Method for processing straw pulp

Abstract

A method for processing straw pulp that includes caustic treatment is provided. The caustic treated straw pulp can be incorporated into a papermaking furnish to provide a paper product. The caustic treated pulp imparts strength to papers incorporating the pulp.

The embodiments of the invention in which an exclusive property or privilege is claimed defined as follows:  
     
         1 . A method for pulping straw comprising: 
 mixing straw chips with steam and water to form a mixture;    exposing the mixture to temperatures and pressures sufficient to significantly soften the straw chips to form straw pulp, lignins and hemicellulose when exposed to a rapid decrease in pressure;    passing the mixture through a press to separate a portion of lignins and hemicellulose from the straw pulp;    passing the straw pulp through a defiberizer to form fiberized straw pulp; and    treating the fiberized straw pulp with a caustic solution to provide caustic treated straw pulp.    
     
     
         2 . The method of    claim 1    wherein the straw chips are mixed with a caustic before the mixture of straw chips, steam and water is exposed to temperatures and pressures sufficient to significantly soften the straw chips to form straw pulp, lignins and hemicellulose in the mixture when exposed to a rapid decrease in pressure.  
     
     
         3 . The method of    claim 2    wherein the caustic is present in the mixture in about less than two percent (2%) by weight based upon the dry straw chips.  
     
     
         4 . The method of    claim 2    wherein the caustic is selected from the group consisting of sodium hydroxide, potassium hydroxide, and mixtures thereof.  
     
     
         5 . The method of    claim 1    wherein the mixture is exposed to temperatures and pressures sufficient to significantly softened the mixture when exposed to a rapid decrease in pressure for between about two and one half (2½) minutes to about eight (8) minutes.  
     
     
         6 . The method of    claim 1    wherein the straw chips are selected from the group consisting of ryegrass, wheat, a mixture of grain and cereal straws, and mixtures thereof.  
     
     
         7 . The method of    claim 1    wherein at least about seventy percent (70%) by weight of the straw chips are formed into straw pulp.  
     
     
         8 . The method of    claim 1    wherein the pressures sufficient to significantly soften the straw chips when exposed to a rapid decrease in pressure from between about 140 psig and about 200 psig to about atmospheric pressure.  
     
     
         9 . The method of    claim 1    wherein the straw chips are formed by chopping straw to form a mixture of straw chips, meal, ash and grit and screening said mixture to separate a substantial portion of the straw chips from the meal, ash and grit.  
     
     
         10 . The method of    claim 1    wherein the straw pulp has a Canadian Standard Freeness of between about 200 and about 700.  
     
     
         11 . The method of    claim 1    wherein treating the fiberized straw pulp with a caustic solution comprises soaking the pulp in a caustic solution.  
     
     
         12 . The method of clam  1  wherein the caustic solution is an aqueous solution comprising a caustic selected from the group consisting of sodium hydroxide, potassium hydroxide and mixtures thereof.  
     
     
         13 . The method of    claim 1    wherein the caustic solution comprises a caustic present in an amount from about 1 to about 5 percent by weight of the solution.  
     
     
         14 . The method of    claim 1    wherein the caustic solution comprises a caustic present in about 2 percent by weight of the solution.  
     
     
         15 . The method of    claim 11    wherein the straw pulp is soaked in the caustic solution for a time from about 0.5 to about 2.0 hours.  
     
     
         16 . The method of    claim 11    wherein the straw pulp is soaked in a 2 percent by weight sodium hydroxide in water for about 0.5 hour.  
     
     
         17 . The method of    claim 9    wherein the separated meal, ash, and grit is used as animal feed.  
     
     
         18 . The method of    claim 1    wherein passing the mixture through a press to separate a portion of lignins and hemicellulose from the straw pulp provides a usable byproduct comprising water, reacted lignins, and hemicellulose.  
     
     
         19 . The method of    claim 18    wherein the byproduct is mixed with meal, ash, and grit to form an animal feed.  
     
     
         20 . Animal feed comprising meal, ash, and grit separated from straw pulp according to the method of    claim 9   .  
     
     
         21 . The animal feed of    claim 20    further comprising the usable byproduct formed by the method of    claim 18   .  
     
     
         22 . Animal feed comprising the usable byproduct formed by the method of    claim 18   .  
     
     
         23 . Straw pulp produced by the method of    claim 1   .  
     
     
         24 . Straw pulp produced by the method of    claim 2   .  
     
     
         25 . A paper product comprising caustic treated straw pulp.  
     
     
         26 . The paper product of    claim 25    wherein the caustic treated straw pulp is formed by: 
 mixing straw chips with steam and water to form a mixture;  
 exposing the mixture to temperatures and pressures sufficient to significantly soften the straw chips to form straw pulp, lignins and hemicellulose when exposed to a rapid decrease in pressure;  
 passing the mixture through a press to separate a portion of lignins and hemicellulose from the straw pulp;  
 passing the straw pulp through a defiberizer to form fiberized straw pulp; and  
 treating the fiberized straw pulp with a caustic solution to provide caustic treated straw pulp.  
 
     
     
         27 . A method for forming a paper product comprising forming a papermaking furnish comprising caustic treated straw pulp and forming a paper product from the papermaking furnish.  
     
     
         28 . The method of    claim 27    wherein the caustic treated straw pulp is formed by: 
 mixing straw chips with steam and water to form a mixture;  
 exposing the mixture to temperatures and pressures sufficient to significantly soften the straw chips to form straw pulp, lignins and hemicellulose when exposed to a rapid decrease in pressure;  
 passing the mixture through a press to separate a portion of lignins and hemicellulose from the straw pulp;  
 passing the straw pulp through a defiberizer to form fiberized straw pulp; and  
 treating the fiberized straw pulp with a caustic solution to provide caustic treated straw pulp.  
 
     
     
         29 . A method for increasing the strength of a paper product comprising: 
 combining a papermaking furnish and caustic treated straw pulp to provide a straw pulp furnish; and    forming a paper product from the straw pulp furnish to provide a paper product having increased strength compared to a paper product formed the papermaking furnish.    
     
     
         30 . The method of    claim 29    wherein the caustic treated straw pulp is formed by: 
 mixing straw chips with steam and water to form a mixture;  
 exposing the mixture to temperatures and pressures sufficient to significantly soften the straw chips to form straw pulp, lignins and hemicellulose when exposed to a rapid decrease in pressure;  
 passing the mixture through a press to separate a portion of lignins and hemicellulose from the straw pulp;  
 passing the straw pulp through a defiberizer to form fiberized straw pulp; and  
 treating the fiberized straw pulp with a caustic solution to provide caustic treated straw pulp.