CA2107496C - Geosynthetic barrier - Google Patents
Geosynthetic barrier Download PDFInfo
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- CA2107496C CA2107496C CA002107496A CA2107496A CA2107496C CA 2107496 C CA2107496 C CA 2107496C CA 002107496 A CA002107496 A CA 002107496A CA 2107496 A CA2107496 A CA 2107496A CA 2107496 C CA2107496 C CA 2107496C
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- isocyanate
- filler
- prepolymer
- water
- barrier according
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
- B65D90/00—Component parts, details or accessories for large containers
- B65D90/22—Safety features
- B65D90/24—Spillage-retaining means, e.g. recovery ponds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L75/00—Compositions of polyureas or polyurethanes; Compositions of derivatives of such polymers
- C08L75/04—Polyurethanes
Abstract
A gelled continuous barrier to contain liquid is the product of reaction between water, a hydrophilic isocyanate-terminated prepolymer and a water insoluble high density filler, the weight of the filler being at least twice the weight of the gelling agent. The barrier can be prepared in situ as a secondary containment barrier for a Petroleum-Oil-Lubricant (POL) facility.
Description
21 07+9 6 The invention relates to barriers for containment of liquids, for example liquids from spills or leaks, particularly for containment of spills of noxious or hazardous substances. The invention also relates to compositions and methods for forming such barriers.
BACKGROUND OF THE INVENTION
Petroleum-Oil.-Lubricant (POL) facilities require, by law, a secondary containment dike capable of containing hydrocarbons for a short; time in the event of a leakage or rupture of a primary storage vessel. Several materials have been used for secondary containment d3.kes. These include polyethylene, polypropylene, polyvinyl chloride, concrete, asphalt, geosynthetic clay liners, and geotextiles. Each of these materials has disadvantages. Concrete is too brittle in the severe Arctic environment. Asphalt is attacked by hydrocarbon fuels.
Geosynthetic clay liners and geotextiles are only suitable for containment of water or solids. Polyethylene, polypropylene and polyvinyl chloride are available as sheets and require heat sealing between sheets, which leaves them susceptible to failure at the joined seams. These liners are also susceptible to cracking, puncture and tearing. Further, they are difficult to repair.
It will be appreciated that the demands upon the material forming a secondary containment dike are substantial. It must have high integrity; the function of the dike is to contain liquids when primary containers fail. It must be impermeable to the liquid to be contained. It must be weather resistant. In _.._~___ ..,..._..~......_._....~w.....,..........r.._.._...~,.._.....
~.._...._.A.~...._ __.__.~~ _.
BACKGROUND OF THE INVENTION
Petroleum-Oil.-Lubricant (POL) facilities require, by law, a secondary containment dike capable of containing hydrocarbons for a short; time in the event of a leakage or rupture of a primary storage vessel. Several materials have been used for secondary containment d3.kes. These include polyethylene, polypropylene, polyvinyl chloride, concrete, asphalt, geosynthetic clay liners, and geotextiles. Each of these materials has disadvantages. Concrete is too brittle in the severe Arctic environment. Asphalt is attacked by hydrocarbon fuels.
Geosynthetic clay liners and geotextiles are only suitable for containment of water or solids. Polyethylene, polypropylene and polyvinyl chloride are available as sheets and require heat sealing between sheets, which leaves them susceptible to failure at the joined seams. These liners are also susceptible to cracking, puncture and tearing. Further, they are difficult to repair.
It will be appreciated that the demands upon the material forming a secondary containment dike are substantial. It must have high integrity; the function of the dike is to contain liquids when primary containers fail. It must be impermeable to the liquid to be contained. It must be weather resistant. In _.._~___ ..,..._..~......_._....~w.....,..........r.._.._...~,.._.....
~.._...._.A.~...._ __.__.~~ _.
some applications there: will be foot traffic or even vehicular traffic over the dike arid the material must have the mechanical strength to withstand that, so it must be tough and wear-and-abrasion-resistant. Ideally, it should also be easily formed, of inexpensive materials.
Lagoon liners; and artificial ponds for the containment of tailings from mining operations, for instance, are subject to similar demands.
DISCUSSIQN OF THE PRIOR ART
United States Patent number 3,719,050 discloses a technique for stabilizing soils, by injecting a polyurethane prepolymer having terminal isocyanate groups, alone or in admixture with water, into the soil to stabilize the soil. Soil stabilizing effects and containment of water are mentioned but there is no suggestion that this technique can be used for containment of naxious or hazardous liquids. The technique involves injection of isocyanate into the soil, and soil may, in effect, be regarded as a filler in the composition formed thereby.
There is mention, in passing, of mixing the polyurethane prepolymer with inorganic materials such as clay, cement, and the like, but there is no discussion of quantities of inorganic filler, and no exemplification of this suggestion.
United States Patent number 4,315,703, and Patent number 4,476,276, which is divided out of 4,315,703, disclose a composition and method for sealing structures such as sewer lines, to minimize or prevent water leakage through voids, joints, .~ _ _.~ ~,~.r..~-.,..._.__..~~__..~_.~ ... ......w_.~...._..-...._.-.._._....
..~..~.~._~.....~.....__ ____.._.__~_.~. _~_.~._.
2107~E96 3 . 60557-4535 cracks, fissures or otruer openings therein. The composition is a curable latex-reinforced polyurethane composition, which may contain up to 60s by weight of fillers, organic or inorganic, having a specific gravity in the range of 0.1 to 4.0, preferably 1.0 to 3Ø The fillers are required to have a particular size of 500 microns or less, which requires use of refined or synthetically prepared fillers. Preferably the composition contains 5 to 20 parts by weight of filler per 100 parts by weight of composition. In examples there are used diatomaceous silica filler and clay fillers.
United States Patent number 4,749,592 is also concerned with a two part grouting composition and uses a composition composed of a hydrophilic prepolymer having olefinic terminal groups, a tertiary amine catalyst and a water soluble peroxy initiator.
SUMMARY OF THE INVENTION
In one aspect the present invention provides a continuous barrier fox containing a liquid, which barrier is composed of the gelled product of reaction between water, a gelling agent that comprises a hydrophilic isocyanate-terminated prepolymer and optionally up to 40 parts by weight, based on 100 parts by weight of the hydrophilic isocyanate-terminated prepolymer, of a hydrophobic isocyanate-terminated prepolymer, and a water insoluble high density filler, wherein the weight of the water insoluble high density filler exceeds twice the weight of the gelling agent.
21074.96 The continuous barrier, which is sometimes referred to hereafter as a Geosynthetic Barrier, may be formed, for example on the ground surrounding a POL facility, i.e., on bare earth. The gelled product, although having some flexibility, can be shaped, or can be laid on earth, that is shaped to form the required containment dike. In other applications the barrier serves as a lagoon liner or to form an artificial pond for containment of liquids such as, for example, tailings from mining operations.
Typical flow rates of most fluids through the gelled composition are very low, being in the range of 10~~ to 10-8 cm/sec, and toluene shows a flow rate of 10-~ cm/sec.
It will be appreciated that the demands placed on a composition for the purpose of the present invention differ from the demands placed in United States Patent number 4,315,703 and 4,476,276. In those patents, the composition is present in relatively small quantity and is contiguous with some other material, for instance concrete if being used to seal fissures in a concrete sewer. Goad adhesion to the concrete will be required and also strength, to enable the composition to withstand high pressures that can build. up in a sewer. The composition is not exposed to the weather, so weather resistance is of no significance, and it is not subjected to foot traffic or vehicular traffic, so abrasion-resistance and wear-resistance are not major concerns. The composition is taught to be of value only in environments where the liquid to be contained is water. As it is used in small quantities, it is not so critical that the materials used to form the composition shall be inexpensive. Concrete sewers are not norma115~ used to contain hydrocarbons, so resistance to hydrocark>ans is not a requirement. It is not clear, therefore, that compositions in accordance with United States Patent numbers 4,315,703 and 4,476,276 can be modified to yield compositions that can be used to form secondary containment dikes for containing, e.g., Liquid hydrocarbons.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As is well kn.awn, isocyanates react with water to form urethanes, or there may occur elimination of carbon dioxide from the urethane, resulting in the formation an amine which reacts with an isocyanate to farm a urea. There is formed a crosslinked structure that is foamed to some extent by carbon dioxide that is released from the urethane but trapped in the crosslinked matrix that is formed. The reactions proceed rapidly, so it is normally necessary to supply the components in two or more streams, one containing the isocyanate or isocyanates and one containing the water. Usually the other components of the composition are included in the water stream. Thus the water stream can be a pumpable slurry in which water carries the water insoluble high density filler.
As indicated above, the barrier requires strength and wear-and abrasion-resistance. It is found that if only hydrophilic isocyanate-terminated prepolymer is used the gelled product is itself hydrophilic and will absorb water, which is retained in the crosslinked matrix. As water is absorbed the gel loses strength; the dry strength of the gel is considerably greater than the wet strength. If hydrophobic isocyanate terminated prepolymer ~.s also incorporated, the hydrophobic properties result in repulsion of water, so that less water, or ideally no water, is ax>sorbed into the gel and hence the gel is less susceptible to this weakening effect. Hydrophobic isocyanate-terminated polymer gels only very slowly and consequently is not suitable for use as the sole gelling agent.
The amount of hydrophobic prepolymer used is not greater than 40 parts per 100 parts by weight of hydrophilic prepolymer, and is preferably not greater than about 35 parts. A particulary preferred gelling agent. has from 15 to 30 parts by weight more particulary 25 parts by weight, of hydrophobic prepolymer, combined with 85 to 70 parts by weight, more particularly 75 parts by weight of the,hydrophilic prepolymer, based on 100 parts by weight of gelling agent. By varying the amount of hydrophobic prepolymer it is possible to tailor to some extent the properties of the gelled product.
When applied to the ground, little preparation of the soil is required. Thus, the soil may be levelled or shaped somewhat, but it is not necessary to remove small sharp objects, as it is in the case when using sheet materials as a liner that might be punctured by sharp objects.
One form of hydrophilic isocyanate-terminated prepolymer useful in this invention may be expressed in terms of the formula:
RC(R'O}a-C(0)NH-R"(NCO)b~c wherein R is an active hydrogen-free residue of a polyol, e.g., ethylene glycol, glycerol, or 1,1,1-trimethylolpropane, (R'0)a is a hydrophilic poly(oxyalH:ylene) chain having a plurality of randomly distributed oxyethylene: and higher oxyalkylene units. The subscript "a" is the number of oxyalkylene units in the poly(oxyalkylene) chain, this number being sufficient to impart water-solubility and preferably noncrystallinity to the prepolymer and suitably has a value between about 50 and about 500. The moiety -C(0)NH- together with the adjacent oxygen atom of the poly(oxyalkylene) chain. is a carbamate (or urethane) group resulting from the reaction of a hydroxy group from polyether polyol precursor with an isocyanate moiety from a polyisocyanate precursor. R" is a residue or nucleus of the polyisocyanate precursor, and is preferably an aromatic nucleus, e.g. toluene, and "b" is an integer, generally 1-5, where (b+1) is the number of isocyanate moieties present in the polyisocyanate precursor. The subscript "c" is a number equal to the functionality or number of the active-hydrogen atoms in the polyether polyol, and generally "c" will be 2-6. The terminating isocyanate groups can react with water, resulting in the formation of a gelled mass.
Preferred hydrophilic prepolymers are those of the formula:
CH3 n R [ ( CHZCH20 ) a ( CHCHZO ) a ( CHZCHZO ) f-CNH-R"-NCo 1 c where R, R", and "c" are as defined above, "d", "e" and "f" are integers such that the ratio of (d+f):e is 2:1 to 4:1. For adequate hydrophilicity, it is preferred that, of the alkylenoxy moieties present in the isocyanate-terminated prepolymers, at least about 70% shall be ethylenoxy moieties.
When these prepol.ymers are used,.the prepolymer reacts with water mixed with the prepolymer, forming in situ a cross-linked, gelled polyurethane-urea) polymer. The mixture of water and prepolymer i.:nitially and rapidly forms_a viscous mass, typically having a viscosi.t:y of about 5 to 10 cpa When measured with a BrookfieldTMViscomex.e~r at 25oC using a standard No. 3 spindle rotated at 20 rpm. In a very short perlod of Lime this mass gels to form a cross-:linked mass having an infinite viscosity. The composition may also contain other additives, as discussed further below. t)epending upon the amount of fillers and other additives, the initial viscosity of the viscous mass typically varies between 5 and 1000 cps, the viscosity being higher at higher loadings of additives.
The hydrophilic prepolymers, when reacted with water, form a gelled mass in a very short time, e.g., about 5-200 seconds, although the time,necessary to gel will vary depending on the ambient temperature, with a longer cure time usually being observed in colder conditions. The curing time may be extended or shortened by the addition of an appropriate agent. For example, the curing time may be extended by the addition of minor amounts of the aqueous solution ~:7f organic acids, e.g., from about 5% to about 50°~ by weight of O,.1N oxalic acid. The curing time may be shortened by the addition of from about 1% to 10% by weight of dicyanoethylatecf polypropylene diamine.
Although a gelled mass with some green strength may be formed very qui<:kly, curing and increasing of strength do continue and days, or even weeks, may elapse before the full strength of the cured composition is realized.
The hydrophilic prepolymers form gels which exhibit good compressive strength and shrink-resistance through cycles of expansion and contraction <~s well as cyclical changes from wet to dry conditions. It has been .found that the gels formed have high compressive strength and substantial resistance to chemical, physical, and biological a<:tivity.
The isocyanate-terminated prepolymers can be tailored in structure to obtain controlled water-solubility in order to attain practical reaction times and achieve desired physical properties in the gelled mass.
The preparation of isocyanate-terminated prepolymers is disclosed in, far instance,, t7nited States Patent numbers 4,315,703 and 4,476,276 arid in references mentioned in those patents.
The isocyanate 1>y-epolymers can be prepared by reacting an aliphatic or aromatic poly-isocyanate with a polyoxyethylene polyol using an NCOIOH equ:lva:lent ratio in the range of about 5=1 to about 1.0511.
The polyether palyo:l will generally have a molecular weight range of about 3,000-20,000, preferably 5,000 to 10,000.
Commercially available polyol precursors useful in making the above described hydrophilic: isocyanate-terminated prepolymers are the hydrophilic polyols, e.g., '"Carbowax", and ethylenoxy capped polyether triols. The degree of overall hydrophilicity of the prepolymeric mixtures can hemodified by using small amounts of poly(oxyethylene-oxypropylene)polyols sold under the trade-mark 2107~9fi "Pluronic", such as Plu,ronic-L35, F38, and P46.
Isocyanates which can be used to prepare the hydrophilic isocyanate-terminated p~repolymer, i.e., the polyisocyanate precursors mentioned above, include conventional aliphatic and aromatic polyisocyanates. The preferred isocyanates are aromatic isocyanates because the prepolymers made therefrom will generally react faster with water. One of the most useful isocyanate compounds which can be used for this purpose is tolylene diisocyanate, particularly as a blend of 80 weight percent of 10 tolylene-2,4-diisocyana.te, and 20 weight percent of tolylene-2,6-diisocyanate; a 65:35 blend of the 2,4- and 2,6-isomers is also useable. These isocyan.ates are commercially available under the trade-marks Hylene TM, Nacconate 80, and Mondur RD-80. Other useable isocyanate comp~aunds which can be used are other isomers of tolylene diisocyanat.e, hexamethylene-1,6-diisocyanate, diphenyl-methane-4,4'diisocyanate, m- or p-phenylene diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate and the triisocyanate that is available under the trade-mark Desmodur-N100 (Bayer). Polymeric isocyanates can also be used, such as polymethylene polyphenyl. isocyanates, such as those sold under the trade-mark, Mondur, MRS, and PAPI. A list of useful commercially available polyisocyanat.es is found in Encyclopedia of Chemical Technology by Kirk - Ot.hmer, 3rd Ed., Vol. 13, page 802, Interscience Pub. (1981). The isocyanate moieties present in excess over the hydroxy groups of the polyol, so that the product will contain the free isocyanate groups necessary to enable it to serve as the isocyanate-terminated prepolymer.
It is not normally necessary to include a catalyst in the composition, but in some circumstances it may be desirable to include one, and the presence of a catalyst is not outside the scope of the invention. Compounds suitable for use as catalysts in isocyanate reactions are well known; an example is dibutyl tin dilaurate.
The isocyanate-terminated prepolymers are liquids or greasy or pasty solids at room temperature. They are reactive in the presence of water to form a cross-linked, water-insoluble, water-containing gelatinous mass having a high degree of elasticity. Reaction times to convert the prepolymer to the gel in the presence of water may be on the order of less than a minute to several hours.
The solvents 'which may be used if needed to dissolve the prepolymers are water-miscible, polar organic solvents which are preferably volatile at 'the ambient conditions of the environment where the sealing composition is to be used. The solvent chosen should be such that the resulting solution of prepolymers and solvent will not freeze at the ambient conditions present in the environment where the structure is located. For example, where the ambient temperature is about 50°F, a solution of about 60-90 weight percent of prepo:lymer solids in dry acetone is a very effective composition. rather useful water-miscible solvents include tetrahydrofuran,, dimethyl formamide, ethylene glycol monoethyl ether acetate (sold under the trade designation "Cellosolve" acetate) ethylene glycol mono-and di-lower alkyl 210746 , ether such as ethylene glycol monomethyl, dimethyl, monoethyl and diethyl ethers, and diethyl acetal.
The water-reaction product of the prepolymer is a gelatinous mass, sometimes referred to herein as a gel or hydrogel. While the reaction produces by-product carbon dioxide, which normally produces a foamed structure in a cured polyurethane, foaming of the gelatinous mass is normally not noted since the amount of carbon dioxide by-product produced will generally be readily dissolved in the water contained within the gelatinous mass and/or readily liberated from the water or the gel because of the low viscosity of the gel.
Suitable hydrophobic prepolymers include compounds that are similar in structure to the hydrophilic polymers discussed above, except that in the alkyleneoxy moieties the number of ethyleneoxy moieties is reduced and the number of propyleneoxy or higher alkyleneoxy moieties is increased. To ensure adequate hydrophobicity it is desirable that, of the total alkylenoxy moieties present, less than 70% are ethyleneoxy moieties.
It is preferred that the hydrophobic prepolymer contains propylene oxide units as the alkylene oxide portion of the polymer. Other hydrophobic moieties such as butadiene, acrylonitrile and castor oil can be included in the prepolymer backbone.
Examples of suitable hydrophobic prepolymers include:
Prepolymer A= prepared from a mixture of a polypropylene oxide diol having a molecular weight of about 3000, a triol based on glycerol and having a molecular weight of about 6000, (all Arco chemicals), the ratio of diol to triol being 1:1, and tolylene diisocyanate (TDI, 80/20 isomer), the ratio of NCO: OH being 2:1;
Prepolymer B: ~~repared from a mixture of a diol having a molecular weight: of about:: 2000, a triol having a molecular weight of about 4000, the ratio of diol to triol being 1:2 and TDI, the ratio of NCO:OH being 2::'a; and Prepolymer C= prepared from a mixture of a triol based polymer polyol t:hat has ~~ high content of acrylonitrile/styrene and an OH equivalent weight of 1635 (Arco 34-28, from Arco Chemicals), an ethylene c7xide capped polyether triol of OH
equivalent weight 1602 (Poly G 85-34, from Olin Chemicals) and IPDI (isophorone diisocy~~nate), the ratio NCO: OH being 2:1.
Prepol.ymer D: based on Castor oil and aromatic TM
isocyanate, such as Vorit:e 689 from Caschem Inc.
It is preferred that the gelling agent is reacted with water at a water=gelling agent weight ratio of from about 4:1 to about 10:1, preferably ataout 6:1. Generally it is preferred to keep the water to the minimum that is required to obtain a pumpable slurry with the filler and other components of the water stream.
The water inso:kuble high density filler material may be any of the fillers used in the coating industry including, for example, siliceous mater~.als such as sand and silane treated TM
fillers such as silane treated Wollastonite, rubber particles, TM
mini fibers such as the laulk form of Kevlar (Du Pont), clay and calcium carbonate. Hy high density is meant that the material has a specific gravity of at least about 1.1, preferably at least about 1.6. Hydrophobic fillers are preferred and hydrophobicity can be enhanced by, for c}xample, coating a filler with a silane material. Sand is part;icularly preferred. The particle size, provided it does not interfere with the formation of a slurry, is not important. Thus the particle size may be as high as about 6500 microns, although usually it will be less. The invention does not impose stringent demands on the filler; for instance it does not require the refined, finely divided fillers of United States Patent numbers 9.,315,703 and 4,476,276, although finely divided filler can be used. The smaller the particle size, the closer the particles can pack in the gelled composition and therefore the denser an,d stronger in compression the composition will be. For reasons o~f economy it is anticipated that in many instances the filler will be ordinary sand, of a particle size between about 1000 and about 6500 microns, preferably between about 2500 and 6500 microns.
The quantity of filler material is at least 200 parts by weight based on 100 parts by weight of the total gelling agent.
However, larger quantities of filler are normally used, say in excess of 80%. If this is expressed as a percentage of filler, based on the weight of filler plus gelling agent, the quantity of filler is 67%. Preferably the filler ranges from 90% to 99%, more preferably at least 95% up to 98%, by weight of the combined total of gelling agent and filler.
As is usual with isocyanate-terminated prepolymers, the final product is formed by combining at least two separate streams of ingredients. The isocyanate is in an "A" stream and the isocyanate-reactive components are in a "B" stream. In the present case, water is the major isocyanate reactive component.
The filler is normally in the "B" stream and, with the water forms a slurry, e.g., a sand and water slurry. Whilst it is preferred to avoid the use of surfactant, some surfactant may be used to assist in the formation ~~f a pumpable slurry. The presence of suspending agent may increase the gelling time so it is preferred to use as little as poss~.ble, desirably Sts by weight or less, based on the weight of gelling agent. Ln some instances success has been achieved with ass little as 0.5%.
The compression strength of the composition, both wet strength and dry st.rengtlv, can be enhanced by incorporation of a 10 polyurethane dispersion. The pH of the polyurethane dispersion preferably is below 9.5, more preferably below 9 and particularly should be maintained aro~~nd 8. A preferred polyurethane TM
dispersion is Neo Rez R-X679 (available from ICI) which is an aliphatic aqueous colloi<~al dispersion of a urethane polymer with excellent chemical and U~ light resistance.
The weight ratio of: polyurethane dispersion to gelling agent is preferably between the limits of about 1~1 and 2~1"
Preferably the ~fispersion should contain not more than 10%
volatile organic; compone7ats and preferably much less.
The strength of they composition can be enhanced by inclusion of a Aatex, for example an acrylonitrile-butadiene-styrene latex or a natural rubber latex, or a polyethylene dispersion. This is somet.ime~s accompanied by the disadvantage that surfactant contained i.n the latex or dispersion may lead to enhanced water uptake by t;he cured composition. The use of such latexes and dispersions is still within the scope of the invention, however.
The sand/water slurry may contain the minimum amount of suspending agent: necessary to produce a pumpable slurry. There are known polys<~ccharides for this purpose and mention is made particularly of a heteropoly~saccharide available from the Kelco Division of Merck & Co. J_nc. To the extent possible, it is preferred to avoid the ueae of: suspending agents, and surfactants, since they block the iso::vyanate moieties and may increase the gelling time, and also they encourage uptake of,water, which is undesirable.
Other additives which may be used include UV
stabilizers, defoamers, titanates, silane coupling agents, accelerators or retarders to control the gelling time, antioxidants and pigments.
Particularly useful additives are defoaming agents such TM
as Surfynol DF :L10L (a h:i.gh molecular weight acetylenic glycol non-ionic defoamer available from Air Products and Chemicals, Inc.), DB-31 additive and DB--65 additive (silicone additives TM
available from Dow Corning) and UV stabilizers such as Tinuvin 292 TM
(a hindered amine photostabilizer) and Tinuvin 328 (an ultraviolet absorber) which are availablE~ commercially from Ciba-Geigy Ltd.
A topcoat is preferably applied to the surface of the cured consolidated hydroge:l-filler mass to protect it from UV
radiation. Since the wet compression strength of the hydrogel is less than the d:ry strength, it is preferred to protect it also from unnecessary exposure to water, for example, rain water. The topcoat is suitably a moi~>ture-cured polyurethane layer. It should be durable, flexib7.e, water-resistant and resistant to UV
radiation. It should also be easy to apply as a thin film.
21074qfi 17 ~ 60557-4535 Suitable moisture-curable polyurethanes include isocyanate-terminated or thioisocyanate terminated polyurethane prepolymers which cure by reaction with atmospheric moisture, such as prepolymers obtained by reaction of an equivalent excess of at least one organic polyisocyanate or polythioisocyanate with one or more organic compounds having a plurality of hydroxy, thiol or amine groups. As polyisocyanate, commercially available mixtures of toluene diisocyanates, such as a mixture of 80% 2,4-toluene diisocyanate and 20% 2,6-tolylene diisocyanate, are suitable.
Suitable hydroxy-group containing compounds are hydroxy terminated polyesters such as polyethylene propylene adipate and polyethylene adipate and hydroxy terminated polyethers such as glycols for example poly (oxyethylene} glycols, poly (oxypropylene) glycols and poly (oxybutylene) glycols. The reaction of the moisture-curable isocyanate can be catalyzed, for example with oxazolidine, which is supplied separately, giving a two part system. The top coat prepolymer preferably also contains fillers such as titanium dioxide or carbon black. Moisture-curable polyisocyanates that are suitable for use in the top coat are described in United States Patent number 3,'723,163.
Alternatively, a top coat can be provided by means of a two part system, one part being an isocyanate-terminated prepolymer and the other part being a golyol or a hydroxy-terminated polyether po:lyol. Suitable isocyanate-terminated prepolymers include those useful as moisture-curable prepolymers, discussed above. Again" the top coat can contain filler, for example titanium dioxide or carbon black.
21a749s A particular topcoat composition which is suitable contains titanium dioxide, carbon black, defoamer, ODEBA (octyl diethyl bis aniline crosslinker), A 189 Silane, DBTDL (dibutyltin dilaurate), Tinuvin 144,. Byk P104, toluene and DMDEE, (d-morpholine-4,4'-(oxydi-1,2 ethanediyl)bis) from Union Carbide.
The topcoat moisture-curable polyurethane compositions are preferably applied directly to the surface of the cured hydrogel by spreading with a suitable tool such as a sawtooth notched rubber squeezer, a paint roller, a standard push broom or brushes. The topcoat is preferably spread thinly to provide a thickness of from about. 0.25 mm to about 1 mm, preferably about 0.25 mm.
The topcoat gives the product resistance to UV light, protects the product from water such as rain water and is flexible. It is best t.a apply the topcoat after curing of the hydrogel preferably after six hours of applying the hydrogel ingredients, more preferably 16 hours and particularly 24 hours afterwards.
The sand/water slurry may suitably be prepared by mixing in a cement mixer. Any other additives, such as the polyurethane dispersion, should also be included in the mixing of the slurry.
It is important that the ingredients are well mixed or the performance of the cured hydrogel may be adversely affected. If a cement mixer is used or other equipment which has previously been used for cement, in view of the high alkalinity of some cement mixes, it may be necessary to use some acid additive, such as acetic acid, to ensure that the pH is not too high. Above a pH of about 10.2 the gelling rnay be affected, gelling time may be increased and an unfavourable product obtained. It is preferred that the pH is less than 9.5 and more preferred that it is less than 9 and particularly less than 8.
After mixing, the sand/water slurry is combined with the gelling agent. Suitably a concrete pumping device can be used to pump the slurry to a mixing nozzle where the gelling agent is introduced, mixed and directed at the support surface. Curing takes place shortly thereafter. These same steps can be used to repair a barrier layer that has been damaged; the invention permits easy repair.
In the preferred embodiment using a topcoat, the hydrogel composition is preferably allowed to cure for 6 hours, more preferably ~6 hours, still more preferably 24 hours, before applying the topcoat.
In one embodiment of the invention a sand/water/polyurethane dispersion slurry is dumped into a concrete pumping device. The slurry is then pumped to a mixing nozzle where a hydrogel prepolymer is introduced, mixed and propelled to the work surface. Curing takes place shortly thereafter to produce the consolidated sand liner. This application method using a concrete pumper allows easy placement of a controlled thickness of hydrogel/consolidated sand mass.
Typically 25 to 50 mm of hydrogel mass and a 0.25 mm topcoat are recommended for areas which are not subject to vehicular traffic.
If a high level of traffic is anticipated, then 50 to 100 mm of consolidated sand and the 0.25 mm topcoat are recommended.
In one embodiment of the method, sand to be used as filler is taken and placed in a container. Water is added to the 21 074 ~ 6 container until it reac;hes the level of the surface of the sand.
The amount of water present is observed. To the water/sand slurry so formed are added any other required ingredients, for instance a suspending agent to prevent the sand from settling out and defoaming agents. The formed slurry is pumped to the desired location where it is admixed with the gelling agent that is supplied from a separate stream. Just before gelling occurs the composition can be sprayed into position and then shaped, if necessary for instance by paddles or dikes or moulds or formwork.
The amount of gelling agent supplied is determined with regard to the amount of water present and the desirability of having a water: gelling agent ratio in the range of about 4:1 to 10:1, preferably about 6:1. In tests it was found that when 200g samples of sand was taken, about 40g of water was required to raise the level of water to the level of the sand, and a pumpable slurry could be formed. To react with 40g of water in 1:6 ratio, 6.7g of gelling agent was required. It was found that this amount was sufficient to form a barrier composition with the required properties, in accordance with the invention.
The amount of gelling agent, as a percentage of the total pre-gelled composition, is 6.7 x 100 = 2.7%. The amount of 246.7 filler in the pre-gelled composition is 80%. It is surprising that a satisfactory barrier composition can be formed with so little gelling agent, together with the inexpensive materials sand and water.
Cured compositions according to the invention, coated with the topcoat, when immersed in water for a week had a water 2~ 0~49~ s uptake of less than 5%. The permeability rate of the geosynthetic barrier for water may be as low as 10 8cm/s and for gasoline and toluene may be as low as 10 7cm/s. The wet compression strength of a 19 mm thickness of: hydrogel mass (at 50% compression) can be as great as about 700 l~:Pa and dry compressions strength (at 50%
compression) can be as great as about 3500 kPa. Compression strength values may vary with the particle size of the filler.
The compositi.an of the invention can be used with other materials to make a mul.ti-layer barrier or liner. For example, there can be applied a layer of the composition over a shaped surface of soil to a suitable depth, for instance about 6 mm.
There can be laid on the cured composition a sheet liner. High density polyethylene, high density polypropylene and PVC are suitable materials for such a liner and a suitable thickness of liner is again about 6 mm. A further layer of the composition of the invention can then be applied over the liner suitably of thickness of about 38 mm, thereby providing a liner of about 50 mm. This can be covered with a UV-protective lining, as discussed above.
The barrier campositions can be used in primary or secondary containment. In secondary containment they may be applied directly to the ground under or adjacent and around a primary container. To ensure that no liquid escapes they can be applied more thickly towards the perimeter and more thinly in the centre to provide a gradient to keep liquid in the centre, or a vertical lip or wall can be provided at the perimeter. They can also be applied as a coating directly on the outer surfaces of a primary container. Since the permeability rate of the barriers is low for gasoline and toluene they are suitable for use in petroleum-oil-lubricant. secondary containment. The permeability rate for water is also l.ow and they are suitable in a wide range of uses such as, for example, as liners or barriers in primary or secondary containers in settling ponds, at landfill sites and transformer sites.
The invention has been described with particular reference to containment. of toxic or noxious substances, but it will be appreciated that. the invention can be used to contain non-toxic or non-noxious substances.
The invention is further illustrated in the following examples, in which parts are by weight unless otherwise indicated.
There are first described the experimental test methods.
EgPERIMENTAL TEST HETHODS
Density Approximately a 1 inch square sample of Geosynthetic Barrier was cut from the sample prepared. Exact measurements were taken with a micrometer and the sample Weighed. From this information the density of the sample could be obtained.
Note: Since Geosynthetic Barrier samples take up water albeit slowly), in the name of accuracy the water displacement method of determining sample volumes was not used.
Water Absorption After allowing the GB samples to cure for two weeks water uptake was determined gravimetrically. The samples were weighed, submerged in water for 1 week, removed and then re-21 07~+q 6 weighed. Water uptake is reported as a percentage of weight increase.
Permeability Permeability was used to evaluate the water/solvent resistance of Geosynthetic Barrier samples. The constant head method of determining permittivity was used. A two week cure was allowed before testing. At this time a head of water/solvent was applied to the geosynthetic barrier and the rate of loss of water/solvent monitored. The following equation was used to determine the permittivi.ty of the Geosynthetic Barrier sample.
= 1 I n bo t hl where t is the time in seconds, hQ is the initial head in mm and hl is the final head in mm.
The normal coefficient of permeability can be determined by multiplying the permittivity by the sample thickness (ASTM
D4491).
Compression (Wet and Dry) An instron 1123 was used to test the compression resistance of the Geosynthetic Barrier samples. One inch square samples were placed between instron compression plates. The cross-head speed was 20 mm/min and the chart speed was maintained at 50 mm/min. A maximum load of 25,000 N was placed on the samples. The compression strength at 33% and 50~ compression was determined and the integrity of the sample after full load was recorded for comparison purposes.
Ultraviolet (UV) Resistance An atlas UVCON was used to expose the Geosynthetic Barrier samples to UV radiation. Eight FS-40-T12 UV florescent lamps were used as a source of radiation. The samples were exposed for 2000 hours at a temperature of approximately 5loC.
The flexibility and degradation of the top coat was determined after 2000 hours.
Additional samples were exposed to a 1000 hour xenon-arc accelerated UV weathering cycle.
Weathering Cycles The weathering cycle consists of placing samples at 40°C
for 20 hours, followed by room temperature for 4 hours followed by -18°C for 20 hours. This cycle was repeated continually and observations were recorded weekly. The flexibility, integrity and peel strength of the geasynthetic barrier and top-coat were of interest.
EBAMPLES
Example 1 A homogeneous. mixture of washed all-purpose anhydrous sand (100 parts) and water (20 partsy was prepared and is referred to as Part A (if the sand is wet the amount of water is adjusted accordingly). Part B consists of 3.3 parts of a hydrophilic isocyanate-terminated prepolymer E. Prepolymer E is an ethylene oxide capped polyether triol derived from glycerol, of molecular weight approximately 5000, that has been reacted with TDI with a ratio of NCO:OH of 2:1, dissolved in acetone. Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 1.3224 g/mL wa:c obtained. One week and four week water absorptions were 13.03 and 23.3 weight per cent. The 50 per cent wet and dry compression values were 380 and 2160 kPa respectively.
Permeability values of water, toluene and gasoline were 1.5 x 10~, 2.7 x 10-6 and 2.9 x 10-'' cm/s respectively.
In field trials the same hydrophilic isocyanate-terminated prepo.lymer, but dissolved in diethylene glycol monoethyl ether acetate, not acetone (Prepolymer F) was used and similar results were obtained.
Example 2 A homogeneous mixture of sand (100 parts), water (16.7 parts) and polyurethane dispersion (6.7 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B consists of 3.3 parts of the hydrophilic isocyanate-terminated prepolymer E.
Part B was added to part: A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 1.8173 g/mL was obtained.
One week water absorption was 10.66 weight per cent. The 50 per cent wet and dry compression values were 770 and 3415 kPa respectively. Permeability values of water, toluene and gasoline were 4.0 x 10-8, 2.8 x 10-6 and 4.6 x 106 cm/s respectively. The marked increase in the wet compression value demonstrated the effect of addition of the polyurethane dispersion.
Field trials with prepolymer F gave similar results.
210749fi Example 3 A homogeneous mixture of sand (100 parts), water (20 parts) and polyurethane dispersion (3.33 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B
consists of 3.33 parts of the hydrophilic isocyanate-terminated prepolymer E. Part B was added to part A and the mixture stirred until just before gelat.ion. The composition was poured into a mold and allowed to cure for two weeks before testing. A
consolidated sand/polyu,rethane mixture of density 2.00 g/mL was obtained. One week water absorption was 11.08 weight per cent.
The 50 per cent wet and. dry compression values were 700 and 2710 kPa respectively. Permeability values of water, toluene and gasoline were <- 10-8, 1.6 x 10~? and <- 10-a cm/s respectively.
Field trials with prepolymer F gave similar results.
Example 4 A homogeneous mixture of sand (100 parts), water (20 parts ) and polyurethane dispersion (3.33 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B
consists of 3.33 parts of a mixture of hydrophilic/hydrophobic isocyanate-terminated prepolymers (prepolymer E/prepolymer A =
85/15). Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 2.302 g/mL was obtained. One week water absorption was 9.76 weight per cent. The 50 per cent wet and dry compression values were 770 and 1550 kPa respectively.
Permeability values of toluene and gasoline were 2.9 x 10~T and s 108 cm/s respectively.
.. 2'~07~9~
Field trials with prepolymer F gave similar results.
Example 5 A homogeneou:c mixture of sand (100 parts), water (20 parts) and polyurethane: dispersion (3.33 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B
consists of 3.33 parts of a mixture of hydrophilic/hydrophobic isocyanate-terminated prepolymers (prepolymer E/prepolymer A
75/25). Part B was added to part A and the mixture stirred until just before gelation to ensure a homogeneous mixture. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 1.971 g/mL was obtained. One week water absorption was 8.99 weight per cent. The 50 per cent wet and dry compression values were 890 and 3875 kPa respectively. Permeability values of toluene and gasoline were 1.63 x 10-~ and 1.4 x 10-6 cm/s respectively.
Field trials with prepolymer F gave similar results.
Example 6 A homogeneous mixture of sand (100 parts) and water (20 parts) was prepared and is referred to as Part A. Part B consists of 3.3 parts of the hydrophilic isocyanate-terminated prepolymer E. Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for 16 hours after which time a top-coat consisting of 5891E (3M: Company) was applied at a 10 mil.
thickness. The total Geosynthetic Barrier was allowed further cure for 1 week and four weeks. One week water absorptions were 3.72 and 3.83 weight per cent respectively. UV resistance and weathering of thE~ top-coat were excellent compared to the Geosynthetic Barrier without: t:op-coat.
Field trials with prepolymer F gave similar results.
Example 7 A homogeneous mi~:t,ur.e of sand (100 parts) and water (20 parts) was prepared and is referred to as Part A. Part B consists of 3.3 parts of the hydrophilic isocyanate-terminated prepolymer E. Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for 16 hours <~fter which time a top-coat consisting of 58'~lE (3M Company), 2 parts carbon black, 0.25 parts TinuvinM328 and 0.1 parts Texacat DMDEE was applied at a 0.25 mm.
thickness. The total Geosynthetic Barrier was allowed further cure for 1 week. Four week water absorption was 8.77 weight per cent. UV resistance and V~e~athering resistance were excellent compared to Geosynthetic Barrier materials in the absence of top-coats.
Field trials with prepolymer F gave similar results.
Lagoon liners; and artificial ponds for the containment of tailings from mining operations, for instance, are subject to similar demands.
DISCUSSIQN OF THE PRIOR ART
United States Patent number 3,719,050 discloses a technique for stabilizing soils, by injecting a polyurethane prepolymer having terminal isocyanate groups, alone or in admixture with water, into the soil to stabilize the soil. Soil stabilizing effects and containment of water are mentioned but there is no suggestion that this technique can be used for containment of naxious or hazardous liquids. The technique involves injection of isocyanate into the soil, and soil may, in effect, be regarded as a filler in the composition formed thereby.
There is mention, in passing, of mixing the polyurethane prepolymer with inorganic materials such as clay, cement, and the like, but there is no discussion of quantities of inorganic filler, and no exemplification of this suggestion.
United States Patent number 4,315,703, and Patent number 4,476,276, which is divided out of 4,315,703, disclose a composition and method for sealing structures such as sewer lines, to minimize or prevent water leakage through voids, joints, .~ _ _.~ ~,~.r..~-.,..._.__..~~__..~_.~ ... ......w_.~...._..-...._.-.._._....
..~..~.~._~.....~.....__ ____.._.__~_.~. _~_.~._.
2107~E96 3 . 60557-4535 cracks, fissures or otruer openings therein. The composition is a curable latex-reinforced polyurethane composition, which may contain up to 60s by weight of fillers, organic or inorganic, having a specific gravity in the range of 0.1 to 4.0, preferably 1.0 to 3Ø The fillers are required to have a particular size of 500 microns or less, which requires use of refined or synthetically prepared fillers. Preferably the composition contains 5 to 20 parts by weight of filler per 100 parts by weight of composition. In examples there are used diatomaceous silica filler and clay fillers.
United States Patent number 4,749,592 is also concerned with a two part grouting composition and uses a composition composed of a hydrophilic prepolymer having olefinic terminal groups, a tertiary amine catalyst and a water soluble peroxy initiator.
SUMMARY OF THE INVENTION
In one aspect the present invention provides a continuous barrier fox containing a liquid, which barrier is composed of the gelled product of reaction between water, a gelling agent that comprises a hydrophilic isocyanate-terminated prepolymer and optionally up to 40 parts by weight, based on 100 parts by weight of the hydrophilic isocyanate-terminated prepolymer, of a hydrophobic isocyanate-terminated prepolymer, and a water insoluble high density filler, wherein the weight of the water insoluble high density filler exceeds twice the weight of the gelling agent.
21074.96 The continuous barrier, which is sometimes referred to hereafter as a Geosynthetic Barrier, may be formed, for example on the ground surrounding a POL facility, i.e., on bare earth. The gelled product, although having some flexibility, can be shaped, or can be laid on earth, that is shaped to form the required containment dike. In other applications the barrier serves as a lagoon liner or to form an artificial pond for containment of liquids such as, for example, tailings from mining operations.
Typical flow rates of most fluids through the gelled composition are very low, being in the range of 10~~ to 10-8 cm/sec, and toluene shows a flow rate of 10-~ cm/sec.
It will be appreciated that the demands placed on a composition for the purpose of the present invention differ from the demands placed in United States Patent number 4,315,703 and 4,476,276. In those patents, the composition is present in relatively small quantity and is contiguous with some other material, for instance concrete if being used to seal fissures in a concrete sewer. Goad adhesion to the concrete will be required and also strength, to enable the composition to withstand high pressures that can build. up in a sewer. The composition is not exposed to the weather, so weather resistance is of no significance, and it is not subjected to foot traffic or vehicular traffic, so abrasion-resistance and wear-resistance are not major concerns. The composition is taught to be of value only in environments where the liquid to be contained is water. As it is used in small quantities, it is not so critical that the materials used to form the composition shall be inexpensive. Concrete sewers are not norma115~ used to contain hydrocarbons, so resistance to hydrocark>ans is not a requirement. It is not clear, therefore, that compositions in accordance with United States Patent numbers 4,315,703 and 4,476,276 can be modified to yield compositions that can be used to form secondary containment dikes for containing, e.g., Liquid hydrocarbons.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As is well kn.awn, isocyanates react with water to form urethanes, or there may occur elimination of carbon dioxide from the urethane, resulting in the formation an amine which reacts with an isocyanate to farm a urea. There is formed a crosslinked structure that is foamed to some extent by carbon dioxide that is released from the urethane but trapped in the crosslinked matrix that is formed. The reactions proceed rapidly, so it is normally necessary to supply the components in two or more streams, one containing the isocyanate or isocyanates and one containing the water. Usually the other components of the composition are included in the water stream. Thus the water stream can be a pumpable slurry in which water carries the water insoluble high density filler.
As indicated above, the barrier requires strength and wear-and abrasion-resistance. It is found that if only hydrophilic isocyanate-terminated prepolymer is used the gelled product is itself hydrophilic and will absorb water, which is retained in the crosslinked matrix. As water is absorbed the gel loses strength; the dry strength of the gel is considerably greater than the wet strength. If hydrophobic isocyanate terminated prepolymer ~.s also incorporated, the hydrophobic properties result in repulsion of water, so that less water, or ideally no water, is ax>sorbed into the gel and hence the gel is less susceptible to this weakening effect. Hydrophobic isocyanate-terminated polymer gels only very slowly and consequently is not suitable for use as the sole gelling agent.
The amount of hydrophobic prepolymer used is not greater than 40 parts per 100 parts by weight of hydrophilic prepolymer, and is preferably not greater than about 35 parts. A particulary preferred gelling agent. has from 15 to 30 parts by weight more particulary 25 parts by weight, of hydrophobic prepolymer, combined with 85 to 70 parts by weight, more particularly 75 parts by weight of the,hydrophilic prepolymer, based on 100 parts by weight of gelling agent. By varying the amount of hydrophobic prepolymer it is possible to tailor to some extent the properties of the gelled product.
When applied to the ground, little preparation of the soil is required. Thus, the soil may be levelled or shaped somewhat, but it is not necessary to remove small sharp objects, as it is in the case when using sheet materials as a liner that might be punctured by sharp objects.
One form of hydrophilic isocyanate-terminated prepolymer useful in this invention may be expressed in terms of the formula:
RC(R'O}a-C(0)NH-R"(NCO)b~c wherein R is an active hydrogen-free residue of a polyol, e.g., ethylene glycol, glycerol, or 1,1,1-trimethylolpropane, (R'0)a is a hydrophilic poly(oxyalH:ylene) chain having a plurality of randomly distributed oxyethylene: and higher oxyalkylene units. The subscript "a" is the number of oxyalkylene units in the poly(oxyalkylene) chain, this number being sufficient to impart water-solubility and preferably noncrystallinity to the prepolymer and suitably has a value between about 50 and about 500. The moiety -C(0)NH- together with the adjacent oxygen atom of the poly(oxyalkylene) chain. is a carbamate (or urethane) group resulting from the reaction of a hydroxy group from polyether polyol precursor with an isocyanate moiety from a polyisocyanate precursor. R" is a residue or nucleus of the polyisocyanate precursor, and is preferably an aromatic nucleus, e.g. toluene, and "b" is an integer, generally 1-5, where (b+1) is the number of isocyanate moieties present in the polyisocyanate precursor. The subscript "c" is a number equal to the functionality or number of the active-hydrogen atoms in the polyether polyol, and generally "c" will be 2-6. The terminating isocyanate groups can react with water, resulting in the formation of a gelled mass.
Preferred hydrophilic prepolymers are those of the formula:
CH3 n R [ ( CHZCH20 ) a ( CHCHZO ) a ( CHZCHZO ) f-CNH-R"-NCo 1 c where R, R", and "c" are as defined above, "d", "e" and "f" are integers such that the ratio of (d+f):e is 2:1 to 4:1. For adequate hydrophilicity, it is preferred that, of the alkylenoxy moieties present in the isocyanate-terminated prepolymers, at least about 70% shall be ethylenoxy moieties.
When these prepol.ymers are used,.the prepolymer reacts with water mixed with the prepolymer, forming in situ a cross-linked, gelled polyurethane-urea) polymer. The mixture of water and prepolymer i.:nitially and rapidly forms_a viscous mass, typically having a viscosi.t:y of about 5 to 10 cpa When measured with a BrookfieldTMViscomex.e~r at 25oC using a standard No. 3 spindle rotated at 20 rpm. In a very short perlod of Lime this mass gels to form a cross-:linked mass having an infinite viscosity. The composition may also contain other additives, as discussed further below. t)epending upon the amount of fillers and other additives, the initial viscosity of the viscous mass typically varies between 5 and 1000 cps, the viscosity being higher at higher loadings of additives.
The hydrophilic prepolymers, when reacted with water, form a gelled mass in a very short time, e.g., about 5-200 seconds, although the time,necessary to gel will vary depending on the ambient temperature, with a longer cure time usually being observed in colder conditions. The curing time may be extended or shortened by the addition of an appropriate agent. For example, the curing time may be extended by the addition of minor amounts of the aqueous solution ~:7f organic acids, e.g., from about 5% to about 50°~ by weight of O,.1N oxalic acid. The curing time may be shortened by the addition of from about 1% to 10% by weight of dicyanoethylatecf polypropylene diamine.
Although a gelled mass with some green strength may be formed very qui<:kly, curing and increasing of strength do continue and days, or even weeks, may elapse before the full strength of the cured composition is realized.
The hydrophilic prepolymers form gels which exhibit good compressive strength and shrink-resistance through cycles of expansion and contraction <~s well as cyclical changes from wet to dry conditions. It has been .found that the gels formed have high compressive strength and substantial resistance to chemical, physical, and biological a<:tivity.
The isocyanate-terminated prepolymers can be tailored in structure to obtain controlled water-solubility in order to attain practical reaction times and achieve desired physical properties in the gelled mass.
The preparation of isocyanate-terminated prepolymers is disclosed in, far instance,, t7nited States Patent numbers 4,315,703 and 4,476,276 arid in references mentioned in those patents.
The isocyanate 1>y-epolymers can be prepared by reacting an aliphatic or aromatic poly-isocyanate with a polyoxyethylene polyol using an NCOIOH equ:lva:lent ratio in the range of about 5=1 to about 1.0511.
The polyether palyo:l will generally have a molecular weight range of about 3,000-20,000, preferably 5,000 to 10,000.
Commercially available polyol precursors useful in making the above described hydrophilic: isocyanate-terminated prepolymers are the hydrophilic polyols, e.g., '"Carbowax", and ethylenoxy capped polyether triols. The degree of overall hydrophilicity of the prepolymeric mixtures can hemodified by using small amounts of poly(oxyethylene-oxypropylene)polyols sold under the trade-mark 2107~9fi "Pluronic", such as Plu,ronic-L35, F38, and P46.
Isocyanates which can be used to prepare the hydrophilic isocyanate-terminated p~repolymer, i.e., the polyisocyanate precursors mentioned above, include conventional aliphatic and aromatic polyisocyanates. The preferred isocyanates are aromatic isocyanates because the prepolymers made therefrom will generally react faster with water. One of the most useful isocyanate compounds which can be used for this purpose is tolylene diisocyanate, particularly as a blend of 80 weight percent of 10 tolylene-2,4-diisocyana.te, and 20 weight percent of tolylene-2,6-diisocyanate; a 65:35 blend of the 2,4- and 2,6-isomers is also useable. These isocyan.ates are commercially available under the trade-marks Hylene TM, Nacconate 80, and Mondur RD-80. Other useable isocyanate comp~aunds which can be used are other isomers of tolylene diisocyanat.e, hexamethylene-1,6-diisocyanate, diphenyl-methane-4,4'diisocyanate, m- or p-phenylene diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate and the triisocyanate that is available under the trade-mark Desmodur-N100 (Bayer). Polymeric isocyanates can also be used, such as polymethylene polyphenyl. isocyanates, such as those sold under the trade-mark, Mondur, MRS, and PAPI. A list of useful commercially available polyisocyanat.es is found in Encyclopedia of Chemical Technology by Kirk - Ot.hmer, 3rd Ed., Vol. 13, page 802, Interscience Pub. (1981). The isocyanate moieties present in excess over the hydroxy groups of the polyol, so that the product will contain the free isocyanate groups necessary to enable it to serve as the isocyanate-terminated prepolymer.
It is not normally necessary to include a catalyst in the composition, but in some circumstances it may be desirable to include one, and the presence of a catalyst is not outside the scope of the invention. Compounds suitable for use as catalysts in isocyanate reactions are well known; an example is dibutyl tin dilaurate.
The isocyanate-terminated prepolymers are liquids or greasy or pasty solids at room temperature. They are reactive in the presence of water to form a cross-linked, water-insoluble, water-containing gelatinous mass having a high degree of elasticity. Reaction times to convert the prepolymer to the gel in the presence of water may be on the order of less than a minute to several hours.
The solvents 'which may be used if needed to dissolve the prepolymers are water-miscible, polar organic solvents which are preferably volatile at 'the ambient conditions of the environment where the sealing composition is to be used. The solvent chosen should be such that the resulting solution of prepolymers and solvent will not freeze at the ambient conditions present in the environment where the structure is located. For example, where the ambient temperature is about 50°F, a solution of about 60-90 weight percent of prepo:lymer solids in dry acetone is a very effective composition. rather useful water-miscible solvents include tetrahydrofuran,, dimethyl formamide, ethylene glycol monoethyl ether acetate (sold under the trade designation "Cellosolve" acetate) ethylene glycol mono-and di-lower alkyl 210746 , ether such as ethylene glycol monomethyl, dimethyl, monoethyl and diethyl ethers, and diethyl acetal.
The water-reaction product of the prepolymer is a gelatinous mass, sometimes referred to herein as a gel or hydrogel. While the reaction produces by-product carbon dioxide, which normally produces a foamed structure in a cured polyurethane, foaming of the gelatinous mass is normally not noted since the amount of carbon dioxide by-product produced will generally be readily dissolved in the water contained within the gelatinous mass and/or readily liberated from the water or the gel because of the low viscosity of the gel.
Suitable hydrophobic prepolymers include compounds that are similar in structure to the hydrophilic polymers discussed above, except that in the alkyleneoxy moieties the number of ethyleneoxy moieties is reduced and the number of propyleneoxy or higher alkyleneoxy moieties is increased. To ensure adequate hydrophobicity it is desirable that, of the total alkylenoxy moieties present, less than 70% are ethyleneoxy moieties.
It is preferred that the hydrophobic prepolymer contains propylene oxide units as the alkylene oxide portion of the polymer. Other hydrophobic moieties such as butadiene, acrylonitrile and castor oil can be included in the prepolymer backbone.
Examples of suitable hydrophobic prepolymers include:
Prepolymer A= prepared from a mixture of a polypropylene oxide diol having a molecular weight of about 3000, a triol based on glycerol and having a molecular weight of about 6000, (all Arco chemicals), the ratio of diol to triol being 1:1, and tolylene diisocyanate (TDI, 80/20 isomer), the ratio of NCO: OH being 2:1;
Prepolymer B: ~~repared from a mixture of a diol having a molecular weight: of about:: 2000, a triol having a molecular weight of about 4000, the ratio of diol to triol being 1:2 and TDI, the ratio of NCO:OH being 2::'a; and Prepolymer C= prepared from a mixture of a triol based polymer polyol t:hat has ~~ high content of acrylonitrile/styrene and an OH equivalent weight of 1635 (Arco 34-28, from Arco Chemicals), an ethylene c7xide capped polyether triol of OH
equivalent weight 1602 (Poly G 85-34, from Olin Chemicals) and IPDI (isophorone diisocy~~nate), the ratio NCO: OH being 2:1.
Prepol.ymer D: based on Castor oil and aromatic TM
isocyanate, such as Vorit:e 689 from Caschem Inc.
It is preferred that the gelling agent is reacted with water at a water=gelling agent weight ratio of from about 4:1 to about 10:1, preferably ataout 6:1. Generally it is preferred to keep the water to the minimum that is required to obtain a pumpable slurry with the filler and other components of the water stream.
The water inso:kuble high density filler material may be any of the fillers used in the coating industry including, for example, siliceous mater~.als such as sand and silane treated TM
fillers such as silane treated Wollastonite, rubber particles, TM
mini fibers such as the laulk form of Kevlar (Du Pont), clay and calcium carbonate. Hy high density is meant that the material has a specific gravity of at least about 1.1, preferably at least about 1.6. Hydrophobic fillers are preferred and hydrophobicity can be enhanced by, for c}xample, coating a filler with a silane material. Sand is part;icularly preferred. The particle size, provided it does not interfere with the formation of a slurry, is not important. Thus the particle size may be as high as about 6500 microns, although usually it will be less. The invention does not impose stringent demands on the filler; for instance it does not require the refined, finely divided fillers of United States Patent numbers 9.,315,703 and 4,476,276, although finely divided filler can be used. The smaller the particle size, the closer the particles can pack in the gelled composition and therefore the denser an,d stronger in compression the composition will be. For reasons o~f economy it is anticipated that in many instances the filler will be ordinary sand, of a particle size between about 1000 and about 6500 microns, preferably between about 2500 and 6500 microns.
The quantity of filler material is at least 200 parts by weight based on 100 parts by weight of the total gelling agent.
However, larger quantities of filler are normally used, say in excess of 80%. If this is expressed as a percentage of filler, based on the weight of filler plus gelling agent, the quantity of filler is 67%. Preferably the filler ranges from 90% to 99%, more preferably at least 95% up to 98%, by weight of the combined total of gelling agent and filler.
As is usual with isocyanate-terminated prepolymers, the final product is formed by combining at least two separate streams of ingredients. The isocyanate is in an "A" stream and the isocyanate-reactive components are in a "B" stream. In the present case, water is the major isocyanate reactive component.
The filler is normally in the "B" stream and, with the water forms a slurry, e.g., a sand and water slurry. Whilst it is preferred to avoid the use of surfactant, some surfactant may be used to assist in the formation ~~f a pumpable slurry. The presence of suspending agent may increase the gelling time so it is preferred to use as little as poss~.ble, desirably Sts by weight or less, based on the weight of gelling agent. Ln some instances success has been achieved with ass little as 0.5%.
The compression strength of the composition, both wet strength and dry st.rengtlv, can be enhanced by incorporation of a 10 polyurethane dispersion. The pH of the polyurethane dispersion preferably is below 9.5, more preferably below 9 and particularly should be maintained aro~~nd 8. A preferred polyurethane TM
dispersion is Neo Rez R-X679 (available from ICI) which is an aliphatic aqueous colloi<~al dispersion of a urethane polymer with excellent chemical and U~ light resistance.
The weight ratio of: polyurethane dispersion to gelling agent is preferably between the limits of about 1~1 and 2~1"
Preferably the ~fispersion should contain not more than 10%
volatile organic; compone7ats and preferably much less.
The strength of they composition can be enhanced by inclusion of a Aatex, for example an acrylonitrile-butadiene-styrene latex or a natural rubber latex, or a polyethylene dispersion. This is somet.ime~s accompanied by the disadvantage that surfactant contained i.n the latex or dispersion may lead to enhanced water uptake by t;he cured composition. The use of such latexes and dispersions is still within the scope of the invention, however.
The sand/water slurry may contain the minimum amount of suspending agent: necessary to produce a pumpable slurry. There are known polys<~ccharides for this purpose and mention is made particularly of a heteropoly~saccharide available from the Kelco Division of Merck & Co. J_nc. To the extent possible, it is preferred to avoid the ueae of: suspending agents, and surfactants, since they block the iso::vyanate moieties and may increase the gelling time, and also they encourage uptake of,water, which is undesirable.
Other additives which may be used include UV
stabilizers, defoamers, titanates, silane coupling agents, accelerators or retarders to control the gelling time, antioxidants and pigments.
Particularly useful additives are defoaming agents such TM
as Surfynol DF :L10L (a h:i.gh molecular weight acetylenic glycol non-ionic defoamer available from Air Products and Chemicals, Inc.), DB-31 additive and DB--65 additive (silicone additives TM
available from Dow Corning) and UV stabilizers such as Tinuvin 292 TM
(a hindered amine photostabilizer) and Tinuvin 328 (an ultraviolet absorber) which are availablE~ commercially from Ciba-Geigy Ltd.
A topcoat is preferably applied to the surface of the cured consolidated hydroge:l-filler mass to protect it from UV
radiation. Since the wet compression strength of the hydrogel is less than the d:ry strength, it is preferred to protect it also from unnecessary exposure to water, for example, rain water. The topcoat is suitably a moi~>ture-cured polyurethane layer. It should be durable, flexib7.e, water-resistant and resistant to UV
radiation. It should also be easy to apply as a thin film.
21074qfi 17 ~ 60557-4535 Suitable moisture-curable polyurethanes include isocyanate-terminated or thioisocyanate terminated polyurethane prepolymers which cure by reaction with atmospheric moisture, such as prepolymers obtained by reaction of an equivalent excess of at least one organic polyisocyanate or polythioisocyanate with one or more organic compounds having a plurality of hydroxy, thiol or amine groups. As polyisocyanate, commercially available mixtures of toluene diisocyanates, such as a mixture of 80% 2,4-toluene diisocyanate and 20% 2,6-tolylene diisocyanate, are suitable.
Suitable hydroxy-group containing compounds are hydroxy terminated polyesters such as polyethylene propylene adipate and polyethylene adipate and hydroxy terminated polyethers such as glycols for example poly (oxyethylene} glycols, poly (oxypropylene) glycols and poly (oxybutylene) glycols. The reaction of the moisture-curable isocyanate can be catalyzed, for example with oxazolidine, which is supplied separately, giving a two part system. The top coat prepolymer preferably also contains fillers such as titanium dioxide or carbon black. Moisture-curable polyisocyanates that are suitable for use in the top coat are described in United States Patent number 3,'723,163.
Alternatively, a top coat can be provided by means of a two part system, one part being an isocyanate-terminated prepolymer and the other part being a golyol or a hydroxy-terminated polyether po:lyol. Suitable isocyanate-terminated prepolymers include those useful as moisture-curable prepolymers, discussed above. Again" the top coat can contain filler, for example titanium dioxide or carbon black.
21a749s A particular topcoat composition which is suitable contains titanium dioxide, carbon black, defoamer, ODEBA (octyl diethyl bis aniline crosslinker), A 189 Silane, DBTDL (dibutyltin dilaurate), Tinuvin 144,. Byk P104, toluene and DMDEE, (d-morpholine-4,4'-(oxydi-1,2 ethanediyl)bis) from Union Carbide.
The topcoat moisture-curable polyurethane compositions are preferably applied directly to the surface of the cured hydrogel by spreading with a suitable tool such as a sawtooth notched rubber squeezer, a paint roller, a standard push broom or brushes. The topcoat is preferably spread thinly to provide a thickness of from about. 0.25 mm to about 1 mm, preferably about 0.25 mm.
The topcoat gives the product resistance to UV light, protects the product from water such as rain water and is flexible. It is best t.a apply the topcoat after curing of the hydrogel preferably after six hours of applying the hydrogel ingredients, more preferably 16 hours and particularly 24 hours afterwards.
The sand/water slurry may suitably be prepared by mixing in a cement mixer. Any other additives, such as the polyurethane dispersion, should also be included in the mixing of the slurry.
It is important that the ingredients are well mixed or the performance of the cured hydrogel may be adversely affected. If a cement mixer is used or other equipment which has previously been used for cement, in view of the high alkalinity of some cement mixes, it may be necessary to use some acid additive, such as acetic acid, to ensure that the pH is not too high. Above a pH of about 10.2 the gelling rnay be affected, gelling time may be increased and an unfavourable product obtained. It is preferred that the pH is less than 9.5 and more preferred that it is less than 9 and particularly less than 8.
After mixing, the sand/water slurry is combined with the gelling agent. Suitably a concrete pumping device can be used to pump the slurry to a mixing nozzle where the gelling agent is introduced, mixed and directed at the support surface. Curing takes place shortly thereafter. These same steps can be used to repair a barrier layer that has been damaged; the invention permits easy repair.
In the preferred embodiment using a topcoat, the hydrogel composition is preferably allowed to cure for 6 hours, more preferably ~6 hours, still more preferably 24 hours, before applying the topcoat.
In one embodiment of the invention a sand/water/polyurethane dispersion slurry is dumped into a concrete pumping device. The slurry is then pumped to a mixing nozzle where a hydrogel prepolymer is introduced, mixed and propelled to the work surface. Curing takes place shortly thereafter to produce the consolidated sand liner. This application method using a concrete pumper allows easy placement of a controlled thickness of hydrogel/consolidated sand mass.
Typically 25 to 50 mm of hydrogel mass and a 0.25 mm topcoat are recommended for areas which are not subject to vehicular traffic.
If a high level of traffic is anticipated, then 50 to 100 mm of consolidated sand and the 0.25 mm topcoat are recommended.
In one embodiment of the method, sand to be used as filler is taken and placed in a container. Water is added to the 21 074 ~ 6 container until it reac;hes the level of the surface of the sand.
The amount of water present is observed. To the water/sand slurry so formed are added any other required ingredients, for instance a suspending agent to prevent the sand from settling out and defoaming agents. The formed slurry is pumped to the desired location where it is admixed with the gelling agent that is supplied from a separate stream. Just before gelling occurs the composition can be sprayed into position and then shaped, if necessary for instance by paddles or dikes or moulds or formwork.
The amount of gelling agent supplied is determined with regard to the amount of water present and the desirability of having a water: gelling agent ratio in the range of about 4:1 to 10:1, preferably about 6:1. In tests it was found that when 200g samples of sand was taken, about 40g of water was required to raise the level of water to the level of the sand, and a pumpable slurry could be formed. To react with 40g of water in 1:6 ratio, 6.7g of gelling agent was required. It was found that this amount was sufficient to form a barrier composition with the required properties, in accordance with the invention.
The amount of gelling agent, as a percentage of the total pre-gelled composition, is 6.7 x 100 = 2.7%. The amount of 246.7 filler in the pre-gelled composition is 80%. It is surprising that a satisfactory barrier composition can be formed with so little gelling agent, together with the inexpensive materials sand and water.
Cured compositions according to the invention, coated with the topcoat, when immersed in water for a week had a water 2~ 0~49~ s uptake of less than 5%. The permeability rate of the geosynthetic barrier for water may be as low as 10 8cm/s and for gasoline and toluene may be as low as 10 7cm/s. The wet compression strength of a 19 mm thickness of: hydrogel mass (at 50% compression) can be as great as about 700 l~:Pa and dry compressions strength (at 50%
compression) can be as great as about 3500 kPa. Compression strength values may vary with the particle size of the filler.
The compositi.an of the invention can be used with other materials to make a mul.ti-layer barrier or liner. For example, there can be applied a layer of the composition over a shaped surface of soil to a suitable depth, for instance about 6 mm.
There can be laid on the cured composition a sheet liner. High density polyethylene, high density polypropylene and PVC are suitable materials for such a liner and a suitable thickness of liner is again about 6 mm. A further layer of the composition of the invention can then be applied over the liner suitably of thickness of about 38 mm, thereby providing a liner of about 50 mm. This can be covered with a UV-protective lining, as discussed above.
The barrier campositions can be used in primary or secondary containment. In secondary containment they may be applied directly to the ground under or adjacent and around a primary container. To ensure that no liquid escapes they can be applied more thickly towards the perimeter and more thinly in the centre to provide a gradient to keep liquid in the centre, or a vertical lip or wall can be provided at the perimeter. They can also be applied as a coating directly on the outer surfaces of a primary container. Since the permeability rate of the barriers is low for gasoline and toluene they are suitable for use in petroleum-oil-lubricant. secondary containment. The permeability rate for water is also l.ow and they are suitable in a wide range of uses such as, for example, as liners or barriers in primary or secondary containers in settling ponds, at landfill sites and transformer sites.
The invention has been described with particular reference to containment. of toxic or noxious substances, but it will be appreciated that. the invention can be used to contain non-toxic or non-noxious substances.
The invention is further illustrated in the following examples, in which parts are by weight unless otherwise indicated.
There are first described the experimental test methods.
EgPERIMENTAL TEST HETHODS
Density Approximately a 1 inch square sample of Geosynthetic Barrier was cut from the sample prepared. Exact measurements were taken with a micrometer and the sample Weighed. From this information the density of the sample could be obtained.
Note: Since Geosynthetic Barrier samples take up water albeit slowly), in the name of accuracy the water displacement method of determining sample volumes was not used.
Water Absorption After allowing the GB samples to cure for two weeks water uptake was determined gravimetrically. The samples were weighed, submerged in water for 1 week, removed and then re-21 07~+q 6 weighed. Water uptake is reported as a percentage of weight increase.
Permeability Permeability was used to evaluate the water/solvent resistance of Geosynthetic Barrier samples. The constant head method of determining permittivity was used. A two week cure was allowed before testing. At this time a head of water/solvent was applied to the geosynthetic barrier and the rate of loss of water/solvent monitored. The following equation was used to determine the permittivi.ty of the Geosynthetic Barrier sample.
= 1 I n bo t hl where t is the time in seconds, hQ is the initial head in mm and hl is the final head in mm.
The normal coefficient of permeability can be determined by multiplying the permittivity by the sample thickness (ASTM
D4491).
Compression (Wet and Dry) An instron 1123 was used to test the compression resistance of the Geosynthetic Barrier samples. One inch square samples were placed between instron compression plates. The cross-head speed was 20 mm/min and the chart speed was maintained at 50 mm/min. A maximum load of 25,000 N was placed on the samples. The compression strength at 33% and 50~ compression was determined and the integrity of the sample after full load was recorded for comparison purposes.
Ultraviolet (UV) Resistance An atlas UVCON was used to expose the Geosynthetic Barrier samples to UV radiation. Eight FS-40-T12 UV florescent lamps were used as a source of radiation. The samples were exposed for 2000 hours at a temperature of approximately 5loC.
The flexibility and degradation of the top coat was determined after 2000 hours.
Additional samples were exposed to a 1000 hour xenon-arc accelerated UV weathering cycle.
Weathering Cycles The weathering cycle consists of placing samples at 40°C
for 20 hours, followed by room temperature for 4 hours followed by -18°C for 20 hours. This cycle was repeated continually and observations were recorded weekly. The flexibility, integrity and peel strength of the geasynthetic barrier and top-coat were of interest.
EBAMPLES
Example 1 A homogeneous. mixture of washed all-purpose anhydrous sand (100 parts) and water (20 partsy was prepared and is referred to as Part A (if the sand is wet the amount of water is adjusted accordingly). Part B consists of 3.3 parts of a hydrophilic isocyanate-terminated prepolymer E. Prepolymer E is an ethylene oxide capped polyether triol derived from glycerol, of molecular weight approximately 5000, that has been reacted with TDI with a ratio of NCO:OH of 2:1, dissolved in acetone. Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 1.3224 g/mL wa:c obtained. One week and four week water absorptions were 13.03 and 23.3 weight per cent. The 50 per cent wet and dry compression values were 380 and 2160 kPa respectively.
Permeability values of water, toluene and gasoline were 1.5 x 10~, 2.7 x 10-6 and 2.9 x 10-'' cm/s respectively.
In field trials the same hydrophilic isocyanate-terminated prepo.lymer, but dissolved in diethylene glycol monoethyl ether acetate, not acetone (Prepolymer F) was used and similar results were obtained.
Example 2 A homogeneous mixture of sand (100 parts), water (16.7 parts) and polyurethane dispersion (6.7 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B consists of 3.3 parts of the hydrophilic isocyanate-terminated prepolymer E.
Part B was added to part: A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 1.8173 g/mL was obtained.
One week water absorption was 10.66 weight per cent. The 50 per cent wet and dry compression values were 770 and 3415 kPa respectively. Permeability values of water, toluene and gasoline were 4.0 x 10-8, 2.8 x 10-6 and 4.6 x 106 cm/s respectively. The marked increase in the wet compression value demonstrated the effect of addition of the polyurethane dispersion.
Field trials with prepolymer F gave similar results.
210749fi Example 3 A homogeneous mixture of sand (100 parts), water (20 parts) and polyurethane dispersion (3.33 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B
consists of 3.33 parts of the hydrophilic isocyanate-terminated prepolymer E. Part B was added to part A and the mixture stirred until just before gelat.ion. The composition was poured into a mold and allowed to cure for two weeks before testing. A
consolidated sand/polyu,rethane mixture of density 2.00 g/mL was obtained. One week water absorption was 11.08 weight per cent.
The 50 per cent wet and. dry compression values were 700 and 2710 kPa respectively. Permeability values of water, toluene and gasoline were <- 10-8, 1.6 x 10~? and <- 10-a cm/s respectively.
Field trials with prepolymer F gave similar results.
Example 4 A homogeneous mixture of sand (100 parts), water (20 parts ) and polyurethane dispersion (3.33 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B
consists of 3.33 parts of a mixture of hydrophilic/hydrophobic isocyanate-terminated prepolymers (prepolymer E/prepolymer A =
85/15). Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 2.302 g/mL was obtained. One week water absorption was 9.76 weight per cent. The 50 per cent wet and dry compression values were 770 and 1550 kPa respectively.
Permeability values of toluene and gasoline were 2.9 x 10~T and s 108 cm/s respectively.
.. 2'~07~9~
Field trials with prepolymer F gave similar results.
Example 5 A homogeneou:c mixture of sand (100 parts), water (20 parts) and polyurethane: dispersion (3.33 parts, Neo Rez R-9679 from ICI) was prepared and is referred to as part A. Part B
consists of 3.33 parts of a mixture of hydrophilic/hydrophobic isocyanate-terminated prepolymers (prepolymer E/prepolymer A
75/25). Part B was added to part A and the mixture stirred until just before gelation to ensure a homogeneous mixture. The composition was poured into a mold and allowed to cure for two weeks before testing. A consolidated sand/polyurethane mixture of density 1.971 g/mL was obtained. One week water absorption was 8.99 weight per cent. The 50 per cent wet and dry compression values were 890 and 3875 kPa respectively. Permeability values of toluene and gasoline were 1.63 x 10-~ and 1.4 x 10-6 cm/s respectively.
Field trials with prepolymer F gave similar results.
Example 6 A homogeneous mixture of sand (100 parts) and water (20 parts) was prepared and is referred to as Part A. Part B consists of 3.3 parts of the hydrophilic isocyanate-terminated prepolymer E. Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for 16 hours after which time a top-coat consisting of 5891E (3M: Company) was applied at a 10 mil.
thickness. The total Geosynthetic Barrier was allowed further cure for 1 week and four weeks. One week water absorptions were 3.72 and 3.83 weight per cent respectively. UV resistance and weathering of thE~ top-coat were excellent compared to the Geosynthetic Barrier without: t:op-coat.
Field trials with prepolymer F gave similar results.
Example 7 A homogeneous mi~:t,ur.e of sand (100 parts) and water (20 parts) was prepared and is referred to as Part A. Part B consists of 3.3 parts of the hydrophilic isocyanate-terminated prepolymer E. Part B was added to part A and the mixture stirred until just before gelation. The composition was poured into a mold and allowed to cure for 16 hours <~fter which time a top-coat consisting of 58'~lE (3M Company), 2 parts carbon black, 0.25 parts TinuvinM328 and 0.1 parts Texacat DMDEE was applied at a 0.25 mm.
thickness. The total Geosynthetic Barrier was allowed further cure for 1 week. Four week water absorption was 8.77 weight per cent. UV resistance and V~e~athering resistance were excellent compared to Geosynthetic Barrier materials in the absence of top-coats.
Field trials with prepolymer F gave similar results.
Claims (20)
1. A gelled continuous barrier to contain a liquid, the barrier comprising the product of reaction between:
(a) water (b) a gelling agent comprising an isocyanate-terminated hydrophilic prepolymer or a mixture of an isocyanate-terminated hydrophilic prepolymer and up to 40 parts by weight, based on 100 parts by weight of the isocyanate-terminated hydrophilic prepolymer, of an isocyanate-terminated hydrophobic prepolymer (c) a water insoluble high density filler wherein the weight of filler exceeds twice the weight of the gelling agent.
(a) water (b) a gelling agent comprising an isocyanate-terminated hydrophilic prepolymer or a mixture of an isocyanate-terminated hydrophilic prepolymer and up to 40 parts by weight, based on 100 parts by weight of the isocyanate-terminated hydrophilic prepolymer, of an isocyanate-terminated hydrophobic prepolymer (c) a water insoluble high density filler wherein the weight of filler exceeds twice the weight of the gelling agent.
2. A barrier according to claim 1, wherein the filler is a hydrophobic material.
3. A barrier according to claim 1, wherein the filler is a siliceous compound, a rubber, a clay or calcium carbonate.
4. A barrier according to claim 1, wherein the filler is sand.
5. A barrier according to claim 1, wherein the filler is from 90 to 99% of the total weight of the pre-gelled composition.
6. A barrier according to any one of claims 1 to 4, wherein the filler is from 95 to 98% of the total weight of the gelling agent and the filler.
7. A barrier according to any one of claims 1 to 4, wherein the filler is from 90 to 99% of the total weight of the gelling agent and the filler.
8. A barrier according to any one of claims 1 to 4, wherein the filler is in excess of 67% of the total weight of the gelling agent and the filler.
9. A barrier according to any one of claims 1 to 8, wherein the said product further incorporates a polyurethane dispersion.
10. A barrier according to claim 9, wherein the weight ratio of the polyurethane dispersion to the gelling agent is from 1:1 to 2:1.
11. A barrier according to any one of claims 1 to .LO, which is covered by a flexible waterproof, UV resistant topcoat.
12. A barrier according to claim 11, wherein the topcoat is a filled moisture-cured polyurethane.
13. A barrier according to claim 11, wherein the topcoat is a filled, cured two part polyurethane.
14. A barrier according to any one of claims 1 to 13, wherein the ratio of the water to the prepolymer is from 10:1 to 4:1.
15. A barrier according to any one of claims 1 to 13, wherein the ratio of the water to the prepolymer is from 6:1 to 4:1.
16. A barrier according to any one of claims 1 to 15, wherein the gelling agents comprises a. hydrophilic isocyanate-terminated prepolymer of the formula R[ R'O)a-C(O)NH-R"(NCO)b]c wherein R is an active hydrogen-free residue of a polyol having a hydroxy functionality of c, R' is an alkylene radical, R" is the residue of an isocyanate precursor bearing (b+1) isocyanate moieties, a has a value in the range of from about 50 to 500, b has a value from 1 to 5 and c has a value from 2 to 6, and at least 70% of the alkylene radicals R' are ethylene radicals.
17. A barrier according to any one of claims 1 to 15, wherein the gelling agent includes up to 40% of a hydrophobic isocyanate-terminated prepolymer of the formula R[(R'O)a-C(O)NH-R"(NCO)b]c wherein R is an active hydrogen-free residue of a polyol having a hydroxy functionality of c, R' is an alkylene radical, R" is the residue of an isocyanate precursor bearing (b+1) isocyanate moieties, a has a value in the range of from about 50 to 500, b has a value from 1 to 5 and c has a value from 2 to 6, and fewer than 70% of the alkylene radicals R' are ethylene radicals.
18. A barrier according to claim 17, wherein more than 30% of the alkylene radicals R' are propylene radicals.
19. A barrier according to any one of claims 1 to 15, wherein the gelling agent includes up to 40% of a hydrophobic isocyanate-terminated prepolymer that is based on Castor oil reacted with an aromatic isocyanate.
20. A method of forming a barrier as claimed in claim 1, which method comprises admixing, at a location to be occupied by the barrier, water, a water insoluble high density filler and a gelling agent comprising an isocyanate-terminated hydophilic prepolymer or a mixture of an isocyanate-terminated hydrophilic prepolymer and up to 40 parts by weight, based on 100 parts by weight of the isocyanate-terminated hydrophilic polymer, of an isocyanate-terminated hydrophobic prepolymer, wherein the weight of filler exceeds twice the weight of the gelling agent, and applying the composition so formed to the location and permitting it to cure to form the required barrier.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002107496A CA2107496C (en) | 1993-10-01 | 1993-10-01 | Geosynthetic barrier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002107496A CA2107496C (en) | 1993-10-01 | 1993-10-01 | Geosynthetic barrier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2107496A1 CA2107496A1 (en) | 1995-04-02 |
| CA2107496C true CA2107496C (en) | 2004-09-21 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002107496A Expired - Fee Related CA2107496C (en) | 1993-10-01 | 1993-10-01 | Geosynthetic barrier |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5882142A (en) * | 1996-09-03 | 1999-03-16 | Sioux Steel Company, Inc. | Containment dike assembly and method for construction thereof |
| US20030092848A1 (en) | 2001-09-11 | 2003-05-15 | Ashok Sengupta | Sprayable liner for supporting the rock surface of a mine |
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- 1993-10-01 CA CA002107496A patent/CA2107496C/en not_active Expired - Fee Related
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