JPH02182958A - Preparation of non-woven web - Google Patents

Abstract

PURPOSE: To obtain a nonwoven web having a uniform size in the lateral direc tion, a uniform fiber distribution and a uniform weight distribution by blowing air flows on the side surfaces of a melted resin extruded from the opening of a die having convergent side surfaces in a specific state. CONSTITUTION: A melt flow die 14 comprises a die main body 20 containing split molds 22, a die tip extended on the central line 44 of the die main body 20, an air chamber 24, a pair of air-deflecting plate assemblies 52, a pair of air plates 58, etc. Air flows distributed from the air chamber are mixed in a groove 214 through plural distribution holes 182, 184 and then released from the air plates 58 through gas-deflecting plates.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for melt-blowing carbon fibers and thermoplastic resin fibers.
More particularly, the present invention relates to a melt blowing die and its support apparatus and its application in the attenuation of fine carbon fibers and thermoplastic fibers using a controlled flow of heated gas.

Carbon fibers and graphite fibers are produced by extruding molten carbonaceous material through fine extrusion orifices and spinning into fine threads or filaments. For further stabilization, the filaments are made infusible by heat treatment in an oxidizing atmosphere and then converted into carbon or graphite fibers by further heat treatment in an inert atmosphere.

Similarly, thermoplastic resin fibers can be formed into shapes such as mats and rovings by extruding a molten thermoplastic resin material through an extrusion orifice and blowing air into the extrudate. In the past, many problems have arisen regarding the shaping and control of supply air and the temperature control of molten thermoplastic resin and air.

Spinning carbon or graphite fibers involves drawing filaments through an extrusion die using heated oxygen-enriched (air) gases to produce fibers of extremely small diameter (approximately 2 microns).

Oxygen enters the molten fiber and becomes trapped as the fiber cools. The presence of oxygen inside the fiber helps stabilize the fiber during further processing. The molten fiber precursor pitch is fed from a suitable tank and then pressurized from a die using a suitable pump. The molten pitch is forced into an air stream through a die opening formed as a number of laterally spaced vertical holes within the melt blowing die. Compressed air is blown through the angled grooves onto the extruded pitch material to form a plurality of fine pitch fibers. the die tip has a triangular cross-section, with a triangular opening defined by opposing air plates or near lips forming an elongated air flow path with sloped sides formed downwardly and inwardly in further opposite directions; mated to. The molten pitch passes through the die opening and, upon exiting the die opening, comes into contact with a high velocity stream of heated gas discharged from angled grooves formed to intersect directly below the gas opening. The air flow elongates the molten pitch fibers,
It is stretched to a diameter much smaller than the diameter of the opening at the tip of the die.

Various problems have previously arisen in maintaining a uniform pitch temperature over the length of the die for the large number of extrusion openings within the die tip. Using airflow for the purpose of elongating the fibers not only maintains a uniform set temperature of the pitch, but also
Pressure extrusion of pitch from multiple orifices can have a significant negative impact. A number of orifices are formed by small holes inside the die head and open at the tip of the die tip nose. In the presence of airflow, pitch tends to accumulate at the tip of the melt blowing die and impede the attenuation airflow.

Various efforts have been made to improve meltblowing dies to facilitate the fiber or filament drawing process; U.S. Pat. A particularly suitable die is disclosed. This die is designed to eliminate dead air space on the edges of the triangular two-sided contact point of the die tip nose where the orifice opens at the apex end of the die.

U.S. Pat. No. 4,285.655 relates to a coat hanger die in which the inlet radius of the manifold is selected with consideration of the flow characteristics of the molten resin to provide a low inlet velocity for the melt and to A formula is used in which the material is pumped to multiple remote extrusion orifices.

U.S. Pat. No. 4,295,809 discloses that by moving a near lip relative to a die tip nose having a triangular cross section,
A device is provided for controlling the flow of heated gas blown through air grooves on both sides of the nose. Adjusting the set pack of the lower surface of the near lip to the contact point of the inclined surface of the die tip, and adjusting the gap between the near lip and the die tip (the gap that allows air flow to pass through and guide the melt to the downstream intersection of the small diameter hole from which it is extruded). This is done through a suitable spacer.

Although these patented techniques address the operation of melt-blown dies and the production of melt-blown-like filaments without die blockage, problems remain unsolved, particularly with respect to molten materials with relatively high softening temperatures.

Accordingly, the main object of the present invention is to provide a melt blowing die that is particularly suited for the process of spinning carbonized fibers with high softening temperatures and then converting them into carbon or graphite fibers homogeneously and at low cost. This die maintains controllability of the air flow used for elongation.
The presence of airflow does not adversely affect the molten pitch material's ability to maintain a suitable temperature during extrusion, the airflow is thermally isolated from the die body, and the die has excellent thermal stability and control. Furthermore, the die has the characteristics that the component parts can be easily disassembled and assembled, and specific parts can be removed without disassembling the die assembly.

It would also be desirable to provide a method for forming a nonwoven web of thermoplastic resin with controlled uniformity or nonuniformity as desired by the operator.

Referring to FIG. 1, the air branching frame and melt blowing die assembly (10) consists of two main components: the air branching frame (12), and the pitch spinning of thin filaments of carbonaceous material with a high softening temperature. After that, it includes a melt blow die (14) for converting into carbon or graphite.

The melt-blowing die (14) has air manifolds (16) fixed to both sides thereof, and is installed in the center of the frame (12) through a mounting block (18) formed integrally with the opposing frame member (19). and is fixed to the frame (12). The die (14) is bolted or screwed at both ends to the mounting block (18) so as to be integral with the frame (12).

The melt-blowing die (14) is formed of a machined metal die body (20), as shown in FIG. )including. On the outside of the split mold (22) is a rectangular, parallelepiped air chamber (24) secured with bolts or screws. The die body (20) transfers the melted pitch to the die (14).
The extrudate is extruded from a large number of closely aligned micro-extrusion holes inside the tip of the die (14), and the extrudate is bombarded with a stream of inert gas such as air as it is discharged from the tip of the die (14). This makes it elongated. The extrudate forming the filament is passed through the small diameter extrusion hole inside the tip of the die (14).
) is stretched by blowing an air stream against the extrudate from the opposite direction.

An inert compressed gas, such as air, is transferred from a gas source into the interior of the air manifold (16) by means of a hose or vibe fitting (30) at one end of each cylindrical air manifold (16), as shown by the arrow (28). Supplied via.

Both ends of the air manifold (16) are fitted with end caps (3).
2) is blocked. Compressed air within the air manifold (16) is fed to both ends of the air chamber (24) via one end (26a) of the tube coupling (26). Pipe fitting (26
) is the center 1s of the corrugated tube that joins each end of the rigid hollow metal tube.
(26b) to maintain the leak-proof joint despite axial expansion and contraction due to temperature changes. Pipe fitting (26)
Both ends (26c) of are attached to both ends of the air chamber (24) and open to the inside thereof. The length of the air chamber (24) is the same as the length of the die body (20).

The opposing mounting 7 langes (34) fix both sides of the die body (20) to the mounting block (18) with screws (35). The block (18) is integrally formed with the air distribution frame (12) to hold the die (14) in place during use as well as to facilitate removal of the die for maintenance or replacement. The fitting (26) also facilitates removal of the air chamber (26) from the air manifold (16) for maintenance or replacement.

The split mold (22) of the die body (20) is, as described later,
It has a series of longitudinally spaced wells (38) that retain the flow of molten pitch and ensure that the carbonaceous filament is extruded through the extrusion hole at the die tip. Cartridge is placed. Furthermore, as shown in Fig. 1, a large diameter circular cylindrical vertical pitch inlet (
42) is formed on the centerline (44) of the die body (20) defined by the mating sidewalls of the mold halves (22).

The inlet (42) receives pressurized molten pitch from a pitch supply line (as shown), as best shown in FIGS. 2 or 4.

To explain Fig. 2, this figure shows the melt blow die (
14) Shows its main components. The melt blow die (14) includes a die body (2o) including a split mold (22),
In addition to the air chambers (24) each attached to the outer surface (48) of the split mold (22), a die tip is attached to the split mold (22) and extends on the centerline (44) of the die body (20). (
50), a pair of air deflection plate assemblies (52), and a pair of air plates (58). Air deflection plate assembly (5
2) includes two machined basic metal blocks: a male deflection block (54) and a female deflection block (56).

The die split molds (22) are generally rectangular and have parallel piping, and each split mold (22) has a vertical inner surface (60), a top surface (62), and a bottom surface ( 64). Both sides (48), (60) are perpendicular to the top (62) and bottom (64). Inwardly of the bottom surface (64) are the bottom wall (68) of the narrow groove and the vertical side 1! of the laterally opposed groove. (
70), (72), and horizontal positions! ! (74) and a large L-shaped groove (66) is formed therein. On the other hand, the horizontal wall (74) is recessed (
78) is the formation. Therefore, it is! The bottom of (22) has laterally spaced vertical projections (76), (79).
) extend along the entire length of the die head on both the inner and outer sides of the splitter (22).

Both male and female deflection blocks (54) are provided inside each L-shaped groove (66).
), (56) and air plates (58) are attached to both sides of the die tip (50).

Referring to FIG. 4, the die split mold (22) has a screw hole (8
The opposite side surface (60) of the mating side W (22) is
) and are in flush contact with each other. The connecting bolts (82) are arranged on both left and right sides and on the outside of the coat hanger cavity (86). The cavity (86) has a vertical pitch inlet (4
2) Coat hanger type mirror image ilI! (88).

Pitch used as a raw material for carbon fiber or graphite fiber with a micron diameter has a high softening point, so the pitch is first heated at a temperature of about 204°C to 426°C (40”
After being heated and melted to a temperature between This melting temperature must be maintained during extrusion into filaments through a vertical extrusion orifice (90) (FIG. 4).

By maximizing the number of filaments to be drawn, and therefore the number of extrusion orifices (90), the coat hanger plastic die (20) has an extremely long pitch residence time, which accelerates the thermal deterioration of the molten pitch; A large die body (22) is required to resist extrusion of filaments from a small diameter extrusion orifice (90) at high pressure, making temperature control difficult and making it difficult to extrude filaments of - It has the disadvantage of becoming A coat hanger type die (20) facilitates this method. After the molten pitch is deflected to the branched coat hanger type manifold (92) through the inlet (42), the manifold part (92a) is tapered toward the vertical manifold end (92b), so that the pitch remains The time distribution is the extrusion oriice (
90) is relatively uniform over the entire length of the die body (20).

The inlet (42) merges with the manifold (92), as shown in FIG. The lateral side walls (94) become progressively narrower as they descend into the lower portion of the cavity (86). The melted pitch coats the hanger cavity (
86) and forced downwardly between the convergent sidewalls (94) of the cavity (86), pitch is most restricted along the flow path (96) inside the cavity (86). In this flow path (96), the side wall (94
) widens at the end at (94a) (Figure 2)
, the sloped side wall (94a) of the coat hanger cavity (86)
) defines a cavity portion (86a) that widens toward the end inside the protrusion (79) of the pair of die split molds (22).

The melt blowing die (14) is comprised of a metal machined nib block component that extends the entire length of the die assembly (14) including a die split (22) and a die tip (50).

The metal block can be made of stainless steel.

The die tip (50) is connected to the central protrusion (79) of the die split mold (22).
) has a lateral width equal to the full width of the upper surface (102
), a base portion (100) of rectangular cross section having side surfaces (104) and a bottom surface (106) perpendicular thereto.

A triangular nose (108) is provided at the center of the base portion (100) and integrally projects downward. A plurality of extruded orifices (9n) are drilled in the center of the die tip (50) and are connected to the tip of the nose (108). A groove (112) of rectangular cross section is provided inside the top surface (102) of the die tip (50) in the coat hanger cavity (86).
) and somewhat through the extrusion orifice (90). A screen pack (114) is installed inside the rectangular groove (112) so as to fill the groove (112). The screen pack (114) is a standard filtration media such as a 150 mesh stainless steel screen and includes a die tip (5
0) Serves to shear the molten pitch material to reduce the viscosity of the melt flowing into the internal small diameter extrusion orice (90). The screen pack (114) faces the largest part of the triangular portion (86a) of the coat hanger cavity (86), so that the melt pitch
) and then into the extrusion orifice (90).

The top surface (102) of the base portion (100) of the die tip (50)
) includes a groove (116) forming a step on both sides thereof, and the serving part of the base portion (100) is a groove (7) of the die split mold (22).
9) is fitted.

An important feature of the invention is that the components of the die (14) are easy to maintain and repair! It is an object of the present invention to provide a melt blowing die which can be detachably attached to each other and which can melt-spun filaments of mesophase carbon pitch having a high softening temperature under pressure. The die tip (50) is attached along the contact surface of the die split mold (22) to the lower end of the split mold (22) using a number of depth-bored screws (120) (Fig. 3). conduct. Inside the groove (78) of the inner protrusion (79) of the die split mold (22) is a series of longitudinally spaced aligned screw holes (12).
2) is a provision. Also, the base part of the die tip (50) (
100) is bored with a series of longitudinally spaced holes (124) opposite the extrusion orifice (90) system;
124) has a depth boring portion (126), and has a mounting screw (
120) to receive the head (120a) of the head (120a). Therefore, the head (120a) is the bottom surface (
IO2) is fitted inside.

A pressurized inert gas such as air to elongate the extruded pitch material as it exits the extrusion orifice (90) maintains the split die (22) from which the molten material is extruded at a uniformly high temperature. offset the need to

Since the die part ffi (22) according to the present invention is quite wide, it has a large die mass compared to a commonly used melt blowing die. Also, usually, a carrot-type cartridge heater is charged in the die body (20) and the pitch is maintained at or above the melting temperature, so that the pitch is released under pressure from the coat hanger cavity (86) and the die tip (50 )
Ensure even distribution to the internal extrusion orifice (90). By increasing the lateral thickness of the die split W (22), the cartridge heater can be connected to the pitch inlet (22).
42) and the center line (44) of the die body (20)
The distance from the coat hanger cavity (86) above is increased. The die thus acts as a heat sink to ensure that the pitch material maintains the desired melting temperature and is pumped to the extrusion orifice (90).

Another feature of the invention is that the die split mold (22) has a series of longitudinally spaced vertical holes (38) for insertion of cartridge heaters.
), (Figures 2 and 4) and the vertical hole (38)
is for receiving a rod type cartridge heater (132). The vertical hole (38) is a die split type (22)
It extends downwardly from the top surface (62) of the die and extends substantially the entire vertical distance of the die split (22), terminating before the bottom wall (68) of the L-shaped groove (66). The vertical hole (38) opens into the bottom wall (68) through a small diameter hole (136) with a deep bore (138). Depth recess (13
8) receives a retractable threaded plug (140). A plug (140) provided at the bottom of the die splitter (22) is used to remove the cartridge heater (132) if it expands and becomes tethered during use. Therefore, the mechanical tolerance of the vertical hole (38) is reduced and the adhesion and heat transfer between the cartridge heater (132) and the die body (20) is improved. At this time, air deflection blocks (54), (5
6) and the air plate (58), one or more plugs (140) can be removed so that the holes (
A plunger (not shown) smaller than the diameter of 136) can be inserted. At the end of the plunger there is a cartridge heater (1
32), the heater (132) is pushed axially upward and away from the vertical hole (38).

The main feature of the present invention is that the molten pitch is
0) to precisely control the blowing of the air flow to elongate the extruded filament as it exits from the inlet (42).
Temperature control of the molten pitch from the die body (20) as it is pumped through the coat hanger cavity (86) to the extrusion orifice (90) of the die body (20) is to be carried out without being adversely affected.

The heated air is a pair of air installed on both sides of the die body (20)! ! (24). These air chambers (2
4) consists of cutting parts made of steel or other thermally conductive metals. The air chamber (24) has an upper part (142) and a lower part (
144), (Fig. 2), and the upper part (142
) has an inverted U-shaped cross section, the bottom wall or top! ! (14ft
) and both inside and outside! ! (148) and (150). U
The open end of the glyph upper portion (142) is closed by a lower portion (144) formed in a modified rectangular block. The lower portion (144) includes an upper surface (152), a lower surface (154), and inner and outer walls (156), (158). Top surface (
152) has grooves formed at its edges for receiving the outer ends of the inner and outer walls (148) and (150) of the upper portion (146).

Both ends of the air chamber (24) are closed by end walls (164), and as shown in FIG. 2, each end wall (164) serves as an intake port, and one end (26c) of the transfer pipe (26) It has a circular hole (166) leaktightly connected to the air manifold (16) for supplying pressurized air to the air manifold (16). Air chamber (24)
The upper and lower portions (142) and (144) are attached to the outside of the die split mold (22) with mounting screws (170), and the mounting screws (170) are attached to both the upper and lower portions (142),
It passes through the screw holes (169) and (171) provided in (144) and is screwed into the screw hole (168) of the die-in cavity (22).

The side walls (148) of each air chamber (24) are important to the invention and serve to provide effective thermal isolation from the die body (20) to the air flow. The side wall (148) is provided with a shallow groove (176) along almost its entire length to form an air chamber (2).
4) and the dead air space (17) between the die body (20)
8). This gap (178) is for reducing heat loss from the die body (2o) to the air chamber (24) due to the air flow from the inert air source (28)>1.

The lower part (144) of the air chamber (24)
2) forming a relatively deep V-shaped groove (180) in the center;
Also a number of horizontally spaced air distribution holes (182)
is bored inwardly from the inner surface (156) of the lower portion (144) and opens into a V-shaped groove (180). A number of distribution holes (182) are shown in FIG. In addition, air distribution holes (184) with the same number and dimensions are located in the die body (22).
' is formed inward from the outer surface (48) of the L-shaped groove (66) and is aligned so as to communicate with the bottom of the L-shaped groove (66).
(See Figure 2). The air distribution hole (184) is a die split type (22
) passes through the outer protrusion (76).

The present invention includes an air deflection plate assembly (52) with both male and female deflection blocks (56), (54) mounted within the narrow bottom portion (66a) of the L-shaped groove (66). . The female deflection block (54) has an inverted-shaped cross section and has a base portion (190
) and a leg portion (192) perpendicular thereto. The width of the base portion (190) is the same as the lateral width of the bottom portion (66a) of the L-shaped groove (66), and the vertical height of the leg portion (192) is the same as the width of the bottom portion (66a) of the L-shaped groove (66). 66a). Both the male and female deflection blocks (56) and (54) have an elongated shape spanning the entire length of the die body (20) in the vertical direction, and are made of metal such as stainless steel. - Deflection block (54)
has a right-angled band (194) extending parallel to and laterally spaced from the base portion (190) to the leg portion (192). The protrusion (194) is a die split type (
22) Projects across the internal air distribution hole (184).

Further, on the inner wall (148) of the air chamber (24), the base portion (190) of the female deflection block (54) has a shallow surface that forms a dead space (198) between it and the die split mold (22) over almost its entire width. It has a groove (196), and the dead space (198) is for thermally insulating the base portion (190) directly facing the die split W (22) from the die body (20). The leg portion of the female deflection block (54) (
192) is provided with a shallow groove (202) defining a dead air space (204) for thermally insulating the female deflection block (54) together with the groove side wall (72) and the wide surface (104) of the die tip (50). ing.

The female deflection block (56) has a generally rectangular cross-section, the width of which is equal to the narrow portion (66) of the L-shaped groove (66) that carries it.
It is narrower than the lateral width of a). Female deflection block (5
6) has a top surface (206), a bottom surface (208), and an outer surface (
210) and an inner surface (212). Top surface (
The block (206) extends over the entire length of the block (56) and has a groove (214) of generally rectangular cross section cut therein with a strip projection (194) projecting therein. Groove (214
) is considerably wider than the thickness of the strip projection (194).

Lateral width and depth of groove (214) and strip projection (194)
, i.e. the base portion of the female deflection block (54) (
190), a considerable spacing relative to the airflow in the tortuous airflow path defined by the male and female deflection blocks (54), (56), as indicated by the arrows in FIG. give. Side surface (21) of female deflection block (56)
2) improves the flow of the air deflection plate assembly (52) by providing a recess (212a) directly opposite the leg portion (192) of the female deflection block (54) over most of its vertical height. The downstream portion of the channel is formed.

Both male and female deflection blocks (54), (56) are rounded to smooth air flow along the air passages defined by opposing surfaces. However, the shape of the opposing surfaces of the male and female deflection blocks (54) and (56) is such that the airflow becomes significantly turbulent when it passes through the flow path formed by both blocks. , to prevent laminarization of the air flow and heat loss from the die body (20) to the air flow and deterioration of the filament forming process.

In each air deflection plate assembly (52), the female deflection block (54) is fixedly secured, but the female deflection block (56) is different. Referring to Fig. 3, the screw hole (216) inside the die split mold (22) has a mounting screw (2
18), and the head (218a) of the mounting screw (218) is provided at a longitudinal position corresponding to the longitudinally spaced screw holes (216) through which the mounting screw (218) passes. It also projects into a tapered hole (220) in the base portion (190) of the female deflection block (54).

The female deflection block (56) is vertically adjustable and is secured to the L-shaped groove (6) by a series of set screws (224), (Fig. 2).
6) Fixed and held in a predetermined position internally. Set screw (
224,) is an outward protrusion (224,) provided at the bottom of each male mold (22).
226) Projecting into an internal oval elongated vertical hole (226). A screw hole (228) into which a set screw (224) is screwed is provided inside the female deflection block (56).

The vertical movement of the female lateral block (56) is carried out by a special adjustment method, and this adjustment is carried out using at least two sets of holes horizontally drilled inside the die split mold (22) and inside the outer protrusion (76). This is done using oblique and smooth bore dowel holes (230). Each female lateral block (56) is also provided with at least two sets of horizontally aligned and spaced dowel holes (232) drilled to the same diameter as the dowel holes (230) of the die split mold (22). , when the dowel holes (230) and (232) are aligned, the dowel pin (2
34), (Figs. 3 and 5) are fitted into the dowel holes (232).

The adjustment bin (234) works to raise and lower the female lateral block (56) in stages, but this adjustment adjusts the size of the air passage defined by the male and female lateral blocks (54) and (56). The purpose is not to modify, but to adjust the amount by which the top of the air plate (58), tip (50), and nose (108) is moved up and down. Therefore, the air plate (58) is attached to the bottom surface (20) of the female lateral block (56).
8), and is raised and lowered together with the block (56). Also, by adjusting the position of the air plate (58) in the horizontal direction with respect to the die tip (50), the air plate (58) and the die tip nose (108)
), the air gap G near the open end of the extrusion orifice (90) inside the die tip nose (50) can be varied. The overall dimensions of the air grate (58) are:
Approximately 315°C to 343°C, which corresponds to the increase in mass of the die body' (20) and is required for extruding mesophase pitch with a high softening temperature.
In order to prevent the air plate (58) from being deformed over its entire length at high processing temperatures of 600-650 degrees Fahrenheit (600-650 degrees Fahrenheit), it is larger than conventional devices. Each air play 1
- (58) generally has a parallelepiped or rectangular block shape and has a top surface (240), a bottom surface (242);
It includes an outer surface (244) and a sloped inner surface (246).

The inclination angle of the inner surface (246) corresponds to the inclination angle of both side surfaces (110) of the nose (108) at the die tip (50), and is in close contact with the side surfaces (110). Air plate (58)
The vertical height of the die tip nose (1
The upper surface (240) of the air plate (58) is made slightly smaller than the vertical height of the die tip base (
100) and defines a portion of the air flow path.

Also, the lateral width of the air plate (58) is the same as the die splitting protrusion (76) and the inclined side wall (108) of the die tip nose (108).
10). The arrow in Figure 2 (
As shown at 248), the air plate (58) can be moved laterally. This movement is guided by grooves (250) inside the top surface (240) of each air plate (58), with grooves (250) in the male air plate (58) corresponding to the bottom surface (208) of the female lateral block (56). come into contact with.

The male air plate (58) is attached to the female lateral block (56) in the manner shown in FIG. A set of aligned horizontal oblong holes (252) are formed within the air plate (58) extending to opposite ends of the air plate (58);
A mounting screw (254) is inserted through it. Mounting screw (25
The threaded end of 4) is threaded into the vertical threaded hole (256) inside the female lateral block (56) and is threaded into the threaded hole (256).
6) are arranged in number and position to correspond to the screw holes (252) inside the air plate (58). Mounting screw (
The head (254b) of 254) engages with the bottom surface (242) of the air plate (58) on the side of the screw hole (252).

When removing the mounting screw (254), remove the air plate (58).
) and the female lateral block (56) so that the air plate (58) can move laterally on the female lateral block (56). Next, install the mounting screw (25
4) Tighten. Further, the air grate (58) can be raised and lowered in the vertical direction to protrude in front and behind the die tip nose (108). Retracting the tips of the air plates (58) to the rear of the plane of the die tip nose (108) allows the air slot ends JR ( 24
5) is called "setback."

Further, the air gap G between the inclined surface (110) of the die tip nose (108) and the side surface (246) of the air plate (58) can be easily adjusted using a plurality of jack screws (260). A series of jack screws (260) extend the entire length of the melt blowing die (14). The jack screw group (260) is attached to the outer projection (
76) inserted into an internally open vertically extending oblong slot (262), (FIG. 2); In the illustrated embodiment, the slot (262) is inserted into the female lateral block (56).
) for receiving set screws (224) of slots (226
). The jack screw group (260) has a head (
260a) and a threaded end (260b), the end (260b) being connected to the slot (260) and the threaded end (260b).
60), and is threaded into the screw hole (264) of the air plate (58) at a longitudinally spaced position corresponding to the air plate (58).

Also, each jack screw (260) has a collar (266).
is provided, and the jack screw (260) is connected to the collar (26
6) and the head (206a). When the jackscrew group (260) is rotated, the air plate (58) moves laterally with respect to the die tip nose (108) as shown by the double-headed arrow (261) in FIG. 2, so that the extruded filament The dimensions of the air gap G vary for both sides of the shaped pitch material. Die split mold (22
) The air plate (58) can be adjusted up and down by providing the internal oval slots (226) and (262), so the extrusion orifice (90) opens at the top of the die tip nose (108). , die tip nose (
108), the set pack of air plates (58) can be changed.

The advantages of using a pitch material, ie, a carbonaceous material, for the die body have been described in detail above, but the entire explanation can be applied directly to thermoplastic resins. Processes using molten plastic resins may have different flow rates and processing temperatures, but the die operating instructions are applicable to thermoplastic resins.

Thermoplastic materials suitable for the manufacturing method of the present invention include polyolefins such as monopolymers, copolymers and terpolymers. Suitable materials include polymethyl methactylate and polyester resins such as polyethylene Tele7 grade. Also suitable are polyamides such as polyhexamethylene adipamide, polyomega tyruluramide and polyhexamethylene sebaamide. Also suitable are polyvinyls such as polystyrene. Although polymers such as polytrifluorochloroethylene can also be used, preferred materials are polyolefins, including homopolymers, polypropylene-based and polypropylene-based copolymers, and other high molecular weight polyolefins. Polyethylene is LDPE.

Includes HDPE, LLDPE and very low density polyethylene.

From the foregoing description, it will be apparent that the melt blowing die and supporting air branch frame assembly is particularly suited for melt blowing mesophase pitches at high softening temperatures.

In the past, mats produced using conventional melt-blown dies generally had poor quality and poor filling, and also caused die blockage and die overpressure after short periods of operation. Additionally, as pitch softening points exceed approximately 250°C (approximately 500°F), the propensity for mesophase increases, with attendant negative effects on die operation stability and fiber homogeneity and quality.
Trouble grows even more. When a feedstock containing a high concentration of mesophase is charged to the meltblowing, a meltblowing die made in accordance with the present invention is required due to the high viscosity and increased coking tendency of this feedstock. The melt blowing die of the present invention has improved control accuracy and uniformity of fiber diameter, so that the air flow rate to maintain a constant average diameter can be reduced from, for example, about 1.670 Q/min (600 FM) to about 2.
．． The air temperature increases significantly to 265 ff/min (80 CFM) and the air temperature increases from approximately 320°C to 327°C (610”F to 6
20@F) is acceptable. In terms of die operation, the temperature at the extrusion die tip can be set within the range of about 299'C to 307C (570F to 585F). A die tip with approximately 20 holes per inch, an extrusion orifice diameter of approximately 0.30 mm (0,012 inch), and a die tip of approximately 0.05 mm on each side of the air plate. .28m
The work was significantly improved when it was set forward by m (0,011 inches). The support frame facilitates removal of the die unit and allows for rapid separation of the air chambers attached to both sides of the die from the air manifold. The die body of the present invention is wider than the conventional die body, so the cartridge heater is moved outward from the coat hanger cavity, and the metal mass of the die split mold is increased, so melting from the inlet (42) is prevented. As the body flows into the coat hanger cavity and into the extrusion orifice (90), the heating of the melt is more effective and even than in the past.

Furthermore, as a result of this, the cartridge heater vertical hole (
38) is the L-shaped groove (66) of the air deflector assembly (52).
becomes in series with Therefore, by drilling a vertical hole (38) through the die split mold, providing a deep recess at the L-shaped groove (66) on the lower surface of the die split mold, and screwing the screw plug into it, the vertical hole (38) can be occluded. Therefore, if necessary, the cartridge heater can be forcibly removed by simply removing the air plate and both the male and female deflection blocks, unscrewing the plug inserted into the vertical hole (38) of the cartridge heater, and inserting the rod. Thus, the cartridge heater's vertical hole (38) can be approximately the same diameter as the cartridge heater's diameter, even if the heater expands in its center. As a result, even if the cartridge heater expands and becomes locked, it can be forcibly removed from one end of the split die in the axial direction. Since the cartridge heater and the vertical hole of the die split mold are in close contact with each other, the pitch melt in the coat hanger cavity is heated under conditions of high heat conduction efficiency and with precise control of the pitch melting temperature.

In the present invention, by bringing the outer surface of the die split mold into frontal contact with the groove in the side wall of the air chamber, the shallow groove forms a dead air space together with the die body, and thermally insulates the air chamber from the die split mold. These shallow grooves and their associated dead air spaces can be filled with a suitable thermal insulating material to improve thermal insulation between the die body and the air chamber. This type of insulation can be formed from a heat-resistant graphite compound. Similarly, the base portion (190) and leg portion (192) of the female deflection block (54)
The shallow groove inside and the L-shaped groove (6) inside the die split mold (22)
The dead air spaces (198) and (204) defined by the bottom wall (68) and side wall (72) of 6) can be filled with an insulating material. With this configuration, males,
Heat loss from the die split mold is minimized for the air flow passing through the curved air path defined by the female and female deflection blocks (54), (56).

Transverse movement of the air plate (58) relative to the die tip nose (108) having a triangular cross-section opens the extrusion orifice (90) to an air flow which directs the extrusion at the die exit. Air gaps G on both sides of the die tip nose (108) are blown from both sides of the object.
can be changed. In addition, the air plate (58) is installed in stages in front or behind the die tip nose (108).
It is preferable to set it slightly behind the die tip nose (108) to prevent extrudate from accumulating at the tip of the air plate (58) and impeding air flow.

Attachment of the air plate (58) to the female deflection block allows the air plate (58) to be moved laterally relative to the block and also allows set-pack step adjustment of the air plate in the vertical direction. This kind of adjustment is a big deal! (22) and female deflection block (56) using suitable set screws, elongated slots, and dowels selectively placed within the smooth lumen.

The opposing surfaces of the male and female deflection blocks (54) and (56) are shaped to form a winding flow path to impart turbulence to the airflow, and then the airflow is directed to the die tip nose (
The extruded material discharged from the extrusion orifice (90) of 108) is sprayed through a dual air gap G. The turbulence that occurs in the airflow from the air chamber to the air gap G is best illustrated by the airflow arrows in FIG.

Although the invention has been described in terms of preferred embodiments, it will be obvious that changes may be made in various forms and details without departing from the scope and spirit of the invention.

In accordance with the manufacturing method of the present invention and the accompanying drawings, after a thermoplastic polymer such as polypropylene is processed, for example in an extruder (as shown), there is an inlet (42) from the extruder to a die (14).
(Figures 1, 2 and 4) and then into the coat hanger cavity (86) before being directed to the melt blowing process described for processing carbon fibers.

The thermoplastic polymer is extruded in the presence of a gas flow through an extrusion orifice (
90), but the polymer is forced out from the air stream.
After being elongated into fibers, the fibers are collected on a movable collection device such as a drum (as shown) to form a continuous mat.

The properties and quality of thermoplastic polymer nonwoven mats or other nonwoven molded articles produced by melt blowing vary considerably depending on the operating conditions and their control. That is, product properties and properties such as tensile strength and tear resistance are significantly influenced by air flow rate, polymer flow rate, air temperature, and polymer temperature.

These operating conditions are particularly important to the length or profile of the extruded fiber and air knife. In the past, manufacturing efforts have been abandoned due to the inability to control air flow uniformity over the length of the air knife.

A wide range of operating conditions can be used in accordance with the manufacturing method of the present invention depending on the type of thermoplastic material and the type of web or desired characteristics of the product. The operating temperature for extruding the thermoplastic material through the extrusion die to make the nonwoven product is optional. The allowable temperature range of the thermoplastic material inside the extrusion die, and thus the approximate temperature of the die head surrounding the material, is about 176° C. to 482° C. (350° F. to 900° F.);
The preferred temperature range is about 204°C to 399°C (40
0"F to 750°F). The most preferred temperature range for polypropylene is about 204°C to 343°C.
(400°F to 650°F).

The operating temperature of the air in the air knife is arbitrary as long as a nonwoven product suitable for use is produced, but the acceptable range is approximately 176°C to 482°C (350°F to 900°F).
F).

Thermoplastic resin and air flow rates vary widely depending on the type of thermoplastic material to be extruded, the distance between the extrusion head and the winding device, and the operating temperature. Acceptable air to polymer ratios are generally from 30 to 100, more generally for polypropylene from about 20 to 5001.

Typical polymer flow rates are in the range of about 0.39 to 1.5 g/min, preferably about 0.5 to 1.0 for each formula.

In the preferred manufacturing method of the present invention, heating of the die body is performed by seven rows of cartridge heaters, each row of heaters is individually and independently controlled, and the weight distribution over the entire length of the die is determined by the type of resin and its extrusion amount. can be changed.

A heating zone can protrude from the coat hanger to eliminate heat loss from the ends of the die assembly.

Uniform air flow rate over the entire length of the extrusion die is essential for uniform web weight. The design of the air chamber preferably allows the airflow to flow evenly from two large diameter inlets to a plurality of small diameter holes, and then the airflow flows at an even velocity over the entire length of the extrusion die. If desired, an insert (not shown) provided inside the intake pipe of the air chamber (24) can be modified to change the uniformity of the outflow velocity distribution in the narrow group inside the pipe (26). The insert has a bell-curve cross-section for even gas distribution and mixing, so that the flow space at the midpoint of the pipe (26) is e.g. approximately 0.3+m+1 from the wall of the pipe (26).
I (l/8 inch) and a pipe (26)
The taper is attached so that there is almost complete flow space at the end. The gas preferably flows out through a slit in the upper part of the pipe (26), mixes at the upper corner of the end wall (164), further mixes at the lower bottom part of the pipe (26), and then flows through the die body (26). ) into the air passage.

The distance between the die tip and the air knife is about 10 minutes from the effective die tip length.
By protruding by 1 mm (4 inches), eddy currents that can adversely affect web edge quality can be eliminated.

The adjustability of the die assembly allows for independent, precise and reproducible adjustment of the air gap width and setback of the die tip relative to the air knife, allowing air gaps and set packs to be adjusted depending on the resin type. The optimal value of can be selected. This optimization feature can also target web quality and/or production scale.

By thermally insulating the molten resin and the air passages from each other, the temperature difference between the resin temperature and the air temperature during operation of the extrusion die is significantly increased, preferably about 37.8"0 (too F
), it is possible to produce high-quality sushibu and optimize the manufacturing process. This feature is particularly useful for polyolefins, polyamides and polyesters.

We can also undertake custom production of webs with specific properties.

EXAMPLE In addition to the equipment described above with a 20 inch die assembly, a polypropylene resin (Exxon #3
145 Himelt 70-) was used to produce a nonwoven web with excellent uniformity in size, shape, and quality.

The test was conducted twice, and the resin temperature in the first test was 300'C and the air temperature was 300'C! In addition, the resin temperature in the second test was 285°C and the air temperature was 285°C. The air volume is approximately 11.328M (4000FM). The test time was 2 hours each. In each test, the fibers were only sprayed with water and wound up immediately after being ejected from the extrusion die.

After the resin was charged into a Can Air q-hopper, it was transferred to a Nic6tas Zen
It is equipped with a metering type pump made by David Standard Co., Ltd., approximately 50.
Melt extrusion was carried out through an extrusion die through an 8 mm (21/2 inch) extruder.

Ingersoll is used to feed air into the extrusion die.
An Ingersoll Rand bed compressor and an ArmsLrong air heater were used. A microprocessor was used to adjust the flow rate and record the work. For each test, the fortune is about 508m
m (20 inches) four webs (10, 20, 30
and 50 g/I11") and collected on a drum winder. The microprocessor was set to maintain an even air velocity distribution along the air knife, so each web had uniform dimensions and fibers across its width. distribution and weight distribution, such that in continuous operation of the extrusion die, the air flow rate varied by less than 10% over the length of the air knife, and furthermore, the air temperature and resin temperature did not vary substantially. This is by design.As the web temperature decreased, the texture hardened.

[Brief explanation of the drawing]

1 is a plan view of an assembly of an air branching frame and a melt blowing die according to a preferred embodiment of the present invention; FIG. The figure is a horizontal and vertical cross-sectional view of the melt blowing die along line 3-3 in Figure 1, Figure 4 is a vertical cross-sectional view showing the vertical contact surface of the die splitter in the melt blowing die, and Figure 5 is a vertical cross-sectional view showing the vertical contact surface of the die splitter in the melt blowing die. FIG. 3 is a partially cutaway side view showing the connection points and adjustment device between the mold, air deflection plate assembly, and air plate; 10...Air branch frame and melt flow die assembly 12...Air branch frame 14...Melt flow die 16...Air manifold 18...Mounting block 19...7 frame member 20 ...Die body 22...Die split mold 24...No changes to the cleaning content in the air chamber drawing) Procedure arrival 1j Positive Uyo (voluntary) March - 22, 1999

Claims (9)

[Claims] (1) A method for producing a nonwoven web made of thermoplastic polymer fibers, which comprises the steps of: extruding a thermoplastic polymer through a die opening having a convergent side surface that tapers toward the exit; and directing the molten resin to the die opening. a process in which gas is released along each side of the molten resin as it is extruded into elongated planar fibers from the die, the gas flowing at substantially the same flow rate over the entire length of the die; The gas released from each side of the die is fed into the air chamber through a slit or holes through a pipe, so that the gas from the air chamber flows into the die body at the same flow rate. The gas from the plurality of distribution holes passes through a plurality of distribution holes, and the gas from the plurality of distribution holes is discharged into longitudinal grooves in the die body as a plurality of gas streams, and the longitudinal grooves also direct the gas flow from the plurality of distribution holes. and releasing the gas along the sides of the die opening to both sides of the molten resin, with gas deflection plates to impart substantially the same gas flow rate and the elongated fibers. A method for producing a nonwoven web, comprising a step of collecting the nonwoven web on a winding device disposed in the planar flow path to form the nonwoven web. (2) The manufacturing method according to claim 1, wherein the temperature of the gas and the temperature of the molten resin are individually controlled by substantially isolating the gas from the die body. (3) The manufacturing method according to claim 1 or 2, wherein the thermoplastic polymer is a polyolefin. (4) The manufacturing method according to claim 3, wherein the polyolefin is polypropylene. (5) The polypropylene is about 26 mm thick from the die head.
5. The method of claim 4, wherein the extrusion is carried out at a temperature of about 500 to 650 degrees Fahrenheit. (6) The gas is about 260 to 34 mm from the gas slit.
released at a temperature of 3°C (500 to 650°F),
The manufacturing method according to claim 4 or 5. (7) by providing a dead air space along the flow path of a major portion of the flute, the dead air space being interposed between the flute and a major portion of the die body that contacts the thermoplastic polymer; 7. A method as claimed in any one of claims 1 to 6, including the step of: blocking the flow of gas within the die body from conducting heat from the flow of thermoplastic polymer within the die body. (8) The difference between the polymer temperature inside the die body and the gas temperature inside the longitudinal groove is at least about 37.8°C (1
00°F)
The manufacturing method according to any one of the above. (9) A melt blowing device, comprising: an extrusion die having a die tip having a convergent side surface and a plurality of extrusion orifices formed between the convergent side surfaces for passing the molten resin; and molten resin fibers. A device for releasing gas along the sides of the molten resin when extruding the molten resin so as to elongate it in a direction away from the die orifice, the device being disposed on both sides of the die. , an air chamber having a pipe with an outlet disposed along both sides of the air chamber, the air chamber having a device disposed within the pipe for providing the same gas flow rate over the entire length of the air chamber; and the die tip. an elongated groove formed inside the die substantially parallel to both sides of the die, and an elongated channel formed on the die body on both sides of the die, one of the grooves; a flow path extending from the outlet to the outlet provided on the side surface of the tip of the die, a deflection plate installed inside each groove, and each gas chamber communicating with the associated groove to direct the gas in the gas chamber to the deflection plate. a gas emitting device having a plurality of dispensing holes aligned to emit the gas;