CA2143297C - Water proofing liner - Google Patents

Abstract

There is described a water-proofing material (10) basically made from a plastic mass containing a liquid and particulate smectite clay, usually montmorillonite such as bentonite, which can be united with a carrier sheet (20). The plastic mass can contain aqueous and/or non-aqueous liquid which can be expelled after forming.
The smectite clay can be a smectite liner intercalation complex and the mass desirably formed by extrusion, in the latter case preferably during reaction of the clay and can have a density of at least 1000 kg/m-3 and can be 1 m or more wide.

Description

~'~O 94/05863 PCT/GB93/01807 2~ 43297 WATER PROOFING LINER
This invention relates to a waterproofing material suitable for waterproofing ponds, lakes,, lagoons or comparable sites whereby eater is retained, or wherE:in waste is deposited and the ground beneath has to be protected against leakage of aqueous or other liquid. The material. can also be used in relation to water proofing structures, covering contaminated land to prevent flow of water into such contaminated land and lining trenches which separate contaminated areas from clear areas. The material can also be used as roofing material on flat or sloping roofs.
Several materials have been proposed in the past which include a layer of swe11ab1E~ smectite such as montmorillonite and/or sponite incorporated within the material to act as the sealing agent. The montmorillonitE~ has been carried by a support layer or base which has been provided in various ways. A support layer acts as protection but also gives additional strength within the material.
European patent number 596.25 (CLEM) describes a waterproofing material which is a laminate comprising a fabric base, particles of montmorillonite adhered to the base and a scrim adhered over the montmorillonite particles to retain them on the base. The CLEM specification requires as an essential feature thereof that the base be capable of venting gas. Although venting of gas from beneath a contained body of water or other matter can be an advantage, it is a great disadvantage to incorporate such ventibility into th~~ actual base. Although there are few sites where venting is :necessary it is, when venting is needed, desirable to provide a separate venting layer quite separate from the waterproof ing materia:L overlapping the first sheet ( 10 ) . The sheet (10) has a venting base (13), a layer of montmorillonite (14) adhered to the base (13) and a scrim (15) on top of the montmorillonite. In similar manner sheet (12) has base (16), montmorillonite (17) and scrim (18). As will be seen from the drawing and the arrows (19) the layer of base (16) overlying the montmorillonite (14) provides a path, between the two layers of montmorillonite (14) and (17) which, because it is designed to vent air can also allow Liquid such as water to wick out along the path indicated. Thug;, the incorporation of a venting base in the sheets (10) and (12) can have undesirable results.
Figure 2 shows how the construction described in European patent application 246 311 (McGROARTY) overcomes these problems. In the MCGROARTY construction a lower sheet (19) has a base (20) and montmorillonite (21.). An overlaid sheet (22) has base (23) and montmorillonite ( 24. ) . I:n McGROARTY the base ( 20 ) and ( 23 ) are of solid plastics non-venting and impermeable material. Thus in the construction shown in figure 2 the base (23) forms a non-AMENfDED SHEET
I IPEA/EP

water transmissivE=_ layer between the two layers of montmorillonite (21; and (~4) thus giving a very good seal. This is a significant advantage over the prior art of figure 1.
Unfortunately, however, 'the McGROARTY construction does have several practical, other difficulties. Firstly, the bases (20) and (23) are made from a thick, impervious and essentially solid plastics material, described in the specification as HDPE.
Further, the specification describes the fact that granules of montmorillonite are adhered not only to the base but also to each other.
Waterproofing materials of this kind are usually supplied in rolls and have to be unrolled and placed to lie in the pond, lagoon or storage space. With the base (20) (23) made from high density polyethylene the McGROARTY material is less flexible that when using a fabric (non--woven or woven) for the base. This means that the product is much more difficult to handle and the montmorillonite is likely to crack during folding and unfolding.
Further, because of the nature of an HDPE plastic sheet the adhering of the montmori:L.lonite to its surface is not easy.
~~uite large quantities of very strong glue have to be used. As .mentioned, in the McGROF,RTY construction the montmorillonite ;particles or granule: are applied in layers which are adhered not ~~nly to the base but also to each other. This makes the product even less flexible and more difficult to handle. Because of the WO 94/05863 PC~/GB93/01807 high stiffness cf the product McGROARTY has to dispense with any scrim such as the scrim (15) (18) and this means that if any montmorillonite is loosened due to folding and unfolding it can easily become displaced leaving voids in the montmorillonite layer. The McGROARTY material is also very stiff and difficult to handle.
A further waterproof ing barrier material is disclosed in British patent number 2 202 185 (NAUE). In the NAUE specification a layer of montmorillonite is sandwiched between a pair of layers of non-woven textile material, in which two layers are united by needling, the needles passing through the layer of montmorillonite and uniting all three layers. This product again has disadvantages. Firstly, both the non-woven layers of textile material are essentially gas venting. Therefore, when they are laid they have the same disadvantages as the CLEM construction.
Further, because the montmorillonite is not adhered to the layers, as the material is unfolded, folded and manhandled during installation, the montmorillonite can move relative to the two layers leaving voids and/or more permeable thinner areas in the montmorillonite layer.
There is a further disadvantage in that all these earlier materials tend to use particulate montmorillonite which may be from 2 - 5, usually about 3mm in size. Although finer material can be poured to fill gaps between the larger granules, such granules tend to make up the bulk of the montmorillonite layer in the waterproofing material. As the water proofing material is only relatively l~hin, :Eor example containing only perhaps one or two layers of montmori:Llonite granules, problems can arise in connection with foreign bodies in the montmorillonite used. In its natural state montmorillonite is found alongside shale and other impurities. Whilst the montmorillonite can be quite highly purified, it is not unusual for a low percentage of shale particles to remain i.n the final sized and graded montmorillonite. An unfortunate result of the use of relatively large granules of montmor:illonite in the layer is that granules of impurities can also become incorporated in the material. The chemical nature of shale and some other impurities have the effect that not onl~~ are they not montmorillonite (and therefore do not swell upon contact with water), but, when wetted, act as to inhibit swelling in adjacent montmorillonite granules. Thus, a single granule of shale in a layer of waterproofing material can form a small area (pe:rhaps lOmm in diameter) which does not swell upon being contacted with water. Small such areas are generally water impermeax>le, but medium and larger such areas allow water to pass through the sheet. When water pressure is high this flow can cau~ae significant wash out of adjacent montmorillonite leading to failure of the sealing system.
Although the percentage of: impurities is small, and although the failure rate is sma:Ll, wizen a large area is sealed using sheet material incorporating such impurities it needs only a single leak for the whole system to have failed. A pond or lagoon which has a single leak is no pond or lagoon at all!
Particulate montmorillonite has also been mixed with various organic components to form a thick putty (see US Patent Number 4 534 925). Typical components are polypropene and polybutene.
This material has been extruded in the form of rods and sheets, usually being stored between layers of release paper. Such material has been used for sealing ground foundations and similar structures. It has not, however, being extruded so as to become united with a carrier sheet and be capable of use in large rolls for covering large areas. Indeed, the polypropene and polybutene used is intended deliberately to give the extruded material a rubbery or formable consistency enabling it to be moulded by hand around small areas such as chimneys, at joints in concrete panels or where drains penetrate foundations. These materials are also quite expense and prohibitively so for use in relation to large area sheets.
It is an object of the present invention to provide a waterproofing material whereby the above described disadvantages are reduced or minimised.
Smectite includes montmorillonite (dioctahedral) and saponite (trioctahedral) clay minerals and their chemical varieties. They have commercially valuable swelling and ion-exchange properties.

21 ~E32~~7 The smectites have a layer of lattice structure, but differ from micas in that the bonds between layers are weakened because of internal chemical :~ubsti~tutions. Montmorillonite consists of layers of negatively charged oxygen (O) atoms within which several types of positively-charged cations are fixed in specific positions. In a two dimensional schematic diagram of the structure (figure 11), four layers of oxygen atoms can be seen to define upper and .lower tetrahedral sheets containing tetravalent silicon (Si) <~nd sometimes trivalent cations (3+) of aluminium (A1) and uron (he). The apices of the tetrahedra point toward each other and oxygen atoms at the apices form part of the octahedral sheet that may contain trivalent cations (A1, Fe), divalent cations (Fe, Mg), both divalent (+2) and trivalent cations, or divalent and monovalent (+1) lithium (Li) cations.
The presence of two tetralZedral sheets and one octahedral sheet is the basis for classifying the montmorillonite structure as 2.1 (2x tetrahedral 1 x octahedral sheet structure). The 2.1 structural units are separated by interlayers of loosely held hydrated cations. These cations are present to balance the negatively charged structure.
If a particle of Montmorillonite is to expand it needs to take in water into its intEarlayers. This mechanism is valency dependent. Ionic compounds are formed because a metal atom donates one or two electrons to a non-metal atom (or acid radical group). For example, in table salt (sodium chloride), the AMENDED SHEET
iPEA/EP -N'O 94/05863 PCf/GB93/0180~

n O
electron from the highest energy level in the sodium atom is donated to the chlorine atom and they both form ions a sodium one plus cation and chloride one minus anion. The higher the valency the shorter the bond length the more stable is the montmorillonite, ie calcium two plus cations will replace sodium one plus cations. Ln order for this replacement to take place the cation must c~et close enough to the montmorillonite substrate, to do this other mechanisms must be considered.
If a particle of montmor.illonite is dropped into a beaker of water its interlaye:rs take in water, and gradually the clay spreads until eventually it is uniformly distributed. What causes montmorilloni.te mo:Lecules to behave this way? The answer depends on the fact that the molecules within the inter layers are in a state of random motion. Although they can move in any direction, the fact that initially (wetting of the particle) there are far more molecules in the immediate vicinity of the interlayers increases the probability of their moving away from each other resulting in expansion. This process is diffusion, and is defined in this insstance as a movement of molecules from a region where they are at a comparatively high concentration (dry) to a region where they are at a lower concentration (hydration) giving a volume increase. Diffusion will always proceed whenever such a c:ancentration gradient exists, and it will continue until event=ually the molecules are uniformally distributed and lattice stabilisation is achieved, at which time 'VfO 94/0863 PCT/GB93/01807 21 4 3~ 2 9 ;~
_ g _ equilibrium is said to be reached.
Osmosis for the present purpose can be regarded as a special case of diffusion; the diffusion of water from a weaker to a stronger concentration. A wE:ak sol.utionlof table salt, for example, will contain relatively less salt and more water than a strong solution of salt. Thus the concentration gradient is from the weak to the strong solution. If two such solutions were in contact, the water molecules would move one way and the salt molecules the other until both were uniformly distributed (equilibrium). If, :however, the two solutions are separated by a membrane which allows water but not salt to pass through, only water can diffuse. Such a membrane is said to be selectively permeable or "semi permeable" and the water movement is called osmosis, and is defined in this instance as the movement of a solvent (water) a~~ross a selectively permeable interface (membrane) from a weak to a strong concentration of ions in solution. Montmorillonit:e interlayers are water selective due to the attraction of dipolar water molecules to the highly charged clay particles.
As has been discussed above, the montmorillonite clay is made up of a plurality of structural plates each of which has four layers of oxygen atoms. The outs~r layer of each plate has a generally tetrahedral format and presents a surface to the interlayer to which cations are loosely bonded. In sodium montmorillonite which is a popular and useful material the cations are sodium ions and are connected to the tetrahedral layers by relatively weak Van Der Waal bonds. The interlayers contain a certain amount of hydrating water molecules. When the montmorillonite is contacted with water more water enters the interlayer, being attracted to the charged cations in the interlayer and moving by diffusion and capillary reaction so as to increase the thickness of the interlayer. If a body of montmorillonite is confined between a pair of relatively immobile surfaces the pressure within it upon contact with water can become so high such as to prevent any further movement of water~into the structure. This build up of a high pressure layer which cannot absorb any water makes montmorillonite an excellent water-proofing agent. It is widely used in civil engineering structures.
Often used as a substitute for sodium montmorillonite is calcium montmorillonite wherein the loosely held cations in the interlayer are mainly Ca 2+ rather than Na +. Because of their divalancy the calcium ions bind more strongly to the outer tetrahedral layers than does sodium. In use calcium bentonite has a property that when initially wetted it will swell and expand in the same way as sodium montmorillonite. However, if the material should dry out, for example due to low rain fall or a falling water table calcium montmorillonite cannot shrink back to its original size upon loss of water without cracking. After cracking and upon re-wetting the interlayer becomes incapable of WO 94/05863 PC7/GB93/0180 i 21 4 ;s 2 9 ;~
_~,_ absorbing more water and t=herefore the clay can not re-wet so as to reform the water proo:E barrier. Thus, a calcium bentonite water proofing material should only be used in cases where permanent wetness i:~ to be encountered. It is possible to treat calcium bentonite with a wrong sodium containing solution so as to displace a certain percentage of the calcium ions from the interlayer and replace them with sodium so as to give the calcium montmorillonite propertiE~s closer to sodium montmorillonite.
However, this material is not as good as pure sodium montmorillonite, and tends to suffer from the same problems as calcium montmorillonite.
All sodium containing montmorillonites do have a problem when the water which comes into contact with them is contaminated by salts, particularly sea water or other salts which render the ground water ionised and highly active. In ground water calcium is invariable present in quantity from soil and minerals. When such ionic calcium comes into contact with montmorillonite it invariably tends to migrate into the interlayers. Once in the interlayer the double va:lency of the Ca+ cations makes the calcium selectively adhere to the four sides of the tetredral layers displacing sodium. Such contamination can quite quickly result in complete .stripping of sodium from the interlayer, so converting the montmorill.onite from the sodium to the calcium form with the disadvantage which has been outlined above.

WO 94/OS863 PCT/GB93/0180'' This particular process makes it generally unwise to use even sodium montmorillonite in a situation where the ground water can become rapidly ionised or contaminated by leachates or the like.
In particular, fertilisers are a particularly notorious cause of ground water ionisation and can cause sodium montmorillonite break down. It is an object of the present invention to provide an improved smectite clay.
In a paper entitled "Preparation of Montmorillonite -Polyacrylate Intercalation Compounds and the Water Absorbing Property" by Ogawa et al published in Clay Science Number 7, 243 251 (1989), the authors have described the introduction of a acrylamide into montmorillonite and the polymerisation of the acrylamide to form a polyacrylamide intercalation compound. The enhanced water-absorbing properties of the compound are noted.
It is to be appreciated, of course, that the processes carried out in the Ogawa paper were essentially laboratory processes involving small amounts of material. No techniques were described for making any useful product and there was not discussion of the advantages of high density such compounds as waterproofing agents.
The present invention is additionally concerned with smectite liner intercalation complex (herein after referred to as a "SLIC") materials h<~ving improved properties.
Desirably the smect:ite containing layer is sandwiched between a carrier or support :sheet and a cover sheet.
Reinforcement can be provided in the middle of the smectite containing layer.
The reinforcement c,~n be secured to the cover sheet and/or the support sheet.
The invention also provides a method of making a waterproofing material including mixing particular smectite with at least a carboxymethyl celluose (Cr2C) compound and water to form a plastic mass, and preferably forming that mass into a layer and uniting it with a carrier or support sheet.
The laminate of the smectite layer and the support sheet can be treated after union to cause the layer to loose a degree of plasticity to enable it to be handled and stored without undergoing further deformation.
Desirably the smectite is mixed primarily with water to form a paste or a putty like plastic mass which can be extruded rolled or otherwise farmed into a continuous layer.
nMENt)ED SHEET
I P'E~/E P

After forming the 7_ayer can be subjected to a drying step to remove excess water to convert the smectite layer into a more dimensionally stable cone=iguration unlikely to deform further during transportation and storage and further to increase the swellability of the smectite upon contact with water in use.
Additives which modify the behaviour the smectite under certain specified conditions such as salt water, or presence of strong leachates, radiation hydrocarbons or organic chemicals can be added at the mixing stage: to be operative when the smectite is in use.
Union of the smectite containing layer with the support sheet can be by adhesive, but desirably no adhesive is used, the mixture of smectite (and other :~ubstance(s)) being such as to allow pressure to force the plastic mass into the interstices of the cover sheet (which :is desirably of a textile nature) physically to unite the two. Similar connection can be effected between the layer and the cover sheet.
In addition to water and C:MC, organic materials such as methanol, ethanol and other al.cohols, glycerine, diesel and other oils and fats can be used. 'these materials do have the advantage that it is not necessary to drive of f so much water so as to increase the swellability of the smectite layer, but they also have the disadvantages that 'they do need a drying step so that ~~MENG1ED SHEET
IPI~~/GP

214.3297 the material is not subject to further deformation under its own weight during storage and transportation and many organic materials are usually far more expensive then water.
Alcohols, particularly methyl alcohol do, however, have particular advantages. Whilst alcohols are generally expensive, they are also usually fa.r more volatile than water. Thus, a plastic mass made using methyl alcohol can, after having been formed into a cohesive continuous layer be dried using far less heat than would be necessary to drive out the water from a similar mass. In addition to this however, the alcohol driven off can be condensed and reu~;ed thus offsetting the cost thereof.
The montmorillonite mesh size can be anything from 50 mesh or smaller, desirably, however the size is a maximum of 100. In practice a mesh size of 200 has been found useful although variations downwards from about 100 mesh do work although with less desirable qualuties. Finer meshes are perfectly acceptable, but tend to be unnecessary. The smectite used is desirably sodium montmorillonite although calcium montmorillonite modified by treatment with sodium hydroxide) can be used. As the montmorillonite is u:~ually broken down significantly during mixing to micro sizes, initial grain size is not critical.
The fabrics used as ;support and/or cover layer can be conventional woven or non-woven textiles such as nylon or AMIENDED SHEET
iPE~VEP -2143297 , polypropylene or polyester. They should be non-venting (that is to say they do not allow gas or liquid to pass along the structure in use to any significant degree). The fabrics are desirably woven and this degree of non-venting can be achieved by ensuring that the fabric is of relatively open mesh and fairly thin, a significant portion thereof being embedded in and physically uniting 'with the outer layer of the montmorillonite layer.
The invention includes of course, a waterproofing sheet made by the methods aforesaid.
Apparatus for making such a waterproofing material includes a conveyor, means for feeding a support to the conveyor, means for applying a plastic s:mectite-containing mass onto the support, and means for forming ;aid plastic mass into a uniform continuous layer.
Means can be provided for sizing the laminate in thickness and/or in width.
Desirably the apparatus includes means for conditioning the laminate after formation t:o render it stable in use and storage.
Said means can include an oven for evaporating substances, from the laminate.
AMENC)ED SHEET
IPEA/EP _ -1~-Means for supplying the p:Lastic mass to the conveyor can include one or more nozzles, and/or an extrusion head.
Means can also be provided for supplying a cover sheet to a surface of the layer remote from the support sheet.
Means can also be providled for feeding a reinforcement to be embedded within the smect.ite containing layer.
Means can be providE=d for uniting said reinforcement with one or both of the cover and support sheets; for example by heat sealing.
The invention also provides a method of waterproof ing a structure to prevent ingress and/or' egress of aqueous fluids including the steps of pi°oviding a plurality of sheets each in the form of a laminate of a support sheet and a layer of cohesive smectite, formed from a plastic mass, as aforesaid, laying the sheets to cover the surface of said article in overlapping relationship and protecting said sheets against accidental damage in use.
AMENDED SHEET
~I'EA/EP

Waterproofing material in accordance with the invention can be used, for example, .as roofing material or to provide a seal for a pipe or other plumbing fittings.
The smectite mixture can be in the form of a sealing ring or annulus or can be providE~d as a continuous length for wrapping around joints. The sealing material can be made by the aforesaid methods of forming a plastic mass and extruding, cutting or moulding therefrom.
AMEf~JDED SHEET
I P EA/EP

The invention provides as a second feature thereof a waterproofing material in the form of a body of material formed from a plastic mass, wlZerein said plastic mass contains a smectite/liner intercalation complex.
The liner can closely bind sodium cations to the outer layers of plates of the smectite structure therefore reducing the possibility of their replacement by calcium cations.
Alternatively the lining can replace the sodium cations leaving a generally neutra:L face which can absorb water by capillary action, but which .is generally neutral and therefore does not attract calcium cations.
The liner used will. norm<~:lly be an organic compound compatible with the outer layers of the smectite plates. Suitable compounds can be sugars such as fructose, glucose, dextrose and the like which have comparable molE~cular shapes and will complex with the tetrahedral layers on thE: outside of the plate.
~~MENCIED SHEET
IPE~4/EP

a .y ~ ' 1 A further and desired liner is an acrylate. The material can be added as the polyacrylate or an acrylation process can be carried out in contact with the clay.
Another possible liner is alkylammonium trimethyl alkyl ammonium.
The acrylate can have thE: formula shown in figure 12.
Although the sodium salt of polyacrylate is shown other cation forms can be used.
In the sodium cation form the acrylate can replace the sodium cations which normally coat the outer layers of the smectite plates.
The acrylate polymer can be doped with various desirable material to alter various properties of the clay.
One particular doping agent is glycerol. The introduction of glycerol can increase the flexibility of the clay so that a length of the clay can be' bent easily without breaking.
Methanol can also be :introduced as a useful material for increasing the flexibility and reducing the stiffness of the mixture thus assisting in its processing.
~~MENC)ED SHEET
tPEAJEP

The invention further provides a method of treating a smectite clay to form a leach-rE~sistant clay including the step of reacting it with a liner capable of complexing with faces of the clay structural plates adjacent the interlayers to form a coating which resists repla~~ement of sodium cations.
The liner can be polyacrylate.
The liner can be al:kylammonium trimethyl alkylammonium.
The liner can be mixed with the clay as a monomer or in the polymer form and in the first case can polymerise within the clay.
The invention includes a smectite clay made by the method aforesaid.
The invention also provides a smectite clay having interlayers provided with an organic liner preventing replacement of sodium cations and capable of absorbing water and swelling.
A further problem of smectite clay when used as a waterproofing material, is that its function is very dependent on the amount of montmorillonite used. For example when a body of a montmorillonite is c:onstr~ained between two surfaces, such as the concrete of a structure and the ground, when contacted by water AMENDED SI-I~ET
IPEAIEP

it swells and forms the aforesaid high pressure layer which prevents ingress ~of water to the structure and therefore effectively waterproofs it. To increase the waterproofing efficiency of the clay body, larger quantities of montmorillonite can be used. However, higher quantities of montmorillonite mean thicker sheets of materia:L which are more difficult to handle and which are heavier have more transportation costs and are bulky.
In sheets which consists principally of particulate montmorillonite there can be significant difficulty in getting a large quantity into a small area. Sheet material used for waterproofing in ground situation or for roofs, walls and the like tend to have relatively low densities. This is because they are generally made from particulate montmorillonite adhered to a supporting sheet as of plastics material or textile material and secured thereto by a variety of means ranging from adhesive to needling to sewing or by embedment in a mesh of fibres.
The invention provides a smectite clay waterproofing material having a density greater than 1000 kg. m3.
The waterproofing material can be a sheet at least a metre wide and desirably up to four metres wide or more.
AME:NDE=C) SHEET
I PE~~EP

2~ X32.97 The invention further provides a waterproofing material including smectite clay in combination with an organic material forming a liner on its interlayers and having a density greater than 1000 kg m 3 .
The material can be formed by rolling, extrusion or the like.
Desirably the material is extruded.
The invention additionally provides a method of forming a SLIC
wherein alcohol is used to facilitate introduction of the liner into the smectite interlayer and to remove excess liner.
The alcohol can be methy7L alcohol, ethyl alcohol or any higher fluid alcohol.
The invention also provides a method of forming a SLIC including exposing the forming complex to suction to remove gas whilst the reaction is proceeding.
The gas will usual:Ly be air but may be air together with by-product gas from the reacaion.
Desirably the degassed material is subsequently subjected to AMENDED SHEEN _ IPEi~IEP

WO 94/05863 PCT/GB93/0180? -2~ 43297 pressure.
The invention also provides a method of forming a SLIC including exposing the forming complex to pressure during reaction to increase the density of the product.
Desirably the pre=sure .is used after a suction treatment which has removed exces~c air and possible other gases. The pressure step can, therefore, reduce the number of voids in the product as well as urging the molecules of the product closer together to enhance the reaction to produce a denser product.
Desirably the density of the product is greater than 1000 kilogrammes per cubic ne~tre.
The pressure can be applied by extrusion or by passing the forming material through rollers, or by any other convenient means.
We have also found that the temperature at which the reaction between the smectite and the liner takes place is important. The invention therefore, further provides a method of forming a SLIC
wherein the reaction is ~~onstrained to proceed at such a rate as to ensure that the temperature of the. forming product varies between 15 and 30°C. De~~irably the temperature is maintained in a range from 20 tc 25°C.

Where the product i.s subjected to pressure as aforesaid it is desirable that the pressure is applied 'when the temperature is within the ranges aforesaid.
A further disadvantage of existing smectite-based waterproofing materials is that upon exposure to water they tend to swell (this is the very factor which gives them their waterproofing properties in that they produce an area of such high pressure that additional water cannot penetrate). However, the pressures can tend to be very high and, therefore a very significant overlay of either a, heavy earth layer (for example one to two metres) or up to 3" or more of concrete are necessary in order that the expansion pressure of the smectite cannot cause movement or displacement of .any structure.
Accordingly the invention provides, as a further feature a SLIC
having a significantly reduced expansion pressure compared with known smectite based waterproofing material.
The expansion pres:~ure c.an be as low as lOmm of concrete as carried out in the test later defined herein.
As a further feature the invention provides a barrier against aggressive ionic fluid, the barrier being in the form of a constrained layer of: a SLI:C, wherein interlayers of the smectite have been treated with said liner to form the complex, the AfUIEND~=D SHEET _ I PE;AlEP

...

interlayer being capable of absorbing water to swell the complex to a barrier pressure and said liner preventing ion exchange between said fluid and the smectite.
The fluid will normally be aqueous and can be highly ionised fluid such as leachate or fluid containing fertilizer and the like. However, thEa barrier can be equally effective against organic fluids or :Fluids containing organic material, as the smectite interlayers remain proof against ion exchange with such fluid. Further, :~t is desirable that the liner be inert in order that its possiblity of reaction with materials in the fluid is reduced.
The layer needs to be constrained in order that the barrier pressure can be achieved. THe constraint can be a back-fill or overlay of earth or other material or in solid structure an adjacent or surrounding area of concrete or the like can be used.
A further problem with known smectite based waterproofing materials is that it. has been very difficult to secure them to surfaces to be waterproofed. Whilst a flat or gradually sloping surface can be easiuy waterproofed simply by laying a sheet of the smectite material thereon. When vertical surfaces (such as adjacent edges of concrete panels) are to be waterproofed it has been necessary somehow to.attach a smectite based strip thereto.
Existing methods used have included the provision of rebates into - ~; -which strips of seal material can be pushed and the use of clips or nails. Although nails can be used they tend to be frowned upon as they pierce a waterproof layer and they can introduce metal ions into the surrounding water which may have a detrimental effect. Because oflthe generally incohesive nature of clays and their friability, adhesives have not been very effective. Some heavy soaking adhesives have been used, particularly the type of adhesive used in the adherence of smectite particles vo sheets. However these adhesives have a great tendency to inhibit the swelling properties of the clay and to react adversely.
Accordingly the invE:ntion provides a method of securing a seal material to a surface wherein the seal material is a SLIC, comprising use of an adheaive compatible to the liner to cause adhesion.
Where the liner is a polyacrylate the adhesive can be a cyano acrylate adhesive.
Because molecules of the liner extend outwardly from the particles of smectit:e they form a very convenient anchor which can become attached to glue molecules. Because they themselves are securely anchored within the interlayer they form adhesion between the entire complex and the structure to which the complex is to be adhered.

Desirably the adhesive used is an ephemeral adhesive which will hold the seal material for a sufficient period of time to allow it to be installed and for further structure to be formed adjacent, but will soon degrade to allow water entry so as to avoid the provision of any adhesive film or layer which might allow water seepage past the seal.
The invention further provides a method of making a fluid barrier including forming blocks of a high density SLIC and arranging said blocks in a layer.
The layer can be a wall, a floor or a roof. The blocks can be bonded as bricks.
A bentonite containing paste can be used as a lute. The paste can contain a SLIC.
The invention will be described further, by way of example, with reference to the accompanying drawings wherein;
Figures 1 and 2 are cross sectional view illustrating overlap joints in the prior art and their disadvantages;
Figure 3 is a cross sectional view illustrating a preferred waterproofing material of the invention;

WO 94/05863 PCT/GB93/0180i ~ c, Figure 4 is an en:Larged cross sectional view illustrating a surface of a preferred material of the invention;
Figure 5 is a schematic view illustrating the apparatus of the invention suitable for carrying out a preferred method of the invention;
Figure 6 is a plan view of part of the apparatus of figure 5 and illustrating two possible variations;
Figure 7 is a view similar to figure 3 but illustrating a modified material of the :invention;
Figure 8 is a view similar to figure 7 but illustrating a still further modified mat:erial;;
Figure 9 is a view comparable to figure 1, but illustrating an overlap join made using the material of the present invention;
Figure 10 is an enlarged view of the portion ringed at numeral in figure 9.
Figure 11 is a basic t:wo dimensional sketch illustrating structure of montmorilloni.te;
Figure 12 is a chemical formula illustrating the structure of an acrylate useable in the invention;
Figure 13 is an enlarged view illustrating the structure of montmorillonite;
Figure 14 is attempted three dimensional representation of montmorillonite after acylation;
Figure 15 is a view similar to figure 14 but illustrating the addition of doping elements; and Figure 16 is a view similar to figure 15 but illustrating the microscopic effects of the acrylation.
The preferred waterproofing material (10) of the invention is a laminate consisting of: a core layer (11) containing montmorillonite. The core layer (11) is united with a support sheet (12) and is desiraibly but not essentially overlaid by a cover sheet (13).
The essentials of the material (10) of the invention will probably be best apparent from a detailed description of the way it is made and the a.pparat:us (of the invention) which is used to make it.
Referring, therefore, to figure 5 it will be seen that a AME=NDED SHEET
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N'O 94/05863 PCT/GB93/0180~
21 ~4329~ _ ~1 -preferred apparatus. (14) of the invention comprises a conveyor (15) having an upper run (16) and a lower run (17) entrained about end rollers ( 7_8 ) and ( 19 ) . The upper run ( 16 ) travels from left to right in f figure 5~ .
At the upstream end of run (16) a support sheet (20) is fed from a supply roll (21) by a guide roll (22) so as to run on and in synchronism with the conveyor (16).
The support sheet (20) is a sheet of woven or non-woven textile material (preferably woven) which is relatively loose weave, being quite porous .in a direction transverse to its plane.
The web forming the support sheet can be made of any geotextile material which is suitab7Le for disposal within the ground for long periods. Typical materials for weaving or forming the fabric of the sheet (20) can be polypropylene, polyesters including nylon, and many other plastics materials alone or in blends. The materi~sl should be sufficiently strong to support the composite laminate to be formed and can be similar to many of the facing sheets u:~ed in relation to the prior known materials discussed in the introduction hereto. Polypropylene and cotton mixers can a:Lso be used. A typical support and/or cover sheet can be of a print weave and of a weight 700g per sq.metre.
Downstream of the supply roll is a hopper mixer (23) in which particulate montmorillonite can be supplied as indicated by the arrow (24) . The particulate montmorillonite can be supplied from a mill or like supply and in the preferred embodiment is of 200 mesh. Finer mesh c:~n be used although great advantages are not obtained. Meshes u~> to 50 mesh can be used, but at sizes greater then 100 mesh, union between the montmorillonite particles is less effective.
The process which takes place in the hopper mixer (23) can be either a continuous or a batch process. Within the hopper mixer (23) a measured quantity of montmorillonite is mixed with a measured quantity of lic;uid to produce a fluent mass. The liquid can be supplied from a tank or comparable supply (25) and when mixed with the montmorillonite will form a shapable mass.
The liquid used can include an organic liquid such as glycerine, diesel oil or comparable .oils or mixes thereof. For economy and for ease of handling and simplicity the liquid is usually primarily water. In the preferred embodiment of method of the invention water is mixed with the montmorillonite there being approximately from :LO to 30% water, desirably about 15 to 200.
Alternatively the liquid can include a proportion of alcohol.
Methyl, ethyl or propyl. alcohol can be used. Methyl is preferred. An alcohol water mixture needs less drying power than water alone. Some alcohol can be reclaimed and reused.
AN1ENDE;D SHEET
~. . tP.~ ~IEP .~.

2143297 .

The liquid for the mixture is, in the preferred embodiment, as mentioned, pure wager. however, where the final product is to have special qualities the chemicals of those special qualities can be included in the mixture of water.
In making a typical_ product in accordance with the invention 5 killogrammes of montmorillonite were mixed with 0.446 killogrammes of sodium ca:rboxymethyl cellulose (CMC), 2.5 litres of methanol and 1.8 litres of water. Both the CMC and the methanol make the mixed <~nd kneaded product more flexible and extrudable. The more water that is used the more heat is required to drive it out. This means added expense.
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Although the above particular mixtures have proved suitable many variations can be made.
The material desirably contains a bulking agent, an anti fungicidal preserving agent, to prevent growth of mould in or on the material and desirably a lubricant to assist in the extrusion process and convey also a degree of flexibility to the plastic mass. CMC is a very desirable substance in that it provides all these properties. It has anti fungicidal properties, it is a lubricant and it makes the product more flexible. It also :has the great advantage that upon contact by water, in use, it dissolves. Those areas of the outer surface of the material wren first contacted by water have the CMC
dissolved out of them leaving micro pores into which more water can penetrate, wash out more CMC and cause rapid expansion of the adjacent montmorillonite. This greatly increases the rate of water transfer into the material. A bulking agent which dissolves in water and aids water ingress to the montmorillonite is very desirable.
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Any convenient liquid alcohol can be used having from 1 to 12 carbon atoms. Above the 12 alcohols tend to be too viscose for use but below that number any convenient alcohol can be used. It is expected, however, th<~t methyl alcohol will be used because of its cheapness anal easy availability. The CMC can be in the form of sodium carboxy methyl cellulose or any other convenient compound thereof. Protection against bacterial attack is important because i~he bacterial reactions can produce hydro carbons which react with the sodium irons in the clay. This can reduce the swellability of the clay.
As a possible variation a soluble coating can be provided to surround a body o:E matE_rial of the invention. This can be arranged to degrade over a relatively short period of time (such as a week). This would enable block seals and the like to be installed without bE=_coming greasy and unhandlable due to adverse weather conditions, but would not affect the function of material AMENDED SHEET' IPEA/EP

2143.297 to swell in use after a brief period of time.
The montmorillonite used is desirably sodium montmorillonite and but calcium montmorillonite or treated calcium montmorillonite and other smectites can also be used. As shown the materials are first mixed by means of a mixer ( 2'7 ) and then extruded by screws (28) to an extrusian nozzle (29). Where the fluid mass is spread out as a thin layer covering the entire width of the conveyor run (16).
If reinforcement is required within the montmorillonite layer in order that it can be laid on steep slopes without loss of function it can be desirable to incorporate within the plastic mass a reinforcing layer,. This can be done by embedding the reinforcing layer into they mass as it is being extruded or as it is being spread out into a layer. The reinforcing layer can be made in the form of a core having bristles or comparable formations extending outwards which, with the core disposed centrally in the body of montmorillonite extend to the surface thereof and contact. and possibly project through the surface layers. The material of the reinforcement and the surface layers can be made such that the exposed bristles can be heat sealed to contact and be secured to the outer layers. It is envisaged that it would be possible for the montmorillonite mass to be extruded or formed into a pair o~f sheets and the reinforcement feed between them and to have its bristles projecting through each of the two part layers of th.e montmorillonite core and project to the other surfaces thereof nMENDED SHEET
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WO 94/0,863 PCf/GB93/01807 21 4 ;3 2 9 ',7 and be united with the s;upport/cover sheets.
Although the extrusion of a thin layer of the plastic mass containing montmorillonite is desirable, as it can be 3 or more metres wide, it could well be that a three metre wide extrusion nozzle is either e~:pensive, slow, or requires inordinate amounts of power to be successful. Such a extrusion nozzle (29) is shown in figure 5 which also shows an alternative which will be described later.
It is expected that the mass will be extruded as a rod and rolled flat.
Downstream of noz::le (29) the layer (30) of montmorillonite containing plastic mass is levelled and formed into a uniform uninterrupted layer. This can be achieved by means of an initial doctor blade (31) or more likely, a roller, and subsequent sizing rollers (32) to (3.~). The pairs of sizing rolls (32) (33) (34) can effect kneading and levelling of the fluid material and subsequent size thickness reductions.
Figure 6 shows one of the rollers and shows the plastics material extruded outwards beyond the edge of the conveyor and being removed by trimming knives (36).
At one of the sets of rollers (32) (33) (34) there is fed a web of cover sheet (37), from a supply roll (38). Of course, if roll 21 4 ;3 2 9 '7 (31) or (32) and (3:3) are needed to effect creation of a uniform flat layer of the montmo:rillonite containing mass, application of the cover sheet can be left until roll (34). However, this is not desirable as rollers ( 3 2 ) and ( 3 3 ) are best protected from the plastic montmorilloni.te layer by the cover sheet (38).
The liquid which convert: the powdered montmorillonite into a plastic fluent mass will need some degree of treatment, for example by evaporation, drying or partial chemical change so as to ensure that the final material can not deform further in use or in storage. This can be effected by means of a treatment facility indicated by the reference numeral (39).
When the mixture substance is essentially water or an evaporable liquid the treatment facility (39) will be in the form of an oven and will reduce the solvent water content of the montmorillonite containing layer from 20% down to 5% or less. The treatment facility can be in the form of an oven casing (40) to which hot air is supplied at an inlet (41) and leaves via outlet (42).
After leaving the treatment facility (39) the laminate (40) can be allowed to cool and then be fed to a store roll (44). A knife or the like can be provided for cutting the laminate as it leaves the oven when roll (44) i.s full.
As discussed previously i.n relation to the extrusion of the AMENDED SI-IEE~
I P E_A/E P

product, the consistency of the plastic/fluent mass containing montmorillonite can vary widely from almost a liquid condition to a stiff paste. Idhen water is used, the stiffer the paste the better as water has to be: expelled by passage through the oven.
Again, in the case of organic or organic-containing mixture substances the stiffer the material the less later treatment is necessary to render the final laminate stable and non-deformable during transportation and storage and use. This process will usually involve evaporation comparable to oven drying or a chemical treatment.
As has previously been mentioned the use of a very wide extrusion nozzle (29) may not: be practical in view of the power required for such a device. Instead, as illustrated in figure 6 a smaller extrusion or fluid delivery nozzle (45) can be used which can be mounted so as to ps:rform a generally sinuous path transversely of the direction o:E travel of the run (17) of the belt (15).
Thus, the nozzle (~E5) can follow a path indicated by the line (46). By altering the speed of travel of the nozzle and/or the rate of delivery of the i=luent material it can be assured that sufficient material is applied to the belt to allow a layer of desired thickness to be i:ormed throughout the area of the belt without voids, cracks or the like which would be most undesirable. To this end it is advantageous if the material can be applied to some significant excess and after having been formed into a uniform coherent layer excess material extruded A,Mtt~DED SHEET
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sideways is removed by means of the trimming knives or the like (36). Of course, such material can be reclaimed and re-used.
It has been mentioned treat the support sheet and/or the cover sheet can be of woven or non-woven material. Woven material is preferred as it gives significant strength with lesser weight of material. A non-woven material might have advantage, however, in that it can form a physical union with the montmorillonite containing core ( 11 ) . The term core ( 11 ) is used even though the cover sheet (13) may not be provided.
As best seen in figures ~6 and 10 the action of the rollers (32) (33) and (34) is to cause the support/cover sheets (12) (13) to be partially embedded in surface zones of the plastic mass of material forming the core (11) whilst the core is in a plastic state. There is no need for any adhesive, which is an expensive and unreliable component"
As the core is treated in the facility (39) either by evaporation or chemically so as to cause the core to harden there is a physical locking of the aurface portions of the core (11) with portions of the fabrics (12) (13) physically uniting them to the surface without the: need for adhesive.
This has two important consequences.
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Firstly, because a good portion of the sheets (12) and (13) are embedded within the material of the core, only a small portion of the body of the :Fabric is exposed above the surface. Thus, in use that fabric surface will be in contact either with anchoring overburden (at least 150mm of overlying material is recommended to protect such layers) the underlying earth. The overburden or the earth penetrates the fabric quite easily ( it is a very open fabric and after there is intimate contact between the overburden and the underlying earth). This again has two important consequences. Firstly, once the support layer (12) (which will normally be in contact with underlying earth) is intimately contacted by the .earth, ground water enters, contacts the montmorillonite and. causEa swelling which creates a seal.
It is a further advantages that because of the intimate contact of the underlying soil or the overburden with the montmorillonite through the support and over sheets (12), (13) there is no possibility that eiither the cover sheet ( 12 ) or the support sheet can allow any venting of gas laterally though the fabric.
The second advantage of this is illustrated in figures 9 and 10 which are comparable to figures 1 and 2, but relate to the present invention. In figure 9 a first piece (47) of the material of the invention is shown overlapping a lower piece (48), both lying on the ground (49). The overlap cover sheet (50) of the second sheet (48) is in contact with the support sheet (51) on the piece (47). As illustrated in figure 10 the AMENDED SHEET' IPEA/EP

sheets (50) and (51) are in intimate contact and they are significantly penetrated by montmorillonite from the respective cores of the two panels. Upon entry of water in the direction of arrow (52) or (53) the montmorillonite in one or each of the cores can swell and expand into the unfilled portions of the fabrics (50) (51) and forming effectively a continuous layer of expanded montmorillonite uniting the two cores and providing a completely water tight seal.
As mentioned earlier, thE~ invention includes the waterproofing material itself, the method of and apparatus for producing it and a method of waterproofing a structure including the steps of placing sheets material. of the invention in overlapping relationship and placing overburden to protect the sheets against damage in use.
The invention is not limited to the precise details of the foregoing and variations can be made thereto.
A further disadvantage of existing methods of waterproofing large sites such as pond filled sites, ponds, lagoons and the like is that the material has to be made in bulk in a factory and then transportation to the site. The material is manufactured in as wide a width as possible consistent with manufacturing problems and transpiration. In a similar manner the length of the load which can be transported is strictly limited. The material may be A~~IENDE=D SHEET
E~EA/EP

tfr from a minimum of 4 up to 10 or 20mm or more in thickness , the length of roll which can be transported is not very high. On large sites the eli.minat_Lon of large amounts of joints and the elimination of road transportation can mean significant cost savings.
The apparatus of th.e invEantion can be divided into a number of mobile units, for Example the main conveyor, the mixing hopper and the drying could forrr~ three separate unit loads.
As is mentioned earlier, the invention envisages the use of a material comprising expandable montmorillonite clay on a flat or slightly slopping roof as the whole or a significant part of the water proofing component 'thereof. The material of the invention is particularly suitable for this purpose as it can be laid on relatively higher slopes than previously known montmorillonite sheets without them being very expensive. Thus, in the case of a roof which has upstands the montmorillonite sheet of the present invention can be laid to extend not only over the flat surface but also over the upstands to form a water proof layer.
The montmorillonite core will normally be overlaid by several cm of gravel or like material providing a bearing layer protecting the montmorill.onite beneath. The montmorillonite used will, desirably, be of thc~ sort which can be allowed to dry out and be rewetted repeatedly as this will often happen to a roof structure.
~~M~NC)ED SI~E~T
IPE~IEi~

--: 2143297 As mentioned earlier the invention envisages the use of montmorillonite expandable clay as sealant in pipes and other plumbing. The mont:morillonite material can be in the form of rings, annular strips or sheets and incorporated in underground drainage or supply pipes" domestic plastics or metal pipes and comparable plumbing installations. The cheapness of the montmorillonite means that they are ready and cheap substitute for rubber or plastic sealing rings and are cheap enough to be replaced when ever the joint needs to be opened or replaced.
In this case the use of an alcohol or a comparable liquid is advantageous because the oven stages do not have to be as long and as powerful as is necEasary in the case of driving water from the plastic mass.
When carrying the invention into effect using a SLIC, polyacrylate can be used as the liner. In a specific example a quantity of untreated sodium montmorillonite and approximately 10% by weight of a polyac:rylate of the formula shown in figure 12, from 2% to 7% of a sodium carboxymethyl cellulose (CMC), 14%
of methanol and 5% of glycerol were intimately mixed together.
Kneading and mixing were continued until the mixture reached a suitable consistency for extrusion. This can take longer than would normally be necessary for simple mixing as the chemical reaction between the acrylate and the structural plates of the clay takes some time' to occur. The heat emitted by such reaction is an ~°~MENDED SHEET
i PE=,,4/EP -~~?~'O 94/05863 PC1~/GB93/0180 i important factor in bringing the forming smectite acrylic complex to a suitable consistency and structure.
Once this has occurred (Its occurrence can be tested by initial trial extrusions. The products of such extrusions, if unacceptable can be returned for recycling) the mixture is passed to an extruder where it is driven towards an extrusion screw, and subjected to a suction stage to remove significantly all entrained gas from it be:Eore being extruded in the form of a rope, profile or sheaet as desired.
The montmorillonite used i.n the process is finely ground and has the structural formula and shape shown in figures 1 and 3, the cations in the interlayer being essentially sodium cations.
During the reaction the clay becomes acrylated and the long organic chains of po:lyacrylate penetrate into the interlayers and displace water. At the ?article surfaces, polyacrylate bonds 'with strong hydrogen bonds to the free unsatisfied OH groups.
'this effectively shields the sodium cations, thus greatly resisting their replacement by calcium c:ations in contaminated ~~round water.
On the microscopic scale (which is illustrated very schematically in figure 6) a parti~~le of clay consists of a plurality of small ;structural plates between which the helical acrylate molecules _YE_ are disposed. The surfaces of the helical acrylate molecules are bonded to the tetrahedra within the faces of the structure plates opposite the interlayers and project beyond the edges of the particle. This projection of the acrylate molecules beyond the surface of the particle has a significant effect in the abortion of water by the clay. Thus although the acrylate does, to some extent mask the electro-chemical water absorbing properties of the clay by effectively neutralising the sodium cations in the interlayer the extending helical polyacrylate molecules extending outwardly from the particles have a surface tension effect which draws water towards the particles and causes it to enter into the interlayers by capillary action thus causing a swelling of the particle which is comparable to the electro-chemical swelling which previously occurred but which is not dependent on the presence of cations within the interlayers.
This has the important effect that any cations which enter within the inter layer can not replace sodium cations and thus do not reduce the capacity of the clay to expand, shrink and re-expand after drying out.
Instead of carrying out the method of the invention using acrylate other materials can be used. For example sugars such as fructose, glucose, dextrose can be used. All act in very similar way to the acrylic molecule and have comparable and similar effects. The use of sugar may, however, be undesirable in some circumstanc:es in view of its encouragement of microbial growth. Of cour:~e, there may well be advantages in this particular property in certain situations.
A further alternative liner material is alkylammonium trimethyl alkyl ammonium whit:h can be used in the manner very similar to the polyacrylic compound to give a similar complex with similar properties.
Turning now to the second aspect of the invention reference is again made to our prior application 9218178.3 and to the aforegoing description. In making a smectite clay water proofing material :in accordance with the second aspect of the invention the method aforEasaid is carried out with or without the acrylic material. In the preferred method of this invention sodium montmorillonite powder was mixed with polyacrylate, glycerol and methanol. 7~he mass was mixed together for some fifteen minutes and then extruded through a 25mm square orifice at a rate of about 0.5 metres per second to produce a rope like concrete sealing strip having a density of about 1350 kg m m3.
The actual density can b~e varied by varying the proportion of materials in the complex.
~~MENC1ED SE-iEET
IPiEA/EP

2143!97 Of course, the waterproofing material can be made without using the liner such as polyacrylate. In addition it is possible to use CMC either in addition to the acrylate or as a substitute therefore. The CMC can be useful in varying the reaction rate of the clay but it also has a property of forming, on the surface of the extruded material a layer which improves the life of the sealing material by resi~;ting degradation and swelling by rain over a first few hours ar days.
In testing the smect:ite organic complex of the present invention a layer of conventional particulate smectite clay waterproofing sheet was laid on the ground and contacted with typical water high in ionic leaching chE_micals. After six hours the bentonite layer had absorbed 'the liquid and had swelled to form a uniform water retaining layer.
A complex according to the invention was similarly treated and had, within six hours reached precisely the same condition.
The two sheets were' then allowed to dry. In the complex clay sheet according to the invention the sheet reduced in thickness to its original thickness with no significant cracking. In the untreated prior art clay particulate layer sheet there was significant cracking and large gaps appeared in the material.
Both sheets where then rewetted (whether pure water or contaminated leachate water was used made no difference). The AME~~~E~ SHEE1"
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prior art material, wherein clearly sodium montmorillonite had been converted to calcium montmorillonite there was no significant re-swelling. The cracks remained and water was able to penetrate through tho~~e cracks even after prolonged soaking with water as would happen in an underground situation. The prior art material was no longer waterproof and did not itself form a waterproof layer by expansion.
On the contrary, however, the complex montmorillonite clay of the present invention formed a uniform waterproofing layer.
In the past it has been possible to adhere particles of bentonite to sheets to form cohesive layers, but rather large quantities of adhesive have been necessary and the bonds which may form with the bentonite have nat been particularly strong.
With a liner material incorporated within the actual structure of the clay itself very :strong adhesive bonds can, it has been found, be made between bodies of the smectite complex and structures such as concrete walls, roofs and the like. To obtain such a bond it is only necessary to formulate an adhesive which is suitable for attachment to the liner molecules which protrude from the surface of the c7Lay particles or the clay body if it has been extruded or otherwise formed into a sheet rod or the like.
AMENDED SHEET
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'N'O 94/OS863 PCT/GB93/0180 In the case of the acrylate smectite complexed clay a cyano-acrylic adhesive ca:n be formulated which can adhere the smectite complex clay body t:o concrete and the like and which can allow the body to expand and contract as it is wetted, dried and re-wetted over many cycles.
Further possibilities include the adhesion of a sheet of the clay, either as a cohesive body formed by extrusion or otherwise or in a particular manner to a supporting sheet, for example of high density polyethylene:, a geotextile or the like by means of adhesive, needle punching or the like.
Adhesive and/or stitching or penetration by polymer spikes weldable to a sheet on the other side of the clay can be used to form a stable slope engaging material.
As well as montmorillonit.e, saponite and other smectites can be used.
In carrying out a further' preferred process a batch of about 60 kilogrammes was prepared, the figures given in the following being percentage figures for the various components.
Firstly, 25% water was added to a mixer, followed by 16% sodium polyacrylate. To these w<is added 5 % methyl alcohol . When these N'O 94/OS863 PCT/GB93/0180-three had been mixed half of the total bentonite load of 63o was added. Once the mixture had become smooth to carboxy methyl cellulos (CMC) and a small (about 0.1%) of sodium hexametaphosphate was added. Both these materials were added slowly and after thE~y had been added the mixture was stirred for some while. Thereafter the other half of the bentonite was added, the mixture kneaded for a short time and then passed to an extrusion machine wherein it was first driven towards a perforated plate whence it emerged in vermicelli-like form into a vacuum chamber. In the vacuum chamber air and any other gases such as reaction products. and probably some evaporated alcohol are extracted.
The material then falls to the base of the vacuum chamber and is engaged by the rollers of the extrusion machine and driven towards a 25mm squat-a extrusion head having 3mm radius corners.
The forming camplex (intercalation commences in the mixer and is still continuing as extrusion takes place) has a smooth outer surface and is a coherent flexible and useful seal material for use at the junction between the structural components such as concrete slabs, pan<=_ls and where service conduits pass through foundations and the like.
The percentages of l.he various materials used can be varied as follows:-W'O 94/0,863 PCT/GB93/0180-- _J .; -ITEM PERCENTAGE RANGE

Water 15 ~- 2 5 Sodium Polyacrylate 8 - 16 (Methyl) Alcohol 0 - 5 Wyoming Bentonite ~ ~0 - %5 Carboxy Methyl Cellulose 0 - 3 Sodium Hexameta Phosphate 0 - 0.5 The alcohol used can be methyl alcohol, ethyl alcohol or any other liquid alcohol and serves to facilitate introduction of the liner into the smectite interlayers. Further, some of the alcohol is, during the heating stage, (the heating is due to the heat of the reaction which begins to effect the material towards the end of the reaction period) is expelled and carries with it VVO 94/0,863 PCT/GB93/0180;

_ ?; _ excess polyacrylate which can be deposited on the outside of the , extruded strip as a shiny layer. This layer may serve as lubricant as the atrip passes through the die and helps to produce a smooth continuous surface. In addition this deposited acrylate also form=_. a coating for the material which delays the onset of severe water briefly and helps in allowing the material to be installed and perhaps wetted or exposed to the atmosphere before additional material is applied to the surround.
The function of the pressure during extrusion is to increase the density of the product by eliminating voids which might otherwise form within a less than coherent mass. This, together with the vacuum step which h.as removed air has the effect of compressing the material to a high density. This moves the molecules slightly closer together during extrusion thus increasing the rate of reaction and encouraging the formation of the complex from the intercalated po:Lyacrylate liner.
Desirably the density is greater than 1, 000 kilogrammes per metre cube and a preferred density is over 1, 3000 kilogrammes per metre cubic.
The process described above produces a sealing strip very suitable for use in concrete foundations and the like and also in plumbing applications in the sealing ef pipes and comparable fittings. The material can be extruded in many shapes for example square, strip, triangular or in any other convenient form. By rolling or extrusion the material can be formed into sheets which can be used to form an ideal barrier against aggressive ionised fluid~~. Such ionised fluid will usually be leachate from planter or sites or may be atmospheric water or ground water contacting the capping of a landfill site. It has been found that fertili:aer and other materials which may be applied to foliage .above a landfill site forms a highly ionised material as aggressive a~~ any leachate and which can seriously damage conventional bentonite liners and capping.
The material made in accordance with the invention above, however, has the acrylate or other liner so securely attached to the bentonite interl.ayers that the cation exchange capacity (CEC) of the material is nil or very low. This means that there is no possiblity of the s:mectite turning to a calcium form which will not reswell after drying out. Further, as the liner is preferably a plastic material the inherently stable nature of a polymeric plastics material makes the possiblity of it being attacked by leachate or strong solutions quite remote.
Instead of being extruded as a strip the material of the invention can be formed into bricks, either on a block making machine into which. portions of the forming complex can be introduced and compressed. to shape, or a generally rectangular AMENIDED SHEC~' IF'E~JEP

21 4 ;3 2 9 '7 strip can be extruded and cut as by travelling knives to form blocks. The blocks can be used then to form a barrier by building in the nature oi= a wall, or by laying them on a floor, or lying them on some support to form a roof for a containment area. The blocks can b~e bonded as conventional bricks and a bentonite containir.:g or other paste can be used as a lute in the joints. Desirably a SLIC, paste is used as the lute. In a wall a cavity layer can :be provided and individually drained in order to allow testing of the integrity of a "front line" layer of the wall and provide an air gap to prevent transfer of water from one wall to the other k>y direact contact.
A further advantage: of the material of the invention resides in the fact that by appropriate selection of the liner the susceptibility of the material to adherence can be greatly increased. It is often useful to be able to attach a sealing strip to a, for ex<~mple, vertical surface. This can be at the junction of various concrete components, between concrete panels or the like. In the past this has involved the provision of a recess into which the strip must be pushed (and the recess accordingly rather carefully dimensioned to receive the strip as a push fit) or the strip must be clipped or nailed in position.
Whilst the clipping and nailing are effective methods of securing the strip they can be expensive and the provision of nails in the sealing strip is ge~.neral7Ly felt to be undesirable as they might form a path for leal~:age, or they might introduce metal atoms into ~~MENC)ED SH~~='F' IPIE~t/EP

water surrounding them with the possiblity of reducing the waterproofing qualities of the smectite.
Therefore, by selecting the liner to be compatible with a convenient adhesive it is possible for a layer of adhesive to be made which will secure a strip of the material of the invention to, for example, a vertical surface. In the case of a polyacrylate inter7_iner, the ends of the acrylate molecules protruding from thEa various particles of smectite form ideal sites for forming an adhesive bond with glue such as cyano acrylate adhesive 'to give a bond to concrete and comparable surfaces.
The bonding can be by means of spaced portions of the adhesive spotted at intervals along the line to which the strip is to be attached. Desirab7_y, the adhesive used is designed to be an adhesive which will hold the strip securely over a maximum period of perhaps three or six days in order to allow the user to carry out all processes in relation to the installation of the seal and the creation of other structures nearby. However, it is important that the adhesive thereafter degrades in order to prevent the possiblity of a waterproof adhesive film remaining which might provide. a water path which could by-pass the seal strip.
As mentioned the material can be extruded as a strip profile or as a wide sheet. When producing a wide sheet it is desirable to AMENDED SHE'S-~1°
IPEA,~EP

21432'97 ~ .. r . _ extrude the material in the form of a hollow formation and then split that hollow formation to form a sheet. Desirably the material is extruded in t:he form of a hollow cylinder and then slit and laid flat.
Many other variations are possible within the scope of the invention.
AMIENDEI) SHEE r, .~.r _ . .._..~P.EA/F~P.. ..._~_~ . _ ._. _. ._ _ . _. _

Claims (18)

Claims

1. A waterproofing material which is formed by extrusion under vacuum from a substantially homogenous deformable mass consisting of a mixture of particulate smectite clay and a liquid, in which respect the clay is in a range from 50% to 75% by weight of the mixture and the liquid comprises water in a range from 10% to 30% by weight of the mixture.

2. A waterproofing material which is formed by extrusion under vacuum from a substantially homogeneous deformable mass consisting of a mixture of particulate smectite clay and a liquid, in which respect the clay is in a range from 50% to 75% by weight of the mixture and the liquid comprises water and an organic material in a range from 10% to 30% by weight of the mixture.

3. A waterproofing material as claimed in any one of claim 1 and 2 wherein said liquid in said mixture comprises an alcohol having 1-12 carbon atoms.

4. A material as claimed in claim 3, wherein said alcohol is selected from the group consisting of methanol; ethanol; and propanol.

5. A material as claimed in any preceding claim, wherein said liquid in said mixture also contains acrylate or polyacrylate.

6. A material as claimed in any one of claims 1-5 preceding claim wherein said liquid in said mixture also contains glycerol.

7. A laminate material as claimed in any one of claims 1-6, wherein said liquid in said mixture also contains a carboxmethyl cellulose (CMC) compound.

8. A waterproofing material as claimed in any one of claims 1-7 which is extruded in sheet form and united with a flexible porous carrier sheet.

9. A material as claimed in claim 8 wherein said waterproofing sheet is sandwiched between said carrier sheet and a cover sheet.

10. A material as claimed in any one of claims 8-9 wherein reinforcement is provided in said waterproofing sheet.

11. A material as claimed in claim 10 wherein said reinforcement is secured to at least one of said carrier sheet and said cover sheet.

12. A material as claimed in any one of claims 1-11 which has a density greater than 1000kg m-3.

13. A waterproofing material as claimed in any one of claims 8 - 11 wherein said waterproofing sheet is less than 1cm thick.

14. A waterproofing material as claimed in claim 1 wherein said waterproofing sheet is between 1m and 4m wide.

15. A method of making a waterproofing material comprising the steps of mixing a particulate smectite clay in a range from 50% to 75% by weight and liquid, including water, in a range 10% to 300, kneading said mixture in a mixer to form a substantially homogeneous deformable mass and forming said mass by extrusion under vacuum into a waterproofing material.

16. A method of making a waterproofing material as claimed in claim 15 wherein said mass is extruded to sheet form and united with a flexible, porous, carrier sheet.

17. A method as claimed in claim 16 which comprises treating said waterproofing sheet united with said carrier sheet to cause said waterproofing sheet to lose a degree of plasticity.

18. A method as claimed in any one of claims 15 - 17 which comprises treating said waterproofing material to a drying step by passing said material through an oven to remove liquid by evaporation.