Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06L—DRY-CLEANING, WASHING OR BLEACHING FIBRES, FILAMENTS, THREADS, YARNS, FABRICS, FEATHERS OR MADE-UP FIBROUS GOODS; BLEACHING LEATHER OR FURS
  • D06L4/00—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs
  • D06L4/20—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen
  • D06L4/22—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents
  • D06L4/23—Bleaching fibres, filaments, threads, yarns, fabrics, feathers or made-up fibrous goods; Bleaching leather or furs using agents which contain halogen using inorganic agents using hypohalogenites
• • 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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S260/00—Chemistry of carbon compounds
  • Y10S260/28—Peroxide
• • 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
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S8/00—Bleaching and dyeing; fluid treatment and chemical modification of textiles and fibers
  • Y10S8/06—Resin bleach

Definitions

• This invention relates to the removal of. color from shaped articles comprising a polymer of acrylonitrile and is particularly concerned with the bleaching of yarn composed of acrylonitrile polymer.
• Polymers of acrylonitrile such as acrylonitrile polymers in which the polymers are composed entirely of acrylonitrile, and interpolymers and copolymers of acrylonitrile with other materials such as vinyl chloride, vinyl acetate, acrylic acid, its esters and homologues, styrene, butadiene, isobutylene and other polymerizable substances, especially those containing olefinic and diolefinic linkages, although potentially of great value on account of their highly desirable properties, are insoluble in ordinary organic solvents when the polymers contain at least 85% by weight of acrylonitrile (vinyl cyanide) in the polymer molecule.
• acrylonitrile vinyl cyanide
• Dolyacrylonitrile yarn is the so-called dry" or evaporative spinning process which comprises extruding a solution of polyacrylonitrile through a nozzle into air or other gas inert to the polymer, maintained at such a temperature and under such other conditions as will cause the complete vaporization of the solvent contained in the polvymer solution.
• the yarn may be subjected, if desired, to a stretching operation in order to increase tenacity as well as otherwise to improve physical properties by orienting the micelles of which the yarn is composed.
• the stretching may be efiected by subjecting the yarn at an elevated temperature of the order of 100 and above, to a tension adequate to effect the desired degree of stretching, this stretching procedure being described and claimed in the copending application of Daniel T. Meloon Serial No. 496,397, filed July 28, 1943.
• Yarn produced by the dry and wet spinning processes described above has excellent physical properties, but does not possess that degree of freedom from color which is required by the exacting standards of the textile industry. Moreover, the customary methods utilized inthe textile art for the bleaching of color from filaments, fibers and the like do not effect the desired elimination of color from polyacrylonitrile yarn.
• the yellowish or golden-brown color present in polyacrylonitrile articles occurs either during polymerization or processing of the polymer prior to or during shaping of the polymer to the desired form and may be caused by prolonged treatment of the polymer at high temperature, e. g. 100 C. and above.
• the invention will be described most particularly with reference to yarn composed of continuous filaments, but it will be understood that this is merely by way of illustration since the invention may also be applied to staple fibers, thin transparent films such as may be used as Wrapping tissue, monofils, artificial straw, hollow pellicles such as tubing and other industrial products composed of acrylonitrile polymer.
• the objects of the invention are accomplished in general by spinning polyacrylonitrile yarn by a dry or by a wet spinning process, preferably collecting the dry yarn on a bobbin or other suitable collecting device and soaking the dry yarn for a short period of time in an aqueous solution of hypochlorous acid at a temperature of at least 90 C., the solution when temperatures above the boiling point at atmospheric pressure are used, i. e. temperatures of 100 C. or above, being maintained in the liquid state by the use of superat- 55 mospheric pressure, e. g. in an autoclave.
• jectionable coloring present in the yarn is removed by the bleaching treatment with no substantial impairment of the desired physical properties of the yarn.
• centages and proportions are by weight unless otherwise specified and which are intended to be illustrative instead of limitative, set forth preferred forms of the invention.
• Example A Yarn to be treated in accordance with the present invention may be prepared as follows:
• the walls of the cell are maintained at a temperature of approximately 400 C.
• the fresh air enters the lower portion of the chamber at a temperature of about 100 C. while the waste air leaving the upper portion of the cell is at a temperature of about 200 C.
• the cell has a length of 8 feet, sufiicient for the evaporation of the dimethyl formamide from the extruded solution.
• the solidified, multifilament polyacrylonitrile yarn issuing from the bottom of the cell is collected on a rotating bobbin at a speed of 100 yards per minute.
• the yarn which has a denier of 248, is soft and pliable and has a dry tenacity of 0.62 gram per denier and a wet tenacity of 0.53 gram per denier. Its elementary analysis corresponds to that of the polymer of acrylonitrile originally dissolved in the dimethyl formamide.
• the collected yarn is then unwound from the collecting bobbin, passed without slippage about a positively driven roller, heated to a temperature of 140 C. and wound upon a rotating bobbin, the peripheral speed of which is eight times that of the heated roller.
• the resulting yarn which has been permanently stretched by this treatment has a dry tenacity of 3.4 grams per denier.
• Example I A solution of sodium hypochlorite containing 025% available chlorine was acidified with sulfuric acid to a pH of 2.1. Three hundred (300) cc. of this solution were placed in an autoclave and a skein containing 45 yards of polyacrylonitrile yarn prepared by. a dry spinning process such as that described in Example A was immersed in the bath. The autoclave was closed and steam was introduced, the autoclave being bled to remove air. The steam pressure. was allowed ultimately to build up to 25 pounds, at which pressure it was maintained for one half hour (at a temperature of approximately 130 C.) At the end of that time, the autoclave was bled off, the skein was removed, washed with cold distilled water and dried.
• gel polyacrylonitrile yarn which was wet spun by extrusion of the solution through a nozzle into a coagulating liquid was collected, subjected to the same bleaching treatment, but with only 0.125% available chlorine present and after being dried, showed a decrease in dry te- 4 nacity of about 28%, compared with the dried, wet-spun yarn which had not been subjected to the bleaching treatment, and showed a color rating of 3.
• Example II A 50-yard skein of polyacrylonitrile yarn prepared by a dry-spinning process such as that described in Example ,A was placed in 300 ml. of a. bleaching solution made from sodium hypochlorlte (0.25% available chlorine) and acidified with sulfuric acid to a pH of 2.0. The solution contained in a 400 ml. beaker covered with a watch glass was placed in a steam bath and was heated to 97 C. Bleaching action first became pronounced when the temperature rose to about C. After about a thirty minute treatment, no further bleaching took place. The yarn was then washed and dried as in Example I. The degree of freedom from color was at least as good as in Example I.
• a bleaching solution made from sodium hypochlorlte (0.25% available chlorine) and acidified with sulfuric acid to a pH of 2.0.
• the bleached yarn had a dry tenacity of 4.24 grams per denier and a. dry elongation of 14.8% as compared with a. dry tenacity of 4.21 grams per denier and a dry elongation of 14.5% for the same yarn before the bleaching treatment, this comparison showing that the bleaching treatment did not impair the physical properties of the yarn.
• Example III Dried polyacrylonitrile yarn obtained by a wetspinning process, exhibiting a dry tenacity of 4.49 grams per denier and a dry elongation of 16.9% and having a color rating of 10 was treated in a covered beaker at 97 C. and at atmospheric pressure as was the yarn of Example II with the same bleaching solution of Example II having 0.25% available chlorine and a pH of 2.0, followed by washing with cold distilled water and drying, the periods of bleaching being respectively five minutes and thirty minutes. Two other experiments were run under the same conditions except that the bleachin solution contained 0.125% available chlorine with a pH of about 2.0 for respective periods of five and thirty minutes. The results of these experiments are tabulated as follows:
• the acrylonitrile polymer for use with this inuseful effect, in the customary concentrations and vention is preferably prepared by the ammonium at temperatures below those used in the practice persulfate catalyzed polymerization of monoof the present invention, as far as acrylonitrile meric acrylonitrile dissolved or emulsified in wapolymer yarn is concerned. Alternatively, the ter.
• the molecular weight of the polymer obtained is 3: prysmal characteristics as the unbleached s c u es.
• aqueous, hypocmomus acid solutions used ment with an aqueous solution containing hypoin accordance with the present invention will morons acid corresponding to o'o5% to 19% by contain 095% to 19% available chlorine and weight of said solution of available chlorine and preferably 0.1% to 0.5%,with the most preferred at temperature 90' to 150 and for a concentration being in the neighborhood of period not exceeding thirty minutes 025% hypochlorous acid solution may readily be In the
• the temperature for the bleaching treatment ROBERT ALBERT ERBA should be within the range to 150 C., and REFERENCES mm preferably 90' to C., with the pressure being sumciently high to maintain the treating solution 60
• the following references are of record in the liquid.
• the time of treatment will be short and file of this Patent! preferably thirty minutes or less, but will depend on the temperature and the available chlo- UmED STATES PATENTS rine concentration. It is preferred that the ves- Number Name Date 8 in which the bleaching treatment i carri d 65 2,021,763 Bauer Nov. 19, 1935 on be covered; for example, as in the case of an 2,226,353 McCarthy Dec. 24.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Artificial Filaments (AREA)

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Cited By (12)

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Citations (7)

• 0
  • BE BE465916D patent/BE465916A/xx unknown
• 1945
  • 1945-01-10 US US572260A patent/US2432447A/en not_active Expired - Lifetime
• 1946
  • 1946-02-18 GB GB5000/46A patent/GB605771A/en not_active Expired
  • 1946-05-22 FR FR927216D patent/FR927216A/fr not_active Expired

Patent Citations (7)

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