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
  • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/12—Stretch-spinning methods
  • D01D5/14—Stretch-spinning methods with flowing liquid or gaseous stretching media, e.g. solution-blowing
• • 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
  • D01F1/103—Agents inhibiting growth of microorganisms
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber
  • Y10T428/2973—Particular cross section

Definitions

• the present application relates to Iyocell fibers with antimicrobial activity.
• Figure 1 is a scanning electron photomicrograph at IOOOX of the longitudinal section of control Sample A.
• Figure 2 is a scanning electron photomicrograph at IOOOX of the cross section of S ample 6.
• Figure 3 is a backscattering electron photomicrograph at 2000X of the cross section of Sample 7.
• Figure 4 is a scanning electron photomicrograph at IOOOX of the longitudinal section of Sample 11.
• Figure 5 is a scanning electron photomicrograph at 1000X of the longitudinal section of Sample 15.
• Figure 6 is backscattering electron photomicrograph at IOOOX of the cross section of Sample 13.
• the present application is directed to Iyocell fibers with antimicrobial activity.
• Iyocell fibers comprising antimicrobial agents in which the fibers are extruded by the meltblown process.
• meltblown Iyocell fibers with antimicrobial activity are particularly suitable for use in nonwoven applications because of their characteristic soft feel, water absorbtion, microdiameter size, biodegradability and the ability of these fibers to be combined in the spinning process to form either selfbonded or spunlaced webs. Fibers made from pulp with a high hemiceilulose content are particularly suited for this application because of the added interf iber bonding attributed to hemiceilulose.
• Iyocell fibers are produced from high quality wood pulps that have been extensively processed to remove non-cellulose components, especially hemiceilulose.
• high alpha pulps These highly processed pulps are referred to as dissolving grade or high ⁇ (high alpha) pulps, where the term ⁇ refers to the percentage of cellulose remaining after extraction with 17.5 % caustic.
• Alpha cellulose can be determined by TAPPI 203.
• a high alpha pulp contains a high percentage of cellulose, and a correspondingly low percentage of other components, especially heraicellulose.
• the processing required to generate a high alpha pulp significantly adds to the cost of lyocell fibers and products manufactured therefrom.
• the cellulose for these high alpha pulps comes from both hardwoods and softwoods; softwoods generally have longer fibers than hardwoods.
• a relatively low copper number, reflective of the relative carbonyl content of the cellulose, is a desirable property of a pulp that is to be used to make lyocell fibers because it is generally believed that a high copper number causes cellulose and solvent degradation, before, during, and/or after dissolution in an amine oxide solvent.
• the degraded solvent can either be disposed of or regenerated, however, due to its cost it is generally undesirable to dispose of the solvent.
• a low transition metal content is a desirable property of a pulp that is to be used to make lyocell fibers because, for example, transition metals accelerate the undesirable degradation of cellulose and NMMO (N-methyl morpholine N-oxide) in the lyocell process.
• NMMO N-methyl morpholine N-oxide
• Low alpha (e.g., high yield) pulps can be used to make lyocell fibers.
• the desired low alpha pulps will have a low copper number, a low lignin content and a desirably low transition metal content but broad molecular weight distribution.
• Pulps which meet these requirements have been made and are described in US 6,797,113, US 6,686,093 and US 6,706,876, the assignee of the present application. While high purity pulps are also suitable for use in the present application, low cost pulps such as Peach®, Grand Prairie Softwood and C-Pine, all available from Weyerhaeuser are suitable. These pulps provide the benefit of lower cost and better bonding for nonwoven textile applications because of their high hemicellulose content. Selected pulp properties are given in Table 1. Table 1: Pulp Properties
• the degraded shorter molecular weight components in the pulp are measured by the Rig and Rio content as described in TAPPI 235.
• Rio represents the residual undissolved material that is left extraction of the pulp with 10 percent by weight caustic
• R ⁇ represents the residual amount of undissolved material left after extraction of the pulp with an 18% caustic solution.
• hemicellulose and chemically degraded short chain cellulose are dissolved and removed in solution.
• generally only hemicellulose is dissolved and removed in an 18% caustic solution.
• the difference between the R io value and the R 18 value, ( ⁇ R R
• g - Rio), represents the amount of chemically degraded short chained cellulose that is present in the pulp sample, hi one embodiment the pulp has a ⁇ R from about 2 to a ⁇ R of about 10. In another embodiment the ⁇ R is from about 4 to a ⁇ R of about 6.
• hemicellulose refers to a heterogeneous group of low molecular weight carbohydrate polymers that are associated with cellulose in wood. Hemicelluloses are amorphous, branched polymers, in contrast to cellulose which is a linear polymer.
• the principal, simple sugars that combine to form hemicelluloses are: D-glucose, D-xylose, D-mannose, L-arabinose, D-galactose, D-glucuronic acid and D-galacturonic acid.
• Hemicellulose was measured in the pulp and in the fiber by the method described below for sugar analysis and represents the sum of the xylan and mannan content of the pulp or fiber.
• Lyocell fibers prepared with the antimicrobial agents can be spun, from cellulose dissolved in NMMO by various processes.
• the fibers are spun by the meltblown process.
• meltblown it will be understood that it refers to a process that is similar or analogous to the process used for the production of thermoplastic fibers, even though the cellulose is in solution and the spinning temperature is only moderately elevated.
• the fibers are spun by the centrifugal spinning process, in another embodiment the fibers are spun by the dry-jet-wet process and in yet another the fibers are spun by the spun bonding process. Fibers formed by the meltblown process can be continuous or discontinuous depending on air velocity, air pressure, air temperature, viscosity of the solution, D.P.
• spunbonded fibers are longer than meltblown fibers which usually come in discrete shorter lengths.
• centrifugal spinning differs in that the polymer is expelled from apertures in the sidewalls of a rapidly spinning drum. The fibers are stretched somewhat by air resistance as the drum rotates. However, there is not usually a strong air stream present as in meltblowing.
• the other technique is dry jet/wet. In this process the filaments exiting the spinneret orifices pass through an air gap before being submerged and coagulated in a liquid bath. All four processes may be used to make nonwoven fabrics.
• the fibers are made from a pulp with greater than 3% percent by weight hemicellulose. In another embodiment the fibers are made from a pulp with greater than 8 % by weight hemicellulose. In yet another embodiment the fibers are made from a pulp with greater than 12% by weight hemicellulose.
• the fibers contain from about 4 to 18 % by weight hemicellulose. In another embodiment the fibers contains from 7 to 14 % by weight hemicellulose and in yet another embodiment the fibers contain from 9 % to 12 percent by weight hemicellulose.
• the D.P. of the fibers is from about 200 to about 2000. In another embodiment the D.P is from about 350 to about 900 and in yet another embodiment the D. P. is from about 400 to about 800.
• degree of polymerization refers to the number of anhydro-D-glucose units in the cellulose chain. D. P. was determined by ASTM Test 1795-96.
• Antimicrobial fibers may be used in a wide variety of fibrous products, among them textiles and garments (including athletic wear, incontinence and medical garments, etc.), air and water filters, wound and burn care dressings, medical wipes and gowns, shoe components, and institutional and home furnishings including bed sheets, pillow cases, mattress pads, blankets, towels, drapes, bedspreads, pillow shams, carpets, walk-off mats, napkins, linens, wall coverings, upholstered furniture, liners, mattress ticking, mattress filling, pillow filling, carpet pads, upholstery fabric and the like.
• textiles and garments including athletic wear, incontinence and medical garments, etc.
• air and water filters including wound and burn care dressings, medical wipes and gowns, shoe components, and institutional and home furnishings including bed sheets, pillow cases, mattress pads, blankets, towels, drapes, bedspreads, pillow shams, carpets, walk-off mats, napkins, linens, wall coverings, upholstered furniture, liners, mattress ticking
• Antimicrobial agents can be inorganic or organic compounds.
• Inorganic compounds include but are not limited to compounds that contain tin, copper, silver and zinc and may be in the form of the oxide or carried in such compounds as zirconium phosphate, a zeolite or similar carriers.
• Other inorganic compounds containing metals such as potassium, magnesium and calcium can also be used as antimicrobial agents.
• Inorganic antimicrobial agents include silver zeolite complexes sold by Milliken Chemical as ALPHASAN, and AGION by Agion Technologies.
• zeolite of the formula Ag 84 Na 2 (AlO 2 ) 8 e (SiO 2 ) ]06 x H 2 O was obtained from Aldrich as a silver exchanged zeolite in granular form and was ground to pass through a screen of ⁇ 20 micron.
• Zinc oxide, grade AZO 66USP was obtained from US Zinc; >99.9 percent of the particles passed through a 325 mesh screen.
• Calcium carbonate was obtained from Aldrich (CAS 471-34-1) and had a particle size of less than 10 microns.
• the inorganic antimicrobial agent is added at a level of from about 1 percent by weight on pulp to about 40 percent by weight on cellulose. In another embodiment the additive is added at a level of from 10 percent by weight on cellulose to about 25 percent by weight on cellulose. In yet another embodiment it is added at a level of from about 15 percent by weight on pulp to about 20 percent by weight on cellulose.
• the inorganic antimicrobial agent is at a level of from about 1 percent by weight to about 40 percent by weight in the fiber.
• the additive is at a level of from 10 percent by weight to about 25 percent by weight in the fiber. In yet another embodiment it is at a level of from about 15 percent by weight to about 20 percent by weight in the fiber.
• Organic compounds useful as antimicrobial agents include but are not limited to Triclosan, quaternary ammonium compounds, diammonium ring compounds, chitosans, N-halamine siloxanes and chlorine. Organic compounds depend on the antimicrobial agent to leach or migrate from inside the fiber to the surface.
• the additive is added at a level of from about 0.01 to about 5 percent by weight of a 5 % by weight solution of the organic silver complex compound on cellulose. In another embodiment the additive is added at a level of from about 0.5 to about 3 % by weight solution of the organic silver complex compound on cellulose. In one embodiment the fibers contain from about 5 to about 1000 ppm silver. Lyocell fibers with silver compounds have lower brightness than a control sample but combining silver based antimicrobial agents with zinc oxide or calcium carbonate improves fiber brightness (sample 11, Table 4, v sample 10 Table 2 and sample H v sample 17 Table 4, respectively).
• Meltblown lyocell fibers containing inorganic zinc compounds reduced E.coli colony forming units at twenty four hours by at least 98 percent compared to a control at the same time.
• C. albicans count was reduced at least ninety five percent at four and twenty four hours compared to a control at the same times.
• Both the inorganic additive calcium carbonate and the organic additive SILVIO containing an organic silver complex reduced the four and twenty four hour colony forming units of E. colt by more than ninety five percent compared to a control at the same times.
• Zinc oxide reduced the four hour colony forming units of C. albicans by at least ninety five percent and the twenty four hour colony forming units of both E. coli and C. albicans by at least ninety five percent.
• FIG. 1 is a scanning electron photomicrograph (SEM) of a control sample showing a longitudinal section and cross section of the fibers at 1000 X. The fibers are relatively smooth with oblong to circular cross sections.
• Figure 2 is a SEM at 2000 X of the cross section of Sample 6 showing uniformly distributed zinc oxide particles in the fiber and a grainy or granular surface.
• Figure 3 is a backscattering electron photomicrograph (BSE) at 2000 X of the cross section of fibers of Sample 7 showing the uniform distribution of zinc in the fibers.
• Figure 4 is a SEM at 1000 X of the longitudinal section meltblown fibers containing about 0.1 percent by weight of SILVIO.
• Fibers containing this additive have a relatively smooth surface.
• Figure 5 is a SEM at ] 000 X of the meltblown lyocell fibers of Sample 15 containing 22.39 percent by weight calcium carbonate in the fiber. The fibers are characterized by a rough and granular surface.
• Figure 6 shows a BSE at 1000 X of the cross section of Sample 13 containing 1.9 percent by weight zeolite in the fiber and the distribution of zinc in the fiber and on the fiber surface.
• a wide range of fiber properties can be obtained by the meltblowing process.
• the fibers have a fiber diameter of from about 5 ⁇ to about 50 ⁇ . In another embodiment the fibers have a fiber diameter of from about lO ⁇ to about 30 ⁇ and in yet another embodiment the fibers have a fiber diameter of from about 15 to about 20 ⁇ . Fiber diameter measurements represent the average diameter of 100 randomly selected fibers and measurement with a light microscope.
• Birefringence of the antimicrobial fibers indicates a high degree of molecular orientation of the cellulose fibers which is virtually unchanged from the control. Control values ranged from 0.026 to 0.034 and samples with zinc oxide were unchanged at 0.026. This suggests that in spite of the zinc oxide additive, the molecular orientation is not adversely affected.
• the birefringence is at least 0.02. In another embodiment the birefringence is at least 0.025. Birefringence was determined by the method described below.
• a typical birefringence value for lyocell is 0.045, for viscose staple, 0.022, Modal, 0.038, for cotton, 0.047, for ramie, 0.074 and NB416, a commercially available market pulp available from Weyerhaeuser, 0.026.
• Fiber brightness was determined by TAPPI T452.
• Peach® a bleached kraft southern pine pulp, available from Weyerhaeuser, Federal Way, WA, was acid hydrolyzed and treated with sodium borohydride to yield a pulp having an average degree of polymerization of about 420, a hemicellulose content of 12.0 % by weight hemicellulose in pulp (6,5 % and 5.5% by weight xylan and mannan, respectively) and an Ri 0 and Ri 8, of about 77 and 87, respectively.
• the pulp was dissolved in NMMO (N-methyl morpholine N- oxide) as follows.
• a 250 mL three necked flask was charged with, for example, 66.4 g of 97 % NMMO, 24.7 g of 50 % NMMO, 10.4 g pulp, 0.1 g of propyl gallate, and 1.2 g of zinc oxide.
• the flask was immersed in an oil bath at 120° C, a stirrer inserted and stirring continued for about 1 hr.
• a readily fiowable dope resulted that was suitable for spinning.
• the cellulose concentration in the dope was about 12% by weight.
• the dope was extruded from a melt blowing die that had 3 nozzles having an orifice diameter of 457 microns at a rate of 1.0 gram / hole / minute.
• the orifices had a length/diameter ratio of 5.
• the nozzle was maintained at a temperature of 95° C.
• the dope was extruded into an air gap 30 cm long before coagulation in water and collected on a screen as either continuous or discontinuous filaments depending on dope rehology and meltblown conditions.
• Air at a temperature of 95° C and a pressure of about 10 psi, was supplied to the head. Air pressures of from 8 to 30 psi were used to achieve varying fibers diameters shown in Table 2 and Table 4.
• fibers can be characterized as having an index of refraction parallel (axial) to the fiber axis and an index of refraction which is perpendicular to the fiber axis.
• the birefringence for purposes of this method is the difference between these two refractive indices. The convention is to subtract the perpendicular R.I. (refractive index) from the axial R.I.
• the axial R.I. is typically represented by the Greek letter ⁇ , and the perpendicular index by the letter ⁇ .
• Oils are manufactured with known refractive index at a given wavelength of exciting light and at a given temperature.
• the fibers were compared to Cargile refractive index oils.
• Polarized light
• the refractive index is measured using a polarizing filter.
• the exciting light is polarized in a direction parallel to the axis of the fiber the axial refractive index can be measured.
• the polarizing filter can be rotated 90 degrees and the refractive index measured perpendicular to the fiber axis. Measurement using the light microscope
• the image of the fiber When the refractive index of the fiber matches the refractive index of the oil in which it is mounted, the image of the fiber will disappear. Conversely, when the fiber is mounted in an oil which greatly differs in refractive index, the image of the fiber is viewed with high contrast.
• the fiber When the R.I. of the fiber is close to the R.I. of the oil, a technique is used to determine whether the fiber is higher or lower in refractive index. First the fiber, illuminated with the appropriately positioned polarizing filter, is brought into sharp focus in the microscope using the stage control. Then the stage is raised upward slightly. If the image of the fiber appears brighter as the stage is raised, the fiber is higher in refractive index man the oil. Conversely if the fiber appears darker as the stage is raised, the fiber is lower in refractive index than the oil. Fibers are mounted in RJ. oils and examined until a satisfactory match in refractive index is obtained. Both the axial and the perpendicular component are determined and the birefringence is calculated.
• Polymers of pulp sugars are converted to monomers by hydrolysis using sulfuric acid.
• Samples are ground, weighed, hydrolyzed, diluted to 200-mL final volume, filtered, diluted again ( 1.0 mL + 8.0 mL H 2 O) in preparation for analysis by HPAEC/PAD.
• Gyrotory Water-Bath Shaker Model G76 or some equivalent.
• Dionex metal-free gradient pump with four solvent inlets Dionex ED 40 pulsed amperometric detector with gold working electrode and solid state reference electrode
• CarboPac PAl (Dionex P/N 035391) ion-exchange column, 4 mm x 250 mm CarboPac PAl guard column (Dionex P/N 043096), 4 mm x 50 mm
• H 2 O Miliipore H 2 O 72% Sulfuric Acid Solution (H2SO4) - Transfer 183 mL of water into a 2-L
• Fucose is used for the kraft and dissolving pulp Samples.
• 2-Deoxy-D -glucose is used for the wood pulp Samples.
• Fucose internal standard. 12.00 ⁇ 0.005 g of Fucose, Sigma Cat. No. F 2252, [2438-80-4], is dissolved in 200.0 mL H 2 O giving a concentration of 60.00 ⁇ 0.005 mg/mL. This standard is stored in the refrigerator. 2-Deoxy-D-glucose, internal standard. 12.00 ⁇ 0.005 g of 2-Deoxy-D-glucose,
• Fluka Cat. No. 32948 g [101-77-9] is dissolved in 200.0 mL H 2 O giving a concentration of 60.00 ⁇ 0.005 mg/niL. This standard is stored in the refrigerator.
• Wood Pulp Working Solution Use the Kraft Pulp Stock solution and the fucose and rhamnose stock solutions. Make working standards as in the following table. PULP SUGAR STANDARD CONCENTRATIONS FOR KRAFT PULPS
• Shaker Off Place the test tube rack in gyrotory water-bath shaker. Stir each Sample 3 times, once between 20-40 min, again between 40-60 min, and again between 60-80 min. Remove the Sample after 90 min. Dispense 1.00 mL of internal standard (Fucose) into Kraft Samples.
• Solvent A is distilled and deionized water (18 meg-ohm), sparged with helium while stirring for a minimum of 20 minutes, before installing under a blanket of helium, which is to be maintained regardless of whether the system is on or off.
• Solvent B is 400 mM NaOH. Fill Solvent B bottle to mark with water and sparge with helium while stirring for 20 minutes. Add appropriate amount of 50% NaOH.
• Solvent D is 200 mM sodium acetate. Using 18 meg-ohm water, add approximately 450 mL deionized water to the Dionex sodium acetate container. Replace the top and shake until the contents are completely dissolved. Transfer the sodium acetate solution to a 1 -L volumetric flask. Rinse the 500-mL sodium acetate container with approximately 100 mL water, transferring the rinse water into the volumetric flask. Repeat rinse twice. After the rinse, fill the contents of the volumetric flask to the 1 -L mark with water. Thoroughly mix the eluent solution. Measure 360 ⁇ 10 mL into a 2-L graduated cylinder. Bring to 1800 ⁇ 10 mL.
• Injection volume is 5 uL for all Samples, injection type is "Full”, cut volume is 10 uL, syringe speed is 3, all Samples and standards are of Sample Type "Sample”. Weight and Int. Std. values are all set equal to 1.
• Xylose and arabinose amounts are corrected by 88% and fucose, galactose, rhamnose, glucose, and mannose are corrected by 90%. Report results as percent sugars on an oven-dried basis.
• Phosphate Buffer Solution a. Stock PBS (1 liter):
• MGM 2- Minimum Growth Media
• E. colt Prep Culti-Loop in 1.0 ml sterile TSB for 10 min.
• ATCC 8739 Streak to TSA slant and grow for 24 hours @ 35C.
• C. albicans Prep Culti-Loop in 1.0 ml of sterile dilute PBS ATCC 10231 Solution for 10 min. Streak onto SDA and grow for 24 hours @ 35C.
• Dilute culture a. Prepare 9.0 ml dilute PBS tubes. Remove (wash) each culture organism from slants and add to PBS tubes. Adjust so the turbidity of the culture matches a 0.5 McFarland solution (In BAM
• BME vitamins 20 ml 10% Peptone. 10 ml 10% (NH 4 ) 2 SO 4
• USE TSA for S. aureus and E. coli.
• USE SDA for C. albicans.

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