US 3475198 A
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Description (OCR text may contain errors)
Oct. 28, 1969 DRUM 3,475,198
E. W. METHOD AND APPARATUS FOR APPLYING A BINDER MATERIAL TO A PREARRANGED WEB OF UNBOUND, NON-WOVEN FIBERS BY ELECTROSTATIC ATTRACTION Filed April 7. 1965 2 Sheets-Sheet 1 mvsm'on 2 EDWARD w. DRUM Oct. 28, 1969 E. w. DRUM 3,475,198 METHOD AND APPARATUS FOR APPLY A BINDER MATER IAL TO A PREARRANGED WEB UNBOU NON-WOVEN FIBERS BY ELECTR ATIC ATTRACTION Filed April 7, 1965 2 Shets-Sheef 2 INVENTOR EDWARD W. DRUM United States Patent 3,475,198 METHOD AND APPARATUS FOR APPLYING A BINDER MATERIAL TO A PREARRANGED WEB 0F UNBOUND, NON-WOVEN FIBERS BY ELEC- TROSTATIC ATTRACTION Edward W. Drum, Indianapolis, Ind., assignor to Ransburg Electro-Coating Corp., Indianapolis, Ind, a corporation of Indiana Filed Apr. 7, 1965, Ser. No. 446,290 Int. Cl. B05b 5/06, 13/02 US. Cl. 117-93.4 11 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved method and apparatus for treating arrangements of unbound fibers and more particularly to a method and apparatus for manufacturing a non-Woven fiber web by electrostatically applying binder materials to an arrangement of unbound fibers.
Increasing use is being made today of non-woven fiber webs. Typical examples of such uses include thermal insulation, acoustical insulation, packing materials and furniture padding. A desirable characteristic of such nonwoven fiber web materials is low cost since they are predominantly used to replace inferior inexpensive materials; their manufacturing cost must be correspondingly low. Older methods of manufacturing these materials did not result in a non-woven web at a low enough cost to enable them to compete successfully with the unbound fiber materials that were being used. US. Patent 2,466,906 indicates an older method of manufacturing such non- Woven fiber webs. The method indicated in this patent required the coating to take place within a coating chamber into which the fibrous material and the binder were simultaneously sprayed. Obviously, some of the material would be attracted to the chamber walls reducing the efiiciency of production and requiring frequent cleaning of the chamber. Furthermore, it was difiicult to obtain a web of uniform thickness using this method.
Recently, production methods have been devised by which fiber materials are formed into a uniform arrangement of non-woven fibers directly on the belt conveyor that moves it into a treating zone for the application of the binder material. Since the individual fibers in the web are unbound and have very large surface areas for their weight, such as animal or vegetable fiber or wood pulp fibers, any air currents or mechanical forces exerted on the prearranged fiber web will disturb the arrangement and create non-uniformities in its thickness. Of course, a binding material must be applied to create a usable web material. The application of the binder must be done with rapidity and Without disturbing the arrangement of the fibers. A prior method of applying binder materials to preformed non-woven fiber mats involved holding the prearranged fibers between two screens and dipping them into the binder material. This materially reduced the thickness of the web.
An object of this invention is a method and apparatus for electrostatically treating a preformed arrangement of unwoven fibers rapidly and economically to render them capable of handling and use.
A- further object of this invention is a method and apparatus for manufacturing a non-Woven fiber web from an arrangement of unbound fibers supported by a belt conveyor means in a uniform prearrangement without materially affecting its thickness or uniformity.
A still further object of this invention is a method and apparatus for atomizing, distributing and depositing hardto-atomize liquid binding materials upon a web-like arrangement of unbound fibers that are light enough to be disarranged by any substantial air current at the surface of the arrangement.
In accordance with the present invention, the nonwoven fibers are formed and arranged upon a grounded supporting conveyor means uniformly to suit the intended purpose. The supporting means conveys the prearranged fibers as they are formed to a treating zone. An electrostatic depositing field is established to the non woven fibers. In many cases the electrostatic field in the treating zone temporarily binds the fibers of the Web together as they pass through the zone. The binding material is delivered to a sprayer in the treating zone at a controlled rate where it is distributed and charged. The binder spray is mechanically directed essentially parallel to the unbound Web and is attracted to the Web by electrostatic forces. Thus the application of binder will take place in the form of a spray being gently attracted to the fiber Web in quiescent air. Where the spray particles are liquid they must be sufficiently atomized to prevent a substantial impact due to the action of mechanical forces upon the droplet. With many liquid materials, this can be accomplished with electrostatic atomization; however, there are Water-based binders such as pigmented polyvinyl acetate emulsions in water, styrene/butadiene emulsions in water or cornstarch solutions in water which do not readily atomize electrostatically.
By supplying such liquid materials to rotating atomizers turning at speeds of revolution on the order of several thousands of revolutions per minute, these materials can be atomized through the combined effects of electrostatic and centrifugal forces; however, such a rotating atomizing device creates a strong wind which would disturb the fiber particles that comprise the web. By properly bafiling or blocking air flow adjacent the rotating atomizer, the liquid material is projected into quiescent air and deposition of binder materials that are difficult to atomize electrostatically can be achieved without disturbing the thickness or uniformity of the resulting web.
Another method of atomizing liquid binder materials which are diflicult to atomize electrostatically is by projecting the coating material through a small orifice under the action of high pressure to create a thin expanding film from which atomization is effected by interaction with quiescent air. Using this method, the mechanical forces needed for atomization can be exerted upon the binder material while maintaining the atmosphere at or near the web surface in-a quiescent state. The term quiescent is used herein to indicate the absence of air currents of such a magnitude to disturb the arrangement of the fibers and result in non-uniformity of the web. Issuance of a thin film of binder material at a high velocity into a relatively quiescent air substantially parallel to the web surface and adjacent an electrostatic charging electrode results in atomization and charging of the spray particles and dissipation of the spray particle momentum, enabling deposition of the binding materials by electrostatic attraction without disagreement of the 3 ticles of spray so formed, it is possible to obtain a chargeto-mass ratio great enough to render the spray particles responsive to electrostatic forces so that the particles if directed parallel to the path of travel of the unbound fiber web will be deposited with great efficiency.
It is possible to practice this method with electrostatichydrostatic deposition apparatus as described; however, with such an apparatus the relatively small longitudinal dispersion or pattern of the spray particles obtained from a single atomizing device requires a plurality of such devices to coat a web of any great width. Further, blending of the spray patterns of the atomizing device is necessary to obtain uniform treatment across the web. In addition, many of the binding materials are gummy and easily dried and have a tendency to clog the small orifices which are used in this apparatus. With these materials where a plurality of atomizers are required, the tendency of the materials to clog the nozzle may result in installations in which production with this treating method may be more frequently interrupted than with the rotary electrostatic atomizer previously described.
In the method of this invention an electrostatic field having an average potential gradient of at least 3000 volts per inch is advisable to achieve eflicient deposition.
Application of binder material as described will permit the manufacture of a uniform low density, nonwoven fiber web economically and without compacting the fibers of the web and destroying the chosen thickness of the web. Other features and advantages of the invention will be apparent in the following specification and the drawings in which:
FIGURE 1 is a side elevation of a disk, its associated air battles and their supports, with the spacing between the disk and the bafiles being somewhat exaggerated for clarity of illustration, showing the supported non-Woven web in spaced relation from the rotating disk and the voltage and material supply equipment (shown schematically) FIGURE 2 is a broken sectional view of a rotary disk atomizer showing the construction of this rotary device.
FIGURE 3 is a side elevational view of bell-type devices arranged transversely of the path of travel of the web material to apply the binder evenly across the fibrous web and showing bafiles to prevent the air movement at the surface of the web.
FIGURE 4 is a side elevational view of an embodiment of my invention employing a series of hydrostatic electrostatic devices adapted to apply the liquid binder materials to the fibrous web.
FIGURE 5 is an end view along line 5--5 of FIGURE 4 of the embodiment shown in FIGURE 4 indicating the arrangement of hydrostatic atomizers across the extent of the web to obtain an even distribution of binding material upon the web.
Referring now to FIGURE 1 of the drawings, the unbound web being coated is carried by a suitable conveyor 11 into the treating zone adjacent a rotating spray device here generally identified as 12. Rotating disk 12 is spaced from the conveyor a distance sufficient to permit the building material being applied to be distributed throughout the width of the unbound web. The rotating disk is also oriented so that rotation occurs in a plane generally parallel to the plane of the web being coated. Thus, any air currents permitted by the baffies adjacent the disk circulate about the disk rotator in a plane parallel with the web which is quite removed from the surface of the web by the spacing between the disk and the web surface.
Where, for example, liquid binder materials are used, they are pumped from the material container 13 which is either grounded or, as shown, insulated from ground by an insulating stand 14 to permit the use of binding materials which are highly conductive. Where conductive materials are used, the pump 15 is insulated for high voltage. The material is pumped from container 13 through conduit 17 to a feed tube which distributes the coating material upon the upper surface of the disk as will be described. High voltage is brought to the rotating disk 12 from high voltage supply 18 through high voltage cable 19 which is connected to the conductive case of the rotating disk. Insulator 20 supports the rotating disk from overhead, while isolating it from the grounded supporting structure. Supporting conveyor 11 is grounded and provides means such as backing electrodes to keep the web at a spray attracting potential. The high voltage supply contains a three phase transformer with secondary windings that are insulated from the core and the primary windings so that they may be charged to as much as 100,000 volts at which the disk may operate. This three phase transformer supplies the power for the electric disk rotator motor by means of the high voltage cable 19 from high voltage supply 18. Container 13, insulating stand 14, pump 15, drive 16 and high voltage supply 18 are all schematically shown since these elements are commonly known to those skilled in the art.
The vertical spacing of rotating disk unit 12 above the web being coated is determined in part by the extent of distribution of thecharged particles which is desired. A greater spacing between the disk unit and the Web surface is necessary for wider distributions. The extent of distribution of the charged spray particles is also dependent upon the speed of rotation and the diameter of the disk. With liquid materials that atomize well electrostatically, satisfactory atomization can usually be obtained at 900 revolutions per minute with a disk atomizer charged to approximately kilovolts; however, some liquid binder materials are difficult to atomize electrostatically. To obtain satisfactory atomization with these materials, it is necessary to increase the speed of rotation of the disk. The mechanical forces associated with the higher lineal velocity and rotational velocity of the disk edge which are exerted upon the material being discharged there cause the liquid film to be thinner and more uniform. By choosing the speed of rotation and the disks diameter, it is possible to satisfactorily atomize any binder material so that efficient deposition over the desired area can be attained.
To prevent dislodging the unbound fiber elements of the non-woven fiber web, it is necessary to provide baffles to prevent the creation of air currents by the rotating disk element. Baffiing is sometimes desirable even with rotating elements which rotate at relatively low rates, for example at 900 rpm. By placing stationary plates above and below the rotating disk and extending almost to the edge of the disk, it is possible to reduce substantially the air velocities that are created remotely from the disk edge without disturbing the film or reducing the concentration of the electrostatic field at the edge of the rotating member. These baffles can be made of insulating materials to avoid reduction of the electrostatic field at the edge of the rotating disk. With the baflles in place, a quiescent atmosphere can be maintained adjacent the fibers although the rotational speed of the disk exceeds 900 rpm.
Since, however, some circulating air currents are still generated by friction at the exposed edge of the disk, it is necessary to space the rotating disk from the web a distance suflicient to prevent this air current from dislodging the fibers and disturbing the uniformity of the web. Additionally, the disk is oriented so that the plane of the rotating edge is substantially parallel to the plane of the web. This prevents the circulating air current that lies substantially in the plane of the disk from impinging on the unbound fibers. The substantially parall l rotating disk-web configuration materially reduces the impact of the spray particles upon the web fibers since the momentum given the spray particles by the disk edge is substantially dissipated by friction with the quiescent air in the treating zone before deposition upon the web.
Referring now more particularly to FIGURE 2, the broken cross-sectional view of a rotating disk atomizer indicates in more detail the location of the baffies and the manner in which they are supported in the disk assembly. In a preferred embodiment the upper baflle disk 21 is spaced as close to the upper surface of the rotating disk 22 as possible without collecting the coating material or disturbing the film of the liquid binder material, inch proving satisfactory in one example. It is preferable to space the lower bafiie disk 23 closer to the lower surface of the disk, about of an inch having proved satisfactory in practice. Even though the bafiie disks are made of dielectric or non-conductive material, optimum concentration of the electrostatic field at the disk edge 22a of the disk 22 is obtained by having the baffle edges lie slightly inwardly of the disk edge, as inch to the inside thereof. The air blocking or bafiie means is preferably unbroken or uninterrupted in order to completely close over or protect each side of the rotating disk, and baffie means on each side of the rotating disk is important in achieving the desired results. The rotating disk 22 has a hollow shaft portion 22b which is sized to mate with the hollow rotating shaft of the rotator motor 2 4. Disk member 22 is held onto the rotating'shaft 24 by means of set screw 25 which passes through the shaft of the disk member 22b into a depression in the rotating shaft 24. A stationary hollow tube 26 passes through the center of the shaft 24 of the rotator motor and is supported at its upper end by the motor housing 27 by holding the hollow tube 26 in a mating portion of the motor housing 27 with set screw 28. Lower baflie 23 is supported from the end of hollow tube 26 by means of support member 32 to which the baffie is held by screws. Liquid binder material is then brought through plastic tube 17 through pipe fitting 29 to the interior of feed tube 31 through which it flows. The binder material is expelled through the distributing portion of the feed tube 31 onto a well-shaped portion 220 of the upper surface of disk member 22. Rotation of the disk member forces the liquid material deposited on this surface into a thin film and to the atomizing edge 22a for atomization and charging. Upper bafiie 21 is supported from the lower end of motor housing 27.
High voltage and power for the rotation of the disk motor are brought to the motor by means of high voltage cable 19 which has three separate conductors interconnecting the secondaries of the three-phase isolating transformer in the voltage supply 18.with the windings of the rotator motor. The three conductors are connected to the winding leads 33, 34 and 35 within the motor housing. Lead 33, in addition, is connected to the motor housing to charge the disk to high voltage.
It will be understood that the bafiling or air blocking disclosed here is not concerned with eddy currents, the changes in direction of air movement, or with other effects at or near the edge of the rapidly moving rotator. Instead, the action desired is reduction of air velocities at a substantial distance from the rotator, as for example, immediately adjacent the surface of the fibers being treated. Particularly, with a disk-type rotating device it is the action of the air stream at or near the fibers which is undesired and which this air bafiiing or blocking arrangement obviates. Moreover, this can be accomplished without reducing the desirable high concentration of field forces at disk edge and where liquid materials are used, without disturbing the liquid film on the rotating surface.
FIGURE 1 shows a deflecting electrode 37 arranged above a disk and outside the edge thereof around the entire periphery. This deflecting electrode is attached to the disk rotator, is chraged to its full voltage, and thus repels the charged spray leaving the disk to provide a downward component of force thus assist in directing the spray particles onto the fibers and confining the extent of their distribution. Shown in more detail in FIGURE 2', the electrode consists of a wire ring 37 suspended from the disk rotator by a spider 38.
A specific example of my method of applying binder materials to non-woven fiber webs follows. The binder material applied was a 10% solution of Amica No. starch of the National Starch and Chemical Co. which had been heated to -l95 F. for 15 minutes and to which /2% formaldehyde and 1% of Tergitol TMN, a wetting agent, had been added. A rotating disk was located 24 inches above the surface of the web being coated and oriented in a plane which was parallel to the plane of travel of the web. The water-based binding material was pumped to the lower surface of the rotating disk at the rate of two liters per minute. The 15 inch diameter, electrically-charged metal disk was used to spray the binding material and was rotated at 3600 rpm. To prevent the substantial air currents that would otherwise blow away the unbound fibers comprising the web, baffles of insulating material were closely positioned inch above and inch below the rotating disk member. These baflies were 14% inches in diameter and were concentric with the rotating disk. To atomize and charge the binder material, a voltage of 100,000 volts was applied to the disk rotator and, thus, to the rotating disk itself. A 19 inch diameter deflecting electrode of A inch diameter' tubing was located concentrically with the rotating disk and positioned with the plane of its center inch above the plane of the atomizing edge. Defiecting electrode was supported from the body of the disk rotator and was also charged to 100,000 volts. Under these conditions binder material was successfully applied to an 84 inch width of unbound fiber particles arranged to comprise a uniform inch non-woven fabric web moving at a rate of 30 to 50 feet per minute on a fiat grounded conveyor. After treatment of each side of the fiber arrangement, the fibers were bound into a continuous nonwoven fabric web with a uniform thickness of inch by the tissue-like surfaces of the web to which the binder material had been applied.
FIGURE 3 shows an installation utilizing bell-type rotating atomizers 39 for liquid materials. As with the disk, the speed of the rotation can be chosen to assist the atomization of the binder materials. With many materials the speed of rotation would be only that sufficient to form the binder material into a film over the inside surface of the bell atomizer. However, with some materials higher rotational speeds may be necessary to take advantage of the effect of the mechanical forces ap-' plied to the binder material at the edge of the atomizer. Bafiies are frequently necessary to prevent air currents which might disturb the arrangement of the fibers. The outer baflies 40 may be supported from the motor enclosure 41 and positioned concentric with the bell atomizer as closely as possible. The inner baffles 42 are supported through the hollow rotating shaft of the bell mot r in a manner and at a spacing similar to that described previously for the disk. The bell atomizers may be charged to 100,000 volts by high voltage supply 43. Material is fed to the inside of the bells from a pump unit 44 driven by a power unit 45. The pump 44 may be insulated from the drive unit if the binding materials are conductive. Spacing of the rotating bell atomizers 39 above the web material 10 and the spacing between bell atomizers 39 is chosen to achieve a uniform deposition of binder material across the extent of the web. As illustrated in FIGURE 3, more than one atomized may be necessary to cover an extensive web. The diameter of the bell atomizers is relatively small, for example four inches. These atomizers will be spaced so that the spray deposited by the adjacent atomizers will give relatively even distribution of the binding material across the web. It will be understood, of course, that in the preferred v embodiment the conveyors themselves are at ground potential; however the fiber arrangement may be maintained at any spray-attracting potential by electrodes producing the depositing electrostatic field.
FIGURES 4 and 5 show another embodiment of apparatus by which my method may be practiced. In this embodiment, a hydrostatic-electrostatic spraying device of the type described in US. Patent No. 3,169,883 is positioned above a supported body of unbound fibers 10 which is supported and carried by conveyor 11 into the coating zone. Hydrostatic-electrostatic atomizing devices 51 are located in spaced relationship above the fiber arrangement 10 and oriented to spray in a plane substantially parallel to the plane of the arrangement. The high atomizing pressure is supplied by air-driven reciprocating pump 53 through a conduit 54 which is capable of withstanding pressures of the order of several thousand p.s.i. to the forward end of the electrostatic-hydrostatic atomizing device 51. High voltage from high voltage power supply 55 is carried through a high voltage cable 56 into the body of the hydrostatic-electrostatic spraying gun, which may be made of insulating material, for connection with the nozzle of the atomizing device or with a slender elongated electrode which may be spaced adjacent to the orifice in this nozzle. Air from pressure source 57 is carried by means of hose 58 to drive the high pressure pump 53. It is also carried by hose 59 to air cylinder 60 which may be used to control the valve of the hydrostatic-electrostatic spraying device 51.
During application of the binder material, air is supplied at pressure through hoses 58 and 59 to pump 53 and to air cylinder 60. Pump 53 thus supplies binder material to the small elongated orifice of the atomizing device 51 under pressure in excess of 250 pounds per square inch. The binder material is forced through a small orifice spaced at least several inches above the web at very high velocity into a thin expanding film for atomization by interaction with the quiescent surrounding air. Charging of the spray particles created by hydrostatic atomization may be achieved by either charging the nozzle through which the binder material is forced or a slim pointed electrode positioned adjacent to but spaced from the thin fan-like film to create an electrostatic field having an average potential gradient of at least 3000 volts per inch extending from these elements to the web. Since there are no jets of pressurized air impinging upon the binder material to achieve atomization such as are used with normal air spray guns, the air adjacent the fibers in the treating zone is quiescent. Any air currents that may be induced by the high velocity movement of the spray particles adjacent the gun may be prevented from interfering with the uniformity of the web by means of a baflie 61 arranged between the gun and the web material. The hydrostatic-electrostatic device is arranged to project the spray in a direction substantially parallel to the plane of the web material; thus, any momentum imparted the spray particles in leaving the spray orifice will be dissipated in the relatively quiescent air and the particles will thus be gently and efiiciently deposited by electrostatic attraction upon the fiber arrangement which is maintained at a spray attracting potential.
For web materials that have too great an extent to be coated with one such atomizer, a multiplicity of atomizers may be arranged across the extent of the web material as shown in FIGURE 5. When they are so used, the atomizers are spaced so that the fan-like sprays 49 from the adjacent atomizing devices overlap slightly as they are deposited upon the fiber arrangement to produce a uniform distribution of binder material across the width of the web. In arriving at a satisfactory spacing between the adjacent atomizers, it is necessary to select the angle of the fan-like spray and the proper spacing of the atomizer above the web so that their spray patterns blend and the momentum of the coating material particles is substantially dissipated prior to impingement upon the web fibers. The individual atomizers 51 may be supported from a plate 62 which is attached to supports 63 and supported from overhead. In addition, the atomizers 51 may be reciprocated to widen the extent of their deposited pattern. Battle 61 may be carried from plate 62 by means of supporting members 64, or if the atomizers are reciprocated, it may be carried from supports 63 below the moving guns to block any air currents which would otherwise be created by the reciprocation of the atomizers.
While I have shown and described certain embodiments of my invention it is to be understood that it is capable of many modifications. For example, powdered coating materials may be applied to non-woven webs and unbound fiber arrangements with this invention by replacing the rotating atomizers shown and described with distributors specifically designed to spray powdered materials. Rotating sprayers may be made with non-conducting materials as described in US. Patent No. 3,128,- 045.
1. In a method of manufacturing non-woven fiber webs the steps of moving a prearranged web of unbound non-woven fibers through a treating zone under a rotating device supplying a liquid binder material from a source of supply to the rotating device, forming the binder material into a thin expanding film supported on said rotating device, advancing said suporting film towards an atomizing edge by rotating said edge in a plane generally parallel with the plane of the unbound web, charging said rotating device to create an electrostatic field between said supported film and the unbound web of sufficient strength to effect charging and deposition of the binder material discharged from said rotating device in the form of spray particles, and blocking air flow adjacent said rotating device to maintain the atmosphere quiescent adjacent the unbound fibers in the treating zone.
2. A method of applying liquid binder materials to unbound fibers including the steps of moving an arrangement of unbound fibers through a treating zone, supplying liquid binder material at a high hydrostatic pressure to a small elongated orifice in a single fluid atomizing device, project the binder material into the surrounding atmosphere in a direction generally parallel to the fiber arrangement as a thin expanding film and with such velocity as to effect atomization of coating material from said film into fine spray particles, maintaining a quiescent atmosphere adjacent the fibers, said projection being spaced from the fiber arrangement a sufiicient distance to permit substantial dispersion of the spray particles and to permit substantial loss of momentum imparted the spray particles by the discharge from said high hydrostatic pressure, and providing an electrostatic charging field from an electrode adjacent to said thin expanding film to said fibers to charge said spray for deposition on the fibers while still in a liquid state.
3. Apparatus for treating unbound fibers comprising: means for moving an arrangement of unbound fibers through a treating zone; atomizing means for forming the liquid material into a thin expanding film in a plane generally parallel with the plane of the unbound fibers for atomization therefrom and applying a mechanical distributive force to the liquid material, said force acting generally in a plane parallel to the plane of the unbound fibers adjacent the zone of atomization; means for flowing a liquid material at a controlled rate from a source of supply to said atomizing means; means for charging the resulting spray of liquid material and for establishing an electrostatic depositing field extending between Said film forming means and the fibers; means for maintaining the atmosphere quiescent adjacent the unbound fibers; and means for spacing the atomizing means from the unbound fibers to effect the distribution of a charged spray of liquid material over the width of the unbound fibers and to substantially dissipate the momentus imparted to the spray particles by 'the atomizer in the quiescent atmosphere.
4. Apparatus for applying liquid materials to nonwoven fibers comprising means for transporting a supported arrangement of non-woven fibers through a treating zone, an atomizer, means for supplying a stream of liquid material from a supply source to said atomizer, means for rotating said atomizer about an axis generally perpendicular to the plane of the fiber arrangement for advancing said liquid material over a surface of the atomizer to an atomizing zone from which it emanates in the form of a spray of liquid particles, means for creating between said fibers and said atomizer an electrostatic field of sufficient strength to eifect the charging, dispersion and deposition of the liquid spray particles on the fibers, means for blocking air flow adjacent substantially the entire extent of said atomizer to reduce air velocity adjacent the fibers, and means for maintaining the fibers at a spray attracting potential.
5. The appartus of claim 4 including means for deflecting the charged spray down onto the web by electrostatic force.
6. Apparatus for treating non-woven webs comprising: means for moving a prearranged web of non-woven fibers through a treating zone; means for supplying a treating material at a controlled rate from a source of supply to a zone of distribution; means for applying a mechanical distributive force to the treating material to form a spray, said force acting generally in a plane parallel to the plane of the web adjacent the zone of distribution; means for charging the spray of treating material and establishing an electrostatic depositing field to the web; means for blocking air flow adjacent the mechanical distributor means to maintain the atmosphere quiescent adjacent the Web; means for spacing the zone of distribution above the web to effect the deposition of the charged spray of treating material over the width of the web and to substantially dissipate the momentum imparted to the spray by the distributor.
7. The method of treating an arrangement of nonwoven fibers comprising: moving a prearranged web of unbound fibers through a treating zone; supplying a treating material to a distributor in said treating zone; distributing said treating material from said distributor in a direction generally parallel to sad fibers and at a sufficient distance from said fibers to permit dissipation of the momentum imparted to said material by the distributor and to maintain a quiescent atmosphere adjacent the fibers; blocking air flow adjacent the distributor to prevent the creation of air currents in said treating zone; and charging the treating material to attract the treating material to said fibers.
8. The method of claim 7 including the step of deflecting the treating material toward said fibers by means of an electrode.
9. The method of applying a liquid binder to an arrangement of non-woven fibers comprising: moving a prearranged web of unbound fibers through a treating zone; supplying a liquid binder to an atomizer in said treating zone; forming the liquid binder into a thin expanding film and atomizing it as a spray from the edge of said film while projecting the spray in a direction generally parallel to the arrangement of unbound fibers and at such a distance from the unbound fibers that the arrangement is not disturbed by air movement or the impact of the spray; and charging the spray and establishing an electrostatic depositing field to the fibers.
10. The method of claim 9 including the step of deflecting the charged spray of binder material toward said fibers by an electrode having the same charge as the spray.
11. In a method of making non-woven fiber webs the steps of moving a prearranged web of non-woven fibers through a treating zone; supplyinga binder to a distributor in said treating zone; distributing said binder from said distributor in a direction generally parallel to the web and at such distance to permit dissipation of the momentum imparted to the binder by the distributor; blocking air flow adjacent the distributor to prevent disarrangement of the web; and establishing an electrostatic field between the distributor and the web to charge the binder and deposit it with the air of electrostatic forces.
References Cited UNITED STATES PATENTS 1,160,980 11/1915 Geer 118-325 X 1,978,034 10/1934 Sutherland 118-325 X 2,595,342 5/1952 Dosmann 118-325 X 3,014,812 12/l96l Sallie 118-324 X 3,130,066 4/1964 Brady 239-3 X 3,251,551 5/1966 Walber 239-15 X ALFRED L. LEAVITT, Primary Examiner J. H. NEWSOME, Assistant Examiner US. Cl. X.R.