CA2310484A1 - Networked polymer/clay alloy - Google Patents

Abstract

A networked polymer/clay alloy is produced from a monomer/clay mixture comprising a monomer, a cross-linking agent and clay particles. An initiator means is used to initiate polymerization of the monomer/clay mixture. The day is chemically integrated with the polymer such that, on exposure to water, the networked polymer/clay alloy swells wide substantially no clay separating from the alloy.

Description

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NETWORKED POLYMEfRICLAY A!_!_OY
FIELD OF THE INVENTION
s The present invention relates to an absorbent polymer and a process far making an absorbent polymer. More specifically, the present invention relates to a networked polyrnerlclay alloy useful for example, withbut limit8tion, in co~lt2~irv'r5e~lt applications as landf~l liners or covers, reservoir liners, underground storage tank liners, secondary containment liners, and man-made bodies of water, or personal care absorbent articles, including diapers, training pants, fem~ine hygiene products such as sanitary napkins, incontinence devices and the like.
BACKGROUND DISCUSSION
Super absorbent polymers ("9APs") have been produced since the 1978s fvr use in a variety Qf products including, amongst others, hygiene products, such as disposable diapers, training pants, feminine hygiene products and incontinence devices, agricultural and horticultural products and industrial and environmental absorbents. SAt's are primarily utilized to increase or enhance the product's water-absorbency.
SAPS are produced from a variety of components by a variety of processes. Far 2o example, SAPS are often made from monomers such as acrylamide, acrylic acid and aaylate, which are particularly suitable for application in hygiene products.
For example, U8 4,432.741 (Hughes, ,3une 28. 1877) describes a process for pr4ducing polyacrytamide in dry and solid form using a polymerization catalyst selected from a group consisting of an alkali mete! and ammonium sulfite, bisulfite and persulfate, US
4.1713,221 (8autin et al, December 11. 1979) describes a process for producing water-sotuble acrylic polymers using a sequential photopolymerization tachnique-PhQtopolymerizatlon promoters are incorporated In the monomer solution to facilitate polymerization. US 4,283,617 (Perricone et al, August 11, 1981 ) produces polyacrylamlde using a quaternary ammonium salt as a cross-linking agsrtt, while US 4,285,987 (Parks, so October 20, 1981 ) uses two cross-linking agents to produce a cross-linked sodium polyacrylate absorbent.
Further examples of the production of SAPs providing improved properties ere provided by US 4,731,087 (Le-Khac, March 15, 19$8), US 5,185,~t09 (Sortwetl.
Fepruary 9.
1993), US 5,145,90& (Chambers et al, September 8, 1992), US 5,482,972 (Smith et al, sent ny: VAN IASStL l~ ASSUUlAttS ll;i d;l~ 1/SU ; U5l2EilUU lfi:U4; J tFex #fit3l;rage 5 October 31, 1995), US 5,672,633 (Brehm et al, September 30, i 997) and US
5,858,535 (lNang et al, January 12, 1999).
The SAP produced by each of the above-noted patents is manufactured from a chemical monomer to produce a synthetic polymer. Such d~emical monomers tend to be relalively expensive and therefore, the use of the SAP produced therefrom tends to be lirYlited to applications requiring a relatively small amount of SAP. For example, SAP made from chemical monomers tends to be too expensive for use in environmental applications given the large volumes that are typically rewired. The most significant expense in producing SAP is the cost of the chemical monomer. In add~ion, these synthetic polymers may be subject to chemical, electromagnetic (radiation) and biological (bacterial) degradation when placed in the surface environment.
Alternately, swelling Gays may be used to provide water-absorbency to a product.
With respect to cost, the cost of swelling days tends to be minimal compared to that of the chemical monomers described above. In addition, swelling clays are relatively stable t5 compared to chemical monomers and are not as subject to degradation.
However, swelling clays have a water absorption capar~ty significantly less tf,an that of SAP.
Thus, in order to reduce the cost of producing SAP and address the problems associated with using SAP in some applications. the polymers may be physically mixed into swelling clays to form a composite. Alternately, the monomers may be intercalated in the swelling clays and polymerized into a nanocorrlposite. Ire either event, the incorporation of tt~s swelliryg days into the SAP reduces the total cost of the SAP and enhances its resistance to chemical, electromagnetic and biological degradation, while still providing an improved water absorption capaaty as compared to that of the swelling clays alone.
As indicated ono techni9ue for producing the improved SAP is to physically mix the 26 polymer or othennrise intercalate or combine the polymer with the swelling clay to produce a water absorbent composite. For example, US 4,418,163 (Murakami et al, November 29, 1983) describes a method of making a water absorbing composite that is comprised of an in~ganic powder and an absorbent resin covering the surfaces of the individual particles of the inorganic powder. The inorganic powder is white carbon, synthetic silicate white carbon, basic magnesium carbonate, ultrafine magnesium silicate, light and heavy calcium carbonate, soft and hard clay, talc, vermiculite, pearllte, barium sulfate (baryte) or mica.
Thus, this patent describes a process for coating an inorganic powder with a polymer.
Similar processes are described in US 4,889.885 (Usuki at al. December 26, 1988) and US
6,$132.2$7 (Vlfason et al> Odober4, 1994).
_2_ sent ny: VAN IASStL f~ ASSUUlAItS /1a t3~~J 1/SU ; U5l2tilUU 1l3:U4; ll~tFsa #fil3l;rage An altematave tecllnlque for producing the improved 5AP is to polymerize an intercalated monomer. ~'or example, Blumstein, R. et al (Applied Polymer Sym,~posium 25:
81$8; 1974) prepares a clay-polymer complex with monolayers between the structural layers of day minerals, namely montmorillonite clay. Spedfically, clay-monomer complexes, s of nearly monolayer coverage, are polymerized through free radical initiation with y-ray Irradiation to produce day-polymer complexes. Blumstein, A (Journal of Polymer Science:
Part A, 8:2653-2861; 1995) similarly describes the polymerization of monolayers of an acrylic monomer adsorbed on the surface of the clay, namely montmorillonite, initiated with y-ray irradiation or by free radical catalysts.
Similarly. Chinese Patent No. t35-1-02158-A January 14, 1987) describes a method of preparing a bentonite-acrylamide based SAP using c4balt-60 Y-ray irradiation.
Specifically, the Chinese patent uses y-ray irradiation to initialize polymerization. As well, Nagae H. et al I;Kobunshi Ranbun 47:8:63138; 1990) describes the pnsparation of complex composite films by adding acrylamide and water to montmorillonite and polymerizing the product using y-ray irradiation. Thus, as with Blumstein, each of these processes requires an irradiation source for polymerization.
Further, Ogawa M_ et al, iCla~r Science 7:243-251; 1989) describes the preparation of montrnorillonite-polyacrylamide intercalation compounds by polymer'~ing the intercalated acrylamide monomers in the interlayer region of the montmorlllonite using a free radical 2a initiator. The polymerization is performed using a relatively complex process involving the use of an organic solvent, namely n-heptane. First, the montmorillonite is intercalated Into an acrylamide aqueous solu3ion. The product is then dryad and washed with an organic solvent. namely CCI, or n-heptane, to remove excess acrylamide. Finally, the intercalated acrylamide is polymerized by heating the intercalation compounds with benzoyl peroxide as 2s an initiator in n-heptane.
Kato, G. et al (Claus and Clav Minerals 29:4:294-298; 1981 ) describes the polymerization of intercalation compounds of styrene and ammonium montmorillonite.
Specifically, clay suspensions, namely montmorillonite, are mixed with arnmor,ium solutions.
After washing and drying the resulting product, the dried organoammonium-montmorillonites 3o are immersed in styrene monomer. The resulting siJearyltrlmethyiemmonium-montmorilfonite is died and polymerized using benzoyl peroxide as an initiator.
It would be desirable to produce an absorbent material having intimately integrated components that do not disperse andlor migrate from the product.

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SUMMARY of THE INvENrlol~
According to the invention, there is provided a process for producing a networked pofymedclay alloy, comprising the steps of: (a) preparing a monomerlclay mixture by mixing at least a monomer, day particles, a cross-linking agent, and a mixing fluid in a vessel; (b) s exposing the monom~Iclay mixture to a polymerization initiator means; and (c) polymerizing the monomerlday mixture so that a networked polymerlclay alloy is farmed.
According to the lnventian, there is also provided a product produced by the process described above.
According to the invention, there is further provided a networked polymerlday alby t4 comprising a chemically intograted composition of polymer and clay, so that, when the alloy is immersed in deionizad water. at a temperature in a range of from about 20°C to about 30°C, the alloy swells with substantially no clay sBparating from the alloy.
Accarcling to the invention, there is provided the method of using the networked polymerlclay alloy for making an absort~ent materiat used in a personal care product or for 15 making a fluid barrier fc~r use under a confnittg stress range of from about 0 kPa to about lOOpU kl~a, wherein, when the barrier is placed under a zero confining stress, the barrier has a deioniaed water flux less than about 1 x f g'~ m3/m~ls.
BRIEF DESCRIPTION OF THE DRAWINGS
2o The networked polymerlclay alloy and the process fer producing the networked polymerlday alloy of the present invention wilt be better understood by referring to the following detailed descrlptfon of preferred embodiments and the drawings referenced therein, in which:
Fig. 1 is a scanning electron microscope (8EM) micrograph of a top plan perspective 25 of the reinforcing agent used in Example 3, at a magnific~tiorl of laOX;
Fig. 2 is an s>_M micrograph of a hydrated polymer used for comparison in Example 3, at a magnfication of 700X;
Fig. 3 is an BEM micrograph of a cross-section of a reinforced networked polymerlday alloy composite produced in Example 3, at a magn~icatlon of sOX;
30 Fig. 4 is an BEM micrograph of a cross-section of a reinforced networked polymerlday alloy composite produced in Example 3, at a magnmcatlon of 27DX;
Fig. 5 is an 8EM mlcrograph of a cross-section of a water sw~Iled reinforced networked polymerlday alloy composite produced in Example 3, at a magnification of 500x;

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Fig. 7 is an SEM micrograph of a cross-section of a water-swelled polyrnar, without day, at a magn~cation of 650X;
Figs. 8A and 8B are drawings based on photographs taken of Sample A in Example 4 prior to immersion (8A) and after 3 hours immersion in deianized water (8B);
Figs. 9A and 913 are drawings based on photographs taken of Sample B in Example 4 prior to immersion (A) and after 3 hours immersion in deionized water (9B);
and 16 Figs. 10A and 10B are drawings t5assed Or1 photographs t8kerl of Sample E
irt F-xample 4 prior to immersion (1flA) and after 3 hours immersion in deionized water (10B).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Definitions 1s "Monomer" is an orpanlc molecule that can combine with a number of the same or different molecules to form a large molecule having repeating monomeric units, wherein the repeating m~omeric units have a similar chemical architecture and atom composition as the monomeric units.
"Polymer is a large molecule built from the same or different repeating monomeric 24 units and typically has a molecular weight in a range from about 10,000 to about 20,000,000. Polymer, as used herein, also includes any polymer made from two or mflre different repeating units, such as copolymers (i.e., comprising two different monomeric units), terpolymers (i.e., comprising three different monameric units), tetrapolymers (i.e., comprising four different monomeric units) and so on- Moreover, the repeating moryorneric 2s units can alternate in a sequential pattern (e.g., A-B-A-B), block pattern (e.g., A-P~
-B), random pattern (A p--°-A -B--A) or combinations thereof.
"Qligomer" is also built from the same ar different repeating monomer units but is a smaller molecule than a polymer and typically has a molecular weight in a range of from about 200 up to about 9.000.
30 "Polymerization Initiator Means" is a chemical substance, gamma ray irradiation, X-ray irradiation. irradiation py high energy sub-atomic particles, each type of radiation having a wavelength less than about 10 nm, (collectively, high energy irradiation) and combinations thereof that can increase the reactivity of a monomer so that a polymerization ar olipomerieation chain reackiQn between monomers is initiated and a polymer or oligorner is sent ny: VAN I ASStL l~ ASSUUlA I t5 /1;i f3:1'~ 1 IyU ; U5l2til UU 1 d: U5;
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fnm~ed. At the appropriate temperature, certain chemical substances become either an ionic or free radical species that can react with a monomer alone to produce an ionic or free radical monomeric species, which can, in tum, react with another monomer, thereby initiating a pQlymerizativn reaction. Also, high energy irradiation can be used to produce an ionic ar free radical monomeric species from a monomer andlar a cheniical Sut)StBnf~ bther than a monomer to initiate a polymerization reaction.
"Cross-linking Agent" is a chemical substance, photons produced from a radiation source and combinations tharevf that assist in forming a bridging moiety between two or m4re backbarre structures farmed by multiple monomeric units (e.g., oligon>eric ar polymeric to units. Thus, a cross-linking agent can bridge aligometic or polymeric species either during or after their formation.
"Networked Polymer" is a very large polymer molecule formed by cross-linking multiple aliganers andlor polymers to farm an interconnected polymeric network. A
networked polymer can have cross-linking moieties between oligomers andlor polymers, where the moieties are fom~ed from either the cross-linking agent itself, branches attached tn the backbone of each oligamer andlar polymer or combinations thereof.
"Networked PolymerlClay Alloy" ("NPC Alloy") is a chemically integrated composition of polymer and clay. Clay parkicles form a unique chemical association with the networked polymer as it is farmed. The chemical association may be, for example, without limitation, through hydrogen bonding, ionic bonding, Van der waal'sldipole bonding, affinity bending, covalent bonding and combinations thereof.
General Df:cusslon M NPG alloy of the present invention is an absorbent material useful, for example, without limitation, for making quid barriers, such as landfill liners or covers, reservoir liners, underground storage tank liners, secorxiary containment liners, and liners for man-madE
bodies of water, or personal care ab&orbertt articles, iryCludirtg diapers, training pants, feminine hygiene products such as sanitary napkins, incontinence devices and the like.
In containment applications, the alloy preferably absorbs water to form a barrier, so witid~ then has a relatively low permeability to water, oil and other tiquids_ In pgtsvnal care articles, the alllay preferably has a high water absorbency capacity. As discussed more fully bebw, the properties a( the NPC alloy can be adjusted depending on the application.
The NPC alloy of the present invention has Improved resistance to chemical, electromagnetic radiation and biological degrddatiOrt ir1 surface and subsurface Conditions.

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For example, the permeability of a liner produced with the NPC alloy is not signmcantly affected by salt water, or other aq ueous solutions with heavy metals andlor addic pN. Thus, a liner produced with the NPC alloy represents an improvement over a conventional geosynthetic clay liner ("GCL°), which typically loses its effectiveness on exposure to salt water.
As another example. polyacrylamtde is stable at surtace and sub-surtace conditions.
However, it is susceptible to chemical and UV degradation. The clay reduces degradation in ~8 the NPC allay by protecting the polymer. Also, the NPC alloy is more resistaryt to biological degradation than, far example, polyacrylic acid aksne.
When used in barrier applications. the NPC alloy weighs less than a compar~ly effective day loading for a conventional GCL per urwt area. Also, a liner produced with the NPC alloy can be used without pre-hydration, as is often required for conventional GCL's.
2o An NPC alloy is produced by mixing a monomer, clay particles, a cross-linking agent and a mixing fluid. The monomerlclay mixture is exposed to an initiator means to initiate polymerization io form a networked potymerlclay alloy.
The polymer and clay in the NPC alloy cooperate physically and chemically (i.e., physicochemieally) to contrtbute to the alloy's water absorbency. Thus, the alloy can swell 2s while only negligible amounts of clay, if any. (i.e., substantially no clay) separate from the composite when it is imrr~rsed in deionized water at temperatures in a range of from about 1 °e to about BO°G.
MonomerlCiay Mixture 3o Tire monomerlday mixture used in making the NPC alloy includes, without limitation, a monomer, day partldes, a cross-linking agent and a mixing fluid. For brevity, we may refer to the mixture of monorner, clay, cross-linfcing agent and mixing fluid as "MGX."
The monomer is at least partially soluble in the mixing fluid. A monomer soluble in the mixing fluid may tie mixed with other monomers that are soluble or Insoluble In the -7.

sent ny: VAN IASStL f~ ASSUUlAItS 11~ l3;iy 1/yU ; U512fjIUU lt3:U(:f; )~tFea #bt3/;F'8gB m~5 mixing fluid. Preferably, at least one water-soluble monomer has khe following general formula:
R1 Ra R O
I I I Il cH c x n ~2 wherein X is selected from the group consisting of oM, OR° and NRsR°, M is an alkali or alkaline earth metal ion or NH4', R', Ra, R3, R5, R6 and R' are independently selected from the group consisting of H, CHs, CH2CHa, CHzCHzCH3, CH(CH9)z, CHzCHzCHzCHs, and CN, and OR4 is selected from the group consisting of Oil, OCH~. OCHzCHs, CaCH2CWaCH3, OCH(CHs)z. OCHzCHzCHzCHs. QCHzCH20H and (QCHzCHz)mQH, n= 0 to about 10 and m=
t tp about 10.
1o Mae preferably, the monomer is selected from the group consisting of acrylic acid (where R'=H, RZ=H, R~=H, n=0, X=ORS, R4=H), acrylamide (where R'=H, RZ=H, R3=H, n=0, X=NR$Re. R$=H, Rs=H), sodium acrylate (where R'=H, R2=H, R3=H, n=0, X=OM. M-Na).
potassium acrylate (where R'=H, R2=H, Rg=H, n-o, x=OM, M=K), methacrylic acid (where R'=H, Rz--H, Rs--CH3, n=0, X=OR4, R'=H), N-isopropylacryiamide (where R'-H, RAH, is Ra=H, n=0, X=NRSRe, R5=CH(CHa)2. RB=H), and combinations thereof.
An example of a mor~orner that can be co-polymerized with a mor~ort~er of tire above general formula are vinyl esters, such as vinyl acetate. Vinyl acetate is readily co-polymerized and may be retainEd as a vinyl acetate moiety or subsequently hydrolyzed to the corresponding vinyl alcohol.
2o Tne day particles may be swelling or non-swelling clays. Suitable swelling clay particles include, without limitation, montrrxxillonite, saponite, nontronite, laponi e, beidellite, iron-saponite, hecborite, sauconite, stavensite, vermiculiie. and combinations thereof.
Suitable non-swelling clay particles include, without limitation, kaolin minerals (including kaaiinite, dickite and naalte), serpentine minerals, mica minerals (including illite), chlorite 25 minerals, sepiollte, palygorskite, bauxite, silica and combinations thereof.
Preferably, the day is a swelling clay such as, for example, smectite and vermiculite type days. More prefer2~bly, the clay Is a smectitg type d2ry. Ex2~mples of suitatrla smedates are, without limitation, montmorillonite (sometimes referred to as bentonite), beidellite, nontronite, hec~orate, eaponite, saucanite and laponite. Bentonite is an example of a 30 naturally-occurring combination of clay partioles_ Bentonite is a rook rich in montmorillonite _g_ sent ny: VAN I AS~tL ~~ ASSUUlA I tS !1 ~ ti;ly 1 /SU ; U512fi1 UU 1 ti: U l;
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and may also comprise other smectltes as weu as other non-clay mineral constituents.
Consequently, montmortllonites or their mixtures with other smedltes are often referred to simply as bentonite. Bentonite clays are fine crystals or particles, usually plate-like in shape, with a lateral dimension up to 2 Nm and a thickness in a range of a few to tens of nanometers (nm).
Swelling clays have the ability to absorb water and are less expensive than monomer. Accordingly. the reinforced networked polymer composite of the present invention is less expensive than orre produced without clay. Moreover, clay particles are resistant to degradation In long-term environmental applications, while still providing water 1o absorbency for long periods of tune.
Non-swelling clays urould provide increased resistance to salt water for the NPC
alloy. Also, non-swelling clays, like swelling clays, are less expensive than monomer and would reduce an application's cflst.
Preferably, the weight ratio of day to monomer in the MCX mixture is in a range of frorrl about 0.05:1 to about 19:1. More preferably, the weight ratio of clay to monomer in the MCX mixture is in a range of from about 0.5:1 to about 3:1.
Suitable chemical substances far use as cross-linking agents include, without (imitation, N,N'-methylene bisacrylamide, phenol formaldehyde, terephthalaldehyde, allylmethacrylate, diethyleneglycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethylene carbonate, ethylene glycol diglycidal ether, tetraallylaxyethane, triallylamine, trimethylolproparyetriacrylate, and combinations thereof.
As a general rule, depending on the selected polymerization reartiQn time and temperature, a higher ratio of cross-linking agent to monomer will generally produce a lower cahoentration of residual monomer, but the networked polymer's water absorption capadty (VIIAC) may drop if the ratio gets too high. The weight ratio of the crass-linking agent to the monomer is preferably in a range of from about 0.05:100 to about 1.5:100. More preferably, the weight ratio of the cross-linking agent to the monomer is in a range of from about 0.05:1 ob to about 4.7:100. Most preferably, the weight ratio of the cross-linking agent to the monomer is in a range of from about 0.1:100 to at~out 0.5:100.
3o The mixing fluid is a polar solvent. F-~camples of suitable mixing fluids include, without limitation, water, alcohol, oxygen-containing organic solvents, and combinations thereof, in whioh the monomer can be at least partiauy dissolved. Examples of suitable oxygen-containing organic solvents Include, without limitation, alcohols, glycols, polyols, sulfoxides, sulfvnes, ketoses and odmbinatyons thereof. Preferably, the mixing ttuid Is sent ny: VAN IASStL ~~ ASSUCIAItS 11~ t3:i~J 115U ; U512f~1UU 1l3:U1; JI~tFaa #fif3l;h'AgB 1145 water, alcohol or a combination thereof. Most preferably, the mixing fluid is water.
Preferably, the amount of mixing fluid in khe MCX mixture is in a range of from about 30~/o to abcmt 90% by weight. More preferably, the amount of mixing fluid in the MCX
mixture is in a range of from about ~09~o to about $0% by weight. Most preferably, the amount of mixing fluid in the MCX mixture is in a range of from about 4U°/° to about 60% by weight.
Additionally, the MCX mixture preferably comprises one Qr mare additives.
Buffering agents andlor neutralizing agents may be used as additives to maintain the pM
of the mixture in a predetermined range andlot neutralize acidic andlor basic monomers.
Also, metal complexing agents may be used as additives to form metal complexes, thereby sequestering metal ions that might otherwise interfere with forming the NPC alloy.
For example, acrylamide monomer is typically manufactured with cupric salts as a stabilizer (e.g., to Inhibit polymerization during shipment or in storage). Thus, a metal complexing agent, such as a sodium carbonate or ethylenediaminetetrace~c acid (EDTA), can be added to the MCX mixture to complex the metal Ion and thereby sequester the metal.
It should be understood that some additives can be used to satisfy multiple functions. For example, sodium carbonate (Na2COa) and sodium bicarbonate (NaHC03), could function as both a buffering agent (i.e., maintaining pH) and a neutralizing agent (i.e., neutralizing aadic m4nomers), while also working as a metal comptexing agent. Therefore, it win be apparent 2o to those skilled in the art that one or more additives can be used for forming an NPG alloy depending on the monomer and crass-linking agEnt used, type of stabilizing agent mixed with the monomer. type of polymerization reaction and the desired reaction pH
and temperature.
Examples of buffering agents andlor neutralizing agents include, without limitation, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, oxylate-containing comp~nds, sulfate-containing compounds, phosphate-containing compounds, and combinations thereof.
Examples of metal complexlng agents Indude, without limitation, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, ethyienediaminetstraacetic acid (EDTA), EDTA salts, orthophosphate, pyrophosphate, metaphosphate, hydrogen phosphate, and combinations thereof.
Each of the components of the MCX mixture may be added in any order.
Preferably, however, the mixing fluid and monomer are mixed with any other desired component, sent ny: VAN IASStL ~~ ASSUUlAItS /1:i f3:i~J 1/SU ; U5I2tilUU lf3:Ul; JIEtFex #fifil;Nege 14145 followed by adding a chemical in'rtiata and then adding the clay. Also, caution should be exercised in mixing any mixture components to avoid any significant exotherms.
otherwise, any significant exatherm should be allowed to cool. A large exotherm from mixing components might otherwise lead to premature polymerization shortly after the initiator is added, but before the mixture is heated under a controlled condltion_ The MCX mixture fomls a slurry type mixture, which should be mixed until it is substantially homogeneous.
Polymerization 1o An NpC alloy is produced by polymerization of the MCX mixture while the cross-linking agent, acting in concert with the polymerization process, helps to form a networked polymerlclay alloy structure. Polymerization of the MCx mixture is initiated by a polymerization initiator means for generating an ionic or free radical monomeric species.
initiation may be accomplished by adding a suitable chemical substance to the MCX
mixture. Also, electromagnetic radiation having a wavelength of 10 nanometars (nm) or less may be used al4ne or in combination with a chemical initiator.
Suitable chemical substances for initiating polymerization Include, without limitation, free radical initiators, carbanions, carbonium ions, and combinations thereof.
Examples of free radical initiators include, without limitation, thermal initiators, and 2o relax systems, which are typically two or mare chemicals, which are added simultaneously as different solutions.
Examples of thermal initiators include, without limitation. (1 ) alkali metal salts of sulfife, bisulfate, persulfate, benzoyl peroxide, and combinations thereof, (2) ammonium salts of sulfite, bisulfate, persulfate, basnzoyl peroxide, and combinations thereof, (3) 2,2'-azabis(2-amidino-propane~dihydrochloride, (R} 2,2'-azotiis(4-cyanopentanoic acid), and combinations thereof.
'The desired palymarizatian temperature far forming an NPC alloy composite is primarily dependent on the type and oonoentration of initiator means selected.
For example.
lower polymerization temperatures may pe used where a thermal initiator prone to forming fry radicals at a lower temperature (e.g., about 40°C to about 5D°C) is used. Thus, where the polymerization reaction used for making the NPC alloy is initiated with a thermal initiator, the reaction 1s preferably at a temperature in a range of from about 40°C to about 9spc.
More preferably, however, the reaction temperature Is at a temperature in a range of from about 60°C to about 85°C and most preferably, in a range of from about 65°C to about 80°C.

sent ny: VAN IASBtL ~~ ASSUCIAItS /1~ B:1~J I/yU ; Ubl~(iIUU 1l3:Ul3; l~tFex #fjtil;h'2g2 X5145 Also, where a high energy radiation source, such as gamma ray radiation is used, the polymerization reaction may be conducted as low as about ambient temperature, for example about 20°C.
The polymeri~tlon reaction time is also primarily dependent on the type of initiator means used and its concentration. However; other factors affecting the desired reaction time include the type of monomer and its concentration, and the depth of the MCX mixture.
Also, once a polymerization reaction is initiated, typically, it will not terminate in response to a si~arp temperature drop. Far example, once the MCX mixture is exposed td the desired initiation temperature, the polymerization reaction will proceed for some time thereafter, to depending on the roaction temperature selected and the time period that the MCX mixture is exposed to the selected temperature (i.e., heat exposure period). Also, we have discovered that higher initiator concentrations generally produce residual monomer cor~centreGons of abput 200 ppm or less. However, these higher initiator concentrations are more likely to promote premature polymerization unless the temperature is kept sufficiently telow ~4o°C.
Accordingly, It is important to maintain the MCX mixture below 40°C to reduce premature polymerization.
The time period that tho MGX mixture is exposed to the selected reaction temp8raturs may be in a range from as low as about ~ minute to as high as about 24 hours.
For exempla, where an MCX mixture having a clay to monomer ratio of about 2:7 is pressed into a porous substrate to a depth of about z-3 mm, potassium persulfate is used as a thermal initiator and the selected temperature is about 80°C, the duration of the heat exposure period is preferably in a range of from about 2 minutes to about 60 minutes. More pr~fembly, under similar conditions, the heat exposure period is in a tangs of from about 2 minutes to 45 minutes and, most preferably, in a range from about 3 minutes to abo~ 30 minutes.
I=xarnples of redox systems include, without limitation, petsulfatelbisulfte, petsulfatelthiosulfate, persulfatelascortate, hydrogen peroxidelascorbate couples, and cornbinationa thereof. Typically, additional heat is not required when using a redox systems initiator because the reactions are often exothermic, so such systems can work effectively at so temperatures in a range of from about the freezing point of the MCX mixture to the toiling point of thm mixing fluid. Typically, the temperature is ambient, abaut 20°G.
Aiternaatively, polymerization may be initiated by eleCtrwriagnatic radiation having a wavelength below about 10 nm such as, for exempla, without limitation, by gamma rays. X-rays, or high energy sub-atomic partides. (n such a case, the polymerization reaction is sent ny: VAN I ASStL (~ ASSUC1A I t5 /1 ~ t3;lJ 1 /yU ; U5lltil UU 1 t3: Ufi;
J tFaa #fit3/; rage i a145 typically conducted at ambient temperatures. However, the temperature can be higher or lower.
However, it is well known to those skilled in the art that UV radiation, with wavelengths ranging from about 200 nm to 3B0 nm is not suitable for polymerization initiation pf the MCX m~ure because the clay will interfere with UV light's ability to penettate into the sample, and thereby initiate the polymerization reaction, even with a photo-initiator present. More specifically, it is believed that the clay preferentially absorbs the UV light, thereby inhibiting the UV light's effectiveness as an initiator means.
Optionally. Qnce poly~rie~zed, III of a portion of the mixing fluid remaining in the NPC
~o allay product may be removed, far example by desiccating at room temperature or oven-drying. If oven-dried, the composite should be dried at a temperature that does not adversely affect the properties or characteristics of the product, for example, at a temperature less than about 110°C.
The moisture content of the products made with an NPC alloy is dependent on the applica~on and other factors. For example, a higher moisture content product provides greater flexibility and a lower initial permeability. But a lower moisture content product can have reduced transportation costs. Consequently, the desired moisture content will bs determined by the environment in which the product will be used anti maximum acceptable transportation costs.
zo Therefore, for a product with at least some flexibility, the moisture content is preferably in a range of from about 25°~ to about i59'o by weight.
NpC Allay In use, the NPC alloy swells on contact with water as the alloy absorbs water.
Because of the networked structure, the composite swells substantially as an integrated unit while only negligible amounts of clay, it any (i.e., substantially na clay), separate from the vomposite when it is immersed in ws~ter at a temperature in a range of from about 1 °C tar about 60°C, whether the water is saline or not.
It will bs understood by those skilled in the art that the degree to which the NPC alloy 8o is networked will affect the alloy's capacity to absorb water. Of course, if insufficient eross-Iinklng agent is used, the NPC alloy may become water soluble under certain conditions and the day could then substantially separate from the alloy. On the other hand, if excessive amounts 4f amss-linking agent ors used, the NpC ahoy may be so inflexible that it is unable sent ny: VAN IASStL l~ ASSUCIAItS /1~ t3;~~J 11SU ; U512EjlUU lf3:Uy; ,letFaa #filif;h'8ge i f~45 to absorb suffcieni amounts water and thereby reach either the desired fluid permeability andlor water absorption performance.
In containment applications, a barrier made using the NPC alloy is often under a confining stress due to overburden. Udder a standard effective confining stress of 20 kPa or 2.9 psi, the flux (i.e., the rate water travels at the specified pressurey of the composite is about 10$ m31m21s or less, as measured by ASTM 5887-85. As the confining stress increases with additional overburden, the hydraulic conductivity of the barrier will decrease because the barrier will become compressed.
70 The following non-limiting examples of embodiments of the present invention that may be made and used as dairned herein are provided for illustrative purposes only.

Hiact of Clay to Monomer Ratio on Water Absorption Capacity NPC dltoy preparatfo~
Seven MCX mixtures were prepared In the amounts shown in Table 1. Clay to monomer weight ratios ranged from 4.1 to 9.62 in the seven MCX mixtures. The clay used in the MCX mixtures was f~ATuRAL GELr"", a natural swelling clay often referred to as 2o Wyoming bentonite, commercially available from American Colloid. The monomer was acrylamidE, obtained from Cytec, West Paterson, NJ. A Control sample was made using acryiamide monomer without added clay.
Water, sodium hydroxide (Na~H), radium bicarbonate (NaHC~3}, EDTA, acryiamide, N,N'-methylene bisacrylamide (NBAM) and potassium persulfate (i~SzO,) were mixed in a 250-mL HDPE bottle. The aqueous solution was mixed well, prior to addttion of clay. Clay was added and mixed again to farm a homogeneous MCX mixture. All MCX
mixtures were viscous but fluid before polymerization.

Sent ny: VAN IA53tL L~ ASSUC;lAItS /1;~ 13:~~J 1/SU ; U512f~1UU 1li:Uy;
IIBtFa~r #fit3l;Nage 113145 Table 1 __ -..
~-...-.
_..........
__.._..-Sam le ,~) T

Cpm onentControl1 2 3 4 $ g 7 Water 79.98 72.5 98.77874.4 291.16374.4 151.2391.91 NaQH 3.78 3.108 3.904 2.28 7.498 1.891 1.563 0.506 NaHC 0.931 0.802 0.931 0.60 0.20A 0.468 0.323 0,1 DS

EdTA 0.109 0.09 0.116 0.08 0.217 0.06 0.042 0.025 amide 25.07321.02824.87115.00 50.Q0 7-72 iQ-0422.294 NI3AM 0.057 0.05 0.058 0.04 0.123 0.028 0.022 D.012 S O 0.21 0.183 0.217 0.132 0.418 0.085 0.088 0,032 Cta -- 2.121 B-388 7.602 50.22 16.38930.00 22.029 Total 110.12899.882137243100.034399.833100-041193-31116.913 Clay:
Monomer 0 ~ 0.10 0.34 O.SO 1.OD 2.00 3.00 9.60 ~ ~ ~ ~ ~ ~
Ratio (wt?

The Contrd and MCX mixtures were left in an oven overnight at 65°C
for polymerization. Alter palyrnerization, the Control and NPC alloys wars transferred to glass dishes and dried at 105°C for 48 hours.
Water Absorption Capacity (WAG) of NPC Alloys Approximately 1 gm of each NPC alloy and the Control was plaoad in a 500 mL
HDPE bottle with 400 rnl distilled water. After 48 hours, free water was decanted off the swollen NPC alloy using a 115 mesh screen.
The swollen NPG alloy was weighed and the water absorption capacity (WAC} was calculated according to the following equation:
(H20 SwoIIBfS NPC Alloy MBBS - Dried NPC Alloy Maf6) WAC =
Dried NPC Alloy Mass A projected WAC, WACp~;, bawd on the Control WAC and clay content was also calculated according to the following equation:
Parts Monomer _ x Contro * I x Max. F_st.
WACp,I ~.ro~l parts Monomer + Clay WAC ~ Total Parts Monomer * Clay Glay WAC
where the Control WAC = 362 and the Maximum Estimated WAC for clay = 10. For example, where a 1:9 clay to monomer ratio is used to produce the NPG alloy, the NPG
alloy's WACph is [(3/4) x 362] + (1l4)1D =2613. LiK$wise, where o 2:1 Clay to monomer ratio is ao used, the NPC alloy's WACp,~ is [(113) x 352J + (213)10 = 124.
_13_ sent ny: VAN IASStL l~ ASSUCIAItiS /1:i f3;~~J I/yU ; U5/2tilUU 1l3:U5; letFax #~t3/;Nage tW 45 ARGbl1 CA
Fin~liy, the trlonomer WAC (INACm) was also calculated to determine the water absorption capacity based on the amount of monomer used to produce the polymerlGay alloy sample being tasted. The WAGm was calculated according to the following equation:
(M20 Swollen NPC Ahoy Mass - Dried NPC Alloy Mass) WACm =
Masss of Monomer used to produce NPC Alloy The results are tabulated in Table 2.
Table 2 Sam Control1 2 3 4 5 6 7 Ie IA

Cla 0.00 0. 0.34 0.601.00 2.003.00 9.61 ~ ~
Monomer 0 Ratio WAC g H20 352 339 332 213 207 134 83 14 per g WACp,;pQlymerlclay 321 266 238 1$1 124 84 42 alloy WAC~,g HzC 421 441 472 364 414 403 349 250 per g monomer in polymerlclay alto As shown in Table 2, the WAC for NPC alloy Samples 1 and 2 is 339 arid 332, respectively. This means that the NPC alidy absorbs 339 and 332 times its own weight in water for these two samples, respectively, versus a 352 WAC for the clay-free Control.
Bantonite clay typically has a pasts-like cansistsncy up to a water absorption of 5 to 10 times its wEight, after which the day becomes dispersed in water to form a slurry.
Consequently. beaause~ bentonite clay is not knanrn as being highly water-absorbent on a per unit mass basis, as compared with a water-absorbent polymer, the drop in WAC shown in Table 2 with increasing day to monomer ratio was a surprising and unexpected result.
For example, at a 1:1 ratio, those skilled in the art might have projected a WAC of Just slightly more than 0.5 x the Control's WAC because only half of the NPC
alloy is networked polymer. So, taking into account the water absorption for clay alone (i.e., about 5-10), a 1:1 clay to monomer ratio in an NPC alloy would have been expected to be, at best, about 1I2 the Controls WAC (l.e., ~ 78) plus s for the day's expected water absorption for a WAC~ of 1$1. But Sample ~1, with a 1:1 clay to monomer ratio, has a X07 WAC, which is 14.4°~ greater than expected. Similarly, a 2:1 clay to monomer ratito has a WAC~ of about 124, while Sample 5 produced a 194 WAC, which is 8.19'o greater than expected.
The -1g_ Sent ny: VAN I ASStL F~ ASSUUlA I t5 /1:i t3a~ 1 IyU ; U5! ZEjI UU 1 f3:1 U;
II~tFax #bt3l; rage zo145 general trend is that WAC, across a broad range of clay to monomer ratios, is substantially comparable, if riot slightly improved versus the clay-free Control until a significantly high day loading in the NPC alloy is reached. At a significantly high clay loading, it appears that the polymer loading is so low that the clay's inherent WAC is dominant.
s This is a surprising and unexpected result, particularly at high Gay to monomer ratios of 2:1 and 3:1. Ogawa et al ("Preparation of Montmorillonite- Palyacrylamide Intercalation Compounds and the Water Absorbing Property" Clav Sdenoe 7:243-251; 1989) suggest on pg. 250 that clay acts as a cross-linking agent. Thus, Ogawa et al suggest that clay would act in convert with a cross-linking agent in an MCX mixture to severely constrain a polymer io formed from that mixture. Moreover, the results in example 2 illustrate that a cross-linking agent concentration as low as about 0.1 wt.% can over cross-link a polymer, thereby substantially reducing its water absorption capacity. Thus, the sensitivity of WAC to excess cross-linking agent and flgawa et al suggest that increasing the clay content would produce a highly constrained NPC alloy with inhibited WAC. Consequently, it is surprising and 15 unexpected that using an MCX mixture with both a cross-linking agent and clay, for example, at a 2:1 clay to monomer ratio, would produce an NPC alloy with comparable ar slightly better perfom~r~ce than the clay-free Control.
When calculated on the basis of an equivalent amount of acrylamide monomer used to produce an alloy, the WACm of the palymerlclay alloys Samples 1-5 is similar to that of 20 the Control sample. As mentioned above, monomers are more costly than clay.
Thus, the WACm results demonstrate the economic advantages of the NPC alloy.
Table 2 demonstrates that good WAC results were obtained for the composition described in Table 1 in a clay to monomer ratio of about 0.3 to about 3Ø The optimal clay to monomer ratio will depend on the intended use of the compositions falling within the 25 sct~pe of the claimed invention. For instance, beyond adjusting thg clay to monomer ratio, as discussed more fully under Cxample 2, the cross-linking agent to monorner ratio can also be adjusted to increase or decrease the WAC to the desired level.
For example, when used for making a landfill liner, a WAC for the NPC alloy only needs to be high enough to ensure that the NPC alloy swells sufficiently to occupy any 3b int~lrstitial spaces that were not occupied by NPC alloy when the liner was formed. This degree of swelling will ensure that the liner has sufficiently low permeability to water arid other fluids. For example, the WAC for an NPC alloy used in a landfill liner could be as low as about 5. Of course, a higher WAC up to about 5~0 could also be used in a landfill liner.

sent ny: VAN IASStL & ASSUCIAItS /1~ ti;i~J I/yU ; USI~tiIUU 1t3:1U;
j$,t~#f38l;cage 21145 However, a WAG signficantly much higher than 50 could reduce the structural integrity of the alloy due to excess water.
Consequently, in personal care type applications, where structural integrity is likely to be a factor as well, a WAG in a range of from about 20 to about 100 would be most likely 6 desired for an absorbent material made from the NPG alloy.
Accordingly, the above data illustrates that the unique polymarlday alloy can provide effective water absorption. As well, the clay component in the NPC alloy provides a cost effective rrleans to make an NPG alloy while delivering the water absorbing andlor permeability Prpperty performance desired for the Intended use.

>rffect of Cross-Linking Agent to Monomer Ratio oa 11YAG
NPG Alloy Preparation Three MCX mixtures ware mixed in the amounts shown in Table 3. The cross-linking 1s agent to monomer weight ratios ranged from 1.10 x 10'~ to 9.41 x 10'' in the three MCX
mixtures. The clay to monomer weight ratio was held constant at about 1:1. The clay used in the MCX mixtures was NATURAL CELT"". The monomer was a 1'4 (wt) mixture of acrylic acid (Aldrich) and acxylamide (Cytec).
Water, NaOH, sodium carbonate (Na2CQs), acrylic avid, acrylamide, NSAM and 2o K2S~a were mixed in the proportions shown in Table 3 in a 2-L Erlenmeyer flask. Tha aqueous solution was mixed well, prior to addition of clay. Clay was added and mixed again to form a homogeneous MCX mixture. All MCX mixtures were viscous but fluid before polymerization.
Table 3 sam le Ca anent 8 s 10 Water 1000 1000 1000 NaOH 1 0 10 10 Na2CO3 12 12 12 lic Acid 20 ao 20 AA

lamide AM 80 80 BO

NBAM 0.941 D.303 0.11 SzOe 0.6 0.6 0.6 Gla 99 1 Q6 105 Total 1222.541 1227.9431227.71 NBAM/(AA+AM)9.d1 3.03 1.10 Wt Ratio x 1 b' Sent ny: VAN I ASStL I~ AS5UUlA I t~ /1 ~ 13:~~ 1 /yU ; U5I2tilUU t ti: 1 U;
l2tFe~t #f~til; rage zm45 AFtC-011 CA
The MCX mixtures were left in ~n Qven Qvemight at 65~G far polymerization.
After polymerization, the NPt: alloys were transferred to glass dishes and dried at 106°C far 48 hours.
Water Absorption Capacity (vVAC) of PolymerlClay Alloys Approximately 1 gm of NPC alloy Sample 8 was placed in a 50o mL HDPE bottle with 40o ml distilled water. After 48 hours, free water was decanted off the swellen NPC
alloy using a 115 mesh screen.
The swollen NPC allay wa$ weighed and the water absorption capacity (WAC) was to calculated as described in Example 1. Samples 9 and 10 were treated in the same manner.
The results are tabulated in Table 4.
The monomer WAC (WAC~,) was also calculated to determine the water absorption capacity based on tfre amount of monomer used to produce the NPG alloy sample being tested. These results ors also tabulated in Tabte 4.
Table 4 Sam 8 9 10 Ie NBAMI(AA+AM) 8.41 3.03 1.10 Wt Ratio x WAC g H20 per 145 281 281 g polymerlclay auo WAC~rnA Hz~ ~r 324 641 640 monomer in polymerlclay alto As shown in Table 4, the NPC alloy's WAC increases as the cross-linking agent to monomer ratio decreases from 9.41 x 10g to 3.03 x 1 Os. However, it is believed that a further signficant decrease in cross-linking agent to monomer ratio (e.g., to about U.10 x 10~) would sufficiently reduce the mechanical strength of the NPC alloy's networked polymer and thereby Ilmit NPC alloy's ability to absorb and retain water.
Of course, to the extant the polymer is not cross-linked, the polymer will dissolve in water. Also, at low levels of cross-linkir~, the polymer may fracture and become water-2s soiuble_ However, if the degree of cross-linking is too high, there is too much constraint on the polymer and its water absorption capacity is reduced.
_ 1g _ Bent Dy: VAN I AB~tL ~ ASSUUlA I t5 /1 ~ B;i~ 1 IyU ; U5l2eilUU 1 B:11 ;
jBtFax #fiBl; rage 2145 Accordingly, the above data illustrates that the unique NPC alloy can provide effective water absorption. As well, controlling the cross-linking agent to monomer ratio, alone or in combination with the clay to monomer ratio, provides a means for designing the water absorbing andlar permeability property performance desired fnr the intended use.

SEM and X-Ray ~4nalyais The following SEM micrographs and X-ray analyses illustrate that (1) clay ire the NPC
ahoy is chemically 85SOCiated with the polymer, (2) clay does not become dissociated from 1o the NPC alloy when the polymer is swollen, and (3) the reinforced NPC alloy composite can contain a significant amount of occluded water retained from manufacture.
MQrtomeNClay Mixture Preparation An MCX mixture was prepared as shown in Table 5. The clay used in the MCX
t~ mixture was NArUF~AL GELT"~. The monomer was a 1:4 (wt) mixture of acrylic acid (Aldrich) and acrylamide (Cytec).
Water, NaOH, NaHC~3, aaylic acid, acrylamlde, NBAM and ICzszoa were mixed in a 10-! HDPE pail. The aqueous solution was mixed well, prior to addition of clay. Ciay was added and mixed again to farm a homogeneous MCX mixture. The MCX rnixture was 2U viscous but fluid before polymerization.
Table 5 Com orient Amount Water b009.9 NaQH 65. ~

NaHG4 51.5 A lic Aad 100.8 Ac lamide 400.5 NBAM 1.62 S O 12.13 Cia 1000.8 Total 8633.02 Clay to Monomer 2.00 Ratio wt 25 Fte~nforced NPG Illioy Compoalte Preparation The MCX mixture was poured in a thickness of about 1.S mm onto a 0.95 m x 0.80 m Sent ny: VAN I ASStL i~ ASSUC1A I t5 /1:i t3:i~J 1 /yU ; U511filUU 1 f3:11 ~
JI~tFex #fjt3l; Page 24145 piece of TERRAF1Xe270R-A geotextile (Terraflx Geosynthetics Inc., Toronto, Ontario, Canada), as a reinforcing agent. A polyethylene cover sheet was placed on tap of the MCX
mixture and a vacuum pressure in a range of from about 15 to about 80 kPa was applied to the sample from the geotextile's opposing side. The MCX mixture was intimately distributed s in and on the geatextite material by applying the vacuum.
The reinforced MCX mixture sample was put under an infrared heater at 80°C for 8 minutes tar polymerization to farm a reinforced NPC alloy composite. The moisture content of the reinforced NPC alloy composite was about 75%.
14 Scanning EIQCtron Microscopy (SEM) The reinforced NPC alloy composite was examined using a JEOL Model No. JSM
6301 FXV Scanning Electron Microscope (SEM, Japan Electron Optics Limited, Japan) at the SEM Faality, Department of Earth 8~ Atmospheric Sciences. University of Alberta, Edmonton, Alberta, Canada.
t5 Samples were pretreated for SEM examination by placing the samples in ~
holder and immersing khan in liquid nitrogen (i.e., about -196°C). Once frozen, the samples were removed from the liquid nitrogen, using pliers or a knife, quickly torn or cut, as indicated below, to obtain a cross-sectional perspective of the sample. Ths samples were then quickly transferred to the SEM vacuum chamber, where they were warmed to ~0°C to 2o sublime any surface ice crystals. Next, the samples were placed in a coating chamber where a thin Payer of gold was applied to the samplrr to increase electrical conductivity. The samples were then returned to the SEM vacuum chamber for examination. The samples were maintained at or near liquid nitrogen temperature during the gotd castling arid subsequent SEM examination. This was done so that the structure of the sample would be 2s preserved. The samples contained considerable moisture and thus had to be maintained in a frozen state for the SEM to operate properly.
The sample in Figs. 3 and 4 was cut with a knife prior to mounting. Both micrographs show the cut edges of fibers of the reinforcing agent. Particles seen in Fig. 4 are fragments from the cutting step in preparing the sample for SEM
examinat'ron. The 3o sample in Figs. 5 and S was severed with a pair of pliers, instead of a Knife, prior to mounting. Fig. 5 shows the fractured edges of fibers of the reinforcing agent and other fragments produced by fracturing. The SEM micrographs of Figs. 1 to 7 are discussed in Tak~te 6.

Sent by: VAN IASStL ~~ ASSUCIAItS /1;i fi~~ 1/SU ; U512~IUU ltj:ll; JBtFaa #bt3l;h'age 25!45 Discussion of SAM Micrographs Ire summary, the SEM micrographs illustrate that (1 ) clay in the NPC alloy is chemically associated with the polymer, (2) clay does not become dissociated from the NPG
alloy when the polymer is swollen, and (3) the reinforced NPG alloy composite can contain a significant amount of occluded water retained from manufacture.
Taal~ 6 Fig. Magni-Description Observations #

tication 1 140X Comparative. Tap plan perspective of reinforcing a ent without NPC
ally .

2 7DODX Comparative. PotassiumSwollen polymer has crater like open-acrylate cross-linkedcell structure. The apes and cells were polymerized without previously occupied by clay. No occluded watar, reinforcing agent. which was removed by SEM
Sample pre-immersed In water treatment procedures. It for 18 is expected minutes prior tv SEM.that acrylamidelsodium acrylate copolymer would behave in a similar manner-3 50X Reinforced NPC alloy Illustrates NPC alloy intimately composite. Sample integrated with reinforcing dried from agent. AIsQ

the original 75 wt.~billustrates thin layer moisture of NPC alloy (right-to about 25-50wt.!o hand side of micrograph) with integrated with ambient drying conditionsNPC alloy in reinforcing over agent; i.e., not a a 2 week period. The laminate struckure.
NPC

alloy shrank around the reinforcing agent fibers. The shrinkage indicates the volume occupied by previously occluded water.

4 2'70X Same as Fig. 3 No individual Gay particles can be seen in fha SPM micrographs, illustrating that the clay particles ara chemically assoaated with polymer in NPC alloy, even at cla to monomer ratio of 2:1, 5 bDOX Reinforced NPC alloy Illustrates haw swollen NPG alloy campflsite immersed expands to conform to and in water substantially for 9b minutes prior occupy interstipal spaces to BEM. in reinforcing a ent.

-z~-Sent ny: VAN IASStL f~ ASSUC;lAItS /1:1 13:i~J 1/SU ~ U~l2tilUU lti:l2~ JBtFax #fjl3/;h'2ge ZU145 ARCr01 ~ CA
Fig. Magni-Description Observations # fication 6 4500X Same as Fig. 5. Illustrates that clay particles are chemically associated with polymer in NPC alloy. No free clay partiGes are seen, therefore indicating that the Clay does nit dissociate from NpC alloy when water-swollen. Swollen NPC alloy has open-cell structure, similar to polymer without clay (Fig.
2). Also, the degree of occluded water is substantially similar to polymer without day (Fig. 2), therefore indicating that clay even at high loading does not have a disproportionately detrimental effect on NPC alloy's swelling capacity versus a ola -free water absarbin al mer.

7 BsOX ~omparatlve. Same Swollen polymer fills interstitial spaces monomedcxoss-linking in reinforcing agent in agent same manner as mixture as used for NPC alloy in Fig. 5. Open-cell Fig. 5 structure sample, but without of polymer without clay clay. similar to that of Immersed in water the clay-based sample shown for 10 in Fig. 10.

minutes prior to SEM.Comparison to Fig. 5 illustrates how the clay is (a) integrated in the NPC alloy and (b) does not have a disproportionately datrimerrtal effect o~n NPC olio 's swellin ca aci .

As shown more c1$arly in the comparison between Fig. 5 (reinforced NPC alloy cornpasite) and Fig. 2 (swollen polymer without clay) or t=ig. 7 ($wollen polymer without clay in reinforcing agent), the swollen NPC alloy open-cell structure is similar to that of clay-free polymers. Accordingly, the clay does nit constrain the NPC alloys water swelling capacity.
In view of ogawa et al (discussed mere fully in Example 1 ), which suggests that clay acts as a aoss-linking agent for making water absorbent polymers, this is a surprising and unexpected result. Also, in view of the cross-linking agent results in Example ~, which illustrate that a cross-linking agent concentration as low as about 0.1 wt.°/a can over aass-~o link a polymer, thereby substantially reducing its water absorption capacity. these results are most particularly surprising and unexpected at a relatively high clay to monomer ratio of Z:1.
X-Ray Malyses The Energy Dlsparalve X-Ray (EDX) analysis device of the 8EM oolleGts signals 16 frarn an area of 1 um x 1 pm at a penetration depth of about 1 p.rn. X-ray analysis was conducted at numerous sites on the samp~te in Fig. fi, including the NPC alloy at the center SB112 Dy: VAN I ASStL f~ ASSUUlA I t5 I1 ~i B:iy 1 ISU ; U5I2EilUU 1 B:12;
J~tFsx #~B /; rage 2!!45 arc-o~ i ca of Fig. 6. Consistently at each site, peaks appeared for gold (2.z, 8.5 keV), silicon (1.74 keV), aluminum (1.49 keV), sodium (1.04 keV), magnesium (1.25 keV), and iron (0.615, 8.40 keV). The gold peak was a result of the gold treatment for the SEM
examination. The relative strengths and positions of the silicon and aluminum peaks in the EDX
spectra were consistent with those expected for bsntanita clay. All s(tcs examined showed the presence of silicon, aluminum, sodium, magnesium and iron. This analysis shows that the NPC alloy is homogeneous throughout the sample, even at the 1 Nmy Isvel. Accordingly, the clay in the NPC alloy is chemically assoaated with the polymer.

Clay Migration Tests This example illustrates that, when the reinforced NPC alloy composite is immersed in water, the NPC alloy swells with s~stantially no Gay separating from the alloy.
~5 NPC Alloy An MCX mixture was prepared by mixing 40.51 g acrylic acid with 5Q0 g water.
36.6 potassium hydroxide and 0.624 g NBAM were then added with stirring. After the potassium hydroxide was in solution, 24.39 g potassium carbonate was dissolved, followed by addition of 160.33 g acrylamide, 4.83 g potassium parsulfate and 500 g water. 594.07 g of the monomer mixture was blended with 199.79 g bentonite clay in a Rood blender to give a creamy suspension.
The MCX mixture was polymerized by heating in a 75°C oven for 8 minutes.
This NPC aIIQy was labeled as Sample A in the day migration tests.
Reinforced NPC Alloy Composite A layer of the MCX mixture prepared aborrE was pourod onto a 2 cm x 2 cm piece of TERRAFIX~ 2708-A geotextile. The MGX mixture was intimately distributed in and on the geptextile material by hand. Ths MCX mixture was polymerized ir5 the reinforcing agent by heating in a 75°C oven for 8 minutes.
This reinfan:ed NPC camposlte was labeled as Sample 8 in the clay migration tests.
C~rrtparatlve Sample C - Na Polymerization Initiator. No Cross-linking Agent The manomerlclay mixture for Compawative Sample C was prepared by mixing 1$.7 g acrylic add, 6.1 g sodium hydroxide, 34.9 g clay and 18 g water to form a viscous paste.

sent ny: VAN IASSN f~ ASSUUlAItS /1;i t3;i~J 1 /yU ; U5/1fi/UU 1S:l;i; ll~tFea #bl3/;Nage za145 The paste was then forced into a 2 cm x 2 cm piece of TERRAFIX~' 2708-A. The mdnomerlclay mixture could not be embedded into the geotextile at 100kPa. 84, one of the inventors, weighing about 80 kg, placed a piece of PLEXIGLAST"" on tap of the sample and stood an it while rocking back and forth. About halt of the monomerlctay mixture was forced into the fabric using this method. No polymerization initiator or crass-linking agent was added to the monomeNclay mixture.
The sample was dried in an oven at '~5°C far one hour.
Comparative Sample D - No Polymerization initiator id A monomerlclay mixture was prepared by mixing 79.89 g acrylamide, 20.5B g acrylic acid, 0.3 g NBAM as cross-linking agent, 9.995 sodium hydroxide, 9.962 g sodium carbonate, and 1000 g water. 552.8 g of the monomer mixture was blended with 104.a~a g bentonite Gay in a flood blender to give a creamy suspension. No polymerization initiator was added to the monomerlGay mixture.
A layer of the monomerlday mixture was poured onto a 2 cm x 2 cm piece of T~f2RAFIX" 2701-A geotextlle. The mixture was intimately distributed in and on the geotextile material by hand. The monomerlclay mixture was heated in a 70°C oven for 1 hour in the reinforang agent.
This sample was labeled as Sample D in the clay migration tests.
Comparative Sample E - Pre-formed bilgamer (MW 2,DOOy Comparative Sample E was prepared by mixing fi.5 g pre-formed palyacrylic acid, i.6 g sodium hydroxide, 26 g water and 10.70 g day. The polyacrylic acid, having a molecular weight of 2,000, was obtained from Aldriotl Chemical Co.
A layer of the pre-formed oligomeNGay mixture was poured onto a 2 cm x 2 cm piece of TERRAFIXe 2708-A geotextile. The pre-formed oligomerlclay mixture was intimately distributed in and on the geotextile material by hand. The sample was dried in an oven at 7~°C for one hour.
so Comparative Sample F - Pre-formed polymer (MW 45D,OOt)) Comparative Sampl~ F was prepared by mixing 4.74 g pre-formed palyaaryllc acid, i.4~t g radium hydroxide, 86 g water and 11.52 g clay_ The polyacrylic acid, having a molecular weight of 450,OOp, was obtained from Aldrich Chemical Co.

sent ny: UAN I A~StL f~ ASSUG1A I tS I1 ~ t3~~J 1 /SU ; U5l2fjl UU 1 t3:1 ~;
II~tFax ;~f3f31; Page 2yI45 A layer of the pre-fomled polymerlclay mixture was poured onto a 2 cm x 2 am piece of TERRAFIX~ 270-A geatextile. The mixture was intimately distributed in arid on the geotextile material using a wooden rolling pin. The sample was dried in an even at 75°C for one hour.
s Clay Migration Test Procedure each of the samples was placed in a glass bottle. 1 Do mt- dsionized water at room temperature (about 20°C) were then poured info the horde.
The bottle was left standing without disturbance at room temperature. The sample io was observed at ~ hours and 22 hours after addition of water, as described in Table 7.
Talale T
Sam Desari lion of Barn le observations ~
ale A MCX mixture: acrylamide, After 3 hours, the sample sodium had swelled acrylate, cross-linking considerably. After 22 agent, hours, there was persulfate polymerizationsome additional swelling initiator, of the NPC

and slay. alloy. The swelled NPC
alloy was puffy in appearance. The clay remained as The MCX mixture was polymerizedan integral part of the NPC alloy. (see (~ 75C for 8 minutes. Figs. 8A and 8B). Substantially na clay separated fnam the NPC
alloy after 22 hours of immersion dme.

S MCX mixture: acrylamide, After 3 hours, the sample sodium had swelled acrylate, crass-linking considerably. After 22 agent, hours, there was persulfate polymerizationsame additional swelling initiator, of the NPC

and clay. alloy. The swelled NPC
alloy was puffy in appaaran~. Soth the fabric and clay The MGX mixture was pressedremained as an integral into a part of the NPC

fabric and polymerized alloy. (see Figs. 9A and in a fabric ~ 9B).

75~ for 8 minutes. Substantially no clay separated from the NPC alloy after 22 hcurs of immersion time.

C ~omparakrve_ Monomerlday After 3 bouts, the acrylic acid and mixture: acrylic acid, sodium acrylate dissolved NaCH, water in the water.

and clay. No polymerizationThe day had migrated off initiator the fabric and or cross-linking agent swelled at the bottom of was used. the test bottle.

There was no change after 22 hours.

The monomerlday mixture was pressed into a fabrio and dried ~

~ 'C fnr one hour_ . 2B

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Sam Descri 'on of cam le Observations le D Comparative. MonomerlclayAfter 3 hours, the acrylamide and mixture: acrylamida, acrylicsodium acrylate dissdYed acid, in the water.

NaoH, NI3AM (cross-linkingThe clay had migrated off agent), the fabric and water and clay. No polymerizationdispersed in the water.
There was no initiator was used. change after 22 hours.

The monomer/clay mixture was pressed into a fabric and heated tdr one hour 70C.

E Comparative. A pre-fonr~edAfter 3 hours, the polyaaylic acid polyacryiic acid (MW=2000)dissolved in the water.
was The Gay mixed wikh clay and pressedmigrated off the fabric into a and dispersed in fabric. the water. There was no change after 22 hours. see Fi s. 1 QA
and 1 DB

F Comparativ$. A pre-formedAfter 3 hours, the polyacrylic acid polyacryllc acid (MW=450.000)dissolved in the water was and some clay mixed with clay and pressedhad migrated off the fabric.
into a After 22 fabric. hour'$, the remaining clay had rTpg1'ated off the fabric and swelled at the bottom of the bottle.

Line drawings were prepared from some of the photographs taken during the Gay migration tests summarized in Table 7.
Sample A was an NPC alloy. Fig. 8A illustrates the NPC alloy 36 prior to immersl4n in ~eianized water. Fig. 8B illustrates the sample after 3 hours immersion in deionized water. The swelled NPC allay 38 had a puffy appearance. Substantially no clay separated from the composite.
Sample B was a reinforced NPC allay composite. Fig. 9A illustrates Sample B
prior to immersion in deionized water. The NPC alloy is in the reinforcing agent 40.
Fig. 98 illustrates the sample after ~ hours immersion in deionized water. The swelled NPC alloy 46 had a puffy appearance. Substantially no clay separated from the comp4site.
Fig. 10A illustrates Comparative Sample E prior to immersion in deionized water.
The pre-formed polymer and clay mixture is in the reinforcing agent 40. Fig.
1DB illustrates the sample after 3 hours immersion in deionized water. The polymer had dissolved in wafer ~ 5 and the day 44 migrated off the reinforcing agent ~0 and dispersed in the water. Some settling of the Gay ~I is observed at the bottom of the bottle.
The results in Table 7 and Figs. BB and 9B illustrate how the Gay is an integral part of the NPC alloy. Moreover, the results demonstrate how the NPC alloy is an integral part of the composite. In all of the oornparative samples, clay migrates from the mixture andlor the sent ny: YAN IASStL ~~ ASSUUlAItS Il;i t3;~9 1/SU ; U512f~1UU 18:14; ll~tFax ~f~Bl;rage 3W45 reinforcing agent. Also, monomer and pre-fomned polymer mixture migrate from the reinforcing agent. This is shown more clearly in Fig. 108.
The NPC alloy remains substantially intact an exposure to deionized water at about 20°G. Spec~cally, substantially no clay separates from the NPC alloy.
Moreover, the alloy is expected to exhibit saabstantially similar performance in deionized water in a temperature range of about 1 °C to about 80°C. This represents a significant improvement over the conventional techniques.

id Residual Monomer Content One concern about using aaylamide as a monomer for preparing an NPC allay is the leaching of any residual monomer. The FDA limit for teachable acrylamide in polyacrylamide is 0.05~A (500 ppm, 500 uglg) when the polyacrylamide is used in treatment of potable water and for paper and paperooard for food contact applications (EPAIGOOIX-851270 July 1985, P688-170824).
This example provides residual monomer data far a polymer and an NPC alloy.
~eneraliy, the amount of residual monomer is dependent an initiator concentration, reaction time, and reaction temperature. Far example, residual monomer content generally decreases with increased temperature, increased reaction time and increased initiator concentration.
Sample Preparation A monomer mixture was prepared by mixing 20 g acrylic acid, 80 g acrylamide, 10 g sodium hydroxide, 12 g sodium carbonate, and 0.6 g potassium persulfate in 1000 mL
water. The monomer mixture was divkied into three parts and NBAM was added as a cross-linking agent at 0.1 ~o. 0.3% and 0.90, by weight, rESpectively. Each of the three monarner mixtures was sub-divided into three parts. Clay was added to some of the mixt~es in an amount of about i:1 monomer to clay or about 1:2 monomer to clay, as shown in Table 8.
The MCX mixtures were blended in a food blender to produce a smooth, homogeneous mixture.
Samples of the monomer and MCX mixtures were transferred to plastic beaKers and placed in an 80°C oven for one hour for polymerization. The samples were removed from the oven and allowed to cool to room temperature. The samples were dried at 95°C for a couple of days.

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A weighed sample of dried polymer or polymerlclay alloy (1-2 g) was placed in a polyethylene beaker with about 20o mL water end allowed to stand overnight at room temperature (about 20°) overnight. The polymer and NPC alloy samples swelled and absorbed some of the water- The remaining water was decanted from each swollen 1o polymer and NPC alloy and analyzed for acrylarnlde content. Tha results ~e presented in Table 15.
Table 8 Sample Monomer Monomer:ClayLeached Mixture (wt.) Acrylamide (wt.) ppm (Frglg of mer 8 209Ac lic 80~ amide 0.1 No Cla 13.1 Acid Ac /a NsAM

9 20/A lic :~0~ amide, 0.3h No Cla 128 Acid Ac NSAM

20%Ac lic 80% amide 0.9% No Cla 22 Acid Ac NBAM
l y 1 20%A lic 80/a amid80.3% BAM 9 :1 108 Acid,A~ N

'~2 20~I lic amide0.9~ BAM 1:1 7s98 Acid, N
8(16 Ac l 13 20lA Itc 80~/ amide, 1:2 90.1 Acid,Ac 0.396 NBAM

The amount of leached acrylamide, leached by water from the dried polymer and NPC alloy samples, was well below the FDA limit of 500 ppm for all samples except one.
Sample 12 resulted in a very high leached acrylamide concentration. Because of the inordinately high residual monomer, it appears that Sample 12 did not polymerize properly.
Th~ls, Sample 12 is an aberrant data point, especially in view of the Sample 11 r~esuh, based also on a 1:1 MCX mixture, but with only 108 ppm residual acrylamide, and the Sample 9 result, a clay-free, monomer, cross-linking agent mixture, but with only 128 ppm residua!
acrylamide.
It was expected that polymeriaatian may not proceed as extensively and, ttlerefore, the amount of leached acrylamide would be greater, for samples containing clay, Especially apt higher amounts of clay. Surprisingly, how~ver, as shown in Table B, the amount of z5 leadted acrylamide was similar for Samples 11 and 13 (4.3°~ NBAM, 1:'1 and 1:2 monomer to clay, respectively) and Sample 9 (0.396 NBAM. no clay).

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This and the other examples presented herein demonstrates the advantages of the NPC alloy for use in fluid barrier applica#ions and water absorbency applications.
Preferred compositions and processes for practicing the invention have been described. It will be understood that the foregoing is illustrative only and that other embodiments of the process for producing an NPC alloy can be employed without departing from the true scope of the invention defined in the following claims.

Claims (23)

1. A process for producing a networked polymer/clay alloy, comprising the steps of (a) preparing a monomer/clay mixture by mixing at least a monomer, clay particles, a cross-linking agent, and a mixing fluid in a vessel;
(b) exposing the monomer/clay mixture to a polymerization initiator means; and (c) polymerizing the monomer/clay mixture so that a networked polymer/clay alloy is formed.

2. The process of claim 1, wherein the polymerization initiator means is selected from the group consisting of a chemical substance, electromagnetic radiation having a wavelength less than about 10 nm, and combinations thereof.

3. The process of claim 2, wherein the chemical substance is selected from the group consisting of free radical initiators, carbanions, carbonium ions, and combinations thereof.

4. The process of claim 3, wherein the free radical initiator is selected from the group consisting of (a) alkali metal salts of sulfite, bisulfite, persulfate and benzoyl peroxide;
(b) ammonium salts of sulfite, bisulfite, persulfate and benzoyl peroxide; (c) 2,2'-azobis(2-amidino-propane)-dihydrochloride; (d) 2,2'-azobis(4,-cyanopentanoic acid);
and combinations thereof.

5. The process of claim 1, wherein the mixing fluid is selected from the group consisting of water, alcohol, organic solvents, and combinations thereof.

6. The process of claim 1, wherein the clay particles are swelling clay particles selected from the group consisting of montmorillonite, saponite, nontronite, laponite, beidellite, iron-saponite, hectorite, sauconite, stevensite, vermiculite and combinations thereof.

7. The process of claim 1. wherein the clay particles are non-swelling clay particles selected from the group consisting of kaolin minerals, serpentine minerals, mica minerals, chlorite minerals, sepiolite, palygorskite, bauxite, silica and combinations thereof.

8. The process of claim 1, wherein the weight ratio of clay to monomer in the monomer/clay mixture is in a range of from about 0.05:1 to about 19:1.

9. The process of claim 1, wherein the weight ratio of clay to monomer in the monomer/clay mixture is in a range of from about 0.5:1 to about 3:1.

10. The process of claim 1, wherein the monomer has the following general formula:
wherein x is selected from the group consisting of OM, OR4 and NR5R5, M is an alkali or alkaline earth metal ion or NH4, R1, R2, R3, R5, R6 and R7 are independently selected from the group consisting of H, CH3. CH2CH3, CH2CH2CH3, CH(CH3)2, CH2CH2CH2CH3, and CN, and OR4 is selected from the group consisting of OH, OCH3, OCH2CH3, OCH2CH2CH3, OCH(CH3)2, OCH2CH2CH2CH3, OCH2CH2OH, and (OCH2CH2)m OH, n= 0 to about 10 and m= 1 to about 10.

11, The process of claim 1, wherein the monomer is selected from the group consisting of acrylic acid, acrylamide, sodium acrylate, potassium acrylate, methacrylic acid, isopropylacrylamide, and combinations thereof.

12. The process of claim 1, wherein the cross-linking agent is selected from the group consisting of N,N'-methylene bisacrylamide, phenol formaldehyde, terephthalaldehyde, allylmethacrylate, diethyleneglycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethylene carbonate, ethylene glycol diglycidal ether, tetraallyloxyethane, triallylamine, trimethylolpropanetriacrylate, and combinations thereof.

13. A product produced by the process according to any one of the preceding claims.

14. A networked polymer/clay allay comprising a chemically integrated composition of polymer and clay, so that, when the alloy is immersed in deionized water, at a temperature in a range of from about 20°C to about 30°C, the alloy swells with substantially no clay separating from the alloy.

15, The networked polymer/clay alloy of claim 14, wherein the day particles in the alloy are swelling clay particles selected from the group consisting of montmorillonite, saponite, nontronite, laponite, beidellite, iron-saponite, hectorite, sauconite, slevensite, vermiculite and combinations thereof.

16. The networked polymer/clay alloy of claim 14, wherein the play particles in the alloy are non-swelling clay particles selected from the group consisting of kaolin minerals, serpentine minerals, mica minerals, chlorite minerals, sepiolite, palygorskite, bauxite, silica and combinations thereof.

17. The networked polymer/clay alloy of claim 14, wherein the weight ratio of clay to polymer in the alloy is in a range of from about 0.05:1 to about 19:1.

18. The networked polymer/clay alloy of claim 14, wherein the weight ratio of clay to polymer in the alloy is in a range of from about 0.5:1 to about 3:1.

19, The networked polymer/clay alloy of claim 14, wherein the polymer of the alloy is a copolymer of a water-insoluble monomer and a monomer having the following general formula:
wherein X is selected from the group consisting of OM, OR4 and NR5R6, M is an alkali or alkaline earth metal ion or NH4+, R1, R2, R3, R6, R6 and R7 are independently selected from the group consisting of H, CH3. CH2CH3. CH2CH2CH3. CH(CH3)2, CH2CH2CH2CH3, and CN, and OR4 is selected from the group consisting of OH, OCH3, OCH2CH3, OCH2CH2CH3, OCH(CH3)2, OCH2CH2CH2CH3, OCH2CH2OH, and (OCH2CH2)m OH, n= 0 to about 10 and m= 1 to about 10.

20. The networked polymer/clay alloy of claim 14, wherein the alloy is formed by exposure to an energy source selected from the group consisting of thermal energy, electromagnetic radiation having a wavelength less than about 10 nm and combinations thereof.

21. The networked polymer/clay alloy of claim 14, wherein the residual monomer content is less than 200 ppm by weight of the polymer in the alloy.

22. The method of using the networked polymer/day alloy of claim 14 for making a fluid barrier for use under a confining stress range of from about 0 kPa to about kPa, wherein, when the barrier is placed under a zero confining stress, the barrier has a deionized water flux lees than about 1 x 10 -6 m3/m2/s.

23. The method of using the networked polymer/clay alloy of claim 14 for making an absorbent material used in a personal care article.