Patent Application
20070248823
Referring now to the attached drawings which form a part of this original disclosure:
Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Referring initially to
A non-hollow fiber in accordance with the present invention contains a fluorine containing polymer. More specifically, a non-hollow fiber in accordance with the present invention preferably contains an ethylenic polymer (Ethylene (Et) Tetrafluoroethylene (TFE) Hexafluoropropylene (HFP), hereinafter referred to as EFEP) that is generally expressed as the following formula:
where l, m, and n are natural numbers and X and Y are functional groups. As mentioned above, a non-hollow fiber 100 in accordance with the present invention is preferably a monofilament fiber. Thus, the fiber 100 is preferably constructed essentially of EFEP. In any case, a non-hollow fiber in accordance with the present invention preferably contains EFEP at least at its entire outer surface such that at least 25% (by weight) of the fiber is preferably constructed of EFEP. Preferably, a non hollow fiber in accordance with the present invention is solely made of EFEP. In other words, as close to 100% of the non-hollow fiber is constructed of EFEP (i.e., except for trace elements and/or impurities) as possible.
The functional groups expressed as X and Y above are preferably carboxyl groups. Such carboxyl groups should preferably include a carbonate group and/or a carboxyl halide group.
The carbonate group in the fluorine containing polymer is generally expressed as
—OC(═O)O—R
where R is a hydrogen atom; or an organic group such as an alkyl group with 1-20 carbon atoms; or an alkyl group with 2-20 carbon atoms and an ether coupling; or an element of the first, second, or the seventh group. Examples of such carbonate group include:
—OC(═O)OCH3;
—OC(═O)OC3H7;
—OC(═O)OC8H17; and
—OC(═O)OCH2CH2OCH2CH3.
The carboxyl halide group is generally expressed as:
—COY
where Y is halogen. Examples of such carboxyl halide group include:
—COCl; and
—COF.
Such EFEP (represented by the above formulae) generally results from copolymerization of, for example, at least: 20 to 90 mole percent of tetrafluoroethylene; 10 to 80 mole percent of ethylene; and 1 to 70 mole percent of a compound represented by the general formula:
CF2═CF—Rf1
where Rf1 represents CF3 or ORf2, Rf2 represents a perfluoroalkyl group having 1 to 5 carbon atoms.
EFEP copolymer should contain preferably 5-20 mol %, more preferably 8-17 mol %, of HFP units. Such EFEP copolymer can contain, in addition to the monomer units that are contributed by TFE, HFP and Et, one type or more than one types of additional monomers, as long as preferable properties of the resulting EFEP copolymer are unaffected. Examples of such additional monomers include trichlorofluoroethylene, propylene, and monomers expressed as the following formulae:
CX32═CX4—(CF2)n-X5
CF2═CF—O—Rf3
where X3 is either a hydrogen atom or a fluorine atom, X4 is either a hydrogen atom or a fluorine atom, with X3 and X4 being either the same or different, X5 is a hydrogen atom, a fluorine atom, or a chlorine atom, and n is a natural number of 1-10, and where Rf3 is a perfluoroalkyl group with carbon number 1-5. It is generally well known how to construct EFEP having the composition described above. Such EFEP is usually produced in pellet form by Daikin Industries, Ltd. (Osaka, Japan).
EFEP constructed as described above has a relatively low melting point, which is approximately between 165° C. and 195° C., i.e., less than 200° C. In any case, EFEP constructed as described above has a melting point below 240° C., preferably well below 240° C. Also, EFEP constructed as described above has is generally known to have desirably adhesive properties (e.g., superior adhesiveness). Finally, EFEP constructed as described above has a relatively low melt index (MI) of about 35. In any case, EFEP constructed as described above has a melt index (MI) below 100.
“Fibers” as used herein include filament fibers as well as staple fibers and yarns made of staple fibers. A “filament fiber” as used herein means a fiber having a continuously elongated shape with an indefinite length. Filament fibers generally have a fineness of approximately 44-700 denier, although the fineness of filaments as used herein is not limited to this range. A “monofilament fiber” as used herein means a filament fiber constructed essentially of a single type of thermoplastic material, as mentioned above. A “staple fiber” as used herein means relatively short pieces of filament fibers that are formed by mechanically cutting or shredding filament fibers or by skiving films. “Fabrics” as used herein include materials that are formed with fibers using woven or knit methods such as weaving, knitting, and plaiting, or with non-woven methods such as carding, felting, air-laying, wet-laying, melt-blowing, needle-punching, hydro-entangling, adhesive bonding, electro-spinning, and solvent-spinning, or using other techniques such as braiding.
Fabrics are made of filament fibers and/or staple fibers. Some of the most common methods of manufacturing fabrics from filament fibers and staple fibers include woven or knit methods such as weaving, knitting, and plaiting, as well as non-woven web forming methods such as carding, needle-punching, air-laying, wet-laying, melt-blowing, hydro-entangling, electro-spinning, solvent spinning and other techniques like braiding. In the non-woven mechanical fabric forming methods, the filaments may be converted into staple fibers and blended with other materials or fibers.
Fabrics can be made from a single type of fiber, or from more than one type of fiber.
The non-woven forming methods can be performed by, for example, a melt-blown process, with molten filaments being laid out to form a fabric made of a single type of fiber, or onto other types of fibers or fabrics such as nylon and/or polyester to form a composite fabric. For example,
Fluorine containing polymer filament fibers including those specifically containing EFEP can be generally manufactured by melting pellets of the fluorine containing polymer (EFEP) and extruding or melt spinning the melted polymer. Monofilament fibers are manufactured using a melt spinning apparatus such as the ones shown in
In melt spinning apparatuses shown in
The melt extrusion process begins as the solid pellets are supplied to the open flights of a rotating extrusion screw inside of a heated metal barrel beneath the pellet feed hopper 1 (feed zone). While the pellets are in the feed zone, the polymer pellets are transported forward and heated without being completely melted. Since the pellets are not totally melted into liquid, the pellets can be transported and move from the deeper flights of the feed zone to the shallower flights of the compression zone by the rotation of the screw. In this manner, these pellets are forced down the hot barrel through the “feed” section into the tighter spaces of the “compression” section of the screw. In the “compression” zone, as the flights of the screw becomes shallower, the core or “root” of the screw becomes thicker thus compressing the pellets together and forcing them into more complete contact with the heated barrel. This close contact to the heat from the metal barrel in the compression zone helps the pellets to melt rapidly. The melting pellets are further transported down the screw, exiting the “compression” section into the final “metering” section, where they complete the melting process and are forced under pressure into the “spinpack”. Once the molten polymer enters the “spinpack,” the pressure is further increased by the “gearpump” in zone #C, which continuously provides a precise amount of molten polymer to the “spinneret”. This spinneret in zone #C acts as an extrusion die with precision holes or shapes of holes drilled or cut through its thickness, through which the polymer is forced under pressure to exit the “spinpack” to form molten filament fibers.
The molten EFEP filament fiber is cooled while being drawn from the spinneret and passed over godets 4 (roll #1 and roll #2). The filament fiber cools and gains strength as it is passed over the godets 4. The speeds at which these godet rolls #1 and #2 operate are independently controlled to allow the filament fiber to accelerate and be stabilized as the filament fiber is wound up onto tubes or bobbins on the winder 5. Furthermore, a spin finish is often applied to the filament fibers to ease downstream processing and handling and/or to ease the removal from the tubes.
When woven or knit fabrics are to be manufactured from the filament fibers, the filament fiber is unwound from these bobbins or tubes to be knit or woven to make a fabric. Non-woven fabrics can also be manufactured from the filament fibers by mechanical forming methods, or combined into composite fabrics using a melt blowing processes.
To manufacture staple fibers out of the filament fiber, the filament fiber is typically fed into a cutting device called a “tow cutter” directly off of the godets 4, instead of being fed into the winder 5, so that the filament fiber is cut into staple pieces and deposited into a storage container. Staple fibers can also be made by cutting filament fibers into small pieces off the bobbins or tubes which have been made using equipment similar to those shown in
An extrusion apparatus for manufacturing EFEP monofilament fibers can be alternatively structured as shown in
As the molten polymer is spun out of the melt die holes, hot air is blown from a hot air supply tube past the die and the molten fiber, which helps to attenuate the molten fiber and reduce its diameter. The hot air also transports the molten fiber from the melt blowing die and deposits it in a random pattern onto a hot melt blowing collection zone of the conveyor belt, creating a non-woven fabric. This hot air accelerates the filaments from the outlet of the extrusion die and reduces substantially the fiber diameter as the cooling fibers are blown out onto the conveyor belt or collection device. The cooling fibers are laid out onto the porous conveyor belt such that the tacky fibers bond to one another and form a strong randomly oriented fabric. The speed at which the conveyor belt operates, die to the collector belt distance (DCD), temperature of the fibers, and the rate with which the molten fiber is forced from the die control the thickness and weight of the non-woven fabric produced with this apparatus. The newly laid non-woven fabric cools as the conveyor moves the fabric away from the hot melt blowing collection zone and allows the fabric to cool and be wound up on a roll or tube for later use or conversion. Extrusion temperatures, hot air temperatures, hole diameter, air gap size, conveyor speed, and melt rheology of the polymer are just some of the variables that can be varied to adjust the quality of the melt blown fabrics.
Examples of monofilament fibers that were manufactured using the extrusion apparatus shown in
During the manufacturing of EFEP monofilament fibers, conditions were varied to produce fibers of varying diameters or denier (grams per 9000 meter of length), tenacity in grams per denier, and elongation to break. These monofilament spinning conditions are shown in table 1-1.
The conditions under which the EFEP fibers shown in table 1-1 were produced are as follows. The extruder barrel temperature setting was 203° C. for zone #A, and 235° C. for zone #B. The temperature at zone #C, which includes the gear pump and the spinneret 3, was varied from 243 to 250° C. The speed of the gear pump 3 was varied in the range of 15 to 25% of the total drive speed. The surface speed of the first position godet roll #1 was varied from 125 to 400 meters per minute (mpm), while the rate of the second godet roll #2 was varied from 150 to 500 mpm. The surface speed of the rotating godet roll #1 was always lower than the surface speed of the rotating godet roll #2 in order to provide tension on the monofilament fiber. In addition, the speed of the surface driven winder 5 was varied from 243 to 608 mpm, while the winder traverse frequency was varied from 25 to 33 hertz. Overall, when the rates of the godets 4 and winder 5 were changed, they were always changed to increase, rather than decrease, the filament speed toward the winder, in order to maintain the fiber tension to the winder 5.
As seen in Table 1-1, samples Nos. 3-7 demonstrated high elongation to break, while sample No. 8 demonstrated high tenacity.
Additional spinning of EFEP fibers using equipment similar to that shown in
Experiments were performed with EFEP RP-5000, available from Daikin America, Inc. (Orangeburg, N.Y.), using polymers with relatively high molecular weight and low melt flow indexes of around 35, on melt blowing equipment similar to that shown in
EFEP polymer pellets were loaded into the feed hopper of the melt blowing machine extruder and melted in a process similar to the melt spinning machine of example #1. Molten EFEP polymer passes from the extruder, thru a ˜200 micron stainless steel screen filter, into the coat hanger style melt blowing die. The pressurized molten EFEP viscous resin is forced into the 10/1 length to diameter (L/D) ratio lead holes, exiting the melt blowing die thru the 120 linearly arranged 0.025 inch (0.635 mm) holes. The hot air (ranging from 277° C. to 329° C.) slows the cooling of the viscous liquid polymer and transports the stretching fibers onto the conveyor belt. This hot air blows the fibers onto the belt while creating a heated environment around the stretching fibers allowing them to reduce in diameter in a controlled way as they leave the melt blowing die holes. Higher air temperatures at the die with increased air velocity created finer diameter fibers. Increasing the air gap around the melt blowing die where the hot air carries the fibers away from the melt blowing die holes also resulted in finer fiber diameter.
RP-5000 EFEP polymer pellets with a melt index of 78.7 were produced by Daikin for melt blowing trials on the same equipment as used in Example #2. The six inch (152.4 mm wide die) melt blowing machine with a 1.25 inch (˜32 mm) diameter single screw extruder with 30/1 L/D was set up using a 120 hole melt blowing die with 25 mil (0.635 mm) orifices and 0.1 inch (2.54 mm) air gap with a 10 inch (25.4 cm) die to collector distance (DCD), in this case the collector was a continuous loop take up belt. Higher production rates were obtained with the 78.7 MI EFEP resin with extruder rpm of over 8.4 and conveyor belt speeds of over 3.5 meters per minute.
With improved operating conditions nonwoven webs with fiber diameters as low as 4.5 microns were able to be produced with average diameters as low as 6.39 micron for sample MB2-6 as evidenced by fiber diameter analysis using an electron microscope in Table 1-4. The webs produced in Example #3 had very good fiber diameter uniformity with sample MB2-6 varying approximately +/−2.5 micron from the average diameter of 6.39 micron (Table 1-4).
It is important to note that the melt index of the improved EFEP RP-5000 polymer used in Example #3 was well below 100. High quality nonwovens were produced, with fiber diameters below 7 microns, with low airflow resistance (Table 1-5). Nonwoven samples MB2-3 and MB2-6 also had with good first pass collection efficiencies over a wide range of particle sizes using an ASHRAE 52.2 test method (Table 1-6). It is important to note that the collection efficiencies method by which samples MB2-3 and MB2-6 were evaluated was using a modified ASHRAE 52.2 procedure that tested only for initial collection efficiency without the benefits of accumulated dust cake loadings. It is well know to those skilled in the art that the dust cake loading build up of previous exposures to dirt, or particles in filter testing often substantially increases overall collection efficiency ratings of filters. In many cases collection efficiencies of first pass tests, like those detailed in table 1-6, will double or exponentially improve collection of particles as the “seasoning” process of previous captured dirt blocks filter passages and renders the filter more efficient, as well as increasing pressure drop or resistance to airflow.
The melt index (MI) referred to herein refers the number of grams of the material that can be forced through the ASTM recommended orifice in 10 minutes using the ASTM recommended temperature and pressure (i.e., using ASTM standards for the material). The melt indices (MI) of the fluorine containing copolymers disclosed herein are preferably below 100 as indicated above (e.g. about 35 or about 78).
As used herein, the following directional terms “forward, rearward, above, downward, vertical, horizontal, below and transverse” as well as any other similar directional terms refer to those directions of a device equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a device equipped with the present invention.
The term “configured” as used herein to describe a component, section or part of a device includes hardware and/or software that is constructed and/or programmed to carry out the desired function.
Moreover, terms that are expressed as “means-plus function” in the claims should include any structure that can be utilized to carry out the function of that part of the present invention.
The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.
While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments.
This application claims benefit of U.S. Provisional Application No. 60/794,101 filed on Apr. 24, 2006. The entire disclosure of U.S. Provisional Application No. 60/794,101 is hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60794101 | Apr 2006 | US |
