Low density paperboard sheet and tube incorporating the same

Abstract

The present invention provides a low-density paperboard sheet of at least one paperboard layer made from a stock solution that includes a proportion of standard wood flour or fine sawdust in addition to traditional cellulose fibers. The proportion of sawdust can range from 1% to 40% by weight. Advantageously the sawdust of the present invention does not require a costly refining or micronization operation in order to produce low-density, high yield paperboard layers. Additionally, the low-density layers of the present invention may be readily combined with other layers of varying densities in order to tailor the physical properties of the resulting multi-layer sheet to a given application.

1 . A paperboard sheet comprising: 
 at least one layer containing cellulose fibers and a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 1 and 40 percent wood sawdust by weight, wherein at least 95 percent of the sawdust by weight has a particle size greater than 350 micrometers and less then 3175 micrometers.    
     
     
         2 . A paperboard sheet as recited in  claim 1 , wherein said at least one layer contains a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 1 and 6 percent sawdust by weight.  
     
     
         3 . A paperboard sheet as recited in  claim 1 , wherein said at least one layer contains a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 10 and 20 percent sawdust by weight.  
     
     
         4 . A paperboard sheet as recited in  claim 1 , wherein said at least one layer contains a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 1 and 30 percent sawdust by weight.  
     
     
         5 . A multi-layer paperboard sheet comprising: 
 at least one relatively low-density paperboard layer containing cellulose fibers and a quantity of wood sawdust, wherein at least 95 percent of the sawdust by weight has a particle size greater than 350 micrometers and less then 3175 micrometers;    at least one relatively high-density layer containing cellulose fibers, wherein there is at least a 1% difference in density between the at least one relatively low-density layer and the at least one relatively high-density layer; and    wherein the at least one relatively low-density layer and the at least one relatively high density layer are joined together producing a multi-layer paperboard sheet, and wherein the resulting paperboard sheet contains between 1 and 40 percent wood sawdust by weight.    
     
     
         6 . A multi-layer paperboard sheet as recited in  claim 5 , wherein said at least one relatively low-density layer and said at least one relatively high-density layer combine to contain a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 1 and 6 percent sawdust by weight.  
     
     
         7 . A multi-layer paperboard sheet as recited in  claim 5 , wherein said at least one relatively low-density layer and said at least one relatively high-density layer combine to contain a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 10 and 20 percent sawdust by weight.  
     
     
         8 . A multi-layer paperboard sheet as recited in  claim 5 , wherein said at least one relatively low-density layer and said at least one relatively high-density layer combine to contain a sufficient quantity of wood sawdust such that the resulting paperboard sheet contains between 1 and 30 percent sawdust by weight.  
     
     
         9 . A multi-layer paperboard sheet as recited in  claim 5 , having at least two relatively low-density layers sandwiched between two relatively high-density layers.  
     
     
         10 . A multi-layer paperboard sheet as recited in  claim 5 , having at least one relatively high-density layer that is free of sawdust.  
     
     
         11 . A multi-layer paperboard sheet as recited in  claim 5 , having at least one relatively high-density layer that contains sawdust.  
     
     
         12 . A multi-layer paperboard sheet as recited in  claim 5 , having at least one relatively low-density layer that contains between 1 and 40 percent sawdust by weight.  
     
     
         13 . A multi-layer paperboard sheet as recited in  claim 5 , wherein the relatively low-density and the relatively high-density layers are placed in intimate contact, prior to drying, in order to cause bonding between fibers, thereby joining the layers and producing a multi-layer paperboard sheet.  
     
     
         14 . A multi-layer paperboard sheet as recited in  claim 5 , wherein the relatively low-density and relatively high-density layers are adhered together, thereby producing a multi-layer paperboard sheet.  
     
     
         15 . A paperboard tube comprised of a plurality of paperboard plies, wherein 
 at least one of the plies has at least one layer that contains cellulose fibers and a sufficient quantity of wood sawdust such that the resulting at least one paperboard ply contains between 1 and 40 percent wood sawdust by weight, wherein at least 95 percent of the sawdust by weight has a particle size greater than 350 micrometers and less then 3175 micrometers; and    wherein said plurality of paperboard plies are wound about an axis and adhered together to form a paperboard tube.    
     
     
         16 . A paperboard tube as recited in  claim 15 , wherein said at least one layer contains cellulose fibers and a sufficient quantity of wood sawdust such that the resulting at least one paperboard ply contains between 1 and 6 percent sawdust by weight.  
     
     
         17 . A paperboard tube as recited in  claim 15 , wherein said at least one layer contains cellulose fibers and a sufficient quantity of wood sawdust such that the resulting at least one paperboard ply contains between 10 and 20 percent sawdust by weight.  
     
     
         18 . A paperboard tube as recited in  claim 15 , wherein at said at least one layer contains cellulose fibers and a sufficient quantity of wood sawdust such that the resulting at least one paperboard ply contains between 1 and 30 percent sawdust by weight.  
     
     
         19 . A paperboard tube comprised of: 
 a paperboard ply having at least one layer containing cellulose fibers and a sufficient quantity of wood sawdust such that the resulting paperboard ply contains between 1 and 40 percent wood sawdust by weight, wherein at least 95 percent of the sawdust by weight has a particle size greater than 350 micrometers and less then 3175 micrometers; and    wherein the paperboard ply is wound about an axis and overlapped on itself and adhered together to form a low-density paperboard tube.    
     
     
         20 . A paperboard tube as recited in  claim 19 , wherein the at least one layer contains a sufficient quantity of wood sawdust such that the resulting paperboard ply contains between 1 and 6 percent sawdust by weight.  
     
     
         21 . A paperboard tube as recited in  claim 19 , wherein the at least one layer contains a sufficient quantity of wood sawdust such that the resulting paperboard ply contains between 10 and 20 percent sawdust by weight.  
     
     
         22 . A paperboard tube as recited in  claim 19 , wherein the at least one layer contains a sufficient quantity of wood sawdust such that the resulting paperboard ply contains between 1 and 30 percent sawdust by weight.