JPH04228606A - Method and apparatus for manufacturing very fine thread of melt-spinnable synthetic material - Google Patents

Abstract

PURPOSE: To provide the subject method and apparatus having such advantages as to afford ultrafine continuous filaments or fibers without rupture, afford not necessarily continuous ultrafine fibers each 5-10 μm, esp. about 1 μm in diameter, improve gas or air flow distribution with respect to individual filaments issued from a spinning head, and accept high melt flow. CONSTITUTION: The subject method and apparatus intended for producing ultrafine continuous filaments or melt-blown ultrafine fibers have such a scheme that each of the melt holes or spinning holes of a spinneret is individually surrounded by a pref. circular blow nozzle; therefore each of the corresponding filaments is enclosed by concentric gas flow promoting the deformation of the filament.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing fine or very fine threads.

0002

[Prior art and its problems] U.S. Patent No. 3,379,
No. 811 discloses an apparatus and method for producing yarn, in which an elongated spinneret is provided, the spinneret having a plurality of coplanar spinning openings. The polymer is supplied to these spinning orifices. Air or gas channels are provided on both sides of the spinning opening, which air or gas channels are connected to an air or gas supply source. A plurality of threads emerge from the spinning head, and air or gas exiting from passages on either side of the threads encounters the threads at a velocity greater than the thread velocity, so that the threads are drawn out by the gas flow.

[0003] Conventionally known devices are disclosed in the above-mentioned US patent or Naval Research Lab.
ratory technical report No. PB111437 (T
ech. Rep. No. PB111437; 1
In 954) V. A. As first disclosed of this type by Vente, the melt outlet holes are arranged in rows and the hot gas stream exits through slots located on the sides of said outlet holes. The problem with the above devices is that, on the one hand, maintaining the air outlet slot at a constant width over the large width of the spinneret, and on the other hand, discharging the air flow uniformly over such a width is difficult or requires considerable expense. This is in fact impossible if the width of the gap changes. If the melt holes are arranged in rows, the distribution channels are arranged above these melt holes and the air outlet slots are arranged along the melt holes, the structure It has limited strength with respect to both the slot deformation and the elongated melt distribution chamber deformation due to air pressure or more. In US Pat. No. 4,486,161, this type of device is protected by connecting opposing melt walls by webs to increase resistance to swelling.

0004

[Means for solving the problem] Based on the above conventional technology,
It is an object of the present invention to be able to supply continuous very fine threads or fibers without breaking the threads, and to reduce the diameter of said threads, which do not necessarily have to be continuous, from 5 to 10 micrometers, in particular to 1 micrometer. very thin, on the order of a meter, can improve the distribution of gas or air flow to the individual yarns exiting the spinning head, and can also allow large flow rates of melt. An object of the present invention is to provide a method and apparatus for producing fine thread.

[0005] The above object can be achieved by the following configuration.

That is, the apparatus and method of the present invention for producing very fine threads or fibers is characterized in that each melt outlet opening is provided with an air or gas outlet slot axially symmetrically surrounding these openings. The melt thread is constructed with its own blowing nozzle, thereby overcoming the drawbacks of the prior art described above. The above configuration provides a high degree of uniformity of the flow and therefore a higher degree of uniformity in the formation of the threads compared to a flat jet that is regularly interrupted at predetermined intervals by the threads present. , the number of melt outlet holes per unit area of the spinneret face is increased, which is generally required to improve the flow rate and therefore the economy, and furthermore the blowing nozzle / The strength of the spinneret assembly (melt outlet opening) becomes very large.

The invention allows the production of continuous very fine threads. Such yarns are currently being used in textile engineering for highly titered fabrics for producing women's stockings, or for highly capillary fabrics with advanced thermal insulation and moisture transmission properties for good physiological wearing properties. is needed in The individual yarns of the knit formed by some of such yarns need to have a fineness of less than 1 denier per filament. One denier (den) is the weight of a 9,000 m long thread, and another unit is the decitex (dtex), in which the weight of a 10,000 m long thread is expressed in grams (grams).
g).

By providing each spinning orifice with its own blowing nozzle and connecting these blowing nozzles to a gas source, a very good distribution of the gas to the individual yarns is achieved. Since the gas flow is uniformly supplied to the yarn, no breakage of the yarn occurs and the diameter of the yarn after cooling remains approximately constant. There are also fewer constraints on the design and construction of the spinning head compared to the prior art, where only a limited number of spinning openings can be provided.

According to the present invention, it is also possible to produce extremely thin threads of about 1 micrometer, which do not necessarily have to be continuous. These yarns are melt blown fibers and have many uses in fields such as filtration, absorption and insulation in connection with engineering, medical and textile functions. The difference compared to continuous yarn production is that the processing is usually carried out at high melt temperatures and especially at high air velocities, i.e. high air pressures, which draw out yarns of corresponding fineness through large shear stresses. I can do it. It is generally not important whether the thread breaks or not. That is, the fibers can have a finite length or be very short fibers, so long as large droplets are not formed that could disrupt the capillary structure formed by very thin wires for a particular application. Both of these can be achieved by uniform flow around the molten thread.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail below with reference to the drawings.

The die pack 1 shown in FIG. 1 is part of a spinning head used for extruding the plastic melt during the production of blown textile yarn. The cap pack is connected via a melt line 2 to pump means, not shown. The cap pack consists of two parts 3 screwed together,
It has a casing consisting of 4 parts. Casing 3, 4
A spinneret 5 is provided in the lower part of the spinneret 5, which will be explained in more detail below. The spinneret 5 has a plurality of juxtaposed melt holes 6. A support plate 7 is supported above the spinneret and has a plurality of through holes 8 for passing the melt. A filter unit 9 is provided above the support plate 7 and a displacer 10 is provided above the filter unit for passing the melt entering via the melt line 2. Defines a specific gap. As the melt flow passes from one element to another, the melt flow is sealed in a conventional manner by a soft metal seal, such as aluminum.

The spinneret 5 with melt holes 6, only some of which are shown in FIG. 1 on a non-realistic scale for ease of illustration and whose details are shown in FIG. It has two plates 11 and 12 that are screwed together. The upper plate 11 having the melt hole 6 has a plurality of conical projections 13 arranged around the hole 6.
is provided. The lower plate 12 has a conical opening 14 which coincides with the projection 13 and into which the projection penetrates when the plates 11, 12 are screwed together. , whereby an annular passage or slot is formed around each protrusion 13 between the outer surface of the protrusion and the inner surface of the conical opening 14 . The inner surface of the opening 14 surrounding the melt hole 6 and the opposing lower plate 1
This arrangement with the annular outer surface of the protrusion 13 at 2 forms a blowing nozzle 16 . Each blowing nozzle 16 surrounding the melt hole 6 is connected to a gas distribution chamber 17 formed by a corresponding shape between the plates 11 and 12. The flow cross section for the individual blowing nozzles 16 is several times larger than the cross section of the annular slot 15 in order to achieve optimal distribution.

One or more gas passages 18 , 19 pass through parts 3 and 4 of the base pack 1 and are connected to a source of pressurized gas and connected to an annular passage in the base plate 11 below. 20 , which is connected to the gas distribution chamber 17 via a connecting line 21 . Here too, seals are provided between the individual elements to prevent escape of gas during its passage through the mouth pack into the gas distribution chamber 17.

The gas (air) can be heated directly in the spinning head. Generally such a yarn spinning head is
It is heated by an organic heated carrier medium in liquid or vapor form at the desired melting temperature. The gas supply line of the spinning head can be led through the chamber filled with the heated conveying medium, and the gas can be heated to the melting temperature if there is a sufficiently large heat transfer surface. This results in a very compact and easily controllable device. However, this makes it impossible to vary the gas temperature above or below the melting temperature.

[0015] In order to spin very fine continuous threads that are neatly collected on the rolls, it is sufficient to obtain approximately equal high melt and gas temperatures. Blow nozzle 1
The hot gas flow exiting 6 and concentrically surrounding the melt hole 6 promotes the deformation of the thread to a smaller diameter, which is affected by the influence of gravity and, more importantly, by the tension created by the winding unit. deforms and becomes molecularly arranged as a function of velocity. As the distance from the spinneret increases, the hot gas jet mixes with the surrounding air and exhibits a rapidly lower mixing temperature. Below the melting temperature of the spun polymeric material or other yarn-forming material, the yarn begins to solidify and assume its final diameter. By reducing the flow rate and therefore the output for the same winding speed and increasing the air and melt temperature to a given possible limit in the event of a break,
You can get thinner threads.

The action of the accompanying hot gas stream, which is approximately at melt temperature and causes the deformation to a smaller diameter than normal, does not cool the yarn as quickly and is normally due to the lateral blowing action of the cold air stream during the deformation. In this embodiment, the first step is to avoid inhibition. The hot gas flow actually makes the cross section of the thread asymmetric during cooling and also causes disturbances such as movement, vibration, etc. of the thread as a result of unilateral forces. The hot air jet from the blowing nozzle surrounds the yarn and protects it from such interference until cooling occurs gradually and no interference appears that would cause the yarn to break.

Gas heaters, usually electrically heated, that are independent of the temperature of the spinning head can be used to produce very fine melt-blown fibers. Gas flows through this heater and is not supplied to the spinneret via the heating zone of the spinning head. This occurs structurally in the embodiment shown in FIG. Another possibility is
The heated gas is passed laterally into the spinneret and simultaneously pressed against the melt and the gas opening at a laterally arranged melt opening, connecting the melt to the gas opening via the seal. The gas temperature can be raised well above the melting temperature to produce thinner fibers. Such melt blown very fine fibers, which are generally finer than 10 micrometers and can be finer than 1 micrometer, are
They are usually fixed in a woolly manner in an irregular manner. The gas stream from the blowing nozzle 16 exits laterally below the spinneret and either mixes with the surrounding air or passes through the wool-like fibers (fleece). Very fine fibers or yarn fleeces can be spun directly onto the carrier material.

The apparatus of the invention eliminates the previously known disadvantage of having to readjust the narrow flat air gap after each cleaning of the spinneret. In the spinneret of the invention, during the production of the two halves 11 and 12 only one of these halves is provided with the precision achievable with modern machine tools (i.e. the melt hole 6 and the conical shape). Hole 1
4 have the same center point with appropriate tolerances), the above gap can be obtained automatically. 0.2 to 0.6mm
In the case of the annular slot 15, a separation (deviation) of several hundredths of 1 mm is permissible. Preferably, the same material is selected for both parts 11 and 12 so that there are no differences in thermal expansion. Conventional machining techniques can be used to join the two parts with close tolerance finishes at their edges.

The spinning holes 6 and the blowing nozzles 16 surrounding these spinning holes are distributed over a circular cross section in the embodiment described above, which can be understood in more detail from FIG. 2. The melt holes 6 can be distributed in any desired manner on the nozzle surface. For this purpose, FIG. 2 shows a circular nozzle, in which the individual melt holes 6 and thus also the blowing nozzles 16 are arranged concentrically. However, the holes and nozzles can be arranged in one row or in several rows, which offers the advantage of maintaining the air gap more precisely than in conventional devices. Multiple rows of longitudinal nozzles with such large numbers of holes are effective in producing very fine fibers used as fleece, but they can also be used to produce continuous fibers that become knitted or woven fibers in the following steps. Circular nozzles can be used to produce very fine fibers for textiles. It is also conceivable to produce cables from very thin fibers in this way, which are then cut into stable fibers. Both circular and rectangular nozzles can be used. However, the principles of the present invention are not limited to these nozzle shapes.

The following two examples illustrate the use of the apparatus of the present invention in the process of producing very fine threads or melt-blown microfibers.

Example 1 A melt of polyamide 6 having a relative viscosity of 2.4, measured in 96% sulfuric acid with a concentration of 1 g/dl at 25° C., was continuously passed from an extruder through a melt line. The yarn was fed into a conventional spinning head for spinning yarn. The spinning head has an air pipe as an attached mechanism,
These air pipes pass through a heating chamber heated with diphenyl vapor and terminate at the mounting surface of the cap pack. 6
A spinneret with a diameter of 0 mm was screwed into a spinneret pack 1 roughly corresponding to FIG. 1 having the features of the invention. The spinneret has 12 holes and the diameter of the melt hole is 0.2
It was 5 mm. The lower part 12 of the spinneret has spinning holes 1
4/A cone portion with a width of 0.4 mm consisting of an annular slot 15 was formed. The temperature of the polyamide melt was 228°C and the air fed to the spinneret had approximately the same temperature. The air amount was 1.8 Nm3/h. 1
The amount of melt distributed into holes No. 2 was 3 g/min. Met.

The other parts of the apparatus corresponded to standard melt spinning means for synthetic resin yarns. A blowing shaft is provided below the spinneret, in which a temperature of 25° C. and a relative humidity of 40% are provided for the purpose of cooling the yarn.
of air at a distance of 0.3 m in the transverse direction perpendicular to the direction of yarn movement.
The air was blown at a speed of /s. The thread is 5540m/min. It was wound on a winder that rotates rapidly at a speed of . The titre obtained was 12 x 0.45 dtex, corresponding to an individual capillary diameter of approximately 7.2 micrometers.
Met.

Example 2 Using the same spinneret in the same spinneret pack, MF
Polypropylene with a melt index of I35 was spun (35 g flowed through a capillary tube with a diameter of 2.1 mm in 10 minutes at a temperature of 230° C.). The melt temperature is 305°C and the melt flow rate is 2.4 g/min.
．． (ie, 0.2 g/min. per hole). The air passed from above into the middle cavity 17 by means of a pipe was heated to a temperature of 470° C. by passing through an electric heating element upstream of the base pack. When passing through the cap pack, the temperature inside this cap pack is approximately 30℃.
Some cooling occurred due to the temperature being 0°C. Air volume is 4
．． It was 2Nm3/h. This caused longer and shorter fibers to accumulate on the lower screen surface of the spinneret of the present invention. The average diameter of the fibers was 4-5 micrometers, with a minimum of 2 micrometers and a maximum of 6 micrometers. Thread diameter was determined using a microscope.

[Brief explanation of the drawing]

FIG. 1 is a sectional view through the cap pack.

FIG. 2 shows a view from below of a mouthpiece hole with a blowing nozzle.

FIG. 3 is a cross-sectional view showing enlarged details of the spinneret.

[Explanation of symbols]

5 Spinneret
6 Melt hole 11 Upper plate
12 Lower plate 13 Projection part
14 Hole 15 Annular slot
16 Blowout nozzle 17 Gas distribution chamber

Claims (12)

[Claims] 1. A method for producing very fine yarns of melt-spunable synthetic material, wherein the melt is extruded through a spinneret having a plurality of melt holes, and the yarn exiting the spinneret comprises: In the method in which the yarn is wound or collected, the yarn exiting the spinneret is surrounded concentrically by a gas stream passing through a circular blowing nozzle in the direction of exit of the yarn, and the gas stream assists in deforming the yarn. How to characterize it. [Claim 2] Claim 1 for producing continuous yarn
A method, characterized in that the gas stream is heated to a temperature approximately corresponding to the melt temperature. 3. A method according to claim 1 for producing fibers, characterized in that the gas stream is heated to a temperature above the melt temperature. 4. An apparatus for producing very fine yarns, comprising a spinneret pack with a spinneret having a plurality of melt holes into which melt is fed, and an air passage surrounding the spinneret. , each melt hole (6) of said spinneret is provided with a respective blowing nozzle (16), said blowing nozzle being connected to at least one gas source (17, 18, 19, 20). A device characterized by: 5. Device according to claim 4, characterized in that the blowing nozzles (16) are arranged axially symmetrically around the melt hole (6). 6. Device according to claim 4, characterized in that the melt holes (6) with the blowing nozzles (16) are uniformly distributed over a circular cross section. 7. Device according to claim 4, characterized in that the melt holes (6) with the blowing nozzles (16) are arranged in at least one longitudinal row. 8. Apparatus according to any one of claims 4 to 7, wherein the spinneret (5) comprises two interconnectable plates (11, 12), between which a gas distribution chamber (17) is provided. ) is surrounded, and the lower plate (12) has holes (14) and the upper plate (11
) is a protrusion (1) extending through said gas distribution chamber (17).
3), in which the melt hole (6) for the melt to exit is arranged, and the protrusion (13) is located in the hole (14). an annular slot (15) that engages therein to form a blowout nozzle (16);
). 9. A device according to claim 8, wherein the holes (14) and the projections (13) of the lower and upper plates (12, 11) are arranged concentrically to form a conical annular slot (15). A device characterized by forming. 10. Device according to claim 4, characterized in that the gas distribution chamber (17) is connected to a gas passage (18, 19) passing through the mouthpiece pack. 11. Apparatus according to any one of claims 4 to 10, characterized in that the gas passage also passes through the spinning head, and the passing gas is heated by the spinning head. 12. Apparatus according to any one of claims 4 to 10, characterized in that additional electrical gas heating means are provided for heating the gas stream.