Patent Application
20190292684
The present invention relates to a spinneret, apparatus, and method for making filaments for fibrous nonwoven fabrics with more uniform filament and fabric formation while minimizing filament breaks and hard spot defects in webs and fabrics made therefrom.
In the melt-spinning of filaments from synthetic organic polymers, the polymer is extruded downwardly with the aid of a spinning pump or some other device through a plurality of orifices in a spinneret (or spinnerette) to form molten filaments. The extruded molten filaments are attenuated while passing through a quench zone where a stream of fluid, such as air, is passed across the path of the filaments to cool or solidify them. By application of a draw force the filaments are attenuated into finer filaments until their surface solidifies. When solidified the filaments can be deposited onto a collection surface to form a web. Beams used for melt-spinning polymeric filaments are typically provided with spinnerets that comprise capillaries that are uniformly spaced and have similar exit diameters as well as similar lengths throughout the entire array of capillaries in the spinneret. Several previous variations of these uniform designs of capillary layouts and capillary dimensions in spinnerets are discussed hereinbelow.
In U.S. Pat. No. 4,248,581 (“'581 patent”), a process for determining the arrangement of orifices in a spinneret is disclosed. The '581 patent does not appear to disclose variations in any orifice dimensions other than the spacing between orifices.
In U.S. Pat. No. 4,514,350 (“'350 patent”), spinnerets are shown which have “graduated orifice sizes” (GOS) that are used in manufacturing melt-spun filaments with good birefringence (i.e., molecular orientation) uniformity at high polymer extrusion rates. The '350 patent does not relate to providing changes in length to hydraulic diameter ratio in different groups of different shaped capillaries in the spinneret, nor changes in length to hydraulic diameter ratio for any two or more different adjacent groups of capillaries in the spinneret, nor indicate that these parameters may effect spinneret, filament, and fabric performance.
In U.S. Pat. No. 5,266,255 (“'255 patent”), a process is shown for high stress spinning of polyethylene terephthalate yarns to produce a yarn of high birefringence by using a spinneret having at least one row of orifices with a diameter greater than an adjacent row of orifices. The '255 patent does not appear to disclose variations in any other orifice dimension than diameter.
In U.S. Pat. No. 5,112,550 (“'550 patent”), a process and apparatus for producing superfine fibers is shown that uses a spinneret having nozzle orifices arranged in a lattice pattern extending toward a quench direction and the right angled direction to the quench direction with the arrangement being provided to satisfy certain formulae described therein. However, the '550 patent does not appear to disclose orifices (e.g., capillaries) that have different diameters or lengths, or different ratios thereof.
The present inventors have recognized that there is a need for a spinneret with a plurality of zones having various combinations of capillaries with various dimensions that can accommodate higher overall polymer throughputs and produce uniform filaments while minimizing filament breaks and nonwoven web and fabric hard spot defects.
A spinneret for melt-spinning polymeric filaments is provided which includes a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body, wherein each of the plurality of different zones has a capillary density; and each of the capillaries in each of the plurality of zones has a particular capillary length, cross-sectional shape, hydraulic diameter and a length to hydraulic diameter ratio. The hydraulic diameter is a calculated value using a formula defined herein with reference made to a cross-sectional area and a perimeter of the cross-sectional shape of the capillary of a given zone. The spinneret bodies of the spinnerets of the present invention have at least three of the indicated zones at the face of the spinneret body. Spinneret bodies of the spinnerets of the present invention each have a plurality of zone-to-zone length to hydraulic diameter ratios. The spinnerets of the present invention can reduce frost line variation at commercial throughputs, which generally improve fiber and nonwoven fabric uniformity and may allow higher production throughput without increasing occurrence of defects like filament break and merged filaments which can cause defects in the fabric.
In one embodiment, the spinneret body of the spinneret of the present invention has an overall length to hydraulic diameter ratio of at least 3 percent, or even higher range values. In this embodiment, the spinneret body, provides a plurality of different capillary zones which have different relative proximities to the quench gas discharge outlet or outlets. The spinneret body is designed such that a plurality of the different zones, such as at least two, or three, or four, or five or more zones, have different length to hydraulic diameter ratios, such that the greatest difference between these various ratio values of all the zones is at least 3 percent or higher. This design can provide unexpectedly better fiber uniformity and performance by reducing frost line variation and problems associated therewith while providing enhanced or at least comparable commercial throughputs as spinneret bodies that use a single uniform design of capillaries throughout.
In another embodiment, the spinneret body has a plurality of zone-to-zone length to hydraulic diameter ratios; and at least one of the zone-to-zone length to hydraulic diameter ratios is at least 2 percent, or at least 3 percent, or even higher. In this embodiment, the spinneret body, provides a plurality of different capillary zones which have different relative proximities to the quench gas discharge outlet or outlets on an adjacent zone-to-zone basis. The spinneret body is designed such that a plurality of the various adjacent zones on the spinneret body have different length to hydraulic diameter ratios, such that the zone-to-zone difference between the ratio values of at least one, or two, or three, or four, or five, or more, of the adjacent zones is at least 2 percent. This design also can provide or enhance unexpectedly fiber and fabric uniformity and performance.
In another embodiment, the hydraulic diameters, lengths, and length to hydraulic diameter ratios of capillaries in different zones at the face of the spinneret body in spinnerets of the present invention progressively increase or decrease, such as zone-to-zone or at least in the same direction across the spinneret body, for at least three, or four, or five or more, different zones of capillaries depending on the relative proximity of the various different zones to the quench gas discharge outlet or outlets. This configuration can be used with single-side quench or cross-flow quench processing.
In another embodiment of the invention, the capillary density may be the same or may be different among the different zones. In an embodiment of the invention, when different zones are designed to be disposed along an axis oriented perpendicular to the direction of the stream of quench air towards the spinneret body, the zones located at the lateral sides of the spinneret body along this axis can have lower capillary density than the zone or zones located in between those two zones. This embodiment may be useful when the filaments produced by the zone or zones at the lateral sides of the face of the spinneret body of spinnerets of the present invention are impacted by wall effects as further defined herein. In another embodiment of the invention, when different zones are designed to be disposed along an axis oriented parallel to the direction of the stream of quench air towards the spinneret body, all the zones can have the same density of capillaries, such as where there are no wall effects (as described more fully herein) impacting the zones or the wall effects were compensated by other means.
In another embodiment of the invention, one or more of the at least three zones has a plurality of capillaries with a length, cross-sectional shape, hydraulic diameter and/or a length to hydraulic diameter ratio that varies from and is not substantially the same as the length, cross-sectional shape, hydraulic diameter, and/or length to hydraulic diameter ratio of a plurality of capillaries in at least one of the other zones. Generally, the length of each of the capillaries in one or more zones generally closer to the quench gas discharge outlet is longer than the capillary length of each of the plurality of capillaries that is located at the face of the spinneret body furthest away from the quench gas discharge outlet. Assuming the quench gas discharge outlet is located closer to the edges of the face of the spinneret body, the capillary lengths of the plurality of each of the capillaries in a zone near the center of the face of the spinneret body will tend to be shorter than the capillary lengths of each of the plurality of capillaries located in a zone at the edge of the face of the spinneret body. Generally, the hydraulic diameter (e.g., the diameter for a capillary having a circular shaped cross-section) of each of the plurality of capillaries located in a zone at the face of the spinneret body furthest away from a quench gas discharge outlet will be smaller than the hydraulic diameter of each of the plurality of capillaries located in a zone at the face of the spinneret body that is closer to the quench gas discharge outlet. In addition, the ratio of length to hydraulic diameter of each of the plurality of capillaries in a zone that is closer to the quench gas discharge outlet will tend to be larger than the length to hydraulic diameter ratio of each of the plurality of capillaries located in a zone that is further away from the quench gas discharge outlet. Generally, the capillary length and/or capillary hydraulic diameter can be selected for each zone in a way to minimize the difference in throughput between capillaries located in different zones.
In a preferred embodiment of the invention, the spinneret body of the spinneret has an overall length to hydraulic diameter ratio and has at least three zones with a first zone located centrally at the face of the spinneret body. The first zone having a plurality of first rows, and each of the first rows having a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio. The second zone in this preferred embodiment of the invention, is located adjacent to the first zone at the face of the spinneret body, and has a plurality of second rows. Each of the second rows having a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio. In this preferred embodiment of the invention, a third zone is located adjacent to the first zone at the face of the spinneret body, and includes a plurality of third rows, each of the third rows contains a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density, and the third capillaries each individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio. In this preferred embodiment, the first zone is located between the second and third zones, and the first zone is closer to a center of the face of the spinneret body than the second and third zones, and the overall length to hydraulic diameter ratio is at least 3 percent. In another embodiment of this spinneret, the spinneret body has an overall length to hydraulic ratio of at least 5 percent. In another embodiment of this spinneret, the spinneret body has a zone-to-zone hydraulic ratio of at least 2 percent.
In a more preferred embodiment of this invention, the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries are the same. In another preferred embodiment of this invention, the spinneret body includes at least one of (i) and (ii). Wherein (i) is the first hydraulic diameter of each of the first capillaries is less than the second hydraulic diameter of each of the second capillaries, and the first hydraulic diameter of each of the first capillaries is less than the third hydraulic diameter of each of the third capillaries; and (ii) is the first length of each of the first capillaries is less than the second length of each of the second capillaries, and the first length of each of the first capillaries is less than the third length of each of the third capillaries. In another preferred embodiment of the invention, the first length to hydraulic diameter ratio of each of the first capillaries is less than the second length to hydraulic diameter ratio of each of the second capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the third length to hydraulic diameter ratio of each of the third capillaries. In another preferred embodiment of the invention, the second length to hydraulic diameter ratio of each of the second capillaries and the third length to hydraulic diameter ratio of each of the third capillaries are the same. In another preferred embodiment of the invention, the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries are circular or oval. In another preferred embodiment of the invention, the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries are not necessarily the same, but each is circular or oval. In another preferred embodiment of the invention, the sum of the capillaries that open at a face of the spinneret body is at least 3000. In another preferred embodiment of the invention, the face of the spinneret body is polygonal (e.g., rectangular, or polygonal shapes such as rectangular middle with trapezoidal ends, or other polygonal shapes).
In another preferred embodiment of this invention, the second zone is located at an end of the face of the spinneret body, and the third zone is located at an end of the face of the spinneret body opposite to the end at which the second zone is located, wherein the three zones are disposed in a linear arrangement oriented perpendicular to the direction of the flow of quenching air. In a further embodiment of this spinneret, the first capillary density is greater than each of the second capillary density and the third capillary density.
As another option, the spinneret can include at least four different types of capillary zones including a central zone having a first type of capillaries located centrally at the face of the spinneret body that is located between a pair of inner side zones having a second type of capillaries and a pair of outer side zones having a third type of capillaries. The third, second, and first types of capillary hydraulic diameters and lengths can progressively decrease in the direction extending from the outer side zones located nearer to an outer edge of the spinneret body towards the first zone located at the center of the spinneret body. As an option, the indicated zones of the first, second, and third types of capillaries can be positioned between a pair of end zones having a fourth type of capillaries. The capillary hydraulic diameters and lengths of these different capillary zones can progressively decrease from the fourth, to the third, to the second, to the first types of capillaries.
In a more preferred embodiment of the invention, the spinneret has at least five zones at the face of the spinneret body. In addition to the first three zones generally described above, the spinneret body includes a fourth zone having a plurality of fourth rows, each of said fourth rows comprising a plurality of fourth capillaries, wherein the fourth capillaries are arranged in a fourth capillary density, and the fourth capillaries individually having a fourth cross-sectional shape, a fourth hydraulic diameter, a fourth length, and a fourth length to hydraulic diameter ratio. The spinneret body of this preferred embodiment also has a fifth zone having a plurality of fifth rows, and each of said fifth rows having a plurality of fifth capillaries, wherein the fifth capillaries are arranged in a fifth capillary density and the fifth capillaries individually have a fifth cross-sectional shape, a fifth hydraulic diameter, a fifth length, and a fifth length to hydraulic diameter ratio; wherein the first zone is located between the fourth and fifth zones, and wherein the fourth cross-sectional shape of each of the fourth capillaries and the fifth cross-sectional shape of each of the fifth capillaries are the same as the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries, and wherein the fourth hydraulic diameter of each of the fourth capillaries and the fifth hydraulic diameter of each of the fifth capillaries are less than the second hydraulic diameter of each of the second capillaries and are less than the third hydraulic diameter of each of the third capillaries; and the first hydraulic diameter of each of the first capillaries is less than the fourth hydraulic diameter of each of the fourth capillaries, and the first hydraulic diameter of each of the first capillaries is less than the fifth hydraulic diameter of each of the fifth capillaries; and wherein the fourth length of each of the fourth capillaries and the fifth length of each of the fifth capillaries are less than the second length of each of the second capillaries and the third length of each of the third capillaries; and the first length of each of the first capillaries is less than the fourth length of each of the fourth capillaries, and the first length of each of the first capillaries is less than the fifth length of each of the fifth capillaries. In another preferred embodiment, the first capillary density, the fourth capillary density, and the fifth capillary density are the same. In another preferred embodiment of this invention, the first length to hydraulic diameter ratio of each of the first capillaries is less than the fourth length to hydraulic diameter ratio of each of the fourth capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the fifth length to hydraulic diameter ratio of each of the fifth capillaries.
In another preferred embodiment of the invention, there are at least seven zones at the face of the spinneret body in the spinneret. There are the five zones mentioned above, and at least two additional zones as follows. There is a sixth zone having a plurality of sixth rows, each of said sixth rows comprising a plurality of sixth capillaries, wherein the sixth capillaries are arranged in a sixth capillary density, and each of the sixth capillaries individually having a sixth cross-sectional shape, a sixth hydraulic diameter, a sixth length, and a sixth length to hydraulic diameter ratio. In this preferred embodiment, the seventh zone has a plurality of seventh rows, each of said seventh rows having a plurality of seventh capillaries, wherein the seventh capillaries are arranged in a seventh capillary density, and the seventh capillaries individually having a seventh cross-sectional shape, a seventh hydraulic diameter, a seventh length, and a seventh length to hydraulic diameter ratio; wherein the first, fourth, and fifth zones are located between the sixth and seventh zones, and wherein the sixth cross-sectional shape of each of the sixth capillaries and the seventh cross-sectional shape of each of the seventh capillaries are the same as the first cross-sectional shape of each of the first capillaries, the second cross-sectional shape of each of the second capillaries, the third cross-sectional shape of each of the third capillaries, the fourth cross-sectional shape of each of the fourth capillaries, and the fifth cross-sectional shape of each of the fifth capillaries; wherein the sixth hydraulic diameter of each of the sixth capillaries and the seventh hydraulic diameter of each of the seventh capillaries are less than the second hydraulic diameter of each of the second capillaries and the third hydraulic diameter of each of the third capillaries; and the fourth hydraulic diameter of each of the fourth capillaries and the fifth hydraulic diameter of each of the fifth capillaries are less than the sixth hydraulic diameter of each of the sixth capillaries and less than the seventh hydraulic diameter of each of the seventh capillaries; and wherein the sixth length of each of the sixth capillaries and the seventh length of each of the seventh capillaries are less than the second length of each of the second capillaries and the third length of each of the third capillaries; and the fourth length of each of the fourth capillaries and the fifth length of each of the fifth capillaries are less than the sixth length of each of the sixth capillaries and are less than the seventh length of each of the seventh capillaries.
In a further more preferred embodiment, the first capillary density, the fourth capillary density, the fifth capillary density, the sixth capillary density, and the seventh capillary density are the same. In addition, in another further preferred embodiment of this invention, the fourth length to hydraulic diameter ratio of each of the fourth capillaries and the fifth length to hydraulic diameter ratio of each of the fifth capillaries are respectively less than the sixth length to hydraulic diameter ratio of each of the sixth capillaries and the seventh length to hydraulic diameter ratio of each of the seventh capillaries. In other words, in this embodiment, both of the fourth and fifth length to hydraulic diameter ratios of each of the fourth and fifth capillaries are less than the sixth and seventh length to hydraulic diameter ratios of each of the sixth and seventh capillaries.
In another preferred embodiment of this invention, a spinneret for melt-spinning polymeric filaments has a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body, wherein the plurality of different zones has at least a first zone, second zone, and a third zone. The first zone in this preferred embodiment is located centrally at the face of the spinneret body, and comprises a plurality of first rows, each of said first rows comprising a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio. The second zone in this preferred embodiment is located adjacent to the first zone at the face of the spinneret body, and comprises a plurality of second rows, each of said second rows comprising a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio. The third zone in this preferred embodiment is located adjacent to the first zone at the face of the spinneret body, and comprises a plurality of third rows, each of said third rows comprising a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density, and the third capillaries individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio. In this preferred embodiment, the first zone is located between the second and third zones, and the first zone is closer to a center of the face of the spinneret body than the second and third zones. Also, in this preferred embodiment, the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries are the same, wherein the first hydraulic diameter of each of the first capillaries is less than the second hydraulic diameter of each of the second capillaries, and the first hydraulic diameter of each of the first capillaries is less than the third hydraulic diameter of each of the third capillaries, and the first length of each of the first capillaries is less than the second length of each of the second capillaries, and the first length of each of the first capillaries is less than the third length of each of the third capillaries. In a more preferred embodiment, the first length to hydraulic diameter ratio of each of the first capillaries is less than the second length to hydraulic diameter ratio of each of the second capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the third length to hydraulic diameter ratio of each of the third capillaries. In addition, the first capillary density and second capillary density and the third capillary density in this more preferred embodiment can be the same. Further, in a preferred embodiment, the face of the spinneret body can be polygonal, such as rectangular.
In addition to at least the first three zones mentioned above of a preferred embodiment, a spinneret body can more preferably have the following additional zones. In this more preferred embodiment, the face of the spinneret body further can have fourth and fifth zones, wherein the fourth zone comprising a plurality of fourth rows, each of said fourth rows comprising a plurality of fourth capillaries, wherein the fourth capillaries are arranged in a fourth capillary density, and the fourth capillaries individually having a fourth cross-sectional shape, a fourth hydraulic diameter, a fourth length, and a fourth length to hydraulic diameter ratio; and the fifth zone comprising a plurality of fifth rows, each of said fifth rows comprising a plurality of fifth capillaries, wherein the fifth capillaries are arranged in a fifth capillary density and the fifth capillaries individually having a fifth cross-sectional shape, a fifth hydraulic diameter, a fifth length, and a fifth length to hydraulic diameter ratio. In this more preferred embodiment, the first zone, second zone, and third zone are located between the fourth zone and fifth zone, wherein the fourth cross-sectional shape of each of the fourth capillaries and the fifth cross-sectional shape of each of the fifth capillaries are the same as the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries. Also, in this more preferred embodiment, the second hydraulic diameter of each of the second capillaries and the third hydraulic diameter of each of the third capillaries are less than the fourth hydraulic diameter of each of the fourth capillaries and the fifth hydraulic diameter of each of the fifth capillaries, and the second length of each of the second capillaries and the third length of each of the third capillaries are less than the fourth length of each of the fourth capillaries and the fifth length of each of the fifth capillaries. In other words, in this embodiment, both the second and third hydraulic diameters of each of the second and third capillaries, respectively, are less than both the fourth and fifth hydraulic diameters of each of the fourth and fifth capillaries, respectively. In addition, in this embodiment, both the second and third lengths of each of the second and third capillaries, respectively, are less than the fourth and fifth lengths of each of the fourth and fifth capillaries, respectively.
In addition to the more preferred embodiment of this invention with at least five zones, the spinneret can have the second length to hydraulic diameter ratio of each of the second capillaries and the third length to hydraulic diameter ratio of each of the third capillaries that are less than the fourth length to hydraulic diameter ratio of each of the fourth capillaries and the fifth length to hydraulic diameter ratio of each of the fifth capillaries. Furthermore, in this more preferred embodiment, the first capillary density, the second capillary density, the third capillary density, the fourth capillary density, and the fifth capillary density can be the same. Furthermore, in spinnerets of the present invention, the capillary density and dimensions of capillaries in each zone of capillaries can be selected to produce an equal and targeted polymer throughput among the different zones of capillaries based on the equation for shear stress calculated for a given polymer processed at a given set of process conditions.
In another preferred embodiment of this invention, a spinneret for melt-spinning polymeric filaments has a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body, wherein the plurality of different zones has at least a first zone, second zone, and a third zone. The first zone in this preferred embodiment is located centrally at the face of the spinneret body, and comprises a plurality of first rows, each of said first rows comprising a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio. The second zone in this preferred embodiment is located adjacent to the first zone at the face of the spinneret body, and comprises a plurality of second rows, each of said second rows comprising a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio. The third zone in this preferred embodiment is located adjacent to the first zone at the face of the spinneret body, and comprises a plurality of third rows, each of said third rows comprising a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density, and the third capillaries individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio. Also, in this preferred embodiment, the first zone is located between the second and third zones, wherein the third hydraulic diameter of each of the third capillaries is less than the first hydraulic diameter of each of the first capillaries, and the first hydraulic diameter of each of the first capillaries is less than the second hydraulic diameter of each of the second capillaries, and the third length of each of the third capillaries is less than the first length of each of the first capillaries, and the first length of each of the first capillaries is less than the second length of each of the second capillaries, and the third length to hydraulic diameter ratio of each of the third capillaries is less than the first length to hydraulic diameter ratio of each of the first capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the second length to hydraulic diameter ratio of each of the second capillaries. In a further embodiment, the overall length to hydraulic diameter ratio can be at least 3%. In a further embodiment, the face of the spinneret body can be annular. In a further embodiment, the spinneret body has a plurality of zone-to-zone length to hydraulic diameter ratios, and at least one of said zone-to-zone length to hydraulic diameter ratios is at least 2%. In addition, in a further embodiment of the spinneret, the first, second, and third capillary densities are the same.
These various features of the spinneret of the invention can allow more uniform quenching of the filaments at higher line speeds and polymer throughputs while minimizing variability in polymer throughput through the capillaries and enhancing filament uniformity than when a single zone design of capillaries is used in the spinneret or than when only one of the capillary dimensions varies and is not substantially the same from zone to zone. This type of controlled filament extrusion allows more polymer to be extruded through the capillaries at higher throughputs with more uniform filament and nonwoven web and fabric formation while minimizing the filament breaks and nonwoven web and fabric hard spot defects.
As another option, an apparatus is provided for producing a melt-spun nonwoven web that is useful in a nonwoven fabric, and the apparatus includes a polymer supply system; a collection surface; the indicated spinneret located above the collection surface for extruding polymer received from the polymer supply system for producing extruded filaments that move downward along a path toward the collection surface; at least one quench gas supply device for supplying at least one stream of cooling gas; a cooling region below the spinneret in which the at least one stream of cooling gas is directed to flow beneath the spinneret and across extruded filaments. In an embodiment of this apparatus, a cooling region arranged below the spinneret has streams of cooling gas directed to cross-flow from opposite directions beneath the spinneret and across extruded filaments along the path toward the collection surface. In another embodiment of this apparatus, a cooling region arranged below the spinneret has a stream of cooling gas directed to flow from a single direction beneath the spinneret and across extruded filaments. Preferably, there is a means to apply a force on the filaments that is located between the cooling region and the collection surface and that force causing the filaments to be attenuated while still in the molten state.
In one embodiment of this invention, an apparatus for producing a melt-spun nonwoven web includes: a) a polymer supply system; b) a filament collection surface; c) a spinneret located above the collection surface for extruding polymer received from the polymer supply system for producing extruded filaments that move downward along a path toward the collection surface; d) at least one quench gas supply device for supplying at least one stream of cooling gas; and e) a cooling region below the spinneret in which the at least one stream of the cooling gas is directed to flow beneath the spinneret and across extruded filaments along the path toward the collection surface. In this embodiment, the spinneret includes: a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body. In this embodiment, the plurality of different zones comprises: a first zone located centrally at the face of the spinneret body, comprising a plurality of first rows, each of said first rows comprising a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio; a second zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of second rows, each of said second rows comprising a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio; and a third zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of third rows, each of said third rows comprising a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density and the third capillaries individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio. In this embodiment, the first zone is located between the second and third zones, and the first zone is closer to a center of the face of the spinneret body than the second and third zones, wherein the overall length to hydraulic diameter ratio is at least 3 percent. In another embodiment of this apparatus, the spinneret body has an overall length to hydraulic ratio of at least 5 percent. In a further embodiment of this apparatus, the spinneret body has a plurality of zone-to-zone length to hydraulic diameter ratios, and wherein at least one of the zone-to-zone length to hydraulic diameter ratios is at least 2%. In another embodiment of this apparatus, the first capillary density can be greater than each of the second capillary density and the third capillary density and the three zones are disposed in a linear arrangement oriented perpendicular to the direction of the flow(s) of cooling gas (e.g., quenching air).
In a further embodiment of this apparatus, the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries are the same. In another preferred embodiment of this apparatus, the sum of the capillaries that open at a face of the spinneret body is at least 3000. In another preferred embodiment of this apparatus, the face of the spinneret body is polygonal, such as rectangular.
In another embodiment of this apparatus, the spinneret body includes at least one of (i) and (ii). Wherein (i) is the first hydraulic diameter of each of the first capillaries is less than the second hydraulic diameter of each of the second capillaries, and the first hydraulic diameter of each of the first capillaries is less than the third hydraulic diameter of each of the third capillaries; and (ii) is the first length of each of the first capillaries is less than the second length of each of the second capillaries, and the first length of each of the first capillaries is less than the third length of each of the third capillaries.
In yet another embodiment of this apparatus, the first length to hydraulic diameter ratio of each of the first capillaries is less than the second length to hydraulic diameter ratio of each of the second capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the third length to hydraulic diameter ration of each of the third capillaries. Further, the second length to hydraulic diameter ratio of each of the second capillaries and the third length to hydraulic diameter ratio of each of the third capillaries can be the same.
A further embodiment of this apparatus includes a spinneret having the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries are circular or oval. Another embodiment of this invention includes the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries being circular or oval, and the second zone can be located at an end of the face of the spinneret body, and the third zone can be located at an end of the face of the spinneret body opposite to the end at which the second zone is located, wherein the three zones are disposed in a linear arrangement oriented perpendicular to the direction of the flow(s) of cooling gas (e.g., quenching air).
An even further embodiment of the apparatus of this invention can also include a spinneret having in addition to the first three zones described above a fourth zone containing a plurality of fourth rows, each of said fourth rows comprising a plurality of fourth capillaries, wherein the fourth capillaries are arranged in a fourth capillary density, and the fourth capillaries individually having a fourth cross-sectional shape, a fourth hydraulic diameter, a fourth length, and a fourth length to hydraulic diameter ratio, and a fifth zone comprising a plurality of fifth rows, each of said fifth rows having a plurality of fifth capillaries, wherein the fifth capillaries are arranged in a fifth capillary density, and the fifth capillaries individually having a fifth cross-sectional shape, a fifth hydraulic diameter, a fifth length, and a fifth length to hydraulic diameter ratio, wherein the first zone is located between the fourth and fifth zones. In this even further embodiment of the apparatus of the present invention, the fourth cross-sectional shape of each of the fourth capillaries and the fifth cross-sectional shape of each of the fifth capillaries are the same as the first cross-sectional shape of each of the first capillaries and the second cross-sectional shape of each of the second capillaries and the third cross-sectional shape of each of the third capillaries, wherein the fourth hydraulic diameter of each of the fourth capillaries and the fifth hydraulic diameter of each of the fifth capillaries are less than the second hydraulic diameter of each of the second capillaries and are less than the third hydraulic diameter of each of the third capillaries; and wherein the first hydraulic diameter of each of the first capillaries is less than the fourth hydraulic diameter of each of the fourth capillaries, and the first hydraulic diameter of each of the first capillaries is less than the fifth hydraulic diameter of each of the fifth capillaries; and wherein the fourth length of each of the fourth capillaries and the fifth length of each of the fifth capillaries are less than the second length of each of the second capillaries and the third length of each of the third capillaries; and wherein the first length of each of the first capillaries is less than the fourth length of each of the fourth capillaries, and the first length of each of the first capillaries is less than the fifth length of each of the fifth capillaries.
An apparatus in an additional embodiment of this invention can also have a spinneret having at least seven zones, wherein, in addition to the above indicated five zones, sixth and seventh zones also can be included. In this additional embodiment of the apparatus, the sixth zone includes a plurality of sixth rows, each of said sixth rows having a plurality of sixth capillaries, wherein the sixth capillaries are arranged in a sixth capillary density, and the sixth capillaries individually having a sixth cross-sectional shape, a sixth hydraulic diameter, a sixth length, and a sixth length to hydraulic diameter ratio, and wherein the seventh zone has a plurality of seventh rows, each of said seventh rows comprising a plurality of seventh capillaries, wherein the seventh capillaries are arranged in a seventh capillary density and the seventh capillaries individually having a seventh cross-sectional shape, a seventh hydraulic diameter, a seventh length, and a seventh length to hydraulic diameter ratio; and wherein the first, fourth, and fifth zones are located between the sixth and seventh zones, and wherein the sixth cross-sectional shape of each of the sixth capillaries and the seventh cross-sectional shape of each of the seventh capillaries are the same as the first cross-sectional shape of each of the first capillaries, the second cross-sectional shape of each of the second capillaries, the third cross-sectional shape of each of the third capillaries, the fourth cross-sectional shape of each of the fourth capillaries, and the fifth cross-sectional shape of each of the fifth capillaries; and wherein the sixth hydraulic diameter of each of the sixth capillaries and the seventh hydraulic diameter of each of the seventh capillaries are less than the second hydraulic diameter of each of the second capillaries and the third hydraulic diameter of each of the third capillaries, and wherein the fourth hydraulic diameter of each of the fourth capillaries and the fifth hydraulic diameter of each of the fifth capillaries are less than the sixth hydraulic diameter of each of the sixth capillaries and less than the seventh hydraulic diameter of each of the seventh capillaries; and wherein the sixth length of each of the sixth capillaries and the seventh length of each of the seventh capillaries are less than the second length of each of the second capillaries and the third length of each of the third capillaries, and wherein the fourth length of each of the fourth capillaries and the fifth length of each of the fifth capillaries are less than the sixth length of each of the sixth capillaries and are less than the seventh length of each of the seventh capillaries.
The apparatus of this invention can also have a spinneret having the above described first capillary density, the fourth capillary density, the fifth capillary density, the sixth capillary density, and the seventh capillary density be the same. The apparatus of this invention can also have a spinneret having the above described fourth length to hydraulic diameter ratio of each of the fourth capillaries and the fifth length to hydraulic diameter ratio of each of the fifth capillaries be less than the sixth length to hydraulic diameter ratio of each of the sixth capillaries and the seventh length to hydraulic diameter ratio of each of the seventh capillaries.
In another embodiment of the present invention, an apparatus for producing a melt-spun nonwoven web includes: a) a polymer supply system; b) a filament collection surface; c) a spinneret located above the collection surface for extruding polymer received from the polymer supply system for producing extruded filaments that move downward along a path toward the collection surface; d) at least one quench gas supply device for supplying at least one stream of cooling gas; and e) a cooling region below the spinneret in which the at least one stream of cooling gas is directed to flow beneath the spinneret and across extruded filaments along the path toward the collection surface. In this embodiment, the spinneret includes: a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body. In this embodiment, the plurality of different zones comprises: a first zone located centrally at the face of the spinneret body, comprising a plurality of first rows, each of said first rows comprising a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio; a second zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of second rows, each of said second rows comprising a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio; and a third zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of third rows, each of said third rows comprising a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density and the third capillaries individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio. In this embodiment, the first zone is located between the second and third zones, wherein the third hydraulic diameter of each of the third capillaries is less than the first hydraulic diameter of each of the first capillaries, the first hydraulic diameter of each of the first capillaries is less than the second hydraulic diameter of each of the second capillaries, the third length of each of the third capillaries is less than the first length of each of the first capillaries, the first length of each of the first capillaries is less than the second length of each of the second capillaries, the third length to hydraulic diameter ratio of each of the third capillaries is less than the first length to hydraulic diameter ratio of each of the first capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the second length to hydraulic diameter ratio of each of the second capillaries.
As another embodiment, a process for melt-spinning polymeric filaments is provided which includes steps of extruding molten polymer through an indicated spinneret to produce filaments extruded below the spinneret; passing the extruded filaments through a quench zone below the spinneret, wherein said filaments are quenched by directing a flow of at least one stream of cooling gas beneath the spinneret and across the extruded filaments; and collecting the filaments after the quenching thereof.
In an embodiment of the invention, a process for melt-spinning polymeric filaments, includes: a) extruding molten polymer through a spinneret to produce filaments extruded below the spinneret; b) passing the extruded filaments through a quench region below the spinneret, wherein said filaments are quenched by directing at least one stream of cooling gas beneath the spinneret and across the extruded filaments; and c) collecting the quenched filaments. In this embodiment of a process of the invention, the spinneret includes: a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body, wherein the plurality of different zones comprises: a first zone located centrally at the face of the spinneret body, comprising a plurality of first rows, each of said first rows comprising a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio, a second zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of second rows, each of said second rows comprising a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio, a third zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of third rows, each of said third rows comprising a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density and the third capillaries individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio; wherein the first zone is located between the second and third zones, and the first zone is closer to a center of the face of the spinneret body than the second and third zones, wherein the overall length to hydraulic diameter ratio is at least 3 percent. In another embodiment of this process, the overall length to hydraulic ratio is at least 5 percent. In another embodiment of this process, the spinneret body has a plurality of zone-to-zone length to hydraulic diameter ratios, and wherein at least one of the zone-to-zone length to hydraulic diameter ratios is at least 2%. In another embodiment of this process, the passing of the extruded filaments through the quench region below the spinneret comprises quenching the filaments by directing the at least one stream of cooling gas in cross-flowing directions beneath the spinneret and across the extruded filaments. In another preferred embodiment of this process, the sum of the capillaries that open at a face of the spinneret body is at least 3000. In another preferred embodiment of this process, the face of the spinneret body is polygonal, such as rectangular or trapezoidal.
A process of this invention can also include a spinneret having at least five zones, wherein fourth and fifth zones are added to the first three zones as described above. In this embodiment of the process of the invention, the fourth zone comprises a plurality of fourth rows, each of said fourth rows comprising a plurality of fourth capillaries, wherein the fourth capillaries are arranged in a fourth capillary density, and the fourth capillaries individually having a fourth cross-sectional shape, a fourth hydraulic diameter, a fourth length, and a fourth length to hydraulic diameter ratio, and the fifth zone comprises a plurality of fifth rows, each of said fifth rows comprising a plurality of fifth capillaries, wherein the fifth capillaries are arranged in a fifth capillary density and the fifth capillaries individually having a fifth cross-sectional shape, a fifth hydraulic diameter, a fifth length, and a fifth length to hydraulic diameter ratio; wherein the first zone is located between the fourth and fifth zones, and wherein the fourth hydraulic diameter of each of the fourth capillaries and the fifth hydraulic diameter of each of the fifth capillaries are less than the second hydraulic diameter of each of the second capillaries and are less than the third hydraulic diameter of each of the third capillaries; and the first hydraulic diameter of each of the first capillaries is less than the fourth hydraulic diameter of each of the fourth capillaries, and the first hydraulic diameter of each of the first capillaries is less than the fifth hydraulic diameter of each of the fifth capillaries; and wherein the fourth length of each of the fourth capillaries and the fifth length of each of the fifth capillaries are less than the second length of each of the second capillaries and the third length of each of the third capillaries; and the first length of each of the first capillaries is less than the fourth length of each of the fourth capillaries, and the first length of each of the first capillaries is less than the fifth length of each of the fifth capillaries. In another embodiment of the process of this invention, the spinneret can have the first cross-sectional shape of each of the first capillaries, the second cross-sectional shape of each of the second capillaries, and the third cross-sectional shape of each of the third capillaries all be circular or all oval, and wherein the extruded filaments from each of said first capillaries, second capillaries, and third capillaries have cross-sectional shapes that correspond to each of said capillaries.
In an embodiment of the invention, a process for melt-spinning polymeric filaments, includes: a) extruding molten polymer through a spinneret to produce filaments extruded below the spinneret; b) passing the extruded filaments through a quench region below the spinneret, wherein said filaments are quenched by directing at least one stream of cooling gas in one direction free of opposite flowing cooling gas beneath the spinneret and across the extruded filaments; and c) collecting the quenched filaments. In this embodiment of a process of the invention, the spinneret includes: a spinneret body having an overall length to hydraulic diameter ratio and defining orifices extending through the spinneret body, wherein the orifices comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom, wherein the capillaries are arranged in a plurality of different rows at the face of the spinneret body, and wherein the plurality of different rows are arranged into a plurality of different zones at the face of the spinneret body, wherein the plurality of different zones comprises: a first zone located centrally at the face of the spinneret body, comprising a plurality of first rows, each of said first rows comprising a plurality of first capillaries, wherein the first capillaries are arranged in a first capillary density, and the first capillaries individually having a first cross-sectional shape, a first hydraulic diameter, a first length, and a first length to hydraulic diameter ratio, a second zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of second rows, each of said second rows comprising a plurality of second capillaries, wherein the second capillaries are arranged in a second capillary density, and the second capillaries individually having a second cross-sectional shape, a second hydraulic diameter, a second length, and a second length to hydraulic diameter ratio, a third zone located adjacent to the first zone at the face of the spinneret body, comprising a plurality of third rows, each of said third rows comprising a plurality of third capillaries, wherein the third capillaries are arranged in a third capillary density and the third capillaries individually having a third cross-sectional shape, a third hydraulic diameter, a third length, and a third length to hydraulic diameter ratio; wherein the first zone is located between the second and third zones, wherein the third hydraulic diameter of each of the third capillaries is less than the first hydraulic diameter of each of the first capillaries, the first hydraulic diameter of each of the first capillaries is less than the second hydraulic diameter of each of the second capillaries, the third length of each of the third capillaries is less than the first length of each of the first capillaries, the first length of each of the first capillaries is less than the second length of each of the second capillaries, the third length to hydraulic diameter ratio of each of the third capillaries is less than the first length to hydraulic diameter ratio of each of the first capillaries, and the first length to hydraulic diameter ratio of each of the first capillaries is less than the second length to hydraulic diameter ratio of each of the second capillaries.
In another embodiment the process of this invention may include the filaments being extruded from the spinneret at commercially useful throughputs and fiber uniformities.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide a further explanation of the present invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate some of the embodiments of the present invention and together with the description, serve to explain the principles of the present invention. Features having the same referencing numeral in the various figures represent similar elements unless indicated otherwise. The figures and features depicted therein are not necessarily drawn to scale.
As used herein, the term “filament(s)” refers to a continuous polymer strand that is not intentionally broken during the regular course of formation.
As used herein, the term “fiber(s)” refers to filaments, substantially continuous filaments, staple fibers, discontinuous fibers, and other fibrous structures having a fiber length that is substantially greater than its cross-sectional dimension(s).
As used herein, the terms “nonwoven(s)” or “nonwoven web(s)” refer to randomly oriented filament-containing material(s) that are formed without the aid of a textile weaving, sewing, or knitting process.
As used herein, the terms “nonwoven fabric” or “nonwoven component(s)” may be used interchangeably and refer to a collection of one or more nonwoven webs in a close association to form one or more layers, as defined herein. The one or more layers of the nonwoven fabric or nonwoven component along with the one or more nonwoven webs can include staple length fibers, substantially continuous or discontinuous fibers, and combinations or mixtures thereof, unless specified otherwise. The one or more layers of the nonwoven fabric or nonwoven component can be stabilized or unstabilized.
The term “spunbond” or “S” refers to filaments which are formed by extruding a molten material from a plurality of capillaries in a spinneret body. The term “spunbond” also includes filaments that are formed as defined above, and which are then deposited on a collection surface or otherwise formed in a layer in a single step. Fabric structures encompassed by the invention also can include spunbond-spunbond (SS), spunbond-spunbond-spunbond (SSS), as well as other combinations and variations of layers.
As used herein, “meltspun” or “melt-spun” generally refers to fiber forming processes of spunbonding or melt-blowing.
As used herein, “substantially the same,” as used with respect to a dimension of spinneret capillaries or orifices refers to differences in such dimension of less than machining tolerances.
As used herein, “comprising” or “comprises” is synonymous with “including,” “containing,” “having”, or “characterized by,” and is open-ended and does not exclude additional, unrecited elements or method steps, and thus should be interpreted to mean “including, but not limited to . . . ”.
As used herein, “consisting of” excludes any element, step, or ingredient not specified.
As used herein, “consisting essentially of”, refers to the specified materials, spinneret, apparatus, or steps and those additional items that do not materially affect the basic and novel characteristic(s) of the spinneret, apparatus, methods, or nonwoven fabrics of the invention as described herein.
As used herein, “spinneret body(ies)” is typically one or more metal plates that comprises orifices, and these orifices comprising capillaries through which polymer is extruded to form filaments or other fibers. The spinneret body also may be an assembly of metal plate elements each having orifices that can form part of an overall pattern of orifices. A spinneret body can be, for example, a single-piece construction having an overall pattern of orifices or, alternatively may be assembled in modular fashion from a plurality of metal plate elements which as assembled together provide a body having an overall pattern of orifices.
As used herein, a “spinneret” is a structure which includes a spinneret body having a number of small through-holes through which a fiber-forming polymer fluid is forced to form filaments or other fibers, and typically but not necessarily includes additional components used therewith, such as an overlying breaker plate for providing more uniform polymer feed distribution to the spinneret body, a filter layer or layers for filtering the polymer prior to its entering the breaker plate and/or spinneret body, or combinations thereof.
As used herein, “capillary(ies)” refers to the small through-holes from which polymer exits the spinneret body to form the fiber. Capillaries have a length, a cross-sectional shape, hydraulic diameter, and length to hydraulic diameter ratio. While not mandatory in the present invention, in general the hydraulic diameter and cross-sectional shape are substantially uniform along the length of a capillary.
As used herein, “capillary density” refers to the number of capillaries on a linear width basis at the face of the spinneret body or in a square area from the working area at the face of the spinneret body.
As used herein, “capillary length” or “length” refers to the length of the capillary through the spinneret body to a capillary opening at the face of the spinneret.
As used herein, the term “capillary cross-sectional area” or “CA” is a measurement of the exit area of the cross-sectional shape of one or more capillaries at the face of the spinneret body of the spinneret as described herein.
As used herein, “capillary perimeter” or “perimeter” or “CP” is the distance along the periphery defined by the exit geometry of the capillary at the face of the spinneret body surface. For a capillary having a circular cross-sectional shape, the perimeter is defined as the circumference of the capillary.
As used herein, “hydraulic diameter” or “DH” is calculated by the formula:
D
H=4RH
wherein RH represent hydraulic radius. Hydraulic radius (RH) is calculated from the ratio: CA/CP, wherein CA is the capillary cross-sectional area of the capillary opening at the polymer exit at the face of the spinneret body of spinnerets of the present invention, and CP is the capillary perimeter of the same capillary opening. For calculating the hydraulic diameter of a capillary having a circular cross-sectional shape and a diameter “D” thereof, for example, use of the indicated formula for hydraulic diameter provides: DH=4*(πD2/4)/(πD), which reduces to D, which refers to a measurement of the longest dimension from one side of the circular cross-sectional shape or area to the other. The CA and CP values can be determined for the capillary openings at the polymer exit at the face of the spinneret body in spinnerets of the present invention, such as by capturing a digital image of a representative opening of a zone of capillaries, such as by Scanning Electron Microscope (SEM) or optical microscope which can include a calibration scale on the viewer and/or digital images generated therewith. One knowledgeable in the art will select a method to measure the capillary perimeter and cross-sectional area that is appropriate to the shape of the opening at the polymer exit at the face of the spinneret body in spinnerets of the present invention. These methods are typically based on studying the capillary opening at the polymer exit at the face of the spinneret body using a microscope and more typically an optical microscope. For example, for simple geometric shapes such as a circle, square, rectangle or triangle, one can use an optical microscope in combination with a calibration standard (e.g., optical grid calibration slide 03A00429 Stage Mic 1MM/0.01 DIV from Pyser-SGI Limited, Kent UK) to measure the variables used to calculate either the perimeter or cross-sectional area. For more complex cross-sectional shapes, such are multi-lobal, an example of a method is to use a microscope capable of capturing the image of the polymer exit of the capillary opening at the face of the spinneret body digitally, and using software to analyze the image to calculate the perimeter and cross-sectional area of the exit at the face of the spinneret body. For example, a microscope such as the Digital Microscope KH-7700 from Hirox Company, Ltd 2-15-17 Koenji Minami, Suginami-ku, Tokyo 155-0003 Japan, which is supplied with a proprietary software that can be used to analyze the digital image recorded by the microscope. More precisely, one could use the length and area measurement methodologies described in Chapter 3, pages 117 to 132 of the operation manual for this microscope, 1st edition with a revision date of October 2006 to calculate the perimeter and/or cross-sectional area of the capillary opening at the polymer exit at the face of the spinneret body. The cross-sectional area and perimeter dimensions of the capillary opening shape can be determined with use of any of calculations with known rules of geometry, or determinations using known or commercially available software algorithms applicable to evaluating digital or photographic images of cross-sectional shapes, or manual determinations. As manual determinations, a weight method can be used, which may be useful for very complex shapes, where a digital image or photograph of the opening shape can be provided at a known enlarged scale relative to the actual capillary shape on a discrete regular shaped piece of paper or the like of known overall dimensions (such as a square, rectangle, or circle). Then, the image of the opening shape can be cut out from the paper, and the weight proportion of the separated opening shape relative to overall weight of the original digital imaged piece of paper can be considered to yield the same ratio value as the cross-sectional area of the opening shape to the cross-sectional area of the piece of paper. The cross-sectional area of the opening shape in the enlarged digital image on the piece of paper can be readily calculated from these ratios, and then the cross-sectional area of the actual capillary shape can be calculated from that value by scaling it down based on the indicated known enlargement scale used in the digital image on the piece of paper. The peripheral length of the shape, such as a simple or complex shape, also may be determined by manually measuring the perimeter of the shape in the enlarged image by tracing it with a filament or the like of measurable length, and scaling the result back for the actual capillary shape based on the known enlargement scale used for the digital image.
As used herein, “capillary length to capillary hydraulic diameter ratio” or “length to hydraulic diameter ratio” refers to the numerical result of dividing a capillary length by a capillary hydraulic diameter.
As used herein, the “overall length to hydraulic diameter ratio” is calculated from the formula:
100×[(L/DH)G−(L/DH)S]/(L/DH)G
wherein (L/DH)G is the greatest value of capillary length to hydraulic diameter ratio for all the capillary zones of a spinneret body, and (L/DH)S is the smallest value of capillary length to hydraulic diameter ratio for all the capillary zones at the face of a spinneret body. The result is expressed as a percentage value.
As used herein, the “zone-to-zone length to hydraulic diameter ratio(s)” is calculated from the formula:
100×[(L/DH)zG−(L/DH)zs]/(L/DH)zG
wherein (L/DH)ZG is the greater value of capillary length to hydraulic diameter ratio for one of a pair of adjacent capillary zones at the face of a spinneret body, and (L/DH)zs is the smaller value of capillary length to hydraulic diameter ratio of the other capillary zone. The result is expressed as a percentage value.
As used herein, “capillary dimension(s)” or “dimension(s)” refers to one or more of the capillary length, capillary cross-sectional shape, capillary hydraulic diameter, capillary cross-sectional area, capillary perimeter, or capillary length to hydraulic diameter ratio.
The terms “cooling” and “quench(ing)” when referencing a fluid, such as a gas, are used interchangeably herein and refer to the function and temperature of the gas used to solidify the molten polymer exiting from capillaries at the face of the spinneret body of spinnerets of the present invention.
The present invention is directed to a spinneret that can be used for the production of melt-spun filaments. The spinneret has zones each with different capillary designs. The zones can differ from each other based on capillary density, capillary dimensions, or both. The capillary dimensions that can differ can be, for example, capillary polymer exit opening: hydraulic diameter, cross-sectional area, perimeter, length, cross-sectional shape, and the length to hydraulic diameter ratio. The design of each different zone at the face of the spinneret body can be selected to allow an increase in the overall number of capillaries, therefore potentially allowing for higher polymer throughput for the entire spinneret and/or improved filament uniformity, which facilitates improved nonwoven web and fabric uniformity while maintaining a stable process. The design of each different zone at the face of the spinneret body can also be selected to allow for an improvement in filament denier uniformity at higher polymer throughputs without increasing the capillary density. Other benefits of the multi-zone spinneret of the invention may include more uniform polymer flow rates through the capillaries across the face of the spinneret body, minimization of variation in polymer throughput per capillary, and minimization of variation in filament denier among capillaries in various zones at the face of the spinneret body. The quenching of the filaments can be made more uniform across the face of the spinneret body by using the spinnerets of this invention. It is also believed that variation in the “quench distance to spinneret body face” for each filament, which is the distance from the face of the spinneret body to the location on each filament at which the surface of the filament becomes solid (also known as the “frost line”) may be minimized by use of spinnerets of the present invention. The principles of spinneret design of the present invention indicated herein can be used to provide spinnerets useful for different quench modalities, such as cross-flow or dual side quenching of filaments or single side quenching of filaments produced by the spinnerets.
Embodiments of spinnerets of the present invention can be operable with higher polymer throughputs than a comparable spinneret made with only one type of capillary design and uniform capillary dimensions across the face of the spinneret body, while maintaining similar or achieving better filament, nonwoven web, and nonwoven fabric uniformity. This design can allow drawing of more of the filaments to achieve a lower average fiber denier than feasible with a standard spinneret having only a single capillary design while still maintaining a stable spinning process.
Based at least in part on results of experimental studies conducted and described in the examples herein, the present investigators believe that a predominant cause for the filament breaks and nonwoven web and fabric hard spot defects observed when operating such single capillary design and dimension spinnerets at high polymer throughputs can be significant variability in cooling of the filaments across the face of the spinneret body. More precisely, it is thought that the filaments extruded furthest away from the quench gas discharge outlet (e.g., in the center rows of capillaries of a spinneret body that has a single capillary design and receives quench air from two opposite sides) are being cooled less efficiently by the quench gas (e.g., air) than those filaments extruded from rows of capillaries that are located closer to the quench gas discharge outlet (e.g., closer to the edges of the spinneret body where the quench air penetrates the filament bundle), and those filaments that are further away from the quench gas discharge outlet to be contacted by quench gas having risen in temperature, causing the solidification point for the surface of those filaments to occur further away from the spinneret body face than for filaments extruded closer to the quench gas discharge outlet. For example, filaments extruded from the center rows of a spinneret used in a cross-flow or dual quench configuration (i.e., further away from the quench gas discharge outlet), have more opportunities to come in contact with each other when still molten or tacky causing breakage or touching of each other and producing a disturbance that can result in hard spot defects in the nonwoven web or nonwoven fabric. It is also believed that the filaments from these center rows may have a lower denier than those filaments extruded from the capillaries closer to the quench gas discharge outlet because of their lower frost line, allowing them to be drawn (i.e., attenuated) more. A similar problem can occur in single-sided quench configurations or modalities wherein filaments extruded furthest away from the quench gas discharge outlet (e.g., in the rows of capillaries that have a single capillary design that are located on the side of the spinneret body opposite to the side closest to the quench gas discharge outlet or quench source in single side quench modalities) can be cooled less efficiently by the quench gas than those filaments extruded from rows of capillaries that are located closer to the quench gas discharge outlet (e.g., closer to the edge of the spinneret body where the quench air initially penetrates the filament bundle).
A way to deal with the frost line variation among filaments that are closer and further away from the quench gas discharge outlet in spinneret bodies used in cross-flow quench configurations has been to leave a strip free of capillaries in the middle of the single capillary design spinneret, which, however, would reduce polymer throughput and require the collection surface to be slowed to provide a fabric with the same collected basis weight. A multi-zone spinneret of this invention can reduce or eliminate these drawbacks of the single capillary design spinneret to allow higher overall polymer throughput through the spinneret and more uniform nonwoven web and nonwoven fabric formation, while minimizing filament breaks and nonwoven web and nonwoven fabric hard spot defects.
The multi-zone spinnerets of the present invention can achieve this goal by combining several elements, which are illustrated herein with reference to the accompanying drawings. The spinneret body of the spinneret of the invention defines orifices extending through the spinneret body that comprise capillaries that open at a face of the spinneret body for polymer filament extrusion therefrom. The capillaries are arranged in a plurality of different rows, which are arranged in a plurality of zones at the face of the spinneret body. These capillaries have a distinct length, a distinct cross-sectional shape, a distinct cross-sectional area, a distinct perimeter, and a distinct hydraulic diameter calculated using the cross-sectional area and perimeter, at their exit or opening at the face of the spinneret body. The capillary length extends from the capillary opening at the bottom face of the spinneret body to an opposite capillary end thereof, such as where the capillary may merge structurally and fluidly with a larger hole portion of the orifice that extends from the opposite top face of the same spinneret body. The spinnerets of the invention have a plurality of zones of capillaries that can differ, for example, based on the overall length to hydraulic diameter ratio, the zone-to-zone length to hydraulic diameter ratios, the density of capillaries, the hydraulic diameter of the capillaries, the lengths of the capillaries, the cross-sectional shape of the capillaries, or any combinations thereof.
In one embodiment, the spinneret body of the spinneret has an overall length to hydraulic ratio of at least 3 percent (i.e., 3% or greater up to 100%), or at least 4 percent, or at least 5 percent, or at least 10 percent, or at least 15 percent, or at least 20 percent, or at least 25 percent, or at least 50 percent, or at least 75 percent, or 100 percent, or from 3 to 100 percent, or from 4 to 75 percent, or from 5 to 50 percent, or from 10 to 25 percent, or any other values between 3 and 100 percent.
In another embodiment, the spinneret body has a plurality of zone-to-zone length to hydraulic diameter ratios, and wherein at least one of the zone-to-zone length to hydraulic diameter ratios is at least 2 percent (i.e., 2% or greater up to 100%), or at least 3 percent, or at least 4 percent, or at least 5 percent, or at least 10 percent, or at least 15 percent, or at least 20 percent, or at least 25 percent, or at least 50 percent, or at least 75 percent, or 100 percent, or from 2 to 100 percent, or from 3 to 75 percent, or from 4 to 50 percent, or from 5 to 25 percent, or any other values between 2 and 100 percent.
As another option, the inventive spinneret can be divided into zones that are differentiated from each other by their capillary hydraulic diameter and capillary length. For example, the capillary hydraulic diameter and capillary length can be smaller in zones of capillaries that are located on the face of the spinneret body further away from the quench gas discharge outlet as compared to different zones of capillaries located relatively closer to the quench gas discharge outlet. As another option, the inventive spinneret can be divided into zones that are differentiated from each other by their capillary hydraulic diameter, length, and length to hydraulic diameter ratio. For example, the capillary hydraulic diameter, length, and length to hydraulic diameter ratio can be smaller in zones of capillaries that are located on the face of the spinneret body further away from the quench gas source (e.g., discharge outlet) when compared to different zones of capillaries located relatively closer to the quench gas source. As another option, the inventive spinneret can be divided into zones that are differentiated from each other by any combination of these features or any combination of capillary dimensions. Further, the capillary hydraulic diameter, the capillary length, or both, can be reduced in the zone(s) of capillaries closer to the geometric center at the face of the spinneret body, assuming the geometric center is further away from the quench gas discharge outlet than those zone(s) that are closer to the quench gas discharge outlet.
The difference in any one or more capillary dimensions (excluding cross-sectional shape) provided between the capillaries of adjacent zones, for example, can be at least greater than machining tolerances in making the capillaries, and specifically may be different from each other by at least 2% different, or at least about 2.5%, or at least 3%, or at least 4%, or at least 5%, or at least 6%, or at least 7%, or at least 8%, or at least 9%, or at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 35% different, or at least 40%, or any ranges based on any two different ones of these nonzero values (e.g., about 2% to about 30%), or other values. Similar values as these can apply to differences in capillary length to hydraulic diameter ratios provided between the capillaries of different zones and used to calculate the overall length to hydraulic diameter ratio and the various zone-to-zone length to hydraulic diameter ratios for zones at the face of the spinneret body. The difference in capillary length provided between the capillaries of adjacent zones, for example, can be at least greater than machining tolerances in making the capillaries, and specifically may be different from each other by at least 2% different, or at least 2.5%, or at least 3%, or at least 4%, or at least 5%, or at least 6%, or at least 7%, or at least 8%, or at least 9%, or at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least about 35%, or at least 40%, or any ranges based on any two different ones of these nonzero values (e.g., about 2% to about 35%), or other values. All of these percentage differences can be calculated by dividing the absolute positive value of the numerical difference of the two numbers by the larger number of the two, and multiplying the resulting value by 100.
As another option, the inventive spinneret can be divided into zones that are differentiated from each other by their capillary density. For example, at least one zone of capillaries can be located centrally between two other zones of capillaries located at opposite ends of the spinneret body wherein the three zones are disposed in a linear arrangement oriented perpendicular to the direction of the flow of cooling gas (e.g., quenching air), wherein the centrally located zone or zones of capillaries have a greater capillary density than each of the outer (i.e., less centrally located) zones of capillaries. The indicated difference in capillary densities that can be provided, such as between the indicated central zone and outer zones of capillaries wherein the three zones are disposed in a linear arrangement oriented perpendicular to the direction of the flow of cooling gas (e.g., quenching air), can be at least greater than machining tolerances in making the capillaries, and, for example, can be different from each other by at least 1% different, or at least about 2%, or at least 3%, or at least 4%, or at least 5%, or at least 6%, or at least 7%, or at least 8%, or at least 9%, or at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 35%, or any ranges based on any two different ones of these nonzero values (e.g., about 1% to about 30%), or other values. These capillary density values can be based on spinneret body width.
The inventive spinneret also can contain more capillaries without proportionally increasing the open area at the face of the spinneret body, and the open area can also be reduced without sacrificing polymer throughput. When compared to the indicated single capillary design spinneret, this can be, for example, about up to a 20% to about 25% increase in number of capillaries at the face of the spinneret body with about an open face of the spinneret body area that can be reduced up to 5% or up to 7%, or other improved values thereof.
With reference to
The cross-sectional shapes of the indicated capillaries shown in
In an embodiment, the capillary density 161 of the first or central zone 111 can be greater than each of the capillary densities 162 and 163 of the end (or outer) zones 121 and 122. In addition to location of a zone of capillaries with respect to the cooling gas source (e.g., quench air discharge outlet), location of a zone with respect to a wall or other cooling gas flow obstruction may dictate capillary density differences between zones. For example, capillary density 161 may be not substantially the same as capillary density 162 and capillary density 163, because capillary density 162 and capillary density 163 may be closer to a wall (not shown) located at the outer edge(s) of the spinneret body. As walls have the potential to disrupt cooling gas flow which may cause more turbulence and likelihood of filament contact while in the molten state, the capillary density 162 and capillary density 163 at the edges of the face of the spinneret body may be less than the capillary density 161 even though zones 111, 121, and 122 are all closer to the quench air discharge outlet (not shown) but the air flow from which is indicated by general directions 171A and 171B. In embodiments, the capillary densities 162 and 163 of the end zones 121 and 122 can be the same or different from each other. In an embodiment, they are the same. As indicated, the capillary densities described herein can be expressed based on a linear width basis of the spinneret body or based on square area of the face of the spinneret body. The linear width direction co of the spinneret body 101 is indicated in
As shown in more detail in
As shown in
The cross-sectional shapes of the indicated capillaries shown in
Arrows are included in
With respect to the dimensions of the capillaries of spinneret body 301, the orifices 203 and first capillaries 231 of zone 211 of spinneret body 201 shown in
As shown in more detail in
Referring again to the spinneret shown in
The sum of the capillary openings per meter width at a face of the spinneret body can be, for example, at least 3000, or at least 4000, or at least 5000, or at least 6000, or at least 6500, or at least 7000, or at least 7500, or at least 8000, or at least 9000, or at least 9500, or at least 10000, or other values. By increasing the overall number of capillaries per meter width of the spinneret body in a spinneret of the present invention as compared to a spinneret having a single design of capillary, for example, higher throughput can be allowed. More uniform quenching of the filaments also may be allowed, causing less variability in frost line distance from the spinneret body to the fiber collection surface. In that regard, the dimensions of the capillaries for each zone can be selected based on the features of hydraulic diameter, and length selected to maintain a uniform throughput (e.g., in grams per hour per meter, which is also referred to herein as “ghm” or “grams/hour/meter”) based on shear stress (Tcw). Generally, hydraulic diameter of the capillaries decreases going from the outer zones toward the inner zones at the face of the spinneret body to increase the exit filament speed and reduce the initial filament diameter as the zone is closer to the center of the spinneret body in a dual opposing cross-direction quench gas configuration as described herein. Based on experimental results such as described herein, it is believed that using smaller hydraulic diameter capillaries further away from the quench gas discharge outlet can improve the heat transfer from the filament, therefore compensating in part for any higher air temperature and lower air volume expected toward the middle of the spinneret body in a dual opposing cross-directional quench gas configuration. For cross-flow quench designs, for example, a spinneret with different zones having capillaries of different dimensions can be provided, for example, wherein the capillary length, the hydraulic diameter, and the capillary length to hydraulic diameter ratio of the capillaries is reduced progressively going from the outer zones facing the incoming streams of quench air that flow in opposite directions from the outer zones toward the inner and central zone(s). This reduction can be provided zone-to-zone in successive adjacent zones of the capillaries in the spinneret body for at least two zones, and in some embodiments in at least three, four, five, six, seven, or more zones. This can be done to improve quenching toward the middle of the face of the spinneret body and therefore can allow an increase in overall polymer throughput in ghm or improvement in fabric uniformity (e.g. more uniform fibers at equivalent polymer throughput). The capillary length and hydraulic diameter for the capillaries of different zones can be selected based on shear stress (Tcw) in order to produce even polymer throughput from one zone of capillaries to another one. For purposes herein shear stress is defined as Tcw=ΔPc DHc/4Lc. As pressure drop is assumed to be constant across the length of each capillary and across the face of the spinneret body and solving this equation for ΔP, then Tcwa Lca/DHa=Tcwb Lcb/DHb=Tcwc Lcc DHc, where Tcwx (e.g., Tcwa, Tcwb, Tcwc) is shear stress as obtained from the rheology curves for capillary X having a hydraulic diameter DHx (e.g., DHa, DHb, DHc), and where LCx (e.g., Lca, Lcb, Lcc) is the length of the capillary and ΔP is the pressure drop across the capillary. As the shear stress changes with capillary hydraulic diameter the capillary length can be adjusted to keep the expression (Tcwx*Lcx/DHx) constant among the different capillary designs. As an option, for circular cross-sectional shaped capillaries, the combination of length to hydraulic diameter ratio for the capillaries can be arranged such that the Tcwx*Lcx/DHx expression is kept constant or within ±35, or ±30, or ±25, or ±20%, or ±15, ±10%, ±5%, or ±3% or ±1%, of the same based on the indicated equation that can be used to design the capillary zones at the face of the in the spinneret body.
These principles also can be adapted to the design of capillaries and capillary zones at the face of the spinneret body of spinnerets of the present invention which can be used in single side quench gas modalities. For example, for single side quench gas modalities, a spinneret body having a face with different zones having capillaries of different dimensions can be provided, for example, wherein the capillary length, the hydraulic diameter, and the capillary length to hydraulic diameter ratio of the capillaries is reduced progressively going from the outer zone nearest the incoming quench gas discharge outlet toward the capillaries located closer to the opposite side of the spinneret body and further away from the quench gas source. This progressive reduction can be provided zone-to-zone in successive adjacent zones of the capillaries at the face of the spinneret body for at least two zones, and in some embodiments of the present invention in at least three, four, five, six, seven, or more zones.
It will be understood that the end zones 321 and 322 of the spinneret body 301 shown in
Spinneret and spinneret body polymer throughput in the invention can be provided for processing thermoplastic polymers, such as polyolefins, at values of at least about 15,000 grams per hour per meter width of the face of the spinneret body (i.e., “ghm”), or at least about 25,000 ghm, or at least about 50,000 ghm, or at least about 75,000 ghm, or at least about 100,000 ghm, or at least about 150,000 ghm, or at least about 200,000 ghm, or at least about 250,000 ghm, or at least about 300,000 ghm, or from about 15,000 to about 1,000,000 ghm, or from about 25,000 to about 800,000 ghm, or from about 50,000 to about 700,000 ghm, or from about 75,000 to about 700,000 ghm, or from about 100,000 to about 600,000 ghm, or from about 150,000 to about 500,000 ghm, or from about 150,000 to about 400,000 ghm, or from about 200,000 to about 350,000 ghm, or other values. The “width” associated with ghm is measured in the co direction of the face of the spinneret body such as shown in
It should also be noted that the strategy used to adjust the capillary length in function of the capillary hydraulic diameter assumes negligible effect from the entrance geometry to the capillary. However, if that entrance geometry is selected such as to have a non-negligible effect, it can be taken into consideration in the calculation and/or can be used in lieu or in part to compensate for the change in capillary hydraulic diameter. For example, the angle of the counterbore may affect the flow rate (e.g., a tighter angle might have the same effect as lengthening the capillary). In other words, generally, it is assumed that the hydraulic diameter is the same at the capillary opening entrance as at the capillary opening exit at the face of the spinneret body and for the length of the capillary therebetween. However, it is believed that for spinneret bodies of the invention that do not have capillaries having this uniform capillary diameter along its length, then this lack of uniformity can be taken into consideration in the design of the zones and capillaries therein at the face of the spinneret body.
The plurality of different rows 661, 662, 663, 664, and 665, are arranged into the indicated plurality of different zones 611, 621, 622, 631, and 632. The first zone 611 is located between the zones 621 and 622 in the direction a on the face 605 of the spinneret body 601 that is oriented orthogonally to the width direction co on the face of the spinneret body 601, and zones 621 and 622 are located between zones 631 and 632 in the direction a of the face 605 of the spinneret body 601. The first zone 611 is located closer to an imaginary geometric center 615 of the face 605 of the spinneret body 601 than the other zones 621, 622, 631, and 632. The first capillaries 651 of the first zone 611 individually have a first cross-sectional shape 671. The first rows 661 of the capillaries 651 of the first zone 611 are arranged in a first capillary density 681. The second capillaries 652 of the second zone 621 individually have a second cross-sectional shape 672. The rows 662 of the capillaries 652 of the zone 621 are arranged in a second capillary density 682. The third capillaries 653 of the third zone 622 individually have a third cross-sectional shape 673. The rows 663 of the capillaries 653 of the zone 622 are arranged in a third capillary density 683. The fourth capillaries 654 of the fourth zone 631 individually have a fourth cross-sectional shape 674. The rows 664 of the capillaries 654 of the zone 631 are arranged in a fourth capillary density 684. The fifth capillaries 655 of the fifth zone 632 individually have a fifth cross-sectional shape 675. The rows 665 of the capillaries 655 of the fifth zone 632 are arranged in a fifth capillary density 685. In an embodiment, the capillaries can be equispaced within a given row for all or substantially all of the rows. In an embodiment, the adjacent rows of capillaries can be equispaced for all or substantially all of the rows relative to the width direction co of spinneret body 601, or orthogonal direction a, or both.
The cross-sectional shapes of the indicated capillaries shown in
With respect to the dimensions of the orifices and capillaries of spinneret body 601, the orifices 203 and first capillaries 231 of zone 211 of spinneret body 201 shown in
The plurality of different rows 761, 762, and 764, are arranged into the indicated plurality of different zones 711, 721, and 731. The first zone 721 is located between zones 731 and 711 at the face 705 in the direction a of the face 705 of spinneret body 701 that is oriented orthogonally to the width direction co of the face 705 of spinneret body 701. The first zone 721 is located closer to the quench air source than third zone 711, and the second zone 731 is located closer to the quench air source than the first zone 721. The first capillaries 752 of the first zone 721 individually have a first cross-sectional shape 772. The rows 762 of the capillaries 752 of the zone 721 are arranged in a first capillary density 782. The second capillaries 754 of the second zone 731 individually have a second cross-sectional shape 774. The rows 764 of the capillaries 754 of the zone 731 are arranged in a second capillary density 784. The third capillaries 751 of the third zone 711 individually have a third cross-sectional shape 771. The third rows 761 of the capillaries 751 of the third zone 711 are arranged in a third capillary density 781. In an embodiment, the capillaries can be equispaced within a given row for all or substantially all of the rows. In an embodiment, the adjacent rows of capillaries can be equispaced for all or substantially all of the rows relative to the width direction co of the face 705 of spinneret body 701, or orthogonal direction a, or both.
The cross-sectional shapes of the indicated capillaries shown in
With respect to the dimensions of capillaries of spinneret body 701, the orifices 203 and first capillaries 231 of zone 211 of spinneret body 201 shown in
Although not desiring to be bound to theory, it is believed that the apparatus 800 using spinneret body 821 may allow provision of a frost line 818A that has a uniform or at least more uniform distance to the bottom face 820B of the spinneret body 821 in the indicated width direction (co direction) of the spinneret body 821 than comparison frost line 818B′ provided to represent a frost line where the spinneret includes only a single dimensional design of capillaries therein. The comparison frost line 818B extends downwardly or sags below the central area of the spinneret body 821, indicative of an uneven filament surface cooling and solidification through the bundle of extruded filaments 803A. The belt 814 can be used to carry away the web of attenuated filaments 803B to additional process stations or units, such as for at least one treatment among edge trimming (e.g., to remove the filaments extruded from any of the indicated zones A used in the spinneret), bonding, compressing, consolidating (e.g., hydraulic entangling, mechanical needling, stitching), convective or radiation heat welding, laminating, or other treatments that can be applied to nonwoven webs to make nonwoven fabrics. For example, filaments formed in this manner can be collected on a screen (“wire”) or porous forming belt to form the web, and then the web may be further processed, for example, by passing the web through compression rolls and then between heated calendar rolls where the raised lands on one roll bond the web at points thereof to form a bonded nonwoven fabric. Some properties of the deposited and collected web 802, such as basis weight, can be controlled or further controlled by factors such as, but not limited to, one or more of spinning speed, mass throughput, temperature, polymer composition, or attenuating conditions. The general operation of such a meltspun forming apparatus which has been adapted to include a multi-zone spinneret as described herein can be within the ability of those of ordinary skill in the art in view of the descriptions and examples provided herein.
Suitable polymers to be used as the meltspun material in melt-spinning filaments can include any natural or synthetic polymer that is suitable for forming spunbond fibers such as polyolefin, polyester, polyamide, polyimide, polylactic acid, polyhydroxyalkanoate, polyvinyl alcohol, polyacrylates, viscose rayon, lyocell, regenerated cellulose, or any copolymers or combinations thereof. As a preferred option, the polymer is a thermoplastic polymer. As used herein, the term “polyolefin” includes polypropylene, polyethylene, polybutylene, and co-polymers and combinations thereof. As used herein, the term “polypropylene” includes all thermoplastic polymers where at least 50% by weight of the building blocks used are propylene monomers. Polypropylene polymers also include homopolymer polypropylenes in their isotactic, syndiotactic or atactic forms, polypropylene copolymers, polypropylene terpolymers, and other polymers comprising a combination of propylene monomers and other monomers. As an option, polypropylenes, such as isotactic homopolymer polypropylenes made with Ziegler-Natta, single site or metallocene catalyst system, may be used as the polymer. Polypropylene, for example, may be used which has a melt flow rate (MFR) of from about 5 g/10 min. to about 400 g/10 min. or preferably from 15 to 45 g/10 min., or other values. With respect to polypropylene, MFR refers to the results achieved by testing the polymer composition by the standard test method ASTM D1238 performed at a temperature of 230° C. and with a weight of 2.16 kg. Optionally, other processing aids or performance ingredients or additives can be incorporated into the polymer or polymer resin compositions. Optional additives for the polymer or polymer resin can include, for example, pigments, viscosity modifiers, aromatics, antimicrobials, fire retardants, thermochromics, fluoro-chemistries, softness additives, and any combinations thereof. The optional additives can further be used to modify the processability and/or to modify physical properties of the nonwoven web or fabric or an article incorporating such web or fabric.
Nonwoven fabrics and webs made with the spinnerets and apparatus of the present invention can be used singly or in combination with similar or different materials. For example, the nonwoven webs made using the spinnerets and/or apparatus of the present invention can be combined with other materials such as compositionally different spunbond webs (S) or with different types of webs, such as but not limited to, meltblown webs (M), such as S, SS, SSS, SMS, SMMS, or other combinations thereof. One or more of the nonwoven webs or fabrics also can be combined with film materials. Suitable films in this respect can include, for example, cast films and extruded films and can further be selected from microporous films, monolithic films, and reticulated films. The multi-layer materials, if provided, can be consolidated or unified in known manners. The nonwoven webs and fabrics also can be used in a variety of articles that perform at least one function. For example, the nonwoven webs can be used alone or as a component or components of apparel, hygiene, home furnishings, health care, engineering, industrial, and consumer goods, or other articles. Articles can include, but are not limited to, surgical gowns, drapes, scrubs, face masks, caps, shoe covers, diapers, wipes, bandages, filters, geotextiles, bags, covers, wrappings, disposable clothing, acoustical system components, packaging, or other articles.
Test Methods
Basis Weight (BW)
Basis weight of the following examples was measured in a way that is consistent with ASTM D756 and EDANA ERT-40,3-90 test methods. The results were provided in units of mass per unit area in g/m2 (gsm) and were obtained by weighing a minimum of ten 10 centimeter by 10 centimeter samples described in each of the Examples or Comparative Examples below.
Denier and DPF Determination
Denier is the mass in grams per 9,000 meters length of fiber. If individual filaments are used to form a nonwoven web, then denier is the same as denier per filament or DPF. Determining the average denier of individual filaments formed into a spunbond fabric is a common test for those knowledgeable in the art (for meltspun fibers, the diameter is typically between 10 and 50 microns). For circular cross-sectional shaped fibers, it typically involves measuring the width of the individual fibers using an optical microscope and, for such a circular fiber width is equal to the diameter. The measurement device is first calibrated using an acceptable standard (e.g., Optical grid calibration slide 03A00429 S16 Stage Mic 1MM/0.01 DIV from Pyser-SGI Limited, Kent, UK or SEM Target grid SEM NIST SRM 4846 #59-27F). A common method to select fibers at random is to measure the width of fibers along a line drawn between two points set across the sample piece (a nonwoven web) being examined. This approach minimizes multiple measurements of the same fiber. For the examples described herein, 15 readings were done in 6 locations spread across the width of the samples, therefore providing a total of 90 data points per sample. That average fiber diameter is then converted into denier by using the following formula:
Denier=D2*G*0.007069
where D is the average width or diameter of circular filaments expressed in microns and G is the polymer density at solid state expressed in grams per cubic centimeter. For polypropylene used in the examples, a density of 0.91 grams per cubic centimeter was used for the polymer density at solid state.
For filaments having a cross-section other than circular, another approach is to cut the filaments and examine their cross-section under a microscope. The area of the cross-section can be measured by different well known methods including the use of commercially available image analysis software. Knowing this fiber or filament cross-section area (CSA) in square microns, the denier can be calculated using the following formula:
Denier=CSA*0.009*G
where CSA is cross-section area of the filament in square microns, and G is the density of the polymer in grams per cubic centimeter.
Capillary Length, Cross-Sectional Area, Perimeter and Hydraulic Diameter
Capillary length and hydraulic diameter were used as indicated in the specification on the engineering drawing of the spinneret manufacturer. For circular capillaries, the capillary hydraulic diameter (DH) and the capillary diameter (Dc), as indicated in the specification of the spinneret manufacturer, are the same as calculated herein; and capillary cross-sectional area CAc, is calculated per the following equations:
D
c=internal diameter of the capillary
CAc=πDc2/4 or 3.1416*Dc2/4.
A method to calculate cross-sectional (CA) and perimeter (CP) for a capillary having a cross-section that is circular or other than circular involves studying the capillary exit using a microscope and, more typically an optical microscope. As an example, for simple regular geometric shapes like a circle, a square, a rectangle or a triangle, one could use an optical microscope in combination with a calibration standard (e.g. Optical grid calibration slide 03A00429 Stage Mic 1MM/0.01 DIV from Pyser-SGI Limited, Kent UK) to measure the key dimensions used to either calculate the perimeter or determine the capillary cross sectional area.
For more complex shapes like multi-lobal capillaries, an example of a method that can applied includes the use a microscope capable of capturing the image digitally and, using a software to analyze the image in order to calculate the perimeter and cross section for the area contained inside the wall of the capillary. For example, one can use a microscope like the Digital Microscope KH-7700 from Hirox Company, Ltd 2-15-17 Koenji Minami, Suginami-ku, Tokyo 155-0003, Japan. This microscope is supplied with a proprietary software used to analyze the digital imaged recorded. More precisely, one can use the length and area measurement methodologies for the indicated microscope as described in Chapter 3, pages 117 to 132 of the Operation manual 1st Edition with a revision date of October 2006, to calculate the perimeter or the cross section area of the capillary shape. From those measurements the hydraulic radius RH and the hydraulic diameter DH can be computed using the indicated formulas of RH=CA/CP and DH=4RH.
Nonwoven fabrics were prepared on a meltspun line designed by Reifenhauser Reicofil GmbH & Co. KG of Troisdorf, Germany, in which the typical Reicofil 4 meltspun beam was modified to use a multi-zone spinneret of a type such as illustrated in
For the comparison spinneret, the Reicofil 4 meltspun beam was provided with spinnerets that comprise only one dimensional type of capillaries and that were uniformly spaced and had similar exit diameter as well as similar length, wherein a 3.5 meter wide spinneret contained 22,454 total capillaries having an exit geometry that is circular at a hydraulic diameter of 0.6 mm (6349 square mm open area) and had a length (L) of 2.7 mm, and these capillaries had a length to hydraulic diameter ratio of 4.5 and a capillarity density of 6800 capillaries per linear meter width of the face of the spinneret body and 3.37 capillaries per centimeter squared. The capillaries having these dimensions are also referred to herein as zone A capillaries. It is noted that since circular cross-sectional shaped capillaries were used for all the capillaries in all the zones of the spinneret of these examples that the indicated capillary hydraulic diameter values for these examples also are equivalent to the diameter values for these examples, and the indicated length to hydraulic diameter ratio values for these examples also are equivalent to the length to diameter ratio values for these examples.
For the multi-zone spinneret, and with reference made to
The following explain how the length of the capillaries of different selected hydraulic diameters were arrived at for this example of the inventive spinneret.
First, rheological curves were developed or obtained from the resin supplier for the resin of interest at the melt temperature at which the resin is expected to be processed. Typically, those curves are obtained by measuring the pressure at different flow rates for a capillary of known length and diameter as described in test method ISO 11443.
For this specific example rheological curves were obtained for polypropylene resin Isplen® 089Y 1E, a 30 MFR isotactic homopolymer polypropylene sold by Repsol Quimica S.A. Madrid, Spain at melt temperature of 230° C. Those curves provided shear viscosities (SV) over a range of shear rates (SR). Those curves can be used to calculated the shear stress (Tw) for a given polymer at a given temperature as per the expression Tw=SR*SV.
Those data were plotted as Log (SR) vs. Log (Tw). For that resin at 230° C., the best fitted curve could be expressed as per the following equation:
Log(Tw)=2.092+1.367*log(SR)−0.1573*log(SR)2
where Tw is expressed in Pascals and SR is in s−1
Next, the characteristics of a capillary B of the inventive spinneret were selected: A hydraulic diameter DHb of 0.55 mm (this is a circular capillary so the hydraulic diameter is the same as the actual diameter) with a capillary length Lb equal to 2.2 mm for a Lb/DHb ratio of 4.0. A throughput per capillary of 0.5 gcm was selected as it is within a typical range of throughputs at which the spinneret was expected to operate. This throughput of 0.5 gcm could be converted into a volumetric flow (Q) of 0.01126 cm3/sec assuming a density for molten polypropylene that is 0.74 g/cm3 and using the following expression:
Q=throughput per orifice in gcm/(60*density of the molten polymer in g/cm3).
For the circular capillary B having a hydraulic diameter of 0.55 mm and for a volumetric flow of polymer Qb of 0.01126 cm3/sec, the shear rate (SRb) for that polymer at 230° C. was calculated based on the following power law equation used for non-Newtonian fluid:
SRb=((3n+1)In)*(Qb/(3.1416*(DHb/2)3)=778 sec−1
where: n is 0.35, the power law constant for polypropylene (Page 46, Giles, Harold F., “Extrusion: the definitive processing guide and handbook”, William Andrew Inc., 2005 ISBN: 0-8155-1473-5), DHb is the radius for the capillary B, and Qb is the mass flow rate in cm3/sec.
Using this value of SRb and the results from the rheological curve for this polymer at 230° C., a shear stress TWb of 53603 Pascals was obtained.
The diameters for the other capillaries A, C and D were selected as 0.6, 0.5 and 0.45 mm respectively. The shear rates (SR) were calculated for those capillaries using the following expression and assuming a constant throughput per capillary of 0.5 gcm:
SRx=((3n+1)In)*(Qx/(3.1416*(DHx/2)3).
Knowing the shear rate (SR) for each capillary diameter, the shear stress (Tw) was calculated based on the results of the rheological curve and is reported in Table 1. Using the calculated shear stress (Tw) for this polymer processed at 230° C. for each capillary diameter and, assuming that the pressure drop during operation is the same for all the capillaries of a given spinneret, the following expressions could be resolved for the capillary length La, Lc, and Ld that would produce the same theoretical throughput:
L
a=(TWb*2.2 mm*0.6 mm)/(TWa*0.55 mm)=2.69
L
c
=T
Wb*2.2 mm*0.5 mm)/(TWc*0.55 mm)=1.78
L
d
=T
Wb*2.2 mm*0.45 mm)/(TWd*0.55 mm)=1.43.
The resolution of those equations is based on the shear stress equation for a non-newtonian fluid flowing through a circular capillary at a given throughput and polymer viscosity: Tw=ΔP*DHI(4*L) where Tw is the shear stress of a fluid flowing through a capillary having a hydraulic diameter DH and a length L and, where the pressure drop is ΔP. ΔP is assumed constant across all the capillaries going through the spinneret body, therefore knowing the shear stress, length and hydraulic diameter for a capillary allows the calculation of the lengths of capillaries having different diameter and for which the shear stress has been estimated.
The actual lengths of the capillary A, B, C and D for the manufactured spinneret were respectively about 2.7, 2.2, 1.73 and 1.4 mm.
Using the same approach in reverse, the theoretical throughputs were calculated for the actual dimension of the capillaries A, B, C, and D operated with the same polymer and temperature and, the largest difference among the capillaries was about 9%
The spinneret having a multi-zone capillary design at the face of the spinneret body of an embodiment of the present invention was manufactured having the indicated capillary dimensions and used to evaluate its spinning, processing conditions and resulting nonwoven fabric properties. These trials were performed using a single beam from an SSS/RF4 commercial line suitable for light basis weight products. Those trials were performed using an isotactic polypropylene resin having a nominal viscosity of 30 MFR and sold under the name Isplen® 089Y1 by Rep sol Quimica S.A. Madrid, Spain. Some of the samples were run with and without the addition of a baseline of TiO2 pigment. The multi-zone spinneret (i.e., having about 8000 capillaries per meter in the indicated zones A, B, C, and D) was installed on the line in the same manner as the comparison spinneret (i.e., having 6800 single dimension capillaries per meter).
The melt spinning system generally had the configuration shown in
While operating the system as similarly shown in
Using a comparative “single zone” (i.e., one zone of single dimensional capillaries) spinneret with uniformly dimensioned capillaries at a density of about 6800 capillaries per meter width of the face of the spinneret body with each capillary having a hydraulic diameter of 0.6 mm and a capillary length of 2.7 mm), a sample was prepared using a calculated average throughput of 0.525 gcm or a total throughput of about 717 Kg/h, a cooling chamber pressure chamber of 3600 Pascals, and a ratio of air volume of about 1:5.5 between the upper and lower quench zone with air temperatures that are reported in Table 1. Additional process conditions as well as test results can be found in Table 2. The calender was set-up the same as used for Examples 1 and 2.
Examples 4 and 5 were produced the same way as Examples 1 and 2 with the exception of the cooling chamber pressure which was raised to 5000 Pascals. The ratio of quench air volume was set at about 1:2. The calender was set-up the same as for Examples 1 and 2. Those samples were produced to demonstrate the ability of the multi-zone spinneret to produce nonwoven filaments for use in nonwoven fabrics at the same process stability and with at least no reduction in the denier variability.
Example 6 was also run using the multi-zone inventive spinneret, however the calculated average throughput was raised to 0.5 gcm or total throughput of about 832 Kg/h and, the line speed was adjusted to produce a basis weight of 27 gsm. The ratio of quench air volumes was set at about 1:2 between the upper and lower quench zones. For this example, the calender set up was the same as for Examples 1 and 2. This Example was made to illustrate the ability of the inventive spinneret to provide a stable spinning process at higher throughput with no or little reduction in the average fiber denier or its variability.
Results:
With a few minor process adjustments the spinning stability for Examples 1 and 2 made at 716 Kg/h as well as Example 6 made at 832 Kg/h while using the inventive multi-zone spinneret at a cooling chamber pressure of 3600 Pascals was observed to be comparable to the spinning stability observed for Example 3 using the comparison RF4/6,800 capillary per meter spinneret body at a throughput of 716 Kg/h and the same cooling chamber pressure and while using the same indicated polypropylene resin. No polymer drips or hard spots were observed for Examples 1, 2 and 6. The cooling chamber pressure of 3600 Pascals was selected because this is near the maximum cooling chamber pressure at which a very stable process can be obtained with the standard spinneret body and the indicated polypropylene resin. It was also observed that the average denier of the filaments from Examples 1 and 2 were lower than the denier measured for the comparative Example 3. Denier variability was also comparable or better for Examples 1 and 2 than for Example 3. The results can be found in Table 2.
Spinning stability of Examples 4 and 5 made using a cooling chamber pressure of 5000 Pascals with the inventive spinneret at throughput of 716 Kg/h was also comparable to spinning stability observed for the comparative Example 3 produced at a cooling chamber pressure of 3600 Pascals. No polymer drips or hard spots were observed for those Examples. As a result of using the higher cooling chamber pressure, average denier was significantly reduced with an improved or about equal denier variability. The results can be found in Table 2.
Air permeability, strength, and elongation properties of the nonwoven webs made in Examples 1-6 were determined and found to be commercially suitable.
Overall nonwoven fabric appearance was found to be improved with the spinneret containing the spinneret body having the multi-zone capillary design as compared to the comparison spinneret body. The improvement was more noticeable at 5000 Pascals cooling chamber pressure.
In summary, the experimental test results showed that the indicated multi-zone spinneret body design of the present invention can maximize filament uniformity without compromising spinning quality. The 8000 capillaries per meter containing spinneret body of the multi-zone spinneret design of the present invention had approximately 10% less flow area as compared to the indicated 6800 capillary per meter containing spinneret body in the comparison spinneret (6022 mm2). This created slightly higher initial operational pressure. However, the back pressure combined with the differential capillary hydraulic diameter per zone, helped to compensate for polymer speed differences at spinning in complement to the asymmetric breaker plate used in the spinneret. The indicated four different capillary configurations with differential length to hydraulic diameter ratios in the indicated spinneret body of the multi-zone spinneret were used to help compensate for non-uniform filament quenching speed and are believed to have helped avoid sections with frost line sag and non-uniformity. The designation of number of capillaries per row and number of rows per zone was determined by maintaining the same resulting polymer flow open area. Pitch between capillaries was maintained constant across the high capillary density zone.
As additional observations made during the trials, while the density of the capillaries in the multi-zone spinneret is close to 20% higher than the comparison spinneret, the spinning of filaments was observed to be comparable to the comparison spinneret in terms of nonwoven fabric hard spots. These results for the high capillary density zone showed improved formation with lower filament deniers and higher polymer throughputs. A multi-zone spinneret design of the present invention with the different zones of capillaries enabled a spinning quality comparable to the comparison spinneret and this featured enabled the increase of cooling chamber pressure up to 5000 Pascals. Using progressively increasing length to hydraulic diameter ratios in various zones of the spinneret body of the multi-zone spinneret to compensate for filament quenching inefficiency made a significant impact that enabled use of different hydraulic diameters adjacent to each other without impacting performance.
Unless indicated otherwise, all amounts, percentages, ratios and the like used herein are by weight. When an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention include modifications and variations that are within the scope of the appended claims and their equivalents.
This application is a divisional application of U.S. patent application Ser. No. 13/652,740 filed Oct. 16, 2012, which is incorporated herein by reference in entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13652740 | Oct 2012 | US |
| Child | 16375120 | US |
