CA2092153A1

CA2092153A1 - Waterproof sheeting

Info

Publication number: CA2092153A1
Application number: CA002092153A
Authority: CA
Inventors: Gottlieb Ernst; John Derek Gribbin
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1992-03-23
Filing date: 1993-03-22
Publication date: 1993-09-24
Also published as: EP0562447A1; JPH0615771A; KR930019402A; MX9301628A; DE4209342A1

Abstract

Abstract of the Disclosure A sheeting comprising a carrier layer provided with a bituminous coating on both sides, wherein the carrier layer is a film of thermoplastic which has holes at numerous points results in a waterproof sheeting which can be used, for example, as a roof covering.

Description

2 ~ 5 3 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 -2 2~9~1~3 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 C~

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.

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 ~5~ ~2~

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 2 ~ 5 3 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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_7_ 2~2~S3 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 .

2~21~3 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.

Claims

1. 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.

2. A waterproof sheeting as claimed in claim 1, wherein said thermoplastic film is a polyolefin film.

3. A waterproof sheeting as claimed in claim 1, wherein said polyolefin film is a polypropylene film.

4. A waterproof sheeting as claimed in claim 1, wherein the carrier film has a thickness in the range from about 1 to about 500 µm.

5. A waterproof sheeting as claimed in claim 4, wherein the thickness is in the range from about 20 to about 80 µm.

6. A waterproof sheeting as claimed in claim 1, wherein the carrier film is a multilayer film.

7. A waterproof sheeting as claimed in claim 1, wherein the holes of the carrier film have an average diameter of from about 0.1 to about 20 mm.

8. A waterproof sheeting as claimed in claim 7, wherein the holes of the carrier film have an average diameter of from about 1 to about 5 mm.

9. A waterproof sheeting as claimed in claim 1, wherein the number of holes in the carrier film corresponds to an amount such that the area of the holes covers about 5 to about 60% of the film surface.

10. A waterproof sheeting as claimed in claim 1, wherein the holes in the carrier film are formed by flame perforation.

11. A waterproof sheeting as claimed in claim 1, wherein the thermoplastic film is a polyester film.

12. A waterproof sheeting as claimed in claim 11, wherein said polyester film is a polyethylene terephthalate film.

13. A waterproof sheeting as claimed in claim 1, wherein the carrier film is a biaxially stretch-oriented and heat-set film.

14. A waterproof sheeting as claimed in claim 1, wherein the bitumen is non-modified, oxidized, or blown bitumen.

15. A waterproof sheeting as claimed in claim 1, wherein the bitumen is admixed with a polymeric modifying agent, the weight of the modifying agent being about 5 to about 40% of the total weight of the resulting mixture.

16. A waterproof sheeting as claimed in claim 15, wherein the said polymeric modifying agent is polypropylene or a block copolymer of styrene and butadiene.

17. A process for the production of a sheeting as claimed in claim 1, comprising the steps of:
a) perforating a thermoplastic 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.

18. A process as claimed in claim 17, wherein the holes are produced by flame perforation.

19. A process for the production of a waterproof roof or a structure comprising laying a sheeting as claimed in claim 1 onto a structure to be covered.