KNEADER MIXER FOR PROCESSING A TRANSFER MIXTURE INTO A MOULDING SOLUTION ACCORDING TO THE DIRECT DISSOLVING METHOD

Abstract

Mixing kneader for processing a transfer mixture into a molding solution, according to the direct dissolution method, having a feed, a housing and a discharge, wherein the feed introduces a product consisting essentially of cellulose, water and a functional liquid into the housing, wherein a kneader shaft situated in the housing rotationally mixes and kneads the product and sweeps wipes it over heated inner surfaces of the mixing kneader, wherein reducing the amount of undissolved particles in the product and the size of the particles are reduced, and evaporating some of the water evaporates to produce form a molding solution, wherein the process volume of the mixing kneader is determined only by the requirements of a molding solution flow capacity.

Claims

1. Mixing kneader for processing a transfer mixture into a molding solution according to a direct dissolution method, comprising a feed, a housing and a discharge, wherein the feed introduces a product consisting essentially of cellulose, water and a functional liquid into the housing, wherein a kneader shaft situated in the housing rotationally mixes and kneads the product and wipes it over heated inner surfaces of the mixing kneader, wherein the amount of undissolved particles in the product and the size of the particles are reduced and some of the water evaporates to form a molding solution, wherein the process volume of the mixing kneader is determined only by the requirements of a molding solution flow capacity.

2. Mixing kneader for processing a transfer mixture into a molding solution according to a direct dissolution method, comprising a feed, a housing and a discharge, wherein the feed introduces a product consisting essentially of cellulose, water and a functional liquid into the housing, wherein a kneader shaft situated in the housing rotationally mixes and kneads the product and wipes it over heated inner surfaces of the mixing kneader, wherein the amount of undissolved particles in the product and the size of the particles are reduced and some of the water evaporates to form a molding solution, wherein the residence time for the product in the mixing kneader is at most 15 minutes.

3. Mixing kneader according to claim 2, wherein the product remains in the mixing kneader for at least two minutes.

4. Mixing kneader according to claim 1, wherein the composition of the transfer mixture is
maximum x.sub.H2O=0.235x.sub.Cell+0.235 and
minimum x.sub.H2O=0.59x.sub.Cell+0.2047.

5. The mixing kneader according to claim 4, wherein the transfer mixture has a composition of
maximum x.sub.H2O=0.2864x.sup.2.sub.CeII0.6786x.sub.CeII+0.2288
minimum x.sub.H2O=0.2864x.sup.2.sub.Cell0.6786x.sub.CeII+0.2188.

6. Mixing kneader according to claim 1, wherein the transfer mixture passes at least one preceding transfer organ.

7. Mixing kneader according to claim 1, wherein the transfer mixture is produced from a starting material in a preceding process organ.

8. Mixing kneader according to claim 7, wherein a machine control monitors the amount of water, cellulose and functional liquid in the composition of the product in all states up to the molding solution, wherein the machine control monitors the composition of the product in all states up to the molding solution over sensors.

9. Mixing kneader according to claim 7, wherein the preceding process organ is a thin film evaporator.

10. Mixing kneader according to claim 1, wherein the kneader shaft structures of the mixing kneader are designed without heating cavities.

11. Method for processing a transfer mixture to a molding solution according to a direct dissolution method in a mixing kneader with a feed, a housing and a discharge, wherein the feed introduces a product consisting essentially of cellulose, water and a functional liquid from a preceding process organ into the housing, wherein a kneader shaft situated in the housing rotationally mixes and kneads the product and wipes it over heated inner surfaces of the mixing kneader, wherein the amount of undissolved particles in the product and the size of the particles are reduced and some of the water evaporates to form a molding solution, and wherein the process volume of the mixing kneader is determined exclusively by the requirements of a molding solution flow capacity.

12. Method according to claim 11, wherein the product remains in the mixing kneader for at most 15 minutes.

13. Method according to claim 11, wherein the product remains in the mixing kneader for at least two minutes.

14. Method according to claim 11, wherein the transfer mixture has the following composition of
maximum x.sub.H2O=0.235x.sub.CeII+0.235 and
minimum x.sub.H2O=0.59x.sub.CeII+0.2047.

15. The method according to claim 14, wherein the transfer mixture has the following composition of
maximum x.sub.H2O=0.2864x.sup.2.sub.CeII0.6786x.sub.CeII+0.2288
minimum x.sub.H2O=0.2864x.sup.2.sub.CeII0.6786x.sub.CeII+0.2188.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Further advantages, features and details of the invention result from the following description of preferred embodiment and from the drawings; these show in

[0090] FIG. 1 a diagram showing the general and preferred material properties of a transfer mixture.

DETAILED DESCRIPTION

Example 1

[0091] The subject of this example is the production of a molding solution with a cellulose content of 12 wt % using the direct dissolution method. The functional liquid used in this example is NMMO. All subsequent proportions refer to the total mass of the cellulose-NMMO-water mixture. A starting material with a cellulose content of approx. 7.2 wt % is prepared from cellulose and aqueous NMMO solution, resulting in an NMMO content of approx. 46.1 wt %. This starting material is fed into a thin film evaporator at a flow rate of about 417 kg/h, where it is concentrated into a transfer mixture. In the example, the thin film evaporator is operated at a process pressure of 70 mbara, so that the equilibrium temperature of the starting material is approximately 43 C. The heating temperature of the thin film evaporator is 130 C. In the present example, the transfer of the mixture occurs within the preferred transfer range at a cellulose amount of about 11.5 wt % and an NMMO amount of about 73.9 wt %. Under the present process conditions this corresponds to an equilibrium temperature of the transfer mixture of about 100 C. The ratio of water and NMMO at this point corresponds approximately to that of a 1.3 hydrate. The transfer mixture provided by the thin film evaporator is subsequently transferred to the mixing kneader at a flow rate of about 261 kg/h. There, the cellulose is completely dissolved, homogenized and the mixture is finally concentrated by evaporation to give a complete molding solution. The residence time of the mixture in the mixing kneader is 8.5 minutes. The process volume of the kneader is therefore approx. 70 L. The molding solution leaves the mixing kneader with a flow of approx. 217 kg/h with a cellulose amount of 12.0 wt %, an NMMO amount of approx. 77.0 wt % and a temperature of approx. 107 C.

Example 2

[0092] The subject of this example is the production of a molding solution with a cellulose content of 12 wt % using the direct dissolution method. The functional liquid used in this example is an ionic liquid. All subsequent proportions refer to the total mass of the mixture. A starting mixture with a cellulose amount of about 8.2 wt % is prepared from cellulose and aqueous IL solution, resulting in an IL amount of about 58.6 wt %. This starting material is fed into a thin film evaporator at a flow rate of about 475 kg/h, where it is concentrated into a transfer mixture. In the present example, the transfer of the mixture takes place at a cellulose amount of about 11.5 wt % and an IL amount of about 79.6 wt %. The transfer mixture provided by the thin film evaporator is subsequently transferred to the mixing kneader at a flow rate of approx. 347 kg/h. There, the mixture is finally concentrated by evaporation and homogenized to give a complete molding solution. The residence time of the mixture in the mixing kneader is 12 minutes. The process volume of the kneader is therefore approx. 115 L. The molding solution leaves the mixing kneader with a flow rate of approx. 333 kg/h with a cellulose amount of 12.0 wt % and an IL amount of approx. 83.0 wt %.

[0093] FIG. 1 shows a diagram showing the general and the preferred material composition of the transfer mixture. Thereby the general composition a has the following parameters of

maximum x.sub.H2O=0.235x.sub.Cell+0.235

minimum x.sub.H2O=0.59x.sub.Cell+0.2047

and thus shows a larger margin than the preferred composition b, which has the following parameters of

maximum x.sub.H2O=0.2864x.sup.2.sub.Cell0.6786x.sub.Cell+0.2288

minimum x.sub.H2O=0.2864x.sup.2.sub.Cell0.6786x.sub.Cell+0.2188.

[0094] As the water content decreases, the area of solution L is first reached and as the water content continues to decrease, crystallization K of the NMMO occurs.

TABLE-US-00001 Reference list A General composition of the tansfer mixture B Preferred composition of the tansfer mixture K Crystallization L Solution