Abstract:
A lamellar die apparatus for extruding a heated liquid into filaments and directing air at the filaments. The apparatus includes a plurality of plates each having opposite side faces. At least two of the side faces confront each other and have a liquid passage positioned therebetween for transferring the heated liquid. At least two of the side faces confront each other and have an air passage positioned therebetween for transferring the air. At least two of the side faces confront each other and have a heating element passage therebetween. A heating element is positioned within the heating element passage for heating at least two of the plates. An extrusion die is coupled with the plurality of plates and communicates with the liquid passage and the air passage for discharging the heated liquid as multiple filaments and for discharging the air at the filaments.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to apparatus and methods for extruding thermoplastic filaments and, more particularly, apparatus for melt blowing multi-component or single component filaments.  
       BACKGROUND OF THE INVENTION  
       [0002]     Melt spinning techniques, such as spunbonding or meltblowing techniques, for extruding fine diameter filaments find many different applications in various industries including, for example, in nonwoven material manufacturing. This technology generally involves extruding a thermoplastic material from multiple rows of discharge outlets extending along the lower surface of an elongate spinneret. Spunbonded and/or meltblown materials are used in such products as diapers, surgical gowns, carpet backings, filters and many other consumer and industrial products. The machines for meltspinning such materials can be very large and include numerous filament discharge outlets.  
         [0003]     For certain applications, it is desirable to utilize two or more types of thermoplastic liquid materials to form individual cross-sectional portions of each filament. Often, these multi-component filaments comprise two components and, therefore, are referred to as bicomponent filaments. For example, when manufacturing nonwoven materials for use in the garment industry, it may be desirable to produce bicomponent filaments having a sheath-core construction. The outer sheath may be formed from a softer material which is comfortable to the skin of an individual and the inner core may be formed from a stronger, but perhaps less comfortable material having greater tensile strength to provide durability to the garment. Another important consideration involves cost of the material. For example, a core of inexpensive material may be combined with a sheath of more expensive material. For example, the core may be formed from polypropylene or nylon and the sheath may be formed from a polyester or co-polyester. Many other multi-component fiber configurations exist, including side-by-side, tipped, and microdenier configurations, each having its own special applications. Various material properties can be controlled using one or more of the component liquids. These include, as examples, thermal, chemical, electrical, optical, fragrance, and anti-microbial properties. Likewise, many types of die tips exist for combining the multiple liquid components just prior to discharge or extrusion to produce filaments of the desired cross-sectional configuration.  
         [0004]     One problem associated with multi-component extrusion apparatus involves the cost and complexity of the manifolds used to transmit liquid(s) to the spinneret or extrusion die. Typical manifolds are typically machined with many different passages to ensure that the proper flow of each component liquid reaches the die under the proper pressure and temperature conditions. These manifolds are therefore relatively complex and expensive components of the melt spinning apparatus.  
         [0005]     For these reasons, it would be desirable to provide a meltblowing apparatus having a manifold system which may be easily manufactured while still achieving the goal of effectively transmitting the heated liquid or liquids to the die tip.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention generally provides a lamellar meltblowing die apparatus for extruding a heated liquid into filaments and directing air at the filaments. The apparatus is constructed with a plurality of plates each having opposite side faces. At least two of the side faces confront each other and have a liquid passage positioned therebetween for transferring the heated liquid. At least two of the side faces confront each other and have an air passage positioned therebetween for transferring the air. At least two of the side faces confront each other and have a heating element passage therebetween. A heating element is positioned within the heating element passage for heating at least one of the liquid and the air. An extrusion die is coupled with the plurality of plates and communicates with the liquid passage and the air passage for discharging the heated liquid as multiple filaments and for discharging the air at the filaments. The air may, for example, be heated or unheated process air with or without quench air.  
         [0007]     The liquid passage is preferably formed by respective first and second recesses on adjacent plates that abut one another. Likewise, the air passage is formed by respective third and fourth recesses on adjacent plates that abut one another, and the heating element passage is formed by respective fifth and sixth recesses on adjacent plates that abut one another. Recesses from different ones of these pairs of recesses may, for example, be located on opposite sides of the same plate. In the preferred embodiment, multiple heating element passages are positioned between two of the plates and multiple heating elements are respectively contained in the heating element passages. The heating element passage or passages are preferably located between the liquid passage and the air passage.  
         [0008]     The liquid passage and the air passage each include an inlet portion and an outlet portion with the outlet portion being wider than the inlet portion. The outlet portion of the liquid passage forms an elongate liquid outlet slot. A plurality of distribution passages communicate with an elongate air outlet slot in one of the plates and the distribution passages further communicate with the air passage. The extrusion die includes an elongate liquid inlet slot and an elongate air inlet slot respectively aligned in communication with the elongate liquid outlet slot and the elongate air outlet slot.  
         [0009]     The invention further contemplates methods of meltblowing liquid filaments, such as single or multiple component thermoplastic polymeric filaments, in general accordance with the use of the apparatus described above.  
         [0010]     Various advantages, objectives, and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a perspective view of a multi-component meltblowing apparatus constructed in accordance with a preferred embodiment of the invention.  
         [0012]      FIG. 1A  is an exploded perspective view of the apparatus shown in  FIG. 1 .  
         [0013]      FIG. 2  is a cross sectional view taken along line  2 - 2  of  FIG. 1 .  
         [0014]      FIG. 3  is a fragmented view of the assembled apparatus taken generally along line  3 - 3  of  FIG. 2 .  
         [0015]      FIG. 4  is a cross sectional view similar to  FIG. 2 , but illustrating an alternative embodiment of the apparatus.  
         [0016]      FIG. 5  is a cross sectional view taken along line  5 - 5  of  FIG. 4 .  
         [0017]      FIG. 6  is a cross sectional view similar to  FIG. 2 , but illustrating another alternative embodiment of the apparatus.  
         [0018]      FIG. 7  is a cross sectional view similar to  FIG. 4 , but illustrating another alternative embodiment of the apparatus.  
     
    
     DETAILED DESCRIPTION  
       [0019]      FIGS. 1, 1A ,  2  and  3  illustrate a die apparatus  10  constructed in accordance with a first embodiment. Apparatus  10  is comprised of a manifold structure  12  coupled for fluid communication with an extrusion die  14 . Manifold structure  12  is a lamellar construction or plate assembly comprised of multiple plates  16   a - c ,  18   a - c  and  20 . These plates are securely fastened together in side-by-side relation using appropriate fasteners  22  (only one shown in  FIG. 1 ) extending through holes  24  in each of the plates. As best shown in  FIG. 2 , respective outside pairs of plates  16   a ,  16   b  and  18   a ,  18   b  form process air manifold sections and include respective air input ports  26 ,  28 . Plates  16   a ,  16   b  and  18   a ,  18   b  respectively abut each other and contain air passages  27 ,  29  therebetween. Air passages  27 ,  29  are respectively formed by pairs of recesses  30 ,  32  and  34 ,  36  that align with each other in abutting faces of the plates  16   a ,  16   b  and  18   a ,  18   b.    
         [0020]     As shown best in  FIG. 1A , these recesses  30 ,  32  and  34 ,  36  take the form of so-called coat hangar recesses which become wider in dimension from the inlet portion  40  located proximate input ports  26 ,  28  to an outlet portion  42  located proximate respective distribution passages  44 . Distribution passages  44  extend respectively through plates  16   b  and  18   b  and lead to similar distribution passages  46 ,  48  in plates  16   c  and  18   c  and, finally, into elongate air outlet slots  50 ,  52  which extend lengthwise along the undersides of plates  16   c ,  18   c  and communicate with coextensive elongate inlet slots  53 ,  55  in the top of the extrusion die  14 . Plates  16   c  and  18   c  respectively abut central plate  20 .  
         [0021]     Respective liquid passages  54 ,  56  are formed between plates  16   c ,  20  and  18   c ,  20  and, again, are formed by respective pairs of coat hangar recesses  58 ,  60  and  62 ,  64  that align with each other in abutting surfaces of these plates  16   c ,  20  and  18   c ,  20 . As shown in  FIG. 1A , these recesses  58 ,  60  and  62 ,  64  are also formed with a coat hangar configuration between inlet portions adjacent respective liquid input ports  66 ,  68  and outlet portions which form elongate liquid outlet slots  70 ,  72  for abutting the top surface of the extrusion die  14  and aligning with coextensive liquid inlet slots  73 ,  75 . In this embodiment, the two liquid input ports  66 ,  68  and coat hangar passages  54 ,  56  are provided for producing bicomponent filaments from extrusion die  14 . Extrusion die  14  may be any suitable extrusion die having, for example, a laminated plate construction with appropriate porting and passages to combine and extrude filaments from the outlet orifices extending along the underside of the extrusion die  14  and to attenuate or otherwise affect those filaments with process air. Representative dies are, for example, disclosed in U.S. Pat. Nos. 5,562,930; 5,551,588; and 5,344,297, however, such dies would require modification with suitable passages (not shown) to transfer and discharge process air received from air outlet slots  50 ,  52 .  
         [0022]     Also in accordance with the invention, heating elements  74 ,  76  are respectively contained in passages  80 ,  82  between plates  16   b ,  16   c  and  18   b ,  18   c . Each passage is again preferably formed by respective pairs of aligned and abutting recesses  84 ,  86  and  88 ,  90  in plates  16   b ,  16   c  and  18   b ,  18   c . These heating elements  74 ,  76 , which are preferably electrically operated heating elements, may be advantageously situated between the respective air and liquid passages  27 ,  54  and  29 ,  56  so as to heat both the liquid and the air traveling to extrusion die  14 . Sufficient heat may also be supplied to heat the extrusion die  14  itself to the appropriate operating temperature.  
         [0023]      FIGS. 4 and 5  illustrate another apparatus  100  constructed in accordance with the invention. In this embodiment, apparatus  100  again comprises a multiple plate assembly or manifold structure  102  coupled with an extrusion die  104 . Manifold structure  102  is similar to that described with respect to the first embodiment in that a seven plate construction  106   a - c ,  108   a - c ,  110  is used for providing both process air and two component liquids, such as polymers, to the extrusion die  104 . However, in this embodiment, two additional plates  112 ,  114  have been added to the outside of the manifold structure  102  to supply quenching air through respective input ports  116 ,  118  and air passages  120 ,  122  in the form of coat hangar passages as described above, and respective transfer passages  124 ,  126  and  128 ,  130  respectively extending through plates  106   a ,  106   b  and  108   a ,  108   b  and communicating with appropriate passages (not shown) in the extrusion die  104 . This quenching air functions to cool the filaments after they have been discharged.  
         [0024]     As further shown in  FIGS. 4 and 5 , input ports  140 ,  142  are provided for introducing two different component liquids, such as two different types of polymer materials, into apparatus  100 . In addition, input ports  144 ,  146  are provided for process air. Liquid input ports  140 ,  142  communicate with respective pairs of abutting and aligned recesses  148 ,  150  and  152 ,  154  which form coat hangar passages and communicate directly with elongate slots (not shown) in the top of extrusion die  104 . Input ports  144 ,  146  communicate with respective pairs of abutting recesses  156 ,  158  and  160 ,  162  in plates  106   a ,  106   b  and  108   a ,  108   b . These recess  156 ,  158  and  160 ,  162  also form coat hanger air passages which communicate with respective elongate slots  164 ,  166  in plates  106   c ,  108   c  through respective transfer passages  168 ,  170  and  172 ,  174  in plates  106   b ,  106   c  and  108   b ,  108   c  to provide process or attenuating air to die  104 . Passages  120 ,  122  are likewise formed as coat hangar passages formed by abutting recesses  176 ,  178  and  180 ,  182  having narrower portions adjacent input ports  116  and  118  and wider portions adjacent respective transfer passages  124  and  128 . Electric heaters  184 ,  186  are provided as in the first embodiment.  
         [0025]      FIG. 6  illustrates another alternative die apparatus  200  having a laminated plate construction. This apparatus  200  is similar to that described above with respect to the first embodiment ( FIGS. 1, 1A ,  2 ,  3 ), but is configured to discharge single component filaments or monofilaments rather than a bicomponent filament. Thus, the central plate  20  used in the first embodiment has been eliminated thereby resulting in a six plate construction rather than a seven plate construction for manifold structure  202 . As with the previous embodiments, an extrusion die  204  is coupled to manifold structure  202  for discharging one or more filaments and, optionally, discharging air to facilitate a meltblowing operation. However, for spunbond apparatus, it will be appreciated that the process air passages and structure associated therewith may be eliminated. A single liquid input port  206  and coat hanger passage  208  receive the liquid, such as a thermoplastic polymer. Coat hanger passage  208  is formed by aligned recesses  210 ,  212  in abutting faces of plates  16   c ′ and  18   c ′. Plates  16   c ′ and  18   c ′ are designated with prime marks (′) to denote that they are slightly modified, as illustrated, from plates  16   c ,  18   c . All other aspects of apparatus  200  are as described above with respect to the first embodiment and, therefore, identical reference numerals have been used and no further description is necessary.  
         [0026]      FIG. 7  illustrates another alternative apparatus  220  similar to that described above with respect to  FIGS. 4 and 5  but, like the embodiment of  FIG. 6 , apparatus  220  is configured to discharge single component filaments or monofilaments rather than bicomponent filaments. Again, the central plate  110  of the embodiment illustrated in  FIGS. 4 and 5  has been eliminated and an eight plate manifold structure  222  results. Manifold structure  222  is configured to deliver liquid, process air and quench air to an extrusion die  224 . A single liquid input port  206  and a coat hanger passage  208  is formed between abutting plates  106   c ′,  108   c ′ to communicate with an appropriate elongate inlet slot (not shown) in the top of the extrusion die  224 . Plates  106   c ′ and  108   c ′ are designated with prime marks (′) to denote that they are slightly modified, as illustrated, from plates  106   c ,  108   c . All other aspects of the embodiment shown in  FIG. 7  are described with respect to the embodiment of  FIGS. 4 and 5  and, therefore, identical reference numerals have been used and no further description is necessary.  
         [0027]     While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments has been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The various features of the invention may be used alone or in numerous combinations depending on the needs and preferences of the user. This has been a description of the present invention, along with the preferred methods of practicing the present invention as currently known.