Abstract:
An adhesive dispensing die module for mounting on a manifold incudes (a) a die body having formed therein polymer and air flow passages, and a valve for selectively closing the polymer flow passage and (b) a die tip or die nozzle detachably mounted on the die body. The die tip or die nozzle is secured to the die body by a pair of clamping members depending from the die body and adapted to engage die tip or die nozzle therebetween. The clamping members can selectively be moved toward one another to clampingly secure the die tip or die nozzle therebetween or moved away from one another to release the die tip or die nozzle, permitting it to be replaced without the need to remove the die module from the manifold.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to dies for applying hot melt adhesives to a substrate using meltblowing, spiral, bead, spray, or coating patterns. In one aspect, the invention relates to modular die bodies with interchangeable and replaceable die tips or nozzles. In still another aspect the invention relates to an inexpensive disposable die module. 
     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, and 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). 
     At the present, the most commonly used adhesive applicators are intermittently operated air assisted dies. U.S. Pat. No. 5,618,566 discloses a modular die assembly comprising a row of side-by-side modules mounted on a manifold. Each module is provided with a die tip or nozzle through which the adhesive is extruded. U.S. Pat. No. 5,728,219 discloses a modular die assembly comprising side-by-side modules mounted on a manifold. Selected modules of the array may be provided with different types of extrusion die tips or nozzles. The term “nozzle” is used herein in the generic sense to describe the part of the applicator which determines the pattern of adhesive deposition (e.g. spray, bead, spiral, coating or meltblown). The nozzles for bead and spiral deposition are adapted to deposit a monofilament onto a substrate. The nozzles for meltblown applicators, also referred to as die tips, are designed to meltblow a row of filaments onto the substrate. Nozzles for bead and coating deposition are non-air assisted. 
     The availability of different types of nozzles for each module permits the operator to select a variety of deposition patterns. Each of the nozzle types has its own advantages and disadvantages. Meltblown nozzles provide a generally uniform covering of a predetermined width of the substrate, but do not provide precise edge control which is needed or desirable in some applications. On the other hand, the spiral nozzles deposit a controlled spiral bead on the substrate giving good edge control but not uniform substrate coverage. The bead and coating nozzles provide a heavier adhesive deposit than the meltblown or spiral patterns. 
     In order to replace a nozzle of a particular die module in the die assembly disclosed in U.S. Pat. No. 5,618,566, or change a nozzle type of a module in the die assembly disclosed in U.S. Pat. No. 5,728,219, it generally is necessary to (1) remove the module from the manifold (2) unscrew the four bolts mounting the nozzle assembly to the module, (3) substitute the new nozzle for the old nozzle, (4) resecure the nozzle assembly to the module, and (5) reattach the module to the manifold. Although this is a simple procedure compared to the non-modular die constructions, it nevertheless requires some shutdown time (on the order of 30 to 60 minutes). For this reason, the entire module is generally replaced and the old module repaired. 
     SUMMARY OF THE INVENTION 
     The modular dies of the present invention feature a die module having a quick disconnect assembly that permits the die tip or nozzle to be replaced without removing the module from the die manifold. Briefly, the die module comprises two main components: a die body mounted on a manifold, and a die tip or nozzle mounted on the die body. The die tip or nozzle is secured to the die body by a pair of clamping members adapted to engage opposite edges or sides of the die tip or nozzle. The members with the die body mounted on the manifold are movable between a clamping position and a nonclamping position. In the clamping position, the die tip or nozzle is forcefully secured to the die body. In the nonclamping position, the die tip or nozzle is free to be removed from the die body. 
     A novel feature of the invention vis-a-vis prior art die modules is the principle of operation of the clamping means for securing the die tip or nozzle to the body. 
     In the prior art devices (e.g. those disclosed in U.S. Pat. No. 5,618,566), the die tip is secured to the die body by bolts which apply a force in a direction normal to the plane of the mounting surface. In the module of the present invention, the mounting clamps create opposite forces on the opposite ends of the die tip, each force having a major component in a direction parallel to the plane of the die tip mounting surface and a component of forcing action in a direction normal to the mounting surface. The clamping force thus may be activated by a single pressure member (e.g. bolt) acting on one of the clamping members. 
     Another important novel feature of the clamping means is the location of the pressure member. Since only a single pressure applying member is needed it can be conveniently placed on the exposed front surface of the die body, permitting the clamping member to be activated or deactivated without removing the module from the manifold. 
     The die body comprises three main components: an upper body portion, a lower body portion and a cap. These components may be fabricated by interference fits which avoids the expensive machining required in prior art modules. 
     The interference-fit construction prevents access to the die body interior for repair. However, this is not a problem because economically it is cheaper to dispose of the damaged or faulty module and replace it with a new one. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of the die assembly constructed according to the present invention and provided with three different applicator nozzles. 
     FIG. 2 is an enlarged sectional view of the modular die shown in FIG. 1 with cutting plane indicated by  2 — 2  thereof. 
     FIG. 3 is an enlarged view of FIG. 2, illustrated internal features of the die module. 
     FIG. 4 is a fragmented view of the module shown in FIG. 3, illustrating the removal of a die tip from the die body. 
     FIG. 5 is a sectional view of the module shown in FIG. 3 with the cutting plane taken along line  5 — 5  thereof. 
     FIG. 6 is a view of the die tip shown in FIG. 4 taken from the perspective of the plane along line  6 — 6  thereof. 
     FIG. 7 is a cross-sectional view of the die tip nozzle shown in FIG. 4 with the cutting plane taken along line  7 — 7  thereof. 
     FIG. 8 is a sectional view of the die tip nozzle of FIG. 4, with the cutting plane taken along line  8 — 8  thereof. 
     FIG. 9 illustrates the angle β of the air holes in relation to the apex. 
     FIGS. 10 and 11 are sectional views of different applicator nozzles useable in the module disclosed in FIGS. 2,  3  and  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1 and 2, the modular die assembly  10  of the present invention comprises a manifold  11 , a plurality of side-by-side self-contained die modules  12 , and a valve actuator assembly including actuator  20  for controlling the polymer flow through the modules  12 . As best seen in FIG. 2, each module  12  includes a die body  16 , a die tip or a nozzle  18 , and nozzle retainer  19 . Filaments  14  are discharged from modules  12  onto a substrate  15  (or collector). The manifold  11  distributes a hot melt adhesive and hot air to each of the modules  12 . The modular die  10  includes meltblowing die tips  18  mounted on most of the die bodies  16 . Some of the modules  12 , however, may be provided with various types of nozzles. As illustrated in FIG. 1, end modules  12 A are provided with spiral nozzles and center modules  12 B are provided with coating nozzles. Spray nozzles and bead nozzles may also be used. 
     The main components mentioned above are described in detail below. 
     Die Body 
     As best seen in FIG. 3, the die body  16  may be constructed in two parts, an upper die body portion  16 A and a lower die body portion  16 B. For convenience of description these body portions will be referred to a merely as upper die body  16 A and lower die body  16 B. Die body  16 A has an upper circular recess  17  formed therein, the upper end of which is closed by cap  24 . The cap  24  has a skirt portion  24 A, which in combination with the wall of recess  17  defines a generally cylindrical chamber  23 . 
     A diaphragm  25  is mounted in chamber  23  dividing it into an upper chamber  23 A and a lower chamber  23 B. 
     Side ports  26  and  27  are formed in the wall of the die body  16 A to provide communication to chambers  23 A and  23 B, respectively. As described in more detail below, the ports  26  and  27  serve to conduct air (referred to as instrument gas) to and from chambers  23 A and  23 B. 
     Die body  16 A has formed therein a lower downwardly opening recess  28  surrounded by annular surface  29  and defined in part by surface  33 . A central bore  31  formed in die body  16 A extends downwardly from chamber  23 B to recess  28 . As described below, bore  31  receives valve stem  30 . 
     The lower die body  16 B has a cylindrically shaped projection  35  adapted to fit in the recess  28  as illustrated in FIG.  3 . Surface  36  surrounding the base of cylindrical member  35  engages surface  29  of die body  16 A, with o-ring  32  provided at the junction thereof. Surfaces  29  and  36  may be of the same general shape. 
     A bore  37  extends downwardly through die body  16 B terminating at bottom surface  39 . A stem seal  40  (e.g. spring lip seal) is mounted in the upper end of the bore  37 , and a valve insert  38  is mounted in the lower end of the bore  37  in contact with bottom surface  39  (see FIG.  4 ). Ports  41  and  42  formed, respectively, in insert  38  and surface  39  serve as a fluid outlet for bore  37 . The lower end of opening  42  is provided with an O-ring  43 . The bore  37  may be of variable diameter to accommodate the parts mounted therein. 
     The inlet to opening  41  is chamfered to provide a valve seat  44  for a valve stem  30  as described below. 
     As shown in FIGS. 4 and 5 the lower end of the die body  16 B has formed therein a downwardly opening air chamber  49  which surrounds a central cylindrical portion  45 . The air chamber  49  is defined by interior walls  48  and cylindrical portion  45 . Bore  37  and port  42  are formed in the cylindrical projection  45 . Bottom surfaces  46  and  47  of die body  16 B are coplanar for receiving a die tip or nozzle  18  as described in detail below. 
     The back side  56  (side mounted on the manifold  11 ) of body  16 B has a downwardly projecting narrow edge portion  51  terminating at end  52 . 
     The inner surface  53  of edge portion  51  is shaped to receive and support a complementary shaped edge portion of a die tip or nozzle  18 . As illustrated, the inner surface  53  is provided with a vertical wall and a downwardly tapered shoulder  54  projecting inwardly (with respect to die body  16 A) from the lower edge of wall  53 . The shoulder  54  has a flat angular surface for supporting an edge portion of die tip or nozzle  18 . 
     A polymer flow passage  57  formed in die body  16 A registers with polymer flow passage  58  formed in projection  35 . These passages deliver polymer melt to bore  37 . 
     Air passage  59 , formed in die body  16 B, serves to deliver air to air chamber  49 . 
     A valve assembly is provided in the module  12  to selectively start and stop the polymer flow therethrough. The valve seat  44  is opened or closed by movement of the diaphragm  25  which in turn moves stem  30 . 
     The valve stem  30  extends from chamber  23 B through opening  31  and into bore  37 . The upper end  61  of stem  30  is secured to diaphragm  25  and a lower end portion  62  of stem  30  is specially shaped to fit into the valve insert  38 . The insert  38  may be made of wear resistant material (carbide) and may include internal longitudinal ribs (spider members, one shown as  55 ) for guiding the stem portion  62  into the interior of the insert  38  and to permit the flow of fluid therethrough. The tip  63  of the stem is shaped to seat on the valve seat  44 . 
     The stem upper end  61  is provided with a collar  64  which is threaded for receiving bolt  65 . Bolt  65  secures the diaphragm  25  to the upper end  61  of stem  30 . A spring  66 , interposed between cap  24  and diaphragm  25 , urges the diaphragm  25  and valve stem  30  downwardly causing the valve tip  63  to seat on valve seat  44 . A wipe seal  67  is provided around stem  30  at the upper end of opening  31  formed in die body  16 A. 
     As described in detail below, the valve seat  44  is opened by activating chamber  23 B with instrument gas moving the diaphragm  25  and valve stem  30  upwardly, and compressing spring  66 . This moves valve tip  63  off of its valve seat  44 . The upper extent of the diaphragm  25  movement is set by the space between bolt head  65  and downwardly projecting head  69 . 
     Die Tip or Nozzle and Retainer 
     The die tip or nozzle  18  is adapted to be mounted on the downwardly facing and coplanar surfaces  46  and  47  of body  16 B. The nozzle  18  illustrated in FIGS. 2,  3  and  4 , is a meltblowing die tip, but as described below, may be a nozzle such as a spiral nozzle, a bead nozzle, a spray nozzle or a coating nozzle. 
     As shown in FIGS. 3 and 4, the die tip  18  comprises a base member  71  which is generally coextensive with the mounting surface  47  of die body  16 B, and a triangular nosepiece  72  which may be integrally formed with the base  71 . The nosepiece  72  is defined by converging surfaces  73  and  74  which meet at apex  76 . The apex  76  may be discontinuous, but preferably is continuous along the die module  12 . The height of the nosepiece  72  may vary from 100% to 25% of the overall height of the die tip  18 , but preferably is not more than 50% and most preferably between 20% and 40%. 
     The portions of the base  71  extending laterally from the nosepiece  72  serve as flanges for mounting the die tip  18  to the die body  16 B and having passages for conducting air and polymer melt through the base  71 . As best seen in FIG. 6, the flanges of the base  71  have two rows of air holes  77  and  78  formed therein. As shown in FIG. 4 the rows of air holes  77  and  78  define converging planes. The plane defined by air holes  77  extends at the same angle as nosepiece surface  73 , and the plane defined by air holes  78  extend at the same angle as nosepiece surface  74 . The included angles (α) of the planes and surfaces  73  and  74  ranges from 30° to 90°, preferably from 60° to 90°. (It is understood that reference to holes lying in a plane means the axes of the holes lie in the plane.) 
     While each row of air holes  77  and  78  lie in their respective planes, at least some of the air holes  77  and  78  within their respective planes need not be parallel. As best seen in FIGS. 8 and 9, the die tip  18  is provided with an odd number (e.g.  17 ) of air holes  77 , each having an inlet  79  and an outlet  80 . (Note the row of air holes  78 , on the opposite side of the nosepiece  72  is preferably the mirror image of the row of air holes  77 , although they need not be. For example the air holes  78  may be offset from air holes  77 .) 
     The die tip  18  further includes surface  70  which is mounted on surface  47  of the die body  16 A, closing cavity  49 . Surface  70  also engages surface  46  with O-ring  43  providing a fluid seal at the junction of these two surfaces. Surface  70  is substantially coextensive with the outer periphery of surface  47 . 
     With the die tip  18  mounted on the die body  16 , the inlets  79  of all of the air holes  77  and  78  register with cavity  49  as shown in FIG.  3 . 
     The central air holes (in this embodiment air hole  77 A) extends perpendicular to the apex  76  as shown in FIG.  8 . One or more air holes  77  located at the longitudinal center of the die tip  18  may extend parallel to air hole  77 A. In designs with an even number of air holes  77 , at least two of the center air holes  77 A are preferably provided. 
     The air holes  77  flanking the center air hole  77 A form an angle β (see FIG. 9) with the apex  76  which decreases progressively (arithmetic) and symmetrically from the center hold  77 A outwardly. The outermost holes are shown as  77 B on FIGS. 8 and 9. The air holes  77 B form an angle with the apex  76  that decreases in constant increments outwardly. For example, center air hole  77 A forms an angle of 90° with the apex  76 . If the angle increment is −1°, then the two air holes  77  adjacent air hole  77 A form an angle of 89° with the apex  76 . Continuing the incremental arithmetic progression to the eighth (outermost) air holes  77 B, the angle of these air holes would be 82°. Of course, the incremental angle may vary, but preferably is between ½ and 4° most preferably between 1° and 3.5°. The arithmetic progression may be represented by the following equation: 
     
       
         Angle β=90 °−nι   
       
     
     Where n is the hole position or each side of the center air hole and preferably ranges from 4 to 15, most preferably 5 to 10 and ι is the constant incremental degree change. 
     Polymer passages  85  are formed in the die tip  13 , as shown in FIGS. 4 and 7. The passages  85  may be in the form of a distribution system comprising a plurality of passages  85  connected to inlet  87  by passage  88 . Inlet  87  registers with die body port  42  with die tip  18  mounted on die body  16 A. 
     The passages  85  have outlets at  89  which are uniformly spaced along the apex  76 . Passages  85  preferably extend perpendicular to apex  76 . The design illustrated in FIG. 7 serves well for small modules (i.e. lengths less than about 3″ to 4″). For longer dies, a pressure balance coat hanger design may be preferred. The passages  85  are preferably small diameter orifices and serve as the fiber forming means. The die tip body  71  has beveled edges  81  and  82  as shown in FIG. 4 which define surfaces for engaging complementary shaped retaining shoulders  54  and  84  of the clamping members. 
     The nozzle retainer means is a quick disconnect design permitting the die tip  18  to be quickly and easily replaced, requiring only a few minutes. Key to the quick disconnect feature is a retainer plate  80  mounted on the front of die body  16 A as shown in FIGS. 3 and 4. The plate  80  comprises body portion having an inwardly projecting (with respect to the die body  16 A) shoulder  84  at its lower end and a inwardly projecting rounded member  86  at its upper end. 
     A hole  91  found in an intermediate portion of plate  80  receives bolt  92  which screws into threaded hole  93  found in die body  16 A. Two side by side compression springs, one shown at  94 , are mounted in recesses  95  and  96  and bias plate  80  outwardly with respect to die body  16 A. 
     The rounded member  86  extends horizontally along the face of die body  16 A and is received in a complementary shaped round groove  97  to form a hinge structure. 
     The die tip  18  is secured to the die body  16 A by unscrewing the bolt  92  sufficiently to permit the lower end  84  to move outwardly by action of springs  94 . The die tip  18  is inserted in place with beveled edge  82  supported on shoulder  54  of member  52 . The bolt  92  is screwed into body  16 A. This compresses the springs  94  and brings shoulder  84  into contact with beveled edge  81  of die tip  18 . 
     The clamping action of the plate  80  squeezes the die tip  183  between clamping member  51  and lower clamping member  80  (plate). The wedging action of beveled surfaces  81  and  82  engaging surfaces  54  and  84  causes the die tip  18  to move upwardly into sealing engagement with surfaces  46  and  47  of die body  16 A and o-ring  43 . The wedging action of the clamping member imparts a squeezing horizontal force component and a vertical force component on the die tip  18 . 
     The rounded member  86  pivots within groove  97  as the plate  80  is moved by action of the bolt  92 . 
     The die tip  18  is replaced by merely unscrewing the bolt  92  sufficiently to permit the die tip  18  to be removed from the die body  16 A, as illustrated in FIG.  4 . 
     As mentioned above, the quick change feature enables the die tip  18  to be replaced with the same or different type nozzles. FIGS. 10 and 11 depict different types of nozzles  18  that may be mounted on die body  16 A. 
     As shown in FIG. 10, the nozzle  18  for generating a spiral filament comprises a circular nozzle  130  threadedly mounted in a body  135 . Extending axially through the circular insert member  130  is a polymer passage  134  that discharges at the apex of cone  133 . Angular air passages  136  extend through the body member and are angularly oriented with respect to the axis of polymer passage  134 . The direction of the air passages  136  are such to impart a circular or helical motion to the polymer as the air from the plurality of air passages  136  contact the polymer discharging from the polymer passage  134 . The orientation of the air passages with respect to the polymer filament can be in accordance with U.S. Pat. No. 5,102,484 or U.S. Pat. No. 4,983,109, the disclosures of which are incorporated herein by reference. 
     The body  135  is adapted to be mounted on the module body  16 A as described with respect to the meltblowing die tip  18 . With the nozzle  130  positioned in body  135  and mounted on surfaces  46  and  47 , air passage  136  are in fluid communication with air cavity  49 , and polymer flow passage  134  is in fluid communication with port  42 . 
     A bead or coating nozzle  18  (without air assistance) is disclosed schematically in FIG.  11 . With this structure, the bead nozzle  141  is threadedly mounted in body  142 , similar to body  135  described with reference to the spiral nozzle  130 , and a polymer flow passage  143  extends axially therethrough, but this nozzle has no air passages. When mounted on the die body  16 A, the inlet of flow passage  143  is in fluid communication with polymer flow passage port  42 . The nozzle has an inverted conical portion  144 , through which passage  143  extends to a position within about ½ to 1 inch from the substrate for depositing the bead or coating thereon. Since air is not used with this nozzle, the nozzle  141  in combination with the body  142  blocks out or seals the air chamber  49 . 
     Since the bodies of the die tip or nozzles  18 , regardless of the type, are shaped to fit onto the die body  16 A in the same manner as described above, they are interchangeable. That is, a module  12  along the die assembly  10 , (as shown in FIG. 1) may be provided with any of the nozzles or die tip, or may change one for another at any time by merely releasing the clamping means and replacing the nozzle as described above. 
     The Manifold 
     As best seen in FIG. 2, the manifold  11  is constructed in two parts: an upper body  98 , and a lower body  99  bolted to the upper body by spaced bolts  100 . The upper body  98  and lower body  99  have mounting surfaces  101  and  102 , respectively, which lie in the same plane for receiving modules  12 . Surface  56  of each module engage surfaces  101  and  102  of manifold  11 . 
     The upper manifold body  98  has formed therein polymer header passages  103  extending longitudinally along the interior of body  98  and side feed passages  104  spaced along the header passage  103  for delivering polymer to each module  12 . The polymer feed passages  104  have outlets which register with passage  57  of its associated module  12 . The polymer header passage  103  has a side inlet at one end of the body  98  and terminates at near the opposite end of the body  98 . A connector block  90  (see FIG. 1) bolted to the side of body  98  has a passage for directing polymer from feed line to the header channel  103 . The connector block  90  may include a polymer filter. A polymer melt delivered to the die  10  flows from a source such as an extruder or metering pump through connector block  90  to passage  103  and in parallel through the said feed passages  104  to the individual modules  12 . 
     Returning to FIG. 2, air is delivered to the modules  12  through the lower block  99  of the manifold  11 . The air passages in the lower block  99  are in the form of a network of passages comprising a pair of passages  101 A and  102 A, interconnecting side ports  103 A, and module air feed ports  105  longitudinally spaced along bore  101 A. Air inlet passage  106  connects to air feed line  107  near the longitudinal center of block  99 . Air feed ports  105  register with air passage  59  of its associated module. 
     Heated air enters body  99  through line  107  and inlet  106 . The air flows through passage  102 A, through side passages  103 A into passage  101 A, and in parallel through module air feed ports  105  and module passages  59 . The network design of manifold  99  serves to balance the air flow laterally over the length of the die  10 . 
     The instrument air for activating each module valve is delivered to the chamber  23  of each module  12  by air passages formed in the block  98  of manifold  11 . As best seen in FIG. 2, instrument air passages  110  and  111  extend through the width of body  98  and each has an inlet  112  and an outlet  113 . Outlet  113  of passage  110  registers with port  26  formed in module  12  which leads to chamber  23 A; and outlet  113  of passage  111  registers with port  27  of module  12  which leads to chamber  23 B. 
     An instrument air block  114  bolted to block  98  and traverses the full length of the instrument air passages  110  and  111  spaced along body  98 . The instrument air block  114  has formed therein two longitudinal channels  115  and  116 . With the block  114  bolted to body  98 , channels  115  and  116  communicate with the instrument air passages  110  and  111 , respectively. Instrument tubing  117  and  118  delivers instrument air from control valve  119  to flow ports  108  and  109  and passages  110  and  111  in parallel. 
     For clarity, actuator  20  and tubing  117  and  118  are shown schematically in FIG.  2 . Actuator  20  comprises three-way solenoid air valve  119  coupled with electronic controls  120 . 
     The manifold  11  is described in more detail in U.S. Pat. No. 5,618,566, the disclosure of which is incorporated herein by reference. 
     Assemblage and Operation 
     The three main components of the die body  16  may be assembled by interference fit. Other fabrication means may be used such as those described in the above referenced U.S. Pat. No. 5,618,566, but the interference assemblage is inexpensive. Since the interference fit precludes disassembly for repair, they are disposable after use. The nozzles and plates, of course can be removed before disposal. 
     The three body components  24 ,  16 A and  16 B are assembled by an interference fit. The skirt  24 A fits in circular recess  17  and cylindrical member  35  fits in recess  28 . The clearance between the male members and female members of these couplings is 0.0015 to 0.0020. The parts are hydraulically pressed together at a high pressure (in the range of 1,000 to 2,000 psi, typically 1,500 psi). 
     The hydraulic pressing procedure may be as follows: 
     (a) the upper die body  16 A with internal members (diaphragm  25 , wiper seal  67 , spring  66 , and stem  30 ) inserted therein is pressed fit with cap  24 . The diaphragm  25 , is inserted in recess and is held in place by skirt  24 A; and the wiper seal  67  is held in place by retainer ring  75 . 
     (b) This assembly then is press fit with the lower die body  16 B (recess  27  mated with projection  35 ) having internal parts mounted therein. 
     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 using standard sized manifolds and interchangeable, self-contained and disposable 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 coating substrates of different sizes from one application to another. The following sizes and numbers are illustrative of the versatility of modular construction. 
     
       
         
               
               
               
               
             
           
               
                   
               
               
                 Die Assembly 
                 Broad Range 
                 Preferred Range 
                 Best Mode 
               
               
                   
               
             
             
               
                 Number of Modules 
                   3-6,000 
                  5-100 
                 10-50 
               
               
                 Length of Modules 
                 0.25-3.00″ 
                  0.5-1.50″ 
                  0.5-0.8″ 
               
               
                 (inches) 
               
               
                 Orifice Diameter 
                 0.005-0.050″ 
                  0.01-0.040″ 
                  0.015-0.030″ 
               
               
                 (inches) 
               
               
                 Orifices/Inch (for 
                 5-50 
                 10-40 
                 10-20 
               
               
                 each module) 
               
               
                 No air holes (77)/ 
                 15-50  
                 20-40 
                 25-35 
               
               
                 Inch 
               
               
                 No air holes (78)/ 
                 15-50  
                 20-40 
                 25-35 
               
               
                 Inch 
               
               
                 Air hole Diameter 
                 0.05-0.050 
                 0.010-0.040 
                  0.15-0.030 
               
               
                 (inch) 
               
               
                 No Air hole/No 
                 1-10 
                 3-8 
                 4-6 
               
               
                 Orifices 
               
               
                   
               
             
          
         
       
     
     Depending on the desired length of the die, standard sized manifolds may be used. For example, a die length of one member could employ 54 modules mounted on a manifold 40 inches long. For a 20 inch die length, 27 modules would be mounted on a 20 length manifold. Note that the modules  10  are mounted in side-by-side relation using bolts  79  which extend through the die body  16 A and screw into manifold block  98 . O-rings may be mounted around passages extending from manifold  11  into die body  16 . 
     As indicated above, the modular die assembly can be tailored to meet the needs of a particular operation. As exemplified in FIG. 1 the die assembly  10  comprises fourteen modules  12 , two of which have spiral nozzles, two have coating nozzles and ten have meltblowing die tips. The lines, instruments, and controls are connected and operation commenced. A hot melt adhesive is delivered to the die  10  through block  90 , hot air is delivered to the die through line  107 , and instrument air or gas is delivered through lines  117  and  118 . 
     Actuation of the controls  20 , pressurizes chamber  23 B, and vents chamber  23 A. This moves diaphragm  25  and stem  30  upwardly, opening port  42  of each module as described previously causing polymer melt to flow through each module  12 . In the meltblowing modules  12 , the melt flows in parallel streams through manifold passages  104 , through side ports  57 , through bore  37 , and through ports  41  and  42  into the die tip  18 . The polymer melt is distributed laterally and discharges through orifices  85  as side-by-side filaments  14 . Hot air meanwhile flows from manifold passages  103 A into port  59  through chamber  49 , holes  78  and  79 , and discharges it as converging air jets at the nosepiece  72 . The converging air jets contact the filaments discharging from the orifices and by drag forces stretch them and deposit them onto an underlying substrate  15  in a random pattern. This forms a generally uniform layer of meltblown material on the substrate. 
     In each of the flanking spiral nozzle modules  12 A the polymer flows from manifold through passage  57 , through bore  37 , through ports  41  and  42 , through passage  134  of nozzle  130  (FIG. 10) discharging at the apex of cone  133 . Air flows from manifold passage  105 , passage  59  into chamber or cavity  49 , through passages  136 . Air discharging from passages  136  impart a swirling motion of the polymer issuing from passage  134 . The polymer is deposited on the substrate as a circular or helical bead, giving good edge control for the adhesive layer deposited on the substrate. 
     Typical operational parameters are as follows: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Polymer 
                 Hot met 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 10 grms/hole/min. 
               
               
                   
                 Hot Air Flow Rate 
                 0.1 to 2 SCFM/inch 
               
               
                   
                 Deposition 
                 0.5 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&#39;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 disclosed in U.S. Pat. Nos. 4,497,941, 4,325,853, and 4,315,842, 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 copolymers, tackifier, and oil in various ratios. The above melt adhesives are by way of illustration only; other melt adhesives may also be used. 
     The wide bead nozzles  12 B are positioned at an interval location of the assembly shown in FIG.  1 . This array of modules with three different applicator heads deposits a layer of meltblown (random filaments) onto the substrate with an internal wide bead for increased strength as required in diaper lamination, and flanking spiral beads for edge control. 
     The locations of the types of die tips and nozzles may be changed along the die by merely unscrewing the retainer plate bolt, withdrawing the nozzle and replacing it with another nozzle. If the internal parts become inoperative, the module may be removed from the manifold and replaced with a new module. 
     In summary, the die assembly of the present invention embodies several features: 
     (a) a quick change die tip or nozzle 
     (b) interferences fit construction 
     (c) a solid state die tip 
     (d) interchangeable nozzles on each module. 
     Although the die modules and assemblies of the present invention has been described with particular reference to hot melt adhesive applications, it will be appreciated by those skilled in the art that the invention also applies to meltblowing of polymers to form nonwovens.