Method of producing fibrous structure

• US 4,223,101 A
• Filed: 07/17/1978
• Issued: 09/16/1980
• Est. Priority Date: 07/17/1978
• Status: Expired due to Term

• Current Assignee: Inmont Corp. (BASF SE)
• Original Assignee: Inmont Corp. (BASF SE)
• Inventors: De Tora, Sigismondo A., Fine, Jerome
• Primary Examiner(s): Arnold, Donald J.
• Assistant Examiner(s): Hall, James R.
• Application Number:
  US05/925,646
• Time in Patent Office: 792 Days
• Field of Search: 264/6, 264/8, 264/24, 264/10, 528/76, 260/30.4 N
• US Class Current: 528/76
• CPC Class Codes: B29C 41/08 Coating a former, core or other substrate by spraying or fluidisation, e.g. spraying powder spray-up of reinforcing fibres B29C70/305
• CPC Class Codes: B29C 41/085 by rotating the former around its axis of symmetry
• CPC Class Codes: D01D 5/0038 the fibre formed by solvent evaporation, i.e. dry electro-spinning
• CPC Class Codes: D01D 5/0069 characterised by the spinning section, e.g. capillary tube, protrusion or pin
• CPC Class Codes: D01D 5/18 by means of rotating spinnerets
• CPC Class Codes: D01F 6/70 from polyurethanes
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: D04H 1/728 by electro-spinning electro-spinning methods and apparatus D01D5/0007
• CPC Class Codes: D04H 1/76 otherwise than in a plane, e.g. in a tubular way
• CPC Class Codes: Y10S 428/904 Artificial leather
• CPC Class Codes: Y10T 428/2395 Nap type surface
• CPC Class Codes: Y10T 428/24438 Artificial wood or leather grain surface

Abstract

A solution of elastomeric polyurethane in a volatile solvent is centrifugally sprayed onto a base in a strong electrostatic field to form long fibers that are swept across the base and deposited thereon in generally straight condition, overlapping and adhered to previously deposited fibers. Novel fibrous sheets of high strength are thus produced. The intersecting fibers may be ribbon-like.

Claims

1. A process for producing fibrous structures comprising:

(a) supplying a liquid solution of a thermoplastic elastomeric polyurethane in a volatile solvent to a surface rotating about an axis to form thereon a film which is whirled from said surface by centrifugal force,

(b) maintaining an electrostatic potential between said film and a collecting surface transverse to said axis to form said solution into electrically charged fibers, to attract said fibers to said collecting surface in a fiber pattern which, owing to said centrifugal force, is a whirling pattern annular to said axis, and to deposit, on said collecting surface, fibers oriented circumferentially of said annular pattern in paths having a radius of curvature above 4 cm.

(c) evaporating said solvent during the travel of said solution from the rotating surface to said collecting surface so that the deposited fibers contain sufficient solvent to bond to fibers previously deposited upon said collecting surface, and thereby form a fibrous structure and

(d) removing said deposited fibrous structure from said collecting surface,

the distance between said collecting surface and said film being sufficient that there is no spark or visible corona discharge passing through the atmosphere from the rotating surface carrying said film to said collecting surface,

said supplied solution of step (a) having a viscosity of above 500 centipoises and said polyurethane having an intrinsic viscosity of above 0.7.

2. Process as in claim 1 in which the rotating surface is maintained at a positive potential of at least about 50 KV and said collecting surface is grounded.

3. Process as in claim 1 in which the solution contains about 5 to 20% of the polyurethane dissolved in tetrahydrofuran and the polyurethane is a polyester polyurethane having an intrinsic viscosity of at least about 0.9.

4. Process as in claim 1 and including the step of moving said collecting surface whereby to transverse said annular pattern over said surface.

5. Process as in claim 4 in which said collecting surface is a moving endless web having a substantially flat collecting face perpendicular to said axis and said axis is stationary.

6. Process as in claim 4 in which said collecting surface if a moving endless web having a substantially flat collecting face perpendicular to said axis and said axis is traversed in a direction transverse to the movement of said collecting face.

7. Process as in claim 1 in which the process is effected in a substantially quiescent atmosphere.

8. Process as in claim 1 in which said rotating surface has an external circular rim over which said film of solution flows, the rate of rotation being such that said rim moves at a speed above about 3000 inches per minute.

9. Process as in claim 1 in which said process is continued so as to deposit fibers one onto the other until the deposited fibrous structure weighs at least about 30 grams per square yard, and a volatile solvent for said elastomer is then applied to one face of the fibrous structure in amount sufficient to smooth it and increase its abrasion resistance but insufficient to destroy its main fibrous structure.

10. Process as in claim 1 in which said fibers are deposited on a three dimensional body whose surface is said collecting surface, and said body and said axis are moved relative to one another whereby to deposit a continuous hollow fibrous structure around said body.

11. Process as in claim 10 and including the step of stripping said hollow fibrous structure from said body.

12. Process as in claim 1 and including the step of heating said deposited fibrous structure to remove residual volatile solvent.

13. Process as in claim 1 in which said axis is vertical and said collecting surface is horizontal and situated above said rotating surface, and the process is effected in a substantially quiescent atmosphere.

14. Process as in claim 1 in which said solution contains a polyurethane having an intrinsic viscosity of at least about 0.9 dissolved in tetrahydrofuran.

15. A process as in claim 1, said process yielding a fibrous structure consisting essentially of substantially straight elastomeric fibers extending substantially parallel to the surface of said structure, said fibers criss-crossing in all directions and being autogenously bonded to each other at crossing points without substantial change in width at their bond points, said structure having a density within the range of 0.1 to 0.6 g/cc., the process being continued until the weight of the deposited structure is above 15 grams per square yard.

16. Process as in claim 15 and including the step of heating said structure to remove residual volatile solvent after removing said structure from said collecting surface.

17. Process as in claim 5 in which there are a plurality of said rotating surfaces each having a stationary vertical axis of rotation, said rotating surfaces being spaced across the width of said web.

18. Process as in claim 14 in which the radius of curvature in step (b) is greater than 7 cm, the construction and arrangement is such that in its flow at said rim said film is in contact with a solid confining surface only at one face of said film, the opposite face of said film at said rim being exposed to the atmosphere, and in which said collecting surface is a moving endless web having a substantially flat horizontal collecting face, there are a plurality of said rotating surfaces below said collecting face, each of said plurality having a stationary vertical axis of rotation, said rotating surfaces being spaced across the width of said web, said process being effected in a substantially quiet atmosphere and yielding a fibrous structure consisting essentially of substantially straight elastomeric fibers extending substantially parallel to the surface of said structure, said fibers criss-crossing in all directions and being autogenously bonded to each other at crossing points without substantial change in width at their bond points, said structure having a density within the range of 0.1 to 0.6 g/cc., the deposition being continued until the weight of the deposited structure is above 15 grams per square yard.

19. The fibrous structure produced by the process of claim 1.

20. A fibrous structure produced by the process of claim 18.