US RE39399 E1
A segmented die assembly comprises a plurality of side-by-side and separate units. Each die unit, includes a manifold segment and a die module mounted thereon. The manifold segments are interconnected and function to deliver process air and polymer melt to the modules. Each module including a nozzle through which the polymer melt is extruded forming a row of filament(s). The filaments from the array of modules are deposited on a substrate or collector. The die assembly is preferably used to apply a hot melt adhesive to a substrate, but also may be used to produce meltblown webs.
1. A segmented die assembly, comprising:
(a) a plurality of manifold segments, each manifold segment having a polymer flow passage and an air flow passage formed therein; said manifold segment being interconnected in side-by-side relationship wherein said air passages and polymer passages are in fluid communication, respectively;
(b) a die module mounted on each manifold segment, said die module comprising a die body having a polymer flow passage and an air flow passage in fluid communication with said polymer flow passage and said air flow passage of its associated manifold segment, respectively; and a die tip or nozzle mounted on said die body and having a polymer flow passage in fluid communication with said polymer flow passage of its associated die body for receiving the polymer melt and discharging a filament or filaments therefrom;
(c) means for delivering a polymer melt to at least one manifold segment whereby the melt is distributed through said other interconnected manifold segments and flows through each die module discharging as a filament or filaments from each die tip or nozzle; and
(d) means for delivering air to at least one manifold segment whereby air is distributed in said interconnected manifold segments and flows through each die module discharging through said die tip or nozzle.
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3. The assembly of
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9. The die assembly of
10. A meltblowing die comprising:
(a) a manifold with at least two manifold segments, each segment having a polymer flow passage and an air flow passage, said polymer flow passages and air flow passages being interconnected, respectively;
(b) a die module secured in each manifold segment, each die module having a polymer flow passage which registers with its associated manifold segment polymer flow passage, an air flow passage which registers with its associated manifold segment air flow passage, a die tip or nozzle for discharging polymer as a filament or filaments, and an air flow discharge for delivering air onto said filament or filaments;
(c) means for delivering a polymer melt to at least one of said manifold segments whereby said melt flows through said interconnected polymer flow passages of each manifold segment and is delivered to said associated die modules; and
(d) means for delivering air to at least one of said interconnected manifold segments whereby said air flows through each manifold segment and is delivered to said associated die modules.
11. The meltblowing die of
12. A segmented die assembly comprising a plurality of separate air-assisted die units interconnected in side-by-side relationship, each die unit comprising:
a) a manifold segment having formed therein (i) a process air flow passage, (ii) a polymer flow passage, and (iii) and instrument air flow passage, said process air flow passages and said polymer flow passages respectively being in fluid communication;
b) a die module having a die body detachably mounted on said manifold segment, and an air-assisted die tip or nozzle mounted on said die body, said die body having formed therein (i) a process air flow passage, (ii) a polymer flow passage and (iii) an instrument air flow passage which, respectively, are in fluid communication with said process air flow passage, said polymer flow passage, and said instrument air flow passage of said manifold segment, said die body further having an air-actuated valve mounted therein for opening and closing said polymer flow passage thereof, which is in fluid communication with instrument air flow passage thereof;
said tip having (i) a process air flow passage and (ii) a polymer flow passage which, respectively, are in fluid communication with said process air flow passage and said polymer flow passage of said die body; and
c) means for selectively delivering air to and from said instrument air flow passages of said manifold segment for actuating said air-actuated valve.
13. The segmented die assembly of
14. A die assembly comprising:
a manifold having first and second sections, a fluid passageway in said first section for conveying therethrough a material to be dispensed, and an air passageway in said second section for conveying therethrough process air to be discharged adjacent the material being dispensed,
first and second heaters respectively contained in said first and second sections and configured to separately heat the material in said fluid passageway and the process air in said air passageway to different temperatures,
a plurality of holes positioned between said first and second sections to disrupt the flow of heat between said fluid passageway and said air passageway,
a dispensing valve coupled with said manifold for receiving and dispensing the material conveyed through said fluid passageway of said first section and for receiving and discharging the process air conveyed through said air passageway of said second section.
15. A segmented die assembly comprising first and second side by side die units, each of said first and second die units comprising:
(a) an integral manifold block formed from a single piece of material having first and second sections, a fluid passageway in said first section for conveying therethrough a material to be dispensed, an air passageway in said second section for conveying therethrough process air to be discharged adjacent the material being dispensed, a front wall and a pair of oppositely disposed side walls,
(b) first and second heaters respectively contained in said first and second sections and configured to separately heat the material in said fluid passageway and the process air in said air passageway to different temperatures,
(c) a thermal isolator hole positioned between said first and second manifold block sections to disrupt the flow of heat between said fluid passageway and said air passageway, and
(d) a dispensing valve mounted upon said front wall of said manifold block for receiving and dispensing the material conveyed through said fluid passageway of said first section and for receiving and discharging the process air conveyed through said air passageway of said second section, and
a fastener connecting one of said oppositely disposed side walls of said manifold block of said first die unit to one of said oppositely disposed side walls of said manifold block of said second die unit.
16. The segmented die assembly of
This application claims the benefit of U.S. Provisional Application Ser. No. 60/077,780, filed Mar. 13, 1998.
This invention relates generally to dies for applying hot melt adhesives to a substrate or producing nonwovens. In one aspect the invention relates to a modular die provided with at least one air-assisted die tip or nozzle. 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 mounted thereon.
The deposition of hot melt adhesives onto substrates 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. Pat. No. 4,687,137, to air-assisted deposition such as that disclosed in U.S. Pat. No. 4,891,249, to spiral deposition such as that disclosed in U.S. Pat. Nos. 4,949,668 and 4,983,109. More recently, meltblowing dies have been adapted for the application of hot melt adhesives (see U.S. Pat. No. 5,145,689).
Modular dies have been developed to provide the user with flexibility in selecting the effective length of the die. For short die lengths only a few modules need be mounted on a manifold block. (See U.S. Pat. No. 5,618,566). Longer dies can be achieved by adding more modules to the manifold. U.S. Pat. No. 5,728,219 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 also the deposition pattern.
At the present, the most commonly used adhesive applicators are intermittently operated air-assisted dies. These include meltblowing dies, spiral nozzles, and spray nozzles.
Meltblowing is a process in which high velocity hot air (normally referred to as “primary air”) is used to blow molten filament 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 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.
The filaments extruded from the air-assisted die may be continuous or discontinuous. For the purpose of the present invention the term “filament” is used interchangeably with the term “fiber” and refers to both continuous and discontinuous strands.
Another popular die head is a spiral spray nozzle. Spiral spray nozzles, such as those described in U.S. Pat Nos. 4,949,668 and 5,102,484, 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 thereto. The filaments thus assume an expanding swirling cone shape pattern while moving from the extrusion nozzle to the substrate. As the substrate is moved in the machine direction 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 adhesive applications include the older non-air assisted bead nozzles such as bead nozzles and coating nozzles.
The segmented die assembly of the present invention is of modular construction, comprising a plurality of side-by-side and interconnected die units. Each die unit includes a manifold segment and a die module mounted on the manifold segment. The die module has mounted thereon an air-assisted die tip or nozzle. The die tip may be a meltblowing type and the nozzle may be a spiral nozzle or a spray nozzle. For convenience of description, the term “nozzle” is used herein in the generic sense, meaning any air-assisted die tip or nozzle; and the term “air-assisted” means a nozzle through which is extruded a molten thermoplastic filament or filaments, and air jets, air streams, or air sheets which contact the molten filaments to divert, attenuate or change the flow pattern of the filament(s) and impart a desired characteristic to the filaments, either in terms of the size of the filaments or the deposition pattern.
The main components of each die unit, the manifold segment and the module, are provided with (a) air passages for delivering air to the nozzles and (b) a polymer flow passage for delivering a polymer melt to the nozzle. In the preferred embodiment, the nozzle is a meltblowing die tip provided with a row of orifices and flanking air slits, so that as a row of filaments are extruded through the meltblowing die tip, they are contacted with converging sheets of hot air that attenuate or draw down the filaments to microsize. As described in detail below, the nozzle may also be a spiral or spray nozzle. In practice, the die assembly may include segmented units having different types of nozzles.
The segmented die units are assembled by interconnecting several identical manifold segments, wherein the air passages and the polymer flow passage of each segment are in fluid communication. In the assembled condition, the interconnected manifold segments function much in the manner of an integrated manifold. A die module is mounted on each manifold segment and, in combination with other die modules, form a row thereon. Thus, polymer melt is extruded as a row of filaments from the array of modules and deposited on a moving substrate positioned under the assembly.
In a preferred embodiment, each module is provided with an air-actuated valve to selectively open and close the polymer flow passage. The instrument air for activating the valve is delivered through each manifold segment to the module. The valves may be individually actuated or actuated as a bank, depending on the instrument air passages and the number of control valves used.
The segmented die assembly of the present invention offers several advantages over the prior art:
These and other advantages of the assembly of the present invention will be apparent to those skilled in the art.
With reference to
In the embodiment illustrated in
Each of the main components, manifold segment, die module, and controls is described in detail below.
The preferred die modules 12 are the type described in U.S. Pat. Nos. 5,618,566 and 5,728,219, the disclosures of which are which are incorporated herein by reference. It should be understood, however, that other die modules may be used. See, for example, U.S. patent application Ser. No. 09/021,426, filed Feb. 10, 1998, entitled “MODULAR DIE WITH QUICK CHANGE DIE TIP OR NOZZLE.”
As best seen in
Side ports 26 and 27 are formed in the wall of the die body 16 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 or air) to and from each side of piston 22.
Mounted in the lower recess 18 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 18 and has a plurality (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 36 interconnecting the ports 37.
Valve stem 25 extends through body opening 19 and axial opening 31 of insert member 30, and terminates at end 40 which is adapted to section valve port 32. The annular space 45 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 illustrated in FIG. 4. As discussed below, actuation of the valve assembly 21 moves stem end 40 away from port 32 (open position), permitting the flow of polymer melt therethrough. Melt flows from the manifold 11 through side port 38, through 37, through annular space 45 discharging through port 32 into the die tip assembly 13. Conventional o-rings may be used at the interface of the various surfaces as illustrated in the drawings.
The die tip assembly 13 comprises a stack up of four parts; a transfer plate 41, a die tip 42, and two air plates 43a and 43b. The assembly 13 can be preassembled and adjusted prior to mounting onto the body 16 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 FIG. 4. When mounted on the lower mounting surface of body 16, the transfer plate 41 covers the cavity 34 and therewith defines an air chamber with the air holes 49 providing outlets for air from cavity 34. Opening 44 registers with port 32 with an o-ring between these providing a fluid seal at the interface surrounding port 32. Holes 49 register with air holes 57 formed in die tip 42.
The die tip 42 comprises a base member which is co-extensive with the transfer plate 41 and the mounting surface die body 16, and a triangular nose piece 52 which may be integrally formed with the base.
The nose piece 52 terminates in apex 56 which has a row of orifices 53 spaced therealong.
Air plates 43a and 43b are in flanking relationship to the nose piece 52 and define coverging air slits which discharge at the apex of nose piece 52. Air (referred to as process air) is directed to 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 the filaments 14 emerging from the row of orifices 53.
The module 12 of the type disclosed in
As seen in
As seen in
Adjacent middle sections 11A-F are joined by bolts 85 arranged in an alternating pattern of threaded and countersunk bolt holes. As seen in
Polymer melt thus enters the die through plate 61 at 64, fills passage 92, flows in parallel through holes 93A-F, fills continuous passage 94, flows in parllel through holes 96A-F, and enters die modules 12A-F through passages 38 (see FIG. 4). The polymer which enters the die modules is extruded to form filaments 14 as has been described. The polymer manifold design wherein the polymer flows between the two continuous passages 92 and 94 via a plurality of parallel holes serves to equalize the flow over the die length. Heating element 97 maintains the polymer of the proper operating temperature.
As seen in
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
In a second preferred embodiment a single solenoid valve may be used to activate valve 21 in a plurality of adjacent die modules. In this configuration the tops of holes 116 and 117 (labeled 116a and 117a) are plugged and side holes 126 and 127 opened. Side holes 126 and 127 are continuous holes and will intersect each of the flow lines 116 and 117 to be controlled. This is the closed position, pressurized air would be delivered to all of the modules simultaneously through hole 126 while hole 127 would be opened to the exhaust. The instrument air flow is reversed to open the valve.
As indicated above, the modular die assembly 10 of the present invention an be tailored to meet the needs of a particular operation. As exemplified in
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, and (b) variation of die nozzles (e.g. meltblowing, spiral, or bead applicators) to achieve a predetermined and varied pattern. 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 module die construction of the present invention.
The lines, instruments, and controls are connected and operation commenced. A hot melt adhesive is delivered to the die 10 through line 64, process air is delivered to the die through line 66, and instrument air or gas is delivered through line 67.
Actuation of the control valves 21 opens port 32 of each module 12 as described previously, causing polymer melt to flow through each die module 12. In the meltblowing modules 15, the melt flows through manifold passages 91, 93, 94, 96, through side ports 38, through passages 37 and annular space 45, and through port 32 into the die tip assembly 13. The polymer melt is distributed laterally in the die tip 13 and discharges through orifices 53 as side-by-side filaments 14. Multi-pass process air meanwhile flows through manifold passages 103 where it is heated, into slots 109 and 111, through air passage 113 and is delivered to modules 20A-F through ports 114A-F, respectively. Air enters each module 12 through port 39 and flows through holes 49 and 57 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 orifices 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.
In each of the flanking spiral nozzle modules 12, the polymer and air flows are basically the same, with the difference being the nozzle tip. 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. Pat. No. 5,728,129.
Typical operational parameters are as follows:
As described 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 % EVA). These polymers generally have lower viscosities than those used in meltblown webs. Conventional hot melt adhesives usable include those disclosed in U.S. Pat. Nos. 4,497,941, 4,325,853, and 4,315,842, the disclosures of which are incorporated herein by reference. The preferred hot melt adhesives include SIS and SBS block copolymer based adhesives. The adhesives contain block copolymer, tackifier, and oil in various ratios. The above 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. Pat. Nos. 5,145,689 and 5,618,566.
The typical meltblowing web forming resins include a wide range of polyolefins such as propylene and ethylene homopolymers and copolymers. Specific thermoplastics include ethylene acrylic copolymers, nylon, polyamides, polyesters, polystyrene, poly(methyl metharylate), 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 of objects with thermoplastics.
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.