Note: Descriptions are shown in the official language in which they were submitted.
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SPRAYABLE COMPOSITION AND METHOD FOR FORMING A FOAMED
OUTDOOR PROTECTIVE COVER LAYER
BACKGROUNiD OF THE INVENTION
The present invention relates to a sprayable foamed composition, and
to a method of spraying the composition for covering a material to be
protected such as soil, refuse at a disposal site, or other material in a
stockpile to form a protective water-resistant layer thereover.
It is common in landfill or dump operations which receive garbage,
trash and/or other deposits during the day to provide a covering layer of
compacted earth approximately six inches to two feet deep at the end of the
day. This earth layer prevents the escape of odors, the blowing of papers
and other trash into the adjacent area, the proliferation of pests such as
flies,
rodents, and birds, and the leaching of toxic ar disagreeable components
from the dumped material. This cover material provision, often termed "daily
cover", is frequently required by municipal, state, and/or federal regulations
which govern such landfill or dump operations.
The task of placing and compacting an earth "daily cover"
represents a very significant porkion caf the landfill operating cost since
it employs significant labor and heavy equipment. Such compacted
earth cover pertorms its principle function ~oniy for a day or sa, that
is, each day's garbage or trash layer is covered at the end of the
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day and further garbage and trash layers are then piled
directly on top of the previous day's "daily cover".
Besides the cost of applying the compacted earth
cover, it is recognized that multiple earth fill layers
used in this way consume a significant volume of the
valuable landfill space which might otherwise be used for
disposal. Many areas are rapidly exhausting their
available landfill acreage and reducing the consumption
rate of the available landfill volume is, accordingly,
desirable.
One solution to the provision of such compacted earth
cover has been proposed and described in U.S. Pat. Nos.
4,421,788 and 4,519,338 in which means are disclosed for
coating the landfill surface with a non-biodegradable
plastic foam spray which, in effect, provides the "daily
cover". An alternate solution to this problem is disclosed
in U.S. Patent Nos. 4,909,667 and 4,927,317 wherein a
canvas or plastic sheet is daily retracted and extended to
protect the working face of the disposal site.
Sprayable compositions have also been proposed for
agricultural and erosion control purposes. U.S. Patent No.
2,802,303 discloses a soil surface treatment utilizing a
mixture of a water-soluble cellulose derivative and a
finely divided expanding lattice clay for control of
natural wind and water erosion of surface soil. The
mixture can be applied dry to the soil surface being
treated or injected into a stream of water to form a slurry
which is sprayed onto the surface.
U.S. Patent No. 3,763,072 discloses a method of
forming a relatively thick semi-impervious crust on soil to
inhibit erosion, or in hydroseeding applications to apply ,
seed, fertilizer, herbicide and fibrous mulch. The method
includes the step of spraying an aqueous composition onto ,
the soil surface and allowing the composition to cure in
the treated soil surface. The aqueous composition contains
an aqueous 100 latex emulsion (for binding soil particles
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together) and sodium silicate (to assist the composition in
penetrating into the soil to prevent the formation of a
. mere surface layer).
U.S. Patent No. 2,961,799 discloses a sprayable latex
composition for treating soil which forms a surface film
intimately bonded to the soil particles. The composition
includes a water-insoluble counter-penetrant (which
inhibits soil penetration by the rubber, and is absorbed
preferably by the soil).
Another method for inhibiting erosion and applying
seed to a soil surface is disclosed in U.S. Patent No.
3,600,852, wherein an aqueous slurry consisting mainly of
gypsum (as a binder material) and a minor amount of seed is
sprayed over a soil surface. The slurry can also contain
~5 minor amounts of fertilizer, high bulking water-absorbing
filler materials such as cellulosic fibers to facilitate
germination, and a set retarder to lengthen the setting
time. Foaming agents may also be used.
Other sprayable or extrudable agricultural mulches are
disclosed in U.S. Patent Nos. 3,812,615 and 4,297,810.
Other soil sealing methods which require the
composition to be mixed with the top layer of soil to
provide a water holding area are disclosed in U.S. Patent
Nos. 3,772,893 and 3,986,365.
SUMMARY OF THE INVENTION
The present invention provides a sprayable composition
for forming an outdoor cover layer over material to be
protected such as, for example, (1) soil, (2) refuse at a
disposal site, a sanitary landfill, or hazardous material
3o iandfill, (3) a stockpile of material such as grain, ash
pits, salt or coal, (4) a temporary cover for remediation
sites, or (5) tire piles (which may optionally be covered
with a netting material before spraying the composition).
When used over soil, the composition can function as a
means of providing erosion control and/or a means for
distributing seed and fertilizer over the soil. The cover
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layer so formed remains ~:~tact for up to 6 to 12 months and
then biodegrades.
The composition includes the following ingredients: ,
(a) a major amount of a bulking/setting material,
such as gypsum or fly ash, for example; .
(b) one or more water soluble polymers, such as a
cellulosic polymer or a super absorbent polymer,
for providing the composition with the desired
film forming, gelling and/or adhesive properties;
and
(c) a carrier such as water for the bulking/setting
material and the polymer such that the
composition, after spraying, becomes
water-resistant, tough and flexible.
Preferably, the composition also includes a foaming
agent to extend the coverage of the composition and enhance
the ability of the composion to adhere to sloping and
vertical surfaces.
The above composition can also include a clay, such as
bentonite, as a non-shrinking inert filler. Furthermore, a
fibrous material, such as paper and/or wood fiber, can be
added to the composition as a filler and a binder for a
matrix formed by the polymer.
A retarder can be included in the above composition to
slow the hardening of the bulking/setting agent to allow
preparation of larger batches at one time.
Other ingredients can be advantageously added to the
composition such as one or more of the following additives:
an anti-dusting agent, a dye, and an odor control agent.
For planting applications, seed and fertilizer can be
added. .
The ingredients are combined with the water carrier to
form an aqueous slurry which is sprayed or spread by other ,
means over the surface being treated.
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The present invention also provides a preferred method
of using the above described sprayable composition to form
a cover layer over material, the method comprising:
(a) mixing the above ingredients in effective
proportions to produce a foamed sprayable slurry;
(b) spraying the foamed slurry at ambient temperature
over the material to form a layer of thickness
sufficient to cover and protect the top of the
material for a predetermined period of time; and
(c) protecting the material by allowing the layer to
set up and form a water-resistant, tough and
flexible cover layer.
The composition, when sprayed, forms a protective,
water-resistant covering layer over material, which has
been found to last up to six months to a year, depending
upon the ambient weather conditions. The resulting
covering layer has the following advantages:
1) easily sprayed at ambient temperature;
2) does not mist in the air when sprayed;
3) tacks down dust or papers that are blown
unwantedly by wind;
4) becomes water-resistant when cured and set up
after spraying;
5) resists cracking even in hot temperatures
~5 including temperatures above 100°F;
6) after setting up, the sprayed layer has decreased
surface penetration by precipitation;
7) reduces volatile emissions and controls odor.
In addition, the present invention concerns an
apparatus for foaming and spraying the above composition.
The apparatus includes means for ensuring the foaming agent
is thoroughly blended in the composition before spraying.
Other advantages of the present invention will be
apparent to one skilled in the art from reading the
following description of the preferred embodiment.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic diagram of an apparatus for
preparing and applying the foamed covering in accordance ,
with the invention.
Fig. 2 is a schematic diagram of a first alternate .
embodiment of the apparatus shown in Fig. 1.
Fig. 3 is a schematic diagram of a second alternate
embodiment of the apparatus shown in Fig. 1.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the following Example 1, there is
provided a listing of ingredients included in a sprayable
composition for forming a cover according to the invention.
The ingredients are given in pounds per 100 gallons of
water. As is described below, the ingredients are mixed
with water to form an aqueous slurry for a sprayed
application. It is preferred to foam the slurry prior to
application.
EXAMPLE 1
Ingredient Quantity
Bulking/Setting Material 150 to 1300 pounds
Water Soluable Polymer 0.5 to 20 pounds
Water 100 gallons
Examples of particular bulking/setting materials which
have been effectively tested, and for which specific
examples are given below, include gypsum (calcium sulfate)
and fly ash. With gypsum, typically the amount used is in
the range of 150 to 350 pounds (per 100 gallons), and
preferably between 250 and 300 pounds. With fly ash of the
reactive type (which is preferred over the nonreactive
type), typically 200 to 1200 pounds are used, and
preferably between 500 and 900 pounds. With fly ash of the ,
nonreactive type, larger amounts can be used, such as
typically between 600 and 1400 pounds, and preferably
between 800 to 1200 pounds.
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Other bulking/setting materials can be used in large
amounts similar to the above. For example, lime (calcium
oxide), cement, pot ash, silicates such as water glass,
cement kiln dust, Portland stone, dolomite, marble, chalk,
and other similar materials can be effectively utilized.
The bulking/setting material is the major ingredient
of the resulting cover. After being mixed with the other
ingredients and water, this material hardens, or "sets",
independent of the surrounding conditions, which gives the
resulting covering a natural drying advantage over other
types of coverings. The hardened material is water
resistant and functions to preserve the cover. The
hardening of the bulking/setting material will occur under
conditions of inclement weather. Covers have been
successfully applied during light to moderate
precipitation. The hardening of the bulking/setting
material also occurs independently from the ambient
temperature.
A gypsum which has been successfully used is a
hemihydrated calcium sulfate, commonly known as #1 Molding
Plaster, and available from U.S. Gypsum in Chicago, Ill. A
preferred flyash is a low sulfur coal derived flyash from
process flue gas.
One or more water soluable polymers are used in the
composition. The polymers are selected to provide dust
control, increase foam height integrity, increase water
resistance, increase adhesion, provide structural
integrity, allow "wet" setting, increase resistance to
cracking, and to help the sprayed composition to bridge
voids.
One preferred type of polymer is a cellulosic polymer.
The cellulosic polymer is water soluble and binds together
the covering by extending long polymer chains therethrough
when wetted. One water soluble cellulosic polymer which
has been successfully used in the composition is
hydroxyethyl cellulose (HEC) polymer. The HEC polymer
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includes naturally occurring or synthetically produced repeating glucose
units in long chains with hydrophilic substituer~t groups added to the
polysaccharide chain to render the polymer miscible. In non-hydrated form,
the polymer chains are folded into a pleated structure to form a very
compact particle. In the presence of water, the polymer molecules bind with
water molecules and the polymer chains unfold to form macromolecules
which greatly exceed the original molecule size. Preferably, the HEC is an R
treated type with a surface coating to slow the rate of molecule hydration to
allow complete unfolding of the polymer chains. When the matrix is dry, the
polymer chains provide strength and cohesion to the covering. The HEC
polymer also increases the water resistance of covering, thereby (at least in
the case of gypsum) decreasing the amount of bulkinglsetting material
needed. The extended polymer chains would naturally refold as the covering
dries, but are prevented from doing so due to the intertwining of the chains
with the other ingredients of the composition.
A preferred HEC Palyrner is Natrosolc~ HHR-250, available from
Hercules Inc. of Wilmington, Del., as are other Natrosol 250 polymers as
well as Natrosol 150 and 300 polymers. Natrosol is produced in four levels of
hydroxyethyl molar substitutes; 1.5, 1.8, 2.5 and 3.0, the polymers being
designated 150, 180, 250 and 300, respectively.
Another water soluble polymer, such as a carboxymethyl cellulose
(CMC) polymer, can be mixed with the HEC polymer. CMC is similar to the
HEC polymer, but includes different hydrophilic substituent groups which
both render the molecules water hydratable and cause the resulting
molecules and polymer chains to be sticky or tacky. Thus, the CMC polymer
causes the slurry to adhere to the surface being covered. This allows
covering of slopes and generally wertica! surfaces. The CMC bonding chain
links are shorter but have a higher number in a specific area than the HEC
polymer. The CMC polymer is also preferably an R treated type with a
surface coating to slow the rate of hydration to allow complete unfolding of
the polymer chains as macromolecules are formed. As the chains unfold,
they become intertwined with the other ingredients of the composition.
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Similar to the HEC polymer, the chains would naturally refold as the covering
dries, but are prevented from doing so due to the intertwining with the other
composition ingredients.
Preferred CMC polymers are CulminalMC 25 and MC 60 which are
available from the Aqualon Company, of Wilmington, Del. As an alternative
(or in addition) to the CMC polymer, guar gum can be added in small
amounted to increase adhesion properties.
When both the HEG and CMC polymers are used, the HEC polymer
primarily functions as a binder for the covering while the CMC polymer
primarily imparts adhesiveness to the composition. When used together with
gypsum, typically the amount of HEC polymer is equal to or slightly greater
than the amount of CMC polymer.
A further type of polymer which has been effectively used {particularly
with fly ash) is a superabsorbent polymer such as a starch grafted sodium
polyacrylate. This type of polymer will hydrate with water to cause sufficient
thickening of the slurry to the extent necessary to suspend the other
ingredients to a uniform consistency.
Water forms the greatest part of the aqueous slurry, being
approximately 65 to 85 percent of the slurry by weight. Water functions as
the carrier for the ingredients and provides the mixing medium for combining
the ingredients. As explained above, the water combines with the polymers
to extend the binding chains. Once the slurry is applied, the majority of the
water leaves the covering by evaporation or leachate action. Only a small
portion of the water is retained in the covering.
While the carrier used herein is preferably water, it has been found
desirable in some instances to use a carrier other than water, as disclosed in
U.S. Pat. No. 5,082,500. For example, if the cover is to be applied to a
refuse site containing organic material, the leachate which is collected at
the
site can be used as a carrier for the ingredients. It is believed that
recycling
the leachate into the site will enhance the natural bacterial action which
acts
to reduce the volume of the organic material, while also eliminating the need
to transport the leachate to a treatment plant
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Other ingredients can advantageously be added to the composition,
such as clay, fibrous material, a foaming agent, a retarder, an antidust
agent, a dye, or an odor cantrol agent.
One or more types of clay can be included in the composition as a
bulking aid which provides an inert filler for the cover. In addition, the
clay
assists the polymer in absorbing orate and allowing the bulking/setting
material to "wet set". The clay further increases the foam integrity, and adds
color to the composition. As known in the art, clay comprises a group of
crystalline, finely divided earthy materials generally considered to be
hydrates of alumina and silica, with iron oxide and magnesia as common
minor components.
The preferred clay ingredient of the composition is a bentonite
clay, typically used in the range of 10 to 75 pounds (per 100 gallons
of water) and preferably abaut 10 to 50 pounds. However, kaalin,
attapulgite and montmorillonite clays also can be used. Other .suitable
clays are set forth in an IMV bulletin entitled MVITONE~3 TM
organoclays and clay products, Bentonite-Hectorite-Saponite-~epcolite.
Suitable clays have relatively small particle sizes, being in the range of 60
to
325 mesh size. Elentanite particle size is determined during crushing of
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the clay. The particles do not break down into smaller
particles during mixing of the solution. A suitable
bentonite clay has a mesh size of 200 mesh and is available
from NL Bariod Supplies.
. 5 A small amount of attipugite clay can be combined with
the bentonite to provide thickening of the aqueous slurry.
Typically, 1 to 15 pounds (and preferably about 2 to 10
pounds) of attipugite are added per 100 gallons of water.
When the aqueous slurry is foamed, as will be described
below, the attipugite provides a gelling aid to add
stability to the foamed slurry allowing the slurry to
bridge and not collapse upon itself. Typical types of
attipugite clay which have been successfully used include
hectorite, saponite and sepcolite, all of which can be
obtained from NL Bariod Supplies.
The fibrous material provides additional non-shrinking
filler and a binder for the polymer matrix which adds mass
and toughness to the resulting covering, and helps the
covering bridge voids. Typically, about 25 to 125 pounds
of fibrous material are added, and preferably about 60 to
90 pounds.
The fibrous material preferably comprises cellulose
fibers, such as shredded paper formed from recycled
newspapers. However, any small particles of paper
including cardboard bag house material can be used. Under
the mechanical agitation of the mixing process (described
below), the paper fiber is loosened to form smaller fiber
sizes of a random nature. Thus, any small grind of
recycled newsprint will be satisfactory.
Wood fiber formed from shredding wood scraps and
recycled wood products can also be used as an alternative
in addition to the paper fibers. The individual wood
fibers are much longer in length than in diameter. The
edges of the wood fibers include microscopic hooks formed
by the shredding process. The hooks function to engage the
other fibers and polymer chains.
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Other sources of the fibrous material include fibers formed from rice
paper, straw and textile fibers such as cotton linens. A combination of the
various fibrous materials has been successfully used in the composition.
With respect to the non-paper fibrous materials, it is preferred that the
fibers
are short in length and thin in diameter, having a maximum length of
approximately'/Z inch and an average diameter of less than approximately'/4
inch.
As described above, it is preferred to include a foaming agent in the
composition to produce a foamed slurry. The foaming agent functions to
expand the slurry by entraining air therein. The resulting foamed slurry has a
lowered density which both helps adhesion and lowers the cost of the
coating. The foamed slurry also contains a higher dispersion of the
ingredients to produce a more uniform and consistent coating. Foaming
agents are typically liquid, ands as described below, from one quart to two
gallons of a foaming agent per 100 gallons of water has been successfully
used to form a foamed slurry.
Preferred foaming agents include Merle~ 3005, which is available
from The Mearl Corporation of Raselle Park, N.J., or Foam X~, which is
available from ChemTech of Canton, Ohio, as a foaming agent.
In order to utilize larger volumes of slurry, a retarder can be included
to slow the hardening of the bulkinglsetting material to allow adequate time
for mixing and spraying the larger volume of slurry before the slurry hardens.
With either gypsum or flyash, it has been found that from 0.1 to 1.0 pound of
a retarder (such as sodium citrate) per 100 gallons of water sufficiently
delays the hardening of the bulkingisetting material to allow coverage of a
large surface area with a single batch of slurry.
An anti-dust agent carp be included to control dusting
when the dry ingredients are being added to the water
carrier. From one to five pounds of anti-dust agent added
to the ingredients shown in the above tables has been found
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to be workable. It is preferred to use from 0.1 to 5
pounds of anti-dust agent per 100 gallons of water with
about 0.5 pounds being preferred. A preferred anti-dust
agent is a blend of propylene glycol and N-60 Surfactant in
a 9 to 1 ratio. Propylene glycol is a common industrial
solvent. Both the glycol and surfactant are available from
TAG Chemical in Lakewood, Ohio.
A colorant such as a dye can be included in the slurry
to add an aesthetic quality of color. Proper selection and
use of a color can cause the cover to blend in with the
natural setting, thereby drawing less attention to the
operation. Both brown and green alkali/acid based dyes
have been used successfully.
In addition, when the cover is applied to a refuse
site, an odor control agent can be added to the slurry.
A preferred formulation of the protective cover which
utilizes gypsum includes the following ingredients, as
shown in the following Example 2:
EXAMPLE 2
Ingredient Quantity
Gypsum 200 to 350 pounds
Cellulosic Polymer 1 to 20 pounds
Clay 2 to 40 pounds
Fibrous Material 50 to 100 pounds
Water 100 gallons
A very effective formulation of the composition
includes the following ingredients, as shown in the
following Example 3:
EXAMPLE 3
Ingredient Quantity
Gypsum 250 to 300 pounds
Cellulosic Polymer 2 to 10 pounds
Clay 20 to 35 pounds
Fibrous Material 60 to 80 pounds
Retarder 0.1 to 0.5 pounds
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Foaming Agent 1 qt. to 2 gallons
Water 100 gallons
A preferred formulation of the protective cover which
utilizes reactive type fly ash includes the following ,
ingredients, as shown in the following Example 4:
EXAMPLE 4
Ingredient Quantity
Reactive Flyash 400 to 1200 pounds
Cellulosic Polymer 0 to 5 pounds
Superabsorbant Polymer 0.1 to 5 pounds
Clay 5 to 100 pounds
Fibrous Material 0 to 100 pounds
Water 100 gallons
A very effective formulation of the reactive fly ash
composition includes the following ingredients, as shown in
the following Example 5:
EXAMPLE 5
Ingredient Quantity
Reactive Flyash 600 to 1200 pounds
Cellulosic Polymer 0 to 3 pounds
Superabsorbant Polymer 0.5 to 3 pounds
Clay 40 to 60 pounds
Fibrous Material 0 to 100 pounds
Retarder 0.3 to 0.7 pounds
Foaming Agent 1 qt. to 2 gallons
Water 100 gallons
In the above examples, a cellulosic polymer (such as
CMC) is used when increased adhesion properties are
required. Also, when a large amount of flyash (e. g. 1200
pounds) is used, typically little or no fibrous material is .
required.
If nonreactive flyash is used, for the above Examples
4 and 5, typically about 200 to 300 additional pounds are
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required per 100 gallons of water. In this case, it has
been desirable to use both HEC and CMC cellulosic polymer.
The above listed ingredients are mixed with the water
on site, typically in a portable apparatus as shown
. 5 schematically in Fig. 1 at 10. The apparatus 10 has a
slurry mixing and storage tank 11. A variable speed mixer
14 fitted with multiple, medium pitched mixing paddles 15
is mounted upon the tank 11 for mixing the tank contents.
A pump inlet line 16 connects the tank 11 to an inlet
17 of a hydraulic pump 18. Positive displacement sludge
pumps having 100 to 150 psi output pressure have been
successfully used for the hydraulic pump 18.
The pump 18 has an outlet 19 connected through a pump
discharge line 20 to an inlet port 21 of a three-way two
position recirculation valve 22. The recirculation valve
22 has a first outlet port 23 connected through a discharge
line 24 to a spray cannon 25 and a second outlet port 26
connected through an intermediate line 27 to a first
injection fitting 28. The first injection fitting 28
discharges through a recirculation line 29 into the tank 11
in close proximity to the mixing paddles 15.
The first injection fitting 28 has an injection port
connected by a foam discharge line 31 to an outlet port
32 of a foam nozzle 33. The foam nozzle 33 has an inlet
25 port 35 connected by a foam intermediate line 36 to the
discharge of a second injection fitting 37. The second
injection fitting 37 receives compressed air through a
first air line 38 from an air compressor 39. The second
injection fitting 37 has an injection port 40 connected
30 through a supply line 41 to a pressure tank 42. The
pressure tank 42 contains liquid foaming agent and is
pressurized by compressed air supplied through a second air
line 43 which branches from the first air line 38.
The entire apparatus 10 is typically mounted upon a
trailer (not shown) for towing to the work site. A mixing
and storage tank 11 having a 1700 gallon capacity has been
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successfully used in this manner, although smaller tanks
also have been used. The spray cannon 25 can be mounted
upon a platform (not shown) attached to the top of the tank
11 to provide maximum coverage of the surface being
sprayed. Spraying distances of 75 to 200 feet have been .
successfully achieved with the apparatus 10. A hose on a
reel and a small nozzle (not shown) can also be included
with the apparatus 10 for covering small areas.
To use the apparatus 10, the required amount of water
is first added to the tank 11. The tank 11 is not
completely filled, leaving an empty space to receive the
volume increase when the slurry is foamed. With the mixer
14 operating at high speed, the appropriate amount of
ingredients listed above are fed into the tank 11. The
high mixer speed is required because the ingredients do not
bond chemically, but are held together in a matrix bound by
polymer chains. High shear mixing, as provided by the
paddles 15 when rotated at high speed, is required for
proper matrix formation. The ingredients are mixed by the
paddles 15 with the water for several minutes until an
uniform slurry is formed.
If fibrous material is used, an additional 10 minutes
of mixing is typically needed to throughly coat the fibrous
material with the slurry. If paper fibers are used, the
mixing further reduces the size of the fibers.
The recirculation valve 22 is positioned to discharge
through the second outlet port 26 and the pump 18 started
to recirculate the slurry through the injection fitting 28
and back into the tank 11. The recirculation continually
agitates the slurry to assure through mixing and slow the
hardening thereof.
The slurry is foamed by injecting foam into the slurry
stream through the first injection fitting 28. The air _
compressor 39 is started to supply compressed air through
lines 38 and 43 to the pressure tank. The compressed air
pressurizes the pressure tank 42, forcing liquid foaming
'~JO 94/15886 PCT/US94I00618
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agent through the supply line 41 and into the second
injection fitting 37. The second injection fitting 37
injects the liquid foaming agent into the compressed air
flowing through the first air line 38. The combined
foaming agent and compressed air passes through the foam
intermediate line 36 and into the foam nozzle 33 to
generate foam. The foam flows through the foam discharge
line 31 to the first injection fitting 28 which injects the
foam into the stream of slurry to form foamed slurry. The
foamed slurry is returned to the tank 11 through the
recirculation line 29. The mixing paddles 15 blend the
foamed slurry into the unfoamed slurry, decreasing the
density of the mixture while increasing the volume thereof.
Blending is assured by the discharge of the recirculation
line 29 being located near the mixing paddles 15.
Foam continues to be added to the slurry until the
desired density of foamed slurry is formed. Typically, a
ratio of one part of nonfoamed slurry to three parts of
foamed slurry is used to form a cover. Thus, 300 gallons
of nonfoamed slurry is combined with foam to produce 900
gallons of foamed slurry for application. Successful
covers have also been formed using ratios of foamed to
nonfoamed slurry of 1 to 1, 1 to 2 and 1 to 5.
Once the foamed slurry reaches the desired density,
the recirculation valve 22 is positioned to discharge
through the first outlet port 23, causing the foamed slurry
to be pumped through the discharge line 24 to the spray
cannon 25. The spray cannon 25 sprays the foamed slurry
onto the surface being coated.
A second embodiment of the apparatus is shown at 50 in
Fig. 2. The second embodiment 50 differs from the
apparatus 10 shown in Fig. 1 in that a foam discharge line
31A supplies the foam directly into the tank 11 in close
proximity to the mixing paddles 15. Accordingly, the first
injection fitting 28 shown in Fig. 1 has been eliminated
form the second embodiment 50. The other components of the
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second embodiment 50 which are similar to the components
shown in Fig. 1 are numbered the same.
A third embodiment of the apparatus is shown at 60 in .
Fig. 3. The third embodiment 60 differs from the
previously described apparatuses 10 and 50 in that a foam
discharge line 31B supplies the foam to a regulating valve
51 which is inserted into the discharge line 24 between the
recirculation valve 22 and the spray cannon 25. The
regulating valve 51 injects the foam into the stream of
slurry flowing through the discharge line 24. Accordingly,
the first injection fitting 28 shown in Fig. 1 has been
eliminated from the third embodiment 60. The regulating
valve 51 is adjusted to inject a sufficient quantity of
foam to produce the desired density for the foamed slurry.
A blending chamber 62 having a plurality of mixing blades
64 is connected between the valve 51 and the spray cannon
to ensure the foam and slurry are thoroughly mixed
before spraying. In addition, a control 66 is provided to
automatically adjust the valve 51 and/or the speed of the
20 pump 18 to achieve the desired foaming of the slurry. The
other components of the third embodiment 60 which are
similar to the components shown in Fig. 1 are numbered the
same.
As described in the above tables, the density of the
25 foam layer depends upon the degree to which the slurry has
been foamed. From one quart to two gallons of foaming
agent are added to the composition for every 100 gallons of
water. The amount of foaming agent added to the mixture
determines the density of the foamed slurry.
The thickness of the foam layer covering depends upon
the amount of foamed slurry sprayed onto the surface being
coated. A foam layer of one eighth to one quarter inch
thick has been found to form a successful cover having a
thickness of one sixteenth to one eighth inch thick after
drying. The cover takes approximately one hour to dry at
an ambient temperature of 70° F. Drying occurs faster at a
~'VO 94/15886 PCT/US94/00618
warmer ambient temperature and slower with a lower ambient
temperature. However, the sprayed foam will function as a
. cover even when not dry as the polymer matrix binds
together the ingredients.
The amount of bulking/setting agent included in the
foamed slurry provides a cover lifetime of up to six months
to a year, after which the cover breaks up and biodegrades.
The cover resists cracking, even in temperatures in excess
of 100°F. The cover lifetime will vary with the
environment. Exposure to severe weather causes the shorter
lifetime of approximately six months while exposure to mild
environments typically extends the cover lifetime to the
upper value of approximately one year.
As described above, the foamed slurry is continuously
agitated by the mixer 14 prior to application.
Furthermore, the foamed slurry should be applied
immediately due to the limited time available before the
slurry sets up and becomes unpumpable. A 200 gallon flush
tank containing water (not shown) is typically included
with the apparatus 10 to flush the equipment after the
cover is applied. Since the cover is not affected by
additional water after application, the flushing can be
carried out by spraying flushed material onto the sprayed
area.
As an alternative to the above described spray cannon
25, the foamed slurry can be applied by using a spreader
bar equipped with spray jets.
While the above description has included a foaming
agent, for an extremely hard tough surface coat, a minimum
or no foaming agent is added, with no change in setting
time. When no foaming agent is used, a surfactant is
included to assure a uniform application. Useful
surfactants include biodegradable non-ionic materials such
as ethoxylated nonyl phenol (6 mole adduct) that is both
water and oil soluble. A suitable non-ionic surfactant is
N-60 available from Tag Chemical, as previously mentioned.
WO 94/15886 PCT/US94/00618
~1~~'~9~
. -20-
For hydroseeding applications, seed and fertilizer can be
added to the slurry to provide a plant covering to retain
the soil after the covering biodegrades. ,
In accordance with the provisions of the patent
statutes, the principle and mode of operation of this ,
invention have been explained and illustrated in its
preferred embodiment. However, it must be understood that
this invention may be practiced otherwise than as
specifically explained and illustrated without departing
from its spirit or scope.
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