Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ANTI-CORROSION COMPOSITION
Related Applications
This application claims priority to US Provisional Application No. 60/417,708;
filed
on October 10, 2002, the disclosure of which is incorporated herein by
reference in its
entirety.
Field and Background of the Invention
The present invention relates to an anti-corrosion composition suitable for
use on a
variety of substrates. Of particular interest is the use of the composition as
a coating for
corrosive industrial environments such as smoke stacks, rail caxs, hoppers,
factory floors,
pipe linings, engine rooms and the like.
Metal substrates and related parts in such industrial environments are
subjected to a
number of acids and bases due to the variety of compositions that pass
through, contact, or
are contained in the industrial environment. For example, a rail car may have
a solvent such
as a highly polar alcohol sitting in the rail car for months or even longer
periods of time.
Similarly, an acid such as sulphuric acid may be generated due to an
industrial process and
caused to exit a smokestack on a substantially constant basis. Often, the only
way to avoid
the corrosive nature of such acids or bases is to completely scrap the article
after a period of
use. Alternatively, use of the article can be discontinued so that a lengthy
cleaning can occur.
These alternatives are expensive and can lead to long down times caused by
replacement or
the discontinued use. It would be desirable to have an alternative that would
allow the article
to be used for a longer time. Thus, there is a need for an anti-corrosive
coating that can
withstand a wide variety of acid or base conditions, and can be simply and
inexpensively
applied to a substrate.
Summary of the Invention
The anti-corrosion composition of the present invention includes a glass
matrix
formed by crosslinking a mixture of an amine-functionalized silane and an
alkoxy-
functionalized siloxane, an epoxy, and optionally and preferably a
compatibilizing agent for
coupling the epoxy and the alkoxy-functionalized siloxane of the glass matrix.
The epoxy
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can further include a curing agent, preferably an amine. The amine-
functionalized silane
preferably is compatible with the amine curing agent. The composition, once
crosslinked, is
an epoxy-modified interpenetrating network of glass and epoxy. The present
invention also
provides a treated substrate for use in an industrial environment, and
includes various metals
such as steel, stainless steel, aluminium, magnesium and zinc.
Detailed Description of the Invention
As discussed above, the anti-corrosion composition comprises a glass matrix
formed
by crosslinking a mixture of an amine-functionalized silane and an alkoxy-
functionalized
siloxane, an epoxy, and, optionally, a compatibilizing agent for coupling the
epoxy and the
alkoxy-functionalized siloxane of the glass matrix. The glass matrix is
crosslinked using a
titanium or tin catalyst. Suitable catalysts include, without limitation,
titanium alkoxides
such as titanium methoxide, titanium ethoxide, titanium isopropoxide, titanium
propoxide,
titanium butoxide, titanium diisopropoxide (bis 2,4-pentanedionate), titanium
diisopropoxide
bis(ethylacetoacetateo) titanium ethylhexoxide, and organic tin compounds such
as dibutyl
tin diacetate, dibutyltin dilaurate, dimethyl tin dineodecanoate, dioctyl
dilauryl tin, and
dibutyl butoxy chlorotin, as well as mixtures thereof. The glass matrix can be
formed by
using a Sol-Gel process such as described in U.S. Patent No. 6,313,193, the
disclosure of
which is incorporated herein by reference in its entirety. Other methods of
forming the
matrix will be within the skill of one in the art. The glass matrix provides
good adhesion to
the surface being coated, as well as toughness, crack resistance, durability,
abrasion
resistance, heat resistance and stability in the particular environment.
The matrix formulation may also include fillers (e.g., fumed silica, mica,
kaolin,
bentonite, talc), zinc oxides, zinc phosphates, iron oxides, cellulose,
pigments, corrosion
inhibitors, UV light stabilizers, thixotropic agents, epoxy modifiers,
polytetrafluoroethylene
powder, ultra high molecular weight polyethylene powder, high, medium and low
molecular
weight polyethylene powder, or other additives, as will be readily apparent to
those skilled in
the art.
Suitable amino-functionalized silanes include 3-aminopropyltriethoxy silane, 3-
aminopropyldimethylethoxy silane, 3-aminopropyl methyldiethoxy silane and 3-
aminopropyltrimethoxy silane. Suitable alkoxy-functionalized siloxanes include
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polydiethoxysiloxane, tetraethoxysilane, tetramethoxysilane and polydimethoxy
siloxane.
Inasmuch as these compounds form silicates through a water condensation
reaction, the
inherent moisture of metal being treated can be used to facilitate the
reaction without having
to remove the moisture. Thus substrates such as stem pipes can be easily and
inexpensively
treated by using the moisture on the outside of the pipe to facilitate the
crosslinking reaction.
Epoxy compounds are well known and are described in, for example, U.S. Patent
Nos. 2,467,171; 2,615,007; 2,716,123; 3,030,336; and 3,053,855 which are
incorporated
herein by reference in their entirety. Useful epoxy compounds include the
polyglycidyl
ethers of polyhydric polyols, such as ethylene glycol, triethylene glycol, 1,2-
propylene
glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol and 2,2-bis(4-hydroxy
cyclohexyl)
propane; the polyglycidyl esters of aliphatic or aromatic polycarboxylic
acids, such as oxalic
acid, succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene
dicarboxylic acid and
dimerized linoleic acid; the polyglycidyl ethers of polyphenols, such as 2,2-
bis(4-
hydroxyphenyl) propane (commonly known as bis-phenol A), l,l-bis(4-
hydroxyphenyl)
ethane, l,l-bis(4-hydroxyphenyl) isobutane, 4,4'-dihydroxybenzophenone, 2,2-
bis(4-
hydroxyphenyl) butane, bis(2-dihydroxynaphthyl) methane, phloroglucinol, bis(4-
hydroxyphenyl)sulfone, 1,5-dihydroxynaphthalene, and novolak resins; with the
bifunctional
epoxies such as polyglycidyl ethers of a polyphenol, polybisphenol A-
epichlorohydrin
glycidyl end-capped and polybisphenol F-epichlorodydrin glycidyl end-capped
being
currently preferred.
Generally the preferred epoxy compounds are resins having an epoxide
equivalent
weight of about 100 to 2000, preferably about 110 to 500. A presently
preferred epoxy is
EPON 862 available from Resolution Performance Products, Houston, Texas. Epoxy
modifiers may be added to improve flexibility.
Suitable curing agents include Ancamide 220, a polyamide curing agent
available
from Air Products, Allentown, Pennsylvania.
Silanes capable of compatibilizing the epoxy and the alkoxy-functionalized
siloxane
include glycidyl-modified silanes such as 3-(glycidoxypropyl)trimethoxysilane,
3-
(glycidoxypropyl)dimethylethoxysilane and 3-
(glycidoxypropyl)methyldimethoxysilane.
Benzyl alcohol can also be used to help compatibilize the epoxy and alkoxy-
functionalized
siloxane.
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The matrix preferably comprising about 10 to 50 percent by weight of the glass
matrix, about S to 50 percent by weight epoxy, 0 to 10 percent by weight
compatibilizing
agent and 5 to 20 percent by weight curing agent.
In operation, the anti-corrosion composition of the present invention can be
applied
by roll-coating, brush, spray coating, dipping and the like. As discussed
above, it is preferred
that the user mix the catalyst with the other components right before or
substantially
contemporaneously with application. The composition is preferably applied at a
thickness of
about 0.25 mm to 1.0 mm.
EXAMPLES
The following examples are provided to afford a better understanding of the
present
invention to those skilled in the art. It is to be understood that these
examples are intended to
be illustrative only and are not intended to limit the invention in any way.
Example 1
Component wt
Epon 862 epoxy resin 10.98
Ancamide 220 polyamide curing agent 10.98
(3-glycidoxypropyl)trimethoxysilane 14.00
3-aminopropyltriethoxysilane 6.98
polydiethoxysiloxane 12.16
titanium isopropoxide 5.75
benzyl alcohol 4.72
pigment 1.57
mica flakes 32.96
The composition is formulated such that the epoxy functionality on the 3-
(glycidoxypropyl)-methoxysilane is at a 1:1 stoichiometric ratio with the
amine functionality
of the Ancamide 220. The epoxy functionality of the 862 resin is at a 1:1
stoichiometric ratio
with the amine functionality of the aminopropyl triethoxysilane. The ethoxy
groups on
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polydiethoxy siloxane are at a I :1 stoichiometric ratio with the sum of the
number of moles
of aminopropyl triethoxysilane and the 3-(glycidoxyproply)trimethoxysilane.
Pencil hardness measurements of the coating after 7 days indicate that the
coating has
a hardness value of 6H. Samples were exposed to toluene, MEK, ethanol, paint
thinner, 50%
acetic acid and grill cleaner (e.g., potassium hydroxide, ethylene glycol
monobutyl ether and
monoethanolamine) for a period of 1 hour under a watch glass.
Pencil hardness measurements were then conducted on the areas of the sample
which
had been exposed to the chemical. For all cases, except the acids, there were
no changes in
the pencil hardness. Samples formulated with mica and exposed to the acids
decreased in
hardness to H or less. Samples formulated with glass and exposed to the acids
only
decreased in hardness to SH.
Example 2
Component wt
I S Epon 862 (epoxy resin) 8.34
3-(glycidoxypropyl)trimethoxy silane 10.63
polydiethoxy siloxane 9.24
titanium isopropoxide 4.29
Heucophos ZPO (organo-zinc corrosion inhibitor)8.20
Heucorin RZ (zinc salt corrosion inhibitor)0.91
Custermica A325 (mica) 35.76
fumed silica TS-720 (thixotropic agent) 0.89
Kronos 2160 (titanium oxide) 5.97
Vulcan XC72R (carbon black) 0.12
Ancamide 220 (polyamide curing agent) 8.34
3-aminopropyltriethoxy silane 5.31
Hostavin N24 (UV light stabilizer) 2.00
The resulting coating displays good adhesion with conventional topcoats. It is
more
thermally resistant than conventional epoxy resins. Using ASTM G26 and
continuous
exposure to a xenon arc for 500 hours, no cracking or delamination occurs.
With respect to
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fluid resistance, ASTM D5402 is used to test a variety of fluids. The coating
is resistant to
toluene, paint remover, ethanol, brake fluid, grill cleaner, mineral spirits,
MEK and caustic
acid.
Example 3
Component
Epon 862 (epoxy resin) 4.99
Heloxy 505 (epoxy modifier) 4.99
3-(glycidoxypropyl)methyldiethoxy silane 10.52
polydiethoxy siloxane 9.15
titanium isopropoxide 4.24
Heucophos ZPO (organo-zinc corrosion inhibitor)8.11
Heucorin RZ (zinc salt corrosion inhibitor)0.90
Custermica A325 (mica) 35.39
fumed silica TS-720 (thixotropic agent) 0.88
Kronos 2160 (titanium oxide) 5.91
Vulcan XC72R (carbon black) 0.11
Ancamide 220 (polyamide curing agent) 9.43
3-aminopropyltriethoxy silane 3.38
Hostavin N24 (UV light stabilizer) 2.00
In the specification and example, there have been disclosed typical preferred
embodiments of the invention and, although specific terms are employed, they
are used in a
generic and descriptive sense only and not for purposes of limitation of the
scope of the
invention set forth in the following claims.
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