Crossed-linked pulp and method of making same
View Patent ↗The invention provides a method for preparing cross-linked cellulosic fibers. A sheet of mercerized cellulosic fibers with a purity of at least 95% is treated with a solution containing a carboxylic acid cross-linking agent. The treated cellulosic fibrous material is dried and cured in sheet form to promote intrafiber cross-linking. Cross-linked fiber products produced are economic and possess good porosity, bulking characteristics, wet resiliency, absorption characteristics, low fines, low nits and low knots. The invention also includes blended cellulose compositions comprising a minor proportion of cross-linked mercerized cellulosic fibers and a major proportion of other cellulosic fibers. The invention further provides individualized, chemically cross-linked mercerized cellulosic fibers of high purity.
1. A method for preparing cross-linked cellulosic fibers in sheet form, the method comprising:
(a) applying a polymeric carboxylic acid cross-linking agent to a wet laid sheet of mercerized cellulosic fibers; and
(b) curing the cross-linking agent on said sheet of mercerized cellulosic fibers to form a sheet of cross-linked cellulosic fibers having substantial intrafiber cross-links without substantial interfiber cross-links and a Fiber Knot Ratio not greater than about 1.2.
2. The method of claim 1 , wherein the α-cellulose purity of the mercerized cellulosic fibers is at least 95%.
3. The method of claim 2 , wherein the Fiber Knot Ratio of said sheet is not greater than about 1.1.
4. The method of claim 1 , wherein said mercerized cellulosic fibers in said wet laid sheet are free of mechanical refining.
5. The method of claim 4 , wherein the polymeric carboxylic acid cross-linking agent comprises a homopolymer of maleic acid monomer, a copolymer of maleic acid monomer, a terpolymer of maleic acid monomer or a mixture thereof.
6. The method of claim 1 , wherein the polymeric carboxylic acid cross-linking agent comprises a homopolymer of maleic acid-monomer, a copolymer of maleic acid monomer, a terpolymer of maleic acid monomer or a mixture thereof.
7. The method of claim 5 , wherein the polymeric carboxylic acid cross-linking agent has an average molecular weight from about 400 to about 10000.
8. The method of claim 6 , wherein the polymeric carboxylic acid cross-linking agent has an average molecular weight from about 400 to about 10000.
9. The method of claim 7 , wherein the polymeric carboxylic acid cross-linking agent has a pH from about 2.5 to about 3.5.
10. The method of claim 8 , wherein the polymeric carboxylic acid cross-linking agent has a pH from about 2.5 to about 3.5.
11. The method of claim 1 , wherein the cross-linking agent comprises a C 2 –C 9 polycarboxylic acid.
12. The method of claim 3 , wherein the cross-linking agent comprises a C 2 –C 9 polycarboxylic acid.
13. The method of claim 1 , wherein said sheet of cross-linked cellulosic fibers has a Fines Ratio not greater than about 1.3.
14. The method of claim 4 , wherein said sheet of cross-linked cellulosic fibers has a Fines Ratio not greater than about 1.2.
15. A method of preparing a sheet of cross-linked cellulosic fibers having superior liquid acquisition and rewet properties, the method comprising:
(a) forming a wet laid sheet of mercerized cellulosic fiber;
(b) applying a polymeric carboxylic acid cross-linking agent to said sheet of mercerized cellulosic fibers to form a sheet impregnated with the cross-linking agent; and
(c) curing the cross-linking agent on said impregnated sheet of mercerized cellulosic fibers to form a sheet of cross-linked cellulosic fibers having substantial intrafiber cross-links without substantial interfiber cross-links and a Fiber Knot Ratio not greater than about 1.2.
16. The method of claim 15 , wherein the impregnated sheet produced in step (b) is dried prior to step (c).
17. The method of claim 16 , wherein said mercerized cellulosic fibers used to form said wet laid sheet are free of mechanical refining.
18. The method of claim 17 , wherein said sheet of cross-linked cellulosic fibers has a Fiber Knot Ratio not greater than about 1.1.