TAMPON INCLUDING CROSSLINKED CELLULOSE FIBERS AND IMPROVED SYNTHESIS PROCESSES FOR PRODUCING SAME
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.
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.