JPS6315372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Polypropylene yarns, particularly continuous filament textile yarns, are typically produced in conventional "down-the-stack" air-cooled extrusion equipment. These have several floors, with an extruder on the upper floor and an air-cooled room on the lower floor, with tubes between the floors extending down to the floor below, where the thread is wound. It will be done. Chilled air is flowed through the cooling chamber to solidify and cool the yarn. One of its disadvantages is that resonance occurs during filamentation of the yarn. As the polypropylene melt is extruded through the spinneret capillary, it expands at the bottom of the spinneret and the filament is drawn down from its swell. However, this drawdown tends to be uneven, and to exaggerate it, the filament looks like a string of sausages. This is called resonance. This resonance then tends to cause draw failure in the filament when the filament is fully drawn. As this resonance becomes stronger, the frequency of draw destruction also increases.

The point at which the filament is completely drawn down to its undrawn denier in the cooling chamber varies. This can be observed as a raindrop effect in an air-cooled room. This too works unevenly.

The temperature at which the polypropylene melt is extruded is usually around 500°C. However, lower temperatures may be attempted. It is generally known that when the temperature is low, expansion or swell increases below the spinneret, increases resonance, and causes spin breakage near the spinneret.

The problem of resonance and subsequent draw failure is even more pronounced with thinner denier threads per filament. For example, unstretched denier per filament
For yarns of 30 or less, the final drawn yarn has a denier of 10 or less per filament. In addition, the problem of the difference in denier between filaments becomes more pronounced with fine denier yarns as well as with the length of the filaments.

The present invention reduces the extrusion temperature without increasing the expanded volume at the spinneret surface if the filament yarn is extruded through a relatively short thermal zone at or slightly below its extrusion temperature before contacting the cooling air. This is based on the recognition that it is possible. It has been found that the resonance in the filament decreases when the extrusion temperature decreases. The optimum temperature is around 400〓. As the temperature gradually decreases below this optimum temperature, the resonance increases again. Spin destruction also occurs. It is believed that the exact optimum temperature is influenced by the swell value of the polypropylene and its melt flow. It has been argued that as the melt temperature decreases, the melt approaches Newtonian fluid in its behavior. This occurs when the swell value of polypropylene decreases, e.g.
I believe it will be even more effective for versions below 2.5.

The present invention provides a method for manufacturing a plurality of polypropylene filaments, in which polypropylene having a relatively narrow molecular weight distribution and having a swell value of 3 or less at the melting temperature is heated, and the molten polypropylene is = Extruding into a plurality of filaments at a lower temperature, passing this filament through a first zone having a temperature high enough to slow cooling of the filament therein, and drawing the filament to its undrawn denier in this first zone. down and then pass the filament through the second zone. In this second zone, cooling gas is blown onto the filament to cool it. The swell value of the polypropylene, the extrusion temperature and the temperature of the first zone interact to avoid resonance in the filament as it draws down the first zone.

Preferably, the polypropylene has a swell value of 2.5 or less. Further, the melt flow of polypropylene may be greater than 20, preferably 30 or greater.

The first zone is preferably shorter than the second zone and preferably contains gas in a stationary state.

The temperature of the first zone may be lower than the extrusion temperature by a temperature difference of 70° or less, or may be 350° or more. It is preferable that the difference between the temperature and the extrusion temperature is within 60°.

The filaments are drawn down in the first zone to an undrawn denier of less than 40 denier, such as less than 30 denier, per filament.

In the second zone, a cooling gas may be blown onto the filament at right angles to cool it. The temperature of this cooling gas is preferably below 90° when entering the cooling zone.

The extrusion temperature may be below 420°, for example from 415° to 350° or from 410° to 360°, preferably about 400°.

At least two multifilament yarns may be produced simultaneously by extruding a quantity of molten polypropylene through a spinneret having at least two groups of orifices.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the extruder 10 has a supply hopper 11,
Screw 12 and band heaters 13a, 13
b, 13c, and 13d. A transfer pipe 14 connects the discharge end of this extruder 10 to a metering pump 15. Transfer pipe 14 and metering pump 15 are covered with band heaters 16 and 17, respectively. The discharge side of the metering pump 15 is connected by a tube 18 to a spin block 20 covered by a band heater 21.
It is connected to a spin pack 19 attached to the. The spin pack 19 has a cover plate 22 and a main body 2.
3. It has a blocking plate 24 and a spinneret 25. The conventional thermal insulation covering the band heater and other parts of the equipment are not shown. Shroud 26 is attached to the underside of spin block 20 by bolts 27 (see FIG. 2). An air chamber 28 is mounted below the cover 26, and the bottom of this air chamber 28 terminates in a finishing guide 29. Just below the guide 29 is a denier control roll 30.

The cover 26 is rectangular in horizontal cross-section as shown in FIG. Its upper end is a flange 31, through which the bolt 27 passes. At the lower end of the shroud 26 is an inwardly collecting trough 32.

The spinnerets 25 are arranged in three groups 34, 3 to produce multifilament yarns 37, 38, 39, respectively.
It has capillary 33 arranged in 5 and 36. Spinnerets with different numbers of capillaries can be used to produce yarns with different numbers of filaments.

Cooling chamber 28 has a top cover 40 closely fitted around the outside of gutter 32 . One wall of the cooling chamber is formed of a wire mesh 41 supported by a frame 42. The opposite wall is formed from a metal plate with elongated holes supported by a frame 44. The cooling air filling space 45 is separated by a wire mesh 41. The cross section of the cooling chamber is rectangular, as are the surfaces of the cover 26 and the spinneret 25. The face of the spinneret 25 has three groups of capillaries 2 parallel to the long sides of the rectangle.
4, 25, and 26 are held separately.

The shroud 2 is relatively short and the capillary group 34,3
It is fitted close to the circumference of 5, 36, but with enough room, so that even if the thread sways, the thread 37,
38 and 39 do not contact the inner end of the gutter 32. As shown in FIG. 3, the long side of shroud 26 is 12 inches and the short side is 7 inches. Further, the length of the surface of the spinneret 25 is 8 inches and the width is 4 inches. The height of the shroud is 9 inches as shown in FIG.

In the method of the present invention, polypropylene resin pellets and colorant concentrate pellets are fed from a hopper 11 to an extruder 10. Polypropylene is
Has a melt flow of 30 and a swell value of 2 or less,
i.e. has a dice well (1.9 in this example),
It has a narrow molecular weight distribution. This resin and colorant are melted and heated to 400 〓 by the heater of the extruder.
and mixed by screw 12.
Heaters 13a, 13b, 13c, and 13d adjust the temperature of their zones to 300〓, 350〓, 375〓 and 375〓, respectively.
It is installed to control at 400〓.

The heaters 16, 17, and 21 on the downstream side are installed so as to control their respective bands to 400°. The molten material is transferred to the transfer pipe 14 through the screw 12.
is fed to a metering pump 15 from which the metered melt is discharged through a tube 18 to a spin pack 19. Inside the spin pack, this metered flow is divided hydraulically and forced downwardly through the capillary 33 into a multifilament, formed into three separate threads 37, 38, 39. The number of capillaries in the spinneret is selected depending on the number of filaments contained in each yarn. In this example it is 70 filaments. The yarn passes through a shroud 26 that delimits the thermal zone and then through a cooling chamber 28 where it is cooled. The yarn is effectively cooled by blowing air at right angles to the yarn. Air from space 45 enters the cooling chamber through wire mesh 41 and is discharged to the atmosphere through holes in metal plate 43. After that, the cooled yarn is guided to the guide 29.
The three yarns are then separated and wound into package cages 47, 48, 49. The denier control roll pulls the yarn down from the capillary 33 at a constant rate (600 meters per minute in this example) and determines the undrawn denier (900 meters per minute in this example).
Denier).

The air inside the shroud 26 is trapped there and remains stationary. This air is heated by the metal above it, namely the face of the spinneret 25, the lower end of the pack body 23, and a portion of the spin pack 20. The latter is heated by a spin block heater 21. The molten filament leaving the capillary 33 is also heated by this air. In this method, cover 26
the air inside is close to the temperature at which the melt is forced out,
Alternatively, it may be kept at a slightly hotter temperature to substantially prevent the filament from cooling as it passes therethrough. The temperature in the lower part of the shroud 26 may be lower than the upper part, but high enough to slow cooling of the filament.

FIG. 4 shows an exaggerated polypropylene filament extruded from a capillary 50 into a cooling zone 51 by conventional air cooling. This molten polypropylene expands below the face of the spinneret 52 and then undergoes a series of small swells 53,5 before complete drawdown to filament size.
4 is formed. This series of swells cannot be fully stretched, resulting in significant resonance in the filament.

FIG. 5 shows how the swell of the present invention is drawn down. The first swell 55 occurs below the face of the spinneret. But then, due to the low extrusion temperature and the extrusion of the filament in a stationary thermal zone 56, the drawdown is short and produces a fast and uniform filament 57. Furthermore, the total volume of swell 55 is smaller than the volume of elongated swells 52, 53, and 54 as seen in FIG.

Unstretched denier 900 produced by the method of the present invention
When the 70 filament yarn is then drawn to a continuous filament 300 denier 70 filament yarn at a draw ratio of 3 to 1, it produces a good quality yarn with substantially no resonance and uniform denier from filament to filament. The yarn also draws efficiently without substantial draw failure. Furthermore, this method allows multi-end drawing, for example eight threads drawn together in the same draw frame.

A high melt flow (e.g. 35 to 45) is required for producing threads with a fine denier per filament.
It is preferred to use polypropylene with a narrow molecular weight distribution and a low swell value (eg 1.2-1.7).

Polypropylene with a narrow molecular weight distribution is usually produced by thermally decomposing a resin in a reactor.
Of course, it can also be produced chemically. The purpose is to reduce high molecular weight products to low ones.
The swell value is the ratio of the diameter of the extrudate just below the face of the spinneret divided by the diameter of the capillary through which it is extruded. This is 190℃
should be measured using a capillary of essentially zero land (length to radius ratio not greater than 0.221) with a shear rate of 1/1000th of a second at a temperature of . The shear rate is defined as the volume flow rate (q expressed in cm ³ /sec) and the cube of the capillary radius (cm) as π.
It's equal to four times the value divided by the multiplied value.

In other words, shear rate = 4q/π x radius ³

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of the device used in the present invention, Fig. 2 is an enlarged sectional view taken along line 2-2 in Fig. 1, and Fig. 3 is a cross-sectional view taken along line 3-3 in Fig. 1. However, this is a plan view of the spin block seen from above the line, and is taken to the same scale as FIG. 2. FIG. The figure is an enlarged illustration of a filament extruded from a spinneret according to the present invention. 11...hopper, 10...extruder, 12...
...screw, 13a, 13b, 13c, 13
d, 16, 17, 21... Heater, 15... Metering pump, 25... Spinneret, 26... Cover, 2
8...Cooling chamber, 29...Guide, 30...Denier control roll.

Claims (1)

[Claims] 1 Heating polypropylene with a narrow molecular weight distribution and a swell value of 3 or less to a temperature at which it is melted, extruding the molten polypropylene into a plurality of filaments at a temperature of 425 or less, and extruding the filaments into a plurality of filaments. , passing the filament to a first zone having a sufficiently high temperature to retard cooling of the filament, drawing the filament down to its undrawn denier in the first zone, and then passing the filament to a second zone, A cooling gas is directed over the filament in a second zone to cool the filament, wherein the combination of the swell value of the polypropylene, the extrusion temperature and the temperature of the first zone interact to cause the filament to cool the filament. A method for producing a polypropylene filament, characterized in that resonance is substantially prevented from occurring in the filament during drawdown in a first zone. 2. Claim 1, characterized in that the first zone contains a gas at a temperature lower than the temperature at which the molten polypropylene is extruded by a temperature difference of 75° or less.
The method described in section. 3. The method of claim 1, wherein said first zone contains gas at a temperature greater than 350°C. 4. The method according to claim 1, wherein the temperature in the first zone differs from the temperature at which the molten polypropylene is extruded by within 60 degrees. 5. A method according to claim 1, characterized in that the cooling gas is blown sideways onto the filament in the second zone. 6. The method according to claim 5, wherein the temperature of the cooling gas when entering the second zone is 90° or less. 7. The method of claim 5, wherein the first zone is shorter than the second zone and contains gas in a quiescent state. 8. The method of claim 1, wherein said filament is drawn down to less than 40 denier per filament in said first zone. 9. The method according to claim 8, wherein the denier number is 30 or less. 10. Extruding the constant stream of molten polypropylene through a spinneret having at least two groups of orifices to produce from the constant stream at least two threads, each having a plurality of filaments. The method described in Section 1. 11 Heat polypropylene with a narrow molecular weight distribution having a swell value of 2.5 or less and a melt flow of 30 or more to a temperature at which it is melted, meter the molten polypropylene flow, and calculate the flow from 360 to 420. At a temperature in the range of 0, extrude downward through a spinneret having at least two groups of orifices to produce at least two groups of filaments, the two groups of filaments being exposed to still air at a temperature sufficiently high to retard their cooling. passing the filament through a second zone, blowing cooling air sideways onto the filament in the second zone to cool the filament, and passing the filament into a second zone, cooling the filament; The filament of is pulled at a constant rate,
While the filament is in the first zone, the filament is drawn down to an undrawn denier of 40 denier or less per filament,
The combination of the swell value of the polypropylene, the extrusion temperature, and the temperature of the first zone interact to prevent resonance from occurring in the filament when the filament is drawn down in the first zone. Method of manufacturing polypropylene filament. 12 Polypropylene having a narrow molecular weight distribution with a swell value of 2.5 or less and a melt flow of 20 or more is heated to a temperature at which it is melted, and a plurality of filaments producing at least two groups of filaments, passing the filaments through a first zone having a temperature sufficiently high therein to retard cooling of the filaments;
In the first zone, the filament is drawn down to its undrawn denier, and then the filament is passed through a second zone, and cooling air is directed over the filament in the second zone to cool the filament. The combination of the swell value of the polypropylene, the extrusion temperature, and the temperature of the first zone interact to prevent resonance from occurring in the filament when the filament is drawn down in the first zone. A method for producing polypropylene filament. 13. Process according to claim 12, characterized in that the molten polypropylene is extruded at a temperature in the range of 410° to 360°. 14. The method according to claim 13, wherein the extrusion temperature is 400°C. 15. The method according to claim 12, wherein the swell value is 2.0 or less. 16. The method of claim 15, wherein the swell value is between 1.2 and 1.7. 17. The method according to claim 16, characterized in that the melt flow is between 35 and 45. 18. The method of claim 12, wherein the cooling gas comprises air and is blown across the filament and discharged into the atmosphere. 19. The method of claim 18, wherein the temperature of the air is below 90° when entering the second zone. 20. The method according to claim 12, wherein the filament is manufactured as a multifilament yarn, and the yarn is wound into separate packages, and then the yarn is multi-end drawn. Filament manufacturing method. 21. The method of claim 20, wherein said multi-end drawing comprises drawing eight threads together. 22 Using polypropylene with a narrow molecular weight distribution and a swell value of 3 or less, extrude the filament at a temperature of 425〓 or less.
= The filament is drawn down to its final drawn denier by passing through a relatively short thermal zone containing a low temperature gas with a temperature difference of less than A process for the production of homogeneous polypropylene filaments, characterized in that the closeness of the temperature of said thermal zone therein interacts with respect to the drawdown of the filament and substantially prevents resonances from occurring in the filament. 23. A method according to claim 22, characterized in that the gas temperature in the thermal zone is higher than 350°C.