US2681265A - Spinning artificial filaments - Google Patents

Description

Patented June 15, 1954 2,681,265 SPINNING ARTIFICIAL FILAMENTS Howard M. Hoxie, Cheste ican Viscose Corporation, corporation of Delaware r, Pa., assignor to Amer- Wilmington, DeL, a

N Drawing. Application November 27, 1948, Serial No. 62,413

8 Claims.

This invention relates to the production of synthetic filaments or yarns comprising acrylonitrile polymers.

The patent literature contains statements to the effect that acrylonitrile polymers containing at least 85% by weight acrylonitrile in the polymer molecule can be formed into synthetic filaments or yarns by extruding a dimethyl formamide solution of the polymer into water at a temperature of 70 C., and stretching the filaments or yarns thus obtained to 6.3 times their original length.

In actual practice, it has been found to be impossible to obtain useful filaments or yarns by spinning the dimethyl formamide solutions into a bath consisting of water, regardless of variations in such factors as immersion length, bath temperature, spinning speed, jet design, or filament size. The filaments obtained by spinning the solutions into a bath consisting of water are extremely weak, fragile, and brittle, and are practicaly inextensible. Such filaments or yarns pletely coagulated, lated areas occuring, generally, at the surfaceof the filament, which thus comprises a layer of coagulated polymer surrounding a plastic core. Evidently, this condition of the filaments obtained by spinning the dimethyl formamide solutions into a bath consisting of water is due to difierences between the rate of difiusion (or extraction) of the dimethyl formamide from the interior of the fiber outwardly, and the rate of diffusion of the coagulating liquid inwardly, whereby diffusion of the spinning solvent out of the fiber is prevented or hampered by the coagulated layer formed initially at the surface of the filament. Whatever may be the explanation of the diificulty, it is a fact that when the solutions water, the filaments withdrawn from the bath are not capable of accepting sufficient stretch to efiect appreciable molecular it has been necessary to employ organic solvents such as isopropanol, glycerol, or aqueous salt solutions, such as aqueous solutions of calcium chloride, as the coagulating liquid. All such liquids entail troublesome problems of coagulating bath regeneration and solvent recovery.

It is, therefore, an object of this invention to provide a new method of producing filaments and yarns from solutions of the acrylonitrile polymers in dimethyl formamide by a wet spinning procedure, whereby homogeneous filaments given a stretch of from 200 to 300%. merits withdrawn from the bath are coagulated so that they possess sufiicient plasticity to permit extension thereof under stretching, without rupture. It is known that stretching of the acrylonitrile polymer filaments efiects an improvement in the physical properties such as tenacity and resilience. While it has been stated in the patent literature that acrylonitrile polymer yarns produced by wet spinning a dimethyl iormamide solution of the polymer can be stretched at any the usual after the filaments have been withdrawn from the coaguwashing to remove the remaining solvent. The filaments produced by the present method are generally stretched by 200 to 300% after they are withdrawn from the dimethyl formamide-water spinning bath prior to washing thereof. This stretching can be accomplished at room temperature by passing the in dimethyl formamide and spun into a coagulating bath consisting of a water-dimethyl formamide mixture containing from 35 to volume per cent of dimethyl formamide in accordance Alternately, while the I introduced as dope 3 the group C'=C such as for example, 2-vinyl pyridine, vinyl acetate, vinyl chloride, acrylic acid and its esters, styrene, isobutene, and butadiene, as well as other vinyl and acrylic com-- pounds, and other olefin or diolefin hydrocarbons. The coagulating baths of the present invention are particularly useful in the spinning of dimethyl formamide solutions of acrylonitrile polymers containing at least 65% by weight acrylonitrile in the polymer molecule and having a molecular weight of 15,000 to 250,000 as determined by specific viscosity data using the standinger equation, since those polymers are suitable for the production of filaments and yarns which may be used for general textile purposes.

The advantages of the method of this invention are numerous and important. Spinning can be performed at room temperature, thus eliminating the need for means for heating the bath. Once the spinning operation has been initiated the only expedient required in order to maintain the composition of the spinning bath constant is the periodical or continuous addition of the calculated amounts of plain water, so that expensive bath recirculating and regenerating systems are entirely avoided. In addition, the solvent recovery procedure is simple since in order to recover the solvent, it is only necessary to distill ofi the water, which can be accomplished rapidly and at comparatively little exing bath consisting of 30% The acrylonitrile polymers which are formed into filaments or yarns in accordance with the invention may be produced by any suitable polymerization procedure, e. g., by emulsion, suspension, bulk, or solution polymerization procedures.

The following examples are illustrative of preferred methods of practicing the invention, although the invention is not to be limited by the details set forth therein.

Example I 13% dimethyl formamide solution of a copolymer which was prepared by the solution copoiymerization of acrylonitrile and 2-viny1 pyridine and which contained 15% of 2-vinyl pyridine by weight in the polymer molecule was extruded through a spinneret having 44 holes each having a diameter of 4 mils into a coagulatwater and 70% dimethyl formamide, by volume, at 23 C. After a bath travel of 9.5 inches, at a speed of 260 inches/min. the yarn was withdrawn from the bath and stretched 220% between two pairs of canted godets. The yarn was then washed with water, collected, and dried in air. It had a dry tenacity of 1.3 gms. per denier; dry extensibility, 25%. The yarn was then stretched 350% by passing it through a tube heated to 175 C. at a speed of 70 it./min. The resulting yarn had the following characteristics:

Tensile Filaments Denier Strength, 7 figfl gins/denier p H Before Reiaxationnu 44 54 4.9 8 After Relaxation in Boiling Water 44 62 4. 2 20 pense. Further advantages are that the coagulating bath is non-inflammable, non-volatile, and relatively non-toxic.

In the practice of this invention, the concentration of dimethyl iormamide in the bath must be maintained at from to 80% by volume throughout the entire spinning operation.

This requires 'the addition of only small amounts of water. In the case of other spinning baths, for example, glycerol, the presence of more than a small amount, not over 20%, of dimethyl formamide is detrimental and results in breaking of the filaments at the jet and excessively weak yarns. In order to keep the concentration of dimethyl formamide introduced during spinning into a glycerol precipitating bath at or below the comparatively low critical value for satisfactory spinning, it is necessary to add. substantial amounts of the expensive glycerol to the bath. Thus, for each liter of dimethyl formamide pumped into the bath as dope, it is necessary to add four liters of glycerol in order to prevent increase in the dimethyl formamide concentration above 20%. In contrast to this, when the spinning bath comprises a mixture of, say, 67% dimethyl formamide and 33% water, amounts of dimethyl formamide greater than are do not have to be added, and it is necessary to add only a liter of water to the bath, for each liter of dimethyl formamide pumped in as dope, in order to maintain the necessary bath composition.

The filaments or yarns obtained by the present method compare favorably with, and in many cases are superior to, the yarns which can be obtained by spinning the solutions of the acrylonitrile polymers into organic solvents such as glycerol, or into salt solutions.

The tenacity and extensibility of the final heatstretched yarn are essentially the same as those of a yarn obtained by spinning the dimethyl formamide solution into glycerol or calcium chloride solution, at elevated temperatures, in spite of the fact that, prior to the final heating and stretching step, the tensile strength of the yarn was somewhat lower than thatv of yarns obtained when organic solvents or salt solutions were used to effect the coagulation. The yarn produced by the present method exhibits excellent stability at high temperature, is not cemented, and can be dyed by means of wool dyes of the strong acid type, such as Wool Fast Scarlet. The yarn is substantially free from voids when examined under a microscope which magnifies the cross section 500 times.

Example II A 15 solution of polyacrylonitrile in dimethyl formamide was extruded through a O-holeB-mil jet into a bath comprising 32% water and 68% dimethyl formamide by volume. After an immersion of five inches (speed- 260 in./min.) the yarn was withdrawn..from the bath, stretched 200%, washed in water, and dried.

.This yarn had a tensile strength of 1.2 g./d. and an extensibility of 24%. 300% stretch was applied to the yarn duringits passage through a tube heated to C. The tenacity of. the heat-stretched yarn was i5 ms/denier. After relaxation in boiling water the tenacity was 3.82 gms./denier, the extensibility 13%, and the denier 74.

v I Example HI A copolymer containing 17% acrylamide and 83% acrylonitrile by weight was prepared by water solution polymerization. :A 12% solution Of this p l m in dim thyl formamide w s X- 2. A method as in claim 1, wherein the coagutruded through a 9o-hole 3-mil jet into a bath lating bath consists of a mixture of water and comprising water and 45% dimethyl by volume of dimethyl formamide. formamide, After an immersion of three inches 3. A method as in claim 1, wherein the acry- (speed=2-60 iii/mind the yarn was withdrawn 5 lonitrile polymer is a oopolymer of acrylonitrile from the bath, stretched 200%, washed, and and 2-viny1 pyridine containing by weight dried. The yarn so obtained had a tenacity of of acrylonitrile in the polymer molecule.

1.42 gins/denier and extensibility of 28.3%. 4. A method as in claim 1, wherein the acry- Passage through a tube heated to 180 0. perlonitl'ile po ymer is polyacrylom'trile.

mitted application of 400% stretch and pr0- 1o 5.A method as in claim 1, wherein the acryduced a yarn of denier which had a tenacity l nitrile polymer is a copolymer of acrylonitrile of 5.1 gms/denier and an extensibility of 8%. d ylamid containing y W ht 1 Since it is obvious that some changes and mociiaclylfiniblile n he P y moleculefications can be made in the above described A method as n claim wherein the p ndetails without departing from the nature and 5 g is performed at room temperature. spirit of the invention, it is to be understood that A method as in Claim wherein the ythe invention is not to be limited thereto exce t lonitrile p lym r is a p lym r of acryl nitrile as defined in th appended claims and vinyl acetate containing at least 65% by I l weight of acrylonitrile in the polymer molecule. 1. A method for the production 01 yarns from 0 A method as in 0391111 1, wherein the a ya solution of a fiber-forming acrylonitrile polylollitlilo P ymer is a oopolymer of acrylonitrile mgr containing in th pglymer molecule, at least and an acrylic acid ester containing at least 65% 65 of acrylonitrile in dimethyl formamide whi h by weight of acrylonitrile in the polymer molecule. comprises spinning the solutions into a coagu- Peferences Cited in the 1 f lating bath consisting essentially of a mixture of O fi e 0 thls patent Water and from 35 to 80% by volume of dimethyl UNITED STATES PATENTS formamide, withdrawing the yarn thus formed Numbe Name Date from the bath, and stretching the yarn by 200 2,236,061 zard Mar. 25, 1941 to 300% of its length, the composition of the 2,360,405 r yfus Oct. 17, 1944 coagulating bath being maintained substan- 0 2,404,714 a ham July 23, 1946 tially constant from the beginning to the end 2,404,723 Memer July 23, 1946 of the spinning operation. 2,420,565 Rugeley et a1. May 13, 1947

Claims (1)

1. A METHOD FOR THE PRODUCTION OF YARNS FROM A SOLUTION OF A FIBER-FORMING ACRYLONITRILE POLYMER CONTAINING, IN THE POLYMER MOLECULE, AT LEAST 65% OF ACRYLONITRILE IN DIMETHYL FORMAMIDE WHICH COMPRISES SPINNING THE SOLUTIONS INTO A COAGULATING BATH CONSISTING ESSENTIALLY OF A MIXTURE OF WATER AND FROM 35 TO 80% BY VOLUME OF DIMETHYL FORMAMIDE, WITHDRAWING THE YARN THUS FORMED FROM THE BATH, AND STRETCHING THE YARN BY 200 TO 300% OF ITS LENGTH, THE COMPOSITION OF THE COAGULATING BATH BEING MAINTAINED SUBSTANTIALLY CONSTANT FROM THE BEGINING TO THE END OF THE SPINNING OPERATION.