|Publication number||USRE32171 E|
|Application number||US 06/517,937|
|Publication date||Jun 3, 1986|
|Filing date||Aug 1, 1983|
|Priority date||Mar 25, 1974|
|Also published as||CA1050481A, CA1050481A1, DE2512885A1, DE2512885C2, US3998916, USRE30782|
|Publication number||06517937, 517937, US RE32171 E, US RE32171E, US-E-RE32171, USRE32171 E, USRE32171E|
|Inventors||Jan van Turnhout|
|Original Assignee||Minnesota Mining And Manufacturing Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Referenced by (112), Classifications (44)|
|External Links: USPTO, USPTO Assignment, Espacenet|
.Badd.This is a continuation reissue of application Ser. No. 315,139 filed Oct. 26, 1981, now abandoned, which is a division reissue of Ser. No. 929,680 filed July 31, 1978, now Re. 30,782. .Baddend.
The invention relates to a method for the manufacture of an electrically charged fibrous filter, whose fibre material consists of a high molecular non-polar substance.
Such a method is known in the art and from this method it appears that charging of fibre material in an electric field to obtain a charged fibrous filter is difficult because of electric breakdown through the pores of the material. Covering the electrodes, between which the forming field strength is applied, with a semi-conducting material, admittedly offers the possibility of bringing the fibre material to a higher charged state, but at the same time has the drawback that this state is reached only after a longer period of time.
It is the object of the invention to provide for a rapid manufacture of highly charged fibre filters.
According to the invention the method is characterized in that it comprises continuously feeding a film of the high molecular non-polar substance, stretching the film, homopolarly charging the stretched film with the aid of corona elements, fibrillating the stretched charged film, collecting the fibre material and processing the collected fibre material into a filter of the desired shape.
Because the risk of breakdown of charging a solid film material is much less than that of an open fibre material, a charging system known per se, operating much faster and much more effectively, comprising corona elements can be used.
In the preferential embodiment of the invention the film is locally bilaterally charged by means of corona elements that carry on either side of the film equal but opposite potentials. Thereby the film is charged to almost twice as high a voltage as by means of unilateral charging, at one and the same corona voltage.
Charging with the aid of corona elements in turn entails that the film can be fed continuously and be stretched into a well splittable material. This material can be fibrillated in several ways. For this purpose, a needle roller with metal needles running against the film is used with, surprisingly no substantial loss of charge.
Preferably, the fibre material is collected in layers onto a take-up roller and there processed into filter cloth of the thickness and shape desired by taking one or more layers, which are laying one on top of the other, together and at the same time from the roller.
The invention will now further be elucidated with reference to the following drawings, wherein.
FIG. 1 schematically shows an embodiment of a device in which, for the manufacture of a well splittable charged film, use has been made for the method according to the invention.
FIG. 2 shows an improved second stage for stretching a film with which the film can be provided with an injected charge on both surfaces.
FIG. 3 shows a preferential construction of a process stage .[.charging for improved and higher of the film.]. .Iadd.for improved and higher charging of the film.
FIG. 4 shows on an enlarged scale an example of a set-up of electrodes for injecting charge into the film.
In the figures like numbers refer to like elements.
FIG. 1 shows film 1, which, either from a storage roller, or direct from an extruder is fed between roller 3 and 4 into a stretching device to make film 1 splittable.
In this arrangement the charge is injected into film 1 from above.
The stretching device contains fixed pins 5 and 6, block 8 heated by heater 15, a pair of rollers 9 and 10, arcuate plate 12 heated by heater 16 and a pair of rollers 13 and 14.
A stretching device that contains the above mentioned elements has been described in Netherlands Patent Application 71 13047. In this device stretching takes place in two stages. Therefore, it is very well suitable to fibrillate films that are difficult to split.
In the first stage of stretching, which takes place between pin 6 and pair of rollers 9 and 10, film 1 is drawn over edge 7 of block 8 in such a way that film 1 is subjected to an increase in length ratio of approximately 1 to 4 at the cost of its thickness and hardly at the cost of its width.
In the second stage of stretching, which takes place between a pair of rollers 9 and 10 and a pair of rollers 13 and 14, film 1 is drawn over curved plate 12 in such a way that it is subjected to a further increase in length ratio of approximately 1 to 1.5.
The temperature of block 8 greatly depends on the speed of the film and at high speeds can be chosen close below the melting temperature of film 1.
It is of importance that film 1 does not touch the plane of block 8 that lies in front of edge 7, so as to prevent a premature and a too high heating or film 1. The position of plane 11 of block 8, which plane lies behind edge 7 is also of importance, because it is determinative of the speed at which film 1, coming from edge 7, cools down.
Plate 12 is heated to a temperature that is only a little lower than the melting temperature of the film material and because film 1 for an important part lies against the curved surface, film 1 will here receive the highest temperature in the stretching process.
This has schematically been indicated by a triple flame 16 at plate 12, in contrast with a single flame 15 at block 8.
A charging device 18, consisting of a number of thin tungsten wires 25 across the grounded curved plate 12 and connected with the negative terminal of a voltage source, sprays a negative charge on to the top of film 1 by means of the corona effect. This is implemented preferably where the temperature of film 1 on plate 12 is the highest.
It may be of advantage, however, to place the charging device more towards the beginning of plate 12. In this case film 1 will partially discharge over the further part of the heating plate. In particular the charges that have been embedded in the least stable way, will be lost in the process. In this way the electret film is aged thermally, as a result of which only the charges are left that have been embedded in a very stable way. As a result the remaining charge of the electret will have an exceptionally high persistence at ambient temperature. In fact, the thermal stability of the charge that is left is also increased. Moreover, surprisingly, the stability against moisture is also considerably improved.
The device furthermore shows a means 29 for the fibrillation of film 1.
According to the embodiment film 1 is fibrillated into fibres 21 by guiding it via fixed pin 20 along a needle roller 29. By giving the needle roller 29 a higher peripheral velocity than the moving speed of film 1, this film 1 is fibrillated mainly in longitudinal direction. Fibres 21 thus obtained spread themselves to a high extent because of their electrostatic charges, so that a nicely spread layer of fibres is produced, which is wound upon collecting roller 24. By taking one or more layers, which are lying one on top of the other, from the roller together and at the same time, a filter of the desired shape and thickness can be obtained.
From charge measurements it has been found that when negative charges are injected on the top of film 1 on plate 12, at the bottom positive charges are produced. These charges are a result of ionization of the air enclosed between the film and the bottom plate. Thus positive ions are produced in such a region, which charges are drawn to the bottom of the negatively charged film. So, the positive charge actually is a compensating charge. As a result, it is somewhat less high than the injected negative charge.
This unexpected two-sided charging of film 1 can be of importance for use in fibrous filters, because most aerosol particles that must be captured are electrically charged, and this charge can be positive as well as negative or both.
So as to manufacture a film that is as highly positively as negatively charged, charging must be implemented on both sides. FIG. 2 shows an embodiment, with which this is possible.
A second curved plate 17, which has been mounted between pairs of rollers 9/10 and 13/14, by means of an additional charging device 19, enables the injection of positive charges on the surface of film 1 that has not yet been sprayed upon.
On the contrary, so as to filter aerosol particles that .[.have been.]. .Iadd.are .Iaddend.charged unipolarly, it is preferable to apply .[.unipolarly.]. .Iadd.unipolar .Iaddend.charges of opposite polarity to the fibre. Even for bipolarly charged aerosols the filter mat can be composed of alternatively positively and negatively charged fibre layers. The unipolar charging can also be implemented by the two-stage charging of FIG. 2. Preferably, then the potential of plate 17 is chosen the same as that of spraying wires 25 and at spraying wires 30 a voltage is applied that is sufficiently .[.negative.]. .Iadd.of greater magnitude .Iaddend.with respect to plate 17.
FIG. 3 shows a preferential embodiment of a charging step with corona elements 18, 19 on each side of the film carrying equal but opposite potentials. This charging step 18, 19 can follow a stretching step that is already known in the art. If, however, charging step 18, 19 coincides with the stretching step, then charging preferably is implemented in a furnace that is not shown.
FIG. 4 shows one of the applied charging devices 18 and 19 on an enlarged scale. Between spraying wires 25/30 and curved plates 12/17 over which film 1 is guided, there is a metal grid 27 so as to better distribute the charge that is injected by the thin corona wires. The charge the film acquires is determined by the potential of the grid. In case of a slow throughput rate the film is roughly charged up to the potential of the grid. An additional advantage of the device used is that the risk of dielectric breakdown of the film and also of a spark discharge to the bare parts of plates 12/17 is very small, because the grid screens the corona wires from the film. Due to this grid, it is also possible to feed the small corona wires with an alternating current instead of with a direct current, if so desired.
Metal plate 26 over spraying wires 25/30 is interconnected with grounded plates 12/17. Because plate 26 increases the corona formation considerably, the spraying intensity with an upper plate is substantially higher than in an arrangement without it.
In a simplified construction of the charging device, which gives a somewhat less uniform charging, the grid is left out. In that case plate 26, preferably, must be connected via terminal 32 to a positive voltage with respect to plate 12/17. For in case of a positive voltge on plates 26 there need not be applied a large negative corona voltage on the small corona wires. In fact the corona voltage can be halved, if the potential is chosen equal (but opposite) to that of the cornoa wires. This, too, reduces the risk of dielectric breakdown in the film considerably, particularly when the film is very thin.
A film of isotactic polypropylene with a thickness of 45μ and a width of 5 cm was stretched to a ratio of 1:6 over block 8 the temperature of which was 110° C. In a second stage stretching and charging was implemented over plate 12 of a temperature of 130° C., at a stretching ratio of 1:1.5. The transport velocity was 12.2 m/min. In spraying device 18 placed over plate 12 corona wires 25 had been connected to -3.2 KV and top plate 26 to +3 KV. The distance from corona wires 25 to plate 12 amounted to 5 mm. The film was fibrillated with a needle roller of 60 rows, the needles of which stood 500μ apart. The charged fibrillate was spread to approx. 45 cm and wound up on roller 24 into a filter with a thickness of 3 mm.
The collection efficiency of this filter and an equivalent uncharged filter was tested with a heterodisperse NaCl aerosol at a linear air velocity of 10 cm/sec and an aerosol concentration of 15 mg-NaCl/m3. For comparison also a commercial filter made from glass fibres from 1 to 10μ was tested.
______________________________________ filter initial pressure weight penetration loss gram/m2 % mm H2 O______________________________________charged filter 163 0.5 1.5non-charged filter 163 53 2.8filter with glass fibers 167 21 5.0______________________________________
The method of Example I was repeated, but the charging was now done with the spraying device of FIG. 3, with the voltage on the corona wires amounting to -10 KV and that on the grid to -2.3 KV. The processing into a filter was equal to that of the above mentioned example.
______________________________________ filter initial pressure weight penetration loss gram/m2 % mm H2 O______________________________________charged filter 163 0.3 1.1non-charged filter 163 53 2.8______________________________________
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US30782 *||Nov 27, 1860||John wright|
|US31285 *||Jan 29, 1861||Making- finger-guards for harvesters|
|US2612966 *||Mar 29, 1950||Oct 7, 1952||Wingfoot Corp||Polyethylene air filter|
|US3003304 *||Oct 31, 1955||Oct 10, 1961||Rasmussen Ole-Bendt||Method of manufacturing non-woven fabrics and yarns|
|US3333032 *||Nov 12, 1963||Jul 25, 1967||Union Carbide Corp||Treated polymer surfaces of shaped articles|
|US3336174 *||Apr 6, 1965||Aug 15, 1967||Eastman Kodak Co||Method of making a fibrous filter product|
|US3438504 *||Aug 11, 1966||Apr 15, 1969||Gen Electric||Filter element and method of production|
|US3474611 *||Aug 31, 1967||Oct 28, 1969||Mitsubishi Heavy Ind Ltd||Method of making fibrous yarns and apparatus therefor|
|US3487610 *||Mar 26, 1965||Jan 6, 1970||Du Pont||Electrostatic filter unit with high stable charge and its manufacture|
|US3571679 *||Oct 8, 1969||Mar 23, 1971||Tno||Device for forming electrets|
|US3644605 *||Feb 11, 1969||Feb 22, 1972||Bell Telephone Labor Inc||Method for producing permanent electret charges in dielectric materials|
|US3691264 *||Jul 16, 1970||Sep 12, 1972||Kureha Chemical Ind Co Ltd||Process for producing stable electret consisting of a crystalline high molecular weight material|
|US3880966 *||Aug 27, 1973||Apr 29, 1975||Celanese Corp||Corona treated microporous film|
|US4069026 *||Nov 15, 1973||Jan 17, 1978||Bayer Aktiengesellschaft||Filter made of electrostatically spun fibres|
|GB292479A *||Title not available|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US4973517 *||Aug 4, 1988||Nov 27, 1990||Minnesota Mining And Manufacturing Company||Fibrillated tape|
|US5035240 *||Jun 19, 1990||Jul 30, 1991||Minnesota Mining And Manufacturing Company||Elastomeric filtration materials|
|US5084121 *||Oct 15, 1990||Jan 28, 1992||Minnesota Mining And Manufacturing Company||Method of making fibrillated tape|
|US5221573 *||Dec 30, 1991||Jun 22, 1993||Kem-Wove, Inc.||Adsorbent textile product|
|US5246637 *||May 1, 1992||Sep 21, 1993||Mitsui Petrochemical Industries, Ltd.||Method for producing electret filter|
|US5271780 *||Nov 12, 1992||Dec 21, 1993||Kem-Wove, Incorporated||Adsorbent textile product and process|
|US5271997 *||Feb 27, 1992||Dec 21, 1993||Kem-Wove, Incorporated||Laminated fabric material, nonwoven textile product|
|US5417785 *||Oct 12, 1993||May 23, 1995||Kem-Wove, Incorporated||Laminated fabric material, nonwoven textile product and methods|
|US5496507 *||Aug 17, 1994||Mar 5, 1996||Minnesota Mining And Manufacturing Company||Method of charging electret filter media|
|US5614303 *||May 22, 1995||Mar 25, 1997||Kem-Wove, Incorporated||Laminated fabric product, brassiere shoulder pad and shoe insole pad|
|US5807366 *||Jun 18, 1997||Sep 15, 1998||Milani; John||Absorbent article having a particle size gradient|
|US5814570 *||May 15, 1996||Sep 29, 1998||Kimberly-Clark Worldwide, Inc.||Nonwoven barrier and method of making the same|
|US5821178 *||Nov 6, 1996||Oct 13, 1998||Kimberly-Clark Worldwide, Inc.||Nonwoven laminate barrier material|
|US5830810 *||Feb 20, 1997||Nov 3, 1998||Kimberly-Clark Worldwide, Inc.||Nonwoven barrier and method of making the same|
|US5834384 *||Nov 28, 1995||Nov 10, 1998||Kimberly-Clark Worldwide, Inc.||Nonwoven webs with one or more surface treatments|
|US5877099 *||Jan 27, 1997||Mar 2, 1999||Kimberly Clark Co||Filter matrix|
|US5908598 *||Aug 14, 1995||Jun 1, 1999||Minnesota Mining And Manufacturing Company||Fibrous webs having enhanced electret properties|
|US5916204||Jan 26, 1998||Jun 29, 1999||Kimberly-Clark Worldwide, Inc.||Method of forming a particle size gradient in an absorbent article|
|US5998308||May 22, 1996||Dec 7, 1999||Kimberly-Clark Worldwide, Inc.||Nonwoven barrier and method of making the same|
|US6268495||Jan 4, 1999||Jul 31, 2001||3M Innovative Properties Company||Compounds useful as resin additives|
|US6365088||Jun 24, 1999||Apr 2, 2002||Kimberly-Clark Worldwide, Inc.||Electret treatment of high loft and low density nonwoven webs|
|US6375886||Oct 8, 1999||Apr 23, 2002||3M Innovative Properties Company||Method and apparatus for making a nonwoven fibrous electret web from free-fiber and polar liquid|
|US6397458||Jan 6, 2000||Jun 4, 2002||3M Innovative Properties Company||Method of making an electret article by transferring fluorine to the article from a gaseous phase|
|US6398847||Jan 6, 2000||Jun 4, 2002||3M Innovative Properties Company||Method of removing contaminants from an aerosol using a new electret article|
|US6406657||Oct 8, 1999||Jun 18, 2002||3M Innovative Properties Company||Method and apparatus for making a fibrous electret web using a wetting liquid and an aqueous polar liquid|
|US6409806||Jul 26, 2000||Jun 25, 2002||3M Innovative Properties Company||Fluorinated electret|
|US6420024||Dec 21, 2000||Jul 16, 2002||3M Innovative Properties Company||Charged microfibers, microfibrillated articles and use thereof|
|US6432175||Jul 2, 1998||Aug 13, 2002||3M Innovative Properties Company||Fluorinated electret|
|US6432532||Apr 9, 2001||Aug 13, 2002||3M Innovative Properties Company||Microfibers and method of making|
|US6454986||Oct 8, 1999||Sep 24, 2002||3M Innovative Properties Company||Method of making a fibrous electret web using a nonaqueous polar liquid|
|US6537932||Oct 8, 1998||Mar 25, 2003||Kimberly-Clark Worldwide, Inc.||Sterilization wrap, applications therefor, and method of sterilizing|
|US6562112||Apr 19, 2002||May 13, 2003||3M Innovative Properties Company||Fluorinated electret|
|US6573205||Jan 27, 2000||Jun 3, 2003||Kimberly-Clark Worldwide, Inc.||Stable electret polymeric articles|
|US6627563||Aug 19, 1999||Sep 30, 2003||3M Innovative Properties Company||Oily-mist resistant filter that has nondecreasing efficiency|
|US6630231||Mar 15, 2001||Oct 7, 2003||3M Innovative Properties Company||Composite articles reinforced with highly oriented microfibers|
|US6660210||Mar 18, 2003||Dec 9, 2003||3M Innovative Properties Company||Method of making fluorinated electrets|
|US6680114||May 15, 2001||Jan 20, 2004||3M Innovative Properties Company||Fibrous films and articles from microlayer substrates|
|US6743464||Apr 13, 2000||Jun 1, 2004||3M Innovative Properties Company||Method of making electrets through vapor condensation|
|US6759356||Jun 28, 1999||Jul 6, 2004||Kimberly-Clark Worldwide, Inc.||Fibrous electret polymeric articles|
|US6783574||Sep 2, 1997||Aug 31, 2004||Minnesota Mining And Manufacturing Company||Electret filter media and filtering masks that contain electret filter media|
|US6808551||Oct 7, 2003||Oct 26, 2004||3M Innovative Properties Company||Method of using fluorinated electrets|
|US6824718||Jun 4, 2002||Nov 30, 2004||3M Innovative Properties Company||Process of making a fibrous electret web|
|US6846449 *||Sep 7, 2001||Jan 25, 2005||S. C. Johnson Home Storage, Inc.||Method of producing an electrically charged film|
|US6849329||Apr 9, 2002||Feb 1, 2005||3M Innovative Properties Company||Charged microfibers, microfibrillated articles and use thereof|
|US6858551||Mar 12, 1999||Feb 22, 2005||Kimberly-Clark Worldwide, Inc.||Ferroelectric fibers and applications therefor|
|US6893990||Apr 8, 2003||May 17, 2005||Kimberly Clark Worldwide, Inc.||Stable electret polymeric articles|
|US6953544||May 7, 2004||Oct 11, 2005||3M Innovative Properties Company||Method of making a respirator that has a fluorinated electret|
|US7014803||Jul 14, 2003||Mar 21, 2006||3M Innovative Properties Company||Composite articles reinforced with highly oriented microfibers|
|US7244291||May 2, 2005||Jul 17, 2007||3M Innovative Properties Company||Electret article having high fluorosaturation ratio|
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|US7553440||May 12, 2006||Jun 30, 2009||Leonard William K||Method and apparatus for electric treatment of substrates|
|US7642208||Dec 14, 2006||Jan 5, 2010||Kimberly-Clark Worldwide, Inc.||Abrasion resistant material for use in various media|
|US7758327||Jun 3, 2009||Jul 20, 2010||Leonard William K||Method and apparatus for electric treatment of substrates|
|US7765698||Jun 2, 2008||Aug 3, 2010||3M Innovative Properties Company||Method of making electret articles based on zeta potential|
|US7883562||Feb 27, 2008||Feb 8, 2011||Hollingsworth & Vose Company||Waved filter media and elements|
|US7981177||Jul 26, 2007||Jul 19, 2011||Transweb, Llc||Filtration media having a slit-film layer|
|US7985060||Jun 15, 2010||Jul 26, 2011||Leonard William K||Method and apparatus for electric treatment of substrates|
|US8197569 *||Dec 30, 2010||Jun 12, 2012||Hollingsworth & Vose Company||Waved filter media and elements|
|US8202340||Mar 6, 2009||Jun 19, 2012||Hollingsworth & Vose Company||Waved filter media and elements|
|US8257459||Jul 24, 2009||Sep 4, 2012||Hollingsworth & Vose Company||Waved filter media and elements|
|US8323554||Jun 21, 2011||Dec 4, 2012||Leonard William K||Method and apparatus for electric|
|US8529671||Nov 25, 2008||Sep 10, 2013||3M Innovative Properties Comany||Electret webs with charge-enhancing additives|
|US8534294||Oct 9, 2009||Sep 17, 2013||Philip Morris Usa Inc.||Method for manufacture of smoking article filter assembly including electrostatically charged fiber|
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|US8882875||Aug 2, 2012||Nov 11, 2014||Hollingsworth & Vose Company||Waved filter media and elements|
|US9134471||Jun 28, 2006||Sep 15, 2015||3M Innovative Properties Company||Oriented polymeric articles and method|
|US9259885||Aug 7, 2015||Feb 16, 2016||3M Innovative Properties Company||Oriented polymeric articles and method|
|US9284669||Mar 30, 2010||Mar 15, 2016||3M Innovative Properties Company||Processing aids for olefinic webs, including electret webs|
|US9539532||Jan 13, 2011||Jan 10, 2017||3M Innovative Properties Company||Air filter with sorbent particles|
|US9687771||Oct 8, 2014||Jun 27, 2017||Hollingsworth & Vose Company||Waved filter media and elements|
|US20020110610 *||Feb 12, 2002||Aug 15, 2002||3M Innovative Properties Company||Apparatus for making a nonwoven fibrous electret web from free-fiber and polar liquid|
|US20020172816 *||Apr 9, 2002||Nov 21, 2002||3M Innovative Properties Company||Charged microfibers, microfibrillated articles and use thereof|
|US20020190434 *||Jun 4, 2002||Dec 19, 2002||3M Innovative Properties Company||Method and apparatus for making a fibrous electret web using a wetting liquid and an aqueous polar liquid|
|US20030047844 *||Sep 7, 2001||Mar 13, 2003||Jose Porchia||Method of producing an electrically charged film|
|US20030049294 *||Sep 7, 2001||Mar 13, 2003||Jose Porchia||Film material|
|US20030060350 *||Sep 7, 2001||Mar 27, 2003||Taylor Pamela J.||Method of protecting a surface|
|US20030207642 *||Apr 8, 2003||Nov 6, 2003||Myers David Lewis||Stable electret polymeric articles|
|US20040207125 *||May 7, 2004||Oct 21, 2004||3M Innovative Properties Company||Method of making a respirator that has a fluorinated electret|
|US20060138686 *||Dec 23, 2004||Jun 29, 2006||Ouderkirk Andrew J||Method of making a uniaxially stretched polymeric film having structured surface|
|US20060138694 *||Dec 23, 2004||Jun 29, 2006||Biernath Rolf W||Method of making a polymeric film having structured surfaces via replication|
|US20060138705 *||Dec 23, 2004||Jun 29, 2006||Korba Gary A||Method of making a structured surface article|
|US20060141219 *||Dec 23, 2004||Jun 29, 2006||Benson Olester Jr||Roll of a uniaxially oriented article having a structured surface|
|US20060141220 *||Dec 23, 2004||Jun 29, 2006||Merrill William W||Uniaxially oriented article having a structured surface|
|US20060204720 *||Dec 23, 2004||Sep 14, 2006||Biernath Rolf W||Uniaxially oriented birefringent article having a structured surface|
|US20060243138 *||May 2, 2005||Nov 2, 2006||3M Innovative Properties Company||Electret article having high fluorosaturation ratio|
|US20060243139 *||May 2, 2005||Nov 2, 2006||3M Innovative Properties Company||Electret article having heteroatoms and low fluorosaturation ratio|
|US20060254419 *||May 12, 2006||Nov 16, 2006||Leonard William K||Method and apparatus for electric treatment of substrates|
|US20070031140 *||Aug 4, 2005||Feb 8, 2007||Biernath Rolf W||Article having a birefringent surface and microstructured features having a variable pitch or angles for use as a blur filter|
|US20070222119 *||Jun 7, 2007||Sep 27, 2007||3M Innovative Properties Company||Electret article having heteroatoms and low fluorosaturation ratio|
|US20080142433 *||Dec 14, 2006||Jun 19, 2008||Kimberly-Clark Worldwide, Inc.||Abrasion resistant material for use in various media|
|US20080202078 *||Feb 27, 2008||Aug 28, 2008||Hollingsworth & Vose Company||Waved filter media and elements|
|US20080257149 *||Jul 26, 2007||Oct 23, 2008||Transweb, Llc||Filtration media having a slit-film layer|
|US20090272084 *||Mar 6, 2009||Nov 5, 2009||Hollingsworth & Vose Company||Waved filter media and elements|
|US20090272269 *||Jun 3, 2009||Nov 5, 2009||Leonard William K||Method and apparatus for electric treatment of substrates|
|US20090293279 *||Jun 2, 2008||Dec 3, 2009||3M Innovative Properties Company||Method of making electret articles based on zeta potential|
|US20100107881 *||Jul 24, 2009||May 6, 2010||Hollingsworth & Vose Company||Waved filter media and elements|
|US20100252047 *||Apr 3, 2009||Oct 7, 2010||Kirk Seth M||Remote fluorination of fibrous filter webs|
|US20100263696 *||Jun 15, 2010||Oct 21, 2010||Leonard William K||Method and apparatus for electric treatment of substrates|
|US20110041471 *||Nov 25, 2008||Feb 24, 2011||Sebastian John M||Electret webs with charge-enhancing additives|
|US20110083686 *||Oct 9, 2009||Apr 14, 2011||Philip Morris Usa Inc.||Method and apparatus for manufacture of smoking article filter assembly including electrostatically charged fibers|
|US20110091717 *||Jun 29, 2009||Apr 21, 2011||Weiss Douglas E||Method for in situ formation of metal nanoclusters within a porous substrate field|
|US20110137082 *||May 4, 2009||Jun 9, 2011||Li Fuming B||Charge-enhancing additives for electrets|
|US20110154987 *||May 4, 2009||Jun 30, 2011||Li Fuming B||Electret webs with charge-enhancing additives|
|US20110162337 *||Dec 30, 2010||Jul 7, 2011||Hollingsworth & Vose Company||Waved filter media and elements|
|USRE35062 *||Jun 17, 1993||Oct 17, 1995||Minnesota Mining And Manufacturing Company||Filter element|
|WO2000000267A2||Jun 25, 1999||Jan 6, 2000||Kimberly-Clark Worldwide, Inc.||Stable polymeric electret materials|
|WO2010096285A2||Feb 5, 2010||Aug 26, 2010||3M Innovative Properties Company||Antimicrobial electret web|
|WO2010114826A1||Mar 30, 2010||Oct 7, 2010||3M Innovative Properties Company||Remote fluorination of fibrous filter webs|
|WO2014172308A2||Apr 15, 2014||Oct 23, 2014||3M Innovative Properties Company||Electret webs with charge-enhancing additives|
|WO2015199972A1||Jun 9, 2015||Dec 30, 2015||3M Innovative Properties Company||Electret webs with charge-enhancing additives|
|U.S. Classification||96/99, 210/508, 307/400, 361/233, 128/205.29, 55/528, 264/435, 264/DIG.47, 361/226, 264/413, 264/484, 264/479|
|International Classification||D06M101/16, D06M101/20, B01D39/14, D01D5/42, D06M101/00, B29C71/00, D04H13/02, D06M101/18, B01D39/16, D06M101/22, D06M10/00, B01D39/08, H01G7/02, D06M10/02|
|Cooperative Classification||Y10S264/47, Y10S264/48, B01D39/1623, B01D39/083, B01D2239/10, B29C71/0081, D01D5/423, B01D39/10, H01G7/023, B01D2239/065, B01D2239/0654, B01D2239/0695|
|European Classification||B01D39/10, B01D39/08B, D01D5/42B, H01G7/02B2, B29C71/00F, B01D39/16B4|