Method for preparing regenerated cellulose fiber by two-step coagulating bath process
The present invention relates to a non-toxic process and system for pilot-scale production of cellulose products, and particularly to a process and system for pilot-scale production of cellulose products by using aqueous sodium hydroxide/urea solution pre-colled to lower than −8° C., in which cellulose could dissolved rapidly. The said process and system can be used to produce fibers, films, chromatographic packings, or nonwovens of regenerated cellulose, as well as to produce a variety of high added-value products by adding other materials such as functional materials, nano-materials, etc.
1. A process for pilot-scale production of cellulose products, the process comprising:
(a) pre-cooling a mixed aqueous solution of sodium hydroxide and urea to a first temperature of −15° C. to −8° C.;
(b) placing the pre-cooled mixed aqueous solution at a second temperature of 0° C. to 20° C., and then adding a cellulose raw material which is thereby dissolved sufficiently under agitation to obtain a cellulose solution;
(c) filtering and deaerating the cellulose solution; and
(d) using a molding device for pilot-scale production to allow the filtered and deaerated cellulose solution to form a cellulose product, said molding device comprising a two-step coagulation bath spinning device comprised of a first coagulation bath and a second coagulation bath,
wherein said filtered and deaerated cellulose solution first enters said first coagulation bath for initial processing and then enters said second coagulation bath for further processing,
wherein said first coagulation bath is comprised of a mixed aqueous solution of H 2 SO 4 and Na 2 SO 4 , wherein the concentration of H 2 SO 4 is in a range of 5 wt % to 20 wt %, the concentration of Na 2 SO 4 is in a range of 5 wt % to 25 wt %, and the bath temperature is in a range of 10 to 15° C., and
wherein said second coagulation bath is comprised of an aqueous H 2 SO 4 solution, wherein the concentration of H 2 SO 4 is in a range of 3 wt % to 20 wt %, and the bath temperature is in a range of 0 to 60°.
2. The process according to claim 1 , wherein in the mixed aqueous solution, the concentration of sodium hydroxide is in a range of 5.0 wt % to 12.0 wt %, and wherein the concentration of urea is in a range of 8.0 wt % to 20.0 wt %.
3. The process according to claim 1 , wherein the said cellulose raw material is a cellulose pulp selected from the group consisting of cotton linter pulp, bagasse pulp, wood pulp and straw pulp.
4. The process according to claim 3 , wherein the said cellulose pulp has a viscosity-average molecular weight of below 1.1×10 5 .
5. The process according to claim 3 , wherein said cellulose pulp has a polymerization degree of below 700.
6. The process according to claim 3 , wherein said cellulose pulp has a polymerization degree of 250 to 650.
7. The process according to claim 1 , wherein after the cellulose raw material being added at the second temperature, the agitation is performed for 10 minutes or more.
8. The process according to claim 1 , wherein the concentration of the resulting cellulose solution is in a range of 3.0 wt % to 8.0 wt %.
9. The process according to claim 1 , wherein in the mixed aqueous solution, the concentration of sodium hydroxide is in a range of 6.0 wt % to 8.0 wt %, and wherein the concentration of urea is in a range of 10.0 wt % to 20.0 wt %.
10. The process according to claim 1 , wherein the said first temperature is in the range of −13° C. to −10° C.
11. The process according to claim 1 , wherein after the cellulose raw material being added at the second temperature, the agitation is performed for 15 minutes or more.
12. The process according to claim 1 , wherein the concentration of the resulting cellulose solution is in a range of 3.0 wt % to 7.0 wt %.
13. The process according to claim 1 , wherein the cellulose products include regenerated cellulose products including filaments, chopped fibers, films, chromatographic packings and/or nonwovens.
14. The process according to claim 1 , wherein the said first temperature is −12° C.
15. A process for pilot-scale production of cellulose products, the process comprising:
(a) pre-cooling a mixed aqueous solution of sodium hydroxide and urea to a first temperature;
(b) bringing the pre-cooled mixed aqueous solution to a second temperature that is higher than the first temperature;
(c) following (b), adding a cellulose raw material which is thereby dissolved sufficiently under agitation to obtain a cellulose solution;
(d) filtering and deaerating the cellulose solution; and
(e) using a molding device for pilot-scale production to allow the filtered and deaerated cellulose solution to form a cellulose product, said molding device comprising a two-step coagulation bath spinning device comprised of a first coagulation bath and a second coagulation bath, wherein said filtered and deaerated cellulose solution first enters said first coagulation bath for initial processing and then enters said second coagulation bath for further processing,
wherein said first coagulation bath is comprised of a mixed aqueous solution of H 2 SO 4 and Na 2 SO 4 , wherein the concentration of H 2 SO 4 is in a range of 5 wt % to 20 wt %, the concentration of Na 2 SO 4 is in a range of 5 wt % to 25 wt %, and the bath temperature is in a range of 10 to 15° C., and
wherein said second coagulation bath is comprised of an aqueous H 2 SO 4 solution, wherein the concentration of H 2 SO 4 is in a range of 3 wt % to 20 wt %, and the bath temperature is in a range of 0 to 60°.
16. The process according to claim 15 , wherein the second coagulation bath has a temperature greater than the temperature of the first coagulation bath.