Note: Descriptions are shown in the official language in which they were submitted.
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WATERPROOF SHEETING
Backqround of the Invention
Field of the Invention
The present invention relates to a waterproof
sheeting comprising a carrier layer covered with a
bituminous coating on both sides and to a process for the
production of such a sheeting. The invention also
relates to a process of producing a roof covering using
such a sheeting.
Description of Related Art
Waterproof sheeting is used for covering many
different types of buildings, in particular for covering
flat-roofed constructions or underground building
constructions, such as, for example, tunnels and the
like, and as lining membranes for saddleback roofs.
Bituminous waterproof sheeting usually comprises a
carrier material coated with bitumen on both sides.
Oxidized or modified bitumen, the viscosity and elas-
ticity properties of which are modified by admixing
polymeric additives of a plastomeric or elastomeric
nature are generally used for high-quality sheeting.
Materials which are generally used as the carrier
material or bonding inlay for bituminous roof sheeting
are laid-, woven- or fleece-like materials, in particular
non-woven materials of polyester fibers or filaments,
which are bonded in a suitable manner. Non-woven fabrics
are preferred because, compared with woven fabrics, they
have good elastic properties which are not confined to
one direction.
The carrier layer with the bitumen layers applied on
both sides forms a three-layer composite which must meet
certain requirements. On the one hand, the bitumen layer
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must adhere firmly -to the carrier material, since
detached areas can easily become leaky. On the other
hand, the composite must have good mechanical properties,
in particular a good mechanical strength and at the same
time an outstanding elasticity which allows for the
laying over and around parts of the roof to be covered
which are not flat, by the sheeting without problem.
Various carrier materials which have individual
improvements in respect of the desired properties but do
not meet all requirements at the same time have been
proposed in the art.
For example, DE-A-31 45 266 describes a high-strength
elastic roof and waterproof sheeting of at least one
bitumen-impregnated non-woven layer of organic material,
if appropriate at least one further fleece or non-woven
layer of inorganic material and a bitumen coating on both
- - sides, the bitumen being rendered elastic, if
appropriate, by addition of modifiers, for example
plastomers having sufficiently low glass transition
points. This roof and waterproof sheeting has elastic
properties which allow cracks to be bridged even at low
temperatures, so that it can be laid without
complications in a wide temperature range. No cracks or
leaks are said to occur even after long lying times on
problematical objects, for example flat roofs. However,
the adhesion between the bitumen layer and the carrier
fleece is deficient, especially at the high temperatures
achieved in strong sunlight.
EP-A-0 410 275 describes a waterproof sheeting having
water and water vapor barrier layers. It comprises at
least one biaxially stretch-oriented and heat-set film of
thermoplastic which is metallized on at least one side.
This waterproof sheeting effectively prevents penetration
of moisture into thermal insulation layers in buildings,
because the carrier film has a particularly good tear
strength due to the stretch orientation, and because, as
a result of the heat-set, it guarantees a sufficiently
high dimensional stability of the sheeting under the
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action of the usual temperature differences caused by
weathering over a period of several years. However,-the
adhesion between the bitumen layer and the carrier layer
is still in need of improvement in this sheeting.
Moreover, because of the additional metal coatings on the
carrier film, this waterproof sheeting is considerably
more expensive than conventional waterproof sheeting, and
is only worthwhile if particularly high impermeabilities
to water and water vapor are required.
EP-A-0 233 488 describes waterproof sheeting for
roofs which comprises a laid-, woven- or fleece-like
carrier layer covered with a bituminous coating on both
sides, and which is provided on its outer surface with a
covering film of biaxially stretch-oriented polypropylene
which has perforation holes at numerous points. The
perforated film applied to the outside replaces the usual
spreading with talc, sand or slate and prevents the
bitumen layers from sticking to one another when the
sheeting is rolled up.
DE-A-34 05 109 describes a highly elastic bituminous
roof sheeting which comprises a reinforcing insert of a
polyester spunbonded fabric coated with bitumen on both
sides. The polyester spunbonded fabric has pores over
its entire surface, the fiber structure of the non-woven
fabric being compacted in the form of collars at the
edges of the pores. To produce the roof sheeting, the
polyester spunbonded fabric is perforated with heated
conical needles, and then impregnated and coated with
liquid bitumen. This waterproof sheeting is
distinguished by perfect adhesion of the bitumen, in
spite of the shearing forces which occur due to the
different material properties, i.e., different elastic
properties, of the bitumen and ~punbonded fabric.
However, the perforation process is relatively
complicated and expensive, due to the requirement that
the carrier non-woven fabric should not be damaged, i.e.
its structure should not be destroyed, so that the good
mechanical properties of the composite are maintained.
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Moreover, spunbonded fabrics as a carrier material
generally have certain disadvantages. In particular, the
resulting waterproof sheeting is relatively thick and
rigid and does not offer the desired flexibillty, since
the inlaid spunbonded fabrics have a certain minimum
thickness of 400 ~m. Although thinner spunbonded fabrics
are in principle obtainable, they are disproportionately
expenslve.
Summary of the Invention
The various attempts described in the art to improve
the properties of the waterproof sheeting show that in
spite of the known solutions, there is a need for
improved developments.
The invention was therefore based on the object of
avoiding the disadvantages described above. A waterproof
sheeting which has excellent adhesion between the carrier
layer and the bitumen and at the same time has a good
mechanical strength and excellent elastic properties and
an outstanding flexibility is to be provided. In
addition to meeting these requirements, it should be
possible to produce the waterproof sheeting simply and
without a great deal of effort and therefore inexpen-
sively.
It is also an object of the invention to provide a
process for producing such a sheeting and to provide a
method of using the sheeting in the production of
weatherproof roof covering.
In accomplishing the foregoing objectives, there has
been provided, in accordance with one aspect of the
present invention a waterproof sheeting comprising a
thermoplastic film having holes at numerous points as a
carrier layer and a bituminous coating on each side of
said carrier layer.
In accordance with another aspect of the present
invention, there has been provided a process for the
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production of a sheeting as described above, comprising
the steps of:
a) perforating a thermoplastlc film so as to produce
a perforated film having numerous holes, and
b) applying a bituminous coating on both sides of
the perforated thermoplastic film.
In accordance with another aspect of the present
invention there has been provided a process for the
production of a waterproof roof on a structure comprising
laying a sheeting as described above onto a structure to
be covered.
Further objects, features, and advantages of the
present invention will become apparent from the detailed
description of preferred embodiments which follows.
Detàiled Description of the Preferred Embodiments
All plastics or mixtures of plastics which can
be processed into films are suitable as the thermoplastic
used in the carrier layer of the present invention.
Examples of these include polyolefins, polystyrenes,
polyamides, polyvinyl chlorides or polyesters.
Polyolefins, in particular polypropylene, and polyesters,
in particular polyethylene terephthalate, are preferred
in the context of the invention.
The covering films can comprise a relatively high
content of regenerated material, and may also comprise
100% regenerated material. In the context of the present
invention, regenerated material is to be understood as
meaning waste film material obtained in earlier
processes, for example material obtained during
production of films, which is recycled to the production
process for the instant sheeting.
The customary additives, such as, for example,
lubricants, antiblocking agents, antistatics,
antioxidants, neutralizing agents and the like, can
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additionally be added to the film raw material in the
usual amounts so as to obtain the desired results.
The carrier layer may be a single-layer or multi-
layer film. Single-layer and two- and three-layer films
are preferred. Multi-layer carrier films can be produced
in any desired manner such as by known coextrusion
processes or by the lamination of individual layers to
each other.
The thickness of the carrier film employed can vary
within wide limits, but should not generally exceed about
500 ~m, so as to maintain the desired flexibility and
elasticity of the finished roof sheeting. The film
thickness is preferably in the range from about 1 to
about 200 ~m, about 20 to about 80 ~m being particularly
preferred.
Depending on the quality of the sheeting, in order
to improve additional properties, the carrier film can be
coated on one or both of the surfaces. For example,
corona or flame treatment can be carried out on the
surfaces of the carrier film.
It is preferable to subject the film to biaxial
stretching with subsequent heat-setting in order to
improve the mechanical properties of the sheeting.
The carrier films may be produced in any desired
manner. For example, the film raw materials may be
melted in an extruder, and the melt forced through a slit
die and cooled to give a pre-film. The pre-film is then
preferably stretch-oriented in two directions running
perpendicular to one another, preferably first stretched
longitudinally and then stretched transversely, and is
subsequently heat-set. The stretching ratio, depends on
the type of film employed and the desired product and is
generally in the range from about 5 to about 60.
The thermoplastic film is perforated to produce the
carrier film according to the invention. The perforation
may be produced in any desired manner. In particular,
punching processes, needle perforations and/or flame
perforations, are suitable for forming the perforations.
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The number of holes is selected so as to give excellent
adhesion between the carrier layer and the bitumenous
coating, while maintaining the mechanical strength of the
resulting sheeting.
It has been found that flame perforation is a
particularly suitable perforation process. The flame
perforation process is known per se, and comprises
passing the film over a roll which is provided with
perforation holes and through which a cooling medium
flows. At the same time, within the region wound round
the roll, the film is charged with a flame from the side
facing away from the perforated cooling roll. In the
region of the perforation holes, the film which is not in
contact with the cooled roll surface melts, and the
perforation holes form in the film.
The perforation holes present in the carrier film may
have any desired average diameter, so long as the desired
sheeting is formed. In particular, the range from about
0.1 to about 20 mm, preferably about 1 to about 5 mm has
been found to be a useful average diameter. The number
of perforation holes per unit area in the carrier film
should be high enough so that the desired adhesion and
mechanical properties result. Generally, it is preferred
for the area of the holes to cover about 5 to about 60%
of the entire film surface.
The distance of the holes from one another can be any
desired multiple of the hole diameter, but it is
preferably in the range from about 0.5 to about 10 times
the average hole diameter.
For production of the sheeting, the carrier film thus
produced and provided with holes is coated with bitumen
on both sides. The bitumen can be applied to the carrier
film in any desired manner so long as a good adhesion
results between the carrier film and the outer bitumenous
coating.
The bitumen coating can comprise any known bitumen,
but preferably comprises a non-modified, oxidized or
blown bitumen. It has found to be expedient to use
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homogenized mixtures of bitumen with other polymers. The
bitumen can be modified in any desired manner so as to
modify the properties of the bitumen. Modifying
components which can be used include, for example,
atactic polypropylene or a mixture of stereoisomers of
polypropylene. Elastomers are also useful for the
modification. Any elastomers can be used. A block
copolymer of styrene/butadiene and styrene is expedient.
The content of modifying component in the modified
bitumen composition can be varied depending on desired
results and is generally from about 5 to about 40% by
weight, preferably about 10 to about 20% by weight, based
on the total weight of the modlfied bitumen composition.
The waterproof sheeting according to the invention
is distinguished by outstanding adhesion between the
bitumen layer and the carrier layer. The adhesion is
also ensured at high temperatures. At the same time, the
waterproof sheeting has very good mechanical properties.
Moreover, in addition to the outstanding quality, the
sheeting is simple and inexpensive to produce.
The sheeting of the present invention can be used
anywhere waterproof sheeting is needed. For example, the
sheeting can be used to produce a permanently
weatherproof roof covering. The roof covering can be
formed from the sheeting in any desired manner, such as
by laying the sheeting onto a structure to be covered and
bonding two or more sheetings which partly overlap to
form a seal by means of a flame process, pouring process,
or cold-bonding process.
