WO1995006522A1 - Applicateur par pulverisation de couche uniforme sur substrats - Google Patents

Applicateur par pulverisation de couche uniforme sur substrats Download PDF

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Publication number
WO1995006522A1
WO1995006522A1 PCT/US1994/009790 US9409790W WO9506522A1 WO 1995006522 A1 WO1995006522 A1 WO 1995006522A1 US 9409790 W US9409790 W US 9409790W WO 9506522 A1 WO9506522 A1 WO 9506522A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquid
substrate
fluid
applicator
outlet
Prior art date
Application number
PCT/US1994/009790
Other languages
English (en)
Inventor
Ted Mcdermott
John J. Watkins
Michael J. Yancey
Scott A. Wallick
Walter D. Watt
Terry N. Adams
Original Assignee
Weyerhaeuser Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Weyerhaeuser Company filed Critical Weyerhaeuser Company
Priority to AU77177/94A priority Critical patent/AU7717794A/en
Publication of WO1995006522A1 publication Critical patent/WO1995006522A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/08—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point
    • B05B7/0884—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point the outlet orifices for jets constituted by a liquid or a mixture containing a liquid being aligned
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B14/00—Arrangements for collecting, re-using or eliminating excess spraying material
    • B05B14/30—Arrangements for collecting, re-using or eliminating excess spraying material comprising enclosures close to, or in contact with, the object to be sprayed and surrounding or confining the discharged spray or jet but not the object to be sprayed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/025—Nozzles having elongated outlets, e.g. slots, for the material to be sprayed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/08—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point
    • B05B7/0807—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point to form intersecting jets
    • B05B7/0861—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point to form intersecting jets with one single jet constituted by a liquid or a mixture containing a liquid and several gas jets

Definitions

  • the present invention relates to an apparatus for coating a substrate. More particularly, it concerns an apparatus for depositing a uniform coating of liquid, or a liquid containing particulates, on a broad variety of substrates such as paper, cloth and organics.
  • Paper webs are frequently treated to increase their surface strength and enhance their printability by providing a smooth printing surface on the paper.
  • Paper coating is often performed by applying an excess amount of coating material onto an applicator roll for transfer to the web.
  • the coating liquid is applied directly to the web in excess, and then metered to the correct thickness with a blade or rod.
  • roll and blade coating systems apply relatively uniform layers on a substrate, such systems suffer from the drawback of requiring an expensive piece of heavy machinery that occupies a large amount of space.
  • a typical roll coating system in a paper mill such as a conventional two-roll size press or a gate roll system, can cost millions of dollars and require an in-line space of 10 to 30 meters (30 to 100 feet). Placing a roll coating system within an existing line of equipment also requires removal and relocation of existing equipment, which greatly increases the installation costs.
  • Spray systems are a less expensive and more compact alternative to roll coaters.
  • pressure is applied directly to liquid in the spray head. Passage of the liquid through a constricted orifice in the spray head breaks the liquid into droplets of many sizes.
  • spray systems do not uniformly apply material to a substrate. The resulting coated product is streaky and blotched, rendering it less appealing to consumers. The irregular surface coverage may also diminish the appearance of subsequent printing on the surface.
  • a cross-section of a typical prior art pressure spray head is shown in
  • the spray head 10 has a body 11 with a circular horizontal cross-section and a central interior bore 12 that tapers in the direction of a small cylindrical spray orifice 13.
  • the liquid material is forced under pressure through the tapering central bore and out of the orifice at a high velocity to produce liquid droplets.
  • the design of the central bore 12 and the orifice 13, in combination with the internal pressure on the material, determines the pattern of spray produced by the nozzle.
  • the size distribution of the resulting droplets varies across a broad range, and the spray is difficult to control or direct. It also deposits unevenly across the surface width of a paper sheet or other object being coated.
  • a typical lateral mass distribution of material from a conventional spray head is shown in FIG. 2.
  • the applied coating is markedly non-uniform with two peaks 14 and 15 spaced laterally from the center line of the spray head.
  • the volume flow at each of the peaks 14 and 15 is approximately twice the volume flow at the center 17 of the spray pattern, and approximately seven times the flow at the outer edges 18 and 19 of the pattern.
  • the flow at the center 17 is itself approximately four times the flow at the edges 18 and 19.
  • This lateral non- uniformity of application causes undesirable streaking of the coating on the substrate with thicker and thinner application of the material across its width.
  • a series of nozzles is normally required for covering a wide web and the uneven deposition of each is compounded when a number are used.
  • Air assisted atomization Another type of spray system is air assisted atomization, in which liquid emerges from a circular opening and is changed into droplets by an annular stream of air. Air assisted atomization has been used, for example, in spray painting devices. This technology has not been suitable for uniformly coating substrates because of nonuniformities in the coating when applied in single or multiple linear passes.
  • Another object of the invention is to provide an apparatus and method that is less expensive and space consuming than roller or other conventional applicators, and which can be more easily retrofitted into existing production lines.
  • Yet another object is to provide an improved system for applying liquid coatings to a variety of substrates having many different topographies.
  • Yet another object is to provide an improved application system that combines the benefits of mist reduction with enhanced coating uniformity.
  • the process of the present invention uniformly deposits a liquid coating on a substrate by directing an elongated linear flow of the liquid from an outlet, such as multiple orifices or an elongated slot, toward the substrate.
  • a fluid is impinged against both sides of the flow to form droplets that can deposit a uniform coating on the substrate.
  • the substrate and flow move relative to one another as the flow is changed into droplets such that a coating may be evenly or thoroughly deposited over an area of the substrate.
  • the flow rates and velocities of the coating material and impingement fluid can be varied over a broad range to alter the characteristics of droplet formation and the resulting uniformity of droplet deposition on the substrate.
  • the droplets can be formed at the outlet or between the outlet and the substrate.
  • the location of droplet formation will depend on the coating material viscosity, fluid impingement velocity, and changes in viscosity of the material as the droplets are forming.
  • the coating material does not change phase from a liquid to a solid after it leaves the outlet to such an extent that droplets will not form. This is a difference between the present invention and meltblown technology, because in meltblowing the extruded thermoplastic material solidifies to form networks of fibers.
  • the coating materials of the present invention include non-thermoplastic materials that do not form fiber networks of the meltblowing variety. Instead, the liquid coating materials form liquid droplets that are deposited on a substrate.
  • the plurality of orifices can be linear, and may be in staggered or sequential rows.
  • the slot can also be linear and may be continuous, discontinuous, or in staggered or sequential rows.
  • linear is used in its usual technical manner to refer to the shape traced by a moving point, which can include a straight, chevron, arcuate, or even serpentine line. As used herein, the term “linear” does not include a circular shape.
  • the coating material is a liquid, such as an aqueous liquid, that is (by definition) liquid at less than 100°C (212°F).
  • the liquid is non-aqueous, for example, an isocyanate such as PMDI, or acrylics, styrene-maleic anhydride, and epoxy resins.
  • the coating process can be carried out entirely at ambient temperature (15°C-40°C or 60°F-100°F).
  • the viscosity of the liquid can vary over a broad range, for example 1 - 2000 cP (0.001-2 Pa-s).
  • the liquid can be directed through an outlet toward the substrate under low pressures, such as 0.3 - 100 psi (2.1 - 700 kPa). In such low pressure embodiments the liquid moves at relatively low velocities from the outlet toward the substrate, and is impinged by a fluid that moves at a greater velocity than the liquid.
  • the fluid temperature is preferably less than 100°C, and preferably is ambient temperature.
  • the fluid may be humidified. Moisture or other additives in the fluid streams may also be used to catalyze or modify the liquid as it travels to the substrate.
  • the elongated liquid distribution emerging from the outlet has opposing sides, and the fluid is impinged against both sides at a wide range of velocities, from 200 feet per second (60 m/s) to sonic velocities.
  • the liquid is formed into increasingly finer droplets as the fluid velocity is increased, for example, as it approaches sonic velocity.
  • the liquid is immediately blasted into droplets as the liquid emerges from the outlet.
  • Much lower impingement velocities are also suitable for many applications where large droplet size can be tolerated. Immediate atomization can also be achieved at relatively low fluid velocities when the liquid has a low viscosity.
  • the present invention can be used to coat a broad variety of substrates, such as cellulosic, fiber, organic, synthetic, rubber, cloth, wood, leather, food, and plastic substrates.
  • a wide variety of coating materials can also be applied to substrates using this method.
  • the coating material is a liquid at room temperature such that it can be sprayed on the substrate in a liquid form without having first solidified before reaching the substrate.
  • the coating fluid may contain particulate matter that is also to be deposited on the substrate.
  • the apparatus of the present invention includes an applicator, movement means for establishing relative movement between the substrate and applicator, and an outlet in the applicator that directs a flow of coating material toward the substrate.
  • Fluid outlets in the applicator impinge a fluid against the coating material to form droplets that are directed toward the substrate to deposit a coat of liquid on the moving substrate.
  • a liquid passage of the applicator contains the outlet (which can be a plurality of outlets) through which the coating material is ejected under pressure.
  • Impingement fluid slots extend along the applicator adjacent the coating material outlet to provide a curtain of a fluid that is propelled at a velocity greater than that of the coating material against the coating material.
  • the described apparatus is capable of depositing a uniform coating of a liquid coating material in droplet form on the substrate, and the thickness of the coating can be varied.
  • the applicator includes a cleaning means that removes a build-up of matter from the applicator.
  • the applicator is made of matable bipartite portions that are easily disassembled for cleaning and meet to define an internal liquid passageway that communicates with an outlet.
  • the cleaning means may also be an internal or external wiper that moves along or through the applicator to remove solids build-up.
  • the accumulation of agglomerated coating material in or on the applicator may be diminished by coating the surfaces of the applicator with a low surface energy material that reduces adhesion of the coating liquid to the applicator and outlet. Examples of such materials include polytetrafluoroethylene, amorphous carbon or polycrystalline diamond. Adhesion to the applicator is also diminished by providing sharp edges around the outlets or orifices from which the coating material liquid and impingement fluid emerge. The sharp edges also enhance the uniformity of the coating on the substrate.
  • the coating apparatus may also include a mist collection device.
  • the mist is preferably collected with a pressure differential, for example, by providing a suction pressure from a hood adjacent the applicator.
  • An air curtain may be directed toward the substrate between the hood and moving substrate to prevent escape of mist between the substrate and hood.
  • FIG. 1 is a cross-sectional view of a prior art conventional spray nozzle.
  • FIG. 2 is a graph representing the lateral flow distribution of liquid from the prior art spray nozzle of FIG. 1
  • FIG. 3 is a perspective view of the apparatus of the present invention in use coating a moving substrate.
  • FIG. 4 is a view taken along view lines 4-4 of FIG. 3.
  • FIG. 5 is an enlarged cross-sectional view of the applicator of FIGS. 3 and 4.
  • FIG. 6 is an enlarged view of the central apex of the applicator, showing the liquid orifices.
  • FIG. 7 is a perspective view of the central portion of the applicator taken along view lines 7-7 of FIG. 5.
  • FIG. 8 is an enlarged view of the liquid passageway portion of the applicator circled in FIG. 7.
  • FIG. 9A is a view similar to FIG. 4 showing another embodiment of the applicator in which the liquid outlet is a slot, an enlarged portion of the slot being shown in the FIG. 9B circle.
  • FIG. 10 is a perspective view of an alternative modular embodiment of the applicator.
  • FIG. 11 is a view similar to FIG. 3 showing an alternative embodiment of the applicator in which a collection hood surrounds the applicator.
  • FIG. 12 is a cross-sectional view of the applicator taken along section lines 12-12 of FIG. 11.
  • FIGS. 13 and 14 are schematic views of applicators applying a coating to substrates moving in different planes, wherein the coating on each side of the substrate can be different materials.
  • FIG. 15 is a series of photographs of iodine stained coating liquid on sheets of paper demonstrating the effect of air pressure and application rate on coverage uniformity with the applicator of the present invention.
  • FIG. 16 is a series of photographs of iodine stained coating liquid on sheets of paper demonstrating the effect of air pressure and air gap width on coverage uniformity with the applicator of the present invention.
  • FIG. 17A is an image
  • FIG. 17B is a column average
  • FIG. 17C is a single line grey intensity profile for a gate roll coated sample of paper.
  • FIG. 18A is an image
  • FIG. 18B is a column average
  • FIG. 18C is a single line grey intensity profile for a material coated with the apparatus of the present invention.
  • FIGS. 19A - 22A are graphs showing column average intensity profiles and FIGS. 19B - 22B are single line grey intensity profiles for materials coated with the apparatus of the present invention.
  • FIGS. 23A-E and 24A-D are single line grey intensity profiles in the direction of substrate movement for the runs referenced on the face of the tracing.
  • FIG. 25 is a cross-sectional view of an alternative embodiment of the applicator.
  • FIG. 26 is a fragmentary view of the applicator taken along section lines 26-26 of FIG. 25, the central portion of the elongated applicator having been omitted from the drawing.
  • FIGS. 27 and 28 are schematic diagrams of the apparatus of FIG. 3 showing several possible locations of filter screens.
  • FIG. 29 is a schematic view showing droplet formation as liquid emerges from the applicator.
  • FIG. 30 is a schematic cross-sectional view of another embodiment of the applicator in which liquid flows through a series of holes and on to a target plate before entering liquid outlets.
  • FIG. 31 is yet another embodiment of the applicator in which a replaceable tip is provided inside the applicator.
  • FIGS. 32 and 33 are schematic cross-sectional views of other embodiments of the applicator.
  • FIG. 34 and 35 are views of a cleaning apparatus for the applicator.
  • FIG. 34 is a side elevational view and
  • FIG. 35 is a cross-sectional view taken along line 35-35 of FIG. 34.
  • FIG. 36 is a photograph at two times magnification showing a coating from a commercial gate roll. This gate roll is a newer gate roll than that shown in Figure 17.
  • FIG. 37 is a photograph at two times magnification showing a coating from a commercial air atomizer nozzle.
  • FIGS. 38 - 41 are diagrams of applicator with two-sided impingement used in certain tests.
  • FIGS. 42 - 45 are photographs at two times magnification showing coatings from applicators of the present invention having 0.008", 0.020", 0.050" and 0.080" wide liquid outlet sharp edges.
  • FIGS. 46 and 47 are graphs illustrating the coverage for the gate roll, for the air atomizer nozzles and for the applicators of the present invention using different edge thicknesses.
  • FIG. 46 is a graph showing gray level standard deviation and
  • FIG. 47 is a graph showing cumulative fraction of coverage by particle size.
  • FIGS. 48 - 51 are diagrams of applicator with one-sided impingement used in certain tests.
  • FIGS. 52 - 55 are photographs at two times magnification showing coatings using applicators with fluid impingement on one side of the liquid in which the outlet edgesare 0.008", 0.020", 0.050" and 0.080" wide.
  • FIGS. 56 - 58 are graphs illustrating coverage for one-sided and two- sided fluid impingement and using different edge thicknesses.
  • FIG. 56 is a graph showing gray level standard deviation and
  • FIGS. 57 - 58 are graphs showing cumulative fraction of coverage by particle size.
  • FIGS. 3 - 8 One preferred embodiment of the apparatus 56 of the present invention is shown in FIGS. 3 - 8 to include an applicator 58 suspended by a mechanical arm 59 above a paper web substrate 60 that is moving below applicator 58 over rollers 61 in the direction of arrow 63.
  • Applicator 58 is shown in greater detail in FIG. 5 to be a bipartite applicator with a central portion that in cross-section defines an equilateral triangle.
  • the central portion has mating, complementary wedge halves 82, 84 that meet along opposing faces to form a linear junction 86 that bisects an apex of the triangular cross-section.
  • Each wedge 82, 84 has a notch 88 along the opposing junctional faces that, in combination with the corresponding notch from the other half portion of the applicator, forms a liquid chamber 90 along the length of applicator 58.
  • the cross-sectional width of chamber 90 widens and then tapers along junction 86 to communicate with a plurality of narrow liquid passageways 92 (FIGS. 5, 7 and 8) that extend through applicator 58 along junction 86 to the apex of the applicator.
  • Each passageway 92 terminates in a circular cross-section orifice 93 (which may also be square, elliptical or diamond-shaped in section) that is machined to sharp edges 95, as shown in FIGS. 6 and 8.
  • the faces 101, 103 of the applicator meet along a sharp apex 97 and each hemi-orifice extends in the plane of the face and is outlined by edges 95.
  • the sharp edges 97 (a sharp edge being defined as an edge having a of radius ⁇ .025 inch or truncated to a flat surface perpendicular to the liquid or air passage of a width ⁇ .050 inch) help diminish build-up of coating material at the liquid and fluid outlet and provide a uniform coating of material on the substrate.
  • one or more continuous elongated linear slots or other outlet configurations could replace the plurality of orifices 93, such as the slot described below in connection with FIG. 9.
  • Such a slot is easier to manufacture and clean than a multiple orifice configuration.
  • Complementary mating wedges 82, 84 are selectively held together by bolts 94, 96 that extend through bores 98, 100 in the wedges. Bore 98 communicates with an outer face 101 of wedge 84 and includes a land 102 against which the applicator of bolt 94 rests. Bore 98 communicates with the opposite side face 103 of applicator 58 formed by wedge 82, and bore 100 similarly has a land 104 against which the head of bolt 96 abuts.
  • a notch 106 in wedge 84 of applicator 58 seats an elastomeric seal 108 to enhance the fluid tight nature of junction 86.
  • An enclosure channel 116 is bolted to wedge 84 to form a fluid chamber 118 that extends along face 101 of wedge 84.
  • Channel 116 is secured to portion 84 by a bolt 120 that extends through a bore 122 in channel 116 and an aligned bore 124 in wedge 84.
  • Channel 116 includes an upper segment 126 that abuts tightly against face 101 of portion 84 and forms a relatively fluid tight seal therewith.
  • Middle segment 128 and lower segment 130 of the channel extend downwardly and inwardly toward face 101 in the direction of the tapering end of applicator 58.
  • Segment 130 terminates just short of face 101 in a flat face that extends parallel to face 101 and forms a narrow fluid passageway slot 132 that communicates at one end with fluid chamber 118 and at the other end forms a fluid outlet 134.
  • the segement 130 has a sharp edge at the fluid outlet 134.
  • the sharp edge has the same dimensions as sharp edge 97.
  • Fluid passageway 132 travels along face 101 at a 20 to 40, preferably 30, degree angle to liquid passageways 92 such that fluid emerging from slotted fluid outlet 134 impinges the liquid from outlets 93 at a 20 to 40, preferably 30, degree angle.
  • FIG . 5 also includes a second channel 116 attached to face 103 of wedge 82.
  • a second fluid passageway is formed along face 103 such that the impingement fluid strikes the liquid from outlets 93 at the same angle as the fluid from the first fluid channel. Hence the liquid droplets are formed by fluid striking both faces of the emerging liquid.
  • a coating liquid 72 (FIG. 3) is supplied under pressure to conduit 70 that communicates with chamber 90 such that the liquid distributes evenly across the length of the applicator.
  • the pressurized liquid is propelled through the plurality of orifices 92 (FIG. 8) and emerges as a distribution 78 of liquid (FIG. 3) that extends across the width of substrate 60.
  • Pressurized fluid 66 enters conduits 62, 64 such that each communicates with a fluid chamber 118 and the fluid is distributed through chambers 118 along the length of applicator 58 into passageways 132.
  • the fluid emerges at slots 134 to impinge against liquid distribution 78 and form droplets either at the liquid outlet or between the liquid outlet and the substrate.
  • the droplets substantially completely cover and adhere to the top surface of the substrate.
  • the droplets are formed at the liquid outlet or between the liquid outlet and the substrate will depend on the viscosity and flow rate of the coating liquid, and the impingement fluid velocity.
  • Multiple applicators may be placed sequentially along a line to provide multiple coats of the same or different liquids on the substrate. If a thick single coating is desired, the operating parameters of the applicator may be changed, for example, to increase the volume flow of liquid. If less uniformity is acceptable, the impingement fluid velocity may be reduced to decrease the liquid atomization. Larger droplets will reach the substrate and form a less uniform coating. Application of larger droplets may be preferred when saturation is desired.
  • the impingement fluid can be air.
  • the co-flowing airstream forms the liquid into droplets for deposition on a substrate.
  • the liquid flow from the outlet is in a linear distribution.
  • a linear distribution of liquid is a liquid flow that has an elongated linear width.
  • the width of the distribution is elongated in the direction that orifices 93 extend.
  • An elongated distribution is not necessarily linear (although it may be).
  • the elongated distribution has a width that extends in the direction perpendicular to the direction of flow of coating material from the outlet to the substrate, and typically is elongated in the direction that the plurality of orifices 93 extend.
  • the liquid distribution is in the form of a straight line, a variety of shapes would be suitable, such as an elongated arcuate or chevron shaped distribution. Uniformity or symmetry of the array or distribution is not required.
  • the liquid passageway 92 and liquid orifices 93 are a continuous elongated slot 282, as best seen in FIG. 9. That drawing is similar to FIG. 4, and like parts have been given like reference numerals.
  • a magnified slotted portion of the applicator is shown in the circle.
  • the liquid emerges from slot 282 as a curtain array, and is formed into droplets by air emerging from the slots defined by edges 134.
  • the edges forming the end of the slot outlet and the fluid outlets are sharp and have the dimensions of edge 97.
  • the fluid gap has a width of about 4 mils (0.004 inch or 100 ⁇ m).
  • the liquid gap is about 8 mils (0.008 inches or 200 ⁇ m).
  • the sharp edges 310, 328 thereby cooperatively define an elongated slot that serves as a liquid outlet.
  • the present invention also includes a cleaning means for removing build-up of solidified coating material on the applicator.
  • cleaning means include external wipers, internal wipers, and flushes of pressurized water or other solvent for removing build-up of solidified coating material from the applicator.
  • a flush pan of a cleaning fluid (such as water or another solvent) can also be brought into contact with the fluid and liquid outlets of the applicator to clean it.
  • a build-up of coating material on the surfaces of the applicator can also be diminished by coating the interior and/or exterior of the applicator, or at least the portions that contact the coating liquid, with a low surface energy material that reduces adhesion of materials that contact it.
  • a low surface energy material that reduces adhesion of materials that contact it.
  • materials include polytetrafluoroethylene, polycrystalline diamond and amorphous carbon coatings.
  • a suitable polycrystalline diamond coating can be obtained from Diamonex of Allentown, Pennsylvania.
  • the applicator may be coated with amorphous diamond to a thickness of 500A by a chemical vapor deposition process at 800°C (1470°F). Such a coating has the advantage of being microscale smooth, closely replicating the surface it is applied to, and is chemically bonded to the surface.
  • Modular Applicators One, of the advantages of the present invention is that it can be used to apply a uniform coating across very wide substrates, from several feet to several hundred inches wide.
  • the applicator in such instances may be quite long, unwieldy and heavy.
  • These problems can be minimized by constructing the applicator from a plurality of aligned modules that can be individually removed or replaced.
  • An example of such a module 590 is shown in FIG. 10.
  • Module 590 includes an applicator 592 having a flat top 594, a pair of side walls 596 perpendicular to top 594, and a nozzle 598 that tapers to form a pair of air slots.
  • a module attachment member 600 having a flat top face 602 and inwardly tapering faces 604, 606. Attachment member 600 slides into a complementary shaped recessed channel along a support member (not shown) to suspend applicator 592 above a substrate.
  • a plurality of modules 590 can in this manner be positioned end to end with fluid and liquid supply lines 608, 610 aligned for communication along the length of the apposed modules.
  • FIGS. 11 - 12 An embodiment of a collection device for reducing the amount of ambient mist is shown in FIGS. 11 - 12, which show an applicator 642 suspended above a moving substrate 643. A liquid inlet 644 introduces a liquid to be coated into a liquid chamber inside applicator 642.
  • Fluid conduits 645, 646 convey pressurized fluid, such as air, into applicator 642 for impinging on the liquid as it emerges from the applicator.
  • a linear distribution of liquid 647 emerges from applicator 642 along its length, and droplets are formed from the liquid, either at the outlet or between the outlet and the substrate, by the impinging fluid which also directs the liquid toward the substrate 643.
  • a collection hood is suspended over substrate 643 spaced from applicator 642 on each side along an axis of movement 648 of the substrate.
  • the hood on each side of the applicator includes an elongated tubular collector 650 with a collection slot 652 facing downwardly. Each tubular collector is oriented perpendicular to axis 648.
  • Slot 652 subtends an arc of about 45 degrees to 60 degrees below a horizontal diameter 653 of tubular collection 650.
  • a rectangular cover panel 654 extends from the upper edge of slot 652 and angles down toward substrate 643 at about a 15 degree angle. Cover panel 654 spans the width of substrate 643, and extends part of the distance to applicator 642 before terminating along a distal edge 656 that is parallel to the liquid array 647. The distal edges 656 of the two panels define an open area therebetween into which the liquid is directed at substrate 643.
  • Another rectangular panel 657 extends from a lower edge of the opening 652 and projects downwardly toward substrate 643 to provide a mist barrier.
  • An upright wall 658 closes the free ends of each tubular collector 650, and extends between the collectors 650 to form a continuous barrier along a portion of one longitudinal edge of substrate 643.
  • a similar wall 660 extends between the collectors 650, but does not close the end faces of each collector. Instead, exhaust tubes 662, 664 communicate with collectors 650 and extend away from substrate 643.
  • a negative relative pressure (such as a vacuum suction) is provided in each tube 662, 664 to withdraw a mixture of mist and impingement fluid out of the collectors, as indicated schematically by arrow 666.
  • the enclosure formed by collectors 650, panels 654, 657 and walls 658, 660 is suspended slightly above substrate 643 to permit free movement of the substrate beneath the enclosure. Suspension of the enclosure thereby creates a small separation 670 between the bottom of the enclosure and the surface of substrate 643 that would normally permit some of the mist to escape from the enclosure. Most of the mist tends to spread out along the substrate, in both directions from applicator 642, along the axis of arrow 648. The majority of the mist is directed toward separation 670 in the direction 648 of movement of the substrate because the substrate carries the mist along with it. Hence some of the mist passes under barrier 657 in the direction 648.
  • An air curtain is directed below the bottom edge of each barrier 657 to diminish the amount of mist that escapes from the enclosure underneath the edge.
  • a tubular conduit 674 is mounted across the width of substrate 643 below each collector 650 on the outside face of each panel 657.
  • the conduit 674 contains an air slot 675 that extends the length of the conduit, and communicates with an air directing member 676 that propels air downwardly at substrate 643 at an angle of about 45 degrees to the surface of the substrate.
  • Air 678 (FIG. 11) is supplied to each conduit 674 such that a curtain of air is propelled out of member 676 and forms an air curtain 680 (FIG. 12) between the bottom of the enclosure hood and the surface of the substrate to diminish the amount of mist that escapes from the enclosure.
  • FIG. 12 shows that the mist inside the hood rises to form a cloud 682 inside the enclosure.
  • Upward recirculation 683 of the mist can direct currents of mist back toward applicator 642, and lead to deposition of coating material on the undersurface of panels 654, and growth of stalactites from the panels.
  • the stalactites serve as foci from which drips of coating material drop onto the substrate to disrupt uniformity of the deposited coat. Such drops also impair the appearance of the sheet.
  • the inventors have introduced a secondary flow of air into the hood adjacent the applicator to disrupt formation of the undesirable cloud.
  • the secondary flow is shown schematically by arrows 684 in FIG. 12, and can be any external source of air directed into the hood adjacent the applicator.
  • FIG. 25 and 26 Another embodiment of the invention is an apparatus 829 (FIGS. 25 and 26) designed in accordance with the present invention.
  • a central bore 830 extends through applicator 831, and a series of spaced cylindrical passages 832 communicate with and extend downwardly from the central bore 830.
  • the size and shape of the passages 832 may be changed through the use of plugs 833 that have central passages 834.
  • the passages 834 and the plugs 833 aid the even distribution of material along the length of the apparatus.
  • the passages 834 enter the top of a central distribution chamber 835.
  • a screen 836 which is designed to be easily removed and cleaned, extends transversely across the central distribution chamber 835.
  • a tip 837 having a triangular cross-section is attached to the applicator 831, and the central distribution chamber 835 extends through the tip 837.
  • the central distribution chamber 835 extends through the tip 837.
  • Each passage 838 terminates in an orifice 821 such that a series of linearly aligned orifices 821 are present along the length of the applicator.
  • the central distribution chamber 835 may be omitted and the passages 838 or several passages 838 would be connected directly with a passage 832.
  • the tip 837 may be of metal, such as aluminum, brass or stainless steel, and may be covered with a lubricating substance or a coating that prevents the buildup of material around the orifice 821 or on the tip 837.
  • the lubricating substance coating may be Teflon (polytetrafluoroethylene) or another low surface energy coating.
  • the tip 837 may also be made of Teflon.
  • the orifices 821 may have a diameter in the range of 0.005 inch to 0.050 inch and be spaced in the range of 2 per inch to 30 per inch. A preferred diameter is in the range of 0.012 inch to 0.035 inch and a preferred spacing is in the range of 3 per inch to 24 per inch. The actual diameter and spacing may be varied depending on the product requirements and the coating material being applied.
  • a pair of side plates 840 are attached parallel to and spaced from the sides of the central section 831, covering the sides of the central section 831 and the tip 837.
  • the side plates 840 define, in cooperation with the sides of section 831 and tip 837, a fluid or air passage 841 having openings 824 adjacent the orifices 821.
  • the air passages 841 and the openings 824 may be continuous along the apparatus or may be broken into a series of openings by ridges formed in the passages 841. The ridges could be on the section 831 and tip 837 or on the inner face of plates 840.
  • Air or other fluid is supplied to the passages 841 through pipes 842.
  • a cylindrical screen 843 inside pipe 842 removes any dirt or debris from the fluid supply and aids in the even distribution of fluid along the length of the apparatus.
  • a fluid distribution chamber 844 extends the length of section 831 between the pipes 842 and the passages 841. There are openings, either continuous or discontinuous, between the pipes 842 and the chambers 844. The chambers 844 in turn communicate directly with the passages 841.
  • the chambers 844 may be filled with a porous material to assist distribution of the fluid.
  • FIG. 27 contains a material screen 836 in the distribution chamber 835 and the fluid screen 843 is in the pipe 842 as has been described.
  • FIG. 28 is a diagram of an alternative apparatus 829 which illustrates the use of external screens.
  • the screen 836' is in housing 851.
  • the coating material is pumped through pipe 852 into the interior of housing 851, and then passes outwardly through screen 836' and pipe 853 into central bore 830.
  • the screen 843' is in housing 854.
  • the air or fluid is pumped through pipe 855 into the interior of housing 854. The fluid then passes outwardly through screen 843' and through pipe 856 that carries the fluid to pipes 842.
  • FIG. 29 shows droplet formation at the liquid outlet. As the liquid emerges from outlet 821, the liquid is formed into droplets 827 at the plane of exit 829 of the liquid from the orifices or slot. Under different conditions, the droplets may be formed after the liquid exits the outlet between the outlet and the substrate.
  • the air or fluid in the fluid streams 823 may include steam or water vapor to prevent the coating material in the droplets 827 from drying out before it is placed on the substrate.
  • the present invention also includes a process for uniformly or thoroughly depositing a coating of a liquid coating material on a substrate by directing droplets of the liquid toward the substrate. Formation and propulsion of the droplets may be simultaneously achieved by directing a flow of an elongated distribution of liquid from an outlet, such as multiple orifices or a slot, toward the substrate.
  • the elongated distribution can be any shape that provides for distribution of the droplets on the substrate across a desired swath.
  • the distribution can be linear as defined herein. Sequential or staggared applicators may be used to form desired distributions.
  • a fluid is impinged against the liquid to form liquid droplets and deposit a uniform coating of the droplets on a substrate that is moving relative to the distribution.
  • paper is coated by directing an elongated distribution of a liquid toward a substrate from a coating applicator.
  • the liquid is formed into droplets by fluid emerging from slots and impinging on both faces of the liquid.
  • the slots from which the fluid emerges are preferably adjacent the liquid outlet or outlets.
  • the liquid can have a wide range of viscosities but typical coating liquids have relatively low viscosities and are liquids at room temperature.
  • the melting point of the liquid may preferably be below room temperature to reduce or prevent solidification of the liquid before it reaches the substrate.
  • the coating liquid is an aqueous liquid, such as an aqueous solution of starch, carboxymethylcellulose, polyvinyl alcohol, latex, a suspension of bacterial cellulose, or any aqueous material, solution or emulsion.
  • the aqueous liquid is dispersed from an applicator at less than 100°C (212°F), because by definition an aqueous liquid would boil above that temperature and no longer be in a liquid phase. It is not necessary for the aqueous liquid temperatures to be as high as 100°C (212°F), and they can be sprayed at temperatures less than 70°(160°F), or even at ambient temperatures (25°C - 40°C or 77°F - 104°F).
  • the aqueous liquid does not solidify before reaching the substrate, hence the aqueous process should be performed above about 0° (32°F). It may be preferable with some liquids, such as those that contain starch, to warm the liquid to 40° - 70°C (104°F - 158 °F) to prevent precipitation of the starch in the applicator.
  • the process of the present invention can also be used to deposit non-aqueous liquids on substrates. In specific examples, this process can apply slurries of particulate materials or organic liquids, such as polymeric methylene diphenyl diisocyanate (PMDI) or emulsifiable polymeric methylene diphenyl diisocyanate (EMDI).
  • PMDI polymeric methylene diphenyl diisocyanate
  • EMDI emulsifiable polymeric methylene diphenyl diisocyanate
  • the liquids can be directed through a series of orifices, elongated slots or other outlets in the applicator at low pressures.
  • Liquid pressures are typically less than 25 psi (170 kPa). Liquid pressure is directly related to the velocity with which liquid leaves the applicator, hence the liquid velocities can also be quite low, for example less than about 1 meter/second (3.28 feet/ second).
  • the droplets may have a diameter, for example, of about 100 ⁇ m or less.
  • the diameter of droplets emerging from the outlet is less than the diameter of the orifice, or less than the width of the slot.
  • the diameters of droplets emerging from an outlet having an effective diameter or width of 500 ⁇ m will be smaller than 500 ⁇ m after droplet formation.
  • the sizes of smaller droplets are difficult to measure, and although the inventors do not wish to be bound by theoretical computations or estimates, the size of many of the droplets appears to be 5 - 50 ⁇ m in diameter.
  • the droplets are not necessarily uniform in diameter, and usually have a broad distribution of diameters. Some of the droplets may exceed 100 ⁇ diameter.
  • the droplets of a particular liquid can have a range of diameters that are sufficiently small to thoroughly coat a desired swath on a substrate, if such uniformity is desired.
  • Small droplets of the present invention can selectively form a more uniform coating with less graininess, as defined below.
  • the droplets are small enough to provide a thin, uniform coat on a substrate. Coatings in the range of 0.10 - 30.0 g/m 2 can be provided on a surface of the substrate.
  • the impingement fluid include gases and liquid vapors.
  • Specific examples of impingement fluids are water vapor, steam or other types of vapor, air, oxygen, nitrogen gas or gases that may participate in catalyzing or reacting with the coating liquid.
  • the fluid need not be heated, and may be any temperature between, for example, 25°C - 100°C (77°F - 212°F), or ambient temperatures between 25°C - 40°C (77°F - 104°F), or even lower.
  • the preferred impingement fluid is air.
  • the impingement fluid and liquid should preferably be co-flowing, and the velocity of the liquid is less than the velocity of the impingement fluid. Very good droplet formation has been observed when the mass ratio of an impingement fluid to coating material is in the range of from 0.03: 1 to 7.7: 1 and most preferably in the range 0.2: 1 to 5: 1.
  • the relative velocities and flow rates of the impingement fluid and coating material can be varied over a wide range to achieve a desired mass ratio of impingement fluid to coating material that forms the liquid into droplets of a sufficiently small size to deposit a thorough or a uniformly thorough coating on the substrate. Some applications do not require uniform coatings, and these parameters need not be followed.
  • Minimal graininess is optimally illustrated by the images and grey intensity profile graphs of FIGS. 17 and 18.
  • the liquid distribution has opposing faces, and the impingement fluid is impinged against both of the faces of the distribution to form the liquid into small droplets.
  • the desired velocity of the impingement fluid varies depending on the viscosity and flow rate of the liquid. For many applications, however, the fluid is impinged against the liquid at a fluid velocity of 200 - 1100 feet/ second (60 - 335 meters/second).
  • the minimum size droplet formation occurs as the velocity of the fluid approaches sonic speeds (335 meters/second or 1100 feet/second).
  • Coating Materials One of the advantages of the present method is that it can be used to apply a wide variety of coating materials to a broad variety of substrates. Practically any aqueous or other liquid material can be coated on a substrate using the present method. Materials such as starch (ethylated and other types of starch), polyvinyl alcohol (PVA), pigmented coatings, carboxymethylcellulose (CMC), pure water, aqueous cellulose suspensions, latex and PMDI are applied to substrates such as paper and container board. The viscosity of these enumerated liquids is typically in the range of 1 - 2000 cP (2 Pa-s) at ambient temperature. The coating process is facilitated by providing material which is a liquid at ambient temperature, thereby removing the need for heating the material to lower its viscosity and permit its extrusion from an applicator.
  • coating materials include ethylated corn starch, such as that available from Cargill, Inc. of Cedar Rapids, Iowa; Penford Gum starches, such as PG200, 220, 230, 240, 250, 260, 270, 280, 290, 295, 300, 330, 360, or 380 available from Penford Products Co. of Cedar Rapids, Iowa; Airvol polyvinyl alcohol from Air Products and Chemicals, Inc. of AUentown, Pennsylvania; and clay pigments such as those that can be obtained from Englehard Corporation of Edison, New Jersey under the names Exsilon, Ultra Gloss 90, Ultra White 90, Lustra, Ultra Cote.
  • Penford Gum starches such as PG200, 220, 230, 240, 250, 260, 270, 280, 290, 295, 300, 330, 360, or 380 available from Penford Products Co. of Cedar Rapids, Iowa
  • Airvol polyvinyl alcohol from Air Products and Chemicals, Inc. of AUentown, Pennsylvania
  • the present apparatus may be used to .apply acid or caustic in an etching or cleaning operation; to treat cloth, leather or wood materials with acid or caustic, for example to treat leather with tannic acid; to etch glass with hydroflouric acid; and to distribute bleach or other chemical solutions uniformly onto washer drums, deckers, flumes, or conveyors.
  • the present method is versatile enough to coat a liquid at one or both faces of a substrate moving in many different planes.
  • a distribution of droplets 754 is directed downwardly at web 750 to deposit a coating 756 on its surface.
  • a second applicator 758 is positioned below the substrate pointing upwardly such that a distribution of droplets 760 is directed upwardly at the substrate and deposits a coating 762 on the undersurface of the paper web 750.
  • FIG. 14 An alternative embodiment is shown in FIG. 14 in which the paper web 766 is moving in a vertical plane in the direction of arrow 767 between a pair of applicators 768, 770 that are spraying each side surface of the web.
  • the applicators are positioned to spray the attenuated liquid in a generally horizontal direction on the vertically moving substrate.
  • the method of the present invention is suitable for coating many types of substrates, including cellulosic, fiber, organic and synthetic substrates.
  • cellulosic substrates include finished paper, pulp mats, linerboards, newsprint and already coated papers.
  • Organic substrates can include foods being coated with additives or spices, or plants being coated with insecticide.
  • substrates include formed non-cellulosic fiber mats, rubber, cloth, wood, leather and plastic.
  • the substrate can even be metallic, and need not be planar, for example, a transfer roller that in turn transfers the liquid to a substrate.
  • the angle at which the applicator directs the liquid toward the substrate is preferably a normal angle. Better coverage with enhanced uniformity of deposition is observed when the liquid is directed at a right angle to a flat surface being coated. Other angles are possible, especially when coating objects with irregular, non-planar surfaces.
  • Another aspect of the invention is that more than one applicator can be placed sequentially along the substrate, such that layers of coating are applied one on top of the other on a single face of the substrate.
  • a similar plurality of applicators can be placed in coating relationship to another surface of the substrate such that multiple layers are applied to both surfaces.
  • a paper web for example, can have multiple coatings applied to each of its flat faces.
  • Parallel plural liquid outlet slots can also be provided in the applicator to apply multiple coatings to the substrate.
  • the distance between the substrate and applicator can vary widely, but very thorough and uniform deposition occurs with the liquid emerging from the applicator at a distance of 0.5 - 12 inches (1.25 cm - 30 cm) from the surface of the substrate, more preferably 0.5 - 3 inches (1.25 cm - 7.5 cm).
  • the applicator should preferably be at least far enough away from the substrate to permit the liquid to form substantially entirely into droplets. This distance will vary depending on such variables as the viscosity of the liquid and the flow rate and velocities of the liquid and impingement streams. It is possible to ascertain whether the liquid has been formed sufficiently into droplets by determining the thoroughness and uniformity of deposition on the substrate, as discussed in connection with FIGS. 17 - 24 and 36 - 50 below.
  • Droplet formation uses a fluid stream, such as a curtain of air, to impinge upon a co-flowing liquid to form droplets of a diameter or width that is smaller than an orifice or slot from which the liquid emerged.
  • a fluid stream such as a curtain of air
  • the co-flowing impingement fluid stream directs the droplets downwardly toward the substrate and also creates a cross-flowing turbulence in the region below the applicator outlet that results in a more uniform deposition of the droplets onto the substrate.
  • Droplets can be formed at the outlet or between the outlet and the substrate.
  • the impingement velocity at which atomization (droplet formation) at the outlet occurs depends on the viscosity of the liquid. Coating materials with greater viscosities (e.g. PMDI) require higher impingement velocities for atomization than low viscosity liquids such as water.
  • the fluid may include an additive that modifies the liquid. Humidified air, for example, provides moisture that catalyzes the polymerization of PMDI during coating. When using a catalyst, such as moist air, it is preferable to prevent initiation of polymerization at or near the outlet. In alternative embodiments, moisture may be harmful to the coating liquid, in which case the impingement fluid is used to purge moist air from the applicator. Purging is achieved by introducing a dry gas, such as nitrogen gas, through the applicator and outlets.
  • a dry gas such as nitrogen gas
  • EXAMPLE I The basic features of this multiple orifice or slot design, are a slow moving liquid stream located between two fast, co-flowing fluid, preferably air, streams.
  • the fast moving air stream impinges the liquid immediately as it emerges from the outlet and changes the liquid stream either gradually or instantaneously into droplets having a smaller dimension than its initial characteristic dimension (orifice diameter or slot width).
  • the liquid issues from either a straight slot or a series of closely spaced holes arranged in a linear line, and is directed linearly toward the substrate.
  • the air issues from two gaps located on either side of and immediately adjacent the liquid slot or line of holes.
  • the typical air or fluid gap dimension (the width of the gap through which the air or fluid emerges) is about 250 ⁇ m (0.010 inches).
  • One applicator configuration used was one with 0.024 inch equivalent diameter holes (24 mils or 610 ⁇ m) spaced 18 per inch (i.e. center-to-center spacing of 0.056 inches which is 56 mils or 1.4 mm) and a total length of 4 inches (10 cm).
  • the air gap for this applicator was varied from 0.005 to 0.015 inches (5 mils to 15 mils or 125 ⁇ m to 375 ⁇ m).
  • a second configuration used a similar but longer applicator. This second applicator was 12 inches (30 cm) long with 0.020 inch equivalent diameter holes (20 mils or 0.5 mm) spaced 20 per inch (787 per meter).
  • Another set of applicators substituted a single slot for the plurality of holes such that the liquid emerged from the applicator as a continuous curtain array.
  • the liquid velocity refers to the velocity of the liquid immediately before it exits from the holes or slot and comes in contact with the air stream or streams. This velocity is typically less than 3 ft/s (1 m/s).
  • the air velocity is the velocity of the air as it exits the air gaps immediately prior to the zone of initial air/liquid impingement. The air velocity ranges from 200 ft/s to 1100 ft/s (61 m/s to 335 m/s or Mach number of 0.2 to 1.0), where 1100 feet/second is sonic velocity.
  • the fluid gap is the dimension of the slot formed between the fluid plate and the main body of the applicator which contains the liquid passages and orifices.
  • the slot width of the air gap is between 5 mils and 20 mils (125 ⁇ m - 500 ⁇ m), and extends about 0.5 inches (1.25 cm) beyond the line of liquid orifices or liquid slot on both ends.
  • the outlet-to-paper separation distance was typically between 1 inch and 10 inches (2.5 cm to 25 cm).
  • the orientation of the applicator is defined by the angle between the plane in which liquid flows out of the line of liquid orifices in the applicator, and the plane of travel of the paper being coated. Typically the applicator is oriented such that the liquid is approximately normal to the plane of paper travel. Some tests were conducted with the applicator rotated such that the plane of the liquid array was about 45° to the plane of travel of the paper.
  • the coating formulation can vary widely in concentration, temperature, constituents, and batches. Typical formulations used with the multiple orifice applicator have been Cellulon bacterial cellulose with CMC at 0.5% to 1.5% concentration, starch (PG290) at 10% concentration and 120°F (50° C), and PMDI at 100%. Several other constituents and several variations in concentration and batch have also been tried.
  • the air plate setback is the distance between the end of the air plate and the end of the liquid orifices. Typically the air plate sets back from the liquid orifice tip about 10 to 15 mils (0.010 to 0.015 inches; 250 ⁇ m to 380 ⁇ m).
  • the coating formulation for a 0.8% Cellulon bacterial cellulose/0.2% CMC mixture with 1100 ppm sorbic acid in water was homogenized in the Gaulin Homogenizer (from APV Gaulin, Inc. of Hilversum, Holland) for three passes through the cell disruptor (CD) valve, followed by one pass through a 150 ⁇ m filter and one pass through a 125 ⁇ m filter.
  • the applicator orientation was normal to the direction of travel of the paper and the air plate setback was constant at 15 mils (0.015 inches or 380 ⁇ m).
  • the liquid velocity for these trials was selected based on coating application rate. Two levels of application were used, 3 lbm/ton/side and 5 lbm/ton/side. These coverages correspond approximately to 0.11 g/m 2 /side and 0.19 g/m 2 /side for a 50 lbm/3300 sq.ft. sheet. Differences in liquid hole size and number per inch result in differences in actual liquid velocity for two applicators at the same level of coverage.
  • the nominal or equivalent air pressure was varied from 5 psig (35 kPa) to 30 psig (210 kPa) in 5 psig (35 kPa) increments.
  • the air gap for various runs was set at one of three values: 5, 10, or 15 mils (125, 250 or 380 ⁇ m).
  • Trials were conducted with a outlet-to-paper separation distance of 3 inches (7.5 cm), but a few runs were conducted with 1 inch 2.5 cm) and 10 inch (25 cm) distances. The separation distance is measured from the tip of the applicator, where liquid emerges from the orifice or slot to the surface of the substrate. A distance of 3 inches 7.5 cm) was found to produce less mist than a 10 inch (25 cm) distance, while unexpectedly retaining uniformity of coating application.
  • An exemplary range of variables is expressed in Table I.
  • the fluid preparation and handling system consisted of a conical storage tub, a Moyno pump, a wire mesh filter, a spray collection tub, and a return pump. All tubing and fittings between the filter and the applicator were of food- grade quality to ensure freedom from orifice pluggage.
  • a sled system was constructed to move single sheets of paper under the applicator at high speed.
  • the sled consisted of a frame and a set of rails along which a pair of runners traveled. A platen to hold the paper sheet was attached to the runners, and bungee cords were used to propel the platen/runner combination along the rails.
  • the applicator was suspended from a framework above the rails at the location where the platen/sled reached its maximum velocity. High-speed video data was used to determine that this velocity was approximately 1800 ft/min. After passing under the applicator location the platen/runner combination was slowed and stopped with an arresting wire.
  • the paper sheets were removed after one exposure to the coating spray, thus simulating the exposure that would be obtained on a paper machine at a similar speed.
  • the paper samples were allowed to dry without further treatment and were stored in loose bundles.
  • the paper used was a sized printing grade, although some unsized newsprint was also used. Visual comparison of these two types of sheets under the same spray conditions showed no apparent difference.
  • the uniformity of the coating thickness is a measure of coating uniformity.
  • Most substrates are not smooth and flat on the scale of nominal coating thickness (-0.5 to 10 ⁇ m). It is therefore more appropriate to measure the quantity of dry coating applied per unit area instead of coating thickness.
  • the selected units for coat weight are grams per square meter (g/m 2 ). Because a continuous coating is usually sought, the scale over which the coat weight is measured is small, less than 1 mm by 1 mm. The variation in coat weight per unit area on this small scale is a measure of the coating uniformity. Under most conditions, Cellulon bacterial cellulose and starch coatings applied to papers are transparent.
  • a fluorescent dye was added to the Cellulon bacterial cellulose or CMC coating mixtures used in these trials. Under ultraviolet light this rendered the coating distribution on the paper samples visible. The dye is distributed in the liquid phase of the coating, hence it is actually the uniformity of the distribution of the liquid phase that is visible. Although this distribution may not correspond exactly to the distribution of the coating solids, it is an adequate approximation for these studies.
  • FIGS. 17 - 24 were generated from test sheets obtained during starch runs.
  • a starch run consisted of spraying starch under prescribed conditions onto a sheet of paper attached to a sled which moved under the applicator. The conditions for these runs is given in Table II. Insert Table II The coated sheet was allowed to air dry.
  • Starch is a clear coating so either a fluorescent dye or a staining agent must be used to make the coating visible.
  • an iodine stain was used to produce a dark brown color wherever starch was applied. The stain is darker where there is more starch, so the intensity of the color can be used to judge the coat weight uniformity of the starch.
  • the color intensity of the test sheets was digitized using a color scanner. This device measures the darkness or intensity at each location in the stained area of the test sheet using very small sample areas. The size of the sample areas is specified in terms of the number of dots or pixels per inch. In this case, 75 dots per inch (dpi) was used, resulting in a sampled area size of about 0.33 mm square. For a typical test sheet, the stained area was about 100 mm x 100 mm, so a total of about 90,000 intensity samples were taken per test sheet. The intensity range was broken into 256 levels of grey with a value of 0 (zero) corresponding to black and a value of 255 corresponding to white. All other levels of grey are in between these two extremes.
  • the images shown in FIGS. 17A - 18A are printouts of the scanned test sheets using a Macintosh computer and a LaserWriter printer.
  • the graphs of FIGS. 17 - 24 were produced using one of many available image analysis programs for grey-intensity images.
  • the program was a public domain program called "Image 1.22y” that resulted from work carried out for the National Institutes of Health.
  • Two types of graphs are shown, both of which are grey intensity profile graphs.
  • the bottom graph is a line profile, which represents the variation in the grey intensity along a line drawn on the image. All the lines used here were drawn near the mid-point of the stained area in the cross direction, i.e. the line is drawn perpendicular to the direction of motion of the test sheet when it was coated.
  • the top graph is also a grey intensity profile, but represents the "column average” values for grey intensity. For this plot, the average of the grey intensities along a column of sampled areas in the machine direction was taken. The variation of these values in the cross direction was then plotted. This type of graph eliminates some of the point-to-point variations, but shows any streakiness in the coat weight variations.
  • the aspect of these graphs that most indicates uniformity of coating is the low amplitude variation of the grey intensity columns and lines.
  • the column intensity profile of these graphs varies no more than about 10 units of intensity, while the single line intensity varies no more than about 30 - 50 units of intensity. Consistent values below 200 on each graph indicate completeness of coverage; the farther below 200 the line remains, the more likely there will be no discontinuities of coverage on the sheet.
  • the lines in FIGS. 17 and 18 are at about 80 - 150, preferably below 125, and indicate a high probability of thorough coverage across a desired swath of substrate being coated.
  • Graininess is a non-uniformity on the scale of approximately 1 mm. Streaks are generally aligned with the direction of paper travel. The whole paper sample is coated, but the coating is noticeably thinner or lighter in some areas than in others. The thin or light areas typically are approximately 1 cm wide and may be continuous in length, though streaks of 3 or 4 inches in length are more common. As a reference for the streak duration, a three inch streak in a paper sample traveling 1800 ft/min (550 m/min) corresponds to non-uniformity for 83 milliseconds.
  • FIG. 15 is a set of twelve photographs of samples for both 3 and 5 lbm/ton/side application rates (approximately 0.11 to 0.19 g/m 2 ) and for nominally 5 and 30 psig (35 kPa - 210 kPa) air pressures at an air gap of 10 mils (250 ⁇ m) using the 4-inch (10 cm) multiple orifice applicator with 3 inch (7.5 cm) outlet-to- paper separation.
  • These photographs compare coating uniformity for the given range of application rate and air pressure. From the comparison in FIG. 15 it appears that the coating application rate of the Cellulon bacterial cellulose/CMC affects the density of the image but not the general character of the coating uniformity either in terms of graininess or streakiness. Increased air pressure significantly reduces graininess and somewhat reduces streakiness for this set of trials with this given coating material.
  • FIG. 16 Shown in FIG. 16 is a set of photographs of samples for 5 mil and 15 mil (125 ⁇ m and 375 ⁇ m) air gaps at 5 lbm/ton/side (0.19 g/m 2 ) application rate and for 5 to 30 psig (35 kPa to 210 kPa) air pressure. From the comparison in FIG. 16 it appears that the air gap width at constant pressure only modestly affects coating uniformity except at the lowest air pressure. Increased air pressure significantly reduces graininess and somewhat reduces streakiness.
  • the liquid passage length is selected which results in a relatively larger pressure drop along the flow path, thus providing uniformity of liquid flow from one end to another and avoiding streakiness in particular applications where streaks are not desired.
  • Applicator pressures above 21 kPa (3 psi) appear to be adequate for many coating materials tested so far.
  • each new material or liquid flow condition is started with relatively low air pressure, approximately 28 kPa (4 psi).
  • the coating pattern is observed for graininess and the air pressure is increased until graininess is eliminated, if graininess is not desired. So far, air pressures less than 104 kPa (15 psi) have been sufficient to reduce graininess.
  • FIGS. 17 and 18 Desireable attributes for some applications are illustrated by FIGS. 17 and 18.
  • the single line grey intensity profile FIG. 17C is always below 200, demonstrating no discontinuities in the coating made with a conventional gate roll.
  • a comparable single line density graph in FIG. 18C is similarly always below 200 and has no coating discontinuities.
  • a low amplitude of variation of the single line density graph corresponds visually to a low level of graininess.
  • a high amplitude reflects excessive graininess.
  • Variation from baseline of the column density graph is associated with streakiness of the coating.
  • FIG. 19, for example, shows an undulating column density line. Displacement of the graph away from 200 toward 80 reflects the amount of coating on the substrate.
  • process parameters may be assessed and selected for a wide variety of materials by determining their column average and single line densities. In a general sense, higher liquid flows produce less streaky coatings, higher air flows produce a less grainy distribution, and higher coating liquid pressure produces less streaky coatings.
  • the apparent viscosity, ⁇ can be related to the Brookfield viscosity at 100 RPM, ⁇ B by the expression:
  • the target value for pressure drop for many applications is between 13,000 Pa and 250,000 Pa depending on applicator size and expected flow range.
  • Sharp edges such as edges 95, 97, may have a radius of less than 0.025 inch or be truncated to a flat surface perpendicular to the liquid passage of a width of less than 0.050 inch. Sharp edges can diminish build-up of coating material at or around the outlet for the coating material and provide a uniform coating of material on the substrate.
  • the present invention can be used to apply bacterial cellulose (cellulose produced by bacteria) to paper webs.
  • bacterial cellulose cellulose produced by bacteria
  • a suitable bacterial cellulose is disclosed in
  • a preferred concentration would be in the range of 0.25% to 1.3%. All concentrations are on a weight basis.
  • the process and apparatus of the present invention can also be used to enhance the strength of corrugated board packaging materials.
  • This strength enhancement is achieved by applying relatively low amounts of selected isocyanate compounds to the corrugated packaging board.
  • One suitable isocyanate resin compound is polymeric methylene diphenyl diisocyanate (PMDI).
  • PMDI polymeric methylene diphenyl diisocyanate
  • EMDI emulsifiable polymeric methylene diphenyl diisocyanate
  • These chemical compounds in liquid form, or in the form of an emulsion in the case of EMDI may be sprayed onto a fluted containerboard medium (over a selected width) thereby coating all surfaces of the fluted medium.
  • the short column or top-to-bottom stacking strength improvement of the container will approximate 33 % .
  • the EMDI cures more quickly, needing only two days to cure. If the application is 10% by weight of these materials, strength is improved approximately 40%. It is believed that strength enhancement will occur as the isocyanate resin compound is added in an amount within a range of from 0.5 % - 50% by weight of the medium.
  • Suitable chemical compounds that may be utilized to provide a stiffer fluted medium are various acrylics, polyvinyl acetates/alcohols, various latexes, styrene-maleic anhydride, epoxy resins, and others.
  • EXAMPLE V This Example concerns designing the liquid flow passage in the applicator to obtain uniform liquid distribution along the length of the applicator. This design keeps the flow velocity low so that both the dynamic head and the friction losses are small compared to the pressure drop across the exit slot or orifices.
  • the design shown in FIG. 30 places a series of holes 780 and a target plate 782 within the liquid passage above the orifice inlets 784. This series of holes and target plate separate the liquid passage into two sections.
  • the "upper” section 786 is the passage intended for distributing the liquid along the entire length of the applicator.
  • the “lower” section 788 is intended to distribute the liquid uniformly to the inlet of the slot or orifices.
  • the size and number of holes 780 is selected to avoid pluggage and to present a total flow area equal to or less than the slot or multiple orifice area.
  • the series of holes represent a significant resistance to flow and aids in uniform distribution of liquid along the length of the applicator. The pressure drop across the slot or multiple orifices will then only have to distribute liquid uniformly over the dimension of the separation of the holes.
  • the target plate 782 is preferably located a short distance below the series of holes at a distance approximately equal to the hole diameter. Its purpose is to dissipate the dynamic head of the liquid and redirect it away from the. slot or multiple orifice inlet.
  • EXAMPLE VI Another embodiment of the applicator is shown in FIG. 31, and includes a manifold body 790 and two fluid plates 792.
  • a removable, triangular cross-section tip 794 is held in place between portions 790, 792.
  • a central, tubular manifold chamber 796 extends the length of top portion 790 and distributes coating material through a passageway 798 to a cross passage 800 in tip 794, and eventually out of a liquid outlet 801 which may be either a plurality of linearly aligned liquid orifices or a narrow liquid outlet slot.
  • a pair of longitudinally extending tubular fluid manifold chambers 802, 804 extend parallel to chamber 796 and introduce fluid into passageways 806, 808 that communicate with passageways 810, 812 and provide an impingement fluid.
  • Tip 806 may be selectively removed from the applicator by separating portions 790, 792. The tip may be replaced when it is worn or when a different dimension outlet orifice or slot 801 is desired.
  • FIGS. 32 Another embodiment of the invention is shown in FIGS. 32. It is a four piece unit, similar to the apparatus shown in FIG. 5.
  • the central liquid manifold is formed from a pair of elements 900 and 901. The elements are held together by a bolt 902. The faces 903 and 904 of the elements 900 and 901 fit firmly together to lock the elements in place.
  • the liquid supply passage 905 is formed only in element 900.
  • the passage communicates with the liquid supply chamber 906 formed in both elements 900 and 901.
  • a passage 907 connects chamber 906 with liquid chamber 908.
  • a liquid passage 909 extends between chamber 908 and liquid outlet 910. If liquid outlet 910 is a slot then the edges 911 and 912 which form the edges of the slot are sharp edges.
  • liquid outlet 910 is a series of orifices formed in both faces of elements 900 and 901 then the apex 913 formed by the two elements is a sharp edge.
  • the passages 907 and 909 and the outlet 910 need not be formed in both elements but can be formed only in the face of one of the elements 900 and 901.
  • the edge 911 or 912 of the other element will be a sharp edge. In the case of a slot both edges 911 and 912 will be sharp.
  • the fluid passage plates 914 are the same.
  • the plate has a face 915 that is bolted to the side face 916 of the elements 900 and 901.
  • the fluid supply pipe 917 is bolted on the upper end of plate 914 and communicates with fluid chamber 918 through passage 919.
  • a fluid passage 920 extends between the chamber 919 and the fluid outlet 921.
  • the edges 922 of the plate 914 which form the outlet are sharp edges.
  • the number and placement of the passages will depend on the fluid being used. The purpose of the placement is to maintain a constant or equal pressure drop and velocity along the entire length of the fluid outlet.
  • FIG. 33 shows a similar apparatus and like reference numerals are used.
  • the liquid chamber can be in either plate.
  • FIGS. 34 and 35 illustrate a cleaning device that may be used with the apparatus if a liquid slot is used. It is made of a soft material and has an optional arm 930 that fits within the liquid slot and arms 931 and 932 that fit within the fluid slots. Outer section 933 extends along the outside of the apparatus. It is used in conjuction with a cleaning pan during a cleaning cycle. It is pulled across the apparatus and, in conjunction with cleaning fluid, removes particles and debris from the passages and the outside of the apparatus.
  • EXAMPLE IX The purpose of this example is to determine whether sharp edges had any effect on the uniformity of the coating.
  • Four different liquid outlets were used. Each was a slot outlet. The edges of the liquid outlets were truncated and the width of the edges were 0.008", 0.020", 0.050" and 0.080". Diagrams of these applicators are in FIGS. 38 - 41, respectively.
  • the samples were dipped in dilute iodine solution to stain the starch.
  • a 3" by 3" stained area was scanned at 300 dots per inch on a flatbed scanner and the data stored for image analysis.
  • the image analysis was performed using standard Matlab routines. Before analysis, standard routines were used to cancel the effects of uneven lighting, paper formation and long wavelength features unrelated to the spray process.
  • FIGS. 42 - 45 The gate roll is shown in FIG. 36, the conventional air atomizer nozzle in FIG. 37, two- sided impingement with a 0.008" flat liquid outlet slot edge in FIG. 42, two-sided impingement with a 0.020" flat liquid outlet slot edge in FIG. 43, two-sided impingement with a 0.050" flat liquid outlet slot edge in FIG. 44 and two-sided impingement with a 0.080" flat liquid outlet slot edge in FIG. 45.
  • the photographs show many differences in the spray pattern between the air atomizer nozzles and two-sided impingement with sharp edges
  • the air atomizer nozzles have many large droplets. The pattern is uneven.
  • the images were examined for gray scale uniformity to access the overall uniformity of coverage without regard to spatial information such as droplet size distributions and pattern.
  • the analysis presents the coverage uniformity as a single number.
  • the results are shown in FIG. 46.
  • the photographs demonstrate better uniformity using two-sided impingement with sharp edges and demonstrate good uniformity in relation to the gate roll.
  • Image analysis routines were used to study feature distributions of the samples. Following image flattening and eroding, the digitized images were density threshholded and analyzed to examine the size, frequency and density of features on the sheet. Histograms of feature frequency by feature were generated for each sample.
  • the histograms closely fit the Weibull probability distribution.
  • the Weibull distribution is a two-parameter family of distributions; those distributions being the shape of the parameter ⁇ and the scale parameter ⁇ .
  • the Weibull probability density of a variable x (size) is given by:
  • the graphs show that edge sharpness has a definite influence on the uniformity of the coating on the substrate and is near that of a gate roll.
  • the air atomizer nozzles which showed favorable uniformity in the gray scale tests, did not show good uniformity in the cumulative fraction test.
  • FIGS. 48 - 51 are diagrams of the one sided impingement apparatus.
  • the liquid outlet edges are the same as in FIGS. 38 - 41 respectively.
  • FIGS. 52 - 55 Photographs, which are at two times magnification, are FIGS. 52 - 55.
  • FIG. 52 is one sided impingement with a 0.008" flat liquid outlet slot edge
  • FIG. 53 is one sided impingement with a 0.020" flat liquid outlet slot edge
  • FIG. 54 is one sided impingement with a 0.050" flat liquid outlet slot edge
  • FIG. 55 is one sided impingment with 0.080" flat liquid outlet edge.
  • the images were examined for gray scale uniformity to access the overall uniformity of coverage without regard to spatial information such as droplet size distributions and pattern.
  • the analysis presents the coverage uniformity as a single number. The results are shown in FIG. 56.
  • FIG. 57 is the coverage using an applicator having two-sided impingement.
  • FIG. 58 is the coverage using an applicator having one-sided impingement.
  • the cumulative fraction tests for one-sided and two sided impingement indicate that in two sided impingement that there is good predictability and good uniformity with narrow edges but less predictability and less uniformity with the

Abstract

Cet applicateur (58) dirige le flux de liquide (78) vers un substrat (60) et produit des gouttelettes qui se déposent uniformément sur le substrat (60). L'applicateur (58) comporte une sortie de liquide qui envoie un flux oblong de liquide en direction du substrat (60), pendant qu'un fluide incident est propulsé contre le liquide (78) au travers d'une fente adjacente pour fluide incident. Le fluide incident transforme le flux de liquide qu'il vient rencontrer en fines gouttelettes qui se déposent uniformément sur le substrat (60). Cet applicateur est capable de recouvrir très uniformément des substrats (60) et de produire des couches moins filandreuses et moins grenues que dans le cas des applicateurs à pulvérisation par gicleur. Cet applicateur (58) autorise une vaste gamme de vitesses d'application pour le dépôt des liquides en couches et permet d'appliquer les couches sur une grande variété de substrats (60).
PCT/US1994/009790 1993-09-02 1994-08-29 Applicateur par pulverisation de couche uniforme sur substrats WO1995006522A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU77177/94A AU7717794A (en) 1993-09-02 1994-08-29 Spray applicator for coating substrates uniformly

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US11727293A 1993-09-02 1993-09-02
US11642493A 1993-09-02 1993-09-02
US117,272 1993-09-02
US116,424 1993-09-02

Publications (1)

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WO1995006522A1 true WO1995006522A1 (fr) 1995-03-09

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WO (1) WO1995006522A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0827783A1 (fr) * 1996-02-21 1998-03-11 Matsushita Electric Industrial Co., Ltd. Buse d'application de liquide, son procede de fabrication, methode d'application d'un liquide, dispositif d'application d'un liquide et procede de fabrication d'un tube a rayons cathodiques
DE19726890A1 (de) * 1997-06-25 1999-01-28 Kampf Gmbh & Co Maschf Sprühdose und Sprühsystem zum Aufsprühen von Flüssigkeit auf eine Materialbahn
WO2002072952A1 (fr) 2001-03-13 2002-09-19 Metso Paper, Inc. Procede de couchage d'une bande de papier ou de carton et sorte de papier couche
EP1314363A1 (fr) * 2000-08-31 2003-05-28 Japan Tobacco Inc. Machine de fabrication de filtre
EP1862592A2 (fr) * 1999-01-18 2007-12-05 Metso Paper, Inc. Procédé de pose de revêtement par pulvérisation et revêtement par pulvérisation
WO2014178841A1 (fr) * 2013-04-30 2014-11-06 Armstrong World Industries, Inc. Système et procédé d'humidification d'un système permettant d'appliquer un revêtement sur une pièce de travail
US9078947B2 (en) 2013-03-15 2015-07-14 Kimberly-Clark Worldwide, Inc. Composition for forming a porous absorbent structure
US10556246B2 (en) 2012-03-28 2020-02-11 Gf Corporation Liquid ejecting device and method of liquid ejection
CN113578618A (zh) * 2021-07-02 2021-11-02 泰兴市中亚烘干设备制造有限公司 一种特氟龙喷涂烘干机用滴液收集回收装置及回收方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991018682A1 (fr) * 1990-05-30 1991-12-12 Weyerhaeuser Company Applicateur servant a diriger des materiaux de revetement sur un substrat
WO1992012803A1 (fr) * 1991-01-24 1992-08-06 Weyerhaeuser Company Procede permettant de diriger un ecoulement allonge de materiaux de revetement, vers un substrat

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991018682A1 (fr) * 1990-05-30 1991-12-12 Weyerhaeuser Company Applicateur servant a diriger des materiaux de revetement sur un substrat
WO1992012803A1 (fr) * 1991-01-24 1992-08-06 Weyerhaeuser Company Procede permettant de diriger un ecoulement allonge de materiaux de revetement, vers un substrat

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0827783A4 (fr) * 1996-02-21 2000-12-06 Matsushita Electric Ind Co Ltd Buse d'application de liquide, son procede de fabrication, methode d'application d'un liquide, dispositif d'application d'un liquide et procede de fabrication d'un tube a rayons cathodiques
EP0827783A1 (fr) * 1996-02-21 1998-03-11 Matsushita Electric Industrial Co., Ltd. Buse d'application de liquide, son procede de fabrication, methode d'application d'un liquide, dispositif d'application d'un liquide et procede de fabrication d'un tube a rayons cathodiques
DE19726890A1 (de) * 1997-06-25 1999-01-28 Kampf Gmbh & Co Maschf Sprühdose und Sprühsystem zum Aufsprühen von Flüssigkeit auf eine Materialbahn
DE19726890B4 (de) * 1997-06-25 2007-11-15 Kampf Gmbh & Co Maschinenfabrik Sprühdüse und Sprühsystem zum Aufsprühen von Flüssigkeit auf eine Materialbahn
EP1862592A2 (fr) * 1999-01-18 2007-12-05 Metso Paper, Inc. Procédé de pose de revêtement par pulvérisation et revêtement par pulvérisation
EP1862592A3 (fr) * 1999-01-18 2008-06-11 Metso Paper, Inc. Procédé de pose de revêtement par pulvérisation et revêtement par pulvérisation
EP1314363A4 (fr) * 2000-08-31 2008-07-09 Japan Tobacco Inc Machine de fabrication de filtre
EP1314363A1 (fr) * 2000-08-31 2003-05-28 Japan Tobacco Inc. Machine de fabrication de filtre
US7390557B2 (en) 2001-03-13 2008-06-24 Metso Paper, Inc. Method for coating a web of paper or paperboard and a coated paper grade
WO2002072952A1 (fr) 2001-03-13 2002-09-19 Metso Paper, Inc. Procede de couchage d'une bande de papier ou de carton et sorte de papier couche
US10556246B2 (en) 2012-03-28 2020-02-11 Gf Corporation Liquid ejecting device and method of liquid ejection
US9078947B2 (en) 2013-03-15 2015-07-14 Kimberly-Clark Worldwide, Inc. Composition for forming a porous absorbent structure
WO2014178841A1 (fr) * 2013-04-30 2014-11-06 Armstrong World Industries, Inc. Système et procédé d'humidification d'un système permettant d'appliquer un revêtement sur une pièce de travail
CN113578618A (zh) * 2021-07-02 2021-11-02 泰兴市中亚烘干设备制造有限公司 一种特氟龙喷涂烘干机用滴液收集回收装置及回收方法

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