U.S. patent number 10,385,216 [Application Number 12/742,558] was granted by the patent office on 2019-08-20 for anti-corrosive particles.
This patent grant is currently assigned to GRACE GMBH. The grantee listed for this patent is Timothy Edward Fletcher. Invention is credited to Timothy Edward Fletcher.
United States Patent |
10,385,216 |
Fletcher |
August 20, 2019 |
Anti-corrosive particles
Abstract
The present invention relates to dispersion of surface modified
inorganic particles including (a) fluid comprising a complexing
agent, and (b) the surface modified inorganic particles comprising
polyvalent metal ions.
Inventors: |
Fletcher; Timothy Edward
(Worms, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Fletcher; Timothy Edward |
Worms |
N/A |
DE |
|
|
Assignee: |
GRACE GMBH (Worms,
DE)
|
Family
ID: |
40601416 |
Appl.
No.: |
12/742,558 |
Filed: |
November 19, 2008 |
PCT
Filed: |
November 19, 2008 |
PCT No.: |
PCT/EP2008/009777 |
371(c)(1),(2),(4) Date: |
September 01, 2010 |
PCT
Pub. No.: |
WO2009/065569 |
PCT
Pub. Date: |
May 28, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20110048275 A1 |
Mar 3, 2011 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61003623 |
Nov 19, 2007 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09C
1/3063 (20130101); C09C 3/08 (20130101); C01P
2006/12 (20130101); C01P 2006/22 (20130101); C01P
2006/14 (20130101); C01P 2004/61 (20130101) |
Current International
Class: |
C09D
5/08 (20060101); C09C 3/08 (20060101); C09C
1/30 (20060101) |
Field of
Search: |
;106/14.05,14.44 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1767332 |
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Apr 1968 |
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DE |
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2840820 |
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Sep 1978 |
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DE |
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2849712 |
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Nov 1978 |
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DE |
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0412686 |
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Feb 1991 |
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EP |
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0522678 |
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Jan 1993 |
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EP |
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825976 |
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Dec 1959 |
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GB |
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914707 |
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Jan 1963 |
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GB |
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915512 |
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Jan 1963 |
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GB |
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918802 |
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Feb 1963 |
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GB |
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1089245 |
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Nov 1967 |
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GB |
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1263945 |
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Feb 1972 |
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GB |
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1567609 |
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May 1980 |
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GB |
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53007550 |
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Jan 1978 |
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JP |
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2003-286589 |
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Oct 2003 |
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JP |
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Primary Examiner: Ali; Shuangyi Abu
Claims
The invention claimed is:
1. A dispersion of surface modified inorganic particles comprising:
(a) fluid comprising (i) water and (ii) a complexing agent
comprising acidic or basic materials, and (b) particles dispersed
throughout said fluid, said particles consisting of surface
modified inorganic particles having an average particle diameter of
less than about 10 microns, wherein each surface modified inorganic
particle consists of (i) an inorganic particle having a particle
surface and (ii) polyvalent metal ions along said particle surface,
said polyvalent metal ions having replaced protons of hydroxyl
groups along said particle surface.
2. A dispersion according to claim 1 wherein said average particle
diameter is less than about 3 micron.
3. A dispersion according to claim 1, wherein said average particle
diameter is less than about 1 micron.
4. A dispersion according to claim 1, wherein the inorganic
particles consist of silica, silicate, alumina, aluminosilicate,
titania, zirconia, ceria or mixtures thereof; and the polyvalent
metal ions consist of calcium, zinc, cobalt, lead, strontium,
lithium, barium, magnesium, manganese, cerium, aluminum, or
mixtures thereof.
5. A dispersion according to claim 1 wherein the inorganic
particles are in a form of a gel, a colloidal, a precipitate, fumed
particles, or mixtures thereof.
6. A dispersion according to claim 1, wherein said complexing agent
comprises phosphorus acid, phosphoric acid, tri- and polyphosphoric
acids, organophosphonic acids or mixtures thereof.
7. A dispersion of surface modified inorganic particles comprising:
(a) fluid comprising a complexing agent, said complexing agent
comprising (i) phosphorus acid, phosphoric acid, tri- and
polyphosphoric acids, organophosphonic acids or mixtures thereof,
or (ii) one or more alkanolamines, and (b) particles dispersed
throughout said fluid, said particles consisting of surface
modified inorganic particles, wherein each surface modified
inorganic particle consists of (i) an inorganic particle having a
particle surface and (ii) polyvalent metal ions along said particle
surface, said polyvalent metal ions having replaced protons of
hydroxyl groups along said particle surface.
8. A dispersion according to claim 7, wherein said surface modified
inorganic particles have an average particle diameter of less than
about 10 microns.
9. A dispersion according to claim 7, wherein said surface modified
inorganic particles have an average particle diameter of less than
about 5 microns.
10. A dispersion according to claim 7, wherein the inorganic
particles consist of silica, silicate, alumina, aluminosilicate,
titania, zirconia, ceria or mixtures thereof; and the polyvalent
metal ions consist essentially of calcium, zinc, cobalt, lead,
strontium, lithium, barium, magnesium, manganese, cerium or
mixtures thereof.
11. A dispersion according to claim 7, wherein the inorganic
particles are in the form of a gel, a colloidal, a precipitate,
fumed particles, or mixtures thereof.
12. A dispersion according to claim 7, wherein said fluid further
comprises at least one of water, binder, film former, bacteriacide
and polymer.
13. A dispersion according to claim 7, wherein said complexing
agent comprises phosphorus acid, phosphoric acid, tri- and
polyphosphoric acids, organophosphonic acids or mixtures
thereof.
14. A dispersion according to claim 7, wherein said dispersion is
made by a process of milling said surface modified inorganic
particles in the presence of the complexing agent.
15. A method of making the dispersion according to claim 7, said
method comprising: (a) mixing the surface modified inorganic
particles with the fluid comprising the complexing agent; and (b)
milling the inorganic particles in the presence of the complexing
agent to form an average diameter of less than about 10 microns for
the surface modified inorganic oxide particles.
16. A method according to claim 15, wherein said complexing agent
comprises phosphorus acid, phosphoric acid, tri- and polyphosphoric
acids, organophosphonic acids or mixtures thereof.
17. An inorganic oxide dispersion made by the method according to
claim 15.
18. A dispersion according to claim 2, wherein the inorganic
particles consist of silica, silicate, alumina, or aluminosilicate;
and the polyvalent metal ions consist of calcium.
19. A dispersion according to claim 18, wherein said complexing
agent comprises phosphorus acid, phosphoric acid, tri- and
polyphosphoric acids, organophosphonic acids or mixtures
thereof.
20. A dispersion according to claim 19, wherein said complexing
agent comprises 2-hydroxyphosphonoacetic acid.
21. A dispersion according to claim 19, wherein said fluid further
comprises a bacteriacide.
22. A dispersion according to claim 10, wherein said surface
modified inorganic particles have an average particle diameter of
less than about 5 microns.
23. A dispersion according to claim 22, wherein said complexing
agent comprises phosphorus acid, phosphoric acid, tri- and
polyphosphoric acids, organophosphonic acids or mixtures
thereof.
24. A dispersion according to claim 23, wherein said fluid further
comprises water and a bacteriacide.
25. A dispersion according to claim 24, wherein said particles have
an average particle diameter of less than about 1.0 micron, and
each surface modified inorganic particle consists of (i) a silica,
silicate, alumina, aluminosilicate, titania, zirconia or ceria
particle having a particle surface and (ii) calcium, zinc, cobalt,
lead, strontium, lithium, barium, magnesium or manganese ions along
said particle surface.
26. A dispersion according to claim 25, wherein said complexing
agent comprises 2-hydroxyphosphonoacetic acid.
27. A dispersion according to claim 23, wherein said fluid further
comprises aluminate ions therein.
28. A dispersion according to claim 22, wherein said complexing
agent comprises one or more alkanolamines.
29. A dispersion of surface modified inorganic particles
comprising: (a) fluid comprising a complexing agent, said
complexing agent being selected from the group consisting of
2-hydroxyphosphonoacetic acid, glycolic acid, 1,2,3-benzotriazole,
2-mercaptobenzothiazole, and (2-benzothiazolythio)succinic acid;
and (b) surface modified inorganic particles dispersed throughout
said fluid, said surface modified inorganic particles having an
average particle diameter of less than about 5 microns and
comprising (i) silica, silicate, alumina, aluminosilicate, titania,
zirconia or ceria particles or mixtures thereof with each inorganic
particle having a particle surface and (ii) polyvalent metal ions
selected from the group consisting of calcium, zinc, cobalt, lead,
strontium, lithium, barium, magnesium, manganese, cerium, aluminum,
or mixtures thereof along said particle surface, said polyvalent
metal ions having replaced protons of hydroxyl groups along said
particle surface.
30. A dispersion according to claim 29, wherein said complexing
agent comprises 2-hydroxyphosphonoacetic acid.
31. A dispersion according to claim 29, wherein said complexing
agent comprises 1,2,3-benzotriazole, 2-mercaptobenzothiazole or
(2-benzothiazolythio)succinic acid.
32. A dispersion according to claim 29, wherein said surface
modified inorganic particles have an average particle diameter of
less than about 1.0 micron and comprise (i) silica particles with a
silica particle surface and (ii) calcium ions forming at least a
portion of said silica particle surface.
Description
FIELD OF THE INVENTION
The present invention relates to dispersions of particles including
anti-corrosive submicron particles. The present invention is also
related to methods of making such dispersions and coatings made
therefrom.
BACKGROUND OF THE INVENTION
It is known that certain cations and anions, have corrosion
inhibiting properties and that compounds containing them can be
included in protective films and coatings that are intended to
provide adhesion and corrosion inhibiting properties to metallic
surfaces and structures. Typical examples include cations of
calcium, magnesium, strontium, barium, manganese, zinc, cerium and
other rare earth elements as well as anions such as silicate,
borate, molybdate, nitrophthalate, phosphate, hydrogen phosphate,
phosphite, phosphonates and phosphonocarboxylates. Classic
inhibitors based on lead compounds and cations and compounds of
some other heavy metals such as chromium e.g. chromate and zinc are
however of less interest these days for environmental and health
and safety reasons.
The inhibitive compounds may be in the form of sparingly
water-soluble salts and can for example be prepared by a process of
particle growth and precipitation in the presence of the required
cations and anions under suitable conditions. The inhibitive
compounds may also be in the form of particles of inorganic oxides
such as silica, silicates, alumina and aluminosilicates comprising
additional inhibitive cations and anions. These inhibitive
compounds can for example be prepared by a process of precipitation
or gelation of the oxide in the presence of the required cations
and anions under suitable conditions.
Inhibitive compounds based on inorganic oxides can alternatively be
made through a process of ion-exchange, in which surface protons
and hydroxyl groups of the pre-formed oxide are replaced by
contacting the oxide with a solution containing the required
inhibitive cations and anions, again under suitable conditions. In
either case, the inorganic oxides involved are often characterized
by having certain surface areas and porosities with corrosion
inhibiting ions attached to the internal and external surface of
the particles, producing surface modified inorganic particles,
although ions may be found through the bulk of the particles as
well, depending on the method of preparation.
Of course, from the above description, combinations of inhibitive
compounds based on sparingly soluble salts and those based on
inorganic oxides may be prepared simultaneously in various ways
according to the composition of the solution or slurry from which
the inhibitive compounds are to be prepared and the processing
route, allowing for a great variety in properties displayed by the
resulting inhibitive compound.
In many cases, the films and coatings employed in anti-corrosion
have a certain permeability to water and it is believed that the
mechanism of corrosion inhibition involves gradual dissolution of
the compounds in water, releasing ions as the active inhibitors.
For such systems to be effective over a long period, the solubility
of the compound is particularly important. If the compound is too
soluble, blistering of the coating may occur and the compound will
be rapidly depleted; if it is insufficiently soluble the compound
will be ineffective. Whether the inhibitive compound is a sparingly
soluble salt, or based on an inorganic oxide or is some combination
of the two, the typical solubility of such compounds suitable for
use in films and coatings results in inhibitive ion concentrations
in aqueous media of around 10.sup.-5M to 10.sup.-2M.
For inhibitive compounds based on inorganic oxides, the inorganic
oxide may itself have a certain solubility with respect to the
provision of inhibitive substances, according to the nature of the
environment in which the corrosion inhibiting particles are used
e.g. in the case of silica, silicic acid has a background
solubility of about 10.sup.-3M with the concentration of silicate
being pH dependent and having a value of 10.sup.-2M for example at
a pH of about 10.5. It is however sometimes believed that these
types of corrosion inhibiting particles can act to release
inhibitive cations and anions into solution by ion exchange with
aggressive ions existing in that environment as an additional or
alternative mechanism of action to one based on dissolution. The
rate of release of the corrosion inhibiting ions would then be
influenced by the permeability of the film or coating to the
exchanging ions in addition to or rather than dissolution of
inhibitive ions into the permeating aqueous environment. Corrosion
inhibiting ions would in that case be released to a greater extent
from the inorganic oxide in those areas where the desired barrier
properties of the coating were weakest, leading thereby to improved
performance properties.
The inhibitive compounds referred to above are usually made
available in the form of dry powders, making use of washing, drying
and milling operations as required as additional processing steps
and average particle sizes of the powders usually exceed about 1 to
2 microns making them most suitable for films and coatings that
exceed a few microns in thickness. For suitability of incorporation
into a wide variety of film and coating systems as well as
suitability with respect to corrosion resistance, besides the
criteria of solubility, the pH of an aqueous slurry of such
inhibitive compounds will in most cases typically fall within the
range of 4 to 10.5 although lower or higher values can be suitable
depending on the actual chemistry of the coating or film in
question and the nature of the metallic substrate. For example,
many surface pre-treatments can be quite acidic and display a pH in
the range of 1 to 4.
Making anti-corrosive particles available in dispersion form would
render the operation of incorporating the particles into the
coating more convenient and would avoid generation of dust.
However, like the dry powder, known anti-corrosive particle
dispersions contain pigment particles that are relatively large in
size and greater than about 1 to 2 microns. Such dispersions are
not suitable for use in filming and coating applications that
require small particle sizes, such as chromium-free surface
treatments or thin film primers where the film thickness may be
less than a few microns going down to the sub-micron region. It is
additionally believed that both the particle size and state of
dispersion of the inhibitive pigment may influence the availability
and mobility of inhibitive ions derived from the inhibitive
compound within the film or coating under environmental exposure.
Small particle pigments may therefore provide potential benefits in
anti-corrosive treatment films and coatings regardless of the
thickness of the film applied.
The general principles covering the operations of milling,
dispersion and dispersions of particles such as inorganic and
organic coloring pigments or fillers in liquids and surface
coatings, as well as the properties of such suspensions are of
course well known. For example, a comprehensive review including
the role of surface active, wetting and dispersion agents as a
means of producing and stabilizing pigment dispersions is given in
"Dispersion of Powders in Liquids with Special Reference to
Pigments" 3.sup.rd Edition, Edited by G. D. Parfitt, Applied
Science Publishers, 1981. Further details on the fundamentals and
preparation of the colloidal state can be found in "Foundations of
Colloid Science" by R. J. Hunter, Vol 1-2, Academic Press,
1986.
Needless to say, a number of patents discuss specific aspects of
the dispersion of particles and pigments and the properties of
particulate and pigment suspensions with respect to surface active,
wetting and dispersion agents and other additives designed to
control some feature of the dispersion. U.S. Pat. No. 4,186,028 for
example concerns the use of phosphonocarboxylic acids as
dispersants to lower the viscosity and reduce settling of highly
concentrated aqueous suspensions of pigments and fillers such as
titanium dioxide, iron oxides, zinc oxides, chromium oxides, talcs,
calcium carbonate, barium sulphate and quartz at a level of
phosphonocarboxylic acid ranging from 0.01% to 1% based on the
pigment solids. The preferred pH range of the suspensions was 6 to
10.
It should be noted that many surface active, wetting and dispersion
agents and other additives can display a certain compatibility or
even solubility in water and as such can detract from the
performance properties of coatings and film forming layers intended
to provide anti-corrosive and/or adhesion promoting properties. The
type and amount of such substances may therefore require careful
selection.
In overview, for convenience in use, for suitability in thin films
and for performance gains, there is therefore interest and a need
in the industry for anti-corrosive small diameter particle
dispersions that may be utilized in a variety of treatment films,
primers and coatings. Ideally, these dispersions would be free of
compounds of lead, chromium and some other heavy metals such as
zinc. The present work is therefore concerned with the question of
producing stable small particle dispersions of inhibitive compounds
suitable for use in aqueous and non-aqueous protective films,
surface treatments, primers, coatings, adhesives and sealants that
are intended to provide adhesion and corrosion inhibiting
properties to metallic surfaces and structures.
SUMMARY OF THE INVENTION
The present invention relates to dispersion and dispersions of
surface modified inorganic particles including (a) fluid, and (b)
the surface modified inorganic particles comprising polyvalent
metal ions and having an average particle diameter of about 10
microns or less. The present invention also relates to coating
compositions including the above-mentioned dispersion.
The present invention further relates to dispersion and dispersions
of surface modified inorganic particles including (a) fluid
comprising a complexing agent, and (b) the surface modified
inorganic particles comprising polyvalent metal ions. Again coating
compositions including these dispersions are also part of the
present invention.
A still further embodiment of the present invention comprises a
method of making a dispersion of surface modified inorganic
particles including (a) mixing said surface modified inorganic
particles with a fluid; and (b) milling said inorganic particles to
form particles having an average diameter of about 10 microns or
less, wherein said inorganic oxide particles further comprise
polyvalent metal ions.
DETAILED DESCRIPTION
The present invention is concerned with corrosion inhibitors
suitable for use in protective films, surface treatments, primers,
coatings, adhesives and sealants that are intended to provide
adhesion and corrosion inhibiting properties to metallic surfaces
and structures. As described herein, all of these fields of
application are encompassed by the single term "coating".
According to the present invention, a corrosion inhibitor comprises
particles of an inorganic oxide having corrosion inhibiting ions
chemically bound to the particles. As defined herein, the term
"inorganic oxides" means oxides of metals or metalloids. Metals
include those elements on the left of the diagonal line drawn from
boron to polonium on the periodic table. Metalloids or semi-metals
include those elements that are on this line and include also
silicon. Examples of inorganic oxides include silica, silicates,
alumina, aluminosilicates, titania, zirconia, ceria and the like,
or mixtures thereof.
It must be noted that as used herein and in the appended claims,
the singular forms "a", "and", and "the" include plural referents
unless the context clearly dictates otherwise. Thus, for example,
reference to "an oxide" includes a plurality of such oxides and
reference to "oxide" includes reference to one or more oxides and
equivalents thereof known to those skilled in the art, and so
forth.
"About" modifying, for example, the quantity of an ingredient in a
composition, concentrations, volumes, process temperatures, process
times, recoveries or yields, flow rates, and like values, and
ranges thereof, employed in describing the embodiments of the
disclosure, refers to variation in the numerical quantity that can
occur, for example, through typical measuring and handling
procedures; through inadvertent error in these procedures; through
differences in the ingredients used to carry out the methods; and
like proximate considerations. The term "about" also encompasses
amounts that differ due to aging of a formulation with a particular
initial concentration or mixture, and amounts that differ due to
mixing or processing a formulation with a particular initial
concentration or mixture. Whether modified by the term "about" the
claims appended hereto include equivalents to these quantities.
Inhibitive compounds based on inorganic oxides may, for example, be
prepared by a process of precipitation or gelation of the oxide in
the presence of the required cations and anions under suitable
conditions. Inhibitive compounds based on inorganic oxides can
alternatively be made through a process of ion-exchange, in which
surface protons and hydroxyl groups of the pre-formed oxide are
replaced by contacting the oxide with a solution containing the
required inhibitive cations and anions, again under suitable
conditions. In either case, the inorganic oxides involved are often
characterized by having certain surface areas and porosities with
corrosion inhibiting ions attached to the internal and/or external
surface of the particles, producing surface modified inorganic
particles, although ions may be found through the bulk of the
particles as well, depending on the method of preparation.
According to the present invention, a corrosion inhibitor may also
comprise combinations of inhibitive cations and anions in the form
of sparingly soluble metal salts of the anion. Inhibitive compounds
in the form of sparingly water-soluble salts can for example be
prepared by a process of particle growth and precipitation from
slurries or solutions in the presence of the required cations and
anions under suitable conditions.
Combinations of inhibitive compounds based on sparingly soluble
salts and those based on inorganic oxides may be prepared by mixing
the pre-formed substances, mixing pre-formed inorganic oxides or
alternatively pre-formed inorganic oxides bearing inhibitive
cations and anions with the appropriate inhibitive cations and
anions as necessary such that particle growth and precipitation of
sparingly soluble salts occurs in the presence of the inorganic
oxide, where in all three cases, the inorganic oxide would exist in
the presence of polyvalent cations.
Combinations may also be made in which sparingly soluble inhibitive
salts are combined with precursors to inorganic oxides like sodium
silicate, alkyl silicates such as tetraethyl orthosilicate,
aluminum chloride, aluminum hydroxychloride or sodium aluminate and
so forth in the case of silica, alumina and aluminosilicates such
that precipitation or gelation, or simply formation, of the
inorganic oxide occurs, intimately associated with inhibitive
cations and anions. Similarly, mixtures of inhibitive cations and
anions and precursors to inorganic oxides can be prepared such that
particle growth, precipitation and/or gelation of sparingly soluble
compounds and oxides occur simultaneously, intimately associated
with one another.
Clearly, a number of ways to prepare inhibitive combinations exist
according to the composition of the solution or slurry from which
the inhibitive compounds are to be prepared and the processing
route, allowing for a great variety in properties displayed by the
resulting inhibitive compound.
Preferred cations are those of calcium (Ca.sup.2+), magnesium
(Mg.sup.2+), zinc (Zn.sup.2+), manganese (Mn.sup.2+), and cations
of the rare earth elements such as cerium (Ce.sup.3+/Ce.sup.4+)
cations, but other suitable cations may be cobalt (Co.sup.2+), lead
(Pb.sup.2+), strontium (Sr.sup.2+), lithium (Li.sup.+), barium
(Ba.sup.2+) and aluminium (Al.sup.3+). Preferred anions are those
derived from silicate, borate, molybdate, hydrogen phosphate,
phosphate, phosphite, nitrophthalates, phosphonate and
phosphonocarboxylates as well as azoles and their derivatives such
as 1,2,3-benzotriazole, tolytriazole, benzothiazole,
2-mercaptobenzothiazole, benzimidazole, 2-mercaptobenzimidazole and
2-mercaptobenzoxazole but other suitable anions may be
permanganate, manganate, vanadate and tungstate. With respect to
the aforementioned components providing anions, it is to be
understood that the free acid form or any other partially
neutralized or fully neutralized form, i.e., the conjugate species
may be employed in any particular case as appropriate.
By way of example, the process of cation exchange with inorganic
oxides can be considered. Particles of inorganic oxides such as
silica, alumina and other oxides may be prepared such that a
proportion of hydroxyl groups are present on the surface of the
particles. The particles may differ in porosity from non-porous to
highly porous, and may be in any shape from spherical to any
non-spherical shape, and may be in the form of a gel, a
precipitate, a sol (colloidal), fumed or other common form readily
recognized in the art. Such oxide particles may be prepared
according to the processes set forth in or referenced by U.S. Pat.
Nos. 5,336,794, 5,231,201, 4,939,115, 4,734,226, and 4,629,588 as
well as DE1,000,793, GB 1,263,945, DE 1,767332, U.S. Pat. Nos.
5,123,964, 5,827,363, 5,968,470, US2004/0249049 and 2005/0228106
the entire subject matter of which is incorporated herein by
reference. Details regarding methods of making these particles may
also be found in textbooks such as "The Chemistry of Silica" by R.
K. Iler, John Wiley & Sons, 1979 and "Sol-Gel Science" by C. J.
Brinker and G. W. Scherer, Academic Press, 1990. These kinds of
particles are also commercially available, such as, for example,
from W. R. Grace & Co.--Conn. under the trade names
SYLOID.RTM., PERKASIL.RTM. or LUDOX.RTM..
The protons of the hydroxyl groups may be replaced by contacting
the oxide with a solution containing the required cations. To carry
out exchange the oxide may be stirred in water at room temperature
and the pH monitored by a meter. Then the substance to be exchanged
(e.g. calcium hydroxide or basic zinc carbonate) is added slowly
whilst not allowing the pH to rise too far (e.g., above 10.5 for
silica or 12 for alumina). The pH needs to be high enough to remove
protons but not so high as to dissolve the inorganic oxide. The
uptake can be followed by observing the fall of pH over a period of
time following the addition of the base. When the pH no longer
falls then exchange is complete and the oxide particles may be
milled, if necessary, washed and dried under vacuum. Uptake of
cations in the oxide can be measured by XRF spectroscopy. Processes
for making such exchanged oxides may be found in or referenced by
U.S. Pat. Nos. 4,687,595, 4,643,769, 4,419,137 and 5,041,241, the
entire subject matter of which is incorporated herein by reference.
Typically, the inorganic oxide inhibitor particles will have BET
surface areas ranging from about 5 m.sup.2/g up to about 750
m.sup.2/g. with average porosities varying from about 0.1 ml/g to
about 3 ml/g.
As noted earlier, similar compounds based on inorganic oxides can
for example be prepared by a process of precipitation or gelation
of the oxide in the presence of the required cations and anions
under suitable conditions and processes for making such compounds
may be found for example in U.S. Pat. No. 4,849,297 and GB Patent
No. 918,802, the entire subject matter of which is incorporated
herein by reference. Similarly, examples of inhibitive compounds
based on sparingly soluble salts and processes for preparing them
can for example be found in U.S. Pat. Nos. 4,247,526, 4,139,599,
4,294,621, 4,294,808, 4,337,092, 5,024,825, 5,108,728, 5,126,074,
5,665,149, and 6,083,308, U.S. Patent Application No. 2007/0012220
as well as GB Patents Nos. 825,976, 914,707, 915,512, 1,089,245, DE
Patents Nos. 2,849,712, 2,840,820, and 1,567,609 and EP Patent No.
522,678, the entire subject matter of which is incorporated herein
by reference.
In many cases, the films and coatings employed in anti-corrosion
have a limited permeability to water and the mechanism of corrosion
inhibition is believed to involve gradual dissolution of the
compounds in water with release of ions as the active inhibitors.
For such systems to be effective over a long period, the solubility
of the compound is very important. If the compound is too soluble,
blistering of the coating may occur and the compound will be
rapidly depleted; if it is insufficiently soluble the compound will
be ineffective. Whether the inhibitive compound is purely a
sparingly soluble salt, or based on an inorganic oxide or is some
combination of the two, the typical water solubility of such
compounds suitable for use in films and coatings results in
inhibitive ion concentrations in aqueous media of around 10.sup.-5M
to 10.sup.-2M.
For inhibitive compounds based on inorganic oxides, the inorganic
oxide may itself have a certain solubility with respect to the
provision of inhibitive substances, according to the nature of the
environment in which the corrosion inhibiting particles are used
e.g. in the case of silica, silicic acid has a background
solubility of about 10.sup.-3M with the concentration of silicate
being pH dependent having a value of 10.sup.-2M for example at a pH
of about 10.5.
It is sometimes believed that inhibitors based on inorganic oxides
can act to release inhibitive cations and anions into solution by
ion exchange with aggressive ions existing in the environment in
which the inhibitive particles are used. It would then be
permeability of the film or coating to the exchanging ions that
would influence the rate of release of the corrosion inhibiting
ions in addition to or rather than the mechanism involving
solubilisation of inhibitive ions into the permeating aqueous
environment. Corrosion inhibiting ions would in that case be
preferentially released from the inorganic oxide in those areas
where the desired barrier properties of the coating were weakest,
leading thereby to improved performance properties.
For reasons related to the ability to incorporate corrosion
inhibitors into a wide variety of film and coating systems as well
as suitability with respect to corrosion resistance, in addition to
the criteria of solubility, the pH of an aqueous slurry of
inhibitive compounds will in most cases typically fall within the
range of 4 to 10.5 although lower or higher values can be suitable
depending on the actual chemistry of the coating or film in
question and the nature of the metallic substrate.
By way of example, in the case of simple cation exchange with
inorganic oxides, and depending on the proportion of hydroxyl
groups on the inorganic oxide, it has been found that up to 2.5
millimoles/g of cation may be combined with the oxide whilst
satisfying the criteria of solubility and pH. Since, as indicated
above, the technique of ion-exchange is relatively simple the
selection of preferred inorganic oxides and the treatments to give
maximum uptake of corrosion inhibiting cations can be determined by
simple comparative experiments. A lower limit consistent with the
requirements of solubility and pH would be 0.05 millimoles/g.
The corrosion inhibiting particles may act as filler for the
coating and may be included in relatively large amounts of up to
40% wt, based on the composition to be applied and up to 80% wt
based on the dry film weight.
Again by reference to the case of simple cation exchange with
inorganic oxides, and having regard to the quantity of cations
which can be combined with the oxide as discussed previously, it
will be seen that the coatings in that case may contain up to 2
millimoles/g of corrosion inhibiting cations based on the dry film
weight.
Control over actual solubility's and pH values is obtained
according to the broad range of compositions falling within the
scope of the corrosion inhibitor chemistry reviewed above and the
variety of ways by which corrosion inhibitors and combinations of
corrosion inhibitors may be prepared as outlined above, where
nature of the ions being combined, pore structures where inorganic
oxides are involved as well as nature of the inorganic oxide are
important considerations.
In accordance with the present invention, it has been found that
attempting to mill inorganic oxide particles in the presence of
polyvalent metal ions to less than a few microns, or mixing small
inorganic oxide particles in the presence of polyvalent metal ions,
results in dispersions that may be unsuitable for use in certain
coating compositions.
The polyvalent cations may arise from the pre-existing association
of inhibitive cations with the inorganic oxide such as in the case
of ion-exchanged oxides, or those produced by precipitation or
co-gelation, or by addition of polyvalent cations during milling in
the form of soluble or sparingly soluble compounds or they may be
present according to any of the variety of ways by which
combinations of inhibitive compounds can be prepared as discussed
earlier.
The polyvalent metal ions may cause significant aggregation of the
small inorganic oxide particles or cause instability with respect
to aggregation, agglomeration, high viscosities or settling when
attempting to produce such small inorganic particles by
milling.
The present invention alleviates this problem with the use of
suitable acidic or basic agents to produce stable dispersions of
small particles by controlling pH and/or by complexing the cations,
thereby avoiding or minimizing excessive viscosity build-up,
reagglomeration of particles and hard settling of the dispersed
particles that may otherwise occur during or after milling.
Accordingly, an embodiment of the present invention includes a
dispersion of surface modified inorganic particles having fluid or
liquid, the surface modified inorganic particles being modified by
polyvalent metal ions and have an average particle diameter of
about ten microns or less.
As utilized herein, the term "surface modified inorganic particle"
relates to inorganic oxide particles in the presence of polyvalent
cations, where the polyvalent cations may arise from processes such
as are involved in preparing corrosion inhibitors based on
inorganic oxides, from the presence of soluble and sparingly
soluble compounds such as those involved in preparing corrosion
inhibitors based on sparingly soluble salts and/or from other types
of combinations of corrosion inhibiting species and compounds as
previously detailed, under conditions such that uptake of the
cations by the inorganic oxide can be expected.
The average particle diameter may be less than about 10 microns,
about 9 microns, about 8 microns, about 7 microns, 6 microns, about
5 microns, about 4 microns, about 3 microns, about 2 microns or
less than about 1 micron. In a more typical embodiment, the average
particle diameter is less than about 1 micron.
The polyvalent metal ions may include calcium, zinc, cobalt, lead,
strontium, lithium, barium, magnesium, manganese and cations of the
rare earth elements such as cerium or mixtures thereof. In a more
typical embodiment, the polyvalent metal ions include those of
calcium, magnesium, manganese, zinc, and rare earth elements such
as cerium.
The particles may be corrosion inhibitors based on inorganic
oxides, such as silicas and aluminas, milled separately or in
combination with other inorganic oxides. Other examples include
inorganic oxides and corrosion inhibitors based on inorganic oxides
milled in combination with partially or sparingly soluble metal
salts as described earlier, such as those based on phosphates,
phosphates, hydrogenphosphates, phosphonates,
phosphonocarboxylates, borates, molybdates nitrophthalates, azole
derivatives, permanganate, manganate, vanadate and tungstate and
any suitable combination thereof. Mixtures of different particle
types are also included as are combinations of inhibitive compounds
based on sparingly soluble salts and those based on inorganic
oxides that may be prepared simultaneously in various ways
according to the composition of the solution or slurry from which
the inhibitive compounds are to be prepared and the processing
route as described earlier.
Another embodiment of the present invention relates to a dispersion
of surface modified inorganic particles including (a) fluid
comprising a stabilizing or complexing agent, and (b) the surface
modified inorganic particles comprising polyvalent metal ions. The
present invention also relates to coating compositions including
the above-mentioned dispersion.
In some cases, the added substance used to stabilize the dispersion
and/or complex the polyvalent cations may be a soluble or partially
soluble component of the corrosion inhibiting compound, particle or
mixture of particles. The added substances may be discrete
compounds or may be oligomeric or polymeric in nature.
The stabilizing and complexing agents may include various
phosphorus and phosphorus free acidic substance as well as basic
substances such as amines and alkanolamines. Of course the actual
species present and state of ionization will depend on the pH
and/or state of acidity or basicity at the point of use. Examples
of phosphorus containing acidic substances include phosphorus acid,
phosphoric acid, tri- and polyphosphoric acids, organophosphonic
acids containing one phosphonic acid group per molecule such as
2-hydroxyphosphonoacetic acid,
2-phosphonobutane-1,2,4-tricarboxylic acid, phosphonated oligomers
and polymers of maleic and acrylic acids as well as co-oligomers
and copolymers thereof. Other examples include organophosphonic
acids containing two or more phosphonic acid groups per molecule
like diphosphonic acids such as
alkylmethane-1-hydroxy-1,1-diphosphonic acids where the alkyl group
may be substituted or unsubstituted and contain from 1 to 12 carbon
atoms e.g. methyl-1-hydroxy-1,1-diphosphonic acid or
propyl-1-hydroxy-1,1-diphosphonic acid. Also suitable are amino
compounds containing two or more N-alkylene phosphonic acid groups
per molecule such as alkylamino-di(alkylene phosphonic acids) where
the alkyl group can be substituted or unsubstituted and have from
1-12 carbon atoms e.g propyl, isopropyl, butyl, hexyl, or
2-hydroxyethyl and the alkylene group may have from 1 to 5 carbon
atoms as well as amino-tri(alkylene phosphonic acids) such as
nitrilo-tris-(methylene phosphonic acid) and
nitrilo-tris-(propylene phosphonic acid). Other suitable
aminoderivatives from amino compounds are alkylene
diamine-tetra-(alkylene phosphonic acids), such as ethylene
diamine-tetra-(methylene phosphonic acid), dialkylene
triamine-penta-(alkylene phosphonic acids such as diethylene
triamine-penta-(methylene phosphonic acid) and so on.
Phosphorus free acidic substances include hydroxyacids which may be
monocarboxylic acids with one or more hydroxyl groups such as
glycolic acid, lactic acid, mandelic acid,
2,2-bis-(hydroxymethyl)-propionic acid,
2,2-bis-(hydroxymethyl)-butyric acid,
2,2-bis-(hydroxymethyl)-valeric acid,
2,2,2-tris-(hydroxymethyl)-acetic acid and 3,5.dihydroxybenzoic
acid, dicarboxylic acids with one or more hydroxyl groups such as
tartaric acid and tricarboxylic acids with one or more hydroxyl
groups such as citric acid. Phosphorus free acidic substances also
include polymers of methacrylic acid, acrylic acid and maleic
anhydride or maleic acid as well as copolymers thereof such as
acrylate-acrylic acid copolymers, olefin-maleic anhydride
copolymers like isobutylene-maleic anhydride copolymers,
styrene-maleic acid copolymers and vinyl alkyl ether-maleic acid
copolymers like poly(vinyl methyl ether-co-maleic acid). Phosphorus
free acidic substances further include azoles and their derivatives
containing two or more heteroatoms such as 1,2,3-benzotriazole,
tolytriazole, benzothiazole, 2-mercaptobenzothiazole,
benzimidazole, 2-mercaptobenzimidazole, benzoxazole,
2-mercaptobenzoxazole and (2-benzothiazolylhio)succinic acid.
Basic substances include alkanolamines, which may be a
monoalkanolamine, a dialkanolamine, a trialkanolamine, these being
primarily the ethanolamines and their N-alkylated derivatives,
1-amino-2-propanols and their N-alkylated derivatives.
2-amino-1-propanols and their N-alkylated derivatives and
3-amino-1-propanols and their N-alkylated derivatives or a mixture
thereof. Examples of suitable monoalkanolamines include
2-aminoethanol(ethanolamine), 2-(methylamino)-ethanol,
2-(ethylamino)-ethanol, 2-(butylamino)-ethanol, 1-methyl
ethanolamine (isopropanolamine), 1-ethyl ethanolamine, 1-(m)ethyl
isopropanolamine, n-butylethanolamine, cyclohexanolamine,
cyclohexyl isopropanolamine, n-butylisopropanolamine,
1-(2-hydroxypropyl)-piperazine, 4-(2-hydroxyethyl)-morpholine and
2-Amino-1-propanol. Examples of suitable di-alkanolamines are
diethanolamine (2,2'-iminodiethanol), 3-amino-1,2-propanediol,
2-amino-1,3-propanediol, diisobutanolamine
(bis-2-hydroxy-1-butyl)amine), dicyclohexanolamine and
diisopropanolamine (bis-2-hydroxy-1-propyl)amine). An example of a
suitable trialkanolamine is tris(hydroxymethyl)aminomethane. Cyclic
aliphatic amines may also be used such as morpholine, piperazine
and their N-alkyl derivatives as well as fatty amines. Mixtures of
any of the above phosphorus containing, phosphorus free or amine
substances are also suitable. Also included are azole derivatives
with amine functionality, such as 3-amino-1,2,4-triazole.
Preferred stabilizing or complexing agents include phosphorus acid,
phosphoric acid, tri- and polyphosphoric acids and organophosphonic
acids containing one or more phosphonic acid groups per molecule
such as 2-hydroxyphosphonoacetic acid, together with monocarboxylic
acids and dicarboxylic acids with one or more hydroxyl groups per
molecule such as glycolic acid. Preferred stabilizing or complexing
agents include azole derivatives, such as 1,2,3-benzotriazole,
2-mercaptobenzothiazole and (2-benzothiazolylhio)succinic acid.
Another embodiment of the present invention relates to a method of
making a dispersion of surface modified inorganic particles
including mixing the surface modified inorganic particles and a
fluid and milling the inorganic particles to form particles having
an average diameter of about ten microns or less, wherein the
inorganic oxide particles are surface modified with polyvalent
metal ions.
In this embodiment, dispersions of small particles where the
dispersions contain inorganic particles are obtained in the
presence of polyvalent cations by wet-milling techniques, with
addition of the suitable acidic, basic or complexing substances
described above prior to milling whereby pH is adjusted and/or
cations are complexed. The cations are present intentionally or are
present as a result of prior preparation techniques. In some cases,
the added substance may be a soluble or partially soluble component
of the corrosion inhibiting composition that is to be milled and
extra additions of the substance may not then be necessary. Stable
dispersions are thereby obtained, avoiding or minimizing excessive
viscosity build-up, reagglomeration of particles and hard settling
that may otherwise occur during or after wet milling.
The average particle sizes produced are about 10 microns or less
and all or most of the particles in the dispersion may be less than
1 micron. The particles may be non-porous, substantially non-porous
or porous according to the nature of the inorganic oxide used in
the process or prepared during the overall process of preparing the
inhibitor. In the light of the previous discussion, porosities may
therefore vary up to about 3 ml/g. Milling may commonly be carried
out in an aqueous phase but may also be carried out in a
non-aqueous phase. For the non-aqueous embodiments, suitable
solvents may be any of the known solvents commonly used in coatings
applications such as alcohols, esters, ketones, glycol ethers,
aromatic and aliphatic hydrocarbons, as well as aprotic solvents
such as N-Methyl pyrrolidone, N-Ethyl pyrrolidone, Dimethyl
sulphoxide, N,N-Dimethylformamide and N,N-Dimethylacetamide. For
the case where the particles already exist as suitably small
particles but in an aqueous phase either as a consequence of
particle formation and growth in that phase, a situation
encompassed by the embodiments described earlier, or as a result of
milling larger particles in the aqueous phase, the inorganic oxides
may be transferred to any of the solvent classes mentioned above by
techniques known in the prior art. Examples are those discussed in
the Journal of Colloidal & Interface Science 197, 360-369, 1998
A. Kasseh & E. Keh, "Transfers of Colloidal Silica from water
into organic solvents of intermediate polarities" and the Journal
of Colloidal & Interface Science 208, 162-166, 1998 A. Kasseh
& E. Keh, "Surfactant mediated transfer of Colloidal Silica
from water into an immiscible weakly polar solvent" or recited in
U.S. Pat. Nos. 2,657,149, 2,692,863, 2,974,105, 5,651,921,
6,025,455, 6,051,672, 6,376,559 and GB Patent No. 988,330, the
entire subject matter of which is incorporated herein by reference.
Introduction of polyvalent cations, stabilizing and complexing
components and/or combination with sparingly soluble salts may
occur prior to solvent transfer or following solvent transfer.
The corrosion inhibiting particles may be included in protective
and adhesion promoting coatings and layers, such as surface
pretreatments, surface films, anti-corrosive primers, adhesives and
sealants and the present invention includes protective coatings and
adhesion promoting coatings and layers containing corrosion
inhibiting particles as described above. The protective coatings
and adhesion promoting coatings and layers may be based on any of
the known types of organic and inorganic chemistries used in
anti-corrosion e.g. epoxy resins, polyesters resins, phenolic
resins, amino resins such as melamine-formaldehyde,
urea-fomaldehyde or benzoguanamine resins, vinyl resins, alkyd
resins, chlorinated rubbers or cyclised rubbers, acrylic and
styrene-acrylic chemistries, styrene.butadiene resins,
epoxy-esters, silicate based coatings such as zinc-rich silicates,
sol-gel coatings based on alkyl silicates and/or colloidal silicas,
films, treatments and coatings derived from organofunctional
silanes, as well as acidic or alkaline metal pretreatment solutions
and primer-pretreatment solutions.
EXAMPLES
The following Examples are given as specific illustrations of the
claimed invention. It should be understood, however, that the
invention is not limited to the specific details set forth in the
Examples.
Example 1
A 10 L Drais Laboratory Pearl mill (available from Draiswerke,
Inc,) is filled with 1.2 Kg of ZrO.sub.2 beads (0.6-1 mm in
diameter). An aqueous slurry of Shieldex.RTM. C303 pigment
(available from W. R. Grace & Co.), having an average particle
size of 3-4 .mu.m, to which is added a small amount of
2-hydroxyphosphonoacetic acid is circulated for 6 hours at a rotor
speed of 2800 rpm (slow setting) and at a pump speed of 40% of the
maximum. Subsequently, 0.2% by weight of Acticide.RTM. 1206
bacteriacide (available from Thor Chemicals) is mixed in. The
suspension of Shieldex.RTM. C303 pigment and water is stirred for 1
hour at room temperature before addition under mixing of the
solution of 2-hydroxyphosphonoacetic acid. This causes the pH to
drop from 8.42 to 8.04. The composition of the slurry in % by
weight is Shieldex.RTM. C303 pigment 16.21%; water 72.93%; 10.66%
of a 5% aqueous solution of 2-hydroxyphosphonoacetic acid and 0.2%
Acticide.RTM. 1206 bacteriacide.
Following milling, a free flowing dispersion of Ca/SiO2 particles
results, having an average particle size of about 0.3 .mu.m which
remains stable on storage for more than 90 days. 98% of the
particles are less than 1 .mu.m. Particle size is determined with a
Mastersizer.RTM. 2000 light scattering equipment available from
Malvern Instruments.
Example 2
Comparative
The above example is repeated except that 2-hydroxyphosphonoacetic
acid is not added to the mixture. This led to a fairly viscous
dispersion in which the particles reagglomerated on milling, with a
reagglomeration peak appearing at an average size of about 10
.mu.m.
Example 3
Comparative
2-hydroxyphosphonoacetic acid is again not added and different
milling conditions are adopted. A 2 L vertical laboratory pearl
mill (available from Draiswerke, Inc.), half filled with ZrO.sub.2
beads (0.6-1 mm in diameter) is used at a rotor speed of 2000 rpm.
Milling is carried out for 6 hours. The resulting dispersion has a
greater tendency to reagglomerate, becoming more viscous with a
peak appearing at a size of about 10 to 100 .mu.m.
Example 4
An anti-corrosive pigment is prepared in-situ by reacting together
silica gel, having a particle size of 3-4 .mu.m (available from W.
R. Grace & Co.--Conn.), Ca(OH).sub.2, and
2-hydroxyphosphonoacetic acid. The resultant mixture is then
subjected to pearl milling for about 30 minutes in a laboratory
Dispermat.RTM. mill (available from DISPERMAT) using 1 mm glass
beads at a rotor speed of 1800 rpm. This results in a free flowing
dispersion of Ca/SiO.sub.2/HPA particles having an average particle
size of about 2 .mu.m. The composition of the slurry in % by weight
is silica gel 5.60%; water 81.12%; 5.52% Ca(OH).sub.2 and 7.76% of
a 50% aqueous solution of 2-hydroxyphosphonoacetic acid. After
adding the Ca(OH).sub.2 to the suspension of silica in water, the
mixture is aged for 16 hours at 40.degree. C. prior to adding the
solution of 2-hydroxyphosphonoacetic acid at a rate such that the
pH does not drop below 9. The reaction mixture is aged at
90.degree. C. for 1 hour prior to cooling and milling. The
particles in the milled dispersion do not reagglomerate after
sitting for over 90 days, and the dispersion may be added to a
variety of protective coating formulations.
Example 5
Anti-corrosive tests are carried out on Example 1 and compared to
the Shieldex.RTM. C303 pigment alone, since the dispersions of
Examples 2 and 3 are not stable. In the absence of being able to
apply coatings down to a thickness of a micron or so, tests are
carried out in a water-borne acrylic coating applied by applicator
bar to Sendzimir.RTM. galvanized steel (i.e., Chemetall Test
Panels) so as to obtain a dry film thickness of about 40 .mu.m in
order to assess whether the dispersion offers any improvements in
anti-corrosive performance compared to Shieldex.RTM. C303 pigment
alone. The formulations employed are given below in Table 3, in
which the dispersion is incorporated by simple stirring, whereas
Shieldex.RTM. C303 pigment is incorporated with the aid of glass
beads in the normal way.
After 7 days of drying at room temperature, the coated panels are
scribed and subjected to salt spray (using ASTM B117) for 240
hours, after which the panels are briefly rinsed, dried and
evaluated within 30 minutes of withdrawal from the salt spray
cabinet. The results are given in Table 1, where ratings are given
on a scale of 0 to 5 in which 0 signifies no breakdown and 5
signifies complete breakdown.
TABLE-US-00001 TABLE 1 Salt spray results for Example 1 against
Shieldex .RTM. C303 pigment in a water-borne acrylic coating on
galvanized steel (Ratings are from 0 to 5 with 0 being best)
Crosshatch Scribe Adhesion Blistering Adhesion Loss Loss Rusting
Shieldex .RTM. 0 3 5 2 C303 pigment Example 1 0 1 2 0
The results in Table 1 show that improvements in anti-corrosive
performance are found for the dispersion of the present invention
compared to a commercial product coupled with simpler
incorporation.
Example 6
Anti-corrosive tests are also carried out on Example 4. In this
case, a zinc-free dispersion of the present invention is compared
against a commercially available zinc based anti-corrosive pigment
(Heucophos.RTM. ZPO anticorrosive pigments available from Heubach
GmbH) commonly used in water-borne acrylic coatings. Shieldex.RTM.
AC5, a commercially available zinc-free anti-corrosive pigment is
also included in the testing as a reference. Coatings are applied
by applicator bar to cold rolled steel (Q-Panels S412 available
from the Q-Panel Co.) so as to obtain a dry film thickness of about
40 .mu.m. The formulations employed are given below in Table 3,
where again the dispersion is incorporated by simple stirring, but
Heucophos.RTM. ZPO pigment is incorporated with the aid of glass
beads as referenced herein.
As in Example 5, the coated panels are scribed and subjected to
salt spray (using test ASTM B117) for 240 hours, after 7 days of
drying at room temperature. Subsequently, the panels are briefly
rinsed, dried and evaluated within 30 minutes of withdrawal from
the salt spray cabinet. The results are given in Table 2, where
again ratings are given on a scale of 0 to 5 in which 0 signifies
no breakdown and 5 signifies complete breakdown.
TABLE-US-00002 TABLE 2 Salt spray results for Example 4 on cold
rolled steel against a standard zinc-based anti-corrosive pigment
and a standard zinc-free pigment in a water-borne acrylic coating
(Ratings are from 0 to 5 with 0 being best) Scribe Adhesion
Crosshatch Blistering Loss Adhesion Loss Rusting Heucophos .RTM.
ZPO 0 1 0 1 pigment Shieldex .RTM. AC5 3 3 5 4 pigment Example 4 0
1 0 1
The results in Table 2 demonstrate that a zinc-free dispersion
according to the present invention provides superior anticorrosion
properties over commercially available heavy metal and zinc-free
coatings.
TABLE-US-00003 TABLE 3 Water-Borne Acrylic Formulations to assess
Example 1 on galvanized steel against Shieldex .RTM. C303
anticorrosive pigment and Example 4 on cold rolled steel against a
standard zinc-based anti-corrosive pigment and a standard zinc-free
pigment. 1 2 3 4 5 1). Neocryl XK-85 11.20 11.20 9.84 11.20 9.90
2). Water 5.23 5.23 0.88 5.23 0.88 3). Drew 210-693 0.14 0.14 0.12
0.14 0.12 4). Disperse-Ayd W33 1.43 1.43 1.26 1.43 1.26 5). Acrysol
TT935 0.29 0.29 0.25 0.29 0.26 6). Water 0.30 0.30 0.26 0.30 0.27
7). Ser-AD FA179 0.48 0.48 0.42 0.48 0.42 8). Butyl Glycol 2.15
2.15 1.89 2.15 1.90 9). Neocryl BT-24 2.74 2.74 2.41 2.64 2.42 10).
Aerosil R972 0.57 0.57 0.52 0.57 0.52 11a). Shieldex C303 3.39 --
-- -- -- 11b). Shieldex AC5 3.39 11c). Example 1* -- -- 19.87 -- --
11d). Heucophos ZPO -- -- -- 6.72 -- 11e). Example 4* -- -- -- --
17.68 12). TiO.sub.2 Kronos 2190 4.31 4.31 3.79 4.15 3.81 13). Talc
20MOOS 10.18 10.18 8.94 9.81 10.69 14). Hostatint Black 0.81 0.81
0.71 0.78 0.72 GR-30 15). Neocryl XK-85 44.66 44.66 39.24 42.64
39.48 16). Texanol 1.11 1.11 0.98 1.08 0.98 17). Nacorr 1652 1.91
1.91 1.68 1.91 1.69 18). Resydrol AX 237W 5.06 5.06 4.45 4.88 4.47
19). Butyl Glycol 2.42 2.42 2.13 2.25 2.14 20). Octa Soligen 0.06
0.06 0.05 0.05 0.05 Co-10% 21). Ammonia 25% 0.36 0.36 0.32 0.34
0.32 22). Water 1.20 1.20 -- 0.96 -- 100.00 100.00 100.00 100.00
100.00 *The dispersions had a concentration of about 15% by
weight.
Example 7
Calcium hydroxide (3.1 g) and 1,2,3-benzotriazole (BTA) (26.9 g) in
a 1:5 molar ratio are added under stirring to water (70 g) so as to
achieve a solution having a solid content of 30% by weight. To 100
g of LUDOX.RTM. AM silica (an aluminate modified colloidal silica
obtainable from W. R. Grace & Co.--Conn., having a solid
content 0f 34% by weight), 20 g of the BTA containing solution is
added slowly under stirring to produce a fine particle dispersion
having a calcium content of 0.25 mmoles/g silica and a BTA content
of 0.15 g/g silica, expressed alternatively as 6.3% by weight of
BTA based on the total water content of the dispersion. The pH of
the dispersion is 8.5. Adding calcium hydroxide without BTA led to
immediate gelation.
Example 8
The anti-corrosive properties of example 7 are determined as
follows. To 100 g of the dispersion of example 7, 0.39 g of sodium
chloride is added under stirring so that after dissolution, the
concentration of sodium chloride based on the total water content
of the dispersion is about 0.1M. Aluminium alloy 2024-T3 was used
as the test electrode in a three electrode configuration employing
a saturated Ag/AgCl reference electrode and a platinum counter
electrode in which the sodium chloride containing dispersion is
used as the electrolyte. Four hours after the test electrode came
into contact with the electrolyte, a current-voltage curve is
generated by sweeping 250 mV either side of the rest potential
under potentiodynamic conditions using Gi118AC electrochemical
corrosion test equipment (available from ACM Instruments). The
slope of the curve 10 mV either side of the rest potential is used
as a measure of corrosion inhibition in which the slope has units
of resistance. Three comparisons are employed. The first involved
adding 0.39 g of NaCl under stirring to 100 g of LUDOX.RTM. AM
silica to produce a dispersion about 0.1M in NaCl without calcium
or BTA. The second involved preparing a solution of calcium
hydroxide (0.767 g) and BTA (6.684 g) in a 1:5 molar ratio in 0.1M
NaCl (100 g) so that the resulting concentration of BTA is 6.3% by
weight of BTA based on the total water content of the solution. The
third is simply a 0.1M sodium chloride solution. The results are
shown in Table 4.
TABLE-US-00004 TABLE 4 Slope of the current-voltage curve 10 mV
either side of the rest potential on 2024-T3 aluminum alloy after 4
hours of contact with inhibited electrolytes, 0.1M in sodium
chloride. Appearance of curre nt- Inhibitor Slope (ohms cm.sup.2)
voltage curve Example 7 ~10.sup.6 Smooth LUDOX .RTM. AM silica
~10.sup.7 Jagged Ca/BTA ~10.sup.3 Smooth BLANK Unmeasurable
Unstable
As can be seen, both Example 7 and LUDOX.RTM. AM silica provide
evidence of corrosion inhibition on 2034-T3 compared to BTA alone
and the blank, but only Example 7 provides stable inhibition as
evidenced by a high slope and a smooth curve, where a jagged curve
is indicative of alternating surface breakdown and repair.
While the invention has been described with a limited number of
embodiments, these specific embodiments are not intended to limit
the scope of the invention as otherwise described and claimed
herein. It may be evident to those of ordinary skill in the art
upon review of the exemplary embodiments and description herein
that further modifications and variations are possible. All parts
and percentages in the examples, as well as in the remainder of the
specification, are by weight unless otherwise specified. Further,
any range of numbers recited in the specification or claims, such
as that representing a particular set of properties, units of
measure, conditions, physical states or percentages, is intended to
literally incorporate expressly herein by reference or otherwise,
any number falling within such range, including any subset of
numbers within any range so recited. For example, whenever a
numerical range with a lower limit, R.sub.L, and an upper limit
R.sub.U, is disclosed, any number R falling within the range is
specifically disclosed. In particular, the following numbers R
within the range are specifically disclosed:
R=R.sub.L+k(R.sub.U-R.sub.L), where k is a variable ranging from 1%
to 100% with a 1% increment, e.g., k is 1%, 2%, 3%, 4%, 5% . . .
50%, 51%, 52% . . . 95%, 96%, 97%, 98%, 99%, or 100%. Moreover, any
numerical range represented by any two values of R, as calculated
above is also specifically disclosed. Any modifications of the
invention, in addition to those shown and described herein, will
become apparent to those skilled in the art from the foregoing
description. Such modifications are intended to fall within the
scope of the appended claims.
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