Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to preformed sheet-like
structures and to methods of making them. The structures
of the invention are particularly, but not exclusively,
useful for application to concrete surfaces.
In the past, concrete surfaces such as flat concrete
roofs have usually been sealed by application of hot
asphalt, a roofing felt with the aid of hot bitumen, or
sheet-like membranes laid with the aid of hot bitumen or
solvent-or emulsion-based adhesives. Such methods suffered
10 from the disadvantages that they require the employment of
skilled men, local heating of the bitumen or the use of
liquid applied materials so that the labour costs are high.
To avoid this difficulty there previously have been
proposed sheet-like structures comprising two layers of
15 bituminous material attached to each other, one layer
being substantially non-adhesive and the other layer being
a pressure-sensitive adhesive, the compositions of each
layer having at least one polymer distributed therein.
In practice, the two layers may differ from one
20 another in the proportions of the polymer in the bituminous
compositions and/or by reason of the use of different
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~ polymers or bituminous substances in them.
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A drawback with the prior proposals is that there is
a tendancy for the oils in the bituminous substances to
migrate from one of the layers to the other, and it has been
founcl that this tendency is increased if the polymers in
the two layers are different and have different affinities
with oils. There is, in fact a need to use such different
polymers as the polymer in what will be the upper layer
must be of a type which offers good weather resistance
while that in the lower layer must be of a type which
10 retains its adhesive properties so that over a long period
of time the structure will remain adhered to any surface
to which it is applied. Eventually, an equilibrium stage
is reached and it can happen that the layer which was
initially non-adhesive becomes adhesive while the layer
15 which was initially adhesive becomes substantially
non-adhesive. In extreme cases, and in particular where
different polymers are employed in the two layers, it can
come about that the two layers actually reverse their
properties. This is, of course, unacceptable, because
20 such a preformed structure cannot be regarded as a
success if the two layers reverse or alter their
properties after it has been installed.
One way in which it might be expectad ~hat this
difficulty could be overcome would be including a preformed
25 ~ilm or foil between the two layers of bituminous material.
When this has been tried, however, the drawback is
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1145109
encountered that delamination of the product tends to occur, for instance due
to different coefficients of expansion, rendering the product useless initially
or after only a short period of use.
According to the present invention there is provided a waterproofing
sheet for waterproofing concrete structures and the like, said waterproofing
sheet being of the type comprised of a preformed, pressure-sensitive-adhesive
sheet laminate of (a) a first layer of polymer-containing bituminous composition
which is pressure-sensitive-adhesive and (b) a second layer of polymer-contain-
ing bituminous composition which is subst~ntially non-adhesive, at least one of
said bituminous compositions containing oil which subsequent to lamination has
the tendency to migrate between the two bituminous compositions (a) and (b),
the improvement which comprises providing an oil barrier layer between the
layers (a) and (b) by applying to a surface of (a) or (b) prior to lamination
a coating of oil-resistant polymer in liquid form whereby intimate contact is
achieved between the layer (a), said oil barrier layer, and the layer (b) to
effect a more improved non-delaminating bond between such layers.
It is preferable, thought not essential, to employ an oil resistant
polymer which presents a tacky surface when it solidifies.
Rather than take the step of providing a preformed film or foil
between the two layers, or to try to modify that step so as to be more success-
ful, an oil resistant coating is used which is in more intimate contact with
1145~09
both layers than could ever be achieved by a preformed further member. The
coating is preferably formed by application of the oil resistant material to
one of the layers, when it is hot, in liquid form so that the coating closely
follows the microscopic contours of the surface of the layer to which it is
applied. The liquid rapidly solidifies and the second layer is applied hot to
the thus formed coating and in turn closely conforms to the microscopic con-
tours of the surface beneath. As a consequence, far greater affinity and mutual
adhesion between the layers and the coating, in effect a non-detachability, is
obtained than can be obtained using a preformed film insert between layers, and
a satisfactory oil barrier is achieved.
By the term "pressure-sensitive-adhesive" we mean in this specifica-
tion a material which, at ambient temperatures and without the application of
heat or a solvent will adhere permanently under normal hand pressure to a con-
crete surface. Clearly, therefore, the pressure-sensitive-adhesive is for
application to a surface to be covered, the non-adhesive surface being suitable
for exposure.
The bituminous compositions of which the two layers of the structure
of the invention are constituted each include at least one bituminous con-
stituent, that is to say one or more of bitumen, asphaltic bitumen, tars and
pitches and their derivatives both natural and synthetic
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and at least one polymer. The polymers may for instance
be natural or synthetic rubber, elastomeric or non-elastomeric,
there being no requirement for the polymers in the two
layers to be the same or for the polymers to be uniformly
distributed within the layers. The compositions of the
layers can differ from one another as to the proportions
of bituminous constituents to polymer, in the bituminous
constituents, in the polymers or by reason of a combination
of two or three of these features. For the adhesive layer,
10 preferably, the bituminous composition is a bitumen-rubber
composition, preferably formed of natural or synthetic
rubber, virg;n or reclaimed, blended into bitumen to provide
a smooth mix. The ratio by weight of bitumen to rubber is
preferably from 70:30 or 80:20 of 95:5, especially about
15 90:10. Alternatively the bitumen can be a blend of-
different bitumen~-containing also, if desired, heavy or
light mineral oils and other plasticisers. Generally,
suitable bitumen compositions have softening points
(measured by the Ring and~Ball method) of 70 to 195C and
20 penetration values of1~300 at 25C (100 g. 5 sec.-Institute
of Petroleum method) the softening point and penetration
value may vary, within these ranges, from one side of the
layer to the other-, or they may be the same throughout
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If desired a-layer of reinforcing material can be
contained within either or both of the layers. The
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ll~n-adh~sive layer of the structure can if desired ~e
provided with an outer coating of a light mineral aggregate
or metallic powder to increase its weathering propertieS.
A protective coating which can be physically removed
without damaging substantially the self-adhesive layer of
the structure can usefully be applied thereto for storage -
and transportation purposes, as the structure will
normally be supplied in roll form. A wide variety of
materials can be used to provide the protective coating.
10 Paper having a release coating therebn, e.g. siliconised
paper or paper having a coating thereon of a suitable
polymer, is satisfactory. Other materials include films
of organic polymers, particularly vinyl chloride polymers.
As stated, the structure is conveniently available in the
15 form of rolls and in use can be unrolled, the protective
coating being simultaneou~ly removed, and laid directly
into place.
In referring to the "non-adhesi~e" layer, we mean that
this layer is substantially non-adhesive at ambient
20 temperatures but it will obviously be adhesive when
sufficiently heated and will be so in the manufacturing
atep. It can comprise any suitable bituminous composition
including a polymer such as are well known to those skilled
in the art~ If de~ired, this non-adhesive layer can be
25 treated to protect it from damage and/or so that it offers
an improved keying surface for other material, e.g. concrete
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or asphalt, subsequently applied thereto,- Thus this face
can be textured or gritted.
In width, the structures can vary for instance from
2.5 to 120 centimetres or more, depending~upon the use to
which they are to be put and generally they are at least 5
centimetreS wide, for instance 15-90 or 100 centimetres
- wide with the larger range of widths being preferred where
a whole surface, for instance a roof, is to be rendered
waterproof. The thickness can also vary depending upon the
10 intended use, but in the adhesive layer will generally be
greater than 0.025 cms in order to ensure good adhe~ion
over a long period of time even if the underlying surface
should move and expand and contractwith age and seasons.
While the thickness can be,as much as 0..6 to 0.9 cms, a
15 maximum thickness of the adhesive layer of 0.4 cms may be
preferable to ensure against slippage, especially if the
structure bears loads.
Among oil resistant materials which can be used for
the coatiny on and between the layers and be applied in
20 liquid form according to the method of the invention there
may be mentioned polyvinyl acetate, polyvinyl alcohol, a
carboxylated-styrene-butàdiene ,polymer, a ,styrene-butadiene
polymer with high styrene content, an aarylonitrile-butadiene
polymer, an acrylonitril'.e-styrene-butadiene polymer, polyurethane,
25 polyvinylchloride, acrylic resins, chlorinated rubber ~ ..
and polymethacrylates but other natural or synthetic
oil ~esist,ant polymers or
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other ~uitable materials which can be applied in liquid
form can alternatively be employed.
In one way of performing the method of the invention,
one of the layers of the composition is firstly prepared
and, while it is hot, the liquid is sprayed thereon. The
heat of the layer quickly solidifies the liquid and
immediately thereafter the second layer, while itself hot
is placed in contact with the thus formed coating on the
first layer. The two layers are thus bound to one another,
10 and each coated most intimately by the coating which is
compatible w~h both layers. An extremely good and even
contact between the coating and the first layer is obtained
by reason of the initial application in the form of a
liquid, and this enhances the coating effect with regard to
15 the second layer. '~ith the coating in place, oil migration
from one layer to the other can be avoided where it might
take place for instance by reason of different oil contents,
or by reason of different polymers in the two layers or both.
The structures are intended for use in providing a
ZO waterproof seal over a surface, particularly a concrete
surface, by applying the adhesive layer to the surface, a
plurality of overlapping structures being used if necessary
in order to form a continuous membrane over the whole surface.
The structure may be left exposed to the weather, or, if
25 desired, after the structure has thus been applied, another
surface, e.g. another mass of concrete, a sand or cement
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screed or other floor finish, a layer of asphalt or a
cladding material, can be placed on the structure or
can be formed in situ.
Exa~ples of suitable materials for the reinforcement
for incorporation within the layers are glass fibre
(woven, mesh, tissue or strand), synthetic polymers
(woven, mesh or strand), expanded or perforated metal
or fabric (woven or non-woven).
The structures can be used on floors and roofs,
10 particularly the flat roofs-of factories or blocks of
flats. They can slo be used on bridge decks where the
structures are applied as indicated above and hot
asphalt is laid on top as a wearing course.
The accompanying drawing is a cut-away perspective
15 view of a structure according to the invention. The
sheet-like structure shown comprises a pressure
sensitive adhesive layer 10 of a bituminous-rubber
composition. Upon the upper face of layer 10 is a
very thin coating of an oil resistant material such as
20 polyvinyl acetate in intimate contact with layer 10.
In intimate contact with coating 11 is an upper layer
o a bituminous composition 12, this being substantially
non-adhesive. In use, the structure which is supplied
in rolls, is laid in adjacent strips on a surface to be
25 protected, such as of concrete, with the lower surface
of layer 10 in contact therewith, normally witXout any~
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preparation save removal of dust from the concrete
although in certain situations use of a primer may,
despite the self adhesive nature of the layer 1~,
be recommended. A release sheet, not shown, is
provided on the lower surface of layer 10 to be
removed prior to installation.
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