Classifications

• • D—TEXTILES; PAPER
  • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
  • D02G—CRIMPING OR CURLING FIBRES, FILAMENTS, THREADS, OR YARNS; YARNS OR THREADS
  • D02G1/00—Producing crimped or curled fibres, filaments, yarns, or threads, giving them latent characteristics
  • D02G1/004—Producing crimped or curled fibres, filaments, yarns, or threads, giving them latent characteristics by heating fibres, filaments, yarns or threads so as to create a temperature gradient across their diameter, thereby imparting them latent asymmetrical shrinkage properties
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
  • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
  • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
  • D01F9/225—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles from stabilised polyacrylonitriles
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/32—Apparatus therefor
• • D—TEXTILES; PAPER
  • D02—YARNS; MECHANICAL FINISHING OF YARNS OR ROPES; WARPING OR BEAMING
  • D02G—CRIMPING OR CURLING FIBRES, FILAMENTS, THREADS, OR YARNS; YARNS OR THREADS
  • D02G1/00—Producing crimped or curled fibres, filaments, yarns, or threads, giving them latent characteristics
  • D02G1/20—Combinations of two or more of the above-mentioned operations or devices; After-treatments for fixing crimp or curl
  • D02G1/205—After-treatments for fixing crimp or curl

Definitions

• the present invention is directed to a process and an apparatus for crimping and permanently heat setting polymeric fibers without imparting stress or tension to the fibers.
• the invention relates to an apparatus and a process for providing a loop, coil or sinusoidal configuration to polymeric precursor fibers by heat treating the fibers without subjecting the fibers to stress or tension either before or during crimping.
• the process and apparatus of the invention is relatively inexpensive and simple and does not require the prior formation of a knitted fabric.
• the apparatus is especially useful to produce crimped fibers utilizing a multiplicity of precursor fibers of from 40,000 to
• 320,000 fibers (40K to 320K) which are assembled in the form of large size tows.
• the crimped fibers formed by the present invention when dyed possess good dye uniformity.
• crimp can generally be defined as a nonlinearity or waviness of a fiber or, more particularly, as the waviness of a fiber expressed as crimps per unit length.
• the crimp or bend in the fiber is induced by thermal/mechanical techniques, e.g. a stuffer box.
• the crimping of fibers is important in the manufacture of carpets because it provides bulk to the fibers by preventing two or more fibers from lying parallel to one another. As a result, the tufts of a carpet have greater covering power, appear softer, and provide greater resistance to wear and abrasion, among other benefits.
• Crimping is also useful in the processing of staple fibers and in the processing of high modulus fibers which are difficult to work with because of slipperiness.
• the crimp which is placed in most fibers, using a stuffer box is rarely uniform.
• the stuffer box technique produces fibers having a wavy, random zigzag type crimp which is V-shaped having sharp bends or kinks.
• the randomness of the crimp which is obtained causes the fibers to have a non-uniform crimp.
• the crimp produced by this method is regular or consistently irregular.
• Crimping of fibers in a stuffer box is achieved by passing the fibers into a uniformly heated chamber which is at the temperature required to heat set the fibers in their crimped or nonlinear configuration. As the fibers are forced into the chamber by feed rolls, they are pushed against fibers which are already in the chamber, thereby causing the fibers to bend and buckle (crimp) .
• a weighted tube fitted into the top of the stuffer box governs the flow and quantity of fibers into the stuffer box.
• the frequency (crimps per unit length) and the crimp amplitude of the fibers are controlled by regulating the speed of the feed rolls to that of the take up rolls as well as the weight of the tube. Crimp setting by this technique can be done for single fibers or tows having multiple fiber ends using the spunize technique.
• the crimps are generally characterized by numerous sharp bends in the fiber.
• the fiber In order to obtain a crimp in the fiber by present methods and apparatus, the fiber must undergo severe bending stresses. During bending two types of stress modes are developed in the fiber simultaneously. A tensile stress is developed along the outer curvature of the bent fiber, while a compressive stress is acting on the inner portion of the bend.
• crimp permanency after loading can differ between fiber producers and even among various types (e.g., bright and semidull) made by the same producer. Since the application of some tension on fibers inevitably occurs during normal fiber processing, it is to be expected that some loss in crimp definition will occur. This loss must be near identical from spindle to spindle, twister to twister, etc., otherwise the fibers will appear to be different since crimped fibers differ in appearance from uncrimped fibers as a result of the reduced bulking factor. At the same time, some fiber elongation is obtained during crimp removal which would tend to order the fiber microstructure. This could influence dyeing since a more ordered microstructure will take up dye differentially than fibers which have not undergone any elongation.
• European Publication No. 0199567 published October 29, 1990, of McCullough et al. discloses a method for preparing nonlinear carbonaceous fibers having physical characteristics resulting from heat treating stabilized polymeric fibers in the form of a knitted fabric. There is described a process wherein the knitted fabric is substantially irreversible heat set under conditions free of stress and tension. In order to obtain individual fibers or fiber tows which are nonlinear, it is necessary to knit and then deknit the fabric. However, the knitting and deknitting of a fabric to obtain the nonlinear fibers substantially increases the cost in producing the fibers.
• U.S. Patent No. 2,245,874 to Robinson discloses a method for forming curled fibers by passing the fibers over cold rollers under conditions to bend and stretch the fibers beyond their elastic limit. Such a process cannot be used to produce the stress free, nonlinear fibers having the physical properties of the invention.
• U.S. Patent No. 2,623,266 to Hemmi discloses the mechanical preparation of sinusoidal or spirally crimped fibers.
• the fibers are heated and passed through a series of bars which impart a meander-like crimp.
• the fibers are formed in a crimped and stretched state, i.e. a stress induced state.
• the apparatus of the invention comprises a conveying means in the form of a belt having a plurality of openings.
• a precursor polymeric fiber or fiber tow is supplied to the conveying means and a crimping mechanism is provided for inserting the fibers into the openings in the conveying means such that the fiber assumes a nonlinear configuration.
• the fiber positioned within the openings of the conveying means is transported substantially without stress or tension through at least one heating zone at a temperature and at a rate of speed sufficient to provide the fiber with a temporary or permanent heat set, and/or to carbonize the fiber.
• Each heating zone can comprise one or more heating units with one heating unit serving as a fiber oxidation or stabilization zone. Another heating unit serving as a means for substantially irreversibly or permanently heat set the fiber in an inert atmosphere.
• the invention resides in an apparatus for crimping and heat setting at least one polymeric precursor fiber, comprising a conveying means having a planar surface with a multiplicity of openings, means for supplying the fiber to said conveying means, means for inserting said fiber into the openings in the conveying means and for retaining said fiber in a nonlinear configuration in the openings substantially without imparting stress or tension on the fiber, and a heating zone through which said conveying means and fiber pass to heat set said fiber.
• the invention also resides in a process for crimping and heat setting at least one polymeric precursor fiber, comprising the steps of supplying the fiber to an apertured conveying means having a planar surface, inserting said fiber into at least two apertures of the conveying means so that the fiber is maintained in a nonlinear configuration without substantially imparting stress or tension on the fiber while the fiber is being held within said apertures, passing said nonlinear fiber in said unstressed condition through a heating zone at a temperature and at a rate of speed sufficient to provide the fiber with a temporary or permanent heat set, and/or to carbonize the fiber, and then cooling said fiber while in said nonlinear configuration.
• polymer or "polymeric precursor material” used herein applies to organic polymers as defined in Hawley's Condensed Chemical Dictionary, Eleventh Edition, published by Van Nostrand Rheinhold Company.
• the organic polymers generally include:
• fiber used herein is intended to include one or more fibers or filaments as well as an assembly of a multiplicity of fibers in the form of a 0 fiber tow.
• oxidized used herein applies to fibers that have been oxidized at a temperature of typically less than 250°C for acrylic fibers. It will 5 be understood that, in some instances, the fibers can also be oxidized by chemical oxidants at a lower temperature.
• permanent heat set used herein 0 applies to nonlinear carbonaceous fibers which have been heat treated until they possess a degree of irreversibility where the nonlinear fibers, when stretched to a substantially linear shape, without _ ⁇ exceeding their internal tensile strength, will revert to their original nonlinear configuration once the stress on the fiber is released. Accordingly, what is meant by “permanently set” is that a fiber possesses a degree of resiliency which manifests itself in a "reversible deflection" of the fiber when it is placed under stress such that the fiber is substantially linear in shape. When the stress is relieved, the fiber will return to its unstressed and nonlinear condition.
• reversible deflection defines the minimum limit of stretching the fiber which is expressed as a ratio of 1.2:1 where the fiber in the stretched condition is at least 1.2 times the length of the fiber in its relaxed or unstretched condition.
• the carbonaceous fibers are prepared from a suitable polymeric precursor fiber, which is stabilized, as for example by oxidation at a temperature which is typically less than 250°C for acrylic fibers.
• the stabilized fiber is then heat treated, in a relaxed and unstressed condition and in an inert atmosphere for a period of time sufficient to produce a heat induced thermoset reaction wherein additional cross-linking and/or a cross-chain cyclization reactions occur between the original polymer chains.
• the carbonaceous fiber of the invention can be classified into three groups depending upon the particular use of the fiber and the environment in which the fiber is used.
• the carbonaceous fiber is partially carbonized and has a carbon content of greater than 65 percent but less than 85 percent, is electrically nonconductive and does not possess any electrostatic dissipating characteristics, i.e., the fiber is not able to dissipate an electrostatic charge.
• electrically nonconductive as utilized in the present invention relates to a resistance of greater than 4 x 10 6 ohms/cm when measured on a 6K (6000 filaments) tow of fibers in which the individual fibers each have a diameter of from 7 to 20 microns.
• the specific resistivity of the carbonaceous fiber is greater than about 10 "1 ohm-cm and is -re ⁇
• the fiber is a stabilized and heat set acrylic fiber it has been found that a nitrogen content of 18 percent or higher results in an electrically nonconductive fiber.
• the carbonaceous fiber is classified as having a low electrical conductivity, i.e. 0 being partially electrically conductive, and having a carbon content of greater than 65 percent but less than 85 percent.
• Low conductivity means that a 6K tow of fibers has a resistance of from 4 x 10 6 to 4 x 10 3 ohms/cm.
• the carbonaceous fiber is derived 5 from a stabilized acrylic fiber and possesses a percentage nitrogen content of from 16 to 22 percent, preferably from 16 to 18.8 percent. Such a fiber finds particular use in sound absorbing and thermal barrier Q structures.
• the fiber has a carbon content of at least 85 percent and a nitrogen content of less than 10 percent.
• the fiber is characterized c as having a high electrical conductivity. That is, the fiber is substantially graphitic and has an electrical resistance is less than 4 x 10 3 ohms/cm. Correspondingly, the electrical resistivity of the fiber is less than 10" 1 ohm-cm. This fiber is useful as furnace insulation or in applications where electrical grounding or shielding is desired.
• the carbonaceous fiber of the third group can have imparted to it an electrically conductive property on the order of that of a metallic conductor by heating the fiber to a temperature above 1000°C in a non- oxidizing atmosphere.
• the electroconductive property can be obtained from selected starting materials such as pitch (petroleum or coal tar), polyacetylene, acrylic materials, e.g., a polyacrylonitrile copolymer such as PANOXTM (trademark of R.K. Textiles) or GRAFIL-01TM (trademark of E.I. du Pont de Nemours & Co.), polyphenylene, polyvinylidene chloride (SARANTM, a trademark of The Dow Chemical Company), and the like.
• pitch petroleum or coal tar
• polyacetylene acrylic materials, e.g., a polyacrylonitrile copolymer such as PANOXTM (trademark of R.K. Textiles) or GRAFIL-01TM (trademark of E.I. du Pont
• the fibers may comprise any polymeric precursor material capable of being heat set in the apparatus of the invention.
• the polymeric precursor fibers employed in the present invention are the high performance fibers such as oxidizied acrylic fiber (OPF) , aramid fibers, PBI fibers, etc.
• the polymeric precursor fibers are acrylic fibers selected from acrylonitrile homopolymers, acrylonitrile copolymers and acrylonitrile terpolymers, wherein said copolymers and terpolymers contain at least 85 mole percent acrylic units and up to 15 mole percent of one or more monovinyl units copolymerized with another polymer.
• the apparatus is particularly suited to prepare carbonaceous fibers as disclosed in the aforementioned European Publication No. 0199567.
• the apparatus of the invention is utilized to produce carbonaceous fibers from polymeric precursor material fibers without subjecting the fibers to a knit/deknit step.
• the apparatus comprises a conveying means which is provided with a multiplicity of openings into which the fibers are inserted to provide the fiber with a nonlinear shape, i.e. for crimping the fiber, without the application of tensile stress to the fiber.
• the conveying means transports the fiber without tension or stress through a heating zone comprising one or more heating units.
• One heating unit may comprise a fiber oxidation or stabilization zone.
• the fiber is provided with a nonlinear temporary set.
• Another heating unit may comprise a heating means for substantially irreversibly heat setting the fiber in an inert atmosphere to produce a carbonaceous fiber having a carbon content of greater than 65 percent.
• Fibers that are derived from nitrogen containing polymeric materials, such as acrylic based polymers, generally have a nitrogen content of from 5 to 35 percent, preferably from 16 to 25 percent, and more preferably from 18 to 20 percent.
• Figure 1 is a perspective view, partly in section of a crimping mechanism of the invention
• Figure 2 is an elevation view showing a section of the crimping unit of Figure 1;
• Figure 3 is a side elevation of the apparatus.
• the apparatus 10 of the invention comprises an apertured endless conveying belt 11 which travels around drive rolls 14, 14' and which extends through a closure or housing 12.
• the conveying belt can be in the form of a wire grid, screen or apertured belt.
• the housing 12 can contain one or more compartments for heating and, optionally, cooling.
• a heating chamber 16 containing one or more heaters 17, 17' through which a fiber or tow 18 passes followed by a cooling chamber 20 with one or more cooling fans 21.
• the fiber 18 is first passed between a crimping mechanism 13 and the apertured conveyor belt and is pushed by a plurality of finger members 22 on the crimping-mechanism into the apertures of the conveyer belt 11.
• the fiber 18 After passage through the housing 12, the fiber 18 is taken up on a take up roll 26. In operation, the fiber 18 is introduced into the apertures of the conveyor belt 11 by the crimping mechanism 13 where they are held in a relaxed condition and without the application of tension on the fiber during conveyance through the heating chamber 16.
• the crimper mechanism 13 comprises a plurality of the fingers 22 which are slideably mounted in sockets 15 extending from a rigid, reciprocating board.
• the lengths of the fingers 22 can be adjusted by sliding the fingers inwardly or outwardly of the sockets and by securing them in the desired position by means of adjustment screws 27.
• the depth of a loop of the fiber 18 extending through the apertures of the conveying belt can be adjusted.
• the configuration (amplitude of crimp) of the fiber 18 is determined by the length of the fiber loop extending through the apertures. It will be apparent that with a uniform length of the fingers 22, the fiber 18 will be provided with a uniform amplitude of a generally sinusoidal configuration. Similarly, if the fingers 22 are of a nonuniform or different lengths, the fiber will be provided with a corresponding nonuniform amplitude of sinusoidal configuration.
• the flat, reciprocating board illustrated in the figure
• the fingers can be generally tubular in shape, as illustrated in the drawing, or they can be in the form of relatively short, longitudinally extending, rib-like members. When the fingers are of a rib-like configuration, the openings provided in the conveying belt have correspondingly shaped rectangular openings to allow the ribs to enter the openings.
• the fiber 18 is delivered from a supply roll 28 onto the apertured conveying belt 11.
• the reciprocating crimping device 13 with its adjustable fingers 22, inserts or pushes the fiber 18 into the apertures of the belt 11 so that the fiber 18 is formed into a generally sinusoidal configuration-. After insertion of the fiber 18 into the apertures, it is conveyed into the housing 12 without the application of any stress or tension on - 1 li ⁇
• Housing 12 can contain one or more heating chambers 16. Where a preoxidized or stabilized fiber 18 is being carbonized, the heating chamber 16 is filled with an inert gas. The carbonization of the fiber 18 may be conducted by means of radiant heaters 17, by irradiation with a high energy source, or by any other means known in the art.
• the fiber 18, once it is heat set in chamber 16 in a nonlinear configuration is then, preferably, cooled in chamber 20 by cooling means 21 and carried out of the housing to be taken up on roll 26.
• the speed of the conveying belt 11 and rolls 26, 28 are synchronized so that the fiber placed on the conveyor belt 11 is not pulled out of the openings of the conveying belt or placed under stress or tension while passing through the heating chamber 16.
• the oxidized fiber is heated to a temperature of from 250°C to 1500°C in a nonoxidizing atmosphere such as nitrogen, argon, helium or hydrogen.
• the heating zone can be a single or multigradient furnace comprising a number of heating zones.
• the inert gases can be supplied to the heating zone through an opening 19 in the housing or may be injected at various points along the path of the fiber through a conduit into the housing.
• the fiber residence time in the heating zone is dependent upon the particular fiber utilized, the degree of heat set desired, and the temperat re(s) utilized.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Yarns And Mechanical Finishing Of Yarns Or Ropes (AREA)
• Inorganic Fibers (AREA)
• Preliminary Treatment Of Fibers (AREA)
• Disintegrating Or Milling (AREA)
• Reinforced Plastic Materials (AREA)
• Treatment Of Fiber Materials (AREA)

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Citations (14)

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• 1990
  • 1990-10-31 JP JP3502342A patent/JPH05505855A/ja active Pending
  • 1990-10-31 AT AT91902323T patent/ATE132209T1/de not_active IP Right Cessation
  • 1990-10-31 WO PCT/US1990/006314 patent/WO1992007982A1/en active IP Right Grant
  • 1990-10-31 BR BR909008033A patent/BR9008033A/pt not_active Application Discontinuation
  • 1990-10-31 EP EP91902323A patent/EP0507847B1/de not_active Expired - Lifetime
  • 1990-10-31 DE DE69024502T patent/DE69024502T2/de not_active Expired - Fee Related

Patent Citations (14)

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