Abstrict A vapor phase corrosion inhibitor-desiccant composite comprising
silica gel granules coated with a vapor phase corrosion inhibitor
component. The corrosion inhibitor component is selected from a
formulation comprising anhydrous molybdates such as ammonium dimolybdate,
sodium molybdate and amine molybdates mixed with benzotriazole and
sodium nitrate, or from a formulation comprising amine benzoates,
amine nitrates and benzotriazole. The composites can be impregnated
into foam, extruded with polyolefin films which can additionally
be laminated with metallized second film, or encapsulated in an
air-permeable container. The corrosion inhibitor formulations have
vapor pressures which provide ongoing corrosion protection for susceptible
articles situated favorably with respect to the composite.
Claims What is claimed is:
1. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite comprising:
(a) a vapor phase corrosion inhibitor component comprising, by
weight, from about 22% to about 28% sodium nitrite, from about 4%
to about 6% benzotriazole, and an anhydrous molybdate selected from
the group consisting of sodium molybdate, ammonium dimolybdate,
amine molybdates, and mixtures thereof;
(b) a desiccant component comprising a granular silica gel having
a particle size between about 2 .mu.m and about 8 .mu.m and upon
whose surface the inhibitor component is deposited to thereby produce
a vapor phase corrosion inhibitor-desiccant formulation; and
(c) a substrate wherein the inhibitor-desiccant formulation is
retained.
2. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 1 wherein the substrate
comprises a foam.
3. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 2 wherein the inhibitor-desiccant
formulation is present in the range of from about 1% to about 30%
by weight.
4. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 1 wherein the substrate
comprises an aliphatic hydrocarbon film selected from the group
consisting of polyethylene and polypropylene, and wherein the inhibitor-desiccant
formulation is retained within the substrate by extrusion therewith.
5. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 4 wherein the inhibitor-desiccant
formulation is present in the range of from about 2% to about 3%
by weight.
6. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite comprising:
(a) a vapor phase corrosion inhibitor component consisting essentially
of a substantially anhydrous amine molybdate having the following
structural formula: ##STR5## wherein R.sub.1 is an aliphatic hydrocarbon
having up to 7 carbon atoms, and R.sub.2 is either hydrogen or an
aliphatic hydrocarbon having up to 7 carbon atoms;
(b) a desiccant component comprising a granular silica gel having
a particle size between about 2 .mu.m and about 8 .mu.m and upon
whose surface the inhibitor component is deposited to thereby produce
a vapor phase corrosion inhibitor-desiccant formulation; and
(c) a substrate wherein the inhibitor-desiccant formulation is
retained.
7. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 6 wherein the substrate
comprises an aliphatic hydrocarbon film selected from the group
consisting of polyethylene and polypropylene, and wherein said anhydrous
amine molybdate is retained within the substrate by extrusion therewith.
8. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 6 wherein the substrate
comprises a foam.
9. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite comprising:
(a) a vapor phase corrosion inhibitor component comprising, by
weight, from about 50% to about 97% cyclohexylamine benzoate, from
about 1% to about 20% ethylamine benzoate, from about 1% to about
20% dicyclohexylamine nitrate, and from about 1% to about 10% benzotriazole;
(b) a desiccant component comprising a granular silica gel having
a particle size between about 2 .mu.m and about 8 .mu.m and upon
whose surface the inhibitor component is deposited to thereby produce
a vapor phase corrosion inhibitor-desiccant formulation; and
(c) a substrate wherein the inhibitor-desiccant formulation is
retained.
10. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 9 wherein the substrate
comprises a foam.
11. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 10 wherein the inhibitor-desiccant
formulation is present in the range of from about 1% to about 30%
by weight.
12. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 9 wherein the substrate
comprises an aliphatic hydrocarbon film selected from the group
consisting of polyethylene and polypropylene, and wherein the inhibitor-desiccant
formulation is retained within the substrate by extrusion therewith.
13. A vapor phase corrosion inhibitor-desiccant formulation and
substrate composite as claimed in claim 12 wherein the inhibitor-desiccant
formulation is present in the range of from about 2% to about 3%
by weight.
Description FIELD OF THE INVENTION
The present invention relates to a formulation which is particularly
adapted for use as a vapor phase corrosion inhibitor-desiccant,
the material being useful for either inhibiting the corrosion of
the metallic items and/or passivating the surfaces thereof, the
formulation being particularly adapted for direct incorporation
within foam by impregnation therein or within synthetic resinous
films through extrusion or deposition into a film, such as into
an olefinic film, polyethylene, or the like. Film products prepared
in accordance with the present invention find particular application
in the formation of enclosures about metallic articles susceptible
to corrosion, and provide a relatively dry corrosion inhibiting
atmosphere therewithin. Air-permeable capsules and impregnated foam
products prepared in accordance with the invention find application
in their placement at the site of the items to be protected.
Specifically, the compositions of the present invention comprise
a vapor phase corrosion inhibitor-desiccant wherein the vapor phase
corrosion inhibitor component is selected from the group consisting
of anhydrous sodium molybdate and mixtures of such molybdates with
sodium nitrite and benzotriazole, and mixtures of benzoates of amine
salts with benzotriazole and nitrates of amine salts. The desiccant
component of the composition is a solid-phase granular particle
consisting essentially of silica gel onto which the vapor phase
corrosion inhibitor component, in powdered form, has been deposited
thereon. These compositions provide a vapor phase corrosion inhibitor-desiccant
which may be extruded along with a film material, with the film
thereafter being utilized to form an enclosure housing the item
or items being protected. Alternatively, the compositions may be
placed within enclosures or packages containing items which are
to be protected from corrosion. One manner in which this approach
is effective is to provide an air-permeable capsule or other similar
container containing the compositions therein. Of course, the capsule
or other container must have sufficient permeability so that the
components of the corrosion inhibitor-desiccant therein can enter
the ambient environment of the items to be protected. A second manner
in which the corrosion inhibitor-desiccant compositions can be placed
within enclosures or packages containing items to be protected is
to impregnate foam with the compositions and then place the foam
in proximity to the items.
For most purposes, anhydrous powdered or finely divided mixtures
of certain molybdates including anhydrous sodium molybdate, ammonium
dimolybdate and amine molybdates along with mixtures of such molybdates
with sodium nitrite and benzotriazole and mixtures of amine benzoates
with amine nitrates and benzotriazole are preferred. These materials
are then deposited upon the larger silica gel granules, with such
vapor phase corrosion inhibitor components being preferred for such
deposition applications. This composite mixture is preferably extruded
into polyethylene film at a concentration of from between about
2% and 3% by weight. It is preferably impregnated into foam at a
concentration of from between about 1% and 30% by weight. Preferably,
the silica gel particulate material has an average particle size
ranging from between about 2 .mu.m and 8 .mu.m, with the vapor phase
corrosion inhibitor component deposited on the surface of the granules
having a size ranging from between about 0.001 micron and 0.1 micron.
As an added feature of the invention, film materials extruded with
the formulations of the present invention may, in turn, be laminated
to a second metallized film, such as, for example, metallized polyethylene
terephthalate. The combined laminate provides a means to reduce
and/or eliminate static build-up in or along the film, and accordingly
improves the properties of the film when employed as an enclosure.
BACKGROUND OF THE INVENTION
In commerce and industry today, the useful life of corrodible items
may be extended and/or preserved by providing corrosion inhibitors
which protect the corrodible item from the adverse effects of its
ambient environment. Corrosion inhibitors, particularly vapor phase
corrosion inhibitors, have been found useful in protecting certain
corrodible items against reaction with elements or compounds which
may be found within their environment, and thereby losing their
effectiveness, reducing their useful life, or otherwise diminishing
their value. Such protection is typically needed during times of
packaging, handling, shipment, or during end use. Elements or compounds
which are normally of primary concern are gases such as oxygen,
water vapor, sulfides, carbon dioxide, and the like. The vapor phase
corrosion inhibitor-desiccant formulations of the present invention
find particular application in the preparation of packaging material
and in the preparation of formulation-impregnated foam. Packaging
material is produced through in-situ extrusion of the material with
films, with the films thereafter being utilized to form an envelope
or other enclosure about the article being protected. The films
may also be employed as a member of a multi-layer laminate including
a metallized film having good tear resistant properties such as
stress-oriented polyethylene terephthalate containing a vapor deposited
film or layer of metallic aluminum on a surface thereof. Such films
are commercially available and are commonly designated as "aluminized"
films. Foam impregnation is accomplished by liquid dispersion, as
known in the art, of the formulations into the foam, followed by
controlled evaporation of the liquid carrier to thereby deposit
the formulations in the cellular interstices of the foam. The resultant
product can be placed in proximity to items to be protected, with
such protection occurring as the corrosion inhibitor-desiccant is
released from the foam.
Among the common indications of corrosion manifested in useful
metallic articles are oxidation, pitting, tarnishing, mottling,
or discoloration of the surfaces of these items. These manifestations
occur in the articles, particularly when exposed to oxygen and in
either gaseous or liquid phase. Additionally, sulfides may present
corrosion or tarnishing problems as well. Inasmuch as both oxygen
and water, including water vapor, occur normally and are available
in nature, it is normally necessary to take precautions against
corrosion when packaging metallic items for shipment or storage,
or when subjecting such items to normal use. Metals which are frequently
found to be susceptible to corrosion under normal atmospheric and
ambient conditions are iron, copper, brass, aluminum, silver, and
alloys of these metals. The formulations of the present invention
are particularly useful in providing protection to both ferrous
and non-ferrous metals, including such non-ferrous metals as aluminum,
copper and brass. Care must frequently be taken to protect articles
fabricated from such metals, even when their surfaces have been
treated so as to be provided with sacrificial or aesthetic coatings
of zinc or cadmium on their surfaces. Such sacrificial or aesthetic
coatings are, of course, in wide use, but restrictions of use of
these materials may appear from time to time due to their potential
contribution to pollution or the like. Accordingly, means must be
provided to find alternate techniques for the protection and/or
preservation of metallic articles.
In the past, it has been known to provide a package or other enclosure
which includes one or more inhibiting compounds along with the corrodible
item or items to be protected. Additionally, articles have been
protected by means of utilization of protective coatings in the
form of solids, liquids, greases, or pastes, however such coatings
tend to be temporary in nature and further present certain disadvantages
to normal handling and packaging. Furthermore, removal of such protective
coatings may present problems either due to incomplete removal,
or the costs of such removal. The composite vapor phase corrosion
inhibitor-desiccant materials of the present invention find application
as a solid phase composite which may be impregnated into foam or
be co-extruded with film which is to form an enclosure about an
article being protected.
Solid phase and liquid phase compounds have been used in the past
to provide a source of vapor phase corrosion inhibitors. These materials
typically undergo either evaporation or sublimation so as to provide
the substantially constant availability of the inhibitors. In other
words, vapor phase corrosion inhibitors typically emit vapors which
protect corrodible surfaces through the deposition or condensation
of a protective film or coating upon the surface. In order to be
assured that a constant supply of inhibitor be present, adequate
quantities of the solid phase or liquid phase corrosion inhibiting
compounds must be provided, with the corrosion inhibiting compounds
being released at or adjacent the location where needed.
Granular silica gel is widely available for use as a desiccant.
Frequently, granular silica gel is placed within a woven or knit
pouch and placed within the confines of a package or enclosure for
enveloping a corrosion-susceptible article. The granular material,
when maintained at a particle size of below about 8 .mu.m may be
utilized as a solid-phase substrate upon which powdered vapor phase
corrosion inhibitor materials may be deposited.
When a laminate is formed in which one layer comprises a heat sealable
film such as polyethylene with composite compositions of the present
invention extruded in-situ, and with a second film layer being a
material such as metallized stress-oriented polyethylene terephthalate
films with desirable combinations of properties are achieved. Specifically,
the polyethylene film layer retains its conventional heat sealing
properties, while the stress-oriented polyethylene terephthalate
provides a tear-resistant property. The metallized layer is utilized
to reduce and/or eliminate static build-up, thereby further enhancing
the properties and qualities of the laminate. Stress-oriented polyethylene
terephthalate is normally biaxially oriented, and is, of course,
commercially available. The composite vapor phase corrosion inhibiting/desiccant
materials of the present invention enhance the protective qualities
of films which incorporate or otherwise include the composite materials.
SUMMARY OF THE INVENTION
In accordance with the present invention, a solid phase material
has been found which provides a source of vapor phase corrosion
inhibiting material along with a substrate of granular silica gel.
The vapor pressure of the composite material is balanced with the
quantities normally required to be emitted for effective and long
term protection of the metallic surfaces being exposed for treatment.
The formulations of the present invention provide for emission of
vapors in a concentration which is appropriate for strong protection
of the metallic surfaces, and yet at a rate sufficiently low so
as to provide for relatively long-lasting and long-term effective
economic treatment. The presence of granular silica gel as a substrate
for the vapor phase corrosion inhibiting component has been found
to enhance the protective qualities of the product. The formulations
of the present invention are compatible with and may be impregnated
into foam such as an isocyanate-derived polymer foam, or extruded
or otherwise deposited with synthetic resinous films, such as aliphatic
hydrocarbon or olefinic films such as polyethylene and polypropylene.
Such films may be incorporated with other films in a laminate, and
in particular may be combined with a metallized film so as to enhance
the static elimination and mechanical properties of the composite.
Additionally, the vapor phase corrosion inhibitor-desiccant composites
of the present invention have been found to produce little, if any,
visible residue. The lack of residue enhances the utility of the
materials, inasmuch as little, if any, mechanical or electrical
problems result from the continuous use of these materials. Additionally,
when granular silica gel component is used as a substrate for the
corrosion inhibitor component, smoke and fume evolution of the corrosion
inhibitor component is greatly reduced.
Typical corrosion inhibiting articles and materials used in the
past are disclosed in Miksic et. al. U.S. Pat. No. 4051066 and
Miksic et. al. U.S. Pat. No. 4275835.
The composite formulations of the present invention have been found
to be particularly well adapted to be housed in an air-permeable
capsule for placement with an item to be protected, to be impregnated
into foam, or to be combined as an extrudate with films fabricated
from aliphatic hydrocarbon such as polyethylene and polypropylene.
For facilitating impregnation or extrusion operations, composites
consisting of powdered anhydrous molybdates such as ammonium dimolybdate,
sodium molybdate and amine molybdates mixed with benzotriazole and
sodium nitrate or amine benzoates mixed with amine nitrates and
benzotriazole are deposited upon granular silica gel particles.
These composites are, in turn, impregnated into the foam or co-extruded
with appropriate film-forming materials. Generally speaking, the
formulations of the present invention are utilized for retention
and/or packaging within modestly porous envelopes or other enclosures
formed of plastic film or plastic foam. Typically, those certain
enclosures disclosed and claimed in the Miksic et. al. U.S. Pat.
Nos. 4051066 and 4275835 as identified hereinabove, are well
adapted for use with the formulations or compounds of the present
invention. Also, when extruded with a heat sealable film such as
polyethylene, a metallized (aluminized) layer such as biaxially
stress-oriented polyethylene terephthalate may be employed to enhance
the mechanical properties of the overall film arrangement. Techniques
for laminating these films together are, of course, well known in
the art.
In accordance with the present invention, the vapor phase corrosion
inhibitor components comprising molybdates which have been found
particularly desirable for use in combination with metallic surfaces
susceptible to corrosion comprise anhydrous sodium molybdate [Na.sub.2
Mo O.sub.4 ], anhydrous ammonium dimolybdate [(NH.sub.4).sub.2 Mo
O.sub.4 ], or an anhydrous amine-molybdate having the general structural
formula: ##STR1## wherein R.sub.1 is an aliphatic hydrocarbon having
up to 7 carbon atoms, and wherein R.sub.2 is either hydrogen or
an aliphatic hydrocarbon having up to 7 carbon atoms. The preferred
amine molybdates of this component of the composites of the present
invention are amine-molybdates derived from the group consisting
of dicyclohexylamine, 2-ethylhexylamine, and cyclohexylamine. Such
molybdates are readily synthesized and can be prepared in anhydrous
form without requiring unusual processing or handling problems.
As indicated above, these molybdates are utilized in anhydrous form
when provided in a permeable capsule, impregnated into a foam, or
extruded with a film, and are employed in a mixture in combination
with sodium nitrite and benzotriazole. Alternatively, anhydrous
sodium molybdate and ammonium dimolybdate may be utilized in combination
with sodium nitrite and benzotriazole. A second group of components
also having particularly desirable utility as vapor phase corrosion
inhibitor components is a mixture comprising amine benzoates, amine
nitrates and benzotriazole. A preferred composition comprises cyclohexylamine
benzoate, ethylamine benzoate, dicyclohexylamine nitrate and benzotriazole.
In use, these materials provide a highly desirable balance between
continuous emission from the solid phase, with this emission being
at a rate sufficiently low so as to provide for relatively effective
long-term and economic protection and treatment.
The granular silica gel component of the present invention preferably
has a particle size range of less than about 8 .mu.m. Such granular
silica gel is, of course, widely commercially available and as indicated
above, provides a solid phase substrate for the vapor phase corrosion
inhibitor component.
It is therefore a primary object of the present invention to provide
an improved vapor phase corrosion inhibitor-desiccant which is particularly
adapted for use in the protection of metallic surfaces exposed to
environments which are corrosive to the exposed surfaces.
It is a further object of the present invention to provide an improved
vapor phase corrosion inhibitor-desiccant which is formulated so
as to possess a vapor pressure or other property which allows transport
of the inhibitor to the metal surface appropriate for transport
of appropriate quantities of the inhibitor from solid phase in the
film to the metal surface, with the balance of the inhibitor being
retained in the film, to provide a continuous supply of emitted
corrosion inhibiting material.
It is yet a further object of the present invention to provide
an improved vapor phase corrosion inhibitor-desiccant composite
which is formulated so as to be capable of impregnation into a foam
or extrusion with conventional aliphatic hydrocarbon resinous films
such as polyethylene, polypropylene, and the like.
It is still a further object of the present invention to provide
an improved vapor phase corrosion inhibitor-desiccant composite
which is formulated so as to be capable of extrusion with conventional
heat sealable films such as polyethylene, with such polyethylene
films being, in turn, laminated to a metallized second film so as
to enhance mechanical properties as well as static elimination properties
of the composite laminate.
Another object of the present invention is to provide a foam product
impregnated with the vapor phase corrosion inhibitor-desiccant material
here described.
Yet another object of the present invention is to provide an air-permeable
capsule containing the vapor phase corrosion inhibitor-desiccant
material of the present invention for placement in the proximity
of an item to be protected.
Other and further objects of the present invention will become
apparent to those skilled in the art upon a study of the following
specification, appended claims, and accompanying drawing.
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