Title of Invention

METHOD AND DEVICE FOR CUTTING SPUN FILAMENTS CONTAINING NMMO AND FOR CELLULOSE STAPLE FIBERS

Abstract

The present invention relates to the production of staple fibers consisting of spun filaments (2) which are produced according to the lyocell method from a spinning solution containing water, cellulose and tertiary amine oxide. According to the invention the tertiary amine oxide is not washed out of the spun filaments (2) prior to cutting by cutting means (9). The loop strength can be enhanced with this measure. To be more specific, in the method and the device according to the invention, loop strengths can be achieved in lyocell staple fibers of at least 15 cN/tex, partially even at least 20 cN/tex. (Fig. 1)

Full Text

Method and device for cutting spun filaments containing NMMO and for cellulose staple fibers The present invention relates to a method in which spun filaments are continuously extruded from a spinning solution containing water, cellulose and tertiary amine oxide, and are then stretched and passed through an air gap and a precipitation bath and cut into staple fibers, the spun filaments containing tertiary amine oxide during cutting. The present invention further relates to a device for cutting lyocell spun filaments, comprising a precipitation bath stage which during operation contains a precipitation bath containing a nonsolvent for a lyocell spinning solution, and comprising a continuously operable cutting means by which the lyocell spun filaments can be cut into staple fibers during operation. The method for producing cut spun fibers or continuous spun filaments from a spinning solution containing cellulose, water and a tertiary amine oxide, such as N-methylmorpholine-N-oxide, is called lyocell method. The name "lyocell" was given by the Standardization Organization for Chemistry, BISFA. The advantage of this method lies in its environmentally friendly production of fibers and filaments. This is made possible by the measure that tertiary amine oxide is returned in the production process and not discharged to the environment. The fundamentals of the lyocell method are described in US-A-4,144,080, US-A-4,246,221, US-A-4,261,943 and US-A-4,416,698. According to these publications a spinning solution containing water, cellulose and tertiary amine oxide is first fed as a solvent at a temperature between 90X and 120'C to a spinning head where the spinning solution is extruded into an air gap through spinnerets to obtain spun filaments. The spun filaments cross the air gap and immerse into a precipitation bath consisting of a nonsolvent. The cellulose is precipitated in the precipitation bath. These fundamental process steps have been maintained in this form even up to the present when lyocell filaments and fibers are produced on a large industrial scale. To produce lyocell staple fibers from spun filaments, the prior art has developed different approaches. WO 97/14829 A1 relates to a method for producing cellulosic fibers in which the water-containing swollen filaments are squeezed at very different points so that on average at least two squeezing points are present per millimeter of filament length. The squeezed filaments are then dried to obtain cellulosic fibers, and the squeezing points should here also be maintained on the dried fiber. The squeezing points should exhibit an enhanced adhesion of the fibers among one another and thus yield more easily cardable fibers. US 5,417,909 describes that spun filaments can be stretched by precipitation bath liquid which, following gravity, flows out of a long spinning funnel. According to the teaching imparted in US 4,863,478 the fiber properties can be improved if the tensile stress remains below 5.5 cN/tex in the finishing treatment of the filaments, including cutting. WO-A-94/28220, WO-A-94/27902, WO-A-94/27903. WO-A-95/24520 and WO-A-02/31236 describe methods in which after the precipitation bath the spun filaments are first washed in a water bath, subsequently dried and then crimped prior to cutting. The washing stage serves to remove tertiary amine oxide from the spun filaments prior to cutting. WO-A-92/14871 also deals with washing the spun filaments prior to cutting in order to remove tertiary amine oxide from the spun filaments. The washing process takes place in countercurrent baths kept at a controlled pH-value. V\/O-A-00/18991 adopts this idea and extends it to the washing of a nonwoven, i.e. also after the cutting of the spun filaments into staple fibers. In WO-A-00/18991, the pH-value of the wash baths is also set to specific values. WO-A-01/86043 and EP-A-1 362 935 describe how nonwoven mats of lyocell fibers are produced without cutting by centrifugal spinning or by direct formation of a random layer or nonwoven on a conveyor belt. Finally, in WO-A-04/088010, which also gives an extensive survey of the prior art regarding the cutting of staple fibers, the spun filaments are also washed and crimped prior to cutting. However, in order to enhance the tear strength of the staple fibers, these are post-stretched with simultaneous heat treatment. Although the known methods and devices already yield useful staple fibers, the mechanical strength values of the staple fibers produced with the known methods are too small for many applications. A strength value of particular relevance to staple fibers is here the loop strength which furnishes infornnation on a multitude of fiber characteristics, such as deformation behavior and brittleness. The loop strength is determined by a standardized test method according to DIN 53 843 Part 2. It is thus the object of the present invention to improve the known lyocell methods for producing staple fibers such that the loop strength is enhanced. This object is achieved for the above-mentioned method according to the invention in that after the precipitation bath and prior to cutting the spun filaments are passed through a treatment liquid which leaves tertiary amine oxide in the spun filaments or applies tertiary amine oxide to the spun filaments during cutting. As for the above-mentioned cutting device, this object is achieved according to the invention in that the precipitation bath and the cutting means have arranged thereinbetween at least one treatment bath with a treatment liquid that does not substantially reduce the concentration of tertiary amine oxide in the spun filaments. This method and this device yield lyocell staple fibers having a loop strength of at least 15 cN/tex and even at least 20 cN/tex during cutting at increased concentrations of tertiary amine oxide in the spun filaments. The solution according to the invention is not simple, but it is based on the surprising finding that the loop strength of the finished staple fiber will increase if the spun filaments still contain tertiary amine oxide at the time of cutting. Hence, the invention adopts exactly the opposite approach as described in the above-mentioned publications WO-A-94/28220, WO-A-94/27902, WO-A-94/27903, WO-A-95/24520, WO-A-02/31236, WO-A-00/18991 and WO-A-04/88010, for if one proceeds in compliance with the teachings imparted in these publications, the tertiary amine oxide must be fully washed out of the spun filaments prior to cutting. The loop strengths achievable with these methods are however below the loop strengths as are achievable with the method according to the invention. The reason for the increase in loop strength in the method according to the invention and the device according to the invention seems to be that the spun filaments are cut in a condition in which they are still highly swollen by the aqueous amine oxide and that the spun filaments can freely shrink after cutting into fiber form, for in contrast to the spun filaments which according to the above publications are washed and dried prior to cutting and are thus subjected to uncontrollable tensile stresses during drying, the staple fibers produced according to the invention are not restrained in any way in their shrinkage possibilities while being fully strain-relieved due to their short lengths. This seems to result in enhanced strength across the fiber direction and thus in improved loop strength. The consequence is increased elasticity which is important especially in the field of textile refining and to the performance of the staple fibers. The staple fibers produced according to the invention are insensitive to further textile processing steps, such as spinning, dyeing, finishing, crosslinking, etc. Starting from this solution principle, further advantageous developments are possible that can each be realized independently of one another. For instance, the spun filaments after the precipitation bath stage and prior to cutting can be brought in treatment stages into contact with treatment liquid that does not substantially reduce the concentration of tertiary amine oxide in the spun filaments and, in particular, does not completely wash the tertiary amine oxide out of the spun filaments. To be more specific, the precipitation bath stage and cutting means may have arranged thereinbetween treatment baths with corresponding treatment liquids that have a high content of tertiary amine oxide, such as N-methylmorpholine-N-oxide, in the treatment liquid. To prevent tertiary amine from being washed out of the spun filaments prior to the cutting operation, the concentration of tertiary amine oxide should not be below the concentration of tertiary amine oxide in the spun filaments. Likewise, with high concentrations of tertiary amine oxide in the treatment liquid, tertiary amine oxide can additionally be introduced into the finished spun filaments. It has been found in tests described hereinafter that already a first and quite considerable increase in the loop strength will be achieved if the concentration of tertiary amine oxide in the treatment liquid is at least 2 to 4 percent by mass. A further considerable increase in loop strength can be achieved if the content of tertiary amine oxide in the treatment liquid is at least between 10 and 12 percent by mass. To perform the cutting operation in the case of spun filaments that are highly swollen by the aqueous amine oxide, the spun filaments should be cut within 10 to 180 s or 20 to 180 s after extrusion. The reason is that if the extrusion process took place more than 180 s ago, partly crystalline structures are already found on the surface of the spun filaments, such structures being subjected to great mechanical loads in the course of the shrinking process of the spun fibers after cutting, resulting in loop strengths that are not so high any more. Preferably, however, the cutting process takes place not more than 80 s, even more preferably not more than 60 s, after the extrusion process. To keep the equipment small and the process concise, it is also of advantage when the first treatment of the spun filaments with a treatment liquid takes place directly before the cutting operation. To be more specific, the spun filaments can be passed in a stream of treatment liquid to the cutting operation. To this end an injector device may for instance be used which has a spun-filament guide channel arranged therein. The spun-filament guide channel ends directly before the cutting stage, and a treatment liquid stream directed onto the cutting means is flowing through the channel during operation. In this stream the spun filaments are entrained and transported to the cutting means. Instead of an injector, injecting or spraying means as well as baths may be provided for wetting the spun filaments with treatment liquid. If washing operations are performed prior to cutting, in which tertiary amine oxide can be washed with a washing liquid out of the spun filaments, these should be carried out according to the present teaching for the first time directly before or during the cutting operation. Otherwise, a treatment stage with treatment liquid should be arranged after the washing stage, by which treatment stage the spun filaments can again be doped or enriched with tertiary amine oxide. After cutting the spun filaments cut at a high NMMO content are subject to stronger shrinkage than is the case with the washed spun filaments cut without NMMO. Therefore, in order to set the desired staple fiber length in the cutting operation, the cutting length of the fibers should be set to be at least 12-15% above the desired length of the dried staple fiber. The NMMO content of the treatment liquid in the treatment steps can be controlled automatically in an advantageous development, with the NMMO content being detected via sensors, and deviations from a desired value being compensated by automatic metered additions of NMMO or a diluent, such as water, to the treatment liquid. For this purpose the above-mentioned device may be provided with dosing pumps and an electronic control unit connected to the sensors and the dosing pumps in a signal-transmitting manner. Alternatively, the NMMO content may also be determined by hand and set by manual addition of NMMO or a diluent in a corresponding way. The invention will now be explained by way of example with reference to an embodiment taken in conjunction with the drawings, in which: Fig. 1 is a schematic view of a first embodiment together with an alternative design; Fig. 2 is a schematic view of a second embodiment; Fig. 3 is a schematic view illustrating the influence of the NMMO concentration in the treatment liquid for the spun filaments on the loop strength of the staple fibers. The structure of a device 1 designed according to the invention and used for cutting lyocell spun filaments 2 shall first of all be described with reference to the schematic illustration of Fig. 1. The spun filaments 2 are continuously extruded into an air gap 4 through a spinneret (not shown in Fig. 1) with several thousand extrusion orifices from a spinning solution containing cellulose, water and tertiary amine oxide. As for the extrusion of the lyocell spun filaments, full reference is made to WO-A-03/57951 and V\/O-A-03/57 952, and with respect to the design and function of the spinneret reference is made to WO^A-01/81663. After having crossed the air gap 4, the spun filaments 2 immerse into the precipitation bath 3a of the precipitation bath stage 3. The precipitation bath 3 contains a nonsolvent for the extruded spun filaments 2, so that the cellulose in the spun filaments is precipitated. The individual spun filaments from the spinnerets are collected on a roller-like deflector 6 arranged in the precipitation bath 3a and are passed on to several or a pair of take-off rollers 7 as a fiber cable 6 consisting of a multitude of spun filaments 2. Instead of the configuration shown in Fig. 1 with one pair of take-off rollers 7, it is also possible to arrange pairs of take-off rollers 7 one after the other. The take-off rollers 7 continuously introduce a drawing force acting in the area of the air gap 4 into the spun filannents 2. In the air gap 4, this force causes a stretching of the spun filaments to the desired titer and orients the cellulose molecules in parallel with the stretching force. After the precipitation bath the fiber cable 6 is supplied to a cutting stage 8'. The cutting stage 8' has integrated thereinto a treatment stage 8" by which the spun filaments 2 are impregnated directly or shortly before the cutting process with a treatment liquid containing amine oxide. The treatment stage 8" can e.g. be configured as an injector 8. The injector conveys the spun filaments continuously to the cutting means 9 which cut the spun filaments into staple fibers. The cutting means 9 are located at a position reached by the spun filaments 2 within not more than 180 s, but preferably not more 80 s, and ideally within not more than 60 s, after extrusion. The injector 8 comprises a spun-filament guide channel 10 through which during operation treatment liquid flows towards the cutting means 9, thereby transporting the spun filaments 2, combined in fiber cable 6, to the cutting means 9. Thus the injector 8 simultaneously forms a conveying means and a treatment stage for the spun filaments. In this configuration the treatment stage is structurally integrated with the cutting means 9 into a structural unit. The cutting means 9 are e.g. rotating cutting knives which are mounted on a rotating cutting disk 11 and pressed via a spring mechanism 12 against an abrasive ring 13 which keeps the knives in a sharp condition during operation. A motor 14 serves as a drive of the cutting means 9. The exit of the spun-filament guide channel 10 is arranged such that it is swept over by the turning circle of the cutting means 9, and the spun filaments 2 combined in the fiber cable 6 are cut each time when a cutting means 9 is sweeping over the exit of the injector 8. The staple fibers 15 obtained in this way are washed out together with the treatment liquid after the cutting operation. For instance, the staple fibers 15 can fall in random orientation onto a conveying means 16 from which they are transported to further processing stages. The treatment liquid from the injector is collected in a collection tank 17 and can, as illustrated by arrow 18, be subjected to a cleaning operation, for instance filtration. After cleaning the regenerated treatment liquid can again be supplied according to arrow 19 and under pressure to the treatment stage. A control unit 20 measures, via a sensor 21, the content of tertiary amine oxide, particularly N-methylmorpholine-N-oxide, in the treatment liquid 22. If the concentration of tertiary amine oxide in the treatment liquid 22 deviates from a predetermined desired value for the concentration, for instance a desired value of 4 % by mass of NMMO, this deviation can be corrected through the control device 20. For instance, when the concentration of tertiary amine oxide falls below the desired value, amine oxide can additionally be fed via a dosing pump 23a and a line 23b from a resen/oir 23c into the treatment liquid returned to the injector 8. By contrast, if the concentration of tertiary amine oxide rises above the desired value, a nonsolvent, such as water, can be admixed via a further dosing pump 24a and a further line 24b from a tank 24c or another source to the treatment liquid returned to the injector 8. For operating the dosing pump 23a, 24a and for recording the signals of the sensor 21 the control unit 20 is connected in a signal-transmitting way via data lines 25, which may also be implemented to be wireless, to said devices. Also highly swelling liquids which are miscible with the tertiary amine oxide can be used as treatment liquids for the spun filaments. For instance, hydrophilic polymers, such as polyethylene glycol or polyethylene glycol derivatives, with different molecular weights of e.g. 200, 400 or 1000 can be added in diluted form and in concentrations of 0.2 g/l and 1 g/l to the treatment liquid in the cutting stage. The concentration of the tertiary amine oxide in the treatment liquid returned to the injector amounts to at least 2 to 4 percent by mass, preferably at least 10 to 12 percent by mass. If, as illustrated in the embodiments of Figs. 1 and 2, the treatment liquid comes into contact with the spun filaments directly before the cutting operation, the treatment liquid can also be used for washing the spun filaments. In actual fact, due to the short contact time of the washing liquid and the integration of said first washing stage into the cutting machine, the tertiary amine oxide cannot be completely washed out. In this case the cutting operation is still performed at an adequate NMMO concentration in the spun filaments 2. As further shown in Fig. 1 by a double-dash-dotted line, the precipitation bath stage 3 and the treatment liquid stage adjoining the cutting means 9 may have disposed thereinbetween treatment stages in the form of treatment baths 26 through which the spun filaments 2 of the fiber cable 6 are passed. These treatment stages may be provided instead of or together with the treatment stage integrated into the cutting machine. Fig. 1 just shows by way of example a single optional treatment bath 26. However, it is also possible to arrange several treatment baths one after the other. It is essential for the quality of the treatment liquid in the treatment bath 26 that the tertiary amine oxide is not washed out of the fiber cable 6, so that the spun filaments 2 still have an adequately high content of tertiary amine oxide on the cutting means 9. For this purpose the treatment bath 26 and possible further treatment baths 25 between the precipitation bath 3 and the cutting means 9 also have a concentration of at least 2 to 4 percent by mass, preferably at least 10 to 12 percent by mass of tertiary amine oxide. Since after the cutting process the staple fibers cut while containing NMMO shrink to a greater degree than the staple fibers in which the tertiary amine oxide was washed out before cutting, a cutting length which is 12-15% above the length of the finished stable fiber must be set on the cutting means 9. The influence of the concentration of the tertiary amine oxide N-methylmorpholine-N-oxide in the treatment liquid 22 and 25, respectively, on the loop strength of the staple fiber was checked in tests in which spun filaments 2 were extruded at a spinning velocity of 20 m/min. The fiber cable 6 had a total titer of 174,500 dtex. The staple fibers were cut to an average length of 38 mm. To this end a cutting length of 44 mm was set on the cutting device. Fig. 2 shows a further embodiment of the cutting stage 8' with integrated amine oxide treatment stage 8". It is just the differences with respect to the preceding embodiment of Fig. 1 that shall be discussed in the following. As for elements that in their structure and function correspond to those of the first embodiment, the same reference numerals as employed in the first embodiment shall be used hereinafter. In the embodiment of Fig. 2, the cutting means 9 is designed in a different way. The cutting means 9 comprises a plurality of cutting knives 30 which are arranged between two axially spaced-apart rotating disks 31, 32 and are oriented radially outwards, so that the cutting surface of the cutting knives 30 in radial direction is oriented outwards. A press roH 33 rotating with disks 31. 32 is pressed against the cutting knives 30. The fiber cable 6 extends between the press roll 33 and the cutting means 9 and is pressed by the press roll 33 into the cutting knives 30 and cut into staple fibers 15 which are transported via a conveying means 16 to further processing stages. The length of the staple fibers 15 can be set through the distance 34 of the cutting knives 30 from each other in circumferential direction. . Due to the treatment stage 8" integrated into the cutting stage 8', the fiber cable is wetted with a treatment liquid 35 which is directed by injecting or spraying means 36 onto the area of the fiber cable 6 directly in front of the cutting means 9. The treatment liquid 35 has preferably a concentration of tertiary amine oxide corresponding to the concentration of the tertiary amine oxide in the spun filaments at said place. Alternatively, the treatment liquid 35 can also flow in radial direction through the gaps between the cutting knives 30, i.e. between the two cutting disks 31, 32, so that the knives are washed and freed from deposits by the treatment fluid at the same time and the treatment fluid, in particular, is directly guided onto the cutting place. The NMMO concentration was set in eight test runs each time to different values, with the NMMO concentration being kept constant at said values. Subsequently, the loop strength of the staple fibers obtained in this way was measured with the loop tensile test according to DIN 53 843 Part 2. The following Table shows the values of the loop strength in dependence upon the NMMO concentration in the treatment liquid: Fig. 3 is a schematic illustration showing the values of the above table. As can be seen in Fig. 3, substantially three different areas A, B and C are obtained in dependence upon the NMMO concentration in the treatment liquid. In each of these areas the loop strength shows a different dependence on the NMMO concentration. In the first area A, which extends from an NMMO concentration in the treatment liquid for the spun filaments from 0 to a first limit CAB, the loop strength varies already considerably in dependence upon only a minor change in the NMMO concentration. The absolutely achievable values for the loop strength are however still small and range between 8 cN/text and about 13 cN/text to 14cN/tex.The concentration CAB is between 2 percent by mass and 4 percent by mass after the tests. In the second area B, which ranges from the limit value CAB to a second limit value CBC for the concentration of the treatment liquid for the spun filaments, the loop strength only rises at a slower rate with the increase in the NMMO concentration than in the first area A, but the achievable values for the loop strength are on the whole higher and are about 20 cN/tex near the limit CBC- The second limit value CBC is between 10 percent by mass and 12 percent by mass. In the third area C, which is obtained at NMMO concentrations in the treatment liquid for the spun filaments of at least CBC. the loop strength only changes to a minor degree. The achievable values for the loop strength in area C are at least 20 cN/tex; as shown in the above test examples, even around 21 cN/tex. Hence, it has been shown by way of the test examples that with an increasing NMMO concentration in the treatment fluids 22 or 25 the loop strength is rising. This means that the content of tertiary amine oxide in the lyocell spun filament 2 is of relevance to the increase in loop strength. New Claims 1. A method in which spun filaments (2) are continuously extruded from a spinning solution containing water, cellulose and tertiary amine oxide, and are then stretched and passed through an air gap (4) and a precipitation bath (3a) and cut into staple fibers (15), the spun filaments (2) containing tertiary amine oxide during cutting, characterized in that after the precipitation bath (3a) and prior to cutting the spun filaments (2) are passed through a treatment liquid which leaves tertiary amine oxide in the spun filaments or applies tertiary amine oxide to the spun filaments. 2. The method according to claim 1, characterized in that prior to cutting the tertiary amine oxide is not completely washed out of the spun filaments (2). 3. The method according to any one of the above-mentioned claims, characterized in that the treatment liquid (22, 25) has a concentration of least 2 percent by mass to 4 percent by mass of tertiary amine oxide. 4. The method according to claim 3, characterized in that the concentration of the tertiary amine oxide in the treatment liquid is at least 10 percent by mass to 12 percent by mass. 5. The method according to any one of the above-mentioned claims, characterized in that a stream of treatment liquid (22) is generated in which the spun filaments (2) are guided to cutting. 6. The method according to any one of the above-mentioned claims, characterized in that the spun filaments (2) are brought into contact with the treatment liquid (22, 25) for the first time directly before or during cutting. 7. The method according to any one of the above-mentioned claims, characterized in that the cutting length of the fibers is set to be at least 12-15% above the average desired length of the finished staple fibers (15). 8. The method according to any one of the above-mentioned claims, characterized in that the concentration of tertiary amine oxide in at least one treatment liquid (22, 25) with which the spun filaments (2) are brought into contact after leaving the precipitation bath (3a) and before being cut is set in dependence upon the average desired loop strength of the finished staple fiber. 9. The method according to any one of the above-mentioned claims, characterized in that the spun filaments (2) are cut within 180 s after extrusion. 10. The method according to claim 9, characterized in that the spun filaments (2) are cut within 80 s after extrusion. 11. The method according to claim 10, characterized in that the spun filaments (2) are cut within 60 s after extrusion. 12. A device (1) for cutting lyocell spun filaments (2), comprising a precipitation bath stage (3) which during operation contains a precipitation bath (3a) containing a nonsolvent for a lyocell spinning solution, and comprising a continuously operable cutting means (9) by which the lyocell spun filaments (2) can be cut into staple fibers (15) during operation, characterized in that the precipitation bath (3) and the cutting means (9) have arranged thereinbetween at least one treatment bath (8) with a treatment liquid that does not substantially reduce the concentration of tertiary amine oxide in the spun filaments. 13. The device (1) according to claim 12, characterized in that treatment baths (9, 10) arranged between the precipitation bath stage (3) and the cutting means (9) have a concentration of at least 2 percent by mass to 4 percent by mass of tertiary amine oxide. 14. The device (1) according to claim 13, characterized in that treatment baths arranged between the precipitation bath stage (3) and the cutting means (9) have a concentration of at least 10 percent by mass to 12 percent by mass of NMMO. 15. The device (1) according to any one of claims 12 to 14, characterized in that the first treatment bath (22) is arranged directly in front of the cutting means (9). 16. The device (1) according to any one of claims 12 to 15, characterized in that the first treatment bath (22) extends up to the cutting means (9). 17. The device (1) according to any one of claims 12 to 16, characterized in that a spun- filament guide channel (10) which during operation can generate a treatment liquid stream directed towards the cutting means (9) is arranged directly in front of the cutting means. 18. The device according to any one of claims 12 to 17, characterized in that the first treatment stage is structurally integrated into the cutting machine.

Documents:

5914-CHENP-2007 AMENDED PAGES OF SPECIFICATION 02-03-2012.pdf

5914-CHENP-2007 AMENDED CLAIMS 02-03-2012.pdf

5914-CHENP-2007 FORM-3 02-03-2012.pdf

5914-CHENP-2007 OTHER PATENT DOCUMENT 02-03-2012.pdf

5914-CHENP-2007 POWER OF ATTORNEY 02-03-2012.pdf

5914-CHENP-2007 CORRESPONDENCE OTHERS 20-10-2011.pdf

5914-CHENP-2007 CORRESPONDENCE OTHERS.pdf

5914-CHENP-2007 CORRESPONDENCE PO.pdf

5914-CHENP-2007 EXAMINATION REPORT REPLY RECEIVED 02-03-2012.pdf

5914-chenp-2007 form-13 18-06-2008.pdf

5914-chenp-2007 form-13 (1) 18-06-2008.pdf

5914-chenp-2007 form-6 18-06-2008.pdf

5914-chenp-2007-abstract.pdf

5914-chenp-2007-claims.pdf

5914-chenp-2007-correspondnece-others.pdf

5914-chenp-2007-description(complete).pdf

5914-chenp-2007-drawings.pdf

5914-chenp-2007-form 1.pdf

5914-chenp-2007-form 18.pdf

5914-chenp-2007-form 3.pdf

5914-chenp-2007-form 5.pdf

5914-chenp-2007-pct.pdf

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