Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM FOR NICKEL-FREE ZINC PHOSPHATE PRETREATMENT
FIELD OF THE INVENTION
[0001] A system for pretreating a substrate with a nickel-free zinc
phosphate
pretreatment composition is disclosed.
BACKGROUND
[0002] Phosphate conversion coatings are well known for treating metal
surfaces,
particularly ferrous, zinc and aluminum metals and their alloys. When applied,
these
phosphate coatings form a phosphate layer, primarily of zinc and iron
phosphate crystals,
which provides corrosion resistance and/or enhances the adhesion of
subsequently applied
coatings.
[0003] Prior to application of the phosphate coating, the metal substrate
is typically
"conditioned" or "activated" by subjecting the surface of the metal substrate
to a diluted
aqueous dispersion, sometimes referred to as an activating rinse or activator,
by introducing
or immersing the metal substrate into a tank that contains the activating
rinse. "Activation" of
the surface of the metal substrate often is achieved due to the adsorption of
colloidal
titanium-phosphate particles, which are present in the activating rinse, to
the metal's surface.
These colloidal titanium-phosphate particles, however, have a tendency to
agglomerate in the
activating rinse bath due to dissolved cations that are typically present in
the activating rinse
conditioner bath.
[0004] The phosphate conversion coating is typically applied to a
substrate by
immersing the substrate into a heated bath comprising metal phosphate
particles.
[0005] Conventional techniques for coating such substrates include
techniques that
involve pretreating the metal substrate with nickel-containing compositions.
The use of such
nickel-containing compositions, however, impart environmental concerns.
SUMMARY
[0006] Disclosed is a substrate pretreatment system, comprising (a) an
activating rinse
for treating at least a portion of a substrate comprising a dispersion of
metal phosphate
particles having a D90 particle size of no greater than 10 m, wherein the
metal phosphate
comprises divalent or trivalent metals or combinations thereof; and (b) a
pretreatment
composition for treating at least a portion of the substrate treated with the
activating rinse,
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comprising zinc ions and phosphate ions, wherein the pretreatment composition
is
substantially free of nickel.
[0007] Also disclosed is a method of treating a substrate with the
substrate
pretreatment system.
[0008] Also disclosed is a substrate treated with the substrate
pretreatment system.
DETAILED DESCRIPTION
[0009] According to the present invention, the substrate pretreatment
system
comprises, or in some instances consists of, or in some instances consists
essentially of: an
activating rinse for treating at least a portion of a substrate comprising a
dispersion of metal
phosphate particles having a D90 particle size of no greater than 10 um,
wherein the metal
phosphate comprises divalent or trivalent metals or combinations thereof; and
(b) a
pretreatment composition for treating at least a portion of the substrate
treated with the
activating rinse, comprising zinc ions and phosphate ions, wherein the
pretreatment
composition is substantially free of nickel.
[0010] As used herein, the phrase "activating rinse" refers to a
continuous aqueous
medium having dispersed and/or suspended therein metal phosphate particles
that is applied
onto at least a portion of a substrate and/or into which at least a portion of
a substrate is
immersed to "activate" or "condition" the substrate in order to promote the
formation of a
metal phosphate coating on at least a portion of the substrate that was
treated with the
activating rinse. As used herein, to "activate" or "condition" the substrate
surface means to
create nucleation sites on the substrate surface. While not wishing to be
bound by theory, it
is believed that such nucleation sites promote the formation of metal
phosphate crystals on
the substrate surface when the substrate surface subsequently is treated with
a metal
phosphate pretreatment composition. For example, activation of the substrate
surface is
believed to create nucleation sites that promote the formation of zinc and
zinc/iron phosphate
crystals on the substrate surface when the substrate surface is pretreated
with a zinc
phosphate pretreatment composition.
[0011] Non-limiting examples of a suitable substrate that can be treated
with the
activating rinse include, but are not limited to, a metal and/or a metal alloy
substrate. For
example, the metal and/or metal alloy can comprise or be aluminum, steel, or
zinc.
According to the present invention, a steel substrate could include cold
rolled steel,
electrogalvanized steel, and hot dipped galvanized steel. According to the
present invention,
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the substrate may comprise a portion of a vehicle such as a vehicular body
(e.g., without
limitation, door, body panel, trunk deck lid, roof panel, hood, and/or roof)
and/or a vehicular
frame.
[0012] As used herein, the term "vehicle" or variations thereof includes,
but is not
limited to, civilian, commercial, and military land vehicles such as cars and
trucks.
[0013] As used herein, the term "dispersion" refers to a two-phase
transparent,
translucent or opaque system in which metal phosphate particles are in the
dispersed phase
and an aqueous medium, which includes water, is in the continuous phase. An
"aqueous
medium" is a liquid medium that is 50 weight percent or greater of water, with
weight
percent based on non-solid content of the activating rinse. The aqueous medium
may
comprise 50 weight percent or less of other organic co-solvents, such as 10
weight percent or
less. According to the present invention, the organic co-solvents are at least
partially
miscible with water. In the aqueous medium, water miscible organic solvents
may be
present, for example, alcohols with up to about 8 carbon atoms such as
methanol,
isopropanol, and the like, or glycol ethers such as the monoalkyl ethers of
ethylene glycol,
diethylene glycol, or propylene glycol, and the like.
[0014] As used herein, the term "pulverized" refers to particles having
variable aspect
ratios, where the term "aspect ratio" refers to the ratio of the length to the
width of a particle
(i.e., the aspect ratio does not define a sphere).
[0015] According to the present invention, the metal phosphate particles
of the
dispersion of metal phosphate particles of divalent or trivalent metals or
combinations thereof
may have a D90 particle size that is not greater than 10 p.m, such as not
greater than 8 p.m,
such as not greater than 5 p.m, such as not greater than 2 p.m, such as not
greater than 1 p.m
and in some cases may be at least 0.06 p.m, such as at least 0.1 p.m, such as
at least 0.2 p.m.
According to the present invention, the metal phosphate particles of the
dispersion of
phosphate particles of divalent or trivalent metals or combinations thereof
may have a D90
particle size of 0.06 p.m to 8 p.m, such as 0.1 p.m to 5 p.m, such as 0.2 p.m
to 2 p.m.
[0016] As used herein, the term "D90" particle size refers to a volume-
weighted
particle distribution in which 90% of the particles in the particle
distribution have a diameter
smaller than the "D90" value. As used herein, the term "Dio" particle size
refers to a volume-
weighted particle distribution in which 10% of the particles in the particle
distribution have a
diameter smaller than the "Dio" value. As used herein, the term "Dso" particle
size refers to a
volume-weighted particle distribution in which 50% of the particles in the
particle
distribution have a diameter smaller than the "Dso" value.
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[0017] According to the present invention, particle size may be measured
using an
instrument such as a Mastersizer 2000, available from Malvern Instruments,
Ltd., of Malvern,
Worcestershire, UK, or an equivalent instrument. The Mastersizer 2000 directs
a laser beam
(0.633 mm diameter, 633 nm wavelength) through a dispersion of particles (in
distilled,
deionized or filtered water to 2-3% obscuration), and measures the light
scattering of the
dispersion (measurement parameters 25 C, 2200 RPM, 30 sec premeasurement
delay, 10 sec
background measurement, 10 sec sample measurement). The amount of light
scattered by the
dispersion is inversely proportional to the particle size. A series of
detectors measure the
scattered light and the data are then analyzed by computer software (Malvern
Mastersizer
2000 software, version 5.60) to generate a particle size distribution, from
which particle size
can be routinely determined.
[0018] According to the present invention, the sample of dispersion of
particles
optionally may be sonicated prior to analysis for particle size. According to
the present
invention, the sonication process comprises: (1) mixing the dispersion of
particles using a
Vortex mixer (Fisher Scientific Vortex Genie 2, or equivalent); (2) adding 15
mL of distilled
deionized, ultra-filtered water to a 20 mL screw-cap scintillation vial; (3)
adding 4 drops of
the dispersion to the vial; (4) mixing the contents of the vial using the
Vortex mixer; (5)
capping the vial and placing it into an ultrasonic water bath (Fisher
Scientific Model F530, or
equivalent) for 5 minutes; (6) vortexing the vial again; and (7) adding the
sample dropwise to
the Mastersizer to reach an obscuration between 2-3 for particle size
distribution analysis
described above.
[0019] According to the present invention, the metal phosphate particles
may be
substantially pulverized, such that more than 90% of the metal phosphate
particles in the
activating rinse composition are pulverized, such as more than 91%, such as
more than 92%,
such as more than 93%, such as more than 94%, such as more than 95%, such as
more than
96%, such as more than 97%, such as more than 98%, such as more than 99%.
According to
the present invention, the metal phosphate particles may be completely
pulverized, such that
100% of the particles are pulverized.
[0020] According to the present invention, the metal phosphate (as total
metal
compound) may be present in the activating rinse in an amount of at least 50
ppm, based on
total weight of the activating rinse, such as at least 150 ppm, and in some
instances may be
present in the activating rinse in an amount of no more than 5000 ppm, based
on total weight
of the activating rinse, such as no more than 1500 ppm. According to the
present invention,
the metal phosphate (as total metal compound) may be present in the activating
rinse in an
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amount of 50 ppm to 5,000 ppm of total metal phosphate based on the total
weight of the
activating rinse, such as of 150 ppm to 1,500 ppm.
[0021] According to the present invention, the divalent or trivalent metal
of the metal
phosphate may comprise zinc, iron, calcium, manganese, aluminum, nickel, or
combinations
thereof If combinations of different metal phosphates are employed, they may
comprise the
same or different metals, and may be selected from the particular zinc, iron,
calcium,
manganese and aluminum phosphates mentioned in the following.
[0022] Suitable zinc phosphates useful in the activating rinse bath
include, without
limitation Zn3(PO4)2, Zn2Fe(PO4)2, Zn2Ca(PO4)2, Zn2Mn(PO4)2, or combinations
thereof.
[0023] Suitable iron phosphates useful in the activating rinse bath
include, without
limitation FePO4, Fe3(PO4)2, or combinations thereof.
[0024] Suitable calcium phosphates useful in the activating rinse bath
include, without
limitation CaHPO4, Ca3(PO4)2, or combinations thereof
[0025] Suitable manganese phosphates useful in the activating rinse bath
include,
without limitation Mn3(PO4)2, MnPO4, or combinations thereof.
[0026] Suitable aluminum phosphates useful in the activating rinse bath
include,
without limitation A1PO4.
[0027] According to the present invention, the activating rinse may
further comprise a
dispersant. The dispersant may be ionic or non-ionic. Suitable ionic
dispersants useful in the
activating rinse may comprise an aromatic organic acid, a phenolic compound, a
phenolic
resin, or combinations thereof. Suitable non-ionic dispersants useful in the
activating rinse
may include non-ionic polymers, in particular those comprised of monomers (or
residues
thereof) including propylene oxide, ethylene oxide, styrene, a monoacid such
as (meth)acrylic
acid, a diacid such as maleic acid or itaconic acid, an acid anhydride such as
acrylic
anhydride or maleic anhydride, or combinations thereof. Examples of suitable
commercially
available non-ionic dispersants include DISPERBYK4D-190 available from BYK-
Chemie
GmbH and ZetaSperse 3100 available from Air Products Chemicals Inc.
[0028] According to the present invention, the activating rinse may be
substantially
free or completely free of ionic dispersants. As used herein, an activating
rinse is
substantially free of ionic dispersants if ionic dispersants are present in an
amount less than
1% by weight, based on the total weight of the activating rinse. As used
herein, an activating
rinse is completely free of ionic dispersants if ionic dispersants are not
present in the
activating rinse, meaning 0% by weight based on the total weight of the
activating rinse.
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[0029] According to the present invention, the activating rinse optionally
may include
a metal sulfate salt. The metal of the metal sulfate may be the same as or
different from the
metal of the metal phosphate particles. According to the present invention,
the metal of the
metal sulfate salt may comprise a divalent metal, a trivalent metal or
combinations thereof,
such as, for example, nickel, copper, zinc, iron, magnesium, cobalt, aluminum
or
combinations thereof.
[0030] According to the present invention, when present, if at all, the
sulfate ion of the
metal sulfate salt may be present in the activating rinse in an amount of at
least 5 ppm based
on the total weight of the activating rinse, such as at least 10 ppm, such as
at least 20 ppm,
such as at least 50 ppm, and in some cases, no more than the solubility limit
of the metal
sulfate salt in the activating rinse, such as no more than 5,000 ppm, such as
no more than
1,000 ppm, such as no more than 500 ppm, such as no more than 250 ppm.
According to the
present invention, the sulfate ion of the metal sulfate salt may be present in
an amount of 5
ppm to 5,000 ppm based on a total amount of sulfate in the metal sulfate salt,
such as 10 ppm
to 1,000 ppm, such as 20 ppm to 500 ppm, such as 50 ppm to 250 ppm. According
to the
present invention, the activating rinse may be substantially free, or in some
instances,
completely free, of sulfate ions. As used herein with respect to the sulfate
ion of a metal
sulfate salt, the term "substantially free" means that the sulfate ion is
present in the activating
rinse in an amount of less than 5 ppm based on the total weight of the
activating rinse. As
used herein with respect to the sulfate ion of a metal sulfate salt, the term
"completely free"
means that the activating rinse does not comprise a sulfate ion (i.e., there
are 0 ppm of sulfate
ion (based on the total weight of the activating rinse) present in the
activating rinse).
[0031] According to the present invention, the activating rinse may be in
the form of a
concentrate, wherein the concentrate has a viscosity sufficient to prevent the
metal phosphate
particles and metal sulfate salt (if present) from settling out. According to
the present
invention, in use, the concentrated activating rinse may be diluted with water
and/or an
organic solvent.
[0032] According to the present invention, the activating rinse may be a
1K ("One-
Component", or "One Part") composition or a multi-component composition, such
as, for
example, 2K ("Two-Component", or 'Two Part") compositions. As defined herein,
a "1K"
composition is a composition in which all of the ingredients may be premixed
and stored. By
contrast, a multi-component composition is one in which at least two of the
ingredients are
stored separately and are mixed together to form the treatment bath.
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[0033] According to the present invention, the activating rinse may be a
1K
composition, wherein the 1K composition is formed from: a dispersion of metal
phosphate
particles of divalent metals, trivalent metals or combinations thereof, the
metal phosphate
particles having a D90 particle size that is not greater than 10 [tm; a
dispersant; and a metal
sulfate salt (if present). Optionally, the 1K activating rinse may be a
concentrate that is
diluted to form the bath containing the activating rinse.
[0034] According to the present invention, the activating rinse may be a
2K
composition wherein a dispersion of metal phosphate particles of divalent
metals, trivalent
metals or combinations thereof, the metal phosphate particles having a D90
particle size that is
not greater than 10 [tm, and a dispersant form a part of a first component. A
metal sulfate salt
may form a part of a second component. Additional components comprising any of
the
optional ingredients described below also may be added to the bath containing
the activating
rinse. Any of the components of the activating rinse may be a concentrate that
is diluted to
form the bath containing the activating rinse.
[0035] According to the present invention, the activating rinse may include a
wetting agent.
According to the present invention, wetting agents may be present at amounts
of up to 2 percent
by weight, such as up to 0.5 percent by weight, based on the total weight of
the activating rinse.
In some instances, wetting agents may be present in amounts of 0.1 percent by
weight to 2
percent by weight, based on total weight of the activating rinse, such as 0.3
percent by weight
to 0.5 percent by weight. As used herein, a "wetting agent" reduces the
surface tension at the
interface between the surface of the particles of the dispersed phase and the
aqueous medium
to allow the aqueous medium to more evenly contact or "wet" the surface of the
particles of
the dispersed phase.
[0036] According to the present invention, the activating rinse may have a
pH of 6 to
12, such as 6.5 to 9, such as 7.5 to 8.5, such as 7 to 8. An alkaline
component may be present
in the activating rinse in an amount sufficient to adjust the pH of the
activating rinse.
Suitable alkaline components may include, for example, sodium hydroxide,
sodium
carbonate, sodium tripolyphosphate, potassium orthophosphate, or combinations
thereof.
[0037] According to the present invention, the activating rinse may also
include a
biocide. Suitable biocides include, for example, methyl chloro
isothiazolinone, methyl
isothiazolinone, or combinations thereof When utilized, the biocide may be
present in an
amount of at least 10 ppm based on active material in the activating rinse,
such as at least 20
ppm, such as at least 80 ppm, such as at least 100 ppm, and in some instances,
no more than
140 ppm, such as no more than 120 ppm, such as no more than 40 ppm, such as no
more than
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30 ppm. According to the present invention, the biocide may be present in an
amount of 10
ppm to 140 ppm based on active material, such as 10 ppm to 40 ppm, such as 20
ppm to 30
ppm, such as 80 ppm to 140 ppm, such as 100 ppm to 120 ppm. The skilled
artisan will
recognize that biocides may be included in the activating rinse in amounts
based on
manufacturer instructions.
[0038] According to the present invention, the activating rinse may
further comprise
silica. According to the present invention, the silica may be a precipitated
silica, such as a
synthetic amorphous precipitated silica. According to the present invention,
the silica may be
friable under shear. As used herein, "friable under shear" means that particle
size may be
reduced with shear. According to the present invention, the silica may
comprise, for
example, Hi-SilTm EZ 160G silica (commercially available from PPG Industries,
Inc.).
According to the present invention, if present, the silica may be present in
an amount of at
least 50 ppm, based on total weight of the activating rinse, such as at least
100 ppm, such as
at least 150 ppm, and in some instances, no more than 5000 ppm, based on total
weight of the
activating rinse, such as no more than 1000 ppm, such as no more than 500 ppm.
According
to the present invention, the silica may be present in the activating rinse in
an amount of 50
ppm to 5,000 ppm based on the total weight of the activating rinse, such as
100 ppm to 1,000
ppm, such as from 150 ppm to 500 ppm.
[0039] The activating rinse may optionally further comprise components in
addition to
the dispersant (i.e., components different than the dispersant), such as
nonionic surfactants
and auxiliaries conventionally used in the art. Such additional optional
components include
surfactants that function as defoamers. Amphoteric and/or nonionic surfactants
may be used.
Defoaming surfactants may be present, if at all, in amounts of at least at
least 0.1 percent by
weight, based on total weight of the activating rinse bath, such as at least
0.5 weight percent
by weight, and in some instances, may be present in amounts of no more than 1
weight
percent, such as no more than 0.7 percent by weight, based on the total weight
of the
activating rinse bath. In some instances, defoaming surfactants may be
present, if at all, in
amounts of 0.1 weight percent to 1 weight percent, such as 0.5 weight percent
to 0.7 percent
by weight, based on total weight of the activating rinse bath.
[0040] According to the present invention, the activating rinse may
further comprise a
rheology modifier in addition to the dispersant (i.e., different than the
dispersant). The
rheology modifier may comprise, for example, polyurethanes, acrylic polymers,
lattices,
styrene/butadiene, polyvinylalcohols, clays such as attapulgite, bentonite,
and other
montmorillonite, cellulose based materials such as carboxymethyl cellulose,
methyl cellulose,
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(hydroxypropyl)methyl cellulose or gelatin, gums such as guar and xanthan, or
combinations
thereof
[0041] According to the present invention, the activating rinse may be
substantially or,
in some cases, completely, free of titanium-phosphate particles. As used
herein, the term
"substantially free," when used in reference to the absence of titanium-
phosphate particles in
the activating rinse, means that any titanium-phosphate particles present in
the activating
rinse are not purposefully added and are present in a trace amount of less
than 5 ppm, based
on the total weight of the activating rinse. As used herein, the term
"completely free," when
used in reference to the absence of titanium-phosphate particles, means that
there are no
titanium-phosphate particles at all.
[0042] The activating rinse of the present invention can be prepared fresh
with the
above-mentioned ingredients in the concentrations specified or can be prepared
in the form
aqueous concentrates in which the concentration of various ingredients is
considerably higher
such that the concentrates may be diluted with aqueous medium such as water or
are diluted
by feeding them into an activating bath containing an activating rinse that
has been in use for
some time.
[0043] According to the present invention, the activating rinse bath may
comprise a
chelator. The chelator may comprise, for example, carboxylates such as
tartrates, citrates or
gluconates, acetate based complexes such as ethylenediaminetetraacetate or
nitrilotriacetate,
phosphates such as pentasodium triphosphate or tetrapotassium pyrophosphate,
phosphonates, polycarboxylates, the acids, esters, or salts of any of the
aforementioned, or
combinations thereof.
[0044] The substrate pretreatment system of the present invention also
comprises a
pretreatment composition comprising zinc ions and phosphate ions. The
pretreatment
composition may be substantially free, or in some cases, essentially free, or
in some cases,
completely free, of nickel. [As used herein, the term "pretreatment
composition" refers to a
composition that, upon contact with a substrate, reacts with and chemically
alters the
substrate surface and binds to it to form a protective layer and which
contains phosphates of
zinc, iron, and/or other divalent metals known in the art.] As used herein,
the term
"substantially free," when used with respect to the absence of nickel, means
nickel, if present
at all in the bath containing the pretreatment composition, the pretreatment
composition,
and/or layers formed from and comprising same, and, if present at all, only is
present in a
trace amount of 5 ppm or less, based on a total weight of the composition or
layer(s), as the
case may be. As used herein, the term "essentially free," when used with
respect to the
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absence of nickel, means nickel, if present at all in the bath containing the
pretreatment
composition, the pretreatment composition, and/or layers formed from and
comprising same,
and, if present at all, only is present in a trace amount of 1 ppm or less,
based on a total
weight of the composition or layer(s), as the case may be. As used herein, the
term
"completely free," when used with respect to the absence of nickel, means
nickel, is absent
from the bath containing the pretreatment composition, the pretreatment
composition, and/or
layers formed from and comprising same (i.e., the bath containing the
pretreatment
composition, the pretreatment composition, and/or layers formed from and
comprising same
contain 0 ppm of nickel, excluding nickel derived from drag-in, substrate(s),
and/or
dissolution of equipment.
[0045] According to the present invention, the zinc ion content of the
pretreatment
composition may be at least 500 ppm, based on total weight of the pretreatment
composition,
such as at least 800 ppm, and in some instances, may be no more than 1500 ppm,
based on
total weight of the pretreatment composition., such as no more than 1200 ppm.
According to
the present invention, the zinc ion content of the aqueous acidic compositions
may be 500
ppm to 1500 ppm, based on total weight of the pretreatment composition, such
as at least 800
ppm to 1200 ppm. The source of the zinc ion may be conventional zinc ion
sources, such as
zinc nitrate, zinc oxide, zinc carbonate, zinc metal, and the like.
[0046] According to the present invention, the phosphate content of the
pretreatment
composition may be at least 8000 ppm, based on total weight of the
pretreatment
composition, such as at least 12000 ppm, and in some cases may be no more than
20000 ppm,
based on total weight of the pretreatment composition, such as no more than
14000 ppm.
According to the present invention, the phosphate content of the pretreatment
composition
may be 8000 ppm to 20000 ppm, based on total weight of the pretreatment
composition, such
as 12000 ppm to 14000 ppm. The source of phosphate ion may be phosphotic acid,
monosodium phosphate, disodium phosphate, and the like.
[0047] The pretreatment composition of the present invention may have a pH
of at
least 2.5, such as at least 3.0, and in some cases, no more than 5.5, such as
no more than 3.5.
The pretreatment composition may have a pH of 2.5 to 5.5, such as 3.0 to 3.5.
[0048] According to the present invention, the pretreatment composition
may also
comprise an accelerator. The accelerator may be present in an amount
sufficient to accelerate
the formation of the zinc phosphate coating and may be present in the
pretreatment
composition in an amount of at least 500 ppm, based on total weight of the
pretreatment
composition, such as at least 1000 ppm, such as at least 2500 ppm, and in some
instances
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may be present in an amount of no more than 20000 ppm, based on total weight
of the
pretreatment composition, such as no more than 10000 ppm, such as no more than
5000 ppm.
According to the present invention, the accelerator may be present in the
pretreatment
composition in an amount of 500 ppm to 20000 ppm, based on total weight of the
pretreatment composition, such as 1000 ppm to 10000 ppm, such as 2500 ppm to
5000 ppm.
Useful accelerators may include oximes such as acetaldehyde oxime and
acetoxime, nitrites
such as sodium nitrite and ammonium nitrite, peroxides such as hydrogen
peroxide, or
combinations thereof.
[0049] According to the present invention, the pretreatment composition
may also
comprise fluoride ion, nitrate ion, and various metal ions, such as cobalt
ion, calcium ion,
magnesium ion, manganese ion, iron ion, copper ion, and the like.
[0050] Fluoride ion may be present in the pretreatment composition in an
amount of at
least 100 ppm, based on total weight of the pretreatment composition, such as
at least 250
ppm, and in some instances may be present in an amount of no more than 2500
ppm, based
on total weight of the pretreatment composition, such as no more than 1000
ppm, and in some
cases may be present in an amount of 100 ppm to 2500 ppm, based on total
weight of the
pretreatment composition, such as 250 ppm to 1000 ppm.
[0051] According to the present invention, nitrate ion may be present in
the
pretreatment composition in an amount of at least 1000 ppm, based on total
weight of the
pretreatment composition, such as at least 2000 ppm, and in some instances may
be present in
an amount of no more than 10000 ppm, based on total weight of the pretreatment
composition, such as no more than 5000 ppm, and in some cases may be present
in an
amount of 1000 ppm to 10000 ppm, based on total weight of the pretreatment
composition,
such as 2000 ppm to 5000 ppm.
[0052] According to the present invention, calcium ion may be present in
the
pretreatment composition in an amount of at least 100 ppm, based on total
weight of the
pretreatment composition, such as at least 500 ppm, and in some cases, n.o
more than 4000
ppm, based on total weight of the pretreatment composition, such as no more
than 2500 ppm,
and in some cases may be present in an amount of 100 ppm to 4000 ppm, based on
total
weight of the pretreatment composition, such as 500 ppm to 2500 ppm.
[0053] According to the present invention, manganese ion may be present in
the
pretreatment composition in an amount of at least 100 ppm, based on total
weight of the
pretreatment composition, such as at least 200 ppm, such as at least 500 ppm,
and in some
cases no more than 1500 ppm, based on total weight of the pretreatment
composition, such as
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no more than 1000 ppm, such as no more than 800 ppm, and in some cases, in an
amount of
100 ppm to 1.500 ppm, based on total weight of the pretreatment composition,
such as from
200 ppm to 1000 ppm, such as 500 ppm to 800 ppm.
[0054] According to the present invention, iron ion may be present in the
pretreatment
composition in an amount of at least 5 ppm, based on total weight of the
pretreatment
composition, such as at least 50 ppm, and in some cases, no more than 500 ppm,
based on
total weight of the pretreatment composition, such as no more than 300 ppm,
and in some
cases, may be present in the pretreatment composition in an amount of 5 ppm to
500 ppm,
such as 50 ppm to 300 ppm.
[0055] According to the present invention, copper ion may be present in
the
pretreatment composition in an amount of at least I ppm, based on total weight
of the
pretreatment composition, such as at least 3 ppm, and in some cases, no more
than 30 ppm,
based on total weight of the pretreatment composition, such as no more than 15
ppm, and in
some cases, may be present in the pretreatment composition in an amount of 1
ppm.
[0056] The pretreatment composition of the present invention can be
prepared fresh
with the above mentioned ingredients in the concentrations specified or can be
prepared in
the form of aqueous concentrates in which the concentration of the various
ingredients is
considerably higher such that the concentrates may be diluted with aqueous
medium such as
water or are diluted by feeding them into a zinc phosphating composition which
has been in
use for some time. Typical concentrates may contain at least 10,000 ppm zinc
ions, based on
total weight of the pretreatment composition concentrate, such as at least
12,000 ppm zinc
ions, such as at least 16,000 ppm zinc ions, and in some cases may contain no
more than
100,000 ppm zinc ions, based on total weight of the pretreatment composition
concentrate,
such as no more than 30,000 ppm zinc ions, such as no more than 20,000 ppm
zinc ions, and
in some cases may contain 10,000 ppm to 100,000 ppm zinc ions, based on total
weight of
the pretreatment composition concentrate, such as 12,000 ppm to 30,000 ppm
zinc ions, such
as from 16,000 ppm to 20,000 ppm zinc ions.
[0057] The substrate pretreatment system of the present invention may be
used in a
method of treating a metal substrate comprising contacting at least a portion
of a surface of
the substrate with the activating rinse comprising a dispersion of metal
phosphate particles
having a D90 particle size of no greater than 10 nm, wherein the metal
phosphate comprises
divalent or trivalent metals or combinations thereof, and subsequently
contacting at least a
portion of the surface that has been contacted with the activating rinse with
the pretreatment
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composition comprising zinc ions and phosphate ions, wherein the pretreatment
composition
is substantially free of nickel.
[0058] Optionally, the substrate surface to be treated in accordance with
the methods
of the present invention may be cleaned to remove grease, dirt, or other
extraneous matter
and/or rinsed prior to applying the activating rinse. Cleaning the substrate
surface is often
done by employing mild or strong alkaline cleaners, such as are commercially
available and
conventionally used in metal pretreatment processes. Examples of alkaline
cleaners suitable
for use in the present invention include ChemkleenTM 163, ChemkleenTM 177,
ChemkleenTM
181ALP, ChemkleenTM 490MX, and ChemkleenTM 2010LP each of which is
commercially
available from PPG Industries, Inc.
[0059] Following cleaning, the substrate optionally may be rinsed with tap
water,
deionized water, and/or an aqueous solution of rinsing agents in order to
remove any residue.
The wet substrate surface optionally may be dried, such as air dried, for
example, by using an
air knife or warm air blower.
[0060] According to the present invention, the activating rinse can be
applied to the
substrate surface by spray, roll-coating or immersion techniques. The
activating rinse may be
applied onto the substrate at a temperature of, for example, 15 C to 50 C,
such as 25 C to
35 C for any suitable period of time, such as at least 1 second, such as at
least 10 seconds,
such as at least 2 minutes, such as at least 5 minutes.
[0061] According to the present invention, the method for treating a
substrate further
includes contacting at least a portion of the surface that has been contacted
with the activating
rinse with the pretreatment composition described above to form a phosphate
coating on the
surface of the "activated" substrate. The pretreatment composition may be
applied by spray
application or immersion of the activated substrate in an phosphate bath which
contains zinc
at a temperature typically ranging from 20 C to 75 C for 1 to 3 minutes. The
bath typically
may be an acidic phosphate bath and may comprise iron and/or other divalent
metals known
in the art in addition to the zinc ions, as already discussed above.
[0062] After application of the phosphate coating, the substrate may be
optionally
post-rinsed with a chromium or non-chromium containing solution, optionally
rinsed with
water and/or optionally dried. Paint may then be applied, if desired, such as,
by
electrodeposition or by conventional spray or roll coating techniques.
[0063] The present invention is also directed to a substrate treated with
the
pretreatment system that is disclosed herein. The substrate may comprise
nucleation sites
formed from an activating rinse described above, and may further comprise a
metal
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phosphate coating formed from a metal phosphate pretreatment composition
described above
applied over the nucleation sites formed on at least a portion of the
substrate by the activating
rinse. The metal phosphate coating may comprise crystals having a crystal size
of at least 0.4
p.m, such as at least 0.5 p.m, such as at least 0.6 p.m, such as at least 0.9
p.m, and in some
cases no larger than 4 p.m, such as no larger than 2.7 p.m, such as no larger
than 2.5 p.m, such
as no larger than 2 p.m. The metal phosphate coating may comprise crystals
having a crystal
size of 0.4 p.m to 4 m, such as 0.5 p.m to 2.5 p.m, such as 0.6 p.m to 2 p.m.
[0064] Crystal size of a phosphate coating may be determined by methods
known to
those skilled in the art. For example, a representative area of the panel
(i.e., a coated area of
approximately 1.27 cm by 1.27 cm with no obvious coating defects) may be
selected and an
image of the representative area may be acquired an image at either 5,000x or
10,000x
magnification using a scanning electron microscope (SEM), such as, for
example, a Tescan
Vega 2 SEM. The magnification utilized will be dependent on the crystal size
as high
magnification (10,000x) will be required for crystal sizes that are not
distinguishable at
5,000x magnification using an SEM. Nine to twelve evenly-spaced crystals, e.g.
ten, on each
image may be measured using software known to those skilled in the art, such
as, for
example, ImageJ (version 1.46), and the representative crystal sizes may be
averaged to
determine crystal size. One skilled in the art will recognize that there can
be variations in this
procedure that retain the essential elements of microscopic imaging and
averaging of
representative crystal size.
[0065] In an example, the present invention also may be directed to an
activating stage
such as those used in an automotive manufacturing facility. According to the
present
invention, the activating stage comprises immersion of the substrate in a bath
which contains
the activating rinse of the substrate pretreatment system that is disclosed
herein. According
to the present invention, the activating rinse is contained within the
immersion tank at a
temperature of 15 C to 50 C. At least a portion of a surface of the substrate
is subjected to
the activating rinse by immersing the substrate in the activating rinse for
any suitable period
of time, e.g. those already described above. After being immersed in the
activating rinse, a
portion of the activated substrate then may be subjected to a phosphatizing
step by applying a
metal phosphate pretreatment composition, e.g. a zinc phosphate pretreatment
composition,
to the activated substrate. It should be noted, however, that prior to the
application of the
metal phosphate pretreatment composition to the activated substrate,
additional activating
rinse can be sprayed onto a portion of the activated substrate via a spraying
nozzle as the
activated substrate is removed from the immersion tank. For example, the
spraying nozzle
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could be a spray bank of nozzles which is positioned downstream from the
immersion tank.
After the activated substrate exits the immersion tank and/or after additional
activating rinse
is applied onto the activated substrate, the activated substrate is
phosphatized by applying a
metal phosphate pretreatment composition to the activated substrate using
techniques that are
known in the art such as a spray and/or an immersion technique.
[0066] According to the present invention, the activating stage may
comprise a
number of spraying nozzles that are used to apply the activating rinse bath
onto a least a
portion of a substrate. Disposed beneath the spraying nozzles is a spray tank
which is
adapted to collect the activating rinse that exits the spraying nozzles and/or
any excess
activating rinse that drips off the surface of the activated substrate. The
spray tank is
connected to the spraying nozzles in a manner that allows the spraying nozzles
to utilize the
activating rinse that is collected in the spray tank thereby recycling the
activating rinse bath.
After the activating rinse is applied onto at least a portion of the
substrate, the activated
substrate is then phosphatized as described in the preceding paragraph.
[0067] According to the present invention, after the substrate is
contacted with the
pretreatment composition, a coating composition comprising a film-forming
resin may be
deposited onto at least a portion of the surface of the substrate that has
been contacted with
the pretreatment composition. Any suitable technique may be used to deposit
such a coating
composition onto the substrate, including, for example, brushing, dipping,
flow coating,
spraying and the like. In some instances, however, as described in more detail
below, such
depositing of a coating composition may comprise an electrocoating step
wherein an
electrodepositable composition is deposited onto a metal substrate by
electrodeposition. In
certain other instances, as described in more detail below, such depositing of
a coating
composition comprises a powder coating step. In still other instances, the
coating
composition may be a liquid coating composition.
[0068] According to the present invention, the coating composition may
comprise a
thermosetting film-forming resin or a thermoplastic film-forming resin. As
used herein, the
term "film-forming resin" refers to resins that can form a self-supporting
continuous film on
at least a horizontal surface of a substrate upon removal of any diluents or
carriers present in
the composition or upon curing at ambient or elevated temperature.
Conventional film-
forming resins that may be used include, without limitation, those typically
used in
automotive OEM coating compositions, automotive refinish coating compositions,
industrial
coating compositions, architectural coating compositions, coil coating
compositions, and
aerospace coating compositions, among others. As used herein, the term
"thermosetting"
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refers to resins that "set" irreversibly upon curing or crosslinking, wherein
the polymer chains
of the polymeric components are joined together by covalent bonds. This
property is usually
associated with a cross-linking reaction of the composition constituents often
induced, for
example, by heat or radiation. Curing or crosslinking reactions also may be
carried out under
ambient conditions. Once cured or crosslinked, a thermosetting resin will not
melt upon the
application of heat and is insoluble in solvents. As used herein, the term
"thermoplastic"
refers to resins that comprise polymeric components that are not joined by
covalent bonds
and thereby can undergo liquid flow upon heating and are soluble in solvents.
[0069] As previously indicated, according to the present invention, a
coating
composition comprising a film-forming resin may be deposited onto the
substrate by an
electrocoating step wherein an electrodepositable composition is deposited
onto the metal
substrate by electrodeposition. In the process of electrodeposition, the metal
substrate being
treated, serving as an electrode, and an electrically conductive counter
electrode are placed in
contact with an ionic, electrodepositable composition. Upon passage of an
electric current
between the electrode and counter electrode while they are in contact with the
electrodepositable composition, an adherent film of the electrodepositable
composition will
deposit in a substantially continuous manner on the metal substrate.
[0070] According to the present invention, such electrodeposition may be
carried out
at a constant voltage in the range of from 1 volt to several thousand volts,
typically between
50 and 500 volts. Current density is usually between 1.0 ampere and 15 amperes
per square
foot (10.8 to 161.5 amperes per square meter) and tends to decrease quickly
during the
electrodeposition process, indicating formation of a continuous self-
insulating film.
[0071] According to the present invention, the electrodepositable coating
composition
may comprise a resinous phase dispersed in an aqueous medium wherein the
resinous phase
comprises: (a) an active hydrogen group-containing ionic electrodepositable
resin, and (b) a
curing agent having functional groups reactive with the active hydrogen groups
of (a).
[0072] According to the present invention, the electrodepositable
compositions may
contain for instance, as a main film-forming polymer, an active hydrogen-
containing ionic,
often cationic, electrodepositable resin. A wide variety of electrodepositable
film-forming
resins are known and can be used in the present invention so long as the
polymers are "water
dispersible," i.e., adapted to be solubilized, dispersed or emulsified in
water. The water
dispersible polymer is ionic in nature, that is, the polymer will contain
anionic functional
groups to impart a negative charge or may contain cationic functional groups
to impart a
positive charge.
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[0073] Examples of film-forming resins suitable for use in anionic
electrodepositable
coating compositions are base-solubilized, carboxylic acid containing
polymers, such as the
reaction product or adduct of a drying oil or semi-drying fatty acid ester
with a dicarboxylic
acid or anhydride; and the reaction product of a fatty acid ester, unsaturated
acid or anhydride
and any additional unsaturated modifying materials which are further reacted
with polyol.
Also suitable are the at least partially neutralized interpolymers of hydroxy-
alkyl esters of
unsaturated carboxylic acids, unsaturated carboxylic acid and at least one
other ethylenically
unsaturated monomer. Still another suitable electrodepositable film-forming
resin comprises
an alkyd-aminoplast vehicle, i.e., a vehicle containing an alkyd resin and an
amine-aldehyde
resin. Yet another anionic electrodepositable resin composition comprises
mixed esters of a
resinous polyol, such as is described in United States Patent No. 3,749,657 at
col. 9, lines 1 to
75 and col. 10, lines 1 to 13, the cited portion of which being incorporated
herein by
reference. Other acid functional polymers can also be used, such as
phosphatized
polyepoxide or phosphatized acrylic polymers as are known to those skilled in
the art.
[0074] As aforementioned, it is often desirable that the active hydrogen-
containing
ionic electrodepositable resin (a) is cationic and capable of deposition on a
cathode.
Examples of such cationic film-forming resins include amine salt group-
containing resins,
such as the acid-solubilized reaction products of polyepoxides and primary or
secondary
amines, such as those described in United States Patent Nos. 3,663,389;
3,984,299;
3,947,338; and 3,947,339. Often, these amine salt group-containing resins are
used in
combination with a blocked isocyanate curing agent. The isocyanate can be
fully blocked, as
described in United States Patent No. 3,984,299, or the isocyanate can be
partially blocked
and reacted with the resin backbone, such as is described in United States
Patent No.
3,947,338. Also, one-component compositions as described in United States
Patent No.
4,134,866 and DE-OS No. 2,707,405 can be used as the film-forming resin.
Besides the
epoxy-amine reaction products, film-forming resins can also be selected from
cationic acrylic
resins, such as those described in United States Patent Nos. 3,455,806 and
3,928,157.
[0075] Besides amine salt group-containing resins, quaternary ammonium
salt group-
containing resins can also be employed, such as those formed from reacting an
organic
polyepoxide with a tertiary amine salt as described in United States Patent
Nos. 3,962,165;
3,975,346; and 4,001,101. Examples of other cationic resins are ternary
sulfonium salt
group-containing resins and quaternary phosphonium salt-group containing
resins, such as
those described in United States Patent Nos. 3,793,278 and 3,984,922,
respectively. Also,
film-forming resins which cure via transesterification, such as described in
European
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Application No. 12463 can be used. Further, cationic compositions prepared
from Mannich
bases, such as described in United States Patent No. 4,134,932, can be used.
[0076] According to the present invention, the resins present in the
electrodepositable
composition are positively charged resins which contain primary and/or
secondary amine
groups, such as described in United States Patent Nos. 3,663,389; 3,947,339;
and 4,116,900.
In United States Patent No. 3,947,339, a polyketimine derivative of a
polyamine, such as
diethylenetriamine or triethylenetetraamine, is reacted with a polyepoxide.
When the
reaction product is neutralized with acid and dispersed in water, free primary
amine groups
are generated. Also, equivalent products are formed when polyepoxide is
reacted with excess
polyamines, such as diethylenetriamine and triethylenetetraamine, and the
excess polyamine
vacuum stripped from the reaction mixture, as described in United States
Patent Nos.
3,663,389 and 4,116,900.
[0077] According to the present invention, the active hydrogen-containing
ionic
electrodepositable resin may be present in the electrodepositable composition
in an amount of
1 to 60 percent by weight, such as 5 to 25 percent by weight, based on total
weight of the
electrodeposition bath.
[0078] As indicated, the resinous phase of the electrodepositable
composition often
further comprises a curing agent adapted to react with the active hydrogen
groups of the ionic
electrodepositable resin. For example, both blocked organic polyisocyanate and
aminoplast
curing agents are suitable for use in the present invention.
[0079] Aminoplast resins may be used as the curing agent for anionic
electrodeposition, are the condensation products of amines or amides with
aldehydes.
Examples of suitable amines or amides are melamine, benzoguanamine, urea and
similar
compounds. Generally, the aldehyde employed is formaldehyde, although products
can be
made from other aldehydes, such as acetaldehyde and furfural. The condensation
products
contain methylol groups or similar alkylol groups depending on the particular
aldehyde
employed. Often, these methylol groups are etherified by reaction with an
alcohol, such as a
monohydric alcohol containing from 1 to 4 carbon atoms, such as methanol,
ethanol,
isopropanol, and n-butanol. Aminoplast resins are commercially available from
American
Cyanamid Co. under the trademark CYMEL and from Monsanto Chemical Co. under
the
trademark RESIMENE.
[0080] The aminoplast curing agents are often utilized in conjunction with
the active
hydrogen containing anionic electrodepositable resin in amounts ranging from 5
percent to 60
percent by weight, such as from 20 percent to 40 percent by weight, the
percentages based on
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the total weight of the resin solids in the electrodepositable composition. As
indicated,
blocked organic polyisocyanates are often used as the curing agent in cathodic
electrodeposition compositions. The polyisocyanates can be fully blocked as
described in
United States Patent No. 3,984,299 at col. 1, lines 1 to 68, col. 2, and col.
3, lines 1 to 15, or
partially blocked and reacted with the polymer backbone as described in United
States Patent
No. 3,947,338 at col. 2, lines 65 to 68, col. 3, and col. 4 lines 1 to 30, the
cited portions of
which being incorporated herein by reference. By "blocked" is meant that the
isocyanate
groups have been reacted with a compound so that the resultant blocked
isocyanate group is
stable to active hydrogens at ambient temperature but reactive with active
hydrogens in the
film forming polymer at elevated temperatures usually between 90 C and 200 C.
[0081] Suitable polyisocyanates include aromatic and aliphatic
polyisocyanates,
including cycloaliphatic polyisocyanates and representative examples include
diphenylmethane-4,4'-diisocyanate (MDI), 2,4- or 2,6-toluene diisocyanate
(TDI), including
mixtures thereof, p-phenylene diisocyanate, tetramethylene and hexamethylene
diisocyanates,
dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, mixtures of
phenylmethane-4,4'-diisocyanate and polymethylene polyphenylisocyanate. Higher
polyisocyanates, such as triisocyanates can be used. An example would include
triphenylmethane-4,4',4"-triisocyanate. Isocyanate prepolymers with polyols
such as
neopentyl glycol and trimethylolpropane and with polymeric polyols such as
polycaprolactone diols and triols (NCO/OH equivalent ratio greater than 1) can
also be used.
[0082] The polyisocyanate curing agents are typically utilized in
conjunction with the
active hydrogen containing cationic electrodepositable resin in amounts
ranging from 5
percent to 60 percent by weight, such as from 20 percent to 50 percent by
weight, the
percentages based on the total weight of the resin solids of the
electrodepositable
composition.
[0083] The electrodepositable coating compositions described herein may in
particular
be in the form of an aqueous dispersion. The average particle size of the
resinous phase is
generally less than 1.0 micron and usually less than 0.5 microns, often less
than 0.15 micron.
[0084] The concentration of the resinous phase in the aqueous medium is
often at least
1 percent by weight, such as from 2 to 60 percent by weight, based on total
weight of the
aqueous dispersion. When such coating compositions are in the form of resin
concentrates,
they generally have a resin solids content of 20 to 60 percent by weight based
on weight of
the aqueous dispersion.
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[0085] The electrodepositable coating compositions described herein are
often
supplied as two components: (1) a clear resin feed, which includes generally
the active
hydrogen-containing ionic electrodepositable resin, i.e., the main film-
forming polymer, the
curing agent, and any additional water-dispersible, non-pigmented components;
and (2) a
pigment paste, which generally includes one or more colorants (described
below), a water-
dispersible grind resin which can be the same or different from the main-film
forming
polymer, and, optionally, additives such as wetting or dispersing aids.
Electrodeposition bath
components (1) and (2) are dispersed in an aqueous medium which comprises
water and,
usually, coalescing solvents.
[0086] As aforementioned, besides water, the aqueous medium may contain a
coalescing solvent. Useful coalescing solvents are often hydrocarbons,
alcohols, esters,
ethers and ketones. Coalescing solvents that may be used may be alcohols,
polyols and
ketones. Specific coalescing solvents include isopropanol, butanol, 2-
ethylhexanol,
isophorone, 2-methoxypentanone, ethylene and propylene glycol and the
monoethyl
monobutyl and monohexyl ethers of ethylene glycol. The amount of coalescing
solvent is
generally between 0.01 and 25 percent, such as from 0.05 to 5 percent by
weight based on
total weight of the aqueous medium.
[0087] After deposition of the electrodepositable coating composition, the
coating is
often heated to cure the deposited composition. The heating or curing
operation is often
carried out at a temperature in the range of from 120 to 250 C, such as from
120 to 190 C,
for a period of time ranging from 10 to 60 minutes. According to the
invention, the thickness
of the resultant film is from 10 to 50 microns.
[0088] Alternatively, as mentioned above, according to the present
invention, after the
substrate has been contacted with the pretreatment composition, a powder
coating
composition may then be deposited onto at least a portion of the surface of
the substrate that
has been contacted with the pretreatment composition. As used herein, "powder
coating
composition" refers to a coating composition which is completely free of water
and/or
solvent. Accordingly, the powder coating composition disclosed herein is not
synonymous
to waterborne and/or solvent-borne coating compositions known in the art.
[0089] According to the present invention, the powder coating composition
comprises
(a) a film forming polymer having a reactive functional group; and (b) a
curing agent that is
reactive with the functional group. Examples of powder coating compositions
that may be
used in the present invention include the polyester-based ENVIROCRON line of
powder
coating compositions (commercially available from PPG Industries, Inc.) or
epoxy-polyester
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hybrid powder coating compositions. Alternative examples of powder coating
compositions
that may be used in the present invention include low temperature cure
thermosetting powder
coating compositions comprising (a) at least one tertiary aminourea compound,
at least one
tertiary aminourethane compound, or mixtures thereof, and (b) at least one
film-forming
epoxy-containing resin and/or at least one siloxane-containing resin (such as
those described
in US Patent No. 7,470,752, assigned to PPG Industries, Inc. and incorporated
herein by
reference); curable powder coating compositions generally comprising (a) at
least one tertiary
aminourea compound, at least one tertiary aminourethane compound, or mixtures
thereof, and
(b) at least one film-forming epoxy-containing resin and/or at least one
siloxane-containing
resin (such as those described in US Patent No. 7,432,333, assigned to PPG
Industries, Inc.
and incorporated herein by reference); and those ccomprising a solid
particulate mixture of a
reactive group-containing polymer having a Tg of at least 30 C (such as those
described in
US Patent No. 6,797,387, assigned to PPG Industries, Inc. and incorporated
herein by
reference).
[0090] Suitable film forming polymers that may be used in the powder
coating
composition of the present invention comprise a (poly)ester (e.g., polyester
triglycidyl
isocyanurate), a (poly)urethane, an isocyanurate, a (poly)urea, a (poly)epoxy,
an anhydride,
an acrylic, a (poly)ether, a (poly)sulfide, a (poly)amine, a (poly)amide,
(poly)vinyl chloride,
(poly)olefin, (poly)vinylidene fluoride, or combinations thereof.
[0091] According to the present invention, the reactive functional group
of the film
forming polymer of the powder coating composition comprises hydroxyl,
carboxyl,
isocyanate (including blocked (poly)isocyanate), primary amine, secondary
amine, amide,
carbamate, urea, urethane, vinyl, unsaturated ester, maleimide, fumarate,
anhydride, hydroxyl
alkylamide, epoxy, or combinations thereof
[0092] Suitable curing agents (crosslinking agents) that may be used in
the powder
coating composition of present invention comprise an aminoplast resin, a
polyisocyanate, a
blocked polyisocyanate, a polyepoxide, a polyacid, a polyol, or combinations
thereof
[0093] After deposition of the powder coating composition, the coating is
often heated
to cure the deposited composition. The heating or curing operation is often
carried out at a
temperature in the range of from 150 C to 200 C, such as from 170 C to 190 C,
for a period
of time ranging from 10 to 20 minutes. According to the invention, the
thickness of the
resultant film is from 50 microns to 125 microns.
[0094] As mentioned above, the coating composition may be a liquid coating
composition. As used herein, "liquid coating composition" refers to a coating
composition
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which contains a portion of water and/or solvent. Accordingly, the liquid
coating
composition disclosed herein is synonymous to waterborne and/or solventborne
coating
compositions known in the art.
[0095] As mentioned above, according to the present invention, the coating
composition may be a liquid coating composition. As used herein, "liquid
coating
composition" refers to a coating composition which contains a portion of water
and/or
solvent. Accordingly, the liquid coating composition disclosed herein is
synonymous to
waterborne and/or solventborne coating compositions known in the art.
[0096] According to the present invention, the liquid coating composition
may
comprise, for example, (a) a film forming polymer having a reactive functional
group; and (b)
a curing agent that is reactive with the functional group. In other examples,
the liquid coating
may contain a film forming polymer that may react with oxygen in the air or
coalesce into a
film with the evaporation of water and/or solvents. These film forming
mechanisms may
require or be accelerated by the application of heat or some type of radiation
such as
Ultraviolet or Infrared. Examples of liquid coating compositions that may be
used in the
present invention include the SPECTRACRON line of solventbased coating
compositions,
the AQUACRON line of waterbased coating compositions, and the RAYCRON line
of
UV cured coatings (all commercially available from PPG Industries, Inc.).
[0097] Suitable film forming polymers that may be used in the liquid
coating
composition of the present invention may comprise a (poly)ester, an alkyd, a
(poly)urethane,
an isocyanurate, a (poly)urea, a (poly)epoxy, an anhydride, an acrylic, a
(poly)ether, a
(poly)sulfide, a (poly)amine, a (poly)amide, (poly)vinyl chloride,
(poly)olefin,
(poly)vinylidene fluoride, (poly)siloxane, or combinations thereof
[0098] According to the present invention, the reactive functional group
of the film
forming polymer of the liquid coating composition may comprise hydroxyl,
carboxyl,
isocyanate (including blocked (poly)isocyanate), primary amine, secondary
amine, amide,
carbamate, urea, urethane, vinyl, unsaturated ester, maleimide, fumarate,
anhydride, hydroxyl
alkylamide, epoxy, or combinations thereof
[0099] Suitable curing agents (crosslinking agents) that may be used in
the liquid
coating composition of the present invention may comprise an aminoplast resin,
a
polyisocyanate, a blocked polyisocyanate, a polyepoxide, a polyacid, a polyol,
or
combinations thereof.
[00100] In addition, a colorant and, if desired, various additives such as
surfactants,
wetting agents or catalyst can be included in the coating composition
(electrodepositable,
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powder, or liquid). As used herein, the term "colorant" means any substance
that imparts
color and/or other opacity and/or other visual effect to the composition. The
colorant can be
added to the composition in any suitable form, such as discrete particles,
dispersions,
solutions and/or flakes. A single colorant or a mixture of two or more
colorants can be used.
[00101] Example colorants include pigments, dyes and tints, such as those
used in the
paint industry and/or listed in the Dry Color Manufacturers Association
(DCMA), as well as
special effect compositions. A colorant may include, for example, a finely
divided solid
powder that is insoluble but wettable under the conditions of use. A colorant
can be organic
or inorganic and can be agglomerated or non-agglomerated. Colorants can be
incorporated
by use of a grind vehicle, such as an acrylic grind vehicle, the use of which
will be familiar to
one skilled in the art.
[00102] Example pigments and/or pigment compositions include, but are not
limited to,
carbazole dioxazine crude pigment, azo, monoazo, disazo, naphthol AS, salt
type (lakes),
benzimidazolone, condensation, metal complex, isoindolinone, isoindoline and
polycyclic
phthalocyanine, quinacridone, perylene, perinone, diketopyrrolo pyrrole,
thioindigo,
anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone,
anthanthrone,
dioxazine, triarylcarbonium, quinophthalone pigments, diketo pyrrolo pyrrole
red ("DPPBO
red"), titanium dioxide, carbon black and mixtures thereof The terms "pigment"
and
"colored filler" can be used interchangeably.
[00103] Example dyes include, but are not limited to, those that are
solvent and/or
aqueous based such as phthalo green or blue, iron oxide, bismuth vanadate,
anthraquinone,
perylene, aluminum and quinacridone.
[00104] Example tints include, but are not limited to, pigments dispersed
in water-based
or water miscible carriers such as AQUA-CHEM 896 commercially available from
Degussa,
Inc., CHARISMA COLORANTS and MAXITONER INDUSTRIAL COLORANTS
commercially available from Accurate Dispersions division of Eastman Chemical,
Inc.
[00105] As noted above, the colorant can be in the form of a dispersion
including, but
not limited to, a nanoparticle dispersion. Nanoparticle dispersions can
include one or more
highly dispersed nanoparticle colorants and/or colorant particles that produce
a desired
visible color and/or opacity and/or visual effect. Nanoparticle dispersions
can include
colorants such as pigments or dyes having a particle size of less than 150 nm,
such as less
than 70 nm, or less than 30 nm. Nanoparticles can be produced by milling stock
organic or
inorganic pigments with grinding media having a particle size of less than 0.5
mm. Example
nanoparticle dispersions and methods for making them are identified in U.S.
Patent No.
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6,875,800 B2, which is incorporated herein by reference. Nanoparticle
dispersions can also
be produced by crystallization, precipitation, gas phase condensation, and
chemical attrition
(i.e., partial dissolution). In order to minimize re-agglomeration of
nanoparticles within the
coating, a dispersion of resin-coated nanoparticles can be used. As used
herein, a "dispersion
of resin-coated nanoparticles" refers to a continuous phase in which is
dispersed discreet
"composite microparticles" that comprise a nanoparticle and a resin coating on
the
nanoparticle. Example dispersions of resin-coated nanoparticles and methods
for making
them are identified in United States Patent Application Publication 2005-
0287348 Al, filed
June 24, 2004, U.S. Provisional Application No. 60/482,167 filed June 24,
2003, and United
States Patent Application Serial No. 11/337,062, filed January 20, 2006, which
is also
incorporated herein by reference.
[00106] Example special effect compositions that may be used include
pigments and/or
compositions that produce one or more appearance effects such as reflectance,
pearlescence,
metallic sheen, phosphorescence, fluorescence, photochromism,
photosensitivity,
thermochromism, goniochromism and/or color-change. Additional special effect
compositions can provide other perceptible properties, such as opacity or
texture. According
to the invention, special effect compositions can produce a color shift, such
that the color of
the coating changes when the coating is viewed at different angles. Example
color effect
compositions are identified in U.S. Patent No. 6,894,086, incorporated herein
by reference.
Additional color effect compositions can include transparent coated mica
and/or synthetic
mica, coated silica, coated alumina, a transparent liquid crystal pigment, a
liquid crystal
coating, and/or any composition wherein interference results from a refractive
index
differential within the material and not because of the refractive index
differential between
the surface of the material and the air.
[00107] According to the invention, a photosensitive composition and/or
photochromic
composition, which reversibly alters its color when exposed to one or more
light sources, can
be used. Photochromic and/or photosensitive compositions can be activated by
exposure to
radiation of a specified wavelength. When the composition becomes excited, the
molecular
structure is changed and the altered structure exhibits a new color that is
different from the
original color of the composition. When the exposure to radiation is removed,
the
photochromic and/or photosensitive composition can return to a state of rest,
in which the
original color of the composition returns. According to the invention, the
photochromic
and/or photosensitive composition can be colorless in a non-excited state and
exhibit a color
in an excited state. Full color-change can appear within milliseconds to
several minutes, such
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as from 20 seconds to 60 seconds. Example photochromic and/or photosensitive
compositions include photochromic dyes.
[00108] According to the invention, the photosensitive composition and/or
photochromic composition can be associated with and/or at least partially
bound to, such as
by covalent bonding, a polymer and/or polymeric materials of a polymerizable
component.
In contrast to some coatings in which the photosensitive composition may
migrate out of the
coating and crystallize into the substrate, the photosensitive composition
and/or
photochromic composition associated with and/or at least partially bound to a
polymer and/or
polymerizable component in according to the invention, have minimal migration
out of the
coating. Example photosensitive compositions and/or photochromic compositions
and
methods for making them are identified in U.S. Application Serial No.
10/892,919 filed July
16, 2004, incorporated herein by reference.
[00109] In general, the colorant can be present in the coating composition
in any
amount sufficient to impart the desired visual and/or color effect. The
colorant may comprise
from 1 to 65 weight percent, such as from 3 to 40 weight percent or 5 to 35
weight percent,
with weight percent based on the total weight of the composition.
[00110] According to the present invention, it has been unexpectedly and
surprisingly
discovered that the application of the activating rinse disclosed herein to a
surface of the
metal substrate prior to application of the metal phosphate pretreatment
composition enables
the bath containing the metal phosphate pretreatment composition to be
maintained (and
therefore the metal phosphate pretreatment composition to be applied) at a
lower temperature
than methods employing conventional activating rinses, such as Jernstedt type
activators or
other zinc phosphate activating rinses comprising metal phosphate particles
having a D90
particle size of greater than 10 p.m. As G. W. Jernstedt discovered the
beneficial effects of
activating metal surfaces by treating them with a solution containing titanium
together with
sodium phosphate prior to zinc phosphating, titanium containing activating
compositions are
now generally referred to as "Jernstedt type activators". For example,
according to the
present invention, the phosphate bath containing the nickel-free metal
phosphate pretreatment
composition may be at a temperature of no greater than 60 C, such as no
greater than 50 C,
such as no greater than 40 C, such as no greater than 30 C, such as no greater
than 25 C.
According to the present invention, the temperature of the bath containing the
nickel-free
metal phosphate pretreatment composition may range from 20 C to 60 C, such as
from 25 C
to 50 C, such as from 30 C to 40 C. According to the present invention,
application of the
activating rinse disclosed herein to a surface of the metal substrate prior to
application of the
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nickel-free metal phosphate pretreatment composition may enable the bath
containing the
nickel-free metal phosphate pretreatment composition to be maintained at room
temperature
(20 C).
[00111] It also has been unexpectedly and surprisingly discovered that
application of
the activating rinse disclosed herein to a surface of the metal substrate
prior to application of
the nickel-free metal phosphate pretreatment composition results in a metal
phosphate
coating formed on the substrate surface that has a lower coating weight,
smaller phosphate
crystal size, increased coating coverage, and improved adhesion performance
compared to
metal phosphate coatings formed on substrate surfaces treated with
conventional activating
rinses, such as Jemstedt type activators or activating rinses comprising metal
phosphate
particles having a D90 particle size of greater than 10 m. While not wishing
to be bound by
theory, it is believed that smaller phosphate crystal sizes are the result of
faster reaction of the
activating rinse with the substrate surface and impart more complete coverage
of the substrate
surface with nucleation sites, which leads to more complete coverage of the
substrate surface
with the subsequently applied nickel-free metal phosphate-containing
pretreatment
composition.
[00112] As used herein, unless indicated otherwise, a plural term can
encompass its
singular counterpart and vice versa, unless indicated otherwise. For example,
although
reference is made herein to "a" metal sulfate salt and "a" dispersant, a
combination (i.e., a
plurality) of these components can be used. In addition, in this application,
the use of "or"
means "and/or" unless specifically stated otherwise, even though "and/or" may
be explicitly
used in certain instances.
[00113] As used herein, "including," "containing" and like terms are
understood in the
context of this application to be synonymous with "comprising" and are
therefore open-ended
and do not exclude the presence of additional undescribed or unrecited
elements, materials,
ingredients or method steps. As used herein, "consisting of' is understood in
the context of
this application to exclude the presence of any unspecified element,
ingredient or method
step. As used herein, "consisting essentially of' is understood in the context
of this
application to include the specified elements, materials, ingredients,
solvents, or method
steps, where applicable, while other non-specified materials are not
purposefully added to the
composition and are only present as impurities in a combined amount of less
than 5% by
weight based on a total weight of the composition.
[00114] As used herein, unless indicated otherwise, the term "substantially
free" means
that a particular material is not purposefully added to the activating rinse,
and is only present
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as an impurity in a trace amount of less than 1% by weight based on a total
weight of the
activating rinse. As used herein, unless indicated otherwise, the term
"completely free"
means that an activating rinse does not comprise a particular material, i.e.,
the activating rinse
comprises 0% by weight of such material.
[00115] For purposes of the following detailed description, it is to be
understood that
the invention may assume various alternative variations and step sequences,
except where
expressly specified to the contrary. Moreover, other than in any operating
examples, or
where otherwise indicated, all numbers such as those expressing values,
amounts,
percentages, ranges, subranges and fractions may be read as if prefaced by the
word "about,"
even if the term does not expressly appear. Accordingly, unless indicated to
the contrary, the
numerical parameters set forth in the following specification and attached
claims are
approximations that may vary depending upon the desired properties to be
obtained by the
present invention. Notwithstanding that the numerical ranges and parameters
setting forth the
broad scope of the invention are approximations, the numerical values set
forth in the specific
examples are reported as precisely as possible. Any numerical value, however,
inherently
contains certain errors necessarily resulting from the standard variation
found in their
respective testing measurements. At the very least, and not as an attempt to
limit the
application of the doctrine of equivalents to the scope of the claims, each
numerical
parameter should at least be construed in light of the number of reported
significant digits and
by applying ordinary rounding techniques. Where a closed or open-ended
numerical range is
described herein, all numbers, values, amounts, percentages, subranges and
fractions within
or encompassed by the numerical range are to be considered as being
specifically included in
and belonging to the original disclosure of this application as if these
numbers, values,
amounts, percentages, subranges and fractions had been explicitly written out
in their
entirety.
[00116] Illustrating the invention are the following examples that are not
to be
considered as limiting the invention to their details. All parts and
percentages in the
examples, as well as throughout the specification, are by weight unless
otherwise indicated.
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EXAMPLES
Activating Rinse Compositions
[00117] The following activating rinse compositions were prepared as follows:
[00118] RC: RC (a Jernstedt-type activating rinse concentrate commercially
available
from PPG Industries, Inc., also known as VERSABOND RC) was diluted in
deionized (DI)
water to a concentration of 1 g concentrate/L DI water to prepare a bath
containing the
activating rinse composition.
[00119] RC30: 1.1 grams of RC30 (a zinc phosphate-based activating rinse
concentrate
with an average zinc phosphate particle size of about 1 p.m and a D90 of 1-3
m,
commercially available from PPG Industries, Inc., also known as VERSABOND 30)
was
added to 1 liter of deionized water to produce a dispersion of zinc phosphate
with a
concentration of 1.1 g/L.
[00120] Micromedia-milled zinc phosphate-based activator (MMM): Micromedia-
milled zinc phosphate (MMM) is a zinc phosphate-based activating rinse that
was prepared as
follows: 1288.4 grams of zinc phosphate pigment was sifted into a pre-blended
mixture of
724 grams deionized water, 787.7 grams of dispersant (Disperbyk-190,
commercially
available from BYK-Chemie GmbH), and 25.6 grams of defoamer (BYK-011,
commercially
available from BYK-Chemie GmbH) and mixed for 30 minutes using a Fawcett Air
Mixer,
model LS-103A with a type 1 angled tooth/Cowles style blade. This mixture was
then milled
in recirculation mode through an Eiger Mini 250 horizontal media mill (from
EMImills)
containing 1.2-1.7 mm zirconium oxide media for 8.1 minutes of residence time.
To 1695.7
grams of this preliminary dispersion was added 150.3 grams of deionized water.
This
material was then milled in recirculation mode through the above-described
Eiger mill,
except that 0.3 mm zirconium oxide media was used. The mixture was milled for
an
additional 40.1 minutes residence time. An additional 718 grams of deionized
water, as well
as 158.3 grams Disperbyk-190 and 2 grams of Byk-011, were added throughout the
milling
process. Several interim process samples were taken throughout the milling,
such that a final
yield of 1657.3 grams was obtained. This material had a concentration of 27%
by weight of
zinc phosphate. 1.85 grams of the above dispersion of zinc phosphate was mixed
per liter of
deionized water, to give an activator bath with a zinc phosphate concentration
of 0.5 grams
per liter.
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[00121] In the Examples that follow, some activating baths included metal
sulfates of the
type and in the amounts indicated in Tables 1 and 2, below.
Nickel-Free Phosphate Pretreatment Composition
[00122] A nickel-free zinc phosphate pretreatment concentrate was prepared by
carefully
combining the following materials and mixing thoroughly until clear:
Chemical Quantity
Phosphoric Acid (85%), available from Fisher Chemical 595.6
grams
Nitric Acid (Reagent Grade), available from Fisher Chemical 28.7
grams
Zinc Oxide, available from Umicore Zinc Chemicals 62.25
grams
IManganese Oxide, available from Sigma-Aldrich Corporation 32.7
grams
Acetaldoxime (50% wt), available from Sigma-Aldrich Corporation 1.95
grams
Ferrous Sulfate, available from Sigma-Aldrich Corporation 3.75
grams
Dowfax 2A1 Surfactant, available from The Dow Chemical Co. 1.05
grams
I 50% Sodium Hydroxide Solution, available from The Dow Chemical Co. 72 grams
Deionized Water 702 grams
[00123] Five gallons of a nickel-free zinc phosphate pretreatment bath was
then prepared
by adding the following materials in order into deionized water:
Chemical _________________________________________________ Quantity
,,0000004
Nickel-free zinc phosphate concentrate 756 grams
Chemfos 700 F* (partially neutralized fluosilicic acid) 56.75 grams
Chemfos 700 F/F* (a solution of ammonium bifluoride) 122.85 grams
Chemfos AZN* (zinc nitrate solution) 15.4 grams
Acetaldoxime (50% w/w) 8.505 grams
Hydrogen Peroxide (30% w/w), available from Acros Organics 1.7 grams
Buffer M* (a solution of strong base) 321.3 grams
*Materials available from PPG Industries, Inc.
[00124] The nickel-free zinc phosphate pretreatment bath was adjusted to a
free acid value
of 0.8-1.0 mL with Buffer M. The free acid value was measured by titrating a
10 mL sample
of the bath with 0.1 N sodium hydroxide solution, using bromophenol blue as an
indicator
and titrating to a blue-gray endpoint.
Example 1
[00125] Four hot dipped galvanized panels (4 inches x 6 inches, automotive-
grade material
from Salzgitter Mannesmann Stahlservice GmbH) and four cold rolled steel
panels (4.13
inches x 6 inches, standard test panels from Chemetall GmbH) were spray
cleaned with a
mixture of Chemkleen 2010LP (1.25% v/v)/Chemkleen 181ALP (0.125% v/v) for 2
minutes
at 49 C followed by immersion rinse in DI water for 15 seconds and spray rinse
with DI
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water for 15 seconds. Panels were then immersed in a bath (20 C-25 C)
containing the
MMM activating rinse (either with or without metal sulfate, pre-dissolved in a
minimal
amount of DI water before being added to the MMM activating rinse, as shown in
Table 1)
for 1 minute. All panels were then immersed in the nickel-free zinc phosphate
pretreatment
bath (50 C) for 3 minutes. Panels then were spray rinsed with DI water for 20-
30 seconds.
Panels were warm air dried using a Hi-Velocity handheld blow-dryer made by
Oster (model
number 078302-300-000) on high-setting at a temperature of about 50-55 C until
the panel
was dry (about 1-5 minutes).
[00126] For each run, one panel was used to determine phosphate coating
completeness.
The other panel was cut in half to yield two panels each 2"x 3" and one of the
half panels was
used to determine coating weight and the other half panel was used to
determine average
crystal size.
[00127] Zinc phosphate coating weight was determined on one of the 2"x 3"
panels by the
weigh-strip-weigh method. Treated panels were weighed on an analytical balance
to the
nearest 0.1 mg. Cold roll steel panels were immersed in a solution comprised
of 100 g
sodium hydroxide pellets and 25 milliliters 98% triethanolamine diluted to 1
liter total
volume with deionized water for 1.5 minutes to dissolve all of the zinc
phosphate coating off
of the panels without dissolution of the substrate. Hot dipped galvanized
steel panels were
immersed in a solution comprised of 16 g ammonium dichromate [(NH4)2Cr207]
dissolved
into 1 liter concentrated ammonium hydroxide for 2 minutes to dissolve all of
the zinc
phosphate coating off of the panels without dissolution of the substrate.
After the stripping
procedure, panels were rinsed thoroughly with deionized water, wiped gently
with a tissue to
remove any loosely-adherent phosphate coating, rinsed with deionized water
again, and dried
in warm air by using a Hi-Velocity handheld blow-dryer made by Oster (model
number
078302-300-000) on high-setting at a temperature of about 50-55 C until the
panel was dry,
typically 1-5 minutes. The dried panel was then weighed, and the weight loss
was used to
calculate the coating weight per unit area.
[00128] Zinc phosphate average crystal size was determined on 2"x 3" panels by
first
selecting a representative area of the panel, i.e., a coated area of
approximately 0.5 inch by
0.5 inch near the center of the 2"x3" panel with no obvious coating defects,
then acquiring an
image at either 5,000x or 10,000x magnification using a Tescan Vega 2 scanning
electron
microscope (SEM). The magnification was determined by the crystal size with
the 10,000x
magnification required for smaller crystal sizes. Nine to twelve evenly-spaced
crystals on
each image were measured using ImageJ software (version 1.46), and the results
averaged.
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ImageJ software is public domain software, available from
http://imagej.nih.gov/ij/. Further
details of the method have already been described above.
[00129] Following pretreatment, for each run, two panels of the treated panels
then were
electrocoated using Enviroprime NT, a cathodic electrocoat available from PPG
Industries,
Inc. and applied according to the manufacturer's instructions. The
electrodeposition was
carried out at 220 volts, using a 30 second ramp. The electrodeposition bath
temperature was
90 F. The current density was 1.5 A/ft2 and the panels were coated to 27
Coulombs to reach
a dry film thickness of 18-20 p.m.
[00130] The electrocoated panels were tested for paint adhesion (dry adhesion
and
exposed adhesion, described in more detail below) by crosshatching and tape-
pulling. For
the dry adhesion test, a razor blade was used to scribe eleven lines parallel
and perpendicular
to the length of the one of the electrocoated panels. The resultant grid area
of the scribed
lines was 0.5" x 0.5" to 0.75" to 0.75" square. Dry adhesion was assessed by
using 3M's
Scotch 610 tape, which was firmly adhered over the scribed grid area by finger
rubbing it
multiple times prior to pulling it off The crosshatch area was evaluated for
paint loss on a
scale from 0 to 10, with 0 being total paint loss and 10 being absolutely no
paint loss. An
adhesion value of 7 is considered acceptable in the automotive industry. For
the exposed
adhesion test, following electrodeposition, the other panel was immersed in
deionized water
(40 C) for ten days, at which time the panels were removed, wiped with a towel
to dry and
allowed to sit at ambient temperature for one hour prior to crosshatching and
tape-pulling to
evaluate paint adhesion as described above.
[00131] Metal phosphate coating weight (g/m2), metal phosphate crystal size,
and dry and
exposed adhesion performance for the treated panels are reported in Table 1,
below.
Table 1
Hot Dipped Galvanized
Activating Crystal Coating Cry
Metal Sulfate Dry
Exposed
Rinse Weight Size
Adhesion Adhesion
(g/m2) (Pm)
MMM None
4.0 1.8 10 0
(Comparative)
Zinc Sulfate (66 ppm
MMM 37 1.8 9 0
zinc, 100 ppm sulfate) .
Nickel Sulfate (61 ppm
MMM 2.1 1.0 9 9
nickel, 100 ppm sulfate)
Cobalt Sulfate (62 ppm
MMM 2.1 0.9 9 9
cobalt, 100 ppm sulfate)
Metal Sulfate Cold Rolled Steel
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Coating Crystal
Activating Dry
Exposed
Weight Size
Rinse
Adhesion Adhesion
(g/m2) (pm)
MMIVI None
0.9 3.1 10 10
(Comparative)
Zinc Sulfate (66 ppm
MMNI 0.8 2.2 10 10
zinc, 100 ppm sulfate)
Nickel Sulfate (61 ppm
MMNI 0.8 2.4 10 10
nickel, 100 ppm sulfate)
Cobalt Sulfate (62 ppm
MMNI 2.3 10 10
cobalt, 100 ppm sulfate)
[00132] As shown in Table 1, immersion of hot dipped galvanized steel panels
in
activating baths made from MMNI activating rinse compositions that did not
include a metal
sulfate or that included zinc sulfate had an exposed adhesion value of zero,
indicating
extremely poor adhesion. In contrast, when panels were immersed in activating
baths made
from activating rinse compositions that included either nickel sulfate or
cobalt sulfate,
exposed adhesion performance was significantly improved to a rating of 9. As
stated above,
an adhesion value of at least 7 is considered acceptable in the automotive
industry. Inclusion
of nickel sulfate or cobalt sulfate in the activating rinse composition also
resulted in a
decreased coating weight and decreased crystal size.
Example 2
[00133] For each run shown in Table 2, four "North American" hot dipped
galvanized
(HDG) panels (4 inches x 6 inches, from ACT Test Panels) and four "European"
HDG panels
(4.13 inches x 6 inches, from Chemetall GmbH) were spray cleaned with a
mixture of
Chemkleen 2010LP (1.25% v/v)/Chemkleen 181ALP (0.125% v/v) for 2 minutes at 49
C
followed by immersion rinse in DI water for 15 seconds and spray rinse with DI
water for 15
seconds. Panels were then immersed in a bath (20 C-25 C) containing either the
RC, RC30,
or MMNI activating rinse (either with or without metal sulfate, as shown in
Table 1) for 1
minute. Panels were then immersed in either a nickel-free zinc phosphate
pretreatment bath
(30 C or 50 C) for 3 minutes or a nickel-containing zinc phosphate
pretreatment bath (50 C)
for 3 minutes. Panels then were spray rinsed with DI water for 20-30 seconds.
Panels were
warm air dried using a Hi-Velocity handheld blow-dryer made by Oster (model
number
078302-300-000) on high-setting at a temperature of about 50-55 C until the
panel was dry
(about 1-5 minutes).
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[00134] Coating weight and average zinc phosphate crystal size was measured as
described in Example 1.
[00135] Two panels were electrocoated using Enviroprime NT, a cathodic
electrocoat
available from PPG Industries, Inc. using the same process described in
Example 1. One
panel was then tested by the dry adhesion test and the other panel was tested
by the exposed
adhesion test, as described in Example 1.
[00136]
Coating weight (g/m2), crystal size, and dry and exposed adhesion performance
for the treated North American HDG panels are reported in Table 2 and for the
treated
European HDG panels are reported in Table 3.
Table 2
Zinc
Phosphate-
Activating
Metal Sulfate containing North American HDG
Rinse
Pretreatment
Bath Temp.
Coati
ng Crystal Dry Exposed
Weig Size
Adhesion Adhesion
ht (un)
::.:::iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii:iiiiiiiiiiiii:iiiiiii:i*i*::::::i*iii
iiiiiiiiiiiiiiii:iiivii:iiiiiiiiiiiiiiiimim
UM11100tVifkgØ1.100.1AfiVCNI04.0401.04$11kiiiMOPOOPRPOVOit.01.P.Wiii.COMPA*Mi
ffimS
.............................................................. .......
............................................................. .........
......... ........ ...........................................................
....... ..........................
RC None 50 C 2.7 2.0 10 10
RC30 None 50 C 3.3 2.0 10 10
..................................:...................:::::::::::::::::::::::::
::.:::::::::::::::..........::::::::::::....õ..::::::::::::::::::::::::::::::::
:::,õ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:::::::::::::
iSIMENNEMMTratMeItt MAtitMckt6firec Phosphatc Proreatment ComposmoommEmmg
RC None 50 C 3.0 2.6 10 0
Nickel Sulfate (61 ppm
RC 50 C 3.1 4.6 10 2
nickel, 100 ppm sulfate)
RC30 None 50 C 4.6 3.4 10 7
Nickel Sulfate (61 ppm
RC30 50 C 3.9 2.7 10 9
nickel, 100 ppm sulfate)
MIMM None 50 C 4.1 2.4 10 6
Nickel Sulfate (31 ppm
MIMM 50 C 4.2 1.9 10 7
nickel, 50 ppm sulfate)
Nickel Sulfate (61 ppm
MIMM 50 C 3.3 1.0 9 8
nickel, 100 ppm sulfate)
Nickel Sulfate (122 ppm
MIMM 50 C 2.3 1.0 10 10
nickel, 200 ppm sulfate)
Nickel Sulfate (305 ppm
MIMM 50 C 1.8 1.0 10 10
nickel, 500 ppm sulfate)
Nickel Sulfamate (61 ppm
MIMM 50 C 3.9 1.7 9 0
nickel, 200 ppm sulfamate)
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Nickel Nitrate (61 ppm
MIVIM 50 C 4.5 1.3 10 0
nickel, 129 ppm nitrate)
Nickel Chloride (61 ppm
MIVIM 50 C 4.0 1.6 9 3
nickel, 74 ppm chloride)
Nickel Acetate (61 ppm
MIVIM 50 C 4.2 2.1 8 2
nickel, 123 ppm acetate)
Cobalt Sulfate (31 ppm
MIVIM 50 C 3.3 1.5 9 7
cobalt, 50 ppm sulfate)
Cobalt Sulfate (62 ppm
MIVIM 50 C 3.0 1.8 10 8
cobalt, 100 ppm sulfate)
Cobalt Sulfate (124 ppm
MIVIM 50 C 1.8 1.0 9 9
cobalt, 200 ppm sulfate)
Cobalt Sulfate (310 ppm
MIVIM 50 C 1.6 0.8 10 10
cobalt, 500 ppm sulfate)
MIVIM None 30 C 6.0 4.2 10 0
Nickel Sulfate (31 ppm
MIVIM 30 C 4.4 0.6 10 7
nickel, 50 ppm sulfate)
Cobalt Sulfate (62 ppm
MIVIM 30 C 3.1 0.6 9 7
cobalt, 100 ppm sulfate)
Table 3
European HDG
Zinc Coating
Activating Phosphate- Weight Crystal
Metal Sulfate Dry
Exposed
Rinse containing (g/m2) Size
Adhesion Adhesion
Pretreatment (Pm)
Bath Temp.
:::::-
.......::::::::::::.........,......::::::::..................::::::::::::::...:
:::::....f.:00,00,0*.z:::::::::::::::::::::::::::
TrootmgotiogthiiiCommiwtiNogkgbpgRifilimggiiipholphiggiiirrgupapiligoticgparomp
imi
RC None
50 C 2.9 2.1 10 10
(Jernstedt)
RC30 None 50 C 3.2 1.8 10 10
:,::::::::,::::::::-
..:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::,::::-
..*::::::::::::::::::::::::::::::::,:::::::::::::::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::::::
nottmgotimighiiimoffrogighowhogimroftwffigoiiicompoompoiminisinisinisini
RC None
50 C 2.9 3.5 10 0
(Jernstedt)
RC Nickel Sulfate (61
ppm nickel, 100 50 C 3.2 4.2 10 0
(Jernstedt)
ppm sulfate)
RC30 None 50 C 5.2 3.9 10 7
Nickel Sulfate (61
RC30 ppm nickel, 100 50 C 3.5 2.0 9 8
ppm sulfate)
MNINI None 50 C
4.6 2.1 9 7
Nickel Sulfate (31
MNINI ppm nickel, 50 50 C 4.0 1.8 9 6
ppm sulfate)
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Nickel Sulfate (61
MMNI ppm nickel, 100 50 C 3.1 0.7 8 7
ppm sulfate)
Nickel Sulfate
MMNI (122 ppm nickel, 50 C 2.4 0.9 10 10
200 ppm sulfate)
Nickel Sulfate
MMNI (305 ppm nickel, 50 C 1.6 1.1 10 10
500 ppm sulfate)
Nickel Sulfamate
(61 ppm nickel,
MMNI 50 C 3.4 1.0 8 1
200 ppm
sulfamate)
Nickel Nitrate (61
MMNI ppm nickel, 129 50 C 4.0 0.9 9 1
ppm nitrate)
Nickel Chloride
MMNI (61 ppm nickel, 50 C 3.8 1.5 10 1
74 ppm chloride)
Nickel Acetate
MMNI (61 ppm nickel, 50 C 3.7 0.9 9 0
123 ppm acetate)
Cobalt Sulfate (31
MMNI ppm cobalt, 50 50 C 2.7 1.2 7 7
ppm sulfate)
Cobalt Sulfate (62
MMNI ppm cobalt, 100 50 C 2.8 1.3 9 8
ppm sulfate)
Cobalt Sulfate
MMNI (124 ppm cobalt, 50 C 1.7 0.7 10 10
200 ppm sulfate)
Cobalt Sulfate
MMNI (310 ppm cobalt, 50 C 1.7 0.7 10 10
500 ppm sulfate)
MMNI None 30 C 6.0 3.1 10 0
Nickel Sulfate (31
MMNI ppm nickel, 50 30 C 4.1 0.7 10 1
ppm sulfate)
Cobalt Sulfate (62
MMNI ppm cobalt, 100 30 C 3.8 0.5 10 9
ppm sulfate)
[00137] The results in Tables 2 and 3 show that the inclusion of nickel
sulfate or cobalt
sulfate in RC30 or MMNI activating rinse results in reduced crystal size and
coating weight
of a subsequently applied nickel-free zinc phosphate coating compared to the
use of
activating rinses that do not include nickel sulfate or cobalt sulfate. Table
2 further shows
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that the inclusion of nickel sulfate or cobalt sulfate in an activating rinse
generally improves
the dry and exposed adhesion of a subsequently applied electrodepositable
coating over the
phosphate coating, even when the zinc phosphate pretreatment composition was
applied at
low-temperatures.
Example 3
[00138]
Comparative Example I was made according to Example 2 of US Publication
2012/0160129A1 to Inbe. RC and Composition 2A were made as described above.
[00139] The dispersion of Comparative I was characterized as follows and was
compared
to the activation properties of Composition 2A.
[00140] X-ray diffraction of dried solids of Comparative I showed both ZnO and
zinc
phosphate.
[00141] Particle size (Dio, Dso, and Doo) were measured using a Mastersizer
2000
(available from Malvern Instruments, Ltd., of Malvern, Worcestershire, UK). A
laser beam
(0.633 mm diameter, 633 nm wavelength) was directed through a dispersion of
particles (in
deionized water to 2-3% obscuration). The light scattering of the dispersion
was measured
(measurement parameters 25 C, 2200 RPM, 30 sec premeasurement delay, 10 sec
background measurement, 10 sec sample measurement) and the data were analyzed
by
computer software (Malvern Mastersizer 2000 software, version 5.60) to
generate a particle
size distribution, from which particle sizes (mean, Dio, Dso, and Doo) were
determined and are
reported in Table 4.
Table 4.
Mean PS D10 D50 D90
Sample
(11) 0-0 (11) (11)
Composition I (Initial) 3.914 1.528 3.495 6.904
Composition I (60 min) 0.643 0.125 0.456 1.31
Composition I (120 min) 0.493 0.109 0.338 0.985
Composition I (180 min) 0.474 0.096 0.284 0.917
Composition 2A 0.181 0.068 0.119 0.332
Composition RC30 0.846 0.079 0.215 2.75
[00142] For each run shown in Table 5, cold rolled steel, electrogalvanized
steel, or
aluminum alloy 6022 panels (4"x6", all available from ACT Test Panels, LLC)
were spray
cleaned with a mixture of Chemkleen 2010LP (1.25% v/v)/Chemkleen 181ALP
(0.125% v/v)
for 2 minutes at 49 C/120F followed by immersion rinse in DI water for 15
seconds and
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spray rinse with DI water for 15 seconds. Panels were then immersed in a bath
(20 C-25 C)
containing either Comparative Example I or Composition 2A, as shown in Table
5, for 1
minute. Activated panels (Comparative Example I or Composition 2A) then were
immersed
in a zinc phosphate pretreatment bath (made from Chemfos 700AL, commercially
available
from PPG Industries, Inc., prepared according to instructions provided by the
supplier) at a
bath temperature of either 78F for 2 minutes. All panels then were spray
rinsed with DI
water for 20-30 seconds. Panels were warm air dried using a Hi-Velocity
handheld blow-
dryer made by Oster (model number 078302-300-000) on high-setting at a
temperature of
about 50-55 C until the panel was dry (about 1-5 minutes).
[00143] For each run, one of the panels was used to determine phosphate
coating
completeness. The other panel was cut in half to yield two panels each 2"x 3"
and one of the
half panels was used to determine coating weight and the other half panel was
used to
determine average crystal size.
[00144] Zinc phosphate coating completeness and coating weight were determined
as
described in Example 1. Zinc phosphate average crystal size was determined as
described in
Example 1. Data are reported in Table 5, below.
Table 5.
Coating
Coating Crystal
Substrate Activator weight
Completeness size ( m)
(mg/ft2)
Cold rolled steel Composition 2A 100% 1.20 94
Cold rolled steel Comparative I 60% 2.88 153
Electrogalvanized steel Composition 2A 100% 1.22 289
Electrogalvanized steel Comparative I 100% 3.00 359
Aluminum alloy 6022 Composition 2A 95% 1.45 142
Aluminum alloy 6022 Comparative I 40% 3.05 153
[00145] As shown in Table 5, Composition 2A gave 100% coating completeness on
CRS
and 95% coating completeness on aluminum alloy 6022 panels. In contrast,
Comparative I
gave only 60% coating completeness on CRS and 40% coating completeness on
aluminum
alloy 6022 panels. Both Composition 2A and Comparative I gave 100% coating
completeness on EG steel panels, but the skilled artisan understands that EG
panels are
typically 100% coated. Also as shown in Table 5, additionally, crystal size
was smaller and
coating weight was lower on panels treated with Composition 2A than those
treated with
Comparative I, regardless of substrate.
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[00146] It will be appreciated by skilled artisans that numerous
modifications and
variations are possible in light of the above disclosure without departing
from the broad
inventive concepts described and exemplified herein. Accordingly, it is
therefore to be
understood that the foregoing disclosure is merely illustrative of various
exemplary aspects of
this application and that numerous modifications and variations can be readily
made by
skilled artisans which are within the spirit and scope of this application and
the
accompanying claims.
ASPECTS OF THE INVENTION
1. A substrate pretreatment system, comprising:
a) an activating rinse for treating at least a portion of a substrate
comprising a
dispersion of metal phosphate particles having a D90 particle size of no
greater than 10
um, wherein the metal phosphate comprises divalent or trivalent metals or
combinations thereof; and
b) a pretreatment composition for treating at least a portion of the substrate
treated
with the activating rinse, comprising zinc ions and phosphate ions, wherein
the pretreatment
composition is substantially free of nickel.
2. The pretreatment system of Aspect 1, wherein the D90 particle size is
measured from a
sample of the activating rinse that has been sonicated.
3. The pretreatment system of Aspect 1 or 2, wherein the activating rinse
further
comprises a metal sulfate salt, wherein the sulfate of the metal sulfate salt
is present in an
amount of 5 ppm to 5000 ppm based on a total weight of the activating rinse.
4. The pretreatment system of any of the preceding Aspects, wherein the
metal
phosphate particles have a D90 particle size of no more than 1 um, preferably
of 50 nm to 500
nm.
5. The pretreatment system of any of the preceding Aspects, wherein the
divalent or
trivalent metals of the metal phosphate in the activating rinse comprise zinc,
iron or a
combination thereof.
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6. The pretreatment system of any of the preceding Aspects, wherein the
activating rinse
comprises a dispersant comprising non-ionic polymers.
7. The pretreatment system of any of the preceding Aspects, wherein the
activating rinse
is substantially free of ionic dispersants.
8. The pretreatment system of any of the preceding Aspects, wherein the
metal of the
metal sulfate salt comprises nickel, copper, zinc, iron, magnesium, cobalt,
aluminum or
combinations thereof, preferably nickel, cobalt or combinations thereof.
9. A method of treating a substrate comprising:
a) contacting at least a portion of a surface of the substrate with an
activating rinse
comprising a dispersion of metal phosphate particles having a D90 particle
size of no greater
than 10 m, wherein the metal phosphate comprises divalent or trivalent metals
or
combinations thereof; and
b) contacting at least a portion of the surface that has been contacted with
the
activating rinse with a pretreatment composition comprising zinc ions and
phosphate ions,
wherein the pretreatment composition is substantially free of nickel.
10. The method of Aspect 9, wherein the D90 particle size is measured from
a sample of
the activating rinse that has been sonicated.
11. The method of Aspect 9 or 10, wherein the contacting with the
pretreatment
composition comprises immersing the substrate in a bath comprising
pretreatment
composition, wherein the bath temperature is 20 C to 60 C.
12. The method of Aspects 9 to 11, wherein the activating rinse further
comprises a metal
sulfate salt, wherein the metal of the metal sulfate salt comprises nickel,
copper, zinc, iron,
magnesium, cobalt, aluminum or combinations thereof, preferably nickel, cobalt
or
combinations thereof.
13. The method of any of Aspects 9 to 12, wherein the substrate is treated
with the
substrate pretreatment system according to any of Aspects 1 to 8.
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14. A substrate treated with the pretreatment system of any of Aspects 1 to
8, preferably
in a method according to any of Aspects 9 to 13.
15. The substrate of Aspect 13, wherein the phosphate coating formed from
the
pretreatment composition comprises metal/zinc phosphate crystals having an
average crystal
size of 0.4 um to 2 um, preferably of 0.7 um to 1.5 um as measured by a
scanning electron
microscope at 10,000x magnification.
16. The substrate of Aspects 14 or 15, wherein the phosphate coating has a
weight of 4.4
g/m2 or less and an exposed adhesion value of 6 or greater.
17. The substrate of any of Aspects 14 to 16, wherein the phosphate coating
has a weight
of 0.5 to 4 g/m2 as measured by the weigh-strip-weigh method.
18. The substrate of any of Aspects 14 to 17, wherein the pretreatment
composition has
been applied from a pretreatment bath having a temperature of 20 C to 60 C.
19. The substrate of any of Aspects 14 to 18, wherein the substrate further
comprises an
electrodeposited layer.
