Storage stable autodepositable dispersions of epoxy resins and processes therefor and therewith

Epoxy resins, particularly those based on bisphenol A, can constitute the principal film forming polymer component of a storage stable autodepositable composition wherein the particle size distribution of all the film forming polymers in the composition satisfies certain criteria of size distribution, and an accelerator component which is an acid, oxidizing agent or complexing agent is present in amount sufficient to provide an oxidation-reduction potential at least 100 mV more oxidizing than a standard hydrogen electrode. Such dispersions can conveniently be prepared using a two stage process in which a solution of the film forming polymers is emulsified into water to form a preliminary dispersion and this preliminary dispersion is subjected to at least one particle size refinement stage in which the preliminary dispersion is forced through a narrow aperture.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the use of aqueous liquid compositions (either 
dispersions or true solutions) with which active metal surfaces can be 
coated, by mere contact with the liquid composition, with an adherent 
polymer film that increases in thickness the longer the time of contact, 
even though the liquid composition is stable for a long time against 
spontaneous precipitation or flocculation of any solid phase, in the 
absence of contact with active metal. (For the purposes of this 
specification, the term "active metal" is to be understood in its broadest 
sense as including all metals and alloys more active than hydrogen in the 
electromotive series, or, in other words, a metal which is 
thermodynamically capable of dissolving to produce dissolved cations 
derived from the metal, with accompanying evolution of hydrogen gas, when 
contacted with an aqueous solution of a non-oxidizing acid in which the 
activity of hydrogen ions is 1 equivalent per liter.) Such liquid 
compositions are denoted in this specification, and commonly in the art, 
as "autodeposition" or "autodepositing" compositions, dispersions, 
emulsions, suspensions, baths, solutions, or a like term. Autodeposition 
is often contrasted with electrodeposition, which can produce very similar 
adherent films but requires that the surface to be coated be connected to 
a source of direct current electricity for coating to occur. 
In particular, this invention is concerned with autodeposition of high 
quality, corrosion inhibiting coatings that include epoxy resins and/or 
products of reaction of molecules of epoxy resins with one another and/or 
with other materials. 
2. Statement of Related Art 
It is generally believed in the art that autodeposition works because 
cations dissolving from the metal surface to be coated, which cations when 
initially dissolved are, of course, confined to the volume of contacting 
liquid in the immediate vicinity of the metal surface from which they are 
dissolving, interact with the liquid autodepositing composition in at 
least one of the following ways: (i) The dissolved cations precipitate 
previously dissolved polymers by displacing previously associated cations 
or cation-forming moieties, in association with which the polymers are 
soluble, by the newly dissolved cations in association with which the 
polymers are much less soluble; and/or (ii) the dissolved cations 
destabilize numerous individual dispersed phase units in a dispersion of a 
polymer with inherently low water solubility, which nevertheless can 
remain in stable suspension for a long time in the absence of dissolved 
polyvalent cations, because the outer surfaces of the dispersed phase 
units carry a net negative electrical charge, derived from anionic 
components of the dispersed polymer itself and/or from an anionic 
dispersing agent used to prepare the autodepositing composition in 
question. 
The net negative charge on the units of the dispersed phase in an 
autodepositing liquid composition is believed to be electrically 
counterbalanced by a diffuse excess of cations, usually monovalent 
cations, in the surrounding continuous phase of the dispersion, this 
excess of cations together with the negative charges on the dispersed 
phase units constituting an example of the well known "electrical double 
layer" or "Helmholz double layer" that is characteristic of most 
interfaces between liquid phases containing charged solute particles and 
solids in contact with such liquid phases. As long as this double layer 
remains intact, the net negative charge on the exterior of each unit of 
dispersed phase causes it to repel other units of the disperse phase that 
also carry a net negative charge, and thereby prevents spontaneous 
coalescence of the dispersed phase units. 
When the double layer is sufficiently disturbed, or in the case of a 
soluble polymer, when the solubility is reduced, by introduction of new 
cations, the polymeric parts of numerous dispersed phase units and/or 
solute polymer molecules can aggregate to form a continuous coating layer, 
if the chemical nature of the polymer favors such a transition and the 
temperature is sufficiently far above the glass transition temperature of 
the polymer concerned. 
A practically useful autodepositing liquid composition therefore must have 
a balance between its needs for (i) stability during storage in the 
absence of particular kinds of metallic cations and (ii) quick transition 
to local instability, in the presence of the concentrations of these 
particular kinds of metallic cations that are developed in the vicinity of 
solid metals that are dissolving to produce these particular kinds of 
metallic cations. In the past practically successful autodepositing liquid 
compositions have been made from a variety of polymers, but all or almost 
all of them have been polymers that were initially prepared by 
polymerization of emulsified vinyl monomers, a process that is usually 
denoted in the art as "emulsion polymerization". However, by no means all 
polymers made by emulsion polymerization have been found useful in 
autodepositing liquid compositions, and some of the best protective 
coating properties achieved by other methods of coating have been achieved 
with polymers, such as urethane and epoxy resins, that have not been 
successfully prepared on a practical scale by emulsion polymerization. 
Practical success in autodepositing polymers of this type has been 
generally elusive heretofore. 
DESCRIPTION OF THE INVENTION 
Objects of the Invention 
A major object of this invention is to provide autodepositing liquid 
compositions from which it is possible to deposit on contacted metal 
surfaces epoxy resin based coatings that will provide at least 
approximately as much protection against corrosion and against mechanical 
stresses as do the best quality electrodeposited coatings based on epoxy 
resins. Another object is to provide an at least reasonably economical 
method of making such autodepositing liquid compositions on a commercial 
scale. Still another object is to utilize the autodepositing liquid 
compositions provided by the invention for superior and/or more economical 
coating processes to produce useful articles. Other objects will be 
apparent from the further description below. 
General Principles of Description 
Except in the claims and the specific examples, or where otherwise 
expressly indicated, all numerical quantities in this description 
indicating amounts of material or conditions of reaction and/or use are to 
be understood as modified by the word "about" in describing the broadest 
scope of the invention. Practice within the numerical limits stated is 
generally preferred, however. Also, throughout unless expressly stated to 
the contrary: percent, amount, "parts of", and ratio values are by weight; 
the term "polymer" includes "oligomer", "copolymer", "terpolymer", and the 
like; the first definition or description of the meaning of a word, 
phrase, acronym, abbreviation or the like applies to all subsequent uses 
of the same word, phrase, acronym, abbreviation or the like and applies, 
mutatis mutandis, to normal grammatical variations thereof; the term 
"mole" and its variations may be applied to ions, moieties, elements, and 
any other actual or hypothetical entity defined by the number and type of 
atoms present in it, as well as to materials with well defined neutral 
molecules; the description of a group or class of materials as suitable or 
preferred for a given purpose in connection with the invention implies 
that mixtures of any two or more of the members of the group or class are 
equally suitable or preferred; description of preparation of 
autodepositing liquid compositions or components thereof by utilizing 
electrically neutral chemical constituents refers to the constituents at 
the time of first addition to any combination specified in the 
description, and does not necessarily preclude chemical interactions among 
the constituents of a mixture, or physical changes in such properties as 
dispersed particle sizes and distribution of materials between dispersed 
and continuous phases in a dispersion, after mixing has occurred; 
specification of materials in ionic form implies the presence of 
sufficient counterions to produce electrical neutrality for the 
composition as a whole; and any counterions thus implicitly specified 
preferably are selected from among other constituents explicitly specified 
in ionic form, to the extent possible; otherwise such counterions may be 
freely selected, except for avoiding counterions that act adversely to the 
objects of the invention. 
SUMMARY OF THE INVENTION 
It has been found that one of the most important characteristics 
determining the suitability of an autodepositing liquid composition 
containing dispersed epoxy resin is the size distribution of the dispersed 
phase units in the autodepositing liquid composition. The large number of 
the dispersed phase units requires in practice that the size distribution 
be described statistically. The most effective method of measurement and 
definition of particle distribution for purposes of this description has 
been found to be one which measures the scattering of laser generated 
light by particles in Brownian motion in the dispersion and relates the 
fluctuations in scattered light intensity to the sizes of the light 
scattering units (also optionally called "particles"). This type of 
analysis is performed by a commercially available apparatus, a NICOMP.TM. 
Model 370 Microparticle Analyzer, supplied by Particle Sizing Systems, 
Inc., Santa Barbara, Calif. USA, which provides a machine-generated 
histogram plot, and corresponding numerical data, for the volume percent 
of the light scattering units in the dispersion falling within various 
particle size ranges, and also automatically calculates various 
statistical measures such as the mean diameter, "effective particle size", 
standard deviation, coefficient of variation, cumulative volume to various 
limits, and the like. The machine is capable of analyzing the statistical 
results either according to an assumption of a Gaussian distribution or 
according to another method that allows for bimodal distributions. For the 
purposes of this specification, however, analysis according to the 
assumption of a Gaussian distribution is generally preferred, even when 
the statistics indicate a low probability that this is the actual 
distribution of the light scattering units. Any errors that this method of 
analysis may cause have not been found to substantially affect the 
preferences set forth below. 
A closely related particle size distribution measurement technique that has 
also been used measures the scattering of laser generated light by 
particles in electrophoretic motion rather than more random Brownian 
motion. The particular commercial apparatus used was a ZETAPLUS.TM. Zeta 
Potential Analyzer commercially supplied by Brookhaven Instruments Corp., 
Austin, Tex., USA. For preferred particle size distributions, this method 
of analysis generally appears to give nearly the same results as the most 
preferred method noted in the immediately preceding paragraph. Other 
methods may well also be suitable, but the method described in the 
immediately preceding paragraph is to be understood as definitive for 
determining whether particular compositions conform to any description 
below that prescribes limits on particle size distributions. 
An autodepositing liquid composition according to the present invention 
comprises, preferably consists essentially of, or more preferably consists 
of, water and: 
(A) a concentration of at least 1.0%, based on the whole composition, of 
dispersed or both dispersed and dissolved film forming polymer molecules 
that include a concentration of at least 0.2%, based on the whole 
composition, of dispersed molecules selected from the group consisting of 
all organic molecules that contain at least two 1,2-epoxy moieties per 
molecule, all of said dispersed or dissolved and dispersed film forming 
polymer molecules collectively having the following size distribution 
characteristics, which are measured as indicated above, in the absence of 
other light scattering materials such as pigments, in a dispersion, or 
dispersion and solution, the phrase "dispersion, or dispersion and 
solution" being hereinafter usually abbreviated as "DDS", of the film 
forming polymer molecules in water: 
(1) the mean light scattering particle size in the DDS is at least 100 but 
not more than 300 nanometres (hereinafter usually abbreviated "nm"); 
(2) no more than 1.0% of the light scattering particles volume in the DDS 
consists of particles with a diameter larger than 450 nm; 
(3) no more than 25% of the light scattering particles volume in the DDS 
consists of particles with a diameter larger than 250 rnm; 
(4) no more than 50% of the light scattering particles volume in the DDS 
consists of particles with a diameter larger than 200 nm; and 
(5) no more than 75% of the light scattering particles volume in the DDS 
consists of particles with a diameter larger than 175 nm; 
(B) an emulsifying agent component in sufficient quantity to emulsify all 
dispersed constituent molecules of component (A) so that, in the 
autodepositing liquid composition, no separation or segregation of bulk 
phases that is perceptible with normal unaided human vision occurs during 
storage at 25.degree. C. for at least 24 hours after preparation of the 
autodepositing liquid composition, in the absence of contact of the 
autodepositing liquid composition with any metal, particularly any metal 
that dissolves in the autodepositing composition to produce therein metal 
cations with a charge of at least two, or other material that reacts with 
the autodepositing liquid composition; and 
(C) a dissolved accelerator component, selected from the group consisting 
of acids, oxidizing agents, and complexing agents, sufficient in strength 
and amount to impart to the total autodepositing liquid composition an 
oxidation-reduction potential that is at least 100 millivolts hereinafter 
usually denoted "mV") more oxidizing than a standard hydrogen electrode 
(hereinafter usually abbreviated "SHE"); and, optionally, one or more of 
the following: 
(D) a component of pigment, filler, or other dispersed solid phase 
materials other than the materials that constitute any part of any of the 
preceding components; 
(E) a component of dyes or other dissolved coloring materials other than 
materials that constitute any part of any of the preceding components; 
(F) a component of solvent in which constituents of component (A) that are 
insoluble in water were dissolved during some step in the preparation of 
the autodepositing liquid composition, other than materials that 
constitute any part of any of the preceding components; 
(G) a component of coalescing agent, other than materials that form any 
part of any of the preceding components; 
(H) a plasticizer component, other than materials that constitute part of 
any of the preceding components; 
(J) a component of non-polymeric cross-linking agents and monomers that do 
not constitute part of any other component described above but are 
chemically reactive with epoxy resin constituents of component (A) at a 
temperature of 165.degree. C. 
In this description and hereinafter: The phrase "film forming polymer 
molecules" means that the molecules so described, when separated from any 
water in which they are dispersed or dissolved and dispersed, by drying or 
other removal of the water at a temperature of at least 30.degree. C. from 
a substantially uniformly thick continuous liquid layer of a DDS of the 
film forming polymer molecules, will spontaneously form a continuous body 
that is solid at 30.degree. C.; the term "solvent" means a single phase, 
whether consisting of a single chemical substance or a mixture of chemical 
substances, that (i) is liquid at 25.degree. C. and (ii) is not 
constituted exclusively of water and inorganic solutes only; and the term 
"coalescing agent" means a material that (i) is liquid at 100.degree. C., 
(ii) has a boiling point at normal atmospheric pressure that is at least 
110.degree. C. or preferably, with increasing preference in the order 
given, at least 120, 130, 140, 150, 160, or 165.degree. C. and 
independently is not more than 300.degree. C., or preferably, with 
increasing preference in the order given, not more than 290, 280, 270, 
265, 260, 255, 250, 245.degree. C., and (iii) promotes the formation of 
unblistered coatings, as determined by comparison of the degree of 
blistering obtained, under identical processing conditions, by (i) 
autodeposition from an autodepositing liquid composition containing the 
material being tested for its coalescing properties, followed by cure of 
the film thus deposited and (ii) an otherwise identical process in which 
the material being tested for its coalescing properties is replaced, in 
the autodepositing liquid composition used in the process, by an equal 
mass of water. 
In addition to a complete autodepositing liquid composition as described 
above, another embodiment of the invention is a liquid dispersion in water 
of epoxy resin and, optionally, other components that is useful as a 
replenisher composition to replace polymer molecules consumed by use of an 
autodepositing liquid composition according to the invention. Such a 
liquid replenisher composition according to the invention comprises, 
preferably consists essentially of, or more preferably consists of, water 
and: 
(A') an amount of dispersed or both dispersed and dissolved film forming 
polymer molecules that include the same chemical substances in the same 
relative proportions as are consumed during use from component (A) of the 
autodepositing liquid composition to be replenished, said amount being at 
least 5 times greater than the amount of the same chemical substances in 
the autodepositing liquid composition to be replenished; and 
(B') an emulsifying agent component in sufficient quantity to emulsify all 
dispersed constituent molecules of component (A') so that, in the liquid 
replenisher composition, no separation or segregation of bulk phases that 
is perceptible with normal unaided human vision occurs during storage at 
25.degree. C. for at least 5 days after preparation of the liquid 
replenisher composition, in the absence of contact of the liquid 
replenisher composition with any metal, particularly any metal that 
dissolves in the autodepositing composition to produce therein metal 
cations with a charge of at least two, or other substance that reacts with 
the liquid replenisher composition; and, optionally, one or more of the 
following: 
(C') a dissolved accelerator component, selected from the group consisting 
of acids, oxidizing agents, and complexing agents; 
(D') a component of pigment, filler, or other dispersed solid phase 
materials other than the materials that constitute any part of any of the 
preceding components; 
(E') a component of dyes or other dissolved coloring materials other than 
materials that constitute any part of any of the preceding components; 
(F') a component of solvent in which constituents of component (A) that are 
insoluble in water were dissolved during some step in the preparation of 
the liquid replenisher composition, other than materials that constitute 
any part of any of the preceding components; 
(G') a component of coalescing agent, other than materials that form any 
part of any of the preceding components; 
(H') a plasticizer component, other than materials that constitute any part 
of any of the preceding components; 
(J') a component of non-polymeric cross-linking agents and monomers that do 
not constitute part of any other component described above but are 
chemically reactive with epoxy resin constituents of component (A) at a 
temperature of 165.degree. C. 
A process according to the invention for making a liquid replenisher 
composition according to the invention as described above comprises 
steps.sup.1 of: 
FNT .sup.1 The word "step" in this specification and in the claims, unless 
explicitly noted to the contrary, is to be understood as the equivalent of 
the phrase "part of a process", without any implication that all the 
actions recited in the step are necessarily continuous in time. 
(I) providing a collection of film forming polymer molecules suitable for 
component (A') as described above; 
(II) dissolving the entire collection of film forming polymer molecules 
provided in step (I) in a solvent component to form a single phase 
solution from the combination of the collection of film forming polymer 
molecules and the solvent component; 
(III) emulsifying the single phase solution formed in step (II), along with 
other materials as needed, into a volume of water, so as to form a DDS in 
water of at least those parts of the solution that constitute component 
(A) as recited above, said DDS comprising, preferably consisting 
essentially of, or more preferably consisting of, water, components (A') 
and (B') as recited above, and, optionally, one or more of components (C') 
through (J') as recited above. 
A process according to the invention for making an autodepositing liquid 
composition according to the invention as described above comprises steps 
of: 
(I') providing a collection of film forming polymer molecules suitable for 
component (A) as described above; 
(II') dissolving the entire collection of film forming polymer molecules 
provided in step (I') in a solvent component to form a single phase 
solution from the combination of the collection of film forming polymer 
molecules and the solvent component; 
(III') emulsifying the single phase solution formed in step (II'), along 
with other materials as needed, into a volume of water, so as to form a 
DDS in water of at least those parts of the solution that constitute 
component (A) as recited above, said DDS comprising, preferably consisting 
essentially of, or more preferably consisting of, water, components (A) 
and (B) as recited above, and, optionally, one or more of components (C) 
through (J) as recited above; and, if component (C) as described above is 
not present in said DDS, 
(IV') adding to the DDS formed in step (III') sufficient additional 
material to provide component (C) and, optionally, any one or more of 
components (D) through (J) as recited above that is not already present in 
the DDS formed in step (III'). 
A process according to the invention for using an autodepositing liquid 
composition according to the invention in its simplest form comprises, 
preferably consists essentially of, or more preferably consists of, steps 
of: 
(I") contacting a solid active metal surface with an autodepositing liquid 
composition according to the invention for a sufficient time to form over 
the contacted solid active metal surface a wet continuous coating which 
contains molecules derived from component (A) of the autodepositing liquid 
composition according to the invention, the wet continuous coating being 
sufficiently coherent and adherent to the metal surface for at least some 
part thereof to remain on the metal surface against the force of natural 
ambient gravity when the metal surface and any non-adherent part of the 
autodepositing liquid composition according to the invention are removed 
from contact with each other; 
(II") after step (I"), removing the wet continuous coating formed over the 
metal surface from contact with any non-adherent part of the 
autodepositing liquid composition according to the invention with which it 
was contacted in step (I") and, optionally, rinsing the coating with at 
least one liquid rinse composition that is not an autodepositing liquid 
composition; and 
(III") after step (II"), expelling from the wet continuous coating a 
sufficient amount of water so as to convert the wet continuous coating 
into a dry continuous coating. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
For reasons of practicality and economy with commercially available 
equipment, it is normally preferred to carry out process step (III') or 
(III") as described above in at least two stages: (0.1) a primary mixing 
stage in which there is formed a preliminary DDS which is sufficiently 
stable that no separation or segregation of bulk phases in the preliminary 
DDS that is perceptible with normal unaided human vision would occur 
during storage at 25.degree. C. for at least 5 hours after preparation of 
the preliminary DDS, in the absence of contact of the preliminary DDS with 
any metal or other material that can react with or dissolve into the 
preliminary DDS to form solute cations with a charge of at least two 
therein; and (0.2) a particle size refinement stage, in which the 
preliminary DDS formed in stage (0.1), preferably before it shows any 
visually perceptible evidence of phase segregation, is forced as least 
once through a narrow aperture of carefully controlled size and shape 
under high pressure, so as to generate a flow velocity high enough to 
produce cavitation, turbulence, and/or shear forces which divide the 
product into particles that meet the size distribution criteria specified 
for component (A) or (A') above. 
Stage (0.1) can be conveniently achieved by use of any of a wide variety of 
laboratory or commercial scale equipment known generally in the art as 
"high shear" or "high speed" mixers. In this stage emulsifying agent and 
water are generally added slowly together to the solution of the film 
forming polymer molecules, with constant agitation, until the mixture, 
which initially becomes increasingly more viscous as more water is added, 
at least begins to become substantially less viscous with further 
additions of water, indicating inversion of the emulsion from one of water 
in "oil" to the desired final "oil" in water emulsion, having water and 
constituents dissolved in water as the continuous phase. If "high shear" 
mixing equipment is used in this stage, the emulsion produced in this 
mixing stage will normally have a mean particle diameter no more than 450 
nm, while if the more common "high speed" type of mixing equipment is used 
instead, an emulsion with a mean particle diameter of about 1000 nm is 
usually produced, in both cases with preferred materials as described 
further below. 
Stage (0.2) is physically analogous to the homogenization of milk and may 
be accomplished with equipment suited to that and similar purposes. 
Preferred equipment is exemplified by RANNIE.TM. Hyper Homogenizers 
supplied by the APV Homogenizer Division of APV Corp., Wilmington, Mass., 
USA and MICROFLUIDIZER.TM. Processors supplied by Microfluidics 
International Corporation, Newton, Mass., USA. The operations of step 
(0.2) may be repeated as many times as desired, without apparent harm to 
the resulting product, and with substantially to slightly increased 
particle refinement normally being achieved with each of at least the 
first few repetitions. If the initial mean particle diameter of the 
preliminary DDS is more than 500 nm, at least one repetition of Stage 
(0.2) is normally preferred, in order to achieve a preferred degree of 
stability of the finally prepared autodepositing liquid composition, while 
if the initial mean particle diameter is less than 450 nm, a single mixing 
in Stage (0.2) is often sufficient. 
The amount of component (A) in a working autodepositing composition 
according to the invention preferably is at least, with increasing 
preference in the order given, 2.0, 2.5, 3.0, 3.5, 4.0, or 4.5% of the 
total amount of the composition and independently preferably is not more 
than, with increasing preference in the order given, 50, 30, 25, 20, 10, 
9.0, 8.5, 8.0, 7.5, 7.0, 6.5, 6.0, or 5.5% of the total amount of the 
composition. 
Numerous types of epoxy resin are known in the art and may be utilized in 
this invention. Such resins are often described by the type of central 
organic moiety or moieties to which the 1,2-epoxy moieties are attached in 
a monomer unit having at least two epoxy moieties. Non-exclusive examples 
of such central moieties are those derived from bis-phenol A and its 
analogs in which one or two --NH.sub.2 moieties are substituted for an 
equal number of --OH moieties in bis-phenol A; novolak condensates of 
formaldehyde with phenol and substituted phenols and their amino analogos, 
the condensates containing at least two aromatic nuclei; triazine; 
hydantoin; and other organic molecules containing at least two hydroxyl 
and/or amino moieties each, in each instance with as many hydrogen atoms 
deleted from hydroxy and/or amino moieties in the parent molecule as there 
are epoxy moieties in the molecules of epoxy resin; optionally, the 
1,2-epoxide moieties may be separated from the central moieties as defined 
above by one or more, preferably only one, methylene groups. Oligomers of 
such monomers, either with themselves or with other organic molecules 
containing at least two hydroxyl and/or amino moieties each, may also 
serve as the central organic moiety. 
Preferably, independently for each criterion stated, the particle size 
distribution of those parts of component (A) in an autodepositing liquid 
composition according to the invention or of component (A') in a liquid 
replenisher composition according to the invention that are constituted of 
molecules for which the epoxide equivalent weigh.sup.2 is at least 374 
conforms to the following criteria, each independently of the others, or 
most preferably to all: The ratio of the mean light scattering particle 
diameter.sup.3 in nm divided by the cube root of the average epoxide 
equivalent weight for the molecules of component (A) expressed in daltons, 
this ratio being usually briefly denoted hereinafter as the "diameter 
ratio", is not more than, with increasing preference in the order given, 
FNT .sup.2 The epoxide equivalent weight is defined as the molecular weight 
divided by the number of 1,2-epoxy moieties in the molecule. The epoxide 
equivalent weight of commercial resins is generally specified by the 
supplier as a range; when such materials are used, the midpoint of the 
stated range is taken as the epoxide equivalent weight for calculation of 
diameter ratios. 
FNT .sup.3 These particle diameter values generally may most conveniently be 
measured in the absence of any substantial amount in component (A) of any 
epoxy resin for which the epoxide equivalent weight is less than or equal 
to 200. Such low molecular weight epoxy resins are preferably used only as 
cross-linking agents in formulations according to this invention, and do 
not need any particular precautions or special techniques to become 
properly suspended in the final DDS formed, because such low molecular 
weight epoxy resins are liquids rather than solids at the normal 
temperature of addition to a composition according to this invention. 
29.2, 28.1, 27.0, 26.0, 25.0, 24.0, 23.5, 23.0, 22.5, 22.0, 21.7, or 21.4 
{nm/(dalton.sup.1/3)}; no more than 1.0% of the light scattering particles 
volume in the distribution consists of particles with a diameter ratio 
larger than, with increasing preference in the order given, 44.2, 43.1, 
42.0, 41.0, 40.0, 39.0, 38.0, 37.0, 36.5, 36.0, 35.5, 35.0, or 34.5 
{nm/(dalton.sup.1/3)}; no more than 25 % of the light scattering particles 
volume in the distribution consists of particles with a diameter ratio 
larger than, with increasing preference in the order given, 25.1, 24.0, 
23.0, 22.5, 22.0, 21.5, 21.0, 20.7, or 20.4 {nm/(dalton.sup.1/3)}; no more 
than 50% of the light scattering particles volume in the distribution 
consists of particles with a diameter ratio larger than, with increasing 
preference in the order given, 20.4, 19.0, 18.5, 18.0, 17.5, 17.0, 16.8, 
or 16.6 {nm/(dalton.sup.1/3)}; no more than 75% of the light scattering 
particles volume in the distribution consists of particles with a diameter 
ratio larger than, with increasing preference in the order given, 17.8, 
17.3, 17.0, 16.5, 16.0, 15.5, 15.0, 14.5, 14.0, or 13.6 
{nm/(dalton.sup.1/3)}. 
Preferably, with increasing preference in the order given, at least 10, 20, 
30, 40, or 45% of the molecules of component (A) of an autodepositing 
liquid composition according to the invention are molecules that contain 
at least two 1,2-epoxide moieties and have an epoxide equivalent weight of 
at least 374, and independently, with increasing preference in the order 
given, at least 10, 20, 30, 40, 50, 60, 70, 75, 80, 85, or 89% of the 
molecules containing at least two 1,2-epoxide moieties in component (A) of 
an autodepositing liquid composition according to the invention are 
selected from the group consisting of molecules with an epoxide equivalent 
weight that is at least, with increasing preference in the order given, 
446, 574, 731, 873, 1015, 1158, 1299, 1442, 1584, 1726, 1868, or 2010 and 
independently preferably is, with increasing preference in the order 
given, not more than 4527, 3816, 3106, 2721, 2437, 2295, or 2152. 
Independently, it is preferred that an autodepositing liquid composition 
according to the invention contain a subcomponent (AoJ) selected from the 
group consisting of molecules having exactly two 1,2-epoxide moietes and 
an epoxide equivalent weight that is not more than 200 in an amount that 
is, with increasing preference in the order given, at least 1, 2, 3, 4, 5, 
6, 7, 8, 9, or 10% of the amount of molecules having two or more 
1,2-epoxide moieties and an epoxide equivalent weight of at least 873 and 
independently, but only if at least 90% of component (A) is constituted of 
molecules having at least two 1,2-epoxide moieties, preferably is not more 
than, with increasing preference in the order given, 25, 24, 23, 22, 21, 
or 20% of the amount of molecules having two or more 1,2-epoxide moieties 
and an epoxide equivalent weight of at least 873, because excessive 
rinse-off of uncured wet autodeposited coatings has sometimes been 
observed when a higher ratio of epoxides with low epoxide equivalent 
weights to those with higher molecular weights was used and there was 
little or no other film forming material in component (A) to stabilize the 
wet autodeposited films. In contrast, when other film forming materials, 
such as those contained in most commercially available acrylic polymer 
latexes, are also included in substantial amounts in component (A), larger 
ratios of molecules with low epoxide equivalent weights may be included 
and can even be preferred, if the amount of other film forming polymer is 
sufficient to prevent excessive rinse-off of the uncured wet autodeposited 
films. 
In addition to the diepoxide molecules of subcomponent (AoJ), component (A) 
and/or component (J) as described above preferably include(s) a 
subcomponent (CL) of cross-linking agents selected from the group 
consisting of both of the following molecular types: 
(CL.1) molecules each containing at least two functional groups, such as 
amine, amide, imine, thiol, hydroxyl, carboxyl, and carboxylic acid 
anhydride, that are capable of rapid chemical addition reactions with 
epoxy moietiess when mixed with molecules containing such epoxy moieties 
and heated to a temperature of at least 100.degree. C.; and 
(CL.2) molecules that are not part of component (CL.1) and that contain at 
least two blocked isocyanate groups, each such group being blocked with a 
conventional blocking agent or internally blocked by formation of a 
uretdione structure, so that the blocked isocyanate group does not react 
at any appreciable rate at room temperature with hydroxyl groups but does 
react rapidly with such groups after being unblocked by heating, 
unblocking occurring at a temperature that is at least 100.degree. C. and 
preferably is, with increasing preference in the order given, at least 
105, 110, 115, or 120.degree. C. and independently preferably is, with 
increasing preference in the order given, not more than 190, 185, 180, 
175, 170, or 165.degree. C. 
If subcomponent type (CL. 1) is used, its constituents preferably have 
terminal hydroxyl, amine, carboxylic acid, or amide groups. If 
subcomponent type (CL.2) is used, its constituents preferably are chosen 
from molecules that conform to general formula 
(II): 
##STR1## 
wherein each of B and B' independently is a monovalent moiety formed by 
removing the most easily ionized hydrogen atom from an amine, alcohol, 
amide, or oxide molecule, or B and B' are joined to each other to form a 
uretdione; each of R and R' independently is a divalent hydrocarbon or 
carbonyl-hydrocarbon moiety derived by removing from any hydrocarbon, or 
from an oxyhydrocarbon in which all oxygen atoms present are in carbonyl 
groups, any two hydrogen atoms not attached to the same carbon atom, said 
divalent hydrocarbon or carbonyl-hydrocarbon moiety having from 2 to 20 
carbon atoms and having no unsaturation except aromatic and carbonyl 
unsaturation; and m is an integer from 0-20, preferably, with increasing 
preference in the order given, not more than 15, 10, 8, 6, 4, 3, 2, 1, or 
0. The blocking groups B and B', which preferably are the same or are 
joined to form a uretdione, can be derived from any suitable aliphatic, 
cycloaliphatic, aromatic, or alkylaromatic monoalcohol, monoamide, 
monoamine, or monooxime. Ketoximes are especially useful when unblocking 
at relatively low temperatures such as 120.degree. C. is desired, although 
their instability in acidic solutions may become a problem if an 
autodepositing composition according to the invention is to be stored for 
a considerable time without being used. More sterically hindered and/or 
more acid stable blocking groups, such as those derived from the lactam of 
6-aminohexanoic acid and/or benzotriazole are preferred if unblocking is 
desired to begin at a substantial rate only at or above 160.degree. C. In 
some instances, as described in the examples below, both types of blocking 
groups are used, in order to effect part of the cross-linking during an 
early part of the cure and part of the cross-linking during a later part 
of the cure. 
The preferred cross-linking agents as specified above are believed to be 
reactive with hydroxyl groups as well as with any intact epoxide groups 
that may be present in the relatively acidic environment of an 
autodepositing composition according to this invention, where most or all 
of such groups are believed likely to be hydrolyzed to produce hydroxyl 
groups. Furthermore, even if epoxy groups remain as such, there will 
normally be at least some hydroxyl groups available for cross-linking 
reactions such as esterification and esterification. Other constituents of 
component (A) that do not contain 1,2-epoxide moieties may also, and 
preferably do, have hydroxyl, carboxyl, or similarly reactive groups 
available for cross-linking reactions. 
Satisfactory autodeposited coatings for most purposes can be produced when 
molecules containing at least two 1,2-epoxide moieties are substantially 
the only constituents of component (A) as defined above. However, it is 
also possible, and can be advantageous, especially to achieve economy 
without unduly sacrificing quality, to utilize blends of the epoxy resin 
with other types of polymers, particularly acrylic polymers containing 
some acrylic acid monomer residues, which can react with the hydroxyl 
groups on epoxy resins to form ester groups and thereby cross-link the 
polymer coating formed by autodeposition. 
Primarily for reasons of economy and commercial availability, it is 
generally preferred to utilize epoxy resins derived from bis-phenol A in 
this invention. More particularly, epoxy moiety containing molecules 
utilized in this invention preferably conform to general chemical formula 
(I): 
##STR2## 
and n is an integer from 0 to 50. 
Preferably, independently for each criterion stated, the particle size 
distribution of those parts of component (A) in an autodepositing liquid 
composition according to the invention or of component (A') in a liquid 
replenisher composition according to the invention constituted of 
molecules for which the value of n in general formula (I) above is at 
least one conforms to the following criteria: The ratio of the mean light 
scattering particle diameter in nm divided by the cube root of the average 
epoxide equivalent weight.sup.4 for the molecules of component (A) 
expressed in daltons, this ratio being usually 
FNT .sup.4 This value, for resins conforming to general formula I, is equal to 
half of the average molecular weight. The epoxide equivalent weight of 
commercial resins is generally specified by the supplier as a range; when 
such materials are used, the midpoint of the stated range is taken as the 
epoxide equivalent weight for calculation of diameter ratios. briefly 
denoted hereinafter as the "diameter ratio", of the part of component (A) 
or (A') constituted of molecules for which the value of n in general 
formula (I) above is at least one is not more than, with increasing 
preference in the order given, 29.2, 28.1, 27.0, 26.0, 25.0, 24.0, 23.5, 
23.0, 22.5, 22.0, 21.7, or 21.4 {nm/(dalton.sup.1/3)}; no more than 1.0% 
of the light scattering particles volume in the dispersion consists of 
particles with a diameter ratio larger than, with increasing preference in 
the order given, 44.2, 43.1, 42.0, 41.0, 40.0, 39.0, 38.0, 37.0, 36.5, 
36.0, 35.5, 35.0, or 34.5 {nm/(dalton.sup.1/3)}); no more than 25% of the 
light scattering particles volume in the dispersion consists of particles 
with a diameter ratio larger than, with increasing preference in the order 
given, 25.1, 24.0, 23.0, 22.5, 22.0, 21.5, 21.0, 20.7, or 20.4 
{nm/(dalton.sup.1/3)}; no more than 50% of the light scattering particles 
volume in the dispersion consists of particles with a diameter ratio 
larger than 20.4, 19.0, 18.5, 18.0, 17.5, 17.0, 16.8, or 16.6 
{nm/(dalton.sup.1/3)}; no more than 75% of the light scattering particles 
volume in the dispersion consists of particles with a diameter ratio 
larger than, with increasing preference in the order given, 17.8, 17.3, 
17.0. 16.5, 16.0, 15.5, 15.0, 14.5, 14.0, or 13.6 {nm/(dalton.sup.1/3)}. 
Preferably, with increasing preference in the order given, at least 10, 20, 
30, 40, or 45% of the molecules in component (A) of an autodepositing 
liquid composition according to the invention conform to formula I when n 
has a value of at least 1, and independently, with increasing preference 
in the order given, at least 10, 20, 30, 40, 50, 60, 70, 75, 80, 85, or 
89% of the molecules conforming to formula I in component (A) of an 
autodepositing liquid composition according to the invention are selected 
from the group consisting of molecules in which the average value of n in 
formula (I) is at least, with increasing preference in the order given, 2, 
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13 and independently preferably is, 
with increasing preference in the order given, not more than 30, 25, 20, 
18, 16, 15, or 14. 
Independently, it is preferred that an autodepositing liquid composition 
according to the invention contain a subcomponent (AoJ) selected from the 
group consisting of diglycidyl ether molecules with an epoxide equivalent 
weight that is not more than 200 in an amount that is, with increasing 
preference in the order given, at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10% 
of the amount of molecules conforming to formula (I) when n has a value of 
5 or greater and independently, but only if at least 90% of component (A) 
is constituted of molecules conforming to formula (I), preferably is not 
more than, with increasing preference in the order given, 25, 24, 23, 22, 
21, or 20% of the amount of molecules conforming to formula I when n has a 
value of 5 or greater, because excessive rinse-off of uncured wet 
autodeposited coatings has sometimes been observed when a higher ratio of 
diglycidyl ethers with low epoxide equivalent weights to the molecules 
conforming to formula (I) when n has a value of 5 or greater was used and 
there was little or no other film forming material in component (A) to 
stabilize the wet autodeposited films. In contrast, when other film 
forming materials, such as those contained in most commercially available 
acrylic polymer latexes, are also included in substantial amounts in 
component (A), larger ratios of diglycidyl ethers with low epoxide 
equivalent weights may be included and can even be preferred, if the 
amount of other film forming polymer is sufficient to prevent excessive 
rinse-off of the uncured wet autodeposited films. 
Most preferably, the diglycidyl ether of bisphenol-A, corresponding to 
general formula (I) when n=0 and having an epoxide equivalent weight of 
182 daltons is used as subcomponent (AoJ). Subcomponent (AoJ) when present 
will form part of component (A) and/or part or all of component (J) as 
described above. 
When subcomponent (CL.2) is present in an autodepositing liquid composition 
according to the invention in which substantially all of the molecules 
containing at least two 1,2-epoxide moieties conform to general formula 
(I), the ratio of (i) the number of gram-equivalents of the total of epoxy 
and hydroxyl groups in that part of component (A) that conforms.sup.5 to 
general formula (I) to (ii) the number of gram-equivalents of the total of 
isocyanate and blocked isocyanate groups in subcomponent (CL.2) preferably 
is, with increasing preference in the order given, at least 1.0, 2.0, 3.0, 
3.5, 3.8, 4.0, or 4.1 and independently preferably is, with increasing 
preference in the order given, not more than 50, 45, 40, 35, 30, 28, 26, 
24, 23, 22, 21, or 20. 
FNT .sup.5 As with all other materials as already noted generally above, the 
word "conforms" in this instance is to be interpreted as "conformed at the 
time of first addition to a mixture as described herein." Therefore, even 
if the terminal epoxy groups in general formula (I) have hydrolyzed after 
addition, these groups are still counted for purposes of the calculation 
described in this paragraph as single epoxy groups rather than as the up 
to two hydroxyl groups that they may have become after addition. 
Satisfactory autodeposited coatings for most purposes can be produced when 
epoxy resins, particularly those constituted of molecules conforming to 
general formula (I), are substantially the only constituents of component 
(A) as defined above. However, it is also possible, and can be 
advantageous, especially to achieve economy without unduly sacrificing 
quality, to utilize blends of the epoxy resin with other types of 
polymers, particularly acrylic polymers containing some acrylic acid 
monomer residues, which can react with the hydroxyl groups on epoxy resins 
to form ester groups and thereby cross-link the polymer coating formed by 
autodeposition. 
Component (B) preferably includes a subcomponent (B.a), which may be the 
only constituent of component (B), selected from the group consisting of 
anionic surfactants, and in many circumstances it may advantageously 
contain other types of emulsifying agents also. Preferred anionic 
surfactants are ether sulfates that conform to general formula (III): 
EQU M.sup.+- O--SO.sub.2 --O--(CH.sub.2 --CH.sub.2 --O).sub.p -R",(III) 
where M.sup.+ represents a monovalent cation or monvalent fraction of 
cation of higher valence, preferably sodium or ammonium, more preferably 
ammonium; p is a positive integer that preferably is at least, with 
increasing preference in the order given, 2, 3, or 4; and R" represents an 
alkyl or alkylaryl moiety, more preferably an alkyl phenol moiety. 
Independently R" preferably has at least, with increasing preference in 
the order given, 8, 10, 12, 13, 14, or 15 carbon atoms and independently 
preferably has not more than, with increasing preference in the order 
given, 30, 28, 26, 24, 22, or 20 carbon atoms. Suitable commercially 
available anionic emulsifiers include Dowfax.TM. 2A-1 (sodium salt of 
alkylated diphenyl oxide disulfonate); Abex.TM. 26-5; Texapon.TM. E-12 and 
K-1 2; Rhodapex.TM. CO-128, -433, and -436 and EP-100, -110, -1 15, -120, 
and -227; Disponsil.TM. AES-13, and Aerosol.TM. OT (sodium 
dioctylsulfosuccinate). The single most preferred anionic emulsifying 
agent is Rhodapex.TM. CO-436, which is reported by its supplier to be an 
ammonium salt of sulfonated nonylphenol ethoxylate and to contain 58% of 
this active ingredient. The preferred amount of active anionic emulsifying 
agent used is, with increasing preference in the order given, not less 
than 0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.4, or 1.5%, based on the content 
in an autodepositing liquid composition according to the invention of the 
sum of molecules conforming to general formula I and any other parts of 
component (A) that do not include sufficient anionic moieties in the 
polymer molecules themselves to be "self-emulsifying".sup.6, and 
independently preferably is, with increasing preference in the order 
given, not more than 5, 4, 3.0, 2.7, 2.4, 2.2. 2.0, 1.9, 1.8, or 1.7%, on 
the same basis. 
FNT .sup.6 As described in detail in U.S. Pat. No. 5,352,726 of Oct. 4, 1994 to 
Hall at column 6 lines 31-44, column 7 line 11 through column 8 line 7, 
and column 8 line 64 through column 9 line 23, which portions are, to the 
extent not inconsistent with any explicit statement herein, hereby 
incorporated herein by reference, when utilizing addition polymers of 
vinyl monomers as the principal ingredient of the binder for an 
autodepositing liquid composition, the emulsifying agent is preferably 
incorporated into the polymer chain. Any polymers of this type that are 
present as part of component (A) herein do not need "external" emulsifying 
agent component (B) as described herein. 
Accelerator component (C) is preferably chosen from the group consisting of 
hydrofluoric acid and its salts, fluosilicic acid and its salts, 
fluotitanic acid and its salts, ferric ions, acetic acid, phosphoric acid, 
sulfuric acid, nitric acid, hydrogen peroxide, peroxy acids citric acid 
and its salts, and tartaric acid and its salts. More preferably, the 
accelerator comprises, still more preferably consists essentially of, or 
most preferably consists of the following subcomponents: 
(C.1) a total amount of fluoride ions, which may be simple or complex 
fluoride ions or both, that provides a concentration thereof in the total 
autodepositing liquid composition of at least 0.4 g/L and more preferably 
of, with increasing preference in the order given, at least 0.6, 0.8, 1.0, 
1.2, 1.4, 1.6, 1.8, or 1.9 g/L and independently preferably provides to 
the autodepositing liquid composition a total concentration of fluoride 
ions that is, with increasing preference in the order given, not more than 
5, 4.5, 4.0, 3.7, 3.4, 3.1, 2.9, 2.7, 2.5, 2.3, or 2.1 g/L; 
(C.2) an amount of dissolved trivalent iron atoms that is at least 0.003, 
or, with increasing preference in the order given, at least 0.007, 0.010, 
0.013, 0.016, 0.019, 0.022, 0.025, or 0.027 and independently preferably 
is, with increasing preference in the order given, not more than 0.20, 
0.15, 0.11, 0.090, 0.070, 0.055, 0.045, 0.040, 0.035, or 0.030; and 
(C.3) a source of hydrogen ions in an amount sufficient to impart to the 
autodeposition composition a pH that is at least 1.6, or preferably is, 
with increasing preference in the order given, at least 1.7, 1.8, 1.9, 
2.0, or 2.1 and independently preferably is, with increasing preference in 
the order given, not more than 5, 4.5, 3.8, 3.6, 3.4, 3.2, 3.0. 2.8, 2.6, 
2.4, or 2.3; and, optionally, 
(C.4) hydrogen peroxide. 
It should be understood that subcomponents (C.1) through (C.3) need not all 
be derived from different materials. Hydrofluoric acid, in particular, is 
preferred as a source for both (C.1) and (C.3), and ferric fluoride can 
supply both (C.1) and (C.2). 
Independently of other preferences, an autodepositing liquid composition 
according to the invention, when used to coat bare steel, preferably has 
an oxidation potential, measured by the potential of a platinum or other 
inert metal electrode in contact with the autodepositing liquid 
composition, that is, with increasing preference in the order given, at 
least 150, 175, 200, 225, 250, 275, 290, or 300 mV more oxidizing than a 
SHE and independently preferably is, with increasing preference in the 
order given, not more than 550, 525, 500, 475, 450, 425, 410, or 400 mV 
more oxidizing than a SHE. 
Pigment and/or filler component (D) and soluble colorant component (E) may 
generally be selected for compositions according to this invention from 
materials established as satisfactory for similar uses in other 
autodepositing liquid compositions. 
Solvent component (F) is generally required in the preparation of 
autodepositing liquid compositions according to this invention, but it is 
not believed in most cases to contribute any desirable characteristic to 
the final autodepositing liquid compositions formed, although it may 
function as a coalescing agent. The preferred solvents, however, are not 
particularly effective coalescing agents when used alone. The solvent 
component may be removed, when desired or necessary to comply with 
anti-pollution requirements, by means known in the art, such as 
distillation under reduced pressure after formation of an oil-in-water 
type dispersion of the desired final components of an autodepositing 
liquid composition according to the invention. However, in many cases the 
solvents do not diminish the technical benefits of the final 
autodepositing liquid compositions according to the invention, and may be 
left in place in the autodepositing liquid compositions according to the 
invention if legal requirements are not thereby violated. Any such 
residual solvent will normally be expelled during cure of the 
autodeposited coatings. 
The most preferred solvents are mixtures of (i) aromatic hydrocarbons with 
from 6 to 10 carbon atoms and (ii) ketones with from 3 to 8 carbon atoms. 
Preferably, with increasing preference in the order given, the percentage 
of each of components (i) and (ii) in the mixture is at least 10, 20, 25, 
30, 35, 40, or 45%. The single most preferred constituent of type (i) is 
toluene and the single most preferred constituent of type (ii) is methyl 
isobutyl ketone. 
Generally, the presence of a coalescing agent component (G) in an 
autodepositing liquid composition according to the invention is preferred. 
This component is preferably selected from the group consisting of 
monoethers and monoesters of glycols, preferably glycols with at least one 
terminal hydroxy group. Monoethers of ethylene glycol are readily 
available and effective in blistering reduction but are restricted in use 
by anti-pollution laws in many locations and also have been found to be 
more likely than monethers of propylene glycol to destabilize the 
emulsions formed in products according to the invention, so that 
monoethers of propylene glycol, particularly the n-butyl and phenyl 
monoethers of propylene glycol, are preferred from this class. When glycol 
monoethers are used, their percentage in an autodepositing liquid 
composition according to the invention preferably is, with increasing 
preference in the order given, at least 5, 10, 12, 14, 16, 18, or 19% of 
the total solids in components (A) and (J) (or (A') and (J')) of the 
composition and independently preferably is, with increasing preference in 
the order given, not more than 30, 28, or 26% on the same basis. 
Monoesters are slightly less preferred than monoethers where maximum 
corrosion resistance in the final product is needed, but are generally 
effective at lower concentrations and may therefore be preferred if 
economy and/or compliance with stringent solvent emission standards is 
more important than maximum corrosion resistance. A particularly preferred 
monoester is 2,2,4-trimethyl-1,3-pentanediol mono 2-methyl propionate. 
This and other monoesters if used preferably are present in an amount of 
at least 0.5% of the total autodepositing liquid composition and more 
preferably, with increasing preference in the order given, are present in 
amounts of at least 1.0, 1.5, 2.0, 2.5, or 2.9% but, independently, not 
more than with increasing preference in the order given, 10, 8.0, 6.0, 
5.0, 4.5, 4.0, 3.5, or 3.1%. 
The invention and its benefits may be further appreciated from 
consideration of the examples and comparisons below.