Plastic article or earthenware shaping or treating: apparatus – Shaping orifice and downstream work contacting gaseous... – Orifice for filaments or fibers
Patent
1987-11-05
1989-12-26
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
Shaping orifice and downstream work contacting gaseous...
Orifice for filaments or fibers
264 12, 4251925, 4253782, 425464, B29C 4712
Patent
active
048894761
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the melt blowing of carbon fibers, and more particularly to an improved melt blowing die and its support for controlled hot gas stream attenuation of fine carbon fibers.
BACKGROUND OF THE INVENTION
Carbon and graphite fibers are currently manufactured by extruding molten carbonaceous material through fine extrusion holes, and spun into fine threads or filaments. The filaments are subsequently stabilized, i.e. rendered infusible through a heat treatment in an oxidizing atmosphere and then heat treated in an inert atmosphere to convert them into carbon or graphite fibers.
Spinning of the carbon or graphite fibers involves using an oxygen rich (air) hot gas to draw the filaments from an extrusion die to produce fibers of very small diameter, as low as about 2 microns. The oxygen penetrates the molten fibers and is entrapped as the fibers cool. The presence of oxygen within the individual fibers assists in stabilizing the fibers in the subsequent steps of the process. Melted fiber precursor pitch is supplied from a suitable tank, fed under pressure through a die by operation of a suitable pump. The molten pitch is expressed through die openings as a series of vertical laterally spaced holes within a melt-blow die into the oxygen rich gas stream. The compressed air impinges through oblique slots against the extruded pitch material to form a plurality of fine pitch fibers. The die tip is of triangular cross-section, having downwardly, inwardly, and oppositely directed sloping walls fitted into a triangular shaped opening defined by opposed air plates or air lips forming the attenuating air passages. The melted pitch passes through the die openings and upon discharge therefrom, is contacted by the high velocity hot gas streams which pass through the oblique slots angled to intersect just below the die openings. The air streams attenuate the molten pitch fibers and draw them down to a diameter significantly smaller than the diameter of the multiple die openings within the die tip.
Problems have been encountered in maintaining the pitch at proper uniform temperature along the length of the die relative to the hundreds of extrusion holes within the die tip. The utilization of the air streams for fiber attenuating purposes has in some cases materially adversely affected the maintenance of a uniform and set temperature and the extrusion of the pitch under pressure through multiple orifices created by the fine holes within the die head and opening to the apex of the die tip nose. The presence of the air streams have tended to cause build up of the pitch at the tip of the melt blowing die, interfacing with the attenuating air stream.
Attempts have been made to improve melt blowing dies to facilitate the fiber or filament drawing process. U.S. Pat. No. 3,825,380 is directed to a die having a special nose configuration of triangular cross-section and particularly suitable for melt blowing of very fine fibers with the design of the melt blowing die eliminating dead spaces on the edge of the junction of two sides of the triangle of the die tip nose where the orifices open at the apex end of the melt blowing die.
U.S. Pat. No. 4,285,655, which is directed to a coat hanger die, employs a formula wherein the radius of the manifold at its inlet is selected in consideration of the flow characteristics of the resin melt to provide a low melt velocity at the inlet for the melt led under pressure to the plurality of extrusion orifices remote from that inlet.
U.S. Pat. No. 4,295,809 provides a mechanism for shifting the air lips relative to the triangular cross-sectional die tip nose for controlling the flow of heated gas blown out through air slots on either side of the die nose. Adjustments are made via appropriate spacers of the set back of the lower face of the air lips relative to the point of intersection of the oblique surfaces of the die tip, as well as the gaps between the air lips and the die tip itself through which the dual air streams pass for intersection downstream
REFERENCES:
patent: 828155 (1906-08-01), Vittenet
patent: 2045326 (1936-06-01), Kinsella
patent: 3352653 (1967-11-01), Speth
patent: 3357808 (1967-12-01), Eberle
patent: 3379811 (1968-04-01), Hartmann et al.
patent: 3547610 (1970-12-01), Holman
patent: 3621531 (1971-11-01), Feltgen et al.
patent: 3653861 (1972-04-01), Stalego et al.
patent: 3825380 (1974-07-01), Harding et al.
patent: 3942723 (1976-03-01), Langdon
patent: 3970417 (1976-07-01), Page
patent: 3978185 (1976-08-01), Buntin et al.
patent: 3985481 (1976-10-01), Brackmann et al.
patent: 4295809 (1981-10-01), Mikami et al.
patent: 4486161 (1984-12-01), Middleton
patent: 4526733 (1985-07-01), Lau
patent: 4606872 (1986-08-01), Watanabe
Accurate Products Co.
Bushey C. Scott
Graham R. L.
Woo Jay H.
LandOfFree
Melt blowing die and air manifold frame assembly for manufacture does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Melt blowing die and air manifold frame assembly for manufacture, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Melt blowing die and air manifold frame assembly for manufacture will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1574949