Classifications

• • 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
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/07—Addition of substances to the spinning solution or to the melt for making fire- or flame-proof filaments
• • 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
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
• • A—HUMAN NECESSITIES
  • A41—WEARING APPAREL
  • A41D—OUTERWEAR; PROTECTIVE GARMENTS; ACCESSORIES
  • A41D13/00—Professional, industrial or sporting protective garments, e.g. surgeons' gowns or garments protecting against blows or punches
  • A41D13/008—Professional, industrial or sporting protective garments, e.g. surgeons' gowns or garments protecting against blows or punches protecting against electric shocks or static electricity
• • A—HUMAN NECESSITIES
  • A41—WEARING APPAREL
  • A41D—OUTERWEAR; PROTECTIVE GARMENTS; ACCESSORIES
  • A41D31/00—Materials specially adapted for outerwear
  • A41D31/04—Materials specially adapted for outerwear characterised by special function or use
  • A41D31/08—Heat resistant; Fire retardant
• • 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
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/04—Pigments
• • 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
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/09—Addition of substances to the spinning solution or to the melt for making electroconductive or anti-static filaments
• • 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
  • D01F1/00—General methods for the manufacture of artificial filaments or the like
  • D01F1/02—Addition of substances to the spinning solution or to the melt
  • D01F1/10—Other agents for modifying 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
  • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
  • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
  • D01F8/12—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyamide as constituent
• • 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
  • D02G3/00—Yarns or threads, e.g. fancy yarns; Processes or apparatus for the production thereof, not otherwise provided for
  • D02G3/02—Yarns or threads characterised by the material or by the materials from which they are made
  • D02G3/04—Blended or other yarns or threads containing components made from different materials
  • D02G3/047—Blended or other yarns or threads containing components made from different materials including aramid fibres
• • 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
  • D02G3/00—Yarns or threads, e.g. fancy yarns; Processes or apparatus for the production thereof, not otherwise provided for
  • D02G3/22—Yarns or threads characterised by constructional features, e.g. blending, filament/fibre
• • 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
  • D02G3/00—Yarns or threads, e.g. fancy yarns; Processes or apparatus for the production thereof, not otherwise provided for
  • D02G3/44—Yarns or threads characterised by the purpose for which they are designed
  • D02G3/441—Yarns or threads with antistatic, conductive or radiation-shielding properties
• • 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
  • D02G3/00—Yarns or threads, e.g. fancy yarns; Processes or apparatus for the production thereof, not otherwise provided for
  • D02G3/44—Yarns or threads characterised by the purpose for which they are designed
  • D02G3/443—Heat-resistant, fireproof or flame-retardant yarns or threads
• • D—TEXTILES; PAPER
  • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B2331/00—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products
  • D10B2331/02—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyamides
  • D10B2331/021—Fibres made from polymers obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polycondensation products polyamides aromatic polyamides, e.g. aramides
• • D—TEXTILES; PAPER
  • D10—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B—INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES
  • D10B2501/00—Wearing apparel
  • D10B2501/04—Outerwear; Protective garments

Definitions

• This invention relates to yarns of bicomponent aramid filaments suitable for use in arc protection, wherein each filament has a distinct region of aramid polymer having discrete carbon particles homogeneously dispersed therein and a distinct region of aramid polymer being free of discrete carbon particles but having at least one pigment homogeneously dispersed therein.
• US Pat. No. 4,309,476 to Nakamura et al. discloses a core-in-sheath type aromatic polyamide fiber having satisfactory dyeing properties made from a single aromatic polyamide material. When the core-in-sheath fiber is dyed with acid dyes, only the sheath portion is colored.
• US Pat. No. 4,398,995 to Sasaki et al. discloses the use of the fiber of Nakamura in a paper.
• US Pat. No. 3,038,239 to Moulds discloses improved composite filaments that have crimp reversibility.
• the filaments have at least two hydrophobic polymers in eccentric relationship, wherein one of the hydrophobic polymers further contains mixed therewith a minor amount of polymer having a high water absorption rate.
• This invention relates to a yarn comprising a plurality of bicomponent filaments, the bicomponent filaments having a first region comprising a first polymer composition and a second region comprising a second polymer composition; each of the first and second regions being distinct and present in the bicomponent filaments in a sheath-core structure or a side-by-side structure; wherein the first polymer composition comprises aramid polymer containing 0.5 to 20 weight percent discrete carbon particles, based on the amount of carbon particles in the first composition, homogeneously dispersed in the first region in the filament; and wherein the second polymer composition comprises aramid polymer being free of discrete carbon particles and having at least one masking pigment homogeneously dispersed in the second region of the filament; the yarn having a total content of 0.5 to 5 weight percent discrete carbon particles.
• This invention further relates to a process for forming a yarn comprising bicomponent filaments, each of the filaments comprising a distinct core of a first aramid polymer comprising carbon particles homogeneously dispersed therein, and a distinct sheath of a second aramid polymer being free of discrete carbon particles and having at least one masking pigment homogeneously dispersed therein, with the sheath surrounding the core; the process comprising the steps of:
• This invention also relates to a process for forming a yarn comprising
• bicomponent filaments having a side-by-side structure, each of the filaments comprising a distinct first side of a first aramid polymer comprising carbon particles homogeneously dispersed therein, and a distinct second side of a second aramid polymer being free of carbon particles and having at least one masking pigment; the process comprising the steps of:
• Figure 1 is an optical microscope image of the cross section of sheath-core bicomponent filaments having a sheath of a poly(metaphenylene isophthalamide) polymer comprising titanium dioxide particles that is free of carbon particles and a core of poly(metaphenylene isophthalamide) polymer comprising carbon particles.
• Figure 2 is an optical microscope image of the cross section of sheath-core bicomponent filaments having a sheath of a poly(metaphenylene isophthalamide) polymer that is free of both titanium dioxide and carbon particles and a core of poly(metaphenylene isophthalamide) polymer comprising carbon particles.
• Figure 3 shows the relationship of arc performance versus the total amount of discrete carbon particles in the fabric made from the yarn, normalized for a fabric having a basis weight of 6.3 oz/yd 2 .
• This invention relates to yarns useful in the making of articles that provided arc protection for workers and other personnel.
• An arc flash is an explosive release of energy caused by an electrical arc. Electrical arcs typically involve thousands of volts and thousands of amperes of electrical current, exposing the garment to intense incident heat and radiant energy. To offer protection to a wearer, an article of protective apparel must resist the transfer of this incident energy through to the wearer. It has been believed that this occurs best when the article of protective apparel absorbs a portion of the incident energy while resisting what is called "break-open". During "break-open", a hole forms in the article. Therefore, protective articles or garments for arc protection have been designed to avoid or minimize break-open of any of the fabric layers in the garment.
• thermally stable means the polymer or fiber retains at least 90 percent of its weight when heated to 425 degrees Celsius at a rate of 10 degrees per minute.
• FIG. 3 illustrates the ATPV of such a fabric containing carbon particles, normalized for a fabric having a basis weight of 6.3 oz/yd 2 .
• the presence of carbon can have a significant effect on the fabric arc performance, as measured by ATPV, even at very low loadings.
• the best performance is found for carbon particles amounts of greater than about 0.5 weight percent in the fabric, with a preferred performance of 12 cal/cm 2 or greater occurring for fabrics having about 0.75 weight percent carbon particles or greater, with an especially desired range being 0.75 to 2 weight percent carbon particles in the fabric.
• this invention relates to a yarn comprising a plurality of bicomponent filaments, the bicomponent filaments having a first region comprising a first polymer composition and a second region comprising a second polymer composition; the regions being distinct and preferably uniform-density in the bicomponent filaments.
• the regions are in the form of a sheath-core structure with the first region being the core and the second region being the sheath.
• the regions are in the form of a side-by-side bicomponent structure.
• the first polymer composition comprises aramid polymer containing 0.5 to 20 weight percent discrete carbon particles, based on the amount of carbon particles in the first composition, homogeneously dispersed in the first region in the filament.
• the second polymer composition comprises aramid polymer being free of discrete carbon particles but having at least one masking pigment homogeneously dispersed in the second region of the filament.
• the yarn has a total content of 0.5 to 5 weight percent discrete carbon particles, based on the amount of carbon particles in all the bicomponent filaments in the yarn.
• this invention relates to yarns of bicomponent aramid filaments that have dispersed carbon particles that dramatically improve arc performance versus standard aramid filaments.
• the bicomponent aramid filaments further include a spun-in pigment to mask the presence of the black carbon-containing fiber in the yarn, fabric or article.
• the filaments can be further colored in yarn, fabric or article form to further mask the presence of the black carbon particles in the fiber.
• the yarn comprises a plurality of bicomponent filaments.
• “Bicomponent” means the filaments are formed from at least two polymer compositions that differ in some way.
• the polymer used in the two polymer compositions is the same, with the difference in the compositions being the presence or absence of certain additives. Since at least two differing polymer compositions are needed in the making of the bicomponent filaments, this means that two differing polymer solutions are made, however, the two differing polymer solutions can use the same or different solvent.
• the solvent is the same for the two differing polymer solutions.
• the bicomponent filaments have a first region comprising a first polymer composition and a second region comprising a second polymer composition.
• the regions are distinct and preferably uniform-density in a sheath-core structure or a side- by-side structure.
• One representative region for the sheath-core structure is the sheath, while another representative region is the core.
• Side-by-side structures can have a more oblong or dog-bone shape in cross section, or can be more bean-shaped or round in cross section, so a representative region is either one side of the filament or the other.
• the side-by-side structure can be made wherein the two sides or regions are similarly sized and substantially symmetrical, if the relative amounts of the two polymers are similar; or the side-by-side structure can be made wherein one side or region overlaps the other side or region; that is, one side or region covers more than 50 percent of the circumference of the other side or region. This can be the case when the relative amounts of the two polymers are very different, and one side or region can cover 75 percent or more of the circumference of the other side or region.
• the sheath-core structure preferably the sheath is continuous.
• continuous is meant, in the case of the sheath of the sheath- core filament, that the sheath polymer completely radially surrounds the core polymer, and that the coverage of the core polymer by the polymer sheath is substantially continuous linearly along the length of the filament.
• the core is continuous or semi-continuous.
• the core polymer is substantially continuous linearly along the length of the filament, and “semi-continuous” means the core may have minor discontinuities linearly along the filament that do not appreciably affect the ability of the carbon particles in the core to function in the filaments as desired.
• each of the sides is “continuous", meaning the polymer regions on each side of the
• the bicomponent filament is substantially continuous linearly along its length.
• the region or side containing the carbon particles can be continuous or semi-continuous, with semi-continuous meaning the carbon particle-containing region may have minor discontinuities linearly along the filament that do not appreciably affect the ability of the carbon particles in the filament to function in the filaments as desired.
• uniform-density with regards to the sheath, it is meant that by visual inspection under suitable magnification using an optical or electron microscope the filament cross section shows the sheath to be generally solid and to be free of objectionable porosity.
• a uniform-density core is also present in the filament.
• uniform-density with regards to the core, and with regards to each of the sides in a side-by-side structure, it is meant that visual inspection under suitable magnification using an optical or electron microscope, a majority of the filament cross sections show the filaments to have solid, dense centers or character and to be relatively free of objectionable porosity and voids.
• the core has a substantially solid cross section and uniform density.
• the sheath-core filaments are oval, oblong, bean-shaped, cocoon-shaped, dog-bone-shaped, or a mixture of these.
• the first polymer composition comprises aramid polymer containing 0.5 to 20 weight percent discrete carbon particles, and those carbon particles are homogenously dispersed in the first region of the filament.
• the first region is the core of the filament; when the bicomponent structure is side- by-side, the first region is one of the sides of the filament.
• the phrase "homogeneously dispersed" means that the carbon particles can be found in the region uniformly distributed in both the axial and radial directions in the desired region in the fiber.
• the first polymer composition comprises aramid polymer containing 0.5 to 15 weight percent discrete carbon particles; and in some other embodiments the first polymer composition comprises aramid polymer containing 0.5 to 10 weight percent discrete carbon particles. In some embodiments, the first polymer composition comprises aramid polymer containing 0.5 to 6 weight percent discrete carbon particles. In some embodiments it is desirable the first polymer composition comprises aramid polymer containing 5 to 10 weight percent discrete carbon particles. In some
• each bicomponent filament has a total content of 0.5 to 3 weight percent discrete carbon particles, based on the total weight of each filament.
• the first polymer composition comprises aramid polymer that preferably has a Limiting Oxygen Index (LOI) above the concentration of oxygen in air (that is, greater than 21 and preferably greater than 25). This means the fiber or a fabric made solely from that fiber will not support flame in the normal oxygen concentrations in air and is considered fire-resistant.
• the first polymer further preferably retains at least 90 percent of its weight when heated to 425 degrees Celsius at a rate of 10 degrees per minute, meaning that this fiber has high thermal stability. It is believed the combination of this fire-resistant and thermally stable polymer with the discrete carbon particles
• the carbon particles have an average particle size of 10 micrometers or less, preferably averaging 0.1 to 5 micrometers; in some embodiments an average particle size of 0.5 to 3 micrometers is preferred. In some embodiments an average particle size of 0.1 to 2 micrometers is desirable; and in some embodiments an average particle size of 0.5 to 1.5 micrometers is preferred.
• Carbon particles include such things as carbon black produced by the incomplete combustion of heavy petroleum products and vegetable oils. Carbon black is a form of paracrystalline carbon that has a higher surface-area-to-volume ratio than soot but lower than that of activated carbon. They are typically incorporated into the fibers by adding the carbon particles to the spin dope prior to the formation of the fibers via spinning. In the sheath-core filament, the first polymer composition containing carbon particles is present in the core of the filament.
• any commercially available carbon-black can be used to supply the discrete carbon particles to the aramid polymer composition.
• a separate stable dispersion of the carbon-black in a polymer solution, preferably an aramid polymer solution, is first made, and then the dispersion is milled to achieve a uniform particle distribution. This dispersion is the preferably injected into the aramid polymer solution prior to spinning to form the first polymer composition.
• the second polymer composition also comprises aramid polymer, but is free of discrete carbon particles, meaning that the filament region containing that composition in the does not contain carbon particles as defined herein.
• the aramid polymer used in the second polymer composition also preferably has a Limiting Oxygen Index (LOI) above the concentration of oxygen in air (that is, greater than 21 and preferably greater than 25).
• LOI Limiting Oxygen Index
• the second polymer composition that is free of carbon particles is present in the sheath of the filament.
• the second polymer composition further has at least one pigment
• the at least one masking pigment is present in the second polymer composition in an amount of 5 to 25 weight percent. In some other embodiments, the at least one masking pigment is present in the second polymer composition in an amount of 10 to 20 weight percent. In some embodiments, the at least one masking pigment is present in the bicomponent filaments in an amount of 2.5 to 24 weight percent, based on the total bicomponent filament weight.
• One especially preferred pigment is titanium dioxide (T1O2).
• aramid is meant a polyamide wherein at least 85% of the amide (-CONH-) linkages are attached directly to two aromatic rings. Additives can be used with the aramid and, in fact, it has been found that up to as much as 10 percent, by weight, of other polymeric material can be blended with the aramid or that copolymers can be used having as much as 10 percent of other diamine substituted for the diamine of the aramid or as much as 10 percent of other diacid chloride substituted for the diacid chloride of the aramid. Suitable aramid fibers are described in Man-Made Fibers- Science and Technology, Volume 2, Section titled Fiber-Forming Aromatic Polyamides, page 297, W.
• Aramid fibers are, also, disclosed in U.S. Pat. Nos. 4, 172,938; 3,869,429; 3,819,587; 3,673, 143; 3, 354, 127; and 3,094,511.
• the aramid polymer is a meta-aramid.
• Meta- aramid are those aramids where the amide linkages are in the meta-position relative to each other.
• the meta-aramid polymer has an LOI typically at least about 25.
• One preferred meta-aramid is poly(metaphenylene isophthalamide).
• the bicomponent filaments comprise 5 to 50 weight percent of the first polymer composition and 50 to 95 weight percent of the second polymer composition.
• the sheath/core weight ratio is preferably 95:5 to 50:50.
• the maximum sheath/core weight ratio is from 90: 10 and the minimum sheath/core weight ratio is 60:40.
• the preferred sheath/core weight ratio ranges from to 90: 10 to 70:30.
• this invention further relates to a process for forming a yarn comprising sheath-core bicomponent filaments having a core comprising carbon particles homogeneously dispersed therein wherein the yarn further comprises a pigment in the sheath of the bicomponent filaments for masking the presence of the carbon-containing core, preferably a titanium dioxide pigment.
• this invention further relates to a process for forming a yarn comprising bicomponent filaments having a side-by-side structure having a first side comprising carbon particles homogeneously dispersed therein wherein the yarn further comprises a pigment in the second side of the bicomponent filaments for masking the presence of the carbon- containing side, preferably a titanium dioxide pigment.
• this invention relates to a process for forming a yarn comprising bicomponent filaments, each of the filaments comprising a distinct core of a first aramid polymer comprising carbon particles homogeneously dispersed therein, and a distinct, preferably uniform-density, sheath of a second aramid polymer being free of discrete carbon particles and having at least one masking pigment homogeneously dispersed therein, with the sheath surrounding the core; the process comprising the steps of:
• the process for forming a sheath-core structure is accomplished using dry spinning.
• the extracting of solvent from the plurality of dope filaments to make a yarn includes the steps of:
• this invention relates to a process for forming a yarn comprising bicomponent filaments having a side-by-side structure, each of the filaments comprising a distinct first side of a first aramid polymer comprising carbon particles homogeneously dispersed therein, and a distinct, preferably uniform-density,
• the process for forming the side-by-side structure is accomplished using dry spinning.
• the extracting of solvent from the plurality of dope filaments to make a yarn includes the steps of:
• the process includes dry-spinning the yarns of sheath-core filaments.
• dry spinning means a process for making filaments by extruding a polymer solution in continuous streams through spinneret holes into dope filaments into a heated chamber, known as a spin cell that is provided with a heated gaseous atmosphere.
• the heated gaseous atmosphere removes a substantial portion of the solvent, generally 40 percent or greater, from the dope filaments leaving semi-solid filaments having enough physical integrity that they can be further processed.
• dry spinning is distinct from “wet spinning” or "air-gap wet spinning” (also known as air-gap spinning) wherein the polymer solution is extruded in or directly into a liquid bath or coagulating medium to regenerate the polymer filaments.
• a gas is the primary initial solvent extraction medium
• wet spinning (and air-gap wet spinning) a liquid is the primary initial solvent extraction medium.
• the filaments can then be treated with additional liquids to cool the filaments and possibly extract additional solvent from them. Subsequent washing, drawing, and heat treatments can further extract solvent from the filaments in the yarn.
• the dope filaments are contacted or exposed to an environment that contains essentially only inert heated gas and amounts of the solvent removed from the dope filaments.
• Preferred inert gases are those that are gases at room temperature.
• the process involves forming at least two different polymer composition in differing solutions, a first polymer solution containing the first aramid polymer in a solvent and containing carbon particles and a second polymer solution containing the second aramid polymer in preferably the same solvent and being free of carbon particles, but further comprising at least one masking pigment that is not carbon black.
• the solvent is preferably selected from the group consisting of those solvents that also function as proton acceptors, for example dimethylforamide (DMF),
• DMAc dimethylacetamide
• NMP N-methyl-2-pyrrolidone
• DMAc dimethylacetamide
• NMP N-methyl-2-pyrrolidone
• DMAc dimethylacetamide
• DMSO dimethyl sulfoxide
• DMAc dimethylacetamide
• solubility of any particular polymer in any particular solvent is dependent on a variety of parameters, including the relative amounts of polymer and solvent, the molecular weight or inherent viscosity of the polymer, the temperature of the system. Further, while a polymer may be initially soluble in a solvent, with time, the polymer may precipitate out of the solvent, meaning that the solution is not a stable solution.
• the first and second polymer solutions are stable polymer spinning solutions.
• stable polymer spinning solution it is meant that the polymer is soluble in the solvent or solvent system in a concentration and temperature suitable for spinning fibers, and that the polymer remains soluble in the solvent indefinitely.
• solvent system is meant to include a solvent and a
• solubility/stability aid such as an inorganic salt.
• aramid polymer will form a useful stable polymer spinning solution only if a solubilizing/stabilizing salt is present. Therefore, if desired and needed, the aramid polymer solution includes at least 4 percent inorganic salt by weight, based on the amount of the salt, the polymer, and the solvent in the solution, to maintain the polymer in solution. In some embodiments the solution includes at least 7 weight percent inorganic salt.
• Inorganic salts that can be used include chlorides or bromides having cations selected from the group consisting of calcium, lithium, magnesium or aluminum. Calcium chloride or lithium chloride salts are preferred. As used herein, the word “salt” is meant to include the compounds that increase the solubility of the polymer in the selected solvent or help provide stable spinning solutions and excludes any additives (especially flame retardant additives) that might be salts but are only added to increase the limiting oxygen index of the polymer.
• Useful polymer solutions are those that can be extruded, preferably dry-spun, into useful dope filaments. Parameters that can be balanced to form useful polymer solutions include the polymer molecular weight and concentration of the polymer in the solvent. Obviously, the specific parameters are dependent on the polymer and solvent chosen. However, it is known that certain polymer solutions of a certain viscosity tend to make useful filaments. All of the variables that could impact viscosity, e.g., temperature, concentration, polymer and solvent type, polymer molecular weight, etc. can be used to create a useful polymer solution. Generally, such solutions have a so-called zero shear rate or Newtonian viscosity of about 10 to 1000 Pascal seconds (Pa-sec) and preferably about 50 to 500 Pa-sec.
• Pa-sec Pascal seconds
• the dry spinning process includes providing a spinneret assembly having separate inlets for the first solution and the second solution, and a plurality of exit capillaries for extruding (spinning) dope filaments.
• a spinneret assembly having separate inlets for the first solution and the second solution, and a plurality of exit capillaries for extruding (spinning) dope filaments.
• One preferred spinneret assembly useful for spinning the dope filaments is disclosed in US Pat. No. 5,505,889 to Davies. However, other spinneret assemblies are potentially useful and can have many different features such as the spinneret assemblies shown in US Pat. Nos. 2,936,482; and 3,541 , 198, which are just some of the possible spinneret assemblies that can be used.
• the process further involves forming a plurality of dope filaments having preferably a continuous sheath of the second aramid polymer solution and a generally continuous core of first aramid polymer solution.
• the core need not be strictly continuous to provide adequate carbon particles for the bicomponent filaments to perform as desired.
• the plurality of dope filaments having a continuous region of the polymer that is free of carbon particles is spun together with a continuous region of polymer that contains carbon particles in a side-by-side bicomponent filament structure. Both of these filament structures are made by extruding through the exit capillaries in the spinneret assembly a plurality of conjoined streams of first and second solutions into a spin cell.
• spin cell is meant to include any sort of chamber or bath that can remove solvent from the dope filaments.
• first solution and the second solution are supplied via separate inlets to and into the spinneret assembly where they are combined.
• the spinneret assembly distributes the two solutions such that the two solutions are both supplied to each exit capillary in the spinneret assembly, which forms a bicomponent dope filament.
• the bicomponent dope filament preferably has a continuous sheath of the second aramid polymer solution and a semi-continuous or continuous core of the first aramid polymer solution made by conjoining the first and second polymer solutions in each exit capillary of the spinneret; that is, the solutions are supplied in a manner suitable to provide a sheath-core arrangement and then extruded through the same exit capillary, each exit capillary being one of a plurality of exit capillaries in the spinneret assembly. While this is a preferred embodiment, any other arrangement of exit capillaries or apertures or methods that conjoins the first and second polymer solutions into suitable bicomponent dope filaments of the desired structure can be used.
• the preferred process continues with contacting the dope filaments with heated gas in the spin cell to remove solvent from the plurality of dope filaments to form reduced solvent filaments.
• the heated gas is generally an inert gas like nitrogen.
• the dope filaments are contacted solely with the heated gas in the spin cell.
• the dope filaments are therefore converted to reduced-solvent filaments in the spin cell.
• the reduced-solvent filaments are then quenched with an aqueous liquid to cool the filaments, forming a yarn of polymer filaments.
• the quench also serves to remove some of the surface tackiness from the filaments for more efficient downstream processing. Further, the quench can remove some additional solvent, and once quenched it is possible that 75 percent or higher of the total original solvent in the dope filaments has been removed. Additional steps to further extract solvent from the yarn of polymer filaments are then conducted. These steps can include additional washing, drawing, and/or heat treating, as desired.
• a yarn generally refers to the assemblage of bicomponent filaments that are spun which are known as a continuous multifilament yarn.
• the filaments spun herein can be converted into what is known in the art as a singles yarn, which is the simplest strand of textile material suitable for such operations as weaving and knitting.
• a staple fiber yarn can be formed from the bicomponent fibers in staple fiber form, the yarn having more or less twist. When twist is present in the singles yarn, it is all in the same direction.
• the phrases “ply yarn” and “plied yarn” can be used interchangeably and refer to two or more yarns, i.e. singles yarns, twisted or plied together.
• fiber and “filament” are used interchangeably and are defined as a relatively flexible, macroscopically homogeneous body having a high ratio of length to the width of the cross-sectional area perpendicular to that length. Also, such fibers preferably have a generally solid cross section for adequate strength in textile uses; that is, the fibers preferably are not appreciably voided or do not have a large quantity of objectionable voids.
• the yarns can comprise the herein described bicomponent fibers that are blended with other fibers, in either continuous multifilament or staple form.
• the yarns of bicomponent filaments can be cut into staple fibers.
• staple fibers refers to fibers that are cut to a desired length or are stretch broken, or fibers that are made having a low ratio of length to the width of the cross-sectional area perpendicular to that length, when compared with continuous filaments.
• Man-made staple fibers are cut or made to a length suitable for processing on, for example, cotton, woolen, or worsted yarn spinning equipment.
• the staple fibers can have (a) substantially uniform length, (b) variable or random length, or (c) subsets of the staple fibers have substantially uniform length and the staple fibers in the other subsets have different lengths, with the staple fibers in the subsets mixed together forming a substantially uniform distribution.
• suitable staple fibers have a cut length of from 1 to 30 centimeters (0.39 to 12 inches). In some embodiments, suitable staple fibers have a length of 2.5 to 20 cm (1 to 8 in). In some preferred embodiments the staple fibers made by short staple processes have a cut length of 6 cm (2.4 in) or less. In some preferred embodiments the staple fibers made by short staple processes have a staple fiber length of 1.9 to 5.7 cm (0.75 to 2.25 in) with the fiber lengths of 3.8 to 5.1 cm (1.5 to 2.0 in) being especially preferred. For long staple, worsted, or woolen system spinning, fibers having a length of up to 16.5 cm (6.5 in) are preferred.
• the staple fibers can be made by any process.
• the staple fibers can be cut from continuous straight fibers using a rotary cutter or a guillotine cutter resulting in straight (i.e., non-crimped) staple fiber, or additionally cut from crimped continuous fibers having a saw tooth shaped crimp along the length of the staple fiber, with a crimp (or repeating bend) frequency of preferably no more than 8 crimps per centimeter.
• the staple fibers have crimp.
• the staple fibers can also be formed by stretch breaking continuous fibers resulting in staple fibers with deformed sections that act as crimps.
• Stretch broken staple fibers can be made by breaking a tow or a bundle of continuous filaments during a stretch break operation having one or more break zones that are a prescribed distance creating a random variable mass of fibers having an average cut length controlled by break zone adjustment.
• Spun staple yarn can be made from staple fibers using traditional long and short staple ring spinning processes that are well known in the art. However, this is not intended to be limiting to ring spinning because the yarns may also be spun using air jet spinning, open end spinning, and many other types of spinning that converts staple fiber into useable yarns.
• Spun staple yarns can also be made directly by stretch breaking using stretch-broken tow-to-top staple processes.
• the staple fibers in the yarns formed by traditional stretch break processes typically have length of up to 18 cm (7 in) long; however, spun staple yarns made by stretch breaking can also have staple fibers having maximum lengths of up to around 50 cm (20 in.) through processes as described for example in PCT Patent Application No. WO 0077283. Stretch broken staple fibers normally do not require crimp because the stretch- breaking process imparts a degree of crimp into the fiber.
• the staple fiber made from the bicomponent filaments, or the bicomponent filaments themselves can further be used in a fiber blend if desired.
• fiber blend it is meant the combination of two or more staple fiber types, or two or more continuous filaments, in any manner.
• the staple fiber blend is an "intimate blend", meaning the various staple fibers in the blend form a relatively uniform mixture of the fibers.
• the two or more staple fiber types are blended prior to or while the staple fiber yarn is being spun so that the various staple fibers are distributed homogeneously in the staple yarn bundle.
• the blend optionally contains antistat fibers.
• One suitable fiber is a melt-spun thermoplastic antistatic fiber in an amount of 1 to 3 weight percent, such as those described in United States Pat. No. 4,612,150 to De Howitt and/or United States Pat. NO. 3,803,453 to Hull. These fibers, while they contain carbon black, have a negligible impact on arc performance, since the fiber polymer does not have the combination of being flame resistant and thermally stable; that is, it does not have in combination a LOI of greater than 21 and does not retain at least 90 percent of its weight when heated to 425 degrees Celsius at a rate of 10 degrees per minute.
• thermoplastic antistat fibers lose in excess of 35 weight percent when heated to 425 degrees Celsius at a rate of 10 degrees per minute.
• the total content in the weight percent of discrete carbon particles is based on the total weight of the fiber blend, excluding any minor amount of antistat fibers.
• Fabrics can be made from the yarns, and in some embodiments the preferred fabrics include, but are not limited to, woven or knitted fabrics.
• General fabric designs and constructions are well known to those skilled in the art.
• woven fabric is meant a fabric usually formed on a loom by interlacing warp or lengthwise yarns and filling or crosswise yarns with each other to generate any fabric weave, such as plain weave, crowfoot weave, basket weave, satin weave, twill weave, and the like. Plain and twill weaves are believed to be the most common weaves used in the trade and are preferred in many embodiments.
• knitted fabric is meant a fabric usually formed by interlooping yarn loops by the use of needles.
• spun staple yarn is fed to a knitting machine which converts the yarn to fabric.
• multiple ends or yarns can be supplied to the knitting machine either plied of unplied; that is, a bundle of yarns or a bundle of plied yarns can be co-fed to the knitting machine and knitted into a fabric, or directly into an article of apparel such as a glove, using conventional techniques.
• the tightness of the knit can be adjusted to meet any specific need.
• a very effective combination of properties for protective apparel has been found in for example, single jersey knit and terry knit patterns.
• the spun staple yarns can be used to make arc-resistant and flame-resistant garments.
• the garments can have essentially one layer of the protective fabric made from the spun staple yarn.
• Garments of this type include jumpsuits, coveralls, pants, shirts, gloves, sleeves and the like that can be worn in situations such as chemical processing industries or industrial or electrical utilities where an extreme thermal event might occur.
• the garment is made from the fabric comprising the yarns described herein.
• Protective articles or garments of this type include protective coats, jackets, jumpsuits, coveralls, hoods, etc. used by industrial personnel such as electricians and process control specialists and others that may work in an electrical arc potential environment.
• the protective garment is a coat or jacket, including a three-quarter length coat commonly used over the clothes and other protective gear when work on an electrical panel or substation is required.
• the protective articles or garments in a single fabric layer have a ATPV of greater than 2 cal/cm 2 /oz, which is at least a Category 2 arc rating or higher as measured by either of two common category rating systems for arc ratings.
• the National Fire Protection Association (NFPA) has 4 different categories with
• Category 1 having the lowest performance and Category 4 having the highest performance Under the NFPA 70E system, Categories 1 , 2, 3, and 4 correspond to a minimum threshold heat flux through the fabric of 4, 8, 25, and 40 calories per square centimeter, respectively.
• the National Electric Safety Code (NESC) also has a rating system with 3 different categories with Category 1 having the lowest performance and Category 3 having the highest performance.
• Categories 1 , 2, and 3 Under the NESC system, Categories 1 , 2, and 3 correspond to a minimum threshold heat flux through the fabric of 4, 8, and 12 calories per square centimeter, respectively. Therefore, a fabric or garment having a Category 2 arc rating can withstand a thermal flux of 8 calories per square centimeter, as measured per standard set method ASTM F1959 or NFPA 70E.
• the fabics and articles preferably have an "L*" value ranging from 30 to 70.
• the arc resistance of fabrics of this invention is determined in accordance with ASTM F-1959-99 "Standard Test Method for Determining the Arc Thermal Performance Value of Materials for Clothing".
• fabrics of this invention have an arc resistance (ATPV) of at least 0.8 calories and more preferably at least 2 calories per square centimeter per ounce per square yard.
• ThermoGravimetric Analysis Fiber that retains at least 90 percent of its weight when heated to 425 degrees Celsius at a rate of 10 degrees per minute can be determined using a Model 2950 Thermogravimetric Analyzer (TGA) available from TA Instruments (a division of Waters Corporation) of Newark, Delaware.
• TGA Thermogravimetric Analyzer
• the TGA gives a scan of sample weight loss versus increasing temperature.
• percent weight loss can be measured at any recorded temperature.
• the program profile consists of equilibrating the sample at 50 degrees C; ramping the temperature at from 10 or 20 degrees C per minute from 50 to 1000 degrees C; using air as the gas, supplied at 10 ml/minute; and using a 500 microliter ceramic cup (PN 952018.910) sample container.
• the specific testing procedure is as follows.
• the TGA was programmed using the TGA screen on the TA Systems 2900 Controller.
• the sample ID was entered and the planned temperature ramp program of 20 degrees per minute selected.
• the empty sample cup was tared using the tare function of the instrument.
• the fiber sample was cut into approximately 1/16" (0.16 cm) lengths and the sample pan was loosely filled with the sample.
• the sample weight should be in the range of 10 to 50 mg.
• the TGA has a balance therefore the exact weight does not have to be determined beforehand. None of the sample should be outside the pan.
• the filled sample pan was loaded onto the balance wire making sure the thermocouple is close to the top edge of the pan but not touching it.
• the furnace is raised over the pan and the TGA is started. Once the program is complete, the TGA will automatically lower the furnace, remove the sample pan, and go into a cool down mode.
• the TA Systems 2900 Universal Analysis program is then used to analyze and produce the TGA scan for percent weight loss over the
• the limited oxygen index (LOI) of fabrics of this invention is determined in accordance with ASTM G-125-00 "Standard Test Method for Measuring Liquid and Solid Material Fire Limits in Gaseous Oxidants".
• a Hunter Lab UltraScan® PRO spectrophotometer was used, including the industry standard of 10-degree observer and D65 illuminant.
• the color scale used herein uses the coordinates of the CIE ("L*-a*-b*) color scale with the asterisk, as opposed to the coordinates of the older Hunter color scale, which are designated (“L-a-b”) without the asterisk.
• Weight Percent of Carbon Particles The nominal amount of carbon black in the fiber, when making the fiber, is determined by a simple mass balance of ingredients.
• the amount of carbon black present in the fiber can be determined by measuring the weight of a sample of fiber, removing the fiber by dissolution of the polymer in a suitable solvent that does not affect the carbon black particles, washing the remaining solids to remove any inorganic salts that are not carbon, and weighing the remaining solids.
• One specific method includes weighing about a gram of the fiber, yarn, or fabric to be tested and heating that sample in an oven at 105°C for 60 minutes to remove any moisture, followed by placing the sample in a desiccator to cool to room temperature, followed by weighing the sample to obtain an initial weight to a precision of 0.0001 grams.
• the sample is then placed in a 250 ml flat bottom flask with a stirrer and 150 ml of a suitable solvent, for example 96% sulfuric acid, is added.
• a suitable solvent for example 96% sulfuric acid
• the flask is then placed on a combination stir/heater with a chilled water condenser operating with enough flow to prevent any fumes from exiting the top of the condenser.
• the heat is then applied while stirring until the yarn is fully dissolved in the solvent.
• the flask is then removed from the heater and allowed to cool to room temperature.
• the contents of the flask are then vacuum filtered using a Millipore vacuum filter unit with a tared 0.2 micron PTFE filter paper.
• the Millipore unit is then removed from the vacuum flask and reset on a new clean glass vacuum flask. With vacuum, the residue on the filter paper is washed with water until a pH paper check on the filtrate indicates the wash water to be neutral. The residue is then finally washed with methanol.
• the filter paper with residue sample is removed, placed in a dish, and heated in an oven at 105°C to dry for 20 minutes. The filter paper with residue sample in then put in a desiccator to cool to room temperature, followed by weighing the filter paper with residue sample to obtain the final weight to a precision of 0.0001 grams.
• the weight of the filter is subtracted from the weight of the filter paper with residue sample. This weight is then divided by the initial weight of the yarn or fiber or fabric and multiplied by 100. This will give the weight percentage of the carbon black in the fiber, yarn, or fabric.
• Carbon black particle size can be measured using the general provisions of ASTM B822-10 - "Standard Test Method for Particle Size Distribution of Metal Powders and Related Compounds by Light Scattering". Weight Percent of Pigments. The nominal amount of pigment in the fiber that is not carbon black, when making the fiber, is determined by a simple mass balance of ingredients. After the fiber is made, the amount of pigment present in the fiber can be determined by a general method of measuring the weight of a sample of fiber, ashing the sample, and weighing the remaining solids to calculate a weight percent.
• One specific method for determining the amount of T1O2 in a fiber sample includes weighing about 5 grams of the fiber to be tested and heating that sample in an oven at 105°C for 60 minutes to remove any moisture, followed by placing the sample in a desiccator for about 15 minutes to cool to room temperature.
• a synthetic quartz crucible is then placed in a muffle furnace operating at 800° C for 15 minutes, after which it is removed and allowed to cool in a desiccator for 15 minutes.
• the crucible is then weighed to a precision of 0.0001 grams.
• the dried yarn sample is also weighed to a precision of 0.0001 grams to obtain its initial weight.
• the dried yarn sample is placed in the crucible, and the crucible with sample is then placed in the muffle furnace operating at 800° C for 60 minutes.
• the crucible is then removed and is placed in a desiccator to cool for 15 minutes, after which the final sample plus crucible is weighed to a precision of 0.0001 grams.
• the amount of T1O2 is then calculated by first subtracting the weight of the crucible from the weight of the final sample plus crucible, and then dividing that amount by the initial weight of the fiber sample, followed by multiplying by 100. This provides the amount of T1O2 in weight percent.
• Shrinkage To test for fiber shrinkage at elevated temperatures, the two ends of a sample of multi-filament yarn to be tested are tied together with a tight knot such that the total interior length of the loop is approximately 1 meter in length. The loop is then tensioned until taut and the doubled length of the loop measured to the nearest 0.1 cm. The loop of yarn is then hung in an oven for 30 minutes at 185 degrees Celsius. The loop of yarn is then allowed to cool, it is re-tensioned and the doubled length is re- measured. Percent shrinkage is then calculated from the change in the linear length of the loop.
• a yarn containing sheath/core bicomponent poly(metaphenylene isophthalamide) (MPD-I) filaments was spun, each filament having a core of MPD-I polymer having discrete carbon particles homogeneously distributed throughout and a sheath of the same MPD-I polymer further containing a masking pigment.
• the filaments were produced from two different solutions of MPD-I polymer in dimethyl acetamide (DMAc) that were fed to a sheath/core filament spinneret assembly in the top of a dry spinning spin-cell.
• DMAc dimethyl acetamide
• the flow rates of the MPD-I polymer solution streams for the sheath and core were controlled independently with two different metering pumps.
• the stream used for the sheath contained a dispersion of rutile titanium dioxide (T1O2) pigment in addition to the MPD-I polymer solution in DMAc.
• T1O2 rutile titanium dioxide
• This stable dispersion contained about 7 percent MPD-I and about 30 weight percent T1O2 in DMAc, which was milled to achieve a uniform distribution of the Ti02 in the dispersion.
• This dispersion was then added to the stream of sheath polymer in an amount that was equal to final concentration of 15 weight percent T1O2 on a sheath polymer basis in the sheath polymer stream.
• a stable dispersion of carbon black in to a low viscosity polymer solution of about 6 weight percent MPD-I and about 9 weight percent carbon black in DMAc was made and then milled to achieve a uniform distribution of the carbon particles in the dispersion.
• the stream used for the core contained the MPD-I polymer solution in DMAc with this additional carbon black dispersion, which was injected into the core stream prior to the spinneret at a flow rate suitable to obtain a 6.6 weight percent carbon-black loading in the core stream.
• the two metering pulps controlled the relative amounts of polymer solution such that the weight ratio of the sheath to core was 60:40 on a total final weight basis after the addition of the dispersion.
• the spinneret assembly included an appropriately designed distribution/meter plate and spinneret to produce the desired sheath core structure from the two solutions.
• the spinneret comprised of 791 exit holes, each with a diameter of 0.005 inches and a length of 0.01 inches.
• the spinneret assembly further comprised steam passages to maintain the temperature of the solutions as they traveled through the meter plate and spinneret between 100 °C and 150 °C.
• the individual sheath/core filaments leaving the spinneret assembly were subjected to heated nitrogen gas to remove some of the DMAc from the filaments before the filaments entered an aqueous quench at the exit of the spin-cell.
• the quenched sheath/core fiber with was then processed on a wash/draw machine to draw the fiber between three to four times and reduce the DMAc concentration in the fiber to a value of less than 1 weight percent.
• the fiber was then subjected to dryers and further heat treatment to remove the residual water from the fiber, followed by the application of spin- finish before being wound on a bobbin.
• the resulting filaments had a core of MPD-I polymer having on average a 6.6 weight percent carbon-black loading; the filaments had a sheath of MPD-I polymer that had 15 weight percent ⁇ 2 uniformly distributed therein, with each filament having on average 2.6 weight percent carbon black and about 9 weight percent masking pigment ( ⁇ 2), on a total filament weight basis.
• Example 1 was repeated but the two metering pumps controlled the relative amounts of polymer solution such that the weight ratio of the sheath to core was 80:20 on a total final weight basis after the addition of the dispersion. Further, the amount of carbon black dispersion and ⁇ 2 dispersion was selected such that the core of the filaments had 10 weight percent carbon black and the sheath had 10 weight percent ⁇ 2.
• a sample of the filament threadline produced after quenching was taken and an optical microscope image of the cross section of these sheath-core bicomponent filaments is shown in Figure 1. The sheath core structure of the fiber is apparent along with the carbon black in the core and pigments in the sheath.
• Example 1 was repeated to make a yarn containing sheath/core bicomponent poly(metaphenylene isophthalamide) (MPD-I) filaments was spun, each filament having a core of MPD-I polymer having discrete carbon particles
• Example 1 filaments were spun, quenched, wash-drawn, dried, heat-treated, etc., and wound up on bobbins.
• Example 3 A sample of the filament threadline produced after quenching was taken and an optical microscope image of the cross section of the sheath-core bicomponent filaments was taken and shown in Figure 2.
• the resulting filaments had a core of MPD-I polymer having on average a 6.6 weight percent carbon-black loading; the filaments had a sheath of MPD-I polymer that was free from any pigments, with each filament having on average 2.6 weight percent carbon black, on a total filament weight basis.
• Example 3 A sample of the filament threadline produced after quenching was taken and an optical microscope image of the cross section of the sheath-core bicomponent filaments was taken and shown in Figure 2.
• the resulting filaments had a core of MPD-I polymer having on average a 6.6 weight percent carbon-black loading; the filaments had a sheath of MPD-I polymer that was free from any pigments, with each filament having on average 2.6 weight percent carbon black, on a total filament weight basis.
• Example 3
• Example 1 was repeated, however, the flowrates of the sheath and core streams were adjusted to create filaments having sheath/core weight ratios of 70:30, 80:20, and 87: 13.
• the injection rate of the dispersion containing carbon black varied as the size of the core was reduced to keep the total average carbon black concentration in the filaments constant at a value of 2.6 weight percent. This resulted in carbon black concentrations in the core of 8.7 weight percent, 13 weight percent, and 20 weight percent as the size of the core was reduced from about 30% to 13%.
• each undyed fiber sample was carded to create a "puff" ball of fibers for lightness measurement.
• the difference in filament lightness resulting from the addition of carbon particles in the core and T1O2 in the sheath was quantified using a HunterLab UltraScan® PRO spectrophotometer with the following viewing conditions: Large Area View/10-degree observer/D65 illuminant.
• the color scale used for reporting L* values is the CIE 1976 L*a*b* (CIELAB) color scale. A low value on this scale indicates a dark shade, while a high value indicates a light shade.
• the L* value increases from a value of 20 with a 60% sheath with no T1O2 to 54 with an 87% sheath containing 15 weight percent T1O2.
• a Control sample of MPD-I filament sample without any T1O2 or carbon black has a L* value of approximately 80.
• Table 1 also shows the weight percent of carbon particles used in the core, which was increased as the weight percent of the sheath was increased, to maintain a nominal carbon particle weight in the fiber steady at 2.6 weight percent.
• the lightness of the fiber sample increased as the amount of sheath covering the black core (and containing T1O2) was increased.
• Example 1 which had a 60 weight percent sheath with 15 weight percent T1O2
• Example 3-2 which had an 80 weight percent sheath with 15 weight percent T1O2, where then dyed.
• One set was dyed blue; the other was dyed yellow.
• the yarns were dyed as follows. Approximately 1 gram of a sample of each of the yarns was placed in individual nylon bags. The bags were then placed in a dye pot containing 500 ml of water, 15 gm/liter of Cindye C-45, a carrier known to facilitate the dyeing of aramid fibers, and 3 weight percent of dye based on the total weight of all the fiber samples. The specific dyes used were Basic Blue 41 and Basic Yellow 40. In each case, the dye pot was heated and held at 100 °C for 30 minutes. Each fiber sample was then removed from the pot and rinsed with water, dried in an oven at 85 °C, and then carded to create a "puff" ball of fibers for lightness measurement.
• Example 1 yarn which had a 60 weight percent sheath with 15 weight percent T1O2
• Example 3-2 yarn which had an 80 weight percent sheath with 15 weight percent T1O2
• Table 3 the Delta a* and Delta b* values of the Example 1 yarn, which had a 60 weight percent sheath with 15 weight percent T1O2 and Example 3-2 yarn, which had an 80 weight percent sheath with 15 weight percent T1O2, when dyed, showed considerable change in the a* and b* numerical values, indicating that the yarns are actually being colored.
• the difference is not as great as the Control yarns without carbon particles, but does show that the addition of the T1O2 allowed these yarns to accept some color while also having the desired carbon particles.
• An intimate blend of staple fibers in the form of a picker blend sliver of 93 weight percent of the bicomponent fiber made in Example 1 , having a sheath/core weight ratio of 60/40 and having carbon particles dispersed in the core and T1O2 particles dispersed in the sheath, 5 weight percent natural para-aramid fiber, and 2 weight percent antistat fiber was prepared, and then was made into spun staple yarn using cotton system processing and an air-jet spinning frame.
• the natural para-aramid fiber was poly(p-phenylene terephthalamide) (PPD-T) that was free of carbon particles, that is, it did not contain any added carbon-black.
• the antistatic fiber was a carbon-core nylon-sheath fiber known commercially as P140® available from Invista.
• the calculated percent total amount of carbon (percent) for the intimate blend (and in the fabric) was based on the weight of the carbon particles in the carbon- containing black meta-aramid fiber, which had a nominal 2.1 weight percent carbon, divided by the weight of the total fiber blend, times 100. Any carbon in the antistat fiber is not considered in the calculation of percent carbon in the blend.
• the resultant yarn was a 21 tex (28 cotton count) single yarn. Two single yarns were then plied on a plying machine to make a two-ply yarn having a ply twist of 10 turns/inch. The yarn was then used as the warp and fill yarns of a fabric that was woven on a shuttle loom in a warp-faced 2x1 twill construction.
• the greige twill fabric had a construction of approximately 31 ends x 16 picks per cm (77 ends x 47 picks per inch) and a basis weight of 203 g/m 2 (6.0 oz/yd 2 ). The fabric was then submitted for arc testing and the results are shown in Table 2.
• the calculated percent total amount of carbon (percent) for the intimate blend (and in the fabric) was based on the weight of the carbon particles in the carbon- containing black meta-aramid fiber, which had a nominal 2.1 weight percent carbon, divided by the weight of the total fiber blend, times 100. Any carbon in the antistat fiber is not considered in the calculation of percent carbon in the blend.
• the greige fabric was then mock dyed to crystallize the MPD-I in the fiber using the same dyeing procedure as Example 4 but using only the Cindye C-45 dye carrier and no additional dye.
• the final fabric weight is 267 g/m 2 (7.9oz/yd 2 ).
• Example 5 was repeated; however, the bicomponent fiber was replaced with natural meta-aramid fiber.
• the natural meta-aramid fiber was amorphous or
• Example 5 was repeated; however, the bicomponent fiber used was Example A fiber, which did not contain any added T1O2 in the sheath. Yarns and fabrics were made as in Example 5. The fabric was then submitted for arc testing and the results are shown in Table 4. The greige fabric was then mock dyed to crystallize the MPD-I in the fiber using the same dyeing procedure as Example 4 but using only the Cindye C-45 dye carrier and no additional dye. The final fabric weight is 240 g/m 2 (7.1 oz/yd 2 ). Table 4
• Example 5 As can be seen from Table 4, the lightness of the mock dyed fabric, as measured by the L* value, was increased for Example 5 fabric which used the bicomponent fiber having a sheath containing T1O2 that covered the black carbon-particle containing core.
• Examples 1 and 2 are repeated but with a spinneret that provides a side-by-side bicomponent filament structure, wherein the weight ratio of the first side without carbon particles but containing T1O2 to the second side containing carbon particles is 60:40 and 80:20 as in those examples. Due to the additional mass on the first side, that side encloses more than 50 percent of the circumference of the second side, making a side- by-side bicomponent filament that functions similar to a sheath-core. The method of Example 4 to evaluate the lightness and dyeability of the yarns is repeated with similar results.

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