Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reissue Patent
1995-12-11
2001-07-24
Raimund, Christopher (Department: 1711)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S220000, C428S332000
Reissue Patent
active
RE037295
ABSTRACT:
The present invention relates to a water and/or oil-impermeable sealing mat and more particularly to a water and/or oil-impermeable sealing mat particularly suitable as a water and/or oil-barrier for hydraulic engineering, for environmental pollution control for the building of ponds, lagoons, as a soil sealant for hazardous or nuclear waste or for the retention of animal waste as for example, on farms, and such other uses as will become apparent to those skilled in the art upon reading the following description.
Said water and/or oil-impermeable sealing mat consists of a flexible substrate layer, a layer of swellable clay, preferably bentonite, and a flexible cover layer.
In the past, bentonite was widely used in various forms to act as a water barrier. So it is already known to provide seepage resistant structures by employing a mass of swellable bentonite across the path of possible seepage or flow. One such method and composition for impeding the seepage or flow of water is disclosed in U.S. Pat. No. 2,277,286 (Bechtner). As therein more fully described, commercial bentonite is used to block leakage or flow of water seepage, and structures of various types are safeguarded against leakage by blocking the path of flow of the water with bentonitic or highly colloidal clay which possess the capacity to swell and gelatinize upon contact with water. One of the clays found best suited for this purpose was the true bentonite obtained in regions of Wyoming and South Dakota, although other highly colloidal, or bentonitic clays which possess the property of swelling and gelatinizing in water to a substantial degree are also useful.
Further in the past,
finally
finely
divided bentonite was fabricated into a laminate with water absorbent paper sheeting as described for example in the U.S. Pat. Nos. 4,048,373, 4,070,839 and 4,139,588. Such laminates are especially developed for use as a water barrier and are made from corrugated paperboard sheets.
The channels in said corrugated paperboard sheets are filled with finely divided bentonite. When such pannel is placed at the bottom of the pond and is exposed to water, the water passes through the top layer of kraft paper and is adsorbed into the bentonite material. At the same time the paper loses its tensile strength due to the wetting process. The bentonite has the capacity to expand and swell in response to absorbing the water. This expansion of bentonite and the loss of tensile strength of the kraft paper cause that the bottom sheet member and the cover sheet member to not longer hold together.
Another way to package bentonite material in sheets or rolls, which can be placed on the bottom of the pond or lagoon so as to form a waterproof barrier thereon, is disclosed in U.S. Pat. No. 4,501,788 (corresponding to European Patent
8 059 625
0 059 625
). In said Patent is described a method for providing such a packaged bentonite sheet material
utilized
utilizing
the following process steps:
(a) Using a support polyester sheet material (for example a porous non-woven fabric) having the ability to permit gases to escape therethrough in a lateral direction.
(b) Applying an adhesive to the upper surface of this sheet material, the adhesive being formed from a starch-like glue.
(c) Applying approximately one-fourth inch of bentonite on top of the adhesive.
(d) Spraying a second coat of adhesive over the top of the bentonite.
(e) Placing a scrim or fine mesh material on top of the adhesive.
(f) Press rolling the above combination into a elongated flat sheet material.
(g) Baking the sheet material in a long oven at approximately 300° F. so as to bake all the moisture out of the sheet material and the bentonite.
Not only is the above process cumbersome, expensive and time consuming, but also the support sheet and the cover sheet lose their stick firmly contact with each other. This is a very important disadvantage, because the bentonite layer acts in a wet condition like a sliding path on the sides of the pond or other places. This sliding effect is further enhanced by the dissolved adhesive in the wet condition.
Therefore other people tried by a further development to avoid at least one of the before mentioned shortcomings, that means to avoid the use of an adhesive and the necessary baking process by using such an adhesive. Such a new process which does not require baking or adhesive as above mentioned is disclosed in the U.S. Pat. No. 1,565,468. The process of said patent involves the use of the following steps:
(a) Using a flat polyester sheet material, preferably a synthetic non-woven fabric which is a porous, flexible poly propylene material. The sheet material is capable of dissipating gas in a laterial direction so as to permit gas which gathers adjacent the sheet material to pass laterally outwardly through the sheet material.
(b) Applying approximately one-fourth inch of bentonite over the top of the base material.
(c) Applying plain kraft paper or other biodegradable material over the top of the bentonite. This material must be capable of degrading after hydration.
(d) Stitching the sheet material to the base material with the bentonite being positioned between the two sheets of material. In the preferred form the stitches extend in crossing diagonal lines with respect to the longitudinal axis of the sheet material so as to form diamond shaped quilted compartments between the upper sheet material and the base sheet material. The quilted compartments contain bentonite therein. The quilted arrangement prevents the bentonite from shifting during the rolling of the quilted material and during transportation. In another form the kraft paper is corrugated so as to form elongated corrugated compartments for containing the bentonite material.
When the above material is placed within a water environment, such as at the bottom of a pond or lagoon, the bentonite expands and breaks the kraft paper layer at the top of the barrier. The bentonite continues expanding so as to cover the stitch holes formed by the stitching, and thereby forms a water impervient layer.
As seen from the above description it may be that the process for the production of the sheet material according to the U.S. Pat. No. 4,565,468 is better than according to the process of the U.S. Pat. No. 4,501,788 (corresponding to European Patent 0 059 625), but there is still the large disadvantage that the bentonite layer during the use as a water barrier in a wet condition acts like a sliding path on slopes.
All of the sealing mats described in the above U.S. patents serve merely to “package” bentonite and always consist in principle of a substrate layer,
an
a
bentonite layer and a cover layer. After these sealing mats have been laid out and subsequently moistened, the substrate and cover layers are connected only via the swollen bentonite layer therebetween, which has the consistency of grease. Now if it is considered that the sealing mats must further be weighted down with a sand or soil filling and then with gravel or rocks not only on flat surfaces, but also on slopes, it is easily conceivable that such a filling on the swollen intermediate bentonite layer, which acts like a slide, slips off, which is often observed in practice.
Thus, in principle, the sealing mats described in the above-given U.S. patents—as already indicated—serve only to pack the bentonite in flat form, such that the cover layer disconnects from the substrate layer upon the swelling of the bentonite and a continuous bentonite layer takes shape.
However, in reality such a bentonite layer can be produced more simply and inexpensively in situ in the manner described in the U.S. Pat. No. 4,344,722. Said patent provides a method and a system for waterproofing a desired substrate and further contemplates a waterproof and chemical-resistant product. The method comprises providing a length of flexible moisture-permeable thin, synthetic sheet material having desired characteristics, placing in contact with the substrate to be waterproofed a layer of the material, covering the layer of material with a centra
Heerten Georg
Johannssen Karsten
Muller Volkhard
Kasper Horst M.
Naue-Fasertechnik GmbH & Co. KG
Raimund Christopher
LandOfFree
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