Method and apparatus for producing a highly oriented yarn

• US 6,478,996 B1
• Filed: 07/06/2000
• Issued: 11/12/2002
• Est. Priority Date: 11/09/1998
• Status: Expired due to Fees

• Current Assignee: Barmag AG (OC Oerlikon Corporation AG)
• Original Assignee: Barmag AG (OC Oerlikon Corporation AG)
• Inventors: Schulz, Detlev, Meise, Hansjörg, Schäfer, Klaus
• Primary Examiner(s): Tentoni, Leo B.
• Application Number:
  US09/610,275
• Time in Patent Office: 859 Days
• Field of Search: 264/103, 264/210.8, 264/211.14, 264/211.17, 264/237, 425/72.2, 425/104, 425/377, 425/378.2, 425/379.1, 425/382.2, 425/464, 282/45
• US Class Current: 264/103
• CPC Class Codes: D01D 5/092 in shafts or chimneys
• CPC Class Codes: D01D 5/098 with simultaneous stretching
• CPC Class Codes: D01F 6/62 from polyesters

Abstract

A method and an apparatus for producing a highly oriented yarn (HOY) wherein the yarn is withdrawn from the nozzle of a spinneret at a withdrawal speed of at least 6,500 m/min. The filaments forming the yarn are drawn during their solidification, so that a highly oriented molecular structure forms in the polymer. To withstand the withdrawal tension generated by the high withdrawal speed without overstressing the filaments, the filaments are assisted in their advance before they solidify such that prior to the solidification a tensile stress relief is effective on the filaments, and that during the solidification a reduced withdrawal tension is effective on the filaments while they are drawn.

Claims

1. A method of producing a highly oriented yarn from a thermoplastic material, comprising the steps of

extruding a melted thermoplastic material through a nozzle to form a plurality of downwardly advancing filaments, and such that the filaments solidify at a location spaced below the nozzle,

withdrawing the filaments under a withdrawal tension so as to cause the filaments to be drawn while being solidified, with the withdrawal tension being generated by a withdrawal speed of at least about 6,500 m/min, and

assisting the filaments in their advance before their solidification with help of an airflow while passing the filaments through a constrictor and a diffuser that are interconnected by a seam at the most narrow cross-section such that before their solidification the filaments are relieved from tensile stress and during solidification and drawing a reduced withdrawal tension is effective on the filaments, wherein shortly downstream of the seam the filaments solidify.

2. The method as defined in claim 1 comprising the further steps of combining the filaments after their solidification to form an advancing multifilament yarn, and winding the advancing multifilament yarn into a package.

3. The method as defined in claim 2 wherein the step of assisting the filaments in their advance includes injecting the melted thermoplastic at a high injection speed during the extruding step.

4. The method as defined in claim 2 wherein the step of assisting the filaments in their advance with an airflow includes generating a cooling air stream that flows along with the advancing filaments.

5. The method as defined in claim 4 wherein the cooling air stream has a flow velocity that is substantially the same as the advancing speed of the filaments before their solidification.

6. The method as defined in claim 4 wherein the cooling air stream has a flow velocity that is greater than the advancing speed of the filaments before their solidification.

7. The method as defined in claim 4 wherein the constrictor has its most narrow cross section at an outlet end thereof with the outlet end connecting to the diffuser to which a vacuum is applied for generating the cooling air stream.

8. The method as defined in claim 4 wherein the assisting step includes guiding the advancing filaments before their solidification through a cooling shaft that connects to the ambient air through an air permeable cylindrical wall, so that the ambient air forms the cooling air stream.

9. The method as defined in claim 4 comprising the further step of guiding the advancing filaments through a heating zone located immediately below the extrusion nozzle so as to heat the advancing filaments.

10. The method as defined in claim 2 wherein the withdrawal tension is generated by the winding step, such that the withdrawal speed is determined by the winding speed.

11. The method as defined in claim 2 wherein the withdrawal tension is generated by a feed system arranged in the path of the advancing multifilament yarn upstream of the winding step, and with the withdrawal speed of the feed system being greater than the winding speed of the winding step.

12. The method as defined in claim 11 wherein the feed system comprises two rolls that are looped by the advancing yarn in S-shape or Z-shape.

13. A melt spinning apparatus for producing a highly oriented yarn from a thermoplastic melt, comprising

an extruder for heating a thermoplastic material and extruding the resulting melt through a nozzle having a plurality of nozzle bores to form a plurality of downwardly advancing filaments,

a cooling chamber disposed below the nozzle,

a lubrication device for combining the downwardly advancing filaments to form an advancing multifilament yarn, and

a yarn winding device for winding the advancing yarn into a package,

said cooling chamber comprising a constrictor through which the filaments advance, and a diffuser arranged at the outlet end of the constrictor, with the constrictor and the diffuser each having a flow cross section that varies in the direction of the advancing filaments so that the most narrow cross section is present in a connecting seam between the constrictor and the diffuser shortly upstream of the solidification point of the filaments.

14. The apparatus as defined in claim 13 further comprising a cooling cylinder positioned between the nozzle and the constrictor, said cooling cylinder comprising an air permeable tubular wall which encloses the downwardly advancing filaments.

15. The apparatus as defined in claim 14 wherein the diffuser is connected to a vacuum generator.

16. The apparatus as defined in claim 15 wherein the diffuser is connected at its outlet end to an air permeable tubular screen cylinder which surrounds the advancing filaments so as to define a vacuum chamber which forms a connection between the vacuum generator and the diffuser.

17. The apparatus as defined in claim 13 wherein the constrictor and the diffuser are each frustoconical, with the angle of cone of the constrictor being greater than the angle of cone of the diffuser.

18. The apparatus as defined in claim 14 wherein the cooling cylinder is subdivided in the direction of the advancing yarn into several zones, with each zone having a different gas permeability.

19. The apparatus as defined in claim 13 wherein the nozzle bores are arranged in one or more annular lines of bores, with the bores of each line of bores being equally spaced from one another.

20. A method of producing a highly oriented yarn from a thermoplastic material, comprising the steps of

extruding a melted thermoplastic material through a nozzle to form a plurality of downwardly advancing filaments, and such that the filaments solidify at a location spaced below the nozzle,

withdrawing the filaments under a withdrawal tension so as to cause the filaments to be drawn while being solidified, with the withdrawal tension being generated by a withdrawal speed of at least about 6,500 m/min,

assisting the filaments in their advance before their solidification such that before their solidification the filaments are relieved from tensile stress and during solidification and drawing a reduced withdrawal tension is effective on the filaments,

combining the filaments after their solidification to form an advancing multifilament yarn,

winding the advancing multifilament yarn into a package, and

wherein the step of assisting the filaments in their advance includes injecting the melted thermoplastic at a high injection speed during the extruding step.

21. A method of producing a highly oriented yarn from a thermoplastic material, comprising the steps of

extruding a melted thermoplastic material through a nozzle to form a plurality of downwardly advancing filaments, and such that the filaments solidify at a location spaced below the nozzle,

withdrawing the filaments under a withdrawal tension so as to cause the filaments to be drawn while being solidified, with the withdrawal tension being generated by a withdrawal speed of at least about 6,500 m/min,

assisting the filaments in their advance before their solidification such that before their solidification the filaments are relieved from tensile stress and during solidification and drawing a reduced withdrawal tension is effective on the filaments,

combining the filaments after their solidification to form an advancing multifilament yarn,

winding the advancing multifilament yarn into a package, and

wherein the withdrawal tension is generated by a feed system arranged in the path of the advancing multifilament yarn upstream of the winding step, and with the withdrawal speed of the feed system being greater than the winding speed of the winding step.

22. The method as defined in claim 21 wherein the feed system comprises two rolls that are looped by the advancing yarn in S-shape or Z-shape.

23. A melt spinning apparatus for producing a highly oriented yarn from a thermoplastic melt, comprising

an extruder for heating a thermoplastic material and extruding the resulting melt through a nozzle having a plurality of nozzle bores to form a plurality of downwardly advancing filaments,

a cooling chamber disposed below the nozzle,

a lubrication device for combining the downwardly advancing filaments to form an advancing multifilament yarn,

a yarn winding device for winding the advancing yarn into a package,

said cooling chamber comprising a constrictor through which the filaments advance, and a diffuser arranged at the outlet end of the constrictor, with the constrictor and the diffuser each having a flow cross section that varies in the direction of the advancing filaments so that the most narrow cross section is present in a connecting seam between the constrictor and the diffuser, and

wherein the constrictor has in its most narrow cross section a diameter between about 10 mm and 40 mm.

24. A melt spinning apparatus for producing a highly oriented yarn from a thermoplastic melt, comprising

an extruder for heating a thermoplastic material and extruding the resulting melt through a nozzle having a plurality of nozzle bores to form a plurality of downwardly advancing filaments,

a cooling chamber disposed below the nozzle,

a lubrication device for combining the downwardly advancing filaments to form an advancing multifilament yarn,

a yarn winding device for winding the advancing yarn into a package,

said cooling chamber comprising a constrictor through which the filaments advance, and a diffuser arranged at the outlet end of the constrictor, with the constrictor and the diffuser each having a flow cross section that varies in the direction of the advancing filaments so that the most narrow cross section is present in a connecting seam between the constrictor and the diffuser, and

a feed system arranged in the yarn path between the diffuser and the yarn winding device.

25. The apparatus as defined in claim 24 wherein the feed system comprises two rolls with at least one of the rolls being driven, and wherein the rolls are arranged relative to each other in the yarn path such that they are partially looped by the advancing yarn.