JPS6342922A - Production of pitch fiber - Google Patents

Abstract

PURPOSE:To produce a non-woven fabric of pitch fibers without forming any pitch shot, by melting and spinning pitch in a state that each of melted pitch fibers extruded through orifices is surrounded with a spouted stream of a heated high-temperature gas. CONSTITUTION:Cylindrical nozzles 14 constituting orifices 16 are respectively arranged inside of plural orifices 12 and a hot gas is spouted between the outer walls of the nozzles 14 and the inner walls of the orifices 12. Each cylindrical nozzle 14 is surrounded with a heated gas-discharging area separated independently from the neighboring gas-discharging areas and the hot gas stream is spouted under a similar condition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of forming fibers. More particularly, the present invention relates to a method of forming nonwoven or spunbond mats from carbonaceous materials, particularly pitch.

PRIOR ART The conventional method of making nonwoven fabrics from pitch generally involved cutting spun pitch filaments to make pitch fibers. Japanese Patent Publication No. 47-32148 discloses a method of producing pitch fibers several centimeters long by using a rotating cylindrical nozzle to spin pitch filaments. It becomes a nonwoven fabric by being attached. Such conventional methods of forming nonwoven fabrics of fibers have the disadvantage of the presence of unfibered pitch (commonly referred to as pitch shot). The presence of such pitch shots is detrimental to further processing of such nonwovens. US Patent 43805
No. 70 discloses a melt blowing system and method for forming fine fibers by forcing a molten fibril-forming thermoplastic polymer through an orifice in a nozzle, in which the molten fibers are blown at sonic speed by gas. Accelerated nearby.

[Problems to be Solved by the Invention It is an object of the present invention to provide an improved method of forming copitch fibers.

Another object of the present invention is to provide an improved method of extruding pitch fibers to substantially eliminate pitch shot and form a nonwoven fabric of pitch fibers.

[Means for Solving the Problems] These objects of the present invention are such that under conditions where there is a jet stream of heated gas having an increased temperature surrounding each fiber discharging from each orifice of each nozzle, , by extruding molten pitch through an orifice of a nozzle to form pitch fibers.

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of pitch m-fibers from pitch. Pitch refers to a carbonaceous substance, generally obtained as a by-product in the cracking distillation or pyrolysis of coal or petroleum. A nonwoven fabric is also formed from the pitch fibers.

The method of the present invention will be explained in detail with reference to the drawings. First, FIG. 1 shows a general nozzle structure 10 formed by a plurality of circular orifices 12. Inside each orifice 12, cylindrical nozzles 14 constituting an orifice 16 are arranged. In FIG. 1, between the outer wall of each cylindrical nozzle 14 and the inner wall of the circular orifice 12 is a gas discharge area that completely surrounds each cylindrical nozzle 14 and from which the heated gas exits.

Figure 2 shows orifices made in multiple rectangular shapes.
Another embodiment of the invention is illustrated in which a nozzle arrangement 10 is formed at 12, each orifice 1
2 is a cylindrical nozzle with orifice I6 inside.
14 are arranged.

In FIG. 2, the space between the outer wall of each cylindrical nozzle 14 and the inner wall of the rectangular orifice 12 is that of each cylindrical nozzle 1.
4 is partially surrounded by a gas discharge area for the heating gas to flow out.

In embodiments of the invention, each cylindrical nozzle 14 is surrounded by separate and independent heated gas evacuation areas, with adjacent gas evacuation areas separate and independent, such that the heated gas evacuation area is different from all cylindrical nozzles 14. This is in contrast to the nozzle arrangement of FIG. 3, which has a shared gas exhaust area surrounding it.

According to the invention, the temperature and flow rate of the heated gas stream (air, nitrogen, etc.) is adjusted for each individual discharge area, whereas in the nozzle arrangement of Figure 3, the temperature and flow rate of the heated gas stream (air, nitrogen, etc.) is adjusted around each cylindrical nozzle 14. The flow rate of the heated gas stream is not uniform for all nozzles. Therefore, a nozzle arrangement such as that shown in FIG. 3 tends to cause variations in the mill length of the nonwoven fabric and the diameter of the la fibers, resulting in a nonwoven fabric with excessive shot.

The nozzle arrangement of the present invention can provide a homogeneous nonwoven fabric because each cylindrical nozzle 14 is individually controlled and the heated gas flow is blown under similar conditions.

Another feature of the invention resides in that the temperature of the nozzle die is adjusted such that the melt pitch being spun has a melt viscosity of 50 voids or less. (In melt spinning of ordinary polyester fibers, the melt viscosity is several thousand voids.) Such a low melt viscosity is the reason why a nonwoven fabric substantially free of pitch shot can be obtained. For example, for a pitch having a softening point of 270°C, such a low melt viscosity can be obtained by heating the nozzle die temperature to about 420°C and maintaining the heated gas flow at about 480°C.

According to the present invention, the heated gas flow is at least about 10 psi.
g (0,7 J/cm2) preferably 30 psig (
2.1 kg/cm2) and a flow rate of at least 30 m/sec, preferably 200 m/sec.
It will be discharged after this. Such operating conditions are suitable for producing fine pitch fibers having a diameter of about 108 m or less.

Pitch m fiber nonwovens formed according to the present invention are typically further processed. For example, it may be processed using infusibility and carbonization processes that are carried out in the production of conventional carbon fibers. The nonwoven fabric obtained by smelting is used as fiber for concrete reinforcement and phosphoric acid fuel cells.

It is to be understood that the following examples are provided for the purpose of illustrating the invention, and the scope of the invention should not be limited thereby.

Example 1 Petroleum-based pitch having a softening point of 282°C was melt-spun and spun under the following conditions. The nozzle die used was 74.
It had 3 nozzles (inner diameter 0.2 mm). The cylindrical nozzle 14 and heated gas discharge area had the shape and arrangement as shown in FIG.

Extruder Inner diameter: 25 mm Length: 600 mm Rotation speed: 6 rpm Discharge rate: 3 g/min Extruder heating Population: 400°C Center: 42δ°C Outlet = 435°C Heated air flow Temperature: 610°C Pressure crab 45 psig Flow rate: 150 m /sec Nozzle die temperature: 430°C Pitch spinning temperature) Melt viscosity: 20 voids Pitch spinning was carried out continuously for 2 hours under the above conditions. As a result, 300 g of pitch fiber nonwoven fabric was obtained. Samples (10 g) randomly taken from the nonwoven fabric were examined for fiber length, fiber diameter, and pitch shot. The w4 fiber length was mostly between 10 and 15 mm, the fiber diameter was mostly between 8 and 9 μm, and only 7 pitch shots were detected in the sample. The nonwoven fabric was heat treated in a conventional manner and carbonized to produce carbon fibers having a strength of 75 kg/+nm2 and an elongation of 1.5%.

Example 2 Melt blow spinning was carried out using the same pitch used in Example 1 under the following conditions.

Nozzle inner diameter: 0.3 mm Extruder inner diameter: 25 mm Length: 600 mm Rotation speed near, 5 rpm Discharge amount: 8 g/win Extruder heating Population: 280'C Center = 350 °C Outlet: 380 °C Heated air flow Temperature: 480'C Pressure crab 12 psig Flow rate: 250 m/sec Nozzle die Temperature: 480°C Pitch (spinning temperature) Melt viscosity: 10 Samples (10 g) randomly taken from voided nonwoven fabric were examined for fiber length, fiber diameter, and pitch shot. .

The average fiber length was 15 mm, the fiber diameter was about 10 μm, and only 5 pitch shots were detected in the sample. This non-woven fabric was heat treated in the usual way and carbonized to 70 kg and 7 mm.
Carbon fibers with a strength of 2 and an elongation of 2% were made.

Example 3 (control example) Example 1 except that the nozzle die temperature was maintained at 300°C
Melt blow spinning was carried out in the same manner as above. The melt viscosity of the pitch was 150 voids.

Approximately half of the nozzle orifices became clogged 5 minutes after the start of spinning, and it became impossible to continue the operation any longer due to this blockage.

Example 4 (control example) Example 1 except that the nozzle die temperature was maintained at 340°C
Melt blow spinning was carried out in the same manner as above. The pitch had a melt viscosity of 60 voids. Melt blow spinning was carried out smoothly. However, 17 pitch shots were detected in a 10 g sample of the obtained nonwoven fabric, which was larger than the pitch shots of Example 1.

Example 5 (control example) Thirty-seven nozzles (inner diameter 0.2 mm
) Melt blow spinning was carried out using a nozzle arrangement as shown in FIG.

The melt blow spinning conditions were the same as in Example 1 except that the discharge rate was 23/min. Melt blow spinning was continued for 2 hours to produce about 150 g of pitch fiber nonwoven fabric. Fiber length of sample (10g) taken randomly from nonwoven fabric,
Fiber diameter and pitch shot were inspected. The fiber length ranges from 5 to 40 mm, and the fiber diameter ranges from 10 to 1
At 5 μm, 40 pitch shots were detected in the sample and were of no commercial value.

Although the invention has been described with specific examples based on several embodiments, many changes will be obvious to those skilled in the art, and this application is intended to cover any improvements and changes. What you are doing will be understood. Accordingly, it is intended that this invention be limited only by the claims and their equivalents.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a nozzle arrangement of the invention with a plurality of circular orifices for gas exit, and FIG. 2 shows a nozzle arrangement of the invention with a plurality of square orifices for gas exit. FIG. 3 shows a cross-sectional view of a comparative nozzle structure in which a plurality of nozzles share a gas outlet. (1%)

Claims (4)

[Claims] (1) a) Extrude molten pitch into multiple nozzles b) passing heated gas around each of the nozzles independently; c) Consists of collecting pitch fibers A method of forming fibers from pitch. (2) The method according to claim 1, wherein the melted pitch is pitch melted at a temperature such that the melt viscosity is 50 poise or less. (3) the heating gas is at least 10 psig (0.7 k)
2. A method according to claim 1, wherein the pressure is .g/cm^2). 4. The method of claim 1, wherein said heated gas has a flow rate of at least 30 m/sec.