WO1983001925A1 - Method and apparatus for producing plastic microfilaments - Google Patents

Method and apparatus for producing plastic microfilaments Download PDF

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Publication number
WO1983001925A1
WO1983001925A1 PCT/US1982/001616 US8201616W WO8301925A1 WO 1983001925 A1 WO1983001925 A1 WO 1983001925A1 US 8201616 W US8201616 W US 8201616W WO 8301925 A1 WO8301925 A1 WO 8301925A1
Authority
WO
WIPO (PCT)
Prior art keywords
plastic
nozzle
cylinder
microfilaments
orifice
Prior art date
Application number
PCT/US1982/001616
Other languages
French (fr)
Inventor
Leonard B Torobin
Original Assignee
Torobin, Leonard, B.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US06/325,594 external-priority patent/US4363646A/en
Priority claimed from US06/442,108 external-priority patent/US4536361A/en
Application filed by Torobin, Leonard, B. filed Critical Torobin, Leonard, B.
Priority to AU10446/83A priority Critical patent/AU1044683A/en
Publication of WO1983001925A1 publication Critical patent/WO1983001925A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/075—Manufacture of non-optical fibres or filaments consisting of different sorts of glass or characterised by shape, e.g. undulated fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/065—Spherical particles
    • B22F1/0655—Hollow particles
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/06—Manufacture of glass fibres or filaments by blasting or blowing molten glass, e.g. for making staple fibres
    • 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
    • D01D5/08—Melt spinning methods
    • D01D5/098—Melt spinning methods with simultaneous stretching
    • D01D5/0985—Melt spinning methods with simultaneous stretching by means of a flowing gas (e.g. melt-blowing)
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H13/00—Other non-woven fabrics
    • D04H13/02—Production of non-woven fabrics by partial defibrillation of oriented thermoplastics films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • B22F2009/088—Fluid nozzles, e.g. angle, distance
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/02—External structure or shape details
    • C03B2203/06—Axial perturbations, e.g. twist, by torsion, undulating, crimped
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C03B2203/14—Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
    • C03B2203/16—Hollow core

Definitions

  • No. 325,594 is a continuation-in-part of applicant's application Serial No. 152,693, filed May 23, 1980, which is a continuation of Serial No. 059,297, filed July 20, 1979
  • Application Serial No. is a continuation of application Serial No. 103,113, filed December 13, 1979, which is a divisional of application Serial No. 059,296 filed July 20, 1979.
  • the application Serial No. 059,297 and the application Serial No. 059,296 are each continuation in-part applications of Serial Nos. 937,123 and 944,643 filed August 28, 1978 and September 21, 1978, respectively.
  • the present invention relates to a method and apparatus for making microfilaments from organic film forming materials or compositions and particularly for making plastic microfilaments.
  • the present invention also relates to plastic microfilaments spun into fibers for the manufacture of woven plastic fabrics or rope and for the manufacture of matted fabrics.
  • the present invention also relates to plastic microfilaments used to make an improved reinforcing and filler material.
  • the present invention also relates to plastic microfilaments suitable for use as filler material and reinforcing materi-il in rubber, plastics, concrete and asphalt compositions.
  • the present invention particularly relates to a method and. apparatus for using a .coaxial blowing nozzle to blow plastic microfilaments from liquid plastic compositions comprising forming an elongated hollow tube or cylinder of said plastic composition and subjecting the tube or cylinder during its formation to an external pulsating or fluctuating pressure field having periodic oscillations.
  • the pulsating or fluctuating pressure field produces a laminar flow of entraining fluid in the vicinity of the forming elongated tube or cylinder which laminar flow assists in the formation of the tube or cylinder and in detaching the microfilaments from the blowing nozzle.
  • the invention more particularly relates to a method and apparatus for blowing microfilaments from plastic film forming compositions.
  • Means are provided for forming"a thinned wall or weakened portion of the forming elongated hollow plastic tube or cylinder.
  • the thinned wall or weakened portion of the elongated plastic tube or cylinder causes a longitudinal break along the length of the elongated plastic tube or cylinder.
  • the pulsating or fluctuating pressure field causes the broken elongated tube or cylinder to flap and to form a multiplicity of small diameter plastic microfilaments
  • the continued feeding of liquid plastic to the coaxial nozzle stabilizes the longitudinal break in the elongated tube or cylinder a short distance below the coaxial nozzle.
  • the plastic microfilaments are entrained in the entraining fluid, increase in length, are stretched and pulled and break away from the portion of the elongated cylinder attached to the coaxial nozzle.
  • a transverse jet is used to induce the external pulsating or fluctuating pressure field by directing the entraining fluid over and around the blowing nozzle at an angle to the axis of the blowing nozzle.
  • the entraining fluid as it passes over ' nd around the blowing nozzle envelops and acts on the liquid plastic as it is being
  • Quench or heating means may be disposed close to and below the blowing nozzles to direct a quench or heating fluid onto the microfilaments to rapidly cool or heat and cure, solidify and harden the microfilaments.
  • the process and apparatus of the present invention are believed to overcome the disadvantages of the prior art processes and are capable of producing microfilaments of uniform diameter and relatively uniform length of controlled and predictable physical and chemical character ⁇ istics, quality and strength at economical low costs.
  • the present invention relates to plastic micro ⁇ filaments and to a process and apparatus for making the microfilaments.
  • microfilaments are preferably made from ther o- setting or -thermoplastic compositions.
  • the plastic microfilaments of the present invention are made by forming a liquid film of thermoplastic or thermosetting plastic composition across a coaxial blowing nozzle, applying a blowing gas or an inert blowing gas at a positive pressure on the inner surface of the plastic film to blow the film and form an elongated hollow tube or cylinder shaped liquid film of liquid plastic.
  • the elongated tube or cylinder is initially closed at its outer end and is attached at its inner end to the coaxial blowing nozzle.
  • Means are provided in the coaxial blowing nozzle for forming a thinned wall or weakened portion of the forming elongated tube or cylinder.
  • a transverse jet is used to direct an entraining fluid over and around the blowing nozzle.
  • the entraining fluid as it passes over and around the blowing nozzle fluid dynamically induces a pulsating or fluctuating pressure field at the opposite or lee side of the blowing nozzle in the wake or shadow of the coaxial blowing nozzle and produces a laminar flow of entraining fluid in the area of the forming elongated tube or cylinder.
  • the fluctuating pressure field has regular periodic lateral oscillations similar to those of a flag flapping in a breeze.
  • the continued movement of the entraining fluid over the elongated cylinder produces asymmetric fluid drag forces on the cylinder, and at the thinned walled or weakened portion longitudinally breaks the cylinder to from a multiplicity of plastic microfilament and detaches the microfilaments from the elongated cylinder and from the coaxial blowing nozzle and the detached filaments are carried away from the blowing nozzle.
  • the surface tension forces of the liquid plastic composition act on the microfilament and causes the diameter of the microfilament to seek a minimum surface area and to form a circular cross-section.
  • the thin walled or weakend section of the elongated cylinder causes the cylinder to break along its longitudinal length.
  • the induced fluctuating pressure field causes the elongated cylinder to flap and to quickly enlarge the break and to form a multiplicity of small diameter microfilaments.
  • the break proceeds up the length of the elongated cylinder towards the coaxial nozzle.
  • the continued feeding of liquid plastic to the coaxial nozzle stabilizes the break a short distance below the coaxial nozzle.
  • the micro ⁇ filaments are entrained in the transverse jet entraining fluid, are stretched, increase in length and pulled and break away from the portion of the elongated cylinder attached to the coaxial blowing nozzle.
  • the means for providing the thinned wall or weakened portion of the forming elongated hollow tube or cylinder may be contained within the coaxial blowing nozzle in the annular space between the outer coaxial nozzle and the inner coaxial -nozzle.
  • the means provided may take the form of one or more thickened or enlarged portions of the inner nozzle-disposed lengthwise on the outer surface of the inner nozzle. The length, diameter and height of the thickened or enlarged portions are such that they cause the flow of liquid plastic as it passes over and around the thickened or enlarged portions to become thinned and weakened.
  • the thinned and weakened portion of the liquid plastic is carried downwardly and outwardly into the forming elongated hollow cylinder or tube.
  • the thickened portion of the inner nozzle is disposed at or near the outer edge of the inner nozzle.
  • the liquid plastic temperature and feed rate, the transverse jet entraining fluid linear velocity, the blowing gas pressure and the quench rate at a given coaxial nozzle gap will to some extent determine the microfilament length and diameter and size distribution.
  • a balancing but slightly lower gas pressure than the blowing gas pressure is provided in the area in which the elongated cylinder is formed.
  • Quench nozzles where the plastic is thermoplastic and heating nozzles where the plastic is thermosetting may be disposed below and on either side of the blowing nozzle to direct cooling or heating fluid at and into
  • the microfilaments may be heated and cured and the cured plastic microfilament can be subsequently cooled.
  • the present invention overcomes may of the problems associated with prior attempts to produce plastic micro ⁇ filaments and fibers.
  • the process and apparatus of the present invention allows the production of plastic micro ⁇ filaments of relatively long length ⁇ a d relatively uniform diameter such that superior structural materials and improved filler and reinforcing materials can be designed, manufactured and tailor made to suit a particular desired use.
  • the relatively long plastic microfilaments produced in accordance with the present invention have the distinct advantage that due to the method of manufacture microfilaments of small uniform diameter and relatively uniform length- can be obtained.
  • the process and apparatus of the present invention provide a practical means by which relatively long plastic microfilaments can be made at economic prices and in large quantities for use as filler and reinforcing materials and in the manufacture of fibers and fabrics.
  • microfilaments of the present invention because of their relatively long length can be spun into fibers and ropes, and can be woven into fabrics, and can be used to make matted fabrics.
  • the Figure 1 of the drawings shows in cross-section an apparatus having multiple coaxial blowing nozzle means for supplying the gaseous material for blowing plastic micro filaments, a transverse jet for providing an entraining fluid to assist in the formation and detachment of the microfilaments from the blowing nozzles, and means for supplying a quench or heating fluid to cool or heat the microf laments.
  • Figure 2 of the drawings is an enlarged detailed cross-section of the nozzle means of apparatus shown in Figure 1.
  • FIG. 3 of the drawings is an enlarged detailed cross-section of a modified form of a blowing nozzle in which the lower end of the nozzle is tapered inwardly.
  • FIG. 4A of the drawings is a detailed cross- section and a top plane view of a coaxial blowing nozzle tip of the type shown in Figure 2.
  • FIG. 4B of the drawings is a detailed cross- section and top plane view of a coaxial blowing nozzle tip of the type illustrated in Figure 3 of the drawings.
  • FIG. 4C of the drawings is a detailed cross- section and top plane view of a modified form of a coaxial blowing nozzle.
  • a vessel 1 made of suitable con ⁇ tainer material and heated, as necessary, by means not shown for holding liquid plastic 2.
  • the bottom floor 3 of vessel 1 contains a plurality of openings 4 through which liquid plastic 2 is fed to coaxial blowing nozzles 5.
  • the coaxial blowing nozzle 5 can be made separately or can be formed by a downward extension of the " bottom 3 of vessel 1.
  • the coaxial blowing nozzle 5 consists of an inner nozzle 6 having an orifice 6a for a blowing gas or an inert blowing gas and an outer nozzle 7 having an orifice 7a for liquid plastic.
  • the inner nozzle 6 is disposed within and co ⁇ axial to outer nozzle 7 to form annular space 8 between nozzles 6 and 7, which annular space provides a flow path for liquid plastic 2.
  • the orifice 6a of inner nozzle 6 terminates at or a short distance above the plane of ori ⁇ fice 7a of outer nozzle 7.
  • a thickened or enlarged portion 20 means for providing the thinned wall or weakened por ⁇ tion of the elongated hollow plastic tube or cylinder.
  • the length, diameter and height of the thickened or enlarged portion 20 are such that they cause the flow of liquid plastic as it passes over and around the thickened or enlarged portion 20 to become thinned and weakened.
  • liquid plastic 2 at about atmospheric pressure or at elevated pressure flows downwardly through annular space 8 and fills the area 9 between orifice 6a and 7a.
  • the surface tension forces in liquid plastic 2 form a thin liquid plastic ' 'film 9 across orifice 6a and 7a.
  • a blowing gas 10 which is at or below ambient temperature or which is heated by means not shown to about the temperature of the liquid plastic and which is at a pressure above the liquid plastic pressure at the
  • OMPI blowing nozzle is fed through distribution conduit 11 and inner coaxial nozzle 6 and brought into contact with the inner surface of liquid plastic film 9.
  • the blowing gas exerts a positive pressure on the liquid plastic film to blow and distend the film outwardly to form the elongated cylinder shaped liquid film 12 of liquid plastic filled with the blowing gas 10.
  • the elongated cylinder 12 is initially closed at its outer end and is connected at its inner end to outer nozzle 7 at the peripheral edge of orifice 7a. The thinned and weakened portion of the liquid plastic is carried downwardly and outwardly to form the elongated hollow plastic tube or cylinder 12.
  • the elongated hollow plastic tube or cylinder is subjected during its formation to an external pulsating or fluctuating pressure field having periodic oscillations.
  • the pulsating or fluctuating pressure field produces a laminar flow of entraining fluid in the vicinity of the forming elongated hollow plastic tube or cylinder 12.
  • the thinned wall or weakened portion of the elon ⁇ gated cylinder or tube 12 causes a longitudinal break along the length, of the elongated cylinder 12.
  • the pulsating or fluctuating pressure field causes the broken elongated cylinder 12 to flap and to form a multiplicity of small diameter microfilaments 17.
  • the continued feeding of liquid plastic 2 to the coaxial nozzle 5 stablizes the longitudinal break in the elongated cylinder a short distance below the coaxial nozzle 5.
  • the plastic micro ⁇ filaments remain connected to each other at the end of the elongated cylinder connected to the coaxial blowing nozzle.
  • the microfilaments 17 are entrained in the entraining fluid 14, increase in length, are stretched and pulled and break away from the portion of the elon- gated cylinder attached to the coaxial nozzle.
  • a balancing pressure of a gas or of an inert gas i.e. a slightly lower pressure, is provided in the area of the blowing nozzle into which the elongated tube or
  • the illustrated coaxial nozzle can be used to produce plastic micro ⁇ filaments having relatively long lengths and relatively thick uniform diameters and is useful in blowing plastic microfilaments from low viscosity plastic material.
  • a transverse jet 13 is used to induce the external pulsating or fluctuating pressure field by directing an entraining fluid 14 over and around the blowing nozzle 5 at an angle to the axis of the blowing nozzle.
  • the entraining fluid 14 is heated to about, below or above the temperature of the liquid plastic 2., by means not shown.
  • the entraining fluid 14 is fed through distri ⁇ bution conduit 15, nozzle 13 and transverse jet nozzle orifice 13a and directed at the coaxial blowing nozzle 5.
  • the transverse jet 13 is aligned to direct the flow of entraining fluid 14 over and around blowing nozzle 7 in the microfilament forming region at and behind the orifice 7a.
  • the entraining fluid as it passes over and around the blowing nozzle 5 envelops and acts on the liquid plastic as it is being blown to form the elongated hollow tube or cylinder 12 and the microfilaments 17 and to detach the microfilaments from the coaxial blowing nozzle.
  • the surface tension forces of the liquid plastic act on the diameter of the entrained, falling micro- filaments 17 and cause the diameter of the microfilaments to seek a minimum surface area and to form a circular shaped cross-section area.
  • Quench or heating nozzles 18 having orifices 18a are disposed below and on both sides of coaxial blowing nozzle 5 and direct cooling or heating fluid 19 at and into contact with the liquid plastic microfilaments 17 to rapidly cool or heat and cure and solidify the liquid plastic and form a smooth, hardened plastic microfilaments.
  • the quench or heating fluid 19 also serves to carry the plastic microfilaments away from the coaxial blowing nozzle 5.
  • Sufficient heating and curing time can be provided by using a heated fluidized bed, heated liquid carrier or belt carrier system for the thermosetting plastic microfilaments to cure and harden the micro ⁇ filaments with substantially little or no distortion or effect on the size of shape of the microfilaments.
  • the solidified and hardened plastic microfilaments are collected by suitable means not shown.
  • FIG. 3 of the drawings illustrates a pre ⁇ ferred embodiment of the invention in. ⁇ ic the ower por ⁇ tion of the outer coaxial nozzle 7 is tapered downwardly and inwardly at 21.
  • This embodiment as in the previous embodiment comprises coaxial blowing nozzle 5 which consists of inner nozzle 6 with orifice 6a and outer nozzle 7 with orifice 7a.
  • the figure of the drawings also shows elongated hollow plastic tube or cylinder shaped liquid film 12 with a pinched portion 16 and a multiplicity of plastic microfilaments 17.
  • annular space 8 there is shown disposed in annular space 8 on two opposite sides of the lower outer surface of inner nozzle 6 two thickened or enlarged portions 20 means for providing the thinned wall or weakened portion of the elongated plastic tube or cylinder 12.
  • the length, diameter and height of the thickened or enlarged portions 20. are such that they cause the flow of liquid plastic as it passes over and around the enlarged or thickened portions 20 to become thinned and weakened.
  • the use of the tapered nozzle 21 construction is found to substantially assist in the formation of a thin liquid plastic film 9 in the area between orifice 6a of . inner nozzle 6 and orifice 7a of outer nozzle 7.
  • the inner wall surface 22 of the taper portion 21 of the outer nozzle 7 when pressure is applied to liquid plastic 2 forces the liquid plastic 2 to squeeze through a fine gap formed between the outer edge of orifice 6a and the inner surface 22 of form the thin liquid plasitc film 9 across orifice 6a and 7a.
  • the illustrated coaxial nozzle can be used to produce plastic microfilaments having relatively long lengths and allows making microfilaments of smaller diameter than those made using the Figure 2 apparatus and is particularly useful in blowing high viscosity plastic materials and compositions....
  • the diameter of the microfilaments is determined in part by the thickness of the wall of the elongated hol ⁇ low plastic tube or cylinder which is determined by the gap formed by the tapered nozzle 21 and the outer edge of the inner nozzle 6a.
  • This apparatus allows the use of larger inner diameters of outer nozzle 7 and larger inner diameters of inner nozzle 6, both of which reduce the possiblity of plugging of the coaxial nozzles when in use.
  • the Figure 3 of the drawings also shows an embodi ⁇ ment of the invention in which the outer portion of the transverse jet 13 is flattened to form a generally rectangular or oval shaped orifice opening 13a.
  • the orifice opening 13a can be disposed at an angle relative to a line drawn through the central axis of coaxial nozzle 5.
  • the preferred angle is that illustrated in the drawing. That is, at an angle of about 90° to the central axis of the coaxial nozzle 5.
  • FIG. 4C there is shown disposed in annu ⁇ lar space 8 equally spaced on the outer surface of inner nozzle 6 four thickened or enlarged portions 20 for providing the thinned wall or weakened portions of the elongated hollow tube or cylinder 12.
  • the organic film forming material and compositions and particularly the plastic materials and compositions from which the plastic microfilaments of the present in ⁇ vention are made can be varied to obtain the desired phy ⁇ sical characteristics for blowing and forming, cooling or heating and curing the microfilaments and the desired stren gth characteristics of the plastic microfilaments produced.
  • the constituents of the plastic compositions can vary de ⁇ pending on their intended use.
  • the process and apparatus of the present invention can be used to blow microfilaments from suitable film formi plastic materials or compositions having sufficient vis ⁇ cosity at the temperature at which the microfilaments are blown to form a stable elongated cylinder shape of the plastic material being blown and the microfilaments.
  • the plastic materials to be used to form the micro ⁇ filaments are selected and can be treated and/or mixed with other materials to adjust their viscosity and surface ten ⁇ sion characteristics such that at the desired blowing tem ⁇ peratures they form stable films and are capable of forming the elongated hollow plastic tubes or cylinders and micro ⁇ filaments of the desired length and diameters.
  • the plastic compositions that can be used to form microfilaments include thermosetting and thermoplastic materials such as polyethylene, polypropylene, polystyrene, polyesters, polyurethanes, polychloro-trif ⁇ uoro ethylene, polyvinyl fluoride, polyvinylidene, polymethyl methacrylate acetyl, phenol-formaldehyde resins and silicone and poly ⁇ carbonate resins.
  • thermosetting and thermoplastic materials such as polyethylene, polypropylene, polystyrene, polyesters, polyurethanes, polychloro-trif ⁇ uoro ethylene, polyvinyl fluoride, polyvinylidene, polymethyl methacrylate acetyl, phenol-formaldehyde resins and silicone and poly ⁇ carbonate resins.
  • the plastic compositions that can be used also include cellulose acetate, cellulose acetate-butyrate, and cellulose acetate-propionate.
  • OMPI Thermoplastic resins that can be used are poly- vinyl resins such as polyvinyl alcohol, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl butyral, polystyrene, polyvinylidene chloride, and acrylic resins such as polymethyl methacrylate, polyallyl, poly ⁇ ethylene, and polyamide (nylon) resins.
  • poly- vinyl resins such as polyvinyl alcohol, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl butyral, polystyrene, polyvinylidene chloride, and acrylic resins such as polymethyl methacrylate, polyallyl, poly ⁇ ethylene, and polyamide (nylon) resins.
  • Thermosetting resins that can be used include alkyd, polysiloxane, phenol-formaldehyde, urea-formaldehyde and melamine-formaldehyde resins.
  • Suitable chemical agents are materials that act as solvents for the plastic compositions.
  • the solvents that are used will, of course, depend on the solu ⁇ bility in the solvent of the plastic composition used. Water, alcohols, eithers, esters, organic acids, hydro ⁇ carbons and chlorinated hydrocarbons can be used as solv ⁇ ents.
  • suitable surface active agents such as colloidal particles of insoluble substances and viscosity stabilizers can be added to the plastic composition as additives. These additives can affect the viscosity of the surface film of the hollow elongated tube or cylinder to stabilize the film during cylinder formation.
  • the plastic compositions of the present inven ⁇ tion are formulated to have a relatively narrow temperatur difference between the liquid temperature and the plastic hardening temperature (thermoplastic) or a relatively narrow temperature difference between the liquid temperatur and the thermosetting and curing temperature.
  • the plastic compositions are formulated such that they have a high rate of viscosity increase with the hardening temperature or the thermosetting temperature such that the microfilaments will rapidly solidify, harden and strengthen. That is, they change from liquid to solid within a. relative narrowly defined temperature range and/or cure in a relatively short time.
  • the plastic microfilaments can be blown with a gas, e.g. an inert gas.
  • Suitable blowing gases can be argon, nitrogen and air.
  • the blowing gases can be selected to react with the plastic film forming material or composition, e.g. to assist in the hardening and/or curing of the micro ⁇ filaments.
  • the blowing gas in reacting with the film formin material as the elongated cylinder is being blown and forme can to some extent help to stabilize (against break-up) the film forming plastic material used to form the elongated cylinder and microfilaments and allow- sufficient time for the microfilaments to form and harden.
  • oxygen or air can be used as or added to the blowing gas.
  • the blowing gas can include a catalyst or hardening agent for the plastic compositions.
  • a catalyst or hardening agent for the plastic compositions.
  • the addition of a catalyst or hardening agent to the blowing gas prevents contact of the catalyst or hardening agent with the plastic composition until a time just before the hollow elongated tube or cylinder is formed.
  • the entraining fluid can be a gas at a high or low temperature and can be selected to react with or be inert to the plastic composition. Suitable entraining fluids are nitrogen, air, steam and argon. A gaseous catalyst for the plastic can also be included in the entraining fluid.
  • the quench or heating fluid can be a liquid, a iiquid dispersion or a gas. Suitable quench or heating fluids are steam, a fine water spray, air, nitrogen or mixtures thereof. The selection of a specific quench or heating fluid and quench or heating temperature depends to some extent on the plastic composition from which the " hollow elongated tube or cylinder is blown.
  • the organic film forming materials and/or plastic materials and compositions of the present invention are in a liquid-fluid form at the desired blowing temperature and during the blowing operation.
  • the liquid plastic compositio can be at a temperature of about 0°C. to about 400°C, preferably 10°C. to 300°C and more preferably 20°C to 200°C, depending on the constituents and state of polymerization of, for example, the plastic composition.
  • the plastic comp- sition at the blowing temperature is liquid, fluid and flows easily.
  • the liquid plastic just prior to the blowing oper ⁇ ation can have a viscosity of 0.10 to 600 poises, usually 10 to 350 poises and more usually 30 to 200 poises.
  • the liquid plastic is continuously fed to the coaxial blowing nozzle during the blowing operation to pre ⁇ vent premature breaking and detaching of the elongated tube or cylinder shaped liquid plastic film as it is being formed by the blowing gas.
  • the blowing gas or, inert blowing gas will be at about the same temperature as the liquid plastic being blown.
  • the blowing gas temperature can,however, be at a higher temp ⁇ erature than the liquid plastic to assist in maintaining the fluidity of the hollow liquid plastic tube or cylinder during the blowing operation or can be at a lower temperature than the liquid plastic to assist in the solidification and hard ening of the plastic microfilaments as they are formed.
  • the pressure of the blowing gas is sufficient to blow the micro filaments and will be slightly above the pressure of liquid plastic film at the orifice 7a of the outer nozzle 7.
  • the blowing gas pressure will also depend on and be slightly above the ambient pressure external to the blowing nozzle.
  • the temperatures of the blowing gases will depend on the blowing gas used and the viscosity-temperature-shear relationship for the film forming plastic materials used to make the microfilaments.
  • the ambient pressure external to the blowing nozzle will be such that it substantially balances, but is slightly less than the blowing gas pressure.
  • the transverse jet inert entraining fluid which is directed over and around the coaxial blowing nozzle to assist in the formation of the hollow elongated tube or cylinder and detaching of the plastic microfilaments from the coaxial blowing nozzle can be at about the same temper ⁇ ature as the liquid plastic being blown.
  • the entraining fluid can, however, be at a higher temperature than the liquid plastic to assist in maintaining the fluidity of the hollow elongated tube or cylinder and the microfilaments during the blowing operation or can be at a lower temper ⁇ ature than the liquid plastic to assist in the stabilization of the forming elongated hollow tube or cylinder film and in the solidification and hardening of the microfilaments.
  • the transverse jet entraining fluid which assists in detaching of the plastic microfilaments from the coaxial blowing nozzle can have a linear velocity in the region of microfilament formation of 1 to 120 ft/sec, usually 5 to 80 ft/sec and more usually 10 to 60 ft/sec.
  • the length of the plastic microfilaments and the diameter of the plastic microfilaments depends to some extent on the viscosity of the plastic material and the linear velocity of the transverse jet entraining fluid.
  • the quench or heating fluid is at a temperature suc that it rapidly cools or heats the microfilaments to solid ⁇ ify, harden and strengthen the liquid plastic microfilaments
  • the quench cooling fluid can be at a temperature of 0 to 200°F., usually 40 to 200°F. and more usually 50 to 100°F.
  • the heating fluid can be at a temperature of 100 to 800°F. , usually 200 to 600°F. and more usually 300 to 500°F., depending on the plastic composition.
  • the time elapsed from commencement of the blowing of the thermoplastic composition to the cooling and initial hardening of the microfilaments can be .0001 to 60.0 seconds preferably .0010 to 30.0 seconds and more preferably 0.10 to 10.0 seconds.
  • the time elapsed from commence ⁇ ment of the blowing of the plastic elongated hollow tube or cylinder to the heating and curing of the microfilaments can be 0.10 second to 30 minutes, preferably 1 second to 20 minutes and more preferably 10 second to 10 minutes.
  • the container vessel is constructed to maintain the liquid plastic at the desired operating temperatures.
  • the liquid plastic 2 is fed to coaxial blowing nozzle 5.
  • the coaxial blowing nozzle 5 consists of an inner nozzle 6 having an outside diameter of 0.32 to 0.010 inch, preferably 0.20 to 0.015 inch and more preferably 0.10 to 0.20 inch and an outer nozzle 7 having an inside diameter of 0.420 to 0.020 inch, preferably 0.260 to 0.025 and more preferably 0.130 to 0.030 inch.
  • the inner nozzle 6 and outer nozzle 7 form annular space 8 which provides a flow path through which the liquid plastic 2 is extruded.
  • the distance between the inner nozzle 6 and outer nozzle 7 can be 0.050 to 0.004, preferably 0,030 to 0.005 and more preferably 0.015 to 0,008 inch.
  • the orifice 6a of inner nozzle 6 terminates a short distance above the plane of orifice 7a of outer nozzle 7.
  • the orifice 6a can be spaced above orifice 7a at a distance of 0.001 to 0.125 inch, proferably 0.002 to 0.050 inch and more preferably 0.003 to 0.025 inch.
  • the liquid plastic 2 flows downwardly and is extruded through annular space 8 and fills the area between orifice 6a and 7a.
  • the orifices 6a and 7a can be made from stainless steel, platinum alloys, glass of fused alumina. Stainless steel, however, is preferred.
  • the surface tension forces in the liquid plastic 2 form a thin liquid plastic film 9 across orifices 6a and 7a which has about the same or a smaller thickness as the distance of orifice 6a is spaced above orifice 7a.
  • the liquid plastic film 9 can be 25 to 3175 microns, preferably 50 to 1270 microns and more preferably 76 to 635 microns thick.
  • blowing nozzle can be used to blow liquid plastic at relatively low viscosities, for example, of 10 to 60 posies, and to blow plastic microfilaments of relatively thick diameter, for example, of 20 to 100 microns or more.
  • the transverse jet 13 is used to direct an entraining fluid 14 through nozzle 13 and transverse jet nozzle orifice 13a at the coaxial blowing nozzle 5.
  • the coaxial blowing nozzle 5 has an outer diameter of 0.52 to 0.30 inch, preferably 0.36 to 0.035 inch and more preferably 0.140 to 0.040 inch.
  • the transverse jet 13 is aligned to direct the flow of entraining fluid 14 over and around outer nozzle 7 in the hollow elongated tube or cylinder and microfilament forming region of the roifice 7a.
  • the orifice 13a of transverse jet 13 is locatd a distance of 0.5 to 14 times, preferably 1 to 10 times and more preferably 1.5 to 8 times and still more preferably 1.5 to 4 times the outside diameter of coaxial blowing nozzle 5 away from the point of intersect of a line drawn along the center axis of transverse jet 13 and a line drawn along the center axis of coaxial blowing nozzle 5.
  • the center axis of transverse jet 13 is aligned at an angle of 15 to 85°, preferably 25 to 75° and more preferably 35 to 55° relative to the center axis of the coaxial blowing nozzle 5.
  • the orifice 13a can be circular in shape and have an inside diameter of 0.32 to 0.010 inch, preferably 0.20 to 0.015 inch and more preferably 0.10 to 0.020 inch.
  • the line drawn through the center axis of transverse jet 13 intersects the line drawn through the center axis or coaxial blowing nozzle 5 at a point above the orifice 7a of outer nozzle 7 which is .5 times to 4 times, preferably 1.0 to 3.5 times and more preferably 2 to 3 times the " outside diameter of the coaxial blowing nozzle 5.
  • the entraining fluid assists in the formation and detaching of the plastic microfilaments from the coaxial blowing nozzle.
  • the use of the transverse et and entraining fluid in the manner described also discourages wetting of th outer wall surface of the coaxial blowing nozzle 5 by the liquid plastic being blown.
  • the quench or heating nozzles 18 are disposed below and on both sides of coaxial blowing nozzle 5 a sufficient distance apart to allow the microfilaments 17 to fall between the quench nozzles 18.
  • the quench nozzles 18 direc cooling or heating fluid 19 at and into contact with the liquid plastic microfilaments 17 to cool or heat and solidify the liquid plastic and form hard, smooth, plastic microfilaments.
  • the Figure 3 of the drawings illustrates a preferred embodiment of the invention. It is found that in blowing liquid plastic compositions at high viscosities that is is advantageous to immediately prior to blowing the liquid plastic to provide by extrusion a very thin liquid plastic film for blowing into the elongated cylinder shape liquid film 12.
  • the thin liquid plastic film 9 is provided by having the lower portion of the outer coaxial nozzle 7 tapered downwardly and inwardly at 21.
  • the tapered portion 21 and inner wall surface 22 thereof can be at an angle of 15 to 75°, preferably 30 to 60° and more preferably about 45° relative to the center axis of coaxial blowing nozzle 5.
  • the orifice 7a can be 0.10 to 1.5 times, preferably 0.20 to 1.1 times and more preferably 0.25 to .8 times the. inner diameter of orifice 6a of inner nozzle 6.
  • the thickness of the liquid plastic film 9 can be varied by adjusting the distance of orifice 6a of inner nozzle 6 above orifice 7a of outer nozzle 7 such that the distancebetween the peripheral edge of orifice 6a and the inner wall surface 22 of tapered nozzle 21 can be varied.
  • the proper gap can best be determined by pressing the inner coaxial nozzle 6 downward with sufficient pressure to completely block-off the flow of plastic, and to then very slowly raise the inner coaxial nozzle 6 until a stable system is obtained, i.e. until the hollow elongated plastic cylinder and the plastic microfilaments are being formed.
  • the tapered' nozzle construction illustrated in Figure 3 can be used to blow plastic compositions at relatively high viscosities as well as to blow plastic compositions at the relatively low viscosities referred to with regard to Figure 2 of the drawings.
  • the Figure 3 embodiment of the invention is of particular advantage in blowing relatively long small diameter microfilaments.
  • thickened or enlarged portion 20 means for providing the thinned wall or weakened portion of the elongated hollow tube or cylinder.
  • the length, diameter and height of the thickened or enlarged portion 20 are such that they cause the flow of liquid plastic as it passes over and around the thickened or enlarged portion 20 to become thinned and weakened.
  • the thinned and weakened portion of the liquid plastic is carried down ⁇ wardly and outwardly to form the elongated hollow plastic tube of cylinder 12, which as a result of the thinned and weakened portion breaks up into a multiplicy of relatively long microfilaments 17.
  • microfilaments made in accordance with the present invention can be made from a variety of organic film forming materials and compositions, particularly plastic compositions.
  • the plastic microfilaments made in accordance with the present invention can be made from suitable composition selected to have relatively high temperature resistance, be resistant to chemical attack and be resistant to weathering.
  • the plastic microfilaments can be made in various lengths and diameters, depending upon the desired end use of the microfilaments.
  • the microfilaments can have a length one half to twelve inches, preferably one to eight inches and more preferably two to six inches.
  • the microfilaments can have a diameter of 0.5 to 40 microns, preferably- 1.0 to 30 microns and more preferably 2 to 10 microns.
  • thermoplastic composition comprising polyethylene polymer is used to make plastic microfilaments .
  • a plastic composition is heated to form a fluid plastic having a viscosity of about 10 to 20 poises at the blowing nozzle.
  • the liquid plastic is fed to the apparatus of • Figures 1 and 2 of the drawings.
  • the liquid plastic passes through annular space 8 of about 0.005 inch, of blowing nozzle 5 and forms a thin liquid plastic film across the orifices 6a and 7a.
  • a heated blowing gas consisting of nitrogen at a positive pressure is applied to the inner surface of the liquid plastic film causing the film to distend downwardly into a elongated cylinder shape with its inner end attached to the outer edge or orifice 7a.
  • the transverse jet is used to direct an entraining fluid which consists of nitrogen heated to about the temperature of the liquid plastic, at a linear velocity of 20 to 80 feet per second over and around the blowing nozzle 5 which entraining fluid assists in the formation of the elongated cylinder and of a multiplicity of plastic micro ⁇ filaments and detaching of the plastic microfilaments from the elongated cylinder and causing the plastic microfilament to be entrained in the entraining fluid and carried away fro theblowing nozzle 5.
  • the transverse et is aligned at an angle of 35 to 50° relative to the blowing nozzle.
  • the entrained plastic microfilaments are cooled to about ambient temperature by a cool quench fluid consisting of a fine water spray which quickly cools, solidifies and hardens the plastic microfilaments.
  • Plastic microfilaments having a diameter of 2 to 6 microns diameter and a one to five inch length are obtained.
  • thermosetting plastic composition comprising a mixture of 50% by weight acrylonitrile and 50% by weight vinylidene chloride and a suitable catalyst is used to make plastic microfilaments.
  • the plastic composition mixture at the blowing nozzle has a viscosity of about ten poises.
  • the liquid plastic mixture is heated and is fed to the apparatus of Figures 1 and 3 of the drawings.
  • the liquid plastic is passed through annular space 8 of blowing nozzle 5 and into tapered portion 21 of outer nozzle 7.
  • the liquid plastic under pressure is squeezed and extruded through a fine gap • formed between the outer edge of orifice 6a and the inner surface 22 of the tapered portion 21 of outer nozzle 7 and forms a thin liquid plastic film across the orifices 6a and 7a.
  • a heated blowing gas consisting of nitrogen at a positive pressure is applied to the inner surface of the liquid plastic film causing the fil to distend outwardly into an elongated cylinder shape with its inner end attached to the outer edge of orifice 7a.
  • the transverse jet is used to direct an entraining fluid which consists of heated nitrogen at about the temperature of the liquid plastic at a linear velocity of 20 to 80 feet per second over and around the blowing nozzle 5.
  • the entraining fluid assists in the formation of the elongated cylinder and of a multiplicity of plastic microfilaments and detaching of the plastic microfilaments from the elongated cylinder and causes plastic micro ⁇ filaments to be entrained in the fluid and carried away from the blowing nozzle.
  • the entrained microfilaments are contacted with a heating fluid consisting of heated nitrogen which solidifies, hardens and begins to cure the liquid plastic microfilaments.
  • Plastic microfilaments having a 1 to 5 micron diameter and having a length of 2 to 10 inches are obtained.
  • the plastic microfilaments of the present invention have many uses including the use of the microfilaments as a filler or reinforcing material in rubber, cement, plaster and asphalt compositions.
  • the plastic microfilaments and fibers can be used to make tire cords and filter media.
  • microfilaments can be spun into fibers and woven into fabrics or can be used to make matted fabrics.
  • the plastic microfilaments can advantageously be used in plastic or resin boat construction to produce high strength hulls.
  • OMPI Quench nozzles 18 where the plastic is thermo ⁇ plastic and heating nozzles where the plastic is thermosetting may be disposed below and on either side of the blowing nozzle 5 to direct cooling fluid or heating fluid 19 at and into contact with the plastic micro ⁇ filaments 17 to cool or heat and cure, solidify and harden the plastic to form hard, smooth plastic micro ⁇ filaments 17.

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Abstract

Relatively long plastic microfilaments made from a plastic composition. The plastic microfilaments may be used to make reinforcing, filler materials and fabrics. The microfilaments are made by forming a liquid film of plastic across a coaxial blowing nozzle (5), applying a blowing gas (10) at a positive pressure on the inner surface of the plastic film to blow the film and form an elongated hollow tube or cylinder shaped liquid film (12) of plastic. Means are provided for forming a thinned wall or weakened portion of the plastic film forming the wall of elongated tube or cylinder. A transverse jet (13) is used to direct an entraining fluid (14) over and around the blowig nozzle (5) at an angle to the axis of the blowing nozzle. The entraining fluid (14) as it passes over and around the blowing nozzle (5) fluid dynamically induces a pulsating or fluctuating pressure field at the opposite or lee side of the blowing nozzle in the wake or shadow of the coaxial blowing nozzle and produces a laminar flow of entraining fluid in the vicinity of the forming elongated tube or cylinder. The continued movement of the entraining fluid (14) over the elongated tube or cylinder (12) produces asymmetric fluid drag forces on the tube or cylinder, and at the thinned walled or weakened wall portion longitudinally breaks the tube or cylinder to form a multiplicity of plastic microfilaments, and detaches the plastic microfilaments from the elongated tube or cylinder and from the coaxial blowing nozzle and the detached microfilaments are carried away from the blowing nozzle.

Description

MEIHOD AND APPARATUS FOR PRODUCING PLASTIC MICROFILAMENTS SUMMARY OF INVENTION
Th"e present application is a continuation-in- part of applicant's copending application Serial No. 325,594 filed November 27, 1981 and copending application Serial
No. , filed September 30, 1982. Application Serial
No. 325,594 is a continuation-in-part of applicant's application Serial No. 152,693, filed May 23, 1980, which is a continuation of Serial No. 059,297, filed July 20, 1979
Application Serial No. is a continuation of application Serial No. 103,113, filed December 13, 1979, which is a divisional of application Serial No. 059,296 filed July 20, 1979. The application Serial No. 059,297 and the application Serial No. 059,296 are each continuation in-part applications of Serial Nos. 937,123 and 944,643 filed August 28, 1978 and September 21, 1978, respectively.
The application Serial No. 152,693 is now U.S. Patent
4,303,431.- The applications Serial Nos. 059,297,. 059,296,
103,113-, 937,123 and 944,643 are now abandoned.
The present invention relates to a method and apparatus for making microfilaments from organic film forming materials or compositions and particularly for making plastic microfilaments.
The present invention also relates to plastic microfilaments spun into fibers for the manufacture of woven plastic fabrics or rope and for the manufacture of matted fabrics.
The present invention also relates to plastic microfilaments used to make an improved reinforcing and filler material.
The present invention also relates to plastic microfilaments suitable for use as filler material and reinforcing materi-il in rubber, plastics, concrete and asphalt compositions. The present invention particularly relates to a method and. apparatus for using a .coaxial blowing nozzle to blow plastic microfilaments from liquid plastic compositions comprising forming an elongated hollow tube or cylinder of said plastic composition and subjecting the tube or cylinder during its formation to an external pulsating or fluctuating pressure field having periodic oscillations. The pulsating or fluctuating pressure field produces a laminar flow of entraining fluid in the vicinity of the forming elongated tube or cylinder which laminar flow assists in the formation of the tube or cylinder and in detaching the microfilaments from the blowing nozzle.
The invention more particularly relates to a method and apparatus for blowing microfilaments from plastic film forming compositions.
Means are provided for forming"a thinned wall or weakened portion of the forming elongated hollow plastic tube or cylinder. The thinned wall or weakened portion of the elongated plastic tube or cylinder causes a longitudinal break along the length of the elongated plastic tube or cylinder. The pulsating or fluctuating pressure field causes the broken elongated tube or cylinder to flap and to form a multiplicity of small diameter plastic microfilaments The continued feeding of liquid plastic to the coaxial nozzle stabilizes the longitudinal break in the elongated tube or cylinder a short distance below the coaxial nozzle. The plastic microfilaments are entrained in the entraining fluid, increase in length, are stretched and pulled and break away from the portion of the elongated cylinder attached to the coaxial nozzle.
A transverse jet is used to induce the external pulsating or fluctuating pressure field by directing the entraining fluid over and around the blowing nozzle at an angle to the axis of the blowing nozzle. The entraining fluid as it passes over' nd around the blowing nozzle envelops and acts on the liquid plastic as it is being
O ?I blown to form the elongated plastic tube or cylinder and the plastic microfilaments and to detach the plastic microfilaments from the coaxial blowing nozzle.
Quench or heating means may be disposed close to and below the blowing nozzles to direct a quench or heating fluid onto the microfilaments to rapidly cool or heat and cure, solidify and harden the microfilaments.
BACKGROUND OF THE INVENTION
In recent years, the substantial increases in costs of basic materials such as metals, metal alloys, plastics, cement, asphalt, rubbers and the like has encouraged development and use of light weight structural materials, reinforcing materials and of filler materials to reduce the amount and cost of the basic materials used and the weight of the finished materials. One of the suggested filler materials utilizes plastic fibers. The present invention which produces relatively long plastic microfilaments at an economical low price provides an improved plastic micro- filament material for use as a filler and reinforcing material.
The known methods of making plastic filaments and fibers suffer from the disadvantages of requiring the use of relatively large amounts of energy to manufacture a given amount of filaments or fibers and/or requiring large capital investments in filament or fiber drawing apparatus.
The known methods of producing plastic filaments and fibers also suffer the disadvantage of relatively low production rates.
The known methods of producing plastic filaments and fibers are also believed to suffer the disadvantage of not being able to produce filaments and fibers of relatively small uniform diameters and uniform lengths at economical costs.
" The process and apparatus of the present invention are believed to overcome the disadvantages of the prior art processes and are capable of producing microfilaments of uniform diameter and relatively uniform length of controlled and predictable physical and chemical character¬ istics, quality and strength at economical low costs.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide a process and an apparatus for making relatively long plasti microfilaments of uniform small diameters.
It is another object of the present invention to provide plastic microfilaments that are useful in the manufacture of improved structural materials.
It is another object of 'the present invention to produce plastic microfilaments having relatively long lengths and relatively uniform diameter size distribution.
It is another object of the present invention to provide plastic microfilaments for use in producing fibers, ropes and woven-and matted fabrics.
It is another object of the present invention to produce in an economical simple .manner plastic micro¬ filaments which are substantially uniform in diameter, lengt and strength characteristics.
BRIEF DESCRIPTION OF THE INVENTION
The present invention relates to plastic micro¬ filaments and to a process and apparatus for making the microfilaments.
The microfilaments are preferably made from ther o- setting or -thermoplastic compositions.
The plastic microfilaments of the present invention are made by forming a liquid film of thermoplastic or thermosetting plastic composition across a coaxial blowing nozzle, applying a blowing gas or an inert blowing gas at a positive pressure on the inner surface of the plastic film to blow the film and form an elongated hollow tube or cylinder shaped liquid film of liquid plastic. The elongated tube or cylinder is initially closed at its outer end and is attached at its inner end to the coaxial blowing nozzle. Means are provided in the coaxial blowing nozzle for forming a thinned wall or weakened portion of the forming elongated tube or cylinder. A transverse jet is used to direct an entraining fluid over and around the blowing nozzle. The entraining fluid as it passes over and around the blowing nozzle fluid dynamically induces a pulsating or fluctuating pressure field at the opposite or lee side of the blowing nozzle in the wake or shadow of the coaxial blowing nozzle and produces a laminar flow of entraining fluid in the area of the forming elongated tube or cylinder. The fluctuating pressure field has regular periodic lateral oscillations similar to those of a flag flapping in a breeze. The continued movement of the entraining fluid over the elongated cylinder produces asymmetric fluid drag forces on the cylinder, and at the thinned walled or weakened portion longitudinally breaks the cylinder to from a multiplicity of plastic microfilament and detaches the microfilaments from the elongated cylinder and from the coaxial blowing nozzle and the detached filaments are carried away from the blowing nozzle. The surface tension forces of the liquid plastic composition act on the microfilament and causes the diameter of the microfilament to seek a minimum surface area and to form a circular cross-section.
The thin walled or weakend section of the elongated cylinder causes the cylinder to break along its longitudinal length. The induced fluctuating pressure field causes the elongated cylinder to flap and to quickly enlarge the break and to form a multiplicity of small diameter microfilaments.
The break proceeds up the length of the elongated cylinder towards the coaxial nozzle. The continued feeding of liquid plastic to the coaxial nozzle stabilizes the break a short distance below the coaxial nozzle. The micro¬ filaments are entrained in the transverse jet entraining fluid, are stretched, increase in length and pulled and break away from the portion of the elongated cylinder attached to the coaxial blowing nozzle.
The means for providing the thinned wall or weakened portion of the forming elongated hollow tube or cylinder may be contained within the coaxial blowing nozzle in the annular space between the outer coaxial nozzle and the inner coaxial -nozzle. The means provided may take the form of one or more thickened or enlarged portions of the inner nozzle-disposed lengthwise on the outer surface of the inner nozzle. The length, diameter and height of the thickened or enlarged portions are such that they cause the flow of liquid plastic as it passes over and around the thickened or enlarged portions to become thinned and weakened. The thinned and weakened portion of the liquid plastic is carried downwardly and outwardly into the forming elongated hollow cylinder or tube. It is this thinned or weakened portion of the forming elongated hollow cylinder or tube that causes the cylinder or tube to break along its length and form the microfilaments. The thickened portion of the inner nozzle is disposed at or near the outer edge of the inner nozzle.
The liquid plastic temperature and feed rate, the transverse jet entraining fluid linear velocity, the blowing gas pressure and the quench rate at a given coaxial nozzle gap will to some extent determine the microfilament length and diameter and size distribution.
A balancing but slightly lower gas pressure than the blowing gas pressure is provided in the area in which the elongated cylinder is formed.
Quench nozzles where the plastic is thermoplastic and heating nozzles where the plastic is thermosetting may be disposed below and on either side of the blowing nozzle to direct cooling or heating fluid at and into
O ?I - 1- contact with the liquid plastic microfilaments to rapidly cool or heat and solidify the liquid plastic and form hardened, smooth microfilaments of relatively long length. Where a thermosetting plastic is used, the microfilaments may be heated and cured and the cured plastic microfilament can be subsequently cooled.
THE ADVANTAGES
The present invention overcomes may of the problems associated with prior attempts to produce plastic micro¬ filaments and fibers. The process and apparatus of the present invention allows the production of plastic micro¬ filaments of relatively long length ^a d relatively uniform diameter such that superior structural materials and improved filler and reinforcing materials can be designed, manufactured and tailor made to suit a particular desired use.
The relatively long plastic microfilaments produced in accordance with the present invention have the distinct advantage that due to the method of manufacture microfilaments of small uniform diameter and relatively uniform length- can be obtained.
The process and apparatus of the present invention provide a practical means by which relatively long plastic microfilaments can be made at economic prices and in large quantities for use as filler and reinforcing materials and in the manufacture of fibers and fabrics.
The microfilaments of the present invention because of their relatively long length can be spun into fibers and ropes, and can be woven into fabrics, and can be used to make matted fabrics. BRIEF DESCRIPTION OF THE DRAWINGS
The attached drawings illustrate exemplary forms of the method and apparatus of the present invention for making plastic microfilaments.
The Figure 1 of the drawings shows in cross-section an apparatus having multiple coaxial blowing nozzle means for supplying the gaseous material for blowing plastic micro filaments, a transverse jet for providing an entraining fluid to assist in the formation and detachment of the microfilaments from the blowing nozzles, and means for supplying a quench or heating fluid to cool or heat the microf laments.
Figure 2 of the drawings is an enlarged detailed cross-section of the nozzle means of apparatus shown in Figure 1.
The Figure 3 of the drawings is an enlarged detailed cross-section of a modified form of a blowing nozzle in which the lower end of the nozzle is tapered inwardly.
The Figure 4A of the drawings is a detailed cross- section and a top plane view of a coaxial blowing nozzle tip of the type shown in Figure 2.
The Figure 4B of the drawings is a detailed cross- section and top plane view of a coaxial blowing nozzle tip of the type illustrated in Figure 3 of the drawings.
The Figure 4C of the drawings is a detailed cross- section and top plane view of a modified form of a coaxial blowing nozzle.
DETAILED DISCUSSION OF THE DRAWINGS
The invention will be described with reference to the accompanying Figures of the drawings wherein like numbers designate like parts throughout the several views.
OM?I Referring to Figures 1 and 2 of the drawings, there is illustrated a vessel 1, made of suitable con¬ tainer material and heated, as necessary, by means not shown for holding liquid plastic 2. The bottom floor 3 of vessel 1 contains a plurality of openings 4 through which liquid plastic 2 is fed to coaxial blowing nozzles 5. The coaxial blowing nozzle 5 can be made separately or can be formed by a downward extension of the "bottom 3 of vessel 1. The coaxial blowing nozzle 5 consists of an inner nozzle 6 having an orifice 6a for a blowing gas or an inert blowing gas and an outer nozzle 7 having an orifice 7a for liquid plastic. The inner nozzle 6 is disposed within and co¬ axial to outer nozzle 7 to form annular space 8 between nozzles 6 and 7, which annular space provides a flow path for liquid plastic 2. The orifice 6a of inner nozzle 6 terminates at or a short distance above the plane of ori¬ fice 7a of outer nozzle 7.
There is disposed in annular space 8 on the outer surface of inner nozzle 6 a thickened or enlarged portion 20 means for providing the thinned wall or weakened por¬ tion of the elongated hollow plastic tube or cylinder. The length, diameter and height of the thickened or enlarged portion 20 are such that they cause the flow of liquid plastic as it passes over and around the thickened or enlarged portion 20 to become thinned and weakened.
The liquid plastic 2 at about atmospheric pressure or at elevated pressure flows downwardly through annular space 8 and fills the area 9 between orifice 6a and 7a. The surface tension forces in liquid plastic 2 form a thin liquid plastic''film 9 across orifice 6a and 7a.
A blowing gas 10 which is at or below ambient temperature or which is heated by means not shown to about the temperature of the liquid plastic and which is at a pressure above the liquid plastic pressure at the
-gJREA
OMPI blowing nozzle, is fed through distribution conduit 11 and inner coaxial nozzle 6 and brought into contact with the inner surface of liquid plastic film 9. The blowing gas exerts a positive pressure on the liquid plastic film to blow and distend the film outwardly to form the elongated cylinder shaped liquid film 12 of liquid plastic filled with the blowing gas 10. The elongated cylinder 12 is initially closed at its outer end and is connected at its inner end to outer nozzle 7 at the peripheral edge of orifice 7a. The thinned and weakened portion of the liquid plastic is carried downwardly and outwardly to form the elongated hollow plastic tube or cylinder 12.
The elongated hollow plastic tube or cylinder is subjected during its formation to an external pulsating or fluctuating pressure field having periodic oscillations. The pulsating or fluctuating pressure field produces a laminar flow of entraining fluid in the vicinity of the forming elongated hollow plastic tube or cylinder 12.
The thinned wall or weakened portion of the elon¬ gated cylinder or tube 12 causes a longitudinal break along the length, of the elongated cylinder 12. The pulsating or fluctuating pressure field causes the broken elongated cylinder 12 to flap and to form a multiplicity of small diameter microfilaments 17. The continued feeding of liquid plastic 2 to the coaxial nozzle 5 stablizes the longitudinal break in the elongated cylinder a short distance below the coaxial nozzle 5. The plastic micro¬ filaments, however, remain connected to each other at the end of the elongated cylinder connected to the coaxial blowing nozzle. The microfilaments 17 are entrained in the entraining fluid 14, increase in length, are stretched and pulled and break away from the portion of the elon- gated cylinder attached to the coaxial nozzle.
A balancing pressure of a gas or of an inert gas, i.e. a slightly lower pressure, is provided in the area of the blowing nozzle into which the elongated tube or
O ?I cylinder shaped liquid film is blown. The illustrated coaxial nozzle can be used to produce plastic micro¬ filaments having relatively long lengths and relatively thick uniform diameters and is useful in blowing plastic microfilaments from low viscosity plastic material.
A transverse jet 13 is used to induce the external pulsating or fluctuating pressure field by directing an entraining fluid 14 over and around the blowing nozzle 5 at an angle to the axis of the blowing nozzle. The entraining fluid 14 is heated to about, below or above the temperature of the liquid plastic 2., by means not shown. The entraining fluid 14 is fed through distri¬ bution conduit 15, nozzle 13 and transverse jet nozzle orifice 13a and directed at the coaxial blowing nozzle 5. The transverse jet 13 is aligned to direct the flow of entraining fluid 14 over and around blowing nozzle 7 in the microfilament forming region at and behind the orifice 7a. The entraining fluid as it passes over and around the blowing nozzle 5 envelops and acts on the liquid plastic as it is being blown to form the elongated hollow tube or cylinder 12 and the microfilaments 17 and to detach the microfilaments from the coaxial blowing nozzle. The surface tension forces of the liquid plastic act on the diameter of the entrained, falling micro- filaments 17 and cause the diameter of the microfilaments to seek a minimum surface area and to form a circular shaped cross-section area.
Quench or heating nozzles 18 having orifices 18a are disposed below and on both sides of coaxial blowing nozzle 5 and direct cooling or heating fluid 19 at and into contact with the liquid plastic microfilaments 17 to rapidly cool or heat and cure and solidify the liquid plastic and form a smooth, hardened plastic microfilaments. The quench or heating fluid 19 also serves to carry the plastic microfilaments away from the coaxial blowing nozzle 5. Sufficient heating and curing time can be provided by using a heated fluidized bed, heated liquid carrier or belt carrier system for the thermosetting plastic microfilaments to cure and harden the micro¬ filaments with substantially little or no distortion or effect on the size of shape of the microfilaments. The solidified and hardened plastic microfilaments are collected by suitable means not shown.
The Figure 3 of the drawings illustrates a pre¬ ferred embodiment of the invention in.^ic the ower por¬ tion of the outer coaxial nozzle 7 is tapered downwardly and inwardly at 21. This embodiment as in the previous embodiment comprises coaxial blowing nozzle 5 which consists of inner nozzle 6 with orifice 6a and outer nozzle 7 with orifice 7a. The figure of the drawings also shows elongated hollow plastic tube or cylinder shaped liquid film 12 with a pinched portion 16 and a multiplicity of plastic microfilaments 17. There is shown disposed in annular space 8 on two opposite sides of the lower outer surface of inner nozzle 6 two thickened or enlarged portions 20 means for providing the thinned wall or weakened portion of the elongated plastic tube or cylinder 12. The length, diameter and height of the thickened or enlarged portions 20. are such that they cause the flow of liquid plastic as it passes over and around the enlarged or thickened portions 20 to become thinned and weakened.
The use of the tapered nozzle 21 construction is found to substantially assist in the formation of a thin liquid plastic film 9 in the area between orifice 6a of . inner nozzle 6 and orifice 7a of outer nozzle 7. The inner wall surface 22 of the taper portion 21 of the outer nozzle 7 when pressure is applied to liquid plastic 2 forces the liquid plastic 2 to squeeze through a fine gap formed between the outer edge of orifice 6a and the inner surface 22 of form the thin liquid plasitc film 9 across orifice 6a and 7a. Thus, the formation of the liquid plastic film 9 does not in this embodiment rely solely on the surface tension properties of the liquid plastic. The illustrated coaxial nozzle can be used to produce plastic microfilaments having relatively long lengths and allows making microfilaments of smaller diameter than those made using the Figure 2 apparatus and is particularly useful in blowing high viscosity plastic materials and compositions....
The diameter of the microfilaments is determined in part by the thickness of the wall of the elongated hol¬ low plastic tube or cylinder which is determined by the gap formed by the tapered nozzle 21 and the outer edge of the inner nozzle 6a. This apparatus allows the use of larger inner diameters of outer nozzle 7 and larger inner diameters of inner nozzle 6, both of which reduce the possiblity of plugging of the coaxial nozzles when in use.
The Figure 3 of the drawings also shows an embodi¬ ment of the invention in which the outer portion of the transverse jet 13 is flattened to form a generally rectangular or oval shaped orifice opening 13a. The orifice opening 13a can be disposed at an angle relative to a line drawn through the central axis of coaxial nozzle 5. The preferred angle, however, is that illustrated in the drawing. That is, at an angle of about 90° to the central axis of the coaxial nozzle 5.
The use of the flattened transverse jet entrain¬ ing fluid was found, at a given velocity, to concentrate the effect of the fluctuating pressure field and to increase the amplitude of the pressure fluctuations induced in the region of the formation of the elongated hollow plastic tube or cylinder at the opposite or lee side of the blowing nozzle 5.
The Figures 4A, 4B and 4C of the drawing's show detailed cross-sections and top plane views of three embodiments of the coaxial blowing nozzle tips of the present invention.
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O PI In the Figure 4A there is shown disposed in annular space 8 on the lower outer surface of inner nozzle 6 a single thickened or enlarged portion 20 for providing the thinned wall or weakened portion of the elongated hollow tube or cylinder 12.
In the Figure 4B there is shown disposed in annular space 8 on opposite sides of the lower outer surface of inner nozzle 6 two thickened or enlarged portions 20 for providing the thinned wall or weakened portions of the elongated hollow tube or cylinder 12.
In the Figure 4C there is shown disposed in annu¬ lar space 8 equally spaced on the outer surface of inner nozzle 6 four thickened or enlarged portions 20 for providing the thinned wall or weakened portions of the elongated hollow tube or cylinder 12.
O PI ORGANIC FILM FORMING' MATERIAL AND PLASTIC COMPOSITIONS
The organic film forming material and compositions and particularly the plastic materials and compositions from which the plastic microfilaments of the present in¬ vention are made can be varied to obtain the desired phy¬ sical characteristics for blowing and forming, cooling or heating and curing the microfilaments and the desired stren gth characteristics of the plastic microfilaments produced. The constituents of the plastic compositions can vary de¬ pending on their intended use.
The process and apparatus of the present invention can be used to blow microfilaments from suitable film formi plastic materials or compositions having sufficient vis¬ cosity at the temperature at which the microfilaments are blown to form a stable elongated cylinder shape of the plastic material being blown and the microfilaments.
The plastic materials to be used to form the micro¬ filaments are selected and can be treated and/or mixed with other materials to adjust their viscosity and surface ten¬ sion characteristics such that at the desired blowing tem¬ peratures they form stable films and are capable of forming the elongated hollow plastic tubes or cylinders and micro¬ filaments of the desired length and diameters.
The plastic compositions that can be used to form microfilaments include thermosetting and thermoplastic materials such as polyethylene, polypropylene, polystyrene, polyesters, polyurethanes, polychloro-trifϊuoro ethylene, polyvinyl fluoride, polyvinylidene, polymethyl methacrylate acetyl, phenol-formaldehyde resins and silicone and poly¬ carbonate resins. The plastic compositions that can be used also include cellulose acetate, cellulose acetate-butyrate, and cellulose acetate-propionate.
OMPI Thermoplastic resins that can be used are poly- vinyl resins such as polyvinyl alcohol, polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, polyvinyl butyral, polystyrene, polyvinylidene chloride, and acrylic resins such as polymethyl methacrylate, polyallyl, poly¬ ethylene, and polyamide (nylon) resins.
Thermosetting resins that can be used include alkyd, polysiloxane, phenol-formaldehyde, urea-formaldehyde and melamine-formaldehyde resins.
The plastic compositions disclosed in applicant's U. S . Patent 4,303,603, Veatch et al U.S. Patent 2,797,201 and the Morehouse, Jr. U.S. Patent 3,615,972 can be used in carrying out the present invention and the disclosures of said patents are accordingly incorporated herein in their entirety by reference.
There may be added to the plastic compositions chemical agents or additives which effect the viscosity of the compositions or of the surface film of the micro¬ filaments in order to obtain the desired viscosities needed to obtain a stable film for blowing the hollow elongated tube or cylinder. Suitable chemical agents are materials that act as solvents for the plastic compositions. The solvents that are used will, of course, depend on the solu¬ bility in the solvent of the plastic composition used. Water, alcohols, eithers, esters, organic acids, hydro¬ carbons and chlorinated hydrocarbons can be used as solv¬ ents. To assist in the blowing and formation of the plastic microfilaments and to control the surface tension and vis¬ cosity of the elongated cylinder being formed suitable surface active agents, such as colloidal particles of insoluble substances and viscosity stabilizers can be added to the plastic composition as additives. These additives can affect the viscosity of the surface film of the hollow elongated tube or cylinder to stabilize the film during cylinder formation.
For a more specific description of the plastic and resin compositions see Zimmerman and Lavine,- "Handbook of Material Trade Names", Vols. I-IV, 1953-1965.
O PI The plastic compositions of the present inven¬ tion are formulated to have a relatively narrow temperatur difference between the liquid temperature and the plastic hardening temperature (thermoplastic) or a relatively narrow temperature difference between the liquid temperatur and the thermosetting and curing temperature. The plastic compositions are formulated such that they have a high rate of viscosity increase with the hardening temperature or the thermosetting temperature such that the microfilaments will rapidly solidify, harden and strengthen. That is, they change from liquid to solid within a. relative narrowly defined temperature range and/or cure in a relatively short time.
BLOWING GAS
The plastic microfilaments can be blown with a gas, e.g. an inert gas. Suitable blowing gases can be argon, nitrogen and air. The blowing gases can be selected to react with the plastic film forming material or composition, e.g. to assist in the hardening and/or curing of the micro¬ filaments. The blowing gas in reacting with the film formin material as the elongated cylinder is being blown and forme can to some extent help to stabilize (against break-up) the film forming plastic material used to form the elongated cylinder and microfilaments and allow- sufficient time for the microfilaments to form and harden. For certain uses, oxygen or air can be used as or added to the blowing gas. The blowing gas can include a catalyst or hardening agent for the plastic compositions. The addition of a catalyst or hardening agent to the blowing gas prevents contact of the catalyst or hardening agent with the plastic composition until a time just before the hollow elongated tube or cylinder is formed.
OMH The entraining fluid can be a gas at a high or low temperature and can be selected to react with or be inert to the plastic composition. Suitable entraining fluids are nitrogen, air, steam and argon. A gaseous catalyst for the plastic can also be included in the entraining fluid.
The quench or heating fluid can be a liquid, a iiquid dispersion or a gas. Suitable quench or heating fluids are steam, a fine water spray, air, nitrogen or mixtures thereof. The selection of a specific quench or heating fluid and quench or heating temperature depends to some extent on the plastic composition from which the "hollow elongated tube or cylinder is blown.
PROCESS CONDITIONS
The organic film forming materials and/or plastic materials and compositions of the present invention are in a liquid-fluid form at the desired blowing temperature and during the blowing operation. The liquid plastic compositio can be at a temperature of about 0°C. to about 400°C, preferably 10°C. to 300°C and more preferably 20°C to 200°C, depending on the constituents and state of polymerization of, for example, the plastic composition. The plastic comp- sition at the blowing temperature is liquid, fluid and flows easily. The liquid plastic just prior to the blowing oper¬ ation can have a viscosity of 0.10 to 600 poises, usually 10 to 350 poises and more usually 30 to 200 poises.
The liquid plastic is continuously fed to the coaxial blowing nozzle during the blowing operation to pre¬ vent premature breaking and detaching of the elongated tube or cylinder shaped liquid plastic film as it is being formed by the blowing gas.
The blowing gas or, inert blowing gas will be at about the same temperature as the liquid plastic being blown. The blowing gas temperature can,however, be at a higher temp¬ erature than the liquid plastic to assist in maintaining the fluidity of the hollow liquid plastic tube or cylinder during the blowing operation or can be at a lower temperature than the liquid plastic to assist in the solidification and hard ening of the plastic microfilaments as they are formed. The pressure of the blowing gas is sufficient to blow the micro filaments and will be slightly above the pressure of liquid plastic film at the orifice 7a of the outer nozzle 7. The blowing gas pressure will also depend on and be slightly above the ambient pressure external to the blowing nozzle. The temperatures of the blowing gases will depend on the blowing gas used and the viscosity-temperature-shear relationship for the film forming plastic materials used to make the microfilaments. The ambient pressure external to the blowing nozzle will be such that it substantially balances, but is slightly less than the blowing gas pressure.
The transverse jet inert entraining fluid which is directed over and around the coaxial blowing nozzle to assist in the formation of the hollow elongated tube or cylinder and detaching of the plastic microfilaments from the coaxial blowing nozzle can be at about the same temper¬ ature as the liquid plastic being blown. The entraining fluid can, however, be at a higher temperature than the liquid plastic to assist in maintaining the fluidity of the hollow elongated tube or cylinder and the microfilaments during the blowing operation or can be at a lower temper¬ ature than the liquid plastic to assist in the stabilization of the forming elongated hollow tube or cylinder film and in the solidification and hardening of the microfilaments.
The transverse jet entraining fluid which assists in detaching of the plastic microfilaments from the coaxial blowing nozzle can have a linear velocity in the region of microfilament formation of 1 to 120 ft/sec, usually 5 to 80 ft/sec and more usually 10 to 60 ft/sec.
The length of the plastic microfilaments and the diameter of the plastic microfilaments depends to some extent on the viscosity of the plastic material and the linear velocity of the transverse jet entraining fluid. The quench or heating fluid is at a temperature suc that it rapidly cools or heats the microfilaments to solid¬ ify, harden and strengthen the liquid plastic microfilaments The quench cooling fluid can be at a temperature of 0 to 200°F., usually 40 to 200°F. and more usually 50 to 100°F. The heating fluid can be at a temperature of 100 to 800°F. , usually 200 to 600°F. and more usually 300 to 500°F., depending on the plastic composition.
The time elapsed from commencement of the blowing of the thermoplastic composition to the cooling and initial hardening of the microfilaments can be .0001 to 60.0 seconds preferably .0010 to 30.0 seconds and more preferably 0.10 to 10.0 seconds.
Where a thermosetting plastic composition is used to form the microfilaments, the time elapsed from commence¬ ment of the blowing of the plastic elongated hollow tube or cylinder to the heating and curing of the microfilaments can be 0.10 second to 30 minutes, preferably 1 second to 20 minutes and more preferably 10 second to 10 minutes.
CMPI ' APPARATUS
Referring to Figures 1 and 2 of the drawings, the container vessel is constructed to maintain the liquid plastic at the desired operating temperatures. The liquid plastic 2 is fed to coaxial blowing nozzle 5. The coaxial blowing nozzle 5 consists of an inner nozzle 6 having an outside diameter of 0.32 to 0.010 inch, preferably 0.20 to 0.015 inch and more preferably 0.10 to 0.20 inch and an outer nozzle 7 having an inside diameter of 0.420 to 0.020 inch, preferably 0.260 to 0.025 and more preferably 0.130 to 0.030 inch. The inner nozzle 6 and outer nozzle 7 form annular space 8 which provides a flow path through which the liquid plastic 2 is extruded. The distance between the inner nozzle 6 and outer nozzle 7 can be 0.050 to 0.004, preferably 0,030 to 0.005 and more preferably 0.015 to 0,008 inch.
The orifice 6a of inner nozzle 6 terminates a short distance above the plane of orifice 7a of outer nozzle 7. The orifice 6a can be spaced above orifice 7a at a distance of 0.001 to 0.125 inch, proferably 0.002 to 0.050 inch and more preferably 0.003 to 0.025 inch. The liquid plastic 2 flows downwardly and is extruded through annular space 8 and fills the area between orifice 6a and 7a. The orifices 6a and 7a can be made from stainless steel, platinum alloys, glass of fused alumina. Stainless steel, however, is preferred. The surface tension forces in the liquid plastic 2 form a thin liquid plastic film 9 across orifices 6a and 7a which has about the same or a smaller thickness as the distance of orifice 6a is spaced above orifice 7a. The liquid plastic film 9 can be 25 to 3175 microns, preferably 50 to 1270 microns and more preferably 76 to 635 microns thick.
The Figure- 2. blowing nozzle can be used to blow liquid plastic at relatively low viscosities, for example, of 10 to 60 posies, and to blow plastic microfilaments of relatively thick diameter, for example, of 20 to 100 microns or more. The transverse jet 13 is used to direct an entraining fluid 14 through nozzle 13 and transverse jet nozzle orifice 13a at the coaxial blowing nozzle 5. The coaxial blowing nozzle 5 has an outer diameter of 0.52 to 0.30 inch, preferably 0.36 to 0.035 inch and more preferably 0.140 to 0.040 inch.
The transverse jet 13 is aligned to direct the flow of entraining fluid 14 over and around outer nozzle 7 in the hollow elongated tube or cylinder and microfilament forming region of the roifice 7a. The orifice 13a of transverse jet 13 is locatd a distance of 0.5 to 14 times, preferably 1 to 10 times and more preferably 1.5 to 8 times and still more preferably 1.5 to 4 times the outside diameter of coaxial blowing nozzle 5 away from the point of intersect of a line drawn along the center axis of transverse jet 13 and a line drawn along the center axis of coaxial blowing nozzle 5. The center axis of transverse jet 13 is aligned at an angle of 15 to 85°, preferably 25 to 75° and more preferably 35 to 55° relative to the center axis of the coaxial blowing nozzle 5. The orifice 13a can be circular in shape and have an inside diameter of 0.32 to 0.010 inch, preferably 0.20 to 0.015 inch and more preferably 0.10 to 0.020 inch.
The line drawn through the center axis of transverse jet 13 intersects the line drawn through the center axis or coaxial blowing nozzle 5 at a point above the orifice 7a of outer nozzle 7 which is .5 times to 4 times, preferably 1.0 to 3.5 times and more preferably 2 to 3 times the" outside diameter of the coaxial blowing nozzle 5.
The entraining fluid assists in the formation and detaching of the plastic microfilaments from the coaxial blowing nozzle. The use of the transverse et and entraining fluid in the manner described also discourages wetting of th outer wall surface of the coaxial blowing nozzle 5 by the liquid plastic being blown.
' O P The quench or heating nozzles 18 are disposed below and on both sides of coaxial blowing nozzle 5 a sufficient distance apart to allow the microfilaments 17 to fall between the quench nozzles 18. The quench nozzles 18 direc cooling or heating fluid 19 at and into contact with the liquid plastic microfilaments 17 to cool or heat and solidify the liquid plastic and form hard, smooth, plastic microfilaments.
The Figure 3 of the drawings illustrates a preferred embodiment of the invention. It is found that in blowing liquid plastic compositions at high viscosities that is is advantageous to immediately prior to blowing the liquid plastic to provide by extrusion a very thin liquid plastic film for blowing into the elongated cylinder shape liquid film 12. The thin liquid plastic film 9 is provided by having the lower portion of the outer coaxial nozzle 7 tapered downwardly and inwardly at 21. The tapered portion 21 and inner wall surface 22 thereof can be at an angle of 15 to 75°, preferably 30 to 60° and more preferably about 45° relative to the center axis of coaxial blowing nozzle 5. The orifice 7a can be 0.10 to 1.5 times, preferably 0.20 to 1.1 times and more preferably 0.25 to .8 times the. inner diameter of orifice 6a of inner nozzle 6.
The thickness of the liquid plastic film 9 can be varied by adjusting the distance of orifice 6a of inner nozzle 6 above orifice 7a of outer nozzle 7 such that the distancebetween the peripheral edge of orifice 6a and the inner wall surface 22 of tapered nozzle 21 can be varied. By controlling the distance between the peripheral edge of orifice 6a and the inner wall surface 22 of the tapered nozzle to form a very fine gap and by controlling the pressure applied to feed the liquid plastic 2 through annular space 8 the liquid plastic 2 can be squeezed or extruded through the very fine gap to form a relatively thin liquid plastic film 9.
OMPI The proper gap can best be determined by pressing the inner coaxial nozzle 6 downward with sufficient pressure to completely block-off the flow of plastic, and to then very slowly raise the inner coaxial nozzle 6 until a stable system is obtained, i.e. until the hollow elongated plastic cylinder and the plastic microfilaments are being formed.
The tapered' nozzle construction illustrated in Figure 3 can be used to blow plastic compositions at relatively high viscosities as well as to blow plastic compositions at the relatively low viscosities referred to with regard to Figure 2 of the drawings. The Figure 3 embodiment of the invention is of particular advantage in blowing relatively long small diameter microfilaments.
Referring to Figures 4A, 4B and 4C of the drawings there is shown disposed in annular space 8 on the outer surface of inner nozzle 6 thickened or enlarged portion 20 means for providing the thinned wall or weakened portion of the elongated hollow tube or cylinder. The length, diameter and height of the thickened or enlarged portion 20 are such that they cause the flow of liquid plastic as it passes over and around the thickened or enlarged portion 20 to become thinned and weakened. The thinned and weakened portion of the liquid plastic is carried down¬ wardly and outwardly to form the elongated hollow plastic tube of cylinder 12, which as a result of the thinned and weakened portion breaks up into a multiplicy of relatively long microfilaments 17.
DESCRIPTION OF THE MICROFILAMENTS
The microfilaments made in accordance with the present invention can be made from a variety of organic film forming materials and compositions, particularly plastic compositions.
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OMPI The plastic microfilaments made in accordance with the present invention can be made from suitable composition selected to have relatively high temperature resistance, be resistant to chemical attack and be resistant to weathering.
The plastic microfilaments can be made in various lengths and diameters, depending upon the desired end use of the microfilaments. The microfilaments can have a length one half to twelve inches, preferably one to eight inches and more preferably two to six inches. The microfilaments can have a diameter of 0.5 to 40 microns, preferably- 1.0 to 30 microns and more preferably 2 to 10 microns.
It is found that for a given set of operating conditions that the plastic microfilaments that are obtained have a relatively uniform, narrow diameter size and length size distribution.
EXAMPLES
Example 1
A thermoplastic composition comprising polyethylene polymer is used to make plastic microfilaments .
A plastic composition is heated to form a fluid plastic having a viscosity of about 10 to 20 poises at the blowing nozzle.
The liquid plastic is fed to the apparatus of •Figures 1 and 2 of the drawings. The liquid plastic passes through annular space 8 of about 0.005 inch, of blowing nozzle 5 and forms a thin liquid plastic film across the orifices 6a and 7a. A heated blowing gas consisting of nitrogen at a positive pressure is applied to the inner surface of the liquid plastic film causing the film to distend downwardly into a elongated cylinder shape with its inner end attached to the outer edge or orifice 7a.
O _?I The transverse jet is used to direct an entraining fluid which consists of nitrogen heated to about the temperature of the liquid plastic, at a linear velocity of 20 to 80 feet per second over and around the blowing nozzle 5 which entraining fluid assists in the formation of the elongated cylinder and of a multiplicity of plastic micro¬ filaments and detaching of the plastic microfilaments from the elongated cylinder and causing the plastic microfilament to be entrained in the entraining fluid and carried away fro theblowing nozzle 5. The transverse et is aligned at an angle of 35 to 50° relative to the blowing nozzle.
The entrained plastic microfilaments are cooled to about ambient temperature by a cool quench fluid consisting of a fine water spray which quickly cools, solidifies and hardens the plastic microfilaments.
Plastic microfilaments having a diameter of 2 to 6 microns diameter and a one to five inch length are obtained. Example 2
A thermosetting plastic composition comprising a mixture of 50% by weight acrylonitrile and 50% by weight vinylidene chloride and a suitable catalyst is used to make plastic microfilaments.
The plastic composition mixture at the blowing nozzle has a viscosity of about ten poises.
The liquid plastic mixture is heated and is fed to the apparatus of Figures 1 and 3 of the drawings. The liquid plastic is passed through annular space 8 of blowing nozzle 5 and into tapered portion 21 of outer nozzle 7. The liquid plastic under pressure is squeezed and extruded through a fine gap • formed between the outer edge of orifice 6a and the inner surface 22 of the tapered portion 21 of outer nozzle 7 and forms a thin liquid plastic film across the orifices 6a and 7a. A heated blowing gas consisting of nitrogen at a positive pressure is applied to the inner surface of the liquid plastic film causing the fil to distend outwardly into an elongated cylinder shape with its inner end attached to the outer edge of orifice 7a.
The transverse jet is used to direct an entraining fluid which consists of heated nitrogen at about the temperature of the liquid plastic at a linear velocity of 20 to 80 feet per second over and around the blowing nozzle 5. The entraining fluid assists in the formation of the elongated cylinder and of a multiplicity of plastic microfilaments and detaching of the plastic microfilaments from the elongated cylinder and causes plastic micro¬ filaments to be entrained in the fluid and carried away from the blowing nozzle.
The entrained microfilaments are contacted with a heating fluid consisting of heated nitrogen which solidifies, hardens and begins to cure the liquid plastic microfilaments.
Plastic microfilaments having a 1 to 5 micron diameter and having a length of 2 to 10 inches are obtained.
UTILITY
The plastic microfilaments of the present invention have many uses including the use of the microfilaments as a filler or reinforcing material in rubber, cement, plaster and asphalt compositions. The plastic microfilaments and fibers can be used to make tire cords and filter media.
The microfilaments can be spun into fibers and woven into fabrics or can be used to make matted fabrics.
The plastic microfilaments can advantageously be used in plastic or resin boat construction to produce high strength hulls.
O Π WIFO These and other uses of the present invention will become apparent to those skilled in the art from the foregoing description and the following appended claims.
It will be understood that various changes and modifications may be made in the invention, and that the scope thereof is not to be limited except as set forth in the claims.
OMPI Quench nozzles 18 where the plastic is thermo¬ plastic and heating nozzles where the plastic is thermosetting may be disposed below and on either side of the blowing nozzle 5 to direct cooling fluid or heating fluid 19 at and into contact with the plastic micro¬ filaments 17 to cool or heat and cure, solidify and harden the plastic to form hard, smooth plastic micro¬ filaments 17.
OMFI

Claims

WHAT IS CLAIMED
Claim 1. A method for making microfilaments from an organic film forming material which comprises forming liquid organic film forming material, forming a liquid film of said organic material across an orifice, applying a blowing gas at a positive pressure on the inner surface of the liquid organic film to blow the film and form an elon¬ gated hollow organic material tube or cylinder, forming a thinned wall or weakened portion of the elongated hollow tube or cylinder, subjecting the elongated hollow tube or cylinder during its formation to an external pulsating or fluctuating pressure field having periodic osciallations, said pulsating or fluctuating pressure field acting on said elongated hollow tube or cylinder to assist in its formatio and to assist in the formation of a multiplicity of organic material microfilaments and in detaching the organic material microfilaments from said orifice.
Claim 2. The method of Claim 1 wherein the liquid film of organic film forming material is formed across the orifice of a coaxial blowing nozzle, said blowing nozzle having an inner nozzle to convey said blowing gas to the inner surface of the liquid organic material film, and an outer nozzle to convey said organic material to said orifice and means disposed near said orifice form the thinned wall or weakened portion of said elongated hollow organic material tube or cylinder, and pulsating or fluctuating pressure inducing means is directed at an angle to said coaxial blowing nozzle to induce said pulsating or fluctuating pressure filed at the opposite or lee side of said coaxial blowing nozzle in the wake or shadow of said coaxial blowing nozzle.
Claim 3. The method of Claim 1 wherein an entrainin fluid is directed at an angle to a coaxial blowing nozzle having an orifice, an inner nozzle and an outer nozzle, the liquid film of organic film forming material is formed
( O PI ° across the orifice, the blowing gas is conveyed to the inn surface of the liquid organic film through said inner nozz the film forming organic material is conveyed through said outer nozzle to said orifice, and means disposed near said orifice between the inner and outer nozzle form a thinned wall or weakened portion of said elongated hollow organic material tube or cylinder and the entraining fluid passes over and around said coaxial nozzle to fluid dyanmically induce the pulsating or fluctuating pressure field at the opposite or lee side of the blowing nozzle in the wake or shadow of the coaxial blowing nozzle.
Claim 4. The method of Claim 3 wherein the lower portion of the outer nozzle is tapered inwardly to form with the outer edge of the inner nozzle a fine gap and the film forming organic material is fed under pressure and extruded through said gap to form a thin film of film forming organic material across the orifice of the blowing nozzle.
Claim 5. A method for making plastic microfilament which comprises forming liquid plastic, forming a liquid plastic film across an orifice, applying a blowing gas at a positive pressure on the inner surface of the liquid plastic film to blow the film and form an elongated hollow plastic tube or cylinder, forming a thinned wall or weakened portion of the elongated hollow tube or cylinder, subjecting the elongated hollow tube or cylinder during its formation to a pulsating or fluctuating pressure field havin periodic oscillations, said pulsating or fluctuating pressure field acting on said elongated hollow tube or cylinder to assist in its formation and to assist in the formation of a multiplicity of plastic microfilaments and in detaching the plastic microfilaments from said orifice.
OMPI
Claim 6. The method of Claim 5 wherein the liquid plastic film is formed across the orifice of a coaxial blowing nozzle, said blowing nozzle having an inner nozzle to convey said blowing gas to the inner surface of the liqu plastic film, and an outer nozzle to convey said liquid plastic to said orifice and means disposed near said orific between the inner and outer nozzle form a thinned wall or weakened portion of said elongated hollow tube or cylinder, and pulsating or fluctuating pressure inducing means is directed at an angle to said coaxial blowing nozzle to indu said pulsating or fluctuating pressure field at the opposit or lee side of said coaxial blowing nozzle in the wake or shadow of said coaxial blowing nozzle.
Claim 7. The method of Claim 6 wherein the liquid plastic has a viscosity of 0.10 to 600 poises.
Claim 8. The method of Claim 6 wherein the liquid plastic has a viscosity of 10 to 350 poises.
Claim 9. the method of Claim 6 wherein the liquid plastic has a viscosity of 30 to 200 poises.
Claim 10. The method of Claim 3 wherein said entraining fluid has a linear velocity in the region of the elongated hollow tube or cylinder formation of 1 to 120 ft/sec and entrains and transports the microfilaments away from the blowing nozzle.
Claim 11. The method of Claim 10 wherein said entraining fluid has" a linear velocity in the region of elongated hollow tube or cylinder formation of 5 to 80 ft/sec.
Claim 12. The method of Claim 10 wherein said entraining fluid has a linear velocity in the region of elongated hollow tube or cylinder formation of 10 to 60 ft/sec.
Claim 13. The method of Claim 6 wherein the plastic microfilaments are one to 8 inches in length and have a diameter of 1.0 to 30 microns.
OMP
Claim 14. The method of Claim 6 wherein the plast microfilaments are 2 to 6 inches in length and 2.0 to 10 microns in diameter.
Claim 15. A method for making plastic micro¬ filaments which comprises forming liquid plastic, forming a liquid plastic film across an orifice of a coaxial blowi nozzle, said blowing nozzle having an inner nozzle to convey a blowing gas to the inner surface of the liquid film and an outer nozzle to convey said liquid plastic to said orifice, applying said blowing gas through said inner nozzle at positive pressure on the inner surface of the liquid plastic film to blow the film downwardly and outwar to form an elongated hollow plastic tube or cylinder, means disposed near said orifice between the inner and outer nozzle form a thinned wall or weakened portion of said elongated hollow tube or cylinder, continuously feeding sai liquid plastic to said outer nozzle while said elongated hollow tube or cylinder is being formed, directing an entraining fluid at said coaxial blowing nozzle at an angle relative to a line drawn through the center axis of said coaxial blowing nozzle, said entraining fluid passing over and around said coaxial blowing nozzle to fluid dynamically induce a pulsating or fluctuating pressure field having periodic oscillations at the opposite or lee side of the blowing nozzle in the wake or shadow of said blowing nozzle said entraining fluid acting on the elongated hollow plasti tube or cylinder to break up said tube or cylinder into a multiplicity of plastic microfilaments which are connected to • said tube or cylinder at a point proximate to the coaxial blowing nozzle and said entraining fluid acting to detach the plastic microfilaments from the coaxial blowing nozzle and solidifying said plastic microfilaments.
Claim 16. the method of Claim 15 wherein the lower portion of the outer nozzle is tapered inwardly to form with the outer edge of the orifice of the inner nozzle a fine gap and feeding the liquid plastic under pressure through said gap to form a thin film of liquid plastic across the orifice of the blowing nozzle. /^IRE
( OMPI
Claim 17. The method of Claim 16 wherein the plastic microfilaments are one to 8 inches in length and have a diameter of 1.0 to 30 microns.
18. The method of Claim 16 wherein the plastic microfilaments are 2 to 6 inches in length and 2.0 to 10 microns in diameter.
Claim 19. An apparatus for blowing plastic microfilaments comprising means for holding plastic film forming material, a coaxial blowing nozzle comprising an inner nozzle having an inner orifice at the lower end thereof for a blowing gas and an outer nozzle having an outer orifice for the plastic material, and means for feedi said plastic material to said coaxial nozzle, said inner nozzle orifice being disposed proximate to said outer orifice, and means disposed near said inner nozzle orifice between the inner and outer nozzle for forming a thinned wall or weakened portion of an elongated hollow plastic material tube or cylinder, there being disposed external to said blowing nozzle a transverse jet cooperating with said blowing nozzle by which an entraining fluid is directed at said coaxial blwoing nozzle at an angl relative to a line drawn through the center, axis of said coaxial blowing nozzle such that said entraining fluid dynamically induces a pulsating or fluctuating pressure field having periodic oscillations at the opposite or lee side of the blowing nozzle in the wake or shadow of said blowing nozzle and means for solidifying and hardening said plastic microfilaments .
Claim 20. The apparatus fo Claim 19 wherein the lower portion of the outer nozzle is tapered inwardly to form with the outer edge of the orifice of the inner nozzle a fine gap.
> WiP
PCT/US1982/001616 1981-11-27 1982-11-17 Method and apparatus for producing plastic microfilaments WO1983001925A1 (en)

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US06/325,594 US4363646A (en) 1979-07-20 1981-11-27 Method and apparatus for producing microfilaments
US325,594 1981-11-27
US442,108821116 1982-11-16
US06/442,108 US4536361A (en) 1978-08-28 1982-11-16 Method for producing plastic microfilaments

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GB2112704A (en) 1983-07-27
AU1044683A (en) 1983-06-17
EP0095487A1 (en) 1983-12-07

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