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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a composition which in the form of a dried
film is waterproof and elastic, and has particular advantages as a coating
for roofs and walls.
Certain applications for waterproof coatings have the most stringent
properties required for the applications to be successful. These stringent
property requirements are usually orders of magnitude greater than the
property requirements for more conventional coatings, such as conventional
house paints. The use of traditional mastic compositions will generally
result in an initially waterproof coating. However, the conventional
mastic coating has almost no ability to absorb movement of the underlying
surface, either by crack development or by shifting of roof tiles or the
like, unless applied in relatively heavy thick coatings. In this regard,
most mastic coatings will be applied at a total film thickness in the
neighborhood of 30 or 40 mils or even more. These coatings are quite
difficult to apply to roofs of cement tile or similar structures.
Because of the quite thick coatings which are required for the successful
use of conventional mastic coatings, the economics of the coating system
are not particularly attractive, even though in some instances relatively
cheap starting materials are used. Mastic coatings generally lack the
desired degree of adhesion, and have little or no moisture vapor
transmission ability. Thus, moisture which may be trapped underneath the
coating, or which passes from underneath the roof to the coating-roof
interface, is most likely to cause blistering and adhesion failure of the
mastic coating. This can rapidly lead to failure of the entire coating.
Furthermore, the high viscosity of the mastic coatings allows little if any
penetration into layers of gravel which are commonly found on flat roofs.
With the mastic sitting on top of the gravel, little or no adhesion will
exist between the coating and the roof underlying the gravel.
The prior art mastic-type roof coatings described hereinabove generally had
to be quite thick, due to the relatively low level of physical properties
of the mastic composition. Many of these mastic compositions were based
upon relatively low cost components, but because of the significant
amounts of material required to produce an acceptable waterproof layer,
the prior art coatings were not economical. Many leaks in roofs were most
difficult to patch with the prior art coating compositions, especially in
the case of gravel roofs. In order to insure the best roof patch, it was
normally necessary to remove the gravel from the area to be patched, or
else to put a coating of mastic over the entire roof.
Acrylic resins of the acrylate and methacrylate type have been used for
several decades in conventional house paints, of both the flat and gloss
type. Normally the paints will exhibit a pigment volume concentration, or
PVC, of at least 8-20, and in the case of flat paints, the PVC may be as
high as 50-65 or even higher. Such high levels of pigment generally result
in relatively poor extensibility properties of the resulting film. The
prior art has been reluctant to utilize acrylic resins at a PVC level
below about 20, as the resulting paint generally has poor hiding power,
such that it would not be considered a satisfactory paint.
U.S. Pat. No. 3,142,578 is directed to a finish coat for roofs, and is
based on an asphalt emulsion, glass fibers, and hogs' hair. The asphalt
emulsion has a high solids content, and is used in very high amounts in
the final composition, so that the final content of asphalt in the coating
may be as high as 60% or so. The patent teaches that the use of hogs'
hairs is absolutely necessary in order to obtain an acceptable coating,
and that the asphaltic emulsion alone cannot be used as a final sealing
coat, as the resultant film checks and pin holes and has other
imperfections develop (note column 2, lines 23-26). Various types of
asphaltic emulsions can be used, of the nature described at column 5,
lines 3-26.
U.S. Pat. No. 3,741,922, discloses aqueous latex paint compositions which
are an intimate blend of cellulose esters. U.S. Pat. No. 3,725,328
discloses latex coating compositions adapted for airless spray
applications, having pigment volume concentrations in the range between
about 45% and about 70%. A number of various types of latexes can be used,
including acrylic polymer and copolymer latexes.
U.S. Pat. No. 2,372,108 relates to viscous thixotropic emulsions of
acrylate and methacrylate polymers. The polymers are prepared by use of
cation-active emulsifying agents, used in a particular manner of
polymerizing the corresponding monomeric materials to form the acrylate or
methacrylate polymer.
U.S. Pat. No. 3,810,852 discloses thixotropic aqueous dispersions of
polymers suitable for use as emulsion paints, wherein the thixotropic
agent is a zirconium carbonate complex. U.S. Pat. No. 3,955,997 discloses
a semi-solid emulsion coating composition containing a polymeric
component, including acrylic resins, a water-soluble organic solvent, a
thixotropic material, and a hydrophilic polymer, such as certain cellulose
derivatives.
U.S. Pat. No. 3,849,357 discloses pigmented masonry water-repellant
compositions, which compositions contain pigment, acrylic polymers, and a
silicone resin.
U.S. Pat. No. 3,950,283 discloses the production of multi-colored paint, by
admixing two or more differently colored hydroxyethyl cellulose-containing
aqueous polymer emulsions, together with a clay dispersion, to form a
dispersion wherein the aqueous polymer emulsion particles are the disperse
phases in a continuous phase of the clay dispersion.
U.S. Pat. No. 3,505,509 discloses a rubber latex roofing composition. The
roofing composition also includes glass fibers, and can contain a surface
active agent, an antioxidant, a filling agent, a thickening agent, a
wetting agent and a curing agent. Normally the latex constituent is
employed in a ratio of 1.2:1 to about 1.5:1 with respect to the glass
fiber constituent.
U.S. Pat. No. 3,799,902 discloses a coating composition containing sodium
aluminate, and a dispersion of a polymeric latex based on an anionic
vinyl-addition polymer, and a water-soluble cationic polymer. The total
amount of polymer present in the dispersion is indicated to be within the
range of 0.001% to 0.75% by weight. The coating composition is indicated
as suitable for forming films which can be cast on surfaces such as glass
or metals, or can be used for coating fibers, or corrosion-resistant
coatings.
SUMMARY OF THE INVENTION
The present invention is directed to a composition for applying elastic,
waterproof, long-lasting coatings to roofs and walls of buildings. The
composition has an ultimate elongation of at least 250%, when measured in
the form of a dried film 7 mils thick and at 90% R.H. and 78.degree. F., a
visco-elastic flow such as to permit a 7 mil thick film which is firmly
adhered to a surface to withstand, without loss of the waterproofing
characteristics of the film, the development of a crack of up to 1
millimeter in width in said surface, while maintaining firm adherence to
the surface immediately adjacent the crack, even over extended periods of
time, up to as much as 10 years in length, and an adhesion, under both wet
and dry conditions, when applied to tar, gravel and paper-built roofs,
cement tile roofs, plywood roofs and asphalt roofs, such as to prevent the
passage of water between the coating and the roof.
The composition is based upon a polymer-rich latex. The composition has a
pigment volume concentration (PVC) no greater than 10 and has
substantially the maximum possible content of polymer. The polymer latex
preferably contains at least 50% by weight of polymer, and the composition
contains at least 40% by weight of polymer.
The present invention is based on the discovery that by using resins of a
particular nature, especially acrylic resins, which are not generally
considered to be particularly economical resins, and by using higher resin
contents than previously utilized by the waterproofing paint industry, the
physical properties of the resulting coating are unexpectedly increased to
the level that such low amounts of the coating are required that the
resulting coat of the coating composition, on an applied basis, is most
advantageous with respect to the prior art coating compositions
acknowledged above. In this regard, it should be appreciated that by
applying enough of even a quite marginal waterproofing composition, a
coating can generally be obtained which will initially satisfactorily
exclude water. However, it will be readily appreciated that it is not
practical to apply a coating six feet thick of a marginally acceptable
coating composition in order to waterproof the flat roof of a building.
The waterproofing coatings produced in accordance with the present
invention will give protection extending up to ten years and more to
roofs, if properly applied, and cracks and leaks in existing roofs can be
most readily patched with the coating composition of the present
invention. Roofs which have been coated with the composition of the
present invention may substantially develop cracks therein, but the
elasticity and adhesion properties of the coating composition of this
invention permit the coating itself to withstand cracks of greater than 1
mm. in width, up to 2 mm. in width, and even up to 4 mm. in width, without
rupture. This is a significant advance over the properties exhibited by
prior art waterproofing compositions.
DETAILED DESCRIPTION OF THE INVENTION
A number of various film-forming latexes can be utilized as the polymer
latex of the present compositions. Homopolymers, copolymers and
terpolymers can be employed in the present compositions, as will be clear
to the art. Ordinarily these latexes are made by emulsion polymerization
of ethylenically unsaturated monomers. Suitable emulsions include those of
vinyl resins including vinyl acetate, vinyl chloride, vinylidine chloride
and the like, and acrylic latexes including polymers and copolymers
containing units of acrylic acid, methacrylic acid, their esters and
acrylonitrile. Broadly, suitable latexes are latexes containing
elastomeric synthetic polymers which are obtainable in stable aqueous
latex form, containing at least 50% of the polymer in the latex, and
capable of coalescing into a film when applied to a surface at ordinary
room conditions, such as, for instance, 75%F and 25% relative humidity and
at one atmosphere total pressure. It is critical that the polymer latex be
chosen such that the resulting composition has an ultimate elongation of
at least 250% when measured in the form of a dried film 7 mils thick and
at 90% R.H. and 78.degree. F. Furthermore, the resulting dried film must
be in a form such as to exhibit the desired elastic and adhesive
properties to permit a 7 mil thick film which is firmly adhered to a
surface to withstand the development of a crack up to 1 mm. in width,
preferably up to 2 mm. in width, and more preferably up to 4 mm. in width,
in the surface without significant loss of waterproofing properties
thereof, even over extended periods of time, including periods of time up
to ten years or so. The adhesion of the polymer latex composition should
be such that when applied to various types of conventional roofs the dried
film will prevent the passage of water between the coating and the roof.
The polymer latex of this invention should tolerate water, hydrophilic
protective colloids and thickeners such as water-soluble hydroxyethyl
cellulose, carboxymethyl cellulose, sodium caseinate, natural gums such as
gum tragacanth, locust bean gum, guar gum , and alkali metal alginates,
various surfactants such as anionic surfactants, e.g., sodium
dodecylbenzene sulfate and sodium dodecylbenzene sulfonate, and nonionic
surfactants such as alkyl phenoxy poly(ethyleneoxy)ethanol having alkyl
groups of about 7 to about 12 carbon atoms and the like, ampholytics such
as coconut fatty acid amides, coconut fatty acid amide condensates and the
like, freeze-thaw recovery agents such as the lower alkylene glycols,
alkali-fast colorants such as Hansa yellow dyes, phthalocyanine blues and
greens, red or yellow oxide or iron toners and toulidine reds, and the
like. The latex coating composition of the present invention may be
manufactured with some or all ingredients, i.e. freeze-thaw stabilizers,
coalescents, antifoams, and can also include fungicides, other
stabilizer-thickeners such as hydroxyethylcellulose, and various other
anionic and nonionic surfactants.
The coating composition of the present invention is preferably based on an
acrylate polymer latex, wherein the acrylate polymer is a lower alkyl
ester, such as a methyl, ethyl or butyl ester, of acrylic and methacrylic
acids, and copolymers of such esters with other ethylinically unsaturated
copolymerizable monomers which are known to the art to be suitable in the
preparation of acrylic polymer latexes, can also be utilized. Suitable
comonomers include vinyl acetate, which may be used as a comonomer with,
for instance, butyl acrylate in a ratio of 70/30 or smaller of the vinyl
acetate to the butyl acrylate. Various crosslinking agents known to the
art may be utilized, such as, for instance, trimethylolpropane
triacrylate.
It is critical that a polymer be chosen which can be utilized at the
maximum possible level in the coating composition, and the minimum amount
of polymer in the composition will be about 40% by weight. Preferably, at
least about 45% by weight of polymer will be in the aqueous coating
composition. Such high resin contents in the coating composition can be
obtained by using a latex containing at least 50% by weight of polymer,
and preferably the latex contains at least 55% by weight of polymer, more
preferably at least 60% by weight of polymer.
The maximum content of polymer in the composition is obtained by using
polymer latexes containing the high polymer contents mentioned above, and
also by using the minimum amount of other agents, and especially by
avoiding the addition of unnecessary amounts of water to the composition.
A thixotropic thickening agent may be added in the minimum amount to give
the desired viscosity, and the minimum amount of coloring agent required
to produce a desired level of coloration may be utilized. A coalescing
agent may be added for the acrylate polymers in an amount which is the
minimum amount to produce the desired coalescence of the polymer.
Normally the amount of non-polymer non-aqueous constituents will be less
than 20% by weight, with a strong preference for these additives being
less than 15% by weight, especially less than 10% by weight, based on the
weight of the final coating composition. By so minimizing the quantity of
constituents other than film-forming polymer in the dried film, the
resulting film will exhibit the desired flexibility and durability.
The coating composition is normally covered by an acrylic paint or other
conventional paint after drying, for tack reduction purposes and also for
a more attractice appearance.
The purpose of the coloring agent in the coating composition is to allow
the workmen in the field to determine which areas have been covered, and
which have not yet been covered, by the coating composition during the
application thereof. After the coating composition has dried, any uncoated
areas should be readily detectable. In addition, at least in some
instances the workmen in the field will be able to obtain a rough idea of
the amount of composition which is being applied. Thus, the amount of
coloring agent which may be added is only enough to distinguish the
freshly applied coating composition from the uncoated substrate. It is
critical that the coating composition have a PVC or pigment volume
concentration no greater than 10, in order to maintain the high acrylate
polymer concentration. Preferably, the PVC of the coating composition will
be less than 6, and more preferably if pigment is used the PVC is in the
neighborhood of 4.
The coloring agent is preferably a pigment, more preferably titanium
dioxide, such as Rutile titanium dioxide. However, other pigments which
are chemically inert to the acrylate polymer may be utilized, and dyes may
be utilized, although the use of dyes, which are known to have relatively
poor ultraviolet resistance, is not preferred. When only dyes are
utilized, the PVC may be 0.
For applications to other than gravel roofs and to walls, it is preferred
that at least one thickening agent which imparts thixotropic
characteristics to the composition be used. Attapulgite clay has been
found to be particularly effective, although other thixotropic thickening
agents known to the art may be utilized if desired.
When the coating composition is used to coat a gravel roof, normally little
or no thickening agent will be utilized, as it is preferred for the
coating composition to then be of a very low viscosity, in order to
penetrate through the gravel to the surface of the roof. In fact, the
coating composition of the present invention will frequently be diluted
with water up to 50% by volume, preferably about 20% by volume, for such
applications, in order to reduce the hangup of solid components on the
gravel.
For other coating applications, however, it is preferred that the coating
composition be thickened to the point so that after application little if
any flow will occur. Of course, with the thixotropic thickening agents,
the coating viscosity will reduce upon the application of shear, so that
the coating may be readily applied by conventional techniques. Once the
coating is applied to walls or roofs, however, it is preferred that it
remain substantially in the place of application, without significant sag
or other movement. Within these parameters, those in the art can readily
choose appropriate thickening agents, and the appropriate amounts of such
thickening agents.
The coalescing agent may be any conventional coalescing agent for acrylate
polymers, but a coalescing agent which has been found to be particularly
suitable is 2,2,4-trimethyl-1,3-pentanediolmonoisobutyrate. Normally the
coalescing agent will be used in an amount of less than 5% by weight,
preferably less than 3% by weight, and more preferably about 2.5% by
weight.
Some types of film-forming polymers do not require the presence of a
coalescing agent under certain conditions, as known to the art, so that it
will be readily appreciated that the use of coalescing agents is optional.
In certain instances it may be desired to incorporate fibers, such as
asbestos fibers or glass fibers, into the coating composition to increase
the tear strength of the thin films of the coating. This approach might be
more useful for roofs wherein subsequent crack development of significant
magnitude was expected, as the incorporation of the fibers may permit the
coatings to resist failure in spite of the development of even wider
cracks than the 4 mm. cracks mentioned above.
The coating composition may be sprayed upon roofs and walls, or may be
brushed or applied by a roller. Normally, the coating composition will be
applied in two coats, to insure full coverage, with the coats cross-lapped
to insure full coverage. A total coverage rate of 70 square feet per
gallon will result in a coating thickness in the order of 10 mils, which
has been found to be quite satisfactory. Normally, the coating composition
should not be less than 2-4 mils in thickness, in order to obtain adequate
physical properties, resistance to pinholing and the like. There is no
real upper limit on the coating thickness, other than limitations imposed
by economic considerations and by the maximum design weight which the roof
can withstand. Because of economic factors, however, it would be most
unusual to have a coating as thick as 50 mils, and it is preferable that
the coating be no more than 20 mils in thickness. These thickness ranges
do not account for the thickness of coating composition required to patch
a crack, of course.
In addition to the critical ingredients set forth above, the coating
composition of the present invention will normally have other conventional
paint additives therein. For example, the coating composition generally
contains one or more wetting agents, dispersants, fungicides, sticking
agents, defoamers, and the like. It is helpful to utilize a basic
dispersant to disperse the titanium dioxide or other pigment in the
coating composition. The presence of a fungicide is particularly
recommended in hot, humid climates, although for more northern climatic
conditions, the presence of a fungicide will normally still be
recommended, in view of the long potential life of the coating composition
of this invention. The presence of a sticking agent will assist the
composition to adhere to greasy or glassy surfaces, and thus will be
helpful for some applications. The presence of a defoamer is particularly
useful to avoid foaming problems and the defoamers which may be utilized
are conventional.
The coating composition of the present invention has its outstanding
utility when used as a waterproofing agent for roofs, but is also useful
in waterproofing walls. The surfaces which may be coated with the
composition of the present invention include cement tile roofs, gravel
roofs, asphalt shingle roofs, wood shingle roofs and walls, tarpaper roofs
and walls, cement walls, brick walls, masonry block walls, plywood walls
and roofs, and any other exterior or interior building surfaces to which
adequate adhesion is obtained. The products which are presently
commercially available are generally satisfactory as waterproofing
coatings for walls, as long as the wall does not crack. However, the
products now available are generally subject to coating failure if a crack
of any magnitude develops in the wall. In contrast, the coating produced
from the composition of the present invention will stretch and retain its
waterproofing ability, even if cracks of 1 mm. in width or greater develop
in the coated wall.
The present coating composition is based on the use of a minimum amount of
water, commensurate with the production of a stable latex, and also for
certain applications with the viscosity reduction of the composition to
the point where desired penetration through gravel can be obtained. If too
great a dilution with water is used, the shrinkage of the composition
during drying will be too great, and the properties of the resulting dried
film will be adversely affected.
For almost all other applications, however, to other types of roofs and to
walls, the concentrated composition, such as a product of Example 1,
having maximum resin content, will be utilized.
When the resin coating is applied to a gravel roof, to penetrate through
the gravel to the underlying substrate, in some instances the gravel may
have had enough dirt penetrate through it that the resin will basically
adhere to a dirt layer, rather than the underlying roof surface. In any
event, the polymer must exhibit an adhesion, especially a wet adhesion,
such as to adequately resist any tendency to separate from the surface to
which it is adhered.
As indicated, it is preferred to utilize a thickening agent in the coating
composition of the present invention, with the sole exception of coatings
which are to be applied to gravel roofs, and it is quite preferred that at
least one of the thickening agents utilized impart thixotropic
characteristics to the composition. The ultimate viscosity and the
thixotropic nature of the composition will vary, depending upon the
particular end use which is contemplated, and also depending upon the
particular method of application to the substrate that is contemplated.
For instance, a higher thixotropic viscosity can be utilized for spray
application than for roller application, thus permitting greater build-up
on walls and similar surfaces during spray application.
As mentioned hereinabove, in some instances it may be desirable to
incorporate fibrous reinforcement into the coating composition, to
increase the physical properties of the dried films. However, when the
coating composition is to be applied to gravel roofs, it is definitely
preferred that the coating composition contain no fibrous components, as
such components would hang up in the gravel layer and thus would not form
a significant function in the waterproofing coating formed on the
underlying substrate. For most applications it is preferred that the
coating composition be in the non-fibrous form -- that is, that no fibers
or filaments be incorporated therein.
The elasticity of candidate coating compositions may be readily tested by
determining the Mar Elasticity Value thereof, using the following
procedure. A conventional asbestos cement shingle, such as a shingle 1/8"
thick, is liberally coated on a smooth side thereof with a sealer (such as
Acryloid B-72, an ethyl methacrylate copolymer produced by Rohm and Haas,
having a T.sub.g of 40.degree. C. and a viscosity of 470-770 cps at
25.degree. C. in the form of a 50% toluene solution, dissolved in xylol to
a 12% resin content). After 1 hour of drying time, the sealer-coated
surface is spray coated in two spray applications with the candidate
waterproofing composition to a total film thickness of 7-10 mils, dry
basis. The thus coated shingle is permitted to dry under ambient
conditions for 7 days.
The asbestos shingle is then broken, from the uncoated side toward the
coated side, and the two shingle sections on either side of the crack are
moved apart increasingly greater distances, and the film checked for
integrity at each such distance. This provides an indication of the
initial crack development resistance, or elasticity in use, of the
candidate waterproofing composition.
The viscoelastic flow characteristics of the candidate waterproofing
composition film are checked by taking similar broken, coated asbestos
cement shingles and clamping the two sections in rigid clamps maintained a
fixed distance apart, with the film integrity observed over the desired
periods of time. A Mar Elasticity Value is the width, in mm., of a crack
which the candidate waterproofing composition film (7 mils thick) can
withstand over a period of 1 month or more, without loss of waterproofing
characteristics and without significant loss of adhesion to the shingle.
The waterproofing coating composition to the present invention will have a
Mar Elasticity Value of at least 1, and preferably at least 2. In some
instances the compositions may have a Mar Elasticity Value as high as 4 or
even higher. In contrast, a conventional flat latex paint may have a Mar
Elasticity Value of 0.25, or even less. Thus, with the high Mar Elasticity
Value exhibited by the present coating compositions, the compositions are
able to withstand, in the form of dried films, significant crack
development in the underlying surface.
An unexpected advantage of the polymer-rich waterproofing coating
compositions of the present invention is that the conventional fungicides
used therein are much more effective, at a given level of fungicide in the
resulting film, than in compositions having conventional PVC values, i.e.
PVCs of 20 and greater, and the present compositions are especially much
more resistant to fungus attack than flat paints of 50 PVC or more
containing corresponding amounts of fungicide. While this observation
appears true for any conventional fungicide, it has been found to be of
particular advantage with mercuric fungicides, such as phenyl mercuric
succinate or phenyl mercuric acetate. Normally the fungicide will be used
in the coating composition in an amount of about 1-2 lbs., based on active
metal, such as mercury, per 100 gallons of coating composition, although
in some instances the fungicides level may be as low as 1/2 lbs. of active
metal per 100 gallons of composition, and there is no technical reason why
greater amounts of fungicide cannot be used, but economic considerations
generally dictate that no more than 2 or 3 lbs. of fungicide based on
active metal will be used per 100 gallons of composition.
An illustration of the greatly increased fungicidal activity which can be
obtained will be noted if a coating composition of the present invention
is compared to a conventional flat paint having a PVC of perhaps 60, using
the same film-forming polymer in the two compositions, and the same type
and amount of fungicide therein. The conventional flat paint may be
subject to substantial fungus attack after only four months of Southern
Florida exposure, whereas the coating of the present invention may show no
signs of fungus attack after two years or more of the same exposure.
The art has experimented with the concept of reacting the active fungicide
onto the film forming polymer or other coating compositions, and if such
attempts are successful, no reason is seen why the same concept could not
be used in the coating compositions of the present invention.
EXAMPLES OF THE INVENTION
EXAMPLE 1
A 100 gallon acrylic-rich coating composition was prepared by adding, in
order, the following ingredients to a stirred mixing vessel:
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Water 7 gal.
Potassium tripolyphosphate
60 gms.
AMP-95 amine dispersant (2-amino-
1-methylpropanol, International
Minerals and Chemicals) 200 ml.
Attagel-50 thickener (Attapulgite
clay, Englehart Industries)
14 lbs.
Titanium dioxide, Rutile type
25 lbs.
Rhoplex AC-64 acrylic latex (60%
aqueous dispersion of methyl
methacrylate copolymer, Rohm &
Haas) 80 gal.
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The following ingredients were mixed together in a separate mixing vessel:
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Super Adit fungicide (phenylmercuric
succinate, Tenneco Chemicals)
18 lbs.
Texanol coalescent agent (2,2,4-
trimethyl-1,3-pentane diol
monoisobutyrate, Eastman
Chemical) 23 lbs.
AMP-95 amine dispersant 2 lbs.
Water 5 gal.
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After the above ingredients in the second mixing vessel were thoroughly
mixed, they were added to the main batch of material in the first mixing
vessel. This procedure prevented undue shocking of the system, which would
tend to cause precipitation.
Thereafter, to the above mixture the following ingredients were added:
______________________________________
GR-7M sticking agent (a 64%
aqueous dispersion of
dioctylsodium sulfosuccinate,
Rohm & Haas) 29.5 oz.
F-142 defoamer (Tenneco Chemicals)
64 oz.
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Thereafter, in a separate mixing container, 270 grams of J12 MS thickener
(hydroxypropylmethylcellulose, Dow Chemical) and 64 oz. of water were
mixed together, and then added to the stirred main batch.
The acrylic-rich coating composition produced by this example was highly
suitable as a waterproofing coating for roofs, especially roofs built up
of various layers including gravel. The coating composition could be
sprayed on a cement tile roof and the viscosity of the coating composition
was such that it would stay in place after application, and would coalesce
thereon to form the desired waterproof coating. This coating exhibits
excellent adhesion to various substrates, and has a high degree of
elasticity, compared to conventional latex paints and other waterproofing
coatings for roofs. That is, the coating appeared to have maximum stretch
and resiliency, commensurate with coating strength. Thus, the coating
could withstand significant crack development in the roof after coating
application, up to 2mm. wide crack development, without resulting in
coating failure and water leakage. Excellent adhesion could also be
obtained on conventional tar roofs, and the coating composition has
excellent penetration of moderately chalky surfaces.
The present coating compositions are suitable for application to
below-grade walls, and in particular a test coat has been applied to the
inside masonry block wall of a below-ground basement, which previous to
such application had exhibited leaks. The application of the coating of
Example 1 to form a coating about 10 mils thick appeared to adequately
stop the water leaks in the test area. It does appear to be important, for
applications wherein the water, or hydrostatic, pressure on the film would
tend to push the film away from the substrate to which it is adhered, for
adequate keying of the film to occur in the substrate. In other words, a
relatively porous masonry block construction substrate would be definitely
preferred over a smooth finished poured concrete wall.
With the open pore structure of the substrate, the resin can enter into
various pores and intersticies therein, and obtain firm adherence by
keying. The dried film will still permit moisture vapor to pass
therethrough, and can be finished with a top coat of acrylic or other
paint, which can be conventional or textured as desired. Thus, an
attractive interior finish can be achieved, while at the same time
waterproofing of the walls is accomplished.
EXAMPLE 2
Example 1 was repeated, but the Attagel attapulgite clay was increased to
20 lbs. and the J12MS was increased to 1800 gms. This resulted in a
coating composition which had a pasty, barely pourable viscosity which
could be thinned upon the application of shearing forces thereto. The
thick coating composition or this example was highly suitable for patching
cracks in existing walls and roofs, wherein the viscosity was at the
stop-flow level.
To repair a roof having wide cracks therein, it is preferred that the
cracks be patched with a conventional patching composition, in order to
provide structure to support the coating composition of this invention,
and then the crack is covered with the composition of this Example 2.
Thereafter, the entire roof is preferably covered with the composition of
Example 1. After these compositions have dried, it is then preferred to
coat the entire roof with a conventional acrylic exterior paint, because
of the relatively sticky nature of the dried coating of Example 1, caused
by the high resin content.
The above compositions were formulated for use in Southern Florida and may
require some modification for use in other areas having different
environments, as will be clear to those in the art.
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