MXPA00005635A - Curtain coater for fluid binder application - Google Patents

Abstract

A binder applicator (10) for applying binder to a moving substrate includes a distribution pipe (12) extending transverse to the direction of movement of the substrate, with the distribution pipe (12) having a bottom (30) provided with a discharge opening (32). A distributor channel (14) receives liquid binder from the discharge opening (32) and directs the liquid binder upward. A horizontal reservoir (48) receives the liquid binder material from the distributor channel (14), and a weir meters the discharge of the binder from the horizontal reservoir (48) to form a thin horizontal flow of liquid binder material. A curved surface (62) receives the thin flow of binder material and gradually changes the flow path to a substantially vertical thin flow of binder material for discharge onto the moving substrate.

Description

COATING APPLICATOR FLUID BINDING CURTAIN TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION This invention relates to the application of liquid binder material to substrates, such as fibrous nonwoven web material, traveling on a conveyor that passes through a binder application station. More particularly, the invention relates to an apparatus for presenting a very thin but uniform flow of liquid binder material for application on a substrate, to form a bonded fibrous nonwoven web. An example of a nonwoven web that can be made using the binder applicator of the invention is a wet process mat suitable for use as a tile mat. BACKGROUND OF THE INVENTION The fibrous web material, both as a woven and a non-woven matrix, has many uses, but is particularly useful as reinforcement for various products. These webs are also useful for their absorbent properties. The fibrous web material can be made of mineral fibers, such as glass fibers or synthetic or organic fibers, such as polyester fibers or cellulose fibers. Typically, these fibrous webs are held together or bound together by the application of an organic binder material. Examples of organic binders include urea formaldehyde binders, starch-based binders and latex binders. One method of binder application is the use of a curtain coating applicator that uses a dam or weir to form a thin water fall or curtain of liquid binder material, directed over the fibrous web. The curtain of free fall liquid extends transversely through the path of travel of the moving frame. An example of this curtain coating applicator is the U.S. patent. No. 4,427,722 granted to Keller. After application of the binder, the fibrous web is usually passed through an oven where the binder material is dried and cured. In the interest of reducing manufacturing costs of fibrous web material, while still maintaining the desired strength and flexibility attributes for these webs, weft manufacturers have attempted to reduce the amount of binder material applied to webs. For this purpose, the circulating liquid binder curtain coming from a curtain coating applicator is restricted to an increasingly thinner flow. Unfortunately, thin streams of liquid binder material can be more easily disrupted by several different factors, including the presence of undissolved solids in the liquid binder material and foam or air bubbles in the solution. Any interruption of the curtain of liquid material causes defects in the fibrous web product. The patent of the U.S.A. No. 3,205,089 issued to Kinzelman, discloses a liquid coating applicator having a fluid channel forming a tray supplied with binder fluid through a long pipe having binder outlet holes. The liquid binder circulates upwardly through the tray and laterally through the rather short surface of a weir. Then, the liquid rotates abruptly 90 degrees and circulates downward on an inclined surface before falling on the fibrous web. To avoid turbulence in the liquid surface of the upper part of the tray, a diffuser separates the lower tray region from the upper tray region. Despite these advances, there are still problems in supplying these liquid curtains while avoiding interruptions in the application of liquid material to the substrate. It would be advantageous if a liquid curtain coating applicator could be developed which provides an even more uniform flow of coating material than previously available.

COMPENDIUM OF THE INVENTION The above objectives, as well as others not specifically listed, are achieved by a binder applicator to a substrate in motion, wherein the binder applicator includes a distribution pipe that is obtained transverse to the direction of movement of the substrate, with the distribution pipe having a bottom that is provided with a discharge opening. A distributor channel receives liquid binder from the discharge opening and directs the liquid binder in ascending fashion. A horizontal reservoir receives the liquid binder material from the distributor channel and a weir doses the discharge of the binder from the horizontal reservoir to form a thin horizontal liquid binder material stream. A curved surface receives the thin flow of binder material and gradually changes the flow path to a flow of substantially vertical thin binder material for discharge onto the moving substrate. In another embodiment of the invention, the binder applicator includes a distribution pipe that extends transverse to the direction of movement of the substrate. With the distribution pipe having a bottom that is provided with a plurality of discharge orifices and having an upper part. A dispensing channel for receiving liquid binder from discharge orifices and for directing the liquid binder upwards, a horizontal reservoir for receiving the liquid binder material from the distributor channel, and a weir for dosing the binder discharge from the horizontal reservoir are also included. to form a flow of thin and horizontal liquid binder material. A curved surface receives the thin flow of binder material and gradually changes the flow path to a substantially vertical and thin flow path of binder material for discharge onto the moving substrate. In another embodiment of the invention, a method for applying binder to a substrate includes moving the substrate over the machine direction, and discharging liquid binder from the bottom of a distribution pipe extending transverse to the direction of movement of the substrate. The liquid binder from the discharge orifice is received from the discharge orifice and directs upwardly through a distributor channel. The binder material is received from the distributor channel in a horizontal reservoir and the discharge of the binder is dosed from the horizontal reservoir with a weir, to form a flow of thin horizontal liquid binder material. The flow path of the binder material is gradually changed with a curved surface from a thin horizontal flow to a thin vertical stream of binder material and the binder material is discharged onto the moving substrate. Various objects and advantages of the invention will be apparent to those with skill in the art, from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic cross-sectional elevation view of a liquid binder applicator of the invention. - Figure 2 is a schematic elevational front view of the liquid binder applicator of Figure 1. Figure 3 is a schematic elevation view of the baffle plate at the inlet of the binder applicator shown in Figures 1 and 2. Figure 4 is a schematic cross-sectional elevation view of another embodiment of the liquid binder applicator of the invention. DETAILED DESCRIPTION AND PREFERRED MODALITIES OF THE INVENTION The description and drawings illustrate a process for applying a solution of liquid binder to a moving substrate consisting of glass fibers. It will be understood that the substrate may also consist of different mineral fibers, such as basalt fibers or ceramic fibers as well as organic and synthetic fibers such as polyester fibers, cellulose fibers or nylon fibers. Further, although the invention is described as applicable to a binder in a wet process mat, it will be understood that the binder applicator may be employed during the manufacture of other substrates such as continuous filament mats. The invention is suitable for any water-based binder. As illustrated in Figures 1 and 2, the liquid binder applicator is generally indicated at 10. The applicator is constituted by a distribution pipe 12 and a distributor channel 14. The pipe extends transversely on a conveyor 16 traveling in a machine direction, indicated by the arrow 18. On the conveyor 16, a substrate travels in the form of a non-woven web 20 of glass fibers. Typically, this screen 16 contains approximately 50 percent water. The applicator deposits liquid binder material on the non-woven web 20 in the form of a stable, uniform liquid curtain 22, to form a non-woven web with binder 24. The non-woven web with binder 24 is then a condition for passing through. of a furnace, not shown, wherein the binder material is dried and to form a complete non-woven mat, not shown. Typically, the binder material is also cured while the mat is in the furnace. The pipe 12 is preferably of a large diameter, such as approximately 30.48 cm (12 inches) in diameter, to impart rigidity to the pipe and prevent warping. The pipe is supported at both ends by means not shown. Any suitable material, such as stainless steel, may be used for the pipe, and the pipe may have a circular cross-sectional shape as shown, or may have other shapes such as oval, or rounded or square rectangle, not shown. Ideally, the structure of the pipe is strong enough that any buckling in the pipe is relatively small compared to the thickness of the liquid binder as it flows through the top 34 of the pipe. Typical machines for production of wet process mat have an approximate width of 3 or 4 meters, and the pipe must be dimensioned in such a way that the ratio of the width of the machine to the diameter of the pipe is within the range of approximately 10: 1 a approximately 15: 1. Another critical aspect in dimensioning the pipe is the time required for air bubbles to rise or float to the top of the pipe. The larger the diameter of the pipe, the slower the flow of liquid binder material and the greater the probability that undesirable bubbles will be removed by floating the liquid. The residence time required for the removal of the bubbles will also be a function of the liquid viscosity, which can vary anywhere from about 1 centipoise or less to about 20 centipoise or higher. The pipe 12 is supplied with liquid binder from a source not shown, in a first or inlet end 26 of the pipe by an inlet conduit 28. The pipe 12 is provided on its bottom surface 30 with a through discharge opening. from which the liquid binder circulates within the channel 14. As illustrated, the discharge opening may be a plurality of discharge orifices 32, but it will be understood that other types of discharge opening, such as a single slot, not shown It can be used. One of the characteristics of the binder applicator of the invention is that the liquid binder flows from the bottom of the pipe instead of from the top of the pipe. This flow path maintains any additional foam or air trapped in the upper portion 34 of the pipe, where it can be separated by the foam discharge conduit 36 at the distal or discharging end 38 of the pipe. The removal of foam from the liquid binder is important because if any part of the foam falls on the non-woven web 20, a product defect will be created. In addition, the foam can cause an interruption in the curtain 22 of the liquid binder, resulting in a point without binder in the non-woven web and a consequent product defect. The purpose of the distributor channel 14 is to provide a uniform flow of the liquid binder on a path designed to minimize and eliminate turbulence. Another important aspect of the distributor channel design is to eliminate dead spots and regions of stagnant flow to reduce the accumulation of binder solids within the distributor channel. The distributor channel is generally constituted by a binder receiving leg 44 and an upturned leg 46. The ascending leg 46 leads to a horizontal tank 48. The distributor channel is preferably made of stainless steel, but can be made of other materials equally. The binder receiving leg 44 is adapted to receive the liquid binder material from the pipe holes and direct the liquid binder on a curved path, to begin a transition to a generally laminar, non-turbulent flow. A preferred width of the binder-receiving leg is approximately 3.81 cm (1 1/2 inches), although the dimensions for any particular system will depend on factors such as the flow rate required, the viscosity of the binder, the flow resistance of the material constituting the binder. the distributor channel and the operating pressure of the system. The upward tilting leg 46 directs the liquid binder upward, and is preferably approximately the same width as that of the receiving leg 44. The upward inclined leg 46 helps the liquid binder to be even less turbulent as the liquid circulates in ascending form. The horizontal reservoir 48 is formed as the binder circulates around the corner 50 and on a shelf 52. The flow of liquid binder on the shelf provides an even greater chance of turbulence for the liquid to deteriorate. The shelf 52 should be easy to clean. The upper surface 53 of the liquid binder in the horizontal reservoir 48 should be a liquid surface free of disturbance. A surface in the upper part 34 of the pipe 12 acts as a dam or weir for the liquid binder in the horizontal tank 48 of the distribution channel-14, in this way to dose the binder discharge and form a thin flow of binder material. liquid having a uniform depth extending all the way through the applicator 10. The depth of the horizontal reservoir is defined by the distance 54 between the height of the shelf 52 and the height of the upper part 34 of the pipe. The depth 54 of the horizontal reservoir 48 must be sufficient to avoid significant currents within the liquid binder. A preferred depth 54 is approximately 3.81 cm (approximately 1 1/2 inches) although the optimum depth for this apparatus will vary as a function of factors such as the flow rate or flow rate required, the viscosity of the binder, the material flow resistance which constitutes the horizontal reservoir channel and the liquid velocity in the horizontal reservoir. The critical aspect of the operation of the horizontal deposit is the requirement for a smooth surface. Ideally, any surface imperfections in the liquid binder as the liquid approaches the point where it is withdrawn from the horizontal reservoir as a thin flow, are small compared to the height or thickness of the flow of the binder leaving the horizontal reservoir.

The horizontal reservoir preferably is provided with an inclined exit surface 55, which can already be curved or linear. This surface with slope 55 allows the liquid binder to be extracted with a minimum of laminar flow disturbance. The inclined surface may follow the contour of the pipe, as illustrated or may have a different contour. For reasons of convenience, the distributor channel 14 can be provided with removable parts such as a cleaning panel 56, to allow the distributor channel to be cleaned. As the binder material circulates from the pipe 12, through the binder-receiving leg 44, upwardly of the upwardly sloping leg 46 and towards the horizontal tank 48, the amount of flow that flows to the applicator 10 will determine the flow rate of the binder. that circulates outside the applicator. A typical flow rate is within the range of approximately 18.93 -56.78 liters (approximately 5 to approximately 15 gallons) of liquid binder material per minute, per .3048 meter (foot) wide of the applicator 10 and preferably approximately 37.85 liters (10 gallons) of liquid binder material per minute, per .3048 meter (foot) width of the applicator. This will give the liquid binder in the top 34 of the pipe, a depth in the range of about .13 - 1.27 cm (about 0.05 to 0.5 inches) and typically about .38 cm (.15 inches). Too much binder will produce a mat that is too wet, and too little binder will create an unstable film, possibly resulting in the mat having unbonded areas. A preferred binder is a urea formaldehyde latex binder having about 10 percent latex, about 20 percent solids and a viscosity of about 4 centipoise. - The binder applicator of the invention is to be operated under liquid pressure. This is typically achieved by a liquid binder pump, not shown, placed upstream from the inlet conduit 28. The pressures within the binder applicator 10 will vary, depending on the location within the applicator, but the pressure at the binder inlet. 28 is typically in the order of about 7.62 or 10.16 cm (three or four inches) of water pressure. Obviously, the time when the liquid reaches the horizontal reservoir, the pressure is zero. The liquid binder material circulating on the upper part 34 of the pipe circulates in a path 60 which initially follows a curved surface 62. As shown, this curved surface generally follows the curvature of the pipe 12, although this is not required. The curved surface 62 directs the thin layer of binder material onto a reinforced sheet metal plate that slopes downwardly 64 to form the curtain 22 of liquid binder. The plate is substantially vertical, which for purposes of this invention is defined as at an angle 63 that is at any point from zero to about 50 degrees from vertical. Preferably, the plate is oriented at an angle no greater than about 40 degrees from vertical, and more preferably at an approximate angle of 60 degrees from vertical. As the thin layer of binder material flows downward from the sheet metal plate 64, the liquid accelerates and becomes thinner, typically reducing its depth or thickness from about 0.38 cm (0.15 inch) at the top 34 of the pipe to approximately .13 cm (0.05 inch) at the bottom 66 of the sheet metal plate, although the thin flow of binder material may have a thickness as large as .76 cm (0.3 inch). The sheet metal plate 64 is placed as closely as possible to the nonwoven web 20 to prevent deterioration or distortion of the free fall curtain 22. Typically, the bottom 66 of the plate 64 will be approximately 2.54 to 7.62 cm (approximately 1 to approximately 3 inches) from the plot.

The thin flow of the binder material is an inherently unstable hydrodynamic condition. The use of a curved surface for the path 60 allows the liquid binder to have a smooth transition, without abrupt changes in direction, from the horizontal flow at the top 34 of the pipe 12 to an almost vertical flow on the plate 64. The slight curve of the surface 62 reduces the possibility of interruptions or ruptures of flow that can occur in application systems that have abrupt changes of direction. It is also imperative that both the curved outer surface 62 of the pipe and the sheet metal plate 64 are formed with an absolutely smooth surface construction. There should be no joints or connection fittings on these surfaces and preferably, these surfaces should be formed by laminating a stainless steel sheet. More preferably, the curved surface 62 and the sheet metal plate are formed from a single piece of sheet metal of stainless steel. An additional optional feature of the binder applicator of the invention is an inlet chamber 70 positioned between the inlet conduit 28 and the pipe 12. The inlet chamber helps to diffuse the flow of binder material into the pipe. A baffle or diffuser plate 72 shown in Figures 2 and 3 can be located at the inlet end 26 of the pipe to help prevent backflow, liquid dispersion and liquid velocity drop such that trapped air and foam may ascend to the top of the pipe for removal through the foam discharge conduit 36. The baffle 72 may be positioned such that the inlet conduit impinges on the central portion 74 of the baffle. The liquid binder is forced to divide and circulate through openings 76 in the baffle plate and the increase in cross-sectional area of the openings over the cross-sectional area of the inlet duct, necessarily results in a decrease in the speed for the binder material. A further optional feature of the invention is the use of wedges not shown in conjunction with the mounting of each end of the pipe, to allow adjustments in the height of the pipe at each end. In another embodiment of the invention, the upper surface 53 of the liquid binder is intentionally disturbed to effect a non-uniform distribution of the liquid binder constituting the thin flow running over the path 60. For example, it may be necessary to have a larger amount of binder material on a particular edge of the mat. Any means for effecting a non-uniform flow of binder can be employed, such as for example a non-uniform shape to the inclined outlet surface 55. In another embodiment of the invention, as illustrated in Figure 4, the flow path 60A of the applicator 10A runs over an independent flow surface 80 that is not part of line 12. The flow path is separated in line 12A by a substantial distance. Even though the independent flow surface 80 does not coincide with the curved outer surface 62 of the pipe, the independent flow surface still provides a gradual change in the flow path to a substantially vertical direction. The principle and mode of operation of this invention have been described in their preferred embodiments. However, it should be noted that this invention can be practiced differently than as illustrated and described specifically without departing from its scope.

Claims (18)

1. CLAIMS 1. A binder applicator for a moving substrate, comprising a distribution pipe containing liquid binder, the pipe extends transverse to the direction of movement of the substrate, and has a bottom that is provided with a discharge opening, to discharge the liquid binder contained therein; a distributor channel for receiving liquid binder from the discharge opening and directing the liquid binder upwards, a horizontal reservoir for receiving the liquid binder material from the distributor channel; a weir for dosing the discharge of the liquid binder from the horizontal reservoir to form a thin horizontal flow of the liquid binder; and a curved surface for receiving the thin horizontal flow of the binder and gradually changing the flow path of the liquid binder from the thin horizontal flow of the binder to a thin, substantially vertical flow of the binder material for discharge onto the moving substrate.
2. 2. The binder applicator according to claim 1, characterized in that the discharge opening consists of a plurality of holes.
3. 3. The binder applicator according to claim 1, characterized in that the pipe has a circular cross-sectional shape.
4. 4. The binder applicator according to claim 1, characterized in that it includes means for disturbing the liquid binder effecting a non-uniform distribution of the liquid binder discharged from the horizontal reservoir.
5. 5. The binder applicator according to claim 1, characterized in that the horizontal reservoir has an inclined exit surface.
6. 6. The binder applicator according to claim 1, characterized in that the curved surface is formed by winding sheet metal. The binder applicator according to claim 1, characterized in that it includes an inlet conduit at one end of the pipe to supply liquid binder from the pipe, an entrance chamber placed between the inlet conduit and the pipe and a baffle placed inside the inlet chamber to divide the liquid binder and slow the speed of the liquid binder before the liquid binder reaches the pipe. The binder applicator according to claim 7, characterized in that it includes a foam discharge conduit placed at a distal end of the pipe, for removing the foamed binder. 9. The binder applicator according to claim 1, characterized in that it includes a plate on which the flow of substantially vertical binder flows. 10. The binder applicator according to claim 9, characterized in that the plate is oriented at an angle less than approximately 40 degrees from the vertical. 11. A binder applicator for a substrate in motion, comprising: a distribution pipe for containing liquid binder, the pipe extends transverse to the direction of movement of the substrate having a bottom that is provided with a plurality of discharge orifices , to discharge the liquid binder contained therein and having an upper part; a distributor channel for receiving liquid binder from the discharge orifices and directing the liquid binder upwards; a horizontal reservoir for receiving the liquid binder from the distributor channel; a weir to dose the discharge of the liquid binder from the horizontal reservoir, to form a thin horizontal flow of liquid binder; and a curved surface for receiving the thin flow of binder and gradually changing the flow path of the liquid binder from the horizontal binder flow to a substantially vertical and thin binder flow for discharge on the moving substrate. 12. The binder applicator according to claim 11, characterized in that the horizontal reservoir has an inclined exit surface. The binder applicator according to claim 11, characterized in that the pipe has a circular cross-sectional shape and further includes an inlet conduit at one end of the pipe to supply liquid binder from the pipe, an inlet chamber placed between the inlet duct and the pipe, a baffle placed inside the inlet chamber to divide the liquid binder and slow down the speed of the liquid binder before the liquid binder reaches the pipe, a foam discharge duct placed at one end away from the pipe, to remove foamed binder and a plate on which the substantially vertical binder flow circulates. 14. The method for applying agglutinate to a substrate, characterized in that it comprises: moving the substrate on a machine direction; liquid binder discharge from the discharge orifice disposed at the bottom of a distribution pipe extending transverse to the direction of movement of the substrate; and receiving the liquid binder from the discharge orifice and directing the liquid binder upwards through a distributor channel; receiving the liquid binder material from the distributor channel within a horizontal reservoir; metering the discharge of the liquid binder from the horizontal reservoir with a weir to form a thin horizontal flow of liquid binder; gradually changing the flow path of the liquid binder with a curved surface from the thin horizontal flow of the liquid binder to a substantially vertical and thin binder flow; and discharging the flow of substantially vertical and thin binder onto the moving substrate. 15. The method according to claim 14, characterized in that the liquid binder is disturbed to effect a non-uniform distribution of the liquid binder discharged from the horizontal reservoir. 16. The method according to claim 14, characterized in that it includes supplying liquid binder to one end of the pipe with an inlet duct at one end of the pipe, placing an inlet chamber between the inlet duct and the pipe and placing a deflector inside the. inlet chamber for dividing the liquid binder and slowing the speed of the liquid binder before the liquid binder reaches the pipe. 1
7. 7. A binder applicator to a moving substrate, comprising: a distribution pipe for containing liquid binder extending transverse to the direction of movement of the substrate, the pipe has a bottom or is provided with a discharge opening for the liquid binder there content; a distributor channel for receiving the liquid binder from the discharge opening and directing the liquid binder upwards; and a horizontal reservoir for receiving the liquid binder from the distributor channel; wherein the pipe has an upper part and the upper part of the pipe acts as a weir, to dose discharge of the liquid binder from the horizontal tank to form a thin horizontal flow of the liquid binder and where the pipe has a curved outer surface and the curved outer surface provides a curved surface to receive the horizontal and thin binder flow and gradually change the flow path of the liquid binder from the thin horizontal flow of the binder material to a substantially vertical and thin binder flow for discharge onto the substrate moving. 1
8. 8. The method for applying binder to a substrate characterized in that it comprises: moving the substrate over a direction of the machine; discharging the liquid binder from a discharge orifice disposed at the bottom of a distribution pipe extending transverse to the direction of movement of the substrate; receiving the liquid binder from the discharge orifice and directing the liquid binder upwards through a distributor channel; receiving the liquid binder from the distribution channel in a horizontal channel; dose the discharge of the liquid binder from the horizontal reservoir to the top of the pipe that acts as a weir to form a thin horizontal flow of liquid binder; gradually changing the flow path of the liquid binder with the curved surface of the pipe from a thin, horizontal flow of the liquid binder to a substantially vertical and thin flow of binder; and discharging the substantially vertical flow of binder onto the moving substrate.