Abstract:
A melt spinning apparatus including a spinpack with a die tip block having a recess with a converging portion, such as an angled trough, which terminates in a row of filament discharge outlets. The recess selectively receives a configuration insert, such as a side-by-side insert or a sheath-core insert, that separates the converging portion of the recess into two sheets of liquid that combine at the filament discharge outlets. The spinpack may be configured by inserting either of the inserts to produce filaments having different cross sectional configurations of two different materials. Separation of the two liquids prevents premature interaction between the two liquid flows which minimizes instabilities between the liquid flow interface. The minimization of these instabilities can result in less formation of shot and improve other significant finished product properties. In addition, each type of liquid material may be maintained at an optimum temperature for proper extrusion.

Description:
CROSS-REFERENCE TO RELATES APPLICATIONS 
     This application is a divisional of application Ser. No. 09/802,651, filed Mar. 9, 2001 now U.S. Pat. No. 6,565,344 (pending) and is related to co-pending and commonly-owned application Ser. No. 09/802,646, filed on Mar. 9, 2001 (pending), entitled “APPARATUS AND METHOD FOR EXTRUDING SINGLE-COMPONENT LIQUID STRANDS INTO MULTI-COMPONENT FILAMENTS” and the disclosures of which are hereby incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to extruding filaments and, more particularly, to a melt spinning apparatus for producing spunbond or meltblown multi-component filaments. 
     BACKGROUND OF THE INVENTION 
     Melt spun fabrics manufactured from synthetic thermoplastics have long been used in a variety of applications including filtration, batting, fabrics for oil cleanup, absorbents such as those used in diapers and feminine hygiene products, thermal insulation, and apparel and drapery for medical uses. 
     Melt spun materials fall in the general class of textiles referred to as nonwovens since they comprise randomly oriented filaments, or fibers, made by entangling the fibers through mechanical means. The fiber entanglement, with or without some interfiber fusion, imparts integrity and strength to the fabric. The nonwoven fabric may be converted to a variety of end use products as mentioned above. 
     Although melt spun nonwovens may be made by a number of processes, the most popular processes are meltblown and spunbond processes, both of which involve melt spinning of thermoplastic material. Meltblown is a process for the manufacture of a nonwoven fabric wherein a molten thermoplastic is extruded from a die tip to form a row of filaments. The fibers exiting the die tip are contacted with converging sheets or jets of hot air to stretch or draw the filaments 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 with multiple rows of filaments. The extruded filaments are maintained apart and the desired orientation of the filaments is achieved, for example, 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 rolls and/or hot roll calendaring. 
     Nonwoven materials are used in such products as diapers, surgical gowns, carpet backings, filters and many other consumer and industrial products. The most popular machines for manufacturing nonwoven materials use meltblown and spunbond apparatus. For certain applications, it is desirable to utilize multiple 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 more specifically 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 sheath may be formed from a softer material that is comfortable to the skin of an individual and the core may be formed from a stronger, but perhaps less comfortable material having greater tensile strength to provide durability to the fabric. Another important consideration involves the cost of the material. For example, a core of inexpensive material may be combined with a sheath of more expensive material. 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 to produce filaments of the desired cross-sectional configuration. 
     Various apparatus form bi-component filaments with a die tip comprising vertically or horizontally stacked plates. In particular, a meltblown die tip directs two flows of liquid material to opposing sides near the top of a stack of vertical plates. A spunbond die tip directs two different material flows to the top plate of a stack of horizontal plates. Liquid passages etched or drilled into the vertical or horizontal stack of plates direct the two different types of liquid material to a location at which they are combined and extruded at the discharge outlets as multi-component filaments. Various cross-sectional configurations of filaments are achieved, such as side-by-side and sheath-core configuration. 
     Using a stack of thin plates in either a vertical or horizontal orientation manner suffers from imperfect seals between plates. In a production environment, liquid pressure will cause adjacent plates to move slightly away from each other. Thus, small amounts of liquid of one type can leak through these imperfect seals, causing “shot” or small balls of polymer to be formed in the extruded filaments. The shot causes the multi-component filaments to form with problems such as reduced strength or increased roughness. Also, the stacked plates may not offer a substantial thermal barrier between the two types of liquid material. Consequently, the filaments of each liquid material may not combine at their respective optimum temperatures, possibly adversely affecting extrusion thereof. 
     Other apparatus avoid the use of stacked plates by having the two types of liquid material combine in a cavity prior to extrusion of the two types of liquid through multiple discharge passages. More specifically, two different types of liquid materials, such as thermoplastic polymers, initially reside side-by-side in the cavity and are delivered under pressure to the discharge passages where they are extruded in side-by-side relation as bicomponent filaments. Since the two liquid materials reside in side-by-side relation in the die cavity and discharge passages, this may lead to thermal problems or problems related to the materials improperly combining or mixing prior to extrusion. 
     For these reasons, it is desirable to provide apparatus and methods for melt spinning multi-component filaments without encountering various problems of prior melt spinning apparatus. 
     SUMMARY OF THE INVENTION 
     The present invention therefore provides an apparatus for melt spinning multiple types of liquid materials into multi-component filaments. In particular, a melt spinning apparatus of this invention includes a spinpack which forms either a side-by-side or sheath-core multi-component filament by combining strands formed from two different types of liquid at a plurality of discharge outlets. 
     In accordance with the invention, an apparatus for extruding at least first and second types of liquid into side-by-side filaments comprises a die tip block including a recess communicating with first and second sets of liquid discharge outlets communicating with each other. An insert is received in the recess and separates the recess into first and second liquid passages. The first liquid passages communicates with the set of first liquid discharge outlets and the second liquid passage communicates with the set of second liquid discharge outlets. The insert includes a first liquid input configured to receive the first type of liquid and to communicate with the first liquid passage and includes a second liquid input configured to receive the second type of liquid and to communicate with the second liquid passage. The first and second liquid passages respectively deliver the first and second types of liquid to the first and second sets of liquid discharge outlets to form the multi-component, side-by-side filaments. 
     The apparatus of this invention can also be configured for extruding first and second types of liquid material into sheath-core filaments. The apparatus includes a die tip block with a recess communicating with a plurality of multi-component filament discharge outlets. A sheath-core insert is received in the recess for separating the recess into first and second liquid passages. The sheath-core insert also has a central liquid passage. The first and second liquid passages are adapted to receive the first type of liquid and the central liquid passage is adapted to receive the second type of liquid. The first and second liquid passages converge toward the central liquid passage and intersect with the central liquid passage at the multi-component filament discharge outlets to form the multi-component filaments. 
     Preferably, the strands extruded at each liquid discharge outlet combine together immediately after extrusion to form the multi-component filaments. In another aspect of the invention, the sheath-core insert may be replaced with another insert for producing side-by-side filaments. This can allow the same die tip block to be used to produce either sheath-core or side-by-side filaments. 
     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 
         FIG. 1  is an exploded perspective view of a multi-component melt spinning apparatus constructed in accordance with the invention. 
         FIG. 2  is an exploded perspective view of a spinpack of the melt spinning apparatus of  FIG. 1  constructed in accordance with the invention for producing a side-by-side filament. 
         FIG. 3  is a cross section taken generally along line  3 — 3  of  FIG. 2 , but illustrating the spinpack in assembled condition. 
         FIG. 3A  is an enlarged cross-sectional view of a discharge outlet portion of the spinpack of  FIG. 3 . 
         FIG. 4  is a partial bottom view of the assembled spinpack of  FIG. 3 . 
         FIG. 5  is an exploded perspective view of one end of an insert constructed in accordance with the invention for producing a sheath-core filament. 
         FIG. 6  is a cross section similar to  FIG. 3 , but based on  FIG. 5 . 
         FIG. 6A  is an enlarged cross-sectional view of a discharge outlet portion of the spinpack of  FIG. 6 . 
         FIG. 6B  is an enlarged cross-sectional view similar to  FIG. 6A  but illustrating an alternative insert. 
         FIG. 7  is a partial bottom view of the assembled spinpack of  FIG. 6 . 
         FIG. 8  is a diagrammatic view of a meltblown apparatus incorporating a meltspinning assembly of the present invention. 
         FIG. 9  is a diagrammatic view of a spunbond apparatus incorporating a meltspinning assembly of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of this description, words such as “vertical”, “horizontal”, “vertex”, “right”, “left” and the like are applied in conjunction with the drawings for purposes of clarity. As is well known, melt spinning devices may be oriented in substantially any orientation, so these directional words should not be used to imply any particular absolute directions for a melt spinning apparatus consistent with the invention. In addition, the terms “different”, “two types”, and similar terminology with regard to the liquids employable with this invention are not meant to be restrictive, except to the extent that the two liquids have one or more different properties. The liquids may be the same polymer, for example, but have different physical properties due to different treatments. 
     With reference to  FIGS. 1–4 , a melt spinning assembly  10  constructed in accordance with the inventive principles includes a manifold assembly  12  for supplying two types of liquid material (e.g., polymer A and polymer B) respectively to liquid inputs  14 ,  16  of a spinpack  18 . The particular liquid materials used will depend on the application and suitable types are well known in the art. The inputs  14  and  16  are sealed to the manifold assembly  12  such as by static seals retained within recesses (not shown) around each input  14 ,  16 . 
     Although melt spinning assembly  10  is specifically shown as an assembly for producing meltblown filaments, it will be readily understood that the same principles may be applied to a spinpack for spunbond applications. Manifold assembly  12  further supplies pressurized air (process air) to air passage inputs  20 ,  22  of the spinpack  18  when used for meltblown purposes. The process air attenuates multi-component filaments  24  extruded along the longitudinal length of the spinpack  18  from a row of multi-component filament discharge outlets  26 . Extrusion of the two types of material actually occurs through separate outlets or orifices  26   a ,  26   b , as shown in  FIGS. 3A and 4 . These orifices  26   a ,  26   b  merge or intersect into the oblong outlet  26 . Outlets having other shapes may be used as well. The attenuated multi-component filaments  24  form a nonwoven fabric  28  upon a substrate  30  that generally is moving transverse to the melt spinning assembly  10 , such as shown by arrow  32 . 
     With reference to  FIG. 2 , the spinpack  18  includes the filament producing features of the melt spinning assembly  10 . A die tip block  34  includes a recess  36  for receiving an insert, which in this instance is an insert  38  for producing multi-component filaments having a side-by-side cross-section of two types of liquid. Thus, insert  38  is referred to herein as a side-by-side insert. Insert  38  may sometimes be referred to as a configuration insert since, in one aspect, it can allow an apparatus of the invention to be reconfigured in terms of he type of multi-component filament produced. The spinpack  18  further includes a pair of air knife plates  40 ,  42  attached below the die tip block  34  to focus process air upon multi-component filaments  24  extruded from the die tip block  34 . Although air knife plates  40 ,  42  are shown with their lower surfaces  40   a ,  42   a  even or level with the apex of die tip block  34 , these surfaces  40   a ,  42   a  may alternatively be above or below the apex depending on the application. 
     The side-by-side insert  38  may be adjusted laterally relative to its longitudinal axis within the recess  36 , the advantages of which are discussed below with regard to  FIG. 3 . Spacers  44  of a predetermined thickness are inserted in a corresponding spacer slot  46  along one or both long sides  48 ,  50  of the side-by-side insert  38 . 
     With reference to  FIG. 3 , the spinpack  18  is depicted in assembled condition showing how the process air and the two types of liquid material are brought together at each multi-component filament discharge outlet  26   a ,  26   b . The two types of liquid material (polymers A and B) are kept separate from one another until being brought into contact immediately after extrusion. With this unique configuration, premature leakage of one liquid material into the other is avoided. In addition, each liquid material is advantageously maintained at an optimum temperature for proper extrusion. 
     In particular, the recess  36  includes a converging portion, illustrated as an angled trough  56 . The side-by-side insert  38  has a corresponding converging block portion  58  with longitudinal sidewalls  64 ,  66  spaced away from the angled trough  56  to form first and second slots  60 ,  62 . The first and second slots  60 ,  62  communicate with all of the multi-component filament discharge outlets  26  at a vertex of the angled trough  56 . 
     Typically, each filament discharge outlet  26   a ,  26   b  is to receive the same flow rates of the two types of liquid material. Liquid filters  68 ,  70  at the liquid inputs  14 ,  16  protect the discharge outlets  26  from receiving contaminants to help ensure this uniform flow rate. 
     The relative lateral spacing of the converging block portion  58  with respect to the angled trough  56  advantageously shifts the relative cross-sectional area of slot portions  60 ,  62 . Consequently, selection of spacers  44  of a desired thickness may be used to change the proportions of each liquid material, and may even be used to shut off one of the two types of liquid materials altogether. Further, the spacers  44  may accommodate differences in liquid material flow characteristics to achieve the desired proportions. 
     The die tip block  34  further includes air passages  72 ,  74  that respectively communicate between the air passage inputs  20 ,  22  and converging air channels  76 ,  78  formed between the air knife plates  40 ,  42  and the die tip block  34 . The converging air channels  76 ,  78  communicate with each other to form an impinging air flow upon each extruded filament  24  at a slot  80 , defined between the air knife plates  40 ,  42 . 
     With reference to  FIGS. 3A and 4 , the discharge outlets  26   a ,  26   b  in the die tip block  34  are depicted as being configured to extrude two single component strands that combine after extrusion into a multi-component filament  24 . In particular, the first slot portion  60  communicates with a row of first outlet passages  81  and the second slot portion  62  communicates with a row of second outlet passages  82 . Slot portions  60 ,  62  advantageously have a lateral width sufficient for communication with the respective row of outlet passages  81 ,  82  when the insert  38  has been laterally adjusted for a desired proportional flow. A lower surface  83  of the side-by-side insert  38  is spaced away from the row of discharge outlets  26  by the length of the outlet passages  81 ,  82 . Surface  83  seals against an upper surface of die tip block portion  84  defined between the rows of outlet passages  81 ,  82  and the angled trough  56 . 
     The exact dimensions and relative placement of each outlet passage  81 ,  82  to form the respective discharge outlet  26  will depend upon the types of liquid materials extruded, temperatures employed, pressure of the process air, degree of filament attenuation desired, flow rate of liquid materials, the preferred configuration of the resulting nonwoven material, and other factors that will be apparent to those of ordinary skill. Furthermore, the width of converging air channels  76 ,  78  and slot  80  may vary, as well as the height between each discharge outlet  26  and slot  80  and the diameters of outlet passages  81 ,  82 , according to the needs of the application. 
     With particular reference to  FIG. 4 , a bottom view of the spinpack  18  depicts the row of multi-component filament discharge outlets  26   a ,  26   b , with each outlet formed by adjacent outlets of first and second outlet passages  81 ,  82 . Thereby, each single component strand is kept separate from the other single component strand until immediately after extrusion. 
     With reference to  FIGS. 5–7 , elements with prime marks (′) refer to corresponding, but slightly modified structure, relative to  FIGS. 1–4 . In this embodiment an insert  88 , and a die tip block  34 ′ are used to produce sheath-core filaments. Air knife plates  40 ,  42  may be reused when reconfiguring the spinpack  18 ′ to produce sheath-core filaments  24 . 
     The discussion above for  FIGS. 1–4  for producing side-by-side filaments  24  is generally applicable to the sheath-core insert  88 . The principle differences are that the sheath-core insert  88  conducts liquid material (polymer A) from the first liquid input  14  to central liquid passages  90  that communicate to the converged edge  83  of the sheath-core insert  88 , each central liquid passage  90  aligned with a corresponding discharge outlet  26 . Furthermore, the sheath-core insert  88  conducts liquid material (polymer B) from the second liquid input  16  to both slot portions  60 ′,  62 ′ between the side walls of converging block portion  58 ′ and the angled trough  56 ′ of the spinpack. 
     It is typically preferable to center the polymer A core within a cladding of the polymer B in the sheath-core filament  24 . Consequently, the sheath-core insert  88  is not depicted as including spacers  44 . The sheath-core insert  88  comprises a stacked filter plate  92 , transfer plate  94 , and converging block  96 . The filter plate  92  holds each liquid filter  68 ,  70  in filter recesses  98 ,  100  respectively. A first row of vertical filter passages  102  communicates with the first filter recess  98  and a second row of vertical filter passages  104  communicates with the second filter recess  100 . 
     The transfer plate  94  receives the two types of filtered liquid material from the filter plate  92 . In particular, a first row of transfer passages  106  communicates respectively with the first row of filter passages  102 . A transfer recess  108  on an upper surface  110  of the transfer plate  94  communicates with the second row of filter passages  104  from the filter plate  92  and with second and third rows of transfer passages  112 ,  114 . 
     The converging block  96  includes a plurality of central recesses  116  that communicate respectively with each of the first row of transfer passages  106  and each of the central passages  90 . The converging block  96  also includes a first row of side passages  118  that communicates respectively with the second row of transfer passages  112  and with the first slot portion  60 ′. The converging block  96  further includes a second row of side passages  120  that communicates with the third row of transfer passages  114  of the transfer plate  94  and with the second slot portion  62 ′. 
     Referring now to  FIGS. 6A and 7 , die tip block  34 ′ includes three liquid passages  130   a ,  130   b ,  130   c  which intersect at a liquid discharge outlet  26 ′ to essentially form a sheath-core filament. Liquid discharge passages  130   a ,  130   c  respectively communicate with slot portions  60 ′,  62 ′ and liquid discharge passage  130   b  communicates with central passage  90 . A first type of liquid is introduced into slot portions  60 ′,  62 ′ and flows through passages  130   a ,  130   c  and a second type of liquid flows through central passage  90  and into liquid discharge passage  130   b . The two types of liquid combine immediately after extrusion at outlet  26 ′, formed by outlet portions  26   a′ ,  26   b′ ,  26   c ′, to form a sheath-core filament. The filament may be impinged with process air directed through channels  76 ,  78 . Alternatively, this type of sheath-core filament spinning apparatus may be used in a spunbond application without process air. 
     Referring to  FIG. 6B , an alternative insert  88 ′ is shown having an alternative converging portion  58 ″ which eliminates the central liquid passage  90 . Insert  88 ′ would also be configured as generally illustrated in  FIG. 1  to receive first and second types of liquid material into the respective slot portions  60 ′ and  62 ′. Thus, as in the first embodiment, the two types of liquid material will travel down passages  130   a ,  130   c  to discharge outlets  26   a′ ,  26   c ′ and combine together just after extrusion into a multi-component side-by-side filament. Other structural elements shown in  FIG. 6B  have like reference numerals with respect to the previously described embodiments and the description thereof applies equally to this embodiment. 
       FIG. 8  illustrates a meltblown apparatus  200  using a melt spinning assembly  10  and a spinpack  18  constructed in accordance with this invention. The apparatus  200  may be any suitable meltblown apparatus, such as the apparatus disclosed in U.S. Pat. No. 6,182,732, assigned to the assignee of the present invention and the disclosure of which is hereby fully incorporated by reference herein. The apparatus  200  generally includes an extruder  202  with a polymer feedline  204  for feeding the first type of material to the melt spinning assembly  10 . The second type of liquid material is also fed from a similar extruder and polymer feedline (not shown). The apparatus  200  is suitably supported above a substrate or carrier  206  for receiving the extruded multi-component filaments  24 . The various other details of the apparatus  200  are not described herein as these details will be readily understood from a review of the patent disclosure incorporated above. 
       FIG. 9  illustrates a spunbond apparatus  210  using a melt spinning assembly  10 ′ constructed in accordance with the invention, except that in the case of a spunbond application, the spinpack  18 ′ need not include air knife components and air passages for delivering process air to the extruded multi-component filaments  24 . The spunbond apparatus  210  shown in  FIG. 9  may be constructed in a conventional manner, or as disclosed in U.S. Pat. No. 6,182,732. This apparatus further includes air quench ducts  212 ,  214  for purposes that will be readily understood by those of ordinary skill in the art. It will be understood that spinpack  18 ′ may also be modified by those of ordinary skill to include multiple rows of multi-component filament discharge outlets. 
     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. However, the invention itself should only be defined by the appended claims, wherein what is claimed is: