CA1148287A - Rendering porous structures impermeable by treatment with ph insensitive gelable compositions of amide polymers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Aqueous solutions of amide polymers, such as polyacrylamide when treated with small amounts of a water-soluble polyaldehyde and a hypohalite salt at an alkaline pH, react to form firm gels within a short time at ambient temperature. Such gels, which are stable under alkaline as well as acidic conditions, are usefully employed to plug porous subterranean forma-tions, for grouting of leaking soil pipes or wells, and to otherwise render porous structures impermeable to the passage of liquids such as water.

Description

:

2~37 GELABLE AQUEOUS REACTION MIXTURES CONTAINING
A WATER-SOLUBLE POLYMER ~ERIVED FROM AN
ET~LENICALLY UNSATURATED AMIDE, AN ALIPHATIC
5POLYALDEHYDE AND A METAL SALT OF A HYPOHALITE;
THE GEL PREPARED BY REACTING THE REACTION
MIXTURE, AND A METHOD OF RENDERING A
POROUS STRUCTURE IMPERMEABLE BY EMPLOYING
THE REACTION MIXTURE

10The present invention is directed to a gelable aqueous reaction mixture characterized by comprising an aqueous medium having dispersed therein a water-soluble polymer derived from an ethylenically unsa-turated amide, an aliphatic polyaldehyde and a:metal salt of a hypohalite in proportions such that when the reaction mixture is subjected to an efffective reaction temperature and an alkaline pH greater than 7.5, the reaction mixture reacts to form a water-insoluble gel. The invention is also directed to a gel characterized by being made by subjecting the above reaction mixture to~an effectiYe reaction temperature and an alkaline pH greater than 7.5.
The invention is further directed to a method for render-ing a porous structure impermeable which comprises treating the porous structure with a gelable aqueous reaction mixture characterized in that the reaction 27,2g4-F
~"

~~ ~

mixture as hereinbefore described is forced into and over the porosities of the structure and reacts to form a gel capable of rendering said structure impermec~ble to the passage of aqueous liquids.

An embodiment of particular interest involve~
placing the aforementione~ gelable composition in a porous subterranean formation and subsequently gelling the composition to render the formation impermeable.
In a similar embodiment of interest, the gelable compo-sition is pumped or otherwise forced into cracks or similar porosities in sewer pipes, potable water wells and like conduits and then gelled in place thereby plugging and alleviating leakage from or into the conduits. This latter embodiment is hereinafter referred to as "grouting of porous structures."

It is among the advantages of the invention that water-insoluble gels, preferably those that are also ~irm, nonweeping, structurally sturdy and liquid impervious, are obtained from the gelable compositions employed in the practice of the present invention. It is a further advantage of the invention that the gelation reaction is initiated within a controlled reasonable period of time after the amide polymer, the hypohalite s~lt and the alipha-tic polyaldehyde, preferably dialde-hyde, are contacted in an aqueous medium having theproper controlled alkaline pH. Such gelation reaction proceeds readily at ambien-t or higher temperatures.

It is, indeed, surprising that the method of the present invention provides a firm gel capable of rendering a porous substrate impermeable. It is even 27,294-F

~3--more surprising that such gel, which forms very rapidly at alkaline pH, is very stable in both alkaline and acidic envirollments.

In addition to the aforementioned utilities S of the present invention, the compositions employed in the present invention may also be employed in such appl;.cations as blocking off seepage under buildings or high~7ays, preventing seepage loss through dams, dikes and irrigation ditches, blocking infiltration of pol-luted ground ~ater into potable water wells or to replace aqueous gels prepared from gelatin or vegetable gums as, for example, in air freshener devices or in gelled cosmetics such as roll on deodorants and the like.

The amide polymers employed in the practice of this invention have polyethylenic backbones bearing pendant carboxamide moieties. Such amide polymers are normally addition polymers containin~ polymerized ethylenically unsaturated carboxamide monomers which may contain up to 50 mole percent of another eihylenically unsaturated monomer copolymerizable with the carbox-amide monomer or monomers. So lon~ as the amide polymer has sufficient molecular weight to react with the poly-aldehyde and hypohalite salt to form a desired firm gel, molecular weight of the amide polymer is not particularly critical. The viscosity of an aqueous solution of the amide polymer is an index of the molecular weight of said polymer and, thus, for most of the purposes of the present invention it is desirable to employ poly-mers of relatively low molecular weight so that a sub-stantial proportion of solids can be incorporated inthe aqueous sol.ution of polymer without producing 27,294-F

excessive viscosity such as to render the solution difficult or impossible to pump. Gelation in accord-ance with the invention can be obtained with amide polymers having such low molecular weiyhts as to be characterized by a viscosity of only about 50 centi-poises for an a~ueous 40 percent by weight solution of the polymer. On the other hand, gelation can be obtained with amide polymPrs of very high molecular weight chaxacterized, for example, by a viscosity of 60 centi-poises for an aqueous 0.2 percent by weight solutionthereof. In practice, to provide the firmness, abrasion resistance and structural stability desired in gels employed for plugging porous structures, as, for example, in and around sewer pipes, it is preferred to produ.ce a gel containing at least 5 percent of amide polymer solids. Thus, for ease of handling and placing in the porous structure, it is preferred to employ amide polymers having viscosities of from 100 centipGises to 15,000 centipoises for an a~ueous 20 percent by weight solution thereof.

To form the desired gel capable of rendering the porous structure impermeable, the amide polymer preferably contains from 50 to 100 mole percent of one or more ethylenically unsaturated carboxamide monomers, more prefexably from 70 to 10G mole percent, and most preferably from 90 to 100 mole percent of amide monomers. Exemplary carboxamide monomers include acryl-amide, methacrylamide, fumaramide, ethacrylamide or N-methylacrylamide. It is understood that the finished polymer contains sufficient water-solvating carboxamide moieties to render the finished polymer soluble in 27,294-F

2~
--s--water to the extent of at least 5 percent by weight and preferably to the exkent of 20 percent or more by weight. Acrylamide, per se, is the preferred carbox-amide monomer.

Examples of other monomers which may be copolymerized with the aforementioned amide monomers and which do not generally interfere with the gelation reaction include unsaturated aliphatic acids such as acrylic and methacrylic acid, and their water--soluble salts, particularly alkali metal salts, such as sodium acrylate or sodium methacrylate; hydroxy alkyl and alkyl esters of a,~-ethylenically unsaturated carboxylic acids such as ethyl acrylate, methyl acrylate, butyl acrylate, methyi methacrylate, hydroxyethyl acrylate;
sulfoalkyl esters of ~ ethylenically unsaturated carboY.ylic acids such as sulfoethyl acrylate and the sodium salt thereof, vinylbenzyl chloride and vinyl benzyl quaternary ammonium halides such as vinyl benzyl trimethyl ammonium chloride; isopropenyl oxa-zoline; monovinylidene aromatics and sulfonated mono-vinylidene aromatics such as styrene and sodium styrenesulfonate. of course, it is understood that said other monomers should also be chosen so that they do not react with the amide monomer or otherwise inter-fere with the gelation reaction. Amide polymers aressmetimes subject to some degree of hydrolysis during preparation or may purposely have a proportion of their amide groups hydrolyzed to carboxylate groups during or after preparation. For the purposes of this invention, such partially hydrolyzed amide polymers are equivalent to the corresponding copolymers of carboxamide monomer and unsaturated aliphatic acid salt.

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~7 Also included within suitable amide polymers are graft polymers wherein the amide monomers or other sui.table monomers are grafted on cellulosic polymers such as cellulose, methylated cellulose and hydroxy-propyl methylcellulose.

In general, any aliphatic polyaldehyde, hav-ing sufficient solubility or dispersibili.ty in water to enable rapid, intimate mixing with an aqueous solution of amide polymer, may be employed in the method of the present invention. In practice, saturated aliphatic polyaldehydes are preferred. Suitable polyaldehydes include dialdehydes, such as glyoxal, succinaldehyde and glutaraldehyde, as well as more complex chemicals such as water-soluble or water-dispersible polyaldehyde starch deriv~tives. For most purposes a dialdehyde, particularly glyoxal, is preferred.

The hypohalite salt is suitably any metal hypohalite, but is preferably an alkali metal hypo-chlorite or hypobromite, most preferably sodium or potassium h~pochlorite.

In practicing the method of this invention, it is only necessary that the amide polymer, hypohalite salt and the polyaldehyde be thoroughly mixed in the proper proportions in an aqueous medium under conditions of suitable alkalinity to provide a gelable agueous reaction mixture. One such procedure is carried out by thoroughly mixing an a~ueous solution of the hypohalite salt with an aqueous solution of the amide polymer and the polyaldehydP under proper alkaline conditions.
Alternatively, an agueous solution of polyaldehyde is 27,29~-F

~14~ZB7 mixed with an aqueous solution of amide polymer and hypohalite salt under proper alkaline conditions.

In the gelable aqueous reaction mixture, the concentration of the amide polymer varies depending upon the molecular weight of the polymer and the firmness of the gel desired. If the amide polymer has a relatively low molecular weight, the concentration of amide polymer is advantageously from 0.25 to 30, preferably from 3 to 20, most preferably from 5 to 15, weight percent based on the reaction mixture. For the purposes of this invention, an amide polymer has a relatively low molecular weight if a 40 weight percent aqueous solution of the polymer exh.ibits a viscosity in the range from 50 to I5,000 centipoises as determined by a Brookfield LVT viscometer (#2 spindle, 15 rpm, 25C). It is under-stood, however, that somewha-t lower concentrations than the aforementior.ed can be employed with higher molecular weight amide polymers.

The concentration of polyaldehyde in the gel-able reaction mixture is at least an amount sufficientto cause the reaction mixture to form a water-insoluble, three dimensional gel within 5 minutes after the mixture is subjected to gelation conditions, up to the satura-tion concentration of the polyaldehyde in the reaction mixture. Advantageously, however, the gelable reaction mixture contains enough polyaldehyde to provide from 1 to 300, preferably from 5 to 100, millimoles of aldehyde moiety per mole of carboxamide moiety (-C-NE12 ) 27,294-F

~48~8~

in the amide polymer. When the polyaldehyde is gly-oxal, the concentrations of glyoxal sufficient to provide the aforementioned mole ratios are within the range from 0.004 to 1.2, preferably, from 0.~2 to 0.4, weight percent based on the gelable reaction mixture.
For sewer grouting and simi]ar subterranean plugging applications, it is preferred to employ from 15 to 60 millimoles of polyaldehyde per mole of carboxamide moiety in the amide pol~mer.

The concentration of the, hypohalite salt in the gelable reaction mixture is an amoun-t sufficient to provide the resulting gel with alkaline stability. A
gel possesses the requisite alkaline stability if it does not dissolve in an aqueous medium having a p~ of 8 in a period of at least a week after the gel is placed in the aqueous medium. Gels having preferred alkaline stability do not dissolve in an aqueous medium having a pH of 8-10 for a period of six months, those gels which are insoluble in 5N NaO~ for a week being most preferred. The concentration of hypohalite salt is in the ranse from 2 to 600, preferably from 10 to 250, most preferably from 15 to 160 millimoles of the hypohalite anion per mole of carboxamide moiety in the amide polymer. The hypohalite salt is advantageously employed in the form of an aqueous solution prepared by dissolving the corresponding free halogen in a slight molar excess of alkali metal hydroxide or other rela-tively strong base with cooling to prevent the forma-tion of halites or halates. As a result of this preferred practice, a solution is made which contains a mole of halide ion for each mole of hypohalite ion formed. A slight excess of the base is beneficially 27,294-F

'~7 --g .

employed to stabilize the hypohalite ~olution and to provide an aqueous solution of hypohalite having a pH
of at least 12 and preferably a pH over 13 without containing such an excess of alkali as to cause unde-sired hydrolysis of the amide groups of the polymerwhen the hypohalite solution is mixed with the amide polymer solution. For economical reasons, it is desir-able to employ a commercial household bleach which is an aqueous solution containins 5.25 to 5.5 weight per-cent of sodium hypochlorite, an approximately equi-molar proportion of sodium chloride and sufficient excess of sodium hydroxide to provide a solution having a pH of 13.5 or slightly higher. In commercial bleach, the stabilizing excess of NaOH corresponds to 0.3 to 1 percellt by weight of the solution.

Advantageously, the pH of the reaction mixture at the initiat:ion of gelation should be in the range from 7.5 to 14, pre~erably from 8 to 13.5, most prefer-ably from 10 to 13. This desired alkalinity at the outset of gelation is accomplished by the addition of a relatively strong base to one of the aforementioned starting ingredients, preferably the polyaldehyde ~nd/or the hypohalite salt, most preferably the hypohalite ~alt, or to the reaction mixture prior to gelation.
Generally, any base capable of generating the needed alkaline pH which does not interfere with the gelation reaction is usefully employed. Examples of relatively strong bases advantageously employed to provide this desired alkalinity include alkali metal hydroxides such as sodium and potassium hydroxide; metal phos-phates such as trisodium phosphate; metal carbonates such as sodium carbonate; alkylamines such as dimethyl-amine, methylamine and trimethylamine; and other organic 27,294-F

bases such as ethylenediamine. Of the foregoing bases, those such as trisodium phosphate which provide a maxi-mum pH in the range from 9 to 14 are preferred.

In practice, when operating temperatures from about 20C up to a temperature at which the amide polymer or other reactants degrade prematurely, the gelation reaction is initiated rapidly when an aqueous solution of the amide polymex and polyaldehyde is brought together with the hypohalite salt dissolved in the alkaline solu-tion, particularly when the reaction mixture has a pHin the preferred pH range from 10 to 13. Thus, for example, when an aqueous polyacrylamide/glyoxal solu-tion at a pH below 7 and at a temperature between 20C and 25C is combined with an aqueous solution of sodium hypochlorite containing sufficient trisodium phosphate so that the pH of the resulting reaction mixture is in the range from 10 to i3.5, the resulting mixture sets to a firm water-insoluble gel within a matter of seconds while the pH falls to a value within ~0 the range of 7 to 11. It will be apparent to the skilled artisan that a wide range o gel times can be obtained with any particular mixture of amide polymer, hypohalite salt and polyaldehyde by suitable adjustment of the temperature or pH or both. Although less pre-ferred than the gels made by the foregoing techni~ue,suitable gels can be formed by first reacting the poly-aldehyde with amide polymér and then contacting this gel reaction product with the hypohallte salt.

The amide polymer solutions employed may be prepared by known methods. ~hus, for example, an amide 27,294-F

'~37 monomer or monomer mixture as defined above may be dis-solved in water and subjected to catalytic solution polymerization by addition thereto of a redox catalyst system such as a peroxide-bisulfite system or by the use of a peroxide or azo catalyst with controlled heat-ing. Alternatively, the polymer may be prepared by known methods, e.g., U.S. Patent 3,284,393, as a water~
in-oil suspension or emulsion in a water-insoluble liquid such as a liquid hydrocarbon and the desired polymer solution be prepared by invert:ing said emulsion or solution in water, for example, with the aid of a sur-factant. It is further understood that the amide poly-mer may be dried and then redissol~ed in an aqueous medium to form a sui-table aqueous solution.

In the practice of the invention, it is generally necessary to provide means for placing the gelable reaction mixture in the position desired before gelation occurs. Thus, for example, an aqueous solution of the amide polymer and polyaldehyde and an alkaline solution of the hypohalite salt may be pumped by separate pipe systems and mixed at (or immediately adjacent to) the site where it is desired to deposit the gel. In the plugging of porous subterranean strata, as when unde-sired seepage is polluting a water well, packers can be placed above and below the porous strata. The amide polymer/polyaldehyde solution and alkaline hypo-halite solution can then be introduced into the space between the packers through separate pipes whereby the ~olutions are mixed in said space and forced under pres-sure into the porous formation where gelation providesthe desired plugging.

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When a crack or perforated area is detected in a sewer pipe or well casing, for example, by remote television survey or other pipe or well logging method, it is convenient to employ a packer having end pieces S which can be inflated h~draulically to provide positive pressure seals on either side of the cracked or perfor-ated area, said end pieces being connected by a cylin-drical member of somewhat smaller diameter than the diameter of the pipe or casing to define an annular space contiguous to the cracked or perforated area.
A~ueous solutions of amide polymer polyaldehyde and hypohalite salt are preferably introduced rapidly under pressure through separate pipes in the proper proportions and at the proper alkalinity into the annular space where mixing occurs and the mixture is forced by pressure through the cracked or perforated area and into any porosities in the surrounding medium.
When a sharp rise in back pressure is detected ~hich indicates that gelation is occurring in the available porosities, pumping is discontinued and the packer is deflated and removed. Alternatively, one of the solu-tions employed above may be a solution of an amide polymer and polyaldehyde adjusted to an acidic pH in the range of 4 to 5 while ~he second solution consists of the hypohalite salt dissolved in an aqueous alkaline reagent such as a solution of sodium hydroxide or tri~odium phosphate.

The following examples illustrate the inven-tion but are not to be construed as limiting its scope.
All parts and percentages are by weight unless otherwise indicated.

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~ ~ .
Z~7 Example 1 and Comparative Run A
An aqueous solution containing 20 percent of a homopolymer of acrylamide was prepared and found to have a pH of 5 and a viscosity of 475 centipoises at 27C as determined with a Brookfield LVT viscometer using a #2 spindle at 30 rpm. To 25 grams of the fore-going solution was added with stirring 0.2 ml of a 40%
solution of glyoxal in water. To this solution at 21C
was added w:ith mixing a second solution consisting of 17 g of deionized water, 0.425 g. of Na3PO4 12H2O and 8 g of 5.25% a~ueous solution of NaOCl. The resulting mix-ture had an initial pH of 11.5 and formed a firm, non-pourable, water-insoluble gel in 19 seconds. The gel was self-supporting and did not exude water on standing.
The gel was immersed in 5N NaOH for several days without any noticeable deterioration.

When the gelable composition of this example was placed in a porous subterranean structure and gelled by the foregoing procedure, the structure was rendered impermeable to the passage of aqueous liquid.

For purposes of comparison, a gel was pre-pared according to the foregoing procedure except that no NaOCl is employed. While a nonpourable gel was formed by this procedure within 15 seconds, the gel was entirely destroyed when immersed in 5N NaOH for one hour.

~xamples 2 Through 10 An ayueows solution containing 20 percent of a homopolymer of acrylamide was prepared and found to have a pH of 4.9 and a viscosity of 388 centipoises at 27,294-F

-25C as determined with a Brookfield LVT viscometer using a #2 spindle at 60 rpm. To a 40 g portion of this solution was added with stirring an amount of a 40% solution of glyoxal in water as specified in Table I. To the resulting stirred solution was added with mixing a 40 g portion of a second solution contain-ing 0.4 g of Na3PO4, an amount of 5.25% active sodium hypochlorite aqueous solution as specified in Table I
and a remaining amount of water. The resulting mixture had an initial pH of 11 and formed a firm, nonpourable, water-insoluble gel in the time specified in Table I.
The gel did not dissolve or otherwise deteriorate significantly when it was immersed in 5N NaOH for 17 days. The foregoing procedure was repeated eight times using various amounts of glyoxal and sodium hypochlorite as specified in Table I. In each instance, a firm, nonpourable gel was formed which exhibits con-siderable alkaline stability.

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27, 294-F

~17-Example 11 A packing device was positioned in a sewer wherein a large eroded crac~ had developed where the seal between two sections o~ pipe h~d failed. The device had inflatable collars at either end of a rigid cylinder having a diameter sufficiently smaller than the sewer pipe to enable the device to be maneuvered into the desired position by cables. The rigid cylin-der carried dual piping which connected to nozzles positioned in the annular space between the cylindex and the sewer pipe and directed so that streams of fluid issuing ~rom the nozzles impinyed on each other and mixed together. The piping was connected to pre-sure hoses which were carried back through a manhole and connected to the outputs of positive displacement metering pumps. At least one of said outputs was fitted with a pressure gauge. The input end of one pump was connected to a first tank containing a known weight of an aqueous solution containing 20 percent of a polyacrylamide similar to that of Example 1 above.
The pH of this solution was adjusted to 5 by addition of concentrated H2S04. This solution is characterized by a viscosit~ of 450 cps (Brookfield LVT, #2 spindle, 30 rpm, 27C) and had been treated with a small amount of sodium sulfite to react out most of the residual acrylamide monomer and with an antimicrobial a~ount of sodium pentachlorophenate to protect against mold growth. To said solution there was admixed about 0.
part of an aqueous solution containing 40 percent glyoxal for each 100 parts of the polyacrylamide solution.
No gelation occurred at the predetermined pH o~ 5 for the mixture when it was maintained at room temperature for relatively short periods, e.g., one to two weeks.

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The input end of the second pump was connected to a second tank containing an aqueous solution of 1.5 percent of trisodium phosphate and 1.7 percent of NaOCl such that the pH of this solution was 12.3. The amount of solution in the second tank was approximately equal in volume to the aqueous solution in the first tank.
The pumps were calibrated so that they deliver equal volumes in equal times. When a test sample of solution ; from the first tank was mixed with an equal volume of the solution from the second tank, it was found that the resuiting mixture formed a nonpourable gel in less than 40 seconds.

The packing device was positioned so that one of the collars was on either side of the crack in the sewer and the collars were inflated to form a positive pressure seal against the interior of the sewer pipe.
The pumps were started so that the pol~ner-dialdehyde solution and the trisodium phosphate-sodium hypo-chlorite solution were mixed in the annular space of the packing device and the resulting mixture forced into and through the cracks into the surrounding medium. When the pressure gauge showed a sharp rise in pressure, the pumps were disconnected and the packing device deflated and removed from the sewer.
On subsequent inspection, it was found that the cracked area was filled and covered with a firm adherent - aqueous polymer gel.
:' In cases where a highly porous formation or - void exists outside a cracked or perforated sewer pipe or well casing it is generally desirable to first introduce a more dilute solution containing from 2 to 27,29~-~

:

10 percent of amide polymer toyether with a corre-spondingly decreased proportion of polyaldehyde, hypo-halite salt and relatively strong base so that the gelable cornposition may be pumped into the porosities ox voids more readily. In such cases, it is usually desirable to increase the concentration of amide poly-mer and proportion of polyaldehyde and hypohalite salt toward the end of the treatment in order to assure the desired structural integrity in the final seal.

In instances wherein it is desirable to have a noticeable delay between the time when the amide polymer, the dialdehyde, hypohalite salt and the alka-line agent are contacted and the time in which the gel reaction occurs, it is desirable to reduce the alkalin-ity of the mixed solutions such that the pH of such solution is at a value between 8 to 11, preferably from 9 to lQ. At the lower values of pH in the aforementiolled ranges, the time between initial contacting of the reactants and gelation (while i-t ~epends significantly on the concentration of the reactants) will generally vary from minutes to 48 hours. In contrast, at the higher levels of p~, gelation occurs at times from 5 to 30 seconds.

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A gelable aqueous reaction mixture characterized by comprising an aqueous medium having dispersed therein a water-soluble polymer derived from an ethylenically unsaturated amide, an aliphatic polyaldehyde and a metal salt of a hypohalite in propor-tions such that when the reaction mixture is subjected to an effective reaction temperature and an alkaline pH greater than 7.5 the reaction mixture reacts to form a water-insoluble gel.

2. The mixture of Claim 1 characterized in that the amide polymer is a homopolymer or copolymer of acrylamide, the polyaldehyde is glyoxal and the hypohalite salt is sodium hypochlorite.

3. A gel characterized by being made by subjecting the reaction mixture of Claim 1 to an effective reaction temperature and an alkaline pH
greater than 7.5.

4. A method for rendering a porous structure impermeable which comprises treating the porous structure with a gelable aqueous reaction mixture characterized in that the reaction mixture of Claim 1 is forced into and over the porosities of the structure and reacts to form a gel capable of rendering said struc-ture impermeable to the passage of aqueous liquids.

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5. The method of Claim 4 characterized in that the gelable reaction mixture is prepared by mixing in an aqueous medium the polyaldehyde with amide polymer, a metal hypohalite at a pH greater than 7.5 in or immediately adjacent to said porosities.

6. The method of Claim 4 characterized in that the water-soluble polymer is a homopolymer or copolymer of acrylamide and the polyaldehyde is a dialdehyde.

7. The method of Claim 6 characterized in that the dialdehyde is glyoxal.

8. The method of Claim 2 characterized in that the metal hypohalite is sodium hypochlorite.

9. The method of Claim 4 characterized in that a solution of polymer and polyaldehyde and an alkaline hypohalite solution are introduced into the porous structures via separate streams.

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