Crosslinked kraft pulp compositions and method

Abstract

Pulps in accordance with certain embodiments include crosslinked cellulose fibers and have high brightness, reactivity, and intrinsic viscosity, and therefore can be well suited for use as a precursor in the production of low-color, high-viscosity cellulose derivatives. A method in accordance with the present technology includes forming a pulp from a cellulosic feedstock, bleaching the pulp, crosslinking cellulose fibers within the pulp while the pulp has a high consistency, and drying the pulp. Crosslinking the cellulose fibers can include exposing the fibers to a glycidyl ether crosslinker having two or more glycidyl groups and a molecular weight per epoxide within a range from 140 to 175. Another method in accordance with the present technology includes providing an aqueous suspension of pulp that includes chemical wood pulp fibers that were previously bleached and dried, crosslinking the fibers with such a glycidal ether crosslinker, and drying the pulp.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . Pulp, comprising:
 crosslinked cellulose fibers,   wherein the pulp has:
 a resultant carboxymethyl cellulose (CMC) viscosity greater than or equal to 60 centipoise (cP), 
 a brightness greater than or equal to 75%, and 
 a water retention value (WRV) greater than or equal to 1.0 g/g. 
   
     
     
         2 . The pulp of  claim 1 , wherein the pulp has:
 a resultant CMC viscosity greater than or equal to 60 cP,   a brightness greater than or equal to 75%, and   a WRV greater than or equal to 1.1 g/g.   
     
     
         3 . The pulp of  claim 1 , wherein the pulp is a kraft pulp. 
     
     
         4 . The pulp of  claim 1 , wherein the pulp is bleached. 
     
     
         5 . The pulp of  claim 1 , wherein the pulp is at least partially insoluble in cupriethylenediamine (cuen). 
     
     
         6 . The pulp of  claim 1 , further comprising less than or equal to 0.09% lignin by oven-dried weight of the crosslinked cellulose fibers. 
     
     
         7 . The pulp of  claim 1 , further comprising greater than or equal to 10% hemicellulose by oven-dried weight of the crosslinked cellulose fibers. 
     
     
         8 . The pulp of  claim 1 , having a resultant CMC viscosity greater than or equal to 90 cP. 
     
     
         9 . The pulp of  claim 1 , having a resultant CMC color less than or equal to 5. 
     
     
         10 . The pulp of  claim 1 , having a resultant CMC turbidity less than or equal to 25 Nephelometric Turbidity Units (NTU). 
     
     
         11 . The pulp of  claim 1 , having a WRV less than or equal to 1.4 g/g. 
     
     
         12 . The pulp of  claim 1 , having an R18 value greater than or equal to 88. 
     
     
         13 . The pulp of  claim 12  having an R18 value less than or equal to 92. 
     
     
         14 . The pulp of  claim 1 , having a falling ball viscosity greater than or equal to 200 cP. 
     
     
         15 . The pulp of  claim 1  having no cellulose-II as determined by x-ray crystallography. 
     
     
         16 . The pulp of  claim 1 , having a crystallinity index less than or equal to 80%. 
     
     
         17 . The pulp of  claim 16  having a crystallinity index less than or equal to 75%. 
     
     
         18 . The pulp of  claim 1  having a brightness greater than or equal to 80%. 
     
     
         19 . The pulp of  claim 18  having a brightness less than or equal to 88.5%. 
     
     
         20 . The pulp of  claim 1 , having a basis weight of greater than or equal to 500 g/m 2 . 
     
     
         21 . The pulp of  claim 20  having a basis weight less than or equal to 1200 g/m 2 . 
     
     
         22 . The pulp of  claim 1  having a density greater than or equal to 0.20 g/cm 3 . 
     
     
         23 . The pulp of  claim 1  having a freeness greater than or equal to 700 mL. 
     
     
         24 . The pulp of  claim 1  having an AOX content less than or equal to 200 ppm. 
     
     
         25 . The pulp of  claim 3  having an AOX content less than or equal to 100 ppm. 
     
     
         26 . The pulp of  claim 3  having an AOX content less than or equal to 50 ppm. 
     
     
         27 . The pulp of  claim 3  having an AOX content less than or equal to 20 ppm. 
     
     
         28 . The pulp of  claim 1 , wherein the crosslinked cellulose fibers include crosslinks derived from a glycidyl ether crosslinker having two or more glycidyl groups. 
     
     
         29 . The pulp of  claim 1 , wherein the crosslinked cellulose fibers include crosslinks derived from a glycidyl ether crosslinker having a weight average molecular weight within a range from 174 to 500. 
     
     
         30 . The pulp of  claim 1 , wherein the crosslinked cellulose fibers include crosslinks derived from a glycidyl ether crosslinker having a weight per epoxide within a range from 140 to 175. 
     
     
         31 . The pulp of  claim 1 , wherein the crosslinked cellulose fibers include crosslinks derived from a glycidyl ether crosslinker having a first glycidyl group, a second glycidyl group, and either three or four linear chain carbon atoms between the first and second glycidyl groups. 
     
     
         32 . The pulp of  claim 1 , wherein the crosslinked cellulose fibers are derived from wood. 
     
     
         33 . A pulp comprising crosslinked cellulose fibers, the pulp having an R18 value in a range of 90% to 92.8%; a kink index in a range of 2.6 mm −1  to 3.2 mm −1 ; and a curl index in a range of 0.261 to 0.341. 
     
     
         34 . The pulp of  claim 33 , wherein the pulp has a WRV in a range of 1.0 g/g to 1.5 g/g. 
     
     
         35 . The pulp of  claim 33 , wherein the pulp has a resultant CMC viscosity greater than or equal to 60 cP; a brightness greater than or equal to 75%; and a WRV greater than or equal to 1.1 g/g. 
     
     
         36 . The pulp of  claim 33 , wherein the pulp is at least partially insoluble in cuen. 
     
     
         37 . The pulp of  claim 33 , further comprising less than or equal to 0.09% lignin by oven-dried weight of the crosslinked cellulose fibers. 
     
     
         38 . The pulp of  claim 33 , wherein the pulp has a resultant CMC viscosity in a range of 60 cP to about 500 cP. 
     
     
         39 . The pulp of  claim 33 , wherein the pulp has a resultant CMC color less than or equal to 5. 
     
     
         40 . The pulp of  claim 33 , wherein the pulp has a resultant CMC turbidity less than or equal to 25 NTU. 
     
     
         41 . The pulp of  claim 33 , wherein the crosslinked cellulose fibers include crosslinks derived from a glycidyl ether crosslinker having two or more glycidyl groups. 
     
     
         42 . The pulp of  claim 33 , wherein the pulp has a hemicellulose content in a range of 6 wt. % to 20 wt. % 
     
     
         43 . A pulp comprising crosslinked cellulose, the pulp having a hemicellulose content in a range of 6 wt. % to 20 wt. %; a WRV in a range of 1.0 g/g to 1.5 g/g; and a kink index in a range of 2.6 mm −1  to 3.2 mm −1 . 
     
     
         44 . The pulp of  claim 43 , wherein the pulp has an R18 value in a range of 90% to 92.8%. 
     
     
         45 . The pulp of  claim 43 , wherein the pulp has a curl index in a range of 0.261 to 0.341. 
     
     
         46 . The pulp of  claim 43 , wherein the pulp has a resultant CMC viscosity greater than or equal to 60 cP; a brightness greater than or equal to 75%; and a WRV greater than or equal to 1.1 g/g. 
     
     
         47 . The pulp of  claim 43 , wherein the pulp is at least partially insoluble in cuen. 
     
     
         48 . The pulp of  claim 43 , wherein the pulp includes less than or equal to 0.09% lignin by oven-dried weight of the crosslinked cellulose fibers. 
     
     
         49 . The pulp of  claim 43 , wherein the pulp has a resultant CMC viscosity in a range of 60 cP to about 500 cP. 
     
     
         50 . The pulp of  claim 43 , wherein the pulp has a resultant CMC color less than or equal to 5. 
     
     
         51 . The pulp of  claim 43 , wherein the pulp has a resultant CMC turbidity less than or equal to 25 NTU. 
     
     
         52 . The pulp of  claim 43 , wherein the crosslinked cellulose fibers include crosslinks derived from a glycidyl ether crosslinker having two or more glycidyl groups. 
     
     
         53 . A pulp blend comprising:
 a first pulp comprising crosslinked cellulose fibers, wherein the first pulp has a resultant CMC viscosity greater than or equal to 60 cP, a brightness greater than or equal to 75%, and a WRV greater than or equal to 1.1 g/g; and   a second pulp.   
     
     
         54 . The pulp blend of  claim 53 , wherein the first pulp is partially soluble in cuen. 
     
     
         55 . The pulp blend of  claim 53 , wherein the first pulp is insoluble in cuen. 
     
     
         56 . The pulp blend of  claim 53 , wherein the second pulp is a dissolving-grade pulp. 
     
     
         57 . The pulp blend of  claim 56 , wherein the dissolving-grade pulp has a cellulose content of greater than 90% by oven dried weight. 
     
     
         58 . The pulp blend of  claim 53 , wherein the first pulp makes up greater than 20% by cellulose oven-dried weight of the pulp blend. 
     
     
         59 . The pulp blend of  claim 53 , wherein the first pulp has a hemicellulose content in a range of 6 wt. % to 20 wt %; a WRV in a range of 1.0 g/g to 1.5 g/g; and a kink index in a range of 2.6 mm −1  to 3.2 mm −1 . 
     
     
         60 . The pulp blend of  claim 53 , wherein the first pulp has an R18 value in a range of 90% to 92.8%; a kink index in a range of 2.6 mm −1  to 3.2 mm −1 ; and a curl index in a range of 0.261 to 0.341. 
     
     
         61 . A crosslinked CMC having a 0.5 wt. % solution viscosity in a range of 60 cP to 500 cP. 
     
     
         62 . The crosslinked CMC of  claim 61 , wherein the crosslinked CMC has a color less than or equal to 5. 
     
     
         63 . The crosslinked CMC of  claim 61 , wherein the crosslinked CMC has a turbidity less than or equal to 25 NTU. 
     
     
         64 . The crosslinked CMC of  claim 61 , wherein the crosslinked CMC is made from pulp according to  claim 1 . 
     
     
         65 . The crosslinked CMC of  claim 61 , wherein the crosslinked CMC is made from pulp according to  claim 10 . 
     
     
         66 . The crosslinked CMC of  claim 61 , wherein the crosslinked CMC includes crosslinks derived from a glycidyl ether crosslinker having two or more glycidyl groups. 
     
     
         67 . A CMC fiber having a 0.5 wt. % solution viscosity in a range of 60 cP to 500 cP. 
     
     
         68 . The CMC fiber of  claim 67 , wherein the CMC fiber has a degree of substitution in a range of 1 to 3. 
     
     
         69 . The CMC fiber of  claim 67 , wherein the CMC fiber is a crosslinked CMC fiber including crosslinks derived from a glycidyl ether crosslinker having two or more glycidyl groups.