Fire-resistant material and method of manufacture

Abstract

The present invention provides a building material derived from straw, such as rice straw, that has significantly improved fire-resistance properties over traditional cellulose-based materials. In one embodiment, the invention provides a method of fabricating a board from milled rice straw. The milled rice straw is blended with a binder to form a mixture. The mixture is then formed into a mat with sufficient size to achieve a predetermined board thickness and density. The mat is then pressed into the board. In another embodiment, the present invention provides a fire resistant board that includes milled rice straw, a resin binder, and a fire retardant material such as an organic phosphate, zinc borate, aluminum trihydrate, sodium silicate, or even rice hulls.

1 . A method of fabricating a board from milled straw comprising the steps of: 
 blending the milled straw with a binder to form a mixture;    forming the mixture into a mat with sufficient size to achieve a predetermined board thickness and density; and    pressing and curing the mat into the board.    
   
   
       2 . The method as recited in  claim 1 , wherein the milled straw is rice straw.  
   
   
       3 . The method as recited in  claim 1 , further comprising the step of removing a portion of fines from the milled straw prior to blending.  
   
   
       4 . The method as recited in  claim 1 , further comprising the step of milling straw.  
   
   
       5 . The method as recited in  claim 1 , wherein the milled straw has an average longitudinal length of approximately 0.125 inches to 1.5 inches.  
   
   
       6 . The method as recited in  claim 1 , further comprising the step of controlling the moisture content of the milled straw from approximately 1% to 12% of the milled straw weight.  
   
   
       7 . The method as recited in  claim 6 , wherein the moisture content is controlled with an oven.  
   
   
       8 . The method as recited in  claim 1 , further comprising the step of blending the mixture with a fire retardant material comprising one or more of: organic phosphates, borates, sodium silicates, aluminum trihydrates, or rice hulls.  
   
   
       9 . The method as recited in  claim 8 , wherein the binder and the fire retardant material are added at a rate of approximately 2% to 20% of the milled straw weight on a dried basis.  
   
   
       10 . The method as recited in  claim 8 , wherein the milled straw weight is determined by a scale with a feedback control mechanism to regulate the rate of the binder and the fire retardant material.  
   
   
       11 . The method as recited in  claim 1 , wherein the blending is performed in a high-speed blender.  
   
   
       12 . The method as recited in  claim 1 , wherein the board is attached to one or more door skins.  
   
   
       13 . A fire resistant board comprising: 
 milled rice straw;    a resin binder; and    a fire retardant material comprising one or more of an organic phosphate, a borate, sodium silicate, aluminum trihydrate, or rice hulls.    
   
   
       14 . The board as recited in  claim 12 , wherein the milled rice straw has an average longitudinal length of about 0.125 inches to about 1.5 inches.  
   
   
       15 . The board as recited in  claim 12 , wherein the resin binder is an isocyanate resin.  
   
   
       16 . The board as recited in  claim 12 , wherein the resin binder comprises between about 2% and about 10% of the weight on an oven dry basis.  
   
   
       17 . The board as recited in  claim 12 , wherein the fire retardant material comprises between about 2% and about 20% of the weight on an oven dry basis.  
   
   
       18 . The board as recited in  claim 12 , wherein the board is attached to one or more door skins.  
   
   
       19 . The board as recited in  claim 12 , wherein the board is attached to a doorframe.  
   
   
       20 . A fire resistant door comprising: 
 an inner door core comprising milled rice straw fiber in a cured resin matrix; and    a doorframe comprising a fire-resistant material.    
   
   
       21 . The door as recited in  claim 20 , wherein the milled straw fiber has an average longitudinal length of approximately 0.125 inches to 1.5 inches.  
   
   
       22 . The door as recited in  claim 20 , wherein the door core further comprises a fire retardant material comprising one or more of: an organic phosphate, a borate, sodium silicate, aluminum trihydrate, or rice hulls.  
   
   
       23 . The door as recited in  claim 20 , further comprising one or more door skins.