Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,... – Repair – replacement – or improvement
Reexamination Certificate
2001-03-15
2003-08-05
Swann, J. J. (Department: 3677)
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
Repair, replacement, or improvement
C405S150200, C405S184100, C405S150100, C138S145000, C524S589000, C524S590000
Reexamination Certificate
active
06602025
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a process for lining a surface of a canal, ditch or pipe with a polyurethane/geofabric composite (As used herein, the term “geofabric” means a geotextile or a geogrid, or a combination of both). Specifically, the invention relates to a process for applying a non-sagging polyurethane composition to at least one broken, concave and/or angled surface of a ditch, canal and/or pipe and then contacting a geofabric with that surface in a manner such that the geofabric becomes substantially impregnated with the non-sagging polyurethane composition, which cures to form a polyurethane/geofabric composite. The invention further relates to a process for applying a non-sagging polyurethane composition to an overhead surface or a ceiling of a canal and/or pipe and then applying a geofabric in a manner such that the geofabric becomes impregnated with the non-sagging polyurethane composition which cures to form a polyurethane/geofabric composite. The present invention also relates to a ditch, pipe and/or canal lined with a polyurethane/geofabric composite wherein the integrity of the pipe, canal and/or ditch has been maintained with a non-sagging polyurethane/geofabric composite.
BACKGROUND OF THE INVENTION
In recent years, the management of natural resources has become important in many countries throughout the world. Efforts have been directed both toward the conservation of our resources and toward the elimination of pollution from our environment. Particular emphasis has been placed on waste leakage and water loss.
Losses in the distribution of water using unlined irrigation ditches are estimated at a minimum to be 25% and in some situations to be more than 50% depending upon the porosity of the ditch surface and the distance the water is being moved. In most rural areas, ditches are formed by excavating the soil to the desired depth and width. The water moves through the ditch in contact with the exposed natural surface. This can be sand, clay, rocks, etc. and, more commonly, mixtures thereof. The porosity will depend upon the proportions of the different components.
The loss of water in unlined irrigation ditches was at one time considered acceptable only because the supply of water exceeded demand. However, as civilization has developed and world population has increased, more water is required for both greater food production and for markedly increasing non-agriculture uses. In addition to greater domestic uses in sanitation, industry now employs large quantities of water in manufacturing and processing procedures.
This high level of consumption plus the very high cost of developing new water supplies has shifted attention to water conservation. Domestic appliances that use less water have been developed. Also, industry has installed recycling purification systems to reduce water consumption.
Although conservation efforts have reduced water consumption to a degree, water is still in relatively short supply, particularly in recent years with the severe droughts in the United States and other countries. Since the most cost effective conservation opportunities and readily accessible water supplies already have been developed, greater attention must be directed to improving the efficiency of water distribution systems.
Improvements in water distribution have been made. A limited number of ditches and canals have been lined with concrete and/or preformed concrete pipes. Concrete is durable and has a long life when properly used. However, concrete is expensive to place and finish and is damaged by unfavorable temperatures during curing. Also, concrete is subject to frost damage, cracking and heaving which results in leaks.
Processes for forming composite liners for canals and ditches and apparatus to perform such a processes are disclosed, for example, in U.S. Pat. Nos. 4,872,784; 4,955,759; 4,955,760; 5,049,006; 5,062,740; 5,421,677; 5,607,998; and 5,639,331.
U.S. Pat. No. 5,421,677 (“the '677 patent”) is directed to an improved process of forming a ditch liner. The process of the '677 patent discloses the use of a mixture comprising one or more polyisocyanates, a polyol mixture, one or more fillers, and a catalyst. The mixture of the '677 patent is dispensed on a geotextile, thereby forming a liquid polyurethane soaked geotextile composite. The liquid polyurethane soaked geotextile composite is then placed over the surface of an area to be lined and allowed to cure, thereby forming a polyurethane/geotextile composite.
Sometimes, however, the surface or surfaces of a pipe, ditch and/or canal to be lined are broken, concave, and/or sloped at an angle equal to or greater than 90°. Additionally, at times, water flow is directed through canals and/or pipes located underneath roadways. The area to be lined for such canals and/or pipes includes the overhead surfaces or ceiling of the canal and/or pipe. It is not feasible to use the composite disclosed in the '677 patent for such elevated surfaces because the disclosed composite is soaked with liquid polyurethane which cannot be applied and adhered to surfaces which are broken, concave, and/or at an angle equal to or greater than 45° relative to the “floor”. Nor can the composite as disclosed in the '677 patent be applied and adhered to overhead surfaces.
A non-sagging polyurethane composition would be specifically well suited for lining concave, broken and/or angled surfaces of a ditch, pipe and/or canal, as well as overhead surfaces of ceilings of canals and/or pipes because it can be applied to those surfaces as a bead which can subsequently be spread over substantially the entire surface using, for example, a roller or spatula. A geofabric can then be brought into contact with the applied non-sagging polyurethane composition. The non-sagging polyurethane composition would exhibit excellent adhesion to the surface of a ditch, pipe and/or canal as well as to the geofabric and, upon curing, form a polyurethane/geofabric composite, which would provide a watertight seal with the surface of a ditch, pipe and/or canal.
Various non-sagging polyurethane compositions are known in the art and are described in, for example, in U.S. Pat. Nos. 4,444,976; 4,552,934; 4,698,408; 4,728,710; 4,743,672; 4,954,199; 4,994,540; 5,059,672; 5,164,473; and 5,166,303. These patents disclose two-component polyurethanes basically consisting of a polyisocyanate or polyisocyanate prepolymer component and a curative component containing a polyol and a polyamine.
U.S. Pat. No. 4,444,976 (“the '976 patent”) discloses sag-resistant adhesive two-component compositions. These compositions require an isocyanate prepolymer, a low molecular weight polyol containing at least 2-5 hydroxyl groups and a secondary diamine having a molecular weight of up to about 325. The adhesive claimed in the '976 patent exhibits a gel time at 24° C. of at least two minutes. The relatively short gel time of the adhesive disclosed in the '976 patent makes it suitable for outdoor applications where gel times of more than 10 minutes are usually required.
U.S. Pat. No. 5,607,998 (“the '998 patent”) also discloses non-sagging polyurethane compositions. These compositions require a liquid polyisocyanate, a liquid isocyanate-reactive mixture which includes one or more hydroxyl group containing compounds, one or more organic compounds containing diamines, polyamines, amine terminated polyethers and mixtures thereof, with at least one of the organic compounds containing at least one aromatic amine group, and one or more low molecular weight diols or triols, and an inorganic filler mixture composed of glass flakes and talc. The addition of talc to glass flakes containing liquid polyurethane raw materials provides homogeneous, phase stable systems. The reaction mixture as described in the '998 patent forms a non-sagging polyurethane composition, which is sandable once it is fully cured. The use of two fillers, one being an extremely abrasive glass filler, is a disadvantage in applications where sa
Guether Ralf
Markusch Peter H.
Bayer Corporation
Mitchell Katherine
Swann J. J.
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