Composite structures for packaging articles and related methods

Abstract

The composite structure includes a fiber-containing layer, such as a fiberboard layer or other layer having fibers from natural and/or synthetic sources, and a mineral-containing layer covering the fiber-containing layer. The fiber-containing layer and mineral-containing layer can be shaped, sized and manufactured such that the composite structure formed therefrom is capable of being machined to form a storage article. The composite structure has advantages in that it can improve whiteness, opacity, ink adhesion, materials reduction, barrier properties, recyclability, and printability. The composite can reduce polymer mass requirements for heat seal, barrier, and fiber adhesion. Further improvements include economics, pliability, and flexibility that is increased over the pliability of the fiber-containing layer alone.

What is claimed is: 
     
         1 . A composite packaging structure, comprising:
 a fiber-containing layer; and   an outer layer bonded to the fiber-containing layer, the outer layer including mineral particles in a matrix of a polymer bonding agent;   wherein the outer layer comprises from about 20% to about 70% by weight of the mineral particles;   wherein the outer layer has a density from about 1.05 g/cm 3  to about 1.65 g/cm 3 , and a basis weight from about 4.5 lbs/3 msf to about 50 lbs/3 msf; and   wherein the polymer bonding agent of the outer layer has a basis weight from about 1 lbs/3 msf to about 20 lbs/3 msf.   
     
     
         2 . The composite packaging structure of  claim 1 , wherein the mineral particles are evenly dispersed in the polymer matrix. 
     
     
         3 . The composite packaging structure of  claim 1 , wherein the outer layer is extruded. 
     
     
         4 . The composite packaging structure of  claim 1 , wherein the outer layer has a basis weight from about 7 lbs/3 msf to about 21 lbs/3 msf, and the polymer bonding agent of the outer layer has a basis weight from about 2.45 lbs/3 msf to about 16.8 lbs/3 msf. 
     
     
         5 . The composite packaging structure of  claim 1 , wherein the mineral particles of the outer layer comprise calcium carbonate. 
     
     
         6 . The composite packaging structure of  claim 5 , wherein the polymer bonding agent of the outer layer comprises polypropylene. 
     
     
         7 . The composite packaging structure of  claim 6 , wherein the outer layer comprises about 40% by weight of the calcium carbonate particles. 
     
     
         8 . The composite packaging structure of  claim 1 , wherein the polymer bonding agent has an isotactic run length from about 1 to about 40. 
     
     
         9 . The composite packaging structure of  claim 1 , wherein the polymer bonding agent has a shear rate from about 1 to about 10,000 at temperatures from about 180° C. to about 410° C. 
     
     
         10 . The composite packaging structure of  claim 1 , wherein the outer layer provides hot tack operating ranges from about 25° C. to about 225° C. having from about 1.0 N/mm to about 6.0 N/mm seal strengths. 
     
     
         11 . The composite packaging structure of  claim 1 , wherein the polymer bonding agent comprises a polyethylene copolymer, and the outer layer provides hot tack operating ranges from about 80° C. to about 220° C. having from about 2.5 N/mm to about 15 N/mm seal strengths. 
     
     
         12 . The composite packaging structure of  claim 1 , wherein the outer layer is about 20% to about 40% mineralized, with a structure that is about 20% to about 60% amorphous and about 20% to about 55% crystalline. 
     
     
         13 . The composite packaging structure of  claim 12 , wherein the outer layer has a density from about 1.20 g/cm 3  to about 1.35 g/cm 3 . 
     
     
         14 . A method of making a container from a sheet of a composite packaging structure, the sheet including a fiber-containing layer and a mineral-containing layer, the method comprising:
 cutting the sheet into a desired shape;   folding the sheet to form a three-dimensional shape; and   heat sealing abutting surfaces of the container to secure the abutting surfaces to one another;   wherein the heat sealing is performed under the following conditions:
 a dwell time in the range from about 0.30 seconds to about 15 seconds; 
 a temperature range from about 115° C. to about 240° C.; and 
 a seal pressure at or below about 0.80 MPa. 
   
     
     
         15 . The method of  claim 14 , wherein the folding is performed manually. 
     
     
         16 . The method of  claim 14 , wherein the folding is performed by machine. 
     
     
         17 . The method of  claim 14 , wherein the three-dimensional shape comprises a box having a bottom wall, one or more side walls, and a lid portion. 
     
     
         18 . The method of  claim 14 , wherein the three-dimensional shape comprises a container liner. 
     
     
         19 . The method of  claim 14 , wherein the three-dimensional shape comprises an envelope. 
     
     
         20 . The method of  claim 14 , wherein peel strengths between the heat sealed abutting surfaces range from about 1 J/m 2  to about 45 J/m 2 .