U.S. patent number RE32,476 [Application Number 06/855,001] was granted by the patent office on 1987-08-18 for consolidation of aggregate material.
This patent grant is currently assigned to Minnesota Mining and Manufacturing Company. Invention is credited to John F. Kistner.
United States Patent |
RE32,476 |
Kistner |
August 18, 1987 |
Consolidation of aggregate material
Abstract
Aggregate material is contacted with a fluid agent comprising a
hydrophilic urethane prepolymer to form a hydrophilic
polyurethane-polyurea polymeric matrix which adhesively bonds the
aggregate together as a resilient, integral, water-permeable mass
which will sustain plant growth. This is a Reissue of a Patent
which was the subject of a Reexamination Certificate No. [B1
3,805,532], dated [Jul. 16, 1985], Request No. [90/000,598], [Jul.
30, 1984].
Inventors: |
Kistner; John F. (Oakdale,
MN) |
Assignee: |
Minnesota Mining and Manufacturing
Company (St. Paul, MN)
|
Family
ID: |
27379012 |
Appl.
No.: |
06/855,001 |
Filed: |
April 22, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
100378 |
Dec 21, 1970 |
4417004 |
|
|
Reissue of: |
190358 |
Oct 18, 1971 |
03805532 |
Apr 23, 1974 |
|
|
Current U.S.
Class: |
405/264; 521/99;
521/905; 47/58.1R |
Current CPC
Class: |
C08G
18/10 (20130101); C08G 18/4833 (20130101); A01G
24/42 (20180201); A01G 24/35 (20180201); C09K
17/30 (20130101); E02B 3/16 (20130101); C08G
18/10 (20130101); C08G 18/302 (20130101); C08G
2310/00 (20130101) |
Current International
Class: |
C09K
17/30 (20060101); C08G 18/48 (20060101); C08G
18/00 (20060101); E02B 3/16 (20060101); E02B
3/00 (20060101); C09K 17/14 (20060101); C08G
18/10 (20060101); A01G 9/10 (20060101); A01G
009/10 (); C08G 018/14 (); E02D 003/12 () |
Field of
Search: |
;166/295 ;405/264
;71/1,28 ;523/131,132 ;521/100,99,116,120,905,902,904 ;47/58 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Novosad; Stephen J.
Attorney, Agent or Firm: Sell; D. M. Smith; J. A. Truesdale;
C.
Parent Case Text
This application is a continuation-in-part of my copending
application filed Dec. 21, 1970, Ser. No. 100,378, .Badd.now U.S.
Pat. No. 4,417,004.Baddend..
Claims
What is claimed is: .[.
1. A method for consolidating aggregate material to form a
resilient, integral, water-permeable mass which comprises
contacting said aggregate material with a fluid agent comprising a
hydrophilic urethane prepolymer having a plurality of oxyethylene
units in its polymer backbone, and curing said prepolymer with
sufficient water to form a hydrophilic cellular polymer which bonds
said aggregate together, said prepolymer being used in an amount
sufficient, when cured, to bond said aggregate to form said
water-permeable mass..].
2. The method according to claim .[.1.]. .Iadd.18, .Iaddend.wherein
said aggregate material comprises superficial soil. 3. The method
according to claim .[.1.]. .Iadd.18, .Iaddend.wherein said
aggregate material and said prepolymer are physically intermixed
before being contacted with water. 4. The method according to claim
.[.1.]. .Iadd.18, .Iaddend.wherein said prepolymer and water are
sprayed onto said aggregate material, followed by curing of said
prepolymer. 5. The method according to claim .[.1.]. .Iadd.18,
.Iaddend.wherein said fluid agent further comprises a minor amount
of a surfactant. 6. The method according to claim .[.1.].
.[..[.8,.]..]. .Badd.18 .Baddend. wherein said prepolymer has the
formula
where Y.sub.1 is an active hydrogen-free residue of a compound
having a plurality of active hydrogen atoms, (RO).sub.o is a
hydrophilic polyoxyalkylene chain having a plurality of oxyethylene
units, o is the number of oxyalkylene units in said chain, Y.sub.2
is an organic linkage bonding said chain to the isocyanate moieties
shown in said formula, p is 1 to 5, and z is the number of said
active hydrogen atoms in said compound from which Y.sub.2 is
derived. 7. A method .[.for consolidating aggregate material to
form a resilient, integral, water-permeable mass which comprises
contacting said aggregate material with a fluid agent comprising a
hydrophilic urethane prepolymer and curing said prepolymer with
sufficient water to form a hydrophilic cellular polymer which bonds
said aggregate together,.]. .Iadd.according to claim 18, wherein
.Iaddend.said prepolymer having the formula ##STR3## where Y.sub.1
is an active hydrogen atom-free residue of a compound having a
plurality of active hydrogen atoms, R' is an aromatic nucleus
derived from an organic polyisocyanate, o is the number of
oxyethylene units shown in said formula, p is 1 to 3, and z is 2 to
3.[.; said prepolymer being in an amount sufficient, when cured, to
bond said aggregate to form said
water-premeable mass.].. 8. The method according to claim 7 wherein
said compound from which Y.sub.1 is derived is ethylene glycol, R'
is tolylene, o is about 21, p is 1, and z is 2. .[.9. The method
according to claim 7, wherein said aggregate material and said
prepolymer are physically intermixed before being contacted with
water..]. .[.10. The method according to claim 7, wherein said
prepolymer and water are sprayed onto said aggregate material,
followed by curing of said prepolymer..]. .[.11. The method
according to claim 7, wherein said fluid agent further comprises a
minor amount of a surfactant..]. .[.12. A resilient, integral,
water-permeable mass comprising aggregate material bonded in a
water-insoluble cellular, hydrophilic polyurethane-polyurea polymer
matrix, said polymer being derived from a hydrophilic urethane
prepolymer having a plurality of oxyethylene units in its polymer
backbone..]. 13. A .[.resilient mass.]. .Iadd.potting media
.Iaddend.in accordance with claim .[.1.]. .Iadd.19,
.Iaddend.wherein said aggregate is superficial soil. 14. A
.[.resilient, integral water-permeable mass comprising aggregate
material bonded in a water-insoluble, cellular, hydrophilic
polyurethane-polyurea polymer matrix.]. .Iadd.potting media of
claim 19, .Iaddend.said polymer being derived from a prepolymer of
the formula ##STR4## where Y.sub.1 is an active hydrogen atom-free
residue of a compound having a plurality of active hydrogen atoms,
R' is an aromatic nucleaus derived from an organic polyisocyanate,
o is the number of oxyethylene units shown
in said formula, p is 1 to 3, and z is 2 to 3. 15. A resilient mass
according to claim 14 wherein said compound from which Y.sub.1 is
derived is ethylene glycol, R' is tolylene, o is about 21, p is 1,
and z is 2. .[.16. A resilient mass in accordance with claim 14,
wherein said aggregate is wood pulp, ground tree bark, sawdust,
ground corn cobs, wheat
hulls, peat moss, or other organic matter..]. .Iadd.17. A method
for forming potting media comprising mixing aggregate material with
a fluid agent comprising a hydrophilic urethane prepolymer having a
plurality of oxyethylene units in its polymer backbone and water to
form a slurry, the weight ratio of water to prepolymer being in the
range of 1:1 to 5:1 and said prepolymer comprising about 1 to 40
weight percent based on the weight of the aggregate material,
pouring said slurry into a mold and allowing said prepolymer to
cure to form a porous cellular, cohesive resilient, integral,
water-permeable, hydrophilic, flexible, spongy, breathable, cast
potting media for supporting plant growth. .Iaddend. .Iadd.18. The
method according to claim 17, wherein said prepolymer comprises 3
to 20 weight percent, based on the weight of the aggregate
material. .Iadd.19. A resilient, integral, water-permeable,
hydrophilic, breathable potting media comprising aggregate material
bonded in a water-insoluble, cellular, hydrophilic
polyurethane-polyurea polymer matrix, said polymer matrix being the
reaction product of a hydrophilic urethane prepolymer having a
plurality of oxyethylene units in its polymer backbone and water,
the weight ratio of water to prepolymer forming the reaction
product being 1:1 to 5:1 and the amount of prepolymer used to form
the polymer matrix being about 1 to 40 weight percent based on the
weight of the aggregate material in the potting media. .Iaddend.
.Iadd.20. The potting media of claim 19 wherein said aggregate is
selected from soil, perlite, vermiculite, wood pulp, ground tree
bark, sawdust, ground corn cobs, wheat hulls, peat moss, and other
organic matter. .Iaddend. .Iadd.21. The potting media according to
claim 19, wherein the amount of prepolymer used to form the polymer
matrix is 3 to 20 weight percent, based on the weight of the
aggregate material. .Iaddend. .Badd.22. A method for forming
potting media comprising mixing aggregate material with a fluid
agent comprising a hydrophilic urethane prepolymer having a
plurality of oxyethylene units in its polymer backbone and water to
form a slurry, the weight ratio of water to prepolymer being at
least 1:1 and said prepolymer comprising about 1 to 40 weight
percent based on the weight of the aggregate material, pouring said
slurry into a mold and allowing said prepolymer to cure to form a
porous cellular, cohesive resilient, integral, water-permeable,
hydrophilic, flexible, spongy, breathable, cast potting media for
supporting plant growth. .Baddend.
.Badd.23. A method for forming potting media comprising mixing
aggregate material with a fluid agent comprising a hydrophilic
urethane prepolymer having a plurality of oxyethylene units in its
polymer backbone and water to form a slurry, the weight ratio of
water to prepolymer being in the range of 1:1 to 20:1 and said
prepolymer comprising about 1 to 40 weight percent based on the
weight of the aggregate material, pouring said slurry into a mold
and allowing said prepolymer to cure to form a porous cellular,
cohesive resilient, integral, water-permeable, hydrophilic,
flexible, spongy, breathable, cast potting media for supporting
plant growth. .Baddend. .Badd.24. A resilient, integral,
water-permeable, hydrophilic, breathable potting media comprising
aggregate material bonded in a water-insoluble, cellular,
hydrophilic polyurethane-polyurea polymer matrix, said polymer
matrix being the reaction product of a hydrophilic urethane
prepolymer having a plurality of oxyethylene units in its polymer
backbone and water, the weight ratio of water to prepolymer forming
the reaction product being at least 1:1 and the amount of
prepolymer used to form the polymer matrix being about 1 to 40
weight percent based on the weight of the aggregate material in the
potting media. .Baddend. .Badd.25. A resilient, integral,
water-permeable, hydrophilic, breathable potting media comprising
aggregate material bonded in a water-insoluble, cellular,
hydrophilic polyurethane-polyurea polymer matrix, said polymer
matrix being the reaction product of a hydrophilic urethane
prepolymer having a plurality of oxyethylene units in its polymer
backbone and water, the weight ratio of water to prepolymer forming
the reaction product being 1:1 to 20:1 and the amount of prepolymer
used to form the polymer matrix being about 1 to 40 weight percent
based on the weight of the aggregate material in the potting media.
.Baddend.
Description
FIELD OF THE INVENTION
This invention relates to stabilization or consolidation of
aggregate material. In another aspect, this invention relates to in
situ stabilization of superficial or surface-lying aggregate
material. In another aspect, this invention relates to
consolidation of aggregate material for agricultural purposes to
form an integral, water-permeable mass.
BACKGROUND OF THE INVENTION
Consolidation or stabilization of aggregate materials is generally
undertaken to provide a tough, rigid, water-permeable consolidated
mass in which some structural strength is inherent. It would be
extremely desirable to provide aggregate material with a degree of
consolidation while allowing the consolidated mass to retain some
of the characteristics of the aggregate material, e.g.,
water-permeability and the ability to sustain growth of plant life.
In order to accomplish this, it is apparent that the consolidated
aggregate must be somewhat porous to allow the roots of plant life
to obtain oxygen and water vital to sustain growth.
One area where there is a need for the benefits afforded by this
invention is in the nursery practice of potting plants or seeds for
germination and later transplant. Normally, pots are packed with a
growing media such as black dirt, peat moss, etc., which is a time
consuming and costly operation. For those nurseries which ship
potted plants, substantial freight costs are incurred from the
weight of the pots and potting media. Also, the consumer must
remove each plant from its pot prior to transplant, again a
time-consuming operation.
Another area where a need for the benefits afforded by this
invention is apparent is surface area receiving heavy pedestrian
traffic such as a playground, backyard play area, or park. These
areas usually have bare spots resulting from abrading away of the
grass or other cover growth and compaction of the soil inhibiting
access of air and water to the roots of said cover growth.
Stabilization of such areas to wear and compaction would be
desirable but of necessity would require the ability to maintain
grass or other cover growth.
Hillsides or sandy slopes or other surface areas which are
susceptible to erosion from the action of rain and wind, and on
which cover growth is difficult to maintain provide still another
area where this invention can be of benefit.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a method for
consolidating aggregate materials to form a resilient, integral,
water-permeable mass by contacting these materials with a fluid
agent comprising a hydrophilic urethane polymer and curing the
prepolymer with sufficient water to form a hydrophilic cellular
polymer which bonds the aggregate material together.
The novel consolidated material is flexible, resilient,
non-compactible, i.e., having a spongy nature, and is hydrophilic
and water-permeable (i.e., water will diffuse or permeate through
the consolidated mass).
Aggregate material suitable for contacting in accordance with the
invention is generally solid particulate matter such as soil (e.g.,
black dirt, sand), and can include mineral aggregate (e.g.,
perlite, vermiculite), organic matter (e.g., wood pulp, ground tree
bark, sawdust, ground corn cobs, wheat hulls, peat moss), or
synthetic aggregate (e.g., ground glass).
The urethane prepolymer or isocyanate-terminated prepolymer useful
in this invention is in general a reaction product of a material
having a plurality of active hydrogen atoms, such as polyols, with
an amount of organic polyisocyanate (or polyisothiocyanate) in
excess of stoichiometry. The fluid agent comprising the urethane
prepolymer is advantageous in that it is a one-part system,
requiring no elaborate equipment for preparation or for application
thereof to the aggregate material, with water being the only
necessary co-reactant material.
DETAILED DESCRIPTION OF THE INVENTION
The aggregate material can in general be contacted by physically
mixing the fluid agent with the aggregate material to be
consolidated and then adding water to the mixture to effect the
curing, i.e., polymerizing or cross-linking, reaction. For
superficial or surface-lying aggregate, contacting is generally
obtained by spraying the aggregate with the prepolymer fluid agent
and water to provide a thin, polymeric layer overlying and
adhesively bonding to the superficial aggregate.
The urethane prepolymers useful in this invention are known in the
art and in general can be prepared by reacting a material having a
plurality of active hydrogen atoms, such as polyols, with an amount
of organic polyisocyanate (or polyisothiocyanate) in excess of
stoichiometry. The equivalent ratio of isocyanate moiety, --NCO, to
active hydrogen will be at least 2/1, and preferably at least 2.1/1
to 2.5/1, and can be as high as 4/1 or even higher.
The mechanism of the urethane prepolymer-water reaction is well
known; it results in the formation of urea linkages, the water
acting as a chain extender, and in the evolution of carbon dioxide
which tends to foam the reaction mixture to form a cellular
polymer.
One useful class of prepolymers which can be used in this invention
are those which are water-miscible and can be expressed in terms of
the formula
where Y.sub.1 is an active hydrogen-free residue of a compound
having a plurality of active hydrogen atoms, e.g., polyhydroxy
alkane or polyamino alkane such as ethylene glycol or ethylene
diamine; (RO).sub.o is a hydrophilic polyoxyalkylene chain having a
plurality of oxyethylene units, such as (1) a polyoxyethylene chain
(the preferred type of chain), (2) a chain having alternating
blocks or backbone segments of oxyethylene and oxypropylene units,
or (3) a chain of randomly distributed oxyethylene and oxypropylene
units; 0 is the number of oxyalkylene units in the polyoxyalkylene
chain; Y.sub.2 is a linkage or bridge the function of which is to
bond the polyoxyalkylene chain to the isocyanate moieties shown in
the formula; p is the number of isocyanate moieties and generally
will be 1 to 5, preferably 1 to 3; and z is a number equal to the
functionality, or number of this plurality of active-hydrogen
atoms, in said compound (e.g., said polyhydroxyalkane or
polyaminoalkane) which provides the residue Y.sub.1 and generally z
will be 2 to 6. Where the prepolymer is prepared by reacting a
polyol and a polyisocyanate, the polyoxyalkylane chain will be
terminated with --OC(O)NH--R'(--NCO).sub.p, where --OC(O)NH-- is a
carbamate (or urethane) group resulting from the reaction of a
hydroxyl group from the polyol precursor with an isocyanate moiety
from the polyisocyanate precursor, R' is the residue or nucleus of
the polyisocyanate precursor (which will be tolylene where the
polyisocyanate precursor is tolylene diisocyanate), and p is an
integer equal to q-1, where q is the number of isocyanate moieties
of the polyisocyanate precursor.
The term "active hydrogen atom" as used herein refers to a hydrogen
atom which reacts with the isocyanate moiety under urethane or urea
bond forming conditions. The term "water-miscible" in this context
means the prepolymer is dispersible (or soluble) in water.
A useful subclass of water-miscible prepolymers within the scope of
formula I are those of the formula ##STR1## where Y.sub.1, R', o,
and z are defined above, R' is tolylene, o is the number of
oxyethylene units shown, p is 1 to 3, and z is equal to the
functionality, e.g., 2 or 3, of said compound from which Y.sub.1 is
derived.
Another subclass of water-miscible prepolymers useful in the
consolidation of aggregate according to this invention can be
expressed by the formula ##STR2## where Y.sub.1, R', and z are as
defined above in formula II, and a, b, and c are integers such that
the ratio of (a+c)/b is greater than 1 (and thus the prepolymers
are water-miscible).
Commercially available polyol precursors useful in making the
above-described water-miscible isocyanate-terminated prepolymers
used in this invention are the hydrophilic
poly-(oxyethylene-oxypropylene) polyols sold under the trademark
"Pluronic," such as Pluronic L35, F38, and P46, and hydrophilic
polyols with heteric oxyethylene-oxypropylene chains sold as
"Polyol Functional Fluids," such as WL-580, WL-600, and WL-1400.
Generally, the hydrophilic or water-soluble oxyethylene-containing
polyols to be used will have molecular weights of at least 200 and
as high as 8000; preferably they will have molecular weights of 600
to 2000. Lower molecular weight polymers, i.e., below about 600,
are liquids having decreasing solubility in water. When used in
this invention they provide decreased hydrophilicity and increased
hardness or rigidity and friability to the consolidated aggregate
mass. Conversely, higher molecular weight polymers, i.e., greater
than about 2000, tend to provide solid prepolymers which require
solvation when used in the invention. These also provide increased
rigidity or hardness to the consolidated aggregate mass, but are
extremely hydrophilic. This increased hydrophilicity causes
swelling of the consolidation when saturated with water, affording
a wrinkled effect. A preferred polyol (particularly when reacted
with tolylene diisocyanate to form the prepolymer) is "Carbowax"
1000, which is a polyethylene glycol having a molecular weight of
about 1000.
Polyisocyanates which can be used to prepare the
isocyanate-terminated prepolymers used in this invention and
described above include conventional aliphatic and aromatic
polyisocyanates. The preferred polyisocyanates to be used will be
aromatic polyisocyanates because the prepolymers made therefrom
will generally react faster with water. One of the most useful
polyisocyanate compounds which can be used for this purpose is
tolylene diisocyanate, particularly as a blend of 80 weight percent
of toluene-2,4-diisocyanate, and 20 weight percent of
toluene-2,6-diisocyanate. A 65:35 blend of the 2,4- and 2,6-isomers
is also useful. These polyisocyanates are commercially available
under the trademark Hylene TM, Nacconate 80, and Mondur TD-80.
Other useful polyisocyanate compounds which can be used are other
isomers of tolylene diisocyanate, hexamethylene-1,6-diisocyanate,
diphenylmethane-4,4'-diisocyanate, m- or p-phenylene diisocyanate,
and 1,5-naphthalene diisocyanate. Polymeric polyisocyanates such as
polymethylene polyphenyl polyisocyanates can also be used, such as
those sold under the trademarks Mondur MRS and PAPI. A list of
useful commercially available polyisocyanates is found in
"Encyclopedia of Chemical Technology," by Kirk and Othmer, 2nd Ed.,
Vol. 12, pp. 46-47, Interscience Pub., (1967).
The prepolymers per se used in this invention are generally very
viscous liquids and though they can be used by themselves as
treating agents, it is preferred to employ the same in the form of
a solution in a suitable solvent which is non-reactive with the
isocyanate moiety. Thus, organic solvents, or other organic
compounds which contain active hydrogen atoms are to be avoided in
making up and using the prepolymer agents of this invention.
Generally these solvents can be water-miscible polar organic
solvents, preferably volatile at ambient conditions. Alternatively,
the solvent can be a water-immiscible organic solvent which
volatilizes under ambient conditions and escapes to the atmosphere
from the treated mass of aggregate. Representative solvents which
can be used include acetone, tetrahydrofuran, methyl ethyl ketone,
methylene chloride, toluene, and methoxyethylacetate. Water itself
can be used as a solvent though the resulting solution will have to
be applied to the aggregate before the curing of the prepolymer
takes place. By controlling the temperature of the aqueous
solution, the hiatus between making up the aqueous solution and its
application to the aggregate can be varied; the lower the
temperature, the longer the pot-life of the solution. The
concentration of the prepolymer in the solvent can vary, depending
upon such factors as the viscosity desired, the technique of
treating the aggregate, and the amount of materials such as grass
and fertilizer contained in the solution. Generally concentrations
of 5 to 90 weight percent, will be suitable.
While effective consolidation of the aggregate can be realized
without the use of a surfactant, it is preferable to include a
small amount of a surfactant in the prepolymer solution. The use of
a surfactant is desirable because it enhances the stability of the
cell structure of the polymeric matrix during cure and insures
complete wetting of the aggregate particles by the prepolymer
agent. Suitable surfactants are known to the art and include
polyoxyethylene derivatives of alkyl- and aryl-hydroxy and -carboxy
compounds as well as sulfonated alkyl and aryl compounds, fatty
acid soaps, e.g., calcium octoate, and fluorocarbon surfactants. A
preferred surfactant is a polyoxyethylene derivative of fatty acid
partial esters of hexatol anhydrides, available commercially from
the Atlas Powder Company under the trade name designation "Tween
80." An additional commercial surfactant suitable for the use in
this invention includes "Silicone Oil 120" available from Dow
Chemical Co. If a surfactant is utilized, its concentration should
be in the range of 1 to 2 weight percent of the prepolymer.
Concentrations above this range, while not detrimental, provide no
additional benefit.
The aggregate material for which the invention is useful is in
general unconsolidated or loose particulate matter such as soil
(e.g., black dirt, sand), including superficial soil, mineral
aggregate (e.g., perlite, vermiculite), organic matter (e.g., wood
pulp, ground tree bark, sawdust, ground corn cobs, wheat hulls,
peat moss), synthetic aggregate (e.g., ground glass), or mixtures
of the same.
The manner of contacting the aggregate material to form an integral
water-permeable mass can vary depending on the intended use for the
consolidated mass. For example, if the aggregate is to be
consolidated in such a manner as to provide a potting compound for
seeds or seedlings, the prepolymer agent is merely inter-mixed with
the aggregate (which is preferably moisture-free), together with
desired fertilizer, herbicides, etc., followed by mixing with water
to yield a pourable slurry. This slurry can then be cast into a
reuseable mold of desired configuration until cured, at which time
the mold can be removed yielding a cohesive, hydrophilic,
consolidated mass which retains the mold configuration.
Seeds can be inserted in the consolidated mass by making a small
slit or hole in the surface of the mass with a knife, pencil, or
similar object, and merely placing the seed in the opening.
Alternately, the seeds can be placed on the surface of the
consolidated mass and covered lightly with a layer of agricultural
media such as black dirt until germination, much the same as
present nursery practice. Seedlings can be inserted in a hole in
the consolidated mass made by pencil or similarly shaped
object.
When consolidating aggregate material for use in potting plants,
etc., as just described, it is preferable to dry the aggregate
prior to contacting it with the prepolymer so that it has a
free-flowing consistency without clumps or lumps. This will insure
adequate contact of aggregate surface area by the prepolymer agent
with a minimum of agitation of the mixture prior to curing.
Where a thin layer of aggregate is desired to be consolidated in
situ, as on a sandy slope or hillside to reduce erosion, a spray
application of the prepolymer can be utilized. Concentration of
prepolymer in a sprayable solvent composition should be on the
order of about 50 to 75 percent, although lesser concentrations may
be desirable when the composition includes grass seed, fertilizer,
etc. in amounts which would increase the viscosity of the
composition. Sprayable compositions containing 50-75 percent
prepolymer are generally applied at the rate of approximately 1/2
to 2 gallons per 100 square feet of superficial aggregate. Spray
equipment useful for applying such compositions is preferably a
dual hose arrangement whereby water is delivered from one source
and the prepolymer agent from a separate source, with mixing of the
prepolymer and water occurring in a common spray nozzle or
occurring by the individual spray streams impinging on one another.
The water can also be sprayed separately after the prepolymer
coating has been applied to the superficial aggregate, with
satisfactory results. The polymer may be sprayed by utilizing a
commercial hydroseeder or hydromulcher, followed by a water
spray.
The amount of water required to effect a cure with the prepolymer
should be that sufficient to yield a water-insoluble, solid,
cellular polymer matrix in which the aggregate is bonded. Normally
the weight ratio of water to prepolymer will be in the range of
0.1:1 to 20:1. When consolidating aggregate material to provide a
potting compound, a ratio of 1:1 to 5:1 is preferred, and when
consolidating superficial aggregate in situ a ratio of 3:1 to 15:1
is preferred.
The amount of prepolymer required to consolidate the aggregate
material will in general be in the range of about 1 to 40 weight
percent, or higher, and preferably 3 to 20 weight percent, based on
the weight of the aggregate material. When utilizing the preferred
polyol of about 1000 molecular weight, lower concentrations of
prepolymer, i.e., below 3 weight percent of the aggregate, provide
greater porosity and dimensional stability (i.e., the cured mass
will not swell when saturated with water), and afford less
resiliency and strength to the cured mass. Increasing
concentrations tend to increase resiliency and compression and
tensile strength while decreasing porosity and dimensional
stability.
The prepolymer can be cured under atmospheric conditions in hot or
cold weather to provide a cellular polymeric matrix which provides
a flexible, non-compactible, somewhat spongy, hydrophilic,
water-permeable mass of aggregate which has the appearance of the
initial aggregate. Since the cured mass is water-permeable, water
will diffuse through or permeate the mass. The hydrophilicity of
the polymer making up the cell walls of the consolidation allows
water to be retained by the mass, and the cellular nature allows
"breathing" of the consolidated mass. The density of the
consolidated mass is reduced from that of the unconsolidated
aggregate, thereby affording a nursery man who ships potted plants
or seedlings a substantial reduction in shipping costs.
Objects and advantages of this invention are illustrated in the
following examples, but the various materials and amounts thereof
and various other conditions and details recited therein should not
be construed to unduly limit this invention.
EXAMPLE 1
One-thousand parts by weight of polyoxyethylene diol (Carbowax
1000, having a molecular weight of about 1000) was stirred and
reacted with 351 parts of tolylene diisocyanate (80/20 mixture of
the 2,4- and 2,6-isomers) under substantially anhydrous conditions
for about 2 hrs., and the reaction mixture was allowed to stand for
several days. The resulting urethane prepolymer was a viscous
liquid (at 25.degree. C.) having a structure in accordance with
formula II, where Y.sub.1 is the residue of ethylene glycol, R' is
tolylene, o is about 21, p is 1, and z is 2.
EXAMPLE 2
A potting media was prepared by intimately mixing 20 parts of the
prepolymer of Example 1 (in a 90 percent solids solution with
acetone) with 291 parts of free-flowing sand (sp. gr. 1.7), adding
60 parts water to the resulting mixture and stirring vigorously
with a spatula for about 20 seconds. The stirred mixture cured in
about 10 minutes at room temperature to provide an integral,
resilient (even when very wet), non-friable, porous,
water-permeable consolidated structure.
The density of the cured system was 43 percent less than the sand
itself. Germination and growth of tomatoes, cucumbers, beans,
flowers (e.g., African Violets, Begonias), and jack pine seedlings
progressed in the cured polymeric mass.
EXAMPLE 3
A potting media was prepared utilizing the following
components:
______________________________________ Specific Gravity Wt., gms.
______________________________________ Peat Moss - 1/3 by volume)
Vermiculite - 1/3 by volume) 0.65 260 Sand - 1/3 by volume)
prepolymer solution of Ex. 2 1.1 40 acetone 0.8 24 water 1.0 150
After Cure 0.37 474 ______________________________________
The prepolymer, acetone, and water were rapidly mixed together,
poured onto the physically mixed aggregate, and the entire mixture
was then vigorously stirred for 30 seconds with a spatula. After 10
minutes at room temperature, the stirred mixture was cured to a
porous, resilient, non-friable, water-permeable, consolidated
structure. The density of the consolidated structure was 43 percent
less than the initial aggregate material mixture. This consolidated
structure is useful for growing the same products illustrated in
Example 1.
EXAMPLE 4
A 30 sq. ft. plot of superficial soil was raked and smoothed and
then sprinkled with one gallon of a 33 wt. percent acetone solution
of the prepolymer of Example 1. Immediately thereafter, grass seed
was uniformly spread over the treated soil in the amount of 2-5
pounds/1000 ft.sup.2 and raked into the treated soil to a depth of
1-2". The treated soil was immediately watered lightly. The
prepolymer consolidated the soil in about 10-20 min. to a resilient
mass which readily soaked up water. A laboratory test, run in a
similar manner, using rye grass seed, resulted in a higher rate of
germination of the seed than was obtained with seed planted in
untreated soil.
EXAMPLE 5
A sandy hillside was sprayed with a 50 weight percent acetone
solution of the prepolymer of Example 1 utilizing low pressure
spray equipment to provide 36 gm. of active prepolymer per square
foot of contact surface. This area was then raked with a common
garden rake and sprinkled with grass seed. Approximately 20 minutes
later the contacted area was sprayed with water from a common
garden hose until the area was saturated and runoff began to occur.
Within 15 to 20 minutes the prepolymer cured and consolidated the
soil to a resilient, water-permeable mass. A control area adjacent
to the treated area was raked and seeded at the same time. Eleven
months later the treated area showed no signs of erosion, and the
grass seed germinated. The control area had rivulets or channels
11/2 to 2 inches deep through it due to erosion, and most of the
grass seed was washed away.
EXAMPLE 6
An aluminum tray, approximately 9.times.13 inches and one inch deep
was filled with sand. 20 grams of the prepolymer solution described
in Example 2 was mixed with 250 ml. water and immediately sprinkled
evenly over the surface of the sand. After 15 minutes, the tray was
tilted at a 45.degree. angle and flushed with a strong stream of
water from a water faucet. No sand was washed away from the tray by
the water. A resilient skin bonding the sand particles into an
integral covering prevented erosion of the sand in the tray. The
same results were obtained when 20 g. of the prepolymer solution
was mixed with 60 ml., 100 ml., 150 ml., 200 ml., and 300 ml., of
water.
Modifications and variations of this invention will become apparent
to those skilled in the art without departing from the scope of
this invention, and this invention is not to be unduly limited to
the illustrative embodiments set forth herein.
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