Process for the Production of Polymeric Moulded Bodies
The invention relates to a process for the production of polymeric moulded bodies, wherein a mouldable mass containing the polymer is extruded via a forming tool comprising a carrier material and at least one extrusion orifice arranged in the carrier material and the polymeric moulded body is obtained from the extruded moulded mass in a manner known per se, for instance, by precipitation or cooling.
In particular, the invention relates to a process for the production of polymer fibres, wherein the forming tool is hence a spinneret comprising extrusion orifices in the shape of spinning holes.
Forming tools whose extrusion orifices are produced mechanically by a displacement of material are usually used for the production of polymeric moulded bodies.
In the case of spinnerets, the spinning hole is made by means of a piercing tool. Said procedure usually consists of several steps. One reason for this is that the materials which are usually used must exhibit a certain minimum thickness because of the high spinning pressures that are prevailing. However, from a certain material thickness, the hole can no longer be made in a single piercing process. The displacement of material during the piercing process furthermore gives rise to undesired accumulations of displaced material. Therefore, complex aftertreatment steps are partly necessary. The thickness of spinnerets ranges from about 300 urn to several millimeters.
For instance, gold/platinum alloys, soft steels or ceramics are used as nozzle materials, In general, materials must be selected which exhibit sufficient ductility and softness for being able to withstand the process of material displacement occurring during the mechanical formation of holes. Thereby, the strength of the materials that are used is limited. Since, as mentioned, high spinning pressures may occur during the spinning process, the size of the spinneret and hence also the productivity are thereby limited.
In particular, the above-mentioned considerations are also applicable in the field of producing cellulosic moulded bodies, in particular cellulose fibres, in accordance with the viscose process or the Lyocell process.
A mechanical production of spinning holes permits great precision in terms of the reproducibility of the shape of the holes. Furthermore, the shape of the nozzle hole can be
determined by way of the shape of the manufacturing tools. That applies, for instance, to the course of the nozzle-hole radius across the length of the nozzle hole or generally to the cross-section shape of the nozzle hole as such. A serious drawback of those manufacturing methods consists in the enormously high manufacturing costs associated therewith.
Nozzle materials that are used in the Lyocell process are described, for instance, in PCT-WO 94/28211 or in EP 0 430 926.
It is an object of the present invention to provide a process for the production of polymeric moulded bodies, wherein a forming tool is used whose extrusion orifices can be produced with little effort but nevertheless are suitable for the production of high-quality moulded bodies.
According to one aspect of the invention, said object is achieved by means of a process for the production of polymeric moulded bodies, wherein a mouldable mass containing the polymer is extruded via a forming tool comprising a carrier material and at least one extrusion orifice arranged in the carrier material and the polymeric moulded body is obtained from the extruded moulded mass in a manner known per se, for instance, by precipitation or cooling, which process is characterized in that the mouldable mass is extruded via a forming tool on which at least one extrusion orifice was produced by the application of thermal energy by means of electron rays.
Preferably, the forming tool is a spinneret comprising extrusion orifices in the shape of one or several spinning holes.
As an alternative to the mechanical production of extrusion orifices, in particular spinneret holes, it is thus suggested that the holes are produced by means of electron rays.
It is known to use electron rays for the manufacture of screens and the like. In those applications, however, rather low demands are made to the kind and degree of the reproducibility of holes. Therefore, this technique has so far not been employed for the manufacture of forming tools for polymers.
A measure for the production accuracy of spinneret holes is the scattering of the nozzle-hole outlet diameters of, e.g., round spinning holes. This is an important value since the hole diameter is a contributory factor to the determination of the amount of spinning dope that is conveyed through the hole per unit of time and hence of the titre of the spun filaments that

are obtained. The stronger the scattering of the hole diameters (in particular the outlet diameters) within a spinneret, the larger the scattering of the fibre titre and hence the less secure the spinning behaviour (f.i. the occurrence of filament breaks in the air gap).
It now has been found that the scattering of the diameters of the nozzle-hole outlets of spinnerets whose spinning holes were produced by electron rays is larger than that occurring in conventional spinnerets. Typical scattering values of the nozzle-hole outlet diameter of mechanically produced spinnerets are, f.i., within a range that is well below 5%, whereas said value is well above 5%, reaching up to 15%, in case of holes produced by electron rays.
Surprisingly, however, said fact is not reflected in the scattering of the counts of spun filaments (titre). Comparative measurements produced equally good, partly even better distribution values of the titre. Surprisingly, the spinning stability was also not adversely affected by the larger scattering of the diameter of the nozzle-hole outlet (expressed by the area of the hole).
Hitherto known shapes of nozzle holes for the spinning of polymers, in particular cellulose fibres in accordance with the Lyocell process, may exhibit complex sequences of cylindrical and conical sections. Thereby, the attempt is made to imitate a funnel-like shape. In doing so, one wishes to achieve an as favourable as possible flow behaviour within the nozzle hole and hence the best possible spinning behaviour.
However, a hole formed by means of electron rays inherently exhibits an essentially funnellike shape (without the need of manufacturing various cylindrical or conical sections in separate steps) and thus comes very close to that ideal.
Thereby, the mean diameter of the cross-section of the flow of mouldable mass extruded through the spinning hole is continuously decreased.
Furthermore, spinning holes produced by means of electron rays have an extremely smooth and homogeneous surface, such as supported by examinations of single holes, constituting an advantage for the passage of the spinning dope.
Moreover, the edges on the hole outlet and hole inlet, respectively, are rounded in case of a spinning hole produced by means of electron rays, whereas said edges are sharp in case of mechanically produced spinning holes.

Thus, it can be noted that forming tools whose extrusion orifices were produced by means of electron rays are perfectly suitable for the production of polymeric moulded bodies, while, at the same time, involving comparatively low manufacturing costs. As no displacement of material has to occur, the selection of usable materials is dramatically increased. High-strength steels may be used, for instance, which permit an increase in the size of the forming tools, in particular the spinnerets, and hence in the productivity of the production units. Furthermore, it is feasible to substantially increase the hole density of spinnerets, since no displacement of material has to occur.
In addition, it has turned out that it is possible to produce spinning holes by means of electron rays which exhibit small diameters of, f.i., 100 µm or less, also in comparatively thick sheet metals with a thickness of up to 4 to 5 mm.
The ratio of the length of the nozzle L to the diameter of the outlet hole D preferably amouts to L/D < 50, particularly preferably L/D < 30, most preferably L/D < 20.
In the preferred embodiment of the process according to the invention, wherein the forming tool is a spinneret comprising extrusion orifices in the shape of spinning holes, the carrier material is preferably configured in the shape of a ring. A ring-shaped design of a spinneret is known, f.i., from PCT-WO 95/04173.
Alternatively, the carrier material can be configured in the shape of a square, in particular in the shape of a rectangle. Spinnerets with a rectangular shape are known, f.i., from PCT-WO 94/28218.
The carrier material can be configured in the shape of a lamina in which the spinning holes are realized, with the lamina being inserted in holes, in particular stepped bores, of a support plate, such as known per se from EP 0 430 926 A2.
The carrier material can be configured in the shape of a deep-drawn spinning insert.
The carrier material can also be flush with and welded into a nozzle body, such as known from the previously quoted PCT-WO 94/28218.
Preferably more than 1000, particularly preferably more than 10000, spinning holes are provided in the spinneret. The diameter of the outlet of the spinning holes preferably ranges from 50 µm to 1000 µm, particularly preferably from 100 µm to 500 µm.

The mouldable mass containing the polymer preferably has a zero shear viscosity of at least 100 Pas at 90°C. Such mouldable masses can be extruded excellently through extrusion orifices produced by electron rays.
A particularly preferred embodiment of the process according to the invention is characterized in that the mouldable mass is a cellulose solution in an aqueous tertiary amine oxide. Upon extrusion, the cellulose solution is preferably conveyed via an air gap into a precipitation bath. Said process is known as the „amine-oxide process" or „Lyocell process", respectively. Cellulose fibres produced by said process are denoted by the generic name „Lyocell".
A further aspect of the present invention relates to a moulded body obtainable by means of the process according to the invention, in particular to a cellulosic moulded body obtainable by applying the process according to the invention in the amine-oxide process.
In another aspect, the object of the present invention is achieved by means of a forming tool for the production of polymeric moulded bodies, which forming tool contains a carrier material and at least one extrusion orifice arranged in the carrier material and is characterized in that at least one extrusion orifice was produced by the application of thermal energy by means of electron rays.
The forming tool according to the invention is preferably configured as a spinneret comprising extrusion orifices in the shape of spinning holes.
The spinning holes drilled by means of electron rays preferably exhibit an essentially funnel-shaped course.
Processes for the manufacture of bores in materials such as sheet metals by means of electron rays are known to a person skilled in the art. Appropriate processes are implemented, for instance, by Messrs. Pro-Beam KgaA and Acceleron Inc.
Figures:
Fig. 1 shows a microphotograph of the longitudinal section through a spinning hole produced by means of electron rays as in accordance with the invention.

Fig. 2 shows a microphotograph of the longitudinal section through a spinning hole produced in a conventional mechanical way.
In order to produce those photographs, the spinning holes were each filled with a filling material, whereupon said filling material was extracted from the holes. The filling material moulded according to the inner profile of the holes was then photographed under the microscope.
When comparing those two figures, what is striking is the course of the spinning hole drilled by means of electron rays (Fig. 1) which is essentially funnel-shaped throughout its entire length, whereas two distinct areas, i.e. a cone-shaped first area and an essentially cylindrical second area, are clearly visible in Fig. 2.
Furthermore, in Fig. 1 the longitudinal course of the hole wall which, by comparison, is more irregular than that of Fig. 2 is clearly visible.
Examples:
Example 1:
Two spinnerets each comprising appx. 47.500 spinning holes, whose diameters were specified as 100 urn in each case, are compared with each other, whereby the spinning holes of one spinneret were produced by means of electron rays and the spinning holes of the other nozzle were pierced in a conventional mechanical way.
The spinnerets were configured as ring nozzles, such as described in PCT-WO 95/04173. The ring-shaped carrier material consisted of stainless steel.
In the following Table 1, the data of the spinnerets that were used are indicated in greater detail:

Table 1
Spinneret (manufacturing method) Steel quality Sheet thickness of the carrier material (mm) Strength of the steel (N/mm2)
Prior art (mechanically pierced holes) 1.4016 1.0 450-600
According to the invention (holes produced by means of electron rays) 1.4310 0.5 1,600 to 1,800
In the following, the properties of the spinning holes of the two nozzles that were used are first compared with each other. In doing so, the area F and the respective maximum diameter Dmax of the outlets of several spinning holes were determined by means of image-processing methods known per se, and from this the mean value was derived. From the area, the theoretical diameter Dtheor. of the outlet (i.e. assuming that the outlet is circular) was calculated. The ratio of the measured maximum diameter to the theoretical diameter as calculated from the area results in a measure for the deviation of the outlet from the ideal of a circular opening. Furthermore, the scattering of the measured areas, of Dmax and of Dtheor was determined, and the smallest values that were in each case measured and calculated, respectively, were juxtaposed with the largest values that were in each case measured and calculated, respectively.
In the following Table 2, the results of those measurements and calculations, respectively, are listed:

Table 2
Nozzle comprising spinning holes produced by means of electron rays Nozzle comprising spinning holes produced in a conventional (mechanical) way
AreaF (urn2) dmax (urn) dtheor. (um) AreaF (Hm2) dmax (urn) dtheor. (nm)
Mean value from the measurements 7138 100 95 8591 108 105
Standard deviation Cv (%) 8 5 4 3 2 2
Minimum value 5942 90 87 7814 104 100
Maximum value 8331 109 103 8974 111 107
Table 2 shows that the spinning holes produced by means of electron rays are by far more irregular than the holes produced in a conventional mechanical way, both in terms of their roundness and in terms of their area. It is possible to determine, in particular, a significantly larger scattering of the outlet areas F (from 5942 µm2 to 8331 µm2) in spinning holes produced by means of electron rays.
A solution of cellulose in a tertiary amine oxide, produced in accordance with the process as described in EP 0 356 419, was then extruded through the two above-described spinnerets. The extruded filaments were conveyed via an air gap into a precipitation bath in accordance with the process as described in PCT-WO 93/19230 and were processed to cellulose fibres in a manner known per se.
Thereby, it was first observed that, when extruding through the spinneret comprising spinning holes produced by means of electron rays, the spinning behaviour (i.e. the occurrence of filament breaks or of other spinning disturbances) was just as good as the spinning behaviour of the prior art spinneret.
The titre was measured at a representative cross-section of the produced fibres, and from this the mean value and the standard deviation Cv were evaluated and the maximum and minimum titres that were found were recorded.

The results are listed in the following Table 3:
Table 3
Nozzle comprising spinning holes produced by means of electron rays Nozzle comprising spinning holes produced in a conventional (mechanical) way
Titre (mean value) 1.34 dtex 1.20 dtex
Titre (minimum value) 0.94 dtex 0.77 dtex
Titre (maximum value) 1.66 dtex 1.55 dtex
Standard deviation Cv (%) 11.4 11.4
Table 3 shows that the two spinnerets that were tested achieve virtually equally good results in terms of the titre distribution that was obtained; and that was the case even though the spinning holes produced by means of electron rays had more irregular dimensions than the mechanically pierced spinning holes.
Example 2:
Two spinnerets each comprising appx. 25.000 spinning holes, whose diameters were specified as 160 µm in each case, are compared with each other, whereby the spinning holes of one spinneret were produced by means of electron rays and the spinning holes of the other nozzle were pierced in a conventional mechanical way.
Again, the spinfierets were configured as ring nozzles, such as described in PCT-WO 05/04173. The ring-shaped carrier material consisted of stainless steel.
In the following Table 4, the data of the spinnerets that were used are indicated in greater detail:

Table 4
Spinneret (manufacturing method) Steel quality Sheet thickness of the carrier material (mm) Strength of the steel (N/mm2)
Prior art (mechanically pierced holes) 1.4016 0.8 450-600
According to the invention (holes produced by means of electron rays) 1.4310 0.8 1,600 to 1,800
In the following, the dimensions of the outlets of the spinning holes were compared with each other, such as in Example 1.
In the following Table 5, the results of those measurements and calculations, respectively, are listed:
Table 5
Nozzle comprising spinning holes produced by means of electron rays Nozzle comp produced in (mechanicaf rising spinning holes a conventional way
AreaF (um2) dmax (um) dtheor. (urn) AreaF (um2) dmax (um) dtheor. (um)
Mean value from the measurements 18993 159 155 21193 166 164
Standard deviation Cv (%) 13.6 7.2 7.3 1.7 1.0 0.8
Minimum value 7325 105 97 20532 163 162
Maximum value 29620 200 194 21910 170 167

Again, Table 5 shows that the spinning holes produced by means of electron rays are by far more irregular than the holes produced in a conventional mechanical way, both in terms of their roundness and in terms of their area.
Solvent-spun cellulose fibres were then produced such as in Example 1 by using said spinnerets, and the titre distribution was measured.
Thereby, it was again observed that, when extruding through the spinneret comprising spinning holes produced by means of electron rays, the spinning behaviour was just as good as the spinning behaviour of the prior art spinneret.
The results with regard to the titre distribution are listed in the following Table 6:
Table 6
Nozzle comprising spinning holes produced by means of electron rays Nozzle comprising spinning holes produced in a conventional (mechanical) way
Titre (mean value) 6.6 dtex 6.6 dtex
Titre (minimum value) 4.6 dtex 4.8 dtex
Titre (maximum value) 7.9 dtex 10.7 dtex
Standard deviation Cv (%) 9.6 % 18.2%
Table 6 shows that, in this case, a significantly better titre distribution (smaller standard deviation) could be achieved by means of the spinneret used in accordance with the invention.
The spinnerets of the invention according to Example 1 and Example 2 can be manufactured at lower costs than the spinnerets involving a mechanical production of spinning holes which were used in each case for comparison purposes. Moreover, as per Table 1 and Table 4, the spinnerets according to the invention exhibit a markedly higher strength and therefore are capable of withstanding higher production pressures. Therefore, it is possible to significantly increase the productivity of the process by means of the spinnerets according to the invention.

WE CLAIM
1) A process for the production of cellulosic moulded bodies, wherein a moldable cellulose solution in an aqueous tertiary amine oxide polymer is extruded via a forming tool comprising a carrier material and at least one extrusion orifice arranged in the carrier material and the cellulosic moulded body is obtained from the extruded moulded mass in a manner known per se, by precipitation, characterized in that the moldable mass is extruded via a forming tool on which at least one extrusion orifice was produced by the application of thermal energy by means of electron rays.
2) A process as claimed in claim 1, wherein the use of a spinneret comprising extrusion orifices in the shape of one or several spinning holes as a forming tool.
3) A process as claimed in claim 2, wherein the mean diameter of the cross-section of the flow of cellulose solution extruded through the spinning hole is continuously decreased.
4) A process as claimed in claim 2 or 3, wherein the use of a carrier material configured in the shape of a ring.
5) A process as claimed in claim 2 or 3, wherein the use of a carrier material configured in the shape of a square, in particular in the shape of a rectangle.
6) A process as claimed in claims 2 to 5, wherein the use of a carrier material configured in the shape of a lamina in which the spinning holes are realized, with the lamina being inserted in holes, in particular stepped bores, of a support plate.
7) A process as claimed in claims 2 to 5, wherein the use of a carrier material configured in the shape of a deep-drawn spinning insert.
8) A process as claimed in claims 2 to 5, wherein the use of a carrier material which is flush with and welded into a nozzle body.
9) A process as claimed in claims 2 to 8, wherein the use of a spinneret in which more than 1000, preferably more than 10000, spinning holes are provided.
10) A process as claimed in claims 2 to 9, wherein the use of spinning holes whose outlet diameters range from 50 µm to 1000 µm, preferably from 100 µm to 500 µm.

11) A process as claimed in any of the previous claims, wherein the cellulose solution
has a zero shear viscosity of at least 100 Pas at 90°C.
12) A process as claimed in claim 11, wherein upon extrusion, the cellulose solution
is conveyed via an air gap into a precipitation bath.
13) A cellulosic moulded body, obtainable by a process according to any of the preceding claims.