US3756441A - Flash spinning process - Google Patents

Flash spinning process Download PDF

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US3756441A
US3756441A US00280202A US3756441DA US3756441A US 3756441 A US3756441 A US 3756441A US 00280202 A US00280202 A US 00280202A US 3756441D A US3756441D A US 3756441DA US 3756441 A US3756441 A US 3756441A
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solution
pressure
temperature
mfr
polymer
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R Anderson
R Woodell
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C3/00—Structural elongated elements designed for load-supporting
    • E04C3/02—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces
    • E04C3/12—Joists; Girders, trusses, or trusslike structures, e.g. prefabricated; Lintels; Transoms; Braces of wood, e.g. with reinforcements, with tensioning members
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/11—Flash-spinning
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/04—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F6/30—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising olefins as the major constituent
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
    • E04B1/00—Constructions in general; Structures which are not restricted either to walls, e.g. partitions, or floors or ceilings or roofs
    • E04B1/18—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons
    • E04B1/26—Structures comprising elongated load-supporting parts, e.g. columns, girders, skeletons the supporting parts consisting of wood
    • E04B1/2604—Connections specially adapted therefor

Definitions

  • ABSTRACT MFR/c B 1.13-0.04 (T-220) where MFR is the melt flow rate of the isotactic polypropylene at the instant of extrusion, with 2 s 24 MFR s 30, c is the concentration of the isotactic polypropylene in the solution, expressed in weight percent, and T is the temperature of the solution in C.
  • FIG-3 Ill PRESS PSI A PATENTEUSEP. 4m; I 3.756441 SHEET 3 OF 3 FIG-4 FLASH SPINNING PROCESS BACKGROUND OF THE INVENTION 1.
  • This invention relates to a process for preparing a high quality plexifilamentary product from isotactic polypropylene. More particularly, the invention is concerned with the flash-extrusion of solutions of isotactic polypropylene in trichlorofluoromethane under certain specified conditions.
  • the resulting multifibrous yarn-like strand has an internal fine structure of morphology characterized as a three-dimensional integral plexus consisting of a multitude of essentially longitudinally extended, interconnecting, random-length, fibrous elements referred to as film-fibrils.
  • filmfibrils have the form of thin ribbons of a thickness less than four microns which intermittently unite and separate at irregular intervals called tie points in various places throughout the width, length, and thickness of the strand to form the integral three-dimensional plexus.
  • the fibrous strand comprising a threedimensional network of film-fibril elements is referred to as a plexifilament and has utilities similar to those of spun staple textile yarns.
  • these interconnected fibrous networks may be spread laterally, as by extruding through slot-shaped post-orifice shrouds or by impinging the nascent strand on a solid deflecting surface, to form continuous plexifilamentary webs which may be deposited on a belt to form highly desirable nonwoven sheet structures.
  • Certain plexifilamentary structures are desirably prepared from isotacttc polypropylene, a relatively inexpensive polymer which provides improved creep resistance, higher resilience, and higher melting point as compared to plexifilaments of, e.g.,' linear polyethylene.
  • isotacttc polypropylene a relatively inexpensive polymer which provides improved creep resistance, higher resilience, and higher melting point as compared to plexifilaments of, e.g.,' linear polyethylene.
  • FIG. 3 is a cross-sectional view of a spinneret having a letdown chamber suitable for spinning transient twophase solutions, according to one of the preferred processes of this invention.
  • FIG. 4 is a graph showing combinations of temperature and pressure for a'blend of isotactic polypropylene and trichlorofluoromethane when heated in a closed vessel.
  • FIG. 5 is a diagram of a convex slot shroud, as employed in several of the Examples hereinafter.
  • FIG. 1 is a graphical representation of the parameters (MFR/c) and T depicting the results for some 70 flash extrusion experiments detailed in the examples included hereinafter.
  • MFR/c parameters
  • T parameters parameters-has some finite width rather than the infinite sharpness of a geometrical line.
  • This feature is suggested in FIG. 1 by the shaded band which covers all conditions within percent of the key relationship boundary line. However, even within this boundary region, the morphology of the product is predicted correctly most of time.
  • the isotactic propylene polymer employed in this invention is not necessarily composed of 100 percent propylene units.
  • the polymer may have as much as 15 percent by weight of units derived from other ethylenically unsaturated monomers such as ethylene, isobutylene, vinyl acetate, or methyl methacrylate.
  • the polymer may contain some nonisotactic polypropylene units.
  • isotactic polypropylene as used herein refers to such polymers containing at least percent by weight, of isotactic polypropylene macromolecules. A further description is given by Natta et al. in US. Pat. No. 3,l66,608.
  • the polymer in the solution to be flash extruded should have a MFR high enough to satisfy the abovedescribed key relationship at the particular concentration and solution temperature chosen, but preferably not substantially in excess of MFR 30, since otherwise the physical properties-particularly the tenacitiesof the resulting plexifilamentary products drop off to unattractive levels simultaneously with a deterioration of the morphology of the yarn (degrees and uniformities of fibrillation).
  • the MFR of the polymer is determined according to ASTM method 123 8T Condition L.
  • lsotactic polypropylene with MFR meeting the above conditions may be employed directly in making up the flash spinning solutions or alternatively and preferably, isotactic polypropylene of lower initial MFR may be employed and be deliberately thermally degraded to the required MFR during solution preparation, storage, and transfer to the extrusion orifice.
  • the MFR of the isotactic polypropylene in solution just prior to extrusion is inferred by running the ASTM test on the quenched and dried (solvent free) plexifilamentary product produced on flash extrusion.
  • high quality plexifilament means a continuous, three-dimensional, interconnected strand or web of film-fibrils which is highly fibrillated, i.e., is substantially free of foamy material but not over-fibrillated, i.e., is not shredded or torn apart, has substantially all its film-fibrils interconnected at both ends, and is produced without generation of appreciable quantities of loose particles (fly).
  • Such a high quality plexifilament is also described herein as a product having good morphology.
  • the polymer and solvent are mixed by any of a number of known methods.
  • powdered isotactic polypropylene may be blended with liquid trichlorofluoromethane at room temperature to form a dispersion.
  • the resulting dispersion (slurry) may then be heated with stirring in the vessel which is to serve as a supply reservoir for spinning, or it may be continuously pumped through a heat exchanger to a spinneret or spinning cell.
  • the solution should be delivered to the spinneret at a temperature of at least 200C. and at a pressure greater than the two-liquid-phase boundary pressure described in subsequent paragraphs.
  • this pressure is above 900 psig and is well above the vapor pressure of the solvent.
  • This superautogenous pressure can be created by pressurizing the system with an inert gas such as nitrogen.
  • the inert gas should preferably not be mixed with the solution but rather should be present as a force pressing against it. No upper pressure limit exists, of course, save those imposed by the equipment design.
  • the required superautogenous pressure can be generated (1) by mechanical means such as one or more pumps or (2) by heating the blend to the desired temperature in a vessel filled with the blend such that thermal expansion of the confined blend generates sufficient pressure to prevent formation of any gas phase above the solution at the desired extrusion temperature.
  • Trichlorofluoromethane has only limited solvent power for isotactic polypropylene, i.e., it dissolves appreciable quantities of polymer only at temperatures above its normal boiling point and at superatmospheric pressures. However, at progressively higher temperatures the solvent power again decreases (as thermal expansion tends to decrease the solvent density) and such super-hot flash spinning solutions generally form cloudy dispersions which, if allowed to stand without adequate agitation, separate into two distinct layers, one being polymer-rich and the other being polymer-lean. This partial dissolution may be avoided by applying still higher super-autogenous pressure to the system to prevent the solvent density decrease and loss of solvent power and thus maintain a single phase solution.
  • Such single phase solutions are preferred in order to avoid the undesirable discontinuities which otherwise could occur in attempting to store, transfer and extrude a gross two-phase system of nonuniform composition.
  • each curve represents a series of pressure/temperature combinations which are herein referred to as the twoliquid-phase pressure boundary.
  • the two-liquidphase pressure boundary for a 10 percent solution of a given sample of isotactic polypropylene in trichlorofluoromethane at various temperatures is represented by line L.
  • the system at equilibrium under all temperature-pressure combinations to the left of line L consists of two liquid phases: a polymer-rich liquid, and a polymer-lean liquid.
  • under temperature-pressure combinations to the right of line L the system consists of a single liquid phase.
  • the solution in the main reservoir and solution transfer lines upstream of the inlet orifice to the pressure letdown chamber should have a temperature-pressure relationship corresponding to a point within the area to the right of line L.
  • the solution might be maintained at a temperature of 220C. and a pressure of 1,600 psig as indicated by point Y on the graph. Under these conditions the solution consists of a single liquid phase.
  • the solution When such a solution passes through a properly sized inlet orifice into the pressure letdown chamber, its pressure can be madeto drop, for example, to 1,200 psig, while the temperature drops only slightly, e.g., 1 to 2C., as represented by point Z on the graph.
  • the solution consists of two-liquid phases in the form of a very fine dispersion.
  • the continuous phase is a solution of isotactic polypropylene of relatively high concentration as compared to the dispersed phase.
  • the dispersed phase is essentially pure solvent with a very small amount of polymer dissolved therein.
  • the volume of the letdown chamber should be selected such that the residence time of the two-phase solution within the letdown chamber will be sufficiently brief to avoid separation of the two phases into distinct layers.
  • such residence time is preferably kept below 30 seconds.
  • the solution passes through the final constriction, i.e., the spinneret orifice, into the atmosphere in a very finely divided dispersed form, and the solvent evaporates instantaneously giving a highly fibrillated strand of polypropylene.
  • the residence time in the letdown zone substantially exceeds 30 seconds, the two phases are likely to separate into layers or into large droplets. Commonly a strand produced under the latter conditions would be discontinuous or otherwise possess nonuniform morphology.
  • the location of the two-liquid-phase pressure boundary may be established for a given polymer batch and solvent combination by observing the solution at various temperatures and pressures through a highpressure sight glass in an apparatus equipped with a mechanical pump or other means for providing the necessary superautogenous pressures. At pressures above the two-liquid-phase pressure boundary, the solution will be clear; at pressures below the two-liquidphase pressure boundary the solution will be cloudy.
  • the phase boundary (temperature and pressure) for a given set of conditions is read at the point where incipient cloudiness of the solution in the sight tube is first observed.
  • a graph may be constructed by plotting the boundary pressure for each temperature as in line I of FIG. 2. It is desirable to observe the solutions under static conditions as well as under flow.
  • a needle valve can be used in place of the spinneret, and this valve may be closed while the solution is being observed through the sight glass.
  • batch extrusion experiments may for convenience employ nitrogen gas to maintain a selected superautogenous pressure during extrusion of the solution
  • the gas simply exerts a pressure on the surface of the solution and dissolution of the gas in the system is minimized by avoiding stirring of the gaspressurized system and minimizing the exposure time of the system to the gas.
  • mechanical means such as pistons or screw extruders for building up pressures in commercial processes.
  • the spinnable concentrations for flash spinning are advantageously above the level of 10 percent polymer in solution.
  • concentrations usually below 2 percent
  • another phase boundary will be found in which the phase relationships are reversed from those discussed in the preceding paragraphs.
  • the dispersed phase will consist of a small percent polymer in solution while the continuous phase will consist mainly of clear solvent.
  • the pressure boundary curves will move closer to the autogenous vapor pressure curve A as lower concentrations are used.
  • solutions or dispersions having such low polymer concentration i.e., less than 2 percent, ordinarily do not give continuous fibrillated strands of uniform morphology and hence are unsuitable in the practice of this invention.
  • an upper polymer concentration level of percent is provided.
  • a batch process is used for preparing solutions, and a thermal-expansion technique is employed for generating the required superautogenous pressures.
  • a thermal-expansion technique is employed for generating the required superautogenous pressures.
  • it is important to charge a sufiicient quantity of polymer and solvent such that thermal expansion of the mixture will completely fill the autoclave when the temperature reaches some intermediate value. Further heating of the confined solution will generate the required superautogenous pressure when the desired extrusion temperature is reached.
  • the required amount of material may be closely estimated if the density of the solution is known for the desired spinning temperature and pressure. Use of a slight excess of material is recommended, since any excess pressure may be released by venting a small amount of solution during the heating operation.
  • pressure is plotted versus temperature for a blend of 10 percent polypropylene and percent trichlorofluoromethane heated while confined in an autoclave.
  • Isotactic polypropylene weighing, for example, 2,050 g. is added to a steam jacketed, stirred autoclave containing a void space of 18,000 ml.
  • the autoclave containing the polymer is then evacuated to remove the air and 18,450 grams of Freon-l1" trichlorofluoromethane solvent is added while the autoclave is under vacuum.
  • the autoclave is then closed.
  • the agitator is turned on and the autoclave heated as rapidly as possible while a graph of the temperature and pressure is made during the heat-up cycle.
  • Line Q of FIG. 4 represents the vapor pressure of solvent at various temperatures during the first stage of the heating cycle. Departure of the pressure level from the vapor pressure curve for Freon-ll at R defines the temperature and pressure conditions at the point of filling" the autoclave, i.e., the point at which the solvent vapor phase disappears. As the heating is continued, the pressure rises sharply. If no material is released from the autoclave the temperature and pressure combinations shown by line S will be recorded. It should be understood that a family of curves similar to line S will be generated by charging various amounts of ingredi ents. The temperature required for filling the auto clave will increase as the amount of ingredients decreases.
  • Excessive pressure may be released by bleeding off small portions of the material from the autoclave from time to time. In order not to alter the relative quantities of polymer and solvent, it is desirable that this bleeding not be required until after the polymer has dissolved, which occurs rapidly at a temperature of about I 10C. When the correct quantity of ingredients has been charged, bleeding the autoclave will not be necessary before reaching a temperature of approximately 180C. as indicated in FIG. 4.
  • the agitator is stopped and the solution is pressurized with nitrogen gas to the desired extrusion pressure, e.g., a pressure to 200 psig above the two-phase boundary pressure. Stirring is avoided from this point on to prevent mixing and dissolution of the nitrogen gas in the solution.
  • the applied nitrogen pressure within the autoclave is maintained constant during spinning.
  • EXAMPLE 1 A series of solutions of isotactic polypropylene and trichlorofluoromethane was prepared at various concentrations from several commercial sources of polymer, as described in Table 1A. These solutions were prepared in a five-gallon autoclave by the filled-system technique described above. The computed quantities of polymer and solvent were charged into the autoclave which was then sealed, and stirring and heating commenced to reach the fill-point temperature of approximately 160C. (corresponding to point R of FIG. 4) in about twenty minutes. Further heating to reach the spinning temperature of 220C. required a minimum of about 70 minutes additional time, and even longer heating times were sometimes employed when additional polymer degradation in solution was desired.
  • the spinneret assemblies employed included a pressure letdown chamber as shown at 13 in FIG. 3 and preceded by a letdown orifice 12 and leading to a spinneret orifice l4 terminating in an exit (slot) shroud 16. All the runs except No. 6 employed a rectangular slot shroud, i.e., the exit face is flat and perpendicular to the axis of the cylindrical spinneret orifice, which is centrally located in the bottom of the slot shroud, as indicated in the FIG. 3 side view.
  • Run No. 6 employed a convex shroud, i.e., the exit face is a spherical segment such that the ends of the slot are shallower than the central portion (which is directly in line with the spinneret axis), as illustrated in FIG. 5.
  • the function of these shrouds is to spread the expanding vaporizing solution laterally in order to generate a web-shaped plexifilament.
  • Table 1B The pertinent dimensions of the spinnerets employed for each run are tabulated in Table 1B.
  • EXAMPLE 11 Another series of flash extrusion experiments employing isotactic polypropylene/trichlorofluoromethane was conducted in a 20-gallon autoclave employing filling and heating techniques similar to those described above. However, in order to explore extrusion performance at higher temperatures, the maximum autoclave solution temperature for this series was generally held between -200C. (where polymer degradation rates are not excessive) and the autoclave was connected to the spinneret by a heated l86-inch long %-inch diameter transfer line whereby the solution temperature could be raised rapidly during flow through the line to extrusion temperatures between 220-240C. with minimum exposure time to these polymer-degrading temperatures.
  • a process for the flash spinning of high quality plexifilamentary material which comprises in sequence:
  • melt flow rate (MFR) of the isotactic polypropylene fulfills the following formula:
  • step (2) an before step (3), the solution is passed through a pressure letdown chamber where the pressure on the solution is lowered to a point at which the solution forms a two-phase liquid, said solution remaining in said letdown chamber not more than 30 seconds.
  • step (2) 8. The process of claim 6 wherein the temperature of the solution in step (2) is between about 220 and 235C.

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US00280202A 1972-08-14 1972-08-14 Flash spinning process Expired - Lifetime US3756441A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010229A (en) * 1974-01-18 1977-03-01 Solvay & Cie Process for the manufacture of short fibrils
US4127623A (en) * 1974-08-03 1978-11-28 Sumitomo Chemical Company, Limited Process for producing polyolefin short fibers
US4352650A (en) * 1981-03-24 1982-10-05 E. I. Du Pont De Nemours And Company Nozzle for flash-extrusion apparatus
US4810440A (en) * 1986-06-26 1989-03-07 Kanegafuchi Kagaku Kogyo Kabushiki Kaisha Process for pre-expanding thermoplastic resin particles
US5030403A (en) * 1989-01-17 1991-07-09 Ppg Industries, Inc. Method for making polymeric fibrils
US5032326A (en) * 1988-08-31 1991-07-16 E. I. Du Pont De Nemours And Company Flash-spinning of polymeric plexifilaments
US5227103A (en) * 1990-02-07 1993-07-13 E. I. Du Pont De Nemours And Company High speed insulated conductors
US5286422A (en) * 1991-08-03 1994-02-15 Asahi Kasei Kogyo Kabushiki Kaisha Process for producing three-dimensional fiber using a halogen group solvent
US5436074A (en) * 1989-07-12 1995-07-25 Asahi Kasei Kogyo Kabushiki Kaisha Polypropylene highly spread plexifilamentary fiber
US5512357A (en) * 1987-06-20 1996-04-30 Asahi Kasei Kogyo Kabushiki Kaisha Polypropylene flexifilamentary fiber containing 0.1 to 10 weight percent of an organic spreading agent and nonwoven fabric made therefrom
WO1997005307A1 (en) * 1995-07-28 1997-02-13 E.I. Du Pont De Nemours And Company Process for modifying porosity in sheet made from flash spinning olefin polymer
WO1997049846A1 (en) * 1996-06-27 1997-12-31 E.I. Du Pont De Nemours And Company Spinneret for flash-spinning
US6153134A (en) * 1998-12-15 2000-11-28 E. I. Du Pont De Nemours And Company Flash spinning process

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6233816A (ja) * 1985-08-06 1987-02-13 Asahi Chem Ind Co Ltd フイブリル化繊維の製造方法
JP2617962B2 (ja) * 1987-06-20 1997-06-11 旭化成工業株式会社 ポリプロピレンフィブリル化繊維及びその製造方法
JP2617961B2 (ja) * 1987-06-26 1997-06-11 旭化成工業株式会社 ポリプロピレン高開繊網状繊維及びその製造方法
CN107206540B (zh) * 2015-02-05 2019-08-27 本田技研工业株式会社 机器人选择方法和机器人选择设备

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3227794A (en) * 1962-11-23 1966-01-04 Du Pont Process and apparatus for flash spinning of fibrillated plexifilamentary material
US3467744A (en) * 1968-10-15 1969-09-16 Du Pont Process for flash spinning polypropylene plexifilament
US3564088A (en) * 1968-10-15 1971-02-16 Du Pont Process for flash spinning an integral web of polypropylene plexifilaments

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3227794A (en) * 1962-11-23 1966-01-04 Du Pont Process and apparatus for flash spinning of fibrillated plexifilamentary material
US3467744A (en) * 1968-10-15 1969-09-16 Du Pont Process for flash spinning polypropylene plexifilament
US3564088A (en) * 1968-10-15 1971-02-16 Du Pont Process for flash spinning an integral web of polypropylene plexifilaments

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4010229A (en) * 1974-01-18 1977-03-01 Solvay & Cie Process for the manufacture of short fibrils
US4127623A (en) * 1974-08-03 1978-11-28 Sumitomo Chemical Company, Limited Process for producing polyolefin short fibers
US4352650A (en) * 1981-03-24 1982-10-05 E. I. Du Pont De Nemours And Company Nozzle for flash-extrusion apparatus
US4810440A (en) * 1986-06-26 1989-03-07 Kanegafuchi Kagaku Kogyo Kabushiki Kaisha Process for pre-expanding thermoplastic resin particles
US5512357A (en) * 1987-06-20 1996-04-30 Asahi Kasei Kogyo Kabushiki Kaisha Polypropylene flexifilamentary fiber containing 0.1 to 10 weight percent of an organic spreading agent and nonwoven fabric made therefrom
US5032326A (en) * 1988-08-31 1991-07-16 E. I. Du Pont De Nemours And Company Flash-spinning of polymeric plexifilaments
US5030403A (en) * 1989-01-17 1991-07-09 Ppg Industries, Inc. Method for making polymeric fibrils
US5436074A (en) * 1989-07-12 1995-07-25 Asahi Kasei Kogyo Kabushiki Kaisha Polypropylene highly spread plexifilamentary fiber
US5227103A (en) * 1990-02-07 1993-07-13 E. I. Du Pont De Nemours And Company High speed insulated conductors
US5369165A (en) * 1991-08-03 1994-11-29 Asahi Kasei Kogyo Kabushiki Kaisha Polyolefin solution using halogen group solvents
US5286422A (en) * 1991-08-03 1994-02-15 Asahi Kasei Kogyo Kabushiki Kaisha Process for producing three-dimensional fiber using a halogen group solvent
WO1997005307A1 (en) * 1995-07-28 1997-02-13 E.I. Du Pont De Nemours And Company Process for modifying porosity in sheet made from flash spinning olefin polymer
US5833900A (en) * 1995-07-28 1998-11-10 E. I. Du Pont De Nemours And Company Process for modifying porosity in sheet made from flash spinning olefin polymer
WO1997049846A1 (en) * 1996-06-27 1997-12-31 E.I. Du Pont De Nemours And Company Spinneret for flash-spinning
US5788993A (en) * 1996-06-27 1998-08-04 E. I. Du Pont De Nemours And Company Spinneret with slotted outlet
US6153134A (en) * 1998-12-15 2000-11-28 E. I. Du Pont De Nemours And Company Flash spinning process

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Publication number Publication date
CA1005610A (en) 1977-02-22
IT1006073B (it) 1976-09-30
LU68235A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1973-10-23
FR2196362B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1978-02-10
GB1430165A (en) 1976-03-31
JPS4942917A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1974-04-23
DE2341086A1 (de) 1974-02-28
FR2196362A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1974-03-15
BE803608A (fr) 1974-02-14
NL7311211A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1974-02-18
AR195854A1 (es) 1973-11-09

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