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 oriented strands interconnected by junctions and having an array of openings therebetween,   said integral geogrid having at least coextruded first, second, and third layers of polymeric materials,   with the polymeric material of the first layer and of the third layer having a first molecular weight and each being from 25 to 34 weight % of a coextruded multilayer polymer starting sheet, and the polymeric material of the second layer having a second molecular weight different from the first molecular weight and being from 32 to 50 weight % of the starting sheet, and the second layer being positioned between the first layer and the third layer.   
     
     
         30 . The integral geogrid according to  claim 29 , wherein the first layer and the third layer of the integral geogrid are arranged on opposite planar surfaces of the second layer of the integral geogrid. 
     
     
         31 . The integral geogrid according to  claim 29 , wherein the first layer, the second layer, and the third layer are in contact both at the junctions and along the plurality of strands. 
     
     
         32 . The integral geogrid according to  claim 29 , wherein the coextruded multilayer polymer starting sheet has a thickness of from at least 2 mm to about 12 mm. 
     
     
         33 . The integral geogrid according to  claim 29 , wherein the first layer and the third layer of the coextruded multilayer polymer starting sheet each has a thickness of from about 0.5 mm to about 4.5 mm, and the second layer has a thickness of from about 1 mm to about 9 mm. 
     
     
         34 . The integral geogrid according to  claim 29 , wherein the polymeric material of the first layer and of the third layer is a virgin polypropylene, and the polymeric material of the second layer is a post-industrial or post-consumer polypropylene. 
     
     
         35 . The integral geogrid according to  claim 29 , wherein the plurality of oriented strands includes transverse strands, interconnected via the junctions, with substantially longitudinally oriented strands. 
     
     
         36 . The integral geogrid according to  claim 29 , wherein the coextruded multilayer polymer starting sheet has an oriented thickness of from about 0.2 mm to about 9 mm. 
     
     
         37 . The integral geogrid according to  claim 29 , wherein the integral geogrid exhibits an increased flexural stiffness and torsional rigidity relative to the flexural stiffness and torsional rigidity of a non-coextruded geogrid having a substantially same starting thickness. 
     
     
         38 . The integral geogrid according to  claim 29 , wherein the integral geogrid is a uniaxial integral geogrid. 
     
     
         39 . The integral geogrid according to  claim 29 , wherein the integral geogrid is a biaxial integral geogrid. 
     
     
         40 . The integral geogrid according to  claim 29 , wherein the integral geogrid is a triaxial integral geogrid. 
     
     
         41 . The integral geogrid according to  claim 29 , wherein the second layer has a thickness that is greater than a thickness of either of the first layer and the third layer. 
     
     
         42 . The integral geogrid according to  claim 29 , wherein the plurality of oriented strands have an aspect ratio of greater than 1.0. 
     
     
         43 . The integral geogrid according to  claim 29 , wherein the integral geogrid is configured for structural or construction reinforcement purposes. 
     
     
         44 . A starting material for making an integral geogrid, said starting material comprising:
 a coextruded multilayer polymer starting sheet having at least coextruded first, second, and third layers of polymeric materials, and having holes or depressions therein that provide openings when the starting sheet is uniaxially or biaxially stretched,   the polymeric material of the first layer and of the third layer having a first molecular weight and each being from 25 to 34 weight % of the starting sheet, and the polymeric material of the second layer having a second molecular weight different from the first molecular weight and being from 32 to 50 weight % of the starting sheet, and   the second layer being positioned between the first layer and the third layer.   
     
     
         45 . The starting material according to  claim 44 , wherein the first layer and the third layer are arranged on opposite planar surfaces of the second layer. 
     
     
         46 . The starting material according to  claim 44 , wherein the coextruded multilayer polymer starting sheet has an initial thickness of at least 2 mm. 
     
     
         47 . An integral geogrid soil construction, comprising:
 a mass of particulate material strengthened by embedding therein an integral geogrid,   the integral geogrid including a plurality of oriented strands interconnected by junctions and having an array of openings therebetween, and having at least coextruded first, second, and third layers of polymeric materials,   with the polymeric material of the first layer and of the third layer having a first molecular weight and each being from 25 to 34 weight % of a coextruded multilayer polymer starting sheet, and the polymeric material of the second layer having a second molecular weight different from the first molecular weight and being from 32 to 50 weight % of the starting sheet, and the second layer being positioned between the first layer and the third layer.