MOLDING TOOL AND METHOD FOR PRODUCING A MOLDING TOOL FOR EXTRUDING CELLULOSE MOLDED BODIES

Abstract

The invention relates to a molding tool (1, 51) for the extrusion of cellulosic molded bodies (4) from a spinning dope (2), having an entry side (6, 56) and an exit side (7, 57) for the spinning dope (2), with at least one nozzle body (8, 58a, 58b, 58c) including a planar carrier (9, 59a, 59b, 59c) with extrusion openings (10, 60) that penetrate the carrier from the entry side (6, 56) to the exit side (7, 57) and have a mouth diameter (12, 62) at the exit side (7, 57) and through which the spinning dope (2) is extruded into the cellulosic molded bodies (4). In order to provide a molding tool of the afore-mentioned type, which is easier and more inexpensive to manufacture while providing excellent strength and pressure stability at the same time, it is proposed that the ratio of the thickness (13, 63) of the carrier (9, 59a, 59b, 59c) to the mouth diameter (12, 62) of the extrusion openings (10, 60) at the exit side (7, 57) be at least 6:1, preferably at least 10:1, and that the extrusion openings (10, 60) be formed in the carrier (9, 59a, 59b, 59c) by applying laser energy.

Claims

1. A molding tool for the extrusion of cellulosic molded bodies from a cellulose-containing spinning dope comprising an entry side and an exit side for the cellulose-containing spinning dope, with at least one nozzle body including a planar carrier with extrusion openings that penetrate the carrier from the entry side to the exit side and have a mouth diameter at the exit side and through which the cellulose-containing spinning dope is extruded into the cellulosic molded bodies, wherein a ratio of the thickness of the carrier to the mouth diameter of the extrusion openings at the exit side is at least 6:1, and that the extrusion openings were formed in the carrier by applying laser energy.

2. The molding tool as claimed in claim 1, wherein the carrier has a thickness of at least 600 μm.

3. The molding tool as claimed in claim 1, wherein the extrusion openings are burr-free at the exit side.

4. The molding tool as claimed in claim 1, wherein the at least one nozzle body is annular or rectangular.

5. The molding tool as claimed in claim 1, wherein the molding tool comprises several nozzle bodies.

6. The molding tool as claimed in claim 1, wherein the molding tool further comprises at least one first web which is firmly connected to the at least one nozzle body by material bonding and protrudes from the at least one nozzle body towards the entry side.

7. The molding tool as claimed in claim 6, wherein the molding tool further comprises at least one second web, wherein the nozzle body extends between the at least one first web and the at least one second web.

8. The molding tool as claimed in claim 6, wherein at least portions of the at least one first web extend essentially normal to the nozzle body.

9. The molding tool as claimed in claim 7, wherein a distance normal to a lengthwise extension of the at least one nozzle body between the at least one first web and the at least one second web is at least less than 100 times the thickness of the carrier.

10. The molding tool as claimed in claim 7, wherein the at least one first web fully encircles the at least one second web.

11. The molding tool as claimed in claim 6, wherein, at the entry side, the molding tool further comprises a flange with at least one flange limb, the flange limb adjoining the web and protruding outward from the molding tool.

12. A method for producing a molding tool as claimed in claim 1, comprising forming the extrusion openings in the carrier by applying laser energy to it from the entry side of the molding tool, and creating at the exit side, burr-free extrusion openings in the carrier without any further finishing.

13. The method as claimed in claim 12, further comprising as a final procedural step, forming the extrusion openings in the carrier.

14. A method for producing regenerated cellulose molded bodies, comprising extruding the cellulose-containing spinning dope through the molding tool as claimed in claim 1 and precipitating in a spinning bath in order to produce the cellulosic molded bodies.

15. The method as claimed in claim 14, wherein the cellulose-containing spinning dope comprises a tertiary amine oxide in which the cellulose is dissolved and the spinning bath includes a mixture of water and tertiary amine oxide.

16. The molding tool as claimed in claim 1, wherein the ratio of the thickness of the carrier to the mouth diameter of the extrusion openings at the exit side is at least 10:1.

17. The molding tool as claimed in claim 2, wherein the thickness of the carrier is at least 800 μm.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0026] The embodiments of the invention are described hereinafter with reference to the drawings, wherein:

[0027] FIG. 1 is a sectional view along I-I of FIG. 2 of a molding tool according to a first embodiment,

[0028] FIG. 2 is a plan view of the molding tool of FIG. 1,

[0029] FIG. 3 is a torn-away sectional view along II-II of FIG. 4 of a molding tool according to a second embodiment,

[0030] FIG. 4 is a plan view of the molding tool of FIG. 3, and

[0031] FIG. 5 is a partially torn-away sectional view of a spinning machine with an inventive molding tool of FIG. 1.

MODES OF CARRYING OUT THE INVENTION

[0032] FIG. 1 shows an annular molding tool 1 according to a first embodiment of the invention, which is used in a spinning device 100 of FIG. 5 and in a method for the extrusion of cellulosic molded bodies 4. The molding tool 1 has an entry side 6 for the spinning dope 2 and an exit side 7 for the extruded spinning dope 3 (cf. FIG. 5). In addition, a nozzle body 8 with a planar carrier 9 is provided in the molding tool 1. In this case, the nozzle body 8 can be integrally formed with the remaining molding tool 1 (for example, by deep drawing, milling, etc.) or be firmly connected to it by material bonding in another way (for example, by welding, etc.).

[0033] The carrier 9 includes extrusion openings 10 that penetrate it from the entry side 6 to the exit side 7. At the exit side 7, the extrusion openings 10 form a mouth 11 having a mouth diameter 12. In this case, the size of the mouth diameter 12 decisively influences the titer (or diameter) of the extruded cellulosic molded body 4. In addition, the extrusion behavior and the geometry of the molded bodies 4 can be controlled via the cross-sectional shape of the extrusion opening 10. For example, this can be used to change the discharge behavior of the spinning dope 2 from the extrusion openings 10 in order to prevent sticking together of the extruded spinning dope 3 prior to precipitation in the spinning bath 5. In this case, preferred cross-sectional shapes of the extrusion openings 10 may have a configuration that is tapering toward the exit side 7, as is shown in FIG. 1. However, the cross-sectional shape can be arbitrarily varied by laser radiation so that, for example, hourglass-shaped configurations widening toward the exit side 7 are possible.

[0034] The extrusion openings 10 have a mouth diameter 12 between 70 and 150 μm. Such mouth diameters 12 can ensure that fibers or filaments having a titer greater than 0.7 dtex are produced as the extruded cellulosic molded bodies 4. In another preferred embodiment of the invention, regenerated cellulose fibers having a titer between 1.0 and 2.5 dtex are produced.

[0035] The ratio of the thickness 13 of the carrier 9 to the mouth diameter 12 of the extrusion opening 10 is at least 6:1, thereby ensuring sufficient resistance of the carrier 9 to the high pressures exerted by the spinning dope 2. In further preferred embodiments of the invention, a ratio of at least 10:1, of at least 12:1, or of at least 15:1, is chosen.

[0036] The thickness 13 of the carrier 9 is at least 600 μm. This way, the carrier 9 is able to permanently withstand a pressure load of up to 150 bar from the entry side 6. In another embodiment, the preferred thickness 13 of the carrier 9 is at least 800 μm, or preferably 1000 μm, in order to ensure a particularly high resistance of the carrier 9.

[0037] The extrusion openings 10 were formed in the carrier 9 by applying laser energy to it, and allowing laser energy to act on it. This makes it easy to produce the molding tool 1 in technical processes. In addition, with the laser radiation acting on the material of the carrier 9, particularly high dimensional accuracy in the positioning, the dimensions, and the geometry of the extrusion openings 10 is achieved. In particular, the extrusion openings 10 have a constant average distance 14 from one another that is between 50 and 1000 μm, the standard deviation of the distance 14 being no more than 1%. In order to avoid sticking together of the fibers as they exit the extrusion openings 10, larger distances 14 from 250 to 800 μm are usually employed. In this connection, the extrusion openings 10 can be disposed as distributed over the carrier 9 in an arbitrary, regular pattern (e.g., radial, grid-shaped, etc.) or irregularly. Also, the laser radiation makes it possible to obtain a standard deviation of the mouth diameters 12 of less than 2%. In addition, the extrusion openings 10 formed in the carrier 9 by using laser radiation do not have burrs at the exit side 7 right after being formed and thus do not have to be subjected to any further finishing steps such as grinding or polishing which might adversely affect the geometry of the extrusion openings 10. In particular, the burr-free and smooth extrusion openings 10 also ensure that the individual strands of the extruded spinning dope 3 will not stick together before being precipitated into the molded bodies 4 in the spinning bath 5.

[0038] The molding tool 1 shown in FIGS. 1 and 2 and having an annular nozzle body 8, includes a first web 15 and a second web 16, both of which are firmly connected to the annular nozzle body 8 by material bonding. Thus, the webs 15, 16 can, for example, be integrally formed with the carrier 9 of the nozzle body 8, for example in that the molding tool 1 is configured as deep drawn or milled in one piece, or be firmly connected to it by material bonding, for example, by welding. In this case, the annular nozzle body 8 extends between the first and second webs 15, 16. The webs 15 and 16 protrude from the nozzle body 8 toward the entry side 6. Due to the firm material bonding connection to the nozzle body 8, the webs 15, 16 act as an edge-side support of the carrier 9, whereby it is able to withstand a higher pressure load by the spinning dope 2. Due to the annular configuration of the nozzle body 8, the first web 15 fully encircles the second web 16 and the nozzle body 8. Thus, the two webs 15 and 16 always extend parallel to one another and maintain a constant normal distance 17 transversely to the lengthwise extension 18 of the nozzle body 8, along the carrier 9, from one another. In this case, the normal distance 17 is no more than 100 times the thickness 13 of the carrier 9 in order to ensure the maximum stability of the nozzle body 8.

[0039] In the interior of the molding tool 1, the webs 15 and 16 act as guide surfaces 19 for the spinning dope 2, which advantageously support the flow behavior of the highly viscous spinning dope 2 and prevent the formation of dead spaces within the molding tool 1. Thus, the webs 15, 16 form a guide passage 20 for the spinning dope 2 starting from the entry side 6. Preferably, the webs 15 and 16 extend, as shown in FIG. 1, normally to the nozzle body 8 and thus normally to the carrier 9.

[0040] In addition, the molding tool 1 includes a flange 23 by means of which the molding tool 1 can be—as is shown in FIG. 5—connected to a spinning device 100. In this case, the flange 23 includes two flange limbs 21, 22, each adjoining the webs 15 and 16 at the entry side 6, and which protrude outward from the webs 15 and 16 and thus from the molding tool 1. As such, the flange limbs 21, 22 do not obstruct the guide passage 20 for the spinning dope 2 and thus reliably avoid having a negative influence on the flow conditions in the guide passage 20.

[0041] FIGS. 3 and 4 show a molding tool 51 according to a second embodiment, which includes several rectangular nozzle bodies 58a, 58b, 58c. The molding tool 51 can be used in a spinning device 100 of FIG. 5 and in a method for the extrusion of cellulosic molded bodies 3, just like the molding tool 1. Equivalent to the description for the first embodiment, the molding tool 51 includes an entry side 56 for the spinning dope 2 and an exit side 57 for the extruded spinning dope 3 (cf. FIG. 5).

[0042] In this case, the molding tool 51 includes three nozzle bodies 58a, 58b, and 58c, each of which comprises a planar carrier 59a, 59b, 59c. Generally, it is to be mentioned that a molding tool 51, as shown in FIGS. 3 and 4, need not be limited to three nozzle bodies. Rather, any other number and arrangement of nozzle bodies in the molding tool is possible.

[0043] In this case, the nozzle bodies 58a, 58b, 58c are firmly connected to the remaining molding tool 51 by material bonding, preferably by welds 73. The carriers 59a, 59b, 59c include respective extrusion openings 60 which penetrate them from the entry side 56 to the exit side 57 and are formed in them through the action of laser radiation. At the exit side 57, each of the extrusion openings 60 forms a mouth 61 having a mouth diameter 62. As described for the first embodiment, the mouth diameters 62 can be varied in order to change the titer of the extruded cellulosic molded bodies 4. The preferred mouth diameter 62 of the extrusion openings 60 is between 70 and 150 μm in order to produce cellulosic molded bodies 4, particularly fibers, having a titer greater than 0.7 dtex. In addition, by forming the extrusion openings 60 by means of laser radiation, a standard deviation of the mouth diameters 62 of less than 1% is obtained. More preferably, this is used to produce regenerated cellulose fibers having a titer between 1.0 and 2.5 dtex. Also, as described for the first embodiment, the cross-sectional shapes of the extrusion openings 60 can be changed in order to control the exit behavior of the extruded spinning dope 3.

[0044] The carriers 59a, 59b, 59c of the nozzle bodies 58a, 58b, 58c have a preferred thickness 63 of at least 600 μm. In other advantageous configurations of this embodiment, the thickness 63 is at least 800 μm, or at least 1000 μm, in order to obtain a particularly permanently resistant molding tool 51 that withstands the high pressures of up to 150 bar acting from the entry side 56. Here, the ratio of the thickness 63 of the carriers 59a, 59b, 59c to the mouth diameter 62 of the extrusion openings 60 is at least 6:1 in order to obtain the necessary resistance. In preferred configurations of the invention, the ratio is at least 10:1, at least 12:1, or at least 15:1.

[0045] Very high dimensional accuracy in the positioning and the dimensions of the extrusion openings 60 is obtained by forming the extrusion openings 60 in the carriers 59a, 59b, 59c by applying laser energy to them. As is shown in FIG. 4, the extrusion openings 60 are disposed at a constant distance 64 of 50 to 1000 μm from one another, the standard deviation being no more than 2% of the distance 64. In addition, by using laser radiation, the extrusion openings 60 can be formed as essentially burr-free, which makes any further grinding or polishing steps unnecessary and thus helps avoid the formation of stress effects in the carriers 59a, 59b, 59c.

[0046] The molding tool 51 includes first webs 65a, 65b, 65c, 65d, provided at the outside of the molding tool 51. Inside the molding tool 51 second webs 66a, 66b are provided that extend in a rib-like manner between the first webs 65c and 65d and are firmly connected to them by material bonding. In this case, each of the nozzle bodies 58a and 58c extends transversely to its lengthwise extension 68 between a first web 65a, 65b and a second web 66a, 66b. The nozzle body 58b extends between the second webs 66a, 66b. The webs 65a, 65b, 65c, 65d, 66a, 66b and the carriers 59a, 59b, 59c of the nozzle bodies 58a, 58b, 58c are firmly material-bond-connected to one another via welds 73. Preferably, the webs 65a, 65b, 65c, 65d, 66a, 66b are configured as one integral piece (for example, as a milled, deep-drawn, rolled piece, etc.), and protrude from the nozzle bodies 58a, 58b, 58c toward the entry side 56.

[0047] The webs 65a, 65b, 66a, 66b extend parallel to one another and maintain a constant normal distance 67 (normal to the lengthwise extension 68) to one another along the carriers 59a, 59b, 59c. In this case, the normal distance 67 is no more than 100 times the thickness 63 of the carriers 59a, 59b, 59c so that the highest possible stability of the nozzle bodies 58a, 58b, 58c is obtained.

[0048] Inside the molding tool 51, the webs 65a, 65b, 65c, 65d 66a, 66b act as guide surfaces 69 for the spinning dope 2. Thus, the webs 65a, 65b, 65c, 65d, 66a 66b create a guide passage 70 starting from the entry side 56, through which the spinning dope 2 is guided to the extrusion openings 60.

[0049] In addition, the molding tool 51 includes a flange 73, by means of which the molding tool 51 can be connected to a spinning device 100 in a force-locking engagement. In this case, four flange limbs 71a, 71b, 71c, and 71d, each of which adjoins a first web 65a, 65b, 65c, 65d, form the flange 73 which protrudes outward from the molding tool 51 at the entry side 56 and encircles the molding tool 51.

[0050] FIG. 5 shows a spinning device 100 in which, according to a method for producing regenerated cellulose molded bodies 4, a spinning dope 2 is extruded into the cellulosic molded bodies 4 through a molding tool 1 according to the first embodiment of the invention. In order to obtain the molded bodies 4, in such a method for producing regenerated cellulose molded bodies 4, the extruded spinning dope 3 is—after the extrusion—guided through an air gap 8 into a spinning bath 5 where the cellulose precipitates from the extruded spinning dope 3. According to another preferred configuration of the invention, the method for producing the regenerated molded bodies 4 is a lyocell process wherein the spinning dope 2 contains a solution of cellulose in a tertiary amine oxide. In this case, the spinning bath 5 for the precipitation of the extruded spinning dope 3 contains a mixture of water and a tertiary amine oxide (for example, NMMO-N-methylmorpholine-N-oxide).