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 - 20 . (canceled) 
     
     
         21 . A pulp sheet comprising Southern pine fibers, wherein a TAPPI T-205 tissue-grade handsheet having a target basis weight of 20 grams per square meter (gsm) produced therefrom exhibits a tensile stiffness according to TAPPI T-494, normalized to a tensile index of 1, of 0.040 or below. 
     
     
         22 . The pulp sheet of  claim 21 , wherein the Southern pine fibers have a fiber length to coarseness ratio of at least 0.11, wherein fiber length (LWAFL) is in mm, and coarseness is in mg/100 m. 
     
     
         23 . The pulp sheet of  claim 22 , wherein the length to coarseness ratio of the Southern pine 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.   
     
     
         24 . The pulp sheet of  claim 22 , 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. 
     
     
         25 . The pulp sheet of  claim 22 , wherein the Southern pine fibers have a fiber length to coarseness ratio of at least 0.12. 
     
     
         26 . The pulp sheet of  claim 21 , wherein the Southern pine fibers are refined. 
     
     
         27 . The pulp sheet of  claim 26 , wherein the TAPPI T-205 tissue grade handsheet exhibits a tensile stiffness according to TAPPI T-494, normalized to a tensile index of 1, of 0.037 or below. 
     
     
         28 . The pulp sheet of  claim 21 , wherein the content of Southern pine fibers is at least 20%. 
     
     
         29 . The pulp sheet of  claim 28 , also comprising hardwood fibers. 
     
     
         30 . The pulp sheet of  claim 29 , wherein the hardwood fibers comprise eucalyptus fibers. 
     
     
         31 . The pulp sheet of  claim 30 , comprising a blend of Southern pine fibers and eucalyptus fibers in a 1:2 ratio. 
     
     
         32 . The pulp sheet of  claim 28 , wherein the content of Southern pine fibers is at least 30%. 
     
     
         33 . The pulp sheet of  claim 21 , wherein the Southern pine fibers are bleached Southern pine pulp fibers. 
     
     
         34 . The pulp sheet of  claim 21 , wherein the Southern pine fibers are kraft Southern pine pulp fibers. 
     
     
         35 . The pulp sheet of  claim 21 , wherein the Southern pine fibers are SBSK pulp fibers. 
     
     
         36 . The pulp sheet of  claim 21 , wherein the Southern pine 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. 
     
     
         37 . The pulp sheet of  claim 21 , wherein a majority of the Southern pine fibers are loblolly pine ( Pinus taeda ) fibers. 
     
     
         38 . A composite pad comprising a matrix of pulp fibers and superabsorbent particles (SAP) distributed throughout the matrix of pulp fibers, wherein SAP constitutes at least 50% of the weight of the composite pad, and wherein Southern pine fibers having a coarseness of from about 16 to about 20 mg/100 m constitute at least 75% of the weight of the pulp fibers. 
     
     
         39 . The composite pad of  claim 38 , wherein the Southern pine fibers have a fiber length of from about 1.6 to about 2.7 mm. 
     
     
         40 . An absorbent core that incorporates the composite pad of  claim 38 .