APPARATUS AND METHOD FOR THE MANUFACTURE OF NONWOVEN WEBS AND LAMINATES

Abstract: Nonwoven laminates are made by a multi-station line (10A, 10B, 10C) comprising at least one spunbond die assembly and at least one meltblowing die assembly. Each station includes (a) a melt spinning die (51) which can be selectively equipped with a spunbond die insert (97) or a meltblowing die insert (96) and (b) a moveable support structure (15) for adjusting the proper die-to-collector distance, depending on the spunbond or meltblowing mode of operation. The multi-station line (10A, 10B, 10C) permits the selective manufacture of a variety of spunbond (S) and meltblown (M) laminates, including the S-M-S laminate.

Description: APPARATUS AND METHOD FOR THE MANUFACTURE OF NONWOVEN WEBS AND LAMINATES BACKGROUND OF THE INVENTION This invention relates generally to the manufacture of nonwoven webs by meltblowing and/or or spunbond processes. In one aspect, it relates to an apparatus with interchangeable meltblowing and spunbond dies. In another aspect, the invention relates to a novel filament drawing or stretching device. In still another aspect, the invention relates to the in-line manufacture of spunbond-meltblown laminates. Nonwoven fabrics have received commercial application in a variety of industries ranging from medical, diapers, filtration, apparel, draperies, absorption, environmental, to name but a few of such uses. The term "nonwoven" refers to a sheet, web or batt of directionally or randomly oriented fibers, made by bonding or entangling the fibers through mechanical, thermal, or chemical means. Nonwoven fabrics exclude paper and products which are woven, knitted, tufted, or felted by web milling. The fibers generally are man-made synthetics. Although nonwovens may be made by a number of processes, the most popular processes currently in use are meltblowing and spunbond processes. Meltblowing is a process for the manufacture of a nonwoven fabric wherein a molten thermoplastic is extruded from a die tip to form a -2- row of filaments (e.g. fibers) . The fibers exiting from the die tip are contacted with converging sheets or jets of hot air to stretch or draw the fibers down to microsize diameter. The fibers are then deposited onto a collector in a random manner and form a nonwoven fabric. The spunbond process involves the extrusion of continuous filaments through a spinneret. The extruded filaments are maintained apart and the desired orientation of the filaments are achieved by rotating the spinneret, by electrical charges, by controlled air streams, or by the speed of the collector. The filaments are collected on the collector and bonded by passing the layer of filaments through compacting roll and/or hot row calendering. Spunbonded webs generally have large average diameter (e.g. 1 2-1 00 microns, typically 1 5-50 microns) which are heavier and stiffer then meltblown fibers (e.g. 0.5-1 5 microns, typically 1 -10 microns) . A paper presented at "Fiber Producer Conference 1 983", in Greenville, South Carolina, entitled "Nonwoven Fabrics: Spunbonded and Meltblown Processes" describes the two processes in detail. The disclosures of this paper are incorporated herein by reference. It should be noted that the terms "fibers" and "filaments" when used in connection with nonwovens are interchangeable. The meltblown fabrics are characterized as soft, porous with good hand, but are deficient in strength properties such as tensile strength and are not very wear resistant. On the other hand, the spunbond fabrics possess good strength properties and wear resistant but are not flexible as meltblown fabrics. -3- It was discovered several years ago that the properties of the meltblown and spunbond fabrics could be combined by a laminate consisting of at least one layer of the meltblown web and at least one layer of the spunbond web. U.S. Patent 4,041 ,203 discloses such a laminate. Over the years, improvements have been made in the laminate, the most popular being the so-called S-M-S structure (spunbond-meltblown- spunbond) wherein a meltblown layer is flanked by two spunbond layers. The layers may be bonded together by compaction or by calendering, and exhibit outstanding strength properties, energy absorption, tensile strength, and tear resistance, and yet possess a soft, flexible feel or hand. The S-M-S structures can be made by laminating the preformed webs or can be made by in-line operations wherein (a) spunbond filaments are laid on a moveable collector forming a first layer, (b) meltblown filaments are deposited on the first layer, and finally, (c) a second layer of spunbond filaments is deposited on top of the meltblown layer. The three layered structure then can be bonded together. The in-line operation thus requires two spunbond apparatus and one meltblowing apparatus. The spunbond apparatus are large structures because of the long distance of the collector from the spinneret and are not readily adapted to other processes such as meltblowing. The meltblowing apparatus, on the other hand, employs a relatively short distance from the die to the collector and is not readily adapted to the spunbond process. The in-line apparatus thus is restricted to manufacturing only one type of laminate: the S-M-S laminate or portions thereof. .4. SUMMARY OF THE INVENTION It is an object of the present invention to provide an apparatus which features interchangeable dies. That is, a spunbond apparatus can be readily converted to a meltblowing apparatus; or alternatively, a meltblowing apparatus can be readily converted to a spunbond apparatus. It is further an object of the present invention to provide a multi-station, in-line spinning operation or method wherein each station can be selectively operated to produce a spunbond web, or a meltblown web. The flexibility of each station permits the selective manufacture of a variety of laminates which include meltblown and/or spunbond layers in different combinations. It is a further object of the present invention to provide a meltblowing die with a filament drawing device to increase the filament drawdown and produce finer filaments. The filament drawing device can also be used with advantage on the spunbond apparatus. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side plan view of an in-line three station assembly showing the first and third stations in the spunbonding mode and the middle station in a meltblowing mode. Figure 2 is a side plan view of the apparatus shown in Figure 1 showing the side view of the first station. Figure 3 is an enlarged front view of the melt spinning assembly shown in each of the three stations. -5- Figure 4 is an enlarged cross-sectional view of a portion (die body) of the melt spinning assembly shown in Figure 3. Figure 5 is a cross-sectional view of the die body shown in Figures 3 and 4 without a die-insert mounted therein. Figure 6 is a cross-sectional view of the die body shown in Figure 5 with the cutting plane taken along 6-6 thereof. Figure 7 is an enlarged view of a meltblowing die insert shown detached from the die body and shown in transverse cross-section. Figure 8 is an enlarged view of a spunbond die insert and shown in transverse cross-section. Figure 9 is a bottom plan view of the spinneret shown in Figure 8. Figure 1 0 is an enlarged top plan view of the filament drawing device shown in Figures 1 , 2 and 1 2. Figure 1 1 is a partial cross-sectional view of the filament drawing device shown in Figure 1 0 with the cutting plane taken along lines 1 1 -1 1 thereof. Figure 1 2 is a side plane view illustrating a modified meltblowing die assembly equipped with a filament drawing device shown in Figures 1 0 and 1 1 . Figure 1 3 is a fragmentary, enlarged view of a portion of the support structure illustrating a lifting jack for telescopically moving concentric legs of the support structure. -6- Figure 14 is a cross sectional view of a different meltblowing die insert. DESCRIPTION OF THE PREFERRED EMBODIMENTS Because of the complexity of the structures embodied in the present invention, the invention will be described first, and with general reference, to the three station in-line assembly (Figure 1 ), followed by the description of the various components thereof, including the melt spinning assembly, the meltblowing die insert, the spunbond die insert, the filament drawing device, and an alternative design for the meltblowing assembly. Following the description of the various components, the operation of the assembly will be described illustrating the flexibility of the multi-station line, particularly with respect to the interchangeability of the dies at each station. General Description of the Multi-Station Line (Figures 1 and 2) The stations 10A, 10B and 10C of the multi-station line may include many identical components. The same reference numerals will designate the corresponding component at each station. For example, the extruder at each station is designated by reference numeral 22. Referring specifically to station 1 0A, this station comprises a support structure which may be in the form of four vertical legs 1 1 interconnected by cross beams 1 2. Each of the legs 1 1 are hollow and are concentrically mounted over interior legs 1 3 which are anchored to the floor. The legs 1 1 and 1 3 may be of any cross section but are preferably square and are sized to permit telescopic movement therebetween. The -7- means for telescopically moving the outer legs 1 1 in relation to the inner legs 1 3 may take a variety of forms including hydraulic rams. The preferred means, however, is a conventional screw jack assembly 50 located at the upper end of each leg 1 1 as illustrated in Figure 1 3. The jack assembly 50 comprises a gear box 55 driven by drive shaft 59 which turns screw 60. Screw 60 is threaded to bushing 69 affixed to the upper end of leg 1 1 . Turning the screw 60 in one direction raises the legs 1 1 and support structure 1 5. Turning the screw 60 in the opposite direction lowers the legs 1 1 and support structure 1 5. The support structure 1 5 and equipment mounted thereon is thus moveable vertically between an upper position (station 1 0A) and a lower position (station 1 0B) . A melt spinning assembly, shown generally as 1 6, is mounted on the moveable support structure 1 5 by air pipes which include a pair of vertical air pipes 1 8 (see Figure 2) and a horizontal pipe section 1 9. There are two pairs of air pipes 1 8, one pair being mounted on each side of the melt spinning assembly 1 6. One pair, shown in Figure 2, is connected to opposite ends of air box 20 of the melt spinning assembly 1 6 as described in detail below. The horizontal pipe 1 9 of each pair of pipes may be secured to cross beam 1 2. Thus the melt spinning assembly 1 6 is suspended on the moveable support structure 1 5. (The term "melt spinning assembly" is used herein in the generic sense referring to both meltblowing and spunbond die assemblies.) An extruder 22 is mounted on the moveable support structure 1 5 as illustrated in Figure 2 and comprises hopper 23, barrel 24, and -8- polymer feed line 25. The polymer feed line 25 delivers polymer melt to the melt spinning assembly 1 6 as described in more detail below. Positioned directly under the melt spinning assembly 1 6 and in alignment therewith are a pair of air quench ducts 26 and a filament drawing device 27. These two components, 26 and 27, are both supported on a platform 28 in stacked relationship by brackets (see Figure 2). The pair of ducts 26 define a quench zone 49 therebetween. The drawing device 27 is also constructed as a pair of conduits defining a filament drawing or stretching zone 46 therebetween. The vertical space between the quench ducts 26 and the drawing device 27 may include sheet metal housing 47 and the vertical space between drawing device 26 and platform 28 may include sheet metal housing 48. The platform 28 has an opening 32 formed therein. The filaments 30 discharging from the melt spinning assembly the descend through the quench zone 45, housing 47, draw zone 46, housing 48, opening 32 and are deposited on belt or conveyor 36. The components 26, 27, 47 and 48 are mounted on a wheeled carriage 33, as illustrated in Figure 2, so that this assembly may be moved as a unit to the operating position (Figure 2) or moved at right angles to the conveyor 36 to an inoperative position. The conveyor 36 traverses all three stations as illustrated in Figure 1 and is adapted to collect filaments from each station. The conveyor 36 is perforated or a fine-mesh screen to permit the passage of air therethrough. Vacuum means 25 positioned under conveyor 36 at each station may be used to withdraw the air and debris. -9- Air is delivered to the quenching ducts 26 as shown schematically at 34, and air is delivered to the filament drawing device 27 as shown at 35. Station 1 0C is substantially identical to station 1 0A, both of which depict the spunbond mode of the equipment mounted thereon. The melt spinning assembly 1 6 at these stations are provided with spunbond die inserts as described below. Station 1 0B represents the meltblowing mode of the apparatus. In this mode, the carriage 33 and equipment mounted thereon is moved to the inoperative position and therefore does not appear in Figure 1 for station 1 0B. In this station, the moveable support structure 1 5 is moved to its lower position. The lower position of the moveable support structure 1 5 is required because of the short distance between the meltblowing die outlet and the conveyor 36. The melt spinning assembly 1 6 of station 10B is provided with a meltblowing die insert. The operation of the three station line shown in Figure 1 is as follows: spunbond filaments 30 are deposited on the conveyor 36 forming a filament layer 42. Layer 42 is carried under the meltblowing die at station 1 0B which deposits meltblown filaments thereon forming layer 43. These layers are carried under station 10C where another layer 44 of spunbond filaments are laid thereon. As noted above, layers may be further processed through calendering or compaction to bond them together. -1 0- Melt Spinning Assembly (Figure 3) The term "melt spinning" as used herein means the conversion of a polymer melt to filaments by extruding the melt through orifices. The spinning assembly comprises a die assembly 51 , positive displacement pump 52, motor 53, gear box 54, and shaft 56. The polymer feed line 25 delivers polymer melt to the spinning assembly 1 6. Motor 53 drives the gear pump 52 which receives the polymer melt and delivers the same at metered rates to the die assembly 51 which distributes and discharges the melt through orifices as filaments 30. Air connectors 57 and 58 mounted on each side of the die assembly 51 connect to the air lines 1 8 which delivers pressurized hot air to the die assembly 51 in meltblowing mode. The gear pump 52, motor 53, and gear box 54 may be similar to that described in U.S. Patent 5,236,641 , the disclosure of which is incorporated herein by reference. As best seen in Figure 5, the die assembly 51 comprises a die body 61 having a downwardly opening cavity 62 formed in its lower end. Die body 61 may be constructed in halves as illustrated in Figure 5, wherein one half has a polymer inlet passage 67 connected to line 25 for feeding the polymer melt to the inlet of the gear pump 52. The cavity 62 is defined by two elongate side walls 63 and top surface 64. Elongate, v-shaped grooves 66 are formed on each side wall 63. -1 1 - The die body 61 has longitudinally spaced air passages 68 for interconnecting air connectors 57 and 58 with opposite sides of the cavity 62. As best seen in Figure 6, the die body 61 has formed therein a "coathanger" distribution configuration comprising inlet 71 , lateral channels 72 and 73, the ends of which are interconnected with channel 74. The area circumscribed by channel 72, 73 and 74 is specially shaped to effect a uniform distribution of the polymer entering inlet 71 to channel 74, consistent with known coathanger type distribution systems. Holes 76 shown in Figure 6 adapted to receive bolts for bolting the two body halves 61 together. Electrical heaters may be mounted in the die block 61 for maintaining the temperature of the die body at the operating level. Inlet passage 71 registers with the outlet of the gear pump 52 to receive polymer melt therefrom and to distribute the same equally to channel 74. As mentioned previously, the air box 20 on each side of the die body 61 is suspended between pipes 18. (See Figure 2) . As best seen in Figure 4, each air box 20 defines an internal elongate square chamber 81 which extends substantially the entire length of the die body 61 and is connected to the air connector 57 through plate 82 as by welded connections. Each connector 57 may be a welded assembly of plates 83, 84, 85 and 86 which in combination define an internal air chamber 87 and is bolted to each side of body 61 by bolts 92. Plate 82 has a plurality of air -1 2- passage holes 88 distributed along the length thereof for feeding air from chamber 81 to chamber 87. Mounted within chamber 87 are baffles 89 and 90 which define a tortuous flow path within chamber 87. The outlet for chamber 87 is provided by a plurality of air holes 91 which register with the plurality of air holes 68 formed in the die body 61 . The air passage 68 formed in each die half of body 61 extends to the interior of the die body and forms a right angle discharge into cavity 62 as at 92. The right angle turn in the flow passage 68 may be smoothed by the use of inserts 93 bolted to the die body as illustrated. Air delivered to each connector 57 flows from the air chamber 81 defined thereby inwardly to air passage 68 and enters the cavity at air passages 92. As indicated previously, the die assembly comprises die body 61 and a die insert assembly 96 or 97 which fits into and is mounted within cavity 62. The insert assembly may be in the form of a meltblowing die (herein referred to as meltblowing die die insert 96) shown in Figures 4 and 7 or may be in the form of a spunbond spinneret (herein referred to as spunbond insert 97) shown in Figures 8 and 9. Meltblowing Die Insert (Figures 4 and 7) Referring first to the embodiment using the meltblowing die insert 96, this assembly comprises a support member 98 (sometimes referred to as a transfer plate) and a die tip 99 mounted thereon. Members 98 and 99 are joined by a series of bolts (one shown as 1 09) . Member 98 as a top surface 1 01 which contacts surface 64 of cavity 62, and has side -1 3- walls 1 02 which fit in close conformity with the side walls 63 of cavity 62. Also formed in the support member 98 are a pair of longitudinally extending V-shaped grooves 1 04. These grooves align with the cavity grooves 66 with the insert 96 mounted in cavity 62. A plurality of air holes 1 03 extend vertically through the support member 98. The inlet of each air passage 1 03 is aligned with the outlet 92 of each air passage formed in the die body 61 . Also formed in the support member 98 is an elongate channel 106 that extends through the longitudinal axis thereof. The inlet of channel 1 06 registers with channel 74 of the die body 61 with the meltblowing die insert 96 mounted in cavity 62 (see Figure 4). An o-ring 1 07 surrounds the inlet 1 06. The die tip assembly 99 comprises a die tip 1 07 and a pair of air plates 108. The die tip 99 has a downwardly projecting triangular nosepiece 1 1 1 defined by converging surfaces 1 1 2 and 1 1 3. Surfaces 1 1 2 and 1 1 3 meet at apex 1 14, and a plurality of orifices 1 1 6 are spaced longitudinally along the apex 1 14. A polymer flow channel 1 1 7 extends through the die tip 99 and has an inlet which is aligned with polymer flow passage 106 of support member 98. The flow passage 1 1 7 pinches down to deliver polymer to the orifices 1 1 7. The nosepiece 1 1 1 may be integrally formed in the die tip 99 as illustrated or may be a separate piece bolted to the body of the die tip 99. Also formed in the die tip 99 are air passages 1 1 8 which register with air passages 1 03 of support member 98. The air plates 1 08 are mounted on the die tip 99 by a plurality of bolts, one shown as 1 1 9. -1 4- The air plates 1 08 flank the nosepiece 1 1 1 and with surfaces 1 1 2 and 1 1 3 define converging air gaps 1 21 . Each air plate 1 08 defines with a confronting surface of the die tip a tortuous air passage 1 24. The meltblowing die tip insert 96 fits in close conformity in cavity 62 of the die body 61 . As described, the polymer flow passages and air passages of the assemblies are respectively in fluid communication so that air flows through the assembly discharging from air gaps 1 21 as converging air sheets at the apex 1 14 of the nosepiece as polymer flows from the gear pump 52 through the die body 61 , the meltblowing die insert 96 discharging as filaments through orifices 1 1 6 of the die tip. The meltblowing assembly at Station 10B may include chilled quench air (secondary air) by separate air ducts (not shown) which discharge chilled air onto the filaments as they are extruded from the orifices 1 1 6. Figure 14 illustrates an alternative meltblowing die insert design. Corresponding parts illustrated in Figure 7 are indicated by the same reference numerically in Figure 1 4. The die insert is also described in more detail in U.S. Patent 5, 1 45,689, the disclosure of which is incorporated herein by reference. Spunbond Die Insert (Figures 8 and 9) The spunbond die insert 97 comprises a support member 1 26 which may be substantially identical to support member 98 described previously except no air passages are formed therein. The support member 1 26, however, does have the top surface 1 27, side surfaces 1 28, and v- -1 5- shaped grooves 1 29 which may be identical surfaces 1 01 , 1 02, and grooves 1 04, respectively of the meltblowing die insert 96. Support 1 26 is provided with a polymer opening or channel 1 31 which aligns with channel 74 of the die body 61 with the die insert 1 26 mounted in cavity 62. Note that since there are no air passages in support member 1 26, the air passages in the die body 61 are blocked off by surface 1 27. The support member 1 26 is attached to spunbond spinneret 1 32 which comprises a body member 1 33 and a spinneret plate 1 34 bolted together by a plurality of bolts 1 35. The body member 1 33 in combination with the plate 1 34 defines a feed chamber 1 36 having an inlet in registry with passage 1 31 of the support member 1 28. The spinneret plate 1 34 has a plurality of flow passages 1 37 formed therein which reduce down to orifices 1 38 at their outlets. As shown in Figure 9, the orifices 1 38 form a grid through which the filaments are extruded. The number and spacing of the orifices 1 38 may be in accordance with well known spunbond practices. (See for example U.S. Patent 4,340,563, 5,028,375 and 5,545,371 .) Each of the die inserts 96 and 97 are selectively inserted into the cavity 62 of the die body 61 and maintained there in place by a pair of square bars 1 41 which fit into square holes defined by v-grooves 66 and 1 04 or 1 29 on each side wall of the cavity 62. With the selected die insert 96 or 97 in place and the bars 1 41 inserted, bolts 1 42 spaced therealong, and threaded thereto on each side of die body 61 engage one side of the -1 6- bar 1 41 so that turning the bolts in one direction clampingly secures the insert sealingly onto cavity top surface 64. The above description of the die body 61 and meltblowing and spunbond die inserts 96 and 97 makes it clear that the system can be readily converted from one mode to the other by simply selecting the insert die and inserting it into the cavity 62. This, of course, requires the adjustment of the moveable support structure 1 5 to accommodate the operating mode. The means for inserting the die inserts 96 or 97 into cavity 61 may be manual or automatic. Stations 10A and 10C in Figure 1 depicts the spunbond mode and station 10B depicts the meltblowing mode. At station 1 0B, polymer melt is delivered from the extruder 22 through the melt spinning assembly 1 6 provided with meltblowing die insert 96 and discharged as microsized filaments from the row of orifices 1 1 6. The filaments 1 1 6 are contacted on opposite sides by converging hot air streams and carried to and deposited on the conveyor 36. In the meltblowing mode, the moveable support structure is positioned at its lower position. For the spunbond mode of operation (stations 10A and 10B), the spunbond die insert 97 is inserted in the die body 61 and the moveable substructure 1 5 is moved to its upper position. The quench air assembly 26 and filament drawing device 27 are positioned in place by moving the carriage 33 to the position in Figure 2. Air is delivered to the quench ducts 26 and to the drawing device 27 while filaments 30 extruded through -1 7- orifices 1 38 descend from the spinning assembly 1 6 through the quench zone 45 and drawing zone 46 and are finally deposited on the conveyor 36. Filament Drawing Device (Figures 1 0 and 1 1 ) The filament drawing device 27 serves to drawdown or stretch the filaments of either the spunbond mode or meltblowing mode of operation. As illustrated in Figures 1 and 2, a pair of longitudinally extending air conduits 1 42 are disposed below the quench ducts 26. The air conduits 1 42 are separated by space (the stretching zone 46), through which the extruded filaments pass. Each of the conduits 1 42 is connected to an air supply 35 and, as shown in Figure 1 1 , comprises a rectangular chamber 1 44 which receives air from two pipes 35 at opposite ends thereof. Each conduit 142 is divided by a separation plate 147 into a second chamber 146. Plate 147 has a plurality of holes 148 distributed longitudinally therealong, providing fluid communication between chambers 1 44 and 1 46. Mounted in each chamber 1 46 are a pair of baffles 1 49 and 1 50 which define a tortuous path for the air flowing through chamber 1 46. An end wall 1 51 defining chamber 1 46 is secured a pair of elongate members 1 52 and 1 53 which in combination define a tortuous path for the air flowing therethrough. A plurality of holes 1 54 formed in end wall 1 51 discharge into a plurality of air passages 1 56 which discharge into air passage 1 59 defined by confronting surfaces of member 1 52 and 1 53. The outlet 1 58 of the air passage 1 57 is directed downwardly with respect to the filaments flowing through stretching zone 46. The angle of contact of the air discharging from the elongate passage 1 58 with respect to the -1 8- filaments passing therethrough should be between about 1 and 80 degrees (including angle β) preferably between 5 and 50 degrees, most preferably 1 0 to 30 degrees. As the filaments pass through zone 46, the converging air sheets from passages 1 58 of each half of the drawing device 27 impart drag forces thereto and stretches or draws down the filaments to a smaller diameter. Meltblowing Die Assembly With Filament Drawing Device (Figure 1 2) Figure 1 2 illustrates an alternative meltblowing mode of operation, wherein the melt spinning assembly 1 6 is provided with a meltblowing die insert 96 and is mounted above the drawing device 27. As illustrated, the device 27 may be mounted on the platform 28 which, as described above, is mounted on a carriage 33 for removing or inserting the device 27 in the line. Sheet metal may be also used to define housings 38 and 39 through which the meltblown fibers must pass. As the fibers pass through housing 38, drawing zone 1 46 and housing 39, the downwardly converging sheets of air contact the meltblown filaments imparting drag forces to further drawdown the fibers. The additional drawdown by the use of the filament drawing device produces microsized fibers in the range of 0.5 to 5 microns, preferably 1 to 2 microns. Note that in this alternative mode of meltblowing operation, the DCD (die to collector distance) is much larger than the DCD for conventional meltblowing as is apparent by comparing station 1 0B with -1 9- Figure 1 2. With the drawing device 27, the DCD ranges from 3 to 8 feet, preferably from 3 to 7 feet, most preferably 4 to 6 feet. OPERATION Operating Parameters for the Spunbond Station(s) The resin used in the spunbond die(s) can be any of the commercially available spunbond grades, including a wide range of thermoplastics such as polyolefins, polyamides, polyesters, PVA, PVC, polyvinyl alcohol, cellulose acetate and the like. Polypropylene, because of its availability, is the preferred thermoplastic. The operation parameters of the spunbond stations using polypropylene (MFR 1 0 to 400) may be as follows: Broad Range Preferred Ranqe Spinning Plate length (m) 0.5 to 6 0.5 to 4.5 width (in) 2 to 1 2 3 to 6 Orifices spacing (in) 0.05 to 0.250 0.1 to 0.1 25 diameter (in) 0.001 to 0.040 0.01 6 to 0.020 Quench Ducts size height (m) 0.5 to 2 0.8 to 1 .2 width (m) 0.5 to 6 0.5 to 4.5 Die to Collector (m) 0.1 to 5 0.1 to 2 Distance (DCD) Polymer Melt Temp. (°F) 325 to 750 375 to 550 Rate (Gr./hole/min) 0.05 to 5 0.3 to 1 .2 Quench Air Temp. (°C) 2 to 20 5 to 1 5 Rate (SCFM/in) 1 ,000 to 20,000 5,000 to 1 5,00 -20- Drawing Device Temp. Ambient Rate (SCFM/in) 1 to 1 00 5 to 20 The specification and operating parameters listed above are for purposes of illustration. The spinning plate and chamber, as well as the quenching ducts may be conventional. Reference is made to U.S. Patents 3,692,61 8, 4,041 ,203 and 4,340,563, the disclosure of which are incorporated herein. Operating Parameters for the Meltblowing Station The meltblowing die (e.g. orifices, size and spacing) may be constructed in accordance with a variety of designs including those disclosed in U.S. Patents 3,92,759, 4,81 8,463, the disclosure of which are incorporated herein by reference. The specification and operating parameters listed above are for purposes of illustration. The spinning plate and chamber, as well as the quenching ducts, may be conventional. Reference is made to U.S. Patents 3,692,61 8, 4,041 ,203 and 4,340,563, the disclosure of which are incorporated herein. Operating Parameters for the Meltblowing Station(s) The meltblowing die (e.g. orifices size and spacing) may be constructed in accordance with a variety of designs including those disclosed in U.S. Patents 3,972,759 and 4,81 8,463, the disclosure of which are incorporated herein by reference. The meltblowing die may process any of the commercially available meltblowing grade thermoplastic resins. These include a wide -21 - range of polyolefins such as propylene and ethylene homopolymers and copolymers. Specific thermoplastics includes ethylene acrylic copolymers, nylon, polyamides, polyesters, polystyrene, poly(methyl meth-acrylate), polytrifluoro-chloroethylene, polyurethanes, polycarbonates, 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 preferred resin is a meltblowing grade of polypropylene. The following is an illustrative example of a meltblowing station: Broad Range Preferred Range Orifice Row (length) 0.5 to 6 meters 0.5 to 4.6 meters Orifice Diameter (inches) 0.01 0 to 0.050 0.01 to 0.2 (Typically 0.01 5) Spacing (orifices/in) 1 0 to 40 20 to 35 Polymer Temp (°C) 1 75 to 300 200 to 270 Rate (Ger/hole/min) 2 to 5 0.3 to 1 .2 Primary Air Temp (°C) 1 75 to 300 200 to 275 Rate (SCFM/in) 2 to 1 00 5 to 30 Quench Air (if used) Temp (°C) 2 to 20 5 to 1 5 Rate (SCFM/in) 1 ,000 to 20,000 5,000 to 1 5,000 Drawing Air Temp Ambient Rate (SCFM/in) 1 to 1 00 5 to 20 -22- DCD Distance to Collector (inches) 3 to 24 5 to 20 DCD Distance to Collector (feet) 2 to 6 3 to 5 (Intermediate setting) Operating Procedure The multi-station line shown in Figure 1 illustrates the mode for manufacturing a spunbond meltblown-spunbond (S-M-S) laminate. In station 1 0A, the spinning assembly 1 6 is provided with a spunbond die insert 97 and the moveable support structure 1 5 is adjusted to the upper position to provide the desired DCD. The quench ducts 26 and filament stretching device 27 are moved into place. In station 1 0B, the carriage 33 with the equipment mounted thereon has been removed and the melt spinning assembly 1 6 is provided with a meltblowing die insert 96. The moveable support structure 1 5 is positioned at its lower position placing the spinning assembly 1 6 at its proper meltblowing DCD. Station 1 0C is identical to station 1 0A. The operations are commenced by spinning continuous filaments from the spunbond die 97 of station 1 0A. The filaments pass through the quenching zone 45 which not only cools the filaments but maintains them apart to prevent the filament from sticking together. The quenched filaments pass through the stretching zone 46 of device 27 wherein air discharging therefrom further drawsdown and attenuates the filaments. The filaments are deposited on the conveyor 36 in a random fashion. The spunbond filaments have an average diameter of 1 2 to 50 -23- microns, preferably 1 5 to 40 microns. Air passes through the conveyor 36 and is withdrawn by the vacuum system 25. Layer 42 is conveyed under the spinning assembly of station 1 0B wherein a microsized fibers having an average fiber diameter of 0.5 to 1 5 microns, preferably 1 to 10 microns, most preferably 2 to 6 microns, is blown onto layer 42 forming meltblown layer 43 on spunbond layer 42. The two layer laminate is then conveyed under Station 1 0C wherein another layer 44 of spunbond filaments are deposited on top of the meltblown layer 43, completing the S-M-S structure. The three layer structure may then be passed through a calendering or other device to bond the layers together in the conventional manner. Based on the description contained herein, it will be readily apparent to those skilled in the art that the apparatus of the present invention offers flexibility not attainable with prior art devices. By selectively modifying the stations, the line can produce, in addition to S-M-S structure, the following laminates: S-S, M-M, S-M, M-S using only two of the stations. S-S-S, M-M-M wherein each layer may have different properties, or additives, or colors. S-S-M, M-S-M, M-M-S, S-M-M, M-S-S lamination using all three stations. The following summarizes the more important features of the present invention: (a) a moveable support structure for meltblowing or spunbond. -24- (b) a melt spinning assembly adapted to receive either meltblowing or spunbond die inserts. (c) a meltblowing die having an auxiliary or supplementary filament stretching device. (d) a novel filament stretching device that can be used with spunbond or meltblowing dies.

Claims: -25- WHAT IS CLAIMED IS: 1 . A die assembly for manufacturing thermoplastic nonwoven web which comprises (a) a melt spinning assembly which includes a die body having formed therein a cavity, an air passage, and a polymer flow passage, said air passage and polymer flow passage each having an inlet in an outer surface of the die body and an outlet discharging into the cavity; (b) a meltblowing die insert comprising (i) a die tip having formed therein a polymer flow passage and an air passage, a triangular nosepiece terminating in an outer apex, orifices formed in and spaced along the apex, the orifices being in fluid communication with the die tip polymer flow passage, and (ii) air plates mounted on each side of the nosepiece and therewith defining converging air slits which are in fluid communication with the die tip air passage; the meltblowing die insert being mountable in the cavity wherein the air passage of the die body are in fluid communication with the air passage of the die tip, and wherein the polymer flow passage of the die body is in fluid communication with the polymer flow passage of the die tip; (c) a spunbond die insert comprising a spinning plate and polymer flow passage formed therein; said spunbond insert being mountable in the cavity wherein the air passage in the die body is blocked and wherein the polymer flow passage of the spinning plate is in fluid communication with the polymer flow passage of the die body; and -26- (d) means for selectively inserting the meltblowing die insert or the spunbond die insert in the cavity of the die body and for securing the selected die insert therein. 2. The assembly of Claim 1 and further comprising means for delivering a polymer melt to the polymer flow passage of the die body wherein the polymer melt flows through the die body, through the flow passage of the die insert mounted in the die body cavity discharging as filaments therefrom. 3. The assembly of Claim 1 wherein the meltblowing die insert is mounted in the cavity and the assembly further comprises means for delivering a polymer melt to the melt spinning assembly wherein the polymer melt flows through the polymer flow passages of the die body and the meltblowing die tip discharging as filaments from the orifices of the nosepiece, and means for delivering hot air to the melt spinning assembly air passage whereby air discharges as converging air sheets from the air slits into contact with the filaments discharging from the orifices. 4. The die assembly of Claim 1 wherein the die assembly further comprising a moveable collector disposed under the melt spinning assembly for receiving and collecting filaments thereon. -27- 5. The die assembly of Claim 4 and further comprising a moveable support structure for supporting the melt spinning assembly, and means for moving the support structure vertically to selectively adjust the die-to-collector distance between an upper position for the spunbond die insert and a lower position for the meltblowing die insert. 6. The assembly of Claim 1 and further comprising a carriage having mounted thereon a pair of quenching air ducts defining a quenching zone therebetween, said carriage being moveable into an operable position below the melt spinning assembly having the spunbond die insert therein and having the moveable support structure in the upper position whereby filaments extruded from the spinning plate pass through the quenching zone, said carriage being moveable to a withdrawn nonoperative position permitting the support structure to be lowered to the lower position. 7. The die assembly of Claim 6 wherein the carriage further has a filament drawing device mounted thereon, said filament drawing device comprising a pair of air conduits defining a drawing zone therebetween, and being positioned below the quench ducts to receive filaments therefrom, said conduits also having air slits discharging into the drawing zone to impart downward drag forces on the filaments passign therethrough. 8. An apparatus for the in-line manufacture of a laminate of thermoplastic layers comprising -28- (a) first and second side-by-side stations, each station having (i) a vertically moveable support structure, (ii) an extruder mounted on the moveable support structure, (iii) a melt spinning die body mounted on the moveable support structure, said die body having a downwardly facing cavity formed therein, and (iv) means for delivering a polymer melt from the extruder to the die body; (b) a spunbond die insert mounted in the cavity of the die body of one of the stations and including means for receiving polymer melt from the die extruder and converting the melt into filaments; (c) a meltblowing die insert mounted in the cavity of the die body of the other of the stations and including means for receiving polymer melt from the extruder and converting the melt into meltblown filaments, said spunbond die insert and said meltblowing die insert being interchangeable; (d) a moveable filament collector positioned under the spunbond die insert and the meltblowing die insert for receiving filaments therefrom to form layers thereon; and (e) means for selectively moving each support structure to adjust the distance of the die-to-collector for each station. -29- 9. The apparatus of Claim 8 wherein the spunbond die insert includes means for producing filaments having an average diameter of 1 2 to 50 microns, and the meltblowing die insert includes means for producing filaments having an average diameter of 1 to 1 0 microns. 1 0. The apparatus of Claim 8 and further comprising means for bonding the two layers together. 1 1 . The apparatus of Claim 8 wherein the means for delivering polymer to the die body includes a positive displacement pump mounted on the moveable support structure. 1 2. An in-line method of manufacturing thermoplastic nonwoven components comprising: (a) mounting a spunbond spinning assembly on a vertically moveable support structure having an upper position and a lower position; (b) positioning the support structure to its upper position wherein the spunbond spinning assembly is positioned at least four feet above the lower position; (c) positioning a quenching device and filament drawing device under the spinning assembly in vertical alignment therewith; (d) extruding filaments from the spinning device; (e) passing the filaments through the quenching device and a filament drawing device; -30- (f) depositing the filaments onto a conveyor to form a first layer; (g) mounting a meltblowing spinning assembly on a vertically moveable support structure; (h) positioning the support structure in its lower position wherein the meltblowing spinning assembly is from 6 inches to 3 feet above the conveyor; (i) passing the conveyor with the first layer under the meltblowing spinning assembly; (j) meltblowing filaments from the meltblowing spinning assembly; and (k) depositing the meltblown filaments on top of the first layer. 1 3. The method of Claim 1 2 wherein the filaments in step (d) are polyolefins selected from homopolymers and copolymers of ethylene and propylene and the filaments have an average filament diameter of in excess of 1 2 microns. 1 4. The method of Claim 1 3 wherein the meltblown filaments are polyolefins selected from homopolymers and copolymers of ethylene and propylene and have an average diameter of 1 to 1 0 microns. -31 - 1 5. The method of Claim 1 4 wherein the filaments are polypropylene. 1 6. The method of Claim 1 2 and further comprising the step of bonding the two layers together. 1 7. A meltblowing die comprising: (a) die body; (b) a die tip mounted thereon and having a triangular nosepiece terminating in an apex, a row of orifices formed in the apex and a polymer flow passage extending through the die body, the die tip and the nosepiece for conducting a polymer melt to the orifices; (c) air plates mounted in flanking relationship to the nosepiece and therewith defining converging air slits; (d) a filament drawing device positioned below the row of orifices, and comprising a pair of air conduits extending parallel to the row of orifices and being spaced apart to form a drawing zone, each air conduit having a flow slit directed to discharge air downwardly into contact with the filaments passing through the drawing zone, the angle of contact being from 1 ° to 80° with respect to the vertical plane. 1 8. An apparatus for forming thermoplastic filaments comprising (a) an elongate melt spinning assembly for discharging a plurality of filaments downwardly therefrom; -32- (b) a filament drawing device comprising a pair of air conduits positioned below the melt spinning device and defining a filament drawing zone therebetween, each conduit having formed therein an air slit positioned to deliver air downwardly into the drawing zone and contact the filaments passing therethrough at an angle of 5° to 50°; and (c) means for delivering air to each air conduit. 1 9. A method of manufacturing meltblown and spunbond webs which comprises (a) positioning an extruder and a melt spinning assembly on a vertically moveable support structure having an upper position and a lower position at least four feet below the upper position, said spinning assembly including a die body and a spunbond die insert, said extruder being connected to the melt spinning assembly; (b) positioning the moveable support structure to the upper position; (c) extruding filaments from the spunbond die insert; (d) collecting the filaments on a collector to form a nonwoven layer, said filaments having an average diameter of 1 2 to 50 microns; (e) discontinuing the extruding step (a) and replacing the spunbond die insert with a meltblowing die insert in the melt spinning assembly; -33- (f) positioning the moveable support structure to the lower position wherein the meltblowing insert is less than three feet from the collector; (g) meltblowing filaments from the meltblowing die insert; and (h) collecting the filaments on a collector, the filaments having an average diameter of between 1 to 10 microns. 20. The method of Claim 1 9 and further comprising the steps of positioning an air quench ducts below the melt spinning assembly with the moveable support at its upper position to receive filaments extruded from the spunbond die insert; and removing the air quench ducts following step (e) to permit the positioning of the moveable support structure to its lower position.

Inventors: ALLEN MARTIN A, ALLEN, MARTIN, A.
Applicants: NORDSON CORP, NORDSON CORPORATION
Application year: 1999
Main classification: D04H3
IPC codes: B32B5, D01D4, D01D5, D04H1, D04H3, D04H13