Apparatus and process for uniformly melt-blowing a fiberforming thermoplastic polymer in a spinnerette assembly of multiple rows of spinning orifices

• US 5,476,616 A
• Filed: 12/12/1994
• Issued: 12/19/1995
• Est. Priority Date: 12/12/1994
• Status: Expired due to Term

• Current Assignee: Reifenhauser GmbH & Co
• Original Assignee: Eckhard C.A. Schwarz
• Inventors: Schwarz, Eckhard C. A.
• Primary Examiner(s): THEISEN, MARY LYNN F
• Application Number:
  US08/354,432
• Time in Patent Office: 372 Days
• Field of Search: 264/6, 264/12, 425/7, 425/72.2, 156/167
• US Class Current: 264/6
• CPC Class Codes: B29C 48/05 Filamentary, e.g. strands
• CPC Class Codes: B29C 48/345 Extrusion nozzles comprising two or more adjacently arranged ports, for simultaneously extruding multiple strands, e.g. for pelletising
• CPC Class Codes: D01D 4/025 Melt-blowing or solution-blowing dies
• CPC Class Codes: D01D 5/0985 by means of a flowing gas (e.g. melt-blowing)
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres

Abstract

There is disclosed a novel apparatus and process for melt-blowing fiberforming thermoplastic polymers to form fine fibers by extruding through spinning nozzles arranged in four or more rows. The molten fibers are accelerated to near sonic velocity by gas being blown in parallel flow through small circular gas orifices surrounding each nozzle. The air orifices are formed by a family of plates which effect the perfect centering of each nozzle in each of the circular air orifices.

Claims

1. An improved apparatus for producing melt blown fibers of the type wherein a fiberforming thermoplatsic polymer is formed into a fiber stream and wherein said fibers are collected on a receiver surface in the path of said fiber stream to form a non-woven mat, the improvement of which comprises:

a polymer feed chamber for receiving said molten polymer;

a plurality of nozzles means mounted in a spinnerette plate arranged in multiple rows for receiving said molten polymer from said polymer feed chamber and for forming fine melt blown fibers, and having;

a) a multiplicity of nozzles arranged in at least four rows;

b) a nozzle spacing at least 1.3 times the outside nozzle diameter;

c) a first gas cavity having a height of at least six times the outside diameter;

d) a first gas plate to receive said nozzles, said gas plate having the same hole pattern as the nozzle mounts and having gas holes intermittantly spaced between the nozzle holes through which the gas passes into a second gas cavity;

e) a second gas cavity formed by a spacer plate and a second gas plate;

f) said second gas cavity having a height of at least one half of said nozzle diameter;

g) said second gas plate having a hole pattern identical to said nozzle mounts and having and having holes which are larger than said outside nozzle diameter of said nozzles to pass gas from said second gas cavity around said nozzles at high velocity to form said fibers.

2. The apparatus of claim 1 wherein said first gas plate, said spacer plate and said second gas plate have a total combined thickness of less than ten times the outside diameter of said nozzles.

3. The apparatus of claim 1 wherein the second gas plate is formed by a multiplicity of plates having holes in a pattern identical to said nozzle mounts, and a hole diameter larger than the outside diameter of said nozzles.

4. The apparatus of claim 1 having a baffle means to direct gas streams to the nozzle bases at said nozzle mounts from a gas supply chamber.

5. A process for forming a non-woven mat of melt-blown fibers comprising:

the steps of,

a) introducing a molten polymer into a feed chamber for receiving said polymer, said feed chamber communicating with a multiplicity of extruding nozzles means mounted in a spinnerette plate and arranged in multiple rows said rows having at least four rows of at least four nozzles per row and said nozzles having a spacing of at least 1.3 times the outside nozzle diameter,

b) extruding the molten polymer through the nozzles to form a fine filament,

c) simultaneously introducing a gas stream into a first gas cavity said gas cavity being bounded on one side by said spinnerette plate and bounded on an opposite side by a first gas plate and said nozzles pass through said first gas chamber and said first gas plate and said first gas chamber has a height of at least six times the outside nozzle diameter, and said first gas plate defines a gas hole pattern wherein the hole pattern is the same as the nozzle mounts and the gas holes are intermittently spaced between the nozzle holes and said gas may pass from said first gas chamber to a second gas chamber through said gas holes,

d) passing said gas through said gas holes into said second gas chamber, said second gas chamber being bounded on one side by said first gas plate and bounded on an opposite side by a second gas plate and said first gas plate and said second gas plate are spaced apart by a spacer plate and said second gas chamber has a height of at least one half of said nozzle diameter and said nozzles pass through said second chamber and said second gas plate defines a hole pattern identical to the nozzle pattern of said nozzle mounts and the holes of said hole pattern are larger than the outside diameter of said nozzles so that said gas can pass through said holes around said nozzles which pass through said holes in said second gas plate said gas is passed around said nozzles at high velocities so as to attenuate said fine filament exiting said extruder nozzles to form said fibers, and

e) collecting said fibers on a receiver in the path of said fibers to form a non-woven mat.