SEGMENTED METERING DIE FOR HOT MELT ADHESIVES OR OTHER POLYMER MELTS

Abstract: A segmented die assembly (10) comprising a plurality of side-by-side and separate units. Each die unit includes (a) a manifold segment (11A-11D) having an internal gear pump (15A-15D), (b) a die module (12A-12D) mounted on the manifold segment, and (c) a recirculating module (2A-2D) mounted on the manifold segment. The manifold segments (11A-11D) are interconnected and function to deliver process air and polymer melt to the modules (12A-12D). Each die module (12A-12D) includes (a) a fiberization nozzle (13), and (b) a valve (21) for controlling the flow of polymer therethrough. The gear pump (15) of each manifold segment receives a polymer melt and delivers it either to the die module (12) (with its valve open) or to the recirculation module (2) (with the die module valve closed). Polymer melt flowing through the die module (12) is discharged as a filament or filaments onto a moving substrate (9) or collector. On the other hand, polymer flow through the recirculation module (2) is returned to the polymer melt hopper or reservoir for recirculation through the die assembly (10).

Description: SEGMENTED METERING DIE FOR HOT MELT ADHESIVES OR OTHER POLYMER MELTS RELATED APPLICATION This application is a continuation-in-part of Application Serial No. 09/063,651 , filed April 20, 1 998. BACKGROUND OF THE INVENTION This application is a continuation-in-part of Application Serial No. 09/063,651 , filed April 20, 1 998. This invention relates generally to fiberization dies for applying hot melt adhesives to a substrate or for producing nonwovens. In one aspect the invention relates to a modular die provided with an internal rotary positive displacement pump. In another aspect, the invention relates to a segmented die assembly comprising a plurality of separate die units, each unit including a manifold segment and a die module and recirculation module mounted thereon. The deposition of hot melt adhesives onto substrates by fiberization dies has been used in a variety of applications including diapers, sanitary napkins, surgical drapes, and the like. This technology has evolved from the application of linear beads such as that disclosed in U.S. Patent 4,687, 1 37, to air-assisted deposition such as that disclosed in U.S. Patent 4,891 ,249, to spiral deposition such as that disclosed in U.S. Patents -2- 4,949,668 and 4,983, 109. More recently, meltblowing dies have been adapted for the application of hot melt adhesives (see U.S. Patent 5, 1 45,689) . As the term suggests, "fiberization" refers to a process wherein a thermoplastic melt is extruded into and set into fibers. Modular dies have been developed to provide the user with flexibility in selecting the effective length of the fiberization die. For short die lengths only a few modules need be mounted on a manifold block. (See U.S. Patent No. 5,61 8,566). Longer dies can be achieved by adding more modules to the manifold. U.S. Patent 5,728,21 9 teaches that the modules may be provided with different types of die tips or nozzles to permit the selection of not only the die length but the deposition pattern. U.S. Patent 5,236,641 discloses a metering die which comprises a plurality of metering pumps which feed polymer to individual regions of a single elongated die tip. The tip is mounted on a single polymer manifold which has a plurality of side-by-side flow channels which feed a predetermined number of orifices of the tip. Each pump supplies polymer to a single channel. The pumps may be turned on or off so that polymer flow may be discontinued to some of the orifices of the integral elongate tip. In this design the length of the die is not variable because the manifold and die tip are of fixed length and are not formed from individual segments. At the present, the most commonly used adhesive fiberization dies are intermittently operated air-assisted dies. These include meltblowing dies, spiral nozzles, and spray nozzles. -3- Meltblowing is a process in which high velocity hot air (normally referred to as "primary air" or "process air") is used to blow molten fibers or filaments extruded from a die onto a collector to form a nonwoven web or onto a substrate to form an adhesive pattern, a coating, or composite. The terms "primary air" and "process air" are used interchangeably herein. The process employs a die provided with (a) a plurality of openings (e.g. orifices) formed in the apex of a triangular shaped die tip and (b) flanking air plates which define converging air passages. As extruded rows of the polymer melt emerge from the openings as filaments, the converging high velocity hot air from the air passages contacts the filaments and by drag forces stretches and draws them down forming microsized filaments. In some meltblowing dies, the openings are in the form of slots. In either design, the die tips are adapted to form a row of filaments which upon contact with the converging sheets of hot air are carried to and deposited on a collector or a substrate in a random pattern. Meltblowing technology was originally developed for producing nonwoven fabrics but recently has been utilized in the meltblowing of adhesives onto substrates. Meltblown filaments may be continuous or discontinuous. Another type of die head is a spiral spray nozzle. Spiral spray nozzles, such as those described in U.S. Patents 4,949,668 and 5, 1 02,484, operate on the principle of a thermoplastic adhesive filament being extruded through a nozzle while a plurality of hot air jets are angularly directed onto the extruded filament to impart a circular or spiral motion -4- thereto. The filaments thus form an expanding swirling cone shape pattern while moving from the extrusion nozzle to the substrate. As the substrate moves with respect to the nozzle, a circular or spiral or helical bead is continuously deposited on the substrate, each circular cycle being displaced from the previous cycle by a small amount in the direction of substrate movement. The meltblowing die tips offer superior coverage whereas the spiral nozzles provide better edge control. Other fiberization dies include the older non-air-assisted bead nozzles such as bead nozzles and coating nozzles. SUMMARY OF THE INVENTION The die assembly of the present invention may be viewed as a fiberization device for processing a thermoplastic material into fibers or filaments. (The terms "fibers" and "filaments" are used interchangeably herein.) The fiberization may be air-assisted as in meltblowing, spiral monofilaments, or melt spraying; or may be non-air-assisted as in bead or coating depositions. The fiberization of hot melt adhesives is the preferred use of the die assembly of the present invention; but as will be recognized by those skilled in the art, it can be used in the meltblowing of polymers to form nonwoven webs. The die assembly of the present invention features a number of novel features, but in a broad embodiment, it comprises three main components: a manifold segment; a fiberization module; and a recirculation -5- module. The manifold, in a preferred embodiment, includes an internal rotary positive displacement pump (e.g. gear pump) for receiving a polymer melt from a polymer delivering system (e.g. extruder) and discharging the same at a metered rate (constant rate) to one of the modules. Each module includes a valve for controlling the flow of the polymer melt therethrough. Controls are provided so that the flow from the gear pump is uninterrupted; that is, the pump discharge flows either to the fiberization module or the recirculation module. This is achieved by selectively activating the valves of the fiberization module and the recirculating module. Generally, the flow will be to one or the other module, but not both. The preferred embodiment of the invention contemplates the use of a plurality of the manifold segments (with each having the two modules described above mounted thereon), interconnected in a side-by- side relationship. The number of segment/module units define the effective length of the die assembly. The side-by-side fiberization modules form a row of nozzles (e.g. meltblowing die tips, spiral nozzles, etc.) for generating the fibers (or filaments) and depositing the same onto a substrate or collector. The driven rotary member of each internal gear pump rotates about an axis generally parallel to the row of nozzles. In a preferred embodiment, a motor driven shaft extends through the side-by-side manifold segments along the axis of rotation and is keyed to each driven rotary member. Thus, only one driven shaft is required for the entire assembly. -6- An alternate embodiment of the present segmented die includes a self-contained modular rotary pump in each segment, and wherein each pump comprises metering gears and a segmented drive shaft. The drive shaft of each pump has a tang at one end and a slot at the opposite end. In the assembled configuration, the tang of one pump shaft couples with the slot of the adjacent pump. The tang of the adjacent pump will couple with the slot of the pump adjacent to it; and so on along the die length. Thus in the modular pump embodiment, the integral drive shaft whereon al! the driven pump gears are mounted is replaced with coupled drive shaft segments. This embodiment has the advantage that die segments may be removed or added without the need for disassembling the manifold, as well as eliminating the need for using integral drive shafts of various lengths to accommodate additional segments and pumps. The modular pumps may also be preassembled and rapidly installed into the die manifold. In summary, the die assembly of the present invention comprises the following novel features: (a) a die with an internal metering pump; (b) a die with a fiberization module and a recirculation module, and means for selecting the flow through each module; (c) a plurality of manifold segments, each segment having an internal metering pump; -7- (d) a plurality of side-by-side manifold segments having internal metering pumps driven by a single shaft or a segmented shaft; and (e) a plurality of side-by-side manifold segments, each having a fiberization module and a recirculation module, and means for selectively controlling the polymer melt flow to either module of each manifold/module unit. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view of the present segmented die. Figure 2 is a top plan view, with portions cut away, of the die illustrating die segments, gear pumps, and polymer flow passages. Figure 3 is a top plan view illustrating the process and instrument air flow passages. Figure 4 is a side semi-sectional view illustrating die modules, recirculation modules, and gear pumps, with the cutting plane shown generally by line 4-4 of Figure 2. Figure 5 is a perspective view of a manifold segment, shown partially exploded. Figures 6 and 7 are side views of the interior surfaces of the die endpiates with the cutting planes taken generally along lines 6-6 and 7- 7 of Figures 2 and 3, respectively. -8- Figure 8 is a sectional view taken generally along line 8-8 of Figure 4 illustrating the process air flow to the die modules. Figure 9 is an elevational view of the modular pump. Figure 1 0 is an exploded view showing the internal structure of the modular pump. Figure 1 1 is an elevational view of an endplate and metering gears of the modular pump. Figure 1 2 is a side view of a manifold segment for use with the modular pump. Figure 1 3 is a top sectional view showing the coupling of the drive shafts of the modular pumps. DESCRIPTION OF THE PREFERRED EMBODIMENTS As seen in Figure 1 , die assembly 10 comprises segmented manifold 1 1 , fiberization die modules 1 2, recirculation modules 2, and pneumatic controllers 3 and 4. Manifold 1 1 supplies a pressurized molten polymer to module 1 2. Die module 1 2 has a die tip 1 3 through which a molten polymer is extruded to form a stream of polymer fibers or filaments 1 4 which are deposited on a moving collector or substrate 9 to form a continuous or discontinuous layer 20. Filaments 1 4 may be in the form of continuous or discontinuous filaments as in meltblowing, or beads, sheets, or spirals as in the application of adhesives. -9- As seen in Figures 2 and 3, manifold 1 1 is of segmented design comprising a number of separate segments 1 1 A-D interconnected in side-by-side relationship and sealed at each end by endpiates 7 and 8. Since the segments 1 1 are substantially identical in structure, reference numerals without upper case letters will represent corresponding parts in each segment. In describing the assembly, reference numerals with upper case letters (e.g. 1 1 A-1 1 D) will represent the corresponding parts of the assembly. General Description Each segment 1 1 A-1 1 D contains rotary positive displacement pump 1 5A-1 5D and associated flow passages which feed molten polymer to die modules 1 2A-D in parallel and are discharged therefrom as filaments 1 4. The manifold segments 1 1 A-D also contain flow passages which feed polymer from pumps 1 5A-D to recirculation modules 2A-D. Pneumatic controls 3A-D and 4A-D activate valves within modules 1 2A-D and 2A-D which can be selectively and individually opened or closed to control the flow of polymer to either module. In the operational mode, the controls of an individual segment will activate the valves which route the flow of polymer to the die module 1 2 and there will be flow to the recirculation module 2. In the by-pass or recirculation mode the controls route the polymer to the recirculation module 2 where the polymer is recirculated to a polymer supply reservoir (not shown) and no polymer is discharged from the die module 1 2. By controlling which of segments 1 1 A-D are in the -10- operational mode or in the recirculation mode, different patterns of polymer may be discharged from the die modules. Rotary pumps 1 5A-D act as metering pumps which when in the operation mode will deliver polymer to each die module 1 2 at substantially the same rate. The variation in polymer flow rate from module to module will typically be less than 5% thus providing excellent uniformity along the die length. The rotary pumps are preferably gear pumps that provide a constant output for a given rpm. One feature of the segmented design is that segments may be added or removed to vary the die length from application to application. As described below, in a preferred embodiment, the fiberization module 1 2 is provided with an air-assisted nozzle (e.g. meltblowing, spray, or spiral). End plate 7 has process air inlet 29 which feeds air passages formed in manifold 1 1 . The air flows through manifold 1 1 and is delivered to the die modules 1 2A-D in a parallel flow pattern. The process air assists in the formation of filaments 1 4 as will be described. Each of the main components and functions of the segmented manifold with internal metering pumps, die module, recirculation module, and controllers of the die assembly 10 are described in detail below. Die Modules The preferred die modules 1 2 for fiberizing the polymer melt are the type described in U.S. Patents 5,61 8,566 and 5,728,21 9, the disclosures of which are incorporated herein by reference. It should be understood, however, that other die modules may be used. See, for -1 1 - example, U.S. Patent Application Serial No. 09/021 ,426, filed February 10, 1 998, entitled "MODULAR DIE WITH QUICK CHANGE DIE TIP OR NOZZLE." As best seen in Figure 4, each die module 1 2 consists of a die body 1 6 and a die tip 1 3. The die body 1 6 has formed therein an upper circular recess 1 7 and a lower circular recess 1 8 which are interconnected by a narrow opening 1 9. The upper recess 1 7 defines a cylindrical chamber 23 which is closed at its top by threaded plug 24. A valve assembly 21 mounted within chamber 23 comprises piston 22 having depending therefrom stem 25. The piston 22 is reciprocally movable within chamber 23, with adjustment pin 24a limiting the upward movement. Conventional o-rings may be used at the interface of the various surfaces for fluid seals as illustrated. Side ports 26 and 27 are formed in the wall of the die body 1 6 to provide communication to chamber 23 above and below piston 22, respectively. As described in more detail below, the ports 26 and 27 serve to conduct air (referred to as instrument gas) to and from each side of piston 22. Mounted in the lower recess 1 8 is a threaded valve insert member 30 having a central opening 31 extending axially therethrough and terminating in valve port 32 at its lower extremity. The lower portion of insert member 30 is of reduced diameter and in combination with the die body inner wall defined a downwardly facing cavity 34. Upper portion 36 of insert member 30 abuts the top surface of recess 1 8 and has a plurality -1 2- (e.g. 4) of circumferential ports 37 formed therein and in fluid communication with the central passage 31 . An annular recess extends around the upper portion of 36 interconnecting the ports 37. Valve stem 25 extends through body opening 1 9 and axial opening 31 of insert member 30, and terminates at end 40 which is adapted to seat on valve port 32. The annular space between stem 25 and opening 31 is sufficient for polymer melt to flow therethrough. End 40 of stem 25 seats on port 32 with piston 22 in its lower position within chamber 23. As discussed below, actuation of the valve moves stem end 40 away from port 32 (open position as illustrated in Figure 4), permitting the flow of polymer melt therethrough. Melt flows from the manifold segment 1 1 through side port 38, through 37, through the annular space around stem 25 discharging through port 32 into the die tip assembly 1 3. Conventional o-rings may be used as the interface of the various surfaces as illustrated in the drawings. The die tip assembly 1 3 illustrated in the drawings comprises a stack up of four parts: a transfer plate 41 , a die tip 42, and two air plates 43a and 43b. The assembly 1 3 can be preassembied and adjusted prior to mounting onto the die body 1 6 using bolts 50. Transfer plate 41 is a thin metal member having a central polymer opening 44 formed therein. Two rows of air holes 49 flank the opening 44 as illustrated in Figure 4. When mounted on the lower mounting surface of body 1 6, the transfer plate 41 covers the cavity 34 and therewith defines an air chamber with the air holes 49 providing outlets -1 3- for air from cavity 34 on each side of opening 44. Opening 44 registers with port 32 with an o-ring providing a fluid seal at the interface surrounding port 32. The die tip 42 comprises a base member which is co-extensive with the transfer plate 41 and the mounting surface of die body 1 6, and a triangular nose piece 52 which may be integrally formed with the base. As described in U.S. Patent 5,61 8,566, the nose piece 52 terminates in apex which has a row of orifices spaced therealong and air plates 43a, b are in flanking relationship to the nose piece 52 and defined converging air slits which discharge at the apex of nose piece 52. Process air is directed onto opposite sides of the nose piece 52 into the converging slits and discharge therefrom as converging air sheets which meet at the apex of nose piece 52 and contact filaments 1 4 emerging from the row of orifices. Process air is delivered from manifold segment 1 1 to the die body 1 6 through port 53. Also useable in the present invention are modules disclosed in U.S. Patent 5,728,21 9 and U.S. Patent Application Nos. 08/820,559 and 09/021 ,426. Other types of modules may also be used. The modules may dispense meltblowing, spirals, beads, sprays or polymer coatings from the nozzle. Thus the module may be provided with a variety of nozzles including meltblowing nozzles, spiral spray nozzles, bead nozzles, and coating nozzles. -14- Recirculation Module As best seen in Figure 4, recirculation module 2 comprises upper body 54 which is of the same design as body 1 6 of die module 1 2. Module 2 comprises valve assembly 55 which operates in the same manner as valve assembly 21 of module 1 2. Assembly 55 comprises piston 57 and valve stem 58 which, when pneumatically activated by controller 4, will open or close polymer flow port 59 as has been described in relation to piston 22, stem 25, and port 32 of die module 1 2. With valve 55 open, a molten polymer will enter module 2 from manifold passage 78 through port 61 , flow around stem 58 and through port 59 into lower recirculation block 62. Block 62, for convenience of manufacture, may be constructed in one piece, or as illustrated in two pieces. The block 62 may be mounted on the body 54 by bolts (not shown), or by a quick change connector described in the aforementioned USSN 08/820,559 Application. Block 62 has orifice 63 which registers with port 59 and polymer flow passage 64. Orifice 63 intersects passage 66 which leads to right-angled passage 67 and module outlet 69. Outlet 69 registers with manifold segment inlet 71 which discharges the polymer to passage 72 which recirculates the polymer back to a supply tank (not shown) . In the recirculation mode, valve 21 of the associated die module 1 2 will be closed and valve 55 opened. Flow passage 66 extends to outer outlet 65 which is sealed by plug 65a. -1 5- Manifold Construction Segmented manifold 1 1 comprising segments 1 1 A-D and end plates 7 and 8 are secured together using a plurality of countersunk bolts arranged in an alternating pattern. Referring to Figure 2, each manifold segment has a plurality of bolt hole pairs with one hole being a threaded hole and the other hole being a bored and countersunk hole. Segment 1 1 A for example contains holes 91 A which is threaded and hole 92A which is bored and countersunk as at 97A. Segment 1 1 B likewise has threaded hole 91 B and bored and countersunk hole 92B. For joining segments 1 1 A and 1 1 B, bolt 93 passes through bored hole 92A and is threaded into hole 91 B and tightening of bolt 93 joins segments 1 1 A and 1 1 B. Segment 1 1 C is likewise joined to segment 1 1 B using bolt 94 which passes through bored and countersunk hole 92B into threaded hole 91 C. The pattern is repeated over the length of the die at several locations 95a-g (threaded holes) and 96a-g (bored and countersunk) as seen in Figures 4 and 5. The bolt hole pattern alternates between adjacent segments so that a bored and countersunk hole will always align with a threaded hole. In other words, in adjacent segments 1 1 , the locations of holes 95a-g and 96a-g will alternate. End plate 7 is joined to segment 1 1 A and end plate 8 is joined to segment 1 1 D in a similar manner as illustrated in Figure 2 at 97 and 98, respectively. Upon tightening bolts 93 (at all locations 96a-g) a metal-on- metal fluid seal between segments 1 1 A and 1 1 B is established around registering polymer and air flow passages. Similarly, tightening bolt 94 -1 6- creates a fluid seal between segments 1 1 B and 1 1 C. The depth of the countersunk hole in each location (as at 97A) is sufficient so that the head of the bolt therein lies below the opening of the hole and, therefore, when the bolts are tightened the lateral surfaces of the segments and end plates are flush with one another. A large o-ring 89 in a suitable groove 89a (shown in Figure 5) is provided around pump housing 73 as seen in Figure 4 to seal the pump. Referring to Figures 2, 3, 4 and 5 manifold 1 1 is of segmented design and comprises segments 1 1 A-D. Although four segments are shown this is by way of illustration only and the number of segments may vary over a wide range depending on the application. Manifold 1 1 also comprises end plates 7 and 8. Plate 8 has a polymer inlet 81 which feeds all of the segments through continuous flow passage 75. Each segment also has a machined recess 73A-D (shown as 73 in Figures 4 and 5) which houses a rotary positive displacement pump (e.g. gear pumps 1 5A-D), respectively, and registers with polymer inlet passage 75. Each pump comprises a pair of intermeshing gears 82A-D and 83A-D. Keyed gears 82A-D (driven members) are driven simultaneously by motor 84 connected to the gears by continuous shaft 85 through coupling 86. As viewed in Figure 4 gear 82 is driven in a clockwise direction causing gear 83 to rotate in the counterclockwise direction. Gears 83A-D are supported on continuous free-wheeling shaft 80. -1 7- Gears 82A-D and 83A-D have slip fits on shafts 85 and 80, respectively. Shaft 85 will be sealed using an o-ring (not shown) disposed around the shaft in end plate 8. Although not shown the drive system may also include electric controls to vary the speed of the motor and a gearbox speed reducer to reduce the speed of the pump drive shaft 85 from that of the motor shaft. For illustration purposes only, the motor speed may be in the range of 1 500 to 2000 rpm whereas the speed of shaft 85 may be in the range of 0 to 1 05 rpm so that a 20: 1 speed reducer may be required. Motor speed control and shaft speed reduction are within the realm of well-known art in the field and may vary within broad ranges to fit almost any application. Polymer entering through inlet 75 is entrained between the teeth of each gear as at 88 and carried thereby in the rotating direction into lower part of housing 73 and into central passage 76 which registers with the bottom (downstream side) of recess 73. The clearance between the gear teeth and the walls of housing 73 is very small so that polymer between the gear teeth cannot escape and, therefore, the pumps function as positive displacement pumps wherein the throughput of polymer through each pump is determined by the speed at which the gears are driven. Gear pumps 1 5A-D are of substantially the same design as those disclosed in U.S. Patent 5,236,641 the disclosure of which is incorporated herein by reference. As shown in Figure 4, pump 1 5 delivers a pressurized molten polymer to discharge flow passages 76, 77, and 78 which lead to -1 8- fiberization die 1 2 and recirculation module 2. In the assembled segments 1 1 A-D, as best seen in Figures 2 and 4, pumps 1 5A-D deliver pressurized molten polymer to the fiberization die or the recirculation module. Passages 76A-D are individual passages within each segment and do not communicate with passages of adjacent segments. Passages 76A-D register with passages 77A-D which feed die modules 1 2A-D through ports 38A-D in the operating mode, respectively. On the opposite side passages 76A-D register with passages 78A-D which feed modules 2A-D through ports 61 A-D in the recirculation mode. Because of the complexity of the structure, Figure 4 illustrates one side of manifold segment 1 1 and sections of the modules 1 2 and 2 mounted thereon from a perspective of irregular line 4-4 of Figure 2. It is recognized that several of the flow passages 77, 78, 71 , 1 14, 1 1 6, 1 1 7, 1 23 should be properly represented by dashes - because they are hidden - but for clarity of description these passages are shown in solid lines. Gear pumps 1 5A-D rotate at the same speed and deliver a pressurized polymer to polymer discharge passages 76A-D. The polymer therein will either flow to an individual die module 1 2 or to the associated recirculation module 2. By way of illustration consider the case where it is desired to deliver polymer to die modules 1 1 A-C only. In this instance valves 21 A-C of the die modules would be opened by controllers 3A-C and valves 55A-C would be closed by controllers 44A-C. Whereas die module valve 21 D would be closed and valve 55D opened by controllers 3D and 4D. Polymer would thus flow in parallel from passages 76A-C through -1 9- passages 77A-C into modules 1 2A-C and be extruded to form polymer streams 1 4A-C on one side of the die. On the other side of the die, passage 76D will deliver polymer to passage 78D and recirculation module 2D. As has been described the polymer will flow through module 2D and be recirculated via outlet 72 within manifold 1 1 to the polymer supply reservoir. Any other operation/recirculation combination of segments 1 1 A- D is also possible by selectively programming controller 3A-D and 4A-D. Outlet 72 of each segment 1 1 is aligned with the corresponding outlets of the other manifold segments and thus serves as a common outlet for all of the recirculation modules. Each individual module outlet 69A-D registers with an individual manifold inlet 71 A-D (shown as 71 in Figure 4) which all register with a continuous outlet flow passage 72 extending the length of the die which has an outlet at one side of the die which leads to a supply tank. As has been mentioned, pumps 1 5A-D are rotary positive displacement pumps whose throughput is determined by the speed of the pump. In this way the pumps act as flow meters for delivering the polymer at a very precise flow rate. Furthermore, because all the pumps operate at the same speed the flow rate of polymer to each die module will be the same (typically less than 5% variation from module-to-module) . The result is an extremely uniform polymer stream 14 and end-product 20 (see Figure 1 ) over the die length. An important aspect of the present design is that the polymer flow system downstream of pumps 1 5A-D while in the operational mode -20- (i.e. flow through die modules 1 2) is constantly under pressure induced by the pumps. When switching a segment from operational mode to recirculation mode it is important to maintain the same operating pressure so that there will be a smooth transition in polymer flow when the segment is switched back to the operational mode. If the pressure is significantly higher or lower than the operating pressure while in the recirculation mode, a transient such as a surge in polymer flow through the die module may occur when the segment is switched again from the recirculation to the operational mode. Maintaining operating pressure while in the recirculation mode is accomplished by sizing orifice 63 in the recirculation block 62 in relation to the viscosity of the polymer being processed so that the orifice will provide the correct amount of flow resistance to maintain operating pressure upstream of the orifice. Different size orifices are required for different polymers. In another preferred embodiment, outlet 72 may be sealed with a threaded plug, and plug 65a in outlet 65 may be removed. A spring- loaded needle valve (not shown) may be disposed in outlet 65 with the tension in the spring determining the pressure required to displace the needle of the valve and thereby regulate the operating pressure. A recirculation hose may be connected to the outlet of 65 and to the polymer supply tank. An adjustable needle valve may be provided to allow the variation of operating and recirculation pressure through valve spring tension for polymers having different flow properties. -21 - Another important aspect of the present invention is the location of the rotary positive displacement pump internally of the manifold segment. This streamlines the structure and facilitates connecting a single drive shaft to all the pumps in the assembly. The axis of rotation of the driven gear or rotary member is parallel to the row of fiber forming means of the assembled die. Electric heaters 70 may be provided in the aligned segments 1 1 to maintain the polymer melt flowing through the manifold segments 1 1 at the proper temperature. Modular Pump In an alternative preferred embodiment of the present metering die, pump 1 5 which is assembled within manifold 1 1 is replaced with a self- contained modular pump. Manifold segment 1 1 is modified to contain a cavity wherein the modular pump is placed for operation. The modular pumps are of rotary gear design and similar to non-modular pumps 1 5A-D in terms of the principles of operation (i.e. polymer flow and metering) . As seen in Figure 2, pump gears 82A-D are mounted on integral drive shaft 85 which extends through each manifold segment, and gears 83A-D are supported on integral shaft 80. The lengths of shafts 85 and 80 must be sized in relation to the number of manifold segments to be used. Adding or removing manifold segments would require replacing the two shafts with shafts of different length. Therefore, to add even a single segment onto the end of the die, all the gears on the two shafts would have -22- to be removed and remounted on new shafts in the configuration described previously in relation to Figures 2, 4 and' 5. The only way this can be accomplished is to disconnect each manifold segment, which amounts to disassembling the entire manifold. Note also that if a pump becomes clogged or damaged requiring cleaning or replacement, a similar situation arises. Disassembling the manifold is time-consuming and inefficient. In addition, housing 73 (including o-ring groove 89a) in manifold 1 1 is expensive to manufacture. The modular pump described below is designed to overcome these difficulties. A principal advantage of the modular pump is that each pump comprises its own drive shaft that connects to the drive shafts of adjacent pumps using a tang-in-slot coupling. Each pump also has its own idler shaft as will be described. Thus integral shafts 85 and 80 are replaced with segmented shafts. The modular design allows manifold segments to be added or removed without the need to disassemble the entire manifold. Housing 73 in the manifold segment is replaced with a simplified mounting cavity for the modular pump that is less expensive to manufacture. With reference to Figures 9 and 10, modular pump 1 30 comprises endpiates 1 31 and 1 32 and center plate 1 33 sandwiched therebetween. Note in Figure 1 3 four pump units are shown labeled 1 30A- D. Endplate 1 31 has pins 1 36 and 1 37 which mate with holes in plates 1 32 and 1 33 for precisely aligning the plates. Plate 1 32 has countersunk and bored holes 1 37a-e whereas middle plate 1 33 has clearance holes 1 38a-e and endplate 1 31 has threaded holes 1 39a-e. Bolts (not shown) are -23- inserted into holes 1 37a-e, pass through holes 1 38a-e and are threaded into holes 1 39a-e for joining the three plates together and for providing a fluid seal at the interfaces of the plates. Holes 1 37a-e are sized so that the heads of the bolts do not extend beyond the outer surface of plate 1 32. As seen in Figures 1 0 and 1 1 , pump 1 30 also comprises intermeshing gears 1 41 and 142 rotatably disposed in housing 140 formed in center plate 1 33. Gear 1 41 is a driven gear and 142 is an idler gear. The thickness of plate 1 33 is slightly larger than that of gears 1 41 and 1 42 so that the gears are free to rotate after plates 1 31 , 1 32 and 1 33 have been bolted together. Pump 1 30 further comprises drive shaft 143 having tang 144 at one end and slot 145 on the opposite end. Shaft 143 passes through holes 146 and 147 in the endpiates 1 31 and 1 32, respectively. The holes are slightly larger than the diameter of the shaft so that the shaft is free to rotate. The holes are sized, however, so that they provide a bearing-type support for the drive shaft as it rotates. Driven gear 1 41 is secured to shaft 143 using a key inserted in slot 1 48 and a corresponding slot in the shaft (not shown). As best seen in Figure 10, idler shaft 149 is press fit into hole 1 51 of plate 1 31 at one end, passes rotatably through the center hole of idler gear 1 42, and is press fit into hole 1 52 of plate 1 32. The press fit into holes 1 51 and 1 52 is accomplished as the plates are bolted together. The press fit on each end of shaft 149 establishes a fluid seal between the shaft and the endpiates. -24- Manifold segment 1 50 (Figure 1 2) has formed therein pump cavity 1 53. The outer dimensions of the cavity are slightly larger by about 0.01 inch than the outer periphery of the modular pump so that the pump fits into the cavity without requiring a press fit. The width of pump 1 30 is approximately 0.001 inches smaller than the depth of cavity 1 53. Pump 1 30 is manufactured from a type of steel that has a higher thermal expansion rate than the steel used for manifold 1 50. The pump width is smaller than the cavity depth to allow for the pump to expand as the die is heated. The preferred overall thickness of pump 1 30 is between 0.5 and 0.7 inches. Manifold 1 50 has polymer outlet 1 55 which registers with polymer inlet 1 54 of pump 1 30 (see Figures 9 and 1 0) with the pump unit inserted into the cavity. The outlet of the pump is formed in endplate 1 31 as best seen in Figures 1 0 and 1 1 . The outlet comprises recess 1 60 which opens into flow channels 1 56 and 1 57. Channel 1 56 has outlet hole 1 58 which registers with inlet 1 59 of manifold 1 50 for feeding die module 1 2. Channel 1 57 has outlet 1 61 which registers with manifold inlet 1 62 for feeding recirculation module 2. Thus polymer enters the pump at inlet 1 54, is entrained by the teeth of gears 1 41 and 1 42, flows around the outer periphery of the gears (gear 1 41 is driven clockwise as viewed in Figure 1 1 ) into recess 1 60, into channels 1 56 and 1 57, into outlets 1 58 and 1 59, and enters the manifold at 1 59 and 1 62. After the polymer leaves pump 1 30 to either the die module or the recirculation module, the polymer flow is the same as has been described with reference to non-modular pump 1 5. The -25- process air flow and instrument gas flow (described below) are identical to the embodiment of Figures 3 and 4. Pump 1 30 also comprises outlet hole 1 63 which allows polymer to flow into an adjacent manifold and pump segment. Thus a portion of the polymer entering the pump flows through the pump and the rest flows through hole 1 63 into a neighboring segment. With a plurality of manifold segments and pumps assembled in stacked relation, holes 1 54, 1 55, and 1 63 of all the segments form a continuous flow passage along the length of the die. O-rings (not shown) are provided around polymer holes 1 55, 1 59, 1 62, and shaft hole 1 64 in manifold 1 50 to establish fluid seals between the manifold and pump 1 30. O-rings are also provided around the outside of hole 1 63 and shaft hole 1 47 of pump plate 1 32 to establish a seal at the abutting surface of the adjacent manifold segment. The present modular pump wherein each pump has its own drive shaft and idler shaft allows segments to be added or removed without the necessity of disassembling the manifold. As seen in Figures 1 2 and 1 3, manifold 1 50 has hole 1 64 which allows pump drive shaft 143 to pass therethrough. Shaft 1 43 has tang 144 at one end and slot 145 at the other end. As best seen in Figure 1 3, adjacent pumps are oriented so that the slot of one shaft will align and mate with the tang of the adjacent shaft as shown at 144A and 145B, 144B and 145C, and so on along the length of the die. Drive shaft 1 65 has slot 1 68 which is coupled to tang 144D of pump shaft 1 43D. Drive shaft 1 65 passes through endplate 1 66 and is coupled to a motor for driving all of the coupled shafts 1 43A-D together. -26- Cavity 1 53 of manifold 1 50 is slightly oversized (viz. 0.01 inch) in relation to the outer dimensions of pump 130 so that in the coupled configuration each pump may move slightly whereby no binding between the coupled shafts occurs Also a small amount of tolerance between the tang and slot is provided to eliminate binding. The present design allows segments to be added or removed without the need for replacing the drive shaft and idler shaft as in the integral shaft design of Figure 2. For example if segment 1 50A in Figure 1 3 is to be removed, die endplate 1 67 will be unbolted from segment 1 50A, the segment along with pump 1 30A will be unbolted and disconnected from segment 1 50B with drive shafts thereof being uncoupled at 1 44A and 145B, and endplate 1 67 bolted onto segment 1 50B to complete the procedure. Manifold segments 1 50A-D are bolted together in the same fashion as has been described in relation to Figure 2. The polymer flow through from the manifold to the inlets of modules 1 2 and 2 is the same as has been described in relation to Figures 2 and 4. Process Air Flow Referring to Figures 3 through 7, heated process air enters through inlet 29 which registers with circular groove 1 01 (Figure 6) formed along the inner wall of the endplate 7. Middle sections 1 1 A-D have a plurality of holes 102a-h which when assembled form continuous flow passages -27- 1 03a-h which travel the length of the die as seen in Figure 2 (103c,d not shown) . Process air inlet 29 registers with groove 1 01 as seen in Figure 6. The inlets of passages 1 03a-d register with groove 1 01 so that air entering the groove via inlet 29 will enter the passages and flow the length of the die from plate 7 to plate 8 in parallel. The outlet of passages 1 03a-d register with groove 1 06 formed in end plate 8 (Figure 7) . Groove 106 also registers with inlets to flow passages 103e,f which turns the air and causes the air to flow back along the length of the die in the direction opposite that of passages 1 03a-d. The outlets to passages 103e,f register with groove 1 07 formed in plate 7 which receives the air and turns the air again to travel back along the length of the die through passage 103g which discharges into groove 1 08 of end plate 8. A portion of the air travels back along the die length through passage 103h while the rest of the air flows from groove 1 08 towards the manifold discharge through slot 109 in plate 8. Air which returns to plate 7 through passage 1 03h flows towards the manifold discharge through slot 1 1 1 . Thus the air makes three or four passes along the length of the die before being discharged to the die modules. The direction of air flow in passages 103a-h is illustrated by arrows 90 in Figure 2. Central heating element 1 1 2 heats the multi-pass air to the operating temperature. Because the process air temperature is hotter than the polymer operating temperature isolation slots 99 are provided in plates 7 and 8, and 1 1 A-D to disrupt heat flow between the process air flow and polymer flow passages of the manifold. -28- As seen in Figures 3 and 8, process air flows towards the manifold discharge along both sides of the manifold through slots 109 and 1 1 1 . Plates 1 1 A-F have holes which define air passage 1 1 3 which extends the length of the die. Slots 109 and 1 1 1 discharge from opposite sides into passage 1 1 3 which feeds in parallel holes 1 14A-D which in turn feed air inputs 39A-D in die modules 1 2A-D, respectively. The air flows through the die modules as has been described and is discharged as converging sheets of air onto fibers 14 extruded at die tip apex 56. Instrument Air Referring to Figures 2 and 3 each die module 1 2 and recirculation module 2 have valve assemblies which are activated (opened or closed) by a pneumatic controller (actuator) 3 and 4, respectively. The operation of each controller is identical and, therefore, only actuator 3 for the die module will be described it being understood that the functioning of recirculation actuator 4 will be the same. The same reference numerals for the instrument air passages and controls for actuating the valve assembly 55 of recirculation module 2 are used for corresponding passages and controls for activating die module 1 2. It is also to be understood, however, that associated actuators (e.g. 3A and 4A) will generally operate in opposite modes. When controller 3A commands die module valve 21 A to open, controller 4A will simultaneously command recirculation module valve 55 to be closed and visa-versa. However, as has been described some die segments may be in the operational mode (polymer flow to die modules) -29- while others are in the recirculation mode (polymer flow to recirculation module) to produce stream 14 having different patterns. Each die module comprises a valve assembly 21 which is actuated by compressed air acting above or below piston 22. instrument air is supplied to the top and bottom air chambers on each side of valve piston 22 (see Figure 4) by flow lines 1 1 6 and 1 1 7 formed in each middle plate 1 1 A-D. Controller 3 comprises three way solenoid valve 1 20 with electronic controls 1 21 to control the flow of instrument air. Instrument air enters the die through inlet 1 1 5 into continuous flow passage 1 1 8 which serves all the die segments (the configuration of inlet 1 1 5 and passage 1 1 8 in relation to the modules is illustrated in Figure 3 for the recirculation modules, the configuration being the same for the die modules). Passage 1 1 9 in each segment delivers the air in parallel (see Figure 3) to each of solenoid valves 1 20A-D (shown schematically in Figure 4). The valve delivers the air to either passage 1 1 6 or 1 1 7 depending on whether the module valve 21 is to be opened or closed. As illustrated in Figure 4, pressurized instrument air is delivered via line 1 1 7 to the bottom of the piston 22 which acts to force the piston upward, while the controller simultaneously opens the air chamber above the piston (to relieve the air pressure above) to exhaust port 1 22 via lines 1 1 6 and 1 23. In the upward position, valve stem 25 unseats from port 32 thereby opening the polymer flow passage to the die tip. In the closed position, solenoid 1 20 would deliver pressurized air to the upper side of piston 22 through line 1 1 6 and would simultaneously open the lower side of the piston to exhaust port 1 24 -30- via line 1 25. The pressure above the piston forces the piston downward and seats valve stem 25 onto port 32 thereby closing the valve. Thus in a preferred mode each die module has a separate solenoid valve such that the polymer flow can be controlled through each die module independently. In this mode side holes 1 26 and 1 27 which intersect passages 1 1 6 and 1 1 7, respectively, are plugged. In a second preferred embodiment a single solenoid valve may be used to activate valves 21 in a plurality of adjacent die modules. In this configuration the tops of holes 1 1 6 and 1 1 7 (labeled 1 1 6a and 1 1 7a) are plugged and side holes 1 26 and 1 27 opened. Side holes 1 26 and 1 27 are continuous holes and will intersect each of the flow lines 1 1 6 and 1 1 7 to be controlled. Thus in the closed position, pressurized air would be delivered to all of the die modules simultaneously through hole 1 26 while hole 1 27 would be opened to the exhaust. The instrument air flow is reversed to open the valve. As has been stated the principle of operation of the controllers 4 is the same as has been described for controls 3. The mode of operation (i.e. operational mode/recirculation mode), however, of controller 4 will generally be opposite that of controller 3. Manifold segments 1 1 A-D and endpiates have inwardly tapered surfaces 1 28 beneath controllers 3A-D and 4A-D to provide a large heat transfer surface area. This is done to dissipate sufficient heat to maintain the area above the tapers at a low temperature to protect the electronic controls of controllers 3 and 4. -31 - ASSEMBLY AND OPERATION As indicated above, the modular die assembly 1 0 of the present invention can be tailored to meet the needs of a particular operation. As illustrated in Figures 1 , 2 and 3, four die segments 1 1 A-D, each about 0.75 inches in width are used in the assembly 10. The manifold segments 1 1 are bolted together as described previously, and the heater elements installed. The length of the heater elements will be selected based on the number of segments 1 1 employed and will extend through most segments. The die modules 1 2 and recirculation modules 2 may be mounted on each manifold segment 1 1 before or after interconnecting the segments 1 1 , and may include any of the nozzles 1 3 previously described. These may include meltblowing nozzles (die tips), spiral spray nozzles, bead or coating nozzles, or combinations of these. A particularly advantageous feature of the present invention is that it permits (a) the construction of a meltblowing die with a wide range of possible lengths, interchangeable manifold segments, and self contained modules, (b) variation of die nozzles (e.g. meltblowing, spiral, or bead applicators) to achieve a predetermined and varied pattern, (c) metering of polymer flow rate to each nozzle to provide uniformity along the die length, and (d) the production of polymer coatings having a pre-determined pattern. The segments 1 1 are assembled by installing each segment on the shaft, bolting the segment in place, and continuing the addition of segments until the desired number has been installed on the shaft. -32- Variable die length and adhesive patterns may be important for applying adhesives to substrates of different sizes from one application to another. The following sizes and numbers are illustrative of the versatility of the modular die construction of the present invention. Die Assembly Broad Range Preferred Range Best Mode Number of Segments 1 -1 ,000 2-1 00 5-50 Length of each Segment 0.25-1 .50" 0.5-1 .00" 0.5-0.8" in machine direction (inches) Different Types of 2-4 2-3 2 Nozzles (13) (e.g. meltblowing, spiral, spray, and bead) The lines, instruments, and controls are connected and operation commenced. A hot melt adhesive is delivered to the die 1 0 through line 81 , process air is delivered to the die through line 29, and instrument air to gas is delivered through line 1 1 5. Although the preferred embodiment of the present invention is in connection with a plurality of manifold/module segments, there are aspects of the invention applicable to single manifold/module constructions or unitary dies. For example the internal metering pump can be used with advantage on most any type of fiberization die. Also, the recirculation module can be used with a fiberization die fed by an external metering pump. Actuation of the control valves 21 opens port 32 of each module 1 2 as described previously, causing polymer melt to flow through each module 1 2. In the meltblowing segments 1 1 , the melt flows through -33- anifold passage 75, through pump 15, into passages 76 and 77, through side ports 38, through passages 37 and annular space 45, and through port 32 into the die tip assembly 13. The pumps 15 used in the present invention are similar in design to those of U.S. Patent 5,236,641 . The polymer melt is distributed laterally in the die tip 13 and discharges through orifices 53 as side-by-side filaments 14. Air meanwhile flows from manifold passages 29, 103, 1 1 1 , 109, 1 13 and 1 14 where the air is heated. Air enters each module 12 through port 39 and flows through holes 49 and into slits discharging as converging air sheets at or near the die tip apex of the nose piece 52. The converging air sheets contact the filaments 14 discharging from the orifice 53 and by drag forces stretch them and deposit them onto the underlying substrate in a random pattern. This forms a generally uniform deposit of meltblown material on the substrate. Once production has begun, and the die assembly is in the operational mode, the pattern of meltblown material may be varied by switching any combination of the die segments from the operational mode to the recirculation mode. Controller 3 of a segment to be switched would command valve 21 of the fiberization die module 12 to close while controller 4 would command valve 55 of the recirculation module to open whereby the flow of polymer through the discharge line from the pump switches from the die module to the recirculation module. Because the die segments are narrow in the machine direction, and because a large number of segments may be employed, a wide variety of precisely placed coatings -34- may be produced. Die segments may be switched back and forth between the operational mode and recirculation mode at the will of the operator. In each of the modules 1 2, the polymer and air flows are basically the same, with the difference being, however, in the nozzle type provided on the module. In the spiral nozzle, a monofilament is extruded and air jets are directed to impart a swirl on the monofilament. The swirling action draws down the monofilament and deposits it as overlapping swirls on the substrate as described in the above referenced U.S. Patent 5,728,21 9. In the non-air assisted nozzles, the air ports are sealed off, and only a continuous bead or layer is dispensed from the die module. As noted above the assembly 10 may be provided with different nozzles to achieve a variety of deposition patterns. Typical operational parameters are as follows: Polymer Hot melt adhesive Temperature of the 280°F to 325°F Die and Polymer Temperature of Air 280°F to 325°F Polymer Flow Rate 0.1 to 1 0 grms/hole/min Hot air Flow Rate 0.1 to 2 SCFM/inch Deposition 0.05 to 500 g/m 2 As indicated above, the die assembly 10 may be used in meltblowing any polymeric material, but meltblowing adhesives is the preferred polymer. The adhesives include EVA's (e.g. 20-40 wt% VA). These polymers generally have lower viscosities than those used in meltblown webs. Conventional hot melt adhesives useable include those -35- disclosed in U.S. Patents 4,497,941 , 4,325,853, and 4,31 5,842, the disclosure of which are incorporated herein by reference. The preferred hot melt adhesives include SIS and SBS block copolymer based adhesives. These adhesives contain block copolymer, tackifier, and oil in various ratios. The above melt adhesives are by way of illustration only; other melt adhesives may also be used. Although the present invention has been described with reference to meltblowing hot melt adhesive, it is to be understood that the invention may also be used to meltblow polymer in the manufacture of webs. The dimensions of the die tip may have a small difference in certain features as described in the above referenced U.S. Patents 5, 1 45,689 and 5,61 8,566. The typical meltblowing web forming resins include wide range of polyolefins such as propylene and ethylene homopolymers and copolymers. Specific thermoplastic include ethylene acrylic copolymers, nylon, polyamides, polyesters, polystyrene, poly(methyl methacrylate), polytrifluoro-chloroethylene, polyurethanes, polycarboneates, silicone sulfide, and poly(ethylene terephthalate), pitch, and blends of the above. The preferred resin is polypropylene. The above list is not intended to be limiting, as new and improved meltblowing thermoplastic resins continue to be developed. The invention may also be used with advantage in coating substrates or objects with thermoplastics. -36- The thermoplastic polymer, hot melt adhesives or those used in meltblowing webs, may be delivered to the die by a variety of well known means including extruders metering pumps and the like. It will be understood by those skilled in the art that the present invention may be used with air assisted or non-air assisted die assemblies.

Claims: -37- WHAT IS CLAIMED IS: 1 . A segmented die assembly, comprising (a) a plurality of manifold segments, each having a polymer flow passage formed therein; the manifold segments being interconnected in side-by-side relationship wherein the polymer passages are in fluid communication, respectively and each manifold segment including a rotary positive displacement pump for receiving a polymer melt from the polymer flow passage and discharging the polymer melt into a polymer discharge flow passage, said positive displacement pump including a driven rotary member; (b) a shaft extending through the manifold segments and connected to the driven rotating member of each manifold segment; (c) a motor for driving the shaft whereby the rotary positive displacement pumps of each manifold segment pumps polymer melt into its respective polymer discharge flow passage; (d) a die module comprising (i) a die body mounted on each manifold segment and having a polymer flow passage in fluid communication with the polymer discharge flow passage of its associated manifold segment; and (ii) a nozzle mounted on the die body and having a polymer flow passage in fluid communication with the polymer flow passage of its associated die body for receiving the polymer melt and discharging a filament or filaments therefrom; and (e) means for delivering a polymer melt to the polymer flow passage of each manifold segment whereby the melt is distributed to the -38- polymer flow passages of the manifold segments and flows in each segment to the pump, the discharge flow passage and the die module flow passage and the nozzle. 2. The segmented die assembly of Claim 1 wherein the nozzles of each die module are arranged in a row and wherein the drive rotating member of each manifold segment rotates about an axis parallel to the row of nozzles. 3. The segmented die assembly of Claim 1 wherein each manifold segment further includes a recirculation module mounted thereon and having a polymer flow passage in fluid communication with the polymer discharge flow passage, said die assembly further including means for selectively controlling the flow of polymer melt in the polymer discharge flow line to either the die module or the recirculation module. 4. The segmented die assembly of Claim 1 wherein each die module and each recirculation module includes a valve for opening and closing the polymer flow passages therein, and control means for selectively opening and closing the valve of the die module and the valve of the recirculation module whereby polymer melt in the polymer discharge flow passage flows to the die module or to the recirculation module. -39- 5. The segmented die assembly of Claim 4 wherein the valve of the die module and the valve of the recirculation module are air-actuated and the control means are pneumatic. 6. The die assembly of Claim 1 wherein at least two manifold segments are identical. 7. The die assembly of Claim 1 wherein the assembly comprises from 2 to 1 00 die segments. 8. The die assembly of Claim 1 wherein each manifold segment and the module mounted thereon is from 0.25 to 1 .5 inches in length. 9. The die assembly of Claim 3 wherein the assembly further includes a passage for recirculating the polymer melt from the recirculation module to the means for delivering polymer melt to the polymer flow passage of each manifold segment. 1 0. The die assembly of Claim 1 wherein the positive displacement pump is a gear pump. 1 1 . The die assembly of Claim 1 wherein the pump is located internally of the manifold segment. -40- 12. A segmented die assembly, comprising: (a) a plurality of manifold segments, each having a polymer flow passage and an air flow passage formed therein; the manifold segments being interconnected in side-by-side relationship wherein the air passages and polymer passages are in fluid communication, respectively, and each manifold segment includes an internal gear pump for receiving a polymer melt from the polymer flow passage; (b) a die module comprising a die body mounted on each manifold segment and having a polymer flow passage and an air flow passage in fluid communication with the polymer discharge flow passage and air passage of its associated manifold segment, respectively; and a nozzle mounted on the die body and having a polymer flow passage and an air flow passage, each being in fluid communication with the polymer flow passage and the air flow passage of its associated die body, respectively, for receiving the polymer melt and discharging an air-assisted filament or filaments therefrom; (c) means for delivering a polymer melt and an instrument gas to the polymer flow passage and air flow passage of each manifold segment, respectively; (d) means for selectively opening and closing the polymer flow passage of the die module whereby polymer melt flows from the polymer discharge flow passage through the die module with the polymer flow passage of the module open; -41 - (e) means for recirculating the polymer melt from the polymer discharge flow passage of the manifold segment to the means for delivering a polymer melt to each manifold segment with the polymer flow passage of the die module closed; and (f) means for delivering air to the air flow passages of each manifold segment whereby air flows through each die module discharging through the nozzle into contact with the filament or filaments discharging from the die module polymer flow passage. 1 3. The die assembly of Claim 1 2 wherein the die tip or nozzle is selected from the group consisting of meltblowing die tip, spiral spray nozzle, and spray nozzle. 1 4. The die assembly of Claim 1 3 wherein the die tip on at least one module is a meltblowing die tip. 1 5. The die assembly of Claim 1 2 wherein each die module has an air actuated valve mounted therein to open and close the polymer flow passage therein and each manifold segment having instrument air flow passages formed therein for delivering air to and from the air actuated valve, said assembly further comprising control means for selectively delivering air to and from the air passages of the manifold segment. -42- 1 6. The die assembly of Claim 1 2 wherein the manifold segments are identical. 1 7. The die assembly of Claim 1 2 wherein each manifold segment includes electric heaters for heating the polymer and the air and wherein, the air passage of a particular manifold segment is in fluid communication with the air passages of the other manifold segments whereby air flows through each segment before flowing to the module mounted on the particular manifold segment. 1 8. The die assembly of Claim 1 2 wherein the means for recirculating the polymer melt includes a recirculation module mounted on each manifold segment, said recirculation module including a polymer flow passage in fluid communication with the polymer discharge flow passage, its associated manifold segment, and valve means for selectively opening and closing its polymer flow passage. 1 9. The die assembly of Claim 1 2 wherein the gear pump of each manifold segment includes a driven gear, and the assembly further includes a drive shaft extending through the side-by-side manifold segments and being connected to each driven gear of each gear pump. -43- 20. A die assembly comprising: (a) a manifold having a polymer discharge flow passage formed therein; (b) a metering pump for delivering a polymer melt to the polymer discharge flow passage of the manifold; (c) a fiberization die module mounted on the manifold for receiving a polymer melt from the polymer discharge passage and discharging the polymer melt as a filament or filaments; (d) a recirculation module mounted on the manifold for receiving polymer melt from the polymer discharge passage of the manifold and recirculating the polymer melt to the metering pump; and (e) means for controlling the flow of the polymer melt to either the fiberization die module or the recirculation module. 21 . A die assembly comprising: (a) a manifold having a polymer flow passage formed therein; (b) a gear pump mounted internally of the manifold for receiving a polymer melt from the polymer flow passage and discharging the melt into a polymer discharge passage; (c) a fiberization die module mounted on the manifold for receiving a polymer melt from the polymer discharge passage and converting the polymer melt into filament or filaments; -44- (d) means for interrupting the flow of the polymer melt through the fiberization die module; and (e) means in fluid communication with the polymer discharge passage for recirculating the polymer melt flow to the gear pump with flow through the fiberization die module interrupted. 22. The segmented die assembly of Claim 1 wherein the shaft comprises a stub shaft mounted in each segment, and the stub shafts are interconnected so in end-to-end relationship so that the motor drives the interconnected stub shafts as a unit. 23. A segmented die assembly, comprising: (a) a plurality of manifold segments interconnected in side- by-side relationship, each manifold segment having (i) a polymer flow passage formed therein; (ii) a rotary positive displacement pump mounted therein for receiving a polymer melt from its respective polymer flow passage and discharging the polymer melt into a polymer discharge flow passage, said positive displacement pump including a driven rotary member; and (iii) a stub shaft drivingly connected to the driven rotary member. -45- (b) a means for interconnecting the stub shafts in end-to- end relationship whereby rotation of the interconnected stub shafts rotates the rotary member in unison; c) a motor for rotating the interconnected stub shafts whereby the rotary positive displacement pumps of each manifold segment pumps polymer melt into its respective polymer discharge flow passage; (d) a die module comprising (i) a die body mounted on each manifold segment and having a polymer flow passage in fluid communication with the polymer discharge flow passage of its associated manifold segment; and (ii) a nozzle mounted on the die body and having a polymer flow passage in fluid communication with the polymer flow passage of its associated die body for receiving the polymer melt and discharging a filament or filaments therefrom; and (e) means for delivering a polymer melt to the polymer flow passage of each manifold segment whereby the melt is distributed to the polymer flow passages of the manifold segments and flows in each segment to the pump, the discharge flow passage and the die module flow passage and the nozzle.

Inventors: ALLEN MARTIN A, ALLEN, MARTIN, A.
Applicants: NORDSON CORP, NORDSON CORPORATION
Application year: 1999
Main classification: B05C5
IPC codes: B05B7, B05C5, B05C11, D01D4, D01D5, F04C2