Adducts of imidazolidine compounds, such as the reaction product of ethylene diamine with cyclohexanone, are provided with organic polyepoxides, especially with low molecular weight polyepoxides where the imidazolidine acts as a chain extender, and the adduct is reacted with an acid to protonate at least 50% of the amine groups in the adduct. These protonated adducts can be dispersed in water to form dispersion which cure with various curing agents. Aqueous electrocoating baths can be provided which electrodeposit at the cathode.

DESCRIPTION 
TECHNICAL FIELD 
This invention relates to water dispersible cationic resins based on 
polyepoxides, their production, and to the cationic electrocoating of such 
resins from an aqueous bath containing the same. 
BACKGROUND ART 
It is known to react polyepoxides with ketimine-blocked amines which 
include a single secondary amino hydrogen atom. The reaction products can 
be reacted with an acid to quaternize the tertiary amine groups in the 
reaction product, and the quaternized reaction product can be dispersed in 
water. The water reacts with the ketimine groups to release ketone into 
the water medium and this provides primary amine groups. The resulting 
amine-functional resin is electrodepositable from aqueous medium at the 
cathode of a unidirectional electrical system, and it can be cured with a 
curing agent which is introduced into the water medium for this purpose. 
The curing agents primarily selected in the prior art have been blocked 
polyisocyanates. When electrodeposited coatings containing the 
amine-functional resin and the blocked polyisocyanate are baked, the 
blocking agent is removed and the amine resin cures. All of the foregoing 
is illustrated in U.S. Pat. No. 4,031,050. 
It would be desirable to replace the blocked polyisocyanate curing agent 
with an aminoplast resin because these are less costly, but the amine 
functionality (which is largely constituted by primary amine groups) 
creates a strongly alkaline environment which inhibits cure with an 
aminoplast resin. 
Another point of importance is the fact that the ketimine-blocked secondary 
amines which are used in the prior process are derived from diethylene 
triamine, and it is desired to be able to use ethylene diamine, which is 
less costly. 
Also, and in our prior application Ser. No. 477,432 filed Mar. 21, 1983 
entitled Oxazolidine-Blocked Amine Polymers, we reacted a monoalkanol 
amine, such as monoethanol amine, with an unhindered ketone or aldehyde, 
and water was removed to generate an oxazolidine which contains a single 
reactive secondary amino hydrogen atom. This product was then adducted 
through its secondary amino hydrogen atom with a polyepoxide resin, 
sufficient oxazolidine being preferably used to consume all of the epoxy 
groups in the polyepoxide. Upon protonation of at least about 50% of the 
amine groups in the adduct (which could be nonvolatile when electrocoating 
was intended) and dispersion in water, hydrolysis of the oxazolidine 
occurs to generate a secondary amine group. The ketone or aldehyde which 
formed the oxazolidine was released into the water. 
It is desired to employ reaction products possessing a relatively high 
amine functionality to enable a good cure to be had with blocked 
polyisocyanates which have lower functionality than typical aminoplast 
resins, like hexamethoxymethyl melamine. Also, primary amine groups are 
more reactive and can be used when polyisocyanates are relied upon, and 
such primary amine groups are not produced in our prior application. It is 
also desirable to increase the molecular weight of the polyepoxide in some 
instances by chain extension, and this is also not available in our prior 
application or in the normal practice of said U.S. Pat. No. 4,031,050. 
DISCLOSURE OF INVENTION 
In this invention, a mono- or poly- alkylene polyamine, and preferably a 
monoalkylene amine like ethylene diamine, is reacted with an unhindered 
ketone, such as cyclohexanone, or an aldehyde, such as formaldehyde, to 
form an imidazolidine containing a plurality of secondary amino hydrogen 
atoms. When the imidazolidine is reacted with an organic polyepoxide one 
forms an adduct reaction product which is dispersible in water when 
protonated with an acid. Using appropriate proportions one obtains chain 
extension to provide a higher molecular weight polyimidazolidine 
containing a plurality of secondary hydroxy groups to enhance water 
dispersibility and tertiary amine groups which enable water dispersibility 
with the aid of an acid. On dispersion in water, the imidazolidine groups 
hydrolyze to release the ketone or aldehyde used in their formation, and 
amino hydrogen atoms are made available for cure. 
The amino hydrogen atoms can all be secondary amino hydrogen atoms, but 
when desired to increase reaction with a polyisocyanate or polyacrylate, 
primary amino hydrogen atoms may be present. One can limit the primary 
amine content when desired, or one can include such groups for greater 
reactivity. 
As will now be evident, the amine polymers of this invention can be cured 
in various ways, the use of organic polyisocyanates being described in 
U.S. Pat. No. 4,031,050 noted previously, or one can employ polyacrylates 
as suggested in U.S. Pat. No. 3,975,251, or one can use aminoplast resins 
or phenoplast resins, as described in our prior application. 
The monoalkylene polyamines and also the polyalkylene polyamines which may 
be used herein are all diprimary amines. The monoalkylene polyamine 
preferably used herein is desirably ethylene diamine, but propylene 
diamine and butylene diamine are also useful. 
The polyalkylene polyamines are illustrated by triethylene tertramine and 
tetraethylene pentamine, but the latter increases the amount of branching 
because it has three secondary amine groups present. Monoalkylene 
polyamines with 2-4 carbon atoms and triethylene tetramine are preferred 
herein. 
The ketones and aldehydes which are selected herein to cause imidazolidine 
production in a reaction involving the removal of water are unhindered. 
Hindered ketones form ketimines with the primary amine group, and these 
are not reactive with epoxy resins. Suitable ketones and aldehydes for use 
herein, in addition to the preferred cyclohexanone, are: formaldehyde, 
acetaldehyde, benzaldehyde, isobutyraldehyde, acetone, methyl ethyl 
ketone, and cyclopentanone. 
In preferred practice, the imidazolidine is formed using cyclohexanone 
which is an unhindered ketone which forms the desired ring structure 
easily. Cyclohexanone is water immiscible and it remains associated with 
the resin particles which are dispersed in the water medium. As a result, 
the cyclohexanone is codeposited with that resin at the cathode. As a 
solvent, the cyclohexanone assists film coalescence, especially as the 
deposited films are baked. This tends to enhance film gloss and to 
minimize film defects, like pinholes. 
The imidazolidines formed herein contain two secondary amine groups, one 
for each primary amine group in the starting diprimary amine. There is 
also present one imidazolidine group for each secondary amine group 
present in the starting diprimary amine. Thus, using ethylene diamine one 
obtains two secondary amine groups, and using triethylene tetramine, one 
obtains two imidazolidine groups and two secondary amine groups. 
The polyepoxides which are used herein should have at least 1.2 epoxy 
groups per molecule, it being preferred to use those polyepoxides having a 
1,2-epoxy equivalency up to about 2.0. Since chain extension may be 
desired, an epoxy equivalency of at least about 1.7 is preferred. It is 
also preferred to employ a polyepoxide having an average molecular weight 
determined by calculation of from 1100 to 2500, though higher and lower 
molecular weights are also useful. 
Diglycidyl ethers of a bisphenol are particularly desirable for use as the 
polyepoxide herein, these being illustrated by the commercially available 
bisphenol A. Especially preferred polyepoxides are diglycidyl ethers 
having a 1,2-epoxy equivalency of from about 1.7 to 2.0. The Shell product 
Epon 829 is particularly preferred, and its molecular weight is increased 
to the preferred range by prereaction with bisphenol A. Epon 1001 will 
further illustrate useful diglycidyl ethers. Polyepoxide mixtures 
containing 10% to 50% of the mixture of a low viscosity polyepoxide, such 
as the Ciba-Geigy product Araldite RD-2 may be present to provide a less 
crystalline polymer product having superior flow on baking. These low 
viscosity polyepoxides are aliphatic diol diepoxides, namely: butane diol 
diglycidyl ether. 
Since electrocoating utility is preferred herein, relatively nonvolatile 
acids, like dimethylol propionic acid, are quite useful. For 
electrocoating, and also for other purposes, volatile acids, like acetic 
acid, can be used. 
Since electrocoating utility is preferred, one should employ enough of the 
imidazolidine reactant to consume all of the epoxy functionality by 
reaction thereof with secondary amine. With a stoichiometric excess of 
epoxy functionality, the final water-dispersed product will have both 
epoxy and amine functionality, and thus it will be unstable and 
self-curing. With more imidazolidine to include an excess of amino 
hydrogen, the final product will include some primary amine groups as a 
result of hydrolysis in the water medium. 
Enough acid is used to enable dispersion in water. Normally this requires 
at least about 50% of the amine groups in the polyimidazolidine reaction 
product to be neutralized, and typically about 60% will be neutralized. 
Complete neutralization is permissible, though this is not desired in 
electrocoating because it decreases the pH of the bath. 
While proportions are not of primary significance in this invention, they 
are helpful in specifying the amounts normally used. On this basis, the 
imidazolidine is formed by reacting substantially stoichiometric amounts 
of diprimary amine with the unhindered ketone or aldehyde (one molar 
proportion for each imidazolidine group to be formed) and the 
imidazolidine is used in an amount to react with at least 10% of the 
1,2-epoxy groups in the polyepoxide. When all the epoxy groups are 
consumed by reaction, the curing agent which is employed and which is 
desirably selected from the group of blocked polyisocyanates, aminoplast 
resins and phenoplast resins of the type which are well known to be useful 
in aqueous medium, is used in an amount of from 5% to 40% of total resin 
solids, preferably from 8% to 25% on the same basis. The electrocoating 
baths which are preferred normally have a resin solids content of from 3% 
to 20%, preferably from 5% to 15%.

Throughout this specification and claims, and in the examples which follow, 
all proportions are by weight, unless otherwise specified. These examples 
show preferred operation to provide an electrocoating system in accordance 
with this invention. They also show the use of preferred materials. 
EXAMPLE 1 
(Procedure for the preparation of the imidazolidine of ethylenediamine and 
cyclohexanone [1,4-diaza spiro(4.5)decane]) 
Benzene (1 liter, 874 g), ethylenediamine (60.1 g, 1.0 equivalent) and 5.0 
g of a sulfonic acid ion exchange resin catalyst providing 0.013 
equivalents of acid (the Dow product Dowex 50W-X12 may be used) were 
charged into a 2000 ml. single neck round bottom flask equipped with a 
Snyder fractionating column, Dean Stark trap, cold finger reflux 
condenser, drying tube, heating mantle, transformer, teflon coated 
magnetic stir bar and a magnetic stir motor. The mixture in the flask was 
heated to reflux temperature to azeotropically remove water formed during 
the reaction. Heating was continued overnight collecting a total of 19.35 
g water (theoretical=18.02 g). The product was then cooled and filtered 
through a glass wool plug followed by concentration on a rotary evaporator 
using aspirator suction and heating to a maximum of 60.degree. C. The 
amine equivalent weight was then determined to be 75.64 g 
(theoretical=70.115 g). The infrared spectrum of the product showed traces 
of residual benzene, cyclohexanone and ketimine by-product and confirmed 
the desired chemical structure. NMR spectroscopy also confirmed the 
desired chemical structure and indicated the presence of less than one 
percent of ketimine. 
EXAMPLE 2 
(Preparation of imidazolidine-functional epoxy resin derivative) 
Epon 829 (122.51 g, 0.6156 equivalent), bisphenol A (54.72 g, 0.4794 
equivalent) and 2-butoxy ethanol (78 g) were placed in a 500 ml. flask 
equipped with stirrer, thermometer, nitrogen inlet, condenser with drying 
tube, and heating mantle. The mixture was heated under a nitrogen blanket 
and held at 170.degree. C. until an epoxy value of 0.534 meq./g sample was 
reached. This took approximately 3 hours. 
The reaction mixture was then cooled to 60.degree. C. and the imidazolidine 
product of Example 1 (17.77 g, 0.2349 equivalent) was rapidly added over a 
period of 3 minutes. The temperature was then slowly increased to 
100.degree. C. and held there until the epoxy value had reached zero, 
which occurred in 3 hours. The product was then cooled to 60.degree. C., 
at which time 26.0 g of methyl ethyl ketone and 26.0 g of isopropanol were 
added. 
EXAMPLE 3 
(Preparation of water dispersion, incorporation of curing agent, and 
electrodeposition and cure) 
The imidazolidine-functional epoxy resin derivative of Example 2 (44.31 g 
of solution, 0.0346 equivalent of secondary amine) was mixed with a 
blocked-isocyanate crosslinking agent (see note 1) in an amount to provide 
1.5 equivalents of isocyanate for each equivalent of primary amine 
functionality which it is expected will be liberated on hydrolysis. This 
mixture was then neutralized to an extent of 60% with acetic acid (1.25 g, 
0.0208 equivalent). The resulting solution was then dispersed in deionized 
water (245 g) using a high speed mixer to yield a solution at 
approximately 12% nonvolatile solids content. 
This solution was then electrodeposited on a steel cathode by the 
application of 50 volts for 90 seconds. The coated steel panel was then 
baked in an oven maintained at 325.degree. F. for 25 minutes. The cured 
film so-provided was 1-2 mils in thickness and resisted 100 methyl ethyl 
ketone double rubs. 
Note 1: Isooctanol-blocked toluene diisocyanate (a mixture of isomers 
mostly constituted by the 2,4-isomer). The material is used in solution 
containing 80% solids in 2-butoxy ethanol solvent. 7.0 grams (0.026 
equivalent) is used in this example.