Low coarseness southern softwood pulps

Abstract

Pulp sheets produced from Southern pine fibers are disclosed. Embodiments in which the fibers have a fiber length to coarseness ratio equal to or greater than 0.11, with fiber length (LWAFL) in mm and coarseness in mg/100 m, are found to impart stiffness properties to tissue grade handsheets made therefrom comparable to those achieved using of standard NBSK. Embodiments in which the fibers have a low coarseness (of from about 16 to about 20 mg/100 m, at a fiber length (LWAFL) of from about 1.6 to about 3.0 mm) are found to impart wicking properties to absorbent structures made therefrom that are improved relative to those achieved using standard high coarseness SBSK.

1 . A pulp sheet comprising Southern pine fibers that have a fiber length to coarseness ratio from about 0.125 to 0.142, wherein fiber length (LWAFL) is in mm, and coarseness is in mg/100 m, wherein the length to coarseness ratio of the fibers is at a coarseness of from about 19 to about 20 mg/100 m and a fiber length of from about 2.5 to about 2.7 mm, and wherein the content of said Southern pine fibers is at least 20%. 
     
     
         2 . The pulp sheet of  claim 1 , wherein the length to coarseness ratio of the fibers is about 0.13. 
     
     
         3 . The pulp sheet of  claim 1 , wherein the length to coarseness ratio of the fibers is at one or more of
 a coarseness of from about 16 to about 25 mg/100 m, and   a fiber length of from about 1.6 to about 3.0 mm.   
     
     
         4 - 6 . (canceled) 
     
     
         7 . The pulp sheet of  claim 1 , wherein the fibers are bleached Southern pine pulp fibers. 
     
     
         8 . The pulp sheet of  claim 1 , wherein the fibers are kraft Southern pine pulp fibers. 
     
     
         9 . The pulp sheet of  claim 1 , wherein the fibers are SBSK pulp fibers. 
     
     
         10 . The pulp sheet of  claim 1 , wherein the fibers are one or more of slash pine ( Pinus elliottii ), longleaf pine ( Pinus palustris ), shortleaf pine ( Pinus echinata ), loblolly pine ( Pinus taeda ), Virginia pine ( Pinus virginiana ), eastern white pine ( Pinus strobus ), pitch pine ( Pinus rigida ), sand pine ( Pinus clausa ), pond pine ( Pinus serotina ), and Table Mountain pine ( Pinus pungens ) fibers. 
     
     
         11 . The pulp sheet of  claim 10 , wherein a majority of the fibers are loblolly pine ( Pinus taeda ) fibers. 
     
     
         12 . The pulp sheet of  claim 1 , having a basis weight from about 500 to about 900 gsm. 
     
     
         13 . The pulp sheet of  claim 1 , having a density of from about 0.5 to about 0.9 g/cc. 
     
     
         14 . The pulp sheet of  claim 1 , in bale or roll form. 
     
     
         15 . The pulp sheet of  claim 1 , wherein a TAPPI T-204 tissue grade handsheet having a basis weight of 20 gsm produced therefrom and including eucalyptus pulp in a 1:2 ratio of said Southern pine fibers to eucalyptus pulp fibers has a tensile stiffness at a normalized tensile index that is equal to or less than that of a TAPPI T-204 tissue grade handsheet produced from NBSK and eucalyptus pulp in a 1:2 ratio of NBSK fibers to eucalyptus pulp fibers. 
     
     
         16 . A pulp sheet comprising Southern pine fibers that have a coarseness of from about 16 to about 20 mg/100 m and a fiber length (LWAFL) of from about 1.6 to about 3.0 mm, wherein a composite absorbent core having a basis weight of 500-550 gsm and a density of 0.18-0.22 g/cc produced therefrom and including 30% of said Southern pine fibers and 70% SAP has an inclined plane wicking rate of at least 130 gm/500 s. 
     
     
         17 . (canceled) 
     
     
         18 . The pulp sheet of  claim 16 , comprising a blend of said Southern pine fibers with Northern bleached softwood pulp fibers, with said Northern bleached softwood pulp fibers having a coarseness of from about 13 to about 18 mg/100 m and a fiber length (LWAFL) of from about 2.0 to about 2.5 mm;
 wherein the pulp sheet is in roll form with a basis weight of from about 500 to about 900 gsm and a density of from about 0.4 to about 0.8 g/cc.   
     
     
         19 . The pulp sheet of  claim 18 , wherein the blend consists of up to 25% of said Northern bleached softwood pulp fibers, with the balance being said Southern pine fibers. 
     
     
         20 . (canceled) 
     
     
         21 . The pulp sheet of  claim 16 , wherein said Southern pine fibers have a coarseness of from about 19 to about 20 mg/100 m and a fiber length (LWAFL) of from about 2.5 to about 2.7 mm.