Note: Descriptions are shown in the official language in which they were submitted.
~'~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
2143297
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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-
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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
WO 94/05863 PCT/GB93/01807
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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
WO 94/05863 PCT/GB93/01807
2143297
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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
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21 43297
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
WO 94/0863 PCT/GB93/01807
2143297
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''
2143297
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
2143297 - 13 -
"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.
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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
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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
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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.
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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.
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2143297
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.
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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.
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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.
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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
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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.
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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
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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.
2143297
- 25 -
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
WO 94/0863 PCT/GB93/01807
...
21 43297
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
ENO 94/05863 PCT/GB93/0180
2143297
- ~; -
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.
WO 94/0863 PCT/GB93/01807
2143297
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
2143297
~ 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
- 30 -
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
IPEA~~EP
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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
2143297
- 32 -
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 .
- 33 -
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.
AMENDED SHEET
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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.
AMENDED SHEEN
IPEAIEP
2143297
- 35 -
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
- 36 -
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
- 38 -
(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
2143297
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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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2143297
- 40 -
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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2143297
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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
2143297
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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
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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
- 44 -
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
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~~?~'O 94/05863 PC1~/GB93/0180 i
2143297
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
WO 94/05863 PCT/GB93/0180
214329
_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
2143297
- 47 -
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
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2143!97
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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
IPEA/EP
'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-
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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-
21 43297
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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;
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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
2143297
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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
- 55 -
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
T 2143297
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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 . _
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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.. ..._~_~ . _ ._. _. ._ _ . _. _
