Cathodic electrocoating binders based on polycondensation products which contain amino groups and which are, at least partially, in the form of their ammonium salts or quaternary ammonium salts. The polycondensation products containing amino groups are obtained by adduct formation of p-hydroxyacetophenone with polymers containing epoxide groups, followed by reaction of these adducts with formaldehyde and a secondary amine. The electrocoating binders of the invention may be used for coating metallic substrates and give coatings which are particularly corrosion-resistant and adhere particularly firmly.

The present invention relates to cathodic electrocoating binders based on 
polycondensation products which contain amino groups and which are, at 
least partially, in the form of their ammonium salts or quaternary 
ammonium salts. 
Cathodic electrocoating binders are already known and have been described 
in a number of patents. 
The corrosion protection afforded by coatings produced from aqueous coating 
compositions is essentially limited by hydrophilic groups which remain in 
the binders even after baking. 
It is an object of the present invention to provide cathodic electrocoating 
binders which give particularly advantageous baked finishes and which 
provide improved corrosion protection. 
We have found that this object is achieved, according to the invention, if 
the polycondensates used as binders contain .beta.-aminoketone groups. 
The present invention relates to cathodic electrocoating binders based on 
polycondensation products which contain amino groups and which, at least 
partially, are in the form of their ammonium salts or quaternary ammonium 
salts, wherein the polycondensation products containing amino groups have 
been obtained by adduct formation of p-hydroxyacetophenone with polymers 
containing epoxide groups, followed by reaction of these adducts with 
formaldehyde and a secondary amine. 
Preferred cathodic electrocoating binders according to the invention are 
those where the polycondensation products containing amino groups have a 
nitrogen content of from 0.1 to 15 percent by weight. 
Combinations of the surface-coating binders of the invention with 
aminoplast resins, phenoplast resins, epoxy resins or modified resins of 
these types are also preferred. 
Polymers with .beta.-aminoketone groups have already been described in 
another context. For example, German Published Application DAS No. 
1,023,583 discloses the preparation, by free radical chain polymerization, 
of crosslinked polymers with aminoketone groups, which contain the 
nitrogen in a quaternary form. These polymers are used as ion exchangers. 
They cannot be used for surface-coating purposes since they are insoluble. 
Japanese Pat. No. 9,129,539 discloses copolymers with aminoketone groups, 
prepared using free radical initiators, which are used for the manufacture 
of electrophotographic developers. 
Polystyrenes with aminoketone groups in the p-position are disclosed in 
Chemical Abstracts 72, 89971 Z and 69, 78078a. 
However, none of these publications discloses polycondensation products, 
containing .beta.-aminoketone groups, which can be used as aqueous 
surface-coating binders. 
Polymeric .beta.-amino-esters, as described, for example, in German Pat. 
No. 2,223,241, are also unsuitable for use as cathodic electrocoating 
binders, since they are insufficiently stable in aqueous solution and 
since, on aging of the electrocoating baths, the coating in part begins to 
deposit on the anode instead of on the cathode. 
In contrast, the cathodic electrocoating binders according to the present 
invention give stable electrocoating baths which conform to requirements 
even on aging. 
A particular advantage of the binders according to the invention is that 
the baked finishes obtained therewith provide excellent corrosion 
protection. On thermal curing of the finish, the hydrophilic groups of the 
binder are eliminated and hydrophobic coatings which cannot be attacked by 
aqueous agents are obtained. 
The polycondensation products, containing .beta.-aminoketone groups, of the 
invention are prepared by adduct formation of p-hydroxyacetophenone with 
polymers containing epoxide groups, followed by reaction with formaldehyde 
and a secondary amine. 
Suitable polymers with epoxide groups for the preparation of the novel 
binders are glycidyl ethers of polyhydric alcohols and phenols, eg. 
glycidyl ethers of glycol, polyethylene glycols, propylene glycol, 
polypropylene glycols, 1,4-butylene glycol, 1,5-pentanediol, 
1,6-hexanediol, 1,3,6-hexanetriol, glycerol, pentaerythritol, 
bis-(4-hydroxyphenyl)-2,2-propane, 4,4'-dihydroxybenzophenone, 
bis-(2-hydroxynaphthyl)-methane, 1,5-hydroxynaphthalene and 
bis-(4-hydroxyphenyl)-1,1-isobutane. 
Commercially available polymeric epoxy resins based on 
2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin are particularly 
suitable. 
Epoxy resins of the type of glycidyl isocyanurate, for example triglycidyl 
isocyanurate, are also suitable. 
p-Hydroxyacetophenone is generally reacted with the polymers containing 
epoxide groups in a molar ratio of from 0.5:1 to 1:1 
(p-hydroxyacetophenone:epoxide group), preferably 1:1. 
Particularly suitable secondary amines are aliphatic amines, eg. 
dimethylamine, methylethylamine, diethylamine and the like. Aliphatic 
amines which carry no further functional groups are preferred. The 
reaction can very easily also be carried out with amines which carry 
functional groups but as a rule this does not offer any advantages in the 
present process. In some cases, the improved solubility or dispersibility 
of the reaction products in water, achieved by the presence of OH groups, 
may be desirable. 
Formaldehyde is either used as such, with or without dissolution in water 
or a lower alcohol, eg. in n-butanol, or in the form of formaldehyde 
donors, eg. paraformaldehyde. 
In general, the secondary amine and formaldehyde are reacted with the 
adduct of p-hydroxyacetophenone plus polymer containing epoxide groups in 
a molar ratio of from 0.5 to 1, preferably about 1, mole of secondary 
amine and from 0.5 to 1.2, preferably about 1, mole of formaldehyde per 
mole of the p-hydroxyacetophenone contained in the adduct. 
The content of .beta.-aminoketone groups in the binder according to the 
invention can vary within wide limits, for example within limits which 
correspond to a nitrogen content of the polymer or polycondensate of from 
0.1 to 15, preferably from 0.5 to 10, especially from 1 to 5, percent by 
weight, based on the polycondensate. 
Examples of preferred surface-coating binders according to the invention 
are reaction products based on epoxy resins or epoxy resin derivatives 
obtained by reaction of epoxy resins with p-hydroxyacetophenone, 
formaldehyde and secondary amines. 
The polymeric bases containing .beta.-aminoketone groups can be rendered 
dilutable with water, or genuinely water-soluble, by partial or complete 
neutralization with inorganic or organic acids or by quaternization, for 
example as described in German Published Application DAS No. 1,023,583. A 
preferred form of quaternization comprises reaction with an epoxide, for 
example by such methods as those described in German Published Application 
DAS No. 1,023,583, or with ethylene oxide, propylene oxide, butylene 
oxide, glycidol or higher molecular weight monoepoxides, such as are 
obtained from diepoxides or polyepoxides by partial blocking of epoxide 
groups by adduct formation with a proton-active compound (eg. phenol, or a 
mercaptan, amine or acid). 
Suitable reactants for neutralization or partial neutralization of the 
.beta.-aminoketone polycondensates are inorganic acids, eg. phosphoric 
acid, boric acid, sulfuric acid or hydrogen chloride, or, preferably, 
organic acids, eg. formic acid, acetic acid, propionic acid, butyric acid 
or lactic acid. 
The binders of the invention may be used for the manufacture of aqueous 
baking finishes, especially for cathodic electrocoating compositions. On 
baking at 140.degree. C. or above, the binder loses the hydrophilic 
character attributable to the basic groups. The coatings obtained from 
such binders afford improved corrosion protection, and the binder is more 
easily crosslinkable, if the crosslinking takes place by acid catalysis. 
The binders according to the invention may be crosslinkable by extraneous 
molecules, or self-crosslinkable. Crosslinking may take place via amide, 
methylol, methylol-ether, methyleneamimo, or hydroxyl groups and the like, 
which are present in the polymeric binders. Crosslinking agents capable of 
reacting with the reactive groups of the polymeric binder are especially 
aminoplast resins, phenoplast resins and blocked isocyanates. 
In order to modify certain technical properties, such as the 
rinse-resistance of the wet coating, the throwing power or the pigment 
wetting, further binders may be incorporated in the composition, eg. 
polyesters, alkyd resins, cellulose derivatives, drying or non-drying 
oils, natural resins, eg. unmodified or modified rosin, and synthetic 
copolymers with or without reactive groups. 
Organic solvents, eg. alcohols, including higher alcohols, esters, ketones 
and aromatics, may also be present in minor amounts, in order to improve 
the deposition characteristics, and the surface quality, of 
electrophoretically deposited films. 
The aqueous solutions or dispersions of the polycondensation products of 
the invention, which are at least partially in the form of salts, may 
contain other auxiliaries which can be deposited electrophoretically as a 
mixture with the polycondensates, eg. pigments, soluble dyes, high-boiling 
solvents, stabilizers, anti-foam agents and other auxiliaries and 
adjuvants. 
The electrophoretic deposition takes place from an aqueous medium, at a 
cathode. Advantageously, the coating composition is diluted with water or 
a water/solvent mixture to a solids content of from 8 to 20 percent by 
weight. The deposition voltages may range from a few volt to several 
thousand volt, but are as a rule from 100 to 600 volt. After rinsing the 
film deposited on the electrically conductive cathode, baking of the film 
takes place at from about 140.degree. to 190.degree. C. for from 10 to 30 
minutes. 
The coating compositions of the invention give coatings which afford 
excellent corrosion protection and exhibit excellent adhesion both on 
iron-phosphatized or zinc-phosphatized, and on untreated, metallic 
substrates. The particular advantage of the novel binders over 
conventional binders is that on crosslinking the surface-coating films 
harden thoroughly, with methylol, methylol-ether, OH and COOH groups being 
involved, at relatively low baking temperatures. In contrast, hardening of 
conventional cationic surface-coating binders frequently requires very 
high temperatures and relatively long baking times. 
In the Examples, parts and percentages are by weight, unless stated 
otherwise.

EXAMPLE 1 
760 parts of an epoxy resin which has been obtained by reacting 
2,2-bis-(4-hydroxyphenyl)-propane with epichlorohydrin and has an epoxide 
value (moles of epoxide/100 g of resin) of 0.53 are reacted with 544 parts 
of 4-hydroxy-acetophenone at 175.degree. C. The melt of the reaction 
product is discharged onto a cooling belt. When it has cooled, the solid 
resin is milled (reaction product (I). 
326 parts of this powder, 44 parts of dimethylamine, 33 parts of 
p-formaldehyde and 60 parts of glacial acetic acid are stirred at 
80.degree. C. until the resultingproduct has become water-soluble. 
10 parts of the resulting reaction product and 3 parts of a water-insoluble 
phenoplast resin for crosslinking of baking finishes are homogeneously 
dissolved by addition of 4 parts of ethyl glycol, and the solution is 
ddispersed in water. A 10% strength dispersion of the binder mixture is 
introduced into anelectrocoating cell and a film is cathodically deposited 
on a zinc-phosphatized bodywork panel by applying a deposition voltage of 
350 volt for 120 seconds. After baking for 30 minutes at 170.degree. C., 
the film was 17 .mu.m thick and had a hardness of 6 H. It was resistant to 
organic solvents and to aqueous alkali. 
EXAMPLE 2 
326 parts of reaction product I, 44 parts of dimethylamine, 33 parts of 
p-formaldehyde and 30 parts of glacial acetic acid are stirred at from 
75.degree. to 85.degree. C. until the mixture has become water-soluble. 90 
parts of water are then added and ethylene oxide is forced into a pressure 
vessel containing the mixture. 36 parts of ethylene oxide are taken up by 
the reaction mixture. 100 parts of a phenoplast resin conventionally used 
for baking finishes, 150 parts of butyl glycol and 30 parts of a 
polybutadiene oil are then added, after which the mixture is diluted with 
water to give a 10% strength surface-coating dispersion. 
A bodywork panel treated with iron phosphate was cathodically coated in 
this dispersion for 2 minutes at a voltage of 350 V. 
The film was then rinsed with a vigorous jet of demineralized water and 
baked for 30 minutes at 170.degree. C. No detachment of the film occurred 
on rinsing, and the baked film was free from water spotting. The coating 
was 18 .mu.m thick and adhered very firmly to the substrate. It provided 
very good corrosion protection both in the salt spray test according to 
ASTM B 117-64 and in various test arrangements for examining the filiform 
corrosion and scab corrosion. 
EXAMPLE 3 
A non-pretreated bodywork panel was cathodically electrocoated in the 
surface-coating dispersion described in Example 2, for 2 minutes at a 
voltage of 350 volt. The film was then rinsed with demineralized water as 
described in Example 2, and baked for 30 minutes at 170.degree. C. 
There is very little difference between the thickness of this coating and 
the surface-coating on iron-phosphatized panel; the coating is 20.5 .mu.m 
thick. 
Welds are also coated very uniformly compared to the surrounding zone, 
without frothing and blistering.