JPH0524261B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for widening a web. More specifically, it is a method for uniformly widening a web when producing a long fiber nonwoven fabric made of a thermoplastic polymer. Conventionally, a method is known in which a thermoplastic polymer is melt-spun, and a web made of long fibers is formed by pulling, thinning, and opening the fibers using an air sucker.
This method is generally called the spunbond method, and has the advantage that a cloth-like article can be obtained directly from the thermoplastic polymer without knitting or weaving it. Polyester, polyamide, and polypropylene have already been commercialized as thermoplastic polymers. Japanese Patent Publication No. 37-4993 is known as a typical patent related to the spunbond method, which forcibly charges the yarn by pulling it at high speed with an air suture car and applying an electrostatic charge at a position before the entrance of the air suction car. After that, the fibers are opened. When air suttlers are used as the pulling and opening means, it is generally necessary to arrange a large number of air sutchers in the width direction of the web. At that time, simply arranging them at a certain interval in the width direction of the net conveyor will cause interference between the air flows ejected from the air sutcher, resulting in thinner areas between the air sutchers (usually called streaks). . Therefore, in order to eliminate streaks, the air sutchers are not lined up in the width direction, but are staggered in the diagonal direction, so that the piles of threads ejected from one air sutcher overlap to some extent in the manufacturing width direction of the nonwoven fabric. A method is disclosed. In this method, the threads ejected from several air suttlers are stacked and deposited in the width direction of the nonwoven fabric, making streaks less noticeable on the nonwoven fabric. The problem is the spread width of the web. In other words, if the single fiber spreadability of the web is poor, no matter how many layers are laminated, the apparent quality of the nonwoven fabric will be significantly impaired, and if the web has a narrow spread width, a large number of air sutters will have to be lined up in the width direction. be. Many techniques have been disclosed in the past regarding web widening methods. Various width widening techniques are known, including those using mechanical rocking, those using reflection from a collision plate, and those using air flow. For example, in Japanese Patent Publication No. 46-34373, the aim is to widen the web by colliding the yarn coming out of the air sutsuka against a collision plate and injecting pressurized air from behind the collision plate, but the widening effect is small. Conversely, if the collision plate is a flat plate, increasing the pressure may cause the web width to become narrower.
In addition, in Japanese Patent Publication No. 57-48657, the yarn coming out of the air sukkah is made to collide with a collision plate, and a fluid jet is injected into the filament collision area (collision point), and at the same time, a deflecting member on the exit side of the collision plate is vibrated at high speed. This is to expand the width of the web. However, such a method of vibrating the deflecting member on the exit side of the collision plate at high speed is mechanically complicated, and macro unevenness is likely to occur due to uneven distribution of the web due to vibration, and the single fiber opening performance is not sufficient. Moreover, if the pressure air flow is simply applied without high-speed vibration, only a slight widening effect can be seen. The present inventor completed the present invention as a result of extensive research into a method for widening the web that does not cause macroscopic spots and has good single fiber opening properties. That is, in the present invention, when a yarn forcibly charged by corona discharge collides with a plurality of collision plates and falls toward a net conveyor while changing its traveling direction, and deposits the web on the net conveyor, the collision plate Downstream of the point where the yarn collides with the charged yarn running along the collision plate of the final stage,
This is a method for widening a web, characterized in that the width of the yarn is widened by applying a secondary pressure air flow from a nozzle having a cross-sectional area of 3 ^to 20 mm2. The present invention will be explained in detail below. The present invention has no mechanically moving parts and uses a forced charging method using corona discharge and a plurality of collision plates, and the present invention uses a forced charging method using corona discharge and a plurality of collision plates. By combining the method of applying sub-pressure airflow, a method is provided that can uniformly and sufficiently widen the web width. Thermoplastic polymers according to the present invention include general polyethylene terephthalate, polybutylene terephthalate, copolymerized esters containing isophthalic acid, adipic acid, etc., nylon 6,66,610, or copolymerized or blended polyamides containing a third component. In general, any material that can be melt-spun may be used, such as polyolefins such as polyethylene, isotactic polypropylene, etc. It goes without saying that the polymer may contain a dissipating agent, a heat stabilizer, a coloring agent for the purpose of dyeing, etc. Of course, it may also be a composite fiber or a mixed fiber yarn having a sheath-core structure, a lamination structure, a sea-island structure, or the like. The present invention can be applied to a yarn pulling method using a normal air sutcher. As an air suction car, a regular round air suction car is preferable because it can be towed at high speed. Naturally, a high-speed rotating roll (3000 to 9000 m/min) is installed between the spinneret and the air suction car.
It may be a method in which the fibers are taken up with a roll and then opened with an air suction car. The spun yarn is forcibly charged by corona discharge before it enters the air sutcher, or the yarn exits the air sutcher,
It is necessary to apply an electrostatic charge. An example of an embodiment of the web widening method according to the present invention is shown in FIG. 1 (perspective view), FIG. 2 (cross-sectional view), and FIG. 3 (overall explanatory view). In FIGS. 1, 2, and 3, the yarn 2 leaving the air sucker 1 is forcibly charged by corona discharge between the needle electrode 4 and the target electrode 5 as it passes through the corona discharge channel 3. It will be done. The charged thread 13 exiting the corona discharge channel 3 is caused to collide with a plurality of collision plates. Figures 1 and 2
3 and 3 show the case of two collision plates. 1st
After colliding with the collision plate 6 and the second collision plate 7 in sequence, the particles are deposited on the net conveyor 15. Deposited web 1
4 is static-eliminated using an AC static eliminator or a DC/AC static eliminator 17 in combination with the normal manufacturing method, and then thermally pressed with an embossing roll 18 and then wound up with a winder. The nonwoven fabric according to the present invention may be bonded by a thermocompression bonding method using an embossing roll, a needle punching method, or a resin processing method. The key point of the present invention is that unlike the conventional method of mechanically changing the destination of the yarn such as vibration, rocking, or rotation to widen the web, the present invention uses a forced charging method using corona discharge, multiple collision plates, and the final The point is to combine a method of applying a secondary pressure air flow to the yarn running along the collision plate downstream of the collision point. The corona discharge device used here consists of a needle electrode 4 and a target electrode 5, and a high DC voltage (usually 10 to 40 KV) is applied between them to cause corona discharge.
Corona discharge electrodes can be used in one or more stages in the running direction of the yarn. As the speed of the yarn increases, the amount of charge on the yarn tends to decrease.
In particular, when the yarn running speed exceeds 500 m/min, it is preferable to use multiple stages, especially two stages of corona discharge devices. Charged thread 13 exiting the corona discharge electrode
is caused to collide with the first collision plate 6. At this time, the angle θ formed by the first collision plate 6 and the traveling direction of the yarn is preferably 20 to 45 degrees, particularly around 35 degrees, since macroscopic unevenness does not occur. 1st
The charged yarn 13 that has left the collision plate collides with the second collision plate 7 that is 2 to 5 mm away, and is deflected in the direction of the net conveyor. In FIGS. 1, 2, and 3, the second collision plate 7 serves as the final collision plate, and this final collision plate moves the charged yarn 13 almost perpendicularly onto the net conveyor in a direction perpendicular to the net conveyor. It is preferable to deposit it on the surface since macroscopic spots will not occur. By applying a secondary pressure airflow from the air nozzle 8 to the charged yarn 13 running along the final collision plate downstream of the collision point, the effect of widening the web becomes significantly greater. The air nozzle used at this time may be of a round hole or slit type, but the cross-sectional area of the nozzle of the air jetting portion must be 3 to 20 mm ² , and a round hole nozzle is preferable.
By applying a secondary pressure air flow to the charged yarn 13 running along the second collision plate 7 on the downstream side of the collision point, it expands in the width direction while falling almost vertically, causing the accompanying It is thought that the electrostatic charge generated near the net conveyor, where the influence of the flow is small, improves the opening properties of the single filament. Even if a secondary pressure airflow is applied to the charged yarn 13 running on the first collision plate 6 under similar conditions, a similar widening effect can be seen, but as shown in the example, the widening width of the web itself is also clearly affected. There is a difference, and also when a secondary pressure airflow is applied to the collision point of the second collision plate 7, the charged yarns 13 tend to become entangled, and sufficient opening properties cannot be obtained and the width-spreading effect is also small. Therefore, it is essential to apply a secondary pressure airflow to the charged yarn 13 running along the second collision plate 7 downstream of the collision point. In addition, it is naturally possible to reduce the number of filaments that can be opened, but especially
If it is about 50 to 500 filaments, it can be expanded without any problem. Rather than the method of applying a secondary pressure air flow to the yarn colliding with and running on one stage of collision plates, the present invention uses multiple stages of collision plates and the yarn running along the collision plate of the last stage. The reason why the method of applying a secondary pressure air flow downstream of the collision point is superior has not yet been completely clarified, but one reason is that the charged yarn 13 leaving the final collision plate is Since the material is deposited almost vertically toward the net conveyor 15, it is not easily affected by the suction air flow generated by the air suction device 16 (if the material is deposited diagonally toward the net conveyor 15, the surface of the net conveyor 15 Due to the suction air flow generated almost at right angles to
(The yarn becomes easily disordered), and two are the first collision plate 6.
The yarn 13 is electrically charged to a certain extent and the width of the yarn 13 is widened by colliding with the second collision plate 7, which causes the yarn 13 to become even more electrically charged. is performed, and then by applying a secondary pressure air flow, the width of the charged yarn 13 is gradually expanded,
This is thought to be because macroscopic spots are less likely to occur when the web is deposited because the width is not widened all at once.
For example, one way to make a wide non-woven fabric is to use air sutsuka in a staggered arrangement, and increase the lamination rate of the web to 30~30.
If it is 75%, a nonwoven fabric with no streaks and good single fiber spreadability can be obtained. Further, the deposition distribution of the web according to the present invention is, for example, the fourth
As shown in the figure (Example 2), when two stages of collision plates are used and no secondary pressure airflow is used (Comparative Example B), the central portion is raised and narrow. On the other hand, when a secondary pressure air flow is applied to the first collision plate 6, as in Comparative Example E, the deposition distribution becomes wider;
At this stage, macroscopic spots are already visible in some areas, and the dispersion is by no means clear. On the other hand, in the case of Example A according to the present invention, there is no bulge in the center and a substantially flat deposition distribution is shown. Moreover, in this method, unlike the case where the secondary pressure airflow is applied to the first collision plate 6, by finely adjusting the position of the secondary pressure airflow and the pressure of the secondary pressure airflow, the results from Comparative Example B to Example A can be improved. It is also possible to arbitrarily change the deposition distribution to some extent. In this case, macroscopic spots do not occur even when a secondary pressure airflow is applied, and a nonwoven fabric with good dispersion can be obtained. However, if this secondary pressure air flow is too large, the distribution of deposits becomes concave in the center, which may be undesirable. The deposition distribution of the web here is determined by cutting the web by 10 cm in the direction of travel, cutting it into pieces in 1 cm units in the width direction, and measuring the weight of the web in an area of ¹ x 10 cm. It is converted into . The nonwoven fabric of the present invention can be used for civil engineering materials and roofing materials using polyester, bag materials using polyamide for agricultural materials, diaper top sheets, teabags, etc. using polypropylene. In particular, the apparent quality of thin spunbond nonwoven fabrics with a basis weight of about 30 g/m ² or less is greatly affected by macroscopic unevenness and single fiber spreadability, and conventional web widening methods have not been able to provide satisfactory results. The spunbond nonwoven fabric produced by the above method has extremely little macroscopic unevenness and excellent single-filament opening properties, making it possible to obtain satisfactory results even in the field of these thin materials. Examples of the present invention will be described below. Example 1 Asahi Kasei M1300 (melt flow rate = 4.0) as a thermoplastic polymer was added as a molecular weight reducing agent.
Polypropylene mixed with 200 ppm of n-butyltin malate was used for spinning at 300° C. using four spindles (0.40 mmφ×68 holes) (see FIG. 3). 1st roll 10 at 1500m/min, 2nd roll 11 at 300m/min
Stretching was carried out on a Gotetstrol roll consisting of two pairs of Nelson rolls rotated at m/min. At this time, the discharge amount was set so that the single filament denier was 1.5 denier. One stage of corona discharge channel 3 was used and a current of 0.25 mA was applied to open the fibers. Using the first collision plate 6 made of copper, a round hole nozzle with a diameter of 3 mm was set as the secondary pressure air flow blowing nozzle 8 at a position 4 mm away from the second collision plate 7, and a pressure of 0.5 kg/cm ² G was applied. A secondary pressure airflow was used. Air Satsuka is 200mm
There were 4 pitches. By using secondary pressure airflow, the web width of one spindle is approximately 4550 mm (net conveyor,
The distance from the lower end of the second collision plate was 400 mm), and a nonwoven fabric without streaks was obtained by lamination. If secondary pressure airflow is not used, the web width of one spindle is only about 200mm,
Streaks were seen between the air sutures. Example 2 Polyethylene terephthalate (intrinsic viscosity =
0.68) and extruded with one spindle at a discharge rate of 461 g/min using a spindle with a diameter of 0.40 mm and 83 holes. At this time, the first roll 10 was not used and the second roll 11 was taken off at a speed of 5000 m/min. An intermediate air sucker was installed at a position 2 m below the spinneret to achieve stable spinning. 2nd roll 1
An air suction car for fiber opening was placed at a position 100 mm directly below No. 1, and the fiber was pulled under a pressure of 4.5 Kg/cm ² G. Two stages of corona discharge electrodes were used, and the distance between the needle electrode 4 and the target electrode 5 was adjusted so that 0.3 mA flowed through each stage using separate power supplies. Table 1 shows the results when the angle θ of the first collision plate 6 was set to 35°.
It was found that the examples of the present invention were superior in terms of the single yarn spreadability evaluated in each stage, and in particular, in Example A, as shown in Figure 4, the deposition distribution was flatter and the web deposition was lower than that of the comparative example. The width is increasing. Example 3 Using S5056 manufactured by Chitsuso Corporation as a thermoplastic polymer, extrude four spindles of 0.23φ x 120 holes at a total discharge rate of 400 g/min, and cool the first roll 10 at 2000 m/min and the second roll 11 at 5000 m/min. Stretched and doweled,
The pressure of one air suction car was 4.5Kg/cm ² G. Corona discharge was performed in the same manner as in Example 2, and the second
Charged yarn 13 running along collision plate 7
As a secondary pressure air flow, a secondary pressure air blowing nozzle with a round hole of 4 mm in diameter was used to blow out air at 1.0 Kg/cm ² G. At this time, the web width expanded to approximately 450 mm, and although the edges were slightly thin, a uniform nonwoven web was obtained, and the temperature was increased to 146°C.
Thermocompression bonding was possible using a textured embossing roll with a surface temperature of . The obtained nonwoven fabric has no macroscopic spots, has a basis weight of 32g/ ^m2 , and has a height of 4.5Kg/3cm width.
The elongation was 48%, the width was 6.8Kg/3cm, and the elongation was 45%.

【table】

【table】 [Brief explanation of the drawing]

Fig. 1 is a perspective view of a web widening device according to the present invention, Fig. 2 is a schematic sectional view, Fig. 3 is an overall explanatory view schematically showing an example of the spunbond method, and Fig. 4 is Example 2. Fig. 3 shows the web deposition distribution in . DESCRIPTION OF SYMBOLS 1... Air suction car, 2... Yarn, 3... Corona discharge channel, 4... Needle electrode, 5... Target electrode, 6... First collision plate, 7... Second collision plate, 8... Secondary pressure air flow blowing nozzle, 9... Spinneret, 10... First roll, 11... Second roll, 12... High voltage generation source, 13... Charged yarn, 14... Web, 15...Net conveyor,
16...Air suction device, 17...Static eliminator, 18...
...Emboss roll.

Claims (1)

[Claims] 1. The yarn forcibly charged by corona discharge collides with multiple stages of collision plates and falls toward the web conveyor while changing the traveling direction. When depositing the web on the web conveyor, the collision of the last stage of the collision plates occurs. Downstream of the point where the yarn collides with the charged yarn running along the plate, the width of the yarn is widened by applying a secondary pressure airflow from a nozzle with a cross-sectional area of 3 to 20 ^mm2 . A web widening method characterized by: