JPH01246406A - Melt-blow spinning process and die therefor - Google Patents

Abstract

PURPOSE:To increase the throughput of the melted resin without change in fiber diameter by notching the top of capillaries in the axis direction so that the high-speed gas blown out of the orifice around the capillary flows in the capillary through the notches. CONSTITUTION:Each capillary 11 is notched on its top end in the axis direction, and the capillaries are arranged in a line. The melted resin is extruded through the capillaries 11 and a gas is blown from the orifices 31. The gas flow from the notch into the free end of the capillary to divide the melted resin. The divided resin flows along the projection 12 formed by notches and flies from the top of the projection, as it is drawn, into fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to 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. The present invention relates to a melt blowing die used in the method.

BACKGROUND OF THE INVENTION A method for producing a fibrous web by a melt blowing method using a capillary in a melt blowing die is known. FIG. 10 shows an example of this. A thermoplastic resin is melt-kneaded in an extruder 2 and extruded through a capillary 3 of a melt-blowing die 1. A high-speed gas is blown out from an orifice formed around the capillary 3 to form a fibrous resin. The capillary is stretched horizontally and wound into a web shape in a collection bag W5, and the melt blowing die has a capillary placed horizontally within the tip of the die, which has a triangular cross section, as shown in Japanese Patent Publication No. 58-44470. The capillaries are arranged side by side in the direction and each capillary is soldered, and a gas plate is provided above and below the die tip with an appropriate clearance. Hold it firmly and support it in a cantilever shape,
There is a type in which the tips of the gas plates provided above and below are opposed to the free end of the capillary with an appropriate clearance, and due to the clearance between the gas plate and the die tip or the free end of the capillary. From the orifice formed, gas is blown at a predetermined angle onto the molten resin extruded from the capillary, causing it to be stretched into a fiber shape. Also, JP-A-56-159336
As shown in this issue, capillaries arranged in a grid pattern on a nozzle plate are inserted into the mesh-like holes of the screen and their tips protrude, and the orifices formed around the capillaries inserted into the mesh-like holes are Some methods blow out gas to stretch the resin extruded from the capillary into a fiber shape. Compared to conventional dies that have many microholes formed in the die block, dies that use such capillaries can avoid electrical discharge machining to drill microholes, and also allow the capillaries to be aligned accurately and the microholes to be aligned in a straight line. Since it is easy to do, it reduces the manufacturing cost of the die, and since the tip of the capillary protrudes outside the die, it has the advantage of being able to monitor the condition of the tip of the capillary 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, and increases the amount of molten resin discharged per unit micropore, increasing 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 inventors found that when an axial cut is made at the tip of a capillary, the flow of molten resin is split due to the cut, It was found that fibers were formed.

The present invention was made based on this knowledge, and its purpose is to divide the flow of molten resin by making a cut at the tip of the capillary, thereby increasing the amount of molten resin discharged without changing the fiber diameter. It is an object of the present invention to provide a spinning method using a melt blowing method that enables the spinning method, and a melt blowing die for use in the method.

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 shape using high-speed gas blown out from an orifice around the capillary, a thermoplastic resin is added to the tip of the capillary. A spinning method is provided in which a notch is provided in the axial direction, and high-speed gas blown from the orifice flows through the notch to generate a flow of molten resin divided into two or more, and each capillary is arranged in parallel in series. A melt blowing die having an axial notch at the tip is provided.

A capillary usually has an outer diameter of 0.2 to 3 mm and an inner diameter of 0.1
Although it refers to a pipe of ~2 fl, 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 gas plate.

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

The orifice is a conventional one, for example, the Japanese Patent Publication No. 58-444.
As shown in No. 70, JP-A No. 56-159336, etc., the cross section is triangular and is formed by a die tip in which capillaries are arranged in parallel in the horizontal direction, and gas plates arranged above and below the die tip; - An example is a screen formed between the free end of a capillary supported in a cantilevered manner by a die block and the tip of a gas plate disposed above and below it with an appropriate clearance from the capillary. It may be formed around a capillary that is inserted into a rope hole, but preferably the free end of the capillary is sandwiched between the lip of the gas plate so that the flat holding surface of the lip and the capillary It is formed by 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 to a certain level, there is a risk that the clearance will be distorted due to subsequent thermal strain or strain over time, and if the capillary is supported in a cantilevered manner, the tip of the capillary is likely to be uneven, and high-speed gas There is a risk of vibration when blowing out. Furthermore, when inserting the tip of a capillary into the mesh-like holes of the screen, it is not easy to form the mesh-like holes of the screen uniformly, and many capillaries must be inserted one by one into the mesh-like holes of the screen at a small pitch. It takes a lot of effort. On the other hand, if the capillary is clamped between the flat holding surface of the lip part, it is possible to easily and reliably obtain a die for melt blowing with uniform clearance. As long as the holding surface is in contact with the capillary, each orifice can be maintained substantially uniform even if it is not flat to some extent.

Moreover, since the capillary is firmly supported even at its tip, there is no possibility of vibration when blowing out the gas or irregularities in the outlet.Furthermore, the flow of gas that does not contribute to stretching is reduced, increasing the efficiency of gas stretching. be able to.

The number of cuts in the axial direction formed at the tip of the capillary may be one, but preferably, a plurality of cuts are formed at regular or irregular intervals in the circumferential direction. FIGS. 4A to 4G show an example in which a plurality of cuts are provided at regular intervals. That is, in FIG. 4A, the free end of the capillary 11 is cut into a tapered shape to form a V shape, and protrusions 1 are formed on both sides of the parabolic recess 13.
2, and FIG. 4B shows the capillary 11.
A pair of U-shaped cut grooves 13 are provided at the free end of the 4D, a pair of V-shaped cut grooves 14 are provided in FIG. The figure shows eight U-shaped cut grooves 16. In addition, FIG. 4F shows a cone-shaped tip with a pair of U-shaped grooves 17.
Figure G shows a rectangular capillary 18 with V-shaped grooves 19 provided at each corner.

In the illustrated examples, the cuts are formed at equal intervals in the circumferential direction and are symmetrical, but they may be formed at irregular intervals.

In the former case, the divided fibers have uniform thicknesses, whereas in the latter case, the thicknesses are uneven, resulting in fiber webs with different textures.

Thermoplastic resins used in the present invention include polyamide, polyacrylonitrile, ethylene glycerol, polyesters containing coal and terephthalic acid, and 1,4-butanediol, dimethyl terephthalic acid or terephthalic acid. Linear polyesters such as esters, 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 Examples include butyrate and cellulose butyrate, to which dyes, additives, or modifying materials may be added depending on the case.

In order to ensure continuous flow of the molten resin, it is necessary to secure a certain placement plate, and even if the amount of molten resin blown away by the high-speed gas is greater than the supply amount, 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 melting fat varies depending on the hole diameter and tip shape of the capillary, the viscosity of the molten resin, the flow rate of the high-speed gas, and other factors.

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 and tip shape of the capillary, the flow rate of high-speed gas, etc., but is generally around 100 poise or less.

A typical example of the gas used is air τ.

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. Figures 5A and 15B show an example of a capillary with a tapered tip cut into a V-shape. When the flow of molten resin 20 from the capillary tip was minutely observed, it was found that the flow from the concave portion 13 as shown in the figure. It was confirmed that the thread was separated into upper and lower parts and flowed out along the protrusion 12, pulling the thread from its tip.

Increasing the capillary pore diameter and increasing the discharge amount,
As shown in FIG. 6, the flow of the molten resin 2o tends to be interrupted and become intermittent. This problem can be solved to some extent by canting the tip of the protrusion 12. In other words, as shown in Figures 7A and 7B, when the discharge amount increases, a pool 23 of molten resin is formed on the cut end face, and it is confirmed that the resin flows out by pulling a string from this, and the pool 23 is extremely stable. It was something.

When the tip of the protrusion 12 was cut, and when the viscosity of the molten resin was low, the flow was further divided into a plurality of parts from the canted end face, as shown in FIGS. 8A and 8B.

As described above, the molten resin is divided by the high-speed gas blown out from the orifice and flows out from the tip along the protrusion, but it is desirable that the protrusions are not placed back to back to each other in adjacent capillaries. This is because, if they are arranged, lobes are likely to occur in which the outflowing fibers become entangled with each other.

Therefore, for example, in a capillary of the type shown in FIG. 4A whose free end is tapered into a V-shape, the protrusions 12 are arranged vertically as shown in FIG. 9, rather than being arranged horizontally. It is preferable to line them up.

Example 1 Conditions As a thermoplastic resin Number average molecular N (Mn) 3800
0. Mw/Mn3. Polypropylene having an intrinsic viscosity (77) of 1.1 was used. A capillary with an outer diameter of 0°81M and an inner diameter of 0.51 mm 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 had a flat part with a force of 0.2fi (circumferential direction) and 15m (radial direction).
As shown in Fig. 3, the protrusions 12 are arranged in a row in the horizontal direction so that they are oriented vertically, and the other ends are sandwiched from above and below by die blocks 25 to firmly support the free ends. Using a melt blowing die with the tip sandwiched between the lip part 30 of the gas plate 26 from above and below and the tip protruding from the lip part 30, molten polypropylene is introduced into the chamber 27 and extruded from the capillary 11, while Gas chamber 2 from inlet 28
The gas introduced into the capillary 9 was blown out from the orifice 31 around the capillary 11. Pressure 4Kg/cd for stretching gas
The resin was molded using air at a temperature of 280° C. and a discharge rate of 0.22 gr/min/hole.

Resin balls that did not become fibrous (hereinafter referred to as shots)
A nonwoven fabric with an extremely pleasant feel was obtained, with almost no thick ropes (hereinafter referred to as ropes) formed by tangled fibers and fibers in a molten state. During this molding, when the tip of the nozzle was observed under a 40x microscope, it was found that Fig. 7A and ? The situation was as shown in Figure B. Resin analysis of the obtained nonwoven fabric revealed that
Number average molecule 33000, Mw/Mn 2.4, (η) 0.
It was 78. In addition, we took a microscopic photograph of this nonwoven fabric at 500x magnification and measured the average fiber diameter of the 20 fibers.
Simple average fiber diameter 2.3 μm, root mean square fiber diameter 2.6 μm
Met.

Example 2 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 very good texture and almost no shots or lobes 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 FIG. 8A, and a part was in the state shown in FIG. 8B. Resin analysis of the obtained nonwoven fabric revealed that the number average molecular weight was 131,000, Mw/Mn was 2.2, (η
) 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 2.1ηm,
The root mean square fiber diameter was 2.3 ηm. Compared to Example 1, even if the discharge amount was approximately doubled, the fiber diameter was smaller.
It was confirmed that the resin flow splits again at the tip of the protrusion as the viscosity of the resin decreases.

Example 3 Conditions Molding was carried out under the same conditions as in Example 1 except that the tip of the capillary was kept sharp, that is, the tip of the capillary was not canted.

As a result, a nonwoven fabric with good texture and less shot and lobes was obtained. During this molding, when the tip of the nozzle was observed under a microscope with a magnification of 40 times, the resin flow was divided at the tip of each protrusion as shown in FIGS. 5A and 5B.

Example 4 Conditions: Number average molecular weight for thermoplastic resin: 138,000. Mw/K
Polypropylene with n3.0 (v)1.1 was used. A capillary having an outer diameter of 1.06 m and an inner diameter of 0.7 mm was used as the nozzle, and four square-shaped cuts each having a length of 1.3 fi were made in the axial direction at the tip thereof as shown in Fig. 4D. Furthermore, the tip cant 0.2n (circumferential direction) Xo, 1B+
m (radial direction) flat section was provided. This capillary is placed in an X-shape with four protrusions, arranged so that the protrusions are not back to back, and sandwiched between the upper and lower lips with the tip protruding 1.5 mm from the lip. Using air at a pressure of 4 kg 10 J and a temperature of 350°C, the resin was molded at a temperature of 350°C and a discharge rate of 1.26 gr/min/hole.

As a result, a nonwoven fabric with good texture and less shot and lobes was obtained. During this molding, when the tip of the nozzle was observed under a microscope with a magnification of 40 times, the resin flow was divided into a plurality of parts at the tip of each protrusion as shown in FIGS. 8A and 8B. When the resulting nonwoven fabric was analyzed for fat return, it was found that the number average molecular weight was 27000.
Mw/Mn2. Ol(η) was 0.58. In addition, when this nonwoven fabric was photographed with a gJ mirror at 500 times magnification and the average fiber diameter of 20 fibers was measured, the simple average fiber diameter was 1.
．． 6 ηm, and the root mean square fiber diameter was 1.8 ηm.

Example 5 In Condition Example 4, the number of V-shaped cuts was increased to six. Other conditions were the same as in Example 4 for molding.

As a result, a nonwoven fabric with a good feel was obtained, although it contained some shots and robes. During this molding, the tip of the nozzle is
When observed under a magnification microscope, it was found that the resin flow was divided into a plurality of parts at the tip of each protrusion, as in Example 4.

Example 6 Conditions In Example 4, the tips of the protrusions were not canted but were made into sharp circles, and a die was manufactured in the same manner as in Example 4 except for the above. The same polypropylene as in Example 4 was used as the resin, and molding was carried out at a resin temperature of 330°C, a discharge rate of ff1O, 57 gr/min/hole, and a stretching air pressure of 4 kg/ci and a temperature of 330°C.

As a result, a nonwoven fabric with good texture and less shot and lobes was obtained. During this molding, when the tip of the nozzle was observed under a microscope with a magnification of 40 times, it was found that each protrusion was formed with one resin flow at the tip, as shown in FIGS. 5A and 5B. Resin analysis of the obtained nonwoven fabric revealed a number average molecular weight of 27,000. Mw
/Mn2.1, (η)0.61. Further, when the average fiber diameter was measured in the same manner as in Example 4, the simple average fiber diameter was 2.0 ηm, and the root mean square fiber diameter was 2.1 ηm. In comparison with Example 4, the fiber diameter was on the contrary increased despite the reduction in the discharge amount, and it can be seen that no re-splitting at the protrusions occurred.

Comparative Example Conditions A capillary with the same inner and outer diameters as in Example 1 was used for the nozzle,
The tip of the capillary was machined into a conical shape with an angle of 20 degrees (the shape without a groove in Fig. 4F), and this capillary was arranged as shown in Fig. 9, with the upper and lower lips protruding 1.5n from the lip part. The other conditions were the same as in Example 1.

As a result, a nonwoven fabric with good texture and less shot and lobes was obtained. During this molding, when the tip of the nozzle was observed under a microscope with a magnification of 40 times, it was found that one resin flow was formed from one hole.

When the average fiber diameter was measured in the same manner as in Example 1, the simple average fiber diameter was 3.2 ηm, and the root mean square fiber diameter was 3.5 ηm.
Met. As compared with Example 1, the fiber diameter is larger even though the discharge amount is the same, and it can be seen that splitting of the resin flow at the nozzle tip does not occur.

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, so the discharge amount of molten resin can be increased without changing the fiber diameter, and production can be improved. You can improve your sexuality.

According to the die of claim 3, it is possible to easily and reliably obtain a die for melt blowing with uniform clearance, and even if the presser surface is not flat due to processing errors, thermal distortion, aging distortion, etc., the presser surface can be capillary. Each orifice can be maintained substantially uniform as long as it is in contact with the orifice. Moreover, since the capillary is firmly supported even at its tip, there is no possibility of vibration when blowing out the gas or irregularities in the outlet.Furthermore, the flow of gas that does not contribute to stretching is reduced (this reduces the gas stretching efficiency). can be increased.

According to the die of the fourth aspect, by making the capillary tip slightly protrude from the lip portion, it becomes easy to observe the capillary tip, and an abnormality can be detected at an early stage.

In the die according to the fifth aspect of the present invention, fibers of uniform thickness can be obtained by providing the cuts at regular intervals.

In the die according to the sixth aspect of the present invention, fibers having irregular thicknesses can be obtained by changing the intervals of the cuts.

In the die according to claim 7, even if the protrusion is tapered, it has a truncated shape as if the tip is canted, so that even if the amount of molten resin discharged is large, the flow is interrupted and becomes intermittent. The phenomenon is less likely to occur, and the flow of molten resin can be further divided into multiple parts.

In the die according to the eighth aspect, since the protrusions of adjacent capillaries are arranged side by side so as not to come into contact with each other, it is possible to eliminate lobes where the fibers become entangled with each other.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a melt blowing die 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.
Figure -E is a perspective view of the capillary tip with different shapes, Figures 5A and 5B are front and plan views of the capillary tip during spinning, and Figure 6 is the flow rate when the discharge amount of molten resin is increased. Front view showing the condition, No. 7A and 7
Figure B is a front and plan view of the tip of the capillary during spinning when a capillary with a canted tip is used, Figures 8A and 8B are plan views of the tip of the capillary, and Figure 9 is a plan view of the tip of the capillary. Perspective view of main parts of die, 1st O
The figure is a perspective view of a spinning device using the melt blow method. 11...Capillary 12...Protrusion 14.15.1
6.17.19... Cut groove 18... Capillary 2
3.Liquid pool 25..Die block 26..Gas plate 30..Lip part Applicant Mitsui Petrochemical Industries Co., Ltd. agent Patent attorney Akira Sato - No. +C Figure Shun 2 +D F (Method) July 14, 1983 Patent No. 75420 2, Title of invention Melt-blowing spinning method and melt-blowing die 3, Relationship to the case of the person making the amendment Patent applicant address Chiyoda, Tokyo 3-2-5 Kasumigaseki, Ward Name Shogo Takebayashi 4, representative of Mitsui Petrochemical Industries Co., Ltd. Agent address: 7-3-12-5 Okiichi Chuo 7-chome, 737 Date of amendment order June 8, 1988 Date of dispatch (Showa 63
(June 28, 2016) 6. Subject of amendment: Brief description of drawings in the specification and document certifying power of attorney

Claims (7)

[Claims] (1) In a spinning method using a melt-blowing method in which a thermoplastic resin is extruded in a molten state from a capillary and stretched into a fiber shape using high-speed gas blown out from an orifice around the capillary, a notch is provided in the axial direction at the tip of the capillary,
A spinning method in which high-speed gas blown out from the orifice flows into the notch to generate a flow of molten resin divided into two or more parts. (2) having a large number of capillaries arranged in series and orifices arranged on both sides of the outlet of each capillary;
A die for melt blowing that extrudes thermoplastic resin in a molten state from a capillary and stretches it with high-speed gas blowing out of an orifice to form fibers.A die for melt blowing that has a notch in the tip of the capillary in the axial direction. (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 3, wherein the capillary tip slightly protrudes from the lip portion. (5) The melt blowing die according to claim 2, wherein a plurality of cuts are formed at regular intervals in the circumferential direction. (6) The melt blowing die according to claim 2, wherein a plurality of cuts are formed at different intervals. (7) A die for melt blowing according to claim 5 or 6, wherein a plurality of tapered protrusions are formed by the incision, and each protrusion has a truncated shape with a cut-off tip. 8. The melt blowing die according to claim 7, wherein the melt blowing die is arranged in parallel so that the backs of the parts do not come into contact with each other.