METHOD OF MAKING CELLULOSE ESTER POLYMER AND PRE-TREATING CELLULOSE FOR THE MANUFACTURE OF CELLULOSE ESTER POLYMER
A method of making cellulose ester polymer comprises the steps of: pre-treating a cellulose source; esterifying the pretreated cellulose source to form a cellulose ester; and optionally hydrolyzing the cellulose ester. The pretreatment step further comprises: mixing, in a first stage, the cellulose source with a first solution of a weak acid and water, whereby the cellulose source being suspended in the first solution; de-liquefying the first stage suspension; mixing, in a second stage, the de-liquefied mass with a second solution of weak acid and water, whereby the mass being suspended in the second solution; and de-liquefying the second stage suspension.
1 . A method of making cellulose ester polymer comprising the steps of:
pre-treating a cellulose source by
mixing, in a first stage, the cellulose source with a first solution of a weak acid and water, whereby the cellulose source being suspended in the first solution,
de-liquefying the first stage suspension, mixing, in a second stage, the de-liquefied mass with a second solution of weak acid and water, whereby the mass being suspended in the second solution, and
de-liquefying the second stage suspension; and
esterifying the pretreated cellulose source to form a cellulose ester.
2 . The method of claim 1 further comprising the step of hydrolyzing the cellulose ester.
3 . The method of claim 1 wherein the first solution comprising the weak acid being in excess of the water.
4 . The method of claim 1 wherein the second solution containing more weak acid than the first solution.
5 . The method of claim 1 wherein the cellulose source being selected from the group consisting of: acetate grade pulp, viscose grade pulp, paper/fluff grade pulp, cotton linter, and combinations thereof.
6 . The method of claim 1 wherein the first mentioned de-liquefying being accomplished via centrifuging.
7 . The method of claim 1 wherein the second mentioned de-liquefying being accomplished via centrifuging.
8 . The method of claim 1 wherein the second solution further comprises a strong acid.
9 . The method of claim 8 wherein the strong acid being sulfuric acid.
10 . The method of claim 1 wherein the first stage suspension comprising 1-18 wt % solids.
11 . The method of claim 1 wherein the second stage suspension comprising 1-18 wt % solids.
12 . The method of claim 1 wherein the second stage suspension being de-liquefied to a mass of greater than 20 wt % solids.
13 . The method of claim 5 wherein the cellulose source being in a form selected from the group consisting of sheet, roll, bale, shred, chip, fluff, cotton linter, and combinations thereof.
14 . The method of claim 1 further comprising recycling the liquid from the first de-liquefying step back to the first stage.
15 . The method of claim 1 further comprising recycling the liquid from the second de-liquefying step back to either the first stage, or the second stage, or both.
16 . The method of claim 14 further comprising a controlled withdrawal of recycled liquid for the purpose of composition control.
17 . The method of claim 15 further comprising a controlled withdrawal of recycled liquid for the purpose of composition control.
18 . The method of claim 1 wherein esterifying being conducted at a temperature in the range of 35° C.-100° C. under reduced or atmospheric pressure.
19 . The method of claim 2 wherein hydrolyzing being conducted at a temperature in the range of 50° C.-170° C.
20 . The method of claim 2 further comprising the step of cooling the cellulose ester dope to a temperature in the range of 70° C.-110° C.
21 . The method of claim 20 wherein cooling being flash cooling the cellulose ester dope under reduced or atmospheric pressure.
22 . The method of claim 1 further comprising the step of finishing the cellulose ester dope.
23 . The method of claim 22 wherein finishing the cellulose ester dope comprising the steps of:
precipitating the cellulose ester polymer from the dope,
washing the cellulose ester polymer, and
drying the cellulose ester polymer.
24 . The method of claim 22 further comprising the step of:
bleaching the cellulose ester polymer.
25 . The method of claim 24 wherein bleaching comprising the step of contacting the cellulose ester polymer with hydrogen peroxide or other oxidants.
26 . The method of claim 1 being continuous.
27 . The method of claim 1 being continuous pre-treating with esterification and hydrolysis by batch.
28 . A process for pre-treating a cellulose source for the production of cellulose esters comprising the steps of:
mixing, in a first stage, the cellulose source with a first solution of a weak acid and water, whereby the cellulose source being suspended in the first solution, the cellulose source being selected from the group consisting of: acetate grade pulp, viscose grade pulp, paper/fluff grade pulp, cotton linter, and combinations thereof;
de-liquefying the first stage suspension;
mixing, in a second stage, the de-liquefied mass with a second solution of weak acid and water, whereby the mass being suspended in the second solution; and
de-liquefying the second stage suspension.
29 . The method of claim 28 wherein the first solution comprising the weak acid being in excess of the water.
30 . The method of claim 28 wherein the second solution containing more weak acid than the first solution.
31 . The method of claim 28 wherein the first mentioned de-liquefying being accomplished via centrifuging.
32 . The method of claim 28 wherein the second mentioned de-liquefying being accomplished via centrifuging.
33 . The method of claim 28 wherein the second solution further comprises a strong acid.
34 . The method of claim 33 wherein the strong acid being sulfuric acid.
35 . The method of claim 28 wherein the first stage mixture comprising 1-18 wt % solids.
36 . The method of claim 28 wherein the second stage mixture comprising 1-18 wt % solids.
37 . The method of claim 28 wherein the second stage mixture being de-liquefied to a mass of greater than 20 wt % solids.
38 . The method of claim 28 wherein the cellulose source being in a form selected from the group consisting of sheet, roll, bale, shred, chip, fluff, cotton linter, and combinations thereof.
39 . The method of claim 28 further comprising recycling the liquid from the first de-liquefying step back to the first stage.
40 . The method of claim 28 further comprising recycling the liquid from the second de-liquefying step back to either the first stage, or the second stage, or both.
41 . The method of claim 39 further comprising a controlled withdrawal of recycled liquid for the purpose of composition control.
42 . The method of claim 40 further comprising a controlled withdrawal of recycled liquid for the purpose of composition control.