Patent Grant
12241180
This is the U.S. National Phase application of PCT/JP2020/012328, filed Mar. 19, 2020, which claims priority to Japanese Patent Application No. 2019-063203, filed Mar. 28, 2019, the disclosures of each of these applications being incorporated herein by reference in their entireties for all purposes.
The present invention relates to a production method for a stable, high-quality, high-grade acrylonitrile based fiber bundle suitable for producing a carbon fiber bundle.
For the production of an acrylonitrile based fiber bundle used as a precursor fiber bundle for a carbon fiber bundle, it is important to reduce the production cost by increasing the production efficiency. To meet this objective, various methods have been adopted such as increasing the number of spinneret holes per spindle, increasing the number of spindles or fibers, and increasing the traveling speed of the fibers. Of these, the method of increasing the number of spinneret holes per spindle (increasing the number of holes, adopting an arrangement with higher discharge hole density) and the method of increasing the traveling speed of the fibers (adopting a higher speed) are highly advantageous from the viewpoint of meeting the above objective without requiring large equipment investment.
In particular, the dry-jet wet spinning method, which adopts an air layer (air gap) provided between the spinneret and the surface of the coagulation bath liquid, is a good means for increasing the traveling speed of the fiber because the spinning dope solution discharged from the spinneret surface can thin as it runs through the air gap where air resistance is small. If this spinning method is used, furthermore, the distance across the air gap can be maintained constant, serving to produce an acrylonitrile based fiber bundle with stable quality and grade and ensures high productivity.
In general, in this dry-jet wet spinning method, the spinning dope solution is first extruded into the air from a spinneret and then the spinning dope solution comes into contact with a coagulation bath liquid to form coagulated fibers, which travel downward (toward the bottom of the coagulation bath) through the coagulation bath liquid. After traveling over a certain distance, their traveling direction is changed by a direction changing guide part to cause them to travel diagonally upward (toward the surface of the coagulation bath liquid), and they finally run out of the coagulation bath liquid into the air, followed by being conveyed into the next process. Since accompanying flows are generated as a result of the traveling of the coagulated fibers, the accompanying flows increase with increasing traveling speed, number of holes, and density of discharge holes. As accompanying flows increase, the flow velocity of the coagulation bath liquid around the coagulated fibers increases, which causes uneven tension and physical properties of the coagulated fibers, resulting in deterioration of the quality and grade of the acrylonitrile based fiber bundle. In addition, as the flow speed of the flowing coagulation bath liquid increases, the surface of the coagulation bath liquid fluctuates more largely, which causes a decrease in spinnability and then leads to a decrease in production efficiency. This suggests that control of the flow of the coagulation bath liquid is an extremely important factor in the improvement in quality, grate, and production efficiency of an acrylonitrile based fiber bundle.
Here, an available method for controlling the flow of the coagulation bath liquid around the coagulated fibers is described in Patent document 1. For the method described in Patent document 1, it is proposed that a block containing a plurality of spinneret discharge holes is formed, followed by dividing the block into two or more parts in such a manner that the distance between any two adjacent blocks is at least twice the distance between the spinneret and the surface of the coagulation bath liquid. Furthermore, it is also described that a protrusion should be formed on the direction changing guide part existing in the coagulation bath liquid to work to change the traveling course of the coagulated fibers, which ensures improved control of the flow of the coagulation bath liquid and an increased spinnability of the coagulated fibers.
In addition, according to the spinning method described in Patent document 2, a thin tube having two or more openings is used to separate the coagulated fibers and the coagulation bath liquid, and a plurality of direction changing guide parts are arranged on the downstream side thereof so that the coagulated fibers are divided into two or more parts in the take-up direction of the coagulated fibers. This works to control the turbulence and vortex generation in the coagulation bath liquid near the surface of the coagulation bath liquid and accordingly serves for the production of coagulated fibers having high quality and a certain required level of quality.
However, these conventional spinning methods have problems as described below.
The spinning method proposed in Patent document 1 sometimes fails in sufficiently relaxing the accompanying flows around coagulated fibers in the coagulation bath liquid, resulting in an insufficient improvement in the spinnability of the coagulated fibers.
Furthermore, if fibers among the coagulated fibers are in a densely packed state as they travel, the accompanying flows can increase and in addition, the flow speed of the coagulation bath liquid moving toward the coagulated fibers can increase in the vicinity of the surface of the coagulated bath liquid, possibly leading to collisions between the fibers and generation of local vortices near the surface of the coagulation bath liquid (hereinafter referred to simply as local vortices). If such local vortices occur, it causes fluctuations in the air gap, i.e., the distance between the spinneret and the surface of the coagulation bath liquid. In addition, as the accompanying flows increase, the sway of the coagulated fibers grows between the spinneret and the direction changing guide part, and these troubles can cause larger fluctuations in the surface of the coagulation bath liquid and yarn breaks, possibly leading to a spinning failure in the worst case.
Furthermore, the spinning method proposed in Patent document 1 uses blocks containing a plurality of spinneret discharge holes and the distances between the blocks are increased. Accordingly, it requires spinnerets with larger widths. It also requires a coagulation bath with a larger width. As the use of equipment containing multiple coagulation baths spindles arranged side-by-side has now become the mainstream, increases in the widths of spinnerets and widths of coagulation baths mean that equipment with a larger width will be necessary and the required equipment cost will increase in some cases.
Next, for the spinning method proposed in Patent document 2, insight of the present inventors suggests that, as described above for Patent document 1, the accompanying flows around the coagulated fibers in the coagulation bath liquid cannot be relaxed sufficiently in some cases, which may cause disturbances in the flow of the coagulation bath liquid, generation of local vortices, and yarn breaks, possibly leading to a spinning failure in some cases. As a result, it becomes impossible in some cases to produce coagulated fibers with high quality and a certain required level of quality. In particular, as described in Examples of Patent document 2, the speed of winding after stretching is as low as 400 m/min (the take-up speed in the coagulation bath liquid is 10 m/min or less), and the number of discharge holes in the spinneret is also as small as 400, indicating that the size of the accompanying flows is small and does not pose a problem. However, the above problems can begin surfacing in some cases as the take-up speed and the number of holes are increased (up to a take-up speed of 25 m/min or more, several thousands of holes).
For the spinning method proposed in Patent document 2, furthermore, a plurality of direction changing guide parts are provided to divide the coagulated fibers and as a result, it is necessary to the thread each of the direction change guides, which may cause deterioration of operating performance in some cases. In addition, since a thin tube is provided under the coagulation bath to allow the flow of the coagulation bath liquid to move out of the coagulation bath, the equipment has a complicated structure because it requires multiple circulation lines and recovery lines for the flow of the coagulation bath liquid, leading to an increase in equipment cost in some cases.
Thus, for producing an acrylonitrile based fiber bundle, control of the flow of the coagulation bath liquid around coagulated fibers and control of the surface fluctuations of the coagulation bath liquid are extremely important factors. As described above, however, various problems remain and have hindered the production of acrylonitrile based fiber bundles. Therefore, solving these problems has an important industrial meaning.
Thus, the main object of the present invention is to provide a method for producing an acrylonitrile based fiber bundle by dry-jet wet spinning that serves to allow a high-grade, high-quality acrylonitrile based fiber bundle to be produced stably even if the traveling speed of the coagulated fibers is increased or the number of spinneret discharge holes is maximized in an attempt to enhance the production efficiency.
The present inventors have set the following hypotheses to explain why the spinnability of coagulated fibers cannot be sufficiently improved by the techniques proposed in Patent documents 1 and 2.
In the case of the technique proposed in Patent document 1, if the traveling speed of coagulated fibers is increased, accompanying flows are generated in the traveling region of the coagulated fibers. Then, to compensate for the accompanying flows, flows of the coagulation bath liquid moving from around the coagulated fibers toward the coagulated fibers are generated. The speed of the liquid flows is highest in the vicinity of the surface of the coagulation bath liquid. It is considered that along with this, a large drag force is applied to the coagulated fibers in the direction perpendicular to the traveling direction of the coagulated fibers, and fibers among the coagulated fibers come into a densely packed state.
In the case of the technique proposed in Patent document 2, if the direction in which the coagulated fibers are divided is the same as the flow direction Dc of the coagulation bath liquid moving toward the coagulated fibers, the collisions of liquid flows of the coagulation bath liquid cannot be avoided. Therefore, if the take-up speed of the coagulated fibers is increased, accompanying flows are generated in the traveling region of the coagulated fibers and accordingly, flows of the coagulation bath liquid moving from around coagulated fibers toward the coagulated fibers are generated. The speed of the flows is highest in the vicinity of the surface of the coagulation bath liquid. In particular, it is considered that the flows of the coagulation bath liquid moving toward coagulated fibers from around them collide from the direction perpendicular to the traveling direction of the coagulated fibers and this acts to cause the fibers among the coagulated fiber to come into a densely packed state.
The invention proposed herein was conceived as a result of intensive studies performed based on the above hypotheses with the aim of solving these problems.
Specifically, the present invention according to exemplary embodiments provides a production method for an acrylonitrile based fiber bundle characterized by first extruding a spinning dope solution through a plurality of discharge holes in a spinneret, then allowing the spinning dope solution to move downward into a coagulation bath liquid stored in a coagulation bath to form coagulated fibers, turning the coagulated fibers upward on a direction changing guide part located in the coagulation bath liquid below the spinneret, and pulling them out of the coagulation bath liquid, wherein the requirements 1) to 3) given below are met.
1) The axis direction of the direction changing guide part is perpendicular to both the traveling direction of the coagulated fibers moving from the surface of the coagulation bath liquid toward the direction changing guide part and the take-up direction of the coagulated fibers moving from the direction changing guide part and exiting out of the coagulation bath liquid.
2) The traveling region of the coagulated fibers ranging from the surface of the coagulating bath liquid to the direction changing guide part includes two or more fiber-existing regions containing coagulated fibers that exist continuously in the traveling direction of the coagulated fibers, and at least one fiber-free region free of coagulated fibers, which are continuously absent in the traveling direction of the coagulated fibers, wherein each fiber-free region is located between two fiber-existing regions.
3) For at least one of the fiber-free regions, the width thereof measured at the surface of the coagulation bath liquid in the axis direction of the direction changing guide part is at least four times the shortest distance between discharge holes in the spinneret.
According to embodiments of the present invention, a high-grade, high-quality acrylonitrile based fiber bundle can be produced stably by the dry-jet wet spinning technique performed under conditions characterized by high flow controllability for the coagulation bath liquid in the vicinity of the coagulated fibers and high production efficiency (higher speed (increased traveling speed of the fibers), multiple holes (increased number of discharge holes in the spinneret), and high densification (increased density of discharge hole arrangement in the spinneret)).
The production method for an acrylonitrile based fiber bundle according to embodiments of the present invention is described in detail below with reference to drawings.
Here, the traveling region of the coagulated fibers 3 means the region ranging between the outermost ones of the set of coagulated fibers 3 traveling from the surface 9 of the coagulation bath liquid to the direction changing guide part 4. On the other hand, the fiber-free region refers to the region 23 in
Here, in its best form, the coagulation bath 2 has a coagulation bath bottom face 6 that gradually becomes shallow along the take-up direction Db in which the coagulated fibers 3 travel after being turned upward by the direction changing guide part 4. This serves to ensure a decrease in the capacity of the coagulation bath 2 and a decrease in the volume of the coagulation bath liquid. As compared with this, as illustrated in
Described below is the principle of stable production of a high-grade, high-quality acrylonitrile based fiber bundle that serves to realize a high productivity, which represents the most important point of the present invention, even if:
A. the traveling speed of the coagulated fiber 3 is increased,
B. the number of discharge holes in the spinneret 1 is maximized, or
C. densification of discharge hole arrangement is implemented.
For the present invention, the flows of the coagulation bath liquid in the coagulation bath are referred to simply as liquid flows, and among the liquid flows, those caused by the traveling of a coagulated fiber 3 and flowing in parallel with the coagulated fiber 3 in the traveling direction Da or the take-up direction Db of the coagulated fiber 3 are defined as accompanying flows.
It should be noted first that accompanying flows in the coagulation bath increase if any of the above schemes (A. to C.) is carried out in an attempt to enhance the productivity of the conventional acrylonitrile based fiber bundle production method, which is outside the scope of the present invention. The mechanism thereof is described below with reference to
As compared with this, the production method for an acrylonitrile based fiber bundle according to an embodiment of the present invention is characterized in that the speed of the liquid flows colliding against the coagulated fibers 3 can be decreased even if the schemes (A. to C.) are implemented in order to achieve a high productivity. There are two techniques to meet this object: one is intended to directly reduce liquid flows by reducing the accompanying flows that act as driving force to move liquid flows toward the coagulated fibers 3 and the other is intended to reduce the proportion of liquid flows colliding against the coagulated fibers 3 by dividing the liquid flows moving toward the coagulated fibers 3 to form a fiber-free region 23 where the resistance to liquid flows is small. These two techniques can be applied simultaneously to the production method according to embodiments of the present invention.
The technique for decreasing the speed of the liquid flows colliding against the coagulated fibers 3 is described below. For the production method according to an embodiment of the present invention, as illustrated in
As an advantage of this, the coagulated fibers 3 traveling from the surface 9 of the coagulation bath liquid to the direction changing guide part 4 are divided into a plurality of fiber groups (two groups in
In addition, as another great advantage, if two types of regions, that is, the fiber-existing region 24, which contains coagulated fibers 3, and the fiber-free region 23, which does not contain coagulated fibers 3, exist at the surface 9 of the coagulation bath liquid as illustrated in
To realize the above effect, therefore, it is important to form a fiber-free region 23 at the position where accompanying flows start to occur and at the position where the speed of the liquid flows colliding against the coagulated fibers 3 reaches a maximum, suggesting that when looking at the surface 9 of the coagulation bath liquid, a fiber-free region 23 exists between fiber-existing regions 24. At this time, liquid flows attributed to accompanying flows generated in the take-up direction Db move into the region below the spinneret 1 from the direction perpendicular to the axis direction of the direction changing guide part 4 and accordingly, it should have a width, i.e. the size in the axis direction of the direction changing guide part 4, equal to or larger than a certain value (at least four times the shortest distance between discharge holes in the spinneret 1).
As compared with this, in the case of the setup illustrated in
Furthermore, the width of the fiber-free region 23 free of coagulated fibers 3 measured in the direction of the direction changing guide part 4 is preferably at least four times the shortest distance between discharge holes in the spinneret 1 and such a width is preferably maintained continuously from the surface 9 of the coagulation bath liquid to the direction changing guide part 4. As a result, this works more effectively to vary the generation directions of accompanying flows, leading to a more remarkable effect in decreasing liquid flows colliding against the coagulated fibers 3. Here, in the case where there exist a plurality of fiber-free regions 23 and fiber-existing regions 24, their widths measured in the axis direction of the direction changing guide parts 4 may be constant or variable.
Furthermore, as compared with the maximum width S of the coagulated fibers 3 at the surface 9 of the coagulation bath liquid measured in the axis direction of the direction changing guide part 4 (i.e., the width of the fiber-existing regions 23 located outermost in the direction of the direction changing guide part 4), it is preferable for the maximum width of the coagulated fibers 3 measured on the direction changing guide part 4 in the axis direction of the direction changing guide part 4 to be 1.2 S or less. If it is in this range, accompanying flows are generated in varied directions and at the same time, the width of the discharge holes in the spinneret 1 can be reduced to serve to realize decreased equipment costs.
As described above, furthermore, as the use of equipment containing a plurality of coagulation baths arranged side-by-side has now become the mainstream, a decrease in the width H of each coagulation bath leads to a reduction in the equipment cost and the resulting decrease in the required volume of the coagulation bath liquid leads to a reduction in the collection load. To decrease the width H of the coagulation bath, it is effective to shorten the maximum width S of the coagulated fibers 3 at the surface 9 of the coagulation bath liquid and to make the S/H ratio closer to 1, preferably in the ratio of 0.5≤S/H≤0.95. As the S/H ratio becomes closer to 1, it leads to a higher flow speed of the liquid flows attributed to accompanying flows, but the use of the production method according to embodiments of the present invention will have more noticeable effect to realize a decrease in the liquid flow speed.
In addition, as the production method according to embodiments of the present invention is designed to reduce the liquid flows colliding against the coagulated fibers 3, it is preferable for the average flow speed of the coagulation bath liquid moving toward the coagulated fibers to be 14 mm/second or less at any position that is 40 mm away in the depth direction from the surface of the coagulation bath liquid and 20 mm away from a point that is included in the traveling region of the coagulated fibers and located closest to the exit where the coagulated fibers are pulled out of the coagulation bath, which is measured in the take-up direction Db of the coagulated fibers and in parallel with the surface of the coagulation bath liquid, as illustrated in
Next, another embodiment of the present invention is described in detail below. There may exit only one fiber-free region 23 free of the coagulated fibers 3 as shown in
As a method to form a fiber-free region 23 free of coagulated fibers 3 in carrying out the production method according to the present invention, a fiber-dividing guide part 13 may be provided between the surface 9 of the coagulation bath liquid and the direction changing guide part 4 as illustrated in
For the production method according to the present invention, furthermore, as illustrated in
Described next are features and shapes of members that are common to all dry-jet wet spinning apparatuses useful for the production method according to embodiments of the present invention.
For the production method according to embodiments of the present invention, it is best to use a spinneret 1 having a rectangular cross section, but its cross-sectional shape is not particularly limited and may be circular, elliptic, or polygonal. In addition, it is best for the discharge holes to be arranged in a rectangular region in the spinneret 1, although there are no particular limitations. Furthermore, the number of discharge holes is preferably in the range of 1,000 to 60,000, more preferably in the range of 6,000 to 24,000. The advantageous effect of the present invention can be realized to the maximum when it is in this range. In regard to the density of the discharge holes arranged in the discharge face of the spinneret 1, it is preferable for the number of discharge holes per mm2 in the spinneret 1 is preferably 0.06 holes/mm2 or more, more preferably 0.25 holes/mm2 or more.
In regard to the number of spinnerets 1 used for the production method according to the present invention, it is preferable to adopt only one spinneret to ensure reduced equipment cost, but coagulated fibers 3 may be extruded from two or more spinnerets 1 arranged side-by-side in the width direction of the coagulation bath.
If the take-up speed of the coagulated fibers 3 is increased, furthermore, accompanying flows in the coagulation bath will increase, and the speed of the liquid flows moving toward the coagulated fibers 3 that are traveling from the spinneret 1 to the direction changing guide part 4 will also increase near the surface 9 of the coagulation bath liquid. For the production method according to the present invention, the take-up speed of the coagulated fibers pulled out of the coagulation bath is preferably controlled at 50 m/min or less. From the viewpoint of preventing a decrease in the production efficiency, on the other hand, the speed of the coagulated fibers 3 pulled out of the coagulation bath is preferably controlled at 25 m/min or more.
The coagulation bath 2 used for the production method according to the present invention preferably has a structural feature that a supply inlet 10 is provided on the coagulation bath bottom face 6, wherein the supply inlet 10 is connected to a liquid circulation pump (not shown in the figures) to supply a coagulation solution from the liquid circulation pump. In this case, it is preferable for the coagulation solution in the coagulation bath 2 to be flowing out over the top edges of the coagulation bath front face 7 and the coagulation bath rear face 8.
It is preferable for the direction changing guide part 4 used for the production method according to the present invention to have a single step guiding structure to turn the coagulated fibers 3 to an upward direction, but there are no particular limitations on the structure, and a two or more step guiding structure may be adopted to turn them through a large angle to an upward direction.
Furthermore, it is preferable for the spinning dope solution used for the production method according to the present invention to be one prepared by dissolving an acrylonitrile based polymer in a solvent, although there are no particular limitations thereon. Useful monomers to be copolymerized with acrylonitrile (AN) include, for example, acrylic acid, methacrylic acid, itaconic acid, alkali metal salts thereof, ammonium salts, lower alkyl esters, acrylamide, derivatives thereof, allyl sulfonic acid, methallylsulfonic acid, salts thereof, and alkyl esters thereof.
In addition, useful solvents for the spinning dope solution used for the production method according to embodiments of the present invention include, for example, aqueous zinc chloride solution, dimethyl acetamide, dimethyl sulfoxide (hereinafter abbreviated as DMSO), and dimethyl formamide.
Then, it is preferably spun by the production method according to the present invention, followed by pulling out the coagulated fibers 3 into the air and drawing them in water. Here, after the spinning step, the resulting coagulated fibers 3 are preferably drawn in water and then rinsed, or rinsed first and then drawn in water, to remove the remaining solvent. After being drawn in water, it is commonly supplied with an oil agent and then dried and densified by a hot roller etc. In addition, it is subjected to secondary drawing such as steam drawing as required. For the present invention, the plurality of acrylonitrile based fiber bundles prepared by carrying out these steps is combined by a group of free roller guides designed for bundling before winding-up or storing in a can and subsequently, it is wound up into a package by a winding machine or stored in a can. According to another embodiment, acrylonitrile based fiber bundles are wound up once and then a plurality thereof is unwound or pulled out of the can, followed by combining them using a group of free roller guides designed for bundling. It is preferable for an acrylonitrile based fiber bundle to contain 1,000 or more, more preferably 2,000 or more, single fibers. Although there is no specific upper limit to the number of single fibers, the common range is 100,000 or less.
Described next is the method for producing a carbon fiber bundle from an acrylonitrile based fiber bundle prepared by the production method according to an embodiment of the present invention.
The acrylonitrile based fiber bundle prepared by the production method for a acrylonitrile based fiber bundle described above is subjected to oxidization treatment in an oxidizing atmosphere such as air at 200° C. to 300° C. To produce a good oxidized fiber bundle, it is preferable to raise the treatment temperature stepwise from a low temperature to a high temperature. To provide a carbon fiber bundle showing highly developed performance, furthermore, it is preferable to stretch the fiber bundle to a high stretching ratio unless fuzz generation occurs. Then, the resulting oxidized fiber bundle is heated to a temperature of 1,000° C. or more in an inert atmosphere such as nitrogen to produce a carbon fiber bundle. Subsequently, it is anodized in an aqueous electrolyte solution to form functional groups on the carbon fiber surface in order to increase adhesiveness to resin. In addition, it is preferable to subsequently supply a sizing agent such as epoxy resin to produce a carbon fiber bundle having high abrasion resistance.
The present invention will now be illustrated in detail with reference to Examples although the invention is not limited thereto.
(1) Average flow speed of coagulation bath liquid near the liquid surface
While keeping a microbubble generator (BT-50-5, manufactured by Nishiyama Pump Service Co., Ltd.) operating to generate microbubbles in a coagulation bath, the flow speed of the coagulation bath liquid was measured (sampling frequency 25 Hz, measuring period 30 seconds) using an ultrasonic Doppler current meter (10-MHZ ADV, manufactured by SonTek). The flow speed of the coagulation bath liquid was measured at three points located on the rear side of (nearer to coagulation bath front face 8 than) the center line of the spinneret 1 as shown in
(2) Number of Generated Vortices
A water tank having transparent acrylic walls was installed at the side of the coagulation bath front face 8, and the surface of the coagulation bath liquid was pictured using a video camera. The surface of the coagulation bath liquid was pictured for one minute, and 60 images were taken at intervals of one second. The number of local vortices included in each image was counted and the average number of vortices was calculated.
(3) Grade of Acrylonitrile Based Fiber Bundle
The acrylonitrile based fiber bundle was observed immediately before it was wound up and the number of fuzz hairs on 1,000 m of the acrylonitrile based fiber bundle was counted to make a quality evaluation. The criterion for the evaluation was as given below.
A: (number of fuzz hairs on 1,000 m of a fiber bundle)≤1
B: 1<(number of fuzz hairs on 1,000 m of a fiber bundle)≤5
C: 5<(number of fuzz hairs on 1,000 m of a fiber bundle)<60
D: (number of fuzz hairs on 1,000 m of a fiber bundle)≥60.
(4) Fiber Division
Fibers were divided in the axis direction of the direction changing guide part or in the direction from rear face to the front face of the coagulation bath (hereinafter referred to occasionally as front-rear direction). In addition, the division width associated with the fiber division was measured at the three positions shown in
A dry-jet wet spinning apparatus as illustrated in
Described below is Example 2 where the division width of fibers was larger at the center and lower levels than in Example 1. Except that the division width of fibers at the center level was 10 mm and that the division width at the lower level was 10 mm as illustrated in
Described below is Example 3 where the number of fiber divisions was larger than in Example 2. Except that fibers were divided into four groups in the axis direction of the direction changing guide part, that the division width of fibers at the upper level was 10 mm, that the division width at the center level was 10 mm, and that the division width at the lower level was 10 mm as illustrated in
Described below is Example 4 where two of the spinneret adopted in Example 1 were used. Except that two spinnerets were used as illustrated in
Described below is Comparative example 1 where the fibers were not divided. Except that the fibers were not divided, the same equipment and operating conditions as in Example 1 were adopted to produce an acrylonitrile based fiber bundle. The coagulation bath liquid near the surface of the coagulation bath liquid had an average flow speed V of 30 mm/second and vortices were generated at a rate of 1.8 per second, resulting in an acrylonitrile based fiber bundle of a low grade.
Described below is Comparative example 2 where the fibers were not divided at the upper level. Except that the fibers were not divided at the upper level as illustrated in
Described below is Comparative example 3 where the fibers were divided in the front-rear direction. Except that the fibers were not divided in the axis direction of the direction changing guide part, but divided into two groups in the front-rear direction as illustrated in
Described below is Comparative example 4 where the division width of fibers was less than the required width specified for the present invention. Except that the division width of fibers at the upper level was 5 mm, that the division width at the center level was 5 mm, and that the division width at the lower level was 5 mm, the same equipment and operating conditions as in Example 1 were adopted to produce an acrylonitrile based fiber bundle. The coagulation bath liquid near the surface of the coagulation bath liquid had an average flow speed V of 22 mm/second and vortices were generated at a rate of 1.2 per second, resulting in an acrylonitrile based fiber bundle of a low grade.
Described below is Comparative example 5 where the fibers were not divided at the center level to leave separated fiber-free regions. Except that the fibers were not divided at the center level to leave separated fiber-free regions as illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-063203 | Mar 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/012328 | 3/19/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/196277 | 10/1/2020 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7887728 | Takatani | Feb 2011 | B2 |
| Number | Date | Country |
|---|---|---|
| 0291206 | Mar 1990 | JP |
| 02112409 | Apr 1990 | JP |
| 2000355829 | Dec 2000 | JP |
| 2017172081 | Sep 2017 | JP |
| 2006001324 | Jan 2006 | WO |
| Entry |
|---|
| International Search Report and Written Opinion for International Application No. PCT/JP2020/012328, dated Jun. 9, 2020, 5 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220186405 A1 | Jun 2022 | US |
