Patent Application
20050110185
The present invention is related to an apparatus for controlled width extrusion of a filamentary curtain or filamentary web, and to a method for controlling the extruded width of a curtain of filaments.
Many of the medical care garments and products, protective wear garments, mortuary and veterinary products, and personal care products in use today are partially or wholly constructed of extruded filamentary web materials such as nonwoven web materials. Examples of such products include, but are not limited to, medical and health care products such as surgical drapes, gowns and bandages, protective workwear garments such as coveralls and lab coats, and infant, child and adult personal care absorbent articles such as diapers, training pants, disposable swimwear, incontinence garments and pads, sanitary napkins, wipes and the like. Other uses for extruded filamentary web materials include geotextiles and house wrap materials. For these applications extruded filament web materials provide functional, tactile, comfort and/or aesthetic properties that can approach or even exceed those of traditional woven textiles or knitted cloth materials, yet these products must be manufactured at a cost that is consistent with single- or limited-use disposability.
Various types of equipment for making extruded filament web materials by extruding a plurality or curtain of filaments are well known in the art, and are available in a variety of widths such as 1 meter and 2 meter wide filament extrusion dies and as large as meter wide filament extrusion dies. However, where it is desired that the extruded web of filaments produced by such apparatus be less wide than the full extrusion width of the apparatus or extrusion die, the extra width of the thus-produced filamentary web must be trimmed off and either discarded or somehow recycled back into the filament extrusion process. It would be highly desirable to be able to control the extruded width of the filamentary curtain in-process in order to avoid or decrease the waste associated with trimming substantial portions of the width of the product.
Therefore, there is a continuing need for efficient and controllable filament extrusion apparatus and methods for extruding filaments.
The present invention provides a method for controlling the cross machine direction width of a plurality of extruded filaments, the method including the steps of providing a polymer supply and an extrusion die in fluid communication with the polymer supply, the extrusion die comprising extrusion capillaries and counterbores allowing fluid communication between the extrusion capillaries and the polymer supply, and providing at least one adjustable insert for interrupting the fluid communication between the polymer supply and at least one of the extrusion capillaries, providing at least one fluidized polymer, conveying the polymer through the polymer supply, counterbores and extrusion capillaries to extrude filaments, and interrupting the fluid communication between the polymer supply and at least one of the extrusion capillaries by adjusting the insert.
The adjustable insert may be a plate, such as a plate having a rectangular cross section, or may be a rod having a substantially circular cross section. The adjustable insert may have a plurality of spaced apart holes through it. The fluid communication may be interrupted by moving the insert axially or by rotating the insert. In embodiments, a second adjustable insert may be provided. In embodiments, the adjustable insert may be a rod having a substantially circular cross section, a diameter and a length, and the rod having at least a first portion and a second portion along its length, the first portion having at a plurality of spaced apart locations a single hole through the diameter, and the second portion having at a plurality of spaced apart locations at least two holes through the diameter, wherein the fluid communication is interrupted to a first plurality of extrusion capillaries by a first rotational adjustment of the insert, and wherein the fluid communication is interrupted to a second plurality of the extrusion capillaries by a second rotational adjustment of the insert.
The invention further provides an apparatus for extruding filaments, the apparatus comprising an extrusion die, a polymer supply in fluid communication with the extrusion die, a plurality of extrusion capillaries in the extrusion die, a plurality of counterbores in the extrusion die allowing fluid communication between the capillaries and polymer supply, and an adjustable insert for interrupting the fluid communication between the polymer supply and at least one of the extrusion capillaries. The adjustable insert may be, for example, a solid plate such as a plate having a rectangular cross section, or a rod having a substantially circular cross section, and the rod or the plate may have spaced apart holes through it or may be a substantially solid rod or substantially solid plate.
In embodiments, the insert is a rod having a substantially circular cross section, a diameter and a length, the rod having at least a first portion and a second portion along its length, the first portion having at a plurality of spaced apart locations a single hole through the diameter, and the second portion having at a plurality of spaced apart locations at least two holes through the diameter. In another embodiment, the apparatus further comprises a second adjustable insert, where the second adjustable insert is a rod having a substantially circular cross section, a diameter and a length, the rod having at least a first portion and a second portion along its length, the first portion having at a plurality of spaced apart locations a single hole through the diameter, and the second portion having at a plurality of spaced apart locations at least two holes through the diameter.
As used herein and in the claims, the term “comprising” is inclusive or open-ended and does not exclude additional unrecited elements, compositional components, or method steps. Accordingly, the term “comprising” encompasses the more restrictive terms “consisting essentially of” and “consisting of”.
As used herein the term “polymer” generally includes but is not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and random symmetries. As used herein the term “thermoplastic” or “thermoplastic polymer” refers to polymers that will soften and flow or melt when heat and/or pressure are applied, the changes being reversible.
As used herein the term “fibers” refers to both staple length fibers and substantially continuous filaments, unless otherwise indicated. As used herein the term “substantially continuous” with respect to a filament or fiber means a filament or fiber having a length much greater than its diameter, for example having a length to diameter ratio in excess of about 15,000 to 1, and desirably in excess of 50,000 to 1.
As used herein the term “monocomponent” filament refers to a filament formed from one or more extruders using only one polymer. This is not meant to exclude filaments formed from one polymer to which small amounts of additives have been added for color, anti-static properties, lubrication, hydrophilicity, etc.
As used herein the term “multicomponent filaments” refers to filaments that have been formed from at least two component polymers, or the same polymer with different properties or additives, extruded from separate extruders but spun together to form one filament. Multicomponent filaments are also sometimes referred to as conjugate filaments or bicomponent filaments, although more than two components may be used. The polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent filaments and extend continuously along the length of the multicomponent filaments. The configuration of such a multicomponent filament may be, for example, a concentric or eccentric sheath/core arrangement wherein one polymer is surrounded by another, or may be a side by side arrangement, an “islands-in-the-sea” arrangement, or arranged as pie-wedge shapes or as stripes on a round, oval or rectangular cross-section filament, or other. Multicomponent filaments are taught in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 5,336,552 to Strack et al., and U.S. Pat. No. 5,382,400 to Pike et al. For two component filaments, the polymers may be present in ratios of 75/25, 50/50, 25/75 or any other desired ratios. In addition, any given component of a multicomponent filament may desirably comprise two or more polymers as a multiconstituent blend component.
As used herein the term “biconstituent filament” or “multiconstituent filament” refers to a filament formed from at least two polymers, or the same polymer with different properties or additives, extruded from the same extruder as a blend. Multiconstituent filaments do not have the polymer components arranged in substantially constantly positioned distinct zones across the cross-section of the multicomponent filaments; the polymer components may form fibrils or protofibrils that start and end at random.
As used herein the term “nonwoven web” or “nonwoven fabric” means a web having a structure of individual filaments or filaments that are interlaid, but not in an identifiable manner as in a knitted or woven fabric. Nonwoven fabrics or webs have been formed from many processes such as for example, meltblowing processes, spunbonding processes, airlaying processes, and carded web processes. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm) or ounces of material per square yard (osy) and the filament diameters useful are usually expressed in microns. (Note that to convert from osy to gsm, multiply osy by 33.91).
The term “spunbond” or “spunbond nonwoven web” refers to a nonwoven fiber or filament material of small diameter filaments that are formed by extruding molten thermoplastic polymer as filaments from a plurality of capillaries of a spinneret. The extruded filaments are cooled while being drawn by an eductive or other well known drawing mechanism. The drawn filaments are deposited or laid onto a forming surface in a generally random manner to form a loosely entangled filament web, and then the laid filament web is subjected to a bonding process to impart physical integrity and dimensional stability. The production of spunbond fabrics is disclosed, for example, in U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,692,618 to Dorschner et al., and U.S. Pat. No. 3,802,817 to Matsuki et al. Typically, spunbond fibers or filaments have a weight-per-unit-length in excess of about 1 denier and up to about 6 denier or higher, although both finer and heavier spunbond filaments can be produced. In terms of filament diameter, spunbond filaments often have an average diameter of larger than 7 microns, and more particularly between about 10 and about 25 microns, and up to about 30 microns or more.
As used herein the term “meltblown fibers” means fibers or microfibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads filaments or fibers into converging high velocity gas (e.g. air) streams that attenuate the fibers of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Buntin. Meltblown fibers may be continuous or discontinuous, are often smaller than 10 microns in average diameter and are frequently smaller than 7 or even 5 microns in average diameter, and are generally tacky when deposited onto a collecting surface.
The present invention provides an apparatus and method for controlled-width extrusion of a filamentary curtain by use of an adjustable die insert. The invention will be described with reference to the following Figures which illustrate certain embodiments. It will be apparent to those skilled in the art that these embodiments do not represent the full scope of the invention which is broadly applicable in the form of variations and equivalents as may be embraced by the claims appended hereto. It is intended that the scope of the claims extend to all such variations and equivalents. As disclosed herein, the extruded width of a curtain of extruded filaments may be controlled by selectively interrupting or occluding fluid communication to the filament extrusion capillaries, from one or both ends or sides of the extrusion apparatus, thus narrowing the extruded width of the filamentary curtain.
Typically, the fibers or filaments of molten polymer are extruded into converging high velocity gas streams (such as heated or unheated air) which attenuate the fibers of molten thermoplastic material to reduce their diameter. The converging high velocity gas streams are supplied along the sides of the meltblown die through the slots formed between the die and the air plates 13 and 15 that are shown in
In
Turning to
In use, fluidized polymer such as a molten thermoplastic polymer is pumped or otherwise provided to the die 40 by a polymer supply such as, for example, heated polymer piping (not shown), is conveyed to and flows through counterbore 42 and thus to and through extrusion capillary 44 to be extruded as fine threads or filaments or fibers of molten polymer (not shown) from capillary 44 at extrusion edge 46. However, when insert 48 is adjusted to interrupt the fluid communication between the polymer supply and the extrusion capillary, the molten or otherwise fluidized polymer is unable to flow through the counterbore to the extrusion capillary, and therefore no polymer is extruded in the form of a fiber. Similarly, the type of meltblown die that was shown in
In a very simple embodiment the adjustable insert may be a solid rod, such as a cylinder having a generally circular cross-section, or a flat plate having a generally rectangular cross section or a bar with a square cross-section. The rod or plate may then indexed axially (that is, indexed or pushed inwardly along the longitudinal axis of the rod, which will generally be in the cross machine direction and along the longitudinal axis of the extrusion die) in order to occlude or interrupt fluid communication such as polymer flow between the polymer supply and the extrusion capillary. As a solid rod or plate is indexed or pushed inwardly deeper into the extrusion die it sequentially occludes or interrupts fluid flow between the polymer supply generally and greater and greater numbers of the extrusion capillaries. The rod or plate is desirably placed either in or just above the counterbores. As each counterbore is occluded, polymer cannot flow to the capillary or capillaries served or supplied by the occluded counterbore and therefore no filaments will be extruded from those capillaries. As mentioned, many cross sectional shapes may be used for the insert and other cross sectional shapes are of course possible, and generally the exact shape of the insert will not be important so long as the insert is capable of being adjusted in order to occlude the counterbore and thus interrupt or block off the fluid communication between the polymer supply and the extrusion capillary or capillaries, so that polymer cannot be extruded from those extrusion capillaries for which fluid communication has been interrupted.
It should be noted that when the adjustable insert is a solid rod and when the insert has not yet been adjusted to interrupt any fluid flow, lateral fluid flow from counterbore to counterbore through the cavity provided for the insert may be possible and may not always be desirable. Therefore, the adjustable insert may desirably be a cylindrical rod having a substantially circular cross-sectional shape as was described above, but rather than being a solid rod that must be pushed into the die to occlude fluid flow, it has one or more holes drilled or otherwise formed through the insert and perpendicular to its long axis. The insert may have multiple holes drilled along its longitudinal axis in spaced apart locations matching the spacing of the counterbores. Such adjustable inserts may then be maintained at all times substantially fully within the cavity provided for the insert and adjusted by axial indexing a single time to occlude polymer flow to multiple extrusion capillaries, such that the polymer flow is occluded or interrupted when the hole or holes in the insert are no longer located in line with the counterbores. However, such an insert may also be adjusted by rotating the insert about its longitudinal axis in clockwise or counter-clockwise fashion. An example of such an adjustable insert is shown in
In certain embodiments, it may be desired to be able to interrupt fluid communication to one or more extrusion capillaries in a first adjustment, thereby reducing the cross-machine direction width of the filamentary curtain by a first amount, and then be able to interrupt fluid communication to greater numbers of extrusion capillaries in a second adjustment, thereby reducing the cross-machine direction width of the filamentary curtain by a second amount, and/or to interrupt fluid communication to still greater numbers of extrusion capillaries in a third adjustment, still further reducing the width of the curtain produced. As an example, in
When polymer is supplied to an extrusion die having such an insert, prior to adjustment the polymer will be able to flow through the counterbores to the extrusion capillaries in all three portions because each counterbore will have a hole 62 aligned within it to allow fluid communication. Then, the insert may be adjusted, for example, by rotating the adjustable insert 45 degrees in a clockwise fashion. Once so adjusted, all of the counterbores served by the insert in the first portion of the extrusion die will be occluded as shown in
Then, when it is desired to further reduce the cross-machine direction width of the filamentary curtain, the adjustable insert may be adjusted by turning another 45 degrees in a clockwise fashion, thereby rotating holes 62′ out of alignment with the counterbores and interrupting fluid communication through the counterbores in the second portion of the adjustable insert. However, the counterbores of the third portion of the extrusion die will continue to allow fluid communication through the counterbores to the extrusion capillaries via holes 62″ that have now been rotated into alignment with the counterbores in the third portion. If it is desired to still further reduce the cross-machine direction width of the filamentary curtain, the adjustable insert may be adjusted by turning another 45 degrees to rotate holes 62″ in the third portion out of alignment, thereby interrupting polymer flow to the extrusion capillaries that had been in fluid communication with those counterbores in the third section or portion of the extrusion die.
A top view of such an adjustable insert as might be used in the embodiment described above wherein multiple adjustments are capable is shown in
Other embodiments of the apparatus of the invention as embodied in a meltblown die are shown schematically in
As discussed above, where adjustable insert 78 is a solid rod it may be adjusted by indexing axially to interrupt fluid communication sequentially as it is pushed deeper and deeper into the apparatus. Alternatively, where holes are drilled through the insert matching the spacing of the counterbores, the insert 78 may be used to interrupt polymer to multiple extrusion capillaries at the same time by indexing the insert a single time. Another embodiment is shown in
Turning to
In use, fluidized polymer such as a molten thermoplastic polymer is pumped or otherwise provided to the polymer distribution channel 116 by a polymer supply (not shown), is conveyed to and flows through counterbores 106 and 108 and thus to and through respective extrusion capillaries 102 and 104 to be extruded as continuous filaments at extrusion surface 110. When it is desired to interrupt fluid flow to the extrusion capillaries the adjustable insert 118 may be indexed axially as discussed above. Or, where the adjustable insert 118 comprises holes drilled or otherwise formed through the insert and perpendicular to its long axis such as holes 120 and 122 shown in
Turning to
In use, fluidized polymer such as a molten thermoplastic polymer is pumped or otherwise provided by a polymer supply such as heated polymer piping (not shown) to the polymer distribution channel 152, is conveyed to and flows through counterbores 144 and thus to and through the extrusion capillaries 142 to be extruded as continuous filaments at the extrusion surface 146. When it is desired to interrupt fluid flow to the extrusion capillaries the adjustable inserts 154 may be indexed axially as discussed above. Or, where the adjustable inserts 154 comprise holes drilled or otherwise formed through the inserts perpendicular to their long axis such as holes 156 shown in
Turning to
Turning to
In use, fluidized polymer such as a molten thermoplastic polymer is pumped or otherwise provided to the counterbore 212 by a polymer supply (not shown), is conveyed through the counterbore 212 and flows downwardly to and through the expanding slot 214 and the supply slot 204 and thus to and through the extrusion capillaries 202 to be extruded as continuous filaments at the extrusion surface 206. When it is desired to interrupt fluid flow to the extrusion capillaries the adjustable insert 218 may be indexed axially as discussed above. Or, where the adjustable insert 218 comprises holes drilled or otherwise formed through the insert perpendicular to its long axis such as was discussed above, the adjustable insert 218 may be indexed axially or more desirably rotated until the holes are no longer aligned within the counterbore, thereby interrupting fluid flow. The adjustable insert may also comprise areas having multiple holes such as was discussed with respect to
Turning to
In another embodiment of the extrusion apparatus shown in
Although the embodiments of the invention have been described with respect to apparatus conventionally utilized in the melt extrusion of various types thermoplastic filaments, we believe the invention is not limited thereto and may also be beneficially used in controlling the extruded width of filamentary curtains in other types of filament extrusion processes such as for example in flash spun filament production processes and in solution spun filament production processes. However, the invention may be particularly well suited to the extrusion of thermoplastic polymer filaments. Polymers generally suitable for extrusion from a thermoplastic melt include the known polymers suitable for production of nonwoven webs and materials such as for example polyolefins, polyesters, polyamides, polycarbonates and copolymers and blends thereof. It should be noted that the polymer (or polymers, where it is desired to produce multicomponent or multiconstituent filaments) may desirably contain other additives such as processing aids or treatment compositions to impart desired properties to the filaments, residual amounts of solvents, pigments or colorants and the like.
Suitable polyolefins include polyethylene, e.g., high density polyethylene, medium density polyethylene, low density polyethylene and linear low density polyethylene; polypropylene, e.g., isotactic polypropylene, syndiotactic polypropylene, blends of isotactic polypropylene and atactic polypropylene; polybutylene, e.g., poly(1-butene) and poly(2-butene); polypentene, e.g., poly(1-pentene) and poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl-1-pentene); and copolymers and blends thereof. Suitable copolymers include random and block copolymers prepared from two or more different unsaturated olefin monomers, such as ethylene/propylene and ethylene/butylene copolymers. Suitable polyamides include nylon 6, nylon 6/6, nylon 4/6, nylon 11, nylon 12, nylon 6/10, nylon 6/12, nylon 12/12, copolymers of caprolactam and alkylene oxide diamine, and the like, as well as blends and copolymers thereof. Suitable polyesters include poly lactide and poly lactic acid polymers as well as polyethylene terephthalate, poly-butylene terephthalate, polytetramethylene terephthalate, polycyclohexylene-1,4-dimethylene terephthalate, and isophthalate copolymers thereof, as well as blends thereof.
In addition, many elastomeric polymers are known to be suitable for forming filaments. Elastic polymers useful in making extruded filaments may be any suitable elastomeric filament forming resin including, for example, include elastic polyesters, elastic polyurethanes, elastic polyamides, elastic co-polymers of ethylene and at least one vinyl monomer, block copolymers, and elastic polyolefins. Examples of elastic block copolymers include those having the general formula A-B-A′ or A-B, where A and A′ are each a thermoplastic polymer endblock that contains a styrenic moiety such as a poly (vinyl arene) and where B is an elastomeric polymer midblock such as a conjugated diene or a lower alkene polymer such as for example polystyrene-poly(ethylene-butylene)-polystyrene block copolymers. Also included are polymers composed of an A-B-A-B tetrablock copolymer, as discussed in U.S. Pat. No. 5,332,613 to Taylor et al. An example of such a tetrablock copolymer is a styrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene) or SEPSEP block copolymer. These A-B-A′ and A-B-A-B copolymers are available in several different formulations from the Kraton Polymers of Houston, Tex. under the trade designation KRATON®.
Examples of elastic polyolefins include ultra-low density elastic polypropylenes and polyethylenes, such as those produced by “single-site” or “metallocene” catalysis methods. Such polymers are commercially available from the Dow Chemical Company of Midland, Mich. under the trade name ENGAGE®, and described in U.S. Pat. Nos. 5,278,272 and 5,272,236 to Lai et al entitled “Elastic Substantially Linear Olefin Polymers”. Also useful are certain elastomeric polypropylenes such as are described, for example, in U.S. Pat. No. 5,539,056 to Yang et al. and U.S. Pat. No. 5,596,052 to Resconi et al., incorporated herein by reference in their entireties, and polyethylenes such as AFFINITY® EG 8200 from Dow Chemical of Midland, Mich. as well as EXACT® 4049, 4011 and 4041 from Exxon of Houston, Tex., as well as blends.
A 56 centimeter (cm) long (cross-machine direction dimension) meltblowing apparatus die having 3.43 cm long vertical counterbores in the die such as are described above and in U.S. Pat. No. 6,579,084 to Cook was modified by having 1.0 cm diameter cylindrical cavities drilled into it from both ends, parallel to the cross machine direction axis of the meltblowing apparatus. The cavities were 19 cm long and extended perpendicularly across the space occupied by 50 counterbores each, and were situated such that they passed through the counterbores approximately 1.1 cm from the top of the counterbore or counterbore entry. Each cavity was then fitted with a solid cylindrical rod inserted into the meltblowing apparatus approximately 3.5 cm, such that the rod did not yet occlude fluid flow through any of the counterbores. The counterbores were machined on 0.254 cm centers, and comprised the center 48 cm portion of the die. Thus, the first counterbore was approximately 4 cm from the ends where the rods were inserted. Each counterbore had three extrusion capillaries drilled from the bottom of the counterbore to the bottom extrusion surface or edge of the meltblowing die.
A commercially available polypropylene polymer was melted by an extruder and supplied to the meltblowing apparatus and was pumped through a polymer supply channel and thus was conveyed to and through all the available counterbores and thus to the extrusion capillaries. As the molten polymer was extruded from the extrusion capillaries it was entrained in and drawn by converging high velocity air streams which attenuated the polymer filaments to form meltblown filaments. The meltblown filaments were collected onto a moving foraminous forming surface to form a meltblown mat or web of fibers having about a 48 cm cross machine direction width. Then, when it was desired to reduce the cross machine direction width of the web of meltblown fibers, the adjustable inserts were adjusted by indexing the cylindrical rods further into the meltblown die about 12 cm each to occlude fluid flow through the counterbores and thus to interrupt polymer flow to the extrusion capillaries. The web thus produced after adjustment of the adjustable insert was 24 cm in cross machine direction width, having been reduced by about 12 cm in width on each side of the web. It should be noted that where desired to reduce the cross machine direction width of the web from only one side, only one of the adjustable inserts would be adjusted by indexing into the apparatus.
A 60 centimeter (cm) long (cross-machine direction dimension) continuous strand filament apparatus similar to the apparatus shown in
A commercially available polypropylene polymer was melted by an extruder and supplied to the filament apparatus and was pumped through a polymer supply channel and thus conveyed to and through all the available counterbores and thus to the extrusion capillaries to form continuous strand filaments. The filaments were collected onto a moving foraminous forming surface to form a filament mat of fibers having about a 48 cm cross machine direction width. Then, when it was desired to reduce the cross machine direction width of the fiber curtain produced, the two adjustable inserts were adjusted by indexing the cylindrical rods further into the extrusion die about 13 cm to occlude fluid flow through the counterbores and thus to interrupt polymer flow to the extrusion capillaries. The filament mat thus produced after adjustment of the adjustable inserts was 34 cm in cross machine direction width, having been reduced by about 7 cm in width on each side of the web. It should be noted that where desired to reduce the cross machine direction width of the filament curtain extruded from only one side, only one of the adjustable inserts would be adjusted by indexing into the apparatus.
While various patents have been incorporated herein by reference, to the extent there is any inconsistency between incorporated material and that of the written specification, the written specification shall control. In addition, while the invention has been described in detail with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various alterations, modifications and other changes may be made to the invention without departing from the spirit and scope of the present invention. It is therefore intended that the claims cover all such modifications, alterations and other changes encompassed by the appended claims.
