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
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/18—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polymers of unsaturated nitriles, e.g. polyacrylonitrile, polyvinylidene cyanide

Definitions

• This invention relates to the production of artificial filaments and is particularly concerned with the production of polyacrylonitrile threads by wet spinning.
• polyacrylonitrile as used in this specification includes simple polymers of acrylonitrile and copolymers of a major proportion of acrylonitrile with a minor proportion of other polymerisable compounds such as styrene, methyl acrylate and vinyl acetate.
• the object of the present invention is to provide an improved coagulant bath for polyacrylonitrile solutions suitable for use at ordinary temperatures.
• a process for the production of polyacrylonitrile threads includes the step of extruding a solution of polyacrylonitrile in .a water-miscible organic solvent into an aqueous coagulating bath containing potassium acetate in a concentration of from 20 per cent by weight up to saturation point.
• the coagulating bath is preferably used at ordinary temperatures that is from about to 25 centigrade but raised temperatures up to about 50 centrigrade may be used.
• the polyacrylonitrile is preferably dissolved in dimethyl formamide but any other water-miscible solvent may be used.
• concentration of the polymer in the solution is not critical and solutions containing from 15 per cent to per cent by weight of polyacrylonitrile have been spun satisfactorily into aqueous 55 per cent potassium acetate solutions.
• the tensile properties of the threads obtained by the process of the present invention can be increased by subjecting the freshly formed threads either to a hot stretching process or to a cold stretching operation followed by a hot stretching process, for example in heated glycerol at 100 to 140 centigrade.
• the cold stretching step may be efiected in air at 15 to 40 centigrade by passing the thread over a series of rollers or godets which are designed to give the desired degree of stretch.
• the degree of cold stretch may vary between 20 per cent and 40 per cent.
• the hot stretching may also be efiected in known manner using rollers or godets. Such hot stretching is preferably at least 400 per cent and may be as high as 1000 per cent or more.
• the process of the present invention is also particularly useful for the production of polyacrylonitrile staple fibres;
• the use of aqueous potassium acetate solutions as the coagulating bath permits the use of jets having a large number of holes; for example jets having 500, 1000, 2500 and 3750 holes may be used.
• the filaments issuing from such jets can be collected into a tow of substantially parallel filaments, processed in tow form, cut and dried.
• tows By applying a high degree of stretch as described above, for example using a combination of cold and hot stretching, high strength staple fibres of deniers as low as 1.5 can readily be produced.
• the stretching of tows is preferably effected by using a series of take-up devices each consisting of two take-up reels with their axes inclined.
• the reels preferably have a discontinuous surface made up of a number of interdigitating bars mounted on reel members as in normal reel construction, but instead of the axes of the reel members being offset and askew, they are concentric.
• Example 1 A polyacrylonitrile prepared by p-olymerising acrylonitrile in aqueous solution with ammonium persulphate as catalyst and having an intrinsic viscosity of 1.42, was dissolved in dimethyl form- The skein was washed withwater till it was free from potassium acetateaandz: glycerol and then dried, free from tension, in an air. current at 65 centigrade.
• the thread obtained was pale cream in colour The thread was then.
• Example 2 The procedure described in Example 1 was repeatedwith the following variations only:
• the spinning solution was a per cent solution in dimethyl formamide ofa polyacrylonitrile having an intrinsic viscosity of 1.10.
• Example 3 Q A polyacrylonitrile. prepared by polymerising acrylonitrile in aqueous solution with ammonium persulphate as catalystand having an intrinsic viscosity of 1.08 was dissolved in dimethyl formamideto form a 17 per cent solution. The solution, after filtration and de-aeration,. was ex-' tru'ded. through a multi hole jet into acoagulating bath at 23 centigrade consisting, of a neutral concentrated aqueous potassium acetate solu' tion, specific gravity 1.32 at 25 centigrade: The length of immersion was 20 inches and the thread was then passed on to a seriesof'thread advancing'rollers designed to stretch the thread 33 percent in air at 23 centigrade.
• the thread was then stretched a further 1079 per cent while passing through a bath of glycerol at about 135 centigrade and the stretched thread was collected on a skein reel at a'rate of 83 metres per minute.
• the skein was washed with water till it was free from potassium acetate and glycerol and then dried, free from tension, in an air current at 60 Centigrade.
• Example 4 A polyacrylonitrile prepared by polymerising acrylonitrile in aqueous solution with ammonium persulphate as catalyst and having an intrinsic viscosity of 1.10 to 1.15, was dissolved in dimethyl formamide to form a 16 per cent solution.
• the solution after filtration and cle-aeration, was extruded through a jet having 500', 2.5 mil holes into a coagulating bath at 23 Centigrade consisting of a neutral concentrated aqueous potassium acetate: solution, specific gravity 1.32 at 25 Centigrade.
• the length of immersion was 21 inches and the filaments were collected into tow formand passed on to a pair of rotating threadadvancing rollers having a peripheral speed of 5.04 metres per.
• the tow was then stretched a further 1105 per cent (giving 1520 per cent total-stretch) while passing through a bath of glycerol at to centigrade and the stretched tow was passed to a pair of inclined reels arranged-to form a tow collecting and advancing device.
• the tow was then passed to a cutter where the filaments were cutinto 1% inches stap'lelength andthe cut fibres were washed with water till free from potassium acetate and glycerol and then dried.
• Example 5 A 16 per cent solution of polyacrylonitrile in dimethyl formamide as used in Example 1, after filtration and de-aeration, was extruded through a jet having 2500.holes,.each 2 mils indiameter, into an aqueous 58 per cent potassium acetate solution at 25 Centigrade.
• the filament immersion was 20 inches and the tow of filaments'was passed on' withdrawal from the bath to a pair of rotating thread-advancing rollers having a peripheral speed of 5.7 metres per minute and then to a second pair of rollers having' a peripheral speed of 7.7 metres per minute giving a 35 per cent air stretch.
• the tow was then stretched in glycerol at centigrade to a speed of 56.0 metres per minute, giving a total stretch of 880 per cent.
• the tow was then cut to staple length, washed-and dried as described in Example 4.
• the tow was then further stretched in glycerol at 135 centigrade to a speed of 69 metres per minute giving a total stretch of 5'76 per cent.
• the filaments were collected on a skein reel, washed with water till free from glycerol and potassium acetate and then dried.
• Example 7 Example 6 was repeated with the following variations only:
• the coagulating bath was a 40 per cent aqueous potassium acetate solution and (b) The final speed was 73.5 metres per minute giving a total stretch of 600 per cent.
• Example 8 Denier 1.40. Tenacity 4.11 grams per denier. Extensibility 29.9 per cent.
• a process for the production of polyacrylonitrile threads which includes the step of extruding a solution of polyacrylonitrile in dimethyl Number formamide into an aqueous coagulating bath containing potassium acetate in a concentration of from 20 per cent by weight up to saturation point.
• a process for the production of polyacrylonitrile threads which includes the step of extruding a solution of polyacrylonitrile in dimethyl formamide into an aqueous coagulating bath, said bath being at a temperature of from about 15 centigrade to about 25 centigrate and containing potassium acetate in a concentration of from 20 per cent by weight up to saturation point.
• a process for the production of polyacrylonitrile threads which includes the step of extruding a solution of polyacrylonitrile in dimethyl formamide into an aqueous coagulating bath containing potassium acetate in a concentration of from about to per cent by weight.
• a process for the production of polyacrylonitrile staple fibres comprising the steps of extruding a solution of polyacrylonitrile in dimethyl formamide through a jet having at least 500 holes into an aqueous coagulating bath containing p0- tassium acetate in a concentration of from 20 per cent by weight up to saturation point, collecting the filaments issuing from the jet into a tow of substantially parallel filaments, processing the tow, cutting the tow into staple lengths and drying the cut fibres.

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• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Artificial Filaments (AREA)

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Citations (3)

• 0
  • NL NL80598D patent/NL80598C/xx active
  • BE BE513124D patent/BE513124A/xx unknown
  • NL NLAANVRAGE7116966,A patent/NL171218B/xx unknown
• 1951
  • 1951-07-25 GB GB17596/51A patent/GB706263A/en not_active Expired
• 1952
  • 1952-06-04 US US291804A patent/US2645556A/en not_active Expired - Lifetime
  • 1952-07-24 FR FR1060598D patent/FR1060598A/fr not_active Expired
  • 1952-07-25 DE DEC6157A patent/DE915492C/de not_active Expired

Patent Citations (3)

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