Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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2012739
COATING RENOVAL ~OMPO~ITION~
AND MET~OD FOR U~E THEREOF
Backaround of the Invention
The present invention relates to coating removal and,
more particularly, to the stripping of labels, paint and other
finishes from various substrates.
It is well-known to those in the refinishing arts that
coatings are removed by sanding and/or with the aid of
chemical strippers. When using a chemical stripper, typically
a liquid, or more usually, a semi-liquid thin paste containing
the active paint stripper is applied to the surface to be
stripped and allowed to stand until the coating has been
lifted from the surface. This may require several hours or
even standing overnight. When the coating is at its loosest,
it is removed by scraping. This produces a messy deposit on
the floor of the work place consisting of strips or scraps of
coating film swollen with the still wet paint remover.
Inasmuch as the active coating removing agents in the remover
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are irritating to the skin and eyes, protective gloves and
goggles are preferably worn for this work. In any event, it
is a difficult and unpleasant task to clean up and dispose of
the wet residue. Furthermore, federal and many local
regulations restrict the disposal of wet solvent-containing
residue. ~--
Another disadvantage of commercially available coatingremovers, particularly for automotive and aircraft use, is
that they have varying degrees of effectiveness, removing most
of the coating in some cases, but only part of the coating or
hardly any of it in others. Previously available wet coating
removers are particularly ineffective on epoxy, urethane and
lacquer finishes, and some automotive undercoats.
Still another disadvantage of currently available wet
chemical coating strippers is that the coating layer tends to
re-adhere to the stripped surface if the coating remover is
allowed to stand too long. Therefore, the scraping operation
must be conducted at the optimum time to avoid the need to
re-apply paint remover with consequent loss of time. This
presents a scheduling problem and necessarily reduces
efficiency.
The deficiencies of presently available chemical coating
removers are so great that some shops resort to the more
time-consuming and therefore, expensive sand-blasting and
grinding techniques. These methods of coating removal also
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have the disadvantage of creating a dust problem, requiring
the workers to wear protective masks and clothing. Also, as
with any operation that creates a dust-laden atmosphere, there
is always the possibility of a dust explosion.
A paint stripping formulation for removing paint from a
substrate as a dry, frangible mass (a "dry stripper") is
disclosed in Canadian Patent No. 1,229,778. Dry strippers
differ from wet stripping compositions in that the stripper is
permited to dry without substantial re-adherence to the
substrate prior to removal of the coa'ing. According to the
disclosure, the formulations comprise an inert, absorbent
particulate material. These compositions are not well suited
for application to a surface by spraying, because the
particulate material such as diatomaceous earth is abrasive
and also tends to clog conventional spraying equipment with
continued use.
Another dry stripper is disclosed in U.S. Patent No.
4,801,397. The compositions disclosed therein purport to be
an improvement over the dry stripper containing the
particulate material in that they also comprise a resin binder
and 1/16" to 5" fibers which permit the coating-stripper mass
to dry in 4 to 8 hours and be removed as "flakes". Because of
the fibers, these formulations are not at all suited for use
as a sprayable coating removal formulations.
Thus, there is a need for a composition which is both a
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dry stripper and may be applied by conventional spraying
equipment. It would also be desirable for a dry stripper to
lift the coating and dry in a relatively short period of time.
It is a primary object of the present invention,
therefore, to provide an improved method for removing
coatings, and particularly paint and labels, and improved
chemical compositions for this purpose, which are not subject
to the disadvantages of the prior art.
It is another object of the invention to provide an
improved method and compositions for coating removal, which
reduce labor, increase efficiency, and which permit easy clean
up of the stripped coating.
It is another object of the invention to provide a method
and compositions for coating removal, which prevent
re-adhesion of stripped coating to the treated surface.
It is another object of the invention to provide a method
and compositions for coating removal which are not only more
efficient and convenient than those of the prior art, but
which are also less expensive.
It is another object of the invention to provide a method
and compositions capable of completely removing all commercial
finishes, including acrylics, synthetics, epoxies, urethanes,
certain lacquers and undercoating, down to the bare substrate
with minimal effort in the stripping operation.
It is another object of the invention to provide a method
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and compositions for automotive and aircraft paint removal in
which the paint is removed in dry flake form without the need
for heavy manual scraping.
It is another object of the invention to provide coating
removing compositions which have good flow and adhesion, long
shelf life, non-flammability, good color and low odor.
It is yet another object of the invention to provide
coating removing compositions which may be readily applied to
the coating using hand pump bottles or conventional siphon or
pressure spray equipment.
It is still another object of the invention to provide
such compositions which are capable of removing multiple coats
of paint and/or labels adhered to the surface in a single
operation.
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20~2739
Summary of the Invention
The foregoing and other objects of the invention which
will become apparent below are achieved by formulating
ingredients in a paint stripping composition which permits the
primary active paint removing agent, such as methylene
chloride, to achieve complete paint removal and to convert the
stripped paint and paint remover to a dry, peelable mass,
which is easily removed from the treated surface to leave bare
substrate.
According to the present invention, a coating removal
composition is formulated so that the composition is capable
of being applied to a coating using conventional spraying
equipment and of forming a dry, peelable mass which may be
removed from a surface as a dry powder or flake material. A
process for removing coatings is disclosed wherein the coating
removal composition is applied to a surface, preferably by
spraying, which dries in less than an hour to form a dry,
peelable mass. The dry mass is then removed as a dry powder
or flake material. The composition is also useful for
removing labels from substrates.
A coating remover of the present invention consists
essentially of methylene chloride in the range of from 50 to
90%, preferably 65 to 85%, by weight; a penetrating agent such
as aqua ammonia in the range of from O to 8%, preferably 2 to
8%, by weight; an evaporation retarder such as paraffin wax or
201Z739
tlle equivalellt ln t~le xange ~ from ~.5 to 2.5~ by weight: a
solve~t for tl~e evaporatlon retarder, for example ~
wax solvent such as mineral splrits or the equlvalent ln the
range of from 1 to 20% by welgllt; an alcohol or mlxture of
alcollols ln tlle range of from ~ to 22~, preferably 9 to 13~,
by weigh~ (preferably a mix~ure of denatured ethyl alcollol ln
tlle range of from o to 11% by welght and methanol in tlle range
of from o to 11% by weigh~ of the total compositlon): and a
thickening agent such as hydroxypropyl-metllylcellulose or tlle
equivalent in the range o from 0.5 to 3.0%, pre~erably ~.8 to
2.~%, by weight.
~ ccording to a fur~ller aspect of the lnvention tllere ls
provided a method o~ ma1cing sucll preeerred coating remover
comprising dissolving tlle paraffln wax or equlvalent ln the
mlneral spirits with heatlng, slowly adding the dissolved
wax-mineral splrlts mixture to the methylene chloride or
equivalent, witll s~irring, slowly adding the
hydroxyproplymethyl cellulose, or equlvalent, eollowed by,
wltll s~irring, adding tl~e ammonla,.addlng a mlxture of
denatured ethyl alcohol or equlvalen~, and the methanol.
Description Oe the_Inve~ntion
More speclflcally, the preferred coating removers havQ
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the following compositions:
Preferred Compositions Percent By Weiaht
Ingredients Min. Preferred Max.
Methylene chloride 50 77.1 90
Paraffin refined wax 0.5 o.g 2.5
Mineral Spirits 1 5.8 20
Ethyl alcohol, 0 5.5 11
denatured
Aqua ammonia 2 4 8
Hydroxypropyl 0.5 1.2 3.0
methylcellulose
Methanol 0 5.5 11
It should be understood that the foregoing proportions
are approximate and that they are based on the weight of the
total composition.
While not intending to be bound by a particular theory,
it is believed that the present compositions have the ability
to encapsulate active coating-removing solvent and penetrating
agent for a temporary yet sufficient time to inhibit
evaporation and permit the loosening of the coating without
re-adherence to the substrate before complete drying of the
loosened coating. This feature results in short drying
periods, the gradual release of solvent into the air and low
odor in the working environment.
The preferred active stripping agent, methylene chloride,
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is commonly used for this purpose in chemical coating
removers. While less than about 50% methylene chloride may
be used, if desired, there is a consequent loss of paint
stripping effectiveness. It is preferred to use about 65 to
85% to provide a composition which will have the desired
effectiveness. While more than 90% methylene chloride could
be used, it has not been found necessary to do so, and such
large amounts increase the rate o~ evaporation from the
composition, and consequently its odor.
A penetrating agent is desirable to enhance the
effectiveness of the solvents in removing durable coatings
such as polyurethane- and epoxy-based coatings. The
penetrating agent may be omitted when, for example, the
composition is to be used to remove less durable coatings such
as ~arnishes, laquers and enamels or when the penetrating
agent would otherwise damage a substra~e such as wood. The
preferred penetrating agent is aqua ammonia. Any suitable
concentration of aqua ammonia, which is typically an aqueous
solution containing up to about 30% ammonia, by weight, may be
used. While somewhat more than about 8~ aqua ammonia may be
employed, it has not been found to be necessary and it is
undesirable to add more water to the composition than is
contained in that amount of aqua ammonia. Other suitable
penetrating agents include organic amines such as
isopropylamine, monoethanolamine, triethanolamine and triethyl
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amine; organic acids such as formic acid, crysilic acid,
polyacrylic acids, acetic acids and other carboxylic acids;
phenols and cresols. When using acids such as formic or
acetic acids, a corrosion inhibitor such as sodium dichromate
should be used. When a corrosion inhibitor is employed, it
may be present in amounts of from O.l to 3% by weight of the
total composition. Certain penetrating agents such as phenol
may be less desirable because of their flammability.
A thickening agent is added to lend body to the
composition, not only in holding it in place on the surface to
be treated, but to aid in the formation of the dry, peelable
mass. Any suitable thickening agent known to the art may be
employed. Modified cellulose available under the tradenames
"Methocel" (Registered Trademark) and "Cellosize" (Registered
Trademark) are suitable. Carboxymethylcellulose, methyl
cellulose and hydroyxethylcellulose are also very effective.
~he preferred thickening agent is hydroypropyl
-methylcellulose, such as Methocel F4M-PRG available from Dow
Chemicals, Midland, Michigan. While less than 0.5% thickening
agent may be employed the resulting compositions are thin and
difficult to use~ More than 3.0% by weight of the thickening
agent may be used, but the sprayability of the composition may
be impaired.
Other suitable thickening agents include cellulose
derivatives such as Methocel 311 available from Dow Chemicals,
:
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Midland, Michigan; ethylcellulose derivatives such as K-5000
and HG available from Hercules, Inc., Wilmington, Delaware;
polyvinyl chloride and polyvinyl acetate polymers or
co-polymers such as UCAR solution vinyl VYHH and VYNS
available from Union Carbide, Danbury, Connecticut; polyvinyl
alcohol.s as Vinyl 205 available from Air Products and
Chemicals, Inc., Allentown, Pennsylvania; a methyl
styrene/vinyl toluene copolymer such as PICOT~C LC available
from Hercules, Inc., Wilmington, Delaware; bentonite clays
such as Bentone LT available from N.L. Industries; sodium
silicates such as those available from PQ Company,
Philadelphia, Pennsylvania; potassium silicates such as those
available from E.I. Dupont De Nemours, Inc., Wilmington,
Delaware; colloidal and fumed amorphous silica such as Aerosil
200 available from Degussa Corp., Teterboro, New Jersey; and
precipitated silica such as Zeothix 177 and 265 available from
Huber Chemicals, Haver De Grace, Maryland.
An alcohol component is present in the range of from 4 to
22%, preferably 9 to 13%, by weight. Suitable alcohols are
methanol, ethanol, denatured ethyl alcohol, isopropyl alcohol
and the like. The methanol is a desirable ingredient, since
it swells the modified cellulose thickening agent and enhances
its thickening properties. More than about 4% methanol may be
used, but would require labeling the composition as a poison.
Methanol may be added up to 11% by weight of the total
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compositlon. The ethyl alcohol is desirable, since it aids in
the penetration of various paint surfaces. It is preferred
that the combined amount of methanol and ethanol or their
equivalents i8 in the range of from 4 to 22%, preferably 9 to
13%, by weight o~ total composition.
Optionally, ketone 601vents such as acetone, methyl ethyl
ketone, methyl isobutyl ~etone and the like may be added up to
50% by weight of the composition. However, the coating
removal compositions will become increasingly flammable upon
the addition of such ketone solvents.
Any suitable evaporation retarder may be employed in
amounts from about 0.5 to about 2.5% by weight. Examples of
commonly used evaporation retarders are paraffin wax, beeswax,
vegetable wax, montan and petroleum wax. Paraffin waxes are
preferred for most paint removers. The wax serves several
functlons, i.e., it reduces evaporation of the volatile
ingredients and for this reason also reduces the odor of
ammonia. The wax al~o forms a film on the surface to be
treated. ThQ wax film aids in holding the other ingredients
in place while the composition is working. While less than
about 0.5% wax may be employed, such small amounts reduce
control o~ evaporation. More than about 2.5% wax is
undesirable, since it reduces the effectiveness and
sprayability o the composition.
A solvent employed to
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dissolve the evaporation retarder for addition to the liquid
or semi-liquid composition. Typical wax solvents are aromatic
and aliphatic solvents such as toluene, xylene, mineral
spirits and aromatic blends. The preferred wax solvent is
mineral spirits. The preferred mineral spirits are a
hydrocarbon cut having a--boiling point in the range from about
200F to about 400F. From about 1 to about 20% wax solvent
may be employed depending on the amount of wax used. The
solid wax is placed in the solvent in a container and the
solvent is heated sufficiently to dissolve the wax: typically
to about 132F.
A preferred method of making new compositions is as
follows: The methylene chloride is stirred in a suitable
container with conventional blending equipment. In a separate
container, the wax is dissolved in the mineral spirits or
other wax solvent by heating and melting the wax in the
solvent. The solution of wax and solvent is then added to the
methylene chloride, slowly with continued stirring. Next,
while the stirring continues, the hydroxypropylmethyl
cellulose is slowly added. The aqua ammonia is added next,
followed by the ethyl alcohol and methanol mixture.
In this way a coating removal composition is made which
has long shelf life, is non-flammable, has good color and a
low odor, and which is capable of completely removing paint
finishes and labels to the bare substrate.
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The new compositions may be applied to the surface to be
treated by techniques known in the art, such as by brushing,
rolling, or spraying. However, a primary advantage of the
present compositions is that they are formulated such that
they may be applied using a hand spray bottle or conventional
siphon or pressure spray-equipment. In this manner, the
compositions may be conveniently and quickly applied to the
coating in a substantially uniform layer. This greatly
reduces the labor required in a paint or label removing
operation, and particularly in an operation where paint and
labels are removed in an assembly-line fashion, such as in the
recycling of oil drums. The compositions of the present
invention may also be applied as an aerosol spray. An aerosol
spray may be obtained by placing the composition in an aerosol
can with any suitable propellant such as carbon dioxide.
In addition to being sprayable using conventional
equipment, the compositions of the present invention have a
very low odor, even when sprayed on the surface to be treated.
Typically, no extraordinary ventilation is required as is
usually necessary when solvent-based coating removers are
used. The compositions may be used to remove a variety of
coatings such as varnishes, epoxies, urethane and
nitro-cellulose lacquers, acrylics, grease, adhesives and the
like from a variety of substrates such as metal, glass, wood,
urethane and other plastics, fiberglass, tile, concrete,
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masonry and the like. The compositions may also conviently be
used to remove plastic, paper and plastic coated paper labels
and the underlying adhesives from substrates.
The coating removing compositions may be applied to
vertical and even overhead surfaces without dripping away or
impairing the effectiveness of the compositions. Since the
compositions typically dry in less than about thirty minutes
at ambient temperature, problems with running or dripping away
are obviated. Because one object of the invention is to
provide a coating remover that dries quickly without running,
the use of wetting agents or surfactants should be avoided.
The new compositions lift the paint from the substrate in
about 7 to 15 minutes and dry in about one half to one hour at
ambient temperatures in most cases. If desired, the
compositions may be removed by scraping or wiping while still
wet after the paint has been lifted. This is not preferred
however, since a primary advantages of dry stripping and clean
up are lost. It is preferred to wait until the coating and
coating remover mixture has fully dried to a peelable, dry
mass. This mass is then very easily peeled from the surface
by any suitable mechanical method with minimal effort, as by
scraping or brushing, either manually or by the use of a power
tool. The easiest method of all is to use compressed air
from commercially available hand held air guns, which direct a
jet of air at the peelable mass to swiftly and fully remove it
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from the bare substrate. The dry mass containing the removed
paint is then simply swept up and discarded as clean dry,
easily handled loose material.
The invention will now be described in greater detail in
the following examples.
Example I
Place 7.5 lbs of solid, refined paraffin wax into a metal
pot containing 48 lbs of mineral spirits, the wax should be
cut or chopped into small pieces to facilitate melting and
solution. The pot is heated with occasional mild stirring,
until the mineral spirits reach the melting point of the wax,
i.e., about 132F., and stirring is continued until all of the
wax has melted and dissolved.
The mineral spirits - wax solution is added very 510wly
to 643.5 lbs of methylene chloride in a vessel fitted with a
conventional stirrer. The mixture is stirred slowly, during
the gradual addition of the wax solution, until all of the wax
has been added and the solution in the vessel is homogeneous.
While continuing mild stirring, 10 lbs of hydroxypropylmethyl
cellulose is added. Then, while continuing mild stirring, 34
lbs of aqua ammonia is added followed by a mixture of 58.4 lbs
of denatured ethyl alcohol and 33.4 lbs of methanol. Stirring
is continued until the mixture is homogeneous. Stirring is
continued while filling the finished paint stripper into drums
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or cans in order to insure the uniformity of the composition.
Example II
The stripping composition of Example I is sprayed onto
the surface of an oil drum having a label affixed thereto.
The stripper is allowed to stand in contact with the oil drum
for about half an hour, until the lifted label, adhesive,
paint and stripper is thoroughly dry to the touch.
The dry, peelable label is then removed from the oil drum
by hand or by any suitable mechanical means, such as a scraper
or a common scrub brush. The dislodged residue is swept up
and disposed of as clean fill.
Example III
The stripping composition of Example I is sprayed from a
hand held pump spray bottle to form a uniform layer of the
composition on an automobile fender painted with acrylic
enamel base coat, urethane clear coat and acrylic primer.
After 7 to 14 minutes the paint composition lifts from the
metal surface and does not re-adhere to the metal. In
approximately one hour the paint composition and stripper is
dry and easily peeled away as a dry powder or flake material
using a scraper.
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Example IV
The stripping composition of Example I is sprayed from an
ordinary siphon-type spray gun assembly onto a polyurethane
bumper coated with a urethane paint, primer and flex agent
additive. After 14 minutes the paint/remover composition
lifts from the surface^and drys in approximately one hour.
The dry flake material is easily peeled away from the surface
by brushing the surface. The stripping composition did not
cause swelling on the surface of the urethane bumper which can
occur with certain other strippers.
It will be apparent to those skilled in the art that the
foregoing description and examples are merely illustrative,
and that other compositions, and other methods of making and
using them are included in the scope of the invention. For
example, and without limitation, any known active paint
stripping ingredient other than the preferred methylene
chloride may be used. The ammonia may be supplied from any
known source. Thickeners other than the preferred,
hydroxypropylmethyl cellulose, may be employed. Indeed,
functional equivalents of any of the ingredients may be used,
and any other ingredients commonly employed in such
compositions may also be added as long as they do not alter
the character of the claimed compositions.
