JPH01260010A - Method for spinning by melt blowing method and melt blowing die - Google Patents

Abstract

PURPOSE:To divide a flow of a molten resin while eliminating a rope or shot, by arranging capillaries having a tapered cut at the tip and cut into the form of V in a specific state and admitting a high-speed gas from an orifice through the cuts. CONSTITUTION:Capillaries 11 are arranged in a direction so as not face protruding parts formed by cuts in the opposite directions and the tips thereof are protruded from an orifice 31. A high-speed gas blowing from the orifice is admitted from the cuts into the free ends of the capillaries to divide a molten resin, which is then discharged along the protruding parts from the tips thereof and drawn into a fibrous form.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a spinning method using a melt blow method in which a thermoplastic resin is extruded in a molten state from a capillary and drawn into a fiber form using high-speed gas blown out from an orifice around the capillary, and the method. Regarding melt blowing dies used in

BACKGROUND OF THE INVENTION A method for producing a fibrous web by a mesitoblowing method using a capillary in a meltblowing die is known. FIG. 9 shows an example of this. A thermoplastic resin is melt-kneaded in an extruder 2, extruded through a capillary 3 of a melt-blowing die 1, and then blown out from an orifice formed around the capillary 3 to form fibers. The capillary is stretched horizontally and wound into a web shape on a collection device 5, and as shown in Japanese Patent Publication No. 58-44470, a capillary is placed horizontally in the tip of the die, which has a triangular cross section. Capillaries are arranged side by side in the direction and soldered together, and gas plates are provided on the top and bottom of the die tip with appropriate clearance, and capillaries arranged side by side in the horizontal direction are vertically connected with a die block. There is a device that is firmly held and supported in a cantilever shape, and the tips of the gas plates provided above and below the capillary are faced to the free end of the capillary with a suitable clearance, and the gas plate and the tip of the die are Gas is blown onto the molten resin extruded from the capillary at a predetermined angle through an orifice formed by a clearance between the capillary and the free end of the capillary, thereby stretching it into a fiber shape. Furthermore, as shown in JP-A-56-159336, capillaries arranged in a grid pattern on a nozzle plate are inserted into the mesh-like holes of the screen so that their tips protrude, and the capillaries inserted into the mesh-like holes are Some devices blow gas out of an orifice formed around the capillary to stretch the resin extruded from the capillary into a fiber shape. Dies using these capillaries are
Compared to the conventional method in which a large number of microholes are formed in the die block, it is possible to avoid electrical discharge machining for drilling microholes, and it is also possible to easily arrange the capillaries accurately and line up the microholes in a straight line, which reduces die production costs. In addition, by making the capillary tip protrude outside the die, there are advantages such as being able to monitor the condition of the capillary tip during operation and detect abnormalities at an early stage.

Problems to be Solved by the Invention In general, in the melt blowing method, increasing the diameter of the micropores eliminates clogging, makes maintenance easier, increases the amount of molten resin discharged per unit micropore, and improves productivity. However, the discharge rate and the diameter of the fibers formed are related to each other, as long as the flow rate of high-speed gas is constant, the fiber diameter increases as the discharge rate increases, so it is impossible to increase productivity without changing the fiber diameter. There are limits.

As a result of various experiments to increase the productivity of capillaries, the present inventor found that when an axial cut is made at the tip of a capillary, the flow of molten resin is divided by the cut, and fibers on two sides from one capillary are separated. When the protrusions formed by the cuts of adjacent capillaries come into contact with each other back-to-back, the fibers intertwine with each other in a molten state, forming a thick lobe (hereinafter referred to as a lobe), and the fibers It was discovered that the shot does not form a shape, but instead becomes a bead (hereinafter referred to as a shot).

Regarding making a cut at the tip of the capillary,
The capillary shown in Japanese Patent Publication No. 58-44470 also has a triangular tip shape with tapered cuts on the top and bottom by machining the die block and capillary to form a triangular cross section at the die tip. The capillaries shown here are arranged so that the protrusions formed by the tapered cuts are oriented horizontally, and the protrusions of adjacent capillaries are back-to-back with each other.

An object of the present invention is to provide a spinning method using a melt blowing method that uses a capillary whose tip end is cut into a V shape to divide the flow of molten resin and eliminate lobes and slag, and a die for melt blowing. It is something.

According to the present invention, a thermoplastic resin is extruded from a capillary in a molten state, and in a spinning method using a melt-blowing method in which a thermoplastic resin is extruded in a molten state from a capillary and drawn into a fiber form using high-speed gas blown out from an orifice around the capillary, a taper is attached to the tip. Capillaries cut into a V shape with a V-shaped notch are lined up so that the protrusions formed by the notch are not back to back, and their tips protrude from the orifice. A spinning method is provided in which a flow of molten resin is generated divided into two, and a melt blowing die is provided in which a tapered cut is made at the tip of each capillary arranged in a series to form a V-shape. Ru.

A capillary usually has an outer diameter of 0.2 to 3 mm and an inner diameter of 0.2 mm.
Although it refers to a pipe of 1 to 2 fi, the outer and inner shapes are not limited to circular shapes, and include polygonal shapes such as triangular and quadrangular shapes. The tip thereof is preferably made to protrude appropriately from the tip of the die block or gas plate.

This facilitates monitoring of the capillary tip and enables early detection of abnormalities.

The orifice, as shown in the prior art, for example, in Japanese Patent Publication No. 58-44470, has a triangular cross section and is formed by the tip of a die on which capillaries are arranged horizontally and gas plates placed above and below it. There may be, but
Preferably, the capillary is formed by sandwiching the free end of the capillary between the lip of the gas plate and the flat holding surface of the lip. If the orifice is formed between the die tip with a triangular cross section and the gas plate, strict precision is required in the machining of the gas plate and die tip to ensure uniform clearance. Even if the clearance is assembled at a constant level, there is a risk that the clearance will be distorted due to subsequent thermal distortion or distortion over time.However, by clamping the capillary with the flat holding surface of the lip, a die for melt blowing with uniform clearance can be created. can be obtained easily and reliably, and even if the holding surface is somewhat flat due to processing errors, thermal distortion, aging distortion, etc. (However, as long as the holding surface is in contact with the capillary, each orifice will be maintained substantially uniform.) In addition, since the capillary is firmly supported even at its tip, it does not vibrate when gas is blown out, and there is no possibility of lobes or shifts occurring due to uneven exits. The gas flow can be reduced, and the gas stretching efficiency can be increased.

The protrusions formed by the cuts may be oriented so that the protrusions are not back-to-back with each other, but are preferably oriented vertically as shown in FIG.

Thermoplastic resins used in the present invention include polyamide, polyacrylonitrile, ethylene glycerol, polyesters containing coal and terephthalic acid as constituent monomers, and esters of 1,4-butanediol and dimethyl terephthalic acid or terephthalic acid. linear polyester, polyvinylidene chloride, polyvinyl
Butyral polyvinyl acetate, polystyrene, linear polyurethane resins, polypropylene, polyethylene polystyrene, polymethylpentene, polycarbonate and polyisobutylene Also within this category are thermoplastic cellulose derivatives such as cellulose acetate, cellulose propionate, cellulose acetate butyrate. Examples include cellulose butyrate and cellulose butyrate, to which dyes, additives, or modifying materials may be added depending on the case.

The amount of molten resin discharged must be at least a certain amount in order to ensure continuous flow, and even if the amount of molten resin blown away by the high-speed gas is greater than the amount supplied, the flow will not continue. This causes inconveniences such as being intermittent or concentrating on the protrusions at the negative part.

The critical flow rate of the molten resin varies depending on the hole diameter of the capillary, the angle of the tip, the viscosity of the molten resin, the flow rate of the high-speed gas, etc.

The viscosity of the molten resin is adjusted so that the molten resin easily splits upon contact with the high velocity gas. The appropriate viscosity varies depending on the hole diameter of the capillary, the angle of the tip, the flow rate of high-speed gas, etc., but is generally around 100 poise or less.

Air is a typical example of the gas used.

The molten resin is split by high velocity gas blowing from an orifice around the working capillary and flowing through the notch into the free end of the capillary. Then, along the protrusion formed by the cut, it flows out from the tip and is stretched into a fibrous form. By the way, when we closely observed the flow of molten resin from the tip of the capillary, we found that it separated vertically from the recess 13, followed by the protrusion 12, and flowed out from the tip in a thread-like manner. %f1 was recognized as doing so.

When the hole diameter of the capillary 11 is increased to increase the discharge amount, the flow of the molten resin 20 tends to be interrupted and become intermittent as shown in FIG. 5. This problem can be solved to some extent by cutting the tip of the protrusion 12. That is, the 6th A.

As shown in Figure 6B, when the discharge amount increased, a pool 23 of molten resin was formed on the cut end face, and it was confirmed that the resin flowed out by pulling a string from this, and the pool 23 was extremely stable. .

Example 1 Conditions As thermoplastic resin Number average molecular weight (Mn) 38000
．． Polypropylene with Mw/Mn of 3.0 (Mw is weight average molecular weight) and intrinsic viscosity (y) of 1.1 was used. A capillary with an outer diameter of 0.81 mm and an inner diameter of 0.5 inch was used as the nozzle, and the tip was machined as shown in Figures 6A and 6B. ■The tip angle of the cut was 30°, and the tip of the protrusion was canted to provide a flat part of 0°2 xo (circumferential direction) and 15n (radial direction). As shown in FIGS. 1 to 3, the capillaries 11 are lined up in a series in the horizontal direction so that the protrusions 12 are oriented vertically, and the other ends are clamped from above and below with die blocks 25 to fix them vertically. Using a die for melt blowing, the free end of which is sandwiched between the lip part 30 of the gas plate 26 from above and below and whose tip protrudes 1 m from the lip part 30, the molten polypropylene is introduced into the chamber 27 and formed into a capillary. 1
1, the gas introduced into the gas chamber 29 from the inlet 28 was blown out from the orifice 31 around the capillary 11. The stretching gas has a pressure of 4 Kg/d and a temperature of 28
Using air at 0℃, resin is discharged at a temperature of 280℃! 0.2
Molded at 2gr/min/hole.

As a result, a nonwoven fabric with very good texture and almost no shot or rope was obtained. During this molding, when the tip of the nozzle was observed with a 40x U-microscope, it was in the state shown in Figures 6A and 6B. Resin analysis of the obtained nonwoven fabric revealed a number average molecular weight of 33,000. Mw/Mn2゜4, (η)0.7
It was 8. Further, this nonwoven fabric was photographed with a microscope at a magnification of 500 times, and the average fiber diameter of the 20 fibers was measured, and the simple average fiber diameter was 2.3 μm and the root mean square fiber diameter was 2.6 μm.

Example 2 Conditions All the capillary protrusions 12 were arranged on the same side so as to be inclined at 45°, and everything else was molded in the same manner as in Example 1.

As a result, a nonwoven fabric with a slightly increased shot content compared to Example 1 but with almost no rope and an extremely pleasant feel was obtained. During this molding, when the tip of the nozzle was observed under a microscope with a magnification of 40 times, it was in the state shown in Figures 6A and 6B. Further, when the average fiber diameter was measured in the same manner as in Example 1, the simple average fiber diameter was 2.3 μm and the root mean fiber diameter was 2.6 μm.

Comparative Example Conditions All capillaries were molded in the same manner as in Example 1 except that the protrusions 12 of all the capillaries were arranged horizontally so that they were back to back.

As a result, compared to Example 1, the amount of shot and rope increased significantly, and as a result, a nonwoven fabric with a rough texture was obtained. During this molding, when the tip of the nozzle is observed under a microscope with a magnification of 40 times, one resin flow is formed from two protrusions placed back to back, and a liquid pool 23 as shown in Fig. 6B is continuously formed. I saw many things like that.

Example 3 Conditions Using air at a temperature of 320°C, the resin temperature was 320°C, and the discharge rate was 0.40gr/min/hole, other conditions were as in Example 1.
It was molded in the same way.

As a result, a nonwoven fabric with almost no shots or lobes and an extremely pleasant texture was obtained. When the tip of the nozzle was observed under a microscope with a magnification of 40 times during this molding, it was found to be in the state shown in FIG. 7A, and partially in the state shown in FIG. 7B. Resin analysis of the obtained nonwoven fabric revealed that the number average molecular weight was 31000, Mw/Mn 2.2,
(77) It was 0.71. In addition, when the average fiber diameter was measured in the same manner as in Example 1, the simple average fiber diameter was 2.1μ.
m, and the root mean square fiber diameter was 2.3 μm. Compared to Example 1, even when the discharge amount was approximately doubled, the fiber diameter was smaller, indicating that the resin flow was re-divided at the tips of the protrusions as the viscosity of the resin decreased.

Example 4 Conditions The tip of the capillary was sharpened and the tip of the capillary was used without being cut, and molding was carried out under the same conditions as in Example 1 except for the fact that the tip of the capillary was used without being cut.

As a result, a nonwoven fabric with good texture and less shot and rope was obtained. During this molding, the tip of the nozzle was heated to 40 times the i! When observed with an LI microscope, the resin flow was divided at the tip of each protrusion as shown in FIGS. 4A and 4B.

Example 5 Conditions A capillary with a sharp tip was used as in Example 4, and molding was carried out under the same conditions as in Example 3 except for the same conditions.

As a result, there was a slight increase in shots compared to Example 4, but there were almost no lobes, and a nonwoven fabric with a good feel was obtained.

During this molding, when the tip of the nozzle was observed under a microscope with a magnification of 40 times, it was confirmed that there were protrusions where the resin intermittently flowed and formed shots as shown in FIG. 5.

Effects of the Invention The present invention is configured as described above, and has the following effects.

According to the method of claim 1 and the die of claim 2, it is possible to form a flow of molten resin divided into a plurality of parts from one capillary, thereby increasing the discharge amount of molten resin without changing the fiber diameter, and improving production. Not only can the properties be improved, but a nonwoven fabric with fewer ropes and shots can be obtained.

According to the die of claim 3, it is possible to easily and reliably obtain a die for melt blowing with a uniform orifice, and even if the presser surface is not flat due to processing errors, thermal distortion, aging distortion, etc., the presser surface can be easily and reliably obtained. Each orifice can be maintained substantially uniform as long as it is in contact with the capillary. Moreover, since the capillary is firmly supported even at its tip, it does not vibrate when gas is blown out, and the outlet does not become uneven, making it less likely that lobes or shots will occur.
Furthermore, the flow of gas that does not contribute to stretching is reduced, and the gas stretching efficiency can be increased.

In the die according to the fourth aspect, since the tip of the protrusion of the capillary has a cut-off shape, even if the amount of molten resin discharged is large, the phenomenon that the flow is interrupted and becomes intermittent is less likely to occur. Moreover, since the flow of molten resin can be further divided into a plurality of parts, the amount of molten resin discharged can be further increased without changing the fiber diameter, and productivity can be further increased.

In the die of claim 5, the protrusions of adjacent capillaries are farthest apart, and ropes in which fibers are entangled with each other are less likely to occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a die for melt blowing according to the present invention, FIG. 2 is a side view of the same, FIG. 3 is an enlarged view of the main part of FIG. 2, and FIG.
Figures 4B and 4B are front and plan views of the tip of the capillary during spinning, Figure 5 is a front view showing the flow state when the amount of molten resin discharged is increased, and Figures 6A and 6B are the tips of the protrusions (cuffed). 7A and 7B are also plan views of the capillary tip, FIG. 8 is a perspective view of the main parts of the die, and FIG. 9 1 is a perspective view of a spinning device using a melt blow method. 11...Capillary 12...Protrusion 13...Concave part
23...Liquid pool

Claims (5)

[Claims] (1) In a spinning method using the melt blow method, in which thermoplastic resin is extruded in a molten state from a capillary and stretched into fibers using high-speed gas blown out from an orifice around the capillary, a tapered cut is made at the tip to form a V-shape. The cut capillaries are arranged in such a way that the protrusions formed by the cuts are not back to back, and their tips protrude from the orifice, and the high-speed gas blown from the orifice flows through the cuts, creating a flow of molten resin divided into multiple parts. Spinning method (2) It has a large number of capillaries that are partially or completely narrowed and fixed by a die block and arranged in a series between the die blocks, and orifices arranged on both sides of the outlet of each capillary, and has a thermoplastic resin. A die for melt blowing used in the spinning method according to claim 1, wherein the melt is extruded from a capillary in a molten state and stretched with high-speed gas blown from an orifice to form a fiber. (3) The melt blowing die according to claim 2, wherein the orifice is formed by pinching the free end of the capillary supported in a cantilever shape between the flat holding surfaces of the lip part. (4) The melt blowing die according to claim 2, wherein each protrusion has a shape with a cut end. (5) The melt blowing die according to claim 2, wherein the protrusions are vertically oriented when the capillaries are arranged horizontally.