Geogrid made from a coextruded multilayered polymer

Abstract

An integral geogrid includes a plurality of interconnected, oriented strands having an array of openings therein that is produced from a coextruded multilayer polymer sheet starting material. By virtue of the construction, the coextruded multilayer sheet components provide a crystalline synergistic effect during extrusion and orientation of the integral geogrid, resulting in enhanced material properties that provide performance benefits to use of the integral geogrid in soil geosynthetic reinforcement.

1 .- 28 . (canceled) 
     
     
         29 . An integral geogrid comprising a plurality of interconnected, oriented strands having an array of openings therein, the integral geogrid being produced from a multilayer polymer starting sheet having layers of different materials and formed in a single coextrusion. 
     
     
         30 . The integral geogrid according to  claim 29 , wherein the oriented strands have been uniaxially or biaxially stretched. 
     
     
         31 . The integral geogrid according to  claim 29 , wherein the coextruded multilayer polymer starting sheet includes a first layer, a second layer, and a third layer, with the first layer and the third layer being arranged on opposite planar surfaces of the second layer. 
     
     
         32 . The integral geogrid according to  claim 29 , wherein the coextruded multilayer polymer starting sheet has a thickness of from about 2 mm to about 12 mm. 
     
     
         33 . The integral geogrid according to  claim 31 , wherein the first layer has a thickness of from about 0.5 mm to about 4.5 mm, the second layer has a thickness of from about 1 mm to about 9 mm, and the third layer has a thickness of from about 0.5 mm to about 4.5 mm. 
     
     
         34 . The integral geogrid according to  claim 31 , wherein the first layer has a material of construction of a high molecular weight polyolefin, the second layer has a material of construction of a broad specification polymer, and the third layer has a material of construction of a high molecular weight polyolefin. 
     
     
         35 . The integral geogrid according to  claim 34 , wherein the high molecular weight polyolefin of the first layer is a polypropylene, the broad specification polymer of the second layer is a post-industrial polypropylene, and the high molecular weight polyolefin of the third layer is a polypropylene. 
     
     
         36 . The integral geogrid according to  claim 29 , wherein the plurality of interconnected, oriented strands includes transverse strands interconnected by substantially longitudinally oriented strands. 
     
     
         37 . The integral geogrid according to  claim 29 , wherein the integral geogrid is configured for structural or construction reinforcement purposes. 
     
     
         38 . A starting material for making an integral geogrid comprising a multilayer polymer starting sheet having layers of different materials and formed in a single coextrusion, and having holes or depressions therein that provide openings when the starting sheet is uniaxially or biaxially stretched. 
     
     
         39 . The starting material according to  claim 38 , wherein the coextruded multilayer polymer starting sheet includes a first layer, a second layer, and a third layer, with the first layer and the third layer being arranged on opposite planar surfaces of the second layer. 
     
     
         40 . The starting material according to  claim 38 , wherein the coextruded multilayer polymer starting sheet has an initial thickness of at least 2 mm. 
     
     
         41 . The starting material according to  claim 38 , wherein the coextruded multilayer polymer starting sheet has a stretched thickness of from about 0.2 mm to about 9 mm. 
     
     
         42 . The starting material according to  claim 38 , wherein the coextruded multilayer polymer starting sheet once stretched exhibits an increased flexural stiffness and torsional rigidity relative to the flexural stiffness and torsional rigidity of a non-coextruded sheet having a substantially same starting thickness. 
     
     
         43 . A soil construction comprising a mass of particulate material strengthened by embedding therein an integral geogrid as claimed in  claim 29 . 
     
     
         44 . A method of strengthening a mass of particulate material, comprising embedding in the mass of particulate material the integral geogrid as claimed in  claim 29 . 
     
     
         45 . A method of making an integral geogrid, comprising:
 providing a multilayer polymer starting sheet having layers of different materials and formed in a single coextrusion;   providing a patterned plurality of holes or depressions in the coextruded multilayer polymer starting sheet; and   orienting the coextruded multilayer polymer starting sheet having the patterned plurality of holes or depressions therein to provide a plurality of interconnected, oriented strands and to configure the holes or depressions as grid openings.   
     
     
         46 . The method according to  claim 45 , wherein the coextruded multilayer polymer starting sheet having the patterned plurality of holes or depressions therein is oriented by uniaxial or biaxial stretching. 
     
     
         47 . The method according to  claim 45 , wherein the coextruded multilayer polymer starting sheet includes a first layer, a second layer, and a third layer, with the first layer and the third layer being arranged on opposite planar surfaces of the second layer. 
     
     
         48 . The method according to  claim 45 , wherein the coextruded multilayer polymer starting sheet has an initial thickness of at least 2 mm. 
     
     
         49 . The method according to  claim 45 , wherein the first layer has a thickness of from about 0.5 mm to about 4.5 mm, the second layer has a thickness of from about 1 mm to about 9 mm, and the third layer has a thickness of from about 0.5 mm to about 4.5 mm. 
     
     
         50 . The method according to  claim 45 , wherein the first layer has a material of construction of a high molecular weight polyolefin, the second layer has a material of construction of a broad specification polymer, and the third layer has a material of construction of a high molecular weight polyolefin. 
     
     
         51 . A method of providing an integral geogrid construction, comprising:
 uniaxially or biaxially stretching a starting material that is a multilayer polymer starting sheet having layers of different materials and formed in a single coextrusion, and having a patterned plurality of holes or depressions therein, to provide an integral geogrid having a plurality of oriented strands and a plurality of grid openings; and   embedding the integral geogrid in a mass of particulate material.   
     
     
         52 . The integral geogrid according to  claim 29 , wherein the integral geogrid is a triaxial integral geogrid. 
     
     
         53 . The method according to  claim 45 , wherein the integral geogrid is a triaxial integral geogrid. 
     
     
         54 . The method according to  claim 45 , wherein the integral geogrid is a uniaxial integral geogrid. 
     
     
         55 . The method according to  claim 45 , wherein the integral geogrid is a biaxial integral geogrid. 
     
     
         56 . The method according to  claim 45 , wherein the integral geogrid includes a color identification layer.