US2467553A - Wet-spinning acrylonitrile polymers - Google Patents

Description

April 19, 1943. w, ALHARE 2,467,553

WET-SPINNING ACRYLONITRILE POLYMERS Filed May 8, 1947 40 INVENTOR Weston Andmu/Hare,

BY a.

ATTORNEY shapedarticles iromtlloseobtalnedhomthc Patented Apr. is, 1949 2,467,553 WET-SPINNING ACRYLONITBILE POLYMERS Weston Andrew Hare, Kenmore, N. E. I. du Pont de Nemours &

Y., alaignor to Company, Wiln, DeL, a corporation of Delaware Application May 8, 1947, Serial No. 38551 9 Claims.' (Cl. 18-54) a 1 v This invention relates to process of producing shaped articles, such as yarns, illms, bristles; tubings and the like, of acrylonitrile polymers. More particularly, the invention relates to a process for the wet-spinning or casting of acrylonitrile polymcrstoobtainshapedarticles ahigh tenacity, a desirable elongation and a lustrous appearance and being substantially free of voids.

Although the process of this invention is generaliy applicable to the production of any shaped article or an acrylonitrile polymer, it will, for convenience, be discussed in connection with the wetspinning of yarns of 'acrylonitrile polymer.

Acrylonitrile polymers possess, in addition to other desirable properties, a high degree of toughness and insolubility in and resistance to the action of common solvents. British Patent No. 459,596 discloses that acrylonitrile polymers are soluble inhighly concentrated aqueous solutions of hydrated salts, such as lithium bromide, zinc chloride and sodium suliocyaiiate. and that the polymers can be precipitated from such solutions by the addition of water, aqueous salt solutions or acids. When such solutions of acrylonitrile polymers are extruded into the aforementioned precipitating liquids with the view of obtaining shaped articles such the shaped articles are extremely weak and filled with voids. They are soextremely brittle that they are practically incapable of being used as yarns or films. Moreover, particularly in the case or multi-fllament yarns, the individual filaments tendtosticktogethertoiormoslnglarisid British Patent No. 461,675 that acrylonitrile polymers can be'dissolved iii-molten quatemaryammoniumsaltasuchasbepsylpyrldinium chloride and repr clpi l by'the addition of water, dilute salt solutions or acids. However, prepared by the extrusion of such solutions into with voids and extremely equally incapable of being MorerecentlyJthasbeendiscoveredthat acrlonitriie po ymers can be wired in certain volatile organic solvents, and shaped articles, such as yarns. illms, ctc., oi the polymer have been obtained by such solutions into They are usedasgarnsorfllms.

precipitating baths oi the type mentioned above.

The structures obtained in this manner diiier previouslyproposed inthattheyare not so extremel brittle. lloreover, in the case of a multi-illament yam. the individual filaments donotappcartobemattedorstucktosethcr.

these liquids weak, filled 2 However, the structures still numerous voids throughout their length and the yarns possess too low a tenacity and elongation to permit themtobeusedinthe'textileart.

It is an object of this invention to provide an improved process for the wet-spinning of an acrylonitrile polymer yarn and produce thereby a yarn that possesses a sufliciently high tenacity and elongation to render it suitable for use in the textile art, has a lustrous appearance, and is substantially free of voids along its length. Another object of this invention is to provide an improved spinning bath for use in such process. Other objects will become apparent from the description is of the invention hereinafter set forth.

'\of an acrylonitrile 2o bath heated to a v The objects of this invention are accomplished, in general, by the steps ofextruding a solution polymer in a volatile organic shaped orifice into a spinning temperature 01' at least 90 C. and comprising a liquid that is a non-solvent for the polymyer but is capable of producing a comsolvent through a pact yarn, i. e. a yarn having an area ratio oi not more than 2.1, passing the yarn through as the bath for a distance suillciently long to cause fcrred substantially complete coagulation, and maintainingtheyarnduring atleastthelatterpore tion of its travel sion oi about 0.3 gram per denier. The liquid used in this invention as the spinning bath comprises an aqueous, at least 10% (by weight) solution oi a sine halide selected from the group consisting of zinc chloride, zinc bromide and zinc iodide 35 following description of the process of this invention and the examples showing its practice will be more clearly understood it reference is made to the accompanying drawings wherein:

Figure 1 illustrates tically a. preapparatus suitable for use inthe practice ofthis invention; and

Figure 2 illustrates tically a modifled form of apparatus that is also suitable for 5 use in the practice of this invention.

Referring now to Figure 1, the reference numeral i indicates a multi-hole spinneret through which an acrylonitrile polymer solution is extruded into a spinning bath 2 contained in a trough m 8 provided with heating coils I. In its travel 'through the-spinning bath 2, the yarn 5 formed by the coagulation of the polymer is subjected to tension by tension means comprising a pair of stationary snubbing pins 6. The tensioned yarn,

after being led through the bath for the remainder of its travel by a guide I, is passed without through the bath under a ten 3 slippage about a positively driven roller or feed wheel 8, and the yarn is subsequently passed to a collecting device, such as a rotating bobbin I.

Referring now to Figure 2 wherein a modified form of apparatus for use with the invention is illustrated, the reference numeral 3| designates a multi-hole spinneret through which an acrylonitrile polymer solution is extruded into a spinning bath 3! contained in a trough 33, provided with heating coils 34 capable of maintaining the bath at a temperature of at least 90 C. The yarn 35 is led through the bath 32 by a guide 36 and is conducted over guides 31 which serve to lead the yarn 35 from the bath 32 into a bath 33 contained in a trough 39, which is also provided with heating coils l capable of maintaining the bath 33 at a temperature of at least 100 C., and preferably 150 C. or higher. Roller guides 4| serve to lead the yarn 35 through the bath 33. The roller guides 35, 31 and ll are of the type which exert no substantial tension on the yarn passing there-' over or thereunder.

A tension device 42, which comprises a pair of stationary snubber pins 43, is mounted in the bath 38 in the path of travel of the yarn 35 therein and it imparts a tension to the yarn passing therethrough. The tensloned yarn is then withdrawn from the bath by a positively driven feed wheel 44 and passed to a collection device, such as a rotating bobbin 45.

In the following examples, which illustrate preferred methods of practicing this invention, the parts are by weight.

Exmu: I

A spinning solution was prepared using 84 parts of dimethyl formamide and 16 parts of polyacrylonitrile, the molecular weight of which was about 121,000. The solution was heated to 100 C. and was extruded at that temperature through a 60-hole spinneret (hole diameter of 0.003 inch) into a spinning bath consisting of 30% aqueous zinc chloride heated to a temperature of 96 C. The yarn was led through the bath for a total distance of 1'] inches with a snubbing pin 2 inches from the spinneret and another inches from the jet. The yarn was drawn out of the bath at a total tension of '14 grams and at a speed of 1800 inches per minute. After being collected on a bobbin and washed with soft water, it was dried, skeined and heated at 125 C. for one hour. This yarn is designated as yarn A" in the table immediately below. A portion of the yarn was then after-stretched to a total stretch of five times its original length and was then heated for one hour at 125 C. after coning. This yarn is designated as yarn B. The yarns had the following Dhysi cal properties:

An aqueous zinc chloride spinning bath con taining 10% by weight of zinc chloride was heated to a temperature of 93" C. A spinning solution containing 16% by weight of polyacrylonitrile in dimethyl formamide was extruded into the zinc chloride spinning bath through a 60-hole spinneret (hole diameter of 0.003 inch), pump delivery being 4.4 grams per minute. The yarn so formed, was passed around a snubbing pin 1.5 inches from the spinneret and around another suchpin 17.5 inches from the spinneret for a total bath travel of 14 inches. The second snubbing pin was located in the air above the bath. The spin tension was 67 grams. Yarn was wound up on a bobbin at a speed of 1800 inches per minute. After being washed and dried on the bobbin it was skeined and then heat-treated as a skein for one hour at 125 C. This yarn is designated as yarn C. A portion of the yarn was stretched to a 5X stretch ratio, was then coned and heattreated one hour at 125 C. on the cone. This yarn was designated as yarn D. The physical properties of the yarn were as follows:

Table Tenacity, g./d. Elongation, per cent D y Wet Loop Dry Wet Loop Yarn C Yarn D Examu III A spinning solution similar to that used in Example I was extruded at a rate of 4.2 grams per minute into an aqueous bath containing 25% zinc chloride and 18% calcium chloride, the bath being heated to a temperature of 110 C. The yarn was passed around a snubber pin 10 inches and a second snubber pin 16 inches from the spinneret face, the total bath travel being 18 inches. The yarn was drawn from the bath at a spin tension of 138 grams and at a speed of 1800 inches per minute. It was collected on a bobbin, washed and then skeined and heat-treated for one hour at 135 C. This yarn is designated as yarn E. A portion of the yarn was then stretched around a heated pin to a 3X stretch ratio, was then coned and finally heat-treated on the cone for one hour at 125 C. This yarn is designated as yarn F. The physical properties are tabulated below:

Table Tenacity, gJd. Elongation, per cent Dry Wet Loop Dry Wet Loop Yarn E Yarn F From the above data in Examples I and II it can be seen that in the case of aqueous spinning baths containing only zinc chloride, by reason of rapid coagulation of the spinning solutions, the first snubbing pin is located close to the spinneret and relatively short bath travels may be used. Yarns produced using such baths possess very good yarn properties. Zinc chloride baths containing around 10% zinc chloride are satisfactory in baths although the concentration may be lower and may be considerably higher, saturated solutions being operable under certain conditions. It

' is preferred to use baths containing at least 10% by weight of zinc chloride and generally baths containing 30% to 50% of. the inorganic solute are employed.

As shown in Example III zinc chloride may be used in combination with calcium chloride. The

' amount of zinc chloride, for example, may be from 10% to 40% with the added calcium chloride varying from 10% by weight up to the amount chloride is used alone, it is preferred to have the' primary bath stretching occur at a point close to the spinnerets and, accordingly, the first snubber pin is placed about 1.5 to 2 inches away, although longer distances may be used. When zinc chloride is used in combination. with other bath ingredients, such as calcium chloride, primary stretching may be applied at a greater distance from the spinneret, for example, 10 inches as is shown in Example III.

The acrylonitrlle polymer, of which the shaped articles are formed, is preferably prepared by the ammonium persulfate catalyzed polymerization of monomeric acrylonitrile dissolved or emulsified in water. It can, however, be prepared by any other suitable type of polymerization reaction, such as, for example, the'emulsion-type reaction disclosed by United States Patent No. 2,160,054 to Bauer et a1.

The polymer, of which the shaped articles are formed in accordance with this invention, must of course be of a sufliciently high molecular weight to possess filmor filament-forming properties.

The polymer employed possessesan average-mo lecular weight within the rangeof 25,000 to 750,000, or even higher, and preferably within the range of 40,000 to 250,000, as calculated'from viscosity measurements by the Staudinger equation I Molecular weight= wherein N specific viscosity and The molecular weight of the polymer obtained is dependent on such factors as the concentration of the monomer in the water, the amount and type of catalyst present, the temperature of the reaction, etc. when the monomer is present in 5% aqueous solution maintained'at a temperature of from 3 C. to 5 C., it is found that the use of 4% of ammonium persulfate catalyst (based on the weight of the acrylonitrile) results in the formation of a polymer having a molecular weight (as calculated by the above equation) of approximately 60,000. Increasing or decreasing the amount of the catalyst, while maintaining the other conditions constant, decreases or increases the molecular weight of the polymer. The polymer preferably comprises a simple polymer of acrylonitrile. However, interpolymers of acryloviscosity of solution viscosity of solvent 1 nitrile and other polymerizable substances, such as vinyl acetate, vinyl chloride, esters or other derivatives of acrylic or methacrylic acids, styrene,

isobutylene and other polymerizable substances,

may also be used. However, for the final yarn to possess the desirable properties of polymerized acrylonitrile' (such as resistance to acids anticomanother polymerizable substance are preferred The polymer can be dissolved in any suitable solvent. However, it is preferred that the solvent comprise a volatile organic substance. The term volatile organic solvent," as used in this specification, is meant to include those organic substances that are capable of forming stable homogeneous solutions with an acrylonitrile polymer and that can be distilled without decomposition at atmospheric pressure. Suitable volatile organic solvents for use with this invention include dimethyl formamide, dimethyl methoxyacetamide, N-formyl morpholine, N-formyl hexamethylene imine, butadiene cyclic sulfone, tetramethylene cyclic sulfone, p-phenylene diamine. and the m and p-nitrophenols, as mentioned in copending application to Houtz, Serial No.

447,446 now abandoned. This class of substances is further exemplified in U. S. Patents Nos. 2,404,714-'2,404,728, inclusive. Accordingly, any volatile organic solvent which forms the requisite polymer solutions and which has the desired stability may be used in the process of this invention.

The preferred concentration of the spinning solution is, of course, dependent on the average molecular weight of the polymer employed, it generaily being desirable to use more dilute solutions in the spinning of-polymers of high molecular weight. In general, it is preferred that the solution contain from 10% to 30% of the polymer, and a 17% solution of an acrylonitrile polymer possessing an average molecular weight of 120,000 is admirably suited for use with the invention. when the solution is to be extruded through a conventional yp orifice, it should possess a viscosity of from 50 to 500 poises, this viscosity being obtained by properly adjusting the temperature of the solution prior to extrusion. In general, solution temperatures of from to C. are preferred.

As indicated in the above examples, spinning baths comprising zinc chloride baths at a temperature of 90 C'. are eminently suited for use in the spinning of desirable yarns of an acrylonitrile polymer. However, the invention is not limited to the use or these specific baths. For example, zinc bromide baths, zinc. iodide baths or baths containing calcium chloride along with the zinc chloride, bromide or iodide may be used. On the other hand, liquids, such as ethyleneglycol, carbitol, water, dilute solutions of inorganic salts, etc., that do not meet this requirement are not suited for use with the invention. Yarns formed in the latter baths are brittle and are filled with large, undesirable voids. They cannot be subiected. without menus; to the high spinnin! vention act to precipitate the polymer in the form of a more compact structure than do the baths of the prior art. This compactness of structure can be shown by determining the area ratio" of the yarn obtained. This term "area ratio refers to the ratin or themeasured cross-sectional area-of accuses the individual filaments of an acrylonitriie polymer yarn to the theoretical cross-sectional area of those filaments as calculated from the denier of the yarn and the known density of the polymer (1.165 for an acrylonitrile polymer prepared according to the method of U. S. Patent No. 2,140,048 to Fikentscher and possessing an average molecu. lar weight of 120,000, as determined from viscosity measurements by the Staudinger formula).

The following table indicates the area ratio of yarns obtained by spinning an acrylonitrile polymer solution into various baths, including the baths of this invention. In each case, the yarn was prepared by extruding a 20% solution of an acrylonitrile polymer, possessing an average molecular weight of 120,000, in dimethyl formamide into the desired bath, the spinning solution being heated prior to extrusion to a temperature of 100 C. and extruded through a 40- hole spinneret having a hole diameter of 0.003 inch. The solution was extruded at a rate of 4.2 grams per minute and the yarn, after a total bath travel of 24 inches, was collected on a bobbin at a rate of 860 inches per minute (equalto the cal culated jet velocity employed). The yarn was then washed with water and dried on the bobbin. The denier of the yarn was thendetermined by weighing 90 cm. lengths, from which value the calculated cross-sectional area of the filaments (column of the table) was determined by the formula:

Area (cmFX Yarn denier 9 density of polymerXnumber of filaments in yarn I In all cases, a value of 1.165 was used for the above, yield yarns having an area ratio of not more than 2.1) are substantially free of voids and can be subjected without breaking to relatively high spinning tensions (of the order of 0.7 gram per denier or more) to yield oriented yarns that possess-a high tenacity and a good elongation and that are generally suited for use in the textile art.

The description previously set forth indicates that the spinning baths of this invention should be maintained at a temperature of C. or higher, for example, C. However, there is nothing critical about this temperature and, generally speaking, the bath can be maintained at any desired temperature, provided only that the bath at that temperature is capable of precipitating the polymer in the form of a yarn possessing an area ratio of not more than 2.1. The bath temperature should, of course, not exceed the boiling point of the solvent employed in the spinning solution. If it does, undesirable boiling of the solvent will occur with the resultant formation of minute bubbles in the yarn.

It is generally preferred in the practice of this invention to employ a bath travel of the order of 20 to 25 inches. However, this is not essential and bath travels as short as 4 inches can be used if desired. On the other hand, much longer bath travels of the order of 100 to 200 or more inches can also be used. Such long bath travels are especially useful in the spinning of a heavy denier yarn or a large bundle of filaments intended for conversion into staple fibers.

As already mentioned, the baths of this invention, in distinct contrast to previously proposed baths for the spinning of acrylonitrile polymer yarns, make possible the application of an appreciable tension to the yarn during the spinning operation. The process of this invention includes, as one preferred step, the use of such tension, the tension preferably being of the order of at least 0.1 gram per denier. As shown in the examples, admirable results are obtained by the use of tensions of the order of 0.7 to

Table CrossSectional Area Filaments (av.) Bath Deni- (cmJ/lo) Area Rat Spinning Bath Temp., er of )Mealumd Area: "C. Yarn Cal alculated Area) In Mea ured hm GIG] ms 344 1.14 0.822 1.39 ioerol- 1:? 341 1. 3S 0. 815 1. 70 48;, NaSCN (aq.)--- H5 :00 1.51 0. 72 1 l 1 0 3180s 1m sos 1.77 0. 74 3.4 Carbitul 140 341 1 02 0. 815 2 48 Ethylene g1 col 140 341 2. Z) 0.8N 2. 06 m CaClg sq 1(1) 341 2.21 0. 815 172 Wat! 96 327 3. 24 0. 782 3. 87

As shown by this table, the area ratio a of an 00' 1.2 grams per denier, and these tensions or even acrylonitrile polymer yarn prepared by the wetspinning technique is greatly aflected by the composition of the spinning bath employed and this invention is based on the discovery that the desirable physical properties of such a yarn are inversely related to the area ratio of the yarn as spun. Yarns spun in baths which, when tested in the above manner, yield a yarn having an area ratio greater than 2.1 are generally undesirable. They possess large voids and cannot be stretched to form yarns possessing a high tenacity, i. e., a tenacity'of the order of 4 grams per denier or higher. On the other hand, yarns spun in the baths of this invention, including the zinc chloride baths, (these baths which, when tested as higher ones, for example as high 'as 1.7 grams per denier, can be used if desired.. It is generally preferred to apply this tension to the yarn over a relatively short range of bath travel, for example, by means of one or more snubbing bars mounted in the bath. However, this is not critical to the invention and 'other types of tension devices, such as a plurality ofroller guides, etc., can also be used, either alone or in conjunction with one or more stationary snubblng bars. In some cases. it is. preferred to apply the tension to the yarn only during the latter portion of its bath travel. However, this is not essential and the tension can, if desired, be applied at an earlier stage. As a matter of fact, satisfactory results can be obtained when the tensioning device is mounted within one inch of the spinneret face.

As indicated above. the process of this invention lends itself admirably to use with a doublebath set-up, the yarn being first passed through a primary bath (preferably heated to a temperature of 100 C.) for a distance sufiicient to completely coagulate the yarn and then led through a second bath heated to a much higher temperature, at which time it can be subjected to a high stretching tension by suitable devices mounted in this bath. As in the single-bath set-up, it is preferred but not essential that this high tension be applied to the yarn over a very short range by a tensioning device positioned at a point aproximately two-thirds along the length of this second bath travel. The primary and secondary baths employed in this double-bath spinning set-up are preferably of the same composition and comprise liquids that are capable of precipitating an acrylonitrile polymer from solution in the form of a yarn possessing an area ratio of not more than 2.1. However. this is not essential and the baths can, if desired, differ in their composition. It is only necessary that the liquid comprising the first or primar bath be such a liquid and that the second bath comprise a liquid that is incapable of dissolving an acrylonitrile polymer, and that is maintained at an elevated temperature, for example a temperature of 100 C. to 140 C.

On leaving the spinning bath, the yarn is collected in suitable package form, preferably on a rotating bobbin under somewhat reduced tension. The yarn package is then washed to free it of occluded spinning bath and dried. If desired, a finishing agent may be applied to the yarn at the end of the washing operation and the dried yarn twisted and wound into final package form for commercial use. The yarns are bright, lustrous, and free of voids. Their filaments have substantially non-crenulated surfaces and are ellipsoidal in cross-section. The yarns possess dry tenacities of from 3 to 6.5 or 7 grams per denier, together with elongations of from 13% to 10%. They possess desirable knot and loop tenacities. Moreover, when heated under tension for extended periods of time, the yarns show a remarkable retention of tenacity with only a very slight gain in elongation; for example, a typical yarn possessing a tenacity of 4.2- grams per denierand an elongation of 13% will possess, after being heated for one hour at 100 C. under tension, a tenacity of 4.1 grams per denier and an elongation of 13%. This is quite surprising in view of the normal behavior of polymeric yarns which customarily show a marked loss in tenacity (30% to 40%) and a sharp gain in elongation (100% or more of the original value) when treated in such a manner. This remarkable property of the yarns produced by this invention makes them eminently suited for many purposes.

On the other hand, if the purified dried yarns produced by this invention are heated in arelaxed state to temperatures of the order of 130 C. to 200 C., in accordance with the teachings of copending application (Q-107L), Serial No. 496,396 now U. S. Patent No. 2,445,042, filed July 28, 1943, the yarns do tend to shrink somewhat and such an after-treatment can be used to increase the elongation of the yarns to a point where they are satisfactory for use in the textile art. It isonlyinthecaseofyarnspossessingaveryhish 10 tenacity (for example a tenacity of 6.4 grams per denier) that any appreciable loss in tenacity is occasioned by this treatment. Even then, the tenacity does not usually fall below 4.5 grams per denier. yarnpossesses a dried tenacity of 4 grams per denier or less, this relaxed heating treatment serves to increase both the elongation and the tenacity, the final yarn in any event possessing a tenacity of 4.5 to 5 grams per denier and an elongation of from 18% to 25%.

This invention provides a class of spinning baths that is eminently suited for use in the wetspinning of acrylonitrile polymer yarns. It also provides a wet-spinning process for the manufacture of such yarns, which yarns possess a desirable tenacity and elongation and are eminently suited for use in the textile art. The freshly spun yarns produced by this invention are lustrous and free of voids. Any voids that are present are submicroscopic in size and are not visible when examined under a magnification of 500 times. The yarns are not brittle. Moreover, the yarns exhibit an unexpectedly high retention of their tenacity and elongation on exposure under tension to elevated temperatures.

The process of this invention makes it possible to produce such highly desirable yarns in a single spinning operation without the use of additional after-treatments of any sort. However, if desired, the yarns can be subjected to a simple after-treatment to greatly improve elongation without at the same time causing any marked lowering in tenacity or loss of other desirable properties. If desirable an after-stretch treatment may be used to improve properties and increase production rate. The process of this invention does not require the use of complicated apparatus. It can be performed on existing machinery of the type employed, for example, in the wet-spinning of viscose rayon yarns.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be'limited thereto except as set forth in the appended claims,

I claim:

1. A process for wet-spinning of acrylonitrile polymer yarn which comprises extruding a solution, in a volatile organic solvent, of acrylonitrile polymer containing a major portion of acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution of a zinc halide selected from the group consisting of zinc chloride, zinc bromide and zinc iodide.

2. A process for wet-spinning of acrylonitrile polymer yarn which comprises extruding a solution, in a volatile organic solvent, of acrylonitrile polymer containing a major portion of acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution of a zinc halide selected from the group consisting of zinc chloride, zinc bromide and zinc iodide, the said solution being heated to a temperature of at least' C.

3. A process for wet-spinning of acrylonitrile polymer yarn which comprises extruding a solution, in a volatile organic solvent, of acrylonitrile polymer containing a major portion of acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution of a zinc halide selected from the group consisting of zinc chloride, zinc bro- On the other hand, when the dried ll mide and zinc iodide, the said solution being heated to a temperature of at least 90 (3., passing the yarn through said bath until it is substantially completely coagulated and subjecting the yarn during its travel through the bath to a tension of at least 0.3 gram per denier.

4. A process of wet-spinning of acrylonitrile polymer yarn which comprises extruding a solution in dimethyl iormamide or acrylonitrile polymer containing a major portion of acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution of a zinc halide selected from the group consisting oi zinc chloride, zinc bromide and zinc iodide.

5. A process of wet-spinning of acrylonitrile polymer yarn which comprises extruding a solution in dimethyl iormamide oi acryionitrile polymer containing a major portion of acrylonltrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution of zinc chloride.

6. A process for wet-spinning of 'acrylonitrile polymer yarn which comprises extruding a solution, in a volatile organic solvent, of acrylonltrile polymer containing a major portion of acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution of zinc chloride.

7. A process for wet-spinning of acrylonitrile polymer yarn which comprisesextruding a solution, in a volatile organic solvent, of acrylonitrile 12 polymer containing a major portion or ac'rylonitrile, through a shaped orifice into aspinning bath comprising an aqueous, 10% to 50% (by weight) solution of zinc bromide.

8. A process for wet-spinning oi acrylonitriie polymer yarn which comprises extruding a solution, in a volatile organic solvent, 0! acrylonitrile polymer containing a major portion or acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous, 10% to 50% (by weight) solution oi zinc iodide.

9. A process for wet-spinning of acrylonitrile polymer yarn which comprises extruding a solution, in a volatile organic solvent, of acrylonitrile polymer containing a major portion of acrylonitrile, through a shaped orifice into a spinning bath comprising an aqueous solution containing 10% to 40% by weight of zinc chloride and at least 10% by weight of calcium chloride.

wns'ron ANDREW HARE.

, REFERENCES CITED The following references are oi record in the Certificate of Correction Patent No. 2,467,553. April 19, 1949. WESTON ANDREW HARE It is hereby certified that error appears in the printed specification of the above' numbered patent requiring correction as follows:

Columns 7 and 8, in the table, first 3 lines, immediately under the headings, should appear as shown below instead of as shown in the printed patent:

30% mom-10% CaOh me an .35 as: 1. e3

" m ZnCla 105 340 1. 46 O. 81 L N mmscn m.) 100 an us cm 2.35

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 29th day of November, A. D. 1949.

' THOMAS F. MURPHY, Auistantflommiuioner of Patents.

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