliphatic hydroxy sulfonic acids and aliphatic or
aromatic aminosulfonic acids with primary or secondary
amino groups. These acids preferably have molecular
weights below 400. It should be emphasized that the
20 carboxylic acid groups are not considered to be
isocyanate-reactive groups due to their sluggish
reactivity with isocyanates.
It is also possible to incorporate lateral
and/or terminal nonionic hydrophilic groups as a portion
25 of the hydrophilic groups. However, the nonionic
hydrophilic groups are less preferred than the anionic
groups. Suitable nonionic groups are disclosed in U.S.
Patent 4,408,008.
The preferred anionic groups for incorporation
30 into the blocked polyisocyanates in the present invention
are carboxylate groups and these groups may be introduced
by using hydroxy-carboxylic acids of the general formula:
(H)xQ(cH)y
wherein
Mo-3018 -10-
~,
.~ .,.~;~
13382!~
Q represents a straight or branched, hydrocarbon
radical containing 1 to 12 carbon atoms, and
x and y represent values from 1 to 3.
Examples of these hydroxy-carboxylic acids include citric
acid and tartaric acid.
The preferred acids are those of the above-
mentioned formula wherein x = 2 and y = 1. These
dihydroxy alkanoic acids are described in U.S. Patent
3,412,054. The preferred group of dihydroxy alkanoic
acids are the a ,a -dimethylol alkanoic acids represented
by the structural formula:
CH2H
Q'-C-COOH
CH2H
wherein Q' is hydrogen or an alkyl group containing 1 to
8 carbon atoms. The most preferred compound is a, a
-dimethylol propionic acid, i.e, wherein Q' is methyl
in the above formula.
In order to prepare water dispersible poly-
isocyanates containing about 1.1 to 8, preferably about 2
to 6 blocked isocyanate groups per molecule from a
difunctional polyisocyanate starting component such as a
diisocyanate, it is necessary to use hydrophilic
components containing at least two isocyanate-reactive
hydrogens. For example, the reaction of an excess of a
diisocyanate with a dihydroxy alkanoic acid to provide
hydrophilicity results in the linking of 2 diisocyanate
molecules and maintains the isocyanate functionality of
the molecule at 2. It is more preferred to prepare water
dispersible blocked polyisocyanates with a functionality
higher than 2. This can be accomplished by using
polyisocyanates with a functionality of greater than 2 or
by using mixtures mixtures of these polyisocyanates with
difunctional polyisocyanates as starting materials.
Mk-3018 -11-
~.~
133829~
In contrast, the reaction of a diisocyanate with amonohydroxy alkanoic acid produces a monoisocyanate.
While a small portion of monoisocyanates is acceptable
since they may function as cross-linking agents as
explained in more detail below, in order to provide
higher degrees of cross-linking the isocyanate
functionality should preferably be maintained at about 2
to 6.
The above-mentioned acid groups may be
converted into hydrophilic anionic groups by treatment
with a neutralizing agent such as an alkali metal salt,
ammotlia or a primary, secondary or preferably tertiary
amine in an amount sufficient to render the blocked
polyisocyanates water dispersible. Suitable alkali
metal salts include sodium hydroxide, potassium
hydroxide, sodium hydride, potassium hydride, sodium
carbonate, potassium carbonate, sodium bicarbonate and
potassium bicarbonate. The use of alkali metal salts as
neutralizing agents is less preferred than the use of
volatile organic compounds such as volatile amines since
they lead to reduced resistance to water swell in the
coatings produced from the water dispersible
compositions of the present invention. Therefore, less
than 50%9 preferably less than 20~ and most preferabLy
none of the acid groups should be neutralized with
alkali metals.
The preferred volatile amines for neutralizin~
the acid groups are the tertiary amines, while ammonia
and the primary and secondary amines are less preferred.
Examples of suitable amines are trimethylamine,
triethylamine, triisopropylamine, tributyl~ine,
N,N-dimethyl-cyclohexylamine, N,N-dimethylstearylamine,
N,N-dimethylaniline, N-methylmorpholine, N-ethyl-
morpholine, N-methylpiperazine, M-methylpyrro-
lidine, N-methylpiperidine, N,N-dimethylethanolamine,
N,N-diethylethanolamine, triethanolamine, N-methyl-
Mo-3018 - 12 -
`- 133829~
diethanolamine, dimethylaminopropanol, 2-methoxy-
ethyldimethylamine, N-hydroxyethylpiperazine,
2-(2-dimethylaminoethoxy)-ethanoL and 5-diethylamino-
2-pentanone. The most preferred tertiary amines are
those which do not contain isocyanate-reactive groups as
determined by the Zerewitinoff test since they are
capable of reacting with isocyanate groups during the
curing of the compositions of the present invention.
In a preferred embodiment of the present
invention volatile tertiary amines are used so that when
the water dispersible coating composition of the subject
application cures at elevated temperatures, the tertiary
amine volatilizes, preferably at a lower temperature
than the unblocking temperature of the blocked
polyisocyanate, and is removed from the coated
substrate. The reformed carboxylic or sulfonic acid
groups may then react with the epoxide ring of the epoxy
resin component thus generating an additional hydroxyl
group for subsequent cross-linking with an isocyanate
group which is also generated during the baking process.
In order to prepare the water dispersible
blocked polyisocyanate the starting polyisocyanate is
preferably reacted at a temperature above about 50C,
preferably at a temperature in the range of about 60 to
lOQC, with a quantity of blocking agent which
corresponds to a ratio of NCO-groups to NCO-reactive
groups of about 1:0.3 to 1:0.95, preferably about 1:0.50
to 1:0.85. However, it is also possible in principle to
use an excess of blocking agent and to stop the blocking
reaction at the required degree of blocking of about 30
to 95%, preferably about 50 to 85%, of the isocyanate
groups originally present, by cooling to room
temperature. In such a case, the excess blocking agent
is generally removed by distillation on completion of
the reaction of the partially blocked isocyanate with
the hydrophilic components. The blocking reaction is
Mo-3018 - 13 -
1338294
usually carried out in the absence of a solvent. It may
be advisable to carry out the blocking reaction in the
presence of a catalyst, depending upon the type of
blocking agent used. In cases where alcohols are used
as blocking agent, it is advisable to use a metal
catalyst, for example dibutyl tin dilaurate. In cases
where blocking agents containing activated methylene
groups are used, it is advisable to use basic catalysts,
such as d~azabicyclooctane, triethyl amine, alkali metal
alcoholates or alkali metal pkenolates such as sodium
phenolate. The catalysts are used in quantities of
about 0.05 to 0.5%, by weight, based on the reaction
mixture as a whole.
The free isocyanate groups still present on
completion of the blocking reaction are reacted with the
hydrophilic components in a second reaction stage. The
hydrophilic components are preferably used in such a
quantity that there is at least one NCO-reactive group
of the hydrophilic components for every isocyanate group
still present. Reaction of the partially blocked poly-
isocyanate with the hydrophilic components may be
carried out in the presence or even in the absence of
solvents. Suitable solvents include the water-miscible
solvents normally used in polyurethane chemistry such as
esters, ketones, halogenated hydrocarbons, alkanes and
arenes. Low boiling solvents include those boiling at
temperatures in the range of about 40 to 90C such as
acetone and methyl ethyl ketone. In addition, higher
boiling solvents such as N-methyl pyrrolidone, dimethyl
formamide, dimethyl sulfoxide, propylene glycol
monomethyl ether acetate and ethylene glycol
mono(-methyl, -ethyl or -butyl) ether acetate may be
utilized.
Mo-3018 - 14 -
- 1338294
In one embodiment of the process according to
the invention, for example, solutions of the partially
blocked polyisocyanate and the reaction component
containing the hydrophilic group are combined at room
temperature or moderately elevated temperature (the
hydrophilic component may also be added as such to the
solution of the partial~y blocked polyisocyanate), and
kept at a moderately elevated temperature, for example,
at a temperature in the range of about 20 to 110C,
until the addition reaction is over. On completion of
the reaction, the dissolved end product may either be
obtained as such by distilling off the solvent (if a low
boiling solvent is present) and any unreacted blocking
agent still present, or, if there is no need to remove
excess blocking agent, the end product may be converted
into an aqueous dispersion by stirring the solution into
water and subsequently distilling off the solvent (if a
iow boiling solvent is present). When higher boiling
solvents are used, they are maintained in the end
product.
Instead of initially blocking the
poiyisocyanate component in a first step, it is also
possible to initially react the polyisocyanate with the
reaction components containing the hydrophilic groups
(and optionally with the high molecular weight
isocyanate-reactive component when socyanat~-
terminated prepolymers are desired). The adduct or
prepolymer may then be blocked in a subsequent step as
previously described. ~en low molecular weight poly-
isocyanate adducts are desired, it is preferred toinitially block the polyisocyanate, while when higher
molecular weight isocyanate-terminated prepolymers are
desired, it is also possible to block the isocyanate
groups after reaction with the isocyanate-reactive
component containing hydrophilic groups and the high
molecular weight isocyanate-reactive component.
Mo-3018 - 15 -
`- 133829~
The acid groups may be converted into
hydrophilic anionic groups by treatment with the alkali
metal or preferably the volatile amine either before,
during or after the reaction of the hydrophilic
component with the blocked polyisocyanate. However, it
is preferred to neutralize the acid groups after the
reaction of the blocked polyisocyanate with the
hydrophilic component and prior to dispersing it in
water.
The water dispersible blocked polyisocyanates
have a content of blocked isocyanate groups, calculated
as NCO, of about 2 to 20%, preferably about 5 to 15% by
weight; an average functionality, based on blocked NCO
groups, of about 1.1 to 8, preferably about 2 to 6; a
content of chemically incorporated anionic groups of
about 1~ to 180, preferably about 20 to 100
milliequi~Talents per 100 g of solids; a content Gf
urethane groups, -NH-CO-O-, of about 2 to 30~,
preferably about 5 to 20% by weight; and an average
molecular weight from about 500 to 10,000, preferably
about 1000 to 3Q00.
The materials to be used for the preparation of
the water dispersible, hydroxy-functional prepolymer are
the same as those used for the preparation of the water
dispersible blocked polyisocyanate with the exception of
the blocking agents. In contrast to the blocked
polyisocyanates, the water dispersible urethane
prepolymers have hydroxyl groups in terminal and/or
lateral positions. The type and proportions of the
above-mentioned starting materials are therefore
selected such that the resulting prepolvmers have
terminal hydroxyl groups. This component may be
produced according to methods known in the art. For
example, the above-mentioned reaction components may be
added in any sequence. One preferred method comprises
introducing all of the isocyanate-reactive components
~o-3018 - 16 -
- 1338294
and subsequently adding the polyisocyanate. The number
of isocyanate-reactive groups per isocyanate group is
maintained at about 1.05:1 to 5:1, preferably about
~ l to 3:1. The mixture is then reacted until no
further NCO groups can be detected. As previously
discussed for the production of the blocked
polyisocyanate, the reaction may take place in the melt
or in the presence of organic solvents. In this case
the solvents and the reaction temperatures are similar
to those used or the production of the blocked
polyisocyanate.
The water dispersible, hydroxyl-terminated
urethane prepolymer has a content of alcoholic hydroxyl
groups of about 0.5 to 10%, preferably about 1 to 5% by
weight; an average functionality, based on the hydroxyl
groups, of about 1.1 to 8, preferably about 2 to 6; a
content of chemically incorporated anionic groups of
about 10 to 180, preferably about 2Q to 100
milliequivalents per 100 g of solids; a content of
urethane groups, NH-CO-O-, of about 2 to 30%, preferably
about 5 to 20Z by weight; and an average molecular
weight of about 500 to 10,000, preferably about 800 to
4,000.
The final component of the aqueous compositions
of the present invention is an epoxy resin which is
optionally water dispersible and hzs an average
molecular weight of about 150 to 20,000, preferably
about 300 to 1500. Suitable epoxy resins include those
3Q containing one or more, preferably two or more and most
preferably two epoxide groups. The epoxy resins may be
prepared from aliphatic, cycloaliphatic or, preferably,
aromatic monoalcohols, diols or polyols. Optionally, a
non-ionic or an anionic external emulsifier and/or a
chemically incorporated non-ionic emulsifier (based on a
polyoxyalkylene glycol) or a chemically incorporated
anionic emulsifier is used to provide hydrophilicity to
the epoxy resin.
Mo-30~8 - 17 -
1338294
Preferred reactants for preparing the epoxy
resins are the dihydric phenols which may optionally
contain other substituents such as alkyl, aryl, sulphido,
sulfonyl, halo, etc. Suitable dihydric phenols include
2,2-bis(4-hydroxylphenyl)propane,
2,2-bis(3-bromo-4-hydroxyphenyl)propane,
2,2-bis(3-chloro-4-hydroxyphenyl)propane,
bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)-
sulfone, bis(4-hydroxyphenyl)sulfide, resorcinol,
hydroquinone and the like. The preferred dihydric
phenols are 2,2-bis(4-hydroxyphenyl)propane (bisphenol A)
and bis(4-hydroxyphenyl)methane for reasons of cost and
availability.
The epoxy resins are prepared by reacting the
dihydric phenol with a halogen-containing epoxide or a
dihalohydrin, especially epichlorohydrin, in the presence
of an alkaline medium. By varying the ratios of the
dihydric phenol and the epichlorohydrin reactants,
different molecular weight products may be obtained as
described in U.S. Patent Nos. 2,582,985; 2,615,007; and
2,633,458.
For purposes of the present invention,
optionally at least a portion of the diglycidyl ether of
the dihydric phenol component can be replaced with a
diglycidyl ether of a hydrogenated dihydric phenol
derivative. For example, the diglycidyl ether of the
dihydric phenol can have up to essentially 100% of its
weight substituted by a diglycidyl alicyclic ether such
as 2,2-bis(4-hydroxycyclohexyl)propane or
bis(4-hydroxycyclohexyl)methane. Suitable external and
chemically incorporated nonionic emulsifiers are
disclosed in U.S. Patent 4,522,851.
Since it is primarily the presence of the
epoxide groups and not the length of the backbone
connected to these groups which provides the
M~-3018 -18- .
,, , i
~,.'
133829~
improvements in accordance with the present invention, it
is preferred to use low molecular weight epoxides due to
their lower melt viscosity such as the diepoxides of low
molecular weight hydroxy functional compounds. Aromatic
diepoxides such as those based on bisphenol A are most
preferred due to their higher reactivity when compared to
the aliphatic or cycloaliphatic epoxides. Suitable
hydroxyl compounds for preparing the cycloaliphatic
epoxides include those previously mentioned and the
hydrogenated derivatives of the above-mentioned dihydric
phenols, while the aliphatic epoxide resins may be
prepared by combining the halogen-containing epoxide or
dihalohydrin with any of the low molecular weight chain
extenders containing one or more hydroxyl groups
previously set forth for the preparation of the
polyisocyanate adducts containing urethane or urea groups
or the high molecular weight polyether polyols.
Monoepoxides may also be used in accordance with
the present invention and include aliphatic,
cycloaliphatic or, preferably, aromatic monoepoxides.
The monoepoxides may be prepared by reacting the
corresponding monoalcohols with a halogen-containing
epoxide such as epichlorohydrin.
Other suitable compounds for connecting the
epoxide groups can be prepared from compounds containing
one or more carboxylic acid groups or their anhydrides,
one or more amino groups, dienes and other compounds
known in the art. Other suitable epoxy resins include
epoxidized fatty acid esters such as epoxidized soybean
oil, the cycloaliphatic epoxides disclosed at column 8 of
the U.S. Patent 4,212,781 and the epoxy resins disclosed
at columns 1-3 of U.S. Patent 4,569,951.
Mk-3018 -19-
~s
- 1~3829~
When the aqueous coating compositions
containing epoxy resins are cured at elevated
temperature, the epoxide groups react with the potential
anionic groups of both the blocked polyisocyanate and
the hydroxyl-terminated polyurethane prepolymer and with
the anionic groups which have counterions derived from
volatile organic compounds. It is believed that the
potential anionic groups neutralized with volatile
organic compounds are reformed at elevated temperatures.
The amount of the epoxy resin is selected such that the
minimum equivalent ratio of potential anionic groups and
anionic groups having counterions derived from volatile
organic compounds to epoxide groups is about 0.2,
preferably about 0.5 and most preferably about 1Ø The
maximum equivalent ratio is about 20.0, preferably about
15.0 and most preferably about 10Ø
The aqueous stoving lacquers of the present
invention may be produced by several methods. In
accordance with one method when the epoxy resin is
either externally emulsified or contains a chemically
incorporated emulsifier, each of the individual
components are separately dispersed in water and the
resulting aqueous dispersions are mixed together. A
preferred method for preparing the aqueous compositions
is to mix the epoxy resin with either or both of the
blocked polyisocyanate component or the hydroxyl-
terminated urethane prepolymer and then disperse these
components in water. As discussed in U.S. Patent
4,306,998, by proceeding in accordance with this method,
it is possible to form a stable aqueous dispersion of
the epoxy resin even when using epoxy resins which are
neither soluble nor dispersible in water.
The aqueous composition obtained from mixing
the blocked polyisocyanate component, the hydroxyl-
terminated urethane prepolymer and the epoxy resinshould have a solids content of about 2 to 60,
Mo-3018 - 20 -
1338294
preferably about 10 to 40. The aqueous composition
should also have a content of about 10 to 180, preferably
about 20 to 100 milliequivalents of chemically
incorporated anionic groups, preferably carboxylate
5 groups, per 100 g of solids.
The individual components are used in quantities
which correspond to an equivalent ratio of blocked
isocyanate groups of component (a) to hydroxyl groups of
component (b) of about 0.6:1 to 2:1, preferably about
0.9:1 to 1.5:1.
The aqueous coating compositions may be applied
to substrates using any of the various techniques known
in the art. In addition, the aqueous compositions may be
blended with other types of resins optionally containing
isocyanate-reactive groups and with amine- or
phenol-formaldehyde condensates known in the art. They
can also contain pigments, levelling agents, catalysts,
and other auxiliaries known in the art. Examples of the
application techniques, resins and auxiliaries are set
20 forth in U.S. Patent 4,408,008.
The invention is further illustrated but is not
intended to be limited by the following examples in which
all parts and percentages are by weight unless otherwise
specified.
EXAMPLES
EXAMPLE 1
506.5 parts of a 90~ solution of the
isocyanurate of l,6-hexamethylene diisocyanate (Desmodur
N-3390, Mobay Corp., 19.4~ NCO) in a 1:1 mixture of
30 n-butyl acetate and Aromatic 100 (a mixture of aromatic
hydrocarbon solvents, Eastman Chem.) were stirred and
150.7 parts of methyl ethyl ketoxime were slowly added
with cooling to keep the temperature below 90C. The
mixture was stirred and the temperature was maintained at
35 90C for 0.5 hr. The mixture was cooled to 65C and
M~-3018 -21-
,.,~
133829~
after 30 minutes, ~ dimethylol propionic acid (42.0
parts) was added with cooling and stirring. The
reaction was maintained at 65C for 15 min. at which
time triethylamine (30.0 parts) was added. After
stirring for 30 min., 239.6 parts of N-methyl
pyrrolidinone were added. The reaction was stirred
overnight, maintaining the temperature at 50C. An
infrared spectrum of the product showed that no residual
isocyanate remained.
Based on solid resin:
Average equivalent weight: 390
Blocked NCO content: 11.3%
Carboxylate content: 2.0%
Viscosity: 19,200 mPa.s (22C)
For use in coatings formulations, an equal
quantity of distilled water was added to the resin, and
the dispersion was mixed thoroughly. The pH of the
dispersion at 35% solids was then adjusted to 8.3 with
triethylamine.
pH: 8.3
Viscosity: 12,400 mPa.s
% Solids: 35
EXAMPLE 2
A mixture of 244.2 parts of a polyester of
phthalic acid and 1,6-hexanediol (molecular weight
2000), 65.5 parts trimethylol propane, 16.4 parts of
~,~-dimethylol propionic acid and 173.7 parts of
N-methyl pyrrolidinone were heated with stirring to
70C. To this mixture was added 160.2 parts of
bis(4-isocyanatocyclohexyl)methane. The reaction was
heated to 105C and maintained at that temperature for 5
hr. until no free NCO could be detected by infrared
spectrum. The resin was cooled to 70C and a mixture of
40 parts of N-methyl pyrrolidinone and 12.4 parts of
triethylamine were added.
Mo-3018 - 22 -
- ~33829~
Based on solid resin:
Average molecular weight: 3979
Average functionality: 6.0
Hydroxyl group content: 2.56%
Urethane group content: 14.8%
Carboxylate group content: 1.1%
712.4 parts of distilled water (preheated to
80C) were added to the resin (at 70C) with vigorous
stirring. The resulting dispersion was heated and
stirred for 1 hr. before cooling to ambient temperature.
pH: 7.44
Viscosity: 11 mPa.s (25C)
% solids: 35
EXAMPLE 3
15A dispersion was made according to Example 2
with the exception that 244.2 parts of a hexanediol
polycarbonate (molecular weight 2000) were substituted
for the phthalic acid/1,6-hexanediol polyester.
pH: 7.40
20Viscosity: 18 mPa.s (25C)
% Solids: 34
Based on solid resin
Average molecular weight: 3979
Average functionality: 6.0
25Hydroxyl group content: 2.56%
Urethane group content: 14.8%
Carboxylate group content: 1.1%
EXAMPLE 4
A mixture of 84.6 parts of a polyester of
phthalic acid and 1,6-hexanediol (molecular weight
2000), 5.7 parts of neopentyl glycol, 13.7 parts of
a,~-dimethylol propionic acid and 54.2 parts of N-methyl
pyrolidinone was heated to 70C. 45.9 parts of
bis(4-isocyanatocyclohexyl)methane were then added. The
reaction mixture was heated to 110C and maintained at
that temperature for 4 hr. until no free NCO groups were
Mo-3018 - 23 -
-` 133829~
detected by infrared spectrum. The resin was then cooled
to 70C, and 10.0 parts of N-methyl pyrrolidinone and 7.2
parts of triethylamine were added with stirring.
Based on solid resin:
Average molecular weight: 6000
Functionality: 2.0
Hydroxyl group content: 0.57%
Urethane group content: 13.8%
Carboxylate group content: 2.1%
210.7 parts of distilled water (preheated to
80C) were added to the resin (at 70C) with vigorous
stirring. The dispersion was heated at 70C and stirred
for 1 hour before cooling to ambient temperature.
pH: 6.8
Viscosity: 32 mPa.s (25C)
% Solids: 37
EXAMPLE 5 (Comparison)
388.6 parts of the dispersion from Example 2
were stirred with 226.8 parts of the dispersion from
20 Example 1 and 5 drops of a 5% aqueous solution of a
fluorocarbon surfactant (FC-430, 3M Company) until
thoroughly mixed.
pH: 7.3
Viscosity: 22 mPas (25C)
This composition was used to make 5 mil (wet
film thickness, WFT) drawdowns on steel panels and 10 mil
(WFT) films on glass. Most of the solvent was allowed to
evaporate for 30 min. at ambient temperature and then the
films were baked for 1 hr. at 140C.
30 EXAMPLE 6
250 parts of the coating composition from
Example 5 were thoroughly mixed with 15.9 parts of a
non-ionic internally emulsified bisphenol A-based epoxy
resin dispersion (CMD 35201, Celanese Plastics and
35 Specialities Corporation, 55% solids in water). The
epoxy resin dispersion is solvent-free and has a viscosity
M~-3018 -24-
c'~ .
133829~
of 12,000 cps at 25C (Brookfield RVT at 10 RMP; because
the product is thixotropic, the viscosity readings vary
with the spindle speed of the viscometer), a density of
9.2 lbs/gal, an average particle size of 2 and a pH of
7Ø Films were made on glass and steel panels as in
Example 5.
Mo-3018 -24a-
,,
,3~S
133829~
pH: 7.3
Viscosity: 71 mPa.s (25C)
EXAMPLE 7 (Comparison)
388.6 parts of the dispersion from Example 3
were thoroughly mixed with 226.8 parts of the dispersion
from Example 1 and 5 drops of the fluorocarbon
surfactant described in Example 5. Films were made on
glass and steel panels as in Example 5.
pH: 7.5
Viscosity: 28 mPa.s (25C)
EXAMPLE 8
250 parts of the formulation from Example 7
were thoroughly mixed with 15.9 parts of the epoxy resin
described in Example 6. Films were made on glass and5 steel panels as in Example 5.
pH: 7.5
Viscosity: 45 mPa.s (25C)
EXAMPLE 9 (Comparison)
33.2 parts of the dispersion from Example 4
were thoroughly mixed with 4.3 parts of the dispersion
from Example 1 and 1.5 parts of a 5% aquecus solution of
the fluorocarbon surfactant described in Example 5.
Films were made on glass and steel panels as in
Example 5.
pH: 7.1
EXAMPLE 10
The undispersed blocked NCO resin from Example
1 was mixed with 10% by weight of a bisphenol A-based
diepoxide, (Epon 828, Shell Chemical Corporation,
epoxide equivalent weight 185 to 192) until homogeneous.
The resin mixture was dispersed with an equal quantity
of distilled water. The pH of the dispersion was
adjusted to 8.3 with triethylamine.
4.6 parts of the blocked NCO dispersion were
3~ then mixed until homogeneous with 33.2 parts of the
dispersion from Example 4 and 1.5 parts of a 5~ aqueous
Mo-3018 - 25 -
1338294
solution of the fluorocarbon surfactant described in
Example 5. Films were made on steel panels and glass as
in Example 5.
pH: 7.2
EXAMPLE 11
101.7 parts of methyl ethyl ketoxime were
slowly added to 280.5 parts of the biuret of 1,6-hexa-
methylene diisocyanate (Desmodur N-3200, Mobay
Corporation, 23.1% NCO) while stirring so that the
temperature was kept below 90C. The temperature was
maintained at 90C for 1 hr., 15 min. Powdered , ,-
dimethylol propionic acid (26.1 parts) and N-methyl
pyrrolidinone (143.9 parts) were added and the mixture
was stirred ~or 1 hr., 45 min. while maintaining the
temperature at 90C. An infrared spectrum of the
product showed that no residual isocyanate remained at
this time. The mixture was cooled to 70C and 18.7
parts of triethylamine and 39.2 parts of N-methyl
pyrrolidinone were added and the temperature was
maintained at 70C for an additional 15 min. The
resulting mixture had a viscosity of 14,80Q mPa.s
(25C)
Based on solid resin:
Average esuivalent weight: 350
Blocked isocyanate content: 12.6%
Carboxvlate group content: 2.1~
For use in coating formulations, the blocked
~CO resin was dispersed in an equal quantity of
distilled water at ambient temperature.
pH: 8.7
Viscosity: 11,200 mPa.s (25C)
% Solids: 35
EXAMPLE 12 (Comparison)
To 4.3 parts of the dispersion from Example 11
were added 33.2 parts of the dispersion from Example 4
and 1.5 parts of a 5% aqueous solution of the
Mo-3018 - 26 -
1338294
-
fluorocarbon surfactant described in Example 5 and the
mixture was thoroughly mixed. Films were made on steel
panels and glass as in Example 5.
EXAMPLE 13
A coating ~ormulation was made according to
Example 12 with the exception that an additional 0.2
parts of the 5% aqueous solution of the fluorocarbon
surfactant described in Example 5 and 2.4 parts of the
epoxy resin from Example 6 were added. The composition
was thoroughly mixed and films were made on steel panels
and glass as in Example 5.
EXAMPLE 14
96.9 parts of -caprolactam were added to 225.3
parts of the isocyanurate of 1,6-hexamethylene diiso-
cyanate described in Example 1. The mixture was heatedto 90C until the exothermic reaction raised the
temperature to 108C. It was then cooled to 90C and
stirred at that temperature for 40 min. until the
theoret~cal NCO (2.55~) content was attained. 13.4
parts of ~, ~-dimethylol propionic acid were added and
the mixture was cooled to 70C. 10.1 parts of triethyl-
amine were added and the mixture was stirred for 70 min.
at 70C. 116.0 parts N-methyl pyrrolidinone were added
and then the external heat source was removed. After
the product was stirred overnight, no free NC0 groups
could be detected in an infrared spectrum. The product
had a viscosity of 5,600 mPa.s (~5C).
Based on solid resin:
Average equivalent weight: 365
Blocked NCO content: 11.5
Carboxylate content: 1.4%
For coatings formulations, an equal quantity of
distilled water was added to the resin and the
dispersion was stirred until thoroughly mixed.
Mo-3018 - 27 -
133829~
pH: 8.3
Viscosity: 71 mPa.s (25C)
% Solids: 35
EXAMPLE 15 (Comparison)
To 26.7 parts of the dispersion from Example 14
were added 205.1 parts of the dispersion from Example 4
and 10 drops of a 5% aqueous solution of the fluoro-
carbon surfactant described in Example 5. The mixture
was stirred until thoroughly mixed and films were made on0 steel panels and glass as in Example 5.
pH: 6.95
Viscosity: 27.5 mPa.s (23~C)
EXAMPLE 16
To 25.4 parts of the dispersion from Example 14
were added 195.3 parts of the dispersion from Example 4,
10 drops ofa 5% aqueous solution of the fluorocarbon
surfactants described in Example 5 and 14.0 parts of the
epoxy resin described in Example 6. The mixture was
stirred until thoroughly mixed and films were made on0 glass and steel panels as in Example 5.
pH: 6.94
Viscosity: 31.4 mPa.s (23C)
EXAMPLE 17
To an anhydrous mixture of 13.4 parts of trim-5 ethylol propane and 168.0 parts of a polyester of adipic
acid and 1,6-hexanediol (OH number 134, molecular weight
840) preheated to 60C were added 222.0 parts of
isophorone diisocyanate. The mixture was stirred at 90 C
until the calculated NCO content of 13.5% was attained
(3 hr.). 45.2 parts of~-caprolactam were then added.
The temperature of the exothermic reaction rose to about
100C. The mixture was diluted with 27 parts of N-methyl
pyrrolidinone and 40.2 parts of a~ -dimethylol
propionic acid were then added. The mixture was stirred
for 30 min. at 120C, and then a further 33.9 g of
~-caprolactam were added and the mixture was again
Mb-3018 -28-
~- 1338~9~
stirred for about 30 minutes at 120C until no free NCO
could be detected in an infrared spectrum. Following the
M~-3018 -28a-
~.'
~ . ~
- 13~8294
addition of 25.6 parts of N,N-dimethylethanolamine, a
highly viscous resin was obtained.
Based on solid resin:
Average molecular weight: 1830
Average functionality: 2.33
- Blocked NCO content: 5.4%
-~ Urethane content: 14.0%
Carboxylate group content: 2.4%
918 parts of distilled water (preheated to
90C) were added to the resin (at 90GC) while stirring.
A stable, slightly opaque, solution-like dispersion was
obtained.
- pH: 7.8
Viscosity: 350 mPa.s (25C)
~ Solids: 35
EXAMPLE 18
Example 17 was repeated using an additional 7.6
parts of N-methyl pyrrolidinone as solvent. Following
the addition of N,N-dimethylethanolamine, the resin was
mixed thoroughly and 27.6 parts of the epoxy resin
described in Example 10 were added while stirring.
1644.6 parts of distilled water (preheated to 90C) were
added to the resin (at 90C) and the resulting
dispersion was stirred for 1 hr. at that temperature
before cooling to ambient temperature.
pH: 8.9
Viscosity: 10.5 mPa.s (25C)
% Solids: 23
EXAMPLE 19
25 parts of N-methyl pyrrolidinone, 6.7 parts
trimethylol propane and 23.5 parts of~,c,,-dimethylol
propionic acid were added to 292 parts of an anhydrous
polyether of propylene oxide and bisphenol A (OH number,
197; molecular weight,570). The mixture was stirred and
heated to 110C until clear and then cooled to 80C. 84
parts of hexamethylene diisocyanate were added and the
Mo-3018 - 29 -
133829~
exothermic reaction raised the temperature of the
mixture to 113C. The mixture was cooled to 100C and
stirred for 1.5 hr. until no free NCO groups were
detectable by infrared spectrum. After adding 13.4
parts of N,N-dimethylethanolamine, a highly viscous
hydroxy functional resin was obtained.
Based on solid resin:
Average molecular weight: 1790
Average functionality: 2.22
Hydroxy group content: 2.lZ
Urethane content: 14.7%
Carboxylate group content: 1.6~
684.5 parts of distilled water (at 90~C) were
added with stirring to the resin (at 90C). The
dispersion which was obtained was stable, slightly
opaque and solution-like.
pH: 7.2
Viscosity: 90 mPa. 5 (25C)
~ Solids: 35
EXAMPLE 20
Example 19 was repeated using an additional 1.4
parts of N-methyl pyrrolidinone. After the addition of
N,N-dimethylethanolamine, the resin was stirred
thoroughly. 21.4 parts o the epoxy resin described in
Example 10 were then added and the mixture was
thoroughly stirred. 792.2 parts of distilled water
(preheated to 80GC) were added to the resin (at 90C)
and the dispersion was stirred for 1 hr. at that
temperature before cooling to ambient temperature.
pH: 7.7
Viscosity: 250 mPa.s (25C)
~ Solids: 35
EXAMPLE 21 (Comparison)
A mixture of 74.0 parts of the dispersion from
Example 19 and 69.0 parts of the dispersion from Example
17 was stirred thoroughly. A drawdown bar was used to
Mo-3018 - 30 -
1338294
-
make 10 mil (WFT) films on steel panels and glass. Most
of the solvent was allowed to evaporate at ambient
temperature and humidity ~or 30 min. before the films
were baked at 180C for 30 min.
EXAMPLE 22
82.5 parts of the dispersion from Example 20
and 69.0 parts of the dispersion from Example 17 were
thoroughly mixed. Films were made on steel panels and
glass as in Example 21.
EXAMPLE 23
74.0 parts of the dispersion from Example 19
and 106.5 parts of the dispersion from Example 18 were
thoroughly mixed. Films were made on steel panels and
glass as in Example 21.
EXAMPLE 24
82.5 parts of the dispersion from Example 20
and 106.5 parts of the dispersion from Example 18 were
thoroughly mixed. Films were made on steel panels and
glass as in Example 21.
EXAMPLE 25
24.2 parts of the dispersion from Example 19
and 22.4 parts of the dispersion from Example 17 were
thoroughly mixed with 3.0 parts of the epoxy resin
described in Example 6 and 2.6 parts of a 5% aqueous
solution of the fluorocarbon surfactant described in
Example 5. Films were made on steel panels and glass as
in Example 21.
TEST RESULTS
1) All films passed the 180 bend test which
involved bending a coated steel panel with the
coating on the outside of the bend until the
panel was bent 180 and then inspecting the
coating for defects.
2) All films passed the Gardner impact resistance
test (ASTM D 3029-&4, method G) at 160 in. lb.,
front and rear.
Mo-3018 - 31 -
133829~
3) The pencil hardness (tested according to ASTM D
3363 with a Micrometric Company pencil hardness
gauge) was essentially equivalent for comparable
films regardless of the presence of epoxy
resins.
4) Hydrolytic stability studies were carried out on
Examples 5, 6, 7, 8, 9, 10, 12 and 13 by
measuring the tensile properties after
hydrolysis aging. Even though slight
differences were present, the hydrolytic
stability was very good for all samples tested
regardless of the presence of epoxy resin. The
tensile properties were determined according to
AS~ D 638 using a type 4 die. The tests were
conducted on free films removed from glass and
aged for one or two weeks in an environmental
chamber maintained 70C at 95% relative humidity
prior to testing of the tensile properties.
5) Solvent resistance (MF,K Double Rubs) was
measured by wetting a cloth with methyl ethyl
ketone and rubbing the cloth across the coating
~mtil the coating was removed; each back and
forth motion constituting one rub.
Mo-3018 - 32 -
TABLE I 1338291
SOLVENT RESISTANCE (MEK Couble Rubs)
Example MEK 2X Rubs Comments
5 (Comp) 50 No epoxy resin added.
6 100 Epoxy resin added to blended dispersion.
7 (CQmP) 95 No epoxy resin added.
8 100 Epoxy resin added to blended dispersion.
9 (Comp) 20 No epoxy resin added.
Epoxy resin added to polyisocyanate component.
12 (Comp) 10 No epoxy resin added.
13 145 Epoxy resin added to blended dispersion.
15 (Comp) 70 No epoxy resin added.
16 175 Epoxy resin added to blended dispersion.
21 (Comp) 15 No epoxy resin added.
22 65 Epoxy resin added to polyhydroxyl component.
23 40 Epoxy resin added to polyisocyanate component.
24 85 Epoxy resin added to both polyhydroxyl and
polyisocyanate components.
- 70 Epoxy resin added to blended dispersion.
Mo-3018 - 33 -
1338291
Although the invention has been described in
detail in the foregoing 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 the claims.
Mo-3018 - 34 -
