NON-WOVEN MATS BY MELT BLOWING

• US 3,849,241 A
• Filed: 02/22/1972
• Issued: 11/19/1974
• Est. Priority Date: 12/23/1968
• Status: Expired due to Term

• Current Assignee: James P. Keller, John W. Harding, Robert R. Butin
• Original Assignee: James P. Keller, John W. Harding, Robert R. Butin
• Inventors: Harding, John W., Butin, Robert R., Keller, James P.
• Primary Examiner(s): Woo, Jay H.
• Application Number:
  US05/227,769
• Time in Patent Office: 1,001 Days
• Field of Search: 264/21F,176F,121 156/167,181,62.4,229,244 161/169,402 425/71
• US Class Current: 428/137
• CPC Class Codes: D01D 5/0985 by means of a flowing gas (e.g. melt-blowing)
• CPC Class Codes: D04H 1/724 forming webs during fibre formation, e.g. flash-spinning
• CPC Class Codes: D04H 3/007 Addition polymers
• CPC Class Codes: D04H 3/16 with bonds between thermoplastic filaments produced in association with filament formation, e.g. immediately following extrusion
• CPC Class Codes: Y10T 428/24322 Composite web or sheet

Abstract

Melt blown non-woven mats prepared from thermoplastic polymer fibers and substantially completely free of polymer shot are produced at high polymer throughput rates in an improved melt blowing process in which thermoplastic polymer resins, preferably polypropylene, having initial intrinsic viscosities of at least 1.4, are degraded, optionally in the presence of a free radical source compound, to have both reduced intrinsic viscosities and an apparent viscosity in the melt-blowing nozzle orifices of from about 50 to about 300 poise.

Claims

1. IN A PROCESS FOR PRODUCING A MELT-BORWN NON-WOVEN MAT WHEREIN A FIBER-FORMING THERMOPLASTIC POLYMER RESIN IS EXTRUDED IN MOLTEN FORM FROM ORIFICES OF A HEATED NOZZLE INTO A STREAM OF HOT INERT GAS WHICH ATTENUATES SAID MOLTEN RESIN INTO FIBERS THAT FORM A FIBER STREAM, AND SAID FIBERS ARE COLLECTED ON ARE RECEIVER IN THE PATH OF SAID FIBER STREAM TO FORM SAID NONWOVEN MAT, THE IMPROVEMENT WHICH COMPRISES SUBJECTING A FIBER-FORMING THERMOPLASTIC POLYMER RESIN HAVING AN INITIAL INTRINSIC VISOCISTY OF AT LEAST 1.4 DEGRADATION IN THE PRESENCE OF A FREE RADICALY SOURCE COMPOUND PRIOR TO EXTRUSION FORM SAID NOZZLE ORIFICES UNTIL SAID RESIN HAS BOTH A REDUCED INTRINSIC VISCOSITY OF FROM ABOUT 0.6 TO LESS THAN 1.4 AND AN APPARENT VISCOSITY IN SAID NOZZLE ORIFICES OF FROM ABOUT 50 TO ABOUT 300 POISES.

2. The process of claim 1 wherein said resin is subjected to thermal degradation at a temperature within the range from about 550* F. to about 900* F. for a period of time effective to cause said resin to have said reduced intrinsic viscosity and said apparent viscosity.

3. The process of claim 2 in which said thermoplastic polymer resin is subjected to said thermal degradation at least partially in an extruder feeding said resin into said nozzle.

4. The process of claim 3 wherein said resin is thermally degraded in an extruder for from about 1 to about 10 minutes effective to cause said resin to have said reduced intrinsic viscosity and said apparent viscosity.

5. The process of claim 1 wherein said free radical source compound is selected from organic peroxides, thiyl compounds, and organo-tin compounds.

6. The process of claim 1 wherein said thermoplastic polymer resin is selected from C3-C8 polyolefins and mixtures thereof which have an initial intrinsic viscosity of at least 1.4.

7. In a process for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin is extruded in molten form from orifices of a heated nozzle into a stream of hot inert gas which attenuates said molten resin into fibers that form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of producing said mat at high resin flow rates, which comprises:

extruding from said nozzle orifices, at a resin flow rate of from about at least 0.1 to about 5 grams per minute per orifice, a fiber-forming thermoplastic polymer resin degraded to have both an intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise.

8. The process of claim 7 wherein said apparent viscosity is from about 100 to about 300 poise.

9. The process of claim 7 wherein said resin is subjected to said degradation at least partially in an extruder feeding said resin to said nozzle.

10. The process of claim 9 wherein said resin is subjected to a temperature within the range from about 550* F. to about 900* F. for a period of time from about 1 to about 10 minutes effective to cause said degradation of said resin until said resin has said apparent viscosity and said intrinsic viscosity.

11. The process of claim 7 wherein said resin is selected from C3-C8 polyolefins and mixtures thereof.

12. In a process for producing a melt-bloWn non-woven mat wherein a fiber-forming thermoplastic polymer resin in molten form is forced by an extruder through a row of orifices in a heated nozzle into a stream of hot inert gas which is issued from outlets adjacent to said row of orifices so as to attenuate said molten resin into fibers which form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of increasing the production of said non-woven mats while preventing the inclusion of coarse shot in such mats, by the method which comprises in combination:

subjecting a fiber-forming thermoplastic polymer resin having an initial intrinsic viscosity of at least 1.4 to thermal degradation, at least partially in an extruder, for a sufficient time at a temperature within the range of from about 550* F. to about 900* F. effective to cause said resin to have both a reduced intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise, said heated nozzle having a temperature within the range of from about 500* F. to about 900* F., operating said extruder so as to force said degraded resin in molten form from said row of nozzle orifices at a resin flow rate of from about 0.1 to about 5 grams per minute per nozzle orifices, and issuing said hot, inert gas at a temperature from about 500 F. to about 900* F. from said outlets at a gas flow rate of from about 2.5 to about 20 pounds per minute per square inch of outlet area, effective to attenuate said extruded degraded resin into fibers having diameters of from about 8 to about 400 microns, said resin flow rate being selected from rates in said resin flow rate range which are not below a minimum rate below which, for a chosen combination of gas flow rate and degraded resin apparent viscosity, coarse shot is formed, said minimum resin flow rate increasing in its aforesaid range as said gas flow rate is increased in its range or as said degraded resin has a decreased apparent viscosity in its range, or both.

13. The method of claim 12 in which said resin is selected from C3 to C8 polyolefins and mixtures thereof.

14. The method of claim 13 in which said resin flow rate is at least 1.0 gram per minute per orifice and said apparent viscosity is from about 100 to about 300 poise.

15. In a process for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin in molten form is forced by an extruder through a row of orifices in a heated nozzle into a stream of hot inert gas which is issued from outlets adjacent to said row of orifices so as to attenuate said molten resin into fibers which form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of increasing the production of said non-woven mats while preventing the inclusion of coarse shot in such mats, by the method which comprises in combination:

subjecting a fiber-forming thermoplastic polymer resin having an initial intrinsic viscosity of at least 1.4 to thermal degradation, at least partially in an extruder, for a sufficient time at a temperature within the range of from about 550* F. to about 900* F. effective to cause said resin to have both a reduced intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise, said heated nozzle having a temperature within the range of from about 500* F. to about 900* F., operating said extruder so as to force said degraded resin in molten form from said row of nozzle orifices at a resin flow rate of from about 0.1 to abOut 5 grams per minute per nozzle orifice, and issuing said hot, inert gas at a temperature from about 500* F. to about 900* F. from said outlets at a gas flow rate of from greater than 20 to about 100 pounds per minute per square inch of outlet area effective to attenuate said extruded degraded resin into fibers having a diameter of from about 0.5 to about 5 microns, said resin flow rate being selected from rates in said resin flow rate range which do not exceed a maximum rate above which, for a chosen combination of gas flow rate and degraded resin apparent viscosity, coarse shot is formed, said maximum resin flow rate decreasing in its aforesaid range as said gas flow rate is decreased in its range or as said degraded resin has an increased apparent viscosity in its range, or both.

16. The method of claim 15 in which said resin is selected from C3 to C8 polyolefins and mixtures thereof.

17. The method of claim 16 in which said resin flow rate is at least 1.0 per minute per orifice and said apparent viscosity is from about 100 to about 300 poise.

18. In a process for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin in molten form is forced by an extruder through a row of orifices in a heated nozzle into a stream of hot inert gas which is issued from outlets adjacent to said row of orifices so as to attenuate said molten resin into fibers which form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of increasing the production of said non-woven mats while preventing the inclusion of coarse shot in such mats, by the method which comprises in combination:

subjecting a fiber-forming thermoplastic polymer resin having an initial intrinsic viscosity of at least 1.4 to thermal degradation, at least partially in an extruder, for a sufficient time at a temperature within the range of from about 550* F. to about 900* F., effective to cause said resin to have both a reduced intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise, said heated nozzle having a temperature within the range of from about 500* F. to about 900* F., operating said extruder so as to force said degraded resin in molten form from said row of nozzle orifices at a resin flow rate of from about 0.1 to about 5 grams per minute per nozzle orifices, and issuing said hot, inert gas at a temperature from about 500* F. to about 900* F. from said outlets at a gas flow rate of from about 2.5 to about 20 pounds per minute per square inch of outlet area, effective to attenuate said extruded degraded resin into fibers having diameters of from about 8 to about 400 microns, said gas flow rate being selected from rates in said gas flow rate range that do not exceed a maximum rate above which, for a chosen combination of resin flow rate and degraded resin apparent viscosity, coarse shot is formed, said maximum gas flow rate decreasing in its aforesaid range as said resin flow rate decreases in its range or said degraded resin has a decreased apparent viscosity in its range, or both.

19. The method of claim 18 in which said resin is selected from C3 to C8 polyolefins and mixtures thereof.

20. The method of claim 19 in which said resin flow rate is at least 1.0 gram per minute per orifice and said apparent viscosity is from about 100 to about 300 poise.

21. In a process for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin in molten form is forced by an extruder through a row of orifices in a heated nozzle into a stream of hot inert gas which is issueD from outlets adjacent to said row of orifices so as to attenuate said molten resin into fibers which form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of increasing the production of said non-woven mats while preventing the inclusion of coarse shot in such mats, by the method which comprises in combination. subjecting a fiber-forming thermoplastic polymer resin having an initial intrinsic viscosity of at least 1.4 to thermal degradation, at least partially in an extruder, for a sufficient time at a temperature within the range of from about 550* F. to about 900* F., effective to cause said resin to have both a reduced intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise, said heated nozzle having a temperature within the range of from about 500* F. to about 900* F., operating said extruder so as to force said degraded resin in molten form from said row of nozzle orifices at a resin flow rate of from about 0.1 to about 5 grams per minute per nozzle orifice, and issuing said hot, inert gas at a temperature from about 500* F. to about 900* F. from said outlets at a gas flow rate of from greater than 20 to about 100 pounds per minute per square inch of outlet area effective to attenuate said extruded degraded resin into fibers having a diameter of from about 0.5 to about 5 microns, said gas flow rate being selected from rates in said gas flow rate range which are not below a minimum rate below which, for a chosen combination of resin flow rate and degraded apparent viscosity, coarse shot is formed, said minimum gas flow rate increasing in its aforesaid range as said resin flow rate increases in its range or said degraded resin has an increased apparent viscosity in its range, or both.

22. The method of claim 21 in which said resin is selected from C3 to C8 polyolefins and mixtures thereof.

23. The method of claim 22 in which said resin flow rate is at least 1.0 gram per minute per orifice and said apparent viscosity is from about 100 to about 300 poise.

24. In a process for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin in molten form is forced by an extruder through a row of orifices in a heated nozzle into a stream of hot inert gas which is issued from outlets adjacent said row of orifices so as to attenuate said molten resin into fibers which form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of increasing the production of said non-woven mats while preventing the inclusion of coarse shot in such mats, by the method which comprises in combination:

subjecting a fiber-forming thermoplastic polymer resin having an initial intrinsic viscosity of at least 1.4 to thermal degradation, at least partially in an extruder, for a sufficient time at a temperature within the range of from about 550* F. to about 900* F., effective to cause said resin to have both a reduced intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise, said heated nozzle having a temperature within the range of from about 500* F. to about 900* F., operating said extruder so as to force said degraded resin in molten form from said row of nozzle orifices at a resin flow rate of from about 0.1 to about 5 grams per minute per nozzle orifices, and issuing said hot, inert gas at a temperature from about 500* F. to about 900* F. from said outlets at a gas flow rate oF from about 2.5 to about 20 pounds per minute per square inch of outlet area, effective to attenuate said extruded degraded resin into fibers having diameters of from about 8 to about 400 microns, said resin being degraded to a selected apparent viscosity in said range of apparent viscosities that are not below a minimum apparent viscosity below which, for a chosen combination of resin flow rate and gas flow rate, coarse shot is formed, said minimum apparent viscosity increasing as said gas flow rate is increased in its range or as said resin flow rate is decreased in its range, or both.

25. The method of claim 24 in which said resin is selected from C3 to C8 polyolefins and mixtures thereof.

26. The method of claim 25 in which said resin flow rate is at least 1.0 gram per minute per orifice and said apparent viscosity is from about 100 to about 300 poise.

27. In a process for producing a melt-blown non-woven mat wherein a fiber-forming thermoplastic polymer resin in molten form is forced by an extruder through a row of orifices in a heated nozzle into a stream of hot inert gas which is issued from outlets adjacent to said row of orifices so as to attenuate said molten resin into fibers which form a fiber stream, and said fibers are collected on a receiver in the path of said fiber stream to form said non-woven mat, the improvement of increasing the production of said non-woven mats while preventing the inclusion of coarse shot in such mats, by the method which comprises in combination:

subjecting a fiber-forming thermoplastic polymer resin having an initial intrinsic viscosity of at least 1.4 to thermal degradation, at least partially in an extruder, for a sufficient time at a temperature within the range of from about 550* F. to about 900* F. effective to cause said resin to have both a reduced intrinsic viscosity of from about 0.6 to less than 1.4 and an apparent viscosity in said nozzle orifices of from about 50 to about 300 poise, said heated nozzle having a temperature within the range of from about 500* F. to about 900* F., operating said extruder so as to force said degraded resin in molten form from said row of nozzle orifices at a resin flow rate of from about 0.1 to about 5 grams per minute per nozzle orifice, and issuing said hot, inert gas at a temperature from about 500* F. to about 900* F. from said outlets at a gas flow rate of from greater than 20 to about 100 pounds per minute per square inch of outlet area effective to attenuate said extruded degraded resin into fibers having a diameter of from about 0.5 to about 5 microns, said resin being degraded to a selected apparent viscosity in said range of apparent viscosities that does not exceed a maximum apparent viscosity above which, for a chosen combination of resin flow rate and gas flow rate, coarse shot is formed, said maximum apparent viscosity decreasing as said gas flow rate is decreased in its range or as said resin flow rate is increased in its range, or both.

28. The method of claim 27 in which said resin is selected from C3 to C8 polyolefins and mixtures thereof.

29. The method of claim 28 in which said resin flow rate is at least 1.0 gram per minute per orifice and said apparent viscosity is from about 100 to about 300 poise.

30. A melt-blown non-woven mat produced by the process of claim

31. A melt-blown non-woven mat produced by the method of claim 7.

32. A melt-blown non-woven mat produced by the method of claim 12.

33. A melt-blown non-woven mat produced by the method of claim 15.

34. A melt-blown non-woven mat produced by the method of claim 18.

35. A melt-blown non-woven mat produced by the method of claim 21.

36. A melt-blown non-woven mat produced by the method of claim 24.

37. A melt-blown non-woven mat produced by the method of claim 27.