EP0563453B1 - Method for making a water- and/or oil-impervious liner containing expansive clay - Google Patents

Abstract

Described is a process for the continuous production of a water- and/or oil-impermeable (impervious) liner (sealing matt) wherein expansive (swellable) clay is needled into between a carrier layer and a nonwoven top (cover) layer while at the same time an expansive clay additionally sprinkled onto the upper surface of the top layer is incorporated into the top layer. Subsequently the expansive clay present in the top layer is incipiently moistened and re-dried. A modified embodiment uses only a carrier layer made of a nonwoven, woven fabric or knitted fabric and/or a foil, the foil being a plastic film, a fabric-reinforced plastic film or paper, and a coarsely porous nonwoven or a non-consolidated crosslaid (fibre-crossed) card web or a random-laid fibre web, to which the pulverulent expansive clay is applied and needled in, moistened and dried. Instead of the needling technique it is also possible to use the knitting and/or sew-knitting technique.

Description

The present invention relates to a water and / or oil impermeable sealing mat which essentially consists of a layer of swellable clay provided with cover layers.

Such a sealing mat is known from European patent 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 backing layer, which can be a nonwoven fabric, the bentonite layer and the cover layer, which can be an unspecified mat, 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, the applicant has already developed a sealing mat which is described in its own German patent specification 37 04 503. This sealing mat essentially consists 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, whereby all three layers are needled together. With such a sealing mat, the carrier layer and the top layer remain by the needling also during and after the swelling of the swellable clay firmly connected, the bentonite particles being trapped in the cage by the fibers which extend from the cover layer through the bentonite layer to the carrier layer and vice versa. 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. In addition, this own German patent specification 37 04 503 already states 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 only then 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.

Despite this treatment and even if one additionally uses the carrier and cover layers pretreated with bentonite by shaking or impregnation as described above, studies in the field and in the laboratory show that in the overlap area the fine-pored nonwovens that lie one on top of the other in this area are not yet complete the water permeability coefficients are achieved, like that of the sealing mat itself. This can certainly be attributed to the fact that the fine-pored nonwovens are not completely filled with bentonite, for example because the bentonite powder or the bentonite paste or the bentonite slurry does not penetrate completely into the interstices of the nonwoven fabric or part of the fine-powdered bentonite introduced when rolling up , has fallen out of the nonwoven during storage, transportation and when rolling out and laying. This is probably also the reason why the carrier and cover layers pretreated with bentonite by vibrating as described above alone do not meet the requirements that good sealing mats should meet.

The object of the present invention is therefore to provide a method by which it is possible to fill the carrier and / or top layer consisting of nonwoven fabric with powdery or granular swellable clay, in particular with powdered bentonite, in such a way that not only achieves an excellent sealing effect in the overlap area, but that the filling, in particular in the top layer of the finished sealing mat, is in such a state that it prevents the swellable clay or bentonite introduced when rolling up, during storage, during transport and / or falls out or dusts out of the nonwoven layers when rolling out.

This object is achieved according to the present invention in that the backing and / or cover layer consists of a nonwoven fabric, into which swellable clay applied from outside is also needled during the needling of the three layers and which is subsequently moistened and then dried again, wherein a fiber-reinforced skin is formed from swellable clay, which is firmly connected to the overall structure.

It is essential to the invention that at least one layer consists of a nonwoven and the swellable clay applied to it is needled from the outside into the nonwoven during the needling process, and then the top layer provided with the needled swellable clay is swollen with water and then dried again.

The present invention thus relates to a process for the continuous production of a water and / or oil-impermeable sealing mat which essentially consists of a carrier layer, a layer of swellable clay, in particular bentonite, and a cover layer, at least one of the layers being a nonwoven and whereby the dry powdery or granular swellable clay is applied to the carrier layer, the covering layer is laid over it and the three-layer material obtained is passed through a needle chair for the needling of the carrier layer and covering layer, which is characterized in that prior to the needling on the top of the nonwoven fabric applying the existing top layer of powdery swellable clay, needling the four-layer laminate obtained, then moistening the swellable clay needled in the top layer with water and then drying again, and if appropriate subsequently subsequently carrying the carrier treats.

According to a preferred embodiment of the invention, the cover layer consists of a nonwoven fabric and the carrier layer consists of a woven fabric or a film, the use of a woven fabric being preferred. Not only plastic films, but also paper, preferably sodium kraft paper, are suitable as films.

If floury bentonite is used, the fabrics used according to the invention must be woven so tightly that even finely powdered bentonite with particle sizes in the »m range cannot penetrate the fabric. A ribbon fabric is preferably used.

Humidification with water can be done with cold, warm or hot water or with steam.

When laying a sealing mat produced according to the invention using fabrics as a backing layer, in which the top layer consists of a non-woven fabric filled with bentonite, it is also ensured that practically the same water-impermeability values apply in the overlapping area as for the sealing mat itself.

The sealing mats produced according to the invention are also outstandingly suitable as sealing safety underlays under a waterproof covering made of plastic film. In the event of injury to such a plastic film, e.g. due to the formation of holes or cracks, the water penetrating through this leak causes the swellable clay in the sealing mat produced according to the invention, which is preferably a naturally occurring sodium bentonite, to swell and thus closes the leak in a quasi "self-healing process".

The nonwovens used preferably consist of quality plastic fibers, in particular of polyethylene, polypropylene, polyester, polyacrylic and / or polyamide fibers. Nonwovens made of high density polyethylene (HDPE) or polypropylene are particularly preferred in the field of landfill technology. 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 varied depending on the area of application set the area of use coarser or finer 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 modified embodiment of the invention, a carrier layer made of nonwoven fabric, woven fabric, knitted fabric and / or film is used, the film being a plastic film, a plastic film or paper reinforced with fabric, preferably sodium kraft paper, and a porous structure a coarse-pore chemically or mechanically consolidated or only partially consolidated nonwoven fabric or from a non-consolidated fiber-crossed carded nonwoven or a random fiber nonwoven, in contrast to the embodiments described above, no layer of swellable clay is applied directly to the carrier layer, but only in a correspondingly larger amount the porous structure is applied or introduced, a naturally occurring sodium bentonite in powder or granule form preferably being used as the swellable clay. The fabric thus obtained is then passed through appropriate needle chairs, the swellable clay being incorporated into the porous structure and the porous structure itself being mechanically solidified as in the conventional needling technique. The consolidation can also take place by means of knitting and / or sewing technology. The fabric obtained is then moistened with water on the side on which the bentonite was applied or on both sides.

In the case of needling technology, it can be advantageous to arrange needle chairs one behind the other, one of which with Needles are equipped, the barbs of which are directed downwards, and the other is equipped with such needles, the barbs of which are directed upwards. But you can also use combination needle chairs that are equipped with both types of needles at the same time.

The fabric consolidated by means of the needling technique is then sprayed with water on the top and / or bottom and then dried. Drying can be carried out, for example, by means of infrared radiation or by passing the web through an oven or a hot air duct. For various applications it can be advantageous if the bentonite retains a certain residual moisture.

The sealing mat obtained in this way can then either be used with the carrier layer as a sealing mat or the paper layer is removed and the embedded clay is swollen with water from this side and dried. Such a product naturally results in an optimal seal in the overlap area. According to a preferred variation, the paper web is removed only at the edges and in a width that corresponds to the overlap width. This technique can also be used in the other embodiments described above, in which paper is used as a carrier layer.

The sealing sheets according to the invention are used in particular as seals for groundwater protection and are preferably used as a mineral component of a combination seal in conjunction with plastic sealing sheets. In the event of partial leakage or perforation of the plastic sealing sheets covering them, the sealing sheets according to the invention, as already mentioned, bring about a self-healing effect in relation to the damaged plastic sealing sheet.

The present invention is illustrated by the following examples, but without restricting it thereto.

example 1

A roll of ribbon fabric with a width of 4 m is unrolled over a winding block and fed to a needle chair as a carrier layer. During the unwinding process, an amount of approx. 3,500 g / m² bentonite powder is applied to the ribbon fabric serving as the backing layer. At the same time, a roll of nonwoven (6.7 dtex fibers) is fed to the bentonite layer as a top layer via a further winding block. Bentonite powder in an amount of 1,500 g / m² is also applied to this top layer. These 4 layers then pass through the needle chair, the bentonite powder on the top layer being needled into the top layer and the layers being mechanically firmly bonded to one another.

The needle chair has several needle boards. Each needle board is equipped with thousands of needles. The needle boards are moved up and down very quickly (up to approx. 1,000 strokes per minute). The needles provided with notches penetrate all layers, the notches ensuring that the individual fibers are intertwined with one another, so that a firm bond is created in which the bentonite particles are virtually encapsulated. As a result of the needling process, part of the bentonite also penetrates into the cover layer from the bentonite intermediate layer, insofar as space is still available there.

After leaving the needle chair, the top layer is moistened with water from above, in an amount of approximately 300 g / m 2 and then dried again, which is advantageously carried out using infrared radiators.

The sealing mat obtained in this way makes the top layer appear in the form of a coherent, fiber-reinforced skin that fulfills the task.

Example 2

To produce a water and / or oil-impermeable sealing mat, a PP ribbon fabric (100 g / m²) is covered with a 350 g / m² carded pile and then 3000 g / m² of activated sodium bentonite is sprinkled in. The fiber web filled with bentonite and the carrier fabric are passed through a needle chair and mechanically consolidated.

The non-woven fabric filled with bentonite is then sprayed with 300 ml / m² of water to fix the bentonite on the top and dried for 2 minutes at 300 ° C. using an infrared radiator. Here, too, the water treatment forms a coherent, fiber-reinforced "elephant skin".

For the production of sealing mats according to this example, nonwovens, woven fabrics, knitted fabrics and / or foils of any raw material and any surface masses and combinations thereof can of course also be used as the carrier layer. The basis weight and the raw material as well as the fiber fineness of the cardboard pile or the random fiber nonwoven can also be varied depending on the area of application. The bentonite or the swellable clay can be applied both in powder form and in granulate form.

Claims (7)

1. Method for the continuous production of sealing sheeting impervious to water and/or oil, which essentially consists of a substrate layer, a layer of swellable clay, more particularly bentonite, and a covering layer, at least one of the layers being a non-woven material and the dry pulverulent or granular swellable clay being applied to the substrate layer, the covering layer is placed thereover and the resulting triple-layer material is passed through a needle punching machine for the purpose of needle punching together the substrate layer and the covering layer, characterized in that prior to needle punching pulverulent swellable clay is applied to the top surface of the covering layer consisting of non-woven material, the resulting quadruple-layer material is needle punched, then the swellable clay needle punched into the covering layer is moistened with water to cause swelling of the clay and then dried again and if desired then the substrate layer is processed in a suitable manner.
2. Method according to claims 1, characterized in that the substrate layer is a film or a fabric.
3. Method for the continuous production of sealing sheeting impervious to water and/or oil, which essentially consists of a non-woven material and a swellable clay, characterized in that a porous structure composed of a large pored, consolidated or a non-woven material or even a nonconsolidated intersecting fiber crimped non-woven material which is not particularly consolidated or a random fiber non-woven material is applied to a substrate layer of non-woven material, woven or knitted fabric, and/or a film, the film being a synthetic resin film, a paper or a synthetic resin film reinforced with fabric, following which application the desired quantity of pulverulent or granular swellable clay and more particularly bentonite is strewn on the structure, the coated substrate is passed through a needle punching machine, the swellable clay being needle punched into the porous structure and the entire structure is then consolidated simultaneously by means of needle punching and then the free side or both sides of the composite material are moistened with water and finally dried.
4. Method according to claims 1 to 3, characterized in that instead of needle punching a knitting and/or sewing method is utilized.
5. Method according to claims 1 to 4, characterized in that the substrate layer consisting of paper, possibly after previously being moistened, is completely removed or removed only at the edge side and then the exposed parts are moistened and dried again.
6. Method according to claims 1 to 5, characterized in that the drying operation is performed by means of infrared heating or in a kiln or in a hot air tunnel.
7. Method according to claims 1 to 7, characterized in that such drying is only performed until the bentonite only contains a certain quantity of residual moisture.