WO2001073242A1

WO2001073242A1 - Waterproofing membrane with a rough surface and a process for producing waterproofing membranes

Info

Publication number: WO2001073242A1
Application number: PCT/HU2001/000034
Authority: WO
Inventors: Zoltán MANDZSU; József MANDZSU, Jr.
Original assignee: MANDZSU, József, Sen.
Priority date: 2000-03-27
Filing date: 2001-03-26
Publication date: 2001-10-04
Also published as: AU2001248651A1; WO2001073242A8

Abstract

The invention relates to waterproofing membranes with rough surfaces, which are suitable for waterproofing constructional components, and a process for producing the said membranes. The waterproofing membrane has a surface coated at least partially with a plastic film and/or plastic fabric, the outer surface of the plastic film and/or plastic fabric coating its surface is roughened at least partially with protrusions. A special embodiment of the invention relates to waterproofing membranes with surfaces roughened with light granules.

Description

Waterproofing membrane with a rough surface and a process for producing waterproofing membranes

Technical Field

The invention relates to waterproofing membranes with rough surfaces, which are suitable for waterproofing constructional components, and a process for producing the said membranes. A special embodiment of the invention relates to waterproofing membranes with surfaces roughened with light granules.

Background of the Invention

Waterproofing membranes are known to be used for damp-proofing or waterproofing constructional components (e.g. foundations or flat or pitched roofs, etc.). When applied, the membranes are fixed to the surface to be waterproofed (generally several membrane layers are used) and the top layer is covered with durable components (e.g. slates, tiles, rubbles, concrete, etc.) or the waterproofing membrane is manufactured with a durable surface (e.g. by slate-chip finishing) to sufficiently withstand UN radiation, heat and cold. The waterproofing membrane is gen- erally a multi-layered product, and each layer is used to provide the membrane with an important feature. The most important features of the membranes are the sufficient mechanical strength; capability to be adhered or fixed easily, quickly and perfectly; sufficient waterproofing; satisfactory behaviour associated with water vapor (e.g. satisfactory vapor-proofing or vapor-permeability or vapor-equalizing); suffi- cient surface strength; abrasion resistance and durability; capability for easy and safe handling during transport and mounting, etc.

The strengthening layer can be, for example, paper, glass cloth or plastic fabric, or plastic film or metal foil, or a combination thereof, and the strengthening layer can be inside the membrane or on either of its outer surfaces. The waterproofing layer is typically a bitumen (e.g. an oxidized bitumen, distilled bitumen, modified bitumen, etc.) or a plastic (e.g. a plastomer, elastomer etc.). Due to the generally adhesive nature of the waterproofing layer, at least one or rather both surfaces of the waterproofing membrane are coated with a layer, which prevents the non-desirable adhesion of the adhesive component of the membrane to the transfer rolls of the machine producing the membrane, the surrounding objects, people's clothing or successive windings of the wound membrane during and after transport, storage and mounting. Plastic films or an aggregate surfacing, typically fine or coarse sand, talc or ground slate can be used as release layers (the ground slate can be used as a top layer as well).

The required vapor-equalizing nature can be provided, for example, by coating the waterproofing surface facing the building with a plastic fabric, which achieves the required effect by its height and gas-permeability: it works as a spacer to facilitate free vapor migration along the membrane surface. The said fabric can be a non-woven, e.g. a heat-bound fabric or a felt as well.

During the manufacture of waterproofing membranes, the strengthening layer is generally impregnated or provided otherwise with the waterproofing layer (e.g. bitumen) when it is rewound, and then a plastic film or fabric is laminated and/or aggregate surfacing is carried out (e.g. with sand, talc, ground slate or other materi- als) on the outer surfaces of the membrane, which facilitates also the release of the possibly adhesive layers while transferring the membrane on further rolls. The plastic film used for laminating can contain small holes made by microperforation that facilitate removing the non-desirable air inclusions during laminating and, hereby, the perfect mounting of the film on the membrane. Waterproofing membranes are generally available as rolls, and they are to be laid down as overlapping stripes when lower, middle or top waterproofing layers are produced. However, in some applications, the waterproofing membranes are precut to shapes, shingles that can be used, for example, for covering pitched roofs. In most cases, at least one of the boundary surfaces of the waterproofing membrane is a plastic film even if this film differs from the strengthening support layer of the membrane. This widespread application is due to the fact that the plastic film coating the surface facilitates release (thus, prevents the non-desirable premature re-adhesion of the adhesive material to another surface) and also provides an advantageous property of adherability. During mounting, the membrane is to be adhered to the pretreated construction surface and generally to an other waterproofing membrane that has been previously adhered (using partial or total overlapping). The bitumen required for adhering modern waterproofing membranes is spread over the membrane during the manufacture of the membrane, so these membranes are ad- hered by torch melting. They are mounted by special torch melting equipment that melts the bitumen on the membrane surfaces rolling onto each other when the waterproofing membrane rolls are rolled down, so the surfaces rolled onto each other are adhered. In this case, the advantage of the said coating film is that the (typically thin) film melts quickly and easily, it disappears almost in a moment when the torch is applied and essentially does not hinder, delay or pollute the adhesion of the bituminous surfaces.

In another typical adhering process of modern waterproofing membranes the lower surface of the waterproofing membrane is self-adhesive so it can be adhered to the lower, pretreated surface to be waterproofed and to the upper surface of the previously adhered membranes. The said surfaces should be clean and dust-free, which can be ideally achieved by coating the upper surface of the waterproofing membrane with a plastic film.

When the waterproofing membranes are laid on a horizontal or inclined surface, the workers necessarily walk on the laid waterproofing membranes during the mounting of the first waterproofing layer or a further membrane layer on an existing waterproofing layer. With a view to workers' safety, the slipperiness of the free top surface of the laid waterproofing membranes is a main issue. As the said smooth plastic film (which can be adhered otherwise advantageously by torch melting) makes the surface very slippery, especially in the presence of condensed dew or white frost, the surfaces of the waterproofing membranes intended to be the upper sides are coated with granule coating instead of plastic films, however, considering the speed, energy consumption and cleanness of torch melting used to adhere the surfaces, granule coating is not an ideal solution. Some waterproofing membranes are coated with plastic films on both surfaces: their both sides can be easily melted, so they can be easily adhered as a lower or middle waterproofing layer but due to their slipperiness, walking is cumbersome and dangerous on them.

Cutting the waterproofing membranes to size before laying and their positioning (especially on pitched roofs) are often difficult because the membranes very easily slip on the base surface and each other (especially if their surfaces are covered with smooth plastic layers).

On the other hand, the PCT/HU98/00010 application of the present applicants is known. The application describes a process for roughening thermoplastic films where particles consisting of the material of the film and/or other plastics be- ing able to weld together with that, and having suitable size and/or demanded abrasion resistance are brought and dispersed in suitable closeness and configuration on the surface to be roughened of a semi-finished product having sufficient reserved heat content to maintain the condition appropriate for welding the thermoplastic film surface to be roughened or on one or both film surfaces heated to the same temperature, and the condition of the roughened surface is maintained until the desired welding process is completed. The object of the referred invention is to diminish the slipping of packages on each other by applying roughened packaging films. The referred invention describes also a process to prevent thermoplastic packaging films from slipping on each other, where a system is formed, which comprises the films to be fixed, at least one of them is roughened, and a binding element, such that a roughened film is used, which comprises protrusions in its surface in sufficient closeness, and a binding element with a loose fibrous structure and inherent strength is placed on the film or its predetermined portions, on the entire surface or part(s) of the surface, and the binding element comprises the elemental fibers in a density and layer thickness such that a mechanical joint is formed between the elemental fibers of the binding element and the protrusions of the roughened film. According to the referred invention, the binding element can be a suitably chosen, preferably non-woven, plastic fabric. It is also known that the object of the vapor-equalizing waterproofing membranes is to facilitate the parallel vapor migration along the surface (typically facing the building) of the waterproofing membranes (where the migration is brought about by a greater or lesser excess pressure). Therefore, a spacer layer is used between the waterproofing membrane and the contact surface in order to prevent the tight adhe- sion of the said layers and provide space for the vapor flow. This can be effected, for example, by coating the surface of the waterproofing membrane, facing the building, with a plastic felt of several millimetres thickness, which achieves the desired effect by its height and gas-permeability: it facilitates free vapor transport along the membrane as a spacer. The said felt can be also a heat-bound felt. This solution is extremely expensive. According to another solution, foamed polystyrene beads are spread on the surface of the waterproofing membrane during the manufacture; the beads sink and are embedded in the hot, plastic bitumen in a depth of one or two millimetres, so they are permanently bound to it. A drawback of this method is that the very light, flying polystyrene beads which often have an electro- static charge can only be handled with difficulty during the manufacture of the waterproofing membranes; after touching the bitumen, they fly away and cover the manufacturing equipment and its surroundings with sticky bituminous beads. An other drawback of the product manufactured with this method is that the free bituminous surface between the beads of the bituminous membrane laid down horizon- tally, with the beads downwards, may creep down between the beads during the years and, by reaching the base surface, it may fill the vapor-equalizing gap. Sometimes lightened clay balls are used instead of the polystyrene beads but they make the product too heavy, since the body density of the polystyrene beads is about 35 kg/m³, while that of the clay balls is about 500 kg/m³.

Disclosure of the Invention

Considering the more general part, the object of the present invention is a waterproofing membrane which, by eliminating the shortcomings of prior art, pos- sesses an outer plastic surface layer which essentially does not slip when one walks on it even if the surface is wet or frosty, thus, it facilitates a safe waterproofing process. Our aim is also to describe a new process required for the production of the said waterproofing membrane. Our aim is to describe a system that facilitates the positioning of the waterproofing membranes to be laid down and reduces their slip- ping.

Considering the special embodiment represented by a waterproofing membrane roughened with light granules, the object of the invention is the forming of a product, which, eliminating the drawbacks of prior art, possesses an outer plastic surface layer roughened with light granules that permanently maintains the vapor- equalizing surface roughness as the flow of the waterproofing material to the free space is prevented by the plastic film coating the waterproofing material between the protrusions. Our aim is also to describe a new process required for the manufacturing of this waterproofing material which releases the manufacturer of the waterproofing membrane from the known problems resulting from the non-desired fly of the free polystyrene beads.

Returning to the more general form of the invention, it has been recognized by the applicants that the use of a film roughened with protrusions as the plastic film creating the outer surface of the waterproofing membrane then, due to the film firmly laminated to the waterproofing membrane and the outwardly projecting pro- trusions which are firmly fixed to the film and provide external roughness, the outer surface of the waterproofing membrane is not slippery when one walks on it, instead, it possesses a sufficiently high frictional coefficient, therefore, the product is suitable for realizing the object of the present invention. Moreover, due to their relatively low surface closeness, the granules that preferably form the protrusions (preferably made of plastics and preferably fixed by welding) do not have, during the torch melt adhering of the waterproofing membrane, a substantial adverse effect on the speed, energy consumption, cleanness, safety, etc. of adhesion, thus, a waterproofing membrane like this can be very advantageously adhered by torch melting. The surface closeness of the roughening granules mentioned above (i.e. the number of protrusions or granules per unit surface of the waterproofing membrane) is high enough to provide the desired antislip effect, but it is not necessarily higher than that, so in contrast to the granule layer (e.g. comprising sand) used for the known aggregate surfacing release, the closeness of the roughening granules is preferably not high enough to, in itself, provide a perfect release, since the release is now effected by the supporting plastic layer below the granules rather than the granules themselves, and the mere role of the granules is to provide the sufficient frictional coefficient, which needs a considerably lower granule closeness than the aggregate surfacing release. Thus, the waterproofing membrane with a rough surface according to the invention is essentially a waterproofing membrane whose surface is coated at least partially with a plastic film and/or plastic fabric, and the waterproofing membrane according to the invention is formed such that the outer surface of the plastic film and/or plastic fabric coating its surface is roughened at least partially with protru- sions.

The advantage of the waterproofing membrane according to the invention is that, beside maintaining other advantages of the plastic coating layer, it possesses a surface frictional coefficient higher than that of the known waterproofing membranes, which significantly increases the safety of those walking on the membranes. The protrusions can be formed in various ways, however, with respect to the antislip nature and duration of the protrusions, the protrusions are preferably granules (preferably solid granules) fixed firmly to the outer surface of the plastic film or fabric. The material of the protrusions can be any suitable material (e.g. sand, talc, slate, clay, etc.), but with respect to the speed and energy saving of torch melting used to adhere the membranes, the specific heat of the protrusion material is preferably not significantly higher (preferably is not higher) than the specific heat of the plastic, and the protrusion material is more preferably a plastic. With respect to the torch melting used to adhere the membranes, the plastic film and/or plastic fabric and/or the protrusion material are preferably thermoplastics.

The granules forming the protrusions can be fixed to the plastic film or fabric in various ways, e.g. with an adhesive, lacquer, etc., but with respect to economy, the granules forming the protrusions are preferably fixed to the plastic film or fabric by welding. In this respect, preferably, the material of the granules forming the pro- trusions and that of the plastic layer supporting them are the same or the materials are different plastics being able to weld with each other.

The shape of the protrusions is preferably formed suitably with respect to tack and resistance against surface abrasion. The flatter protrusions with small slopes are more resistant to abrasion and breaking off, while the protrusions pro- jecting steeper, which may eventually have an envelope of a concave character, enhance the antislip nature. The mechanical strength of the fixing between the protrusions and the supporting plastic layer (e.g. film or fabric) must be high enough to withstand the mechanical stress associated with the given application.

As it was shown, in a part of the possible applications the plastic film and/or fabric is roughened with antislip protrusions enhancing adhesion. Moreover, after mounting, the protrusions may work as spacers and may be capable of facilitating vapor migration along the surface of the waterproofing membrane. In these applica- tions the size, shape, closeness, heat-resistance, durability, and mechanical strength of the protrusions make them suitable to work as permanent, durable vapor- equalizers. Thus, in these applications the plastic film and/or fabric are roughened with protrusions facilitating vapor flow. With respect to the speed of adhesion achieved by torch melting, the plastic film or fabric is preferably relatively thin, while with respect to the antislip nature, the protrusions are preferably relatively high. Thus, in a preferable embodiment of the product the ratio of the average height of the rise of the protrusions from the outer level of the film or fabric to the thickness of the plastic film or fabric is greater than 2, more preferably greater than 5, even more preferably greater than 20 and even more preferably greater than 60.

With respect to the speed of adhesion achieved by torch melting, the protrusion closeness is preferably not too high on the surface, since the less protrusions (e.g. granules) are on a unit surface, the less heat and time are required to melt the bitumen (and simultaneously to sufficiently heat and melt the protrusions or granules) on the surface. Therefore, in this respect, the surface closeness of the protrusions on the roughened surface portions is preferably less than 100 pieces/cm², more

9 9 preferably less than 50 pieces/cm , even more preferably less than 20 pieces/cm , and even more preferably less than 10 pieces/cm . With respect to the antislip nature, the surface closeness of the protrusions is preferably as high as possible. Thus, when the antislip nature is very important (e.g. in case of pitched roofs) the surface closeness of the protrusions on the roughened surface portions is preferably higher than 0.1 pieces/cm , more preferably higher

9 9 than 10 pieces/cm , even more preferably higher than 50 pieces/cm and even more preferably higher than 100 pieces/cm .

The roughening of the different surface portions may be essentially uniform or different. Thus, for example, the roughening of the surface portion to overlap the edges of the neighboring membranes and that of another surface portion, which is left free, may differ from each other. One surface portion may be more densely or more sparsely roughened than the other or some surface portions may be free of roughening. For example, in order to facilitate self-adhesion, a surface portion to be self-adhered to another waterproofing membrane by overlapping may be free of roughening or may be roughened just to a degree that does not prevent proper self- adhesion.

For decreasing production costs and facilitating torch melting, the plastic (preferably a polyolefine, e.g. polyethylene or polypropylene) film is preferably thinner than 20 microns, more preferably thinner than 10 microns, even more preferably is 8-micron thin or thinner. In order to achieve a desirable tack, the height of at least a part of the protrusions measured from the base layer is preferably greater than 20 microns, more preferably higher than 100 microns, more preferably higher than 150 microns, even more preferably higher than 250 microns and even more preferably higher than 400 microns or higher. In a possible embodiment, the outer surface of the plastic film and/or plastic fabric coating both main surfaces of the waterproofing membrane is roughened at least partially with protrusions.

With respect to the durability of the membrane, the plastic film and/or fabric coating the membrane surface (and preferably also the protrusions) are preferably protective from UV radiation which can be preferably achieved if it is (they are) made of a black plastic. Besides, the color of the protrusions roughening the surface can be preferably different (preferably markedly different) from that of the supporting plastic surface, because it draws attention to the rough nature and the improved tack associated with it, which can be important for commercial and/or safety rea- sons. The geometric arrangement and/or color of the protrusions of the rough surface may carry visual information (e.g. a trademark, logo, etc.).

During the mounting process, for example during precutting to size or positioning, waterproofing membranes facing each other with their roughened surfaces, are less liable to undesirably slip on each other than membranes coated with smooth film surfaces. This advantageous effect can be enhanced in an embodiment, where a binding element with a loose, fibrous structure and an inherent strength is fixed against slipping to at least a portion of the surface of the wateφroofing membrane, the binding element comprising the fibers with such density and layer thickness that a mechanical joint is formed between the fibers of the binding element and the protrusions of another roughened wateφroofing membrane portion when the two are laid on each other. The binding element can be a suitably chosen, preferably non- woven, plastic fabric, for example, a polyethylene or polypropylene fleece with a weight from about 10 to about 20 g/m². The binding element is fixed against slip- ping to the wateφroofing membrane; the fixing may be achieved with an adhesive or with other known means and/or (using the firm mutual grip of the protrusions and the binding element) the surface of the wateφroofing membrane covered by the binding element can be at least partially roughened with protrusions. The binding element fixed to the wateφroofing membrane (e.g. a polypropylene fleece) forms a firm, antislip mechanical joint with other pieces of wateφroofing membranes (more precisely with their roughening protrusions) when the binding element contacts these overlapping wateφroofing membrane pieces during the mounting process, thus, it prevents further slipping of the contacting overlapping membranes on each other. Thus, the said wateφroofing membrane with an enhanced tack is essentially a wateφroofing membrane whose surface is at least partially covered with a plastic film and/or plastic fabric, the wateφroofing membrane according to the present invention being such that the outer surface of the plastic film and/or plastic fabric coating its surface is at least partially roughened with protrusions, and a binding element with a loose, fibrous structure and inherent stability is fixed against slipping to at least a portion of its surface, the binding element comprising the fibers with such closeness and layer thickness that a mechanical joint is formed between the fibers of the binding element and the protrusions of the roughened wateφroofing membrane to be contacted with it. The wateφroofing membrane can contain the binding element on its one or both main surfaces, on the entire surface or on a surface portion, in stripes or patches or in any suitable arrangement.

The antislip tack between the suitable materials with a loose, fibrous structure and the roughening protrusions can be used to further increase the safety of the persons walking on the roughened surface of the wateφroofing membrane if the footwear soles and/or further elements of clothing of the persons walking on the membranes possess a contact surface with such a loose, fibrous structure, upon whose contacting the suitably roughened surface of the wateφroofing membrane, an an- tislip mechanical joint is formed between the fibers of the contact surface and the roughened surface of the wateφroofing membrane. This can be particularly advantageous in case of pitched roofs. If the surfaces of objects (e.g. ladders, tools, boardwalks, etc.) to be supported are provided with the mentioned contact surface, these objects can be placed on the roughened surface of the wateφroofing mem- branes without the risk of slipping, which again has its significance in that the slipping of the said contact surfaces is also prevented by the said tack on a pitched roof. Thus, the system preventing the slipping on a wateφroofing membrane is essentially a system comprising a wateφroofing membrane whose surface is at least partially coated with a plastic film and/or plastic fabric and an object provided with a contact surface with a fibrous structure in order to contact the wateφroofing membrane, the system according to the invention being such that the outer surface of the plastic film and/or plastic fabric coating the surface of the wateφroofing membrane is roughened at least partially with protrusions, and the fibrous structure of the contact surface is so loose and contains the fibers in such a density and layer thickness that an antislip mechanical joint is formed between the fibers of the contact surface and the protrusions of the roughened wateφroofing membrane.

The process suitable for manufacturing the wateφroofing membrane with a roughened surface differs from the traditional one essentially in the fact that it comprises a feature providing the surface roughness of the product. Thus, the process for manufacturing a wateφroofing membrane with a roughened surface is essentially a process in which one or both main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric, the process according to the invention being such that before and/or after the forming, the outer surface of the plastic film and/or fabric is at least partially roughened with protrusions.

In another process being also suitable for manufacturing the wateφroofing membrane with roughened surface, one or both of the main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric as a boundary layer, the process according to the invention being such that a plastic film and/or fabric, roughened at least on its surface intended to be the outer surface, at least partially, with protrusions, is used as the boundary layer.

The embodiment of the process, in which the roughening is carried out after forming the plastic film or fabric as a boundary layer, e.g. by sprinkling granules and fixing the granules on the surface, is advantageous since a traditional non- roughened film or fabric can be used as a starting material and the roughening can be carried out similarly to the aggregate surfacing release well-known in the manufacture of wateφroofing membranes, except for that in this case the material of the granules, their formed surface closeness and the way of their fixing can be opti- mized for the antislip effect and the ease of torch melting instead of the previous release effect. A plastic film can be advantageously applied which is laminated on the hot bituminous wateφroofing membrane and then plastic particles are brought, preferably by spraying, possibly in a melted or plastic state, onto the hot or softened plastic surface and the particles are fixed to the surface by welding and/or with an adhesive. A plastic powder, for example, ground polyethylene powder or granules made of a hot melt adhesive can be used.

The embodiment of the process in which the boundary layer of the waterproofing membrane is formed of a pre-roughened film or fabric is advantageous due to the fact that granule dispersing can be omitted when the layers of the water- proofing membrane are joined, for example, when the layers of the bituminous wateφroofing membrane are laminated to each other during rewind, thus, the lamination of the hot bituminous membrane and the roughening of the plastic film are not necessarily carried out simultaneously, which can be advantageous as both processes can be optimal under different conditions. Thus, for example, the traditional process of laminating both sides of the semi-finished, hot bituminous membrane with a smooth polyethylene film must be modified only by using a roughened film instead of the previous smooth film on one or both sides and this modified process can be readily used to produce antislip wateφroofing membranes. The advantage of this embodiment lies in the fact that the lamination technology of the wateφroofing membranes needs to be varied only very slightly and the essential technology modification appears in the film production, which can be a substantial economic advantage (the modification of the film production can be carried out more easily and flexibly in this case than that of the bituminous technology). As it was shown, the rough plastic film or fabric laminated on the surface of the semi-finished wateφroofing membrane is roughened on its outer or both on its outer and inner surfaces. The application of the plastic layer roughened also on its inner surface can be advantageous as it facilitates the forming of a firm joint between the bituminous layer of the wateφroofing membrane and the boundary plastic layer and prevents the slipping of the said layers on each other, so it stabilizes and keeps the outer (typically thin) plastic layer in a smooth state. This can be important because the hot bituminous membrane can heat the contacting thermoplastic film during lamination so much that it loses its strength and, therefore, it is damaged, wears through, tears or gets creased. The protrusions of the film pressed into the bitumen also prevent the undesirable shrinkage of the film due to the orientation stress that may be released by heat.

With respect to the integrity of the plastic surface layer and roughness, the heat-resistance of the applied plastic film or fabric and granules forming protrusions on it is preferably high enough to suitably maintain their shapes and strength even under the heat transferred to the film or fabric and the protrusions from the hot laminated bituminous wateφroofing membrane. Polyethylene, more preferably high-density polyethylene and polypropylene can be used as materials of the plastic layer and the protrusions because they are sufficiently heat-resistant in ordinary bi- tuminous wateφroofing membrane applications.

Considering the wateφroofing membrane with a surface roughened with light granules, it is recognized by the applicants that if a plastic film roughened with protrusions, as roughening elements, consisting of sufficiently big granules made of a light, foamed plastic material is used as a plastic film forming the outer surface of the wateφroofing membrane then due to the film firmly laminated to the waterproofing membrane and the outwardly projecting protrusions which provide outer roughness and are firmly fixed to the film, a durable vapor-equalization is maintained by this outer surface_of the wateφroofing membrane. In the free space between the protrusions, the vapor can easily flow par- allel with the surface, even without being subjected to a substantial excess pressure, and this effect is permanently maintained because the free wateφroofing material between the protrusions, typically bitumen, will not flow in between the protrusions due to the coating plastic film, instead, it lets the space between the protrusions free for the vapor migration in long term. It is recognized by the applicants that the new product described above can be manufactured with the usual film-laminating process and without the common production problems caused by polystyrene beads, if during the usual manufacturing process a plastic film roughened on its outer surface with sufficiently big protrusions, as roughening elements, made of a light, foamed plastic is used as a plastic film instead of the usual, smooth plastic film. The wateφroofing membrane with a surface roughened with light granules according to the invention differs from the more general embodiment according to the invention in that the outer surface of the plastic film and/or plastic fabric coating at least partially its surface is roughened at least partially with protrusions, where the material of the granules forming the protrusions is a foamed plastic, where the body density of the granules is at most 250 kg/m³, and at least a part of the protrusions is as high as at least 0.5 mm.

The material of the protrusions is of low density due to the foaming. The body density of a granule is the ratio of the mass to the volume of a granule. The height of a protrusion is the level-difference between the average level of the free outer surface between the protrusions and the outer point of the protrusion being farthest from this level.

The advantage of this wateφroofing membrane according to the invention is that it durably maintains the vapor-equalizing surface roughness as the plastic film and/or fabric coating the wateφroofing material between the protrusions prevents the flow of the wateφroofing material into the free space. A further advantage of the wateφroofing material is that the granules are not deeply embedded in the bitumen so the granules of the same size can form higher protrusions.

The granules forming the protrusions can be fixed to the plastic film or fabric with various methods as described for the more general embodiment, for example with an adhesive, lacquer, by welding, hot melt polymer adhesion, etc.

The shapes of the protrusions are preferably formed to meet the demands set by the vapor-equalizing effect, stability against normally directed compression and resistance to surface abrasion. The considerations mentioned in connection with the more general embodiment also apply, i.e. flatter protrusions with small slopes are more resistant to abrasion and breaking off. The steeper protrusions, which may even have a concave envelope, increase the height of the air gap. The mechanical strength of the fixing between the protrusions and their supporting plastic layer (e.g. film or fabric) must be high enough also in this case to withstand the stress charac- teristic to the given application. The size, closeness, heat-resistance, durability and mechanical strength of protrusions are such which make them suitable for durable vapor-equalization. The protrusions are preferably so close to each other that the wateφroofing membrane is firmly supported on the free surfaces, which durably prevents the material of the wateφroofing membrane from substantially filling the free space between the protrusions. The protrusions are preferably positioned randomly, densely and often touching each other.

With respect to the weight of the product, the body density of the foamed plastic material is preferably at most 60 kg/m , more preferably at most 40 kg/m . In order to achieve an effective vapor flow, the height of at least a part of the protrusions is preferably at least 1 mm, more preferably at least 2 mm, even more preferably at least 3 mm. However, the height of the protrusion can reach even 4 mm or 6 mm or 12 mm.

The amount of the moisture absorbed by the foamed plastic granules, which depends on the relative humidity of the ambient air, may influence the granule characteristics. In order to achieve a vapor-equalizing effect of permanent quality, the foamed plastic is preferably closed-celled to such an extent that its water absoφtion during a 24-hour soaking, without excess pressure, is less than 15 v/v%, more preferably less than 5 v/v%. If the surface is subjected to a strong abrasive/drifting force the surface roughened with protrusions is preferably provided with a flexible covering layer. The flexible covering layer must follow more or less the shapes of the protrusions in order to become protuberant itself. With respect to a good vapor flow, the height of at least a part of the protrusions measured from the flexible covering layer, i.e. the level-distance between the highest outer point of a protrusion and the average level of the outer surface of the free flexible covering layer between the protrusions must be at least 0.5 mm.

After mounting, the roughened plastic layer can be subjected to a relatively higher temperature (e.g. 50° C). In the simplest embodiment where the free surface portions between the protrusions of the plastic film or fabric are also coated by the adhesive, the behaviour of the adhesive at this temperature plays a significant role. Several common adhesives already show certain softening, adhesion, and activity on the free surface portions at 50° C or higher temperatures, though the adhesion strength of the granules remains intact. This activity of the adhesive on the free sur- face portions is disadvantageous since the free surface portions of the wateφroofing membrane can accidentally adhere to the opposite facing surface, which might block the vapor flow. In order to be used at higher temperatures, the roughened surface at least on the freely accessible surface portions between the protrusions preferably comprises at most a non-thermoplastic adhesive layer or an adhesive layer with an activation temperature higher than 50° C, where the activation temperature of an adhesive is a temperature where the adhesive loses its sand-dry characteristics. This temperature is more preferably at least 80° C.

With respect to heat-resistance and considering sunshine, the softening tem- perature of at least a part of the protrusions is preferably at least 75° C.

With respect to the stability of protrusions, the height of at least a part, preferably the majority of the protrusions is preferably less than or essentially the same as their width.

The roughening granules can be economically produced, for example, by grinding foamed plastics, which may even mean the recycling of plastics. The grist can be properly adhered to the supporting plastic layer. However, with respect to stability, at least a part, preferably the majority of the granules has preferably an essentially planar surface portion facing the supporting plastic layer. • -

The granules can have a regular, e.g. cylindrical, truncated conical shape, etc.(which can be achieved, for example, by expanding them in molds). With respect to the great volume maintained for free vapor flow due to the high spacing, at least a part of the protrusions, preferably their majority has preferably a flattened or non- flattened spherical or a flattened or non-flattened spherical segment shape. The said spherical segment shape preferably contains essentially one of the hemispheres or an even greater portion of the (flattened or non-flattened) sphere.

It is important that the protrusions are required to be as light and cheap as possible while being as solid as possible. In this respect, the protrusions are preferably made of a foamed polystyrene material. This includes expanded and extruded foamed polystyrene as well as polystyrene materials with additives. Moreover, foamed polystyrene is a closed-cell material and can be manufactured in any regular shape (e.g. essentially as balls or beads) or as a grist, and it is cheap.

In order to maintain a great volume for free vapor flow, the distance of at least a part of the protrusions from their nearest neighboring protrusions is prefera- bly at least equal to the quarter of the smaller of the two protrusion widths.

In order to prevent the free space from being filled by the wateφroofing material, the distance of at least a part of the protrusions from their nearest neighboring protrusions is preferably at most equal to the tenfold of the greater of the two protrusion widths. The protrusions can be torn off from the plastic layer with a sufficiently great external force. This can also occur while the wateφroofing membrane is laid down and mounted, therefore, it is important that the plastic film or fabric itself, which supports the protrusions and coats the surface of the wateφroofing membrane on the free spaces between the protrusions as a release layer, will not wear through due to the occasional tear caused by the granules torn off, because this might enable the sticky wateφroofing material, willing to creep, to get through the plastic release layer, which can lead finally to the filling of the space enabling vapor migration. Therefore, in order to prevent wearing through, the normally directed tear strength of the fixing of the majority of the protrusions is preferably smaller than the nor- mally directed tear force required to wear through the plastic layer supporting the protrusions. In this case only the fixing is released and the plastic layer, e.g. the plastic film, does not wear through.

The protrusions serve to withstand a normally directed compression and vapor-equalizing does not necessarily require for them a substantial peφendicular-to- normal fixing strength. However, the granules can be subjected to tangential forces during the mounting process. With respect to safe mounting, the fixing strength parallel to the layer of at least a part of the protrusions is preferably at least 5 grams. The fixing strength parallel to the layer of a protrusion is the smallest force to be exerted to the protrusion parallel to the fixed supporting plastic layer by a peφen- dicular to the force, planar, rigid surface covering the entire side view of the protrusion in order to entirely eliminate by the force the fixing between the protrusion and its supporting layer.

With respect to economy, the ratio of the height of at least a part of the pro- trusions to the thickness of their supporting film or fabric is preferably greater than 4.

With respect to strong and durable spacing, the compressive strength of at least a part of the protrusions is preferably at least 50 grams, more preferably at least 200 grams. In this case, namely, a wateφroofing membrane of a given compression resistance may comprise less protrusions. In this sense, the compressive strength of a protrusion is the greatest force to be exerted in order to compress the protrusion peφendicularly to its supporting plastic layer by 50 percent, in 1 second, applying a uniform compression speed.

Wateφroofing membranes are preferably manufactured and commercialized in rolls. In order to facilitate overlapping required to cover the greater surfaces, the wateφroofing membranes are preferably free from protrusions on one or more edges parallel to the winding direction. The width of this protrusion-free strip can preferably be from about 10 mm to about 250 mm. The roughened layer in the roll can face the interior as well as the exterior of the roll, but more preferably it faces the interior of the roll.

The vapor equalizing air layer below the mounted wateφroofing membrane works also as a heat-insulating air layer. The remarkable heat-insulation of the air layer, considering its width, can preferably be achieved if the layer supporting and/or covering the protrusions and/or the protrusions have a radiation-reflective layer, preferably a metal layer, preferably a vapor deposited aluminum layer.

The process suitable for manufacturing wateφroofing membranes with roughened surfaces differs from the traditional one essentially in the fact that it comprises a feature providing the surface roughness of the product. Thus, the process suitable for manufacturing wateφroofing membranes with surfaces roughened with light granules is essentially a process in which one or both main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric, the process according to the invention being such that be- fore and/or after the forming, the outer surface of the plastic film and/or fabric is at least partially roughened with protrusions wherein the protrusions are formed of granules of foamed plastics having a body density of at most 250 kg/m , and at least a part of the protrusions are formed with heights of at least 0.5 mm.

In another process also being suitable for manufacturing wateφroofing membranes with surfaces roughened with light granules, one or both of the main outer surfaces of the wateφroofing membrane are made at least partially of a plastic film and/or fabric as a boundary layer, the process according to the invention being such that a plastic film and/or fabric, roughened on its surface intended to be the outer surface, at least partially, with protrusions consisting of granules of foamed plastics, having a body density of at most 250 kg/m , and at least a part of the protrusions having heights of at least 0.5 mm, is used as the boundary layer.

The embodiment of the process in which the boundary layer of the waterproofing membrane is formed of a pre-roughened film or fabric is advantageous due to the fact that granule dispersing can be omitted when the layers of the waterproofing membrane are joined, for example, when the layers of the bituminous wateφroofing membrane are laminated to each other during rewind, thus, the lamination of the hot bituminous membrane and the roughening of the plastic film are not necessarily carried out simultaneously, which can be advantageous since both proc- esses can be optimal under different conditions. Thus, for example, the traditional process of laminating both sides of the semi-finished, hot bituminous membrane with a smooth polyethylene film must be modified only by using a roughened film instead of the previous smooth film on one or both sides and this modified process can be readily used to produce roughened wateφroofing membranes. The advantage of this embodiment lies in the fact that the lamination technology of the waterproofing membranes needs to be varied only very slightly and the essential technology modification appears in the film production, which can be a substantial economic advantage (the modification of the film production can be carried out more easily and flexibly in this case than that of the bituminous technology).

With respect to the integrity of the plastic surface layer and roughness, the heat-resistance of the applied plastic film or fabric and the granules forming protrusions on it is preferably high enough to suitably retain their shapes and strength even under the heat transferred to the film or fabric and the protrusions from the hot laminated bituminous wateφroofing membrane. Polyethylene, more preferably high-density polyethylene and polypropylene can be used as materials of the plastic layer and the protrusions and polystyrene or polyurethane can be used as a material of the protrusions because they are sufficiently heat-resistant in ordinary bituminous wateφroofing membrane applications. In order to achieve good lamination, such a plastic film or fabric is preferably used as a boundary layer whose non-roughened side is essentially planar.

Best Mode of Carrying out the Invention

The more general embodiment of the wateφroofing membrane with a rough surface according to the invention is detailed further with an example illustrated with Fig. 1.

Example 1

Wateφroofing membrane with a roughened surface The strengthening layer of the 1 -meter wide and 25-meter long wateφroofing membrane is glass cloth 1 impregnated and surrounded on both sides by modified bituminous layers 2 providing wateφroof behavior. On both sides, the bituminous layers are coated on their outer surfaces with high-density polyethylene films 3 having an average thickness of 9 microns, as release layers, which are fixed to the bitumen by lamination and hot adhesion, where the adhesion is provided by the adherence of the bitumen to the film material. The films on both edges of the waterproofing membrane reach beyond the bituminous layer by about 15 mm. The films are made of black plastics. On one of the main surfaces of the wateφroofing mem- brane (intended to be the upper side when laid down), protrusions are formed by granules fixed firmly to the outer side of the polyethylene film by welding, which constitute antislip layer 4. The granule material is a high-density polyethylene powder whose size is from about 100 microns to about 300 microns, and in this region the size of 95% of the granules is from about 300 microns to about 350 microns. The granules are made of a white colored plastic. The roughened film layer is more or less evenly roughened in its entire width and the closeness of the protrusions on the surface is about 25 protrusions/cm .

Example 2 System preventing slipping on wateφroofing membranes

The wateφroofing membrane constituting a part of the system is identical with the product described in example 1. In this example the object provided with a contact surface of a fibrous structure serving to contact the wateφroofing membrane is a footwear having a sole provided with a velour fabric having loose, empty loops, which is intended to facilitate the wearer's safe walking on the wateφroofing membrane while working. The fibrous structure of the velour fabric covering a part of the sole surface of the footwear is loose to such an extent and it contains fibers in such a density and layer thickness that an antislip mechanical joint is formed between the fibers of the contact surface and the protrusions of the roughened water- proofing membrane.

The processes of the production of wateφroofing membranes with rough surfaces are illustrated by the examples below. (Process) example 3

In the first process example a 1 -meter wide glass cloth substrate is impregnated with hot, melted bitumen while it is rewound, and thus a semi-finished product with a thickness of about 4 mm is produced. Then a 12-micron thick, high- density polyethylene film is laminated on the main surfaces still being hot, so release layers are formed on both main surfaces. Then hot state hot-melt-polymer granules are sprayed on the entire width of one of the main surfaces, while the roll is further being rewound, and the granules are spread on the outer surface of the film in a more or less uniform distribution, with an average closeness of about 5 granules/cm and with an average protrusion height of about 500 microns. With cooling the product the protrusions are solidified_and then the product is wound up in 25-meter long pieces and packaged.

(Process example) 4 In this example a 1 -meter wide glass cloth substrate is impregnated with hot, melted bitumen while it is rewound, and a semi-finished product with a thickness of about 5 mm is produced. Then release layers are formed on the main surfaces still being hot by that one of the main surfaces is laminated with an 8-micron thick, high- density polyethylene film and the other main surface is laminated with a high- density polyethylene film also having a thickness of 8 microns and having protrusions constituted by granules welded into the film on its side remaining free. The granules are made of medium-density polyethylene. The entire film surface is uni- formly covered with the protrusions in a closeness of about 35 protrusions/cm . The height of the protrusions is from about 150 microns to about 400 microns. During the lamination process, the heat transferred to the film from the wateφroofing membrane is kept at such a low level that the roughness of the film will not essentially change due to the heat. The product is cooled, wound up in 10-meter long pieces and packaged. Example 5

Wateφroofing material with a surface roughened with light granules

The product according to the title is described further with the help of Fig. 2. The strengthening layer of the 1 -meter wide and 10-meter long wateφroofing mem- brane is glass cloth 1 impregnated and surrounded on both sides by modified bituminous layers 2 providing wateφroof behavior. On both sides, the bituminous layers are coated on their outer surfaces with high-density polyethylene films 3 which are aluminum deposited on their outer surfaces as compared to the wateφroofing membrane and have an average thickness of 9 microns, as release layers, and the films are fixed to the bitumen by lamination and hot adhesion, where the adhesion is provided by the adherence of the bitumen to the film material. The films on both edges of the wateφroofing membrane reach beyond the bituminous layer by about 15 mm. On one of the main surfaces of the wateφroofing membrane (intended to be the lower side when laid down), protrusions are formed by granules fixed firmly to the outer side of the polyethylene film with a cross-linking adhesive, which constitute vapor-equalizing spacer layer 4'. The granules are made of expanded polystyrene; their height is from about 1 mm to about 4 mm, and in this region the height of 95% of the granules is from about 3.00 mm to about 3.50 mm. The material of the granules is white. Except for a 10-centimeter wide strip left free on one side, roughened film layer 3 is more or less uniformly roughened in its entire width, and the close- ness of the protrusions on the surface is generally about 3 protrusions/cm . The shape of the protrusions is a slightly flattened spherical section being greater than a hemisphere. The adhered surface of the granules is planar. The granules are randomly positioned. Several granules touch their neighbors. The body density of the granules is 30 kg/m³. The material of the granules possesses a closed-cell structure to such an extent that its water absoφtion during a 24-hour soaking, without excess pressure, is less than 0.5 v/v%. The roughened surface comprises a non- thermoplastic, cross-linked adhesive layer on the freely accessible surface portions between the protrusions. The softening temperature of the granules is 80° C. The height of the protrusions is less than their width. The distance of at least a part of the protrusions from the nearest neighboring protrusions is at least equal to the quarter of the smaller of the two protrusion widths, while the distance of at least a part of the protrusions from the nearest neighboring protrusions is at most the tenfold of the greater of the two protrusion widths. The normally directed tear strength of the fixing of the majority of the protrusions is smaller than the normally directed tear force required to wear through film 3. The fixing strength parallel to the layer of each protrusion is at least 5 grams, that of most protrusions is at least 50 grams. As it was shown, the thickness of film 3 is substantially smaller than the quarter of the height of the highest protrusion. The compressive strength of each protrusion is at least 100 grams, that of most protrusions is at least 400 grams.

Example 6

Wateφroofing membrane with a surface roughened with light granules The wateφroofing membrane with a surface roughened with light granules in this example differs from the previous one described in example 5 in that the surface roughened with protrusions is covered with a flexible covering layer. The flexible covering layer is a 12-micron thick, linear, low-density polyethylene film fitting tightly to the plane of the film supporting the protrusions essentially everywhere on the free surface portions between the protrusions and it is fixed there with an adhesive. Thus, the flexible covering layer follows properly the outlines of the granules and allows the spacing and ventilating effect of the protrusions to show. The flexible covering layer takes on the non-planar shape due to its creases and stretched parts, which does not disturb the function of the product. Due to the flexible cover- ing layer, the protrusions do not tear off from the wateφroofing membrane even if a strong friction occurs. (Process) example 7

The process of the production of wateφroofing membranes with rough surfaces is described in the present example. In this example a 1 -meter wide glass cloth sub- strate is impregnated with hot, melted bitumen while it is rewound and thus an about 5-millimeter thick semi-finished product is produced. Then release layers are formed on the main surfaces, still being hot, by laminating one of the main surfaces with an 8-micron thick high-density polyethylene film and laminating the other main surface with a high-density polyethylene film also having a thickness of 8_microns, and having protrusions formed by granules adhered to its free surface. The material and size of the granules and other characteristics of the coating film are identical with those described in example 5. During the lamination process, the heat transferred to the film from the wateφroofing membrane is kept at such a low level that the shape of the granules providing roughness to the film will not essentially change due to heat, which means that they do not shrink so much as to significantly decrease their vapor-equalizing effect, and also their fixing remains firm. The product is cooled, wound up in 10-meter long pieces and packaged.

Claims

1. Wateφroofing membrane with a surface coated at least partially with a plastic film and/or plastic fabric (3), characterized in that the outer surface of the plastic film and/or plastic fabric (3) coating its surface is roughened at least partially with protrusions (4).

2. Wateφroofing membrane according to Claim 1, characterized in that the protrusions (4) are granules fixed firmly to the outer surface, preferably solid.

3. Wateφroofing membrane according to any one of Claims 1 and 2, characterized in that the material of the protrusions (4) is a plastic, preferably a thermoplastic material.

4. Wateφroofing membrane according to any one of Claims 1-3, characterized in that the granules forming the protrusions (4) are fixed to the plastic film and/or fabric (3) by welding.

5. Wateφroofing membrane according to any one of Claims 1-4, characterized in that the ratio of the average height of the rise of the protrusions (4), measured from the outer level of the plastic film or fabric (3), to the thickness of the plastic film or fabric (3) is greater than 2.

6. Wateφroofing membrane according to any one of Claims 1-5, characterized in that the surface closeness of the protrusions (4) on the roughened surface portions is less than 100 pieces/cm .

7. Wateφroofing membrane according to any one of Claims 1-6, characterized in that the surface closeness of the protrusions (4) on the roughened surface portions is higher than 0.1 pieces/cm².

8. Wateφroofing membrane according to any one of Claims 1-7, characterized in that the height of at least a part of the protrusions (4) projecting from the base layer (3) is greater than 20 microns.

9. Wateφroofing membrane according to any one of Claims 1-8, character- ized in that a binding element with a loose, fibrous structure and an inherent strength is fixed against slipping to at least a part of its surface, the binding element comprising the fibers with such density and layer thickness that a mechanical joint will be formed between the fibers of the binding element and the protrusions (4) of the roughened wateφroofing membrane to be contacted with it.

10. Antislip system to prevent slipping on wateφroofing membranes comprising a wateφroofing membrane whose surface is at least partially coated with a plastic film and/or plastic fabric and an object provided with a contact surface with a fibrous structure in order to contact the wateφroofing membrane, characterized in that the outer surface of the plastic film and/or plastic fabric coating the waterproofing membrane surface is roughened at least partially with protrusions, and the fibrous structure of the contact surface is so loose and contains the fibers in such a density and layer thickness that an antislip mechanical joint will be formed between the fibers of the contact surface and the protrusions of the roughened wateφroofing membrane.

11. Process for producing a wateφroofing membrane with a rough surface in which one or both main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric, characterized in that before and/or after the forming, the outer surface of the plastic film and/or fabric is at least partially roughened with protrusions.

12. Process for producing a wateφroofing membrane with a rough surface in which one or both main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric as a boundary layer, characterized in that a plastic film and/or fabric roughened at least on its surface intended to be the outer surface, at least partially, with protrusions, is used as the boundary layer.

13. Wateφroofing membrane with a surface coated at least partially with a plastic film and/or plastic fabric (3), characterized in that the outer surface of the plastic film and/or plastic fabric (3) coating its surface is roughened at least partially with protrusions, where the material of the granules forming the protrusions is a foamed plastic and the body density of the granules is at most 250 kg/m³ and the height of at least a part of the protrusions is at least 0.5 mm.

14. Wateφroofing membrane according to Claim 13, characterized in that its surface roughened with protrusions has a flexible covering layer.

15. Wateφroofing membrane according to any one of Claims 13-14, characterized in that its roughened surface, at least on the freely accessible surface portions between the protrusions, comprises at most a non-thermoplastic adhesive layer or an adhesive layer with an activation temperature higher than 50° C.

16. Wateφroofing membrane according to any one of Claims 13-15, characterized in that at least a part of the roughening granules has an essentially planar surface portion facing the supporting plastic layer.

17. Wateφroofing membrane according to any one of Claims 13-16, characterized in that the distance of at least a part of the protrusions from the nearest neighboring protrusions is at least equal to the quarter of the smaller of the two protrusion widths.

18. Wateφroofing membrane according to any one of Claims 13-17, characterized in that the distance of at least a part of the protrusions from the nearest neighboring protrusions is at most equal to the tenfold of the greater of the two protrusion widths.

19. Wateφroofing membrane according to any one of Claims 13-18, characterized in that the normally directed tear strength of the fixing of the majority of its protrusions is smaller than the normally directed tear force required to wear through the plastic layer supporting the protrusions.

20. Wateφroofing membrane according to any one of Claims 13-19, characterized in that the fixing strength parallel to the layer of at least a part of its protrusions is at least 5 grams.

21. Wateφroofing membrane according to any one of Claims 13-20, characterized in that the compressive strength of at least a part of its protrusions is at least 50 grams.

22. Wateφroofing membrane according to any one of Claims 13-21 , charac- terized in that along its one or more edges parallel to its winding direction it is free from protrusions.

23. Wateφroofing membrane according to any one of Claims 13-22, characterized in that the layer supporting and/or covering the protrusions and/or the protrusions are provided with a radiation-reflective coating.

24. Wateφroofing membrane according to any one of Claims 13-23, characterized in that the ratio of the height of at least a part of its protrusions to the thickness of their supporting plastic film or fabric is greater than 4.

25. Process for producing a wateφroofing membrane with a rough surface in which one or both main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric, characterized in that before and/or after the forming, the outer surface of the plastic film and/or fabric is at least partially roughened with protrusions, wherein the protrusions are formed of granules of foamed plastic with a body density of at most 250 kg/m³, and at least a part of the protrusions are formed with heights of at least 0.5 mm.

26. Process for producing a wateφroofing membrane with a rough surface in which one or both main outer surfaces of the wateφroofing membrane are formed at least partially of a plastic film and/or fabric as a boundary layer, characterized in that a plastic film and/or fabric, roughened on its surface intended to be the outer surface, at least partially, with protrusions consisting of granules of foamed plastics, having a body density of at most 250 kg/m , and at least a part of the protrusions having heights of at least 0.5 mm, is used as the boundary layer.