Treated kraft pulp compositions and methods of making the same

Abstract

Compositions including treated Kraft pulp, useful for making rayon fibers, having a lower degree of polymerization, a high R18, a low hemicellulose content, and high reactivity, are described. Methods of making the compositions are also described.

1 . A treated Kraft pulp, comprising:
 a hemicellulose content of 5% or more;   a R18 value of 88% or more; and   at least one reactivity value selected from:
 a standard reactivity of 3.5 mL or more, 
 a modified reactivity of 30 mL or more, 
 a filter value Kr of 10,000 or less, 
 a SEM fiber segment count of 11 or less per 100 μm2 of a filter when the pulp is subjected to a modified reactivity test, and 
 a crystallite cross-section of less than 20.6 nm2; 
   wherein the treated pulp has less than 8% by weight of cellulose II as determined by x-ray crystallography.   
     
     
         2 . The treated pulp of  claim 1 , wherein the hemicellulose content is greater than 7%. 
     
     
         3 . The treated pulp of  claim 1 , wherein the R18 value is from 88% to 92%. 
     
     
         4 . The treated pulp of  claim 1 , wherein the treated pulp further comprises one or more of a pentosan content of from 4.6% to 9%, a xylan content of 4 to 8%, and a mannan content of 3% to 8%. 
     
     
         5 . The treated pulp of  claim 1 , wherein the treated pulp comprises a standard reactivity of 5 mL or more. 
     
     
         6 . The treated pulp of  claim 1 , wherein the treated pulp comprises a modified reactivity of 50 mL or more. 
     
     
         7 . The treated pulp of  claim 1 , wherein the treated pulp comprises a filter value Kr of 8,000 or less. 
     
     
         8 . The treated pulp of  claim 1 , wherein the treated pulp further comprises a carboxyl content of less than 3.6 meq/100 g. 
     
     
         9 . The treated pulp of  claim 1 , wherein the treated pulp further has an ASTM degree of polymerization of from 600 to 900. 
     
     
         10 . The treated pulp of  claim 1 , wherein the treated pulp further has a copper number of from 0.3 to 1.2. 
     
     
         11 . The treated pulp of  claim 1 , wherein the treated pulp has 0% cellulose II as determined by x-ray crystallography. 
     
     
         12 . The treated pulp of  claim 1 , wherein the treated pulp has an ageing time of 50 hours or less to reach a target Cuox DP of 340. 
     
     
         13 . A pulp blend comprising:
 a treated pulp according to  claim 1 ;   a dissolving pulp having a R18 of greater than 92%; and   a total xylan and mannan content of 6% or more.   
     
     
         14 . The blend of  claim 13 , further comprising a surfactant. 
     
     
         15 . The blend of  claim 13 , wherein the blend comprises at least 20% by weight of the treated pulp. 
     
     
         16 . The blend of  claim 13 , wherein the blend further comprises a filter value Kr of 15,000 or less. 
     
     
         17 . The blend of  claim 13 , wherein the blend further comprises a gamma number of 45.1% or more. 
     
     
         18 . The blend of  claim 13 , wherein the blend has an ageing time of 50 hours or less to reach a target Cuox DP of 340. 
     
     
         19 . A rayon fiber formed from a pulp blend of  claim 13 . 
     
     
         20 . A method of making a treated pulp, the method comprising:
 a bleaching sequence that further comprises the following steps:
 exposing a pulp to an oxygen bleaching stage to provide a first delignified pulp; 
 exposing the first delignified pulp to a first chlorine dioxide bleaching stage to provide a second delignified pulp; 
 exposing the second delignified pulp to a lignin extraction stage to provide an extracted pulp; and 
 exposing the extracted pulp to a second chlorine dioxide bleaching stage to provide a treated pulp; and 
   at least one of an acid treatment stage and an enzyme treatment stage, each of the at least one of the acid treatment stage and the enzyme treatment stage occurring between the oxygen bleaching stage and the first chlorine dioxide bleaching stage, between the lignin extraction stage and the second chlorine dioxide bleaching stage, or after the second chlorine dioxide stage.