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(11) | EP 0 189 134 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Improved warp knit fabric containing weft inserted activated carbon yarn |
| (57) New and improved activated carbon fiber yarns and fabrics are disclosed. It has been
discovered that if precursor yams are intertwined to form a multi-fold yarn prior
to being subjected to an activation process, activated carbon yarns having improved
tenacity and excellent sorbitivity to toxic gases are provided. The new and improved
yarns can be woven into fabric with reduced breakage and/or weak points on conventional
weaving equipment. In preferred embodiments the new and improved multi-fold yarns
are surface-treated with a polymeric fluorocarbon resin to improve abrasion resistance
and reduce fly. In alternate embodiments, improved activated carbon containing fabrics
are disclosed which provide protection to the wearer from toxic vapors and gases. |
Field
Background
[0002] The use of activated carbon for sorption of toxic chemical vapors or gases is well-known. The use of activated carbon in the form of activated carbon yarns for sorption of toxic substances is also known. There have been several attempts to produce activated carbon yarns which could be incorporated into fabrics that would provide the wearer with protection from toxic chemical vapors or gases.
[0003] Several problems have been encountered in making these fabrics. These problems appear to be due to the physical characteristics of the activated carbon yarn. After the activation process, the activated carbon yarn has very low strength, such as low tensile strength, and poor abrasion resistance. The low strength of the activated carbon yarn results in a greater tendency of the yarn to break during commercial weaving processes and results in fabrics that are susceptible to failure at stress points. This tendency to break and to fail at stress points makes fabric production difficult.
[0004] U.S. 4,285,831 relates to a process for producing activated carbon fibers reportedly having high adsorption capacity. This patent discloses that by adjusting the amount of bonded oxygen in the oxidized fiber to a certain amount of oxygen, and by controlling the shrinkage of the fiber during the oxidation to a limited value an activated carbon fiber reportedly having excellent adsorption capacity and excellent mechanical properties can be obtained. The oxidized fiber is activated by heating in a gas selected from C02, NH3, steam or a mixture thereof, at a temperature of about 200oC to about 1000°C for 10 minutes to 3 hours while the fiber is allowed to shrink freely. The activated carbon fiber produced has a specific surface area of from 300 m2/g to 2,000 m2 (B.E.T. method using nitrogen gas adsorption isotherm at 25°C). The activated carbon fiber also has a tensile strength of about 20 to about 80 kg/mm2, a tensile elongation of about 0.5 to 3% and a tensile modulus of about 1,500 to about 5,000 kg/mm2.
[0005] U.S. 4,412,937 relates to a method for manufacturing activated carbon fiber reportedly having high strength, high adsorbing ability and high processability. The method disclosed comprises preoxidation and activation steps. Before preoxidation, a treating agent, selected from phosphorus and borax compounds, is incorporated with an acrylic fiber. The acrylic fiber is then preoxidized in an oxidizing atmosphere. The concentration of the phosphorous and/or borax in the oxidized fiber is adjusted and then the oxidized fiber is activated. The temperature of activation is in the range of 9000C to 1,300°C.
[0006] U.S. 4,362,646 discloses that the use of an acrylonitrile-based fiber containing an iron compound prevents the coalescence of fibers at the oxidation step, markedly shortens the oxidation time and provides a fibrous activated carbon reportedly having excellent performance in high yields. The patent discloses that the activation processing can be accomplished by physical activation or a method comprising impregnating the fiber with an activating agent used in chemical activation and then applying physical activation. The activation is generally carried out at a temperature of from about 600°C to 1,300°C, preferably about 800°C to about 1,3000C for from about 6 seconds to 2 hours.
[0007] U.S. 4,256,607 relates to a process for producing. an activated carbon fiber reportedly having excellent adsorption capacities and sufficient mechanical strength. The patent discloses a process whereby an acrylonitrile based fiber is subjected to sufficient oxidation in an oxidizing atmosphere at a temperature of about 200oC to about 300°C while applying a tension until the amount of bonded oxygen reaches about 50% to about 90% of the saturated amount of bonded oxygen. The fiber so obtained is then subject to activation. The activation can be carried out by known methods. The activation is generally carried out at a temperature of about 7000 to about 1,000° for about 10 minutes to about 3 hours.
[0008] In fact, a variety of char forming synthetic polymers have been used as precursors to activated carbon fibers and fabrics. Some examples of synthetic polymers which form a char on pyrolysis are given in Jenkins, G.M. and Kawamura, K., Polymeric Carbons - Carbon Fibre, Glass and Char, Cambridge University Press, New York, 1976--see for example, page 14. A method of producing activated carbon fibers by subjecting the fiber of a phenol resin to carbonization and activation processings is known and described, for example, in Ling R. Y. and Ecomomy, J., "The Preparation and Properties of Activated Carbon Fibers Derived From Phenolic Precursor," in Applied Polymer Symposium No. 21, pp. 143-152 (John Wiley & Sons Inc, 1973).
[0009] U.S. patent 4,401,588 relates to making activated carbon fabric by heating an aramid fabric of poly-(benzimidazole) or poly(p-phenylene terephthalamide) under a gaseous stream containing a mixture of inert gas, preferably nitrogen and about 20% by volume steam at a temperature in the range of 850-950oC for at least 10 minutes.
[0010] It is also known in the art to use a continuous process for the activation of tow. However, the activated yarn produced from such a process has low tensile strength and poor abrasion resistance.
[0011] A translation of Japanese Applicantion No. 123784 filed July 17, 1982 and laid-open (published) as No 59-015531-A on January 20, 1984 discloses an active carbon fiber spun yarn which is composed of single fibers whose twist coefficient is 30 to 60. The activated carbon fiber yarn is spun yarn of single yarn or at least two folded yarn. In the case of single yarn that twist coefficient is of the yarn itself. In the case of a two folded yarn the twist coefficient is of the primary twist or first twist. If the twist coefficient surpasses 60, the tenacity of the yarn becomes high but snarls will form easily and the processability will become bad; when less than 30, not only will the tenacity of the yarn drop to the extreme but clogging of yarn scraps toward the yarn guide will occur frequently. When the spun yarn is at least two folded yarn, it is best to cause the ratio of the final twist and the primary twist to be 0.50 to 0.70. See also UK Patent Application GB 2,125,078A published February 29, 1984 which claims priority based on the aforementioned Japanese Application.
[0012] It is also known that non-carbon-containing precursor yarns can be intertwined together to form a plied yarn having improved elasticity over the component yarns. However, since these type of plied yarns are not activated carbon yarns they do not have and therefore do not solve the problem associated with activated carbon yarns.
Summary of the Invention
[0013] This invention provides an activated carbon yarn comprising a plurality of carbon containing precursor yarns, intertwined together to produce a multi-fold yarn and then subjected to an activation process.
[0014] Another embodiment of this invention provides an activated carbon yarn comprising a plurality of carbon containing precursor yarns, intertwined together to produce a multi-fold yarn and then subjected to an activation process, said activated yarn having a tenacity of greater than about 0.1 gram/denier (g/d) with about 1.0 g/d to about 4 g/d being preferred and a carbon tetrachloride (CC14) sorptivity of greater than about 25% by weight, based on the weight of activated carbon yarn, with about 25% to about 140% being preferred.
[0015] In yet another embodiment of this invention, there is provided an activated carbon yarn comprising a plurality of oxidized yarns, intertwined together to produce a multi-fold yarn and then subjected to an activation process, said activated carbon yarn having a tenacity greater than about 1 g/d and a CC14 sorptivity of greater than about 60% by weight based on the weight of activated carbon yarn. Preferably, the oxidized yarn is an oxidized acrylic yarn.
[0016] In still another embodiment of this invention there is provided an activated carbon yarn made from a carbon containing yarn by a process comprising the steps of:
(1) longitudinally intertwining together a plurality of said carbon containing yarns thereby forming a multi-fold yarn; and
(2) continuously pulling or feeding said multi-fold yarn through at least one heated furnace zone while passing an oxidizing gas through said furnace
wherein the temperature of said furnace, the gas flow rate and the through-put rate (i.e., the rate at which the yarn is pulled or fed through the furnace, feed rate) are sufficient to produce an activated carbonized yarn having a tenacity greater than about 0.1 g/d and a CC14 sorptivity of greater than about 25% by weight based on the weight of activated carbon yarn.
[0017] Yet another embodiment of this invention provides articles of manufacture made from the activated carbon yarns of this invention, in particular articles of manufacture which are fabrics and the objects made therefrom --e.g. garments (clothing), tents, masks, and the like.
[0018] Surprisingly it has been discovered that activated carbon material can be treated with an aqueous dispersion of polymeric fluorocarbon resin particles to provide an activated carbon material coated with a polymeric fluorocarbon. The polymeric fluorocarbon coating provides the activated carbon material with increased abrasion resistance without decreasing CC14 sorptivity. This is surprising and unexpected because one skilled in the art would expect that a coating placed on the activated carbon material would occlude the activation sites causing decreased sorptivity. However, contrary to expectations, activated carbon materials do not exhibit a decreased sorptivity when coated with polymeric fluorocarbons.
[0019] Therefore, this invention in another embodiment provides an activated carbon material coated with a polymeric fluorocarbon and having increased abrasion resistance comprising an activated carbon material treated with an aqueous dispersion of polymeric fluorocarbon resin particles.
[0020] In another embodiment this invention provides an activated carbon yarn comprising a plurality of carbon containing precursor yarns, intertwined together to produce a multi-fols yarn, and then subjected to an activation process, and then treated with an aqueous dispersion of polymeric fluorocarbon resin particles.
[0021] In yet another embodiment this invention provides a process for making an abrasion resistant activated carbon material comprising immersing or dipping an activated carbon materia in, or spraying an activated carbon material with, an aqueous dispersion of polymeric fluorocarbon resin particles and then drying said material.
[0022] In still another aspect, this invention provides an improved warp knitted activated carbon fabric comprising a weft of a multi-fold activated carbon yarn and a warp of a hydrophobic, monofilament yarn.
[0023] In another embodiment, a hydrophilic layer is incorporated on one side of the above described warp knitted activated carbon fabric.
[0024] The fabrics of this invention may be used in clothing or fabric enclosures -- e.g., tents, window covers, and the like -- to protect individuals from toxic chemical vapors. The invention may also be used as air filters and in water treatment as well as other applications requiring the filtration of toxic chemical vapors, gases and liquids.
[0025] Preferably, the carbon containing precursors in the above embodiments are oxidized acrylic yarns.
[0026] Surprisingly, the multi-fold activated carbon yarns of this invention can be activated to a higher CC14 sorptivity on a weight for weight basis than a single ply yarn (of which the multi-fold yarn is composed of) and still maintain high levels of tenacity. This is unexpected because it appears that the multi-fold yarn.has less fiber surface exposed to the activating gas stream due to the intertwining of the single plies. Thus, it would be expected that the reduced surface area would result in reduced activation of the yarn resulting in reduced sorptivity capabilities.
[0027] The multi-fold activated carbon yarns of this invention also have greater ability to deform or distort in response to an applied force (such as that encountered during a commercial weaving process). This ability to deform or distort is due to increased elasticity resulting from intertwining the plies of yarn together before the activation process.
[0028] Term "carbon containing yarn" as used herein means a yarn that has a char yield. The term "char yield" means that a carbon residue remains after the yarn has been pyrolyzed (usually at 1000°C).
Twist Number Per Meter
[0031] The term "twist ratio" as used herein means the ratio of the twist (final twist) of the activated carbon yarn to the twist of the primary yarns.
[0032] The term "primary yarn" as used herein refers to the individual plies or the multi-fold yarn.
Brief Description of the Drawings
[0033]
FIG. 1 is a schematic diagram of the activation Process.
FIG. 2 is a diagram of the yarn feed-through entrance.
FIG. 3 is a diagram of the yarn feed-through exit.
FIG. 4 is a graph of data showing "tenacity versus Twist Coefficient" for GB 2,125,078A and the presently claimed invention.
FIG. 5 is a schematic diagram of the dipping process for coating an activated carbon fiber.
FIG. 6 is a representative diagram of the testing method used to determine the abrasion resistance of the activated carbon yarns both coated and uncoated.
FIG. 7 is a schematic diagram of the aparatus used to test the dynamic sorptivities of both nonwoven and woven fabrics of Example 72.
FIG. 8 is a point diagram for a tricot or raschel type warp knit fabric as described in Example 73.
FIG. 9 is a point diagram for a tricot or raschel type warp knit fabric with a backing layer incorporated into the fabric.
Detailed Description of the Invention
[0034] Carbon containing yarns comprising one of the following precursors may prove useful in producing the activated carbon yarns of this invention: phenolic, poly(benzimidazole), poly(p-phenyleneterephthalamide), polyacrylonitrile, pitch (petroleum or coal tar), and the like.
[0035] Examples of commercially available yarns are: KYNOL, a produce designation for a phenolic-aldehyde yarn available from American Kynol, Inc.; KEVLARO 49, brand of aramid yarn from E. I. du Pont de Nemburs & Co., Inc.; PYRONO brand of oxidized polyacrylonitrile yarn from Stackpole Fibers Co., Inc.; CELIOXO brand of oxidized polyacrylonitrile yarn from Celanese Corporation, Celion Fiber Division; GRAFIL '0', a product designation for an oxidized polyacrylonitrile yarn from Hysol Grafil Limited; FORTAFIL® OPF brand of oxidized polyacrylonitrile yarn from Great Lakes Carbon Corp.
[0036] Of these yarns, oxidized acrylic yarns are widely used with acrylonitrile oxidized yarns being preferred. A preferred oxidized acrylonitrile based acrylic yarn is available from Celanese Corporation, Celion Carbon Fiber Division under the trademark CELIOX®.
[0037] Production of acrylic yarns, as well as oxidation and activation processes are well known in the art. For example, see U.S. 4,285,831, U.S. 4,412,937, U.S. 4,362,646 and U.S. 4,256,607.
[0038] Yarns made from fibers of acrylonitrile homopolymers and acrylonitrile copolymers and then oxidized are suitable for use in this invention. Examples of such copolymers may include copolymers containing not less than about 60% by weight, preferably not less than 85% by weight, acrylonitrile.
[0039] It is also believed that mixtures of homopolymers and copolymers or mixtures of copolymers themselves may be used to produce the fiber that will be used to make the yarn from which the oxidized yarns are made. Copolymers containing less than about 60% by weight acrylonitrile may be used in admixture with acrylonitrile polymers to produce the fiber, if the amount of acrylonitrile in the ultimate fiber exceeds 60% by weight.
[0040] Comonomers which may be introduced into the above copolymers include addition-polymerizable vinyl compounds such as vinyl chloride, vinylidene chloride, vinyl bromide, acrylic acid, methacrylic acid, itaconic acid; the salts (e.g., the sodium salts) of these acids; derivatives of these acids, e.g., acrylic acid esters (e.g., alkyl esters containing 1 to 4 carbon atoms in the alkyl moiety such as methyl acrylate, butyl acrylate, and the like), methacrylic acid esters (e.g., alkyl esters containing 1 to 4 carbon atoms in the alkyl moiety such as methyl methacrylate, and the like); acrylamide, N-methylolacrylamide; allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, and the salts (e.g., the sodium salts) of these acids; vinyl acetate; 2-hydroxyethylacrylate; 2-hydroxyethylmethacrylate; 2-hydroxyethylacrylonitrile; 2-chloroethylacylate; 2-hydroxy-3-chloropropylacrylate; vinylidene cyanide; alpha-chloroacrylonitrile; and the like. In addition, other compounds which may be used maybe selected from among those described in U.S. 3,202,640.
[0041] The degree of polymerization of these polymers or polymer mixtures will be sufficient if a fiber can be formed, and it is generally about 500 to about 3,000, preferably 1,000 to 2,000.
[0042] These acrylonitrile based polymers can be produced using hitherto known methods, for example, suspension polymerization or emulsion polymerization in an aqueous system, or solution polymerization in a solvent. These methods are described in, for example, U.S. 3,208,962, U.S. 3,287,307 and U.S. 3,479,312.
[0043] Spinning of the acrylonitrile based polymer can be carried out by hitherto known methods. Examples of spinning solvents which can be used include inorganic solvents such as a concentrated solution of zinc chloride in water, concentrated nitric acid and the like, and organic solvents such as dimethylformamide, dimethyl- acramide, dimethyl sulfoxide, and the like. Examples of spinning methods which can be used are dry spinning and wet spinning. In wet spinning, in general, steps such as coagulation, waterwashing, stretching, shrinking, drying and the like are suitably combined. These spinning methods are described in U.S. 3,135,812 and U.S. 3,097,053.
[0044] This stretching is carried out to the same extent as in a usual acrylonitrile based fiber, and a suitable degree of stretching is generally about 5 to about 30 times the original length.
[0045] It is believed that the conditions by which the yarn is oxidized effect the physical properties of the resulting oxidized yarn. Depending on the polymers or copolymers from which the yarn is made and the oxidation method used, it is believed that the resulting oxidized yarn will vary in physical properties--e.g., stability. By stability it is meant that the fiber structure is heat resistant and will not melt, nor will neighboring fibers coalesce in the temperature range 200°C to 1000oC. Without wishing to be bound by theory, it is believed that the physical properties and the polymeric makeup of the oxidized yarn effect the activation conditions under which the activated carbon yarns of this invention having optimum properties can be obtained. By optimum properties it is meant a tenacity of at least about 1 g/d and a CC14 sorptivity of greater than about 60% by weight, based on the weight of the activated carbon yarn. Therefore, those skilled in the art can appreciate that oxidized yarns, differing in polymeric makeup and/or method of oxidation, may have to be activated under conditions-- e.g., temperature, gas flow rate, and through-put rate--which vary from yarn to yarn in order to obtain activated carbon yarns having optimum properties. However, such conditions may be determined by those skilled in the art without undue experimentation.
[0046] In the activated carbon yarns of this invention a plurality of carbon containing precusor yarns, preferably oxidized acrylic yarns, or a combination of different carbon containing precusor yarns are brought together and arranged spatially by intertwining to form a multi-fold yarn structure. Intertwining is defined as including any method for making yarns including the art recognized methods for making yarns from staple or continuous filaments--e.g., twisting or braiding. Methods for making yarns and the configurations by which yarns are made--e.g., braided or twisted--are well known in the art. Preferably, the multi-fold yarn for the activation process is made by longitudinally twisting or braiding together a plurality of carbon containing precusor yarns. The carbon containing precuror yarns generally have a twist coefficient greater than about 65 and usually within the range of from about'65 to about 150. The multi-fold yarn made by twisting generally has from about 0.5 to about 10 turns per inch. The twist ratio is generally within the range of about 0.1 to about 0.5.
[0047] The multi-fold yarn is generally made from about 2 to about 20 carbon containing yarns, preferably oxidized acrylic yarns, with about 3 to about 10 being preferred. The yarns can be intertwined together at one time or a given number of yarns can be intertwined together to form a unit and then a given number of units can be intertwined together to form the multi-fold yarn for activation. For example, 2 oxidized acrylic yarns can be intertwined to form a pair and then 3 pairs can be intertwined to form the multi-fold yarn for activation.
[0048] Those skilled in the art will appreciate that the denier of the individual plies and consequently the denier of the plied yarn are generally chosen to meet specific requirements of the end product. Thus, as shown by the examples below, 6 oxidized acrylic spun yarns of 10 worsted count (797 denier) were plied and activated to yield a plied yarn of from about 20 to 6 worsted count (400 to 1300 denier).
[0049] The multi-fold yarn is then subjected to an activation process. For example, a continuous activation process can be utilized. In a continuous process the multi-fold yarn is continuously pulled or fed through at least one hot zone (furnace) while passing an activating gas through the hot zone. The gas, for example, can be passed through the hot zone counter current to the direction of the multi-fold yarn. Multiple hot zones, for example 2, can be utilized--see for example FIG. I--to supply the energy requirements of the process. The conditions of the temperature, gas flow rate, through-put rate and the tension the yarn is held at during the process are such that an activated carbon yarn is produced having a tenacity greater than about 0.1 g/d and a CC14 sorptivity of greater than about 25% by weight, based on the weight of the activated carbon yarn. The activated carbon yarn produced preferably has a tenacity of about 0.1 g/d to about 4 g/d with about 1 to about 4 g/d being most preferred and greater than about 2 g/d being even more preferred. Preferably, the yarn produced has a CC14 sorptivity of about 25% to about 140% by weight, based on the weight of activated carbon yarn, with greater than about 60% being most preferable and greater than about 75% being even more preferable. The physical properties of the activated carbon yarn obtained will have some variation based upon the denier of the precursor yarn and, as discussed above, the denier is generally chosen for specific applications.
[0050] An example of activation conditions for a continuous process are as follows: the temperature range of the furnace(s) is high enough to allow activation to occur under the conditions of operation, but not so high as to cause unnecessary degradation of the multi-fold yarn; thus the temperature is generally from about 700 to about 1300°C with about 900 to about 1150 being preferred. Those skilled in the art can appreciate that the gas flow rate, yarn through-put rate, and yarn tension can vary because they are dependent on the precursor, the precursor's denier, and hot zone lengths, and these parameters are interactive with each other. Thus, as indicated, some experimentation may be required to determine the ranges for these parameters that will yield optimum physical properties of the yarn.
[0051] The gases which are suitable for use in the activation process are well known in the art. For example, C02, NH3, steam or a mixed gas thereof--e.g., C02 and H20--are used. The amount of allowable oxygen is such that the fiber does not burn, and the concentration is generally not more than 3 vol %. One or more inert gases such as N2, Ar or He may be contained in an activation gas in an amount of up to about 50 vol % of--e.g., C02 and N2, and the like. Preferably, C02, which is bubbled through a gas washing bottle containing H20 imparting a H20 vapor content to the C02 is utilized.
[0052] A diagram showing an example of a continuous activation process scheme for the production of an activated carbon yarn utilizing two furnaces is shown in FIG. 1. A precursor spool (1) contains the carbon containing yarn (2). Tension is applied to the yarn with a spring tension device (12) with the tension being monitored by a tension meter (3). The yarn is pulled longitudinally, entering into a quartz reaction tube (4a) which is heated in a furnace (5a), for example, a Lindberg furnace. The yarn exits the quartz reaction tube (4a') and enters the second quartz reaction tube (4b) which is in a furnace, (5b), for example, a Lindberg furnace. The yarn exits the quartz reaction tube (4b') to take-up rolls (6) and then,to a precision winder (7), for example, a Leesona winder. An oxidizing gas, flowing from a cylinder (9), passes through a mass flow controller (10) into a gas washing bottle (8). From the gas washing bottle the gas enters the furnace (5) countercurrent to the direction of yarn movement. A digital thermometer monitors the temperature of entering gas. The equipment in processing unit 14 is equivalent to the equipment in processing unit 13. If only one furnace is used in the activation process then either unit 13 or unit 14 would be eliminated. If more than two furnaces are utilized, other units equivalent to units 13 and 14 would be added.
[0053] Precursor yarns of this invention may be activated in furnace at 9000-13000C containing a flowing activating gas. The residence time would determine the degree of activation.
[0054] FIG. 2 is a schematic of the yarn feed-through entrance (4a and 4b of FIG. 1). FIG. 3 is a schematic of the yarn feed-through exit (4a' and 4b' of FIG. 1). The yarn enters through 15 (FIG. 2) and exits through 17 (FIG. 3). The activating gas enters through 18 (FIG. 3). The yarn feed-througbs are connected to pyrex and caps, which in turn are connected to the quartz reaction rube by ground glass joints, for example 24/40 around glass joints, (16 and 19, FIG. 2 and 3, respectively).
[0055] In an alternate embodiment, the present invention provides new and improved activated carbon fiber yarns and cloths provided with a polyfluorocarbon coating which are characterized by imprpoved abrasion resistance and weav- ability of the fibers, without adversely affecting their toxic chemical sorbitivity.
[0056] The polymeric fluorocarbon resins utilized in this aspect of the invention are those capable of being made into an aqueous dispersion and are well known to those skilled in the art. Such polymeric fluorocarbons include for example: polytetraflurooethylene and fluorinated ehtylenepropylene polymers, and the like. Polyhexa- fluoropropylene may also prove useful. These polymeric fluorocarbon resins are available, for example, from E. I. duPont de Nemours & Co., Inc. under the trademark TEFLON@. An example of such a resin is TEFLON® 30B TFE.
[0057] It has been discovered that the polymeric fluorocarbon resin coating imrpoits the abrasion resistance of activated carbon fibers, reduces the release of carbon fiber particulates, i.e., fly, produced by abrasion, and creates a hydrophobic surface without reducing the chemical sorptivity'of the cloth.
[0058] The activated carbon material can be immersed or dipped in an aqueous dispersion of the fluorocarbon resin particles or can be sprayed with an aqueous dispersion of the fluorocarbon resin particles. An example of such a resin is TEFLONO 30B TFE which is a tetrafluoroethylene resin.
[0059] In general any commercially available aqueous dispersion of fluorocarbon resin particles can be used, such as those available under the trademark TEFLON®. Thus, for example, a suspension having particles ranging in size from about 0.05 microns to about 0.5 microns (available as TEFLON® 30B TFE) can be used.
[0060] The coated activated material is then dryed to remove the water at ambient temperatures or with the application of heat, such as in an oven at a temperature of about 90 to about 250°C.
[0061] The concentration of the aqueous dispersion can vary depending on the amount of coating desired on the activated carbon material. In general, the amount of coating placed on the activated carbon material will not effect sorptivity, but will effect the weight of the activated carbon material. Thus, considerations of the desired weight of the coated activated carbon material will basically determine the amount of coating placed on the material. Therefore, any concentration of % solids of fluorocarbon resin in an aqueous dispersion sufficient to coat the activated carbon material can be used. For example, among the aqueous dispersions that can be used are those containing about 0.01% to about 10% solids (e.g., 0.01%, 0.1%, 0.5%, 1%, 5%, and 10% solids).
[0062] The use of this coating should allow activated fibers or yarns to be processed with conventional textile equipment that would destroy or greatly reduce the properties of uncoated fibers or yarns. Thus activated yarns or fibers may be woven or knit into useful articles. The life of the garment, made from coated fibers or coated subsequent to manufacture, should increase as a result of improved abrasion resistance. Less fly is produced, which decreases safety hazards, when materials are coated. The coating also creates a hydrophobic surface and repels water and chemical agents that might be contained within an aqueous media.
[0063] The abrasion resistance of any activated carbon material can be increased by coating with the fluorocarbon resin as described herein. However, it is desirable to coat an activated carbon yarn or activated carbon material made from an activated carbon yarn comprising a plurality of carbon containing precursor yarns, intertwined together to produce a multi-fold yarn and then subject to activation process.
[0064] In still another embodiment, the invention provides and improved warp knitted activated carbon fabric comprising a weft of a multi-fold activated carbon yarn and a warp of a hydrophobic polymeric monofilament yarn wherein every course of said activated yarn is inserted across the full width of said fabric with said monofilament being in the wales and courses of said fabric.
[0065] The activated carbon fabrics of this invention, as those skilled in the art can appreciate, can be produced by a variety of knitting designs known in the art e.g., tricot or raschel knit fabric design.
[0066] A tricot knit fabric of this invention has a design pattern represented by the bar movement pattern:
front guide bar: 1-0, 0-1
back guide bar: 1-0, 1-2 .
[0067] A raschel knit fabric having a design represented by the bar movement pattern:
front guide bar: 1-0, 0-1
back guide bar: 1-0, 1-2
may also be used to weave (knit) the fabrics of this invention.
[0068] Without wishing to be bound by theory, it is believed that the leakage encountered with prior art fabrics is at least partially due to a "wicking effect." Since the protective yarn is, for example, wrapped or braided along the entire length of the activated carbon yarn a leakage path is established from outside to inside by a "wicking effect" when, for example, the fabric gets wet. This wicking effect is overcome by the use in this invention of a hydrophobic monofilament yarn as the warp. The monofilament yarns suitable for use include for example: polyesters such as DENIER 20/1 SEMIDOLL MONOFIL available from Hanover Mills Inc., NY, NY.
[0069] The monofilament generally has a denier of about 10 to about 100, with about 10 to about 30 being preferred and about 15. to about 20 being most preferred.
[0070] The warp knit fabrics of this invention have monofilament yarn in the warp while activated carbon yarn is weft inserted a selected number of courses per inch- i.e., from about 20 to about 60 courses per inch with about 24 to about 50 being preferred and about 30 to about 40 being most preferred--to provide a warp knit fabric which is flexible and has high sorptive capacity for toxic chemical vapors and gases and liquids, is reasonably strong, and has sufficiently good abrasion resistance to retain a large amount of sorptivity for toxic chemical vapors even after being subjected to considerable abrasion. The warp knit fabrics may be produced on tricot type or raschel type warp knitting machines modified so as to insert the unprotected activated carbon yarn as weft while the monofilament yarn is being warp knitted. Such apparatuses and methods are exemplified by U.S. Patent No. 3,364,701 and U.S. Patent No. 3,495,423.
[0071] Although the activated carbon yarn utilized has excellent tenacity, flexibility and abrasion resistance, during experimental testing in a commercial weaving process, it occasionally snags and is subject to a minimal amount of breakage around sharp angle bends in the commercial weaving equipment. It is to be noted that the breakage which occurs with these multi-fold activated carbon yarns is much less than that which occurs with other activated carbon yarns. To overcome this, the knitting equipment may be modified, for example, by placing plastic sleeves at sharp angle bends to guide the yarn through.
[0072] It is preferred for the purposes of the invention that the warp knit fabric contain at least 2 oz/yd2 of the activated carbon yarn with about 3 oz/yd2 to about 7 oz/yd2 being most preferred. It is also preferred that the warp knit fabric have an ai" permeability of at least 50 cubic feet/minute/square foot of fabric wiht about 200 ft3/min/ft2 to about 1000 ft3/min/ft2 being most preferred. Clothing constructed of warp knit fabric having the above-stated-preferred characteristics will be effective for protecting the wearer of such clothing against toxic chemical vapors or gasses for a reasonable length of time, depending on the concentration of such vapors or gases in the atmosphere, and may be worn without experiencing undue heat stress since the fabric breathes while sorbing the toxic chemical vapors or gases and is relatively light weight due to the absence of multilayers and excessive support yarns to protect the activated carbon yarn.
[0073] In another embodiment of this invention a layer of hydrophilic fiber is incorporated on to one side of the warp knit fabric described above. This can be done by known knitting methods as for example, in the manner described in FIG. 9 by, for example, the addition of a third beam to a knitting machine of the Karl Mayer type. When the added layer is placed toward the skin of the wearer it improves abrasion resistance, protects the wearer against carbon fiber cut ends and serves to spread perspiration for easy release through to the outside of the fabric Since this added layer is on one side only and does not penetrate the activated carbon yarn layer, it does not produce a leakage path for toxic liquid agents.
[0074] Hydrophilic fibers or yarns which are useful include but are not limited to: 50/50 polyester/cotton (polycotton), 100% cotton, 100% polyester, rayon, wool, and linen.
[0075] The hydrophilic yarns have a denier of about 100 to about 300 with about 150 to about 250 being preferred and about 175 to about 190 being most preferred. It is anticipated that the addition of the second layer will add only about 1 to about 1.5 oz/yd2 to weight of the warp knitted fabric described above.
[0076] While the invention has been described in terms of warp knit fabrics produced with weft insertion of activated carbon yarn to provide toxic vapor sorptive capacity to the fabrics, it is to be understood that similar results may be obtained employing weft knitting machines in which warp yarns of activated carbon yarn are inserted and held in place in the fabric by the knit weft monofilament yarn.
PROCEDURE FOR DETERMINING
ACTIVATED CARBON YARN'S STRENGTH
[0077] In the following examples, the tenacity of the activated carbon yarns was determined by measuring the load required to break the multi-fold yarn. These loads were measured with a tensile testing machine manufactured by Testing Machines, Inc. of New York. Six-inch yarn lengths were gripped by two pairs of one-inch square rubber-faced jaws, three inches apart. The loads were measured to the nearest 0.01 pound. Tenacities were then calculated by dividing that load, in grams, by the denier of the yarn tested. Yarn deniers (yarn weight per 9000 meters of yarn) were determined by weighing 20 cm. lengths of yarn.
PROCEDURE FOR DETERMINING ACTIVATED CARBON YARN'S CARBON TETRACHLORIDE SORPTIVITY
[0078] In the following examples, static sorption of carbon tetrachloride was used to evaluate the level of activation in the samples produced. Fiber samples of approximately 500 mg. were placed in a vacuum desiccator which was then evacuated with a mechanical vacuum pump for 0.5 hours. The desiccator was then back-filled with nitrogen. Each sample was then weighed to the nearest 0.01 mg and quickly placed in a second desiccator, saturated with carbon tetrachloride vapor,. for 4 hours. The samples were again weighed immediately after their removal from the desiccator to determine the percentage weight gain of carbon tetrachloride with respect to the initial sample weight.
EXAMPLE 1
CONTINUOUS PRODUCTION OF ACTIVATED CARBON YARN UTILIZING TWO FURNACES IN THE ACTIVATION PROCESS
[0079] An oxidized acrylic yarn was activated in the system own in FIG 1. CELIOXO brand of oxidized acrylic yarn, available from Celanese Corporation, was pulled through two 5.4 cm (ID) by 120 cm long quartz reaction tubes. Each tube was placed within a Lindberg Model 54352 tube furnace. The speed of the yarn through the system was controlled by take-up rolls and tension in the yarn was monitored with a Tensilon tension meter. Yarns entered and exited the reaction tube through pyrex end caps and feed throughs. Flowing countercurrent to the fiber line was a stream of humidified carbon dioxide. Humidificaticn was achieved by bubbling the gas through heated gas washing bottles. The temperature of the gas was measured just prior to entering the furnace. A Tylan mass flow controller was used to control and monitor the flow of carbon dioxide into each washing bottle.
[0080] Six CELIOX® brand of oxidized acrylic yarns each having a 10 worsted count were twisted to form a single plied yarn of about 4800 denier with about two turns per inch. The temperature of the first furnace was held at about 10350C with a flow rate of about 3L/min (liters/miute) of carbon dioxide while the second furnace was held at about 10150C with a flow rate of about 4L/min and a gas inlet temperature of about 30°C. A tension of about 30 grams and a line speed of about 10 cm/min produced an activated carbon yarn with a denier of 600, an average tenacity of 3.1 g/d and an average carbon tetrachloride sorptivity of 83%.
[0081] The sample of activity carbon yarn for determining tenacity and CC14 sorptivated was taken from the end of about a 200 yard length of the activated carbon yarn-- i.e., after about 200 yards of yarn had been subjected to the activation process, a sampling was taken from the end of that length for testing.
[0082] Table 1 reports the results for the 19 samples from which the average tenacity and average CC14 sorptivity was determined.
COMPARATIVE EXAMPLE 1 ATTEMPT TO ACTIVATE SEPARATE 10 WORSTED COUNT YARNS
[0083] In an attempt to activate 6 separate 10 worsted count yarns, using the same conditions as in Example 1, the yarns repeatedly failed in the oven, presumably as a result of being over oxidized. The yarns similarly failed even after reducing the temperature of both ovens 200C and lowering the total tension to 10 grams.
EXAMPLE 2
CONTINUOUS PRODUCTION OF ACTIVATED CARBON YARN UTILIZING TWO FURNACES IN THE ACTIVATION PROCESS
[0084] Using the same procedure described in Example 1, 6 yarns of 6 ply 10 worsted count CELIOX® brand of oxidized acrylic yarn with approximately 2 turns per inch were activated with temperatures of about 10520C and about 1043°C and flow rates of about 4 and about 5 L/min in the first and second furnaces, respectively. A line speed (through-put rate) of about 9.5 cm/min and line tension of about 30 grams produced yarns with an average carbon tetrachloride static sorptivity of 89% and an average tenacity of 3.0 g/d at a denier of about 670. The tenacity and CC14 sorptivity averages were the result of six trials. The tenacity of these trials ranged from 2.8 to 3.4 g/d and the CC14 sorptivity of these trials ranged from 75 to 96%.
EXAMPLES 3 - 6
[0085] A single furnace was used to activate 6 ply 10 worsted count CELIOXO brand of oxidized acrylic yarn at various temperatures and flow rates as shown in Table 2. Within the range examined increases in temperature increased carbon tetrachloride sorptivity while an optimum B.E.T. surface area was obtained at a CC14 sorptivity of 63%. Tenacity appears uneffected by conditions until high carbon tetrachloride sorptivities are reached when apparently the fibers become over oxidized.
EXAMPLES 7-23
[0086] Table 3, Examples 7-23, lists the % CC14 sorptivity and the tenacity (Example 12 only) for activated carbon yarns made from CELIOXO brand of oxidized acrylic yarn. Following the procedure of Examples 3-6, six oxidized yarns each having a worsted count of 10 were intertwined by twisting to form a single plied yarn (multi-fold yarn). The multi-fold yarn was activated in a single furnace at the conditions listed in Table 3, using carbon dioxide as the oxidizing gas. One multi-fold yarn was activated at a time and line tensions are approximate.
EXAMPLES 24-26
[0087] Table 4, Examples 24-26, lists the % CC14 sorptivity and the tenacity for activated carbon yarns made from CELIOX® brand of oxidized acrylic yarn.
[0088] Following the procedure of Example 1, six oxidized yarns each having a worsted count of 10 were intertwined by twisting to form a single plied yarn (multi-fold yarn). The multi-fold yarn was activated using two furnaces at the conditions listed in Table 4 using carbon dioxide as the oxidizing gas. One multi-fold yarn was activated at a time and gas temperature and line tensions are approximate.
EXAMPLES 27-34
[0089] Table 5, Examples 27-34, lists the % CC14 sorptivity and the tenacity for activated carbon yarns made from CELIOXO brand of oxidized acrylic yarns.
[0090] Following the procedure of Example 1, six oxidized yarns each having a worsted count of 10, were intertwined together by twisting to form a single plied yarn (multi-fold yarn). The multi-fold yarn was activated using two furnaces at the conditions listed in Table 5. Nitrogen gas was used in the first furnace and carbon dioxide gas was used in the second furnace. One multi-fold yarn was activated at a time and gas temperatures are approximate.
[0091] The foregoing examples demonstrate the production of activated carbon yarns having excellent tenacity and sorptivity. Those skilled in the art will appreciate that there are many parameters -- e.g., furnace temperature, gas flow rate, through-put rate (feed rate), and the like -- subject to variation. It can be appreciated that, in trying initially to determine the conditions which would yield an activated carbon yarn with optimum properties, several experiments yielded yarns with less than optimum properties. Possible explanations for these variants involve the parameters either individually or in some combination, e.g., unrecorded temperature differences (fluctuations), a gas flow rate that is too slow, a temperature that is too low, a feed rate that is too fast or too slow, a gas flow rate that is too low in combination with a temperature that is too low, and the like.
[0092] Set forth below are examples of experiments which did not yield activated carbon yarns having optimum properties.
EXAMPLES 35 - 49
[0093] Table 6, Examples 35 to 49, lists the results of experiments which provided yarns with less than optimum properties when the single furnace technique was used. The oxidized yarns used, their ply, worsted count and the procedure followed was the same as for Examples 7-23 except as follows:
- Example 35: utilized PYRONe brand of acrylonitrile based oxidized yarn available from Stackpole Fibers Co. Inc. The yarn was supplied as a 20 ply yarn (plied yarn), made by intertwining (by twisting) 20 oxidized yarns having a worsted count of 10.
- Example 36: utilized PYRONe brand of acrylonitrile based oxidized yarn as in Example 35 except that 2 oxidized yarns having a worsted count of 10 were twisted together.
- Example 40: two multi-fold yarns, made of six CELIOXO brand of oxidized acrylic yatn having a worsted count of 10 were drawn through the
furnace parallel to each other. The multi-fold yarn was activated in a single furnace
at the conditions listed in Table 6 using carbon dioxide as the oxidizing gas and
line tensions are approximate.
EXAMPLES 50-59
[0094] Table 7, Examples 50-59, lists the results of experiments which provided yarns with less than optimum properties. The procedure and oxidized yarns used were the same as in Examples 1 and 24-26. The multi-fold yarn was activated at the conditions listed in Table 7 using carbon dioxide as the oxidizing gas and gas temperatures and line tesions are approximate.
EXAMPLES 60-68
[0095] Table 8, Examples 60-68, lists the results of experiments which provided yarns with less than optimum properties. The procedures and oxidized yarns used were the same as in Examples 27-34. The multi-fold "arn was activated at the conditions listed in Table 8 using carbon dioxide as the oxidizing gas. The gas temperatures are approximate.
[0096] As of the date of filing of this application, there has been limited testing on various fibers, including an oxidized acrylic fiber, KEVLARO 49 brand of Aramid fiber, and a phenolic-aldehyde fiber available under the product designation KYNOL in the form of continuous tows with no twist which however have not been adequate to suggest conditions which would result in an activated carbon yarn with optimum properties. As indicated, it is desirable to use fibers with either a twisted continuous tow or spun yarn for the yarns of this invention.
[0097] It will be appreciated by those skilled in the art that commercial applications of the multi-fold yarns of this invention, such as fabric weaving operations, will be subject to quality control constraints as to processability of the yarns. Thus, as of the date of filing of this application, experimental testing of the multi-fold yarns of this invention, such as those exemplified by Example 2, in a commercial weaving process have been about 95% successful. That is, when tested in a Karl Meyer commercial knitting process there was only about 5% breakage of the yarn. Possible reasons for such breakage may include over oxidation of the multi-fold yarn during activation causing weak spots (areas) in the yarn from variations in process procedures, such as variation in gas flow rates during activation and non-uniformity of the carbon containing yarns from batch to batch. It will be further appreciated that this level of breakage, while low in magnitude, may be additionally reduced to essentially negligible levels through suitable quality control adjustments in the multi-fold yarn manufacturing process and/or commercial weaving process.
PROCEDURE FOR DETERMINING ACTIVATED CARBON YARN'S CARBON TETRACHLORIDE SORPTIVITY
[0098] Static sorption of carbon tetrachloride was used to evaluate the level of sorptivity in coated and uncoated samples. Samples were placed in a vacuum desiccator which was then evacuated with a mechanical vacuum pump for 0.5 hours. The desiccator was then back-filled with nitrogen. Each sample was then weighed to the nearest 0.01 mg and quickly placed in a second desiccator, saturated with carbon tetrachloride vapor, for 4 hours. The samples were again weighed immediately after their removal from the desiccator to determine the percentage weight gain of carbon tetrachloride with respect to the initial sample weight. For coated materials the sorptivity can be based on the weight of the activated material or the weight of the activated material plus the coating weight.
Example 69
[0099] Six ply activated carbon fiber yarns of approximately 600 denier were cut to about 1 meter lengths. The yarns were placed in a vacuum desiccator which was evacuated with a mechanical pump for 0.5 hours. The desiccator was then backfilled with nitrogen and each yarn was weighed to obtain a base weight. Each yarn was then dipped into a dispersion of TEFLONO 30B TFE resin particles 0.05 to 0.5 microns in size suspended in water. Concentrations of 0.01%, 0.1%, 0.5%, 1%, 5%, and 10% solids were used and were prepared by mixing TEFLON® 30B TFE resin with varying amounts of deionized water. Each yarn was left in one of the above suspensions for about 10 seconds. The yarns were then laid on aluminum foil and were dried at 1150C for 1 hour. To determine the percentage weight gain of TEFLONO 30B TFE resin, the yarns were evacuated for 1 hour, backfilled with nitrogen and reweighed. Each yarn was then tested to determine CC14 sorptivity. The results are shown in Table 9.
[0100] The same concentrations of solids in suspensions were used to continuously coat the same activated carbon yarns for mechanical testing. As shown in FIG. 5, the activated carbon yarn contained on a spool (1) was pulled through a dip tank containing the suspension (2) and then through an 18 inch hot zone (3), at about 170°C, with take-off rolls (4) at a speed of about 20 inches/minute.
[0101] FIG. 6 represents how the abrasion resistance of the yarn was tested by drawing a weighted yarn over a yarn hook/guide (1) from a Karl Meyer Weftamatic Warp Knit Machine. The yarn was pulled down one inch and released up one inch (2) with a 50 gm weight (3) attached to the other end of the yarn. This down-up motion comprised one cycle. This was repeated until the yarn broke. The number of cycles to failure was noted and are listed in Table 9.
EXAMPLE 70
[0102] A TEFLON® 30B TFE suspension containing about 1% solids was used to dip and spray coat activated carbon fiber yarns described in Example 69. A glass atomizer similar to Kontes Model Number 42250 Thin Layer Chromatography Sprayer was used to spray the suspension. Samples were dried at about 1350C for about 0.5 hours. The yarns were tested for CCL4 sorptivity and abrasion resistance as described in Example 69. CC14 sorptivities are based on the yarn plus coating weight. The results are shown in Table 10.
EXAMPLE 71
[0103] Activated carbon yarn, in the form of continuous untwisted tow, was dipped into a TEFLON® 30B TFE suspension containing about 1% solids. The tow was then dried at 135°C for about 0.5 hours. The coating weight was found to be about 2% based on the weight of the uncoated fiber. CC14 sorptivity and abrasion resistance were determined as in Example 69 and the.results are shown in Table 11.
EXAMPLE 72
[0104] Nonwoven sheets containing 14.8 mg of activated carbon fiber, 1.64 mg of acrylic fiber, and 0.5 ml of MAGNIFLOC® 1839A brand of flocculant available from American Cyanamid Co., were made by a wet paper making process as described in copending Application Serial No 531,366, filed September 12, 1983. One sheet was dipped into a suspension containing about 1% of TEFLON® 30B TFE solids and was dried at 1350C to yield a coating weight of about 15% based on the initial fabric weight.
[0105] Similarly, a plain weave fabric of Kuractive activated carbon fiber cloth (available from Kuraray Chemical Co., Ltd., Japan) was dipped into a suspension containing about 1% of TEFLON® 30B TFE solids and was dried at 1350C. The coating weight was determined to be about 6% based on the initial fabric weight. Water was found to bead up on the TEFLON® 30B TFE coated Kuractive woven cloth whereas water was quickly absorbed into the uncoated cloth.
[0106] Dynamic sorptivities of both fabrics, nonwoven and woven were tested with the apparatus shown in FIG. 7. This aparatus is a modification of the MIL-C-43858 test specification apparatus. Purified nitrogen (1) was preheated (2) and was bubbled through CC14 (3). The saturated gas was then passed into a mixing manifold (4). The flow of nitrogen was controlled by a mass flow controller (5). By adjusting the flow of a second source of nitrogen (6) into the manifold, a concentration of 5 mg of CC14 per liter of gas was established. This gas was then pulled through the activated cloth, contained in a sample cup (7), and a Foxboro MIRAN Model 973 Infrared Analyzer (8) by a vacuum pump (9). The analyzer was tuned to the 12.6 micron absorbance band of CC14. Calibration of the analyzer was achieved prior to the run by injecting known amounts of CC14 into a recirculating air pump. At a flow of one 1/min, as establizhed by a rotometer (10), the breakthrough concentration of CC14 downstream from the filler was set at 0.5 mg/l as specified in MIL-C-43558. Excess gas was vented through (11). Apparatus (2), (3), (4), and (7) were maintained at a constant temperature of 32.5 ±1°C in an oven (12). The dynamic CC14 adsorption was calculated as follows:
where tb is the breakthrough time in minutes. The military specification for chemical protective clothing is 1.8 mg/cm2. The results of these tests are shown in Table 12.
EXAMPLE 73
Tricot Warp Knit Activated Carbon Fabric
[0107] A six-ply CELIOXO oxidized stabilized yarn having a worsted count of 6/10 was activated using the single furnace technique described in copending Application Serial No. (Case 29,733), filed (herewith). The multi-fold yarn had a twist coefficient of about 87.5 and a twist ratio of about 0.2. The activated carbon yarn has a tenacity of 1.3 g/d, weight 1300 denier and static sorption to CC14 greater than 80% by weight, based on the weight of the activated carbon yarn. The yarn was knitted into fabric using a Karl Mayer Weftamatic Warp Knit Machine and a 2 bar chain stitch plus tricot. Monofilament polyester of 20 denier was machine fed in the warp while-the activated carbon yarn was fed in the weft. Testing yielded the following characteristics:
[0108] Static and Dynamic sorption of CC14 was tested according to the standard method for Military Clothing Material.
[0110] Dynamic sorption testing using the standard 5 mg/L CC14 threat oncentration in nitrogen at 1 L/min rate through 100 cm sample cup area to a downstream limit of 0.5 mg/L resulted in 43 minutes test time to the end point (2.15 mg/cm2).
[0111] This data is significantly better than the requirements of a U.S. specified military laminate for chemical protection which describes a carbon powder loaded polyurethene foam system. MIL-C-43858 (GL) lists the following requirements:
1. A multi-fold activated carbon yarn comprising from about 2 to about 20 precursor
yarns selected from oxidized acrylic yarns, said precursor yarns being intertwined
or braided together at at least about 0.5 turns per inch to form a multi-fold yarn,
and said multi-fold yarn having an activated carbon exterior surface, said multi-fold
activated carbon yarn characterized by having tenacity of greater than 1 g/d and a
carbon tetrachloride sorptivity of between 25% and 140% by weight, based on the weight
of said multi-fold activated carbon yarn.
2. A method for making a multi-fold activated carbon yarn having improved tenacity
and excellent sorptivity said method comprising:
(a) providing from 2 to 20 precursor yarns selected from oxidized acrylic yarns;
(b) intertwining or braiding said precursor yarns together at at least 0.5 turns per inch to provide a multi-fold yarn;
(c) activating said multi-fold yarn to provide an activated carbon surface thereon by exposing said yarn to an oxidizing atmosphere at a temperature of between 7000 and 1300°C for a time sufficient to provide a multi-fold activated carbon yarn having a tenacity of between 0.1 g/d and 4.0 g/d and a carbon tetrachloride sorptivity of between 25% and 140% by weight, based on the weight of said multi-fold activated carbon yarn.
3. A multi-fold activated carbon yarn having improved abrasion resistance comprising
a multi-fold activated carbon yarn as recited in Claim 1 said activated carbon exterior
surface has polymeric fluorocarbon resin particles deposited thereon.
4. A method for making a multi-fold activated carbon yarn having improved abrasion
resistance, said method comprising the method of Claim 2 with the additional step
(d) of applying an aqueous dispersion of polymeric fluorocarbon resin particles containing
between 0.01% to 10% resin solids and drying the fluorocarbon coating thereon.
5. An improved knitted activated carbon fabric comprising:
(a) a weft of multi-fold activated carbon yarn as recited in Claim 1; and
(b) a warp of a hydrophobic monofilament yarn.
6. A fabric as recited in Claim 6 wherein said fabric is a tricot knit having a design
pattern represented by the bar movement pattern:
and wherein said hydrophobic monofilament yarn is a polyester yarn.
and wherein said hydrophobic monofilament yarn is a polyester yarn.
7. An improved knitted activated carbon fabric comprising:
(a) a weft of a multi-fold activated carbon yarn, said activated carbon yarn being produced by intertwining a plurality of carbon containing yarns together to produce a multi-fold yarn and then subjecting said multi-fold yarn to an activation process; and
(b) a warp of hydrophobic monofilament yarn; and
(c) a hydrophilic yarn incorporated as a layer by one side of said fabric.
8. A fabric of Claim 8 wherein said fabric is a tricot knit having a design pattern
represented by the bar movement pattern:
and wherein a third beam is added having the design pattern 0-0, 2-2 to incorporate said hydrophilic yarn as a layer on one side.
and wherein a third beam is added having the design pattern 0-0, 2-2 to incorporate said hydrophilic yarn as a layer on one side.
9. A fabric of Claim 8 wherein said fabric is a tricot knit having a design pattern
represented by the bar movement pattern:
wherein a third beam is added having the design pattern 0-0, 2-2 to incorporate said hydrophilic fibers as a layer on one - side; wherein said carbon containing yarn is an oxidized 'acrylic yarn; wherein said intertwining is by twisting, and about 2 to about 20 of said acrylic yarns are twisted together having at least about 0.5 turns per inch; wherein said activated carbon yarn has a tenacity of about 0.1 to about 4 g/d and a CC14 sorptivity of about 25 to about 140% by weight, based on the weight of said activated carbon yarn; wherein said monofilament of (b) is a polyester; and wherein said hydrophilic yarn of (c) is a polyester/cotton blend.
wherein a third beam is added having the design pattern 0-0, 2-2 to incorporate said hydrophilic fibers as a layer on one - side; wherein said carbon containing yarn is an oxidized 'acrylic yarn; wherein said intertwining is by twisting, and about 2 to about 20 of said acrylic yarns are twisted together having at least about 0.5 turns per inch; wherein said activated carbon yarn has a tenacity of about 0.1 to about 4 g/d and a CC14 sorptivity of about 25 to about 140% by weight, based on the weight of said activated carbon yarn; wherein said monofilament of (b) is a polyester; and wherein said hydrophilic yarn of (c) is a polyester/cotton blend.