METHOD FOR PRODUCING A TRANSFER MIXTURE BY THE DIRECT DISSOLUTION PROCESS, USING A THIN LAYER EVAPORATOR

Abstract

A method for producing a transfer mixture by the direct dissolution method in a thin film evaporator (D) 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 an evaporator shaft (5) situated in the housing (4) rotationally wipes the product over the heated interior of the housing (4), wherein the product heats up and some of the water evaporates, so that the transfer mixture is obtained, wherein (a) the transfer mixture is discharged before the product substantially overheats; and (b) all heating surfaces of the thin film evaporator in contact with the product are subjected to a heating temperature, which is at least 20K above the temperature of the product.

Claims

1. Method for producing a transfer mixture by a direct dissolution method in a thin film evaporator (D) 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 an evaporator shaft (5) situated in the housing (4) rotationally wipes the product over the heated interior of the housing (4), wherein the product heats up and some of the water evaporates, so that the transfer mixture is obtained, wherein (a) the transfer mixture is discharged before the product substantially overheats; and (b) all heating surfaces of the thin film evaporator in contact with the product are subjected to a heating temperature, which is at least 20K above the temperature of the product.

2. A Method for producing a transfer mixture by a direct dissolution method in a thin film evaporator (D) having a feed, a housing and a discharge, wherein the feed introduces a product consisting essentially of cellulose, water and N-Methylmorpholine-N-Oxide (NMMO) into the housing, wherein an evaporator shaft (5) situated in the housing (4) rotationally wipes the product over the heated interior of the housing (4), wherein the product heats and some of the water evaporates to form the transfer mixture, wherein the composition of the transfer mixture is $\mathrm{maximum}{x}_{H2O}=-0.235x_{\mathrm{CeII}}+0.235\mathrm{and}$ $\mathrm{minimum}{x}_{H2O}=-0.59x_{\mathrm{CeII}}+0.2047.$

3. Method according to claim 2, wherein the transfer mixture has a preferred composition of $\mathrm{maximum}{x}_{H2O}=0.2864x_{\mathrm{CeII}}^2-0.6786x_{\mathrm{CeII}}+0.2288$ $\mathrm{minimum}{x}_{H2O}=0.2864x_{\mathrm{CeII}}^2-0.6786x_{\mathrm{CeII}}+0.2188$

4. Method according to claim 1, wherein the transfer mixture passes at least one subsequent transfer organ.

5. Method according to claim 1, wherein the transfer mixture is transferred to a subsequent processing organ.

6. The method according to claim 5, wherein the subsequent processing organ processes the transfer mixture further to form a molding solution.

7. Method according to claim 1, wherein a machine control monitors the amount of water, cellulose and functional liquid in the composition of the transfer solution from the feed to the discharge.

8. Method according to claim 7, wherein the machine control system monitors the composition of the product in all states up to the transfer mixture over sensors.

9. Method according to claim 5, wherein the subsequent processing organ is a mixing kneader.

10. Method according to claim 9, wherein the mixing kneader further processes the transfer mixture by water evaporation and stirring into a molding solution according to the direct dissolution method, wherein the kneader shaft structures are designed without heating cavities.

11. Thin film evaporator (D) for processing a starting material into a transfer mixture according to a direct dissolution method, comprising a feed, a housing and a discharge, wherein the feed introduces the product of essentially cellulose, water and a functional liquid into the housing (4), wherein an evaporator shaft (5) situated in the housing (4) rotationally wipes the product over the heated interior of the housing (4), wherein the product heats and some of the water evaporates to form the transfer mixture, wherein all heating surfaces of the thin film evaporator in contact with the product are subjected to a heating temperature that is at least 20K above the temperature of the product.

12. Thin film evaporator (D) for processing a starting material into a transfer mixture according to a direct dissolution method, comprising a feed, a housing and a discharge, wherein the feed introduces the product consisting essentially of cellulose, water and N-Methylmorpholine-N-Oxide (NMMO) into the housing (4), wherein an evaporator shaft (5) situated in the housing (4) rotationally wipes the product over the heated interior of the housing (4), wherein the product heats and some of the water evaporates to form the transfer mixture, wherein upon reaching the composition of the transfer mixture of $\mathrm{maximum}{x}_{H2O}=-0.235x_{\mathrm{CeII}}+0.235\mathrm{and}$ $\mathrm{minimum}{x}_{H2O}=-0.59x_{\mathrm{CeII}}+0.2047$ the transfer mixture can be passed on through the discharge.

13. Thin film evaporator according to claim 12, wherein the transfer mixture has a preferred composition of $\mathrm{maximum}{x}_{H2O}=0.2864x_{\mathrm{CeII}}^2-0.6786x_{\mathrm{CeII}}+0.2288$ $\mathrm{minimum}{x}_{H2O}=0.2864x_{\mathrm{CeII}}^2-0.6786x_{\mathrm{CeII}}+0.2188.$

14. Thin film evaporator (D) according to claim 11, wherein the transfer mixture is operatively connected to at least one subsequent transfer organ.

15. Thin film evaporator (D) according to claim 11, wherein the transfer mixture is operatively connected to a subsequent processing organ.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Further advantages, features and details of the invention result from the following description of preferred embodiment and from the drawings; these show in

[0083] FIG. 1 a diagram showing the preferred material properties of a transfer mixture;

[0084] FIG. 2 a diagram showing the general material properties of a transfer mixture.

DETAILED DESCRIPTION

Example 1

[0085] 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 introduced into a thin film evaporator where it is concentrated into a transfer mixture. In this example, the thin film evaporator is operated at a process pressure of 70 mbara, so that the equilibrium temperature of the starting material is approx. 43? C. The heating temperature of the thin film evaporator is 130? C. In the present example, the transfer of the mixture takes place within the preferred transfer range at a cellulose content of about 11.5 wt % and an NMMO content 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 to NMMO at this point is approximately that of a 1.3 hydrate. The transfer mixture provided by the thin film evaporator is subsequently transferred to a mixing kneader. There, the mixture is finally concentrated by evaporation and homogenized to give a complete molding solution. The molding solution leaves the mixing kneader with a cellulose content of 12.0 wt %, an NMMO content of approx. 77.0 wt %, and a temperature of approx. 107? C.

Example 2

[0086] 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 content of about 8.2 wt % is produced from cellulose and aqueous IL solution, resulting in an IL content of about 58.6 wt %. This starting mixture is introduced into a thin film evaporator where it is concentrated to form a transfer mixture. In the present example, the transfer of the mixture takes place at a cellulose content of about 11.5 wt % and an IL content of about 79.6 wt %. The transfer mixture provided by the thin film evaporator is subsequently transferred to a mixing kneader. There, the mixture is finally concentrated by evaporation and homogenized so that a complete molding solution is obtained. The molding solution leaves the mixing kneader with a cellulose content of 12.0 wt % and an IL content of approx. 83.0 wt %.

[0087] 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

[00005]$\mathrm{maximum}{x}_{H2O}=-0.235x_{\mathrm{CeII}}+0.235$$\mathrm{minimum}{x}_{H2O}=-0.59x_{\mathrm{CeII}}+0.2047$

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

[00006]$\mathrm{maximum}{x}_{H2O}=0.2864x_{\mathrm{CeII}}^2-0.6786x_{\mathrm{CeII}}+0.2288$$\mathrm{minimum}{x}_{H2O}=0.2864x_{\mathrm{CeII}}^2-0.6786x_{\mathrm{CeII}}+0.2188.$

[0088] 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