JP2001200422A - Cooling device for hollow fiber and method for producing hollow fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a uniform hollow fiber having uniformly adjusted film thickness and diameter by uniformly sending cooling gas in the length and circumferential directions to a hollow fiber extruded from a nozzle so as to eliminate unevenness in cooling. SOLUTION: This hollow fiber is obtained by cooling and solidifying hollow fiber by using a cooling device for hollow fiber, blowing a cooling gas upon the peripheral surface of the melt-spun hollow fiber to cool and solidify and to obtain the hollow fiber. The cooling device is characterized by being equipped with a cooling cylinder 10 having an inner cylinder 11 and an outer cylinder 12 and being formed a space 13 between those cylinders and has a cooling fluid feeder supplying a cooling fluid to the above-mentioned space 13. The inner cylinder 11 has blowing out nozzles blowing out a cooling fluid to the outer surface of the hollow fiber traveling in the inner cylinder in the length direction wherein the blowing nozzles are uniformly set all over periphery of at least a part of length direction of the lateral face of the cylinder 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling apparatus for hollow fibers and a method for producing hollow fibers, which is capable of stably producing uniform hollow fibers having a constant diameter and thickness.

[0002]

2. Description of the Related Art Polyolefin porous hollow fiber membranes produced by melt-spinning and then spinning crystalline polyolefins are excellent in chemical stability, strength characteristics, flexibility, etc. It is used in a wide range of fields such as production of ultrapure water, purification of air, etc., and its production method is described in JP-A-57-66114 and JP-A-2-112404.
No. 6,009,036. The production of such a polyolefin porous hollow fiber membrane includes a spinning step in which a polyolefin such as polyethylene and polypropylene is melt-spun to obtain hollow fibers, and a hollow fiber obtained in the spinning step is drawn to make the side surfaces porous. Stretching process. In this case, if a uniform hollow fiber having a constant diameter and a constant film thickness is used, yarn breakage in the drawing step hardly occurs, and a uniform porous hollow fiber membrane can be stably obtained. Further, the spinning step usually includes a cooling and solidifying step of continuously blowing cooling air to the hollow fiber with a blower or the like to cool and solidify the hollow fiber into a hollow fiber when the molten polyolefin resin is discharged from the nozzle. . Here, conditions such as the amount and direction of the cooling air when the cooling air is blown onto the hollow fiber to cool and solidify the hollow fiber affect the uniformity of the film thickness and the diameter of the obtained hollow fiber. This is important because it also affects the performance of the porous hollow fiber membrane obtained by drawing the polymer.

[0003]

However, in the conventional cooling method in which the cooling air is blown by a blower, it is impossible to uniformly send the cooling air in the length direction and the circumferential direction to the hollow fiber discharged from the nozzle. It is very difficult, and there is a problem that a temperature distribution is generated in the length direction and the circumferential direction of the hollow fiber being cooled, resulting in uneven cooling and uneven cooling. When cooling unevenness occurs, there is a problem that the thickness and diameter of the obtained hollow fiber become inhomogeneous, and as a result, the porous hollow fiber membrane obtained from such a hollow fiber also becomes inhomogeneous.

[0004] The present invention has been made in view of the above-mentioned circumstances, and uniformly sends cooling air in the length direction and the circumferential direction to the hollow fiber discharged from the nozzle, thereby eliminating cooling unevenness. It is an object to provide a homogeneous hollow fiber whose diameter and diameter are controlled to be constant.

[0005]

The hollow fiber cooling device of the present invention is a hollow fiber cooling device for obtaining a hollow fiber by spraying a cooling fluid onto an outer peripheral surface of a melt-spun hollow fiber to cool and solidify the hollow fiber. Having an inner cylinder and an outer cylinder, a cooling cylinder having a sealed gap formed therebetween, and a cooling fluid supply unit for supplying a cooling fluid to the gap. A blow-out port for blowing the cooling fluid in the void portion toward the outer peripheral surface of the hollow fiber that advances in the length direction in the inner cylinder, and having a uniform outlet over at least a part of the length direction of the side surface of the inner cylinder over the entire circumference. Features. The method for producing a hollow fiber of the present invention includes a cooling step of spraying a cooling fluid onto the outer peripheral surface of the discharged hollow fiber to cool and solidify in a spinning step of discharging a molten resin from a discharge surface of a nozzle to obtain a hollow fiber. A method for producing a hollow fiber, wherein a cooling step is performed using the above-described cooling apparatus for a hollow fiber.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The method for producing a hollow fiber of the present invention is a method of producing a hollow fiber by discharging a molten resin in which a resin of a polyolefin such as polyethylene or polypropylene is heated to a melting point or higher from an annular nozzle. A cooling step of spraying a cooling gas onto the surface to cool and solidify to form hollow fibers. In the cooling step, a cooling device for a hollow fiber having a cooling cylinder and a cooling fluid supply unit is used. The hollow fiber discharged from the nozzle and traveling in the length direction inside the cooling cylinder is provided with a cooling gas toward the outer peripheral surface thereof. To cool and solidify. FIG. 1 is a longitudinal sectional view showing an example of a cooling cylinder 10 of the cooling apparatus for hollow fibers of the present invention. In FIG. 1, solid arrows indicate the flow of the cooling gas, and broken arrows indicate the traveling direction of the hollow fiber discharged from the nozzle.

The cooling cylinder 10 has an inner cylinder 11 and an outer cylinder 12 provided outside the inner cylinder 11, and a sealed gap 13 is formed between the inner cylinder 11 and the outer cylinder 12. I have. The inner tube 11 of this example has a net-like tubular body composed of an opening 11a of 300 to 2,000 mesh as shown in FIG. 2 and a striated portion 11b around the opening 11a. Consisting of A cooling fluid inlet 14 connected to a cooling fluid supply unit (not shown) is formed in a lower portion of the side surface of the outer cylinder 12. Cooling gas whose temperature is appropriately controlled is supplied to the gap 13 from the cooling fluid supply unit through the cooling fluid introduction port 14. The opening 11a of the net-shaped tubular body serving as the inner cylinder 11 is an outlet for the cooling gas, and the hollow fiber from which the cooling gas supplied to the gap portion 13 travels in the inner cylinder 11 in the longitudinal direction from the outlet. Is blown out toward the outer peripheral surface.

In the illustrated cooling cylinder 10, a middle cylinder 15 is provided in a gap 13 between the inner cylinder 11 and the outer cylinder 12. As shown in FIG. 3, the middle cylinder 15 is formed of a tubular body having a through hole 15a on the side surface.
5 divides the outer gap 13b and the inner gap 13a. In the inner space 13a, six baffle plate rings 16 having the shape shown in FIG. 4 for controlling the flow direction of the cooling gas are stacked and installed in the longitudinal direction. A fixing jig 17 for fixing the cooling cylinder is attached to an upper portion of the side surface of the outer cylinder 12. The cooling cylinder 10 is usually made of metal such as stainless steel and has a length of 500 to 30.
About 00 mm is preferable. The inner cylinder 11 has an inner diameter of 50 to 500
mm, the outer cylinder 12 has an inner diameter of 300 to 800 mm, and the middle cylinder 15 has an inner diameter of 100 to 700 mm. In addition, any number of baffle plate rings 16 having any size can be used. Further, in the illustrated example, the cooling fluid inlet 14 is provided at a lower portion of the side surface of the outer cylinder 12, but may be provided at an upper portion of the side surface.

When the hollow fiber is cooled and solidified by the cooling device, first, the hollow fiber discharged from the discharge surface of the nozzle is put into the inner cylinder 11 of the cooling device at 10 to 1000 m / min.
Is introduced along the length direction from above at a spinning speed of, and the hollow fiber is advanced downward. Nozzles usually have an inner diameter of 1-3
An annular nozzle having a diameter of 0 mm and an outer diameter of 2 to 50 mm is used.
On the other hand, the cooling gas whose temperature is controlled by the cooling fluid supply unit is slightly pressurized into the gap 13 from the cooling fluid introduction port 14 provided on the side surface of the outer cylinder 12 to about 20 to 300 Pa in the gap 13. To be introduced. A part of the cooling gas horizontally introduced into the outer gap 13b changes its flow upward, and becomes a rising flow that rises in the outer gap 13b. The remaining part goes straight in the horizontal direction, passes through the through-hole 15a of the middle cylinder 15, then proceeds in the circumferential direction along the outer circumference of the baffle plate ring 16 installed at the lowest position, and then forms the outer space. 1
3b merges with the rising flow. Then, the updraft is
A part of the flow is a flow that further rises in the outer gap 13b, and the remaining part is the inner gap 13 between the lowermost baffle ring 16 and the second lower baffle ring 16.
a, proceeding obliquely downward, and then 2
The inner space 11a between the two baffle plate rings 16 travels in the circumferential direction and is blown from the outlet on the side surface of the inner cylinder 11 toward the outer peripheral surface of the hollow fiber.

The ascending flow that rises in the outer space 13b as described above is partly diverted one after another into a flow that progresses between two vertically adjacent baffle rings 16 while ascending. . And finally, the gap 1 of the cooling cylinder 10
All the cooling gas introduced into 3 blows out from all the outlets of the inner cylinder 11 toward the outer peripheral surface of the hollow fiber.
The blown cooling gas is supplied to the opening surface 18a at the upper end of the inner cylinder 11.
And it is discharged | emitted out of a cooling device from the opening surface 18b of a lower end. As described above, by continuously blowing the cooling gas whose temperature is controlled from the outlet of the inner cylinder 11, the hollow fiber discharged from the discharge surface of the nozzle advances in the inner cylinder 11, and the diameter thereof is reduced. Cooled and solidified uniformly while the outer diameter is 10
The hollow fiber has a thickness of about 0 to 3000 μm and a thickness of about 10 to 500 μm.

Here, as the inner cylinder 11, 300 to 200
A fine opening 11a of about 0 mesh and this opening 1
When a net-like tubular body composed of the striated portions 11b around 1a is used, the cooling gas introduced from the cooling fluid introduction port 14 is supplied to each of the air gaps 13 while easily maintaining the inside of the gap 13 in a slightly pressurized state. It can be blown out from the opening 11a toward the hollow fiber with a uniform pressure. Therefore, the hollow fiber can be uniformly cooled in the length direction and the circumferential direction, and the occurrence of uneven cooling can be prevented. Further, by using the net-like tubular body in a double layer, the cooling gas can be more uniformly blown out while maintaining the inside of the cavity 13 in a slightly pressurized state. As described above, the shape of the inner cylinder 11 is such that the fine opening portion 11a and the linear portion 1 around the opening portion 11a are formed.
It is preferable to use a net-like tubular body composed of the tubular member 1b and further use this tubular body in a double-layered manner.
There is no particular limitation as long as the inside of 3 can be maintained in a slightly pressurized state and the cooling gas can be uniformly blown toward the hollow fiber in a certain length direction and circumferential direction. For example, only one net-like tube may be used instead of being double-layered, or three or more tubes may be used. Furthermore, a thin long slit-shaped outlet 11c as shown in FIG.
An inner cylinder 11 or the like provided in a part of the side surface in the length direction can also be used.

Further, by providing a middle cylinder 15 having a large number of through holes 15a on the side surface between the inner cylinder 11 and the outer cylinder 12, the cooling gas supplied from the cooling fluid supply unit through the cooling fluid inlet 14 is provided. Since the pressure can be sent to the inner gap 13a after the pressure is made substantially constant in the outer gap 13b, the cooling gas can be blown out from the outlet of the inner cylinder 11 with a more uniform pressure. The through hole 15a has a diameter of 1 to
It is preferable to be provided evenly with about 10 mm and a center-to-center distance of about 2 to 20 mm. Further, by providing the baffle plate ring 16 in the inner gap portion 13a, the cooling gas introduced into the gap portion 13 can be cooled by the inner gap portion 13a between two vertically adjacent baffle plate rings 16, particularly in the circumferential direction. Can be forced to proceed. Therefore, a uniform and even cooling gas in the circumferential direction can be blown out from the blowout port. In the illustrated example, the flow of the cooling gas is mainly a co-current flow with respect to the hollow fibers. However, each baffle plate ring 16 is installed upside down so that a counter-current flow with respect to the hollow fibers is made main flow. Can also.

Further, the inner cylinder 11 of the hollow fiber cooling device
A blowout adjusting member that adjusts the blowout section of the cooling gas by covering a part of the blowout opening in the length direction can be provided inside. As the blowout adjusting member, for example, a blowout adjusting ring 1 provided as shown in FIG.
9 is mentioned. The blow-out adjusting ring 19 can be moved up and down.
Can be provided at an arbitrary position in the length direction in the inner cylinder 11. For example, as shown in FIG.
By providing a blow-out adjusting ring 19 having a length about the upper part of the inner cylinder 11, the length of the blow-out section L can be reduced to about 2/3, and the same blow-out adjusting ring 19 is used as shown in FIG.
As shown in (b), the position of the blowout section can be set lower than when it is provided below the inner cylinder 11. By using the blowout adjusting member and closing a part of the lengthwise direction of the blowout port, the length of the blowout section and the position in the lengthwise direction in the inner cylinder 11 can be arbitrarily adjusted. By adjusting the time from solidification to cooling and solidification, it is possible to minimize unevenness in the diameter and thickness of the hollow fiber and to easily control the crystal structure. The length of the blowing section is usually set in the range of 50 to 2000 mm.

Further, the inner cylinder 1 of the hollow fiber cooling device
At least one end of the device 1 may be provided with a discharge control member for controlling the discharge amount of the cooling gas. As the exhaust adjustment member, for example, it is attached to at least one of the upper end and the lower end of the inner cylinder 11 to reduce the area of at least one of the upper end opening surface 18a or the lower end opening surface 18b. Cooling gas discharge amount and lower opening surface 18
diameter reducing ring 2 for changing the ratio with the amount of cooling gas discharged from b
0. When the reduced diameter ring 20 is attached to the lower end of the inner cylinder 11 as shown in FIG.
The larger amount of air is discharged from the opening surface 18a at the upper end than the upper surface 8b. As a result, ascending flow is the main flow of the cooling gas in the inner cylinder 11, and the hollow fiber that has just been discharged from the nozzle is more likely to be cooled. Another example of the exhaust adjustment member is a ring having the same diameter as the inner cylinder 11 and a tube having the same diameter. When the same-diameter ring is mounted on the upper end of the inner cylinder and the distance between the upper end of the same-diameter ring and the discharge surface of the nozzle is reduced, more cooling gas is discharged from the opening surface 18a at the lower end. As a result, the flow of the cooling gas in the inner cylinder 11 is mainly a descending flow, and the hollow fiber immediately after being discharged from the nozzle is not hit by the cooling gas and is hardly cooled. Such an installation of the discharge adjusting member can provide the same effect as that obtained when the above-described blow-out adjusting member is used.

When the hollow fiber discharged from the discharge surface of the nozzle is cooled by using the hollow fiber cooling device, the distance between the discharge surface of the nozzle and the upper end of the cooling cylinder 10 can be set arbitrarily. For example, when cooling a hollow fiber having a large film thickness that is difficult to cool and solidify, this distance can be reduced to immediately cool the hollow fiber immediately after being discharged from the nozzle. The distance between the discharge surface of the nozzle and the upper end of the cooling cylinder 10 is usually set in the range of 10 to 1000 mm. As described above, by appropriately using the blowing control member and the exhaust controlling member, and further arbitrarily setting the distance between the discharge surface of the nozzle and the upper end of the cooling cylinder 10, the type and melt viscosity of the polyolefin as the raw material of the hollow fiber are adjusted. Alternatively, the hollow fiber can be cooled under appropriate cooling conditions in accordance with the outer diameter, the film thickness, and the like of the hollow fiber, and the thinning of the hollow fiber can be completed and solidified in a cooling cylinder to obtain a hollow fiber. In addition, such a method can uniformly send a cooling gas in the length direction and the circumferential direction with respect to the hollow fiber discharged from the nozzle. It is particularly suitable for producing hollow fibers having a porosity of 25% or more.

[0016]

As described above, according to the cooling apparatus for hollow fibers of the present invention, since the cooling gas is uniformly blown out from the outlet of the inner cylinder in the length direction and the circumferential direction toward the hollow fibers, the hollow fibers are cooled. Can be uniformly cooled in the longitudinal and circumferential directions,
It is possible to produce a hollow fiber having a uniform crystal structure without cooling unevenness. Further, the cooling device for hollow fibers is provided with an exhaust adjustment member and a blowing adjustment member, and the distance between the upper end of the cooling cylinder of the cooling device for hollow fibers and the discharge surface of the nozzle that discharges the molten resin is arbitrarily set. Thereby, various cooling conditions can be set according to the properties of the resin, the thickness and the diameter of the hollow fiber, and the like, and a homogeneous hollow fiber can be stably produced. When such a hollow fiber is drawn to produce a porous hollow fiber membrane, yarn breakage during drawing hardly occurs and a homogeneous porous hollow fiber membrane can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a cooling cylinder.

2 (a) is a perspective view and FIG. 2 (b) is a partially enlarged view showing an example of an inner cylinder.

FIG. 3 is a perspective view showing an example of a middle cylinder.

FIG. 4 is a perspective view showing an example of a baffle plate ring.

FIG. 5 is a perspective view showing another example of the inner cylinder.

FIG. 6 is a cross-sectional view illustrating an example (a) of a cooling cylinder provided with a blow-out adjusting member and another example (b).

FIG. 7 is a cross-sectional view illustrating an example of a cooling cylinder provided with a discharge adjusting member.

[Explanation of symbols]

10 ... Cooling cylinder, 11 ... Inner cylinder, 12 ... Outer cylinder, 13 ... Void part, 19 ... Blow-out adjustment ring

Claims (11)

[Claims] 1. A hollow fiber cooling device for spraying a cooling fluid onto an outer peripheral surface of a melt-spun hollow fiber to cool and solidify the hollow fiber to obtain a hollow fiber, comprising an inner cylinder and an outer cylinder. A cooling cylinder having a gap portion sealed therein, and a cooling fluid supply section for supplying a cooling fluid to the gap portion, wherein the inner cylinder is formed of a hollow fiber that travels in the length direction in the inner cylinder. A cooling device for a hollow fiber, comprising: a blow-off port for blowing a cooling fluid in a void portion toward an outer peripheral surface, at least in a part of a length direction of a side surface of an inner cylinder over the entire circumference. 2. The hollow fiber cooling device according to claim 1, wherein the inner cylinder is formed of a net-like tubular body. 3. The size of the opening of the net-like tube is 300.
The cooling device for hollow fibers according to claim 2, wherein the size of the cooling device is from 2000 to 2000 mesh. 4. A blow-out adjusting member for adjusting a blow-out section of a cooling fluid by blocking a part of the blow-out opening in a longitudinal direction is provided inside the inner cylinder. The cooling device for hollow fibers according to the above. 5. The length of a blowing section is 50 to 2000.
The cooling device for hollow fibers according to claim 4, wherein 6. The hollow fiber according to claim 1, wherein a discharge adjusting member for adjusting a discharge amount of the cooling fluid is provided at at least one end of the inner cylinder. Cooling system. 7. A method for producing a hollow fiber, comprising: in a spinning step of discharging a molten resin from a discharge surface of a nozzle to obtain a hollow fiber, a cooling step of spraying a cooling fluid onto an outer peripheral surface of the discharged hollow fiber to cool and solidify it. A method for producing hollow fibers, wherein the cooling step is performed using the cooling apparatus for hollow fibers according to any one of claims 1 to 6. 8. The method according to claim 7, wherein the distance between the discharge surface of the nozzle and the upper end of the cooling cylinder is 10 to 1000 mm. 9. The length of the blowing section is 50 to 2000.
The method for producing a hollow fiber according to claim 7 or 8, wherein the diameter is set to mm. 10. The method for producing a hollow fiber according to claim 7, wherein the hollow fiber is made of a polyolefin. 11. The method for producing a hollow fiber according to claim 7, wherein the porosity of the hollow fiber is 25% or more.