U.S. patent application number 15/137016 was filed with the patent office on 2017-10-26 for activating rinse and method for treating a substrate.
The applicant listed for this patent is PPG Industries Ohio, Inc.. Invention is credited to Richard F. Karabin, Steven Joseph Lemon, Mark W. McMillen, Nathan J. Silvernail, Peter L. Votruba-Drzal, Matthew E. Wehrle.
Application Number | 20170306498 15/137016 |
Document ID | / |
Family ID | 58664890 |
Filed Date | 2017-10-26 |
United States Patent
Application |
20170306498 |
Kind Code |
A1 |
McMillen; Mark W. ; et
al. |
October 26, 2017 |
ACTIVATING RINSE AND METHOD FOR TREATING A SUBSTRATE
Abstract
Disclosed is an activating rinse for treating at least a portion
of a substrate, comprising a dispersion of metal phosphate
particles having a D.sub.90 particle size of no greater than 10
.mu.m, wherein the metal phosphate comprises divalent or trivalent
metals or combinations thereof; a dispersant; and a metal sulfate
salt. Methods of treating a substrate with the activating rinse
also are disclosed. Optionally, substrates treated with the
activating rinse also are disclosed.
Inventors: |
McMillen; Mark W.; (Cabot,
PA) ; Lemon; Steven Joseph; (Lower Burrell, PA)
; Votruba-Drzal; Peter L.; (Pittsburgh, PA) ;
Wehrle; Matthew E.; (Apollo, PA) ; Silvernail; Nathan
J.; (Allison Park, PA) ; Karabin; Richard F.;
(Ruffs Dale, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PPG Industries Ohio, Inc. |
Cleveland |
OH |
US |
|
|
Family ID: |
58664890 |
Appl. No.: |
15/137016 |
Filed: |
April 25, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 22/12 20130101;
C23C 22/182 20130101; C23C 22/22 20130101; C23C 22/78 20130101;
C23C 22/20 20130101 |
International
Class: |
C23C 22/78 20060101
C23C022/78; C23C 22/20 20060101 C23C022/20; C23C 22/18 20060101
C23C022/18; C23C 22/22 20060101 C23C022/22; C23C 22/12 20060101
C23C022/12 |
Claims
1. An activating rinse for treating a substrate comprising: a
dispersion of metal phosphate particles having a D.sub.90 particle
size of no greater than 10 .mu.m, wherein the metal phosphate
comprises divalent or trivalent metals or combinations thereof; a
dispersant; and a metal sulfate salt.
2. The activating rinse of claim 1, wherein the D.sub.90 particle
size is measured from a sample of the activating rinse that has
been sonicated.
3. The activating rinse of claim 1, wherein the dispersant
comprises a non-ionic dispersant.
4. The activating rinse of claim 1, wherein the activating rinse is
substantially free of ionic dispersants.
5. The activating rinse of claim 1, wherein a sulfate ion of the
metal sulfate salt is present in an amount of 5 ppm to 5,000 ppm
based on a total weight of the activating rinse.
6. The activating rinse of claim 1, wherein the metal of the metal
sulfate salt comprises a divalent metal.
7. The activating rinse of claim 6, wherein the divalent metal
comprises nickel, cobalt, zinc, iron, copper, or combinations
thereof.
8. The activating rinse of claim 1, wherein the metal phosphate
particles have a D.sub.90 particle size of no more than 1
.mu.m.
9. The activating rinse of claim 1, wherein the metal phosphate
particles are substantially pulverized.
10. The activating rinse of claim 1, wherein the activating rinse
comprises a multi-component system, and wherein the dispersion of
metal phosphate particles and the dispersant form a part of a first
component and the metal sulfate salt form a part of a second
component.
11. A method for treating a substrate comprising contacting at
least a portion of a surface of the substrate with the activating
rinse of claim 1.
12. The method of claim 11, further comprising contacting at least
a portion of the surface of the substrate that has been contacted
with the activating rinse with a metal phosphate pretreatment
composition.
13. The method of claim 12, wherein contacting the surface of the
substrate with the metal phosphate pretreatment composition
comprises immersing the substrate in a bath comprising the metal
phosphate pretreatment composition, wherein the bath temperature is
from 20.degree. C. to 60.degree. C.
14. The method of claim 12, wherein contacting the surface of the
substrate with the metal phosphate pretreatment composition
comprises immersing the substrate in a bath comprising the metal
phosphate pretreatment composition, wherein the bath temperature is
20.degree. C. to 25.degree. C.
15. A substrate treated with the activating rinse of claim 1.
16. The substrate of claim 15 further comprising a phosphate
coating.
17. The substrate of claim 16, wherein the phosphate coating
comprises phosphate crystals having a crystal size of 0.4 .mu.m to
4 .mu.m.
18. The substrate of claim 16, wherein the phosphate coating
comprises phosphate crystals having a crystal size of 0.9 .mu.m to
2.7 .mu.m.
19. The substrate of claim 15, wherein the substrate is hot dipped
galvanized steel.
20. An activating rinse for treating a substrate comprising: a
dispersion of substantially pulverized metal phosphate particles
having a D.sub.90 particle size of no greater than 1 .mu.m, wherein
the metal phosphate comprises divalent or trivalent metals or
combinations thereof; and a dispersant.
21. The activating rinse of claims 20, wherein the D.sub.90
particle size is measured from a sample of the activating rinse
that has been sonicated.
22. The activating rinse of claim 20, wherein the metal phosphate
particles having a D.sub.90 particle size of no greater than 0.75
.mu.m.
23. A method for treating a substrate comprising contacting at
least a portion of a surface of the substrate with the activating
rinse of claim 20.
24. The method of claim 23, further comprising contacting at least
a portion of the surface of the substrate that has been contacted
with the activating rinse with a metal phosphate pretreatment
composition.
25. The method of claim 23, wherein contacting the surface of the
substrate with the metal phosphate pretreatment composition
comprises immersing the substrate in a bath comprising the metal
phosphate pretreatment composition, wherein the bath temperature is
20.degree. C. to 25.degree. C.
26. A substrate treated with the activating rinse of claim 20.
Description
FIELD OF THE INVENTION
[0001] An activating rinse for treating a metal substrate 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.
SUMMARY
[0005] An activating rinse for treating a substrate is disclosed,
the activating rinse comprising: a dispersion of metal phosphate
particles having a D.sub.90 particle size of no greater than 10
.mu.m, wherein the metal phosphate comprises divalent or trivalent
metals or combinations thereof; a dispersant; and a metal sulfate
salt.
[0006] An activating rinse for treating a substrate is disclosed,
the activating rinse comprising: a dispersion of substantially
pulverized metal phosphate particles having a D.sub.90 particle
size of no greater than 1 .mu.m, wherein the metal phosphate
comprises divalent or trivalent metals or combinations thereof; and
a dispersant.
[0007] Also disclosed are methods of treating a substrate with the
one of the activating rinses.
[0008] Also disclosed are substrates treated with one of the
activating rinses.
DETAILED DESCRIPTION
[0009] According to the present invention, an activating rinse for
treating a substrate is disclosed. According to the present
invention, the activating rinse comprises, or in some instances
consists of, or in some instances consists essentially of: a
dispersion of metal phosphate particles of divalent metals,
trivalent metals or combinations thereof, the metal phosphate
particles having a D.sub.90 particle size that is not greater than
10 .mu.m; a dispersant; and optionally, a metal sulfate salt.
[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, 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
D.sub.90 particle size that is not greater than 10 .mu.m, such as
not greater than 8 .mu.m, such as not greater than 5 .mu.m, such as
not greater than 2 .mu.m, such as not greater than 1 .mu.m and in
some cases may be at least 0.06 .mu.m, such as at least 0.1 .mu.m,
such as at least 0.2 .mu.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
D.sub.90 particle size of 0.06 .mu.m to 8 .mu.m, such as 0.1 .mu.m
to 5 .mu.m, such as 0.2 .mu.m to 2 .mu.m.
[0016] As used herein, the term "D.sub.90" 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 "D.sub.90" value. As used herein, the term "D.sub.10" 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 "D.sub.10" value. As used herein, the term
"D.sub.50" 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 "D.sub.50" value.
[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.degree. 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 FS30, 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 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(PO.sub.4).sub.2,
Zn.sub.2Fe(PO.sub.4).sub.2, Zn.sub.2Ca(PO.sub.4).sub.2,
Zn.sub.2Mn(PO.sub.4).sub.2, or combinations thereof.
[0023] Suitable iron phosphates useful in the activating rinse bath
include, without limitation FePO.sub.4, Fe.sub.3(PO.sub.4).sub.2,
or combinations thereof.
[0024] Suitable calcium phosphates useful in the activating rinse
bath include, without limitation CaHPO.sub.4,
Ca.sub.3(PO.sub.4).sub.2, or combinations thereof.
[0025] Suitable manganese phosphates useful in the activating rinse
bath include, without limitation Mn.sub.3(PO.sub.4).sub.2,
MnPO.sub.4, or combinations thereof.
[0026] Suitable aluminum phosphates useful in the activating rinse
bath include, without limitation AlPO.sub.4.
[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
DISPERBYK.RTM.-190 available from BYK-Chemie GmbH and
ZetaSperse.RTM. 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.
[0029] According to the present invention, the activating rinse may
include a metal sulfate salt, such as, for example, where the metal
phosphate particles have a D.sub.90 particle size of greater than 1
.mu.m to 10 .mu.m, or, for example, where the metal phosphate
particles have a D.sub.90 particle size of less than 1 .mu.m. 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.
[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 D.sub.90 particle size that is not greater than
10 .mu.m; 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 D.sub.90 particle
size that is not greater than 10 .mu.m, 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 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-Sil.TM. 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,
(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 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 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 present invention may also be a method for treating a
substrate comprising contacting at least a portion of a surface of
the substrate with the activating rinse that is disclosed herein.
The method may further include contacting at least a portion of the
substrate surface that has been contacted with the activating rinse
with a metal phosphate pretreatment composition.
[0045] 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 Chemkleen.TM.
163, Chemkleen.TM. 177, Chemkleen.TM. 181ALP, Chemkleen.TM. 490MX,
and Chemkleen.TM. 2010LP each of which is commercially available
from PPG Industries, Inc.
[0046] 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.
[0047] 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.degree. C. to
50.degree. C., such as 25.degree. C. to 35.degree. 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.
[0048] According to the present invention, the method for treating
a substrate may further include contacting at least a portion of
the surface that has been contacted with the activating rinse with
a metal phosphate pretreatment composition, such as a zinc
phosphate pretreatment composition, to form a phosphate coating on
the surface of the "activated" substrate. 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.
[0049] According to the present invention, the pretreatment
composition may comprise zinc ions and phosphate ions. 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 pp, 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.
[0050] 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
phosphoric acid, monosodium phosphate, disodium phosphate, and the
like.
[0051] The pretreatment composition of the present invention a 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.
[0052] 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 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.
[0053] According to the present invention, the pretreatment
composition may also comprise fluoride ion, nitrate ion, and
various metal ions, such as nickel ion, cobalt ion, calcium ion,
magnesium ion, manganese ion, iron ion, copper ion, and the
like.
[0054] 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.
[0055] 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.
[0056] According to the present invention, nickel 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 300 ppm, and in some
instances, may be present in the pretreatment composition in an
amount of no more than 1800 ppm, such as no more than 1200 ppm,
such as no more than 800 ppm, and in some instances, may be present
in the pretreatment composition in an amount of 100 ppm to 1800
ppm, based on total weight of the pretreatment composition, such as
200 ppm to 1200 ppm, such as 300 ppm to 800 ppm.
[0057] 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, no 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.
[0058] 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 no more than 1000 ppm, such as no
more than 800 ppm, and in some cases, in an amount of 100 ppm to
1500 ppm, based on total weight of the pretreatment composition,
such as from 200 ppm to 1000 ppm, such as 500 ppm to 800 ppm.
[0059] 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.
[0060] According to the present invention, copper ion may be
present in the pretreatment composition in an amount of at least 1
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.
[0061] 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.
[0062] The metal phosphate pretreatment composition may be applied
to the activated substrate by spray application or immersion of the
activated substrate in a phosphate bath comprising said composition
at a temperature typically ranging from 20.degree. C. to 75.degree.
C. typically 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 zinc ions, as already
discussed above.
[0063] 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.
[0064] 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 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 .mu.m, such as at least 0.5 .mu.m, such as at least 0.6
.mu.m, such as at least 0.9 .mu.m, and in some cases no larger than
4 .mu.m, such as no larger than 2.7 .mu.m, such as no larger than
2.5 .mu.m, such as no larger than 2 .mu.m. The metal phosphate
coating may comprise crystals having a crystal size of 0.4 .mu.m to
4 .mu.m, such as 0.5 .mu.m to 2.5 .mu.m, such as 0.6 .mu.m to 2
.mu.m.
[0065] 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 5,000.times. or 10,000.times.
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
(10,000.times.) will be required for crystal sizes that are not
distinguishable at 5,000.times. 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.
[0066] The present invention is also 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 that is disclosed herein. According to the present invention,
the activating rinse is contained within the immersion tank at a
temperature of 15.degree. C. to 50.degree. 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 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.
[0067] 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.
[0068] 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.
[0069] 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" 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.
[0070] 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.
[0071] 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.
[0072] 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).
[0073] 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.
[0074] 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 U.S. Pat. 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.
[0075] 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 U.S. Pat.
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 U.S. Pat. No. 3,984,299, or the isocyanate
can be partially blocked and reacted with the resin backbone, such
as is described in U.S. Pat. No. 3,947,338. Also, one-component
compositions as described in U.S. Pat. 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
U.S. Pat. Nos. 3,455,806 and 3,928,157.
[0076] 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 U.S. Pat. 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 U.S. Pat. Nos.
3,793,278 and 3,984,922, respectively. Also, film-forming resins
which cure via transesterification, such as described in European
Application No. 12463 can be used. Further, cationic compositions
prepared from Mannich bases, such as described in U.S. Pat. No.
4,134,932, can be used.
[0077] 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 U.S. Pat. Nos. 3,663,389; 3,947,339; and 4,116,900. In
U.S. Pat. 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 U.S. Pat. Nos. 3,663,389
and 4,116,900.
[0078] 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.
[0079] 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.
[0080] 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.
[0081] 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 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 U.S. Pat. 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 U.S. Pat. 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.degree. C. and
200.degree. C.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
[0086] 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.
[0087] 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.
[0088] 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.degree. C., such
as from 120 to 190.degree. 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.
[0089] 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.
[0090] 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 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 U.S. Pat.
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 U.S. Pat.
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 T.sub.g of
at least 30.degree. C. (such as those described in U.S. Pat. No.
6,797,387, assigned to PPG Industries, Inc. and incorporated herein
by reference).
[0091] 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.
[0092] 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.
[0093] 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.
[0094] 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.degree. C. to 200.degree. C., such as from
170.degree. C. to 190.degree. 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.
[0095] As mentioned above, 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] 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.
[0097] 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.RTM. line of solventbased coating compositions, the
AQUACRON.RTM. line of waterbased coating compositions, and the
RAYCRON.RTM. line of UV cured coatings (all commercially available
from PPG Industries, Inc.).
[0098] 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.
[0099] 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.
[0100] 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.
[0101] In addition, a colorant and, if desired, various additives
such as surfactants, wetting agents or catalyst can be included in
the coating composition (electrodepositable, 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.
[0102] 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.
[0103] 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.
[0104] 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.
[0105] 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.
[0106] 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. Pat. No. 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 A1, filed Jun. 24, 2004, U.S.
Provisional Application No. 60/482,167 filed Jun. 24, 2003, and
U.S. patent application Ser. No. 11/337,062, filed Jan. 20, 2006,
which is also incorporated herein by reference.
[0107] 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. Pat. 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.
[0108] 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 as from 20 seconds to 60 seconds. Example photochromic and/or
photosensitive compositions include photochromic dyes.
[0109] 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 Ser. No. 10/892,919 filed Jul. 16,
2004, incorporated herein by reference.
[0110] 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.
[0111] 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 D.sub.90 particle size of
greater than 10 .mu.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 metal phosphate pretreatment composition may be at a
temperature of no greater than 60.degree. C., such as no greater
than 50.degree. C., such as no greater than 40.degree. C., such as
no greater than 30.degree. C., such as no greater than 25.degree.
C. According to the present invention, the temperature of the bath
containing the metal phosphate pretreatment composition may range
from 20.degree. C. to 60.degree. C., such as from 25.degree. C. to
50.degree. C., such as from 30.degree. C. to 40.degree. 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 metal phosphate pretreatment composition may
enable the bath containing the metal phosphate pretreatment
composition to be maintained at room temperature (20.degree.
C.).
[0112] 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 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 Jernstedt type activators or activating
rinses comprising metal phosphate particles having a D.sub.90
particle size of greater than 10 .mu.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 metal phosphate-containing pretreatment composition, even
on aluminum substrate.
[0113] 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.
[0114] 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.
[0115] 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 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.
[0116] 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.
[0117] 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.
EXAMPLES
Activating Rinse Compositions
[0118] The following activating rinse compositions were prepared as
follows:
[0119] RC: RC (a Jernstedt-type activating rinse concentrate
commercially available from PPG Industries, Inc., also known as
VERSABOND.RTM. 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.
[0120] RC30, 1.1 g/L: 1.1 grams of RC30 (a zinc phosphate-based
activating rinse concentrate with an average zinc phosphate
particle size of about 1 .mu.m and a D.sub.90 of 1-3 .mu.m,
commercially available from PPG Industries, Inc., also known as
VERSABOND.RTM. 30) was added to 1 liter of deionized water to
produce a dispersion of zinc phosphate with a concentration of 1.1
g/L.
[0121] RC30, 3.3 g/L: 3.3 grams of RC30 were added to 1 liter of
deionized water to produce a dispersion of zinc phosphate with a
concentration of 3.3 g/L.
[0122] Composition 1A: An RC30 (1.1 g/L) composition was prepared
as above. To this composition was added 0.3 g/L of zinc sulfate
heptahydrate (available from Fisher Scientific and other chemical
supply houses). The zinc sulfate heptahydrate was pre-dissolved in
a minimal amount of DI water before adding to the RC30 composition.
The resulting composition had a sulfate concentration of 100
ppm.
[0123] Composition 1B: An RC30 (1.1 g/L) composition was prepared
as above. To this composition was added 0.29 g/L of ferrous sulfate
heptahydrate (available from Fisher Scientific and other chemical
supply houses). The ferrous sulfate heptahydrate was pre-dissolved
in a minimal amount of DI water before adding to the RC30
composition. The resulting composition had a sulfate concentration
of 100 ppm.
[0124] Composition 1C: An RC30 (1.1 g/L) composition was prepared
as above. To this composition was added 0.27 g/L of nickel sulfate
hexahydrate (available from Fisher Scientific and other chemical
supply houses). The nickel sulfate hexahydrate was pre-dissolved in
a minimal amount of DI water before adding to the RC30 composition.
The resulting composition had a sulfate concentration of 100
ppm.
[0125] Composition 1D: An RC30 (1.1 g/L) composition was prepared
as above. To this composition was added 0.26 g/L of copper sulfate
pentahydrate (available from Fisher Scientific and other chemical
supply houses). The copper sulfate pentahydrate was pre-dissolved
in a minimal amount of DI water before adding to the RC30 bath. The
resulting composition had a sulfate concentration of 100 ppm.
[0126] Composition 2A: 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.
[0127] To make Composition 2A, 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.
[0128] Composition 2B: A micromedia milled (MMM) dispersion was
prepared in the same manner as was Composition 2A. To make
Composition 2B, 5.55 grams of the dispersion of zinc phosphate were
mixed per liter of deionized water, to give an activator bath with
a zinc phosphate concentration of 1.5 grams per liter.
Example 1
[0129] For each run shown in Table 1, two cold rolled steel panels
(4''.times.6'' 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.degree. C./120 F 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.degree. C.-25.degree. C.) containing one of the activating
rinses described above (RC, RC30, Composition 1A, or Composition
2A, as shown in Table 1) for 1 minute. Activated panels (RC, RC30,
1A, or 2A) then were immersed in a zinc phosphate pretreatment bath
(made from Chemfos 700, commercially available from PPG Industries,
Inc., prepared according to instructions provided by the supplier)
at a bath temperature of either 73 F, 90 F, 100 F, or 125 F (as
indicated in Table 1) 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.RTM. (model
number 078302-300-000) on high-setting at a temperature of about
50-55.degree. C. until the panel was dry (about 1-5 minutes).
[0130] 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''.times.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.
[0131] Zinc phosphate coating weight was determined on one of the
2''.times.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 [(NH.sub.4).sub.2Cr.sub.2O.sub.7] 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.RTM. (model number
078302-300-000) on high-setting at a temperature of about
50-55.degree. 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.
[0132] Zinc phosphate average crystal size was determined on
2''.times.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''.times.3'' panel with no obvious
coating defects, then acquiring an image at either 5,000.times. or
10,000.times. magnification using a Tescan Vega 2 scanning electron
microscope (SEM). The magnification was determined by the crystal
size with the 10,000.times. 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. ImageJ software is public domain software, available from
http://imagej.nih.gov/ij/. Further details of the method have
already been described above.
[0133] Coating completeness (based on a qualitative scale
estimating the % bare area), coating weight (g/ft.sup.2), and
crystal size for the treated panels are reported in Table 1,
below.
TABLE-US-00001 TABLE 1 Phosphate Coating Average Coating Weight
Crystal Activator Completeness (mg/ft.sup.2) size (.mu.m) RC
(Jernstedt) 100% 266 3.4 RC30 (dispersed zinc phosphate) 100% 232
1.8 Composition 1A 100% 131 1.3 Composition 2A 100% 176 1.3 RC
(Jernstedt) 95% 265 4.1 RC30 (dispersed zinc phosphate) 100% 209
2.3 Composition 1A 100% 132 1.0 Composition 2A 100% 153 1.2 RC
(Jernstedt) 50% 184 3.7 RC30 (dispersed zinc phosphate) 100% 187
1.8 Composition 1A 100% 133 1.1 Composition 2A 100% 155 1.1 RC
(Jernstedt) ~0% 40 None RC30 (dispersed zinc phosphate) 70% 169 2.2
Composition 1A 100% 108 0.9 Composition 2A 100% 142 1.2
[0134] The results indicate that the use of an activating rinse
that includes either a metal sulfate salt or pulverized metal
phosphate particles having a D.sub.90 of less than 1 .mu.m results
in decreased coating weight and crystal size of a subsequently
applied phosphate coating compared to the use of a conventional
Jernstedt type activating rinse or an activating rinse that does
not include a metal sulfate salt. Additionally, the inclusion of a
metal sulfate salt or pulverized metal phosphate particles having a
D.sub.90 of less than 1 .mu.m in the activating rinse allows for
the subsequent application of a complete phosphate coating at low
temperatures, such as 73.degree. F., whereas activating rinses that
do not include a metal sulfate salt or pulverized metal phosphate
particles having a D.sub.90 of less than 1 .mu.m do not have
complete phosphate coatings at such low temperatures.
Example 2
[0135] For each run shown in Table 2, cold rolled steel panels
(4''.times.6'' available from ACT TestPanels, 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.degree. C./120 F 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.degree. C.-25.degree. C.) containing one of the activating
rinses described above (RC30 1.1 g/L, RC30 3.3 g/L, Composition 2A,
Composition 2B, as shown in Table 2) for 1 minute. Panels were then
immersed in a zinc phosphate pretreatment bath (made from Chemfos
700 LT, commercially available from PPG Industries, Inc., prepared
according to instructions provided by the supplier) (bath
temperature 86.degree. F.) for 30, 60, 90, or 120 seconds (as shown
in Table 2). 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.RTM. (model number 078302-300-000) on
high-setting at a temperature of about 50-55.degree. C. until the
panel was dry (about 1-5 minutes).
[0136] 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''.times.3'' and one of the half panels was
used to determine coating weight.
[0137] Phosphate coating completeness of the treated panels was
evaluated as described in Example 1. Zinc phosphate coating weight
on the treated panels was determined by the weigh-strip-weigh
method described in Example 1.
[0138] Coating completeness and coating weight (g/m.sup.2) of the
treated panels are reported in Table 2, below.
TABLE-US-00002 TABLE 2 Phosphate Coating Coating Weight Activator
Completeness (mg/ft.sup.2) Zinc phosphate treatment time 30 seconds
RC30, 1.1 g/L 25% 72 RC30, 3.3 g/L 50% 86 Composition 2A 90% 83
Composition 2B 95% 85 Zinc phosphate treatment time 60 seconds
RC30, 1.1 g/L 60% 119 RC30, 3.3 g/L 90% 109 Composition 2A 100% 86
Composition 2B 100% 88 Zinc phosphate treatment time 90 seconds
RC30, 1.1 g/L 100% 176 RC30, 3.3 g/L 100% 130 Composition 2A 100%
118 Composition 2B 100% 104 Zinc phosphate treatment time 120
seconds RC30, 1.1 g/L 100% 187 RC30, 3.3 g/L 100% 122 Composition
2A 100% 119 Composition 2B 100% 83
[0139] The skilled artisan knows that is not possible to deposit a
zinc phosphate coating onto a substrate when the bath containing
the zinc phosphate pretreatment composition is maintained at
86.degree. F. using conventional Jernstedt salt activators, such as
composition RC described above. The results shown in Table 2
demonstrate that activation of the substrate surface with either
Composition 2A or Composition 2B (i.e., micromedia milled zinc
phosphate particles) resulted in a reduced immersion time in the
zinc phosphate pretreatment composition to achieve a complete
phosphate coating compared to activation by activating rinses that
do not include micromedia milled zinc phosphate particles.
Example 3
[0140] For each run shown in Table 3, two cold rolled steel panels
(4''.times.6'', available from ACT TestPanels, LLC) and two
aluminum panels (6022 alloy) (4''.times.6'', available from ACT
TestPanels, 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.degree. C./120 F 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.degree. C.-25.degree. C.) containing
either RC or one of Compositions 1A-1D described above for 1
minute. Panels were then immersed in a zinc phosphate pretreatment
bath (made from Chemfos 700 AL, commercially available from PPG
Industries, Inc., prepared according to instructions provided by
the supplier) (bath temperature 86.degree. F. and 125 F) for 2
minutes (as shown in Table 2). 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.RTM. (model number
078302-300-000) on high-setting at a temperature of about
50-55.degree. C. until the panel was dry (about 1-5 minutes).
[0141] 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''.times.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.
[0142] Zinc phosphate coating completeness and coating weight were
determined by the weigh-strip-weigh method described in Example
1.
[0143] Zinc phosphate average crystal size was determined as
described in Example 1.
[0144] Coating completeness, coating weight (g/m.sup.2), and
crystal size for the treated panels are reported in Table 3,
below.
TABLE-US-00003 TABLE 3 Cold Rolled Steel Aluminum Phosphate Coating
Crystal Phosphate Coating Crystal Coating Weight Size Coating
Weight Size Activator Temperature Completeness (mg/ft.sup.2)
(.mu.m) Completeness (mg/ft.sup.3) (.mu.m) RC30 (dispersed
86.degree. F. 60% 153 3.4 80% 169 3.3 zinc phosphate) 125.degree.
F. 100% 203 2.2 100% 273 3.1 Composition 1A 86.degree. F. 100% 171
1.8 100% 132 2.7 125.degree. F. 100% 193 1.4 100% 172 1.8
Composition 1B 86.degree. F. 100% 153 1.0 100% 112 2.2 125.degree.
F. 100% 210 1.2 100% 192 2.0 Composition 1C 86.degree. F. 100% 149
1.7 100% 149 1.9 125.degree. F. 100% 196 1.3 100% 168 1.1
Composition 1D 86.degree. F. 100% 165 1.5 80% 128 2.7 125.degree.
F. 100% 220 1.5 100% 176 1.8
[0145] The results indicate that the use of an activating rinse
that includes a metal sulfate salt results in decreased phosphate
crystal size of a subsequently applied phosphate coating compared
to the use of an activating rinse that does not include a metal
sulfate salt. Additionally, the use of an activating rinse that
includes a metal sulfate salt generally improved phosphate coating
completeness of a subsequently applied phosphate coating at
low-temperature compared to the use of an activating rinse that
does not include a metal sulfate salt.
Example 4
[0146] For each run shown in Table 4, two Cold rolled steel panels
were spray cleaned with a mixture of Chemkleen 2010LP (1.25%
v/v)/Chemkleen 181ALP (0.125% v/v) for 2 minutes at 49.degree.
C./120 F 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.degree. C.-25.degree. C.) containing one of the
activating rinses described above (RC30, Composition 1A,
Composition 2A, as shown in Table 4) for 1 minute. Panels were then
immersed in a zinc phosphate pretreatment bath (made from Chemfos
700 AL, commercially available from PPG Industries, Inc., prepared
according to instructions provided by the supplier) (bath
temperature 86.degree. F. or 125 F, as shown in Table 2) for 2
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.RTM. (model number 078302-300-000) on
high-setting at a temperature of about 50-55.degree. C. until the
panel was dry (about 1-5 minutes).
[0147] Four panels were treated as described above and then were
coated with ED7000 electrocoat, made from materials provided by PPG
Industries, Inc. and applied according to the manufacturer's
instructions. Two panels were subsequently coated with a typical
automotive decorative layering system topcoat. The panels that were
not topcoated were subjected to GMW 14872 cyclic corrosion testing
for 48 days. The topcoated panels were exposed to Volvo Florida
Exposure corrosion testing for six months. The corrosion results
appear in Table 4, below:
TABLE-US-00004 TABLE 4 GMW Volvo 14872, Florida average Exposure,
Zinc Coating Crystal scribe Average phosphate Weight Size creep
Scribe Activator temperature (mg/ft.sup.2) (.mu.m) (mm) Creep (mm)
RC (Jernstedt) 125.degree. F. 234 3.2 7.2 12.7 Composition
86.degree. F. 140 1.9 6.9 10.9 1A Composition 86.degree. F. 106 1.3
5.8 10.1 2A
[0148] The results show that, even though the coating weight and
crystal size is much lower than the control, the panels treated
with an activating rinse including a metal sulfate salt or
pulverized metal phosphate particles having a D.sub.90 of less than
1 .mu.m at low temperature performed comparably, if not better, in
corrosion testing.
Example 5
[0149] 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.
[0150] The dispersion of Comparative I was characterized as follows
and was compared to the activation properties of Composition
2A.
[0151] X-ray diffraction of dried solids of Comparative I showed
both ZnO and zinc phosphate.
[0152] Particle size (D.sub.10, D.sub.50, and D90) 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.degree. 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, D.sub.10, D.sub.50, and D.sub.90) were determined and
are reported in Table 5.
TABLE-US-00005 TABLE 5 Mean PS D10 D50 D90 Sample (.mu.) (.mu.)
(.mu.) (.mu.) Composition I 3.914 1.528 3.495 6.904 (Initial)
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
[0153] For each run shown in Table 6, cold rolled steel,
electrogalvanized steel, or aluminum alloy 6022 panels
(4''.times.6'', 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.degree. C./120 F 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.degree. C.-25.degree. 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 78 F 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.RTM.
(model number 078302-300-000) on high-setting at a temperature of
about 50-55.degree. C. until the panel was dry (about 1-5
minutes).
[0154] 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''.times.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.
[0155] 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 6, below.
TABLE-US-00006 TABLE 6 Crystal Coating Coating size weight
Substrate Activator Completeness (.mu.m) (mg/ft.sup.2) Cold rolled
steel Composition 2A 100% 1.20 94 Cold rolled steel Comparative I
60% 2.88 153 Electrogalvanized Composition 2A 100% 1.22 289 steel
Electrogalvanized Comparative I 100% 3.00 359 steel Aluminum
Composition 2A 95% 1.45 142 alloy 6022 Aluminum Comparative I 40%
3.05 153 alloy 6022
[0156] 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.
[0157] 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
[0158] 1. An activating rinse for treating a substrate
comprising:
[0159] a dispersion of metal phosphate particles having a D.sub.90
particle size of no greater than 10 .mu.m, wherein the metal
phosphate comprises divalent or trivalent metals or combinations
thereof;
[0160] a dispersant; and
[0161] a metal sulfate salt.
2. The activating rinse of Aspect 1, wherein the D.sub.90 particle
size is measured from a sample of the activating rinse that has
been sonicated. 3. The activating rinse of Aspect 1 or 2, wherein
the dispersant comprises a non-ionic dispersant. 4. The activating
rinse of any of the preceding Aspects, wherein the activating rinse
is substantially free of ionic dispersants. 5. The activating rinse
of any of the preceding Aspects, wherein a sulfate ion of the metal
sulfate salt is present in an amount of 5 ppm to 5,000 ppm based on
a total weight of the activating rinse. 6. The activating rinse of
any of the preceding Aspects, wherein the metal of the metal
sulfate salt comprises a divalent metal, wherein the divalent metal
preferably comprises nickel, cobalt, zinc, iron, copper, or
combinations thereof. 7. The activating rinse of any of the
preceding Aspects, wherein the metal phosphate particles have a
D.sub.90 particle size of no more than 1 .mu.m. 8. The activating
rinse of any of the preceding Aspects, wherein the metal phosphate
particles are substantially pulverized. 9. The activating rinse of
any of the preceding Aspects, wherein the activating rinse
comprises a multi-component system, and wherein the dispersion of
metal phosphate particles and the dispersant form a part of a first
component and the metal sulfate salt forms a part of a second
component. 10. An activating rinse for treating a substrate
comprising:
[0162] a dispersion of substantially pulverized metal phosphate
particles having a D.sub.90 particle size of no greater than 1
.mu.m, wherein the metal phosphate comprises divalent or trivalent
metals or combinations thereof; and
[0163] a dispersant.
11. The activating rinse of Aspect 10, wherein the D.sub.90
particle size is measured from a sample of the activating rinse
that has been sonicated. 12. The activating rinse of Aspect 10 or
11, wherein the metal phosphate particles having a D.sub.90
particle size of no greater than 0.75 .mu.m. 13. A method for
treating a substrate comprising contacting at least a portion of a
surface of the substrate with the activating rinse of any of the
preceding Aspects. 14. The method of Aspect 13, further comprising
contacting at least a portion of the surface of the substrate that
has been contacted with the activating rinse with a metal phosphate
pretreatment composition, wherein contacting the surface of the
substrate with the metal phosphate pretreatment composition
preferably comprises immersing the substrate in a bath comprising
the metal phosphate pretreatment composition, wherein the bath
temperature is from 20.degree. C. to 60.degree. C. and more
preferably is 20.degree. C. to 25.degree. C. 15. A substrate
treated with the activating rinse of any of Aspects 1 to 12,
preferably in a method according to Aspect 13 or 14. 16. The
substrate of Aspect 15 further comprising a phosphate coating,
wherein the phosphate coating preferably comprises phosphate
crystals having a crystal size of 0.4 .mu.m to 4 .mu.m, more
preferably of 0.9 .mu.m to 2.7 .mu.m. 17. The substrate of any of
Aspects 15 to 16, wherein the substrate is hot dipped galvanized
steel.
* * * * *
References