Urethane modified waterborne dispersions

An excess of a urethane modified polyfunctional epoxide compound is reacted with a tertiary amine salt to form a quaternized epoxy resin. The quaternized epoxy resin is then dispersed in water. Therein the residual epoxy functionality is reacted with a polyamine, to form a waterborne epoxy resin system. The urethane modification leads to significant improvements in properties such as dry rate, adhesion, and chemical resistance, particularly aviation hydraulic fluid resistance. The waterborne dispersions of the urethane modified epoxy resins are useful in coating, ink and adhesive applications at ambient and elevated temperature curing conditions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to urethane modified water dispersible epoxy resin 
systems and their method of preparation. 
2. Description of the Prior Art 
In the prior art, the problems of viscosity control and gelation during the 
processing of waterborne epoxy amine adducts are often discussed. For 
instance, U.S. Pat. No. 4,608,405 to DeGooyer discloses the use of large 
excesses of amine which must later be vacuum stripped from the product 
(column 5, lines 15-33). U.S. Pat. No. 5,089,100 to Debroy discloses the 
partial defunctionalization of the epoxy with a secondary monoamine prior 
to the polyamine reaction in order to prevent gelation (column 3, lines 
48-50). U.S. Pat. No. 5,096,556 to Corrigan discloses the use of blocked 
polyamines (ketimines) and the use of excess amine to minimize the danger 
of gelation (column 3, lines 64-68 and column 4, lines 48-53). 
U.S. Pat. No. 5,204,385 to Naderhoff discloses the preparation and use of 
amine functional curing agents that are suitable for crosslinking epoxy 
resins in waterborne systems. 
Although waterborne epoxy systems have been in commercial use for nearly 20 
years, disadvantages such as slow cure rate, short pot life, and poor 
chemical resistance have limited their widespread acceptance. 
It is an objective of the present invention to provide improvements in cure 
speed, adhesion, and chemical resistance in waterborne dispersions, and to 
provide an improved process for preparing waterborne dispersions. 
SUMMARY OF THE INVENTION 
The present invention relates to reaction of urethane modified 
polyfunctional epoxide compounds with a tertiary amine salt to form a 
quaternized epoxy resin that is dispersed in water and wherein the 
residual epoxy functionality is then reacted with a polyamine, to form a 
waterborne epoxy resin system. 
The urethane modification leads to significant improvements in properties 
such as dry rate, adhesion, and chemical resistance, particularly aviation 
hydraulic fluid resistance. 
The waterborne dispersions of the urethane modified epoxy resins are useful 
in coating, ink and adhesive applications at ambient and elevated 
temperature curing conditions. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The waterborne dispersions of the present invention are prepared by: 
1. reacting an excess of urethane modified polyfunctional epoxide compound 
with a tertiary amine salt to form a quaternized epoxy resin; 
2. dispersing the quaternized epoxy resin in water; and 
3. reacting the residual epoxy functionality in the quaternized epoxy resin 
with a polyamine containing primary amine groups to form a chain extended 
urethane modified waterborne epoxy resin dispersion. 
Suitable polyfunctional epoxide compounds for the present invention are 
disclosed in U.S. Pat. No. 5,204,385 to Naderhoff, and are incorporated by 
reference herein. The term "polyfunctional epoxide compound" includes 
within its meaning epoxy resins. 
The epoxides generally used to prepare the waterborne dispersions are 
glycidyl ethers of polyhydric phenols. Preferred epoxides are the 
diglycidyl ether of 2,2-bis(hydroxyphenyl) propane and the glycidyl ethers 
of phenolformaldehyde condensates, which are also known respectively as 
Bisphenol A and Bisphenol F epoxy resins. Particularly suitable epoxides 
are higher molecular weight analogs of the diglycidyl ether of Bisphenol A 
which have epoxy equivalent weights ranging from 300 to 1500. 
The epoxy resin can be urethane modified by reacting the secondary hydroxyl 
groups contained on the epoxy backbone with an isocyanate functional 
compound. The isocyanate can be reacted in a number of ways, however, the 
preferred method is to react the isocyanate during the epoxy advancement 
reaction. 
The term "epoxy advancement reaction" is well known in the art and relates 
to the increase in molecular weight when, for example, the epoxy groups on 
the diglycidyl ether of Bisphenol A are reacted with Bisphenol A to 
increase the molecular weight, and also the viscosity. This method of 
reacting the isocyanate is preferred because the isocyanate can be added 
when the reaction temperature and resin viscosity are low. This avoids the 
possibility of forming gel particles when the isocyanate is added at high 
temperatures and high resin viscosity. 
Suitable isocyanate functional compounds are monomeric isocyanates such as 
isophorone diisocyanate, diphenylmethane 4,4'-diisocyanate, 2,4-toluene 
diisocyanate, 1,6-hexamethylene diisocyanate, bis(4-isocyanatocyclohexyl) 
methane, and trimethylhexamethylene diisocyanate. Suitable isocyanate 
compounds also include isocyanate prepolymers and polymeric isocyanates. 
The level of urethane modification is limited by viscosity. High levels of 
urethane modification will lead to high viscosities, and can cause 
gelation of the epoxy resin. The amount of isocyanate functional compound 
generally varies from about 0.5 to 15 percent, and preferably about 1 to 
10 percent of the epoxy resin weight. 
Suitable tertiary amines used to prepare the tertiary amine salts are also 
disclosed in U.S. Pat. No. 5,204,385 to Naderhoff, and are incorporated by 
reference herein. The preferred tertiary amines are cyclic compounds such 
as 4-methyl morpholine or 4-ethyl morpholine. 
The preferred acids used to prepare the tertiary amine salt are low 
molecular weight acids such as acetic acid, formic acid, or lactic acid. 
The molar ratio of tertiary amine to acid is about 1 to 1. 
The reaction of the tertiary amine salt with the urethane modified epoxy 
resin is conducted at temperatures of about 40.degree. to 100.degree. C., 
with about 50.degree. to 80.degree. C. being preferred. The amount of 
tertiary amine salt can vary from about 0.05 to 0.8 moles of amine salt 
for each epoxy equivalent. The preferred amount of tertiary amine salt is 
about 0.1 to 0.5 moles of amine salt for each epoxy equivalent. 
In order to maintain a workable viscosity, on the order of less than about 
25,000 centipoises (cps), and preferably less than about 20,000 cps, it is 
advantageous to conduct the tertiary amine salt/epoxy reaction in the 
presence of a solvent. Suitable solvents are glycol ethers, esters of 
glycol ethers, alcohols, and water. These would include solvents such as 
ethylene glycol monopropyl ether, propylene glycol t-butyl ether, 
propylene glycol monopropyl ether, propylene glycol monomethyl ether 
acetate, ethylene glycol butyl ether acetate, diacetone alcohol, methyl 
ethyl ketone and benzyl alcohol. Also, nitroparaffins such as nitroethane 
or nitropropane are suitable solvents. Water can be used as a co-solvent. 
The completion of the reaction of the tertiary amine salt with the urethane 
modified polyfunctional epoxide compound to form a quaternized epoxy resin 
(an epoxy resin which contains quaternized amine salt groups as well as 
epoxy groups) can be monitored by measuring the residual epoxy 
concentration, until substantially all of the tertiary amine salt has been 
reacted, preferably at least 80%, and more preferably at least 90% or 
greater conversion. 
At the desired reaction conversion the quaternized epoxy resin is dispersed 
in water. The amount of water in which the quaternized epoxy resin or 
quaternized polyfunctional epoxide compound is dispersed is based upon the 
amount of solids content in the quaternized compound. Preferably, the 
total weight of the water and the polyfunctional epoxide compound contains 
about 10 to 70 weight % and more preferably about 20 to 60 weight % of the 
solids content in the polyfunctional epoxide compound. 
In some epoxy titration measurements, such as ASTM 1652, the amine salt 
will be titrated in addition to the epoxide groups. In this case it is 
necessary to subtract out the contribution of the amine salt in order to 
obtain an accurate value for the epoxide content. 
Immediately after the quaternized epoxy resin is dispersed in water, a 
polyamine containing primary amine groups is reacted with the residual 
epoxy groups or residual epoxy functionality of the resin. It is necessary 
to add the amine immediately after the quaternized epoxy is dispersed in 
water in order to minimize the possible loss of epoxy functionality due to 
hydrolysis side reactions. 
In general, the same polyamines that can be used in non-waterborne systems 
as epoxy curing agents can be used to prepare the waterborne dispersions 
of the present invention. Examples of suitable polyamines are disclosed in 
U.S. Pat. No. 5,204,385 to Naderhoff, which is incorporated by reference 
herein and include ethylene diamine, diethylene triamine, triethylene 
tetramine, hexamethylene diamine, 2-methyl pentamethylene diamine, 
trimethylhexamethylene diamine, and 1,3-pentanediamine. 
Another suitable class of polyamines are polyoxyalkylamines such as 
polyoxypropylene triamine which is available from Texaco Chemical Co. 
under the trademark JEFFAMINE.TM.. The most preferred polyamines are 
cyclic amines such as isophorone diamine, m-xylene diamine, 
1,2-diaminocyclohexane, 1-(2-amino ethyl) piperazine, and 
bis(paraaminocyclohexyl) methane. 
The advantage of this process is that the epoxy and polyamine reaction 
occurs after dispersion in water. This allows the polyamine and epoxy 
reaction to occur within the dispersed epoxy particles, and the ratio of 
polyamine to epoxy groups can be varied widely without gelation. Another 
advantage is that the necessity of using blocked amines or excess amine is 
eliminated. 
The amount of polyamine can range from about 0.1 to 1.0 mole of polyamine 
for each epoxy equivalent. The preferred range is about 0.2 to 0.6 moles 
of polyamine for each epoxy equivalent. 
The waterborne dispersions of the present invention can be prepared in a 
single reaction vessel or in multiple vessels. In the multi-vessel 
process, the epoxy-tertiary amine salt reaction is carried out in the 
first vessel. After the epoxy and tertiary amine salt reaction has been 
completed, the reaction product is pumped or transferred to a second 
vessel which contains water, and is dispersed therein. 
After the epoxy is dispersed in water, the polyamine is added to the 
dispersion. The multi-vessel process is preferred over the single vessel 
process because the multi-vessel process leads to increased yields and 
reduced cleaning requirements between batches. It is also possible when 
using a two vessel process to disperse the quaternized epoxy resin 
directly into a solution of the water and the polyamine. In this manner, 
the epoxy dispersion and epoxy-polyamine reaction takes place 
simultaneously. 
The waterborne dispersions of the present invention have small 
finely-divided particle sizes which typically vary from about 0.05 to 0.15 
microns. The dispersions have excellent stability properties and can be 
stored in excess of 3 months at 120.degree. F. 
The waterborne dispersions can be formulated with other epoxy resins and/or 
resins containing blocked isocyanate groups to yield systems which are 
useful in coating, ink, and adhesive applications. These systems can be 
used at ambient temperature or at elevated temperatures generally of about 
140.degree. to 400.degree. F. for baking applications. 
The waterborne dispersions of the present invention can be used as coatings 
for furniture, wood, concrete floors, high performance architectural 
coatings, aerospace primers, industrial-maintenance primers, automotive 
refinish primers, and cathodic electrodeposition primers. 
The compositions of the present invention offer further improvement in the 
areas of cure speed, adhesion, and chemical resistance. Specifically, the 
inventive compositions have improved resistance to aviation hydraulic 
fluids, such as SKYDROL.RTM. (Monsanto Co.). Resistance to aviation 
hydraulic fluids is an important property for aerospace coatings. 
SKYDROL.RTM. is acidic in nature and to be fire resistant contains 
phosphate esters, and consequently is corrosive. Therefore, the coatings 
coming in contact with SKYDROL.RTM. have to be resistant to these 
corrosive effects. 
The following examples illustrate the preparation and use of the inventive 
waterborne dispersions. In the examples, and throughout the specification, 
all parts and percentages are by weight, unless otherwise indicated. 
EPOTUF.RTM. 37-140 is the diglycidyl ether of 2,2-bis(4-hydroxyphenyl) 
propane with an average molecular weight of 370, and is commercially 
available from Reichhold Chemicals, Inc. 
EPOTUF.RTM. 37-143 is a dispersion of EPOTUF.RTM. 37-140 modified with a 
non-ionic surfactant at 78% solids in water, and is also commercially 
available from Reichhold Chemicals, Inc. The average epoxy equivalent 
weight on a solution basis is 256.

EXAMPLE 1 
A urethane modified, waterborne dispersion was prepared by charging 148.1 
grams of EPOTUF.RTM. 37-140 (Reichhold Chemicals, Inc.) to a 1 liter 
reaction vessel equipped with stirrer, nitrogen blanket, temperature 
controller, condenser, and heating mantle. 45.0 grams of Bisphenol A was 
charged, and the temperature was increased to 80.degree. C., at which time 
a mixture of 3.3 grams of isophorone diisocyanate and 3.3 grams of 
bis(4-isocyanatocyclohexyl) methane was added dropwise to the vessel. 
After mixing for 15 minutes, 0.1 gram of ethyl triphenylphosphonium 
acetate (70% in methanol) was added and the temperature was increased over 
1 hour to 172.degree. C. After 30 minutes at 170.degree.-175.degree. C., 
the epoxide equivalent weight was 515, in accordance with ASTM 1652, Test 
Method B. Heating was discontinued, and 50.0 grams of 2-propoxyethanol was 
added dropwise. The resin solution was cooled to 63.degree. C. and 33.3 
grams of a tertiary amine salt prepared by mixing 20.0 grams of water, 8.3 
grams of 4-methyl morpholine, and 5.0 grams of acetic acid was added to 
the vessel. After 1 hour at 65.degree. C., the epoxide equivalent weight 
("EEW") was measured by titration as 716 on a solution basis (903 EEW when 
corrected for amine salt contribution). Over 6 minutes, 255.3 grams of 
deionized water was charged to the vessel which formed a dispersion of 
quaternized epoxy in water. A mixture of 9.8 grams of m-xylene diamine and 
12.4 grams of isophorone diamine was added to the vessel, and stirring was 
continued for 30 minutes at 45.degree. C. The final product was a stable 
dispersion with a solids content of 41%, a viscosity of 60 cps at 
25.degree. C., and a particle size of 0.1 micron. 
EXAMPLE 2 
For comparison purposes, a waterborne dispersion was prepared identical to 
Example 1 except that no isocyanate monomers were added to the reaction. 
EXAMPLE 3 
Separate clear coatings were prepared from each of the dispersions of 
Examples 1 and 2 using the formulation shown below: 
______________________________________ 
Material Weight (grams) 
______________________________________ 
Dispersion from Ex. 1/2 
85.0 
Propylene glycol t-butyl ether 
5.9 
2-butoxyethanol 9.3 
deionized water 20.7 
EPOTUF .RTM. 37-143 12.2 
Total 133.1 grams 
______________________________________ 
Drawdowns were prepared from each coating formulation on glass plates and 
cold rolled steel with a wet film thickness of 3-4 mils and a dry film 
thickness of 1.5 mils. Shown below is data for the dry times, Sward 
hardness development, and the resistance to SKYDROL.RTM. hydraulic fluid. 
______________________________________ 
Example 1 Example 2 
Coating Coating 
______________________________________ 
Dry time* (hours) 
Set to Touch 0.25 0.50 
Through Dry 1.25 3.50 
Dry Hard 3.00 5.00 
______________________________________ 
*Measured with Gardner Circular Drying Time Recorder (Gardner Co.). See 
Paint Testing Manual by Gardner & Sward, p. 115 (12th edition, March 
1962). 
Sward Hardness* after 
1 day 18 12 
3 days 26 22 
7 days 32 28 
______________________________________ 
*Measured with Sward Rocker Hardness Test. See also Paint Testing Manual 
by Gardner & Sward, p. 138 (12th edition, March 1962). 
SKYDROL .RTM. LD-4 
Resistance 
Exposure Time 
(hours) 
@ Temp. Example 1 Example 2 
______________________________________ 
24 at 77.degree. F. 
Slight* Severe 
Softening Softening 
1 at 140.degree. F. 
Slight* Severe 
(scribed) Softening Softening and 
Delamination 
______________________________________ 
*Recovered after 1 hour. 
As shown above, the urethane modification results in faster dry times, 
faster Sward hardness development, and better resistance to SKYDROL.RTM. 
hydraulic fluid at room temperature and elevated temperature. 
EXAMPLE 4 
Anticorrosive primers were prepared using the waterborne dispersions 
prepared in accordance with Example 1 and Example 2 using the following 
formulation: 
______________________________________ 
Ingredient 
Weight (grams) 
______________________________________ 
T A - Curing Agent Component 
(a) Waterborne Dispersion from 
194.4 
Example 1/Example 2 
(b) Defoamer - (Patcote 841 - 
2.9 
Patco Specialty Products) 
(c) Propylene glycol t-butyl ether 
33.0 
(d) 2 butoxyethanol 33.0 
(e) Propylene glycol phenyl ether 
11.3 
(f) Red iron oxide 100.7 
(g) Wollastonite (magnesium silicate) 
230.4 
(h) Modified zinc phosphate 
100.0 
(Heucophos ZBZ - Heucotech Co.) 
(i) Waterborne dispersion from examples 
227.1 
(j) 2-butoxyethanol 21.2 
(k) Deionized water 32.2 
Total 986.2 grams 
T B - Epoxy Component 
(l) EPOTUF .RTM. 37-143 82.1 
(m) Deionized water 92.9 
(n) 3 glycidoxypropyltrimethoxysilane 
3.2 
Total 178.2 grams 
______________________________________ 
Constituents (a), (b), (c), (d) and (e) were premixed for about 3 minutes 
at low agitation of about 200 rpm. Thereafter, pigment constituents (f), 
(g) and (h) were added and the mixture was agitated at high speeds of 
about 800 to 1000 rpm until the pigment particles dispersed to a size of 
about 30 microns. This was then followed by the addition of constituents 
(i), (j) and (k) to complete the formulation of the curing agent 
component. 
Paint was prepared by mixing the 986.2 parts of the curing agent 
component--Part A with 178.2 parts of the epoxy component--Part B. Films 
were sprayed on cold rolled steel panels and were allowed to cure for 
seven days at room temperature. The dry film thickness was 1 mil. The 
coatings were tested for water resistance and wet adhesion according to 
Military Specification Mil-P-53030A, which covers waterborne epoxy 
anticorrosive primers. The results are shown below: 
______________________________________ 
Results 
Test Conditions Example 1 Example 2 
______________________________________ 
Wet Adhesion 
24 hour water 100% 90% 
immersion, Adhesion Adhesion 
scribed, room 
temperature 
Water Resistance 
7 days water No Severe 
immersion, room 
wrinkling wrinkling 
temperature or and 
blistering 
blistering 
______________________________________ 
As shown above, the urethane modified waterborne dispersion from Example 1 
has improved wet adhesion and water resistance compared to Example 2, 
which contains no urethane modification. Primer prepared using the Example 
1 composition passed the wet adhesion and water requirements of Mil. Spec. 
Mil-P-53030A, whereas primers prepared from Example 2 did not. 
EXAMPLE 5 
A urethane modified, waterborne dispersion which has highly crosslinked 
particles was prepared by charging 156.6 grams (0.84 equivalents epoxy) of 
EPOTUF.RTM. 37-140 to a 1 liter flask equipped as in Example 1. 
47.5 grams (0.42 equivalents hydroxyl) of Bisphenol A was added to the 
flask. The temperature was increased to 80.degree. C., and 3.5 grams of 
isophorone diisocyanate and 3.5 grams of bis(4-isocyanatocyclohexyl) 
methane was added to the vessel. After mixing for 30 minutes, 0.12 grams 
of ethyl triphenylphosphonium acetate (70% in methanol) was added and the 
temperature was increased to 177.degree. C. over 30 minutes. After 30 
minutes at 170.degree.-175.degree. C., the epoxide equivalent weight was 
538 in accordance with ASTM 1652, Test Method B. Heating was discontinued, 
and 30 grams of benzyl alcohol was slowly added while cooling. At 
71.degree. C., 35.0 grams of a tertiary amine salt prepared by mixing 21 
grams of deionized water, 8.75 grams of 4-methyl morpholine, and 5.25 
grams of glacial acetic acid was added. After 70 minutes at 65.degree. 
C., the epoxide equivalent weight of the solution was 740 (963 EEW when 
corrected for amine salt contribution). Next, 269 grams of deionized water 
was added over 11 minutes. Immediately after the water addition, 5.3 grams 
(0.039 moles) of m-xylene diamine and 6.7 grams (0.039 moles) of 
isophorone diamine were added to the vessel, and stirring was continued 
for 2 hours while cooling to 25.degree. C. The final product was a stable 
dispersion with an opalescent appearance. The dispersion had a solids 
content of 42.8% and a viscosity of 90 cps at 25.degree. C.