JP3550109B2 - Melt blown nonwoven spinning die - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a spinning die used when manufacturing a nonwoven fabric by a melt blow method.
[0002]
[Prior art]
In the melt blow method, as shown in FIG. 5, a raw material chip put into a hopper 1 is heated and melted by an extruder 2, supplied to a die 3 and spun, and the spun short fibers are conveyed from a collecting net. This is a method of manufacturing a nonwoven fabric by depositing the sheet on a sheet 4, passing the sheet through a calendar roll 5 while separating the sheet from the conveyor 4, and winding the sheet by a winder 6.
[0003]
[Problems of the Invention]
The die 3 spins the molten polymer discharged from the spinning port 3a with the high-temperature air jetted from the hot-air discharging port 3b, and discharges the molten polymer from the spinning port 3a and discharges the high-temperature air. A delicate balance is required in the amount, and it is difficult to spun fibers with an arbitrary diameter, especially with small diameter fibers, and it is not possible to obtain a bulky nonwoven fabric with a good feel. Was. In addition, a large amount of hot air needs to be sent, so that there is a problem in that energy costs are high.
[0004]
Therefore, the present inventor has proposed a spinning die in which a hot air discharge slit is arranged near the tip of a nozzle for extruding a molten polymer, and a slit for discharging a large amount of cold air is arranged downstream of the slit to stretch the molten polymer. (JP-A-2000-336517). It has been confirmed that using such a spinning die, a nonwoven fabric having a high bulky property composed of small-diameter fibers can be obtained. Irregularities are generated on the surface of the woven fiber under the influence of the vortex, and sometimes the fiber is caught at the spinning outlet, which causes a problem of lowering the spinning efficiency.
[0005]
An object of the present invention is to provide a spinning die capable of preventing the occurrence of the vortex and efficiently spinning a fiber having a smooth surface.
[0006]
[Means for solving the problem]
In order to solve the above-mentioned problem, the present invention provides a pair of hot air discharge slits disposed near the tip of a nozzle for extruding a molten polymer, with a pair of hot air discharge slits opposed to each other around the nozzle. In a spinning die in which the nozzles are arranged opposite to each other, a vent slit or a row of vent holes is provided at an inner end of a spinning outlet from which the cool air is discharged . Also, between the hot air discharge slit and the cold air discharge slit, preferably a pair of slits communicating with the ambient air keep to face disposed about said nozzle.
[0007]
Embodiment
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. As shown, a spinning die 20 is attached to the lower end of the spin pack 10. The spinning pack 10 is obtained by joining body parts 11a and 11b divided into two parts with bolts 12, and a molten polymer such as a polypropylene resin, a polyester resin, and a nylon (trademark) resin is provided on the upper parts of the body parts 11a and 11b. An inlet 13 is provided, and hot air inlets 14a and 14b are provided below. Panel heaters 15a and 15b are in contact with the side surfaces by holding plates 16a and 16b.
[0008]
The spinning die 20 is provided with a plurality of nozzles 21 in a row at the tip of a polymer passage 17 following the polymer injection port 13, and the tip 21 a of the nozzle 21 is opposed to discharge hot air from the hot air chambers 22 a and 22 b. It faces the center of the arranged pair of discharge slits 23a and 23b. The hot air chambers 22a and 22b communicate with the hot air inlets 14a and 14b via passages 24a and 24b.
[0009]
Open the hot air discharge slit 23a, a constant from 23b spacing _{S 1,} cold air chamber 25a, 25b and a pair of cool air discharge slits 26a, 26b are opposed around the nozzle 21, the cold air chamber 25a, 25b is cold It communicates with the inlets 27a and 27b. The front of the cold air discharge slits 26a, 26b is a spinning outlet 29. The distance _{S 1} is near the tip of the nozzle 21, the suction slit 28a of the outside air (accompanying flow) to form a 28b. The spacing _{S 1} is about 2~10mm are preferred.
[0010]
As clearly shown in FIG. 2, opposite the vent slits 30a communicating between spinning outlet 29 and the outside air from the inner end at a certain distance S ₂ of the spinning outlet 29, 30b is over the entire length of the spinning outlet 29 It is formed. The spacing _{S 2} about 1~10mm are preferred. Further, as shown in FIG. 3, instead of the ventilation slits 30a and 30b, ventilation hole rows 30c and 30d may be provided to face each other. When forming the air hole rows 30c and 30d, a large number of air holes are provided at narrow intervals in the length direction of the die 20, and grooves 31a and 31b are formed at the inner end opening to the spinning outlet 29 over the entire length of the spinning outlet 29. It is good to provide.
[0011]
Now, when the molten polymer is extruded from the nozzle 21, the molten polymer is drawn out from both sides of the molten polymer so as to be sandwiched by the hot air blown out through a pair of hot air discharge slits 23a, 23b inclined in the extrusion direction, and further cooled air discharge slits 26a, 26b. , A large amount of cold air is discharged from the nozzle 21, so that the molten polymer extruded from the nozzle 21 is rapidly drawn and drawn under negative pressure, and at the same time, crystallization proceeds. At this time, the temperature of the hot air is preferably 200 to 300 ° C., the temperature of the cold air is preferably about 10 to 30 ° C., and the amount of the hot air is preferably about 5 to 20% of the cold air. For example, when the cool air is 100 to 250 m / sec, the hot air is about 5 to 50 m / sec. That is, in this case, the hot air only needs to be heated to such an extent that the molten polymer extruded from the nozzle 21 does not rapidly cool, and is rapidly drawn by the negative pressure generated by the cool air to form fine fibers. Then, the vortex generated near the inner end of the spinning outlet 29 due to the rapid discharge of the cool air is extinguished by the ventilation slits 30a, 30b or the row of ventilation holes 30c, 30d, and a fiber having a smooth surface is spun. The cold air discharge slits 26a and 26b are also inclined so as to descend in the direction of the spinning outlet 29 similarly to the hot air discharge slits 23a and 23b. In addition, if the slits 28a and 28b that generate the entrained flow are formed, the air volume can be reduced.
[0012]
【The invention's effect】
According to the present invention, as described above, what is heated with a small amount of hot air that does not cool the molten polymer extruded by the nozzle, is stretched by negative pressure due to a large amount of cold air, and the vortex generated at that time is eliminated. As a result, fibers having a small diameter and a smooth surface can be obtained, whereby a nonwoven fabric having a high bulkiness and a good feel can be obtained.
[0013]
In addition, since the fiber is not caught at the spinning outlet, the amount of the discharged polymer can be increased as compared with the related art, thereby improving the productivity.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a spinning pack incorporating a spinning die of the present invention. FIG. 2 is an enlarged cross-sectional view of the spinning die. FIG. 3 is a partially enlarged cross-sectional view of the spinning die. FIG. 5 is a schematic partial cross-sectional view showing a conventional method for producing a nonwoven fabric by a melt blow method.
DESCRIPTION OF SYMBOLS 1 Hopper 2 Extruder 3 Die 3a Spinning port 3b Hot air discharge port 4 Conveyor 5 Calendar roll 6 Winding machine 10 Spinning pack 11a, 11b Main body 12 Bolt 13 Inlet 14a, 14b Inlet 15a, 15b Panel heater 16a, 16b Pressing plate 17 Passage 20 Spinning die 21 Nozzle 21a Nozzle tip 22a, 22b Hot air chamber 23a, 23b Hot air discharge slit 24a, 24b Passage 25a, 25b Cold air chamber 26a, 26b Cold air discharge slit 27a, 27b Cold air inlet 28a, 28b Suction slit 29 Spinning outlet 30a, 30b ventilation slits 30c, 30d vent columns 31a, 31b groove _S 1, _{S 2} interval

Claims (2)

Near the tip of the nozzle that extrudes the molten polymer, a pair of hot air discharge slits are arranged facing each other around the nozzle, and a pair of cool air discharge slits is arranged downstream thereof at a spinning die where the cold air is discharged. A melt-blowing nonwoven spinning die, characterized in that a vent slit or a row of vent holes is provided at the inner end of the spinning outlet. The spinning die for a melt-blown nonwoven fabric according to claim 1 , wherein a pair of slits communicating with the outside air is disposed between the hot air discharge slit and the cool air discharge slit so as to face each other around the nozzle.

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