Tampon including crosslinked cellulose fibers and improved synthesis processes for producing same

Abstract

A tampon pledget includes crosslinked cellulose fibers having microstructures treated to provide improved absorbency and higher wet strength. The fibers are treated with a crosslinking agent to provide at least one of a molecular weight between crosslinks of from about 10 to 200 and a degree of crystallinity of from about 25% to 75%. The crosslinking agent includes citric acid in 1% by weight. The crosslinking agent may further include sodium hypophosphite in 1% by weight. In another embodiment, the crosslinking agent may be a difunctional agent including a glyoxal or a glyoxal-derived resin. In still another embodiment, the crosslinking agent is a multifunctional agent including a cyclic urea, glyoxal, polyol condensate. The crosslinking agent is added in an amount from about 0.001% to 20% by weight based on a total weight of cellulose fibers to be treated and, preferably, in an amount of about 5% by weight.

What is claimed is: 
     
         1 . A method for forming crosslinked cellulose fibers, comprising
 selecting a cellulose raw material;   steeping the raw material in a sodium hydroxide immersion to provide alkali cellulose;   pressing the alkali cellulose;   shredding the pressed cellulose;   aging the shredded cellulose;   reacting the aged cellulose with carbon disulphide to form cellulose xanthate;   dissolving the cellulose xanthate to form viscose;   ripening the viscose;   filtering the ripened viscose to remove undissolved materials;   degassing the filtered viscose;   spinning the degassed viscose through a spinneret to form cellulose filaments;   drawing the filaments to lengthen the cellulose chains;   purifying the drawn filaments;   cutting the purified filaments to form cellulose fibers; and   post-crosslinking by at least one of chemical or hydrothermal treatment;   wherein for a dry crosslinking formation, the method includes adding a crosslinking agent to the pressing step, and for a wet crosslinking formation, the method includes adding the crosslinking agent to at least one of the dissolving and ripening steps.   
     
     
         2 . The method for forming of  claim 1 , wherein the crosslinking agent includes at least citric acid in one percent (1%) by weight based on the total weight of cellulose fibers. 
     
     
         3 . The method of forming of  claim 2 , wherein the crosslinking agent further includes at least sodium hypophosphite in one percent (1%) by weight based on the total weight of cellulose fibers. 
     
     
         4 . The method of forming of  claim 1 , wherein the crosslinking agent is comprised of a difunctional crosslinking agent. 
     
     
         5 . The method of forming of  claim 4 , wherein the difunctional crosslinking agent is comprised of at least one of glyoxal and a glyoxal-derived resin. 
     
     
         6 . The method of forming of  claim 1 , wherein the crosslinking agent is comprised of a multifunctional crosslinking agent. 
     
     
         7 . The method of forming of  claim 6 , wherein the multifunctional crosslinking agent is comprised of a cyclic urea, glyoxal, polyol condensate. 
     
     
         8 . The method of forming of  claim 1 , wherein the crosslinking agent is added in an amount from about a hundredth of one percent (0.001%) to about twenty percent (20%) by weight based on a total weight of cellulose fibers to be treated. 
     
     
         9 . The method of forming of  claim 1 , wherein the crosslinking agent is added in an amount of about five percent (5%) by weight based on the total weight of cellulose fibers. 
     
     
         10 . The method for forming of  claim 1 , further including expanding a duration of the drawing step to further lengthen cellulose chains and improve interchain hydrogen bonds to provide greater areas of crystallinity. 
     
     
         11 . The method for forming of  claim 1 , wherein said post-crosslinking is by hydrothermal treatment. 
     
     
         12 . The method for forming of  claim 11 , wherein said hydrothermal treatment is carried out at a temperature of about 90 to about 150 degrees Celsius. 
     
     
         13 . The method for forming of  claim 11 , wherein said hydrothermal treatment is carried out at a temperature of about 100 to about 125 degrees Celsius.