Electrophoretic coating process

A coating process in which an article to be coated is immersed as an anode in a dispersion of a film-forming material stabilized by non-ionic stabilization and an electric current is passed between the anode and another electrode immersed in the dispersion. The dispersion is destabilized in the region of and is deposited on the anode by interaction between a moiety providing the non-ionic stabilization (e.g. of polyethylene glycol) and a further interactive moiety (e.g. carboxyl groups present in polymethacrylic acid) present in the dispersion. Suitable coating compositions and coated articles are defined.

This invention relates to a coating process and to coating compositions 
useful in the process. 
It is known that certain aqueous dispersions of film-forming materials 
which contain or are associated with ionisable groups can be employed to 
deposit a coating either at an anode or at a cathode in an electrical 
circuit when an electrical current is passed between suitable electrodes, 
as the anode and the cathode of the circuit, which are immersed in the 
dispersion. Usually the film-forming materials contain ionisable groups 
within their structure, for example carboxyl groups or amino groups, which 
are primarily responsible for the stability of the dispersion; but 
alternatively the ionisable groups may be present in an external 
surfactant which is associated with the film-forming material and which is 
present in order to stabilise the aqueous dispersion. Thus in each of 
these cases the stability of the dispersion is determined primarily by the 
presence of ionisable groups in their ionised form. 
We have now found that certain aqueous dispersions of film-forming 
materials may be deposited as a coating at the anode of an electrical 
circuit when the film-forming material is stabilised in an aqueous medium 
by non-ionic stabilisation and does not contain any ionic charges or does 
not contain and/or is not associated with such a proportion of ionic 
charges as will determine primarily the stability of the dispersion. 
According to this invention we provide a process of coating an electrically 
conductive substrate with a film-forming material wherein the substrate is 
immersed as an anode in a dispersion of the film-forming material in an 
aqueous medium and an electrical current is passed between the anodic 
substrate and a counter-electrode in electrical contact with the 
dispersion for a sufficient period of time to form a coating of desired 
thickness, characterised in that: 
(a) the film-forming material is stabilised in the aqueous medium at a pH 
of greater than 3.9 by non-ionic stabilisation as herein defined, 
(b) the film-forming material is free from ionic charges or contains and/or 
is associated with only an amount of ionic charges such as will not alone 
primarily determine the stability of the dispersion, and 
(c) the dispersion also contains a chemical moiety, which is present in a 
further material constituent of the dispersion and/or in the film-forming 
material, which moiety is interactive with a hydrophilic non-ionic 
chemical moiety providing the non-ionic stabilisation of the dispersion of 
film-forming material, the interaction between the moieties causing 
destabilisation and flocculation or precipitation of the dispersed 
film-forming material at a pH of 3.9 or less as herein defined. 
By a dispersion of film-forming material in aqueous medium we mean that the 
material can be present, for example, as a colloidal dispersion of solid 
or liquid particles, as a solution or as an aggregate or association of 
polymer molecules or a micellar solution or an emulsion. 
By a film-forming material which is free from ionic charges or which 
contains and/or is associated with only an amount of ionic charges such as 
will not alone primarily determine the stability of the dispersion, we 
mean that these charges alone would not produce a stable dispersion of the 
film-forming material in the given aqueous medium at a pH of greater than 
3.9 when the non-ionic stabilisation is absent. Conversely a stable 
dispersion for use in the invention would remain stable even in the 
absence of the ionic charges. We use the term `stable dispersion` to mean 
that the dispersion must be sufficiently stable to enable its use as a 
coating composition in a coating process. 
By non-ionic stabilisation of the film-forming material we mean that the 
stabilisation of the material in the given aqueous medium is primarily due 
to the presence of non-ionic surface-active constituents of the dispersion 
which comprise a non-ionic hydrophilic moiety. The non-ionic hydrophilic 
moiety may be present in the structure of the film-forming material and/or 
it may be present in a distinct surface-active constituent of the 
dispersion which is associated with the film-forming material. Preferably 
the hydrophilic non-ionic moiety is polymeric. 
By an aqueous medium we mean water or a mixture of water and at least one 
other liquid miscible with water. Preferably there is present at least 20% 
by weight of water and more preferably at least 50% by weight of water. 
Suitable water-miscible liquids include alcohols, glycols, polyols and 
ketones. Inorganic salts may also be present in the aqueous medium. 
The chemical moiety interactive with a hydrophilic non-ionic moiety 
providing the non-ionic stabilisation of the dispersion of the 
film-forming material, so as to cause destabilisation and flocculation or 
precipitation of the dispersed film-forming material at a pH of 3.9 or 
less, is preferably contained in a further material constituent of the 
aqueous dispersion. The further material constituent of the dispersant may 
be polymeric. Preferably the further material constituent is soluble in 
the aqueous medium. There may be present in the dispersion more than one 
dispersed film-forming material. In such a case one of the film-forming 
materials may contain a chemical moiety interactive with a hydrophilic 
non-ionic moiety contained in the other film-forming material, the 
stabilisation of the other dispersed film-forming material being provided 
by the hydrophilic non-ionic moiety. 
Preferably the dispersed film-forming material stabilised by non-ionic 
stabilisation is associated with a plurality of non-ionic hydrophilic 
moieties. Preferably the further material constituent of the dispersion 
contains a plurality of chemical moieties interactive with the non-ionic 
hydrophilic groups associated with the film-forming material so as to 
cause destabilisation of the dispersion of film-forming material. 
Whether or not a given dispersion of film-forming material, stabilised in 
the aqueous medium by non-ionic stabilisation and stable at a pH of 
greater than 3.9, and a given material constituent of the dispersion 
containing groups interactive with the hydrophilic non-ionic moieties 
(associated with the film-forming material) are a useful combination in 
the invention, can be determined as follows: 
The selection of materials containing chemical moieties interactive with 
appropriate hydrophilic non-ionic moieties providing non-ionic 
stabilisation for the film-forming material are discussed below. To 
confirm the suitability and the proportion of a selected material there is 
first added to the dispersion of film-forming material, at a pH of greater 
than 3.9, quantities of the selected material to give compositions of 
desired concentration. The compositions are then titrated with dilute 
hydrochloric acid or other mineral acid to pH 2 and any composition that 
is flocculated or precipitated by the change in pH is suitable for use in 
this invention. When the interactive moieties are both contained in the 
film-forming material the titration is carried out on the dispersion 
alone. If the reduction of pH leads to destabilisation and flocculation or 
precipitation the dispersion contains sufficient interactive moieties for 
deposition by the method of the invention. 
In order to ensure that any selected material containing chemical moieties 
interactive with the non-ionic hydrophilic moieties is not by itself 
destabilised and precipitated or flocculated under the process conditions, 
the above titration should also be carried out on an aqueous dispersion of 
that material at the same concentration as is to be used in the deposition 
process. 
Although the stability of the dispersed film-forming material in aqueous 
medium at a pH of greater than 3.9 is due primarily to non-ionic 
stabilisation, the film-forming material and/or other constituents of the 
dispersion may contain a small proportion of ionic charges provided that 
this proportion does not primarily determine the stability of the 
dispersed constituents and does not interfere with non-ionic 
stabilisation. Thus the film-forming material may comprise, for example, a 
small proportion of ionisable groups such as carboxyl, sulphonic or 
sulphato groups. In general it is preferred, when there may be carboxyl 
groups present in the film-forming material, that the acid value of the 
film-forming material is less than 20 mg KOH/g, more preferably less than 
10 mg KOH/g and still more preferably less than 5 mg KOH/g. Preferably the 
film-forming material is substantially free from ionic charges. Although 
the dispersion of film-forming material in aqueous medium must be stable 
at a pH greater than 3.9 it is preferable that it is stable at a pH 
greater than 5. 
Non-ionic hydrophilic moieties which may be present in the structure of the 
film-forming material or in a non-ionic surfactant associated with the 
film-forming material include moieties derived from poly(ethylene glycol), 
also referred to as polymers of ethylene oxide; copolymers of ethylene 
oxide, eg. poly(ethylene oxide)/poly (propylene oxide) copolymers; 
partially or completely hydrolised polymers of vinyl acetate, eg. 
poly(vinyl alcohol); poly(vinyl pyrrolidone and poly(meth)acrylamide, all 
of which moieties are solvatable by water. These materials, of course, may 
be useful non-ionic surfactants in their own right. 
Suitable film-forming materials useful in the invention include natural 
oils, modified natural oils and synthetic oils such as linseed oil, 
linseed stand oil, paraffin oil; synthetic resins such as alkyd resins, 
oil-modified alkyd resins, polyurethane resins, epoxy resins, resins based 
on addition polymers (eg. polymers or copolymers of styrene such as 
styrene/butadiene, petroleum resins (eg. poly(isobutylene)), nitrogen 
resins (such as melamine/formaldehyde & urea/formaldehyde), and phenolic 
resins. 
Preferably the dispersion in aqueous medium to be used in the process of 
the invention comprises at least 4% by weight of film-forming material and 
more preferably the dispersion comprises at least 10% by weight of 
film-forming material. 
When a non-ionic hydrophilic moiety is desired to be present in the 
structure of the film-forming material for example a moiety derived from 
poly(ethylene glycol) or poly (vinyl alcohol) it may be introduced by 
conventional methods, for example by esterification, by etherification, or 
by block or graft polymerisation. In one example, moieties of 
poly(ethylene glycol) may be introduced into a carboxyl group-containing 
alkyd resin by esterification of the alkyd resin with poly(ethylene 
glycol). Usually it will be necessary for the film-forming material to 
contain at least 1% of the non-ionic hydrophilic moieties to effect a 
stable dispersion. 
When a non-ionic hydrophilic moiety providing the non-ionic stabilisation 
of the dispersion of the film-forming material is present in a distinct 
surface-active component of the dispersion which is associated with the 
film-forming material, the surface-active material will normally comprise 
one or more such non-ionic hydrophilic moieties. Suitable non-ionic 
hydrophilic moieties are derived from, or the surface-active component 
itself may be, poly(ethylene glycol) (for example in a polymer prepared by 
reaction with hydroxystearic acid), poly(vinyl alcohol), a hydroxy 
cellulose, or other polyol. Other suitable dispersions of film-forming 
polymer stabilised in an aqueous medium by non-ionic stabilisation which 
are suitable in the invention may be prepared as described in our 
co-pending British patent application No. 7940088 filed 20th November 
1979. 
In our British patent application No. 7940088 is described a process for 
the production of a sterically stabilised dispersion of polymer particles 
of a size in the range 0.1 to 10 microns in an aqueous medium, the process 
comprising the free radical-initiated polymerisation in the aqueous medium 
of one or more ethylenically unsaturated monomers at a temperature which 
is at least 10.degree. higher than the glass transition temperature as 
hereinbefore defined of the polymer which is formed, in the presence in 
the aqueous medium as steric stabiliser of a block or graft copolymer 
which contains in the molecule a polymeric component of one type which is 
solvatable by the aqueous medium and a polymeric component of another type 
which is not solvatable by the aqueous medium and is capable of becoming 
associated with the polymer particles formed, the aqueous medium being a 
mixture comprising (a) at least 30% by weight of water and (b) not more 
than 70% by weight of a second constituent which is miscible with water, 
the nature and proportion of the second constituent being such that the 
mixture as a whole is capable of dissolving the monomer or monomers being 
polymerised to the extent of at least 3% by weight but is a non-solvent 
for the polymer formed, the concentration of free monomer in the 
polymerisation mixture being maintained throughout the process at a level 
such that at no time does the free monomer form a separate phase and the 
total amount of monomer polymerised being such that the resulting 
dispersion contains at least 20% by weight of polymer. 
Preferably there is present in the dispersion at least 0.1% by weight based 
on the film-forming material of a distinct surface-active constituent when 
this constituent is responsible for the stability of the dispersion of 
film-forming polymer. 
Chemical moieties which are interactive at a pH of 3.9 or less with 
specific hydrophilic non-ionic chemical moieties comprising the non-ionic 
stabilisation of a dispersion of film-forming material will be known to 
those skilled in the art. Particularly suitable such chemical moieties in 
the present invention are carboxyl groups, and carboxyl groups are 
interactive at a pH of less than 3.9 with hydrophilic non-ionic moieties 
such as those derived from poly(ethylene glycol) or poly(vinyl alcohol). 
Carboxyl groups may be present in a film-forming polymer to be deposited 
at an anode by the present process provided that they are not in such a 
proportion as will determine primarily the stability of the polymer in an 
aqueous medium. Preferably the carboxyl groups are present in a further 
material component of the dispersion which is preferably soluble in the 
aqueous medium. Preferably the carboxyl groups are present in a polymer. 
Suitable carboxyl group-containing polymers include polyacrylic acid; 
polymethacrylic acid; copolymers of acrylic acid and/or methacrylic acid 
with copolymerisable monomers such as lower alkyl esters and amides of 
(meth)acrylic acid, polymers and copolymers of itaconic acid, maleic acid 
and crotonic acid. Suitable non-polymeric carboxyl group-containing 
materials include lauric acid. 
The present process is applicable to any substrate which is a conductor of 
electricity. Suitable substrates include ferriferous substrates, for 
example iron, steel, phosphated steel; zinciferous substrates, for example 
galvanised steel; aluminium; copper; and carbon. 
In practising the process of the present invention there is employed, 
according to a further aspect of the invention, a stable dispersion of a 
film-forming material in an aqueous medium at a pH greater than 3.9, 
preferably at a pH greater than 5 and more preferably at a pH in the range 
6-9, wherein the film-forming material is stabilised by non-ionic 
stabilisation as herein defined which comprises a non-ionic hydrophilic 
moiety, there being also present in the dispersion chemical moieties which 
are contained in a further material constituent of the dispersion and/or 
in the structure of the film-forming material which are interactive with 
the non-ionic hydrophilic moiety to cause instability of the dispersion at 
a pH of 3.9 or less. The preparation of such stable dispersions will be 
well understood by those skilled in the art. 
The substrate to be coated is immersed as an anode in the dispersion and 
electrical current is passed for a suitable period of time and under such 
conditions as will provide a desired thickness and type of coating. The 
thickness of the coating may be controlled, for example, by the quantity 
of electricity passed; the concentration of film-forming polymer; and the 
concentration of hydrophilic non-ionic moieties and of the interactive 
moieties. A wide range of electrical conditions may be employed. The 
coated substrate may be rinsed and subsequently dried and heated to an 
elevated temperature. 
The stable dispersions may contain other ingredients, not already 
mentioned, which are used in the art of coating, for example pigments, 
fillers, anti-corrosive agents, cross-linking agents and other 
polymer-modifying materials. The process may be made continuous by passing 
a series of substrates to be coated through a bath containing the stable 
dispersion described above, and replenishing the bath ingredients as they 
are consumed by a suitable replenishment concentrate similar in 
composition to that of the dispersion described above. 
The invention is illustrated by the following Examples in which parts and 
percentages are by weight unless otherwise stated.

EXAMPLE 1 
This Example illustrates the deposition of a coating of paraffin oil on 
steel and aluminium anodes, using an emulsion of paraffin oil stabilised 
by a non-ionic surfactant. 
100 parts of a paraffin oil (commercially obtainable as "liquid paraffin") 
were emulsified in 500 parts of distilled water in the presence of 5 parts 
of a polymer prepared by condensing 62 parts of polyethylene glycol of 
molecular weight 4000 with 38 parts of hydroxystearic acid. 
(a) To the emulsion was added 1 part of a 16% solution of a polymethacrylic 
acid in water. The polymethacrylic acid had been made by polymerising a 
solution of 16 parts of methacrylic acid in 100 parts of water in the 
presence of ammonia and ammonium persulphate as initiator. Aqueous ammonia 
was added to produce a pH 9 in the emulsion and an electrical current was 
passed between a steel anode and a counter electrode immersed in the 
emulsion at 100 volts for 3 minutes. An even adherent coating of paraffin 
oil was obtained on the steel anode. 
(b) When 0.1 part of the 16% solution of polymethacrylic acid used above 
was added to another sample of the emulsion at pH 6 an even adherent 
coating of paraffin oil was obtained on an aluminium anode at 100 volts 
over 3 minutes. A similar result was obtained when aqueous ammonia had 
been added to the emulsion to give a pH of 9. 
EXAMPLE 2 
This Example illustrates the importance of the presence of both a suitable 
carboxyl group-containing material and a suitable interactive non-ionic 
hydrophilic moiety in a surface active material associated with a film 
forming material free from carboxyl groups in order to perform the present 
invention with paraffin oil. 
(a) 100 parts of paraffin oil were emulsified in 400 parts of distilled 
water in the presence of a polyvinyl alcohol (commercially obtainable as 
"Gohsenol" GH17 from British Traders and Shippers), 0.25 part of the 16% 
solution of polymethacrylic acid prepared in Example 1 (concentration of 
polymethacrylic acid) were added to the emulsion. The pH of the stable 
emulsion was adjusted to 6. A heavy coating of paraffin oil was obtained 
on an aluminium anode immersed in the emulsion by passing an electrical 
current between the anode and a counter-electrode at 180 volts for 3 
minutes. 
(b) 0.25 part of the 16% polymethacrylic acid solution made in Example 1 
was dissolved in 400 parts of distilled water, the pH of the solution 
being 6, and an electrical current was passed at 180 volts for 3 minutes 
between an aluminium anode and a counter-electrode immersed in the 
solution. There was no visible adherent coating on the anode. 
(c) Paraffin oil could not be emulsified in water in the presence of only 
polymethacrylic acid. 
(d) An emulsion of pH 7 in range 6-7 was prepared as in (a) but the 
polymethacrylic acid was omitted. No visible adherent coating was observed 
on an aluninium anode when an electrical current was passed at 180 volts 
for 3 minutes. 
EXAMPLE 3 
This Example illustrates the deposition of linseed oil on an aluminium 
substrate. 
(a) 100 parts of linseed oil were emulsified in 400 parts of distilled 
water in the presence of 2 parts of the polyethylene glycol/hydroxystearic 
acid condensation polymer used in Example 1. 2 parts of a 5% solution of a 
polymethacrylic acid (as made in Example 1) were added to the emulsion and 
the pH adjusted to 9. An adherent coating of linseed oil was obtained on 
an aluminium panel as anode when an electrical current was passed between 
the panel and a counter-electrode for 3 minutes at 210 volts. (Initial 
deposition current was 0.8 amps falling to 0.05 amps at the end of the 3 
minutes). 
(b) An emulsion of 2 parts linseed oil in 400 parts distilled water was 
prepared in the presence of 2 parts Gohsenol GH17 (see Example 2) 2 parts 
of a 6% polymethacrylic acid solution in water was added and an adherent 
coating film was deposited on an aluminium anode at 240 volts over 3 
minutes (Initial current 0.85 amps; final current 0.09 amps). 
EXAMPLE 4 
This Example illustrates the deposition of linseed stand oil on various 
substrates. 
(a) An emulsion of 100 parts linseed stand oil of viscosity 5 poise was 
prepared in 400 parts distilled water in the presence of 5 parts of the 
polyethylene glycol/hydroxystearic acid condensation polymer of Example 1. 
2 parts of a 6% solution of polymethacrylic acid (made as in Example 1) 
were added to the emulsion followed by ammonia to give a pH of 7. An 
adherent film of linseed stand oil was deposited on an anode of phosphated 
steel when electric current was passed at 240 volts over 3 minutes. 
(b) A similar result to that obtained in (a) was also obtained when the 
anode was of aluminium. 
(c) A similar result to that obtained in (a) was also obtained when the 
anode was of carbon. 
(d) A similar result to that obtained in (a) was also obtained when the 
polymethacrylic acid was replaced by an equimolar proportion of 
polyacrylic acid. 
EXAMPLE 5 
This Example illustrates the use of (a) a methacrylic acid copolymer and 
(b) a maleic anhydride copolymer as the carboxyl group-containing 
material. 
(a) To the emulsion described in Example 4(a) was added 1 part of a 3% 
aqueous solution of Rohagit SLV (a 35/65 copolymer of methyl 
methacrylate/methacrylic acid commercially available from Rohm & Haas) 
instead of the polymethacrylic acid to give an emulsion of pH 9. A 
phosphated steel anode was coated with an adherent coating of linseed 
stand oil when an electrical current was passed. 
(b) To the emulsion described in Example 4(a) was added 1 part of a 20% 
aqueous solution of a styrene-maleic anhydride copolymer instead of the 
polymethacrylic acid to give an emulsion of pH 9. A phosphated steel anode 
was coated with an adherent coating of linseed stand oil when an 
electrical current was passed. 
EXAMPLE 6 
This Example illustrates the deposition of an unsaturated alkyd resin at 
various types of anode and the effect of including a metal drier salt, 
pigment and cross-linking agent. 
(a) 100 parts of an alkyd resin prepared from the ingredients 
pentaerythritol/glycerol/polyethylene glycol of a molecular weight 
600/tall oil fatty acids/trimellitic anhydride=1/1/2/5/2 molar were 
emulsified in 400 parts of distilled water in the presence of the 
condensation polymer described in Example 1(a). To the emulsion was added 
1 part of 6% solution of polymethacrylic acid, the emulsion pH being 6. A 
steel panel (6".times.2") as anode was coated with alkyd resin when an 
electric current was passed for 3 minutes at 140 volts with resin. The 
initial current was 0.5 amps and the final current was 0.02 amps, 18 
coulombs of current having been passed. 
(b) In a similar experiment to (a) 1 part of a 6% solution of lead 
naphthenate in white spirit was emulsified together with the alkyd resin. 
The coated steel panel produced after passing the electric current was 
rinsed and left to dry. 
(c) A similar result to that obtained in (a) was achieved when using an 
aluminium anode. 
(d) A similar result to that obtained in (a) was achieved when using a 
carbon anode. 
EXAMPLE 7 
This Example illustrates the effect of a material comprising interactive 
moieties, in aiding destabilisation of a sterically stabilised 
film-forming material. 
A dispersion in aqueous medium of an addition polymer comprising 
styrene/methyl methacrylate/hydroxypropyl methacrylate/n-butoxy 
acrylamide=1/1/1/1, stabilised by a surfactant comprising a moiety of 
poly(ethylene glycol) of molecular weight 2000, and prepared as described 
in our pending British patent application No. 7940088 filed 20th Nov. 
1979, was diluted with distilled water to give 20% non-volatile material 
in dispersion. 800 parts of the above dispersion was divided into two 
equal portions, A and B. 
A. 
1. To 400 parts sample A 8 parts of a 16% by weight solution of 
polymethacrylic acid solution (prepared as in Example 1) were added. The 
polymer dispersion remained stable at pH 3.9. 
2. 20 g of sample A1 were further acidified with HCl to a pH 2. 
Flocculation of the dispersion occurred. 
3. A steel panel was immersed as an anode in a sample of A1. When electric 
current was passed between the steel panel and a counter-electrode at 200 
volts a thick, heavy coat of the dispersed polymer deposited after 1 
minute. 
B. 
1. 20 g of portion B were acidified with HCl to pH 2. The polymer 
dispersion remained stable, no precipitation taking place. 
2. On immersing a steel panel as an anode in sample B1 and passing 
electrical current at 200 volts for 1 minute no deposition at the anode 
was observed. 
EXAMPLE 8 
A white non-ionically-stabilised paint was prepared comprising: 
______________________________________ 
Titanium dioxide 72 parts ground 
Polyethylene glycol 
9.2 parts to form 
(PEG)-containing alkyd* a mill- 
base A 
White spirit 18.8 parts 
______________________________________ 
*(described in Example 6). 
To 63 parts of millbase `A` were added: 88 parts PEG-alkyd, 30 parts of a 
commercially available melamine/formaldehyde resin and 2 parts of the 
polyethylene glycol/12-hydroxystearic acid polymer used in Example 1, to 
produce a white paint `B`. 
To 183 parts of paint `B` were added 400 g of distilled water containing 1 
g of a 6% polymethacrylic acid solution in water. The pH was adjusted to 
6. 
The mixture was emulsified by mechanical agitation using a "silverson" 
homogeniser. 
The above emulsion was electrodeposited in a conventional apparatus using a 
steel panel as anode. 
6.5 g of dry paint (after stoving for 1/2 hour at 180.degree. C.) were 
found to have been deposited by 22 coulombs of electricity at an applied 
voltage of 140 V. 
EXAMPLE 9 
A dispersion in an aqueous medium of a 60/40 methyl 
methacrylate/2-ethylhexyl acrylate copolymer was prepared by the procedure 
of our copending British patent application No. 7940088 filed 20th Nov. 
1979, and in a similar manner to the dispersion of Example 7 except that 
the moiety of poly(ethylene glycol) was replaced by a moiety of poly(vinyl 
pyrrolidone) of molecular weight 1600. To 50 parts of the dispersion (60% 
non-volatile solids) was added 364 parts of distilled water and 1.5 parts 
of poly(methacrylic acid) (8% non-volatile solids solution in water) and 
the pH adjusted to 7.2. An adherent film of the copolymer was obtained on 
a steel panel as anode after passing electric current for 2 minutes at 100 
volts. 
EXAMPLE 10 
The epoxy groups of an epoxy resin commercially available as "Epikote" 1004 
were substantially hydrolysed in the presence of acid and the resulting 
hydroxyl groups were ethoxylated using ethylene oxide to give a 
poly(ethylene oxide) content of 70%. 20 parts of the thus ethoxylated 
epoxy resin were mixed with 50 parts of another epoxy resin commercially 
available as "Epikote" 828. The resin mixture was emulsified in 270 parts 
of distilled water, and 1.5 parts of an 8% aqueous solution of 
poly(methacrylic acid) in ammoniacal water were added, the pH being 7.3. A 
coating was deposited on a steel anode by passing electric current for 2 
minutes at 100 volts. 
EXAMPLE 11 
50 parts of a solution of poly(methyl methacrylate) (consisting of a 40% 
solids content solution in a 70/30 mixture of toluene and methyl isobutyl 
ketone) were mixed with 21 parts of a solution of a 40/60 methyl 
methacrylate/poly(ethylene glycol molecular weight 750) methacrylate graft 
copolymer (consisting of a 30% solids solution in toluene) and 300 parts 
of distilled water, and the mixture emulsified. 3 parts of an 8% aqueous 
ammoniacal solution of poly(methacrylic acid) was added, the emulsion pH 
being 7.2. 7.3 parts of polymer was deposited as a film on a steel anode 
after 2 minutes at 100 volts. 
EXAMPLE 12 
50 parts of a phenol/formaldehyde resin (commercially available as "Uranol" 
L9 from Ciba-Geigy) were emulsified in 300 parts of water with 20 parts of 
the 40/60 methyl methacrylate/poly(ethylene glycol) methacrylate copolymer 
of Example 11, and 1.5 parts of an 8% aqueous ammoniacal solution of 
poly(methacrylic acid) added. The resin was deposited as a film on a steel 
anode after 2 minutes at 100 volts. 
EXAMPLE 13 
An aqueous dispersion was prepared by mixing and emulsifying in 300 parts 
of water, 40 parts of an epoxy resin (commercially available as "Epikote" 
1004) which was esterified with linseed oil fatty acids, 10 parts of a 
phenol/formaldehyde resin (commercially available as "Uranol" L9) and 10 
parts of an ethoxylated epoxy resin similar to that used in Example 10 
except that the poly(ethylene oxide) content was 60%. 1.5 parts of an 8% 
aqueous solution of poly(methacrylic acid) was added and the dispersion 
deposited as a film on an anode at 100 volts over 2 minutes. 
EXAMPLE 14 
192 parts of the epoxy resin esterified with linseed oil fatty acids used 
in Example 13 were mixed with 8 parts of the alkyd resin described in 
Example 6 and the mixture emulsified in 800 parts of distilled water. 1.5 
parts of an 8% aqueous solution of poly(methacrylic acid) was added, the 
pH being about 7. 
A coating (A) was deposited on a bare steel anode of area 40 square inches 
from this emulsion by passing 100 coulombs at 100 volts. After stoving at 
165.degree. C. for 30 minutes 1 g of resin was found to be deposited. 
A coating (B) was deposited under the same conditions (i.e. to give 1 g of 
stoved resin on the panel) using an emulsion of a commercially available 
non-pigmented epoxy ester carboxyl group-containing resin dispersed in the 
presence of alkali and recommended for application to an anode by 
electrodeposition. 
Both coatings (A) and (B) were tested by the recognised procedure of 
"scribing" the coated panels 1 inch from their edges with two parallel 
scratches and subjecting them to a salt-spray treatment. After 6 days 
exposure panel (A) only had slight rusting whereas panel (B) showed bad 
blistering and rust under cut. After 11 days (A) had some rust under cut 
and blistering but panel (B) had failed due to severe rust under cut. 
EXAMPLE 15 
A resin was prepared by reacting 112 parts of an epoxy resin (commercially 
available as "Epikote" 1004) 10.6 parts of a dimer fatty acid 
(commercially available as "Epikote" 1024), 120 parts of carboxyl 
group-terminated poly(ethylene glycol) of molecular weight 2000, 200 parts 
of toluene and 0.4 part of an amine catalyst ("Armeen" DMCD) to a zero 
acid value. 
200 parts of this resin were mixed with 40 parts of the ethoxylated epoxy 
resin described in Example 10 and 30 parts of a methoxy 
melamine/formaldehyde resin (commercially available as "Cymel" 301) and 
the mixture emulsified in 900 parts water to which was added 2 parts of an 
8% ammoniacal solution of acrylic acid. A film was deposited on a steel 
panel as an anode after 2 minutes at 100 volts. 
EXAMPLE 16 
60 parts of acrylamide and 40 parts of methyl methacrylate were 
copolymerised in a mixture of 315 parts of isopropanol and 315 parts of 
distilled water in the presence of 3 parts of azodiisobutyronitrile. The 
turbid, viscous product had a solids content of 13.7%. 
40 parts of the above product were added to 50 parts of a solution of 
polymethylmethacrylate in a 70/30 mixture of toluene/methyl isobutylketone 
(40% solids content) and emulsified in 300 parts of water. To this 
emulsion was added 1.5 parts of the 8% solution poly(methacrylic acid) 
used in the previous Examples. A film was deposited on an anode immersed 
in the emulsion when current was passed for 30 seconds at 200 volts.