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 comprising
a vapor phase corrosion inhibitor component and a desiccant component,
wherein the corrosion inhibitor component comprises, 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 benzoate, and from about 1% to about 10% benzotriazole,
and wherein the desiccant component comprises a granular silica
gel, with said corrosion inhibitor component deposited upon said
granular silica gel.
2. A vapor phase corrosion inhibitor-desiccant formulation as claimed
in claim 1 wherein the corrosion inhibitor component comprises,
by weight, about 68% cyclohexylamine benzoate, about 10% ethylamine
benzoate, about 20% dicyclohexylamine nitrate, and about 2% benzotriazole.
3. A vapor phase corrosion inhibitor-desiccant formulation as claimed
in claim 1 wherein the corrosion inhibitor component is a dry powder
having a particle size less than about 0.1 micron, and the desiccant
component has a granular size between about 2 .mu.m and about 8
.mu.m.
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 coextruded 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 airpermeable
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
MoO.sub.4 ], anhydrous ammonium dimolybdate [(NH.sub.4).sub.2 MoO.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.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a typical laminate prepared
in accordance with the present invention, with the center or metallized
layer being shown in somewhat exaggerated form due to limitations
of draftsmanship;
FIG. 2 is an enlarged cross-section of an open cell foam within
which a corrosion inhibitor-desiccant formulation is impregnated;
FIG. 3 is a roll or coil of the foam of FIG. 2; and
FIG. 4 is an air-permeable capsule in which a corrosion inhibitor-desiccant
formulation is housed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In accordance with the preferred embodiment of the present invention,
a particularly useful vapor phase corrosion inhibitor component
for the composite material to be supplied in an air-permeable capsule,
incorporated with foam, or extruded polyethylene film includes a
mixture of either anhydrous sodium molybdate, anhydrous ammonium
dimolybdate, or amine molybdates, together with sodium nitrite and
benzotriazole. Specifically, in a particularly preferred embodiment,
a mixture is provided in the following formulation:
______________________________________ Component Percent by Weight
______________________________________ Anhydrous sodium molybdate
about 70% Sodium nitrite about 25% Benzotriazole about 5% ______________________________________
This mixture is particularly effective when prepared in powdered
form having a particle size below about 1 micron, and deposited
upon granular silica gel. The relative weight ratios are preferably
from between about 45% vapor phase corrosion inhibitor component,
balance silica gel, although ratios of from between about 30% and
50% vapor phase corrosion inhibitor component, balance silica gel
may be employed. The composite material is impregnated into foam
at a concentration of from about 1% to about 30% by weight. It is
extruded into polyethylene film at a concentration of from about
2% to about 3% by weight.
In the formulation provided above, the useful range of the components
present in the vapor phase corrosion inhibiting constituent may
be set forth as follows:
______________________________________ Component Percent by Weight
______________________________________ Anhydrous sodium molybdate
about 65%-about 75% Sodium nitrite about 22%-about 28% Benzotriazole
about 4%-about 6% ______________________________________
These ranges may be found useful for certain applications.
A second particularity useful vapor phase corrosion inhibitor component
for the composite material comprises a mixture of amine benzoates,
amine nitrates and benzotriazole. Specifically, the following formulation
provides a particularly preferred embodiment:
______________________________________ Component Percent by Weight
______________________________________ Cyclohexylamine benzoate
about 68% Ethylamine benzoate about 10% Dicyclohexylamine nitrate
about 20% Benzotriazole about 2% ______________________________________
This mixture, also in powdered form and having a particle size
below about 1 micron, is deposited upon granular silica gel, with
relative weight ratios the same as recited above for the formulations
containing molybdates. Likewise, its impregnation into foam or extrusion
into film is at the same concentration as stated for the molybdate
formulations. The useful range of the preferred formulation shown
above is as follows:
______________________________________ Component Percent by Weight
______________________________________ Cyclohexylamine benzoate
about 50%-about 97% Ethylamine benzoate about 1%-about 20% Dicyclohexylamine
nitrate about 1%-about 20% Benzotriazole about 1%-about 10% ______________________________________
Preparation of compositions containing these components are prepared
by simply blending the individual powdered components together.
While there are various techniques that may be employed for providing
an appropriate extrudate including, for example, polyethylene and
a vapor phase corrosion inhibitor-desiccant of the type described
herein, one particular technique has been found to be particularly
useful. Specifically, the composite formulation is formed and rendered
as uniform in particle size and configuration as possible. This
composite is then combined with a relatively limited quantity of
polyethylene with the mixture then being passed through the barrel
of a conventional extruder to form a master batch. The resultant
master batch is then chopped and rendered into pellet form. These
pellets are, in turn, combined with additional polyethylene and
then extruded as the film containing a vapor phase corrosion inhibitor-desiccant
of the type described.
Preparation of a foam-impregnated product is accomplished by dispensing
a corrosion inhibitor-desiccant formulation of the present invention
in a liquid carrier in which the foam is then immersed. The formulation
becomes dispensed throughout the foam structure during immersion,
and is there retained upon removal of the foam from the liquid carrier.
Subsequent evaporation of the carrier is effectuated to thereby
yield the impregnated foam product. An adhesive backing can be applied
to the foam product to permit convenient placement and retention
of the product at the site of needed protection.
A preferred air-permeable capsule product is constructed of a plastic
vessel containing a corrosion inhibitor-desiccant formulation of
the present invention and having an opening which is covered by
an air-permeable Tyvek membrane (manufactured by Du Pont Co., Wilmington,
Delaware) through which emission of the formulation can occur.
In order to describe alternate materials useful in connection with
the present invention, the synthesis of three amine-molybdate compounds
will be described hereinbelow, it being understood that each resultant
compound possesses appropriate physical and chemical properties
in its anhydrous form so as to be highly useful in connection with
the various aspects of the present invention.
The aliphatic amines employed are from the group consisting of
dicyclohexylamine, 2-ethylhexylamine, and cyclohexylamine, it being
understood that other aliphatic amines within this general category
may be found useful as well.
AMINE-MOLYBDATE "A"
Pursuant to this embodiment, dicyclohexylamine having a molecular
weight of 181.36 and the empirical formula C.sub.12 H.sub.23 N is
employed. The method and procedure set forth in Example I hereinbelow
is followed.
EXAMPLE I
A formulation is prepared with the following components:
______________________________________ Component Percent by Weight
______________________________________ Dicyclohexylamine 10% Phosphoric
acid 4% Water 36% Aqueous solution of ammonium 50%. molybdate (20%)
______________________________________
The 20% ammonium molybdate solution is prepared by adding pure
molybdenum trioxide to a 5% aqueous solution of ammonium hydroxide.
The pH of the resulting solution is normally in the range of 7.5
to 8.5. The dicyclohexylamine, phosphoric acid and water are mixed
together to form a neutral to slightly alkaline solution, the pH
being in the range of 7.5 to 8.5. The 20% aqueous solution of ammonium
molybdate is then added. The reaction that occurs is a simple displacement
reaction in which a white powdery precipitate is formed upon addition
of the ammonium molybdate solution. Following the completion of
the reaction, the mixture is cooled to approximately 60.degree.
F., after which the precipitate is filtered, washed, and dried until
the anhydrous form is obtained. The anhydrous finished product is
a fine white powder having the following structural formula: ##STR2##
wherein R.sub.1 and R.sub.2 are cyclohexyl radicals.
AMINE-MOLYBDATE "B"
Pursuant to this embodiment, 2-ethylhexylamine having a molecular
weight of 129.2 and the empirical formula C.sub.8 H.sub.19 N is
employed. The method and procedure set forth in Example II hereinbelow
is followed.
EXAMPLE II
A formulation is prepared with the following components:
______________________________________ Component Percent by Weight
______________________________________ 2-ethylhexylamine 5% Phosphoric
acid 2.5% Water 67.5% Aqueous solution of ammonium 25%. molybdate
(20%) ______________________________________
The 20% ammonium molybdate solution is prepared as set forth in
Example I hereinabove. The 2-ethylhexylamine, phosphoric acid and
water are mixed together to form a neutral to slightly alkaline
solution, the pH being in the range of 7.5 to 8.5. The 20% aqueous
solution of ammonium molybdate is then added. The reaction that
occurs is a simple displacement reaction in which a white powdery
precipitate is formed upon addition of the ammonium molybdate solution.
Following the completion of the reaction, the mixture is cooled
to approximately 60.degree. F., after which the precipitate is filtered,
washed, and dried until the anhydrous form is obtained. The anhydrous
finished product is a fine white powder having the following structural
formula: ##STR3## wherein R.sub.1 is a 2-ethylhexyl radical and
R.sub.2 is hydrogen.
AMINE-MOLYBDATE "C"
Pursuant to this embodiment, cyclohexylamine is employed in the
preparation of cyclohexylamine-molybdate. Cyclohexylamine having
a molecular weight of 99.17 and the empirical formula C.sub.6 H.sub.11
NH.sub.2 is employed. The method and procedure set forth in Example
III hereinbelow is followed.
EXAMPLE III
A formulation is prepared with the following components:
______________________________________ Component Percent by Weight
______________________________________ Cyclohexylamine 20% Molybdenum
trioxide (pure) 13% Water 67%. ______________________________________
The water, molybdenum trioxide and cyclohexylamine are mixed together
all at once. While mixing, the solution is heated to approximately
175.degree. F. When the solution becomes clear, the mixture is cooled
to 60.degree.-70.degree. F., whereupon a grey-white precipitate
forms. The precipitate is filtered, washed and dried until the anhydrous
form is obtained. The anhydrous finished product is a white crystalline
powder with the following structural formula: ##STR4## wherein R.sub.1
is a cyclohexyl radical and wherein R.sub.2 is hydrogen.
The amine-molybdates as set forth above are, of course, employed
in anhydrous form with the silica gel substrate. It has been found
that such molybdates, when employed in anhydrous form and deposited
onto granular silica gel will be readily incorporated into a foam
or into olefinic films such as polyethylene and polypropylene. Effective
mixtures of the amine-molybdate components are normally formulated
utilizing 70% by weight anhydrous amine-molybdate of the type shown
in Examples I, II and III above, 25% sodium nitrite and 5% benzotriazole.
As indicated in connection with such formulations discussed above
utilizing anhydrous sodium molybdate, these formulations incorporate
aminemolybdates A, B or C, are impregnated into foam at a concentration
of from about 1% to about 30% by weight or extruded into polyethylene
film at a concentration of between 2% and 3% by weight.
In accordance with the examples, the aliphatic amine may be present
in an amount ranging from between about 5% and 20%. In the interests
of completeness of the reaction involved, it has been found that
approximately 10% by weight of the aliphatic amine produces a desirable
end product. The reactions involved occur quite rapidly and have
been found to go substantially to completion at room temperature.
While dicyclohexylamine, 2-ethylhexylamine, and cyclohexylamine
have been indicated as the most desirable materials, it will, of
course, be appreciated that certain conditions of end use along
with certain other considerations and parameters may dictate that
somewhat smaller aliphatic chain lengths be employed. For example,
use of the material in somewhat cooler environments may render it
desirable to utilize materials having a somewhat shorter chain length
in order to achieve an appropriate degree of sublimation while exposed
to ambience. Other considerations may indicate utilization of such
shorter chain lengths, as well.
As has been indicated hereinabove, and with attention being directed
to FIG. 1 of the drawing, the vapor phase corrosion inhibitor-desiccant
composite materials of the present invention are well adapted for
extrusion with resinous film material typically employed in the
packaging industry. When employed as a member or layer of a laminate,
and with continued attention being directed to the drawing, the
film generally designated 10 includes a first layer of plastic film
11 having a metallic or metallizing layer 12 deposited thereon.
Layer 13 of laminate 10 is impregnated with the composite compositions
of the present invention, with the solid particles being introduced
into the film through co-extrusion techniques. For example, the
amine-molybdate of Example I is prepared, and deposited as a fine
white powder onto silica gel to form a composite. The composite
is introduced into conventional polyethylene film. This impregnated
film is, in turn, laminated to the metallized layer 12 of film 11
so as to form the ultimate composite. Laminating techniques for
such films are, of course, well known in the art. Metallized films
of biaxially oriented polyethylene terephthalate are readily bonded
to and laminated with polyethylene films of the type shown at 13.
In like manner, the amine-benzoate composition earlier described
is deposited onto silica gel to form a composite which is then introduced
into film.
FIG. 2 is an cross-section of foam 15 which is impregnated with
a corrosion inhibitor-desiccant formulation of the present invention.
The foam 15 is an open-cell isocyanate-derived polymer as known
in the art. Retained within the cells 16 are discreet particles
17 of the inhibitor-desiccant formulation. These particles 17 are
distributed within the foam by immersing the foam in a liquid in
which the inhibitor-desiccant formulation is dispersed. The immersed
foam 15 behaves much like a sponge in soaking up the loaded liquid
to thereby achieve deposition of the inhibitor-desiccant formulation
therewithin. Evaporation of the liquid results in impregnation of
the formulation by particles 17. The impregnated foam 15 can be
supplied in a roll or coil form 20 as shown in FIG. 3 and can be
provided with an adhesive backing 22 for adhered retention at a
site. A section 23 has been cut from the roll.
Providing the corrosion inhibitor-desiccant formulation of the
present invention is a permeable capsule 30 as shown in FIG. 4 permits
placement of the capsule in proximity to items to be protected.
The body 32 of the capsule 30 is constructed of plastic, while a
cover 34 is made of Tyvek.RTM., a polymer having permeability characteristics
which permit emission of corrosion inhibitor for deposition on items
to be protected.
Vapor phase corrosion inhibitor-desiccant composites of the present
invention are also well adapted for retention and/or packaging within
modestly porous envelopes or other enclosures. These envelopes may
be formed of plastic film or plastic foam, or alternatively, may
be fabricated from cellulosic products such as paper or the like.
In addition to being retained and/or packaged within envelopes or
enclosures, the material may be placed upon or within an appropriate
substrate formed of synthetic resin, foam or cellulosic materials.
Typical examples of useful material include polyethylene, polypropylene,
polymer foams, paper, and the like. When paper is employed, it is
preferred that the drying operation be undertaken so as to provide
reasonably anhydrous amine-molybdate materials.
It will be appreciated, therefore, that examples provided herein
are for purposes of illustration only and are not to be regarded
as a restriction upon the scope of the claims, inasmuch as those
skilled in the art may depart from these specific examples without
actually departing from the spirit and scope of the present invention. |