Hydraulic barrier

#The present invention is directed to a method of manufacturing a polymer/clay slurry-filled sheet material, and particularly to a continuous method of manufacturing the polymer/clay-filled sheet material including a step of embedding a high viscosity aqueous polymerization solution, containing a polymerizable monomer and a water swellable clay, in the form of a slurry, into a liquid-absorbent or liquid adsorbent substrate that contains a polymerization catalyst and/or a polymerization initiator for subsequent polymerization of the monomer, without premature polymerization of the monomer. In the preferred embodiment, the monomer is polymerized, in-situ, at a temperature sufficient to vaporize the slurry water, e.g., at least 100° C. at atmospheric pressure.

#Published PCT application WO 00/72958 A1 ('958) describes a porous substrate, such as a geotextile liner, containing a polymer, such as polyacrylamide and/or a polyacrylic acid, that is partially neutralized (e.g., polyacrylic acid and sodium polyacrylate), and preferably also clay. The polymer is formed for the most part, in situ, while the monomer is embedded into the geotextile, together with the clay, to provide a hydraulic barrier that has excellent, low hydraulic conductivity and has a significantly lower weight of active barrier material than the weight of active barrier material contained in geosynthetic liners in existence at the time of the '958 invention. Further, as disclosed in the '958 publication, there may be some synergy in the combination of a polymerizable monomer, such as acrylic acid, and clay by virtue of intercalation of the monomer between the clay platelets to form an intercalate during the mixing of the monomer and clay to form a slurry for embedment into a geotextile and/or during the embedding of the slurry into the geotextile.

#It has been found that the manufacture of an article, in accordance with WO 00/72958 results in a product that contains a substantial percentage of water, making it more difficult to apply the product over a surface to be protected against water penetration, and making shipping of the product more expensive, thereby detracting from the low weight advantage and cost savings attributed to having less active barrier material in the geotextile. Further, in accordance with WO 00/72958 A1, an aqueous polymerization solution, a polymerization catalyst, and a cross-linker are premixed and embedded into the porous substrate simultaneously during continuous manufacture. It has been found that only small batches of the polymerizable monomer can be prepared or the polymerizable monomer will begin to polymerize prior to embedding the polymerization solution into the porous substrate resulting in lower hydraulic barrier properties and decreased retention of solids.

#The FIGURE is a schematic flow diagram of the preferred method of manufacturing a polymer-loaded sheet material.

#The present invention may be understood more readily by reference to the following detailed description of the invention and the examples provided therein. It is to be understood that this invention is not limited to the specific components, articles, processes and/or conditions described, as these may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

#Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment.

#Referring to the drawing, the invention relates to a hydraulic barrier material 10. In one embodiment, the hydraulic barrier material 10 is an interlocking matrix containing a water-absorbent organic polymer and a water-absorbent clay interlocked to and within a liquid monomer-absorbent or liquid monomer-adsorbent substrate, wherein the polymer is formed (polymerized from one or more monomers), in-situ, while in contact with the substrate during manufacture of the hydraulic barrier to interlock the polymer and clay to the substrate. In the preferred embodiment, the hydraulic barrier material 10 is an interlocking matrix of organic polymer molecules, polymer-intercalated clay, polymer-intercalated clay tactoids, exfoliated clay platelets and fibers of a fibrous substrate 12, preferably a non-woven geotextile. The preferred organic polymer is a water-absorbent polymer preferably comprising a mixture of an alkali metal salt of polyacrylic acid (50-90 mole percent—corresponding to 50-90 mole percent neutralization of acrylic acid) and polyacrylic acid (10-50 mole percent). It has been found that the interlocking of the organic polymer, polymer-intercalated clay tactoids, and clay platelets to the substrate 12 provides a hydraulic barrier material 10 having a relatively low permeability to water while containing a relatively low loading of organic polymer.