U.S. patent application number 17/805797 was filed with the patent office on 2022-09-22 for fast coating compositions.
The applicant listed for this patent is TESLA NANOCOATINGS, INC.. Invention is credited to Joshua ARMSTRONG, Todd HAWKINS, Jorma VIRTANEN.
Application Number | 20220297155 17/805797 |
Document ID | / |
Family ID | 1000006388448 |
Filed Date | 2022-09-22 |
United States Patent
Application |
20220297155 |
Kind Code |
A1 |
VIRTANEN; Jorma ; et
al. |
September 22, 2022 |
FAST COATING COMPOSITIONS
Abstract
An anticorrosive coating includes a first curable liquid layer
to the associated substrate, the first layer having a thickness of
at least about 100 micrometers, wherein the first layer includes at
least one polymer or at least one monomer, quasi-one-dimensional
particles or quasi-two-dimensional particles, sacrificial metal
particles, and a solvent, wherein a percolation threshold of the
particles is not reached in the presence of the solvent, wherein
the percolation threshold of the particles is reached when between
about 1% and about 20% of the solvent evaporates, applying a second
curable liquid layer having a thickness of at least 100 micrometers
on the top of the first layer after the percolation threshold of
the particles is reached and viscosity of the first layer increases
more than 50%, and allowing the first layer and the second layer to
cure simultaneously.
Inventors: |
VIRTANEN; Jorma; (Massillon,
OH) ; ARMSTRONG; Joshua; (Cuyahoga Falls, OH)
; HAWKINS; Todd; (Massillon, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TESLA NANOCOATINGS, INC. |
Massillon |
OH |
US |
|
|
Family ID: |
1000006388448 |
Appl. No.: |
17/805797 |
Filed: |
June 7, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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17315603 |
May 10, 2021 |
11351571 |
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17805797 |
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17077741 |
Oct 22, 2020 |
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17315603 |
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16814385 |
Mar 10, 2020 |
11090687 |
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17077741 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 3/40 20130101; C09D
5/08 20130101; C08K 3/04 20130101; B05D 2301/00 20130101; C09D 7/62
20180101; B05D 7/532 20130101; B05D 2503/00 20130101; B05D 2504/00
20130101; C09D 7/70 20180101; B05D 2401/10 20130101 |
International
Class: |
B05D 7/00 20060101
B05D007/00; C09D 5/08 20060101 C09D005/08; C09D 7/62 20060101
C09D007/62; C09D 7/40 20060101 C09D007/40; C08K 3/40 20060101
C08K003/40; C08K 3/04 20060101 C08K003/04 |
Claims
1. A self-stratifying anticorrosive coating comprising: a zinc-rich
epoxy; a curing agent chosen from the group consisting of amines,
thiols, phenols, and carboxylic anhydrides; a binding agent chosen
from the group consisting of aminoalkyl dialkoxysilane,
dimethoxysilane, and aminoalkyl trialkoxysilane; a graphitic
material; a solvent; and a water scavenger.
2. A self-stratifying anticorrosive coating comprising: sacrificial
metal particles; graphitic material; a first monomer; at least a
second monomer or at least a first polymer; and a material that
prevents the polymerization of at least one monomer inside the
coating.
3. The coating of claim 2 further comprising: a curing agent; and a
binding agent.
4. The coating of claim 3, wherein the first monomer and the at
least a second monomer or at least a first polymer are chosen from
the group consisting of epoxies, polyurethane, acrylates,
methacrylates, vinyl ethers, cycloaliphatic epoxides, oxetanes,
epoxides, photopolymers, siloxanes, and polyurea.
5. The coating of claim 4, wherein the graphitic material is chosen
from the group consisting of single walled carbon nanotubes, double
walled carbon nanotubes, multiwalled carbon nanotubes, single sheet
graphene, double sheet graphene, or multi-sheet graphene.
6. The coating of claim 5, wherein the material that prevents the
polymerization of at least one monomer inside the coating is a
water scavenger chosen from the group consisting of liquid water
scavengers, molecular sieves, silica, metal salts, and metal
oxides.
7. The coating of claim 2, wherein the sacrificial metal particles
are chosen from the group consisting of any metal that has more
positive redox potential then iron.
8. The coating of claim 7, wherein the sacrificial metal particles
are chosen from the group consisting of zinc, magnesium, aluminum,
and alloys thereof.
9. The coating of claim 2, wherein the curing agent is chosen from
the group consisting of amines, thiols, phenols, and carboxylic
anhydrides, and the binding agent is chosen from the group
consisting of silanes with at least two alkyl groups.
10. The coating of claim 2, wherein the coating further comprises a
photoinitiator chosen from the group consisting of
1-hydroxy-cyclohexyl-phenyl-ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
2,2-dimethoxy-2-phenylacetophenone,
Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, triphenyl
sulfonium triflate, triaryl sulfonium hexafluoroantimonate salts,
triaryl sulfonium hexafluorophosphate salts, bis(eta
5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)tit-
anium, 5,7-diiodo-3-butoxy-6-fluorone,
2,4,5,7-tetraiodo-3-hydroxy-6-fluorone, and
2,4,5,7-tetraiodo-3-hydroxy-9-cyano-6-fluorone.
11. A method for a self-stratifying anticorrosive coating on an
associated substrate comprising the steps of: mixing together a
monomer or a polymer, a solvent, a graphitic material, and
sacrificial metal particles; adding a material that prevents
polymerization inside the coating before, and immediately after,
application on the associated substrate; and adding a silane
mixture.
12. The method of claim 11 further comprising the steps of: adding
a curing agent; and applying, in one spraying, the mixture of the
monomer or polymer, the solvent, the graphitic material, and the
sacrificial metal particles, the silane mixture, and the curing
agent to the associated substrate, wherein an external effector
hydrolyzes the silane mixture creating silicic acid, wherein the
silicic acid spontaneously polymerizes into siloxane.
13. The method of claim 11, wherein no insulating layer is
used.
14. The method of claim 13 wherein the external effector is ambient
moisture or photons.
15. The method of claim 11, wherein the monomer or polymer is
chosen from the group consisting of epoxies, acrylates,
methacrylates, vinyl ethers, cycloaliphatic epoxides, oxetanes,
epoxides, photopolymers, siloxanes, and polyurea.
16. The method of claim 11, wherein the graphitic material is
chosen from the group consisting of single walled carbon nanotubes,
double walled carbon nanotubes, multiwalled carbon nanotubes,
single sheet graphene, double sheet graphene, or multi-sheet
graphene.
17. The method of claim 16, wherein the material that prevents the
polymerization inside the coating is a water scavenger chosen from
the group consisting of liquid water scavengers, molecular sieves,
silica, metal salts, and metal oxides.
18. The method of claim 17, wherein the sacrificial metal particles
are chosen from the group consisting of any metal that has more
positive redox potential then iron.
19. The method of claim 18, wherein the sacrificial metal particles
are chosen from the group consisting of zinc, magnesium, aluminum,
and alloys thereof.
20. The method of claim 11, wherein the coating further comprises a
photoinitiator chosen from the group consisting of
1-hydroxy-cyclohexyl-phenyl-ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
2,2-dimethoxy-2-phenylacetophenone,
Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, triphenyl
sulfonium triflate, triaryl sulfonium hexafluoroantimonate salts,
triaryl sulfonium hexafluorophosphate salts, bis(eta
5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)tit-
anium, 5,7-diiodo-3-butoxy-6-fluorone,
2,4,5,7-tetraiodo-3-hydroxy-6-fluorone, and
2,4,5,7-tetraiodo-3-hydroxy-9-cyano-6-fluorone, wherein the curing
agent is chosen from the group consisting of amines, thiols,
phenols, and carboxylic anhydrides, and the binding agent is chosen
from the group consisting of aminoalkyl dialkoxysilane,
dimethoxysilane, and aminoalkyl trialkoxysilane.
Description
[0001] This application is a continuation of U.S. Ser. No.
17/315,603, entitled Fast Coating Compositions and Methods, filed
on May 10, 2021, now U.S. Pat. No. 11,351,571, which is a
divisional application of U.S. Ser. No. 17/077,741, entitled Fast
Coating Compositions and Methods, filed Oct. 22, 2020; which is a
continuation application of U.S. Ser. No. 16/814,385, entitled Fast
Coating Compositions and Methods, filed Mar. 10, 2020.
Anticorrosive coatings often contain several layers. One of the
most commonly used industrial coatings is a three-layer coating
consisting of zinc rich primer, an intermediate layer, and a
topcoat. Currently, two-layer, and up to five-layer, coatings are
also being used.
I. BACKGROUND
[0002] Typically, the primer is applied to the substrate, and
allowed to partially cure, often so that the primer appears to be
dry and can be touched. Then the process is repeated, until all the
layers have been applied. This method may be called wet-on-dry
(WoD) method. This often means that one layer per day may be
applied. Spraying is the most commonly favored application method
for WoD.
[0003] Wet-on-wet (WoW) is a technique in which wet layers are
applied to previously administered wet layers. Due to the
consistency, most wet uncured coatings cannot have a second wet
layer sprayed on top of them; especially for a vertical surface.
There are many problems associated with the WoW method. First,
sagging may be extensive. Sagging is often a problem with a single
layer, and is exponentially more difficult if another wet layer is
added on an existing wet layer. The velocity of the spray creates
significant momentum toward the substrate, which may lead to
partial penetration of the previous wet layer. This can create
serious problems if two different types of polymer systems, such as
epoxies and polyurethanes, are used in consecutive layers. There
may be a chemical problem if two different epoxies are used,
because the stoichiometry may be too different. The same issue
applies to polyurethanes. The problem is more pronounced if layers
have different polymerization chemistries, such as amino-cured
epoxies and polyurethanes. Di-isocyanates in the polyurethane layer
may react extensively with the amines in the epoxy layer. Although
a moderate cross reaction between the layers is desirable, because
adhesion between the layers is increased, excessive reaction might
distort the stoichiometry so much that the polymerization will be
incomplete in both layers.
[0004] Wet on wet coating has been used, for example, in the
fabrication of photographic films. However, in that case the film
is horizontal and moves horizontally. The momentum of the liquid in
that case is almost parallel to the film, thereby reducing the
mixing of the layers.
[0005] Wet on wet coating has also been used for the coating of
cars (e.g. US20040028822, Continuous process for applying a
tri-coat finish on a vehicle). The application is directed to a
process and materials for coating a substrate with a flake or other
effect pigment containing tri-coat color finish in a continuous
wet-on-wet application process. In water, hydrogen bonding is very
important. When water evaporates, even partially, hydrogen bonding
between constituents increases the viscosity.
[0006] Despite the significant success in the car industry, the WoW
method has not been applied in field conditions, and especially not
in oil and gas fields. First, cars already have an anticorrosive
dry coating before they enter the final painting stage. Thus, the
anticorrosive coating does not get diluted with the subsequent
layers. In oil and gas fields, and many other instances, the
anticorrosive coating is the primer. Any dilution of the primer may
be detrimental to its performance. This applies to anticorrosive
coatings that have sacrificial metal particles. These must be in
electrical contact with each other and the substrate. Second, the
thickness of the layers is typically more than 100 .mu.m. Putting
two wet layers on top of each other may result in considerable
sagging. While it is aesthetically undesirable, it also gives
uneven coating and performance.
[0007] Liquid coating materials should have a low enough viscosity
so that they can be sprayed, brushed, or otherwise readily applied.
On the other hand, the viscosity should be high enough that there
is no sagging on vertical surfaces. The suitable viscosity
application range is between about 1000 cP (centipoise) and about
2500 cP, but can be between about 1500 cP and about 2000 cP.
Sagging may be prevented by making the coating thin enough, and
letting it dry before the next layer is applied. This may make the
whole coating process slow and expensive. Thixotropic additives may
be used to increase the viscosity. These additives are beneficial,
but they have limits, and do not allow for the WoW method of the
present teachings.
[0008] Conventional coating methods have several drawbacks. Despite
the correct stoichiometry and proper mixing, one or more components
may partially separate, and be squeezed out from the interior of
the coating layer. This may be harmful to the adhesion with the
substrate and adhesion between the layers. When the curing agent is
an amine, this phenomenon is called amine blush. The amine will
further absorb water and carbon dioxide on to the surface, leading
to amine bloom that is more extensive than amine blush. All this
will have a negative effect on the binding of the next layer, and
on the overall performance of the coating. All these problems may
be alleviated by the present teachings. First, there is no time for
the curing induced separation of the components. Consequently,
there will not be any significant absorption of water and carbon
dioxide. Second, because there is a thin mixing layer, and the
layers are cured at the same time, the polymer will be continuous
without any interface, i.e., there may be a high density of
intermingled polymer chains connecting two consecutive layers. In
conventional methods there will also be some bonding between
layers, but the density is low, if polymerization has been mostly
completed. Amine blush or bloom worsens the situation when
conventional coating methods are used. Excess amine acts as a
polymerization terminator for epoxies and polyurethanes, preventing
chemical bonding between the layers.
[0009] Evonik developed a method utilizing a new curing agent that
will increase the viscosity quickly. The drawbacks are a short pot
life and the use of a plural spray system. The present teachings
alleviate both of these drawbacks.
II. SUMMARY
[0010] The present teachings use the concept of a percolation
threshold to adjust the viscosity of the liquid coating, so the
mixing of the layers and sagging is minimized. Percolation
traditionally means filtering fluids through porous materials.
However, in materials science and physical chemistry it also means
a continuous pathway along a material. Percolation threshold is a
concentration of particles in a medium, in which the particles are
continuously touching each other so that they form a continuous
network. If these particles are electrically conducting, and the
medium is not, a sudden increase of conductivity, as a function of
the concentration of particles, indicates the percolation
threshold. Other physical properties may also change abruptly when
the percolation threshold is reached. Viscosity may be a sensitive
indicator of the percolation threshold.
[0011] Percolation depends strongly on the shape of the particles.
Spherical particles have a high percolation threshold, about 30 vol
%. It is to be understood that "spherical" is to be understood as
an approximate shape, and not an exact geometric sphere. A high
aspect ratio lowers the percolation threshold dramatically.
Quasi-one-dimensional particles, such as CNTs (carbon nanotubes),
may have a percolation threshold under 1 vol %. Platelets, such as
graphene, may have a percolation threshold under 10 vol %. When a
liquid contains spherical, quasi-two-dimensional, and
quasi-one-dimensional, particles, as is often the case in the
materials of the present teachings, the percolation threshold is
found by experimentation. For example, 30 vol % of zinc particles
is about 75 wt %, because zinc has a density of about 7 g/cm.sup.3.
Thus, current zone rich primers have about 80 wt % of zinc, because
zinc to zinc contact is useful for an anticorrosive function.
[0012] The present teachings avoid the problems of coating vertical
stationary substrates, by adding quasi-one-dimensional, and
quasi-two-dimensional, particles, such as carbon nanotubes (CNTs),
graphene, zinc flakes, or glass flakes into the coating. These
particles have a low percolation threshold, such that the viscosity
increases suddenly when the percolation threshold is reached, for
example, due to evaporation of a solvent. CNTs may be single walled
(SWNT), double walled (DWNT), or multiwalled carbon nanotubes
(MWNT). Graphene may be single layer or multilayer graphene. Also,
fast evaporating solvents, such as t-butyl acetate, may be used.
After the solvent has evaporated the viscosity of the coating
material is immediately very high, resembling partially cured
conventional coating materials. Extensive mixing of the layers may
further be avoided by a proper choice of components. One layer may
consist primarily of aliphatic compound, while the other may
consist mostly of aromatic compounds. One layer may also contain
fluorinated compounds.
[0013] Epoxy-amine systems, especially at low temperatures and
humid environments, have serious problems called amine blush and
amine bloom. During, and immediately after, the curing process the
surface may become contaminated by excess amine, water, and/or
carbon dioxide. Sometimes the freshly cured surface must be washed
and sanded, otherwise the adhesion of the next layer may be
adversely affected. Both amine blush and amine bloom can be avoided
by the present teachings on the primer and intermediate layers
(i.e., in all layers that are important for the anticorrosive
properties).
[0014] These additives and compositions allow application of a
second wet layer on top of the first wet layer, i.e., enabling the
WoW method. The two-layer coating of the present teachings competes
favorably with conventional three-layer coatings in anticorrosive
properties. Moreover, it can be applied in one day, while
application of the three-coat system may take three days. Thus, the
present teachings provide materials and methods that can give
considerable economic benefit.
[0015] The present teachings provide materials and methods for the
fast coating of surfaces by two or more different liquid layers
that can be cured at the same time.
[0016] In one aspect of the present teachings, the surface is
coated with a first wet coating material that contains
quasi-one-dimensional particles or quasi-two-dimensional particles,
and then with a second wet coating material before the first wet
coating material is cured.
[0017] In one aspect of the present teachings, the method may be
used in oil or gas fields for the coating of equipment, such as oil
rigs and pipes.
[0018] Another aspect of the present teachings is providing
materials and methods that avoid amine blush and bloom in the
primer and all intermediate layers, especially in humid conditions,
such as off-shore environments.
[0019] Other benefits and advantages will become apparent to those
skilled in the art to which it pertains upon reading and
understanding of the following detailed specification.
III. DEFINITIONS
[0020] WoD (wet on dry)--a liquid layer applied on top of a dry
layer.
[0021] WoW (wet on wet)--a liquid layer applied on top of a wet
layer.
[0022] Quasi one-dimensional--one dimension of a particle is at
least 50 times larger than the other two dimensions. For example,
if MWNT has a diameter of 10 nm, and is more than 500 nm long, it
is classified as quasi one-dimensional in this context. For
simplicity, these particles are called one-dimensional in the
Description.
[0023] Quasi two-dimensional--two dimensions of a particle are at
least 50 times larger than one dimension. For example, if a glass
flake has a thickness of 1 .mu.m and is more than 50 .mu.m wide in
two dimensions, it is classified as quasi two-dimensional in this
context. For simplicity, these particles are called two-dimensional
in the Description.
[0024] Percolation threshold--the concentration of particles,
wherein the particles form a continuous three-dimensional network.
The measure in this context of the percolation threshold is
viscosity, i.e., viscosity will increase significantly after
percolation threshold is reached. This definition may give higher
percolation threshold for some particles than other methods, for
example, CNTs electrical conductivity may indicate that CNTs reach
percolation threshold at very low concentrations, below 0.1%, while
the viscosity stays very low. Also in the present teachings, many
different kinds of particles may participate in percolation
network.
[0025] Curable liquid--a polymer solution or melt that solidifies
when a solvent evaporates or temperature is ambient; or a monomer,
or monomer mixture, that solidifies as a result of a polymerization
reaction.
[0026] Wet coating layer--a wet layer whose thickness can be
measured with a standard wet thickness contact gauge.
IV. FIGURES
[0027] The present teachings are described hereinafter with
reference to the accompanying drawings.
[0028] FIG. 1 shows a conventional two-coat method, wherein A is
the substrate, B is the first layer applied to the substrate, C is
the first layer cured, D is the second layer applied on the
substrate, and E is the second layer cured;
[0029] FIG. 2 shows the two-coat method of the present teachings,
wherein A is the substrate, B is the first layer applied to the
substrate, C is the second layer applied to the substrate, and D is
the first and second layer cured;
[0030] FIG. 3 shows the experimental viscosity (in KU units) of a
coating material of Example 2, when solvent (VOC) is added in small
portions; and
[0031] FIG. 4. Evaporation of the solvent from 125 micrometers
thick layer of material of Example 1.
V. DETAILED DESCRIPTION
[0032] FIG. 1 depicts a method for the fabrication of a
conventional two-coat system (WoD), in which the first layer is
cured before a second layer is applied. Often the first layer must
be washed, and sanded before the second layer is applied, even if
it freshly cured. This step is not included in FIG. 1, because it
is not always mandatory.
[0033] FIG. 2 depicts the method of the present teachings (WoW).
The first layer is applied, and before the first layer is cured,
the second layer is applied. Thus, there is at least one less step.
Also, no washing or sanding of the first layer is done in this
method. Thus, there may be two steps less than in the conventional
method of FIG. 1. These extra steps included in the conventional
method are slow, and often only one layer can be applied in one
day.
[0034] Conventional coating systems have three layers, while the
present teachings may provide equal or better performance with just
two layers. Conventional coating may take up to three days, while
the coating according to present teachings may be performed in one
day. The materials and methods of the present teachings offer
considerable savings, and equal or better performance compared to
the conventional coating materials and methods.
[0035] Coating compositions of the present teachings may contain
polymer or monomer(s), thixotropic agent, sacrificial metal
particles, solvent, and quasi-one dimensional, and
quasi-two-dimensional materials, such as graphitic material, glass
flakes, and mica. In one aspect of the present teachings, the
graphitic materials can be CNTs or graphene. Sacrificial metal
particles may be nickel, zinc, aluminum, or magnesium, or alloys
containing these metals. These particles may be spherical or
essentially 2D flakes. These are non-limiting examples. All
particles and materials may be functionalized so that they bind
with the polymer matrix, other particles, or the substrate.
[0036] The polymer may be polyacrylate, polycarbonate, or
polystyrene. The monomer may be bisphenol A diglycidyl ether
(BPDGE), Novolac (polymer of BPDGE and formaldehyde), SU-8 (cyclic
tetramer of BPDGE and formaldehyde, available from MicroChem.RTM.
of Massachusetts), or any hydrogenated or fluorinated form of
these. These are non-limiting examples, and numerous other di- and
polyepoxies are known in the art. The thixotropic agents may be
diamines, dithiols, amino thiols, carboxylic anhydrides, diphenols,
or Mannich curing agents. These may also contain more than two
functional groups. Specific, non-limiting examples are
1,4-diaminobutane, 1,3-diamino-1-methyl cyclohexane,
1,3-di(aminomethylene)benzene, and diamino polyethyleneoxide.
[0037] Polyurethanes, polyurethane-ureas, or polyureas may be
fabricated from diisocyanates, polyisocyanates, polyols, or
polyamines. Polyisocyanates include, but are not limited to
ethylene diisocyanate, 1,2-propylene diisocyanate,
cyclohexane-1,3-diisocyanate, 4,4'-dicycloheylmethane diisocyanate,
toluene diisocyanate, m-phenylene diisocyanate,
3,3'-dimethyl-4,4'-biphenylene diisocyanate, and naphthalene
diisocyanate. Diisocyanates may be modified by carbodiimide.
Polyols may be, for example, ethylene glycol, glycerol, polyester
polyols, polycaprolactone polyols, polycarbonate polyols,
polyethylene glycol, or polypropylene glycol.
[0038] One-dimensional and two-dimensional materials are used to
adjust viscosity, along with the proper choice of solvent, so that
the material can be easily applied, but does not sag while the
solvent evaporates. One-dimensional and two-dimensional materials
have a low theoretical percolation threshold, between about 0.01
vol % to about 2 vol %, while spherical three-dimensional particles
have a percolation threshold of about 30 vol %. These values may be
obtained if the dispersion of the particles is perfect. However,
many of these particles may aggregate, so that the percolation
threshold may be much bigger, for example, about 0.1 vol % to about
20 vol % for quasi-one-dimensional and quasi-two-dimensional
particles. Low percolation threshold is the reason why
quasi-one-dimensional and quasi-two-dimensional particles are well
suited for the control of viscosity, preventing sagging, and
preventing the mixing of the layers. In one aspect of the present
teachings, quasi-one dimensional particles can have a concentration
between about 0.1 to about 2 wt % (inclusive), quasi-two
dimensional particles can have a concentration between about 2 to
about 20 wt % (inclusive), and three dimensional particles can have
a concentration between about 50 to about 80 wt % (inclusive).
[0039] The composition may be adjusted so that the percolation
threshold is not reached when a solvent is present, but is reached
when the solvent even partially evaporates. When the particles form
a continuous network, the viscosity may increase suddenly and
significantly (more than 50%), and there will be no sagging, even
when a second wet layer is applied on the top of the first wet
layer. The increase of the viscosity may be much more than 50%.
[0040] FIG. 3 shows the viscosity of the primer (Example 2) as a
function of the solvent concentration. The material of the Example
2 is denoted by an arrow, i.e., this material contains 13 wt % of
solvent. FIG. 4 shows the relative weight of 5 mil thick coating on
4''.times.4'' steel plate as a function of time. At the beginning
the weight is 100 wt % but decreases fast. In about 20 minutes the
weight is 97% of the original (3% of the solvent has evaporated),
and after six hours (360 minutes) about 8.5 wt % of total coating
has evaporated. Because there is about 13 wt % of the solvent at
the beginning in the coating, and percolation threshold is at 12%
of the solvent, the percolation threshold will be reached when 3%
of the weight is lost. This will take less than 20 minutes
according to FIG. 4. In FIG. 4 the time axis is only 6-7 hours, but
it can be estimated that all solvent has essentially evaporated in
10 hours, and maximum viscosity is reached.
[0041] FIG. 4 depicts the viscosity of the coating material of
Example 2 as a function of added solvent (VOC). Diamond symbols
represent measured values, and squares are linear least squares
fit. As can be seen in FIG. 4, the viscosity first decreases very
fast, with the slope of -415 cP/1% VOC. At around 13% VOC the slope
changes to -93 cP/1% VOC. Thus, the slope is 4.5 times greater when
the percolation threshold has been reached.
EXAMPLES
Example 1
[0042] Multiwalled carbon nanotubes (25 g) and nanographite (25 g)
were dispersed into 5 kg of Epon.TM. 828 (an undiluted clear
difunctional bisphenol A/epichlorohydrin derived liquid epoxy
resin) using a high speed (10,000 rpm) blade mixer. Mixing was
continued and 7.5 kg of zinc powder was added. Finally, 0.4 kg
t-butyl acetate, 0.5 kg petroleum spirits, and 1.2 kg xylene were
added. Four kilograms of this mixture was mixed with 0.38 kg of
Ancamide.RTM. 702B75 (a low viscosity, solvent based polyamide
adduct curing agent, supplied at 75% solids in n-butanol). This
mixture is the coating material for the first layer (primer) in
Example 4 and was used immediately after fabrication.
Example 2
[0043] Multiwalled carbon nanotubes (25 g) and nanographite (25 g)
were dispersed into 5 kg of Epon.TM. 828 using high speed (10,000
rpm) blade mixer. Mixing was continued, and 7.5 kg of zinc powder
was added. Finally, 0.3 kg t-butyl acetate, 0.3 kg petroleum
spirits, and 0.8 kg xylene was added. Five kilograms of this
mixture was mixed with 0.50 kg of Ancamide.RTM. 702B75
(Airproducts). t-Butyl acetate/Xylene 3:4 mixture was added in
measured portions (between about 25 g and about 100 g), and the
viscosity was measured after each addition. The result is shown in
FIG. 3.
Example 3
[0044] The 5 g sample of the mixture of Example 1 was spread on a
4''.times.4'' substrate using a 5 mil drawdown bar. The total
weight of the substrate and coating was measured every minute for
the first ten minutes, then every five minutes for the next twenty
minutes, then every ten minutes for the next thirty minutes, then
hourly for the next five hours, and then daily. The result of the
first 6 hours is shown in FIG. 4.
Example 4
[0045] 100 g of t-butyl acetate and 120 g Hi Sol.RTM. 10 (a
naphthenic aromatic solvent) were added to 1 kg of Epon.TM. 828.
Similarly, 125 g of t-butyl acetate, and 150 g Hi Sol.RTM. 10 were
added into 1.05 kg of Aradur.RTM. 283 (a formulated polyamidoamine
hardener). Both mixtures were mixed with each other, and the final
mixture constitutes the coating material for the second layer
(topcoat) in Example 3, and was used immediately after
fabrication.
Example 5
[0046] The mixture of Example 1 was sprayed with a Binks.RTM.
Trophy Series II2GX paint gun using a Binks.RTM. 1.4 liquid nozzle
tip, an LVMP air tip, and a Binks.RTM. 1.5-gal pressure pot. Steel
substrates were 10 cm.times.20 cm and were sandblasted to SP10
standard (near-white metal blast cleaning from Society for
Protective Coatings). A 200 .mu.m thick layer was sprayed on these
panels in a vertical position. The solvent was allowed to evaporate
for 20 minutes, and the second epoxy layer was sprayed on using the
material of Example 2 with the same equipment, but using a 1.0
liquid tip, and an HVLP air tip. The thickness of the second layer
(top coat) was 150 .mu.m. The coating was allowed to cure one week.
Adhesion was tested using a PosiTest AT-A (DeFelsko) adhesion
meter, and the result was 2240 psi.
Example 6
[0047] The primer of Example 1 was mixed with Ancamide 2767 in the
ratio 10:1. This mixture contains 75 wt % Zn calculated of solids,
and 2 wt % of MWNTs of epoxy. Solvents comprise about 13 wt % of
the total. About a 5 mil to about a 12 mil (125 to 300 micrometers)
layer of this mixture was sprayed using a cup gun (3M Accuspray
gun) with 1.8 mm nozzle. After 10 to 30 minutes of drying the epoxy
topcoat containing 1 wt % CNTs was sprayed similarly. When the
total wet coat was 20 mil, no sagging was observed. After curing at
ambient temperature for one week there was no amine blush,
blisters, or mud cracking observed.
[0048] The material of Example 1 is representative of the present
teachings. It contains 13.2% solvents (VOC). The freshly fabricated
material of Example 2 contains 9.4% solvents. This material was
used for the viscosity studies depicted in FIG. 3. These materials
are denoted as E1 and E2 in FIG. 3. The dotted line represents the
percolation threshold at 13% solvents.
[0049] Another aspect of the present teachings is the proper choice
of solvents. Low boiling point solvents are used, which evaporate
quickly after the paint is applied to the substrate. On the other
hand, the solvents should not interfere with the curing process.
Thus, in one aspect of the present teachings, no ketones are used.
Alkanes, ethers, and esters may have low boiling points. These
include hexane, cyclohexane, diethyl ether, ethyl propyl ether,
ethyl acetate, and t-butyl acetate. When health effects and
commercial availability are included, hexane, cyclohexane, a
mixture of aliphatic hydrocarbons (mineral spirits or petroleum
ether), or t-butyl acetate are chosen. When used with resins and
curing agents, additional solvents, such as aromatic hydrocarbons
or high boiling ethers, such as ethylene glycol, diethylene glycol
dimethyl ether, or dimethyl phthalate may be used.
[0050] The material of Example 1 was applied to the surface, as
explained in Example 3. The evaporation of the solvent was measured
for several hours. The evaporation was very fast in the beginning
(see FIG. 3). Almost 30% of the solvent evaporated within the first
fifteen minutes, and almost half evaporated within thirty
minutes.
[0051] When the material E1 is applied on a surface, for example a
125 .mu.m layer, the solvent starts to evaporate. During the first
minute, the solvent concentration drops below 13%, i.e., the
percolation threshold is reached within one minute. After 28
minutes the solvent concentration is about 9%, i.e., an additional
4% of the solvent has evaporated, and the composition E2 is
reached. On average, an additional 1% of the solvent will be
evaporated in 7 minutes, and the viscosity will increase at the
same time to 415 cP. This immediate and fast increase of the
viscosity enables the WoW method of the present teachings.
[0052] Graphitic material may be SWNTs, DWNTs, MWNTs, monolayer or
multilayer graphene, graphite, or functionalized forms of these.
Graphitic material may be dispersed into any polymeric component,
or into all of them, for example, into both epoxy and amine.
Dispersion methods include mechanical mixing, such as milling, high
speed blades, ball milling, ultrasonic mixing, or hydrodynamic
injection. Graphitic material may be exfoliated and cut during
dispersion and may be chemically bound with a monomer or polymer
simultaneously, especially in the presence of catalysts. The
concentration of the CNTs may be between about 0.05 vol % and about
5 vol %, or in another aspect of the present teachings, between
about 0.2 vol % and about 1.5 vol %, and the concentration of
graphene, or graphite, may be between about 1 vol % and about 20
vol %.
[0053] Glass flakes may be used to increase viscosity and reduce
the mixing of the consecutive coating layers during and after the
application. The barrier properties of the cured coating will also
be improved. Glass flakes may be silyl coated. Mica flakes may be
similarly used. The amount of glass or mica flakes may be between
about 1 vol % and about 40 vol %, or in another aspect of the
present teachings between about 10 vol % and about 30 vol %.
[0054] The primer may contain sacrificial metal particles,
including aluminum, magnesium, zinc, titanium, iron, and nickel.
Sacrificial metal should be less noble than the substrate (i.e. the
sacrificial metal has a lower reduction potential than the
substrate). These particles may be nearly spherical or platelets,
and in some cases may be rods. Sacrificial metal particles may have
a concentration between about 10% and about 75%. If the sacrificial
metal particles are flakes, their concentration can be between
about 10% and about 50%.
[0055] One method to reduce the viscosity of a coating material is
to add solvent that has a low enough boiling point, such as methyl
ethyl ketone, n-butyl acetate, t-butyl acetate, alkanes, or
arylalkanes, such as octane, nonane, decane, toluene, or xylene
that have boiling points below 200.degree. C. The amount of
volatile organic compounds (VOC) should be kept as low as possible,
and in one aspect of the present teachings, the VOC are below
25%.
[0056] The coating material may be applied by any painting method,
including brush, roller, spraying, and soaking. Spraying may be air
pressure powered, airless, plural spray, ultrasonic spray, or some
other spray. The mixture may be heated or cooled during spraying.
The spraying method chosen sets some limits for the viscosity,
mainly so that viscosity is not too high, i.e., the concentration
of the components in the paint should not exceed the percolation
threshold.
[0057] Most of the solvent will evaporate in less than one hour,
and possibly within 15-30 minutes. Curing will start immediately
after mixing, but full cure may take several days. The surface may
appear dry after several hours and is suitable for conventional WoD
application. However, in many cases it is not possible to apply the
first and second layer during the same day using the conventional
WoD method. The coating materials and methods of the present
teachings allow the application of the second layer as soon as most
of the solvent has evaporated from the first layer, i.e., when the
first layer is still wet. This WoW method will allow coating of the
substrate with two or more layers within one day. This will
significantly reduce the cost of coating. Also, bonding of the
layers may be stronger than in conventional WoD coating.
[0058] Mixing of the consecutive layers may be reduced, and
essentially avoided, if polarities of the mixtures are different.
This may be achieved by making the first mixture essentially
aliphatic, and the second essentially aromatic. Still another
differentiation may be achieved by using fluorinated compounds that
may be immiscible with both aliphatic and aromatic compounds. Also,
the solvent may be chosen so that it is poorly miscible with the
previous layer. Total immiscibility between consecutive layers is
not necessary. Immiscibility may reverse mixing that may happen
during spraying, or other coating method, so that the process
resembles self-stratifying in the vicinity of the interface.
[0059] The primer and all intermediate layers have the composition
of the present teachings when wet surfaces are coated. The topcoat
may also have the composition of the present teachings, but that is
not mandatory, because sagging and mixing of layers may not be
problem.
[0060] In another aspect of the present teaching, after the
anticorrosive coating is applied, a self-stratifying coating can be
applied on top, creating a three layer coating.
[0061] Clause 1--A method of coating an associated substrate with
an anticorrosive coating, the method includes applying a first
curable liquid layer to the associated substrate, the first curable
liquid layer having a thickness of at least about 100 micrometers,
wherein the first curable layer includes at least one polymer or at
least one monomer, quasi-one-dimensional particles or
quasi-two-dimensional particles, sacrificial metal particles, and a
solvent, wherein a percolation threshold of the
quasi-one-dimensional particles or the quasi-two-dimensional
particles is not reached in the presence of the solvent, wherein
the percolation threshold of the quasi-one-dimensional particles or
the quasi-two-dimensional particles is reached when between about
1% and about 20% of the solvent evaporates, and applying a second
curable liquid layer having a thickness of at least 100 micrometers
on the top of the first curable liquid layer after the percolation
threshold of the quasi-one-dimensional particles or the
quasi-two-dimensional particles is reached and viscosity of the
first curable liquid layer increases more than 50%.
[0062] Clause 2--The method of clause 1, wherein the method further
includes allowing the first curable liquid layer and the second
curable liquid layer to cure simultaneously.
[0063] Clause 3--The method of clauses 1 or 2, wherein the at least
one monomer is at least two monomers, wherein one of the at least
two monomers contains at least two epoxy groups, wherein one of the
at least two monomers contains carboxylic anhydride, wherein one of
the at least two monomers contains any combination of the
following: amino, thiol, phenolic hydroxyl.
[0064] Clause 4--The method of clauses 1-3, wherein the coating
absorbs substantially no water or carbon dioxide, and wherein the
polymer will be continuous without any interface.
[0065] Clause 5--The method of clauses 1-4, wherein the first
curable liquid layer contains quasi-one-dimensional particles and
quasi-two-dimensional particles.
[0066] Clause 6--The method of clauses 1-5, wherein the
quasi-one-dimensional particles have a concentration between about
0.1 weight percent and about 2.0 weight percent, and the
quasi-two-dimensional particles have a concentration between about
2.0 weight percent and about 20 weight percent.
[0067] Clause 7--The method of clauses 1-6, wherein the at least
one polymer forms polyurethane, polyurea, or a mixture of the two,
when allowed to cure.
[0068] Clause 8--The method of clauses 1-7, wherein the
quasi-one-dimensional particles or quasi-two-dimensional particles
are chosen from graphitic particles, carbon nanotubes, graphene,
glass flakes, or mica, wherein the solvent contains methyl ethyl
ketone, t-butyl acetate, xylene, aliphatic hydrocarbons, including
hexane, octane, nonane, or decane, wherein the method avoids amine
blush or bloom.
[0069] Clause 9--The method of clauses 1-8, wherein the coating can
be applied in less than twenty-four hours.
[0070] Clause 10--The method of clauses 1-9, wherein the method
contains no washing or sanding of the first curable liquid
layer.
[0071] Clause 11--The method of clauses 1-10, wherein the
quasi-one-dimensional particles or quasi-two-dimensional particles
are functionalized.
[0072] Clause 12--The method of clauses 1-11, wherein the solvent
has a boiling point less than 200.degree. C.
[0073] Clause 13--The method of clauses 1-12, wherein no ketones
are used.
[0074] Clause 14--The method of clauses 1-13, wherein the
quasi-one-dimensional particles or quasi-two-dimensional particles
are graphitic material, wherein the graphitic material is
exfoliated, cut during dispersion, and chemically bound to the at
least one polymer or at least one monomer.
[0075] Clause 15--The method of clauses 1-13, wherein the
quasi-one-dimensional particles or quasi-two-dimensional particles
are glass flakes, wherein the glass flakes are silyl coated.
[0076] Clause 16--The method of clauses 1-15, wherein volatile
organic compounds are less than 25 weight percent in the
coating.
[0077] Clause 17--The method of clauses 1-16, wherein the second
curable liquid layer includes at least one polymer or at least one
monomer, sacrificial metal particles, and a solvent.
[0078] Clause 18--An anticorrosive-coated substrate including a
first curable liquid layer applied to the substrate, the first
curable liquid layer having a thickness of at least about 100
micrometers, wherein the first curable layer includes at least one
polymer or at least one monomer, quasi-one-dimensional particles or
quasi-two-dimensional particles, sacrificial metal particles, and a
solvent, a second curable liquid layer having a thickness of at
least 100 micrometers on top of the first curable liquid layer,
wherein a percolation threshold of the quasi-one-dimensional
particles or the quasi-two-dimensional particles is reached,
wherein the first curable liquid layer and the second curable
liquid were cured simultaneously.
[0079] Clause 19--The substrate of clause 18, wherein the at least
one monomer is at least two monomers, wherein one of the at least
two monomers contains at least two epoxy groups, wherein one of the
at least two monomers contains carboxylic anhydride, wherein one of
the at least two monomers contains any combination of the
following: amino, thiol, phenolic hydroxyl.
[0080] Clause 20--The substrate of clauses 18 or 19, wherein the at
least one polymer forms polyurethane, polyurea, or a mixture of the
two, when allowed to cure, wherein the quasi-one-dimensional
particles or quasi-two-dimensional particles are chosen from
graphitic particles, carbon nanotubes, graphene, glass flakes, or
mica, wherein the solvent contains methyl ethyl ketone, t-butyl
acetate, xylene, aliphatic hydrocarbons, including hexane, octane,
nonane, or decane.
[0081] Clause 21--A self-stratifying anticorrosive coating includes
a zinc-rich epoxy, a curing agent chosen from the group consisting
of amines, thiols, phenols, and carboxylic anhydrides, a binding
agent chosen from the group consisting of aminoalkyl
dialkoxysilane, dimethoxysilane, and aminoalkyl trialkoxysilane, a
graphitic material, a solvent, and a water scavenger.
[0082] Clause 22--A self-stratifying anticorrosive coating includes
sacrificial metal particles, graphitic material, a first monomer,
at least a second monomer or at least a first polymer, and a
material that prevents the polymerization of at least one monomer
inside the coating.
[0083] Clause 23--The coating of clause 22 further includes a
curing agent and a binding agent.
[0084] Clause 24--The coating of clauses 22 or 23, wherein the at
least two different monomers or polymers are chosen from the group
consisting of epoxies, polyurethane, acrylates, methacrylates,
vinyl ethers, cycloaliphatic epoxides, oxetanes, epoxides,
photopolymers, siloxanes, and polyurea.
[0085] Clause 25--The coating of clauses 22-24, wherein the
graphitic material is chosen from the group consisting of single
walled carbon nanotubes, double walled carbon nanotubes,
multiwalled carbon nanotubes, single sheet graphene, double sheet
graphene, or multi-sheet graphene.
[0086] Clause 26--The coating of clauses 22-25, wherein the
material that prevents the polymerization of at least one monomer
inside the coating is a water scavenger chosen from the group
consisting of liquid water scavengers, molecular sieves, silica,
metal salts, and metal oxides.
[0087] Clause 27--The coating of clauses 22-26, wherein the
sacrificial metal particles are chosen from the group consisting of
any metal that has more positive redox potential then iron.
[0088] Clause 28--The coating of clauses 22-27, wherein the
sacrificial metal particles are chosen from the group consisting of
zinc, magnesium, aluminum, and alloys thereof.
[0089] Clause 29--The coating of clauses 22-28, wherein the curing
agent is chosen from the group consisting of amines, thiols,
phenols, and carboxylic anhydrides, and the binding agent is chosen
from the group consisting of silanes with at least two alkyl
groups. As a non-limiting example, aminoalkyl dialkoxysilane,
dimethoxysilane, and aminoalkyl trialkoxysilane.
[0090] Clause 30--The coating of clauses 22-29, wherein the coating
further comprises a photoinitiator chosen from the group consisting
of 1-hydroxy-cyclohexyl-phenyl-ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
2,2-dimethoxy-2-phenylacetophenone,
Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, triphenyl
sulfonium triflate, triaryl sulfonium hexafluoroantimonate salts,
triaryl sulfonium hexafluorophosphate salts, bis(eta
5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)tit-
anium, 5,7-diiodo-3-butoxy-6-fluorone,
2,4,5,7-tetraiodo-3-hydroxy-6-fluorone, and
2,4,5,7-tetraiodo-3-hydroxy-9-cyano-6-fluorone.
[0091] Clause 31--A method for a self-stratifying anticorrosive
coating on an associated substrate including the steps of mixing
together a monomer or a polymer, a solvent, a graphitic material,
and sacrificial metal particles, adding a material that prevents
polymerization inside the coating before, and immediately after
application on the associated substrate, adding a silane
mixture.
[0092] Clause 32--The method of clause 31 further comprising the
steps of adding a curing agent and applying, in one spraying, the
mixture of the monomer or polymer, the solvent, the graphitic
material, and the sacrificial metal particles, the silane mixture,
and the curing agent to the associated substrate, wherein an
external effector hydrolyzes the silane mixture creating silicic
acid, wherein the silicic acid spontaneously polymerizes into
siloxane.
[0093] Clause 33--The method of clauses 31 or 32, wherein no
insulating layer is used.
[0094] Clause 34--The method of clauses 31-33 wherein the external
effector is ambient moisture or photons.
[0095] Clause 35--The method of clauses 31-34, wherein the monomer
or polymer is chosen from the group consisting of epoxies,
acrylates, methacrylates, vinyl ethers, cycloaliphatic epoxides,
oxetanes, epoxides, photopolymers, siloxanes, and polyurea.
[0096] Clause 36--The method of clauses 31-35, wherein the
graphitic material is chosen from the group consisting of single
walled carbon nanotubes, double walled carbon nanotubes,
multiwalled carbon nanotubes, single sheet graphene, double sheet
graphene, or multi-sheet graphene.
[0097] Clause 37--The method of clauses 31-36, wherein the material
that prevents the polymerization inside the coating is a water
scavenger chosen from the group consisting of liquid water
scavengers, molecular sieves, silica, metal salts, and metal
oxides.
[0098] Clause 38--The method of clauses 31-37, wherein the
sacrificial metal particles are chosen from the group consisting of
any metal that has more positive redox potential then iron.
[0099] Clause 39--The method of clauses 31-38, wherein the
sacrificial metal particles are chosen from the group consisting of
zinc, magnesium, aluminum, and alloys thereof.
[0100] Clause 40--The method of clauses 31-39, wherein the coating
further comprises a photoinitiator chosen from the group consisting
of 1-hydroxy-cyclohexyl-phenyl-ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
2,2-dimethoxy-2-phenylacetophenone,
Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, triphenyl
sulfonium triflate, triaryl sulfonium hexafluoroantimonate salts,
triaryl sulfonium hexafluorophosphate salts, bis(eta
5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)tit-
anium, 5,7-diiodo-3-butoxy-6-fluorone,
2,4,5,7-tetraiodo-3-hydroxy-6-fluorone, and
2,4,5,7-tetraiodo-3-hydroxy-9-cyano-6-fluorone, wherein the curing
agent is chosen from the group consisting of amines, thiols,
phenols, and carboxylic anhydrides, and the binding agent is chosen
from the group consisting of aminoalkyl dialkoxysilane,
dimethoxysilane, and aminoalkyl trialkoxysilane.
[0101] The various aspects have been described, hereinabove. It
will be apparent to those skilled in the art that the above methods
and apparatuses may incorporate changes and modifications without
departing from the general scope of the present teachings. It is
intended to include all such modifications and alterations insofar
as they come within the scope of the appended claims or the
equivalents thereof. Although the description above contains much
specificity, this should not be construed as limiting the scope of
the present teachings, but as merely providing illustrations of
some of the aspects of the present teachings. Various other aspects
and ramifications are possible within its scope.
[0102] Furthermore, notwithstanding that the numerical ranges and
parameters setting forth the broad scope of the present teachings
are approximations, the numerical values set forth in the specific
examples are reported as precisely as possible. Any numerical
value, however, inherently contain certain errors necessarily
resulting from the standard deviation found in their respective
testing measurements.
* * * * *