WO2002061186A1

WO2002061186A1 - Process of making perfluoropolymer articles

Info

Publication number: WO2002061186A1
Application number: PCT/US2002/002718
Authority: WO
Inventors: Gary Stanitis; Frank Cistone
Original assignee: Xtreme Fibers, Inc.
Priority date: 2001-01-31
Filing date: 2002-01-29
Publication date: 2002-08-08

Abstract

A process is described to make continuos multifilament yarns andstaple fibers from melt processalbe perfluoropolymers at shear rates higher than the published critical shear rate of the polymer. The fibers produced can be made in many geometrices including round, elliptical, angular, hollow, multilobal, sheath/core, segmented pie, islands-in-the-sea, as well as micro fibers. The technology is applicable to many different fiber producing techniques, including melt spinning, melt blowing and spun bonding. Fibers produced can be further processed such as drawing, heat trating, texturing, air entanglin, spot bonding, hydro-entanglin, and calendaring. Any melt processable perfluoropolymer can be used, including those selected fro mthe group consisting of copolymers of tetrafluoroethylene with 1 to 5 mole % of a least one perfluoroalkoxyvinylether where the alkyl group has from 1 to 4 carbon atoms, copolymers of tetrafluoroethylene with 2 to 20 mole % of at least one perfluoroolefin haivng 3 to 8 carbon atoms, at well as copolymers of tetrafluoroethylene and cyclic perfluorinated dioxoles.

Description

PROCESS TO MAKE FIBERS AND YARNS FROM MELT PROCESSABLE PERFLUOROPOLYMERS AND PRODUCTS RESULTING THEREFROM

Field of the Invention This invention relates to a very high efficiency process for the manufacture of continuous multifilament yarns, staple fibers, and melt blown and spun bonded fibrous webs made from melt processable perfluoropolymer resins which takes advantage of the ability of perfluoropolymers to be processed above their rheological critical shear rate, with unexpectedly good strength and overall fiber properties. The present invention also relates to new forms of melt processable perfluoropolymer multifilament yarns, staple fibers, and melt blown and spun bonded fibrous webs that have very fine individual deniers, (fiber diameters between 0.5 and 16 microns), referred to here as micro fibers. Micro fiber perfluoropolymer multifilament fibers, yarns, and melt blown and spun bonded fibrous webs in accordance with this invention have a wide range of improved properties including improved filtration characteristics and improved fabric characteristics such as drape and hand.

Objects of the Invention

It is an object of this invention to provide a process to make acceptable strength perfluoropolymer continuous multifilament yarns, staple fibers, and melt blown and spun bonded fibrous webs from melt processable perfluoropolymer with very high throughput. The process can be used with perfluoropolymers of widely differing molecular weights.

It is another object of this invention to provide a process to make acceptable strength micro fiber perfluoropolymer continuous multifilament yarns, staple fibers, and melt blown and spun bonded fibrous webs from melt processable perfluoropolymers with very high through put. The process can be used with perfluoropolymers of widely differing molecular weights.

It is still another object of this mvention to provide a process to make acceptable strength perfluoropolymer continuous multifilament yarns, staple fibers, and melt blown and spun bonded fibrous webs, including micro fibers made from melt processable perfluoropolymers that have non-circular cross section with very high through put. Possible cross sections include, but are not limited to, multilobal, hollow, elliptical, angular, multi-component, sheath core, segmented, or dispersed phase ("islands in the sea"). The process can be used with perfluoropolymers of widely differing molecular weights.

It is a further object of this invention to provide novel, single component micro fiber perfluoropolymer continuous multifilament yams, staple fibers, and melt blown and spun bonded fibrous webs made from melt processable perfluoropolymers with good yam, fiber and web properties.

Another object is to provide novel multi-lobal perfluoropolymer fiber forms suitable for use in filtration and a wide variety of other applications. Still yet another object is to provide novel hollow perfluoropolymer fiber forms also suitable for filtration and a wide variety of other applications.

Background

During the last two decades, a number of technologies have been developed to make fibers and yams from polytetrafluoroethylene or "PTFE", often referred to by Dupont's trademark Teflon®. A number of patents exist describing the use of PTFE fibers and yams for high temperature, chemical and weather resistant items such as filter media, bearing cloths, radar coverings, etc. including U.S. Patents 4,840,838; 4,361,619; 4,612,237; 3,986,851; 4,324,574; and 4,861,353. PTFE has a wide range of useful properties because it is a perfluoropolymer, with all hydrogen being substituted by fluorine, leading to a highly inert material. PTFE has several drawbacks as a plastic material. One particular drawback, both as a polymer and as a fiber, is due to certain fundamental mechanical characteristics of the molecular structure. PTFE is made with very high molecular weight, making it impossible to melt process like other polymers. PTFE particles or powders are formed into finished items by being compressed together and then heated or sintered. This type of process makes it difficult to produce very fine or micro fibers, and in fact, commercially available PTFE fibers are relatively coarse, generally greater that 4.5 denier per filament (17 microns in diameter). Once made into a finished part, it is difficult to further thermally process PTFE, limiting its ability to be thermally bonded, calendered, laminated, etc.

In recent years there have been some attempts to overcome PTFE's limitations as a perfluoropolymer fiber and yam. Three U.S. patents, 5,552,219; 5,460,882; and 5,618,481 by Vita et al disclose multifilament yams and staple fibers produced from melt processable perfluoropolymer resins. Like PTFE, these polymers are perfluorinated, with all hydrogen being substituted by fluorine. However, unlike PTFE, they are melt processable, which means the polymer will soften and flow when heated above its melting point. This characteristic allows fibers to be formed using a much wider range of fiber spinning technologies and subsequently for the products produced to be thermally treated, bonded, laminated, calendered, and the like as described in International Application No. PCT/ US00/ 23920 to Cistone et al. Melt processable perfluoropolymers have a limitation in that the most useful, high molecular weight products have very low critical shear rates, typically 10 to 100 sec^"1. When polymers are processed above the critical shear rate the flow typically becomes rough and useful finished goods are difficult to obtain. Vita, whose concern is limited to larger denier round fibers not micro fibers nor fibers with non- circular geometry, is aware of this limitation and overcomes it by using a process incorporating a very high number of holes per unit area, which allows good overall production rate while maintaining very slow throughput at each hole. Vita states "the shear rate gradient at the wall of a single hole is maintained below the typical limit at which the onset of surface defects [melt fracture] on the extrudate occurs". A shear rate of approximately 64 sec^" was used in all of his examples. Vita also uses relatively large diameter die holes of 0.5 millimeters. The larger holes are recommended to maintain a minimum shear rate. Vita demonstrated the ability to produce fibers from a range of molecular weight perfluoropolymers, including polymers characterized by melt indexes of 7, 13.4, and 16.3. Yams with good strength, as high as 180 MPa were achieved. The individual filament deniers achieved by Vita were relatively coarse, even after drawing, ranging from 16 denier (32 micron diameter) to 64 denier (65 micron diameter). Although this range of individual fiber diameter is useful, these are not considered fine or micro fibers. In fact they are not as fine as PTFE fibers commercially available. Because the fibers are generally coarse, and very close together as spun, the Vita process relies on a "a cooling system of high efficiency..." to quench the strands. When strands are quenched in this fashion it is referred to in the fiber industry as an unoriented yam process or UOY, which is common. Unoriented yams can be drawn, either in line during production, or in a second process step as Vita demonstrates. The benefit of the additional drawing is to reduce fiber denier and to increase strength. In an attempt to improve the technology, Dupont has disclosed in PCT/US98/12606 a second method to produce fibers from melt processable perfluoropolymers. The Dupont teaching is much narrower than the Vita patents in that Dupont demonstrated the production of only single fiber filaments, not yam bundles. The Dupont teachings, like the Vita technology, focus on the need to operate at very low shear rate and is concerned only with coarse, round cross section, fibers. Dupont states "higher extrusion speed, more consistent with low-cost commercial production rates, results in melt fracture and fiber breakage". It is also stated that "the rates of extrusion suitable for the process of the invention depend upon the size of the operating window defined by the upper critical shear rate for the onset of melt fracture ... ". As with the Vita teachings, the Dupont PCT specifically requires extrusion at low shear rate, with shear rates of 3 to 73 sec^"1 used in the examples. Also, as in the Vita patent, a relatively coarse range of hole diameters is recommended, specifically 0.5 to 4.0 millimeters. The Dupont teachings are different from Vita in that overall high throughput is obtained by extruding slowly through a large diameter hole, making a large diameter filament exiting the die, but then pulling on that filament very quickly to draw it into a fine filament at high speed. A slightly lower range of melt index polymers is processed by Dupont, including 2, 5.2, and 13 melt index. When a filament is pulled to the maximum degree possible during melt forming it is referred to by the fiber industry as a fully oriented yam process or FOY. This technique is commonly used to obtain fine, high strength fibers. Dupont's claim of greater fiber strength compared with the Vita process is expected considering that an FOY process is used, and perhaps more importantly because Dupont uses a single filament, unlike the Vita process which is a true multifilament spinning approach.

It is well known in the fiber industry that tenacity testing on individual filaments typically leads to strength values 25 to 35% higher than on multifilament bundles. This is due to slippage of individual filaments during testing of multifilament bundles as well as premature breakage of some filaments due to variation of individual filament strength and diameter in a multifilament bundle as well as variations in the applied force from the grips holding the fibers in the testing apparatus. When this is considered the Dupont teachings show no measurable improvement in strength. The Dupont teachings, like Vita, are able to make only relatively coarse individual fibers for a multifilament spinning process, the Dupont examples ranging from 4.5 denier (17 micron diameter) to 115 denier (87 micron diameter). Like the Vita teachings, the fibers disclosed by Dupont are no finer than commercially available perfluoropolymer PTFE fibers and are round in cross section. Although these fibers can be useful, they are not considered very fine, or micro fibers.

In addition to concern about melt fracture and rough filaments when thermoplastic fibers are processed at speeds higher than their critical shear rate there are additional concerns regarding fiber spinning at high speeds. In the article written by Dr. Klaus Fischer "Drawing of Continuous Filament Yams" October 2000 International Fiber Journal, the author states "Experience in the spin drawing of coarse tire yams shows that the higher the spinning and/or draw speed, the lower the achievable strength. Similar dependent relationships also apply to the module and shrink behavior."

Although fibers with individual filament diameters in the ranges of those taught by Vita and Dupont have some broad uses, it has been well taught in the fiber industry that very fine fibers, or "micro" fibers have even greater, and in many cases unexpected, utility. This utility is not always improved as fiber diameter continues to decrease, but often is optimized within a size range of micro fibers that are much smaller than those established by Vita and Dupont, but larger than some minimum value. A number of patents establish the size range and associated benefits of micro fibers. U.S. Patent 4,109,038 by Hayashi et al discloses that "a suede-like raised woven fabric which comprises warp yams; weft yams, each being a single yam consisting of a bundle of fine [polyester] fibers...has excellent suppleness, surface abrasion and pilling resistance." The patent defines 0.05 to 0.8 denier polyester (2.2 to 9 micron diameter) individual fibers as "fine". It further states that "The average monofilmanent denier of the raised portion must be in the range of from 0.05 [2.2 micron] and 0.04 denier [6.5 micron diameter], preferably from 0.1 [3.2 micron diameter] to 0.3 denier [5.5 microns diameter]. When the denier is less than 0.05 denier, the surface abrasion and pilling resistance of the fabric are not good.... On the other hand, when the denier is more than 0.4 denier [6.3 micron diameter], the feel of the fabric tends to be rough and suede-like touch is difficult to obtain." The patent also states "When the denier is 0.4 denier and below, the suppleness of the fabric is not good. On the other hand, when the denier exceeds 0.8 denier [9 micron diameter], the feel of the fabric tends to be rough and suede-like tough becomes difficult to obtain". A useful range of micro fibers defined as about 2.2 to about 9 microns in diameter is established. U.S. Patent 4,588,635 to Donovan regarding a replacement for down insulation similarly identifies an optimal range of useful polyester "microfibers" having unusually good properties. Donovan defines "microfibers as 3 to 12 microns in diameter and identifies that for optimal insulation properties "...the bulk of the fibers must lie within the diameter range of 3.0 to 12.0 microns and measurement of the thermal conductivity of a number of webs confirms this conclusion."

In U.S. Patent 5,810,954 Jacobs et al describes a process for the manufacture of fine denier polyolefin fibers and offers his own definition of what determines a microfiber. Jacobs defines "microfibers" as having a denier of less than about 1.0 to 2.0 dpf (denier per filament) which is about 12 to 16 microns in diameter. He goes on to address the benefits of fine fibers "Strength and drapeability are among the main physical properties which scientists seek to optimize... Softness and drape of a fabric, important for garment and other applications, are critically impacted by the bending modulus of the fabric... Therefore, a round fiber of smaller diameter (fine denier) should result in a much more drapeable material."

U.S. Patent 5,895,710 to Sasse et al describes a process to make "fine fibers" of polyethylene and nylon with a range of useful properties. Sasse describes these polyester and polyamide fibers as being "about 1 denier" which is equivalent to 10 to 12 microns in diameter. He states "woven fabrics containing the split fine fibers that exhibit highly improved softness and uniformity are highly useful for soft apparels, dusting, and wiper cloths and the like".

U.S. Patent 5,002,821 to Browne et al defines small thermoplastic fibers as ranging from 2 to 15 microns in diameter and further recommends their use in Fiberglass reinforced plastic prepegs, said prepegs "...having impact resistance further enhanced by incorporating at the surface of the prepeg a thin layer, less than 80 microns in thickness, of small fibers...".

U.S. Patent 5,437,910 to Raabe et al describes an improved multi-ply vacuum cleaner bag that incorporates "...at least one ply of filter paper and at least one ply of fine fiber web", and defines fine fibers as "Preferred diameters of the fibers of the fine fiber web are from 0.5 micron to 15 micron"

U.S. Patent 5,492,751 to Butt, Sr. et al discloses an improved lightweight disposable garment with improved containment means. The patent states "The present invention is directed to improved nonwoven laminates which can be made in extremely light weights and include at least one fine [polypropylene] fiber component layer." The patent defines fine fibers as "...having an average diameter in the range of up to about 10 microns". The benefits derived are described as "The resulting laminate has an improved combination of properties including softness and conformability... for certain applications a barrier as measured by hydrostatic head of at least 15 cm and breathability as measured in terms of Frazier porosity of at least 50 scfrn." The later properties described are applicable to filtration applications as well.

U.S. Patent 5,955,011 to Closksin et al describes a process to make small diameter glass fibers. In this patent Closkin defines two categories of small fibers, those being "... fine fibers having mean diameter of about 7 microns or less", and "...microfibers having mean diameters between about 0.5 and 2.0 microns.

From these patents it is obvious that industry has identified a category of fibers referred to as either "fine", "very fine", "extremely fine", "micro denier", "fine denier", "small" "micro fibers" and the like. Additionally, a fair reading of the patent literature indicates that there is a lower limit below which important properties are lost. Also, a fair reading of the patent literature indicates that the size range where advantageous characteristics are identified is consistently between 0.5 and 16 micron diameter. As used herein the term "micro fiber" will be used to describe "fine", "very fine", "extremely fine", "micro denier", "fine denier" "small", and the like, and will refer to fibers with individual diameters of 0.5 to 16 microns. In this description the term diameter refers to both the true diameter of circular cross section filaments, as well as the significant dimension of non-circular cross section filaments. Based on the uniqueness and successful commercial use of the micro fibers described in these patents, it demonstrates that a perfluoropolymer micro fiber in the range of 0.5 to 16 micron diameter per filament, could be used in novel ways and represents a significantly different product form than coarse perfluoropolymer fibers as taught by Vita and Dupont.

There are a number of process technologies used to produce micro fibers from melt processable polymers, however all of them have difficulties and limitations when attempted to be practiced on perfluoropolymers if one tries to apply the teachings of Vita and Dupont. One common technology to make micro fibers is referred to as "melt blowing". In U.S. Patent 5,810,954 Jacobs describes melt blowing as "...fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity gas (e.g., air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a mat of randomly dispersed meltblown fibers." In U.S. Patent 3,849,241 to Butin he gives an example of a melt blowing process where the critical shear rate at the die holes is about 300 sec^"1 (more than three times higher than taught by Vita and Dupont) and teaches shear rates at the die as high as 5000 sec^"1 (more than 50 times higher than Vita and Dupont). Jacobs goes on to teach that the resulting melt blown fiber web can be spot bonded and stretched, to give even finer fibers with greater strength. U.S. Patent 5,733,581 to Barboza et gives an example of "a conventional 6-inch wide melt blowing die with twelve (12) 0.015 inch [0.381 millimeter] diameter polymer orifices and gives examples of operation with shear rates as high as 1500 sec^"1 at the die. So, although melt blowing is one method to make micro fibers, the die orifices typically used are small, smaller than those used by Vita and Dupont, making it difficult to melt blow perfluoropolymers below their critical shear rate while maintaining reasonable economics.

Jacobs also describes spun bonding as a process to make "small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced..." Jacobs identifies fibers produced from the spun bonding process as have average diameters "larger than 7 microns". As with melt blowing, Jacobs describes a process to spot bond and stretch a fibrous web, making even finer individual fibers. U.S. Patent to Takashi et al gives an example of spun bonding polyester with a shear rate at the die of about 6900 sec^"1, almost 100 times higher than taught by Vita and Dupont. Like melt blowing, the small die orifices needed to make micro fiber spun bonded webs make it difficult to process melt processable perfluoropolymers below their critical shear rate at commercially attractive throughputs. Another common process to make micro fibers is to produce multi-component fibrous strands using multifilament melt spinning, spun bonding, or melt blowing processes. One of these multi-component processes to make micro fibers can be described as "Islands in the sea", referring to the cross-sectional morphology which shows islands or segments of fine fibers made from one material totally enclosed in a second, incompatible matrix material. U.S. Patents 4,239,720 (Gerlack et al) and 4,364,983 (Briicher et al) give very good descriptions of a variety of different patterns that can be made with the islands or segments. Once the fiber is made, the two incompatible polymers can be split by a variety of methods including stretching, heat treatment, the addition of solvent, mechanical working or twisting, and the like. Additives can be incorporated into one, or both incompatible polymers to further enhance the ease of separation. Separation can be done either with the fibers or yam, or after the fibers have been partially or fully converted to a final product, where in most cases both the segment and matrix fibers remain. In Japanese Patent 63-245259 Umezawa teaches a method to make perfluoropolymer segment fibers in a hydrocarbon polymer matrix (a multi-component fiber). The hydrocarbon is then dissolved. Unfortunately, any residual hydrocarbon polymer, or residual solvent from the process will be an impurity in the perfluoropolymer fibers, which is undesirable since perfluoropolymers are typically used for high temperature, high purity, or chemically resistant applications where the residual impurities will negatively impact the performance. In addition to the concern about impurities resulting from the incompatible fiber or the solvent taught by Umezawa, there is also the problem that, like melt blowing, the process efficiency will be poor due to the low critical shear rate of perfluoropolymers . Finally, there is a second multi-component spinning technology, also applicable to multifilament melt spinning, spun bonding, and melt blowing, referred to here as "side by side" multi-component. U.S. Patent 5,895,710 to Sasse et al teaches a two component fiber with each component being incompatible. In U.S. Patents 4,051,287 and 4,109,038 Hayashi et al teaches multi-segmented side by side multi-component fibers using two or more incompatible polymers, often referred to as "segmented pie" or "hollow segmented pie". Like "islands in the sea" technologies, the "side by side" fibers are split after the spinning process, with all component fibers remaining in the final product form. The same problems occur when applying this technology to perfluoropolymers as with the "islands in the sea" approach. Specifically, if a non-perfluoropolymer is used as one of the incompatible components, it will represent an impurity in the final good. If solvent is used to remove it, residual solvent will be a concern for high purity applications. Additionally, the process efficiency will be poor due to the low critical shear rate of perfluoropolymers considering the very small die hole dimensions required for multi-component fibers processes.

Another fiber form, which has great utility, is hollow fibers. There are a wide variety of hollow fibers and associated applications as well as a number of equipment designs established to create the proper morphology. In U.S. Patent 5,480,598 to Gentile et al he describes fibers which "...may be non-permeable, semi-permeable or permeable. The fibers may be empty or, when semi-permeable or permeable, filled with a material such as a medicament or a biological material such as living cells or proteins." Hollow fibers with non-permeable walls can have utility by improving the insulation value of the fiber, as well as reducing the overall weight of the fiber, leading to lighter, lower cost woven and nonwoven articles. Gentile goes on to describe an apparatus for producing hollow fibers. The nozzle assembly has an elongated hollow inner bore and an outer bore, which is concentric to the inner bore, together defining an annular channel. The nozzle assembly is attached to a source of polymer or other material. The polymer or other material is pumped through the annular space forming a hollow filament. As described in U.S. Patent 4,670,341 to Lundsager, semi-permeable and permeable hollow fibers "...are well known for their usefulness as filter media." He refers to their use for ultrafiltration as well as filtration of bacteria, proteins, viruses, and colloidal substances. To achieve porosity one or more filler(s) and plasticizer(s) is(are) added. The filler acts to absorb the plasticizer and hold it within the polymer matrix. After the hollow fibers a formed the plasticizer is removed by solvent extraction, leaving hollow voids. The process can also be done with no filler if a plasticizer with the proper miscibility versus temperature is selected, so that the plasticizer is at least partly immiscible at the conditions under which the solvent is being extracted. U.S. Patents 4,861,661 and 4,941,812 to Samuelson describe multi-component hollow fibers with internal structure separating the fiber interior into channels or compartments. Samuleson explains that these forms "...can be useful as separation devices or for bioreactor applications...". He goes on to say, "In addition, where the inner or core filament is solid the inner filament may be a light transmitting fiber or an electrically conductive fiber to conduct light or electrical charges...". Because of the chemically inert nature of perfluoropolymers, they are well suited for many of the medical, filtration, and biological applications where hollow fibers are used. Still another fiber form which has great utility for many of the applications where perfluoropolymer fibers are used is a multilobal fiber. Perfluoropolymers themselves are very expensive on a dollar per pound basis when compared with commodity polymers (like polyethylene and polystyrene) and even compared with engineering polymers (such as polycarbonate or polyphenyl oxide). When the very high specific gravity of perfluoropolymers is also considered, typically 2.1 to 2.2, the overall cost for products made from perfluoropolymers is very high. To be cost effective with products fabricated from perfluoropolymers it is important to minimize the amount of perfluoropolymer present. When fibers are converted into fabric forms, either woven, knit, or nonwoven, and used for filtration, coalescing, de-misting and other similar industrial applications, the fibers are compressed together during the knitting, weaving, or nonwovens process. Often times the fibers are textured or crimped prior to these processes to add bulk, reducing the amount of fiber present in the fabric on a volume basis. Another, improved method to add bulk and reduce the density of the final fabric is to use a multilobal fiber. The high bulk characteristics of multilobal fibers made from commodity and engineering plastics has been well documented.

As far back as 1970 U.S. Patent 3,508,390 Entitled "Modified Filament and Fabrics Produced Therefrom" teaches that "polyolefin, polysulfone, polyphenyl oxide, polycarbonate, polyacrylonitrile, polyamide, polyester and the like"... having about 1 to 5 even up to about 10 denier per filament...having a substantially Y shaped cross-section... [have] "a greater degree of covering power [and] bulk..." Fibers with a modification ratio of 2.7 to 5.0 are identified. In U.S. Patent 4,492,731 to Bankar et al, Trilobal carpet fibers are identified with a modification ratio of 2.2 to 4.0. Cut pile carpets produced from round and Trilobal fibers were compared in that Patent's Examples. It was found that carpets made with Trilobal fibers were typically 2 to 3 times bulkier than those made from round fibers. Despite the application of Multilobal technology to many industrial fibers, it has not been successfully applied to perfluoropolymer fibers. This is due most likely to the difficult process of converting PTFE to fibers, as well as the misconception that melt processable perfluoropolymers cannot be processed at a high enough shear rate, which is required for fine, commercially useful, Multilobal fibers. Summary of the Invention

We have discovered that melt processable perfluoropolymers can be processed at sufficiently high shear rates to allow the manufacture of both fine denier fibers as well as micro fibers with multilobal cross sections, with modification ratios of 2 and higher. This allows the production of bulkier, lower density perfluoropolymer fabrics and forms. This not only reduces cost per volume, due to the lower overall density of the fabric form, the rough, uneven nature of the multilobal fiber surface actually improves filtration properties by trapping particulates more effectively than a round fiber.

We have discovered a process to make melt processable perfluoropolymers into continuous multifilament yams, staple fibers, and melt blown and spun bonded fibrous webs over a wide range of individual fiber diameters, including micro fibers, at processing speeds well above their published critical shear rates, yet making very smooth surfaced strong fibers and micro fibers with good color, no voids and good overall properties. Extrusion speeds of more than 10 times the published critical shear rate have been achieved.

We have also unexpectedly discovered that increasing the extrusion speed well above the critical shear rate, within the range of processing conditions defined here, does not diminish fiber strength as suggested by general fiber industry experience, but rather increases the fiber strength and tenacity, giving additional benefits beyond increased production

We have discovered that this process can be used over a wide range of useful molecular weights, including very high molecular weight perfluoropolymers with melt index of 1 or lower, as well as lower molecular weight perfluoropolymers with melt indexes as high as 25 to 50 MI and even as high as 300 MI and higher. We have discovered that this process can be used with a wide range of spinning conditions, ranging from quenched unoriented yams as spun (UOY process) with optional subsequent drawing either on line or in a second process step, partially quenched yams (POY), with optional subsequent drawing either on line or in a second process step, as well as fully oriented yam as spun (FOY) which require little, or no additional yam drawing.

We have discovered a single component perfluoropolymer micro fiber continuous multifilament yam, staple fiber, and melt blown or spun bonded fibrous web, with individual filament diameters ranging from 0.5 to 16 microns, offering the significantly different and improved properties expected of a micro fiber compared with conventional, coarser perfluoropolymer fibers.

We have discovered a process ideally suited for continuous multifilament spinning, melt blowing, and spun bonding a wide range of fiber geometries that include small cross- sections of perfluoropolymer segments, which are difficult to extrude economically when maintained below their critical shear rate. This includes multi-component fiber structures, where one, some, or all of the components are perfluoropolymers, such as segmented pies, segmented hollow pies, side by side, islands in the sea, sheath/core and the like. This also includes single component fibers through very small circular, oval, and angular geometries, multilobal hole geometries, and hollow fiber geometries.

We have discovered multilobal perfluoropolymer fiber and micro fiber continuous multifilament yam, staple fiber, and melt blown or spun bonded forms, either textured (crimped) or non-textured (not crimped)) that lead to knit, woven, and nonwoven fabric forms with 2 to 3 times greater bulkiness and improved filtration characteristics compared with round fibers.

We have discovered hollow perfluoropolymer fiber and micro fiber continuous multifilament yam, staple fiber, and melt blown or spun bonded forms.

Detailed Description of the Preferred Embodiments

This invention relates to the manufacture of continuous multifilament yams, staple fibers, and fibrous webs from melt processable perfluoropolymers. Melt processable perfluoropolymers are those which can be melted and processed like most conventional plastics. This invention is suitable for all melt processable perfluoropolymers, which are typically made from tetrafluoroethylene (TFE) monomer with one or more additional or modifying monomers. The most common modifying monomers are perfluorovinylethers, including methyl, ethyl, and propyl vinyl ethers, hexafluoropropylene, perfluorinated butene, pentene, and heptene, cyclic perfluorinated dioxoles, as well as other fluorinated modifying monomers possibly containing also hydrogen and/or chlorine atoms as described in U.S. Patent 4,675,380. The amount of modifying monomer or monomers present in the polymer can range from about 0.5 to 20 mole % and are typically 1 to 10 mole %, but can be higher. Most commercially available melt processable perfluoropolymers are made with high molecular weights to maximize the physical properties of finished parts produced from them. This often causes them to become rough on the surface when being extmded due to melt fracture, even when processed at moderate speeds. In fact many commercial grades of melt processable perfluoropolymer will melt fracture at processing conditions as low as 10 sec^" shear rate, while others can be processed at shear rates as high as 100 sec^"1 without surface roughness. Even the higher of these two shear rates is low by fiber industry standards. However, due to the unique nature of perfluoropolymers, such as their low surface energy, if conditions are optimized it is possible to process them at speeds well above their critical shear rate, yet maintain a smooth surface and good overall properties. In the case of fiber production, this high speed processing can improve other fiber characteristics such as strength or tenacity as well as allow the production of micro fibers.

For the production of continuous multifilament yams and staple fibers the melt processable perfluoropolymer pellets or granules are loaded into a hopper and fed into a conventional plastics extruder. A wide range of polymer melt indexes can be used, including polymers with melt indexes as low as 1.0. For the production of finer individual fiber multifilament yams and staple fiber, higher melt indexes, ranging from 5 to 25, and as high as 50 to 300 MI and even higher, are more suitable. A blend of melt indexes can also be used, as a small fraction of lower molecular weight polymer can improve processing. In fact, during extrusion, the molecular weight and molecular weight distribution of the polymer will change due to partial thermal degradation. The total amount of polymer molecular weight change is a function of several factors, including the intrinsic thermal stability of the polymer, which varies widely from manufacturer to manufacture, the processing temperature, and the residence time at temperature. For the purposes of this patent, any changes to molecular weight due to processing and the resulting impact on fiber production are considered part of the discovery. A variety of additives can be combined with the melt processable perfluoropolymer, either before, or during the fiber extrusion process. Although not limited to these, some examples of possible additives are pigments and colorants, inorganic fillers, flame and smoke suppressants, additives to effect electrical properties such as carbon black, graphite, and micronized metal and metal oxides, plasticizers and other organic compounds, silica based additives and ceramics and other polymers and plastics. The extruder may be single or twin screw, and should have wetted surfaces made from high nickel alloy materials such as Hastelloy C-276, Inconnel, etc. to protect them due to the corrosive nature of perfluoropolymer melts. A variety of screw configurations can also be used, including low shear profiles with gradual transition zones, low shear profiles with fast transition zones, and with screws having some mixing to improve polymer melt uniformity. The appropriate screw should be chosen based on the polymer composition and molecular weight. The extruder temperature is set in a traditional ramping profile in such a manner as to give the desired melt temperature. Two different approaches may be used to achieve a very high speed extrusion process, well above the published critical shear rate. The preferred process is to use a relatively high polymer melt temperature along with a hot die or spinnerette. For this approach the melt temperature may be set at about 115 ° to 175° C above the melting point of the polymer or higher, with a die or spinnerette temperature set point between 70° C below and 60° C above the melt temperature during processing, although a wider range of die temperatures may be used. Despite the high temperature, because the process is operated at such a high speed, residence time is very short at high temperature and so polymer properties are maintained.

An alternative process within the scope of this invention is to set the melt temperature between 60° to 115° C above the polymer melting point while the die temperature is kept relatively cool, within 1° to 100° C hotter than the polymer melting point, although higher die temperatures may be used. A melt pump may be used to improve control and consistency of polymer flow to the dies or spinnerettes. Additionally, static mixing elements, screen packs, and the like may be used. The polymer is conveyed to one or more dies or spinnerettes, which may have any number of configurations and number of holes. The holes may be any cross-sectional shape used in the industry, including round, multi-lobal, hollow, elliptical, angular, etc. The process may also be done in combination with one or more additional polymers to produce multi-component fibers, again in any geometry commonly used. This includes sheath/core, islands in the sea, side by side, segmented pie, hollow segmented pie, and similar. If it is desirable to produce a multi-component fiber, the other polymer(s) chosen to be processed with the melt processable perfluoropolymer must be sufficiently thermally stable to withstand the processing temperatures required for processing a perfluoropolymer. The major dimension of the die hole used for the perfluoropolymer can be a wide range, from 0.1 millimeters or less in diameter, to greater than 4 millimeters. Ideally the diameter should be chosen to give a shear rate at the die capillary of approximately 1.1 to 30 times the published critical shear rate, although even higher shear rates can be used.

The polymer is extruded vertically downward from the die(s) or spinnerette(s) into a quench chamber. The quench chamber can be mn in a number of conditions, including a hot chamber with additional heat supplied by some form of heated shroud or other heat source, ambient with no cooling or heating, or with a variety of cooling strategies including ambient air, chilled air, submersion into water, or impingement of the fibers by a conductive or evaporative cooling medium such as water mist or other solvent mist. Placement of any heating or cooling mechanism in the quench chamber must take into account both the extrusion speed and the take away speed, ensuring that the filaments remain molten long enough to allow full attenuation. It is preferred to maintain a hot upper portion of the quench chamber to allow maximum filament elongation. The filaments are processed using standard fiber industry equipment including cans or godets, guides, rollers, spin finish applicators, and winders. The godets may be temperature controlled or may be ambient temperature. A variety of spin finishes may be used, including commercial spin finishes, simple finishes such as alcohol or alcohol and water, or no spin finish may be used. In the case of zero spin finish techniques must be employed to control static electricity, which can prevent the formation of good quality packages on the winder.

During spinning the speed of the first godet controls the amount of orientation in the "as spun" yarn. This can be adjusted over a wide range, including unoriented spun yam (UOY) with godet speeds as low as 25 to 150 meters per minute or lower, partially oriented yams (POY) with godet speeds of 100 to 2500 meter per minute, and fully oriented yams (FOY) with godet speeds of 1500 to well over 2500 meters per minute. After the first godet the yam may be passed across additional godets, set at different speeds, to draw the yam as it is being melt spun, or the yam can be taken up on a winder and drawn during a second step at a later time. Drawing can be done at a variety of temperatures, from ambient to 200° C. It is recommended that the yam be passed across heated godets, set at 150 to 275° C or higher, either during the spinning process, or in a secondary step, to heat set the yam, reducing the shrinkage at higher temperatures. The yam can also be heat set in an autoclave or other high temperature device. The fibers can be crimped, air entangled, and/or cut to make staple fibers of any length. Fibers with a wide range of individual diameters, from 1 to 200 microns, with shrinkage of less than 5% at 200° C, and good tenacity as measured on yam bundles of 0.9 grams per denier are made. Melt processable perfluoropolymers may also be converted into a nonwoven fibrous web, with a wide range of average fiber diameter including micro fibers, via a process referred to as spun bonding. The perfluoropolymer is melted and conveyed to a die or spinnerette as described above in the description of continuous multifilament and staple fiber spinning with the flow rate adjusted to give a shear rate at the die capillary of 1.1 to 20 times the published shear rate. Standard industry die configuration, holes sizes, etc., can be used, however, the wetted surfaces should be made of high nickel alloy to keep corrosion to a minimum. Die holes of 0.1 to 4 mm may be used, and more typically 0.2 to 1 mm. Again, any cross-sectional shapes my be used. Throughput rates of 0.1 to 5 grams of polymer per minute per hole are common. The perfluoropolymer may be processed by itself, or may be one or more components of a multi-component fiber. The perfluoropolymer fiber filaments are contacted with one or more air streams in the quench area which serve to cool or quench the strands below their tack or stick point (surface is not sticky) and to draw the filaments, making them finer and stronger.

Good descriptions of typical apparatus are given in U.S. patents 4,340,563; 3,692,618; 3,802,817; and 4,064,605. Separate air streams may be used for quenching and drawing, or the quench chamber may be designed so that the same air performs both functions. As the perfluoropolymer exits the die a heated shroud may be used, prior to contact with the quench air, to allow the melt sufficient time for attenuation prior to quenching. An air temperature of 30 to 400° F may be used, preferably between 120 and 200° F. The quench air flow should be maintained as smooth and laminar as possible to prevent fiber entanglement. Low pressures of 2 to 12 psi are commonly used, and a screen or filter may also be installed to help maintain even flow. Typically a contact distance of 0.1 to 2 feet in length is needed prior to drawing, preferably 3 to 12 inches, a shorter length than other polymers being possible because perfluoropolymers crystallize rapidly. After quenching is completed the filaments enter an air drawing section where the air velocity is higher, ranging from 50 to 1000 feet per second. The air drawing section may be formed by a constriction (either fixed or movable) in the quench chamber, by the use of eductors, or any method that effectively allows a high velocity air stream to contact and draw the filaments. The velocity of the drawing air should be turbulent to the point where filaments loop across themselves to allow entanglement, ensuring good web quality, without excessive large scale turbulence, which causes large loops, reducing web quality. After exiting the drawing section the filaments may be collected on a belt, screen, conveyor, or other surface, either static or moving, to form a nonwoven fibrous web. The speed of a moving screen, belt, etc., can be adjusted relative to the fiber production speed to give a wide range of web weights, typically, but not limited to, 0.1 to 10 ounces per square yard. The nonwoven fibrous web can be further processed, including calendering, spot bonding, drawing, hydroentangling, flame treating, etc. A number of parameters may be adjusted in this process to change the web characteristics. These include, but are not limited to, die configuration (hole size, hole shape, number of holes, hole pattern), quench air characteristics (volume, temperature, velocity, direction, fiber contact location and length), polymer melt temperature and velocity, and polymer molecular weight. Perfluoropolymers may also be converted into nonwoven fibrous webs of a wide range of average fiber diameter, including micro fibers, using a melt blowing process. The perfluoropolymer is melted and conveyed to a die or spinnerette as described above with the flow rate adjusted to give a shear rate at the die capillary of 1.1 to 30 times the published shear rate. Standard industry die configuration, holes sizes, hole shapes, etc. may be used. Many common ones are described in U.S. Patents 2,374,540; 2,411,659; 2,411,660; 2,437,263; 2,508,462; 3,379,811; and 3,502,763. The wetted surfaces should be made of high nickel alloy to keep corrosion to a minimum. It is common practice to use a polymer with high melt flow index for melt blowing, although it is not absolutely necessary for perfluoropolymers since it has been shown here that perfluoropolymers can be processed into fiber at shear rates well above their critical shear rate. Melt flow indexes of 10 to 50 can be processed, however, it may be advantageous to use even higher melt flow index perfluoropolymers, from 50 to 300 melt index and even higher. It may be difficult to polymerize such high melt flow perfluoropolymers since the high concentration of chain transfer agent leads to a very slow reaction rate. It is possible, as per the teaching of Butin et al in U.S. Patent 3,849,241 to decrease the polymer molecular weight during processing. Perfluoropolymers are subject to chain scission and will undergo molecular weight reduction when subjected to shearing and/or high temperature. However, it must be remembered that the decomposition products of perfluoropolymers are toxic, so intentional significant molecular weight reduction during processing can be a safety hazard, and if performed must be done with sufficient ventilation to ensure worker safety. As the polymer exits the die it is contacted by high temperature air, nitrogen, or other gas, heated to 500 to 1000° F, which attenuates the molten strands into fibers. Usually the air (or gas) temperature is slightly higher than the polymer melt temperature, approximately 10 to 50° F for most melt blowing processes, but for perfluoropolymers it can be set even higher, up to 100° F higher than the melt temperature. If the temperature is too high the web becomes very soft and lofty, but fiber breakage occurs and short fibers are carried away from the take up apparatus by the air stream. The fibers are finally collected onto a moving or stationary screen, dmm, conveyor, or other object. Typical polymer throughput rates are 0.1 to 5 grams per minute per nozzle orifice, although they can be higher. The process may be operated at different conditions to give nonwoven fibrous webs having different characteristics. One form of web contains virtually continuous filaments of about 8 to 400 micron diameter. Another web form has very fine non-continuous individual fibers from 0.5 to 5 microns in diameter, with a soft, lofty appearance. This is accomplished primarily by adjusting the airflow rate, although air temperature can be adjusted somewhat also.

To make webs with coarser, 8 to 400 micron diameter fiber a minimum amount of air is used, typically in the range of 2.5 to 40 pounds per minute per square inch of total air slot area (subsonic velocity). The air should be increased so as to prevent fibers from joining and sticking together before reaching the accumulation dmm, belt or screen. Although it is common practice when melt blowing other polymers to place the collection apparatus up to 2 to 3 feet away from the die, for perfluoropolymers it is preferable to maintain a short die to collector distance, from 1 to a few inches. For finer, micro fibrous webs, higher air velocities (sonic velocity) are used, with flow rates of 20 to 150 pounds per minute per air slot area. The speed of the take up apparatus can be adjusted relative to the polymer processing rate to give nonwoven webs in a very wide range of thickness, from 0.0005 to 0.5 inches in diameter. Also, multiple layers can be taken up to give any total thickness desired. The nonwoven web can be further processed, including calendering, spot bonding, drawing, heat treating, hydroentangling, or any other nonwoven fabric process. Examples

Example 1 : Hyflon ® perfluoroalkoxy plastic resin was melts and extmded using conventional perfluoropolymer single screw extruder technology. The molten polymer was extruded through a 218 hole spinnerette die with individual hole diameters of 0.7 mm. The resin melt index was 16 and had a published critical shear rate of about 100 sec^"1. The polymer was processed with a melt temperature controlled at 435° C and a spinnerette temperature controlled at 445° C. Processing speed was approximately 14 pounds per hour, leading to a shear rate at the die orifice of about 112 sec^"1. The filaments were passed through a quench chamber and once cooled were taken up over godets onto a winder at 495 meters per minute, giving a partially oriented yam. The yam was then further drawn 1.67 to 1 producing individual filaments with 5.7 denier per filament. During drawing the fiber was passed across a heated godet at 230° C to heat set the yam. The yam produced had a strength of 0.42 grams per denier as measured on a yam bundle, residual elongation of 52%, shrinkage at 210° C of 2.5%, and shrinkage at 238° C of 15%.

Example 2: The same polymer and extrusion equipment and conditions and spinnerette configuration as Example 1 were used except that the filaments were taken up over a godet at 675 meters per minute, and then were drawn on line at a ratio of 1.37 to 1. The yam was then further drawn off line to produce micro fibers with individual deniers of 3.6 denier per filament (15.4 microns in diameter). Fiber strength as measured on a yam bundle was 0.53 grams per denier with 19% residual elongation.

Example 3: The same polymer, extrusion equipment and conditions and spinnerette configuration as Example 1 was used to produce fiber under a range of feed and melt temperature conditions. The data is shown in Table 1. In all cases the fiber was drawn to a high degree to give low residual elongation, in the range of 16 to 22%. As can be seen the fiber strength is shown to increase as shear rate is increased over the range evaluated. Table 1

Extrusion Melt Spinnerette Take Up Shear Total Denier Residual

Rate Temperature Temperature Speed Rate Draw Per Tenacity** Elongation

Lbs/hour Degrees C Degrees C eters/min Sec-1 Ratio* Filament Gms/denier %

14 437 460 750 1 12 1 74 3 6 0 64 16

19 440 455 750 152 1 87 4 7 0 68 22

21 434 450 750 168 1 5 5 6 0 73 19

28 434 440 1000 224 1 5 6 5 0 75 21

33 450 460 750 264 2 4 5 4 0 82 16

47 450 440 1 150 376 2 3 6 3 0 88 21

* Combines in-line draw with off-line drawing

** Measured on yarn bundles, not individual filaments

Example 4: Hyflon perfluoroalkoxy resin with a melt index of 2.6 and a critical shear rate of about 10 sec^"1, was extmded through the same 218 hole, 0.7 mm diameter spinnerette described in Example 1. Extrusion speed was 10 pounds per hour, giving a shear rate at the die of 80 sec^"1 , approximately 8 times the critical shear rate. Melt temperature was 425° C and spin pack temperature was 435° C. Individual fiber denier was 12.5 with tenacity of 0.26 grams per denier measured on a yam bundle and elongation of 253%

Example 5: The same material was extmded and processed as in Example 4 except that feed rate was increased to 12 pounds per hour (shear rate of 96 sec^"1), the melt temperature was increased to 432° C and the spin pack temperature was increased to 440° C. The fiber was drawn 1.7 to 1. Individual fiber denier was 4.1. Tenacity measured on the ya bundle was 0.43 grams per denier with 86% residual elongation.

Example 6: Hyflon® perfluoroalkoxy resin with a melt index of 12.2 and a critical shear rate of approximately 100 sec^"1 was extruded through a 218 hole spinnerette with individual circular hole diameters of 0.525 mm. The polymer was extmded at 9 pounds per hour giving a shear rate of about 170 sec^"1 at the spinnerette capillaries. The melt temperature was 450° C and the spin block temperature was 470° C. The filaments were passed through a quench chamber and once cooled taken up over godets onto a winder at 400 meters per minute. The yam was further drawn approximately 2.75 to 1 to give a final denier per filament of 3.0. Individual fiber diameters ranged from 12 to 16 microns.

Example 7: Hyflon® perfluoroalkoxy resin with a melt index of 23 can be extmded through a 1090 hole spinnerette with individual circular hole diameters of 0.25 mm. Polymer extmded at 5 pounds per hour gives a shear rate of approximately 175 sec^"1. A melt temperature of 450° C and a spin block temperature of 470° C may be selected. Cooled filaments are taken up over godets and then onto a winder at 195 meters per minute. The yam may be further drawn approximately 2.8 to 1 to give a final denier per filament of about 1.4. Individual fiber diameters average 8 to 10 microns.

Example 8: Perfluoroalkoxy resin with a melt index of 23 is extruded through a 436 hole spinnerette with individual holes being Trilobal shaped (symmetrical "Y" shape).

Each lobe, or leg, of the Trilobal hole is 0.018 inches in length and 0.004 inches in width. Polymer extmded at 18 pounds per hour gives a shear rate of about 325 sec^"1. A melt temperature of 445 °C and a spin block temperature of 465° C are set. Filaments taken up after being cooled are further drawn approximately 2.5 to 1 to give fibers with a final denier per filament of 4 to 5 and with a distinctive non-circular Trilobal shape. The fibers are easily crimped, or textured, using a conventional sniffer box arrangement. Needled felt samples produced from the fiber are much bulkier, with lower overall fabric density.

Claims

The following is claimed:

1. A process to make continuous multifilament yams and staple fibers from melt processable perfluoropolymers at shear rates higher than the published critical shear rate of the polymer, where the melt temperature is set at about 115 ° to 175° C above the melting point of the polymer or higher, with a die or spinnerette temperature set point between 70° C below and 60° C above the melt temperature during processing, where the fiber produced can be further processed such as drawing, heat treating, texturing, air entangling and the like, wherein said perfluoropolymer is selected from the group consisting of copolymers of tetrafluoroethylene with 1 to 5 mole % of at least one perfluoroalkoxyvinylether where the alkyl group has from 1 to 4 carbon atoms, copolymers of tetrafluoroethylene with 2 to 20 mole % of at least one perfluoroolefin having from 3 to 8 carbon atoms, copolymers of tetrafluoroethylene and cyclic perfluorinated dioxoles, and copolymers of tetrarfluoroethylene and other fluorinated modifying monomers possibly containing also hydrogen and/or chlorine atoms.

2. A process to make melt blown fibrous webs from melt processable perfluoropolymers at shear rates higher than the published critical shear rate of the polymer, where the melt temperature is set at about 115 ° to 175° C above the melting point of the polymer or higher, with a die or spinnerette temperature set point between 70° C below and 60° C above the melt temperature during processing, where the web produced can be further processed such as spot bonding, drawing, heat treating, texturing, air entangling, hydro-entangling, calendering and the like, wherein said perfluoropolymer is selected from the group consisting of copolymers of tetrafluoroethylene with 1 to 5 mole % of at least one perfluoroalkoxyvinylether where the alkyl group has from 1 to 4 carbon atoms, copolymers of tetrafluoroethylene with 2 to 20 mole % of at least one perfluoroolefin having from 3 to 8 carbon atoms, copolymers of tetrafluoroethylene and cyclic perfluorinated dioxoles, and copolymers of tetrarfluoroethylene and other fluorinated modifying monomers possibly containing also hydrogen and/or chlorine atoms.

3. A process to make spun bonded fibrous webs from melt processable perfluoropolymers at shear rates higher than the published critical shear rate of the polymer, where the melt temperature is set at about 115 ° to 175° C above the melting point of the polymer or higher, with a die or spinnerette temperature set point between 70° C below and 60° C above the melt temperature during processing, where the web produced can be further processed such as spot bonding, drawing, heat treating, texturing, air entangling, hydro-entangling, calendering and the like, wherein said perfluoropolymer is selected from the group consisting of copolymers of tetrafluoroethylene with 1 to 5 mole % of at least one perfluoroalkoxyvinylether where the alkyl group has from 1 to 4 carbon atoms, copolymers of tetrafluoroethylene with 2 to 20 mole % of at least one perfluoroolefin having from 3 to 8 carbon atoms, copolymers of tetrafluoroethylene and cyclic perfluorinated dioxoles, and copolymers of tetrarfluoroethylene and other fluorinated modifying monomers possibly containing also hydrogen and/or chlorine atoms.

4. A process according to claims 1, 2, and 3 suitable for an initial polymer melt index of 1 to 30.

5. A process according to claims 1 , 2 and 3 suitable for an initial polymer melt index of greater than 30.

6. A process according to claims 1 , 2, 3, 4 and 5 operated with shear rates more than 1.1 times the published critical shear rate of the polymer.

7. A process according to claims 1, 2, 3, 4 and 5 operated with shear rates more than five times the published critical shear rate of the polymer.

8 A process according to claims 1, 2, 3, 4 and 5 operated with shear rates more than

20 times the published critical shear rate of the polymer.

9. A process according to claims 1, 2, 3, 4, and 5 operated at critical shear rates greater than 100 sec -^"1.

10. A process according to claims 1, 2, 3, 4 and 5 operated at critical shear rates greater than 300 sec^"1.

11. A process according to claims 1 , 2, 3, 4 and 5 operated at critical shear rates greater than 2000 sec^"1.

12. A process according to claims 1 through 11 operated with a polymer melt temperature above 400° C, where the die and spin pack temperature are maintained at a temperature between 70° C below the melt temperature and 60° C above the melt temperature.

13. A process according to claims 1 through 11 operated with a polymer melt temperature below 400° C, where the die and spin pack temperature are maintained at a temperature between 1° C and 100 ° C above the melting point temperature of the polymer.

14. A process according to claims 1 through 13 with a fiber take away speed during melt spinning (godet speed) of 25 to 150 meters per minute, in order to produce an unoriented fiber or yarn.

15. A process according to claims 1 through 13 with a fiber take away speed during melt spinning (godet speed) of 100 to 2500 meters per minute, in order to produce a partially oriented fiber or yam.

16. A process according to claims 1 through 13 with a fiber take away speed during melt spinning (godet speed) greater than 1500 meters per minute, in order to produce a fully oriented fiber or yam.

17. A process according to claims 1 through 16, to produce individual filament deniers of 4.5 to 200 denier, with individual filament strengths greater than 0.4 grams per denier and total yam or web strengths greater than 0.3 grams per denier.

18. A process according to claims 1 through 16, to produce individual filament deniers of 4.5 to 200 denier, with individual filament strengths greater than 1.0 grams per denier and total yam or web strengths greater than 0.75 grams per denier.

19. A process according to claims 1 through 16, to produce individual filament deniers of 4.5 to 200 denier, with individual filament strengths greater than 1.5 grams per denier and total yam or web strengths greater than 1.0 grams per denier.

20. A process, according to claims 1 through 16, to produce individual filaments with shrinkage lower than 10% at 200° C.

21. A process, according to claims 1 through 16, to produce individual filaments with shrinkage lower than 5% at 200° C.

22. A process, according to claims 1 through 16, to produce individual filaments with shrinkage lower than 10% at 250° C.

23. A process, according to claims 1 through 22, to make multilobal fibers.

24. A process according to claims 1 through 22 to make hollow fibers.

25. A process according to claims 1 through 22 to make non-circular cross section fibers, including elliptical, angular, multi-component, sheath core, segmented, or dispersed phase ("islands in the sea").

26. A process according to claims 1 through 22 to make micro fibers with individual filament deniers of less than 4.5. melt blown and spun bonded webs having micro fiber individual filaments, with individual filament deniers between 0.01 and 4.5

28. Homofilament perfluoropolymer continuous multifilament yams, staple fibers, and melt blown and spun bonded webs having micro fiber individual filaments, with individual filament deniers between 0.1 and 4

29. Melt processable homofilament perfluoropolymer continuous multifilament yams, staple fibers, and melt blown and spun bonded webs having micro fiber individual filaments, with individual filament deniers between 0.01 and 4.5

30. Melt processable homofilament perfluoropolymer continuous multifilament yarns, staple fibers, and melt blown and spun bonded webs having micro fiber individual filaments, with individual filament deniers between 0.1 and 4

31. Perfluoropolymer continuous multifilament yams, staple fibers, and melt blown and spun bonded webs having multilobal individual filaments.

32. Perfluoropolymer continuous multifilament yams, staple fibers, and melt blown and spun bonded webs having hollow fiber individual filaments with either non- permeable, semi-permeable, or permeable walls, with centers that are either empty or filled with materials such as biological material including living cells and proteins, channels or flow paths, and inner filament(s) or fiber(s) capable of transmitting light, or electrically conductive inner filament(s), or a combination thereof.

33. Melt processable perfluoropolymer continuous multifilament yams, staple fibers, and melt blown and spun bonded webs having multilobal individual filaments.

34. Melt processable perfluoropolymer continuous multifilament ya s, staple fibers, and melt blown and spun bonded webs having hollow fiber individual filaments with either non-permeable, semi-permeable, or permeable walls, with centers that are either empty or filled with materials such as biological material including living cells and proteins, channels or flow paths, and inner filament(s) or fiber(s) capable of transmitting light, or electrically conductive inner filament(s), or a combination thereof.

35. Continuous multifilament yams, staple fibers, and melt blown and spun bonded webs, according to claims 31, 32, 33 and 34, with individual filament deniers 4.5 and 200.

36. Micro fiber continuous multifilament yams, staple fibers, and melt blown and spun bonded webs, according to claims 31, 32, 33 and 34, with individual filament deniers between 0.01 and 4.5

37. Micro fiber continuous multifilament yams, staple fibers, and melt blown and spun bonded webs, according to claims 31, 32, 33 and 34, with individual filament deniers between 0.1 and 4.

38. Continuous multifilament yams, staple fibers, and webs according to claims 27 through 37, with individual filament strengths greater than 0.4 grams per denier and total yam or web strengths greater than 0.3 grams per denier.

39. Continuous multifilament yams, staple fibers, and webs according to claims 27 through 37 with individual filament strengths greater than 1.0 grams per denier and total yam strengths greater than 0.75 Grams per denier.

40. Continuos multifilament yams, staple fibers, and webs according to claims 27 through 37 with individual filament strengths greater than 1.5 grams per denier and total yarn strengths greater than 1.0 grams per denier.

41. Continuous multifilament yams, staple fibers, and webs according to claims 27 through 40 with shrinkage lower than 10% at 200° C.

42. Continuous multifilament yams, staple fibers, and webs according to claims 27 through 40 with shrinkage lower than 5% at 200° C.

43. Continuous multifilament yams, staple fibers, and webs according to claims 27 through 40 with shrinkage lower than 10% at 250° C.