PATENTSCOPE will be unavailable a few hours for maintenance reason on Monday 03.02.2020 at 10:00 AM CET
Search International and National Patent Collections
Some content of this application is unavailable at the moment.
If this situation persists, please contact us atFeedback&Contact
1. (CA2082058) NONWOVEN FILTER AND METHOD OF MANUFACTURE
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters
WO 91/17297 PCT/US91/03017
CLAIMS:
1. A process for manufacturing a filter roving suitable for fluid filters which comprises (a) restrainingly dispensing a thermoplastic nonwoven in a planar disposition; (b) pulling the dispensed web successively through a heated zone and an orifice to produce a roving, the orifice having a circular or oval cross section, the angle of convergence of the web between the restrained web and the orifice being between 10° and 30°, the rate of roving movement exiting from the orifice in the machine direction being at least 15% higher than the dispensed rate of web in the machine direction, whereby fibers of the web are oriented and the web is stretched in the machine direction by at least 15%.
2. The process of claim 1 wherein the nonwoven web is a meltblown web and the thermoplastic is a polyolefin.
3. The process of claim 1 wherein the polyolefin is selected from ethylene and propylene homopolymers and copolymers.
4. The process of claim 1 wherein the pulling of the web through the heated zone causes the web to bulk by at least 30%.
5. The process of claim 4 wherein the meltblown web has a width of between 6 and 10 inches and an aspect ratio of between 240 and 60,000.
6. The process of claim 1 wherein average diameter of the fibers of the nonwoven web is between 1 to 10 microns.
WO 91/17297 PCT/US91/03017
7. The process of claim 6 wherein the heated zone is maintained at a temperature to heat the web therein to a temperature within or near the rubbery zone for the thermoplastic.
8. The process of claim 7 wherein the heated zone is maintained at a temperature at least equal to 10°C below the onset of the rubbery zone temperatures and not greater than the maximum temperature of the rubbery zone.
9. A process for manufacturing filter roving which comprises (a) dispensing a flat thermoplastic meltblown web from a source; (b) moving the web through means for maintaining the web in a flat disposition; and (c) convergingly moving the web from the flat retaining means (i) through an unheated zone causing the web to form main pleats, (ii) through a heated zone to soften the fibers causing the web to form and secondary pleats imposed on the main pleats, and (iii) through an orifice to cause the main and secondary pleats to randomly bundle forming a roving, the movement of the web through the orifice in the machine direction being at least 20% higher than the rate at which the web is dispensed from the source.
10. The process of claim 9 wherein the temperature in the heated zone is at least 20°C above the temperature of the web at the source, and whereby the pleating bulks the web by at least 20%.
11. The process of claim 9 wherein the convergence angle is between 10 and 30°.
12. The process for manufacturing a roving which comprises:
WO 91/17297 PCT/US91/03017
(a) dispensing a meltblown web from a roll; (b) pulling the dispensed web successively (i) through means to maintain the web in a flat disposition; (ii) convergingly through an unheated zone wherein main pleats are formed; (iii) convergingly through a heated zone wherein fibers of the web are oriented in the machine direction and secondary pleats are formed on the main pleats; and (iv) through a trumpet to form a roving; the convergence angle between the flat web and the trumpet being between 10 to 30°, and the rate of movement of the web through the trumpet being between 20 and 100% faster than the rate of web dispensation in the machine direction.
13. The process of claim 12 wherein the meltblown web is a polyolefin.
14. The process of claim 13 wherein the polyolefin is an ethylene or propylene polymer or copolymer and has a width of between 12 and 60 inches and an aspect ratio of between 800 to 24,000.
15. The process of claim 12 wherein the web has fibers of average diameters between 1 and 10 microns and basis weight of between 4 to 26 gr./m2.
16. A process for manufacturing a roving suitable for use as a cigarette filter, which comprises: (a) restrainingly dispensing a meltblown thermoplastic web in a flat disposition having an average fiber diameter between l and 10 microns and a width of between 12 and 48 inches, a thickness between 2 and 15 mils, and a basis weight between 4 and 26 g/m2; and
WO 91/17297 PCT/US91/03017
(b) pulling the web convergingly through nonheated zone and a heated zone, and an orifice, the heated zone being maintained at a temperature at least 35°C above the temperature of the web at ambient conditions to soften and enhance orientation of the fibers; the orifice being sized to form a roving having a diameter of the size for use as a cigarette filter, the rate of movement of the web through the filter being 15 to 75% faster than the rate that the web is dispensed.
17. A filter comprising (a) a cylindrical body composed of a plurality of pleated meltblown thermoplastic web randomly bundled in a cylinder wherein the pleats extend parallel to the axis of the cylinder, being characterized by oriented longitudinal fibers and buckled crossfibers, the crossfibers extending outwardly from the thickness of the longitudinal fibers and impart bulk to the web, thereby providing permeability for the fluid; and (b) a fluid impermeable film extending around the circumference of a longitudinal portion at least of the cylindrical body; whereby fluid flow is axially through the cylindrical body between and through the pleats.
18. The filter of claim 17 wherein the meltblown web is made of a polyolefin and wherein the filter body has a diameter of between 0.16 to 0.35 inches.
19. The filter of claim 17 wherein the fibers of the meltblown web have an average diameter between 1 and 10 microns.
20. The filter of claim 17 wherein the filter is a cigarette filter and has the following non-diluted filtering characteristics: a ratio of Particle Removal Efficiency to pressure drop per 25 mm of filter length of (i) 0.95 or greater at pressure drop of 70 mm H2O or less; or (ii) 0.85 or greater at pressure drop of greater than 70 mm H2O.
WO 91/17297 PCT/US91/03017
21. The filter of claim 20 wherein the ratio is 1.0 or more at all filter pressure drops.
22. The filter of claim 17 wherein the meltblown web is made of polyolefin fibers.
23. The filter of claim 22 wherein the polyolefin is selected from ethylene and propylene homopolymers and copolymers and mixtures thereof.
24. A cigarette filter comprising a cyclindrical body composed of a bundle of overlapped serpentine meltblown web portions which extend axially through the body, said webs being composed of stretch oriented longitudinal fibers and crossfibers which extend transversely through the longitudinal fibers and have crossfiber portions which protrude outwardly from the web thickness defined by the longitudinal fibers, said protruding crossfibers adding bulk to the web, said longitudinal fibers and crossfibers having an average diameter of between 0.5 and 20 microns.
25. The cigarette filter of claim 24 wherein the serpentine meltblown web portions include secondary pleats which prevent the overlapped portions from engaging one another in a flat disposition, the secondary pleats thereby providing smoke passages axially through the body.
26. Apparatus for manufacturing a roving from a nonwoven web which comprises (a) means for restrainingly dispensing a web from a nonwoven web source; (b) means for maintaining a portion of the dispensed web in a flat disposition;
WO 91/17297 PCT/US91/03017
(c) a trumpet for bundling the web to form a roving (d) means operative on the roving for convergingly pulling the web from the flat disposition maintaining means through the trumpet; the converging angles being between 10 to 30° and causing the formation of main pleats; and (e) means for heating an intermediate portion of the converging web so that the pulling force imparts stretching and orientation of fibers of the intermediate portion of the web, thereby causing formation of main secondary pleats in the web.
27. A filter comprising (a) a cylindrical body composed of a pleated meltblown thermoplastic web having a plurality of main pleats and a plurality of secondary pleats formed in each main pleat, said web being bundled in a cylinder wherein portions of the main pleats are overlapped and extend parallel to the axis of the cylinder and wherein the secondary pleats impart bulk to the web, thereby providing permeability for the fluid; and (b) a wrapper extending around the circumference of a longitudinal portion at least of the cylindrical body, whereby fluid flow is axially through cylindrical body between and through the pleats.