EP0555800B1 - Water and/or oil impervious membrane with swellable clay - Google Patents

Abstract

A water- and/or oil-impervious membrane is provided, which consists essentially of a porous material in the pores of which swellable clay is incorporated and which is provided with cover layers on both sides, at least one of which cover layers consists of a water-soluble film. Membranes of this kind have, even in the overlapping region, water permeability coefficients which are of the order of magnitude of the water permeability coefficients of the membrane itself. In addition, it is possible to needle the overlapping regions in situ in order to produce a friction-locking bond, provided that an overlapping region originates from a membrane which has a nonwoven fabric as porous supporting material.

Description

The present invention relates to a water and / or oil impermeable sealing mat according to the preamble of claim 1, which essentially consists of a layer provided with cover layers of swellable clay. Such a sealing mat is known from EP-A-0 445 788.

A sealing mat is known from European patent specification 0 059 625, in which a flexible carrier layer carries a bentonite layer, on which in turn a cover layer can be located. All three layers, i.e. the carrier layer, which can be a nonwoven, the bentonite layer and the cover layer, which could have been an unspecified one, are connected to one another by means of an adhesive. In the case of such a product, the backing layer and the top layer are only connected to one another via the bentonite layer, so that when used, because of the adhesive bond which is released when the bentonite layer becomes moist, there is no firm connection between the backing layer and top layer. This is particularly noticeable when used as intended, since the bentonite layer swells freely in all directions in contact with water and a bentonite layer is formed, which acts like a sliding film between the carrier and cover layers, which is particularly disadvantageous when laying such Geomembranes on embankments.

In order to eliminate the main disadvantage of these sealing mats, sealing mats have already been developed by the applicant, which are described in our own German patent 37 04 503 and EP-A-0 445 788. These sealing mats essentially consist of a backing layer, a layer of swellable clay and a top layer, the backing and / or top layer consisting of a nonwoven fabric and the layer which may not consist of a nonwoven fabric consisting of a woven fabric, knitted fabric or a plastic film, in which all three layers are needled together. In such a sealing mat, the backing layer and the top layer remain firmly connected by the needling even during and after the swellable clay swells, the bentonite particles through the fibers which extend from the top layer through the bentonite layer into the backing layer, and vice versa, like being trapped in a cage. This ensures that when using this sealing mat, the wet bentonite layer can not act as a sliding plane and there is a real transfer of thrust from the cover layer to the carrier layer, so that, for. B. on slopes a slipping of the existing gravel or debris layer is not to be feared. According to one embodiment described in these two protective rights, the sealing mat can have a coarse-pored carrier nonwoven, in the pores of which swellable clay is embedded, the coarse-pored carrier nonwoven having the swellable clay embedded therein being needled on both sides with cover layers. In addition, it is already stated in its own German patent specification 37 04 503 that a reduction in the water permeability of these sealing mats can be achieved by first applying a floury bentonite to the support layer and, if necessary, shaking it in and then only applying the granular bentonite granules. Instead of shaking the floury bentonite into the carrier layer, one can also proceed by first impregnating the carrier layer with an aqueous bentonite suspension or rolling on an aqueous bentonite paste and only then, if necessary after drying beforehand, applying the granular bentonite granules. If desired, the top layer can also be treated in the same way as the carrier layer before it is applied.

In spite of this treatment and even if you add those as described above with bentonite by shaking or impregnation uses pre-treated carrier and cover layers, examinations in the field and in the laboratory show that in the overlap area due to the fine-pored nonwovens that lie on top of each other in this area, the water permeability coefficients are not quite as high as those of the sealing mat itself. This is certainly due to the fact that the fine-pored nonwovens are not completely filled with bentonite, for example because part of the finely powdered bentonite introduced has fallen out of the nonwoven during rolling up, during storage, during transport and during rolling out and laying. This is probably also the reason why the carrier and cover layers pretreated with bentonite by vibrating or impregnation as described above alone do not meet the requirements that good sealing mats should meet.

In order to eliminate this disadvantage in the overlap area, the applicant has already developed the special joining techniques in the overlap area described in our own EP-A-0 522 546, which, however, require a great deal of effort and great care in the execution of the overlap Construction site conditions - as experience shows - is not always guaranteed. Although this own EP-A-0 522 546 was published after the priority date of the present application, it nevertheless belongs to the prior art in accordance with Article 54 (3).

It is therefore an object of the present invention to provide a sealing mat which not only allows the work in connection with the very complex and very carefully carried out joining technology to be reduced, but also simplifies it in principle, while still meeting the requirements regarding the water permeability coefficients in the overlap area, which should be of the same order as the water permeability coefficients of the sealing mat itself, and the requirements regarding the transmission of thrust are met.

This object is achieved according to the present invention in a water and / or oil impermeable sealing mat with a porous carrier material, in the pores of which swellable clay is embedded, wherein the porous carrier material with the swellable clay embedded therein is provided with cover layers on both sides in that at least one cover layer consists of a water-soluble film.

In the sealing mats according to the invention, the carrier material used acts like a framework which gives the moist bentonite layer which is formed when it is used excellent stability and, on the one hand, ensures that the moist bentonite layer does not become a sliding plane and, on the other hand, the desired transmission of thrust is ensured. Since, when laying the sealing mats according to the invention, care must also be taken that the overlapping sealing mats must always be laid such that two water-soluble cover layers always come to lie on one another, it is further ensured that the bentonite layers of the overlapping sealing mats in the moist state so get intimate contact that the water permeability coefficients in the overlap area are in the same order of magnitude as the water permeability coefficients of the sealing mat itself. The fact that the bentonite layers come to lie practically directly on top of one another means that none of the complex and carefully carried out joining techniques need be used, which means an enormous simplification of the laying work with regard to the sealing mats on the construction site.

In the case where the porous carrier material is a nonwoven fabric, there is the additional advantage that the sealing mats according to the invention can be needled in situ in the overlap area, so that a non-positive connection is obtained in the overlap area, which ensures that there is no displacement of the nonwoven layers in the overlap area is possible.

The swellable clay embedded in the pores is preferably a bentonite. Bentonites are clays with a noticeable to high smectite (montmorillonite) content, which decisively determines their properties (high swellability, good water binding capacity, high plasticity). In order to obtain a highly swellable active bentonite from an alkaline earth bentonite which is not readily swellable in water, the alkaline earth ions of the bentonites are replaced by alkali ions, preferably sodium ions. Sodium bentonite with its greatly increased plasticity, viscosity, thixotropy and water absorption is therefore preferred as the "highly swellable" active bentonite. The naturally occurring sodium bentonites are particularly preferred, in particular those that come from the mining area in Wyoming, USA.

The porous carrier material preferably consists of a nonwoven fabric or an open-cell foam plastic.

Of the nonwovens and the foamed plastics, which are at least so elastic that they can be wound on a roll, large-pored are preferred. The preferred foamed plastics include open-pored, flexible polyurethane foams.

The nonwovens used preferably consist of quality plastic fibers, in particular of polyethylene, polypropylene, polyester, polyacrylic and / or polyamide fibers. Particularly preferred in the field of landfill technology are nonwovens made of high density polyethylene (HDPE) or polypropylene, which are rot-proof (resistant) to all substances found in water and soil and are therefore demonstrably extremely high Ensure durability. Their extremely high tensile strength means that they are largely insensitive to mechanical stress.

In terms of structure, the nonwovens used are preferably spunbond nonwovens mechanically consolidated by needling. They are constructed in such a way that the crimped fibers form a flat structure with innumerable labyrinthine passages. The structure of the nonwovens can be adjusted coarser or finer depending on the area of application, so that an optimal adaptation to the requirements is guaranteed. The mechanical strengthening guarantees a framework structure that is essential for the purposes of the invention. Instead of the nonwovens mechanically consolidated by needling, it is also possible to use those nonwovens which have been mechanically consolidated by means of sewing technology or by swirling, or those nonwovens which have been chemically consolidated.

According to a preferred embodiment of the invention, the porous carrier material is a two-layer composite nonwoven made from a coarse-pore nonwoven and a fine-pored nonwoven or a fine-mesh woven or knitted fabric or a finely perforated film, the fine-pored nonwoven or the woven or knitted fabric or the film forming a cover layer.

The two-layer composite nonwovens which can be used according to the invention include, for example, those which have been marketed by Naue-Fasertechnik for years under the trade name "TERRAFIX" as tried and tested hydraulic engineering mats. The production width is usually 4.80 m and the length 100 m. One nonwoven layer consists of a filter layer (fine-pored nonwoven) made of polyester and a drain layer (coarse-pored nonwoven) made of polypropylene fibers. The fibers are by needling solidified mechanically. This two-layer composite fleece, which serves as a carrier layer, has a layer thickness of greater than 6.0 mm. The characteristic values of such a two-layer composite fleece are shown in Table 1 below.

Another two-layer composite fleece suitable for the purposes of the present invention can be constructed such that a coarse-pored Nonwoven fabric is needled with a fabric, preferably a fine-mesh fabric, or a knitted fabric, preferably a fine knitted fabric, or a finely perforated film.

For special purposes, a three-layer composite fleece can also be advantageous, which consists of two coarse-pore nonwovens needled together, with a fine-mesh fabric or knitted fabric or a finely perforated film between the two nonwoven layers, which is also needled. In such a case, only the one large-pore nonwoven layer is filled with bentonite and then sealed with the water-soluble film. The other, non-filled, coarse-pored nonwoven layer is used to compensate for unevenness in the ground and to ensure that the installed sealing mat is non-slip.

In the case of the sealing mats according to the invention, which have a two-layer composite fleece or a three-layer composite fleece, the laying is carried out in such a way that the top layer consisting of water-soluble film comes to lie alternately upwards and downwards, so that the top layers of water-soluble film always lie directly in the overlap region Are in contact with each other. In order to avoid confusion when laying, it has proven to be particularly advantageous if either the water-soluble cover layer or the fine-pored nonwoven, the woven fabric, the knitted fabric or the film is colored.

Advantageously, these "multi-layer composite nonwovens" sealing mats are laid in such a way that first two sheets of the sealing mat are laid parallel to one another at a distance with the water-soluble top layer and then a third sheet of the sealing mat with the water-soluble top layer facing down on the free floor strip, the distance between the two first installed sealing sheets is chosen so that the desired overlap width is obtained on both sides.

If sealing mats according to the invention are used which carry the water-soluble film as a covering layer on both sides, they can be laid in the usual way, since with these sealing mats two covering layers made of water-soluble film always come to lie on top of one another.

In principle, all systems which form a water-soluble film or a film which can be decomposed by water are suitable for the water-soluble cover layers. Such water-soluble films can be either purely inorganic or organic in nature.

Purely inorganic films, as can be used according to the invention, include those based on water glass. Aqueous solutions of alkali silicate, preferably of sodium silicate, are suitable as water glasses. Such water glass solutions are commercially available and form the desired film on drying, it having proven particularly advantageous if bentonite, preferably sodium bentonite, is introduced into such an aqueous water glass solution. The mixing of the water glass solution with the bentonite is most conveniently carried out in such a way that an aqueous bentonite dispersion is prepared beforehand, and this is then mixed with the aqueous water glass solution. The amount of bentonite to be introduced depends entirely on the viscosity with which you want to apply the silicate solution. In addition to low-viscosity mixtures, those which are pasty and which are knife-coated or rolled onto the surfaces to be sealed are also suitable.

Of the organic film-forming substances, in particular aqueous starch, dextrin, casein or glutin glues as well as aqueous cellulose ether or cellulose ester paste and aqueous polyvinyl alcohol solutions have been found. All of the above Aqueous systems are advantageously mixed with bentonite, preferably a sodium bentonite, in a similar way to the aqueous water glass solution, the amount of bentonite introduced likewise again depending on the desired viscosity.

The aqueous starch glues include, in particular, those based on potato and corn starches. If necessary, these starch glues are used in combination with casein solutions.

Similar to the starch glues, the water-soluble dextrin glues are used. The dextrins are thermal breakdown products of the starches.

Casein glues include those that were made in particular from milk protein. In addition, instead of casein glues, so-called collagens from animal hides and bones can be used for glue jellies and glutin glues.

Of the cellulose ethers and cellulose esters, particular mention should be made of methyl cellulose, which in aqueous solutions, for. B. is used as wallpaper paste.

Of the cellulose esters, special mention should be made of cellulose acetate, which is soluble in water with a degree of esterification of 0.6 to 0.9 and a content of bound acetic acid of 18 to 26%.

Furthermore, the water-soluble film formers preferred according to the invention include those based on polyvinyl alcohol. Of these polyvinyl alcohols, only those which form aqueous solutions and which are used, for example, for simple paper gluing are preferred. Such aqueous polyvinyl alcohol solutions are also preferably used in a mixture with bentonite.

However, if water-soluble films which dry relatively quickly are to be obtained, it is advantageous to dispense with appropriate admixtures of bentonite.

Conventional techniques are used to produce the water-soluble cover layers according to the invention, in which case the aqueous coating compositions forming the cover layers can be sprayed on, knife-coated, rolled on or applied by means of other known techniques. Since the cover layers should dry relatively quickly, it is advisable to blow them off with hot air or to move them past appropriate heating elements. B. radiant heaters allow a quick drying process.

According to a preferred embodiment of the invention, both sides of the sealing mat are sealed with the water-soluble films. In the manufacture of such sealing mats, one can proceed in such a way that the bentonite powder is sprinkled and shaken on a coarse-pored nonwoven fabric that is transported lying on a lower conveyor belt and covered with an upper conveyor belt. Both conveyor belts are then guided vertically upwards with the filled sealing membrane in between, with both conveyor belts being deflected at the same height to the return. At this point, the water-soluble film is then applied from both sides at the same time and then dried. The resulting sealing sheet is then wound on a roll for use.

If no "multi-layer composite fleeces" are used in the production of the sealing mats according to the invention, it is necessary that one of the two water-soluble cover layers is first applied to one side of the sealing membrane. After appropriate drying, such a web is then run over a Device in which the bentonite powder is sprinkled from above into the open pores of the porous carrier material and then shaken. The surface is then sealed with the second water-soluble top layer.

Claims (10)

1. Sealing sheeting impervious to water and/or oil with a porous substrate material, in whose pores swellable clay is lodged, wherein the porous material with the swellable clay lodged therein is provided on either side with covering layers, characterized in that at least one of the covering layers consists of a water soluble coating.
2. Sheeting according to claim 1, characterized in that the substrate material consists of a large-pored non-woven material and preferably of such a material composed of synthetic resin fibers, more particularly polyester or polyolefin fibers.
3. Sheeting according to claims 1 and 2, characterized in that both the covering layers consist of a water-soluble coating.
4. Sheeting according to claims 1 and 2, characterized in that the substrate material is a twin-layer non-woven material of a large-pored non-woven material and a fine-pored non-woven material or a fine mesh woven or knitted fabric or a film with extremely fine perforations, such fine-pored non-woven material or such woven or knitted fabric or the film constituting a covering layer.
5. Sheeting according to claims 1 to 3, characterized in that in the case of the presence of only one covering layer of water-soluble coating either such coating or the fine-pored non-woven material, the woven fabric, the knitted fabric or the film is colored.
6. Sheeting according to claim 1, characterized in that the porous substrate material is an elastic synthetic resin foam with large, open pores.
7. Sheeting according to claims 1 to 6, characterized in that the water-soluble coating is formed using a mixture of water-glass solution and bentonite.
8. Sheeting according to claims 1 to 6, characterized in that the water-soluble coating is formed using aqueous starch, dextrin, casein or gluten glues with or without the admixture of bentonite.
9. Sheeting according to claims 1 to 6, characterized in that the water-soluble coating is formed using aqueous cellulose or cellulose ester glues with or without the admixture of bentonite.
10. Sheeting according to claims 1 to 6, characterized in that the water-soluble coating is formed using an aqueous polyvinyl alcohol solution with or without the admixture of bentonite.