Note: Descriptions are shown in the official language in which they were submitted.
CA 02389343 2002-04-29
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COMPOSITION AND PROCESS FOR TREATING METALS
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
s BACKGROUND OF THE INVENTION
This invention relates to compositions and processes for treating metal
surfaces
with acidic aqueous compositions for forming conversion coatings on the
metals; the
conversion coatings provide excellent bases for subsequent painting. The
invention is
well suited to treating iron and steel, galvanized iron and steel, zinc and
those of its al-
io loys that contain at least 50 atomic percent zinc, and aluminum and its
alloys that contain
at least 50 atomic percent aluminum. Preferably the surface treated is
predominantly fer-
rous; most preferably the surface treated is cold rolled steel.
This invention is very closely related to that disclosed in U. S. Patent
5,449,415,
from which it differs primarily in using a particularly advantageous type of
water soluble
and/or dispersible polymer. The object of this invention is to achieve better
corrosion re-
sistance under at least one set of corrosion promoting conditions than does
the invention
illustrated by examples in U. S. Patent 5,449,415, without using any more
hexavalent
chromium in the process than is used in preferred examples in U. S. Patent
5,449,415.
Except in the claims and the operating examples, or where otherwise expressly
2o 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 this description
unless expressly
stated to the contrary: percent, "parts of", and ratio values are by weight;
the term
2s "polymer" includes oligomer; 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 constituents in chemical terms refers to the constituents at
the time of ad-
dition to any combination specified in the description, and does not
necessarily preclude
so chemical interactions among the constituents of a mixture once mixed;
specification of
materials in ionic form implies the presence of sufficient counterions to
produce electrical
neutrality for the composition as a whole; any counterions thus implicitly
specified should
preferably be selected from among other constituents explicitly specified in
ionic form,
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CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
to the extent possible; otherwise such counterions may be freely selected,
except for
avoiding counterions that act adversely to an object of the invention; and the
term "mole"
and its variations means "gram-mole" and its variations and may be applied to
elemental,
ionic, hypothetical, unstable, and any other chemical species defined by
number and
type of atoms present, as well as to compounds with well defined molecules.
BRIEF SUMMARY OF THE INVENTION
It has been found that improved resistance to corrosion, particularly after
subse-
quent conventional coating with an organic binder containing protective
coating such as
a paint or lacquer, can be imparted to active metal surfaces, particularly to
iron and steel
io and other ferrous surfaces, by contacting the metal surfaces for a
sufficient time at a suf-
ficient temperature with an acidic aqueous composition as described in detail
below.
Such a composition differs from some preferred embodiments illustrated by
example in
U. S. 5,449,415 most markedly in the specific chemical nature of the
substituents on the
polymers of hydroxy styrene, modified by substitution on the aromatic rings of
the poly-
is mers of substituted aminomethyl moieties, which are characteristic of both
this invention
and the preferred examples of U. S. 5,449,415. In the latter, at least one of
the two
substituents, exclusive of the single carbon atom that is bonded both to the
amino nitro-
gen and the aromatic ring, on the amino nitrogen atom of each substituent
moiety is a
polyhydroxy moiety, but in the present invention both of these substituents
jointly contain
2o at least two carbon atoms and at least one hydroxy moiety but neither of
these substitu-
ents on the amino nitrogen atoms individually contains more than half as many
hydroxyl
moieties as it has carbon atoms, unless it contains only one carbon atom.
Preferably,
the composition is coated over the metal surface to be treated and then dried
in place
on the surface of the metal, without intermediate rinsing.
25 Various embodiments of the invention include working compositions for
direct use
in treating metals, concentrates from which such working compositions can be
prepared
by dilution with water, processes for treating metals with a composition
according to the
invention, and extended processes including additional steps that are
conventional per
se, such as precleaning, rinsing, and, particularly advantageously, painting
or some sim-
so ilar overcoating process that puts into place an organic binder containing
protective coat-
ing over the conversion coating formed according to a narrower embodiment of
the in-
vention. Articles of manufacture including surfaces treated according to a
process of the
invention are also within the scope of the invention.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
35 An acidic aqueous composition according to the invention comprises,
preferably
consists essentially of, or more preferably consists of, water and:
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(A) a component of "fluorometallate" anions, each of said anions consisting of
(i) at
least four fluorine atoms, (ii) at least one atom of an element selected from
the
group consisting of titanium, zirconium, hafnium, silicon, aluminum, and
boron,
and, optionally, one or both of (iii) ionizable hydrogen atoms, and (iv) one
or more
oxygen atoms; preferably the anions are fluorotitanate (i.e., TiFs2) or
fluorozircon
ate (i.e., ZrFs 2), most preferably fluorotitanate;
(B) a component of divalent or tetravalent cations of elements selected from
the
group consisting of cobalt, magnesium, manganese, zinc, nickel, tin, copper,
zir-
conium, iron, and strontium; independently preferably at least, with
increasing
io preference in the order given, 60, 70, 80, 85, 90, 95, or 99 % by weight of
the
total of component (B) consisting of divalent manganese, cobalt, nickel, or
mag-
nesium, more preferably of divalent manganese, cobalt, or nickel; most
preferably of divalent manganese;
(C) a component of phosphorus-containing inorganic oxyanions and/or
phosphonate
anions; and
(D) a component of water-soluble and/or water-dispersible polymers of vinyl
phenol
having at least mono-substituted aminomethyl moieties as substituents on the
aromatic rings of said polymers; and, optionally, one or more of the following
components:
20 (E) a dissolved oxidizing agent, preferably a peroxy compound, more
preferably hyd-
rogen peroxide;
(F) a component selected from the group consisting of tungstate, molybdate,
silico-
tungstate, and silicomolybdate anions; and
(G) a component selected from dissolved or dispersed complexes stabilized
against
2s settling, said complexes resulting from reaction between:
- "fluorometallate" anions, each of said anions consisting of (i) at least
four
fluorine atoms, (ii) at least one atom of an element selected from the
group consisting of titanium, zirconium, hafnium, silicon, aluminum, and
boron, and, optionally, one or both of (iii) ionizable hydrogen atoms, and
so (iv) one or more oxygen atoms and
- one or more materials selected from the group consisting of metallic and
metalloid elements and the oxides, hydroxides, and carbonates of these
metallic or metalloid elements
to produce a reaction product that is not part of any of components (A)
through
35 (F) as recited above; preferably this component results from reaction with
silica
or vanadium(V) oxide.
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It should be understood that the components listed need not necessarily all be
provided by separate chemicals. For example, "fluorometallate" salts of
protonated poly-
mer molecules of component (D) can be used to provide at least part of both of
compon-
ents (A) and (D). Also, if the acidity of the composition is sufficiently high
and the sub-
s strate that is contacted with it is predominantly ferrous, component (B) can
be provided
by iron dissolved from the substrate and need not be present in the liquid
composition
when the liquid composition is first contacted with the substrate.
The pH value of an acidic aqueous liquid composition according to the
invention
preferably is at least, with increasing preference in the order given, 0.5,
1.0, 1.4, 1.7, 2.0,
~o or 2.3 and independently preferably is not more than, with increasing
preference in the
order given, 5.0, 4.0, 3.5, 3.2, 2.9, 2.6, or 2.4.
Component (C) as defined above is to be understood as including all of the fol-
lowing inorganic acids and their salts that may be present in the composition:
hypophos-
phorous acid (H3P02), orthophosphorous acid (H3P03), pyrophosphoric acid
(H4P20,),
1s orthophosphoric acid (H3P04), tripolyphosphoric acid (H5P30,o), and further
condensed
phosphoric acids having the formula Hx+2PXOsx+,, where x is a positive integer
greater
than 3. Component (C) also includes all phosphonic acids and their salts. In a
con-
centrated composition, the concentration in the total composition of
phosphorus atoms
contained in component (C) is preferably at least, with increasing preference
in the order
2o given, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.34, 0.38, 0.42, or 0.45 moles
of phosphorus
atoms per kilogram of total composition (this unit of measure being
hereinafter freely
applied to any other constituent as well as to phosphorus and being
hereinafter usually
abbreviated as "M/kg") and independently preferably is not more than, with
increasing
preference in the order given, 2.0, 1.5, 1.0, 0.8, 0.60, 0.55, 0.50, or 0.47
M/kg.
2s Generally, inorganic phosphates, particularly orthophosphates, phosphates,
hypo-
phosphates, and/or pyrophosphates, especially orthophosphates, are preferred
for com-
ponent (C) because they are more economical. Phosphonates are also suitable
and
may be advantageous for use with very hard water, because the phosphonates are
more
effective chelating agents for calcium ions. Acids and their salts in which
phosphorous
so has a valence less than five may be less stable than the others to
oxidizing agents and
are therefore less preferred in compositions according to the invention that
are to contain
oxidizing agents; such acids and their salts are less preferred in all
instances for econ-
omy.
The polymers required for component (D) may be prepared by processes as de-
ss scribed in one or more of the following U. S. Patents, the entire
disclosures of all of
which, except for any extent to which they may be inconsistent with any
explicit statement
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WO 01/32952 PCT/US00/29266
herein, are hereby incorporated herein by reference: 5,891,952, 5,116,912,
4,517,028,
4,433,015, and 4,376,000. Preferably, the polymers required for component (D)
are
made in a manner that reduces or eliminates the presence of organic solvent in
the
source of the polymer that is added to a mixture to make an acidic aqueous
liquid
composition according to the invention. Most preferably, these polymers are
made by
a method that does not use any organic solvent, as set forth further in the
paragraphs
following immediately below.
An aqueous solution of substituted aminomethylated polyphenol polymers pro-
duced by this preferred process is a product of reaction of:
~o (A') at least one precursor phenolic polymer or copolymer, which normally
does not
bear any substituted aminomethyl substituents on its aromatic rings;
(B') at least one aldehyde, ketone, or mixture thereof; and
(C') at least one amine.
The preferred process comprises, preferably consists essentially of, or more
pref-
i5 erably consists of, the following operations:
(I') reacting the precursor phenolic polymer component (A') in water with an
organic
or inorganic alkalinizing agent to form an aqueous solution of the
corresponding
phenoxide salt;
(II') mixing the aqueous solution from operation (I') with the amine component
(C'),
2o which preferably consists of one or more secondary amines, and the
component
(B') of aldehyde, ketone, or mixture thereof to form a single aqueous solution
in
which chemical reaction among components (A'), (B'), and (C') occurs at a tem-
perature in the range from 20 to 100 °C, preferably from 50 to 80
°C, to attach
substituted aminomethyl moieties to at least some of the aromatic rings in the
25 precursor polymer and produce an aqueous solution of substituted
aminomethyl-
ated phenolic polymer molecules;
(III') adding at least one acid to the aqueous solution formed at the end of
operation
(II'), the quantity of acid added being sufficient to neutralize the
alkalinizing agent
added in operation (I') and to protonate a sufficient fraction of the amino
nitrogen
so atoms in the substituted aminomethylated phenolic polymer to stabilize
against
settling the solution of the substituted aminomethylated phenolic polymer
formed
in operation (II'); and
(IV') contacting the resulting aqueous solution from the end of operation
(III') with a
cation exchange resin in its protonated form to remove at least, with
increasing
35 preference in the order given, 50, 75, 90, 95, 99.0, 99.50, 99.70, 99.90,
99.95,
or 99.98 % of any inorganic and/or quaternary ammonium cations dissolved in
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said aqueous solution from the end of operation (III').
Ordinarily, as is known in the art, contacting is most conveniently,
economically,
and effectively, and therefore preferably, carried out by passing the aqueous
solution
through a bed of ion-exchange resin beads arranged in a vertical column of
sufficient
s length that the desired level of removal of alkali metal and quaternary
ammonium cations
is achieved by the time the solution has passed through the entire column, and
the ion-
exchange resin in the column can later be returned to its protonated form by
treatment
with strong acid; however, many other methods of establishing contact between
the
solution and the ion-exchange resin for a sufficient time to remove the
unwanted cations
~o from the aqueous solution are known to those skilled in ion-exchange, and
any of these
methods may be used.
If it is desired, as is usually preferred, to remove unreacted amine as well
as
inorganic cations added as part of the alkalinizing agent, a strong acid
cation exchange
resin is used in operation (IV'). If it is desired to remove only inorganic
cations, a weak
i5 acid cation exchange resin may be used instead. Suitable strong acid cation
exchange
resins are those of the sulfonic acid or phosphonic acid types, and suitable
weak acid
cation exchange resins are those of the carboxylic acid type.
The quantities of components (A'), (B') and (C') used to prepare the
substituted
aminomethylated polyphenol polymer product in aqueous solution preferably are
such
2o as to have the following ratios to one another, independently for each
ratio specified:
- the number of moles of carbonyl groups in component (B') has a ratio to the
number of moles of primary and secondary amino nitrogen atoms in component
(C') that is at least, with increasing preference in the order given,
0.5:1.00,
0.7:1.00, 0.80:1.00, 0.85:1.00, 0.90:1.00, 0.95:1.00, or 0.99:1.00 and
independ-
2s ently preferably is not more than, with increasing preference in the order
given,
1.5:1.00, 1.3:1.00, 1.20:1.00, 1.15:1.00, 1.10:1.00, 1.05:1.00, or 1.01:1.00;
- the number of moles of carbonyl groups in component (B') has a ratio to the
num-
ber of moles of aromatic rings in component (A') that is at least, with
increasing
preference in the order given, 0.10:1.00, 0.20:1.00, 0.30:1.00, 0.40:1.00,
so 0.50:1.00, 0.60:1.00, 0.70:1.00, 0.80:1.00, 0.85:1.00, 0.90:1.00, or
0.94:1.00 and
independently preferably is not more than, with increasing preference in the
order
given, 2.00:1.00, 1.90:1.00, 1.80:1.00, 1.70:1.00, 1.60:1.00, 1.50:1.00,
1.40:1.00,
1.30:1.00, 1.20:1.00, 1.15:1.00, 1.10:1.00, 1.05:1.00, 1.00:1.00, or
0.96:1.00; and
- the number of moles of primary and secondary amino nitrogen atoms in compon-
ss ent (C') has a ratio to the number of moles of aromatic rings in component
(A')
that is at least, with increasing preference in the order given, 0.10:1.00,
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0.20:1.00, 0.30:1.00, 0.40:1.00, 0.50:1.00, 0.60:1.00, 0.70:1.00, 0.80:1.00,
0.85:1.00, 0.90:1.00, or 0.94:1.00 and independently preferably is not more
than,
with increasing preference in the order given, 2.00:1.00, 1.90:1.00,
1.80:1.00,
1.70:1.00, 1.60:1.00, 1.50:1.00, 1.40:1.00, 1.30:1.00, 1.20:1.00, 1.15:1.00,
1.10:1.00, 1.05:1.00, 1.00:1.00, or 0.96:1.00.
Additionally and independently, the quantities of components (A'), (B'), and
(C')
preferably are such as to provide an aqueous solution at the end of operation
(IV') that
contains at least, with increasing preference in the order given, 1.0, 3.0,
5.0, 6.0, 7.0, 7.5,
8.0, 8.5, 9.0, 9.5, or 10.0 percent of the total mass of the aqueous solution
as polymer
~o molecules that satisfy the definition for component (A) as given above. To
avoid
impractically high viscosity of the solution, such polymer molecules
independently
preferably constitute not more than, with increasing preference in the order
given, 50, 35,
or 30 % of the total mass of the aqueous solution.
In operation (I') the alkalinizing agent is preferably, for economy, an alkali
metal
hydroxide, e.g. sodium or potassium hydroxide, although tetraalkylammonium
hydroxides, e.g. tetrabutylammonium hydroxide, or tetraarylammonium hydroxides
can
also be used with technically satisfactory results. A sufficient number of
moles of
alkalinizing agent should be present to correspond to at least, with
increasing preference
in the order given, 10, 15, 20, or 25 % of the number of moles of phenolic
hydrogen
2o atoms in component (A').
Operation (I') is preferably carried out at a temperature that is at least,
with in-
creasing preference in the order given, 30, 40, 50, 55, 60, or 65 °C,
in order to minimize
the amount of neutralizing agent that is needed in operation (I') by
increasing the solubili-
ty, or at least the speed of dissolution, in water of at least partially
neutralized polymer
molecules formed in this step. Primarily for operating convenience when using
process
equipment that is not easily pressurized, the temperature during operation
(I') independ-
ently preferably is not more than, with increasing preference in the order
given, 95, 90,
80, or 70 °C.
In operation (III') the acid used to neutralize the alkalinizing agent can be
organic
so or inorganic. Suitable acids for this purpose include carbonic acid, acetic
acid, citric acid,
oxalic acid, ascorbic acid, phenylphosphonic acid, chloromethylphosphonic
acid; mono-,
di- and tri-chloroacetic acids, trifluoroacetic acid, nitric acid, phosphoric
acid, hydrofluoric
acid, tetrafluoroboric acid, hexafluorotitanic acid, hexafluorosilicic acid,
hexafluorozirconic acid, sulfuric acid, boric acid, hydrochloric acid, and the
like. The
s5 most preferred acid is a mixture of at least one of the "fluorometallic"
acids with
phosphoric acid. This mixture is preferred at least for economy, because when
these
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two acids are used as neutralizers in the preparation of an aqueous solution
and/or
dispersion of necessary component (D), this solution and/or dispersion
provides at least
part of both components (A) and (C), which are also needed for a composition
according
to this invention.
s Component (A'); i.e., the precursor phenolic polymer or copolymer, is
preferably
selected from polymer molecules in which at least, with increasing preference
in the
order given, 10, 20, 30, 40, 50, 60, 70, 80, or 90 % of the mass of the
polymer molecules
is constituted of moieties that conform to one of the two following general
formulas, or
would so conform if one of the open bonds shown in the following general
formulas were
io replaced by a bond to a hydrogen atom:
Y3 Y,
TQ s
R, Rz
Wz
I
Yi
Y3 Y z
Rz-
wherein, in either or both of these general formulas when present:
- each of R, through R3 is independently selected from the group consisting of
a
hydrogen atom, alkyl moieties having from 1 to 5 carbon atoms, and aryl
moieties
15 having from 6 to 18 carbon atoms;
- each of Y, through Y4 is independently selected from the group consisting of
a
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hydrogen atom and alkyl and aryl moieties having from 1 to 18 carbon atoms;
and
- W, or W2 is selected from the group consisting of a hydrogen atom and
hydrolyz
able moieties, preferably an acyl group, e.g. acetyl, benzoyl, and the like.
s Most preferably, independently for each such element of the formula, each of
R, through
R3, Y, through Y4, W,, and W2, is a hydrogen atom.
The weight average molecular weight of component (A') preferably is at least,
with increasing preference in the order given, 500, 1000, 1500, 2000, 2400,
2800, 3200,
3600, 4000, 4300, 4600, 4800, or 4900 Daltons and independently preferably is
not more
1o than, with increasing preference in the order given, 30,000, 25,000,
20,000, 15,000,
10,000, 8000, 6000, or 5100 Daltons.
Component (B') is preferably an aldehyde, and most preferably is formaldehyde,
especially in the form of paraformaldehyde. Liquid formaldehyde is generally
commer-
cially available only in a form that contains a significant quantity of
methanol, e.g. 15
i5 methanol, as a polymerization inhibitor for the formaldehyde. Since the
preferred
process is carried out in the absence of organic solvents, formaldehyde free
from
methanol, such as uninhibited aqueous formaldehyde or paraformaldehyde, is
preferably
used.
Component (C') is selected from amine molecules, preferably exclusively from
2o secondary amines, still more preferably from secondary amines in which the
total number
of carbon atoms is not more than, with increasing preference in the order
given, 10, 8,
6, 4, or 3. Examples of suitable secondary amines are methyl methanol amine,
methyl
ethanol amine, methyl butanol amine, ethyl methanol amine, ethyl ethanol
amine, pentyl
ethanol amine, pentyl pentanol amine, hexyl ethanol amine, dimethanol amine,
diethanol
2s amine, dipropanol amine, dibutanol amine, dipentanol amine, nonyl methanol
amine,
octyl ethanol amine, and the like. Primary amines, such as C,-C,2 alkyl and
alkanol
amines and the like, can also be used. Most preferably, component (C') is
selected from
secondary amines in which one of the organic moieties bonded directly to the
amino
nitrogen atom in the amine is an unsubstituted alkyl moiety and the other is a
hydroxyl
so substituted but otherwise unsubstituted alkyl moiety. The single most
preferred sub-
stance for component (C') is methyl ethanol amine with the formula H3C-NH-
(CHz)ZOH.
Even if component (D) of a composition according to this invention is in fact
made
by some other method than the preferred method described in the immediately
preceding
paragraphs, its chemical characteristics preferably are, with the same degree
of prefer-
s5 ence, those that would result from being made according to this preferred
method with
preferred choices as indicated above.
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The term "stabilize(d) against settling" in the description above of component
(G)
and of operation (III') means that the composition containing the material
does not suffer
any visually detectable settling or separation into distinct liquid phases
when stored, with-
out mechanical agitation, for a period of 100, or more preferably 1000, hours
at 25 °C.
Materials for component (G) may be prepared by mixing the two types of
reagents noted in the definition for component (G). A spontaneous chemical
reaction
normally ensues, converting the added element, oxide, hydroxide, or carbonate
into a
soluble species. The reaction to form this soluble species can be accelerated
by use of
heat and by stirring or other agitation of the composition. The formation of
the soluble
~o species is also aided by the presence in the composition of suitable
complexing ligands,
such as peroxide and fluoride.
For a variety of reasons, it is preferred that compositions according to the
inven-
tion as defined above should be substantially free from many ingredients used
in com-
positions for similar purposes in the prior art. Specifically, it is
increasingly preferred in
i5 the order given, independently for each preferably minimized component
listed below,
that these compositions, when directly contacted with metal in a process
according to
this invention, contain no more than 1.0, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01,
0.001, or
0.0002, percent of each of the following constituents: organic materials that
are liquid at
25 °C under normal atmospheric pressure and have a vapor pressure of at
least 0.05 bar
2o at 25 °C; hexavalent chromium; ferricyanide; ferrocyanide; sulfates
and sulfuric acid;
alkali metal and ammonium cations; pyrazole compounds; sugars; gluconic acid
and its
salts; glycerine; a-glucoheptanoic acid and its salts; and myoinositol
phosphate esters
and salts thereof.
Furthermore, in a process according to the invention that includes other opera-
2s tions than the drying into place on the surface of the metal of a layer of
a composition as
described above, it is preferred that none of these other operations include
contacting
the surfaces with any composition that contains more than, with increasing
preference
in the order given, 1.0, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.003, 0.001, or
0.0002 % of
hexavalent chromium, except that a final protective coating system including
an organic
so binder, more particularly those including a primer coat, may include
hexavalent chromium
as a constituent. Any such hexavalent chromium in the protective coating is
generally
adequately confined by the organic binder, so as to avoid adverse
environmental impact.
In one embodiment of the invention, it is preferred that the acidic aqueous
com-
position as noted above be applied to the metal surface and dried thereon
within a short
35 time interval. With increasing preference in the order given, the time
interval during
which the liquid coating is applied to the metal being treated and dried in
place thereon,
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
when heat is used to accelerate the process, is not more than 25, 15, 9, 7, 4,
3, 1.8, 1.0,
or 0.7 second (hereinafter often abbreviated "sec"). In order to facilitate
this rapid com-
pletion of a process according to this invention, it is preferred to apply the
acid aqueous
composition used in the invention to a heated metal surface, such as one
rinsed with hot
s water and subsequently dried after initial cleaning and very shortly before
treating with
the aqueous composition according to this invention, and/or to use infrared or
microwave
radiant heating and/or convection heating in order to effect very fast drying
of the applied
coating. Preheating of the metal substrate before application of a composition
according
to the invention is preferred over postheating of the applied liquid
composition when
1o practical, because the latter is more likely to result in unwanted
deformation of the
coating film or inhomogeneous properties of the film as a result of more rapid
drying in
some areas than in others. Whether preheating, postheating, or both are used,
the peak
metal temperature preferably is in a range from, with increasing preference in
the order
given, 10 - 100, 15 - 95, 20 - 90, 20 - 80, or 20 - 70, °C.
~s In an alternative embodiment, which is equally effective technically and is
satis-
factory when ample time is available at acceptable economic cost, a
composition accord-
ing to this invention may be applied to the metal substrate and allowed to dry
at a tem-
perature not exceeding 40 °C. In such a case, there is no particular
advantage to fast
drying. This alternative embodiment is particularly advantageously used for
"touching
2o up" thinned or damaged coatings that are already in place over most of the
surface of
some article that is too large to fit into any conveniently available oven or
other heating
device. For such uses a composition according to the invention is
advantageously
applied to the substrate to be treated with the aid of an applicator as taught
in U. S.
Patent 5,702,759 of Dec. 30, 1997 to White et al., the entire disclosure of
which, except
25 to any extent that may be inconsistent with any explicit statement herein,
is hereby
incorporated herein by reference.
The effectiveness of a treatment according to the invention appears to depend
predominantly on the total amounts of the active ingredients that are dried in
place on
each unit area of the treated surface, and on the nature and ratios of the
active ingredi-
so ents to one another, rather than on the concentration of the acidic aqueous
composition
used. Thus, if the surface to be coated is a continuous flat sheet or coil and
precisely
controllable coating techniques such as roll coaters are used, a relatively
small volume
per unit area of a concentrated composition may effectively be used for direct
applica-
tion. On the other hand, with some coating equipment, it is equally effective
to use a
s5 more dilute acidic aqueous composition to apply a heavier liquid coating
that contains
about the same amount of active ingredients. As a general guide, it is
normally
11
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
preferable, independently for each preference stated, for a working
composition
according to the invention that is intended to be dried without substantial
external heating
and/or to be applied without precise control of the total amount applied to
have:
- a total concentration of "fluorometallate" anions of component (A) that is
at least,
with increasing preference in the order given, 0.005, 0.010, 0.020, 0.030,
0.035,
0.040, 0.050, or 0.055 M/kg;
- a total concentration of metal cations of component (B) that is at least,
with
increasing preference in the order given, 0.007, 0.011, 0.020, 0.030, 0.035,
0.040, 0.045, 0.050, 0.054, 0.058, or 0.062 M/kg;
~o - a ratio of total concentration in M/kg of metal cations of component (B)
in M/kg
to the total concentration in M/kg of "fluorometallate" anions of component
(A) in
the same composition that is at least, with increasing preference in the order
given, 0.2:1.0, 0.4:1.0, 0.60:1.00, 0.70:1.00, 0.80:1.00, 0.90:1.00,
0.95:1.00,
1.00:1.00, 1.05:1.00, 1.10:1.00, or 1.12:1.00 and independently preferably is
not
is more than, with increasing preference in the order given, 3.0:1.00,
2.6:1.00,
2.2:1.00, 1.8:1.00, 1.6:1.00, 1.40:1.00, 1.30:1.00, 1.20:1.00, or 1.13:1.00;
- a concentration of phosphorus from component (C) that is at least, with
increasing preference in the order given, 0.007, 0.012, 0.017, 0.022, 0.027,
0.032, 0.037, 0.042, 0.047, 0.052, 0.057, 0.062, or 0.067 M/kg;
20 - a ratio of moles of phosphorus from component (C) to moles of
"fluorometallate"
ions from component (A) in the same composition that is at least, with
increasing
preference in the order given, 0.2:1.0, 0.4:1.0, 0.60:1.00, 0.70:1.00,
0.80:1.00,
0.90:1.00, 0.95:1.00, 1.00:1.00, 1.05:1.00, 1.10:1.00, 1.15:1.00, or 1.19:1.00
and
independently preferably is not more than, with increasing preference in the
order
2s given, 3.0:1.00, 2.6:1.00, 2.2:1.00, 1.8:1.00, 1.6:1.00, 1.40:1.00,
1.30:1.00,
1.25:1.00, or 1.20:1.00;
- a ratio of moles of phosphorus from component (C) to moles of total metal
cations from component (B) in the same composition that is at least, with
increas-
ing preference in the order given, 0.2:1.0, 0.4:1.0, 0.60:1.00, 0.70:1.00,
so 0.80:1.00, 0.90:1.00, 0.95:1.00, 1.00:1.00, or 1.05:1.00 and independently
prefer-
ably is not more than, with increasing preference in the order given,
2.6:1.00,
2.2:1.00, 1.8:1.00, 1.6:1.00, 1.40:1.00, 1.30:1.00, 1.25:1.00, 1.20:1.00,
1.15:1.00,
1.11:1.00, or 1.07:1.00;
- a concentration of moles of substituted phenol moieties from component (D)
that
s5 is at least, with increasing preference in the order given, 0.004, 0.008,
0.012,
0.018, 0.024, 0.028, or 0.031 M/kg;
12
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
- a ratio of moles of substituted phenol moieties from component (D) to moles
of
total "fluorometallate" anions from component (A) in the same composition that
is at least, with increasing preference in the order given, 0.060:1.00,
0.12:1.00,
0.16:1.00, 0.20:1.00, 0.25:1.00, 0.30:1.00, 0.35:1.00, 0.40:1.00, 0.43:1.00,
0.46:1.00, 0.49:1.00, or 0.54:1.00 and independently preferably is not more
than,
with increasing preference in the order given, 2.0:1.00, 1.5:1.00, 1.0:1.00,
0.80:1.00, 0.70:1.00, 0.65:1.00, 0.61:1.00, or 0.57:1.00;
- a ratio of moles of substituted phenol moieties from component (D) to moles
of
total metal cations from component (B) in the same composition that is at
least,
~o with increasing preference in the order given, 0.060:1.00, 0.12:1.00,
0.16:1.00,
0.20:1.00, 0.25:1.00, 0.30:1.00, 0.35:1.00, 0.40:1.00, 0.43:1.00, 0.46:1.00,
or
0.49:1.00 and independently preferably is not more than, with increasing
preference in the order given, 2.0:1.00, 1.5:1.00, 1.0:1.00, 0.80:1.00,
0.70:1.00,
0.65:1.00, 0.61:1.00, 0.57:1.00, 0.54:1.00 or 0.51:1.00;
- a ratio of moles of substituted phenol moieties from component (D) to moles
of
phosphorus from component (C) in the same composition that is at least, with
increasing preference in the order given, 0.060:1.00, 0.12:1.00, 0.16:1.00,
0.20:1.00, 0.25:1.00, 0.30:1.00, 0.35:1.00, 0.40:1.00, 0.43:1.00, or 0.46:1.00
and
independently preferably is not more than, with increasing preference in the
order
2o given, 2.0:1.00, 1.5:1.00, 1.0:1.00, 0.80:1.00, 0.70:1.00, 0.65:1.00,
0.61:1.00,
0.57:1.00, 0.54:1.00, 0.51:1.00, or 0.48:1.00.
Working compositions containing up to from five to ten times these amounts of
active
ingredients are also generally fully practical to use when coating control is
precise
enough to meter relatively thin uniform films of working composition onto the
metal
2s surface to be treated according to the invention. Concentrations of at
least six times the
values given above are also preferred for concentrated compositions from which
working
compositions within the more preferred ranges given above are to be made by
dilution
with water.
Ordinarily, at least for economy, all of the optional components indicated
above
so are preferably omitted, because satisfactory quality can be obtained
without them. They
may be useful in special situations, however.
Preferably the amount of composition applied in a process according to this in-
vention is chosen so as to result in a total add-on mass (after drying) in the
range from
5 to 500 milligrams per square meter of the substrate surface treated (this
unit of add-on
ss mass being hereinafter usually abbreviated as "mg/mZ"), more preferably
from 10 to 400
mg/m2, or still more preferably from 50 to 300 mg/m2. The add-on mass of the
protective
13
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
film formed by a process according to the invention may be conveniently
monitored and
controlled by measuring the add-on weight or mass of the metal atoms in the
anions of
component (A) as defined above. The amount of these metal atoms may be
measured
by any of several conventional analytical techniques known to those skilled in
the art.
s The most reliable measurements generally involve dissolving the coating from
a known
area of coated substrate and determining the content of the metal of interest
in the re-
sulting solution. The total add-on mass can then be calculated from the known
relation-
ship between the amount of the metal in component (A) and the total mass of
the part
of the total composition that remains after drying. For the purpose of this
calculation it
~o is assumed that all water in the working composition, including any water
of hydration in
any solid constituent added to the composition during its preparation, is
expelled by
drying but that all other constituents of the liquid film of working
composition coated onto
the surface measured remain in the dried coating. In many instances, fully
practically
satisfactory quality can be achieved by experience in judging the visual
appearance of
is the coating, without directly measuring the amount of coating added on at
all.
A working composition according to the invention may be applied to a metal
work-
piece and dried thereon by any convenient method, several of which will be
readily ap-
parent to those skilled in the art. For example, coating the metal with a
liquid film may
be accomplished by immersing the surface in a container of the liquid
composition,
2o spraying the composition on the surface, coating the surface by passing it
between upper
and lower rollers with the lower roller immersed in a container of the liquid
composition,
and the like, or by a mixture of methods. Excessive amounts of the liquid
composition
that might otherwise remain on some part of the surface prior to drying may be
removed
before drying by any convenient method, such as drainage under the influence
of gravity,
2s squeegees, passing between rolls, wiping with a towel or other absorbent
material, and
the like. Alternatively, the excess may simply be dried into place on the
surface, and any
area of the dried substrate that exhibits a powdery appearance as a result of
dried
excess amounts of coating material can usually be made uniform in appearance
by
wiping the powdery areas with a soft cloth or similar material to remove the
powdery
so excess of dried coating. (Insofar as it has been measured, the protective
quality of the
coating is also uniform after such wiping to remove any powdery excess.)
Drying also
may be accomplished by any convenient method, such as a hot air oven, exposure
to
infra-red radiation, microwave heating, and the like.
For flat and particularly for continuous flat workpieces such as sheet and
coil
s5 stock, application by a roller set in any of several conventional
arrangements, followed
by drying in a separate stage, is generally preferred. The temperature during
application
14
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
of the liquid composition may be any temperature within the liquid range of
the com-
position, although for convenience and economy in application by roller
coating, normal
room temperature, i.e., from 20 - 30 °C, is usually preferred. In most
cases for continu-
ous processing of coils, rapid operation is favored, and in such cases drying
by infrared
s radiative heating, to produce a peak metal temperature in the range already
given above,
is generally preferred.
Alternatively, particularly if the shape of the substrate is not suitable for
roll coat-
ing, a composition may be sprayed onto the surface of the substrate and
allowed to dry
in place. Such cycles can be repeated as often as needed until the desired
thickness
~o of coating, generally measured in mg/mz, is achieved. For this type of
operation, it is pre-
ferred that the temperature of the metal substrate surface during application
of the work-
ing composition be in the range from 20 to 300, more preferably from 30 to
100, or still
more preferably from 30 to 90 °C.
Preferably, the metal surface to be treated according to the invention is
first
cleaned of any contaminants, particularly organic contaminants and foreign
metal fines
and/or inclusions. Such cleaning may be accomplished by methods known to those
skilled in the art and adapted to the particular type of metal substrate to be
treated. For
example, if predominantly chemical cleaning is desired, for galvanized steel
substrates,
the surface is most preferably cleaned with a conventional hot alkaline
cleaner, then
2o rinsed with hot water, squeegeed, and dried. For aluminum substrates, the
surface to
be treated most preferably is first contacted with a conventional hot alkaline
cleaner, then
rinsed in hot water, then, optionally, contacted with a neutralizing acid
rinse, before being
contacted with an acid aqueous composition as described above. Abrasive
cleaning,
particularly with high-loft type coated abrasive products, may also be used
effectively
25 before treatment according to this invention.
The invention is particularly well adapted to treating surfaces that are to be
sub-
sequently further protected by applying conventional organic protective
coatings such as
paint, lacquer, and the like over the surface produced by treatment according
to the in-
vention.
so The practice of this invention may be further appreciated by consideration
of the
following, non-limiting, working and comparison examples.
An aqueous solution of a polymer for component (D) of a composition according
to the invention was prepared as follows: To a 500 milliliter (hereinafter
usually abbrevi-
ated as "ml") size three-neck round bottom flask equipped with an overhead
stirrer, reflux
ss condenser, nitrogen gas inlet, heating mantle and thermocouple, about 350
grams (here-
inafter usually abbreviated as "g") of deionized water, 4.2 grams of sodium
hydroxide,
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
and 29.1 g of N-methyl ethanolamine were added and mixed till dissolved. 48.4
g of
solid poly(4-hydroxystyrene) with a weight average molecular weight of about
5000
Daltons was then added with mixing. The mixture was then heated to 65
°C with
mechanical agitation. After 1.5 hours of mixing at 65 °C the polymer
was completely
s dissolved. The resulting solution was then allowed to cool to 30 °C
and 12.5 g of
paraformaldehyde containing 92 % stoichiometric equivalent as formaldehyde
(i.e.,
HCHO) was added with continued mixing. After 30 minutes, the paraformaldehyde
was
completely dissolved. The solution was then heated with mixing to 65 °C
and held at that
temperature for 1.5 hours. Heating was then discontinued, and after the
solution had
~o cooled to about 30 °C, the solution was transferred to a 1500 ml
beaker equipped with
a stirrer, and therein diluted with about 500 grams of deionized water. The
resulting
solution was well mixed; 33.4 g of 75 % phosphoric acid (i.e., H3P04) in water
was added
quickly. After this addition, the solution changed from transparent to very
turbid; the
solution then became transparent again within one hour. The pH at this stage
was 6.7.
is The solution was then passed through an ion-exchange column containing at
least 100 ml of Rohm and Haas IR-120+ cation exchange resin. The resulting pH
was
5.4; the sodium concentration was less than 1 part of sodium per million parts
of the so-
lution, a concentration unit that may be freely used hereinafter for
specifying the concen-
tration of any noted material and is hereinafter usually abbreviated as "ppm",
and the re-
2o sidual formaldehyde concentration was about 90 ppm. 3.0 g of 60 %
fluorotitanic acid
(i.e., H2TiF6) and sufficient deionized water to give a total mass of 1000 g
of the solution
were then added with mixing. The final solution contained 10.2 % non-volatile
solids on
drying.
A concentrate according to the invention was prepared as follows: 24.6 parts
of
2s deionized water, 3.51 parts of 75 % H3P04 in water solution, and 8.22 parts
of 60
H2TiF6 in water solution were mixed to form a homogeneous liquid. To this was
slowly
added 2.44 parts of solid MnO, with stirring and cooling, and after apparent
homogeneity
had been achieved, stirring was continued for 30 minutes. Finally, to this
mixture was
added 42.2 parts of the 10.2 % solution of substituted aminomethylated
phenolic polymer
so prepared as described in the immediately preceding paragraph.
A working composition according to the invention was made by mixing the con-
centrate described in the immediately preceding paragraph with deionized water
to give
a homogeneous liquid containing 15 % of the concentrate. For use, this working
compo-
sition was put into the reservoir of an applicator as taught in U. S. Patent
5,702,759.
35 Conventional cold rolled steel test panels were prepared for use by rubbing
with
a water-wetted Scotch-BriteT"' 96 General Purpose Scouring Pad (a high loft
coated
16
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
abrasive pad commercially supplied by Minnesota Mining & Manufacturing Co.)
once in
a lengthwise direction, next in a cross-direction, and once again in a
lengthwise direction,
then rinsing with hot tap water and finally wiping dry with a clean, dry, lint-
free towel (Kay-
dryT"' EX-L 34705 Delicate Task Wiper commercially supplied by Kimberly-Clark)
immed-
lately before contact with whatever treatment liquid was to be used on the
particular pan-
els. In a process example according to the invention, panels thus cleaned were
wiped
sparingly with the felt tip of the applicator wetted with the working
composition described
in the immediately preceding paragraph. Each wiping stroke of the applicator
was
spaced so that about half of the width of the immediately previously coated
width of the
1o substrate was overlapped, but puddling of the liquid was avoided. (The
wetness of the
felt tip can be controlled by activating the plunger valve of the applicator
more or less oft-
en and/or by using shorter or longer periods of valve opening. If any
excessive amount
of liquid is deposited in a particular area, the excess amount of it can be
removed by wip-
ing with the applicator felt after its most recent supply of liquid from the
reservoir of the
applicator has been substantially diminished by contact with another part of
the metal
substrate.) The residue of liquid was then allowed to dry in the ambient air.
Some
streaked areas of white dust, indicative of more than optimal liquid coating
thickness,
were observed on the surface after drying. These areas were gently brushed
away with
a clean, soft, dry towel before further treatment of the panels, and
underneath these
2o formerly dusty areas the same bluish coating as on the remainder of the
panel was
observed.
In Comparison Example 1, abrasive cleaning and subsequent drying as
described above for the example according to the invention were used without
any
subsequent treatment before painting. In the remaining comparison examples,
the same
2s abrasive cleaning and subsequent drying were used prior to the following
prepainting
treatments as specified:
Comparison Example 2: The cleaned substrates were treated with TOUCH-N-PREP~
ALODINE~ 1132, a commercial product available from the Henkel Surface
Technologies Div. of Henkel Corporation, Madison Heights, Michigan, U.S.A.
so This product contains as its active ingredients hexavalent and trivalent
chromium,
fluorozirconic acid, and phosphoric acid and also contains a fluorinated
surfact-
ant.
Comparison Example 3: This was first treated as for Comparison Example 2,
dried, and
then post-rinsed with a 0.25 % solution in water of the aqueous solution in
water
ss of polyvinyl phenol) grafted with substituted aminomethyl moieties that was
used
to provide component (D) for the concentrate according to the invention as
17
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
described above.
Comparison Example 4: An aqueous solution of an amine oxide type substituted
phenolic polymer was prepared as follows: To a 2000 ml size three-neck round
bottom flask equipped with an overhead stirrer, reflux condenser, nitrogen gas
inlet, heating mantle and thermocouple, about 1300 g of deionized water, 18.8
g of sodium hydroxide, 129.1 g of N-methyl ethanolamine, and 215 g of solid
poly(4-hydroxy styrene) with a weight average molecular weight of about 5000
Daltons were added and mixed till dissolved. The mixture was then heated to 65
°C with mixing. After 1.5 hours of mixing at 65 °C the polymer
and all other
~o materials added were completely dissolved. The resulting solution was then
allowed to cool to 30 °C and 55.6 g of paraformaldehyde containing 92
stoichiometric equivalent as formaldehyde (i.e., HCHO) and 114 g of additional
deionized water were added with continued mixing. After 30 minutes, the
paraformaldehyde was completely dissolved. The solution was then heated with
mixing to 65 °C. and held at that temperature for 1.5 hours. Heating
was then
discontinued, and after the solution had cooled to about 30 °C, the
solution was
diluted with 1784 g of additional deionized water, then mixed rapidly with 104
g
of 31 % H202 in water and 28 g of 14.6 % H202 in water. The solution became
viscous with a heavy precipitate, but after hand mixing and continued
mechanical
2o stirring for about 40 minutes, the mixture became transparent and
homogeneous
again. The resulting mixture was continuously stirred mechanically for about
16
hours, and was then passed through an ion-exchange column filled with 500 ml
of acid form Rohm and Haas IR-120+ cation exchange resin. A yield of 3.8
kilograms (hereinafter usually abbreviated as "kg") of solution with a pH of
8.1
resulted. To this was added 0.19 kg of 20 % H2ZrF6 solution in water,
resulting
in a total mass of 4.0 kg. Finally, to 1.0 kg of this, 46 g of additional 20 %
HZZrFs
solution in water was added, resulting in a final amine oxide substituted
phenolic
polymer solution with a pH of 3.4. The working composition for Comparison
Example 4 consisted of a 0.25 % solution in water of this final amine oxide
so substituted phenolic polymer solution.
Comparison Example 5: For this example, an aqueous solution of a substituted
amino-
methylated phenolic polymer with polyhydroxyalkyl substituents on the amino
nitrogen atoms was made as follows: 83 parts of propoxylated propane solvent
(PROPASOLT"' P from Union Carbide) and 38 parts of solid poly(4-hydroxy
ss styrene) with a weight average molecular weight of 5000 Daltons were mixed
until homogeneous. Then 62 parts of N-methyl glucamine slurried in about 100
18
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
parts of deionized water were added to this mixture, and the resulting mixture
was warmed with stirring to 65 °C, after which 25 parts of a solution
in water of
37 % formaldehyde (also containing 11 % of pure methanol to inhibit
polymerization of the formaldehyde) were added over the course of 45 minutes.
The resulting reaction product containing mixture was then heated to 90
°C and
held at that temperature for 6 hours. After cooling, 4.2 parts of 75 % H3P04
solution in water was added, and finally the entire mixture was diluted with
deionized water to constitute 1000 total parts.
To make the working treatment composition for Comparative Example 5,
io 602 parts of the polymer solution made as described in the immediately
preceding paragraph was mixed with a precursor mixture formed by mixing 45
parts of 75 % H3P04 solution in water, 82 parts of a 60 % solution of H2TiF6,
and
24 parts of solid MnO, the latter being added slowly in solid form to the
mixture
of the two acids with stirring and cooling.
Comparison Example 6: The working treatment composition for this was
GALVAPREPT"~
SG nickel modified zinc phosphating composition, prepared and used as directed
by its manufacturer, the Henkel Surface Technologies Div. of Henkel
Corporation, Madison Heights, Michigan, U.S.A.
Three panels were treated with the working composition according to the
2o invention as described above and according to each of the Comparison
Examples 1 -
6 as described above and were subsequently painted with PPG ED5050B
cathodically
electrodeposited paint. The painted panels were then submitted to accelerated
corrosion
testing, as further detailed in Table 1 below.
Table 1
Test Identification Result
after
Test
for:
Ex- Com parative
~ Example:
ample1 2 3 4 5 6
Ford Scab (FLTM BI 123-Ol) 1.6 36 1.4 1.8 33 24 24
Salt Spray (504 Hours) -
Rated by:
Maximum Creep, Millimeters 1.4S 3.25 1.4S 1.5s 3.45 1.4S1.85
Average Creep, Millimeters 0.9 1.3 0.8 0.8 2.2 0.7 0.6
ASTM Overall 8 7 8 8 6 8 8
In addition to the results shown in Table 1, all of the samples had the same
ratings in
other tests or rating methods, as follows: Salt spray rated by minimum creep,
00; Conical
19
CA 02389343 2002-04-29
WO 01/32952 PCT/US00/29266
Mandrel, 10; Reverse Impact, 10; Knife Adhesion, 5B; and 1008 hours humidity
testing
according to American Society for Testing and Materials Method D2247, 10. The
example according to the invention is clearly far better in performance in the
aggressive
cyclic "scab" test than any of the comparison examples, except for those that
utilize
s hexavalent chromium, with its accompanying pollution concerns.
