Patent Application
20050012238
The present invention is concerned with a device as well as a process for the production of cellulosic staple fibers.
In conventional processes for the production of cellulosic staple fibers, freshly spun, cellulosic continuous filaments are cut into staple fibers in a cutting machine. From the outlet of the cutting machine, the staple fibers are transported along and treated further. For instance, the staple fibers are suspended to a fleece in a suspension means. Thereafter, said fleece is subjected to further treatment steps such as washing and finishing stages.
Devices known from the state of the art comprise a cutting device for cutting the continuous filaments into staple fibers and a liquid-transport device for transporting the staple fibers.
According to the state of the art, the liquid-transport device usually is configured as a groove the beginning of which is arranged, for instance, underneath the cutting device. A bundle of continuous filaments to be cut enters the cutting device and is cut there into fibers of a particular length usually by means of rotating knives. After cutting, the cut fibers form a bundle or staple, respectively. The cut fibers are flushed from the cutting device into the groove by means of a liquid such as water and are transported along in the groove by means of the liquid, for instance, towards a suspension means.
In those known processes or devices, respectively, the problem arises that the staples formed during cutting fail to come apart into individual fibers by the time the fiber fleece is formed in the suspension means. Staples which have not sufficiently come apart into individual fibers are referred to herein as “aggregated” (or “agglomerated”) staples.
Such aggregated staples in the fiber fleece cause in-homogeneities with respect to the wash-out and exchange behavior in the stages of after treating the fleece. Usually, the staples are washed out worse, bleached less, cross-linked worse, finished worse etc.
Furthermore, aggregated staples often cause quality problems during the subsequent treatment and processing of the fibers.
The present invention relates to a device for the production of cellulosic staple fibers comprising a cutting device for cutting cellulosic continuous filaments into staple fibers and a liquid-transport device for transporting the staple fibers, where the liquid-transport device comprises a syphon.
The object of the present invention is to provide a device as well as a process by means of which the above mentioned drawbacks are avoided and especially the number of aggregated staples and their sizes (i.e. the number of fibers per staple) in the fiber fleece is reduced.
That object is achieved by the aid of a device which comprises a cutting device for cutting cellulosic continuous filaments into staple fibers and a liquid-transport device for transporting the staple fibers and which is characterized in that the liquid-transport device is provided with a portion shaped as a syphon.
It was found that, surprisingly, replacing the groove known from the state of the art with a syphon facilitated the coming apart of the fibers during the transport.
The syphon is filled to capacity by the liquid emerging from the cutting device together with the fibers. Because of that, the transport of the fiber staples is no longer effected in a streaming but in a freely floating manner. The tendency to agglomerate occurring in the known streaming process and the tumbling staple movement is avoided.
Furthermore, the staples are able to swell freely since they are wetted with liquid from all sides.
Preferably, the device according to the invention furthermore comprises a suspension means for suspending the staple fibers to a fleece. The liquid-transport device preferably leads from the outlet of the cutting device to the suspension means.
Preferably, the syphon is immediately adjacent to the cutting device.
In a further preferred embodiment of the device according to the invention, an intermediate portion preferably running essentially horizontally is provided between the downward and upward limbs of the syphon.
The length of said intermediate portion is at least equal to, preferably at least 10 times as long as, particularly preferably at least 30 times as long as, the length of the downward limb of the syphon.
In the intermediate portion, which preferably is a few times as long as the length of the downward limb of the syphon, the flow of the staples in the tube may develop further and the staples are opened up even better.
The lengths of the two limbs of the syphon may essentially be equal.
In a further preferred embodiment it is provided that the liquid-transport device has a further portion preferably also configured as a tube and leading from the syphon to the suspension means.
Said further portion preferably comprises a downward partial section, which, furthermore, preferably leads downward in an essentially vertical way. The vertical dimension of the downward partial section advantageously is essentially equal to the vertical dimension of one of the limbs of the syphon.
By providing a downward partial section, the potential energy of the fiber staples may be utilized even better at the outlet of the syphon-type portion. During the downward movement, the fiber staples are accelerated. To this end, it has proven to be beneficial if an aperture for airing the tube is provided at a high point of the syphon.
Preferably, the downward partial section changes into a further partial section leading to the suspension means, which further partial section preferably runs essentially horizontally.
With the accelerated fiber staples impinging in the passage leading from the downward partial section to the further partial section, a further opening of the staples occurs.
To this end, preferably a downward bulge may be provided at the transitional point between the downward partial section and the further partial section, by means of which bulge the effect of that impact is increased even further.
According to a further aspect, the object of the present invention is achieved by means of a process wherein freshly spun, cellulosic filaments are cut into staple fibers in a cutting machine, the staple fibers are transported from the outlet of the cutting machine to a suspension means and are suspended to a fleece in the suspension means and the fleece is subjected to further treatment steps, which process is characterized in that the transport of the fibers from the outlet of the cutting machine to the suspension means is carried out in a device according to the invention.
In doing so, the retention time of the fibers in the liquid-transport device preferably amounts to from 2 to 40 s. preferably from 10 to 30 s. The flow rate of the fibers in the portion shaped in the manner of a syphon preferably amounts to from 0.15 to 2 m/s, preferably from 0.3 to 1.5 m/s.
In a preferred embodiment of the process according to the invention, which is realized using a device provided with a downward partial section, the fibers in the downward partial section preferably are accelerated to a speed of from 1 to 5 m/s, preferably from 2 to 3 m/s.
The device according to the invention as well as the process according to the invention are particularly suitable for the production of solvent-spun, cellulosic staple fibers. Those fibers are also known under the generic name “Lyocell fibers” and are produced from a solution of cellulose in a tertiary amine oxide (amine-oxide process).
In the following, preferred embodiments of the present invention are explained in more detail by way of the figures as well as the examples:
Thereby,
According to a preferred embodiment of the device according to the invention, the liquid transport device 2, as seen in
At the outlet of the syphon 4, a further portion 8 leading to the suspension means 3 is provided. The portion 8 is provided with a partial section 9 leading downward in an essentially vertical way and changing into a further partial section 10 running essentially horizontally and advantageously being tubular as well. The vertical dimension of the partial section 9 is essentially equal to the vertical dimensions of the two limbs 5,6 of the syphon 4. Optionally, however, the partial section 10 might also be open, i.e., shaped as a groove, for instance.
In the preferred embodiment shown in
In the embodiment shown in
The functioning of the device according to
The staple fibers cut in the cutting device 1 are flushed by means of a liquid from the cutting device 1 into the portion 4 of the liquid-transport device 2, said portion being shaped as a tube, and are transported along from there. Due to the syphon-type configuration of the portion 4, the tube is completely liquid-filled up to the outlet of the syphon. Thus, the fibers are transported in the floating state and are completely surrounded by liquid, whereby the staples are enabled to swell freely and better opening (coming apart to release individual fibers) will occur.
After leaving the syphon 4, the fibers fall down in the downward partial section 9 and hence are accelerated. With the impact on the transitional point between partial section 9 and partial section 10, a further opening of the staples occurs. That effect may even be increased by means of the bulge 11 shown in
In a continuously operating pilot plant for the production of solvent-spun, cellulosic staple fibers, the fibers were cut and transported in a device according to
Thereby, the length of the limbs 5,6 of the syphon-type portion 4 amounted to 0.5 m, the length of the intermediate portion 7 amounted to 10 m. The flow rate of the fibers in the syphon-type portion 4 amounted to about 0.45 m/s. In the downward partial section 9, the fibers were accelerated to a speed of about 2.5 mis. The entire retention time of the fibers in the liquid-transport device 2 amounted to about 20 s.
In order to assess the effect of the device, samples of the fleece formed in the suspension means are taken. The number of aggregated staples per 50 cm2 of fleece cross-section is determined. Furthermore, the staples are grouped according to their size ranges. The number of aggregated staples encountered according to the respective size ranges is multiplied by a conversion factor as follows: size range conversion factor
(Staples of a size of less than 3 mm are not included in the calculation.)
The values thus obtained are summed up. From this calculation, a characteristic staple number results, which supplies information about the quality of the formed fleece with respect to the aggregated staples contained therein.
The characteristic staple number of the fleece made up of fibers transported by means of the device according to the invention amounted to 39. In contrast to that, the characteristic staple number of a fleece made up of fibers produced in the same way but transported in accordance with the state of the art amounted to 67.
| Number | Date | Country | Kind |
|---|---|---|---|
| A2042/2001 | Dec 2001 | AT | national |
The present application is a continuation of International Patent Application No. PCT/AT02/00363, filed Dec. 19, 2002, published in German on Jul. 10, 2003 as International Patent Publication No. W003/056079A1, which claims priority to Austrian Application No. A 2042/2001, filed Dec. 27, 2001, each of which are incorporated herein in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/AT02/00363 | Dec 2002 | US |
| Child | 10877187 | Jun 2004 | US |
